Dietary Alpha-Tocopherol Decreases Alpha-Tocotrienol but Not Gamma-Tocotrienol Concentration in Rats

J Nutr. 2003 Feb;133(2):428-34. doi: 10.1093/jn/133.2.428.

Abstract

We previously showed that alpha- and gamma-tocotrienols accumulate in adipose tissue and skin but not in plasma or other tissues of rats fed a tocotrienol-rich fraction extracted from palm oil containing alpha-tocopherol and alpha- and gamma-tocotrienols. To clarify the nature of tocotrienol metabolism, we studied the distribution of alpha- or gamma-tocotrienol in rats fed alpha- or gamma-tocotrienol without alpha-tocopherol, and the effect of alpha-tocopherol on their distribution. Wistar rats (4-wk-old) were fed a diet with 50 mg alpha-tocotrienol/kg alone or with 50 mg alpha-tocopherol/kg in expt. 1, and a diet with 50 mg gamma-tocotrienol/kg alone or with 50 mg alpha-tocopherol/kg in expt. 2, for 8 wk. alpha-Tocotrienol was detected in various tissues and plasma of the rats fed alpha-tocotrienol alone, and the alpha-tocotrienol concentrations in those tissues and plasma decreased (P < 0.05) by the dietary alpha-tocopherol in the rats fed alpha-tocotrienol with alpha-tocopherol. However, gamma-tocotrienol preferentially accumulated in the adipose tissue and skin of the rats fed gamma-tocotrienol alone, and the dietary alpha-tocopherol failed either to decrease (P >/= 0.05) gamma-tocotrienol concentrations in the adipose tissue and skin or to increase (P >/= 0.05) in the urinary excretion of 2,7,8-trimethyl-2(2'-carboxymethyl)-6-hydroxycroman, a metabolite of gamma-tocotrienol, in the rats fed gamma-tocotrienol with alpha-tocopherol. These data suggest that alpha-tocopherol enhances the alpha-tocotrienol metabolism but not the gamma-tocotrienol metabolism in rats.

MeSH terms

  • Adipose Tissue / drug effects
  • Adipose Tissue / metabolism
  • Animals
  • Antioxidants / administration & dosage
  • Antioxidants / pharmacology*
  • Body Weight / drug effects
  • Chromans / blood
  • Chromans / pharmacokinetics*
  • Diet
  • Male
  • Pyruvate Kinase / blood
  • Rats
  • Rats, Wistar
  • Tissue Distribution
  • Tocotrienols
  • Vitamin E / analogs & derivatives*
  • Vitamin E / blood
  • Vitamin E / pharmacokinetics*
  • alpha-Tocopherol / administration & dosage
  • alpha-Tocopherol / pharmacology*

Substances

  • Antioxidants
  • Chromans
  • Tocotrienols
  • Vitamin E
  • plastochromanol 8
  • tocotrienol, alpha
  • Pyruvate Kinase
  • alpha-Tocopherol