Free radicals in diabetic endothelial cell dysfunction

Changes in foveal avascular zone parameters in individuals with prediabetes compared to normoglycemic controls: a systematic review and meta-analysis

To investigate changes in foveal avascular zone parameters in individuals with prediabetes compared to normoglycemic controls. PUBMED, Scopus and Cochrane Library were searched for published articles comparing the foveal avascular zone between prediabetic individuals and normoglycemic controls as assessed by optical coherence tomography angiography (OCTA). Standardised Mean Difference (SMD) with 95% confidence interval (CI) was computed for the comparison. A total of seven studies were included in our analysis, 6 provided data for the superficial capillary plexus from 345 eyes of individuals with prediabetes and 347 eyes of controls and 4 provided data on the deep capillary plexus from 285 eyes from individuals with prediabetes and 325 eyes of controls. Foveal avascular zone (FAZ) area in the superficial capillary plexus was enlarged in individuals with prediabetes compared to normoglycemic controls (SMD = 0.23, 95% CI = 0.03-0.44, p = 0.03, I2 = 27%, 6 studies). There was no statistically significant change in the deep capillary plexus FAZ area between the two groups (SMD = 1.14, 95% CI = -0.06-2.34, p = 0.06, I2 = 97%, 4 studies). FAZ area in the superficial capillary plexus was larger in individuals diagnosed with prediabetes compared to normoglycemic controls. This finding suggests that prediabetes could induce retinal microvascular changes before the onset of clinical diabetes. More original studies are needed to validate the results of the current meta-analysis.

Nrf2 Pathway and Oxidative Stress as a Common Target for Treatment of Diabetes and Its Comorbidities

Diabetes is a chronic disease that induces many comorbidities, including cardiovascular disease, nephropathy, and liver damage. Many mechanisms have been suggested as to how diabetes leads to these comorbidities, of which increased oxidative stress in diabetic patients has been strongly implicated. Limited knowledge of antioxidative antidiabetic drugs and substances that can address diabetic comorbidities through the nuclear factor erythroid 2-related factor 2 (Nrf2) pathway calls for detailed investigation. This review will describe how diabetes increases oxidative stress, the general impact of that oxidative stress, and how oxidative stress primarily contributes to diabetic comorbidities. It will also address how treatments for diabetes, especially focusing on their effects on the Nrf2 antioxidative pathway, have been shown to similarly affect the Nrf2 pathway of the heart, kidney, and liver systems. This review demonstrates that the Nrf2 pathway is a common pathogenic component of diabetes and its associated comorbidities, potentially identifying this pathway as a target to guide future treatments.

Evaluating the effectiveness of melatonin in reducing the risk of foot ulcers in diabetic patients

Objectives

Diabetes and its complications, as a major health concern, are associated with morbidity and mortality around the world. One of these complications is diabetic foot ulcer. Factors such as hyperglycemia, neuropathy, vascular damage and impaired immune system can cause foot ulcers. The present review aims to study the potential effects of melatonin, the main product of pineal glands, on diabetic foot ulcers.

Methods

A narrative review was performed using present literature in an attempt to identify the different aspects of melatonin's impact on diabetic foot ulcers by searching related keywords in electronic databases without any restriction.

Results

This review shows that, melatonin has anti-diabetic effects. It is effective in reducing the risk of hyperglycemia, neuropathy, vascular damage and immune system impairment in diabetic patients. By reducing these complications with melatonin, correspondingly, the incidence of diabetic foot ulcers may also decrease in these patients.

Conclusions

The results of this study indicate promising properties of melatonin while dealing with diabetic foot ulcers and their common underlying conditions, but still, it needs to be investigated more in future studies.

Glutathionyl Hemoglobin and Its Emerging Role as a Clinical Biomarker of Chronic Oxidative Stress

Hemoglobin is one of the proteins that are more susceptible to S-glutathionylation and the levels of its modified form, glutathionyl hemoglobin (HbSSG), increase in several human pathological conditions. The scope of the present review is to provide knowledge about how hemoglobin is subjected to S-glutathionylation and how this modification affects its functionality. The different diseases that showed increased levels of HbSSG and the methods used for its quantification in clinical investigations will be also outlined. Since there is a growing need for precise and reliable methods for markers of oxidative stress in human blood, this review highlights how HbSSG is emerging more and more as a good indicator of severe oxidative stress but also as a key pathogenic factor in several diseases.

EndMT Regulation by Small RNAs in Diabetes-Associated Fibrotic Conditions: Potential Link With Oxidative Stress

Diabetes-associated complications, such as retinopathy, nephropathy, cardiomyopathy, and atherosclerosis, the main consequences of long-term hyperglycemia, often lead to organ dysfunction, disability, and increased mortality. A common denominator of these complications is the myofibroblast-driven excessive deposition of extracellular matrix proteins. Although fibroblast appears to be the primary source of myofibroblasts, other cells, including endothelial cells, can generate myofibroblasts through a process known as endothelial to mesenchymal transition (EndMT). During EndMT, endothelial cells lose their typical phenotype to acquire mesenchymal features, characterized by the development of invasive and migratory abilities as well as the expression of typical mesenchymal products such as α-smooth muscle actin and type I collagen. EndMT is involved in many chronic and fibrotic diseases and appears to be regulated by complex molecular mechanisms and different signaling pathways. Recent evidence suggests that small RNAs, in particular microRNAs (miRNAs) and long non-coding RNAs (lncRNAs), are crucial mediators of EndMT. Furthermore, EndMT and miRNAs are both affected by oxidative stress, another key player in the pathophysiology of diabetic fibrotic complications. In this review, we provide an overview of the primary redox signals underpinning the diabetic-associated fibrotic process. Then, we discuss the current knowledge on the role of small RNAs in the regulation of EndMT in diabetic retinopathy, nephropathy, cardiomyopathy, and atherosclerosis and highlight potential links between oxidative stress and the dyad small RNAs-EndMT in driving these pathological states.

