Influence of gestational age and fetal iron status on IRP activity and iron transporter protein expression in third-trimester human placenta

New insights into the mechanisms of iron absorption: Iron dextran uptake in the intestines of weaned pigs through glucose transporter 5 (GLUT5) and divalent metal transporter 1 (DMT1) transporters

The purpose of this study was to gain insight into the mechanism of iron dextran (DexFe) absorption in the intestines. A total of 72 piglets (average BW = 7.12 ± 0.75 kg, male to female ratio = 1:1) weaned at 28 d of age were randomly divided into two treatment groups with six replicates for each group. The experimental diets included the basal diet supplemented with 100 mg/kg iron dextran (DexFe group) and the basal diet supplemented with 100 mg/kg FeSO4·H2O (CON group). The experiment lasted for 28 d. The piglets' intestinal iron transport was measured in vitro using an Ussing chamber. Porcine intestinal epithelial cell line (IPEC-J2) cells were used to develop a monolayer cell model that explored the molecular mechanism of DexFe absorption. Results showed that compared to the CON group, the ADG of pigs in the DexFe group was improved (P = 0.022), while the F/G was decreased (P = 0.015). The serum iron concentration, apparent iron digestibility, and iron deposition in the duodenum, jejunum, and ileum were increased (P < 0.05) by dietary DexFe supplementation. Piglets in the DexFe group had higher serum red blood count, hemoglobin, serum iron content, serum ferritin and transferrin levels and lower total iron binding capacity (P < 0.05). In the Ussing chamber test, the iron absorption rate of the DexFe group was greater (P < 0.001) than the CON group, and there was no significant difference between the DexFe group and the glucose group (P > 0.05). Furthermore, when compared to the CON group, DexFe administration improved (P < 0.05) SLC2A5 gene and glucose transporter 5 (GLUT5) protein expression but had no effect (P > 0.05) on SLC11A2 gene or divalent metal transporter 1 (DMT1) protein expression. Once the GLUT5 protein was suppressed, the iron transport rate and apparent permeability coefficient were decreased (P < 0.05) in IPEC-J2 monolayer cell models. The findings suggest the effectiveness of DexFe application in weaned piglets and revealed for the first time that DexFe absorption in the intestine is closely related to the glucose transporter GLUT5 protein channel.

Molecular insights into placental iron transfer mechanisms and maternofetal regulation

PURPOSE

Adequate iron transportation from the mother across the placenta is crucial for fetal growth and establishing sufficient iron stores in neonates at birth. The past decade has marked significant discoveries in iron metabolism with the identification of new players and mechanisms. Immunohistochemical studies rendered valuable data on the localization of substantial iron transporters on placental syncytiotrophoblasts. However, the function and regulation of maternal-placentofetal iron transporters and iron handling is still elusive and requires more attention.

METHODS

A thorough literature review was conducted to gather information about placental iron transfer, the role of regulators and maintenance of iron homeostasis.

RESULTS

The role of classical and new players in maternal-fetal iron transport and the regulation in the placenta has been addressed in this review. Animal and human studies have been discussed. The role of placental iron regulation in thalassemia and hemochromatosis pregnancies has been reviewed.

CONCLUSIONS

The current advances that highlight the mechanisms of placental iron regulation and transport in response to maternal and fetal signals have been presented.

Iron Homeostasis During Pregnancy: Maternal, Placental, and Fetal Regulatory Mechanisms

Pregnancy entails a large negative balance of iron, an essential micronutrient. During pregnancy, iron requirements increase substantially to support both maternal red blood cell expansion and the development of the placenta and fetus. As insufficient iron has long been linked to adverse pregnancy outcomes, universal iron supplementation is common practice before and during pregnancy. However, in high-resource countries with iron fortification of staple foods and increased red meat consumption, the effects of too much iron supplementation during pregnancy have become a concern because iron excess has also been linked to adverse pregnancy outcomes. In this review, we address physiologic iron homeostasis of the mother, placenta, and fetus and discuss perturbations in iron homeostasis that result in pathological pregnancy. As many mechanistic regulatory systems have been deduced from animal models, we also discuss the principles learned from these models and how these may apply to human pregnancy.

The Role of Ferroptosis in Placental-Related Diseases

Ferroptosis is a recently identified form of programmed cell death which is different from apoptosis, pyroptosis, necrosis, and autophagy. It is uniquely defined by redox-active iron-dependent hydroxy-peroxidation of polyunsaturated fatty acid (PUFA)-containing phospholipids and a loss of lipid peroxidation repair capacity. Ferroptosis has recently been implicated in multiple human diseases, such as tumors, ischemia-reperfusion injury, acute kidney injury, neurological diseases, and asthma among others. Intriguingly, ferroptosis is associated with placental physiology and trophoblast injury. Circumstances such as accumulation of lipid reactive oxygen species (ROS) due to hypoxia-reperfusion and anoxia-reoxygenation of trophoblast during placental development, the abundance of trophoblastic iron and PUFA, physiological uterine contractions, or pathological placental bed perfusion, cause placental trophoblasts' susceptibility to ferroptosis. Ferroptosis of trophoblast can cause placental dysfunction, which may be involved in the occurrence and development of placenta-related diseases such as gestational diabetes mellitus, preeclampsia, fetal growth restriction, preterm birth, and abortion. The regulatory mechanisms of trophoblastic ferroptosis still need to be explored further. Here, we summarize the latest progress in trophoblastic ferroptosis research on placental-related diseases, provide references for further understanding of its pathogenesis, and propose new strategies for the prevention and treatment of placental-related diseases.

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.

Spatial-temporal changes of iron deposition and iron metabolism after traumatic brain injury in mice

Excessive iron released by hemoglobin and necrotic tissues is the predominant factor that aggravates the outcome of traumatic brain injury (TBI). Regulating the levels of iron and its metabolism is a feasible way to alleviate damage due to TBI. However, the spatial-temporal iron metabolism and iron deposition in neurons and glial cells after TBI remains unclear. In our study, male C57BL/6 mice (8–12 weeks old, weighing 20–26 g) were conducted using controlled cortical impact (CCI) models, combined with treatment of iron chelator deferoxamine (DFO), followed by systematical evaluation on iron deposition, cell-specific expression of iron metabolic proteins and ferroptosis in ipsilateral cortex. Herein, ferroptosis manifest by iron overload and lipid peroxidation was noticed in ipsilateral cortex. Furthermore, iron deposition and cell-specific expression of iron metabolic proteins were observed in the ipsilateral cortical neurons at 1–3 days post-injury. However, iron overload was absent in astrocytes, even though they had intense TBI-induced oxidative stress. In addition, iron accumulation in oligodendrocytes was only observed at 7–14 days post-injury, which was in accordance with the corresponding interval of cellular repair. Microglia play significant roles in iron engulfment and metabolism after TBI, and excessive affects the transformation of M1 and M2 subtypes and activation of microglial cells. Our study revealed that TBI led to ferroptosis in ipsilateral cortex, iron deposition and metabolism exhibited cell-type-specific spatial-temporal changes in neurons and glial cells after TBI. The different effects and dynamic changes in iron deposition and iron metabolism in neurons and glial cells are conducive to providing new insights into the iron-metabolic mechanism and strategies for improving the treatment of TBI.

