SweetMyx Taste Enhancers, Alapyridains?

---  Here are the other 200 blog posts ---
I was just reading announcements of new synthetic chemicals (SweetMyx) to enhance the taste and help reduce sugar and salt in "health foods".  The new taste enhancers have already been approved by industry organizations that designate the chemicals as GRAS, generally recognized as safe.  I, of course, was curious about how the SweetMyx chemicals made food taste sweeter with less added sugar.  Notice how convenient it is that the food industry has found a way to charge more for less sugar, just as labels have been changed to specifically designate "sugar added:".

Alapyridains are Taste Enhancers

I searched the chemical literature for new taste enhancers, since the chemical ingredients in SweetMyx are trade secrets and will not be disclosed on food labels.  It didn't take long to find that the likely suspects are called alapyridains.  This group of related chemicals are synthesized with a central pyridine ring familiar from the related cytosine and thymidine of nucleic acids, the plant alkaloid nicotine and the vitamin niacin.  A guanide group (half of the diabetes drug metformin, which is a biguanide) is added to make a salt enhancer, and a benzene ring is added to make a sugar enhancer.  Without these additions, the central structure inhibits the ability to taste the bitterness associated with "healthy plant antioxidants," phytochemicals and essential oils.

Will SweetMyx Just Tickle your Taste Buds?

The alapyridains that I expect to be in SweetMyx seem to be similar to common plant alkaloids, which are natural pesticides and antibiotics, i.e. phytoalexins.  So I would expect these compounds to also be antibiotics with unknown impact on our gut flora, nervous and immune systems, just like all of the medical antibiotics.  Based on the general putative structure of the taste enhancers and similarity to other molecules with known reactivities I would also expect these molecules to react with enzymes that bind sugars, e.g. glycosidases, or with hundreds of other proteins that bind to heparin, e.g. embryological growth factors, clotting factors, cytokines, amyloids, etc., etc., etc.  It would also be expected that these enhancers will encourage consumption without satiety and therefore, just as artificial sweeteners, contribute to further obesity.  In other words, these taste enhancers can be expected to have numerous, unpredictable medical and ecological side effects that will not be understood for decades.

Breast Is Still Best, but Second Best is Donor Milk Banks

--  Here are the other 200 posts on this blog --

Milk is a baby's first prebiotic and a major function of mother's milk is to prevent adult gut bacteria from inflaming a newborn's gut, before the gut is sealed up and a new immune system is developed. Formula companies scurry to get parents hooked on their expensive substitutes that promise ease of use and nutritional equivalence, but the sad truth is that these artificial milk substitutes undermine baby gut flora with tragic results.  Even in the rare cases where mothers are not able to breastfeed their babies, there is a safe alternative, donor milk banks.  This post is a plea for new parents to wise up and smell the poop.  You may need to tell hospital staff that you will be checking diapers and taking names to make sure that your baby only gets your breast milk.

Background: Up Close and Personal Birth and Breastfeeding

I have been personally and professionally concerned about the care and nurturing of babies for the past three decades.  I was introduced to breastfeeding, milk and babies by my wife.  My first faculty position was teaching premed students at Harvard and my wife was a nurse at the Harvard Medical School affiliate, Brigham and Women's Hospital.  We honeymooned near a well baby clinic in Malawi.  My three daughters were all born at home and never used formula -- they started to eat some mashed up food at about six months and continued to nurse for more than two years.  My wife worked evening shifts, she provided some pumped milk and I drove the girls back and forth, so she could nurse during her break.  She was also a La Leche League leader for more than 25 years, was co-founder of the Singapore branch of LLL and has been an International Board Certified Lactation Consultant for 20 years.  Because of our applied discussions of lactation, I also spent several years studying passive immunity and tolerance of the mucosal immune system of the gut.

First Flora

Breast milk is nutritive for the newborn, but it also establishes the baby's gut flora.  It is the quality of the gut flora, which species of bacteria, that determines if a newborn will thrive or die.  If the baby is delivered by Caesarian, then her first gut flora will resemble the nursery staff.  If she forces her way out the old fashioned way, her first flora will resemble her mother's vaginal flora.  Interestingly, as birth approaches, the mother's vaginal flora shifts toward that found in fermented dairy products, i.e. dairy probiotics.  As soon as milk starts to reach the mother's nipples prior to birth, it is colonized by lactic acid bacteria, the only bacteria that can survive in the harsh milk environment.  Thus, breast milk is the source of both food and flora, and it is not surprising that breastfed baby poop looks and smells like curds and whey.

Breast Milk Kills Adult Gut Flora

I used to enjoy watching the student perplexity when E. coli in lab experiments progressively died in contact with raw milk.  All of the ingredients in milk conspire against normal adult gut bacteria to withhold essential vitamins, minerals and macronutrients.  The baby' stomach enzymes also convert milk proteins into antimicrobial peptides, e.g. lactoferrin into lactoferricin (FKCRRWQWRMKKLGAPSITCVRRAF, note the heparin-binding domains consisting of basic amino acids, K & R.)  Human milk oligosaccharides (HMOs, bifidus factor) are abundant in breast milk and block the attachment of pathogens to the lining of the gut to prevent infection.  At the same time, milk hormones seal the intestines to prevent leakiness.

Formula Kills Pathogens with Inflammation

Formula provides macronutrients for rapid weight gain (obesity risk), but lacks the protective components of breast milk.  The result is a rapid and irreversible shift to dominant adult gut flora and the fecal smell of E. coli.  It is not surprising that the use of formula in under developed countries results in a high rate of infant mortality.  It is, however, surprising that the gut inflammation caused by formula provides enough protection to permit its use in countries with high hygiene and good water quality.

Hospital Use of Formula and Bovine Products Increases Infant Mortality

Full term babies are pretty tough and have been known to survive major calamities in addition to formula-induced inflammation.  Tiny preterm newborns are a different story and their immature GI tracts are fragile.  Unfortunately, the first line of defense for the newborn gut, newborn gut flora, is frequently ignored in neonatal intensive care nurseries, and a major killer of preterm newborns is necrotising enterocolitis (NEC), in which bacteria common to adults overruns the immature gut.  NEC is dramatically reduced by using only breast milk, but hospital nurseries change slowly and doctors, staff and parents are unaware that formula and cow's milk products put newborns at increased risk.

Night Nurses Would Rather Feed Formula

Recent studies show that newborns designated as "breast milk only" are still given bottles of formula, because night nurses don't understand the risks of formula and enjoy feeding the babies.  The mothers are not usually told that their baby received formula and inexperienced mothers fail to recognize why their baby never had normal bowel movements.  Some hospitals continue to use bovine, cow milk, products simply because they always have and they are unaware of the damage to newborn gut flora and the cause of NEC.

Donor Milk Banks

Some mothers produce more milk than their baby needs and so they arrange to donate the extra to milk banks.  The milk banks pasteurize and distribute the milk.  Many hospitals are unfamiliar with milk banks and donations have not been energetically encouraged, so both the supply and demand for donor milk are developing.  It is important to realize that newborn and premature babies have very small stomachs of only a few ounces, and some mothers can easily produce a cup of milk at each feeding.  Thus, the cost of using only breast milk by all babies for their first few days after birth is negligible compared to the risk of disease caused by formula use. 

