Lipoic acid ameliorates apoptosis in alloxan-induced diabetic rat skeletal muscle

Oxidant increase has been suggested to play a critical role in the progression and pathogenesis of diabetes and its complications, including the loss of skeletal muscle. However, the exact molecular mechanism responsible for the loss of skeletal muscle mass during diabetes is unclear. Since oxidative stress and muscle mitochondrial dysfunction are known to be major components in the induction of apoptosis as well as insulin resistance, we investigated the occurrence of apoptosis in diabetic rat skeletal muscle. Increased oxidants associated with diabetes results in the translocation of mitochondrial-cytochrome c into the cytosol. The enhanced outer mitochondrial membrane permeability accompanied with loss of mitochondrial transmembrane potential may be attributed to the loss of mitochondrial-cytochrome c content. This, in turn, led to the activation of caspase cascade and apoptosis, as evident from evaluated caspase-3 levels and DNA fragmentation, in skeletal muscle of diabetic rats. Oral supplementation of lipoic acid normalized these changes to that of control rats, possibly by enhancing the redox status and by the maintenance of mitochondrial membrane integrity. The maintenance of mitochondrial membrane integrity and the observed decrease in pro-/anti-apoptotic factor ratio, cytosolic cytochrome c content and caspase-3 levels by lipoic acid suggested that lipoic acid supplementation could be beneficial in ameliorating oxidative stress mediated apoptosis during diabetes.