ascorbic-acid and Insulin-Resistance

Background: Nutrient supplements are widely used for type 2 diabetes (T2D), yet evidence-based guidance for clinicians is lacking. Methods: We searched the four electronic databases from November 2015−December 2021. The most recent, most comprehensive, high-ranked systematic reviews, meta-analyses, and/or umbrella reviews of randomised controlled trials in adults with T2D were included. Data were extracted on study characteristics, aggregate outcome measures per group (glycaemic control, measures of insulin sensitivity and secretion), adverse events, and Grading of Recommendations Assessment, Development, and Evaluation (GRADE) assessments. Quality was assessed using A Measurement Tool to Assess Systematic Reviews Version 2.0 (AMSTAR 2). Results: Twelve meta-analyses and one umbrella review were included. There was very low certainty evidence that chromium, Vitamin C, and omega-3 polyunsaturated fatty acids (Ω-3 PUFAs) were superior to placebo for the primary outcome of glycated hemoglobin (HbA1c) (Mean Difference/MD −0.54, −0.54 and ES −0.27, respectively). Probiotics were superior to placebo for HbA1c (Weighted Mean Difference/WMD −0.43%). There was very low certainty evidence that Vitamin D was superior to placebo for lowering HbA1c in trials of <6 months (MD −0.17%). Magnesium, zinc, Vitamin C, probiotics, and polyphenols were superior to placebo for FBG. Vitamin D was superior to placebo for insulin resistance. Data on safety was limited. Conclusions: Future research should identify who may benefit from nutrient supplementation, safety, and optimal regimens and formulations.

Topics: Adult; Ascorbic Acid; Diabetes Mellitus, Type 2; Dietary Supplements; Glycated Hemoglobin; Glycemic Control; Humans; Insulin Resistance; Nutrients; Systematic Reviews as Topic; Vitamin D; Vitamins

Polycystic ovary syndrome (PCOS) is a heterogenous disorder characterized by chronic ovulation dysfunction and hyperandrogenism. It is considered the most common endocrinological disorder, affecting up to 25% of women of reproductive age, and associated with long-term metabolic abnormalities predisposing to cardiovascular risk, such as insulin resistance (IR), dyslipidemia, endothelial dysfunction, and systemic inflammation. PCOS is also characterized by elevated serum levels of luteinizing hormone (LH), causing a condition of hyperandrogenism and a consequent altered ratio between LH and the follicle stimulating hormone (FSH). Over the years, several different approaches have been proposed to alleviate PCOS symptoms. Supplementation with natural molecules such as inositols, resveratrol, flavonoids and flavones, vitamin C, vitamin E and vitamin D, and omega-3 fatty acids may contribute to overcoming PCOS pathological features, including the presence of immature oocyte, IR, hyperandrogenism, oxidative stress and inflammation. This review provides a comprehensive overview of the current knowledge about the efficacy of natural molecule supplementation in the management of PCOS.

Topics: Ascorbic Acid; Dietary Supplements; Dyslipidemias; Fatty Acids, Omega-3; Female; Flavanones; Flavonoids; Follicle Stimulating Hormone; Humans; Hyperandrogenism; Inositol; Insulin Resistance; Luteinizing Hormone; Ovulation; Polycystic Ovary Syndrome; Resveratrol; Vitamin D; Vitamin E; Vitamins

Data regarding the effect of vitamin C (VC) and vitamin E (VE) supplementation on insulin resistance in type 2 diabetes mellitus (T2DM) are controversial. We aimed to systematically review the current data on this topic.. All randomized controlled trials (RCTs) conducted to assess the effect of VC and/or VE on insulin resistance in diabetes published in Google Scholar and PubMed web databases until January 2014 were included. Exclusion criteria were studies conducted in animal, type 1 DM, children or pregnant women. Main outcome measure was insulin resistance by homoeostasis model assessment (HOMA) index. According to degree of heterogeneity, fixed- or random-effect model was employed by stata software (11.0).. We selected 14 RCTs involving 735 patients with T2DM. VE or mixture-mode supplementation did not have any significant effect on HOMA with a standardized mean difference (SMD): 0·017, 95% CI: -0·376 to 0·411 (P = 0·932); and SMD: -0·035, 95% CI: -0·634 to 0·025 (P = 0·070), respectively, by random-effect model. VC supplement alone did not improve insulin resistance with a SMD: -0·150, 95% CI: -0·494 to 0·194 (P = 0·391), by fixed-effect model. Meta-regression test demonstrated that HOMA index may have not been influenced by the year of publication, dosage or duration of treatment.. The sole intake of VC, VE or their combination with other antioxidants could not improve insulin resistance in diabetes.

Topics: Antioxidants; Ascorbic Acid; Diabetes Mellitus, Type 2; Dietary Supplements; Humans; Insulin Resistance; Randomized Controlled Trials as Topic; Treatment Outcome; Vitamin E

Werner syndrome (WS) is a premature aging disorder caused by mutations in a RecQ-like DNA helicase. Mice lacking the helicase domain of the WRN homologue exhibit many phenotypic features of WS. Importantly, mutant Wrn(Deltahel/Deltahel) mice show abnormal increases in visceral fat deposition and fasting blood triglyceride levels followed by insulin resistance and high blood glucose levels. These mice also exhibit increased heart and liver tissue reactive oxygen species concomitantly with oxidative DNA damage, indicating a pro-oxidant status. We treated mice with either ascorbate or catechin hydrate for 9 months. Vitamin C supplementation reduced oxidative stress in liver and heart tissues and reversed hypertriglyceridemia, hyperglycemia, and insulin resistance and reduced fat weight in mutant Wrn(Deltahel/Deltahel) mice. Although the free scavenger catechin hydrate also reduced oxidative DNA damage in heart and liver tissues, it did not reverse any of the metabolic phenotype aspects in treated mutant mice. Finally, vitamin C and catechin hydrate did not affect the metabolic status of wild-type mice. These results indicate that vitamin C supplementation could be beneficial for WS patients.

Topics: Aging, Premature; Animals; Ascorbic Acid; Catechin; DNA Damage; DNA Helicases; Free Radical Scavengers; Humans; Hyperglycemia; Hypertriglyceridemia; Insulin Resistance; Mice; Mutation; Oxidative Stress; Reactive Oxygen Species; RecQ Helicases; Werner Syndrome; Werner Syndrome Helicase

Uric acid has historically been viewed as a purine metabolic waste product excreted by the kidney and gut that is relatively unimportant other than its penchant to crystallize in joints to cause the disease gout. In recent years, however, there has been the realization that uric acid is not biologically inert but may have a wide range of actions, including being both a pro- and anti-oxidant, a neurostimulant, and an inducer of inflammation and activator of the innate immune response. In this paper, we present the hypothesis that uric acid has a key role in the foraging response associated with starvation and fasting. We further suggest that there is a complex interplay between fructose, uric acid and vitamin C, with fructose and uric acid stimulating the foraging response and vitamin C countering this response. Finally, we suggest that the mutations in ascorbate synthesis and uricase that characterized early primate evolution were likely in response to the need to stimulate the foraging "survival" response and might have inadvertently had a role in accelerating the development of bipedal locomotion and intellectual development. Unfortunately, due to marked changes in the diet, resulting in dramatic increases in fructose- and purine-rich foods, these identical genotypic changes may be largely responsible for the epidemic of obesity, diabetes and cardiovascular disease in today's society.

Topics: Animals; Antioxidants; Ascorbic Acid; Blood Pressure; Evolution, Molecular; Fasting; Fructose; Gout; Humans; Inflammation Mediators; Insulin Resistance; Metabolic Syndrome; Models, Biological; Starvation; Urate Oxidase; Uric Acid; Weight Gain

Chronic inflammation is a pathogenic feature of atherosclerosis and cardiovascular disease mediated by substances including angiotensin II, proinflammatory cytokines, and free fatty acids. This promotes generation of reactive oxygen species in vascular endothelial cells and smooth muscle cells, which mediate injury through several mechanisms. Reciprocal relationships between endothelial dysfunction and insulin resistance as well as cross-talk between hyperlipidaemia and the renin-angiotensin-aldosterone system (RAAS) at multiple levels contribute importantly to a variety of risk factors. Therefore, combination therapy that simultaneously addresses multiple mechanisms for the pathogenesis of atherosclerosis is an attractive emerging concept for slowing progression of atherosclerosis. Combined therapy with statins, peroxisome proliferator-activated receptors, and RAAS blockade demonstrates additive beneficial effects on endothelial dysfunction and insulin resistance when compared with monotherapies in patients with cardiovascular risk factors due to both distinct and interrelated mechanisms. These additive beneficial effects of combined therapies are consistent with laboratory and recent clinical studies. Thus, combination therapy may be an important paradigm for treating and slowing progression of atherosclerosis, coronary heart disease, and co-morbid metabolic disorders characterized by endothelial dysfunction and insulin resistance.

Topics: Angiotensin II Type 1 Receptor Blockers; Angiotensin-Converting Enzyme Inhibitors; Animals; Anti-Inflammatory Agents; Antioxidants; Ascorbic Acid; Atherosclerosis; Calcium Channel Blockers; Cardiovascular Agents; Drug Therapy, Combination; Endothelium, Vascular; Humans; Hydroxymethylglutaryl-CoA Reductase Inhibitors; Inflammation; Insulin Resistance; NADPH Oxidases; Oxidative Stress; Peroxisome Proliferator-Activated Receptors; Reactive Oxygen Species; Renin-Angiotensin System; Treatment Outcome; Vitamin E

Growing evidence indicates that insulin resistance and oxidative stress are involved in the pathogenesis of essential hypertension. In insulin-resistant states, like obesity and type 2 diabetes, altered glucose metabolism may lead to increased formation of methylglyoxal and other ketoaldehydes. Animal studies have shown that increased levels of endogenous aldehydes may lead to hypertension and oxidative stress. In animal models, the administration of vitamin C, vitamin B6 or alpha-lipoic acid reduced tissue levels of aldehydes, prevented oxidative stress, and lowered blood pressure. The purpose of this review article is to critically evaluate the available evidence for the role of dietary supplements in hypertension treatment.

Topics: Aldehydes; Animals; Ascorbic Acid; Dietary Supplements; Evidence-Based Medicine; Glucose Intolerance; Humans; Hypertension; Insulin Resistance; Thioctic Acid; Vitamin B 6

The generation by genetic engineering of two murine models to investigate atherosclerosis, such as the apoE- and LDLr- deficient mice, is providing an extraordinaire knowledge of the effect of different nutrients on this complex disease. The present revision provides a comprehensive overview of the advances in this field that point to a remarkable complexity. While some controversies over puzzling results could be explained invoking potential nutrient interactions or different food sources of nutrients, it also appears that other factors such as sex, genetic background or immunological status are emerging as generators of differential responses to nutrients during the atherosclerotic process.

Topics: Alcohol Drinking; Allergy and Immunology; Animals; Antioxidants; Apolipoproteins E; Arginine; Arteriosclerosis; Ascorbic Acid; Atherosclerosis; Cell Proliferation; Dietary Fats; Disease Models, Animal; Energy Metabolism; Fatty Acids, Monounsaturated; Fatty Acids, Unsaturated; Genetic Engineering; Genetic Variation; Genomics; Homocysteine; Insulin Resistance; Iron; Magnesium; Mice; Mice, Inbred C57BL; Mice, Knockout; Models, Biological; Models, Genetic; Phytosterols; Receptors, LDL; Sex Factors; Sodium; Taurine; Vitamin E

Diabetes represents a serious risk factor for the development of cardiovascular problems such as coronary heart disease, peripheral arterial disease, hypertension, stroke, cardiomyopathy, nephropathy and retinopathy. Identifying the pathogenesis of this increased risk provides a basis for secondary intervention to reduce morbidity and mortality in diabetic patients. Hyperglycemia and protein glycation, increased inflammation, a prothrombotic state and endothelial dysfunction have all been implicated as possible mechanisms for such complications. A linking element between many of these phenomena could possibly be, among other factors, increased production of reactive oxygen species. Vascular endothelial cells have several physiological actions that are essential for the normal function of the cardiovascular system. These include the production of nitric oxide (NO), which regulates vasodilatation, anticoagulation, leukocyte adhesion, smooth muscle proliferation and the antioxidative capacity of endothelial cells. However, under conditions of hyperglycemia, excessive amounts of superoxide radicals are produced inside vascular cells and this can interfere with NO production leading to the possible complications. This article aims at reviewing the links between reactive oxygen species, diabetes and vascular disease and whether or not antioxidants can alter the course of vascular complications in diabetic patients and animal models. A possible beneficial effect of antioxidants might present a new addition to the range of secondary preventive measures used in diabetic patients.

Topics: alpha-Tocopherol; Animals; Antioxidants; Ascorbic Acid; Cardiovascular Diseases; Clinical Trials as Topic; Diabetes Complications; Dyslipidemias; Endothelium, Vascular; Glucose; Humans; Hyperglycemia; Hypertension; Insulin Resistance; Nitric Oxide; Oxidative Stress; Reactive Oxygen Species; Risk Factors; Vitamin E

Topics: Ascorbic Acid; Humans; Insulin; Insulin Resistance; Micronutrients; Nutritional Requirements; Trace Elements; Vitamin E

This study aimed to investigate the effect of Vitamin C alone and in combination with Rutin on the glycemic control, insulin resistance, lipid profile and oxidative stress markers in patients with type 2 diabetes.. A prospective, randomized, controlled study conducted on 53 type 2 diabetes patients randomized into 3 groups; (group A) 20 received Rutin with vitamin C, (group B) 20receivedvitamin C and (group C)13 received antidiabetic treatment only. Fasting Blood Glucose (FBG), Hemoglobin A1c (HbA1c), fasting insulin, Malondialdehyde, Superoxide dismutase, Lipid profile and patients' quality of life (QOL) using SF-36 questionnaire were assessed in all patients at baseline and after 8 weeks.. At baseline, the 3 groups were comparable while FBG was lower in group C versus group A and B (p = 0.0021). After 8 weeks, a significant reduction was observed in % change of FBG in groups A and B versus group C (p = 0.0165, 0.0388 respectively). Low Density Lipoprotien-cholesterol (LDL-c) and Total cholesterol (TC) levels significantly improved in group B versus baseline (p = 0.0239,0.0166 respectively). QOL, physical functioning and energy domains improved significantly in group A versus group C (p = 0.0049, 0.0253 respectively), while role limitation to physical health and to emotional problem improved significantly in group B versus group C (p = 0.0267,0.0280 respectively).. Vitamin C supplementation alone or with Rutin significantly reduced the % change of FBG compared to controls but had no effect on HbA1c, FBG,TC, fasting insulin and HOMA-IR or oxidative stress in T2DMpatients.. NCT03437902.

Topics: Adult; Ascorbic Acid; Blood Glucose; Diabetes Mellitus, Type 2; Drug Therapy, Combination; Fasting; Female; Glycated Hemoglobin; Glycemic Control; Humans; Hypoglycemic Agents; Insulin; Insulin Resistance; Lipids; Male; Malondialdehyde; Oxidative Stress; Prospective Studies; Quality of Life; Rutin

Recently, there has been an increasing interest in the influence of antioxidant vitamins on the efficacy of oral hypoglycemic therapy in type 2 diabetic patients (T2DM). This single-blinded randomized controlled clinical trial aimed to investigate the effect of vitamin C and/or E supplementation on the efficacy of oral hypoglycemic therapy in T2DM Palestinian male patients from the Gaza Strip.. Forty T2DM male patients aged 40-60 years on metformin treatment were randomly divided into four groups, each group received an additional one of the following daily oral supplements for 90 days: placebo; vitamin C; vitamin E and vitamin C plus vitamin E. After overnight fasting, venous blood specimens were collected from all individuals into K3-EDTA tubes and serum tubes for measuring the biochemical and hematological parameters of the study at baseline and after 90 days of vitamins supplementation.. The results revealed that vitamin C and/or E improve fasting blood sugar (FBS), HbA1c, lipid profile, insulin, homeostasis model assessment of insulin resistance (HOMA-IR), reduced glutathione (GSH); and Quantitative Insulin Sensitivity Check Index (QISCI) compared with diabetic patients group that received placebo.. This study provided additional evidence on the beneficial effects of supplementing antioxidant vitamins in T2DM which could improve the clinical condition and attenuate or prevent diabetic pathogenesis and complications that, secondly to poor glycemic control, could attribute to the imbalance between the decline in the endogenous antioxidants and increasing production of the reactive oxygen species leading to the oxidant-mediated damage present in the diabetic context.

