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α-Tocopherol Does Not Accelerate Depletion of γ-tocopherol and Tocotrienol or Excretion of Their Metabolites in Rats

α-Tocopherol Does Not Accelerate Depletion of γ-tocopherol and Tocotrienol or Excretion of Their Metabolites in Rats

Tomono Uchida, Saki Nomura, Eri Sakuma, Fumiaki Hanzawa, Saiko Ikeda

Lipids. 2013 Jul;48(7):687-95.

PMID: 23700248

Abstract:

From an enzyme kinetic study using rat liver microsomes, α-tocopherol has been suggested to accelerate the other vitamin E catabolism by stimulating vitamin E ω-hydroxylation, the late limiting reaction of the vitamin E catabolic pathway. To test the effect of α-tocopherol on catabolism of the other vitamin E isoforms in vivo, we determined whether α-tocopherol accelerates depletion of γ-tocopherol and tocotrienol and excretion of their metabolites in rats. Male Wistar rats were fed a γ-tocopherol-rich diet for 6 weeks followed by a γ-tocopherol-free diet with or without α-tocopherol for 7 days. Intake of γ-tocopherol-free diets lowered γ-tocopherol concentrations in serum, liver, adrenal gland, small intestine, and heart, but there was no effect of dietary α-tocopherol on γ-tocopherol concentrations. The level of urinary excretion of γ-tocopherol metabolite was not affected by dietary α-tocopherol. Next, the effect of α-tocopherol on tocotrienol depletion was examined using rats fed a tocotrienol-rich diet for 6 weeks. Subsequent intake of a tocotrienol-free diet with or without α-tocopherol for 7 days depleted concentrations of α- and γ-tocotrienol in serum and tissues, which was accompanied by a decrease in the excretion of γ-tocotrienol metabolite. However, neither the tocotrienol concentration nor γ-tocotrienol metabolite excretion was affected by dietary α-tocopherol. These data showed that dietary α-tocopherol did not accelerate the depletion of γ-tocopherol and tocotrienol and their metabolite excretions, suggesting that the positive effect of α-tocopherol on vitamin E ω-hydroxylase is not sufficient to affect the other isoform concentrations in tissues.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP10191410-B	(±)-α-Tocopherol		10191-41-0	Price
IAR42410594	α-Tocopherol-(trimethylphenyl-13C9)			Price

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