Iron transport across the human placenta is regulated by hepcidin

BACKGROUND

Transport of iron across the placenta is critical for appropriate development of the fetus. Iron deficiency during pregnancy remains a major public health concern, particularly in low- and middle-income countries, often exacerbated by infectious diseases leading to altered iron trafficking via inflammatory responses. Herein, we investigate the role of hepcidin, a master regulator of iron homeostasis, on regulation of iron transport across trophoblast cells.

METHODS

We utilized the Jeg-3 choriocarcinoma cell line for analysis of the expression of transferrin receptor, ferritin, and ferroportin as well as the export of ⁵⁹Fe in the presence of hepcidin. Placental tissue from human term pregnancies was utilized for immunohistochemistry.

RESULTS

Hepcidin treatment of Jeg-3 cells decreased the expression of ferroportin and transferrin receptor (TfR) and reduced the cellular export of iron. Lower expression of TfR on the syncytiotrophoblast was associated with the highest levels of hepcidin in maternal circulation, and ferroportin expression was positively associated with placental TfR. Placentas from small-for-gestational-age newborns had significantly lower levels of ferroportin and ferritin gene expression at delivery.

CONCLUSIONS

Our data suggest that hepcidin plays an important role in the regulation of iron transport across the placenta, making it a critical link in movement of iron into fetal circulation.

IMPACT

Hepcidin has a direct impact on iron transport across the human placenta. This study provides the first evidence of direct regulation of iron efflux from human trophoblast cells by hepcidin. These data extend our understanding of iron transport across the maternal-fetal interface, a process critical for fetal health and development.

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.

Prenatal alcohol-related alterations in maternal, placental, neonatal, and infant iron homeostasis

BACKGROUND

Prenatal alcohol exposure (PAE) is associated with postnatal iron deficiency (ID), which has been shown to exacerbate deficits in growth, cognition, and behavior seen in fetal alcohol spectrum disorders. However, the mechanisms underlying PAE-related ID remain unknown.

OBJECTIVES

We aimed to examine biochemical measures of iron homeostasis in the mother, placenta, neonate, and 6.5-month-old infant.

METHODS

In a prenatally recruited, prospective longitudinal birth cohort in South Africa, 206 gravidas (126 heavy drinkers and 80 controls) were interviewed regarding alcohol, cigarette, and drug use and diet at 3 prenatal visits. Hemoglobin, ferritin, and soluble transferrin receptor (sTfR) were assayed twice during pregnancy and urinary hepcidin:creatinine was assayed once. Infant ferritin and hemoglobin were measured at 2 weeks and 6.5 months and sTfR was measured at 6.5 months. Histopathological examinations were conducted on 125 placentas and iron transport assays (iron regulatory protein-2, transferrin receptor-1, divalent metal transporter-1, ferroportin-1, and iron concentrations) were conducted on 63.

RESULTS

In multivariable regression models, prenatal drinking frequency (days/week) was related to higher maternal hepcidin and to sequestration of iron into storage at the expense of erythropoiesis in mothers and neonates, as evidenced by a lower hemoglobin (g/dL)-to-log(ferritin) (ug/L) ratio [mothers: raw regression coefficient (β) = -0.21 (95% CI: -0.35 to -0.07); neonates: β = -0.15 (95% CI: -0.24 to -0.06)]. Drinking frequency was also related to decreased placental ferroportin-1:transferrin receptor-1 (β = -0.57 for logged values; 95% CI: -1.03 to -0.10), indicating iron-restricted placental iron transport. At 6.5 months, drinking frequency was associated with lower hemoglobin (β = -0.18; 95% CI: -0.33 to -0.02), and increased prevalences of ID (β = 0.09; 95% CI: 0.02-0.17) and ID anemia (IDA) (β = 0.13; 95% CI: 0.04-0.23). In causal inference analyses, the PAE-related increase in IDA was partially mediated by decreased neonatal hemoglobin:log(ferritin), and the decrease in neonatal hemoglobin:log(ferritin) was partially mediated by decreased maternal hemoglobin:log(ferritin).

CONCLUSIONS

In this study, greater PAE was associated with an unfavorable profile of maternal-fetal iron homeostasis, which may play mechanistic roles in PAE-related ID later in infancy.

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.

Pediatric reference intervals for endocrine markers and fertility hormones in healthy children and adolescents on the Siemens Healthineers Atellica immunoassay system

OBJECTIVES

Rapid development in childhood and adolescence combined with lack of immunoassay standardization necessitates the establishment of age-, sex-, and assay-specific reference intervals for immunochemical markers. This study established reference intervals for 11 immunoassays on the new Siemens Healthineers Atellica® IM Analyzer in the healthy CALIPER cohort.

METHODS

A total of 600 healthy participants (birth to 18 years) were recruited from the community, and serum samples were collected with informed consent. After sample analysis, age- and sex-specific differences were assessed, and outliers were removed. Reference intervals were established using the robust method (40-<120 participants) or nonparametric method (≥120 participants).

RESULTS

Of the 11 immunoassays studied, nine required age partitioning (i.e., dehydroepiandrosterone-sulfate, estradiol, ferritin, folate, follicle-stimulating hormone, luteinizing hormone, progesterone, testosterone, vitamin B12), and seven required sex partitioning. Free thyroxine and thyroid-stimulating hormone demonstrated no significant age- and/or sex-specific differences.

CONCLUSIONS

Overall, the age- and sex-specific trends observed closely mirrored those previously reported by CALIPER on other platforms as well as other internationally recognized studies. However, established lower and upper limits demonstrated some discrepancies between published values from healthy cohorts on alternate analytical systems, highlighting differences between manufacturers and the need for platform-specific reference intervals for informed pediatric clinical decision-making.

