Lactate Protects Intestinal Epithelial Barrier Function from Dextran Sulfate Sodium-Induced Damage by GPR81 Signaling.

The dysregulation of the intestinal epithelial barrier significantly contributes to the inflammatory progression of ulcerative colitis. Recent studies have indicated that lactate, produced by gut bacteria or derived from fermented foods, plays a key role in modulating inflammation via G-protein-coupled receptor 81 (GPR81). In this study, we aimed to investigate the potential role of GPR81 in the progression of colitis and to assess the impact of lactate/GPR81 signaling on intestinal epithelial barrier function. Our findings demonstrated a downregulation of GPR81 protein expression in patients with colitis. Functional verification experiments showed that Gpr81 -deficient mice exhibited more severe damage to the intestinal epithelial barrier and increased susceptibility to DSS-induced colitis, characterized by exacerbated oxidative stress, elevated inflammatory cytokine secretion, and impaired expression of tight-junction proteins. Mechanistically, we found that lactate could suppress TNF-α-induced MMP-9 expression and prevent the disruption of tight-junction proteins by inhibiting NF-κB activation through GPR81 in vitro. Furthermore, our study showed that dietary lactate could preserve intestinal epithelial barrier function against DSS-induced damage in a GPR81-dependent manner in vivo. Collectively, these results underscore the crucial involvement of the lactate/GPR81 signaling pathway in maintaining intestinal epithelial barrier function, providing a potential therapeutic strategy for ulcerative colitis.