Increased hepcidin levels in preeclampsia: a protective mechanism against iron overload mediated oxidative stress?

Association between iron status, preeclampsia and gestational hypertension: A bidirectional two-sample Mendelian randomization study

BACKGROUND

Several recent observational studies have reported that iron overload during pregnancy is associated with preeclampsia (PE) and gestational hypertension (GH). However, the causal association between iron status, PE, and GH is still not clear.

METHODS

We performed a two-sample Mendelian randomization (MR) study using the genome-wide association study (GWAS) summary statistics of iron status, included serum iron, ferritin, total iron-binding capacity (TIBC), and transferrin saturation (TSAT) from the largest available GWAS meta-analysis, and the summary statistics of PE and GH were obtained from the FinnGen consortium. Fixed-effect inverse variance weighted (IVW), random-effect IVW, maximum likelihood (ML), MR-Egger regression, weighted median, and MR-PRESSO methods were used.

RESULTS

A total of 21, 58, 28, and 22 SNPs were used as IVs for serum iron, ferritin, TIBC, and TSAT, respectively. The F-statistics of IVs ranged from 95.23 to 421.36. The results of the fixed effects IVW method suggested that for per SD unit increase in serum iron, the risk of PE increases by 24 % (OR = 1.24, 95 % CI: 1.03-1.50, P = 0.02). No significant heterogeneity or horizontal pleiotropy was found. The association between ferritin, TIBC, TSAT and PE were statistically insignificant (P>0.05). Furthermore, the results of each MR methods do not support a causal association between iron status and GH, nor a reverse causal association between PE and GH and iron status.

CONCLUSION

This two-sample MR study provides evidence supporting a causal association between serum iron level and PE.

The crosstalk between cell death and pregnancy related diseases: A narrative review

Programmed cell death is intricately linked to various physiological phenomena such as growth, development, and metabolism, as well as the proper function of the pancreatic β cell and the migration and invasion of trophoblast cells in the placenta during pregnancy. Traditional and recently identified programmed cell death include apoptosis, autophagy, pyroptosis, necroptosis, and ferroptosis. In addition to cancer and degenerative diseases, abnormal activation of cell death has also been implicated in pregnancy related diseases like preeclampsia, gestational diabetes mellitus, intrahepatic cholestasis of pregnancy, fetal growth restriction, and recurrent miscarriage. Excessive or insufficient cell death and pregnancy related diseases may be mutually determined, ultimately resulting in adverse pregnancy outcomes. In this review, we systematically describe the characteristics and mechanisms underlying several types of cell death and their roles in pregnancy related diseases. Moreover, we discuss potential therapeutic strategies that target cell death signaling pathways for pregnancy related diseases, hoping that more meaningful treatments will be applied in clinical practice in the future.

Effect of Prenatal Iron Supplementation Adapted to Hemoglobin Levels in Early Pregnancy on Fetal and Neonatal Growth-ECLIPSES Study

In this randomized clinical trial, we evaluated the effects of prenatal iron supplementation adapted to pregnant women's initial hemoglobin (Hb) levels on fetal growth parameters until birth in women from the Mediterranean coast of northern Spain. All (n = 791) women were iron-supplemented during pregnancy according to Hb levels at the 12th gestational week: stratum 1 (Hb: 110-130 g/L) received 40 or 80 mg iron daily; stratum 2 (Hb > 130 g/L) received 40 or 20 mg iron daily. Fetal biometric and anthropometric measurements were evaluated in the three trimesters and at birth, respectively. In stratum 1, using 80 mg/d instead of 40 mg/d increased the risk of fetal head circumference > 90th percentile (OR = 2.49, p = 0.015) at the second trimester and fetal weight (OR = 2.36, p = 0.011) and femur length (OR = 2.50, p = 0.018) < 10th percentile at the third trimester. For stratum 2, using 40 mg/d instead of 20 mg/d increased the risk of fetal head circumference > 90th percentile (OR = 3.19, p = 0.039) at the third trimester. A higher risk of delivering an LGA baby (OR = 2.35, p = 0.015) for birthweight was also observed in stratum 1 women receiving 80 mg/d. It is crucial to adjust the prenatal iron supplementation to each pregnant woman's needs, i.e., adapted to their initial Hb levels, to achieve optimal fetal development, since excessive iron doses appear to adversely influence fetal growth.

