Marginally reduced maternal hepatic and splenic ferroportin under severe nutritional iron deficiency in pregnancy maintains systemic iron supply

Effects of Maternal Anemia Affecting Fetal Outcomes: A Narrative Review

This review's main objective was to assess the obstacles to anemia prevention, as well as the attitudes and behaviors of anemic women toward their condition. Since iron is crucial for neurodevelopment, iron deficiency anemia (IDA) accounts for the majority of pregnant mothers having anemia. In India and other developing countries, anemia is a serious health problem. More than half of pregnant women have anemia. The search strategy was conducted in PubMed. Few of the articles were searched without using MeSH terms. Strong correlations between mothers' anemia and that of their offspring point to intergenerational anemia with lasting consequences. Children who were underweight at birth and those who were malnourished had a higher risk of having anemia. Clinicians usually evaluate anemia, and the criteria for determining the cause of anemia are outlined in this brief review.

Iron Supplementation of Pregnant Sows to Prevent Iron Deficiency Anemia in Piglets: A Procedure of Questionable Effectiveness

In pigs, iron deficiency anemia (IDA) is a common disorder that occurs during the early postnatal period, leading to the stunted growth and increased mortality of piglets. The main cause of IDA is low iron stores in the liver of newborn piglets; these stores constitute the main source of iron needed to satisfy the erythropoietic requirements of the piglets in their first weeks of life. Insufficient iron stores in piglets are usually due to the inadequate placental iron transfer from the sow to the fetuses. Therefore, iron supplementation in pregnant sows has been implemented to enhance placental iron transfer and increase iron accumulation in the liver of the fetuses. Over the years, several oral and parenteral approaches have been attempted to supplement sows with various iron preparations, and consequently, to improve piglets' red blood cell indices. However, there is debate with regard to the effectiveness of iron supplementation in pregnant sows for preventing IDA in newborn piglets. Importantly, this procedure should be carried out with caution to avoid iron over-supplementation, which can lead to iron toxicity. This article aims to critically review and evaluate the use of iron supplementation in pregnant sows as a procedure for preventing IDA in piglets.

Impact of litter size on the hematological and iron status of gilts, sows and newborn piglets: a comparative study of domestic pigs and wild boars

BACKGROUND

The critically low hepatic iron stores of newborn piglets are considered to be a major cause of neonatal iron deficiency in modern breeds of domestic pig (Sus domestica). The main factor believed to contribute to this phenomenon is large litter size, which has been an objective of selective breeding of pigs for decades. As consequence, iron transferred from the pregnant sow has to be distributed among a greater number of fetuses.

RESULTS

Here, we investigated whether litter size influences red blood cell (RBC) indices and iron parameters in Polish Large White (PLW) piglets and gilts. Small and large litters were produced by the transfer of different numbers of embryos, derived from the same superovulated donor females, to recipient gilts. Piglets from large litters obtained following routine artificial insemination were also examined. Our results clearly demonstrated that varying the number of piglets in a litter did not affect the RBC and iron status of 1-day-old piglets, with all showing iron deficiency anemia. In contrast, gilts with small litters displayed higher RBC and iron parameters compared to mothers with large litters. A comparative analysis of the RBC status of wild boars (having less than half as many piglets per litter as domestic pigs) and PLW pigs, demonstrated higher RBC count, hemoglobin level and hematocrit value of both wild boar sows and piglets, even compared to small-litter PLW animals.

CONCLUSIONS

These findings provide evidence that RBC and iron status in newborn PLW piglets are not primarily determined by litter size, and indicate the need to study the efficiency of iron transport across the placenta in domestic pig and wild boar females.

