Tissue Distribution of α- and γ-Tocotrienol and γ-Tocopherol in Rats and Interference with Their Accumulation by α-Tocopherol

Strategies to Enhance the Solubility and Bioavailability of Tocotrienols Using Self-Emulsifying Drug Delivery System

Tocotrienols have higher medicinal value, with multiple sources of evidence showing their biological properties as antioxidant, anti-inflammatory, and osteoprotective compounds. However, tocotrienol bioavailability presents an ongoing challenge in its translation into viable products. This is because tocotrienol oil is known to be a poorly water-soluble compound, making it difficult to be absorbed into the body and resulting in less effectiveness. With the potential and benefits of tocotrienol, new strategies to increase the bioavailability and efficacy of poorly absorbed tocotrienol are required when administered orally. One of the proposed formulation techniques was self-emulsification, which has proven its capacity to improve oral drug delivery of poorly water-soluble drugs by advancing the solubility and bioavailability of these active compounds. This review discusses the updated evidence on the bioavailability of tocotrienols formulated with self-emulsifying drug delivery systems (SEDDSs) from in vivo and human studies. In short, SEDDSs formulation enhances the solubility and passive permeability of tocotrienol, thus improving its oral bioavailability and biological actions. This increases its medicinal and commercial value. Furthermore, the self-emulsifying formulation presents a useful dosage form that is absorbed in vivo independent of dietary fats with consistent and enhanced levels of tocotrienol isomers. Therefore, a lipid-based formulation technique can provide an additional detailed understanding of the oral bioavailability of tocotrienols.

Anti-fibrotic effect of tocotrienols for bladder dysfunction due to partial bladder outlet obstruction

PURPOSE

To investigate potential beneficial effects of tocotrienols which have been suggested to inhibit hypoxia-inducible factor (HIF) pathway, on partial bladder outlet obstruction (PBOO)-induced bladder pathology.

MATERIALS AND METHODS

PBOO was surgically created in juvenile male mice. Sham-operated mice were used as controls. Animals received daily oral administration of either tocotrienols (T₃) or soybean oil (SBO, vehicle) from day 0 to 13 post-surgery. Bladder function was examined in vivo by void spot assay. At 2 weeks post-surgery, the bladders were subjected to physiological evaluation of detrusor contractility in vitro using bladder strips, histology by H&E staining and collagen imaging, and gene expression analyses by quantitative PCR.

RESULTS

A significant increase in the number of small voids was observed after 1 week of PBOO compared to the control groups. At 2 weeks post-surgery, PBOO+SBO mice showed a further increase in the number of small voids, which was not observed in PBOO+T₃ group. PBOO-induced decrease in detrusor contractility was similar between two treatments. PBOO induced bladder hypertrophy to the same degree in both SBO and T₃ treatment groups, however, fibrosis in the bladder was significantly less prominent in the T₃ group than the SBO group following PBOO (1.8- vs. 3.0-fold increase in collagen content compared to the control). Enhanced levels of HIF target genes in the bladders were observed in PBOO+SBO group, but not in PBOO+T₃ group compared to the control.

CONCLUSIONS

Oral tocotrienol treatment reduced the progression of urinary frequency and bladder fibrosis by suppressing HIF pathways triggered by PBOO.

Absorption, transportation, and distribution of vitamin E homologs

Vitamin E has eight different naturally occurring forms: four tocopherols and four tocotrienols. Because α-tocopherol has three asymmetric carbons, both natural α-tocopherol (RRR-α-tocopherol) and synthetic α-tocopherol (all-rac-α-tocopherol) are utilized in both pharmaceutical products and food additives. Therefore, determining the distribution of vitamin E in the body is very important. With regard to absorption, and transportation of vitamin E, it is suggested that the pathways mediated by three proteins (CD36, SR-BI, and NPC1L1) as well as passive diffusion affect absorption of vitamin E. Vitamin E homologs are mainly transported by very low-density lipoprotein (VLDL) with the α-tocopherol being recognized by the α-tocopherol transfer protein in liver. However, it is also suggested that chylomicrons (CMs) and high-density lipoprotein (HDL) are involved in transportation of vitamin E homologs from the small intestine to each section of peripheral tissue. In particular, it is speculated that vitamin E homologs transportation by CMs and HDL from enterocytes to peripheral tissues such as adipose tissue greatly affects the distribution of vitamin E homologs, excluding α-tocopherol. However, how lipoprotein lipase affects the incorporation of vitamin E homologs containing lipoprotein into peripheral tissues is unclear. Whether there is biodiscrimination when vitamin E homologs are incorporated into peripheral tissues from lipoprotein is an interesting question. It is likely that future research will reveal how individual vitamin E homologs are incorporated into peripheral tissue, especially the brain, adipose tissue, and skin.

