Effect of commercially available vitamin E preparations on arterial compliance and selected cardiovascular parameters

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Date
2006
Authors
Ghulam Rasool, Aida Hanum
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Abstract
Vitamin E is a potent lipid soluble antioxidant. It is the principal chain breaking antioxidant in human tissues, membrane and plasma. Vitamin E comprised of two families, the tocopherols and tocotrienols, each family is further divided into the alpha, gamma, delta and beta isomers. This PhD thesis aimed to address some of the unresolved issues on vitamin E use in vascular health. For tocopherol, a randomised, crossed over, double blind, placebo controlled clinical trial involving 20 healthy post menopausal women was conducted to assess the effect of alpha tocopherol on arterial compliance, an index of vascular health in a group of high cardiovascular risk subjects who has no overt vascular disease. Subjects were randomised to either placebo or tocopherol 400 IU daily for ten weeks, before being crossed over for treatment for another ten weeks. At intervals of 5 weeks, subjects attended afternoon sessions where measurements of arterial compliance, blood pressure and plasma vitamin E level were taken. Mean age of these women were 54.59±1.22 years. After 10 weeks treatment, plasma vitamin E level was 24.22±2.1 μg/ml and 11.89±0.68 μg/ml respectively with vitamin E and placebo (p <0.001). There was no significant difference in pulse wave velocity [PWV] after ten weeks treatment with tocopherol compared to placebo, PWV values being 9.04±0.29 m/s versus 9.14±0.29 m/s respectively. Similarly, no difference in systolic and diastolic blood pressures was seen between placebo and vitamin E at the end of ten weeks. For tocotrienols, two clinical trials were conducted. The first study was a randomised, placebo controlled, blinded end point clinical trial with a parallel design involving 36 healthy male subjects. This study aimed to determine the effects of a normal preparation of tocotrienol rich vitamin E [TRE] on the primary parameter, arterial compliance as assessed by aortic femoral PWV. Other measurements taken were augmentation index [AI], plasma total antioxidant status [TAS], plasma vitamin E levels, serum total cholesterol [TC] and low density lipoprotein [LDL-C]. Subjects were randomised to four treatment, either placebo or TRE at doses of 80 mg, 160 mg, or 320 mg mixed tocotrienol daily for two months. The TRE contained 34.56%, 24.63%, 15.00% and 26.17% respectively of alpha-tocotrienol, gamma-tocotrienol, delta tocotrienol and alpha-tocopherol. Mean age of subjects were 23.28±0.25 years. There were no significant differences between the groups in their change in PWV and AI with treatment [ANOVA, p=0.467 and p=0.092 respectively]. There were also no significant differences between groups in other measurements taken. Group 160 mg however, showed a small but significant improvement in AI after treatment compared to baseline. The TRE capsules used in this study were well tolerated by subjects. The second clinical trial on TRE aims to determine the effect of three doses of a special formulation of tocotrienols (SF-TRE) [claimed to enhance tocotrienol absorption] on arterial compliance. This study was a randomised, placebo controlled, blinded end point clinical trial with a parallel design involving 36 healthy male subjects. Other measurements taken were AI, plasma TAS, plasma vitamin E levels, serum TC and LDL-C. Subjects were grouped into four groups, each group were prescribed either placebo, or SF-TRE at doses of either 50 mg, 100 mg, or 200 mg tocotrienols daily for two months. The SF-TRE contained 23.54%, 43.16%, 9.83%, 23.50% respectively of alpha, gamma, delta tocotrienol and alpha tocopherol. Mean age of subjects were 23.86±0.39 years. There were no significant differences between groups in their change in PWV with treatment; change for each group being -0.06±0.29, -0.44±0.20, - 0.77±0.19 and -0.65±0.14 m/s respectively for groups placebo, 50 mg, 100 mg and 200 mg [p=0.117]. However, groups 100 mg and 200 mg showed significant improvement in PWV after treatment compared to baseline [p=0.007 and p=0.002]. Analysis of variance [ANOVA] for change in AI treatment was of borderline significance at p=0.048, change for groups placebo, 50 mg, 100 mg and 200 mg being 2.22±1.54, -6.59±2.84, -8.72±3.77 and -6.27±2.67 respectively. However, post-hoc analysis showed a borderline p value of 0.076 between groups placebo and 100 mg. All treated groups showed significant improvement in AI after treatment compared to baseline. There were no significant differences between groups in the other parameters measured. The SF-TRE used was well tolerated by subjects. Conclusion: Supplementary vitamin E for ten weeks at 400 IU daily increased plasma level of alpha tocopherol but has no effect on arterial compliance in healthy post menopausal women. For tocotrienol rich vitamin E, treatment with all groups treated with TRE and SF-TRE produced significant elevations of alpha, gamma and delta tocotrienols. The conventional preparation of TRE did not have an effect on arterial compliance in healthy male subjects. Overall, the SF-TRE also did not show significant effect on arterial compliance. However, there was a trend towards improvement in arterial compliance as suggested by the borderline significance value observed for the measurement of AI with SF-TRE. Significant within group improvement were also observed for all treated groups compared to baseline. Future studies to investigate the effect of TRE on arterial stiffness in patients with clinically manifest cardiovascular disease is suggested.
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PhD
Keywords
Medical science , Vitamin E , Arterial compliance , Cardiovascular parameters
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