Effect Of Antioxidant Supplementation Research Articles

Vitamin E neuroprotection for cisplatin neuropathy

The clinical use of cisplatin chemotherapy is limited by severe peripheral neurotoxicity reported in up to 90% of patients receiving a cumulative dose higher than 300 mg/m(2). The present study evaluates the neuroprotective effect of antioxidant supplementation (vitamin E) in patients treated with cisplatin chemotherapy. A total of 108 patients treated with cisplatin chemotherapy were randomly assigned to receive vitamin E supplementation (alpha-tocopherol 400 mg/day) or placebo. Treatment was started orally before chemotherapy and continued for 3 months after the suspension of cisplatin. Of 108 randomized patients, 68 received at least one clinical and neurophysiologic examination after cisplatin CT; 41 patients received a cumulative dose of cisplatin higher than 300 mg/m(2) and were eligible for statistical analysis: 17 in the vitamin E group (group 1) and 24 in the placebo group (group 2). The incidence of neurotoxicity was significantly lower in group 1 (5.9%) than in group 2 (41.7%) (p < 0.01). The severity of neurotoxicity, measured with a validated neurotoxicity score (Total Neuropathy Score [TNS]), was significantly lower in patients receiving vitamin E than those receiving placebo (mean TNS 1.4 vs 4.1; p < 0.01). This phase III study confirms the neuroprotective role of vitamin E against cisplatin peripheral neurotoxicity. Vitamin E supplementation should be adopted in patients receiving cisplatin-based chemotherapy. This study provides Class II evidence that vitamin E supplementation significantly reduces the relative risk of developing signs or symptoms of neurotoxicity (relative risk = 0.14) (95% confidence interval = 0.02-1.00, p < 0.05).

Antioxidant supplementation had positive effects in old rat muscle, but through better oxidative status in other organs

Objective Aged muscle is characterized by a defect in the ability of leucine to stimulate protein synthesis. We showed previously that antioxidant supplementation improved the anabolic response to leucine of old muscle and reduced inflammation. The aim of the present study was to determine if the positive effects observed in muscle could be related to an improvement of local muscle oxidative status. Methods Two groups of 20-mo-old male Wistar rats were supplemented or not with rutin, vitamin E, vitamin A, zinc, and selenium during 7 wk. We measured body weight, food intake, oxidative status in muscle and other tissues, gastrocnemius muscle proteolytic activities, and liver glutathione metabolism. Results Antioxidant supplementation had no effect on muscle antioxidant capacity, superoxide dismutase activities, and myofibrillar protein carbonyl content and induced an increase in muscle cathepsin activities. In other tissues, antioxidant supplementation increased liver glutathione (reduced plus oxidized glutathione) content, reduced oxidative damage in the liver and spleen (as measured by γ-keto-aldehyde content), and reduced heart thiobarbituric acid-reactive substances. Conclusion Our results showed that the positive effects of antioxidant supplementation observed previously on the anabolic response to leucine of old muscle were not directly related to an improvement of in situ muscle oxidative status. It could result from reduced systemic inflammation/oxidative stress. The dialog between muscle and other organs should be studied more thoroughly, especially during aging.

Effects of antioxidant supplements on cancer prevention: meta-analysis of randomized controlled trials

BackgroundThis meta-analysis aimed to investigate the effect of antioxidant supplements on the primary and secondary prevention of cancer as reported by randomized controlled trials. MethodsWe searched Medline (PubMed), Excerpta Medica database, and the Cochrane Review in October 2007. ResultsAmong 3327 articles searched, 31 articles on 22 randomized controlled trials, which included 161045 total subjects, 88610 in antioxidant supplement groups and 72435 in placebo or no-intervention groups, were included in the final analyses. In a fixed-effects meta-analysis of all 22 trials, antioxidant supplements were found to have no preventive effect on cancer [relative risk (RR) 0.99; 95% confidence interval (CI) 0.96–1.03). Similar findings were observed in 12 studies on primary prevention trials (RR 1.00; 95% CI 0.97–1.04) and in nine studies on secondary prevention trials (RR 0.97; 95% CI 0.83–1.13). Further, subgroup analyses revealed no preventive effect on cancer according to type of antioxidant, type of cancer, or the methodological quality of the studies. On the other hand, the use of antioxidant supplements significantly increased the risk of bladder cancer (RR 1.52; 95% CI 1.06–2.17) in a subgroup meta-analysis of four trials. ConclusionsThe meta-analysis of randomized controlled trials indicated that there is no clinical evidence to support an overall primary and secondary preventive effect of antioxidant supplements on cancer. The effects of antioxidant supplements on human health, particularly in relation to cancer, should not be overemphasized because the use of those might be harmful for some cancer.