Ferroptosis, trophoblast lipotoxic damage, and adverse pregnancy outcome

Programmed cell death is a central process in the control of tissue development, organismal physiology, and disease. Ferroptosis is a recently identified form of programmed cell death that is uniquely defined by redox-active iron-dependent hydroxy-peroxidation of polyunsaturated fatty acid (PUFA)-containing phospholipids and a loss of lipid peroxidation repair capacity. This distinctive form of lipotoxic cell death has been recently implicated in multiple human diseases, spanning ischemia-reperfusion heart injury, brain damage, acute kidney injury, cancer, and asthma. Intriguingly, settings that have been associated with ferroptosis are linked to placental physiology and trophoblast injury. Such circumstances include hypoxia-reperfusion during placental development, physiological uterine contractions or pathological changes in placental bed perfusion, the abundance of trophoblastic iron, evidence for lipotoxicity during the pathophysiology of major placental disorders such as preeclampsia, fetal growth restriction, and preterm birth, and reduced glutathione peroxidation capacity and lipid peroxidation repair during placental injury. We recently interrogated placental ferroptosis in placental dysfunction in human and mouse pregnancy, dissected its relevance to placental injury, and validated the role of glutathione peroxidase-4 in guarding placental trophoblasts against ferroptotic injury. We also uncovered a role for the phospholipase PLA2G6 (PNPLA9) in attenuating trophoblast ferroptosis. Here, we summarize current data on trophoblast ferroptosis, and the role of several proteins and microRNAs as regulators of this process. Our text offers insights into new opportunities for regulating ferroptosis as a means for protecting placental trophoblasts against lipotoxic injury.

Iron Availability in Tissue Microenvironment: The Key Role of Ferroportin

Body iron levels are regulated by hepcidin, a liver-derived peptide that exerts its function by controlling the presence of ferroportin (FPN), the sole cellular iron exporter, on the cell surface. Hepcidin binding leads to FPN internalization and degradation, thereby inhibiting iron release, in particular from iron-absorbing duodenal cells and macrophages involved in iron recycling. Disruption in this regulatory mechanism results in a variety of disorders associated with iron-deficiency or overload. In recent years, increasing evidence has emerged to indicate that, in addition to its role in systemic iron metabolism, FPN may play an important function in local iron control, such that its dysregulation may lead to tissue damage despite unaltered systemic iron homeostasis. In this review, we focus on recent discoveries to discuss the role of FPN-mediated iron export in the microenvironment under both physiological and pathological conditions.

Effects of maternal iron status on placental and fetal iron homeostasis

Iron deficiency is common worldwide and is associated with adverse pregnancy outcomes. The increasing prevalence of indiscriminate iron supplementation during pregnancy also raises concerns about the potential adverse effects of iron excess. We examined how maternal iron status affects the delivery of iron to the placenta and fetus. Using mouse models, we documented maternal homeostatic mechanisms that protect the placenta and fetus from maternal iron excess. We determined that under physiological conditions or in iron deficiency, fetal and placental hepcidin did not regulate fetal iron endowment. With maternal iron deficiency, critical transporters mediating placental iron uptake (transferrin receptor 1 [TFR1]) and export (ferroportin [FPN]) were strongly regulated. In mice, not only was TFR1 increased, but FPN was surprisingly decreased to preserve placental iron in the face of fetal iron deficiency. In human placentas from pregnancies with mild iron deficiency, TFR1 was increased, but there was no change in FPN. However, induction of more severe iron deficiency in human trophoblast in vitro resulted in the regulation of both TFR1 and FPN, similar to what was observed in the mouse model. This placental adaptation that prioritizes placental iron is mediated by iron regulatory protein 1 (IRP1) and is important for the maintenance of mitochondrial respiration, thus ultimately protecting the fetus from the potentially dire consequences of generalized placental dysfunction.

Differential Iron Status and Trafficking in Blood and Placenta of Anemic and Non-anemic Primigravida Supplemented with Daily and Weekly Iron Folic Acid Tablets

Abstract

The molecular mechanism of iron transfer across placenta in response to maternal anemic status/ iron supplementation is not clear. We hypothesized that maternal iron/ anemia status during early trimesters can be utilized as a biomarker tool to get estimates of placental iron status. Early interventions can be envisaged to maintain optimum placental/ foetal iron levels for healthy pregnancy outcomes. One hundred twenty primigravida were recruited and divided into non-anemic and anemic group on the basis of hemoglobin levels. The groups were randomly allocated to receive daily and weekly iron folic acid (IFA) tablets till six weeks postpartum. Hematological and iron status markers in blood and placenta were studied along with the delivery notes. Weekly IFA supplementation in anemic primigravidas resulted in significantly reduced levels of hematological markers (p < 0.01); whereas non-anemic primigravidas showed lower ferritin and iron levels, and higher soluble transferrin receptor levels (p < 0.05). At baseline, C-reactive protein and cortisol hormone levels were also significantly lower in non-anemic primigravidas (p < 0.05). A significantly decreased placental ferritin expression (p < 0.05); and an increased placental transferrin expression was seen in anemic primigravidas supplemented with weekly IFA tablets. A significant positive correlation was observed between serum and placental ferritin expression in anemic pregnant women (r = 0.80; p < 0.007). Infant weight, gestational length and placental weight were comparable in both the supplementation groups. To conclude, mother's serum iron / anemia status switches the modulation in placental iron transporter expression for delivering the optimum iron to the foetus for healthy pregnancy outcomes.

Trial Registration

Clinical Trial Registry-India: CTRI/2014/10/005135.

Placental iron transport: The mechanism and regulatory circuits

As the interface between the fetal and maternal circulation, the placenta facilitates both nutrient and waste exchange for the developing fetus. Iron is essential for healthy pregnancy, and transport of iron across the placenta is required for fetal growth and development. Perturbation of this transfer can lead to adverse pregnancy outcomes. Despite its importance, our understanding of how a large amount of iron is transported across placental membranes, how this process is regulated, and which iron transporter proteins function in different placental cells remains rudimentary. Mechanistic studies in mouse models, including placenta-specific deletion or overexpression of iron-related proteins will be essential to make progress. This review summarizes our current understanding about iron transport across the syncytiotrophoblast under physiological conditions and identifies areas for further investigation.

