GPR43 deficiency aggravates sepsis by promoting gut microbiota–dependent barrier disruption and HIF-1α–ENO1 axis–mediated M1 polarization of macrophages

GPR43, a receptor for short-chain fatty acids (SCFAs), is broadly expressed in intestinal epithelial and immune cells and is essential for preserving barrier integrity and immune homeostasis. Nevertheless, how GPR43 influences gut microbiota composition and intestinal barrier integrity while also regulating macrophage immunometabolism in the context of sepsis remains poorly understood. A cecal ligation and puncture model was used to induce sepsis in mice. Survival, histopathology, and immune responses were compared between Gpr43−/− and wild-type mice; 16S ribosomal RNA (rRNA) sequencing and untargeted metabolomics were performed to evaluate gut microbiota composition and metabolic profiles. Antibiotic-mediated microbiota depletion and fecal microbiota transplantation were used to assess functional impacts. Bone marrow-derived macrophages were employed to investigate the effects of GPR43 deficiency on macrophage polarization. RNA sequencing, metabolic flux analysis, and Western blotting were conducted to explore the molecular mechanisms involved. Peripheral blood mononuclear cell samples from patients with sepsis were analyzed for clinical correlation. Gpr43−/− mice exhibited significantly reduced survival following CLP, along with impaired intestinal barrier function and elevated proinflammatory cytokine levels. Microbiota diversity and SCFA-producing bacteria were markedly decreased, accompanied by reduced SCFA levels in fecal metabolites. Fecal microbiota transplantation (FMT) partially restored gut function and survival in Gpr43−/− mice. GPR43-deficient macrophages displayed a strong M1-polarized phenotype with the upregulation of the glycolytic enzyme ENO1 and its upstream regulator HIF-1α. The inhibition of either ENO1 or HIF-1α reversed the proinflammatory phenotype. A clinical data analysis revealed that GPR43 expression was negatively correlated with IL-6, ENO1, and lactate levels. GPR43 exerts a dual protective role in sepsis by maintaining gut microbiota homeostasis and barrier integrity and by modulating macrophage metabolism and polarization via the HIF-1α–ENO1 axis. This study provides novel insights into the GPR43 in pathogenesis of sepsis and suggests potential therapeutic targets for intervention.