Tocotrienol and Its Role in Chronic Diseases

Effects of emulsified and non-emulsified palm tocotrienol on bone and joint health in ovariectomised rats with monosodium iodoacetate-induced osteoarthritis

Postmenopausal women are susceptible to osteoporosis and osteoarthritis. Tocotrienol, a bone-protective nutraceutical, is reported to prevent osteoarthritis in male rats. However, its efficacy on joint health in oestrogen deficiency has not been validated. Besides, data on the use of emulsification systems in enhancing bioavailability and protective effects of tocotrienol are limited. Ovariectomised adult female Sprague-Dawley rats (3 months old) were treated with refined olive oil, emulsified (EPT, 100 mg/kg/day with 25% vitamin E content), non-emulsified palm tocotrienol (NEPT, 100 mg/kg/day with 50% vitamin E content) and calcium carbonate (1% w/v in drinking water) plus glucosamine sulphate (250 mg/kg/day) for 10 weeks. Osteoarthritis was induced with monosodium iodoacetate four weeks after ovariectomy. Baseline control was sacrificed upon receipt, while the sham group was not ovariectomised and treated with refined olive oil. EPT and NEPT prevented femoral metaphyseal and subchondral bone volume decline caused by ovariectomy. EPT decreased subchondral trabecular separation compared to the negative control. EPT preserved stiffness and Young's Modulus at the femoral mid-shaft of the rats. Circulating RANKL was reduced post-treatment in the EPT group. Joint width was reduced in all the treatment groups vs the negative control. The EPT group's grip strength was significantly improved over the negative control and NEPT group. EPT also preserved cartilage histology based on several Mankin's subscores. EPT performed as effectively as NEPT in preventing osteoporosis and osteoarthritis in ovariectomised rats despite containing less vitamin E content. This study justifies clinical trials for the use of EPT in postmenopausal women with both conditions.

The ability of supercritical CO2 carrot and pumpkin extracts to counteract inflammation and oxidative stress in RAW 264.7 macrophages stimulated with LPS or MDA-MB-231 cell-conditioned media

Supercritical fluid extraction with CO2 (SFE) is an alternative technology to conventional solvent extraction (CSE), to obtain food-grade bioactives from plants. Here, SFE and CSE extracts from carrot and pumpkin matrices, impregnated with hempseed or flaxseed oil as co-solvents, were characterized by HPLC and GC-MS, and their ability to counteract the inflammatory and oxidative phenomena underlying the onset of several pathologies was assessed in vitro. All extracts showed dose-dependent anti-inflammatory potential and demonstrated an ability to interfere with the pro-inflammatory effects of breast cancer cell-conditioned media, and to inhibit reactive oxygen species (ROS) accumulation and nitrite production (NP) in lipopolysaccharide-stimulated macrophages. Nuclear factor-erythroid-2-related factor 2 (Nrf2) is involved in these response mechanisms, as highlighted by the increased mRNA levels of its target genes revealed by quantitative real-time PCR analyses. NP and ROS concentrations negatively correlated with α-tocopherol and most carotenoids, but positively with the total tocopherol/total carotenoid ratio, suggesting an idiosyncratic effect of these bioactives on cell responses and emphasizing the need to focus on extract constituents' interactions.

Effect of the Association of Fixed Oils from Abelmoschus esculentus (L.) Moench, Euterpe oleracea Martius, Bixa orellana Linné and Chronic SM® on Atherogenic Dyslipidemia in Wistar Rats