Diverse cytoprotective actions of vitamin E isoforms- role as peroxyl radical scavengers and complementary functions with selenoproteins

Vitamin E, a generic term for tocopherol (T) and tocotrienol (T3), is one of the most potent lipid-soluble antioxidants in the body. It is classified into T and T3 based on the difference in the side chain structure. T and T3 have four isoforms: α-, β-, γ-, and δ, which have different chroman rings. Both T and T3 exhibit a similar ability to scavenge free radicals, and the extent of this ability depends on the difference in the chroman structure. However, they display unique cytoprotective activities in cultured cells depending on the difference in the side chain structure. The cytoprotective effects of vitamin E have received much attention in the prevention of ferroptosis, which is a distinct form of cell death involving iron-dependent lipid peroxidation. This review focuses on the cytoprotective actions of vitamin E isoforms against oxidative stress, particularly the difference between T and T3 and its relation to cellular uptake and distribution. Moreover, the molecular mechanism for cytoprotection of vitamin E oxidation products is explained, and the complementary role of vitamin E and selenoproteins to prevent lipid peroxidation and ferroptosis is described. Furthermore, the evaluation of vitamin E's radical scavenging activity in vivo using oxidative stress markers is discussed, particularly based on kinetic data and the physiological molar ratio of vitamin E to substrates, and the limited role of vitamin E as a peroxyl radical scavenger is described. The future directions and unresolved issues related to vitamin E and lipid peroxidation are also discussed.

Tocopherols and Tocotrienols-Bioactive Dietary Compounds; What Is Certain, What Is Doubt?

Tocopherols and tocotrienols are natural compounds of plant origin, available in the nature. They are supplied in various amounts in a diet, mainly from vegetable oils, some oilseeds, and nuts. The main forms in the diet are α- and γ-tocopherol, due to the highest content in food products. Nevertheless, α-tocopherol is the main form of vitamin E with the highest tissue concentration. The α- forms of both tocopherols and tocotrienols are considered as the most metabolically active. Currently, research results indicate also a greater antioxidant potential of tocotrienols than tocopherols. Moreover, the biological role of vitamin E metabolites have received increasing interest. The aim of this review is to update the knowledge of tocopherol and tocotrienol bioactivity, with a particular focus on their bioavailability, distribution, and metabolism determinants in humans. Almost one hundred years after the start of research on α-tocopherol, its biological properties are still under investigation. For several decades, researchers' interest in the biological importance of other forms of vitamin E has also been growing. Some of the functions, for instance the antioxidant functions of α- and γ-tocopherols, have been confirmed in humans, while others, such as the relationship with metabolic disorders, are still under investigation. Some studies, which analyzed the biological role and mechanisms of tocopherols and tocotrienols over the past few years described new and even unexpected cellular and molecular properties that will be the subject of future research.

Application of Partial Hydrogenation for the Generation of Minor Tocochromanol Homologs and Functional Evaluation of Hydrogenated Tocotrienol-rich Vitamin E Oil in Diabetic Obese Mice

Recent research has identified minor homologs of vitamin E with one or two double bonds in the side-chain, namely tocomonoenol (T1) and tocodienol (T2), in natural products. We first explored the effectiveness of partial hydrogenation for generating minor tocochromanols from tocotrienol (T3). During hydrogenation with pure α-T3 as a substrate, the side-chain was partially saturated in a time-dependent manner, and a large amount of α-T1 and α-T2 was obtained. To investigate the beneficial effects of the hydrogenated product, we fed diabetic obese KK-A y mice with a hydrogenated T3 mixture (HT3). Feeding HT3 revealed tissue-specific accumulation of tocochromanols, ameliorated hyperglycemia and improved ratio of high-density lipoprotein cholesterol to total cholesterol in serum, with invariant body weight and fat mass. Hence, we propose that hydrogenation is a useful method for generating T1 and T2 homologs, which can be applied to explore the structure-related function of tocochromanols.

Pharmacology and Pharmacokinetics of Vitamin E: Nanoformulations to Enhance Bioavailability

Vitamin E belongs to the family of lipid-soluble vitamins and can be divided into two groups, tocopherols and tocotrienols, with four isomers (alpha, beta, gamma and delta). Although vitamin E is widely known as a potent antioxidant, studies have also revealed that vitamin E possesses anti-inflammatory properties. These crucial properties of vitamin E are beneficial in various aspects of health, especially in neuroprotection and cardiovascular, skin and bone health. However, the poor bioavailability of vitamin E, especially tocotrienols, remains a great limitation for clinical applications. Recently, nanoformulations that include nanovesicles, solid-lipid nanoparticles, nanostructured lipid carriers, nanoemulsions, and polymeric nanoparticles have shown promising outcomes in improving the efficacy and bioavailability of vitamin E. This review focuses on the pharmacological properties and pharmacokinetics of vitamin E and current advances in vitamin E nanoformulations for future clinical applications. The limitations and future recommendations are also discussed in this review.

α-Tocomonoenol Is Bioavailable in Mice and May Partly Be Regulated by the Function of the Hepatic α‑Tocopherol Transfer Protein

Tocomonoenols are vitamin E derivatives present in foods with a single double bond at carbon 11' in the sidechain. The α-tocopherol transfer protein (TTP) is required for the maintenance of normal α-tocopherol (αT) concentrations. Its role in the tissue distribution of α-11'-tocomonoenol (αT₁) is unknown. We investigated the tissue distribution of αT₁ and αT in wild-type (TTP^+/+) and TTP knockout (TTP^-/-) mice fed diets with either αT or αT₁ for two weeks. αT₁ was only found in blood, not tissues. αT concentrations in TTP^+/+ mice were in the order of adipose tissue > brain > heart > spleen > lungs > kidneys > small intestine > liver. Loss of TTP function depleted αT in all tissues. αT₁, contrary to αT, was still present in the blood of TTP^-/- mice (16% of αT₁ in TTP^+/+). Autoclaving and storage at room temperature reduced αT and αT₁ in experimental diets. In conclusion, αT₁ is bioavailable, reaches the blood in mice, and may not entirely depend on TTP function for secretion into the systemic circulation. However, due to instability of the test compounds in the experimental diets, further in vivo experiments are required to clarify the role of TTP in αT₁ secretion. Future research should consider compound stability during autoclaving of rodent feed.

