Mohamed A. Haidara

Role of oxidative stress in development of cardiovascular complications in diabetes mellitus.

Diabetes represents a serious risk factor for the development of cardiovascular problems such as coronary heart disease, peripheral arterial disease, hypertension, stroke, cardiomyopathy, nephropathy and retinopathy. Identifying the pathogenesis of this increased risk provides a basis for secondary intervention to reduce morbidity and mortality in diabetic patients. Hyperglycemia and protein glycation, increased inflammation, a prothrombotic state and endothelial dysfunction have all been implicated as possible mechanisms for such complications. A linking element between many of these phenomena could possibly be, among other factors, increased production of reactive oxygen species. Vascular endothelial cells have several physiological actions that are essential for the normal function of the cardiovascular system. These include the production of nitric oxide (NO), which regulates vasodilatation, anticoagulation, leukocyte adhesion, smooth muscle proliferation and the antioxidative capacity of endothelial cells. However, under conditions of hyperglycemia, excessive amounts of superoxide radicals are produced inside vascular cells and this can interfere with NO production leading to the possible complications. This article aims at reviewing the links between reactive oxygen species, diabetes and vascular disease and whether or not antioxidants can alter the course of vascular complications in diabetic patients and animal models. A possible beneficial effect of antioxidants might present a new addition to the range of secondary preventive measures used in diabetic patients.

Evaluation of the effect of oxidative stress and vitamin E supplementation on renal function in rats with streptozotocin-induced Type 1 diabetes

UNLABELLED We investigated the possible role of reactive oxygen species (ROS) on renal function in experimental diabetes. MATERIALS AND METHODS Seven groups of male rats were studied. Group I consisted of control animals. Diabetes was induced (by streptozotocin) in the animals in the other groups and they received either insulin or vitamin E (300 or 600 mg/kg), both insulin and vitamin E, or no treatment for 4 weeks. At the end of the study, blood pressure was measured and parameters of kidney function and oxidative stress were evaluated in serum and kidney tissue samples. RESULTS Diabetic animals had higher blood pressures; increased serum glucose, urea, creatinine, cyclic guanosine monophosphate (cGMP); increased kidney tissue levels of malondialdehyde and inducible nitric oxide synthetase (iNOS); and reduced serum glutathione peroxidase when compared with control animals. Blood glucose levels in diabetic animals were controlled by insulin and not by any dose of vitamin E alone. However, all other measured parameters improved towards control levels with either insulin or vitamin E in either dose. An additive beneficial effect was observed on the levels of iNOS and cGMP when both forms of treatment were used in diabetic animals. CONCLUSIONS We conclude that ROS may play an important role in diabetes-induced nephropathy in this rat model. Vitamin E supplementation in addition to insulin can have additive protective effects against deterioration of renal function in this model.

Oxidative stress as a common mediator for apoptosis induced-cardiac damage in diabetic rats.

Aim: To investigate the possible role of oxidative stress as a common mediator of apoptosis and cardiac damage in diabetes. Materials and Methods: This experimental work was conducted on 5 groups of Wistar rats. Group I was the control group. Diabetes type 1 was induced in other groups (by streptozotocin) and animals received insulin or vitamin E (300 mg /kg body weight), both insulin and vitamin E, or no treatment for 4 weeks according to their group. At the end of the study, serum and cardiac tissues were examined for biochemical parameters of cardiac function, oxidative stress and apoptosis. Electron microscopy pictures of cardiac tissue were also evaluated for signs of cardiac damage Results: Markers of oxidative stress, apoptosis, inflammation as well as manifestations of cardiac damage as assessed by electron microscopy were significantly decreased in rats treated with both insulin and vitamin E when compared with untreated diabetic rats or rats treated with either insulin or vitamin E alone Conclusion: Administration of both vitamin E and insulin was effective in reducing markers of oxidative stress and apoptosis and improving parameters of cardiac function in experiments animals. Antioxidants might prove beneficial as an adjuvant treatment in addition to insulin in type 1 diabetes associated with manifestations of cardiac complications

