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1.
Effects of dietary RRR α-tocopherol vs all-racemic α-tocopherol on health outcomes.
Ranard, KM, Erdman, JW
Nutrition reviews. 2018;(3):141-153
Abstract
Of the 8 vitamin E analogues, RRR α-tocopherol likely has the greatest effect on health outcomes. Two sources of α-tocopherol, naturally sourced RRR α-tocopherol and synthetic all-racemic α-tocopherol, are commonly consumed from foods and dietary supplements in the United States. A 2016 US Food and Drug Administration ruling substantially changed the RRR to all-racemic α-tocopherol ratio of biopotency from 1.36:1 to 2:1 for food-labeling purposes, but the correct ratio is still under debate in the literature. Few studies have directly compared the 2 α-tocopherol sources, and existing studies do not compare the efficacy of either source for preventing or treating disease in humans. To help close this gap, this review evaluates studies that investigated the effects of either RRR α-tocopherol or all-racemic α-tocopherol on health outcomes, and compares the overall findings. α-Tocopherol has been used to prevent and/or treat cancer and diseases of the central nervous system, the immune system, and the cardiovascular system, so these diseases are the focus of the review. No firm conclusions about the relative effects of the α-tocopherol sources on health outcomes can be made. Changes to α-tocopherol-relevant policies have proceeded without adequate scientific support. Additional research is needed to assemble the pieces of the α-tocopherol puzzle and to determine the RRR to all-racemic α-tocopherol ratio of biopotency for health outcomes.
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2.
The Safety of Adjuvanted Vaccines Revisited: Vaccine-Induced Narcolepsy.
Ahmed, SS, Montomoli, E, Pasini, FL, Steinman, L
The Israel Medical Association journal : IMAJ. 2016;(3-4):216-20
Abstract
Despite the very high benefit-to-risk ratio of vaccines, the fear of negative side effects has discouraged many people from getting vaccinated, resulting in the reemergence of previously controlled diseases such as measles, pertussis and diphtheria. This fear has been amplified more recently by multiple epidemiologic studies that confirmed the link of an AS03-adjuvanted pandemic influenza vaccine (Pandemrix, GlaxoSmithKline Biologicals, Germany) used in Europe during the 2009 H1N1 influenza pandemic [A(H1N1) pdm09] with the development of narcolepsy, a chronic sleep disorder, in children and adolescents. However, public misperceptions of what adjuvants are and why they are used in vaccines has created in some individuals a closed "black box" attitude towards all vaccines. The focus of this review article is to revisit this "black box" using the example of narcolepsy associated with the European AS03-adjuvanted pandemic influenza vaccine.
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3.
Effect of vitamin E supplementation on serum C-reactive protein level: a meta-analysis of randomized controlled trials.
Saboori, S, Shab-Bidar, S, Speakman, JR, Yousefi Rad, E, Djafarian, K
European journal of clinical nutrition. 2015;(8):867-73
Abstract
C-reactive protein (CRP), a marker of chronic inflammation, has a major role in the etiology of chronic disease. Vitamin E may have anti-inflammatory effects. However, there is no consensus on the effects of vitamin E supplementation on CRP levels in clinical trials. The aim of this study was to systematically review randomized controlled trials (RCTs) that report on the effects of vitamin E supplementation (α- and γ-tocopherols) on CRP levels. A systematic search of RCTs was conducted on Medline and EMBASE through PubMed, Scopus, Ovid and Science Direct, and completed by a manual review of the literature up to May 2014. Pooled effects were estimated by using random-effects models and heterogeneity was assessed by Cochran's Q and I(2) tests. Subgroup analyses and meta-regression analyses were also performed according to intervention duration, dose of supplementation and baseline level of CRP. Of 4734 potentially relevant studies, only 12 trials met the inclusion criteria with 246 participants in the intervention arms and 249 participants in control arms. Pooled analysis showed a significant reduction in CRP levels of 0.62 mg/l (95% confidence interval = -0.92, -0.31; P < 0.001) in vitamin E-treated individuals, with the evidence of heterogeneity across studies. This significant effect was maintained in all subgroups, although the univariate meta-regression analysis showed that the vitamin E supplementation dose, baseline level of CRP and duration of intervention were not the sources of the observed heterogeneity. The results of this meta-analysis suggest that supplementation with vitamin E in the form of either α-tocopherol or γ-tocopherol would reduce serum CRP levels.
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4.
Vitamin E concentration in human milk and associated factors: a literature review.