Demand at Least Second Best

The bottom line is that parents must demand that only breast milk be used in hospitals, even if it must be from milk banks, and all parents must be able to check diapers for the yogurty smell typical of exclusively breastfed babies.

For more information see the Human Milk Banking Association of North America

200th Post — Diet, Inflammation, Disease & Gut Flora

— all 200 Posts —

I started posting to Cooling Inflammation on 21 Aug, 2008 with How Your Diet Makes You Sick or Healthy.  My impetus for writing was my growing awareness that diet was the major reason why people were sick, and that health myths were preventing people from being healthy.  Inflammation originated by diet-inflicted injury and people attributed their sickness to genetics, environmental toxins and pervasive pathogens. 

My Path to the Obvious

My research background started with plant biochemistry, including carbohydrate structural analysis and polyphenol chemistry.  At that stage I was interested in understanding how plants protected (phytoalexins) themselves from pathogens, and I expected to use this perspective to explore human innate immunity.  From there, I went on to enzymology and protein characterization, biofilm structure, plant genetic engineering and breeding, monoclonal antibody production, mycotoxin detection, stem cell analysis, passive immunity in neonates, computational modeling of collagen and heparin binding, and heparan sulfate proteoglycan inhibition by inflammation.  These were temporary foci and the research imperatives, in retrospect, prevented me from seeing the bigger pictures, although they did leave me with a broad skill set.

Perspective: Water and Surface Tension

When I finally decided to slow down, smell the flowers and start having kids, I switched from research to teaching, from university to small liberal arts college.  For the first time, I actually thought about what I was teaching and my first revelation was that after teaching biochemistry for twenty years, I didn’t understand water and surface tension.  I could provide the platitudes from the Molecular Biology of the Cell, but I couldn’t do it mechanistically with colliding, sticky, energetic water molecules in my mind or at the blackboard.  I had to develop functional explanations of hydrogen bonds, entropy and thermal energy, that translated into the structuring of a layer of water molecules responsible for hydrophobic interactions and surface tension.  I extended that to include an explanation of the two layers of water holding together cytoplasmic membranes, the tube of structured water that holds together the cylinder of stacked bases in DNA or the shrink wrapping water layer surrounding proteins.

Perspective: Heparin Binding and Amphipathy of Sugars and Basic Amino Acids

As the kids got older, I started to dabble in research again and my expertise in carbohydrate chemistry led me into cartilage (mostly the glycosaminoglycan, GAG, chondroitin sulfate) synthesis and ultimately another GAG, heparan sulfate proteoglycans (HSPGs).  I was attracted to the dynamic HSPGs, that recycled with a half-life of six hours and formed layers around chondrocytes that secreted cartilage as they burrowed/ate through living cartilage.  I learned that the heparin filled granules of mast cells could be stained with berberine, which similarly stained the heparin in basement membranes of tissues and amyloids of Alzheimer’s, atherosclerosis and diabetes.  I was led by protein modeling of collagens to the binding of heparin to proteins and the revelation that basic amino acids (heparin binding domains) and sugars (heparin) are amphipathic, i.e. they have both hydrophobic and hydrophilic regions.  This is also true of plant polyphenolics.  Thus, polyphenolics, “basic” amino acids, “hydrophobic” amino acids, and sugars will all stack together.

Amphipathic Interactions

• DNA bases stack.
• Heparin binding sites of proteins are basic amino acids (Arg, Lys).
• Sugar binding sites in enzymes and lectins are hydrophobic amino acids (Trp, Tyr, Phe).
• Nuclear translocation signals, quartets of basic amino acids, bind to receptors with tryptophans.
• Tryptophans are the most highly conserved amino acids in the same proteins across great evolutionary distances.
• Hydrophobic bonding between tryptophan and a sugar or basic amino acid is ten times greater than hydrogen or ionic bonds.
• Tryptophan/Arginine ladders zip regions of proteins together.
• Polyphenols can disrupt cellular protein interactions by binding to receptors for carbohydrates/heparin, steroid hormones, amyloids, etc.
• Heparin holds dozens of hormones to receptors and changes the shapes of proteins, e.g. clotting and complement.
• Most nucleic acid binding proteins will also bind to the more negatively charged heparin.
• Bacteria use a pair of lysines to mark proteins for export.
• Peptides containing the basic amino acids of heparin binding domains (also produced by the specificity of gastric proteases) are antimicrobial, e.g. defensins, and so are plant polyphenols.
• Many drugs are active because they are domesticated plant polyphenols.

From Heparin Binding to Antigen Presentation

As soon as I realized that basic amino acids were involved in heparin binding, I started to look for the basic amino acids (R for arginine and K for lysine in amino acid sequences) in proteins known to bind heparin.  After study of hundreds of structures, it became obvious that heparin binding domains were simply a pair of basic amino acids (RR or KK or RK) with another within a distance of six amino acids.  No particular structure was necessary, as I later deduced, since binding to the heparin provided the structure.  In fact, in many X-ray crystallographic structures, the heparin binding regions on the surface of the protein are missing, because they are not in a defined shape.  I suspected that protein antigens involved in autoimmunity and allergy might be brought into cells for presentation to the immune system by interacting with HSPGs on the surface and so started to check them out for heparin binding domains.  I was very skillful at picking out pairs of Ks or Rs within sequences of hundreds of amino acids by that time, so I was shocked to see that the first dozen antigens that I checked, all had a triplet of basic amino acids.  I had discovered that autoantigens and allergens utilize a basic triplet analogous to the basic quartet used in nuclear translocation!  This also explained why proteins that interact with nucleic acids and are transported into the nucleus with a basic quartet are also prominent autoantigens.

Gut Flora and Immunity

Twenty years ago I read a curious description of leprosy that said that the course of infection could be either innocuous or devastating depending on whether the aggressive or the suppressive part of the immune system dominated.  I remained perplexed until I realized that diet and gut flora were the major determinants.  I was aware of the importance of diet at the outset of this blog, because it was clear that diet trumped genetics.  I was also aware thirty years ago in my studies of passive immunity, that milk contained bifidus factor, now known to be milk oligosaccharides, that controlled the growth of Lactobacilli that in turn controlled the development of the neonate immune system.  It was also known that bacteria-free mice had impaired immune systems.  It still took me several years for the relationship between diet, gut flora and immunity to make sense.  I began searching the literature for connections between gut flora and development of the immune system and soon noted experiments that linked filamentous bacteria with aggressive components and Clostridium spp. with Tregs.  A further refinement was linking resistant starch, a soluble fiber, with Clostridium.

My Current Views are Summarized in Three Health Diagrams

Diet, Gut Flora, Inflammation, Antigen Presentation, Tregs and Autoimmunity

Protein from the body and from food don’t normally stimulate the immune system, because there in no inflammation, the proteins lack basic triplets that enhance presentation, and antibody production and aggressive T cells are suppressed by Tregs.  Diet can throw the balance toward autoimmunity and allergy, by producing inflammation, e.g. hyperglycemia/AGE or high omega-6 fatty acids/prostaglandins, and starving gut flora needed for Treg production by eating processed food lacking soluble fiber.  The combination of inflammation and Treg deficiency causes proteins, either self or potential allergens, which have basic triplets to be presented to the immune system and stimulates attack by the immune system.

