Differences in antioxidant status in skeletal muscle tissue in experimental diabetes.

BACKGROUND: It has been suggested that oxidative stress may play an important role in pathogenesis of diabetic complications. The present study was designed to evaluate the oxidative stress-related parameters in alloxan (A)-induced long-term diabetes in rabbits. METHODS: After 3, 6 and 12 weeks of diabetes, activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), glutathione reductase (GSSG-R) and concentrations of ascorbic acid (AA) and free sulfhydryl compounds (SH) were measured in skeletal muscle of diabetic rabbits and the normal control subjects. The products of lipid peroxidation (MDA) were also estimated. RESULTS: In our tests, the muscle SOD activity, SH and AA concentrations were significantly reduced. CAT activity increased significantly at all time intervals. GSH-Px activity decreased after 3 weeks and then remained at the control level. GSSG-R activity decreased progressively at 3rd and 6th week and then significantly increased. MDA level increased initially, dropped below baseline after 6 weeks and then remained at the level of the control group. CONCLUSIONS: The changes observed in the present experiment suggest a significant imbalance in antioxidative system in the skeletal muscle of rabbits with alloxan-induced diabetes. Such study may lead to therapeutic approaches for limiting the damage from oxidation reactions and preventing the diabetic complications.     

Erythrocyte antioxidant enzyme activities and lipid peroxidation in patients with types IIb and IV hyperlipoproteinemias

We measured lipid peroxidation and antioxidant enzymes in erythrocytes of types IIb and IV hyperlipoproteinemic (HLP) human subjects in comparison with age-matched controls. Thiobarbituric acid-reactive substances (TBARS), a measure of lipid peroxidation, glutathione peroxidase (GSH-Px), superoxide dismutase (SOD), glutathione reductase (GR), and catalase (CAT) were determined in erythrocytes. We also measured lipid parameters including triglycerides (TG), total cholesterol (TC), HDL-cholesterol (HDL-C), LDL-cholesterol (LDL-C), apolipoprotein AI, and apolipoprotein B, and antioxidant related substances such as serum albumin, free iron, ferritin, ceruloplasmin. Thirty-two subjects (females 15, males 17) with type IIb (the mean age 45.6+/-8 [S.E.]), 34 with type IV (females 16, males 18) (the mean age 47+/-10 [S.E.]), and 36 normolipidemic voluntary subjects (females 18, males 18) (the mean age 46+/-8 [S.E.]) were included in the study. Erythrocytes were prepared by classical washing method (0.9% NaCl) from venous blood samples. The mean TBARS levels in plasma and erythrocyte suspensions were found to be significantly higher in both types IIb and IV hyperlipoproteinemics. Erythrocyte SOD and GSH-Px activities were decreased but erythrocyte GR activity did not change in both types IIb and IV hyperlipoproteinemics. Erythrocyte CAT activity was decreased in type IIb, but it was increased in type IV hyperlipoproteinemics. Erythrocyte SOD activity was negatively correlated with plasma TG level, whereas plasma free iron was positively correlated with plasma TBARS level in type IV hyperlipoproteinemics. These results suggest the presence of oxidative injury in patients with type IIb or IV hyperlipoproteinemia, and that the responses of erythrocyte antioxidant enzymes to oxidant stress are different in these conditions.     

Oxidative stress parameters in type I,type II and insulin-treated type 2 diabetes mellitus; insulin treatment efficiency

BACKGROUND: Our aim was to evaluate oxidative stress parameters on three groups of diabetic patients, insulin-dependent diabetes mellitus (IDDM), non-insulin-dependent diabetes mellitus (NIDDM), and insulin-treated type 2 diabetes mellitus (ITDM2), with similar HbA1c value and to determine if insulin's impact on these parameters was the same for IDDM and ITDM2. METHODS: This study has been conducted on 18 IDDM, 55 NIDDM, 27 ITDM2, compared to 12 healthy subjects. Plasmatic concentrations of thiobarbituric acid reactive substances (TBARS), fatty acids, total antioxidant status (TAS), alpha-tocopherol, and erythrocyte reduced glutathione (GSH) were measured as well as enzymatic activities of superoxide dismutase (SOD), and glutathione peroxidase/reductase. RESULTS: Diabetic patients have significant increase of SOD activity, of TBARS concentration (concomitant with low levels of unsaturated fatty acids) and significant decrease of GSH and alpha-tocopherol. NIDDM have significantly lower levels of GSH and higher levels of TBARS compared to IDDM. ITDM2 values are intermediate between IDDM and NIDDM but are far from reaching those of IDDM. CONCLUSION: Diabetic patients undergo an important oxidative stress that is nearly corrected for IDDM, but only partially improved for ITDM2, although length of insulin treatment and HbA1c values are similar, suggesting metabolic differences between the two types of diabetes.     

