Leukocyte lipid peroxidation, superoxide dismutase, glutathione peroxidase and serum and leukocyte vitamin C levels of patients with type II diabetes mellitus

Evaluation of the effects of metformin on antioxidant biomarkers and mineral levels in patients with type II diabetes mellitus: A cross-sectional study

Diabetes mellitus (DM) and arterial hypertension are considered serious public health problems. Several studies have shown that oxidative stress is usually related to the onset of DM and hypertension, as well their associated complications. Moreover, the levels of some minerals are closely related to the pathophysiology of these diseases. Thus, in this study we aimed to evaluate the effect of metformin on the redox profile and mineral levels in the serum of patients with DM type 2 and hypertension. We also tested the effect of metformin on the viability and redox profile of peripheral blood mononuclear cells (PBMCs) for 24 h. As expected, we found that patients with type 2 DM and hypertension + type 2 DM had higher fasting glucose and triglyceride levels. As groundbreaking research, we found that both patients DM type 2 and Hypertension + DM type 2 had reduced myeloperoxidase (MPO) activity. On the other hand, the levels of total thiols (PSH) and vitamin C were increased. There was no statistical significance for the alterations in mineral levels. In addition, metformin treatment had no cytotoxic effect on PBMCs. Similarly, in patients of both groups, MPO activity was reduced and PSH levels were increased in PBMCs. We have shown that metformin is a drug with a protective effect in patients with DM type 2 against oxidative stress by reducing MPO activity and improving the levels of PSH and antioxidant defenders such as vitamin C. The results of in vitro assays support the antioxidant effect of metformin. Furthermore, we suggest studies to assess the biochemical mechanisms of metformin and how it can be used in a pharmacological therapeutic perspective against oxidative damage.

Effects of neferine on retinal tissue in experimental diabetic rat model

PURPOSE

To investigate vascular endothelial growth factor (VEGF) and proliferating cell nuclear antigen (PCNA) immunoreactivities, as well as apoptosis and oxidative stress levels in Streptozotocin (STZ)-induced diabetic rats, and determine how neferine affected these parameters.

METHODS

Thirty-five male Sprague Dawley rats were divided into five groups of seven. Fasting blood glucose was measured 72 h after diabetes mellitus (DM) induction in 21 rats using 60 mg/kg STZ dissolved in 0.4 ml (0.1 M) sodium-citrate buffer (pH:4.5), with values > 250 mg/dl considered diabetic. Group 1 received no treatment. Group 3 (healthy rats) received daily intraperitoneal (IP) 4 mg/kg neferine. Following DM induction: Group 2 (sham) received daily IP 0.25 ml/kg 0.9% normal saline; Group 4 received single IP 0.01 mL (2.5 mg/kg) bevacizumab, followed by daily IP 0.25 mL/kg 0.9% normal saline; and Group 5 received daily IP 4 mg/kg neferine. Total antioxidant capacity (TAC) and total oxidative stress (TOS) levels in serum and ocular tissue homogenates were evaluated using ELISA. TUNEL method was used for determining apoptosis and immuno-histochemical staining for PCNA and VEGF immunoreactivities.

RESULTS

Group 5 had significantly higher TAC and lower TOS in serum and ocular tissue homogenates than Group 4 (p < 0.05). Despite significantly lower VEGF levels and apoptosis (p < 0.05), there was no significant change in PCNA immunoreactivity in Group 5 (p > 0.05).

CONCLUSIONS

DM was associated with lower TAC, higher TOS and apoptotic cells, as well as VEGF and PCNA immunoreactivities in the retina. Neferine altered parameters other than PCNA in the opposite direction, demonstrating reductive effects on DM.

Can antioxidants be effective therapeutics for type 2 diabetes?

The global obesity epidemic and the growing elderly population largely contribute to the increasing incidence of type 2 diabetes. Insulin resistance acts as a critical link between the present obesity pandemic and type 2 diabetes. Naturally occurring reactive oxygen species (ROS) regulate intracellular signaling and are kept in balance by the antioxidant system. However, the imbalance between ROS production and antioxidant capacity causes ROS accumulation and induces oxidative stress. Oxidative stress interrupts insulin-mediated intracellular signaling pathways, as supported by studies involving genetic modification of antioxidant enzymes in experimental rodents. In addition, a close association between oxidative stress and insulin resistance has been reported in numerous human studies. However, the controversial results with the use of antioxidants in type 2 diabetes raise the question of whether oxidative stress plays a critical role in insulin resistance. In this review article, we discuss the relevance of oxidative stress to insulin resistance based on genetically modified animal models and human trials.

Oxidative stress and DNA damage in peripheral blood mononuclear cells from normal, obese, prediabetic and diabetic persons exposed to adrenaline in vitro

Diabetes represents one of the major health concerns, especially in developed countries. Some hormones such as the stress hormone adrenaline can induce reactive oxygen species (ROS) and may worsen the diabetes. Therefore, the main aim of the investigation was to find out whether peripheral blood mononuclear cells (PBMCs) from normal persons have less DNA damage induced by adrenaline (0.1, 1 and 10 μM) in comparison to PBMCs from obese, prediabetic and diabetic patients. Also, the biochemical parameters of oxidative stress (TBARS, catalase) and lactate dehydrogenase were monitored. It was observed that higher concentrations of adrenaline (1 and 10 μM) induced DNA damage in the obese, prediabetic and diabetic groups. In healthy individuals only the highest concentration of adrenaline caused significant increase in the DNA damage. In summary, total comet score (TCS) comparison has shown significant differences between groups, and DNA damaging effects of adrenaline were most evident in diabetic patients. The results of the biochemical analysis also demonstrate that adrenaline exerts most obvious effects in diabetic individuals which is manifested as significant change of parameters of oxidative stress. In summary, the obtained results demonstrated that diabetics are more sensitive to genotoxic effects of adrenaline and this effect probably resulted from decreased antioxidative defence mechanisms in various stages of progression through diabetes. Therefore, these results could contribute to a better understanding of a role of endocrine factors to damage of cellular biomolecules which could be useful in finding novel therapeutic approaches and lifestyle changes with an aim to lower the possibility of diabetes complications.

Effect of Cistanche Tubulosa Extracts on Male Reproductive Function in Streptozotocin⁻Nicotinamide-Induced Diabetic Rats

Diabetes is a chronic disorder characterized by hyperglycemia due to decreased levels of insulin or the inefficiency of the tissue to use it effectively. Infertility is known as a major outcome of diabetes and affects the male reproductive system by causing sperm impairment and gonadal dysfunction. Cistanche tubulosa is a parasitic plant which has the capacity to improve memory, immunity, and sexual ability, reduce impotence, and minimize constipation. This study was focused on the investigation of the anti-inflammatory and protective effects of echinacoside (ECH) in Cistanche tubulosa extract (CTE) on the male reproductive system of the diabetic rats. The antioxidant, anti-inflammatory, and protective effects of CTE were evaluated by both in vitro and in vivo methods. The in vitro results show that the ECH inhibited reactive oxygen species (ROS) production and improved StAR, CYP11A1, CYP17A1, and HSD17β3 protein expression. The in vivo analysis was carried out with three doses of echinacoside (ECH) (80, 160, and 320 mg/kg) in CTE. In total, 0.571 mg/kg of rosiglitazone (RSG) was administered as a positive control. Diabetes was induced by streptozotocin (STZ) (65 mg/kg) and nicotinamide (230 mg/kg) in combination with a high-fat diet (45%). The in vivo studies confirmed that the ECH improved blood sugar levels, insulin resistance, leptin resistance, and lipid peroxidation. It can restore kisspeptin 1 (KiSS1), G protein-coupled receptor GPR 54, suppressor of cytokine signaling 3 (SOCS-3), and sirtuin 1 (SIRT1) messenger ribonucleic acid (mRNA) expression in the hypothalamus and recover sex hormone level. Thus, this study confirmed the antioxidant, anti-inflammatory, and steroidogenesis effects of CTE.

