Leptin and leptin-binding activity in women with recurrent miscarriage: correlation with pregnancy outcome

The Roles of Obesity and ASB4 in Preeclampsia Pathogenesis

Preeclampsia is a complex pregnancy-related hypertensive disorder which poses significant risks for both maternal and fetal health. Preeclampsia affects 5-8% of pregnancies in the United States, causing a significant public health and economic burden. Despite extensive research, the etiology and pathogenesis of preeclampsia remain elusive, but have been correlated with maternal conditions such as obesity. In recent decades, the incidence of preeclampsia increased along with the prevalence of obesity among women of reproductive age. Maternal obesity has been shown to negatively affect pregnancy in almost all aspects. However, the precise mechanisms by which obesity influences preeclampsia are unclear. Ankyrin repeat and SOCS Box Containing protein 4 (ASB4) is an E3 ubiquitin ligase that can promote the degradation of a wide range of target proteins. ASB4-null mice display a full spectrum of preeclampsia-like phenotypes during pregnancy including hypertension, proteinuria, and decreased litter size. Furthermore, maternal obesity induced by a high-fat diet aggravates preeclampsia-like phenotypes in pregnant mice lacking ASB4. Variants in the ASB4 gene have been associated with obesity in humans, and a functional connection between the ASB4 gene and obesity has been established in mice. This review discusses the connections between preeclampsia, obesity, and ASB4.

Decreased Expression of Placental Proteins in Recurrent Pregnancy Loss: Functional Relevance and Diagnostic Value

Miscarriages affect 50-70% of all conceptions and 15-20% of clinically recognized pregnancies. Recurrent pregnancy loss (RPL, ≥2 miscarriages) affects 1-5% of recognized pregnancies. Nevertheless, our knowledge about the etiologies and pathophysiology of RPL is incomplete, and thus, reliable diagnostic/preventive tools are not yet available. Here, we aimed to define the diagnostic value of three placental proteins for RPL: human chorionic gonadotropin free beta-subunit (free-β-hCG), pregnancy-associated plasma protein-A (PAPP-A), and placental growth factor (PlGF). Blood samples were collected from women with RPL (n = 14) and controls undergoing elective termination of pregnancy (n = 30) at the time of surgery. Maternal serum protein concentrations were measured by BRAHMS KRYPTOR Analyzer. Daily multiple of median (dMoM) values were calculated for gestational age-specific normalization. To obtain classifiers, logistic regression analysis was performed, and ROC curves were calculated. There were differences in changes of maternal serum protein concentrations with advancing healthy gestation. Between 6 and 13 weeks, women with RPL had lower concentrations and dMoMs of free β-hCG, PAPP-A, and PlGF than controls. PAPP-A dMoM had the best discriminative properties (AUC = 0.880). Between 9 and 13 weeks, discriminative properties of all protein dMoMs were excellent (free β-hCG: AUC = 0.975; PAPP-A: AUC = 0.998; PlGF: AUC = 0.924). In conclusion, free-β-hCG and PAPP-A are valuable biomarkers for RPL, especially between 9 and 13 weeks. Their decreased concentrations indicate the deterioration of placental functions, while lower PlGF levels indicate problems with placental angiogenesis after 9 weeks.

Obesity and Miscarriage

Obesity affects nearly 40% of reproductive-aged women and has serious implications for women's overall and reproductive health. Women with an elevated body mass index (BMI) have higher rates of anovulation and irregular menses, lower success with fertility treatment, and significantly higher rates of pregnancy complications, such as hypertension/preeclampsia, gestational diabetes, and preterm delivery. Many studies have also shown an association between obesity and early pregnancy loss. However, the causal association between BMI and miscarriage has not been elucidated, likely due to the multifactorial effects that BMI may have on early pregnancy development. In addition, BMI as an isolated variable fails to capture other relevant confounding health risk factors, such as nutrition, physical activity, and insulin resistance. In this review, we will summarize the current literature demonstrating the association between BMI and miscarriage, highlight the research that attempts to explain the association, and finally provide data on therapeutic interventions to improve reproductive outcomes in women suffering from obesity and early pregnancy loss.

The Role of the Adipokines in the Most Common Gestational Complications

Adipocytokines are hormonally active molecules that are believed to play a key role in the regulation of crucial biological processes in the human body. Numerous experimental studies established significant alterations in the adipokine secretion patterns throughout pregnancy. The exact etiology of various gestational complications, such as gestational diabetes, preeclampsia, and fetal growth abnormalities, needs to be fully elucidated. The discovery of adipokines raised questions about their potential contribution to the molecular pathophysiology of those diseases. Multiple studies analyzed their local mRNA expression and circulating protein levels. However, most studies report conflicting results. Several adipokines such as leptin, resistin, irisin, apelin, chemerin, and omentin were proposed as potential novel early markers of heterogeneous gestational complications. The inclusion of the adipokines in the standard predictive multifactorial models could improve their prognostic values. Nonetheless, their independent diagnostic value is mostly insufficient to be implemented into standard clinical practice. Routine assessments of adipokine levels during pregnancy are not recommended in the management of both normal and complicated pregnancies. Based on the animal models (e.g., apelin and its receptors in the rodent preeclampsia models), future implementation of adipokines and their receptors as new therapeutic targets appears promising but requires further validation in humans.

The association of euploid miscarriage with obesity

Objective

To determine whether the frequency of euploid miscarriage is increased in obese women with early pregnancy loss.

Design

Retrospective cohort study.

Setting

Academic medical center.

Patient(s)

A total of 2,620 women with cytogenetic analysis results from products of conception after a pregnancy loss <20 weeks gestation from 2006–2018.

Intervention(s)

None.

Main Outcome Measure(s)

Frequency of euploid miscarriage was compared in obese (body mass index [BMI] ≥30 kg/m²) versus non-obese (BMI <30 kg/m²) patients.

