Folic Acid Levels During Pregnancy Regulate Trophoblast Invasive Behavior and the Possible Development of Preeclampsia

The one-carbon metabolism as an underlying pathway for placental DNA methylation - a systematic review

Epigenetic modifications, including DNA methylation, are proposed mechanisms explaining the impact of parental exposures to foetal development and lifelong health. Micronutrients including folate, choline, and vitamin B12 provide methyl groups for the one-carbon metabolism and subsequent DNA methylation processes. Placental DNA methylation changes in response to one-carbon moieties hold potential targets to improve obstetrical care. We conducted a systematic review on the associations between one-carbon metabolism and human placental DNA methylation. We included 22 studies. Findings from clinical studies with minimal ErasmusAGE quality score 5/10 (n = 15) and in vitro studies (n = 3) are summarized for different one-carbon moieties. Next, results are discussed per study approach: (1) global DNA methylation (n = 9), (2) genome-wide analyses (n = 4), and (3) gene specific (n = 14). Generally, one-carbon moieties were not associated with global methylation, although conflicting outcomes were reported specifically for choline. Using genome-wide approaches, few differentially methylated sites associated with S-adenosylmethionine (SAM), S-adenosylhomocysteine (SAH), or dietary patterns. Most studies taking a gene-specific approach indicated site-specific relationships depending on studied moiety and genomic region, specifically in genes involved in growth and development including LEP, NR3C1, CRH, and PlGF; however, overlap between studies was low. Therefore, we recommend to further investigate the impact of an optimized one-carbon metabolism on DNA methylation and lifelong health.

Placenta-Related Parameters at Delivery in Relation to Folic Acid Supplementation in Different Pregnancies

Folic acid plays an important role in the synthesis, repair, and methylation of deoxyribonucleic acid (DNA). Currently, most studies have focused on the effects of periconceptional folic acid (FA) supplementation on fetal development, and there is still a lack of population-based research exploring the association between FA use during pregnancy and placental development. This study aimed to investigate the impacts of FA supplementation in different pregnancies on placenta-related parameters at delivery. The study included 2708 pregnant women recruited from Ma'anshan City, Anhui Province, China, between May 2013 and September 2014. Information on FA use from one month before conception to delivery was collected. Placental length, width, and thickness were measured. Multivariable logistic regression analysis was used to assess the effects of FA supplementation in different pregnancies on placenta-related parameters. Based on multiple regression analysis, propensity score weighting was adopted to enhance comparability between different FA supplementation groups. Compared with FA non-users, FA supplementation before conception was associated with increased placental width (0.241 cm, 95%CI: 0.052-0.429, p = 0.013) and increased placental surface area (6.398 cm2, 95%CI: 1.407-11.389, p = 0.012), and FA use in early/middle pregnancy was, respectively, related with increased placental thickness (0.061 cm, 95%CI: 0.004-0.117, p = 0.036; 0.066 cm, 95%CI: 0.004-0.129, p = 0.038). FA use before conception could increase placental width and area, and FA use in early/middle pregnancy could increase placental thickness. To confirm the findings, further investigations are needed.

Advances in Folic Acid Biosensors and Their Significance in Maternal, Perinatal, and Paediatric Preventive Medicine

Auxotrophic primates like human beings rely on exogenous dietary vitamin B9 supplementation to meet their metabolic demands. Folates play a crucial role in nucleotide synthesis and DNA methylation. Maternal folate deficiency causes several pregnancy-related complications, perinatal defects, and early childhood cognitive impairments. New evidence suggests excess FA is a potential risk factor resulting in unfavourable genomic and epigenomic alterations. Thus, it is essential to revisit the need to consistently monitor maternal folate levels during pregnancy. Yet, to date, no point-of-care folate-monitoring biosensor is commercially available. Here, we critically appraise the advances in folate biosensors to understand the translational gaps in biosensor design. Further, our review sheds light on the potential role of folate biosensors in strengthening maternal, perinatal, and child healthcare.

Maternal metabolism influences neural tube closure

Changes in maternal nutrient availability due to diet or disease significantly increase the risk of neural tube defects (NTDs). Because the incidence of metabolic disease continues to rise, it is urgent that we better understand how altered maternal nutrient levels can influence embryonic neural tube development. Furthermore, primary neurulation occurs before placental function during a period of histiotrophic nutrient exchange. In this review we detail how maternal metabolites are transported by the yolk sac to the developing embryo. We discuss recent advances in understanding how altered maternal levels of essential nutrients disrupt development of the neuroepithelium, and identify points of intersection between metabolic pathways that are crucial for NTD prevention.

