Psyllium fiber protects against ulcerative colitis and suppresses inflammation by activating the bile acid nuclear receptor, a previously unrecognized mechanism, a new study with mice shows.
The findings reveal that psyllium, which is semi-soluble and derived from Plantago seeds, inhibits inflammation that can lead to colitis in mice by increasing serum bile acids, resulting in the activation of the farnesoid X receptor (FXR), a bile acid nuclear receptor.
Fiber-rich foods promote intestinal and metabolic health, but the extent of protection varies for each fiber type and the mechanisms that offer this protection are poorly defined.
It has been unclear whether dietary fiber can benefit severe forms of intestinal inflammation, such as Crohn’s disease and ulcerative colitis, which are collectively known as inflammatory bowel disease (IBD) and affect 3 million adults in the United States.
Researchers designed the study in the journal Cellular and Molecular Gastroenterology and Hepatology to identify specific fibers that might protect mice in two models of experimental colitis. The study also investigated the mechanism by which protective fibers might suppress inflammation.
Several fibers were tested, including inulin, cellulose, pectin, glucomannan, and psyllium. The authors found psyllium has the unique ability to improve two chronic inflammatory states: metabolic syndrome and colitis.
“The results were impressive in that even modest amounts of psyllium provided strong protection in both colitis models,” says senior author Andrew Gewirtz, professor in the Institute for Biomedical Sciences at Georgia State University.
“That psyllium can offer protection against colitis fits with limited human studies that psyllium is effective in maintaining remission of ulcerative colitis, but its mechanism of action was largely unknown,” says lead author Alexis Bretin, a postdoctoral fellow in the Institute for Biomedical Sciences , noting that the new study fills this gap in knowledge.
Psyllium led to an increase in bile acids that resulted in activation of the FXR bile acid receptor. Such FXR activation was necessary and sufficient to prevent colitis. This suggests that pharmacologic FXR activation might be useful in managing IBD.
The study also provides evidence that dietary fiber can benefit IBD, which has been unclear.
“There has been a lack of consensus on the impact of dietary fiber on IBD, and the notion that soluble/fermentable fibers might negatively impact IBD has prompted many patients to consume low-fiber diets, thus missing out on the broad array of health benefits provided by fiber,” Gewirtz says. “Our findings indicate distinct fibers act quite differently from each other and thus more human studies of specific fibers are warranted.”
Additional coauthors are from the University of Toledo College of Medicine and Life Sciences, the University of Toronto, Purdue University, Research Diets Inc., the Max Planck Institute for Biology, Penn State, the Université Paris Cité, and Georgia State.
The National Institutes of Health funded the work.
Source: Georgia State University