The Cure is to Cool Inflammation and Stimulate Tregs with Diet and Bacteria

I have provided an outline with The Anti-Inflammatory Diet to avoid inflammation, to stimulate existing gut flora with soluble fiber and encourage Treg production.  Mark Sisson, on Mark’s Daily Apple has provided an excellent dietary guide that also provides starch guidelines.  If you already have symptoms of autoimmune disease or allergies, then Richard Nikoley provides gut flora repair advice on Free the Animal, and Dr. B G provides more details on Animal Pharm.

Autoimmunity and allergies are not genetic destiny and they can be cured with diet and bacteria.

Health in Diagrams I — Gut Flora and Diet

---All 200 posts here---

This is the first of three posts to summarize my thoughts on diet, inflammation and disease mediated by gut flora.  I decided that I needed to make my points as explicit as possible by putting them down in diagrams and making references to my other posts.  By the time I finish, I will reach my 200th blog post at Cooling Inflammation.

Health in Diagrams II -- Curing Autoimmunity and Allergies

Health in Diagrams III -- Inflammation from Cell to Tissue

Everyone Leaves Out Gut Flora

I want to first explain and diagram my current understanding of the relationship between gut flora (the complex community of hundreds of different types of bacteria and fungi in the intestines) and diet.  My impression is that many people have health problems based on diet, but when they try to heal their health, they fix their diet and see only limited benefits.  Medicine provides only a temporary treatment using dairy probiotics.  The problem is that they failed to fix their gut flora, which was also damaged by their unhealthy diet.  

Health Requires a Match between Diet and Gut Flora

It is a myth that gut flora will just adjust to diet and a healthy diet leads to a healthy gut flora.  

A damaged gut flora lacks necessary species of bacteria.  Antibiotics, for example, can permanently delete dozens of particular bacterial species of gut flora that can only be replaced by reintroducing the missing bacteria by eating those bacteria again.  The missing bacteria may be needed to digest particular foods and the result is food intolerances, commonly mistaken for food allergies.  Antibiotic use frequently leads to autoimmune diseases, that are caused by deficient regulatory T cells of the immune system that develop in the lining of the intestines in response to particular gut bacteria.  The natural source of gut bacteria is eating the bacteria clinging to raw or fermented vegetables.

Antibiotics and Autoimmunity

Diagram Showing the Interaction of Food, Gut Flora and the Immune System

Food is just Protein, Fat and Soluble Fiber

The human body produces enzymes to fully digest proteins, fats and one polysaccharide, starch.  All other parts of plants and animals are edible (fermented by gut flora) soluble fiber polysaccharides or insoluble, undigestible fiber consisting of cellulose or lignin, which together also make up the undigested organic matter, humus, of soil.  Grains are problematical for health, because their starch is readily converted to sugar, i.e. high glycemic, and their fiber is insoluble (not fermented by gut flora) and high in phytate.  Phytochemicals, plant polyphenolics, are of questionable value as antioxidants and are of unexplored importance for their antimicrobial impact on gut flora.

Phytochemicals, Natural Antibiotics and Antioxidants

Polymers (Protein, Starch) are Hydrolyzed by Enzymes to Oligomers and then Monomers (Amino Acids, Glucose)

The stomach mixes protein digesting enzymes, proteases, and starch digesting amylase, with food protein and starch.  Proteases convert the long chains polypeptides, polymers of protein amino acids, into shorter fragments, oligopeptides.  The specific nature of the stomach proteases leaves groups of basic amino acids (lysine, arginine), heparin-binding domains, intact.  These peptides, similar to the defensins of the microvilli crypts, are anti-microbial and work with residual acidity to reduce bacterial growth in the first part of the small intestines.  Pancreatic enzymes then digest the peptides further and the small peptides are ultimately digested by enzymes on the surface of intestinal epithelial cells just prior to absorption.  Similarly, starch is degraded to oligosaccharide amylodextrins, which are then hydrolyzed to glucose at the intestinal surface prior to absorption.  Amino acids and glucose are not normally available to bacteria in the intestines.

Antimicrobial Heparin-binding Domains

Fats are Dissolved by Bile, Digested by Lipase and Absorbed

Fats are triglycerides, i.e. three fatty acids attached to the three hydroxyl groups of glycerol.  Fats are hard to digest, because they form oily droplets.  The droplets are dissolved in the intestines with bile, which is an acidic form of cholesterol, that is produced in the liver and stored in the gall bladder.  Fat in a meal triggers bile release from the gall bladder into the small intestines.  The bile represents a huge reservoir of the cholesterol that is synthesized by the body and dwarfs the cholesterol content of any meal.  Statins decrease body production of cholesterol, interfere with bile/fat digestion and lower lipid cholesterol levels.  (Unfortunately, lowering lipid cholesterol levels has minimal impact on heart disease and the only impact of statins on cardiovascular disease is through weak anti-inflammatory side effects.)  Pancreatic lipase removes two of the fatty acids from each triglyceride.  The fatty acids (a.k.a. soap) and monoglyceride are absorbed by the intestinal cells and reformed into triglycerides that make their way to lymphatic lacteals and are dumped into the blood, where they circulate as chylomicrons surrounded in lipoprotein.  Lipoprotein lipase binds to heparan sulfate on the surface of blood vessels and gradually removes fatty acids, until the diminished chylomicron is absorbed by the liver and exits as a VLDL.  (Note that this is another connection between lipid metabolism and inflammation, since inflammation decreases heparan sulfate on cell surfaces.  Heparan sulfate also mediates LDL binding to cells and amyloid stacking.)

Heparin-binding Domains

Plant Polysaccharides are Soluble Fiber and Food for Gut Flora

All that remains of food after the protein, fat and glycemic starch (glycogen) have been removed in the small intestines are plant cell wall polysaccharides, resistant starch, storage polysaccharides, e.g. inulin, plant beta-glucan, animal glycans, e.g. chondroitin sulfate and heparan sulfate, and insoluble fiber.  The insoluble fiber passes on to be a minor contributor to the bulk of stools and the rest of the polysaccharide is potentially fermentable by gut flora into short chain fatty acids (formic, acetic, propionic, butyric acids).  Some of the polysaccharides are simple repeating units of one or two sugars in long chains, but others are made of five to ten different sugars in complex branched structures.  Simple repeating polysaccharides require just a few different enzymes for their initial synthesis and a few for their digestion.  Thus, resistant starch can be digested by a couple of enzymes into glucose that can be used by most gut flora.  Arabinogalactan, on the other hand, requires a dozen enzymes for plant synthesis and an equal number of hydrolytic enzymes to produce arabinose and galactose, which require further enzymes for metabolism in a select few of species of gut flora bacteria.  

Resistant Starch as a Panacea

Food Intolerance/“Allergy” Indicates Missing Bacteria

Gut flora in general can produce several hundred different enzymes for digestion of diverse soluble fiber,  but most soluble fiber polysaccharides can only be digested by certain bacteria and those bacteria increase, if the complementary fiber is present in the diet.  If a fiber is absent from the diet, bacteria that specialize in digesting that polysaccharide will be eliminated.  People living on diets limited to just a few types of soluble fiber can only digest those fibers and a shift in diet to other types of soluble fiber will lead to symptoms of dietary upset, such as bloating, gas production and food intolerance.  Food intolerances reflect inadequate diversity in gut flora and a mismatch between bacteria and food.  Food intolerances can be eliminated by repairing gut flora and the typical repair solution is eating homegrown fermented vegetables that provide the missing species of bacteria.

