VDAC: old protein with new roles in diabetes.

A decrease in capillary density due to an increase in endothelial cell apoptosis in the heart is implicated in cardiac ischemia in diabetes. The voltage-dependent anion channel (VDAC) plays a crucial role in the regulation of mitochondrial metabolic function and mitochondria-mediated apoptosis. This study is designed to examine the role of VDAC in coronary endothelial dysfunction in diabetes. Endothelial cells (ECs) were more apoptotic in diabetic left ventricle of diabetic mice and mouse coronary ECs (MCECs) isolated from diabetic mice exhibited significantly higher mitochondrial Ca(2+) concentration and VDAC protein levels than control MCECs. The expression of VDAC-short hairpin RNA (shRNA) not only decreased the resting mitochondrial Ca(2+) concentration but also attenuated mitochondrial Ca(2+) uptake in diabetic MCECs. Furthermore, the downregulation of VDAC in diabetic MCECs significantly decreased mitochondrial superoxide anion (O(2)(-)) production and the activity of the mitochondrial permeability transition pore (mPTP) opening (an indirect indicator of cell apoptosis) toward control levels. These data suggest that the increased VDAC level in diabetic MCECs is responsible for increased mitochondrial Ca(2+) concentration, mitochondrial O(2)(-) production, and mPTP opening activity. Normalizing VDAC protein level may help to decrease endothelial cell apoptosis, increase capillary density in the heart, and subsequently decrease the incidence of cardiac ischemia in diabetes.