Astragalus polysaccharides alleviate DSS-induced ulcerative colitis in mice by restoring SCFA production and regulating Th17/Treg cell homeostasis in a microbiota-dependent manner

Natural polysaccharides from Astragalus membranaceus have been shown to relieve ulcerative colitis (UC). However, the mechanism and causal relationship between the gut microbiota and Astragalus polysaccharides (APS) treatment of UC are unclear. The results of the present study showed that APS ameliorated colonic injury and the disruption of the gut microbiota and restored intestinal immune homeostasis in mice with DSS-induced colitis. Meanwhile, we found that APS treatment was ineffective in antibiotic-treated colitis mice but was effective when FMT (Fecal microbiota transplantation) was performed on UC mice using APS-treated mice as donors. APS increased the proportion of relevant microbiota that produce SCFAs and both direct administration of APS and administration of APS-adjusted gut microbiota significantly promoted the production of SCFAs in colitis mice. We demonstrated that APS dually inhibited NF-κB activation via the TLR4 and HDAC3 pathways and improved the balance in Th17/Treg cells in UC mice. In conclusion, our study revealed that APS is a promising prebiotic agent for the maintenance of intestinal health and demonstrated that APS may ameliorate colitis in a gut microbiota-dependent manner.