Category Archives: Cell Membrane

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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

The Proposed Nine Hallmarks of Aging

Scientist and researchers have attempted to identify and categorize the cellular and molecular hallmarks of aging in a published paper in the research journal Cell on 6th June 2013.  1 

In this paper, researchers proposed nine candidate hallmarks that are generally considered to contribute to the aging process and together determine the aging phenotype.

These nine hallmarks include:

  • altered intercellular communication
  • cellular senescence
  • deregulated nutrient-sensing
  • epigenetic alterations
  • genomic instability
  • loss of proteostasis
  • mitochondrial dysfunction
  • stem cell exhaustion
  • telomere attrition

large Image

The 9 Hallmarks of Aging  (Source: The Hallmarks of Aging)

Researchers set three criteria for each ‘hallmark’:  2

  • it should manifest during normal aging;
  • its experimental aggravation should accelerate aging; and
  • its experimental amelioration should retard the normal aging process and, hence, increase healthy lifespan.

The challenge that the researchers encountered was to show the interconnectedness between the candidate hallmarks and their relative contribution to aging.  The ultimate goal of the research was to “identifying pharmaceutical targets to improve human health during aging with minimal side-effects.”  3

A clear and easy to understand article on the nine Hallmarks of Aging was published by Geroscience.com on 23rd February 2017.  This article, written by Alexandra Bause, PhD, examines each of the nine hallmarks in plain English and provides a better understanding beyond the original publication in the journal Cell.   

Despite the fact that these hallmarks can be complex and complicated and the understanding of them are still limited, there is hope that new medical strategies will emerge that will ameliorate the the normal aging process.

Geroscience.com is the premier site for news, discussion, and scientific insight related to the basic biology of aging and the development of new medicines with the ability to cure or prevent the diseases of aging.

Geroscience.com is committed to bringing its readers the most interesting developments in the science of aging and will: 4

  • Feature a wide range of multimedia content including interviews with experts, looks behind the scenes of everyday lab life, and the latest trends from longevity conferences
  • Capture the perspectives of leading researchers, entrepreneurs, and other experts to act as a platform to share ideas about aging and longevity
  • Cover the emerging biotechnology business of geroscience, including investment coverage, clinical trial data, and insight into the regulatory world
  • Aid collaboration between cross-functional scientific communities, connecting researchers, investors, and industry heads from around the globe

  

Read the article at Geroscience.com:

The hallmarks of aging, in plain English, by Alexandra Bause, PhD at Geroscience.com

 

Oxidative DNA Damage Assessed by Concentrations of 8-Oxo-2′-deoxyguanosine in the Cell

Oxidative damage of DNA has been implicated as a fundamental cause of the physiologic changes and degenerative diseases associated with aging.  When DNA is impacted by oxidative stress, the chemical 8-Oxo-2′-deoxyguanosine (8-oxo-dG) is produced as a byproduct.

Becasue 8-oxo-dG is a major product of DNA oxidation, concentrations of 8-oxo-dG within a cell is a ubiquitous marker and measurement of oxidative stress. 

8-oxo-dG increases with age in DNA of mammalian tissues.  1   8-oxo-dG increases in both mitochonndrial DNA and nuclear DNA with age.  2  DNA is probably the most biologically significant target of oxidative attack and may be implicated in aging, carcinogenesis and other degenerative diseases.  Environmental factors, lifestyle choices such as smoking and recreational drugs, and some pharmaceuticals have also been associated with elevated urine levels of 8-oxo-dG.   For example, according to multiple regression analysis, smokers excreted 50% (31–69%; 95% confidence interval) more 8-oxo-dG than non-smokers.  The results suggest that smoking increases oxidative DNA damage by ∼50%.  3

Exposure to various environmental factors can increase 8-oxo-dG. These environmental factors include, but are not limited to:

  • ionizing radiation (such as indoor radon)
  • asbestos
  • toxic metals
  • metal fumes (such as manganese, chromium and vanadium)
  • diesel exhaust
  • benzene
  • styrene
  • toluene
  • zylenes

8-oxo-dG is the most frequently detected and studied oxidized nucleoside of DNA that is considered to be premutagenic due to its potential for initiation and promotion of carcinogenesis. 8-oxo-dG have been associated with numerous pathological processes including:

  • cystic fibrosis
  • atopic dermatitis
  • rheumatoid arthritis
  • pancreatitis
  • chronic hepatitis
  • hyperglycemia
  • inflammatory bowel disease
  • Parkinson’s disease
  • Alzheimer’s disease
  • Huntington’s disease
  • bladder cancer
  • prostate cancer

8-oxo-dG can be assessed by taking a urine test issued by a licensed medical professional and administered by a qualified medical lab.  (See Informational References)

When 8-oxo-dG levels are elevated, the identity of the sources of oxidative stress should be determined and mitigated as much as possible. 

