Tocotrienols have been reported to have higher biological activities than tocopherols. We investigated the antitumor effect of tocotrienols both in vivo and in vitro. Oral administration of tocotrienols resulted in significant suppression of liver and lung carcinogenesis in mice. In human hepatocellular carcinoma HepG2 cells, delta-tocotrienol exerted more significant antiproliferative effect than alpha-, beta-, and gamma-tocotrienols. delta-Tocotrienol induced apoptosis, and also tended to induce S phase arrest. On the other hand, gene expression analysis showed that delta-tocotrienol increased CYP1A1 gene, a phase I enzyme. Although further study will be necessary to investigate possible adverse effect, the data obtained in present study suggest that tocotrienols could be promising agents for cancer prevention.
Monthly Archives: November 2005
Activation of the NO-cGMP pathway is associated with myocardial protection against ischemia. During ischemia, function of this pathway is disturbed. Little is known about the effects of supplements such as Red Palm Oil (RPO) on the myocardial NO- cGMP- signalling pathway. RPO consists of saturated (SFAs), mono-unsaturated (MUFAs) and polyunsaturated (PUFAs) fatty acids and is an antioxidant rich in natural B-carotene and vitamin E (tocopherols and tocotrienols). This study determined whether dietary RPO-supplementation protects against the consequences of ischemia and identified a possible mechanism for this protection. Long-Evans rats were fed a control diet or control diet plus 7 g RPO per kg diet for six weeks. Hearts were excised and mounted on a working heart perfusion apparatus. Cardiac function was measured before and after hearts were subjected to 25 minutes of global ischemia. Left ventricular systolic (LVSP) and diastolic pressure (LVDP), coronary flow (CF), heart rate (HR) and aortic output (AO) were measured. To assess NO-cGMP pathway activity, hearts subjected to the same conditions, were freeze-clamped and analysed for tissue cAMP and cGMP levels using a RIA method. Furthermore, composition of myocardial phospholipid fatty acids by gas chromatography and blood samples were collected for serum lipid determinations. The percentage aortic output recovery of hearts supplemented with RPO was 72.9 +/-3.43% vs 55.4 +/-2.48% for controls (P< 0.05). Ten minutes into ischemia the cGMP levels of the RPO-supplementation group were significantly higher than the control group (26.5+/-2.78 pmol/g vs 10.1+/-1.78 pmol/g. Total myocardial PUFA content in hearts supplemented with RPO increased from 54.45+/-1.11% before ischemia to 59.03 +/- 0.30% after ischemia P<0.05). Results demonstrated that RPO-supplementation protected hearts against the consequences of ischemia/reperfusion injury. These findings suggest that dietary RPO protects via the NO-cGMP pathway and/or changes in PUFA composition during ischemia/reperfusion.
Effects of tocotrienols on cell viability and apoptosis in normal murine liver cells (BNL CL.2) and liver cancer cells (BNL 1ME A.7R.1), in vitro
Har CH, Keong CK.
Asia Pac J Clin Nutr. 2005;14(4):374-80.
The effects of tocotrienols on murine liver cell viability and their apoptotic events were studied over a dose range of 0-32 microg mL(-1). Normal murine liver cells (BNL CL.2) and murine liver cancer cells (BNL 1ME A.7R.1) were treated with tocotrienols (T(3)), alpha tocopherol (alpha-T) and the chemo drug, Doxorubicin (Doxo, as a positive control). Cell viability assay showed that T(3) significantly (P < or = 0.05) lowered the percentage of BNL 1ME A.7R.1 cell viability in a dose-responsive manner (8-16 microg mL(-1)), whereas T did not show any significant (P>0.05) inhibition in cell viability with increasing treatment doses of 0-16 microg mL(-1). The IC(50) for tocotrienols were 9.8, 8.9, 8.1, 9.7, 8.1 and 9.3 microg mL(-1) at 12, 24, 36, 48, 60 and 72 hours respectively. Early apoptosis was detected 6 hours following T(3) treatment of BNL 1ME A.7R.1 liver cancer cells, using Annexin V-FITC fluorescence microscopy assay for apoptosis, but none were observed for the non-treated liver cancer cells at the average IC(50) of 8.98 microg mL(-1) tocotrienols for liver cancer cells. Several apoptotic bodies were detected in BNL 1ME A.7R.1 liver cancer cells at 6 hours post-treatment with tocotrienols (8.98 microg mL(-1)) using Acridine Orange/Propidium Iodide fluorescence assay. However, only a couple of apoptotic bodies were seen in the non-treated liver cancer cells and the BNL CL.2 normal liver cells. Some mitotic bodies were also observed in the T(3)-treated BNL 1ME A.7R.1 liver cancer cells but were not seen in the untreated BNL 1ME A.7R.1 cells and the BNL CL.2 liver cells. Following T(3)-treatment (8.98 microg mL(-1)) of the BNL 1ME A.7R.1 liver cancer cells, 24.62%, 25.53% and 44.90% of the cells showed elevated active caspase 3 activity at 9, 12 and 24 hours treatment period, respectively. DNA laddering studies indicated DNA fragmentation occurred in the T(3)-treated liver cancer cells, BNL 1ME A.7R.1 but not in non-treated liver cancer cells and the T(3)-treated and non-treated normal liver cells. These results suggest that tocotrienols were able to reduce the cell viability in the murine liver cancer cells at a dose of 8-32 microg mL(-1) and that this decrease in percentage cell viability may be due to apoptosis.
