Effects of piperine on antioxidant pathways in tissues from normal and streptozotocin-induced diabetic rats

Using diabetes mellitus as a model of oxidative damage, this study investigated whether subacute treatment (10 mg/kg/day, intraperitoneally for 14 days) with the compound piperine would protect against diabetes-induced oxidative stress in 30-day streptozotocin-induced diabetic Sprague-Dawley rats. Liver, kidney, brain, and heart were assayed for degree of lipid peroxidation, reduced and oxidized glutathione (GSH and GSSG, respectively) content, and activities of the free-radical detoxifying enzymes catalase, superoxide dismutase, glutathione peroxidase, and glutathione reductase. Piperine treatment of normal rats enhanced hepatic GSSG concentration by 100% and decreased renal GSH concentration by 35% and renal glutathione reductase activity by 25% when compared to normal controls. All tissues from diabetic animals exhibited disturbances in antioxidant defense when compared with normal controls. Treatment with piperine reversed the diabetic effects on GSSG concentration in brain, on renal glutathione peroxidase and superoxide dismutase activities, and on cardiac glutathione reductase activity and lipid peroxidation. Piperine treatment did not reverse the effects of diabetes on hepatic GSH concentrations, lipid peroxidation, or glutathione peroxidase or catalase activities; on renal superoxide dismutase activity; or on cardiac glutathione peroxidase or catalase activities. These data indicate that subacute treatment with piperine for 14 days is only partially effective as an antioxidant therapy in diabetes.     

Effects of coenzyme Q10 treatment on antioxidant pathways in normal and streptozotocin-induced diabetic rats

Coenzyme Q10 is an endogenous lipid soluble antioxidant. Because oxidant stress may exacerbate some complications of diabetes mellitus, this study investigated the effects of subacute treatment with exogenous coenzyme Q10 (10 mg/kg/day, i.p. for 14 days) on tissue antioxidant defenses in 30-day streptozotocin-induced diabetic Sprague-Dawley rats. Liver, kidney, brain, and heart were assayed for degree of lipid peroxidation, reduced and oxidized glutathione contents, and activities of catalase, superoxide dismutase, glutathione peroxidase, and glutathione reductase. All tissues from diabetic animals exhibited increased oxidative stress and disturbances in antioxidant defense when compared with normal controls. Treatment with the lipophilic compound coenzyme Q10 reversed diabetic effects on hepatic glutathione peroxidase activity, on renal superoxide dismutase activity, on cardiac lipid peroxidation, and on oxidized glutathione concentration in brain. However, treatment with coenzyme Q10 also exacerbated the increase in cardiac catalase activity, which was already elevated by diabetes, further decreased hepatic glutathione reductase activity, augmented the increase in hepatic lipid peroxidation, and further increased glutathione peroxidase activity in the heart and brain of diabetic animals. Subacute dosing with coenzyme Q10 ameliorated some of the diabetes-induced changes in oxidative stress. However, exacerbation of several diabetes-related effects was also observed.     

Effects of quercetin on antioxidant defense in streptozotocin-induced diabetic rats.

In light of evidence that some complications of diabetes mellitus may be caused or exacerbated by oxidative damage, we investigated the effects of subacute treatment with the antioxidant quercetin on tissue antioxidant defense systems in streptozotocin-induced diabetic Sprague-Dawley rats (30 days after streptozotocin induction). Quercetin, 2-(3,4-dihydroxyphenyl)-3,5,7-trihydroxy-4H-1-benzopyran-4-one, was administered at a dose of 10mg/kg/day, ip for 14 days, after which liver, kidney, brain, and heart were assayed for degree of lipid peroxidation, reduced and oxidized glutathione content, and activities of the free-radical detoxifying enzymes catalase, superoxide dismutase, glutathione peroxidase, and glutathione reductase. Treatment of normal rats with quercetin increased serum AST and increased hepatic concentration of oxidized glutathione. All tissues from diabetic animals exhibited disturbances in antioxidant defense when compared with normal controls. Quercetin treatment of diabetic rats reversed only the diabetic effects on brain oxidized glutathione concentration and on hepatic glutathione peroxidase activity. By contrast, a 20% increase in hepatic lipid peroxidation, a 40% decline in hepatic glutathione concentration, an increase in renal (23%) and cardiac (40%) glutathione peroxidase activities, and a 65% increase in cardiac catalase activity reflect intensified diabetic effects after treatment with quercetin. These results call into question the ability of therapy with the antioxidant quercetin to reverse diabetic oxidative stress in an overall sense.     

