Oleanolic acid alleviates intestinal injury after hepatic ischemia–reperfusion under steatosis via PPARG-dependent M2 macrophage polarization

Liver transplantation with steatotic donor livers is often complicated by ischemia-reperfusion injury (IRI), leading to intestinal dysfunction, and reduced long-term survival. This study investigates the protective effects of oleanolic acid (OA), a gut microbiota metabolite, against intestinal injury following IRI in rats with hepatic steatosis and explores its mechanisms. 8-week-old male Sprague-Dawley rats were fed a high-fat diet to induce severe hepatic steatosis and IRI with 80-min ischemia. Gut microbiota was analyzed by 16S rDNA sequencing. Rats were treated with OA or the peroxisome proliferator-activated receptor gamma (PPARG) antagonist GW9662. Intestinal injury was modeled in vitro in IEC-6 and Caco-2 co-cultures with macrophages after lipopolysaccharide treatment. Damage was assessed by hematoxylin-eosin staining, immunohistochemistry, immunofluorescence, cell viability assays, Western blotting, and ELISA. Compared with the normal diet group, rats with severe hepatic steatosis exhibited significant intestinal injury and gut microbiota dysbiosis following IRI. OA treatment markedly alleviated intestinal damage, reduced inflammatory cytokine levels, and improved intestinal function in severe hepatic steatosis rats after IRI. Network pharmacology analysis, molecular docking, and both in vitro and in vivo experiments further revealed that OA exerts its protective effects by activating the PPARG receptor and modulating macrophage polarization. OA alleviates intestinal injury secondary to IRI in severe hepatic steatosis via the activation of PPARG receptor, which promotes macrophage polarization toward the M2 phenotype. By modulating macrophages through the PPARG pathway, OA presents a potential therapeutic strategy for mitigating intestinal injury following hepatic steatosis IRI.