Dietary zinc absorption: A play of Zips and ZnTs in the gut.

Studies on dietary zinc absorption are of fundamental nutritional significance, owing to the ubiquity of zinc in biological processes and the severe outcomes of zinc deficiency in humans. Insights into the molecular basis of dietary zinc absorption have advanced in recent years through functional characterization of zinc transporters in cell culture, immunohistochemical studies on rodent intestine and analysis of gene knockout mice. Zinc transporters with manifested expression in enterocytes include ZnT1, ZnT2, ZnT4, ZnT5, ZnT6, ZnT7, Zip4, and Zip5. Among them, ZIP4, the gene responsible for Acrodermatitis enteropathica, an inherited human zinc deficiency, mediates dietary zinc uptake into enterocytes across the apical membrane, while ZnT1 is involved in zinc efflux from enterocytes across the basolateral membrane into circulation. The intracellular trafficking pathways for zinc retention and movement between apical and basolateral sides of the enterocytes have yet to be defined. The utilization of Drosophila model in elucidating molecular mechanisms of dietary zinc absorption is also discussed in this review.