Unveiling the antioxidant superiority of α-tocopherol: Implications for vitamin E nomenclature and classification

Since the discovery of tocopherols a century ago, α-tocopherol has been distinguished for its unique biological functions. In this study, we aim to elucidate the unique characteristics of α-tocopherol from a chemical perspective. Utilizing density functional theory (DFT) calculations, we evaluated the thermodynamic and kinetic properties of tocopherols, tocotrienols and their oxidation products. Our findings highlight the superior thermodynamic and kinetic properties of α-tocopherol. Although tocopherol substrates generally exhibit similar reactivities, α-tocopherol is distinguished by a larger gap between the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) in intermediates, indicating a potential for greater energy release and favoring reaction progression. Moreover, α-tocopherol shows enhanced efficiency in quenching radical intermediates, especially when combined with vitamin C. All these dates provide valuable support for the naming of vitamin E.

A new RPLC-ESI-MS method for the determination of eight vitamers of vitamin E

Vitamin E consists of four (α-, β-, γ-, δ-) isoforms of tocopherols (T) and tocotrienols (T3), collectively known as tocols. Current LC methods for tocols suffer from either the poor ability to resolve the β- and γ- isoforms (RPLC), or require the use of nonpolar solvents (NPLC), which complicates subsequent MS/MS detection. Moreover, we show that coupling of UV with MS leads to tocols photodegradation. To solve these problems, we developed a new RPLC-MS/MS method, allowing to resolve not only α- and δ-, but also β- and γ- tocols in hydrophobic matrices. We took advantage of an observation that the peak area ratios are specific for the given isomer and constant. The new method with a linear range between 0.2 and 60 ng·mL-1 (for α-T) and 1.1-60 ng·mL-1 (for β-T3 and γ-T3) was validated and employed for quantitative analysis of several oils, including false flax (Camelina sativa) oil stored under different conditions.

α-Tocotrienol in rice bran enhances steroidogenesis in mouse Leydig cell via increased gene expression of steroidogenic acute regulatory protein and induction of its mitochondrial translocation

Rice is a staple food in the Asian region and one of the world's major energy sources. Testosterone is a steroid hormone that maintains physical, sexual, and cognitive ability, and its decline causes health problems like late-onset hypogonadism. Evaluation of various grain extracts showed rice bran to stimulate testosterone secretion from Leydig model cells. α-Tocotrienol was found as a bioactive compound in rice bran, and mechanistic analysis showed the stimulation of steroid hormone synthesis through enhanced gene expression of steroidogenic acute regulatory protein as well as inducing mitochondrial localization of the protein. Preliminary study showed an increasing trend in serum testosterone levels in mice by oral intake of α-tocotrienol. These results suggest that α-tocotrienol intake may be effective in preventing symptoms caused by low testosterone levels.

Carotenoids and tocols comparison in different Subspecies of Triticum turgidum and aestivum

Carotenoids and Tocols in six genotypes of Triticum turgidum ssp. durum, five of Triticum turgidum ssp. dicoccum, four of Triticum aestivum ssp. aestivum, and six of Triticum aestivum ssp. spelta were investigated. The aim of the present study was to identify, quantify, and compare the content of tocopherols, tocotrienols, and carotenoids in different primitive and modern genotypes of wheat species in order to evaluate the lines with the highest content and possibly use them for selection and breeding programs. The Triticum durum group showed the highest mean content of total carotenoids, with lutein being the most abundant, accounting for 80.12 % (Triticum spelta) to 86.65 % (Triticum turgidum) of total carotenoids. Among the genotypes, Line 6 (Triticum durum) had the highest lutein content (12.17 μg g-1), significantly differing from the lines within its group and the other groups of dicoccum, aestivum, and spelta.Triticum dicoccum exhibited a lower average content of total tocols compared to other Triticum species. The tocols profile showed a prevalence of tocotrienols over tocopherols. β + γ-T3 was the most abundant individual tocol isomer in all Triticum genotypes, contributing for 50.40 % (Triticum ssp. aestivum) and 42.50 % (Triticum spelta) of the total content, respectively. The highest β + γ-T3 content (23.83 μg/g) was found in Line 6 of Triticum durum. Correlation, principal component, and cluster analyses revealed positive correlations between total tocols and β/γ tocotrienols, significant differences between various groups of the same species, formation of six clusters labeled as I to VI, and the identification of genotypes from the same species grouped in different clusters.

Vitamin E discussion forum position paper on the revision of the nomenclature of vitamin E

This position paper opens a discussion forum of this Journal dedicated to a scientific debate on Vitamin E nomenclature. With this article we provide the scientific and medical communities with what we consider relevant information in favor of revising the nomenclature of vitamin E. To our knowledge, only RRR-α-tocopherol has been medically used to protect against a deficiency disease in humans, and therefore, it would be appropriate to restrict the term vitamin to this molecule. The direct demonstration of a vitamin function to other tocochromanols (including other tocopherols, tocotrienols and eventually tocomonoenols), has not yet been scientifically shown. In fact, the medical prescription of a molecule against the deficiency disease only because it has been included in the "Vitamin E family", but not tested as vitamin E, could lead to ineffective therapy and potentially dangerous consequences for patients. The idea of this revision launched during the recent 3rd Satellite Symposium on Vitamin E of the 2022 SFRR-Europe meeting, offers a open platform of discussion for the scientists involved in vitamin E research and scientific societies interested to this subject.

Dietary Vitamin E Isoforms Intake: Development of a New Tool to Assess Tocopherols and Tocotrienols Intake in Adults

Due to the documented health benefits of tocopherols and tocotrienols as bioactive compounds, it seems important to assess their intake. The aim of this study was to develop a new tool and its application for assessment of tocopherol and tocotrienol intake in adults. Dietary data were collected by semiquantitative FFQ (VitE-FFQ) and by a 1-day dietary record in a group of 447 subjects. The database of the US Department of Agriculture (USDA) was used to calculate the individual isoforms of vitamin E and develop the tool-VIT_E.CAL. The assessment of measuring agreement between the two methods was conducted by analysis of the correlations and Bland-Altman plots. The average α-tocopherol intake was 11.3 mg/day for the data obtained using the FFQ method and 12.8 mg/day for the results obtained using the 1-day dietary record. Depending on the adopted recommendation, only 40-57% of the subjects had adequate vitamin E intake. The intake of α-tocopherol did not exceed the UL value in any of the respondents. The dominant forms of vitamin E in the diet of the studied group were α- and γ- forms (55% and 38% of the total sum) among tocopherols and β- and γ- forms (49% and 24% of the total sum) among tocotrienols. VIT_E.CAL allows us to calculate not only the total amount of vitamin E but also its eight isoforms. It can be a useful tool to assess individual and group intake of various forms of vitamin E in the diet. The use of VIT_E.CAL enables the proper assessment of vitamin E (as α-tocopherol and not α-tocopherol equivalent) in the diet of Poles, and most likely also in the European diet. The obtained results indicate the need to take into account the content of individual forms of vitamin E in food/diet, which will allow for a reliable assessment of its consumption. It also seems necessary to standardize the nomenclature regarding the name of vitamin E and its use for correct nutritional assessment.

Ameliorative Effect of Palm Oil in Aluminum Lactate Induced Biochemical and Histological Implications in Rat Brain

α-Tocotrienol is one of the major constituents of palm oil. It is a well-known antioxidant and cholesterol-lowering neuroprotectant. To prevent the initiation of Alzheimer's like symptoms, much attention has been shifted to the major role played by antioxidants. Previous epidemiological reports correlate the increasing incidence of developing Alzheimer's disease (AD), to the aluminum (Al) content in drinking water. Al, being a ubiquitous element, has a long history of being particularly reactive towards multiple aspects of neurobiology. So, the current study examines the effect of Al-induced behavioral, biochemical, and histopathological changes in rat brain; and the ameliorative effect of palm oil in reducing the resulting neurotoxicity. The experimental design consisted of 4 groups: control group which received rodent chow diet and water ad libitum; Al group received aluminum lactate (50 mg/kg bw); Al + palm oil group was administered with Al (50 mg/kg bw) and palm oil (60 mg/kg bw); and palm oil group received palm oil (60 mg/kg bw). Al was given by oral gavage once daily for 6 weeks and palm oil was administered intraperitoneally. After 6 weeks of supplementation, Al + palm oil group showed significantly lower malondialdehyde (MDA) content, but higher superoxide dismutase (SOD), catalase (CAT), GST, and GPx activity as compared to Al group. Al group has significantly higher level of MDA content, but lower SOD, CAT, GST, and GPx activity as compared to control group. In conclusion, this study suggested that palm oil was effective in preventing the Al-induced brain damage in rats.