Paleo Gut Flora Repair

Immune Cells Develop in Response to Gut Bacteria

Most of the body’s immune cells are in the intestines.  Cells of the immune system are constantly dividing in bones and the thymus gland, developing in the lining of the intestines and migrating to other tissues.  Filamentous bacteria of the gut flora stimulate the development of aggressive immune cells that kill other cells that are infected with pathogens or viruses or are cancerous.  Furrows perpendicular to the flow of food cultivate the growth of Clostridium species that ferment soluble fiber, e.g. resistant starch, and release butyric acid that stimulates the development of regulatory T cells, Tregs.  It is the Tregs that control the aggressive immune cells and prevent attack on self (autoimmunity) or innocuous antigens (allergy).  It appears that merely eating resistant starch, e.g. potato starch, with probiotics that contain butyric acid producing Clostridium bacteria may provide a cure for many autoimmune diseases.

Free the Animal: A Resistant Starch Primer for Newbies

Gut Biofilms Release Vitamins as Quorum Sensing Signals

 The gut flora lines the intestines in numerous biofilm communities, which form from dozens of different species of bacteria that communicate by exchanging molecules called quorum sensing signals.  These signals from the biofilms intimately attached to the lining of the intestines are vitamins.  Thus, healthy gut flora are the major source of vitamins and other sources, such as fruits and vegetables are only needed, if the gut flora is damaged, e.g. by antibiotics.

Dr. Oz, Vitamins, Biofilms

Volume of Stools Reflects Gut Flora Fermenting Soluble Fiber

The bulk of bowel movements, stools, is bacteria, the compressed gut flora that accumulated in the colon while fermenting soluble fiber.  We always hear that we need to eat fiber for regularity, but since insoluble fiber is only a minor contributor to stool volume and it is associated with anti-nutritive attributes, such as the binding and removal of zinc and iron by phytate, the fiber that counts for regularity is soluble fiber.  Regularity results from the fermentation of soluble fiber polysaccharides producing short chain fatty acids, such as butyrate, that are the major source of energy for colon cells.  And the growing bacteria in the colon provide most of the bulk of the hydrated stools.  Inadequate dietary soluble fiber or damaged gut flora, dysbiosis, leave only dehydrated insoluble fiber and compact stools of constipation.  Constipation can result from dehydration or excessive retention, but chronic constipation, even in the presence of adequate dietary soluble fiber, is an indication of damaged gut flora and an increased risk for diseases resulting from deficiencies of Treg production:  autoimmune diseases and allergies.  Constipation and associated autoimmune diseases can be cured by repairing gut flora and supplying adequate dietary soluble fiber.

Milk, Kefir and Gut Flora

Transglutaminase, Gluten, Celiac, Inflammation, Autoimmunity

The point of this post is that the intestines produce an enzyme, transglutaminase (TG) that normally protects the gut from toxic plant proteins, such as grain gluten, but modern food processing and antibiotics corrupt digestion of gluten to produce intestinal inflammation and a series of related autoimmune diseases including celiac, thyroiditis, diabetes, baldness and atherosclerosis. 

Transglutaminase Links Proteins Enzymatically

Transglutaminase is a ubiquitous enzyme produced in the intestines, thyroid, heart, skin, hair follicles, etc.  This enzyme attaches to a protein (TG + ProA ~~> TG-ProA) via amino groups extending from some of the protein's amino acids, e.g. lysine or glutamine, and then the enzyme replaces itself by another protein leaving the two proteins crosslinked (TG-ProA + ProB ~~> TG + ProA-ProB).  Another alternative reaction is to leave the original glutamine without its amino group to yield glutamic acid residues.

Linking Proteins Makes Connective Tissue Tough

Transglutaminase is useful to crosslink the proteins in connective tissue.  Proteins in basement membranes form a matrix by binding to the heparan sulfate sidechains of another basement protein, perlecan.  The heparin-binding domains consist of basic amino acids that TG can react with to crosslink the proteins.

Linking Pathogen Proteins

Transglutaminase is also produced to crosslink the DNA/heparin/matrix polysaccharide-binding domains of pathogenic bacteria leading to aggregation, localization and death of the bacteria.  Inflammation resulting from activation of the inflammatory transcription factor, NFkB, stimulates production of TG.

Gluten is a Plant's Way of Saying "Don't Eat Me!"

Gliadin is a protein component of gluten that contains long stretches of glutamine residues, i.e. it is a polyglutamine protein similar to the protein that causes Huntington's disease.  Gliadin is an advantage as a storage protein for grain, because it is aggregated by the TG that protects the lining of the intestines of herbivores, such as humans, makes the animal sick and thereby discourages eating the grain.  Aggregation of gliadin/gluten inhibits digestion of the grain protein and can leave TG bound to gliadin.  Conversion of the polyglutamine stretches to polyglutamic acid stretches that are negatively charged, produces proteins that will bind to the positively charged heparan sulfates that circulate along the surface of intestinal cells leading to damage and inflammation.

Basic Triplet Leads to Antibody Production

Transglutaminase is also transported into cells, because it contains a region with a triplet of basic amino acids (...EPKQKRKLVA...).  This internalization probably contributes to enhanced presentation of TG to the immune system for subsequent antibody production.

Transglutaminase is Inflammatory

Transglutaminase interaction on the surface of cells also activates, NFkB, the transcription factor responsible for inflammation. Thus, TG turns on inflammation and part of inflammation is the activation of the innate immune system that includes production of TG.  This circular activation may produce autoinflammation that is associated with various forms of inflammatory bowel diseases.

Gluten Sensitivity is Normally Controlled By Gut Flora

Gluten sensitivity expressed by most people, is the intestinal response to the toxicity of gluten as it interacts with TG and causes inflammation.  This inflammation will also result in immune presentation of both gliadin and TG, and production of antibodies to both. Antibody production will normally be controlled by regulatory T cells of the immune system, unless spreading inflammation in the gut and/or antibiotics destabilizes the gut flora and compromises regulatory T cell development in the intestines.  

Anti-Glutaminase Antibodies Attack the Gut

Celiac results from uncontrolled production of antibodies to gliadin and TG with attack by the immune system on the aggregated gliadin/TG on the surface of the intestinal epithelium.  Celiac flare ups in response to eating even small quantities of gluten lead to further inflammation of the gut and further disruption and simplification of gut flora.

Celiac Leads to Thyroiditis and Much More

Transglutaminase is also produced by the thyroid and celiac will develop into a more generalized autoimmune disease that results in Hashimoto's thyroiditis.   TG production in the skin can result in skin rashes and may contribute to rosacea.  The base of hair follicles contains TG involved in hair production, and may contribute to some forms of hair loss.  Another substantial worry about the sequelae of celiac and gluten intolerance is the presence of TG in coronary arteries.

Antibiotics are Part of the Gluten Problem

Celiac and gluten sensitivity seem to be increasing with modern processing of grains and increased use of antibiotics.  Wheat has been gradually changed by traditional breeding, but genetic engineering has not yet been developed for wheat.  So, at least in this case, GM wheat cannot be part of the problem.  Many recent studies show that antibiotics profoundly and permanently alter gut flora.  As a result, the immune system, which is dependent on gut flora diversity is compromised, and various forms of autoimmunity and allergies develop.

