The NR4A receptors Nurr1 and Nur77 are increased in human placenta from women with gestational diabetes

Orphan nuclear receptor NUR77 relieves insulin resistance in HTR-8/SVneo trophoblast cells through activation of autophagy and insulin signaling

Gestational diabetes mellitus (GDM) is a common pregnancy complication with a high incidence in women. Orphan nuclear receptor NUR77 is involved in regulating glucose metabolism. However, its role in GDM has not been fully elucidated yet. In this study, an animal model of GDM was established by feeding mice with a high-fat diet (HFD) before and during pregnancy. NUR77 expression was abnormally upregulated in placenta tissues of GDM mice. We performed gain- and loss-of-function studies of NUR77 in HTR-8/SVneo cells. Cells were incubated with 1 × 10^-6 M insulin for 48 h to induce insulin resistance (IR). The expression of NUR77 was downregulated in HTR-8/SVneo cells following IR induction. Overexpression of NUR77 promoted cell proliferation, migration, and invasion. Notably, NUR77 promoted glucose uptake and enhanced insulin sensitivity in vitro. NUR77 increased the ratio of p-insulin receptor β (IRβ)^Tyr1361/IRβ, p-insulin receptor substrate (IRS)-1^Tyr612/IRS-1, p-Akt/Akt and decreased p-IRS-1^Ser307/IRS-1, as well as lowered the expression of glucose transport protein type 1 (GLUT1) and elevated GLUT4. These results suggest the involvement of IRβ/IRS/Akt/GLUT4 signaling activation in the regulatory effects of NUR77 on IR in HTR-8/SVneo cells. Silencing of NUR77 displayed opposite effects. Besides, NUR77 enhanced the expression of autophagy-related protein Beclin 1 and the ratio of LC3II/LC3I. Further study demonstrated that the inhibitory effect of NUR77 on IR was partially attributed to the activation of autophagy. Therefore, we demonstrate that NUR77 enhances insulin sensitivity in HTR-8/SVneo cells likely through activating IRβ/IRS/Akt/GLUT4 pathway and regulating autophagy.

NR4A2 expression is not altered in placentas from cases of growth restriction or preeclampsia, but is reduced in hypoxic cytotrophoblast

Nuclear Receptor Subfamily 4 Group A Member 2 (NR4A2) transcripts are elevated in the circulation of individuals whose pregnancies are complicated by preterm fetal growth restriction (FGR). In this paper, we show that the cases with preeclampsia (PE) have increased circulating NR4A2 transcripts compared to those with normotensive FGR. We aimed to establish whether the dysfunctional placenta mirrors the increase in NR4A2 transcripts and further, to uncover the function of placental NR4A2. NR4A2 expression was detected in preterm and term placental tissue; expressed higher at term. NR4A2 mRNA expression and protein were not altered in placentas from preterm FGR or PE pregnancies. Hypoxia (1% O₂ compared to 8% O₂) significantly reduced cytotrophoblast NR4A2 mRNA expression, but not placental explant NR4A2 expression. Silencing cytotrophoblast NR4A2 expression under hypoxia (via short interfering (si)RNAs) did not alter angiogenic Placental Growth Factor, nor anti-angiogenic sFlt-1 mRNA expression or protein secretion, but increased expression of cellular antioxidant, oxidative stress, inflammatory, and growth genes. NR4A2 expression was also not altered in a model of tumour necrosis factor-α-induced endothelial dysfunction, or with pravastatin treatment. Further studies are required to identify the origin of the circulating transcripts in pathological pregnancies, and investigate the function of placental NR4A2.

