Tocotrienols have been shown to inhibit proliferation and induce apoptosis in cancer cells. However, the molecular mechanisms involved in tocotrienol-induced apoptosis are still unclear. In the present study, gamma-tocotrienol induced apoptosis in human gastric adenocarcinoma SGC-7901 cell line through down regulation of the extracellular signal-regulated kinase (ERK) signalling pathway. Furthermore, gamma-tocotrienol-induced apoptosis was accompanied by down regulation of Bcl-2, up regulation of Bax, activation of caspase-3, and subsequent poly (ADP-ribose) polymerase cleavage. These results indicated that up or down regulation of Bcl-2 family proteins play a major role in the initiation of gamma-tocotrienol-induced apoptosis as an activator of caspase-3. Gamma-tocotrienol also down regulated the activation of the Raf-ERK signalling pathway, and down regulated c-Myc by decreasing the expressions of Raf-1 and p-ERK1/2 proteins. The results suggest that key regulators in tocotrienol-induced apoptosis may be Bcl-2 families and caspase-3 in SGC-7901 cells through down regulation of the Raf-ERK signalling pathway.
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Dietary tocotrienol reduces UVB-induced skin damage and sesamin enhances tocotrienol effects in hairless mice
Yamada Y, Obayashi M, Ishikawa T, Kiso Y, Ono Y, Yamashita K.
J Nutr Sci Vitaminol (Tokyo). 2008 Apr;54(2):117-23.
We have previously reported that substantial amounts of tocotrienols were present in the skin of animals fed a diet containing a tocopherols andtocotrienols rich fraction (T-mix) extracted from palm oil, and further, that sesame lignans enhanced tocotrienol levels in the skin. The present studies were undertaken to determine whether dietary tocotrienols and those with sesamin could protect the skin from damage induced by UVB irradiation in hairless mice fed four diets: a vitamin E-free diet, a 50 mg/kg alpha-tocopherol diet, a 229 mg/kg T-mix (with 50 mg alpha-tocopherol) diet and a 229 mg/kg T-mix with 2 g/kg sesamin diet. In Experiment 1, mice were fed the diets for 6 wk, and half of the mice were exposed to 180 mJ/cm(2 )of UVB light once daily for 7 d. After the intensity of sunburn was scored, vitamin E and thiobarbituric acid reactive substances (TBARS) concentrations in the skin and liver were determined. In Experiment 2, hairless mice were initiated with a single application of 7, 12-dimethylbenz[a]anthracene (DMBA), then 1 wk later mice were fed the experimental diets and subjected to 180 mJ/cm(2) UVB irradiation twice weekly for 20 wk. Tumor incidences were counted once a week. Tocotrienols were detected in the skin of mice fed T-mix, but their concentrations were significantly lower than for alpha-tocopherol. Sesamin elevated tocotrienol contents in the skin. In spite of the high alpha-tocopherol contents, the effects of alpha-tocopherol on sunburn and incidence of tumor were slight. T-mix fed groups reduced the extent of sunburn and incidence of tumor, and further reduction of sunburn and incidence of tumor were observed in the T-mix with sesamin group. These results suggest that dietarytocotrienols protect the skin more strongly than alpha-tocopherol against damage induced by UVB and sesamin enhances tocotrienol effects.
Can the therapeutic efficacy of tocotrienols in neurodegenerative familial dysautonomia patients be measured clinically?
Rubin BY, Anderson SL, Kapás L.
Antioxid Redox Signal. 2008 Apr;10(4):837-41.
Familial dysautonomia (FD) is an inherited, fatal, neurodegenerative disorder manifested by autonomic/hypertensive crises and cardiac instability. Patients produce little IKAP, the gene product of the affected mutated gene, and have low levels of monoamine oxidase A (MAO A), whose reduced presence appears to result in an increased accumulation of biogenic amines, which is a trigger for hypertensive crises. As ingestion of tocotrienols elevates IKAP and MAO A in FD patients, we examined their impact on the frequency of hypertensive crises and cardiac function. After 3 to 4 months of tocotrienol ingestion, approximately 80% of patients reported a significant (> or = 50%) decrease in the number of crises. In a smaller group of patients, a postexercise increase in heart rate and a decrease in the QT interval were observed in the majority of participants. Based on these findings, we hypothesize that tocotrienol therapy will improve the long-term clinical outlook and survival of individuals with FD.
The familiar role of tocols (tocopherols and tocotrienols) as lipid-soluble chain-terminating inhibitors of lipid peroxidation is currently in the midst of a reinterpretation. New biological activities have been described for tocols that apparently are not dependent on their well-established antioxidant behaviour. These activities could well be real, but there remain large gaps in our understanding of the behaviour of tocols in membranes, especially when it comes to the alpha-, beta-, gamma-, delta-chroman methylation patterns and the seemingly special nature of tocotrienols. It is inappropriate to make conclusions and develop models based on in vivo (or cell culture) results with reference to in vitro measurements of antioxidant activity. When present in biological membranes, tocols will experience a large variation in the local composition of phospholipids and the presence of neutral lipids such as cholesterol, both of which would be expected to change the efficiency of antioxidant action. It is likely that tocols are not homogeneously dispersed in a membrane, but it is still not known whether any specific combination of lipid head group and acyl chains are conferred special protection from peroxidation, nor do we currently appreciate the structural role that tocols play in membranes. Tocols may enhance curvature stress or counteract similar stresses generated by other lipids such as lysolipids. This review will outline what is known about the location and behaviour of tocols in phospholipid bilayers. We will draw mainly from the biophysical literature, but will attempt to extend the discussion to biologically relevant phenomena when appropriate. We hope that it will assist researchers when designing new experiments and when critically assessing the results, in turn providing a more thorough understanding of the biochemistry of tocols.
