Skin Protection Effects Of Vitamin E

Robert Goldfaden And Gary Goldfaden, MD

Over the course of time, healthy skin often succumbs to the cumulative effects of external factors such as ultraviolet radiation and environmental pollutants. Free radical damage caused by normal cell functioning ultimately takes its toll as well, destroying the skin’s integrity from the inside. Fortunately, there are a number of safe and natural substances that have been scientifically proven to effectively help counteract, and in some cases, even help reverse the physical signs of skin aging such as wrinkles and hyperpigmentation. One of these is topically applied vitamin E.

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Osteoclastogenesis and osteoblastogenesis, the balancing acts for optimal bone health, are under the regulation of small guanosine triphosphate-binding proteins (GTPases) including Ras, Rac, Rho and Rab. The activities of GTPases require post-translational modification with mevalonate-derived prenyl pyrophosphates. Mevalonate deprivation induced by competitive inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase (e.g., statins) prevents the activation of GTPases, suppresses the expression of the receptor for activation of nuclear factor kappa B (NFκB) ligand (RANKL) and activation of NFκB and, consequently, inhibits osteoclast differentiation and induces osteoclast apoptosis. In contrast, statin-mediated inactivation of GTPases enhances alkaline phosphatase activity and the expression of bone morphogenetic protein-2, vascular epithelial growth factor, and osteocalcin in osteoblasts and induces osteoblast proliferation and differentiation. Animal studies show that statins inhibit bone resorption and increase bone formation. The anabolic effect of statins and other mevalonate pathway-suppressive pharmaceuticals resembles the anti-osteoclastogenic and bone-protective activities conferred by dietary isoprenoids, secondary products of plant mevalonate metabolism. The tocotrienols, vitamin E molecules with HMG CoA reductase-suppressive activity, induce mevalonate deprivation and concomitantly suppress the expression of RANKL and cyclooxygenase-2, the production of prostaglandin E2 and the activation of NFκB. Accordingly, tocotrienols inhibit osteoclast differentiation and induce osteoclast apoptosis, impacts reminiscent of those of statins. In vivo studies confirm the bone protective activity of tocotrienols at nontoxic doses. Blends of tocotrienols, statins and isoprenoids widely found in fruits, vegetables, grains, herbs, spices, and essential oils may synergistically suppress osteoclastogenesis while promoting osteoblastogenesis, offering a novel approach to bone health that warrants clinical studies.

Chemopreventive properties of dietary rice bran: Current status and future prospects

Henderson AJ, Ollila CA, Kumar A, Borresen EC, Raina K, Agarwal R, Ryan EP.

Adv Nutr. 2012 Sep 1;3(5):643-53.

Emerging evidence suggests that dietary rice bran may exert beneficial effects against several types of cancer, such as breast, lung, liver, and colorectal cancer. The chemopreventive potential has been related to the bioactive phytochemicals present in the bran portion of the rice such as ferulic acid, tricin, β-sitosterol, γ-oryzanol, tocotrienols/tocopherols, and phytic acid. Studies have shown that the anticancer effects of the rice bran-derived bioactive components are mediated through their ability to induce apoptosis, inhibit cell proliferation, and alter cell cycle progression in malignant cells. Rice bran bioactive components protect against tissue damage through the scavenging of free radicals and the blocking of chronic inflammatory responses. Rice bran phytochemicals have also been shown to activate anticancer immune responses as well as affecting the colonic tumor microenvironment in favor of enhanced colorectal cancer chemoprevention. This is accomplished through the modulation of gut microflora communities and the regulation of carcinogen-metabolizing enzymes. In addition, the low cost of rice production and the accessibility of rice bran make it an appealing candidate for global dietary chemoprevention. Therefore, the establishment of dietary rice bran as a practical food-derived chemopreventive agent has the potential to have a significant impact on cancer prevention for the global population.

The vitamin E family consists of eight isomers known as alpha-, beta-, gamma-, and delta-tocopherols and alpha-, beta-, gamma-, and delta-tocotrienols. Numerous studies focused on the health benefits of these isomers have been performed since the discovery of vitamin E in 1922. Recent discoveries on the potential therapeutic applications of tocotrienols have revolutionized vitamin E research. Nevertheless, despite the abundance of literature, only 1% of vitamin E research has been conducted on tocotrienols. Many new advances suggest that the use of tocotrienols for health improvement or therapeutic purposes is promising. Although the mechanisms of action of tocotrienols in certain disease conditions have been explored, more detailed investigations into the fundamentals of the health-promoting effects of these molecules must be elucidated before they can be recommended for health improvement or for the treatment or prevention of disease. Furthermore, many of the studies on the effects of tocotrienols have been carried out using cell lines and animal models. The effects in humans must be well established before tocotrienols are used as therapeutic agents in various disease conditions, hence the need for more evidence-based human clinical trials.