Lima, MS, Dimenstein, R, Ribeiro, KD
Jornal de pediatria. 2014;(5):440-8
Abstract
OBJECTIVE To systematize information about vitamin E concentration in human milk and the variables associated with this composition in order to find possible causes of deficiency, supporting strategies to prevent it in postpartum women and infants. SOURCE Studies published between 2004 and 2014 that assayed alpha-tocopherol in human milk of healthy women by high performance liquid chromatography were evaluated. The keywords used were "vitamin E", "alpha-tocopherol", "milk, human", "lactation", and equivalents in Portuguese, in the BIREME, CAPES, PubMed, SciELO, ISI Web of Knowledge, HighWire Press, Ingenta, and Brazilian Digital Library of Theses and Dissertations databases. SUMMARY OF THE FINDINGS Of the 41 publications found on the subject, 25 whose full text was available and met the inclusion criteria were selected. The alpha-tocopherol concentrations found in milk were similar in most populations studied. The variable phase of lactation was shown to influence vitamin E content in milk, which is reduced until the mature milk appears. Maternal variables parity, anthropometric nutritional status, socioeconomic status, and habitual dietary intake did not appear to affect the alpha-tocopherol levels in milk. However, the influence of the variables maternal age, gestational age, biochemical nutritional status in alpha-tocopherol, and maternal supplementation with vitamin E had conflicting results in the literature. CONCLUSION Alpha-tocopherol concentration in milk decreases during lactation, until the mature milk appears. To confirm the influence of some maternal and child variables on milk vitamin E content, further studies with adequate design are needed.
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5.
The mechanism of photoinhibition in vivo: re-evaluation of the roles of catalase, α-tocopherol, non-photochemical quenching, and electron transport.
Murata, N, Allakhverdiev, SI, Nishiyama, Y
Biochimica et biophysica acta. 2012;(8):1127-33
Abstract
Photoinhibition of photosystem II (PSII) occurs when the rate of light-induced inactivation (photodamage) of PSII exceeds the rate of repair of the photodamaged PSII. For the quantitative analysis of the mechanism of photoinhibition of PSII, it is essential to monitor the rate of photodamage and the rate of repair separately and, also, to examine the respective effects of various perturbations on the two processes. This strategy has allowed the re-evaluation of the results of previous studies of photoinhibition and has provided insight into the roles of factors and mechanisms that protect PSII from photoinhibition, such as catalases and peroxidases, which are efficient scavengers of H(2)O(2); α-tocopherol, which is an efficient scavenger of singlet oxygen; non-photochemical quenching, which dissipates excess light energy that has been absorbed by PSII; and the cyclic and non-cyclic transport of electrons. Early studies of photoinhibition suggested that all of these factors and mechanisms protect PSII against photodamage. However, re-evaluation by the strategy mentioned above has indicated that, rather than protecting PSII from photodamage, they stimulate protein synthesis, with resultant repair of PSII and mitigation of photoinhibition. This article is part of a Special Issue entitled: Photosynthesis Research for Sustainability: from Natural to Artificial.
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6.
Retinol, β-carotene, α-tocopherol and vitamin D status in European adolescents; regional differences an variability: a review.
Valtueña, J, Breidenassel, C, Folle, J, González-Gross, M
Nutricion hospitalaria. 2011;(2):280-8
Abstract
Currently, blood levels to define vitamin deficiency or optimal status in adolescents are extrapolated from adults. This may be not adequate as vitamin requirements during adolescence depend on the process of sexual maturation, rapid increasing height and weight, among other factors. In order to establish the state of the art, Medline database (www.ncvi.nlm.nih.gov) was searched for studies published in Europe between 1981 and 2010 related to liposoluble vitamin status in adolescents. A comparison of the vitamin status published in the reviewed articles was difficult due to the lack of studies, lack of consensus on cut-off levels indicating deficiency and optimal vitamin levels and the different age-ranges used. In spite of that, deficiency prevalence varied for vitamin D (13-72%), vitamin A (3%), E (25%) and β-carotene (14-19%). Additional factors were considered as possible determinants. We conclude that it is necessary to establish a consensus on acceptable ranges and cut-offs of these vitamins during adolescence. Representative data are still missing; therefore, there is a high need to get deeper into the investigation on liposoluble vitamins in this population group.
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7.
Regulation of xenobiotic metabolism, the only signaling function of alpha-tocopherol?
