Dietary and supplemental vitamin E is absorbed and delivered to the liver, but of the various antioxidants with vitamin E activity, only alpha-tocopherol is preferentially recognized by the alpha-tocopherol transfer protein (alpha-TTP) and is transferred to plasma, while the other vitamin E forms (e.g., gamma-tocopherol or tocotrienols) are removed from the circulation. Hepatic alpha-TTP is required to maintain plasma and tissue alpha-tocopherol concentrations. The liver is the master regulator of the body's vitamin E levels in that it not only controls alpha-tocopherol concentrations, but also appears to be the major site of vitamin E metabolism and excretion. Vitamin Es are metabolized similarly to xenobiotics; they are initially omega-oxidized by cytochrome P450s, undergo several rounds of beta-oxidation, and then are conjugated and excreted. As a result of these various mechanisms, liver alpha-tocopherol and other vitamin E concentrations are closely regulated; thus, any potential adverse vitamin E effects are limited.

中文翻译：

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维生素E调节机制。

膳食和补充维生素E被吸收并输送到肝脏，但是在具有维生素E活性的各种抗氧化剂中，只有α-生育酚优先被α-生育酚转移蛋白（alpha-TTP）识别并转移至血浆，而从循环中除去其他形式的维生素E（例如，γ-生育酚或生育三烯酚）。需要肝α-TTP来维持血浆和组织中α-生育酚的浓度。肝脏是人体维生素E水平的主要调节者，它不仅控制α-生育酚的浓度，而且似乎是维生素E代谢和排泄的主要部位。维生素E的代谢与异种生物相似。它们最初被细胞色素P450氧化，经历了几轮β-氧化，然后被结合并排出体外。这些机制的结果是，肝脏α-生育酚和其他维生素E的浓度受到严格调节。因此，任何潜在的不利维生素E的影响都是有限的。