Inflammatory Diseases and Vitamin E-What Do We Know and Where Do We Go?

Inflammation-driven diseases and related comorbidities, such as the metabolic syndrome, obesity, fatty liver disease, and cardiovascular diseases cause significant global burden. There is a growing body of evidence that nutrients alter inflammatory responses and can therefore make a decisive contribution to the treatment of these diseases. Recently, the inflammasome, a cytosolic multiprotein complex, has been identified as a key player in inflammation and the development of various inflammation-mediated disorders, with nucleotide-binding domain and leucine-rich repeat pyrin domain (NLRP) 3 being the inflammasome of interest. Here an overview about the cellular signaling pathways underlying nuclear factor "kappa-light-chain-enhancer" of activated B-cells (NF-κB)- and NLRP3-mediated inflammatory processes, and the pathogenesis of the inflammatory diseases atherosclerosis and non-alcoholic fatty liver disease (NAFLD) is provided; next, the current state of knowledge for drug-based and dietary-based interventions for treating cardiovascular diseases and NAFLD is discussed. To date, one of the most important antioxidants in the human diet is vitamin E. Various in vitro and in vivo studies suggest that the different forms of vitamin E and also their derivatives have anti-inflammatory activity. Recent publications suggest that vitamin E-and possibly metabolites of vitamin E-are a promising therapeutic approach for treating inflammatory diseases such as NAFLD.

Potential Role of Tocotrienols on Non-Communicable Diseases: A Review of Current Evidence

Tocotrienol (T3) is a subfamily of vitamin E known for its wide array of medicinal properties. This review aimed to summarize the health benefits of T3, particularly in prevention or treatment of non-communicable diseases (NCDs), including cardiovascular, musculoskeletal, metabolic, gastric, and skin disorders, as well as cancers. Studies showed that T3 could prevent various NCDs, by suppressing 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR) in the mevalonate pathway, inflammatory response, oxidative stress, and alternating hormones. The efficacy of T3 in preventing/treating these NCDs is similar or greater compared to tocopherol (TF). TF may lower the efficacy of T3 because the efficacy of the combination of TF and T3 was lower than T3 alone in some studies. Data investigating the effects of T3 on osteoporosis, arthritis, and peptic ulcers in human are limited. The positive outcomes of T3 treatment obtained from the preclinical studies warrant further validation from clinical trials.

Tocotrienols and Cancer: From the State of the Art to Promising Novel Patents

BACKGROUND

Tocotrienols (TTs) are vitamin E derivatives naturally occurring in several plants and vegetable oils. Like Tocopherols (TPs), they comprise four isoforms, α, β, γ and δ, but unlike TPs, they present an unsaturated isoprenoid chain. Recent studies indicate that TTs provide important health benefits, including neuroprotective, anti-inflammatory, anti-oxidant, cholesterol lowering and immunomodulatory effects. Moreover, they have been found to possess unique anti-cancer properties.

OBJECTIVE

The purpose of this review is to present an overview of the state of the art of TTs role in cancer prevention and treatment, as well as to describe recent patents proposing new methods for TTs isolation, chemical modification and use in cancer prevention and/or therapy.

METHODS

Recent literature and patents focusing on TTs anti-cancer applications have been identified and reviewed, with special regard to their scientific impact and novelty.

RESULTS

TTs have demonstrated significant anti-cancer activity in multiple tumor types, both in vitro and in vivo. Furthermore, they have shown synergistic effects when given in combination with standard anti-cancer agents or other anti-tumor natural compounds. Finally, new purification processes and transgenic sources have been designed in order to improve TTs production, and novel TTs formulations and synthetic derivatives have been developed to enhance their solubility and bioavailability.

CONCLUSION

The promising anti-cancer effects shown by TTs in several preclinical studies may open new opportunities for therapeutic interventions in different tumors. Thus, clinical trials aimed at confirming TTs chemopreventive and tumor-suppressing activity, particularly in combination with standard therapies, are urgently needed.

α-Tocopherol Protects the Heart, Muscles, and Testes from Lipid Peroxidation in Growing Male Rats Subjected to Physical Efforts

The effect of α-tocopherol supplementation on adaptation to training is still equivocal. The aim of the study was to determine the effect of training and α-tocopherol supplementation on α-tocopherol and thiobarbituric acid reactive substance (TBARS) concentration in the rat liver, heart, muscles, and testes. Male Wistar rats (n = 32) were divided into four groups (nonsupplemented, not trained—C; nonsupplemented, trained—CT; supplemented, not trained—E; supplemented and trained—ET). During the 14-day experimental period, 2 mg/d of vitamin E as α-tocopherol acetate was administered to the animals (groups E and ET). Rats in the training group (CT and ET) were subjected to 15 minutes of treadmill running each day. The α-tocopherol levels in rat tissues were assessed using high-performance liquid chromatography (HPLC). Lipid peroxides were determined by TBARS spectrophotometric method. α-Tocopherol had a significant impact on α-tocopherol concentration in all tissues. Training increased the α-tocopherol concentration in the heart and muscles but reduced it in the liver. Training also caused increased lipid peroxidation in the muscles, heart, and testes; but a higher α-tocopherol content in tissues reduced the TBARS level. The main finding of the study is that impaired α-tocopherol status and its adequate intake is needed to maintain optimal status to prevent damage to the skeletal and cardiac muscles as well as the testes in growing individuals.

