Vitamin E kinetics in smokers and nonsmokers

Does combined training of biofeedback and neurofeedback affect smoking status, behavior, and longitudinal brain plasticity?

Introduction: Investigations of biofeedback (BF) and neurofeedback (NF) training for nicotine addiction have been long documented to lead to positive gains in smoking status, behavior and to changes in brain activity. We aimed to: (a) evaluate a multi-visit combined BF/NF intervention as an alternative smoking cessation approach, (b) validate training-induced feedback learning, and (c) document effects on resting-state functional connectivity networks (rsFCN); considering gender and degree of nicotine dependence in a longitudinal design. Methods: We analyzed clinical, behavioral, and electrophysiological data from 17 smokers who completed five BF and 20 NF sessions and three evaluation stages. Possible neuroplastic effects were explored comparing whole-brain rsFCN by phase-lag index (PLI) for different brain rhythms. PLI connections with significant change across time were investigated according to different resting-state networks (RSNs). Results: Improvements in smoking status were observed as exhaled carbon monoxide levels, Total Oxidative Stress, and Fageström scores decreased while Vitamin E levels increased across time. BF/NF promoted gains in anxiety, self-esteem, and several aspects of cognitive performance. BF learning in temperature enhancement was observed within sessions. NF learning in theta/alpha ratio increase was achieved across baselines and within sessions. PLI network connections significantly changed across time mainly between or within visual, default mode and frontoparietal networks in theta and alpha rhythms, while beta band RSNs mostly changed significantly after BF sessions. Discussion: Combined BF/NF training positively affects the clinical and behavioral status of smokers, displays benefit in smoking harm reduction, plays a neuroprotective role, leads to learning effects and to positive reorganization of RSNs across time. Clinical Trial Registration: https://clinicaltrials.gov/ct2/show/NCT02991781.

Dietary Antioxidants and Lung Cancer Risk in Smokers and Non-Smokers

Smoking is considered a major risk factor in the development of lung diseases worldwide. Active smoking and secondhand (passive) smoke (SHS) are related to lung cancer (LC) risk. Oxidative stress (OS) and/or lipid peroxidation (LP) induced by cigarette smoke (CS) are found to be involved in the pathogenesis of LC. Meta-analyses and other case-control/prospective cohort studies are inconclusive and have yielded inconsistent results concerning the protective role of dietary vitamins C and E, retinol, and iron intake against LC risk in smokers and/or non-smokers. Furthermore, the role of vitamins and minerals as antioxidants with the potential in protecting LC cells against CS-induced OS in smokers and non-smokers has not been fully elucidated. Thus, this review aims to summarize the available evidence reporting the relationships between dietary antioxidant intake and LC risk in smokers and non-smokers that may be used to provide suggestions for future research.

Vitamin E: How much is enough, too much and why!

α-Tocopherol (α-T) is a required dietary nutrient for humans and thus is a vitamin. This narrative review focuses on vitamin E structures, functions, biological determinants and its deficiency symptoms in humans. The mechanisms for the preferential α-T tissue enrichment in the human body include the α-T transfer protein (TTPA) and the preferential metabolism of non-α-T forms. Potential new α-T biomarkers, pharmacokinetic data, and whether there are better approaches to evaluate and set the α-T dietary requirement are discussed. Finally, the possible role of α-T supplements in delay of chronic diseases and the evaluation of vitamin E safety are considered.

Antioxidants in smokers

Cigarette smoke (CS) is likely the most common preventable cause of human morbidity and mortality worldwide. Consequently, inexpensive interventional strategies for preventing CS-related diseases would positively impact health systems. Inhaled CS is a powerful inflammatory stimulus and produces a shift in the normal balance between antioxidants and oxidants, inducing oxidative stress in both the respiratory system and throughout the body. This enduring and systemic pro-oxidative state within the body is reflected by increased levels of oxidative stress and inflammation biomarkers seen in smokers. Smokers might benefit from consuming antioxidant supplements, or a diet rich in fruit and vegetables, which can reduce the CS-related oxidative stress. This review provides an overview of the plasma profile of antioxidants observable in smokers and examines the heterogeneous literature to elucidate and discuss the effectiveness of interventional strategies based on antioxidant supplements or an antioxidant-rich diet to improve the health of smokers. An antioxidant-rich diet can provide an easy-to-implement and cost-effective preventative strategy to reduce the risk of CS-related diseases, thus being one of the simplest ways for smokers to stay in good health for as long as possible. The health benefits attributable to the intake of antioxidants have been observed predominantly when these have been consumed within their natural food matrices in an optimal antioxidant-rich diet, while these preventive effects are rarely achieved with the intake of individual antioxidants, even at high doses.

Validity of a Cochrane Systematic Review and meta-analysis for determining the safety of vitamin E

The public safety of α-tocopherol has been called in question by several meta-analyses which have raised concern among regulatory authorities. The objective of this study was to evaluate the Cochrane Database Systematic Review 2012 (CD007176) which concludes that α-tocopherol forms of vitamin E have a statistically significant effect on mortality, by assessing the trials and datasets used and determining their effect upon the primary outcome.The Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study (ATBC), a factorial design study of Finnish smokers was a pivotal paper in the Cochrane Review owing to the high mortality rate observed which resulted in a substantial weighting (42.6%) in the meta-analysis. The Cochrane meta-analysis used a 3 cell analytical method comparing all vitamin E cells (vitamin E alone plus vitamin E + β-carotene) to the placebo only cell. This had the unfortunate effect of incorrectly inflating the mortality risk attributed to vitamin E by not balancing the contribution to mortality of the β-carotene intervention. Re-analysis of the ATBC trial using data derived from the more generally accepted 'inside the table' (2 cell - vitamin E versus placebo) or 'at the margins' (4 cell - all vitamin E versus all non-vitamin E) analytical methods demonstrates a statistically non-significant result.The data from the ATBC study has been given in 5 datasets (the trial alone and four extended post-trial follow-up time periods). Using the 3 cell analysis method only the 6 and 8-year (used in the meta-analysis) follow-up periods were statistically significant. Using the 2 or 4 cell method the outcome remains non-significant over all time periods.The impartiality of excluding trials with zero mortality is also examined and questioned.This paper raises concerns overall as to the appropriateness of datasets chosen, the validity of methods and generalisability of results when using meta-analysis as a tool to determine safety. Issues raised in this paper are not unique to the Cochrane study in question. Until we have new tools, there may be a need to rely on conventional narrative systematic literature synthesis in the assessment of safety or contain our results to specific sub-populations where more conclusive results can be determined.

