Is SIBO an Autoimmune Condition or Triggered by One?
Gut motility issues are center stage when addressing SIBO (small intestinal organism overgrowth). Food and digestive contents must be kept moving forward through the digestive tract, at a reasonable speed, both during meals and in between meals. This needs to happen to both prevent SIBO from occurring in the first place and to prevent SIBO from coming back after treatment. What if these waves of motion were inhibited by an autoimmune condition?
On quite a few occasions, during intake conversations with my patients, they share that their digestion simply began to stall and they don’t know why it happened. I ask them, “Did you have food poisoning three months prior to this happening?” More often than not, this is the case! So, what happened?
Beginning in the esophagus, food is moved down the tract by a process called peristalsis. These rhythmic waves of smooth muscle contractions help food continue to move forward through the digestive tract. Picture the movement of an earth worm for a moment and you will start to understand how these peristaltic waves move down the smooth muscle of your digestive tract, all the way from your esophagus, down through the small intestine.
In between meals, during a fasting state, the digestive track is swept by cleansing waves signaled by the Migrating Motor Complex. One of its functions is to transport organisms from the small intestine to the large intestine; this includes bacteria, so you can see how important this sweeping motion is to the prevention and the treatment of SIBO. It is regulated by gut hormones and nerve signaling from the central nervous system.
When the Migrating Motor Complex kicks in, there is an increase in gastric, biliary and pancreatic secretions (stomach secretions, bile and digestive enzymes). This helps digest leftover matter in the small intestine and moves it into the large intestine.
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So, where does the autoimmune piece fit in?
Peristaltic waves are waves of contraction and release. They rely on nerve signaling of the smooth muscle that lines the digestive tract. The smooth muscle is relaxed in its normal, resting state. The nerve signals trigger the contraction of the smooth muscle and these coordinated wave like contractions move food and matter down the digestive tract. It is the ability to contract your smooth muscle that is of interest here.
If the body produces antibodies that disrupt the nerve pathways, that end innervation of nerves into the smooth muscle of the digestive tract, the peristaltic waves will be inhibited – the smooth muscle cannot contract. This is one way that gut motility is inhibited.
How does this happen?
It happens when the body is exposed to a toxin, the body then produces antibodies to the toxin and these antibodies not only attack the toxin, they also attack a protein in your gut called vinculin. This is through a process called molecular mimicry. The protein sequences in vinculin resembles the toxin closely enough that the antibodies think vinculin is a foreign invader and begin to attack it. This is an autoimmune condition, where your immune system has produced an antibody that is attacking self.
Where does this toxin come from? The short answer is a food poisoning event.
E. coli, Salmonella, Shigella or Campylobacter all produce a common toxin called Cdt-B toxin (Cytolethal Distending Toxin B). Once exposed to this toxin, some people (not all) will produce antibodies to the Cdt-B toxin. These antibodies will also attack vinculin creating an autoimmune condition.
Where does Vinculin come in?
Vinculin is a protein that connects a network of cells within the pacemaker of the gut, called the Interstitial Cells of Cajal. The pacemaker of the gut does exactly what you think it would, it is the signaling network that signals the coordinated wave like contractions of peristalsis; it sets the pace. Vinculin helps these cells connect and communicate electrical signals to contract your smooth muscle.
If vinculin is damaged or destroyed, it can’t link the cells within the pacemaker and you then can’t transmit the electrical signal to contract your smooth muscle. This stalls gastric motility during meals and in between meals.
We think that 20% of people exposed to this toxin will go onto develop SIBO, with ongoing IBS symptoms and that this takes about three months to develop. Here is what it looks like:
There is a food poisoning event and exposure to Cdt-B toxin which triggers gastritis. 20% of people will create an antibody to the toxin. They will recover from the food poisoning event – gut symptoms will return to normal. The antibodies created to address the toxin start to attack vinculin. Over time, your gut motility slows, leading to a highly fermentable environment in the small intestine and setting the stage for SIBO and IBS symptoms that appear around the three month mark.
Since the gut symptoms seem to recover after the food poisoning event and then begin to rear their head around the three month mark, many people don’t equate the gut symptoms with the food poisoning event.
Currently, a SIBO eating plan, supplemental and prescription prokinetics, stress management, addressing meal timing and addressing SIBO with herbal therapies (so SIBO organisms do not make things worse by furthering constipating you) are the best way to treat this. The Cdt-B toxin and vinculin connection is a new discovery from Dr. Mark Pimentel’s group – that will lead to new medications that will help people treat this form of gut paresis.
Dr. Mark Pimentel and his team are currently developing a blood test that will test for the presence of this anti- antibody to vinculin. This will be the first IBS test that will allow us to quickly identify an IBS diagnosis, as it differentiates between IBS and an inflammatory bowel disease. If we can identify this toxin as a contributing factor for you acquiring SIBO, then this information will help with the formulation of both the short and long term treatment planning to address SIBO.
Gut motility will not easily be reinstated. Long term prokinetic (pro gut motility) medications and/ or supplements will need to be utilized to try to make up for this loss in gut motility. The next step is to find a medication that can target these antibodies to reduce the damage that is done to vinculin.
Angela Pifer is a Functional Medicine Nutritionist with a decade of experience, specializing in the treatment of SIBO.
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