We investigated a dose-dependent hypolipidemic and antioxidant effect of tocotrienol rich fraction (TRF) isolated from rice bran oil on experimentally induced hyperlipidemic rats. Feeding of atherogenic diet (5% hydrogenated fat, 0.5% cholic acid and 1% cholesterol) for three weeks resulted in a significant increase in plasma triglyceride (3.3-fold) and total cholesterol (2.4-fold) levels. There was a 5-fold increase in the level of LDL cholesterol with only a small increase in HDL cholesterol. On the other hand, HMG-CoA reductase activity was significantly reduced in these animals. The formation of TBARS, thiobarbituric acid reactive substances, (86%) and conjugated dienes (78%) were also significantly higher in these rats compared to normals. After the induction of hyperlipidemia for three weeks, rats were supplemented with different doses of TRF for one week. TRF supplementation decreased the lipid parameters in a dose-dependent manner with an optimum effect at a dose of 8 mg TRF/kg/day. HMG-CoA reductase activity, which was increased after the withdrawal of atherogenic diet, remained significantly decreased during the TRF treatment. Feeding of TRF also decreased TBARS and conjugated dienes significantly. These results suggest that TRF supplementation has significant health benefits through the modulation of physiological functions that include various atherogenic lipid profiles and antioxidants in hypercholesterolemia.
Publications
Gamma-tocotrienol inhibits neoplastic mammary epithelial cell proliferation by decreasing Akt and nuclear factor kappaB activity
Shah SJ, Sylvester PW.
Exp Biol Med (Maywood). 2005 Apr;230(4):235-41.
Tocotrienols, a subgroup within the vitamin E family of compounds, have been shown to display potent anticancer activity and inhibit preneoplastic and neoplastic mammary epithelial cell proliferation at treatment doses that have little or no effect on normal cell growth and function. However, the specific intracellular mechanisms mediating the antiproliferative effects of tocotrienols are presently unknown. Because Akt and nuclear factor kappaB (NFkappaB) are intimately involved in mammary tumor cell proliferation and survival, studies were conducted to determine the effects of gamma-tocotrienol on Akt and NFkappaB activity in neoplastic +SA mammary epithelial cells in vitro. Treatment with 0-8 microM gamma-tocotrienol for 0-3 days caused a dose-responsive inhibition in +SA cell growth and mitotic activity, as determined by MTT colorimetric assay and proliferating cell nuclear antigen immunocytochemical staining, respectively. Studies also showed that treatment with 4 microM gamma-tocotrienol, a dose that inhibited +SA cell growth by more than 50% compared with that of untreated control cells, decreased intracellular levels of activated phosphotidylinositol 3-kinase-dependent kinase (PI3K)-dependent kinase 1 (phospho-PDK-1) and Akt, and reduced phospho-Akt kinase activity. Furthermore, these effects were not found to be associated with an increase in either phosphatase and tensin homologue deleted from chromosome 10 (PTEN) or protein phosphatase type 2A phosphatase activity. In addition, gamma-tocotrienol treatment was shown to decrease NFkappaB transcriptional activity, apparently by suppressing the activation of IkappaB-kinase-alpha/beta, an enzyme associated with inducing NFkappaB activation. In summary, these findings demonstrate that the antiproliferative effects of gamma-tocotrienol result, at least in part, from a reduction in Akt and NFkappaB activity in neoplastic +SA mammary epithelial cells.
Synergistic effects of tocopherol, tocotrienol, and ubiquinone in indomethacin-induced experimental gastric lesions
Nafeeza MI, Kang TT.
Int J Vitam Nutr Res. 2005 Mar;75(2):149-55.
