Apoptosis of cardiomyocytes assessed by a novel apoptotic marker [annexin V] and the role of vitamin E in cardioprotection in diabetic rats

Recently it has been shown that annexin V is an apoplolic marker in the heart. The aim of the present study was to explore whether annexin V content in the heart changes during diabetes in order to use it as a prognostic tailor in diabetic cardiac affection. In addition, the study attempted to show the effect of treatment of insulin and vitamin E [300mg and 600mg/Kg] used separately or in combination. The study included 70 male albino rats weighing I70-200gm. They were divided into the following groups of 10 rats each: Group I [cont]: Control group, Group II [DM]: Diabetic, untreated group. Diabetes was induced by intraperitoneal injection of streptozotocin [stz] at a dose of 40mg/kg body weight, Group III [Ins]: Diabetic group, treated with 1 unit insulin injected subcutaneously, Group IV [E-300]: Diabetic group, receiving 300mg/kg vitamin E injected intramuscularly, 3 times/week for one month, Group V [E-600]: Diabetic group, receiving vitamin E i.m injection at a dose of 600mg/kg, 3 times/week for one month, Group VI [I+E-300]: Diabetic group treated with insulin and vitamin E [300mg/kg/dose] and Group VII [I+E-600]: Diabetic group treated with insulin and vitamin E [600mg/kg/dose]. Annexin V and inducible nitric oxide synthase [iNOS] were examined in the hearts of animals by RT-PCR. Also, cGMP, malondialdehyde [MDA], glutathione peroxidase [GPX] and cardiac enzymes were measured. There were three major new findings in the present study. First; annexin V levels were significantly elevated in the heart of diabetic rats compared to controls. This elevation in annexin V content indicates that apoptosis is the basis of cardiac injury as shown by the elevated cardiac enzymes AST, ALT and CPK. Second, levels of iNOS protein of the heart were elevated in diabetic rats. On the basis of theses findings, we can suggest that inflammation could play a role in the pathogenesis of diabetic cardiomyopathy in type I diabetes. Third, the effect of various types of treatment of diabetes which were used here showed the beneficial effects of the use of the antioxidant, vitamin E. These results suggest that annexin V can be used as a prognostic factor in cardiac affection in DM. In addition, they provide further evidence that pharmacological intervention by different antioxidants may have significant implications in the prevention of the pro-oxidant features of diabetes

Protective effect of vitamin E against ischemia: reperfusion induced oxidative stress in isolated hearts from hyperthyroid rabbits

Hyperthyroidism either clinical or experimentally induced is associated with cardiac problems such as sinus tachycardia and atrial fibrillation in addition to reduction in ventricular contractility which is due to increased free radicals. It is now generally accepted that free radical-lipid peroxidation in biological membranes is associated with variety of important pathological events and aging. Vitamin E is one of the well known antioxidants used in clinical practice. The objective of this work is to study the effect of vitamin E on the functional recovery from in vitro induced ischemia-reperfusion of isolated hearts in hyperthyroid rabbits compared to euthyroid and vitamin E treated hyperthyroid ones. In the present study 40 normal male New Zealand rabbits, weighing 2.0-2.25 kg, were used and randomly divided into 4 groups, 10 rabbits each. Group-1 [euthyroid "E"]: rabbits received intramuscular [i.m.] injection of saline [1 ml/kg/day] for 8 days and oral corn oil vehicle [1 ml/kg/day] orally for 10 days, Group-II [hyperthyroid "H"]: as group-I but rabbits received i.m. injection of 1-thyroxin "T[4]" [200 micro g/kg/day] instead of saline, Group-III [vitamin E-treated "VE"]: rabbits received i.m. injection of saline [1 ml/kg/day] and oral vitamin E [200 micro g/kg/day] in corn oil vehicle for 10 days and Group-IV [hyperthyroid vitamin E-treated "HVE"]: as group-Ill but rabbits received i.m. injection of T[4] [200 micro g/kg/day] instead of saline. At the end of therapy, hearts were isolated, weighed and exposed to 30 min. no flow ischemia followed by 25 min. reperfusion. Pre-ischemic and after 25 min. reperfusion coronary effluent, heart rate [HR] and contractility parameters [amplitude of contractions, LVDP and dP/dt[max]] were assessed then hearts of each group were homogenized to measure the malondialdehyde [MDA] and guanosine 3',5'-cyclic monophosphate [cGMP]. The mean heart weight/BW ratio in [H] and [HVE] groups significantly increased after T4 therapy by +32.4% and +35.1% respectively compared to [E] group. Except for the mean coronary effluent, which showed insignificant changes, all other tested parameters significantly increased in [H] and [HVE] groups compared to corresponding pre-ischemic values of [E] group. All pre-ischemic values of [HVE] group insignificantly changed compared to that of [H] group. The mean coronary effluent significantly increased in [HVE] by +19.4% compared to [H] group after 25 min. reperfusion. However, the mean HR was significantly reduced in [HVE] by -34.7%; compared to [H] group after 25 min. reperfusion. The mean contractility parameters "amplitude of contractions, LVDP and dP/dt[max]" significantly increased in [HVE] by "+41.1%, +106%; and +40%;" respectively compared to [H] group after 25 min. reperfusion. The mean MDA and cGMP was significantly reduced in [HVE] by -45.7%- and -39.5%- respectively compared to [H] group. These results suggested that after exposure of isolated hyperthyroid rabbits' hearts to ischemia-reperfusion, as a model for oxidative stress, oral vitamin E could improve the contractility parameters, coronary flow as well as tachycardia response to reperfusion in addition to the improvement of the cardiac capability to face oxidative stresses in hyperthyroidism. This might need a further clinical study to prove the role of vitamin E in preventing ischemic cardiac dysfunction in patients with thyrotoxicosis