Dietary antioxidant supplementation reduces lipid peroxidation but impairs vascular function in small mesenteric arteries of the streptozotocin-diabetic rat

Hypoglycemic, Hypolipidemic and Antioxidant Potentials of Ethanolic Stem Bark Extract of Anacardium occidentale in Streptozotocin-Induced Diabetic Rats

Diabetes mellitus is one of the most widespread diseases affecting the world's population causing substantial morbidity, mortality and long-term complications. This study was designed to investigate possible hypoglycemic, hypolipidemic and antioxidant effect of ethanolic stem bark extract of Anacardium occidentale in streptozotocin (STZ)-induced diabetic rats. Twenty-eight STZ (60 mg/kg body weight)-induced diabetic, male albino rats were randomly distributed into Groups II-V (7 rats each) and orally administered with water, metformin (14.2 mg/kg), 200 mg/kg Anacardium occidentale extract and 400 mg/kg Anacardium occidentale extract respectively daily for 15 days. Group I rats were untreated with STZ and serves as control all under the same sham handling. Blood samples were taken for measurement of fasting blood glucose (FBG) and lipid profile. Liver and kidney tissue samples were taken for determination of glycemic indices (glucose and glycogen), as well as redox status markers such as malondialdehyde (MDA), total glutathione (GSH), activities of superoxide dismutase (SOD) and glutathione-s-transferase (GST). Results showed that treatment with 200 and 400 mg/kg Anacardium occidentale stem bark extract reversed hyperglycemia and hyperlipidemia induced by STZ similar to what was observed with the standard drug, metformin. Similarly, both extract concentration produced a significant reduction in MDA while the activity of SOD and GST, as well as concentration of GSH were elevated. This study suggested that ethanolic stem bark extract of Anacardium occidentale at 200 and 400 mg/kg can ameliorate diabetes and its associated complications via its hypoglycemic, hypolipidemic, antioxidant and free radical scavenging properties.

Epigenetic modulation of autophagy genes linked to diabetic nephropathy by administration of isorhamnetin in Type 2 diabetes mellitus rats

Aim: To assess isorhamnetin efficacy for diabetic kidney disease in a Type 2 diabetes mellitus rat model, through investigating its effect at the epigenetic, mRNA and protein levels. Materials & methods: Type 2 diabetes mellitus was induced in rats by streptozotocin and high-fat diet. Rats were treated with isorhamnetin (50 mg/kg/d) for 4 or 8 weeks. Fasting blood glucose, renal and lipid profiles were evaluated. Renal tissues were examined by light and electron microscopy. Autophagy genes (FYCO1, ULK, TECPR1 and WIPI2) and miR-15b, miR-34a and miR-633 were assessed by qRT-PCR, and LC3A/B by immunoblotting. Results: Isorhamnetin improved fasting blood glucose, renal and lipid profiles with increased autophagosomes in renal tissues. It suppressed miRNA regulation of autophagy genes. Conclusion: We propose a molecular mechanism for the isorhamnetin renoprotective effect by modulation of autophagy epigenetic regulators.

The Potential of South African Herbal Tisanes, Rooibos and Honeybush in the Management of Type 2 Diabetes Mellitus

Diabetes mellitus is a metabolic disease that can lead to high morbidity, mortality and long-term complications. Available treatment strategies, which are mainly based on treating hyperglycemia, with insulin and other pharmacological agents are not completely efficient and can even lead to development of unwanted side effects. Scientific evidence suggests that bioactive compounds from teas and other plant-based foods, which are known source of natural antioxidants, could be an attractive strategy to preferentially treat and manage type 2 diabetes mellitus (T2DM) and thus, have significant therapeutic implications. In this review, we attempt an in-depth analysis and discussion of the current progress in our understanding of the antidiabetic potential of two commercialized South Africa herbal tisanes—Rooibos and Honeybush and their polyphenols.

Whole-food phytochemicals antioxidative potential in alloxan-diabetic rats

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Soybean and whole-wheat have beneficial effects on the oxidative status of AD rats more than broadbean.

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Feeding dried wheat is effective in improving MDA, GSH and α-T levels.

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Germination is favorable than drying and moistened heat. Germination enhances the effect of soybeans on TAGs and in the case of soy and wheat enhanced the effect on total cholesterol.

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Diabetic patients, beside controlling their hyperglycaemia with medication, are recommended to include whole foods containing naturally occurring phytochemicals to ameliorate their oxidative status.

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Possible protective factors in the diet such as flavonoids, lutein, lycopene, lignans, and saponins, may provide new strategies to enhance diet and health of diabetic patients.

Background

The importance of whole-food antioxidants in terms of promoting antioxidant recycling in the body in complex human diseases is not fully understood. We aim to discuss the benefits of whole-food antioxidants in ameliorating the diabetic complications in vivo and to address the effect of germination versus heat processing or drying on the potential therapeutic effect of whole grains and legumes. We studied the antioxidant status of alloxan-diabetic (AD) male Spargue Dawley rats, injected intraperitoneally with alloxan dose of 150 mg/kg body weight, and fed on experimental diets based on the flour of soybean, broadbean and whole-wheat for five weeks.

Results

Diabetes-induced oxidative stress in liver was manifested by significant increase in hepatic malondialdehyde (MDA), erythrocytes superoxide dismutase (eSOD) and plasma alpha-tocopherol (α-T) levels, reduction in hepatic glutathione (GSH) levels and catalase (CAT) activity. Consumption of soybean and whole-wheat both had beneficial effects on the oxidative status of AD rats more than broadbean. Feeding dried wheat was effective in improving MDA, GSH and α-T levels. Soybeans and wheat lowered triacylglycerols (TAGs) and tended to lower total cholesterol. Germination enhanced the effect of soybeans on TAGs and in the case of soy and wheat enhanced the effect on total cholesterol.

Conclusion

Whole foods containing naturally occurring phytochemicals and antioxidant vitamins such as legumes and whole grains are recommended, alongside medication, for controlling hyperglycaemia, blood lipids and oxidative status in diabetes.

The status of diabetic embryopathy

Diabetic embryopathy is a theoretical enigma and a clinical challenge. Both type 1 and type 2 diabetic pregnancy carry a significant risk for fetal maldevelopment, and the precise reasons for the diabetes-induced teratogenicity are not clearly identified. The experimental work in this field has revealed a partial, however complex, answer to the teratological question, and we will review some of the latest suggestions.

Oxidative stress, insulin resistance, dyslipidemia and type 2 diabetes mellitus

Oxidative stress is increased in metabolic syndrome and type 2 diabetes mellitus (T2DM) and this appears to underlie the development of cardiovascular disease, T2DM and diabetic complications. Increased oxidative stress appears to be a deleterious factor leading to insulin resistance, dyslipidemia, β-cell dysfunction, impaired glucose tolerance and ultimately leading to T2DM. Chronic oxidative stress, hyperglycemia and dyslipidemia are particularly dangerous for β-cells from lowest levels of antioxidant, have high oxidative energy requirements, decrease the gene expression of key β-cell genes and induce cell death. If β-cell functioning is impaired, it results in an under production of insulin, impairs glucose stimulated insulin secretion, fasting hyperglycemia and eventually the development of T2DM.