Nonsteroidal anti-inflammatory drugs and their adverse effects on the gastric mucosa are yet another set of unresolved medical problems. This study examined the effects of various antioxidants on several gastric parameters after a single exposure to indomethacin. Forty-eight male rats of the Sprague-Dawley (200-250 g) strain were randomly divided to receive a single antioxidant (tocopherol, tocotrienol, or ubiquinone) or a combination of two (tocopherol-tocotrienol, tocopherol-ubiquinone or tocotrienol-ubiquinone) for 28 days. The rats were then challenged with a single dose of indomethacin and killed six hours later. Findings showed that the severity of gastric lesions was comparable in all groups. Only groups that received a combination of antioxidants exhibited reduced lipid peroxidation compared with all other groups (p < 0.05). The combination groups had a higher level of gastric prostaglandin E2 (PGE2) content compared with all other groups (p < 0.05). There was no significant difference among the groups in the gastric acid concentration and the glutathione/oxidized glutathione (GSH/GSSG) ratio. We conclude that although supplementation of these antioxidants in combination had desirable effects on lipid peroxidation and gastric PGE2 level, they did not reduce the lesions produced by indomethacin.
Tocotrienols: Constitutional effects in aging and disease
Sebastian Schaffer,2 Walter E. Mu¨ ller, and Gunter P. Eckert
J Nutr. 2005 Feb;135(2):151-4.
Tocotrienols, a class of vitamin E analogs, modulate several mechanisms associated with the aging process and aging-related diseases. Most studies compare the activities of tocotrienols with those of tocopherols (“classical vitamin E”). However, some biological effects were found to be unique for tocotrienols. Although the absorption mechanisms are essentially the same for all vitamin E analogs, tocotrienols are degraded to a greater extent than tocopherols. The levels of tocotrienols in the plasma of animals and humans were estimated to reach low micromolar concentrations. One hallmark in the origin of disease and aging is the overproduction of reactive oxygen species (ROS). Tocotrienols possess excellent antioxidant activity in vitro and have been suggested to suppress ROS production more efficiently than tocopherols. In addition, tocotrienols show promising nonantioxidant activities in various in vitro and in vivo models. Most notable are the interactions of tocotrienols with the mevalonate pathway leading to the lowering of cholesterol levels, the prevention of cell adhesion to endothelial cells, and the suppression of tumor cell growth. Furthermore, glutamate-induced neurotoxicity is suppressed in the presence of tocotrienols. This review summarizes the main antioxidant and nonantioxidant effects of tocotrienols and assesses their potential as health-maintaining compounds.
Tocotrienol-induced cytotoxicity is unrelated to mitochondrial stress apoptotic signaling in neoplastic mammary epithelial cells
Shah SJ, Sylvester PW.
Biochem Cell Biol. 2005 Feb;83(1):86-95.
Tocotrienols and tocopherols represent the 2 subgroups within the vitamin E family of compounds, but tocotrienols display significantly greater apoptotic activity against a variety of cancer cell types. However, the exact mechanism mediating tocotrienol-induced apoptosis is not understood. Studies were conducted to determine the effects of tocotrienols on mitochondrial-stress-mediated apoptotic signaling in neoplastic +SA mammary epithelial cells grown in vitro. Exposure for 24 h to 0-20 micromol/L gamma-tocotrienol resulted in a dose-responsive increase in +SA cells undergoing apoptosis, as determined by flow cytometric analysis of Annexin V staining. However, tocotrienol-induced apoptosis was not associated with a disruption or loss of mitochondrial membrane potential, or the release of mitochondrial cytochrome c into the cytoplasm, as determined by JC-1 flow cytometric staining and ELISA assay, respectively. Interestingly, apoptotic +SA cells showed a paradoxical decrease in mitochondrial levels of pro-apoptotic proteins Bid, Bax, and Bad, and a corresponding increase in mitochondrial levels of anti-apoptotic proteins, Bcl-2 and Bcl-xL, suggesting that mitochondrial membrane stability and integrity might actually be enhanced for a limited period of time following acute tocotrienol exposure. In summary, these findings clearly demonstrate that tocotrienol-induced apoptosis occurs independently of mitochondrial stress apoptotic signaling in neoplastic +SA mammary epithelial cells.
Mechanisms mediating the antiproliferative and apoptotic effects of vitamin E in mammary cancer cells
Sylvester PW, Shah SJ.
Front Biosci. 2005 Jan 1;10:699-709. Print 2005 Jan 1.