Effect of ultrasonic pretreatment on tocochromanol and carotenoid biofortification in maize (Zea mays L.) seedlings

BACKGROUND

Maize is a sought-after food crop because it is micronutrient-rich and affordable. It is an excellent source of carotenoids and tocochromanols. To investigate ways to enhance the micronutrients in maize, we grew maize seedlings with ultrasonic pretreatment to study the effect of ultrasound pretreatment on the biofortification of tocochromanols and carotenoids using high-performance liquid chromatography and real-time quantitative polymerase chain reaction.

RESULTS

Four tocopherol isomers, three tocotrienol isomers and six carotenoid components were measured in maize seedlings. Compared with the untreated maize seedlings, carotenoid content increased and reached the highest level at 8 min ultrasonic pretreatment (19.21 ± 0.44 μg g^-1 fresh weight (FW)), but tocotrienol content evidently decreased. Tocopherol dropped at first but began to rise after 8 min ultrasonic pretreatment (258.1 ± 6.4 μg g^-1 FW). In particular, zeaxanthin in maize seedlings doubled after pre-sonication, while lutein was boosted to 11.81 ± 0.20 μg g^-1 FW. Ultrasonic pretreatment changed the predominant component of tocochromanols in maize seedlings from γ-tocotrienol to α-tocopherol, with the latter content being 1.3 times higher than in the untreated group. Up-regulation of key genes involved in the biosynthesis of tocopherols and carotenoids in maize seedlings occurred as a result of both 2 min and 6 min sonication pretreatment. In particular, _Zm HPPD, _Zm ZE, _Zm ZDS and _Zm MPBQ-MT could partly explain the changes in these phytochemicals.

CONCLUSION

Wet ultrasonic pretreatment could increase tocopherol and carotenoid accumulation in maize seedlings but decrease tocotrienol synthesis. Some up-regulating genes are related to relevant syntheses, such as _Zm HPPD, _Zm ZE, _Zm ZDS and _Zm MPBQ-MT, which could influence the accumulation of tocopherols and carotenoids after ultrasonic pretreatment. © 2022 Society of Chemical Industry.

Suppression of Amyloid-β Adsorption on Endoplasmic Reticulum Stress-Mimicking Membranes by α-Tocopherol and α-Tocotrienol

Two forms of hydrophobic vitamin E (VE), α-tocopherol (Toc) and α-tocotrienol (Toc3), have been proposed to be effective against Alzheimer's disease (AD), the etiology of which is thought to involve endoplasmic reticulum (ER) stress. However, previous studies reported conflicting effects of Toc and Toc3 on the risk of AD. We prepared liposomes mimicking the phase separation of the ER membrane (solid-ordered/liquid-disordered phase separation) and studied how VE can influence the interaction between amyloid-β (Aβ) and the ER membrane. We found that Toc could inhibit the formation of the solid-ordered phase more significantly than Toc3. Furthermore, Aβ protofibril adsorption on ER stress-mimicking membranes was more strongly suppressed by Toc compared with Toc3. Therefore, we concluded that VE can relieve ER stress by destabilizing the solid-ordered phase of the ER membrane and subsequently reducing the amount of Aβ adsorbed on the membrane. Moreover, Toc exerted a stronger effect than Toc3.

Effect of vitamins C and E on cancer survival; a systematic review

PURPOSE

Association between vitamins C (VC)/ E (VE) and cancer survival is inconsistent. This systematic review is aimed to summarize trials for effects of VC/VE on cancer survival.

METHODS

Relevant English trials were retrieved from PubMed, Cochrane Library, Embase, Web of Science, Scopus databases, and Clinicaltrials.gov through 21/June/2022. Inclusion criteria were all trials which assessed sole/combinations intake of VC/VE on survival rate, mortality, or remission of any cancer. Exclusion criteria were observational and animal studies.

RESULTS

We reached 30 trials conducted on 38,936 patients with various cancers. Due to severe methodological heterogeneity, meta-analysis was impossible. High dose VC + chemotherapy or radiation was safe with an overall survival (OS) 182 days - 21.5 months. Sole oral or intravenous high dose VC was safe with non-significant change in OS (2.9-8.2 months). VE plus chemotherapy was safe, resulted in stabling diseases for 5 years in 70- 86.7% of patients and OS 109 months. It was found 60% and 16% non-significant reductions in adjusted hazard ratio (HR) deaths or recurrence by 200 mg/d tocotrienol + tamoxifen in breast cancer, respectively. Sole intake of 200-3200 mg/d tocotrienol before resectable pancreatic cancer was safe and significantly increased cancer cells' apoptosis. Combination VC and VE was non-significantly reduced 7% in rate of neoplastic gastric polyp.

CONCLUSION

Although our study is supported improvement of survival and progression rates of cancers by VC/VE, more high quality trials with large sample sizes are required to confirm.

PROSPERO REGISTRATION NUMBER

CRD42020152795.

Cationic N,N-Dimethylglycine Ester Prodrug of 2R-α-Tocotrienol Promotes Intestinal Absorption via Efficient Self-Micellization with Intrinsic Bile Acid Anion

The intestinal absorption of hydrophobic compounds is severely influenced by their transportation rate through the unstirred water layer in the intestinal lumen. A member of the vitamin E family, α-Tocotrienol (α-T3) has remarkable pharmacological effects, but its intestinal absorption is hampered due to its hydrophobicity. Here, we prepared three ester derivatives of 2R-α-T3, and we selected a suitable prodrug compound using rat plasma and liver microsomes. The micellization profile of the selected compound in the presence of taurocholic acid (TCA) was evaluated. After gastrostomy administration of the prodrug candidate or α-T3 solution containing TCA, AUC values were determined for α-T3 in plasma obtained from bile duct-ligated rats. Among the three types in the efficiency of the reconversion to the parent drug, α-T3 N,N-dimethylglycinate (α-T3DMG) was the best prodrug; α-T3DMG formed mixed micelles via ion pairs with anionic TCA. The solubility of α-T3DMG in n-octanol/water depended on its ratio to TCA. The AUC after α-T3DMG administration to ligated rats was 2-fold higher than that after α-T3 administration, suggesting a smooth interaction with intrinsic bile acids. In conclusion, utilization of the prodrug synthesized using N,N-dimethylglycine ester may be a beneficial approach to promote intestinal absorption of α-T3 via self-micellization with intrinsic bile acid.

Fruit tree leaves as valuable new source of tocopherol and tocotrienol compounds

BACKGROUND

Nowadays it is highly important to find new, cheap and widely available sources of tocopherol and tocotrienol compounds, and leaves are promising unconventional sources. The main goal of this study was to extend the currently limited knowledge concerning tocopherol and tocotrienol isomers composition determined using ultra-high performance liquid chromatography with fluorescence detection analysis for various fruit tree leaves such as apple, pear, quince, apricot, peach, plum, sour cherry and sweet cherry. The leaves were collected 2 weeks after tree blooming and after fruit collection. Tocopherol and tocotrienol isomers were identified and quantified for the first time in all fruit tree leaves.

RESULTS

The total tocopherol content ranged from 203.34 to 260.86 μg g^-1 dry weight for spring leaves and from 23.83 to 235.62 μg g^-1 dry weight for autumn leaves and consisted mainly of α-tocopherol. The rest of the isomers of tocopherol and tocotrienols were also found, but in trace amounts. A significantly lower content of tocopherols and tocotrienols was detected in leaves after autumn collection of fruits compared to leaves collected after blooming. Among the analyzed leaves, time collected and species were significantly more important than their cultivars. Regarding quantification analysis, apricot > peach > > plums > apples leaves were identified as the best sources of tocopherols, and sweet and sour cherry leaves exhibited a lower content.

CONCLUSION

Fruit tree leaves are a novel significant source and good material for isolation of α-tocopherol for application in cosmetics, pharmaceuticals or in the food industry - for example, production of beverages or other functional foods. © 2021 Society of Chemical Industry.

