Short-Chain Fatty Acids
A considerable amount of scientific interest has been focused on short chain fatty acids (SCFAs) for improving colonic and systemic health, and specifically reducing the risk of inflammatory diseases, diabetes, and cardiovascular disease.
Researchers have shown that SCFAs have distinct physiological effects: 1
- they contribute to shaping the gut environment
- they influence the physiology of the colon
- they can be used as energy sources by host cells and the intestinal microbiota
- they also participate in different host-signaling mechanisms
Prebiotics, which consist of primarily dietary carbohydrates such as resistant starch and dietary fibers, are the substrates in the large intestine for fermentation that produce SCFAs. The other source of SCFA, although in smaller amounts than dietary carbohydrates, are amino acids. Three amino acids:
obtained from protein breakdown can be converted into isobutyrate, isovalerate, and 2-methyl butyrate, known as branched-chain SCFAs (BSCFAs), which contribute very little (5%) to total SCFA production. 2
There are seven short-chain fatty acids that are produced by the large intestine through the fermentation of dietary fiber and resistant starch. Of these seven short-chain fatty acids, three of them are the most important and common:
These three represent about 90–95% of the SCFA present in the colon. The rate and amount of SCFA production depends on the species and amounts of microflora present in the colon, the substrate source and gut transit time.
Butyrate is the major energy source for colonocytes. Propionate is largely taken up by the liver. Acetate enters the peripheral circulation to be metabolized by peripheral tissues and is the principal SCFA in the colon, and after absorption it has been shown to increase cholesterol synthesis.
Figure 1. Fibers, specific oligosaccharides and resistant starch reach the colon intact, where they induce shifts in the composition and function of intestinal bacteria (shifts indicated by different colors). Intestinal bacteria use these compounds as substrates for the production of the short-chain fatty acids acetate, propionate and butyrate. These microbial metabolites are taken up by intestinal epithelial cells called enterocytes. Butyrate mainly feeds the enterocytes, whereas acetate and propionate reach the liver by the portal vein. (Source: You are what you eat, Nature Biotechnology 32, 243–245 (2014) doi:10.1038/nbt.2845)
Butyrate (Butyric Acid)
The most important short-chain fatty acid is butyrate.
Butyrate is a primary energy source for colonic cells. 3 4 Butyrate also has demonstrated anti-inflammatory properties. 5 Butyrate may also have a role in preventing certain types of colitis. A diet low in resistant starch and fiber, which will result in a low production of SCFAs in the colon, may explain the high occurrence of colonic disorders seen in the Western civilization. 6
Studies have demonstrated that butyrate has anti-carcinogenic properties:
- It inhibits the growth and proliferation of tumor cell lines in vitro. 7
- It induces differentiation of tumor cells, producing a phenotype similar to that of the normal mature cell. 8
- It induces apoptosis or programmed cell death of human colorectal cancer cells. 9 10
- It inhibits angiogenesis by inactivating Sp1 transcription factor activity and down regulating VEGF gene expression. 11
Butyrate has been studied for its role in nourishing the colonic mucosa and in the prevention of cancer of the colon, by promoting cell differentiation, cell-cycle arrest and apoptosis of transformed colonocytes; inhibiting the enzyme histone deacetylase and decreasing the transformation of primary to secondary bile acids as a result of colonic acidification.
Therefore, a greater increase in SCFA production and potentially a greater delivery of SCFA, specifically butyrate, to the distal colon may result in a protective effect. 12
Butyrate is mainly taken up by the colon epithelial cells, only small amounts reach the portal vein and the systemic circulation. The primary beneficial effects of butyrate occurs at the intestinal level, yet there are additional benefits at the extra intestinal level:
- Is the preferred energy source for the colon epithelial cells
- Decreases the pH of the colon (which decreases bile salt solubility, increases mineral absorption, decreases ammonia absorption, and inhibits growth of pathogens)
- Stimulates proliferation of normal colon epithelial cells
- Prevents proliferation and induces apoptosis of colorectal cancer cells
- Affects gene expression of colon epithelial cells
- Plays a protective role against colon cancer and colitis
- Improves the gut barrier function by stimulation of the formation of mucin, antimicrobial peptides, and tight-junction proteins
- Interacts with the immune system and regulates immune function
- Has anti-inflammatory effects
- Stimulates the absorption of water and sodium
- Reduces oxidative stress in the colon
- Assists in ion absorption
- Assists in proper intestinal motility
- Induces cell cycle arrest, differentiation, and apoptosis in colon cancer cells
Figure 2. The multiple effects of butyrate at the intestinal level. (Source: Potential beneficial effects of butyrate in intestinal and extra intestinal diseases)
Extra intestinal effects 13
- Insulin sensitivity
- Cholesterol synthesis
- Energy expenditure
- Ammonia scavenger
- Stimulation of β-oxidation of very long chain fatty acids and peroxisome proliferation
- CFTR function
- HbF production
The major problem with butyrate is achieving high concentrations in the blood. Butyrate is metabolized rapidly as soon as it enters the enteroocytes via its active transport system, and its plasma concentrations are far below those required to exert its antiproliferative/differentiating actions. 14
An alternative and more advantageous form of butyric acid is the triglycerine form called Tributyrin, also known as glyceryl tributyrate. Tributyrin is a triglyceride containing 3 molecules of butyric acid which are bound by a glycerol molecule.