Iron metabolism and ferroptosis: A pathway for understanding preeclampsia

Preeclampsia (PE) is a serious medical condition that poses a significant health risk to women and children worldwide, particularly in the middle- and low-income countries. It is a complex syndrome that occurs as a result of abnormal pregnancy. Hypertension is the most common symptom of PE, with proteinuria and specific organ systems as detrimental targets. PE's pathogenesis is diverse, and its symptoms can overlap with other diseases. In early pregnancy, when the placenta takes over control, oxidative stress may be closely associated with ferroptosis, a type of cell death caused by intracellular iron accumulation. Ferroptosis in the placenta is defined by redox-active iron availability, loss of antioxidant capacity and phospholipids containing polyunsaturated fatty acids (PUFA) oxidation. Recent studies suggest a compelling potential link between ferroptosis and PE. In this article, we comprehensively review the current understanding of PE and discuss one of its emerging underlying mechanisms, the ferroptosis pathway. We also provide perspective and analysis on the implications of this process in the diagnosis, prevention, and treatment of preeclampsia. We aim to bridge the gap between clinicians and basic scientists in understanding this harmful disease and challenge the research community to put more effort into this exciting new area.

Hepcidin across pregnancy and its correlation with maternal markers of iron and inflammation, maternal body weight outcomes, and offspring neurodevelopmental outcomes: a systematic review and meta-analysis

OBJECTIVE

This study evaluated the correlation between maternal hepcidin and other biomarkers of iron status, markers of inflammation, and maternal body weight during pregnancy, as well as neurodevelopment in the offspring.

DATA SOURCES

PubMed, Web of Science, Scopus, and Embase were searched from inception until March 2022.

STUDY ELIGIBILITY CRITERIA

Studies conducted among pregnant women without apparent pregnancy complications were included. Eligible studies reported correlation coefficients between maternal hepcidin and any outcomes of maternal biomarkers of iron status or inflammatory load during pregnancy, prenatal maternal body weight, and offspring neurodevelopment. Studies without correlation data were eligible if they quantitatively reported volumes of both maternal hepcidin and any marker of iron status and/or inflammatory load during gestation.

METHODS

Pooled correlation coefficients between maternal hepcidin and outcomes of interest were calculated using the Fisher r-to-Z transformation. Both fixed-effects and DerSimonian and Laird random-effects models were used to calculate pooled correlation coefficient. When meta-analysis was not feasible, results were descriptively synthesized.

RESULTS

Forty-six studies with 6624 participants were eligible. Hepcidin was significantly correlated with hemoglobin in the third trimester (r=0.21; 95% confidence interval, 0.1-0.32); ferritin in the first (r=0.31; 95% confidence interval, 0.01-0.61) and third trimester (r=0.35; 95% confidence interval, 0.23-0.48); soluble transferrin receptor in the second trimester (r=-0.27; 95% confidence interval, -0.4 to -0.14); total iron-binding capacity in the second trimester (r=0.37; 95% confidence interval, 0.24-0.50); and serum iron in the third trimester (r=0.11; 95% confidence interval, 0.02-0.19). Hepcidin was significantly correlated with the inflammatory marker interleukin-6 in the third trimester (r=0.26; 95% confidence interval, 0.17-0.34) and C-reactive protein in the second (r=0.16; 95% confidence interval, 0.03-0.30) and third trimester (r=0.28; 95% confidence interval, 0.04-0.52). Four out of 5 studies reported weak-to-moderate positive correlation between hepcidin and body mass index. Hepcidin levels varied across body mass index categories. No single study reported the relationship between maternal hepcidin and neurodevelopment in offspring.