Topics: Adult; Antioxidants; Ascorbic Acid; Biomarkers; Blood Glucose; Case-Control Studies; Diabetes Mellitus, Type 2; Dietary Supplements; Drug Synergism; Female; Follow-Up Studies; Glycated Hemoglobin; Hematologic Tests; Humans; Hypoglycemic Agents; Insulin Resistance; Kidney Function Tests; Lipids; Liver Function Tests; Male; Metformin; Middle Aged; Middle East; Oxidative Stress; Prognosis; Single-Blind Method; Vitamin E; Vitamins

Wine grape pomace flour (WGPF) is a fruit byproduct that is high in fiber and antioxidants. We tested whether WGPF consumption could affect blood biochemical parameters, including oxidative stress biomarkers. In a three-month intervention study, 27 male volunteers, each with some components of metabolic syndrome, consumed a beef burger supplemented with 7% WGPF containing 3.5% of fiber and 1.2 mg gallic equivalents (GE)/g of polyphenols (WGPF-burger), daily, during the first month. The volunteers consumed no burgers in the second month, and one control-burger daily in the third month. At baseline and after these periods, we evaluated the metabolic syndrome components, plasma antioxidant status (i.e., 2,2-diphenyl-1-picrylhydrazyl radical scavenging capacity (DPPH), vitamin E, vitamin C), and oxidative damage markers (i.e., advanced oxidation protein products (AOPPs), oxidized low-density lipoproteins (oxLDLs), malondialdehyde (MDA)). The WGPF-burger intake significantly reduced glycemia and homeostatic model assessment-based measurement of insulin resistance. Vitamin C increased and decreased during the consumption of the WGPF-burger and control-burger, respectively. The WGPF-burger intake significantly decreased AOPP and oxLDL levels. Vitamin E and MDA levels showed no significant changes. In conclusion, the consumption of beef burgers prepared with WGPF improved fasting glucose and insulin resistance, plasma antioxidant levels, and oxidative damage markers. Therefore, this functional ingredient has potential as a dietary supplement to manage chronic disease risk in humans.

Topics: Adult; Advanced Oxidation Protein Products; Antioxidants; Ascorbic Acid; Blood Glucose; Dietary Fiber; Dietary Supplements; Eating; Fasting; Flour; Humans; Insulin Resistance; Lipoproteins, LDL; Longitudinal Studies; Male; Malondialdehyde; Metabolic Syndrome; Middle Aged; Postprandial Period; Red Meat; Vitamin E; Vitis

There is limited evidence whether environmental exposure to perfluorinated compounds (PFCs) affects insulin resistance (IR) and whether vitamin C intake protects against the adverse effect of PFCs. This study was carried out to investigate the effect of PFCs on IR through oxidative stress, and the effects of a 4-week consumption of vitamin C supplement compared placebo on development of IR by PFCs.. For a double-blind, community-based, randomized, placebo-controlled crossover intervention of vitamin C, we assigned 141 elderly subjects to both vitamin C and placebo treatments for 4 weeks. We measured serum levels of PFCs to estimate PFC exposures and urinary levels of malondialdehyde (MDA) and 8-hydroxy-2'-deoxyguanosine (8-OHdG) for oxidative stress. We also measured levels of fasting glucose and insulin and derived the homeostatic model assessment (HOMA) index to assess IR.. Perfluorooctane sulfonate (PFOS) and perfluorododecanoic acid (PFDoDA) levels were found to be positively associated with HOMA index at the baseline and after placebo treatment. Risks of IR for the top decile of PFOS and PFDoDA exposures were significantly elevated compared with those with lower PFOS and PFDoDA exposures (both, P < 0.0001). However, the effects of PFOS and PFDoDA on HOMA disappeared after vitamin C supplementation (both, P > 0.30). Furthermore, PFOS and PFDoDA levels were also significantly associated with MDA and 8-OHdG levels, and MDA levels were positively associated with HOMA index.. PFOS and PFDoDA exposures were positively associated with IR and oxidative stress, and vitamin C supplementation protected against the adverse effects of PFOS and PFDoDA on IR.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Aged; Aged, 80 and over; Ascorbic Acid; Asian People; Biomarkers; Blood Glucose; Caprylates; Cotinine; Creatinine; Cross-Over Studies; Deoxyguanosine; Dietary Supplements; Double-Blind Method; Fluorocarbons; Humans; Insulin; Insulin Resistance; Malondialdehyde; Middle Aged; Oxidative Stress; Republic of Korea

Skeletal muscle insulin resistance and oxidative stress are characteristic metabolic disturbances in people with type 2 diabetes. Studies in insulin resistant rodents show an improvement in skeletal muscle insulin sensitivity and oxidative stress following antioxidant supplementation. We therefore investigated the potential ameliorative effects of antioxidant ascorbic acid (AA) supplementation on skeletal muscle insulin sensitivity and oxidative stress in people with type 2 diabetes.. Participants with stable glucose control commenced a randomized cross-over study involving four months of AA (2 × 500 mg/day) or placebo supplementation. Insulin sensitivity was assessed using a hyperinsulinaemic, euglycaemic clamp coupled with infusion of 6,6-D2 glucose. Muscle biopsies were measured for AA concentration and oxidative stress markers that included basal measures (2',7'-dichlorofluorescin [DCFH] oxidation, ratio of reduced-to-oxidized glutathione [GSH/GSSG] and F2-Isoprostanes) and insulin-stimulated measures (DCFH oxidation). Antioxidant concentrations, citrate synthase activity and protein abundances of sodium-dependent vitamin C transporter 2 (SVCT2), total Akt and phosphorylated Akt (ser473) were also measured in muscle samples.. AA supplementation significantly increased insulin-mediated glucose disposal (delta rate of glucose disappearance; ∆Rd) (p=0.009), peripheral insulin-sensitivity index (p=0.046), skeletal muscle AA concentration (p=0.017) and muscle SVCT2 protein expression (p=0.008); but significantly decreased skeletal muscle DCFH oxidation during hyperinsulinaemia (p=0.007) when compared with placebo. Total superoxide dismutase activity was also lower following AA supplementation when compared with placebo (p=0.006). Basal oxidative stress markers, citrate synthase activity, endogenous glucose production, HbA1C and muscle Akt expression were not significantly altered by AA supplementation.. In summary, oral AA supplementation ameliorates skeletal muscle oxidative stress during hyperinsulinaemia and improves insulin-mediated glucose disposal in people with type 2 diabetes. Findings implicate AA supplementation as a potentially inexpensive, convenient, and effective adjunct therapy in the treatment of insulin resistance in people with type 2 diabetes.

Topics: Aged; Ascorbic Acid; Diabetes Mellitus, Type 2; Female; Glucose; Humans; Insulin; Insulin Resistance; Male; Middle Aged; Muscle, Skeletal; Oxidative Stress

The effects of the Dietary Approaches to Stop Hypertension (DASH) eating plan on childhood metabolic syndrome (MetS) and insulin resistance remain to be determined. The present study aimed to assess the effects of recommendations to follow the DASH diet v. usual dietary advice (UDA) on the MetS and its features in adolescents. In this randomised cross-over clinical trial, sixty post-pubescent adolescent girls with the MetS were randomly assigned to receive either the recommendations to follow the DASH diet or UDA for 6 weeks. After a 4-week washout period, the participants were crossed over to the alternate arm. The DASH group was recommended to consume a diet rich in fruits, vegetables and low-fat dairy products and low in saturated fats, total fats and cholesterol. UDA consisted of general oral advice and written information about healthy food choices based on healthy MyPlate. Compliance was assessed through the quantification of plasma vitamin C levels. In both the groups, fasting venous blood samples were obtained at baseline and at the end of each phase of the intervention. The mean age and weight of the participants were 14.2 (SD 1.7) years and 69 (SD 14.5) kg, respectively. Their mean BMI and waist circumference were 27.3 kg/m2 and 85.6 cm, respectively. Serum vitamin C levels tended to be higher in the DASH phase than in the UDA phase (860 (SE 104) v. 663 (SE 76) ng/l, respectively, P= 0.06). Changes in weight, waist circumference and BMI were not significantly different between the two intervention phases. Although changes in systolic blood pressure were not statistically significant between the two groups (P= 0.13), recommendations to follow the DASH diet prevented the increase in diastolic blood pressure compared with UDA (P= 0.01). We found a significant within-group decrease in serum insulin levels (101.4 (SE 6.2) v. 90.0 (SE 5.5) pmol/l, respectively, P= 0.04) and a non-significant reduction in the homeostasis model assessment for insulin resistance score (P= 0.12) in the DASH group. Compared with the UDA group, the DASH group experienced a significant reduction in the prevalence of the MetS and high blood pressure. Recommendations to follow the DASH eating pattern for 6 weeks among adolescent girls with the MetS led to reduced prevalence of high blood pressure and the MetS and improved diet quality compared with UDA. This type of healthy diet can be considered as a treatment modality for the MetS and its components in children.

Topics: Adolescent; Ascorbic Acid; Blood Pressure; Body Mass Index; Child; Cross-Over Studies; Female; Humans; Hypertension; Insulin; Insulin Resistance; Metabolic Syndrome; Patient Compliance; Prevalence; Waist Circumference

While production of reactive oxygen and nitrogen species (RONS) is associated with some of the beneficial adaptations to regular physical exercise, it is not established whether RONS play a role in the improved insulin-stimulated glucose uptake in skeletal muscle obtained by endurance training. To assess the effect of antioxidant supplementation during endurance training on insulin-stimulated glucose uptake, 21 young healthy (age 29 ± 1 y, BMI 25 ± 3 kg/m(2)) men were randomly assigned to either an antioxidant [AO; 500 mg vitamin C and 400 IU vitamin E (α-tocopherol) daily] or a placebo (PL) group that both underwent a supervised intense endurance-training program 5 times/wk for 12 wk. A 3-h euglycemic-hyperinsulinemic clamp, a maximal oxygen consumption (Vo(2max)) and maximal power output (P(max)) test, and body composition measurements (fat mass, fat-free mass) were performed before and after the training. Muscle biopsies were obtained for determination of the concentration and activity of proteins regulating glucose metabolism. Although plasma levels of vitamin C (P < 0.05) and α-tocopherol (P < 0.05) increased markedly in the AO group, insulin-stimulated glucose uptake increased similarly in both the AO (17.2%, P < 0.05) and the PL (18.9%, P < 0.05) group in response to training. Vo(2max) and P(max) also increased similarly in both groups (time effect, P < 0.0001 for both) as well as protein content of GLUT4, hexokinase II, and total Akt (time effect, P ≤ 0.05 for all). Our results indicate that administration of antioxidants during strenuous endurance training has no effect on the training-induced increase in insulin sensitivity in healthy individuals.

Topics: Absorptiometry, Photon; Adult; Anaerobic Threshold; Antioxidants; Ascorbic Acid; Blotting, Western; Body Composition; Dietary Supplements; Double-Blind Method; Glucose Tolerance Test; Humans; Insulin Resistance; Luminescence; Male; Middle Aged; Muscle, Skeletal; Oxygen; Physical Endurance; Physical Fitness; Reverse Transcriptase Polymerase Chain Reaction; RNA; Vitamin E; Young Adult

There are concerns that weight-loss (WL) diets based on very low carbohydrate (LC) intake have a negative impact on antioxidant status and biomarkers of cardiovascular and metabolic health. Obese men (n 16) participated in a randomised, cross-over design diet trial, with food provided daily, at approximately 8.3 MJ/d (approximately 70 % of energy maintenance requirements). They were provided with two high-protein diets (30 % of energy), each for a 4-week period, involving a LC (4 % carbohydrate) and a moderate carbohydrate (MC, 35 % carbohydrate) content. Body weight was measured daily, and weekly blood samples were collected. On average, subjects lost 6.75 and 4.32 kg of weight on the LC and MC diets, respectively (P < 0.001, SED 0.350). Although the LC and MC diets were associated with a small reduction in plasma concentrations of retinol, vitamin E (α-tocopherol) and β-cryptoxanthin (P < 0.005), these were still above the values indicative of deficiency. Interestingly, plasma vitamin C concentrations increased on consumption of the LC diet (P < 0.05). Plasma markers of insulin resistance (P < 0.001), lipaemia and inflammation (P < 0.05, TNF-α and IL-10) improved similarly on both diets. There was no change in other cardiovascular markers with WL. The present data suggest that a LC WL diet does not impair plasma indices of cardiometabolic health, at least within 4 weeks, in otherwise healthy obese subjects. In general, improvements in metabolic health associated with WL were similar between the LC and MC diets. Antioxidant supplements may be warranted if LC WL diets are consumed for a prolonged period.

Topics: Adult; Aged; alpha-Tocopherol; Antioxidants; Ascorbic Acid; Biomarkers; Cardiovascular Diseases; Cross-Over Studies; Cryptoxanthins; Diet, Carbohydrate-Restricted; Diet, Reducing; Dietary Carbohydrates; Dietary Proteins; Endothelium, Vascular; Energy Intake; Humans; Hyperlipidemias; Inflammation Mediators; Insulin Resistance; Male; Metabolic Diseases; Middle Aged; Nutritional Requirements; Obesity; Risk Factors; Vitamin A; Weight Loss; Xanthophylls

The objective of the study was to determine whether short-term antioxidant (AOX) supplementation affects insulin sensitivity, endothelial adhesion molecule levels, and oxidative stress in overweight young adults. A randomized, double-blind, controlled study tested the effects of AOXs on measures of insulin sensitivity (homeostasis model assessment [HOMA]) and quantitative insulin sensitivity check index), endothelial adhesion molecules (soluble intercellular adhesion molecule-1, vascular adhesion molecule, and endothelial-leukocyte adhesion molecule-1), adiponectin, and oxidative stress (lipid hydroperoxides) in overweight and normal-weight individuals (N = 48, 18-30 years). Participants received either AOX (vitamin E, 800 IU; vitamin C, 500 mg; beta-carotene, 10 mg) or placebo for 8 weeks. The HOMA values were initially higher in the overweight subjects and were lowered with AOX by week 8 (15% reduction, P = .02). Adiponectin increased in both AOX groups. Soluble intercellular adhesion molecule-1 and endothelial-leukocyte adhesion molecule-1 decreased in overweight AOX-treated groups by 6% and 13%, respectively (P < .05). Plasma lipid hydroperoxides were reduced by 0.31 and 0.70 nmol/mL in the normal-weight and overweight AOX-treated groups, respectively, by week 8 (P < .05). Antioxidant supplementation moderately lowers HOMA and endothelial adhesion molecule levels in overweight young adults. A potential mechanism to explain this finding is the reduction in oxidative stress by AOX. Long-term studies are needed to determine whether AOXs are effective in suppressing diabetes or vascular activation over time.