Leukocyte Lipid Peroxidation, Superoxide Dismutase and Catalase Activities of Type 2 Diabetic Patients with Retinopathy

Increased oxidative stress might play an important role in the initiation and progression of diabetic complications. The present study has been undertaken to investigate whether there is any relationship between retinopathy degree and leukocyte superoxide dismutase (SOD) and catalase (CAT) activities and lipid peroxidation (LPO) in diabetic individuals with type 2 diabetic retinopathy. Patients were groupped with respect to the degree of retinopathy. Leukocyte malondialdehyde (MDA) levels, and SOD and CAT activities were measured in patients with type 2 diabetes mellitus (n=41) and nondiabetic healthy controls (n=23). Leukocyte LPO of the type 2 diabetic patients with retinopathy was significantly increased (p< 0.001), whereas SOD and CAT activities were decreased (p<0.001 and p<0.001, respectively) compared to those of controls. MDA concentrations rose while SOD and CAT activities fell with increasing severity of diabetic retinopathy, altough there was no significant difference in comprasion of the parameters mentioned above between the diabetic patients with and without retinopathy. Our results show that leukocytes in patients with type 2 diabetic retinopathy are affected by oxidative stress which might be contribute to pathogenesis of diabetic retinopathy. Prospective studies are needed to evaulate the relationship between the leukocyte antioxidants status and DR.

Potential effects of metformin in DNA BER system based on oxidative status in type 2 diabetes

Metformin is used to reduce hyperglycemia that induces energetic stress and leads to reduction in gluconeogenesis. Also, metformin inhibits complex I in oxidative phosphorylation, thereby decreasing cellular ATP levels. Activation of AMPK by the reduced ATP levels can induce inhibition of reactive oxygen species (ROS) production and activate p53-mediated DNA repair. DNA polymerase-β and XRCC1 function to repair DNA damages in the BER (base excision repair) system. In type 2 diabetes patients, metformin can enhance AMPK activation therefore suppress oxidative stress. The changes on oxidative stress may alter p53's function and effect many cellular pathways such as; DNA repair. In our project we aim to understand the effects of metformin on p53 and DNA-BER system based on the oxidative status in type 2 diabetes patients. Oxidative and antioxidative capacity, catalase, SOD, GPx activities and, DNA pol beta, XRCC1 and p53 levels were measured in metformin using or non-using type 2 diabetes patients and controls. Metformin enhanced SOD and GPx activities in type 2 diabetes patients but the reflection of this increase to the total antioxidant capacity was not significant. Although the increase in DNA pol beta was not significant, XRCC1 and p53 levels were significantly upregulated with metformin treatment in type 2 diabetes patients. Our study reinforces the potential benefit of metformin in antioxidative capacity to protect cells from diabetic oxidative stress and in regulation of DNA BER system.

The susceptibility to autoxidation of erythrocytes in diabetic mice: Effects of melatonin and pentoxifylline

Oxidative stress had a great importance in development of complications in diabetes. We investigated effects of melatonin and pentoxifylline in diabetic mice. Swiss albino mice (n = 40) were divided into four groups: alloxan-induced diabetes mellitus (DM), alloxan-induced diabetes with melatonin supplementation (DM + MLT), alloxan-induced diabetes with pentoxifylline supplementation (DM + PTX), and control. Glutathione-peroxidase (GSH-Px) activity, malondialdehyde (MDA) and reduced glutathione (GSH) levels, and susceptibility to oxidation of erythrocytes were measured. MDA levels were higher than control in the DM and DM + MLT. The DM had more MDA level than the DM + MLT and DM + PTX (P < 0.001). After in vitro oxidation, MDA levels of all groups were found higher than the control. However, they were significantly lower than the DM in DM + PTX and DM + MLT (P < 0.001). Although GSH levels of the DM and DM + PTX were less than the control, GSH-Px activity of the DM was lower than the control and DM + PTX (P < 0.05). We suggest that there is increased oxidative stress and compromised antioxidant status of erythrocytes in diabetes; however, it can be effectively prevented by melatonin or pentoxifylline supplementation.

Vitamin D receptor gene FokI variant in diabetic foot ulcer and its relation with oxidative stress

PURPOSE

The patient's suffering and financial costs affiliated with Diabetic Foot Ulcer (DFU), as one of the most important complications of diabetes, are highly undesirable and this highlights the importance of preventive medicine about this disorder. Furthermore hyperglycemia causes generation of free radicals which leads to oxidative stress (OS). Hence, this study aims to examine the association between vitamin D receptor (VDR) gene FokI polymorphism and DFU in Iranian population and also its correlation with OS biomarkers.

MATERIALS AND METHODS

In a case-control study, a total of 212 patients with type 2 diabetes with and without diabetic foot ulcer were included. Genotyping was conducted by polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) analysis. Samples were analyzed for thiobarbituric reactive substances (TBARS) and ferric reducing ability of plasma (FRAP) as markers of OS.

RESULTS

The results indicated a significant difference in genotype frequencies of VDR gene FokI polymorphism in patients with diabetic foot ulcer in comparison to those without diabetic foot ulcer (TT+TC vs. CC p=0.04; OR=1.76; 95% CI=1.02-3.05). Moreover, the patients carrying the T allele had a significantly higher level of TBARS (p=0.01).

CONCLUSIONS

We found a significant association between FokI functional variant of VDR gene and diabetic foot ulcer in an Iranian population. Increased levels of TBARS in patients carrying the T allele of FokI polymorphism indicate an association between this variant and OS in patients with diabetes.

Determination of plasma and leukocyte vitamin C concentrations in a randomized, double-blind, placebo-controlled trial with Ester-C(®)

Background

Rapid uptake of vitamin C into blood and retention in tissues are important indicators of the efficacy of vitamin C supplementation and its immune-supporting role. The objective of this study was to evaluate the bioavailability of vitamin C in plasma (reflective of recent intake) and leukocytes (reflective of tissue stores and influences on immune function) from a novel vitamin C formulation, Ester-C^®.

Methods

The study was a double-blind, placebo-controlled, crossover trial. Thirty-six subjects, 18–60 years of age, were randomized to receive placebo (PL, 0 mg vitamin C), ascorbic acid (AA, 1000 mg vitamin C), and Ester-C^® (EC, 1000 mg vitamin C). Plasma and leukocyte vitamin C were measured baseline and at 2, 4, 8 and 24 h postdose.

Results

The concentration and percent change from baseline in plasma were significantly higher with EC at all time points when compared to PL. No significant differences between EC and AA were observed in plasma concentration. Maximum plasma concentration was higher for EC compared to AA (P = 0.039) and PL (P < 0.001). Plasma area under the curve (AUC_0–24h) was higher for EC (P < 0.001) compared to PL. The concentration change from baseline in leukocyte vitamin C was increased with EC at 24 h post-dose (P = 0.036) while no significant within-group changes were observed in AA or PL at any time point. The percent change in leukocyte vitamin C concentration was higher for EC at 8 and 24 h compared to AA (P = 0.028 and P = 0.034, respectively) and PL (P = 0.042 and P = 0.036, respectively).

Conclusions

A single dose of EC resulted in favorable percent change in leukocyte vitamin C concentration compared to AA and PL, indicating EC is retained longer within leukocytes.

Trial registration ClinicalTrials.gov Identifier NCT01852903

Alteration of hepatic cells glucose metabolism as a non-cholinergic detoxication mechanism in counteracting diazinon-induced oxidative stress

The aim of this study was to evaluate effects of acute exposure to various doses of diazinon, a widely used synthetic organophosphorus (OP) insecticide on plasma glucose, hepatic cells key enzymes of glycogenolysis and gluconeogenesis, and oxidative stress in rats. Diazinon was administered by gavage at doses of 15, 30 and 60 mg/kg. The liver was perfused and removed under anaesthesia. The activities of glycogen phosphorylase (GP), phosphoenolpyruvate carboxykinase (PEPCK), thiobarbituric acid reactive substances (TBARS) and total antioxidant capacity (TAC) were analysed in liver homogenate. Administration of diazinon (15, 30 and 60 mg/kg) increased plasma glucose concentrations by 101.43% (P=0.001), 103.68% (P=0.000) and 160.65% (P=0.000) of control, respectively. Diazinon (15, 30 and 60 mg/kg) increased hepatic GP activity by 43.5% (P=0.05), 70.3% (P=0.00) and 117.2% (P=0.02) of control, respectively. In addition, diazinon (30 and 60 mg/kg) increased hepatic PEPCK by 77.3% (P=0.000) and 93.5% (P=0.000) of control, respectively. Diazinon (30 and 60 mg/kg) decreased liver TAC by 38% (P=0.046) and 48% (P=0.000) of control, respectively. Also diazinon (30 and 60 mg/kg) increased hepatic cell liver lipid peroxidation by 77% (P=0.05) and 280% (P=0.000) of control. The correlations between plasma glucose and hepatic cells TBARS (r2=0.537, P=0.02), between plasma glucose and ChE activity (r2=0.81, P=0.049) and between plasma glucose and hepatic cells GP activity (r2=0.833, P=0.04) were significant. It is concluded that the liver cells are a site of toxic action of diazinon. Diazinon increases glucose release from liver into blood through activation of glycogenolysis and gluconeogenesis as a detoxication non-cholinergic mechanism to overwhelm diazinon-induced toxic stress. The results are in accordance with the hypothesis that OPs are a predisposing factor of diabetes.

