Dose dependent elevation of plasma tocotrienol levels and its effect on arterial compliance, plasma total antioxidant status, and lipid profile in healthy humans supplemented with tocotrienol rich vitamin E

Rasool AH, Yuen KH, Yusoff K, Wong AR, Rahman AR.

J Nutr Sci Vitaminol (Tokyo). 2006 Dec;52(6):473-8.

Tocotrienols are a class of vitamin E reported to be potent antioxidants, besides having the ability to inhibit the HMG-CoA reductase enzyme. This study assessed the effects of 3 doses of tocotrienol-rich vitamin E (TRE) on plasma tocotrienol isomer concentration, arterial compliance, plasma total antioxidant status (TAS), aortic systolic blood pressure (ASBP), serum total cholesterol (TC) and low density lipoprotein cholesterol (LDL-C) in healthy males.

Methodology: This randomised, blinded end-point, placebo-controlled clinical trial with a parallel design involved 36 healthy male subjects who took either an oral placebo or TRE at doses of 80, 160 or 320 mg daily for 2 mo. Baseline and end-of-treatment measurements of vitamin E concentration, arterial compliance [assessed by aortic femoral pulse wave velocity (PWV) and augmentation index (AI)], ASBP, plasma TAS, serum TC and LDL-C were taken.

Results: Baseline tocotrienol isomer concentrations were low and not detectable in some subjects. Upon supplementation, all TRE-treated groups showed significant difference from placebo for their change in alpha, gamma and delta tocotrienol concentrations from baseline to end of treatment. There was a linear dose and blood level relationship for all the isomers. There was no significant difference between groups for their change in PWV, AI, plasma TAS, ASBP, TC or LDL-C from baseline to end of treatment. Groups 160 mg (p = 0.024) and 320 mg (p = 0.049) showed significant reductions in their ASBP. Group 320 mg showed a significant 9.2% improvement in TAS.

Conclusion: TRE at doses up to 320 mg daily were well tolerated. Treatment significantly increased alpha, delta, and gamma tocotrienol concentrations but did not significantly affect arterial compliance, plasma TAS, serum TC or LDL-C levels in normal subjects.

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Proposed mechanisms for red palm oil induced cardioprotection in a model of hyperlipidaemia in the rat

Esterhuyse JS, van Rooyen J, Strijdom H, Bester D, du Toit EF.

Prostaglandins Leukot Essent Fatty Acids. 2006 Dec;75(6):375-84.

High-cholesterol diets alter myocardial and vascular NO-cGMP signaling and have been implicated in ischaemic/reperfusion injury. We investigated the effects of dietary red palm oil (RPO) containing fatty acids, carotonoids, tocopherols and tocotrienols on myocardial ischaemic tolerance and NO-cGMP pathway function in the rat. Wistar rats were fed a standard rat chow+/-RPO, or a standard rat chow+cholesterol+/-RPO diet. Myocardial mechanical function and NO-cGMP signaling pathway intermediates were determined before, during and after 25 min ischaemia. RPO-supplementation improved aortic output recovery and increased myocardial ischaemic cGMP concentrations. Simulated ischaemia (hypoxia) increased cardiomyocyte nitric oxide levels in the two RPO supplemented groups, but not in control non-supplemented groups. RPO supplementation also increased hypoxic nitric oxide levels in the control diet fed, but not the cholesterol fed rats. These data suggest that dietary RPO may improve myocardial ischaemic tolerance by increasing bioavailability of NO and improving NO-cGMP signaling in the heart.

A rice bran oil diet increases LDL-receptor and HMG-CoA reductase mRNA expressions and insulin sensitivity in rats with streptozotocin/nicotinamide-induced type 2 diabetes

Chen CW, Cheng HH.

J Nutr. 2006 Jun;136(6):1472-6.