Topics: Adiponectin; Adolescent; Adult; Antioxidants; Ascorbic Acid; beta Carotene; Body Weight; Diabetes Mellitus, Type 2; Eating; Endothelial Cells; Female; Humans; Insulin Resistance; Intercellular Adhesion Molecule-1; Lipid Peroxidation; Male; Overweight; Oxidative Stress; Oxygen Consumption; Vascular Cell Adhesion Molecule-1; Vitamin E; Vitamins; Young Adult

Exercise promotes longevity and ameliorates type 2 diabetes mellitus and insulin resistance. However, exercise also increases mitochondrial formation of presumably harmful reactive oxygen species (ROS). Antioxidants are widely used as supplements but whether they affect the health-promoting effects of exercise is unknown. We evaluated the effects of a combination of vitamin C (1000 mg/day) and vitamin E (400 IU/day) on insulin sensitivity as measured by glucose infusion rates (GIR) during a hyperinsulinemic, euglycemic clamp in previously untrained (n = 19) and pretrained (n = 20) healthy young men. Before and after a 4 week intervention of physical exercise, GIR was determined, and muscle biopsies for gene expression analyses as well as plasma samples were obtained to compare changes over baseline and potential influences of vitamins on exercise effects. Exercise increased parameters of insulin sensitivity (GIR and plasma adiponectin) only in the absence of antioxidants in both previously untrained (P < 0.001) and pretrained (P < 0.001) individuals. This was paralleled by increased expression of ROS-sensitive transcriptional regulators of insulin sensitivity and ROS defense capacity, peroxisome-proliferator-activated receptor gamma (PPARgamma), and PPARgamma coactivators PGC1alpha and PGC1beta only in the absence of antioxidants (P < 0.001 for all). Molecular mediators of endogenous ROS defense (superoxide dismutases 1 and 2; glutathione peroxidase) were also induced by exercise, and this effect too was blocked by antioxidant supplementation. Consistent with the concept of mitohormesis, exercise-induced oxidative stress ameliorates insulin resistance and causes an adaptive response promoting endogenous antioxidant defense capacity. Supplementation with antioxidants may preclude these health-promoting effects of exercise in humans.

Topics: Adult; Antioxidants; Ascorbic Acid; Biomarkers; Exercise; Health; Humans; Insulin; Insulin Resistance; Male; Oxidative Stress; Substrate Specificity; Time Factors; Vitamin E

No proven treatment exists for nonalcoholic fatty liver disease (NAFLD) in children and adolescents. We sought to determine the efficacy of lifestyle intervention with or without antioxidant therapy in pediatric NAFLD. A total of 53 patients (age 5.7-18.8 years, 37 boys) were included. Lifestyle intervention consisting of a diet tailored to the patient's calorie needs, and increased physical activity was prescribed in all. Patients were concomitantly randomized to alpha-tocopherol 600 IU/day plus ascorbic acid 500 mg/day (n = 25) or placebo (n = 28), and treated for 24 months. The study was an extension of a previous study aimed at evaluating the effect of 12-month lifestyle intervention and antioxidant therapy on serum levels of aminotransferases. The primary end point of the present study was change in liver histology on repeated biopsy at 24 months. Secondary end points were changes in body weight, liver enzymes, and insulin sensitivity indices on 2-hour oral glucose tolerance test. The amount of weight lost at 24 months was similar in the placebo and antioxidant groups (-4.75 [range, -16-4.0] versus -5.5 [range, -12.2-0.4] kg, respectively, P = 0.9). A significant improvement occurred in the grade of steatosis, lobular inflammation, and hepatocyte ballooning, and in the NAFLD activity score in both groups. Levels of aminotransferases, triglycerides, cholesterol, fasting glucose, and insulin, and insulin sensitivity indices improved significantly as well. The improvement in all these parameters was not significantly different between the two groups.. Lifestyle intervention with diet and increased physical activity induces weight loss and is associated with a significant improvement in liver histology and laboratory abnormalities in pediatric NAFLD. Alpha-tocopherol plus ascorbic acid does not seem to increase the efficacy of lifestyle intervention alone.

Topics: Adolescent; alpha-Tocopherol; Antioxidants; Ascorbic Acid; Blood Glucose; Body Weight; Child; Diet, Reducing; Double-Blind Method; Exercise Therapy; Fasting; Fatty Liver; Female; Humans; Insulin; Insulin Resistance; Life Style; Lipids; Liver; Male; Time Factors; Transaminases; Treatment Outcome

Vitamin E and C given separately improve insulin sensitivity due to an inhibitory effect on oxidative stress and inflammation, however their combined effect on glucose control and inflammation is unknown. To investigate combined effect of Vitamin E and C in elderly with Impaired Fasting Glucose (IFG) on insulin action and substrate oxidation.. Controlled-trial administration of Vitamin E (1000 mg/day) and Vitamin C (1000 UI/day) for four weeks. Hyperinsulinemic euglycemic glucose clamp was performed before and following supplementation.. Out-patient clinic.. Thirteen older men with IFG.. Variations in whole body glucose disposal (WBGD), anti-oxidant, and inflammatory cytokines plasma levels.. An increase in plasma Vitamin E (8.3 + 0.8 vs. 64.9 + 2.1 micromol/l; p < 0.001] and C (35.9 + 5.4 vs. 79.4 + 7.4 micromol/l; p < 0.001) was found. Vitamin administration reduced insulin, glucose, lipid, TNF-alpha and [8-]isoprostane levels. Increase in plasma vitamin E levels correlated with decline in both plasma [8-]isoprostane levels (r = -0.58; p = 0.048) and TNF-alpha levels (r = - 0.62; p = 0.025), while no correlations were found for Vitamin C. Whole body glucose disposal (WBGD) (22.7 + 0.6 vs. 30.4 + 0.8 mmol x kg-1 x min-1; p = 0.001) and non-oxidative glucose metabolism rose after supplementation. Rise in plasma levels of Vitamin C and E correlated with WBGD. Multivariate linear regression models showed independent associations among the change in Vitamin E and the decline in TNF-alpha and [8-]isoprostane levels.. Combined administration of Vitamin E and C lowered inflammation and improved insulin action through a rise in non-oxidative glucose metabolism.

Topics: Aged; Anti-Inflammatory Agents; Antioxidants; Ascorbic Acid; Blood Glucose; Cardiovascular Diseases; Cytokines; Diabetes Mellitus, Type 2; Dietary Supplements; Fasting; Humans; Insulin; Insulin Resistance; Lipids; Male; Oxidative Stress; Vitamin E

Endothelial dysfunction is a hallmark of Type 2 diabetes related to hyperglycemia and oxidative stress. Nitric oxide-dependent vasodilator actions of insulin may augment glucose disposal. Thus endothelial dysfunction may worsen insulin resistance. Intra-arterial administration of vitamin C improves endothelial dysfunction in diabetes. In the present study, we investigated effects of high-dose oral vitamin C to alter endothelial dysfunction and insulin resistance in Type 2 diabetes. Plasma vitamin C levels in 109 diabetic subjects were lower than healthy (36 +/- 2 microM) levels. Thirty-two diabetic subjects with low plasma vitamin C (<40 microM) were subsequently enrolled in a randomized, double-blind, placebo-controlled study of vitamin C (800 mg/day for 4 wk). Insulin sensitivity (determined by glucose clamp) and forearm blood flow in response to ACh, sodium nitroprusside (SNP), or insulin (determined by plethysmography) were assessed before and after 4 wk of treatment. In the placebo group (n = 17 subjects), plasma vitamin C (22 +/- 3 microM), fasting glucose (159 +/- 12 mg/dl), insulin (19 +/- 7 microU/ml), and SI(Clamp) [2.06 +/- 0.29 x 10(-4) dl x kg(-1) x min(-1)/(microU/ml)] did not change significantly after placebo treatment. In the vitamin C group (n = 15 subjects), basal plasma vitamin C (23 +/- 2 microM) increased to 48 +/- 6 microM (P < 0.01) after treatment, but this was significantly less than that expected for healthy subjects (>80 microM). No significant changes in fasting glucose (156 +/- 11 mg/dl), insulin (14 +/- 2 microU/ml), SI(Clamp) [2.71 +/- 0.46 x 10(-4) dl x kg(-1) x min(-1)/(microU/ml)], or forearm blood flow in response to ACh, SNP, or insulin were observed after vitamin C treatment. We conclude that high-dose oral vitamin C therapy, resulting in incomplete replenishment of vitamin C levels, is ineffective at improving endothelial dysfunction and insulin resistance in Type 2 diabetes.

Topics: Administration, Oral; Adult; Ascorbic Acid; Blood Pressure; Diabetes Mellitus, Type 2; Endothelium, Vascular; Forearm; Glucose Clamp Technique; Humans; Insulin Resistance; Middle Aged; Placebos; Vasodilation

Glucosamine is a popular nutritional supplement used to treat osteoarthritis. Intravenous administration of glucosamine causes insulin resistance and endothelial dysfunction. However, rigorous clinical studies evaluating the safety of oral glucosamine with respect to metabolic and cardiovascular pathophysiology are lacking. Therefore, we conducted a randomized, placebo-controlled, double-blind, crossover trial of oral glucosamine at standard doses (500 mg p.o. t.i.d.) in lean (n = 20) and obese (n = 20) subjects. Glucosamine or placebo treatment for 6 weeks was followed by a 1-week washout and crossover to the other arm. At baseline, and after each treatment period, insulin sensitivity was assessed by hyperinsulinemic-isoglycemic glucose clamp (SI(Clamp)) and endothelial function evaluated by brachial artery blood flow (BAF; Doppler ultrasound) and forearm skeletal muscle microvascular recruitment (ultrasound with microbubble contrast) before and during steady-state hyperinsulinemia. Plasma glucosamine pharmacokinetics after oral dosing were determined in each subject using a high-performance liquid chromatography method. As expected, at baseline, obese subjects had insulin resistance and endothelial dysfunction when compared with lean subjects (SI(Clamp) [median {25th-75th percentile}] = 4.3 [2.9-5.3] vs. 7.3 [5.7-11.3], P < 0.0001; insulin-stimulated changes in BAF [% over basal] = 12 [-6 to 84] vs. 39 [2-108], P < 0.04). When compared with placebo, glucosamine did not cause insulin resistance or endothelial dysfunction in lean subjects or significantly worsen these findings in obese subjects. The half-life of plasma glucosamine after oral dosing was approximately 150 min, with no significant changes in steady-state glucosamine levels detectable after 6 weeks of therapy. We conclude that oral glucosamine at standard doses for 6 weeks does not cause or significantly worsen insulin resistance or endothelial dysfunction in lean or obese subjects.

Topics: Administration, Oral; Adult; Ascorbic Acid; Blood Pressure; Diabetes Mellitus, Type 1; Endothelium, Vascular; Glucosamine; Heart Rate; Humans; Insulin Resistance; Obesity; Reference Values; Thinness

Few data are available on the effect of antioxidants in paediatric non-alcoholic fatty liver disease (NAFLD).. To compare the effect of a nutritional programme alone or combined with alpha-tocopherol and ascorbic acid on alanine aminotransferase (ALT) levels, and insulin resistance (IR) in biopsy-proven NAFLD children.. IN a 12-month double-blind placebo study, 90 patients were prescribed a balanced calorie diet (25-30 cal/kg/d), physical exercise, and placebo (group A) or alpha-tocopherol 600 IU/day plus ascorbic acid 500 mg/day (group B). IR was estimated by the homeostasis model assessment (HOMA-IR).. At month 12, ALT (32.67 +/- 8.09 vs. 32.18 +/- 11.39 IU/L; P = NS), HOMA-IR (1.52 +/- 0.66 vs. 1.84 +/- 0.95 IU/L; P = NS), and weight loss (32% vs. 35% of excessive body weight; P = NS) did not differ between the two arms. Among subjects who lost >or=20% of their excessive weight, ALT and body weight percentage changes were significantly related (r(o) = 0.260; P = 0.03). In subjects, who lost more than 1.0 kg, HOMA-IR significantly decreased (2.20 +/- 0.21 to 1.57 +/- 0.13 in group A (P

Topics: Adolescent; Alanine Transaminase; Antioxidants; Ascorbic Acid; Blood Glucose; Child; Child, Preschool; Fatty Liver; Female; Humans; Insulin Resistance; Male; Treatment Outcome; Vitamin E

Cigarette smoking impairs endothelial function and is one of the major risk factors for atherosclerosis and coronary heart disease. Insulin resistance is associated with major risk factors for atherosclerosis. We examined the effects of vitamin C on insulin sensitivity and endothelial function by measuring steady-state plasma glucose (SSPG) and flow-mediated dilation (FMD) of the brachial artery. We studied 16 current smokers with normal glucose tolerance, 15 nonsmokers with impaired glucose tolerance (IGT), and 17 nonsmokers with normal glucose tolerance as controls. Both SSPG and FMD were blunted in smokers and nonsmokers with IGT compared with controls. In smokers, vitamin C decreased SSPG (P < 0.01 by ANOVA) with decreasing plasma thiobarbituric acid-reactive substances (TBARS) (P < 0.05 by ANOVA) and improved FMD (P < 0.05 by ANOVA). Furthermore, vitamin C improved both SSPG (P < 0.005 by ANOVA) and FMD (P < 0.05 by ANOVA) in nonsmokers with IGT. SSPG, FMD, or TBARS in controls did not change after vitamin C infusion. There was a significant correlation between SSPG and FMD both in smokers and nonsmokers with IGT, whereas no correlation was observed in controls. In conclusion, both insulin sensitivity and endothelial function were impaired in smokers and nonsmokers with IGT and were improved by vitamin C. Thus increased reactive oxygen species play an important role in the pathogenesis of insulin resistance as well as endothelial dysfunction in smokers and nonsmokers with IGT.

Topics: Analysis of Variance; Ascorbic Acid; Blood Flow Velocity; Blood Glucose; Brachial Artery; Endothelium, Vascular; Female; Glucose Tolerance Test; Humans; Insulin; Insulin Resistance; Male; Middle Aged; Oxidative Stress; Reactive Oxygen Species; Smoking; Thiobarbituric Acid Reactive Substances; Vasodilation

The relation between the self-reported intake of various dietary constituents and insulin-mediated glucose disposal was evaluated in 52 healthy volunteers. Insulin-mediated glucose uptake was independently associated with degree of obesity (inversely) and estimates of level of physical activity (directly). An independent relation between increased intake of vitamin A and insulin action was shown, ie, the greater the intake of vitamin A, the more effective was insulin in stimulating glucose disposal. However, there was no independent relation noted between insulin-mediated glucose disposal and estimates of the intake of carbohydrate, protein, amount or kind of fat, fiber, or vitamins C and E. Furthermore, the 20 individuals with estimates of vitamin A consumption > 10 000 IU/d had significantly lower plasma glucose (P < 0.01) and insulin (P < 0.05) responses to oral glucose, and insulin-mediated glucose disposal values that were higher (P < 0.005) than those of the 20 individuals whose estimated vitamin A intake was < 8000 IU/d. These results suggest that vitamin A intake, but not intakes of vitamin C and E, fiber, fat, or carbohydrate is associated with enhanced insulin-mediated glucose disposal.

Topics: Administration, Oral; Adult; Ascorbic Acid; Blood Glucose; Dietary Carbohydrates; Dietary Fats; Dietary Fiber; Exercise; Female; Glucose; Humans; Insulin; Insulin Resistance; Male; Middle Aged; Nutrition Assessment; Obesity; Regression Analysis; Software; Surveys and Questionnaires; Time Factors; Vitamin A; Vitamin E; Vitamins

Ascorbic acid has been suggested to regulate obesity in obese male rodents. Moreover, increased adipocyte size has been associated with metabolic disease. Thus, we investigated the effects of ascorbic acid on adipocyte hypertrophy and insulin resistance in high-fat diet (HFD)-induced obese ovariectomized (OVX) C57BL/6J mice, an animal model of obese postmenopausal women. Administration of ascorbic acid (5% w/w in diet for 18 weeks) reduced the size of visceral adipocytes without changes in body weight and adipose tissue mass in HFD-fed obese OVX mice compared with obese OVX mice that did not receive ascorbic acid. Ascorbic acid inhibited adipose tissue inflammation, as shown by the decreased number of crown-like structures and CD68-positive macrophages in visceral adipose tissues. Ascorbic acid-treated mice exhibited improved hyperglycemia, hyperinsulinemia, and glucose and insulin tolerance compared with nontreated obese mice. Pancreatic islet size and insulin-positive β-cell area in ascorbic acid-treated obese OVX mice decreased to the levels observed in low-fat diet-fed lean mice. Ascorbic acid also suppressed pancreatic triglyceride accumulation in obese mice. These results suggest that ascorbic acid may reduce insulin resistance and pancreatic steatosis partly by suppressing visceral adipocyte hypertrophy and adipose tissue inflammation in obese OVX mice.