The second step to reducing 8-oxo-dG levels is to consume foods high in antioxidants and when necessary add antioxidant supplements. 

Various research studies have identified certain natural substances that have been identified to reduce levels of 8-oxo-dG:

  • Vitamin C  4
  • Coenzyme Q10  5
  • Glutathione  6
  • Tomato juice  7 
  • Allylisothiocyanate (AITC) (found in some Brassica vegetables, including cabbage, mustard, Brussels sprouts, kale, and cauliflower)   8
  • Pomegranates  9
  • Green tea  10
  • Alpha Lipoic Acid  11
  • Olive oil  12
  • Calorie restriction  13
  • Polypodium leucotomos  14  

The Importance of Maintaining the 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.

myelin

Myelin sheath

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

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 fir 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.

Table 1 illustrates the composition of the myelin in a human as compared to a bovine and rat:

Table 1  Composition of CNS Myelin and Brain

  Myelin White matter  
Substancea  Human Bovine Rat Human Bovine Gray matter 

(human)

Protein 30.0 24.7 29.5 39.0 39.5 55.3
Lipid 70.0 75.3 70.5 54.9 55.0 32.7
Cholesterol 27.7 28.1 27.3 27.5 23.6 22.0
Cerebroside 22.7 24.0 23.7 19.8 22.5 5.4
Sulfatide 3.8 3.6 7.1 5.4 5.0 1.7
Total galactolipid 27.5 29.3 31.5 26.4 28.6 7.3
Ethanolamine phosphatides 15.6 17.4 16.7 14.9 13.6 22.7
Lecithin 11.2 10.9 11.3 12.8 12.9 26.7
Sphingomyelin 7.9 7.1 3.2 7.7 6.7 6.9
Phosphatidylserine 4.8 6.5 7.0 7.9 11.4 8.7
Phosphatidylinositol 0.6 0.8 1.2 0.9 0.9 2.7
Plasmalogensb 12.3 14.1 14.1 11.2 12.2 8.8
Total phospholipid 43.1 43.0 44.0 45.9 46.3 69.5

a Protein and lipid figures in percent dry weight; all others in percent total lipid weight.
b  Plasmalogens are primarily ethanolamine phosphatides.

Source: 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; Copyright © 1999, American Society for Neurochemistry

There are a number of natural substances that have been researched and studied for their ability to enhance the function of the myelin sheath:

How Myelin Sheaths speed up the Action Potential

Neurons, Axons, Myelin Sheath and Demyelinisation

Repairing the Cell Membrane

The human cell membrane separates the interior of all cells from the outside environment of the cell called the extracellular matrix.

The fundamental building blocks of all cell membranes are phospholipids.

 

Phospholipids are a class of lipids that are a major component of all cell membranes. They can form lipid bilayers because of their amphiphilic characteristic. The structure of the phospholipid molecule generally consists of two hydrophobic fatty acid “tails” and a hydrophilic “head”, joined together by a glycerol molecule.

About 50% of the mass of most cell membranes are composed of phospholipids.

They include:

  • Phosphatidyl-choline (PC)
  • Phosphatidyl-ethanolamine (PE)
  • Phosphatidyl-glycerol(PG) (precursor to Cardiolipin)
  • Phosphatidyl-inositol (PI)
  • Phosphatidyl-serine (PS)

Forty percent of the total lipid content of the cell membrane consists of glycolipids and cholesterol. The glycolipids include:

  • Digalactosyldiacylglyceride (DGDG)
  • Monogalactosyldiacylglycerol (MGDG)

Adequate intake of phospholipids and glycolipids is important for the integrity of the cell membranes. A therapy called Lipid Replacement Therapy (LRT®) consists of replacing the appropriate lipids and glycolipids by oral supplementation. [i]

Lecithin contains a balanced amount of phospholipids and glycolipids. Lecithin consists of phospholipids such as phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, Phosphatidic acid, other minor phospholipids and glycolipids.

