Study Finds Gut Bacteria can Affect Intestines' Protective Layer

Celiac.com 03/15/2011 - For celiacs, it's not really the cinnamon bun that's the enemy. Nor the pizza crust, nor the ravioli. It's the gliadin in these foods - the alcohol-soluble portion of the gluten protein - that's the real culprit.

Gliadin is the "gladiator" of the human digestive tract. When we ingest gliadin, enzymes try to break it down into a form that can be absorbed by the small intestine. But gliadin resists, fighting hard to remain intact.

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A regular small intestine has, like any good fortress, a protective wall: the mucosal lining of the intestine. This layer of mucus normally acts as a barrier against gliadin's assaults. But in a celiac intestine, the mucosal lining is permeable. With gliadin's destructive power enhanced by its enzyme sidekick, tissue Transglutaminase (tTG), it quickly gets past this poorly-guarded layer.

Scientists are working to put their finger on exactly what makes the mucosal lining of a celiac's small intestine so permeable.

Now a January study by Czech researchers found at least one thing that affects the permeability of the intestinal mucosa: gut bacteria.

In this study, called "Role of Intestinal Bacteria in Gliadin-Induced Changes in Intestinal Mucosa: Study in Germ-Free Rats", researchers tied off sections of rats' intestines and introduced various kinds of bacteria to each section. They wanted to measure the effect that these bacteria had on the intestinal mucus - or more specifically, on the goblet cells that produce the intestinal mucus. To ensure that the kinds of bacteria in the rats' intestines were under experimental control, the rats had been raised from birth in germ-free conditions.

They found that introducing gliadin to the intestines had the effect of decreasing the mucus-producing cells, thereby eroding the intestines' protective layer. No big surprises there - gliadin is a fighter, a digestive "gladiator", after all.

But when they added strains of so-called harmful bacteria, Escherichia coli (otherwise known as E coli) or Shigella, the mucus-producing cells decreased even more. The cells first secreted massive amounts of mucus, then promptly exhausted themselves and gave up. This left the intestine looking very similar to that of a person in the early stages of celiac disease, say the researchers.

But the tale did indeed have a happy ending. Along came the good bacteria, Bifidobacterium bifidum (or "Biff" for short). The mucus-producing cells in the small intestine increased when Biff was present. In fact, Biff was able to partially reverse the mucus-decreasing effects of E coli and Shigella.

The researchers concluded that the composition of gut bacteria has an effect on the protective mucus of the intestines: an overgrowth of bad bacteria decreases the protective layer, while the addition of good bacteria increases the protective layer. Their study may eventually lead to treatment options for human celiacs, by finding ways to protect tender intestines from the harmful effects of gliadin.

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