R&D, Safety Science Research, Kao Corporation, Tochigi, Japan.
R&D, Safety Science Research, Kao Corporation, Kanagawa, Japan.
J Nutr Biochem. 2022 Sep;107:109071. doi: 10.1016/j.jnutbio.2022.109071. Epub 2022 May 27.
Green tea polyphenols have various beneficial effects on human health, such as antiobesity and anti-carcinogenesis. (-)-Epigallocatechin-gallate (EGCG) is one of the major potent green tea catechins; however, detailed mechanisms of EGCG transport and metabolism in the human small intestine remain unknown due to lack of a suitable model. We investigated metabolite profiles of EGCG in the fresh human duodenal biopsy, cryopreserved human duodenal mucosal enterocytes and Caco-2 cells, and found that EGCG was readily metabolized into methylated and sulphate conjugates, which are major metabolites in these models. Next, we examined possible efflux transporters of EGCG and its metabolites using specific inhibitors of MRP2, P-gp and BCRP in Caco-2 cell monolayers. MRP2 was thereby identified as an efflux transporter, and further analysis using MRP2-knockout Caco-2 cells and vesicular transport assays confirmed that MRP2 is a selective efflux transporter of EGCG and its metabolites. Assuming that functional inhibition of MRP2 would result in efficient uptake of EGCG, we screened for MRP2 functional blockade and identified quercetin, which led to increased intracellular accumulation and basal transport of EGCG in Caco-2 cells. This result suggested that co-administration of quercetin and EGCG would enable efficient transport of EGCG in the human intestine. Therefore, we performed co-oral administration of quercetin and EGCG in human subjects to examine whether this occurred in humans. These studies demonstrated that MRP2 is a selective transporter of EGCG and conjugates and Caco-2 is a model to examine transport mechanisms and metabolites of polyphenols in the human small intestine.
绿茶多酚对人类健康有多种有益作用，如抗肥胖和抗癌发生。（-）-表没食子儿茶素没食子酸酯（EGCG）是绿茶儿茶素中主要的有效成分之一；然而，由于缺乏合适的模型，EGCG 在人小肠中的转运和代谢的详细机制仍不清楚。我们研究了新鲜人十二指肠活检、冷冻保存的人十二指肠黏膜肠上皮细胞和 Caco-2 细胞中 EGCG 的代谢产物谱，发现 EGCG 很容易代谢成甲基化和硫酸结合物，这是这些模型中的主要代谢物。接下来，我们使用 Caco-2 细胞单层中 MRP2、P-gp 和 BCRP 的特异性抑制剂，研究了 EGCG 及其代谢物的可能外排转运体。因此，确定 MRP2 为外排转运体，并且使用 MRP2 敲除 Caco-2 细胞和囊泡转运测定的进一步分析证实，MRP2 是 EGCG 及其代谢物的选择性外排转运体。假设 MRP2 的功能抑制会导致 EGCG 的有效摄取，我们筛选了 MRP2 的功能阻断，并鉴定了槲皮素，这导致 EGCG 在 Caco-2 细胞中的细胞内积累和基础转运增加。这一结果表明，槲皮素和 EGCG 的联合给药可使 EGCG 在人肠中有效转运。因此，我们在人体中进行了槲皮素和 EGCG 的共同口服给药，以检查这种情况是否在人体中发生。这些研究表明，MRP2 是 EGCG 和共轭物的选择性转运体，Caco-2 是研究人小肠中多酚转运机制和代谢物的模型。