Cardioprotective potential of melatonin, quercetin and resveratrol in an experimental model of diabetes

Oxygen radicals participate in the pathogenesis of heart damage. Diabetes accelerates the formation of reactive oxygen species (ROS). We investigated the effects of the antioxidants, melatonin, quercetin and resveratrol, on cardiomyopathy and apoptosis in rats with streptozotocin (STZ) induced diabetes mellitus (DM). Rats were divided into five groups of seven: control, DM, DM + melatonin, DM + quercetin and DM + resveratrol. All treatments were begun with a single dose of STZ to induce diabetes and experimental treatments were continued daily for 30 days. Morphologic and apoptotic changes were analyzed by histological assessment. The heart tissue of the control group exhibited normal histology, whereas the heart tissue of the DM group exhibited vacuolization, necrosis, congestion, infiltration and myofibril loss. The DM group exhibited significantly increased apoptosis compared to the control group. Differences in anti-apoptotic effects were statistically significant for all three antioxidant treatment groups; the anti-apoptotic effects of quercetin and resveratrol were similar. Melatonin, resveratrol and quercetin exhibited protective effects against diabetic heart damage.

Diabetes and Its Complications: Therapies Available, Anticipated and Aspired

Worldwide, diabetes ranks among the ten leading causes of mortality. Prevalence of diabetes is growing rapidly in low and middle income countries. It is a progressive disease leading to serious co-morbidities, which results in increased cost of treatment and over-all health system of the country. Pathophysiological alterations in Type 2 Diabetes (T2D) progressed from a simple disturbance in the functioning of the pancreas to triumvirate to ominous octet to egregious eleven to dirty dozen model. Due to complex interplay of multiple hormones in T2D, there may be multifaceted approach in its management. The 'long-term secondary complications' in uncontrolled diabetes may affect almost every organ of the body, and finally may lead to multi-organ dysfunction. Available therapies are inconsistent in maintaining long term glycemic control and their long term use may be associated with adverse effects. There is need for newer drugs, not only for glycemic control but also for prevention or mitigation of secondary microvascular and macrovascular complications. Increased knowledge of the pathophysiology of diabetes has contributed to the development of novel treatments. Several new agents like Glucagon Like Peptide - 1 (GLP-1) agonists, Dipeptidyl Peptidase IV (DPP-4) inhibitors, amylin analogues, Sodium-Glucose transport -2 (SGLT- 2) inhibitors and dual Peroxisome Proliferator-Activated Receptor (PPAR) agonists are available or will be available soon, thus extending the range of therapy for T2D, thereby preventing its long term complications. The article discusses the pathophysiology of diabetes along with its comorbidities, with a focus on existing and novel upcoming antidiabetic drugs which are under investigation. It also dives deep to deliberate upon the novel therapies that are in various stages of development. Adding new options with new mechanisms of action to the treatment armamentarium of diabetes may eventually help improve outcomes and reduce its economic burden.

Biomechanical Forces and Oxidative Stress: Implications for Pulmonary Vascular Disease

Significance: Oxidative stress in the cell is characterized by excessive generation of reactive oxygen species (ROS). Superoxide (O₂^-) and hydrogen peroxide (H₂O₂) are the main ROS involved in the regulation of cellular metabolism. As our fundamental understanding of the underlying causes of lung disease has increased it has become evident that oxidative stress plays a critical role. Recent Advances: A number of cells in the lung both produce, and respond to, ROS. These include vascular endothelial and smooth muscle cells, fibroblasts, and epithelial cells as well as the cells involved in the inflammatory response, including macrophages, neutrophils, eosinophils. The redox system is involved in multiple aspects of cell metabolism and cell homeostasis. Critical Issues: Dysregulation of the cellular redox system has consequential effects on cell signaling pathways that are intimately involved in disease progression. The lung is exposed to biomechanical forces (fluid shear stress, cyclic stretch, and pressure) due to the passage of blood through the pulmonary vessels and the distension of the lungs during the breathing cycle. Cells within the lung respond to these forces by activating signal transduction pathways that alter their redox state with both physiologic and pathologic consequences. Future Directions: Here, we will discuss the intimate relationship between biomechanical forces and redox signaling and its role in the development of pulmonary disease. An understanding of the molecular mechanisms induced by biomechanical forces in the pulmonary vasculature is necessary for the development of new therapeutic strategies.

Omega-3 polyunsaturated fatty acids exert anti-oxidant effects through the nuclear factor (erythroid-derived 2)-related factor 2 pathway in immortalized mouse Schwann cells

AIMS/INTRODUCTION

Recent studies advocate that omega-3 polyunsaturated fatty acids (ω-3 PUFAs) have direct anti-oxidative and anti-inflammatory effects in the vasculature; however, the role of ω-3 PUFAs in Schwann cells remains undetermined.

MATERIALS AND METHODS

Immortalized mouse Schwann (IMS32) cells were incubated with the ω-3 PUFAs docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). The messenger ribonucleic acid levels of several anti-oxidant enzymes (heme oxygenase-1 [Ho-1], nicotinamide adenine dinucleotide [phosphate] H quinone oxidoreductase 1, catalase, superoxide dismutase and glutathione peroxidase) were identified using real-time reverse transcription polymerase chain reaction. Ho-1 and nicotinamide adenine dinucleotide [phosphate] H quinone oxidoreductase 1 protein levels were evaluated using Western blotting. Nuclear factor (erythroid-derived 2)-related factor 2 (Nrf2) of the nuclear fraction was also quantified using western blotting. Catalase activity and glutathione content were determined by colorimetric assay kits. Nrf2 promoter-luciferase activity was evaluated by a dual luciferase assay system.

RESULTS

Treatment with tert-butyl hydroperoxide decreased cell viability dose-dependently. DHA or EPA pretreatment significantly alleviated tert-butyl hydroperoxide-induced cytotoxicity. DHA or EPA increased the messenger ribonucleic acid levels of Ho-1, nicotinamide adenine dinucleotide (phosphate) H quinone oxidoreductase 1 and catalase dose-dependently. Ho-1 protein level, catalase activity, Nrf2 promoter-luciferase activity and intracellular glutathione content were significantly increased by DHA and EPA.

