Bioavailability of vitamin E as function of food intake in healthy subjects: effects on plasma peroxide-scavenging activity and cholesterol-oxidation products

Key Nutrients for Optimal Blood Glucose Control and Mental Health in Individuals with Diabetes: A Review of the Evidence

Diabetes is associated with an increased risk of mental disorders, including depression, anxiety, and cognitive decline. Mental disorders can also contribute to the development of diabetes through various mechanisms including increased stress, poor self-care behaviors, and adverse effects on glucose metabolism. Consequently, individuals suffering from either of these conditions frequently experience comorbidity with the other. Nutrition plays an important role in both diabetes and mental health disorders including depression and anxiety. Deficiencies in specific nutrients such as omega-3 fatty acids, vitamin D, B vitamins, zinc, chromium, magnesium, and selenium have been implicated in the pathogenesis of both diabetes and mental disorders. While the impact of nutrition on the progression and control of diabetes and mental disorders is broadly acknowledged, there is a notable knowledge gap concerning the implications of distinct nutrients in preventing and mitigating symptoms of both conditions when they coexist. The aim of this study was to examine the role of nutrition in improving glucose homeostasis and promoting mental well-being among individuals with diabetes. Further, we evaluated the preventive or delaying effects of key nutrients on the simultaneous manifestation of these conditions when one of them is present. Our findings indicated that the use of personalized dietary interventions and targeted nutrient supplementation can improve metabolic and mental health outcomes in patients with type 2 diabetes.

Dual-responsive doxorubicin-loaded nanomicelles for enhanced cancer therapy

BACKGROUND

The enhancement of tumor retention and cellular uptake of drugs are important factors in maximizing anticancer therapy and minimizing side effects of encapsulated drugs. Herein, a delivery nanoplatform, armed with a pH-triggered charge-reversal capability and self-amplifiable reactive oxygen species (ROS)-induced drug release, is constructed by encapsulating doxorubicin (DOX) in pH/ROS-responsive polymeric micelle.

RESULTS

The surface charge of this system was converted from negative to positive from pH 7.4 to pH 6.8, which facilitated the cellular uptake. In addition, methionine-based system was dissociated in a ROS-rich and acidic intracellular environment, resulting in the release of DOX and α-tocopheryl succinate (TOS). Then, the exposed TOS segments further induced the generation of ROS, leading to self-amplifiable disassembly of the micelles and drug release.

CONCLUSIONS

We confirms efficient DOX delivery into cancer cells, upregulation of tumoral ROS level and induction of the apoptotic capability in vitro. The system exhibits outstanding tumor inhibition capability in vivo, indicating that dual stimuli nano-system has great potential to function as an anticancer drug delivery platform.

Atherothrombosis and Oxidative Stress: Mechanisms and Management in Elderly

SIGNIFICANCE

The incidence of cardiovascular events (CVEs) increases with age, representing the main cause of death in an elderly population. Aging is associated with overproduction of reactive oxygen species (ROS), which may affect clotting and platelet activation, and impair endothelial function, thus predisposing elderly patients to thrombotic complications. Recent Advances: There is increasing evidence to suggest that aging is associated with an imbalance between oxidative stress and antioxidant status. Thus, upregulation of ROS-producing enzymes such as nicotinamide adenine dinucleotide phosphate (NADPH) oxidase and myeloperoxidase, along with downregulation of antioxidant enzymes, such as superoxide dismutase and glutathione peroxidase, occurs during aging. This imbalance may predispose to thrombosis by enhancing platelet and clotting activation and eliciting endothelial dysfunction. Recently, gut-derived products, such as trimethylamine N-oxide (TMAO) and lipopolysaccharide, are emerging as novel atherosclerotic risk factors, and gut microbiota composition has been shown to change by aging, and may concur with the increased cardiovascular risk in the elderly.

CRITICAL ISSUES

Antioxidant treatment is ineffective in patients at risk or with cardiovascular disease. Further, anti-thrombotic treatment seems to work less in the elderly population.

FUTURE DIRECTIONS

Interventional trials with antioxidants targeting enzymes implicated in aging-related atherothrombosis are warranted to explore whether modulation of redox status is effective in lowering CVEs in the elderly. Antioxid. Redox Signal. 27, 1083-1124.

Low-density lipoprotein oxidation biomarkers in human health and disease and effects of bioactive compounds

Based on the significance of oxidized low-density lipoprotein (LDL) in health and disease, this review focuses on human studies addressing oxidation of LDL, including three lines of biomarkers, (i) ex vivo LDL resistance to oxidation, a "challenge test" model, (ii) circulating oxidized LDL, indicating the "current in vivo status", and (iii) autoantibodies against oxidized LDL as fingerprints of an immune response to oxidized LDL, along with circulating oxysterols and 4-hydroxynonenal as biomarkers of lipid peroxidation. Lipid peroxidation and oxidized LDL are hallmarks in the development of various metabolic, cardiovascular and other diseases. Changes further occur across life stages from infancy to older age as well as in athletes and smokers. Given their responsiveness to targeted nutritional interventions, markers of LDL oxidation have been employed in a rapidly growing number of human studies for more than 2 decades. There is growing interest in foods, which, besides providing energy and nutrients, exert beneficial effects on human health, such as protection of DNA, proteins and lipids from oxidative damage. Any health claim, however, needs to be substantiated by supportive evidence derived from human studies, using reliable biomarkers to demonstrate such beneficial effects. A large body of evidence has accumulated, demonstrating protection of LDL from oxidation by bioactive food compounds, including vitamins, other micronutrients and secondary plant ingredients, which will facilitate the selection of oxidation biomarkers for future human intervention studies and health claim support.