Epigenetic Mechanisms Involved in the Effects of Maternal Hyperhomocysteinemia on the Functional State of Placenta and Nervous System Plasticity in the Offspring

According to modern view, susceptibility to diseases, specifically to cognitive and neuropsychiatric disorders, can form during embryonic development. Adverse factors affecting mother during the pregnancy increase the risk of developing pathologies. Despite the association between elevated maternal blood homocysteine (Hcy) and fetal brain impairments, as well as cognitive deficits in the offspring, the role of brain plasticity in the development of these pathologies remains poorly studied. Here, we review the data on the negative impact of hyperhomocysteinemia (HHcy) on the neural plasticity, in particular, its possible influence on the offspring brain plasticity through epigenetic mechanisms, such as changes in intracellular methylation potential, activity of DNA methyltransferases, DNA methylation, histone modifications, and microRNA expression in brain cells. Since placenta plays a key role in the transport of nutrients and transmission of signals from mother to fetus, its dysfunction due to aberrant epigenetic regulation can affect the development of fetal CNS. The review also presents the data on the impact of maternal HHcy on the epigenetic regulation in the placenta. The data presented in the review are not only interesting from purely scientific point of view, but can help in understanding the role of HHcy and epigenetic mechanisms in the pathogenesis of diseases, such as pregnancy pathologies resulting in the delayed development of fetal brain, cognitive impairments in the offspring during childhood, and neuropsychiatric and neurodegenerative disorders later in life, as well as in the search for approaches for their prevention using neuroprotectors.

Elevated Maternal Folate Status and Changes in Maternal Prolactin, Placental Lactogen and Placental Growth Hormone Following Folic Acid Food Fortification: Evidence from Two Prospective Pregnancy Cohorts

Folic acid (FA) food fortification in Australia has resulted in a higher-than-expected intake of FA during pregnancy. High FA intake is associated with increased insulin resistance and gestational diabetes. We aimed to establish whether maternal one-carbon metabolism and hormones that regulate glucose homeostasis change in healthy pregnancies post-FA food fortification. Circulating folate, B12, homocysteine, prolactin (PRL), human placental lactogen (hPL) and placental growth hormone (GH2) were measured in early pregnancy maternal blood in women with uncomplicated pregnancies prior to (SCOPE: N = 604) and post (STOP: N = 711)-FA food fortification. FA food fortification resulted in 63% higher maternal folate. STOP women had lower hPL (33%) and GH2 (43%) after 10 weeks of gestation, but they had higher PRL (29%) and hPL (28%) after 16 weeks. FA supplementation during pregnancy increased maternal folate and reduced homocysteine but only in the SCOPE group, and it was associated with 54% higher PRL in SCOPE but 28% lower PRL in STOP. FA food fortification increased maternal folate status, but supplements no longer had an effect, thereby calling into question their utility. An altered secretion of hormones that regulate glucose homeostasis in pregnancy could place women post-fortification at an increased risk of insulin resistance and gestational diabetes, particularly for older women and those with obesity.

The role of maternal choline, folate and one-carbon metabolism in mediating the impact of prenatal alcohol exposure on placental and fetal development

Prenatal alcohol consumption (PAE) may be associated with a broad spectrum of impacts, ranging from no overt effects, to miscarriage, fetal growth restriction and fetal alcohol spectrum disorder. A major mechanism underlying the effects of PAE is considered to be altered DNA methylation and gene expression. Maternal nutritional status may be an important factor in determining the extent to which PAE impacts pregnancy outcomes, particularly the dietary micronutrients folate and choline because they provide methyl groups for DNA methylation via one carbon metabolism. This review summarises the roles of folate and choline in development of the blastocyst, the placenta and the fetal brain, and examines the evidence that maternal intake of these micronutrients can modify the effects of PAE on development. Studies of folate or choline deficiency have found reduced blastocyst development and implantation, reduced placental invasion, vascularisation and nutrient transport capability, impaired fetal brain development, and abnormal neurodevelopmental outcomes. PAE has been shown to reduce absorption and/or metabolism of folate and choline and to produce similar outcomes to maternal choline/folate deficiency. A few studies have demonstrated that the effects of PAE on brain development can be ameliorated by folate or choline supplementation; however, there is very limited evidence on the effects of supplementation in early pregnancy on the blastocyst and placenta. Further studies are required to support these findings and to determine optimal supplementation parameters.