The diabetic vasculature: physiological mechanisms of dysfunction and influence of aerobic exercise training in animal models

Diabetes mellitus (DM) is associated with a number of complications of which chronic vascular complications are undoubtedly the most complex and significant consequence. With a significant impact on health care, 50-80% of people with diabetes die of cardiovascular disease (including coronary artery disease, stroke, peripheral vascular disease and other vascular disease), making it the major cause of morbidity and mortality in diabetic patients. A healthy lifestyle is essential in the management of DM, especially the inclusion of aerobic exercise, which has been shown effective in reducing the deleterious effects in vasculature. Interest in exercise studies has increased significantly with promising results that demonstrate a future for investigation. Considering the importance of this emerging field, the aim of this mini-review is to summarize and integrate animal studies investigating physiological mechanisms of vascular dysfunction and remodeling in type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM) and how these are influenced by chronic aerobic exercise training.

Exercise Training and Grape Seed Extract Co-Administration Improves Lipid Profile, Weight Loss, Bradycardia, and Hypotension of STZ-Induced Diabetic Rats

BACKGROUND

Exercise Training (ET) and Grape Seed Extract (GSE) as an antioxidant have many positive effects on controlling diabetes mellitus and its complications.

OBJECTIVES

This study aimed to determine the effects of GSE alone or combined with ET on body weight, plasma lipid profile, blood pressure, and heart rate in STZ-induced diabetic rats.

METHODS

IN THIS STUDY, MALE WISTAR RATS WERE RANDOMLY ASSIGNED TO FIVE GROUPS: sedentary control, sedentary diabetic, trained diabetic, GSE treated sedentary diabetic, and GSE treated trained diabetic. ET was conducted on the treadmill daily for 8 weeks. One way ANOVA followed by LSD test was used for statistical analysis.

RESULTS

Reduction of body weight, high density lipoproteins, heart rate, and systolic blood pressure and increment of total cholesterol, triglyceride, low density lipoprotein, and very low density lipoproteins were observed after STZ injection. Co-administration of GSE and ET had more positive effects on lipid profile compared to each method alone. In addition, GSE and ET modified heart rate partially, while their combination was more effective in improvement of heart rat in conscious rats. On the other hand, administration of ET or GSE alone did not affect systolic blood pressure and body weight, while their combination restored systolic blood pressure completely and improved body weight partially.

CONCLUSIONS

The study findings indicated that ET combined with GSE had more beneficial effects compared to each one alone on the complications of STZ induced diabetes. This may constitute a convenient and inexpensive therapeutic approach to diabetic complications.

Co-administration of Grape Seed Extract and Exercise Training Improves Endothelial Dysfunction of Coronary Vascular Bed of STZ-Induced Diabetic Rats

Background

One of the known complications of diabetes mellitus is vascular dysfunction. Inability of the coronary vascular response to cardiac hyperactivity might cause a higher incidence of ischemic heart disease in diabetic subjects. It has been indicated that regular exercise training and antioxidants could prevent diabetic cardiovascular problems enhanced by vascular damage.

Objectives

The aim of this study was to determine the effects of grape seed extract (as antioxidant), with and without exercise training on coronary vascular function in streptozotocin induced diabetic rats.

Materials and Methods

Fifty male Wistar rats weighing 200 – 232 grams were randomly divided into five groups of 10 rats each: sedentary control, sedentary diabetic, trained diabetic, grape seed extract (200 mg/kg) treated sedentary diabetic and, grape seed extract treated trained diabetic. Diabetes was induced by one intraperitoneal injection of streptozotocin. After eight weeks, coronary vascular responses to vasoactive agents were determined.

Results

The endothelium dependent vasorelaxation to acetylcholine was reduced significantly in diabetic animals; exercise training or grape seed extract administration partially improves this response. However, exercise training in combination with grape seed extract restores endothelial function completely. The endothelium independent vasorelaxation to sodium nitroprusside was improved by combination of exercise training and grape seed extract. On the other hand, the basal perfusion pressure and vasoconstrictive response to phenylephrine did not change significantly.

Conclusions

The data indicated that co-administration of grape seed extract and exercise training had more significant effects than exercise training or grape seed extract alone; this may constitute a convenient and inexpensive therapeutic approach to diabetic vascular complications.

Oxidative stress is not associated with vascular dysfunction in a model of alloxan-induced diabetic rats

OBJECTIVES

To verify if an experimental model of alloxan-diabetic rats promotes oxidative stress, reduces nitric oxide bioavailability and causes vascular dysfunction, and to evaluate the effect of N-acetylcysteine (NAC) on these parameters.

METHODS

Alloxan-diabetic rats were treated or not with NAC for four weeks. Plasmatic levels of malondialdehyde (MDA) and nitrite/nitrate (NOx), the endothelial and inducible nitric oxide synthase (eNOS and iNOS) immunostaining and the vascular reactivity of aorta were compared among diabetic (D), treated diabetic (TD) and control (C) rats.

RESULTS

MDA levels increased in D and TD. NOx levels did not differ among groups. Endothelial eNOS immunostaining reduced and adventitial iNOS increased in D and TD. The responsiveness of rings to acetylcholine, sodium nitroprusside, and phenylephrine did not differ among groups.

CONCLUSIONS

NAC had no effect on the evaluated parameters and this experimental model did not promote vascular dysfunction despite the development of oxidative stress.

The plant extracts of Momordica charantia and Trigonella foenum-graecum have anti-oxidant and anti-hyperglycemic properties for cardiac tissue during diabetes mellitus

Oxidative stress is currently suggested to play a major role in the development of diabetes mellitus. There is an increasing demand of natural anti-diabetic agents, as continuous administration of existing drugs and insulin are associated with many side effects and toxicity. The present study was aimed to investigate the effect of Momordica charantia (MC) and Trigonella foenum graecum (TFG) extracts (aqueous) on antioxidant status and lipid peroxidation in heart tissue of normal and alloxan induced diabetic rats. In a 30 days treatment, rats were divided into six groups (I-VI) of five animals in each,experiments were repeated thrice. Administration of MC (13.33 g pulp/kg body weight/day) and TFG (9 g seeds powder/kg body weight/day) extracts in diabetic rats has remarkably improved the elevated levels of fasting blood glucose. A significant decrease in lipid peroxidation (p<0.001) and significant increase in the activities of key antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), glutathione-s-transferase (GST) and reduced glutathione (GSH ) contents in heart tissue of diabetic rats were observed (group V and VI) upon MC and TFG treatment. Our studies demonstrate the anti-hyperglycemic and anti-oxidative potential of Momordica charantia and Trigonella foenum graecum, which could exert beneficial effects against the diabetes and associated free radicals complications in heart tissue.

Maternal blood glucose levels determine the severity of diabetic embryopathy in mice with different expression of copper-zinc superoxide dismutase (CuZnSOD)

Excess oxygen radical formation is suggested to be involved in the etiology of diabetic embryopathy. We aimed to investigate the effects of altered maternal antioxidative status in conjunction with a varied severity of the maternal diabetic state on embryonic development by using mice with different gene expression of CuZn superoxide dismutase (CuZnSOD). The mice were wild-type (WT), transgenic (TG), or knockout (KO) with regard to CuZnSOD. Alloxan was used to induce diabetes (DWT, DTG, DKO) in female mice before pregnancy and, noninjected mice served as controls (NWT, NTG, NKO). The minimum alloxan dose required to induce diabetes was 80 mg/kg for WT, 100 mg/kg for TG, and 65 mg/kg for KO mice. When KO mice were made diabetic with 80 mg/kg alloxan, they produced no living offspring. The pregnancies were interrupted on gestational day 18, when maternal diabetic state, that is, blood glucose concentration, as well as fetal outcome, genotype and hepatic isoprostane levels were assessed. The mean maternal blood glucose levels were positively associated with the alloxan dose, that is, the DWT and DTG groups had higher blood glucose concentration than the DKO group, and the DWT and DTG fetuses increased their hepatic isoprostane levels, whereas the DKO fetuses did not. However, in all diabetic groups, increased maternal blood glucose concentration was associated with higher resorption and malformation rates as well as lowered fetal and placental weight. Furthermore, diabetes increased the fraction of WT offspring in the TG and KO groups. We conclude that both fetal antioxidative capacity and maternal diabetic state affect the development of the offspring. However, the maternal diabetic state is the major teratogenic factor and overrides the influence of fetal antioxidative capacity.