Annatto () δ-TCT supplementation protected against embryonic DNA damages through alterations in PI3K/ Akt-Cyclin D1 pathway

Protective action by annatto-derived delta-tocotrienol (δ-TCT) and soy-derived alpha-tocopherol (α-TOC) through the regulation of PI3K/Akt-Cyclin D1 pathway against the nicotine-induced DNA damages is the focus of the present study. Nicotine, which has been widely reported to have numerous adverse effects on the reproductive system, was used as reproductive toxicant. 48 female balb/c mice (6-8 weeks) (23-25 g) were randomly divided into 8 groups (G1-G8; n = 6) and treated with either nicotine or/and annatto δ-TCT/soy α-TOC for 7 consecutive days. On Day 8, the females were superovulated and mated before euthanized for embryo collection (46 hours post-coitum). Fifty 2-cell embryos from each group were used in gene expression analysis using Affymetrix QuantiGene Plex2.0 assay. Findings indicated that nicotine (G2) significantly decreased (p < 0.05) the number of produced 2-cell embryos compared to control (G1). Intervention with mixed annatto δ-TCT (G3) and pure annatto δ-TCT (G4) significantly increased the number of produced 2-cell embryos by 127 % and 79 % respectively compared to G2, but these were lower than G1. Concurrent treatment with soy α-TOC (G5) decreased embryo production by 7 %. Supplementations with δ-TCT and α-TOC alone (G6-G8) significantly increased (p < 0.05) the number of produced 2-cell embryos by 50 %, 36 % and 41 % respectively, compared to control (G1). These results were found to be associated with the alterations in the PI3K/Akt-Cyclin D1 gene expressions, indicating the inhibitory effects of annatto δ-TCT and soy α-TOC against the nicotinic embryonic damages. To our knowledge, this is the first attempt on studying the benefits of annatto δ-TCT on murine preimplantation 2-cell embryos.

Annatto (Bixa orellana) δ-TCT Supplementation Protection against Embryonic Malformations through Alterations in PI3K/Akt-Cyclin D1 Pathway

Protective action by annatto-derived delta-tocotrienol (δ-TCT) and soy-derived alpha-tocopherol (α-TOC) through the regulation of the PI3K/Akt-cyclin D1 pathway against nicotine-induced DNA damage is the focus of the present study. Nicotine, which has been widely reported to have numerous adverse effects on the reproductive system, was used as a reproductive toxicant. 48 female balb/c mice (6⁻8 weeks) (23⁻25 g) were randomly divided into eight groups (Grp.1⁻Grp.8; n = 6) and treated with either nicotine or/and annatto δ-TCT/soy α-TOC for seven consecutive days. On Day 8, the females were superovulated and mated before euthanization for embryo collection (46 h post-coitum). Fifty 2-cell embryos from each group were used in gene expression analysis using Affymetrix QuantiGene Plex2.0 assay. Findings indicated that nicotine (Grp.2) significantly decreased (p < 0.05) the number of produced 2-cell embryos compared to the control (Grp.1). Intervention with mixed annatto δ-TCT (Grp.3) and pure annatto δ-TCT (Grp.4) significantly increased the number of produced 2-cell embryos by 127% and 79%, respectively compared to Grp.2, but these were lower than Grp.1. Concurrent treatment with soy α-TOC (Grp.5) decreased embryo production by 7%. Supplementations with δ-TCT and α-TOC alone (Grp.6-Grp.8) significantly increased (p < 0.05) the number of produced 2-cell embryos by 50%, 36%, and 41%, respectively, compared to control (Grp.1). These results were found to be associated with alterations in the PI3K/Akt-Cyclin D1 genes expressions, indicating the inhibitory effects of annatto δ-TCT and soy α-TOC against nicotinic embryonic damage. To our knowledge, this is the first attempt in studying the benefits of annatto δ-TCT on murine preimplantation 2-cell embryos.

Exploring the potential of tocotrienol from Bixa orellana as a single agent targeting metabolic syndrome and bone loss

Metabolic syndrome (MetS) is associated with osteoporosis due to the underlying inflammatory and hormonal changes. Annatto tocotrienol has been shown to improve medical complications associated with MetS or bone loss in animal studies. This study aimed to investigate the effects of annatto tocotrienol as a single treatment for MetS and osteoporosis in high-carbohydrate high-fat (HCHF) diet-induced MetS animals. Three-month-old male Wistar rats were randomly divided into five groups. The baseline group was euthanized at the onset of the study. The normal group received standard rat chow and tap water. The remaining groups received HCHF diet and treated with three different regimens orally daily: (a) tocopherol-stripped corn oil (the vehicle of tocotrienol), (b) 60 mg/kg annatto tocotrienol, and (c) 100 mg/kg annatto tocotrienol. At the end of the study, measurements of MetS parameters, body compositions, and bone mineral density were performed in animals before sacrifice. Upon euthanasia, blood and femur of the rats were harvested for the evaluations of bone microstructure, biomechanical strength, remodelling activities, hormonal changes, and inflammatory response. Treatment with annatto tocotrienol improved all MetS parameters (except abdominal obesity), trabecular bone microstructure, bone strength, increased osteoclast number, normalized hormonal changes and inflammatory response in the HCHF animals. In conclusion, annatto tocotrienol is a potential agent for managing MetS and osteoporosis concurrently. The beneficial effects of annatto tocotrienol may be attributed to its ability to prevent the hormonal changes and pro-inflammatory state in animals with MetS.