Role of dietary bioactive natural products in estrogen receptor-positive breast cancer

Estrogen receptor (ER)-positive breast cancer, including luminal-A and -B, is the most common type of breast cancer. Extended exposure to estrogen is associated with an increased risk of breast cancer. Both ER-dependent and ER-independent mechanisms have been implicated in estrogen-mediated carcinogenesis. The ER-dependent pathway involves cell growth and proliferation triggered by the binding of estrogen to the ER. The ER-independent mechanisms depend on the metabolism of estrogen to generate genotoxic metabolites, free radicals and reactive oxygen species to induce breast cancer. A better understanding of the mechanisms that drive ER-positive breast cancer will help optimize targeted approaches to prevent or treat breast cancer. A growing emphasis is being placed on alternative medicine and dietary approaches toward the prevention and treatment of breast cancer. Many natural products and bioactive compounds found in foods have been shown to inhibit breast carcinogenesis via inhibition of estrogen induced oxidative stress as well as ER signaling. This review summarizes the role of bioactive natural products that are involved in the prevention and treatment of estrogen-related and ER-positive breast cancer.

γ-Tocopherol-rich supplementation additively improves vascular endothelial function during smoking cessation

Oxidative stress and inflammation persist years after smoking cessation thereby limiting the restoration of vascular endothelial function (VEF). Although short-term smoking cessation improves VEF, no studies have examined co-therapy of antioxidants in combination with smoking cessation to improve VEF. We hypothesized that improvements in γ-tocopherol (γ-T) status during smoking cessation would improve VEF beyond that from smoking cessation alone by decreasing oxidative stress and proinflammatory responses. A randomized, double-blind, placebo-controlled study was conducted in otherwise healthy smokers (22 ± 1 years; mean ± SEM) who quit smoking for 7 days with placebo (n=14) or γ-T-rich supplementation (n=16; 500 mg γ-T/day). Brachial artery flow-mediated dilation (FMD), cotinine, and biomarkers of antioxidant status, oxidative stress, and inflammation were measured before and after 7 days of smoking cessation. Smoking cessation regardless of supplementation similarly decreased plasma cotinine, whereas γ-T-rich supplementation increased plasma γ-T by seven times and its urinary metabolite γ-carboxyethyl hydroxychroman by nine times (P<0.05). Smoking cessation with γ-T-rich supplementation increased FMD responses by 1.3% (P<0.05) beyond smoking cessation alone (4.1 ± 0.6% vs 2.8 ± 0.3%; mean ± SEM). Although plasma malondialdehyde decreased similarly in both groups (P<0.05), plasma oxidized LDL and urinary F2-isoprostanes were unaffected by smoking cessation or γ-T-rich supplementation. Plasma TNF-α and myeloperoxidase decreased (P<0.05) only in those receiving γ-T-rich supplements and these were inversely related to FMD (P<0.05; R=-0.46 and -0.37, respectively). These findings demonstrate that short-term γ-T-rich supplementation in combination with smoking cessation improved VEF beyond that from smoking cessation alone in young smokers, probably by decreasing the proinflammatory mediators TNF-α and myeloperoxidase.

Use of food frequency questionnaire to assess relationships between dietary habits and cardiovascular risk factors in NESCAV study: validation with biomarkers

BACKGROUND

Validation of Food frequency questionnaire (FFQ) is particularly important element, as incorrect information may lead to false associations between dietary factors and diseases. The aim of the study was to evaluate the validity of the FFQ used in NESCAV (Nutrition, Environment and Cardiovascular Health) study, by comparing the estimated intakes of fruits and vegetables and of several micro-nutrients with corresponding nutritional biomarkers.

METHODS

Relative validity was assessed in a sample of 922 subjects (452 men and 470 women). Comparisons between FFQ-estimates and their corresponding biomarkers were performed through correlation and cross classification into quintiles by using both crude and energy-adjusted FFQ-estimates. Correlations adjusted for confounders were also computed. All analyses were performed separately for men and women.

RESULTS

Concerning micro-nutrients, significant correlations were found for vitamin B9, D, E, B12 β-carotene and iodine in both men and women. Energy-adjustment led to an increase of all correlations cited previously. However, after excluding supplement users, correlations for vitamin D were not significant anymore. Concerning fruits and vegetables, all correlations were significant. Vegetables alone and fruits and vegetables correlated better in men (r around 0.2) than in women (r around 0.1). In men, correlation was also better for vegetables alone and fruits and vegetables than fruits alone.

CONCLUSION

These data demonstrate that this FFQ is a reasonable tool to assess intakes of fruits and vegetables and of several micro-nutrients. We conclude that our FFQ is suitable to be used in NESCAV study, although protein and vitamin D estimates should be interpreted with caution.