The substances in the Table below have been researched for their ability to maintain and repair the cell membrane.

Table:  Nutraceuticals/Foods/Herbs that Enhance the Function of and Repair the Cell Membrane

Cell Membrane

 

 

Catagory

Nutraceuticals/Foods/Herbs

Reference(s)

Amino Acids

 

 

 

Carnosine

 1

 

Taurine

 2

Herbs

 

 

 

Ginko Biloba

 3

Lipids

 

 

 

Phosphatidyl-choline (PC)

 4

 

Phosphatidyl-ethanolamine (PE)

 4

 

Phosphatidyl-glycerol(PG) (precursor to Cardiolipin)

 4

 

Phosphatidyl-inositol (PI)

 4

 

Phosphatidyl-serine (PS)

 4

 

Digalactosyldiacylglyceride (DGDG)

 4

 

Monoglactosyldiacylglyceride (MGDG)

 4

 

Omega 3 Fatty Acids

 5

Minerals

 

 

 

Calcium 2-AEP

 6

 

Chromium Picolinate

 7

 

Germanium (Ge-132)

 8

 

Zinc

 9

Nootropic

 

 

 

Dimethylaminoethanol (DMAE)

 10

Vitamins

 

 

 

Alpha-GPC (Choline)

 11

 

Vitamin E

 12

A mitochondrion contains outer and inner membranes composed of phospholipid bilayers and proteins.

The inner and outer mitochondrial membrane contains the major classes of phospholipids found in all cell membranes:

  • Phosphatidylcholine (PC)
  • Phosphatidylethanolamine (PE)
  • Phosphatidylinositol (PI)
  • Phosphatidylserine (PS)
  • Phosphatidic acid (PA)
  • Phosphatidylglycerol (PG), the precursor for Cardiolipin (CL)

The inner mitochondrial membrane can be subject to oxidative damage due to the presence of a very oxidation-sensitive phospholipid named Cardiolipin which represents 20% of the total lipid composition of the inner mitochondrial membrane.

Cardiolipin is functionally required for the electron transport system, and it is synthesized inside the mitochondria from two phosphatidylglyerol molecules.

The inner mitochondrial membrane can become damaged and altered due to an increasingly “leaky” membrane. This is caused when Cardiolipin is damaged by oxidation.

Once the Cardiolipin in the inner mitochondrial membrane becomes oxidized, the membrane become compromised and no longer form a tight ionic/electrical “seal” or barrier. With the loss of this ionic/electrical barrier the mitochondria losses electron transport and cellular energy. Ultimately this could result in cell death.

The substances in the Table below have been researched for their ability to enhance the function of Cardiolipin.

Table: Nutraceuticals that Enhance the Function of Cardiolipin

Cardiolipin

 

 

Category

Nutraceuticals

Reference(s)

Amino Acids

 

 

 

Acetyl-L-Carnitine (ALCAR)

 12

Hormones

 

 

 

Melatonin

 13

Vitamins

 

 

 

CDP-Choline

 14 15


References:

[i] Nicolson GL, Ellithrope R. Lipid replacement and antioxidant nutritional therapy for restoring mitochondrial function and reducing fatigue in chronic fatigue syndrome and other fatiguing illnesses. J. Chronic Fatigue Syndr. 2006;13(1): 57-68. 

Ellithorpe RA, Settineri R, Mitchell CA, Jacques B, Ellithorpe E, Nicolson GL. Lipid replacement therapy drink containing a glycophospholipid formulation rapidly and significantly reduces fatigue while improving energy and mental clarity. Funct Food Health Dis. 2011;1(8): 245-254.

Nicolson GL, Ellithorpe R, Ayson-Mitchell C, Jacques B, Settineri R. Lipid Replacement Therapy with a Glycophospholipid-Antioxidant-Vitamin Formulation Significantly Reduces Fatigue Within One Week. J Am Nutraceut Assoc. 2010;13(1):10-14.

Piper BF, Dibble SL, Dodd MJ, Weiss MC, Slaughter RE, Paul SM. The revised Piper Fatigue Scale: psychometric evaluation in women with breast cancer. Oncol Nurs Forum. 1998;25(4):677-684.