Supplementation to an AIN93G-based diet of tocotrienol (T3) for 13 weeks administered to Fischer 344/slc rats showed a safety profile with no side effects. Dose-dependent T3 levels were detected in many tissues. Under the present experimental conditions, a continuous intake of the T3 concentrate would be safe in the rats as long as the T3 content was less than 0.20% of the dietary intake.

The vitamin E family consists of 4 tocopherol and 4 tocotrienol compounds. During recent years, tocotrienols have gained increased interest due to their biological activities that are beyond the vitamin E activity. Here we report the engineering of plasmid-free Escherichia coli strains for an efficient synthesis of 2-methyl-6-geranylgeranyl-benzoquinol (MGGBQ), the central precursor for all four natural tocotrienol compounds. Heterologous genes needed for the in vivo synthesis of MGGBQ in E. coli (crtE, hpd, and hpt) were individually integrated into the chromosome of E. coli. The yield of MGGBQ after cultivation of the plasmid-free recombinant E. coli strain was significantly higher (604μg/gcdw) compared to an E. coli strain that carries these biosynthesis genes on a multi-copy expression plasmid (325μg/gcdw). Further chromosomal integration of an additional copy of the isopentenyl-diphosphate isomerase gene (idi) and a subsequent increase in expression level of the deoxy-xylulose synthase gene (dxs) increased the MGGBQ yield by 80% (1110μg/gcdw) and 135% (1425μg/gcdw), respectively. MGGBQ which accumulated in the membrane fraction of the recombinant E. coli cells was isolated and its structure was completely elucidated by 1D and 2D NMR and MS measurements. The engineered, plasmid-free E. coli strain is a promising host for the heterologous in vivo production of tocotrienol and its derivatives.

Gamma-tocotrienol, a radiation prophylaxis agent, induces high levels of granulocyte colony-stimulating factor

Kulkarni SS, Cary LH, Gambles K, Hauer-Jensen M, Kumar KS, Ghosh SP.

Int Immunopharmacol. 2012 Sep 20;14(4):495-503. 2012.09.001. [Epub ahead of print]

Gamma-tocotrienol (GT3), a promising radioprotectant, is shown to protect CD2F1 mice from radiation-induced neutropenia and thrombocytopenia when given 24h prior to total-body irradiation. GT3 also is shown to increase white blood cells (WBC) and absolute neutrophil counts (ANC) transiently in peripheral blood. We hypothesized that increases in WBC and ANC may involve stimulation of hematopoiesis possibly by cytokines and growth factors. To evaluate the effects of GT3 on hematopoietic system, we measured various cytokines, chemokines and growth factors by cytokine array and Bio-Plex assays. Both showed strong induction of various cytokines and chemokines. GT3 treatment resulted in significant increases in G-CSF, IL-1α, IL-1β, IL-6, IL-12p70, IL-17, MIP-1α, and KC levels. G-CSF levels increased markedly within 12-24h after administration (5441pg/ml in GT3-treated groups compared to 17pg/ml in vehicle control). Most of these cytokine levels were elevated in the presence or absence of radiation. Time-course analysis of G-CSF and IL-6 induction showed that both cytokines were induced transiently after GT3 administration, and returned to normal levels by 48h post-administration. For G-CSF, the peak was observed between 12 and 24h post-administration of GT3; however, the highest levels of IL-6 were obtained between 6 and 12h. These results demonstrate that GT3 induced high levels of G-CSF and other inflammatory cytokines and chemokines within 24h after administration. Survival studies reported showed that the most efficacious time for administering GT3 was 24h prior to irradiation, possibly because it induced key hematopoietic cytokines in that time window. These results also suggest a possible role of GT3-induced G-CSF stimulation in protecting mice from radiation-induced neutropenia and thrombocytopenia.

