Gut-Derived Ursodeoxycholic Acid from Saponins of Quinoa Regulated Colitis via Inhibiting the TLR4/NF-κB Pathway

Alteration of the gut microbiota and its metabolites plays a key role in the development of inflammatory bowel disease (IBD). Here, we investigated the mechanism of saponins, a byproduct from quinoa (SQ) processing, in regulating IBD. SQ ameliorated gut microbiota dysbiosis revealed by 16S rRNA sequencing and improved colonic antioxidant activities and barrier integrity in dextran sulfate sodium (DSS)-treated mice. Broad-spectrum antibiotics further proved that the gut-protective effects of SQ were mediated by gut microbiota. Next, fecal microbiota transplantation (FMT) of SQ-induced gut microbiota/metabolites to inoculate DSS-treated mice alleviated colitis significantly. Untargeted metabolomics and lipidomics revealed that ursodeoxycholic acid (UDCA) was enriched as a microbial metabolite after SQ supplementation. UDCA was then found to attenuate DSS-induced colitis in vivo by targeting the TLR4/NF-κB pathway, which was also verified in a Caco-2 cell model treated with a TLR4 agonist/antagonist. Overall, our findings established that gut microbiota-UDCA-TLR4/NF-κB signaling plays a key role in mediating the protective effects of SQ.