Clinical

Objective: To investigate the oxidative state of glutathione and glutathione peroxidase (GSH-Px'), glutathione reductase (GSSG-R), and glucose-6-phosphate dehydrogenase (G-6-PD) levels in patients with chronic renal failure (CRF) and controls.

Results: Erythrocyte GSH levels of patients were decreased, but GSSG was not significantly different from that of controls. Also, plasma GSH levels were not different, although GSSG was increased. GSSG/GSH ratios in erythrocyte and plasma were significantly higher in CRF patients. Erythrocyte GSSG-R activity was high, but G-6-PD and GPX were low.

Conclusions: The findings suggest that: 1. Low GSH is related to decreased G-6-PD activities. 2. The reduction of peroxides with GPX are decreased by low GSH and low GPX activity. 3. GSSG may react with hemoglobin and causes protein aggregation in erythrocytes. These alterations cause hemolysis and could play a role in the pathogenesis of anemia in hernodialyzed patients.     

Activity of antioxidant enzymes in children from families at high risk of premature coronary heart disease

A positive family history of coronary heart disease (CHD) is one of the most predictive risk factors of CHD. Many children with increased risk of CHD because of their positive family history of CHD do not present other risk factors, such as altered serum lipid profile. Oxidative stress plays an important part in the pathogenesis of atherosclerosis. Serum antioxidants and intracellular enzymatic antioxidants composed mainly of glutathione peroxidase (GSH-Px), catalase (CAT), superoxide dismutase (SOD) and glutathione reductase counterbalance oxidative stress. Diminished activity of this system may lead to accelerated progression of atherosclerosis. The aim of this study was to assess the activity of CAT, GSH-Px, SOD and glutathione reductase in children with a family history of premature CHD who did not present any other major risk factors of CHD (diabetes, obesity, dyslipidaemia or hypertension). Twenty-two healthy children from high-risk families, selected according to the National Cholesterol Education Program definition, were enrolled in the study. The control group comprised 18 children without a family history of CHD. All the children were healthy and had been screened for hyperlipidaemia, diabetes, hypertension and obesity prior to the study. The erythrocyte activity of CAT, GSH-Px, SOD and glutathione reductase was assessed. Children at high risk of CHD had a statistically significant lower level of GSH-Px and CAT activity than the children in the control group. There were no statistically significant differences in the activity of SOD and glutathione reductase.     

Antioxidant capacity of G-6-PD-deficient erythrocytes

Glucose-6-phosphate dehydrogenase (G-6-PD) deficiency is the most common human enzymopathy. In this research, we studied two groups consisting of 30 male subjects who are G-6-PD deficient and 30 normal male subjects matched with the G-6-PD-deficient patients for age. All 30 assays were performed under normal conditions free of any oxidative attack that may result in haemolytic crisis in G-6-PD-deficient subjects. The erythrocyte glucose-6-phosphate dehydrogenase, superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), glutathione-S-transferase (GST) activities, reduced glutathione (GSH) levels and erythrocyte and plasma thiobarbituric acid-reactive substances (TBARS) levels were measured. All parameters in each group did not differ significantly except for G-6-PD levels. These data show that G-6-PD-deficient subjects can survive in normal conditions unless they are exposed to any oxidative stress.     

