Vitamin E: the shrew waiting to be tamed

Lipophilic micronutrients and adipose tissue biology

Lipophilic micronutrients (LM) constitute a large family of molecules including several vitamins (A, D, E, K) and carotenoids. Their ability to regulate gene expression is becoming increasingly clear and constitutes an important part of nutrigenomics. Interestingly, adipose tissue is not only a main storage site for these molecules within the body, but it is also subjected to the regulatory effects of LM. Indeed, several gene regulations have been described in adipose tissue that could strongly impact its biology with respect to the modulation of adipogenesis, inflammatory status, or energy homeostasis and metabolism, among others. The repercussions in terms of health effects of such regulations in the context of obesity and associated pathologies represent an exciting and emerging field of research. The present review will focus on the regulatory effects of vitamin A, D, E and K as well as carotenoids on adipose tissue biology and physiology, notably in the context of obesity and associated disorders.

α-Tocopherol at nanomolar concentration protects PC12 cells from hydrogen peroxide-induced death and modulates protein kinase activities

The aim of this work was to compare protective and anti-apoptotic effects of α-tocopherol at nanomolar and micromolar concentrations against 0.2 mM H(2)O(2)-induced toxicity in the PC12 neuronal cell line and to reveal protein kinases that contribute to α-tocopherol protective action. The protection by 100 nM α-tocopherol against H(2)O(2)-induced PC12 cell death was pronounced if the time of pre-incubation with α-tocopherol was 3-18 h. For the first time, the protective effect of α-tocopherol was shown to depend on its concentration in the nanomolar range (1 nM < 10 nM < 100 nM), if the pre-incubation time was 18 h. Nanomolar and micromolar α-tocopherol decreased the number of PC12 cells in late apoptosis induced by H(2)O(2) to the same extent if pre-incubation time was 18 h. Immunoblotting data showed that α-tocopherol markedly diminished the time of maximal activation of extracellular signal-regulated kinase 1/2 (ERK 1/2) and protein kinase B (Akt)-induced in PC12 cells by H(2)O(2). Inhibitors of MEK 1/2, PI 3-kinase and protein kinase C (PKC) diminished the protective effect of α-tocopherol against H(2)O(2)-initiated toxicity if the pre-incubation time was long. The modulation of ERK 1/2, Akt and PKC activities appears to participate in the protection by α-tocopherol against H(2)O(2)-induced death of PC12 cells. The data obtained suggest that inhibition by α-tocopherol in late stage ERK 1/2 and Akt activation induced by H(2)O(2) in PC12 cells makes contribution to its protective effect, while total inhibition of these enzymes is not protective.

Vitamin E deficiency impairs the somatostatinergic receptor-effector system and leads to phosphotyrosine phosphatase overactivation and cell death in the rat hippocampus

Vitamin E plays an essential role in maintaining the structure and function of the nervous system, and its deficiency, commonly associated with fat malabsorption diseases, may reduce neuronal survival. We previously demonstrated that the somatostatinergic system, implicated in neuronal survival control, can be modulated by α-tocopherol in the rat dentate gyrus, increasing cyclic adenosine monophosphate response element binding protein phosphorylation. To gain a better understanding of the molecular actions of tocopherols and examine the link among vitamin E, somatostatin and neuronal survival, we have investigated the effects of a deficiency and subsequent administration of tocopherol on the somatostatin signaling pathway and neuronal survival in the rat hippocampus. No changes in somatostatin expression were detected in vitamin-E-deficient rats. These rats, however, showed a significant increase in the somatostatin receptor density and dissociation constant, which correlated with a significant increase in the protein levels of somatostatin receptors. Nevertheless, vitamin E deficiency impaired the ability of the somatostatin receptors to couple to the effectors adenylyl cyclase and phosphotyrosine phosphatase by diminishing Gi protein functionality. Furthermore, vitamin E deficiency significantly increased phosphotyrosine phosphatase activity and PTPη expression, as well as PKCδ activation, and decreased extracellular-signal-regulated kinase phosphorylation. All these changes were accompanied by an increase in neuronal cell death. Subsequent α-tocopherol administration partially or completely reversed all these values to control levels. Altogether, our results prove the importance of vitamin E homeostasis in the somatostatin receptor-effector system and suggest a possible mechanism by which this vitamin may regulate the neuronal cell survival in the adult hippocampus.

Inhibition of mitochondrial cytochrome c release and suppression of caspases by gamma-tocotrienol prevent apoptosis and delay aging in stress-induced premature senescence of skin fibroblasts

In this study, we determined the molecular mechanism of γ-tocotrienol (GTT) in preventing cellular aging by focusing on its anti-apoptotic effect in stress-induced premature senescence (SIPS) model of human diploid fibroblasts (HDFs). Results obtained showed that SIPS exhibited senescent-phenotypic characteristic, increased expression of senescence-associated β-galactosidase (SA β-gal) and promoted G₀/G₁ cell cycle arrest accompanied by shortening of telomere length with decreased telomerase activity. Both SIPS and senescent HDFs shared similar apoptotic changes such as increased Annexin V-FITC positive cells, increased cytochrome c release and increased activation of caspase-9 and caspase-3 (P < 0.05). GTT treatment resulted in a significant reduction of Annexin V-FITC positive cells, inhibited cytochrome c release and decreased activation of caspase-9 and caspase-3 (P < 0.05). Gene expression analysis showed that GTT treatment down regulated BAX mRNA, up-regulated BCL2A1 mRNA and decreased the ratio of Bax/Bcl-2 protein expression (P < 0.05) in SIPS. These findings suggested that GTT inhibits apoptosis by modulating the upstream apoptosis cascade, causing the inhibition of cytochrome c release from the mitochondria with concomitant suppression of caspase-9 and caspase-3 activation. In conclusion, GTT delays cellular senescence of human diploid fibroblasts through the inhibition of intrinsic mitochondria-mediated pathway which involved the regulation of pro- and anti-apoptotic genes and proteins.

