Leptin stimulates protein synthesis-activating translation machinery in human 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.

Placental apoptosis increased by hypoxia inducible factor-1 stabilization is counteracted by leptin†

During pregnancy, apoptosis is a physiological event critical in the remodeling and aging of the placenta. Increasing evidence has pointed toward the relevance of hypoxia as modulator of trophoblast cell death. Previous reports have shown that leptin, a placental cytokine, promotes cell survival in both cell culture and placental explant models. The aim of this work is to establish the role of leptin in apoptosis under hypoxic condition in trophoblast cells. In this study, we evaluated the effect of cobalt chloride, a hypoxia mimicking agent that stabilizes the expression of hypoxia-inducible factor-1 alpha, on Swan-71 and human placental explants. Hypoxia chamber was also used to generate 2% oxygen. Apoptosis was determined by the presence of apoptotic nucleus, fragmentation of DNA and Caspase-3 and PARP-1 cleavage. The pro-apoptotic proteins BAX, BID, BAD, and BAK and the anti-apoptotic effectors BCL-2, B-cell lymphoma-extra-large, and myeloid cell leukemia-1 were also analyzed. We found that hypoxia-inducible factor-1 alpha stabilization increased the appearance of apoptotic nucleus, fragmentation of DNA, and Caspase-3 and PARP-1 cleavage. Hypoxia mimicking conditions enhanced the expression of pro-apoptotic effectors BAX, BID, BAD, and BAK. Hypoxia-inducible factor-1 alpha stabilization also downregulated the level of BCL-2, B-cell lymphoma-extra-large, and myeloid cell leukemia-1. All these apoptotic parameters changes were reversed with leptin treatment. Moreover, we showed that leptin action on apoptosis modulation involves PI3K and MAPK signaling pathways. Obtained data demonstrate that hypoxia-inducible factor-1 alpha stabilization induces apoptosis in human placenta and leptin counteracts this effect, reinforcing its role as a survival cytokine.

Placental dysfunction in obese women and antenatal surveillance

Obesity is a significant health concern worldwide and is associated with numerous health complications, including placental dysfunction during pregnancy. Placental dysfunction can lead to adverse outcomes for both the mother and the foetus, such as preeclampsia, gestational diabetes, preterm birth, and foetal growth restriction. Studies have shown that maternal obesity can lead to placental dysfunction through various mechanisms, including chronic inflammation, oxidative stress, and dysregulation of metabolic pathways. These factors can contribute to changes in the placenta's structure and function, impairing nutrient and oxygen exchange between the mother and foetus. Recent research has also suggested that alteration of gene expression in the placenta due to epigenetic changes, such as DNA methylation, may play a role in placental dysfunction associated with maternal obesity. These changes can affect altering foetal growth and development. Prevention and management of maternal obesity are crucial in reducing the risk of placental dysfunction and associated adverse outcomes during pregnancy. This can be achieved through lifestyle modifications, such as diet and exercise, and early detection and management of underlying health conditions. In conclusion, maternal obesity is a significant risk factor for placental dysfunction during pregnancy, which can lead to adverse outcomes for both the mother and the foetus. Further research is needed to understand the relationship and mechanisms to develop effective interventions to prevent and manage placental dysfunction in obese pregnant women.

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.

Impact of Co-Occurrence of Obesity and SARS-CoV-2 Infection during Pregnancy on Placental Pathologies and Adverse Birth Outcomes: A Systematic Review and Narrative Synthesis

Obesity is a risk factor for severe COVID-19 disease during pregnancy. We hypothesized that the co-occurrence of high maternal body mass index (BMI) and gestational SARS-CoV-2 infection are detrimental to fetoplacental development. We conducted a systematic review following PRISMA/SWiM guidelines and 13 studies were eligible. In the case series studies (n = 7), the most frequent placental lesions reported in SARS-CoV-2(+) pregnancies with high maternal BMI were chronic inflammation (71.4%, 5/7 studies), fetal vascular malperfusion (FVM) (71.4%, 5/7 studies), maternal vascular malperfusion (MVM) (85.7%, 6/7 studies) and fibrinoids (100%, 7/7 studies). In the cohort studies (n = 4), three studies reported higher rates of chronic inflammation, MVM, FVM and fibrinoids in SARS-CoV-2(+) pregnancies with high maternal BMI (72%, n = 107/149; mean BMI of 30 kg/m2) compared to SARS-CoV-2(−) pregnancies with high BMI (7.4%, n = 10/135). In the fourth cohort study, common lesions observed in placentae from SARS-CoV-2(+) pregnancies with high BMI (n = 187 pregnancies; mean BMI of 30 kg/m2) were chronic inflammation (99%, 186/187), MVM (40%, n = 74/187) and FVM (26%, n = 48/187). BMI and SARS-CoV-2 infection had no effect on birth anthropometry. SARS-CoV-2 infection during pregnancy associates with increased prevalence of placental pathologies, and high BMI in these pregnancies could further affect fetoplacental trajectories.

Leptin Promotes HTR-8/SVneo Cell Invasion via the Crosstalk between MTA1/WNT and PI3K/AKT Pathways

The process of placental invasion is essential for a successful pregnancy. Leptin is involved in trophoblast invasiveness, and its dysregulation is connected with a series of diseases, including preeclampsia. However, the knowledge of the precise mechanisms in leptin-induced trophoblast invasiveness is still limited. According to the present research, transwell assay suggested that leptin is a dose- and time-dependent regulator in inducing HTR-8/SVneo cell invasion. Western blot analysis and immunofluorescence staining revealed that leptin-induced MMP9 expression is essential in the invasion process of HTR-8/SVneo cells. Mechanistically, we demonstrated that leptin activated β-catenin via the crosstalk between the MTA1/WNT and PI3K/AKT pathways. Besides, we showed that downregulating the key molecules in the signaling pathways by siRNA can inhibit leptin-induced MMP9 expression and further suppress invasion of HTR-8/SVneo cells. In conclusion, our study revealed a new regulatory mechanism of leptin-induced HTR-8/SVneo cell invasiveness and will provide novel insights into the causes and potential therapeutic targets for diseases related to dysregulation of trophoblast invasion in the future.

