Background: The cause of aggravation of diabetic myocardial damage is yet to be elucidated; damage to mitochondrial function has been a longstanding focus of research. During diabetic myocardial ischaemia–reperfusion (MI/R), it remains unclear whether reduced mitochondrial fusion exacerbates myocardial injury by generating free damaged mitochondrial DNA (mitoDNA) and activating the cGAS-STING pathway.Methods: In this study, a mouse model of diabetes was established (by feeding mice a high-fat diet (HFD) plus a low dose of streptozotocin (STZ)), a MI/R model was established by cardiac ischaemia for 2 h and reperfusion for 30 min, and a cellular model of glycolipid toxicity induced by high glucose (HG) and palmitic acid (PA) was established in H9C2 cells.Results: We observed that altered mitochondrial dynamics during diabetic MI/R led to increased mitoDNA in the cytosol, activation of the cGAS-STING pathway, and phosphorylation of the downstream targets TBK1 and IRF3. In the cellular model we found that cytosolic mitoDNA was the result of reduced mitochondrial fusion induced by HG and PA, which also resulted in cGAS-STING signalling and activation of downstream targets. Moreover, inhibition of STING by H-151 significantly ameliorated myocardial injury induced by MFN2 knockdown in both the cell and mouse models. The use of a fat-soluble antioxidant CoQ10 improved cardiac function in the mouse models.Conclusions: Our study elucidated the critical role of cGAS-STING activation, triggered by increased cytosolic mitoDNA due to decreased mitochondrial fusion, in the pathogenesis of diabetic MI/R injury. This provides preclinical insights for the treatment of diabetic MI/R injury.Graphical

Diabetes mellitus represents a major global health challenge and is strongly associated with cardiovascular complications, among which diabetic cardiomyopathy (DCM) is a major contributor to heart failure. Increasing evidence indicates that mitochondrial dysfunction plays a central role in DCM pathogenesis. However, mitochondrial abnormalities in the diabetic heart reflect not merely cellular injury but a coordinated process of mitochondrial metabolic reprogramming, characterized by altered substrate utilization, impaired oxidative phosphorylation, and disruption of mitochondrial quality control. Under diabetic conditions, chronic hyperglycemia, insulin resistance, and lipid overload induce profound metabolic remodeling in cardiomyocytes. These disturbances promote excessive reactive oxygen species production, mitochondrial DNA damage, and dysfunction of the electron transport chain. Concurrently, cardiomyocytes undergo a shift in substrate preference, including enhanced glycolysis, dysregulated fatty acid oxidation, and altered amino acid metabolism. Such metabolic inflexibility compromises ATP production and contributes to lipotoxicity, oxidative stress, and cardiomyocyte apoptosis. Recent studies have revealed that mitochondrial metabolic reprogramming is governed by complex regulatory networks, including signaling pathways such as AMPK/PGC-1α, PI3K/Akt/mTOR, hypoxia-inducible factor-1α, and TGF-β/Smad, together with epigenetic mechanisms and mitochondrial quality control processes. Disruption of mitochondrial dynamics, mitophagy, and mitochondrial biogenesis further promotes the accumulation of dysfunctional mitochondria and accelerates disease progression. In this review, we summarize current advances in the mechanisms underlying mitochondrial metabolic reprogramming in diabetic cardiomyopathy and discuss emerging therapeutic strategies targeting mitochondrial metabolism. By integrating mitochondrial biology with cardiovascular metabolism, this review provides a comprehensive framework for understanding DCM pathogenesis and highlights potential directions for precision therapeutic intervention.