Dyslipidemia presents high levels of serum cholesterol and is characterized as a risk factor for cardiovascular diseases, especially for the development of atherosclerosis. E. oleracea oil (OFEO), A. esculentus oil (OFAE), B. orellana oil (OFBO), and Chronic SM® granules (CHR) are rich in bioactive compounds with the potential to treat changes in lipid metabolism. This study investigated the effects of treatments with oils from A. esculentus, E. oleracea, B. orellana, and Chronic SM® on Cocos nucifera L. saturated-fat-induced dyslipidemia. The chromatographic profile showed the majority presence of unsaturated fatty acids in the tested oils. The quantification of tocotrienols and geranylgeraniol in OFBO and CHR was obtained. Treatments with OFEO, OFAE, OFBO, and CHR were able to significantly reduce glycemia, as well as hypertriglyceridemia, total cholesterol, and LDL-cholesterol, besides increasing HDL-cholesterol. The treatments inhibited the formation of atheromatous plaques in the vascular endothelium of the treated rats. The obtained results suggest that the OFEO, OFAE, OFBO, and CHR exhibit antidyslipidemic effects and antiatherogenic activity.

The Effects of Tocotrienol on Gut Microbiota: A Scoping Review

Gut dysbiosis has been associated with many chronic diseases, such as obesity, inflammatory bowel disease, and cancer. Gut dysbiosis triggers these diseases through the activation of the immune system by the endotoxins produced by gut microbiota, which leads to systemic inflammation. In addition to pre-/pro-/postbiotics, many natural products can restore healthy gut microbiota composition. Tocotrienol, which is a subfamily of vitamin E, has been demonstrated to have such effects. This scoping review presents an overview of the effects of tocotrienol on gut microbiota according to the existing scientific literature. A literature search to identify relevant studies was conducted using PubMed, Scopus, and Web of Science. Only original research articles which aligned with the review's objective were examined. Six relevant studies investigating the effects of tocotrienol on gut microbiota were included. All of the studies used animal models to demonstrate that tocotrienol altered the gut microbiota composition, but none demonstrated the mechanism by which this occurred. The studies induced diseases known to be associated with gut dysbiosis in rats. Tocotrienol partially restored the gut microbiota compositions of the diseased rats so that they resembled those of the healthy rats. Tocotrienol also demonstrated strong anti-inflammatory effects in these animals. In conclusion, tocotrienol could exert anti-inflammatory effects by suppressing inflammation directly or partially by altering the gut microbiota composition, thus achieving its therapeutic effects.

Genotypic variation of tocopherol content in a representative genetic population and genome-wide association study on tocopherol in rapeseed (Brassica napus)

Tocopherols (Tocs) are a kind of lipid-soluble substance required for the normal physiological function of mammals, particularly their antioxidant capacity. Rapeseed (Brassica napus) oil is an important source of exogenous Tocs. However, the genotypic differences in the total Toc contents, the Toc composition in the seeds, and the molecular markers associated with the seed Toc remain largely unknown. Here, we selected 290 rapeseed accessions based on the resequencing of 991 genomes in a worldwide collection of rapeseed germplasm. The contents of the four Toc isoforms, namely, α-, β-, γ-, and δ-Tocs, were also measured. Results show that the total Toc content and the γ-/α-Toc ratio varied greatly across the accessions from 85.34 to 387.00 mg/mg and 0.65 to 5.03, respectively. Furthermore, we conducted genome-wide association studies on the Tocs, which identified 28 and 73 single nucleotide polymorphisms significantly associated with the variation of total Toc content and γ-/α-Toc ratio, respectively. Bna.C02.VTE4, a putative orthologue of Arabidopsis VITAMIN E DEFICIENT 4, was tightly associated with the γ-/α-Toc ratio. This study recommends specific genetic materials with particularly high total Toc and/or low γ-/α-Toc ratio and the molecular markers and haplotypes associated with these quality traits for rapeseed breeding.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11032-023-01394-0.