CONCLUSION

Hepcidin weakly to moderately correlates with biomarkers of iron and inflammation in 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.

Assessing erythroferrone and iron homeostasis in preeclamptic and normotensive pregnancies: A retrospective study

INTRODUCTION

Preeclampsia (PE) is a pregnancy-related disorder associated with maternal hypertension and placental dysfunction. A significant micronutrient during pregnancy is iron, which is important in cellular functions. While iron absorption increases in pregnancy, little is known about the exact mechanisms regulating maternal iron levels and transfer through the placenta in normal and complicated pregnancies.

METHODS

In this retrospective study, we investigated the regulation of maternal and placental iron availability and storage, in normotensive and pregnancies complicated by early- or late-onset PE. Methods used were analysis of clinical records, ELISA analysis on plasma samples, immunofluorescent and Prussian Blue analysis on placenta biopsies.

RESULTS

Focusing on erythroferrone (ERFE) as a new marker and hormonal regulator of iron, our results demonstrated altered maternal ERFE levels in PE. We are the first to report the expression of ERFE in trophoblasts and indicate its lower levels in early-onset PE placentas. These changes were associated with lower placental transferrin receptor 1 (TfR1) in syncytiotrophoblasts in both early- and late-onset PE. In addition, maternal plasma ERFE levels were elevated in both early- and late-onset PE and hepcidin levels reduced in early-onset PE. Unaltered maternal plasma IL-6 levels suggest mechanism other than inflammation being involved in altered iron regulation in PE pregnancy.

DISCUSSION

Our data supports a deregulation in maternal iron bioavailability in early- and late-onset PE vs normotensive pregnancies. The exact role of placental ERFE in regulating maternal-placental-fetal iron transport axis requires further investigation.

Maternal serum iron status, hepcidin and interleukin-6 levels in women with preeclampsia

Introduction: Preeclampsia can lead to a number of adverse maternal and perinatal effects. The association between iron status [serum iron, ferritin and total iron-binding capacity (TIBC)], unsaturated iron-binding capacity, hepcidin, interleukin-6 (IL-6) levels and preeclampsia is not fully understood. Objective: To assess the levels of iron status, hepcidin and interleukin-6 in women with preeclampsia compared with healthy pregnant women. Method: A case-control study (60 women were recruited in each group) was conducted at Saad Abuelela Maternity Hospital in Khartoum, Sudan. Sociodemographic and clinical data were gathered through a questionnaire. The levels of iron status, hepcidin and IL-6 were measured using applicable methods. Results: There was no significant difference in the median [interquartile range (IQR)] of age, parity or body mass index between the two groups. Moreover, the median (IQR) of the iron status, hepcidin and interleukin-6 did not differ between women with preeclampsia and healthy controls. There were no significant correlations between haemoglobin, hepcidin and IL-6. There were also no significant correlations between serum iron, serum ferritin, hepcidin and IL-6. However, there was a significant positive correlation between hepcidin and IL-6 (r = 0.393, p = 0.002). Conclusion: In this study, women with preeclampsia had levels of iron status, hepcidin and IL-6 similar to those observed in healthy pregnant women. There was no significant correlation between iron status, hepcidin and IL-6.

Iron Metabolism and Ferroptosis in Physiological and Pathological Pregnancy

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

Association of Serum Hepcidin With Preeclampsia: A Systematic Review and Meta-Analysis

The objective of the present systematic review and meta-analysis was to compare the levels of serum hepcidin in women who developed pre-eclampsia with those who did not. The databases PubMed, Embase, Scopus, Cochrane, and references of retrieved articles published till September 2020 were searched with no language restriction. Mean differences in iron regulating protein (hepcidin) were compared using a random-effects model based on the level of heterogeneity. A total of 760 individuals were included in the analysis from seven studies. The pooled estimate showed that mean hepcidin levels were significantly higher in women who developed pre-eclampsia [0.3 ng/ml, 95% confidence interval (CI): 0.01-0.59, p=0.003] as compared to women who did not develop pre-eclampsia. Further research can be done to assess the levels of various iron parameters in different trimesters of pregnancy and their association with pre-eclampsia.

