Simvastatin treatment restores vasoconstriction and the inhibitory effect of LPC on endothelial relaxation via affecting oxidizing metabolism in diabetic rats.

Oxidative stress and dyslipidaemia play an important role in the development of diabetes-induced vascular complications. The aim of this study was to examine the reversal effects of simvastatin on some metabolic and oxidative parameters, and vascular functions in diabetic rats. Diabetes was induced by a single injection of streptozotocin (STZ, 45 mg/kg, i.p.). Eight weeks after STZ induction, some of the diabetic and control rats were treated with simvastatin (10 mg/kg rat/d) for 4 weeks. Plasma glucose, triglyceride and total cholesterol concentrations were significantly increased in 12-week diabetic rats. Simvastatin treatment stopped the loss of body weight, completely normalized the increase of plasma lipids and partially reduced the hyperglycaemia in diabetic rats. Increased malondialdehyde levels, catalase and glutathione peroxidase activities were normalised by simvastatin treatment in diabetic aorta. Phenylephrine (PE)-induced contractility in aorta rings was unaffected by diabetes, but was markedly decreased after simvastatin treatment in both control and diabetic rats. Reduction of endothelium-dependent vasorelaxation in diabetes was significantly ameliorated by simvastatin treatment. Incubation of aorta rings with lysophosphatidylcholine, a component of the oxidized LDL, did not significantly affect PE-induced contractions, but reduced endothelium-dependent relaxations more in untreated-diabetic rats than in other experimental groups. The endothelium-independent vasorelaxations were similar in all ring preparations. These results indicate that simvastatin treatment may ameliorate diabetes-induced abnormal vasoconstriction and endothelial dysfunction via affecting general and oxidizing metabolism, nitric oxide disability and intracellular calcium mobilisation.

Ceylan A ，Karasu C ，Aktan F ，Ozansoy G ... -  《diabetes nutrition & metabolism》

Alpha-lipoic acid treatment ameliorates metabolic parameters, blood pressure, vascular reactivity and morphology of vessels already damaged by streptozotocin-diabetes.

The present study investigated the effects of alpha-lipoic acid treatment (50 mg/kg/day) on the metabolism and vascular condition already damaged by streptozotocin (STZ)-diabetes in rats. Carbohydrate and lipid metabolism, oxidative stress and antioxidant status were assessed in non-diabetic controls, 12-week untreated diabetic and 12-week treated diabetic (untreated for 6 weeks and then treated with alpha-lipoic acid for the last 6 weeks) rats. Blood pressures of rats were measured by tail-cuff method. Vascular reactivity was evaluated in isolated aortic rings. Morphology of aorta was examined by electron microscopy technique. Alpha-lipoic acid treatment effectively reversed body weight, blood glucose, plasma insulin, cholesterol, triglycerides and lipid peroxidation levels of diabetic animals. STZ-diabetes resulted in increased blood pressure, which was partially improved by alpha-lipoic acid treatment. Although the superoxide dismutase (SOD) activity in aortic homogenates was not changed by diabetes or antioxidant treatment, catalase or glutathione peroxidase (GPx) activity significantly increased in untreated diabetic rats. Alpha-lipoic acid treatment improved catalase activity in diabetic aorta. The contractile effect of phenylephrine markedly increased in diabetic rings, which was completely reversed by alpha-lipoic acid treatment. The maximum vasorelaxant response of pre-contracted aortic rings exposed to cumulatively increased concentrations of acetylcholine was unaffected by diabetes or antioxidant treatment. Sodium nitroprusside-induced endothelium-independent relaxations were similar in all experimental groups. Various alterations caused by STZ-diabetes in aorta structure were partially ameliorated by alpha-lipoic acid treatment. The potency of alpha-lipoic acid on the reversal of hypertension by affecting vascular reactivity and morphology as well as general metabolism of diabetic rats confirms the importance of hyperglycemia-induced oxidative stress in the development of diabetes-induced vascular complications and suggests a potential therapeutic approach.

Koçak G ，Aktan F ，Canbolat O ，Ozoğul C ，Elbeğ S ，Yildizoglu-Ari N ，Karasu C ，ADIC Study Group--Antioxidants in Diabetes-Induced Complications ... -  《diabetes nutrition & metabolism》

Pioglitazone, a PPARgamma agonist, restores endothelial function in aorta of streptozotocin-induced diabetic rats.

Majithiya JB ，Paramar AN ，Balaraman R 《CARDIOVASCULAR RESEARCH》

Cod liver oil supplementation improves cardiovascular and metabolic abnormalities in streptozotocin diabetic rats.

Abnormalities in the metabolism of essential fatty acids and the results of increased oxidative stress have been implicated in cardiovascular disorders observed in diabetes mellitus. This study, therefore, aimed to investigate the effects of cod liver oil (CLO, Lysi Ltd, Iceland), which comprises mainly an antioxidant vitamin A, n:3 polyunsaturated fatty acids (n:3 PUFAs), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), on cardiovascular abnormalities in streptozotocin (STZ)-diabetic rats. Two days after single STZ (55 mg kg(-1), i.p.) or vehicle injection, diabetes was verified by increased blood glucose, and non-diabetic and diabetic rats were left untreated or treated with CLO (0.5 mL kg(-1) daily, by intragastric probing) for 12 weeks. Plasma glucose, triacylglycerol and cholesterol concentrations were significantly elevated in 12-week untreated-diabetic rats; CLO provided better weight gain, entirely prevented the plasma lipid abnormalities, but partially controlled the glycaemia in diabetic rats. In isolated aorta rings, diabetes resulted in increased phenylephrine-induced vasoconstriction and isoprenaline-induced vasorelaxation, impaired endothelium-dependent vasodilatation and unchanged responsiveness to sodium nitroprusside. CLO treatment completely prevented endothelial deficiency, partly corrected the phenylephrine-induced vasoconstriction and did not affect the responses to isoprenaline and sodium nitroprusside in diabetic aorta. Diabetes also produced a marked decrease in the rate of spontaneously beating right atria and a significant increase in basal contractile force of left ventricular papillary muscle. The responsiveness of right atria to the positive chronotropic effect of isoprenaline was significantly decreased in diabetic rats, and was increased in CLO-treated diabetic rats. The positive chronotropic effect of noradrenaline was markedly increased in diabetic atria, but prevented by CLO treatment. Diabetes also resulted in an increased positive inotropic response of papillary muscle to both noradrenaline and isoprenaline, which were prevented by CLO treatment. CLO treatment also resulted in lower tissue sensitivity (pD(2)) to these agonists in diabetic papillary muscle. Ventricular hydroxyproline content was found to be unchanged among the experimental groups. The ultrastructure of diabetic myocardium displayed various degenerations (i.e. intracellular oedema, myofibrillar fragmentation, condensed pleomorphic mitochondria, thick capillary irregular basement membrane, swollen endothelial cells), which were partially prevented by CLO treatment. We conclude that the supplementation with CLO is effective in preventing cardiovascular disorders observed in experimental diabetes.

Ceylan-Isik A ，Hünkar T ，Aşan E ，Kaymaz F ，Ari N ，Söylemezoğlu T ，Renda N ，Soncul H ，Bali M ，Karasu C ，(Antioxidants in Diabetes-Induced Complications) The ADIC Study Group ... -  《JOURNAL OF PHARMACY AND PHARMACOLOGY》

Endothelial dysfunction in streptozotocin-diabetic rats is not reversed by dietary probucol or simvastatin supplementation.

Palmer AM ，Gopaul N ，Dhir S ，Thomas CR ，Poston L ，Tribe RM ... -  《DIABETOLOGIA》