Alpha-Tocotrienol Enhances Arborization of Primary Hippocampal Neurons via Upregulation of Bcl-xL

Alpha-tocotrienol (α-TCT) is a member of the vitamin E family. It has been reported to protect the brain against various pathologies including cerebral ischemia and neurodegeneration. However, it is still unclear if α-TCT exhibits beneficial effects during brain development. We hypothesized that treatment with α-TCT improves intracellular redox homeostasis supporting normal development of neurons. We found that primary hippocampal neurons isolated from rat feti grown in α-TCT-containing media achieved greater levels of neurite complexity compared to ethanol-treated control neurons. Neurons were treated with 1 μM α-TCT for 3 weeks, and media were replaced with fresh α-TCT every week. Treatment with α-TCT increased α-TCT levels (26 pmol/mg protein) in the cells, whereas the control neurons did not contain α-TCT. α-TCT-treated neurons produced adenosine triphosphate (ATP) at a higher rate and increased ATP retention at neurites, supporting formation of neurite branches. Although treatment with α-TCT alone did not change neuronal viability, neurons grown in α-TCT were more resistant to death at maturity. We further found that messenger RNA and protein levels of B-cell lymphoma-extra large (Bcl-xL) are increased by α-TCT treatment without inducing posttranslational cleavage of Bcl-xL. Bcl-xL is known to enhance mitochondrial energy production, which improves neuronal function including neurite outgrowth and neurotransmission. Therefore α-TCT-mediated Bcl-xL upregulation may be the central mechanism of neuroprotection seen in the α-TCT-treated group. In summary, treatment with α-TCT upregulates Bcl-xL and increases ATP levels at neurites. This correlates with increased neurite branching during development and with protection of mature neurons against oxidative stress.

Metabolism of natural forms of vitamin E and biological actions of vitamin E metabolites

Natural forms of vitamin E comprise four tocopherols and four tocotrienols. During the last twenty years, there have been breakthroughs in our understanding of vitamin E metabolism and biological activities of vitamin E metabolites. Research has established that tocopherols and tocotrienols are metabolized via ω-hydroxylase (CYP4F2)-initiated side chain oxidation to form 13'-hydroxychromanol and 13'-carobyxychromanol (13'-COOH). 13'-COOHs are further metabolized via β-oxidation and sulfation to intermediate carboxychromanols, terminal metabolite carboxyethyl-hydroxychroman (CEHC), and sulfated analogs. Animal and human studies show that γ-, δ-tocopherol and tocotrienols are more extensively metabolized than α-tocopherol (αT), as indicated by higher formation of CEHCs and 13'-COOHs from non-αT forms than those from αT. 13'-COOHs are shown to be inhibitors of cyclooxygenase-1/-2 and 5-lipoxygenase and much stronger than CEHCs for these activities. 13'-COOHs inhibit cancer cell growth, modulate cellular lipids and activate peroxisome proliferator-activated receptor-γ and pregnane X receptor. Consistent with mechanistic findings, αT-13'-COOH or δTE-13'-COOH, respective metabolites of αT or δ-tocotrienol, show anti-inflammatory and cancer-preventive effects, modulates the gut microbiota and prevents β-amyloid formation in mice. Therefore, 13'-COOHs are a new class of bioactive compounds with anti-inflammatory and anti-cancer activities and potentially capable of modulating lipid and drug metabolism. Based on the existing evidence, this author proposes that metabolites may contribute to disease-preventing effects of γ-, δ-tocopherol and tocotrienols. The role of metabolites in αT's actions may be somewhat limited considering controlled metabolism of αT because of its association with tocopherol-transport protein and less catabolism by CYP4F2 than other vitamin E forms.

Interventional study with vitamin E in cardiovascular disease and meta-analysis

Cardiovascular disease (CVD) is one of the major causes of morbidity and mortality and atherosclerosis is the common root to most of the CVD. Oxidative stress is one of the most important factors driving atherosclerosis and its complications. Thus, strategies for the prevention and treatment of cardiovascular events had oxidative changes as a potential target. Natural vitamin E consists of a family of eight different compounds, four tocopherols and four tocotrienols. All tocopherols and tocotrienols are potent antioxidants with lipoperoxyl radical-scavenging activities. In addition, α-tocopherol possesses also anti-inflammatory as well as anti-atherothrombotic effects by modulating platelet and clotting system. Experimental and in vitro studies described molecular and cellular signalling pathways regulated by vitamin E antithrombotic and antioxidant properties. While observational studies demonstrated an inverse association between vitamin E serum levels and CVD, interventional trials with vitamin supplements provided negative results. This review focus on the impact of vitamin E in the atherothrombotic process and describes the results of experimental and clinical studies with the caveats related to the interventional trials with vitamin E to prevent CVD.

Vitamin E research: Past, now and future

The early history of vitamin E from its discovery by Herbert M. Evans and Katharine J. S. Bishop in 1922 up to its chemical synthesis by Paul Karrer and coworkers in 1938 and the development of the concept that vitamin E acts as an antioxidant in vivo are recalled. Some more recent results shedding doubt on this hypothesis are reviewed. They comprise influence of vitamin E on enzyme activities, signaling cascades, gene expression and bio-membrane structure. The overall conclusion is that our knowledge of the vitamin's mechanism of action still remains fragmentary. The metabolism of tocopherols and tocotrienols is presented and discussed in respect to bioactivity of the metabolites, interference with drug metabolism and the future design of clinical trials. Some strategies are recommended how to reach the final goal: the identification of the primary vitamin E target(s) and the analysis of the downstream events up to the physiological phenomena.

A double-blind randomised controlled trial on the effect of Tocovid, a tocotrienol-rich capsule on postoperative atrial fibrillation at the National Heart Institute, Kuala Lumpur: an interim blinded analysis

INTRODUCTION

Post-operative atrial fibrillation (POAF) is associated with poorer outcomes, increased resource utilisation, morbidity and mortality. Its pathogenesis is initiated by systemic inflammation and oxidative stress. It is hypothesised that a potent antioxidant and anti-inflammatory agent such as tocotrienol, an isomer of Vitamin E, could reduce or prevent POAF.

AIMS

The aim of this study is to determine whether a potent antioxidative and anti-inflammatory agent, Tocovid, a tocotrienol-rich capsule, could reduce the incidence of POAF and affect the mortality and morbidity as well as the duration of ICU, HDU and hospital stay.

METHODS

This study was planned as a prospective, randomised, controlled trial with parallel groups. The control group received placebo containing palm superolein while the treatment group received Tocovid capsules. We investigated the incidence of POAF, the length of hospital stay after surgery and the health-related quality of life.

RESULTS

Recruitment commenced in January 2019 but the preliminary results were unblinded as the study is still ongoing. Two-hundred and two patients have been recruited out of a target sample size of 250 as of January 2021. About 75% have completed the study and 6.4% were either lost during follow-up or withdrew; 4% of participants died. The mean age group was 61.44 ± 7.30 years with no statistical difference between the groups, with males having a preponderance for AF. The incidence of POAF was 24.36% and the mean time for developing POAF was 55.38 ± 29.9 h post-CABG. Obesity was not a predictive factor. No statistically significant difference was observed when comparing left atrial size, NYHA class, ejection fraction and the premorbid history. The mean cross-clamp time was 71 ± 34 min and the mean bypass time was 95 ± 46 min, with no difference between groups. There was a threefold increase in death among patients with POAF (p = 0.008) and an increase in the duration of ICU stay (p = 0.01), the total duration of hospital stay (p = 0.04) and reintubation (p = 0.045).

CONCLUSION

A relatively low incidence rate of POAF was noted although the study is still ongoing. It remains to be seen if our prophylactic intervention using Tocovid would effectively reduce the incidence of POAF. Clinical Registration Number: US National Library of Medicine. Clinical Trials - NCT03807037. Registered on 16th January 2019. Link: https://clinicaltrials.gov/ct2/show/NCT03807037.

Vitamin E as an essential micronutrient for human health: Common, novel, and unexplored dietary sources

Vitamin E comprises a group of vitamers that includes tocopherols and tocotrienols. They occur in four homologues according to the number and position of methyl groups attached to the chromanol ring. Vitamin E, a liposoluble antioxidant, may participate as an adjuvant in the prevention and treatment of cardiovascular, neurological, and aging-related diseases. Furthermore, vitamin E has applications in the food industry as a natural additive. In this contribution, the most recent information on the dietary sources of vitamin E, including common, novel, and unexplored sources, is presented. Common edible oils, such as those of corn, olive, palm, rice bran, and peanut, represent the most prominent sources of vitamin E. However, specialty and underutilized oils such as those obtained from tree nuts, fruit seeds, and by-products, emerge as novel sources of this important micronutrient. Complementary studies should examine the tocotrienol content of vitamin E dietary sources to better understand the different biological functions of these vitamers.

Reflections on a century of vitamin E research: Looking at the past with an eye on the future

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.

