Laboratory of Food Function Analysis, Graduate School of Agricultural Science, Tohoku University, 468-1 Aramaki Aza Aoba, Aoba-ku, Sendai, 980-8572, Japan.
Division of Medical Biochemistry, Department of Pathophysiological and Therapeutic Sciences, Tottori University Faculty of Medicine, 86 Nishi-cho, Yonago, 683-8503, Japan.
Sci Rep. 2023 May 6;13(1):7392. doi: 10.1038/s41598-023-34584-z.
Vitamin E is classified into tocopherol (Toc) and tocotrienol (T3) based on its side chains. T3 generally has higher cellular uptake than Toc, though the responsible mechanism remains unclear. To elucidate this mechanism, we hypothesized and investigated whether serum albumin is a factor that induces such a difference in the cellular uptake of Toc and T3. Adding bovine serum albumin (BSA) to serum-depleted media increased the cellular uptake of T3 and decreased that of Toc, with varying degrees among α-, β-, γ-, and δ-analogs. Such enhanced uptake of α-T3 was not observed when cells were incubated under low temperature (the uptake of α-Toc was also reduced), suggesting that Toc and T3 bind to albumin to form a complex that results in differential cellular uptake of vitamin E. Fluorescence quenching study confirmed that vitamin E certainly bound to BSA, and that T3 showed a higher affinity than Toc. Molecular docking further indicated that the differential binding energy of Toc or T3 to BSA is due to the Van der Waals interactions via their side chain. Overall, these results suggested that the affinity of Toc and T3 to albumin differs due to their side chains, causing the difference in their albumin-mediated cellular uptake. Our results give a better mechanistic insight into the physiological action of vitamin E.
维生素 E 根据其侧链分为生育酚（Toc）和生育三烯酚（T3）。尽管负责的机制尚不清楚，但 T3 通常比 Toc 具有更高的细胞摄取率。为了阐明这一机制，我们假设并研究了血清白蛋白是否是导致 Toc 和 T3 细胞摄取差异的一个因素。在血清耗尽的培养基中添加牛血清白蛋白（BSA）会增加 T3 的细胞摄取率，并降低 Toc 的摄取率，α-、β-、γ-和 δ-类似物之间存在不同程度的差异。当细胞在低温下孵育时，α-T3 的摄取没有增加（α-Toc 的摄取也减少），这表明 Toc 和 T3 与白蛋白结合形成复合物，导致维生素 E 的细胞摄取存在差异。荧光猝灭研究证实维生素 E 确实与 BSA 结合，并且 T3 比 Toc 具有更高的亲和力。分子对接进一步表明，Toc 或 T3 与 BSA 的结合能的差异是由于其侧链的范德华相互作用。总的来说，这些结果表明 Toc 和 T3 与白蛋白的亲和力因侧链不同而不同，导致它们在白蛋白介导的细胞摄取方面存在差异。我们的结果为维生素 E 的生理作用提供了更好的机制见解。