Effects of Antioxidant Supplementation and Nitric Oxide Synthesis Inhibition in Murine Malaria by Plasmodium berghei

Effects of Antioxidant Supplementation and Nitric Oxide Synthesis Inhibition in Murine Malaria by Plasmodium berghei

Biomarkers of oxidative stress in overweight men are not influenced by a combination of antioxidants

The effect of antioxidant supplementation on biomarkers of oxidative stress was investigated in a 6-week intervention study in 60 overweight men. The supplement contained a combination of antioxidants aiming to correspond to the antioxidant content found in a diet rich in fruit and vegetables. Placebo, single or double dose of antioxidants was provided to the subjects. Metabolic variables, plasma antioxidants and biomarkers of oxidative stress (lipid peroxidation and DNA damage) were measured. No effect of supplementation on biomarkers of oxidative stress was observed. Both intervention groups showed substantial increases of plasma antioxidants. This study demonstrated that supplementation with a combination of antioxidants did not affect lipid peroxidation and DNA damage in overweight men, despite increased concentrations of plasma antioxidants. The absence of antioxidant supplement effect might possibly be explained by the chosen study group having a normal level of oxidative stress, duration of the intervention and/or doses of antioxidants.

Is vitamin C supplementation beneficial? Lessons learned from randomised controlled trials

In contrast to the promised 'antioxidant miracle' of the 1980s, several randomised controlled trials have shown no effect of antioxidant supplements on hard endpoints such as morbidity and mortality. The former over-optimistic attitude has clearly called for a more realistic assessment of the benefit:harm ratio of antioxidant supplements. We have examined the literature on vitamin C intervention with the intention of drawing a conclusion on its possible beneficial or deleterious effect on health and the result is discouraging. One of several important issues is that vitamin C uptake is tightly controlled, resulting in a wide-ranging bioavailability depending on the current vitamin C status. Lack of proper selection criteria dominates the currently available literature. Thus, while supplementation with vitamin C is likely to be without effect for the majority of the Western population due to saturation through their normal diet, there could be a large subpopulation with a potential health problem that remains uninvestigated. The present review discusses the relevance of the available literature on vitamin C supplementation and proposes guidelines for future randomised intervention trials.

323 POSSIBLE BENEFICIAL EFFECT OF REACTIVE OXYGEN SPECIES ON BOAR SPERM FUNCTION

Boar spermatozoa are sensitive to the attack of reactive oxygen species (ROS) due to the high content of unsaturated fatty acids in its plasma membrane and the relative low antioxidant capacity of boar seminal plasma. The benefical effect of antioxidant supplementation to the semen of boars is still a matter of debate, with different results in the literature, probably due to the empirical methods used to determine the more adequate antioxidant, and to the physiological role or the ROS. The aim of the present experiment was to study which ROS is the most deleterious to the boar sperm. Sperm samples from 4 boars were collected by digital manipulation. Sperm samples were then incubated (1 h, 37°C) with 4 ROS inducer mechanisms: xanthine/xanthine oxidase (produces superoxide anion), hydrogen peroxide (4 mM), ascorbate/ferrous sulfate (4 mM; produced hydroxyl radical), and malondialdehyde (lipid peroxidation product). Samples were analyzed for the 3-3′ diaminobenzidine stain, as an index of mitochondrial activity; the eosin/nigrosin staining, as an index of membrane integrity; the simple stain (fast green/Bengal rose), as an index of acrosome integrity; and the measurement of thiobarbituric acid reactive substances (TBARS), as an index of lipid peroxidation. Results showed that the boar sperm is relatively resistant to all ROS studied in the present experiment. Only for the percentage of sperm showing intact membrane, a difference was found between incubation with superoxide anion and hydroxyl radical (Table 1). The TBARS production was higher in samples incubated with hydroxyl radical, indicating that these samples were more susceptible to the attack of this ROS. Surprisingly, a positive correlation was found between TBARS and membrane integrity (r = 0.51, P = 0.04), indicating that samples more susceptible to the oxidative stress showed higher membrane integrity. A hypothesis to explain such conflicting results would be the physiological role of the ROS on several spermatic events, especially in this particular species. It is well known that boar semen, in order to achieve ideal motility, requires aerobic conditions. Further studies are necessary to study the effect of each ROS on each physiological or pathological event on boar sperm function. Table 1.Effect of different ROS in boar semen The authors thank Nutricell for the media used in the present experiment.

