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.

Antibiotics, Gluten, Hashimoto's Thyroiditis and Baldness

My impression is that Hashimoto's is caused by a combination of an initial immune attack on the thyroid and incompetent regulatory T cells.  In most cases the immune attack on the thyroid is a secondary consequence of celiac/gluten intolerance, in which anti-transglutaminase antibodies attack transglutaminase bound to gluten in the intestines.  Transglutaminase  is an enzyme that is also produced by the thyroid (and hair follicles) and attack by celiac antibodies can enhance or inhibit thyroid hormone production (or baldness.)  Both Hashimoto's and celiac do not occur if the suppressive part of the immune system, i.e. regulatory T cells, is functioning.  

Antibiotics Compromise the Immune System

The major point here is that antibiotics disrupt normal bacterial biofilms that line the intestines and these healthy gut bacteria are required for development of regulatory T cells.  Compromise of Tregs leads to autoimmune diseases, e.g. celiac, Hashimoto’s and baldness, and also allergies.

Antigens/Allergens Have Basic Amino Acid Triplets

The antigens targeted in autoimmune diseases, e.g. tTG, anti-nuclear, TPO, and allergies form an obvious pattern.  All of these antigens and allergens have simple amino acid sequences (rare patches of three basic/positively charged amino acids) that enhance their presentation to the immune system to produce antibodies.  Nuclear proteins, for example, are frequent autoantigens and most of these proteins interact with nucleic acids (negatively charged) and have predictable patches of positively charged amino acids (arginine and lysine).  Other common autoantigens have basic amino acid (arg/lys) patches, because they interact with phospholipids (also negatively charged.)  Proteins with basic patches, e.g. HIV-TAT or heparanase, are also readily transported into cells and nuclei.  Peptides with these sequences are produced by action of stomach enzymes on proteins, e.g. milk lactoferrin, and are antimicrobial.

Allergies / Autoimmune Diseases Are a Predictable Consequence of Antibiotics

Doctors treat with antibiotics, but they fail to repair damage that they cause to gut flora.  The gut flora of most patients treated with antibiotics, especially those who are most fastidiously hygienic, never fully recover.  Constipation is a common symptom of severe dysbiosis and related immunoincompetence.  Probiotics are gut flora bandaids and do not survive as components of gut flora.

Gut bacteria are also needed for development of the aggressive part of the immune system.  Thus, autoimmune diseases can be treated with even more intense use of antibiotics, that will eliminate the rest of the immune system.  Since all vitamins are produced by gut flora as quorum sensing signals, antibiotics can also produce the exotic symptoms of vitamin deficiencies.

Antibiotics are essential to many therapeutic approaches, e.g. surgical procedures or therapy for chronic Lyme disease, but they must be used responsibly and treated patients must be subsequently tested to ensure a repaired gut flora and a functional immune system have been reestablished after antibiotics.  Long term antibiotic use needs special attention, e.g. deliberate Repair of Gut Flora or a fecal transplant.

Thus, I think that it is most likely that ever increasing antibiotic exposure and processed foods, coupled with obsessive hygiene have led to crippled gut flora (as observed in the simplified gut microbiomes of Americans), a net decline in suppressive Tregs and the observed increase of autoimmunity and allergies.  The competence of the immune system may be a major determinant in the course of infection with a pathogen that can produce chronic infections.

Celiac Causes Allergies and Autoimmune Diseases

Anti-Tissue Transglutaminase Can Lead to Hashimoto’s Thyroiditis

Celiac, gluten intolerance, causes intestinal inflammation and immunological presentation of the common intestinal protein, tissue transglutaminase (tTG). The result is anti-tTG autoantibodies that stimulate an immune attack on intestines and other tissues.

Heparan-Binding Proteins Involved in Autoimmunity and Allergy

Those familiar with my blog know that I am obsessed with heparin-binding protein domains. The reason that I am focused on these parts of proteins, is because most cells rapidly sweep heparan sulfate polysaccharides across their surfaces from sites of secretion to sites of internalization. During inflammation, proteins with strong heparin-binding domains, consisting of triplets of basic amino acids, e.g. KRK (lysine-arginine-lysine), are internalized along with the heparan sulfate. The result is an aberrant presentation of these internalized proteins to the immune system and production of inappropriate antibodies, e.g. autoantibodies.

Basic Triplets in Hasimoto’s Autoantigens

One of my hobbies is checking for the unusual occurrence of basic triplets in autoantigens and allergens. I have found dozens of examples. The most recent is associated with Hashimoto’s Thyroiditis. I knew that attack on the thyroid was common in celiacs, because the celiac autoantigen tTG (it has a basic triplet) is also present in the thyroid and the celiac autoantibodies to tTG also cause an attack on the thyroid. But the autoantigen for Hashimoto’s Thyroiditis is thyroid peroxidase (TPO).

I was momentarily perplexed, but then examined the TPO amino acid sequence and immediately found a couple of basic triplets (KKR and KRK).

MRALAVLSVTLVMACTEAFFPFISRGKELLWGKPEESRV
SSVLEESKRLVDTAMYATMQRNLKKRGILSPAQLLSFSK
LPEPTSGVIARAAEIMETSIQAMKRKVNLKTQQSQHPTD
ALSEDLLSIIANMSGCLPYMLPPK...


Hashimoto’ Thyroiditis Linked to Celiac

Then, I did a PubMed search for “celiac and Hashimoto’s”. As expected, there is a recent paper (see below) that shows that celiac commonly leads to Hashimoto’s Thyroiditis.

An obvious explanation is that the initial attack on the thyroid by anti-tTG autoantibodies of celiac leads to thyroid inflammation and presentation of TPO, with a second round of autoantibodies produced to TPO resulting in Hashimoto’s Thyroiditis. Celiac may be the initial autoimmune trigger for many other autoimmune diseases and allergies.

Autism has been associated with maternal autoimmunity and placental abnormalities. Guess where tTG is found in high abundance?

reference:
Bardella MT, Elli L, Matteis SD, Floriani I, Torri V, Piodi L. Autoimmune disorders in patients affected by celiac sprue and inflammatory bowel disease. Ann Med. 2009;41(2):139-43.