Oxidative stress in non-insulin-dependent diabetes mellitus (NIDDM) patients

Diabetes mellitus is a metabolic disorder characterized by hyperglycemia. The oxidative stress in diabetes was greatly increased due to prolonged exposure to hyperglycemia and impairment of oxidant/antioxidant equilibrium. Proteins and lipids are among the prime targets for oxidative stress. In the present study, the oxidative stress was evaluated in 55 diabetic patients and 40 healthy subjects by measuring the levels of protein oxidation, lipid peroxidation and some enzymatic and nonenzymatic antioxidants. The oxidative products of protein (PCG) and lipid peroxidation (MDA) and nitric oxide levels in plasma of NIDDM patients were significantly increased. However, the levels of enzymatic (GPx, SOD, catalase in RBC) and nonenzymatic (β-carotene, retinol, vitamin C & E and uric acid) antioxidants of RBC showed a significant decrease in NIDDM patients compared to normal subjects. Serum protein analysis by polyacrylamide gel electrophoresis (PAGE) showed the significant difference in the ceruloplasmin, transferrin, albumin, retinal binding protein, etc. in diabetic patients compared to healthy controls. In conclusion, the results suggest that increased protein oxidation, lipid peroxidation and NO levels, decreases the levels of enzymatic and nonenzymatic antioxidants and playing a major role in diabetic complications.     

Cardioprotective effect of vitamin E: rescues of diabetes-induced cardiac malfunction, oxidative stress, and apoptosis in rat

AimThis study was designed to assess the effect of vitamin E on cardiac autonomic neuropathy, cardiomyocyte apoptosis, and the status of oxidative stress in the heart under hyperglycemic conditions, in vivo.MethodsWistar male rats (n=16) were made hyperglycemic by streptozotocin at 6 months of age. Normal Wistar rats (n=8) of the same age were used as the control group. Diabetic rats were divided into two groups, nontreated and those treated with vitamin E (300 mg/day). Stable hyperglycemic status was proved by levels of blood sugar and HbA_1c. Lipid peroxidation, protein oxidation, and cellular antioxidant defense were measured by 8-isoprotane, protein carbonyl content, and superoxide dismutase (SOD) activity, respectively.ResultsCardiac complications such as autonomic neuropathy as prolonged QT interval along with significant increases in level of 8-isoprotane, protein carbonyl content, and SOD activity were observed after 6 weeks. Structural abnormality was also observed as severe induction of apoptosis in cardiomyocytes.ConclusionSignificant decline in apoptosis, lipid peroxidation, protein oxidation, and QT interval resulted from vitamin E administration, which strongly implies that this radical scavenger may promote a convalescing effect on diabetic cardiomyopathy through the attenuation of oxidative stress and abrogation of apoptotic signals, which was verified by restoring normal QT interval.     

Dysregulation of hepatic superoxide dismutase, catalase and glutathione peroxidase in diabetes: response to insulin and antioxidant therapies

Recent evidence suggests that impaired antioxidant status is involved in oxidative stress associated with diabetes. The main antioxidant enzymes include superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX). The aim of the present investigation was to evaluate the activities and protein expression of these antioxidant enzymes in streptozotocin-induced diabetes. Furthermore, the effects of insulin and antioxidant therapy alone and in combination were studied. Male Sprague-Dawley rats were rendered diabetic by streptozotocin administration and randomly assigned to untreated, insulin-treated, antioxidant (vitamin E and C)-treated and insulin plus antioxidant-treated groups. Normal rats fed either a regular diet or the antioxidant (vitamin E and C)-rich diet served as controls. The animals were observed for 4 weeks. Diabetic animals showed marked weight loss, decreased activities of Cu Zn SOD and CAT and normal GPX activity. Additionally, the expression of all antioxidant enzyme proteins was decreased in the diabetic rats compared to the untreated controls. Insulin therapy prevented weight loss and normalized the activities and protein expression of all antioxidant enzymes. Antioxidant therapy in the diabetic rats normalized Cu Zn SOD and GPX protein expression. Combined therapy with insulin and antioxidants normalized all measured antioxidant enzyme protein expression and activities. Thus diabetes-associated reductions in antioxidant enzymes can be ameliorated by insulin and/or antioxidant therapy.     

