The chronic gut pain people with irritable bowel syndrome (IBS) experience may be due to long-lasting activation of a select group of gut cells. In mice, these cells continue to react to irritants even after the substances have left the gut.
IBS affects up to 15 per cent of the US population and is two to six times more common in women than men. The condition is characterised by symptoms like bloating, abdominal pain and hypersensitivity to certain foods and irritants, despite there being no intestinal damage.
at the University of California, San Francisco and his colleagues examined the role of enterochromaffin (EC) cells, which line the gut and activate when exposed to irritants. EC cells can remain active even after irritants have left the gut, potentially explaining why chronic gastrointestinal conditions, such as IBS, commonly develop after infections or food poisoning.
Advertisement
Julius and his colleagues coated mice鈥檚 intestines with a fatty acid called isovalerate, one of many chemicals known to activate EC cells. They then inserted a balloon-like device into the animals鈥� colons to simulate intestinal gas and bloating. Like us, mice curl up when experiencing discomfort like abdominal contractions, and that gave the researchers a way to gauge the animals鈥� pain.
They found that male mice given isovalerate were much more sensitive to the expanding balloon than males who weren鈥檛 given the fatty acid: they spent more time curled up in response to the simulated abdominal contractions. Female mice, on the other hand, remained hypersensitive to the balloon regardless of whether they had been exposed to isovalerate. Julius says this is probably because EC cells in female mice have higher levels of baseline activity.
鈥淸This] suggests that one of the elements that might account for sex differences in [gastrointestinal] sensitivity is the sensitivity of these EC cells,鈥� says Julius, who presented at the Advances in Pain conference in New York City on 3 May.
Next, the researchers treated male mice daily for three weeks with artificially engineered proteins that activate EC cells, followed by three days of no treatment. Even after the proteins left the intestines, the mice remained more sensitive to the balloon experiment compared with the controls.
鈥淭he question we have now is what if we [monitored them] for three weeks, two months, a year 鈥� will we still see a sensitisation?鈥� says Julius. Answering that question may explain why people with IBS experience symptoms long after irritants or infections clear from their gut.
Sign up to our free Health Check newsletter for a round-up of all the health and fitness news you need to know, every Saturday
