Comparison of supplementation of RRR-α-tocopherol and racemic α- tocopherol in humans: Effects on lipid levels and lipoprotein susceptibility to oxidation

P. D. Reaven, J. L. Witztum

Research output: Contribution to journalArticle

92 Citations (Scopus)

Abstract

It has been suggested that α-tocopherol, a safe and effective antioxidant, be used in clinical trials to evaluate the ability of antioxidant therapy to inhibit atherosclerosis. Recent reports, however, have raised the possibility that there may be greater enrichment of plasma low density lipoprotein (LDL) in α-tocopherol resulting from the use of the naturally occurring RRR-α-tocopherol isomer compared with the other isomers present in the synthetic racemic form of α-tocopherol. Therefore, we fed equal dosages (1,600 mg/day) of the two forms of vitamin E to 16 men and women for 8 weeks and compared the effects of this supplementation on the susceptibility of isolated lipoproteins to oxidation. Neither form of vitamin E had appreciable effects on lipid or lipoprotein levels. α-Tocopherol levels in LDL increased at a similar rate in both groups and were nearly twofold higher than baseline levels by the end of the study. The susceptibility of LDL to oxidation was measured by formation of conjugated dienes, lipid peroxides, and thiobarbituric acid-reactive substances, as well as by macrophage degradation of LDL exposed to oxidizing conditions in vitro. The susceptibility of LDL to oxidation was decreased in both vitamin E groups compared with the baseline value, and this reduction occurred to a similar extent in both vitamin E-supplemented groups. α-Tocopherol levels in LDL also strongly correlated with all measures of LDL oxidation. This study demonstrates that, at this dosage, supplementation with either the natural or synthetic form of α-tocopherol provided equal antioxidant protection to LDL.

Original languageEnglish (US)
Pages (from-to)601-608
Number of pages8
JournalArteriosclerosis and Thrombosis
Volume13
Issue number4
StatePublished - Jan 1 1993
Externally publishedYes

Fingerprint

Tocopherols
LDL Lipoproteins
Lipoproteins
Lipids
Vitamin E
Antioxidants
Civil Rights
Thiobarbituric Acid Reactive Substances
Lipid Peroxides
Atherosclerosis
Macrophages
Clinical Trials

Keywords

  • antioxidants
  • atherosclerosis
  • conjugated dienes
  • DL-α- tocopherol
  • HDL
  • LDL
  • lipid oxidation
  • macrophages
  • RRR-α-tocopherol
  • vitamin E

ASJC Scopus subject areas

  • Cardiology and Cardiovascular Medicine

Cite this

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title = "Comparison of supplementation of RRR-α-tocopherol and racemic α- tocopherol in humans: Effects on lipid levels and lipoprotein susceptibility to oxidation",
abstract = "It has been suggested that α-tocopherol, a safe and effective antioxidant, be used in clinical trials to evaluate the ability of antioxidant therapy to inhibit atherosclerosis. Recent reports, however, have raised the possibility that there may be greater enrichment of plasma low density lipoprotein (LDL) in α-tocopherol resulting from the use of the naturally occurring RRR-α-tocopherol isomer compared with the other isomers present in the synthetic racemic form of α-tocopherol. Therefore, we fed equal dosages (1,600 mg/day) of the two forms of vitamin E to 16 men and women for 8 weeks and compared the effects of this supplementation on the susceptibility of isolated lipoproteins to oxidation. Neither form of vitamin E had appreciable effects on lipid or lipoprotein levels. α-Tocopherol levels in LDL increased at a similar rate in both groups and were nearly twofold higher than baseline levels by the end of the study. The susceptibility of LDL to oxidation was measured by formation of conjugated dienes, lipid peroxides, and thiobarbituric acid-reactive substances, as well as by macrophage degradation of LDL exposed to oxidizing conditions in vitro. The susceptibility of LDL to oxidation was decreased in both vitamin E groups compared with the baseline value, and this reduction occurred to a similar extent in both vitamin E-supplemented groups. α-Tocopherol levels in LDL also strongly correlated with all measures of LDL oxidation. This study demonstrates that, at this dosage, supplementation with either the natural or synthetic form of α-tocopherol provided equal antioxidant protection to LDL.",
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