Maternal iron nutriture as a critical modulator of fetal alcohol spectrum disorder risk in alcohol-exposed pregnancies

Alcohol consumption during pregnancy places the fetus at risk for permanent physical, cognitive, and behavioral impairments, collectively termed fetal alcohol spectrum disorder (FASD). However, prenatal alcohol exposure (PAE) outcomes vary widely, and growing evidence suggests that maternal nutrition is a modifying factor. Certain nutrients, such as iron, may modulate FASD outcomes. Untreated gestational iron deficiency (ID) causes persistent neurodevelopmental deficits in the offspring that affect many of the same domains damaged by PAE. Although chronic alcohol consumption enhances iron uptake and elevates liver iron stores in adult alcoholics, alcohol-abusing premenopausal women often have low iron reserves due to menstruation, childbirth, and poor diet. Recent investigations show that low iron reserves during pregnancy are strongly associated with a worsening of several hallmark features in FASD including reduced growth and impaired associative learning. This review discusses recent clinical and animal model findings that maternal ID worsens fetal outcomes in response to PAE. It also discusses underlying mechanisms by which PAE disrupts maternal and fetal iron homeostasis. We suggest that alcohol-exposed ID pregnancies contribute to the severe end of the FASD spectrum.

Effect of different sources and levels of iron in the diet of sows on iron status in neonatal pigs

This study was conducted to determine the effects of maternal dietary supplementation of ferrous glycine chelate (Fe-Gly) and ferrous sulfate monohydrate (FeSO₄·H₂O) on the relative organ weight, tissue iron contents, red blood cells (RBC), hemoglobin concentration (HGB) and hematocrit (HCT) in blood, as well as ferritin (Fn), serum iron (SI), and total iron binding capacity (TIBC) in serum of newborn piglets. Forty-five sows (Landrace × Large white, mean parity 3 to 4, no significant differences in BW) were randomly allotted to 9 treatments (n = 5 sows/treatment): control (basal diet with no Fe supplementation), the basal diet supplemented with 50, 80, 110 or 140 mg Fe/kg as Fe-Gly, and the basal diet supplemented with 50, 80, 110 or 140 mg Fe/kg as FeSO₄·H₂O. The neonatal piglets (n = 45) were used to determine the relative organ weight, tissue iron contents and blood biochemical indices. Compared with the control, the relative weight of spleen and kidney were significantly increased (P < 0.05) in the Fe-Gly groups. The iron contents in liver, spleen, kidney and femur were also found increased (P < 0.05) in the Fe-Gly groups. The RBC (d 1 and 21), HGB (d 1 and 21) and HCT (d 1 and 21) in blood and Fn (d 1) and SI (d 1 and 21) significantly increased (P < 0.05), but the TIBC (d 1 and 21) in serum decreased (P < 0.05) in the Fe-Gly groups. Moreover, the kidney relative weight, iron content in liver, spleen, kidney and femur, RBC (d 1) and HGB (d 21) in blood, and SI (d 1) in the Fe-Gly groups increased (P < 0.05) compared with the FeSO₄·H₂O treatment. Linear and quadratic responses of the kidney relative weight, the iron content in liver, spleen, kidney and femur, RBC (d 1 and 21), HGB (d 1 and 21) and HCT (d 1 and 21) in whole blood, SI (d 1) and TIBC (d 1 and 21) in the Fe-Gly groups were observed (P < 0.05). Linear responses of Fn (d 1 and 21) and SI (d 21) in the Fe-Gly groups, and spleen relative weight, HCT (d 1), Fn (d 1) and TIBC (d 1 and 21) in the FeSO₄·H₂O groups were observed (P < 0.05). These finding suggest that Fe-Gly supplemented at the level of 110 mg/kg in the diet of sows in this experiment is superior to other forms of supplementation, based on HGB concentration, the relative organ weight, tissue iron contents and blood biochemical indices of piglets.

Maternal iron status during pregnancy compared with neonatal iron status better predicts placental iron transporter expression in humans

The placenta richly expresses nonheme and heme Fe transport proteins. To address the impact of maternal and neonatal Fe status and hepcidin on the regulation of these proteins, mRNA expression and protein abundance of nonheme and heme Fe transport proteins were evaluated in placental tissue from 154 adolescents. Regression analyses found maternal Fe status was significantly associated with multiple placental nonheme and heme transporters, whereas neonatal Fe status was related to only 3 heme transporters. Across statistical analyses, maternal Fe status was consistently associated with the placental nonheme Fe importer transferrin receptor 1 (TfR1). Protein abundance of TfR1 was related to midgestation maternal serum ferritin (SF) (β = -0.32; P = 0.005) and serum TfR (β = 0.25; P = 0.024). Protein abundance of the heme importer, proton-coupled folate transporter, was related to neonatal SF (β = 0.30; P = 0.016) and serum TfR (β = -0.46; P < 0.0001). Neonatal SF was also related to mRNA expression of the heme exporter feline leukemia virus subgroup C receptor 1 (β = -0.30; P = 0.004). In summary, maternal Fe insufficiency during pregnancy predicts increased expression of the placental nonheme Fe transporter TfR1. Associations between placental heme Fe transporters and neonatal Fe status require further study.-Best, C. M., Pressman, E. K., Cao, C., Cooper, E., Guillet, R., Yost, O. L., Galati, J., Kent, T. R., O'Brien, K. O. Maternal iron status during pregnancy compared with neonatal iron status better predicts placental iron transporter expression in humans.

Expression of Hepcidin and Ferroportin in the Placenta, and Ferritin and Transferrin Receptor 1 Levels in Maternal and Umbilical Cord Blood in Pregnant Women with and without Gestational Diabetes

BACKGROUND

Regulation of iron transfer from mother to fetus via the placenta is not fully understood and the relationship between stored iron status in the mothers' serum and gestational diabetes (GDM) in case-control studies is controversial. The present study aimed to detect circulating soluble transferrin receptor (sTfR) and ferritin levels in maternal and umbilical cord blood. We also examined the expression of hepcidin (Hep), transferrin receptor (TfR1), and ferroportin (FPN) in the placenta in pregnant women with and without GDM at full term.

METHODS

Eighty-two women participated (42 with GDM and 40 without GDM [controls]). Maternal samples were collected at 37-39 weeks' gestation. Umbilical cord blood was collected at birth. Ferritin and sTfR levels in maternal serum and umbilical cord blood, and Hep, TfR1, and FPN protein expression in plac enta were compared between the GDM and non-GDM groups. Serum ferritin (SF) was measured by electrochemiluminescence assay and sTfR was measured by ELISA. Hep, TfR1, and FPN expression was measured by immunohistochemistry.

RESULTS

Maternal serum sTfR levels were significantly elevated in the GDM group compared with the non-GDM group (p = 0.003). SF levels in cord blood in the GDM group were significantly higher than those in the non-GDM group (p = 0.003). However, maternal hemoglobin and SF, and umbilical cord sTfR levels were not different between the groups. In placental tissue, FPN expression was higher and hepcidin expression was lower in the GDM group compared with the non-GDM group (p = 0.000 and p = 0.044, respectively). There was no significant difference in TfR1 between the groups (p = 0.898).

