-
Current Medicinal Chemistry May 2004Molecules in biological systems often can perform more than one function. In particular, many molecules have the ability to chemically scavenge free radicals and thus... (Review)
Review
Molecules in biological systems often can perform more than one function. In particular, many molecules have the ability to chemically scavenge free radicals and thus act in the test tube as antioxidant, but their main biological function is by acting as hormones, ligands for transcription factors, modulators of enzymatic activities or as structural components. In fact, oxidation of these molecules may impair their biological function, and cellular defense systems exist which protect these molecules from oxidation. Vitamin E is present in plants in 8 different forms with more or less equal antioxidant potential (alpha-, beta-, gamma-, delta-tocopherol/tocotrienols); nevertheless, in higher organisms only alpha-tocopherol is preferentially retained suggesting a specific mechanism for the uptake for this analogue. In the last 20 years, the route of tocopherol from the diet into the body has been clarified and the proteins involved in the uptake and selective retention of alpha-tocopherol discovered. Precise cellular functions of alpha-tocopherol that are independent of its antioxidant/radical scavenging ability have been characterized in recent years. At the posttranslational level, alpha-tocopherol inhibits protein kinase C, 5-lipoxygenase and phospholipase A2 and activates protein phosphatase 2A and diacylglycerol kinase. Some genes (e. g. scavenger receptors, alpha-TTP, alpha-tropomyosin, matrix metalloproteinase-19 and collagenase) are modulated by alpha-tocopherol at the transcriptional level. alpha-Tocopherol also inhibits cell proliferation, platelet aggregation and monocyte adhesion. These effects are unrelated to the antioxidant activity of vitamin E, and possibly reflect specific interactions of alpha-tocopherol with enzymes, structural proteins, lipids and transcription factors. Recently, several novel tocopherol binding proteins have been cloned, that may mediate the non-antioxidant signaling and cellular functions of vitamin E and its correct intracellular distribution. In the present review, it is suggested that the non-antioxidant activities of tocopherols represent the main biological reason for the selective retention of alpha-tocopherol in the body, or vice versa, for the metabolic conversion and consequent elimination of the other tocopherols.
Topics: Animals; Antioxidants; Carrier Proteins; Dietary Fats, Unsaturated; Dietary Supplements; Enzyme Activation; Gene Expression Regulation; Humans; Intestinal Mucosa; Lipid Peroxides; Liver; Preventive Medicine; Reactive Oxygen Species; Signal Transduction; Vitamin E; alpha-Tocopherol
PubMed: 15134510
DOI: 10.2174/0929867043365332 -
Nutrition Research Reviews Dec 2014Vitamin E (α-, β-, γ- and δ-tocopherol and -tocotrienol) is an essential factor in the human diet and regularly taken as a dietary supplement by many people, who act... (Review)
Review
Vitamin E (α-, β-, γ- and δ-tocopherol and -tocotrienol) is an essential factor in the human diet and regularly taken as a dietary supplement by many people, who act under the assumption that it may be good for their health and can do no harm. With the publication of meta-analyses reporting increased mortality in persons taking vitamin E supplements, the safety of the micronutrient was questioned and interactions with prescription drugs were suggested as one potentially underlying mechanism. Here, we review the evidence in the scientific literature for adverse vitamin E-drug interactions and discuss the potential of each of the eight vitamin E congeners to alter the activity of drugs. In summary, there is no evidence from animal models or randomised controlled human trials to suggest that the intake of tocopherols and tocotrienols at nutritionally relevant doses may cause adverse nutrient-drug interactions. Consumption of high-dose vitamin E supplements ( ≥ 300 mg/d), however, may lead to interactions with the drugs aspirin, warfarin, tamoxifen and cyclosporine A that may alter their activities. For the majority of drugs, however, interactions with vitamin E, even at high doses, have not been observed and are thus unlikely.