Although vitamin E has been known as an essential nutrient for almost 80 years, we are far from a complete understanding of all the aspects related to bioavailability and its effects on health and milk quality in dairy cows. Vitamin E is a generic descriptor for two families of lipid-soluble compounds, the tocopherols and the tocotrienols, of which α-tocopherol has the highest biological activity. Commercially available α-tocopherol supplements for dairy cows contain either the natural RRR form or the synthetic (all-rac) form, which contains all the eight possible stereoisomers (four possessing the 2R and four possessing the 2S configuration) in equimolar amounts. Recent data clearly suggest that an almost complete discrimination against the 2S isomers occurs in dairy cows. Thus, 1 g of the all-rac form is essentially equivalent to 0.5 g of the RRR form. With respect to the effect of vitamin E supplementation of dairy cows on health and milk quality, the majority of published studies suggests that vitamin E supplementation at the level 1000 to 4000 IU/cow per day during the dry period reduces both the frequency of intramammary infection and that of clinical mastitis and improves milk quality, as shown by a reduction in the levels of somatic cell count (SCC)/ml in milk, decreased plasmin activity and increased oxidative stability of milk. However, a recent study from the Netherlands suggested that vitamin E supplementation at the 3000 IU/cow per day level during the dry period when combined with high levels of plasma vitamin E at dry-off (>14.5 μmol/l) increases the incidence of mastitis. Data from previously unpublished survey studies and those from published vitamin E feeding trials, in which high levels of blood vitamin E were observed, were reanalyzed. All farms selected for the analysis implemented oral administration of vitamin E at the 3000 IU/cow per day level throughout or during the late dry period (4 weeks before the expected day of parturition). Dairy cows were divided into three groups, depending on blood α-tocopherol levels at dry-off: high (>6.25 μg/ml), medium (between 6.25 and 4.25 μg/ml) and low (<4.25 μg/ml). Data indicate that there were no differences in the incidence of mastitis and in the level of SCC/ml of milk between the three groups. Thus, supplementation of 3000 IU vitamin E/cow per day in the late dry period remains recommended because it is generally associated with decreased risk of mastitis. Conditional or opposite effects have not been repeated and require further research before changing recommendations for vitamin E supplementation.

Comparative effects of tocotrienol-rich fraction, α-tocopherol and α-tocopheryl acetate on inflammatory mediators and nuclear factor kappa B expression in mouse peritoneal macrophages

Ng LT, Ko HJ.

Food Chem. 2012 Sep 15;134(2):920-5

The effects of tocotrienol-rich fraction (TRF), α-tocopherol (T) and α-tocopheryl acetate (TA) on lipopolysaccharide (LPS)-induced inflammatory responses in mouse peritoneal macrophages were examined. Results showed that at 5-30μg/ml, all test compounds plus 1μg/ml LPS exhibited no cytotoxic effects on macrophage cells. Compared with T and TA, TRF showed the strongest anti-inflammatory activity as demonstrated by its potency in inhibiting the LPS-induced nitric oxide (NO), prostaglandin E(2) (PGE(2)), and proinflammatory cytokine (TNF-α, IFN-γ, IL-1β and IL-6) production. At 10μg/ml, it significantly blocked the LPS induction of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) expression, but has no effect on cyclooxygenase-1 (COX-1). Furthermore, TRF also showed a greater inhibition on the nuclear factor kappa B (NF-κB) expression than T and TA. These results suggest that TRF could be a better agent than T and TA for use in the prevention of chronic inflammatory diseases.

A key regulator of cholesterol homeostasis, SREBP-2, can be targeted in prostate cancer cells with natural products

James R. Krycer, Lisa Phan, Andrew J. Brown

Biochem J. 2012 Sep 1;446(2):191-201

There is growing evidence showing prostate cancer cells have perturbed cholesterol homeostasis, accumulating cholesterol to promote cell-growth. Consequently, cholesterol lowering drugs like statins are being evaluated in prostate cancer treatment. Furthermore, natural products such as betulin (from birch tree bark) and tocotrienol (a minor form of Vitamin E) have been shown to lower cholesterol levels. Using these drugs and oxysterols, we determine which aspects of cholesterol homeostasis should be targeted in prostate cancer –e.g., cellular cholesterol levels are increased by the transcription factor Sterol-Regulatory Element Binding Protein isoform 2 (SREBP-2), whereas the Liver X Receptor (LXR) promotes cholesterol efflux. Whilst betulin exerted non-specific effects on cell viability, tocotrienols produced a strong direct correlation between SREBP-2 activity and cell viability. Mechanistically, tocotrienols lowered SREBP-2 activity by degrading mature SREBP-2 independently of the proteasome. In contrast, no correlation was seen between LXR activity and cell viability, implying SREBP-2 is a better target than LXR for prostate cancer treatment. Lastly, androgen-dependent and -independent LNCaP cells were both sensitive to tocotrienols. Overall, this suggests that tocotrienols and other drugs targeting the SREBP-2 pathway are a potential therapeutic option for prostate cancer.

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