Glutathione and its related enzymes in the small intestinal mucosa of rats: Effects of starvation and diet

Starvation for 24 h causes a striking fall in glutathione content from 3.19 +/- 0.27 to 1.88 +/- 0.14 (X +/- SEM) mumol/g tissue and of GGT activity from 31.75 +/- 4.17 to 19.49 +/- 3.13 (X +/- SEM) nmol/min/mg protein in the homogenate from whole mucosa of the upper small intestinal segments. This was associated with a significant increase in GSH-Px activity and the content of lipid peroxides (measured by the thiobarbituric assay). On semi-synthetic iron-supplemented diet the activities of GSH-T and GGT were significantly decreased as compared with crude diet. On semisynthetic iron-depleted diet GSH-T and GGT activities were further depressed, but this was accompanied with an additional depression of GSH, glutathione reductase (GSSG-R), and glutathione peroxidase (GSH-Px) activities and lipid peroxide concentrations. Food deprivation significantly lowers the mucosal GSH-content and could lead to a destabilization of this system presumably by increased oxidative stress. As compared to normal "crude" diet, semisynthetic diets and oral iron depletion have been shown to cause a depression of the intestinal GSH system. As a consequence of these effects, the resistance of the small intestinal mucosa toward exogeneous dietary toxins might be reduced.     

Effects of intraperitoneally administered vitamin C on antioxidative defense mechanism in rats with diabetes induced by streptozotocin

We determined the effects of intraperitoneally administered vita-min C on the lipid peroxidation (as thiobarbituric acid-reactive substances, TBARS) and vitamin C and E levels and reduced glutathione (GSH) and glutathione peroxidase (GSH-Px) activity in the plasma, red blood cells (RBC), liver, and muscle of rats in relation to oxidative damage associated with diabetes induced by streptozotocin (STZ). One group was used as control and a second as diabetic. A third group received 30 mg vitamin C i.p. every other day. On day 4 after the injection of vitamin C, animals in the second and third groups were made diabetic by i.p. injection of STZ and administered vitamin C for 21 consecutive days, and we determined TBARS, vitamin E, and GSH levels and GSH-Px activities in plasma, RBC, liver, and muscle samples. Vitamin E levels in the plasma and liver were significantly higher (P<0.05) in the control group than in the diabetic group. Also, TBARS levels in the plasma, RBC, liver, and muscle samples were significantly lower (P<0.05) in controls than in the diabetic group. The TBARS levels in the RBC, liver, and muscle samples of the vitamin C group were significantly lower (P<0.05, P<0.01, and P<0.001, respectively). However, GSH-Px and GSH activities in RBC, liver, and muscle and vitamin C levels in liver were not significantly different between control and diabetic groups. Vitamin E levels in plasma (P<0.05, P<0.01) and liver (P<0.001), vitamin C levels in liver (P<0.001), and GSH (P<0.01) and GSH-Px activities in RBC (P<0.05, P<0.01) were significantly higher in the vitamin C group than both the control and diabetic groups. These results indicate that vitamin C has significant protective effects on the blood, liver, and muscle of rats against oxidative damage in diabetes.     

Oxidative stress in hypercholesterolemia and its association with Ala16Val superoxide dismutase gene polymorphism

ObjectivesTo investigate the role of the oxidative stress and the antioxidant system as well as the influence of the manganese superoxide dismutase (Ala16Val) polymorphism on hypercholesterolemia.Design and methodsLevels of glucose, lipid, high-sensitivity C reactive protein (hs-CRP), thiobarbituric acid reactive substances (TBARS), carbonyl protein, thiols, reduced glutathione (GSH), catalase (CAT), superoxide dismutase (SOD), and vitamin C, vitamin E, as well as the presence of the manganese superoxide dismutase (Ala16Val) polymorphism were determined in 40 subjects with hypercholesterolemia and 40 controls.ResultsLipid profile, hs-CRP, glucose, TBARS, carbonyl protein, CAT, and vitamin E were significantly higher in subjects with hypercholesterolemia. In contrast, GSH and SOD were lower. TBARS, carbonyl protein, thiols, CAT, and vitamin E were significantly higher in hypercholesterolemic subjects with VV genotype for MnSOD, while GSH, SOD, and vitamin C were lower in these subjects.ConclusionsWe suggest an association between the genotypes of MnSOD, hypercholesterolemia, and oxidative stress biomarkers.     

