Shipi Zengye Formula Simultaneously Ameliorates Functional Constipation and Depression by Upregulating SLC6A3 and Remodeling the Prevotella copri-Bile Acid Axis.

ETHNOPHARMACOLOGICAL RELEVANCE: Functional constipation (FC) and depression frequently coexist, yet the gut-brain mechanisms underlying this comorbidity remain poorly understood. Shipi Zengye Formula (SPZY), a traditional Chinese medicine (TCM) formula, is clinically used to treat constipation accompanied by depressive symptoms; however, its therapeutic efficacy and underlying mechanisms require further validation. MATERIALS AND METHODS: A rat model exhibiting both constipation-related and depressive-like phenotypes was established using loperamide combined with chronic unpredictable mild stress (CUMS). Sprague-Dawley rats were assigned to the control, model, lactulose, and SPZY groups and treated for four weeks. Constipation-related parameters, depressive-like behaviors, SLC6A3 expression in the colon and hippocampus, gut microbial composition, serum metabolite profiles, and colonic transcriptomic changes were evaluated using physiological and behavioral assessments, immunofluorescence staining, Western blotting, enzyme-linked immunosorbent assays, 16S rRNA gene sequencing, untargeted metabolomics, and RNA sequencing. The multi-omics datasets were integrated using Spearman correlation analysis. RESULTS: SPZY increased fecal water content and intestinal transit, shortened forced-swimming immobility time, and restored sucrose preference, with greater efficacy than lactulose. SPZY also increased SLC6A3 expression in both the colon and hippocampus. Multi-omics analyses revealed enrichment of Prevotella copri (P. copri), restoration of bile acid profiles, particularly tauro-β-muricholic acid and taurocholic acid, and modulation of colonic genes involved in neural, immune, and metabolic processes. Correlation analyses linked P. copri and bile acids to constipation-related and depressive-like phenotypes, whereas SLC6A3 was not directly associated with the microbiota-metabolite network. CONCLUSION: Shipi Zengye Formula (SPZY) alleviated constipation-depression comorbidity in a combined loperamide-CUMS rat model. Its effects were associated with increased SLC6A3 expression and remodeling of the P. copri-bile acid axis.