Angelica dahurica Polysaccharides Ameliorate Colitis by Reducing the Restriction of Gut Microbiota-Derived Imidazole Propionate on PPAR-γ Signaling Activation.

Angelica dahurica radix (ADR), the root of the botanical family Apiaceae (genus Angelica, species Angelica dahurica (Hoffm.)), has been used to treat colitis in clinical practice. The immunomodulatory effects of ADR are attributed to its polysaccharides (RP). However, its mechanism of action has not been elucidated. In this study, RP's structure was determined through nuclear magnetic resonance analysis. Dextran sulfate sodium-induced colitis in mice was utilized to assess the therapeutic efficacy of RP, while experiments involving fecal microbiota transplantation (FMT) and antibiotic treatment were performed to investigate the contribution of gut microbiota to RP's protective function. Non-targeted metabolomics was utilized to identify potential targets for elucidating the underlying mechanisms. RP is likely composed of (→4)-α-D-Glcp-(1→ and →4)-α-D-Galp-(1→). It effectively alleviated DSS-induced colitis by restoring the balance of the gut microbial community, a finding validated through FMT and antibiotic intervention experiments. Imidazole propionate (ImP) emerged as a potential target for RP's efficacy in treating colitis, which inhibits the activation of peroxisome proliferator-activated receptor gamma (PPAR-γ). Our findings suggest that RP may confer protection against colitis by activating the PPAR-γ signaling pathway through alleviating the constraint imposed by ImP.