Plasma and tissue concentrations of α-tocopherol and δ-tocopherol following high dose dietary supplementation in mice

Vitamin E isoforms are essential nutrients that are widely used as dietary supplements and therapeutic agents for a variety of diseases. However, their pharmacokinetic (PK) properties remain poorly characterized, and high dosage animal studies may provide further information on their in vivo functions and pharmacological effects. In this study, alpha-tocopherol (α-toc) and delta-tocopherol (δ-toc) levels were measured in mouse plasma and tissues following their high dosage dietary supplementation. Average α-toc levels at 5, 10 and 20 g α-toc/kg diet increased over baseline levels 6-fold in plasma, 1.6-fold in brain, and 4.9-fold in liver. These elevated α-toc concentrations remained constant from 5 to 20 g α-toc/kg diet, rather than showing further increases across these dosages. No α-toc-related toxicity occurred at these high dosages, and strain-specific differences in liver and brain α-toc levels between Balb/cJ and C57Bl/6J mice were observed. Relatively high-dosage administration of dietary δ-toc for 1 or 4 weeks resulted in 6-30-fold increases in plasma and liver levels between dosages of 0.33 and 1.67 g δ-toc/kg diet. Co-administration of sesamin with δ-toc further increased δ-toc levels between 1.3- and 14-fold in plasma, liver, and brain. These results provide valuable PK information on high dosage α-toc and δ-toc in mouse and show that supplementation of sesamin with δ-toc further increases δ-toc levels over those seen with δ-toc supplementation alone.

Conjugate addition of isocyanides to chromone 3-carboxylic acid: an efficient one-pot synthesis of chroman-4-one 2-carboxamides

We report a novel Lewis acid catalysed tandem reaction of isocyanides, chromone 3-carboxylic acid and nucleophiles. An experimentally very simple procedure, involving the use of microwave irradiation in the presence of a Lewis acid catalyst, affords a representative collection of chromone-2-carboxamides and chromone-2-carboxamido-3-esters in high yields, in just a few minutes. Such an unprecedented strategy is formally equivalent to a conjugate addition of isocyanides to Michael acceptors.

Vitamin E in aging, dementia, and Alzheimer's disease

Since its discovery, vitamin E has been extensively researched by a large number of investigators in an attempt to fully understand its role in a variety of pathophysiological contexts. The vast majority of published work has focused on vitamin E's antioxidant properties, which is why it is well known as a lipophilic antioxidant that protects membranes from being oxidatively damaged by free radicals. However, several lines of investigation have recently revealed that vitamin E has biological roles unrelated to its antioxidant properties. Among these roles, vitamin E has been described as: a regulator of signal transduction, gene expression, and redox sensor. In parallel with the discovery of novels cellular functions of vitamin E, the introduction of the free radical theory of brain aging has propelled a renewed interest in this vitamin. Most of the resulting work has been based on the postulate that, by preventing and/or minimizing the oxidative stress-dependent brain damage, vitamin E could be used as therapeutic approach. In this article, we will consider the existing literature regarding the biological properties of vitamin E and the potential therapeutic and/or preventative roles that this natural dietary factor plays in brain aging, cognition, and Alzheimer's dementia.

Reactive Secondary Sequence Oxidative Pathology Polymer Model and Antioxidant Tests

Aims

To provide common Organic Chemistry/Polymer Science thermoset free-radical crosslinking Sciences for Medical understanding and also present research findings for several common vitamins/antioxidants with a new class of drugs known as free-radical inhibitors.

Study Design

Peroxide/Fenton transition-metal redox couples that generate free radicals were combined with unsaturated lipid oils to demonstrate thermoset-polymer chain growth by crosslinking with the α-β-unsaturated aldehyde acrolein into rubbery/adhesive solids. Further, Vitamin A and beta carotene were similarly studied for crosslink pathological potential. Also, free-radical inhibitor hydroquinone was compared for antioxidant capability with Vitamin E.

Place and Duration of Study

Department of Materials Science and Engineering and Department of Biomaterials, University of Alabama at Birmingham, between June 2005 and August 2012.

Methodology

Observations were recorded for Fenton free-radical crosslinking of unsaturated lipids and vitamin A/beta carotene by photography further with weight measurements and percent-shrinkage testing directly related to covalent crosslinking of unsaturated lipids recorded over time with different concentrations of acrolein. Also, hydroquinone and vitamin E were compared at concentrations from 0.0–7.3wt% as antioxidants for reductions in percent-shrinkage measurements, n = 5.

Results

Unsaturated lipid oils responded to Fenton thermoset-polymer reactive secondary sequence reactions only by acrolein with crosslinking into rubbery-type solids and different non-solid gluey products. Further, molecular oxygen crosslinking was demonstrated with lipid peroxidation and acrolein at specially identified margins. By peroxide/Fenton free-radical testing, both vitamin A and beta-carotene demonstrated possible pathology chemistry for chain-growth crosslinking. During lipid/acrolein testing over a 50 hour time period at 7.3wt% antioxidants, hydroquinone significantly reduced percent shrinkage greatly compared to the standard antioxidant vitamin E, %shrinkage at 11.6 ±1.3 for hydroquinone and 27.8 ±2.2 for vitamin E, P = .001.

Conclusion

Free radicals crosslinked unsaturated lipid fatty acids into thermoset polymers through Fenton reactions when combined with acrolein. Further, hydroquinone was a superior antioxidant to vitamin E.

Vitamin E deficiency in developing countries

In addition to its role as a potent antioxidant, vitamin E is involved in a wide range of physiological processes, ranging from immune function and control of inflammation to regulation of gene expression and cognitive performance. Results from multiple studies suggest that poor nutritional status and higher prevalence of other oxidative stressors such as malaria and HIV infection predispose populations in developing countries for vitamin E deficiency. Although direct comparison between study outcomes is complicated by varied definitions of vitamin E deficiency, data trends indicate that children and the elderly are more vulnerable age groups and that men may be at higher risk for deficiency than women. Public health initiatives aimed at improving the vitamin E status of high-risk populations in developing countries would be prudent to counteract oxidative stress, improve immune function, and protect against neurologic and cognitive deficits. Additional research is needed to establish dose-response relationships of various interventions and to develop cost-effective, culturally-appropriate, and targeted programs.