Topics: Animals; Aspirin; Cyclosporine; Dietary Supplements; Dose-Response Relationship, Drug; Drug Interactions; Humans; Tamoxifen; Vitamin E; Warfarin
PubMed: 25225959
DOI: 10.1017/S0954422414000146 -
FASEB Journal : Official Publication of... Jul 1999Although vitamin E has been known as an essential nutrient for reproduction since 1922, we are far from understanding the mechanisms of its physiological functions.... (Review)
Review
Although vitamin E has been known as an essential nutrient for reproduction since 1922, we are far from understanding the mechanisms of its physiological functions. Vitamin E is the term for a group of tocopherols and tocotrienols, of which alpha-tocopherol has the highest biological activity. Due to the potent antioxidant properties of tocopherols, the impact of alpha-tocopherol in the prevention of chronic diseases believed to be associated with oxidative stress has often been studied, and beneficial effects have been demonstrated. Recent observations that the alpha-tocopherol transfer protein in the liver specifically sorts out RRR-alpha-tocopherol from all incoming tocopherols for incorporation into plasma lipoproteins, and that alpha-tocopherol has signaling functions in vascular smooth muscle cells that cannot be exerted by other forms of tocopherol with similar antioxidative properties, have raised interest in the roles of vitamin E beyond its antioxidative function. Also, gamma-tocopherol might have functions apart from being an antioxidant. It is a nucleophile able to trap electrophilic mutagens in lipophilic compartments and generates a metabolite that facilitates natriuresis. The metabolism of vitamin E is equally unclear. Excess alpha-tocopherol is converted into alpha-CEHC and excreted in the urine. Other tocopherols, like gamma- and delta-tocopherol, are almost quantitatively degraded and excreted in the urine as the corresponding CEHCs. All rac alpha-tocopherol compared to RRR-alpha-tocopherol is preferentially degraded to alpha-CEHC. Thus, there must be a specific, molecular role of RRR-alpha-tocopherol that is regulated by a system that sorts, distributes, and degrades the different forms of vitamin E, but has not yet been identified. In this article we try to summarize current knowledge on the function of vitamin E, with emphasis on its antioxidant vs. other properties, the preference of the organism for RRR-alpha-tocopherol, and its metabolism to CEHCs.
Topics: Animals; Antioxidants; Biological Availability; Humans; Infertility; Signal Transduction; Vitamin E
PubMed: 10385606
DOI: No ID Found -
Plants (Basel, Switzerland) Mar 2023The seeds of 111 sp. different fruit use (dessert and cider apples) cultivars/genotypes developed in 18 countries were analysed to evaluate composition of tocopherol...
The seeds of 111 sp. different fruit use (dessert and cider apples) cultivars/genotypes developed in 18 countries were analysed to evaluate composition of tocopherol homologues and identify crop-specific profile, including diploid, triploid, and tetraploid apple cultivars with and without scab-resistance to ensure high genetic diversity. The percentage of individual tocopherols was as follows: alpha-tocopherol (alpha-T) (38.36%), beta-tocopherol (beta-T) (40.74%), gamma-tocopherol (gamma-T) (10.93%), and delta-tocopherol (delta-T) (9.97%), represented by average measurements of 17.48, 18.56, 4.98, and 4.54 mg/100 g dry weight, respectively. The values of the variation coefficient showed high variability for delta (0.695) and gamma (0.662) homologue content, whereas measurements of alpha-T and beta-T were less variable (coefficient of variation 0.203 and 0.256, respectively). The unweighted pair group method with arithmetic mean (UPGMA) revealed three main cultivar groups characterised by almost equal content of all four tocopherol homologues (Group I), high concentrations of alpha-T and beta-T, but very low content of gamma-T and delta-T (Group II), and relatively high average content of alpha-T and beta-T, but higher gamma-T and delta-T content (Group III). Specific tocopherol homologues showed association with certain valuable traits, such as harvesting time (total content of tocopherols) and resistance to apple scab (alpha-T and total content of tocopherols). This study represents the first large-scale tocopherol homologue (alpha, beta, gamma, and delta) screening in apple seeds. The dominant tocopherol homologues in cultivated apple cultivars are alpha-T and beta-T, with the prevalence of alpha-T or beta-T depending on genotype. It is a unique finding due to the rare occurrence of beta-T in the plant world and is considered a unique feature of the species.
PubMed: 36904029
DOI: 10.3390/plants12051169 -
Antioxidants (Basel, Switzerland) Nov 2017Vitamin E is a generic term frequently used to group together eight different molecules, namely: α-, β-, γ- and δ-tocopherol and the corresponding tocotrienols. The... (Review)
Review
Vitamin E is a generic term frequently used to group together eight different molecules, namely: α-, β-, γ- and δ-tocopherol and the corresponding tocotrienols. The term tocopherol and eventually Vitamin E and its related activity was originally based on the capacity of countering foetal re-absorption in deficient rodents or the development of encephalomalacia in chickens. In humans, Vitamin E activity is generally considered to be solely related to the antioxidant properties of the tocolic chemical structure. In recent years, several reports have shown that specific activities exist for each different tocotrienol form. In this short review, tocotrienol ability to inhibit cancer cell growth and induce apoptosis thanks to specific mechanisms, not shared by tocopherols, such as the binding to Estrogen Receptor-β (ERβ) and the triggering of endoplasmic reticulum (EndoR) stress will be described. The neuroprotective activity will also be presented and discussed. We propose that available studies strongly indicate that specific forms of tocotrienols have a distinct mechanism and biological activity, significantly different from tocopherol and more specifically from α-tocopherol. We therefore suggest not pooling them together within the broad term "Vitamin E" on solely the basis of their putative antioxidant properties. This option implies obvious consequences in the assessment of dietary Vitamin E adequacy and, probably more importantly, on the possibility of evaluating a separate biological variable, determinant in the relationship between diet and health.
