Category Archives: Nutraceuticals

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Specific Chemical Compounds in Citrus Peels Demonstrates Potential Promise in Cancer Prevention

Citrus is a genus of flowering trees and shrubs in the rue family, Rutaceae. Citrus trees and shrubs produce citrus fruits, which include the five different common varieties:

  • Grapefruit
  • Lemon
  • Lime
  • Orange
  • Tangerine

Within each of these common varieties are a number of species. 

List of Citrus Fruits

Citrus peels are very rich in phenolic compounds, such as phenolic acids, flavonoids, limonoids, as wells as carotenoids.  The main source of polyphenols are contained in the citrus peels.  1    A specific class of flavones exist almost ubiquitously in citrus plants named polymethoxylated flavones (PMFs).  These main polymethoxylated flavones in citrus include:

  • nobiletin
  • tangeretin
  • sinesetin
  • 3,5,6,7,8,3′,4′-heptamethoxyflavone
  • 3,5,6,7,3′,4′-hexamethoxyflavone

Six PMFs and three major 5-demethoxyflavones can be extracted from a variety of citrus peels.  2  Accumulative in vitro and in vivo studies indicate protective effects of polymethoxyflavones (PMFs) against the occurrence of cancer. PMFs inhibit carcinogenesis by the following mechanisms:  3

  • blocking the metastasis cascade
  • inhibition of cancer cell mobility in circulatory systems
  • inducing apoptosis
  • antiangiogenesis

Citrus peels also have an abundant source of polyhydroxyl flavonoids (PHFs) which include:

  • hesperidin
  • neohesperidin
  • naringin

Less studied but equally important are the limonoid glucosides, a class of furan-containing triterpenes.  Up to 53 limonoids have been identified and characterized, yet the most important limonoids that are subject to anticancer research include:

  • limonin
  • nomilin
  • nomilinic acid

The anti-cancer activity of citrus peel flavonoids has been studied on several animal models.  The various cancers that have been studied with citrus peel flavonoids include, among others:  4

  • colon cancer
  • lung cancer
  • liver cancer
  • prostate cancer
  • skin cancer

Citrus peels, in addition to cancer prevention and intervention, exhibit other biological functions with various disease states:  5

  • antiatherogenic
  • antimicrobial
  • antithrombotic
  • cardioprotective
  • delayed onset of Alzheimer’s disease  6 
  • hypolipidemia  7 
  • inflammation inhibition  8 
  • neuroprotective  9
  • regulation of metabolic syndrome  10

The Tabs below lists the individual citrus fruit chemical compounds:

Individual Citrus Fruit Chemical Compounds

Carotenoids:
  • Lycopene
  • Beta-Carotene
Furocoumarins:
  • Bergamottin
  • Bergapten
  • Bergaptol
Limonoids
  • Limonin
  • Nomilin
  • Nomilinic acid
Organic Acids:
  • Citric Acid
  • Glycyrrhetinic Acid
Polyphenols:
  • Naringin
  • Naringenin
  • Quercetin
  • Rutin
  • Kaempferol
  • Hesperidin
  • Eriocitrin
  • Nobiletin
  • Tangeritin
  • Diosmin
Terpenoids:
  • Citral
Carotenoids:
  • Beta-Carotene
  • Cryptoxanthin
Limonoids
  • Limonin
  • Nomilin
  • Nomilinic acid
Organic Acids:
  • Citric Acid
  • P-Coumaric Acid
  • Sinapic Acid
Polyphenols:
  • Diosmin
  • Eriocitrin
  • Didymin
  • Hesperidin
  • Rutin
Terpenoids:
  • Limonene
  • Citronellal
  • Citral
Limonoids
  • Limonin
  • Nomilin
  • Nomilinic acid
Polyphenols:
  • Eriocitrin
  • Hesperidin
Terpenoids:
  • Citral
Alkaloids:*
  • Synephrine
  • Hordenine
Amines:*
  • Octopamine
  • N-Methyltyramine
  • Tyramine
Carotenoids:
  • Alpha-Carotene
  • Beta-Carotene
  • Zeaxanthin
  • Lutein
  • Cryptoxanthin
Limonoids
  • Limonin
  • Nomilin
  • Nomilinic acid
Organic Acids:
  • Citric Acid
Polyphenols:
  • Anthocyanidins
  • Cyanidin
  • Dephinidin
  • Tangeretin
  • Hesperidin
Terpenoids:
  • Limonene
  • Citral
* These Alkaloids and Amines are found primarily in the peel of Oranges.
Alkaloids:
  • Synephrine
Carotenoids:
  • Beta-Carotene
  • Lutein
  • Zeaxanthin
Limonoids
  • Limonin
  • Nomilin
  • Nomilinic acid
Organic Acids:
  • Citric Acid
Polyphenols:
  • Nobiletin
  • Tangeretin
  • Hesperidin
Terpenoids:
  • Limonene
  • Carvone

The Table below lists the 7 groups of chemical compounds found in each of the 5 varieties of citrus.

Chemical Compounds Found in Common Citrus Fruits

Chemical CompoundGrapefruitLemonLimeOrangeTangerine
AlkaloidsXX
AminesX
CarotenoidsXXXX
FuranocoumarinsX
LimonoidsXXXXX
Organic AcidsXXX
PolyphenolsXXXXX

This Table specifically excludes the following chemicals found in citrus fruits: carbohydrates, minerals, vitamins, amino acids, enzymes.

The Table below lists the individual chemical compounds in each of the 5 varieties of citrus.

Individual Chemical Compounds in Common Citrus Fruits

Chemical CompoundsGrapefruitLemonLimeOrangeTangerineTotals
Alkaloids:
HordenineX1
SynephrineXX2
Amines:
OctopamineX1
N-MethyltyramineX1
TyramineX1
Carotenoids:
Alpha-CaroteneX1
Beta-CaroteneXXXX4
CryptoxanthinXX2
LuteinXX2
LycopeneX1
ZeaxanthinXX2
Furocoumarins:
BergamottinX1
BergaptenX1
BergaptolX1
Limonoids
LimoninXXXXX5
NomilinXXXXX5
Nomilinic acidXXXXX5
Organic Acids:
Citric AcidXXXX4
Glycyrrhetinic AcidX1
P-Coumaric AcidX1
Sinapic AcidX1
Polyphenols:
AnthocyanidinsX1
CyanidinX1
DephinidinX1
DidyminX1
DiosminXX2
EriocitrinXXX3
HesperidinXXXX4
KaempferolX1
NaringeninX1
NaringinX1
NobiletinX1
QuercetinX1
RutinXX2
TangeritinXXX3
Terpenoids:
CarvoneX1
CitralXXXX4
CitronellalX1
LimoneneXXX3

The Tabs below lists the specific chemical compounds within each chemical group that show evidence of cancer prevention.

Specific Chemical Compounds in Citrus Fruit that May Show Promise for Cancer Prevention

  • Alpha-Carotene
  • Cryptoxanthin
  • Lutein
  • Lycopene
  • Zeaxanthin
Limonoids
  • Limonin
  • Nomilin
  • Nomilinic acid
  • P-Coumaric Acid
  • Anthocyanidins
  • Cyanidin
  • Didymin
  • Diosmin
  • Hesperidin
  • Kaempferol
  • Naringenin
  • Naringin
  • Nobiletin
  • Quercetin
  • Rutin
  • Tangeritin
  • Limonene

The Tabs below lists the published Abstracts and links to various studies within the 5 carotenoids.

Anticancer Properties of Citrus Peel Carotenoids

Alpha-Carotene

CancerAbstractReference
Bladder cancer
We examined the associations between plasma micronutrients and bladder cancer risk, and evaluated the combined effects of carotenoid and cigarette smoke. Our results show protective effects of carotenoids on bladder cancer. They suggest that bladder cancer may be a preventable disease through nutritional intervention, especially in smokers.1
Breast cancer
An inverse association was observed among premenopausal women was for high levels of vitamin A (OR: 0.82, 95%CI: 0.68–0.98, p for trend = 0.01), β-carotene (OR: 0.81, 95% CI 0.68–0.98, p for trend = 0.009), α-carotene (OR: 0.82, 95% CI: 0.68–0.98, p for trend = 0.07), and lutein/zeaxanthin (OR: 0.83, 95% CI 0.68 – 0.99, p for trend = 0.02). An inverse association was not observed among postmenopausal women. Among premenopausal women who reported ever smoking, these results were stronger than among never smokers, although tests for interaction were not statistically significant. Results from this study are comparable to previous prospective studies and suggest that a high consumption of carotenoids may reduce the risk of pre but not post menopausal breast cancer, particularly among smokers.2
Cervical cancer
The mean serum levels of total carotenoids, alpha-carotene, beta-carotene, cryptoxanthin, and lycopene were lower among cases than they were among controls. These findings are suggestive of a protective role for total carotenoids, alpha-carotene and beta-carotene in cervical carcinogenesis and possibly for cryptoxanthin and lycopene as well.3
Colon cancer
To investigate associations between plasma carotenoids, alpha-tocopherol and retinol with colorectal adenomas risk, we measured concentrations in 224 asymptomatic colorectal adenoma cases and 230 population-based controls matched for age and sex. Our findings suggest a protective effect of carotenoids against the development of colorectal adenomas.4
Laryngeal cancer
Significant inverse relations emerged between laryngeal cancer risk and intake of vitamin C (OR = 0.2, for the highest versus the lowest intake quintile; 95% CI: 0.2–0.4), β-carotene (OR = 0.2; 95% CI: 0.2–0.4), α-carotene (OR = 0.3; 95% CI: 0.2–0.5)5
Liver cancer
Potent preventive action of alpha-carotene against carcinogenesis: spontaneous liver carcinogenesis and promoting stage of lung and skin carcinogenesis in mice are suppressed more effectively by alpha-carotene than by beta-carotene6
Lung cancer
After adjusting for smoking and other covariates, no association was found with lung cancer risk for dietary lycopene or beta-cryptoxanthin intake, whereas dose-dependent inverse associations of comparable magnitude were found for dietary beta-carotene, alpha-carotene, and lutein.7
Neuroblastoma
Analysis by flow cytometry indicated that when GOTO cells were exposed to alpha-carotene, they were arrested in the G0-G1 phase of their cell cycle. However, as the level of the N-myc messenger RNA was recovering, these cells resumed normal cycling. These results indicate that the reduction in the level of the N-myc messenger RNA caused by alpha-carotene is closely linked with G0-G1 arrest.8
Prostate cancer
The adjusted odds ratio for the highest quartiles compared with the lowest were 0.18 (95% CI: 0.08-0.41) for lycopene, 0.43 (95% CI: 0.21-0.85) for α-carotene, 0.34 (95% CI: 0.17-0.69) for β-carotene, 0.15 (95% CI: 0.06-0.34) for α-cryptoxanthin and 0.02 (95% CI: 0.01-0.10) for lutein and zeaxanthin. The dose response relationships were also significant, suggesting that intake of lycopene and other carotenoid rich vegetables and fruits may associate with a reduced risk of prostate cancer.9
Skin cancer
Alpha-carotene was found to have a stronger effect than beta-carotene in suppressing the promoting activity of 12-O-tetradecanoylphorbol-13-acetate on skin carcinogenesis in 7,12-dimethylbenz[a]anthracene-initiated mice.10

Cryptoxanthin

CancerAbstractReference
Breast cancer
Results of this study suggest that the carotenoids beta-cryptoxanthin, lycopene, and lutein/zeaxanthin may protect against breast cancer.1
Cervical cancer
Cryptoxanthin was significantly associated with a lower risk of cervical cancer when examined as a continuous variable. Retinol, lutein, alpha- and gamma-tocopherol, and selenium were not related to cervical cancer risk. Smoking was also strongly associated with cervical cancer. These findings are suggestive of a protective role for total carotenoids, alpha-carotene and beta-carotene in cervical carcinogenesis and possibly for cryptoxanthin and lycopene as well.2
Lung cancer
β-Cryptoxanthin suppresses the growth of immortalized human bronchial epithelial cells and non-small-cell lung cancer cells and up-regulates retinoic acid receptor β expression3
Neuroblastoma
The associations observed in our study suggest that the influence of some antioxidants on survival following a diagnosis of malignant glioma are inconsistent and vary by histology group. Further research in a large sample of glioma patients is needed to confirm/refute our results.4
Prostate cancer
The prostate cancer risk declined with increasing consumption of lycopene, alpha-carotene, beta-carotene, beta-cryptoxanthin, lutein and zeaxanthin. Intake of tomatoes, pumpkin, spinach, watermelon and citrus fruits were also inversely associated with the prostate cancer risk. The adjusted odds ratios for the highest versus the lowest quartiles of intake were 0.18 (95% CI: 0.08-0.41) for lycopene, 0.43 (95% CI: 0.21-0.85) for alpha-carotene, 0.34 (95% CI: 0.17-0.69) for beta-carotene, 0.15 (95% CI: 0.06-0.34) for beta-cryptoxanthin and 0.02 (95% CI: 0.01-0.10) for lutein and zeaxanthin. 5

Lutein

CancerAbstractReference
Bladder cancer
Our results show protective effects of carotenoids on bladder cancer. They suggest that bladder cancer may be a preventable disease through nutritional intervention, especially in smokers.1
Breast cancer
An inverse association was observed among premenopausal women was for high levels of vitamin A (OR: 0.82, 95%CI: 0.68–0.98, p for trend = 0.01), β-carotene (OR: 0.81, 95% CI 0.68–0.98, p for trend = 0.009), α-carotene (OR: 0.82, 95% CI: 0.68–0.98, p for trend = 0.07), and lutein/zeaxanthin (OR: 0.83, 95% CI 0.68 – 0.99, p for trend = 0.02).2
Colon cancer
Lutein was inversely associated with colon cancer in both men and women [odds ratio (OR) for upper quintile of intake relative to lowest quintile of intake: 0.83; 95% CI: 0.66, 1.04; P = 0.04 for linear trend]. The greatest inverse association was observed among subjects in whom colon cancer was diagnosed when they were young (OR: 0.66; 95% CI: 0.48, 0.92; P = 0.02 for linear trend) and among those with tumors located in the proximal segment of the colon (OR: 0.65; 95% CI: 0.51, 0.91; P 3
Liver cancer
Lutein presented inhibitory actions during promotion but not initiation of hepatocarcinogenesis, being classified as a suppressing agent. This reinforces lutein as a potential agent for liver cancer chemoprevention.4
Lung cancer
Protective effects on lung cancer incidence were found for lutein + zeaxanthin, beta-cryptoxanthin, folate, and vitamin C. Other carotenoids (alpha-carotene, beta-carotene, and lycopene) and vitamin E did not show significant associations.5
(Non-Hodgkin’s) Lymphomas
Higher intakes of vegetables, lutein and zeaxanthin, and zinc are associated with a lower non-Hodgkin lymphoma (NHL) risk.6
Ovarian cancer
Micronutrients, specifically ss-carotene, lycopene, zeaxanthin, lutein, retinol, alpha-tocopherol, and gamma-tocopherol, may play a role in reducing the risk of ovarian cancer.7
Prostate cancer
Results demonstrated that both lycopene, in an alpha -cyclodextrin water soluble carrier, and lutein inhibited malignant AT3 cells in a concentration and time-dependent manner. 8
Skin cancer
The results of the photocarcinogenesis experiment were increased tumor-free survival time, reduced tumor multiplicity and total tumor volume in lutein/zeaxanthin-treated mice in comparison with control irradiated animals fed the standard diet. These data demonstrate that dietary lutein/zeaxanthin supplementation protects the skin against UVB-induced photoaging and photocarcinogenesis.9