Stress-activated leukocyte 12/15-lipoxygenase metabolite enhances struggle behaviour and tocotrienols relieve stress-induced behaviour alteration

Stress induces emotional arousal causing anxiety, irritability, exaggerated startle behaviour, and hypervigilance observed in patients with trauma and stress-related mental disorders, including acute stress disorder and post-traumatic stress disorder. Central norepinephrine release promotes stress-induced emotional arousal. However, the regulator of emotional arousal remains unknown. Here, we show that the arachidonate-derived metabolite produced by stress-activated leukocyte 12/15-lipoxygenase is remarkably elevated in the plasma and upregulates the central norepinephrine release, resulting in the enhancement of the struggle behaviour (= escape behaviour) in the tail suspension test. Struggle behaviour is mimicking a symptom of emotional arousal. This stress-induced struggle behaviour was absent in 12/15-lipoxygenase deficient mice; however, intravenous administration of a 12/15-lipoxygenase metabolite to these mice after stress exposure rekindled the struggle behaviour. Furthermore, tocotrienols and geranylgeraniol reduced stress-induced 12/15-lipoxygenase metabolite production and suppressed the struggle behaviour. Our findings indicate that arachidonate-derived 12/15-lipoxygenase metabolite is involved in the regulation of stress-enhanced central norepinephrine release and struggle behaviour. In addition, we propose 12/15-lipoxygenase as a potential therapeutic target for the treatment of emotional arousal observed in stress-related mental disorders.

Production of tocotrienols in seeds of cotton (Gossypium hirsutum L.) enhances oxidative stability and offers nutraceutical potential

Upland cotton (Gossypium hirsutum L.) is an economically important multi-purpose crop cultivated globally for fibre, seed oil and protein. Cottonseed oil also is naturally rich in vitamin E components (collectively known as tocochromanols), with α- and γ-tocopherols comprising nearly all of the vitamin E components. By contrast, cottonseeds have little or no tocotrienols, tocochromanols with a wide range of health benefits. Here, we generated transgenic cotton lines expressing the barley (Hordeum vulgare) homogentisate geranylgeranyl transferase coding sequence under the control of the Brassica napus seed-specific promoter, napin. Transgenic cottonseeds had ~twofold to threefold increases in the accumulation of total vitamin E (tocopherols + tocotrienols), with more than 60% γ-tocotrienol. Matrix assisted laser desorption ionization-mass spectrometry imaging showed that γ-tocotrienol was localized throughout the transgenic embryos. In contrast, the native tocopherols were distributed unequally in both transgenic and non-transgenic embryos. α- Tocopherol was restricted mostly to cotyledon tissues and γ-tocopherol was more enriched in the embryonic axis tissues. Production of tocotrienols in cotton embryos had no negative impact on plant performance or yield of other important seed constituents including fibre, oil and protein. Advanced generations of two transgenic events were field grown, and extracts of transgenic seeds showed increased antioxidant activity relative to extracts from non-transgenic seeds. Furthermore, refined cottonseed oil from the two transgenic events showed 30% improvement in oxidative stability relative to the non-transgenic cottonseed oil. Taken together, these materials may provide new opportunities for cottonseed co-products with enhanced vitamin E profile for improved shelf life and nutrition.

The characterization of tocols in different plants parts of six Japanese rice cultivars relating to their UVB-sensitivity

There has been significant interest in the photosensitivity, or photo-resistance, of Japanese rice cultivars, which synthesize tocols (Vitamin E), a class of phytochemicals including tocol derivatives tocopherol (T) and tocotrienol (T3). In the present study, the distribution of tocols in the leaves, seeds, stems, and roots of six Japanese rice cultivars was investigated. The relationship between the different tocols in cultivars and their ultraviolet B sensitivity index (USB-SI) was analyzed. The leaves contained the highest average total amount of tocols at 230 μg.fresh-g^-1, followed by seeds, stems, and roots. In leaves and stems, the most abundant component was α-T which was more than 85%. On the other hand, the tocols in seeds were 38% δ-T3, 32% α-T, and 20% α-T3. The tocols in roots were 55% α-T, 14% γ-T, and 13% δ-T3. The total tocol content in four plant parts exhibited a negative correlation (P < 0.05) in stem and root, and a negative relationship (r < -0.70) with the UVB-SI of the cultivars, suggesting that the total tocol contents were closely related to the resistance to UVB in Japanese rice plants.

Co-encapsulation of gemcitabine and tocotrienols in nanovesicles enhanced efficacy in pancreatic cancer

Aim: To synthesize niosomes co-encapsulating gemcitabine (GEM) and tocotrienols, and physicochemically characterize and evaluate the antipancreatic effects of the nanoformulation on Panc 10.05, SW 1990, AsPC-1 and BxPC-3 cells. Materials & methods: Niosomes-entrapping GEM and tocotrienols composed of Span 60, cholesterol and D-α-tocopheryl polyethylene glycol 1000 succinate were produced by Handjani-Vila and film hydration methods. Results: The film hydration produced vesicles measuring 161.9 ± 0.5 nm, approximately 50% smaller in size than Handjani-Vila method, with maximum entrapment efficiencies of 20.07 ± 0.22% for GEM and 34.52 ± 0.10% for tocotrienols. In Panc 10.05 cells, GEM's antiproliferative effect was enhanced 2.78-fold in combination with tocotrienols. Niosomes produced a significant ninefold enhancement in cytotoxicity of the combination, supported by significantly higher cellular uptake of GEM in the cells. Conclusion: This study is a proof of concept on the synthesis of dual-drug niosomes and their efficacy on pancreatic cancer cells in vitro.

[Eight vitamin E congeners in seafood and aquatic products in Zhejiang Province]

OBJECTIVE

Comparison and analysis of α-, β-, γ-, δ-tocopherol(T) and α-, β-, γ-, δ-tocotrienol(T3) in 44 species of seafood and aquatic products is under processed to enrich the database of food composition in China and provide a scientific reference for dietary intake choice.

METHODS

Quantitative and correlation analysis of eight vitamin E isomers were based on external calibration method with reversed-phase high-performance liquid chromatography-fluorescence detector, after hot saponification with alkaline and liquid-liquid extraction.

RESULTS

The content of α-tocopherol equivalent(α-TE) in seafood and aquatic products varied greatly(from 0. 10 to 4. 01 mg/100 g edible), as well as the isomer forms. Aspect of vitamin E forms in aquatic fish, detection rates of α-T and α-T3 were both 100%, while the rates of γ-T and γ-T3 were 31. 58% and 68. 42%, respectively. Aspect of vitamin E forms in sea fish, detection rates α-T3, γ-T and γ-T3 were 28. 57%, 28. 57% and 35. 71%, respectively, while the rate of α-T was 100%. The form of vitamin E isomers in fish was at some extent different when they raise up in wild and farming environment, whereas there was no significant different in content of isomers. For shrimp and crabs, the content of α-TE was also various(from 0. 31 to 14. 27 mg/100 g edible), whereas α-T was the primary vitamin E form. And the content of α-T in female crabs was a little higher than that in male crabs, without statistic difference. With respect to correlation analysis, there was a strong correlation between γ-T and α-T3 in sea fish, while weak correlation of isomers in aquatic fish and certain correlations of isomers in shrimp and crab.

CONCLUSION

The level of vitamin E content in seafood and aquatic products are quite different. Thus, it will bring in different effects on total activity and intake of vitamin E isomers by consumption of different species of seafood and aquatic products.

Functional dissection of HGGT and HPT in barley vitamin E biosynthesis via CRISPR/Cas9-enabled genome editing

BACKGROUND AND AIMS

Vitamin E (tocochromanol) is a lipid-soluble antioxidant and an essential nutrient for human health. Among cereal crops, barley (Hordeum vulgare) contains a high level of vitamin E, which includes both tocopherols and tocotrienols. Although the vitamin E biosynthetic pathway has been characterized in dicots, such as Arabidopsis, which only accumulate tocopherols, knowledge regarding vitamin E biosynthesis in monocots is limited because of the lack of functional mutants. This study aimed to obtain gene knockout mutants to elucidate the genetic control of vitamin E composition in barley.

METHODS

Targeted knockout mutations of HvHPT and HvHGGT in barley were created with CRISPR/Cas9-enabled genome editing. High-performance liquid chromatography (HPLC) was performed to analyse the content of tocochromanol isomers in transgene-free homozygous Hvhpt and Hvhggt mutants.

KEY RESULTS

Mutagenesis efficiency among T0 regenerated plantlets was 50-65 % as a result of two simultaneously expressed guide RNAs targeting each gene; most of the mutations were stably inherited by the next generation. The transgene-free homozygous mutants of Hvhpt and Hvhggt exhibited decreased grain size and weight, and the HvHGGT mutation led to a shrunken phenotype and significantly lower total starch content in grains. HPLC analysis revealed that targeted mutation of HvHPT significantly reduced the content of both tocopherols and tocotrienols, whereas mutations in HvHGGT completely blocked tocotrienol biosynthesis in barley grains. Transient overexpression of an HvHPT homologue in tobacco leaves significantly increased the production of γ- and δ-tocopherols, which may partly explain why targeted mutation of HvHPT in barley grains did not eliminate tocopherol production.

CONCLUSIONS

Our results functionally validated that HvHGGT is the only committed gene for the production of tocotrienols, whereas HvHPT is partly responsible for tocopherol biosynthesis in barley.