Consequences of oxidative stress in age-related macular degeneration

The retina resides in an environment that is primed for the generation of reactive oxygen species (ROS) and resultant oxidative damage. The retina is one of the highest oxygen-consuming tissues in the human body. The highest oxygen levels are found in the choroid, but this falls dramatically across the outermost retina, creating a large gradient of oxygen towards the retina and inner segments of the photoreceptors which contain high levels of polyunsaturated fatty acids. This micro-environment together with abundant photosensitizers, visible light exposure and a high energy demand supports a highly oxidative milieu. However, oxidative damage is normally minimized by the presence of a range of antioxidant and efficient repair systems. Unfortunately, as we age oxidative damage increases, antioxidant capacity decreases and the efficiency of reparative systems become impaired. The result is retinal dysfunction and cell loss leading to visual impairment. It appears that these age-related oxidative changes are a hallmark of early age-related macular degeneration (AMD) which, in combination with hereditary susceptibility and other retinal modifiers, can progress to the pathology and visual morbidity associated with advanced AMD. This review reassesses the consequences of oxidative stress in AMD and strategies for preventing or reversing oxidative damage in retinal tissues.

Serum vitamin E concentrations and recovery of physical function during the year after hip fracture

BACKGROUND

Poor nutritional status after hip fracture is common and may contribute to physical function decline. Low serum concentrations of vitamin E have been associated with decline in physical function among older adults, but the role of vitamin E in physical recovery from hip fracture has never been explored.

METHODS

Serum concentrations of α- and γ-tocopherol, the two major forms of vitamin E, were measured in female hip fracture patients from the Baltimore Hip Studies cohort 4 at baseline and at 2-, 6-, and 12-month postfracture follow-up visits. Four physical function measures-Six-Minute Walk Distance, Lower Extremity Gain Scale, Short Form-36 Physical Functioning Domain, and Yale Physical Activity Survey-were assessed at 2, 6, and 12 months postfracture. Generalized estimating equations modeled the relationship between baseline and time-varying serum tocopherol concentrations and physical function after hip fracture.

RESULTS

A total of 148 women aged 65 years and older were studied. After adjusting for covariates, baseline vitamin E concentrations were positively associated with Six-Minute Walk Distance, Lower Extremity Gain Scale, and Yale Physical Activity Survey scores (p < .1) and faster improvement in Lower Extremity Gain Scale and Yale Physical Activity Survey scores (p < .008). Time-varying vitamin E was also positively associated with Six-Minute Walk Distance, Lower Extremity Gain Scale, Yale Physical Activity Survey, and Short Form-36 Physical Functioning Domain (p < .03) and faster improvement in Six-Minute Walk Distance and Short Form-36 Physical Functioning Domain (p < .07).

CONCLUSIONS

Serum concentrations of both α- and γ-tocopherol were associated with better physical function after hip fracture. Vitamin E may represent a potentially modifiable factor related to recovery of postfracture physical function.

Gene-regulatory activity of alpha-tocopherol

Vitamin E is an essential vitamin and a lipid soluble antioxidant, at least, under in vitro conditions. The antioxidant properties of vitamin E are exerted through its phenolic hydroxyl group, which donates hydrogen to peroxyl radicals, resulting in the formation of stable lipid species. Beside an antioxidant role, important cell signalling properties of vitamin E have been described. By using gene chip technology we have identified alpha-tocopherol sensitive molecular targets in vivo including christmas factor (involved in the blood coagulation) and 5alpha-steroid reductase type 1 (catalyzes the conversion of testosterone to 5alpha-dihydrotestosterone) being upregulated and gamma-glutamyl-cysteinyl synthetase (the rate limiting enzyme in GSH synthesis) being downregulated due to alpha-tocopherol deficiency. Alpha-tocopherol regulates signal transduction cascades not only at the mRNA but also at the miRNA level since miRNA 122a (involved in lipid metabolism) and miRNA 125b (involved in inflammation) are downregulated by alpha-tocopherol. Genetic polymorphisms may determine the biological and gene-regulatory activity of alpha-tocopherol. In this context we have recently shown that genes encoding for proteins involved in peripheral alpha-tocopherol transport and degradation are significantly affected by the apoE genotype.

Regulation of the alpha-tocopherol transfer protein in mice: lack of response to dietary vitamin E or oxidative stress

The alpha-tocopherol transfer protein (TTP) plays an important role in the regulation of plasma alpha-tocopherol concentrations. We hypothesized that hepatic TTP levels would be modulated by dietary vitamin E supplementation and/or by oxidative stress. Mice were fed either a High E (1150 mg RRR-alpha-tocopheryl acetate/kg diet) or a Low E (11.5 mg/kg diet) diet for 2 wk. High E increased plasma and liver alpha-tocopherol concentrations approximately 8- and 40-fold, respectively, compared with Low E-fed mice, whereas hepatic TTP increased approximately 20%. Hepatic TTP concentrations were unaffected by fasting (24 h) in mice fed either diet. To induce oxidative stress, chow-fed mice were exposed for 3 d to environmental tobacco smoke (ETS) for 6 h/d (total suspended particulate, 57.4 +/- 1.8 mg/m3). ETS exposure, while resulting in pulmonary and systemic oxidative stress, had no effect on hepatic alpha-tocopherol concentrations or hepatic TTP. Overall, changes in hepatic TTP concentrations were minimal in response to dietary vitamin E levels or ETS-related oxidative stress. Thus, hepatic TTP concentrations may be at sufficient levels such that they are unaffected by either modulations of dietary vitamin E or by the conditions of environmentally related oxidative stress used in the present studies.

Vitamin E Biochemistry and Function: A Case Study in Male Rabbit

Vitamin E supplementation has become a common procedure to promote growth and health and improve the qualitative characteristics of farm animals. It has been demonstrated to be an efficient strategy for improving their reproductive function. Germ cells are particularly vulnerable to oxidative damage and may thus require additional antioxidant protection. The aim of this review is to give a comprehensive overview of the current knowledge of the biochemistry and physiology of vitamin E; successively, the effect of this compound on the reproductive activity of rabbit buck is accurately described. In particular, this review examines studies on the effects of animal age, dose and duration of vitamin E supplementation, as well as the co-supplementation with selenium, vitamin C and polyunsaturated fatty acids. Several investigations have shown beneficial effects in bucks supplemented with vitamin E levels higher than the standard dietary requirement (50 mg/kg) particularly when the semen is stored. However, the exact dietary intake of vitamin E should be decided according to specific tissue needs for the individual vitamin E forms and the specific saturation markers.

Associations of polymorphism of P22(phox) C242T, plasma levels of vitamin E, and smoking with coronary heart disease in China

BACKGROUND

The C242T polymorphisms of P22(phox) and plasma vitamin E have been associated with the risk of coronary heart disease (CHD) in several studies, but the results have been inconsistent. In this study, we sought to examine potential interactions between P22(phox) genotypes, plasma vitamin E concentrations, and smoking in relation to CHD risk.

METHODS

We determined C242T genotype frequency in the P22(phox) gene and plasma levels of vitamin E in 565 Chinese patients with CHD and 609 control subjects. Logistic regression was used to control for potential confounders in multivariate analyses.