Vitamin E is a family of chromanols that vary by the degree of methylation of the chroman ring as well as the nature of the hydrophobic side chain at C2 that serves to anchor these lipids in biological membranes. The tocopherols contain saturated side chains, whereas the tocotrienols contain three sites of unsaturation and are derived from geranylgeranyl diphosphate. A growing interest in the unique biological activities of the tocotrienols has led us to begin syntheses of isotopically substituted forms and other derivatives that will be useful for probing the metabolism and membrane behavior of the tocotrienols. In order to be certain of our ability to selectively modify sites on the parent molecules it was necessary to make as complete an assignment of the 1H and 13C NMR as possible. Herein we report multidimensional NMR data (HSQC, COSY, ADEQUATE(1,1), C–H HMBC, and NOESY) that have allowed us to assign the identity of almost all the resonances for alpha-, beta-, gamma-, and delta-tocotrienol.
The common familial dysautonomia (FD) mutation results in tissue specific mis-splicing with reduced amount of wild-type (WT) IkappaB kinase associated protein gene (IKBKAP) mRNA and ELP1. ELP1 is a subunit of Elongator, formerly called the IkappaB kinase associated protein (IKAP) protein. We measured IKBKAP mRNA in peripheral blood leukocytes to determine whether FD subjects and carriers have characteristic levels. Estimated mean IKBKAP mRNA levels, measured by quantitative PCR and expressed as amount relative to the noncarrier average, were significantly different for the two groups when not adjusted for age and sex (p < 0.001): FD subjects 0.23, 95% confidence interval (CI) (0.19, 0.28); carriers 0.58, 95% CI (0.50, 0.68); or adjusted for age and sex (p < 0.001): FD subjects 0.21, 95% CI (0.16, 0.26); carriers 0.66, 95% CI (0.55, 0.79). Comparison of IKBKAP mRNA levels of the 22 FD subjects and their related carriers showed a strong correlation, providing evidence for genetic control of splicing efficiency. IKBKAP mRNA levels were not higher in those subjects using tocotrienols or epigallocatechin gallate. Levels of IKBKAP mRNA in peripheral blood leukocytes can be used to assess molecular response to therapies aimed at enhancing exon 20 inclusion and increasing cellular levels of ELP1/IKAP.
Influence of pasture intake on the fatty acid composition, and cholesterol, tocopherols, and tocotrienols content in meat from free-range broilers
Ponte PI, Alves SP, Bessa RJ, Ferreira LM, Gama LT, Brás JL, Fontes CM, Prates JA.
Poult Sci. 2008 Jan;87(1):80-8.
Over the last centuries, Western diets acquired a dramatic imbalance in the ratio of polyunsaturated fatty acids (PUFA) to saturated fatty acids (SFA) with a concomitant reduction in the dietary proportion of n-3 PUFA. Pastures are a good source of n-3 fatty acids, although the effect of forage intake in the fatty acid profile of meat from free-range chicken remains to be evaluated. In addition, it is unknown if consumer interest in specialty poultry products derived from free-range or organic production systems is accompanied by a greater nutritional quality of these products. In this study, broilers of the RedBro Cou Nu x RedBro M genotype were fed on a cereal-based diet in portable floorless pens located either on subterranean clover (Trifolium subterraneum) or white clover (Trifolium repens) pastures. Control birds were maintained at the same site in identical pens but had no access to pasture. The capacity of ingested forage to modulate broiler meat fatty acid profiles and the meat content of total cholesterol, tocopherols, and tocotrienols was investigated in broiler chicks slaughtered at d 56. The results suggested that pasture intake (<5% DM) had a low impact on the fatty acid and vitamin E homologue profiles of meat from free-range broilers. However, breast meat from birds with free access to pasture presented lower levels of the n-6 and n-3 fatty acid precursors linoleic acid (18:2n-6) and alpha-linolenic acid (18:3n-3), respectively. In spring the levels of eicosapentaenoic acid (20:5n-3) in breast meat were significantly greater in birds consuming pastures, which suggests greater conversion of alpha-linolenic acid into eicosapentaenoic acid in these birds. Finally, when compared with meat from slower-growing genotypes obtained under the conventional European free-range production systems with slaughtering at d 81, meat from birds of the Ross genotype raised intensively and slaughtered at d 35 seemed to have greater nutritional quality.
Reduction of DNA damage in older healthy adults by Tri E Tocotrienol supplementation
Chin SF, Hamid NA, Latiff AA, Zakaria Z, Mazlan M, Yusof YA, Karim AA, Ibahim J, Hamid Z, Ngah WZ.