Cardiovascular effects of copper deficiency on activity of superoxide dismutase in diabetic nephropathy

BACKGROUND

Copper (Cu) is essential both for its role in antioxidant enzymes, like Cu/zinc (Zn) superoxide dismutase (SOD) and ceruloplasmin, as well as its role in lysyl oxidase, essential for the strength and integrity of the heart and blood vessels. With such a central role in cardiovascular health, Cu has been generally overlooked in the debate over improving our cardiovascular health. Cu deficiency has produced many of the same abnormalities present in cardiovascular disease. It seems almost certain that Cu plays a large role in the development of this killer disease, not because of its excess in the diet, but rather its deficiency.

AIM

This study was undertaken to investigate the cardiovascular effects of Cu deficiency on the activity of SOD in patients with type 2 diabetes mellitus (T2DM) with and without diabetic nephropathy.

MATERIALS AND METHODS

Fifty-five patients with T2DM were recruited in this study which were divided into two subgroups based on the presence of microalbuminuria, the first group (microal buminuric group, n = 31) had a microalbuminuria between 30 and 299 μg/mg. The second group (normoal buminuric group, n = 29) had an albumin level less than 30 μg/mg. The two diabetic groups were compared to the control group (n = 37).

RESULTS

The results of our study showed a significant reduction in the levels of SOD enzyme associated with an increased urinary Cu excretion in microalbuminuric group compared to the control group at P < 0.05.

CONCLUSIONS

The current study illustrates that the regulation of the blood concentrations of Cu may be a potential therapeutic target for prevention and treatment of diabetic nephropathy.

Oxidative stress and antioxidant capacity in patients with chronic pancreatitis with and without diabetes mellitus

AIM

To determine oxidant stress and antioxidant capacity in chronic pancreatitis (CP) patients with and without diabetes mellitus.

METHODS

This study is a secondary data analysis of our earlier study on 127 (male = 86) patients with CP, grouped as those with diabetes (case; n = 23) and those without diabetes (control). Markers of antioxidant status included vitamins A and E, total antioxidant capacity (TAC; measured as ferric-reducing ability of plasma [FRAP]), and total glutathione (T-GSH). Markers for oxidative stress included lipid peroxidation, measured as thiobarbituric acid reactive substances (TBARS) and serum superoxide dismutase (s-SOD).

RESULTS

Patients with diabetes were older (mean [SD] age 36.4 [9.7] vs. 29.3 [10.0] years; p = 0.032), had longer duration of CP [4 (0.3-21) vs. 3 (0.3-24) years; p = 0.07), and had a lower TAC (269.8 [92.4] vs. 355.5 [128.6] μmoles Fe(+2) liberated; p = 0.003) compared to those without diabetes. In multiple logistic regression analysis taking all exploratory variables, FRAP (<270 μmoles Fe(+2) liberated) was associated with diabetes independent of duration of CP, age of patients, and TBARS levels. However, oxidative stress levels were not different between diabetic and nondiabetic patients.

CONCLUSIONS

Diabetes was found to be associated with longer duration of CP and with low antioxidant capacity. Further studies will be needed to evaluate a causal association.

Lactobacillus protected bone damage and maintained the antioxidant status of liver and kidney homogenates in female wistar rats

The aim of the study was to evaluate protective property of Lactobacillus casei and Lactobacillus acidophilus in minimizing oxidative stress associated with arthritis from liver and kidney. Subsequently, protective property of Lactobacillus against the bone damage was also taken into consideration. Arthritis was induced by injecting freund's complete adjuvant (100 μl) into sub plantar surface of hind paw. Oral administration of culture, vehicle, and drug started after induction of arthritis (i.e. on day 9th). Indomethacin was used as a standard drug. Radiographic analysis of the hind paw knee joint was also done at the end of the 21st day. Oxidative stress parameters were studied from liver and kidney homogenate. Histopathology of liver and kidney was also performed. Lactobacillus treatment significantly rescued the enzymatic level of catalase, superoxide dismutase, reduced glutathione, and glutathione peroxidase in both liver and kidney homogenates, whereas it has decreased the malonaldehyde accumulation. Oral administration of Lactobacillus also significantly decreased the serum ceruloplasmin level. Radiographic analysis also corroborated these findings. Lactobacillus treatment maintained the normal histopathology of liver and kidney. Results of this study clearly suggest that L. casei and L. acidophilus, alone or in combination, decreased the bone damaged and effectively restored antioxidant status of liver and kidney. Lactobacillus has a significant antiarthritic and antioxidant activity against freund's complete adjuvant induced arthritis in rats.

Relationship between oxidative stress and apoptotic markers in lymphocytes of diabetic patients with chronic non healing wound

AIMS

Hyperglycemia causes generation of free radicals which leads to oxidative stress and apoptosis in various cells. The present study was undertaken to investigate the correlation between oxidative stress and apoptotic markers in lymphocytes of diabetic patients with chronic non healing wounds.

METHODS

Thirty healthy, thirty uncontrolled type 2 diabetes mellitus (T2DM) and thirty uncontrolled T2DM with chronic, non healing, neuropathic diabetic foot patients were included in this study. Indices of oxidative stress inside the lymphocyte lysate were estimated by measuring content of superoxide dismutase (SOD), Catalase, Glutathione and malonaldialdehyde (MDA). Protein expression studies of pro and anti apoptotic markers were carried out to elucidate their possible involvement in diabetic context.

RESULTS

SOD and MDA activity was significantly higher in the lymphocytes of diabetic patients having chronic, non healing diabetic wound as compared with healthy (p<0.001); whereas catalase and GSH activity was significantly reduced (p<0.001) in the same group. Expressions of pro apoptotic markers (Caspase-3, Fas and Bax) were significantly higher whereas reduced expression of anti-apoptotic marker (Bcl-2) were obtained in lymphocytes of diabetic and non diabetic individuals.

CONCLUSIONS

Hyperglycemia confers pro apoptotic manifestations which are mostly through altered indices of oxidative stress within lymphocytic milieu.

[Physical activity and endothelial dysfunction in type 2 diabetic patients: the role of nitric oxide and oxidative stress]

Type 2 diabetic patients have an increased level of systemic free radicals, which severely restrict the bioavailability of endothelium-derived nitric oxide (NO) and thus contribute to the development of an endothelial dysfunction. This review analyses the influence of physical training on molecular development mechanisms of the endothelial dysfunction and determines the significance of regular physical exercise for the endothelial function in type 2 diabetic patients. Systematic training reinforces the endogenic antioxidative capacity and results in a reduction in oxidative stress. Training - also combined with a change in diet - furthermore reduces hyperglycaemic blood sugar levels, thus curbing a major source of free radicals in diabetes. Moreover, physical exercise enhances vascular NO synthesis through an increased availability/activity of endothelial NO synthases (eNOS). Endurance, as well as resistance training with submaximal intensity or a combination of both forms of training is suitable to effectively improve the endothelial function in type 2 diabetic patients in the long term.

