Microscopic changes in the myocardium of streptozotocin-induced diabetic rats and the effect of vitamin C administration

ABSTRACT

Diabetic cardiomyopathy can be considered as one of the most common complications of diabetes. Oxidative stress and the production of reactive oxygen species [ROS] were considered to play a key role in the pathogenesis of this cardiomyopathy. Accordingly, this study was planned to detect the biochemical disorders and structural changes in the cardiac muscle in experimentally-induced diabetic rats and to emphasize the role of vitamin C, which could be considered to have an antioxidant effect, in the correction of these abnormalities. Thirty adult male albino rats were classified into three equal groups; group A served as Sham-injected control, while group B rats were turned diabetic by a single intraperitoneal injection of streptozotocin in a dose of 50 mg / kg body weight / rat and left under observation for 16 weeks. The animals of group C were turned diabetic by the same method, but they received vitamin C by stomach tubes for one week before and 16 weeks after induction of diabetes in a single daily dose of 200 mg /kg body weight / rat. Biochemically, significant hyperglycemia and an increase in serum malondialdehyde [MDA] levels with a significant decrease in myocardial glutathione [GSH] were noticed in the animals of group 6 [16 weeks after induction of diabetes]. This was accompanied with extensive microscopic changes in the cardiac muscle in the form of depletion of glycogen content, increased collagen deposition and decreased ATPase activity. Ultrastructurally, myofibrillar disarray in the form of discontinuous, irregular and fragmented Z lines, loss of microfilaments and disorganization of sarcomeres was noticed. The mitochondria appeared irregular in shape with heterogeneous electron dense matrix and disrupted or absent cristae. In addition, appearance of secondary lysosomes and absence of glycogen granules were encountered. The intercalated discs showed a large area having no cellular junctions. These biochemical and morphological abnormalities were apparently reduced in the diabetic rats that received vitamin C. Accordingly, the daily use of vitamin C might play an essential role in the protection against diabetes-induced cardiomyopathy with a more positive impact on management