Topics: Adipocytes; Animals; Ascorbic Acid; Diet, High-Fat; Female; Hypertrophy; Inflammation; Insulin; Insulin Resistance; Male; Mice; Mice, Inbred C57BL; Mice, Obese; Obesity; Pancreatic Diseases

Insulin resistance is a common risk factor for metabolic syndrome (MetS), leading to type 2 diabetes mellitus and cardiovascular diseases. This study tested the hypothesis that the polygenic variants associated with the risk of insulin resistance (IR) interact with the lifestyles and nutrient intake of participants aged >40 in a large city hospital-based cohort (n = 58 701).. Polygenic risk score (PRS)-lifestyle interactions were evaluated. The participants were categorized into IR (case) and no IR (control) groups using a cutoff of a homeostasis model assessment of IR of 2.32, as estimated with a prediction model generated from the Ansan-Ansung cohort. Single-nucleotide polymorphism (SNP) with an SNP-SNP interaction influencing IR risk were identified using a genome-wide association study and generalized multifactor dimensionality reduction analysis after adjusting for IR-related variables. The selected genetic variants were confirmed in the Ansan-Ansung cohort.. IR was associated mainly with body mass index by 14.24, fat mass by 4.57, and MetS by 8.10 times. Serum high-sensitive C-reactive protein, aspartate aminotransferase, and alanine aminotransferase concentrations were positively associated with IR risk. Plant-based diet (PBD), vitamin C (V-C), and flavonoid intakes were inversely associated with IR risk. The optimal model with SNP-SNP interaction included seven SNPs (CDKAL1_rs7754840, HNF4A_rs4812829, GCKR_rs780093, SLC30A8_rs11558471, KCNQ1_rs2237895, ANK2_rs12503758, and PTPRD_rs10977434) from generalized multifactor dimensionality reduction. After adjusting for the covariates, a high PRS of the seven-SNP model was positively associated with an IR risk of 1.78 times. The seven-SNP model interacted with the energy and PBD intake (especially, high in fruit, V-C and flavonoid). to influence IR risk. In the participants with low-energy, PBD, fruit, flavonoid, and V-C intakes, the percentage of high IR was higher in the high- than in the low-PRS group.. Adults having a high PRS for IR may benefit from a PBD containing high amounts of fruits, V-C, and flavonoids, which were found inversely related to IR risk. The results can be applied to personalized nutrition.

Topics: Adult; Ascorbic Acid; Diabetes Mellitus, Type 2; Diet, Vegetarian; Flavonoids; Fruit; Genome-Wide Association Study; Humans; Insulin Resistance; Metabolic Syndrome; Polymorphism, Single Nucleotide; Risk Factors

Antioxidant vitamins C and E are inversely associated with type 1 diabetes (T1D). We investigated if antioxidants are also associated with latent autoimmune diabetes in adults (LADA), with low (LADA

Topics: Adult; Antioxidants; Ascorbic Acid; Case-Control Studies; Diabetes Mellitus, Type 1; Diabetes Mellitus, Type 2; Genome-Wide Association Study; Glucose Intolerance; Humans; Insulin Resistance; Latent Autoimmune Diabetes in Adults; Mendelian Randomization Analysis; Nutrients; Sweden; Vitamin E; Vitamins

Maternal diets during pregnancy and lactation are key determinants that regulate the development of metabolic syndrome (MetS) in offspring. l-malic acid (MA) was previously reported to improve antioxidant capacity and aerobic metabolism. However, the effects of maternal MA consumption on the metabolic features of offspring remain largely unexplored. Herein, through pig models consuming MA-enriched diets during late pregnancy and lactation, we found that maternal MA consumption potentiated the anti-inflammatory and antioxidant capacity of sows, thereby improving their reproductive performance and the growth performance of piglets. Maternal MA consumption also induced a transition of slow-twitch to fast-twitch fibers in the early life of offspring. Along with muscle growth and fiber-type transition, insulin sensitivity and glucose metabolism, including aerobic metabolism and glycolysis, were improved in the skeletal muscle of offspring. An untargeted metabolomic analysis further revealed the contribution of modified amino acid metabolism to the improved aerobic metabolism. Mechanistically, maternal MA consumption remodeled colonic microbiota of their offspring. Briefly, the abundance of Colidextribacter, Romboutsia, and Family_XIII_AD3011_group increased, which were positively associated with the antioxidant capacity and glucose metabolism of skeletal muscles. A decreased abundance of Prevotella, Blautia, Prevotellaceae_NK3B31_group, and Collinsella was also detected, which were involved in less insulin sensitivity. Notably, milk metabolites, such as ascorbic acid (AA) and granisetron (GS), were found as key effectors regulating the gut microbiota composition of piglets. The properties of AA and GS in alleviating insulin resistance, inflammation, and oxidative stress were further verified through mice treated with high-fat diets. Overall, this study revealed that maternal MA consumption could modulate the inflammatory response, antioxidant capacity, and glucose metabolism by regulating the gut microbiota of offspring through the vertical transmission of milk metabolites. These findings suggest the potential of MA in the prevention and treatment of MetS in early life.

Topics: Animals; Antioxidants; Ascorbic Acid; Diet, High-Fat; Female; Gastrointestinal Microbiome; Glucose; Insulin Resistance; Metabolic Syndrome; Mice; Pregnancy; Swine

Adequate dietary intakes of essential micronutrients are critical to prevent insulin resistance (IR)-related diseases. Even though the excess calorie intake linked with obesity is also associated with such diseases, no previous studies evaluated the importance of meeting the Dietary Reference Intake (DRI) of micronutrients in relation to calorie intake in those at risk for developing IR.. We evaluated the relationship between the ability or failure to meet the DRI of micronutrients in relation to daily calorie intake in 463 childbearing-age women with a higher prevalence of IR. 56-65% women met the DRIs for vitamin B12, vitamin C, thiamine, and riboflavin while only 0%-49% met the DRIs for folate, pyridoxine, niacin, pantothenic acid, total carotene, vitamins A, D and E by consuming an acceptable number of calories. Women who met the DRIs of folate and vitamin C within acceptable daily calorie intakes were 59% and 66% less likely to have higher Homeostatic Model Assessment for Insulin Resistance (HOMA-IR) compared to women who did not.. Understanding the mechanisms that explain our findings will be of value to address IR-associated with exposure to high calorie/low-micronutrient dense diets consumed by childbearing-age women. Since there is a global recognition that IR has been increasing in adults and children, similar studies of this nature in pregnant women at risk for IR will provide much needed data to assess the burden of such adverse dietary habits in the offspring. Our study approach may form the foundation for such studies.

Topics: Adult; Ascorbic Acid; Child; Diet; Energy Intake; Female; Folic Acid; Humans; Insulin Resistance; Male; Micronutrients; Pregnancy; Vitamins

Aimed to demonstrate the association of VC and metabolism in the obesity or overweight and determine VC changes after laparoscopic sleeve gastrectomy (LSG).. A total of 253 overweight or people with obesity were recruited, including 61 with LSG. They were divided into group A (VC < 34 ug/ml) and group B (VC ≥ 34 ug/ml). Glucose-lipid metabolic parameters were compared, and VC status before and 6 and 12 months after LSG were measured.. (1) Body weight, body mass index (BMI), neck circumference (NC), waist circumference (WC), hip circumference (HC), waist-to-hip ratio, heart rate (HR), diastolic systolic pressure (DBP), 2-hour postprandial glucose (2h-BG), fasting insulin (FINS), 2-hour postprandial insulin (2h-INS), glycosylated hemoglobin (HBG), homeostasis model of insulin resistance (HOMA-IR), total cholesterol (TCH), triglyceride (TG) and free fatty acid (FFA) were higher while high-density lipoprotein (HDL-C) was lower in group A than group B (p < 0.05). (2) VC was negatively correlated with body weight, BMI, NC, WC and HC, HR, SBP, DBP, and 2h-BG, FINS, 2h-INS, HGB, HOMA-IR, TG and FFA, while positively with HDL-C (p < 0.05). (3) Patients with obesity or hypertriglyceridemia or low HDL-C had lower VC than corresponding group. (p < 0.05). (4) Logistic regression analysis showed that VC was the independent risk factor of hypertriglyceridemia, obesity and low HDL-C 5) VC concentrations were slightly increased in 6 months after LSG, and unchanged in 12 months after LSG.. VC was closely associated with glucose-lipid metabolism, and may play a protective role in metabolic disorders. LSG would not worsen the VC status or deficiency.

Topics: Ascorbic Acid; Blood Glucose; Body Mass Index; Body Weight; Cholesterol; Fatty Acids, Nonesterified; Gastrectomy; Glucose; Glycated Hemoglobin; Humans; Hypertriglyceridemia; Insulin; Insulin Resistance; Laparoscopy; Lipid Metabolism; Lipoproteins, HDL; Obesity; Overweight; Triglycerides

Obesity is one of the major risk factor for cardiovascular and metabolic diseases. A disproportional accumulation of fat at visceral (VAT) compared to subcutaneous sites (SAT) has been suspected as a key detrimental event. We used non-targeted metabolomics profiling to reveal metabolic pathways associated with higher VAT or SAT amount among subjects free of metabolic diseases to identify possible contributing metabolic pathways. The study population comprised 491 subjects [mean (standard deviation): age 44.6 yrs (13.0), body mass index 25.4 kg/m² (3.6), 60.1% females] without diabetes, hypertension, dyslipidemia, the metabolic syndrome or impaired renal function. We associated MRI-derived fat amounts with mass spectrometry-derived metabolites in plasma and urine using linear regression models adjusting for major confounders. We tested for sex-specific effects using interactions terms and performed sensitivity analyses for the influence of insulin resistance on the results. VAT and SAT were significantly associated with 155 (101 urine) and 49 (29 urine) metabolites, respectively, of which 45 (27 urine) were common to both. Major metabolic pathways were branched-chain amino acid metabolism (partially independent of insulin resistance), surrogate markers of oxidative stress and gut microbial diversity, and cortisol metabolism. We observed a novel positive association between VAT and plasma levels of the potential pharmacological agent piperine. Sex-specific effects were only a few, e.g. the female-specific association between VAT and O-methylascorbate. In brief, higher VAT was associated with an unfavorable metabolite profile in a sample of healthy, mostly non-obese individuals from the general population and only few sex-specific associations became apparent.

Topics: Adipose Tissue; Adult; Alkaloids; Ascorbic Acid; Benzodioxoles; Biomarkers; Cross-Sectional Studies; Female; Humans; Hydrocortisone; Insulin Resistance; Intra-Abdominal Fat; Magnetic Resonance Imaging; Male; Metabolic Networks and Pathways; Metabolome; Middle Aged; Organ Size; Piperidines; Polyunsaturated Alkamides; Sex Factors; Subcutaneous Fat

Metabolic Syndrome (MetS), a major worldwide concern for the public health system, refers to a cluster of key metabolic components, and represents a risk factor for diabetes and cardiovascular diseases. As oxidative stress (OxS) and inflammation are the major triggers of insulin sensitivity (IS), a cardinal MetS feature, the principal aim of the present work is to determine whether glycomacropeptide (GMP), a milk-derived bioactive peptide, exerts beneficial effects on their expression.. Fully differentiated intestinal Caco-2/15 cells are used to evaluate the preventive action of 2 mg/mL GMP against OxS and inflammation induced by the mixture iron-ascorbate (Fe/Asc) (200 μM:2 mM). The potency of GMP of decreasing the production of lipoproteins, including chylomicrons (CM), very-low-density lipoproteins (VLDL) and low-density lipoproteins (LDL) is also assessed.. The administration of GMP significantly reduces malondialdehyde, a biomarker of lipid peroxidation, and raises superoxide dismutase 2 and glutathione peroxidase via the induction of the nuclear factor erythroid 2-related factor 2, a transcription factor, which orchestrates cellular antioxidant defenses. Similarly, GMP markedly lowers the inflammatory agents tumor necrosis factor-α and cyclooxygenase-2 via abrogation of the nuclear transcription factor-kB. Moreover, GMP-treated cells show a down-regulation of Fe/Asc-induced mitogen activated protein kinase pathway, suggesting greater IS. Finally, GMP decreases the production of CM, VLDL, and LDL.. Our results highlight the effectiveness of GMP in attenuating OxS, inflammation and lipoprotein biogenesis, as well as improving IS, the key components of MetS. Further investigation is needed to elucidate the mechanisms mediating the preventive action of GMP.

Topics: Ascorbic Acid; Caco-2 Cells; Caseins; Glutathione Peroxidase; Humans; Inflammation; Inflammation Mediators; Insulin Resistance; Intestinal Mucosa; Iron; Lipoproteins; Malondialdehyde; Metabolic Syndrome; Mitogen-Activated Protein Kinases; Oxidative Stress; Peptide Fragments; Superoxide Dismutase

Epidemiological studies support the association between inadequate vitamin C (Vc) intake and non-alcoholic fatty liver disease (NAFLD). However, the intervention dose of Vc, and the prophylactic and therapeutic effects on NAFLD are unclear. This study aimed to investigate the prophylactic and therapeutic effects of low (LVc), medium (MVc) and high (HVc) doses of Vc on NAFLD. C57BL/6 mice were randomly assigned to prophylactic groups (mice received a high-fat diet (HFD) concomitant with different doses of Vc) and therapeutic groups (HFD-induced NAFLD mice treated with different doses of Vc). Results showed that prophylactic LVc and MVc administration reduced the risk of NAFLD development in HFD-fed mice, as evidenced by significantly lowered body weight, perirenal adipose tissue mass, and steatosis, whereas prophylactic HVc administration did not prevent HFD-induced NAFLD development. Furthermore, therapeutic MVc administration significantly ameliorated HFD-induced increase in body weight, perirenal adipose tissue mass and steatosis, whereas therapeutic LVc and HVc administration did not ameliorate NAFLD symptoms. In fact, therapeutic HVc administration significantly increased body weight, perirenal adipose tissue mass, and lobular inflammation. Moreover, prophylactic LVc administration was more effective than therapeutic LVc administration as evidenced by significantly lower body weight, perirenal adipose tissue mass, steatosis, ballooned hepatocytes, and lobular inflammation in prophylactic LVc administration. The same trends were observed between prophylactic HVc administration and therapeutic HVc administration. In addition, all Vc-administered mice exhibited low blood glucose, triglycerides and homeostasis model assessment of insulin resistance values and high adiponectin levels compared to HFD-fed mice. Our study suggested that MVc was beneficial for HFD-induced NAFLD prophylaxis and therapy. LVc prevented HFD-induced NAFLD development, while HVc for NAFLD management was risky. This study offers valuable insight into the effect of various Vc doses on NAFLD management.

Topics: Adiponectin; Animals; Antioxidants; Ascorbic Acid; Diet, High-Fat; Disease Models, Animal; Dose-Response Relationship, Drug; Inflammation; Insulin Resistance; Male; Mice; Mice, Inbred C57BL; Non-alcoholic Fatty Liver Disease; Triglycerides; Weight Gain

The aim of this study was to compare antioxidant vitamin C and vitamin E levels in the non-acromegaly control group and in patients with acromegaly with and without remission.. In this study, 100 cases, acromegaly patients of 57% (n=57, 29F, 28M, mean ages of 49.5±12.1) and control subjects of 43% (n=43, 29F, 14M, mean ages of 49.6±9.2). Acromegaly patients were classified into two groups; active acromegaly (AA; n=33) and controlled acromegaly (CA; n=24).. Vitamin C levels were significantly lower in the acromegaly group [7.6 (4.7) mg/L, as median (IQR)] when compared to the control group [12.2 (5.5) mg/L, as median (IQR)] (p <0.001). Vitamin E levels didn't show a significant difference between the acromegaly and the control groups (14.2±3.6 vs. 14.8±3.7, as mean±SD, respectively, p = 0.439). Correlation analysis showed that vitamin C levels were not significantly associated with clinical, anthropometric and laboratory parameters in the acromegaly group. Vitamin E levels were significantly associated with the total cholesterol, triglyceride, LDL-C, HDL-C, APO A1, APO B both in the acromegaly and the control groups.. This study is the first one to investigate the relationship between the levels of vitamin C & E and anthropometric & metabolic parameters in acromegaly patients and control group. In our study, vitamin C level was significantly lower in the acromegaly group compared to the level in the control group. There was no significant difference in vitamin E levels between the acromegaly and control group.