Free Amino Acid-Enriched Diets Containing Rapidly but Not Slowly Digested Carbohydrate Promote Amino Acid Absorption from Intestine and Net Fluxes across Skeletal Muscle of Pigs

BACKGROUND

The approach to matching appropriate carbohydrates alongside free amino acids to achieve optimal muscle growth remains unclear.

OBJECTIVES

We investigated whether the consumption of a diet containing rapidly digested carbohydrate and free amino acids can enhance intestinal absorption and muscular uptake of amino acids in pigs.

METHOD

Twelve barrows (28 kg; 11 wk old) with catheters installed in the portal vein, mesenteric vein, femoral artery, and femoral vein were randomly assigned to consume 1 of 2 free amino acid-enriched diets (3.34%) containing rapidly [waxy corn starch (WCS)] or slowly [pea starch (PS)] digested carbohydrate for 27 d. Blood was collected to determine the fluxes of plasma glucose and amino acids across the portal vein and the hindlimb muscle. Dietary in vitro carbohydrate digestive rates were also determined. Data were analyzed using repeated-measures (time × group) ANOVA.

RESULTS

Carbohydrate in vitro cumulative digestibility at 30 and 240 min was 69.00% and 95.25% for WCS and 23.25% and 81.15% for PS, respectively. The animal experiment presented WCS increased individual amino acids (lysine, 0.67 compared with 0.53 mmol/min; threonine, 0.40 compared with 0.29 mmol/min; isoleucine, 0.33 compared with 0.22 mmol/min; glutamate, 0.51 compared with 0.35 mmol/min; and proline, 0.51 compared with 0.27 mmol/min), essential amino acid (EAA; 3.26 compared with 2.65 mmol/min), and branched-chain amino acid (BCAA; 0.86 compared with 0.65 mmol/min) fluxes across the portal vein during 8 h postprandial, as well as individual amino acids (isoleucine, 0.08 compared with 0.02 mmol/min; leucine, 0.06 compared with 0.02 mmol/min; and glutamine, 0.44 compared with 0.25 mmol/min), EAA (0.50 compared with 0.21 mmol/min), and BCAA (0.17 compared with 0.06 mmol/min) net fluxes across the hindlimb muscle during 8 h postprandial compared with PS (P < 0.05).

CONCLUSIONS

A diet containing rapidly digested carbohydrate and free amino acids can promote intestinal absorption and net fluxes across hindlimb muscle of amino acids in pigs.

Decreased Expression of Sam68 Is Associated with Insulin Resistance in Granulosa Cells from PCOS Patients

BACKGROUND AND OBJECTIVE

Polycystic ovary syndrome (PCOS) is a complex metabolic disorder associated with ovulatory dysfunction, hyperandrogenism, obesity, and insulin resistance, which leads to subfertility. PCOS is the most frequent metabolic disorder in women and the major cause of infertility. Susceptibility to developing PCOS is determined by a complex interaction between environmental and genetic factors. Although different mechanisms have been proposed to explain PCOS manifestations, defects in insulin actions or in the insulin signaling pathways are central in the pathogenesis of the syndrome. However, the mechanisms (molecular players and signaling pathways) underlying its primary origin still remain an unsolved issue. Current research is increasingly focusing on the discovery of novel biomarkers to further elucidate the complex pathophysiology of PCOS. Sam68, an RNA-binding protein, is recruited to insulin signaling, mediating different insulin actions. We aimed to investigate the role of Sam68 in insulin signaling and the possible implications of Sam68 in the insulin resistance in PCOS.

MATERIALS AND METHODS

Granulosa cells were taken from women with PCOS (n = 25) and healthy donors (n = 25) and, within the age range of 20 to 42 years, from GINEMED, Assisted Reproduction Centre, Seville, Spain. The Sam68 expression level was analyzed both by qPCR and immunoblot. Statistical significance was assessed by one-way ANOVA, followed by a post-hoc test. A p value of &lt; 0.05 was considered statistically significant.

RESULTS

We found that insulin stimulation increases the phosphorylation and expression level of Sam68 in granulosa cells from normal donors. The downregulation of Sam68 expression resulted in a lower activation of both the MAPK and the PI3K pathways in response to insulin. Moreover, the granulosa cells from the women with PCOS presented a lower expression of Sam68, as well as insulin receptor and insulin receptor substrate-1 (IRS-1). In these cells, the overexpression of Sam68 resulted in an increased activation of both the MAPK and the PI3K pathways in response to insulin.

CONCLUSIONS

These results suggest the participation of Sam68 in insulin receptor signaling, mediating the insulin effect in granulosa cells, and they suggest the possible role of Sam68 in the insulin resistance of PCOS.