The natural vitamin E tocotrienol (TCT) possesses biological properties not shared by tocopherols (TCP). Nanomolar alpha-TCT, not alpha-TCP, is potently neuroprotective (JBC 275:13049; 278:43508). Tocopherol-transport protein (TTP) represents the primary mechanism for maintaining normal alpha-TCP concentrations in plasma and extrahepatic tissues. TTP primarily transports alpha-TCP and has low affinity for alpha-TCT. There are no studies that have investigated tissue delivery of alpha-TCT when orally gavaged on a long-term basis. A long-term study was conducted to examine the effects of alpha-TCT or alpha-TCP supplementation, either alone or in combination, on tissue levels. Rats were maintained on a vitamin E-deficient diet and gavaged with alpha-TCT or alpha-TCP alone or in combination. Five generations of rats were studied over 60 weeks. TTP-deficient mice were supplemented with TCT and bred to examine tissue delivery of oral alpha-TCT. Orally supplemented alpha-TCT was effectively delivered to most tissues over time. When co-supplemented, alpha-TCP outcompeted alpha-TCT for transport systems delivering vitamin E to tissues. To evaluate the significance of TTP in alpha-TCT delivery to tissues, tissue levels of alpha-TCT in supplemented TTP-deficient mice were studied. alpha-TCT was transported to several vital organs in TTP-deficient mice. alpha-TCT restored fertility in TTP-deficient mice. In sum, orally supplemented alpha-TCT was successfully delivered to several vital organs. The transport efficiency of alpha-TCT to tissues may be maximized by eliminating the co-presence of alpha-TCP in the oral supplement. Examination of whether alpha-TCT may benefit humans suffering from neurological disorders because of congenital TTP deficiency is warranted.
A high performance liquid chromatographic (HPLC) method for the determination of tocopherols and tocotrienols in walnut samples is described. The compounds were extracted with n-hexane, using a simple solid-liquid extraction procedure. Tocol was used as internal standard and BHT as anti-oxidant. The ehromatographic separation was achieved using an Inertsil 5 SI normal phase column operating with isocratic elution of n-hexane/1,4-dioxane (96.5:3.5, v/v), at a flow rate of 0.7 mL/min. The effluent was monitored by a series arrangement of a diodearray detector followed by a fluorescence detector. The detection limits were low, between 0.037 and 0.266 (jig/mL. The method was precise (% CV less than 2.8%), accurate (% CV less than 5.6%), and, as a general rule, the recovery values were high (mean values ranging from 93.4% to 104.0%)
A comparison between tocopherol and tocotrienol effects on gastric parameters in rats exposed to stress
Azlina MF, Nafeeza MI, Khalid BA.
Asia Pac J Clin Nutr. 2005;14(4):358-65.
Rats exposed to stress developed various changes in the gastrointestinal tract and hormones. The present study was designed to compare the impact of tocopherol and tocotrienol on changes that influence gastric and hormonal parameters important in maintaining gastric mucosal integrity in rats exposed to restrain stress. These include gastric acidity, gastric tissue content of parameters such as malondialdehyde, prostaglandin (PGE(2)), serum levels of gastrin and glucagon-like peptide-1 (GLP-1). Sixty male Sprague-Dawley rats (200-250 g) were randomly divided into three equal sized groups, a control group which received a normal rat diet (RC) and two treatment groups each receiving a vitamin deficient diet with oral supplementation of either tocopherol (TF) or tocotrienol (TT) at 60 mg/kg body weight. Blood samples were taken from half the number of rats (non-stressed group) after a treatment period of 28 days before they were killed. The remaining half was subjected to experimental restraint-stress, at 2 hours daily for 4 consecutive days (stressed groups), on the fourth day, blood samples were taken and the rats killed. The findings showed that the gastric acid concentration and serum gastrin level in stressed rats were significantly (P<0.05) reduced compared to the non-stressed rats in the control and TF groups. However, the gastric acidity and gastrin levels in the TT group were comparable in stressed and non-stressed rats. These findings suggest that tocotrienol is able to preserve the gastric acidity and serum gastrin level which are usually altered in stressed conditions. The PGE(2) content and the plasma GLP-1 level were, however, comparable in all stressed and non-stressed groups indicating that these parameters were not altered in stress and that supplementation with TF or TT had no effect on the gastric PGE2 content or the GLP-1 level. The malondialdehyde, an indicator of lipid peroxidation was higher from gastric tissues in the stressed groups compared to the non-stressed groups. These findings implicated that free radicals may play a role in the development of gastric injury in stress and supplementation with either TF or TT was able to reduce the lipid peroxidation levels compared to the control rats. We conclude that both tocopherol and tocotrienol are comparable in their gastro-protective ability against damage by free radicals generated in stress conditions, but only tocotrienol has the ability to block the stress-induced changes in the gastric acidity and gastrin level.