Leptin promotes cell proliferation and survival of trophoblastic cells

JPT2 in subclinical hypothyroidism-related miscarriage as a transcription co-factor: involvement of LEPR/STAT3 activation

BACKGROUND AND PURPOSE

Subclinical hypothyroidism (SCH) has been identified to be associated with implantation failure, in which the dysfunction of trophoblast cells is involved. In this study, the transcriptomics of aborted placenta from SCH rats were analyzed. Jupiter microtubule-associated homolog 2 (JPT2) was downregulated in the aborted placenta. This study aims to investigate its role in SCH-associated miscarriage.

METHODS

Spontaneous abortion was observed in SCH rats generated by thyroidectomy combined with levothyroxine administration. The transcriptomics analysis was performed using aborted placenta. Afterward, the effects of JPT2 on trophoblast cells were explored using gain-and loss-of-function experiments.

RESULTS

Transcriptomics analysis showed 1286 downregulated genes and 2300 upregulated genes in the aborted placenta, and JPT2 was significantly downregulated in the aborted placenta from SCH rats. Afterward, gain-and loss-of-function experiments exhibited that overexpression of JPT2 promoted the proliferation, migration, invasion, spheroid formation of HTR-8/SVneo trophoblast cells and their attachment to endometrial stromal cells, while these biological behaviors were suppressed by JPT2 knockdown. Furthermore, JPT2 accelerated the transcription of leptin receptor (LEPR), and activated signal transducer and activator of transcription 3 (STAT3) signal in a transcription factor AP-2γ-dependent manner. In addition, silencing of LEPR abolished the role of JPT2.

CONCLUSION

Our results revealed that JPT2, which was downregulated in the aborted placenta from SCH rats, promoted proliferation, migration, invasion, spheroid formation, and attachment of trophoblast cells via regulating LEPR/STAT3 axis as a transcription co-factor. It is indicated that low expression of JPT2 may contribute to the abortion in individuals with SCH.

Adipokines in pregnancy

Reproductive success consists of a sequential events chronology, starting with the ovum fertilization, implantation of the embryo, placentation, and cellular processes like proliferation, apoptosis, angiogenesis, endocrinology, or metabolic changes, which taken together finally conduct the birth of healthy offspring. Currently, many factors are known that affect the regulation and proper maintenance of pregnancy in humans, domestic animals, or rodents. Among the determinants of reproductive success should be distinguished: the maternal microenvironment, genes, and proteins as well as numerous pregnancy hormones that regulate the most important processes and ensure organism homeostasis. It is well known that white adipose tissue, as the largest endocrine gland in our body, participates in the synthesis and secretion of numerous hormones belonging to the adipokine family, which also may regulate the course of pregnancy. Unfortunately, overweight and obesity lead to the expansion of adipose tissue in the body, and its excess in both women and animals contributes to changes in the synthesis and release of adipokines, which in turn translates into dramatic changes during pregnancy, including those taking place in the organ that is crucial for the proper progress of pregnancy, i.e. the placenta. In this chapter, we are summarizing the current knowledge about levels of adipokines and their role in the placenta, taking into account the physiological and pathological conditions of pregnancy, e.g. gestational diabetes mellitus, preeclampsia, or intrauterine growth restriction in humans, domestic animals, and rodents.

Exploring the impacts of senescence on implantation and early embryonic development using totipotent cell-derived blastoids

INTRODUCTION

Advanced maternal age is associated with reduced implantation and pregnancy rates, yet the underlying mechanisms remain poorly understood, and research models are limited.

OBJECTIVES

Here, we aim to elucidate the impacts of senescence on implantation ability by employing blastoids to construct a novel research model.

METHODS

We used a novel three-dimensional system with totipotent blastomere-like cells (TBLCs) to construct TBL-blastoids and established senescence-related embryo models derived from oxidative stress-induced TBLCs.

RESULTS

Morphological and transcriptomic analyses revealed that TBL-blastoids exhibited characteristic blastocyst morphology, cell lineages, and a higher consistency in developmental rate. TBL-blastoids demonstrated the ability to develop into postimplantation structures in vitro and successfully implanted into mouse uteri, inducing decidualization and forming embryonic tissues. Importantly, senescence impaired the implantation potential of TBL-blastoids, effectively mimicking the impaired implantation ability and reduced pregnancy rates associated with advanced age. Furthermore, analysis of differentially expressed genes (DEGs) in human homologous deciduae revealed enrichment in multiple fertility-related diseases and other complications of pregnancy. The genes implicated in these diseases and the common DEGs identified in the lineage-like cells of the two types of TBL-blastoids and deciduae may represent potential targets for addressing impaired implantation potential.

CONCLUSION

These results unveiled that TBL blastoids are an improved model for investigating implantation and early postimplantation, offering valuable insights into pregnancy-related disorders in women with advanced age and potential targets for therapeutic interventions.

Infertility Improvement after Medical Weight Loss in Women and Men: A Review of the Literature

Infertility is a modern health problem. Obesity is another expanding health issue associated with chronic diseases among which infertility is also included. This review will focus on the effects of weight loss by medical therapy on fertility regarding reproductive hormonal profile, ovulation rates, time to pregnancy, implantation rates, pregnancy rates, normal embryo development, and live birth rates. We comprised medicine already used for weight loss, such as orlistat and metformin, and emerging medical treatments, such as Glucagon-Like Peptide-1 receptor agonists (GLP-1 RA). Their use is not recommended during a planned pregnancy, and they should be discontinued in such cases. The main outcomes of this literature review are the following: modest weight loss after medication and the duration of the treatment are important factors for fertility improvement. The fecundity outcomes upon which medical-induced weight loss provides significant results are the female reproductive hormonal profile, menstrual cyclicity, ovulation and conception rates, and pregnancy rates. Regarding the male reproductive system, the fertility outcomes that feature significant alterations after medically induced weight loss are as follows: the male reproductive hormonal profile, sperm motility, movement and morphology, weight of reproductive organs, and sexual function. The newer promising GLP-1 RAs show expectations regarding fertility improvement, as they have evidenced encouraging effects on improving ovulation rates and regulating the menstrual cycle. However, more human studies are needed to confirm this. Future research should aim to provide answers about whether medical weight loss therapies affect fertility indirectly through weight loss or by a possible direct action on the reproductive system.

Placental pathologic features in obesity

INTRODUCTION

Obesity in pregnancy is associated with adverse long-term consequences both in the mother and in offspring. Maternal obesity induces a metabolic-inflammatory state that could impact on placental function and could mediate the adverse outcomes. The purpose of this study was to compare the major placental histological characteristics of non-diabetic obese women to lean controls, focusing on uncomplicated pregnancies.

METHODS

Prospective case-control study comparing placental histopathological features between 122 non-diabetic obese women and 185 non-obese controls. The analysis was performed on overall subjects, then uncomplicated pregnancies from both groups were analyzed. Placenta pathologic findings were recorded according to standard classification.

RESULTS

Both in overall analysis and among the subset of subjects with an uncomplicated pregnancy, obese subjects had higher risks of maternal vascular malperfusion (MVM) (respectively OR=2.2, 95%CI =1.3-3.7 and OR=4.2, 95%CI=2.1-8.5), fetal vascular malperfusion (FVM) (respectively OR=6.3, 95%CI=3.1-12.5 and OR=7.2, 95%CI=3-17.2), maternal and fetal inflammatory response placental lesions and villitis (VUE) (respectively OR=2.5, 95%CI=1.1-5.6 and OR=10.8, 95%CI=3.3-35.3) compared to controls. Among uncomplicated pregnancies and after adjustment for confounders, first trimester BMI was significantly associated with overall MVM, overall FVM, maternal inflammatory, fetal inflammatory response and VUE.

DISCUSSION

Placentas from obese women showed a significantly higher risk of maternal and fetal vascular and inflammatory placental lesions, both in overall population and in the subgroup with uncomplicated pregnancies. The metabolic and inflammatory dysfunctions typical of obesity could have an impact on placental development and function, which could be a mediator of the detrimental effects of obesity on pregnancy outcome and on future health of the offspring.

