Effect of Bioactive Dietary Polyphenols on Zinc Transport across the Intestinal Caco-2 Cell Monolayers

Abstract

Polyphenolic compounds are known to possess many beneficial health effects, including the antioxidative activities of scavenging reactive oxygen species and chelating metals, such as iron and zinc. Tea and red wine are thought to be important sources of these compounds. However, some polyphenolic compounds can also reduce the absorption of iron, and possibly other trace metals, when included in a diet. There is very little information on the effect of dietary polyphenolic compounds on the status of trace elements other than iron. We examined the effects of epigallocatechin-3-gallate (EGCG), green tea extract (GT) and grape seed extract (GSE) on the absorption of 65Zn and compared them with their effects on 55Fe absorption in human intestinal Caco-2 cells grown on microporous membrane inserts. The levels of EGCG, GT and GSE used in this study were within the physiological ranges and did not affect the integrity of the Caco-2 cell monolayers. GSE significantly (P < 0.05) reduced zinc transport across the cell monolayer, and the decreased zinc transport was associated with a reduction in apical zinc uptake. However, EGCG and GT did not alter zinc absorption. In contrast, the polyphenolic compounds in EGCG, GT and GSE almost completely blocked transepithelial iron transport across the cell monolayer. The effect of GSE on zinc absorption was very different from that on iron absorption. While GSE decreased zinc absorption by reducing apical zinc uptake, the polyphenolic compounds inhibited iron absorption by enhancing apical iron uptake. GSE inhibited zinc absorption similarly to that observed for phytate. Phytate significantly (P < 0.05) decreased transepithelial zinc transport by reducing apical zinc uptake. The inhibition of zinc absorption may be due to the presence of procyanidins in GSE, which bind zinc with high affinity and block the transport of zinc across the apical membrane of enterocytes. Further research on the absorption of zinc as zinc-polyphenol complexes and free zinc should provide further insight into the process of dietary zinc absorption in the presence of GSE and other bioactive dietary polyphenols. The present study suggests that some individuals should consider their zinc status if they regularly consume procyanidin-containing foods in their diet. However, further studies, especially in vivo studies, are needed to confirm these results.

Soybean extracts increase cell surface ZIP4 abundance and cellular zinc levels: a potential novel strategy to enhance zinc absorption by ZIP4 targeting

“…Another important aspect of this study was our use of AsPC1 cells to verify that soyasaponin Bb enhances hZIP4 expression. Many studies assessing the effects of food components on nutrient absorption, including zinc, have been carried out using Caco2 cells, which have similar morphological and functional characteristics to absorptive small intestinal cells [39,41,43,57,58]. However, in the present study, we detected insufficiently high hZIP4 protein levels in Caco2 cells (see Figure 6A).…”

A Guide to Human Zinc Absorption: General Overview and Recent Advances of In Vitro Intestinal Models

“…While human zinc absorption and transport kinetics were characterized using three-dimensional Caco-2 models (Table 3), a two-dimensional culture of these cells was additionally applied to investigate zinc uptake parameters. Furthermore, this model was widely used to study the effects of various dietary food components on intestinal zinc bioavailability [96,243,247,[258][259][260][261][262][263][264][265][266][267][268][269][270][271][272] and to elucidate the regulatory role of intestinal zinc transporters and metallothionein in zinc absorption [74,86,87,144,242,[273][274][275][276][277][278][279][280]. Notably, the impact of dietary zinc on zinc transporters and [255], which represents about 90% of intestinal cells of the brush border membrane [256,257].…”

Effects of Olive Leaf and Marigold Extracts on the Utilization of Nutrients and on Bone Mineralization using Two Different Oil Sources in Broilers

“…However, a lower absorption of Zn, but not of Fe or Cu were observed in rats fed various levels and types of tea (Greger and Lyle, 1988). The influence of different polyphenols on Zn absorption was assessed in an in vitro study by Kim et al (2011) using human intestinal Caco-2 cell monolayers. While a grape seed extract inhibited Zn absorption, this was not altered by epigallocatechin-3-gallate and green tea extracts compared to the control group.…”