Result(s)

A total of 2,620 women with a mean (± standard deviation) age at time of loss of 34.9 years (± 4.9) and mean (± standard deviation) BMI of 25.3 kg/m² (±5.5) were included in the final analysis. After adjusting for age and race, obese women were 56% more likely to have a euploid pregnancy loss compared with nonobese women (odds ratio 1.56; 95% confidence interval 1.32–1.92). Within the cohort, 63.8% of the losses were aneuploid, of which 41% were trisomies, 8% were monosomies, and 7% were polyploidies. Of the euploid losses, 50.1% were 46,XX and 49.9% were 46,XY, which suggests that the rate of maternal cell contamination was low.

Conclusion(s)

Obese women have an increased frequency of euploid miscarriage when compared with nonobese women.

Preconception leptin levels and pregnancy outcomes: A prospective cohort study

OBJECTIVE

Obesity has become a major, worldwide public health issue and is associated with a greater risk of adverse pregnancy outcomes. Leptin, a hormone produced by adipocytes, is elevated in individuals with obesity and may mediate the association between obesity and pregnancy outcomes. Though leptin levels during pregnancy have been associated with pregnancy outcomes, less is understood regarding preconception levels. Therefore, the objective of this study was to evaluate associations between preconception leptin levels and adverse pregnancy outcomes.

METHODS

This was a prospective cohort study nested within a large randomized controlled trial conducted at four medical centres in the United States. A total of 1078 women completed the parent study; this analysis involved women who became pregnant during that study (n = 776). Patients were healthy women, ages 18 to 40, attempting to conceive, with 1 to 2 prior pregnancy losses. Participants were followed for less than or equal to 6 cycles while trying to conceive and throughout pregnancy if they conceived. Preconception leptin concentrations were measured in serum collected at baseline then categorized by tertiles (using the lowest as reference group). Weighted log-binomial regression estimated risk ratios (RR) and 95% confidence intervals (CIs) for pregnancy loss, preterm delivery (PTD), gestational diabetes (GDM), and hypertensive disorders in pregnancy, adjusting for age, waist-to-hip ratio (WHR), and body mass index (BMI).

RESULTS

The mean (SD) BMI in this cohort was 25.4 ± 6.0. GDM (RR 18.37; 95% CI, 2.39-141.55) and hypertensive disorders of pregnancy (RR 2.35; 95% CI, 1.20-4.61) risks were higher among women in the high tertile after adjusting for age and WHR. The associated risk persisted when adjusting for BMI for GDM but was attenuated for hypertensive disorders in pregnancy. Leptin levels were not associated with risk of pregnancy loss or PTD.

CONCLUSIONS

Women with higher baseline preconception leptin levels had a higher likelihood of experiencing some adverse pregnancy outcomes including GDM and hypertensive disorders of pregnancy. These findings warrant further evaluation, especially in light of the association between leptin and obesity.

Increased Circulating Levels of Tissue-Type Plasminogen Activator Are Associated with the Risk of Spontaneous Abortion During the First Trimester of Pregnancy

Spontaneous abortion is a common complication in early pregnancy, with an incidence of around 20%. Ultrasound scan and measurement of human chorionic gonadotropin are used to identify patients at risk of spontaneous abortion; however, there is a clinical need to find new biomarkers to prospectively identify patients before the onset of clinical symptoms. Here, we aim to investigate potential biomarkers of spontaneous abortion taken in the first clinical appointment of pregnancy. A case–control study was conducted based on a prospectively collected cohort in which cases and controls were retrospectively stratified based on pregnancy outcome: normal healthy pregnancies (controls = 33) and pregnancies that ended in spontaneous abortion (cases = 10). We evaluated extracellular vesicles isolated by precipitation with ExoQuick™ and protein concentrations of tissue plasminogen activator, leptin, and adiponectin measured by ELISA. The extracellular vesicles showed the typical morphology and membrane proteins: CD63, Alix, and Flotilin-1. The size distributions of the isolated extracellular vesicles were 112 ± 27 and 118 ± 28 nm in diameter for controls and spontaneous abortion, respectively, and the total amount of extracellular vesicles did not show any difference between controls and the spontaneous abortion group. The tissue plasminogen activator showed a significant difference (p = 0.0004) between both groups, although neither adiponectin nor leptin revealed significant changes, indicating that women who had spontaneous abortions have significantly higher levels of tissue plasminogen activator than women who had normal pregnancies.

Preconception Leptin and Fecundability, Pregnancy, and Live Birth Among Women With a History of Pregnancy Loss

Context

With the increase of obesity, it is imperative to understand the neuroendocrine mechanisms, including the neuroendocrine hormone leptin, by which obese or overweight women are at increased risk for subfertility and infertility.

Objective

The objective was to examine associations between preconception serum leptin concentrations, fecundability, pregnancy, and live birth.

Design

Secondary analysis of a prospective cohort among women with prior pregnancy losses.

Setting

The study was conducted at four US medical centers (2006 to 2012).

Intervention

Not available.

Materials and Methods

Preconception serum leptin concentrations were measured at baseline, and women were followed for up to six menstrual cycles, and throughout pregnancy if they conceived. Discrete Cox proportional hazard regression models were used to assess fecundability odds ratios (FORs) and log-binomial regression to estimate risk ratios (RRs) for pregnancy and live birth. Models were adjusted for age, physical activity, treatment arm, and adiposity, either by measured waist-to-hip ratio or body mass index (BMI).

Results

High leptin concentrations were associated with decreased fecundability (FOR 0.72, 95% CI 0.58, 0.90), reduced risk of pregnancy (RR 0.87, 95% CI 0.78, 0.96) and live birth (RR 0.76, 95% CI 0.65, 0.89) comparing the upper to the lower tertile. However, adjustment for BMI in lieu of waist-to-hip ratio nullified observed associations.