Ferroptosis and Its Emerging Role in Pre-Eclampsia

Iron is essential for cell survival, and iron deficiency is a known risk factor for many reproductive diseases. Paradoxically, such disorders are also more common in cases of iron overload. Here, we evaluated the role of ferroptosis in women's health, particularly focusing on pre-eclampsia (PE). PE is a multisystem disorder and is one of the leading causes of maternal and perinatal morbidity and mortality, especially when the condition is of early onset. Nevertheless, the exact etiological mechanism of PE remains unclear. Interestingly, ferroptosis, as a regulated iron-dependent cell death pathway, involves a lethal accumulation of lipid peroxides and shares some characteristics with PE pathophysiology. In this review, we comprehensively reviewed and summarized recent studies investigating the molecular mechanisms involved in the regulation and execution of ferroptosis, as well as ferroptosis mechanisms in the pathology of PE. We propose that ferroptosis not only plays an important role in PE, but may also become a novel therapeutic target for PE.

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

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

Novel insights into the SLC7A11-mediated ferroptosis signaling pathways in preeclampsia patients: identifying pannexin 1 and toll-like receptor 4 as innovative prospective diagnostic biomarkers

PURPOSE

Ferroptosis is associated with oxidative stress (OS) and is caused by iron-dependent lipid-peroxidative damage, but its role in PE is unclear. The aim of this study is to determine whether pannexin 1 (Panx1) and toll-like receptor 4 (TLR4) are key regulators of ferroptosis in PE.

METHODS

The study included 65 patients with PE and 25 healthy pregnant women. In normal and PE placental tissues, OS and ferroptosis markers, including Fe²⁺, malondialdehyde (MDA), reduced glutathione (GSH) levels, heme oxygenase-1 (HO-1) and glutathione peroxidase 4 (Gpx4) activity, were estimated. Panx1 and solute carrier family 7 member 11 (SLC7A11) mRNA expression levels were relatively quantified in placental tissues using real-time polymerase chain reaction (RT-PCR), while serum Panx1, serum TLR4, and placental activating transcription factor 3 (ATF3) levels were measured by ELISA.

RESULTS

In placental tissues, Panx1 and TLR4 expression levels were significantly increased in patients with PE compared to controls and were positively correlated with pro-ferroptosis mediators such as placental Fe²⁺ and MDA levels and negatively correlated with anti-ferroptosis regulators such as placental GSH level, HO-1, and Gpx4 activity. Additionally, Panx1 and TLR4 had a positive correlation with ATF3 and a negative correlation with SLC7A11. Serum Panx1 and TLR4 levels were positively correlated with their placental tissue expression and showed good diagnostic capabilities for ferroptosis in PE.

CONCLUSION

Therefore, Panx1 and TLR4 are suggested to induce ferroptosis in PE via SLC7A11-mediated signaling pathways, offering a novel perspective on PE pathogenesis and novel diagnostic tools for PE.

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.

Association Between Serum Ferritin Concentration and Risk of Adverse Maternal and Fetal Pregnancy Outcomes: A Retrospective Cohort Study

OBJECTIVE

This study evaluated the associations of serum ferritin (SF) concentration during pregnancy with the risk of adverse maternal and fetal pregnancy outcomes.

METHODS

We conducted a retrospective study of 2327 pregnant women from 2015 to 2020 in Guangdong, China. SF concentrations were measured at 16-18th and 28-32th week of gestation. Logistic regression models were applied to estimate the association between SF concentration and the risk of adverse pregnancy outcomes.