PubMed: 29156559
DOI: 10.3390/antiox6040093 -
Food Science and Biotechnology Dec 2019Interaction between tocopherol homologs and peppermint extract added to oil-in-water emulsions was studied during iron-catalyzed oxidation. Emulsions consisted of...
Interaction between tocopherol homologs and peppermint extract added to oil-in-water emulsions was studied during iron-catalyzed oxidation. Emulsions consisted of tocopherol-stripped soybean oil and citrate buffer (4:6, w/w) with/without addition of peppermint extract (400 mg/kg) and α-, γ-, or δ-tocopherol (600 mg/kg), and were oxidized in the iron presence at 25 °C. Lipid oxidation of emulsions was evaluated based on hydroperoxide contents and -anisidine values. Lipid oxidative stability of emulsions was improved by added peppermint extract, and co-added γ- and δ-tocopherols further reduced lipid oxidation, however, α-tocopherol increased it. Tocopherol contents did not change during oxidation. Polyphenol degradation in the emulsion with added peppermint extract was lower and slower by γ- and δ-tocopherols, however, α-tocopherol showed opposite results. The results suggest that co-addition of tocopherols to the emulsion containing peppermint extract shift a major role of polyphenols as antioxidants from scavenging lipid (peroxy) radicals to tocopherol radical scavenging.
PubMed: 31807340
DOI: 10.1007/s10068-019-00613-9 -
Free Radical Biology & Medicine Nov 2021The name vitamin E, was given by Barnett and Sure who suggested that the factor proposed by Evans and Bishop as substance "X," be termed vitamin "E" as the next vitamin... (Review)
Review
The name vitamin E, was given by Barnett and Sure who suggested that the factor proposed by Evans and Bishop as substance "X," be termed vitamin "E" as the next vitamin after the A, B, C and D vitamins had been already described. The identification of vitamin E with a-tocopherol was made in 1936 by Evans' group. One year later β-tocopherol and 11 years later δ-tocopherol were isolated. Tocotrienol (named zetatocopherol) was first described in 1957 and later isolated in 1961. The antioxidant property of tocopherols was reported by Olcott and Emerson in 1937. Inherited vitamin E deficiency, AVED, characterized by a form of neuromyopathy was first described in 1981. The disease, was localized to chromosome 8q and found to be caused by a mutation of the a-TTP gene. The subsequent paragraphs are not a comprehensive review but only critical reflections on some important aspects of vitamin E research.
Topics: Antioxidants; Humans; Tocopherols; Tocotrienols; Vitamin E; Vitamin E Deficiency
PubMed: 34478835
DOI: 10.1016/j.freeradbiomed.2021.07.042 -
European Journal of Pediatrics Jul 2006Alpha-, beta-, gamma- and delta-tocopherol are present in many foods and are, in the absence of fat malabsorption, well absorbed from the gut. Their anti-oxidant... (Review)
Review
Alpha-, beta-, gamma- and delta-tocopherol are present in many foods and are, in the absence of fat malabsorption, well absorbed from the gut. Their anti-oxidant property is well known and protects arteries and capillaries as well as blood lipids and nervous tissue against oxidative stress. In contrast to beta-, gamma- and delta-tocopherol, alpha-tocopherol is preferentially conserved by the discriminating action of the liver alpha-tocopherol transfer protein, which also maintains plasma alpha-tocopherol concentration within a range of 20 to 40 microM. In the circulation, alpha-tocopherol, in association with the transfer-protein, is assembled into the very low-density lipoprotein and low-density lipoprotein particles and released for use by the peripheral tissues. Recent data suggest that alpha-tocopherol is not only an anti-oxidant but also a regulator of gene expression through its binding to nuclear receptors. The precise mechanism of regulating gene expression, however, is still unknown. The four tocopherols are ultimately degraded by omega-oxidation and subsequent beta-oxidations followed by the elimination of the metabolites in the bile and in the urine. Patients with a defect of the alpha-tocopherol transfer protein are unable to maintain their alpha-tocopherol reserves and progressively lose tendon reflexes and have signs and symptoms of spinocerebellar ataxia while plasma vitamin E level drops below 2 microg/ml.
