Bile Acids: A Bridge Linking Gut Microbiota and NAFLD

Abstract

Nowadays, nonalcoholic fatty liver disease (NAFLD) becomes the most common cause of liver disease worldwide. Mounting evidence indicates that dysbiosis contributes to the pathogenesis of NAFLD. Bile acids (BAs), the molecules that are first synthesized in hepatocytes and further metabolized by gut microbes, can either circulate in enterohepatic system or be found in circulations to exert various effects. Dysbiosis brings about the dysregulated BA composition, which is also observed in the pathology of NAFLD. As important signaling molecules, BAs bind to broadly expressed bile acid receptors (BARs) and play diverse roles in biological activity. Energy metabolism, immune system, and intestinal barrier function are affected by changes in BAs and their signaling pathways, which may explain the mechanisms of how altered BA pool affect NAFLD. Several novel NAFLD treatments targeting BA signaling are under development and their challenges and limitations are also discussed in this review.