Oral iron therapy: Current concepts and future prospects for improving efficacy and outcomes.

Iron deficiency (ID) and iron-deficiency anaemia (IDA) are global public health concerns, most commonly afflicting children, pregnant women and women of childbearing age. Pathological outcomes of ID include delayed cognitive development in children, adverse pregnancy outcomes and decreased work capacity in adults. IDA is usually treated by oral iron supplementation, typically using iron salts (e.g. FeSO4 ); however, dosing at several-fold above the RDA may be required due to less efficient absorption. Excess enteral iron causes adverse gastrointestinal side effects, thus reducing compliance, and negatively impacts the gut microbiome. Recent research has sought to identify new iron formulations with better absorption so that lower effective dosing can be utilized. This article outlines emerging research on oral iron supplementation and focuses on molecular mechanisms by which different supplemental forms of iron are transported across the intestinal epithelium and whether these transport pathways are subject to regulation by the iron-regulatory hormone hepcidin.

A Decrease in Maternal Iron Levels Is the Predominant Factor Suppressing Hepcidin during Pregnancy in Mice.

In order to supply adequate iron during pregnancy, the levels of the iron regulatory hormone hepcidin in the maternal circulation are suppressed, thereby increasing dietary iron absorption and storage iron release. Whether this decrease in maternal hepcidin is caused by changes in factors known to regulate hepcidin expression, or by other unidentified pregnancy factors, is not known. To investigate this, we examined iron parameters during pregnancy in mice. We observed that hepatic iron stores and transferrin saturation, both established regulators of hepcidin production, were decreased in mid and late pregnancy in normal and iron loaded dams, indicating an increase in iron utilization. This can be explained by a significant increase in maternal erythropoiesis, a known suppressor of hepcidin production, by mid-pregnancy, as indicated by an elevation in circulating erythropoietin and an increase in spleen size and splenic iron uptake. Iron utilization increased further in late pregnancy due to elevated fetal iron demand. By increasing maternal iron levels in late gestation, we were able to stimulate the expression of the gene encoding hepcidin, suggesting that the iron status of the mother is the predominant factor influencing hepcidin levels during pregnancy. Our data indicate that pregnancy-induced hepcidin suppression likely occurs because of reductions in maternal iron reserves due to increased iron requirements, which predominantly reflect stimulated erythropoiesis in mid-gestation and increased fetal iron requirements in late gestation, and that there is no need to invoke other factors, including novel pregnancy factor(s), to explain these changes.

The biology of mammalian multi-copper ferroxidases.

The mammalian multicopper ferroxidases (MCFs) ceruloplasmin (CP), hephaestin (HEPH) and zyklopen (ZP) comprise a family of conserved enzymes that are essential for body iron homeostasis. Each of these enzymes contains six biosynthetically incorporated copper atoms which act as intermediate electron acceptors, and the oxidation of iron is associated with the four electron reduction of dioxygen to generate two water molecules. CP occurs in both a secreted and GPI-linked (membrane-bound) form, while HEPH and ZP each contain a single C-terminal transmembrane domain. These enzymes function to ensure the efficient oxidation of iron so that it can be effectively released from tissues via the iron export protein ferroportin and subsequently bound to the iron carrier protein transferrin in the blood. CP is particularly important in facilitating iron release from the liver and central nervous system, HEPH is the major MCF in the small intestine and is critical for dietary iron absorption, and ZP is important for normal hair development. CP and HEPH (and possibly ZP) function in multiple tissues. These proteins also play other (non-iron-related) physiological roles, but many of these are ill-defined. In addition to disrupting iron homeostasis, MCF dysfunction perturbs neurological and immune function, alters cancer susceptibility, and causes hair loss, but, despite their importance, how MCFs co-ordinately maintain body iron homeostasis and perform other functions remains incompletely understood.

Longitudinal changes in iron homeostasis in human experimental and clinical malaria.