Tocopherols and tocotrienol represent the two subgroups within the vitamin E family of compounds, but only tocotrienols display potent anticancer activity at doses that have little or no effect on normal cell growth or function. Tocotrienols are potent antioxidants, but antitumor activity is independent of antioxidant activity. The exact reason why tocotrienols are more potent than tocopherols is not completely understood, but at least part of the reason is because of greater cellular accumulation. Furthermore, dose-response studies show that growth inhibitory doses of tocotrienolsare 5-6 times lower than their corresponding lethal doses, suggesting that the antiproliferative and cytotoxic effects of tocotrienols are mediated through different mechanisms. Recent studies showed that tocotrienol-induced programmed cell death (apoptosis) results from the activation of specific intracellular cysteine proteases (caspases) associated with death receptor activation and signal transduction. Furthermore, combined treatment with specific caspase inhibitors blocked the cytotoxic effects of tocotrienols in malignant mammary epithelial cells. In contrast, tocotrienolinhibition of cell proliferation appears to involve the suppression of multiple hormone- and growth factor-receptor mitogenic signaling pathways. Although additional studies are required to clarify the intracellular mechanisms mediating the anticancer effects of tocotrienols, experimental evidence strongly suggests that dietary supplementation of tocotrienols may provide significant health benefits in lowering the risk of breast cancer in women.
Health promotion by flavonoids, tocopherols, tocotrienols, and other phenols: direct or indirect effects? Antioxidant or not?
Barry Halliwell, Joseph Rafter, and Andrew Jenner
Am J Clin Nutr. 2005 Jan;81(1 Suppl):268S-276S.
Foods and beverages rich in phenolic compounds, especially flavonoids, have often been associated with decreased risk of developing several diseases. However, it remains unclear whether this protective effect is attributable to the phenols or to other agents in the diet. Alleged health-promoting effects of flavonoids are usually attributed to their powerful antioxidant activities, but evidence for in vivo antioxidant effects of flavonoids is confusing and equivocal. This may be because maximal plasma concentrations, even after extensive flavonoid intake, may be low (insufficient to exert significant systemic antioxidant effects) and because flavonoid metabolites tend to have decreased antioxidant activity. Reports of substantial increases in plasma total antioxidant activity after flavonoid intake must be interpreted with caution; findings may be attributable to changes in urate concentrations. However, phenols might exert direct effects within the gastrointestinal tract, because of the high concentrations present. These effects could include binding of prooxidant iron, scavenging of reactive nitrogen, chlorine, and oxygen species, and perhaps inhibition of cyclooxygenases and lipoxygenases. Our measurements of flavonoids and other phenols in human fecal water are consistent with this concept. We argue that tocopherols and tocotrienols may also exert direct beneficial effects in the gastrointestinal tract and that their return to the gastrointestinal tract by the liver through the bile may be physiologically advantageous.
Lack of oxidative stress in a selenium deficient area in Ivory Coast–potential nutritional antioxidant role of crude palm oil
Tiahou G, Maire B, Dupuy A, Delage M, Vernet MH, Mathieu-Daudé JC, Michel F, Sess ED, Cristol JP.
Eur J Nutr. 2004 Dec;43(6):367-74. Epub 2004 Oct 20.
BACKGROUND:Previous studies have described an important selenium deficiency in a mountain region (Glanle) in the west of Ivory Coast.
AIM OF THE STUDY:To assess the antioxidant capacity of subjects from a selenium deficient area in Ivory Coast (Glanle region).
METHODS:This study involved 57 subjects, 18 to 69 years old, living in the Glanle region and 56 healthy controls living in the southern coastal region (Bodou). In the Glanle region families consume basically a vegetarian and crude palm oil diet, whereas in the Bodou region, families eat a fish-based diet with principally refined palm oil. Fasting blood samples were collected to assess the following parameters: lipid status (plasma total lipids; total-, HDL and LDL-cholesterol; triglycerides; phospholipids; fatty acid composition), plasma protein status (total protein, albumin, transthyretin, orosomucoid, CRP, transferrin), antioxidant capacity (plasma selenium, uric acid, retinol, alpha-tocopherol and tocotrienols levels, plasma seleno-glutathione peroxidase (GSHPx) activity) and oxidative stress markers (malondialdehyde (MDA) and advanced oxidation protein products (AOPP)).