CONCLUSIONS

Women with GDM transport iron more actively than those without GDM at term pregnancy. Maternal iron metabolism in GDM may play a role in fetal/placental iron demand and in the overall outcome of pregnancy.

Iron uptake and transport across physiological barriers

Iron is an essential element for human development. It is a major requirement for cellular processes such as oxygen transport, energy metabolism, neurotransmitter synthesis, and myelin synthesis. Despite its crucial role in these processes, iron in the ferric form can also produce toxic reactive oxygen species. The duality of iron’s function highlights the importance of maintaining a strict balance of iron levels in the body. As a result, organisms have developed elegant mechanisms of iron uptake, transport, and storage. This review will focus on the mechanisms that have evolved at physiological barriers, such as the intestine, the placenta, and the blood–brain barrier (BBB), where iron must be transported. Much has been written about the processes for iron transport across the intestine and the placenta, but less is known about iron transport mechanisms at the BBB. In this review, we compare the established pathways at the intestine and the placenta as well as describe what is currently known about iron transport at the BBB and how brain iron uptake correlates with processes at these other physiological barriers.

The placenta: the forgotten essential organ of iron transport

Optimal iron nutrition in utero is essential for development of the fetus and helps establish birth iron stores adequate to sustain growth in early infancy. In species with hemochorial placentas, such as humans and rodents, iron in the maternal circulation is transferred to the fetus by directly contacting placental syncytiotrophoblasts. Early kinetic studies provided valuable data on the initial uptake of maternal transferrin, an iron-binding protein, by the placenta. However, the remaining steps of iron trafficking across syncytiotrophoblasts and through the fetal endothelium into the fetal blood remain poorly characterized. Over the last 20 years, identification of transmembrane iron transporters and the iron regulatory hormone hepcidin has greatly expanded the knowledge of cellular iron transport and its regulation by systemic iron status. In addition, emerging human and animal data demonstrating comprised fetal iron stores in severe maternal iron deficiency challenge the classic dogma of exclusive fetal control over the transfer process and indicate that maternal and local signals may play a role in regulating this process. This review compiles current data on the kinetic, molecular, and regulatory aspects of placental iron transport and considers new questions and knowledge gaps raised by these advances.

Protein expression of fatty acid transporter 2 is polarized to the trophoblast basal plasma membrane and increased in placentas from overweight/obese women

BACKGROUND

Obese and overweight women are more likely to deliver a large infant or an infant with increased adiposity, however the underlying mechanisms are not well established. We tested the hypothesis that placental capacity to transport fatty acid is increased in overweight/obese women.

METHODS

Pregnant women with body mass index (BMI) ranging from 18.4 to 54.3 kg/m(2) and with uncomplicated term pregnancies were recruited for collection of blood samples and placental tissue. Maternal and fetal levels of non-esterified fatty acids (NEFAs) were measured in plasma. The expression and localization of CD36/fatty acid translocase (FAT), fatty acid transport protein (FATP)2, and FATP4 was determined in fixed placental tissue and in isolated syncytiotrophoblast plasma membranes from normal and high BMI mothers.

RESULTS

Maternal and fetal plasma NEFA levels did not correlate (n = 42). FATP2 and FATP4 expressions were higher in the basal plasma membrane (BPM) compared to the microvillous membrane (P < 0.001; n = 7) per unit membrane protein. BPM expression of FATP2 correlated with maternal BMI (P < 0.01; n = 30); there was no association between CD36/FAT or FATP4 expression and maternal BMI.

CONCLUSION

The polarization of FATPs to the BPM will facilitate fatty acid transfer across the placenta. In overweight/obese pregnancies, the increased FATP2 expression could contribute to increased fatty acid delivery to the fetus and while we have no direct data we speculate that this could lead accelerated fetal growth or increased fat deposition.

Placentophagy: therapeutic miracle or myth?

Postpartum women are consuming their placentas encapsulated, cooked, and raw for the prevention of postpartum depression (PPD), pain relief, and other health benefits. Placentophagy is supported by health advocates who assert that the placenta retains hormones and nutrients that are beneficial to the mother. A computerized search was conducted using PubMed, Medline Ovid, and PsychINFO between January 1950 and January 2014. Keywords included placentophagy, placentophagia, maternal placentophagia, maternal placentophagy, human placentophagia, and human placentophagy. A total of 49 articles were identified. Empirical studies of human or animal consumption of human placentas were included. Editorial commentaries were excluded. Animal placentophagy studies were chosen based on their relevance to human practice. Ten articles (four human, six animal) were selected for inclusion. A minority of women in developed countries perceive placentophagy to reduce PPD risk and enhance recovery. Experimental animal research in support of pain reduction has not been applied in humans. Studies investigating placenta consumption for facilitating uterine contraction, resumption of normal cyclic estrogen cycle, and milk production are inconclusive. The health benefits and risks of placentophagy require further investigation of the retained contents of raw, cooked, and encapsulated placenta and its effects on the postpartum woman.

Prenatal Iron Supplementation Reduces Maternal Anemia, Iron Deficiency, and Iron Deficiency Anemia in a Randomized Clinical Trial in Rural China, but Iron Deficiency Remains Widespread in Mothers and Neonates

BACKGROUND

Previous trials of prenatal iron supplementation had limited measures of maternal or neonatal iron status.

OBJECTIVE

The purpose was to assess effects of prenatal iron-folate supplementation on maternal and neonatal iron status.

METHODS

Enrollment occurred June 2009 through December 2011 in Hebei, China. Women with uncomplicated singleton pregnancies at ≤20 wk gestation, aged ≥18 y, and with hemoglobin ≥100 g/L were randomly assigned 1:1 to receive daily iron (300 mg ferrous sulfate) or placebo + 0.40 mg folate from enrollment to birth. Iron status was assessed in maternal venous blood (at enrollment and at or near term) and cord blood. Primary outcomes were as follows: 1) maternal iron deficiency (ID) defined in 2 ways as serum ferritin (SF) <15 μg/L and body iron (BI) <0 mg/kg; 2) maternal ID anemia [ID + anemia (IDA); hemoglobin <110 g/L]; and 3) neonatal ID (cord blood ferritin <75 μg/L or zinc protoporphyrin/heme >118 μmol/mol).