Possible improvements in human ovarian grafting by various host and graft treatments

BACKGROUND

Anticancer treatment poses a high risk of ovarian failure. In many cases cryopreservation of ovarian tissue is the only option for fertility preservation. Although autologous transplantation of cryopreserved-thawed ovarian tissue has resulted in live births, slow graft revascularization and ischemia after transplantation leads to substantial follicular loss. Therefore, methods to improve and hasten graft vascularization are needed. The aim of the study was to examine the benefits of host and graft treatments with melatonin, hyaluronan (HA), vascular endothelial growth factor A (VEGF-A) and vitamin E with regard to the outcome of human ovarian tissue grafting.

METHODS

Five young cancer patients who underwent laparoscopic ovarian surgery for fertility preservation donated ovarian tissue. Thawed ovarian samples were transplanted into immunodeficient mice divided into seven groups: (A) no treatment; (B) host treatment with melatonin before and after grafting; (C) graft incubation with HA-rich biological glue before transplantation; (D) host as in (B), graft as in (C); (E) host as in (B), graft incubation with VEGF-A and vitamin E; (F) graft as in (C) combined with VEGF-A and vitamin E; (G) host as in (B), graft as in (F). Graft survival was assessed by follicle counts, apoptosis assay and immunohistochemical staining for proliferating cell nuclear antigen and VEGF-A expression.

RESULTS

Only grafts implanted in melatonin-treated hosts and grafts incubated with HA-rich biological glue retained their original size. Apoptosis was significantly lower after host treatment with melatonin and graft incubation with HA-rich biological glue plus VEGF-A and vitamin E than in untreated grafts; apoptosis was specifically low in Group G. There were significantly more atretic follicles in the untreated group than in most treated groups.

CONCLUSIONS

The findings suggest that host treatment with melatonin or graft incubation with HA-rich biological glue, especially when combined with VEGF-A and vitamin E improves graft survival. This protocol can be applied and holds promise in ovarian autotransplantation for fertility restoration.

α-tocopherol and α-tocopheryl phosphate interact with the cannabinoid system in the rodent hippocampus

α-Tocopherol (α-TOH), a dietary component of vitamin E, is well known for its antioxidant capacity. Nevertheless, recent studies have pointed out non-anti-radical properties including cellular and genomic actions. Decreased levels of α-tocopherol in the brain are associated with neuronal dysfunctions ranging from mood disorders to neurodegeneration. All these behavioral effects of α-tocopherol deficiency probably do not rely simply on its anti-radical properties, but could also be reminiscent of a not-yet characterized neuromodulatory action. We have thus measured the direct actions of α-tocopherol and of its natural phosphate derivative, α-tocopheryl phosphate (α-TP), on synaptic transmission in rodent hippocampus. These compounds had opposite actions on both glutamatergic and GABAergic transmission: whereas α-TOH potentiated these transmissions, α-TP inhibited them. Interestingly, these effects were both mediated by cannabinoid receptors (CB1Rs), because they were blocked by the CB1R antagonist AM251. Although α-tocopherol and α-tocopheryl phosphate did not directly bind CB1R, both α-TP and CB1R agonists inhibited forskolin-evoked Erk1/2 phosphorylation in a nonadditive manner. Furthermore, both α-tocopherol and α-tocopheryl phosphate attenuated depolarization-induced suppression of excitation and CB1R agonist-mediated hypothermia. Therefore, we identify α-tocopherol as new lipid modulator of the cannabinoid system in the rodent hippocampus, i.e., a novel "non-anti-radical" action of vitamin E, which may have some preeminent impact in neuronal disorders associated with vitamin E deficiency.

Synthetic chromanol derivatives and their interaction with complex III in mitochondria from bovine, yeast, and Leishmania

Synthetic chromanol derivatives (TMC4O, 6-hydroxy-2,2,7,8-tetramethyl-chroman-4-one; TMC2O, 6-hydroxy-4,4,7,8-tetramethyl-chroman-2-one; and Twin, 1,3,4,8,9,11-hexamethyl-6,12-methano-12H-dibenzo[d,g][1,3]dioxocin-2,10-diol) share structural elements with the potent inhibitor of the mitochondrial cytochrome (cyt) bc(1) complex stigmatellin. Studies with isolated bovine cyt bc(1) complex demonstrated that these compounds partially inhibit the mammalian enzyme. The aim of this work was to comparatively investigate these toxicological aspects of synthetic vitamin E derivatives in mitochondria of different species. The chromanols and atovaquone as reference compound were evaluated for their inhibition of the cyt bc(1) activity in mitochondrial fractions from bovine hearts, yeast, and Leishmania. In addition, compounds were evaluated in vitro for their inhibitory activity against whole-cell Leishmania and mouse peritoneal macrophages. In these organisms, the chromanols showed a species-selective inhibition of the cyt bc(1) activity different from that of atovaquone. While in atovaquone the side chain mediates species-selectivity, the marked differences for TMC2O and TMC4O in cyt bc(1) inhibition suggests that direct substitution of the chromanol headgroup will control selectivity in these compounds. Low micromolar concentrations of TMC2O (IC(50) = 9.5 ± 0.5 μM) inhibited the growth of Leishmania, and an esterified TMC2CO derivative inhibited the cyt bc(1) activity with an IC(50) of 4.9 ± 0.9 μM. These findings suggest that certain chromanols also exhibit beyond their antioxidative properties antileishmanial activities and that TMC2O derivatives could be useful toward the development of highly active antiprotozoal compounds.