Traber, MG
Molecular nutrition & food research. 2010;(5):661-8
Abstract
There is growing concern based on meta-analyses of clinical trials using vitamin E supplements that these supplements increase the risk of all-cause mortality in humans. My laboratory has been investigating the metabolism and disposition of "excess" vitamin E. This review focuses on the various mechanisms that prevent vitamin E intoxication. Non-alpha-tocopherols are aggressively metabolized thereby preventing their tissue accumulation and limiting increases in their plasma concentrations. Moreover, "excess" alpha-tocopherol is also metabolized and its concentrations are limited. The mechanisms for this limitation do not seem to be specific for vitamin E, but rather are general xenobiotic pathways. We suggest that the most relevant cytochrome P450-mediated pathway is the one that is most important for the regulation and activation of vitamin K, specifically the one dependent on CYP4F2.
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8.
Monovalent inactivated split-virion AS03-adjuvanted pandemic influenza A (H1N1) vaccine.
Walker, WT, Faust, SN
Expert review of vaccines. 2010;(12):1385-98
Abstract
The first cases of pandemic influenza A (H1N1) 2009 infection were seen in Mexico in March 2009. Since then, it is thought to have been responsible for at least 18,337 deaths globally. Owing to the young age of fatalities, there have been an estimated 2 million years of life lost, which is comparable to the previous pandemics of 1957 and 1968. In this article, we consider the available data on a monovalent inactivated split-virion AS03-adjuvanted pandemic influenza A (H1N1) vaccine, Pandemrix™ (GlaxoSmithKline, Rixensart, Belgium). At present, Pandemrix appears to be highly immunogenic in all age groups, including children and infants under 3 years of age, with an acceptable safety profile in the context of an influenza pandemic. However, owing to the novel adjuvant, further studies on the safety, immunogenicity and vaccine effectiveness of Pandemrix together with robust post-marketing surveillance are required.
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9.
Micronutrients and diabetic retinopathy a systematic review.
Lee, CT, Gayton, EL, Beulens, JW, Flanagan, DW, Adler, AI
Ophthalmology. 2010;(1):71-8
Abstract
BACKGROUND We have evaluated the evidence for the association between intake and blood levels of micronutrients and diabetic retinopathy. Treatment for diabetic retinopathy requires significant clinical input and specialist ophthalmologic care. Micronutrients, including vitamin C, vitamin E, and magnesium, may interfere with pathologic mechanisms of diabetic retinopathy and potentially alter its risk. METHODS We conducted a search of epidemiologic literature in PubMed and Embase from 1988 to May 2008, using keywords for exposures, including magnesium, ascorbic acid, alpha-tocopherol and antioxidants, and outcomes, including diabetic retinopathy. Two authors independently extracted data and assessed the quality of the studies using the Newcastle-Ottawa Scale. The overall quality of evidence was graded as I (highest), II, or III (lowest). RESULTS Of the 766 studies identified, we reviewed 15 studies, comprising 4094 individuals. For vitamin C, hospital-based studies reported an inverse association between plasma levels with retinopathy, whereas population-based studies showed no association between dietary intake and retinopathy. For vitamin E, there was no association with dietary intake or plasma levels and retinopathy. For magnesium, a single prospective analysis showed an association between low levels in plasma and progression of retinopathy, but cross-sectional studies reported inconsistent results. In the assessment of quality, population-based studies had higher ratings than hospital-based studies. CONCLUSIONS The evidence suggests that dietary intake or plasma levels of vitamins C and E and magnesium do not seem to be associated with diabetic retinopathy. Because of differences in study designs and measurement of micronutrients, incomplete ascertainment of retinopathy, and residual confounding, these findings require confirmation. FINANCIAL DISCLOSURE(S): The authors have no proprietary or commercial interest in any of the materials discussed in this article.
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10.
Vitamin E transport, membrane incorporation and cell metabolism: Is alpha-tocopherol in lipid rafts an oar in the lifeboat?
Lemaire-Ewing, S, Desrumaux, C, Néel, D, Lagrost, L
Molecular nutrition & food research. 2010;(5):631-40
Abstract
Vitamin E is composed of closely related compounds, including tocopherols and tocotrienols. Studies of the last decade provide strong support for a specific role of alpha-tocopherol in cell signalling and the regulation of gene expression. It produces significant effects on inflammation, cell proliferation and apoptosis that are not shared by other vitamin E isomers with similar antioxidant properties. The different behaviours of vitamin E isomers might relate, at least in part, to the specific effects they exert at the plasma membrane. alpha-Tocopherol is not randomly distributed throughout the phospholipid bilayer of biological membranes, and as compared with other isomers, it shows a propensity to associate with lipid rafts. Distinct aspects of vitamin E transport and metabolism is discussed with emphasis on the interaction between alpha-tocopherol and lipid rafts and the consequences of these interactions on cell metabolism.