Effects of L-carnitine treatment on oxidant/antioxidant state and vascular reactivity of streptozotocin-diabetic rat aorta

ABSTRACT In this study, the effects of L‐carnitine treatment on lipids, lipid peroxidation of plasma, reactivity and antioxidant enzyme activity of aorta were evaluated in streptozotocin (STZ)‐diabetic rats. Treatment with L‐carnitine (0.6 g kg−1 daily, i.p.) was started 8 weeks after the induction of diabetes and continued for 2 weeks. Diabetes was induced by a single injection of streptozotocin (45 mg kg−1, i.p.). Plasma cholesterol, triglyceride and thiobarbituric acid reactive substance (TBARS) levels and blood glucose levels were significantly increased, although free carnitine levels were markedly decreased in diabetic rats. L‐Carnitine treatment completely normalized plasma cholesterol, triglyceride, free carnitine and TBARS levels but partially restored blood glucose levels of diabetic rats. STZ‐diabetes caused a significant reduction in the endothelium‐dependent relaxation response to acetylcholine (ACh). In diabetic aorta, TBARS levels and catalase (CAT) activity were significantly increased but glutathione peroxidase (GSH‐Px) activity was unchanged. Treatment of diabetic rats with L‐carnitine resulted in partial restoration of the endothelium‐dependent relaxation response to ACh and completely normalized the oxidant/antioxidant state. These results suggested that the beneficial effects of L‐carnitine treatment partially improve vascular reactivity and antioxidant property beyond its reduction of plasma lipids and it may have an important therapeutic approach in the treatment of diabetic vascular complications.