Significance of Serum-Plasma Leptin Profile during Pregnancy in Gestational Diabetes Mellitus: A Systematic Review and Meta-Analysis

Gestational diabetes mellitus (GDM) represents a stage of subclinical inflammation and a risk factor for subsequent future type 2 diabetes and cardiovascular disease development. Leptin has been related with vascular and metabolic changes in GDM with heterogeneous and contradictory results with respect to their possible involvement in maternal, perinatal, and future complications. Our objective is to evaluate current evidence on the role of leptin in maternal and perinatal complications in women with GDM. PubMed, Embase, Web of Science, and Scopus databases were searched. We evaluated the studies’ quality using the Newcastle-Ottawa scale. Meta-analyses were conducted, and heterogeneity and publication bias were examined. Thirty-nine relevant studies were finally included, recruiting 2255 GDM and 3846 control pregnant women. Leptin levels were significantly higher in GDM participants than in controls (SMD = 0.57, 95%CI = 0.19 to 0.94; p < 0.001). Subgroup meta-analysis did not evidence significant differences in leptin in the different trimesters of pregnancy. Meta-regression showed a positive significant relationship for HOMA in the GDM group (p = 0.05). According to these results, it seems that high levels of leptin can be used as predictive markers in GDM.

Dissimilar regulation of glucose and lipid metabolism by leptin in two strains of gibel carp (Carassius gibelio)

Previous nutritional studies have shown that insulin regulation is different between DT and A strains of gibel carp. As leptin plays a pivotal role in the effects of insulin, we hypothesised that leptin regulation of glucose and lipid metabolism would differ between the two strains. To test our hypothesis, recombinant human leptin was injected into two strains. The results showed that leptin activated the phosphatidylinositol 3-kinase (PI3K)-protein kinase B (AKT), AMP-activated protein kinase-acetyl coenzyme A carboxylase and Janus kinase 2 (JAK2)-signal transducer and activator of transcription (STAT) signalling pathways in both strains. Hypoglycaemia induced by leptin might be due to higher glucose uptake by the liver and muscles together with enhanced glycolytic potential and reduced gluconeogenic potential. Decreased lipogenesis and up-regulated fatty acid oxidation were induced by leptin. In terms of genotype, the PI3K-AKT signalling pathway was more strongly activated by leptin in the muscle tissue of the A strain, as reflected by the heightened phosphorylation of AKT. Furthermore, glycogen content, glycolytic enzyme activity and gluconeogenic capability were higher in the A strain than the DT strain. Strain A had higher levels of fatty acid synthesis and lipolytic capacity in the liver than the DT strain, but the opposite was true in white muscle. Regarding leptin-genotype interactions, the DT strain displayed stronger regulation of glucose metabolism in the liver by leptin as compared with the A strain. Moreover, a more active JAK2-STAT signalling pathway accompanied by enhanced inhibition of fatty acid synthesis by leptin was observed in the DT strain. Overall, the regulation of glucose and lipid metabolism by leptin differed between the two strains, as expected.

Maternal Low-Grade Chronic Inflammation and Intrauterine Programming of Health and Disease

Overweight and obesity during pregnancy have been associated with increased birth weight, childhood obesity, and noncommunicable diseases in the offspring, leading to a vicious transgenerational perpetuating of metabolic derangements. Key components in intrauterine developmental programming still remain to be identified. Obesity involves chronic low-grade systemic inflammation that, in addition to physiological adaptations to pregnancy, may potentially expand to the placental interface and lead to intrauterine derangements with a threshold effect. Animal models, where maternal inflammation is mimicked by single injections with lipopolysaccharide (LPS) resembling the obesity-induced immune profile, showed increased adiposity and impaired metabolic homeostasis in the offspring, similar to the phenotype observed after exposure to maternal obesity. Cytokine levels might be specifically important for the metabolic imprinting, as cytokines are transferable from maternal to fetal circulation and have the capability to modulate placental nutrient transfer. Maternal inflammation may induce metabolic reprogramming at several levels, starting from the periconceptional period with effects on the oocyte going through early stages of embryonic and placental development. Given the potential to reduce inflammation through inexpensive, widely available therapies, examinations of the impact of chronic inflammation on reproductive and pregnancy outcomes, as well as preventive interventions, are now needed.

Relationships between placental adiponectin, leptin, visfatin and resistin and birthweight in cattle

Adipokines can affect intrauterine development while calf birthweight (CBW) is a breeding standard of calves, which reflects the status of fetal intrauterine development. To explore the correlation between placental adipokines and CBW, 54 healthy Chinese Holstein cows were used in the present study. The cows were grouped according to the CBW of their calves. Placentas were collected immediately after delivery and enzyme-linked immunosorbent assay and reverse transcription-polymerase chain reaction were used to detect the placental expression levels of adiponectin, leptin, visfatin and resistin. Our results show that the mRNA transcription and blood placental content of adiponectin, leptin, visfatin and resistin increased with increasing CBW. The analysis showed that the mRNA transcription levels of placental adiponectin, leptin and resistin were positively correlated with CBW. The mRNA and protein expression levels of adiponectin, leptin and visfatin between the three groups were significantly correlated. Placental resistin mRNA levels correlated positively with adiponectin mRNA, but not leptin or visfatin. The protein expression levels of resistin were significantly positively correlated with those of adiponectin, leptin and visfatin. These results suggest that placental adipokines play important roles in regulating calf intrauterine growth.

Leptin Receptor Signaling Regulates Protein Synthesis Pathways and Neuronal Differentiation in Pluripotent Stem Cells

The role of leptin receptor (OB-R) signaling in linking pluripotency with growth and development and the consequences of dysfunctional leptin signaling on progression of metabolic disease is poorly understood. Using a global unbiased proteomics approach we report that embryonic fibroblasts (MEFs) carrying the db/db mutation exhibit metabolic abnormalities, while their reprogrammed induced pluripotent stem cells (iPSCs) show altered expression of proteins involved in embryonic development. An upregulation in expression of eukaryotic translation initiation factor 4e (Eif4e) and Stat3 binding to the Eif4e promoter was supported by enhanced protein synthesis in mutant iPSCs. Directed differentiation of db/db iPSCs toward the neuronal lineage showed defects. Gene editing to correct the point mutation in db/db iPSCs using CRISPR-Cas9, restored expression of neuronal markers and protein synthesis while reversing the metabolic defects. These data imply a direct role for OB-R in regulating metabolism in embryonic fibroblasts and key developmental pathways in iPSCs.