Dose-dependent protective effect of propofol against mitochondrial dysfunction in ischaemic/reperfused rat heart: role of cardiolipin

BACKGROUND AND PURPOSE

Ischaemia damages to the cardiac mitochondria by increasing generation of reactive oxygen species (ROS) and peroxidation of cardiolipin. The inhibited mitochondrial function leads to the cardiac injury during reperfusion. Propofol (2, 6-diisopropylphenol), an intravenous anaesthetic, has been shown to decrease cardiac ischaemia and reperfusion injury. In the present study, we propose that propofol protects mitochondrial function and decreases cardiac injury by prevention of cardiolipin peroxidation during ischaemia and reperfusion.

EXPERIMENTAL APPROACH

After isolation of mitochondria from isolated rat heart perfused on a Langendorff model, various mitochondrial bioenergetic parameters were evaluated such as rates of mitochondrial oxygen consumption, H(2)O(2) production, complex I and III activity as well as the degree of lipid peroxidation and cardiolipin content. The action of propofol was also explored in isolated mitochondria. And the effect of cardiolipin was evaluated by fusing cardiolipin liposome with mitochondria.

KEY RESULTS

Propofol treatment had strong dose-dependent protection attenuating these parameters alterations in reperfused rat heart and isolated mitochondria. Additionally, cardiolipin treatment had the same protective effect, compared with propofol treatment at high concentration.

CONCLUSIONS AND IMPLICATIONS

The protective effect of propofol appears to be due, at least in part, as a chemical uncoupler, to the interruption of the vicious circle of ROS-cardiolipin-complexes of the respiratory chain-ROS through preserving the content and integrity of cardiolipin molecules by ROS attack. These findings may provide an explanation for some of the factors responsible for cardioprotection and one approach exploring an available antioxidant.

Oxidant release is dramatically increased by elevated glucose concentrations in neutrophils from pregnant women

OBJECTIVE

To evaluate the mechanism of oxidative stress at glucose levels accompanying diabetic pregnancy. Specifically, we hypothesize that elevated glucose overwhelms hexose monophosphate shunt (HMS) down-regulation observed during pregnancy.

METHODS

Peripheral blood cells from normal healthy pregnant women were exposed to heightened glucose levels to provide an in vitro model of the effects of diabetic pregnancy. Changes in NAD(P)H, reactive oxygen species (ROS) and nitric oxide (NO) production were evaluated in single cells.

RESULTS

Altered metabolic dynamics, as judged by NAD(P)H autofluorescence of neutrophils from both pregnant and non-pregnant women, were observed during incubation with 14 mM glucose, a pathophysiologic level. In parallel, increased production of ROS and NO was observed. The ROS and NO levels attained in cells from pregnant women were greater than those observed in cells from non-pregnant women. Inhibitors of the HMS and NAD(P)H oxidase blocked these effects. These metabolic and oxidant changes required approximately one minute, suggesting that transient glucose spikes during pregnancy could trigger this response.

CONCLUSIONS

Elevated glucose levels enhance HMS activity and oxidant production in cells from pregnant women. This mechanism may be generally applicable in understanding the role of diabetes in materno-fetal health.

Raised saturated-fat intake worsens vascular function in virgin and pregnant offspring of streptozotocin-diabetic rats

Adult offspring of severely diabetic pregnant rats are insulin resistant and display cardiovascular dysfunction. When pregnant they develop mild hyperglycaemia. Diets high in saturated fat have been implicated in the development of cardiovascular disease and vascular dysfunction. In the present study we have determined vascular function in small mesenteric arteries from offspring of normal (OC) and diabetic (OD) rats fed standard chow and offspring of diabetic rats fed a diet high in saturated fats (OD-HF) from weaning to adulthood, and throughout their subsequent pregnancies. OD rats displayed an increased sensitivity to noradrenaline (P < 0·05) and impaired sensitivity to the endothelium-dependent vasodilator, acetylcholine. The component of acetylcholine-induced relaxation attributable to endothelium-derived hyperpolarizing factor was reduced in OD-HF rats. Pregnant OD rats also demonstrated impaired maximum relaxation to acetylcholine (pregnant OD rats v. pregnant OC rats P < 0·05). In pregnant OD-HF rats noradrenaline sensitivity was enhanced and endothelium-dependent relaxation further reduced (pregnant OD-HF rats v. pregnant OC rats P < 0·001). The isoprostane, 8-epi-prostaglandin F2α, a marker of oxidative stress, was increased in pregnant OD rats (pregnant OD rats v. pregnant OC rats P < 0·001) and further increased in pregnant OD-HF rats (pregnant OD-HF rats v. pregnant OD rats P < 0·05). We conclude that a high-saturated-fat diet leads to deterioration in specific components of vascular function in OD rats. When pregnant, vascular function of OD-HF rats is further compromised. Pregnancy in the OD rats is associated with a striking increase in a marker of oxidative stress, which increases further if the saturated fat intake is raised.

Antihyperglycemic effects of separate and composite extract of root of Musa paradisiaca and leaf of Coccinia indica in streptozotocin-induced diabetic male albino rat

We evaluated the antihyperglycaemic properties of aqueous-methanolic (40:60) extract of root of Musa paradisiaca and leaf of Coccinia indica in separate as well as in composite manner by conducting experiment on streptozotocin-induced diabetic rats. We measured food and water intake ability, the fasting blood glucose level, glucose tolerance, activities of important carbohydrate metabolic enzymes like glucose-6-phosphatase, glucose-6-phosphate dehydrogenase, hexokinase in liver along with quantification of glycogen in liver and in skeletal muscle and serum insulin level. We noted that after treatment of aqueous methanolic extract of above plant parts in separate as well as in composite manner at a concentration of 80 mg/100 g body weight/day to streptozotocin-induced diabetic rat resulted in a significant remedial effect on blood glucose level as well as carbohydrate metabolic enzymes and the quantity of liver and skeletal muscle glycogen. Serum insulin level that was diminished in streptozotocin-induced diabetic rat recovered significantly after the co-administration of extract of above plant parts. All the above parameters showed a more potent remedial effect after composite extract treatment with respect to separate treatment and none of the extract has any general metabolic toxicity induction.

Antioxidants and CVD in diabetes: where do we stand now

Diabetes is an oxidative stress disorder as a result of both hyperglycemia and increased levels of free fatty acids. Oxidative stress has been implicated in the pathogenesis of diabetes-related complications, and treatment with antioxidants seemed to be a promising therapeutic option. Although animal studies and preliminary human studies were initially encouraging, subsequent human studies have failed to show a clear benefit of antioxidants, whereas some studies have even suggested that they can be potentially harmful. Therefore, treatment with antioxidants cannot be currently recommended as a therapeutic option.