Lipid peroxidation and scavenging enzyme activity in streptozotocin-induced diabetes

The aim of this study was to evaluate lipid peroxidation and scavenging enzyme activity in streptozotocin-induced diabetes, and then to establish whether moderate doses of nonenzymatic antioxidant vitamin E play a role in the antioxidant defence system in diabetic pregnant rats and their offspring. The study group consisted of 30 normal female Wistar rats, which were given a single dose of streptozotocin (40 mg/kg) and were mated 7 days later. Subsequently, the diabetic animals were divided into two matched groups: the first supplemented with vitamin E (30 mg/100 g chow), and the other fed with a standard diet lacking vitamine E. Controls consisted of 15 pregnant rats. On the first day after delivery, the rats were decapitated and homogenates of maternal liver and uterus as well as neonatal lungs and liver were prepared. Then the following parameters were measured: malondialdehyde (MDA) concentrations in the homogenates and blood serum, glutathione (GSH) levels, the activity of CuZn-superoxide dismutase (SOD) and glutathione peroxidase (GPx), and glycaemia. The neonates of diabetic rats were smaller than the healthy ones and serum glucose concentration was markedly higher in the diabetic animals. MDA levels were significantly increased, whereas GSH, SOD and GPx were markedly diminished in the diabetic adult rats and their offspring in comparison to the control grouop. In the animals supplemented with α-tocopherol, MDA concentrations were significantly lower, GSH content and SOD activities were markedly elevated most tissues studied, whereas GPx remained unchanged. We conclude that, by monitoring the activity of selected scavenging enzymes, information on ongoing biological oxidative stress and thereby on the fetus/neonate status may be obtained. Our results suggest that diabetic pregnant rats and their neonates are exposed to an increased oxidative stress and that vitamin E supplementation may reduce its detrimental effects. Received: 20 January 2000 / Accepted in revised form: 23 February 2001     

Effect of haemodialysis on the oxidative stress and antioxidants in diabetes mellitus

Abstract Oxidative stress has been defined as a loss of counterbalance between free radical or reactive oxygen species (ROS) production and antioxidant systems. It is involved in the pathogenesis of different chronic diseases. High levels of ROS production via different biochemical mechanisms accompany diseases like type 2 diabetes mellitus (DM) and end-stage renal disease (ESRD). Elevated oxidative status and reduced antioxidant defence systems in patients with DM and ESRD accelerate the prevalence of atherosclerosis and other chronic complications. Our aim was to reveal the effects of diabetes and haemodialysis (HD) separately and together on oxidative stress. In our study, we included 20 diabetic (DM) patients with no renal disease, 20 non-diabetic haemodialysis (HD), 20 diabetic haemodialysis (DHD) patients and 20 healthy volunteers. We have determined the levels of lipid peroxidation expressed as thiobarbituric acid-reactive substances (TBARS), oxidative protein damage as indicated by protein carbonyl (PCO) content and activities of antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSHPx) in all patient groups and healthy subjects. We found enhanced oxidative stress in all patient groups due to an increase in lipid peroxidation (TBARS) and increased oxidative protein damage in terms of PCO content and reduced activities of SOD, CAT and GSH-Px. Oxidative stress was more profound in diabetic patients undergoing haemodialysis. We conclude that both diabetes and dialysis increase oxidative stress and their combined effect on oxidative stress is the highest in magnitude as observed in diabetic patients undergoing haemodialysis.     

Renal and metabolic effects of tempol in obese ZSF1 rats--distinct role for superoxide and hydrogen peroxide in diabetic renal injury