Conclusions

In women with a history of pregnancy loss, relations between higher preconception leptin and fecundability were attenuated after adjustment for BMI, although not after adjustment for other markers of adiposity. Leptin may serve as a complementary marker of adiposity for assessment of obesity and reproductive outcomes.

Adiponectin and leptin serum levels in normal adolescent pregnancies

INTRODUCTION

Adiponectin and leptin play a critical role in pregnancy development, the blood levels of these adipokines have been extensively investigated in healthy adult women, however there are no similar studies in adolescents. The aim of this study was to evaluate adiponectin and leptin serum levels in adolescents during pregnancy.

METHODS

This prospective cohort study recruited 105 healthy, normal-weight adolescents, within the ages from 13 to 19 years old. Leptin and adiponectin serum levels of the 43 pregnant participants were assessed at 10-14, 24-28 and 30-34 weeks and their concentrations were compared with those of the 62 nonpregnant adolescents. Commercial ELISA kits were used for all assessments.

RESULTS

There were no clinical and sociodemographic differences between the pregnant and nonpregnant adolescents. Adiponectin serum levels were significantly lower in the pregnant compared to the nonpregnant adolescents 3600 ± 1730 ng/ml versus 4144 ± 1583 ng/ml, respectively. (p < .0001). Moreover, adiponectin concentration decreased significantly with pregnancy progress: being 4295 (± 2003) ng/ml at the first trimester; 3419 (±1803) ng/ml at the 2nd; and 3112 (±1442) ng/ml at the 3rd trimesters, respectively (p = .004). Overall leptin serum concentrations were significantly higher in pregnant than in nonpregnant adolescents (p < .0001). During pregnancy, leptin concentration increased significantly between the first and third trimesters: 35,688 (±33,637) pg/ml versus 49,388 (±33,186) pg/ml, respectively, (p < .0001).

CONCLUSIONS

The profile of adiponectin and leptin serum levels in adolescent are similar to that observed in adult women. In both cases, there are significant changes with gestational age during healthy pregnancy.Key MessageAdiponectin and leptin serum levels in healthy teenager changes with pregnancy.

Maternal body mass index affects embryo morphokinetics: a time-lapse study

PURPOSE

To assess the effect of body mass index (BMI) on morphokinetic parameters of human embryos evaluated with time-lapse technology during in vitro culture.

METHODS

A retrospective analysis of ART cycles utilizing time-lapse technology was undertaken to assess the potential impact of maternal BMI on morphokinetic and static morphological parameters of embryo development. The cohort of patients was divided into four groups: 593 embryos from 128 underweight women in group A; 5248 embryos from 1107 normal weight women in group B; 1053 embryos from 226 overweight women in group C; and 286 embryos from 67 obese women in group D.

RESULTS

After adjusting for maternal age, paternal age, and cause of infertility, time to reach five blastomeres (t5) and time to reach eight blastomeres (t8) were longer in obese women compared with normoweight women [50.84 h (46.31-55.29) vs. 49.24 h (45.69-53.22) and 57.89 h (51.60-65.94) vs. 55.66 h (50.89-62.89), adjusted p < 0.05 and adjusted p < 0.01, respectively]. In addition, t8 was also delayed in overweight compared with normoweight women [56.72 h (51.83-63.92) vs. 55.66 h (50.89-62.89), adjusted p < 0.01]. No significant differences were observed among groups with regard to embryo morphology and pregnancy rate. Miscarriage rate was higher in underweight compared with normoweight women (OR = 2.1; 95% CI 1.12-3.95, adjusted p < 0.05).

CONCLUSION

Assessment with time-lapse technology but not by classical static morphology evidences that maternal BMI affects embryo development. Maternal obesity and overweight are associated with slower embryo development.

Cross talk between serum Kisspeptin-Leptin during assisted reproduction techniques

Background & objective:

Leptin facilitates onset of puberty by impact on hypothalamic Kisspeptin, gonadotropin releasing hormone, follicle stimulating and luteinizing hormone. The link of peripheral Leptin-Kisspeptin in regulating the ovarian and endometrial tissue in relation to adiposity is unknown. Therefore, we wanted to identify Kisspeptin-Leptin association with body mass index (BMI) and success of assisted reproductive treatments (ART) in infertile females.

Methods:

A cross sectional study was carried from August 2014 till May 2016 after receiving ethical approval at Australian Concept Infertility Medical Centre, and Aga Khan University. The study group comprised of females with an age range of 25-37 year who had duration of unexplained infertility for more than two years. They were grouped as; underweight (<18 kg/m²), normal weight (18-22.9 kg/m²), overweight 23-24.99 kg/m² and obese (>25 kg/m²). Kisspeptin and Leptin levels were measured by enzyme linked immune sorbent assay before down regulation of ovaries and initiation of treatment protocol of ART. Failure of procedure was detected by beta human chorionic gonadotropin <25mIU/ml (non-pregnant) whereas females with levels >25mIU/ml and cardiac activity on trans-vaginal scan were declared pregnant.

Results:

Highest Kisspeptin and Leptin levels were seen in normal weight group (374.80 ± 185.08ng/L; 12.78 ± 6.8 pg/ml) respectively, yet the highest number of clinical pregnancy was observed in overweight group (42%).A strong correlation of Kisspeptin with Leptin (r=0.794, p=0.001) was observed in the overweight females.

Conclusion:

Leptin-Kisspeptin-fertility link is expressed by maximum number of clinical pregnancies in the female group that showed strongest relationship between serum Leptin and Kisspeptin levels, irrespective of their BMI.

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.

Medical conditions associated with recurrent miscarriage-Is BMI the tip of the iceberg?

BACKGROUND

In contrast to sporadic miscarriage, recurrent miscarriage (RM) is a rare entity which affects 1% of couples attempting conception. It is distressing for couples and healthcare professionals as the aetiology is unclear with limited treatment options. Apart from anti-phospholipid syndrome (APS), the strength of associations between RM and commonly investigated endocrine, autoimmune, thrombophilic and uterine structural abnormalities remains uncertain and variable.