Biological Role of Folic Acid in Pregnancy and Possible Therapeutic Application for the Prevention of Preeclampsia

The rationale and importance of folic acid supplementation during pregnancy for fetal congenital defect prevention are accepted worldwide. Moreover, a sufficient plasma concentration of folates can reduce the incidence of spontaneous abortions, and support the normal expansion of placental blood vessels, ensuring physiological placental blood flow, thus promoting appropriate fetal growth and development. Furthermore, there is emerging evidence that long-term supplementation with folic acid can effectively prevent preeclampsia. Preeclampsia is unique to the human species in complications during pregnancy, which contributes to maternal and perinatal mortality worldwide. In the pathogenesis of preeclampsia abnormal placental invasion, the excess of antiangiogenic factors and maternal-placental syndrome play a key role. Increased blood levels of homocysteine during pregnancy are associated with the risk of preeclampsia. Moreover, hyperhomocysteinemia has been proposed to be an independent risk factor for preeclampsia. Folate supplementation helps to decrease elevated levels of homocysteine; thus, the role of folic acid supplementation in pregnancy is even more important. Multiple reports suggest that folate administration decreases the level of serum homocysteine and, therefore, reduce the risk and severity of preeclampsia. However, the association between folic acid supplementation and the decreased risk of preeclampsia has been investigated with controversial conclusions. Currently, the optimal dose of folic acid that is effective for preeclampsia prevention remains uncertain. In this review, we aim to summarize the accumulated knowledge on the role of folic acid in the pathogenesis of preeclampsia, and the possible impact of folate supplementation on the decreased risk of preeclampsia.

Circular RNA hsa-circ-0005238 enhances trophoblast migration, invasion and suppresses apoptosis via the miR-370-3p/CDC25B axis

Background

Fetal growth restriction (FGR) is attributed to various maternal, fetal, and placental factors. Trophoblasts participate in the establishment and maintenance of pregnancy from implantation and placentation to providing nutrition to fetus. Studies have reported that impaired trophoblast invasion and proliferation are among factors driving development of FGR. Circular RNAs (circRNAs) can regulate trophoblast function. We assessed the significance of circRNAs underlying FGR development.

Materials and methods

Next generation sequencing (NGS) was carried out to quantify levels of circRNAs in placenta tissues with and without FGR. In vitro experiments including transfection, (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2Htetrazolium) (MTS) assays, flow cytometry analyses, Transwell assays, wound healing assays, western blotting, qRT-PCR, dual-luciferase assays, immunofluorescence staining, and RIP assay were performed.

Results

There were 18 differentially expressed circRNAs between FGR placentas and uncomplicated pregnancies, while levels of hsa-circ-0005238 were markedly low in FGR placentas. Our in vitro experiments further revealed that hsa-circ-0005238 suppressed apoptosis and enhanced proliferation, migration, invasion of trophoblast cell lines. The hsa-miR-370-3p was identified as a direct target of hsa-circ-0005238. Mechanistically, hsa-miR-370-3p prevents invasion as well as migration of trophoblast cells by downregulating CDC25B.

Conclusion

The hsa-circ-0005238 modulates FGR pathogenesis by inhibiting trophoblast cell invasion and migration through sponging hsa-miR-370-3p. Hence, targeting this circRNA may be an attractive strategy for FGR treatment.

Palmitic Acid Impedes Extravillous Trophoblast Activity by Increasing MRP1 Expression and Function

Normal function of placental extravillous trophoblasts (EVTs), which are responsible for uteroplacental vascular remodeling, is critical for adequate delivery of oxygen and nutrients to the developing fetus and normal fetal programming. Proliferation and invasion of spiral arteries by EVTs depends upon adequate levels of folate. Multidrug resistance-associated protein 1 (MRP1), which is an efflux transporter, is known to remove folate from these cells. We hypothesized that palmitic acid increases MRP1-mediated folate removal from EVTs, thereby interfering with EVTs' role in early placental vascular remodeling. HTR-8/SVneo and Swan-71 cells, first trimester human EVTs, were grown in the absence or presence of 0.5 mM and 0.7 mM palmitic acid, respectively, for 72 h. Palmitic acid increased ABCC1 gene expression and MRP1 protein expression in both cell lines. The rate of folate efflux from the cells into the media increased with a decrease in migration and invasion functions in the cultured cells. Treatment with N-acetylcysteine (NAC) prevented the palmitic acid-mediated upregulation of MRP1 and restored invasion and migration in the EVTs. Finally, in an ABCC1 knockout subline of Swan-71 cells, there was a significant increase in invasion and migration functions. The novel finding in this study that palmitic acid increases MRP1-mediated folate efflux provides a missing link that helps to explain how maternal consumption of saturated fatty acids compromises the in utero environment.