Protective effect of Angelica sinensis polysaccharide on pregnant rats suffering from iron deficiency anemia via regulation of the hepcidin-FPN1 axis

Iron deficiency anemia (IDA) is a common micronutrient deficiency among pregnant women with deleterious maternal and fetal outcomes. Angelica sinensis polysaccharide (ASP) has been shown to reduce hepcidin expression in IDA rats. However, the role of ASP in the treatment of IDA during pregnancy and its potential mechanisms have not been investigated. Moreover, the effect of ASP on duodenal iron absorption is not clear. The aim of this study was to investigate the preventive efficacy of ASP against IDA during pregnancy and clarify the underlying mechanisms. Our results showed that ASP improved maternal hematological parameters, increased serum iron, maternal tissue iron, and fetal liver iron content, and improved pregnancy outcomes. Additionally, ASP combated oxidative stress caused by iron deficiency by improving the body's antioxidant capacity. Western blot results demonstrated that ASP downregulated hepcidin expression by blocking the BMP6/SMAD4, JAK2/STAT3 and TfR2/HFE signaling pathways, which in turn increased the expression of FPN1 in the liver, spleen, and duodenum and promoted iron cycling in the body. Furthermore, ASP increased the expression of DMT1 and Dcytb in the duodenum, thereby facilitating duodenal iron uptake. Our results suggest that ASP is a potential agent for the prevention and treatment of IDA during pregnancy.

Placental ferroportin protein abundance is associated with neonatal erythropoietic activity and iron status in newborns at high risk for iron deficiency and anemia

BACKGROUND

Murine data suggest that the placenta downregulates ferroportin (FPN) when iron is limited to prioritize iron for its own needs. Human data on the impact of maternal and neonatal iron status on placental FPN expression are conflicting.

OBJECTIVES

This study aimed to identify determinants of placental FPN protein abundance and to assess the utility of the placental iron deficiency index (PIDI) as a measure of maternal/fetal iron status in newborns at high risk for anemia.

METHODS

Placental FPN protein abundance was measured by western blots in placentae collected from 133 neonates born to adolescents (17.4 ± 1.1 y) carrying singletons (delivery gestational age [GA]: 39.9 ± 1.3 wk) and from 130 neonates born to 65 females (30.4 ± 5.2 y) carrying multiples (delivery GA: 35.0 ± 2.8 wk). Placental FPN and the PIDI (FPN:transferrin receptor 1) were evaluated in relation to neonatal and maternal iron-related markers (hemoglobin [Hb], serum ferritin [SF], soluble transferrin receptor [sTfR], total body iron [TBI], hepcidin, erythropoietin [EPO], erythroferrone).

RESULTS

FPN protein was detected in all placentae delivered between 25 and 42 wk GA. Placental FPN protein abundance was associated with neonatal iron and erythropoietic markers (EPO: β: 0.10; 95% confidence interval [CI]: 0.06, 0.35; sTfR: β: 0.20; 95% CI: 0.03, 0.18; hepcidin: β: -0.06; 95% CI: -0.13, -0.0003; all P < 0.05). Maternal sTfR was only indirectly associated with placental FPN, with neonatal sTfR as the mediator (β-indirect: 0.06; 95% CI; 0.03, 0.11; P = 0.003). The PIDI was associated with neonatal Hb (β: -0.02; 95% CI: -0.03, -0.003), EPO (β: 0.07; 95% CI: 0.01, 0.14), and sTfR (β: 0.13; 95% CI: 0.004, 0.3) and with maternal SF (β: 0.08, 95% CI: 0.02, 0.14), TBI (β: 0.02; 95% CI: 0.009, 0.04), EPO (β: -0.10; 95% CI: -0.19, -0.01), sTfR (β: -0.16: 95% CI: -0.27, -0.06), and hepcidin (β: 0.05; 95% CI: 0.002, 0.11) at delivery (all P < 0.05).

CONCLUSIONS

Placental FPN abundance was positively associated with neonatal indicators of increased erythropoietic activity and poor iron status. The PIDI was associated with maternal and neonatal iron-related markers but in opposite directions. More data are needed from a lower-risk normative group of females to assess the generalizability of findings. These trials were registered at clinicaltrials.gov as NCT01019902 and NCT01582802.