Actions of annatto-extracted tocotrienol supplementation on obese postmenopausal women: study protocol for a double-blinded, placebo-controlled, randomised trial

INTRODUCTION

Obesity is a major health concern in postmenopausal women, and chronic low-grade inflammation contributes to the development of obesity. Cellular studies and high-fat-diet-induced obese mouse model mimicking obesity show the antiobesity effect of annatto-extracted tocotrienols (TT) with antioxidant capability. We aim to assess the safety and efficacy of TT consumption for lipid-related parameters in obese postmenopausal women.

METHODS AND ANALYSIS

Eligible obese postmenopausal women will be randomly assigned to placebo group (430 mg olive oil) and TT group (DeltaGold Tocotrienol 70%) for 24 weeks. In the present study, the primary outcome is total/regional fat mass and visceral adipose tissue. The secondary outcomes include lipid profile in serum, mRNA expression of fatty acid synthase and carnitine palmitoyltransferase 1A in fat tissue, oxylipins and endocannabinoids in plasma and adipose tissue, abundance and composition of intestinal microbiome in faeces, high-sensitivity C-reactive protein (hs-CRP) in serum and leptin in serum. Every participant will be evaluated at 0 (prior to starting intervention) and 24 weeks of intervention, except for serum lipid profile and hs-CRP at 0, 12 and 24 weeks. 'Intent-to-treat' principle is employed for data analysis. Hierarchical linear modelling is used to estimate the effects of dietary TT supplementation while properly accounting for dependency of data and identified covariates. To our knowledge, this is the first randomised, placebo-controlled, double-blinded study to determine dietary TT supplementation on an obese population. If successful, this study will guide the future efficacy TT interventions and TT can be implemented as an alternative for obese population in antiobesity management.

ETHICS AND DISSEMINATION

This study has been approved by the Bioethics Committee of the Texas Tech University Health Sciences Center, Lubbock. An informed consent form will be signed by a participant before enrolling in the study. The results from this trial will be actively disseminated through academic conference presentation and peer-reviewed journals.

TRIAL REGISTRATION NUMBER

NCT03705845.

Vitamin E in Plants: Biosynthesis, Transport, and Function

Vitamin E, which includes both tocopherols and tocotrienols, comprises lipid-soluble antioxidants that modulate lipid peroxidation. Recently, significant advances have been made in our understanding of vitamin E biosynthesis, transport, and function. The phytyl moiety from chlorophyll degradation is used for tocopherol biosynthesis. An α-tocopherol-binding protein (TBP) has been identified in tomato (SlTBP) serving in intraorganellar vitamin E transport in plants. Moreover, α-tocopherol not only scavenges free radicals through flip-flop movements in the lipid bilayer, but may also contribute to fine-tuning the transmission of specific signals outside chloroplasts. Vitamin E, and α-tocopherol in particular, appear to be essential for plant development and help to provide the most suitable response to a number of environmental stresses.

Neuroprotective effects of α-tocotrienol on kainic acid-induced neurotoxicity in organotypic hippocampal slice cultures

Vitamin E, such as alpha-tocopherol (ATPH) and alpha-tocotrienol (ATTN), is a chain-breaking antioxidant that prevents the chain propagation step during lipid peroxidation. In the present study, we investigated the effects of ATTN on KA-induced neuronal death using organotypic hippocampal slice culture (OHSC) and compared the neuroprotective effects of ATTN and ATPH. After 15 h KA (5 μM) treatment, delayed neuronal death was detected in the CA3 region and reactive oxygen species (ROS) formation and lipid peroxidation were also increased. Both co-treatment and post-treatment of ATPH (100 μM) or ATTN (100 μM) significantly increased the cell survival and reduced the number of TUNEL-positive cells in the CA3 region. Increased dichlorofluorescein (DCF) fluorescence and levels of thiobarbiturate reactive substances (TBARS) were decreased by ATPH and ATTN treatment. These data suggest that ATPH and ATTN treatment have protective effects on KA-induced cell death in OHSC. ATTN treatment tended to be more effective than ATPH treatment, even though there was no significant difference between ATPH and ATTN in co-treatment or post-treatment.

Supervised chemical pattern recognition in almond ( Prunus dulcis ) Portuguese PDO cultivars: PCA- and LDA-based triennial study

Almonds harvested in three years in Trás-os-Montes (Portugal) were characterized to find differences among Protected Designation of Origin (PDO) Amêndoa Douro and commercial non-PDO cultivars. Nutritional parameters, fiber (neutral and acid detergent fibers, acid detergent lignin, and cellulose), fatty acids, triacylglycerols (TAG), and tocopherols were evaluated. Fat was the major component, followed by carbohydrates, protein, and moisture. Fatty acids were mostly detected as monounsaturated and polyunsaturated forms, with relevance of oleic and linoleic acids. Accordingly, 1,2,3-trioleoylglycerol and 1,2-dioleoyl-3-linoleoylglycerol were the major TAG. α-Tocopherol was the leading tocopherol. To verify statistical differences among PDO and non-PDO cultivars independent of the harvest year, data were analyzed through an analysis of variance, a principal component analysis, and a linear discriminant analysis (LDA). These differences identified classification parameters, providing an important tool for authenticity purposes. The best results were achieved with TAG analysis coupled with LDA, which proved its effectiveness to discriminate almond cultivars.

δ- and γ-tocotrienols induce classical ultrastructural apoptotic changes in human T lymphoblastic leukemic cells

Tocotrienols are isomers of the vitamin E family, which have been reported to exert cytotoxic effects in various cancer cells. Although there have been some reports on the effects of tocotrienols in leukemic cells, ultrastructural evidence of tocotrienol-induced apoptotic cell death in leukemic cells is lacking. The present study investigated the effects of three isomers of tocotrienols (alpha, delta, and gamma) on a human T lymphoblastic leukemic cell line (CEM-SS). Cell viability assays showed that all three isomers had cytotoxic effects (p < 0.05) on CEM-SS cells with delta-tocotrienol being the most potent. Transmission electron microscopy showed that the cytotoxic effects by delta- and gamma-tocotrienols were through the induction of an apoptotic pathway as demonstrated by the classical ultrastructural apoptotic changes characterized by peripheral nuclear chromatin condensation and nuclear fragmentation. These findings were confirmed biochemically by the demonstration of phosphatidylserine externalization via flow cytometry analysis. This is the first study showing classical ultrastructural apoptotic changes induced by delta- and gamma-tocotrienols in human T lymphoblastic leukemic cells.

Role of immunoregulatory transcription factors in differential immunomodulatory effects of tocotrienols

Tocotrienols have been shown to possess antioxidant, antitumor, cardioprotective, and antiproliferative effects. This report describes novel immunomodulatory effects of tocotrienols in murine lymphocytes. γ-Tocotrienol (GT) was more effective in suppressing concanavalin A (Con A)-induced T cell proliferation and cytokine production compared to α-tocotrienol (AT) when present continuously in the culture. GT inhibited T cell activation markers and costimulatory molecule. GT modulated intracellular glutathione in lymphocytes, and the suppressive effects of GT could not be abrogated by thiol or nonthiol antioxidants, indicating a poor link between anti-inflammatory properties of tocotrienols and cellular redox status. It was also observed that GT suppressed Con A-induced activation of NF-κB, AP-1, and NF-κB-dependent gene expression. Cellular uptake studies with tocotrienols showed higher accumulation of GT compared to AT. Similar immunosuppressive effects of GT were also observed when administered to mice. In contrast, transient exposure of lymphocytes to GT (4 h) resulted in higher survival and proliferation of lymphocytes in vitro and in vivo in syngeneic and allogeneic hosts. This was attributed to the ability of GT to induce NF-κB, AP-1, and mTOR activation in lymphocytes upon transient exposure. Our results demonstrated that antioxidants such as tocotrienols may exhibit pleiotropic effects by activating multiple mechanisms in cells.

Effects of new combinative antioxidant FeAOX-6 and α-tocotrienol on macrophage atherogenesis-related functions

Pivotal role in atherogenesis is played by macrophages, which are early site for lipid accumulation and mediate the inflammatory and immune response in the intima. Epidemiological evidence indicates that natural antioxidants reduce the risk of heart disease, but, so far, supplementation studies have failed to confirm any protective effects of these compounds against cardiovascular disease. This study evaluated the effects of the natural antioxidant alpha-tocotrienol and of the newly designed compound, FeAOX-6, which combines antioxidant structural features of both tocopherols and carotenoids into a single molecule, on macrophage functions involved in foam cell formation. FeAOX-6 or alpha-tocotrienol induce a strong dose-dependent reduction of cholesterol and reduce cholesterol accumulation in human macrophages. The extent of the reduction found with alpha-tocotrienol was greater than that induced by FeAOX-6 and did not correlate with their respective antioxidant capacities. Treatment of HMDM with alpha-tocotrienol or FeAOX-6 enhanced also tumor necrosis factor-alpha secretion. These results are consistent with a reduction in scavenger receptor activity, but we found that antioxidant treatment did not affect cholesterol uptake from modified LDL. The effects on release on pro-inflammatory prostanoid precursors, PGE(2) and cytokine suggest a variety of metabolic responses that are both dependent on antioxidant compounds and macrophages activation status.