RESULTS

After multivariable adjustment, the odds ratio (OR) of the highest quartile of SF concentration at 16-18th week of gestation was 1.43 (95% confidence interval [CI]: 1.09, 1.89) for gestational diabetes mellitus (GDM) and 1.79 (95% CI: 1.15, 2.79) for small for gestational age (SGA) when compared with the lowest quartile. At 28-32th week of gestation compared with the lowest quartile, women with SF in the highest quartile had an increased risk of SGA (OR: 1.62; 95% CI: 1.01, 2.62). Moreover, the lowest quartile of SF concentration decreased risk of SGA by 90% (95% CI: 0.01, 0.80) when compared with the highest quartile among pregnancy women with GDM.

CONCLUSION

Elevated SF concentrations increased the risk of GDM and SGA during pregnancy. Maintaining an appropriately low level of maternal SF at 28-32th week of gestation in women with GDM could reduce the risk of SGA.

The roles of free iron, heme, haemoglobin, and the scavenger proteins haemopexin and alpha-1-microglobulin in preeclampsia and fetal growth restriction

BACKGROUND

Preeclampsia (PE) is a complex pregnancy syndrome characterised by maternal hypertension and organ damage after 20 weeks of gestation and is associated with an increased risk of cardiovascular disease later in life. Extracellular haemoglobin (Hb) and its metabolites heme and iron are highly toxic molecules and several defence mechanisms have evolved to protect the tissue.

OBJECTIVES

We will discuss the roles of free iron, heme, Hb, and the scavenger proteins haemopexin and alpha-1-microglobulin in pregnancies complicated by PE and fetal growth restriction (FGR).

CONCLUSION

In PE, oxidative stress causes syncytiotrophoblast (STB) stress and increased shedding of placental STB-derived extracellular vesicles (STBEV). The level in maternal circulation correlates with the severity of hypertension and supports the involvement of STBEVs in causing maternal symptoms in PE. In PE and FGR, iron homeostasis is changed, and iron levels significantly correlate with the severity of the disease. The normal increase in plasma volume taking place during pregnancy is less for PE and FGR and therefore have a different impact on, for example, iron concentration, compared to normal pregnancy. Excess iron promotes ferroptosis is suggested to play a role in trophoblast stress and lipotoxicity. Non-erythroid α-globin regulates vasodilation through the endothelial nitric oxide synthase pathway, and hypoxia-induced α-globin expression in STBs in PE placentas is suggested to contribute to hypertension in PE. Underlying placental pathology in PE with and without FGR might be amplified by iron and heme overload causing oxidative stress and ferroptosis. As the placenta becomes stressed, the release of STBEVs increases and affects the maternal vasculature.

Micronutrients in Multiple Pregnancies-The Knowns and Unknowns: A Systematic Review

Maternal diet and nutritional status are of key importance with regard to the short- and long-term health outcomes of both the mother and the fetus. Multiple pregnancies are a special phenomenon in the context of nutrition. The presence of more than one fetus may lead to increased metabolic requirements and a faster depletion of maternal macro- and micro- nutrient reserves than in a singleton pregnancy. The aim of this systematic review was to gather available knowledge on the supply and needs of mothers with multiple pregnancies in terms of micronutrients and the epidemiology of deficiencies in that population. It was constructed in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses Statement (PRISMA). The authors conducted a systematic literature search with the use of three databases: PubMed/MEDLINE, Scopus and Embase. The last search was run on the 18 October 2020 and identified 1379 articles. Finally, 12 articles and 1 series of publications met the inclusion criteria. Based on the retrieved studies, it may be concluded that women with multiple pregnancies might be at risk of vitamin D and iron deficiencies. With regard to other microelements, the evidence is either inconsistent, scarce or absent. Further in-depth prospective and population studies are necessary to determine if nutritional recommendations addressed to pregnant women require adjustments in cases of multiple gestations.