Trial of Lycopene to Prevent Preeclampsia in Healthy Primigravidas: Results Show Some Adverse Effects

It is believed that the mechanism underlying vascular endothelial cell damage in preeclampsia is associated with the formation of lipid peroxides and other reactive free radical oxygen species generated from persistent placental underperfusion. Support for the role of oxidative stress (free radical-mediated lipid peroxidation) in the pathophysiology of preeclampsia is provided by biochemical evidence that the plasma serum of patients with the disorder has a high concentration of lipid peroxidation products and is deficient in endogenous antioxidants. One clinical trial showed that oral administration of lycopene, a strong antioxidant and free radical scavenger, significantly reduced the risk of preeclampsia and intrauterine growth retardation in low-risk primigravidas. Because of this and other evidence, it was expected that lycopene would prevent preeclampsia in a similar low-risk population. This randomized double blind placebo-controlled trial evaluated the effectiveness of antioxidant supplementation with lycopene for the prevention of preeclampsia in 159 healthy singleton primigravidas between 12 and 20 weeks of gestation. The study subjects were randomized to receive oral daily doses of lycopene 2 mg (n = 77) or a placebo (n = 82) and were followed until delivery for the development of preeclampsia. There was no difference between the 2 groups in the percentage of patients who developed preeclampsia (18% in both groups). However, women who received lycopene had a significantly higher incidence of preterm labor than the placebo (10.4% vs. 1.2%, P = 0.02), and more low birth weight (<2.5 kg) babies (22.1% vs. 9.8%, P = 0.05). These findings indicate that the antioxidant lycopene is not effective for prevention of preeclampsia in healthy primigravidas and may be associated with an increased incidence of adverse effects such as preterm labor and low birth weight babies.

Effects of long-term antioxidant supplementation and association of serum antioxidant concentrations with risk of metabolic syndrome in adults

Background:Limited observational evidence suggests lower antioxidant concentrations in individuals with the metabolic syndrome (MetS); few randomized controlled trials have addressed the effect of multiple antioxidants on the risk of MetS. Objective:The objective was to examine the effect of antioxidant supplementation for 7.5 y on the incidence of MetS and the epidemiologic association between baseline serum antioxidant concentrations and the prospective risk of MetS. Design:Adults (n = 5220) participating in the SUpplementation en VItamines et Minéraux AntioXydants (SU.VI.MAX) primary prevention trial were randomly assigned to receive a supplement containing a combination of antioxidants (vitamins C and E,β-carotene, zinc, and selenium) at nutritional doses or a placebo. Subjects were free of MetS at baseline and were followed for 7.5 y. Results:Antioxidant supplementation for 7.5 y did not affect the risk of MetS. Baseline serum antioxidant concentrations ofβ-carotene and vitamin C, however, were negatively associated with the risk of MetS; the adjusted odds ratios (and 95% CIs) for the highest compared with the lowest tertile were 0.34 (0.21, 0.53;P for trend = 0.0002) and 0.53 (0.35, 0.80;P for trend = 0.01), respectively. Baseline serum zinc concentrations were positively associated with the risk of developing MetS; the adjusted odds ratio (and 95% CI) for the highest compared with the lowest tertile was 1.81 (1.20, 2.72;P for trend = 0.01). Conclusions:The experimental finding of no beneficial effects of antioxidant supplementation in a generally well-nourished population is consistent with recent reports of a lack of efficacy of antioxidant supplements. However, the relations observed between the risk of MetS and baseline serum antioxidant concentrations, which probably reflect associations with overall dietary patterns, do support the current recommendations to consume antioxidant-rich foods. This trial was registered at clinicaltrials.gov as NCT00272428.

Effect of oral antioxidant supplementation on lipid peroxidation during radiotherapy in head and neck malignancies

The objectives of the present study were to ascertain the variations in the serum levels of malondialdehyde and total antioxidant status, in head and neck malignancies with different stages, with and without oral antioxidant supplementation, before and after radiotherapy, and to validate the protective effects of an antioxidant supplementation during radiotherapy. The pretreatment values of serum malondialdehyde were significantly raised, while that of serum total antioxidant status were significantly declined in all the stages of head and neck malignancies, when compared with the healthy controls values (P<0.001). A significant correlation was observed related to the studied parameters and different stages of the disease. The study suggests that an oral antioxidant supplementation during radiotherapy is an effective mode in reducing oxidative stress. Antioxidant supplementation during radiotherapy may serve as an adjuvant therapy in malignancies offering a protection to normal cells that may further reduce the risk of developing secondary cancers.