Vitamin E prevents NRF2 suppression by allergens in asthmatic alveolar macrophages in vivo

Asthma is a chronic inflammatory airway disease associated with increased generation of reactive oxidant species and disturbed antioxidant defenses. NRF2 is the master transcription factor that regulates the expression of Phase II antioxidant and detoxifying enzymes. Disruption of NRF2 augments oxidative stress and inflammation in a mouse model of asthma, suggesting a protective role for NRF2 in the lungs in vivo. Yet, little is known about the regulation and function of NRF2 in human asthmatics. Using segmental allergen challenge, a well-established experimental model of IgE-mediated asthma exacerbation in human atopic asthmatics, we investigated the effects of a specific allergen and the modulatory role of vitamin E on NRF2 and a NRF2-target gene, superoxide dismutase, in alveolar macrophages recovered from the airways at 24h after allergen instillation in vivo. Allergen-provoked airway inflammation in sensitive asthmatics caused a profound inhibition of macrophage NRF2 activity and superoxide dismutase, rendering them incapable of responding to the NRF2 inducers. Prolonged treatment with high doses of the antioxidant vitamin E lessened this allergen-induced drop in alveolar macrophage NRF2. These results are the first to demonstrate that NRF2 expression in human asthmatics is compromised upon allergen challenge but can be rescued by vitamin E in vivo.

Pathways of cholesterol oxidation via non-enzymatic mechanisms

Cholesterol has many functions, including those that affect biophysical properties of membranes, and is a precursor to hormone synthesis. These actions are governed by enzymatic pathways that modify the sterol nucleus or the isooctyl tail. The addition of oxygen to the cholesterol backbone produces its derivatives known as oxysterols. In addition to having an enzymatic origin, oxysterols can be formed in the absence of enzymatic catalysis in a pathway usually termed "autoxidation," which has been known for almost a century and observed under various experimental conditions. Autoxidation of cholesterol can occur through reactions initiated by free radical species, such as those arising from the superoxide/hydrogen peroxide/hydroxyl radical system and by non-radical highly reactive oxygen species such as singlet oxygen, HOCl, and ozone. The susceptibility of cholesterol to non-enzymatic oxidation has raised considerable interest in the function of oxysterols as biological effectors and potential biomarkers for the non-invasive study of oxidative stress in vivo.

Vitamin E and risk of cardiovascular diseases: a review of epidemiologic and clinical trial studies

Cardiovascular diseases are the leading cause of worldwide mortality. There is strong epidemiologic evidence for a beneficial effect of vitamin E on cardiovascular disease risk. However, conflicting results have been reported by intervention studies. To assess the potential benefit of vitamin E intake on the risk of cardiovascular diseases, fifty-nine published reports from observational studies, retrospective and prospective, randomised clinical trials, meta-analyses as well as pooling analyses were reviewed. The paper provides a detailed discussion about design, quality and limitations of these studies with regard to the evidence of the hypothesized relationship between vitamin E and cardiovascular diseases.

Biochemical validation of food frequency questionnaire-estimated carotenoid, alpha-tocopherol, and folate intakes among African Americans and non-Hispanic Whites in the Southern Community Cohort Study

Few food frequency questionnaires (FFQs) have been developed specifically for use among African Americans, and reports of FFQ performance among African Americans or low-income groups assessed using biochemical indicators are scarce. The authors conducted a validation study within the Southern Community Cohort Study to evaluate FFQ-estimated intakes of alpha-carotene, beta-carotene, beta-cryptoxanthin, lutein/zeaxanthin, lycopene, folate, and alpha-tocopherol in relation to blood levels of these nutrients. Included were 255 nonsmoking participants (125 African Americans, 130 non-Hispanic whites) who provided a blood sample at the time of study enrollment and FFQ administration in 2002-2004. Levels of biochemical indicators of each micronutrient (alpha-tocopherol among women only) significantly increased with increasing FFQ-estimated intake (adjusted correlation coefficients: alpha-carotene, 0.35; beta-carotene, 0.28; beta-cryptoxanthin, 0.35; lutein/zeaxanthin, 0.28; lycopene, 0.15; folate, 0.26; alpha-tocopherol, 0.26 among women; all P's < 0.05). Subjects in the top decile of FFQ intake had blood levels that were 27% (lycopene) to 178% (beta-cryptoxanthin) higher than those of subjects in the lowest decile. Satisfactory FFQ performance was noted even for participants with less than a high school education. Some variation was noted in the FFQ's ability to predict blood levels for subgroups defined by race, sex, and other characteristics, but overall the Southern Community Cohort Study FFQ appears to generate useful dietary exposure rankings in the cohort.

Absorption, transport, and bioavailability of vitamin e and its role in pregnant women

Vitamin E is an important lipophilic antioxidant. The term refers to eight essential naturally occurring fat-soluble nutrients called tocopherols or tocotrienols. Among these isomers, alpha-tocopherol has the highest biologically active form and is found in all lipoprotein fractions. Vitamin E deficiency during pregnancy may cause miscarriage, preterm birth, preeclampsia, and intrauterine growth restriction. This review highlights recent findings that have led to a better understanding of vitamin E absorption, transport, bioavailability, and its role in pregnancy, and that underline the need for re-evaluation of the potential benefits of vitamin E supplementation in pregnant women.

