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J Nutr. 2014 Nov;144(11):1710-7. doi: 10.3945/jn.114.197939. Epub 2014 Sep 10.

Duodenal absorption and tissue utilization of dietary heme and nonheme iron differ in rats.

Author information

1
Division of Nutritional Sciences, Cornell University, Ithaca, NY;
2
Department of Nutritional Sciences, University of Connecticut, Storrs, CT; and.
3
Department of Internal Medicine, Yale University, New Haven, CT.
4
Division of Nutritional Sciences, Cornell University, Ithaca, NY; koo4@cornell.edu.

Abstract

BACKGROUND:

Dietary heme contributes to iron intake, yet regulation of heme absorption and tissue utilization of absorbed heme remains undefined.

OBJECTIVES:

In a rat model of iron overload, we used stable iron isotopes to examine heme- and nonheme-iron absorption in relation to liver hepcidin and to compare relative utilization of absorbed heme and nonheme iron by erythroid (RBC) and iron storage tissues (liver and spleen).

METHODS:

Twelve male Sprague-Dawley rats were randomly assigned to groups for injections of either saline or iron dextran (16 or 48 mg Fe over 2 wk). After iron loading, rats were administered oral stable iron in the forms of (57)Fe-ferrous sulfate and (58)Fe-labeled hemoglobin. Expression of liver hepcidin and duodenal iron transporters and tissue stable iron enrichment was determined 10 d postdosing.

RESULTS:

High iron loading increased hepatic hepcidin by 3-fold and reduced duodenal expression of divalent metal transporter 1 (DMT1) by 76%. Nonheme-iron absorption was 2.5 times higher than heme-iron absorption (P = 0.0008). Absorption of both forms of iron was inversely correlated with hepatic hepcidin expression (heme-iron absorption: r = -0.77, P = 0.003; nonheme-iron absorption: r = -0.80, P = 0.002), but hepcidin had a stronger impact on nonheme-iron absorption (P = 0.04). Significantly more (57)Fe was recovered in RBCs (P = 0.02), and more (58)Fe was recovered in the spleen (P = 0.01).

CONCLUSIONS:

Elevated hepcidin significantly decreased heme- and nonheme-iron absorption but had a greater impact on nonheme-iron absorption. Differential tissue utilization of heme vs. nonheme iron was evident between erythroid and iron storage tissues, suggesting that some heme may be exported into the circulation in a form different from that of nonheme iron.

PMID:
25332470
PMCID:
PMC4195416
DOI:
10.3945/jn.114.197939
[Indexed for MEDLINE]
Free PMC Article

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