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Pluripotency markers are decreased in db/db iPSCs (lacking functional OB-R)

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Mouse db/db iPSCs exhibit higher protein synthesis mediated by the Stat3/Eif4e axis

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OB-R signaling regulates neuronal development markers—NOGGIN, NESTIN, GFAP

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CRISPR correction reverses defects in db/db iPSCs

Sam68 mediates leptin signaling and action in human granulosa cells: possible role in leptin resistance in PCOS

INTRODUCTION

Polycystic ovary syndrome (PCOS) is a complex metabolic disorder associated with ovulatory dysfunction, hyperandrogenism, obesity, and insulin resistance, that leads to subfertility. Sam68 is an RNA-binding protein with signaling functions that is ubiquitously expressed, including gonads. Sam68 is recruited to leptin signaling, mediating different leptin actions.

OBJECTIVE

We aimed to investigate the role of Sam68 in leptin signaling, mediating the effect on aromatase expression in granulosa cells and the posible implication of Sam68 in the leptin resistance in PCOS.

MATERIALS AND METHODS

Granulosa cells were from healthy donors (n = 25) and women with PCOS (n = 25), within the age range of 20 to 40 years, from Valencian Infertility Institute (IVI), Seville, Spain. Sam68 expression was inhibited by siRNA method and overexpressed by expression vector. Expression level was analysed by qPCR and immunoblot. Statistical significance was assessed by ANOVA followed by different post-hoc tests. A P value of <0.05 was considered statistically significant.

RESULTS

We have found that leptin stimulation increases phosphorylation and expression level of Sam68 and aromatase in granulosa cells from normal donors. Downregulation of Sam68 expression resulted in a lower activation of MAPK and PI3K pathways in response to leptin, whereas overexpression of Sam68 increased leptin stimulation of signaling, enhancing aromatase expression. Granulosa cells from women with PCOS presented lower expression of Sam68 and were resistant to the leptin effect on aromatase expression.

CONCLUSIONS

These results suggest the participation of Sam68 in leptin receptor signaling, mediating the leptin effect on aromatase expression in granulosa cells, and point to a new target in leptin resistance in PCOS.

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.

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.

Leptin stimulates DMP-1 and DSPP expression in human dental pulp via MAPK 1/3 and PI3K signaling pathways

INTRODUCTION

To investigate the physiological function of leptin in human dental pulp, and to determine the specific pathways implicated in its effect.

METHODS

Twenty-seven dental pulp samples were obtained from human third molars. Pulp samples were treated with or without human recombinant leptin. Leptin functional effect was analyzed in terms of regulation of the synthesis levels of DSPP and DMP-1, determined by immunoblot.

RESULTS

Leptin stimulated DMP-1 and DSPP synthesis in all human dental pulp specimens. The stimulatory effect of leptin on DMP-1 and DSPP synthesis was partially prevented by blocking mitogen-activated protein kinase (MAPK 1/3) and phosphatidylinositol 3 kinase (PI3K) pathways, respectively.

CONCLUSIONS

The present study demonstrates the functional effect of leptin in human dental pulp stimulating the expression of DMP-1 and DSPP, both proteins implicated in dentinogenesis. Leptin stimulates DSPP expression via PI3K pathway and DMP-1 synthesis via MAPK 1/3 pathway. These results support the role of leptin in pulpal reparative response, opening a new research line that could have translational application to the clinic in vital pulp therapy procedures.

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.

Hepatic leptin receptor expression can partially compensate for IL-6Rα deficiency in DEN-induced hepatocellular carcinoma

Objective

The current obesity pandemic represents a major health burden, given that it predisposes to the development of numerous obesity-associated disorders. The obesity-derived adipokines not only impair systemic insulin action but also increase the incidence of hepatocellular carcinoma (HCC), a highly prevalent cancer with poor prognosis. Thus, worldwide incidences of HCC are expected to further increase, and defining the molecular as well as cellular mechanisms will allow for establishing new potential treatment options. The adipose tissue of obese individuals increases circulating leptin and interleukin-6 (IL-6) levels, which both share similar signaling capacities such as Signal Transducer and Activator of Transcription 3 (STAT3) and Phosphoinositide 3-kinase (PI3K)/Akt activation. While mouse models with deficient IL-6 signaling show an ameliorated but not absent Diethylnitrosamine (DEN)-induced HCC development, the morbid obesity in mice with mutant leptin signaling complicates the dissection of hepatic leptin receptor (LEPR) and IL-6 signaling in HCC development. Here we have investigated the function of compensating hepatic LEPR expression in HCC development of IL-6Rα-deficient mice.

Methods

We generated and characterized a mouse model of hepatic LEPR deficiency that was intercrossed with IL-6Rα-deficient mice. Cohorts of single and double knockout mice were subjected to the DEN-HCC model to ascertain liver cancer development and characterize metabolic alterations.

Results

We demonstrate that both high-fat diet (HFD)-induced obesity and IL-6Rα deficiency induce hepatic Lepr expression. Consistently, double knockout mice show a further reduction in tumor burden in DEN-induced HCC when compared to control and single LepR^L−KO/IL-6Rα knock out mice, whereas metabolism remained largely unaltered between the genotypes.

Conclusions

Our findings reveal a compensatory role for hepatic LEPR in HCC development of IL-6Rα-deficient mice and suggest hepatocyte-specific leptin signaling as promoter of HCC under obese conditions.