RESULTS

A total of 2371 women were randomly assigned, with outcomes for 1632 women or neonates (809 placebo/folate, 823 iron/folate; 1579 mother-newborn pairs, 37 mothers, 16 neonates). Most infants (97%) were born at term. At or near term, maternal hemoglobin was significantly higher (+5.56 g/L) for iron vs. placebo groups. Anemia risk was reduced (RR: 0.53; 95% CI: 0.43, 0.66), as were risks of ID (RR: 0.74; 95% CI: 0.69, 0.79 by SF; RR: 0.65; 95% CI: 0.59, 0.71 by BI) and IDA (RR: 0.49; 95% CI: 0.38, 0.62 by SF; RR: 0.51; 95% CI: 0.40, 0.65 by BI). Most women still had ID (66.8% by SF, 54.7% by BI). Adverse effects, all minor, were similar by group. There were no differences in cord blood iron measures; >45% of neonates in each group had ID. However, dose-response analyses showed higher cord SF with more maternal iron capsules reported being consumed (β per 10 capsules = 2.60, P < 0.05).

CONCLUSIONS

Prenatal iron supplementation reduced anemia, ID, and IDA in pregnant women in rural China, but most women and >45% of neonates had ID, regardless of supplementation. This trial was registered at clinicaltrials.gov as NCT02221752.

The human placental methylome

This review provides an overview of the unique features of DNA methylation in the human placenta. We discuss the importance of understanding placental development, structure, and function in the interpretation of DNA methylation data. Examples are given of how DNA methylation is important in regulating placental-specific gene expression, including monoallelic expression and X-chromosome inactivation in the placenta. We also discuss studies of global DNA methylation changes in the context of placental pathology and environmental exposures.

Increased glucose and placental GLUT-1 in large infants of obese nondiabetic mothers

OBJECTIVE

Obese women are at increased risk to deliver a large infant, however, the underlying mechanisms are poorly understood. Fetal glucose availability is critically dependent on placental transfer and is linked to fetal growth by regulating the release of fetal growth hormones such as insulin. We hypothesized that (1) umbilical vein glucose and insulin levels and (2) placental glucose transporter (GLUT) expression and activity are positively correlated with early pregnancy maternal body mass index and infant birthweight.

STUDY DESIGN

Subjects in this prospective observational cohort study were nondiabetic predominantly Hispanic women delivered at term. Fasting maternal and umbilical vein glucose and insulin concentrations were determined in 29 women with varying early pregnancy body mass index (range, 18.0-54.3) who delivered infants with birthweights ranging from 2800-4402 g. We isolated syncytiotrophoblast microvillous and basal plasma membranes from 33 placentas and determined the expression of GLUT-1 and -9 (Western blot) and glucose uptake (radiolabeled glucose).

RESULTS

Birthweight was positively correlated with umbilical vein glucose and insulin and maternal body mass index. Umbilical vein glucose levels were positively correlated with placental weight and maternal body mass index, but not with maternal fasting glucose. Basal plasma membranes GLUT-1 expression was positively correlated with birthweight. In contrast, syncytiotrophoblast microvillous GLUT-1 and -9, basal plasma membranes GLUT-9 expression and syncytiotrophoblast microvillous and basal plasma membranes glucose transport activity were not correlated with birthweight.

CONCLUSION

Because maternal fasting glucose levels and placental glucose transport capacity were not increased in obese women delivering larger infants, we speculate that increased placental size promotes glucose delivery to these fetuses.

Neonatal iron status is impaired by maternal obesity and excessive weight gain during pregnancy

OBJECTIVE

Maternal iron needs increase sixfold during pregnancy, but obesity interferes with iron absorption. We hypothesized that maternal obesity impairs fetal iron status.

STUDY DESIGN

Three hundred and sixteen newborns with risk factors for infantile iron deficiency anemia (IDA) were studied to examine obesity during pregnancy and neonatal iron status. Erythrocyte iron was assessed by cord blood hemoglobin (Hb), zinc protoporphyrin/heme (ZnPP/H) and reticulocyte-ZnPP/H, and storage iron by serum ferritin.

RESULT

Women with body mass index (BMI) ⩾ 30 kg m(-)(2), as compared with non-obese women, delivered larger offspring with higher reticulocyte-ZnPP/H and lower serum ferritin concentrations (P<0.05 for both). With increasing BMI, the estimated body iron was relatively lower (mg kg(-)(1)) and the ratio of total Hb-bound iron (mg) per total body iron (mg) increased. Maternal diabetes compromised infant iron status, but multivariate analysis demonstrated that obesity was an independent predictor.

CONCLUSION

Obesity during pregnancy and excessive weight gain are independent risk factors for iron deficiency in the newborn.

Marked Biological Variance in Endocrine and Biochemical Markers in Childhood: Establishment of Pediatric Reference Intervals Using Healthy Community Children from the CALIPER Cohort

BACKGROUND

Reference intervals are indispensable in evaluating laboratory test results; however, appropriately partitioned pediatric reference values are not readily available. The Canadian Laboratory Initiative for Pediatric Reference Intervals (CALIPER) program is aimed at establishing the influence of age, sex, ethnicity, and body mass index on biochemical markers and developing a comprehensive database of pediatric reference intervals using an a posteriori approach.

METHODS

A total of 1482 samples were collected from ethnically diverse healthy children ages 2 days to 18 years and analyzed on the Abbott ARCHITECT i2000. Following the CLSI C28-A3 guidelines, age- and sex-specific partitioning was determined for each analyte. Nonparametric and robust methods were used to establish the 2.5th and 97.5th percentiles for the reference intervals as well as the 90% CIs.

RESULTS

New pediatric reference intervals were generated for 14 biomarkers, including α-fetoprotein, cobalamin (vitamin B12), folate, homocysteine, ferritin, cortisol, troponin I, 25(OH)-vitamin D [25(OH)D], intact parathyroid hormone (iPTH), thyroid-stimulating hormone, total thyroxine (TT4), total triiodothyronine (TT3), free thyroxine (FT4), and free triiodothyronine. The influence of ethnicity on reference values was also examined, and statistically significant differences were found between ethnic groups for FT4, TT3, TT4, cobalamin, ferritin, iPTH, and 25(OH)D.

CONCLUSIONS

This study establishes comprehensive pediatric reference intervals for several common endocrine and immunochemical biomarkers obtained in a large cohort of healthy children. The new database will be of global benefit, ensuring appropriate interpretation of pediatric disease biomarkers, but will need further validation for specific immunoassay platforms and in local populations as recommended by the CLSI.