Tributyrin is naturally present in butter in trace amounts. However, it is not recommended to consume butter as a means to obtain therapeutic amounts of tributyrin. There is no point to recommend consuming butter to someone if the intention is to increase butyric acid consumption.
As an alternative to consuming butter, tributyrin can now be consumed in the form of a supplement or a food additive and can provide considerable amounts of butyrate to the intestine in addition to the endogenous production of SCFAs (butyrate) from the fermentation of dietary fibers.
Tributyrin is known to overcome the pharmacokinetic drawbacks of butyrate. Because it is rapidly absorbed and chemically stable in plasma, tributyrin diffuses through biological membranes and is metabolized by intracellular lipases, releasing therapeutically effective butyrate over time directly into the cell.
Figure 3. Ball-and-stick model of the tributyrin molecule, the triglyceride of butyric acid. Source: By Jynto (talk) – Own workThis chemical image was created with Discovery Studio Visualizer., CC0, https://commons.wikimedia.org/w/index.php?curid=20234384
The technique of attaching butyrate to a glycerol molecule turns the new molecule (tributyrin) into a fat. The attachment of a glycerol molecule to 3 butyric acid molecules is through an ester bond which can only be broken by a specific enzyme called pancreatic lipase.
Pancreatic lipase is secreted from the pancreas into the small intestine (duodenum) and not in the stomach. Because of this, tributyrin stays intact in the stomach but once it reaches the small intestine (duodenum), the 3 butyric acid molecules are released by the pancreatic lipase enzyme.
After the pancreatic lipase action, two free butyric acid molecules and one monobutyrin molecule are formed where they are used in the intestine and taken up by the enterocytes. After transportation through the portal vein they are metabolized in the liver.
Figure 4. Ester bond of glycerol and 3 butyric acid molecules. (Source: Bioremediation of Fats and Oils)
The tributyrin form of butyrate ensures high bioavailability of butyrate in all the sections of the small intestine. Because tributyrin is a delayed release source of butyrate, it achieves more sustained plasma levels.
According the the U.S. Federal Drug Administration (FDA), tributyrin is a food substance affirmed as Generally Recognized As Safe (GRAS). 15
Multiple Health Benefits of Tributyrin
Specific studies on tributyrin have demonstrated multiple benefits in a number of disease conditions by releasing therapeutically effective butyrate over time directly into the cell. The advantage with tributyrin is that it has all the health benefits of butyrate, as evidenced above, as well as its own specific targeted health benefits.
Some of the more important and specific health benefits of tributyrin include:
- Anticarcinogenic potential
- Colon cancer
- Liver cancer (apoptosis)
- Alzheimer’s disease and Dementia
- Antibiotic-associated diarrhea (AAD)
- Lipopolysaccharide (LPS)-induced liver injury
In vitro and in vivo studies have shown that tributyrin acts on multiple anticancer cellular and molecular targets without affecting non-cancerous cells. The mechanisms of action of tributyrin as a anticarcinogenic agent include: 16
- the induction of apoptosis
- cell differentiation
- the modulation of epigenetic mechanisms
Due to the minimum toxicity profile of tributyrin, it is an excellent candidate for combination therapy with other agents for the control of cancer.
Tributyrin was shown to be more potent in inhibiting growth and inducing cell differentiation than natural butyrate on growth, differentiation and vitamin D receptor expression in Caco-2 cells, a human colon cancer cell line. 17
Tributyrin provides a useful therapeutic approach in chemoprevention and treatment of colorectal cancer.
In another in vitro study, tributyrin showed potent antiproliferative, proapoptotic and differentiation-inducing effects in neoplastic cells. 18
In this study monobutyrin (MB) and tributyrin (TB) were studied in vitro for their effects on inducing differentiation of human myeloid leukemia HL60 cells and murine erythroleukemia cells. On a molar basis TB was about 4-fold more potent than either BA or MB for inducing differentiation of HL60 cells. BA, MB, or TB induced erythroid differentiation of murine erythroleukemia cells. 19
A study from February 2011 sought to investigate a possibility to develop tributyrin emulsion as a potent anti-cancer agent against melanoma. Tributyrin emulsion was more potent than butyrate in inhibiting the growth of B16-F10 melanoma cells. Accumulation of cells at sub G(0)/G(1) phase and the DNA fragmentation induced by tributyrin emulsion treatment revealed that tributyrin emulsion inhibited the growth of B16-F10 cells by inducing apoptosis. Treatment with tributyrin emulsion suppressed the colony formation of melanoma cells in a dose-dependent manner. 20
The data from this study suggests that tributyrin emulsion may be developed as a potent anti-cancer agent against melanoma.