Lycopene

CancerAbstractReference
Breast cancer
The inhibition of cell growth by lycopene was accompanied by slow down of cell-cycle progression from G1 to S phase. Moreover, the carotenoids inhibited estrogen-induced transactivation of ERE that was mediated by both estrogen receptors (ERs) ERalpha and ERbeta. The possibility that this inhibition results from competition of carotenoid-activated transcription systems on a limited pool of shared coactivators with the ERE transcription system was tested.1
Cervical cancer
 Increasing concentrations of serum lycopene were negatively associated with CIN1, CIN3 and cancer, with odds ratios (OR) (95% CI) for the highest compared to the lowest tertile of 0.53 (0.27-1.00, p for trend = 0.05), 0.48 (0.22-1.04, p for trend = 0.05) and 0.18 (0.06-0.52, p for trend = 0.002), respectively, after adjusting for confounding variables and HPV status.2
Colon cancer
Lycopene treatment suppressed Akt activation and non-phosphorylated beta-catenin protein level in human colon cancer cells. Immunocytochemical results indicated that lycopene increased the phosphorylated form of beta-catenin proteins. These effects were also associated with reduced promoter activity and protein expression of cyclin D1. Furthermore, lycopene significantly increased nuclear cyclin-dependent kinase inhibitor p27(kip)abundance and inhibited phosphorylation of the retinoblastoma tumor suppressor protein in human colon cancer cells.3
Endometrial cancer
In contrast to cancer cells, human fibroblasts were less sensitive to lycopene, and the cells gradually escaped growth inhibition over time. In addition to its inhibitory effect on basal endometrial cancer cell proliferation, lycopene also suppressed insulin-like growth factor-I-stimulated growth. Insulin-like growth factors are major autocrine/paracrine regulators of mammary and endometrial cancer cell growth. Therefore, lycopene interference in this major autocrine/paracrine system may open new avenues for research on the role of lycopene in the regulation of endometrial cancer and other tumors.4
Esophageal cancer
This review of previous epidemiological studies found that high blood lycopene levels are associated with a reduced risk of esophageal cancer.5
Gliomas
Addition of nutrition supplements such as lycopene may have potential therapeutic benefit in the adjuvant management of high-grade gliomas.6
Liver cancer
The invasion of SK-Hep1 cells treated with lycopene was significantly reduced to 28.3% and 61.9% of the control levels at 5 microM and 10 microM lycopene, respectively (P 7
Leukemia
The combination of low concentrations of lycopene with 1,25-dihydroxyvitamin D3 exhibited a synergistic effect on cell proliferation and differentiation and an additive effect on cell cycle progression. Such synergistic antiproliferative and differentiating effects of lycopene and other compounds found in the diet and in plasma may suggest the inclusion of the carotenoid in the diet as a cancer-preventive measure.8
Lung cancer
In conclusion, lycopene may mediate its protective effects against smoke-induced lung carcinogenesis in ferrets through up-regulating IGFBP-3 and down-regulating phosphorylation of BAD, which promote apoptosis and inhibit cell proliferation.9
Mouth cancer
The results of the present study further support the hypothesis that carotenoids in general, and lycopene in particular, may be effective anticarcinogenic agents in oral carcinogenesis.10
Ovarian cancer
Micronutrients, specifically ss-carotene, lycopene, zeaxanthin, lutein, retinol, alpha-tocopherol, and gamma-tocopherol, may play a role in reducing the risk of ovarian cancer.11
Pancreatic cancer
After adjustment for age, province, BMI, smoking, educational attainment, dietary folate, and total energy intake, lycopene, provided mainly by tomatoes, was associated with a 31% reduction in pancreatic cancer risk among men [odds ratio (OR) = 0.69; 95% CI: 0.46-0.96; P = 0.026 for trend] when comparing the highest and lowest quartiles of intake. Both beta-carotene (OR = 0.57; 95% CI: 0.32-0.99; P = 0.016 for trend) and total carotenoids (OR = 0.58; 95% CI: 0.34-1.00; P = 0.02 for trend) were associated with a significantly reduced risk among those who never smoked. The results of this study suggest that a diet rich in tomatoes and tomato-based products with high lycopene content may help reduce pancreatic cancer risk.12
Prostate cancer
We report the inhibitory effect(s) of lycopene in primary prostate epithelial cell (PEC) cultures, and the results of a pilot phase II clinical study investigating whole-tomato lycopene supplementation on the behavior of established CaP, demonstrating a significant and maintained effect on prostate-specific antigen velocity over 1 year.13

Zeaxanthin

CancerAbstractReference
Breast cancer
Carotenoids could inhibit the proliferation of human beast cancer MCF-7 cell line in vitro and the action of carotenoids may be worked through different pathways.1
Lung cancer
Inverse associations with carotenes, lutein + zeaxanthin, and beta-cryptoxanthin seemed to be limited to small cell and squamous cell carcinomas. Only folate and vitamin C intake appeared to be inversely related to small cell and squamous cell carcinomas and adenocarcinomas. Folate, vitamin C, and beta-cryptoxanthin might be better protective agents against lung cancer in smokers than alpha-carotene, beta-carotene, lutein + zeaxanthin, and lycopene.2
Neuroblastoma
Zeaxanthin strongly induced apoptosis in neuroblastoma cells. Consistent with this finding, zeaxanthin did not inhibit LOX activity. Zeaxanthin is a remarkable dietary factor that is able to induce apoptosis in neuroblastoma cells while being able to prevent apoptosis in healthy cells.3

The Tabs below lists the published Abstracts and links to various studies within the 3 limonoids.

Anticancer Properties of Citrus Peel Limonoids

Limonin

CancerAbstractReference
Colon Cancer
The current study was an attempt to elucidate the mechanism of human colon cancer cell proliferation inhibition by limonin and limonin glucoside (LG) isolated from seeds of Citrus reticulata. Results of the current study provide compelling evidence on the induction of mitochondria mediated intrinsic apoptosis by both limonin and LG in cultured SW480 cells for the first time.1

Nomilin

CancerAbstractReference
Inhibits tumor-specific angiogenesis
These data clearly demonstrate the antiangiogenic potential of nomilin by downregulating the activation of MMPs, production of VEGF, NO and proinflammatory cytokines as well as upregulating IL-2 and TIMP.1
Inhibits chemical-induced carcinogenesis
Limonin and nomilin, two of the most abundant limonoids, have been found to inhibit chemical-induced carcinogenesis. Both compounds are inducers of glutathione S-transferase, a major detoxifying enzyme system. The increased enzyme activity was correlated with the ability of these compounds to inhibit carcinogenesis.2
Melanoma
Nomilin is a triterpenoid present in common edible citrus fruits with putative anticancer properties. In this study, the authors investigated the antimetastatic potential of nomilin and its possible mechanism of action. Metastasis was induced in C57BL/6 mice through the lateral tail vein using highly metastatic B16F-10 melanoma cells. Administration of nomilin inhibited tumor nodule formation in the lungs (68%) and markedly increased the survival rate of the metastatic tumor-bearing animals. 3

Nomilinic acid

CancerAbstractReference
Induces apoptosis
No significant effects were observed on growth of the other cancer cell lines treated with the four individual limonoids at 100 micrograms/ml. At 100 micrograms/ml, the limonoid glucoside mixture demonstrated a partial inhibitory effect on SKOV-3 cancer cells. With use of flow cytometry, it was found that all the limonoid samples could induce apoptosis in MCF-7 cells at relatively high concentrations (100 micrograms/ml). 1
Breast cancer
Although most of the limonoids showed anti-aromatase activity, the inhibition of proliferation was not related to the anti-aromatase activity. On the other hand, the anti-proliferative activity was significantly correlated with caspase-7 activation by limonoids. Our findings indicated that the citrus limonoids may have potential for the prevention of estrogen-responsive breast cancer (MCF-7) via caspase-7 dependent pathways.2
Neuroblastoma
We conclude that citrus limonoid glucosides are toxic to SH-SY5Y cancer cells. Cytotoxicity is exerted through apoptosis by an as yet unknown mechanism of induction. Individual limonoid glucosides differ in efficacy as anticancer agents, and this difference may reside in structural variations in the A ring of the limonoid molecule.3

The Table below lists the published Abstract and links to the studies on P-Coumaric acid.

P-Coumaric Acid

CancerAbstractReference
Colon cancer
We demonstrate that two hydroxycinnamic acids, (E )-ferulic acid and (E )-p-coumaric acid, have the ability to protect against oxidative stress and genotoxicity in cultured mammalian cells. They also show the ability to reduce the activity of the xenobiotic metabolising enzyme, cytochrome P450 1A, and downregulate the expression of the cyclooxygenase-2 enzyme. At equitoxic doses, their activities are equal to or superior to that of the known anticarcinogen, curcumin. The hydroxycinnamic acids are both important components of plant cell walls in certain plant foods. It is known that the action of microbial hydroxycinnamoyl esterases can lead to the release of hydroxycinnamic acids from ester-linkages to cell wall polysaccharides into the human colon. 1
Results depicted that p-Coumaric acid inhibited the growth of colon cancer cells by inducing apoptosis through ROS-mitochondrial pathway.2

The Table below lists the published Abstracts and links to the various studies on Limonene.

Limonene

CancerAbstractReference
Breast Cancer
The blocking chemopreventive effects of limonene and other monoterpenes during the initiation phase of mammary carcinogenesis are due to the induction of Phase II carcinogen-metabolizing enzymes, resulting in carcinogen detoxification. The post-initiation phase chemopreventive and chemotherapeutic activities of monoterpenes may be due to the induction of tumor cell apoptosis, tumor redifferentiation, and/or inhibition of the post-translational isoprenylation of cell growth-regulating proteins.1
Colon Cancer
Diet-cancer and diet-cardiovascular disease interrelationships may be explained by the mevalonate-suppressive action of isoprenoid end products of plant secondary metabolism. Assorted monoterpenes, sesquiterpenes, carotenoids and tocotrienols posttranscriptionally down regulate 3-hydroxy-3-methylglutaryl coenzyme A reductase activity, a key activity in the sterologenic pathway. 2
Leukemia
The results showed that D-limonene (D-L) inhibited HL-60 and K562 cell growth in a dose- and time-dependent manner with the IC50 of 0.75 mmol/L similarly, D-L induced apoptosis of HL-60 and K562 cells, and expression of bcl-2 gene was down regulated by D-L in a concentration-dependent manner in HL-60 cells.3
Liver Cancer
Monoterpenes are nonnutritive dietary components found in the essential oils of citrus fruits and other plants. A number of these dietary monoterpenes have antitumor activity. For example, d-limonene, which comprises >90% of orange peel oil, has chemopreventive activity against rodent mammary, skin, liver, lung and forestomach cancers. 4
Lung Cancer
D-limonene given p.o. 1 h prior to NNK administered i.p. again showed pronounced inhibition of pulmonary adenoma formation. This study provides additional data demonstrating that non-nutrient constituents of the diet can inhibit carcinogen-induced neoplasia when administered at a short time interval prior to carcinogen challenge.5
Lymphomas
Results showed that limonene exhibited antiproliferative action on tumoral lymphocytes exerting a decrease in cell viability that was related to apoptosis induction and to the increase in NO levels at long incubation times. At short times and depending on its concentration, limonene arrested cells in different phases of the cell cycle, related to NO production.6
Skin Cancer
Monoterpenes are nonnutritive dietary components found in the essential oils of citrus fruits and other plants. A number of these dietary monoterpenes have antitumor activity. For example, d-limonene, which comprises >90% of orange peel oil, has chemopreventive activity against rodent mammary, skin, liver, lung and forestomach cancers.7
Squamous Cell Carcinoma
This is the first study to explore the relationship between citrus peel consumption and human cancers. Our results show that peel consumption, the major source of dietary d-limonene, is not uncommon and may have a potential protective effect in relation to skin squamous cell carcinoma (SCC). 8
Stomach Cancer
D-limonene has antiangiogenic and proapoptotic effects on gastric cancer, thereby inhibits tumor growth and metastasis. Combination of d-limonene with cytotoxic agents may be more effective.9

The Table below lists the published Abstract and link to the studies on Limonin.

Limonin

CancerAbstractReference
Colon Cancer
The current study was an attempt to elucidate the mechanism of human colon cancer cell proliferation inhibition by limonin and limonin glucoside (LG) isolated from seeds of Citrus reticulata. Results of the current study provide compelling evidence on the induction of mitochondria mediated intrinsic apoptosis by both limonin and LG in cultured SW480 cells for the first time.1

The Tabs below lists the published Abstracts and links to various studies within the 6 polyphenols of citrus peels.  (Part 1 of 2)

Anticancer Properties of Citrus Peel Polyphenols (Part 1 of 2)

Anthocyanidins

CancerAbstractReference
Breast cancer
At 200 μg/mL, cyanidin, delphinidin and petunidin inhibited the breast cancer cell growth by 47, 66 and 53%, respectively. This is the first report of tumor cell proliferation inhibitory activity by anthocyanidins.1
Non-Hodgkin lymphoma
Higher intakes of flavonols, epicatechins, anthocyanidins, and proanthocyanidins were each significantly associated with decreased NHL risk. Similar patterns of risk were observed for the major NHL subtypes--diffuse large B-cell lymphoma (n = 167) and follicular lymphoma (n = 146). A higher intake of flavonoids, dietary components with several putative anticarcinogenic activities, may be associated with lower NHL risk.2

Cyanidin

CancerAbstractReference
Colon cancer
Anthocyanins and cyanidin also reduced cell growth of human colon cancer cell lines HT 29 and HCT 116. The IC(50) of anthocyanins and cyanidin was 780 and 63 microM for HT 29 cells, respectively and 285 and 85 microM for HCT 116 cells, respectively. These results suggest that tart cherry anthocyanins and cyanidin may reduce the risk of colon cancer.1
Leukemia
These results indicate that cyanidin-3-rutinoside has the potential to be used in leukemia therapy with the advantages of being widely available and selective against tumors.2

Didymin

CancerAbstractReference
Lung cancer
Importantly, a novel chemotherapeutic agent for the treatment of non-small-cell lung cancer, and is supported by animal studies which have shown didymin delay the tumor growth in nude mice. Our study reports here for the first time that the activity of the Fas/Fas ligand apoptotic system may participate in the antiproliferative activity of didymin in A549 and H460 cells.1

Diosmin

CancerAbstractReference
Bladder cancer
The chemopreventive effects of 2 flavonoids (diosmin and hesperidin) on N-butyl-N-(4-hydroxybutyl)nitrosamine (OH-BBN)-induced urinary-bladder carcinogenesis were examined in male ICR mice.  Feeding of the test compounds, singly or in combination, during both phases caused a significant reduction in the frequency of bladder carcinoma and preneoplasia. Dietary administration of these compounds significantly decreased the AgNOR count and the BUdR-labeling index of various bladder lesions. These findings suggest that the flavonoids diosmin and hesperidin, individually and in combination, are effective in inhibiting chemical carcinogenesis of the bladder, and that such inhibition might be partly related to suppression of cell proliferation.1
Colon cancer
These results indicate that diosmin and hesperidin, both alone and in combination, act as a chemopreventive agent against colon carcinogenesis, and such effects may be partly due to suppression of cell proliferation in the colonic crypts, although precise mechanisms should be clarified.2
Esophageal cancer
These findings suggest that diosmin and hesperidin supplementation, individually or in combination, is effective in inhibiting the development of oesophageal cancer induced by MNAN when given during the initiation phase, and such inhibition might be related to suppression of increased cell proliferation caused by MNAN in the oesophageal mucosa.3
Mouth cancer
Diosmin, the 7-rutinoside of diosmetin, surprisingly, was more potent and effective than diosmetin. In contrast, quercitrin, the 3-rhamnoside of quercetin, showed no effect and only minimal cellular uptake and no hydrolysis. In summary, dietary flavonoid glycosides may exert cellular effects in the oral cavity, but this varies greatly with the nature of the glycoside.4

Hesperidin

CancerAbstractReference
Bladder cancer
Dietary administration of these compounds significantly decreased the AgNOR count and the BUdR-labeling index of various bladder lesions. These findings suggest that the flavonoids diosmin and hesperidin, individually and in combination, are effective in inhibiting chemical carcinogenesis of the bladder, and that such inhibition might be partly related to suppression of cell proliferation.1
Breast cancer
Two citrus flavonoids, hesperetin and naringenin, are found in orange and grapefruit, respectively. An experimental study has shown that citrus flavonoids are effective inhibitors of human breast cancer cell proliferation in vitro, especially when paired with quercetin, widely distributed in other foods2
Cervical cancer
This study shows that hesperetin exhibits a potential anticancer activity against human cervical cancer cell lines in vitro through the reduction in cell viability and the induction of apoptosis. Altogether, these data sustain our contention that hesperetin has anticancer properties and merits further investigation as a potential therapeutic agent.3
Colon cancer
Inhibition of Colonic Aberrant Crypt Formation by the Dietary Flavonoids (+)-Catechin and Hesperidin4
Esophageal cancer
These findings suggest that diosmin and hesperidin supplementation, individually or in combination, is effective in inhibiting the development of oesophageal cancer induced by MNAN when given during the initiation phase, and such inhibition might be related to suppression of increased cell proliferation caused by MNAN in the oesophageal mucosa.5
Leukemia
The apoptotic activity of CME was significantly attenuated by Akt augmentation. In conclusion, this study suggested that Citrus aurantium L. (CMEs) should induce caspase-dependent apoptosis at least in part through Akt inhibition, providing evidence that CMEs have anticancer activity on human leukemia cells.6
Lung cancer
Hesperidin (25 mg/kg body weight) supplementation effectively counteracted all the above changes and restored cellular normalcy, indicating its protective role during B(a)P-induced lung cancer.7
Mouth cancer
These findings suggest that supplementation with the flavonoids diosmin and hesperidin, individually and in combination, is effective in inhibiting the development of oral neoplasms induced by 4-NQO, and such inhibition might be related to suppression of increased cell proliferation caused by 4-NQO in the oral mucosa.8
Prostate cancer
t is concluded that hesperidin can inhibit the proliferation of breast cancer cells through mechanisms other than antimitosis and it is suggested that hesperidin be further investigated for the possible interaction with androgenic receptors and involvement in signaling pathway after receptor binding in prostate cancer cells through future research.9