CONCLUSIONS

These findings show that DHA and EPA can induce Ho-1 and catalase through Nrf2, thus protecting Schwann cells against oxidative stress. ω-3 PUFAs appear to exert their neuroprotective effect by increasing defense mechanisms against oxidative stress in diabetic neuropathies.

MiR-130b attenuates vascular inflammation via negatively regulating tumor progression locus 2 (Tpl2) expression

Endothelial cell (EC) activation and dysfunction have been linked to a wide variety of vascular inflammatory diseases. However, the role of microRNAs in EC activation and inflammation remains largely unknown. In this study, we found that miR-130b was significantly decreased in human umbilical vein endothelial cells (HUVECs) after lipopolysaccharides (LPS) treatment. Forced expression of miR-130b inhibited the LPS-induced activation of extracellular signal-regulated kinase (ERK) and the inflammatory genes expression, such as interleukin (IL)-6 and tumor necrosis factor alpha (TNF-α). Furthermore, we identified that tumor progression locus 2 (Tpl2) is a direct target of miR-130b. Finally, in vivo overexpression of miR-130b via miR-130b agomir attenuates acute lung vascular inflammation in the LPS-induced sepsis mouse model. Taken together, our data demonstrated that miR-130b represses vascular inflammation via targeting Tpl2, suggesting that miR-130b mimics might be a promising therapeutic strategy for treatment of vascular inflammatory diseases.

Endothelial dysfunction and vascular disease - a 30th anniversary update

The endothelium can evoke relaxations of the underlying vascular smooth muscle, by releasing vasodilator substances. The best-characterized endothelium-derived relaxing factor (EDRF) is nitric oxide (NO) which activates soluble guanylyl cyclase in the vascular smooth muscle cells, with the production of cyclic guanosine monophosphate (cGMP) initiating relaxation. The endothelial cells also evoke hyperpolarization of the cell membrane of vascular smooth muscle (endothelium-dependent hyperpolarizations, EDH-mediated responses). As regards the latter, hydrogen peroxide (H₂ O₂ ) now appears to play a dominant role. Endothelium-dependent relaxations involve both pertussis toxin-sensitive G_i (e.g. responses to α₂ -adrenergic agonists, serotonin, and thrombin) and pertussis toxin-insensitive G_q (e.g. adenosine diphosphate and bradykinin) coupling proteins. New stimulators (e.g. insulin, adiponectin) of the release of EDRFs have emerged. In recent years, evidence has also accumulated, confirming that the release of NO by the endothelial cell can chronically be upregulated (e.g. by oestrogens, exercise and dietary factors) and downregulated (e.g. oxidative stress, smoking, pollution and oxidized low-density lipoproteins) and that it is reduced with ageing and in the course of vascular disease (e.g. diabetes and hypertension). Arteries covered with regenerated endothelium (e.g. following angioplasty) selectively lose the pertussis toxin-sensitive pathway for NO release which favours vasospasm, thrombosis, penetration of macrophages, cellular growth and the inflammatory reaction leading to atherosclerosis. In addition to the release of NO (and EDH, in particular those due to H₂ O₂ ), endothelial cells also can evoke contraction of the underlying vascular smooth muscle cells by releasing endothelium-derived contracting factors. Recent evidence confirms that most endothelium-dependent acute increases in contractile force are due to the formation of vasoconstrictor prostanoids (endoperoxides and prostacyclin) which activate TP receptors of the vascular smooth muscle cells and that prostacyclin plays a key role in such responses. Endothelium-dependent contractions are exacerbated when the production of nitric oxide is impaired (e.g. by oxidative stress, ageing, spontaneous hypertension and diabetes). They contribute to the blunting of endothelium-dependent vasodilatations in aged subjects and essential hypertensive and diabetic patients. In addition, recent data confirm that the release of endothelin-1 can contribute to endothelial dysfunction and that the peptide appears to be an important contributor to vascular dysfunction. Finally, it has become clear that nitric oxide itself, under certain conditions (e.g. hypoxia), can cause biased activation of soluble guanylyl cyclase leading to the production of cyclic inosine monophosphate (cIMP) rather than cGMP and hence causes contraction rather than relaxation of the underlying vascular smooth muscle.

Review: Targeting therapeutics against glutathione depletion in diabetes and its complications

Glutathione (GSH) is the most abundant intracellular antioxidant, the dysregulation of which is widely implicated in disease states. There is in vitro and clinical evidence that abnormal glutathione status is involved in β-cell dysfunction and in the pathogenesis of long-term complications of diabetes. Interest has developed in the potential for therapeutic modification of glutathione status in the treatment of diabetes. There is evidence which supports the use of glutathione pro-drugs, lipoic acid and vitamin supplementation but further studies are required before these enter widespread use. Studies into the role of oxidative stress in diabetes rely heavily on the ability to measure glutathione, which has been a problematic analyte to measure in the laboratory. New electrochemical methods being developed should speed up the rate at which data can be accumulated and will help define clinical utility for its measurement.

Damaging effects of hyperglycemia on cardiovascular function: spotlight on glucose metabolic pathways

The incidence of cardiovascular complications associated with hyperglycemia is a growing global health problem. This review discusses the link between hyperglycemia and cardiovascular diseases onset, focusing on the role of recently emerging downstream mediators, namely, oxidative stress and glucose metabolic pathway perturbations. The role of hyperglycemia-mediated activation of nonoxidative glucose pathways (NOGPs) [i.e., the polyol pathway, hexosamine biosynthetic pathway, advanced glycation end products (AGEs), and protein kinase C] in this process is extensively reviewed. The proposal is made that there is a unique interplay between NOGPs and a downstream convergence of detrimental effects that especially affect cardiac endothelial cells, thereby contributing to contractile dysfunction. In this process the AGE pathway emerges as a crucial mediator of hyperglycemia-mediated detrimental effects. In addition, a vicious metabolic cycle is established whereby hyperglycemia-induced NOGPs further fuel their own activation by generating even more oxidative stress, thereby exacerbating damaging effects on cardiac function. Thus NOGP inhibition, and particularly that of the AGE pathway, emerges as a novel therapeutic intervention for the treatment of cardiovascular complications such as acute myocardial infarction in the presence hyperglycemia.