Unveiling the hidden players: The crucial role of transposable elements in the placenta and their potential contribution to pre-eclampsia

The human placenta is a vital connection between maternal and fetal tissues, allowing for the exchange of molecules and modulation of immune interactions during pregnancy. Interestingly, some of the placenta's unique functions can be attributed to transposable elements (TEs), which are DNA sequences that have mobilised into the genome. Co-option throughout mammalian evolution has led to the generation of TE-derived regulators and TE-derived genes, some of which are expressed in the placenta but silenced in somatic tissues. TE genes encompass both TE-derived genes with a repeat element in the coding region and TE-derived regulatory regions such as alternative promoters and enhancers. Placental-specific TE genes are known to contribute to the placenta's unique functions, and interestingly, they are also expressed in some cancers and share similar functions. There is evidence to support that aberrant activity of TE genes may contribute to placental pathologies, cancer and autoimmunity. In this review, we highlight the crucial roles of TE genes in placental function, and how their dysregulation may lead to pre-eclampsia, a common and dangerous placental condition. We provide a summary of the functional TE genes in the placenta to offer insight into their significance in normal and abnormal human development. Ultimately, this review highlights an opportunity for future research to investigate the potential dysregulation of TE genes in the development of placental pathologies such as pre-eclampsia. Further understanding of TE genes and their role in the placenta could lead to significant improvements in maternal and fetal health.

Expression of nutrient transporters in placentas affected by gestational diabetes: role of leptin

Gestational diabetes mellitus (GDM) is the most frequent pathophysiological state of pregnancy, which in many cases produces fetuses with macrosomia, requiring increased nutrient transport in the placenta. Recent studies by our group have demonstrated that leptin is a key hormone in placental physiology, and its expression is increased in placentas affected by GDM. However, the effect of leptin on placental nutrient transport, such as transport of glucose, amino acids, and lipids, is not fully understood. Thus, we aimed to review literature on the leptin effect involved in placental nutrient transport as well as activated leptin signaling pathways involved in the expression of placental transporters, which may contribute to an increase in placental nutrient transport in human pregnancies complicated by GDM. Leptin appears to be a relevant key hormone that regulates placental transport, and this regulation is altered in pathophysiological conditions such as gestational diabetes. Adaptations in the placental capacity to transport glucose, amino acids, and lipids may underlie both under- or overgrowth of the fetus when maternal nutrient and hormone levels are altered due to changes in maternal nutrition or metabolic disease. Implementing new strategies to modulate placental transport may improve maternal health and prove effective in normalizing fetal growth in cases of intrauterine growth restriction and fetal overgrowth. However, further studies are needed to confirm this hypothesis.

Maternal obesity and ovarian failure: is leptin the culprit?

At the time of its discovery and characterization in 1994, leptin was mostly considered a metabolic hormone able to regulate body weight and energy homeostasis. However, in recent years, a great deal of literature has revealed leptin's pleiotropic nature, through its involvement in numerous physiological contexts including the regulation of the female reproductive tract and ovarian function. Obesity has been largely associated with infertility, and leptin signalling is known to be dysregulated in the ovaries of obese females. Hence, the disruption of ovarian leptin signalling was shown to contribute to the pathophysiology of ovarian failure in obese females, affecting transcriptional programmes in the gamete and somatic cells. This review attempts to uncover the underlying mechanisms contributing to female infertility associated with obesity, as well as to shed light on the role of leptin in the metabolic dysregulation within the follicle, the effects on the oocyte epigenome, and the potential long-term consequence to embryo programming.

Endocrine disruptor chemicals, adipokines and reproductive functions

The prevalence of adult obesity has risen markedly in recent decades. The endocrine system precisely regulates energy balance, fat abundance and fat deposition. Interestingly, white adipose tissue is an endocrine gland producing adipokines, which regulate whole-body physiology, including energy balance and reproduction. Endocrine disruptor chemicals (EDCs) include natural substances or chemicals that affect the endocrine system by multiple mechanisms and increase the risk of adverse health outcomes. Numerous studies have associated exposure to EDCs with obesity, classifying them as obesogens by their ability to activate different mechanisms, including the differentiation of adipocytes, increasing the storage of triglycerides, or elevating the number of adipocytes. Moreover, in recent years, not only industrial deception and obesity have intensified but also the problem of human infertility. Reproductive functions depend on hormone interactions, the balance of which may be disrupted by various EDCs or obesity. This review gives a brief summary of common EDCs linked with obesity, the mechanisms of their action, and the effect on adipokine levels, reproduction and connected disorders, such as polycystic ovarian syndrome, decrease in sperm motility, preeclampsia, intrauterine growth restriction in females and decrease of sperm motility in males.

Maternal obesity and the impact of associated early-life inflammation on long-term health of offspring

The prevalence of obesity is increasingly common in the United States, with ~25% of women of reproductive age being overweight or obese. Metaflammation, a chronic low grade inflammatory state caused by altered metabolism, is often present in pregnancies complicated by obesity. As a result, the fetuses of mothers who are obese are exposed to an in-utero environment that has altered nutrients and cytokines. Notably, both human and preclinical studies have shown that children born to mothers with obesity have higher risks of developing chronic illnesses affecting various organ systems. In this review, the authors sought to present the role of cytokines and inflammation during healthy pregnancy and determine how maternal obesity changes the inflammatory landscape of the mother, leading to fetal reprogramming. Next, the negative long-term impact on offspring’s health in numerous disease contexts, including offspring’s risk of developing neuropsychiatric disorders (autism, attention deficit and hyperactive disorder), metabolic diseases (obesity, type 2 diabetes), atopy, and malignancies will be discussed along with the potential of altered immune/inflammatory status in offspring as a contributor of these diseases. Finally, the authors will list critical knowledge gaps in the field of developmental programming of health and diseases in the context of offspring of mothers with obesity, particularly the understudied role of hematopoietic stem and progenitor cells.

[Obesity affects the chances of birth after frozen-thawed blastocyst transfer]

OBJECTIVES

Both the number of frozen-thawed embryo transfers and the incidence of obesity have increased sharply in recent years in Assisted Reproductive Technology (ART) centers. The objective of our study is therefore to evaluate the impact of female obesity on pregnancy outcomes for frozen-thawed embryo transfer at blastocyst stage.

METHODS

This is a single-center retrospective study conducted between January 1, 2016, and December 31, 2019, in our Assisted Reproduction Center in Calais. All consecutive cycles of frozen embryo transfers at blastocyst stage with artificial cycle were included. A total of 296 cycles could be included corresponding to 220 cycles realized in normal Body Mass Index (BMI) patients (18.5-24.9kg/m²) and 76 in obese patients (BMI≥30kg/m²).

RESULTS

Live birth rates and implantation rates were significantly lower in obese patients compared with patients with a normal BMI (respectively 9.2 % vs. 22.3 % and 10 % vs. 20.8 %, P=0.01 and P<0.01).

CONCLUSIONS

Therefore, our study showed that obesity is associated with a lower rate of live birth and implantation following frozen-thawed blastocyst transfers in artificial cycles. This could be explained by different factors that can be both embryonic and/or extra-embryonic.

Prenatal exercise in fetal development: a placental perspective

Maternal obesity (MO) and gestational diabetes mellitus (GDM) are common in Western societies, which impair fetal development and predispose offspring to metabolic dysfunction. Placenta is the organ linking the mother to her fetus, and MO suppresses the development of vascular system and expression of nutrient transporters in placenta, thereby affecting fetal development. For maintaining its proper physiological function, placenta is energy demanding, which is met through extensive oxidative phosphorylation. However, the oxidative capacity of placenta is suppressed due to MO and GDM. Recently, several studies showed that physical activity during pregnancy enhances oxidative metabolism and improves placental function, which might be partially mediated by exerkines, referring to cytokines elicited by exercise. In addition, as an endocrine organ, placenta secretes cytokines, termed placentokines, including apelin, superoxide dismutase 3, irisin, and adiponectin, which mediate fetal development and maternal metabolism. Possible molecular mechanisms linking maternal exercise and placentokines to placental and fetal development are further discussed. As an emerging field, up to now, available studies are limited, mostly conducted in rodents. Given the epidemics of obesity and metabolic disorders, as well as the prevalence of maternal sedentary lifestyle, the effects of exercise of pregnant women on placental function and placentokine secretion, as well as their impacts on fetal development, need to be further examined.