Effects of new antioxidant compounds PNU-104067F and PNU-74389G on antioxidant defense in normal and diabetic rats

Diabetes mellitus and its complications are associated with elevated oxidative stress, leading to much interest in antioxidant compounds as possible therapeutic agents. Two new classes of antioxidant compounds, the pyrrolopyrimidines and the 21-aminosteroids, are known to inhibit lipid peroxidation and other biomolecular oxidation. We hypothesized that in the presence of excess oxidants or the impaired antioxidant defense seen in diabetes mellitus, administration of antioxidants such as these may reverse the effects of diabetes on antioxidant parameters. This study measured the effects of subchronic (14 day) treatment with a pyrrolopyrimidine (PNU-104067F) or a 21-aminosteroid (PNU-74389G) in normal and diabetic Sprague-Dawley rats. Activity levels of superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase, concentrations of oxidized and reduced glutathione, and lipid peroxidation were used as measures of antioxidant defense in liver, kidney, heart, and brain tissue. In normal rats, the only effect was a 43% increase in cardiac lipid peroxidation after treatment with PNU-104067F. In diabetic rats, the only reversals of the effects of diabetes were a 30% decrease in hepatic glutathione peroxidase activity after PNU-74389G treatment and a 33% increase in cardiac glutathione disulfide concentration after PNU-104067F treatment. In contrast to these effects, increased cardiac glutathione peroxidase and catalase activities, increased brain glutathione peroxidase activity, increased hepatic lipid peroxidation, decreased hepatic glutathione content, and decreased hepatic catalase activity were seen in diabetic rats, reflecting an exacerbation of the effects of diabetes.     

Characterization of Oxidative Stress in Various Tissues of Diabetic and Galactose-fed Rats

Rats fed a galactose-rich diet have been used for several years as a model for diabetes to study, particularly in the eye, the effects of excess blood hexoses. This study sought to determine the utility of galactosemia as a model for oxidative stress in extraocular tissues by examining biomarkers of oxidative stress in galactose-fed rats and experimentally-induced diabetic rats. Sprague-Dawley rats were divided into four groups: experimental control; streptozotocin-induced diabetic; insulin-treated diabetic; and galactose-fed. The rats were maintained on these regimens for 30 days, at which point the activities of catalase, glutathione peroxidase, glutathione reductase, and superoxide dismutase, as well as levels of lipid peroxidation and reduced and oxidized glutathione were determined in heart, liver, and kidney. This study indicates that while there are some similarities between galactosemic and diabetic rats in these measured indices of oxidative stress (hepatic catalase activity levels and hepatic and renal levels of oxidized glutathione in both diabetic and galactosemic rats were significantly decreased when compared to normal), overall the galactosemic rat model is not closely parallel to the diabetic rat model in extra-ocular tissues. In addition, several effects of diabetes (increased hepatic glutathione peroxidase activity, increased superoxide dismutase activity in kidney and heart, decreased renal and increased cardiac catalase activity) were not mimicked in galactosemic rats, and glutathione concentration in both liver and heart was affected in opposite ways in diabetic rats and galactose- fed rats. Insulin treatment reversed/prevented the activity changes in renal and cardiac superoxide dismutase, renal and cardiac catalase, and hepatic glutathione peroxidase as well as the hepatic changes in lipid peroxidation and reduced and oxidized glutathione, and the increase in cardiac glutathione. Thus, prudence should be exercised in the use of experimentally galactosemic rats as a model for diabetes until the correspondence of the models has been more fully characterized.     

