Bifidobacterium bifidum 1007478 derived indole-3-lactic acid alleviates NASH via an aromatic hydrocarbon receptor-dependent pathway in zebrafish.

Aims: This study investigates the potential of Bifidobacterium bifidum 1,007,478 (BB478) and its metabolite indole-3-lactic acid (ILA) in alleviating non-alcoholic steatohepatitis (NASH) induced by a high-fat diet (HFD) and fructose exposure.

Materials And Methods: A zebrafish model of NASH was established by exposure to HFD and fructose. BB478 was administered, and the effects on liver lipid accumulation, oxidative stress, and inflammation were assessed. ILA production by BB478 was confirmed, and its impact on hepatic lipogenesis and inflammatory pathways was evaluated. The involvement of the aromatic hydrocarbon receptor (AhR) was also examined using an AhR inhibitor.

Key Findings: BB478 supplementation inhibited lipid accumulation in the liver, reduced triglycerides (TG) and total cholesterol (TC), and mitigated oxidative stress, as evidenced by lower levels of reactive oxygen species (ROS) and malondialdehyde (MDA). ILA, produced by BB478, could alleviate the hepatic damage and fat deposition in liver. Mechanistically, it suppressed hepatic lipogenesis by downregulating lipogenesis-related genes, including sterol response element binding protein 1 (SREBP1) and fatty acid synthase (FASN). ILA also inhibited the expression of pro-inflammatory cytokines to suppress inflammation. The therapeutic effects of ILA were reversed by the AhR inhibitor, indicating that ILA's actions are AhR-dependent.

Significance: These findings reveal the potential of ILA, produced by Bifidobacterium bifidum, as a therapeutic agent for NASH. The mechanistic insights into AhR-mediated effects provide a foundation for further exploration of ILA as a novel approach for managing liver diseases.