OBJECTIVES

To assess the prevalence of commonly investigated medical conditions associated with RM.

STUDY DESIGN

A 9-year retrospective analysis of a prospectively collected database was conducted for 592 patients seen between 2008 and 2016, in tertiary level RM clinic in South Africa.

RESULTS

In this period, 592 patients were assessed. The mean age was 29.73±5.46 (mean±SD), gravidity 4.6±1.82 and parity 0.98±1.05. The mean number of miscarriages per patient was 3.34±1.63, of which two-thirds (61.3%) were in the first trimester, a third (33%) in the second trimester and intrauterine fetal deaths (IUFDs) constituted 6% of total losses. Of the 50% of patients with no identified associated disorders, 15% were unexplained (investigations complete but no associations found), 10% became pregnant during investigation (investigations incomplete) and 25% were lost to follow-up (investigations incomplete). Nearly forty percent (38%) of patients had an associated endocrine disorder (22% PCOS, 11% IGT, 3% Diabetes Mellitus and 2% Thyroid Dysfunction) and 10% a uterine factor (4% Cervical Incompetence, 2% Fibroids, 2% Synechiae and 2% Anomalies). APS and Thrombophilias constituted 3% and 2% of patients respectively. The BMI (mean±SD) amongst patients with Unexplained RM, PCOS and IGT were 28.85±5.95, 30.86±7.79 and 33.40±6.47 respectively. Patients with IGT had significantly higher mean BMI in comparison to those with Unexplained RM (p<0.0001)*** and PCOS (p<0.001)**.

CONCLUSION

PCOS, IGT and Type II Diabetes are all likely surrogates for elevated BMI and constitute 70% of those women with RM and identified associated medical disorders. In our population, BMI seems to have a substantial impact on recurrent pregnancy loss and future studies should interrogate its effect on recurrent miscarriage.

The association between level of maternal serum leptin in the third trimester and the occurrence of moderate preterm labor

OBJECTIVE

We aimed to investigate the relationship between the level of maternal serum leptin and the occurrence of moderate preterm labor.

MATERIAL AND METHODS

This was a case control study conducted on pregnant women referred to Al-Zahra Hospital in Rasht, north of Iran in 2013. Cases included 30 moderate preterm delivering women and 30 control pregnant women with the same gestational age. The maternal serum leptin was measured for each mother at the time of entering the study.

RESULTS

The mean serum leptin in the control group (56.66±34.18) was significantly higher than the preterm (33.65±16.70) group. There were no significant differences between the groups in terms of body mass index and age. Logistic regression revealed that age and body mass index did not have a significant relationship to moderate preterm birth. However, an increased leptin level as low as 1 microgram per liter was associated with the risk of moderate preterm birth incidence (OR: 0.973, CI: 0.948-0.997).

CONCLUSION

Higher levels of leptin in pregnant women are associated with a decreased risk of moderate preterm birth. Further investigations are recommended with a larger sample size.

Interleukin-17 and leptin genes polymorphisms and their levels in relation to recurrent pregnancy loss in Egyptian females

Recurrent pregnancy loss (RPL) is a common problem during early gestation. The aim of our study was to investigate the association of IL-17 F( rs763780), IL-17 A (rs2275913), and leptin (2548 G/A) gene polymorphisms with RPL in obese and lean Egyptian females, and to find out whether these gene polymorphisms affect the women’s serum levels. One hundred and twenty patients with RPL and 120 fertile volunteers with no history of pregnancy loss were genotyped for leptin (2548 G/A), IL-17 A (rs2275913), and IL-17 F (rs763780) polymorphisms by RFLP. The serum level of IL-17 was measured by ELISA, while serum leptin level was measured by HPLC. We found that IL-17 F (rs763780) polymorphism was associated with a decreased risk of RPL in Egyptian females, and we also found that IL-17 A (rs2275913) and LEP (2548 G/A) SNP were associated with an increased risk of RPL. We also demonstrated that both the IL-17 and leptin levels were elevated in the women with RPL and in an obese subgroup within RPL in comparison to a lean one.

Leptin and its potential interest in assisted reproduction cycles

BACKGROUND

Leptin, an adipose hormone, has been shown to control energy homeostasis and food intake, and exert many actions on female reproductive function. Consequently, this adipokine is a pivotal factor in studies conducted on animal models and humans to decipher the mechanisms behind the infertility often observed in obese women.

METHODS

A systematic PubMed search was conducted on all articles, published up to January 2015 and related to leptin and its actions on energy balance and reproduction, using the following key words: leptin, reproduction, infertility, IVF and controlled ovarian stimulation. The available literature was reviewed in order to provide an overview of the current knowledge on the physiological roles of leptin, its involvement in female reproductive function and its potential interest as a prognostic marker in IVF cycles.

RESULTS

Animal and human studies show that leptin communicates nutritional status to the central nervous system and emerging evidence has demonstrated that leptin is involved in the control of reproductive functions by acting both directly on the ovaries and indirectly on the central nervous system. With respect to the clinical use of leptin as a biomarker in IVF cycles, a systematic review of the literature suggested its potential interest as a predictor of IVF outcome, as high serum and/or follicular fluid leptin concentrations have correlated negatively with cycle outcome. However, these preliminary results remain to be confirmed.

CONCLUSION

Leptin regulates energy balance and female reproductive function, mainly through its action on hypothalamic-pituitary-ovarian function, whose molecular and cellular aspects are progressively being deciphered. Preliminary studies evaluating leptin as a biomarker in human IVF seem promising but need further confirmation.

Leptin down-regulates γ-ENaC expression: a novel mechanism involved in low endometrial receptivity

OBJECTIVE

To examine epithelial Na(+) channel (ENaC) expression in endometrium of overweight/obese women with polycystic ovary syndrome (PCOS) during the window of implantation, and to explore the mechanism linking leptin-mediated reduction of γ-ENaC to low endometrial receptivity.

