Inositol phosphates influence iron uptake in Caco-2 cells.
Phytate, inositol hexaphosphate (InsP(6)), may be hydrolyzed to inositol phosphates with lower degree of phosphorylation, i.e., inositol penta- to monophosphates (InsP(5)-InsP(1)), during food processing. Each of these lower inositol phosphates exists in different isomeric forms. The objective of this study was to determine if different isomers of InsP(3)-InsP(5) (Ins(1,2,4)P(3), Ins(1,2,3)P(3), Ins(1,2,6)P(3), Ins(1,3,4)P(3), Ins(1,2,3,4)P(4), Ins(1,2,5,6)P(4), Ins(1,2,4,5,6)P(5), and Ins(1,3,4,5,6)P(5)) and InsP(6) affect the uptake of iron. We studied the iron absorption in vitro using the human intestinal epithelial cell line, Caco-2. Addition of a 2-fold molar excess of InsP(6) or InsP(5) in proportion to Fe (1 h incubation at 37 degrees C) reduced iron uptake by 46-52% (p < 0.001). Neither InsP(4) isomers nor InsP(3) isomers affected iron uptake significantly at 1 h incubation with a molar InsP:Fe level of 2:1. Iron uptake was shown to not be a function of the isomeric form of inositol phosphates. The inositol phosphate isomers did not seem likely to interact with each other through iron to form more stable iron complexes. At a molar InsP:Fe level of 20:1 an inhibitory effect of InsP(4) was found, while InsP(3) did not affect the iron absorption even at a 20-fold molar excess.
Skoglund
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Department of Food Science, Chalmers University of Technology, SE-402 29 Göteborg, Sweden. es@fsc.chalmers.se
Lönnerdal
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B
Sandberg
A S
AS
D001692:Biological Transport / Q000187:drug effects; D018938:Caco-2 Cells; D005296:Ferrous Compounds / Q000378:metabolism*; D006801:Humans; D007295:Inositol Phosphates / Q000494:pharmacology*; D007413:Intestinal Mucosa / Q000378:metabolism*; D007501:Iron / Q000378:metabolism*; D007700:Kinetics
D005296:Ferrous Compounds; D007295:Inositol Phosphates; C020748:ferrous sulfate; D007501:Iron