Immunoendocrine Dysregulation during Gestational Diabetes Mellitus: The Central Role of the Placenta

Gestational Diabetes Mellitus (GDM) is a transitory metabolic condition caused by dysregulation triggered by intolerance to carbohydrates, dysfunction of beta-pancreatic and endothelial cells, and insulin resistance during pregnancy. However, this disease includes not only changes related to metabolic distress but also placental immunoendocrine adaptations, resulting in harmful effects to the mother and fetus. In this review, we focus on the placenta as an immuno-endocrine organ that can recognize and respond to the hyperglycemic environment. It synthesizes diverse chemicals that play a role in inflammation, innate defense, endocrine response, oxidative stress, and angiogenesis, all associated with different perinatal outcomes.

Single-cell transcriptome analysis reveals that maternal obesity affects DNA repair, histone methylation, and autophagy level in mouse embryos

Obesity causes many reproductive dysfunctions such as reduced conception, infertility, and early pregnancy loss, and this is largely due to the negative effects of obesity on oocyte and embryo quality. In the present study, we employed single-cell RNA transcriptome sequencing to investigate the potential causes for the maternal obesity effects on mouse embryos. Our results showed that the 4-cell and morula/blastocyst rates were all significantly decreased during embryo development in obese mice. Genome-wide analysis indicated that obesity altered the expression of more than 1100 genes in 2-cell embryos, including the genes which were related to the p53 signaling pathway and apoptosis. Further analysis showed that the expression of 47 genes related to DNA damage was changed, and a positive γH2A signal and the altered expression of Rad51 and Tex15 were observed in the obese embryos. Obesity also affected histone methylation, shown by the decrease of the H3K4-me2 level. Besides this, we observed the occurrence of autophagy and apoptosis in the embryos of obese mice. There were 42 genes that were related to autophagy/apoptosis that showed aberrant expression, and the positive LC3 signal and the decrease of Clec16a, Rraga, and Atg10 level were also observed. In summary, our study suggested that obesity affected early embryonic development by inducing DNA damage, aberrant histone methylation, and autophagy levels in mice.

Leptin promotes proliferation of neonatal mouse stem/progenitor spermatogonia

PURPOSE

To keep and increase spermatogonial stem cell number (SSC) is the only available option for pediatric cancer survivors to maintain fertility. Leptin is secreted by the epididymal white adipose tissue and has receptors on stem/progenitor spermatogonia. The purpose of this study is to demonstrate dose- and time-dependent proliferative effect of leptin on stem/progenitor spermatogonia cultures from prepubertal mice testes.

METHODS

CD90.2 (+) stem/progenitor spermatogonia were isolated from the C57BL/6 mouse testis on postnatal day 6 and placed in culture. The proliferative effect of leptin supplementation was assessed by colony formation (diameter and number), WST proliferation assays, and xCELLigence real-time cell analysis (RTCA) on days 3, 5, and 7 of culture. Expressions of p-ERK1/2, p-STAT3, total STAT3, and p-SHP2 levels were determined by western blot analysis.

RESULTS

Leptin supplementation of 100 ng/ml increased the diameter (p = 0.001) and number (p = 0.01) of colonies in stem/progenitor spermatogonial cultures and caused higher proliferation by WST-1 (p = 0.009) compared with the control on day 7. The EC50 was calculated as 114 ng/ml for leptin by RTCA. Proliferative dose of leptin induced increased expression of p-ERK1/2 (p = 0.009) and p-STAT3 (p = 0.023) on stem/progenitor spermatogonia when compared with the untreated group.

CONCLUSION

The results indicated that leptin supplementation exhibited a dose- and time-dependent proliferative effect on stem/progenitor spermatogonia that was associated with increased expression of ERK1/2 and STAT3 pathways while maintaining their undifferentiated state. This output presents a new agent that may help to expand the stem/progenitor spermatogonia pool from the neonatal testis in order to autotransplant after cancer treatment.

L-carnitine increases cell proliferation and amino acid transporter expression via the activation of insulin-like growth factor I signaling pathway in rat trophoblast cells

Early embryo implantation and development is primarily determined by the homeostasis between cellular apoptosis and proliferation as well as placental nutrient transporters. Recent studies showed that L-carnitine enhances female reproductive performance. However, the potential function of L-carnitine on placenta is largely unknown. In our study, primary rat trophoblast cells were separated and cultured for 12 hr in medium containing various concentrations of L-carnitine (0, 1, 10, and 50 mM). Placenta trophoblast cells treated with 50 mM L-carnitine increased the proportion of cells in S phase of the cell cycle (p < .05). In addition, live cell percentage was increased when treated with either 10 mM or 50 mM L-carnitine, which was accompanied with decreased necrotic cells, late apoptotic cells, and early apoptotic cells (p < .05). Compared with the control treatment, the mRNA expression of insulin-like growth factor I (IGF-1) and insulin-like growth factor I receptor (IGF-1R) was higher in rat placenta trophoblasts treated with either 10 mM or 50 mM L-carnitine (p < .05). Similarly, sodium-dependent neutral amino acid transporter (SNAT)-1 and SNAT2 were up-regulated in both mRNA and protein levels when trophoblast cells were treated with 50 mM L-carnitine (p < .05). Inhibiting downstream targets (Akt or ERK signaling pathways) of IGF-1 signaling pathway partially blocked the effect the L-carnitine-induced increase in protein abundances of SNAT1 and SNAT2. Collectively, our data showed protective role of L-carnitine on placenta trophoblast cells through the involvement of IGF-1 signaling pathway.

Pregnancy immune tolerance at the maternal-fetal interface

Pregnancy is a natural process that poses an immunological challenge because non-self fetus must be accepted. During the pregnancy period, the fetus as 'allograft' inherits maternal and also paternal antigens. For successful and term pregnancy, the fetus is tolerated and nurtured enjoying immune privileges that minimize the risk of being rejected by maternal immune system. Multiple mechanisms contribute to tolerate the semi-allogeneic fetus. Here, we summarize the recent progresses on how the maternal immune system actively collaborates to maintain the immune balance and maternal-fetal tolerance.

A Review of Candidate Genes and Pathways in Preeclampsia-An Integrated Bioinformatical Analysis

: Preeclampsia is a pregnancy-specific disorder characterized by the presence of hypertension with the onset of either proteinuria, maternal organ or uteroplacental dysfunction. Preeclampsia is one of the leading causes of maternal and fetal mortality and morbidity worldwide. However, the etiopathologies of preeclampsia are not fully understood. Many studies have indicated that genes are differentially expressed between normal and in the disease state. Hence, this study systematically searched the literature on human gene expression that was differentially expressed in preeclampsia. An electronic search was performed through 2019 through PubMed, Scopus, Ovid-Medline, and Gene Expression Omnibus where the following MeSH (Medical Subject Heading) terms were used and they had been specified as the primary focus of the articles: Gene, placenta, preeclampsia, and pregnancy in the title or abstract. We also found additional MeSH terms through Cochrane Library: Transcript, sequencing, and profiling. From 687 studies retrieved from the search, only original publications that had performed high throughput sequencing of human placental tissues that reported on differentially expressed genes in pregnancies with preeclampsia were included. Two reviewers independently scrutinized the titles and abstracts before examining the eligibility of studies that met the inclusion criteria. For each study, study design, sample size, sampling type, and method for gene analysis and gene were identified. The genes listed were further analyzed with the DAVID, STRING and Cytoscape MCODE. Three original research articles involving preeclampsia comprising the datasets in gene expression were included. By combining three studies together, 250 differentially expressed genes were produced at a significance setting of p < 0.05. We identified candidate genes: LEP, NRIP1, SASH1, and ZADHHC8P1. Through GO analysis, we found extracellular matrix organization as the highly significant enriched ontology in a group of upregulated genes and immune process in downregulated genes. Studies on a genetic level have the potential to provide new insights into the regulation and to widen the basis for identification of changes in the mechanism of preeclampsia. Integrated bioinformatics could identify differentially expressed genes which could be candidate genes and potential pathways in preeclampsia that may improve our understanding of the cause and underlying molecular mechanisms that could be used as potential biomarkers for risk stratification and treatment.