DESIGN

Controlled, prospective, clinical, experimental study.

SETTING

University-based infertility center.

PATIENT(S)

Blood and endometrium samples were collected from 12 control women and 12 overweight/obese PCOS patients. Pregnancy outcomes were obtained from 245 women with male-factor infertility (533 cycles) and 57 infertile women with PCOS (120 cycles) who underwent intrauterine insemination.

INTERVENTION(S)

Human endometrial biopsies.

MAIN OUTCOME MEASURE(S)

Expression of ENaC mRNA and protein in endometrium.

RESULT(S)

The expression of γ-ENaC decreased in the secretory phase endometrium of PCOS patients who showed increased serum leptin levels. In cultured endometrial cells (Ishikawa cells), leptin dose-dependently down-regulated the expression of γ-ENaC and reduced the JAr spheroid attachment rate, which could be blocked by knockdown of STAT3, a signal in the pathway of leptin receptor activation. The overweight/obese PCOS patients with increased serum leptin levels showed a significantly increased biochemical pregnancy rate, suggesting that high leptin might attenuate endometrial receptivity and increase very early pregnancy loss.

CONCLUSION(S)

High serum leptin may reduce endometrial receptivity by activating the STAT3 signal pathway and down-regulating γ-ENaC expression in the endometrium. These results provide valuable new insights into the molecular mechanisms linking abnormal ENaC gene expression to early pregnancy loss in overweight/obese PCOS patients.

An updated view of leptin on implantation and pregnancy: a review

The hormone leptin, which is thought to be primarily produced by adipose tissue, is a polypeptide that was initially characterized by its ability to regulate food intake and energy metabolism. Leptin appears to signal the status of body energy stores to the brain, resulting in the regulation of food intake and whole-body energy expenditure. Subsequently, it was recognized as a cytokine with a wide range of peripheral actions and is involved in the regulation of a number of physiological systems including reproduction. In the fed state, leptin circulates in the plasma in proportion to body adiposity in all species studied to date. However other factors such as sex, age, body mass index (BMI), sex steroids and pregnancy may also affect leptin levels in plasma. In pregnant mice and humans, the placenta is also a major site of leptin expression. Leptin circulates in biological fluids both as free protein and in a form that is bound to the soluble isoform of its receptor or other binding proteins such as one of the immunoglobulin superfamily members Siglec-6 (OB-BP1). Although the actions of leptin in the control of reproductive function are thought to be exerted mainly via the hypothalamic-pituitary-gonadal axis, there have also been reports of local direct effects of leptin at the peripheral level, however, these data appear contradictory. Therefore, there is a need to summarize the current status of research outcomes and analyze the possible reasons for differing results and thus provide researchers with new insight in designing experiments to investigate leptin effect on reproduction. Most importantly, our recent experimental data suggesting that reproductive performance is improved by decreasing concentrations of peripheral leptin was unexpected and cannot be explained by hypotheses drawn from the experiments of excessive exogenous leptin administration to normal animals or ob/ob mice.

Frequency of euploid miscarriage is increased in obese women with recurrent early pregnancy loss

OBJECTIVE

To determine whether the frequency of euploid miscarriage is increased in obese women with recurrent early pregnancy loss (REPL).

DESIGN

Observational cohort study using prospectively collected data.

SETTING

Academic RPL program.

PATIENT(S)

A total of 372 women with REPL, defined as ≥2 pregnancy losses<10 weeks, and at least one ultrasound-documented miscarriage with chromosome results.

INTERVENTION(S)

Body mass index (BMI) was measured at the initial consultation and at each subsequent pregnancy. Conventional cytogenetic analysis and, when indicated, microsatellite analysis and/or comparative genomic hybridization was performed.

MAIN OUTCOME MEASURE(S)

Frequency of euploid miscarriage in obese (BMI≥30 kg/m2) and nonobese (BMI<30 kg/m2) subjects, before and subsequent to REPL evaluation.

RESULT(S)

There were 578 miscarriages with chromosome results. Of the subjects, 18% were obese at the time of miscarriage. The mean maternal age at miscarriage was similar between the obese and nonobese groups. Due to the high rate of maternal cell contamination in the prior miscarriages, only subsequent miscarriages with chromosome results were included in the primary analysis. Of the 117 subsequent miscarriages, the frequency of an euploid miscarriage among obese women was 58% compared with 37% of nonobese women (relative risk=1.63; 95% confidence interval 1.08-2.47).

CONCLUSION(S)

Obese women with REPL have an increased frequency of euploid miscarriage, which is a known risk factor for subsequent miscarriage.

The relationship between gut and adipose hormones, and reproduction

BACKGROUND

Reproductive function is tightly regulated by nutritional status. Indeed, it has been well described that undernutrition or obesity can lead to subfertility or infertility in humans. The common regulatory pathways which control energy homeostasis and reproductive function have, to date, been poorly understood due to limited studies or inconclusive data. However, gut hormones and adipose tissue hormones have recently emerged as potential regulators of both energy homeostasis and reproductive function.

METHODS

A PubMed search was performed using keywords related to gut and adipose hormones and associated with keywords related to reproduction.

RESULTS

Currently available evidence that gut (ghrelin, obestatin, insulin, peptide YY, glucagon-like peptide-1, glucose-dependent insulinotropic peptide, oxyntomodulin, cholecystokinin) and adipose hormones (leptin, adiponectin, resistin, omentin, chemerin) interact with the reproductive axis is presented. The extent, site and direction of their effects on the reproductive axis are variable and also vary depending on species, sex and pubertal stage.

CONCLUSIONS

Gut and adipose hormones interact with the reproductive axis as well as with each other. While leptin and insulin have stimulatory effects and ghrelin has inhibitory effects on hypothalamic GnRH secretion, there is increasing evidence for their roles in other sites of the reproductive axis as well as evidence for the roles of other gut and adipose hormones in the complex interplay between nutrition and reproduction. As our understanding improves, so will our ability to identify and design novel therapeutic options for reproductive disorders and accompanying metabolic disorders.