Comparative study of the effect of tocotrienols and -tocopherol on fasting serum lipid profiles in patients with mild hypercholesterolaemia: a preliminary report

OBJECTIVES

Hypercholesterolaemia is a risk factor for cardiovascular diseases. Tocotrienols reportedly possess hypocholesterolaemic activity. This study examined the effect of tocotrienols (T3) in TOCOVIDTM Suprabio TM on serum lipids. Patients and Methods :A randomised (2:1), open-label study of patients with mild hypercholesterolaemia (= 5.18mmol/L to <7.77mmol/L) and one additional cardiovascular risk factor was carried out. Subjects received either tocotrienols (as TOCOVIDTM Suprabio TM ) (n=28) or vitamin E (a-tocopherol) 500mg daily (n=16). Fasting lipids were compared at baseline and after 4 weeks therapy.

RESULTS

Following 4 weeks therapy, mean +/- SD total cholesterol declined significantly in the tocotrienol group (from 6.10+/-0.66 to 5.47+/-1.16; P=0.02) compared to the a-tocopherol group (from 5.92+/-0.52 to 5.47+/-0.76; P>0.05). Mean LDL-C levels (mmol/L) were also significantly reduced in the tocotrienol group (3.82+/-0.85 to 3.24+/-1.26; P=0.04), but not in those on a-tocopherol (3.84+/-0.75 to 3.28+/-0.94; P>0.05). There were no significant changes in HDL-C and triglycerides in both groups. The tocotrienol group experienced a net decline in TG (7.1+/-31.4 %; P>0.05) while the a-tocopherol group had a net increase at week 4 (38.6+/-61.7%; P>0.05).

CONCLUSION

The study adds to existing evidence of the favourable effect of tocotrienols on total cholesterol and LDL-C. However, the results need further evaluation.

Triton WR1339, an inhibitor of lipoprotein lipase, decreases vitamin E concentration in some tissues of rats by inhibiting its transport to liver

The aim of this experiment was to clarify the contribution of the alpha-tocopherol transfer activity of lipoprotein lipase (LPL) to vitamin E transport to tissues in vivo. We studied the effect of Triton WR1339, which prevents the catabolism of triacylglycerol-rich lipoproteins by LPL on vitamin E distribution in rats. Vitamin E-deficient rats fed a vitamin E-free diet for 4 wk were injected with Triton WR1339 and administered by oral gavage an emulsion containing 10 mg of alpha-tocopherol, 10 mg of gamma-tocopherol, or 29.5 mg of a tocotrienol mixture with 200 mg of sodium taurocholate, 200 mg of triolein, and 50 mg of albumin. alpha-Tocopherol was detected in the serum and other tissues of the vitamin E-deficient rats, but gamma-tocopherol, alpha- and gamma-tocotrienol were not detected. Triton WR1339 injection elevated (P<0.05) the serum alpha-tocopherol concentration and inhibited (P<0.05) the elevation of alpha-tocopherol concentration in the liver, adrenal gland, and spleen due to the oral administration of alpha-tocopherol. Neither alpha-tocopherol administration nor Triton WR1339 injection affected (P>or=0.05) the alpha-tocopherol concentration in the perirenal adipose tissue, epididymal fat, and soleus muscle despite a high expression of LPL in the adipose tissue and muscle. These data show that alpha-tocopherol transfer activity of LPL in adipose tissue and muscle is not important for alpha-tocopherol transport to the tissue after alpha-tocopherol intake or that the amount transferred is small relative to the tissue concentration. Furthermore, Triton WR1339 injection tended to elevate the serum gamma-tocopherol (P=0.071) and alpha-tocotrienol (P=0.053) concentrations and lowered them (P<0.05) in the liver and adrenal gland of rats administered gamma-tocopherol or alpha-tocotrienol. These data suggest that lipolysis of triacylglycerol-rich chylomicron by LPL is necessary for postprandial vitamin E transport to the liver and subsequent transport to the other tissues.

Characterization of the potent neuroprotective properties of the natural vitamin E alpha-tocotrienol

The natural vitamin E tocotrienols possess properties not shared by tocopherols. Nanomolar alpha-tocotrienol, not alpha-tocopherol, is potently neuroprotective. On a concentration basis, this finding represents the most potent of all biological functions exhibited by any natural vitamin E molecule. We sought to dissect the antioxidant-independent and -dependent neuroprotective properties of alpha-tocotrienol by using two different triggers of neurotoxicity, homocysteic acid (HCA) and linoleic acid. Both HCA and linoleic acid caused neurotoxicity with comparable features, such as increased ratio of oxidized to reduced glutathione GSSG/GSH, raised intracellular calcium concentration and compromised mitochondrial membrane potential. Mechanisms underlying HCA-induced neurodegeneration were comparable to those in the path implicated in glutamate-induced neurotoxicity. Inducible activation of c-Src and 12-lipoxygenase (12-Lox) represented early events in that pathway. Overexpression of active c-Src or 12-Lox sensitized cells to HCA-induced death. Nanomolar alpha-tocotrienol was protective. Knock-down of c-Src or 12-Lox attenuated HCA-induced neurotoxicity. Oxidative stress represented a late event in HCA-induced death. The observation that micromolar, but not nanomolar, alpha-tocotrienol functions as an antioxidant was verified in a model involving linoleic acid-induced oxidative stress and cell death. Oral supplementation of alpha-tocotrienol to humans results in a peak plasma concentration of 3 microm. Thus, oral alpha-tocotrienol may be neuroprotective by antioxidant-independent as well as antioxidant-dependent mechanisms.

Chemoenzymatic synthesis of both enantiomers of α-tocotrienol

The stereoselective acylation of the achiral chromanedimethanol derivative 1 by vinyl acetate in the presence of Candida antarctica lipase B gave the (S)-monoester 2 in high enantiomeric purity (ee > or = 98%). Enzymatic hydrolysis of diesters of compound 1 failed to give (R)-monoester 2 in good yield and high ee. Thus, both enantiomers of alpha-tocotrienol were synthesized from the (S)-monoester 2.

Vitamin E protected cultured cortical neurons from oxidative stress-induced cell death through the activation of mitogen-activated protein kinase and phosphatidylinositol 3-kinase

The role of vitamin E in the CNS has not been fully elucidated. In the present study, we found that pre-treatment with vitamin E analogs including alphaT (alpha-tocopherol), alphaT3 (alpha -tocotrienol), gammaT, and gammaT3 for 24 h prevented the cultured cortical neurons from cell death in oxidative stress stimulated by H2O2, while Trolox, a cell-permeable analog of alphaT, did not. The preventive effect of alphaT was dependent on de novo protein synthesis. Furthermore, we found that alphaT exposure induced the activation of both the MAP kinase (MAPK) and PI3 kinase (PI3K) pathways and that the alphaT-dependent survival effect was blocked by the inhibitors, U0126 (an MAPK pathway inhibitor) or LY294002 (a PI3K pathway inhibitor). Interestingly, the up-regulation of Bcl-2 (survival promoting molecule) was induced by alphaT application. The up-regulation of Bcl-2 did not occur in the presence of U0126 or LY294002, suggesting that alphaT-up-regulated Bcl-2 is mediated by these kinase pathways. These observations suggest that vitamin E analogs play an essential role in neuronal maintenance and survival in the CNS.

Apoptosis induction by gamma-tocotrienol in human hepatoma Hep3B cells

We evaluated the antitumor activity of tocotrienol (T3) on human hepatoma Hep3B cells. At first, we examined the effect of T3 on the proliferation of human hepatoma Hep3B cells and found that gamma-T3 inhibited cell proliferation at lower concentrations and shorter treatment times than alpha-T3. Then, we examined the effect of gamma-T3 apoptosis induction and found that gamma-T3 induced poly (ADP-ribose) polymerase (PARP) cleavage and stimulated a rise in caspase-3 activity. In addition, gamma-T3 stimulated a rise in caspase-8 and caspase-9 activities. We also found that gamma-T3-induced apoptotic cell death was accompanied by up-regulation of Bax and a rise in the fragments of Bid and caspase-8. These data indicate that gamma-T3 induced apoptosis in Hep3B cells and that caspase-8 and caspase-9 were involved in apoptosis induction. Moreover, these results suggest that Bax and Bid regulated apoptosis induction by gamma-T3.