RESULTS

Compared with subjects with a CC genotype, subjects with a CT or TT genotype had a lower risk of CHD (multivariate-adjusted odds ratio [OR] 0.45, 95% CI 0.28-0.74, P = .001). Plasma concentrations of vitamin E were lower in case patients than in control subjects (multivariate-adjusted OR 0.65, 95% CI 0.50-0.86, P = .025). Compared with nonsmokers with a CC genotype, nonsmokers with a CT or TT genotype had a decreased risk of CHD (OR 0.25, 95% CI 0.12-0.53), but smokers with a CT or TT genotype had an increased risk (OR 2.04, 95% CI 0.74-5.61, P for interaction = .039). Smokers with a lower vitamin E concentration had a >3.0-fold greater risk of CHD than did nonsmokers with a higher vitamin E concentration (OR 3.52, 95% CI 2.36-5.24, P for interaction = .041).

CONCLUSIONS

These data provide evidence that P22(phox) genotypes are significantly associated with CHD risk in a Chinese population and suggest potential interactions among smoking, P22(phox) genotypes, and vitamin E in relation to CHD risk.

Estimation of the human daily requirement of vitamin E by turnover kinetics of labeled RRR-alpha-tocopherol

The human daily requirement of alpha-tocopherol was estimated by a determination of the turnover kinetics of deuterium-labeled RRR-alpha-tocopherol in two women and three men. The amount of alpha-tocopherol absorbed varied in proportion to the amount of fat eaten with the vitamin, increasing by 0.43 mg for each gram of fat consumed. A fat-free method for administering alpha-tocopherol was developed by vacuum impregnation of apples with the vitamin. Even in the absence of fat, about 10% of the administered alpha-tocopherol was absorbed. The daily requirement of alpha-tocopherol when consumed with a diet containing 21% fat was estimated to be 15 +/- 2 mg, an amount close to the current Estimated Average Requirement (EAR) of 12 mg/d. The study showed that vacuum-impregnated fruit might be a useful way to supplement vitamin E in people eating a low-fat diet.

Blood cells as functional markers of antioxidant vitamin status

Antioxidants have shown beneficial effects in several biological systems, in which they were able to prevent oxidative stress-associated damage. Vitamins C and E are key antioxidants in man. Dietary intake cannot accurately reflect plasma vitamin levels. However, the plasma levels of antioxidant vitamins could also reflect the acute assimilation of these vitamins. It has been pointed out that antioxidant vitamin blood contents reach a saturation level by intake of dietary supplements. Antioxidant vitamin plasma levels are the parameter most used to determine antioxidant status. However, the vitamin plasma levels may not reflect the nutritional status of vitamins. It has been pointed out that the vitamin E in adipose tissue can be used as a measure of vitamin E status. To determinate antioxidant vitamin contents in lymphocytes and neutrophils after exercise is a useful tool to assess the functional status of antioxidant vitamins.

Vitamin E attenuates acute lung injury in sheep with burn and smoke inhalation injury

INTRODUCTION

A decrease in alpha-tocopherol (vitamin E) plasma levels in burn patients is typically associated with increased mortality. We hypothesized that vitamin E supplementation (alpha-tocopherol) would attenuate acute lung injury induced by burn and smoke inhalation injury.

MATERIALS AND METHODS

Under deep anesthesia, sheep (33 +/- 5 kg) were subjected to a flame burn (40% total body surface area, third degree) and inhalation injury (48 breaths of cotton smoke, < 40 degrees C). Half of the injured group received alpha-tocopherol (1000 IU vitamin E) orally, 24 h prior to injury. The sham group was neither injured nor given vitamin E. All three groups (n = 5 per group) were resuscitated with Ringer's lactate solution (4 ml/kg/%burn/24 h), and placed on a ventilator (PEEP = 5 cmH2O; tidal volume = 15 ml/kg) for 48 h.

RESULTS

Plasma alpha-tocopherol per lipids doubled in the vitamin E treated sheep. Vitamin E treatment prior to injury largely prevented the increase in pulmonary permeability index and moderated the increase in lung lymph flow (52.6 +/- 6.2 ml/min, compared with 27.3 +/- 6.0 ml/min, respectively), increased the PaO2/FiO2 ratio, ameliorated both peak and pause airway pressure increases, and decreased plasma conjugated dienes and nitrotyrosine.

CONCLUSIONS

Pretreatment with vitamin E ameliorated the acute lung injury caused by burn and smoke inhalation exposure.

Monitoring micronutrients in cigarette smokers

Smoking is associated with oxidative stress and increased risks of many chronic diseases that both shorten life and impair its quality. Low concentrations of several micronutrients, especially the antioxidants vitamin C and beta-carotene, are also associated with smoking, and there has been much interest in determining whether deficiencies in micronutrients are involved etiologically in smoking-related diseases. The objective of this review was to bring together reports on dietary intakes, biochemical indicators of micronutrient status, and results of some intervention studies on micronutrients where authors had compared outcomes in smokers and non-smokers. The micronutrients discussed are vitamins A, E, and C; the carotenoids; some of the B-vitamin group; and the minerals selenium, zinc, copper, and iron. The data were then examined to determine whether effects on the biochemical markers of micronutrient status were due to differences in dietary intakes between smokers and non-smokers or to the consequences of inflammatory changes caused by the oxidative stress of smoking. It was concluded that although smoking is associated with reduced dietary intake of vitamin C and carotenoid-containing foods, inflammatory changes increase turnover of these micronutrients so that blood concentrations are still lower in smokers than non-smokers even when there is control for dietary differences. In the case of vitamin E, there is some evidence for increased turnover of this nutrient in smokers, but this has little to no influence on blood concentrations, and there are no differences in dietary intake of vitamin E between smokers and non-smokers. Serum concentrations of vitamin A, folate, and vitamin B12 and B6 markers do not appear to be influenced by smoking, although there is some influence of dietary intake on concentrations of these nutrients in the body. In the case of the minerals examined, the main effects on biochemical markers of mineral status were attributed to inflammation and were therefore greater in heavy or long-term smokers. Serum concentrations of selenium and erythrocyte GPx activity were lower in smokers. Erythrocyte CuZn-SOD activity and serum ceruloplasmin concentrations were elevated, while serum zinc concentrations were depressed only in heavy smokers. Lastly, smoking appears to affect iron homeostasis mainly by changing hemoglobin concentrations, which were in general increased. Serum iron, TfR, and ferritin were mostly unaffected by smoking, except in pregnancy where there is evidence of increased erythropoiesis causing lower saturation of plasma transferrin and some evidence of lowering of iron stores.

Vitamin E biokinetics, oxidative stress and cigarette smoking

Vitamin E is comprised of four tocopherols and four tocotrienols, and functions as a lipophilic chain-breaking antioxidant that prevents lipid peroxidation. Although it is well recognized that cigarette smoke is source of oxidative stress, relatively little is known regarding how oxidative stress alters vitamin E utilization in humans. Therefore, this review will highlight the recent knowledge regarding how cigarette smoking alters vitamin E (as alpha- and gamma-tocopherols) utilization in humans. Specifically, we will discuss the mechanisms by which cigarette smoking increases the turnover of plasma vitamin E, decreases the P450-mediated metabolism of vitamin E, and increases the nitration of gamma-tocopherol to result in the formation of 5-nitro-gamma-tocopherol. In addition, the interrelationship between oxidative stress and vitamin C will also be emphasized as it relates to vitamin E utilization.