Relationship among superoxide-related enzyme, PPARs, and endothelium-dependent relaxation in murine aortas previously organ-cultured in high-glucose conditions

The aim of the present study was to investigate the relationship among superoxide anion, peroxisome proliferator-activated receptors (PPARs), and endothelium-dependent relaxation in murine aortas organ-cultured in a high-glucose condition. Aortas organ-cultured with a high concentration of glucose (40 mmol/L, 20 h; HG group) exhibited the following characteristics (versus aortas cultured in serum-free medium): (i) significantly weaker relaxation to acetylcholine, but unchanged relaxation to SNP and unchanged contractions to norepinephrine and isotonic K+, (ii) significantly greater superoxide generation (indicated by the amount of nitroblue tetrazolium reduced, (iii) significantly higher protein expression levels of gp91phox, NAD(P)H oxidase subunits, and endothelial NO synthase, (iv) significantly lower protein expression level of Mn-superoxide dismutase (SOD), and (v) markedly greater reduction in the protein expression of PPARgamma than in that of PPARalpha. The HG-induced impairment of endothelium-dependent relaxation was prevented by cotreatment with tempol (a SOD mimetic). These results suggest that in the mouse aorta, exposure to high glucose levels may lead to an excessive generation of superoxide via increased gp91phox and decreased Mn-SOD protein expression and that this may in turn trigger an impairment of endothelium-dependent relaxation. Moreover, such protein changes in gp91phox and Mn-SOD may be secondary to a decreased expression of PPARgamma protein.

DNA damage and plasma antioxidant indices in Bangladeshi type 2 diabetic patients

BACKGROUND AND AIM

Diabetes mellitus is a complex metabolic disorder characterized by a disturbance in glucose metabolism. Recent evidence suggests that increased oxidative stress as well as alteration of antioxidant capacity may be related to the complications seen in patients with type 2 diabetes. The aim of this study was to measure serum antioxidant status in type 2 diabetic patients and to assess its relationship with oxidative DNA damage.

METHODS

A total of 57 subjects were included in this study. Of these, 32 were type 2 diabetic patients and 25 were non-diabetic subjects. Comet assay was used to quantify the level of DNA damage in lymphocytes. Spectrophotometric methods were used to assess serum levels of malondialdehyde (MDA) and protein carbonyl, and serum activity of superoxide dismutase (SOD) and the protein thiol (P-SH) group.

RESULTS

A significant increase in mean comet tail DNA, indicating DNA damage, was observed in diabetic patients compared with controls. Diabetic patients had significantly higher levels of MDA and protein carbonyl in parallel with significant decreases in levels of SOD and the P-SH group compared with controls. Serum SOD was also inversely correlated with the increase in comet tail DNA.

CONCLUSION

These results indicate the presence of significant lipid peroxidation, protein oxidation and oxidative DNA damage in patients with diabetes. Perturbation of glucose homoeostasis was associated with an increase in oxidants and a concomitant decrease of antioxidant enzymes in the type 2 diabetic patients' blood. The present study suggests that the status of oxidant-antioxidant imbalance may be one of the mechanisms leading to the DNA damage detected in the lymphocytes of type 2 diabetic patients.

Superoxide dismutase activity in gingiva in type-2 diabetes mellitus patients with chronic periodontitis

OBJECTIVE

Antioxidant defence reduces in diabetes mellitus (DM) and periodontitis. This study investigates antioxidant enzyme; superoxide dismutase (SOD) activity in gingiva and blood glucose and lipid levels in type-2 DM patients and systemically healthy individuals with chronic periodontitis (CP).

MATERIALS AND METHODS

Periodontal parameters, blood glycated-haemoglobin (HbA1c), glucose and lipid levels, and gingival-SOD activities (spectrophotometric assay) were measured in 17 DM patients with CP (DMCP), 17 systemically healthy CP patients, 18 periodontally healthy DM patients (DMPH), and 17 healthy controls (PH).

RESULTS

Periodontal parameters were higher in periodontitis groups than the controls (p<0.05), while there was no difference between the periodontitis groups and between the control groups. HbA1c, glucose, and triglyceride levels were higher in diabetic groups than the non-diabetic groups (p<0.05). Low-density lipoprotein (LDL), very-LDL and cholesterol values of the DMCP group did not significantly differ from the CP group. No differences existed between diabetic patients with and without periodontitis in HbA1c, glucose, and lipid levels and the same was true for non-diabetic patients with and without periodontitis. Gingival-SOD activity was lower in periodontitis groups than the matched control groups (p<0.05). DMPH group had the highest and CP group had the lowest SOD levels. There were correlations between periodontal parameters, gingival-SOD activity, HbA1c, glucose and high-density lipoprotein (HDL) levels.

CONCLUSION

The results suggest that gingival-SOD activity increases in diabetes and decreases in periodontitis and relations may exist between gingival-SOD activity, periodontal status, HbA1c, glucose and HDL levels. The higher gingival-SOD activity in diabetes may be attributed to an adaptive mechanism in the tissue.

Mechanisms and outcomes of drug- and toxicant-induced liver toxicity in diabetes

Increase dincidences of hepatotoxicity have been observed in diabetic patients receiving drug therapies. Neither the mechanisms nor the predisposing factors underlying hepatotoxicity in diabetics are clearly understood. Animal studies designed to examine the mechanisms of diabetes-modulated hepatotoxicity have traditionally focused only on bioactivation/detoxification of drugs and toxicants. It is becoming clear that once injury is initiated, additional events determine the final outcome of liver injury. Foremost among them are two leading mechanisms: first, biochemical mechanisms that lead to progression or regression of injury; and second, whether or not timely and adequate liver tissue repair occurs to mitigate injury and restore liver function. The liver has a remarkable ability to repair and restore its structure and function after physical or chemical-induced damage. The dynamic interaction between biotransformation-based liver injury and compensatory tissue repair plays a pivotal role in determining the ultimate outcome of hepatotoxicity initiated by drugs or toxicants. In this review, mechanisms underlying altered hepatotoxicity in diabetes with emphasis on both altered bioactivation and liver tissue repair are discussed. Animal models of both marked sensitivity (diabetic rats) and equally marked protection (diabetic mice) from drug-induced hepatotoxicity are described. These examples represent a remarkable species difference. Availability of the rodent diabetic models offers a unique opportunity to uncover mechanisms of clinical interest in averting human diabetic sensitivity to drug-induced hepatotoxicities. While the rat diabetic models appear to be suitable, the diabetic mouse models might not be suitable in preclinical testing for potential hepatotoxic effects of drugs or toxicants, because regardless of type 1 or type2 diabetes, mice are resistant to acute drug-or toxicant-induced toxicities.

Oxidant/antioxidant status in men with Behçet’s disease

Behçet's disease (BD) is a chronic, progressive disorder that affects many systems of the body including the eye. The aim of this study was to assess whether the increase in oxidative stress in the affected tissues is reflected by lipid peroxidation and to check for alterations in antioxidants and antioxidant enzyme activities in patients with BD. Erythrocyte antioxidant potential (AOP), glutathione (GSH) and GSH-dependent enzymes (glutathione peroxidase (GSH-Px), glutathione reductase (GRD) and glutathione-S-transferase (GST), catalase (CAT), Cu-Zn superoxide dismutase (Cu-Zn SOD) activities, malondialdehyde (MDA) and some trace elements (zinc, Zn; copper, Cu; manganese, Mn) levels in men with BD. Erythrocyte CAT, GSH-Px activities, MDA, GSH, AOP and serum Zn values were significantly lower in patients with BD than in the control group. However, erythrocyte Cu-Zn SOD, GRD activities, erythrocyte sedimentation rate (ESR), serum C-reactive protein (CRP) and Cu values were significantly higher in patients with BD than in the control group, but GST activity and serum Mn values were unchanged. In conclusion, our results confirm the presence of oxidative stress in patients with BD and suggest that the severity of BD may arise from impaired antioxidant mechanisms. Therapy with antioxidants may lead to the increase in the antioxidant defense system and thus improvement in clinical symptoms.

Therapeutic efficacy of ozone in patients with diabetic foot

Oxidative stress is suggested to have an important role in the development of complications in diabetes. Because ozone therapy can activate the antioxidant system, influencing the level of glycemia and some markers of endothelial cell damage, the aim of this study was to investigate the therapeutic efficacy of ozone in the treatment of patients with type 2 diabetes and diabetic feet and to compare ozone with antibiotic therapy. A randomized controlled clinical trial was performed with 101 patients divided into two groups: one (n = 52) treated with ozone (local and rectal insufflation of the gas) and the other (n = 49) treated with topical and systemic antibiotics. The efficacy of the treatments was evaluated by comparing the glycemic index, the area and perimeter of the lesions and biochemical markers of oxidative stress and endothelial damage in both groups after 20 days of treatment. Ozone treatment improved glycemic control, prevented oxidative stress, normalized levels of organic peroxides, and activated superoxide dismutase. The pharmacodynamic effect of ozone in the treatment of patients with neuroinfectious diabetic foot can be ascribed to the possibility of it being a superoxide scavenger. Superoxide is considered a link between the four metabolic routes associated with diabetes pathology and its complications. Furthermore, the healing of the lesions improved, resulting in fewer amputations than in control group. There were no side effects. These results show that medical ozone treatment could be an alternative therapy in the treatment of diabetes and its complications.