Changes in pregnancy-related serum biomarkers early in gestation are associated with later development of preeclampsia

Background

Placental protein expression plays a crucial role during pregnancy. We hypothesized that: (1) circulating levels of pregnancy-associated, placenta-related proteins throughout gestation reflect the temporal progression of the uncomplicated, full-term pregnancy, and can effectively estimate gestational ages (GAs); and (2) preeclampsia (PE) is associated with disruptions in these protein levels early in gestation; and can identify impending PE. We also compared gestational profiles of proteins in the human and mouse, using pregnant heme oxygenase-1 (HO-1) heterozygote (Het) mice, a mouse model reflecting PE-like symptoms.

Methods

Serum levels of placenta-related proteins–leptin (LEP), chorionic somatomammotropin hormone like 1 (CSHL1), elabela (ELA), activin A, soluble fms-like tyrosine kinase 1 (sFlt-1), and placental growth factor (PlGF)–were quantified by ELISA in blood serially collected throughout human pregnancies (20 normal subjects with 66 samples, and 20 subjects who developed PE with 61 samples). Multivariate analysis was performed to estimate the GA in normal pregnancy. Mean-squared errors of GA estimations were used to identify impending PE. The human protein profiles were then compared with those in the pregnant HO-1 Het mice.

Results

An elastic net-based gestational dating model was developed (R² = 0.76) and validated (R² = 0.61) using serum levels of the 6 proteins measured at various GAs from women with normal uncomplicated pregnancies. In women who developed PE, the model was not (R² = -0.17) associated with GA. Deviations from the model estimations were observed in women who developed PE (P = 0.01). The model developed with 5 proteins (ELA excluded) performed similarly from sera from normal human (R² = 0.68) and WT mouse (R² = 0.85) pregnancies. Disruptions of this model were observed in both human PE-associated (R² = 0.27) and mouse HO-1 Het (R² = 0.30) pregnancies. LEP outperformed sFlt-1 and PlGF in differentiating impending PE at early human and late mouse GAs.

Conclusions

Serum placenta-related protein profiles are temporally regulated throughout normal pregnancies and significantly disrupted in women who develop PE. LEP changes earlier than the well-established biomarkers (sFlt-1 and PlGF). There may be evidence of a causative action of HO-1 deficiency in LEP upregulation in a PE-like murine model.

Apelin and apelin receptor in human placenta: Expression, signalling pathway and regulation of trophoblast JEG‑3 and BeWo cells proliferation and cell cycle

Placentation requires the production of numerous growth factors, hormones and transcription factors. Many of them, like the adipose tissue-derived leptin or adiponectin, have been identified in the placenta and their role has been established in the proliferation and subsequent development of the placenta. Apelin is another adipokine known for proliferative effects in different cell types. PCR, immunoblotting and immunocytochemistry were used to study mRNA and protein expression of apelin and its receptor (APJ) in syncytiotrophoblast (BeWo) and cytotrophoblast (JEG-3) cells as well in immunohistochemistry in human normal placenta slides. The effect of apelin on cell proliferation study was investigated by alamarBlue^® and Cell Counting Kit-8 assays, the cell cycle by the flow cytometry method and the protein expression of cyclins and phosphorylation level of extracellular signal-regulated kinases (ERK)1/2, phosphatidylinositol 3′-kinase/protein kinase B (Akt), signal transducer and activator of transcription 3 (Stat3) and 5′-monophosphate-activated protein kinase (AMPKα) were studied by western blotting. Apelin was increased in JEG-3 compared with in BeWo cells, while APJ was the same in both placenta cell lines. Immunocytochemical analyses revealed high cytoplasmic and/or membrane apelin localisation in JEG-3, while BeWo cells exhibited markedly weaker apelin signal in the cytoplasm. Apelin increased cell proliferation as well as the percentage of cells in the G2/M phase of the cell cycle, cyclin proteins and the expression of all kinases mentioned above. In conclusion, apelin by promotion of trophoblast cell proliferation by APJ and ERK1/2, Stat3 and AMPKα signalling could be a new important adipokine in the regulation of early placental development.

Lactobacillus rhamnosus GG-induced Expression of Leptin in the Intestine Orchestrates Epithelial Cell Proliferation

BACKGROUND & AIMS

Identifying the functional elements that mediate efficient gut epithelial growth and homeostasis is essential for understanding intestinal health and disease. Many of these processes involve the Lactobacillus-induced generation of reactive oxygen species by NADPH oxidase (Nox1). However, the downstream signaling pathways that respond to Nox1-generated reactive oxygen species and mediate these events have not been described.

METHODS

Wild-type and knockout mice were fed Lactobacillus rhamnosus GG and the transcriptional and cell signaling pathway responses in the colon measured. Corroboration of data generated in mice was done using in organoid tissue culture and in vivo gut injury models.

RESULTS

Ingestion of L rhamnosus GG induces elevated levels of leptin in the gut epithelia, which as well as functioning in the context of metabolism, has pleiotropic activity as a chemokine that triggers cell proliferation. Consistently, using gut epithelial-specific knockout mice, we show that L rhamnosus GG-induced elevated levels of leptin is dependent on a functional Nox1 protein in the colonic epithelium, and that L rhamnosus GG-induced cell proliferation is dependent on Nox1, leptin, and leptin receptor. We also show that L rhamnosus GG induces the JAK-STAT signaling pathway in the gut in a Nox1, leptin, and leptin receptor-dependent manner.

CONCLUSIONS

These results demonstrate a novel role for leptin in the response to colonization by lactobacilli, where leptin functions in the transduction of signals from symbiotic bacteria to subepithelial compartments, where it modulates intestinal growth and homeostasis.

Adipokines underlie the early origins of obesity and associated metabolic comorbidities in the offspring of women with pregestational obesity

Maternal pregestational obesity is a well-known risk factor for offspring obesity, metabolic syndrome, cardiovascular disease and type 2 diabetes. The mechanisms by which maternal obesity can induce alterations in fetal and later neonatal metabolism are not fully elucidated due to its complexity and multifactorial causes. Two adipokines, leptin and adiponectin, are involved in fetal and postnatal growth trajectories, and both are altered in women with pregestational obesity. The placenta synthesizes leptin, which goes mainly to the maternal circulation and in lesser amount to the developing fetus. Maternal pregestational obesity and hyperleptinemia are associated with placental dysfunction and changes in nutrient transporters which directly affect fetal growth and development. By the other side, the embryo can produce its own leptin from early in development, which is associated to fetal weight and adiposity. Adiponectin, an insulin-sensitizing adipokine, is downregulated in maternal obesity. High molecular weight (HMW) adiponectin is the most abundant form and with most biological actions. In maternal obesity lower total and HMW adiponectin levels have been described in the mother, paralleled with high levels in the umbilical cord. Several studies have found that cord blood adiponectin levels are related with postnatal growth trajectories, and it has been suggested that low adiponectin levels in women with pregestational obesity enhance placental insulin sensitivity and activation of placental amino acid transport systems, supporting fetal overgrowth. The possible mechanisms by which maternal pregestational obesity, focusing in the actions of leptin and adiponectin, affects the fetal development and postnatal growth trajectories in their offspring are discussed.

Dyslipidemia and the role of adipose tissue in early pregnancy in the BPH/5 mouse model for preeclampsia

The hypertensive pregnancy disorder preeclampsia (PE) is a leading cause of fetal and maternal morbidity/mortality. Obesity increases the risk to develop PE, presumably via the release of inflammatory mediators from the adipose tissue, but the exact etiology remains largely unknown. Using obese PE-like blood pressure high subline 5 (BPH/5) and lean gestational age-matched C57Bl6 mice, we aimed to obtain insight into differential reproductive white adipose tissue (rWAT) gene expression, circulating lipids and inflammation at the maternal-fetal interface during early pregnancy. In addition, we investigated the effect of 7 days 25% calorie restriction (CR) in early pregnancy on gene expression in rWAT and implantation sites. Compared with C57Bl6, female BPH/5 are dyslipidemic before pregnancy and show an amplification of rWAT mass, circulating cholesterol, free fatty acids, and triacylglycerol levels throughout pregnancy. RNA sequencing showed that pregnant BPH/5 mice have elevated gene enrichment in pathways related to inflammation and cholesterol biosynthesis at embryonic day (e) 7.5. Expression of cholesterol-related HMGCS1, MVD, Cyp51a1, and DHCR was validated by quantitative reverse-transcription-polymerase chain reaction. CR during the first 7 days of pregnancy restored the relative mRNA expression of these genes to a level comparable to C57Bl6 pregnant females and reduced the expression of circulating leptin and proinflammatory prostaglandin synthase 2 in both rWAT and implantation sites in BPH/5 mice at e7.5. Our data suggest a possible role for rWAT in the dyslipidemic state and inflammatory uterine milieu that might underlie the pathogenesis of PE. Future studies should further address the physiological functioning of the adipose tissue in relation to PE-related pregnancy outcomes.