Prevalence and predictors of antioxidant supplement use during breast cancer treatment

Although many patients take antioxidant dietary supplements during breast cancer treatment, the benefits of such supplementation are unproven. The authors of this report analyzed the prevalence of and factors associated with antioxidant supplement use during breast cancer (BC) treatment among women who participated in the Long Island Breast Cancer Study Project. From 2002 through 2004, women with BC who had participated a case-control study from 1996 to 1997 were invited to participate in a follow-up interview. Antioxidant supplement use was defined as any self-reported intake of supplemental vitamin C, vitamin E, beta-carotene, or selenium in individual supplements or multivitamins. Follow-up interview participants were younger, more predominantly white, and of higher socioeconomic status than women who did not respond. Among 764 participants who completed the follow-up interview, 663 (86.8%) reported receiving adjuvant treatment for their BC. Of those 663 women, 401 (60.5%) reported using antioxidants during adjuvant treatment: One hundred twenty of 310 women (38.7%) used antioxidants during chemotherapy, 196 of 464 women (42.2%) used them during radiation, and 286 of 462 women (61.9%) used them during tamoxifen therapy. Of 401 antioxidant users, 278 women (69.3%) used high doses (doses higher than those contained in a Centrum multivitamin). The factors that were associated with high antioxidant supplement use during treatment were higher fruit and vegetable intake at diagnosis (relative risk [RR], 1.71; 95% confidence interval [CI], 1.13-2.59), tamoxifen use (RR, 3.66; 95% CI, 2.32-5.78), ever using herbal products (RR, 3.49; 95% CI, 2.26-5.38), and ever engaging in mind-body practices (RR, 1.72; 95% CI, 1.13-2.64). Given the common use of antioxidant supplements during BC treatment, often at high doses and in conjunction with other complementary therapies, future research should address the effects of antioxidant supplementation on BC outcomes.

비만여성의 유산소운동 빈도와 항산화제 섭취가 신체조성, 산화물질 및 총항산화능에 미치는 영향

#body composition #peroxide value #total antioxidant status #exercise frequency #antioxidant supplementation #vitamin C #E #running training #obese women

Oxidative stress and the development of diabetic retinopathy: Contributory role of matrix metalloproteinase-2

Matrix metalloproteinases (MMPs) degrade extracellular matrix and regulate many functions including cell signaling. Oxidative stress is implicated in the development of diabetic retinopathy, and MMP-2, the most ubiquitous member of the MMP family, is sensitive to oxidative stress. This study aimed to determine the regulation of MMP-2 by oxidative stress in the development of diabetic retinopathy and the role of MMP-2 in the apoptosis of retinal capillary cells. The effects of mitochondrial superoxide scavenger on glucose-induced alterations in MMP-2, and its proenzyme activator MT1-MMP and physiological inhibitor TIMP-2, were determined in retinal endothelial cells, and the regulation of their glucose-induced accelerated apoptosis by the inhibitors of MMP-2 was accessed. To confirm in vitro results, the effects of antioxidant supplementation on MMP-2, MT1-MMP, and TIMP-2 were investigated in the retina of streptozotocin-induced diabetic rats. Glucose-induced activation of retinal capillary cell MMP-2 and MT1-MMP and decrease in TIMP-2 were inhibited by superoxide scavengers, and their accelerated apoptosis was prevented by the inhibitors of MMP-2. Antioxidant therapies, which have been shown to inhibit oxidative stress, capillary cell apoptosis, and retinopathy in diabetic rats, ameliorated alterations in retinal MMP-2 and its regulators. Thus, MMP-2 has a proapoptotic role in the loss of retinal capillary cells in diabetes, and the activation of MMP-2 is under the control of superoxide. This suggests a possible use of MMP-2-targeted therapy to inhibit the development of diabetic retinopathy.