The Role of Tocotrienol in Arthritis Management—A Scoping Review of Literature

Arthritis is a cluster of diseases impacting joint health and causing immobility and morbidity in the elderly. Among the various forms of arthritis, osteoarthritis (OA) and rheumatoid arthritis (RA) are the most common. Currently, satisfying disease-modifying agents for arthritis are not available. Given the pro-inflammatory and oxidative stress components in the pathogenesis of arthritis, tocotrienol, a family of vitamin E with both anti-inflammatory and antioxidant properties, could be joint-protective agents. This scoping review aims to provide an overview of the effects of tocotrienol on arthritis derived from the existing scientific literature. A literature search using PubMed, Scopus and Web of Science databases was conducted to identify relevant studies. Only cell culture, animal and clinical studies with primary data that align with the objective of this review were considered. The literature search uncovered eight studies investigating the effects of tocotrienol on OA (n = 4) and RA (n = 4). Most of the studies were preclinical and revealed the positive effects of tocotrienol in preserving joint structure (cartilage and bone) in models of arthritis. In particular, tocotrienol activates the self-repair mechanism of chondrocytes exposed to assaults and attenuates osteoclastogenesis associated with RA. Tocotrienol also demonstrated strong anti-inflammatory effects in RA models. The single clinical trial available in the literature showcases that palm tocotrienol could improve joint function among patients with OA. In conclusion, tocotrienol could be a potential anti-arthritic agent pending more results from clinical studies.

Unraveling the Peculiar Features of Mitochondrial Metabolism and Dynamics in Prostate Cancer

Prostate cancer (PCa) is the second leading cause of cancer deaths among men in Western countries. Mitochondria, the "powerhouse" of cells, undergo distinctive metabolic and structural dynamics in different types of cancer. PCa cells experience peculiar metabolic changes during their progression from normal epithelial cells to early-stage and, progressively, to late-stage cancer cells. Specifically, healthy cells display a truncated tricarboxylic acid (TCA) cycle and inefficient oxidative phosphorylation (OXPHOS) due to the high accumulation of zinc that impairs the activity of m-aconitase, the enzyme of the TCA cycle responsible for the oxidation of citrate. During the early phase of cancer development, intracellular zinc levels decrease leading to the reactivation of m-aconitase, TCA cycle and OXPHOS. PCa cells change their metabolic features again when progressing to the late stage of cancer. In particular, the Warburg effect was consistently shown to be the main metabolic feature of late-stage PCa cells. However, accumulating evidence sustains that both the TCA cycle and the OXPHOS pathway are still present and active in these cells. The androgen receptor axis as well as mutations in mitochondrial genes involved in metabolic rewiring were shown to play a key role in PCa cell metabolic reprogramming. Mitochondrial structural dynamics, such as biogenesis, fusion/fission and mitophagy, were also observed in PCa cells. In this review, we focus on the mitochondrial metabolic and structural dynamics occurring in PCa during tumor development and progression; their role as effective molecular targets for novel therapeutic strategies in PCa patients is also discussed.

Tocotrienol in the Management of Nonalcoholic Fatty Liver Disease: A Systematic Review

The increasing burden of nonalcoholic fatty liver disease (NAFLD) requires innovative management strategies, but an effective pharmacological agent has yet to be found. Apart from weight loss and lifestyle adjustments, one isomer of the vitamin E family-alpha-tocopherol-is currently recommended for nondiabetic steatohepatitis patients. Another member of the vitamin E family, tocotrienol (T3), has anti-inflammatory and antioxidant properties that reach beyond those of alpha-tocopherol, making it a potential agent for use in NAFLD management. This systematic review aimed to provide an overview of the effects of T3 supplementation on NAFLD from both clinical and preclinical perspectives. A literature search was performed in October 2022 using PubMed, Scopus and Web of Science. Original research articles reporting NAFLD outcomes were included in this review. The search located 12 articles (8 animal studies and 4 human studies). The literature reports state that T3 isomers or natural mixtures (derived from palm or annatto) improved NAFLD outcomes (liver histology, ultrasound or liver profile). However, the improvement depended on the severity of NAFLD, study period and type of intervention (isomers/mixture of different compositions). Mechanistically, T3 improved lipid metabolism and prevented liver steatosis, and reduced mitochondrial and endoplasmic reticulum stress, inflammation and ultimately liver fibrosis. In summary, T3 could be a potential agent for use in managing NAFLD, pending more comprehensive preclinical and human studies.

