Uchida Tomono, Nomura Saki, Sakuma Eri, Hanzawa Fumiaki, Ikeda Saiko
Department of Home Economics, Aichi Gakusen University, Okazaki, Japan.
Lipids. 2013 Jul;48(7):687-95. doi: 10.1007/s11745-013-3796-0. Epub 2013 May 23.
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.
通过使用大鼠肝脏微粒体进行的酶动力学研究表明，α-生育酚可通过刺激维生素E ω-羟化作用来加速其他维生素E的分解代谢，维生素E ω-羟化作用是维生素E分解代谢途径中的晚期限速反应。为了测试α-生育酚在体内对其他维生素E异构体分解代谢的影响，我们确定了α-生育酚是否会加速大鼠体内γ-生育酚和生育三烯酚的消耗及其代谢产物的排泄。雄性Wistar大鼠先喂食富含γ-生育酚的饮食6周，然后喂食不含γ-生育酚的饮食7天，该饮食中添加或不添加α-生育酚。摄入不含γ-生育酚的饮食会降低血清、肝脏、肾上腺、小肠和心脏中的γ-生育酚浓度，但饮食中的α-生育酚对γ-生育酚浓度没有影响。γ-生育酚代谢产物的尿排泄水平不受饮食中α-生育酚的影响。接下来，使用喂食富含生育三烯酚饮食6周的大鼠研究了α-生育酚对生育三烯酚消耗的影响。随后摄入不含生育三烯酚的饮食7天，无论是否添加α-生育酚，都会使血清和组织中α-和γ-生育三烯酚的浓度降低，同时γ-生育三烯酚代谢产物的排泄也会减少。然而，饮食中的α-生育酚对生育三烯酚浓度和γ-生育三烯酚代谢产物排泄均无影响。这些数据表明，饮食中的α-生育酚不会加速γ-生育酚和生育三烯酚的消耗及其代谢产物的排泄，这表明α-生育酚对维生素E ω-羟化酶的积极作用不足以影响组织中其他异构体的浓度。
