Carnosic Acid Attenuates Lipotoxicity-Mediated Myocardial Ischemia–Reperfusion Injury by Suppressing Complex I ROS and Modulating the SIRT1–UPRmt Axis

The growing prevalence of high-fat diets and sedentary lifestyles has contributed to a marked rise in metabolic disorders and a concomitant increase in cardiovascular disease (CVD). High-fat diet-induced lipotoxicity is a key pathological driver that exacerbates myocardial ischemia/reperfusion (I/R) injury. Carnosic acid (CA), a natural bioactive compound, shows promise for cardiovascular protection through anti-inflammatory and antioxidant effects. However, the protective effects of CA against lipotoxicity-aggravated myocardial I/R injury and the molecular mechanisms involved remain incompletely understood. In this study, an isolated mouse heart was perfused with a high oleic acid (0.8 mM) solution to create a metabolic stress model of lipotoxicity. Metabolomics was applied to characterize metabolic changes in lipotoxicity-induced myocardial I/R injury. Additionally, the same model was used to investigate the potential mechanisms of action of CA (5 μM). Metabolomic analysis identified pronounced metabolic differences in isolated hearts from the normal and high-fat groups during perfusion, ischemia and reperfusion. Differential metabolites clustered primarily in energy metabolism pathways, consistent with lipotoxicity-driven metabolic derangements that worsen myocardial I/R injury. High-fat perfusion amplified the ischemic accumulation of free fatty acids and succinate in mouse myocardium, thereby aggravating I/R injury. Carnosic acid treatment markedly reversed the lipotoxicity-exacerbated cardiac I/R damage. Mechanistically, CA potentially binds to subunits adjacent to the Q site of mitochondrial complex I, decreasing reactive oxygen species (ROS) production from reverse electron transport (RET). The Sirtuin 1 (Sirt1) inhibitor selisistat (EX527) abolished CA’s protective effect, indicating that CA also modulated the Sirt1-UPRmt pathway to preserve mitochondrial homeostasis and mitigate myocardial injury.