The incidence and mortality of
cardiovascular disease in diabetic patients are 2-3 times higher than those in non-diabetic patients. Abnormal function of the
L-type calcium channel in myocardial tissue might result in multiple
cardiac disorders such as a prolonged QT interval. Therefore, QT prolongation is an independent risk factor of
cardiovascular disease in patients with
diabetes mellitus.
Metformin, a
hypoglycemic agent, is widely known to effectively reduce the occurrence of macrovascular diseases. The aim of the present study was to evaluate the effect of
metformin on prolonged QT interval and to explore potential ionic mechanisms induced by diabetes. Diabetic mouse models were established with
streptozotocin and an electrocardiogram was used to monitor the QT interval after 4 weeks of
metformin treatment in each group. Action potential duration (APD) and L-type
calcium current (I Ca-L) were detected by patch-clamp in isolated mice ventricular cardiomyocytes and neonatal cardiomyocytes of mice. The expression levels of CACNA1C
mRNA and Cav1.2 were measured by real-time PCR, western blot and immunofluorescence. A shortened QT interval was observed after 4 weeks of
metformin treatment in diabetic mice. Patch-clamp results revealed that both APD and I Ca-L were shortened in mouse cardiomyocytes. Furthermore, the expression levels of CACNA1C
mRNA and Cav1.2 were decreased in the
metformin group. The same results were also obtained in cultured neonatal mice cardiomyocytes. Overall, these results verify that
metformin could shorten a prolonged QT interval by inhibiting the
calcium current, suggesting that
metformin may play a role in the electrophysiology underlying diabetic cardiopathy.