Topics: Acromegaly; Adipose Tissue; Adult; Apolipoprotein A-I; Apolipoproteins B; Ascorbic Acid; Body Composition; Body Mass Index; Case-Control Studies; Cholesterol; Cholesterol, HDL; Cholesterol, LDL; Electric Impedance; Female; Human Growth Hormone; Humans; Insulin Resistance; Insulin-Like Growth Factor I; Male; Middle Aged; Receptors, Somatotropin; Triglycerides; Vitamin E; Waist Circumference

Bone health has been associated with oxidative stress and antioxidants have received interest to this end. Serum uric acid (SUA), an end product of purine metabolism in humans, has recently shown antioxidant properties regarding bone health, but there are conflicting results. The aim of this study was to investigate the relationship between SUA levels and lumbar spine bone mineral density (BMD) in clinically apparently healthy males aged 40-60 years. We performed a cross-sectional study of 6588 Korean males who completed a health-screening program from January 2011 to December 2014. Of the study participants, the mean age was 48.2 ± 10.7 years. Multiple regression analyses resulted in a significant positive association with lumbar spine BMD across SUA quintiles in a dose-response manner after adjusting for various confounding factors (p = 0.013); for each 1 mg/dl increase of SUA, BMD rose by 0.0054 g/cm

Topics: Alcoholism; Ascorbic Acid; Body Mass Index; Bone Density; C-Reactive Protein; Calcium; Cross-Sectional Studies; Diet; Exercise; Glomerular Filtration Rate; Humans; Insulin Resistance; Lumbar Vertebrae; Male; Mass Screening; Middle Aged; Smoking; Uric Acid

Intestinal multidrug resistance-associated protein 2 is an ABC transporter that limits the absorption of xenobiotics ingested orally, thus acting as essential component of the intestinal biochemical barrier. Metabolic Syndrome (MetS) is a pathological condition characterized by dyslipidemia, hyperinsulinemia, insulin resistance, chronic inflammation, and oxidative stress (OS). In a previous study we demonstrated that MetS-like conditions induced by fructose in drinking water (10% v/v, during 21 days), significantly reduced the expression and activity of intestinal Mrp2 in rats. We here evaluated the potential beneficial effect of geraniol or vitamin C supplementation, natural compounds with anti-inflammatory and anti-oxidant properties, in reverse fructose-induced Mrp2 alterations. After MetS-like conditions were induced (21 days), animals were cotreated with geraniol or vitamin C or vehicle for another 14 days. Decreased expression of Mrp2 protein and mRNA due to fructose administration was reversed by geraniol and by vitamin C, consistent with restoration of Mrp2 activity evaluated in everted intestinal sacs. Concomitantly, increased intestinal IL-1β and IL-6 levels induced by fructose were totally and partially counterbalanced, respectively, by geraniol administration. The intestinal redox unbalance generated by fructose was improved by geraniol and vitamin C, as evidenced by decreasing lipid peroxidation products and activity of Superoxide Dismutase and by normalizing glutathione reduced/oxidized glutathione ratio. The restoration effects exhibited by geraniol and vitamin C suggest that local inflammatory response and OS generated under MetS-like conditions represent important mediators of the intestinal Mrp2 down-regulation. Additionally, both agents could be considered of potential therapeutic value to preserve Mrp2 function under MetS conditions.

Topics: Acyclic Monoterpenes; Animals; Anti-Inflammatory Agents, Non-Steroidal; Antioxidants; Ascorbic Acid; ATP-Binding Cassette Transporters; Body Weight; Down-Regulation; Eating; Fructose; Glucose; Inflammation; Insulin Resistance; Intestinal Mucosa; Male; Oxidative Stress; Rats, Wistar; Triglycerides

Vitamin C and vitamin E supplementations and their beneficial effects on type 2 diabetes mellitus (T2DM) have been subjected to countless controversial data. Hence, our aim is to investigate the hepatic molecular mechanisms of any diabetic predisposing risk of the chronic administration of different doses of vitamin E or vitamin C in rats.. The rats were supplemented with different doses of vitamin C or vitamin E for eight months.. Vitamin C and vitamin E increased fasting blood glucose, insulin, and homeostasis model assessment index for insulin resistance (HOMA). Vitamin C disrupted glucose tolerance by attenuating upstream hepatic insulin action through impairing the phosphorylation and activation of insulin receptor and its subsequent substrates; however, vitamin E showed its effect downstream insulin receptor in the insulin signaling pathway, reducing hepatic glucose transporter-2 (GLUT2) and phosphorylated protein kinase (p-Akt). Moreover, both vitamins showed their antioxidant capabilities [nuclear factor-erythroid-2-related factor 2 (Nrf2), total and reduced glutathione] and their negative effect on Wnt pathway [phosphorylated glycogen synthase kinase-3β (p-GSK-3β)], by altering the previously mentioned parameters, inevitably leading to severe reduction of reactive oxygen species (ROS) below the physiological levels.. In conclusion, a detrimental effect of chronic antioxidant vitamins supplementation was detected; leading to insulin resistance and impaired glucose tolerance obviously through different mechanisms. Overall, these findings indicate that the conventional view that vitamins promote health benefits and delay chronic illnesses and aging should be modified or applied with caution.

Topics: Animals; Antioxidants; Ascorbic Acid; Glucose; Insulin; Insulin Resistance; Liver; Male; Oxidative Stress; Rats; Rats, Wistar; Signal Transduction; Vitamin E; Vitamins; Wnt Signaling Pathway

In obesity and dyslipidemia, hydrolysis of triacylglycerol (TAG) into non-esterified fatty acids (NEFAs) may contribute to insulin resistance, and production of oxygenated, bioactive polyunsaturated fatty acids may increase oxidative stress. Here we show that after six weeks of high-fat feeding of obese prone rats (Crl:OP(CD), vitamin C was increased both in liver (P < 0.01) and plasma (P < 0.001), while both TAG (P < 0.01) and NEFA (P < 0.001) were lower than in low-fat fed control rats. Hepatic vitamin C biosynthesis was similar between groups, indicating that a new steady state level was established with a higher vitamin C level adequate for supplying the systemic needs. Glucose and insulin sensitivity were unaffected at this stage. Eventually, the mobilization of vitamin C may be seen as a mechanism to protect the host against insulin resistance.

Topics: Animals; Ascorbic Acid; Blood Glucose; Diet, High-Fat; Insulin; Insulin Resistance; Liver; Obesity; Rats; Triglycerides

To examine whether low circulating vitamin C concentrations and low fruit and vegetable intakes were associated with insulin resistance and other Type 2 diabetes risk markers in childhood.. We conducted a cross-sectional, school-based study in 2025 UK children aged 9-10 years, predominantly of white European, South-Asian and black African origin. A 24-h dietary recall was used to assess fruit, vegetable and vitamin C intakes. Height, weight and fat mass were measured and a fasting blood sample collected to measure plasma vitamin C concentrations and Type 2 diabetes risk markers.. In analyses adjusting for confounding variables (including socio-economic status), a one interquartile range higher plasma vitamin C concentration (30.9 μmol/l) was associated with a 9.6% (95% CI 6.5, 12.6%) lower homeostatic model assessment of insulin resistance value, 0.8% (95% CI 0.4, 1.2%) lower fasting glucose, 4.5% (95% CI 3.2, 5.9%) lower urate and 2.2% (95% CI 0.9, 3.4%) higher HDL cholesterol. HbA1c concentration was 0.6% (95% CI 0.2, 1.0%) higher. Dietary fruit, vegetable and total vitamin C intakes were not associated with any Type 2 diabetes risk markers. Lower plasma vitamin C concentrations in South-Asian and black African-Caribbean children could partly explain their higher insulin resistance.. Lower plasma vitamin C concentrations are associated with insulin resistance and could partly explain ethnic differences in insulin resistance. Experimental studies are needed to establish whether increasing plasma vitamin C can help prevent Type 2 diabetes at an early stage.

Topics: Ascorbic Acid; Blood Glucose; Child; Cross-Sectional Studies; Diabetes Mellitus, Type 2; Diet; Eating; Female; Fruit; Humans; Insulin Resistance; Male; Risk Factors; Socioeconomic Factors; United Kingdom; Vegetables

Oxidative stress and insulin resistance (IR) are major contributors in the pathogenesis of non-alcoholic fatty liver disease (NAFLD). The purpose of this study was to find the relation between oxidative stress parameters and histopathological findings in NAFLD patients with and without insulin resistance (IR).. Thirty-two patients with no alcohol intake and biopsy-proven diagnosis of NAFLD were studied (M/F: 17/15; mean age 46.5±11.4 years). Twenty-one NAFLD patients with IR were compared with 11 patients without IR. The fasting insulin level was measured, and the insulin resistance index was calculated using the homeostasis model assessment (HOMA) method. Malondialdehyde (MDA) and superoxide dismutase (SOD) activities were measured in tissue and serum specimens. Glutathione (GH) was measured in tissue homogenates. Nitric oxide (NO), vitamin E and C levels were measured in serum.. Patients with IR had significantly higher tissue MDA levels (p=0.001) and significantly decreased tissue SOD and GH levels (p=0.001 and 0.002, respectively) than those without IR. The steatosis grade, necroinflammatory grade and stage were significantly higher in patients with IR (p=0.035, 0.003 and 0.001, respectively). HOMA IR significantly correlated with the necroinflammatory grade, stage, tissue MDA, SOD and GH (p=0.013, 0.001, 0.008, 0.001 and 0.001, respectively). Serum MDA (β=1.88, p=0.002), serum SOD (β=0.57, p=0.006), tissue MDA (β=0.22, p=0.006), tissue SOD (β=1.48, p=0.071) and stage (β=2.81, p=0.003) were independently associated with increased HOMA IR. Increased MDA [OR: 1.51; 95% CI: (1.03-2.22); p=0.034] was a risk factor for non-alcoholic steatohepatitis (NASH), and increased SOD activity had a preventive effect against NASH [OR: 0.008; 95% CI: (0.001-0.98); p=0.04].. This study shows that insulin resistance in NAFLD correlates with enhanced oxidative stress. Histopathological disease severity significantly correlated with oxidative stress parameters. These data show that NAFLD patients with IR may have increased risk for disease progression.

Topics: Adult; Ascorbic Acid; Female; Glutathione; Humans; Insulin; Insulin Resistance; Liver; Male; Malondialdehyde; Middle Aged; Nitric Oxide; Non-alcoholic Fatty Liver Disease; Oxidative Stress; Severity of Illness Index; Superoxide Dismutase; Vitamin E

The question of whether the consumption of antioxidants prevents and alleviates metabolic syndrome (MetS) by reducing insulin resistance remains controversial. The aim of this study was to assess whether the intake of vitamin A (including β-carotene), vitamin C, fruits, or vegetables was negatively associated with MetS in Korean adults aged ≥ 20 y.. We conducted a cross-sectional study of 27,656 adults ≥ 20 y of age who participated in the 2007-2012 Korean National Health and Nutrition Examination Survey. Daily intake of vitamin A and vitamin C was assessed by 24-h recall, and the consumption of fruits and vegetables was determined using a food frequency questionnaire. Odds ratios (ORs) for MetS were calculated for log2-transformed vitamin A and C intake values and for the interaction of sex with vitamin A and C intake, after covariate adjustment.. Interactions were seen between total vitamin A and C intake and sex for MetS. With a twofold increase in total vitamin A and C intake in women, the ORs (95% confidence intervals) for metabolic syndrome were 0.942 (0.901-0.985) and 0.933 (0.883-0.987), indicating decreases of 5.8% and 6.7% in MetS, respectively. There were no equivalent decreases in men. Women in the second and highest tertiles of fruit intake exhibited 17.5% and 21.8% lower incidences of MetS, respectively, compared with women in the lowest tertile.. The intake of total vitamin A and C, as well as moderate and high fruit intake, may have alleviated MetS in women, but not in men, in a representative sample of the general South Korean population.

Topics: Adult; Antioxidants; Ascorbic Acid; Asian People; Blood Glucose; Blood Pressure; Body Mass Index; Cholesterol, HDL; Cross-Sectional Studies; Fasting; Female; Fruit; Humans; Insulin Resistance; Male; Mental Recall; Metabolic Syndrome; Middle Aged; Nutrition Surveys; Prevalence; Republic of Korea; Risk Factors; Surveys and Questionnaires; Triglycerides; Vegetables; Vitamin A; Waist Circumference; Young Adult

In this study, we examined the relationship between sarcopenic obesity (SO) and nutrition status, according to sex in Korean adults who were 60 years or older. Body composition was categorized as SO, sarcopenic nonobesity, nonsarcopenic obesity, and nonsarcopenic nonobesity. Obesity was defined by body mass index. Sarcopenia was defined as an appendicular skeletal muscle mass divided by weight (Wt) of less than 1 SD below the sex-specific mean for young adults. Subjects included 1433 subjects (658 men and 775 women) who were 60 years or older and who participated in the fifth Korea National Health and Nutritional Examination Survey 2010. Sarcopenic obesity was more prevalent in women (31.3%) than in men (19.6%). Individuals with SO had significantly higher fasting insulin, homeostasis model assessment of insulin resistance (male: 3.2 ± 1.4, female: 3.4 ± 2.1), and triglycerides (male: 167.3 ± 90.6 mg/dL, female: 160.7 ± 85.0 mg/dL). High-density lipoprotein was under the normal criteria (50 mg/dL) in women. Intake of nutrients associated with muscle loss (protein, vitamin D, calcium, and vitamin C) was significantly different among the male but not the female groups. Although protein intake was normal, calcium and vitamin D intakes were insufficient in all groups. In conclusion, body composition changes were related to nutrient intakes in elderly (60 years or older) men but not elderly women. Women had a higher prevalence of SO than did men, suggesting that early nutritional intervention in elderly women may help them address age-associated body composition changes.

Topics: Adult; Aged; Ascorbic Acid; Asian People; Body Composition; Body Mass Index; Body Weight; Calcium, Dietary; Cholesterol, HDL; Dietary Proteins; Energy Intake; Female; Healthy Volunteers; Humans; Insulin; Insulin Resistance; Male; Middle Aged; Muscle, Skeletal; Nutrition Surveys; Nutritional Status; Obesity; Prevalence; Republic of Korea; Risk Factors; Sarcopenia; Triglycerides; Vitamin D; Young Adult

Controversy exists as to whether supplementation with the antioxidants vitamin E and vitamin C blocks adaptation to exercise. Exercise is a first-line means to treat obesity and its complications. While diet-induced obesity alters mitochondrial function and induces insulin resistance (IR), no data exist as to whether supplementation with vitamin E and vitamin C modify responses to exercise in pre-existing obesity. We tested the hypothesis that dietary supplementation with vitamin E (0.4 g α-tocopherol acetate/kg) and vitamin C (0.5 g/kg) blocks exercise-induced improvements on IR and mitochondrial content in obese rats maintained on a high-fat (45% fat energy (en)) diet. Diet-induced obese, sedentary rats had a 2-fold higher homeostasis model assessment of insulin resistance and larger insulin area under the curve following glucose tolerances test than rats fed a low-fat (10% fat en) diet. Exercising (12 weeks at 5 times per week in a motorized wheel) of obese rats normalized IR indices, an effect not modified by vitamin E and vitamin C. Vitamin E and vitamin C supplementation with exercise elevated mtDNA content in adipose and skeletal muscle to a greater extent (20%) than exercise alone in a depot-specific manner. On the other hand, vitamin C and vitamin E decreased exercise-induced increases in mitochondrial protein content for complex I (40%) and nicotinamide nucleotide transhydrogenase (35%) in a muscle-dependent manner. These data indicate that vitamin E and vitamin C supplementation in obese rodents does not modify exercise-induced improvements in insulin sensitivity but that changes in mitochondrial biogenesis and mitochondrial protein expression may be modified by antioxidant supplementation.