Influence of treatment of diabetic rats with combinations of pycnogenol, beta-carotene, and alpha-lipoic acid on parameters of oxidative stress

Treatment with antioxidants may act more effectively to alter markers of free radical damage in combinations than singly. This study has determined whether treatment with combinations of pycnogenol, beta-carotene, and alpha-lipoic acid was more effective at reducing oxidative stress in diabetic rats than treatment with these antioxidants alone. It is not feasible, based on this study, to assume that there are interactive effects that make combinations of these antioxidants more effective than any one alone to combat oxidative stress. Female Sprague-Dawley rats, normal and streptozotocin-induced diabetic, were treated (10 mg/kg/day ip for 14 days) with pycnogenol, beta-carotene, pycnogenol + beta-carotene, or pycnogenol + beta-carotene + alpha-lipoic acid; controls were untreated. Concentrations of thiobarbituric acid reactive substances, glutathione and glutathione disulfide, and activities of glutathione reductase, glutathione peroxidase, superoxide dismutase, and catalase were measured in liver, kidney, and heart. Four types of effects were observed: (1) treatment with beta-carotene alone either reversed (cardiac glutathione disulfide) or elevated (cardiac glutathione, hepatic glutathione peroxidase activity) levels seen in diabetic animals; (2) beta-carotene alone produced no effect, but pycnogenol both alone and in combinations elevated (renal glutathione peroxidase and glutathione reductase activities, hepatic glutathione reductase activity and glutathione disulfide) or depressed (cardiac glutathione disulfide) levels seen in untreated diabetic animals; (3) all treatments with antioxidants, either alone or in combination, either normalized (lipid peroxidation in all tissues), elevated (hepatic GSH, cardiac glutathione peroxidase activity), or had no effect on (activities of hepatic catalase and superoxide dismutase in all tissues) levels seen in diabetic animals; (4) in only one case (cardiac glutathione reductase activity) levels in diabetic animals treated with combinations of antioxidants were normal, but elevated in animals treated with either antioxidant alone. Antioxidant effects seem to be dependent on the nature of the antioxidant used and not on combination effects.     

Influence of treatment of diabetic rats with combinations of pycnogenol, β‐carotene,and α‐lipoic acid on parameters of oxidative stress

Treatment with antioxidants may act more effectively to alter markers of free radical damage in combinations than singly. This study has determined whether treatment with combinations of pycnogenol, β‐carotene, and α‐lipoic acid was more effective at reducing oxidative stress in diabetic rats than treatment with these antioxidants alone. It is not feasible, based on this study, to assume that there are interactive effects that make combinations of these antioxidants more effective than any one alone to combat oxidative stress. Female Sprague‐Dawley rats, normal and streptozotocin‐induced diabetic, were treated (10 mg/kg/day ip for 14 days) with pycnogenol, β‐carotene, pycnogenol + β‐carotene, or pycnogenol + β‐carotene + α‐lipoic acid; controls were untreated. Concentrations of thiobarbituric acid reactive substances, glutathione and glutathione disulfide, and activities of glutathione reductase, glutathione peroxidase, superoxide dismutase, and catalase were measured in liver, kidney, and heart. Four types of effects were observed: (1) treatment with β‐carotene alone either reversed (cardiac glutathione disulfide) or elevated (cardiac glutathione, hepatic glutathione peroxidase activity) levels seen in diabetic animals; (2) β‐carotene alone produced no effect, but pycnogenol both alone and in combinations elevated (renal glutathione peroxidase and glutathione reductase activities, hepatic glutathione reductase activity and glutathione disulfide) or depressed (cardiac glutathione disulfide) levels seen in untreated diabetic animals; (3) all treatments with antioxidants, either alone or in combination, either normalized (lipid peroxidation in all tissues), elevated (hepatic GSH, cardiac glutathione peroxidase activity), or had no effect on (activities of hepatic catalase and superoxide dismutase in all tissues) levels seen in diabetic animals; (4) in only one case (cardiac glutathione reductase activity) levels in diabetic animals treated with combinations of antioxidants were normal, but elevated in animals treated with either antioxidant alone. Antioxidant effects seem to be dependent on the nature of the antioxidant used and not on combination effects. © 2005 Wiley Periodicals, Inc. J Biochem Mol Toxicol 18:345–352, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jbt.20046     