Transcriptomic Analysis of the Anticancer Effects of Annatto Tocotrienol, Delta-Tocotrienol and Gamma-Tocotrienol on Chondrosarcoma Cells

Previous studies have demonstrated the anticancer activities of tocotrienol on several types of cancer, but its effects on chondrosarcoma have never been investigated. Therefore, this study aims to determine the anticancer properties of annatto tocotrienol (AnTT), γ-tocotrienol (γ-T3) and δ-tocotrienol (δ-T3) on human chondrosarcoma SW1353 cells. Firstly, the MTT assay was performed to determine the half-maximal inhibitory concentration (IC₅₀) of tocotrienol on SW1353 cells after 24 h treatment. The mode of cell death, cell cycle analysis and microscopic observation of tocotrienol-treated SW1353 cells were then conducted according to the respective IC₅₀ values. Subsequently, RNAs were isolated from tocotrienol-treated cells and subjected to RNA sequencing and transcriptomic analysis. Differentially expressed genes were identified and then verified with a quantitative PCR. The current study demonstrated that AnTT, γ-T3 and δ-T3 induced G1 arrest on SW1353 cells in the early phase of treatment (24 h) which progressed to apoptosis upon 48 h of treatment. Furthermore, tocotrienol-treated SW1353 cells also demonstrated large cytoplasmic vacuolation. The subsequent transcriptomic analysis revealed upregulated signalling pathways in endoplasmic reticulum stress, unfolded protein response, autophagy and transcription upon tocotrienol treatment. In addition, several cell proliferation and cancer-related pathways, such as Hippo signalling pathway and Wnt signalling pathway were also significantly downregulated upon treatment. In conclusion, AnTT, γ-T3 and δ-T3 possess promising anticancer properties against chondrosarcoma cells and further study is required to confirm their effectiveness as adjuvant therapy for chondrosarcoma.

Tocotrienol as a Protecting Agent against Glucocorticoid-Induced Osteoporosis: A Mini Review of Potential Mechanisms

Glucocorticoid-induced osteogenic dysfunction is the main pathologyical mechanism underlying the development of glucocorticoid-induced osteoporosis. Glucocorticoids promote adipogenic differentiation and osteoblast apoptosis through various pathways. Various ongoing studies are exploring the potential of natural products in preventing glucocorticoid-induced osteoporosis. Preclinical studies have consistently shown the bone protective effects of tocotrienol through its antioxidant and anabolic effects. This review aims to summarise the potential mechanisms of tocotrienol in preventing glucocorticoid-induced osteoporosis based on existing in vivo and in vitro evidence. The current literature showed that tocotrienol prevents oxidative damage on osteoblasts exposed to high levels of glucocorticoids. Tocotrienol reduces lipid peroxidation and increases oxidative stress enzyme activities. The reduction in oxidative stress protects the osteoblasts and preserves the bone microstructure and biomechanical strength of glucocorticoid-treated animals. In other animal models, tocotrienol has been shown to activate the Wnt/β-catenin pathway and lower the RANKL/OPG ratio, which are the targets of glucocorticoids. In conclusion, tocotrienol enhances osteogenic differentiation and bone formation in glucocorticoid-treated osteoblasts while improving structural integrity in glucocorticoid-treated rats. This is achieved by preventing oxidative stress and osteoblast apoptosis. However, these preclinical results should be validated in a randomised controlled trial.

Revisiting the therapeutic potential of tocotrienol

The therapeutic potential of the tocotrienol group stems from its nutraceutical properties as a dietary supplement. It is largely considered to be safe when consumed at low doses for attenuating pathophysiology as shown by animal models, in vitro assays, and ongoing human trials. Medical researchers and the allied sciences have experimented with tocotrienols for many decades, but its therapeutic potential was limited to adjuvant or concurrent treatment regimens. Recent studies have focused on targeted drug delivery by enhancing the bioavailability through carriers, self-sustained emulsions, nanoparticles, and ethosomes. Epigenetic modulation and computer remodeling are other means that will help increase chemosensitivity. This review will focus on the systemic intracellular anti-cancer, antioxidant, and anti-inflammatory mechanisms that are stimulated and/or regulated by tocotrienols while highlighting its potent therapeutic properties in a diverse group of clinical diseases.