Agadjanyan M, Vasilevko V, Ghochikyan A, Berns P, Kesslak P, Settineri R, Nicolson GL. Nutritional supplement (NTFactor) restores mitochondrial function and reduces moderately severe fatigue in aged subjects. J Chronic Fatigue Syndr 2003;11(3):23-26.


Resources:

Allergy Research Group – NTFactor® EnergyLipids Chewables


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Glut2

Glutathione molecule (3D Balls)

“It’s the most important molecule you need to stay healthy and prevent disease — yet you’ve probably never heard of it. It’s the secret to prevent aging, cancer, heart disease, dementia and more, and necessary to treat everything from autism to Alzheimer’s disease. There are more than 89,000 medical articles about it — but your doctor doesn’t know how address the epidemic deficiency of this critical life-giving molecule …”
Excerpt from Glutathione: The Mother of All Antioxidants

Read this important article from Dr. Mark Hyman, M.D. published on April 10. 2010 in The Huffington Post:

Glutathione: The Mother of All Antioxidants


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The Dangers of Lipid Peroxidation

Peroxidized Fats are endogenous or exogenous fats (Fatty Acids) that have been damaged by oxygen free radicals.

The cell membrane consists primarily of layers of phospholipids.  Free radicals can attack the cell membranes, causing lipid peroxidation of the fatty acids that compose the cell membrane, resulting in injury and eventual death of the cell.

The end products of lipid peroxidation are reactive aldehydes, such as:

  • Malondialdehyde (MDA)
  • 4-hydroxynonenal (HNE)

Malondialdehyde (MDA)

Malondialdehyde (MDA) is the organic compound with the formula CH2(CHO)2. This reactive species occurs naturally and is a marker for oxidative stress. Malonaldehyde (which comprises 50% of Lipofuscin) is formed as a breakdown product of Peroxidized Polyunsaturated Fats. This compound is a reactive aldehyde and is one of the many reactive electrophile species that cause toxic stress in cells and form covalent protein adducts referred to as advanced lipoxidation end-products (ALE), in analogy to advanced glycation end-products (AGE). Malondialdehyde is reactive and potentially mutagenic. It has been found in heated edible oils such as sunflower and palm oils.

4-Hydroxynonenal

4-Hydroxynonenal, or 4-hydroxy-2-nonenal or 4-HNE or HNE, (C9H16O2), is an α,β-unsaturated hydroxyalkenal that is produced by lipid peroxidation in cells. 4-HNE is the primary alpha,beta-unsaturated hydroxyalkenal formed in this process.

Lipid peroxidation alters the physiological functions of cell membranes and plays an important role in cellular membrane damage. Peroxidation is believed to be involved in cellular aging and in various diseases, such as Parkinson’s and Alzheimer’s disease as well as schizophrenia, atherosclerosis, inflammatory diseases, and cardiac ischemia reperfusion injury. Unsaturated lipids are easily susceptible to peroxidation. One of the most important mechanisms of membrane damage results from the action of free radicals on the unsaturated lipids in membranes. This leads to an autocatalytic chain reaction called lipid peroxidation which causes widespread damage. The cell has several important protective mechanisms against this type of injury.

Heating causes the oil to undergo a series of chemical reactions like oxidation, hydrolysis and polymerization. During this process, many oxidative products such as hydroperoxide and aldehydes are produced, which can be absorbed into the fried food.

Exposure of Fatty Acids to Light may accelerate their peroxidation.

There are certain substances that have been studied to counteract the toxic effects of lipid peroxidation.  The downloadable Table below list these substances.

[embeddoc url=”http://biofoundations.org/wp-content/uploads/2015/08/LipidPeroxidationTable.pdf” download=”all” viewer=”google”]

References:

Lipid peroxidation in aging brain and Alzheimer’s disease.

Koner, B. C. (2008), Effect of Different Cooking Vessels on Heat-Induced Lipid Peroxidation of Different Edible Oils” Journal of Food Biochemistry, 32: 740–751. doi: 10.1111/j.1745-4514.2008.00195.x

Chemistry of Deep-Fat Frying Oils

Chemistry and Reactions of Reactive Oxygen Species in Foods

Repeatedly Heated Vegetable Oils and Lipid Peroxidation Kamsiah Jaarin and Yusof Kamisah Department of Pharmacology, Faculty of Medicine

Determination of lipid oxidation products in vegetable oils and marine omega-3 supplements


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Aging causes detrimental changes in membrane phospholipid composition

Dan Carter, a naturopathic doctor from Bozeman Montana has written a two-part article on cell membrane structure and function. It is an excellent study of how normal aging causes detrimental changes in the function and structure of the cell membrane.