Effects of beta-carotene on oxidative stress in normal and diabetic rats

Increasing interest in the role of oxidative stress and beta-carotene in disease and prevention led us to examine the results of beta-carotene's administration in diabetic rats, a model for high-oxidative stress. In this experiment, amounts of lipid peroxidation, glutathione, and glutathione disulfide, and activity levels of catalase, glutathione peroxidase, glutathione reductase, superoxide dismutase, and gamma-glutamyl transpeptidase were measured in the liver, kidney, and heart of Sprague-Dawley rats with streptozotocin-induced diabetes, and after treatment with 10 mg/kg/day of beta-carotene for 14 days. Beta-carotene treatment resulted in the reversal of the diabetes-induced increase in hepatic and cardiac catalase activity, the decreased levels of glutathione disulfide in the heart, and the increased cardiac and renal levels of lipid peroxidation. Treatment with beta-carotene exacerbated the increased glutathione peroxidase activity in the heart and the decreased catalase activity in the kidneys. In contrast to reduced hepatic glutathione levels in untreated diabetic rats, beta-carotene treatment increased glutathione levels in diabetic rats. Increased hepatic gamma-glutamyl transpeptidase activity in diabetic rats was not reduced by treatment. Thus, beta-carotene therapy for 14 days prevented/reversed some, but not all, diabetes-induced changes in oxidative stress parameters.     

Effects of combined quercetin and coenzyme Q(10) treatment on oxidative stress in normal and diabetic rats

Reactive oxygen species may be actively involved in the genesis of various pathological states such as ischemia-reperfusion injury, cancer, and diabetes. Our objective was to determine if subacute treatment with combined antioxidants quercetin and coenzyme Q(10) (10 mg/kg/day ip for 14 days) affects the activities of antioxidant enzymes in normal and 30-day streptozotocin-induced diabetic Sprague-Dawley rats. Quercetin treatment raised blood glucose concentrations in normal and diabetic rats, whereas treatment with coenzyme Q(10) did not. Liver, kidney, heart, and brain tissues were excised and the activities of catalase, glutathione reductase, glutathione peroxidase, superoxide dismutase, and concentrations of oxidized and reduced glutathione were determined. In the liver of diabetic rats, superoxide dismutase, glutathione peroxidase, and levels of both oxidized and reduced glutathione were significantly decreased from the nondiabetic control, and these effects were not reversed when antioxidants were administered. In kidney, glutathione peroxidase activity was significantly elevated in the diabetic rats as compared to nondiabetic rats, and antioxidant treatment did not return the enzyme activity to nondiabetic levels. In heart, catalase activity was increased in diabetic animals and restored to normal levels after combined treatment with quercetin and coenzyme Q(10). Cardiac superoxide dismutase was lower than normal in quercetin- and quercetin + coenzyme Q(10)-treated diabetic rats. There were no adverse effects on oxidative stress markers after treatment with quercetin or coenzyme Q(10) singly or in combination. In spite of the elevation of glucose, quercetin may be effective in reversing some effects of diabetes, but the combination of quercetin + coenzyme Q(10) did not increase effectiveness in reversing effects of diabetes.     