Involvement of ERK1/2 Kinase in Insulin- and Thrombin-Stimulated Vascular Smooth Muscle Cell Proliferation

It is well recognized that the proliferation of vascular smooth muscle cells (VSMCs) is a key event in the pathogenesis of various vascular diseases, including atherosclerosis and hypertension. We have previously shown that among extracellular signal-regulated protein kinases (ERKs), the 42- and 44-kDa isoforms (ERK1/2) participate in the cellular mitogenic machinery triggered by several VSMCs activators, including insulin (INS) and thrombin (Thr). However, understanding of the intracellular signal transduction pathways involved is incomplete. This review considers the recent findings in INS and Thr signaling mechanisms that modulate the proliferation of VSMCs with particular emphasis on the ERK1/2 signaling pathway, an important mediator of VSMCs hypertrophy and vascular disease. Moreover, because the ERK1/2 pathway have been acknowledged as an important mediator of VSMCs hypertrophy, ERK1/2 is identified as a key target for novel therapeutic interventions to minimize irreversible tissue damage associated with hypertension and atherosclerosis.

Effects of obesity and estradiol on Na+/K+-ATPase and their relevance to cardiovascular diseases

Obesity is associated with aberrant sodium/potassium-ATPase (Na(+)/K(+)-ATPase) activity, apparently linked to hyperglycemic hyperinsulinemia, which may repress or inactivate the enzyme. The reduction of Na(+)/K(+)-ATPase activity in cardiac tissue induces myocyte death and cardiac dysfunction, leading to the development of myocardial dilation in animal models; this has also been documented in patients with heart failure (HF). During several pathological situations (cardiac insufficiency and HF) and in experimental models (obesity), the heart becomes more sensitive to the effect of cardiac glycosides, due to a decrease in Na(+)/K(+)-ATPase levels. The primary female sex steroid estradiol has long been recognized to be important in a wide variety of physiological processes. Numerous studies, including ours, have shown that estradiol is one of the major factors controlling the activity and expression of Na(+)/K(+)-ATPase in the cardiovascular (CV) system. However, the effects of estradiol on Na(+)/K(+)-ATPase in both normal and pathological conditions, such as obesity, remain unclear. Increasing our understanding of the molecular mechanisms by which estradiol mediates its effects on Na(+)/K(+)-ATPase function may help to develop new strategies for the treatment of CV diseases. Herein, we discuss the latest data from animal and clinical studies that have examined how pathophysiological conditions such as obesity and the action of estradiol regulate Na(+)/K(+)-ATPase activity.

Diabetes and Antioxidants: Myth or Reality?

Numerous studies have shown that increased oxidative stress (OxS) is present in diabetic patients. There is evidence that this OxS can be increased before complications associated with diabetes mellitus (DM) occur. However, the role and influence of OxS in the initiation and progression of DM remains the subject of debate. It has been suggested that in DM, OxS is caused by increased production of reactive oxygen species (ROS), and associated with reduction in antioxidant defenses and altered cellular redox status. Acute and chronic OxS which could enhance the development of complications associated with DM. This review considers recent findings on the role of antioxidants in controlling OxS and the incidence of DM with emphasis on animal and human studies.

Cardiac Adaptive Responses After Hypoxia in an Experimental Model

The role of vascular endothelial growth factor (VEGF) and erythropoietin (EPO) in mediating hypoxic preconditioning under the acute intermittent hypoxic condition (AIH) was investigated in this study. Male Wistar rats were randomly assigned and kept in normoxic conditions, (Nx) or in AIH conditions and subjected to brief cycles hypoxia/reoxygenation. Hearts were isolated, perfused, and subjected to in vitro global ischemia followed by reperfusion. During and at the end of reperfusion, left ventricular developed pressure (LVDP); LV end diastolic pressure (LVEDP); rate pressure product (RPP); peak left ventricular pressure rise (ΔP/Δt max ) and heart rate (HR) were measured. Hearts subjected to AIH displayed a significant higher LVDP (P < .001), RPP (P < .001), and ΔP/Δt max (P < .001). Expression of VEGF and EPO were significantly increased at 3, 8, and 24 hours after AIH. Hypoxic training could provide a new approach to enhance endogenous cardioprotective mechanisms.