Potential of the Compounds from Bixa orellana Purified Annatto Oil and Its Granules (Chronic®) against Dyslipidemia and Inflammatory Diseases: In Silico Studies with Geranylgeraniol and Tocotrienols

Some significant compounds present in annatto are geranylgeraniol and tocotrienols. These compounds have beneficial effects against hyperlipidemia and chronic diseases, where oxidative stress and inflammation are present, but the exact mechanism of action of such activities is still a subject of research. This study aimed to evaluate possible mechanisms of action that could be underlying the activities of these molecules. For this, in silico approaches such as ligand topology (PASS and SEA servers) and molecular docking with the software GOLD were used. Additionally, we screened some pharmacokinetic and toxicological parameters using the servers PreADMET, SwissADME, and ProTox-II. The results corroborate the antidyslipidemia and anti-inflammatory activities of geranylgeraniol and tocotrienols. Notably, some new mechanisms of action were predicted to be potentially underlying the activities of these compounds, including inhibition of squalene monooxygenase, lanosterol synthase, and phospholipase A₂. These results give new insight into new mechanisms of action involved in these molecules from annatto and Chronic^®.

Barley: a potential cereal for producing healthy and functional foods

Barley is the fourth largest cereal crop in the world. It is mainly used for feeding, beer production and food. Barley is receiving more attention from both agricultural and food scientists because of its special chemical composition and health benefits. In comparison with other cereal crops, including wheat, rice and maize, barley grains are rich in dietary fiber (such as β-glucan) and tocols, which are beneficial to human health. It is well proved that diets rich in those chemicals can provide protection against hypertension, cardiovascular disease, and diabetes. Barley has been widely recognized to be great potential as a healthy or functional food. In this review, we present the information about the studies on physical structure of barley grain and the distribution of main chemical components, nutrient and functional composition of barley grain and their health benefits, and the approaches of improving and utilizing the nutrient and functional chemicals in barley grain. With the development of processing technologies, functional components in barley grains, especially β-glucan, can be efficiently extracted and concentrated. Moreover, nutrient and functional components in barley grains can be efficiently improved by precise breeding and agronomic approaches. The review highlights the great potential of barley used as healthy and functional foods, and may be instructive for better utilization of barley in food processing.

The multifaceted roles of mitochondria at the crossroads of cell life and death in cancer

Mitochondria are the cytoplasmic organelles mostly known as the "electric engine" of the cells; however, they also play pivotal roles in different biological processes, such as cell growth/apoptosis, Ca²⁺ and redox homeostasis, and cell stemness. In cancer cells, mitochondria undergo peculiar functional and structural dynamics involved in the survival/death fate of the cell. Cancer cells use glycolysis to support macromolecular biosynthesis and energy production ("Warburg effect"); however, mitochondrial OXPHOS has been shown to be still active during carcinogenesis and even exacerbated in drug-resistant and stem cancer cells. This metabolic rewiring is associated with mutations in genes encoding mitochondrial metabolic enzymes ("oncometabolites"), alterations of ROS production and redox biology, and a fine-tuned balance between anti-/proapoptotic proteins. In cancer cells, mitochondria also experience dynamic alterations from the structural point of view undergoing coordinated cycles of biogenesis, fusion/fission and mitophagy, and physically communicating with the endoplasmic reticulum (ER), through the Ca²⁺ flux, at the MAM (mitochondria-associated membranes) levels. This review addresses the peculiar mitochondrial metabolic and structural dynamics occurring in cancer cells and their role in coordinating the balance between cell survival and death. The role of mitochondrial dynamics as effective biomarkers of tumor progression and promising targets for anticancer strategies is also discussed.

