ascorbic-acid and Diabetic-Nephropathies

The present study was designed to assess the effect of magnesium plus zinc, vitamins C plus E, and a combination of these micronutrients on nephropathy indexes in type 2 diabetic patients.. In a randomized, double-blind, placebo-controlled clinical trial, 69 type 2 diabetic patients were randomly divided into four groups, each group receiving one of the following daily supplement for 3 months: group M (n = 16), 200 mg Mg and 30 mg Zn; group V (n = 18), 200 mg vitamin C and 100 IU vitamin E; group MV (n = 17), minerals plus vitamins; and group P (n = 18), placebo. Urinary albumin excretion and N-acetyl-beta-d-glucosaminidase activity (NAG) in urine were determined at the beginning and at the end of the trial. Treatment effects were analyzed by general linear modeling.. Results indicate that after 3 months of supplementation, levels of urinary albumin excretion decreased in the V and MV groups (P = 0.034 and P = 0.005, respectively). Urinary NAG activity did not significantly change in any treatment groups. Levels of systolic, diastolic, and mean blood pressure significantly decreased in the MV group (P = 0.008, P = 0.017, and P = 0.009, respectively). Also, combination of vitamin and mineral supplementation had significant effects in decreasing fasting serum glucose (P = 0.035) and malondialdehyde concentrations (P = 0.004) and in increasing HDL cholesterol and apolipoprotein A1 levels (P = 0.019). There was no significant change in the levels of these parameters in the other three groups.. In conclusion, the results of the present study provide evidence for the effects of vitamins C and E and also combination of magnesium, zinc, and vitamins C and E supplementation on improvement of glomerular but not tubular renal function in type 2 diabetic patients.

Topics: Adult; Aged; Albuminuria; Ascorbic Acid; Diabetes Mellitus, Type 2; Diabetic Nephropathies; Drug Therapy, Combination; Female; Humans; Kidney Glomerulus; Kidney Tubules; Magnesium; Male; Middle Aged; Treatment Outcome; Vitamin E; Vitamins; Zinc

The hypoglycemic drug, troglitazone (TGZ) has antioxidant activity. Superoxide dismutase (SOD) removes superoxide produced by cells. We measured the response of SOD-like activity (deltaSOD) to ascorbic acid (AA) or TGZ using electron spin resonance at various glucose concentrations in polymorphonuclear leukocytes from 18 type 2 diabetic patients and 18 healthy controls. In control and diabetic subjects, ASOD in response to AA was dose-dependent (maximal effect at 100 ng/ml). Maximal response occurred 2 min after AA addition (50 ng/ml). In cells from diabetic patients, ASOD with 25 ng/ml AA was significantly less than for healthy controls. The deltaSOD with AA changed little at glucose concentration from 0 to 200 mg/dl. In patient and control cells, higher glucose concentrations (400 to 800 mg/dl) reduced ASOD with AA. Response patterns with TGZ resembled those with AA. deltaSOD with AA correlated positively with glycosylated hemoglobin A1c.. The present data suggest that an amerioration of blood glucose on high levels in diabetic patients plays an important role in an antioxidant efficacy of TGZ and AA on leukocytes in patients.

Topics: Aged; Albuminuria; Antioxidants; Ascorbic Acid; Chromans; Diabetes Mellitus, Type 2; Diabetic Nephropathies; Diabetic Retinopathy; Dose-Response Relationship, Drug; Electron Spin Resonance Spectroscopy; Female; Glucose; Glycated Hemoglobin; Humans; Hypoglycemic Agents; Leukocytes; Male; Middle Aged; Superoxide Dismutase; Thiazoles; Thiazolidinediones; Troglitazone

The effects of dietary antioxidants on numerous diseases have been widely studied. However, the evidence regarding composite dietary antioxidant index (CDAI) and diabetic kidney disease (DKD) in individuals with diabetes is scarce. This study aimed to investigate the associations of CDAI with DKD and mortality in adults with diabetes mellitus (DM).. This study utilized data from 5676 adult DM participants from the National Health and Nutrition Examination Survey (NHANES) of 2007-2018. The study followed up on death outcomes by linking the data to records from the National Death Index until December 31, 2019. CDAI was evaluated using a well-established method that included six food-sourced antioxidants derived from 24-h dietary recall: selenium, zinc, vitamin A, vitamin C, vitamin E and carotenoids. The regression models were used to estimate the relationships of CDAI with DKD and mortality in diabetic individuals.. The weighted mean CDAI level for the 5676 participants, which represented 31.36 million noninstitutionalized residents of the US, was 0.33. Based on CDAI quartiles, participants were classified into four groups. CDAI levels were significantly associated with age, gender, race, physical activity, estimated glomerular filtration rate and the prevalence of albuminuria, DKD and hyperuricemia. DKD occurred in 36.44% of diabetic participants, and higher CDAI levels were independently associated with a lower risk of DKD (OR 0.74, 95%CI 0.59-0.94, p for trend = 0.004) in diabetic individuals after multivariate adjustment. During a median follow-up of 67 months (38-104 months), a total of 1065 (15.80%) diabetic individuals died from all causes. Diabetic individuals with higher CDAI levels (Q4) demonstrated a lower risk of all-cause mortality (HR 0.67, 95% CI: 0.52-0.86, p for trend = 0.01) after adjusting for age, gender and race.. Maintaining an adequate antioxidant diet, as reflected in higher CDAI levels, may lower the risk of DKD and mortality in diabetic individuals. These findings offer a promising approach to managing diabetes and highlight the potential of food-based antioxidants as a preventative measure. Further research is warranted to explore the underlying mechanism linking dietary antioxidants and DKD and mortality in diabetic individuals.