A Review on the Relationship between Tocotrienol and Alzheimer Disease

Alzheimer&rsquo;s disease (AD) is plaguing the aging population worldwide due to its tremendous health care and socioeconomic burden. Current treatment of AD only offers symptomatic relief to patients. Development of agents targeting specific pathologies of AD is very slow. Tocotrienol, a member of the vitamin E family, can tackle many aspects of AD, such as oxidative stress, mitochondrial dysfunction and abnormal cholesterol synthesis. This review summarizes the current evidence on the role of tocotrienol as a neuroprotective agent. Preclinical studies showed that tocotrienol could reduce oxidative stress by acting as a free-radical scavenger and promoter of mitochondrial function and cellular repair. It also prevented glutamate-induced neurotoxicity in the cells. Human epidemiological studies showed a significant inverse relationship between tocotrienol levels and the occurrence of AD. However, there is no clinical trial to support the claim that tocotrienol can delay or prevent the onset of AD. As a conclusion, tocotrienol has the potential to be developed as an AD-preventing agent but further studies are required to validate its efficacy in humans.

Quantitative Analysis of the Accumulation of Marine-derived Tocopherol in the Tissue of Mice Fed with Salmon Roe Oil Using HPLC-fluorescence

In this study, we measured the quantity of marine-derived tocopherol (MDT), a monounsaturated vitamin E (VE), stored in the body tissue of mice fed with a diet containing a VE-rich fraction extracted from salmon roe. We first prepared the calibration curves for the MDT concentration using an HPLC-fluorescence system. Ranging from 0.016 to 50 μg/mL, the slope was expressed as first-order equations, with R² values = 0.99. The mice were fed with an AIN-93 based diet containing MDT in doses of 21.4 mg/kg for 4 weeks, and the storage in the heart, lung, liver, stomach, small intestine, large intestine, kidney, pancreas, spleen, testis, skeletal muscle, visceral white adipose tissue (WAT), subcutaneous WAT and brain was quantified. MDT was widely distributed in tissues throughout the whole body, with higher accumulations observed in the adipose tissue, liver and kidney. These results demonstrate means to estimating the MDT concentration in natural products and in the bodies of animals and contribute to the understanding of the physiological functions of MDT in relation to human health.

Methods for efficient analysis of tocopherols, tocotrienols and their metabolites in animal samples with HPLC-EC

Tocopherols and tocotrienols, collectively known as vitamin E, have received a great deal of attention because of their interesting biological activities. In the present study, we reexamined and improved previous methods of sample preparation and the conditions of high-performance liquid chromatography for more accurate quantification of tocopherols, tocotrienols and their major chain-degradation metabolites. For the analysis of serum tocopherols/tocotrienols, we reconfirmed our method of mixing serum with ethanol followed by hexane extraction. For the analysis of tissue samples, we improved our methods by extracting tocopherols/tocotrienols directly from tissue homogenate with hexane. For the analysis of total amounts (conjugated and unconjugated forms) of side-chain degradation metabolites, the samples need to be deconjugated by incubating with β-glucuronidase and sulfatase; serum samples can be directly used for the incubation, whereas for tissue homogenates a pre-deproteination step is needed. The present methods are sensitive, convenient and are suitable for the determination of different forms of vitamin E and their metabolites in animal and human studies. Results from the analysis of serum, liver, kidney, lung and urine samples from mice that had been treated with mixtures of tocotrienols and tocopherols are presented as examples.

Tocotrienols for bone health: a translational approach

Osteoporosis, a degenerative bone disease, is characterized by low bone mass and microstructural deterioration of bone tissue resulting in aggravated bone fragility and susceptibility to fractures. The trend of extended life expectancy is accompanied by a rise in the prevalence of osteoporosis and concomitant complications in the elderly population. Epidemiological evidence has shown an association between vitamin E consumption and the prevention of age-related bone loss in elderly women and men. Animal studies show that ingestion of vitamin E, especially tocotrienols, may benefit bone health in terms of maintaining higher bone mineral density and improving bone microstructure and quality. The beneficial effects of tocotrienols on bone health appear to be mediated via antioxidant/anti-inflammatory pathways and/or 3-hydroxy-3-methylglutaryl coenzyme A mechanisms. We discuss (1) an overview of the prevalence and etiology of osteoporosis, (2) types of vitamin E (tocopherols versus tocotrienols), (3) findings of tocotrienols and bone health from published in vitro and animal studies, (4) possible mechanisms involved in bone protection, and (5) challenges and future direction for research.