Topics: Adipose Tissue; Animals; Antioxidants; Ascorbic Acid; Cholesterol; DNA, Mitochondrial; Endpoint Determination; Glucose Tolerance Test; Insulin; Insulin Resistance; Male; Mitochondrial Proteins; Muscle, Skeletal; NADP Transhydrogenase, AB-Specific; Obesity; Physical Conditioning, Animal; Rats; Rats, Sprague-Dawley; Triglycerides; Vitamin E

There is mounting evidence demonstrating causative links between hyperglycemia, oxidative stress, and insulin resistance, the core pathophysiological features of type 2 diabetes mellitus. Using a combinational approach, we synthesized a vanadium-antioxidant (i.e., l-ascorbic acid) complex and examined its effect on insulin resistance and oxidative stress. This study was designed to examine whether vanadyl(IV)-ascorbate complex (VOAsc) would reduce oxidative stress, hyperglycemia, and insulin resistance in high-fat high-sucrose diet (HFSD)-induced type 2 diabetes in mice. Male C57BL/6J mice were fed a HFSD for 12 weeks to induce insulin resistance, rendering them diabetic. Diabetic mice were treated with rosiglitazone, sodium l-ascorbate, or VOAsc. At the end of treatment, fasting blood glucose, fasting serum insulin, homeostasis model assessment-insulin resistance index, and serum adipocytokine levels were measured. Serum levels of nitric oxide (NO) parameters were also determined. The liver was isolated and used for determination of malondialdehyde, reduced glutathione, and catalase levels, and superoxide dismutase and glutathione peroxidase activities. VOAsc groups exhibited significant reductions in serum adipocytokine and NO levels, and oxidative stress parameters compared to the corresponding values in the untreated diabetic mice. The results indicated that VOAsc is non-toxic. In conclusion, we identified VOAsc as a potentially effective adjunct therapy for the management of type 2 diabetes.

Topics: Adiponectin; Adipose Tissue; Animals; Ascorbic Acid; Blood Glucose; Body Weight; Diabetes Mellitus, Type 2; Diet, High-Fat; Feeding Behavior; Glucose Tolerance Test; Homeostasis; Hyperglycemia; Insulin; Insulin Resistance; Leptin; Liver; Male; Malondialdehyde; Mice, Inbred C57BL; Nitric Oxide; Organ Size; Oxidative Stress; Resistin; Sucrose; Tumor Necrosis Factor-alpha; Vanadates

Obesity-induced changes in lipid metabolism are mechanistically associated with the development of insulin resistance and prediabetes. Recent studies have focused on the extent to which obesity-induced insulin resistance is mediated through oxylipins, derived from enzymatic and nonenzymatic lipid peroxidation. Vitamin E and vitamin C are widely used antioxidant supplements, but conflicting data exist as to whether supplementation with vitamins E and C reduces insulin resistance. The purpose of this work is (1) to test the hypothesis that supplementation with vitamin E and vitamin C prevents the development of insulin resistance and (2) to determine the extent to which antioxidant supplementation modifies obesity-induced changes in hepatic oxylipins. Using obesity-prone Sprague-Dawley rats fed a high-fat, hypercaloric diet, we found that vitamin E and C supplementation did not block the development of insulin resistance, despite increased plasma levels of these antioxidants and decreased hepatic F2-isoprostane (F2-IsoP) concentrations. The obese phenotype was associated with increased hepatic concentrations of cytochrome P450 (CYP450)-dependent linoleic acid and α-linolenic acid-derived epoxides. Antioxidant supplementation, but not obesity, decreased levels of the lipoxygenase (LOX)-dependent, arachidonic acid-derived products lipoxin A4 (LXA4), 8,15-dihydroxtetraenoate (8,15-DiHETE), and 5,15-DiHETE. Our data demonstrate that antioxidant supplementation and obesity impact hepatic LOX- and CYP450-dependent oxylipin metabolism.

Topics: Animals; Antioxidants; Ascorbic Acid; Blood Glucose; Dietary Supplements; Insulin; Insulin Resistance; Lipid Metabolism; Lipid Peroxidation; Liver; Male; Obesity; Oxidation-Reduction; Oxidative Stress; Oxylipins; Rats; Rats, Sprague-Dawley; Vitamin E

High-fat diet (HFD) is known to cause endothelial dysfunction and contribute to atherosclerosis progression. The objective of this study was to evaluate the efficacy of L-arginine (L-Arg) and vitamin C supplementation as a potentially useful strategy for modulation of serum homocysteine (Hcy) levels, tumor necrosis factor alpha (TNF-α), oxidative stress, and insulin resistance induced by HFD in rats. Six weeks-old female and male Wistar rats were divided into five groups of twelve rats each and treated for six weeks with: group 1, standard diet; group 2, HFD; group 3, HFD supplemented with L-Arg (20g/kg diet); group 4, HFD supplemented with L-Arg (20g/kg diet) plus vitamin C (100mg/kg diet); group 5, HFD supplemented with vitamin C (100mg/kg diet). HFD significantly elevated TNF-α, reduced total antioxidant status (TAS), and increased insulin resistance (HOMA-IR). Significant increases of total cholesterol (TCH), LDL cholesterol (LDL), triglyceride (TG) and a decrease of HDL cholesterol (HDL) were observed in HFD rats. Supplementation with l-Arg prevented the decrease of TAS and the increases in HOMA-IR, LDL, and TG levels. Moreover, Hcy and TNF-α levels were reduced in L-Arg supplemented group. Supplementation with vitamin C significantly atenuated TAS decrease and lowered LDL levels. L-Arg plus vitamin C enhanced L-Arg effect on TAS and protected against TNF-α increase. Western blot analysis showed that l-Arg supplementation of HFD rats reduced the level of protein carbonyls. Taken together, these findings indicate that supplemental l-arginine and/or vitamin C, by their abilities to modulate biomarkers of HFD-induced endothelial dysfunction, are anti-atherogenic.

Topics: Animals; Antioxidants; Arginine; Ascorbic Acid; Atherosclerosis; Biomarkers; Diet, High-Fat; Dietary Supplements; Endothelium, Vascular; Female; Insulin Resistance; Lipids; Male; Oxidative Stress; Rats; Rats, Wistar

L-arginine (L-arg) and vitamin C supplementation may decrease fat accumulation and have a favourable effect on carbohydrate metabolism. This is partly caused by matrix metalloproteinases (MMPs), which are involved in adipocyte development and remodelling. Our study evaluated the effects of L-arg and vitamin C supplementation on the content of visceral fat (VF%), activity of MMPs, and insulin resistance (IR) in rats fed a high-fat diet (HFD).. The experiment was performed using 48 Wistar rats divided into four groups: Group 1 was fed a standard diet, Group 2 a HFD, Group 3 a HFD supplemented with L-arg (A), and Group 4 a HFD supplemented with L-arg and vitamin C (AC). The animals were euthanized after six weeks. The concentrations of serum glucose, insulin, MMP-2, and MMP-9, as well as IR by Homeostatic Model Assessment (HOMA) and VF% were measured.. Statistically significant increases in VF%, MMP-2, MMP-9, insulin, and HOMA-IR levels were observed in the HFD group when compared to the control group. A smaller increase in VF%, insulin, and HOMA-IR was seen in Group 3 (A) and 4 (AC). L-arg supplementation protected against increases in MMP-2 and MMP-9 in Group 3 (A) and 4 (AC).. L-arginine could protect from an increase in visceral fat through a change in the activity of MMPs and amelioration of insulin sensitivity in rats fed a HFD. The addition of vitamin C did not improve the effects of L-arginine supplementation.

Topics: Animals; Arginine; Ascorbic Acid; Diet, High-Fat; Dietary Supplements; Female; Gene Expression; Insulin Resistance; Intra-Abdominal Fat; Male; Matrix Metalloproteinase 2; Matrix Metalloproteinase 9; Rats; Rats, Wistar

Using archival data, we conducted a secondary analysis to examine race differences in the relation of serum vitamins A, C, E and β-carotene to insulin resistance (IR), fasting insulin and glucose, high sensitivity C-reactive protein (hs-CRP), and leukocyte count in 176 non-smoking, healthy, white, and African American (AA) adults aged 18 to 65 years (48% women, 33% AA). We hypothesized that micronutrient concentrations would be associated with early risk markers of cardiometabolic diseases in a race-dependent manner. Fasting blood samples were analyzed for micronutrients, insulin, glucose, hs-CRP, and leukocyte count. Insulin resistance was estimated using the homeostatic model assessment. After adjusting for age, body mass index, gender, educational level, use of vitamin supplements, alcohol intake, leisure time physical activity, menopausal status, and total cholesterol, we observed that β-carotene was significantly associated with insulin resistance and fasting insulin in a race-dependent manner. Among AA, lower β-carotene levels were associated with higher estimates of insulin resistance and fasting insulin; whereas, these same associations were not significant for whites. Race also significantly moderated the relation of vitamin C to leukocyte count, with lower vitamin C being associated with higher leukocyte count only in AA but not whites. For all subjects, lower β-carotene was associated with higher hs-CRP. In AA, but not whites, lower levels of β-carotene and vitamin C were significantly associated with early risk markers implicated in cardiometabolic conditions and cancer. Whether or not lower levels of micronutrients contribute uniquely to racial health disparities is a worthwhile aim for future research.

Topics: Adiposity; Adolescent; Adult; Aged; Ascorbic Acid; beta Carotene; Biomarkers; Black or African American; Blood Glucose; C-Reactive Protein; Female; Humans; Inflammation; Insulin; Insulin Resistance; Leukocyte Count; Male; Metabolic Diseases; Middle Aged; Racial Groups; Risk Factors; Vitamin A; Vitamin E; Vitamins; White People

Poor diet and a sedentary lifestyle can contribute to nonalcoholic fatty liver disease (NAFLD).. Our aim was to compare diet and physical activity of patients with NAFLD and healthy controls with current recommendations.. This was a cross-sectional study.. Seventy-four patients with biopsy-proven NAFLD (33 simple steatosis and 41 steatohepatitis [NASH]) and 27 healthy controls participated between 2003 and 2011.. Food records and activity logs were completed for 7 days. Results were compared with Dietary Reference Intakes and Canadian Physical Activity Guidelines. Plasma vitamin C was measured to assess food record accuracy.. Intake/activity for each participant was compared with the recommendations and proportion of subjects not meeting the requirements was calculated. Groups were compared by Kruskal-Wallis and Mann-Whitney U test or z-test with Bonferroni adjustment.. More patients with NASH (58.5%) were obese compared with patients with simple steatosis (24.2%) and healthy controls (7.4%; P<0.01). Patients with NAFLD showed more insulin resistance than healthy controls. The reported energy intake was below estimated requirements in all groups (P≤0.001). The proportion of subjects from each group exceeding acceptable energy intake from fat was as follows: simple steatosis: 27.3%; NASH: 46.3%; healthy controls: 63.0% (simple steatosis vs health controls; P<0.05) and from saturated fat: simple steatosis: 42.4%; NASH: 70.7%; healthy controls: 63.0% (simple steatosis vs. NASH; P<0.05). In each group, >80% of subjects did not consume enough linoleic or linolenic acid, vitamin D, and vitamin E, and >60% exceeded the upper intake level for sodium. Only 53.1% of patients with simple steatosis and 53.8% of patients with NASH, but 84.6% of healthy controls, met recommendations for physical activity (P=0.020). Plasma vitamin C was normal, similar among groups, and correlated with vitamin C intakes.. All participants followed a similar Western diet with high fat and sodium intakes and suboptimal micronutrient intakes. However, physical activity was lower in NAFLD compared with healthy controls and was associated with higher body mass index and insulin resistance.

Topics: Adult; Aged; Ascorbic Acid; Body Mass Index; Canada; Case-Control Studies; Cross-Sectional Studies; Diet Records; Dietary Fats; Energy Intake; Fatty Liver; Female; Guidelines as Topic; Healthy Volunteers; Humans; Insulin Resistance; Male; Middle Aged; Motor Activity; Non-alcoholic Fatty Liver Disease; Nutrition Assessment; Prospective Studies; Sodium, Dietary; Vitamin D; Vitamin E; Young Adult

The objective of this cross-sectional study was to evaluate the relationship between micronutrient status and obesity, lipids, insulin resistance and chronic inflammation in children. Weight, height, waist circumference and body composition (dual-energy X-ray absorptiometry (DEXA)) were determined in 197 school-aged children. Lipids, glucose, insulin, C-reactive protein (CRP), zinc, iron and vitamins A, C and E were analyzed in blood. Vitamin C and vitamin E:lipids were negatively associated with Body Mass Index (BMI), waist-to-height ratio (WHR) and body and abdominal fat (p < 0.05). Vitamin A was positively associated with BMI, BMI-for-age, WHR and abdominal fat (p < 0.05). Iron and vitamin E:lipids were negatively associated with insulin (p < 0.05). Vitamins A, C and E and iron were negatively associated with CRP (p < 0.05). Interaction analysis showed that children who were overweight and obese who also had low concentrations of vitamin A had higher CRP and lower triglycerides (p < 0.1), children with low vitamin E had significantly lower glucose and triglycerides (p < 0.1) and higher low-density lipoprotein (LDL) concentrations (p < 0.05), and children with low zinc concentrations had higher insulin resistance compared with children with adequate weight (p < 0.05). In conclusion, low vitamin C concentration and vitamin E:lipids were associated with obesity. Furthermore, low concentrations of zinc, vitamins A and E in children who were overweight and obese were associated with lipids, inflammation and insulin resistance.

Topics: Ascorbic Acid; Blood Glucose; Body Composition; Body Mass Index; Body Weight; C-Reactive Protein; Child; Cholesterol, HDL; Cholesterol, LDL; Cross-Sectional Studies; Female; Humans; Inflammation; Insulin; Insulin Resistance; Iron, Dietary; Male; Mexico; Micronutrients; Motor Activity; Nutrition Assessment; Pediatric Obesity; Socioeconomic Factors; Triglycerides; Vitamin D; Waist Circumference; Zinc

Diethyl hexyl phthalate (DEHP) is a plasticizer, commonly used in a variety of products, including lubricants, perfumes, hairsprays and cosmetics, construction materials, wood finishers, adhesives, floorings and paints. DEHP is an endocrine disruptor and it has a continuum of influence on various organ systems in human beings and experimental animals. However, specific effects of DEHP on insulin signaling in adipose tissue are not known. Adult male albino rats of Wistar strain were divided into four groups. Control, DEHP treated (dissolved in olive oil at a dose of 10, and 100 mg/kg body weight, respectively, once daily through gastric intubations for 30 days) and DEHP + vitamin E (50 mg/kg body weight) and C (100 mg/kg body weight) dissolved in olive oil and distilled water, respectively, once daily through gastric intubations for 30 days. After the completion of treatment, adipose tissue was dissected out to assess various parameters. DEHP treatment escalated H(2)O(2) and hydroxyl radical levels as well as lipid peroxidation in the adipose tissue. DEHP impaired the expression of insulin signaling molecules and their phosphorelay pathways leading to diminish plasma membrane GLUT4 level and thus decreased glucose uptake and oxidation. Blood glucose level was elevated as a result of these changes. Supplementation of vitamins (C & E) prevented the DEHP-induced changes. It is concluded that DEHP-induced ROS and lipid peroxidation disrupts the insulin signal transduction in adipose tissue and favors glucose intolerance. Antioxidant vitamins have a protective role against the adverse effect of DEHP.

