Rice Bran Insoluble Dietary Fiber and Its Bound Polyphenols Alleviate Colitis by Regulating the Autophagy-NLRP3 Inflammasome Axis.

Although dietary fiber alleviates colonic inflammation, most studies have focused on carbohydrate components, neglecting bound polyphenols (BPs). Rice bran insoluble dietary fiber (RIDF), rich in BPs, improves colitis; however, how BPs work and their specific contributions remain elusive. Our study demonstrates that BPs are important contributors of RIDF in alleviating colitis. Relative to rice bran dietary fiber without BPs (RIDF_DF), RIDF markedly ameliorated colitis symptoms, mitigated endoplasmic reticulum stress (ER stress), restored the gut microbiome and metabolites, and blocked the PI3K/Akt/mTOR cascade and NLRP3 inflammasome activation. 3-MA abolished, whereas RAPA restored, these protective effects via the autophagy-NLRP3 axis, identifying this axis as an important hub. Collectively, BPs served as an important functional component of RIDF. They ameliorated colitis by activating the autophagy-NLRP3 axis, which suppressed ER stress, repaired the intestinal barrier, and restored the gut microbiome and metabolome.