Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/1/2008
Publication Date: 4/1/2008
Citation: Laparra, J., Tako, E., Glahn, R.P., Miller, D. 2008. Inulin affects iron dialyzability from FeSO4 and FeEDTA solutions but does not alter Fe uptake by Caco-2 cells. Journal of Agricultural and Food Chemistry. 56:2846-2851. Interpretive Summary: Our lab has developed a model for studying mineral absorption from different foods and food combinations. Food samples undergo a simulated digestion and are placed over Caco-2 cells, which act as a mimic of the intestinal lining. We wanted to test to see if inulin affected the solubility of iron forms used for food fortification and whether any of these effects led to an increase in iron uptake into cells. Dietary inulin does affect iron solubility but does not affect Fe uptake by Caco-2 cells. This improvement in iron solubility may enhance iron absorption.
Technical Abstract: The in vitro effects of inulin on the fluxes of Fe (FFe), uptake by Caco-2 cells from FeSO4 and FeEDTA which are commonly used for food fortification, were evaluated. For an element to be absorbed it is necessary that it should be soluble in the gastrointestinal tract, thus, changes in FFe diffussion coefficients caused by inulin were calculated. Caco-2 cell ferritin formation was used as a measure of cell Fe uptake. Mitochondrial (MTT test) and lysosomal (Neutral red uptake) activities were monitored as fairly sensitive biomarkers of the changes of cellular metabolism. Relative changes in mRNA expression of Fe transporters, DMT1 and Dcytb, were also evaluated. Inulin decreased FFe from FeSO4, but not FeEDTA, suggesting a mineral binding effect of the inulin. Those cultures exposed to FeEDTA solutions exhibited higher ferritin values than FeSO4 solution. Regardless of Fe source, cell Fe uptake was similar with or without inulin suggesting that inulin did not affect Fe uptake. The MTT conversion was higher in cultures exposed to FeEDTA than FeSO4. Taking together the higher ferritin values and MTT conversion percentages noted in cultures exposed to FeEDTA solutions might indicate a faster cellular Fe internalization than from FeSO4 solutions. From a physiological perspective, the decreased flux of dissociable Fe towards the brush border membrane might be reflected in a decreased Fe uptake.