Oxidative stress, that is, overproduction of reactive oxygen species and reduced antioxidant system activity, is implicated in the pathogenesis of diabetic complications; and therefore, superoxide dismutase (SOD) mimetic tempol should be protective in diabetic kidney. However, the effects of tempol in metabolic syndrome-associated renal injury have not been thoroughly examined. In this study, we examined the effects of 9 weeks of treatment with tempol on metabolic status, renal oxidative stress, and kidney function and structure in obese, diabetic, hypertensive ZSF₁ rats and their nondiabetic, hypertensive, lean littermates. The obese rats had significantly reduced total SOD and catalase activity, increased peroxidase activity and lipid peroxidation, and higher level of protein oxidation in renal cortical tissue compared with their lean littermates. These changes were accompanied by renal injury (proteinuria; reduced excretory function; and markedly increased glomerular and interstitial inflammation, proliferation, and collagen IV synthesis). Tempol treatment slightly increased total SOD activity, significantly reduced lipid peroxidation and peroxidase activity, but had no effect on catalase and protein oxidation. Tempol had no effects on blood pressure, renal hemodynamics and excretory function, and proteinuria in obese rats, yet improved insulin sensitivity and reduced renal inflammatory, proliferative, and fibrotic changes. Because tempol possesses no catalase activity and, in diabetes, not only SOD but also catalase is inhibited, it is possible that the toxicity of hydrogen peroxide (H₂O₂) remains unaltered under tempol treatment. This study suggests that superoxide and H₂O₂ may have distinct roles in the pathogenesis of diabetic renal injury, with superoxide mainly being involved in inflammatory, proliferative, and fibrotic changes, and H₂O₂ in glomerular hemodynamics and proteinuria.     

Cordycepin (3′-deoxyadenosine) attenuates age-related oxidative stress and ameliorates antioxidant capacity in rats

Free radical-induced oxidative damage is considered to be the most important consequence of the aging process. The activities and capacities of antioxidant systems of cells decline with increased age, leading to the gradual loss of pro-oxidant/antioxidant balance and resulting in increased oxidative stress. Our investigation was focused on the effects of cordycepin (3′-deoxyadenosine) on lipid peroxidation and antioxidation in aged rats. Age-associated decline in the activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), glutathione-S-transferase (GST), reduced glutathione (GSH), vitamin C and vitamin E, and elevated levels of malondialdehyde (MDA) were observed in the liver, kidneys, heart and lungs of aged rats, when compared to young rats. Furthermore, serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), urea, and creatinine were found to be significantly elevated in aged rats compared to young rats. Aged rats receiving cordycepin treatment show increased activity of SOD, CAT, GPx, GR and GST, and elevated levels of GSH, and vitamins C and E such that the values of most of these parameters did not differ significantly from those found in young rats. In addition, the levels of MDA, AST, ALT, urea and creatinine became reduced upon administration of cordycepin to aged rats. These results suggest that cordycepin is effective for restoring antioxidant status and decreasing lipid peroxidation in aged rats.     

Alterations of antioxidant enzymes and oxidative stress markers in aging

In accordance with the present state of scientific knowledge, the excessive production of free radicals in the organism, and the imbalance between the concentrations of these and the antioxidant defenses may be related to processes such as aging and several diseases. The aging process has been described by various theories. In particular, the free radical theory of aging has received widespread attention which proposes that deleterious actions of free radicals are responsible for the functional deterioration associated with aging. Although, the relationship between lipid peroxidation and aging have been investigated extensively, the studies have produced conflicting results. To investigate the correlation between the oxidative stress and aging, we have determined the levels of lipid peroxidation expressed as thiobarbituric acid reactive substances (TBARS; MDA) and conjugated dien; oxidative protein damage as indicated by carbonyl content and activities of antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) in a sample of 100 healthy men and women ranging in age from 20 to 70years. In addition, vitamin E, C levels, reduced glutathione and sulphydryl content were determined. The oxidation end product of nitric oxide (nitrate) was also studied to investigate any role of nitrogen radicals in aging. Our data show that there is an age related increase in lipid peroxidation expressed as MDA and oxidative protein damage as indicated by carbonyl content. Aging is not linked to a decline in antioxidant enzymes except GPx. Our data suggests that the level of oxidative stress increase cannot entirely be attributed to a decrease in the activities of antioxidant defense system and probably various factors may contribute to this process.     