Evaluation of the Possible Contribution of Antioxidants Administration in Metabolic Syndrome

The metabolic syndrome (MetS) is common, and its associated risk burdens of diabetes and cardiovascular disease (CVD) are a major public health problem. The hypothesis that main constituent parameters of the MetS share common pathophysiologic mechanisms provides a conceptual framework for the future research. Exercise and weight loss can prevent insulin resistance and reduce the risk of diseases associated with the MetS. Interrupting intracellular and extracellular reactive oxygen species (ROS) overproduction could also contribute to normalizing the activation of metabolic pathways leading to the onset of diabetes, endothelial dysfunction, and cardiovascular (CV) complications. On the other hand, it is difficult to counteract the development of CV complications by using conventional antioxidants. Indeed, interest has focused on strategies that enhance the removal of ROS using either antioxidants or drugs that enhance endogenous antioxidant defense. Although these strategies have been effective in laboratory experiments, several clinical trials have shown that they do not reduce CV events, and in some cases antioxidants have actually worsened the outcome. More research is needed in this field.

Levels of sCD40 Ligand in Chronic and Acute Coronary Syndromes and its Relation to Angiographic Extent of Coronary Arterial Narrowing

We determined the serum levels of soluble CD40 ligand (sCD40L) in patients with chronic coronary artery disease (CAD) and acute coronary syndrome (ACS). Patients with unstable angina (UA) and myocardial infarction (MI) showed significantly higher levels (P < .001) of sCD40L compared with patients with stable angina (SA) and controls; particularly, high levels occurred in patients with UA (UA: 9.23 ± 2.92, MI: 7.38 ± 1.05, SA: 4.42 ± 1.08; control: 4.01 ± 0.87 ng/mL). There was no significant difference in sCD40L levels between patients with UA and MI or between patients with SA and controls. Levels of sCD40L did not show any significant correlation with peak creatine kinase (CK), CK-MB isoenzyme activity in patients with MI, troponin T serum levels in patients with UA or with culprit vessel (CV) complexity score (CVCS), type of CV lesion, or vessel score in patients with UA or MI. These results suggest that CD40L plays a pathogenic role in triggering ACS.

Differentiated mesenchymal stem cells ameliorate cardiovascular complications in diabetic rats

Cardiovascular manifestations are one of the major complications of type 1 diabetes mellitus (T1DM) and supersede the slow progression of DM in most cases as the leading cause of mortality. There have been many studies and trials in regenerating the functional β-cells of islets from mesenchymal stem cells (MSCs) with varied success. The effect of MSCs ex vivo differentiated to mimic functional insulin-secreting β-cells of islets and their impact on restoration of diabetic complications and transplantation via systemic delivery have not been well studied. In the current study, bone marrow MSCs differentiated to insulin-secreting β-cells are used to treat STZ-induced diabetic rats. The post-homing effects of the differentiated MSCs (dMSCs) were endogenous with definite reversal of diabetic parameters. Consequently, the altered cardiac functions like heart beat rate, left ventricular performance, contractility index and physiological body weight gain due to hyperglycemia were amelorated into normacy. The primary onset cardiac perfomance and the endothelial activation were well evidenced by high fibrinogen levels and systolic blood pressure (SBP) being reversed on the treatment by dMSCs. Further high basal [Ca2+]c in isolated endothelial cells and thereby increased ROS confirmed the endothelial activation. The levels of pro-apoptotic makers p53 and Bax were highly expressed in the diabetic groups indicating oxidative stress through ROS induced by high cytosolic calcium skewing the cells towards apoptosis. The expression of the anti-apoptotic marker Bcl-2 was observed to be low in the diabetic group further augmenting the stress state of endothelial cells (ECs) in T1DM. Restoration of [Ca2+]c chelates ROS and the subsequent reversal of pro- and anti-apoptotic markers after the successful treatment of dMSCs proved that endogenous reconstitution of insulin secretion improves diabetic-induced cardiac manifestations.