Modification of cardiac oxidative stress in alloxan-induced diabetic rabbits with repaglinide treatment

The aim of this study was to analyze the antioxidative effect of repaglinide in the heart of alloxan-induced diabetic rabbits. The activities of superoxide dismutase (Cu,Zn-SOD), catalase (CAT), glutathione peroxidase (GSH-Px), glutathione reductase (GSSG-R), glutathione (GSH), ascorbic acid (AA), products of lipid peroxidation (LPO) and protein carbonyl groups (PCG) were estimated after 4 and 8 weeks of repaglinide treatment (1 mg daily). At significance level p<0.05, in diabetic heart the activities of Cu,Zn-SOD and CAT were elevated as compared to control values (by 60.7% and 55.3% for Cu,Zn-SOD, and by 89.7% and 77.4% for CAT after 4 and 8 weeks, respectively). The level of AA was diminished by 52.5% and 41.5% while GSH-Px and GSSG-R activities were decreased after 4 weeks of experiment (by 11.5% and 14.4%, respectively). GSH level was diminished by 33.2% after 8 weeks. Simultaneously, in diabetic heart the levels of LPO and PCG were elevated as compared to control values (by 51.6% and 111.3% for LPO, and by 72.0% and 132.9% for PCG after 4 and 8 weeks, respectively). In diabetic animals, repaglinide normalized GSH-Px activity and GSH level. It modified the activities of Cu,Zn-SOD, CAT and AA as compared to diabetic non-treated animals. In diabetic-treated rabbits the level of LPO was diminished as compared to diabetic non-treated animals, while the level of PCG was not affected. In the present study, repaglinide did not affect blood glucose and plasma insulin concentrations in diabetic rabbits. Nevertheless, the drug showed some beneficial antioxidative properties in the heart tissue.

Antioxidative and anti-inflammatory effects of repaglinide in plasma of diabetic animals

Oxidative stress, defined as an imbalance between the production of reactive oxygen species (ROS) and antioxidant defense, is considered to be an important pathogenic factor in diabetes mellitus and its complications. In diabetic state, ROS might also be implicated in promoting a state of systemic inflammation. Recently, it was demonstrated that antioxidant therapy could be used to stop the initiation and propagation of this inflammatory response. Repaglinide is a new oral antidiabetic agent with a possible antioxidant activity. Therefore, in the present study, a possible therapeutic value of repaglinide in ameliorating the oxidative and inflammatory processes was tested in diabetic animals. In the study, the levels of total antioxidant status (TAS), ascorbic acid (AA), protein carbonyl groups (PCG) and interleukin-6 (IL-6) were determined in plasma of diabetic rabbits after 4 and 8 weeks of repaglinide treatment (1mg daily). Ex vivo analysis revealed that there were significant differences in these markers between hyperglycemic and control animals (P<0.05). Some of these parameters were ameliorated by repaglinide treatment. In diabetic rabbits treated with repaglinide, protein oxidation was diminished by 17.8% after 8 weeks of experiment. The level of AA in plasma of diabetic treated animals was higher than in non-treated diabetic groups (by 9.4 and 22.6% after 4 and 8 weeks, respectively). In diabetic treated animals, the TAS level was also significantly increased (by 23.6 and 16.7%). However, in diabetic rabbits, repaglinide did not affect the concentration of IL-6.

ANTIDIABETIC EFFECT OF A NEW PEPTIDE FROM SQUALUS MITSUKURII LIVER (S-8300) IN ALLOXAN-DIABETES

1. The purpose of the present study was to evaluate the antidiabetic effect of S-8300 in alloxan diabetic mice. 2. Diabetes was induced by single intravenous injection of alloxan (60 mg/kg bodyweight). 3. The effects of S-8300 on diabetic mice were investigated by observing changes in the glycometabolic index (fasting plasma glucose, glycosylated haemoglobin), the lipometabolic index (triglyceride, cholesterol, free fatty acids), anti-oxidant index (superoxide dismutase, malondialdehyde) and in the degree of injury of beta-cells in the pancreatic islets. 4. A significant decrease in fasting plasma glucose, glycosylated haemoglobin, triglycerides, cholesterol, free fatty acids in the plasma and malondialdehyde in the tissues, as well as a significant increase in the activity of superoxide dismutase, was observed in diabetic mice treated with 10, 3 and 1 mg/kg S-8300. 5. Treatment with S-8300 also attenuated the degree of injury of beta-cells. 6. A comparison was made between the action of S-8300 and 6 U/kg insulin. The effects of S-8300 were similar to those of insulin.

Diabetes mellitus worsens antioxidant status in patients with chronic pancreatitis

BACKGROUND

Patients with chronic pancreatitis (CP) are at high risk of antioxidant deficiencies. Furthermore, this disease can lead to diabetes mellitus (DM) that could exacerbate the severity of oxidative stress. Oxidative stress and the resulting LDL oxidation are a major cause of atherosclerosis.

OBJECTIVE

The objective of the study was to ascertain whether diabetes significantly modifies oxidative status in patients with CP.

DESIGN

CP patients with or without DM were compared with type 1 DM patients and healthy control subjects.

RESULTS

Two-way factorial analyses showed that a decrease in the plasma concentrations of vitamin A, vitamin E, and carotenoids accompanied both CP and DM, and CP was also associated with lower plasma concentrations of selenium and zinc, lower catalase activity, and higher plasma concentrations of copper. The lag phase of LDL oxidation was lower in CP patients with or without DM than in the control subjects, whereas there was no significant difference between type 1 DM patients and control subjects. Multivariate analysis showed that LDL vitamin E (R2 = 0.24, P < 0.0001) and fasting plasma glucose (R2 = 0.32, P < 0.0001) concentrations were the main determinants of the lag phase of LDL oxidation.

CONCLUSIONS

Antioxidant status is altered in CP patients, particularly in those who also have DM. In these patients, a vitamin E deficiency and an elevated plasma glucose concentration were associated with significantly higher LDL oxidizability.

Clinical significance of the physicochemical properties of LDL in type 2 diabetes

Atherosclerosis is the leading cause of death in type 2 diabetes. LDL cholesterol and atherosclerosis are related, both in healthy people and those with diabetes; however, people with diabetes are more prone to atheroma, even though their LDL cholesterol levels are similar to those in their non-diabetic peers. This is because LDL particles are modified in the presence of diabetes to become more atherogenic. These modifications include glycation in response to high plasma glucose levels; oxidative reactions mediated by increased oxidative stress; and transfer of cholesterol ester, which makes the particles smaller and denser. The latter modification is strongly associated with hypertriglyceridaemia. Oxidatively and non-oxidatively modified LDL is involved in plaque formation, and may thus contribute to the accelerated atherosclerosis. This review discusses the techniques currently used to determine the physicochemical properties of LDL, and examines the evidence that modification of these properties plays a role in the accelerated atherosclerosis associated with type 2 diabetes.

Modulation of radiation-induced alteration in the antioxidant status of mice by naringin

The alteration in the antioxidant status and lipid peroxidation was investigated in Swiss albino mice treated with 2 mg/kg b.wt. naringin, a citrus flavoglycoside, before exposure to 0.5, 1, 2, 3, and 4 Gy gamma radiation. Lipid peroxidation, glutathione, glutathione peroxidase, catalase and superoxide dismutase were determined in the liver and small intestine of mice treated or not with naringin at 0.5, 1, 2, 4 and 8 h post-irradiation. Whole-body irradiation of mice caused a dose-dependent elevation in the lipid peroxidation while a dose-dependent depletion was observed for glutathione, glutathione peroxidase, superoxide dismutase and catalase in both liver as well as small intestine. Treatment of mice with 2 mg/kg b. wt. naringin inhibited the radiation-induced elevation in the lipid peroxidation as well as depletion of glutathione, glutathione peroxidase, superoxide dismutase and catalase in liver and small intestine. Radiation-induced lipid peroxidation increased with time, which was greatest at 2 h post-irradiation and declined thereafter in the liver and small intestine. Similarly, a maximum decline in the glutathione glutathione peroxidase, and superoxide dismutase was observed at 1 h, while catalase showed a maximum decline at 2 h post-irradiation. Our study demonstrates that naringin protects mouse liver and intestine against the radiation-induced damage by elevating the antioxidant status and reducing the lipid peroxidation.