Hypercholesterolemia-induced oxidative stress in heart and its prevention by vitamin E

Oxygen-free radicals have been implicated in hypercholesteolemic atherosclerosis. It is possible that hypercholesterolemia produces oxidative stress in myocardium. We therefore investigated the effects of a high cholesterol diet in the absence or presence of vitamin E on serum cholesterol and lipid peroxidation product malondialdehyde (MDA), chemiluminescence (M-CL), a measure of antioxidant reserve, and activity of antioxidant enzymes [superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-P_x)] in cardiac muscles of rabbits. Rabbits were divided into four groups: Group I, regular rabbit chow diet; Group II, same as Group I + vitamin E; Group III, high cholesterol diet; Group IV, high cholesterol + vitamin E. The heart was removed under anesthesia at the end of 4 months on their respective diets for various biochemical measurements. Serum cholesterol in Groups III and IV increased to a similar extent. There was an increase in the levels of MDA, M-CL, GSH-P_x activity and a decrease in SOD activity in hypercholesterolemic rabbits in the absence of vitamin E. Vitamin E prevented the hypercholesterolemia-induced changes in cardiac MDA, M-CL, and GSH-P_x. These results suggest that hypercholesterolemia produces oxidative stress in the myocardium which may be due to a decrease in the antioxidant reserve, and that vitamin E is effective in preventing hypercholesterolemia-induced oxidative stress on the myocardium.     

Effects of melatonin or acetylsalicylic acid on gastric oxidative stress after bile duct ligation in rats

Background Antioxidant enzyme activities decrease after bile duct ligation. The aim of this study was to assess the effect of melatonin and acetylsalicylic acid on antioxidant enzyme activities in gastric oxidative stress induced by bile duct ligation. Methods Sixty-four animals were divided into eight groups of eight rats each. Male Sprague-Dawley rats were subjected to either a sham operation or common bile duct ligation (BDL) before treatment with melatonin (MEL) or acetylsalicylic acid (ASA). Gastric superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) activities, and malondialdehyde (MDA) and nitric oxide (NO) levels were determined by spectrophotometers and evaluated. Results Our results indicated that BDL caused a significant increase in lipid peroxidation, whereas coadministration of MEL with ASA significantly decreased MDA and NO levels in BDL rats. Moreover, coadministration of MEL and ASA increased antioxidant enzyme activities after the BDL, and these increases were statistically significant for CAT and GPx. On the other hand, the increase in SOD activity was not significant. Conclusions Melatonin administration, either alone or together with acetylsalicylic acid, decreases lipid peroxidation and increases antioxidant enzyme activities in gastric tissues of rats after bile duct ligation. ASA administration, however, either alone or with a vehicle, increases lipid peroxidation and decreases antioxidant enzyme activities.     

Antioxidant therapy and streptozotocin-induced diabetes in pregnant rats

The aim of our study was to analyse the effect of chronic hyperglycaemia on lipid peroxidation and scavenging enzyme activity in pregnant animals and their offspring supplemented and not supplemented with vitamin E – a natural antioxidant. Thirty pregnant female Wistar rats were used in our experiments. Diabetes was induced on day 7 of pregnancy using a single does of streptozotocin (40 mg/kg). Diabetic animals were divided into two equal groups: vitamin E supplemented and those fed with standard diet. Our controls consisted of 15 healthy rats. On day 1 after delivery homogenates of maternal liver and uterus as well as neonatal lungs and liver were prepared. Then the following parameters were measured: malondialdehyde (MDA) concentrations in the homogenates and blood serum, glutathione (GSH) levels, the activity of CuZn superoxide dismutase (SOD) and glutathione peroxidase (GPx) (Bioxytech, France). Statistical analysis was performed using Mann-Withney U test. The neonates of diabetic rats were smaller than those from healthy rats and serum glucose concentration was markedly higher in diabetic animals, both in mothers and neonates. MDA levels increased significantly, whereas GSH content and SOD as well as GPx activities were markedly diminished in diabetic pregnant rats and their offspring in comparison with the control group. In animals supplemented with tocopherol, MDA concentrations declined significantly, GSH contents and SOD activities were markedly elevated in almost all types of tissues studied, whereas glutathione peroxidase remained suppressed. Our results suggest that diabetic pregnant rats and their neonates are exposed to oxidative stress (OS), but vitamin E supplementation could in part reduce the imbalance between uncontrolled reactive oxygen species generation and scavenging enzyme activity, and may potentially serve as a useful prophylactic factor against OS development: Received: 4 January 1999 / Accepted in revised form: 19 May 1999     

Effect of aminoguanidine on lipid peroxidation in streptozotocin-induced diabetic rats.