Researchers in this study from November 1999 investigated whether butyrate could induce apoptosis in transformed human liver (Hep G2) cells. Hep G2 cells treated with butyrate displayed acetylated histones, increased DNA fragmentation and morphological features consistent with apoptosis.
They also investigated whether butyrate present in tributyrin, a triacylglycerol more compatible for inclusion into colloidal lipid structures than butyrate, could also induce apoptosis in Hep G2 cells.
Tributyrin induced DNA fragmentation and morphological features characteristic of apoptotic cells in Hep G2 cells.
These results are a significant advance towards delivering butyrate via colloidal lipid particles to cancerous sites in vivo. This study showed that butyrate and tributyrin are potent apoptotic agents. 21
Alzheimer’s disease and Dementia
Recent research at MIT has determined that, in rodent models of Alzheimer’s dementia, the negative impact of amyloid beta exposure on neuronal function and new memory formation results largely from increased neuronal expression of an enzyme known as HDAC2 (histone deacetylase 2).
A study from March 2004 showed that tributyrin may have the most practical potential to inhibit HDAC by blunting microglial activation. Tributyrin is anti-inflammatory in primary, brain-derived microglial cells. A blunting of microglial cytokine production might in itself have a favorable impact on progression of Alzheimer’s. 22 23
Antibiotic-associated diarrhea (AAD)
In a recent study from November 2014, researchers hypothesized that antibiotic-induced changes in gut microbiota reduce butyrate production, varying genes involved with gut barrier integrity and water and electrolyte absorption, lending to AAD, and that simultaneous supplementation with the probiotic Lactobacillus GG and/or tributyrin would prevent these changes.
Optimizing intestinal health with Lactobacillus GG and/or tributyrin may offer a preventative therapy for AAD. 24 Lipopolysaccharide (LPS)-induced liver injury
In this study from April 2015, researchers elucidated the protective effect of oral administration of tributyrin against LPS-mediated lipid metabolism disorder in rats. Tributyrin suppresses lipopolysaccharide (LPS)-induced liver injury through attenuating nuclear factor-κB activity with an increased hepatoportal butyrate level. 25
Another study from May 2015 was carried out to investigate the effects of tributyrin (TB) on the growth performance, pro-inflammatory cytokines, intestinal morphology, energy status, disaccharidase activity, and antioxidative capacity of broilers challenged with lipopolysaccharide (LPS).
Taken together, these results suggest that the TB supplementation was able to reduce the release of pro-inflammatory cytokines and improve the energy status and anti-oxidative capacity in the small intestine of LPS-challenged broilers. 26
ELiE Health Solutions
ELiE Health Solutions, based in Sevilla, Spain, was formed through a project based on the science of the microbiota and probiotics.
ELiE Health Solutions is named after Elie Metchnikoff, famed microbiologist and the recipient of the 1908 Nobel Price in Physiology. A century ago he proposed the benefit of acid lactic bacteria to the human host and their role in health and longevity.
David Manrique, a pharmacist with ELiE Health Solutions describes the challenges of finding a more bio-available form of butyric acid:
“The challenge was to find a chemical form of enteric release of butyric acid, and also to ensure microencapsulated as slowly and delayed release possible. It has been a great innovative effort, but we are very satisfied with the results.” 27
ELiE Health Solutions was successful in developing a delayed release form of butyric acid (tributyrin) using microencapsulation technology in their product BUTYCAPS. The microencapsulation technology of BUTYCAPS allows a slower and gradual release along the intestine.
BUTYCAPS contains 900 mg of Tributyrin equivalent to 787 mg of butyric acid in each sachet. Each box contains 30 sachets. BUTYCAPS are non-chewable granules.
Figure 5. BUTYCAPS product from ELiE Health Solutions
BUTYCAPS can be purchased directly from ELiE Health Solutions.
Figure 6. Formulation process of microencapsulated tributyrin. (Source: ELiE Health Solutions)
The research and development of BUTYCAPS on the spanish Canal Sur Radio. David Manrique was interviewed on saturday the 18th of February about the technological process of BUTYCAPS and the uses of tributyrin, a triglyceride of butyric acid, for intestinal health. (In Spanish)