Super Fine Flour Damages Gut Flora

Germ and bran are removed from all wheat before it is ground.  This is true even for whole grain flours, which have some of the germ and bran added back after milling.  Modern milling may be part of the gluten problem, because the flour is ground so fine that the grains of starch are broken.  Broken starch grains are digested by pancreatic amylases in the upper intestines, whereas some of the starch from intact grains is digested by gut flora in the colon.  Thus, modern wheat flour fails to feed gut flora like soluble fiber to produce short chain fatty acids, e.g. proprionic acid that supports Treg development; modern superfine flour supports autoimmune diseases and allergies.

Cultural Practices Make Gluten Safe

Wheat has been bred to produce bread as fast as possible from superfine flour.  This rapid bread production eliminates the exposure of gluten to enzymes from both germinating wheat seed and fermenting bacteria, which are part of traditional bread making.  Coarsely milled, traditional flour responds to soaking in water by activating enzymes that partially digest gluten, since gluten is a storage form of amino acids destined for the seedling.  Sour dough starter, a mixture of bacteria that can ferment the starch and gluten into short chain fatty acids and bubbles of carbon dioxide, has been used traditionally to provide leavening and flavor to bread.  Both flour and bacterial enzymes modify the structure of gluten to render it less toxic to the intestines.  Cultural traditions insured that gluten would be systematically detoxified by enzymes during hydration and fermentation of dough prior to baking.  Modern processing leaves wheat gluten in bread unmodified and toxic.

Prevention and Cure:  Eliminate or Detoxify Wheat and Add Bacteria

Preventing and curing diseases associated with gluten and transglutaminase is simple.  Eliminating wheat would do the trick.  Unfortunately, wheat is the mainstay in many parts of the world.  Fortunately, gluten intolerance is not uniformly observed where wheat is eaten.  This indicates that there are potentially safe ways to eat wheat and bread.  I gained insight into how to eat wheat safely from two books that were recently published:  Cooked by Michael Pollan and Artisan Bread in Five Minutes a Day by Jeff Hertzberg, MD and Zoë François.

Michael Pollan has recently become interested in gut flora and his book revealed how he built up a healthy gut flora eating homemade fermented food and compromised his work with antibiotics.  The major breakthrough that I made by reading Cooked was based on his experiments in baking whole wheat bread.  He hydrated the flour first and then used sour dough starter for lengthy fermentation.  This was the same process that I had used to make great loaves of bread (photo above) using Jeff Hertzberg’s directions in Artizan Bread in Five Minutes a Day.

The answer to gluten intolerance and most autoimmune diseases amounts to eliminating wheat or treating wheat in a safe, traditional process that inactivates the toxic properties of gluten; and maintaining a healthy gut flora (probiotics are not enough) with hundreds of different species of bacteria that promote the development of the suppressive immune system mediated by regulatory T cells:

Safe Traditional Bread 

• Remove bran and discard as toxic insoluble fiber.
• Grind wheat to retain starch grain structure.
• Soak flour to hydrate and activate wheat enzymes to start digestion/detox of gluten.
• Ferment dough with bacteria (sour dough starter) to continue digestion/detox of gluten.
• Bake.

Develop Healthy Gut Flora and Suppressive Immune System

• Avoid antibiotics that kill bacteria.
• Avoid hygiene practices, e.g. antibacterial soaps, bleaching surfaces, closing toilet covers, etc. that eliminate sources of healthy bacteria.
• Kiss your loved ones and pets, and encourage everyone to garden/play in the soil (an excellent source of thousands of different species of bacteria.)
• Recruit healthy gut bacteria by eating a variety of homemade fermented vegetables. My most highly recommended source is my friends at: http://www.fermentista.us
• Remember that cooked or pasteurized foods do not contain useful bacteria.
• Remember that dairy probiotic bacteria cannot live in the human gut and can only provide a temporary help to the immune system.
• Limit the variety of foods that are consumed and gradually change with the seasons to avoid rapid changes in nutrients to which gut flora cannot adapt.  Food intolerances indicate maladapted gut flora.
• Constipation indicates dysfunctional gut flora and a compromised immune system.

Rosacea: Alzheimer’s of the Face

Is Rosacea Caused by Amyloid LL-37, as Alzheimer’s Is Caused by Anti-microbial Abeta?
A recent article in PLoS One (Thanks Daniel!) suggests that the amyloid beta (Abeta) proteins that aggregate to form fibrous plaques in the brain tissue of Alzheimer victims, function as typical defensive anti-microbial peptides (AMPs), similar to the LL-37 cathelicidin implicated in facial tissue in rosacea.  The structural and functional similarities of Abeta and LL-37 suggest to me that Alzheimer’s and rosacea may also be similar in initiation and treatment.  Let’s compare amyloids and AMPs.

[The figure shows a model protein (from ref.) used to examine stain binding to amyloids.  The stains appear to bind to aromatic amino acids spaced evenly between adjacent proteins, but adjacent basic amino acids (blue) are spaced the same way and provide sites for heparin binding.]

Amyloids:

• Amyloid proteins/peptides align into stacks and fibers
• Stacked beta sheets bind amyloid stains: Congo Red, Thioflavin-T
• Fibers form on anionic polymers: heparin, DNA
• Short amyloid stacks are toxic to cells
• Proteases produce multiple sizes of amyloid peptides

Anti-microbial Peptides:

• AMPS typically contain heparin-binding domains -- basic peptides/ plus charge
• Some AMPs, e.g. LL-37, form fibers on DNA, heparin (stain with amyloid stains)
• Toxic to cell membranes
• Kallikrein stimulated by gut flora migrates to face and clips LL-37 to a smaller peptide that binds to host DNA and stimulates the TLR receptor to produce inflammation
• Stomach pepsin hydrolyzes dietary proteins into anti-microbial peptides (heparin is secreted by mast cells onto to the intestinal surface to protect from any amyloid-like effects)
• Defensins, cathelicidins and other AMPs are under transcriptional control of vitamin D receptor

Abeta Is Anti-microbial Like LL-37

Amyloid beta is the well-known source of the fibrous plaques forming brain lesions in Alzheimer’s disease.  The normal function of Abeta has not been firmly established.  The recent article shows data to support Abeta as an anti-microbial peptide comparable to LL-37 against several pathogenic bacteria and yeast.  Knock-out mice deprived of a gene corresponding to Abeta are susceptible to bacterial infections.  The anti-microbial activity present in extracts from Alzheimer’s disease brains was inactivated by anti-Abeta antibodies.

Implications of Abeta as an AMP Like LL-37

The similarities between AMPs and amyloid peptides suggest some implications for both Alzheimer’s disease and rosacea.  Vitamin D is a hormone that binds to a cytoplasmic receptor and the vitD/receptor complex then acts as a transcription factor that controls the expression of defensins in the intestines, LL-37 in facial skin and perhaps Abeta in brains.

Amyloids form fibers on a scaffolding of heparan sulfate (HS).  There is usually an excess of HS on the surface of cells and the HS is rapidly recycled back into cells.  During inflammation, mast cells release heparin, short fragments of HS, that should also inhibit amyloid fiber formation on HS.   Chronic inflammation, however, reduces HS production and may set the stage for amyloid fiber formation.  HS metabolism of the brain may be vitally important to the development of Alzheimer’s disease, especially since the increasing chronic inflammation of aging people should deplete brain HS.