Vitamin E As a Potential Interventional Treatment for Metabolic Syndrome: Evidence from Animal and Human Studies

A constellation of medical conditions inclusive of central obesity, hyperglycemia, hypertension, and dyslipidemia is known as metabolic syndrome (MetS). The safest option in curtailing the progression of MetS is through maintaining a healthy lifestyle, which by itself, is a long-term commitment entailing much determination. A combination of pharmacological and non-pharmacological approach, as well as lifestyle modification is a more holistic alternative in the management of MetS. Vitamin E has been revealed to possess anti-oxidative, anti-inflammatory, anti-obesity, anti-hyperglycemic, anti-hypertensive and anti-hypercholesterolemic properties. The pathways regulated by vitamin E are critical in the development of MetS and its components. Therefore, we postulate that vitamin E may exert some health benefits on MetS patients. This review intends to summarize the evidence in animal and human studies on the effects of vitamin E and articulate the contrasting potential of tocopherol (TF) and tocotrienol (T3) in preventing the medical conditions associated with MetS. As a conclusion, this review suggests that vitamin E may be a promising agent for attenuating MetS.

α-Tocopherol Attenuates the Triglyceride- and Cholesterol-Lowering Effects of Rice Bran Tocotrienol in Rats Fed a Western Diet

Previous studies demonstrated the ability of tocotrienol (T3) to lower levels of lipids, including cholesterol (Cho) and triglycerides (TG). Although α-tocopherol (α-Toc) reportedly inhibits the hypocholesterolemic effect of T3, there is no information about whether α-Toc influences the TG-lowering effect of T3 in vivo. In this study, we investigated the influence of α-Toc on the antihyperlipidemic effects (Cho- and TG-lowering) of rice bran tocotrienols (RBT3) in F344 rats fed a western diet. α-Toc attenuated both the Cho- and TG-lowering effects of RBT3 in vivo, whereas α-Toc alone exhibited no hypolipidemic effects. RBT3-induced Cpt-1a and Cyp7a1 gene expression was reduced by α-Toc. Furthermore, coadministration of α-Toc decreased liver and adipose tissue concentrations of tocotrienols in F344 rats. These results indicate that α-Toc has almost no antihyperlipidemic effect in vivo, but abrogates the antihyperlipidemic effect of RBT3 by reducing tissue concentrations of tocotrienols and regulating expression of genes involved in lipid metabolism. Understanding the underlying mechanism of the beneficial effects of T3 on lipid metabolism and the interaction with α-Toc will be important for developing T3-based therapeutics.

Association between maternal vitamin E status and alpha-tocopherol levels in the newborn and colostrum

Vitamin E is important because of its antioxidant activity in situations of oxidative stress, especially postnatally. Hence, the objective was to verify whether maternal alpha-tocopherol level is associated with the alpha-tocopherol levels of the newborn and colostrum. This is a cross-sectional study of 58 women and their term newborns from a public hospital. Blood and colostrum were collected to measure alpha-tocopherol levels by high-performance liquid chromatography. Mothers with serum alpha-tocopherol levels <16.2 mmol L(-1) and newborns <11.6 mmol L(-1) were indicative of deficiency or low levels. Mothers were divided into two groups: <16.2 mmol L(-1) and those with levels ≥16.2 mmol L(-1) . The mean (95% confidence interval) serum alpha-tocopherol levels of mothers, umbilical cords and colostrum were 28 (24-32), 6 (5-8) and 39 mmol L(-1) (32-45), respectively (P < 0.001); 19% of the women and 90% of the newborns had low alpha-tocopherol levels. Maternal alpha-tocopherol level was associated with that of the umbilical cord. Newborns from mothers at risk of deficiency had low alpha-tocopherol levels (P < 0.001). Colostrum levels of vitamin E were not influenced by maternal serum. Maternal deficiency influenced the vitamin E level of the umbilical cord but does not in the colostrum, evidencing distinct transfer mechanisms via the mammary gland.

Vitamin E therapy beyond cancer: Tocopherol versus tocotrienol

The discovery of vitamin E (α-tocopherol) began in 1922 as a vital component required in reproduction. Today, there are eight naturally occurring vitamin E isoforms, namely α-, β-, γ- and δ-tocopherol and α-, β-, γ- and δ-tocotrienol. Vitamin E is potent antioxidants, capable of neutralizing free radicals directly by donating hydrogen from its chromanol ring. α-Tocopherol is regarded the dominant form in vitamin E as the α-tocopherol transfer protein in the liver binds mainly α-tocopherol, thus preventing its degradation. That contributed to the oversight of tocotrienols and resulted in less than 3% of all vitamin E publications studying tocotrienols. Nevertheless, tocotrienols have been shown to possess superior antioxidant and anti-inflammatory properties over α-tocopherol. In particular, inhibition of 3-hydroxy-3-methylglutaryl-coenzyme A reductase to lower cholesterol, attenuating inflammation via downregulation of transcription factor NF-κB activation, and potent radioprotectant against radiation damage are some properties unique to tocotrienols, not tocopherols. Aside from cancer, vitamin E has also been shown protective in bone, cardiovascular, eye, nephrological and neurological diseases. In light of the different pharmacological properties of tocopherols and tocotrienols, it becomes critical to specify which vitamin E isoform(s) are being studied in any future vitamin E publications. This review provides an update on vitamin E therapeutic potentials, protective effects and modes of action beyond cancer, with comparison of tocopherols against tocotrienols. With the concerted efforts in synthesizing novel vitamin E analogs and clinical pharmacology of vitamin E, it is likely that certain vitamin E isoform(s) will be therapeutic agents against human diseases besides cancer.