Topics: Adult; Antioxidants; Ascorbic Acid; Diabetes Mellitus, Type 2; Diabetic Nephropathies; Humans; Nutrition Surveys; Vitamins

Diabetes is associated with low plasma vitamin C concentrations.. We investigated the contribution of dysregulated vitamin C renal physiology, its prevalence, and associated clinical characteristics.. An essential prerequisite was determination of normal vitamin C renal threshold, the plasma concentration at which vitamin C first appears in urine. Using data from 17 healthy participants who underwent vitamin C depletion-repletion studies with a vitamin C dose range of 15-1250 mg daily, renal threshold was estimated using physiology-based pharmacokinetics modeling. Applying renal threshold 95% CIs, we estimated the minimal elimination threshold, the plasma concentration below which no vitamin C was expected in urine of healthy people. Renal leak was defined as abnormal presence of vitamin C in urine with plasma concentrations below the minimal elimination threshold. Criteria were tested in a cross-sectional cohort study of individuals with diabetes (82) and nondiabetic controls (80) using matched plasma and urine samples.. Vitamin C renal thresholds in healthy men and women were [mean (SD)] 48.5 (5.2) µM and 58.3 (7.5) µM, respectively. Compared with nondiabetic controls, participants with diabetes had significantly higher prevalence of vitamin C renal leak (9% compared with 33%; OR: 5.07; 95% CI: 1.97, 14.83; P < 0.001) and 30% lower mean plasma vitamin C concentrations (53.1 µM compared with 40.9 µM, P < 0.001). Fasting plasma glucose, glycosylated hemoglobin A1c, BMI, micro/macrovascular complications, and protein/creatinine ratio were predictive of vitamin C renal leak.. Increased prevalence of vitamin C renal leak in diabetes is associated with reduced plasma vitamin C concentrations. Glycemic control, microvascular complications, obesity, and proteinuria are predictive of renal leak.

Topics: Adult; Ascorbic Acid; Cross-Sectional Studies; Diabetes Mellitus; Diabetes Mellitus, Type 2; Diabetic Nephropathies; Female; Glycated Hemoglobin; Humans; Male; Middle Aged; Prevalence

Epidemiological studies show that 5-40 % of type 2 diabetes (T2DM) patients have diabetic nephropathy, and oxidative stress is one of several underlying mechanisms. We investigated associations between oxidative stress markers and severity of diabetic nephropathy.. Fifty-nine T2DM patients from the endocrinology outpatient department were included, and their levels of oxidative stress markers were measured. Three groups were determined by their urine albumin-to-creatinine ratio (UACR): group A (UACR < 30 mg/g, n = 22); group B (30 ≤ UACR < 300 mg/g, n = 22); and group C (UACR ≥ 300 mg/g, n = 15).. Vitamin C levels correlated negatively and moderately with serum creatinine (γ = -0.459, p < 0.001), urine albumin (γ. Our results identified several oxidative stress markers that may be clinically important in diabetic nephropathy. Studies with larger sample sizes should be undertaken to confirm these findings.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Aged; Albuminuria; Antioxidants; Ascorbic Acid; Biomarkers; Creatinine; Deoxyguanosine; Diabetes Mellitus, Type 2; Diabetic Nephropathies; Female; Glomerular Filtration Rate; Humans; Male; Middle Aged; Oxidative Stress; Predictive Value of Tests; Prognosis; Prospective Studies; Severity of Illness Index

The aim of this article is to investigate the effects of Aminoguanidine and vitamin C (VitC) on type IV collagen in diabetic nephropathy rats. Diabetic nephropathy rats were induced by intraperitoneal injection of STZ. Rats were randomly divided into five groups: normal control group (n = 10), diabetes group (n = 10), aminoguanidine group (n = 10), VitC group (n = 10), aminoguanidine and VitC group (n = 10). After 16 weeks, the general conditions, blood gloucose, glycosylated hemoglobin, blood urea nitrogen, serum creatinine, serum type IV collagen, urinary albumin excretion rate, and creatinine clearance rate were detected, type IV collagen protein was determined by immunohistochemical analysis as well as the expression of collagen type IVα1 mRNA were determined by in situ hybridization analysis in the kidneys of each group. The results were (1) diabetes mellitus and renal lesions occurred in the diabetes group, aminoguanidine group, VitC group, VitC and aminoguanidine group; (2) aminoguanidine and VitC improved the general conditions of diabetic nephropathy rats, decreased blood urea nitrogen, serum creatinine, and urinary albumin excretion rate as well as increased creatinine clearance rate. The expressions of collagen type IV were significantly down-regulated in treatment groups in contrast to the diabetes group. Aminoguanidine and VitC protect renal lesions in diabetic nephropathy, respectively, by inhibiting expression of type IV collagen, while aminoguanidine and VitC have a synergistic effect on them.

Topics: Animals; Ascorbic Acid; Collagen Type IV; Diabetes Mellitus, Experimental; Diabetic Nephropathies; Drug Synergism; Glycated Hemoglobin; Guanidines; Immunohistochemistry; Kidney; Male; Rats; Rats, Sprague-Dawley; RNA, Messenger

Malakoplakia is an inflammatory granulomatous disease induced by defective phagocytic activity of macrophage. Malakoplakia is histologically characterized by the presence of Michaelis-Gutmann bodies in macrophages. Although not uncommon in the genito-urinary tract, isolated malakoplakia of the kidney is rarely found. Its main clinical presentation associates acute renal failure and acute pyelonephritis. The clue for diagnosis of renal malakoplakia is based on renal biopsy showing Michaelis-Gutmann bodies. Establishing the diagnosis of renal malakoplakia is essential as it determines the choice of antibiotics and duration of treatment. Prognosis remains poor, leading frequently to chronic renal failure. In this paper, we report four cases of renal malakoplakia and discuss clinical presentation, biological and pathological features, treatment and prognosis of this disease.

Topics: Aged; Anti-Bacterial Agents; Ascorbic Acid; Biopsy; Diabetic Nephropathies; Drug Therapy, Combination; Fatal Outcome; Female; Glucocorticoids; Humans; Kidney Diseases; Liver Cirrhosis; Macrophages; Malacoplakia; Male; Middle Aged; Renal Dialysis; Renal Insufficiency; Risk Factors; Treatment Outcome; Vitamins

Diabetes induces oxidative stress in aged human and rat, although daily supplementation of vitamins C and E (VCE) can be beneficial to aged diabetic rats by reducing free radical production. The aim of the present study was to evaluate whether dietary VCE supplementation relieves oxidative stress in streptozotocin (STZ)-induced diabetic in aged rats. Thirty aged rats were randomly divided into three groups. The first group was used as a control. The second group was made diabetic using a single dose of intraperitoneal STZ. VCE-supplemented feed was given to aged diabetic rats constituting the third group. On the 21st day of the experiment, blood, lens and kidney samples were taken from all animals. Glutathione peroxidase (GSH-Px) activity in lens and kidney, reduced glutathione (GSH), vitamin E and β-carotene concentrations in kidney were lower in the diabetic group than in the control whereas plasma glucose, urea and creatinine, and kidney and lens peroxidation (LP) levels were higher in the diabetic group than in the control. However, kidney and lens LP levels, and plasma glucose, urea and creatinine values were decreased by VCE supplementation. Lens and kidney GSH-Px activity, kidney GSH, vitamin E and β-carotene concentrations and erythrocyte counts were increased by VCE treatment. Kidney weights, vitamin A, haemoglobin, hematocrit, leukocyte and platelets values were not changed by diabetes and/or VCE supplementation. VCE ameliorated also diabetes-induced histopathological changes in kidney. In conclusion, we observed that VCE supplementation is beneficial towards kidney and lens of aged diabetic rats by modulating oxidative and antioxidant systems.

