Protective effect of fermented okara on the regulation of inflammation, the gut microbiota, and SCFAs production in rats with TNBS-induced colitis

Dysbiosis of gut microbiota is intimately related to ulcerative colitis. The literature has revealed the gut microbiota metabolism of dietary fiber, which is a key resource for short-chain fatty acids (SCFAs) production and subsequently leads to anti-inflammatory effects. It is known that okara (a soybean byproduct) is rich in dietary fiber, but the effect of fermented okara on relieving colitis remains unclear. The object of this study was to investigate the effects of Aspergillus oryzae-fermented okara (FO) on colitis prevention through gut microbiota manipulation in a 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis rat model. The results showed that administration of FO elevated the relative abundance of SCFAs-producing bacteria (Lachnospiraceae and Bifidobacteriaceae) and SCFAs production, which engaged with GPR43 (SCFAs receptor) consequently decreased the production of proinflammatory cytokines (IL-6, IL-1β, and TNF-α), inflammatory mediators (COX-2, iNOS, PGE2, and NO), and MCP-1 chemokine and increased anti-inflammatory cytokine (IL-10 and IL-4) production through inhibition of HDAC3/MAPK-related proteins and the NF-κB inflammatory pathway in TNBS-induced colitis in rats. Moreover, increased activity of antioxidants, such as SOD, CAT, GSH, and GPx, and decreased MDA and MPO production were also observed after FO administration in TNBS-induced colitis in rats. This study demonstrated the novel potential of soybean byproducts for alleviating TNBS-induced intestinal inflammation and enhancing antioxidant capacity for colitis improvement. This new finding may enhance the value of okara for functional food development.