Resveratrol ameliorates cardiac oxidative stress in diabetes through deacetylation of NFkB-p65 and histone 3

Resveratrol, a phytoalexin, has recently gained attention for protective effects against metabolic and cardiac diseases. The beneficial effects of resveratrol have been linked to sirtuin-1 (SIRT-1) activation. However, little is known about the effect of resveratrol in cardiac complications associated with diabetes. Here, we have demonstrated that resveratrol ameliorates cardiac hypertrophy, electrocardiographic abnormalities and oxidative stress in the fructose-fed diabetic rat heart. Mechanistic studies revealed that fructose feeding to Sprague-Dawley rats over a period of 8 weeks leads to cardiac hypertrophy and increased oxidative stress through increased activity of NADPH oxidase (NOX) and reactive oxygen species production. We found increased activity of nuclear factor kappa B (NFkB) p-65 along with decreased SIRT-1 activity in the diabetic heart. Resveratrol activates SIRT-1, which deacetylates NFkB-p65 at lysine 310 and histone 3 (H3) at lysine 9 position. SIRT1 activation leads to decreased binding of NFkB-p65 to DNA and attenuated cardiac hypertrophy and oxidative stress through reduced transcription of NADPH oxidase subunits. In vitro analysis also revealed that SIRT-1 activation by resveratrol is associated with decreased NFkB-p65 activity and NOX transcription. Similarly, knockdown or inhibition of SIRT1 in H9C2 cells increased acetylation of NFkB-p65 K310 and H3K9. Overall, our data demonstrated that SIRT-1 activation by resveratrol leads to deacetylation of both NFkB-p65 and H3, thereby attenuating cardiac oxidative stress and complications in diabetes.

The Effect of Tomato Juice Consumption on Antioxidant Status in Overweight and Obese Females

Tomatoes and their products are the main source of lycopene, a powerful potent antioxidant. Tomato products improve antioxidant defenses and reduce the risk of oxidative stress, at least partly, due to the presence of lycopene. Lycopene, as an antioxidant, induces the upregulation of antioxidant enzymes and reinforces the total enzyme capacity of the human body. Obesity is a chronic condition in which destructive mechanisms increase the reactive oxygen species and attenuation of antioxidant status. We hypothesized that the consumption of a lycopene-rich food would improve the antioxidant defense of women who were overweight or obese. A total of seventy-five overweight or obese female students of the Tehran University of Medical Sciences were enrolled and randomly allocated to one of two groups, intervention (n = 40) or control (n = 35), consuming 330 ml/d of tomato juice or water, respectively, for a 20-day period. At baseline and day 20, total antioxidant capacity and antioxidant enzyme activity (superoxide dismutase, glutathione peroxidase, and catalase) were analyzed using ELISA kits and spectrophotometric methods and then compared between the two groups. Lycopene consumption had no effect on these aforementioned variables. Therefore, it seems that more research with longer duration and more sensitive indicators will be required.

Effect of Baechu Kimchi Added Ecklonia cava Extracts on High Glucose-induced Oxidative Stress in Human Umbilical Vein Endothelial Cells

Endothelial cell dysfunction is considered to be a major cause of vascular complications in diabetes. In the present study, we investigated the protective effect of a baechu kimchi added Ecklonia cava extract (BKE) against high glucose induced oxidative damage in human umbilical vein endothelial cells (HUVECs). Treatment with a high concentration of glucose (30 mM) induced cytotoxicity, whereas treatment with BKE protected HUVECs from high glucose induced damage; by restoring cell viability. In addition, BKE reduced lipid peroxidation, intracellular reactive oxygen species and nitric oxide levels in a dose dependent manner. Treatment with high glucose concentrations also induced the overexpression of inducible nitric oxide synthase, cyclooxygenase-2 and NF-κB proteins in HUVECs, but BKE treatment significantly reduced the overexpression of these proteins. These findings indicate that BKE may be a valuable treatment against high glucose-induced oxidative stress HUVECs.

HDL and endothelial protection

High-density lipoproteins (HDLs) represent a family of particles characterized by the presence of apolipoprotein A-I (apoA-I) and by their ability to transport cholesterol from peripheral tissues back to the liver. In addition to this function, HDLs display pleiotropic effects including antioxidant, anti-apoptotic, anti-inflammatory, anti-thrombotic or anti-proteolytic properties that account for their protective action on endothelial cells. Vasodilatation via production of nitric oxide is also a hallmark of HDL action on endothelial cells. Endothelial cells express receptors for apoA-I and HDLs that mediate intracellular signalling and potentially participate in the internalization of these particles. In this review, we will detail the different effects of HDLs on the endothelium in normal and pathological conditions with a particular focus on the potential use of HDL therapy to restore endothelial function and integrity.

Molecular mechanisms of diabetic vascular complications

Diabetic complications are the major causes of morbidity and mortality in patients with diabetes. Microvascular complications include retinopathy, nephropathy and neuropathy, which are leading causes of blindness, end‐stage renal disease and various painful neuropathies; whereas macrovascular complications involve atherosclerosis related diseases, such as coronary artery disease, peripheral vascular disease and stroke. Diabetic complications are the result of interactions among systemic metabolic changes, such as hyperglycemia, local tissue responses to toxic metabolites from glucose metabolism, and genetic and epigenetic modulators. Chronic hyperglycemia is recognized as a major initiator of diabetic complications. Multiple molecular mechanisms have been proposed to mediate hyperglycemia’s adverse effects on vascular tissues. These include increased polyol pathway, activation of the diacylglycerol/protein kinase C pathway, increased oxidative stress, overproduction and action of advanced glycation end products, and increased hexosamine pathway. In addition, the alterations of signal transduction pathways induced by hyperglycemia or toxic metabolites can also lead to cellular dysfunctions and damage vascular tissues by altering gene expression and protein function. Less studied than the toxic mechanisms, hyperglycemia might also inhibit the endogenous vascular protective factors such as insulin, vascular endothelial growth factor, platelet‐derived growth factor and activated protein C, which play important roles in maintaining vascular homeostasis. Thus, effective therapies for diabetic complications need to inhibit mechanisms induced by hyperglycemia’s toxic effects and also enhance the endogenous protective factors. The present review summarizes these multiple biochemical pathways activated by hyperglycemia and the potential therapeutic interventions that might prevent diabetic complications. (J Diabetes Invest, doi: 10.1111/j.2040‐1124.2010.00018.x, 2010)