Topics: Adipose Tissue; Animals; Antioxidants; Arrestins; Ascorbic Acid; beta-Arrestins; Biological Transport; Blood Glucose; Diethylhexyl Phthalate; Glucose; Glucose Intolerance; Glucose Transporter Type 4; Hydrogen Peroxide; Insulin; Insulin Resistance; Lipid Peroxidation; Male; Oxidative Stress; Rats; Rats, Wistar; Reactive Oxygen Species; Signal Transduction; Sterol Regulatory Element Binding Protein 1; Vitamin E

Antioxidant-based treatments have emerged as novel and interesting approaches to counteract fat accumulation in obesity and associated metabolic disturbances. Adipocytes from rats that were fed on chow or high-fat diet (HFD) for 50 d were isolated (primary adipocytes) and incubated (72 h) on low (LG; 5.6 mmol/L) or high (HG; 25 mmol/L) glucose levels, in the presence or absence of 1.6 nmol/L insulin and 200 μmol/L vitamin C (VC). Adipocytes from HFD-fed animals presented lower insulin-induced glucose uptake, lower lactate and glycerol release, and lower insulin-induced secretion of some adipokines as compared with controls. HG treatment restored the blunted response to insulin regarding apelin secretion in adipocytes from HFD-fed rats. VC treatment inhibited the levels of nearly all variables, irrespective of the adipocytes' dietary origin. The HG treatment reduced adipocyte viability, and VC protected from this toxic effect, although more drastically in control adipocytes. Summing up, in vivo chow or HFD intake determines a differential response to insulin and glucose treatments that appears to be dependent on the insulin-resistance status of the adipocytes, while VC modifies some responses from adipocytes independently of the previous dietary intake of the animals.

Topics: Adipocytes; Adipokines; Animals; Antioxidants; Ascorbic Acid; Cell Survival; Diet, High-Fat; Glucose; Insulin; Insulin Resistance; Male; Rats; Rats, Wistar; RNA, Messenger; Vitamins

Metabolic syndrome and oxidative stress are common complications of type 2 diabetes mellitus. The present study was designed to determine whether resveratrol, a widely used nutritional supplement, can improve insulin sensitivity, metabolic complication as well as hepatic oxidative stress in fructose-fed rats. Male Sprague Dawley rats (180-200 g) were divided into four groups with 8 animals each. Fructose-fed insulin resistant group (Dia) animals were fed 65% fructose (Research diet, USA) for a period of 8 weeks, whereas control group (Con) animals were fed 65% cornstarch (Research Diet, USA). Resveratrol, 10 mg/kg/day (Dia+Resv) or metformin 300 mg/kg/day (Dia+Met) were administered orally to the 65% fructose-fed rats for 8 weeks. At the end of the feeding schedule, Dia group had insulin resistance along with increased blood glucose, triglyceride, uric acid and nitric oxide (NO) levels. Significant (p<0.05) increase in hepatic TBARS and conjugated dienes, and significant (p<0.05) decrease in hepatic SOD and vitamin C was observed in Dia group compared to Con group. Administration of metformin or resveratrol significantly (p<0.05) normalized all the altered metabolic parameters. However, a marked insulin sensitizing action was only observed in the Dia+Resv group. Similarly, while metformin administration failed to normalize the increased TBARS levels and decreased SOD activity, resveratrol showed a more promising effect of all oxidative stress parameters measured in the present study. Attenuation of hepatic oxidative stress in fructose-fed rat liver after resveratrol administration was associated with significant (p<0.05) increase in nuclear level of NRF2 compared with other groups. The present study demonstrates that resveratrol is more effective than metformin in improving insulin sensitivity, and attenuating metabolic syndrome and hepatic oxidative stress in fructose-fed rats.

Topics: Animals; Ascorbic Acid; Blood Glucose; Body Weight; Catalase; Eating; Fructose; Glucose Tolerance Test; Glutathione; Insulin; Insulin Resistance; Liver; Male; Metabolic Syndrome; Metformin; NF-E2-Related Factor 2; Nitric Oxide; Oxidative Stress; Rats; Rats, Sprague-Dawley; Resveratrol; Stilbenes; Superoxide Dismutase; Thiobarbituric Acid Reactive Substances; Triglycerides; Uric Acid

The cytokines, adipokines, and oxidative stress have been implicated in the pathogenesis of non-alcoholic fatty liver disease (NAFLD); however, such data remain scarce in India. The present study evaluated pro-inflammatory cytokines, adipokines, and markers of oxidative stress in patients with non-alcoholic fatty liver disease (NAFLD), and their association with degree of adiposity, insulin resistance and markers of disease severity.. The present prospective cross-sectional pilot study included 79 subjects; 34 NAFLD, 22 chronic hepatitis B (CH-B) and 23 healthy controls (HC). The parameters studied were adiponectin, leptin, tumour necrosis factor α (TNFα), interleukin-1 and 6 (IL-1, IL-6), and systemic markers of oxidative stress.. The mean body mass index (kg/m 2 ) in NAFLD patients, CHB, and HC were 26.4±3.7, 21.3±2.3, and 22.3±2.7, respectively. The median serum levels of all pro-inflammatory cytokines were significantly higher (P<0.001) in NAFLD compared to control groups. Compared to HC, levels of adiponectin and leptin were significantly (P<0.05, P<0.01) reduced in both NAFLD and CHB. IL-6 showed marked and selective increase only in NAFLD patients. The levels of IL-6 were significantly (P<0.02) higher in NAFLD patients with advanced histology grade and correlated with IR (r=0.42, P=0.02). In a sub-group, markers of oxidative stress were significantly higher, and that of antioxidant potential were significantly lower among NAFLD patients compared to control subjects.. Patients with NAFLD revealed significantly elevated levels of pro-inflammatory cytokines, increased oxidative stress, and a significant association of IL-6 with IR and advanced histopathology.

Topics: Adipokines; Adult; Ascorbic Acid; Cytokines; Fatty Liver; Female; Hepatitis B, Chronic; Humans; India; Inflammation; Insulin; Insulin Resistance; Lipid Peroxidation; Liver; Male; Malondialdehyde; Non-alcoholic Fatty Liver Disease; Obesity; Oxidative Stress; Statistics as Topic; Superoxide Dismutase

To analyse the effects of vitamin C (VC), a potent dietary antioxidant, oral supplementation on body weight gain, behavioural activity, lipolytic response and glucocorticoid metabolism in the early stages of diet-induced overweight in rats.. Food intake, locomotive activity and faecal corticosterone were assessed during the 14 day trial period. After 2 weeks, the animals were sacrificed and the body composition, biochemical markers and lipolytic response from isolated adipocytes from retroperitoneal white adipose tissue were examined.. The intake of a high-fat diet by rats induced a significant increase in body weight, adiposity and insulin resistance markers as well as a decrease in faecal corticosterone levels compared with standard diet-fed rats. Interestingly, the animals fed on the cafeteria diet showed a significant increase in the isoproterenol-induced lipolytic response in isolated adipocytes. Furthermore, this cafeteria-fed group showed a reduced locomotive behaviour than the control rats. On the other hand, oral VC supplementation in animals receiving the high-fat diet restored the cafeteria diet effect in some of the analysed variables such as final body weight and plasma insulin to control group levels. Remarkably, increases in locomotive behaviour and a significant decrease in the lipolytic response induced by isoproterenol on isolated adipocytes from animals treated with VC were observed.. This work demonstrates that an oral ascorbic acid supplementation has direct effects on behavioural activity and on adipocyte lipolysis in early obesity stages in rats, which could indicate a protective short-term role of this vitamin against adiposity induced by chronic high-fat diet consumption.

Topics: Adipocytes; Adiposity; Administration, Oral; Animals; Antioxidants; Ascorbic Acid; Biomarkers; Body Weight; Corticosterone; Dietary Fats; Feces; Glucocorticoids; Insulin; Insulin Resistance; Isoproterenol; Lipolysis; Male; Motor Activity; Overweight; Rats; Rats, Wistar

Topics: Animals; Ascorbic Acid; Catecholamines; Dietary Fats; Energy Metabolism; Humans; Insulin Resistance; Lipolysis; Metabolic Syndrome; Motor Activity; Obesity; Rats

Topics: Antioxidants; Ascorbic Acid; Exercise; Humans; Insulin Resistance; Male; Oxidative Stress; Randomized Controlled Trials as Topic; Research Design; Vitamin E

The high fructose-fed rat is widely used as a model of insulin resistance. Genistein, a soy isoflavone, has been shown to improve insulin sensitivity in this model. The present study investigated whether genistein could prevent fatty liver disease in this model.. Male Wistar rats were fed a diet containing starch (control) or 60% fructose (insulin-resistant model). Fifteen days later, rats in each dietary group were divided into two groups and were treated with either genistein (1 mg/kg per day) in dimethylsulfoxide (DMSO) or 30% DMSO alone. After 60 days, markers of liver injury, oxidative stress, interleukin (IL)-6, tumor necrosis factor (TNF)-α, lipids, lipoprotein profile, nitrite, and nitrosothiol in the plasma and liver were quantified. Liver sections were examined for 3-nitrotyrosine (3-NT) expression and pathological lesions.. Fructose-fed rats displayed hyperlipidemia, significant changes in plasma lipoprotein profile, and increases in IL-6 and TNF-α levels compared with control. In addition, the accumulation of lipids, liver injury, a decline in liver function, inactivation of the glyoxalase system, depletion of antioxidants, and increased 3-NT expression were observed in the fructose-fed group. Administration of genistein to fructose-fed rats significantly reduced these biochemical and histological abnormalities.. Genistein activates the antioxidant profile, decreases IL-6 and TNF-α concentrations, prevents oxidative damage, and ameliorates fatty liver in insulin-resistant rats.

Topics: Animals; Ascorbic Acid; Body Weight; Cholesterol; Fatty Liver; Genistein; Glutathione Peroxidase; Glutathione Reductase; Insulin; Insulin Resistance; Interleukin-6; Liver; Liver Function Tests; Male; Non-alcoholic Fatty Liver Disease; Organ Size; Phospholipids; Phytoestrogens; Rats; Rats, Wistar; Tumor Necrosis Factor-alpha; Vitamin E

Since it is well known that estrogen deficiency or ovariectomy (OVX) results in a reduction of sexual steroids and increased prevalence of cardiovascular diseases (CVD), it was aimed to assess the benefits of hormone replacement therapy (HRT) alone or together with antioxidant vitamins (E and C) for the protection against CVD and oxidative stress.. The effect of ovariectomy and HRT alone or combined with antioxidants (Antiox) on lipid metabolism, insulin sensitivity, oxidative stress, antioxidant and markers of CVD was examined in four groups of female Wistar rats of 10 animals each: Group 1 (sham operated); Group 2 (OVX); Group 3 (OVX + HRT); Group 4 (OVX + HRT + Antiox). After four weeks of treatment total cholesterol, HDL-cholesterol (HDL-C), LDL-cholesterol (LDL-C), triglycerides (TG), Apo B lipoprotein, glucose and insulin as well as malondialdehyde (MDA; as index of lipid peroxidation), oxidized LDL (ox-LDL), homocysteine level, oxidized and reduced glutathione were determined in plasma.. The lipid pattern of OVX rats showed a deviation from sham group in all lipid fractions and atherogenic indexes; LDL/HDL and TC/HDL. HRT group showed partial correction of these abnormalities and the antioxidant adjunct treatment significantly improved the lipid profile. OVX rats had significantly higher insulin and glucose levels compared to the sham group which was abolished by HRT and completely normalized by adjunct antioxidant treatment. HOMA was significantly decreased by HRT and showed normal value with adjunct antioxidant treatment. The oxidative stress parameters; MDA, ox-LDL and GSSG levels were increased, also homocysteine was greatly elevated in OVX rats. The HRT significantly corrected the levels of MDA, ox-LDL and GSSG while it had no effect on homocysteine and GSH. The adjunct antioxidant treatment potentiated the HRT and showed a significant correction of homocysteine and GSH levels.. Our data suggested that adjunct antioxidant treatment together with HRT may ameliorate the cardiovascular protection and improve metabolic syndrome as well as insulin resistance in OVX rats. Further studies are warranted to elucidate the beneficial role of antioxidant treatment on cardiovascular protection of menopause women.

Topics: Adjuvants, Pharmaceutic; Animals; Antioxidants; Ascorbic Acid; Blood Glucose; Cardiovascular Diseases; Estrogen Replacement Therapy; Female; Insulin; Insulin Resistance; Ovariectomy; Oxidative Stress; Rats; Rats, Wistar; Vitamin E

High-fat diets and oxidative damage may contribute to the development of type 2 diabetes. Hypolipidaemic drugs and antioxidants were supposed to prevent the development of the disease. In this study, we investigated preventive effects of fenofibrate (200 mg kg(-1)), vitamin C (30 mg kg(-1)), combination of both in mice induced by streptozotocin (35 mg kg(-1)) and soluble lard (15 ml kg(-1)). The results showed the mice demonstrated hyperglycaemia and hypercholesterolaemia, visceral fat accumulation, and a slight increase in liver glycogen/triglyceride and oxidative stress within 60 days of treatment. Fenofibrate enhanced insulin sensitivity, improved glycaemic control, lowered serum triglycerides, reduced body and visceral fat weights, and decreased liver glycogen/lipid levels but showed hepatotoxicity in the mice. Vitamin C neither itself prevented nor enhanced preventive effects of fenofibrate on glucose and lipid metabolism but partly attenuated the hepatotoxicity of fenofibrate. These results suggest that fenofibrate inhibit development of type 2 diabetes induced by high-fat diets and oxidative stress. However, here, vitamin C just can serve as an adjunct to fenofibrate therapy against its hepatotoxicity. In the future study, we should investigate if higher dosage of vitamin C or other antioxidants would enhance preventive effects of fenofibrate in type 2 diabetes.

Topics: Animals; Antioxidants; Ascorbic Acid; Blood Glucose; Chemical and Drug Induced Liver Injury; Cholesterol; Diabetes Mellitus, Experimental; Diabetes Mellitus, Type 2; Dietary Fats; Drug Therapy, Combination; Fenofibrate; Glycogen; Hypercholesterolemia; Hyperglycemia; Hypoglycemic Agents; Hypolipidemic Agents; Insulin Resistance; Intra-Abdominal Fat; Liver; Liver Diseases; Male; Matrix Metalloproteinase 9; Mice; Oxidative Stress; Streptozocin; Triglycerides

It has been reported that apelin functions as an adipokine, which has been associated to obesity and insulin resistance. The objective of this study was to analyze the apelin mRNA expression in white adipose tissue (WAT) from high-fat (Cafeteria) fed rats, in order to examine potential relationships with obesity markers and other related risk factors. Animals fed on the high-fat diet during 56 days increased their body weight, total body fat and WAT depots weights when compared to controls. Apelin subcutaneous mRNA expression was higher in the Cafeteria than in the Control fed group and this increase was partially reversed by dietary vitamin C supplementation. Statistically significant associations between subcutaneous apelin gene expression and almost all the studied variables were identified, being of special interest the correlations found with serum leptin (r=0.517), liver malondialdehyde (MDA) levels (r=0.477), and leptin, IRS-3 and IL-1ra retroperitoneal mRNA expression (r=0.701; r=0.692 and r=0.561, respectively). These associations evidence a possible role for apelin in the excessive weight gain induced by high-fat feeding and increased adiposity, insulin-resistance, liver oxidative stress and inflammation.

Topics: Adiposity; Animals; Apelin; Ascorbic Acid; Biomarkers; Carrier Proteins; Diet, Atherogenic; Inflammation; Insulin Resistance; Intercellular Signaling Peptides and Proteins; Intra-Abdominal Fat; Leptin; Liver; Male; Malondialdehyde; Oxidative Stress; Rats; Rats, Wistar; Subcutaneous Fat

Free radicals are involved in the pathogenesis of acute liver injury induced by thioacetamide (TAA). We investigated the effects of S-adenosylmethionine (SAMe) combined with/without vitamins C and E on TAA-induced acute liver injury in rats. TAA was given intraperitoneally (200 mg kg-1). Antioxidant treatments (SAMe, 25 mg kg-1; vitamin C, 100 mg kg-1; vitamin E, 200 mg kg-1, intraperitoneal) were given 1 h later. Liver histology, enzymology, and ability to release hepatic insulin-sensitizing substance (HISS) were assessed. TAA caused liver tissue injury, increased liver enzymes, and decreased insulin sensitivity (p<0.01). Blockade of HISS release by atropine did not further decrease insulin sensitivity in rats with TAA insult, indicating that the decrease in insulin sensitivity was HISS dependent. Treatment with SAMe alone or vitamins C+E slightly improved liver histology but not the changes in liver enzymes and insulin sensitivity. Combined treatment with SAMe plus vitamins C+E greatly protected the liver from tissue injury, the increase in liver enzymes, and the decrease in insulin sensitivity. In conclusion, acute liver injury causes HISS-dependent insulin resistance (HDIR). There are synergistic antioxidative effects among the antioxidants, SAMe and vitamins C and E, that protect the liver from TAA-induced HDIR, suggesting that antioxidant treatment may best be done using a balanced "cocktail."