Leptin and leptin receptor polymorphisms and recurrent pregnancy loss

OBJECTIVE

Leptin signaling is important in the establishment of pregnancy. We sought to determine if single nucleotide polymorphisms (SNPs) in the leptin and leptin receptor genes are associated with idiopathic recurrent pregnancy loss (RPL).

STUDY DESIGN

We conducted a case-control study with cases defined as women with idiopathic RPL and controls as parous women without pregnancy losses. A total of 99 cases and 108 controls were genotyped for the leptin (-2548 G/A) SNP and the leptin receptor A223G SNP. Genotype and allele frequencies were compared between cases and controls using χ(2) test.

RESULT

In this population, there was no significant difference in the genotype or allele frequencies for the leptin (-2548 G/A) or leptin receptor A223G SNPs between women with idiopathic RPL and controls.

CONCLUSION

Although leptin signaling is critical to many aspects of reproduction, the maternal leptin and leptin receptor SNPs evaluated in this study are unlikely to have a clinically meaningful role in RPL.

Circulating levels of matrix proteases and their inhibitors in pregnant women with and without a history of recurrent pregnancy loss

BACKGROUND

We have recently shown that serum relaxin-2 levels are attenuated in women with a history of recurrent pregnancy loss (RPL). We sought to determine whether a history of RPL is also associated with changes in serum matrix metalloproteases (MMPs) and tissue inhibitors of matrix metalloproteases (TIMP) -1 and -2.

METHODS

We obtained serum from 20 pregnant women with a history of RPL and 20 age-matched pregnant women with no history of RPL (NRPL) at 6-8, 10-12, 20, and 34 weeks gestation, and from cord blood. We quantified total serum concentrations of MMP-1, MMP-3, MMP-9 and TIMP-1 and TIMP-2 by ELISA. We determined whether these serum marker levels were associated with a history of RPL and delivery before 37 weeks gestation.

RESULTS

There was no difference in the rates of miscarriage, preterm birth or prelabour rupture of fetal membranes between RPL and NRPL. However babies born to RPL were lighter than those born to NRPL. Serum MMP-1, 9, and TIMP-1 did not differ between RPL and NRPL but MMP-3 was higher in RPL vs. NRPL at 6-8 weeks (P < 0.05). Serum TIMP-2 levels were higher in RPL women at all gestations (P < 0.01). The ratio of RLX-2 (reported previously) to TIMP-2 at 10-12 weeks gestation was more strongly associated with a history of RPL than either peptide separately - area under the ROC curves for RLX-2 0.79 (95% CI 0.57 to 0.92), TIMP-2 0.83 (95% CI 0.63 to 0.95), and for RLX-2:TIMP-2 ratio 0.92 (95% CI 0.74 to 0.99).

CONCLUSIONS

Women with a history of RPL demonstrate increased serum TIMP-2 and reduced RLX-2 during a subsequent viable pregnancy. Determination of both markers in early pregnancy enhances the discrimination of women with a history of RPL. These observations suggest roles for these two peptides in early implantation and placental development. Whether these may prove to be reliable early predictive markers for subsequent pregnancy loss in the index pregnancy is unknown and will require further studies.

Reproductive endocrinology and clinical aspects of obesity in women

Obesity is a growing worldwide problem and is associated with a wide range of adverse effects on the female reproductive system. The endocrinological changes in obesity that may cause these adverse effects are complex and include changes in circulating adipokines and sex steroids as well as insulin resistance. Considerable evidence suggests an adverse effect of obesity on the risk of miscarriage and other maternal and fetal complications. Obese patients are also more prone to infertility. The most important single method to improve reproductive performance in obese women is weight loss that can be achieved with lifestyle changes and diet. Antiobesity drugs may also be used and, in severe cases, bariatric surgery.

High and low BMI increase the risk of miscarriage after IVF/ICSI and FET

BACKGROUND

The extremes of BMI are associated with an increased risk of miscarriage both in spontaneously conceived pregnancies and after fertility treatment. The aim of the present study was to study the effect of BMI on miscarriage rate (MR) in fresh IVF/ICSI, and in spontaneous and hormonally substituted frozen-thawed embryo (FET) cycles.

METHODS

Analysis was carried out on 3330 first pregnancy cycles, performed during the years 1999-2004, of which 2198 were fresh, 666 were spontaneous and 466 were hormonally substituted FET cycles. A categorical, a linear and a quadratic models of the effect of BMI on miscarriage were studied by logistic regression. Factors related to patient characteristics, protocol and embryo parameters were also examined.

RESULTS

MR was higher in hormonally substituted FET (23.0%), compared with the fresh cycles (13.8%) and spontaneous FET (11.4%, P < 0.0001). Multivariate logistic regression revealed that the relationship between BMI and the risk of miscarriage is not linear but quadratic (U-shaped) (P = 0.01), indicating a higher risk of miscarriage in underweight and obese women. Hormonal substitution for FET was also associated with a 1.7-fold higher MR, compared with the fresh cycles (P = 0.002, 95% confidence interval 1.2-2.3).

CONCLUSIONS

Obese and underweight women have an increased risk of miscarriage, and hormonally substituted FET is associated with an even higher MR.

Do serum leptin levels have a role in the prediction of pregnancy outcome in case of threatened miscarriage?

OBJECTIVE

To determine whether maternal serum leptin levels can predict pregnancy outcome in cases of threatened miscarriage.

DESIGN

Observational study.

PATIENTS

Fifty-seven women with normal pregnancy (group A), 19 women with threatened miscarriage who delivered at term (group B), 22 women with threatened miscarriage with subsequent miscarriage (group C) and 27 women with delayed miscarriage (group D).

MEASUREMENTS

Maternal serum leptin was determined using a commercial radioimmunoassay (RIA) kit.

