Improvement of Cardiac Function and Subcellular Defects Due to Chronic Diabetes upon Treatment with Sarpogrelate

In order to investigate the subcellular mechanisms underlying the beneficial effects of sarpogrelate-a 5-HT_2A receptor antagonist-on diabetic cardiomyopathy, diabetes was induced in rats by injecting streptozotocin (65 mg/kg). Diabetic animals were treated with or without sarpogrelate (5 mg/kg daily) for 6 weeks; diabetic animals were also treated with insulin (10 units/kg daily) for comparison. Elevated plasma levels of glucose and lipids, depressed insulin levels, hemodynamic alterations and cardiac dysfunction in diabetic animals were partially or fully attenuated by sarpogrelate or insulin treatment. Diabetes-induced changes in myocardial high-energy phosphate stores, as well as depressed mitochondrial oxidative phosphorylation and Ca²⁺-uptake activities, were significantly prevented by these treatments. Reductions in sarcolemma Na⁺-K⁺ ATPase, Na⁺-Ca²⁺ exchange, Ca²⁺-channel density and Ca²⁺-uptake activities were also attenuated by treatments with sarpogrelate and insulin. In addition, decreases in diabetes-induced sarcoplasmic reticulum Ca²⁺-uptake, Ca²⁺-release and Ca²⁺-stimulated ATPase activities, myofibrillar Mg²⁺-ATPase and Ca²⁺-stimulated ATPase activities, and myosin Mg²⁺-ATPase and Ca²⁺-ATPase activities were fully or partially prevented by sarpogrelate and insulin treatments. Marked alterations in different biomarkers of oxidative stress, such as malondialdehyde, superoxide dismutase and glutathione peroxidase, in diabetic hearts were also attenuated by treating the animals with sarpogrelate or insulin. These observations suggest that therapy with sarpogrelate, like that with insulin, may improve cardiac function by preventing subcellular and metabolic defects as a consequence of a reduction in oxidative stress.