Cigarette smokers differ in their handling of natural (RRR) and synthetic (all rac) alpha-tocopherol: a biokinetic study in apoE4 male subjects

We have compared the biokinetics of deuterated natural (RRR) and synthetic (all rac) alpha-tocopherol in male apoE4-carrying smokers and nonsmokers. In a randomized, crossover study subjects underwent two 4-week treatments (400 mg/day) with undeuterated RRR- and all rac-alpha-tocopheryl acetate around a 12-week washout. Before and after each supplementation period subjects underwent a biokinetic protocol (48 h) with 150 mg deuterated RRR- or all rac-alpha-tocopheryl acetate. During the biokinetic protocols, the elimination of endogenous plasma alpha-tocopherol was significantly faster in smokers (P < 0.05). However, smokers had a lower uptake of deuterated RRR than nonsmokers, but there was no difference in uptake of deuterated all rac. The supplementation regimes significantly raised plasma alpha-tocopherol (P < 0.001) with no differences in response between smokers and nonsmokers or between alpha-tocopherol forms. Smokers had significantly lower excretion of alpha-carboxyethyl-hydroxychroman than nonsmokers following supplementation (P < 0.05). Nonsmokers excreted more alpha-carboxyethyl-hydroxychroman following RRR than all rac; however, smokers did not differ in excretion between forms. At baseline, smokers had significantly lower ascorbate (P < 0.01) and higher F(2)-isoprostanes (P < 0.05). F(2)-isoprostanes in smokers remained unchanged during the study, but increased in nonsmokers following alpha-tocopherol supplementation. These data suggest that apoE4-carrying smokers and nonsmokers differ in their handling of natural and synthetic alpha-tocopherol.

Noncompetitive plasma biokinetics of deuterium-labeled natural and synthetic alpha-tocopherol in healthy men with an apoE4 genotype

Previous studies comparing the biokinetics of deuterated natural (RRR) and synthetic (all-rac) alpha-tocopherol (vitamin E) used a simultaneous ingestion or competitive uptake approach and reported relative bioavailability ratios close to 2:1, higher than the accepted biopotency ratio of 1.36:1. The aim of the current study was to compare the biokinetics of deuterated natural and synthetic vitamin E using a noncompetitive uptake model both before and after vitamin E supplementation in a distinct population. Healthy men (n = 10) carrying the apolipoprotein (apo)E4 genotype completed a randomized crossover study, comprised of two 4-wk treatments with 400 mg/d (RRR-alpha-tocopheryl and all-rac-alpha-tocopheryl acetate) with a 12-wk washout period between treatments. Before and after each treatment period, the subjects consumed a capsule containing 150 mg deuterated alpha-tocopheryl acetate in either the RRR or all-rac form depending on their treatment regimen. Blood was obtained up to 48 h after ingestion, and tocopherols analyzed by LC/MS. After deuterated all-rac administration, plasma deuterated tocopherol maximum concentrations and area under the concentration vs. time curves (AUC) were lower than those following RRR administration. The RRR:all-rac ratios determined from the deuterated biokinetic profiles (maximum concentration; C(max)) and AUCs were 1.35:1 +/- 0.17 and 1.33:1 +/- 0.18, respectively. The 4-wk supplementation with either RRR or all-rac significantly increased plasma alpha-tocopherol concentrations (P < 0.001), but decreased the plasma response to newly absorbed deuterated RRR or all-rac alpha-tocopherol. Using a noncompetitive uptake approach, the relative bioavailability of natural to synthetic vitamin E in apoE4 males was close to the currently accepted biopotency ratio of 1.36:1.

Vitamin E bioavailability in humans

It is important to understand factors that can influence vitamin E bioavailability, particularly in populations with increased risk of coronary heart disease such as cigarette smokers. There is also a need to clarify the bioavailability of natural and synthetic vitamin E, which is currently a subject of some controversy. Previous studies using a competitive uptake approach have found bioavailability ratios of natural:synthetic vitamin E close to 2:1, differing from the accepted biopotency ratio of 1.36:1. We used a non-competitive uptake approach to compare the plasma biokinetics of deuterated natural (RRR) and synthetic (all rac) alpha-tocopheryl acetate in smokers and non-smokers. The study was comprised of two 4-week treatments with 400 mg/d (either RRR-alpha-tocopheryl or all rac-alpha-tocopheryl acetates), with a 12-week washout period between. Prior to and after each treatment subjects underwent a 48 h biokinetic protocol with 150 mg deuterated alpha-tocopheryl acetate in either the RRR or all rac form. Smokers had a lower deuterated alpha-tocopherol AUC than did non-smokers following administration of RRR, but there was no difference following administration of all rac. The ratio RRR:all rac from AUCs and C(max) was 1.3:1 in non-smokers and 0.9:1 in smokers. Following vitamin E supplementation, deuterated tocopherol AUCs were lower in both groups. These data suggest that non-smokers and smokers differ in their handling of vitamin E, that the relative bioavailability of natural and synthetic vitamin E is close to the currently accepted biopotency ratio of 1.36:1, and that following supplementation the ability of the plasma to take up newly absorbed vitamin E is decreased.

Cigarette smoking increases human vitamin E requirements as estimated by plasma deuterium-labeled CEHC

Cigarette smoking (CS) is a well-described oxidant burden in humans. We hypothesized that CS would accelerate alpha-tocopherol (alpha-T) utilization leaving less for metabolite (CEHC) production. After labeled alpha-T consumption (75 mg each of d(3)-RRR-alpha-TAc and d(6)-all-rac-alpha-TAc) by smokers and nonsmokers (n = 10/group), CS increased alpha-T disappearance and decreased plasma and urinary CEHCs. Plasma d(3)/d(6)-alpha-T ratios were approximately 1.4 during supplementation and approximately 2 from days 5 to 17. d(3)/d(6)-alpha-CEHC ratios were on average 0.29 +/- 0.05, confirming that all-rac-alpha-tocopherol is metabolized more efficiently. CEHC may be a good marker of vitamin E status, and smokers may have an increased vitamin E requirement.