Kaempferol

CancerAbstractReference
Breast cancer
This paper also presents in vivo data of primary breast cancer prevention by individual compounds and whole berries. Finally, a possible role for berries and berry compounds in the prevention of breast cancer and a perspective on the areas that require further research are presented. 1
Glioblastoma Multiforme
Importantly, kaempferol potentiated the toxic effect of chemotherapeutic agent doxorubicin by amplifying ROS toxicity and decreasing the efflux of doxorubicin. Because the toxic effect of both kaempferol and doxorubicin was amplified when used in combination, this study raises the possibility of combinatorial therapy whose basis constitutes enhancing redox perturbation as a strategy to kill glioma cells.2
Leukemia
Some simple and polyphenols found in honey, namely, caffeic acid (CA), caffeic acid phenyl esters (CAPE), Chrysin (CR), Galangin (GA), Quercetin (QU), Kaempferol (KP), Acacetin (AC), Pinocembrin (PC), Pinobanksin (PB), and Apigenin (AP), have evolved as promising pharmacological agents in treatment of cancer. In this review, we reviewed the antiproliferative and molecular mechanisms of honey and above-mentioned polyphenols in various cancer cell lines.3
Lung cancer
Certain flavonoid compounds, including epicatechin, catechin, quercetin, and kaempferol, were associated inversely with lung cancer among tobacco smokers, but not among nonsmokers. Further studies of these associations may be warranted.4
Ovarian cancer
Recent studies further indicate that apigenin, genistein, kaempferol, luteolin, and quercetin potently inhibit VEGF production and suppress ovarian cancer cell metastasis in vitro. Lastly, oridonin and wogonin were suggested to suppress ovarian CSCs as is reflected by down-regulation of the surface marker EpCAM. Unlike NSAIDS (non-steroid anti-inflammatory drugs), well documented clinical data for phyto-active compounds are lacking. In order to evaluate objectively the potential benefit of these compounds in the treatment of ovarian cancer, strategically designed, large scale studies are warranted.5
Pancreatic cancer
Total flavonols, quercetin, kaempferol, and myricetin were all associated with a significant inverse trend among current smokers (relative risks for the highest vs. lowest quartile = 0.41, 0.55, 0.27, 0.55, respectively) but not never or former smokers. This study provides evidence for a preventive effect of flavonols on pancreatic cancer, particularly for current smokers.6
Stomach cancer
A case controlled study found that “consumption of kaempferol-containing foods was associated with a reduced gastric cancer risk”7

The Tabs below lists the published Abstracts and links to various studies within the 6 polyphenols of citrus peels.  (Part 2 of 2)

Anticancer Properties of Citrus Peel Polyphenols (Part 2 of 2)

Naringenin

CancerAbstractReference
Breast cancer
Collectively, our findings suggest that naringenin inhibits the proliferation of MCF-7 cells via impaired glucose uptake. Because a physiologically attainable dose of 10 µM naringenin reduced insulin-stimulated glucose uptake by nearly 25% and also reduced cell proliferation, naringenin may possess therapeutic potential as an anti-proliferative agent.1
Colon cancer
The ability of dietary apigenin and naringenin to reduce HMACF, lower proliferation (naringenin only) and increase apoptosis may contribute toward colon cancer prevention. However, these effects were not due to mitigation of iNOS and COX-2 protein levels at the ACF stage of colon cancer.2
Melanoma
everal polyphenolic compounds were tested for the inhibition of lung metastasis induced by B16F10 melanoma cells in mice. Oral administration of polyphenols such as curcumin and catechin at concentrations of 200 nmol/kg body weight were found to inhibit the lung metastasis maximally as seen by the reduction in the number of lung tumor nodules (80%). Other polyphenols which inhibited the lung tumor nodule formation were rutin (71.2%), epicatechin (61%), naringin (27.2%) and naringenin (26.1%). 3
Prostate cancer
As part of a systematic study of the effects of phytochemicals beyond antioxidation on cancer prevention, we investigated whether naringenin (NR), a citrus flavonoid, stimulates DNA repair following oxidative damage in LNCaP human prostate cancer cells. In conclusion, the cancer-preventive effects of citrus fruits demonstrated in epidemiological studies may be due in part to stimulation of DNA repair by NR, which by stimulating BER processes may prevent mutagenic changes in prostate cancer cells.4

Naringin

CancerAbstractReference
Breast cancer
Two citrus flavonoids, hesperetin and naringenin, found in oranges and grapefruit, respectively, and four noncitrus flavonoids, baicalein, galangin, genistein, and quercetin, were tested singly and in one-to-one combinations for their effects on proliferation and growth of a human breast carcinoma cell line, MDA-MB-435 These experiments provide evidence of anticancer properties of orange juice and indicate that citrus flavonoids are effective inhibitors of human breast cancer cell proliferation in vitro, especially when paired with quercetin, which is widely distributed in other foods.  1
Lung cancer
To investigate the possible relationship between intake of flavonoids-powerful dietary antioxidants that may also inhibit P450 enzymes-and lung cancer risk, we conducted a population-based, case-control study in Hawaii. If replicated, particularly in prospective studies, these findings would suggest that foods rich in certain flavonoids may protect against certain forms of lung cancer and that decreased bioactivation of carcinogens by inhibition of CYP1A1 should be explored as underlying mechanisms.2
Melanoma
Oral administration of polyphenols such as curcumin and catechin at concentrations of 200 nmol/kg body weight were found to inhibit the lung metastasis maximally as seen by the reduction in the number of lung tumor nodules (80%). Other polyphenols which inhibited the lung tumor nodule formation were rutin (71.2%), epicatechin (61%), naringin (27.2%) and naringenin (26.1%). 3
Mouth cancer
The results with naringin and naringenin show that both of these flavonoids significantly lowered tumor number [5.00 (control group), 2.53 (naringin group), and 3.25 (naringenin group)]. Naringin also significantly reduced tumor burden [269 mm(3)(control group) and 77.1 mm(3)(naringin group)]. The data suggest that naringin and naringenin, 2 flavonoids found in high concentrations in grapefruit, may be able to inhibit the development of cancer.4

Nobiletin

CancerAbstractReference
Colon cancer
Nobiletin (NOB), a citrus flavonoid, was given in the diet (100 p.p.m) for 17 weeks. Thereafter, the incidence and number of colon tumors and serum concentration of adipocytokines were determined at the end of week 20. The serum leptin level in AOM/DSS-treated mice was six times higher than that in untreated mice, whereas there were no significant differences in the levels of triglycerides, adiponectin and interleukin-6. 1
Leukemia
In vitro effects of medicinal plant extracts from the pericarpium of Citrus reticulata (cv Jiao Gan) (PCRJ) on the growth and differentiation of a recently characterized murine myeloid leukemic cell clone WEHI 3B (JCS) were investigated. The survival rate of mice receiving PCRJ treated JCS tumour cells was also increased. Using 1H-NMR, 13C-NMR, and GC/MS, two active components isolated from PCRJ were identified as nobiletin and tangeretin.2
Liver cancer
Dietary phytochemicals can inhibit the development of certain types of tumors. We here investigated the effects of nobiletin (Nob), garcinol (Gar), auraptene (Aur), beta-cryptoxanthin- and hesperidine-rich pulp (CHRP) and 1,1'-acetoxychavicol acetate (ACA) on hepatocarcinogenesis in a rat medium-term liver bioassay, and also examined their influence on cell proliferation, cell cycle kinetics, apoptosis and cell invasion of rat and human hepatocellular carcinoma (HCC) cells, MH1C1 and HepG2, respectively.3
Lung cancer
Furthermore, Nobiletin had overt inhibitory effect on the tumor growth in nude mice model was observed in vivo. Taken together, these results suggest that Nobiletin could induce p53-mediated cell cycle arrest and apoptosis via modulated the Bax:Bcl-2 protein ratio, is effective as a potent antitumor agent on lung tumors.4
Prostate cancer
A further experiment demonstrated that growth of androgen sensitive LNCaP and androgen insensitive DU145 and PC3 human prostate cancer cells, was suppressed by both nobiletin and to a lesser extent auraptene in a dose-dependent manner, with significant increase in apoptosis. In conclusion, these compounds, particularly nobiletin, may be valuable for prostate cancer prevention.5
Squamous Cell Carcinoma
Tangeretin and nobiletin markedly inhibited the proliferation of a squamous cell carcinoma (HTB 43) and a gliosarcoma (9L) cell line at 2-8 micrograms/ml concentrations. 6
Stomach cancer
Although the effective dose and administration route of nobiletin require further investigation, our study represents a potential successful linking of this compound with the treatment of gastric cancer.7

Quercetin

CancerAbstractReference
Breast cancer
There has been considerable evidence recently demonstrating the anti-tumour effects of flavonols. Quercetin, an ubiquitous bioactive flavonol, inhibits cells proliferation, induces cell cycle arrest and apoptosis in different cancer cell types. Taken together, these findings suggest that quercetin results in human breast cancer MDA-MB-231 cell death through mitochondrial- and caspase-3-dependent pathways.1
Cervical cancer
Quercetin showed a marked inhibitive effect on U14 growth, and its antitumor mechanism may be associated with inhibiting the angiogenesis and inducing apoptosis.2
Colon cancer
In conclusion, quercetin, but not rutin, at a high dose reduced colorectal carcinogenesis in AOM-treated rats, which was not reflected by changes in ACF-parameters. The lack of protection by rutin is probably due to its low bioavailability.3
Endometrial cancer
This study suggests a reduction in endometrial cancer risk with quercetin intake and with isoflavone intake in lean women.4
Esophageal cancer
The results of MTT assay showed that flavones (luteolin, apigenin, chrysin) and flavonols (quercetin, kaempferol, myricetin) were all able to induce cytotoxicity in OE33 cells in a dose- and time-dependent manner, and the cytotoxic potency of these compounds was in the order of quercetin > luteolin > chrysin > kaempferol > apigenin > myricetin. 5
Gliomas
Quercetin exposure resulted in proteasomal degradation of survivin. TRAIL-quercetin–induced apoptosis was markedly reduced by overexpression of survivin. In addition, upon treatment with quercetin, downregulation of survivin was also regulated by the Akt pathway. Taken together, the results of the present study suggest that quercetin sensitizes glioma cells to death-receptor–mediated apoptosis by suppression of inhibitor of the apoptosis protein survivin.6
Kidney cancer
These results suggest that the flavonoid quercetin may prevent renal cell cancer among male smokers. The possible risk associated with fish intake warrants further investigation before conclusions may be drawn.7
Laryngeal cancer
Quercetin could effectively inhibit the proliferation of Hep-2 cells and its mechanism is probably related to the apoptosis.8
Leukemia
It is concluded that the quercetin and kaempferol have significant anti-leukemia effect in vitro. Furthermore the apoptosis-inducing effect of quercetin is stronger than that of kaempferol, both of which induce apoptosis of HL-60 cells through depressing cell growth, arresting cell cycle and inhibiting expression of survivin.9
Liver cancer
Quercetin, a dietary flavonoid, has been shown to possess anticarcinogenic properties, but the precise molecular mechanisms of action are not thoroughly elucidated. The aim of this study was to investigate the regulatory effect of quercetin (50 microM) on two main transcription factors (NF-kappa B and AP-1) related to survival/proliferation pathways in a human hepatoma cell line (HepG2) over time. Quercetin induced a significant time-dependent inactivation of the NF-kappa B pathway consistent with a downregulation of the NF-kappa B binding activity (from 15 min onward).10
Lung cancer
Lung cancer was associated inversely with the consumption of epicatechin (in 10 mg per day increment: OR, 0.64; 95% CL, 0.46-0.88), catechin (4 mg per day increment: OR, 0.49; 95% CL, 0.35-0.70), quercetin (9 mg per day increment: OR, 0.65; 95% CL, 0.44-0.95), and kaempferol (2 mg per day increment: OR, 0.68; 95% CL, 0.51-0.90) among tobacco smokers.11
Melanoma
In this paper, the DNA protective free radical scavenging potential of quercetin (QU) and luteolin (LU) against H2O2 and their clastogenic effect alone and in combination with melphalan (MH) were investigated in human melanoma HMB-2 cells. Results are correlated to their structural arrangement and organization of the hydroxyl groups.12
Mouth cancer
In conclusion, our data support a view that quercetin initially induces a stress response, resulting in necrosis of these oral epithelial cells. Prolonged exposure of the surviving cells to quercetin causes apoptosis, presumably mediated by inhibition of TS protein.13
Ovarian cancer
It has been demonstrated that the flavonoid quercetin (3,3',4',5-7-pentahydroxyflavone) (Q) inhibits the growth of several cancer cell lines and that the antiproliferative activity of this substance is mediated by a so-called type II estrogen binding site (type II EBS). Since both rutin and hesperidin do not bind to type II EBS it can be hypothesized that Q synergizes with CDDP by acting through an interaction with these binding sites.14
Pancreatic cancer
Our studies aimed at evaluation of antiproliferative and pro-apoptotic effects of quercetin alone and in combinations with daunorubicin on cells of human pancreatic carcinoma lines. Our data demonstrated that quercetin exerted cytotoxic action on cells of the both neoplastic cell lines in concentration-dependent manner. In the case of EPP85-181RDB cell line, quercetin seemed to sensitize resistant cells to daunorubicin.15
Prostate cancer
Taken together, as shown by the issues of the current study, the manifold inhibitory effects of quercetin on PC-3 cells may introduce quercetin as an efficacious anticancer agent in order to be used in the future nutritional transcriptomic investigations and multi-target therapy to overcome the therapeutic impediments against prostate cancer.16
Squamous Cell Carcinoma
We examined the effects of flavone and two polyhydroxylated plant flavonoids (quercetin and fisetin), either singly or in combination with ascorbic acid, on the growth of a human squamous cell carcinoma cell line (HTB 43) in vitro. Fisetin and quercetin significantly impaired cell growth in the presence of ascorbic acid. 17
Stomach cancer
Cells were divided into the control group and the quercetin (Que)-treated group. Que significantly decreased the expression of VEGF-C and VEGFR-3 at 40 mumol/L compared with the control group after 48 h (P18

Rutin

CancerAbstractReference
Colon cancer
The dietary effect of monoglucosyl-rutin (M-R), a flavonoid, on azoxymethane (AOM)-induced colon carcinogenesis was investigated in two experiments with 5 week old, F344 male rats. At the termination of the experiment (40 weeks after the start), groups 2-5 had significantly smaller numbers of positive cells with anti-proliferating cell nuclea antigen (PCNA) antibody than group 1. Furthermore, group 5 treated with 500ppm M-R for 36 weeks demonstrated tendencies for decrease in the incidence and multiplicity of colon tumors. These data suggest that M-R has the potential to inhibit AOM-induced colon carcinogenesis.1
During the post-initiation phase aspirin, calcium glucarate, ketoprofen, piroxicam, 9-cis-retinoic acid, retinol and rutin inhibited the outgrowth of ACF into multiple crypt clusters. Based on these data, certain phytochemicals, antihistamines, non-steroidal anti-inflammatory drugs and retinoids show unique preclinical promise for chemoprevention of colon cancer, with the latter two drug classes particularly effective in the post-initiation phase of carcinogenesis.2
Melanoma
Consequent to the inhibition of the lung tumor nodules, the life span of animals treated with polyphenols was also found to be increased. Curcumin (143.85%), catechin (80.81%) and rutin (63.59%) had maximal increase in life span. The results indicate a possible use of these compounds in arresting the metastatic growth of tumor cells.3

Tangeritin

CancerAbstractReference
Breast cancer
Tangeretin is a methoxyflavone from citrus fruits, which inhibits growth of human mammary cancer cells and cytolysis by natural killer cells. Attempting to unravel the flavonoid's action mechanism, the authors found that it inhibited extracellular-signal-regulated kinases 1/2 (ERK1/2) phosphorylation in a dose- and time-dependent way. In human T47D mammary cancer cells this inhibition was optimally observed after priming with estradiol. 1
Colon cancer
Tangeretin and nobiletin are citrus flavonoids that are among the most effective at inhibiting cancer cell growth in vitro and in vivo. The antiproliferative activity of tangeretin and nobiletin was investigated in human breast cancer cell lines MDA-MB-435 and MCF-7 and human colon cancer line HT-29. Thus, tangeretin and nobiletin could be effective cytostatic anticancer agents. Inhibition of proliferation of human cancers without inducing cell death may be advantageous in treating tumors as it would restrict proliferation in a manner less likely to induce cytotoxicity and death in normal, non-tumor tissues.2
Leukemia
Tangeretin showed no cytotoxicity against either HL-60 cells or mitogen-activated PBMCs even at high concentration (27 microM) as determined by a dye exclusion test. Moreover, the flavonoid was less effective on growth of human T-lymphocytic leukaemia MOLT-4 cells or on blastogenesis of PBMCs. These results suggest that tangeretin inhibits growth of HL-60 cells in vitro, partially through induction of apoptosis, without causing serious side-effects on immune cells.3
Melanoma
Tangeretin was the most effective of the flavonoids in inhibiting B16F10 and SK-MEL-1 cell growth, showing a clear dose-response curve after 72 h. These results suggest that the absence of the C2-C3 double bond on hydroxylated flavonoids results in a loss of effect on both the cell lines, while the higher activity of tangeretin compared with 7,3'-dimethylhesperetin suggests that the presence of at least three adjacent methoxyl groups confers a more potent antiproliferative effect.4
Squamous Cell Carcinoma
 We investigated the antiproliferative effect of two polyhydroxylated (quercetin and taxifolin) and two polymethoxylated (nobiletin and tangeretin) flavonoids against three cell lines in tissue culture. Tangeretin and nobiletin markedly inhibited the proliferation of a squamous cell carcinoma (HTB 43) and a gliosarcoma (9L) cell line at 2-8 micrograms/ml concentrations. 2