Reduction of diabetes-induced oxidative stress by phosphodiesterase inhibitors in rats

Increased oxidative stress has been suggested to be involved in the pathogenesis and progression of diabetic tissue damage. The aim of this study was to investigate the effect of different phosphodiesterase inhibitors on lipid peroxidation and total antioxidant capacity (TAC) of plasma in streptozotocin-induced diabetic rats (Rattus norvegicus). Rats became diabetic by a single administration of streptozotocin (STZ, 45 mg/kg). The effects of 15-days treatment by milrinone, sildenafil, and theophylline as cyclic-AMP and -GMP phosphodiesterase inhibitors (PDEIs) on diabetes-induced oxidative stress were studied. The levels of glucose, malonedialdehyde (MDA) the by product of lipid peroxides, and TAC (FRAP test) were estimated in plasma of control and experimental groups of rats. A significant increase in the levels of plasma glucose, and MDA and a concomitant decrease in the levels of TAC were observed in diabetic rats. These alterations were reverted back to near normal level after the treatment with PDEIs. Treatment of diabetic rats by PDEIs reduced MDA levels and increased TAC in the order of milrinone>sildenafil>theophylline. In conclusion, the present investigation show that PDIS possesses antioxidant activities, which may be attributed to their enhancing effect on cellular cyclic nucleotides contributing to the protection against oxidative stress in streptozotocin-induced diabetes. Exact mechanism of protective actions of cAMP- and cGMP-phosphodiesterase remains to be elucidated by further studies. This finding may suggest a place for PDEIs in maintaining health in diabetes.

Evidence of oxidative stress in full-term healthy infants

We hypothesized that early infancy would be a time of oxidative stress due to the difficulty of adapting to ambient oxygen. Therefore, we measured levels of products of lipid peroxidation (F2-isoprostanes), antioxidant enzyme activity (catalase (CAT) and superoxide dismutase (SOD)), and ability to resist oxidative stress (ferric reducing ability of plasma (FRAP)) in full-term infants (38-42 wk) fed human milk from birth. Seventy-seven infants were followed at 1, 3.5, 6, and 12 mo of age. F2-isoprostanes in plasma declined significantly (p < 0.05) from 1 to 6 mo (160 +/- 43; 90 +/- 33; 41 +/- 27 pg/mL (mean +/- SD)). FRAP values (775 +/- 196, 723 +/- 133, 697 +/- 126, 669 +/- 145 microM) 1, 3.5, 6, and 12, respectively) declined (p = 0.06) from 1 to 3.5 mo and from 3.5 to 6 mo of age. RBC-SOD (2.7 +/- 2, 3.2 +/- 2.8, 2.1 +/- 1.8, 2.5 +/- 1.8 U, 1, 3.5, 6, 12 mo, respectively) declined from 3.5 to 6 mo. RBC-CAT (76 +/- 23, 94 +/- 28, 81 +/- 22, 85 +/- 31 U, 1, 3.5, 6, 12 mo, respectively) also declined between 3.5 and 6 mo, after a significant increase between 1 and 3.5 mo. These data suggest that the human infant is under oxidative stress early in infancy and further study may be warranted to assess the potential benefits of antioxidant supplementation for either the mother or the infant.

The effects of dietary caloric restriction on antioxidant status and lipid peroxidation in mild and severe streptozotocin-induced diabetic rats

BACKGROUND

Dietary caloric restriction (CR) without malnutrition is effective in the control of diabetes mellitus by stabilizing glucose homeostasis and enhancing glycemic control. Mild and severe streptozotocin-induced diabetic and non-diabetic rats were subjected to caloric restriction and ad libitum feeding to evaluate their effects on oxidative stress and lipid profile in the plasma of experimental animals.

METHODS

Mild and severe diabetes were induced in Male Wistar rats by intraperitoneal injection of 35 and 65 mg/kg streptozotocin respectively. The experimental animals were subjected to 40% caloric restriction and ad libitum feeding for 9 weeks.

RESULTS

CR was effective in significantly reducing body weight, blood glucose, HbA IC and TG concentrations (all p < 0.001) in mild diabetic rats and non-significantly improving the plasma HDL-cholesterol concentrations. However, CR did not produce any significant effect on the antioxidant enzyme activities and MDA concentrations in all the groups nor in any of the parameters measured in non-diabetic rats except their overall weight change. There were significant (p < 0.001) decreases in body weight and non-significant fluctuating results in HbA IC and HDL-cholesterol in severe diabetic animals.

CONCLUSIONS

These results demonstrate that caloric restriction is most effective in mild than in non-diabetic or severe diabetic animals.

Effect of the new thiazolidinedione-pioglitazone on the development of oxidative stress in liver and kidney of diabetic rabbits

Impaired homeostasis under diabetic conditions is connected with the increased production of free radicals and deficiency of antioxidative systems. The aim of this study was to analyze the effect of new oral antidiabetic drug-pioglitazone on activity of antioxidant factors and lipid peroxidation in vivo. The liver and kidney of alloxan-induced diabetic rabbits were examined after 4 and 8 weeks of treatment. After 4 weeks of diabetes the superoxide dismutase (Cu,Zn-SOD) activity in the liver was diminished while the catalase (CAT) activity and the level of ascorbic acid (AA) were elevated in comparison with the control group. Pioglitazone treatment during 4 weeks decreased the catalase activity in relation to the control diabetic animals. After 8 weeks of diabetes the CAT activity in the liver was elevated in comparison with the control group. Pioglitazone treatment during 8 weeks decreased the CAT activity and the level of lipid peroxidation products (LPO), and increased the Cu,Zn-SOD activity in relation to control diabetic animals. After 4 weeks of diabetes in the kidney the Cu,Zn-SOD activity and the level of ascorbic acid (AA) were diminished while the CAT activity and the LPO level were elevated in comparison with the control group. Pioglitazone treatment during 4 weeks increased the AA and decreased the LPO levels in relation to non-treated diabetic animals. After 8 weeks of disease the Cu,Zn-SOD activity in the kidney was diminished in comparison with the control group. Pioglitazone during 8 weeks decreased the LPO level in relation to non-treated diabetic animals. This study shows that diabetic animals undergo an important oxidative stress, which is partially corrected by pioglitazone treatment.

PPARgamma activation, by reducing oxidative stress, increases NO bioavailability in coronary arterioles of mice with Type 2 diabetes

We tested the hypothesis that short-term treatment of mice with Type 2 diabetes mellitus (DM) with rosiglitazone (ROSI), an agonist of peroxisome proliferator-activated receptor-gamma, ameliorates the impaired coronary arteriolar dilation by reducing oxidative stress via a mechanism unrelated to its effect on hyperglycemia and hyperinsulinemia. Control and Type 2 DM (db/db) mice were treated with ROSI (3 mg x kg(-1) x day(-1)) for 7 days, which did not significantly affect their serum concentration of glucose and insulin. Compared with controls, in db/db mice serum levels of 8-isoprostane and dihydroethydine-detectable superoxide production in carotid arteries were significantly elevated and were reduced by ROSI treatment. In coronary arterioles (diameter, approximately 80 microm) isolated from db/db mice, the reduced dilations to ACh, the nitric oxide (NO) donor NONOate, and increases in flow were significantly augmented either by in vitro administration of apocynin, an inhibitor of NAD(P)H-oxidase, or by in vivo ROSI treatment, responses that were then significantly reduced by the NO synthase inhibitor N(omega)-nitro-L-arginine methyl ester. In aortas of db/db mice, activity of SOD and catalase was reduced, whereas NAD(P)H oxidase activity was enhanced. ROSI treatment enhanced catalase and reduced NAD(P)H oxidase activity but did not affect the activity of SOD. These findings suggest that ROSI treatment enhances NO mediation of coronary arteriolar dilations due to the reduction of vascular NAD(P)H oxidase-derived superoxide production and enhancement of catalase activity. Thus, in addition to the previously revealed beneficial metabolic effects, the antioxidant action of rosiglitazone may protect coronary arteriolar function in Type 2 DM.