Pyridoxamine analogues scavenge lipid-derived gamma-ketoaldehydes and protect against H2O2-mediated cytotoxicity

Isoketals and levuglandins are highly reactive gamma-ketoaldehydes formed by oxygenation of arachidonic acid in settings of oxidative injury and cyclooxygenase activation, respectively. These compounds rapidly adduct to proteins via lysyl residues, which can alter protein structure/function. We examined whether pyridoxamine, which has been shown to scavenge alpha-ketoaldehydes formed by carbohydrate or lipid peroxidation, could also effectively protect proteins from the more reactive gamma-ketoaldehydes. Pyridoxamine prevented adduction of ovalbumin and also prevented inhibition of RNase A and glutathione reductase activity by the synthetic gamma-ketoaldehyde, 15-E2-isoketal. We identified the major products of the reaction of pyridoxamine with the 15-E2-isoketal, including a stable lactam adduct. Two lipophilic analogues of pyridoxamine, salicylamine and 5'-O-pentylpyridoxamine, also formed lactam adducts when reacted with 15-E2-isoketal. When we oxidized arachidonic acid in the presence of pyridoxamine or its analogues, pyridoxamine-isoketal adducts were found in significantly greater abundance than the pyridoxamine-N-acyl adducts formed by alpha-ketoaldehyde scavenging. Therefore, pyridoxamine and its analogues appear to preferentially scavenge gamma-ketoaldehydes. Both pyridoxamine and its lipophilic analogues inhibited the formation of lysyl-levuglandin adducts in platelets activated ex vivo with arachidonic acid. The two lipophilic pyridoxamine analogues provided significant protection against H2O2-mediated cytotoxicity in HepG2 cells. These results demonstrate the utility of pyridoxamine and lipophilic pyridoxamine analogues to assess the potential contributions of isoketals and levuglandins in oxidant injury and inflammation and suggest their potential utility as pharmaceutical agents in these conditions.

N-acetylcysteine attenuates TNF-alpha-induced human vascular endothelial cell apoptosis and restores eNOS expression

The circulatory inflammatory cytokine tumor necrosis factor-alpha (TNF-alpha) is increased in pathological conditions, such as diabetes, which initiate or exacerbate vascular endothelial injury. Both nitric oxide (NO) and reactive oxygen species may play a dual role (i.e., inhibiting or promoting) in TNF-alpha-induced endothelial cell apoptosis. We investigated the effects of the antioxidant N-acetylcysteine on TNF-alpha-induced apoptosis in human vascular endothelial cell (cell line ECV304) apoptosis, NO production and lipid peroxidation. Cultured vascular endothelial cell (ECV304) were either not treated (control), or treated with TNF-alpha (40 ng/ml) alone or TNF-alpha in the presence of N-acetylcysteine at 30 mmol/l or 1 mmol/l, respectively, for 24 h. Cell viability was measured by MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) assay. Cell apoptosis was assessed by flow cytometry. TNF-alpha-induced endothelial cell apoptosis was associated with increased inducible NO synthase but reduced endothelial NO synthase (eNOS) protein expression. NO production and the levels of the lipid peroxidation product malondialdehyde were concomitantly increased. Treatment with NAC at 30 mmol/l restored eNOS expression and further increased NO production as compared to TNF-alpha alone, resulting in improved cell viability and reduced apoptosis. This was accompanied by increased superoxide dismutase activity, increased glutathione peroxidase production and reduced malondialdehyde levels. N-acetylcysteine at 1 mmol/l, however, did not have significant effects on TNF-alpha-induced endothelial cell apoptosis and cell viability despite it slightly enhanced glutathione peroxidase production. N-acetylcysteine attenuation of TNF-alpha-induced human vascular endothelial cell apoptosis is associated with the restoration of eNOS expression.

Impairment of dilator responses of cerebral arterioles during diabetes mellitus: role of inducible NO synthase

BACKGROUND AND PURPOSE

During diabetes, expression of inducible nitric oxide synthase (iNOS) plays an important role in the development of endothelial dysfunction in extracranial blood vessels. Progression of vascular dysfunction after the onset of diabetes differs among vascular beds. In this study, the effects of hyperglycemia/diabetes on vasomotor function were examined in cerebral arterioles at 2 different times in control and iNOS-deficient mice and compared with the effects on carotid arteries.

METHODS

Streptozotocin (150 mg/kg IP) was given to induce diabetes. The diameter of cerebral arterioles was measured through a cranial window in diabetic and nondiabetic mice in vivo. Vasomotor function of the carotid artery was examined in vitro.

RESULTS

In diabetic mice, responses of the cerebral arterioles to acetylcholine (1 mumol/L) were normal after 3 weeks of diabetes but were significantly impaired after 5 to 6 weeks of diabetes (4+/-1% [mean+/-SEM] increase in diameter) compared with control mice (14+/-1; P=0.0002). Responses to sodium nitroprusside were similar in diabetic and nondiabetic mice at both time points. In contrast, the vasomotor function of the carotid artery was not affected after 5 to 6 weeks of diabetes. In diabetic iNOS-deficient mice, cerebral arteriolar vasomotor function was not impaired, even after 4 months of diabetes.

CONCLUSIONS

During diabetes, endothelial dysfunction of cerebral arterioles requires expression of iNOS and develops earlier than in carotid arteries.

Effect of gap junction uncoupler heptanol on resistance arteries reactivity in experimental models of diabetes, hyperlipemia and hyperlipemia-diabetes

The understanding of the involvement of the gap junctions (GJ) in the vascular reactivity is an ongoing effort. In this study we questioned on impact of pathologies such as diabetes, hyperlipemia, and simultaneous hyperlipemia-diabetes on GJ involvement in the contractile/relaxant response of the mesenteric resistance arteries. To this purpose, four groups of Golden Syrian hamsters were used: (i) diabetics (D), injected by streptozotocin, (ii) hyperlipemics (H), fed the standard chow of the species supplemented with 3% cholesterol and 15% butter, (iii) simultaneously hyperlipemic-diabetics (HD), and (iv) controls (C), age-matched normal healthy animals. At 24 weeks after the beginning of the experiment, the vascular reactivity of the resistance arteries was measured by the myograph technique in the presence/absence of 1 mM Heptanol (Hep) and of vasoconstrictors and vasodilators. The results showed that: (i) in pathological conditions 1 mM Hep significantly impaired the constrictor response of the hamster resistance arteries to both 10(-5) M NA (noradrenaline, agonist of alpha(1)-adrenoceptors) and 64.1 mM K+ (potassium ion, the major intracellular cation). The impairment occur in the group range: HD < H < D < C being the highest at the simultaneous insult of hyperlipemia and diabetes; (ii) independently of the pathological condition, 1 mM Hep abolishes both endothelium-dependent and independent relaxation of the hamster resistance arteries. At 1 mM Hep we noticed a reversible effect on endothelium-dependent relaxation that may be partially restored (in normal) in the presence of L-arginine. It is hoped that these results may contribute to understanding of the involvement of GJ in vascular pathology/dysfunction.

Effect of vitamin E and C supplementation combined with oral antidiabetic therapy on the endothelial dysfunction in the neonatally streptozotocin injected diabetic rat

BACKGROUND

This study investigates the contribution of vitamin supplementation to the efficacy of oral antidiabetic therapy on the reversal of endothelial dysfunction in a model of type-2 diabetes in rat.

METHODS

Diabetes was induced by streptozotocin injection to neonatal rats which were breastfed for 4 weeks, then fed 6 weeks with normal food or food supplemented with 2% vitamin E and 4% vitamin C. Some diabetic rats were treated with gliclazide for 6 weeks. Endothelium-dependent and -independent relaxations to acetylcholine and sodium nitroprusside (SNP) were recorded in thoracic aortic rings. Plasma insulin, HbA(1c) and antioxidant vitamins (A, C and E); plasma and aortic malondialdehyde (MDA) levels were determined.