A rice bran oil (RBO) diet can reduce plasma lipids; this was attributed to the specific components, gamma-oryzanol and gamma-tocotrienol, which individually were shown to be hypocholesterolemic; however, the mechanism of their effects on diabetic hyperlipidemia and the development of diabetes is not known. Rats with streptozotocin/nicotinamide-induced type 2 diabetes were divided into control, RO10, and RO15 groups, and fed cholesterol-free diets containing 0, 10, and 15 g RBO with 0, 352, and 528 g gamma-oryzanol and 0, 6.0 and 9.0 mg gamma-tocotrienol/100 g diet for 4 wk. Diabetic rats fed the RBO diet had greater insulin sensitivity (P = 0.02) than rats fed the control diet. Diabetic rats fed the RBO diet also had lower plasma triglyceride (P = 0.003), LDL cholesterol (P = 0.028), and hepatic triglyceride concentrations (P = 0.04), as well as greater fecal neutral sterol and bile acid excretion than those fed the control diet. After 4 wk, there was an approximately 100% (P < 0.001) increase in the abundance of hepatic cholesterol 7alpha-hydroxylase, an 89% (P < 0.001) increase in the hepatic LDL-receptor, and a 50% (P < 0.001) increase in hepatic 3-hydroxy-3-methylglutaryl coenzyme A reductase mRNA in rats fed the RBO diet compared with those fed the control diet. These findings support the conclusion that a rice bran oil-containing diet can significantly suppress hyperlipidemic and hyperinsulinemic responses in diabetic rats. The high contents of gamma-oryzanol and gamma-tocotrienol in RBO can lead to increased fecal neutral sterol and bile acid excretion, via upregulation of cholesterol synthesis and catabolism.

Dose-response impact of various tocotrienols on serum lipid parameters in 5-week-old female chickens

Yu SG, Thomas AM, Gapor A, Tan B, Qureshi N, Qureshi AA.

Lipids. 2006 May;41(5):453-61.

The cholesterol-suppressive action of the tocotrienol-rich-fraction (TRF) of palm oil may be due to the effect of its constituent tocotrienols on beta-hydroxy-beta-methylglutaryl coenzyme A (HMG-CoA) reductase activity. The tocotrienols, modulate HMG-CoA reductase activity via a post-transcriptional mechanism. As a consequence small doses (5-200 ppm) of TRF-supplemented diets fed to experimental animals lower serum cholesterol levels. These findings led us to evaluate the safety and efficacy of large supplements of TRF and its constituents. Diets supplemented with 50, 100, 250, 500, 1000, or 2000 ppm of TRF, alpha-tocopherol, alpha-tocotrienol, gamma-tocotrienol, or 6-tocotrienol were fed to chickens for 4 wk. There were no differences between groups or within groups in weight gain, or in feed consumption at the termination of the feeding period. Supplemental TRF produced a dose-response (50-2000 ppm) lowering of serum total and LDL cholesterol levels of 22% and 52% (P < 0.05), respectively, compared with the control group. alpha-Tocopherol did not affect total or LDL-cholesterol levels. Supplemental alpha-tocotrienol within the 50-500 ppm range produced a dose-response lowering of total (17%) and LDL (33%) cholesterol levels. The more potent gamma and delta isomers yielded dose-response (50-2,000 ppm) reductions of serum total (32%) and LDL (66%) cholesterol levels. HDL cholesterol levels were minimally impacted by the tocotrienols; as a result, the HDL/LDL cholesterol ratios were markedly improved (123-150%) by the supplements. Serum triglyceride levels were significantly lower in sera of pullets receiving the higher supplements. The safe dose of various tocotrienols for human consumption might be 200-1000 mg/d based on this study.

The therapeutic impacts of tocotrienols in type 2 diabetic patients with hyperlipidemia

Baliarsingh S, Beg ZH, Ahmad J.

Atherosclerosis. 2005 Oct;182(2):367-74. Epub 2005 Apr 20.

In type 2 diabetics, the progression of atherosclerosis is more rapid than the general population and 80% of these patients will die of an atherosclerotic event. Since in these patients hyperglycemia per se confers increased risk for cardiovascular disease (CVD), the presence of even borderline-high-risk LDL-C signals the need for more aggressive LDL-lowering therapy. Most of the lipid lowering agents, currently in use in the treatment of dyslipidemia in type 2 diabetics, have a host of side effects. In contrast, dietary tocotrienols are Vitamin E and have effective lipid lowering property in addition to their potent antioxidant activity. In this study, we have investigated the therapeutic impacts of tocotrienols on serum and lipoprotein lipid levels in type 2 diabetic patients. Based on known tocotrienol rich fraction (TRF)-mediated decrease on elevated blood glucose and glycated hemoglobin A(1C) (HbA(1C)) in diabetic rats, we have also investigated the effect of TRF on these parameters. A randomized, double blind, placebo-controlled design involving 19 type 2 diabetic subjects with hyperlipidemia was used. After 60 days of TRF treatment, subjects showed an average decline of 23, 30, and 42% in serum total lipids, TC, and LDL-C, respectively. The goal in type 2 diabetics is to reduce LDL-C levels < or = 100mg/dl. In the present investigation tocotrienols mediated a reduction of LDL-C from an average of 179 mg/dl to 104 mg/dl. However, hypoglycemic effect of TRF was not observed in these patients because they were glycemically stable and their glucose and HbA(1) levels were close to normal values. In conclusion, daily intake of dietary TRF by type 2 diabetics will be useful in the prevention and treatment of hyperlipidemia and atherogenesis.

