Diabetic dyslipidaemia is associated with alterations in eNOS, caveolin-1 and endothelial dysfunction in streptozotocin treated rats

Background: Diabetes is a complex progressive disease characterised by chronic hyperglycaemia and dyslipidaemia associated with endothelial dysfunction. Oxidised LDL (Ox-LDL) is elevated in diabetes and may contribute to endothelial dysfunction. The aim of this study was to relate the serum levels of Ox-LDL with endothelial dysfunction in streptozotocin (STZ)-diabetic rats and to further explore the changes in endothelial nitric oxide synthase (eNOS) and caveolin-1 (CAV-1) expression in primary aortic endothelial cells (ECs). Methods: Diabetes was induced with a single intraperitoneal injection of STZ in male Wistar rats. During the hyperglycaemic diabetes state serum lipid markers, aortic relaxation and aortic ECs eNOS and CAV-1 protein expression was measured. Results: Elevated serum Ox-LDL (STZ 1486 ± 78.1 pg/ml vs control 732.6 ± 160.6pg/ml, p<0.05) was associated with hyperglycaemia (STZ 29 ± 0.9 mmol/L vs control: 7.2 ± 0.2 mmol/L, p<0.001) and hypertriglyceridemia (STZ 9.0 ± 1.5 mmol/L vs control: 3.0 ± 0.3 mmol/L, p<0.01) in diabetic rats. A significant reduction was observed in STZ-diabetic aortic endothelial cell eNOS and CAV-1 of 40% and 30% respectively, accompanied by a compromised STZ-diabetic carbachol-induced vasodilation (STZ 29.6 ± 9.3% vs control 77.2 ± 2.5%, p<0.001). Conclusions: The elevated serum Ox-LDL in hyperglycaemic STZ-diabetic rats may contribute to diabetic endothelial dysfunction, possibly through downregulation of endothelial CAV-1 and eNOS.