Redox status and lipid peroxidation in alcoholic hypertensive patients and alcoholic hypertensive patients with diabetes

Background: Free radical-mediated oxidative stress has been implicated in the progression of alcoholic hypertension and diabetic hypertension. Methods: The lipid peroxides and antioxidant status of plasma and erythrocytes were investigated in alcoholic hypertensive patients and alcoholic hypertensive patients with diabetes and compared with normal subjects. Results: A significant increase is observed in the levels of glucose, lipid peroxidation (P<0.05) in the alcoholic hypertensive patients with/without diabetes and the increase was significantly higher in alcoholic hypertensive patients with diabetes. The activities of erythrocyte antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and reduced glutathione (GSH) and plasma concentrations of GSH, vitamin C, vitamin E and β-carotene decreased significantly and the level of ceruloplasmin increased in alcoholic hypertensive patients with/without diabetes when compared to normal subjects. Plasma GSH and vitamin E levels exhibited a further decrease in alcoholic hypertensive patients with diabetes. Conclusions: An enhanced lipid peroxidation is observed in alcoholic hypertensive patients with diabetes and a more pronounced decrease in the levels of plasma GSH and vitamin E among antioxidants.     

Antioxidant effect of ascorbic acid on PCB (Aroclor 1254) induced oxidative stress in hypothalamus of albino rats

BACKGROUND: PCBs are one of the environmental toxicants and neurotoxic compounds which induce the production of free radicals leading to oxidative stress. Vitamin C is well known as an outstanding antioxidant. We determined the protective role of ascorbate on hypothalamic antioxidant system of Aroclor 1254 exposed rats. METHODS: The rats were injected Aroclor 1254 at a dose of 2 mg/kg bw/day intraperitoneally for 30 days. One group of rats received vitamin C (100 mg/kg bw/day) orally simultaneously with Aroclor 1254 for 30 days. Twenty-four hours after last treatment, the animals were killed and hypothalamic region was separated from brain tissue. Enzymatic and non-enzymatic antioxidants such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR) and vitamin C were estimated. Hydrogen peroxide (H(2)O(2)), lipid peroxidation (LPO) and acetylcholine esterase (AchE) activity were determined. Serum gonadotropins such as luteinizing hormone (LH) and follicle stimulating hormone (FSH) were also assayed. RESULTS: Activities of SOD, CAT, GPx, GR, AchE and the concentration of vitamin C were decreased while an increase in H(2)O(2) and LPO were observed in hypothalamus of PCB treated animals. LH and FSH concentrations were also decreased in serum of PCB exposed animals. Vitamin C administration retrieved all the parameters significantly except serum hormonal profiles. CONCLUSION: PCB induces oxidative stress in hypothalamus by decreasing the activities of antioxidant enzymes, which can be protected by vitamin C treatment.     

Effect of pentylenetetrazol-induced epileptic seizure on the antioxidant enzyme activities, glutathione and lipid peroxidation levels in rat erythrocytes and liver tissues

OBJECTIVES: In order to clarify whether oxidative stress accompanies epilepsy, we examined the effects of pentylenetetrazol (PTZ)-induced epilepsy on the lipid peroxidation and antioxidant enzyme activities in erythrocytes and liver tissues of adult Wistar rats. MATERIALS AND METHODS: The activities of antioxidative enzymes (glucose-6-phosphate dehydrogenase (G-6-PD)), copper, zinc-superoxide dismutase (Cu,Zn-SOD), catalase (CAT), selenium-dependent glutathione peroxidase (Se-GSH-Px) and the levels of reduced glutathione (GSH) and thiobarbituric acid-reactive substances (TBARS) were measured in erythrocytes and liver tissues of pentylenetetrazol (PTZ)-induced epileptic adult Wistar rats. RESULTS: Single PTZ treatment in a convulsive dose of 50 mg/kg significantly reduced the erythrocyte Cu,Zn-SOD, CAT enzyme activities and GSH levels compared to controls (P < 0.001, P < 0.001, P < 0.05, respectively). Erythrocyte and liver tissue TBARS levels in the epileptic group were significantly higher than controls (P < 0.0001). There was a significant decrease in liver tissue Cu,Zn-SOD activity and GSH levels in the epileptic group (P < 0.0001), whereas significantly higher activities of G-6-PD and Se-GSH-Px were found in the epileptic group. CONCLUSIONS: Our results demonstrate a generalized diminished antioxidant activity and increased TBARS level indicating enhanced oxidative stress in the liver and erythrocytes of epileptic rats. Increased oxidative stress in the liver of epileptic rats might be due to the activation of the recently found glutamate receptors in the liver. These findings suggest that the use of antioxidants with antiepileptic drugs and new drugs such as type-5 metabotropic glutamate receptor (mGlu5) antagonist (MPEP) might protect erythrocytes and liver tissue against anoxic damage and oxidative stress.     