Topics: Aging; Animals; Ascorbic Acid; Blood Glucose; Diabetes Mellitus, Experimental; Diabetic Nephropathies; Dietary Supplements; Homeostasis; Hypoglycemic Agents; Kidney; Lens Diseases; Lens, Crystalline; Lipid Peroxidation; Male; Oxidative Stress; Rats; Rats, Wistar; Streptozocin; Vitamin E

Some studies have hypothesized the protective role of vitamin C against cardiovascular disorders (CVD) in patients with end-stage renal disease (ESRD). This study was designed to assess plasma vitamin C concentration and its relationship to hemodialysis (HD) patients' morbidity and mortality.. Plasma vitamin C concentrations were assessed in HD patients using spectrophotometry and subjects were prospectively followed for up eighteen months for all-cause mortality. Any association between vitamin C concentration and patients' demographic data, co-morbidities, or the cause of ESRD were investigated using the Chi-square test.. Ninety-one patients with a mean age of 56.7 ± 15.7 years were included in this study. The most frequent cause of ESRD was simultaneous hypertension and diabetes in 30 % of patients, followed by hypertension in 25.6 %, and diabetes in 11.1 %, respectively. About 34 % of patients had CVD as the most prevalent co-morbidity. Forty-nine patients (53.8 %) had low levels of vitamin C concentration. There was a significant relationship between vitamin C insufficiency and presence of any co-morbidity in HD patients (p < 0.05). There was a significant difference in vitamin C concentrations between patients without co-morbidities and those with cardiovascular ones (F[2,88]=3.447, p = 0.036). Twenty-two (24.2 %) patients died over a median duration of 227 days. There was a significant difference in time to death of patients with and without low levels of vitamin C concentration (p = 0.04).. The results showed lower plasma vitamin C levels in HD patients who suffered any co-morbidity and sooner time to death in these patients.

Topics: Adult; Aged; Aged, 80 and over; Ascorbic Acid; Ascorbic Acid Deficiency; Cardiovascular Diseases; Diabetic Nephropathies; Female; Follow-Up Studies; Hospitals, University; Humans; Hypertension; Iran; Kidney Failure, Chronic; Male; Middle Aged; Morbidity; Mortality; Prospective Studies; Renal Dialysis; Survival Analysis; Young Adult

The increase of reactive oxygen species (ROS) in diabetes potentiates the vascular effects of phenylephrine through nitric oxide (NO) impairment, facilitating the development of diabetic nephropathy. We propose that the combination of an antioxidant and L-arginine as diet supplements could prevent the increased vascular response to phenylephrine in diabetic animals.. Changes in the adrenergic system play an important role in the development of vascular complications in the prediabetic condition. The vasoconstrictor effects of phenylephrine are regulated by NO, and the impairment of endothelium-dependent vasodilation in diabetes is associated with ROS.. Diabetes was induced with a low dose (55 mg/kg body weight) of streptozotocin in 7-week-old rats. Diabetic rats were fed with a diet supplement containing a combination of vitamin E, vitamin C, eicosapentaenoic acid, docosahexaenoic acid, and L-arginine, and the effects on phenylephrine-induced renal vascular responses were evaluated.. Phenylephrine increased the renal perfusion pressure of isolated perfused kidneys from diabetic rats compared with nondiabetic rats. This effect was associated with reduced nitrite release as well as reduced plasma tetrahydrobiopterin and increased superoxide anions in the renal tissue. Diet supplementation with a combination of L-arginine and vitamins in diabetic rats partially prevented the generation of superoxide associated with recovery of the renal release of NO and decreased phenylephrine-induced vasoconstrictor effects, compared with untreated diabetic rats. However, the administration of L-arginine or vitamins alone did not affect phenylephrine-induced vasoconstriction. Vitamin treatment alone did decrease superoxide generation.. The protective mechanism of NO on the vasoconstrictor effects of phenylephrine in the kidney is lost during the development of diabetes, probably via the actions of ROS through a decrease in tetrahydrobiopterin, thus contributing to the pathogenesis of diabetic nephropathy. Restoration of this protective NO mechanism can be achieved by simultaneously stimulating NO synthesis and preventing the effects of ROS through the use of L-arginine and a combination of vitamins E and C as diet supplementation.

Topics: Animals; Antioxidants; Arginine; Ascorbic Acid; Biopterins; Diabetes Mellitus, Experimental; Diabetic Nephropathies; Dietary Supplements; Docosahexaenoic Acids; Eicosapentaenoic Acid; Enzyme Inhibitors; Kidney; Male; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Synthase; Phenylephrine; Rats; Rats, Wistar; Reactive Oxygen Species; Superoxides; Vasoconstriction; Vasoconstrictor Agents; Vitamin E

Chromium and cysteine supplementation can improve glucose metabolism in animal studies. This study examined the hypothesis that a cysteinate complex of chromium is significantly beneficial than either of them in lowering blood glucose and vascular inflammation markers in Zucker diabetic fatty (ZDF) rats. Starting at the age of 6 wk, ZDF rats were supplemented orally (daily gavages for 8 more weeks) with saline-placebo (D) or chromium (400 microg Cr/Kg body weight) as chromium dinicocysteinate (CDNC), chromium dinicotinate (CDN) or chromium picolinate (CP) or equimolar L-cysteine (LC, img/Kg body weight), and fed Purina 5008 diet for 8 wk. ZDF rats of 6 wk age before any supplementations and onset of diabetes were considered as baseline. D rats showed elevated levels of fasting blood glucose, HbA(1), CRP, MCP-1, ICAM-1 and oxidative stress (lipid peroxidation) and lower adiponectin and vitamin C, when compared with baseline rats. In comparison to D group, CDNC group had significantly lower blood glucose, HbA(1), CRP, MCP-1, ICAM-1 and lipid peroxidation and increased vitamin C and adiponectin levels. CDN, CP or LC showed significantly less or no effect on these biomarkers. Only CDNC lowered blood creatinine levels in comparison to D. While CDN and CP had no effect, activation of NFkappaB, Akt and glucose transporter-2 levels were decreased, insulin receptor substrate 1 (IRS-1) activation increased in livers of CDNC-rats. CDNC effect on glycemia, NFkappaB, Akt and IRS-1 in liver was significantly greater compared with LC. Blood chromium levels did not differ between Cr-groups. Exogenous vitamin C supplementation significantly inhibited MCP-1 secretion in U937 monocytes cultured in high-glucose-medium. CDNC is a potent hypoglycemic compound with anti-inflammatory activity apparently mediated by elevated blood vitamin C and adiponectin and inhibition of NFkappaB, Akt, and Glut-2 and increased IRS-1 activation in livers of type 2 diabetic rats.