Nutrition. 2008 Jan;24(1):1-10.
Objective: The free radical theory of aging (FRTA) suggests that free radicals are the leading cause of deteriorating physiologic function during senescence. Free radicals attack cellular structures or molecules such as DNA resulting in various modifications to the DNA structures. Accumulation of unrepaired DNA contributes to a variety of disorders associated with the aging process.
Methods: A randomized, double-blinded placebo-controlled study was undertaken to evaluate the effect of Tri E Tocotrienol on DNA damage. Sixty four subjects 37-78 y old completed the study. A daily dose of 160 mg of Tri E Tocotrienol was given for 6 months. Blood samples were analyzed for DNA damage using comet assay, frequency of sister chromatid exchange (SCE), and chromosome 4 aberrations.
Results: Results showed a significant reduction in DNA damage as measured by comet assay after 3 mo (P < 0.01) and remained low at 6 mo (P < 0.01). The frequency of SCE was also reduced after 6 mo of supplementation (P < 0.05), albeit more markedly in the >50 y-old group (P < 0.01) whereas urinary 8-hydroxy-2′-deoxyguanosine (8-OHdG) levels were significantly reduced (P < 0.05). A strong positive correlation was observed between SCE with age, whereas weak positive correlations were observed in DNA damage and 8-OHdG, which were reduced with supplementation. However, no translocation or a stable insertion was observed in chromosome 4.
Conclusion: Tri E Tocotrienol supplementation may be beneficial by reducing DNA damage as indicated by a reduction in DNA damage, SCE frequency, and urinary 8-OHdG.
Reduction of DNA damage in older healthy adults by Tri E Tocotrienol supplementation
Chin SF, Hamid NA, Latiff AA, Zakaria Z, Mazlan M, Yusof YA, Karim AA, Ibahim J, Hamid Z, Ngah WZ.
Nutrition. 2008 Jan;24(1):1-10. Epub 2007 Sep 20.
Published
Objectives: To evaluate the effect of tocotrienol (Tri E) on DNA damage in humans
Study design: Randomized, double-blinded placebo-controlled study
Subjects: Healthy volunteers
Intervention: Tocotrienol
Primary Outcome: DNA damage (comet assay, sister chromatid exchange and chromosome 4 aberrations)
Methodology: A randomized, double-blinded placebo-controlled study was undertaken to evaluate the effect of tocotrienol on DNA damage. Sixty four subjects 37-78 y old completed the study. A daily dose of 160 mg of Tri E Tocotrienol was given for 6 months. Blood samples were analyzed forDNA damage using comet assay, frequency of sister chromatid exchange (SCE), and chromosome 4 aberrations.
Results: Results showed a significant reduction in DNA damage as measured by comet assay after 3 mo (P < 0.01) and remained low at 6 mo (P < 0.01). The frequency of SCE was also reduced after 6 mo of supplementation (P < 0.05), albeit more markedly in the >50 y-old group (P < 0.01) whereas urinary 8-hydroxy-2′-deoxyguanosine (8-OHdG) levels were significantly reduced (P < 0.05). A strong positive correlation was observed between SCE with age, whereas weak positive correlations were observed in DNA damage and 8-OHdG, which were reduced with supplementation. However, no translocation or a stable insertion was observed in chromosome 4.
Conclusion: Tri E Tocotrienol supplementation may be beneficial by reducing DNA damage as indicated by a reduction in DNA damage, SCE frequency, and urinary 8-OHdG.
Synergistic antiproliferative effects of gamma-tocotrienol and statin treatment on mammary tumor cells
Wali VB, Sylvester PW.
Lipids. 2007 Dec;42(12):1113-23. Epub 2007 Aug 14.
Statins are potent inhibitors of 3-hydroxy-3-methylglutaryl-coenzyme A (HMGCoA) reductase and display anticancer activity, but their clinical use is limited by their high-dose toxicity. Similarly, gamma-tocotrienol, an isoform of vitamin E, also reduces HMGCoA reductase activity and displays potent anticancer activity. Studies were conducted to determine if combined low dose treatment of gamma-tocotrienol with individual statins resulted in a synergistic antiproliferative effect on neoplastic mouse +SA mammary epithelial cells. Treatment with 3-4 microM gamma-tocotrienol or 2-8 microM simvastatin, lovastatin or mevastatin alone resulted in a significant decrease, whereas treatment with 10-100 microM pravastatin had no effect on +SA cell growth. However, combined treatment of subeffective doses (0.25 or 10 microM) of individual statins with 0.25-2.0 microM gamma-tocotrienol resulted in a dose-responsive synergistic inhibition in +SA cell proliferation. Additional studies showed that treatment with subeffective doses of individual statins or gamma-tocotrienol alone had no effect, whereas combined treatment of these compounds resulted in a relatively large decrease in intracellular levels of phosphorylated (activated) MAPK, JNK, p38, and Akt. These findings strongly suggest that combined low dose treatment of gamma-tocotrienol with individual statins may have potential value in the treatment of breast cancer without causing myotoxicity that is associated with high dose statin treatment.