The two faces of alpha and gamma tocopherol: An in vitro and ex vivo investigation into VLDL, LDL and HDL oxidation

Nida Nadeem, Jayne Woodside, Sean Kelly, Rachael Allister, Ian Young, Jane McEneny

Research output: Contribution to journalArticle

16 Citations (Scopus)

Abstract

Background

Vitamin E and its derivatives, namely, the tocopherols, are known antioxidants, and numerous clinical trials have investigated their role in preventing cardiovascular disease; however, evidence to date remains inconclusive. Much of the in vitro research has focused on tocopherol's effects during low-density lipoprotein (LDL) oxidation, with little attention being paid to very LDL (VLDL) and high-density lipoprotein (HDL). Also, it is now becoming apparent that γ-tocopherol may potentially be more beneficial in relation to cardiovascular health.

Objectives

Do α- and γ-tocopherols become incorporated into VLDL, LDL and HDL and influence their oxidation potential in an in vitro and ex vivo situation?

Design

Following (i) an in vitro investigation, where plasma was preincubated with increasing concentrations of either α- or γ-tocopherol and (ii) an in vivo 4-week placebo-controlled intervention with α- or γ-tocopherol. Tocopherol incorporation into VLDL, LDL and HDL was measured via high-pressure liquid chromatography, followed by an assessment of their oxidation potential by monitoring conjugated diene formation.

Results

In vitro: Both tocopherols became incorporated into VLDL, LDL and HDL, which protected VLDL and LDL against oxidation. However and surprisingly, the incorporation into HDL demonstrated pro-oxidant properties. Ex vivo: Both tocopherols were incorporated into all three lipoproteins, protecting VLDL and LDL against oxidation; however, they enhanced the oxidation of HDL.

Conclusions

These results suggest that α- and γ-tocopherols display conflicting oxidant activities dependent on the lipoprotein being oxidized. Their pro-oxidant activity toward HDL may go some way to explain why supplementation studies with vitamin E have not been able to display cardioprotective effects.
Original languageEnglish
Pages (from-to)845-851
JournalThe Journal of nutritional biochemistry
Volume23
Issue number7
Early online date28 Jun 2011
DOIs
Publication statusPublished - Jul 2012

ASJC Scopus subject areas

  • Biochemistry
  • Clinical Biochemistry
  • Molecular Biology
  • Endocrinology, Diabetes and Metabolism
  • Nutrition and Dietetics

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