Effect of Antioxidant Supplements on Normal and Atherogenic Dieted Rabbit Fibrinolytic Activity

Ten New Zealand strain rabbits were fed Normal Diet(ND) ( Purina Rabbit Chow‐PRC) vs ten fed Atherogenic Diet(AD) (2% cholesterol, 6% corn oil and 92% PRC). Five animals / diet received the vitamin supplement (VS)=Vitamin C (2gms/day) + Vitamin E (80 IU/day in 0.25 ml. soy lecithin). In 8 weeks, Plasma Fibrinolytic Activity(PFA) was 24.4% in ND+VS vs 14.67% in ND‐VS animals. AD +VS had 16.5% and AD‐VS rabbits 10.4% PFA. In 16 weeks, PFA values were 28.8% in the ND +VS vs 28.8% for ND ‐ VS animals and the AD values were 29.8% +VS and 27.3% ‐VS. FA in homogenized blood platelets was 43.6% in the ND+VS, 35.2 % in ND ‐VS , 43.0% in AD +VS and 42.2% in AD‐VS platelets . Blood Cholesterol values after eight weeks were comparable in the two ND groups. The AD +VS had 915 mg% cholesterol vs 1220mg%for the AD‐VS group. After 16 weeks , cholesterol values in the AD+VS group were slightly above the AD ‐VS group. Plasma and platelet phospholipid levels were not significantly altered by the VS. Addition of the antioxidants to the diet significantly increased FA in the blood plasma and platelets of ND animals. VS slightly increased these values in AD rabbits . At autopsy, the AD+VS group had reduced atherogenic plaque in their aortae compared to AD ‐VS animals.

Oral antioxidant supplementation does not prevent acute mountain sickness: double blind, randomized placebo-controlled trial

Acute mountain sickness may be caused by cerebrovascular fluid leakage due to oxidative damage to the endothelium. This may be reduced by oral antioxidant supplementation. To assess the effectiveness of antioxidant supplementation for the prevention of acute mountain sickness (AMS). A parallel-group double blind, randomized placebo-controlled trial. The study was conducted in a university clinical research facility and a high altitude research laboratory. Eighty-three healthy lowland volunteers ascended to 5200 m on the Apex 2 high altitude research expedition. The treatment group received a daily dose of 1 g l-ascorbic acid, 400 IU of alpha-tocopherol acetate and 600 mg of alpha-lipoic acid (Cultech Ltd., Wales, UK) in four divided doses. Prevalence of AMS was measured using the Lake Louise Consensus score sheet (LLS). Secondary outcomes were AMS severity measured using a novel visual analogue scale, arterial oxygen saturation and pulmonary artery systolic pressure (PASP). Forty-one subjects were allocated to the antioxidant group, and 42 to the placebo group. There was no difference in AMS incidence or severity between the antioxidant and placebo groups using the LLS at any time at high altitude. At the pre-determined comparison point at Day 2 at 5200 m, 69% of the antioxidant group (25/36) and 66% of the placebo group (23/35) had AMS using the LLS criteria (P = 0.74). No differences were observed between the groups for PASP, oxygen saturation, presence of a pericardial effusion or AMS assessed by VAS. This trial found no evidence of benefit from antioxidant supplementation at high altitude. NCT00664001.

Effects of Antioxidant Supplements Intervention on the Level of Plasma Inflammatory Molecules and Disease Severity of Rheumatoid Arthritis Patients

Objective: Excess generation of reactive oxygen species in damaged joints accelerates inflammatory responses in RA (rheumatoid arthritis) patients. The complementary effects of dietary antioxidant supplementation on the blood level of inflammatory mediators and the severity of the disease in RA patients were evaluated.Study Design and Settings: The study was conducted as a randomized, placebo-controlled, double-blind, three-treatment cross-over design trial. The participants visited the hospital as outpatients.Subjects: Twenty patients meeting the 1987 criteria for the classification of rheumatoid arthritis completed the study.Interventions: The subjects were randomized in three groups to receive one of following supplementation; quercetin+vitamin C (166mg+133mg/capsule), α-lipoic acid (300mg/capsule) or placebo for 4 weeks (3 capsules/day). Each treatment period consisted of 4 weeks with 2 weeks of wash-out period before the subject starts next supplementation.Outcome Parameters: Serum levels of tumor necrosis factor-α(TNF-α), interleukin-1β(IL-1β), interleukin -6(IL-6), and C-reactive protein (CRP) were measured. The severity of disease was evaluated using Korean Health Assessment Questionnaire(KHAQ) and Visual Analogue Scale(VAS). Nutrient intake was measured at baseline and at the end of each intervention period.Results: The mean energy and nutrient intakes remained constant during study period. No significant differences were found in the serum concentrations of pro-inflammatory cytokines and CRP between treatments. The scores of disease severity measurements were not significantly different between treatments, although quercetin supplementation had a tendency to reduce VAS.Conclusions: Dietary supplementation of antioxidants at 900 mg/day for 4 weeks did not change the blood biomarkers of inflammation and disease severity of RA patients under conventional medical treatments. Further considerations for dose-response relationships, duration of supplementation, and susceptible biomarkers are required.