Topics: Adiponectin; Animals; Anti-Inflammatory Agents, Non-Steroidal; Ascorbic Acid; Biomarkers; Cell Line; Chromium; Coordination Complexes; Cysteine; Diabetes Mellitus, Type 2; Diabetic Angiopathies; Diabetic Nephropathies; Dietary Supplements; Humans; Hypoglycemic Agents; Liver; Male; Monocytes; Organometallic Compounds; Oxidative Stress; Random Allocation; Rats; Rats, Zucker; Signal Transduction

The apolipoprotein E (APOE) epsilon2 allele is reported to be associated with greater risk of renal impairment in type 2 diabetes. Relationships among APOE polymorphisms, renal impairment, and biochemical parameters were explored. A prospective study of 405 consenting Chinese type 2 diabetic patients [mean age +/- standard deviation (SD): 59.2 +/- 10.3 years] without advanced complications at entry was conducted. APOE genotyping and measurement of plasma biomarkers of oxidative stress and antioxidants were performed at entry. HbA1C, plasma glucose, lipids, creatinine, urine albumin/creatinine, and blood pressure were measured at entry and at up to 4 years of follow-up. APOE allelic frequencies were in Hardy-Weinberg equilibrium. Odds ratios of albuminuria at entry and/or during follow-up for different APOE groups were not significantly different. The non-epsilon2 (epsilon3/3, epsilon3/4, epsilon4/4) group had significantly greater plasma ascorbate (51.6 +/- 20.1 mumol/L) than the epsilon2 (epsilon2/2, epsilon2/3) group (44.5 +/- 16.2 mumol/L, P = 0.021), but higher plasma ascorbate levels did not seem to decrease the risk of renal impairment in the non-epsilon2 group. Baseline plasma lipid-standardized alpha-tocopherol levels were least in epsilon2 subjects with persistent albuminuria (3.6 +/- 1.1 mumol/mmol of total cholesterol plus triglycerides, P = 0.008) compared with epsilon2 subjects who had no albuminuria at entry or during follow-up (4.5 +/- 0.8 mumol/mmol of total cholesterol plus triglycerides). The APOE epsilon2 allele does not seem to be associated with increased risk of renal impairment in Chinese type 2 diabetic patients. Plasma lipid-standardized alpha-tocopherol may play a role in determining risk of renal dysfunction in type 2 diabetes.

Topics: Adult; Aged; alpha-Tocopherol; Apolipoprotein E2; Ascorbic Acid; Asian People; Cross-Sectional Studies; Diabetes Mellitus, Type 2; Diabetic Nephropathies; Female; Gene Frequency; Genetic Predisposition to Disease; Hong Kong; Humans; Lipids; Male; Middle Aged; Polymorphism, Genetic; Prospective Studies

The present study was performed to investigate the effect of astaxanthin in combination with other antioxidants against oxidative damage in streptozotocin (STZ)-induced diabetic Osteogenic Disorder Shionogi (ODS) rats. Diabetic-ODS rats were divided into five groups: control, astaxanthin, ascorbic acid, alpha-tocopherol, and tocotrienol. Each of the four experimental groups was administered a diet containing astaxanthin (0.1 g/kg), in combination with ascorbic acid (3.0 g/kg), alpha-tocopherol (0.1 g/kg), or tocotrienol (0.1 g/kg) for 20 wk. The effects of astaxanthin with other antioxidants on lipid peroxidation, urinary 8-hydroxy-2-deoxyguanosine (8-OHdG) excretion, serum creatinine (Cr) level, creatinine clearance (Ccr), and urinary protein content were assessed. The serum lipid peroxide levels and chemiluminescent (CL) intensity in the liver of the alpha-tocopherol and tocotrienol groups were significantly reduced in comparison to that of the control group. In the alpha-tocopherol group, urinary 8-OHdG excretion, serum Cr level, Ccr, urinary albumin excretion, and urinary protein concentration were significantly decreased as compared with those in the control group. Additionally, the CL intensity in the kidney of the alpha-tocopherol group was significantly lower, but that of the ascorbic acid group was significantly higher than that in the control group. These results indicate that dietary astaxanthin in combination with alpha-tocopherol has an inhibitory effect on oxidative stress. On the other hand, our study suggests that excessive ascorbic acid intake increases lipid peroxidation in diabetic rats.

Topics: alpha-Tocopherol; Animals; Antioxidants; Ascorbic Acid; Diabetic Nephropathies; Diabetic Neuropathies; Drug Therapy, Combination; Kidney; Liver; Organ Size; Oxidative Stress; Rats; Rats, Inbred Strains; Tocotrienols; Xanthophylls

To investigate the effect and mechanism of ascorbic acid on podocyte, last barrier of glomerular filtration, in diabetic rats.. Diabetic rats induced by streptozotocin injection intraperitoneally were treated by ascorbic acid for 5 weeks. The levels of blood glucose (BG), HbA1c, urinary albumin excretion rate (UAER) and superoxide diamutase (SOD), catalase (CAT) and malondialdehyde (MDA) in renal cortex were measured. The podocyte ultrastructure was observed while the expression of desmin protein, a marker of podocyte injury, was examined.. Compared with control group, BG and HbA1c were increased markedly in diabetic group. The activities of SOD and CAT were decreased and the concentrations of MDA were increased significantly in diabetic renal cortex. There were the increased proteinic expression of desmin, foot process effacement in podocytes and UAER markedly in diabetic rats. Compared with diabetic rats, foot process effacement and the changes of UAER were ameliorated markedly while the activities of SOD were increased, the levels of MDA and proteinic expression of desmin were decreased markedly although BG, HbA1c and the activities of CAT were no significant difference in the diabetic rats by ascorbic acid treatment.. The findings suggest that there are marked injury in podocyte, last barrier of glomerular filtration, in diabetic rats and administration of ascorbic acid can protect podocyte by increasing antioxidative capacity and ameliorating the renal oxidative stress.

