Mitophagy disorder mediates cardiac deterioration induced by severe hypoglycemia in diabetic mice

WIPI1-mediated mitophagy dysfunction in ventricular remodeling associated with long-term diabetes mellitus

BACKGROUND

WIPI1 is a member of the WD-repeat protein family that interacts with phosphoinositides and plays a crucial role in autophagy. This study investigated how WIPI1-mediated mitophagy dysfunction contributes to ventricular remodeling in rat and mouse models of diabetes mellitus.

METHODS

The study utilized a 32-weeks diabetic animal model to simulate long-term diabetic conditions. AAV9-cTNT-WIPI1 vectors were employed to overexpress WIPI1 in the myocardium. Cardiac function was assessed by echocardiography. Mitochondrial membrane potential was assessed using JC-1 dye. Oxygen consumption rates were quantified using an Oxygraph-O2K high-resolution respirometry.

RESULTS

Long-term diabetes led to decreased ejection fraction and fractional shortening associated with a marked increase in ventricular fibrosis and elevated expression of fibrotic markers such as collagen type I and periostin. Expression of autophagy markers such as LC3b-II and SQSTM1 was reduced, and colocalization with mitochondria was disrupted, suggesting failures in autophagosome formation and maturation. This impairment was further supported by decreased levels of mitophagy-related proteins (PINK and Parkin), indicating impaired mitophagy. WIPI1 knockdown led to mitochondrial dysfunction, characterized by loss of membrane potential and reduced respiratory capacity.

CONCLUSION

WIPI1 is essential for proper mitophagy function. Its downregulation produces ventricular remodeling and dysfunction. These findings suggest that targeting WIPI1-mediated pathways could be a potential therapeutic strategy for treating diabetic cardiomyopathy by improving mitochondrial health and mitophagic processes.

Urolithin A provides cardioprotection and mitochondrial quality enhancement preclinically and improves human cardiovascular health biomarkers

Cardiovascular diseases (CVDs) remain the primary cause of global mortality. Nutritional interventions hold promise to reduce CVD risks in an increasingly aging population. However, few nutritional interventions are proven to support heart health and act mostly on blood lipid homeostasis rather than at cardiac cell level. Here, we show that mitochondrial quality dysfunctions are common hallmarks in human cardiomyocytes upon heart aging and in chronic conditions. Preclinically, the post-biotic and mitophagy activator, urolithin A (UA), reduced both systolic and diastolic cardiac dysfunction in models of natural aging and heart failure. At a cellular level, this was associated with a recovery of mitochondrial ultrastructural defects and mitophagy. In humans, UA supplementation for 4 months in healthy older adults significantly reduced plasma ceramides clinically validated to predict CVD risks. These findings extend and translate UA's benefits to heart health, making UA a promising nutritional intervention to support cardiovascular function as we age.

Endurance Exercise Training Mitigates Diastolic Dysfunction in Diabetic Mice Independent of Phosphorylation of Ulk1 at S555

Millions of diabetic patients suffer from cardiovascular complications. One of the earliest signs of diabetic complications in the heart is diastolic dysfunction. Regular exercise is a highly effective preventive/therapeutic intervention against diastolic dysfunction in diabetes, but the underlying mechanism(s) remain poorly understood. Studies have shown that the accumulation of damaged or dysfunctional mitochondria in the myocardium is at the center of this pathology. Here, we employed a mouse model of diabetes to test the hypothesis that endurance exercise training mitigates diastolic dysfunction by promoting cardiac mitophagy (the clearance of mitochondria via autophagy) via S555 phosphorylation of Ulk1. High-fat diet (HFD) feeding and streptozotocin (STZ) injection in mice led to reduced endurance capacity, impaired diastolic function, increased myocardial oxidative stress, and compromised mitochondrial structure and function, which were all ameliorated by 6 weeks of voluntary wheel running. Using CRISPR/Cas9-mediated gene editing, we generated non-phosphorylatable Ulk1 (S555A) mutant mice and showed the requirement of p-Ulk1at S555 for exercise-induced mitophagy in the myocardium. However, diabetic Ulk1 (S555A) mice retained the benefits of exercise intervention. We conclude that endurance exercise training mitigates diabetes-induced diastolic dysfunction independent of Ulk1 phosphorylation at S555.