Bupleurum polysaccharide improves CUMS-induced depressive behavior in rats by regulating the "microbiota-gut-brain...

This study aimed to comprehensively investigate the antidepressant mechanisms of Bupleurum polysaccharide (BP) through the microbiota-gut-brain axis, employing an integrated multi-omics approach. Using a chronic unpredictable mild stress (CUMS) rat model of depression, we evaluated BP's effects on depressive-like behaviors and analyzed its regulatory mechanisms on metabolites and gut microbiota through combined metabolomics and metagenomics. Structural characterization revealed that Bupleurum polysaccharide SPAP-1 is an acidic homogeneous polysaccharide with a molecular weight of approximately 100 kDa, primarily composed of glucose, mannose, rhamnose, and other monosaccharides. Pharmacodynamic assessments demonstrated that BP significantly ameliorated CUMS-induced depressive behaviors, including weight loss, reduced food intake, anhedonia, and behavioral despair (P < 0.05). Metabolomic analysis identified 19 differential metabolites, with BP reversing 11 of them, primarily involved in phenylalanine and tryptophan metabolism pathways. Western blot analysis confirmed BP's regulatory effects on key enzymes Got1 and Lta4h. Metagenomic results showed that BP remarkably reshaped gut microbiota structure, restored microbial diversity, optimized the Firmicutes/Bacteroidetes ratio, enriched beneficial genera (Agathobacter, Phocaeicola), and inhibited pathogenic genera (Ruminococcus). Crucially, integrated multi-omics analysis revealed significant microbiota-metabolite correlations, demonstrating that BP-promoted beneficial bacteria positively correlated with neurotransmitter precursors, while BP-inhibited pathogenic bacteria associated with pro-inflammatory mediators. Mediation analysis further established the "microbiota → metabolite → behavior" causal chain, with Ruminococcus → LTB4 → despair behavior accounting for 42.3 % of the mediation effect. In conclusion, Bupleurum polysaccharide ameliorates depressive-like behaviors through multi-target regulation of the metabolite-microbiota interaction network, highlighting its potential as an antidepressant agent or functional food and providing a novel research paradigm for understanding the multi-target characteristics of traditional Chinese medicine polysaccharides.