The effect of feeding a low iron diet prior to and during gestation on fetal and maternal iron homeostasis in two strains of rat

Abstract

Background: Iron deficiency anaemia during pregnancy is a global problem, with short and long term consequences for maternal and child health. Animal models have demonstrated that the developing fetus is vulnerable to maternal iron restriction, impacting on postnatal metabolic and blood pressure regulation. Whilst long-term outcomes are similar across different models, the commonality in mechanistic events across models is unknown. This study examined the impact of iron deficiency on maternal and fetal iron homeostasis in two strains of rat.

Methods: Wistar (n=20) and Rowett Hooded Lister (RHL, n=19) rats were fed a control or low iron diet for 4 weeks prior to and during pregnancy. Tissues were collected at day 21 of gestation for analysis of iron content and mRNA/protein expression of regulatory proteins and transporters.

Results: A reduction in maternal liver iron content in response to the low iron diet was associated with upregulation of transferrin receptor expression and a reduction in hepcidin expression in the liver of both strains, which would be expected to promote increased iron absorption across the gut and increased turnover of iron in the liver. Placental expression of transferrin and DMT1+IRE were also upregulated, indicating adaptive responses to ensure availability of iron to the fetus. There were considerable differences in hepatic maternal and fetal iron content between strains. The higher quantity of iron present in livers from Wistar rats was not explained by differences in expression of intestinal iron transporters, and may instead reflect greater materno-fetal transfer in RHL rats as indicated by increased expression of placental iron transporters in this strain.

Conclusions: Our findings demonstrate substantial differences in iron homeostasis between two strains of rat during pregnancy, with variable impact of iron deficiency on the fetus. Whilst common developmental processes and pathways have been observed across different models of nutrient restriction during pregnancy, this study demonstrates differences in maternal adaptation which may impact on the trajectory of the programmed response.

Figure 1

Maternal and fetal liver iron content. Maternal (A) and fetal (B) liver iron content at day 21 of gestation in Rowett Hooded Lister (RHL) and Wistar rats exposed to a control or low iron diet prior to and during pregnancy. Data are presented as means ± s.e.m. for n = 8–11 per group.

Figure 2

Placental iron content. Placental total iron (A and B), haem iron (C) and non-haem iron (D) content in Rowett Hooded Lister (RHL) and Wistar rats exposed to a control or low iron diet prior to and during pregnancy. Data are presented as means ± s.e.m. for n = 14–21 per group.

Figure 3

Maternal liver TfR and hepcidin expression. Maternal liver TfR (A) and hepcidin (B) mRNA expression in Rowett Hooded Lister (RHL) and Wistar rats exposed to a control or low iron diet prior to and during pregnancy. Data are presented as means ± s.e.m. for n = 8–11 per group. Expression is normalised to cDNA fluorescence at 80°C.

Figure 4

Fetal liver TfR and ferroportin expression. Fetal liver protein expression of TfR (A &B) and ferroportin (C &D) proteins in Rowett Hooded Lister (A &C) and Wistar (B &D) rats exposed to a control or low iron diet prior to and during pregnancy. Data are presented as means ± s.e.m. for n = 16–19 per group. Protein expression is normalised to tubulin expression. Representative sample blots are shown.

Figure 5

Fetal liver hepcidin and ceruloplasmin expression. Fetal liver mRNA expression of hepcidin (A) and ceruloplasmin (B) in Rowett Hooded Lister (RHL) and Wistar rats exposed to a control or low iron diet prior to and during pregnancy. Data are presented as means ± s.e.m. for n = 16–19 per group. Expression is normalised to cDNA fluorescence at 80°C.

Figure 6

Placental TfR, DMT1+IRE and ferroportin expression. Placental expression of TfR protein (A), DMT1+IRE mRNA (B) and ferroportin protein (C) in Rowett Hooded Lister (RHL) and Wistar rats exposed to a control or low iron diet prior to and during pregnancy. Data are presented as means ± s.e.m. for n = 15–21 per group. Protein expression is normalised to tubulin expression and mRNA expression is normalised to β-actin expression. Representative sample blots are shown.