Hypolipidemic and antioxidant properties of tocotrienol rich fraction isolated from rice bran oil in experimentally induced hyperlipidemic rats

Minhajuddin M, Beg ZH, Iqbal J.

Food Chem Toxicol. 2005 May;43(5):747-53.

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.

Dietary antioxidant intake and risk of type 2 diabetes

Montonen J, Knekt P, Järvinen R, Reunanen A.

Diabetes Care. 2004 Feb;27(2):362-6.

Objective: The intake of antioxidants was studied for its ability to predict type 2 diabetes.

Research Design & Methods: A cohort of 2,285 men and 2,019 women 40-69 years of age and free of diabetes at baseline (1967-1972) was studied. Food consumption during the previous year was estimated using a dietary history interview. The intake of vitamin C, four tocopherols, four tocotrienols, and six carotenoids was calculated. During a 23-year follow-up, a total of 164 male and 219 female incident cases occurred.

Results: Vitamin E intake was significantly associated with a reduced risk of type 2 diabetes. The relative risk (RR) of type 2 diabetes between the extreme quartiles of the intake was 0.69 (95% CI 0.51-0.94, P for trend = 0.003). Intakes of alpha-tocopherol, gamma-tocopherol, delta-tocopherol, and beta-tocotrienol were inversely related to a risk of type 2 diabetes. Among single carotenoids, beta-cryptoxanthin intake was significantly associated with a reduced risk of type 2 diabetes (RR 0.58, 95% CI 0.44-0.78, P < 0.001). No association was evident between intake of vitamin C and type 2 diabetes risk.

Conclusion: This study supports the hypothesis that development of type 2 diabetes may be reduced by the intake of antioxidants in the diet.

Suppression of 7,12-dimethylbenz[alpha]anthracene-induced carcinogenesis and hypercholesterolaemia in rats by tocotrienol-rich fraction isolated from rice bran oil

Iqbal J, Minhajuddin M, Beg ZH.

Eur J Cancer Prev. 2003 Dec;12(6):447-53.

The anti-tumour and anti-cholesterol impacts of tocotrienol-rich fraction (TRF) were investigated in rats treated with the chemical carcinogen 7,12-dimethylbenz [alpha]anthracene (DMBA), which is known to induce mammary carcinogenesis and hypercholesterolaemia. DMBA administration to rats was associated with the appearance of multiple tumours on mammary glands after 6 months. Alkaline phosphatase (ALP) and glutathione-S-transferase (GST) are used as marker enzymes to monitor the severity of carcinogenesis. Although no tumours were visible on livers, hepatic ALP and GST activities of DMBA-treated rats were profoundly elevated in comparison to enzyme activities of normal control rats. Feeding of TRF (10 mg/kg body weight/day) for 6 months, isolated from rice bran oil (RBO), to DMBA-administered rats, reduced the severity and extent of neoplastic transformation in the mammary glands. Similarly, plasma and mammary ALP activities increased during carcinogenesis (95% and 43%, respectively), were significantly decreased in TRF-treated rats, whereas TRF mediated a further increase of 51% in hepatic ALP activity. TRF treatment to rats maintained low levels of GST activities in liver ( approximately 32%) and mammary glands ( approximately 21%), which is consistent with anti-carcinogenic properties of TRF. Administration of DMBA also caused a significant increase of 30% in plasma total cholesterol and 111% in LDL-cholesterol levels compared with normal control levels. Feeding of TRF to rats caused a significant decline of 30% in total cholesterol and 67% in LDL-cholesterol levels compared with the DMBA-administered rats. The experimental hypercholesterolaemia caused a significant increase in enzymatic activity (23%) and protein mass (28%) of hepatic 3-hydroxy-3-methylglutaryl co-enzyme A (HMG-CoA) reductase. Consistent with TRF-mediated reduction in plasma lipid levels, enzymatic activity and protein mass of HMG-CoA reductase was significantly reduced. These results indicate that TRF has potent anti-cancer and anti-cholesterol effects in rats.

Nitric oxide synthase activity in blood vessels of spontaneously hypertensive rats: Antioxidant protection by gamma-tocotrienol

Newaz MA, Yousefipour Z, Nawal N, Adeeb N.

J Physiol Pharmacol. 2003 Sep;54(3):319-27.