Diabetes mellitus is postulated to be associated with increased lipid peroxidation, which may contribute to vascular complications. One potential mechanism of the increased lipid peroxidation in diabetes is lipid-linked advanced glycosylation and oxidation. Aminoguanidine (AMGN), the prototype inhibitor of advanced glycosylation end product (AGE) formation, has been recently shown to prevent oxidative modification of low-density lipoprotein (LDL) in vitro at a moderate concentration. It is unknown whether AMGN may act as an antioxidant against lipid peroxidation under hyperglycemia in vivo. To investigate the in vivo effect of AMGN on lipid peroxidation in diabetes, we administered AMGN (1 g/L in drinking water) or vitamin E (400 mg/d for 5 d/wk) to streptozotocin (STZ)-induced diabetic rats for 9 weeks and measured plasma lipid hydroperoxides by ferrous oxidation with xylenol orange II (FOX method) and red blood cell (RBC) membrane malondialdehyde (MDA) and related aldehydes as thiobarbituric acid-reactive substances (TBARS). Plasma lipid hydroperoxide was higher in STZ-induced diabetic rats versus control rats (mean +/- SD, 7.53 +/- 2.03 v 5.62 +/- 0.44 micromol/L, P < .05; n = 8 to 14). RBC membrane TBARS were also higher in STZ-induced diabetic rats than in control rats (2.67 +/- 0.46 v 1.81 +/- 0.19 nmol/mL, P < .05). Plasma lipid hydroperoxide was lower in AMGN-treated (6.23 +/- 0.59 micromol/L, P < .05) and vitamin E-treated (5.29 +/- 0.27 micromol/L, P < .05) diabetic rats than in untreated diabetic rats. RBC membrane TBARS were also lower in AMGN-treated (1.93 +/- 0.12 nmol/mL, P < .05) diabetic rats than in untreated diabetic rats. There was no significant difference in plasma glucose, cholesterol, and triglyceride levels among diabetic groups. Although the mechanism(s) of action of AMGN on lipid peroxidation in vivo should be studied further, these results suggest that AMGN may have an additional beneficial effect as an antioxidant against lipid peroxidation in a prevention trial for diabetic vascular complications.     

Influence of mulberry (Morus indica L.) leaves on antioxidants and antioxidant enzymes in STZ-diabetic rats

To assess the influence of mulberry (Morus indica L.) leaves on antioxidants and antioxidant enzymes in STZ- diabetic rats as the leaves of mulberry (Morus indica L.) of Moraceae, are reported to be rich in a no. of bioactive principles i.e. antioxidant vitamins, flavonoids and moracins that can fight against oxidative stress in diabetes. STZ-diabetic rats were treated with dried mulberry leaves incorporated in the feed at 25 % level (as per dose response) for 8 weeks in standard experimental conditions in comparison with diabetic glibenclamide–treated and diabetic control rats. At the end of experimental period, fasting blood glucose, serum non-enzymatic antioxidants, hepatic lipid peroxidation and antioxidant enzymes were assayed in all the experimental groups. Hyperglycemia, a 274 % (P?<?0.01) rise in fasting blood glucose and increased oxidative stress as shown by a two fold increase in lipid peroxidation in hepatic tissue, decreased serum non enzymatic antioxidants viz. vit.C (51 %) and E (47 %), significantly decreased activities of hepatic antioxidant enzymes such as glucose-6-phosphate dehydrogenase (43 %), glutathione peroxidase (41 %) and superoxide dismutase (44 %) and significantly increased activity of catalase (39 %) in STZ-diabetic rats were ameliorated by mulberry leaves which is evidenced by significant fall in fasting glucose, and lipid peroxidation, rise in antioxidants as well as the activities of defense enzymes and decrease in the activity of catalase while the antidiabetic drug, glibenclamide showed lesser effects than mulberry leaves. Mulberry leaves protected STZ-diabetic rats against oxidative stress by improving antioxidants and the activities of defense enzymes and controlling hyperglycemia and lipid peroxidation in a better way than the drug.     