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High fat diet feeding induces LEPR expression in hepatocytes.

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IL-6Rα deficiency induces LEPR expression in hepatocytes.

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Hepatic LEPR deficiency fails to affect body composition and metabolism.

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Hepatic LEPR deficiency ameliorates HCC burden in IL-6Rα-deficient mice.

Leptin upregulates aquaporin 9 expression in human placenta in vitro

Aquaporins are integral membrane proteins that have permeability functions in many tissues. Aquaporin 9 may transport not only water but also small molecules, such as glycerol, monocarboxylates, purines and pyrimidines. Aquaporin 9 is expressed in syncytiotrophoblast of human term placenta, and it may contribute to the embryonic/fetal growth and survival. We have previously found that Aquaporin 9 expression levels seem to be increased in placenta from gestational diabetes. Since leptin plasma levels and leptin expression are increased in placenta from gestational diabetes, we aimed to study the possible role of leptin on Aquaporin 9 expression in human placenta in vitro. The present work shows that leptin produces a dose-dependent increase of Aquaporin 9 expression, resulting in an increase in Aquaporin-9 protein in human trophoblast explants.

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.

Maternal obesity and inflammatory mediators: A controversial association

The link between maternal obesity and inflammatory mediators is still unclear. Our aim was to summarize the main findings of recently published studies on this topic. We performed a search in Medline for studies published in the last years on obesity, human pregnancy, and inflammatory mediators. We report the findings of 30 studies. The characteristics and number of participants, study design, gestational age at sample collection, and type of sample varied widely. Approximately two-thirds of them investigated more than one mediator, and 50% included participants in only one trimester of pregnancy. The most frequently investigated mediators were leptin, tumour necrosis factor-alpha (TNF-α), and interleukin (IL)-6. Almost all studies reported an association between maternal obesity, leptin, and C-reactive protein (CRP) serum levels but not with IL-1β and IL-10. The association of IL-6, TNF-α, monocyte chemo-attractant protein-1 (MCP-1), adiponectin, and resistin with maternal obesity is still controversial. To clarify the physiopathological link between maternal obesity and inflammation, more high-quality studies are needed.

Cross-fostering reduces obesity induced by early exposure to monosodium glutamate in male rats

Maternal obesity programmes a range of metabolic disturbances for the offspring later in life. Moreover, environmental changes during the suckling period can influence offspring development. Because both periods significantly affect long-term metabolism, we aimed to study whether cross-fostering during the lactation period was sufficient to rescue a programmed obese phenotype in offspring induced by maternal obesity following monosodium L-glutamate (MSG) treatment. Obesity was induced in female Wistar rats by administering subcutaneous MSG (4 mg/g body weight) for the first 5 days of postnatal life. Control and obese female rats were mated in adulthood. The resultant pups were divided into control second generation (F₂) (CTLF₂), MSG-treated second generation (F₂) (MSGF₂), which suckled from their CTL and MSG biological dams, respectively, or CTLF₂-CR, control offspring suckled by MSG dams and MSGF₂-CR, MSG offspring suckled by CTL dams. At 120 days of age, fat tissue accumulation, lipid profile, hypothalamic leptin signalling, glucose tolerance, glucose-induced, and adrenergic inhibition of insulin secretion in isolated pancreatic islets were analysed. Maternal MSG-induced obesity led to an obese phenotype in male offspring, characterized by hyperinsulinaemia, hyperglycaemia, hyperleptinaemia, dyslipidaemia, and impaired leptin signalling, suggesting central leptin resistance, glucose intolerance, impaired glucose-stimulated, and adrenergic inhibition of insulin secretion. Cross-fostering normalized body weight, food intake, leptin signalling, lipid profiles, and insulinaemia, but not glucose homeostasis or insulin secretion from isolated pancreatic islets. Our findings suggest that alterations during the lactation period can mitigate the development of obesity and prevent the programming of adult diseases.

The roles of leptin and adiponectin at the fetal-maternal interface in humans

Infertility now affects one in seven couples, and the prevalence of this condition continues to increase. Ovulatory defects and unknown causes account for more than half of the cases of infertility. It has been postulated that a significant proportion of these cases are directly or indirectly related to obesity, since the presence of excess adipose tissue has a variety of effects on reproductive function. Here, we review on the effects of the two major adipokines (leptin and adiponectin) on fertility, with a focus on the first steps in embryo implantation and the key components of fetal-maternal interface (the placenta and the endometrium). These adipokines are reportedly involved in the regulation of cell proliferation and differentiation, and as such affect local angiogenesis, immune tolerance and inflammatory processes in placental and endometrial tissues. In placental cells, leptin and adiponectin also modulate trophoblast invasiveness and the nutrient supply. These observations strongly suggest by interfering with the placenta and endometrium, adipokines can create a favorable environment for embryo implantation and have a key role in fetal-maternal metabolism, fetal-maternal communication, and gestation. Given that reproductive functions are tightly coupled to the energy balance, metabolic abnormalities may lead to the development of complications of pregnancy and changes in fetal growth. In this context, we suggest that the leptin/adiponectin ratio may be a clinically valuable marker for detecting a number of pathologies in pregnancy.

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.

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.

BMP2 repression and optimized culture conditions promote human bone marrow-derived mesenchymal stem cell isolation

AIM

Human mesenchymal stem cells (hMSC) are multipotent progenitor cells. We propose the optimization of hMSC isolation and recovery using the application of a controlled hypoxic environment.

