Glucose and fatty acid metabolism in infarcted heart from streptozotocin-induced diabetic rats after 2weeks of tissue remodeling

Abstract

Background: The effects of streptozotocin (STZ)-induced diabetes on heart metabolism and function after myocardial infarction (MI) remodelling were investigated in rats. Methods: Fifteen days after STZ (50mg/kg b.w. i.v.) injection, MI was induced by surgical occlusion of the left coronary artery. Two weeks after MI induction, contents of glycogen, ATP, free fatty acids and triacylglycerols (TG) and enzyme activities of glycolysis and Krebs cycle (hexokinase, glucose-6-phosphate dehydrogenase, phosphofructokinase, citrate synthase) and expression of carnitine palmitoyl-CoA transferase I (a key enzyme of mitochondrial fatty acid oxidation) were measured in the left ventricle (LV). Plasma glucose, free fatty acids and triacylglycerol levels were determined. Ejection fraction (EF) and shortening fraction (SF) were also measured by echocardiography. Results: Glycogen and TG contents were increased (p<0.05) whereas ATP content was decreased in the LV of the non-infarcted diabetic group when compared to the control group (p<0.05). When compared to infarcted control rats (MI), the diabetic infarcted rats (DI) showed (p<0.05): increased plasma glucose and TG levels, elevated free fatty acid levels and increased activity of, citrate synthase and decreased ATP levels in the LV. Infarct size was smaller in the DI group when compared to MI rats (p<0.05), and this was associated with higher EF and SF (p<0.05). Conclusions: Systolic function was preserved or recovered more efficiently in the heart from diabetic rats two weeks after MI, possibly due to the high provision of glucose and free fatty acids from both plasma and heart glycogen and triacylglycerol stores.