Topics: Animals; Ascorbic Acid; Catalase; Desmin; Diabetes Mellitus, Experimental; Diabetic Nephropathies; Male; Oxidative Stress; Podocytes; Random Allocation; Rats; Rats, Wistar; Superoxide Dismutase

Accelerated formation of advanced glycation/lipoxidation and endproducts (AGEs/ALEs) has been implicated in the pathogenesis of various diabetic complications. Several natural and synthetic compounds have been proposed and tested as inhibitors of AGE/ALE formation. We have previously reported the therapeutic effects of several new AGE/ALE inhibitors on the prevention of nephropathy and dyslipidemia in streptozotocin (STZ)-induced diabetic rats. In this study, we investigated the effects of various concentrations of a compound, LR-90, on the progression of renal disease and its effects on AGE and receptor for AGE (RAGE) protein expression on the kidneys of diabetic STZ-rats. Diabetic male Sprague-Dawley rats were treated with or without LR-90 (0, 5, 20, 25, and 50 mg/l of drinking water). After 32 weeks, body weight, glycemic status, renal function, and plasma lipids were measured. Kidney histopathology and AGE/ALE accumulation and RAGE protein expression in tissues were also determined. In vitro studies were also performed to determine the possible mechanism of action of LR-90 in inhibiting AGE formation and AGE-protein cross-linking. LR-90 protected the diabetic kidneys by inhibiting the increase in urinary albumin-to-creatinine ratio and ameliorated hyperlipidemia in diabetic rats in a concentration-dependent fashion without any effects on hyperglycemia. LR-90 treatment also reduced kidney AGE/ALE accumulation and RAGE protein expression in a concentration-dependent manner. In vitro, LR-90 exhibited general antioxidant properties by inhibiting metal-catalyzed reactions and reactive oxygen species (OH radical) and reactive carbonyl species (methlyglyoxal, glyoxal) generations without any effect on pyridoxal 5' phosphate. The compound also prevents AGE-protein cross-linking reactions. These findings demonstrate the bioefficacy of LR-90 in treating nephropathy and hyperlipidemia in diabetic animals by inhibiting AGE accumulation, RAGE protein expression, and protein oxidation in the diabetic kidney. Additionally, our study suggests that LR-90 may be useful also to delay the onset and progression of diabetic atherosclerosis as the compound can inhibit the expression of RAGE and inflammation-related pathology, as well as prevent lipid peroxidation reactions.

Topics: Animals; Ascorbic Acid; Body Weight; Butyrates; Cholesterol; Creatinine; Diabetes Mellitus, Experimental; Diabetic Nephropathies; Dyslipidemias; Glycation End Products, Advanced; Glycosylation; Hydroxyl Radical; Hypoglycemic Agents; Kidney; Lipid Metabolism; Lipoproteins, LDL; Male; Molecular Structure; Oxidation-Reduction; Pyridoxal Phosphate; Rats; Rats, Sprague-Dawley; Receptor for Advanced Glycation End Products; Receptors, Immunologic; Triglycerides; Tyrosine

Oxidative stress has been suggested to play a role as a common mediator of apoptosis and kidney damage in diabetes. However, it is uncertain whether the apoptosis occurs in the kidney during the course of diabetes. We investigated the occurrence of apoptosis in the diabetic rat kidney, the role of oxidative stress and the effect of an antioxidant on apoptosis in the diabetic rat kidney.. Otsuka-Long-Evans-Tokushima-Fatty rats, an animal model for type 2 diabetes, were randomized into a non-treated diabetic (n=8) and a vitamin C-treated group (n=8). Long-Evans Tokushima Otsuka rats (n=8) were used as a control.. Apoptosis was present in the epithelial cells of the proximal tubules in diabetic rats. The number of apoptotic cells, albuminuria, proteinuria, glomerular and tubulointerstitial sclerosis, and renal malondialdehyde were significantly decreased in vitamin C-treated diabetic rats when compared to the untreated diabetic rats. The decreased slit pore density (number of slit pores per underlying glomerular basement membrane length) as assessed by electron microscopy was also significantly restored by treatment with vitamin C without significantly affecting plasma glucose in diabetic rats.. By blocking these pathophysiologic processes, a blockade of oxidative stress by vitamin C might become a useful adjunct to albuminuria and renal sclerosis in diabetic nephropathy.

Topics: Albuminuria; Animals; Antioxidants; Apoptosis; Ascorbic Acid; Diabetes Mellitus, Experimental; Diabetic Nephropathies; Kidney; Male; Oxidative Stress; Rats; Rats, Inbred OLETF; Sclerosis

Moderate exercise and vitamin C and E (VCE) supplementation can be beneficial to diabetes due to reducing free radical production in lens and kidney of diabetic pregnant rats. We investigated the effect of VCE supplementation and moderate exercise on lipid peroxidation (MDA) and scavenging enzyme activity in the kidneys and lens of STZ-induced diabetic pregnant rats. Fifty female Wistar rats were used and were randomly divided into five groups. First and second were used as the control and pregnant control group. Third group was the pregnant diabetic group. The fourth group was the diabetic-pregnant-exercise group. VCE-supplemented feed was given to pregnant-diabetic-exercise rats constituting the fifth group. Animals in the exercised groups were moderately exercised daily on a treadmill (16.1 m/min, 45 min/d) for three weeks (five days a week). Diabetes was induced on day zero of the study. Plasma, lens, and kidney samples were taken from all animals on day 20. Exercise and administration of VCE to pregnant diabetic rats resulted in significant decrease in the albumin and total protein values and the elevated MDA, plasma creatinine, and urea levels as an indicator of oxidative stress and renal functional parameters. Exercise and VCE supplementation also increased glutathione peroxidase (GSH-Px), reduced glutathione (GSH), vitamin E, and beta-carotene levels in the kidney, GSH-Px and GSH in the lens, the albumin and total protein values in plasma. In the diabetic pregnant animals, the decreased vitamins A and E concentration and GSH levels in kidney, creatinine, and urea values in plasma did not improve through exercise only although their concentrations were increased by VCE supplementation. Kidney weight did not also affect either by exercise or VCE supplementation. In conclusion, these results suggest that exercise plus VCE affects antioxidant metabolism and reduces lipid peroxidation, thereby improving the damage caused by oxidative stress involved in the pathogenesis of lens and kidney in diabetic pregnant rats. Moderate exercise with dietary VCE may play a role in preventing nephropathy and cataract formation in diabetic pregnant rat.

