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Unleashing the untold and misunderstood observations on vitamin E

机译:释放有关维生素E的未被理解和误解的观察结果

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摘要

Paradoxically, meta-analysis of human randomized controlled trials revealed that natural but not synthetic α-tocopherol supplementation significantly increases all-cause mortality at 95% confidence interval. The root cause was that natural α-tocopherol supplementation significantly depressed bioavailability of other forms of vitamin E that have better chemo-prevention capability. Meta-analysis outcome demonstrated flaws in the understanding of vitamin E. Reinterpretation of reported data provides plausible explanations to several important observations. While α-tocopherol is almost exclusively secreted in chylomicrons, enterocytes secrete tocotrienols in both chylomicrons and small high-density lipoproteins. Vitamin E secreted in chylomicrons is discriminately repacked by α-tocopherol transfer protein into nascent very low-density lipoproteins in the liver. Circulating very low-density lipoproteins undergo delipidation to form intermediate-density lipoproteins and low-density lipoproteins. Uptake of vitamin E in intermediate-density lipoproteins and low-density lipoproteins takes place at various tissues via low-density lipoproteins receptor–mediated endocytosis. Small high-density lipoproteins can deliver tocotrienols upon maturation to peripheral tissues independent of α-tocopherol transfer protein action, and uptake of vitamin E takes place at selective tissues by scavenger receptor–mediated direct vitamin E uptake. Dual absorption pathways for tocotrienols are consistent with human and animal studies. α-Tocopherol depresses the bioavailability of α-tocotrienol and has antagonistic effect on tocotrienols in chemo-prevention against degenerative diseases. Therefore, it is an undesirable component for chemo-prevention. Future research directions should be focused on tocotrienols, preferably free from α-tocopherol, for optimum chemo-prevention and benefits to mankind.
机译:矛盾的是,对人类随机对照试验的荟萃分析显示,自然补充而非人工合成的α-生育酚补充剂可在95%置信区间内显着增加全因死亡率。根本原因是,天然的α-生育酚补充剂显着降低了其他具有更好化学预防能力的维生素E的生物利用度。荟萃分析结果表明,对维生素E的理解存在缺陷。对报告数据的重新解释为一些重要观察提供了合理的解释。虽然α-生育酚几乎完全分泌在乳糜微粒中,但肠上皮细胞在乳糜微粒和小的高密度脂蛋白中都分泌生育三烯酚。乳糜微粒中分泌的维生素E通过α-生育酚转移蛋白被有区别地重新包装成新生的肝脏中非常低密度的脂蛋白。循环中的极低密度脂蛋白会发生脂化作用,形成中等密度脂蛋白和低密度脂蛋白。中密度脂蛋白和低密度脂蛋白中的维生素E通过低密度脂蛋白受体介导的内吞作用在各种组织中发生。少量的高密度脂蛋白可以在成熟时将生育三烯酚传递到周围组织,而与α-生育酚转移蛋白的作用无关,并且通过清除剂受体介导的直接维生素E摄取,维生素E在选择性组织处发生。生育三烯酚的双重吸收途径与人类和动物研究一致。 α-生育酚降低了α-生育三烯酚的生物利用度,并且在化学预防退行性疾病中对生育三烯酚具有拮抗作用。因此,它是化学预防的不良成分。未来的研究方向应集中在生育三烯酚上,最好是不含α-生育酚,以实现最佳的化学预防和对人类有益。

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