Anti-inflammatory γ- and δ-tocotrienols improve cardiovascular, liver and metabolic function in diet-induced obese rats

PURPOSE

This study tested the hypothesis that γ- and δ-tocotrienols are more effective than α-tocotrienol and α-tocopherol in attenuating the signs of diet-induced metabolic syndrome in rats.

METHODS

Five groups of rats were fed a corn starch-rich (C) diet containing 68 % carbohydrates as polysaccharides, while the other five groups were fed a diet (H) high in simple carbohydrates (fructose and sucrose in food, 25 % fructose in drinking water, total 68 %) and fats (beef tallow, total 24 %) for 16 weeks. Separate groups from each diet were supplemented with either α-, γ-, δ-tocotrienol or α-tocopherol (85 mg/kg/day) for the final 8 of the 16 weeks.

RESULTS

H rats developed visceral obesity, hypertension, insulin resistance, cardiovascular remodelling and fatty liver. α-Tocopherol, α-, γ- and δ-tocotrienols reduced collagen deposition and inflammatory cell infiltration in the heart. Only γ- and δ-tocotrienols improved cardiovascular function and normalised systolic blood pressure compared to H rats. Further, δ-tocotrienol improved glucose tolerance, insulin sensitivity, lipid profile and abdominal adiposity. In the liver, these interventions reduced lipid accumulation, inflammatory infiltrates and plasma liver enzyme activities. Tocotrienols were measured in heart, liver and adipose tissue showing that chronic oral dosage delivered tocotrienols to these organs despite low or no detection of tocotrienols in plasma.

CONCLUSION

In rats, δ-tocotrienol improved inflammation, heart structure and function, and liver structure and function, while γ-tocotrienol produced more modest improvements, with minimal changes with α-tocotrienol and α-tocopherol. The most important mechanism of action is likely to be reduction in organ inflammation.

Blood levels of antioxidants during age-related macular degeneration treatment by rheohaemapheresis

AIMS

Rheohaemapheresis treatment influences rheological markers and most likely improves metabolism in affected retinal areas, resulting not only in absorption of soft drusen but also reduction or complete disappearance of drusenoid retinal pigment epithelium detachments. However, the character of the treatment process has raised suspicion that there is a decrease not only in cholesterol but also in antioxidants, such as vitamin E and vitamin A.

METHODS

Twenty-three patients with the progressive dry form of age-related macular degeneration were each treated with 8 procedures of rheohaemapheresis. We measured levels of vitamin E (α-tocopherol), the vitamin E/cholesterol ratio in serum and lipoproteins (VLDL, LDL, HDL). Vitamin E in erythrocyte membrane and serum vitamin A (retinol) were also measured. These parameters were determined before and after rheohaemapheresis. Erythrocyte superoxide dismutase, erythrocyte glutathione peroxidase and serum malondialdehyde were analysed as markers of antioxidant activity and lipid peroxidation, respectively.

RESULTS

In serum, the VLDL and LDL fraction ratios of vitamin E/cholesterol increased significantly. Additionally, the HDL fraction ratio showed an increase but this was not statistically significant. The patients showed no clinical signs of vitamin E deficiency, and their serum concentrations of vitamin E did not differ from normal values. The results show that rheohaemapheresis in addition to causing a significant reduction in atherogenic LDL cholesterol, may have favourable additive anti-atherogenic effects due to a relative increase in the content of vitamin E in the lipoprotein fractions.

Gamma-tocotrienol attenuates high-fat diet-induced obesity and insulin resistance by inhibiting adipose inflammation and M1 macrophage recruitment

BACKGROUND AND OBJECTIVE

We have previously demonstrated that gamma tocotrienol (γT3) potently inhibits adipocyte hyperplasia in human adipose-derived stem cells (hASCs). In this study, our objective was to investigate the γT3 effects on early-onset obesity, inflammation and insulin resistance in vivo.

METHODS

Young C57BL/6J mice were fed a high-fat (HF) diet supplemented with 0.05% γT3 for 4 weeks. The concentrations of γT3 in plasma and adipose tissue were measured using high-performance liquid chromatography. Effects of γT3 on body weight gain, adipose volume, plasma levels of fasting glucose, insulin (enzyme-linked immunosorbent assay (ELISA)), proinflammatory cytokines (mouse cytokine array), insulin signaling (western blotting) and gene expression (quantitative real-time PCR, qPCR) in the liver and adipose tissue were examined. Influences of γT3 on [3H]-2-deoxyglucose uptake and lipopolysaccharide (LPS)-mediated NFκB signaling (western blotting) were assessed in hASCs. Effects of γT3 on macrophage M1/M2 activation were investigated using qPCR in mouse bone marrow-derived macrophages.

