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.