Oxidative stress in the kidney of reproductive male rats during aging

Reproduction alters the male physiology. We performed a comprehensive examination of oxidative stress in the kidneys of male rats with (experienced) or without (naïve) reproductive activity during aging. Oxidative stress was assessed by measuring the activity of catalase, glutathione peroxidase, glutathione S-transferase, and superoxide dismutase, and by measuring protein carbonylation, lipid peroxidation, nitrite and nitrate levels, vitamin C levels, and glutathione (total, reduced, and oxidized forms) levels, and metabolism was accessed by aconitase activity in kidney tissue, as well as testosterone and estradiol levels in serum. Reproductively active animals exhibited increased testosterone levels and altered metabolism. Aging affects tissues and organs and contributes to their functional decline. Elderly naïve rats showed high nitrite and nitrate levels. The experienced rats had less damage in elderly ages, probably because they had higher antioxidant amount and antioxidant enzyme activities at earlier ages, which would have avoided oxidative damage seen in naïve group, and because of the metabolism decline. Glutathione increase in naïve elder rats probably was induced for direct protection against oxidative damage and indirect protection by higher glutathione peroxidase and glutathione S-transferase activities. Linear regression shows that lipid peroxidation levels explained vitamin C levels (B standardized value of 0.42), indicating that vitamin C was properly produced or recruited into kidneys to combat lipid peroxidation. Catalase activity reflected the protein carbonylation and lipid peroxidation levels (B standardized values of 0.28 and 0.48). These results add comprehensive data regarding changes in oxidative stress during aging, and suggest an explanation for the costs of reproduction.     

Melatonin administration differentially affects age-induced alterations in daily rhythms of lipid peroxidation and antioxidant enzymes in male rat liver

A central clock/pacemaker, suprachiasmatic nuclei of the hypothalamus coordinates and entrains circadian oscillations in the peripheral tissues such as the liver, kidney, heart, lungs etc. called peripheral clocks. These also have endogenous circadian oscillations. The circadian rhythms of antioxidants present in cytosol signify redox state of the cell during day/night cycle. The liver has a major impact on homeostasis through its control on serum protein composition and plays a pivotal role in the metabolism of nutrients, drugs, hormones, and metabolic waste products and undergoes substantial changes in structure and function upon aging. In present study, the temporal patterns of oxidative stress indicators in liver were studied. Daily rhythms of lipid peroxidation end products, reduced glutathione (GSH), oxidized glutathione (GSSG) and antioxidant enzymes such as glutathione peroxidase (GPx), superoxide dismutase (SOD) and catalase (CAT) were studied in liver at variable time points (Zeitgeber Time (ZT) 0, 6, 12 and 18) in three age groups: 3 (adult), 12 and 24?months old male Wistar rats. There was increase in oxidative stress in 12 and 24?months old rats indicated through a significant increase in lipid peroxidation, decrease in GSH/GSSG ratio and antioxidant enzyme activities. In 3?months old rats, lipid peroxidation was maximum at ZT-12 whereas GSH, SOD and CAT activities were minimum at ZT-12. The maximum level in 24?h i.e., acrophases of lipid peroxidation, GPx, SOD and CAT activities in liver cell free extracts altered upon aging. As melatonin, messenger of darkness, an endogenous synchronizer of rhythm, an antioxidant and an antiaging drug, declines with aging we studied the effects of melatonin on activities of these antioxidant enzymes in aging rats. Melatonin administration resulted in differential restoration of acrophases, amplitude, mean as well as daily rhythms of lipid peroxidation and antioxidants in liver of 12 and 24?months old rats.     

Amelioration of altered antioxidant enzymes activity and glomerulosclerosis by coenzyme Q10 in alloxan-induced diabetic rats