NURR1 Alterations in Perinatal Stress: A First Step towards Late-Onset Diseases? A Narrative Review

Perinatal life represents a delicate phase of development where stimuli of all sorts, coming to or from the mother, can influence the programming of the future baby's health. These stimuli may have consequences that persist throughout adulthood. Nuclear receptor related 1 protein (NURR1), a transcription factor with a critical role in the development of the dopaminergic neurons in the midbrain, mediates the response to stressful environmental stimuli in the perinatal period. During pregnancy, low-grade inflammation triggered by maternal obesity, hyperinsulinemia or vaginal infections alters NURR1 expression in human gestational tissues. A similar scenario is triggered by exposure to neurotoxic compounds, which are associated with NURR1 epigenetic deregulation in the offspring, with potential intergenerational effects. Since these alterations have been associated with an increased risk of developing late-onset diseases in children, NURR1, alone, or in combination with other molecular markers, has been proposed as a new prognostic tool and a potential therapeutic target for several pathological conditions. This narrative review describes perinatal stress associated with NURR1 gene deregulation, which is proposed here as a mediator of late-onset consequences of early life events.

Human Trophoblast Differentiation Is Associated With Profound Gene Regulatory and Epigenetic Changes

Defective placental implantation and vascularization with accompanying hypoxia contribute to preeclampsia (PE), a leading cause of maternal and neonatal morbidity and mortality. Genetic and epigenetic mechanisms underlying differentiation of proliferative cytotrophoblasts (CytTs) to multinucleated syncytiotrophoblast (SynT) are incompletely defined. The SynT performs key functions in nutrient and gas exchange, hormone production, and protection of the fetus from rejection by the maternal immune system. In this study, we used chromatin immunoprecipitation sequencing of midgestation human trophoblasts before CytT and after SynT differentiation in primary culture to analyze changes in binding of RNA polymerase II (Pol II) and of active and repressive histone marks during SynT differentiation. Our findings reveal that increased Pol II binding to promoters of a subset of genes during trophoblast differentiation was closely correlated with active histone marks. This gene set was enriched in those controlling immune response and immune modulation, including interferon-induced tetratricopeptide repeat and placenta-specific glycoprotein gene family members. By contrast, genes downregulated during SynT differentiation included proinflammatory transcription factors ERG1, cFOS, and cJUN, as well as members of the NR4A orphan nuclear receptor subfamily, NUR77, NURR1, and NOR1. Downregulation of proinflammatory transcription factors upon SynT differentiation was associated with decreased promoter enrichment of endogenous H3K27Ac and H3K9Ac and enhanced binding of H3K9me3 and histone deacetylase 1. However, promoter enrichment of H3K27me3 was low in both CytT and SynT and was not altered with changes in gene expression. These findings provide important insight into mechanisms underlying human trophoblast differentiation and may identify therapeutic targets for placental disorders, such as PE.

Placental Ras Regulates Inflammation Associated with Maternal Obesity

Heightened placental inflammation and dysfunction are commonly associated in pregnant obese women compared to their pregnant lean counterparts. The small GTPase superfamily members known as the rat sarcoma viral oncogene homolog (Ras) proteins, in particular, the K-Ras and H-Ras isoforms, have been implicated to regulate inflammation. The aims were to determine the placental Ras expression and activity with maternal obesity and its role in regulating placental inflammation. Human placenta was obtained at term Caesarean section from lean and obese pregnant women to determine the effect of maternal obesity on Ras protein expression and activity. To determine the effect of Ras on inflammation induced by bacterial endotoxin LPS and proinflammatory cytokines TNF-α or IL-1β, the chemical inhibitor lonafarnib (total Ras inhibitor) and siRNA (siKRAS and siHRAS) were used. Total Ras protein expression together with combined K-Ras and H-Ras activity was significantly increased in the placenta of obese pregnant women and when stimulated with LPS, IL-1β, or TNF-α. Lonafarnib significantly suppressed LPS-, IL-1β-, or TNF-α-induced IL-6, IL-8, MCP-1, and GRO-α expression and secretion in placental tissue. Primary trophoblast cells transfected with siKRAS or siHRAS demonstrated only K-Ras silencing significantly decreased IL-1β-, TNF-α-, or LPS-induced IL-6, IL-8, and MCP-1 expression and secretion. Furthermore, siKRAS significantly reduced downstream ERK-1/2 activation induced by LPS. In trophoblast cells, ERK-1/2 signalling is required for IL-6, IL-8, MCP-1, and GRO-α secretion. These studies implicate a role for K-Ras in regulating inflammation in human placenta. Suppressing overactive placental K-Ras function may prevent adverse fetal outcomes complicated by maternal obesity.