Body iron delocalization: the serious drawback in iron disorders in both developing and developed countries

Over 2 billion people in both developing as well as developed countries - over 30% of the world's population - are anaemic. With the classical preconception that oral iron administration or the intake of foods rich in iron increase haemoglobin concentration and reduce the prevalence of anaemia, specific programs have been designed, but iron supplementations have been less effective than expected. Of note, this hazardous simplification on iron status neglects its distribution in the body. The correct balance of iron, defined iron homeostasis, involves a physiological ratio of iron between tissues/secretions and blood, thus avoiding its delocalization as iron accumulation in tissues/secretions and iron deficiency in blood. Changes in iron status can affect the inflammatory response in multiple ways, particularly in the context of infection, an idea that is worth remembering when considering the value of iron supplementation in areas of the world where infections are highly prevalent. The enhanced availability of free iron can increase susceptibility and severity of microbial and parasitic infections. The discovery of the hepcidin-ferroportin (Fpn) complex, which greatly clarified the enigmatic mechanism that supervises the iron homeostasis, should prompt to a critical review on iron supplementation, ineffective on the expression of the most important proteins of iron metabolism. Therefore, it is imperative to consider new safe and efficient therapeutic interventions to cure iron deficiency (ID) and ID anaemia (IDA) associated or not to the inflammation. In this respect, lactoferrin (Lf) is emerging as an important regulator of both iron and inflammatory homeostasis. Oral administration of Lf in subjects suffering of ID and IDA is safe and effective in significantly increasing haematological parameters and contemporary decreasing serum IL-6 levels, thus restoring iron localization through the direct or indirect modulation of hepcidin and ferroportin synthesis. Of note, the nuclear localization of Lf suggests that this molecule may be involved in the transcriptional regulation of some genes of host inflammatory response. We recently also reported that combined administration of oral and intravaginal Lf on ID and IDA pregnant women with preterm delivery threat, significantly increased haematological parameters, reduced IL-6 levels in both serum and cervicovaginal fluid, cervicovaginal prostaglandin PGF2α, and suppressed uterine contractility. Moreover, Lf combined administration blocked further the shortening of cervical length and the increase of foetal fibronectin, thus prolonging the length of pregnancy until the 37th-38th week of gestation. These new Lf functions effective in curing ID and IDA through the restoring of iron and inflammatory homeostasis and in preventing preterm delivery, could have a great relevance in developing countries, where ID and IDA and inflammation-associated anaemia represent the major risk factors of preterm delivery and maternal and neonatal death.

Ovine uterine space restriction alters placental transferrin receptor and fetal iron status during late pregnancy

BACKGROUND

Fetal growth restriction is reported to be associated with impaired placental iron transport. Transferrin receptor (TfR) is a major placental iron transporter in humans but has not been studied in sheep. TfR is regulated by both iron and nitric oxide (NO), the molecule produced by endothelial nitric oxide synthase (eNOS). We hypothesized that limited placental development downregulates both placental TfR and eNOS expression, thereby lowering fetal tissue iron.

METHODS

An ovine surgical uterine space restriction (USR) model, combined with multifetal gestation, tested the extremes of uterine and placental adaptation. Blood, tissues, and placentomes from non-space restricted (NSR) singletons were compared with USR fetuses at gestational day (GD) 120 or 130.

RESULTS

When expressed proportionate to fetal weight, liver iron content did not differ, whereas renal iron was higher in USR vs. NSR fetuses. Renal TfR protein expression did not differ, but placental TfR expression was lower in USR fetuses at GD130. Placental levels of TfR correlated to eNOS. TfR was localized throughout the placentome, including the hemophagous zone, implicating a role for TfR in ovine placental iron transport.

CONCLUSION

Fetal iron was regulated in an organ-specific manner. In USR fetuses, NO-mediated placental adaptations may prevent the normal upregulation of placental TfR at GD130.

Maternal serum ferritin concentration is positively associated with newborn iron stores in women with low ferritin status in late pregnancy

Iron deficiency (ID) is common in pregnant women and infants, particularly in developing countries. The relation between maternal and neonatal iron status remains unclear. This study considered the issue in a large sample of mother-newborn pairs in rural southeastern China. Hemoglobin (Hb) and serum ferritin (SF) were measured in 3702 pregnant women at ≥37 wk gestation and in cord blood of their infants born at term (37-42 wk gestation). Maternal anemia (Hb <110 g/L) was present in 27.5% and associated with maternal SF <20 μg/L in 86.9%. Only 5.6% of neonates were anemic (Hb <130 g/L) and 9.5% had cord-blood SF <75 μg/L. There were low-order correlations between maternal and newborn iron measures (r = 0.07-0.10 for both Hb and SF; P ≤ 0.0001 due to the large number). We excluded 430 neonates with suggestion of inflammation [cord SF >370 μg/L, n = 208 and/or C-reactive protein (CRP) >5 mg/L, n = 233]. Piecewise linear regression analyses identified a threshold for maternal SF at which cord-blood SF was affected. For maternal SF below the threshold of 13.6 μg/L (β = 2.4; P = 0.001), cord SF was 0.17 SD lower than in neonates whose mothers had SF above the threshold (167 ± 75 vs. 179 ± 80 μg/L). The study confirmed that ID anemia remains common during pregnancy in rural southeastern China. Despite widespread maternal ID, however, iron nutrition seemed to meet fetal needs except when mothers were very iron deficient. The impact of somewhat lower cord SF on iron status later in infancy warrants further study.

Evolution of Placental Function in Mammals: The Molecular Basis of Gas and Nutrient Transfer, Hormone Secretion, and Immune Responses

Placenta has a wide range of functions. Some are supported by novel genes that have evolved following gene duplication events while others require acquisition of gene expression by the trophoblast. Although not expressed in the placenta, high-affinity fetal hemoglobins play a key role in placental gas exchange. They evolved following duplications within the beta-globin gene family with convergent evolution occurring in ruminants and primates. In primates there was also an interesting rearrangement of a cassette of genes in relation to an upstream locus control region. Substrate transfer from mother to fetus is maintained by expression of classic sugar and amino acid transporters at the trophoblast microvillous and basal membranes. In contrast, placental peptide hormones have arisen largely by gene duplication, yielding for example chorionic gonadotropins from the luteinizing hormone gene and placental lactogens from the growth hormone and prolactin genes. There has been a remarkable degree of convergent evolution with placental lactogens emerging separately in the ruminant, rodent, and primate lineages and chorionic gonadotropins evolving separately in equids and higher primates. Finally, coevolution in the primate lineage of killer immunoglobulin-like receptors and human leukocyte antigens can be linked to the deep invasion of the uterus by trophoblast that is a characteristic feature of human placentation.