Biology of diabetic neuropathy

More than half of all patients with diabetes develop neuropathic disorders affecting the distal sensory and/or motor nerves, or autonomic or cranial nerve functions. Glycemic control can decrease the incidence of neuropathy but is not adequate alone to prevent or treat the disease. This chapter introduces diabetic neuropathy with a morphological description of the disease then describes our current understanding of metabolic and molecular mechanisms that contribute to neurovascular dysfunctions. Key mechanisms include glucose and lipid imbalances and insulin resistance that are interconnected via oxidative stress, inflammation, and altered gene expression. These complex interactions should be considered for the development of new treatment strategies against the onset or progression of neuropathy. Advances in understanding the combined metabolic stressors and the novel study of epigenetics suggest new therapeutic targets to combat this morbid and intractable disease affecting millions of patients with type 1 or type 2 diabetes.

Bupropion effects on high-fat diet-induced steatohepatitis and endothelial dysfunction in rats: role of tumour necrosis factor-alpha

OBJECTIVES

This study aimed to elucidate the effect of bupropion (BUP) on high-fat diet (HFD)-treated rats that is to say the action of BUP on diabetes and hyperlipidemia with its consequences on liver and endothelial function.

METHODS

Male Wistar rats were fed HFD or normal chow for 15 weeks then given either BUP (50 mg/kg) or distilled water by gavage for 4 weeks. The effect of BUP on diabetes, hyperlipidemia, hepatic and vascular functions as well as tumour necrosis factor-alpha (TNF)-α were assessed. The intima-media thickness of the aorta was evaluated.

KEY FINDINGS

BUP significantly decreased serum lipid, liver enzyme, homeostasis model assessment for insulin resistance (HOMA-IR), serum TNF-α and the impaired glucose tolerance. Liver from rats with non-alcoholic steatohepatitis (NASH) demonstrated significant higher TNF-α level, inflammatory cell infiltration, ballooning and steatosis which significantly ameliorated by BUP treatment. Neither intima/media ratio nor vascular reactivity to acetylcholine is improved by BUP treatment.

CONCLUSIONS

NASH induced by a HFD was associated with hyperlipidemia, insulin resistance, endothelial dysfunction and increase in liver TNF-α. All of these may contribute to the pathogenesis of NASH. BUP has potential role in improving metabolic and hepatic function with negative vascular effect. Since BUP is a well-known antidepressant, it will be a candidate drug in treatment of depression in hepatic diseased or metabolic disturbed patients.

Effect of l-glutamine on myenteric neuron and of the mucous of the ileum of diabetic rats

The objective of this work was to investigate the effect of the L-glutamine supplementation to prevent - diabetes induced changes in myenteric neurons and also to verify the effect on the mucosa of the ileum of Wistar rats. The animals were divided in five groups (n = 5): untreated normoglycaemic (UN), normoglycaemic treated with L-glutamine (NG), untreated diabetics (UD), diabetics treated with L-glutamine, starting on the 4th (DG4) or 45th day following diabetes induction (DG45). The amino acid was added to the diet at 1%. The density and size of neurons, the metaphasic index in the crypt, the height of the villus, the depth of the crypt and the number of globet cells were determined. There was no difference in the neuronal density and in the cellular body area of the myosin-stained myenteric neurons of groups DG4 and DG45 when compared to group D. The metaphase index and the number of goblet cells showed no significant differences when all groups were compared (P > 0.05). The villi height of groups DG4 and DG45 were 45.5% (P < 0.05) and 32.4% (P > 0.05) higher than those in group UD, respectively. The analyzed crypts showed similar depth for all studied groups.

Percutaneous versus surgical interventions for coronary artery disease in those with diabetes mellitus

Diabetes mellitus (DM) is a metabolic disorder of multiple etiologies that causes long-term damage of various organs including the cardiovascular system. A consistent observation shows that DM amplifies the risk of cardiovascular events by 4- to 6-fold. Since coronary artery disease (CAD) in diabetic patients exhibits diffuse and accelerated lesions, invasive revascularization continues to be a challenge and has worse outcomes than patients without DM. Owing to the pathogenesis of DM and the presence of severe endothelial dysfunction, investigators have been trying to find new treatment modalities that could target the treatment of the disease rather than the treatment of the lesion. Until new treatment modalities are proven and gain acceptance, invasive revascularization remains to be the choice of treatment in such patients. The focus of this review is to compare the results of percutaneous coronary intervention (PCI) with coronary artery bypass grafting (CABG) for the treatment of stable CAD in patients with DM.

Neuronal ER stress impedes myeloid-cell-induced vascular regeneration through IRE1α degradation of netrin-1

In stroke and proliferative retinopathy, despite hypoxia driven angiogenesis, delayed revascularization of ischemic tissue aggravates the loss of neuronal function. What hinders vascular regrowth in the ischemic central nervous system remains largely unknown. Using the ischemic retina as a model of neurovascular interaction in the CNS, we provide evidence that the failure of reparative angiogenesis is temporally and spatially associated with endoplasmic reticulum (ER) stress. The canonical ER stress pathways of protein kinase RNA-like ER kinase (PERK) and inositol-requiring enzyme-1α (IRE1α) are activated within hypoxic/ischemic retinal ganglion neurons, initiating a cascade that results in angiostatic signals. Our findings demonstrate that the endoribonuclease IRE1α degrades the classical guidance cue netrin-1. This neuron-derived cue triggers a critical reparative-angiogenic switch in neural macrophage/microglial cells. Degradation of netrin-1, by persistent neuronal ER stress, thereby hinders vascular regeneration. These data identify a neuronal-immune mechanism that directly regulates reparative angiogenesis.

