Akkermansia muciniphila alleviates metabolic disorders through gut microbiota-mediated tryptophan regulation

Abstract High-fat diet (HFD) consumption poses a significant public health threat due to its strong association with obesity, hyperlipidemia, cardiovascular diseases, and metabolic syndrome. While Akkermansia muciniphila has emerged as a promising probiotic for ameliorating metabolic disorders, the underlying mechanisms-specifically its interplay with intestinal tryptophan metabolism-remain poorly understood. Here, we demonstrate that A. muciniphila supplementation mitigates HFD-induced metabolic dysfunction in zebrafish by orchestrating a gut microbiota-tryptophan metabolite-AhR signaling axis. Firstly, A. muciniphila treatment effectively reduced the final weight of zebrafish, partially mitigated weight gain caused by HFD, and improved survival rate. In addition, A. muciniphila treatment reduced zebrafish adiposity, hepatic steatosis, and endotoxemia while enhancing the antioxidant capacity of the liver. We further found that A. muciniphila exerted anti-apoptotic effects, improved chronic low-grade inflammatory responses, enhanced antioxidant capacity, and repaired intestinal barriers induced by HFD. These effects were partially abolished by antibiotic pretreatment, confirming microbiota dependency. Subsequent 16S rRNA sequencing analysis revealed that A. muciniphila supplementation reshaped gut microbiota, enriching Staphylococcus and Vibrionaceae, while depleting Acinetobacter, Perlucidica, and Massilia. In addition to reducing lipid synthesis, metabolomic profiled the substantial changes in microbiota-regulated tryptophan metabolism, including increased levels of indole-3-lactic acid, indole-3-acetaldehyde, and 5-hydroxyindole acetic acid in Amuc group. These metabolites activated aryl hydrocarbon receptor (AhR), upregulating downstream IL-22 and improving intestinal integrity and chronic inflammatory response. Pathway analysis and enzyme gene expression detection indicated that A. muciniphila may inhibit the KP pathway while promoting the microbiota-dependent tryptophan metabolic pathway. This study establishes a novel link by which A. muciniphila exerts protective effects against HFD-induced metabolic syndrome through microbiota-mediated enhancement of tryptophan metabolism.