MATERIALS & METHODS

We evaluated oxygen, glucose and serum in the recovery of hMSC from bone marrow (BMhMSC). Colony forming units-fibroblastic, cell numbers, tri-lineage differentiation, immunofluorescence and microarray were used to confirm and characterize BMhMSC.

RESULTS

In an optimized (2% O(2), 4.5 g/l glucose and 5% serum) environment both colony forming units-fibroblastic (p = 0.01) and cell numbers (p = 0.0001) were enhanced over standard conditions. Transcriptional analysis identified differential expression of bone morphogenetic protein 2 (BMP2) and, putatively, chemokine (C-X-C motif) receptor 2 (CXCR2) signaling pathways.

CONCLUSION

We have detailed a potential milestone in the process of refinement of the BMhMSC isolation process.

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.

Role of leptin in female reproduction

Reproductive function is dependent on energy resources. The role of weight, body composition, fat distribution and the effect of diet have been largely investigated in experimental female animals as well as in women. Any alteration in diet and/or weight may induce abnormalities in timing of sexual maturation and fertility. However, the cellular mechanisms involved in the fine coordination of energy balance and reproduction are largely unknown. The brain and hypothalamic structures receive endocrine and/or metabolic signals providing information on the nutritional status and the degree of fat stores. Adipose tissue acts both as a store of energy and as an active endocrine organ, secreting a large number of biologically important molecules termed adipokines. Adipokines have been shown to be involved in regulation of the reproductive functions. The first adipokine described was leptin. Extensive research over the last 10 years has shown that leptin is not only an adipose tissue-derived messenger of the amount of energy stores to the brain, but also a crucial hormone/cytokine for a number of diverse physiological processes, such as inflammation, angiogenesis, hematopoiesis, immune function, and most importantly, reproduction. Leptin plays an integral role in the normal physiology of the reproductive system with complex interactions at all levels of the hypothalamic-pituitary gonadal (HPG) axis. In addition, leptin is also produced by placenta, where it plays an important autocrine function. Observational studies have demonstrated that states of leptin excess, deficiency, or resistance can be associated with abnormal reproductive function. This review focuses on the leptin action in female reproduction.

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.

Correlations between circulating levels of adipokines and anti-angiogenic factors in women with BMI <30 and a late-onset preeclampsia

Preeclampsia (PE) is a pregnancy-specific disease, directly related to high rates of maternal-fetal morbidity and mortality worldwide. Upregulation of anti-angiogenic factors (soluble fms-like tyrosine kinase-1; sFLT-1 and soluble endoglin; sENG) have been suggested to trigger the maternal endothelial dysfunction observed in PE. Studies focusing on the role of adiponectin and leptin, in normal pregnancy as well as in complicated pregnancies, have revelated interesting findings due to the vascular actions of such adipokines. The aims of this study were to compare plasma concentrations of the adiponectin, leptin, sENG and sFLT-1 in preeclamptic (PE, n = 27) and healthy pregnant (HP, n = 36) and to evaluate possible correlations among these adipokines and anti-angiogenic factors. There were significant increases in all biomarkers in PE compared to HP (all p < 0.05). In PE group, there were positive strong correlations among adiponectin and leptin with sFLT-1 (r = 0.85 and r = 0.47, respectively) and sEng (r = 0.74 and r = 0.56, respectively). Moreover, we observed significantly correlation among body mass index (BMI) with adiponectin (r = -0.40) and with leptin (r = 0.51) in HP, but not in PE. Moreover, while a negative correlation between sFLT-1 and BMI (r = -0.60) was found in PE, no correlation was observed regarding sEng and BMI. In summary, our findings suggest the existence of a compensatory mechanism that occurs in an attempt to correct this angiogenic imbalance in order to restore the fetal development.

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.

Insulin enhances leptin expression in human trophoblastic cells

Leptin, one of the adipokines that controls energy metabolism via the central nervous system, also has pleiotropic peripheral effects, acting as a proinflammatory cytokine. Leptin is also produced by trophoblastic cells in the placenta, where leptin seems to function as a trophic autocrine hormone. Leptin expression is regulated by various tissue-specific factors, such as insulin, in the adipocyte. However, the complete regulation of leptin production in the placenta is still poorly understood. That is why we investigated the regulation of leptin expression by insulin in JEG-3 trophoblastic cells and human placental explants from normal pregnancies. Western blot analysis and quantitative real time RT-PCR was performed to determine the leptin expression level after treatment of cells or trophoblast explants with different concentrations of insulin (0.1-100 nM). Leptin promoter activity was evaluated by transient transfection with a plasmid construct containing different promoter regions and the reporter luciferase gene. We found a stimulatory, dose-dependent effect of insulin on endogenous leptin expression in human placental explants. Maximal effect was achieved at 10 nM insulin, and this effect can be totally prevented both by blocking phosphatidylinositol 3 kinase (PI3K) pathways and mitogen-activated protein kinase (MAPK). Moreover, insulin treatment significantly enhanced leptin promoter activity up to 40% in JEG-3 trophoblastic cells. Deletion analysis demonstrated that a minimal promoter region between -1951 and -1546 bp is necessary to achieve insulin effects. In conclusion, we provide evidence suggesting that insulin induces leptin expression in trophoblastic cells, enhancing the activity of leptin promoter region between -1951 and -1546 bp, via both PI3K- and MAPK-signaling pathways.