γ-Tocotrienol reverses multidrug resistance of breast cancer cells through the regulation of the γ-Tocotrienol-NF-κB-P-gp axis

The problem of multidrug resistance (MDR) presents a major obstacle in the chemotherapy of cancer. The MDR phenotype is often linked to the overexpression of ATP-binding cassette (ABC) transporters, that pumps out and decreased intracellular drug accumulation. γ-Tocotrienol, an unsaturated tocopherol belonging to the vitamin E family, has been shown to reverse the MDR of MCF-7/Adr cell. To reveal the role of γ-tocotrienol-NF-κB-P-gp axis in the reversal process, the expression level of mdr1/P-gp was determined by real-time PCR and western blot, while NF-κB activity was detected by immunofluorescence and NF-κB transcriptional activity reporter assay. Besides, mdr1 promoter activity and P-gp transport capacity were measured with the effect of γ-tocotrienol and NF-κB agonist/antagonist. Results showed that γ-tocotrienol effectively inhibited the expression levels of mdr1 mRNA and P-gp protein. It is demonstrated that γ-tocotrienol also suppressed mdr1 promoter activity and the efflux activity of P-gp. In addition, the activation of NF-κB signaling pathway and the transcriptional activity of NF-κB were both reduced by γ-tocotrienol. Evidences also showed that the NF-κB pathway is really involved in the regulation of the expression and function of mdr1/P-gp. Taken together, we confirmed that γ-tocotrienol reversed the MDR of MCF-7/Adr through the signaling pathway of NF-κB and P-gp.

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.

Delta-tocotrienol supplementation improves biochemical markers of hepatocellular injury and steatosis in patients with nonalcoholic fatty liver disease: A randomized, placebo-controlled trial

OBJECTIVE

The aim of this study was to examine the effects of delta-tocotrienol (δ-tocotrienol) supplementation on biochemical markers of hepatocellular injury and steatosis in patients with nonalcoholic fatty liver disease (NAFLD).

DESIGN

The study design was a two-group, randomized, double-blind, placebo-controlled trial. The patients with NAFLD were randomly assigned to receive δ-tocotrienol 300 mg twice daily or placebo for 24 weeks.

ENDPOINTS

The primary endpoints were change from baseline in fatty liver index (FLI) and homeostasis model of insulin resistance (HOMA-IR) after 24 weeks. Secondary endpoints included change from baseline in high sensitivity C-reactive protein (hs-CRP), malondialdehyde (MDA), alanine transaminase (ALT), aspartate transaminase (AST) and grading of hepatic steatosis on ultrasound. Between-group differences were tested for significance using ANCOVA. Mean differences (MD) with 95 % CIs are reported.

RESULTS

A total of 71 patients (tocotrienol=35, placebo=36) were randomized and included in the intention to treat analysis. Compared with placebo, δ-tocotrienol significantly reduced (MD [95 % CI]) FLI (-8.52 [-10.7, -6.3]; p < 0.001); HOMA-IR (-0.37 [-0.53, -0.21]; p < 0.001), hs-CRP (-0.61[-0.81, -0.42]; p < 0.001), MDA (-0.91 [-1.20, -0.63]; p < 0.001), ALT (-8.86 [-11.5, -6.2]; p < 0.001) and AST (-6.6 [-10.0, -3.08]; p < 0.001). Hepatic steatosis was also reduced by a significantly greater extent with tocotrienol than with placebo (p =0.047). No adverse events were reported.

CONCLUSION

δ-tocotrienol effectively improved biochemical markers of hepatocellular injury and steatosis in patients with NAFLD. δ-tocotrienol supplementation might be considered as a therapeutic option in the management of patients with NAFLD.

TRIAL REGISTRATION

Sri Lankan Clinical Trials Registry (SLCTR/2015/023, 2015-10-03).

