90735
document
Dose-response comparison of RRR-alpha-tocopherol and all-racemic alpha-tocopherol on LDL oxidation . Much data have accrued in support of the concept that oxidation of LDL is a key early step in atherogenesis . The most consistent data with respect to micronutrient antioxidants and atherosclerosis appear to relate to alpha-tocopherol ( AT ) , the predominant lipid-soluble antioxidant in LDL . There are scant data on the direct comparison of RRR-AT and all-racemic ( rac ) -AT on LDL oxidizability . Hence , the aim of the present study was to examine the relative effects of RRR-AT and all-rac-AT on plasma antioxidant levels and LDL oxidation in healthy persons in a dose-response study . The effect of RRR-AT and all-rac-AT at doses of 100 , 200 , 400 , and 800 IU/d on plasma and LDL AT levels and LDL oxidation was tested in a randomized , placebo-controlled study of 79 healthy subjects . Copper-catalyzed oxidation of LDL was monitored by measuring the formation of conjugated dienes and lipid peroxides over an 8-hour time course at baseline and again after 8 weeks . Plasma AT , lipid-standardized AT , and LDL AT levels rose in a dose-dependent fashion in both the RRR-AT and all-rac-AT groups compared with baseline . There were no significant differences in plasma , lipid-standardized , and LDL AT levels between RRR-AT and all-rac-AT supplementation at any dose comparison . The lag phases of oxidation were significantly prolonged with doses > or = 400 IU/d of RRR-AT and all-rac-AT , as measured by conjugated-dienes assay and at 400 IU/d of RRR-AT and 800 IU/d of both forms of AT by lipid peroxide assay . Again , there were no significant differences in the lag phase of oxidation at each dose for RRR-AT when compared with all-rac-AT . Also , there were no significant differences in LDL oxidation after in vitro enrichment of LDL with RRR-AT and all-rac-AT . Thus , supplementation with either RRR-AT or all-rac-AT resulted in similar increases in plasma and LDL AT levels at equivalent IU doses , and the degree of protection against copper-catalyzed LDL oxidation was only evident at doses > or = 400 IU/d for both forms .
90736
Intervention_Pharmacological
RRR-alpha-tocopherol and all-racemic alpha-tocopherol
90737
Intervention_Pharmacological
alpha-tocopherol
90738
Intervention_Pharmacological
RRR-AT and all-rac-AT
90739
Outcome_Physical
plasma , lipid-standardized , and LDL AT levels
90740
Outcome_Physical
lag phases of oxidation
90741
Outcome_Physical
lag phase of oxidation
90742
Outcome_Physical
LDL oxidation