Bile acids as gatekeepers: Orchestrating gut-liver axis for metabolic and immune balance

Bile acids (BAs) represent the terminal products of cholesterol catabolism and are integral to a wide range of physiological processes. The maintenance of BAs homeostasis is essential for human health, with disruptions being implicated in various liver and intestinal disorders. The gut-liver axis, a bidirectional communication network connecting multiple organ systems, plays a crucial role in preserving both metabolic and immune homeostasis. Recent evidence suggests that BAs are key modulators within this axis, influencing intestinal barrier function, immune responses, and the composition of the gut microbiome. This review synthesizes recent advances in our understanding of BAs, including their origins, circulation within the gut-liver axis, and diverse roles in physiology, thereby highlighting the critical functional significance of this BAs-mediated network.