Increased fatty acid metabolism attenuates cardiac resistance to β-adrenoceptor activation via mitochondrial reactive oxygen species: A potential mechanism of hypoglycemia-induced myocardial injury in diabetes

The mechanism of severe hypoglycemia (SH)-induced cardiovascular disease in diabetes remains unknown. Our previous study found that SH inhibits cardiac function and lipid metabolism in diabetic mice. Conversely, in nondiabetic mice, SH does not induce cardiac dysfunction but promotes cardiac lipid metabolism. This study aims to clarify the effect of increased fatty acid metabolism on the resistance of cardiomyocytes to β-adrenoceptor activation during hypoglycemia in diabetes. Results revealed that cardiomyocytes with enhanced lipid metabolism were more vulnerable to damage due to β-adrenoceptor activation, which presented as decreased cell viability, disorder of mitochondrial structure, dissipation of mitochondrial membrane potential, dysfunction of mitochondrial oxidative phosphorylation, nonapoptotic damage, and accumulation of ROS and calcium from mitochondria to cytoplasm, all of which were partially reversed by mitochondrial antioxidant Mito-TEMPO. The SH-induced cardiac dysfunction, and reduction of myocardial energy metabolism in diabetic mice were rescued by Mito-TEMPO. Our findings indicate that high fatty acid metabolism crippled cardiac resistance to β-adrenoceptor hyperactivation, with mitochondrial ROS playing a pivotal role in this process. Reducing mitochondrial ROS in diabetes could disrupt this synergistic effect and prevent poor cardiac outcomes caused by SH.