Molecular insights into the regulation of iron metabolism during the prenatal and early postnatal periods

Molecular iron metabolism and its regulation are least well understood in the fetal and early postnatal periods of mammalian ontogenic development. The scope of this review is to summarize recent progress in uncovering the molecular mechanisms of fetal iron homeostasis, introduce the molecules involved in iron transfer across the placenta, and briefly explain the role of iron transporters in the absorption of this microelement during early postnatal life. These issues are discussed and parallels are drawn with the relatively well-established system for elemental and heme iron regulation in adult mammals. We conclude that detailed investigations into the regulatory mechanisms of iron metabolism at early stages of development are required in order to optimize strategies to prevent neonatal iron deficiency. We propose that newborn piglets represent a suitable animal model for studies on iron deficiency anemia in neonates.

Fetal regulation of iron transport during pregnancy

During pregnancy, iron is transported from mother to fetus across the placenta. Iron is essential for many biological processes, including the transfer of oxygen in blood, but it can also be toxic. Elaborate and elegant mechanisms have evolved to make sure that the potential for oxidative damage is minimized. In this article, we examine how iron is transferred from the maternal liver to the placenta, taken up, and transferred to the fetal liver. We consider the molecular mechanisms and how they are regulated. In addition, we use data from previously published articles to examine how the processes are regulated and what adaptations can occur to ameliorate the consequences of iron deficiency--an all too common problem in pregnancy, even in the developed world. Finally, we examine some of the many questions that remain about the transfer process and consider how nutrients interact and what the consequences of these interactions may be for the mother and her developing infant.

Transferrin receptor gene and protein expression and localization in human IUGR and normal term placentas

Iron (Fe) deficiency in pregnancy is associated to low birth weight and premature delivery while in adults it can result in increased blood pressure and cardiovascular disease. Cellular Fe uptake is mediated by the Transferrin Receptor 1 (TFRC), located in the trophoblast membranes. Here, we measured TFRC mRNA expression (Real Time PCR) and TFRC protein expression and localization (Western Blotting and immunohistochemistry) in IUGR compared to control placentas. A total of 50 IUGR and 56 control placentas were studied at the time of elective cesarean section. IUGR was defined by ultrasound in utero, and confirmed by birth weight <10th percentile. Three different severity groups were identified depending on the umbilical artery pulsatility index and fetal heart rate. TFRC mRNA expression was significantly lower in IUGR placentas compared to controls (p < 0.05), and this was confirmed for TFRC protein levels. In both experiments the most severe IUGR group presented lower expression compared to the other groups, and this was also related to umbilical venous oxygen levels. TFRC protein localization in the villous trophoblast did not differ in the groups, and was predominantly present in the syncytiotrophoblast. In conclusion, these are the first observations about TFRC expression in human IUGR placentas, demonstrating its significant decrease in IUGR vs controls. Thus, Fe transport could be limited in IUGR placentas. Further studies are needed to study components of the placental Fe transport system and to clarify the regulation mechanisms involved in TFRC expression, possibly altered in IUGR placentas.

Lactoferrin efficacy versus ferrous sulfate in curing iron deficiency and iron deficiency anemia in pregnant women

Iron deficiency (ID) and iron deficiency anemia (IDA) are the most common iron disorders throughout the world. ID and IDA, particularly caused by increased iron requirements during pregnancy, represent a high risk for preterm delivery, fetal growth retardation, low birth weight, and inferior neonatal health. Oral administration of ferrous sulfate to cure ID and IDA in pregnancy often fails to increase hematological parameters, causes adverse effects and increases inflammation. Recently, we have demonstrated safety and efficacy of oral administration of 30% iron saturated bovine lactoferrin (bLf) in pregnant women suffering from ID and IDA. Oral administration of bLf significantly increases the number of red blood cells, hemoglobin, total serum iron and serum ferritin already after 30 days of the treatment. The increasing of hematological values by bLf is related to the decrease of serum IL-6 and the increase of serum hepcidin, detected as prohepcidin, whereas ferrous sulfate increases IL-6 and fails to increase hematological parameters and prohepcidin. bLf is a more effective and safer alternative than ferrous sulfate for treating ID and IDA in pregnant women.

Iron homeostasis in the neonate

The regulation of the availability of micronutrients is particularly critical during periods of rapid growth and differentiation such as the fetal and neonatal stages. Both iron deficiency and excess during the early weeks of life can have severe effects on neurodevelopment that may persist into adulthood and may not be corrected by restoration of normal iron levels. This article provides a succinct overview of our current understanding of the extent to which newborns, particularly premature newborns, are able (or not able) to regulate their iron status according to physiologic need. Postnatal development of factors important to iron homeostasis such as intestinal transport, extracellular transport, cellular uptake and storage, intracellular regulation, and systemic control are examined. Also reviewed are how factors peculiar to the sick and premature neonate can further adversely influence iron homeostasis and exacerbate iron-induced oxidative stress, predispose the infant to bacterial infections, and, thus, compromise his or her clinical situation further. The article concludes with a discussion of the areas of relative ignorance that require urgent investigation to rectify our lack of understanding of iron homeostasis in what is a critical stage of development.

Predictors of serum ferritin and serum soluble transferrin receptor in newborns and their associations with iron status during the first 2 y of life

BACKGROUND

Adequate iron status at birth may prevent iron deficiency in early childhood.

OBJECTIVES

We aimed to identify predictors of serum ferritin (SF) and serum soluble transferrin receptor (sTfR) in healthy newborns and to relate these iron indexes to iron status in the first 2 y of life.

DESIGN

Using bivariate correlations and linear regression, we related various factors in pregnancy to SF (n=363) and sTfR (n=350) in healthy, term infants. Measurements of cord SF and sTfR were compared with those of SF and sTfR at 6, 12, and 24 mo. All 4 measurements were available for 191 and 169 infants for SF and sTfR, respectively.

RESULTS

Geometric mean (and 95% CI) cord SF and sTfR measurements were 159 (148, 171) microg/L and 7.3 (7.0, 7.6) mg/L, respectively. Cord SF correlated with sTfR (rho=-0.21, P<0.001). In regression analysis, cord SF correlated with smoking and the use of iron supplements during pregnancy (partial r=-0.12 and 0.16; P<0.05 for both). Cord sTfR was associated with first trimester BMI, gestational age, and male sex (partial r=0.30, 0.24, and 0.19, respectively; P<0.01 for all). Cord SF correlated with SF at 6, 12, and 24 mo (rho=0.45, 0.31, and 0.16 respectively; P<0.05 for all). At age 6 mo, 16 of 17 infants with SF <15 mug/L were boys.

CONCLUSIONS

Cessation of smoking and adequate iron prophylaxis during pregnancy may improve iron status in infancy. Cord SF is a predictor of iron status in the first 2 y of life. Boys are at particular risk of low iron status in early infancy.