RESULTS

After a 4-week treatment, γT3 accumulated in adipose tissue and reduced HF diet-induced weight gain in epididymal fat, mesenteric fat and the liver. Compared with HF diet-fed mice, HF+γT3-fed mice were associated with (1) decreased plasma levels of fasting glucose, insulin and proinflammatory cytokines, (2) improved glucose tolerance and (3) enhanced insulin signaling in adipose tissue. There were substantial decreases in macrophage specific markers, and monocyte chemoattractant protein-1, indicating that γT3 reduced the recruitment of adipose tissue macrophages (ATMs). In addition, γT3 treatment in human adipocytes resulted in (1) activation of insulin-stimulated glucose uptake and (2) a significant suppression of MAP kinase and NFκB activation. In parallel, γT3 treatment led to a reduction of LPS-mediated M1 macrophage polarization.

CONCLUSION

Our results demonstrated that γT3 ameliorates HF diet-mediated obesity and insulin resistance by inhibiting systemic and adipose inflammation, as well as ATM recruitment.

Excess α-tocopherol decreases extrahepatic phylloquinone in phylloquinone-fed rats but not menaquinone-4 in menaquinone-4-fed rats

SCOPE

The effects of vitamin E on vitamin K metabolism were elucidated by comparing the effect of tocopherol intake on vitamin K concentrations in rats fed phylloquinone (PK) or menaquinone (MK)-4.

METHODS AND RESULTS

Initially, the dietary effect of RRR-α-tocopherol, but not RRR-γ-tocopherol, in decreasing extrahepatic PK concentrations was confirmed. Subsequently, rats were fed a PK or MK-4-containing diet (0.75 mg/kg) with RRR-α-tocopherol (0, 10, 50, or 500 mg/kg) for 6 weeks. In rats fed PK, α-tocopherol consumption decreased PK in kidney, lung, heart, muscle, testis, and brain but not in serum and liver. However, in rats fed MK-4, α-tocopherol consumption did not decrease MK-4 in serum and tissues. Finally, vitamin K- and E-depleted rats were administered PK or MK-4 (0.2 mg) with RRR-α-tocopherol (0, 1, or 10 mg) by gavage. After PK administration, α-tocopherol was observed to decrease PK in kidney, adrenal gland, lung, testis, and brain but not in serum and liver, whereas, after MK-4 administration, α-tocopherol did not affect MK-4 in serum and tissues.

CONCLUSION

Excess α-tocopherol decreased extrahepatic PK in rats fed PK but not MK-4 in rats fed MK-4.

Mechanisms for the prevention of vitamin E excess

The liver is at the nexus of the regulation of lipoprotein uptake, synthesis, and secretion, and it is the site of xenobiotic detoxification by cytochrome P450 oxidation systems (phase I), conjugation systems (phase II), and transporters (phase III). These two major liver systems control vitamin E status. The mechanisms for the preference for α-tocopherol relative to the eight naturally occurring vitamin E forms largely depend upon the liver and include both a preferential secretion of α-tocopherol from the liver into the plasma for its transport in circulating lipoproteins for subsequent uptake by tissues, as well as the preferential hepatic metabolism of non-α-tocopherol forms. These mechanisms are the focus of this review.

Vitamin E: a dark horse at the crossroad of cancer management

It appears that the story on vitamin E and its role in human health remains incomplete. It is apparent that vitamin E supplementation involves many variables, some of which include its uptake from the intestine, the preference for α-tocopherol, transport by tocopherol specific proteins and lipid transporters and the differential metabolism of different vitamin E isoforms. The fundamental differences within population genetics can have significant implications for the effect that dietary supplementation might have on human health. When evaluating the efficacy of vitamin E prophylactic or therapeutic use in previous and future studies, it is critical to consider dosage to be administered, form of vitamin E and source (such as whether from synthetic or purified from natural sources). Further studies are needed to determine the effects of all vitamin E isoforms on cell growth, tumorigenicity, to clarify its possible use as an adjuvant to existing chemotherapeutics. The Alpha-Tocopherol, Beta Carotene (ATBC) Cancer Prevention Study Group and Selenium and Vitamin E Cancer Prevention Trial (SELECT) studies along with the numerous studies of vitamin E should help guide the next chapter of vitamin E research.

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.

Tocotrienols reverse cardiovascular, metabolic and liver changes in high carbohydrate, high fat diet-fed rats

Tocotrienols have been reported to improve lipid profiles, reduce atherosclerotic lesions, decrease blood glucose and glycated haemoglobin concentrations, normalise blood pressure in vivo and inhibit adipogenesis in vitro, yet their role in the metabolic syndrome has not been investigated. In this study, we investigated the effects of palm tocotrienol-rich fraction (TRF) on high carbohydrate, high fat diet-induced metabolic, cardiovascular and liver dysfunction in rats. Rats fed a high carbohydrate, high fat diet for 16 weeks developed abdominal obesity, hypertension, impaired glucose and insulin tolerance with increased ventricular stiffness, lower systolic function and reduced liver function. TRF treatment improved ventricular function, attenuated cardiac stiffness and hypertension, and improved glucose and insulin tolerance, with reduced left ventricular collagen deposition and inflammatory cell infiltration. TRF improved liver structure and function with reduced plasma liver enzymes, inflammatory cell infiltration, fat vacuoles and balloon hepatocytes. TRF reduced plasma free fatty acid and triglyceride concentrations but only omental fat deposition was decreased in the abdomen. These results suggest that tocotrienols protect the heart and liver, and improve plasma glucose and lipid profiles with minimal changes in abdominal obesity in this model of human metabolic syndrome.