RESULTS:The mountain region samples (Glanle) were characterized by significantly lower plasma albumin, total-, HDL- and LDL-cholesterol, retinol and selenium levels, plasma PUFA content and GSHPx activity, but significantly higher alpha-tocopherol index and total tocotrienol level, than controls from the coastal area (Bodou). These results suggest a higher exposure risk to oxidative stress for the mountain region subjects. However, the absence of oxidative damage in this group provides evidence of a selenium independent protection mechanism against oxidative stress. This protection is related to lower plasma LDL cholesterol and PUFA content, and to higher alpha-tocopherol index, delta and total tocotrienols.
CONCLUSION:The long-term consumption of crude palm oil could be considered as an effective protective factor against oxidative stress.
Suppression of diethylnitrosamine and 2-acetylaminofluorene-induced hepatocarcinogenesis in rats by tocotrienol-rich fraction isolated from rice bran oil.
Iqbal J, Minhajuddin M, Beg ZH.
Eur J Cancer Prev. 2004 Dec;13(6):515-20.
The anticancer efficacy of tocotrienol-rich fraction (TRF) was evaluated during diethylnitrosamine (DEN)/2-acetylaminofluorene (AAF)-induced hepatocarcinogenesis in male Sprague-Dawley rats. TRF treatment was carried out for 6 months, and was started 2 weeks before initiation phase of hepatocarcinogenesis. Morphological examination of the livers from DEN/AAF rats showed numerous off-white patches and few small nodules, which were significantly reduced by TRF treatment. Cytotoxic damage by DEN/AAF was estimated by alkaline phosphatase (ALP) release into the plasma from the cell membranes. DEN/AAF caused a twofold increase in the activity of ALP in plasma as compared with normal control rats, and this increase was prevented significantly by TRF treatment. We observed an increase of 79% in liver ALP activity in DEN/AAF rats, which was further increased by another 48% after the administration of TRF. Hepatic activity of glutathione S-transferase (GST) was also increased (3.5-fold) during the induction of hepatic carcinogenesis. Lipid peroxidation and low-density lipoprotein (LDL) oxidation increased threefold following initiation by DEN/AAF as compared with normal control rats. However, TRF treatment to DEN/AAF-treated rats substantially decreased (62-66%) the above parameters and thus limited the action of DEN/AAF. We conclude that long-term intake of TRF could reduce cancer risk by preventing hepatic lipid peroxidation and protein oxidation damage due to its antioxidant actions.
Vitamin E and breast cancer
Kline K, Yu W, Sanders BG.
J Nutr. 2004 Dec;134(12 Suppl):3458S-3462S.
Vitamin E is a term that describes a group of compounds with similar yet unique chemical structures and biological activities. One interesting property possessed by certain vitamin E compounds-namely, delta-tocotrienol, RRR-alpha-tocopheryl succinate [vitamin E succinate (VES), a hydrolyzable ester-linked succinic acid analogue of RRR-alpha-tocopherol], and a novel vitamin E analogue referred to as alpha-TEA (alpha-tocopherol ether linked acetic acid analogue, which is a stable nonhydrolyzable analogue of RRR-alpha-tocopherol)-is their ability to induce cancer cells but not normal cells to undergo a form of cell death called apoptosis. In contrast, the parent compound, RRR-alpha-tocopherol, also referred to as natural or authentic vitamin E and known for its antioxidant properties, does not induce cancer-cell apoptosis. Efforts to understand how select vitamin E forms can induce cancer cells to undergo apoptosis have identified several nonantioxidant biological functions, including restoration of pro-death transforming growth factor-beta and Fas signaling pathways. Recent studies with alpha-TEA show it to be a potent inducer of apoptosis in a wide variety of epithelial cancer cell types, including breast, prostate, lung, colon, ovarian, cervical, and endometrial in cell culture, and to be effective in significantly reducing tumor burden and metastasis in a syngeneic mouse mammary tumor model, as well as xenografts of human breast cancer cells. Studies also show that alpha-TEA, in combination with the cyclooxygenase-2 inhibitor celecoxib and the chemotherapeutic drug 9-nitro-camptothecin decreases breast cancer animal model tumor burden and inhibits metastasis significantly better than do single-agent treatments.