RESULTS

Induction of diabetes resulted in decreased body weight and increased blood glucose, plasma insulin and HbA(1c) levels compared to controls. Acetylcholine relaxation was impaired in diabetic aorta, while SNP relaxation remained unchanged. Aortic MDA level was significantly higher, while plasma vitamin levels were lower in diabetic rats. Diminished acetylcholine response, enhanced aortic MDA level and decreased plasma vitamin levels were all restored after gliclazide and/or vitamin therapy. However, vitamin supplementation in control rats significantly impaired acetylcholine relaxations and increased aortic MDA levels.

CONCLUSIONS

Apparently, a selective endothelial dysfunction accompanies the imbalance in oxidant/antioxidant status in the type-2 diabetes model of rat and gliclazide and/or vitamin supplementation improves the impairment in diabetic vasculature. However, vitamin supplementation triggers oxidative stress in normal aortic tissue, thereby, leads to endothelial dysfunction; indicating that nutritional extra-supplementation of antioxidant vitamins isn't advisable for normal subjects, although it's beneficial in disease status.

Time-Dependent Changes in Antioxidant Enzymes and Vascular Reactivity of Aorta in Streptozotocin-Induced Diabetic Rats Treated With Curcumin

In the present study changes in oxidative stress and vascular reactivity in aortic rings of chronic streptozotocin-diabetic (STZ-CON) and nondiabetic (ND-CON) rats is studied at 4 weekly intervals up to 24 weeks. The effect of chronic curcumin (200 mg/kg) treatment was also studied. Blood glucose and blood pressure levels were significantly higher in the STZ-CON group and curcumin administration had no significant effect on it. Superoxide dismutase and catalase activity were either unchanged or significantly increased during the early stage of diabetes whereas during the medium and late stage were significantly reduced. Reduced glutathione and lipid peroxidation levels significantly decreased as time after STZ administration increased. Phenylephrine (PE)-induced contraction was significantly (P < 0.05) increased during the early stage of diabetes, whereas it was significantly (P < 0.05) reduced at the medium and late stage of diabetes. Acetylcholine (Ach)-induced relaxation significantly decreased with respect to time after STZ administration. Sodium nitroprusside (SNP)-induced relaxation was unaltered up to initial stage but after medium stage there was a rightward shift and the pD2 value significantly decreased. Though curcumin treatment had no significant effect on superoxide dismutase, catalase, and reduced glutathione levels, it significantly reduced lipid peroxidation compared with diabetic control. Curcumin treatment attenuated the phenylephrine-induced increase in contraction during the early stage. However, curcumin treatment had no significant effect at the medium and late stage. Though curcumin administration improved Ach-induced relaxation it did not restore it to normal. Inability of curcumin to prevent oxidative stress during the late stage may be due to the fact that chronic diabetes (hyperglycemia) leads to excessive production of free radicals. Hence the present study shows that variations reported in antioxidant enzymes and vascular reactivity are due to the duration of diabetes or time after diabetes induction in STZ model and this can not be completely reversed by chronic treatment with curcumin.

Mechanisms underlying endothelial dysfunction in diabetes mellitus: therapeutic implications

Hyperglycemia is the major causal factor in the development of endothelial dysfunction in patients with diabetes mellitus. Although the mechanisms underlying this phenomenon are likely to be multifactorial, recent in vivo and in vitro studies have indicated a crucial role of the diacylglycerol (DAG)-protein kinase C (PKC) pathway in mediating this phenomenon. PKC may have multiple adverse effects on vascular function, including the activation of superoxide-producing enzymes such as the nicotinamide adenine dinicleotide phosphate (NADPH) oxidase as well as increased expression of a dysfunctional, superoxide-producing, uncoupled endothelial nitric oxide synthase (NOS III). PKC-mediated superoxide production may inactivate nitric oxide (NO) derived from endothelial NOS III, but also may inhibit the activity and/or expression of the NO downstream target, the soluble guanylyl cyclase. Among the different isoforms of PKC, mainly the beta-isoforms have been shown to be activated. Recent studies with selective (isoform-specific) and non-selective PKC inhibitors show that they are able to beneficially influence glucose-induced endothelial dysfunction in experimental animal models as well as in patients, pointing to the therapeutic potential of these compounds in the prevention and treatment of vascular complications of diabetes.

Protective Effects of Moderate Exercise With Dietary Vitamin C and E on Blood Antioxidative Defense Mechanism in Rats With Streptozotocin-Induced Diabetes

Daily moderate exercise and supplementation of vitamins C and E (VCE) can be beneficial in diabetes by ameliorating the effects of free radical production. The present study sought to analyze the effect of moderate exercise accompanying VCE supplementation on lipid peroxidation (LP) and antioxidative systems in the blood of streptozotocin-induced diabetic rats. Forty female Wistar rats were randomly divided 4 groups. The 1st and 2nd groups served as the control and diabetic groups, respectively. The 3rd group was the diabetic-exercise group. The 4th group, also diabetic-exercise rats, received VCE-supplemented feed. Animals in the exercised groups were moderately exercised on a treadmill 5 days a week for 3 weeks. Diabetes was induced on Day 0 of the exercise. Plasma and red blood cell (RBC) samples were taken from all animals on Day 20. Glutathione peroxidase, catalase, and reduced glutathione levels in plasma and RBCs, and vitamins A, E, and β-carotene in plasma were lower in diabetic rats than in control animals, whereas there was a significant increase in platelet counts in both plasma and RBC LP levels. The decreased antioxidant enzymes and vitamins, and the increased LP levels and WBC counts, did improve through exercise only, although their levels were mostly increased by exercise + VCE supplementation. There were no significant changes in the hemoglobin and hematocrit values in the 4 groups. In conclusion, these data demonstrate an increase in LP in the blood of diabetic animals whereas there was a decrease in the antioxidant vitamins and enzymes. However, dietary VCE with moderate exercise may strengthen the antioxidant defense system by decreasing reactive oxygen species. Key words: hyperglycemia, glutathione peroxidase, oxidative stress, hematological values

Insulin-stimulated endothelial nitric oxide release is calcium independent and mediated via protein kinase B

Insulin exerts a vasodilator effect by stimulating endothelial nitric oxide (NO) production. Studies in cultured cells suggest that insulin might activate endothelial nitric oxide synthase (eNOS) by an atypical, calcium-independent mechanism. This study investigates the mechanism of insulin-stimulated endothelial NO production in intact aortic wall. Real time fluorescence imaging with 4,5-diaminofluorescin diacetate (DAF-2 DA) or 4-amino-5-methylamino-2',7'-difluorofluorescein diacetate (DAF-FM DA) and FURA 2-AM was used to simultaneously visualise NO and intracellular calcium concentrations at multiple locations in the endothelium and vascular smooth muscle of isolated rat and mouse aorta after exposure to insulin. Inhibitors of intracellular insulin signalling were used to determine the pathway for insulin-stimulated NO production. Unlike acetylcholine, which stimulated endothelial NO production with a typical increase in free intracellular calcium, insulin (10(-8) to 10(-6)M) stimulated endothelial NO production without elevating intracellular calcium levels. Insulin-stimulated NO production was concentration dependent and detected within 30s of application. Peak increases in NO occurred between 60 and 120 s and declined slowly thereafter. Separate measurements of NO production by fluorescence of 2,3-diaminonaphthalene (DAN) noted that selective inhibitors of phosphatidylinositol 3-kinase (PI3K) and protein kinase B (PKB) inhibited insulin-stimulated NO production, whereas these inhibitors alone did not alter NO production or acetylcholine-stimulated NO production. Insulin-stimulated NO production by endothelium is an acute calcium-independent effect mediated via the PI3K-PKB signalling pathway.