A number of different varieties of citrus has been used in the numerous studies of citrus peel extracts.  A list of the most commonly used varieties are as follows:

  • Mandarin orange (Citrus reticulata)
  • Satsuma Mandarin (Citrus unshiu)

The Chinese have been using Chenpi or chen pi (Chinese: 陈皮, pinyin: chénpí) as a traditional seasoning in Chinese cooking and traditional medicine.  Chen pi is a sun dried tangerine (mandarin).  Some Chen pi is made from the mandarin orange (Citrus reticulata ‘Blanco’) and bitter orange (C. aurantium).  11

Chen pi contains a high content of 5-demethylated polymethoxyflavones (5-OH PMFs).  12  Oral administration of 0.25 and 0.5% chenpi extract in food over 15 weeks markedly prevented HFD-induced obesity, hepatic steatosis, and diabetic symptoms.  13

The varieties of citrus that are good candidates for citrus peel powder are the following:

  • Bitter Orange  (Citrus aurantium)
  • Sweet Orange (Citrus sinensis L. Osbeck)
  • Mandarin (Chinese) Tangerine  (Citrus reticulata)
  • Satsuma Mandarin  (Citru unshiu)
  • Chinese Honey Orange (Ponkan)  (Citrus poonensis)
  • Yuzu (Citrus ichangensis × C. reticulata)
  • Grapefruit  (Citrus paradisi)
  • Meyer Lemon (Citrus × meyeri)

When consuming citrus peel from any of the above varieties, it is important to choose the organic variety only.  Citrus fruits can be heavily sprayed with pesticides which tend to concentrate on the outer peel.  The fruit should be washed prior to using the peel, whether raw (zest) or dried and ground into citrus peel powder. 

Raw citrus peel (zest) can be used in salads, yogurt, tea, added to smoothies, stews, vegetable dishes as well as added to fish as a garnish.  The dried and grounded citrus peel powder can be added to smoothies and soups.

Images of various citrus fruits used for citrus peel and citrus peel powder:

  • Bitter Orange (Citrus aurantium)

How to Make Pure Orange Peel Powder at Home

Cover Photo from Nan Products

Piperine Enhances the Serum Concentration, Extent of Absorption and Bioavailability of Curcumin

The consumption of curcumin powder, a very lipophilic (fat soluble) substance, which has been obtained from the tumeric root (Curcuma longa L.), has poor bioavailability due to the following factors:

  • low intestinal absorption rate
  • rapid metabolism in the liver and intestinal wall due to glucuronidation
  • rapid systemic elimination

Because of this poor bioavailability, even with large amounts of consumed curcumin, there is low levels in the blood plasma and tissues.  The majority of consumed curcumin is excreted via the feces. This is why consuming large amounts of the curcumin powder may lead to diarrhea.

Glucuronidation

Glucuronidation is a Phase II process in metabolic detoxification which consists of the transfer of the glucuronic acid component of uridine diphosphate glucuronic acid to a toxic substrate resulting in substances known as glucuronides which are water-soluble.  These water-soluble glucuronides are subsequent eliminated from the body through urine or feces (via bile from the liver).

In the case of curcumin (without augmenting absorption), it is rapidly metabolised by glucuronic acid in the liver and intestinal wall and made water-soluble and mostly excreted via the feces. 

There are a number of ways in which to improve the bioavailability of curcumin by augmenting its absorption.  Some of the approaches that have been taken are:  1

  • adjuvant like piperine that interferes with glucuronidation
  • curcumin nanoparticles
  • curcumin phospholipid complex
  • liposomal curcumin
  • structural analogues of curcumin

Piperine

Piperine, which is derived from Black pepper (Piper nigrum) and a number of different varieties of pepper species, has many physiological effects.   Piperine, by favorably stimulating the digestive enzymes of the pancreas, enhances the digestive capacity and significantly reduces the gastrointestinal food transit time. Piperine has been demonstrated in in vitro studies to protect against oxidative damage by inhibiting or quenching free radicals and reactive oxygen species.  2

For more in-depth information on the current research into Piperine, read this article from Healthy But Smart entitled:  Does Piperine Have Health Benefits? The Current Research Examined

Piperine has been documented to enhance the bioavailability of curcumin by modifying the rate of glucuronidation by lowering the endogenous UDP-glucuronic acid content and strongly inhibiting hepatic and intestinal aryl hydrocarbon hydroxylase and UDP-glucuronyl transferase.  Piperine’s bioavailability enhancing property is also partly attributed to increased absorption as a result of its effect on the ultrastructure of intestinal brush border.  3

A study published in 1998, researchers examined the effect of combining piperine, a known inhibitor of hepatic and intestinal glucuronidation, on the bioavailability of curcumin in rats and healthy human volunteers. 

Humans were administered a dose of 2 grams of curcumin by itself and serum levels were either undetectable or very low. They then administered the same dosage of curcumin (2 grams) with a concomitant administration of piperine at 20 mg.  The result was a much higher concentrations from 0.25 to 1 h post drug (P < 0.01 at 0.25 and 0.5 h; P < 0.001 at 1 h), and an increase in bioavailability of 2000% or a 20-fold increase in bioavailability.

The study shows that in the dosages used, piperine enhances the serum concentration, extent of absorption and bioavailability of curcumin in humans with no adverse effects.  4

This study may lead to the conclusion to add some ground-up black pepper kernals with your curcumin powder.  Unfortunately, the consumption of black pepper directly with curcumin will not help achieve enhanced nutrient absorption, as was found in the above referenced study. 

In fact, one would have to consume large quantities of black pepper to achieve even a modest amount of piperine bioavailability, which is impractical.  The reason for this is that piperine remains captive in the form of raw black pepper and it takes time for its bioavailability enhancing property to be released.

Therefore, a purified extract of piperine is necessary to get the increased absorption.  This is where BioPerine® is useful. 

BioPerine®, a natural bioavailability enhancer from Sabinsa Corporation, received Generally Recognized As Safe (GRAS) status after a comprehensive review of safety and toxicology data by an independent panel of scientists with international repute.  Based on scientific procedures and available comprehensive scientific literature, including human and animal data determined the safety-in-use for black pepper extract (BioPerine®).

BioPerine® significantly improved the uptake of Curcumin—the healthful extract from turmeric roots with clinically validated efficacy in a wide range of health conditions ranging from inflammation to cancer.

Bioavailability of Curcumin (2000 mg) when co-administered with BioPerine® (20 mg) was enhanced by 20-fold or 2000% compared to bioavailability of Curcumin alone at doses that were devoid of adverse side effects.

piperinegraph

BioPerine® also increases the bioavailability of other natural substances:

Applications of BioPerine®

The nutritional materials which may be co-administered with BioPerine® are as follows:

Herbal Extracts   Curcuma longa, Boswellia serrata, Withania somnifera, Ginkgo biloba and Capsicum annuum
Water-soluble Vitamins    Vitamin B1, Vitamin B2, Niacinamide, Vitamin B6, Vitamin B12, Folic acid and Vitamin C
Fat-­soluble Vitamins   Vitamin A, Vitamin D, Vitamin E and Vitamin K
Antioxidants   Vitamin A, Vitamin C, Vitamin E, alpha-carotene, beta-carotene, beta-cryptoxanthin, lycopene, lutein/zeaxanthin, pine bark bioflavonoids complex, germanium, selenium and zinc
Amino Acids   Lysine, isoleucine, leucine, threonine, valine, tryptophan, phenylalanine, and methionine
Minerals   Calcium, iron, zinc, vanadium, selenium, chromium, iodine, potassium, manganese, copper and magnesium

Source:  BioPerine®

Informational References:

Health But Smart:  Does Piperine Have Health Benefits? The Current Research Examined

Cover Photo:  Black Pepper tree (piper nigrum)

Natural Compounds That Promote Anti-Aggregation And Clearance of Amyloid Beta

Alzheimer’s disease is the most prevalent neurodegenerative disease in the growing population of elderly people. A hallmark of Alzheimer’s disease is the accumulation of plaques in the brain of Alzheimer’s disease patients. The plaques predominantly consist of aggregates of amyloid-beta generated in vivo by specific, proteolytic cleavage of the amyloid precursor protein. There is a growing body of evidence that amyloid-beta aggregates are ordered oligomers and the cause rather than a product of Alzheimer’s disease.

There are a number of studies that state that the accumulation of amyloid beta within the brain arises from an imbalance of the production and clearance of amyloid beta.  Most of the time in the case of Alzheimer’s disease, amyloid beta clearance is impaired.  1

The process of creating amyloid beta in the brain has multiple roles in the brain, including:  2

  • antioxidant activity
  • calcium homeostasis
  • metal ion sequestration
  • modulation of synaptic plasticity
  • neurogenesis
  • neurotrophic activity

This controlled homeostatic regulation allows for the normal functions of amyloid beta but also prevents accumulation of excess amyloid beta as a metabolic waste product. 

An imbalance in this homeostasis results in pathological and neurotoxic accumulations of cerebral amyloid beta.  3

Scientists have developed a number of therapeutic strategies as possible interventions against amyloid beta, two of which include:

  • Anti-aggregations agents
  • Clearance of amyloid beta

Anti-aggregations agents

Anti-aggregation prevent amyloid beta fragments from aggregating or clear aggregates once they are formed.  4

Clearance of amyloid beta

Impaired clearance of amyloid beta is now widely identified as a contributing factor towards Alzheimer’s disease progression.  5   In order to prevent pathological accumulations of amyloid beta in the brain, amyloid beta clearance from the cerebral milieu into periphery and out of the system is of prime importance. Improving amyloid beta clearance from the brain across the blood–brain barrier (BBB) and into blood plasma.

Clearance of amyloid beta is so important that recent evidence in humans suggests that impaired amyloid beta clearance is the main cause of pathological accumulations of cerebral amyloid beta in late onset Alzheimer’s disease and not the overproduction of amyloid beta.  6 

The purpose of this article is to examine and identify the natural compounds that act as either anti-aggregation agents or an agents for the clearance of amyloid beta, or both.  

Researchers have identified a number of natural compounds that have been effective as therapeutics for Alzheimer’s disease whether as an anti-aggregation agent and/or an agent for clearance of amyloid beta.  7 

These natural compounds include:

  • Baicalein
  • Curcumin
  • Ellagic acid
  • (−)-Epigallocatechin-3-gallate (EGCG)
  • Ferulic acid
  • Fisetin
  • Kaempferol
  • Luteolin
  • Malvidin
  • Melatonin
  • Myricetin
  • Nordihydroguaiaretic acid (NDGA)
  • Oleuropein Aglycone (OLE)
  • Proline Rich Polypeptide (Colostrinin™)
  • Quercetin
  • Resveratrol
  • Rosmarinic acid
  • Rutin
  • Vitamin A

Natural Compounds That Promote Anti-Aggregation And Clearance of Amyloid Beta

Natural CompoundAbstractReferences
BaicaleinOur data showed that baicalein inhibited the formation of α-syn oligomers in SH-SY5Y and Hela cells, and protected SH-SY5Y cells from α-syn-oligomer-induced toxicity. We also explored the effect of baicalein on amyloid-β peptide (Aβ) aggregation and toxicity. We found that baicalein can also inhibit Aβ fibrillation and oligomerisation, disaggregate pre-formed Aβ amyloid fibrils and prevent Aβ fibril-induced toxicity in PC12 cells. Our study indicates that baicalein is a good inhibitor of amyloid protein aggregation and toxicity. 1
CurcuminWhen fed to aged Tg2576 mice with advanced amyloid accumulation, curcumin labeled plaques and reduced amyloid levels and plaque burden. Hence, curcumin directly binds small beta-amyloid species to block aggregation and fibril formation in vitro and in vivo. These data suggest that low dose curcumin effectively disaggregates Abeta as well as prevents fibril and oligomer formation, supporting the rationale for curcumin use in clinical trials preventing or treating AD.2 2a
Ellagic acidHere, we tested the effects of ellagic acid (EA), a polyphenolic compound, on Abeta42 aggregation and neurotoxicity in vitro. EA promoted Abeta fibril formation and significant oligomer loss, contrary to previous results that polyphenols inhibited Abeta aggregation. 3
(−)-Epigallocatechin-3-gallate (EGCG)Here, we show that EGCG has the ability to convert large, mature α-synuclein and amyloid-β fibrils into smaller, amorphous protein aggregates that are nontoxic to mammalian cells. Mechanistic studies revealed that the compound directly binds to β-sheet-rich aggregates and mediates the conformational change without their disassembly into monomers or small diffusible oligomers. These findings suggest that EGCG is a potent remodeling agent of mature amyloid fibrils.4
The polyphenol (-)-epigallocatechin gallate efficiently inhibits the fibrillogenesis of both alpha-synuclein and amyloid-beta by directly binding to the natively unfolded polypeptides and preventing their conversion into toxic, on-pathway aggregation intermediates. Instead of beta-sheet-rich amyloid, the formation of unstructured, nontoxic alpha-synuclein and amyloid-beta oligomers of a new type is promoted, suggesting a generic effect on aggregation pathways in neurodegenerative diseases.5
Ferulic acidFerulic acid dose-dependently inhibited fAbeta formation from amyloid beta-peptide, as well as their extension. Moreover, it destabilized preformed fAbetas. The overall activity of the molecules examined was in the order of: Cur > FA > rifampicin = tetracycline. FA could be a key molecule for the development of therapeutics for AD.6
Chronic (for 6 months from the age of 6 to 12 months) oral administration of ferulic acid at a dose of 5.3 mg/kg/day significantly enhanced the performance in novel-object recognition task, and reduced amyloid deposition and interleukin-1 beta (IL-1β) levels in the frontal cortex. These results suggest that ferulic acid at a certain dosage could be useful for prevention and treatment of AD.7
FisetinFisetin (3,3',4',7-tetrahydroxyflavone) has been found to be neuroprotective, induce neuronal differentiation, enhance memory, and inhibit the aggregation of the amyloid beta protein (Abeta) that may cause the progressive neuronal loss in Alzheimer's disease. 8
The natural flavonoid fisetin (3,3',4',7-tetrahydroxyflavone) is neurotrophic and prevents fibril formation of amyloid β protein (Aβ). It is a promising lead compound for the development of therapeutic drugs for Alzheimer's disease.  9
KaempferolKaempferol was shown to have protective effects against oxidative stress-induced cytotoxicity in PC12 cells. Administration of kaempferol also significantly reversed amyloid beta peptide (Abeta)-induced impaired performance in a Y-maze test.10
Luteolin These results indicated that luteolin from the Elsholtzia rugulosa exerted neroprotective effects through mechanisms that decrease AβPP expression, lower Aβ secretion, regulate the redox imbalance, preserve mitochondrial function, and depress the caspase family-related apoptosis.11
MalvidinWe have identified four novel polyphenols which could be efficient fibril inhibitors in Alzheimer's disease: malvidin and its glucoside and curculigosides B and D. We suggest that molecules with the particular C(6)-linkers-C(6) structure could be potent inhibitors. From the results reported for the flavan-3-ol family, their anti-amyloidogenic effects against whole peptides (1-40 and 1-42) could involve several binding sites.12
MelatoninWe report that melatonin, a hormone recently found to protect neurons against Abeta toxicity, interacts with Abeta1-40 and Abeta1-42 and inhibits the progressive formation of beta-sheets and amyloid fibrils. In sharp contrast with conventional anti-oxidants and available anti-amyloidogenic compounds, melatonin crosses the blood-brain barrier, is relatively devoid of toxicity, and constitutes a potential new therapeutic agent in Alzheimer's disease.13
Inhibition of beta-sheets and fibrils could not be accomplished in control experiments when a free radical scavenger or a melatonin analog were substituted for melatonin under otherwise identical conditions. In sharp contrast with conventional anti-oxidants and available anti-amyloidogenic compounds, melatonin crosses the blood-brain barrier, is relatively devoid of toxicity, and constitutes a potential new therapeutic agent in Alzheimer's disease.14
MyricetinMyricetin was the most potent compound myricetin to the neurotoxic oligomers rather than monomers. These findings suggest that flavonoids, especially Myricetin, exert an anti-amyloidogenic effect in vitro by preferentially and reversibly binding to the amyloid fibril structure of fAbeta, rather than to Abeta monomers.15
Nordihydroguaiaretic acid (NDGA)In cell culture experiments, fAbeta disrupted by NDGA were less toxic than intact fAbeta, as demonstrated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Although the mechanisms by which NDGA inhibits fAbeta formation from Abeta, as well as breaking down pre-formed fAbetain vitro, are still unclear, NDGA could be a key molecule for the development of therapeutics for AD.16
Oleuropein Aglycone (OLE)Here we report that oleuropein aglycon also hinders amyloid aggregation of Aβ(1-42) and its cytotoxicity, suggesting a general effect of such polyphenol. We also show that oleuropein aglycon is maximally effective when is present at the beginning of the aggregation process; furthermore, when added to preformed fibrils, it does not induce the release of toxic oligomers but, rather, neutralizes any residual toxicity possibly arising from the residual presence of traces of soluble oligomers and other toxic aggregates. The possible use of this polyphenol as anti-aggregation molecule is discussed in the light of these data.17
Proline Rich Polypeptide (Colostrinin™)Colostrinin™ is a mixture of proline-rich polypeptides (PRP) from ovine (sheep) colostrums. Colostrinin inhibits amyloid beta aggregation and facilitates disassembly of existing aggregates by disrupting beta-sheets bonding.18
QuercetinQuercetin is an effective amyloid aggregation inhibitor and inhibits amyloid beta fibrillization, but not its toxic oligomerization19
ResveratrolHere we show that resveratrol (trans-3,4',5-trihydroxystilbene), a naturally occurring polyphenol mainly found in grapes and red wine, markedly lowers the levels of secreted and intracellular amyloid-beta (Abeta) peptides produced from different cell lines. Resveratrol does not inhibit Abeta production, because it has no effect on the Abeta-producing enzymes beta- and gamma-secretases, but promotes instead intracellular degradation of Abeta via a mechanism that involves the proteasome. 20
In conjunction with the concept that Abeta oligomers are linked to Abeta toxicity, we speculate that aside from potential antioxidant activities, resveratrol may directly bind to Abeta42, interfere in Abeta42 aggregation, change the Abeta42 oligomer conformation and attenuate Abeta42 oligomeric cytotoxicity. 21
Rosmarinic acidRosmarinic acid had especially strong anti-amylid beta aggregation effects in vitro22
Rosmarinic acid reduced a number of events induced by Abeta. These include reactive oxygen species formation, lipid peroxidation, DNA fragmentation, caspase-3 activation, and tau protein hyperphosphorylation. Moreover, rosmarinic acid inhibited phosphorylated p38 mitogen-activated protein kinase but not glycogen synthase kinase 3beta activation. These data show the neuroprotective effect of sage against Abeta-induced toxicity, which could validate the traditional use of this spice in the treatment of AD. Rosmarinic acid could contribute, at least in part, for sage-induced neuroprotective effect.23
RutinHere, we show that the common dietary flavonoid, rutin, can dose-dependently inhibit Aβ42 fibrillization and attenuate Aβ42-induced cytotoxicity in SH-SY5Y neuroblastoma cells. 24
Vitamin A (beta-carotene)In this study, we used fluorescence spectroscopy with thioflavin T (ThT) and electron microscopy to examine the effects of vitamin A (retinol, retinal, and retinoic acid), beta-carotene, and vitamins B2, B6, C, and E on the formation, extension, and destabilization of beta-amyloid fibrils (fAbeta) in vitro. Among them, vitamin A and beta-carotene dose-dependently inhibited formation of fAbeta from fresh Abeta, as well as their extension. Moreover, they dose-dependently destabilized preformed fAbetas.25
Withanolides (Withania somnifera)The researchers found that using Withania somnifera extracts, comprising 75% withanolides and 20% withanosides, reversed plaque pathology and reduced the amyloid beta burden in middle-aged and old APP/PS1 mice through up-regulation of liver LRPI, leading to increased clearance of amyloid beta.26