The response of gamma vitamin E to varying dosages of alpha vitamin E plus vitamin C

Vitamin E has been studied extensively in the prevention of atherosclerosis. Cross-sectional population studies as well as randomized controlled intervention trials have demonstrated conflicting results. A recent meta-analysis of these trials has emphasized the ineffectiveness of vitamin E in atherosclerosis prevention, with a possibility of harm at higher dosages. However, vitamin E has several isomers, with the alpha form being available via dietary supplements and the gamma form being available via dietary foodstuffs. The gamma form of vitamin E demonstrates several superior properties (such as trapping reactive nitrogen species and detoxifying nitrogen dioxide) compared with alpha vitamin E. All clinical trials have used the alpha isomer, with little concern that this isomer of vitamin E may actually suppress the gamma isomer of vitamin E. We undertook a dose-response study in volunteers with type 2 diabetes mellitus to include all the dosages of alpha vitamin E that have been used in cardiovascular prevention trials to determine the effect of alpha vitamin E on gamma vitamin E. We also assessed the effect of alpha vitamin E on several traditional markers of atherosclerotic risk. We added vitamin C to the vitamin E because several clinical trials included this vitamin to enhance the antioxidant effects of alpha vitamin E. Volunteers received, in randomized order for a 2-week period, one of the following vitamin dosage arms: (1) no vitamins, (2) low-dose supplemental vitamins E plus C, (3) medium-dose supplemental vitamins E plus C, and (4) high-dose supplemental vitamins E plus C. Blood levels of both alpha and gamma vitamin E were measured as well as surrogate markers of oxidative stress, hypercoagulation, and inflammation during a high-fat atherogenic meal (to increase the ambient oxidative stress level during the study). The results demonstrate that alpha vitamin E levels increased in proportion to the dose administered. However, at every dose of alpha vitamin E, gamma vitamin E concentration was significantly suppressed. No beneficial changes in surrogate markers of atherosclerosis were observed, consistent with the negative results of prospective clinical trials using alpha vitamin E. Our results suggest that all prospective cardiovascular clinical trials that used vitamin E supplementation actually suppressed the beneficial antioxidant gamma isomer of vitamin E. No beneficial effects on several potential cardiovascular risk factors were observed, even when the vitamin E was supplemented with vitamin C. If a standardized preparation of gamma vitamin E (without the alpha isomer) becomes available, the effects of gamma vitamin E on atherosclerotic risk will warrant additional studies.

Statin treatment as a confounding factor in human trials with vitamin E

Interventional trials with vitamin E have been planned on the assumption that it could reduce atherosclerotic progression via inhibition of oxidative stress. These trials have been conducted in patients at risk for or with cardiovascular disease, but the results have been divergent. The reason for the equivocal results is still unclear. We have recently demonstrated that in patients with hypercholesterolemia, the administration of a statin is associated with reduced urinary isoprostanes, a marker of oxidative stress, and normalization of circulating levels of vitamin E, indicating that statins enhance the antioxidant status. Based on these arguments, we reanalyzed the interventional trials with vitamin E to see if concomitant use of statins could have created a potential bias. We reviewed 9 interventional trials, each including > 1000 patients. In 5 of the 9 trials, the concomitant use of statins was reported. In the arm randomized to vitamin E, a concomitant use of statins was reported in at least one-third of the population. In some trials, the percentage of patients given statins was > 50%, suggesting that a large part of the follow-up population was likely useless treated with vitamin E in view of the concomitant antioxidant effect of statins. Also, the anti-atherosclerotic effect of statins could have reduced the possibility that a prespecified sample size had an adequate power to observe a difference between vitamin E and placebo-treated groups. We therefore suggest that a meta-analysis of trials with vitamin E should be re-done by excluding patients who concomitantly used statins.

Determination of serum 7-ketocholesterol concentrations and their relationships with coronary multiple risks in diabetes mellitus

Oxysterols have cytotoxic effects and contribute to the development of atherosclerosis. To examine association between 7-ketocholesterol and diabetes mellitus, and other coronary risk factors, we developed a reliable quantitative method to measure serum 7-ketocholesterol (s-7KCHO) and studied s-7KCHO in patients with type 2 diabetes mellitus (T2DM). The s-7KCHO was detected by gas chromatography-mass spectrometry assay. The s-7KCHO was significantly higher in patients with T2DM (n=137, 33.8 ng/ml) compared to non-diabetic healthy subjects (n=89, 16.1 ng/ml). Patients with T2DM were divided into two groups with two or more than two risk factors (defined as multiple risk factors group) and with zero or one risk factor (non-multiple risk factors group). The s-7KCHO was significantly higher in multiple risk factors group (39.5 ng/ml) compared to non-multiple risk factors (30.1 ng/ml). Among patients with multiple risk factors group, s-7KCHO was significantly higher in patients with high low-density lipoprotein cholesterol (LDL-C) levels (45.1+/-5.9 ng/ml) compared to those with normal LDL-C levels (35.3+/-7.0 ng/ml). Furthermore, s-7KCHO increased according to the number of concurrent coronary risk factors. These results suggest that serum 7-ketocholesterol levels may depend on the multiple risk factors and serum LDL-C levels.