An (1)O2 route to γ-hydroxyalkenal phospholipids by vitamin E-induced fragmentation of hydroperoxydiene-derived endoperoxides

Biologically active phospholipids that incorporate an oxidatively truncated acyl chain terminated by a γ-hydroxyalkenal are generated in vivo. The γ-hydroxyalkenal moiety protrudes from lipid bilayers like whiskers that serve as ligands for the scavenger receptor CD36, fostering endocytosis, e.g., of oxidatively damaged photoreceptor cell outer segments by retinal pigmented endothelial cells. They also covalently modify proteins generating carboxyalkyl pyrroles incorporating the ε-amino group of protein lysyl residues. We postulated that γ-hydroxyalkenals could be generated, e.g., in the eye, through fragmentation of hydroperoxy endoperoxides produced in the retina through reactions of singlet molecular oxygen with polyunsaturated phospholipids. Since phospholipid esters are far more abundant in the retina than free fatty acids, we examined the influence of a membrane environment on the fate of hydroperoxy endoperoxides. We now report that linoleate hydroperoxy endoperoxides in thin films and their phospholipid esters in biomimetic membranes fragment to γ-hydroxyalkenals, and fragmentation is stoichiometrically induced by vitamin E. The product distribution from fragmentation of the free acid in the homogeneous environment of a thin film is remarkably different from that from the corresponding phospholipid in a membrane. In the membrane, further oxidation of the initially formed γ-hydroxyalkenal to a butenolide is disfavored. A conformational preference for the γ-hydroxyalkenal, to protrude from the membrane into the aqueous phase, may protect it from oxidation induced by lipid hydroperoxides that remain buried in the lipophilic membrane core.

Dietary supplementation with α-tocopherol reduces neuroinflammation and neuronal degeneration in the rat brain after kainic acid-induced status epilepticus

Vitamin E (as α-tocopherol, α-T) is proposed to alleviate glia-mediated inflammation in neurological diseases, but such a role in epilepsy is still elusive. This study investigated the effect of α-T supplementation on glial activation, neuronal cell death and oxidative stress of rat brain exposed to kainate-induced seizures. Animals were fed for 2 weeks with a α-T-enriched diet (estimated intake of 750 mg/kg/day) before undergoing status epilepticus. Compliance to supplementation was demonstrated by the remarkable increase in brain α-T. Four days after seizure, brain α-T returned to baseline and lipid peroxidation markers decreased as compared to non-supplemented rats. Status epilepticus induced a lower up-regulation of astrocytic and microglial antigens (GFAP and MHC II, respectively) and production of pro-inflammatory cytokines (IL-1β and TNF-α) in supplemented than in non-supplemented animals. This anti-inflammatory effect was associated with a lower neuronal cell death. In conclusion, α-T dietary supplementation prevents oxidative stress, neuroglial over-activation and cell death occurring after kainate-induced seizures. This evidence paves the way to an anti-inflammatory and neuroprotective role of α-T interventions in epilepsy.

Nitric oxide mimics transcriptional and post-translational regulation during α-tocopherol cytoprotection against glycochenodeoxycholate-induced cell death in hepatocytes

BACKGROUND & AIMS

Reactive oxygen species (ROS) and nitric oxide (NO) exert a relevant role during bile acid-induced hepatotoxicity. Whether α-Tocopherol regulates oxidative and nitrosative stress, bile acid transporter expression and their NO-dependent post-translational modifications, and cell death were assessed in vitro and in vivo.

METHODS

α-Tocopherol and/or NO donors (DETA-NONOate or CSNO, and V-PYRRO/NO) were administered to glycochenodeoxycholic acid (GCDCA)-treated cultured human hepatocytes or to bile duct obstructed rats. Cell injury, superoxide anion (O⁻₂) production, as well as inducible nitric oxide synthase (NOS-2), cytochrome P4507A1 (CYP7A1), heme oxygenase-1, (HO-1) and bile acid transporter expression were determined. Cysteine S-nitrosylation and tyrosine nitration of Na(+)-taurocholate co-transporting polypeptide (NTCP), as well as taurocholic acid (TC) uptake were also evaluated.

RESULTS

GCDCA-induced cell death was associated with increased (O⁻₂) production, NTCP and HO-1 expression, and with a reduction of CYP7A1 and NOS-2 expression. α-Tocopherol reduced cell death, (O⁻₂) production, CYP7A1, NTCP, and HO-1 expression, as well as increased NOS-2 expression and NO production in GCDCA-treated hepatocytes. α-Tocopherol and NO donors increased NTCP cysteine S-nitrosylation and tyrosine nitration, and reduced TC uptake in hepatocytes. α-Tocopherol and V-PYRRO/NO reduced liver injury and NTCP expression in obstructed rats.

CONCLUSIONS

The regulation of CYP7A1, NTCP, and HO-1 expression may be relevant for the cytoprotective properties of α-Tocopherol and NO against mitochondrial dysfunction, oxidative stress and cell death in GCDCA-treated hepatocytes. The regulation of NO-dependent post-translational modifications of NTCP by α-Tocopherol and NO donors reduces the uptake of toxic bile acids by hepatocytes.

Effects of vitamin E supplementation on some pregnancy health indices: a randomized clinical trial

Objective:

Available evidence about the role of supplementary vitamin E in normal pregnancy is inadequate. This study assessed the potential benefit of vitamin E supplementation on some pregnancy health indices.

Methods:

A 1:2 weighted simple randomization technique was used to allocate 104 eligible pregnant women to receive vitamin E and 168 women (control) not to receive the drug. Treated women received capsules containing 400 IU vitamin E from week 14 of gestation to the end of the pregnancy.

Results:

Background variables including maternal age were found to be similarly distributed between the study groups. The rate of maternal and perinatal outcomes including Apgar score and birth weight did not differ significantly between groups. Preeclampsia occurred in 1% of treated women vs 1.78% of control women.

Conclusion:

Giving supplemental vitamin E from the second trimester of pregnancy did not appear to affect the risk of pregnancy outcomes and occurrence of preeclampsia.