Early vitamin E supplementation attenuates diabetes-associated vascular dysfunction and the rise in protein kinase C-beta in mesenteric artery and ameliorates wall stiffness in femoral artery of Wistar rats

AIMS/HYPOTHESIS

The impact of early vitamin E supplementation on vascular function in diabetes remains unresolved. Therefore, we examined the effects of vitamin E on functional and structural parameters and on chemical markers that are disturbed in diabetes in mesenteric and femoral arteries.

METHODS

Segments of both arteries, taken from control and 8-week-old streptozotocin diabetic Wistar rats that were treated or not with vitamin E, were mounted on wire and pressure myographs, after which endothelium-dependent and -independent vasodilation was assessed. Passive mechanical wall properties and the localisation and levels of protein kinase C (PKC)-beta(2) and AGE were evaluated in these vessels.

RESULTS

Vitamin E supplementation was associated with improved endothelium-dependent and -independent vasodilatation in mesenteric arteries from diabetic rats. Impaired endothelium-dependent vasodilatation in diabetic mesenteric vessels was associated with PKC-beta(2) up-regulation and this was prevented by vitamin E supplementation. Increased AGE accumulation and plasma isoprostane levels in diabetic rats were not changed by vitamin E. In the femoral artery, vitamin E supplementation had no effect on endothelium-dependent or -independent vasodilatation, but did prevent the wall stiffening associated with diabetes.

CONCLUSIONS/INTERPRETATION

Early vitamin E supplementation has a beneficial effect on diabetes-induced endothelial dysfunction in resistance arteries. This benefit may arise from a direct effect on smooth muscle function, as a result of inhibition of the PKC-beta(2) isoform by vitamin E.

Effect of ascorbic acid on airway responsiveness in ovalbumin sensitized guinea pigs

OBJECTIVE

The most important pathological feature of asthma is airway inflammation, which results in airway hyper-responsiveness. We hypothesized that excessive oxidation is likely to contribute to airway inflammation in asthma. The aim of this study was to evaluate the effects of both acute exposure and a 30-day administration of ascorbic acid (AA), which has an antioxidant effect, on airway responsiveness in sensitized guinea pigs.

METHODOLOGY

Guinea pigs sensitized to ovalbumin (OA), were given drinking water without AA (group 2) or with AA (group 3). The responses of tracheal chains of control animals (group 1) and both groups of sensitized guinea pigs (n = 10, for all groups) to cumulative concentrations of methacholine were measured, and the effective concentrations of methacholine causing 50% of maximum response (EC50 M) were obtained. The response of tracheal chains to 0.1% OA, relative to contraction obtained with 10 micro mol/L methacholine, was also measured. The tracheal responses to methacholine and OA were measured on tissues both incubated and not incubated with AA.

RESULTS

The tracheal responses of group 2 tissues were significantly greater than those of groups 1 and 3 to both OA and methacholine (P < 0.05). There were no significant differences in tracheal responses to OA and methacholine between groups 1 and 3. Acute incubation of tissues caused a reduction of tracheal response to methacholine in all groups, but this was only significantly differ-ent for group 3 (P < 0.05). Acute incubation of tissues did not change tracheal response to OA significantly.

CONCLUSION

These results showed that although short-term administration of AA had no major effect on tracheal responsiveness among sensitized animals, 30-day administration of AA could lead to a decrease in airway responsiveness of sensitized guinea pigs to both OA and methacholine.

Moderate exercise with a dietary vitamin C and E combination protects against streptozotocin-induced oxidative damage to the blood and improves fetal outcomes in pregnant rats

A considerable amount of clinical and experimental evidence now exists suggesting that many biochemical pathways strictly associated with diabetes increase the production of reactive oxygen species (ROS). However, daily moderate exercise and vitamins C and E(VCE ) supplementation can be beneficial to diabetes due to reducing blood glucose and free radical production. In the present study, we investigated the effect of VCE and moderate exercise on lipid peroxidation (MDA) and scavenging enzyme activity in the blood of STZ-induced diabetic pregnant rats.

Fifty female Wistar rats were used and were randomly divided into five groups. The first and second were used as the control and pregnant control groups, respectively. The third group was the pregnant diabetic group. The fourth group was the diabetic-pregnant-exercise group. VCE-supplemented feed was given to pregnant-diabetic-exercise rats constituting the fifth group. Animals in the exercised groups were moderately exercised daily on a treadmill (16.1 m/min, 45 min/d) for three weeks (five days a week). Diabetes was induced on day zero of the study. Body weights in the five groups were recorded weekly. Plasma and red blood cell (RBC) samples were taken from all animals on day 20.

Glutathione peroxidase (GSH-Px), catalase and reduced glutathione (GSH) levels in plasma and RBCs, glucose, vitamins A, E and β-carotene in plasma, the number of fetuses, and body weight were lower in pregnant diabetic rats than in control animals, whereas there was a significant increase in platelet counts and plasma and RBC MDA levels. The decreased antioxidant enzymes did not improve through exercise only. However, the decreased vitamins, and increased MDA, glucose levels and white blood cell (WBC) counts were improved either by exercise or exercise plus VCE supplementation. There were no significant changes in the RBC counts and hemoglobin values in the five groups.

In conclusion, these data demonstrate that there is an increase in MDA in the blood of diabetic pregnant animals, whereas there is a decrease in the number of fetuses, antioxidant vitamins and enzymes. However, dietary VCE with moderate exercise may strengthen the antioxidant defense system due to reducing ROS. They may play a role in preventing diabetes-related diseases of pregnant subjects.

Renal development in high-glucose ambience and diabetic embryopathy

Maternal diabetes has an adverse influence on the intrauterine growth of the fetus, which is attributable to the exposure of the mammalian embryo to an abnormal metabolic environment. A sustained exposure of the fetus to such an environment (ie, elevated concentration of glucose), during the first 6 to 8 weeks of gestation in humans may result in diabetic embryopathy, which is characterized by a multitude of congenital birth defects, including those of the nervous, cardiovascular, skeletal, and urogenital systems. The urogenital abnormalities may be associated with caudal regression syndrome or may occur alone in the form of partial or total renal agenesis. Similarly, an increase in the incidence of morphogenetic defects is observed in offsprings of streptozotocin-induced diabetic rats and mice and also in nonobese diabetic mice. In certain instances, failure in the growth of lower part of embryos or newborn mice has been observed in animals with a severe diabetic state. For further delineation of the mechanisms involved in the pathogenesis of diabetic embryopathy, the investigators used whole-embryo culture systems, and found that glucose can induce defects mainly confined to the lower part of the body involving the genitourinary system. Similarly, dysmorphogenesis of the embryonic metanephros is observed when it is subjected to high concentrations of D-glucose and its epimer D-mannose. This article discusses certain aspects of diabetic embryopathy with an emphasis on changes that occur in the fetal metanephros in high-glucose ambience.

Diabetes, oxidative stress, and antioxidants: a review

Increasing evidence in both experimental and clinical studies suggests that oxidative stress plays a major role in the pathogenesis of both types of diabetes mellitus. Free radicals are formed disproportionately in diabetes by glucose oxidation, nonenzymatic glycation of proteins, and the subsequent oxidative degradation of glycated proteins. Abnormally high levels of free radicals and the simultaneous decline of antioxidant defense mechanisms can lead to damage of cellular organelles and enzymes, increased lipid peroxidation, and development of insulin resistance. These consequences of oxidative stress can promote the development of complications of diabetes mellitus. Changes in oxidative stress biomarkers, including superoxide dismutase, catalase, glutathione reductase, glutathione peroxidase, glutathione levels, vitamins, lipid peroxidation, nitrite concentration, nonenzymatic glycosylated proteins, and hyperglycemia in diabetes, and their consequences, are discussed in this review. In vivo studies of the effects of various conventional and alternative drugs on these biomarkers are surveyed. There is a need to continue to explore the relationship between free radicals, diabetes, and its complications, and to elucidate the mechanisms by which increased oxidative stress accelerates the development of diabetic complications, in an effort to expand treatment options.