Effects of Ingredient Incorporation into Sausage Meat on the Micellarisation and uptake of α-tocopherol by Caco-2 Human Intestinal Cells

Ingredients are incorporated into meat and meat products to produce a ``healthier'' product. However, the effect of ingredient addition on availability of nutrients endogenous to foods is generally not considered. This study investigated the availability and cellular uptake of α-tocopherol from supplemented sausages with the aid of an in vitro digestion procedure coupled with a Caco-2 cell model. Sausages were formulated with the addition of 3% or 10% ingredients (wheat bran, oat bran, soya protein, whey protein, olive oil, linseed oil, sunflower oil, and wheatgerm oil) and subjected to a two-phase in vitro system that simulates the digestive process in humans. Micelles were isolated from the digestate by ultracentrifugation. Of the ingredients selected for addition to sausage meat, only sunflower oil, and wheatgerm oil enhanced the micellarization of α-tocopherol, resulting in increased transfer from the test food to micelles. When ingredients were added at the 3% supplementation level, olive oil enhanced cellular uptake of α-tocopherol. Cellular uptake was not enhanced further with higher oil supplementation (3% vs. 10%). These results indicated that addition of ingredients to sausages (fibres, protein derivatives or vegetable oils) did not have a detrimental effect on α-tocopherol uptake and olive oil at the 3% supplementation level enhanced α-tocopherol availability.

Adição da vitamina E aos alimentos: implicações para os alimentos e para a saúde humana

A ingestão de vitamina E em doses acima das estabelecidas pelas Dietary Reference Intake, na forma de alimentos ou suplementos, está relacionada à prevenção de doenças crônicas não transmissíveis, à estimulação do sistema imune e à modulação dos processos degenerativos relacionados ao envelhecimento. Por outro lado, a adição de vitamina E aos alimentos com o intuito de alcançar tais efeitos ainda não é comum, porque não há consenso sobre a dose a ser consumida. Em muitas populações tem sido necessário ingerir alimentos fortificados com vitamina E, para alcançar os níveis recomendados para a ingestão adequada. Este trabalho enfoca o papel da vitamina E como um componente antioxidante utilizado pela indústria alimentícia, como um composto que exerce funções específicas no organismo humano e no alimento e como um importante nutriente que, quando adicionado aos alimentos, é capaz de atuar contra a lipoperoxidação e contribuir para o aumento de sua ingestão, além de poder reduzir os efeitos deletérios dos processos oxidativos que ocorrem no organismo humano, prevenindo as doenças crônicas não transmissíveis.

Oral lipid-based formulations

Poor drug solubility remains a significant and frequently encountered problem for pharmaceutical scientists. The ability of lipid-based formulations to facilitate gastrointestinal absorption of many poorly soluble drug candidates has been thoroughly documented in the published literature. However, a considerable gap exists between our knowledge of this technology and the know-how required for its application. This commentary provides a comprehensive summary of the development, characterization, and utilization of oral lipid-based formulations, from both physicochemical and biopharmaceutical perspectives. The characteristics of currently available lipid excipients are reviewed in context of their application to the basic lipid-based formulation modalities. The fundamental concepts of in vitro and in vivo evaluation of lipid-based formulations are summarized followed by a forward-looking summary of unrealized opportunities and potential limitations to more widespread use of this technology.

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.

The influence of antioxidant supplementation on markers of inflammation and the relationship to oxidative stress after exercise

Interest in the relationship between inflammation and oxidative stress has increased dramatically in recent years, not only within the clinical setting but also in the fields of exercise biochemistry and immunology. Inflammation and oxidative stress share a common role in the etiology of a variety of chronic diseases. During exercise, inflammation and oxidative stress are linked via muscle metabolism and muscle damage. Because oxidative stress and inflammation have traditionally been associated with fatigue and impaired recovery from exercise, research has focused on nutritional strategies aimed at reducing these effects. In this review, we have evaluated the findings of studies involving antioxidant supplementation on alterations in markers of inflammation (e.g., cytokines, C-reactive protein and cortisol). This review focuses predominantly on the role of reactive oxygen and nitrogen species generated from muscle metabolism and muscle damage during exercise and on the modulatory effects of antioxidant supplements. Furthermore, we have analyzed the influence of factors such as the dose, timing, supplementation period and bioavailability of antioxidant nutrients.

The effect of hot season and nutrition on the oxidative status and metabolic profile in dairy goats during mid lactation

The aim of this study was to evaluate the effects of the hot season and nutrition on the oxidative status and metabolic profile of lactating goats during mid lactation. Twenty-four Red Syrian goats were allocated into three groups that were offered the following diets: natural pasture (P), pasture+500 g/h per day of concentrate (PC) and hay plus 500 g/h per day of concentrate (HC). Blood samples were taken in spring (85±7 days in milk (DIM)) and summer (120±7 DIM) and assayed for reactive oxygen metabolites (ROMs), α-tocopherol, glucose, triglycerides, cholesterol, non-esterified fatty acids, total protein, albumin and globulin concentrations and glutathione peroxidase (GHS-Px) and superoxide dismutase (SOD) activities. Milk yield and milk composition were also measured. SOD, GSH-Px and ROMs levels increased during summer when temperature humidity index values were high. The increase in ROMs in the PC and HC groups could be ascribed to the improved nutritional regime and to their higher production level. The markers of the oxidative status and of the metabolic profile measured in this study indicate that goats may have experienced moderate oxidative stress. It seems that, seasonal rather than nutritional factors have a more pronounced effect on oxidative status markers. Concentrate supplementation sustained milk yield and may represent a useful means to extend the lactation period in dairy goats during late spring and summer.

