Lacticaseibacillus rhamnosus HF01 postbiotics reprogram gut microbial tryptophan metabolism to coordinate enterohepatic barrier-insulin signaling axis

High-fat diet (HFD) disrupts gut microbiota homeostasis, induces intestinal barrier damage and systemic inflammation, ultimately leading to insulin resistance and hepatic glucose metabolism disorders. This study investigated the therapeutic effects of <i>Lacticaseibacillus rhamnosus</i> HF01 (<i>L. rhamnosus</i> HF01) -derived postbiotic (cell-free supernatant, CFS; defined as metabolites derived from probiotics) on HFD-induced metabolic dysregulation and its regulatory mechanisms via the gut-liver axis. The findings revealed that CFS suppressed pro-inflammatory genera (<i>Bacteroides</i>, <i>Colidextribacter</i>, <i>Helicobacter</i>, and <i>Butyricimonas</i>) while enriching beneficial genera such as <i>Muribaculum</i>, <i>norank_f__Muribaculaceae</i>, <i>Odoribacter</i>, <i>unclassified_f__Lachnospiraceae</i>, and <i>norank_f__Ruminococcaceae</i>. Concurrently, CFS drove tryptophan metabolic reprogramming, significantly elevating levels of IAA, TA, and 5-HIAA while reducing 5-HT production. These changes enhanced intestinal tight junction protein expression and inhibited LPS-triggered inflammatory responses. Furthermore, CFS activated the IRS/PI3K/Akt signaling pathway, reversing HFD-induced insulin resistance and glucose metabolism abnormalities. This study elucidated the regulatory mechanisms of CFS in ameliorating metabolic disorders via the gut-liver axis, providing theoretical support for intervention strategies targeting gut microbiota-derived metabolites.