RESULTS

Serum leptin levels were not significantly different among groups A, B and C [median (range) 17.6 (10.1-26.5), 18.2 (12.5-25.6) and 17.3 (11.2-27.6) microg/l, respectively]. Women in group D showed significantly lower serum leptin levels in comparison with other groups [14 (6.7-21.3) microg/l; P < 0.05].

CONCLUSIONS

Serum leptin levels in the first trimester of pregnancy may not be the primary indicator of miscarriage in cases of threatened abortion.

Maternal underweight and the risk of spontaneous abortion

BACKGROUND

To evaluate the risk of spontaneous abortion in relation to maternal pre-pregnant underweight.

METHODS

The study was designed as a cohort study within the framework of the Danish National Birth Cohort (DNBC). The participants were a total of 23 821 women recruited consecutively to the DNBC from October 1, 1997 to March 31, 1999 and interviewed subsequently. The pregnant women were recruited in first half of pregnancy and interviewed about pre-pregnant body size, obstetric history, exposures in pregnancy, and socio-demographic factors. Pregnancies were followed-up regarding spontaneous abortion. Relative risk of spontaneous abortion was calculated as Hazard Ratios using Cox regression with delayed entry.

RESULTS

The outcome measure was spontaneous abortion. The hazard ratio for spontaneous abortion in women with a pre-pregnant body mass index (BMI) below 18.5 was 1.24 (95% confidence limits 0.95-1.63) compared to women with pre-pregnant BMI 18.5-24.9. Women with a BMI of 25 or more had a smaller increase in risk of spontaneous abortion. Adjustment for maternal age, parity, previous miscarriages, and lifestyle factors did not affect the estimates substantially, neither did exclusion of women with metabolic or eating disorders.

CONCLUSION

These results indicate that pre-pregnant underweight may affect the risk of spontaneous abortion negatively.

Leptin in pregnancy: an update

Leptin influences satiety, adiposity, and metabolism and is associated with mechanisms regulating puberty onset, fertility, and pregnancy in various species. Maternal hyperleptinemia is a hallmark of mammalian pregnancy, although both the roles of leptin and the mechanisms regulating its synthesis appear to be taxa specific. In pregnant humans and nonhuman primates, leptin is produced by both maternal and fetal adipose tissues, as well as by the placental trophoblast. Specific receptors in the uterine endometrium, trophoblast, and fetus facilitate direct effects of the polypeptide on implantation, placental endocrine function, and conceptus development. A soluble isoform of the receptor may be responsible for inducing maternal leptin resistance during pregnancy and/or may facilitate the transplacental passage of leptin for the purpose of directly regulating fetal development. The steroid hormones are linked to the regulation of leptin and the leptin receptor and probably interact with other pregnancy-specific, serum-borne factors to regulate leptin dynamics during pregnancy. In addition to its effects on normal conceptus development, leptin is linked to mechanisms affecting a diverse array of pregnancy-specific pathologies that include preeclampsia, gestational diabetes, and intrauterine growth restriction. Association with these anomalies and with mechanisms pointing to a fetal origin for a range of conditions affecting the individual's health in adult life, such as obesity, diabetes mellitus, and cardiovascular disease, reiterate the need for continued research dedicated to elucidating leptin's roles and regulation throughout gestation.

Coelomic Fluid Leptin Concentration in Normal First-Trimester Pregnancies and Missed Miscarriages

OBJECTIVE

Investigation of the possible role of leptin in early pregnancy failure.

METHODS

Leptin concentration was measured in maternal serum, coelomic fluid and amniotic fluid from 15 singleton pregnancies with live fetuses and 7 missed miscarriages at 7-10 weeks of gestation.

RESULTS

In the pregnancies with live fetuses, the median leptin concentration was significantly higher in coelomic fluid (median 33.1 ng/ml) than in maternal serum (median 8.1 ng/ml) or amniotic fluid (median 0.5 ng/ml). In the pregnancies with missed miscarriage, compared to those with live fetuses, the median leptin concentration in coelomic fluid was higher (median 45.3 ng/ml), but in maternal serum it was not significantly different (median 5.5 ng/ml).

CONCLUSIONS

The high coelomic fluid leptin concentration suggests that embryonic death may be preceded by impaired oxygenation of the placenta that stimulates production of leptin.

Inhibin A and activin A may be used to predict pregnancy outcome in women with recurrent miscarriage

OBJECTIVE

To look at the role of inhibin and activin in predicting pregnancy outcome in patients with history of recurrent miscarriage.

DESIGN

Observational clinical study.

SETTING

Recurrent miscarriage clinic of a tertiary care teaching hospital.

PATIENT(S)

Patients with history of recurrent miscarriage.

INTERVENTION(S)

Serial serum inhibin A and activin A concentrations were measured in weeks 5 though 8 of pregnancy.

MAIN OUTCOME MEASURE(S)

Serum concentrations of inhibin A and activin A levels.

RESULT(S)

Mean inhibin A concentration at 5 to 6 weeks for women who miscarried and those who had live births was 33 and 51 pg/mL, respectively; activin A at same gestation for the two groups was 534 and 643 pg/mL, respectively. After 2 weeks, mean inhibin A concentration for women who miscarried and those who had live births was 66 and 145 pg/mL, respectively, and activin A was 747 and 1,123 pg/mL, respectively.

CONCLUSION(S)

It is possible that inhibin A and activin A may be used as markers to predict pregnancies that are likely to miscarry.

