Eucommia polysaccharides alleviate experimental colitis by reshaping colonic microbiota composition, metabolites, and modulating the IL-17 signaling pathway.

Intake of plant polysaccharides are associated with a reduced risk of ulcerative colitis (UC). Eucommia polysaccharides (EUPs) are promising nutritional supplements with notable antibacterial, anticancer, and anti-inflammatory properties. They exhibit a moderate molecular weight and are resistant to gastric acid degradation. Yet, the action mechanisms of microorganisms and metabolites in EUPs for UC treatment remain incompletely elucidated. The current study was formulated to assess the therapeutic efficacy of EUPs against fecal microbiota transplantation (FMT)-induced colitis, focusing on comparing the effects of low-dose and high-dose EUPs. After East Frisian sheep received dextran sulfate sodium (DSS) intervention, their fecal microbiota was used to prepare fecal bacterial suspensions for mouse FMT. Administration of high-dose EUPs alleviated key colitis symptoms, improved colonic epithelial barrier, preserved microbial diversity, and significantly reduced harmful bacterial (e.g., g_Klebsiella and g_unidentified_Enterobacteriaceae). Furthermore, this treatment significantly enriched the bile secretion pathways, particularly those involving deoxycholic acid (DCA) and hyodeoxycholic acid (HDCA). Additionally, DCA and HDCA were significantly negatively correlated with g_unidentified_Enterobacteriaceae and g_Klebsiella, and these two bile acids were also negatively correlated with key genes associated with the IL-17 signaling pathway. Overall, this study elucidates that EUPs ameliorate FMT-induced colitis in a mouse model via restoring gut microbes and metabolites and modulating the IL-17 pathway, thereby providing novel insights into therapeutic strategies for UC.