LL-37 forms complexes with DNA from damaged host cells in rosacea skin.  The LL-37/DNA complexes trigger TLRs and inflammation.  LL-37 may normally bind to cell surface HS and chronic inflammation of the skin may cause the shift to pathogenic autoinflammation.  Topical application or perhaps low dose IV heparin may be effective in disrupting the autoinflammation due to LL-37.  Part of the toxicity of LL-37 in the skin may be due to amyloid like structures that could form with inadequate HS and overabundant LL-37 production.  Vitamin D metabolism should also be very important, since LL-37 synthesis is controlled by vitamin D.  This is consistent with the benefits that some rosaceans observe with high doses of vitamin D3 supplements.

references:
Soscia SJ, Kirby JE, Washicosky KJ, Tucker SM, Ingelsson M, Hyman B, Burton MA, Goldstein LE, Duong S, Tanzi RE, Moir RD.  The Alzheimer's disease-associated amyloid beta-protein is an antimicrobial peptide.  PLoS One. 2010 Mar 3;5(3):e9505.

Abedini A, Tracz SM, Cho JH, Raleigh DP.  Characterization of the heparin binding site in the N-terminus of human pro-islet amyloid polypeptide: implications for amyloid formation.  Biochemistry. 2006 Aug 1;45(30):9228-37.

Biancalana M, Makabe K, Koide A, Koide S. Molecular mechanism of thioflavin-T binding to the surface of beta-rich peptide self-assemblies.  J Mol Biol. 2009 Jan 30;385(4):1052-63. Epub 2008 Nov 14.

Bacterial Amyloid (Curli Fibers) Forms Biofilms

E. coli Curli Stacks in Congo Red Staining Fibers

We can’t cure diseases, because we don’t understand basic chemistry (what is hydrophobic) and biology (which came first the biofilm or the bacterial cell wall?)  Let’s look at a fundamental biological process, how bacteria form biofilms.

Biofilm Formation from Secreted Proteins and Polysaccharides

Investigators passed some E. coli through a special slide chamber so they could watch at high magnification as a single bacterium attached to the surface, divided to produce a colony of a few bacteria and then began to secrete proteins (curli fibers) and polysaccharides (colanic acid and cellulose) to make the biofilm matrix.  The matrix stained red with Congo Red.

Congo Red Stains Amyloids, Cellulose and Rare LPS



Staining with Congo Red shows that the spacing of hydrophobic patches on the surface of the biofilm matrix matches the flat hydrophobic, aromatic rings of the dye, Congo Red.  This particular dye is important, because Congo Red also specifically stains amyloid, e.g. beta amyloid of Alzheimer’s disease.  But Congo Red also binds to cellulose, a linear beta 1,4-glucan polysaccharide.  This seems paradoxical, because we are taught that the sugars of which a polysaccharide are made are hydrophilic.  That turns out to be a half-truth. 

Faces of Sugars Are Hydrophobic

The hydrogen bonding hydroxyl groups that make sugars water soluble and hydrophilic, radiate from a ring of carbons, and the faces of that ring cannot make hydrogen bonds.  The faces of sugars are hydrophobic and in most cases will bind to hydrophobic surfaces, such as aromatic amino acids, e.g. tryptophan, tyrosine and phenylalanine.  Thus, carbohydrate binding enzymes, such as shown in the figure bind cellulose (in grey and red) in a groove lined with aromatic amino acids (yellow and orange) so that each sugar orients over and sometimes sandwiched between aromatic amino acid residues.  This also explains why Congo Red binds to cellulose, since the aromatic rings of the dye bind to neighboring glucose residues along the relatively flat cellulose strand.  Most other polysaccharides and smaller sugars lack this spacing of sugars and they don’t stain red with Congo Red.

Basic Amino Acids Bind Hydrophobically

Another misperception is that basic amino acids, positively charged lysine and arginine, are hydrophilic.  The nitrogen atoms that make these amino acids positively charged, can form hydrogen bonds, but the hydrocarbon tails that have these nitrogenous tips, are hydrophobic.  Thus, basic amino acids and aromatic amino acids can stack to form tryptophan/arginine ladders in which they alternate.  A prominent example of these interdigitations are the way that nuclear localization signals, a quartet of basic amino acids, bind to importin via its projecting, spaced tryptophans and drag proteins through pores into the nucleus.  Similarly, the basic amino acids of heparin-binding domains extend across the hydrophobic faces of the sugars of heparin and hydrogen bond with their tips to the sulfates of the heparin.  In each of these binding examples the binding is primarily hydrophobic.

Amyloid Binds Congo Red by Stacked Heparin-Binding Domains

Amyloids are proteins that stack together like stacking chairs, so that each protein is oriented in the same way all along the stack.  In the case of the beta amyloid that makes up the toxic plaque in Alzheimer’s disease, each amyloid peptide is stacked like a hair pin on top of the next to make a fiber.  At the bend in beta amyloid, is a basic amino acid and the amyloid fiber has a band of basic amino acids along its length.  The spacing between the basic amino acids in an amyloid stack is just spanned by Congo Red, so amyloids are diagnostically stained red.  This same spacing of basic amino acids fits the sugars in heparin.  Thus, heparin can catalyze amyloid formation and is abundant in amyloid plaques in Alzheimer’s

Bacterial Biofilms Form from Amyloids and Polysaccharides

The E. coli cells that formed the biofilms that started this article secrete a protein, curli, that stacks as an amyloid into fibers.  These fibers stained by Congo Red and bind to the cellulose that is also produced by the E. coli.  It should not be surprising that biofilm formation is catalyzed by heparin and biofilm formation is a major problem in catheter infection, since heparin is used to coat catheters to keep them from forming blood clots.  Amyloids are also formed from stacked seminal acid phosphatase proteins that form fibers in the presence of heparin and facilitate HIV infection.

Do Biofilms Foment Amyloid Production?

Basic amino acids, sugars, aromatic amino acids and plant phytochemicals all bind each other via their hydrophobic surfaces.  It would not be surprising that bacteria that produce proteins and acidic polysaccharides that interact hydrophobically would also interact with host molecules with a similar spacing of hydrophobic surfaces, which are common in heparin-binding interactions and nucleic acid interactions.  The bacteria in biofilms produce both proteins and polysaccharides that may catalyze amyloid production.  The acidic biofilm polysaccharide, colanic acid, may replace heparan sulfate and curli should bind to heparin.

Berberine Binds Heparin and Blocks Amyloids and Biofilms

Just as bacterial products may compete for host heparin and heparin-binding domains, phytochemicals that interact with heparin, such as the phytochemical berberine, should disrupt heparin mediated molecular interactions, and by extension also biofilms.  There is experimental evidence for berberine both disrupts amyloid formation and biofilm assembly.

Psoriasis, IL-17, Cathelicidin, TLRs, NFkB, Inflammation and Heparin Therapy

Host DNA Released by Keratinocyte Apoptosis Binds LL-37 and Activates Dendrocytes

Psoriasis is an inflammation of the skin that leads to overproduction of keratinocytes resulting in a thick crust.  Skin inflammation, in this case, is considered a result of autoimmunity, but an autoantigen has not been identified.  It is more likely that psoriasis results from an autoinflammatory condition, in which inflammation produces a complex of self molecules that mimic bacterial DNA and trigger TLR/NFkB inflammation signaling.  And of course, if this is going to be interesting, it has to involve heparin.