Neurodegenerative memory disorders: a potential role of environmental toxins

The hypothesis that neurotoxins may play a role in neurodegenerative disorders remains an elusive one, given that epidemiologic studies often provide conflicting results. Although these conflicting results may result from methodological differences within and between studies, the complexity of chemical disruption of the central nervous system cannot be ignored in attempts to evaluate this hypothesis in different neurodegenerative disorders. Spencer provides a detailed review of the complex processes involved in defining the neurotoxic potential of naturally occurring and synthetic agents. Even concepts such as exposure and dose, as often reported in studies attempting to evaluate the risk imparted by a potential compound, can be deceptive. For example, although dose reflects "that amount of chemical transferred to the exposed subject", factors such as time and concentration in the organism, the ability to access the central nervous system, and how a compound reaches the central nervous system (routes of administration) or secondarily affects other organ systems leading to central nervous system disruption are clearly important to the concept of neurotoxic risk in neurodegenerative disorders. These factors would appear to explain the observed disagreements between studies using animal or neuronal models of neurotoxicity and population-based studies in humans. The importance of these factors and how a potential neurotoxin is investigated are clearly seen in the data on AD and aluminum. In contrast, the impact of MTPT on the central nervous system is more direct and compelling. Added complexity in the study of neurotoxins in human neurodegeneration is derived from data showing that agents may have additive, potentiating, synergistic, or antagonistic effects. Therefore, data from studies evaluating EMF risks could be readily confounded by the presence or absence of heavy metals (eg, arc welding). Other factors that may conceal neurotoxic causes for a given disorder focus on additional features such as genetic predispositions, physiologic changes that occur in aging, and even nutritional status that can support or hinder the affect of a given agent on the central nervous system. Finally, many studies that investigate exposure risk do not readily incorporate the five criteria proposed by Schaumburg for establishing causation. For example, if we apply Schaumburg's first criterion, epidemiologic studies often determines the presence of an agent through history, yet they cannot readily confirm exposure based on environmental or clinical chemical analyses to fulfill this criterion for causation. Additional limitations in research design along with the populations and methods that are sued to study neurotoxins in human neurodegenerative disorders often fail to meet other criteria such as linking the severity and onset with duration and exposure level. Therefore, although studies of agents such as MTPT provide compelling models of neurotoxins and neurodegeneration in humans, disorders such as ALS, PD, and particularly AD will require additional effort if research is to determine the contribution (presence or absence) of neurotoxins to these neurologic disorders.

Lower plasma alpha-carboxyethyl-hydroxychroman after deuterium-labeled alpha-tocopherol supplementation suggests decreased vitamin E metabolism in smokers

BACKGROUND

Cigarette smoking increases the fractional disappearance rates of alpha-tocopherol and is associated with increased oxidative stress, but its effects on alpha-tocopherol metabolism are unknown.

OBJECTIVE

We hypothesized that smokers would have less alpha-tocopherol available and consequently lower plasma alpha-carboxyethyl-hydroxychroman (alpha-CEHC), the alpha-tocopherol metabolite produced by a cytochrome P450-mediated process.

DESIGN

Smokers and nonsmokers (n = 10 per group) were supplemented with deuterium-labeled alpha-tocopheryl acetates (75 mg each d3-RRR-alpha-tocopheryl and d6-all-rac-alpha-tocopheryl acetate) from day -6 to day -1, and plasma tocopherols and CEHCs were measured (day -6 through day 17).

RESULTS

After 6 d of supplementation, plasma d3- and d6-alpha-tocopherol concentrations did not differ significantly between groups. Plasma d3- and d6-alpha-CEHCs were detectable only from day -5 to day 5. Before supplementation, unlabeled alpha- and gamma-CEHCs were approximately 60% and 40% lower, respectively, in smokers than in nonsmokers (P < or = 0.05). In addition, d0-, d3-, and d6-alpha-CEHC areas under the curves were approximately 50% lower in smokers (P < 0.05), and smokers had lower maximal d3-alpha-CEHC (P = 0.004) and d6-alpha-CEHC (P = 0.0006) concentrations. Notably, 2.9-4.7 times as much alpha-CEHC was produced from all-rac-alpha-tocopherol than from RRR-alpha-tocopherol. During supplementation, smokers had about one-half (P < 0.05) the plasma total, d6-, or d3-alpha-CEHC concentrations that nonsmokers did given similar alpha-tocopherol concentrations.

CONCLUSIONS

Smoking did not increase alpha-tocopherol disappearance through P450-mediated tocopherol metabolism. Therefore, the mechanism of increased alpha-tocopherol disappearance in smokers likely operates through oxidation pathways, which is consistent with alpha-tocopherol's antioxidant function. Consequently, evaluating the molecular mechanism or mechanisms responsible for tocopherol metabolism under conditions of oxidative stress and the mechanisms that regulate alpha-tocopherol status is warranted.

Active smoking and a history of smoking are associated with enhanced prostaglandin F(2alpha), interleukin-6 and F2-isoprostane formation in elderly men

The underlying mechanisms by which smoking induces cardiovascular diseases are largely unknown. The effect of smoking status on the cyclooxygenase (COX)-mediated inflammatory indicator prostaglandin F(2alpha) (PGF(2alpha)) has never been studied. Associations of cytokines and antioxidants and smoking status, have shown conflicting results. Urinary 15-keto-dihydro-PGF(2alpha) (a major metabolite of PGF(2alpha)), serum interleukin-6 (IL-6) and high sensitivity C-reactive protein (hsCRP), serum amyloid protein A (SAA), urinary 8-iso-PGF(2alpha) (an F(2)-isoprostane, indicator of oxidative stress), and serum alpha-tocopherol were quantified in a population-based sample (n = 642) of 77-year old men without diabetes. Fifty-five men were current smokers and 391 former smokers. Inflammatory indicators were increased in current smokers (15-keto-dihydro-PGF(2alpha), P < 0.001; IL-6, P = 0.01) than non-smokers. 8-iso-PGF(2alpha) was increased (P < 0.01) and alpha-tocopherol reduced (P < 0.001) in current smokers. Further, former smokers had increased formation of 15-keto-dihydro-PGF(2alpha), IL-6 and 8-iso-PGF(2alpha) compared non-smokers. This is the first study to show that smokers have increased PGF(2alpha) formation, thus enhanced COX-mediated inflammation, in addition to elevated levels of cytokines and isoprostanes. Subclinical COX- and cytokine-mediated inflammation and oxidative stress are ongoing processes not only in active smokers but also in former smokers which may contribute to the accelerated atherosclerosis associated with smoking.

Cigarette smoke alters human vitamin E requirements

Vitamin E is a lipophilic chain-breaking antioxidant that prevents lipid peroxidation. Although cigarette smoke is a potent source of oxidative stress that depletes vitamin E in vitro, it is unclear whether it has a similar effect in vivo, particularly in humans. Therefore, this review will discuss the role of cigarette smoke on gamma-tocopherol (gamma-T) nitration, its effect on alpha-tocopherol (alpha-T) biokinetics in smokers, and the changes in the synthesis, plasma concentrations, and urinary excretion of the vitamin E metabolite (CEHC; carboxy-ethyl-hydroxy-chroman). Last, the possibility of CEHC as a biomarker of vitamin E status will be assessed as will the question whether smokers have increased dietary requirements of vitamin E.