Background: The interaction between iron deficiency and malaria is incompletely understood. We evaluated longitudinal changes in iron homeostasis in volunteers enrolled in malaria volunteer infection studies (VIS) and in Malaysian patients with falciparum and vivax malaria. Methods: We retrieved samples and associated data from 55 participants enrolled in malaria VIS, and 171 malaria patients and 30 healthy controls enrolled in clinical studies in Malaysia. Ferritin, hepcidin, erythropoietin, and soluble transferrin receptor (sTfR) were measured by ELISA. Results: In the VIS, participants' parasitaemia was correlated with baseline mean corpuscular volume (MCV), but not iron status (ferritin, hepcidin or sTfR). Ferritin, hepcidin and sTfR all increased during the VIS. Ferritin and hepcidin normalised by day 28, while sTfR remained elevated. In VIS participants, baseline iron status (ferritin) was associated with post-treatment increases in liver transaminase levels. In Malaysian malaria patients, hepcidin and ferritin were elevated on admission compared to healthy controls, while sTfR increased following admission. Hepcidin normalised by day 28; however, ferritin and sTfR both remained elevated 4 weeks following admission. Conclusion: Our findings demonstrate that parasitaemia is associated with an individual's MCV rather than iron status. The persistent elevation in sTfR 4 weeks post-infection in both malaria VIS and clinical malaria may reflect a causal link between malaria and iron deficiency.

Engineering Peptide Inhibitors of the HFE-Transferrin Receptor 1 Complex.

The protein HFE (homeostatic iron regulator) is a key regulator of iron metabolism, and mutations in HFE underlie the most frequent form of hereditary haemochromatosis (HH-type I). Studies have shown that HFE interacts with transferrin receptor 1 (TFR1), a homodimeric type II transmembrane glycoprotein that is responsible for the cellular uptake of iron via iron-loaded transferrin (holo-transferrin) binding. It has been hypothesised that the HFE/TFR1 interaction serves as a sensor to the level of iron-loaded transferrin in circulation by means of a competition mechanism between HFE and iron-loaded transferrin association with TFR1. To investigate this, a series of peptides based on the helical binding interface between HFE and TFR1 were generated and shown to significantly interfere with the HFE/TFR1 interaction in an in vitro proximity ligation assay. The helical conformation of one of these peptides, corresponding to the α1 and α2 helices of HFE, was stabilised by the introduction of sidechain lactam "staples", but this did not result in an increase in the ability of the peptide to disrupt the HFE/TFR1 interaction. These peptides inhibitors of the protein-protein interaction between HFE and TFR1 are potentially useful tools for the analysis of the functional role of HFE in the regulation of hepcidin expression.

Supplementation with Sucrosomial® iron leads to favourable changes in the intestinal microbiome when compared to ferrous sulfate in mice.

Iron deficiency is one of the most common nutritional deficiencies worldwide and is often treated with oral iron supplements. However, commonly used supplements, including those based on ferrous iron salts, are associated with gastrointestinal side effects and unfavorable changes in the intestinal microbiome. Sucrosomial® iron is a novel iron formulation that is effective at treating iron deficiency, and with fewer gastrointestinal side effects, yet its effect on the gut microbiome has not been examined previously. Thus, we treated mice for two weeks with diets containing either Sucrosomial® iron or ferrous sulfate as the sole iron source and examined bacterial communities in the intestine using 16S Microbial Profiling of DNA extracted from feces collected both prior to and following dietary treatment. Mice treated with Sucrosomial® iron showed an increase in Shannon diversity over the course of the study. This was associated with a decrease in the abundance of the phylum Proteobacteria, which contains many pathogenic species, and an increase in short chain fatty acid producing bacteria such as Lachnospiraceae, Oscillibacter and Faecalibaculum. None of these changes were observed in mice treated with ferrous sulfate. These results suggest that Sucrosomial® iron may have a beneficial effect on the intestinal microbiome when compared to ferrous sulfate and that this form of iron is a promising alternative to ferrous iron salts for the treatment of iron deficiency.