Vitamin D Binds to a Transcription Factor Receptor that Controls Antimicrobial Peptides
A significant component of the innate immune system is a group of antimicrobial peptide  (defensins, cathelicidins, e.g. LL-37).  These short polypeptides owe their natural antibiotic activity to numerous basic (positively charged, arginine and lysine) amino acids.  The transcription factor that controls the expression of these peptides is the vitamin D receptor.  Thus, various forms of vitamin D influence the amount of antimicrobial peptides produced in the mouth, skin and crypts of the intestinal villi.  Oral vitamin D3 would be expected to directly improve defensin production in the gut and LL-37 production in the skin.

IL-17 Stimulates Skin Inflammation and LL-37 Production
A specific group of lymphocytes, called T helper 17 cells, produce IL-17.  These Th17 cells accumulate in some sites of inflammation, such as psoriasis and their secretion of IL-17 is associated with ongoing inflammation and may contribute to LL-37 production, as well as apoptosis of keratinocytes in the thickening skin of psoriasis plaques.
http://www.ncbi.nlm.nih.gov/pubmed/19623255?ordinalpos=1&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_SingleItemSupl.Pubmed_Discovery_PMC&linkpos=2&log$=citedinpmcarticles&logdbfrom=pubmed

Th17 Cells Are Produced in the Gut in Response to Segmented Bacteria
One of my readers brought to my attention an article that shows that one of the hundreds of species of gut bacteria, segmented filamentous baceria, stimulates the gut to develop T helper 17 cells that subsequently migrate to sites of inflammation.
http://www.medpagetoday.com/Gastroenterology/InflammatoryBowelDisease/16472
This emphasizes the link between the gut and inflammatory diseases and parallels other examples of gut influence on disease, such as the ability of Helicobacter pylori to affect asthma or parasitic worms to tame Crohn’s disease, allergies and asthma.

Inflammation Lowers Heparan Sulfate Production and Spreads LL-37
One of my students induced inflammation in cells in vitro and showed by quantitative PCR that genes involved in heparan sulfate proteoglycan production are selectively silenced.  This observation explains in part the loss of heparan sulfate in kidneys and intestines that contributes to the leakiness of these organs in response to inflammation and the partial repair of these organs by heparin treatment.  Decrease of heparan sulfate that normally coats cells and binds antimicrobial peptides, such as LL-37, would explain the enhanced movement of LL-37 in psoriatic skin.

LL-37 Binds to Host DNA and Triggers Toll-Like Receptors
DNA is released from keratinocytes in psoriatic skin and this host DNA binds the antimicrobial peptide cathelicidin LL-37.  The LL-37/DNA complex mimics bacterial DNA and triggers the Toll-like receptors (TLR) on the surface of immune cells, dendrocytes, to activate NFkB, the transcription factor controlling inflammation.
http://www.ncbi.nlm.nih.gov/pubmed/19050268?ordinalpos=1&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_SingleItemSupl.Pubmed_Discovery_RA&linkpos=1&log$=relatedarticles&logdbfrom=pubmed

Heparin Treats Psoriasis
It seemed obvious to me that the heparin binding domains (Look at all the basic amino acids in blue in the illustration of LL-37.) of LL-37 were involved in DNA binding and the reason the LL-37 was binding to host DNA, was that heparan sulfate had been depleted as a result of local inflammation.  It also seemed obvious that topical heparin should eliminate psoriasis plaques.  So I did a Google search of psoriasis + topical heparin and got a hit on a 1991 patent application that claims a broad applicability for heparin use in curing symptoms of a wide variety of diseases, including psoriasis.
http://www.patentstorm.us/patents/5037810/description.html
The only topical form of heparin that I know of is Lipactin (available in Canada and Europe?), a treatment for coldsores, which makes sense because herpes viruses use heparan sulfate to infect cells.

Helicobacter Pylori, Gastric Ulcers and Cancer

Stomach Pathogen or Immune Regulator?

Helicobacter pylori (Hp) has co-evolved with the human stomach.  Hp has always been passed from mother to child as the child started premasticated solid foods.  The advent of processed baby foods and antibiotics has eliminated Hp in 90% of the US population and coincides with a dramatic rise of allergies, asthma and autoimmune diseases (commonly explained by the hygiene hypothesis.)

Hp Is Stomach-Adapted

Hp is adapted for growth in an acidic environment.  It produces ammonia to neutralize stomach acid. It also provided me with great perplexity in searching for heparin-binding domains in Hp proteins suspected of binding to stomach epithelial cells.  I generalized that pathogens must have proteins on their surfaces that bind to the heparan sulfate proteoglycans of epithelial cells.  I checked candidate Hp proteins and found histidines where I expected to find basic amino acids, either lysine or arginine.  The “duh” moment came when I realized that the pH of the Hp milieu was acidic and hence histidine would have a positive charge and function like the other two basic amino acids.  Hp was adapted to its stomach world.

Is Hp Good or Bad?

I have been trying to incorporate Hp as a pathogen into my view of gut function.  After all, Hp causes stomach ulcers and gastric cancer.  Several studies over the last few years have shown an association between Hp and asthma, but it is a negative association.  Hp seems to provide protection from asthma and I think that it is likely that the protection extends to allergies and autoimmune diseases.  It is also noteworthy that analysis of genetic predisposition to gastric cancer only reveals polymorphism in genes associated with inflammation, e.g. IL-1 or TNF.

Hp Lives on Hydrogen from Gut Biofilms

Further evidence of the integral nature of Hp as part of the natural gut flora is its use of molecular hydrogen (H2) as an energy source, i.e. high energy electrons for its electron transport chain to produce ATP or to power membrane transport.  The source of the hydrogen is Klebsiella in biofilms in the intestines.  The hydrogen diffuses into the intestinal blood supply and is circulated to the stomach lining where it provides energy for Hp.  Attacking gut biofilms may starve Hp and feeding starch (indigestible branch oligosaccharides are unique food source only accessed by Hp pullulanase) enhances Hp hydrogen nutrients.  [Since regulation of the Hp genes is not thoroughly understood, it is also possible that ample starch could shut down nitrogenase and starve the Hp.]

Hp Increases Tregs

Allergies and autoimmune diseases point to problems in self/non-self recognition, i.e. immunological tolerance.  And tolerance is dependent on regulatory T cells.  In this context, it is interesting that Hp stimulates the accumulation of regulatory T cells.  The gut is the major repository of cells of the immune system.  It seems to follow that by elimination of the stomach Treg population by curing Hp infections, the body may be deprived of it major resource to suppress immunological responses to innocuous antigens in foods, pollens, etc. and to self antigens.  Coupling a shortage of Tregs with chronic inflammation may lead to allergies and autoimmune diseases.  Another source of Treg depletion that may further compromise the immune system is circulating LPS, endotoxemia, that is associated with obesity (and leaky gut?)

Recombining H1N1 and H5N1 Is Very Scary

Avian Flu Acquired a Basic Internalization Domain in the 1990’s

Avian flu was simply for the birds until its hemagglutinin (the H or H5N1) acquired an extra four basic amino acids that provided another way into human cells.

Basic Amino Acids Accumulate in the Hemagglutinin

During the early 1990’s isolates of avian flu, H5N1 started to appear that eventually developed six basic amino acids in a stretch about 340 residues from the amino terminus. These basic amino acids are thought to be an adaptation to decrease inactivation by a host protease.