Consequences of erythrocytic glutathione reductase deficiency

We have used 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) as a selective and irreversible inhibitor of oxidized glutathione reductase (GSSG-R) to determine how human erythrocytes with various degrees of GSSG-R deficiency recover their reduced glutathione (GSH) after exposure to acetylphenylhydrazine or diamide. Pentose phosphate dehydrogenases and glutathione synthesis were not inhibited, de novo glutathione synthesis was negligible within the experimental time frame, and the reappearance of GSH was strictly under the control of GSSG-R. Results obtained with acetylphenylhydrazine or diamide were concordant. In red cells stressed by these reagents, GSSG-R deficiency began to impair the regeneration of GSH only after greater than 80% of the normal enzyme activity had been abolished. Thereafter GSH recovery deteriorated as drug-induced GSSG-R depression increased. Only erythrocytes that had been rendered almost totally GSSG-R deficient, that is, had lost greater than 90% of baseline activity, became functionally equivalent to GdA- glucose-6-phosphate dehydrogenase-deficient cells. The reserve capacity of GSSG-R in human erythrocytes is extremely large. Of all types of isolated GSSG-R "deficiencies" reported so far, only two can be considered pathogenically significant: the homozygous genetic defect found in a single family, and much more commonly, the acute pharmacologic phenocopy induced by BCNU.     

Oxidative stress indices in IDDM subjects with and without long-term diabetic complications.

BACKGROUND: Numerous animal and population studies of diabetes have identified markers of oxidative stress. However, for most markers that have been measured the results are not consistent. In addition, it is less clear whether oxidative stress is related to the development of diabetic complications. The objective of this study was to evaluate a series of plasma markers and leukocyte markers to test the hypothesis that type 1 Insulin Dependent Diabetes Mellitus (IDDM) subjects experience oxidative stress. A related question was whether markers of oxidative stress are higher in IDDM subjects who have developed long-term complications. METHODS: The study population consisted of 22 IDDM subjects with diabetic complications and 22 IDDM subjects without complications, both groups matched by age and gender and with similar HbA1c levels, and 16 nondiabetic control subjects. Plasma levels of organoperoxides were determined by the ferrous oxidation/xylenol orange (FOX) assay, malondialdehyde by the thiobarbituric acid (TBARS) assay, and vitamin E by HPLC. Mononuclear cells and polymorphonuclear cells were analyzed for ascorbic acid by HPLC and for glutathione (GSH) by enzymatic recycling. In addition, GSH peroxidase, GSH transferase and glucose-6-phosphate dehydrogenase levels were determined in both cell fractions. RESULTS: Plasma organoperoxides were significantly elevated in the IDDM subjects compared to controls (p = 0.02) while TBARS and vitamin E levels were not significantly different. In the IDDM subjects, mononuclear cell levels of ascorbic acid were significantly lower (p < 0.02) and levels of GSH were lower, approaching significance (p = 0.07), compared to controls. Ascorbic acid and GSH levels in polymorphonuclear cells were not significantly different between IDDM subjects and controls, nor were enzyme levels different. In addition, the plasma and intracellular indices of oxidative status in IDDM subjects were not different when IDDM subjects with complications were compared to IDDM subjects without complications. CONCLUSION: Demonstration of oxidative stress in IDDM subjects depends upon which markers are measured. This is in agreement with previous studies of oxidative stress in various disease states including diabetes. Plasma levels of organoperoxides may be the most reliable indicators of oxidative stress. However, it is unclear whether elevated plasma organoperoxides indicate a generalized systemic stress or are produced in localized areas. By comparison, oxidative stress indices determined with isolated blood cells may provide a clearer picture. Depressed levels of ascorbic acid and GSH were observed only in mononuclear cells, which are mainly long-lived T lymphocytes. Mononuclear cells antioxidant status may reflect systemic oxidative stress. In this study, neither plasma markers nor intracellular markers of oxidative stress were different in IDDM subjects with long-term diabetic complications compared to subjects without complications.     