Inflammation and oxidative stress in diabetic nephropathy: new insights on its inhibition as new therapeutic targets

Diabetes and insulin resistance can greatly increase microvascular complications of diabetes including diabetic nephropathy (DN). Hyperglycemic control in diabetes is key to preventing the development and progression of DN. However, it is clinically very difficult to achieve normal glucose control in individual diabetic patients. Many factors are known to contribute to the development of DN. These include diet, age, lifestyle, or obesity. Further, inflammatory- or oxidative-stress-induced basis for DN has been gaining interest. Although anti-inflammatory or antioxidant drugs can show benefits in rodent models of DN, negative evidence from large clinical studies indicates that more effective anti-inflammatory and antioxidant drugs need to be studied to clear this question. In addition, our recent report showed that potential endogenous protective factors could decrease inflammation and oxidative stress, showing great promise for the treatment of DN.

Prevention of hepatic and renal toxicity with bradykinin potentiating factor (BPF) isolated from Egyptian scorpion venom (Buthus occitanus) in gentamicin treated rats

The present investigation report the effect of a bradykinin-potentiating factor (BPF) on gentamicin-induced oxidative stress in rat liver and kidney. BPF is a peptide fraction isolated from the venom of the Egyptian scorpion (Buthus occitanus) has been demonstrated to have antioxidant, free radical scavenger and anti-inflammatory effects. Thirty male Rattus norvegicus (130-150 g) were included and divided into three equal groups as follows: Group I (control), group II was (ip) injected with gentamicin alone (80 mg/kg/day) for 15 days, group III was given (ip) injection of BPF (1mg/kg/day) one hour prior to gentamicin treatment for 15 days with the same dose of gentamicin as group II. Both organs were subjected to histopathological analysis with the light microscope. The activities of alanine aminotransferase (ALT), asparate aminotransferase (AST) and alkaline phosphatase (ALP) in serum were measured as indicators of the liver function. As parameters of the kidney function, creatinine, uric acid and urea concentrations were determined. Also, malondialdehyde (MDA), reduced glutathione (GSH), super oxide dismutase (SOD) and catalase (CAT) were determined in both tissues. Gentamicin caused a significant decrease or inhibition in the activities of GSH, SOD, and CAT, with significant increase in the level of MDA, ALT, AST, ALP, as well as creatinine, uric acid and urea concentrations in versus to control groups in both liver and kidney. Co-administration of gentamicin and BPF significantly increased the activity of GSH, SOD, and CAT, with significant decrease in the level of MDA and maintained serum (ALT); (AST); (ALP), creatinine, uric acid and urea concentrations as the same level as control group. Moreover, administration of gentamicin resulted in damage to liver and kidney structures. Administration of BPF before gentamicin exposure prevented severe alterations of biochemical parameters and disruptions of liver and kidney structures. In conclusion, this study obviously demonstrated that pretreatment with BPF significantly attenuated the physiological and histopathological alterations induced by gentamicin. Also, the present study identifies new areas of research for development of better therapeutic agents for liver, kidney, and other organs dysfunctions and diseases.

Effects of some anti-neoplastic drugs on sheep liver sorbitol dehydrogenase

Stress is an important factor for many diseases in living metabolisms. The mini pathway named as polyol is a critical junction for stress factors. This pathway has two enzymes: aldose reductase (AR) and sorbitol dehydrogenase (SDH). It is linked with some diseases such as diabetes mellitus and some cancer types. In particular, SDH is very sensitive and unstable in in vitro conditions. In this study, SDH was purified by using simple and rapid chromatographic methods such as DEAE-Sephadex and CM-Sephadex C-50 columns. Subunit and active form molecular weights were found as 39.8 kDa and 150 kDa, respectively. The in vitro effects of some antineoplastic drugs were investigated. IC(50) values were 0.025, 0.081, 0.291, 1.62, 4.86, 6.54 mM for dacarbazine, methotrexate, epirubicin hydrochloride, calcium folinate, gemcitabine hydrochloride, oxaliplatin, respectively. From these results, dacarbazine was lowest IC(50) value and it is the strongest inhibitor for liver SDH enzyme activity compared to the other drugs.

Zinc supplementation prevents cardiomyocyte apoptosis and congenital heart defects in embryos of diabetic mice

Oxidative stress induced by maternal diabetes plays an important role in the development of cardiac malformations. Zinc (Zn) supplementation of animals and humans has been shown to ameliorate oxidative stress induced by diabetic cardiomyopathy. However, the role of Zn in the prevention of oxidative stress induced by diabetic cardiac embryopathy remains unknown. We analyzed the preventive role of Zn in diabetic cardiac embryopathy by both in vivo and in vitro studies. In vivo study revealed a significant decrease in lipid peroxidation, superoxide ions, and oxidized glutathione and an increase in reduced glutathione, nitric oxide, and superoxide dismutase in the developing heart at embryonic days (E) 13.5 and 15.5 in the Zn-supplemented diabetic group when compared to the diabetic group. In addition, significantly down-regulated protein and mRNA expression of metallothionein (MT) in the developing heart of embryos from diabetic group was rescued by Zn supplement. Further, the nuclear microscopy results showed that trace elements such as phosphorus, calcium, and Zn levels were significantly increased (P<0.001), whereas the iron level was significantly decreased (P<0.05) in the developing heart of embryos from the Zn-supplemented diabetic group. In vitro study showed a significant increase in cellular apoptosis and the generation of reactive oxygen species (ROS) in H9c2 (rat embryonic cardiomyoblast) cells exposed to high glucose concentrations. Supplementation with Zn significantly decreased apoptosis and reduced the levels of ROS. In summary, oxidative stress induced by maternal diabetes could play a role in the development and progression of cardiac embryopathy, and Zn supplementation could be a potential therapy for diabetic cardiac embryopathy.