Superoxide-NO interaction decreases flow- and agonist-induced dilations of coronary arterioles in Type 2 diabetes mellitus

Type 2 diabetes mellitus (T2-DM) markedly increases the incidence of ischemic heart disease (IHD) and, consequently, mortality. However, the underlying mechanisms leading to IHD in T2-DM are not completely understood. We hypothesized that in T2-DM the regulation of coronary microvascular resistance by local mechanisms is altered. Thus, in coronary arterioles (diameter: approximately 80 microm) isolated from male mice with T2-DM (C57BL/KsJ-db/db) and control littermates, responses to changes in intraluminal pressure, flow, and agonists with known mechanisms of action were studied. Increases in pressure (from 20 to 120 mmHg) resulted in similar myogenic responses of coronary arterioles of control and db/db mice, whereas dilations in response to cumulative concentrations of ACh and the nitric oxide (NO) donor NONOate were significantly decreased compared with those of control vessels. On the other hand, responses to adenosine were not different between vessels of control and db/db mice. Increases in flow (0-20 microl/min) resulted in dilations of control vessels (maximum: 38 +/- 4%) that were inhibited by the NO synthase inhibitor N omega-nitro-L-arginine methyl ester (L-NAME). In contrast, arterioles of db/db mice exhibited greatly reduced dilations to flow (maximum: 4 +/- 6%) that were unaffected by L-NAME. In carotid arteries of db/db mice, superoxide dismutase (SOD)-sensitive, enhanced superoxide production was detected by dihydroethydine staining and lucigenin enhanced chemiluminescence. Correspondingly, intraluminal administration of SOD significantly augmented flow-, ACh-, and NONOate-induced dilations of diabetic arterioles, and then flow- and ACh-induced responses could be inhibited by L-NAME. Collectively, these findings suggest that in T2-DM, due to an enhanced superoxide production, NO mediation of agonist- and flow-induced dilations of coronary arterioles is reduced. This alteration in the regulation of coronary microvascular resistance may contribute to the development of IHD in T2-DM.

Antioxidant status and lipid peroxidation in type II diabetes mellitus

Diabetes Mellitus (DM), a state of chronic hyperglycaemia, is a common disease affecting over 124 million individuals worldwide. In this study, erythrocyte glutathione levels, lipid peroxidation, superoxide dismutase, catalase, and glutathione peroxidase and some extracellular antioxidant protein levels of patients with type II diabetes mellitus and healthy controls were investigated. Thirty-eight patients (21 males; with age of mean +/- SD, 53.1+/-9.7 years) and 18 clinically healthy subjects (10 males; with age of mean +/- SD, 49.3+/-15.2 years) were included in the study. Levels of erythrocyte lipid peroxidation, serum ceruloplasmin and glucose levels, HbA1C levels, and erythrocyte catalase activity were significantly increased, whereas serum albumin and transferrin levels, erythrocyte glutathione levels, and glutathione peroxidase activity were significantly decreased compared to those of controls. There was no significant difference in superoxide dismutase activity compared to controls. The results suggest that the antioxidant deficiency and excessive peroxide-mediated damage may appear in non-insulin dependent diabetes mellitus.

The effect of melatonin against oxidative damage during total-body irradiation in rats

Melatonin has been reported to participate in the regulation of a number of important physiological and pathological processes. Melatonin, which is a powerful endogenous antioxidant, may play a role in the prevention of oxidative damage. The aim of this study was to investigate the effect of pretreatment with melatonin (5 mg kg(-1) and 10 mg kg(-1)) on gamma-radiation-induced oxidative damage in plasma and erythrocytes after total-body irradiation with a single dose of 5 Gy. Total-body irradiation resulted in a significant increase in plasma and erythrocyte MDA levels. Melatonin alone increased the levels of SOD and GSH-Px. Erythrocyte and plasma MDA levels in irradiated rats that were pretreated with melatonin (5 or 10 mg kg(-1)) were significantly lower than those in rats that were not pretreated. There was no significant difference between the effects of 5 and 10 mg kg(-1) on plasma MDA activities and CAT activities. However, erythrocyte MDA levels showed a dose-dependent decrease, while GSH-Px activities increased with dose. Our study suggests that melatonin administered prior to irradiation may protect against the damage produced by radiation by the up-regulation of antioxidant enzymes and by scavenging free radicals generated by ionizing radiation.

DNA damage and antioxidant defense in peripheral leukocytes of patients with Type I diabetes mellitus

We determined relationship among DNA damage, nitric oxide (NO) and antioxidant defense in leukocytes of patients with Type 1 DM. DNA damage was evaluated as strand breakage and formamidopyrimidine DNA glycosylase (Fpg)-sensitive sites by the comet assay in DNA from leukocytes of the subjects. Nitrite level, as a product of NO, superoxide dismutase (SOD) activity and glutathione peroxidase (G-Px) activity of the leukocytes were measured by spectrophotometric kits. Serum glucose level and glycosylated haemoglobin (HbA(1c)) were higher in the patients, as expected. Differences in measured parameters between controls and patients were assessed in men and women separately. There was no significant difference between patient and control groups in neither men nor women for nitrite level. Strand breakage and Fpg-sensitive sites were found to be increased, SOD and G-Px activities of the leukocytes were found to be decreased in both men and women of patient group as compared to their respective controls. Significant correlations were determined between strand breakage and HbA(1c) (r = 0.37, P<0.05); Fpg-sensitive sites and HbA(1c) (r = 0.59, P<0.01); Fpg-sensitive sites and glucose (r = 0.45, P<0.02); Fpg-sensitive sites and SOD (r = -0.48, P<0.02); HbA(1c) and SOD (r = -0.50, P<0.02). In conclusion, impaired antioxidant defense in leukocytes of patients with Type 1 DM may be one of the responsible mechanisms for increased DNA damage in those patients.

Effects of erythropoietin and pentoxifylline on the oxidant and antioxidant systems in the experimental short bowel syndrome

In this study, we investigated the effects of erythropoietin (Epo), and pentoxifylline (Ptx) on the oxidant and antioxidant systems in the experimental short bowel syndrome. Spraque-Dawley rats were divided into four groups and all animals underwent 75% small bowel resection. Group E was treated with 500 IU kg(- 1) Epo subcutaneously (s.c.), group P with 50 mg kg(- 1) day(- 1) s.c. Ptx and group E+P with 500 IU kg(- 1) s.c. Epo plus 50 mg kg(- 1) day(- 1) s.c. Ptx for a period of 28 days. In group C, which is the control group, no drug treatment was given. At the end of 28 days the experimented rats were killed and ileum samples excised for biochemical and histopathological testing. Malondialdehyde (MDA), superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) levels were determined in ileum homogenates. When compared to group C, the MDA and GSH-Px levels were significantly decreased (p < 0.05), but SOD activity was not changed (p > 0.05) in groups P and E+P, whereas both MDA and SOD and also GSH-Px activities were not changed significantly in group E (p > 0.05). The average villous length, crypt depth, muscular thickness and mucosal length were measured in all groups. The average crypt depth and mucosal length were statistically higher in the group P than group C (p < 0.001, p < 0.01, respectively). In addition, the crypt depth was statistically higher in both E and E+P groups as compared to group C (p < 0.001, p < 0.01, respectively). Therefore, our study indicates that Ptx may be more effective than Epo in reducing lipid peroxidation. Moreover, we considered that Ptx may give this protective effect by inhibiting the free oxygen radicals to a greater extent than developing the antioxidant capacity.

Ascorbic acid supplementation restores defective leukocyte-endothelial interaction in alloxan-diabetic rats

BACKGROUND

Defective leukocyte-endothelial interactions are observed in experimental diabetes and may reduce the capacity to mount an adequate inflammatory response. The present study investigated the effect of ascorbic acid, an inhibitor of free radical and glycated protein formation as well as an aldose reductase inhibitor, on leukocyte-endothelial interaction in alloxan-diabetic rats.

METHODS

Rats were rendered diabetic by alloxan injection (40 mg/kg; iv). After 30 days, diabetic and nondiabetic controls were supplemented for 12 days with ascorbic acid (50 or 200 mg/kg/day) or received saline by gavage. The number of rollers, stickers after zymosan-activated plasma (10%) or leukotriene B(4) (1 microM) applied topically, and migrated cells after local injection of carrageenan (100 microg) were determined in the venules of the internal spermatic fascia by intravital microscopy. Erythrocyte velocity and wall shear rate were determined as well. Reactive oxygen species formation by endothelial cells was measured in vivo by the same technique. Immunocytochemistry for ICAM-1 detection on the endothelium of the venules of the internal spermatic fascia was carried out in cross sections of the whole testis of the animals.