A Novel Ferritin-Core Analog Is a Safe and Effective Alternative to Oral Ferrous Iron for Treating Iron Deficiency during Pregnancy in Mice.

BACKGROUND: Many women enter pregnancy with iron stores that are insufficient to maintain maternal iron balance and support fetal development and consequently, often require iron supplements. However, the side effects associated with many currently available iron supplements can limit compliance. OBJECTIVE: This study aimed to test the safety and efficacy of a novel nanoparticulate iron supplement, a dietary ferritin analog termed iron hydroxide adipate tartrate (IHAT), in pregnant mice. METHODS: Female C57BL/6 mice were maintained on either an iron-deficient or a control diet for 2 wk prior to timed mating to develop iron-deficient or iron-sufficient pregnancy models, respectively. Mice from each model were then gavaged daily with 10 mg iron/kg body weight as either IHAT or ferrous sulfate, or with water only, beginning on embryonic day (E) 4.5. Mice were killed on E18.5 and maternal iron and hematological parameters were measured. The expression of genes encoding iron transporters and oxidative stress markers in the duodenum and placenta were determined, along with hepatic expression of the gene encoding the iron regulatory hormone hepcidin and fetal iron. RESULTS: Oral IHAT and ferrous sulfate were equally effective at increasing maternal hemoglobin (20.2% and 16.9%, respectively) and hepatic iron (30.2% and 29.3%, respectively), as well as total fetal iron (99.7% and 83.8%, respectively), in iron-deficient pregnant mice compared with those gavaged with water only, with no change in oxidative stress markers seen with either treatment. However, there was a significant increase in the placental expression of the oxidative stress marker heme oxygenase 1 in iron-replete pregnant mice treated with ferrous sulfate when compared with iron-replete pregnant mice gavaged with IHAT (96.9%, P <0.05). CONCLUSIONS: IHAT has proved a safe and effective alternative to oral ferrous sulfate in mice, and it has potential for treating iron deficiency in human pregnancy.

Increased susceptibility of cystic fibrosis airway epithelial cells to ferroptosis.

BACKGROUND: Defective chloride transport in airway epithelial cells (AECs) and the associated lung disease are the main causes of morbidity and early mortality in cystic fibrosis (CF). Abnormal airway iron homeostasis and the presence of lipid peroxidation products, indicative of oxidative stress, are features of CF lung disease. RESULTS: Here, we report that CF AECs (IB3-1) are susceptible to ferroptosis, a type of cell death associated with iron accumulation and lipid peroxidation. Compared to isogenic CFTR corrected cells (C38), the IB3-1 cells showed increased susceptibility to cell death upon exposure to iron in the form of ferric ammonium citrate (FAC) and the ferroptosis inducer, erastin. This phenotype was accompanied by accumulation of intracellular ferrous iron and lipid peroxides and the extracellular release of malondialdehyde, all indicative of redox stress, and increased levels of lactate dehydrogenase in the culture supernatant, indicating enhanced cell injury. The ferric iron chelator deferoxamine (DFO) and the lipophilic antioxidant ferrostatin-1 inhibited FAC and erastin induced ferroptosis in IB3-1 cells. Glutathione peroxidase 4 (GPX4) expression was decreased in IB3-1 cells treated with FAC and erastin, but was unchanged in C38 AECs. Necroptosis appeared to be involved in the enhanced susceptibility of IB3-1 AECs to ferroptosis, as evidenced by partial cell death rescue with necroptosis inhibitors and enhanced mixed lineage kinase domain-like (MLKL) localisation to the plasma membrane. CONCLUSION: These studies suggest that the increased susceptibility of CF AECs to ferroptosis is linked to abnormal intracellular ferrous iron accumulation and reduced antioxidant defences. In addition, the process of ferroptotic cell death in CF AECs does not appear to be a single entity and for the first time we describe necroptosis as a potential contributory factor. Iron chelation and antioxidant treatments may be promising therapeutic interventions in cystic fibrosis.