The effects of tocotrienol supplementation on lipid profile: A meta-analysis of randomized controlled trials

BACKGROUND & OBJECTIVE

Tocotrienol supplementation has been emerged as a potent candidate for the treatment of dyslipidemia. In the present study, a systematic review and meta-analysis of randomized controlled trials was performed with the aim of examining the effects of tocotrienol supplementation on the lipid profile.

METHODS

Four databases (Scopus, PubMed/Medline, Web of Science and Embase) were used to accomplish the literature search up to November 2019. Clinical trials encompassing the impact of tocotrienol supplementation on lipid profile were extracted regardless of clinical condition, with studies included involving only adults patients.

RESULTS

A total of 15 articles with 20 arms were eligible and included in the meta-analysis to estimate the pooled effect size. Overall results showed a significant effect of tocotrienol supplementation on increasing high-density lipoprotein cholesterol (HDL-C) levels (weight mean difference (WMD): 0.146 mmol/L, I² = 85.9%) and a non-significant influence on total cholesterol (TC) (WMD: 0.010 mmol/L, I² = 64.5%), low-density lipoprotein cholesterol (LDL-C) (WMD: 0.095 mmol/L, I² = 87.4%), and triglycerides (TG) (WMD: -0.112 mmol/L, I² = 67.4%) levels. Increment in HDL-C levels was significant greater for the tocotrienol dosage ≥ 200 mg/d (WMD: 0.202 mmol/L) and ≤8 weeks (WMD: 0.278 mmol/L). Moreover, studies that investigated tocotrienol dose ≥200 mg had no heterogeneity, while showing a significant decrease in TG levels (WMD: -0.177 mmol/L).

CONCLUSION

The present meta-analysis demonstrated that supplementing with tocotrienols does not decrease the concentrations of LDL-C, TC and TG. However, tocotrienol supplementation was considered a candidate for increasing HDL-C levels.

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.

The Effects of Annatto Tocotrienol Supplementation on Cartilage and Subchondral Bone in an Animal Model of Osteoarthritis Induced by Monosodium Iodoacetate

Osteoarthritis is a degenerative joint disease which primarily affects the articular cartilage and subchondral bones. Since there is an underlying localized inflammatory component in the pathogenesis of osteoarthritis, compounds like tocotrienol with anti-inflammatory properties may be able to retard its progression. This study aimed to determine the effects of oral tocotrienol supplementation on the articular cartilage and subchondral bone in a rat model of osteoarthritis induced by monosodium iodoacetate (MIA). Thirty male Sprague-Dawley rats (three-month-old) were randomized into five groups. Four groups were induced with osteoarthritis (single injection of MIA at week 0) and another served as the sham group. Three of the four groups with osteoarthritis were supplemented with annatto tocotrienol at 50, 100 and 150 mg/kg/day orally for five weeks. At week 5, all rats were sacrificed, and their tibial-femoral joints were harvested for analysis. The results indicated that the groups which received annatto tocotrienol at 100 and 150 mg/kg/day had lower histological scores and cartilage remodeling markers. Annatto tocotrienol at 150 mg/kg/day significantly lowered the osteocalcin levels and osteoclast surface of subchondral bone. In conclusion, annatto tocotrienol may potentially retard the progression of osteoarthritis. Future studies to confirm its mechanism of joint protection should be performed.

Anticancer properties of tocotrienols: A review of cellular mechanisms and molecular targets