Coenzyme Q10 is a natural antioxidant and scavenging free radicals. In the present study, we examined antioxidative activities of coenzyme Q10 and possible protective effect of coenzyme Q10 on in vivo and in vitro lipid peroxidation, antioxidant enzymes activity and glomerulosclerosis in alloxan-induced type 1 diabetic rats. Thirty Sprague–Dawley male rats were divided into three groups randomly: group 1 as control, group 2 as diabetic untreatment, and group 3 as treatments with coenzyme Q10 by 15 mg/kg i.p. daily, respectively. Diabetes was induced in the second and third groups by alloxan injection subcutaneously. After 8 weeks, animals were anaesthetized, liver and kidney were then removed immediately and used fresh or kept frozen until their lipid peroxidation analysis. Blood samples were also collected before killing to measure the lipid peroxidation and antioxidant enzymes activity. Kidney paraffin sections were prepared and stained by periodic acid-Schiff method. Glomerular volume and leukocyte infiltration were estimated by stereological rules and glomerular sclerosis was studied semi-quantitatively. Coenzyme Q10 significantly inhibited leukocyte infiltration, glomerulosclerosis and the levels of malondialdehyde (MDA) serum and kidney content in treated group compared with the diabetic untreated group. Coenzyme Q10 significantly inhibited LDL oxidation in vitro. Coenzyme Q10 significantly increased the serum levels of glutathione (GSH) and serum activity of catalase (CAT) and superoxide dismutase (SOD) in treated group compared with the diabetic untreated group. Coenzyme Q10 alleviates leukocyte infiltration and glomerulosclerosis and exerts beneficial effects on the lipid peroxidation and antioxidant enzymes activity in alloxan-induced type 1 diabetic rats.     

Moderate exercise with a dietary vitamin C and e combination protects against streptozotocin-induced oxidative damage to the kidney and lens in pregnant rats.

Moderate exercise and vitamin C and E (VCE) supplementation can be beneficial to diabetes due to reducing free radical production in lens and kidney of diabetic pregnant rats. We investigated the effect of VCE supplementation and moderate exercise on lipid peroxidation (MDA) and scavenging enzyme activity in the kidneys and lens of STZ-induced diabetic pregnant rats. Fifty female Wistar rats were used and were randomly divided into five groups. First and second were used as the control and pregnant control group. 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. Plasma, lens, and kidney samples were taken from all animals on day 20. Exercise and administration of VCE to pregnant diabetic rats resulted in significant decrease in the albumin and total protein values and the elevated MDA, plasma creatinine, and urea levels as an indicator of oxidative stress and renal functional parameters. Exercise and VCE supplementation also increased glutathione peroxidase (GSH-Px), reduced glutathione (GSH), vitamin E, and beta-carotene levels in the kidney, GSH-Px and GSH in the lens, the albumin and total protein values in plasma. In the diabetic pregnant animals, the decreased vitamins A and E concentration and GSH levels in kidney, creatinine, and urea values in plasma did not improve through exercise only although their concentrations were increased by VCE supplementation. Kidney weight did not also affect either by exercise or VCE supplementation. In conclusion, these results suggest that exercise plus VCE affects antioxidant metabolism and reduces lipid peroxidation, thereby improving the damage caused by oxidative stress involved in the pathogenesis of lens and kidney in diabetic pregnant rats. Moderate exercise with dietary VCE may play a role in preventing nephropathy and cataract formation in diabetic pregnant rat.     

Effect of oxidative stress on the uptake of GABA and glutamate in synaptosomes isolated from diabetic rat brain

It has been suggested that increased oxidative stress might be involved in the pathophysiology of diabetic complications. In this study, we investigated the effect of diabetes on the susceptibility of synaptosomes to oxidative stress (induced by the oxidizing pair ascorbate/Fe(2+)) and on the uptake of the amino acid neurotransmitters gamma-aminobutyric acid (GABA) and glutamate. We found a lower susceptibility of synaptosomes isolated from Goto-Kakizaki (GK) rats, a model of non-insulin-dependent diabetes mellitus, to lipid peroxidation as compared with synaptosomes isolated from Wistar control rats (6.40+/-1.05 and 12.14+/-1.46 nmol thiobarbituric acid reactive substance/mg protein, respectively). The lower susceptibility of GK rat synaptosomes to membrane lipid peroxidation correlates with an increase in synaptosomal vitamin E levels (835+/-58.04 and 624.26+/-50.26 pmol/mg protein in diabetic and normal rats, respectively). In the absence of ascorbate/Fe(2+), no significant differences were observed between the levels of lipid peroxidation of synaptosomes isolated from diabetic and normal rats. Studies of neurotransmitter uptake show that the [(3)H]glutamate uptake was decreased by about 30% in diabetic GK rats as compared with control Wistar rats, whereas the [(3)H]GABA uptake was not significantly different from controls. Under oxidizing conditions, the glutamate uptake in diabetic rats was unaffected, and a decreased GABA uptake (41.39+/-4.41 and 60.96+/-6.4% of control in GK and Wistar rats, respectively) was observed. We conclude that the increased resistance to oxidative stress in GK rat synaptosomes may be due to the increased vitamin E content and that diabetic state and oxidative stress conditions differentially affected the uptake of the neurotransmitters GABA and glutamate.     

