Bound Polyphenols in Rice Bran Insoluble Dietary Fiber Ameliorate Intestinal Barrier Damage via Butyrate-Mediated Regulation of Apoptosis-Autophagy Signaling

Bound polyphenols (BPs) are critical to the anti-obesity effects of dietary fiber. However, their role in dietary-fiber-mediated intestinal barrier protection remains unclear. In this study, we demonstrated that rice bran insoluble dietary fiber (RIDF) alleviated intestinal barrier damage in high-fat-diet (high-fat diet)-fed mice, and this beneficial effect was dependent on BPs, as it was attenuated in mice treated with polyphenol-removed dietary fiber (RIDF_DF). Furthermore, fecal supernatant transplantation from RIDF-treated (not RIDF_DF-treated) mice alleviated obesity and reshaped the gut microbiota in recipient mice. Additionally, the fecal supernatant enhanced the intestinal barrier function and augmented the synthesis of short-chain fatty acids. Notably, butyrate administration upregulated intestinal tight junction proteins in Caco-2 cells and HFD-fed mice and increased Oscillospira abundance. Mechanistically, butyrate inhibited apoptosis and promoted autophagy, accompanied by alterations in the AMPK-Akt signaling pathway. These results indicate that BPs contribute to the ameliorative effect of RIDF on intestinal damage.