Fucoidan Ameliorated Dextran Sulfate Sodium-Induced Ulcerative Colitis by Modulating Gut Microbiota and Bile Acid Metabolism.

Gut dysbiosis and bile acid (BA) metabolism disturbance are involved in the pathogenesis of ulcerative colitis. This study aimed to investigate the effect of fucoidan on BA metabolism and gut microbiota in dextran sulfate sodium-induced colitis mice. Our results showed that fucoidan effectively suppressed colonic inflammation and repaired the gut barrier. In addition, fucoidan increased the relative abundance of the Lachnospiraceae family, such as Turicibacter , Muribaculum , Parasutterella , and Colidextribacter , followed by an increase in short-chain fatty acids, especially in butyrate. Moreover, fucoidan modulated bile acid metabolism by elevating cholic acid, ursodeoxycholic acid, deoxycholic acid, and lithocholic acid and decreasing β-muricholic acid, which led to activation of FXR and TGR5 and further enhanced the gut barrier and suppressed colonic inflammation. Our results revealed that the effect of fucoidan alleviating colitis was largely mediated by gut microbiota, which was confirmed by the fecal transplantation experiment. Collectively, these findings provided the basis for fucoidan as a potential functional food for colitis.