Trace elements and vitamins at diagnosis in pediatric-onset inflammatory bowel disease

AIM

To compare serum vitamin and mineral levels at diagnosis in children with inflammatory bowel disease (IBD) versus a control group without.

METHODS

In a retrospective cohort study, serum levels of iron, zinc, folate, selenium, vitamin B( 12), vitamin A, and vitamin E in children with IBD at diagnosis were compared with gender- and age-matched controls.

RESULTS

A total of 154 patients with IBD (mean age 11.27 ± 3.74 years, 83 boys, 80 with Crohn's disease) were recruited. The mean duration of symptoms prior to diagnosis was 5.4 ± 3.2 months for patients with Crohn's disease and 4.6 ± 2.9 months for patients with ulcerative colitis. A control group of 64 children was recruited. The mean serum zinc levels were 11.33 ± 4.16 µmol/L for ulcerative colitis, 8.74 ± 2.08 µmol/L for Crohn's disease and 11.49 ± 1.63 µmol/L for controls (P < .001).

CONCLUSIONS

In newly diagnosed children with IBD, serum zinc levels are significantly lower compared with children without IBD.

Improving posttransplantation survival of human ovarian tissue by treating the host and graft

OBJECTIVE

To improve posttransplantation survival of frozen-thawed human ovarian tissue in immunodeficient mice.

DESIGN

Histologic study of transplanted human ovaries after treating the host and graft.

SETTING

Infertility unit, university-affiliated tertiary medical center.

PATIENT(S)

Ovarian tissue from six girls/women (aged 5-23 years) who had undergone ovarian laparoscopy for fertility preservation.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Thawed ovarian samples were transplanted into the back muscle of immunodeficient mice divided into four groups: A) no treatment; B) host treatment with vitamin E and gonadotropins before and after grafting; C) graft incubation with vascular endothelial growth factor A (VEGF-A) and vitamin E before transplantation; and D) host as in B, graft as in C. Ungrafted thawed samples served as control. Assessment of graft survival was conducted by follicle counts, apoptosis evaluation, immunohistochemical stainings for proliferating cell nuclear antigen (PCNA) and VEGF-A expression.

RESULT(S)

Only grafts incubated before transplantation (groups C and D) retained their original size. Follicle number was low in all grafts. PCNA expression was found in most grafts. Apoptosis was significantly lower in the untreated and treated grafts transplanted into treated hosts (groups B and D) than in ungrafted-thawed samples and group A grafts. All grafted groups had significantly higher expression of VEGF-A than ungrafted-thawed samples.

CONCLUSION(S)

Survival of transplanted human ovarian tissue may be improved by treatment of the host and graft. Further studies to evaluate treatments with a potential benefit in human ovarian autotransplantation are needed.

α-Tocopherol impairs 7-ketocholesterol-induced caspase-3-dependent apoptosis involving GSK-3 activation and Mcl-1 degradation on 158N murine oligodendrocytes

In important and severe neurodegenerative pathologies, 7-ketocholesterol, mainly resulting from cholesterol autoxidation, may contribute to dys- or demyelination processes. On various cell types, 7-ketocholesterol has often been shown to induce a complex mode of cell death by apoptosis associated with phospholipidosis. On 158N murine oligodendrocytes treated with 7-ketocholesterol (20 μg/mL corresponding to 50 μM, 24-48 h), the induction of a mode of cell death by apoptosis characterised by the occurrence of cells with condensed and/or fragmented nuclei, caspase activation (including caspase-3) and internucleosomal DNA fragmentation was observed. It was associated with a loss of transmembrane mitochondrial potential (ΔΨm) measured with JC-1, with a dephosphorylation of Akt and GSK3 (especially GSK3β), and with degradation of Mcl-1. With α-tocopherol (400 μM), which was capable of counteracting 7-ketocholesterol-induced apoptosis, Akt and GSK3β dephosphorylation were inhibited as well as Mcl-1 degradation. These data underline that the potential protective effects of α-tocopherol against 7-ketocholesterol-induced apoptosis do not depend on the cell line considered, and that the cascade of events (Akt/GSK3β/Mcl-1) constitutes a link between 7-ketocholesterol-induced cytoplasmic membrane dysfunctions and mitochondrial depolarisation leading to apoptosis.

Key roles of vitamins A, C, and E in aflatoxin B1-induced oxidative stress

Aflatoxins (Aspergillus flavus toxins) are one of the natural toxic molecules which are produced by a group of fungi called Aspergillus. Foods and drinks contaminated with aflatoxins cause global health and environmental problems. Today in many developing countries, these toxins are leading cause of some liver cancers and serious gastrointestinal problems. Aflatoxins, which are well known to be mutagenic, carcinogenic, hepatotoxic, and immunosuppressive, exert inhibitory effects on biological processes including DNA synthesis, DNA-dependent RNA synthesis, DNA repair, and protein synthesis. Aflatoxins B(1) (AFB(1)) is the most widespread oxidative agent of the aflatoxins. Numerous diverse compounds and extracts have been reported to reduce the aflatoxins induced oxidative stress in the body. Most of these inhibitors including phenylpropanoids, terpenoids, alkaloids, and vitamins are originally derived from plants. Among these, being essential biomolecules, vitamins are used as coenzymes in very significant biological reactions. They also function as nonenzymatic antioxidative agents protecting the cells from oxidative stress-induced toxicity and transformation. This chapter reviews the mechanism of AFB(1)-induced oxidative stress and focuses on the protective effects of vitamins A, C, and E on reducing this stress.

