A High Protein Diet Induces Intestinal Iron Transporter Expression and Improves Iron Absorption in Rats

Abstract

Dietary protein has been shown to increase iron (Fe) absorption by improving bioavailability. Little data are available on the effect of dietary protein on Fe transporter expression.As part of a study designed to evaluate the impact of dietary protein on mineral homeostasis, a whole genome microarray screen was performed using RNA prepared from duodenal intestinocytes of rats ingesting low (5%) or high (40%) casein diets for one week. Of 91 genes that were significantly up‐regulated in the 40% group, 3 were Fe transporters. DMT1 expression was 2.5‐fold greater in the 40% compared to the 5% group, while Cybrd1 and Tfrc were 1.6‐fold greater. Q‐PCR using the same RNA employed in the microarray screen confirmed these findings.When compared to the level of expression on a 20% diet (usual rat chow), DMT1 was 4‐fold higher in the 40% group (p<0.001), Cybrd1 was 2.2‐fold higher (p<0.05) while Tfrc was not different.To determine if the observed changes in expression of DMT1 and Cybrd1 were associated with changes in Fe homeostasis, a balance study was performed in rats ingesting 5, 20 and 40% protein diets. By the Kruskal‐Wallis test there was a significant effect of dietary protein on Fe balance and by post hoc analysis Fe absorption was greater in animals consuming the 40% vs. 5% diet (p<0.01).These data suggest that increasing dietary protein augments Fe absorption in part by inducing the expression of duodenal Fe transporters.Grant Funding Source: USDA