Low-carbohydrate diet and oxidative stress in diabetic and nondiabetic rats

Hyperglycemia of diabetes has been implicated in increased tissue oxidative stress, with consequent development of secondary complications. Thus, stabilizing glucose levels near normal levels is of utmost importance. Because diet influences glycemic control, this study investigated whether a low-carbohydrate (5.5%) diet confers beneficial effects on the oxidative status of the heart, kidney, and liver in diabetes. Male and female normal and diabetic rats were fed standard chow (63% carbohydrates) or low-carbohydrate diet for 30 days. Elevated glucose, HbA(1c), and alanine and aspartate aminotransferases in diabetic animals were reduced or normalized by the low-carbohydrate diet. While diabetes increased cardiac activities of glutathione peroxidase and catalase, low-carbohydrate diet normalized cardiac glutathione peroxidase activity in diabetic animals, and reduced catalase activity in females. Diabetic rats fed low-carbohydrate diet had altered activities of renal glutathione reductase and superoxide dismutase, but increased renal glutathione peroxidase activity in diabetic animals was not corrected by the test diet. In the liver, diabetes was associated with a decrease in catalase activity and glutathione levels and an increase in glutathione peroxidase and gamma-glutamyltranspeptidase activities. Decreased hepatic glutathione peroxidase activity and lipid peroxidation were noted in diet-treated diabetic rats. Overall, the low-carbohydrate diet helped stabilize hyperglycemia and did not produce overtly negative effects in tissues of normal or diabetic rats.     

Effects of aging on the susceptibility to the toxic effects of cyclosporin A in rats. Changes in liver glutathione and antioxidant enzymes

Free radicals are involved in aging and cyclosporin A-induced toxicity. The age-related changes in the liver oxidative status of glutathione, lipid peroxidation, and the activity of the enzymatic antioxidant defense system, as well as the influence of aging on the susceptibility to the hepatotoxic effects of cyclosporin (CyA) were investigated in rats of different ages (1, 2, 4, and 24 months). The hepatic content of reduced glutathione (GSH) increased with aging, peaked at 4 months, and decreased in senescent rats. By contrast, glutathione disulfide (GSSG) and thiobarbituric acid-reactive substances (TBARS) concentrations and superoxide dismutase, catalase, and glutathione peroxidase activities were higher in the oldest than in the youngest rats. CyA treatment, besides inducing the well-known cholestatic syndrome, increased liver GSSG and TBARS contents and the GSSG/GSH molar ratio, and altered the nonenzymatic and enzymatic antioxidant defense systems. The CyA-induced cholestasis and hepatic depletion of GSH, and the increases in the GSSG/GSH ratio, and in GSSG and TBARS concentrations were higher in the older than the mature rats. Moreover, superoxide dismutase and catalase activities were found to be significantly decreased only in treated senescent rats. The higher CyA-induced oxidative stress, lipoperoxidation, and decreases in the antioxidant defense systems in the aged animals render them more susceptible to the hepatotoxic effects of cyclosporin.     

Effects of alpha-lipoic acid on biomarkers of oxidative stress in streptozotocin-induced diabetic rats

Increased oxidative stress and impaired antioxidant defense mechanisms are important factors in the pathogenesis and progression of diabetes mellitus and other oxidant-related diseases. This study was designed to determine whether alpha-lipoic acid, which has been shown to have substantial antioxidant properties, when administered (10 mg/kg ip) once daily for 14 days to normal and diabetic female Sprague-Dawley rats would prevent diabetes-induced changes in biomarkers of oxidative stress in liver, kidney and heart. Serum glucose concentrations, aspartate aminotransferase activity, and glycated hemoglobin levels, which were increased in diabetes, were not significantly altered by alpha-lipoic acid treatment. Normal rats treated with a high dose of alpha-lipoic acid (50 mg/kg) survived but diabetic rats on similar treatment died during the course of the experiment. The activity of glutathione peroxidase was increased in livers of normal rats treated with alpha-lipoic acid, but decreased in diabetic rats after alpha-lipoic acid treatment. Hepatic catalase activity was decreased in both normal and diabetic rats after alpha-lipoic acid treatment. Concentrations of reduced glutathione and glutathione disulfide in liver were increased after alpha-lipoic acid treatment of normal rats, but were not altered in diabetics. In kidney, glutathione peroxidase activity was elevated in diabetic rats, and in both normal and diabetic animals after alpha-lipoic acid treatment. Superoxide dismutase activity in heart was decreased in diabetic rats but normalized after treatment with alpha-lipoic acid; other cardiac enzyme activities were not influenced by either diabetes or antioxidant treatment. These results suggest that after 14 days of treatment with an appropriate pharmacological dose, alpha-lipoic acid may reduce oxidative stress in STZ-induced diabetic rats, perhaps by modulating the thiol status of the cells.     