Isotope-reinforced polyunsaturated fatty acids protect yeast cells from oxidative stress

The facile abstraction of bis-allylic hydrogens from polyunsaturated fatty acids (PUFAs) is the hallmark chemistry responsible for initiation and propagation of autoxidation reactions. The products of these autoxidation reactions can form cross-links to other membrane components and damage proteins and nucleic acids. We report that PUFAs deuterated at bis-allylic sites are much more resistant to autoxidation reactions, because of the isotope effect. This is shown using coenzyme Q-deficient Saccharomyces cerevisiae coq mutants with defects in the biosynthesis of coenzyme Q (Q). Q functions in respiratory energy metabolism and also functions as a lipid-soluble antioxidant. Yeast coq mutants incubated in the presence of the PUFA α-linolenic or linoleic acid exhibit 99% loss of colony formation after 4h, demonstrating a profound loss of viability. In contrast, coq mutants treated with monounsaturated oleic acid or with one of the deuterated PUFAs, 11,11-D(2)-linoleic or 11,11,14,14-D(4)-α-linolenic acid, retain viability similar to wild-type yeast. Deuterated PUFAs also confer protection to wild-type yeast subjected to heat stress. These results indicate that isotope-reinforced PUFAs are stabilized compared to standard PUFAs, and they protect coq mutants and wild-type yeast cells against the toxic effects of lipid autoxidation products. These findings suggest new approaches to controlling ROS-inflicted cellular damage and oxidative stress.

Vegetarian diets and public health: biomarker and redox connections

Vegetarian diets are rich in antioxidant phytochemicals. However, they may not act as antioxidants in vivo, and yet still have important signaling and regulatory functions. Some may act as pro-oxidants, modulating cellular redox tone and oxidizing redox sensitive sites. In this review, evidence for health benefits of vegetarian diets is presented from different perspectives: epidemiological, biomarker, evolutionary, and public health, as well as antioxidant. From the perspective of molecular connections between diet and health, evidence of a role for plasma ascorbic acid as a biomarker for future disease risk is presented. Basic concepts of redox-based cell signaling are presented, and effects of antioxidant phytochemicals on signaling, especially via redox tone, sulfur switches and the Antioxidant Response Element (ARE), are explored. Sufficient scientific evidence exists for public health policy to promote a plant-rich diet for health promotion. This does not need to wait for science to provide all the answers as to why and how. However, action and interplay of dietary antioxidants in the nonequilibrium systems that control redox balance, cell signaling, and cell function provide rich ground for research to advance understanding of orthomolecular nutrition and provide science-based evidence to advance public health in our aging population.

Antioxidant vitamins and their use in preventing cardiovascular disease

Atherosclerosis remains one of the leading causes of death in Western populations. Subsequent to the discovery that oxidative stress plays a pivotal role in the development and progression of atherosclerosis, vitamins C and E, along with other antioxidants, were studied as potential therapies for the disease. However, while in vitro and in vivo studies showed promising antiatherogenic effects for vitamins C and E, clinical trials in which patients were given high doses of vitamin E or C showed no benefit and even possible harm. This review will attempt to summarize the known mechanistic data regarding the biochemical effects of vitamins C and E and their relevance to atherosclerosis, and offer an explanation for the failure of clinical trials to show that supplementation with these vitamins provides any benefit when given indiscriminately. We provide one example of how pharmacogenomics may be used to identify a sub-population which may indeed benefit from antioxidant supplementation.

Effects of vitamin E on stroke subtypes: meta-analysis of randomised controlled trials

OBJECTIVE

To evaluate the effect of vitamin E supplementation on incident total, ischaemic, and haemorrhagic stroke.

DESIGN

Systematic review and meta-analysis of randomised, placebo controlled trials published until January 2010.

DATA SOURCES

Electronic databases (Medline, Embase, Cochrane Central Register of Controlled Trials) and reference lists of trial reports. Selection criteria Randomised, placebo controlled trials with ≥1 year of follow-up investigating the effect of vitamin E on stroke. Review methods and data extraction Two investigators independently assessed eligibility of identified trials. Disagreements were resolved by consensus. Two different investigators independently extracted data. Risk ratios (and 95% confidence intervals) were calculated for each trial based on the number of cases and non-cases randomised to vitamin E or placebo. Pooled effect estimates were then calculated.

RESULTS

Nine trials investigating the effect of vitamin E on incident stroke were included, totalling 118 765 participants (59 357 randomised to vitamin E and 59 408 to placebo). Among those, seven trials reported data for total stroke and five trials each for haemorrhagic and ischaemic stroke. Vitamin E had no effect on the risk for total stroke (pooled relative risk 0.98 (95% confidence interval 0.91 to 1.05), P=0.53). In contrast, the risk for haemorrhagic stroke was increased (pooled relative risk 1.22 (1.00 to 1.48), P=0.045), while the risk of ischaemic stroke was reduced (pooled relative risk 0.90 (0.82 to 0.99), P=0.02). There was little evidence for heterogeneity among studies. Meta-regression did not identify blinding strategy, vitamin E dose, or morbidity status of participants as sources of heterogeneity. In terms of absolute risk, this translates into one additional haemorrhagic stroke for every 1250 individuals taking vitamin E, in contrast to one ischaemic stroke prevented per 476 individuals taking vitamin E.

CONCLUSION

In this meta-analysis, vitamin E increased the risk for haemorrhagic stroke by 22% and reduced the risk of ischaemic stroke by 10%. This differential risk pattern is obscured when looking at total stroke. Given the relatively small risk reduction of ischaemic stroke and the generally more severe outcome of haemorrhagic stroke, indiscriminate widespread use of vitamin E should be cautioned against.