Serum markers of oxidative stress and severity of diabetic retinopathy

OBJECTIVE: To compare serum markers of oxidative stress with diabetic retinopathy severity RESEARCH DESIGN AND METHODS: This cross-sectional study compared patients with types 1 and 2 diabetes with control subjects in western New York and Pennsylvania. Retinopathy severity was graded from funduscopic fields based on the Early Treatment of Diabetic Retinopathy Study. Serum samples were analyzed for thiobarbituric acid-reacting substances (TBARS), superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities, creatinine, HbA1, and triglycerides. Appropriate analysis of covariance models were performed. RESULTS: TBARS (P = 0.019), triglyceride (P = 0.004), and glucose and HbA1 (both P<0.001) levels were elevated in diabetic patients compared with those in control subjects. SOD (P = 0.003) and GSH-Px (P = 0.046) levels were lower in diabetic patients than in control subjects. No correlation existed between SOD levels and either glucose or HbA1 levels. No significant associations existed between levels of TBARS, SOD, or GSH-Px and severity of diabetic retinopathy There was a significant association between poorer visual acuity and worse retinopathy (P = 0.009), which was only partly explained by macular edema. CONCLUSIONS: Increased levels of TBARS and decreased levels of SOD and GSH-Px were found in diabetic patients compared with those in control subjects, but no significant associations were found between the levels of these substances and severity of retinopathy When duration and type of diabetes and serum HbA1 levels were taken into account, only visual acuity remained associated with more severe retinopathy.     

Effects of melatonin on plasma oxidative stress in rats with streptozotocin induced diabetes.

The aim of this study was to evaluate the effect of single melatonin injection on plasma oxidative stress in rats with streptozotocin induced diabetes. Diabetes was induced after a single intraperitoneal dose of streptozotocin (60 mg/kg), while hyperglycemia was determined 10 days upon injection. Diabetic rats were divided into two groups. In the first group the injection of melatonin was applied intraperitoneally (20 mg/kg), while the second group received physiological solution. Twenty-four hours later the rats were killed and their blood was centrifuged. In the rat plasma the following parameters were evaluated: the glucose level, superoxide radical, lipid peroxidation, reduced glutathione, total antioxidant capacity, antioxidant enzymes and the aldose reductase activity. The injected melatonin decreased the superoxide radical in the rat plasma. Moreover, melatonin increased the total antioxidative capacity and the activity of antioxidative enzymes superoxide dismutase and glutathione peroxidase. These results indicate that melatonin is a strong scavenger, which may diminish negative effects of oxidative stress in diabetic rats 24 hours after its application The findings suggest that melatonin is also a strong antioxidant. It increases the antioxidant enzymes activity, inhibiting the release of superoxide radicals. A high total antioxidative capacity and the lower activity of aldose reductase enlarge melatonin scavenger capacity against reactive oxygen species in diabetic rats.     

Oxidative stress and nitric oxide related parameters in type II diabetes mellitus: effects of glycemic control