Cover Photo:  Rosemary plant and flower

Flip Your AMPK switch to the “ON” position

Introduction to AMPK

AMPK (adenosine monophosphate-activated protein kinase) is an enzyme contained in every cell of the human body that serves as the body’s master regulating switch.

When the AMPK master switch is turned “ON” (by activating AMPK), it inhibits multiple damaging factors of aging and enables cells to become revitalized.  Scientists have found that activated AMPK promotes longevity factors that have been shown to extend life span in numerous organisms.  1  2 

There are various studies that show an increase in AMPK supports:

  • Reduced fat storage 3 
  • New mitochondria production  4 
  • Promotion of healthy blood glucose and lipids already within normal range  5 

dmso-7-241Fig1

Roles of AMPK in the control of whole-body energy metabolism. Notes: Activation of AMPK (green lines) stimulates the energy-generating pathways in several tissues while inhibiting the energy-consuming pathways (red lines). In skeletal muscle and heart, activation of AMPK increases glucose uptake and fatty acid oxidation. In the liver, AMPK activity inhibits fatty acid and cholesterol synthesis. Lipolysis and lipogenesis in adipose tissue are also reduced by AMPK activation. Activation of AMPK in pancreatic β-cells is associated with decreased insulin secretion. In the hypothalamus, activation of AMPK increases food intake.  Source: AMPK activation: a therapeutic target for type 2 diabetes? Kimberly A Coughlan, Rudy J Valentine, Neil B Ruderman, and Asish K Saha, Diabetes Metab Syndr Obes. 2014; 7: 241–253. Published online 2014 Jun 24. doi: 10.2147/DMSO.S43731

Activating AMPK:  Turning the Switch “ON”

The two major methods of activating AMPK is through:

  • exercise and
  • calorie restriction

When you exercise, you use up more ATP which generates higher AMP levels, which then activates AMPK.  6

The other method of activating AMPK is through calorie restriction by at least 30%.  This means cutting daily calorie consumption by 30%.  By reducing calorie consumption, the lower levels of available energy leads to rising AMP levels, which then activates AMPK.  7

In addition to exercise and calorie restriction, there are many other ways to activate AMPK, particularly through certain foods, herbs and nutraceuticals.  The Table below lists the many researched methods of activating AMPK:

AMPK Activators

CategorySubstance/ActivityReferences
Physiological
Exercise1
Fasting and Intermittant Fasting2
Cold water exposure (raise AMPK in the hypothalamus)3
Calorie Restriction4
Foods
Extra Virgin Olive Oil 5
Royal Jelly (10-Hydroxy-2-decenoic acid (10H2DA)6
Dashi kombu (Laminaria japonica Areschon)7
Bitter Orange (Citrus aurantum Linn)8
Garlic and Olives (Oleanolic acid)9
Apple Cider Vinegar10
Rose Hips (Trans-Tiliroside)11
Mulberry leaves extracts12
Fish Oil – EPA , DHA 13 14
Anthocyanins 15
Bitter melon16
Fungi
Reishi17
Herbs and Spices
Cinnamon 18
Astragalus 19 20
Marijuana (Cannabinoids)21
Green Tea/EGCG22
Rooibos23
Danshen (Chinese Red Sage)24
Gynostemma pentaphyllum (Jiagulon)25
Baicalin26 27
Hormones
Adiponectin 28 29
Thyroid hormones, especiallly T3 30
Leptin31
Nitric Oxide32 33
Immune System
Interleukin-6 (IL-6)34
Nutraceuticals
Apigenin35
Berberine36
Butyrate (Calcium/Magnesium ) or Sodium Butyrate (Short Chain Fatty-Acid)37
Carnitine38
Co-enzyme Q1039
Creatine40
Curcumin41
Fucoidan42
Genistein43
Glucosamine44 45
Hydroxytyrosol46
Oxaloacetate47
Quercetin48 49
Red yeast rice50
Resveratrol51
R-Lipoic Acid52 53
Vitamin E - gamma tocotrienol54
Pharmaceuticals
Aspirin55
Metformin56


Informational References:

Life Extension – AMPK and Aging “A Technical Review”  (November 2015)

Enhancing and Protecting the Components of the Neurons with Nutraceuticals, Foods and Herbs

Components of a Neuron

A neuron, also known as a nerve cell, is an electrically excitable cell that processes and transmits information through electrical and chemical signals. These signals between neurons occur via specialized connections called synapses.

Neurons are major components of the :

  • brain and spinal cord of the central nervous system (CNS)
  • autonomic ganglia of the peripheral nervous system

Image result for Neuron

Figure 1.  Diagram of a neuron  (Source)

There are a number of components of a neuron that each provide a unique process in the function of the neuron.  These anatomical and physiological components of the neuron include:

  • Neurons (Whole)
  • Nerve Impulses
  • Axons
  • Myelin Sheaths
  • Presynaptic Terminal
  • Presynaptic Membrane
  • Synaptic Vesicles
  • Dendrite
  • Synaptic Cleft

The purpose of this article is to review each component of the neuron and identify the nutraceuticals, foods and herbs that may enhance and protect the function of each individual component of the neuron.

Neurons (Whole)

Neurons are very small. 

In fact, about 30,000 to 50,000 would fit on the tip of a pin.  A tiny slice of brain tissue the size of a grain of sand contains about 100,000 neurons.  They are packed so tightly that a pebble-sized chunk of tissue from the human brain contains about two miles of neuron material.  The entire brain contains about 100 billion neurons. 

Neurons are the only cells in the body that communicate directly with one another by sending messages back and forth in the form of electrochemical signals or impulses. 

The general method of communication between neurons is the same in all humans.  However, each individual is unique based on how neurons are organized in networks or patterns in the human brain.

Neurons resemble the structure of a tree, with the axon resembling the roots of the tree and the dendrites resembling the branches and twigs of the tree.  However, the neuron is not stiff like a tree.  Instead, a live neuron is very elastic and amorphous.

Image result for neuron

Figure 2.  Structure of a neuron (Source) 

Neurons communicate via their axons and dendrites through an electrochemical messaging system.  The axon sends electrochemical information to other neurons and the dendrites receive the messages from other nerve cells. 

Even though there are over 100 billion neurons in the human brain, the amazing fact is that neurons never touch each other.  The space between neurons is called the synaptic cleft and is approximately one-millionth of a centimeter in width. 

The initiation of the neurons communication with other neurons is in the cell membrane.  The neurons cell membrane is the continuous boundary that surrounds the neuron.  The cell membrane is very thin, about 8 nanometers, or 100,000th of a meter.

The Table below lists the Nutraceuticals, Food and Herbs that May Enhance the Function of Neurons

Nutraceuticals, Foods, Herbs that Enhance the Function of the Neurons

CategoryNutraceuticals/Foods/Herbs
Amino Acids
Acetyl-L-Carnitine (ALCAR)
Pyroglutatmate
SAMe
Theanine
Foods
Bee Propolis
Herbs
Ginko Biloba
Ashwangandha
Bacopa Monneir
Gota Kola
Korean Ginseng
Horse Chestnut
Magnolia
Rehmannia
Sanchi Ginseng
Hormones
DHEA
Melatonin
Lipids
DHA
EPA
Ginsenoside Rb1
Ginsenoside Rg1
Phosphatidylserine
Minerals
Calcium
Lithium
Phospherous
Magnesium
Neurotransmitters
GABA
Nootropics
Deprenyl
Hydergine
Piracetam
Vinpocetine
Centrophenoxine
Organic Acids
Malic Acid
Polyphenols
Coenzyme Q10
Pcynogenol
Vitamins
Alpha-GPC
Vitamin E
Vitamin A
Vitamin B1
Vitamin B12

Nerve Impulses

Nerve Impulses are the electrical activity in the membrane of a neuron that and is the means by which information is transmitted within the nervous system. 

Nerve impulses originate in dendrites, are integrated into the soma (cell body of neurons), and are transmitted down the axon to the synapse.

Action potentials in neurons are also known as “nerve impulses” or “spikes”, and the temporal sequence of action potentials generated by a neuron is called its “spike train”.

Nearly all cell membranes in animals, plants and fungi maintain an electric potential difference (voltage)—the membrane potential. A typical voltage across an animal cell membrane is –65 mV—approximately one-fifteenth of a volt. Because the cell membrane is very thin, voltages of this magnitude give rise to very strong electric forces across the cell membrane.

The electrical properties of an animal cell are determined by the structure of the membrane that surrounds it. A cell membrane consists of a layer of lipid molecules with larger protein molecules embedded in it. The lipid layer is highly resistant to movement of electrically charged ions, so it functions mainly as an insulator.

The Table below lists the Nutraceuticals, Food and Herbs that May Improve the Transmission of Nerve Impulses

Nutraceuticals, Food and Herbs that May Improve the Transmission of Nerve Impulses

CategoryNutraceuticals/Foods/Herbs
Amino Acids
Acetyl-L-Carnitine (ALCAR)
Herbs
Ginko Biloba
Lipids
DHA
Phosphatidylserine
Spingomyelin
Minerals
Calcium
Sodium
Potassium
Zinc
Calcium AEP
Magnesium
Nootropics
Hydergine
Vitamins
Choline
Vitamin B6
Vitamin B1
Inositol

Axons

An axon is a long, slender projection of a neuron that conducts electrical impulses away from the neuron’s cell body. Axons are also known as nerve fibers. The function of the axon is to transmit information to different neurons, muscles and glands.

Image result for axon

Figure 3.  Axon  (Source)

An axon is one of two types of protoplasmic protrusions that extrude from the cell body of a neuron, the other type being dendrites. Axons are distinguished from dendrites by several features, including shape (dendrites often taper while axons usually maintain a constant radius), length (dendrites are restricted to a small region around the cell body while axons can be much longer), and function (dendrites usually receive signals while axons usually transmit them).

The Table below lists the Nutraceuticals, Food and Herbs that May Enhance the Function of the Axon

Nutraceuticals, Food and Herbs that May Enhance the Function of the Axon

CategoryNutraceuticals/Foods/Herbs
Amino Acids
Acetyl-L-Carnitine (ALCAR)
Arginine
SAMe
Hormones
Estradiol
Lipids
DHA
Gangliosides
Nucleic Compounds
Inosine
Uridine
Peptides
Proline Rich Peptides
Polyphenols
Nobiletin
Vitamins
Folic Acid
Vitamin D
Vitamin A
Vitamin B12
Herbs
Boswellia serrata
Ashwangandha
Codonopsis
Gota Kola
Korean Ginseng

Myelin Sheath

Acetylcholine is the building block of myelin, which acts to insulate the axon and neuron, thus providing moisture and lubricants to the nervous system.

The myelin insulation of the neuron and axon provides conductivity to the nervous system.

Image result for myelin sheath

Figure 4.  Myelin sheath  (Source)

Myelination provides:

  • neurons circuits to fire more rapidly
  • neurons to recover faster after signals have been sent
  • neurons greater processing capacity

When myelin increases in thickness, the neurons fire at a faster rate and thus you think faster.  The more the neuronal connections are used (through learning), the myelin insulation increases and becomes thicker and heavier.

Cognitive decline and memory loss occurs when the myelin decay and the neurotransmitters get disrupted as their pathways lose their lubrication.  This is when the brain starts to short-circuit due to the lack of optimal myelin and acetylcholine.

The lipid makeup of the myelin sheath is important and cholesterol is an essential constituent.  The primary lipid of myelin is a glycolipid called galactocerebroside. The intertwining hydrocarbon chains of sphingomyelin serve to strengthen the myelin sheath.

Composition of CNS Myelin and Brain

  Myelin White matter    
Substance Human Bovine Rat Human Bovine Gray matter (human) Whole brain (rat)
Protein 30.0 24.7 29.5 39.0 39.5 55.3 56.9
Lipid 70.0 75.3 70.5 54.9 55.0 32.7 37.0
Cholesterol 27.7 28.1 27.3 27.5 23.6 22.0 23.0
Cerebroside 22.7 24.0 23.7 19.8 22.5 5.4 14.6
Sulfatide 3.8 3.6 7.1 5.4 5.0 1.7 4.8
Total galactolipid 27.5 29.3 31.5 26.4 28.6 7.3 21.3
Ethanolamine phosphatides 15.6 17.4 16.7 14.9 13.6 22.7 19.8
Lecithin 11.2 10.9 11.3 12.8 12.9 26.7 22.0
Sphingomyelin 7.9 7.1 3.2 7.7 6.7 6.9 3.8
Phosphatidylserine 4.8 6.5 7.0 7.9 11.4 8.7 7.2
Phosphatidylinositol 0.6 0.8 1.2 0.9 0.9 2.7 2.4
Plasmalogensb 12.3 14.1 14.1 11.2 12.2 8.8 11.6
Total phospholipid 43.1 43.0 44.0 45.9 46.3 69.5 57.6

A  Protein and lipid figures in percent dry weight; all others in percent total lipid weight.