Antioxidant therapy attenuates oxidative stress in the blood of subjects exposed to occupational airborne contamination from coal mining extraction and incineration of hospital residues

Coal mining and incineration of solid residues of health services (SRHS) generate several contaminants that are delivered into the environment, such as heavy metals and dioxins. These xenobiotics can lead to oxidative stress overgeneration in organisms and cause different kinds of pathologies, including cancer. In the present study the concentrations of heavy metals such as lead, copper, iron, manganese and zinc in the urine, as well as several enzymatic and non-enzymatic biomarkers of oxidative stress in the blood (contents of lipoperoxidation = TBARS, protein carbonyls = PC, protein thiols = PT, α-tocopherol = AT, reduced glutathione = GSH, and the activities of glutathione S-transferase = GST, glutathione reductase = GR, glutathione peroxidase = GPx, catalase = CAT and superoxide dismutase = SOD), in the blood of six different groups (n = 20 each) of subjects exposed to airborne contamination related to coal mining as well as incineration of solid residues of health services (SRHS) after vitamin E (800 mg/day) and vitamin C (500 mg/day) supplementation during 6 months, which were compared to the situation before the antioxidant intervention (Ávila et al., Ecotoxicology 18:1150-1157, 2009; Possamai et al., Ecotoxicology 18:1158-1164, 2009). Except for the decreased manganese contents, heavy metal concentrations were elevated in all groups exposed to both sources of airborne contamination when compared to controls. TBARS and PC concentrations, which were elevated before the antioxidant intervention decreased after the antioxidant supplementation. Similarly, the contents of PC, AT and GSH, which were decreased before the antioxidant intervention, reached values near those found in controls, GPx activity was reestablished in underground miners, and SOD, CAT and GST activities were reestablished in all groups. The results showed that the oxidative stress condition detected previously to the antioxidant supplementation in both directly and indirectly subjects exposed to the airborne contamination from coal dusts and SRHS incineration, was attenuated after the antioxidant intervention.

Plasma phospholipid transfer protein deficiency in mice is associated with a reduced thrombotic response to acute intravascular oxidative stress

OBJECTIVE

Earlier in vitro studies suggested a putative role for the plasma phospholipid transfer protein (PLTP) in the modulation of blood coagulation. The effect of PLTP expression on blood coagulation under both basal and oxidative stress conditions was compared here in wild-type and PLTP-deficient (PLTP-/-) mice.

METHODS AND RESULTS

Under basal conditions, PLTP deficiency was associated with an extended tail bleeding time despite a significant depletion of vascular α-tocopherol content and an impairment of endothelial function. When acute oxidative stress was generated in vivo in the brain vasculature, the steady state levels of oxidized lipid derivatives, the extent of blood vessel occlusion, and the volume of ischemic lesions were more severe in wild-type than in PLTP-/- mice.

CONCLUSIONS

In addition to its recognized hyperlipidemic, proinflammatory, and proatherogenic properties, PLTP increases blood coagulation and worsens the extent of ischemic lesions in response to acute oxidative stress. Thus, PLTP arises here as a cardiovascular risk factor for the late thrombotic events occurring in the acute phase of atherosclerosis.

alpha-Tocopherol enhances degranulation in RBL-2H3 mast cells

Based on the observation that 3 months alpha-tocopherol supplementation caused an up-regulation of the mRNA of vesicular transport proteins in livers of mice, the functional relevance was investigated in RBL-2H3 cells, a model for mast cell degranulation. In total, 24 h incubation with 100 muM alpha-tocopherol enhanced the basal and phorbol-12-myristyl-13-acetate/ionomycin-stimulated release of beta-hexosaminidase and cathepsin D as measured by enzymatic analysis as well as Western blotting and immunocytochemistry, respectively. beta-Tocopherol exerted the same effect, whereas alpha-tocopheryl phosphate and trolox were inactive, indicating that both the side chain and the 6-OH group at the chroman ring are essential for activation of degranulation. alpha-Tocopherol did not induce mRNA expression of soluble NSF-attachment protein receptor (soluble N-ethylmaleimide-sensitive factor-attachment protein receptor) proteins, such as N-ethylmaleimide sensitive fusion protein, complexin-2, SNAP23 or syntaxin-3, in the RBL-2H3 cell model. In view of the well known alpha-tocopherol-mediated activation of protein phosphatases, which regulate soluble NSF-attachment protein receptor activities by dephosphorylation, underlying mechanisms are discussed in terms of preventing oxidative inactivation of protein phosphatases and so far unknown functions in certain membrane domains.

Vitamin E and neurological function

The clinical, neuropathological and electrophysiological evidence that vitamin E (alpha-tocopherol) is essential for normal neurological function will be reviewed. The possible reasons why neural tissues should be particularly affected by a deficiency of this fat-soluble vitamin and the mechanism(s) involved will be considered.

Vitamin E transport, membrane incorporation and cell metabolism: Is alpha-tocopherol in lipid rafts an oar in the lifeboat?

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.

Tocopheryl quinones and mitochondria

In the past, the role of tocopherols and tocopheryl hydroquinones as antioxidants in mitochondria has been examined. However, structural properties of tocopherols and tocopheryl quinones (arrangement of polar/apolar moieties) have also been recognized as being crucial for the selective transport of RRR-alpha-congeners compared with other tocopherols in the cell, suggesting that these properties might be generally important for the binding of vitamin E-related compounds to proteins and enzymes in mitochondria. Therefore, direct modulation of mitochondrial activities, such as bioenergetics, production of reactive oxygen species and apoptosis, not exclusively related to the redox activity of these compounds is increasingly studied. This overview focuses on the influence of alpha-/gamma-tocopheryl quinones and their parent alpha-/gamma-tocopherols on mitochondrial functions, including formation of tocopheryl quinones, their analytical aspects, their potential as alternative substrates and their inhibitory activity for some mitochondrial functions. It is shown that the understanding of how tocopheryl quinones and tocopherols interfere with mitochondrial functions on the molecular level is still incomplete and that a better comprehension requires further research activities.

alpha-Tocopheryl phosphate--an active lipid mediator?

The vitamin E (alpha-tocopherol, alphaT) derivative, alpha-tocopheryl phosphate (alphaTP), is detectable in small amounts in plasma, tissues, and cultured cells. Studies done in vitro and in vivo suggest that alphaT can become phosphorylated and alphaTP dephosphorylated, suggesting the existence of enzyme(s) with alphaT kinase or alphaTP phosphatase activity, respectively. As a supplement in animal studies, alphaTP can reach plasma concentrations similar to alphaT and only a part is dephosphorylated; thus, alphaTP may act both as pro-vitamin E, but also as phosphorylated form of vitamin E with possibly novel regulatory activities. Many effects of alphaTP have been described: in the test tube alphaTP modulates the activity of several enzymes; in cell culture alphaTP affects proliferation, apoptosis, signal transduction, and gene expression; in animal studies alphaTP prevents atherosclerosis, ischemia/reperfusion injury, and induces hippocampal long-term potentiation. At the molecular level, alphaTP may act as a cofactor for enzymes, as an active lipid mediator similar to other phosphorylated lipids, or indirectly by altering membrane characteristics such as lipid rafts, fluidity, and curvature. In this review, the molecular and cellular activities of alphaTP are examined and the possible functions of alphaTP as a natural compound, cofactor and active lipid mediator involved in signal transduction and gene expression discussed.