Increased plasma levels of oxysterols, in vivo markers of oxidative stress, in patients with familial combined hyperlipidemia: reduction during atorvastatin and fenofibrate therapy

Familial combined hyperlipidemia (FCHL), the most common inherited disorder of lipid metabolism, is associated with an increased risk of atherosclerosis that is not fully explained by the metabolic disturbances of these patients. Oxidative damage to lipid components accumulating in the plasma of FCHL patients might contribute to explaining this lack of evidence. Cholesterol is one of the preferential targets of oxidation in LDL and this may contribute to setting a proatherogenetic phenotype in FCHL. We investigated plasma oxysterols (7-ketocholesterol and 7beta-hydroxycholesterol) and alpha-tocopherol as in vivo hallmarks of lipid-related oxidative stress. Oxidative stress hallmarks were measured in 45 FCHL patients and 54 sex- and age-matched healthy controls; in FCHL patients, oxidative stress and lipid profile parameters were also assessed in response to lipid-lowering drugs in a 24-week randomized, open-label trial with atorvastatin or fenofibrate. FCHL patients showed markedly increased levels of oxysterols (p < 0.001) and reduced alpha-tocopherol/total lipids (p < 0.001) compared to controls. These differences were independent of the presence of clinical atherosclerosis and persisted after correction for hyperlipidemia. Atorvastatin and fenofibrate significantly improved the lipid profile and caused a comparable decrease in plasma oxysterols, with the normalization of 7-ketocholesterol and a significant reduction of 7beta-hydroxycholesterol (p < 0.001). These drugs also decreased the ratio of alpha-tocopherol/total lipids by more than 30% (p < 0.001). In conclusion, FCHL patients showed increased hallmarks of cholesterol oxidation and decreased levels of alpha-tocopherol/total lipids. Atorvastatin and fenofibrate displayed comparable efficiency in decreasing oxysterols, but they further decreased lipid-corrected alpha-tocopherol levels in plasma. More research work is needed to understand the clinical meaning of these findings, which may help to understand the role of oxidative stress in FCHL and lipid-lowering therapy.

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 and risk of type 2 diabetes in the women's health study randomized controlled trial

We directly assessed the efficacy of vitamin E supplements for primary prevention of type 2 diabetes among apparently healthy women in the Women's Health Study randomized trial. Between 1992 and 2004, 38,716 apparently healthy U.S. women aged >or=45 years and free of diabetes, cancer, and cardiovascular disease were in two randomly assigned intervention groups and received 600 IU of vitamin E (alpha-tocopherol, n = 19,347) or placebo (n = 19,369) on alternate days. During a median 10-year follow-up, there were 827 cases of incident type 2 diabetes in the vitamin E group and 869 in the placebo group, a nonsignificant 5% risk reduction (relative risk [RR] 0.95 [95% CI 0.87-1.05], P = 0.31). There was no evidence that diabetes risk factors including age, BMI, postmenopausal hormone use, multivitamin use, physical activity, alcohol intake, and smoking status modified the effect of vitamin E on the risk of type 2 diabetes. In a sensitivity analysis taking compliance into account, women in the vitamin E group had an RR of 0.93 (95% CI 0.83-1.04) (P = 0.21) compared with those randomized to placebo. In this large trial with 10-year follow-up, alternate-day doses of 600 IU vitamin E provided no significant benefit for type 2 diabetes in initially healthy women.

Les isoprostanes, biomarqueurs de peroxydation lipidique chez l'homme. Partie 3 : biomarqueurs et médiateurs en physiologie et pathologie vasculaire

The 15-series F(2)-isoprostanes mediate vasoconstriction in different vascular beds and species. This contraction is mediated by the thromboxane receptors stimulation, and may be modulated by the endothelium. Furthermore, 15-F(2t)-IsoP induces smooth muscle cells mitogenesis and monocyte adhesion to endothelial cells. Some 15-series E(2)-isoprostanes are more potent than F(2)-isoprostanes. In clinical studies, 15-F(2t)-IsoP levels are increased in vascular disorders involving atherosclerosis, ischemia-reperfusion and inflammation. F(2)-isoprostane levels correlate to the severity of heart failure and pulmonary hypertension, raising the potential prognostic interest of these biomarkers. Whether the effects observed in vitro are observed consistently in vivo at physiological concentrations and whether these effects contribute to pathological states in vivo is still debated.