Ameliorative potential of S-allyl cysteine on oxidative stress in STZ induced diabetic rats

Increased oxidative stress and impaired antioxidant defense mechanism are important factors in the pathogenesis and progression of diabetes mellitus and other oxidant-related diseases. The present study was undertaken to evaluate the possible protective effects of S-allyl cysteine (SAC) against oxidative stress in streptozotocin (STZ) induced diabetic rats. SAC was administered orally for 45 days to control and STZ induced diabetic rats. The effects of SAC on glucose, plasma insulin, thiobarbituric acid reactive substances (TBARS), hydroperoxide, superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), reduced glutathione (GSH), oxidized glutathione (GSSG) and GSH/GSSG ratio were studied. The levels of glucose, TBARS, hydroperoxide, and GSSG were increased significantly whereas the levels of plasma insulin, reduced glutathione, GSH/GSSG ratio, superoxide dismutase, catalase and GPx were decreased in STZ induced diabetic rats. Administration of SAC to diabetic rats showed a decrease in plasma glucose, TBARS, hydroperoxide and GSSG. In addition, the levels of plasma insulin, superoxide dismutase, catalase, GPx and reduced glutathione (GSH) were increased in SAC treated diabetic rats. The above findings were supported by histological observations of the liver and kidney. The antioxidant effect of SAC was compared with glyclazide, a well-known antioxidant and antihyperglycemic drug. The present study indicates that the SAC possesses a significant favorable effect on antioxidant defense system in addition to its antidiabetic effect.     

Enhanced heme oxygenase activity increases the antioxidant defense capacity of guinea pig liver upon acute cobalt chloride loading: comparison with rat liver

Changes in the activity of so-called oxidative stress defensive enzymes, superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase and heme oxygenase, as well as changes in lipid peroxidation and reduced glutathione levels, were measured in guinea pig and rat liver after acute cobalt loading. Cobalt chloride administration produced a much higher degree of lipid peroxidation in guinea pig than in rat liver compared with the control animals. The intrahepatic reduced glutathione content in control guinea pig was higher than that in rat, but was equally decreased in both species after cobalt administration. The enzymatic scavengers of free radicals, superoxide dismutase, catalase and glutathione peroxidase, were significantly decreased in rat liver after acute cobalt loading, and as a compensatory reaction, the heme oxygenase activity was increased (seven-fold). In guinea pig liver, only superoxide dismutase activity was depleted in response to cobalt-induced oxidative stress, while catalase and glutathione peroxidase were highly activated and the heme oxygenase activity was dramatically increased (13-fold). It is assumed that enhanced heme oxygenase activity may have important antioxidant significance by increasing the liver oxidative-stress defense capacity.     

Dietary caloric restriction improves the redox status at the onset of diabetes in hepatocytes of streptozotocin-induced diabetic rats

Enhanced production of free radicals and oxidative stress induced by hyperglycemia play a central role in the pathogenesis of diabetes and its complications. This study assessed the attenuation by dietary caloric restriction on the oxidative and lipid peroxidative effects of diabetes in the liver through reduction in body and organ weights and concomitant metabolic changes. Three-month-old male Wistar rats were subjected to ad libitum feeding and 30% caloric restriction for 9 weeks before induction of diabetes by intraperitoneal injection of 35 mg/kg body weight streptozotocin. The animals were sacrificed 2 weeks after streptozotocin treatment depicting the onset of diabetes. Caloric restriction significantly reduced the organ weights (p<0.01), malondialdehyde (p<0.01) and catalase activity (p<0.01), but significantly increased glutathione reductase activity (p<0.01), and GSH/GSSG ratios (p<0.05). Caloric restriction also non-significantly reduced reactive oxygen species, superoxide dismutase and oxidized glutathione but increased glutathione peroxidase activity and reduced glutathione levels in the diabetic rats. Our data indicate a decrease in lipid peroxidation, improvement in the antioxidant defense systems and restoration of the redox status in the liver by caloric restriction. Therefore, this could provide a non-invasive antioxidant therapy early in diabetes to prevent the development of the complications associated with the disease.     