The location and behavior of alpha-tocopherol in membranes

Vitamin E (alpha-tocopherol) has long been recognized as the major antioxidant in biological membranes, and yet many structurally related questions persist of how the vitamin functions. For example, the very low levels of alpha-tocopherol reported for whole cell extracts question how this molecule can successfully protect the comparatively enormous quantities of PUFA-containing phospholipids found in membranes that are highly susceptible to oxidative attack. The contemporary realization that membranes laterally segregate into regions of distinct lipid composition (domains), we propose, provides the answer. We hypothesize alpha-tocopherol partitions into domains that are enriched in polyunsaturated phospholipids, amplifying the concentration of the vitamin in the place where it is most needed. These highly disordered domains depleted in cholesterol are analogous, but organizationally antithetical, to the well-studied lipid rafts. We review here the ideas that led to our hypothesis. Experimental evidence in support of the formation of PUFA-rich domains in model membranes is presented, focusing upon docosahexaenoic acid that is the most unsaturated fatty acid commonly found. Physical methodologies are then described to elucidate the nature of the interaction of alpha-tocopherol with PUFA and to establish that the vitamin and PUFA-containing phospholipids co-localize in non-raft domains.

Antioxidant intervention compensates oxidative stress in blood of subjects exposed to emissions from a coal electric-power plant in South Brazil

In the process of energy generation, particulate matter (PM) emissions derived from coal combustion expose humans to serious occupational diseases, which are associated with overgeneration of reactive oxygen species (ROS). The purpose of the present study is to better understand the relations between PM exposure derived from a coal electric-power plant and the oxidative damage in subjects (n=20 each group) directly (working at the burning area) or indirectly (working at the office or living in the vicinity of the electric-power plant=group of residents) exposed to airborne contamination, before and after daily supplementation with vitamins C (500mg) and E (800mg) during six months, which were compared to non-exposed subjects (control group). Several biomarkers of oxidative stress were examined such as levels of thiobarbituric acid reactive substances (TBARS), protein carbonyls (PC), protein thiols (PT) and vitamin E in plasma, levels of reduced glutathione (GSH) in whole blood, and of activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR) and glutathione S-transferase (GST) in red cells. Before supplementation, TBARS and PC levels were significantly increased, levels of GSH and vitamin E were decreased, while the activities of SOD and CAT were increased in workers groups and GST were increased in all groups in compared to controls. After the antioxidant supplementation essentially all these biomarkers were normalized to control levels. The antioxidant intervention was able to confer a protective effect of vitamins C and E against the oxidative insult associated with airborne contamination derived from coal burning of an electric-power plant.

Dietary vitamin E deficiency does not affect global and specific DNA methylation patterns in rat liver

The aim of the present study was to determine the effects of a 6-month dietary vitamin E (VE) deficiency on DNA methylation and gene expression in rat liver. Two enzymes, 5-α-steroid reductase type 1 (SRD5A1) and the regulatory subunit of γ-glutamylcysteinyl synthetase (GCLM), which are differentially expressed on the mRNA level, were analysed for promoter methylation in putative cytosine-phospho-guanine (CpG) island regions located at the 5′ end using base-specific cleavage and matrix-assisted laser desorption ionisation time-of-flight MS. A twofold increase in the mRNA level of SRD5A1 gene and a twofold decrease in the mRNA level of GCLM gene in VE-deficient animals were not associated with different CpG methylation of the analysed promoter region. Furthermore, global DNA methylation was not significantly different in these two groups. Thus, the present results indicate that the VE-induced regulation of SRD5A1 and GCLM in rat liver is not directly mediated by changes in promoter DNA methylation.

Interactions between dietary vitamin E intake and SIRT1 genetic variation influence body mass index

BACKGROUND

Genetic variation in SIRT1 has been associated with body mass index (BMI) and risk of obesity. SIRT1 may be influenced by diet.

OBJECTIVE

We studied the gene-diet interaction on BMI at the SIRT1 locus.

DESIGN

In 4575 elderly men and women in the population-based Rotterdam Study, the effect on BMI of 3 SIRT1 genetic variants (rs7895833, rs1467568, and haplotype 1) was studied in relation to dietary intakes of energy, fat, calcium, milk, antioxidant vitamins, and niacin.

RESULTS

There was no difference in energy or fat intakes by SIRT1 genotype. Significant interactions for BMI were shown between SIRT1 genetic variants and intakes of fat, vitamin E, calcium, and milk. Only the interactions between vitamin E intake and rs1467568 and haplotype 1 remained significant (P < 0.001) after Bonferroni correction for multiple testing. Further analyses across vitamin E-intake tertiles showed highly significant associations of SIRT1 genetic variants with BMI in the lowest tertile [effect sizes (in kg/m(2)): 0.5-0.7 per allele copy; P = 1.9 x 10(-4)-5.7 x 10(-7)] with no associations in the higher tertiles.

CONCLUSIONS

Dietary vitamin E intake may modulate the relation of SIRT1 genetic variants with BMI. Associations of SIRT1 variants with BMI in the lowest tertile of vitamin E intake may be explained by low intake of this antioxidant vitamin or by other associated dietary or lifestyle habits. These data provide support that gene-diet interactions influence BMI. Replication of our findings and further in-depth studies of dietary patterns that modify SIRT1 may lead to clinical studies of dietary modification of SIRT1 to influence obesity.

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.