Cigarette smokers have decreased lymphocyte and platelet alpha-tocopherol levels and increased excretion of the gamma-tocopherol metabolite gamma-carboxyethyl-hydroxychroman (gamma-CEHC)

Cigarette smoking is associated with increased oxidative stress and increased risk of degenerative disease. As the major lipophilic antioxidant, requirements for vitamin E may be higher in smokers due to increased utilisation. In this observational study we have compared vitamin E status in smokers and non-smokers using a holistic approach by measuring plasma, erythrocyte, lymphocyte and platelet alpha- and gamma-tocopherol, as well as the specific urinary vitamin E metabolites alpha- and gamma-carboxyethyl-hydroxychroman (CEHC). Fifteen smokers (average age 27 years, smoking time 7.5 years) and non-smokers of comparable age, gender and body mass index (BMI) were recruited. Subjects completed a 7-day food diary and on the final day they provided a 24 h urine collection and a 20 ml blood sample for measurement of urinary vitamin E metabolites and total vitamin E in blood components, respectively. No significant differences were found between plasma and erythrocyte alpha- and gamma-tocopherol in smokers and non-smokers. However, smokers had significantly lower alpha-tocopherol (mean+/-SD, 1.34+/-0.31 micromol/g protein compared with 1.94+/-0.54, P = 0.001) and gamma-tocopherol (0.19+/-0.04 micromol/g protein compared with 0.26+/-0.08, P = 0.026) levels in their lymphocytes, as well as significantly lower alpha-tocopherol levels in platelets (1.09+/-0.49 micromol/g protein compared with 1.60+/-0.55, P = 0.014; gamma-tocopherol levels were similar). Interestingly smokers also had significantly higher excretion of the urinary gamma-tocopherol metabolite, gamma-CEHC (0.49+/-0.25mg/g creatinine compared with 0.32+/-0.16, P = 0.036) compared to non-smokers, while their alpha-CEHC (metabolite of alpha-tocopherol) levels were similar. There was no significant difference between plasma ascorbate, urate and F2-isoprostane levels. Therefore in this population of cigarette smokers (mean age 27 years, mean smoking duration 7.5 years), alterations to vitamin E status can be observed even without the more characteristic changes to ascorbate and F2-isoprostanes. We suggest that the measurement of lymphocyte and platelet vitamin E may represent a valuable biomarker of vitamin E status in relation to oxidative stress conditions.

Correlation of in vitro chemopreventive efficacy data from the human epidermal cell assay with animal efficacy data and clinical trial plasma levels

The human epidermal cell (HEC) assay, which uses carcinogen exposed normal skin keratinocytes to screen for cancer prevention efficacy, was used to screen possible preventive agents. The endpoints measured were inhibition of carcinogen-induced growth and induction of involucrin, an early marker of differentiation. Sixteen of twenty agents (apigenin, apomine, budesonide, N-(2-carboxyphenyl)retinamide, ellagic acid, ibuprofen, indomethacin, melatonin, (-)-2-oxo-4-thiazolidine carboxylic acid, polyphenon E, resveratrol, beta-sitosterol, sulfasalazine, vitamin E acetate, and zileuton) were positive in at least one of the two assay endpoints. Four agents (4-methoxyphenol, naringenin, palmitoylcarnitine chloride, and silymarin) were negative in the assay. Nine of the sixteen agents were positive for both endpoints. Agents that showed the greatest response included: ellagic acid > budesonide, ibuprofen > apigenin, and quinicrine dihydrochloride. Fifty-eight of sixty-five agents that have been evaluated in the HEC assay have also been evaluated in one or more rodent bioassays for cancer prevention and several are in clinical trials for cancer prevention. The assay has an overall predictive accuracy of approximately 91.4% for efficacy in rodent cancer prevention irrespective of the species used, the tissue model, or the carcinogen used. Comparison of the efficacious concentrations in vitro to plasma levels in clinical trials show that concentrations that produced efficacy in the HEC assay were achieved in clinical studies for 31 of 33 agents for which plasma levels and/or C(max) levels were available. For two agents, 9-cis-retinoic acid (RA) and dehydroepiandrosterone (DHEA), the plasma levels greatly exceeded the highest concentration (HC) found to have efficacy in vitro. Thus, the HEC assay has an excellent predictive potential for animal efficacy and is responsive at clinically achievable concentrations.

{alpha}-Tocopherol disappearance is faster in cigarette smokers and is inversely related to their ascorbic acid status

BACKGROUND

Cigarette smokers have enhanced oxidative stress from cigarette smoke exposure and from their increased inflammatory responses.

OBJECTIVE

The objective of this study was to determine whether cigarette smoking increases plasma alpha-tocopherol disappearance in otherwise healthy humans.

DESIGN

Smokers and nonsmokers (n = 10/group) were supplemented with deuterium-labeled alpha-tocopheryl acetates (75 mg each of d(3)-RRR-alpha-tocopheryl acetate and d(6)-all-rac-alpha-tocopherols acetate) for 6 evenings (days -6 to -1). Plasma alpha-tocopherols, ascorbic acid, uric acid, and F(2alpha)-isoprostanes were measured in blood samples collected on days -6 through 17. The urinary alpha-tocopherol metabolite, alpha-carboxy-ethyl-hydroxy-chroman (alpha-CEHC), was measured on days -6, 0, and 17 in 24-h urine samples.

RESULTS

F(2alpha)-isoprostanes were, on average, approximately 40% higher in smokers than in nonsmokers. On day 0, plasma labeled and unlabeled alpha-tocopherol concentrations were not significantly different between groups. Smoking resulted in faster fractional disappearance of plasma alpha-tocopherol (0.215 +/- 0.011 compared with 0.191 +/- 0.009 pools/d; P < 0.05). Fractional disappearance rates of alpha-tocopherol correlated with plasma ascorbic acid concentrations in smokers (P = 0.021) but not in nonsmokers despite plasma ascorbic acid concentrations that were not significantly different between groups. By day 17, cigarette smoking resulted in lower plasma alpha-tocopherol concentrations and urinary excretion of labeled and unlabeled alpha-CEHC (P < 0.05).

CONCLUSIONS

Cigarette smoking increased alpha-tocopherol disappearance. Greater rates of alpha-tocopherol disappearance in smokers appear to be related to increased oxidative stress accompanied by lower plasma ascorbic acid concentrations. Thus, smokers have an increased requirement for both alpha-tocopherol and ascorbic acid.

The Effect of Age on Vitamin E Status, Metabolism, and Function: Metabolism as Assessed by Labeled Tocopherols

The effects of age on vitamin E metabolism were studied in 97 healthy 20-75-year-old male nonsmoking Austrian volunteers of the VITAGE project. After a single oral intake of 30 mg d(6)-RRR-alpha- and d(2)-RRR-gamma-tocopheryl acetate, blood and 24-hour urine was collected. Deuterated tocopherols in plasma and deuterated urinary metabolites were analyzed by GC-MS. A first evaluation revealed a similar uptake of d(6)-alpha- and d(2)-gamma-tocopherol during the first 6 hours, and then d(2)-gamma-tocopherol started to decrease. Urinary d(2)-gamma- carboxyethyl hydroxychroman metabolites (CEHCs) exceeded those of d(6)-alpha-CEHCs by about 10 times. There was no effect of age. Thus, there might be no need for a higher vitamin E intake for healthy elderly nonsmoking men.