Physiological factors influencing vitamin E biokinetics

Limited information is available on factors that can influence vitamin E bioavailability. In several studies we have investigated the influence of dietary, biochemical, and genetic factors on vitamin E biokinetics. In these studies, subjects ingested a capsule containing 150 mg deuterated RRR-alpha-tocopheryl acetate, blood was taken up to 48 hr, and tocopherols were analyzed by liquid chromatography and mass spectroscopy. There was significantly greater plasma-labeled alpha-tocopherol concentrations when the capsule was consumed with a high-fat meal (17.5 g) versus a low-fat meal (2.7 g), and there was also a difference between a high-fat toast and butter and a cereal with full-fat milk meal (both 17.5 g fat), indicating that both the amount of fat and food matrix is important for vitamin E absorption. Dyslipidemic subjects displayed a reduced plasma uptake of newly absorbed alpha-tocopherol, and differences were also apparent in individual lipoproteins. A decreased uptake of labeled alpha-tocopherol was also observed in erythrocytes, platelets, and lymphocytes of dyslipidemics. Following vitamin E supplementation (400 mg/day, 4 weeks), the uptake of newly absorbed alpha-tocopherol was decreased, presumably because of saturation of alpha-tocopherol transfer protein. We also found that apoE3 subjects displayed a considerably reduced uptake of newly absorbed labeled alpha-tocopherol compared to apoE4 subjects, which may be a consequence of the reduced low-density lipoprotein catabolic rate in these subjects. Taken together, these data show that several physiological factors influence the uptake of newly absorbed alpha-tocopherol, and that this is an important consideration in the design of future vitamin E supplementation studies.

Vitamin E for the Treatment of Cardiovascular Disease: Is There a Future?

Oxidative stress seems to play a key role in the pathogenesis of atherosclerosis. Agents that protect low-density lipoprotein from oxidation have been shown in a range of in vitro and animal models to reduce the development and progression of atherosclerosis. These agents include antioxidant micronutrients such as vitamin E. They have gained wide interest because of the potential for prevention of atherosclerotic vascular disease in humans. In the last decade, many trials with antioxidants have been carried out in patients with cardiovascular disease, but the results are equivocal. The reason for the disappointing findings is unclear, but one possible explanation is the lack of identification criteria of patients who are potential candidates for antioxidant treatment. This review analyses the data reported so far to determine whether they clearly support the premise that patients at risk of cardiovascular disease may be candidates for antioxidant treatment.

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.

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.

Should antioxidant status be considered in interventional trials with antioxidants?

The last decade has seen many trials with antioxidants in patients with cardiovascular disease, with equivocal results. One possible explanation for the disappointing findings is the lack of identification criteria of patients who are potential candidates for antioxidant treatment. Several studies have been carried out in patients at risk of cardiovascular disease, indicating that enhanced oxidative stress is associated with the presence of diabetes, hypercholesterolaemia, hypertension, and smoking. This review analyses the data reported so far to determine whether they clearly support the premise that patients at risk of cardiovascular events may be candidates for antioxidant treatment.

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.

Vitamin E and its role in the prevention of atherosclerosis and carcinogenesis: a review

Epidemiological and experimental studies suggest that antioxidants like vitamin E (alpha-tocopherol) may play an important role in prevention of chronic disease. Several observational surveys have linked populations with a large intake of vitamin E with reduced incidence of heart disease. These observations have been strengthened by the demonstration of strong antioxidant activity by vitamin E in cellular, molecular and animal experiments. These results have highlighted a potential role for vitamin E supplementation in the prevention of chronic disease in humans. Interestingly however, large-scale clinical trials of vitamin E and other antioxidants in preventing specific disease processes (e.g., coronary artery disease) have generated conflicting and mixed outcomes. In this review, the role of vitamin E in the prevention of atherosclerosis and carcinogenesis has been carefully examined with particular emphasis on salient human studies (clinical trials) and their limitations. In addition, pertinent biochemical, physiological and metabolic features of vitamin E have also been incorporated. A list of common natural food sources of vitamin E has been provided. Important in vitro and animal studies related to the antiatherosclerotic and anticarcinogenic actions of vitamin E have been discussed in detail. Finally, the direction of future investigations in primary and secondary prevention of chronic diseases by vitamin E supplementation has been outlined.

Factors affecting intestinal absorption of highly lipophilic food microconstituents (fat-soluble vitamins, carotenoids and phytosterols)

Highly lipophilic food microconstituents (HLFMs) with octanol-water partition coefficients log10 P(c) > 8 include the fat-soluble vitamins (A, E, D and K) and phytochemicals with potential health benefits, the carotenoids and phytosterols. It has been assumed that these compounds have the same metabolism in the human upper gastrointestinal tract and that they follow the same fate as lipids. However, a literature review shows that the metabolism of HLFMs in the upper gastrointestinal tract depends on each HLFM species. For example, some HLFM esters are hydrolyzed mainly by pancreatic lipase, others by bile salt-stimulated lipase; some HLFMs are apparently absorbed by passive diffusion, others by a transporter. Also, although some factors (HLFM molecular species, fat, food matrix) affect absorption efficiency of most HLFMs, other factors (fibers, microconstituents) apparently affect absorption only of some HLFMs. The mnemonic acronym SLAMENGHI, previously proposed to list the factors affecting the bioavailability of carotenoids, was used here to review current knowledge of the factors suspected to affect the intestinal absorption of HLFMs. The available data reveal numerous gaps in the knowledge of the metabolism of HLFMs and the factors that affect their absorption. These gaps need to be filled to be able to formulate HLFMs so as to promote greater absorption efficiency.