The relationship between the activates of antioxidant enzymes in red blood cells and body mass index in Iranian type 2 diabetes and healthy subjects

BACKGROUND

Diabetes mellitus is a metabolic disorder characterized by increased production of free radicals and oxidative stress. The aim of this study was to evaluate the activity of antioxidant enzymes, superoxide dismutase (SOD), glutathione reductase (GR), and glutathione peroxide (GSH-PX) in type 2 diabetic patients compared with healthy subjects.

METHODS

This cross-sectional study was conducted on 100 type 2 diabetic patients and 100 healthy controls. Total antioxidant capacity and fasting serum levels of SOD, GR, and GSH-Px were measured. All data were analyzed using SPSS software compatible with Microsoft Windows.

RESULTS

The activity levels of SOD were lower in diabetic patients (111.93 ± 354.99 U/g Hb) than in healthy controls (1158.53 ± 381.21 U/g Hb), but this was not significant. Activity levels of GSH-PX and GR in diabetics (62.33 ± 36.29 and 7.17 ± 5.51 U/g Hb, respectively) were higher than in controls (24.62 ± 11.2 and 3.16 ± 2.95 U/g Hb, respectively). The statistical difference in enzyme activity of both GSH-Px and GR was significant (P <0.05).

CONCLUSION

The increasing production of free radicals and changes in activity levels of antioxidant enzymes in order to scavenge free radicals and/or the effect of diabetes on the activity levels of antioxidant enzymes has an important effect on diabetic complications and insulin resistance. Evaluation of the levels of antioxidant enzymes and antioxidant factors in patients at different stages of the disease, and pharmaceutical and nutritional interventions, can be helpful in reducing oxidative stress in type 2 diabetic patients. There were positive relationship between BMI and the activity of antioxidant enzymes including SOD, GR and GPX in both groups.

Rosa rugosa Attenuates Diabetic Oxidative Stress in Rats with Streptozotocin-Induced Diabetes

The effects of Rosa rugosa on diabetic oxidative stress were investigated using rats with streptozotocin (STZ)-induced diabetes. The diabetic rats showed less body weight gain and heavier kidney and liver weights than normal rats, while the oral administration of Rosa rugosa at a dose of 100 or 200 mg/kg body weight/day for 20 days attenuated the physiological changes induced by diabetes. In addition, administrating Rosa rugosa to diabetic rats resulted in significant and dose-dependent decreases in the serum glucose and glycosylated protein levels, implying that Rosa rugosa improves the abnormal glucose metabolism that leads to oxidative stress. Diabetic rats had higher serum levels of superoxide and nitrite/nitrate. However, the administration of Rosa rugosa dose-dependently reduced the over-production of radicals associated with diabetes, suggesting Rosa rugosa is a radical scavenger that would play a crucial role in protecting against diabetic oxidative stress. Rosa rugosa significantly and dose-dependently reduced thiobarbituric acid-reactive substance levels in serum, hepatic and renal mitochondria, implying that Rosa rugosa would alleviate the oxidative stress associated with diabetes by inhibiting lipid peroxidation. This study provides evidence that Rosa rugosa has potential as a treatment for diabetes through attenuating oxidative stress induced by the diabetic condition

Endothelial dysfunction and diabetes: effects on angiogenesis, vascular remodeling, and wound healing

Diabetes mellitus (DM) is a chronic metabolic disorder characterized by inappropriate hyperglycemia due to lack of or resistance to insulin. Patients with DM are frequently afflicted with ischemic vascular disease or wound healing defect. It is well known that type 2 DM causes amplification of the atherosclerotic process, endothelial cell dysfunction, glycosylation of extracellular matrix proteins, and vascular denervation. These complications ultimately lead to impairment of neovascularization and diabetic wound healing. Therapeutic angiogenesis remains an attractive treatment modality for chronic ischemic disorders including PAD and/or diabetic wound healing. Many experimental studies have identified better approaches for diabetic cardiovascular complications, however, successful clinical translation has been limited possibly due to the narrow therapeutic targets of these agents or the lack of rigorous evaluation of pathology and therapeutic mechanisms in experimental models of disease. This paper discusses the current body of evidence identifying endothelial dysfunction and impaired angiogenesis during diabetes.

Altered redox homeostasis in human diabetes saliva

BACKGROUND

Oxidative stress has been implicated in the pathogenesis of diabetes mellitus (DM). Levels of 8-hydroxy-2'-deoxyguanosine (8-OHdG), 8-epi-prostaglandin-F(2α) (8-epi-PGF2α), and total protein carbonyls were measured to assess whether DM is associated with altered salivary redox homeostasis.

METHODS

A total of 215 patients with diabetes and 481 healthy controls were recruited from the Department of Endocrinology at the Jewish General Hospital in Montreal. Levels of oxidative biomarkers were assayed using enzyme-linked immunosorbent assay (ELISA) in whole unstimulated saliva. Associations of the redox data with exposure to insulin, metformin and dietary control were assessed by logistic regression analyses.

RESULTS

We observed (i) significantly higher mean levels of 8-OHdG and protein carbonyls in whole unstimulated saliva of patients with diabetes compared to controls, (ii) higher mean levels of protein carbonyls in type 1 diabetes as well as higher mean levels of 8-OHdG and protein carbonyls in type 2 diabetes compared to controls, (iii) elevated levels of protein carbonyls in diet-controlled patients and in patients with diabetes on insulin and metformin, (iv) elevated levels of 8-OHdG in patients on metformin, and (v) significant associations between subjects with DM and salivary 8-OHdG and protein carbonyls.

CONCLUSION

DM is associated with increased oxidative modification of salivary DNA and proteins. Salivary redox homeostasis is perturbed in DM and may inform on the presence of the disease and efficacy of therapeutic interventions.