Vitamin E levels, cognitive impairment and dementia in older persons: the InCHIANTI study

There is conflicting evidence that antioxidants contribute to maintaining cognitive function in elderly subjects. We investigated whether vitamin E plasma levels are related to the presence of dementia and cognitive impairment in a population-based cohort study conducted in Italy. A total of 1033 participants aged at least 65 years received clinical and neuropsychological examinations, donated blood for vitamin E analysis and had their diets assessed. Participants with plasma vitamin E levels in the bottom tertile had a significantly higher probability of being demented (OR 2.6, 95% CI 1.0-7.1) and also of suffering from cognitive impairment (OR 2.2, 95% CI 1.2-4.2) compared to those in the highest vitamin E tertile after adjustment for age, gender, education, lipid levels, energy intake, vitamin E intake, and smoking. This study supports the notion that higher vitamin E plasma levels might provide significant protection against cognitive impairment and dementia in elderly subjects.

Effect of cigarette smoking on serum α-tocopherol and the lipid profile in a Portuguese population

BACKGROUND

The present study was conducted to determine the effects of cigarette smoking on the levels of serum alpha-tocopherol and on the lipid profile in humans from the Lisbon population.

METHODS

Serum alpha-tocopherol was evaluated by a reverse-phase HPLC method with UV detection. Enzymatic tests were used for the evaluation of the lipid profile.

RESULTS

Smokers in general and female smokers in particular had decreased alpha-tocopherol levels when compared with nonsmokers. Smokers had also lower HDL cholesterol (HDL-C) contents, but this difference was statistically significant only for females. Regardless of sex, in smokers, there was a positive correlation between alpha-tocopherol and triglyceride (TG) levels. Cluster analysis showed a sex-independent separation between smokers and nonsmokers.

CONCLUSION

These results suggest a different interaction of these blood parameters in smokers versus nonsmokers that should be further investigated.

The effects of tobacco smoke on plasma alpha- and gamma-tocopherol levels in passive and active cigarette smokers

Tobacco smoke is one of the causes of oxidative stress that is leading to attenuation of the antioxidative body protective barrier by means of decreasing the levels of intra- and extracellular antioxidants. The effect of tobacco smoke on plasma levels of two main forms of Vitamin E, alpha- and gamma-tocopherol, in passive smokers (urinary cotinine concentration 50-500 microg/L) and active smokers (urinary cotinine concentration >500 microg/L) were studied. Slight, but statistically significant decreases in plasma alpha-tocopherol level in passive and active smokers in comparison with non-smokers (by 5.7% and 9.2%, respectively) were found. The plasma gamma-tocopherol levels remained unchanged. The Pearson's correlation coefficient for the plasma alpha-tocopherol level and the urinary cotinine concentration in passive and active smokers was -0.431, P = 0.004 and -0.534, P < 0.001, respectively, and for gamma-tocopherol in similar conditions -0.190, P = 0.217 and 0.346, P = 0.027, respectively. The obtained results indicate the secondary role that alpha- and gamma-tocopherol play in the process of tobacco smoke free radical scavenge, or they may also reflect the body increased anti-oxidative mobilization in response to oxidative stress evoked by tobacco smoke.

Re-evaluation of the relative potency of synthetic and natural α-tocopherol: experimental and clinical observations

Nutritionists generally consider all-rac-alpha-tocopherol and RRR-alpha-tocopherol equivalent in vitamin E activity but disagree whether equivalency requires a dosage ratio of 1.36:1 or 2:1. In contrast, we hypothesize that all-rac- and RRR-alpha-tocopherols are not equivalent in any dosage ratio. Previous observations that all-rac- and RRR-alpha-tocopherols are distributed and eliminated via saturable and stereospecific pathways imply that their relative bioavailability varies with the saturation of these pathways and therefore varies with dosage. Indeed, previous studies observed that the relative bioavailability of all-rac- and RRR-alpha-tocopherols varies between tissues as well as with dose, time after dosing, and duration of dosing. This non-constant relative bioavailability predicts non-constant relative activity (i.e., non-parallel dose-concentration curves predict non-parallel dose-effect curves). Non-constant relative bioavailability suggests that a fixed dosage ratio of all-rac- and RRR-alpha-tocopherols cannot produce a fixed ratio of effects on all processes in all tissues at all times after all dosages. However, previous studies suggest that all-rac- and RRR-alpha-tocopherols have equivalent effects (parallel dose-effect curves) in vitamin E-deficient animals and non-vitamin E-deficient humans. We re-evaluate the data from these animal studies and find non-parallel dose-effect and concentration-effect curves. We discuss pharmacokinetic and pharmacodynamic reasons why previous studies in non-vitamin E-deficient humans did not find non-parallel dose-effect curves for all-rac- and RRR-alpha-tocopherols. We note that saturable elimination predicts that all-rac- and RRR-alpha-tocopherols might inhibit and/or induce elimination of other compounds (including 30-40% of prescription drugs) eliminated via the same saturable pathways, and stereospecific elimination predicts that all-rac- and RRR-alpha-tocopherol have non-parallel dose-effect curves for these interactions.

Vitamin E bioavailability from fortified breakfast cereal is greater than that from encapsulated supplements

BACKGROUND

Conflicting results from vitamin E intervention studies suggest supplemental vitamin E malabsorption.

OBJECTIVE

We compared vitamin E bioavailability from a supplement with that from a fortified breakfast cereal.

DESIGN

Vitamin E bioavailability was evaluated by using deuterium-labeled all-rac-alpha-tocopherol in three 4-d trials (2 wk apart). Five fasting subjects sequentially consumed the following (with 236 mL fat-free milk): 400 IU d(9)-alpha-tocopheryl acetate (400-IU capsule), 41 g ready-to-eat wheat cereal containing 30 IU d(9)-alpha-tocopheryl acetate (30-IU cereal), and 45 g cereal containing 400 IU d(9)-alpha-tocopheryl acetate (400-IU cereal). Five months later (trial 4), they consumed a 400-IU capsule with 41 g vitamin E-free cereal. Blood was obtained up to 72 h after the start of each trial.

RESULTS

The mean (+/-SD) vitamin E bioavailabilities of the 30-IU cereal and the 400-IU cereal were 6 +/- 2 and 26 +/- 8 times, respectively, the vitamin E bioavailability of the 400-IU capsule. The areas under the 0-72-h d(9)-alpha-tocopherol curves for the 400-IU capsule, the 30-IU cereal, and the 400-IU cereal were 30 +/- 7, 153 +/- 43, and 765 +/- 164 micro mol. h/L (all trial comparisons, P < 0.0001). In trial 4, 3 subjects barely responded and 2 subjects had areas under the curve that were similar to their 400-IU cereal responses.

