Dietary alpha-tocopherol attenuates the impact of gamma-tocotrienol on hepatic 3-hydroxy-3-methylglutaryl coenzyme A reductase activity in chickens

J Nutr. 1996 Feb;126(2):389-94. doi: 10.1093/jn/126.2.389.


The concentration-dependent impact of gamma-tocotrienol on serum cholesterol can be traced to the posttranscriptional down-regulation of 3-hydroxy-3-methylglutaryl coenzyme A reductase activity. gamma-Tocotrienol also suppresses tumor growth. Palmvitee, the tocopherol and tocotrienol-rich fraction of palm oil, is the sole commercial source of gamma-tocotrienol. Contrary to the universal findings of the efficacy of gamma-tocotrienol there are conflicting reports of the impact of Palmvitee on 3-hydroxy-3-methylglutaryl coenzyme A reductase activity, serum cholesterol concentrations and tumor development. These conflicting reports led us to examine the impact of alpha-tocopherol on the cholesterol-suppressive action of gamma-tocotrienol. Control and experimental diets were fed to groups of White Leghorn chickens (n = 10) for 26 d. The control diet was supplemented with 21 nmol alpha-tocopherol/g. All experimental diets provided 141 nmol of blended tocols/g diet. The alpha-tocopherol and gamma-tocotrienol concentrations of the experimental diets ranged from 21 to 141 and 0 to 120 nmol/g, respectively. We now report that including alpha-tocopherol in tocol blends containing adequate gamma-tocotrienol to suppress 3-hydroxy-3-methylglutaryl coenzyme A reductase activity results in an attenuation of the tocotrienol action (P < 0.001). A summary of results from studies utilizing different Palmvitee preparations shows that effective preparations consist of 15-20% alpha-tocopherol and approximately 60% gamma- (and delta-) tocotrienol, whereas less effective preparations consist of > or = 30% alpha-tocopherol and 45% gamma- (and delta-) tocotrienol.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Chickens
  • Cholesterol / blood
  • Cholesterol / metabolism
  • Chromans / analysis
  • Chromans / pharmacology*
  • Diet
  • Down-Regulation
  • Female
  • Hydroxymethylglutaryl CoA Reductases / analysis
  • Hydroxymethylglutaryl CoA Reductases / metabolism*
  • Hydroxymethylglutaryl CoA Reductases / physiology
  • Hydroxymethylglutaryl-CoA-Reductases, NADP-dependent
  • Liver / drug effects
  • Liver / enzymology*
  • Palm Oil
  • Plant Oils / chemistry
  • Plant Oils / pharmacology
  • Vitamin E / administration & dosage
  • Vitamin E / analogs & derivatives*
  • Vitamin E / analysis
  • Vitamin E / pharmacology*


  • Chromans
  • Plant Oils
  • Vitamin E
  • plastochromanol 8
  • Palm Oil
  • Cholesterol
  • Hydroxymethylglutaryl CoA Reductases
  • Hydroxymethylglutaryl-CoA-Reductases, NADP-dependent