OBJECTIVES: The aim of this study is to investigate the status of oxidative stress and nitric oxide related parameters in type II diabetes mellitus (DM) patients in which heart disease, atherosclerosis, retinopathy, and nephropathy commonly occur, and also to determine the effect of glycemic control on these parameters. DESIGN AND METHODS: Erythrocyte copper zinc-superoxide dismutase (CuZn-SOD), erythrocyte and plasma selenium dependent glutathione peroxidase (Se-GPx), erythrocyte catalase (CAT) activities, erythrocyte and plasma thiobarbituric acid reactive substances (TBARS) levels; nitrite/nitrate (NO(2)(-)/NO(3)(-)), cyclic guanosine monophosphate (cGMP) and nitrotyrosine levels in plasma of type II DM patients were measured. RESULTS: Erythrocyte CuZn-SOD activities in type II DM were significantly higher than those of the control subjects (p < 0.05). TBARS levels in type II DM were significantly higher than the control subjects (p < 0.001). Plasma NO(2)(-)/NO(3)(-) levels in type II DM patients both during poor glycemic control and after three months of oral antidiabetic treatment were significantly higher than those of the control subjects (p < 0.001). Plasma cGMP levels in type II DM patients during poor glycemic control were significantly lower than those of control subjects (p < 0.001). CONCLUSION: These results indicate that oxidative status and nitric oxide metabolism are affected in type II DM patients. We found high CuZn-SOD activity in type II DM patients. This increased activity could not protect the patients against the reactive oxygen species (ROS), since lipid peroxidation (defined by erythrocyte and plasma TBARS levels) still occurs in DM patients. After the therapy with oral antidiabetic agents for three months, erythrocyte SE-GPx and CAT activities were found to be decreased below the control values. Our results suggested that the low cGMP levels in the study may be a good marker of endothelium dysfunction in DM.     

Glutathione, cell proliferation, and 1,3-bis-(2-chloroethyl)-1-nitrosourea in K562 leukemia.

We have pursued our findings of glutathione reductase (GSSG-R) deficiency and disturbed glutathione in cancer patients treated with 1,3-bis-(2-chloroethyl)-1-nitrosourea (BCNU), by investigating how thiol metabolism, cell proliferation, and the nitrosourea interact in human K562 leukemia. Fasting cells arrested in G greatly increased their reduced glutathione (GSH) in response to growth factors. The rise in thiol began after several hours, peaked before DNA synthesis, and resulted from increased production. BCNU inactivated GSSG-R rapidly, and later retarded, doubled, and greatly prolonged GSH formation before stopping DNA synthesis. Pretreatment unlike post treatment with buthionine-S-R-sulfoximine (BSO) diminished BCNU's ability to block GSSG-R. Enzyme inhibition decreased with falling cellular GSH. In the leukemia system as in vivo, sequential BCNU-induced thiol alterations heralded delayed antiproliferative effects. Drug timing markedly affected both thiol and DNA syntheses. By destroying GSSG-R and delaying the upregulation of thiol synthesis while escalating GSH utilization and requirements, the nitrosourea created a striking and previously unrecognized window of vulnerability for GSH-dependent processes. During this period, altered GSH metabolism could contribute indirectly to BCNU's pleiotropic effects by interfering with DNA alkylation repair, glucose decarboxylation, deoxyribose formation, and possibly by influencing other aspects of proliferation. Acquired GSSG-R deficiency was also an early and sensitive marker for prodrug breakdown and activation.     

Protective role of caffeic acid phenethyl ester in the liver of rats exposed to cold stress

Cold exposure can induce a form of environmental stress. Cold stress (CS) alters homeostasis, results in the creation of reactive oxygen species and leads to alterations in the antioxidant defense system. The caffeic acid phenethyl ester (CAPE), an active component of propolis, has an antioxidant capacity. We investigated the effect of CS on oxidative stress and antioxidant defense system and the possible protective effect of CAPE in rat liver tissue. Twenty-four female Wistar Albino rats were divided into four groups: Control, CAPE-treated, CS, and CAPE-treated CS (CS + CAPE) group. Catalase (CAT), glutathione peroxidase (GSH-Px), superoxide dismutase (SOD) activities and total glutathione (GSH) and malondialdehyde (MDA) levels were measured. In addition, histological changes in liver tissue were examined by light microscopy. SOD, CAT and GSH-Px activities and total GSH level were significantly declined in the CS group. In the CS + CAPE group, the activities of these three enzymes and GSH level significantly raised with regard to the CS group. MDA levels increased in the CS group and decreased in the CS + CAPE group. The tissues of the CS group showed some histopathological changes such as necrosis, hepatocyte degeneration, sinusoidal dilatation, hemorrhage and vascular congestion and dilatation. In the CS + CAPE group, the histopathological evidence of hepatic damage was markedly reduced. Histological parameters were consistent with biochemical parameters. In this study, CS increased oxidative stress in liver tissue. CAPE regulated antioxidant enzymes, inhibited lipid peroxidation and reduced hepatic damage.