B  Plasmalogens are primarily ethanolamine phosphatides.

From: Characteristic Composition of Myelin, Basic Neurochemistry: Molecular, Cellular and Medical Aspects. 6th edition. Siegel GJ, Agranoff BW, Albers RW, et al., editors. Philadelphia: Lippincott-Raven; 1999.

The Table below lists the Nutraceuticals, Food and Herbs that May Enhance the Function of Myelin Sheaths

Nutraceuticals, Food and Herbs that May Enhance the Function of Myelin Sheaths

CategoryNutraceuticals/Foods/Herbs
Amino Acids
Acetyl-L-Carnitine (ALCAR)
Taurine
Animal Organ Extracts
Mylein Sheath Extract
Fungi
Lions Mane
Herbs
Ashwagandha
Celastrus paniculatus seeds
Hormones
Progesterone
Pregnenolone
Lipids
Phosphatidylcholine
Phosphatidylserine
Sphingomylein
EPA
Cholesterol
Minerals
Iodine
Lithium
Nucleic Compounds
Uridine
Vitamins
Inositol
Vitmin B6
Vitamin B12

Presynaptic Terminal

Presynaptic Terminals are the end-point or distal terminations of axons which are specialized for the release of neurotransmitters.  They are also called chemical synapses which are biological junctions through which neurons’ signals can be exchanged to each other and to non-neuronal cells such as those in muscles or glands.

There are an astonishing large number of synapses and the human brain is estimated to contain from 1014 to 5 × 1014 (100–500 trillion) synapses.  1 

Image result for presynaptic terminal

Figure 5.  Presynaptic Terminal  (Source)

The Table below lists the Nutraceuticals, Food and Herbs that May Enhance the Function of Presynaptic Terminals

Nutraceuticals, Food and Herbs that May Enhance the Function of Presynaptic Terminals

CategoryNutraceuticals/Foods/Herbs
Amino Acids
N-Acetyl-Cysteine (NAC)
Vitamins
Vitamin B12

Presynaptic Membrane

The presynaptic membrane is that part of the plasma membrane of an axon terminal that faces the plasma membrane of the neuron or muscle fiber with which the axon terminal establishes a synaptic junction. 

It is the excitable membrane located at the end-point of the presynaptic terminal of the axons. 

Image result for presynaptic membrane

Figure 6.  Presynaptic Membrane  (Source)

Presynaptic Membranes contain very high levels of Docosahexaenoic Acid (DHA).  Presynaptic Membranes contain more DHA than almost every other type of tissue of the neuron.

The Table below lists the Nutraceuticals, Food and Herbs that May Enhance the Function of the Presynaptic Membrane

Nutraceuticals, Food and Herbs that May Enhance the Function of the Presynaptic Membrane

CategoryNutraceuticals/Foods/Herbs
Lipids
DHA

Synaptic Vesicles

In a neuron, synaptic vesicles store various neurotransmitters that are released at the synapse. The release is regulated by a voltage-dependent calcium channel. Vesicles are essential for propagating nerve impulses between neurons and are constantly recreated by the cell.

Image result for Synaptic Vesicles

Figure 7.  Synaptic Vesicles  (Source)

Synaptic vesicles are relatively simple because only a limited number of proteins fit into a sphere of 40 nm diameter. Purified vesicles have a protein:phospholipid ratio of 1:3 with a lipid composition of:

  • 40% phosphatidylcholine
  • 32% phosphatidylethanolamine
  • 12% phosphatidylserine
  • 5% phosphatidylinositol
  • 10% cholesterol

The Table below lists the Nutraceuticals, Food and Herbs that May Enhance the Function of Synaptic Vesicles

Nutraceuticals, Food and Herbs that May Enhance the Function of Synaptic Vesicles

CategoryNutraceuticals/Foods/Herbs
Lipids
Alpha-Linolenic Acid
Vitamins
Vitamin B1
Foods
Perilla Oil

Dendrite

Dendrites are the branched projections of a neuron that act to propagate the electrochemical stimulation received from other neural cells to the cell body, or soma, of the neuron from which the dendrites project.

Electrical stimulation is transmitted onto dendrites by upstream neurons (usually their axons) via synapses which are located at various points throughout the dendritic tree.

Image result for dendrites

Figure 8.  Dendrites  (Source)

Dendrites are one of two types of protoplasmic protrusions that extrude from the cell body of a neuron, the other type being an axon.

Axons can be distinguished from dendrites by several features including shape, length, and function. Dendrites often taper off in shape and are shorter, while axons tend to maintain a constant radius and be relatively long.

Typically, axons transmit electrochemical signals and dendrites receive the electrochemical signals.

The Table below lists the Nutraceuticals, Food and Herbs that May Enhance the Function of Dendrites

Nutraceuticals, Food and Herbs that May Enhance the Function of Dendrites

CategoryNutraceuticals/Foods/Herbs
Alkaloids
Huperzine A
Amino Acids
Acetyl-L-Carnitine (ALCAR)
Proline
Hormones
Estrogen
Lipids
DHA
Phosphatidylserine
Organic Acids
Malic Acid
Nootropics
Hydergine
Herbs
Ashwagnadha
Gota Kola

Synaptic Cleft

The synaptic cleft, which is a component of the chemical synapse, is the minute space (approximately 20 nanometers wide) that exists between the presynaptic membrane of axons and the postsynaptic membrane of receiving (normally) dendrites. 

When nerve impulses reach a synapse they cause the release of a neurotransmitter which diffuses across the synaptic cleft and triggers a further impulse in the postsynaptic membrane of the dendrite of the next neuron.

The small volume of the cleft allows neurotransmitter concentration to be raised and lowered rapidly.  2 

Image result for synaptic cleft

Figure 9.  Synaptic Cleft  (Source)

The Table below lists the Nutraceuticals, Food and Herbs that May Prevent Deterioration of the Synaptic Cleft

Nutraceuticals, Food and Herbs that May Prevent Deterioration of the Synaptic Cleft

CategoryNutraceuticals/Foods/Herbs
Lipids
Phosphatidylserine
Minerals
Selenium
Nootropics
Centrophenoxine

Consolidation and Summary Table

The Table below is a consolidation and summary of the Nutraceuticals, Food and Herbs that enhance and protect the nine (9) components of neurons.

Legend:

NEU-Neuron; NIP-Nerve Impluses; AXN-Axons; MYL-Myelin Sheath; PST-Presynaptic Terminal; PSM-Presynaptic Membrane; SNV-Synaptic Vesicles; DEN- Dendrite; SYN-Synaptic Cleft

Consolidation and Summary Table - Components of the Neurons

CategoryNutraceuticals/Foods/HerbsNeuNIpAxnMylPsTPsMSnVDenSyn#
Alkaloids
Huperzine AX1
Amino Acids
Acetyl-L-Carnitine (ALCAR)XXXXX5
NACX1
PyroglutamateX1
SAMeXX2
TaurineX1
TheanineX1
ArginineX1
ProlineX1
Animal O E
Mylein Sheath ExtractX1
Foods
Perilla OilX1
Herbs
Ginko BilobaXX2
American GinsengX1
AswagandhaXXX3
Bacopa MonneriX1
Gota KolaXXX3
Korean GinsengXX2
Magnolia (Honokiol)X1
CodonopsisX1
Lions ManeX1
Hormones
EstrogensX1
EstradiolX1
ProgesteroneX1
MelatoninX1
DHEAX1
Lipids
DHAXXXXX5
EPAXX2
GangliosidesXX3
PhosphatidylserineXXXXX5
Ginsenoside Rb1X1
Ginsenoside Rg1X1
OctacosanolX1
PhosphatidylcholineX1
CholesterolX1
Alpha-Lineloic AcidX1
Minerals
CalciumXX2
LithiumXX2
PhosphrousX1
MagnesiumXX2
SodiumX1
PotassiumX1
SeleniumX1
Calcium AEPX1
Nootropics
DeprenylX1
HydergineXXX3
PiracetamX1
CentrophenoxineXX2
VinpocetineX1
Nucelic Cmd
InosineX1
UridineX1
Neurotrns
GABAX1
Organic Ad
Malic AcidX1
Polyphenols
NobiletinX1
Coenzyme Q10X1
Vitamins
InositolXX2
CholineX1
Alpha-GPCX1
Vitamin EX1
Vitamin AXX2
Vitamin B1XXX3
Vitamin B12XXXX4
Vitamin B6XX2
Folic AcidX1
Vitamin DX1
Vitamin DX1

Top Nine Substances for Neurons

Based on the Consolidations and Summary Table, the Chart below lists the top nine (9) nutraceuticals, foods and herbs for the enhancement and protection of neurons. 

It is of no surprise that the top three substances that enhance and protect the five (5) components of neurons include:

  • Phosphatidylserine
  • DHA
  • Acetyl-l-Carnitine

Chart:  Top 9 Substances for Neurons

Preventing Brain Atrophy and Cognitive Decline with Omega-3 Fatty Acids and B-Complex Vitamins

Brain Atrophy

Brain atrophy, or brain shrinkage, is the opposite of neurogenesis. Brain atrophy describes a loss of neurons and the connections between them.

Image result for brain atrophy

Figure 1.  Normal brain versus Atrophic brain  (Source)

Brain atrophy can be categorized as either general or focal. With general brain atrophy, all of the brain shrinks. With focal brain atrophy, shrinkage of the brain affects a limited area of the brain which often results in decreased functions in the area that area controls. For example, if the cerebrum atrophies, then conscious thought and voluntary processes may be impaired.

Even if you do not have a chronic disease, you may be losing as much as 0.4% of your brain mass every year.  1  The rate of brain shrinkage increases with age and is a major factor in early cognitive decline and premature death.  2  Age related cognitive decline occurs in tandem with the physical degradation of brain structure.

Image result for brain atrophy

Figure 2.  Brain atrophy in Advanced Alzheimer’s Disease  (Source)

By the age of 60, approximately .5 to 1% of brain volume is lost per year. By the time you reach age 75, your brain is on average of 15% smaller than it was when you were in your mid-20’s.

Even though brain shrinkage is progressive, a growing number of neuroscientists believe that brain shrinkage can be slowed or even reversed.  3 

Medical science has recognized a number of conditions and behaviors that cause brain atrophy:

Homocysteine

Homocysteine is a risk factor for brain atrophy. Supplementation with B vitamins that lower levels of plasma total homocysteine can slow the rate of brain atrophy in subjects with mild cognitive impairment.  4  

Sleep

Poor sleep quality was associated with reduced volume within the right superior frontal cortex in cross-sectional analyses, and an increased rate of atrophy within widespread frontal, temporal, and parietal regions in longitudinal analyses.   5

Hypertension

Studies have shown that both high and low blood pressure (BP) may play a role in the etiology of brain atrophy. High BP in midlife has been associated with more brain atrophy later in life.  6

Hypoperfusion

Normal aging is associated with diminished blood flow to the brain. This pathology is known as hypoperfusion and causes cell injury and death. The combination of hypertension and hypoperfusion is associated with smaller brain volume.  7

Type 2 Diabetes

New research has shown that cognitive decline in people with type 2 diabetes is likely due to brain atrophy, or shrinkage, that resembles patterns seen in the early stages of Alzheimer’s disease.  8

Obesity

Higher body mass index (BMI, a measure of obesity) is associated with lower brain volume in obese and overweight people.  9

Smoking

Any lifetime history of smoking (even if you currently do not smoke) is associated with faster brain shrinkage in multiple brain regions, compared with people who never smoked.  10

Alcohol

Heavy drinkers are 80% more likely than nondrinkers to sustain frontal lobe shrinkage, compared with nondrinkers,49 and 32% more likely to have enlargement of the ventricles, indicating shrinkage from within.  11

Preventing Brain Atrophy with Omega-3 Fatty Acids and B Vitamins

A study published in July 2015 in The American Journal of Clinical Nutrition entitled “Brain atrophy in cognitively impaired elderly: the importance of long-chain ω-3 fatty acids and B vitamin status in a randomized controlled trial”, revealed some interesting new findings on brain atrophy.

The researchers investigated whether plasma omega-3 fatty acid concentrations (eicosapentaenoic acid and docosahexaenoic acid) modify the treatment effect of homocysteine-lowering B vitamins on brain atrophy rates in a placebo-controlled trial.

The study included 168 elderly people (≥70 y) with mild cognitive impairment, randomly assigned either to placebo (n = 83) or to daily high-dose B vitamin supplementation formula consisting of:

  • folic acid (800 mcg)
  • vitamin B6 (20 mg)
  • vitamin B12 (500 mcg)

The subjects underwent cranial magnetic resonance imaging scans at baseline and 2 years later. 

In the group of subjects who took the B vitamin formula and that had a high baseline omega-3 blood levels (>590 μmol/L), the mean brain atrophy rate slowed by 40% compared to the placebo group.

In the placebo group there was no slowing of brain atrophy even when this group had a high baseline of omega-3 fatty acids.

In the group receiving the B vitamin formula with a low baseline omega-3 blood levels (390μmol/L), there was no significant effect on the rate of atrophy among subjects.

The researchers conclusion demonstrates the importance to supplement with both omega-3 fatty acids and the B-complex vitamins:

“The beneficial effect of B vitamin treatment on brain atrophy was observed only in subjects with high plasma ω-3 fatty acids. It is also suggested that the beneficial effect of ω-3 fatty acids on brain atrophy may be confined to subjects with good B vitamin status.”  12

Prevention of Cognitive Decline with Omega-3 Fatty Acids and B Vitamins

A more recent study published in January 2016 in the Journal of Alzheimer’s Disease entitled “Omega-3 Fatty Acid Status Enhances the Prevention of Cognitive Decline by B Vitamins in Mild Cognitive Impairment”, investigated whether baseline omega-3 fatty acid status interacts with the effects of B vitamin treatment slowed the rate of cognitive and clinical decline.

For this study 266 participants with MCI aged ≥70 years were randomized to B vitamins (folic acid, vitamins B6 and B12) or placebo for 2 years.

Baseline cognitive test performance, clinical dementia rating (CDR) scale, and plasma concentrations of total homocysteine, total docosahexaenoic and eicosapentaenoic acids (omega-3 fatty acids) were measured.

Final scores for verbal delayed recall, global cognition, and CDR sum-of-boxes were better in the B vitamin-treated group according to increasing baseline concentrations of omega-3 fatty acids, whereas scores in the placebo group were similar across these concentrations.

The results were intriguing among those with good omega-3 status.  In this group, 33% of those on B vitamin treatment had global CDR scores >0 compared with 59% among those on placebo.

For all three outcome measures, higher concentrations of docosahexaenoic acid (DHA) alone significantly enhanced the cognitive effects of B vitamins, while eicosapentaenoic acid  (EPA) appeared less effective.

When omega-3 fatty acid concentrations are low, B vitamin treatment has no effect on cognitive decline in MCI, but when omega-3 levels are in the upper normal range, B vitamins interact to slow cognitive decline.

The concluding remarks from the researchers reinforces the necessity to consume both omega-3 fatty acids, preferably in the form of EPA and DHA (fish oil) and the B-complex vitamins:

“In conclusion, when plasma omega-3 fatty acid concentrations are low, B vitamin treatment does not slow cognitive decline in people with MCI. In contrast, when omega-3 fatty acid levels are in the upper range of normal, the slowing effects of B vitamins on both brain atrophy [27] and cognitive decline are enhanced. We suggest that the effects of this interaction between the two nutrients on brain atrophy and cognition is consistent with the view that they slow down the disease process in MCI.”  13

Probiotic Propionibacterium freudenreichii Extends the Mean Lifespan of Caenorhabditis elegans via Activation of the Innate Immune System

Propionibacterium freudenreichii is a short-chain fatty acid (SCFA)-producing bacterium which ferments lactate to:

  • acetate
  • propionate
  • carbon dioxide

The two short-chain fatty acids, acetate and propionate have been shown to enhance human gut immunity.

A study published in the Journal Scientific Reports in August 2016 evaluated the effects of Propionibacterium freudenreichii on lifespan extension and to elucidate the mechanism of Propionibacterium freudenreichii -dependent lifespan extension in Caenorhabditis elegans.  1 

Caenorhabditis elegans is a small, free-living soil nematode commonly used as a model experimental animal because it is easy to treat, has a short lifespan, can be safely used in the laboratory and propagates through self-fertilization. In particular, C. elegansis frequently used in studies on longevity, immunity, neurodegenerative diseases, fat storage, DNA damage responses and apoptosis.

The results of the study showed that Propionibacterium freudenreichii significantly (p < 0.05) extended the lifespan of C. elegans compared with Escherichia coli OP50, a standard food for the worm.