Bromodomain protein BRD4 is increased in human placentas from women with early-onset preeclampsia

Preeclampsia affects 5% of all pregnancies and is a serious disorder of pregnancy, characterised by high maternal blood pressure, placental hypoxia, fluid retention (oedema) and proteinuria. Women with preeclampsia are associated with exaggerated levels of pro-inflammatory cytokines, chemokines and anti-angiogenic factors such as soluble fms-like tyrosine kinase-1 (sFLT1). Studies in non-gestational tissues have described the bromodomain (BRD) and extraterminal family of proteins, in particular BRD4 to play a critical role in propagating inflammation and is currently a therapeutic target for treating cancer, lung inflammation and asthma. The aims of this study were to: (i) determine the effect of severe early-onset preeclampsia on placental BRD4 expression; (ii) the effect of loss of BRD4 function by siRNA-targeted knockdown or with the BRD inhibitor JQ1 in human primary trophoblast cells and human umbilical vein endothelial cells (HUVECs) on TNF-stimulated production of pro-inflammatory mediators, cell adhesion molecules and anti-angiogenic markers and (iii) the effect of BRD4 suppression on placental sFLT1 secretion under hypoxia conditions and in preeclampic placenta. BRD4 mRNA expression was significantly increased (sevenfold) in severe early-onset preeclampsia placenta. BRD4 silencing resulted in a significant reduction in TNF-induced IL6, CXCL8, CCL2, CXCL1 and sFLT1-e15a mRNA expression and IL6, CXCL8, CCL2, CXCL1 and sFLT1 secretion in primary trophoblast and HUVECs. Additionally, JQ1 treatment significantly reduced placental sFLT1 secretion under hypoxic conditions and in preterm preeclamptic placenta. In conclusion, these findings suggest BRD4 may play a central role in propagating inflammation and endothelial dysfunction associated with the pathophysiology of early-onset preeclampsia.

Placental Pim-1 expression is increased in obesity and regulates cytokine- and toll-like receptor-mediated inflammation

INTRODUCTION

Obesity is a growing epidemic, and as a consequence the number of obese pregnancies has also increased. Pregnancy is characterised by maternal and placental inflammation which is intensified with maternal obesity. The proviral integration site for Moloney murine leukemic virus (Pim)-1 protein is a serine/threonine kinase involved in a wide range of inflammatory diseases. In relation to obesity, however, its role has not been elucidated in human placenta. The aims were to determine the placental expression of Pim-1 with pre-existing maternal obesity and its role in regulating placental inflammation associated with obesity.

METHODS

Human placenta was obtained at the time of term Caesarean section from lean and pre-existing obese pregnant women to determine the effect of maternal obesity on Pim-1 expression. To determine the effect of Pim-1 on the inflammatory response induced by bacterial endotoxin LPS and pro-inflammatory cytokines TNF-α or IL-1β, the chemical inhibitor SMI-4a and siRNA were used.

RESULTS

Pim-1 protein and mRNA expression was significantly increased in placenta of obese women. SMI-4a significantly suppressed the expression and release of pro-inflammatory cytokine IL-6 and chemokines GRO-α and MCP-1 when stimulated with LPS or TNF-α in placenta. Primary trophoblast cells transfected with Pim-1 siRNA had decreased expression and release of pro-inflammatory cytokines IL-1β, IL-6, chemokines GRO-α and MCP-1, when stimulated with LPS, TNF-α or IL-1β.

DISCUSSION

The findings from this study implicate Pim-1 may contribute to placental inflammation in pregnancies complicated by maternal obesity. Thus, therapeutic targets for Pim-1 may improve fetal outcomes complicated by obese pregnancies.

