Relationship between the gut microbiota and bile acid composition in the ileal mucosa of Crohn’s disease Original paper

What was studied?

This study focused on the relationship between the gut microbiota and bile acid composition in the ileal mucosa of patients with Crohn’s disease (CD). The researchers sought to investigate how microbial alterations (dysbiosis) in the small intestine correlate with changes in bile acid metabolism, which plays a crucial role in gut health and disease. The authors analyzed the microbial structure and bile acid composition in CD patients during clinical remission and compared them to non-CD controls. They also explored the link between specific gut microbiota taxa and the alterations in bile acid profiles.

Who was studied?

The study involved 38 CD patients in clinical remission and 12 non-CD controls. The participants were selected based on their clinical status, including disease activity indices (CDAI) for the CD group. The samples were collected using balloon-assisted enteroscopy (BAE) from the distal ileum, with samples categorized into active and inactive lesions based on endoscopic findings. The microbiota was analyzed from mucosal samples, while bile acid composition was analyzed from intestinal fluid.

Most important findings

The study found significant alterations in both the gut microbiota composition and bile acid profiles of CD patients. Specifically, the relative abundance of Escherichia was significantly higher in CD patients compared to non-CD controls, while Faecalibacterium and Roseburia (both butyrate-producing genera) were notably reduced. These findings align with previously reported dysbiosis in IBD, where an increase in facultative anaerobes like Escherichia was observed, particularly in active lesions. Furthermore, the study identified a shift in bile acid composition in CD patients, with a higher proportion of conjugated bile acids (such as glycocholic acid and taurocholic acid) and a reduction in the unconjugated bile acids like lithocholic acid (LCA). The composition of bile acids was linked to the microbial community, as higher levels of Escherichia and Lactobacillus were positively correlated with an increased proportion of conjugated bile acids, while Roseburia and Faecalibacterium were negatively correlated with conjugated bile acids.

Key implications

These findings highlight the interplay between the gut microbiota and bile acid metabolism in the pathophysiology of CD. The alteration of bile acid composition, particularly the increase in conjugated bile acids, may suggest malabsorption of bile acids in the ileum, possibly contributing to inflammation in CD. Moreover, the relationship between specific gut microbial taxa and bile acid metabolism could provide potential biomarkers for diagnosing and monitoring disease activity in IBD. Targeting microbiota profiles or manipulating bile acid metabolism could open up new therapeutic avenues for treating CD. Probiotic therapies or dietary interventions aimed at restoring beneficial microbiota and normalizing bile acid metabolism may offer additional strategies to manage or mitigate disease activity.