Investigating the Links between Lower Iron Status in Pregnancy and Respiratory Disease in Offspring Using Murine Models.

Maternal iron deficiency occurs in 40-50% of all pregnancies and is associated with an increased risk of respiratory disease and asthma in children. We used murine models to examine the effects of lower iron status during pregnancy on lung function, inflammation and structure, as well as its contribution to increased severity of asthma in the offspring. A low iron diet during pregnancy impairs lung function, increases airway inflammation, and alters lung structure in the absence and presence of experimental asthma. A low iron diet during pregnancy further increases these major disease features in offspring with experimental asthma. Importantly, a low iron diet increases neutrophilic inflammation, which is indicative of more severe disease, in asthma. Together, our data demonstrate that lower dietary iron and systemic deficiency during pregnancy can lead to physiological, immunological and anatomical changes in the lungs and airways of offspring that predispose to greater susceptibility to respiratory disease. These findings suggest that correcting iron deficiency in pregnancy using iron supplements may play an important role in preventing or reducing the severity of respiratory disease in offspring. They also highlight the utility of experimental models for understanding how iron status in pregnancy affects disease outcomes in offspring and provide a means for testing the efficacy of different iron supplements for preventing disease.

The Placental Ferroxidase Zyklopen Is Not Essential for Iron Transport to the Fetus in Mice.

BACKGROUND: The ferroxidase zyklopen (Zp) has been implicated in the placental transfer of iron to the fetus. However, the evidence for this is largely circumstantial. OBJECTIVES: This study aimed to determine whether Zp is essential for placental iron transfer. METHODS: A model was established using 8- to 12-wk-old pregnant C57BL/6 mice on standard rodent chow in which Zp was knocked out in the fetus and fetal components of the placenta. Zp was also disrupted in the entire placenta using global Zp knockout mice. Inductively coupled plasma MS was used to measure total fetal iron, an indicator of the amount of iron transferred by the placenta to the fetus, at embryonic day 18.5 of gestation. Iron transporter expression in the placenta was measured by Western blotting, and the expression of Hamp1, the gene encoding the iron regulatory hormone hepcidin, was determined in fetal liver by real-time PCR. RESULTS: There was no change in the amount of iron transferred to the fetus when Zp was disrupted in either the fetal component of the placenta or the entire placenta. No compensatory changes in the expression of the iron transport proteins transferrin receptor 1 or ferroportin were observed, nor was there any change in fetal liver Hamp1 mRNA. Hephl1, the gene encoding Zp, was expressed mainly in the maternal decidua of the placenta and not in the nutrient-transporting syncytiotrophoblast. Disruption of Zp in the whole placenta resulted in a 26% increase in placental size (P < 0.01). CONCLUSIONS: Our data indicate that Zp is not essential for the efficient transfer of iron to the fetus in mice and is localized predominantly in the maternal decidua. The increase in placental size observed when Zp is knocked out in the entire placenta suggests that this protein may play a role in placental development.

Increased susceptibility of cystic fibrosis airway epithelial cells to ferroptosis