Topics: Animals; Antioxidants; Ascorbic Acid; Drug Combinations; Drug Synergism; Insulin Resistance; Liver; Male; Rats; Rats, Sprague-Dawley; S-Adenosylmethionine; Thioacetamide; Vitamin E

To investigate the aetiology of chronic idiopathic axonal polyneuropathy (CIAP), 50 consecutive patients were compared with 50 control subjects from the same region. There were 22 patients with painful neuropathy and 28 without pain, 26 with sensory neuropathy and 24 with sensory and motor neuropathy. The typical picture was a gradually progressive sensory or sensory and motor neuropathy. It caused mild or sometimes moderate disability, and reduced the quality of life. There was no evidence that alcohol, venous insufficiency, arterial disease or antibodies to peripheral nerve antigens played a significant part. There was a possible history of peripheral neuropathy in the first or second-degree relatives of six patients and no controls (P = 0.01), and claw toes were present in 12 patients and four controls (P = 0.03). Thirty-two per cent of the patients and 14% of the controls had impaired glucose tolerance or fasting hyperglycaemia but, after adjusting for age and sex, the difference was not significant (P = 0.45), even in the painful neuropathy subgroup. The mean (SD) fasting insulin concentrations were significantly (P = 0.01) higher in the patients [75.9 (44.4) mmol/l] than the controls [47.3 (37.9) mmol/l], and the mean was higher still in the painful neuropathy subgroup [92.2 (37.1) mmol/l] (P < 0.0001). However, insulin resistance as assessed using the homeostasis model assessment formula was not significantly greater in the patients, even in those with pain, than the controls. After adjustment for body mass index as well as age and sex, there was no significant difference in the serum cholesterol concentrations, but there were significantly higher triglyceride concentrations in the patients [mean 1.90 (1.41) mmol/l] than the controls [mean 1.25 (0.79] mmol/l) (P = 0.02). In the patients with painful peripheral neuropathy, the mean triglyceride concentration was 2.37 (1.72), which was even more significantly greater compared with the controls (P = 0.003). In conclusion, CIAP is a heterogeneous condition. A logistic regression analysis identified environmental toxin exposure and hypertriglyceridaemia, but not glucose intolerance or alcohol overuse as significant risk factors that deserve further investigation as possible causes of CIAP.

Topics: Aged; Anthropometry; Ascorbic Acid; Autoantibodies; Case-Control Studies; Disability Evaluation; Female; Glucose Intolerance; Hazardous Substances; Humans; Hypertriglyceridemia; Insulin Resistance; Male; Middle Aged; Pain; Polyneuropathies; Quality of Life; Risk Factors; Vitamin E

High dosage of fructose induces insulin resistance, glucose intolerance and alterations in plasma lipid profile in normal rats. Recently, it has been shown that these rats also develop oxidative stress, which plays a prominent role in diabetic pathology. We now report the effect of taurine on the susceptibility of the aorta to lipid peroxidation and also on the activities of enzymic and non-enzymic antioxidants in rats fed a high fructose-diet for 4 weeks. Fructose-fed rats were more susceptible to lipid peroxidation as measured by thiobarbituric acid reactivity, and antioxidant status was significantly lower. Taurine supplementation caused a significant reduction in the production of thiobarbituric acid--reactive substances and significant rises in antioxidant enzyme activities. The levels of lipid peroxides, diene conjugates, lipofuscin and hydroperoxides were significantly higher in fructose-fed rats. When these rats received taurine in drinking water, no peroxidative changes were observed. Increased aorta lipid peroxidation could play a role in the pathology associated with fructose-feeding, and taurine reduces the lipid peroxidation by inducing antioxidant enzymes.

Topics: Animals; Antioxidants; Aorta, Thoracic; Ascorbic Acid; Fructose; Insulin Resistance; Lipid Peroxidation; Lipid Peroxides; Lipofuscin; Male; Rats; Rats, Wistar; Sulfhydryl Compounds; Taurine; Thiobarbituric Acid Reactive Substances; Vitamin E

Topics: Ascorbic Acid; Blood Glucose; Coronary Vasospasm; Endothelium, Vascular; Humans; Insulin Resistance; Reactive Oxygen Species

In 9 patients with essential hypertension, we tested whether a high-dose (12 mg. min(-1)) vitamin C infusion into the brachial artery, by improving endothelium-dependent vasodilatation, would also attenuate the insulin resistance of deep forearm tissues. We measured the effect of vitamin C on acetylcholine (Ach)-induced vasodilatation and on forearm glucose uptake during systemic hyperinsulinemia; in all studies, the contralateral forearm served as the control. Intrabrachial Ach infusion produced a stable increase in forearm blood flow, from 2.6+/-0.3 to 10.6+/-2.1 mL. min(-1). dL(-1); when vitamin C was added, a further rise in forearm blood flow (to 13.4 mL. min(-1). dL(-1); P<0.03 vs Ach alone) was observed. In response to insulin, blood flow in both the infused and control forearms did not significantly change from baseline values (+10+/-16% and +2+/-11%, respectively). In contrast, when vitamin C was added, blood flow in the infused forearm increased significantly (to 3.7+/-0.7 mL. min(-1). dL(-1); P<0.02 vs 2.8+/-0.6 mL. min(-1). dL(-1) in the control forearm). Insulin stimulated whole-body glucose disposal to 20+/-2 micromol. min(-1). kg(-1), compatible with the presence of marked insulin resistance. Forearm glucose uptake was similarly stimulated after 80 minutes of insulin infusion (to 2.11+/-0.42 and 2.06+/-0.43 micromol. min(-1). dL(-1), infused and control, respectively). When intrabrachial vitamin C was added, no difference in glucose uptake was observed between the 2 forearms (infused, 2.37+/-0.44 micromol. min(-1). dL(-1)and control, 2.36+/-0. 53 micromol. min(-1). dL(-1)). Forearm O(2) uptake at baseline was also similar in the 2 forearms (infused, 9.7+/-0.7 micromol. min(-1). dL(-1) and control, 9.6+/-1.1 micromol. min(-1). dL(-1)) and was not changed by either insulin or vitamin C. We conclude that in the deep forearm tissues of patients with essential hypertension and insulin resistance, an acute improvement in endothelial function, obtained with pharmacological doses of vitamin C, restores insulin-mediated vasodilatation but does not improve insulin-mediated glucose uptake. Thus, the endothelial dysfunction of essential hypertension is unlikely to be responsible for their metabolic insulin resistance.

Topics: Ascorbic Acid; Blood Flow Velocity; Blood Glucose; Forearm; Humans; Hypertension; Infusions, Intra-Arterial; Insulin; Insulin Resistance; Male; Middle Aged; Regional Blood Flow; Vasodilation

Oxidative stress is produced under diabetic conditions and possibly causes various forms of tissue damage in patients with diabetes. The aim of this study was to examine the involvement of oxidative stress in the progression of pancreatic beta-cell dysfunction in type 2 diabetes and to evaluate the potential usefulness of antioxidants in the treatment of type 2 diabetes. We used diabetic C57BL/KsJ-db/db mice, in whom antioxidant treatment (N-acetyl-L-cysteine [NAC], vitamins C plus E, or both) was started at 6 weeks of age; its effects were evaluated at 10 and 16 weeks of age. According to an intraperitoneal glucose tolerance test, the treatment with NAC retained glucose-stimulated insulin secretion and moderately decreased blood glucose levels. Vitamins C and E were not effective when used alone but slightly effective when used in combination with NAC. No effect on insulin secretion was observed when the same set of antioxidants was given to nondiabetic control mice. Histologic analyses of the pancreases revealed that the beta-cell mass was significantly larger in the diabetic mice treated with the antioxidants than in the untreated mice. As a possible cause, the antioxidant treatment suppressed apoptosis in beta-cells without changing the rate of beta-cell proliferation, supporting the hypothesis that in chronic hyperglycemia, apoptosis induced by oxidative stress causes reduction of beta-cell mass. The antioxidant treatment also preserved the amounts of insulin content and insulin mRNA, making the extent of insulin degranulation less evident. Furthermore, expression of pancreatic and duodenal homeobox factor-1 (PDX-1), a beta-cell-specific transcription factor, was more clearly visible in the nuclei of islet cells after the antioxidant treatment. In conclusion, our observations indicate that antioxidant treatment can exert beneficial effects in diabetes, with preservation of in vivo beta-cell function. This finding suggests a potential usefulness of antioxidants for treating diabetes and provides further support for the implication of oxidative stress in beta-cell dysfunction in diabetes.

Topics: Acetylcysteine; Animals; Antioxidants; Ascorbic Acid; Blood Glucose; Body Weight; Diabetes Mellitus, Type 2; Female; Insulin Resistance; Islets of Langerhans; Mice; Mice, Inbred C57BL; Mice, Mutant Strains; Vitamin E

To investigate underlying mechanisms responsible for the impaired nitric oxide (NO)-dependent vascular relaxation in the insulin-resistant state, we examined production of both NO and superoxide anion radical (O2-) and those modulating factors in aortas obtained from normal (CTR), insulin-treated (INS), or high fructose-fed (FR) rats. FR rats showed insulin resistance with endogenous hyperinsulinemia, whereas INS rats showed normal insulin sensitivity. Only FR aortic strips with endothelium elicited impaired relaxation in response to either acetylcholine or calcium ionophore A23187. Endothelial NO synthase (eNOS) activity and its mRNA levels were increased only in vessels from INS rats (P < 0.001), whereas eNOS activity in FR rats was decreased by 58% (P < 0.05) when compared with CTR rats. NO production from aortic strips stimulated with A23187 was significantly lower in FR than CTR rats. In contrast, A23187-stimulated O2- production was higher (P < 0.01) in FR than CTR rats. These differences were abolished when aortic strips were preincubated in the media including (6R)-5,6,7,8-tetrahydrobiopterin (BH4), an active cofactor for eNOS. Furthermore, as compared with CTR rats, aortic BH4 contents in FR rats were decreased (P < 0.001), whereas the levels of 7,8-dihydrobiopterin, the oxidized form of BH4, were increased, with opposite results in INS rats. These results indicate that insulin resistance rather than hyperinsulinemia itself may be a pathogenic factor for decreased vascular relaxation through impaired eNOS activity and increased oxidative breakdown of NO due to enhanced formation of O2- (NO/O2- imbalance), which are caused by relative deficiency of BH4 in vascular endothelial cells.

Topics: Acetylcholine; Animals; Aorta, Thoracic; Ascorbic Acid; Biopterins; Blood Glucose; Blood Pressure; Calcimycin; Endothelium, Vascular; Fructose; Hyperinsulinism; In Vitro Techniques; Insulin; Insulin Resistance; Isometric Contraction; Male; Muscle Relaxation; Muscle, Smooth, Vascular; Nitric Oxide; Nitric Oxide Synthase; Nitric Oxide Synthase Type III; Nitroprusside; Rats; Rats, Sprague-Dawley; RNA, Messenger; Superoxides; Transcription, Genetic; Vasodilation

In idiopathic recurrent calcium urolithiasis (RCU) the state of insulin and carbohydrate metabolism, and relationships to minerals such as phosphate, are insufficiently understood. Therefore, in two groups of males with RCU (n = 30) and healthy controls (n = 8) the response to an oral carbohydrate- and calcium-rich test meal was studied with respect to glucose, insulin, and C-peptide in peripheral venous blood (taken before and up to 180 min post-load), and phosphate and glucose in fasting and post-load urine. In one RCU group (n = 16) the meal was supplemented with ascorbic acid (ASC; 5 mg/kg body weight). The mean age (RCU 29, RCU + ASC 30, controls 27 years) and mean body mass index [RCU 24.4, RCU + ASC 25.0, controls 24.0 kg/m2] were similar. Insulin resistance (synonymous sensitivity of peripheral organs to insulin) was calculated from insulin serum concentration, as was also integrated insulin, C-peptide, and glucose. Untreated stone patients (RCU) developed hyperinsulinaemia between 60 and 120 min post-load, increased integrated insulin, and insulin resistance (P < or = 0.05 vs controls), whereas the rise of C-peptide and glycaemia (absolute and integrated values) was only of borderline significance. Fasting phosphaturia was low in both RCU subgroups vs controls; however, phosphaturia in untreated RCU rose in response to the meal, contrasting sharply with a decrease in controls. ASC supplementation of the meal (in the RCU + ASC subgroup) normalized insulin, failed to normalize post-load phosphaturia, but reduced post-load glucosuria and urinary pH significantly (mean pH values 5.55 vs 5.93 in untreated RCU, controls 5.50). Postprandial urinary oxalate, calcium, protein, and supersaturation products were not changed. The postprandial changes in phosphaturia and insulin sensitivity were inversely correlated (n = 38, r = -0.44, P = 0.007). It was concluded that in younger RCU males: (1) postprandial hyperinsulinaemia, the failure to reduce phosphaturia and - within limits - glucosuria, appropriately, as well as poor urine acidification are important features of the metabolism; (2) these phenomena are probably caused by insulin resistance of organs, the kidney included; and (3) the addition of a supraphysiological dose of ASC to a meal, the subsequent abolition of hyperinsulinaemia, and the restoration of normal urine acidification suggest that this antioxidant is capable of counteracting some pre-existing basic abnormality of cell metabolism in RCU.

Topics: Adult; Ascorbic Acid; Blood Glucose; C-Peptide; Fasting; Glucose; Humans; Hyperinsulinism; Insulin; Insulin Resistance; Male; Phosphates; Postprandial Period; Time Factors; Urinary Calculi; Urine

Elevated fasting insulin concentrations and insulin resistance have been associated with non-insulin-dependent diabetes mellitus (NIDDM), obesity, atherosclerosis, and hypertension. Vitamin E supplementation in persons with and without NIDDM may be related to greater insulin sensitivity (SI). The cross-sectional associations of the intake of vitamins E and C with SI and insulin concentrations were evaluated among African American, Hispanic, and non-Hispanic white men and women with a wide spectrum of glucose tolerance included in the Insulin Resistance and Atherosclerosis Study (IRAS) (n = 1151). Insulin sensitivity was measured by minimal model analysis of a 12-sample, insulin-modified, frequently sampled intravenous glucose tolerance test. Nutrient intake (including vitamin supplement use) was assessed with a food-frequency questionnaire modified to include foods consumed by the three ethnic groups. Linear-regression models were used, including rank of SI and the log of fasting insulin as the outcome variables. Pearson correlation coefficients for vitamins E and C in relation to rank SI were r = 0.07 (P = 0.01) and r = 0.07 (P = 0.02), respectively. After adjustment for total energy and BMI these associations were no longer statistically significant and did not differ between ethnic groups. Results were similar when vitamins E and C were combined in categories of low and high antioxidant intake. Models replicated with log of fasting insulin as the outcome variable also did not produce significant associations with vitamins E or C. Thus, these cross-sectional analyses do not support the hypothesis of improved SI with increased intake of vitamins E and C.

Topics: Adult; Aged; Ascorbic Acid; Black People; Blood Glucose; Cross-Sectional Studies; Diabetes Mellitus, Type 2; Diet; Female; Humans; Insulin Resistance; Linear Models; Male; Mexican Americans; Middle Aged; Risk Factors; United States; Vitamin E; White People

Topics: Adrenal Glands; Animals; Ascorbic Acid; Desoxycorticosterone; Insulin; Insulin Resistance; Rats; Vitamins

Topics: Animals; Ascorbic Acid; Insulin; Insulin Resistance; Rats; Vitamins