Abstract
Much data has accumulated supporting a proatherogenic role for oxidized low density lipoprotein (Ox-LDL). Micronutrient antioxidants such as alpha-tocopherol, the principal lipid-soluble antioxidant, assume potential significance because levels can be manipulated by dietary measures without resulting in side effects. Co-incubation of LDL in vitro with alpha-tocopherol inhibits its oxidative modification. Hence the effect of dietary supplementation with alpha-tocopherol on the time course of copper-catalyzed oxidation of LDL was tested in a randomized placebo-controlled single-blind study. Two groups of 12 male subjects were given either placebo or alpha-tocopherol (800 IU/day) for a period of 12 weeks. Alpha-tocopherol therapy did not result in any side effects or exert an adverse effect on the plasma lipid and lipoprotein profile. While the lipid standardized alpha-tocopherol levels were similar at baseline, the supplemented group had 3.3-fold and 4.4-fold higher levels compared to placebo at 6 and 12 weeks, respectively. In the 15 subjects in whom both plasma and LDL alpha-tocopherol levels were quantitated, there was a significant correlation (r = 0.79, P less than 0.0001). At baseline there were no significant differences in the time course curves of thiobarbituric acid-reacting substances (TBARS) activity or conjugated diene formation between the alpha-tocopherol and placebo groups. However, at both 6 and 12 weeks the mean levels of TBARS activity and conjugated diene formation were lower in the alpha-tocopherol group; the most significant differences were manifest at the 3-h time point. Also at both 6 and 12 weeks the mean rate of oxidation was lower in the alpha-tocopherol group.2+_
Highlights
Much data has accumulated supporting a proatherogenic role for oxidized low density lipoprotein (Ox-LDL)
Neither placebo nor alpha-tocopherol supplementation had a significant effect on the plasma lipid and lipoprotein profile (Table 1)
There were no significant differences between the two groups with respect to plasma lipid and lipoprotein levels
Summary
Much data has accumulated supporting a proatherogenic role for oxidized low density lipoprotein (Ox-LDL). Blood was obtained for the lipid and lipoprotein profile, plasma alpha-tocopherol, ascorbate and beta-carotene levels and for LDL isolation. Because of insufficient LDL samples after the oxidation studies, only 15 subjects had both plasma and LDL alpha-tocopherol levels assayed at all three time points.
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