Topics: Animals; Antioxidants; Ascorbic Acid; Cataract; Diabetes Mellitus, Experimental; Diabetic Nephropathies; Diet; Drug Combinations; Female; Motor Activity; Oxidative Stress; Pregnancy; Pregnancy, Animal; Rats; Rats, Wistar; Vitamin E

We tested the hypothesis that green tea prevents diabetes-related tissue dysfunctions attributable to oxidation. Diabetic rats were treated daily with tap water, vitamins C and E, or fresh Japanese green tea extract. After 12 months, body weights were decreased, whereas glycated lysine in aorta, tendon, and plasma were increased by diabetes (P < 0.001) but unaffected by treatment. Erythrocyte glutathione and plasma hydroperoxides were improved by the vitamins (P < 0.05) and green tea (P < 0.001). Retinal superoxide production, acellular capillaries, and pericyte ghosts were increased by diabetes (P < 0.001) and improved by green tea and the vitamins (P variable). Lens crystallin fluorescence at 370/440 nm was ameliorated by green tea (P < 0.05) but not the vitamins. Marginal effects on nephropathy parameters were noted. However, suppressed renal mitochondrial NADH-linked ADP-dependent and dinitrophenol-dependent respiration and complex III activity were improved by green tea (P variable). Green tea also suppressed the methylglyoxal hydroimidazolone immunostaining of a 28-kDa mitochondrial protein. Surprising, glycoxidation in tendon, aorta, and plasma was either worsened or not significantly improved by the vitamins and green tea. Glucosepane cross-links were increased by diabetes (P < 0.001), and green tea worsened total cross-linking. In conclusion, green tea and antioxidant vitamins improved several diabetes-related cellular dysfunctions but worsened matrix glycoxidation in selected tissues, suggesting that antioxidant treatment tilts the balance from oxidative to carbonyl stress in the extracellular compartment.

Topics: Animals; Antioxidants; Ascorbic Acid; Blood Glucose; Body Weight; Camellia sinensis; Collagen; Cross-Linking Reagents; Diabetes Mellitus, Experimental; Diabetic Nephropathies; Diabetic Retinopathy; Feeding Behavior; Glycation End Products, Advanced; In Vitro Techniques; Male; Mitochondria; Oxygen Consumption; Phytotherapy; Rats; Rats, Inbred Lew; Tea; Vitamin E

Renal accumulation of AGEs may contribute to the progression of diabetic nephropathy. We evaluated the effect of ramipril (a pure ACE inhibitor) and AVE7688 (a dual inhibitor of ACE and neutral endopeptidase) on renal accumulation of the advanced glycation end-product (AGE) 3-deoxyglucosone-imidazolone, carboxymethyllysine (CML) and pentosidine, and on clearance of CML in type 2 diabetes.. Male Zucker diabetic fatty rats (ZDF, Gmi-fa/fa) rats were treated from age 10 to 37 weeks with ramipril (1 mg.kg(-1).day(-1)), AVE7688 (45 mg.kg(-1).day(-1)) or without drug. Ramipril and AVE7688 reduced albuminuria by 30 and 90%, respectively.. ZDF rats showed increased renal accumulation of the AGE subtypes 3-deoxyglucosone-imidazolone, pentosidine and CML by about 40, 55 and 55%, respectively compared with heterozygous, non-diabetic control animals at the age of 37 weeks. AVE7688 but not ramipril attenuated the renal accumulation of 3-deoxyglucosone-imidazolone, pentosidine and CML and improved CML clearance in ZDF rats. During glycation reactions in vitro, AVE7688 also demonstrated potent chelating activity and inhibited metal-catalysed formation of pentosidine and CML.. Improved AGE clearance and direct inhibition of AGE formation by chelation may contribute to reduced accumulation of renal AGEs and to the nephroprotective effects of vasopeptidase inhibition in type 2 diabetes.

Topics: Angiotensin-Converting Enzyme Inhibitors; Animals; Ascorbic Acid; Blood Glucose; Chromatography, High Pressure Liquid; Creatine; Deoxyglucose; Diabetes Mellitus, Type 2; Diabetic Nephropathies; Glycated Hemoglobin; Glycation End Products, Advanced; Heterocyclic Compounds, 3-Ring; Kidney; Lysine; Male; Oxidation-Reduction; Protease Inhibitors; Ramipril; Rats; Rats, Zucker; Spectrometry, Fluorescence

Topics: Adult; Aged; Ascorbic Acid; Biomarkers; Blood Pressure; C-Reactive Protein; Case-Control Studies; Creatinine; Diabetes Mellitus, Type 2; Diabetic Nephropathies; Female; Humans; Japan; Male; Middle Aged; Regression Analysis

Recent report demonstrates that inadequate iron mobilization and defective iron utilization may cause recombinant erythropoieitin (rEPO) hyporesponsiveness in hemodialysis (HD) patients with iron overload. The effect of intravenous ascorbic acid (IVAA) in HD patients selected on the basis of iron overload and EPO resistance also has been proven. However, it is uncertain whether IVAA still works in diabetic ESRD patients with hyperferritinemia. Therefore, the aim of this study focusing on diabetic ESRD patients was to analyze the potential effect of low dose IVAA on improvement of anemia and erythropoiesis-related parameters when compared with control period.. This study consisted of 22 chronic hemodialysis patients with type II diabetes in a single dialysis unit. In studies of this type, all eligible patients are followed up, but the primary comparison is still between different sequentially treatment including control period and post-IVAA period in same patients. IVAA patients received ascorbic acid, 100 mg each administered intravenously three times per week for eight weeks of treatment and four months of post-treatment follow-up.. The demographic characteristics of 22 diabetic uremic patients show that mean age is 63.6 +/- 10.2 years old. The ratio of sex (M/F) = 10/12. Mean duration of HD is 46.7 +/- 33.2 months. As for the urea kinetic study between these two periods including KT/V, nPCR, and URR, there is no significantly different. As for anemia-related parameters, Hb and Hct increased significantly in post-IVAA period after 3 months compared with control period, while MCV did not increase significantly. Serum ferritin significantly decreased at study completion. The same situation is for iron. As for TS, it significantly increased at one month and further markedly increased at subsequent three months.. This study has demonstrated that short-term low dose IVAA therapy can facilitate iron release from reticuloendothelial system but also increase iron utilization in diabetic hemodialysis patients with iron overload. Therefore, IVAA is a potential adjuvant therapy to treat erythropoeitin-hyporesponsive anemia in iron-overloaded patients.