Decidual Stromal Cell Ferroptosis Associated with Abnormal Iron Metabolism Is Implicated in the Pathogenesis of Recurrent Pregnancy Loss

Iron is necessary for various critical biological processes, but iron overload is also dangerous since labile iron is redox-active and toxic. We found that low serum iron and decidual local iron deposition existed simultaneously in recurrent pregnancy loss (RPL) patients. Mice fed with a low-iron diet (LID) also showed iron deposition in the decidua and adverse pregnancy outcomes. Decreased ferroportin (cellular iron exporter) expression that inhibited the iron export from decidual stromal cells (DSCs) might be the reason for local iron deposition in DSCs from low-serum-iron RPL patients and LID-fed mice. Iron supplementation reduced iron deposition in the decidua of spontaneous abortion models and improved pregnancy outcomes. Local iron overload caused ferroptosis of DSCs by downregulating glutathione (GSH) and glutathione peroxidase 4 levels. Both GSH and cystine (for the synthesis of GSH) supplementation reduced iron-induced lipid reactive oxygen species (ROS) and cell death in DSCs. Ferroptosis inhibitor, cysteine, and GSH supplementation all effectively attenuated DSC ferroptosis and reversed embryo loss in the spontaneous abortion model and LPS-induced abortion model, making ferroptosis mitigation a potential therapeutic target for RPL patients. Further study that improves our understanding of low-serum-iron-induced DSC ferroptosis is needed to inform further clinical evaluations of the safety and efficacy of iron supplementation in women during pregnancy.

Impact of maternal iron deficiency anemia on fetal iron status and placental iron transporters in human pregnancy

Iron deficiency anemia is associated with maternal morbidity and poor pregnancy outcomes. Heme and non-heme iron transport proteins expressed in the placenta help in adequate iron supply from anemic mother to fetus. Here we examined the expression of placental iron trafficking molecules and their association with maternal and neonatal iron status in pregnant women with iron deficiency anemia (IDA). Pregnant women who received prenatal care at Christian Medical College, Vellore, India for childbirth were recruited. Pregnant women who were 18-35 years old with gestational age (GA) of ≥36 weeks were eligible to participate in the study. In a prospective cohort of pregnant women, 22 % were iron deficiency anemia and 42 % were iron replete. Samples were collected (Maternal blood, placental tissue, and cord blood) from pregnant women with a gestational age of ≥38 weeks at the time of delivery. The mean gestational age at the first visit and delivery was 12.8 ± 2.72 weeks and 39 ± 1.65 weeks, respectively. Hemoglobin (9.3 ± 0.9 g/dl) and ferritin (15.4(0.8-28.3) ng/ml) levels at delivery were significantly decreased in IDA as compared to controls. The fetal hemoglobin and ferritin levels were in the normal range in both groups. There was no correlation between maternal and cord blood hepcidin with fetal iron status in IDA. We further analyzed the expression of iron transport genes in the placenta of controls and the IDA group. Under maternal iron insufficiency, the expression of placental iron transporters DMT1, FPN1, and GDF15 was upregulated at the protein level. In IDA, placental GDF15 and ferroportin protein had an association with fetal iron status. These findings confirm that placental iron traffickers respond to maternal iron deficiency by increasing their expression and allowing sufficient iron to pass to the fetus.

Disordered Maternal and Fetal Iron Metabolism Occurs in Preterm Births in Human

Background. Increasing evidence reveals that iron deficiency during pregnancy causes adverse pregnancy outcomes. Thus far, the mechanisms underlying iron deficiency-associated preterm birth are mostly limited to animal studies. Whether the suggested mechanisms exist in human requires further investigation. The goal of this study was to characterize the iron metabolism in both the maternal side and fetal side in pregnant women with preterm birth. Methods. Serum and placenta samples were collected from 42 pregnant women divided into four groups according to the gestational week. Indicators of iron metabolism, including serum iron, serum hepcidin, placental tissue iron, ferroportin (FPN), transferrin receptor 1 (TfR1), and ferritin, were surveyed using enzyme-linked immunosorbent assays (Elisa), Western blots, and real-time quantitative polymerase chain reactions (qRT-PCR). Results. Significant reduction of maternal serum iron was observed in women with preterm birth relative to those with full-term birth, indicative of worsen iron deficiency in those mothers with preterm birth. Meanwhile, the maternal hepcidin levels were notably diminished in women with preterm birth, whereas the fetal hepcidin levels were comparable between the two groups. Moreover, the placental iron stores were remarkably reduced in the preterm group, associated with reduced concentration of TfR1 and increased FPN concentration relative to the normal controls. In other words, the ratio of placental FPN mass to TfR1 mass (PIDI index) was strikingly increased in the preterm group. Conclusions. Dysregulated iron homeostasis in both the maternal and fetal sides was implicated in preterm births, and disordered regulations in maintaining the placental iron equilibrium were also presumed to account for the compromised fetal iron supply.

