Abstract
Background: The role of the placenta in regulating micronutrient transport in response to maternal status is poorly understood.Objective: We investigated the effect of prenatal nutritional supplementation on the regulation of placental iron and zinc transport.Methods: In a randomized trial in rural Gambia [ENID (Early Nutrition and Immune Development)], pregnant women were allocated to 1 of 4 nutritional intervention arms: 1) iron and folic acid (FeFol) tablets (FeFol group); 2) multiple micronutrient (MMN) tablets (MMN group); 3) protein energy (PE) as a lipid-based nutrient supplement (LNS; PE group); and 4) PE and MMN (PE+MMN group) as LNS. All arms included iron (60 mg/d) and folic acid (400 μg/d). The MMN and PE+MMN arms included 30 mg supplemental Zn/d. In a subgroup of ∼300 mother-infant pairs, we measured maternal iron status, mRNA levels of genes encoding for placental iron and zinc transport proteins, and cord blood iron levels.Results: Maternal plasma iron concentration in late pregnancy was 45% and 78% lower in the PE and PE+MMN groups compared to the FeFol and MMN groups, respectively (P < 0.001). The mRNA levels of the placental iron uptake protein transferrin receptor 1 were 30–49% higher in the PE and PE+MMN arms than in the FeFol arm (P < 0.031), and also higher in the PE+MMN arm (29%; P = 0.042) than in the MMN arm. Ferritin in infant cord blood was 18–22% lower in the LNS groups (P < 0.024). Zinc supplementation in the MMN arm was associated with higher maternal plasma zinc concentrations (10% increase; P < 0.001) than in other intervention arms. mRNA levels for intracellular zinc-uptake proteins, in this case zrt, irt-like protein (ZIP) 4 and ZIP8, were 96–205% lower in the PE+MMN arm than in the intervention arms without added zinc (P < 0.025). Furthermore, mRNA expression of ZIP1 was 85% lower in the PE+MMN group than in the PE group (P = 0.003).Conclusion: In conditions of low maternal iron and in the absence of supplemental zinc, the placenta upregulates the gene expression of iron and zinc uptake proteins, presumably in order to meet fetal demands in the face of low maternal supply. The ENID trial was registered at www.controlled-trials.com as ISRCTN49285450.
Highlights
Adequate maternal nutrition before and during pregnancy is important for optimal pregnancy outcomes
In this study we examined the effect of nutritional interventions during pregnancy on maternal iron and zinc status and gene expression of placental iron and zinc transporter proteins in a cohort of rural African women
Low maternal iron values in late pregnancy, as a consequence of the unexpectedly low iron values of women randomly assigned to the 2 lipidbased nutrient supplements (LNSs) groups, resulted in higher placental gene expression of the primary iron uptake protein Transferrin receptor 1 (TfR1) when compared with their corresponding non-LNS equivalent
Summary
Adequate maternal nutrition before and during pregnancy is important for optimal pregnancy outcomes. In subSaharan Africa, many women of reproductive age, especially those living in poor rural settlements, are recognized to have low dietary intakes of essential nutrients, contributing to deficiencies [1]. These nutritional deficiencies are exacerbated during pregnancy, causing risk to both the mother and her unborn infant. In a subgroup of ;300 mother-infant pairs, we measured maternal iron status, mRNA levels of genes encoding for placental iron and zinc transport proteins, and cord blood iron levels.
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