BACKGROUND: Defective chloride transport in airway epithelial cells (AECs) and the associated lung disease are the main causes of morbidity and early mortality in cystic fibrosis (CF). Abnormal airway iron homeostasis and the presence of lipid peroxidation products, indicative of oxidative stress, are features of CF lung disease. RESULTS: Here, we report that CF AECs (IB3-1) are susceptible to ferroptosis, a type of cell death associated with iron accumulation and lipid peroxidation. Compared to isogenic CFTR corrected cells (C38), the IB3-1 cells showed increased susceptibility to cell death upon exposure to iron in the form of ferric ammonium citrate (FAC) and the ferroptosis inducer, erastin. This phenotype was accompanied by accumulation of intracellular ferrous iron and lipid peroxides and the extracellular release of malondialdehyde, all indicative of redox stress, and increased levels of lactate dehydrogenase in the culture supernatant, indicating enhanced cell injury. The ferric iron chelator defer-oxamine (DFO) and the lipophilic antioxidant ferrostatin-1 inhibited FAC and erastin induced ferroptosis in IB3-1 cells. Glutathione peroxidase 4 (GPX4) expression was decreased in IB3-1 cells treated with FAC and erastin, but was unchanged in C38 AECs. Necroptosis appeared to be involved in the enhanced susceptibility of IB3-1 AECs to ferroptosis, as evidenced by partial cell death rescue with necroptosis inhibitors and enhanced mixed lineage kinase domain-like (MLKL) localisation to the plasma membrane. CONCLUSION: These studies suggest that the increased susceptibility of CF AECs to ferroptosis is linked to abnormal intracellular ferrous iron accumulation and reduced antioxidant defences. In addition, the process of ferroptotic cell death in CF AECs does not appear to be a single entity and for the first time we describe necroptosis as a potential contributory factor. Iron chelation and antioxidant treatments may be promising therapeutic interventions in cystic fibrosis.

Dihydrolipoic Acid-Gold Nanoclusters Regulate Microglial Polarization and Have the Potential To Alter Neurogenesis.

Microglia-mediated neuroinflammation is one of the most significant features in a variety of central nervous system (CNS) disorders such as traumatic brain injury, stroke, and many neurodegenerative diseases. Microglia become polarized upon stimulation. The two extremes of the polarization are the neuron-destructive proinflammatory M1-like and the neuron-regenerative M2-like phenotypes. Thus, manipulating microglial polarization toward the M2 phenotype is a promising therapeutic approach for CNS repair and regeneration. It has been reported that nanoparticles are potential tools for regulating microglial polarization. Gold nanoclusters (AuNCs) could penetrate the blood-brain barrier and have neuroprotective effects, suggesting the possibility of utilizing AuNCs to regulate microglial polarization and improve neuronal regeneration in CNS. In the current study, AuNCs functionalized with dihydrolipoic acid (DHLA-AuNCs), an antioxidant with demonstrated neuroprotective roles, were prepared, and their effects on polarization of a microglial cell line (BV2) were examined. DHLA-AuNCs effectively suppressed proinflammatory processes in BV2 cells by inducing polarization toward the M2-like phenotype. This was associated with a decrease in reactive oxygen species and reduced NF-kB signaling and an improvement in cell survival coupled with enhanced autophagy and inhibited apoptosis. Conditioned medium from DHLA-AuNC-treated BV2 cells was able to enhance neurogenesis in both the neuronal cell line N2a and in an ex vivo brain slice stroke model. The direct treatment of brain slices with DHLA-AuNCs also ameliorated stroke-related tissue injury and reduced astrocyte activation (astrogliosis). This study suggests that by regulating neuroinflammation to improve neuronal regeneration, DHLA-AuNCs could be a potential therapeutic agent in CNS disorders.

Mice overexpressing hepcidin suggest ferroportin does not play a major role in Mn homeostasis.

Manganese is an essential metal that is required for a wide range of biological functions. Ferroportin (FPN), the only known cellular exporter of iron, has also been proposed to play a role in manganese export, but this relationship is incompletely understood. To investigate this in more detail in vivo, we examined the relative distributions of manganese and iron in TMPRSS6 deficient mice, which are characterized by constitutively high expression of the iron regulatory hormone hepcidin and, consequently, very low FPN levels in their tissues. Tmprss6-/- mice showed frank iron deficiency and reduced iron levels in most tissues, consistent with FPN playing an important role in the distribution of this metal, but manganese levels were largely unaffected. Associated studies using intestine-specific FPN knockout mice showed that loss of FPN significantly reduced the dietary absorption of iron, but had no effect on manganese intake. Taken together, our data suggest that FPN does not play a major role in Mn transport in vivo. They do not exclude a minor role for FPN in manganese homeostasis, nor the possibility that the transporter may be relevant at high Mn levels, but at physiological levels of this metal, other transport proteins appear to be more important.