CONCLUSION

The low bioavailability of vitamin E from the 400-IU capsule and the variability observed when the capsule was consumed with cereal suggest that encapsulated vitamin E is poorly absorbed when consumed with a low-fat meal and that bioavailability can be enhanced by food fortification with vitamin E.

Oxidative stress and smoking-induced vascular injury

The relative importance of mechanisms relevant to smoking-induced vascular injury is poorly understood. Cigarette smoke is a source of free radicals but also results in cellular activation and consequent generation of free radicals in vivo. Here we consider several approaches to estimating the consequences of free radical generation in vivo, using measurements of modified lipids, proteins, and DNA. Smoking appears to result in elevation of several biomarkers of oxidant stress, some in a dose-related fashion. There is also some evidence that disordered endothelial function in smokers may be partly attributable to oxidant stress. Other effects of smoking on hemostatic activation, sympathoadrenal function, and lipoprotein structure and function may also be modulated by smoking-induced oxidant stress. The emergence and application of rational quantitatively reliable indexes of oxidant stress in vivo is likely to elucidate the relative contribution of oxidant stress to smoking-induced vascular injury.

Preterm premature rupture of the membranes and antioxidants: the free radical connection

AIM

To discuss the role of oxidant stress in preterm, premature rupture of the membranes (PPROM).

RESULTS

There is evidence to suggest that preterm, premature rupture of the membranes occurs secondary to focal collagen damage in the fetal membranes.

CONCLUSION

Oxidant stress caused by increased ROS formation and/or antioxidant depletion may disrupt collagen and cause premature membrane rupture. We propose that supplementation with vitamins C and E may synergistically protect the fetal membranes, and decrease the risks of PPROM.

Effect of vitamin E on glutathione-dependent enzymes

Reactive oxygen species and various electrophiles are involved in the etiology of diseases varying from cancer to cardiovascular and pulmonary disorders. The human body is protected against damaging effects of these compounds by a wide variety of systems. An important line of defense is formed by antioxidants. Vitamin E (consisting of various forms of tocopherols and tocotrienols) is an important fat-soluble, chain-breaking antioxidant. Besides working as an antioxidant, this compound possesses other functions with possible physiological relevance. The glutathione-dependent enzymes form another line of defense. Two important enzymes in this class are the free radical reductase and glutathione S-transferases (GSTs). The GSTs are a family of phase II detoxification enzymes. They can catalyze glutathione conjugation with various electrophiles. In most cases the electrophiles are detoxified by this conjugation, but in some cases the electrophiles are activated. Antioxidants do not act in isolation but form an intricate network. It is, for instance, known that vitamin E, together with glutathione (GSH) and a membrane-bound heat labile GSH-dependent factor, presumably an enzyme, can prevent damaging effects of reactive oxygen species on polyunsaturated fatty acids in biomembranes (lipid peroxidation). This manuscript reviews the interaction between the two defense systems, vitamin E and glutathione-dependent enzymes. On the simplest level, antioxidants such as vitamin E have protective effects on glutathione-dependent enzymes; however, we will see that reality is somewhat more complicated.

Development of a liquid chromatographic time-of-flight mass spectrometric method for the determination of unlabelled and deuterium-labelled alpha-tocopherol in blood components

A method is described for the analysis of deuterated and undeuterated alpha-tocopherol in blood components using liquid chromatography coupled to an orthogonal acceleration time-of-flight (TOF) mass spectrometer. Optimal ionisation conditions for undeuterated (d0) and tri- and hexadeuterated (d3 or d6) alpha-tocopherol standards were found with negative ion mode electrospray ionisation. Each species produced an isotopically resolved single ion of exact mass. Calibration curves of pure standards were linear in the range tested (0-1.5 microM, 0-15 pmol injected). For quantification of d0 and d6 in blood components following a standard solvent extraction, a stable-isotope-labelled internal standard (d3-alpha-tocopherol) was employed. To counter matrix ion suppression effects, standard response curves were generated following identical solvent extraction procedures to those of the samples. Within-day and between-day precision were determined for quantification of d0- and d6-labelled alpha-tocopherol in each blood component and both averaged 3-10%. Accuracy was assessed by comparison with a standard high-performance liquid chromatography (HPLC) method, achieving good correlation (r(2) = 0.94), and by spiking with known concentrations of alpha-tocopherol (98% accuracy). Limits of detection and quantification were determined to be 5 and 50 fmol injected, respectively. The assay was used to measure the appearance and disappearance of deuterium-labelled alpha-tocopherol in human blood components following deuterium-labelled (d6) RRR-alpha-tocopheryl acetate ingestion. The new LC/TOFMS method was found to be sensitive, required small sample volumes, was reproducible and robust, and was capable of high throughput when large numbers of samples were generated.

The influence of cigarette smoking on circulating concentrations of antioxidant micronutrients

Cigarette smoke is a significant source of oxidative stress, one potential mechanism for its untoward health effects. The antioxidant defense system is partly comprised of antioxidant micronutrients, making it important to understand the relationship between cigarette smoking and circulating concentrations of antioxidant micronutrients. A synthesis of the literature shows that compared with nonsmokers, on average, active smokers have greater than 25% lower circulating concentrations of ascorbic acid, alpha-carotene, beta-carotene, and cryptoxanthin. The differences in blood concentrations of these micronutrients in former smokers is intermediate between never and current smokers, but average circulating concentrations of alpha-carotene, beta-carotene, and cryptoxanthin were 16-22% lower in former smokers compared with never smokers. Differences in dietary habits between smokers and nonsmokers could potentially account for these associations. Dietary micronutrient intake is associated with blood micronutrient concentrations. Furthermore, patterns of micronutrient consumption by smoking status mimic the pattern of associations observed for blood concentrations. For example, when pooled across studies intake of vitamin C was 16% lower in current smokers and 2% lower in former smokers than in never smokers; the corresponding figures for beta-carotene were 17 and 4%, respectively. Despite the strong potential for confounding, the differences observed between current smokers and nonsmokers seem to be due to an acute effect of smoking based on results of studies of smoking and antioxidant micronutrient concentrations that have either adjusted for dietary antioxidant micronutrient intake and other potential confounding factors or documented short term changes in circulating antioxidant micronutrient concentrations in smokers before and after smoking cigarettes. The associations observed with active smoking also appear to hold true for passive smoking, implying that even low-dose exposures to tobacco smoke can result in lowered circulating antioxidant micronutrient concentrations. Smoking was more weakly associated with circulating concentrations of vitamin E and the nonprovitamin A carotenoids lutein/zeaxanthin and lycopene. The combined evidence supports the conclusion that cigarette smoking is independently associated with lowered circulating concentrations of ascorbic acid and provitamin A carotenoids. These associations have implications for the design and interpretation of epidemiologic studies of antioxidant micronutrients in relation to health and disease. To the extent that these micronutrients are associated with health and longevity, this evidence documents yet another deleterious consequence of cigarette smoking on human health.