Topics: Aged; Anemia; Ascorbic Acid; Biomarkers; Diabetes Mellitus, Type 2; Diabetic Nephropathies; Dose-Response Relationship, Drug; Erythrocyte Indices; Erythropoietin; Female; Ferritins; Follow-Up Studies; Free Radical Scavengers; Hematocrit; Hemoglobins; Humans; Infusions, Intravenous; Iron; Iron Overload; Kidney Failure, Chronic; Male; Middle Aged; Parathyroid Hormone; Phosphates; Prospective Studies; Recombinant Proteins; Renal Dialysis; Serum Albumin; Taiwan; Time Factors; Treatment Outcome

Vitamin C exists in two major forms. The charged form, ascorbic acid (AA), is taken up into cells via sodium-dependent facilitated transport. The uncharged form, dehydroascorbate (DHA), enters cells via glucose transporters (GLUT) and is then converted back to AA within these cells. Cell types such as certain endothelial and epithelial cells as well as neurons that are particularly prone to damage during diabetes tend to be those that appear to be dependent on GLUT transport of DHA rather than sodium-dependent AA uptake. We hypothesize that diabetic neuropathies, nephropathies and retinopathies develop in part by exclusion of DHA uptake by GLUT transporters when blood glucose levels rise above normal. AA plays a central role in the antioxidant defense system. Exclusion of DHA from cells by hyperglycemia would deprive the cells of the central antioxidant, worsening the hyperglycemia-induced oxidative stress level. Moreover, AA participates in many cellular oxidation-reduction reactions including hydroxylation of polypeptide lysine and proline residues and dopamine that are required for collagen production and metabolism and storage of catecholamines in neurons. Increase in the oxidative stress level and metabolic perturbations can be expected in any tissue or cell type that relies exclusively or mainly on GLUT for co-transport of glucose and DHA including neurons, epithelial cells, and vascular tissues. On the other hand, since DHA represents a significant proportion of total serum ascorbate, by increasing total plasma ascorbate concentrations during hyperglycemia, it should be possible to correct the increase in the oxidative stress level and metabolic perturbations, thereby sparing diabetic patients many of their complications.

Topics: Ascorbic Acid; Biological Transport; Blood Glucose; Dehydroascorbic Acid; Diabetes Mellitus; Diabetic Nephropathies; Diabetic Neuropathies; Diabetic Retinopathy; Endothelium; Humans; Kidney; Models, Biological; Monosaccharide Transport Proteins; Nervous System; Oxidative Stress; Retina

Alterations of intrarenal nitric oxide (NO) synthesis play an important role in the pathogenesis and progression of diabetic nephropathy. We tested the hypothesis that hyperglycemia modulates intrarenal NO synthesis, which might mediate the mesangial cell proliferation and matrix production. Murine mesangial cells were grown in media containing varying glucose concentrations, and cytokine-induced NO synthesis was assayed by chemiluminescence using an NO analyzer. High media glucose (25 mM) inhibited NO synthesis in a time-dependent fashion. This inhibition was posttranslational as revealed by analysis of inducible nitric oxide synthase (iNOS) gene and protein expression. L-Arginine supplementation partially reversed the inhibition whereas addition of tetrahydrobiopterin (BH4), a cofactor for NOS, restored the inducibility of NO synthesis. The in vitro [3H]citrulline assay for iNOS activity indicated that high glucose decreased BH4 availability whereas examination of the BH4 synthetic pathway suggested decreased BH4 stability rather than synthesis, a defect that was corrected by ascorbic acid. We conclude that hyperglycemia inhibits NO synthesis in mesangial cells by a posttranslational defect that might involve the stability and hence availability of BH4.

Topics: Animals; Arginine; Ascorbic Acid; Biopterins; Cell Division; Cells, Cultured; Diabetic Nephropathies; Enzyme Induction; Glomerular Mesangium; Glucose; Mice; Models, Chemical; Nitric Oxide; Nitric Oxide Synthase; Nitric Oxide Synthase Type II

Diabetes mellitus is characterized by complications affecting several organs, including the kidney. Lipid peroxidation increases in diabetes and has been implicated in the pathogenesis of diabetic complications. In this study, we examined the ability of two antioxidants, vitamin E and probucol, to reduce lipid peroxidation in vivo and renal hypertrophy, an early stage of diabetic nephropathy, in rats. Animals were divided into four groups: non-diabetic, diabetic, diabetic treated with vitamin E, and diabetic treated with probucol. Animals were given antioxidants by intraperitoneal injection after induction of diabetes by streptozotocin injection. After 7 wk, lipid peroxidation in vivo was measured by analyzing urinary excretion of lipophilic aldehydes and related carbonyl compounds (LACC) as 2,4-dinitrophenylhydrazones by high-performance liquid chromatography. A number of urinary lipophilic nonpolar and polar aldehydes and related carbonyl compounds were identified, almost all of which increased in diabetes. Antioxidant treatment resulted in significantly decreased excretion of urinary LACC excretion. Antioxidant treatment of diabetic rats reduced renal hypertrophy. There was a high correlation between kidney weight and urinary LACC. Since LACC are accepted markers of lipid peroxidation, these results indicate that antioxidants can reduce the elevated lipid peroxidation of diabetes and may slow the onset of diabetic nephropathy.

Topics: Aldehydes; Animals; Antioxidants; Ascorbic Acid; Blood Glucose; Diabetes Mellitus, Experimental; Diabetic Nephropathies; Feeding Behavior; Kidney; Male; Probucol; Rats; Rats, Wistar; Streptozocin; Vitamin E

In diabetic nephropathy and hypertension, a major cause of mortality is from cardiovascular disease. Since low levels of antioxidants such as vitamin C have been associated with such complications, we have examined the uptake mechanisms for ascorbic acid (AA) and dehydroascorbic acid (DHA) in lymphoblasts from normal control subjects (CON), normoalbuminuric insulin-dependent diabetic (IDDM) patients (DCON), patients with IDDM and nephropathy (DN) and hypertensive patients (HT) using mass assays of uptake and measuring AA using high-performance liquid chromatography. Precautions were taken to prevent oxidation of AA and to take into account the instability of DHA in buffers. DHA uptake was the major mechanism in all four groups of subjects, and the Vmax (maximal uptake rate) was significantly lower in the DN cells (24.7 +/- 1.0 nmol [95% confidence intervals CI 22.5, 26.3] 10(6) cells(-1) h(-1)) compared to CON and DCON cells (33.9 +/- 2.1 [95% CI 29.4, 38.4] and 37.0 +/- 2.2 [95% CI 32.2, 41.8] nmol 10(6) cells(-1) h(-1), respectively, p < 0.001 for both). DHA Vmax was also lower in the HT group (23.2 +/- 1.1 [95% CI 20.7, 25.7] nmol 10(6) cells(-1) h(-1)) compared to the CON group (p < 0.001). There were no significant differences in the Km or passive membrane permeability for DHA or the AA uptake. DHA uptake showed a negative correlation to systolic blood pressure (r(s) = -0.49, p < 0.001). These findings suggest that impaired DHA uptake may be one component of the phenotype expressed by DN cells that may persist in culture. Impaired DHA uptake in vivo, especially in the presence of hyperglycaemia, leads to impaired regeneration of AA and depletion of anti-oxidant defences, exposing such individuals to increased risk of cardiovascular disease.