Iron Metabolism and Ferroptosis in Physiological and Pathological Pregnancy

Iron is a vital element in nearly every living organism. During pregnancy, optimal iron concentration is essential for both maternal health and fetal development. As the barrier between the mother and fetus, placenta plays a pivotal role in mediating and regulating iron transport. Imbalances in iron metabolism correlate with severe adverse pregnancy outcomes. Like most other nutrients, iron exhibits a U-shaped risk curve. Apart from iron deficiency, iron overload is also dangerous since labile iron can generate reactive oxygen species, which leads to oxidative stress and activates ferroptosis. In this review, we summarized the molecular mechanism and regulation signals of placental iron trafficking under physiological conditions. In addition, we revealed the role of iron metabolism and ferroptosis in the view of preeclampsia and gestational diabetes mellitus, which may bring new insight to the pathogenesis and treatment of pregnancy-related diseases.

Materno-fetal iron transfer and the emerging role of ferroptosis pathways

A successful pregnancy and the birth of a healthy baby depend to a great extent on the controlled supply of essential nutrients via the placenta. Iron is essential for mitochondrial energy supply and oxygen distribution via the blood. However, its high reactivity requires tightly regulated transport processes. Disturbances of maternal-fetal iron transfer during pregnancy can aggravate or lead to severe pathological consequences for the mother and the fetus with lifelong effects. Furthermore, high intracellular iron levels due to disturbed gestational iron homeostasis have recently been associated with the non-apoptotic cell death pathway called ferroptosis. Therefore, the investigation of transplacental iron transport mechanisms, their physiological regulation and potential risks are of high clinical importance. The present review summarizes the current knowledge on principles and regulatory mechanisms underlying materno-fetal iron transport and gives insight into common pregnancy conditions in which iron homeostasis is disturbed. Moreover, the significance of the newly emerging ferroptosis pathway and its impact on the regulation of placental iron homeostasis, oxidative stress and gestational diseases will be discussed.

Differences and Interactions in Placental Manganese and Iron Transfer across an In Vitro Model of Human Villous Trophoblasts

Manganese (Mn) as well as iron (Fe) are essential trace elements (TE) important for the maintenance of physiological functions including fetal development. However, in the case of Mn, evidence suggests that excess levels of intrauterine Mn are associated with adverse pregnancy outcomes. Although Mn is known to cross the placenta, the fundamentals of Mn transfer kinetics and mechanisms are largely unknown. Moreover, exposure to combinations of TEs should be considered in mechanistic transfer studies, in particular for TEs expected to share similar transfer pathways. Here, we performed a mechanistic in vitro study on the placental transfer of Mn across a BeWo b30 trophoblast layer. Our data revealed distinct differences in the placental transfer of Mn and Fe. While placental permeability to Fe showed a clear inverse dose-dependency, Mn transfer was largely independent of the applied doses. Concurrent exposure of Mn and Fe revealed transfer interactions of Fe and Mn, indicating that they share common transfer mechanisms. In general, mRNA and protein expression of discussed transporters like DMT1, TfR, or FPN were only marginally altered in BeWo cells despite the different exposure scenarios highlighting that Mn transfer across the trophoblast layer likely involves a combination of active and passive transport processes.

Iron Metabolism in Normal and Pathological Pregnancies and Fetal Consequences

Iron is required for energy production, DNA synthesis, and cell proliferation, mainly as a component of the prosthetic group in hemoproteins and as part of iron-sulfur clusters. Iron is also a critical component of hemoglobin and plays an important role in oxygen delivery. Imbalances in iron metabolism negatively affect these vital functions. As the crucial barrier between the fetus and the mother, the placenta plays a pivotal role in iron metabolism during pregnancy. Iron deficiency affects 1.2 billion individuals worldwide. Pregnant women are at high risk of developing or worsening iron deficiency. On the contrary, in frequent hemoglobin diseases, such as sickle-cell disease and thalassemia, iron overload is observed. Both iron deficiency and iron overload can affect neonatal development. This review aims to provide an update on our current knowledge on iron and heme metabolism in normal and pathological pregnancies. The main molecular actors in human placental iron metabolism are described, focusing on the impact of iron deficiency and hemoglobin diseases on the placenta, together with normal metabolism. Then, we discuss data concerning iron metabolism in frequent pathological pregnancies to complete the picture, focusing on the most frequent diseases.