The alternative Epac/cAMP pathway and the MAPK pathway mediate hCG induction of leptin in placental cells

Pleiotropic effects of leptin have been identified in reproduction and pregnancy, particularly in the placenta, where it works as an autocrine hormone. In this work, we demonstrated that human chorionic gonadotropin (hCG) added to JEG-3 cell line or to placental explants induces endogenous leptin expression. We also found that hCG increased cAMP intracellular levels in BeWo cells in a dose-dependent manner, stimulated cAMP response element (CRE) activity and the cotransfection with an expression plasmid of a dominant negative mutant of CREB caused a significant inhibition of hCG stimulation of leptin promoter activity. These results demonstrate that hCG indeed activates cAMP/PKA pathway, and that this pathway is involved in leptin expression. Nevertheless, we found leptin induction by hCG is dependent on cAMP levels. Treatment with (Bu)₂cAMP in combination with low and non stimulatory hCG concentrations led to an increase in leptin expression, whereas stimulatory concentrations showed the opposite effect. We found that specific PKA inhibition by H89 caused a significant increase of hCG leptin induction, suggesting that probably high cAMP levels might inhibit hCG effect. It was found that hCG enhancement of leptin mRNA expression involved the MAPK pathway. In this work, we demonstrated that hCG leptin induction through the MAPK signaling pathway is inhibited by PKA. We observed that ERK1/2 phosphorylation increased when hCG treatment was combined with H89. In view of these results, the involvement of the alternative cAMP/Epac signaling pathway was studied. We observed that a cAMP analogue that specifically activates Epac (CPT-OMe) stimulated leptin expression by hCG. In addition, the overexpression of Epac and Rap1 proteins increased leptin promoter activity and enhanced hCG. In conclusion, we provide evidence suggesting that hCG induction of leptin gene expression in placenta is mediated not only by activation of the MAPK signaling pathway but also by the alternative cAMP/Epac signaling pathway.

A decrease in DKK1, a WNT inhibitor, contributes to placental lipid accumulation in an obesity-prone rat model

Placenta, as the sole transport mechanism between mother and fetus, links the maternal physical state and the immediate as well as lifelong outcomes of the offspring. The present study examined the consequences of maternal obesity on placental lipid accumulation and metabolism. Pregnant obesity-prone (OP) and obesity-resistant (OR) rat strains were fed a control diet throughout gestation. Placentas were collected on Gestational Day 21 for mRNA and oxidative stress analysis, and frozen placental sections were analyzed for fat accumulation as well as beta-catenin and Dickkopf homolog 1 (Xenopus laevis) (DKK1) localization. JEG3 trophoblast cells were cultured in vitro to determine the relationship between DKK1 and lipid accumulation. Maternal plasma and placental nonesterified fatty acids and triglycerides (TG) were elevated in OP dams. Placental Dkk1 mRNA content was 4-fold lower in OP placentas, and a significant increase was noted in beta-catenin accumulation as well as in mRNA content of fat transport and TG synthesis genes, including Ppard (peroxisome proliferator-activated receptor delta), Slc27a1 (fatty acid transport protein 1; also known as Fatp1), Cd36 (cluster of differentiation 36; also known as fatty acid translocation [Fat]), Lipin1, and Lipin3. Significant lipid accumulation was found within the decidual zones in OP, but not OR, placentas, and thickness of the decidual and junctional zones was significantly smaller in OP than in OR placentas. Overexpression of DKK1 in JEG3 cells decreased lipid accumulation and mRNA content of PPARD, SLC27A1, CD36, LIPIN1, and LIPIN3. Our results demonstrate that DKK1 is regulating certain aspects of placental lipid metabolism through the WNT signaling pathway.

Regulation of leptin expression by 17beta-estradiol in human placental cells involves membrane associated estrogen receptor alpha

The placenta produces a wide number of molecules that play essential roles in the establishment and maintenance of pregnancy. In this context, leptin has emerged as an important player in reproduction. The synthesis of leptin in normal trophoblastic cells is regulated by different endogenous biochemical agents, but the regulation of placental leptin expression is still poorly understood. We have previously reported that 17β-estradiol (E(2)) up-regulates placental leptin expression. To improve the understanding of estrogen receptor mechanisms in regulating leptin gene expression, in the current study we examined the effect of membrane-constrained E(2) conjugate, E-BSA, on leptin expression in human placental cells. We have found that leptin expression was induced by E-BSA both in BeWo cells and human placental explants, suggesting that E(2) also exerts its effects through membrane receptors. Moreover E-BSA rapidly activated different MAPKs and AKT pathways, and these pathways were involved in E(2) induced placental leptin expression. On the other hand we demonstrated the presence of ERα associated to the plasma membrane of BeWo cells. We showed that E(2) genomic and nongenomic actions could be mediated by ERα. Supporting this idea, the downregulation of ERα level through a specific siRNA, decreased E-BSA effects on leptin expression. Taken together, these results provide new evidence of the mechanisms whereby E(2) regulates leptin expression in placenta and support the importance of leptin in placental physiology.

Sam68 mediates leptin-stimulated growth by modulating leptin receptor signaling in human trophoblastic JEG-3 cells

BACKGROUND

Sam68, a member of the signal transduction and activation of RNA metabolism (STAR) family of RNA-binding proteins, has been previously implicated as an adaptor molecule in different signaling systems, including leptin receptor (LEPR) signaling. LEPR activation is known to stimulate JAK-STAT, MAPK and PI3K signaling pathways, thus mediating the biological effects of leptin in different cell types, including trophoblastic cells. We have recently found that leptin stimulation also promotes the overexpression and tyrosine phosphorylation of Sam68 in human trophoblastic JEG-3 cells, suggesting a role for Sam68 in leptin signaling and action in these cells. In the present work, we have studied the participation of Sam68 in the main signaling pathways activated by LEPR to increase growth and proliferation in trophoblastic JEG-3 cells.