L-carnitine attenuates oxidative stress in hypertensive rats

The present study aimed to investigate whether l-carnitine (LC) protects the vascular endothelium and tissues against oxidative damage in hypertension. Antioxidant enzyme activities, glutathione and lipid peroxidation were measured in the liver and heart of spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats. Nitrite and nitrate levels and total antioxidant status (TAS) were evaluated in plasma, and the expression of endothelial nitric oxide synthase (eNOS) and p22phox subunit of NAD(P)H oxidase was determined in aorta. Glutathione peroxidase activity was lower in SHR than in WKY rats, and LC increased this activity in SHR up to values close to those observed in normotensive animals. Glutathione reductase and catalase activities, which were higher in SHR, tended to increase after LC treatment. No differences were found in the activity of superoxide dismutase among any animal group. The ratio between reduced and oxidized glutathione and the levels of lipid peroxidation were respectively decreased and increased in hypertensive rats, and both parameters were normalized after the treatment. Similarly, LC was able to reverse the reduced plasma nitrite and nitrate levels and TAS observed in SHR. We found no alterations in the expression of aortic eNOS among any group; however, p22phox mRNA levels showed an increase in SHR that was reversed by LC. In conclusion, chronic administration of LC leads to an increase in hepatic and cardiac antioxidant defense and a reduction in the systemic oxidative process in SHR. Therefore, LC might increase NO availability in SHR aorta by a reduction in superoxide anion production.     

Synaptosomes isolated from Goto-Kakizaki diabetic rat brain exhibit increased resistance to oxidative stress: role of vitamin E

Increased oxidative stress is believed to be an important factor in the development of diabetic complications. In this study, the effect of diabetes on the susceptibility of synaptosomes to oxidative stress, induced by the oxidizing system ascorbate/Fe2+, on the activity of antioxidant enzymes and on the levels of glutathione and vitamin E was investigated. Synaptosomes were isolated from brain of 29-weeks-old Goto-Kakizaki (GK) rats, a model of non-insulin dependent diabetes mellitus and from normal Wistar rats. Synaptosomes isolated from GK rats displayed a lower susceptibility to lipid peroxidation, as assessed by quantifying thiobarbituric acid reactive substances (TBARS), than normal rats (5.33 +/- 0.79 and 7.58 +/- 0.7 nmol TBARS/mg protein, respectively). In the absence of oxidants, no significant differences were found between the levels of peroxidation in synaptosomes of diabetic or control rats. Superoxide dismutase (SOD), glutathione peroxidase and glutathione reductase activities were unaltered in the brain of diabetic rats. There were no statistically significant differences in fatty acid composition of total lipids and reduced glutathione levels in synaptosomes of diabetic and control rats. The decreased susceptibility to membrane lipid peroxidation of diabetic rats synaptosomes correlated with a 1.3-fold increase in synaptosomal vitamin E levels. Vitamin E levels in plasma were also higher in diabetic rats (21.32 micromol/l) as compared to normal rats (15.13 micromol/l). We conclude that the increased resistance to lipid peroxidation in GK rat brain synaptosomes may be due to the increased vitamin E content, suggesting that diabetic animals might develop enhanced defense systems against brain oxidative stress.     