Dietary iron absorption during early postnatal life.

Inadequate iron levels during early life can have adverse consequences for the developing infant. Iron deficiency during this critical period of growth can affect brain development and cognitive function, problems that can be lifelong despite subsequent correction of the iron deficit. Therefore, it is critical that the suckling infant has sufficient iron for their developmental needs. Much of the iron used in the immediate post-natal period is stored iron that was acquired from the mother in the final trimester of pregnancy, however, despite having low iron levels, breast milk can also make a significant contribution to infant iron needs. This reflects the ability of the suckling infant to absorb dietary iron far more efficiently than is possible after weaning. The mechanisms underlying this enhanced iron absorption are poorly understood. The iron export protein ferroportin is essential for this process, as it is in adults, however, the role of other molecules normally involved in iron absorption following weaning is less clear. The composition and distribution of iron in breast milk may be important, as could the contribution of more distal parts of the gastrointestinal tract. This review discusses the potential role of each of the above components in intestinal iron absorption during suckling and highlights the need for further research into this important process.

Severe Iron Metabolism Defects in Mice With Double Knockout of the Multicopper Ferroxidases Hephaestin and Ceruloplasmin.

Background & Aims: Multicopper ferroxidases (MCFs) facilitate intestinal iron absorption and systemic iron recycling, likely by a mechanism involving the oxidization of Fe2+ from the iron exporter ferroportin 1 for delivery to the circulating Fe3+ carrier transferrin. Hephaestin (HEPH), the only MCF known to be expressed in enterocytes, aids in the basolateral transfer of dietary iron to the blood. Mice lacking HEPH in the whole body (Heph-/- ) or intestine alone (Hephint/int ) exhibit defects in dietary iron absorption but still survive and grow. Circulating ceruloplasmin (CP) is the only other known MCF likely to interact with enterocytes. Our aim was to assess the effects of combined deletion of HEPH and CP on intestinal iron absorption and homeostasis in mice. Methods: Mice lacking both HEPH and CP (Heph-/-Cp-/- ) and mice with whole-body knockout of CP and intestine-specific deletion of HEPH (Hephint/intCp-/- ) were generated and phenotyped. Results: Heph-/-Cp-/- mice were severely anemic and had low serum iron, but they exhibited marked iron loading in duodenal enterocytes, the liver, heart, pancreas, and other tissues. Hephint/intCp-/- mice were moderately anemic (similar to Cp-/- mice) but were iron loaded only in the duodenum and liver, as in Hephint/int and Cp-/- mice, respectively. Both double knockout models absorbed iron in radiolabeled intestinal iron absorption studies, but the iron was inappropriately distributed, with an abnormally high percentage retained in the liver. Conclusions: These studies indicate that HEPH and CP, and likely MCFs in general, are not essential for intestinal iron absorption but are required for proper systemic iron distribution. They also point to important extra-intestinal roles for HEPH in maintaining whole-body iron homeostasis.

Polymeric Nanoparticles Enhance the Ability of Deferoxamine To Deplete Hepatic and Systemic Iron.