Resveratrol ameliorates the chemical and microbial induction of inflammation and insulin resistance in human placenta, adipose tissue and skeletal muscle

Gestational diabetes mellitus (GDM), which complicates up to 20% of all pregnancies, is associated with low-grade maternal inflammation and peripheral insulin resistance. Sterile inflammation and infection are key mediators of this inflammation and peripheral insulin resistance. Resveratrol, a stilbene-type phytophenol, has been implicated to exert beneficial properties including potent anti-inflammatory and antidiabetic effects in non-pregnant humans and experimental animal models of GDM. However, studies showing the effects of resveratrol on inflammation and insulin resistance associated with GDM in human tissues have been limited. In this study, human placenta, adipose (omental and subcutaneous) tissue and skeletal muscle were stimulated with pro-inflammatory cytokines TNF-α and IL-1β, the bacterial product lipopolysaccharide (LPS) and the synthetic viral dsRNA analogue polyinosinic:polycytidylic acid (poly(I:C)) to induce a GDM-like model. Treatment with resveratrol significantly reduced the expression and secretion of pro-inflammatory cytokines IL-6, IL-1α, IL-1β and pro-inflammatory chemokines IL-8 and MCP-1 in human placenta and omental and subcutaneous adipose tissue. Resveratrol also significantly restored the defects in the insulin signalling pathway and glucose uptake induced by TNF-α, LPS and poly(I:C). Collectively, these findings suggest that resveratrol reduces inflammation and insulin resistance induced by chemical and microbial products. Resveratrol may be a useful preventative therapeutic for pregnancies complicated by inflammation and insulin resistance, like GDM.

Lipopolysaccharide and double stranded viral RNA mediate insulin resistance and increase system a amino acid transport in human trophoblast cells in vitro

INTRODUCTION

Inflammation and underlying low-grade maternal infection can impair insulin signalling and upregulate nutrient transport in the placenta which contribute to fetal overgrowth associated with GDM and/or obese pregnancies. There are, however, no studies on the role of infection on placental nutrient transport in pregnancies complicated by GDM and/or obesity. Thus, the aims of this study were to determine the effect of the bacterial product lipopolysaccharide (LPS) or the viral dsRNA analogue polyinosinic:polycytidylic acid (poly(I:C)) on the insulin signalling pathway and amino acid transport in primary human trophoblast cells.

METHODS

Human primary villous trophoblast cells were treated with LPS or poly(I:C). Protein expression of insulin signalling pathway proteins, insulin receptor (IR)-β, insulin receptor substrate (IRS)-1 and protein kinase B (also known as Akt), and phosphatidylinositol-4,5-bisphosphate 3-kinase p85α subunit (PI3K-p85α) protein were assessed by Western blotting. Glucose and amino acid uptake were assessed by radiolabelled assay. Western blotting and qRT-PCR were used to determine amino acid transporter protein and mRNA expression, respectively.

RESULTS

LPS and poly(I:C) significantly decreased phosphorylation of IR-β, IRS-1, Akt, total PI3K-p85α protein expression and glucose uptake. LPS and poly(I:C) also significantly increased expression of System A amino acid transporters SNAT1 and SNAT2, and System A-mediated uptake of amino acids.

DISCUSSION

LPS and poly(I:C) induces insulin resistance and increases amino acid uptake in human primary trophoblast cells. This suggests that the presence of low-grade maternal infection can contribute to excess placental nutrient availability and promote fetal overgrowth in pregnancies complicated by GDM and/or obesity.

Reduced DHA transfer in diabetic pregnancies: mechanistic basis and long-term neurodevelopmental implications

Infants born to diabetic mothers have a higher frequency of impaired neurodevelopment. The omega-3 or n-3 fatty acid docosahexaenoic acid (DHA) is an important structural component of neural tissue and is critical for fetal brain development. Maternal DHA supplementation during pregnancy is linked to better infant neurodevelopment; however, maternal-fetal transfer of DHA is reduced in women with diabetes. Evidence of mechanisms explaining altered maternal-fetal DHA transfer in this population is limited. This review explores existing evidence underpinning reduced maternal-fetal DHA transfer in maternal fuel metabolism in this population. Further research is necessary to evaluate the role of peroxisome proliferator-activated receptors in modulating placental fatty acid binding and maternal-fetal DHA transfer. Considerations for clinical practice include a diet high in DHA and/or provision of supplemental DHA to obstetric diabetic patients within minimum guidelines.