Monocyte chemoattractant protein-1 involvement in the alpha-tocopherol-induced reduction of atherosclerotic lesions in apolipoprotein E knockout mice

We studied the effects of alpha-tocopheryl acetate supplementation on the development of fatty streaks and its ability to modulate the expression of monocyte chemoattractant protein (MCP)-1 in aortic lesions of apolipoprotein E knockout mice. For this purpose, 16-week-old apolipoprotein E knockout mice received alpha-tocopherol supplementation (800 mg)/kg diet) for 6 weeks. After this time, total and lipoprotein cholesterol in the serum, hepatic tocopherol, aortic lesion area and MCP-1 (protein and mRNA) expression were analysed. Our present results showed that the dietary supplementation with alpha-tocopherol did not reduce serum cholesterol nor change lipoprotein profile, but it reduced the area of the aortic lesion by 55 %. The reduction in the lesion size was correlated with the reduced expression of MCP-1 mRNA and protein, as detected by real-time quantitative polymerase chain reaction and immunohistochemistry respectively. In conclusion, the results obtained here are relevant to the study of atherosclerosis, as they correlate the effectiveness of vitamin E supplementation in inhibiting the plaque formation with diminished expression of MCP-1 at the aortic lesion.

Measurement of oxysterols and alpha-tocopherol in plasma and tissue samples as indices of oxidant stress status

Oxidant stress seems to play a role in several setting of human pathology, such as atherosclerosis, cancer, and aging. The study of oxidant stress in human disease should be based on the evaluation of either sensitive and specific markers of enhanced oxidant stress, such as oxysterols, or antioxidant defense, by measuring alpha-tocopherol. We have developed a rapid method to measure the oxysterols 7beta-hydroxycholesterol and 7-ketocholesterol in plasma (50 healthy subjects) and tissue as an index of oxidant stress in vivo, and from the same sample alpha-tocopherol content. The mean plasma concentration of 7beta-hydroxycholesterol and 7-ketocholesterol was 4.6+/-1.1 and 13.4+/-7.6 ng/mL, respectively. Plasma alpha-tocopherol concentration was 5.8+/-1.0 micromol/mol cholesterol. Samples from atherosclerotic plaques contained 20 times more cholesterol, about 45 times higher oxysterols levels, and 600 times more alpha-tocopherol compared to normal arteries. No significant difference in cholesterol and oxysterol content was observed between cirrhotic and normal liver. However, cirrhotic liver contained significantly smaller concentration of alpha-tocopherol compared to normal liver. In conclusion, we have developed a rapid and reliable method for the assay of cholesterol oxidation products and alpha-tocopherol in plasma and tissue useful for estimation of oxidant stress/antioxidant balance.

Analysis of oxidative processes and of myelin figures formation before and after the loss of mitochondrial transmembrane potential during 7beta-hydroxycholesterol and 7-ketocholesterol-induced apoptosis: comparison with various pro-apoptotic chemicals

Among oxysterols oxidized at C7 (7alpha-, 7beta-hydroxycholesterol, and 7-ketocholesterol) 7beta-hydroxycholesterol and 7-ketocholesterol are potent inducers of cell death and probably play central roles in atherosclerosis. As suggested by our previous investigations, 7-ketocholesterol might be a causative agent of vascular damage by inducing apoptosis and enhancing superoxide anion (O2*-) production. To determine the precise relationships between cytotoxicity and oxidative stress, the ability of oxysterols oxidized at C7 to induce apoptosis, to stimulate O2*- production and to promote lipid peroxidation was compared with different pro-apoptotic chemicals: antitumoral drugs (VB, Ara-C, CHX, and VP-16) and STS. All compounds, except 7alpha-hydroxycholesterol, induced apoptosis characterized by the occurrence of cells with fragmented and/or condensed nuclei, loss of mitochondrial potential, caspase-3 activation, PARP degradation, and internucleosomal DNA fragmentation. The highest proportion of apoptotic cells was found with antitumoral drugs and STS, whereas the highest overproduction of O2*- detected before and after the loss of mitochondrial potential was obtained with 7beta-hydroxycholesterol and 7-ketocholesterol. Overproduction of O2*- was always correlated with enhanced lipid peroxidation. Vit E was only capable to significantly counteract apoptosis and oxidative stress induced by 7beta-hydroxycholesterol, 7-ketocholesterol, VB and STS. By electron and fluorescence microscopy, myelin figures evocating autophagic vacuoles were barely observed under treatment with 7beta-hydroxycholesterol and 7-ketocholesterol, and their formation occurring before the loss of mitochondrial potential was reduced by Vit E. In the presence of 7alpha-hydroxycholesterol, no enhancement of O2*- production, no lipid peroxidation, and no formation of myelin figures were observed. Collectively, our data demonstrate, that there can be a more or less important stimulation of oxidative stress during apoptosis. They also suggest that enhancement of O2*- production associated with lipid peroxidation during 7beta-hydroxycholesterol and 7-ketocholesterol-induced apoptosis could contribute to in vivo vascular injury, and that myelin figures could constitute suitable markers of oxysterol-induced cell death.