Ethanol-induced alterations of the antioxidant defense system in rat kidney

We report here the effects of chronic ethanol consumption on the antioxidant defense system in rat kidney. Thirty-two male Wistar rats were randomly divided in two identical groups and were treated as follows: control group (water for fluid) and the ethanol-fed group (2 g/kg body weight/24 h). The animals were sacrificed after 10 weeks, and respectively 30 weeks of ethanol consumption, and the renal tissue was isolated and analyzed. Results revealed that kidney alcohol dehydrogenase activities increased significantly after ethanol administration, but the electrophoretic pattern of alcohol dehydrogenase isoforms was unmodified. The SDS polyacrylamidegel electrophoretic study of kidney proteins has revealed the appearance of two new protein bands after long-term ethanol consumption. The kidney reduced glutathione/oxidized glutathione ratio decreased, indicating an oxidative stress response due to ethanol ingestion. The malondialdehyde contents and xanthine oxidase activities were unchanged. The antioxidant enzymatic defense system showed a different response during the two periods of ethanol administration. After 10 weeks, catalase, glutathione peroxidase, glutathione reductase, and glucose-6-phosphate dehydrogenase were activated, while superoxide dismutase, glutathione transferase, and gamma-glutamyltranspeptidase levels were stationary. After 30 weeks, superoxide dismutase and glutathione peroxidase activities were unmodified, but catalase, glutathione transferase, gamma-glutamyltranspeptidase, glutathione reductase, and glucose-6-phosphate dehydrogenase activities were significantly increased. Remarkable changes have been registered after 30 weeks of ethanol administration for glutathione reductase and glucose-6-phosphate dehydrogenase activities, including an increase by 106 and 216' of control values, respectively. These results showed specific changes in rat kidney antioxidant system and glutathione status as a consequence of long-term ethanol administration.     

Antioxidant status,lipid peroxidation,mixed function oxidase and UDP-glucuronyl transferase activities in livers from control and DOCA salt-hypertensive male Sprague Dawley rats

The effects of DOCA-salt hypertensive treatment on hepatic glutathione-dependent defense system, antioxidant enzymes, lipid peroxidation, mixed function oxidase and UDP-glucuronyl transferase activities were investigated in male Sprague Dawley rats.Compared with controls, DOCA-salt hypertensive rats had lower body weights (linked to liver hypertrophy). Mixed function oxidase and p-nitrophenol-UGT activities were not affected by the treatment but a significant lower rate of the glucuronoconjugation rate of bilirubin (p < 0.001) was observed in DOCA-salt hypertensive rats. While cytosolic glutathione contents and glutathione reductase activity were not affected, glutathione peroxidase (p < 0.001), glutathione transferase (p < 0.001) and catalase (p < 0.01) activities were decreased and associated with higher malondialdehyde contents (p < 0.001) in treated rats. The imbalance in liver antioxidant status (increasing generation of cellular radical species), associated with increases in lipid peroxidation, suggests that oxidative stress might be directly related to arterial hypertension in DOCA-salt treated male Sprague Dawley rats.     

Decreased susceptibility to lipid peroxidation of Goto-Kakizaki rats: relationship to mitochondrial antioxidant capacity.

The respiratory function and the antioxidant capacity of liver mitochondrial preparations isolated from Goto-Kakizaki non-insulin dependent diabetic rats and from Wistar control rats, with the age of 6 months, were compared. It was found that Goto-Kakizaki mitochondrial preparations presented a higher coupling between oxidative and phosphorylative systems, compared to non-diabetic preparations. Goto-Kakizaki mitochondria presented a lower susceptibility to lipid peroxidation induced by ADP/Fe2+, as evaluated by the formation of thiobarbituric acid substances. The decreased susceptibility to peroxidation in diabetic rats was correlated with an increase in mitochondrial vitamin E (alpha-tocopherol) content and GSH/GSSG ratio. Moreover, the glutathione reductase activity was significantly increased, whereas the glutathione peroxidase was decreased. Superoxide dismutase activity was unchanged in diabetic rats. Fatty acid analyses showed that the content in polyunsaturated fatty acids of Goto-Kakizaki mitochondrial membranes was significantly higher compared to controls. These results indicate that the lower susceptibility to lipid peroxidation of mitochondria from diabetic rats was related to their antioxidant defense systems, and may correspond to an adaptative response of the cells against oxidative stress in the early phase of diabetes.