Effects of developmental iron deficiency and post-weaning iron repletion on the levels of iron transporter proteins in rats

Abstract

Background/objectives: Iron deficiency in early life is associated with developmental problems, which may persist until later in life. The question of whether iron repletion after developmental iron deficiency could restore iron homeostasis is not well characterized. In the present study, we investigated the changes of iron transporters after iron depletion during the gestational-neonatal period and iron repletion during the post-weaning period.

Materials/methods: Pregnant rats were provided iron-deficient (< 6 ppm Fe) or control (36 ppm Fe) diets from gestational day 2. At weaning, pups from iron-deficient dams were fed either iron-deficient (ID group) or control (IDR group) diets for 4 week. Pups from control dams were continued to be fed with the control diet throughout the study period (CON).

Results: Compared to the CON, ID rats had significantly lower hemoglobin and hematocrits in the blood and significantly lower tissue iron in the liver and spleen. Hepatic hepcidin and BMP6 mRNA levels were also strongly down-regulated in the ID group. Developmental iron deficiency significantly increased iron transporters divalent metal transporter 1 (DMT1) and ferroportin (FPN) in the duodenum, but decreased DMT1 in the liver. Dietary iron repletion restored the levels of hemoglobin and hematocrit to a normal range, but the tissue iron levels and hepatic hepcidin mRNA levels were significantly lower than those in the CON group. Both FPN and DMT1 protein levels in the liver and in the duodenum were not different between the IDR and the CON. By contrast, DMT1 in the spleen was significantly lower in the IDR, compared to the CON. The splenic FPN was also decreased in the IDR more than in the CON, although the difference did not reach statistical significance.

Conclusions: Our findings demonstrate that iron transporter proteins in the duodenum, liver and spleen are differentially regulated during developmental iron deficiency. Also, post-weaning iron repletion efficiently restores iron transporters in the duodenum and the liver but not in the spleen, which suggests that early-life iron deficiency may cause long term abnormalities in iron recycling from the spleen.

Keywords: Developmental iron deficiency; divalent metal transporter 1; ferroportin; rat.

Fig. 1. Effects of developmental iron deficiency and the post-weaning iron repletion on the protein levels of ferritin and transferrin receptor (TfR) in the liver (A) and spleen (B).

CON: control diet, ID: iron-deficient diet, IDR: iron-deficient diet followed by control diet. Upper panels: representative blots. Lower panels: Densitometric analyses. Data are means ± SEM, n = 6-8/group. Different superscript means significant difference, P < 0.05.

Fig. 2. Effects of developmental iron deficiency and the post-weaning iron repletion on the mRNA levels of hepcidin (A) and BMP6 (B).

CON: control diet, ID: iron-deficient diet, IDR: iron-deficient diet followed by control diet. β-actin was used as the housekeeping gene. Data are means ± SEM, n = 6-8/group. Different superscript means significant difference, P < 0.05.

Fig. 3. Effects of developmental iron deficiency and the post-weaning iron repletion on the protein levels of FPN and DMT1 expression in the duodenum (A), liver (B), and spleen (C).

CON: control diet, ID: iron-deficient diet, IDR: iron-deficient diet followed by control diet. Upper panels: representative blots. Lower panels: Densitometric analyses. Data are means ± SEM, n = 6-8/group. Different superscript means significant difference, P < 0.05.