Dietary protein upregulates fractional intestinal iron absorption and directly increases DMT1 transcript and protein expression

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Iron (Fe) deficiency is endemic worldwide. We have recently found that increasing dietary protein dose‐dependently improves Fe balance in rats. This change is associated with increased DMT1 transcript expression, a key regulator of intestinocyte Fe uptake. To confirm the Fe balance results, Fe absorption studies were performed in rats fed either a 20% (control) or 40% (high) protein diet for 1 wk. Rats on the 40% protein diet absorbed 30±9% of ingested Fe while those on the 20% protein diet absorbed 18±8% (p= 0.005). To determine if DMT1 protein expression is also increased with increasing dietary protein, Western analyses were undertaken using duodenal mucosal lysates prepared from rats on the 20% and 40% protein diets. There was a trend towards higher DMT1 protein levels on the 40% diet (1.7±1.1 fold; p=0.46). To evaluate if amino acids could directly increase DMT1 transcript expression, Caco‐2 Bbe cells were exposed to either a mixture of amino acids or amino acid‐free media for 6 hrs. Amino acid treatment induced DMT1 mRNA by 1.6±0.3 fold as determined by qPCR (p<0.02). These data indicate that increasing dietary protein increases intestinal Fe absorption in part by upregulation of DMT1. Further, there appears to be a direct effect of amino acids on DMT1 transcript expression.This work was supported by a HATCH grant from the Univ. of CT.