Relation between pregestational obesity and characteristics of the placenta

Objective: To evaluate the morphology of the placenta in patients with pregestational overweight (OW), pregestational obesity (PGOB), or normal weight.Methods: A cross-sectional study including women (n = 114) ≥20 years of age with a singleton pregnancy was carried out. The groups were integrated according to pregestational body mass index (BMI): 51 patients had a normal BMI (18.5-24.99 kg/m²), 30 were overweight (25-29.99 kg/m²), and 33 women were obese (≥30.0 kg/m²). A morphometric study of the placenta was performed and the placental maturity index (PMI) was calculated according to the formula: PMI = number of vasculo-syncytial membranes (VSM) in 1 mm²/VSM thickness. In the histopathological study, the presence of infarcts, calcifications, hemorrhage, thrombosis, fibrosis, cysts, and edema was determined.Results: The weight and length of newborns at birth were greater in the group with PGOB (p < .01). We observed a lower number of VSM (29 ± 9 versus 39 ± 13 and 34 ± 11) and a greater thickness (1.05 ± 0.24 versus 0.95 ± 0.08 and 0.89 ± 0.09) and, therefore, a lower PMI (29.75 ± 12.63 versus 40.88 ± 15.25 and 39.28 ± 14.4) in the group of women with PGOB compared with the group of women with OW or normal weight (p < .01). The histopathological analyses showed a greater frequency of edema and cysts in the PGOB group.Conclusion: PGOB is associated with a higher placental weight and newborn weight, a lower PMI, and the presence of histopathological alterations. The preceding points highlight the importance of promoting an appropriate pregestational weight in women of reproductive age.

Leptin protects placental cells from apoptosis induced by acidic stress

Development of the human placenta is critical for a successful pregnancy. The placenta allows the exchange of oxygen and carbon dioxide and is crucial to manage acid-base balance within a narrow pH. It is known that low pH levels are a risk of apoptosis in several tissues. However, there has been little discussion about the effect of acidic stress in the placenta. Leptin is produced by the placenta with a trophic autocrine effect. Previous results of our group have demonstrated that leptin prevents apoptosis of trophoblast cells under different stress conditions such as serum deprivation and hyperthermia. The purpose of the present work is to evaluate acidic stress consequences in trophoblast explant survival and to determine leptin action in these conditions. For this objective, term human trophoblast explants were cultured at physiological pH (pH 7.4) and at acidic pH (pH 6.8) in the presence or absence of leptin. Western blot assays were performed to study the abundance of active caspase-3 and the p89 fragment of PARP-1. Pro-apoptotic and pro-survival members of Bcl-2 family, as Bax, t-Bid, and Bcl-2, were studied. Moreover, p53 pathway was also evaluated including Mdm-2, the main p53 regulator. Active caspase-3 and cleaved PARP-1 abundances were increased at low extracellular pH. Moreover, t-Bid levels were also augmented as well as p53 expression and phosphorylation on S46. Leptin treatment prevents the consequences of acidosis, decreasing p53 expression and increasing Mdm-2 expression. In summary, this work demonstrated for first time that low pH induces apoptosis of human trophoblast explants involving apoptotic intrinsic pathway, and leptin impairs this effect.

The Role of Placental Hormones in Mediating Maternal Adaptations to Support Pregnancy and Lactation

During pregnancy, the mother must adapt her body systems to support nutrient and oxygen supply for growth of the baby in utero and during the subsequent lactation. These include changes in the cardiovascular, pulmonary, immune and metabolic systems of the mother. Failure to appropriately adjust maternal physiology to the pregnant state may result in pregnancy complications, including gestational diabetes and abnormal birth weight, which can further lead to a range of medically significant complications for the mother and baby. The placenta, which forms the functional interface separating the maternal and fetal circulations, is important for mediating adaptations in maternal physiology. It secretes a plethora of hormones into the maternal circulation which modulate her physiology and transfers the oxygen and nutrients available to the fetus for growth. Among these placental hormones, the prolactin-growth hormone family, steroids and neuropeptides play critical roles in driving maternal physiological adaptations during pregnancy. This review examines the changes that occur in maternal physiology in response to pregnancy and the significance of placental hormone production in mediating such changes.

Leptin action in normal and pathological pregnancies

Leptin is now considered an important signalling molecule of the reproductive system, as it regulates the production of gonadotrophins, the blastocyst formation and implantation, the normal placentation, as well as the foeto-placental communication. Leptin is a peptide hormone secreted mainly by adipose tissue, and the placenta is the second leptin-producing tissue in humans. Placental leptin is an important cytokine which regulates placental functions in an autocrine or paracrine manner. Leptin seems to play a crucial role during the first stages of pregnancy as it modulates critical processes such as proliferation, protein synthesis, invasion and apoptosis in placental cells. Furthermore, deregulation of leptin levels has been correlated with the pathogenesis of various disorders associated with reproduction and gestation, including polycystic ovary syndrome, recurrent miscarriage, gestational diabetes mellitus, pre-eclampsia and intrauterine growth restriction. Due to the relevant incidence of the mentioned diseases and the importance of leptin, we decided to review the latest information available about leptin action in normal and pathological pregnancies to support the idea of leptin as an important factor and/or predictor of diverse disorders associated with reproduction and pregnancy.

Involvement of leptin in the molecular physiology of the placenta

Leptin is a homeostatic regulator in the placenta where it promotes proliferation, protein synthesis and the expression of tolerogenic maternal response molecules such as HLA-G. Leptin also exerts an anti-apoptotic action in placenta controlling the expression of p53 master cell cycle regulator under different stress conditions. On the other hand, leptin is an integrative target of different placental stimuli. The expression of leptin in placenta is regulated by hCG, insulin, steroids, hypoxia and many other growth hormones, suggesting that it might have an important endocrine function in the trophoblastic cells. The leptin expression is induced involving the cAMP/PKA or cAMP/Epac pathways which have profound actions upon human trophoblast function. The activation of PI3K and MAPK pathways also participates in the leptin expression. Estrogens play a central role during pregnancy, particularly 17β-estradiol upregulates the leptin expression in placental cells through genomic and non-genomic actions. The leptin promoter analysis reveals specific elements that are active in placental cells. The transcription factors CREB, AP1, Sp1, NFκB and the coactivator CBP are involved in the placental leptin expression. Moreover, placental leptin promoter is a target of epigenetic marks such as DNA methylation and histone acetylation that regulates not only the leptin expression in placenta during pregnancy but also determines the predisposition of acquiring adult metabolism diseases. Taken together, all these results allow a better understanding of leptin function and regulatory mechanisms of leptin expression in human placental trophoblasts, and support the importance of leptin during pregnancy and in programming adult health.

Role of leptin as a link between metabolism and the immune system

Leptin is an adipocyte-derived hormone not only with an important role in the central control of energy metabolism, but also with many pleiotropic effects in different physiological systems. One of these peripheral functions of leptin is a regulatory role in the interplay between energy metabolism and the immune system, being a cornerstone of the new field of immunometabolism. Leptin receptor is expressed throughout the immune system and the regulatory effects of leptin include cells from both the innate and adaptive immune system. Leptin is one of the adipokines responsible for the inflammatory state found in obesity that predisposes not only to type 2 diabetes, metabolic syndrome and cardiovascular disease, but also to autoimmune and allergic diseases. Leptin is an important mediator of the immunosuppressive state in undernutrition status. Placenta is the second source of leptin and it may play a role in the immunomodulation during pregnancy. Finally, recent work has pointed to the participation of leptin and leptin receptor in the pathophysiology of inflammation in oral biology. Therefore, leptin and leptin receptor should be considered for investigation as a marker of inflammation and immune activation in the frontier of innate-adaptive system, and as possible targets for intervention in the immunometabolic mediated pathophysiology.