The MLS of Propionibacterium freudenreichii-fed C. elegans, compared with that of E. coliOP50-fed worms, increased by approximately 13%. The survival rates were similar in both the Propionibacterium freudenreichii- and E. coli OP50-fed C. elegans until day 13.

After day 13, the two groups showed a significant difference in the survival rate.  Analysis of age-related biomarkers showed that Propionibacterium freudenreichii retards ageing.

 

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Figure 1.  The effect of Propionibacterium freudenreichii on the lifespan of C. elegans (N2).  Maturing nematodes were fed E. coli OP50 until the L4 stage, and young adult worms were transferred to a fresh mNGM plate seeded with E. coli OP50 or Propionibacterium freudenreichii . Significant differences shown are relative to E. coli OP50; ***p < 0.001. (Source)

The researchers concluded that Propionibacterium freudenreichii extends the lifespan of C. elegans via the p38 MAPK pathway involved in stress response and the TGF-β pathways associated with anti-inflammation processes in the immune system.  2

Natural Rapalogs that Inhibit the mTOR Pathway

In 1975 scientists discovered the mycelial bacterium Streptomyces hygroscopicus on Rapa Nui, the native name of Easter Island.  From this bacterium they created the molecule named Rapamycin, a pharmaceutical drug which requires a doctor’s prescription.  Also known as Sirolimus, it is an immunosuppressant drug used in orthodox medicine to prevent rejection following organ transplantation.

In addition to its use as an immunosuppressant drug, Rapamycin inhibits the mTOR signalling pathway and studies show it can significantly extend lifespan in mammals, even when taken in later life, with increases in life expectancy for males and females of between 9% and 14% respectively.


 

mTOR Pathway  

“mTOR” or the mechanistic target of rapamycin (mTOR), (formerly mammalian target of rapamycin before it was recognized to be highly conserved among eukaryotes) refers to an enzyme from the serine/threonine protein kinase family encoded by the mTOR gene. It is found in humans as well as worms, mice, flies and yeasts. It regulates the growth, proliferation, motility and survival of cells.

Successfully inhibiting mTOR signalling pathways has been shown to produce increased lifespan in worms, flies, yeasts and even mice if accompanied by calorie restriction and the consumption of adequate protein.

 

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Figure 1.  mTOR Pathway  (Source)

Since Rapamycin is poorly water soluble, which effects its bioavailability, several analogs of Rapamycin have been developed and are termed rapalogs.  Some of these rapalogs have improved pharmacokinetics and include:

  • temsirolimus
  • everolimus
  • ridaforolimus
  • 32-deoxo-rapamycin
  • zotarolimus

The use of these pharamaceutical rapalogs have been generally disappointing in human trials.  One possible explanation for the disappointing results to date is that in human cancer, rapalogs predominately inhibit mTORC1, leading to increased PI3K and AKT signaling by preventing negative feedback through S6K and GRB10.  1 

Recent studies have demonstrated that a number of natural products (or nutraceuticals) isolated from plants (e.g. fruits, vegetables, spices, nuts, legumes, herbs, etc.) also inhibit the mTOR pathway, and exhibit potent anticancer activities. These particular natural products are considered “natural rapalogs”.

The Table below lists the identified natural substances that are considered natural rapalogs or mTOR inhibitors:

Natural Rapalogs (mTOR Inhibitors)

CategorySubstanceReference
Alkaloids
Caffeine1
Amino Acids
NAC2
Herbs
Astragalus3
β-elemene (from the traditional Chinese medicinal herb Rhizoma zedoariae)4
Butein (in the stems of Rhus verniciflua)5
Capsaicin (in chili peppers)6
Celastrol (in the traditional Chinese medicine named “Thunder of God Vine”)7
Cryptotanshinone (Salvia miltiorrhiza Bunge) (Danshen)8
Rhodiola rosea9
Indoles
Indole-3-carbinol and 3,3′-diindolylmethane)10
Mushrooms
Reishi11
Peptides
Carnosine12
Polyphenols
Apigenin13
Curcumin14
Epigallocatechin gallate (EGCG, in green tea)15
Fisetin16
Isoflavones (genistein and deguelin)17
Quercetin18
Resveratrol19
Vitamins
R-Lipoic Acid20
Tocotrienol (Vitamin E)21

Gymnema sylvestre Improves the Function of and Regenerates Pancreatic Beta Cells

The pancreas is a glandular organ in the digestive system located in the abdominal cavity behind the stomach. It serves as an endocrine gland producing several important hormones that circulate in the blood, including:

  • insulin (important in the metabolism of glucose)
  • glucagon
  • somatostatin
  • pancreatic polypeptide

The pancreas also secretes pancreatic juice containing digestive enzymes that assist digestion and absorption of nutrients in the small intestine.

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Figure 1.  Location of the pancreas  (Source)

The region of the pancreas that contain its endocrine (hormone producing) cells is called the pancreatic islets or islets of Langerhans.  The pancreatic islets constitute 1 to 2% of the pancreas volume and receive 10–15% of its blood flow.

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Figure 2.  Islets of Langerhans  (Source)

A type of cell found in the pancreatic islets are Beta cells.  They make up 65-80% of the cells in the islets.  The primary function of a beta cell is to store and release insulin. Insulin is a hormone that brings about effects which reduce blood glucose concentration.

Image result for beta cells

Figure 3.  Beta-cells of the pancreas  (Source)

The functions of the beta cells can become compromised with insulin resistance and the pathogenesis of diabetes.  Beta cell dysfunction results from inadequate glucose sensing to stimulate insulin secretion and therefore elevated glucose concentrations prevail.

Persistently elevated glucose concentrations above the physiological range result in the manifestation of hyperglycemia. With systemic insulin resistance, insulin signaling within glucose recipient tissues is defective therefore hyperglycemia perseveres.

Image result for beta cell dysfunction

Figure 4.  Potential mechanism of beta-cell failure  (Source)

Beta cell dysfunction supersedes insulin resistance in inducing diabetes. Both pathological states influence each other and presumably synergistically exacerbate diabetes.

Preserving beta cell function and insulin signaling in beta cells and insulin signaling in the glucose recipient tissues will maintain glucose homeostasis.   1

Plant-derived Natural Compounds that Inhance the Functionality of Pancreatic Beta Cells

There is a wide selection of published data on the effects of various plant-derived natural compounds on the functionality of pancreatic beta cells. These natural compounds have been found to directly:

  • enhance insulin secretion
  • prevent pancreatic beta cell apoptosis
  • modulate pancreatic beta cell differentiation and proliferation
  • regenerate pancreatic beta cells

Certain bio-active compounds of plants have confirmed anti-diabetic properties.  Table 1 below lists these botanical plants and their active compounds:

Table 1: Biological functions of plants (bio-active compounds) with confirmed anti-diabetic properties.

 

 

Botanical name Active
compounds
Effect
observed
References
 

 

Anoectochilus roxburghii Kinsenoside Increases pancreatic beta cell regeneration [98]
Biden pilosa 3-β-D-Glucopyranosyl-1-hydroxy-6(E)-tetradecene-8,10,12-triyne
2-β-D-Glucopyranosyloxy-1-hydroxy-5(E)-tridecene-7,9,11-triyne
2-β-D-Glucopyranosyloxy-1-hydroxy-5,7,9,11-tetrayne
(cytopiloyne)
Increases insulin production
Enhances insulin
secretion
[1216]
Camellia sinensis Epigallocatechin-3-gallate Enhances insulin secretion
Inhibits pancreatic beta
cell apoptosis
[7886]
Capsicum annuum Capsaicin Enhances insulin secretion [1719]
Carica papaya Flavonoids/alkaloids/saponin/tannins Enhances insulin secretion [20, 21]
Curcuma longa Curcumin Enhances insulin secretion [7177]
Ervatamia microphylla Conophylline Induces differentiation into insulin producing
cells
[6470]
Glycine max Genistein Enhances insulin secretion
Inhibits pancreatic beta
cell apoptosis
[8797]
Gymnema sylvestre Gymnemic acids Enhances insulin secretion [2232]
Momordica charantia Momordicin Increases pancreatic beta cell regeneration [3343]
Nymphaea stellate Nymphayol Enhances insulin secretion [4446]
Panax ginseng Ginsenoside Enhances insulin secretion
Increases
proliferation
[4757]
Rhizoma coptidis Berberine Enhances insulin secretion [5863]
Silybum marianum Silymarin Inhibits pancreatic beta cell apoptosis [113118]
Commonly found in plants Resveratrol Inhibits pancreatic beta cell apoptosis [106112]
Commonly found in plants Quercetin Enhances insulin secretion
Inhibits pancreatic beta
cell apoptosis
[99105]
 

 

Source:  Plant-Derived Compounds Targeting Pancreatic Beta Cells for the Treatment of Diabetes

 

Image result for Plant-Derived Compounds Targeting Pancreatic Beta Cells for the Treatment of Diabetes

Figure 5.  Biological functions of plants (bioactive compounds) with confirmed antidiabetic properties  (Source) (Click on image to enlarge)

Gymnema sylvestre increases pancreatic beta cell regeneration and insulin secretion

Gymnema sylvestre (G. sylvestre) has traditionally been used to treat diabetes in India for centuries and has been an integral part of Ayruvedic medicine.

Image result for Gymnema sylvestre

Figure 6.  Gymnema sylvestre plant and flowers

The bio-active compound of G. sylvestre are triterpenoid saponins.  The main triterpenoid saponin is gymnemic acids and are considered to be the active compounds responsible for the anti-diabetic effects of G. sylvestre.

G. sylvestre extract is known to stimulate insulin secretion in various pancreatic beta cell lines.  It also has showed hypoglycemic effects via the increase in pancreatic beta cell regeneration and insulin secretion.

The many antidiabetic effects of G. sylvestre include:

  • Decreased plasma glucose levels and significantly induced insulin secretion compared with that in control mice.  2
  • Lowered blood glucose levels through the regeneration of pancreatic beta cells.  3
  • Lowered blood glucose levels in type 2 diabetes patients by increasing insulin secretion.  4
  • Induced significant increases in circulating insulin and C-peptide concomitant with a significant reduction in blood glucose levels.  5 
  • Blood glucose homeostasis through increased serum insulin levels provided by repair/regeneration of the pancreas.  6

Repairing the Damaged Plasma Membrane of the Cell and the Membrane-Bound Organelles

Introduction to the Plasma Membrane

The human cell is enveloped in a thin, pliable, elastic structure called the cell membrane or the plasma membrane and is only 7.5 to 10 nanometers thick. It is composed almost entirely of proteins and lipids.  There are approximately 5 × 106 lipid molecules in a 1 μm × 1 μm area of lipid bilayer, or about 109 lipid molecules in the plasma membrane of a human cell.

The main purpose of the plasma membrane is to separate the inner contents of the cell from its exterior environment, much like the outer layer of the skin separates the body from its environment.  In addition to providing a protective barrier around the cell, the plasma membrane regulates which materials pass in and out of the cell.

The plasma membrane envelops the human cell and is also found inside the cell in various intracellular membranes, called organelles.  The structure and composition of the plasma membrane are the same for the plasma membrane surrounding the cell as well as for the various intracellular membranes.  The only difference among them is the proportions which vary from one type of membrane to the other.

The formation of plasma membranes is based on the structural organization of bilayers of lipids with associated proteins.  The lipid content of the plasma membrane ranges from 40 to 80% (of dried weight), which is significant.  The two main lipids that predominate quantitatively in the lipid fraction of the plasma membrane are:

  • phosphatidylcholine
  • phosphatidylethanolamine

The lipid molecules in plasma membranes are amphipathic (or amphiphilic)—that is, they have a hydrophilic (“water-loving”) or polar end and a hydrophobic (“water-fearing”) or nonpolar end.

Functions of the Plasma Membrane

In addition to the plasma membrane providing a protective barrier around the cell and the intracellular organelles, it has many essential functions:

  • transporting nutrients into the cell
  • transporting metabolic wastes out of the cell
  • preventing unwanted materials in the extracellular milieu from entering the cell
  • preventing loss of needed metabolites
  • maintaining the proper ionic composition, pH (≈7.2), and osmotic pressure of the cytosol
  • provides cell to cell communication
  • provides hormone sensitivity and utilization
  • support the many enzymatic reactions that occur along their surfaces

These various functions are carried out by specific transport proteins which restrict the passage of certain small molecules.

The plasma membrane actually has a measurable membrane differential which is the voltage across the plasma membrane.  It has been determined that healthy children has a membrane electrical potential up to 90 millivolts, whereas a healthy adult can have up to 70 millivolts.  The membrane electrical potential can decline to around 40 millivolts in an individual with a chronic disease and to as low as 15 millivolts in an individual with advanced cancer.

The Lipids Comprising the Plasma Membrane of the Human Cell

The plasma membrane of the human cell and certain intracellular organelles inside the cell are composed of three categories of lipids:

  • Phospholipids (Glycerophospholipids or Phospholycolipids or Phosphoglycerides and Phosphosphingolipids)
  • Glycolipids
  • Cholesterol

Of the three categories of  lipids, the most abundant membrane lipids are the phospholipids.

The functions of the plasma membrane determines the lipid compositions of the inner and outer monolayers of the cell plasma membrane.  Different mixtures of lipids are found in the membranes of cells of different types.  The two sides of the plasma membrane of the human cell reflect this difference:

Outer Layer (the side on the exterior of the cell)

Consists mainly of phosphatidylcholine and sphingomyelin

Inner Layer (the side on the interior of the cell)

Consists mainly of phosphatidylethanolamine and phosphatidylserine and phosphatidylinositol.  

Figure 12.2. Lipid components of the plasma membrane.

Figure 1.  Lipid components of the plasma membrane

The outer leaflet consists predominantly of phosphatidylcholine, sphingomyelin, and glycolipids, whereas the inner leaflet contains phosphatidylethanolamine, phosphatidylserine, and phosphatidylinositol. Cholesterol is distributed in both leaflets. The net negative charge of the head groups of phosphatidylserine and phosphatidylinositol is indicated. (Source:  The Cell: A Molecular Approach. 2nd edition., The Molecular Composition of Cells)

The mitochondria, an intracellular organelle, contains two membranes and consists primarily of phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine, and phosphatidic acid.  These phospholipids are asymmetrically distributed between the two halves of the membrane bilayer of the mitochondria.  The inner mitochondrial membrane contains a specific phospholipid called phosphatidylglycerol and is the precursor for cardiolipin.  Cardiolipin is predominantly found in the inner mitochondrial membrane.

Lipids constitute approximately 50% of the mass of most cell membranes, although this proportion varies depending on the type of membrane. Plasma membranes, for example, are approximately 50% lipid and 50% protein.

The lipid composition of different cell membranes also varies:

  Plasma membrane    
Lipid E. coli Erythrocyte Rough endoplasmic reticulum Outer mitochondrial membranes
Phosphatidylcholine 0 17 55 50
Phosphatidylserine 0 6 3 2
Phosphatidylethanolamine 80 16 16 23
Sphingomyelin 0 17 3 5
Glycolipids 0 2 0 0
Cholesterol 0 45 6 <5

Membrane compositions are indicated as the mole percentages of major lipid constituents.

Another source lists the lipid compositions of different cell membranes:

  PERCENTAGE OF TOTAL LIPID BY WEIGHT
LIPID LIVER CELL PLASMA MEMBRANE RED BLOOD CELL PLASMA MEMBRANE MYELIN MITOCHONDRION (INNER AND OUTER MEMBRANES) ENDOPLASMIC RETICULUM E. COLIBACTERIUM
Cholesterol 17 23 22 3 6 0
Phosphatidylethanolamine 7 18 15 25 17 70
Phosphatidylserine 4 7 9 2 5 trace
Phosphatidylcholine 24 17 10 39 40 0
Sphingomyelin 19 18 8 0 5 0
Glycolipids 7 3 28 trace trace 0
Others 22 13 8 21 27 30
(Source: Molecular Biology of the Cell. 4th edition., The Lipid Bilayer; Alberts B, Johnson A, Lewis J, et al. New York: Garland Science; 2002.)
Phospholipids that Compose the Plasma Membrane

Plasma membranes contain 4 major and 1 minor phospholipids:

  • Major phospholipids
    • phosphatidylcholine
    • phosphatidylethanolamine
    • phosphatidylserine
    • sphingomyelin
  • Minor phospholipids
    • phosphatidylinositol

These major phospholipids together account for more than 50% of the lipid in most membranes. Phosphotidylinositol is present in smaller quantities in the plasma membrane but provide important functions like cell signaling.

  Figure 10-12. Four major phospholipids in mammalian plasma membranes.

Figure 2.  Four major phospholipids in mammalian plasma membranes

Note that different head groups are represented by different colors. All the lipid molecules shown are derived from glycerol except for sphingomyelin, which is derived from serine.  (Source: Molecular Biology of the Cell. 4th edition., The Lipid Bilayer; Alberts B, Johnson A, Lewis J, et al. New York: Garland Science; 2002.)