METHODS

We used an antisense strategy to down-regulate Sam68 expression in these cells, and we studied LEPR signaling by immunoprecipitation and poly-U affinity precipitation and by analyzing phosphorylation levels of signaling proteins by immunoblot. The effect of leptin on protein synthesis and proliferation was studied by ³[H]-leucine and ³[H]-thymidine incorporation.

RESULTS

Sam68 knockdown impaired leptin activation of JAK-STAT, PI3K and MAPK signaling pathways in JEG-3 cells. We have also found that leptin-stimulated Sam68 tyrosine phosphorylation is dependent on JAK-2 activity, since the pharmacological inhibitor AG490 prevents the phosphorylation of Sam68 in JEG-3 cells. Finally, the trophic and proliferative effect of leptin in trophoblastic cells is dependent on Sam68 expression, since its down-regulation impaired the leptin-stimulated DNA and protein synthesis.

CONCLUSIONS

These data demonstrate that Sam68 participates in the main signaling pathways of LEPR to mediate the trophic and proliferative effect of leptin in human trophoblastic cells.

Review: Leptin gene expression in the placenta--regulation of a key hormone in trophoblast proliferation and survival

Leptin is a 16000 MW protein originally described as an adipocyte-derived signaling molecule for the central control of metabolism. However, pleiotropic effects of leptin have been identified in reproduction and pregnancy. The leptin gene is expressed in placenta, where leptin promotes proliferation and survival of trophoblast cells. Study of the major signaling pathways known to be triggered by leptin receptor has revealed that leptin stimulates JAK/STAT, MAPK and PI3K pathways in placental cells. Leptin also exerts an antiapoptotic action in placenta and this effect is mediated by the MAPK pathway. Moreover, leptin stimulates protein synthesis by activating the translational machinery via both PI3K and MAPK pathways. Expression of leptin in placenta is highly regulated, suggesting that certain key pregnancy molecules participate in such regulation. An important hormone in reproduction, hCG, induces leptin expression in trophoblast cells and this effect involves the MAPK signal transduction pathway. Moreover, the cyclic nucleotide cAMP, which has profound actions upon human trophoblast function, also stimulates leptin expression and this effect seems to be mediated by crosstalk between the PKA and MAPK signaling pathways. Estrogens play a central role in reproduction. 17β-estradiol upregulates leptin expression in placental cells through genomic and non-genomic actions, probably via crosstalk between estrogen receptor-α and the MAPK and PI3K signal transduction pathways. Taken together these findings give a better understanding of the function of leptin and the regulatory mechanisms of leptin expression in human placental trophoblast and further support the importance of leptin in the biology of reproduction.

Low amino acids affect expression of 11β-HSD2 in BeWo cells through leptin-activated JAK-STAT and MAPK pathways

Maternal protein restriction diminishes placental 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2) activity and causes fetal growth restriction in mammals. However, it is unknown whether such effect was caused directly by nutrient deficiency, or indirectly through the mediation of maternal hormones. In the present study, a human placental cell line (BeWo) was cultured in F12K as control and F12 as low amino acids (LAA) media for 48 h to investigate the effects of amino acids deficiency on 11β-HSD2 expression and activity. Despite a significant up-regulation of 11β-HSD2 mRNA expression in LAA cells, 11β-HSD2 activity and protein content were decreased by 38 and 54%, respectively (P<0.05), indicating a mechanism of post-transcriptional regulation. Among 5 miRNAs targeting 11β-HSD2, miR-498 was expressed significantly higher in LAA cells. Leptin concentration was significantly lower (P<0.01) in LAA medium. The mRNA expression of both isoforms of leptin receptor was significantly higher in LAA cells, although no difference was detected at protein level. To further clarify whether leptin is involved in mediating the effect of LAA on 11β-HSD2 activity, leptin was supplemented to LAA medium, whereas three specific inhibitors of leptin signaling pathways, WP1066 for JAK-STAT, PD98059 for MAPK and LY294002 for PI3K, respectively were added to control medium. Leptin restored the diminished 11β-HSD2 activity in LAA cells, whereas WP1066 (5 nM) and PD98059 (50 nM) significantly decreased 11β-HSD2 activity in control cells. In conclusion, the present results indicate that LAA diminishes 11β-HSD2 expression and activity in BeWo cells through leptin-activated JAK-STAT and MAPK pathways.

Leptin receptor activation increases Sam68 tyrosine phosphorylation and expression in human trophoblastic cells

Leptin is produced in placenta where it has been found to be an important autocrine signal for trophoblastic growth during pregnancy, promoting antiapoptotic and trophic effects. Leptin receptor is present in trophoblastic cells and leptin may fully activate signaling. We have previously implicated the RNA-binding protein Sam68 in leptin signal transduction in immune cells. In the present work, we have studied the possible role of Sam68 in leptin receptor signaling in trophoblastic cells (JEG-3 cells). Leptin dose-dependently stimulated Sam68 phosphorylation in JEG-3 cells, as assessed by immunoprecipitation and immunoblot with anti-phosphotyrosine antibodies. As previously observed in other systems, tyrosine phosphorylation of Sam68 in response to leptin inhibits its RNA binding capacity. Besides, leptin stimulation dose-dependently increases Sam68 expression in JEG-3 cells, as assessed by quantitative PCR. Consistently, the amount of Sam68 protein is increased after 24h of leptin stimulation of trophoblastic cells. In order to study the possible role of Sam68 on leptin receptor synthesis, we employed antisense strategy to knockdown the expression of Sam68. We have found that a decrease in Sam68 expression leads to a decrease in leptin receptor amount in JEG-3 cells, as assessed both by quantitative PCR and immunoblot. These results strongly suggest the participation of Sam68 in leptin receptor signaling in human trophoblastic cells, and therefore, Sam68 may mediate some of the leptin effects in placenta.