Delivery of orally supplemented alpha-tocotrienol to vital organs of rats and tocopherol-transport protein deficient mice

The natural vitamin E tocotrienol (TCT) possesses biological properties not shared by tocopherols (TCP). Nanomolar alpha-TCT, not alpha-TCP, is potently neuroprotective (JBC 275:13049; 278:43508). Tocopherol-transport protein (TTP) represents the primary mechanism for maintaining normal alpha-TCP concentrations in plasma and extrahepatic tissues. TTP primarily transports alpha-TCP and has low affinity for alpha-TCT. There are no studies that have investigated tissue delivery of alpha-TCT when orally gavaged on a long-term basis. A long-term study was conducted to examine the effects of alpha-TCT or alpha-TCP supplementation, either alone or in combination, on tissue levels. Rats were maintained on a vitamin E-deficient diet and gavaged with alpha-TCT or alpha-TCP alone or in combination. Five generations of rats were studied over 60 weeks. TTP-deficient mice were supplemented with TCT and bred to examine tissue delivery of oral alpha-TCT. Orally supplemented alpha-TCT was effectively delivered to most tissues over time. When co-supplemented, alpha-TCP outcompeted alpha-TCT for transport systems delivering vitamin E to tissues. To evaluate the significance of TTP in alpha-TCT delivery to tissues, tissue levels of alpha-TCT in supplemented TTP-deficient mice were studied. alpha-TCT was transported to several vital organs in TTP-deficient mice. alpha-TCT restored fertility in TTP-deficient mice. In sum, orally supplemented alpha-TCT was successfully delivered to several vital organs. The transport efficiency of alpha-TCT to tissues may be maximized by eliminating the co-presence of alpha-TCP in the oral supplement. Examination of whether alpha-TCT may benefit humans suffering from neurological disorders because of congenital TTP deficiency is warranted.

Neuroprotective properties of the natural vitamin E alpha-tocotrienol

BACKGROUND AND PURPOSE

The current work is based on our previous finding that in neuronal cells, nmol/L concentrations of alpha-tocotrienol (TCT), but not alpha-tocopherol (TCP), blocked glutamate-induced death by suppressing early activation of c-Src kinase and 12-lipoxygenase.

METHODS

The single neuron microinjection technique was used to compare the neuroprotective effects of TCT with that of the more widely known TCP. Stroke-dependent brain tissue damage was studied in 12-Lox-deficient mice and spontaneously hypertensive rats orally supplemented with TCT.

RESULTS

Subattomole quantity of TCT, but not TCP, protected neurons from glutamate challenge. Pharmacological as well as genetic approaches revealed that 12-Lox is rapidly tyrosine phosphorylated in the glutamate-challenged neuron and that this phosphorylation is catalyzed by c-Src. 12-Lox-deficient mice were more resistant to stroke-induced brain injury than their wild-type controls. Oral supplementation of TCT to spontaneously hypertensive rats led to increased TCT levels in the brain. TCT-supplemented rats showed more protection against stroke-induced injury compared with matched controls. Such protection was associated with lower c-Src activation and 12-Lox phosphorylation at the stroke site.

CONCLUSIONS

The natural vitamin E, TCT, acts on key molecular checkpoints to protect against glutamate- and stroke-induced neurodegeneration.

Characterization of cellular uptake and distribution of vitamin E

We previously reported that tocotrienols acted as more potent inhibitors against selenium deficiency-induced cell death than the corresponding tocopherol isoforms (J. Biol. Chem. 2003;278:39428-39434). In the present study, we first compared the differences in the cellular uptake between alpha-tocopherol (alpha-Toc) and alpha-tocotrienol (alpha-Toc-3). The initial rate of cellular uptake of alpha-Toc-3 was 70-fold higher than that of alpha-Toc. Subcellular fractionation analysis of alpha-Toc-3 and alpha-Toc-fortified cells showed similar cellular distribution of these antioxidants, which was directly proportional to the lipid distribution. The cells containing similar amounts of alpha-Toc-3 and alpha-Toc showed similar resistance against the oxidative stress caused by peroxides. These results suggest that the apparent higher cytoprotective effect of alpha-Toc-3 than alpha-Toc is primarily ascribed to its higher cellular uptake.

Alpha-tocotrienol provides the most potent neuroprotection among vitamin E analogs on cultured striatal neurons

Oxidative stress and apoptosis play pivotal roles in the pathogenesis of neurodegenerative diseases. We investigated the effects of vitamin E analogs on oxidative stress and apoptosis using primary neuronal cultures of rat striatum. A tocotrienol-rich fraction of edible oil derived from palm oil (Tocomin 50%), which contains alpha-tocopherol, and alpha-, gamma- and delta-tocotrienols, significantly inhibited hydrogen peroxide (H2O2)-induced neuronal death. Each of the tocotrienols, purified from Tocomin 50% by high-performance liquid chromatography, significantly attenuated H2O2-induced neurotoxicity, whereas alpha-tocopherol did not. alpha-, gamma- and delta-Tocotrienols also provided significant protection against the cytotoxicity of a superoxide donor, paraquat, and nitric oxide donors, S-nitrosocysteine and 3-morpholinosydnonimine. Moreover, tocotrienols blocked oxidative stress-mediated cell death with apoptotic DNA fragmentation caused by an inhibitor of glutathione synthesis, L-buthionine-[S,R]-sulfoximine. In addition, alpha-tocotrienol, but not gamma- or delta-tocotrienol, prevented oxidative stress-independent apoptotic cell death, DNA cleavage and nuclear morphological changes induced by a non-specific protein kinase inhibitor, staurosporine. These findings suggest that alpha-tocotrienol can exert anti-apoptotic neuroprotective action independently of its antioxidant property. Among the vitamin E analogs examined, alpha-tocotrienol exhibited the most potent neuroprotective actions in rat striatal cultures.

Vitamin E deficiency reduced lumbar bone calcium content in female rats

Vitamin E deficiency has been found to impair bone calcification. This study was done to determine the effects of vitamin E deficiency and supplementation on parathyroid hormone, i.e. the hormone involved in bone regulation. Female Sprague-Dawley rats were divided into 4 groups: 1) normal rat chow (RC), 2) vitamin E deficiency (VED), vitamin E deficient rats supplemented with 3) 60 mg/kg alpha-tocotrienol (ATT) and 4) 60 mg/kg (alpha-tocopherol (ATF). Treatment was carried out for 3 months. Vitamin E deficiency caused hypocalcaemia during the first month of the treatment period, increased the parathyroid hormone level in the second month and decreased the bone calcium content in the 4th lumbar bone at the end of the treatment. Vitamin E supplementation (ATT and ATF) failed to improve these conditions. The bone formation marker, osteocalcin, and the bone resorption marker, deoxypyridinoline did not change throughout the study period. In conclusion vitamin E deficiency impaired bone calcium homeostasis with subsequent secondary hyperparathyroidism and vertebral bone loss. Replacing the vitamin E with pure ATF or pure ATT alone failed to correct the changes seen.

Molecular basis of vitamin E action: tocotrienol modulates 12-lipoxygenase, a key mediator of glutamate-induced neurodegeneration

Vitamin E is a generic term for tocopherols and tocotrienols. This work is based on our striking evidence that, in neuronal cells, nanomolar concentrations of alpha-tocotrienol, but not alpha-tocopherol, block glutamate-induced death by suppressing early activation of c-Src kinase (Sen, C. K., Khanna, S., Roy, S., and Packer, L. (2000) J. Biol. Chem. 275, 13049-13055). This study on HT4 and immature primary cortical neurons suggests a central role of 12-lipoxygenase (12-LOX) in executing glutamate-induced neurodegeneration. BL15, an inhibitor of 12-LOX, prevented glutamate-induced neurotoxicity. Moreover, neurons isolated from 12-LOX-deficient mice were observed to be resistant to glutamate-induced death. In the presence of nanomolar alpha-tocotrienol, neurons were resistant to glutamate-, homocysteine-, and l-buthionine sulfoximine-induced toxicity. Long-term time-lapse imaging studies revealed that neurons and their axo-dendritic network are fairly motile under standard culture conditions. Such motility was arrested in response to glutamate challenge. Tocotrienol-treated primary neurons maintained healthy growth and motility even in the presence of excess glutamate. The study of 12-LOX activity and metabolism revealed that this key mediator of glutamate-induced neurodegeneration is subject to control by the nutrient alpha-tocotrienol. In silico docking studies indicated that alpha-tocotrienol may hinder the access of arachidonic acid to the catalytic site of 12-LOX by binding to the opening of a solvent cavity close to the active site. These findings lend further support to alpha-tocotrienol as a potent neuroprotective form of vitamin E.