Phosphatidylcholine

Phosphatidylcholine is a vital substance found in every cell of the human body.

Phosphatidylethanolamine

Phosphatidylethanolamines are found in all living cells, composing 25% of all phospholipids. In humans, they are found particularly in nervous tissue such as the white matter of brain, nerves, neural tissue, and in spinal cord, where they make up 45% of all phospholipids.  1

Phosphatidylserine

Phosphatidylserine is a component of the cell membrane. It plays a key role in cell cycle signaling, specifically in relationship to apoptosis.  

Sphingomyelin

Sphingomyelin is a type of sphingolipid found in animal cell membranes, especially in the membranous myelin sheath that surrounds nerve cell axons. It usually consists of phosphocholine and ceramide, or a phosphoethanolamine head group; therefore, sphingomyelins can also be classified as sphingophospholipids.

Phosphatidylinositol (minor phospholipid)

Phosphatidylinositol forms a minor component on the cytosolic side of eukaryotic cell membranes.

Phosphorylated forms of phosphatidylinositol are called phosphoinositides and play important roles in lipid signaling, cell signaling and membrane trafficking.

Phosphatidylglycerols  (Cardiolipin)

Phosphatidic acid reacts with CTP, producing CDP-diacylglycerol, with loss of pyrophosphate. Glycerol-3-phosphate reacts with CDP-diacylglycerol to form phosphatidylglycerol phosphate, while CMP is released. The phosphate group is hydrolysed forming phosphatidylglycerol.

Two phosphatidylglycerols form cardiolipin, the constituent molecule of the mitochondrial inner membrane.  2

Phosphatidic acid

Phosphatidic acids are the acid forms of phosphatidates, a part of common phospholipids, major constituents of cell membranes.  phosphatidic acids are the simplest diacyl-glycerophospholipids.

The role of phosphatidic acid in the cell can be divided into three categories:

  • Phosphatidic acid is the precursor for the biosynthesis of many other lipids
  • The physical properties of phosphatidic acid influence membrane curvature
  • Phosphatidic acid acts as a signaling lipid, recruiting cytosolic proteins to appropriate membranes

The conversion of phosphatidic acid into diacylglycerol (DAG) by LPPs is the commitment step for the production of phosphatidylcholine, phosphatidylethanolamine and phosphatidylserine. In addition, DAG is also converted into CDP-DAG, which is a precursor for phosphatidylglycerol, phosphatidylinositol and phosphoinositides.

Phosphatidic acid is essential for lipid synthesis and cell survival, yet, under normal conditions, is maintained at very low levels in the cell.

Glycolipids

The role of glycolipids is to maintain stability of the membrane and to facilitate cellular recognition.  3 

Carbohydrates are found on the outer surface of all eukaryotic cell membranes. They extend from the phospholipid bilayer into the aqueous environment outside the cell where it acts as a recognition site for specific chemicals as well as helping to maintain the stability of the membrane and attaching cells to one another to form tissues.

Figure 3.  Glycolipid attached to lipid residue

The lipid complex is most often composed of either a glycerol or sphingosine backbone, which gives rise to the two main categories of glycolipids:

  • glyceroglycolipids
  • sphingolipids

The heads of glycolipids contain a sphingosine with one or several sugar units attached to it. The hydrophobic chains belong either to:

  • two fatty acids – in the case of the phosphoglycerides, or
  • one fatty acid and the hydrocarbon tail of sphingosine – in the case of sphingomyelin and the glycolipids

Glycolipids occur in all animal cell plasma membranes, where they generally constitute about 5% of the lipid molecules in the outer monolayer. They are also found in some intracellular membranes.

The most complex of the glycolipids, the gangliosides, contain oligosaccharides with one or more sialic acid residues, which give gangliosides a net negative charge.  More than 40 different gangliosides have been identified. They are most abundant in the plasma membrane of nerve cells, where gangliosides constitute 5–10% of the total lipid mass; they are also found in much smaller quantities in other cell types.

Cholesterol

Cholesterol is a sterol, and is biosynthesized by all animal cells, and is an essential structural component of all animal cell membranes; essential to maintain both membrane structural integrity and fluidity. Cholesterol enables animal cells to dispense with a cell wall (to protect membrane integrity and cell viability), thereby allowing animal cells to change shape and animals to move (unlike bacteria and plant cells, which are restricted by their cell walls).

Cell membranes require high levels of cholesterol – typically an average of 20% cholesterol in the whole membrane, increasing locally in raft areas up to 50% cholesterol.  4 

Within the cell membrane, cholesterol also functions in intracellular transport, cell signaling and nerve conduction. Recent studies show that cholesterol is also implicated in cell signaling processes, assisting in the formation of lipid rafts in the plasma membrane, which brings receptor proteins in close proximity with high concentrations of second messenger molecules.  5  

In multiple layers, cholesterol and phospholipids, both electrical insulators, can facilitate speed of transmission of electrical impulses along nerve tissue. For many neuron fibers, a myelin sheath, rich in cholesterol since it is derived from compacted layers of Schwann cell membrane, provides insulation for more efficient conduction of impulses.  6 

Figure 2.47. Insertion of cholesterol in a membrane.

Figure 4.  Insertion of cholesterol in a membrane

Cholesterol inserts into the membrane with its polar hydroxyl group close to the polar head groups of the phospholipids.

Organelles of the Human Cell

An organelle is a specialized sub-unit within a cell that serves a specific function.  Most organelles of the cell are covered by membranes composed primarily of lipids and proteins.

Organelles either have a single-membrane compartment or a double-membrane compartment. 

There are 10 organelles in the human cell that have either a single or double membrane.  There are 3 organelles with double membranes and 7 organelles with single membranes.  The organelles of the cell with membranes are as follows:

Organelle

Function

Membrane Structure

Autophagosome

vesicle that sequesters cytoplasmic material and organelles for degradation

Double membrane

Endoplasmic reticulum

translation and folding of new proteins (rough endoplasmic reticulum), expression of lipids (smooth endoplasmic reticulum)

Single membrane

Golgi apparatus

sorting, packaging, processing and modification of proteins

Single membrane

Lysosomes

breakdown of large molecules (e.g., proteins + polysaccharides)

Single membrane

Melanosome

pigment storage

Single membrane

Mitochondria

energy production from the oxidation of glucose substances and the release of adenosine triphosphate

Double membrane

Nucleus

DNA maintenance, controls all activities of the cell, RNA transcription

Double membrane

Peroxisome

breakdown of metabolic hydrogen peroxide

Single membrane

Vacoule

storage, transportation, helps maintain homeostasis

Single membrane

Vesicle

material transport

Single membrane

Organelles with double membranes are often critical to the function of the cell, each serveing a different purpose.  There are 3 organelles that have double membranes:

  • Mitochondria

  • Nucleus

  • Autophagosome

Mitochondria

A mitochondrion (singular for mitochondria) contains outer and inner membranes composed of phospholipid bilayers and proteins.   Due to the double membrane structure of the mitochondrion, there are five distinct parts to a mitochondrion. They are:

  • the outer mitochondrial membrane
  • the intermembrane space (the space between the outer and inner membranes)
  • the inner mitochondrial membrane
  • the cristae space (formed by infoldings of the inner membrane)
  • the matrix (space within the inner membrane)

The mitochondrial membrane contains the major classes of phospholipids found in all cell membranes, including phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine, and phosphatidic acid, as well as phosphatidylglycerol, the precursor for cardiolipin; which is predominantly located in the mitochondria.

The outer mitochondrial membrane, which encloses the entire organelle, has a protein-to-phospholipid ratio similar to that of the human plasma membrane (about 1:1 by weight). It contains large numbers of integral membrane proteins called porins.

In the inner mitochondrial membrane, the protein-to-lipid ratio is 80:20, in contrast to the outer membrane, which is 50:50.  7 

The inner membrane is rich in cardiolipin.  Cardiolipin contains four fatty acids rather than two, and may help to make the inner membrane impermeable.  Unlike the outer membrane, the inner membrane doesn’t contain porins, and is highly impermeable to all molecules.

Nuclear Membrane

The nuclear envelope, otherwise known as nuclear membrane, consists of two cellular membranes, an inner and an outer membrane, arranged parallel to one another and separated by 10 to 50 nanometres (nm). The nuclear envelope completely encloses the nucleus and separates the cell’s genetic material from the surrounding cytoplasm, serving as a barrier to prevent macromolecules from diffusing freely between the nucleoplasm and the cytoplasm. 8   The outer nuclear membrane is continuous with the membrane of the rough endoplasmic reticulum.

Autophagosome

An autophagosome is a spherical structure with double layer membranes. It is the key structure in macro autophagy, the intracellular degradation system for cytoplasmic contents (e.g., abnormal intracellular proteins, excess or damaged organelles) and also for invading microorganisms.

After formation, autophagosomes deliver cytoplasmic components to the lysosomes. The outer membrane of an autophagosome fuses with a lysosome to form an autolysosome. The lysosome’s hydrolases degrade the autophagosome-delivered contents and its inner membrane.  9

Damage and Degradation to the Cell Membrane

When cell membranes are intact their receptor surface is able to perform all necessary functions. Communication between cells, and even within the cell components, flows easily. Once the membrane is damaged this communication is disrupted, and the cell cannot function properly, due to the failure of cellular signaling. 

There are a number ways in which cell membranes can be damaged, which eventually leads to pathology and illness.  This is true of both the cell and its outer membrane barrier or cell membrane, and the membrane structures inside the cell.  Various factors can contribute to damage to the cell membrane, such as:

  • Acetaldehyde
  • Aging
  • Alcohol
  • Excessive Saturated Fatty Acids
  • Lipid peroxidation
  • Oxidization of cell membrane
  • Recreational Drugs
  • Smoking
  • Toxin exposure (toxins stored in the lipid environment)
  • Trans-fatty acids  10  11

Aging causes detrimental changes in membrane phospholipid composition. Phosphatidylcholine is one of the main types of phospholipids in the cell membrane, and its concentration within the cell membrane decreases with age, whereas sphingomyelin and cholesterol both increase with age. 

The changes in the relative amounts of phosphatidylcholine and sphingomyelin are especially great in tissues. Plasma membranes associated with the aorta and arterial wall show a 6-fold decrease in phosphatidylcholine and sphingomyelin ratio with aging. Sphingomyelin also increases in several diseases, including atherosclerosis. The sphingomyelin content can be as high as 70-80% of the total phospholipids in advanced aortic lesion.  12  

Decreased cell membrane fluidity and decomposition of cell membrane integrity, as well as break down of cell membrane repair mechanisms, are associated with various disorders, including liver disease, atherosclerosis, several cancers and ultimately cell death.

Fatty acids within the cell membrane degrade when dietary fats are either oxidized (lipid peroxides can form within the body as well) or contain trans fatty acids.

Plasma membranes are one of the preferential targets of reactive oxygen species which cause lipid peroxidation. This process modifies membrane properties such as fluidity, a very important physical feature known to modulate membrane protein localization and function.  13  

Numerous reports have established that lipid peroxidation contributes to cell injury by altering the basic physical properties and structural organization of membrane components. Oxidative modification of polyunsaturated phospholipids has been shown, in particular, to alter the intermolecular packing, thermodynamic, and phase parameters of the membrane bilayer.  14  15

Damage to the Double Membrane Structure of the Mitochondria

Damage to mitochondrial components, especially the delicate inner mitochondrial membrane, leads to the release of toxic proteins, including caspases and other enzymes. These proteins are normally confined in the mitochondria, but once released these proteins go through several steps that trigger the formation of a potent inflammatory molecular complex called an inflammasome.

New evidence has placed inflammasomes at the center stage of complex diseases like metabolic syndrome and cancer, as well as the regulation of the microbial ecology in the intestine and the production of ATP.  16 

Once the inner membrane of the mitochondria is damaged, its core ability to produce energy in the form of ATP and to maintain optimal mitochondrial nutrient uptake and utilization necessary for ATP production are impaired.

The inner mitochondrial membrane is also one of the most sensitive membranes of the cell to oxidative damage. This is because of its unique membrane structure and the presence of a very oxidation-sensitive phospholipid, cardiolipin. Cardiolipin is functionally required for the electron transport system. 

When mitochondrial cardiolipin and to a lesser degree other phosphatidyl phospholipids are damaged by oxidation, the chemical/electrical potential across the inner mitochondrial membrane is altered due to an increasingly “leaky” membrane that allows protons and ions to move across the membrane. This occurs because the oxidized membrane phospholipids no longer form a tight ionic/electrical “seal” or barrier.

Significant oxidative damage to mitochondrial membranes represents the point-of-no-return of programmed cell death pathways that culminate in apoptosis or regulated cell death leading to necrosis.  17

Repairing the Damaged Cell Membrane with Lipid Replacement Therapy®

The good news is that damaged lipids can be replaced.  In fact, a young healthy cell usually replaces damaged lipids in its membranes.  However, due to aging, eating a poor diet, exposure to environmental toxins, getting infections and certain illnesses, it becomes necessary to proactively replace the damaged lipids with new lipids. 

This can be done using Lipid Replacement Therapy (LRT®), which provides for the consumption of lipids that are the same as found in the cell membrane and organelle membranes. 

A product developed and manufactured by Nutritional Therapeutics Inc., called NTFactor®, is intended to reverse the damage done to our cells and mitochondria by oxidative stress through the process of Lipid Replacement Therapy®.

The NTFactor® formula is a unique combination that allows the healthy phospholipids to stay intact during transport through the body.

NT Factor Lipids® is based on U.S. Patent No. 8,877,239.  The lipid blend of NTFactor® includes:

  • Phosphatidic acid (PA)
  • Phosphatidyl-choline (PC)
  • Phosphatidyl-ethanolamine (PE)
  • Phosphatidyl-glycerol(PG) – (precursor for cardiolipin (CL))
  • Phosphatidyl-inositol (PI)
  • Phosphatidyl-serine (PS)
  • Digalactosyldiacylglyceride (DGDG)
  • Monoglactosyldiacylglyceride (MGDG)

NTFactor® uses a form of a stable oral supplement that emulates the amount and composition of the mitochondrial lipids assures that inappropriate oxidative membrane damage is prevented, damaged membrane phospholipids are replaced and mitochondrial membrane permeability is maintained in the optimal range.

Obtaining Phospholycolipids through Diet

Phospholycolipids can be obtained generally in the diet from meat, egg yolks, fish, turkey, chicken and beef.  Organ meats and egg yolks are among the best food sources of phosphoglycolipids, however, one would have to consume large portions of these foods at every meal to obtain the benefit of lipid replacement, which is unlikely and unhealthy.

The various lipids can be found in the following foods:

Phosphatidylcholine

Phosphatidylcholine can be obtained from egg yolk or soybeans.  Phosphatidylcholine is a major component of egg, soy and sunflower lecithin. 

Lecithin’s are mostly phospholipids, composed of phosphoric acid with choline, glycerol or other fatty acids usually glycolipids or triglyceride. Glycerophospholipids in lecithin include phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine, and phosphatidic acid.

Phosphatidylethanolamine

Phosphatidylethanolamine is primarily found in lecithin.

Phosphatidylinositol

Phosphatidylinositol can be found in lecithin. 

Phosphatidylserine

Phosphatidylserine can be found in meat and fish. Only small amounts of phosphatidylserine can be found in dairy products or in vegetables, with the exception of white beans and soy lecithin.

Phosphatidylserine (PS) content in different foods

Food

PS Content in mg/100 g

Bovine brain

713

Atlantic mackerel

480

Chicken heart

414

Atlantic herring

360

Eel

335

Offal (average value)

305

Pig‘s spleen

239

Pig’s kidney

218

Tuna

194

Chicken leg, with skin, without bone

134

Chicken liver

123

White beans

107

Soft-shell clam

87

Chicken breast, with skin

85

Mullet

76

Veal

72

Beef

69

Pork

57

Pig’s liver

50

Turkey leg, without skin or bone

50

Turkey breast without skin

45

Crayfish

40

Cuttlefish

31

Atlantic cod

28

Anchovy

25

Whole grain barley

20

European hake

17

European pilchard (sardine)

16

Trout

14

Rice (unpolished)

3

Carrot

2

Ewe‘s Milk

2

Cow‘s Milk (whole, 3.5% fat)

1

Potato

1

 (Source:  Souci SW, Fachmann E, Kraut H (2008). Food Composition and Nutrition Tables. Medpharm Scientific Publishers Stuttgart)

Sphingomyelin

Sphingomyelin can be obtained from eggs or bovine brain.

Cholesterol

All animal-based foods contain cholesterol in varying amounts.  Cholesterol can be obtained from cheese, egg yolks, beef, pork, poultry, fish, and shrimp.  Cholesterol is not found in plant-based foods.   

#29 Garth Nicolson: How to Repair Mitochondria with Lipid Replacement