Activities for leptin in bovine trophoblast cells

Leptin is involved in various reproductive processes in humans and rodents, including placental development and function. The specific ways that leptin influences placental development and function in cattle are poorly understood. This work was completed to explore how leptin regulates hormone, cytokine and metalloprotease transcript abundance, and cell proliferation in cultured bovine trophoblast cells. In the first set of studies, cells were cultured in the presence of graded recombinant bovine leptin concentrations (0, 10, 50, 250 ng/mL) for 6 or 24 h. Transcript profiles were examined from extracted RNA. Leptin supplementation did not affect abundance of the maternal recognition of pregnancy factor, interferon-tau (IFNT), but leptin increased (P < 0.05) abundance of chorionic somatomammotropin hormone 2 (CSH2; ie, placental lactogen) at both 6 and 24 h at each concentration tested. At 24 h, the greatest CSH2 abundance (P < 0.05) was detected in cells supplemented with 50 ng/mL leptin. Transcript abundance of the remodeling factor, metalloprotease 2 (MMP2), was greater (P < 0.05) in leptin-treated cells at 24 h but not at 6 h. The 24 h MMP2 response was greatest (P < 0.05) at 250 ng/mL. Transcript abundance for MMP9 was not altered by leptin treatment. In a separate set of studies, cell proliferation assays were completed. Leptin supplementation did not affect bovine trophoblast cell line proliferation at any dose tested. In conclusion, leptin supplementation did not affect bovine trophoblast cell proliferation or IFNT expression, but leptin increases CSH2 and MMP2 transcript abundance. Both of these factors are involved with peri-implantation and postimplantation placental development and function, and this implicates leptin as a potential mediator of early placental development and function in cattle.

Leptin Levels Are Higher in Whole Compared to Skim Human Milk, Supporting a Cellular Contribution

Human milk (HM) contains a plethora of metabolic hormones, including leptin, which is thought to participate in the regulation of the appetite of the developing infant. Leptin in HM is derived from a combination of de novo mammary synthesis and transfer from the maternal serum. Moreover, leptin is partially lipophilic and is also present in HM cells. However, leptin has predominately been measured in skim HM, which contains neither fat nor cells. We optimised an enzyme-linked immunosorbent assay for leptin measurement in both whole and skim HM and compared leptin levels between both HM preparations collected from 61 lactating mothers. Whole HM leptin ranged from 0.2 to 1.47 ng/mL, whilst skim HM leptin ranged from 0.19 to 0.9 ng/mL. Whole HM contained, on average, 0.24 ± 0.01 ng/mL more leptin than skim HM (p < 0.0001, n = 287). No association was found between whole HM leptin and fat content (p = 0.17, n = 287), supporting a cellular contribution to HM leptin. No difference was found between pre- and post-feed samples (whole HM: p = 0.29, skim HM: p = 0.89). These findings highlight the importance of optimising HM leptin measurement and assaying it in whole HM to accurately examine the amount of leptin received by the infant during breastfeeding.

Insulin Exhibits an Antiproliferative and Hypertrophic Effect in First Trimester Human Extravillous Trophoblasts

Our aim was to investigate the effect of high levels of glucose, insulin, leptin, and tumor necrosis factor alpha, biomarkers of diabetes in pregnancy, in the process of placentation, using as a cell model a first trimester extravillous human trophoblast cell line (HTR8/SVneo cells). Exposure of HTR8/SVneo cells for 24 hours to either glucose (20 mmol/L) or leptin (25-100 ng/mL) did not cause significant changes in cell proliferation and viability. Tumor necrosis factor alpha (24 hours; 10-100 ng/L) caused a small decrease (10%) in cell proliferation and an increase (9%) in cell viability; however, both effects disappeared when exposure time was increased. Insulin (24 hours; 1-10 nmol/L) caused a concentration- and time-dependent decrease (10%-20%) in cell proliferation; the effect of insulin (10 nmol/L) was more pronounced after a 48 hours exposure (35%). In contrast, exposure to insulin (10 nmol/L; 48 hours) showed no significant effect on cell viability, apoptosis, and migration capacity. Insulin appears to cause hypertrophy of HTR8/SVneo cells as it reduces the cell mitotic index while increasing the culture protein content. The antiproliferative effect of insulin seems to involve activation of mammalian target of rapamycin, phosphoinositide 3-kinase, and p38 mitogen-activated protein kinase. Finally, simvastatin and the polyphenol quercetin potentiated the antiproliferative effect of insulin; on the contrary, the polyphenol resveratrol, the polyunsaturated fatty acids eicosapentaenoic and docosahexaenoic acids, and folic acid were not able to change it. In conclusion, we show that insulin has an antiproliferative and hypertrophic effect on a first trimester extravillous human trophoblast cell line. So insulin might affect the process of placentation.

Maternal Hyperleptinemia Is Associated with Male Offspring's Altered Vascular Function and Structure in Mice

Children of mothers with gestational diabetes have greater risk of developing hypertension but little is known about the mechanisms by which this occurs. The objective of this study was to test the hypothesis that high maternal concentrations of leptin during pregnancy, which are present in mothers with gestational diabetes and/or obesity, alter blood pressure, vascular structure and vascular function in offspring. Wildtype (WT) offspring of hyperleptinemic, normoglycemic, Leprdb/+ dams were compared to genotype matched offspring of WT-control dams. Vascular function was assessed in male offspring at 6, and at 31 weeks of age after half the offspring had been fed a high fat, high sucrose diet (HFD) for 6 weeks. Blood pressure was increased by HFD but not affected by maternal hyperleptinemia. On a standard diet, offspring of hyperleptinemic dams had outwardly remodeled mesenteric arteries and an enhanced vasodilatory response to insulin. In offspring of WT but not Leprdb/+ dams, HFD induced vessel hypertrophy and enhanced vasodilatory responses to acetylcholine, while HFD reduced insulin responsiveness in offspring of hyperleptinemic dams. Offspring of hyperleptinemic dams had stiffer arteries regardless of diet. Therefore, while maternal hyperleptinemia was largely beneficial to offspring vascular health under a standard diet, it had detrimental effects in offspring fed HFD. These results suggest that circulating maternal leptin concentrations may interact with other factors in the pre- and post -natal environments to contribute to altered vascular function in offspring of diabetic pregnancies.

Leptin reduces apoptosis triggered by high temperature in human placental villous explants: The role of the p53 pathway

Maternal fever is common during pregnancy and has for many years been suspected to harm the developing fetus. Whether increased maternal temperature produces exaggerated apoptosis in trophoblast cells remains unclear. Since p53 is a critical regulator of apoptosis we hypothesized that increased temperature in placenta produces abnormal expression of proteins in the p53 pathway and finally caspase-3 activation. Moreover, leptin, produced by placenta, is known to promote the proliferation and survival of trophoblastic cells. Thus, we aimed to study the possible role of leptin preventing apoptosis triggered by high temperature, as well as the molecular mechanisms underlying this effect. Fresh placental tissue was collected from normal pregnancies. Explants of placental villi were exposed to 37 °C, 40 °C and 42 °C during 3 h in the presence or absence of 10 nM leptin in DMEM-F12 medium. Western blotting and qRT-PCR was performed to analyze the expression of p53 and downstream effector, P53AIP1, Mdm2, p21, BAX and BCL-2 as well as the activated cleaved form of caspase-3 and the fragment of cytokeratin-18 (CK-18) cleaved at Asp396 (neoepitope M30). Phosphorylation of the Ser 46 residue on p53, the expression of P53AIP1, Mdm2, p21, as well as caspase-3 and CK-18 were significantly increased in explants at 40 °C and 42 °C. Conversely, these effects were significantly attenuated by leptin 10 nM at both 40 °C and 42 °C. The BCL2/BAX ratio was also significantly decreased in explants at 40 °C and 42 °C compared with explants incubated at 37 °C, which was prevented by leptin stimulation. These data illustrate the potential role of leptin for reducing apoptosis in trophoblast explants, including trophoblastic cells, triggered by high temperature, by preventing the activation of p53 signaling.

