Department of Nutritional Sciences, Pennsylvania State University, University Park, PA 16802, USA.
J Nutr. 2010 Jun;140(6):1117-21. doi: 10.3945/jn.109.117499. Epub 2010 Apr 7.
Because dietary polyphenolic compounds have a wide range of effects in vivo and vitro, including chelation of metals such as iron, it is prudent to test whether the regular consumption of dietary bioactive polyphenols impair the utilization of dietary iron. Because our previous study showed the inhibitory effect of (-) -epigallocatechin-3-gallate (EGCG) and grape seed extract (GSE) on nonheme iron absorption, we investigated whether EGCG and GSE also affect iron absorption from heme. The fully differentiated intestinal Caco-2 cells grown on microporous membrane inserts were incubated with heme (55)Fe in uptake buffer containing EGCG or GSE in the apical compartment for 7 h. Both EGCG and GSE decreased (P < 0.05) transepithelial transport of heme-derived iron. However, apical heme iron uptake was increased (P < 0.05) by GSE. Despite the increased cellular levels of heme (55)Fe, the transfer of iron across the intestinal basolateral membrane was extremely low, indicating that basolateral export was impaired by GSE. In contrast, EGCG moderately decreased the cellular assimilation of heme (55)Fe, but the basolateral iron transfer was extremely low, suggesting that the basolateral efflux of heme iron was also inhibited by EGCG. Expression of heme oxygenase, ferroportin, and hephaestin protein was not changed by EGCG and GSE. The apical uptake of heme iron was temperature dependent and saturable in fully differentiated Caco-2 cells. Our data show that bioactive dietary polyphenols inhibit heme iron absorption mainly by reducing basolateral iron exit rather than decreasing apical heme iron uptake in intestinal cells.
由于膳食多酚化合物在体内和体外具有广泛的作用，包括螯合铁等金属，因此谨慎起见，需要测试经常食用具有生物活性的膳食多酚是否会影响膳食铁的利用。由于我们之前的研究表明（-）-表没食子儿茶素-3-没食子酸酯（EGCG）和葡萄籽提取物（GSE）抑制非血红素铁吸收，我们研究了 EGCG 和 GSE 是否也会影响血红素铁的吸收。在微孔膜插入物上生长的完全分化的肠 Caco-2 细胞在摄取缓冲液中与血红素（55）Fe 在含有 EGCG 或 GSE 的顶侧隔室中孵育 7 小时。EGCG 和 GSE 均降低（P <0.05）血红素衍生铁的跨上皮转运。然而，GSE 增加了（P <0.05）顶侧血红素铁摄取。尽管细胞内血红素（55）Fe 水平增加，但铁穿过肠基底外侧膜的转移极低，表明 GSE 损害了基底外侧的铁输出。相比之下，EGCG 适度降低了血红素（55）Fe 的细胞同化，但基底外侧铁转移极低，表明血红素铁的基底外侧流出也被 EGCG 抑制。血红素加氧酶、亚铁转运蛋白和 hephaestin 蛋白的表达不受 EGCG 和 GSE 的影响。血红素铁的顶侧摄取在完全分化的 Caco-2 细胞中依赖于温度并且是饱和的。我们的数据表明，生物活性膳食多酚主要通过减少基底外侧铁输出而不是减少肠细胞中顶侧血红素铁摄取来抑制血红素铁吸收。