Topics: Adult; Aged; Albuminuria; Ascorbic Acid; Biological Transport; Cells, Cultured; Dehydroascorbic Acid; Diabetes Mellitus, Type 1; Diabetic Nephropathies; Female; Humans; Hypertension; Kinetics; Male; Middle Aged; Models, Biological; Reference Values

Pathogenesis of diabetes-related microvascular complications involving oxidative damage by free radicals has been demonstrated. Free radical generation has been shown to derive largely from iron. Our objectives, therefore, were to determine if there is an increased incidence and/or an accelerated course of nephropathy in patients with diabetes, secondary to transfusional hemochromatosis, and to examine whether free radical activity contributes to the development of this complication.. We evaluated nine patients with homozygous beta-thalassemia, complicated by clinically overt diabetes, for diabetic nephropathy over a 7-year period. Lipid peroxidation was quantified by measuring the presence of 20 saturated and unsaturated aldehydes, and results were compared with five normotensive type 1 diabetic patients without iron overload.. Nephropathy developed in five of nine patients (55%) after a mean duration of overt diabetes of 3.6 +/- 2.0 years. Three patients showed evidence of progressive microalbuminuria over a 7-year period (24.7-46.2, 52.2-430.1, and 17.7-54.3 micrograms/min, respectively). Two patients with borderline microalbuminuria (19.9 and 14.5 micrograms/min, respectively) demonstrated stable albumin excretion rates over the follow-up period. Total aldehyde concentration was significantly higher in beta-thalassemia diabetic patients, compared with nonthalassemic diabetic control subjects (8,106 +/- 1,280 vs. 4,594 +/- 247 nmol/l; P < 0.0001). The three patients with progressive microalbuminuria demonstrated significantly higher total aldehyde concentration, compared with the other beta-thalassemia diabetic patients with stable albumin excretion (9,428 +/- 337 vs. 7,445 +/- 1,003 nmol/l; P < 0.01). Serum vitamin E concentrations were significantly lower in beta-thalassemia patients with diabetes, compared with diabetic patients without iron overload (12.1 +/- 6.0 vs. 25.9 +/- 11.4 mumol/l; P = 0.02). Serum vitamin C concentrations did not differ between the two groups. Multiple regression analysis demonstrated total aldehyde concentration to be the most significant predictor for the development of microalbuminuria (P = 0.01), followed by the duration of diabetes (P = 0.02) and glycemic control (P = 0.02).. Early development and an accelerated course of diabetic nephropathy in iron-loaded patients with beta-thalassemia are observed. These findings may be attributed to high oxidative stress in these patients, which is secondary to iron-derived free radicals and to the patients' diminished antioxidant reserves.

Topics: Adult; Albuminuria; Aldehydes; Antioxidants; Ascorbic Acid; beta-Thalassemia; Blood Glucose; Blood Pressure; Diabetes Complications; Diabetes Mellitus; Diabetic Nephropathies; Fructosamine; Homozygote; Humans; Iron; Kidney Function Tests; Lipid Peroxidation; Oxidative Stress; Retrospective Studies; Transfusion Reaction; Vitamin E

Oxidative stress may be an important pathogenetic factor in the development of diabetic vascular complications. The total antioxidative potential of plasma reflects the ability of an individual to resist oxidative stress. We measured the plasma total peroxyl radical-trapping potential (TRAP) and the concentrations of four plasma chain-breaking antioxidants in 81 patients with non-insulin-dependent diabetes mellitus (NIDDM) nine years after diagnosis and in 102 well-matched non-diabetic control subjects. The association between the total antioxidative potential and the presence of coronary heart disease (CHD) and diabetic kidney disease were also studied. There were no significant differences in plasma TRAP between NIDDM patients and control subjects (1250+/-199 vs. 1224+/-198 microM). Nor were there any significant differences in the concentrations of plasma uric acid, ascorbic acid, alpha-tocopherol, and protein thiols between NIDDM patients and control subjects. Patients with a low glomerular filtration rate and/or high urinary albumin excretion had elevated plasma uric acid. Plasma TRAP was not, however, associated with renal dysfunction. The plasma of NIDDM patients with CHD had a significantly higher value of unidentified antioxidative potential than that of patients without CHD. This relation was strongly dependent upon smoking. In conclusion, these data demonstrate that there are no major defects in the antioxidative potential of plasma caused by NIDDM per se. CHD and diabetic renal dysfunction were not associated with changes in plasma TRAP.

Topics: Aged; Antioxidants; Ascorbic Acid; Biomarkers; Chromatography, High Pressure Liquid; Coronary Disease; Diabetes Mellitus, Type 2; Diabetic Nephropathies; Female; Humans; Male; Matched-Pair Analysis; Middle Aged; Oxidative Stress; Smoking; Statistics as Topic; Sulfhydryl Compounds; Uric Acid; Vitamin E

Reactive oxygen species are thought to be implicated in the pathogenesis of various human diseases. They are generated endogenously under physiological and pathological conditions but also upon exposure to exogenous challenge. The organism maintains defense systems against reactive oxygen species, including enzymes and low-molecular-weight antioxidants. Important antioxidants such as vitamins E and C and carotenoids are provided from the diet. Vitamin E, as the major chain-breaking antioxidant, inhibits lipid peroxidation, thus preventing membrane damage and modification of low-density lipoproteins. It is regenerated by the water-soluble vitamin C. Carotenoids efficiently scavenge singlet molecular oxygen and peroxyl radicals. There is increasing evidence from epidemiological studies, animal experiments, and in vitro investigations that an increased intake of antioxidants is associated with a diminished risk for several diseases.

Topics: Animals; Antioxidants; Ascorbic Acid; Cardiovascular Diseases; Diabetic Nephropathies; Diabetic Retinopathy; Diet; Humans; Reactive Oxygen Species; Vitamin E