The endocrine function of human placenta: an overview

During pregnancy, several tightly coordinated and regulated processes take place to enable proper fetal development and gestational success. The formation and development of the placenta is one of these critical pregnancy events. This organ plays essential roles during gestation, including fetal nourishment, support and protection, gas exchange and production of several hormones and other mediators. Placental hormones are mainly secreted by the syncytiotrophoblast, in a highly and tightly regulated way. These hormones are important for pregnancy establishment and maintenance, exerting autocrine and paracrine effects that regulate decidualization, placental development, angiogenesis, endometrial receptivity, embryo implantation, immunotolerance and fetal development. In addition, because they are released into maternal circulation, the profile of their blood levels throughout pregnancy has been the target of intense research towards finding potential robust and reliable biomarkers to predict and diagnose pregnancy-associated complications. In fact, altered levels of these hormones have been associated with some pathologies, such as chromosomal anomalies or pre-eclampsia. This review proposes to revise and update the main pregnancy-related hormones, addressing their major characteristics, molecular targets, function throughout pregnancy, regulators of their expression and their potential clinical interest.

Placental fatty acid transport in maternal obesity

Pregestational obesity is a significant risk factor for adverse pregnancy outcomes. Maternal obesity is associated with a specific proinflammatory, endocrine and metabolic phenotype that may lead to higher supply of nutrients to the feto-placental unit and to excessive fetal fat accumulation. In particular, obesity may influence placental fatty acid (FA) transport in several ways, leading to increased diffusion driving force across the placenta, and to altered placental development, size and exchange surface area. Animal models show that maternal obesity is associated with increased expression of specific FA carriers and inflammatory signaling molecules in placental cotyledonary tissue, resulting in enhanced lipid transfer across the placenta, dislipidemia, fat accumulation and possibly altered development in fetuses. Cell culture experiments confirmed that inflammatory molecules, adipokines and FA, all significantly altered in obesity, are important regulators of placental lipid exchange. Expression studies in placentas of obese-diabetic women found a significant increase in FA binding protein-4 expression and in cellular triglyceride content, resulting in increased triglyceride cord blood concentrations. The expression and activity of carriers involved in placental lipid transport are influenced by the endocrine, inflammatory and metabolic milieu of obesity, and further studies are needed to elucidate the strong association between maternal obesity and fetal overgrowth.

Mechanisms involved in p53 downregulation by leptin in trophoblastic cells

Leptin, a 16-kDa polypeptide hormone, is produced by the adipocyte and can also be synthesized by placenta. We previously demonstrated that leptin promotes proliferation and survival in placenta, in part mediated by the p53 pathway. In this work, we investigated the mechanisms involved in leptin down-regulation of p53 level. The human first trimester cytotrophoblastic Swan-71 cell line and human placental explants at term were used. In order to study the late phase of apoptosis, triggered by serum deprivation, experiments of DNA fragmentation were carried out. Exogenous leptin added to human placental explants, showed a decrease on DNA ladder formation and MAPK pathway is involved in this leptin effect. We also found that under serum deprivation condition, leptin decreases p53 levels and the inhibitory leptin effect is lost when cells were pretreated with 50 μM PD98059 or 10 μM LY29004; or were transfected with dominant negative mutants of intermediates of these pathways, suggesting that MAPK and PI3K signaling pathways are necessaries for leptin action. Additionally, leptin diminished Ser-46 p53 phosphorylation and this effect in placental explants was mediated by the activation of MAPK and PI3K pathways. Finally, in order to assess leptin effect on p53 half-life experiments with cycloheximide were performed and MDM-2 expression was analyzed. Leptin diminished p53 half-life and up-regulated MDM-2 expression. In summary, we provided evidence suggesting that leptin anti-apoptotic effect is mediated by MAPK and PI3K pathways.

Direct effects of leptin and adiponectin on peripheral reproductive tissues: a critical review

Obesity is a risk factor for infertility and adverse reproductive outcomes. Adipose tissue is an important endocrine gland that secretes a host of endocrine factors, called adipokines, which modulate diverse physiologic processes including appetite, metabolism, cardiovascular function, immunity and reproduction. Altered adipokine expression in obese individuals has been implicated in the pathogenesis of a host of health disorders including diabetes and cardiovascular disease. It remains unclear whether adipokines play a significant role in the pathogenesis of adverse reproductive outcomes in obese individuals and, if so, whether the adipokines are acting directly or indirectly on the peripheral reproductive tissues. Many groups have demonstrated that receptors for the adipokines leptin and adiponectin are expressed in peripheral reproductive tissues and that these adipokines are likely, therefore, to exert direct effects on these tissues. Many groups have tested for direct effects of leptin and adiponectin on reproductive tissues including the testis, ovary, uterus, placenta and egg/embryo. The hypothesis that decreased fertility potential or adverse reproductive outcomes may result, at least in part, from defects in adipokine signaling within reproductive tissues has also been tested. Here, we present a critical analysis of published studies with respect to two adipokines, leptin and adiponectin, for which significant data have been generated. Our evaluation reveals significant inconsistencies and methodological limitations regarding the direct effects of these adipokines on peripheral reproductive tissues. We also observe a pervasive failure to account for in vivo data that challenge observations made in vitro. Overall, while leptin and adiponectin may directly modulate peripheral reproductive tissues, existing data suggest that these effects are minor and non-essential to human or mouse reproductive function. Current evidence suggests that direct effects of leptin or adiponectin on peripheral reproductive tissues are unlikely to factor significantly in the adverse reproductive outcomes observed in obese individuals.

Dose-dependent biphasic leptin-induced proliferation is caused by non-specific IL-6/NF-κB pathway activation in human myometrial cells

BACKGROUND AND PURPOSE

Leptin, an adipokine synthesized by the placenta during pregnancy, has been proposed for the management of preterm labour (PTL), as it is able to prevent in vitro uterine contractility and remodelling associated with labour onset. Another common feature of labour onset is the phenotypic switch of myometrial smooth muscle cells from a proliferative to a hypertrophic state. As proliferative effects have been demonstrated for leptin in other tissues, we aimed to investigate its ability to induce myometrial proliferation and thus to maintain uterine quiescence.

EXPERIMENTAL APPROACH

We stimulated human primary myometrial smooth muscle cells with leptin in the presence or absence of receptor antagonists or signalling pathway inhibitors.

KEY RESULTS

Leptin induced myometrial cell proliferation in a biphasic manner. At 6.25 ng · mL(-1), leptin-induced proliferation was mediated by the leptin receptor and required the early activation of ERK1/2. At a concentration above 25 ng · mL(-1), leptin induced direct non-specific stimulation of the IL-6 receptor, leading to NF-κB activation, and exerted anti-proliferative effects. However, at 50 ng · mL(-1), leptin re-induces proliferation via IL-6 receptor stimulation that requires STAT3 and delayed ERK1/2 activation.

CONCLUSIONS AND IMPLICATIONS

These data bring new insights into leptin signalling-induced myometrial proliferation and its interrelationship with the IL-6/IL-6 receptor axis. In the light of our previous work, the present study emphasizes the potential value of leptin in the pharmacological management of PTL and it also strengthens the hypothesis that leptin might be a contributory factor in the parturition-related disorders observed in obese women.

Leptin in the canine uterus and placenta: possible implications in pregnancy

BACKGROUND

Leptin (Lep) is known for its involvement in the regulation of reproductive functions. It is important for uterine receptivity, implantation, placental growth and maternal energy homeostasis in several species, but Lep's function in the pregnant dog has not been investigated.

METHODS

Pregnant bitches were ovariohysterectomized at pre-implantation, post-implantation, mid-gestation and prepartum luteolysis. Two additional groups were treated with aglepristone in mid-gestation, and ovariohysterectomized 24 or 72 h later. Lep and leptin receptor (LepR) gene expression was detected by semi-quantitative real-time PCR in pre-implantation and inter-placental uterine sections (Ut) and in utero-placental compartments (Ut/Pl). Immunohistochemistry and in situ hybridization (ISH) were performed for Lep and LepR protein and mRNA localization. Parametric one-way ANOVA, paired t-test and Wilcoxon signed-rank test were used for statistical analysis.