RESULTS

The reduced number of rollers, stickers and migrated cells, as well as the higher production of reactive oxygen species by endothelial cells in diabetic rats was corrected by ascorbic acid supplementation. The low immunoreactivity for ICAM-1 in the venules of diabetic rats was improved by ascorbic acid supplementation. Ascorbic acid supplementation did not interfere with erythrocyte velocity or wall shear stress. Ascorbic acid administered to control rats did not alter the parameters studied above.

CONCLUSION

We conclude that ascorbic acid improves leukocyte-endothelial interaction in diabetic rats at least in part by restoring the expression of ICAM-1 in the venules of diabetic rats.

Antioxidant effects of Gongronema latifolium in hepatocytes of rat models of non-insulin dependent diabetes mellitus

Gongronema latifolium is a rainforest plant, which has been traditionally used in the South Eastern part of Nigeria for the management of diabetes. The effects of oral administration of aqueous and ethanolic G. latifolium leaf extracts for 2 weeks on streptozotocin-induced diabetic rats were investigated. Both extracts were shown to significantly increase the activity of superoxide dismutase and the level of reduced glutathione. The aqueous extract further increased the activity of glutathione reductase while the ethanolic extract caused a significant increase in the activity of glutathione peroxidase and glucose-6-phosphate dehydrogenase and a significant decrease in lipid peroxidation. These results suggest that the extracts from G. latifolium leaves could exert their antidiabetic activities through their antioxidant properties.

Glycemic index in chronic disease: a review

AIM

The intent of this review is to critically analyze the scientific evidence on the role of the glycemic index in chronic Western disease and to discuss the utility of the glycemic index in the prevention and management of these disease states.

BACKGROUND

The glycemic index ranks foods based on their postprandial blood glucose response. Hyperinsulinemia and insulin resistance, as well as their determinants (eg high energy intake, obesity, lack of physical activity) have been implicated in the etiology of diabetes, coronary heart disease and cancer. Recently, among dietary factors, carbohydrates have attracted much attention as a significant culprit, however, different types of carbohydrate produce varying glycemic and insulinemic responses. Low glycemic index foods, characterized by slowly absorbed carbohydrates, have been shown in some studies to produce beneficial effects on glucose control, hyperinsulinemia, insulin resistance, blood lipids and satiety.

METHOD

Studies on the short and long-term metabolic effects of diets with different glycemic indices will be presented and discussed. The review will focus primarily on clinical and epidemiological data, and will briefly discuss in vitro and animal studies related to possible mechanisms by which the glycemic index may influence chronic disease.

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.

The effects of some antioxidant vitamin- and trace element-supplemented diets on activities of SOD, CAT, GSH-Px and LPO levels in chicken tissues

The effect of diets containing antioxidant vitamins and trace elements on chicken tissue activities of SOD, CAT, GSH-Px and of LPO levels was investigated. Chickens, 45 weeks of age were divided into six groups: control group, Cu group (13.2 mg Cu kg(-1) diet); Se group (0.07 mg Se kg(-l) diet); vitamin E group (70 mg DL-alpha-tocopherol acetate kg(-1) diet) and a constant level vitamin C, 200 mg kg(-1) diet); vitamin A group (240 mg retinol acetate kg(-1) diet) and vitamin C group (500 mg ascorbic acid kg(-1) diet). Significant variation of these antioxidant enzyme activities and LPO levels according to gender was demonstrated statistically. In the Cu group, CuZnSOD activity in the liver, erythrocyte, kidney and heart significantly increased by 75, 40, 12, 12% respectively (P<0.05). MnSOD activity in the heart, liver, kidney and brain of the vitamin C and in the heart of Cu group were found to be increased by approximately 15%, while in liver tissue of the Cu group it was reduced by 19% (P<0.05). GSH-Px activities in the Se, vitamin E and C groups were significantly increased, conversely LPO levels decreased (P<0.001). CAT activities in the liver and heart of the vitamin C group were significantly decreased (by 32%), but in kidney tissue only that of the Cu group was increased from 30.2 +/- 4.767 to 144.49 +/- 6.93 U mg(-1) P<0.001. The resistance to stress of the vitamin E and C groups, which had significantly increased activities of antioxidant enzymes and decreased lipid peroxide levels, were determined in 60% moisture medium at 45 degrees C.

The effects of impaired trace element status on polymorphonuclear leukocyte activation in the development of vascular complications in type 2 diabetes mellitus

Impaired trace element metabolism may be involved in some of the metabolic dysfunctions, and contribute to the development of vascular complications in diabetic patients. In order to investigate the relationships among diabetes mellitus, trace element status, leukocyte activation and vascular complications, 55 type 2 diabetic patients (34 with vascular complications and 21 without vascular complications) and 50 non-diabetic control subjects were studied. The mean leukocyte count (p<0.001), polymorphonuclear elastase (p<0.001), erythrocyte malondialdehyde (p<0.001), and glycated haemoglobin (p<0.001) levels, and copper/ zinc ratio (p<0.001) were found to be higher in diabetic patients than in the control group, but serum zinc levels (p<0.001) and erythrocyte superoxide dismutase activities (p<0.001) were lower, and serum copper levels showed no differences. In patients with vascular complications, the mean leukocyte count (p<0.05), zinc (p<0.05), polymorphonuclear elastase (p<0.05), erythrocyte malondialdehyde (p<0.001) and glycated haemoglobin (p<0.05) levels, and copper/zinc ratio (p<0.001) were significantly different from those patients without complications. Closer correlations between the copper/zinc ratio and polymorphonuclear elastase (r=0.82, p<0.01), erythrocyte malondialdehyde (r=0.46, p<0.05) or erythrocyte superoxide dismutase (r= -0.85, p<0.01) were found in patients with vascular complications compared to those without, and all of those showed significant relationships with poor glycaemic metabolic control. We conclude that zinc deficiency may provoke polymorphonuclear leukocyte activation, and contributes to the development of vascular complications in type 2 diabetic patients. Furthermore, copper/zinc ratio and polymorphonuclear elastase may be used as important markers to evaluate the presence of vascular complications.

Oral glucose loading acutely attenuates endothelium-dependent vasodilation in healthy adults without diabetes: an effect prevented by vitamins C and E

OBJECTIVES

The goal of this study was to determine whether postprandial hyperglycemia, induced by oral glucose loading, attenuates endothelial function in healthy subjects without diabetes and whether coadministration of vitamins C and E could prevent these postprandial changes.

BACKGROUND

Epidemiologic evidence suggests that postprandial hyperglycemia, below diabetic levels, is a risk factor for cardiovascular disease. Postprandial hyperglycemia may promote atherosclerosis through endothelial dysfunction and oxidative stress.

METHODS

We evaluated the acute effects of oral glucose loading (75 g), alone and with vitamins C (2 g) and E (800 IU), on endothelium-dependent flow-mediated dilation (FMD) of the brachial artery, in a randomized, double-blind, placebo-controlled, crossover study of 10 healthy volunteers. Changes in the levels of markers of oxidative stress (plasma malondialdehyde and erythrocyte glutathione, glutathione peroxidase and superoxide dismutase) were also assessed.

RESULTS

Increases in plasma glucose and insulin after glucose loading were unaffected by vitamin coadministration. With glucose loading alone, FMD fell from 6.5+/-2.2 at baseline to 5.4+/-1.7, 3.7+/-2.1*, 4.1+/-3.5* and 5.7+/-1.9% at 1, 2, 3 and 4 h (*p < 0.05 vs. 0 h). In contrast, FMD did not change significantly after glucose plus vitamins (6.4+/-1.3, 7.6+/-1.8, 7.9+/-2.7, 6.9+/-2.3, 6.9+/-1.9% at 0, 1, 2, 3 and 4 h). By two-way repeated measures analysis of variance we found a significant interaction between vitamin treatment and time (p = 0.0003), indicating that vitamins prevented the glucose-induced attenuation of FMD. Oxidative stress markers did not significantly change with glucose loading alone or with vitamins.

CONCLUSIONS

Oral glucose loading causes an acute, transient decrease of FMD in healthy subjects without diabetes, which is prevented by vitamins C and E.