Dr. Carter provides various approaches on restoring and improving the state of cell membrane function.

Cell Membranes Part 1: Review of Membrane Structure and Changes with Aging By Dan Carter, ND

Cell Membranes Part 2: Restoring Cell Membrane Function By Dan Carter, ND

Dan Carter, ND, graduated from National College of Naturopathic Medicine (NCNM) and completed a 2-year family practice residency. He was appointed to a full-time faculty position in 1997 and served as a core faculty member through 2003. He has been in private practice in Bozeman, Montana since 2004 and is currently offering expert consulting services focusing on cardiovascular disease, metabolic syndrome, hormone restoration and IV nutrient therapies. Dan has been an ACAM member since 2007 and has been a speaker at past ACAM conferences.


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Calcium 2-AEP

The calcium salt of 2-aminoethanol phosphate (Ca-AEP) is a potent sensitizer of hypothalamic function. While also a bioavailable source of calcium, a deficiency of Ca-AEP causes a loss of cellular electrical charge, negatively affecting energy output.

The calcium salt of 2-aminoethanol phosphate (Ca-AEP) has been known as vitamin M1 in German literature.

Ca-AEP is an essential factor for cell membrane integrity and cell sensitivity.

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It binds fatty acids and electrolytes to the cell membrane structure that generates the cell’s electrical charge. Studies over the past 30 years have shown that Ca-AEP is essential for neurotransmission, nerve impulse generation, and muscular contractions.*

*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure or prevent any disease.


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The Cell Membrane

The cell membrane consists of three classes of amphipathic lipids:

  • phospholipids
  • glycolipids
  • sterols

The amount of each depends upon the type of cell, but in the majority of cases phospholipids are the most abundant.

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The fatty chains in phospholipids and glycolipids usually contain an even number of carbon atoms, typically between 16 and 20. The 16- and 18-carbon fatty acids are the most common. Fatty acids may be saturated or unsaturated, with the configuration of the double bonds nearly always “cis”. The length and the degree of unsaturation of fatty acid chains have a profound effect on membrane fluidity as unsaturated lipids create a kink, preventing the fatty acids from packing together as tightly, thus decreasing the melting temperature (increasing the fluidity) of the membrane.
The membrane phospholipids incorporate fatty acids of varying length and saturation. Lipids with shorter chains and ones with more double bonds are less stiff and less viscous.

Incorporation of particular lipids, such as cholesterol and sphingomyelin, into synthetic lipid membranes is known to stiffen a membrane. Such membranes can be described as “a glass state, i.e., rigid but without crystalline order”.

  • Types of phospholipids
    • Phosphatidic acid (phosphatidate) (PA)
    • Phosphatidylethanolamine (cephalin) (PE)
    • Phosphatidylcholine (lecithin) (PC)
    • Phosphatidylserine (PS)
    • Phosphoinositides:
      • Phosphatidylinositol (PI)
      • Phosphatidylinositol phosphate (PIP)
      • Phosphatidylinositol bisphosphate (PIP2) and
      • Phosphatidylinositol triphosphate (PIP3).

Phospholipids are a major component of cell membranes. They form a lipid bilayer in which their hydrophillic (attracted to water) head areas spontaneously arrange to face the aqueous cytosol and the extracellular fluid, while their hydrophobic (repelled by water) tail areas face away from the cytosol and extracellular fluid. The lipid bilayer is semi-permeable, allowing only certain molecules to diffuse across the membrane.

Cholesterol is another lipid component of cell membranes. It helps to stiffen cell membranes and is not found in the membranes of plant cells.

Glycolipids are located on cell membrane surfaces and have a carbohydrate sugar chain attached to them. They help the cell to recognize other cells of the body.

There are 10 main types of lipids in cell membranes. Each type of cell or organelle will have a differing percentage of each lipid, protein, and carbohydrate. The main types of lipids are:

  • Cholesterol
  • Glycolipids
  • Phosphatidylcholine
  • Sphingomyelin
  • Phosphatidylethnolamine
  • Phosphatydilinositol
  • Phosphatidylserine
  • Phosphatidylglycerol
  • Diphosphatidylglycerol (Cardiolipin)
  • Phosphatidic acid

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