Chelators are commonly used to remove excess iron in iron-loading disorders. Deferoxamine (DFO) is an effective and safe iron chelator but an onerous parenteral administration regimen limits its routine use. To develop more effective methods for delivering iron chelators, we examined whether amphiphilic copolymer nanoparticles (NPs) could deliver DFO more efficiently. Physical characterization showed a uniform and stable preparation of DFO nanoparticles (DFO-NPs) with an average diameter of 105.3 nm. In macrophage (RAW264.7) and hepatoma (HepG2) cell lines, DFO-NPs proved more effective at depleting iron than free DFO. In wild-type mice previously loaded with iron dextran, as well as Hbb th3 /+ and Hfe -/- mice, which are predisposed to iron loading, DFO-NPs (40 mg/kg DFO; alternate days; 4 weeks) reduced hepatic iron levels by 71, 46, and 37%, respectively, whereas the equivalent values for free DFO were 53, 7, and 15%. Staining for tissue iron and urinary iron excretion confirmed these findings. Pharmacokinetic analysis showed that NP-encapsulated DFO had a much longer elimination half-life than free DFO (48.63 ± 28.80 vs 1.46 ± 0.59 h), and that DFO-NPs could be readily taken up by tissues and in particular by hepatic Kupffer cells. In vitro, DFO-NPs were less toxic to several cell lines than free DFO, and in vivo they did not elicit any specific inflammatory responses or histological changes. Our results suggest that using a nanoformulation of DFO is a valuable strategy for improving its efficiency as an iron chelator and that this could broaden its clinical use for the treatment of human iron overload disorders.

Circulating iron levels influence the regulation of hepcidin following stimulated erythropoiesis.

The stimulation of erythrocyte formation increases the demand for iron by the bone marrow and this in turn may affect the levels of circulating diferric transferrin. As this molecule influences the production of the iron regulatory hormone hepcidin, we hypothesized that erythropoiesis-driven changes in diferric transferrin levels could contribute to the decrease in hepcidin observed following the administration of erythropoietin. To examine this, we treated mice with erythropoietin and examined diferric transferrin at various time points up to 18 hours. We also investigated the effect of altering diferric transferrin levels on erythropoietin-induced inhibition of Hamp1, the gene encoding hepcidin. We detected a decrease in diferric transferrin levels 5 hours after erythropoietin injection and prior to any inhibition of the hepatic Hamp1 message. Diferric transferrin returned to control levels 12 hours after erythropoietin injection and had increased beyond control levels by 18 hours. Increasing diferric transferrin levels via intravenous iron injection prevented the inhibition of Hamp1 expression by erythropoietin without altering hepatic iron concentration or the expression of Erfe, the gene encoding erythroferrone. These results suggest that diferric transferrin likely contributes to the inhibition of hepcidin production in the period shortly after injection of erythropoietin and that, under the conditions examined, increasing diferric transferrin levels can overcome the inhibitory effect of erythroferrone on hepcidin production. They also imply that the decrease in Hamp1 expression in response to an erythropoietic stimulus is likely to be mediated by multiple signals.

Iron supplementation has minor effects on gut microbiota composition in overweight and obese women in early pregnancy.

Fe is an essential nutrient for many bacteria, and Fe supplementation has been reported to affect the composition of the gut microbiota in both Fe-deficient and Fe-replete individuals outside pregnancy. This study examined whether the dose of Fe in pregnancy multivitamin supplements affects the overall composition of the gut microbiota in overweight and obese pregnant women in early pregnancy. Women participating in the SPRING study with a faecal sample obtained at 16 weeks' gestation were included in this substudy. For each subject, the brand of multivitamin used was recorded. Faecal microbiome composition was assessed by 16S rRNA sequencing and analysed with the QIIME software suite. Dietary intake of Fe was assessed using a FFQ at 16 weeks' gestation. Women were grouped as receiving low (<60 mg/d, n 94) or high (≥60 mg/d; n 65) Fe supplementation. The median supplementary Fe intake in the low group was 10 (interquartile range (IQR) 5-10) v. 60 (IQR 60-60) mg/d in the high group (P<0·001). Dietary Fe intake did not differ between the groups (10·0 (IQR 7·4-13·3) v. 9·8 (IQR 8·2-13·2) mg/d). Fe supplementation did not significantly affect the composition of the faecal microbiome at any taxonomic level. Network analysis showed that the gut microbiota in the low Fe supplementation group had a higher predominance of SCFA producers. Pregnancy multivitamin Fe content has a minor effect on the overall composition of the gut microbiota of overweight and obese pregnant women at 16 weeks' gestation.