Dynamic synchrotron imaging of diabetic rat coronary microcirculation in vivo

OBJECTIVE

In diabetes, long-term micro- and macrovascular damage often underlies the functional decline in the cardiovascular system. However, it remains unclear whether early-stage diabetes is associated with in vivo functional impairment in the coronary microvasculature. Synchrotron imaging allows us to detect and quantify regional differences in resistance microvessel caliber in vivo, even under conditions of high heart rate.

METHODS AND RESULTS

Synchrotron cine-angiograms of the coronary vasculature were recorded using anesthetized Sprague-Dawley rats 3 weeks after treatment with vehicle or streptozotocin (diabetic). In the early diabetic state, in the presence of nitric oxide and prostacyclin, vessel diameters were smaller (P<0.01) and endothelium-dependent vessel recruitment was already depressed (P<0.05). Endothelium-dependent and -independent vasodilatory responses in individual coronary vessels were not different in vivo. Inhibition of NO and PGI(2) production in diabetes uncovered early localized impairment in dilation. Diabetic animals displayed focal stenoses and segmental constrictions during nitric oxide synthase/cyclooxygenase blockade, which persisted during acetylcholine infusion (P<0.05), and a strong trend toward loss of visible microvessels.

CONCLUSIONS

Synchrotron imaging provides a novel method to investigate coronary microvascular function in vivo at all levels of the arterial tree. Furthermore, we have shown that early-stage diabetes is associated with localized coronary microvascular endothelial dysfunction.

Effect of yogic exercise on super oxide dismutase levels in diabetics

Context:

Reactive oxygen species are known to aggravate disease progression. To counteract their harmful effects, the body produces various antioxidant enzymes, viz, superoxide dismutase, glutathione reductase etc. Literature reviews revealed that exercises help to enhance antioxidant enzyme systems; hence, yogic exercises may be useful to combat various diseases.

Aims:

This study aims to record the efficacy of yoga on superoxide dismutase, glycosylated hemoglobin (Hb) and fasting blood glucose levels in diabetics.

Settings and Design:

Forty diabetics aged 40–55 years were assigned to experimental (30) and control (10) groups. The experimental subjects underwent a Yoga program comprising of various Asanas (isometric type exercises) and Pranayamas (breathing exercises) along with regular anti-diabetic therapy whereas the control group received anti-diabetic therapy only.

Materials and Methods:

Heparinized blood samples were used to determine erythrocyte superoxide dismutase (SOD) activity and glycosylated Hb levels and fasting blood specimens collected in fluoride Vacutainers were used for assessing blood glucose.

Statistical Analysis Used:

Data were analyzed by using 2 × 2 × 3 Factorial ANOVA followed by Scheffe's posthoc test.

Results:

The results revealed that Yogic exercise enhanced the levels of Superoxide dismutase and reduced glycosylated Hb and glucose levels in the experimental group as compared to the control group.

Conclusion:

The findings conclude that Yogic exercises have enhanced the antioxidant defence mechanism in diabetics by reducing oxidative stress.

Contributions of dysglycaemia, obesity, and insulin resistance to impaired endothelium-dependent vasodilation in humans

BACKGROUND

Individual effects of hyperglycaemia and obesity to impair vascular health are recognized. However, the relative contributions of dysglycaemia versus other obesity-related traits to vascular dysfunction have not been systematically evaluated.

METHODS

We undertook a cross-sectional evaluation of factors contributing to vascular function in 271 consecutive subjects, categorized as non-obese normal glucose tolerant (n = 115), non-obese dysglycaemic (n = 32), obese normal glucose tolerant (n = 57), obese dysglycaemic (n = 38), or type 2 diabetic (n = 29). Vascular function was measured invasively as leg blood flow responses to methacholine chloride, an endothelium-dependent vasodilator. Categorical and continuous analyses were carried out to assess the contributions of hyperglycaemia to vascular dysfunction.

RESULTS

Even among normoglycaemic subjects, obese subjects had impaired vascular function compared to non-obese subjects (p = 0.004). Vascular function was also impaired in non-obese dysglycaemic subjects (p = 0.04 versus non-obese normoglycaemic subjects), to a level comparable to normoglycaemic obese subjects. Within obese subject groups, gradations of dysglycaemia including the presence of diabetes were not associated with further worsening of these vascular responses beyond the effect of obesity alone (p = not significant comparing all obese groups, p < 0.001 versus lean normoglycaemic subjects). After univariate and multivariable modelling analyses we found that effects of glycaemia were less powerful than effects of insulin resistance and obesity on vascular dysfunction.

CONCLUSIONS

Dysglycaemia contributes to impaired vascular function in non-obese subjects, but obesity and insulin resistance are more important determinants of vascular function in obese and diabetic subjects.

Effects of phenolic compounds of fermented thai indigenous plants on oxidative stress in streptozotocin-induced diabetic rats

We investigated the effects of antioxidant activity of fermentation product (FP) of five Thai indigenous products on oxidative stress in Wistar rats with streptozotocin (STZ)-induced diabetes type II. The rats were fed with placebo and with the FP (2 and 6 mL/kg body weight/day) for 6 weeks. Rutin, pyrogallol and gallic acid were main compounds found in the FP. Plasma glucose levels in diabetic rats receiving the higher dose of the FP increased less when compared to the diabetic control group as well as the group receiving the lower FP dose (13.1%, 29%, and 21.1%), respectively. A significant dose-dependent decrease in plasma levels of thiobarbituric acid reactive substance (P < .05) was observed. In addition, the doses of 2 and 6 mL FP/kg/day decreased the levels of erythrocyte ROS in diabetic rats during the experiment, but no difference was observed when compared to the untreated diabetic rat group. Results imply that FP decreased the diabetes-associated oxidative stress to a large extent through the inhibition of lipid peroxidation. The FP also improved the abnormal glucose metabolism slightly but the difference was not statistically significant. Thus, FP may be a potential therapeutic agent by reducing injury caused by oxidative stress associated with diabetes.