Role of Iron Metabolism-Related Genes in Prenatal Development: Insights from Mouse Transgenic Models

Iron is an essential nutrient during all stages of mammalian development. Studies carried out over the last 20 years have provided important insights into cellular and systemic iron metabolism in adult organisms and led to the deciphering of many molecular details of its regulation. However, our knowledge of iron handling in prenatal development has remained remarkably under-appreciated, even though it is critical for the health of both the embryo/fetus and its mother, and has a far-reaching impact in postnatal life. Prenatal development requires a continuous, albeit quantitatively matched with the stage of development, supply of iron to support rapid cell division during embryogenesis in order to meet iron needs for erythropoiesis and to build up hepatic iron stores, (which are the major source of this microelement for the neonate). Here, we provide a concise overview of current knowledge of the role of iron metabolism-related genes in the maintenance of iron homeostasis in pre- and post-implantation development based on studies on transgenic (mainly knock-out) mouse models. Most studies on mice with globally deleted genes do not conclude whether underlying in utero iron disorders or lethality is due to defective placental iron transport or iron misregulation in the embryo/fetus proper (or due to both). Therefore, there is a need of animal models with tissue specific targeted deletion of genes to advance the understanding of prenatal iron metabolism.

The critical roles of iron during the journey from fetus to adolescent: Developmental aspects of iron homeostasis

Iron is indispensable for human life. However, it is also potentially toxic, since it catalyzes the formation of harmful oxidative radicals in unbound form and may facilitate pathogen growth. Therefore, iron homeostasis needs to be tightly regulated. Rapid growth and development require large amounts of iron, while (especially young) children are vulnerable to infections with iron-dependent pathogens due to an immature immune system. Moreover, unbalanced iron status early in life may have effects on the nervous system, immune system and gut microbiota that persist into adulthood. In this narrative review, we assess the critical roles of iron for growth and development and elaborate how the body adapts to physiologically high iron demands during the journey from fetus to adolescent. As a first step towards the development of clinical guidelines for the management of iron disorders in children, we summarize the unmet needs regarding the developmental aspects of iron homeostasis.

Marginally reduced maternal hepatic and splenic ferroportin under severe nutritional iron deficiency in pregnancy maintains systemic iron supply

The demand for iron is high in pregnancy to meet the increased requirements for erythropoiesis. Even pregnant females with initially iron‐replete stores develop iron‐deficiency anemia, due to inadequate iron absorption. In anemic females, the maternal iron supply is dedicated to maintaining iron metabolism in the fetus and placenta. Here, using a mouse model of iron deficiency in pregnancy, we show that iron recycled from senescent erythrocytes becomes a predominant source of this microelement that can be transferred to the placenta in females with depleted iron stores. Ferroportin is a key protein in the molecular machinery of cellular iron egress. We demonstrate that under iron deficiency in pregnancy, levels of ferroportin are greatly reduced in the duodenum, placenta and fetal liver, but not in maternal liver macrophages and in the spleen. Although low expression of both maternal and fetal hepcidin predicted ferroportin up‐regulation in examined locations, its final expression level was very likely correlated with tissue iron status. Our results argue that iron released into the circulation of anemic females is taken up by the placenta, as evidenced by high expression of iron importers on syncytiotrophoblasts. Then, a substantial decrease in levels of ferroportin on the basolateral side of syncytiotrophoblasts, may be responsible for the reduced transfer of iron to the fetus. As attested by the lowest decrease in iron content among analyzed tissues, some part is retained in the placenta. These findings confirm the key role played by ferroportin in tuning iron turnover in iron‐deficient pregnant mouse females and their fetuses.