H5N1
~PQRE TRGLFG~ ABB88379 Mexico 1994
~PQRK TRGLFG~ ABQ84472 Italy 1993
~PQRK ETRGLFG~ ACH88842 USA 1993
~PQRKRKRKTRGLFG~AAC58990 Mexico 1995
~PQRE RKKRGLFG~ ABQ84473 Italy 1997
~PQRERRRKKRGLFG~ AAD37782 China 1996
~PQRK RKTRGLFG~ ACL79965 Mexico 1994
H1N1
~PSIQ SRGLFG~ AAF87275

The red area is the region that has accumulated the basic amino acids (R and K). Note that the novel H1N1, does not yet have this region.

The New Basic Region Looks Like an Internalization Signal

Those who have followed this blog know that I have an interest in heparin binding domains, groups of basic amino acids (K for lysine and R for arginine) of proteins that bind the common acidic extracellular polysaccharide heparin. Most recently I have been focusing on unusual triplets of basic amino acids that are found in the proteins of allergens and autoantigens. These basic triplets are similar to the basic quartets that are used as signals to move proteins from cytoplasm into the nucleus of cells, i.e. the nuclear localization signal (NLS).

Basic Sextet for Internalization and More

The newly evolved basic sextet, RRRKKR, should be readily transported into cells by the mannose receptor and then taken into the nucleus, because it would also act as a NLS. This should also mean that the new H5N1 viruses with this hemagglutinin should attach to numerous cells of the immune system and potentially transported to other areas of the body.

Is this Dangerous?

I don’t know what the likelihood of recombination between H5N1 and H1N1 is if a bird, pig or human is infected with both nor is the impact of acquisition of the basic sextet by H1N1 on virulence known, but the acquisition of the basic sextet occurred at the same time that H5N1 moved from birds to people and became lethal.

Basic Sextet May Explain New Entry for H5N1

H5N1 has recently been found to infect tissue that lack the sialic acid sugars that are the typical target for avian flu. The new targets are not known. I would start to suspect the mannose receptor that I have postulated to be involved in initiation of allergy and autoimmunity.

Autoimmunity, Allergies and Basic Triplets

Basic Triplets Only in Primate Forms and Allergens

I have examined the proteins, autoantigens, that are the focus of a dozen autoimmune diseases and a similar number of allergens. All of these proteins have basic triplets that I previously associated with heparin-binding. I have had two recent revelations. First, these triplets appear to not be involved with heparan sulfate proteoglycans for internalization. In fact, HSPGs don’t appear to be involved, even though the process is inhibited by heparin. So this suggests a transport system, perhaps using the LDL receptor or the mannose-6-phosphate receptor, (or a protein with an acidic triplet or quartet.)

The second interesting observation is that the mouse, cat, dog, etc. versions of the human autoantigens lack the basic triplets. This suggests that these diseases cannot occur in non-primates by the same mechanisms. So what is the role of these basic triplets in humans? They didn’t evolve to cause problems under unusual conditions of chronic inflammation, so what is their adaptive advantage?

I think that the answers to these questions could yield the identification of a fundamental cellular transport process and associated cellular phenomena that could be worth a Nobel prize in medicine and it could be unravelled by a group of high school kids doing some straightforward bioinformatics.

Oh. I just remembered that IL-1 beta, the inflammatory cytokine, has a basic triplet. I just checked NCBI, and that basic triplet is found in all of the mammalian IL-1 betas. Oddly, the soluble receptor for IL-1 beta has an acidic quartet. I looked up the protein structure of the IL-1 beta bound to the IL-1 receptor and did a quick illustration using Chimera:

I put the surface on the IL-1 beta and left the IL-1R wrapping around it in as a ribbon. The basic triplet of IL-1 beta is in blue and the acidic quartet of the receptor is in red. One of the basic amino acids is stabilized by hydrophobic bonding over the face of a tyrosine, in yellow. Clearly, there is a simple ionic, plus-minus charge, bonding between the basic and acid amino acids. I don’t normally see this interaction between basic heparin-binding domains and other proteins. Other proteins that bind to heparin-binding domains use aromatic amino acids to make hydrophobic bonds with the hydrophobic arms of the basic amino acids, e.g. importin and nuclear localization signals or tryptophan/arginine ladders. The use of simple acid-base connections (with the projection of each stiffened by adjacent prolines) shows that this interaction is selected to be irreversible.

I don’t know all of the ramifications of basic triplets, but they are very important and are the basis for most modern allergic and autoimmune diseases.

An Autoantigen for Pancreatitis

Pancreatic Secretory Trypsin Inhibitor (PSTI) Has Internalization Basic Triplet

Pancreatitis is an inflammation of the pancreas resulting from lack of adequate inhibition of proteases. Autoantibodies against PSTI would explain some forms of pancreatitis.

I was researching the maintenance of baby gut flora by mother’s milk, when the reference discussed here was brought to my attention by my wife, who happens to be a lactation consultant. The paper showed that PSTI is present in colostrom, the first milk that a baby gets, before the true milk comes in. PSTI protects the new gut from digestion by its own pancreatic proteases, since PSTI is a protease inhibitor that sticks to the gut.

I naturally assumed that PSTI stuck to the gut by heparin-binding domains that would stick to the heparan sulfate proteoglycans on the gut surface. [Recall that it is via these HSPGs that viruses and bacteria infect the gut and the HSPGs in turn are protected during infections by the release of heparin from mast cells. The heparin in the guts of cattle and pigs are used to make commercial heparin to block blood clotting.] So I looked up the structure (above, with basic amino acids in blue and basic triplet on right) sequence of human PSTI at NCBI:

>gi|190694|gb|AAA36522.1| PSTI
MKVTGIFLLSALALLSLSGNTGADSLGREAKCYNELNGCTKIYD
PVCGTDGNTYPNECVLCFENRKRQTSILIQKSGPC

The basic triplet (RKR,arg-lys-arg), from my perspective, should result in presentation to the immune system during high levels of inflammation, and as a consequence result in autoantibodies against PSTI. The result would be the neutralization of the protease inhibitor and damaging production of active protease to attack the pancreas, i.e. pancreatitis.

It would be fairly easy to test this hypothesis by looking for the anti-PSTI antibodies in some people with pancreatitis. Other autoantibodies, e.g. against tissue transglutaminase, might also be checked, because the inflammation that produced one autoantibody may produce others and both PSTI and tTG are produced in the intestines. In fact, celiac may be the cause of some cases of autoimmune pancreatitis.

Note added in proof:

I just checked the literature on PubMed and found that PSTI is in fact an autoantigen in pancreatitis and produces antibodies against PSTI:
Raina A, Greer JB, Whitcomb DC. Serology in autoimmune pancreatitis. Minerva Gastroenterol Dietol. 2008 Dec;54(4):375-87.

and
I found that pancreatitis is often found associated with celiac (gluten intolerance):
Patel RS, Johlin FC Jr, Murray JA. Celiac disease and recurrent pancreatitis. Gastrointest Endosc. 1999 Dec;50(6):823-7.

ref:
Marchbank T, Weaver G, Nilsen-Hamilton M, Playford RJ. Pancreatic secretory trypsin inhibitor is a major motogenic and protective factor in human breast milk. Am J Physiol Gastrointest Liver Physiol. 2009 Apr;296(4):G697-703.