RESULTS

In the Ut/Pl, Lep expression was higher at post-implantation and prepartum luteolysis than at mid-gestation, while in the Ut, Lep mRNA levels did not change during pregnancy. LepR expression in the Ut/Pl was up-regulated at prepartum luteolysis compared to the earlier stages. In the Ut, highest LepR mRNA was found at pre- and post-implantation. LepR expression was down-regulated in the Ut/Pl compared to the Ut at post-implantation and at mid-gestation. Aglepristone treatment resulted in a decrease of Lep mRNA levels from 24 to 72 h in the Ut without concomitant changes in the Ut/Pl or in LepR levels. Lep and LepR immunoreactivities were strong in the luminal and glandular epithelium in the Ut with abundant LepR signals in the subepithelial stroma. In the Ut/Pl, fetal trophoblasts stained stronger for Lep and LepR than decidual cells, and signals for both proteins were also detected in the glandular chambers. The myometrium, blood vessel media, and sporadically also the endothelium stained for Lep and LepR. ISH showed similar signal distribution in the Ut and Ut/Pl.

CONCLUSIONS

Lep and LepR are differentially expressed in the canine uterus and placenta during pregnancy, and their presence in various cell types indicates paracrine/autocrine roles. The Lep signaling system may be one of the pathways involved in feto-maternal cross-talk, implantation and maintenance of pregnancy, and may have a regulatory role around parturition.

Leptin promotes HLA-G expression on placental trophoblasts via the MEK/Erk and PI3K signaling pathways

INTRODUCTION

The development of the human haemochorial placenta requires complex regulatory mechanisms to protect invasive trophoblast cells from cytotoxic responses elicited by maternal immune cells. Leptin, the adipocyte derived hormone encoded by the Lep gene, is synthesized by placental trophoblasts and exerts pleiotropic effects on the immune system, including the promotion of inflammation and the activation of T cell responses.

METHODS

To address its possible involvement in the modulation of maternal immune responses during pregnancy, we investigated the effect of leptin on the expression of the class Ib histocompatibility antigen HLA-G as one of the chief immunosuppressive strategies used by trophoblast cells.

RESULTS

In vitro incubation of the trophoblast derived Swan 71 and JEG-3 cell lines with 25-50 ng/ml recombinant leptin significantly boosted HLA-G mRNA and protein expression, and this effect was abrogated upon pharmacological inhibition of the PI3K-Akt and MEK-Erk signaling pathways. A similar stimulatory effect of leptin was observed in term placental tissue explants, though 10-fold higher doses were required for stimulation. Further, JEG-3 cells treated with a leptin antisense oligodeoxynucleotide displayed decreased HLA-G expression levels, which were partially recovered by addition of stimulating doses of exogenous hormone. Immunofluorescence and qPCR analysis confirmed leptin biosynthesis in placental tissue, further showing that invasive extravillous trophoblast cells were a main source of this hormone during the first trimester of normal pregnancies.

DISCUSSION

Taken together, our results show that leptin acts as an autocrine/paracrine signal promoting HLA-G expression in placental trophoblasts suggesting an important role in the regulation of immune evasion mechanisms at the fetal maternal interface.

Leptin is an anti-apoptotic effector in placental cells involving p53 downregulation

Leptin, a peripheral signal synthetized by the adipocyte to regulate energy metabolism, can also be produced by placenta, where it may work as an autocrine hormone. We have previously demonstrated that leptin promotes proliferation and survival of trophoblastic cells. In the present work, we aimed to study the molecular mechanisms that mediate the survival effect of leptin in placenta. We used the human placenta choriocarcinoma BeWo and first trimester Swan-71 cell lines, as well as human placental explants. We tested the late phase of apoptosis, triggered by serum deprivation, by studying the activation of Caspase-3 and DNA fragmentation. Recombinant human leptin added to BeWo cell line and human placental explants, showed a decrease on Caspase-3 activation. These effects were dose dependent. Maximal effect was achieved at 250 ng leptin/ml. Moreover, inhibition of endogenous leptin expression with 2 µM of an antisense oligonucleotide, reversed Caspase-3 diminution. We also found that the cleavage of Poly [ADP-ribose] polymerase-1 (PARP-1) was diminished in the presence of leptin. We analyzed the presence of low DNA fragments, products from apoptotic DNA cleavage. Placental explants cultivated in the absence of serum in the culture media increased the apoptotic cleavage of DNA and this effect was prevented by the addition of 100 ng leptin/ml. Taken together these results reinforce the survival effect exerted by leptin on placental cells. To improve the understanding of leptin mechanism in regulating the process of apoptosis we determined the expression of different intermediaries in the apoptosis cascade. We found that under serum deprivation conditions, leptin increased the anti-apoptotic BCL-2 protein expression, while downregulated the pro-apoptotic BAX and BID proteins expression in Swan-71 cells and placental explants. In both models leptin augmented BCL-2/BAX ratio. Moreover we have demonstrated that p53, one of the key cell cycle-signaling proteins, is downregulated in the presence of leptin under serum deprivation. On the other hand, we determined that leptin reduced the phosphorylation of Ser-46 p53 that plays a pivotal role for apoptotic signaling by p53. Our data suggest that the observed anti-apoptotic effect of leptin in placenta is in part mediated by the p53 pathway. In conclusion, we provide evidence that demonstrates that leptin is a trophic factor for trophoblastic cells.

Increased leptin by hypoxic-preconditioning promotes autophagy of mesenchymal stem cells and protects them from apoptosis

Autophagy is the basic catabolic progress involved in cell degradation of unnecessary or dysfunctional cellular components. It has been proven that autophagy could be utilized for cell survival under stresses. Hypoxic-preconditioning (HPC) could reduce apoptosis induced by ischemia and hypoxia/serum deprivation (H/SD) in bone marrow-derived mesenchymal stem cells (BMSCs). Previous studies have shown that both leptin signaling and autophagy activation were involved in the protection against apoptosis induced by various stress, including ischemia-reperfusion. However, it has never been fully understood how leptin was involved in the protective effects conferred by autophagy. In the present study, we demonstrated that HPC can induce autophagy in BMSCs by increased LC3-II/LC3-I ratio and autophagosome formation. Interestingly, similar effects were also observed when BMSCs were pretreated with rapamycin. The beneficial effects offered by HPC were absent when BMSCs were incubated with autophagy inhibitor, 3-methyladenine (3-MA). In addition, down-regulated leptin expression by leptin-shRNA also attenuated HPC-induced autophagy in BMSCs, which in turn was associated with increased apoptosis after exposed to sustained H/SD. Furthermore, increased AMP-activated protein kinase phosphorylation and decreased mammalian target of rapamycin phosphorylation that were observed in HPC-treated BMSCs can also be attenuated by down-regulation of leptin expression. Our data suggests that leptin has impact on HPC-induced autophagy in BMSCs which confers protection against apoptosis under H/SD, possibly through modulating both AMPK and mTOR pathway.

TREM-1 expression is increased in human placentas from severe early-onset preeclamptic pregnancies where it may be involved in syncytialization

Preeclampsia, a major cause of maternal and perinatal morbidity and mortality, is thought to be attributable to dysregulation of trophoblast invasion and differentiation. Microarray studies have shown that triggering receptor expressed on myeloid cells (TREM) 1, a cell surface molecule involved in the inflammatory response, is increased in preeclamptic placentas. The aim of this study was to determine the level of TREM-1 expression in severe early-onset preeclamptic placentas and its functional role in trophoblast differentiation. Placenta was obtained from women with severe early-onset preeclampsia (n = 19) and gestationally matched preterm controls placentas (n = 8). The TREM-1 expression was determined by quantitative reverse transcriptase polymerase chain reaction and Western blotting. The effect of TREM-1 small interfering RNA on cell fusion and differentiation was assessed in BeWo cells. The effect of oxygen tension on TREM-1 levels, in basal or forskolin-treated BeWo cells, was also assessed. The TREM-1 was localized to the syncytiotrophoblast layer, and TREM-1 messenger RNA and protein expression was significantly increased in preeclamptic placentas. The BeWo cells treated with forskolin were associated with increased TREM-1 expression. The TREM-1 knockdown inhibited forskolin-induced expression of the differentiation marker β-human chorionic gonadotropin but had no effect on the cell-fusion marker E-cadherin. The increase in TREM-1 expression in BeWo cells treated with forskolin during normoxic conditions was reduced in forskolin-treated cells under hypoxic conditions. In conclusion, TREM-1 is increased in preeclamptic placentas and by forskolin treatment. Knockdown of TREM-1 by RNA interference inhibits cell differentiation but has no effect on cell-cell fusion. Finally, we show that TREM-1 upregulation is attenuated under hypoxic conditions in which cell differentiation is impaired.