Involvement of free radicals and nitric oxide (NO) has long been implicated to the pathogenesis of essential hypertension. Several studies using antioxidants as the radical scavenger have shown to confer protection against free radical mediated diseases. This study is designed to investigate the role of antioxidant gamma-tocotrienol on endothelial nitric oxide synthase (NOS) activity in spontaneously hypertensive rats (SHR). SHR’s were divided into four groups namely untreated SHR (HC), treatment with 15 mg gamma-tocotrienol/kg diet (gammal), 30 mg gamma-tocotrienol/kg diet (gamma2) and 150 mg gamma-tocotrienol/kg diet (gamma3) and studied for three months. Wister Kyoto (WKY) rats were used as the control (C). Blood pressure was recorded every fortnightly by tail plethysmography. Animals were sacrificed and NOS activity in blood vessels was measured by [3H]arginine radioactive assay. Nitrite concentration in plasma was determined by Greis assay and lipid peroxides in the blood vessels by spectrofluorometry. This study showed that gamma-tocotrienol significantly reduced systolic blood pressure (SBP) in SHRs with a maximum reduction in group treated with gamma-tocotrienol 15 mg/kg diet (HC: 210 +/- 9 mmHg, gammal:123 +/- 19 mmHg). Blood vessels from untreated SHR showed a reduced NOS activity compare to that of WKY rats (C: 1.54 +/- 0.26 pmol/mg protein, HC: 0.87 +/- 0.23 pmol/mg protein; p<0.001). Gamma-tocotrienol improves NOS activity in all the groups with more significance in group gamma2 (p<0.001) and gamma3 (p<0.05). Plasma level of nitrite was reduced in SHR from 55 +/- 3 microM/ml in WKY to 26+/-2 muM/ml (p<0.001). Plasma nitrite level was reversed by treatment with gamma-tocotrienol. (gammal: p<0.001, gamma2: p<0.005, gamma3: p<0.001, respectively). In all the treatment groups, NOS activity showed significant negative correlation with blood pressure (gammal: r=-0.716, p<0.05; gamma2: r=-0.709, p<0.05; gamma3: r=-0.789, p<0.05). For plasma nitrite, although it shows a negative correlation with blood pressure it was significant only in gammal (r=-0.676, p<0.05) and gamma2 (r=-0.721, p<0.05). From this study we found that compared to WKY rats, SHR has lower NOS activity in blood vessels, which upon treatment with antioxidant gamma-tocotrienol increased the NO activity and concomitantly reduced the blood pressure. These findings further strengthen the hypothesis that free radicals and NO play critical role in pathogenesis of essential hypertension.

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Supplementation with 3 compositionally different tocotrienol supplements does not improve cardiovascular disease risk factors in men and women with hypercholesterolemia

Mustad VA, Smith CA, Ruey PP, Edens NK, DeMichele SJ.

Am J Clin Nutr. 2002 Dec;76(6):1237-43.

Background: Tocotrienols have been reported to lower LDL-cholesterol and fasting glucose concentrations and to have potent antioxidant effects, but the results are contradictory.

Objective: The objective was to study the relative effect of tocotrienol supplements of different compositions (mixed alpha- plus gamma-, high gamma-, or P25-complex tocotrienol) on blood lipids, fasting blood glucose, and the excretion of 8-iso-prostaglandin F(2alpha), a measure of oxidative stress, in healthy hypercholesterolemic men and women.

Design: This was a double-blind, randomized, parallel-design study in which subjects (n = 67 men and women) consumed 1 of 3 commercially available tocotrienol supplements or a safflower oil placebo for 28 d. Blood and urine samples were obtained before and after the 28-d supplementation phase for analysis of fasting blood lipids, glucose, tocotrienols and tocopherols, and 8-iso-prostaglandin F(2alpha).

Results: Overall, serum tocotrienols were increased in subjects who consumed tocotrienols, which showed that the putatively active components were absorbed. No significant differences in mean lipid or glucose concentrations were observed among the 4 treatment groups at the end of the 28-d supplementation phase. However, when the values were expressed as a percentage change from the concentrations during the presupplementation run-in phase, LDL cholesterol increased slightly (7 +/- 2%) but significantly (P < 0.05) in the group consuming the mixed alpha- plus gamma-tocotrienol supplement when compared with LDL cholesterol in the group consuming the P25-complex tocotrienol. Neither mean concentrations nor the percentage change in 8-iso-prostaglandin F(2alpha) differed significantly among treatments.

Conclusion: Supplementation with 200 mg tocotrienols/d from 3 commercially available sources has no beneficial effect on key cardiovascular disease risk factors in highly compliant adults with elevated blood lipid concentrations.

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