Comparative analysis of the protective effects of melatonin and vitamin E on streptozocin-induced diabetes mellitus

There is a clearly documented link between diabetic complications and lipid peroxidation. Hyperglycemia causes a reduction in levels of protective endogenous antioxidants and increases generation of free radicals. The present study was carried out to compare the protective effects of melatonin and vitamin E against streptozocin (STZ)-induced diabetes in rats. Melatonin was administered s.c. (100 microg/kg) whereas vitamin E was given i.p. (100 mg/kg) after induction of diabetes with STZ (60 mg/kg). Plasma total cholesterol, triglyceride and low density lipoprotein (LDL) levels were increased in STZ group while both melatonin and vitamin E injection caused a significant decrease in the levels of all these parameters. The lipid lowering effect of melatonin was greater than that of vitamin E. Melatonin caused a significant decrease in brain, liver and kidney tissue malondialdehyde (MDA) levels which were increased because of STZ-induced diabetes. Vitamin E also reduced elevated MDA concentrations in diabetic rat tissues, but the effect of melatonin was more potent than that of vitamin E. Furthermore, treatment of diabetic rats with melatonin increased brain and kidney glutathione peroxidase (GSH-Px) activity to the levels below that of control rats. Vitamin E was found to be less effective on GSH-Px activity levels in brain and kidney than melatonin whereas it was more potent than melatonin in liver. In summary, melatonin prevents many diabetic complications by reducing oxidative stress and protects organisms from oxidative damage and dyslipidemia. Considering the much lower molar concentration of melatonin compared with vitamin E, melatonin seems to be a more potent antioxidant, especially in the brain and kidney.     

The relation between oxidant and antioxidant parameters and severity of acute coronary syndromes

OBJECTIVE: Acute coronary syndromes (ACS) encompass a continuum of cardiac ischaemic events, ranging from unstable angina pectoris (UA) to ST-segment elevation myocardial infarction (STEMI). Oxidative stress may play an important role in the pathogenesis of acute coronary diseases. In the present study, we examined the associations between lipid and protein susceptibility to oxidation and total sialic acid (SA) and antioxidant status and the severity of ACS as determined by having UA, non-STEMI or STEMI. METHODS AND RESULTS: The study sample consisted of 102 patients with ACS and 45 controls. Malondialdehyde (MDA) as a marker of lipid peroxidation and protein carbonyls as a marker of protein oxidation were measured to show the susceptibility to oxidation.Antioxidant status was determined by measuring the carotenoids, vitamin C and vitamin E levels and paraoxonase and arylesterase activities. In addition to conventional lipid and lipoprotein analysis, MDA and vitamin E were quantitated by high-performance liquid chromatography. Total SA and other oxidant and antioxidant parameters were studied spectrophotometrically.As expected, patients had significantly higher total cholesterol, triacylglycerol, low-density lipoprotein cholesterol, lipoprotein (a), apolipoprotein (apo) B values and lower high-density lipoprotein cholesterol and apoAl values than controls. Our results demonstrated significant increases both in total SA levels and in indicators of oxidative stress in patients with ACS compared with the controls. However, antioxidant parameters were decreased in patients with ACS. When the patients were divided into groups with UA, non-STEMI and STEMI, respectively, total SA and oxidant parameters were significantly increased and antioxidant parameters were significantly decreased in going from UA to STEMI. CONCLUSIONS: Our study shows gradually increased lipid and protein oxidation and total SA and gradually decreased antioxidant status when the conditions advance from UA to STEMI. These results indicate that these markers may be useful both in understanding plaque destabilization and in determination of risk stratification of patients. Also, measurement of these markers may provide a noninvasive window to study atherosclerotic lesions.