title: Dietary ligands as determinants of iron-zinc interactions at the absorptive enterocyte.
abstract: Iron and zinc interact at the enterocyte and influence the absorption of one another. We have previously reported that zinc noncompetitively inhibits iron uptake in Caco-2 cells, a widely accepted model of the absorptive enterocyte. However, the determinants of this interaction, such as the effect of dietary ligands, remain uncharacterized. Dietary ligands selectively chelate iron and zinc in definite stoichiometric proportions and thus alter the bioavailability from food matrices. Here, we have used common dietary ligands, such as ascorbic acid, phytic acid, tannic acid, tartaric acid, cysteine, histidine, and methionine to characterize iron, zinc uptake individually and in combination, using Caco-2 cells. Selective chelation of zinc, using cysteine, decreased the magnitude of inhibition of iron uptake but could not reverse the inhibition. On the other hand, selective increase in iron uptake in the presence of methionine resulted in increased zinc uptake, rather than inhibition. Taken together, these in vitro results suggest that dietary ligands can modulate iron-zinc interaction and that zinc cannot competitively inhibit iron uptake.
authors.affiliation: Micronutrient Research Group, National Institute of Nutrition, Indian Council of Medical Research, Jamai Osmania, Hyderabad 500 604, India.
authors.forename: Vasuprada
authors.initials: V
authors.lastname: Iyengar
authors.forename: Raghu
authors.initials: R
authors.lastname: Pullakhandam
authors.forename: K Madhavan
authors.initials: KM
authors.lastname: Nair
mesh_terms: D000596:Amino Acids / Q000378:metabolism; D001692:Biological Transport; D018938:Caco-2 Cells; D002264:Carboxylic Acids / Q000378:metabolism; D002614:Chelating Agents / Q000378:metabolism; D004032:Diet; D020895:Enterocytes / Q000378:metabolism*; D006801:Humans; D007408:Intestinal Absorption; D007501:Iron / Q000378:metabolism*; D007504:Iron Radioisotopes; D008024:Ligands; D010833:Phytic Acid / Q000378:metabolism; D013634:Tannins / Q000378:metabolism; D015032:Zinc / Q000378:metabolism*; D015037:Zinc Radioisotopes
chemical_list: D000596:Amino Acids; D002264:Carboxylic Acids; D002614:Chelating Agents; D007504:Iron Radioisotopes; D008024:Ligands; D013634:Tannins; D015037:Zinc Radioisotopes; D010833:Phytic Acid; D007501:Iron; D015032:Zinc