The prevalence of inflammatory bowel disease (IBD), which include Crohn’s disease and ulcerative colitis, is on the rise. Now, researchers have found that a type of chemically modified bile acids, in particular taurocholic acid (TCA), play an important role in maintaining gut health during inflammation.

The findings, published in Nature Communications, suggest that TCA can help to manage IBD by supporting the gut barrier and influencing microbiota composition.

Bile acids—natural compounds made by the liver to help digest fats—are modified by gut microbes. One key microbial enzyme turns bile acids into new forms called microbial conjugated bile acids, and recent research suggests that these molecules influence inflammation. Indeed, disruptions in bile acid metabolism have been linked to IBD, but the exact mechanisms remain unclear. 

So, researchers led by Yousi Fu at Michigan State University studied the effects of TCA, a type of conjugated bile acid, in mice with colitis.

Preventing inflammation

Mice lacking a gene important for making TCA showed more severe symptoms of colitis, including greater weight loss and shorter colons, compared to normal mice. However, when these mice were given a supplement of TCA, their gut health improved.

TCA-treated mice also showed signs of better gut barrier function, with increased expression of protective genes and proteins in the colon. TCA supplementation appeared to preserve the mucus layer and maintain the integrity of the intestinal lining.

Finally, TCA was linked to lower levels of bile acids associated with inflammation. These findings suggest that TCA helps rebalance bile acid metabolism during gut inflammation, the researchers say.

Microbiota diversity

Mice with colitis had less diverse gut bacteria than healthy mice, but when TCA was added to their diet, it helped preserve microbiota diversity. TCA also prevented the loss of beneficial bacteria such as Lachnospiraceae, which are known to help process bile acids. 

Further analyses revealed that the gut bacteria that help break down bile acids are often reduced in people with IBD. This observation may explain why certain harmful types of bile acids accumulate in their guts, the authors say.

However, they add, more research is needed to understand how bile acids are combined and broken apart in the gut, as this balance is important for figuring out how to make them work effectively in the clinic.