Effect of chronic treatment with vitamin E on endothelial dysfunction in a type I in vivo diabetes mellitus model and in vitro

Diabetes mellitus often leads to generalized vasculopathy. Because of the pathophysiological role of free radicals we investigated the effects of vitamin E. Twenty-eight rats were rendered diabetic by streptozotocin injection and were fed either with a diet with low (10 mg/kg of chow), medium (75 mg/kg of chow) or high amounts of vitamin E (1300 mg/kg of chow). Nine age-matched nondiabetic rats receiving 75 mg of vitamin E/kg chow served as controls. After 7 months, mesenteric microcirculation was investigated. Smooth muscle contractile function was not altered in diabetic versus nondiabetic vessels. Endothelial function was significantly reduced in diabetics; relaxation upon 1 micro M acetylcholine was reduced by 50% in diabetics with a medium and high vitamin E diet. In vitamin E-deprived rats, a complete loss of endothelium-dependent relaxation was observed, and instead, acetylcholine elicited vasoconstriction. L-N(G)-Nitro-arginine-induced vasoconstriction was reduced in small arteries in diabetics, which was not prevented by vitamin E, but was aggravated by vitamin E deprivation. In a subchronic endothelial cell culture model, cells were cultivated with 5 or 20 mM D-glucose for an entire cell culture passage (4 days) with or without vitamin E (20 mg/l versus 0.01 mg/l). Hyperglycemia led to significant reduction in basal and ATP-stimulated nitric oxide (NO)-production. Hyperglycemia-induced reduction in basal NO-release was significantly prevented by vitamin E, whereas reduction in stimulated NO-release was not influenced. NADPH-diaphorase activity was reduced by 40% by hyperglycemia, which was completely prevented by vitamin E. We conclude that 1) vitamin E has a potential to prevent partially hyperglycemia-induced endothelial dysfunction, 2) under in vivo conditions vitamin E deficiency enhanced diabetic endothelial dysfunction dramatically, and 3) positive effects of vitamin E may be attenuated with a longer disease duration.

The role of ascorbic acid on the redox status and the concentration of malondialdehyde in streptozotocin-induced diabetic rats

We investigated the role of ascorbic acid on the redox status in streptozotocin-induced diabetic rats. In the plasma of diabetic rats, the ratio of reduced/total ascorbic acid was significantly decreased as compared with normal control. Ascorbic acid supplementation increased the reduced and total ascorbic acid contents as compared with diabetic control. In the rutin-treatment group, reduced and total contents of ascorbic acid were significantly decreased, however, the ratio of reduced/total contents of ascorbic acid had no difference as compared with diabetic rats. In the insulin-treatment group, this ratio is not significantly different as compared with diabetic control. However, in the insulin plus ascorbic acid treatment group, reduced form and the ratio of reduced/total ascorbic acid were significantly increased as compared with diabetic control. In addition, we measured the contents of malondialdehyde (MDA) in the plasma of diabetic rats. The contents of MDA was increased as compared with normal control, however, in insulin-treatment group, the contents of MDA was decreased as compared with diabetic rats. Ascorbic acid had no effects on the increases of MDA in diabetic rats. In conclusion, plasma ascorbic acid level and its reduced/total ratio reflects the status of the oxidative stress in the diabetic rats. Supplement of ascorbic acid did not correct the ratio of the reduced/ total ascorbic acid. However, supplement of insulin and ascorbic acid corrected the ratio of reduced/total ascorbic acid.

Effect of Coccinia indica leaves on antioxidant status in streptozotocin-induced diabetic rats

The antioxidant effect of an ethanolic extract of Coccinia indica leaves, an indigenous plant used in Ayurvedic medicine in India, was studied in Streptozotocin-diabetic rats. Oral administration of Coccinia indica leaf extract (CLEt) (200 mg/kg body weight) for 45 days resulted in a significant reduction in thiobarbituric acid reactive substances and hydroperoxides. The extract also causes a significant increase in reduced glutathione, superoxide dismutase, catalase, glutathione peroxidase and glutathione-S-transferase in liver and kidney of streptozotocin diabetic rats, which clearly shows the antioxidant property of CLEt. The effect of CLEt at 200 mg/kg body weight was more effective than glibenclamide

Improved antioxidant and fatty acid status of patients with cystic fibrosis after antioxidant supplementation is linked to improved lung function

BACKGROUND

Oxidative stress, as measured by 8-iso-prostaglandin F(2)(alpha) (8-iso-PGF(2)(alpha)), and depleted antioxidant defenses were shown in stable cystic fibrosis (CF) patients. The plasma fatty acid status of CF patients was linked to oxidative stress after respiratory exacerbations.

OBJECTIVE

We examined changes in plasma 8-iso-PGF(2)(alpha), antioxidant defenses, plasma fatty acid status, and clinical markers resulting from short-term antioxidant supplementation.

DESIGN

Forty-six CF patients were randomly assigned to either group A [low dose of supplement (10 mg vitamin E and 500 micro g vitamin A)] or group B [high dose of supplement (200 mg vitamin E, 300 mg vitamin C, 25 mg beta-carotene, 90 micro g Se, and 500 micro g vitamin A)]. Plasma concentrations of 8-iso-PGF(2)(alpha), vitamins E and C, beta-carotene, zinc, selenium, and copper; plasma fatty acid composition; erythrocyte glutathione peroxidase (EC 1.11.1.9) and superoxide dismutase (EC 1.15.1.1) activities; lung function; and dietary intake were measured before and after 8 wk of supplementation.

RESULTS

Antioxidant defenses in group B improved, whereas those in group A did not: in groups B and A, the mean (+/- SEM) changes (Delta) in vitamin E were 10.6 +/- 1.5 and -1.9 +/- 0.9 micro mol/L, respectively (P < 0.001), (Delta)beta-carotene were 0.1 +/- 0.04 and -0.01 +/- 0.02 micro mol/L, respectively (P = 0.007), (Delta)selenium were 0.51 +/- 0.10 and -0.09 +/- 0.04 micro mol/L, respectively (P < 0.001), and (Delta)glutathione peroxidase activity were 1.3 +/- 0.3 and -0.3 +/- 0.6 U/g hemoglobin, respectively (P = 0.016). There were no significant differences between the groups in Delta8-iso-PGF(2)(alpha), (Delta)vitamin C, (Delta)fatty acid composition, (Delta)superoxide dismutase activity, (Delta)lung function, or (Delta)white cell count. Within group B, (Delta)beta-carotene correlated with (Delta)percentage of forced vital capacity (r = 0.586, P = 0.005), (Delta)selenium correlated with (Delta)percentage of forced expiratory volume in 1 s (r = 0.440, P = 0.046), and (Delta)plasma fatty acid concentrations correlated with (Delta)percentage of forced expiratory volume in 1 s (r = 0.583, P = 0.006) and Delta8-iso-PGF(2)(alpha) (r = 0.538, P = 0.010).

CONCLUSIONS

Whereas increased beta-carotene, selenium, and fatty acid concentrations are linked to improved lung function, increased plasma fatty acid concentrations are linked to oxidative stress. If oxidative stress is deemed to be important to the clinical outcome of CF patients, means of reducing oxidative stress while maintaining a high-fat, high-energy diet must be investigated.