Effects of antioxidant supplementation on insulin sensitivity, endothelial adhesion molecules, and oxidative stress in normal-weight and overweight young adults

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; β-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.

Effect of antioxidant supplementation of cryopreservation medium on post-thaw integrity of human spermatozoa

This study examined whether the addition of an antioxidant to cryopreservation medium could improve the post-thaw integrity of cryopreserved human spermatozoa, particularly from men with abnormal semen parameters. Semen samples were collected by masturbation and assessed following WHO standards. Normal ( n = 23) and abnormal ( n = 20) samples were divided into three aliquots prior to cryopreservation. The first aliquot remained untreated and was mixed with cryopreservation medium (in-house 1:1). The second and third aliquots were mixed with cryopreservation medium containing either 100 µmol or 200 µmol vitamin E analogue. Samples were frozen at −10° C per minute to −80°C, then plunged into liquid nitrogen. Thawed samples were assessed for motility, vitality and DNA integrity. Split-plot repeated-measures ANOVA was used to assess within-subject (dose) and between-group (normal/abnormal) differences in post-thaw motility index, vitality staining and DNA fragmentation. Vitamin E dose was significantly associated with post-thaw motility ( P = 0.041) and the pattern of response across doses was similar for normal and abnormal groups. Post-thaw motility was significantly improved by the addition of 200 µmol vitamin E ( P = 0.006), but neither vitality nor sperm DNA fragmentation were altered. These results suggest that the addition of vitamin E to cryopreservation medium improves post-thaw motility.

Influencia de la dieta sobre marcadores plasmáticos de estrés oxidativo en humanos

Oxidative stress is related to an imbalance between the production of reactive species and the antioxidant defenses. In essence, oxidative stress has been defined as a disturbance in the pro-oxidant/antioxidant balance, leading to potential damage. It has been suggested that oxidative stress is involved in the etiology of several chronic diseases including cardiovascular disease, diabetes, cancer and neurodegenerative processes. The antioxidant defenses include nonenzymatic (especially dietary antioxidants) and antioxidant enzymes. Vitamins, minerals and phytochemicals (polyphenols and carotenoids) are among the major dietary antioxidants. The assessment of oxidative stress status though specific biomarkers has acquired great importance. The major biomarkers include the products of the attack of free radicals and reactive species to various substrates: lipids, proteins and nucleic acids. Measurement of antioxidant capacity may also involve the assessment of specific oxidative stress biomarkers. Most of the studies that have examined the association between diet and oxidative stress consider the effects of antioxidant supplements (vitamins and minerals), drinks and foods with bioactive compounds or dietary patterns on oxidative stress biomarkers. Some of these studies have demonstrated beneficial results on oxidative stress markers. However, the role of diet on oxidative stress biomarkers remains unclear and represents a potentially fruitful area for further research in the health area.

Glutathione Metabolism Under High-Altitude Stress and Effect of Antioxidant Supplementation

Humans have a number of mechanisms for protection against reactive oxygen species, but under stressful conditions these defenses are not completely successful. Glutathione plays an important role in protection against free radicals and reactive oxygen species induced damages. The present study was undertaken to understand the effect of high-altitude (HA) exposure on glutathione metabolism and antioxidant status along with the effects of N-acetyl cysteine (NAC) and vitamin E supplementation in humans. The study was conducted on 30 healthy male volunteers (age 22.9 +/- 2.6, mean +/- SD) divided into three groups. Group 1 was placebo control and 2 and 3 were supplemented with 400 mg of NAC or vitamin E, respectively, per day. The study was conducted initially at sea level (Phase I, 320 m); then the subjects were taken to high altitude (Phase II, 3600 m) by air. After a week at this altitude, subjects ascended on foot to an altitude of 4580 m (Phase III). Significant decreases in reduced glutathione and increases in oxidized glutathione levels were observed on HA exposure. Increase in glutathione peroxidase and glutathione reductase levels were also observed on HA exposure. Lower levels of plasma vitamin C and total antioxidant status were observed during HA exposure. The changes observed were less in the supplemented groups as compared to placebo control. Results indicate that HA exposure adversely affects glutathione metabolism and antioxidant defense mechanisms and these changes can be ameliorated through supplementation of NAC and vitamin E.