Inhibition of THP-1 cell adhesion to endothelial cells by alpha-tocopherol and alpha-tocotrienol is dependent on intracellular concentration of the antioxidants

Vitamin E analogs such as alpha-tocopherol and alpha-tocotrienol have been shown to reduce endothelial expression of adhesion molecules. The reactivity of alpha-tocopherol and alpha-tocotrienol in inhibiting lipid peroxidation in vitro was essentially identical but the inhibition of adhesion of THP-1 cells, a monocytic-"like" cell line, to endothelial cells differs substantially. To determine the mechanism underlying this response, human umbilical vein endothelial cells (HUVECs) were assessed for their ability to accumulate vitamin E analogs. alpha-Tocotrienol accumulated in HUVECs to levels approximately 10-fold greater than that of alpha-tocopherol. The decrease in expression of vascular cell adhesion molecule-1 (VCAM-1) and the adhesion of THP-1 cells to HUVECs by alpha-tocopherol and alpha-tocotrienol was also determined. Both alpha-tocopherol and alpha-tocotrienol suppressed VCAM-1 expression and adhesion of THP-1 cells to HUVECs in a concentration-dependent manner. The efficacy of tocotrienol for reduction of VCAM-1 expression and adhesion of THP-1 cells to HUVECs was also 10-fold higher than that of tocopherol. The inhibitory effects of vitamin E analogs on the adhesiveness of endothelial cells clearly correlated with their intracellular concentrations. The data demonstrated that, in assessing the biological responses of antioxidants, intracellular accumulation and metabolism were additional important factors that must be considered.

HPLC analysis of vitamin E isoforms in human epidermis: correlation with minimal erythema dose and free radical scavenging activity

The content and composition of different vitamin E isoforms was analyzed in normal human skin. Interestingly the epidermis contained 1% alpha-tocotrienol, 3% gamma-tocotrienol, 87% alpha-tocopherol, and 9% gamma-tocopherol. Although the levels of tocotrienol in human epidermis appear to be considerably lower than reported in the hairless mouse, the presence of significant amounts of tocotrienol levels leads to speculation about the physiological function of tocotrienols in skin. Besides antioxidant activity and photoprotection, tocotrienols may have skin barrier and growth-modulating properties. A good correlation was found for epidermal alpha-tocopherol (r = 0.7909, p <.0003), gamma-tocopherol (r = 0.556, p <.025), and the total vitamin E content (r = 0.831, p <.0001) with the free radical 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging in epidermis, as assessed by electron paramagnetic resonance (EPR) spectroscopy. In human epidermis, alpha-tocopherol is quantitatively the most important vitamin E isoform present and comprises the bulk of first line free radical defense in the lipid compartment. Epidermal tocotrienol levels were not correlated with DPPH scavenging activity. The minimal erythema dose (MED), an individual measure for sun sensitivity and a crude indicator for skin cancer susceptibility, did not correlate with the epidermal content of the vitamin E isoforms. Hence it is concluded that vitamin E alone is not a determinant of individual photosensitivity in humans.

Dietary alpha-tocopherol decreases alpha-tocotrienol but not gamma-tocotrienol concentration in rats

We previously showed that alpha- and gamma-tocotrienols accumulate in adipose tissue and skin but not in plasma or other tissues of rats fed a tocotrienol-rich fraction extracted from palm oil containing alpha-tocopherol and alpha- and gamma-tocotrienols. To clarify the nature of tocotrienol metabolism, we studied the distribution of alpha- or gamma-tocotrienol in rats fed alpha- or gamma-tocotrienol without alpha-tocopherol, and the effect of alpha-tocopherol on their distribution. Wistar rats (4-wk-old) were fed a diet with 50 mg alpha-tocotrienol/kg alone or with 50 mg alpha-tocopherol/kg in expt. 1, and a diet with 50 mg gamma-tocotrienol/kg alone or with 50 mg alpha-tocopherol/kg in expt. 2, for 8 wk. alpha-Tocotrienol was detected in various tissues and plasma of the rats fed alpha-tocotrienol alone, and the alpha-tocotrienol concentrations in those tissues and plasma decreased (P < 0.05) by the dietary alpha-tocopherol in the rats fed alpha-tocotrienol with alpha-tocopherol. However, gamma-tocotrienol preferentially accumulated in the adipose tissue and skin of the rats fed gamma-tocotrienol alone, and the dietary alpha-tocopherol failed either to decrease (P >/= 0.05) gamma-tocotrienol concentrations in the adipose tissue and skin or to increase (P >/= 0.05) in the urinary excretion of 2,7,8-trimethyl-2(2'-carboxymethyl)-6-hydroxycroman, a metabolite of gamma-tocotrienol, in the rats fed gamma-tocotrienol with alpha-tocopherol. These data suggest that alpha-tocopherol enhances the alpha-tocotrienol metabolism but not the gamma-tocotrienol metabolism in rats.

Vitamin E isoforms alpha-tocotrienol and gamma-tocopherol prevent cerebral infarction in mice

Alpha-tocopherol and its derivatives have been shown to be effective in reducing cerebral ischemia-induced brain damage. However, the effects of other vitamin E isoforms have not been characterized. In the present study, we investigated the effects of six different isoforms of vitamin E on the ischemic brain damage in the mice middle cerebral artery (MCA) occlusion model. All vitamin E isoforms were injected i.v., twice, immediately before and 3 h after the occlusion. Alpha-tocopherol (2 mM), alpha-tocotrienol (0.2 and 2 mM) and gamma-tocopherol (0.2 and 2 mM) significantly decreased the size of the cerebral infarcts 1 day after the MCA occlusion, while gamma-tocotrienol, delta-tocopherol and delta-tocotrienol showed no effect on the cerebral infarcts. These results suggest that alpha-tocotrienol and gamma-tocopherol are potent and effective agents for preventing cerebral infarction induced by MCA occlusion.

Topical alpha-tocotrienol supplementation inhibits lipid peroxidation but fails to mitigate increased transepidermal water loss after benzoyl peroxide treatment of human skin

Benzoyl peroxide (BPO) is a commonly used drug in the treatment of acne vulgaris, but it induces unwanted side effects related to stratum corneum (SC) function. Since it has been recently shown to oxidize SC antioxidants, it was hypothesized that antioxidant supplementation may mitigate the BPO-induced SC changes. To test this, 11 subjects were selected to be topically supplemented with alpha-tocotrienol (5% w/vol) for 7 d on defined regions of the upper back, while the contralateral region was used for vehicle-only controls. Starting on day 8, all test sites were also treated with BPO (10%) for 7 d; the alpha-tocotrienol supplementation was continued throughout the study. A single dose of BPO depleted 93.2% of the total vitamin E. While continuing the BPO exposure for 7 d further depleted vitamin E in both vehicle-only and alpha-tocotrienol-treated sites, significantly more vitamin E remained in the alpha-tocotrienol-treated areas. Seven BPO applications increased lipid peroxidation. Alpha-tocotrienol supplementation significantly mitigated the BPO-induced lipid peroxidation. The transepidermal water loss was increased 1.9-fold by seven BPO applications, while there was no difference between alpha-tocotrienol treatment and controls. The data suggest that alpha-tocotrienol supplementation counteracts the lipid peroxidation but not the barrier perturbation in the SC induced by 10% BPO.

Influence of route of administration on the absorption and disposition of alpha-, gamma- and delta-tocotrienols in rats

A study was conducted to evaluate the bioavailability of alpha-, gamma- and delta-tocotrienols administered via oral, intravenous, intramuscular and intraperitoneal routes in rats. Three separate experiments, each conducted according to a two-way crossover design, were carried out to compare intravenous and oral, intramuscular and oral, and intraperitoneal and oral administration. Oral absorption of all three tocotrienols was found to be incomplete. Of the three tocotrienols, alpha-tocotrienol had the highest oral bioavailability, at about 27.7+/-9.2%, compared with gamma- and delta-tocotrienols, which had values of 9.1+/-2.4% and 8.5+/-3.5%, respectively. Such biodiscrimination was also observed in their total clearance rates (estimated from the intravenous data). alpha-Tocotrienol showed the lowest clearance rate at about 0.16 L kg(-1) h(-1), whereas that of delta- and gamma-tocotrienols was quite similar, with values of 0.24 and 0.23 L kg(-1) h(-1), respectively. Interestingly, all three tocotrienols were found to be negligibly absorbed when administered intraperitoneally and intramuscularly. Thus, these two routes of administration should be avoided when evaluating the biological activities of the tocotrienols in whole animal experiments.