Vitamin E is composed of two groups of compounds: α-, β-, γ-, and δ-tocopherols (TPs), and the corresponding unsaturated tocotrienols (TTs). TTs are found in natural sources such as red palm oil, annatto seeds, and rice bran. In the last decades, TTs (specifically, γ-TT and δ-TT) have gained interest due to their health benefits in chronic diseases, based on their antioxidant, neuroprotective, cholesterol-lowering, anti-inflammatory activities. Several in vitro and in vivo studies pointed out that TTs also exert a significant antitumor activity in a wide range of cancer cells. Specifically, TTs were shown to exert antiproliferative/proapoptotic effects and to reduce the metastatic or angiogenic properties of different cancer cells; moreover, these compounds were reported to specifically target the subpopulation of cancer stem cells, known to be deeply involved in the development of resistance to standard therapies. Interestingly, recent studies pointed out that TTs exert a synergistic antitumor effect on cancer cells when given in combination with either standard antitumor agents (i.e., chemotherapeutics, statins, "targeted" therapies) or natural compounds with anticancer activity (i.e., sesamin, epigallocatechin gallate (EGCG), resveratrol, ferulic acid). Based on these observations, different TT synthetic derivatives and formulations were recently developed and demonstrated to improve TT water solubility and to reduce TT metabolism in cancer cells, thus increasing their biological activity. These promising results, together with the safety of TT administration in healthy subjects, suggest that these compounds might represent a new chemopreventive or anticancer treatment (i.e., in combination with standard therapies) strategy. Clinical trials aimed at confirming this antitumor activity of TTs are needed.

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.

Overexpression of HvHGGT Enhances Tocotrienol Levels and Antioxidant Activity in Barley

Vitamin E is a potent lipid-soluble antioxidant and essential nutrient for human health. Tocotrienols are the major form of vitamin E in seeds of most monocots. It has been known that homogentisate geranylgeranyl transferase (HGGT) catalyzes the committed step of tocotrienol biosynthesis. In the present study, we generated transgenic barley overexpressing HvHGGT under endogenous D-Hordein promoter (proHor). Overexpression of HvHGGT increased seed size and seed weight in transgenic barley. Notably, total tocotrienol content increased by 10-15% in seeds of transgenic lines, due to the increased levels of δ-, β-, and γ-tocotrienol, but not α-tocotrienol. Total tocopherol content decreased by 14-18% in transgenic lines, compared to wild type. The antioxidant activity of seeds was determined by using 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2'-azinobis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS), and lipid peroxidation assays. Compared to wild type, radical scavenging activity of seed extracts was enhanced by 17-18% in transgenic lines. Meanwhile, the lipid peroxidation level was decreased by about 20% in transgenic barley seeds. Taken together, overexpression of HvHGGT enhanced the tocotrienol levels and antioxidant capacity in barley seeds.

The Effects of Tocotrienol and Lovastatin Co-Supplementation on Bone Dynamic Histomorphometry and Bone Morphogenetic Protein-2 Expression in Rats with Estrogen Deficiency

Both tocotrienol and statins are suppressors of the mevalonate pathway. Supplementation of tocotrienol among statin users could potentially protect them against osteoporosis. This study aimed to compare the effects of tocotrienol and lovastatin co-supplementation with individual treatments on bone dynamic histomorphometric indices and bone morphogenetic protein-2 (BMP-2) gene expression in ovariectomized rats. Forty-eight female Sprague-Dawley rats were randomized equally into six groups. The baseline was sacrificed upon receipt. All other groups were ovariectomized, except for the sham group. The ovariectomized groups were administered orally daily with (1) lovastatin 11 mg/kg/day alone; (2) tocotrienol derived from annatto bean (annatto tocotrienol) 60 mg/kg/day alone; (3) lovastatin 11 mg/kg/day, and annatto tocotrienol 60 mg/kg/day. The sham and ovariectomized control groups were treated with equal volume of vehicle. After eight weeks of treatment, the rats were sacrificed. Their bones were harvested for bone dynamic histomorphometry and BMP-2 gene expression. Rats supplemented with annatto tocotrienol and lovastatin concurrently demonstrated significantly lower single-labeled surface, but increased double-labeled surface, mineralizing surface, mineral apposition rate and bone formation rate compared to individual treatments (p < 0.05). There was a parallel increase in BMP-2 gene expression in the rats receiving combined treatment (p < 0.05). The combination of annatto tocotrienol and lovastatin exerted either additively or synergistically on selected bone parameters. In conclusion, tocotrienol can augment the bone formation and mineralization in rats receiving low-dose statins. Supplementation of tocotrienol in statin users can potentially protect them from osteoporosis.