Rapid increase in serum iron level after oral iron intake as an indicator of duodenal iron absorption and inverse regulation of iron absorption by hepcidin expression

Abstract

Aim: Hepcidin is a hepatocyte-derived peptide that is thought to be involved in the regulation of intestinal iron absorption. Ferric citrate (FC) is a phosphate binder with additional effects on iron absorption. Better understanding of iron absorption under various levels of hepcidin may improve FC supplementation in individuals with renal anemia. We provide a new method to predict the individual iron absorption ability of the duodenum. Methods: Rats on an ordinary diet were given 10 mg of FC, and the serum concentrations of hepcidin and iron were monitored for 24 h. Rats with hepcidin levels induced by using alternative methods such as bloodletting or intravenous iron loading were also given FC, and serum iron level was measured at 2 h after oral iron intake (2-h oral iron absorption test). Results: Serum iron level increased constantly within 2 h after oral iron intake, and serum hepcidin level peaked 4 h after the iron level peaked. In the oral iron absorption test, the hepcidin levels inversely correlated with increased serum iron levels and hepcidin expression levels of >80 ng/mL completely inhibited the increase in iron absorption. Conclusion: This study suggests that hepcidin expression may be a strong mediator to regulate iron absorption and that performing an oral iron absorption test with hepcidin may help improve oral iron dosing schedules in patients undergoing hemodialysis.