Dose-dependent protection of cardiac function by propofol during ischemia and early reperfusion in rats: effects on 15-F2t-isoprostane formation

We examined the effects of propofol (2,6-diisopropylphenol) on functional recovery and 15-F2t-isoprostane generation during ischemia-reperfusion in Langendorff-perfused rat hearts. Before the induction of 40 min of global ischemia, hearts were perfused (10 min) with propofol at 5 (lo-P) or 12 microg/mL (hi-P) in saline or with saline only (control). During ischemia, saline, lo-P, or hi-P was perfused through the aorta at 60 microL/min. During the first 15 min of reperfusion, propofol (5 or 12 microg/mL) was continued, followed by perfusion with 5 microg/mL propofol for 75 min in both propofol-treated groups. After 90 min of reperfusion (Rep-90), heart tissues were harvested for assessment of antioxidant status. In hi-P, we observed increased latency to and greater reduction of ischemic contracture relative to the lo-P or control groups. 15-F2t-Isoprostane concentrations increased during ischemia and were significantly lower in hi-P and lo-P than in control (P < 0.01). At Rep-90, myocardial functional recovery was greater in both propofol-treated groups relative to control, and it correlated positively with tissue antioxidant capacity preservation. Tissue antioxidant capacity was better preserved in hi-P than in lo-P treatment (P < 0.05). We conclude that oxidant injury occurs during ischemia and reperfusion, and propofol provides dose-dependent protection primarily by enhancing tissue antioxidant capacity and reducing lipid peroxidation.

Vascular endothelial dysfunction associated with elevated serum homocysteine levels in rat adjuvant arthritis: effect of vitamin E administration

We aimed to study the alterations in serum homocysteine levels and endothelium-dependent and -independent vascular relaxant responses in adjuvant-induced arthritis of the rat and to determine the effects of vitamin E administration on these changes. Arthritis was induced by a single intradermal injection of Freund's complete adjuvant into the paw. 26 days after the induction of arthritis, serum homocysteine levels and relaxant responses to acetylcholine and sodiumnitroprusside in thoracic aortas were evaluated. The relaxant responses to acetylcholine were decreased in aortas from arthritic rats, whereas the responses to sodiumnitroprusside were not significantly different when compared to the aortas from control rats. A significant increase was observed in serum homocysteine levels of the arthritic rats in comparison to those of controls. Vitamin E administration (100 mg/kg/day, i.m. for 26 days) to arthritic rats resulted in a significant increase in endothelium-dependent aortic responses to acetylcholine and a significant decrease in serum homocysteine levels with respect to the non-treated arthritic rats. However, in healthy rats, vitamin E treatment significantly decreased the acetylcholine-induced relaxant responses. We conclude that adjuvant-induced arthritis in the rat is associated with increased serum homocysteine levels and this is accompanied by a reduction in endothelium-dependent vascular responses in the thoracic aortas. Vitamin E treatment leads to normalization of the increased serum homocysteine levels and improves the endothelium-dependent relaxant responses in this experimental model.

Endothelial function in mesenteric resistance arteries from the genetically hypertensive rat

1. Endothelial function in mesenteric resistance arteries (MRA) from male 12-week-old New Zealand genetically hypertensive (GH) rats and their normotensive control strain (N) was compared in vessels mounted on a wire myograph and by the production of intracellular cGMP. In parallel experiments, MRA from the spontaneously hypertensive (SHR) rat strain, in which there is an endothelial defect, and from GH rats, in which an endothelial defect was induced by chronic nitric oxide synthase (NOS) inhibition with Nomega-nitro-L-arginine methyl ester (L-NAME), were studied. 2. Contractile responses to potassium (124 mmol/L) depolarization and to NA (10(-8) to 10(-4) mol/L) were similar in GH and N rats; however, in SHR, enhanced contractile responses were found (P < 0.05). The endothelium-dependent relaxation induced by acetylcholine (ACh; 10(-9) to 10(-4) mol/L) and endothelium- independent relaxation induced by sodium nitroprusside (SNP; 10(-9) to 10(-4) mol/L) were identical in preparations from GH and N. A significantly attenuated (P < 0.01) vasodilator response to ACh was observed in preparations from SHR. 3. Levels of intracellular cGMP were similar in untreated small mesenteric arterial trees from GH, N and SHR rats. Acetylcholine (10-5 mol/L) significantly (P < 0.001) increased the cGMP content in both GH and N rats. A non-significant increase occurred in cGMP content in preparations from SHR. 4. In GH rats given L-NAME (10 mg/kg per day for up to 5 weeks), an attenuated (P < 0.01) endothelium-dependent relaxation to ACh and an enhanced (P < 0.01) endothelium- independent relaxation to SNP were observed. Lower basal cGMP levels were found in preparations from L-NAME-treated GH rats and ACh (10-5 mol/L) failed to significantly elevate the cGMP content in these preparations. 5. These experiments failed to show evidence of reduced endothelial function in GH rats, although an endothelial defect in SHR rats and after NOS inhibition in GH rats could be demonstrated.

Combination of vitamin C and rutin on neuropathy and lung damage of diabetes mellitus rats

We investigated the role of vitamin C or rutin on neuropathy and lung damage of diabetic mellitus (DM) rats. Norepinephrine content was significantly decreased in sciatic nerves'of DM rats compared with non-DM controls but vitamin C had no effect on decreases of norepinephrine. 2,4-dinitrophenylhydrazine (DNPH) incorporation, which is biomarker of protein oxidation, was increased in sciatic nerve of DM rats as compared with normal control. However, vitamin C had no effects on increases of DNPH incorporation. We measured the content of conjugated dienes (CD) as a biomarker of lipid oxidation in sciatic nerve. CD was increased in DM as compared with normal control. Vitamin C or rutin had no effects on increases of CD. However, Rutin plus vitamin C significantly decreased the content of CD as compared with DM rats. In lung of DM rats, DNPH incorporation or CD was increased as compared with normal control. Vitamin C or Rutin had no effects on increases of CD. However, Rutin plus vitamin C significantly decreased the content of DNPH incorporation or CD in lung tissue. Vitamin C caused marked pathological changes such as the increases of parenchyma and the thickening of alveolar septa in the lung of DM. Rutin had protective effects on the pathological changes in the lung of DM rats. In conclusion, Vitamin C had no effects on oxidative parameter, such as DNPH incorporation or CD, and on the decreases of norepinephrine content in DM rats. Vitamin C caused the marked pathological changes in the lung of DM rats but rutin had protective effects against the pathological changes.

Endothelial dysfunction in children with type 1 diabetes mellitus

Endothelial dysfunction is defined as the loss of endothelium properties, e.g. alteration of protein synthesis, increased vascular tone and permeability, acquisition of prothrombotic and antifibrinolytic properties. Endothelium, a primary target of unbalanced glycaemic control, is involved in the pathogenesis of vascular complications in patients with type 1 diabetes mellitus (DM). Vascular endothelium damage is characterised by an increase of endothelium-derived regulatory proteins. vWF and t-PA may be useful to investigate early endothelium involvement. However, impaired endothelium-dependent vasodilatation may be a more sensitive marker. Abnormal markers of endothelial cell activation and impaired endothelium-dependent vasodilatation have been observed in young patients with type I DM. Hyperglycaemia may alter normal endothelium functions, either directly or indirectly, by inducing different metabolic pathways. Complete understanding of the pathophysiology of endothelial dysfunction may lead to timely therapeutic intervention to prevent its development and to slow the progression of diabetic complications.