Topics: Antioxidants; Diagnosis, Differential; Hepatocytes; Humans; Terminology as Topic; Vitamin E; Vitamin E Deficiency
PubMed: 16491383
DOI: 10.1007/s00431-006-0084-5 -
Clinical Nutrition (Edinburgh, Scotland) Feb 2016The results of studies assessing relationships between vitamin E intake and status and lung function are conflicting. This study aimed to evaluate the effect of vitamin...
BACKGROUND & AIMS
The results of studies assessing relationships between vitamin E intake and status and lung function are conflicting. This study aimed to evaluate the effect of vitamin E intake and serum levels of tocopherol isoforms on lung function in a cross-sectional sample of 580 men from the Normative Aging Study, a longitudinal aging study.
METHODS
Regression models were used to look at associations of serum tocopherol isoform levels and vitamin E intake with lung function parameters after adjustment for confounders. Vitamin E intake was measured using a food frequency questionnaire and serum levels of γ, α, and δ-tocopherol levels were measured using high-performance liquid chromatography.
RESULTS
After adjustment for potential confounders, serum γ-tocopherol had a significant inverse association with forced vital capacity (β = -0.10, p = 0.05). Alpha and δ-tocopherol were not associated with any lung function parameter. After classifying COPD status according to Global Initiative for Obstructive Lung Disease (GOLD) stage criteria, serum levels of δ-tocopherol were lower in participants with more severe COPD (p = 0.01). Serum levels of δ-tocopherol were also lower in participants with greater levels of smoking (p = 0.02). Both vitamin E intake (β = 0.03, p = 0.02; β = 0.03, p = 0.01) and use of vitamin E supplements (β = 0.05, p = 0.03; β = 0.06. p = 0.02) were positively associated with FEV1 and FVC, after adjusting for confounders. Subjects who took vitamin E supplements had significantly higher α-tocopherol levels (p < 0.0001) and lower γ-tocopherol levels (p < 0.0001) than non-users.
CONCLUSION
In this study, there is a positive association between dietary vitamin E intake and lung function, and evidence of an inverse relationship between serum levels of γ-tocopherol and lung function.
Topics: Adult; Aged; Aged, 80 and over; Aging; Body Mass Index; Cross-Sectional Studies; Humans; Longitudinal Studies; Lung; Male; Middle Aged; Multivariate Analysis; Regression Analysis; Risk Factors; Surveys and Questionnaires; Tocopherols; Vitamin E; Young Adult; alpha-Tocopherol; gamma-Tocopherol
PubMed: 25715694
DOI: 10.1016/j.clnu.2015.01.020 -
Journal of Agricultural and Food... Oct 2004Membranes of muscle foods are more susceptible to oxidation than triacylglycerols. Hence, directing a lipid-soluble antioxidant into the membranes may reduce the...
Membranes of muscle foods are more susceptible to oxidation than triacylglycerols. Hence, directing a lipid-soluble antioxidant into the membranes may reduce the oxidative deterioration of muscle tissue. The objective of this research was to use a model system of cod muscle and triacylglycerol to study the distribution of exogenous delta-tocopherol between the membranes and triacylglycerol fractions of muscle. When ethanol was the carrier solvent, more tocopherol was incorporated into the membranes than when oil was the carrier. Addition of tocopherol to the muscle before the triacylglycerol was added allowed more antioxidant to be incorporated into the membranes than for the case when the oil was added before the antioxidant. When the triacylglycerol was solid, the amount of tocopherol incorporated into the membranes was higher than if the triacylglycerol was liquid and the amount of tocopherol incorporated into the membranes was less dependent on the order of tocopherol and triacylglycerol addition. There was a competition between the membrane lipids and triacylglycerol for uptake of the delta-tocopherol. In some circumstances, some of the tocopherol did not enter either the membrane lipid or triacylglycerol phase.
Topics: Animals; Chemical Phenomena; Chemistry, Physical; Fishes; Membrane Lipids; Models, Biological; Muscles; Solvents; Tocopherols; Triglycerides
PubMed: 15453703
DOI: 10.1021/jf040128q