Leptin expression in the fetus and placenta during mouse pregnancy

During pregnancy, leptin concentrations in the maternal circulation are elevated in both humans and rodents but decrease to pre-pregnancy levels at birth, suggesting a role for leptin in the maintenance of pregnancy. Synthesis of leptin by the human placenta is established but whether the murine placenta synthesizes leptin remains controversial. The aims of this study were to determine (a) if the mouse wild-type placenta expresses the ob gene using Reverse Transcription-Polymerase Chain Reaction (RT-PCR) and (b) whether the mouse fetus and placenta contribute to the significant increase of leptin in the maternal circulation during pregnancy. The mouse placenta did not express the ob gene at a level that could be readily detected using RT-PCR. Moreover, both maternal gain in weight and undetectable concentrations of leptin in sera in leptin-deficient ob/ob mothers bearing heterozygote (ob/+) fetuses suggested that the mouse fetus and placenta do not make a significant contribution to the dramatic increase in maternal plasma concentrations of leptin during late gestation. It is therefore concluded that neither fetal- nor placental-derived leptin modulates maternal weight gain during pregnancy.

Effects of leptin on the production of cytokines by cultured human endometrial stromal and epithelial cells

OBJECTIVE

To evaluate the effects of leptin on the production of interleukin (IL)-6 family cytokines and chemokines by human endometrial stromal cells (ESC) and epithelial cells.

DESIGN

The effects of leptin on the production of IL-6, IL-11, leukemia inhibitory factor (LIF), IL-8, growth-regulated oncogene (GRO)-alpha, monocyte chemoattractant protein (MCP)-1, and macrophage inflammatory protein (MIP)-3alpha by ESC and the endometrial epithelial cell line HHUA were investigated.

SETTING

Research laboratory at a medical university.

PATIENT(S)

Eight endometrial specimens in the late proliferative phase were used for the isolation of ESC.

INTERVENTION(S)

ESC and HHUA were incubated for 24 hours with recombinant human leptin.

MAIN OUTCOME MEASURE(S)

The concentration of IL-6, IL-11, LIF, IL-8, GRO-alpha, MCP-1, and MIP-3alpha were measured using ELISAs.

RESULT(S)

Unstimulated ESC and HHUA constitutively secreted IL-6, IL-11, LIF, IL-8, GRO-alpha, MCP-1, and MIP-3alpha. The increase in levels of IL-6, IL-8, GRO-alpha, MCP-1, and MIP-3alpha in the culture media of ESC and HHUA paralleled the addition of increasing amounts of leptin. In contrast, the levels of IL-11 and LIF were not affected by leptin administration.

CONCLUSION(S)

The present findings suggest that leptin may be an additional modulator of IL-6 and chemokine expression in the endometrium. Leptin may contribute to the normal and pathological processes of human reproduction by the regulation of these cytokines in the local environment.

Expression of Leptin Receptor Isoforms in vitro : Lack of Effects of Leptin on Endometrial Cytokine and MMP Production

PROBLEM

Leptin has a key role to play in human female reproduction. Its receptor is expressed highly throughout the reproductive tract. Cytokines have an important role in preparing the endometrium for implantation and leptin is known to modulate cytokine production in other tissues. We, therefore, investigated the possible role of leptin in endometrial growth and function.

METHOD OF STUDY

Reverse transcriptase polymerase chain reaction and immunocytochemistry were used to determine the pattern of expression of leptin receptor isoforms in primary human endometrial epithelial and stromal cells in culture. The effect of leptin on cell growth and on the production of cytokines [Leukaemia Inhibitory Factor (LIF), interleukin 6 and tumour necrosis factor-alpha] and matrix metalloproteinases (MMP) (MMP2 and MMP-9) was also investigated.

RESULTS

Expression of the long form of the leptin was restricted to the cultured endometrial, epithelial cells. Both cultured endometrial stromal and epithelial cells expressed the short and variant isoforms of the receptor. Incubation of epithelial and stromal cell cultures with varying concentrations of leptin (0-1000 ng/mL) had no significant effect on cell growth or levels of MMP-2 or MMP-9 production. Leptin also had no significant effect on cytokine production by epithelial cells.

CONCLUSIONS

This study shows for the first time, the presence of leptin receptor isoforms on endometrial, epithelial and stromal cells in culture. Leptin had no effect on cytokine and MMP production by these cells. However, it is possible that leptin affects other factors within the endometrium not investigated here.

Effect of leptin on progesterone, human chorionic gonadotropin, and interleukin-6 secretion by human term trophoblast cells in culture

Leptin, the 16-kDa protein product of the obese gene, was originally seen as an adipocyte-derived signaling molecule. Recently, it has been suggested to be involved in some functions during pregnancy, particularly in the placenta. In the present study, we investigated the role of leptin in the secretion of hCG, progesterone, and interleukin-6 (IL-6) by human term trophoblast cells in culture. Placentae were obtained from cesarean sections following uncomplicated pregnancies and used immediately after delivery. Leptin, hCG, progesterone, and IL-6 were measured by ELISA, RIA, and immunoradiometric assay in the cultured media of trophoblast cells cultured for 48 and 96 h. Leptin mRNA expression in these cultures was determined by reverse transcription-polymerase chain reaction. Recombinant human leptin added to primary cultures of human term placental trophoblast cells showed a stimulatory effect on hCG and IL-6 secretion and an inhibitory effect on progesterone secretion. Primary cultures of term trophoblast cells expressed leptin mRNA. All these findings suggest a role for leptin in human placental endocrine function.

Prospective function of placental leptin at maternal-fetal interface

Leptin is an endocrine and a growth factor which is important for regulation of body fat, feeding, and energy homeostasis. The anti-obesity function of leptin has been recently extended to reproduction, puberty and pregnancy as an endocrine signal to the hypothalamus. Leptin controls the functional integrity of the feto-placental unit thereby maintaining pregnancy by virtue of its immunomodulatory property via T lymphocytes or other proto-oncogenes. Dysregulation of autocrine/paracrine function of leptin at feto-placento-maternal interface may be implicated in the pathogenesis of recurrent miscarriage gestational diabetes, pre-eclampsia and intra-uterine fetal growth retardation including disturbance of fetal bone turnover. This review will focus on the role of leptin in normal and abnormal pregnancy and fetal growth.