Irritable bowel syndrome: tracking down the causes

Christiane Fux studied journalism and psychology in Hamburg. The experienced medical editor has been writing magazine articles, news and factual texts on all conceivable health topics since 2001. In addition to her work for, Christiane Fux is also active in prose. Her first crime novel was published in 2012, and she also writes, designs and publishes her own crime plays.

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Flatulence, diarrhea, constipation, cramps - the symptoms that irritable bowel syndrome can cause are diverse and can be very stressful. The disease is widespread - it is estimated that every sixth person in Germany suffers from it. But the exact causes are still not known - and there is no therapy that really gets to the root of the problem.

Altered proteins in the intestinal wall

Scientists at the Technical University of Munich have come one step closer to clarifying this. The team around Dr. Sabine Bühner and Prof. Michael Schemann examined samples from the intestinal mucosa of 20 irritable bowel patients. The researchers found that the composition and proportions of more than 200 proteins in it typically deviated from the normal picture.

Altered nerve function as the cause

The proteins are so-called proteases. These act as digestive enzymes, but also as messenger substances in the intestine. Apparently, the changed protease patterns cause a change in nerve activity in the patient's intestine - and that ultimately causes the symptoms typical of irritable bowel syndrome. A key role is played by a receptor that acts as a docking point for the proteases: the protease activated receptor 1 (PAR1).

Differences from ulcerative colitis

Interestingly, the proteases were not only changed in comparison to the intestinal mucosa samples from seven healthy people who served the researchers as a control group. They also differed from the protease patterns obtained from samples from twelve patients with currently inactive ulcerative colitis. This inflammatory bowel disease has symptoms similar to those of irritable bowel syndrome.

Up until now, it had been assumed that irritable bowel syndrome might be a mild form of ulcerative cholitis. The study could not confirm this: PAR1 played no role here.

98 percent hit rate

According to calculations by the researchers, the predictive power of the protease profile for the diagnosis of irritable bowel syndrome was 98 percent. “However, with the small number of samples, this should be treated with caution,” says study leader Schemann when asked by The results would have to be confirmed in a large study with several hundred patients.

The researchers also assume that the discovered protease profile cannot be found in all patients. “It will probably not apply to all irritable bowel patients, as they form a very heterogeneous group of patients,” says Schemann.

Direct evidence of irritable bowel syndrome?

Nevertheless, special protease patterns could make diagnosis easier in the future. Because so far, doctors first have to rule out all other possible causes for the symptoms in order to determine irritable bowel syndrome. In addition to ulcerative colitis, food intolerances can also trigger the typical symptoms.

Effective Medication Option?

In addition, the researchers have succeeded in blocking the excessive nerve activation with a special protease inhibitor. They isolated this from a certain strain of probiotic intestinal bacteria (Bifidobacterium longum NCC3001). “That could be an approach for future treatment with medication,” said Schemann. However, the researcher emphasizes that the blocker is currently not freely available as an active ingredient.

So far, only the symptoms of irritable bowel syndrome can be alleviated: with appropriate remedies for constipation, diarrhea or flatulence. Exercise, reducing stress or psychotherapy can also help calm the irritated bowel. Therapy for the causes of the syndrome is currently not available.

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