Leptin concentrations in the follicular phase of spontaneous cycles and cycles superovulated with follicle stimulating hormone

Novel first-trimester serum biomarkers for early prediction of gestational diabetes mellitus

BACKGROUND

Gestational diabetes mellitus (GDM) is a common obstetric complication worldwide that seriously threatens maternal and fetal health. As the number of women conceiving through in vitro fertilization (IVF) continues to rise, this population is recognized as being at an elevated risk for GDM. However, there is still no consensus on the early prediction of GDM in IVF patients due to the lack of reliable biomarkers.

METHODS

We compared the first-trimester serum cytokine and antibody profiles in 38 GDM women and 38 matched controls undergoing IVF treatment, based on the extensive human biobank of our large‑scale assisted reproductive cohort platform. The 76 samples were divided into a training set (n = 53) and a testing set (n = 23) using a 7:3 ratio, and five diverse machine-learning models for predicting GDM were constructed.

RESULTS

By combining the top five differentially expressed first‑trimester serum biomarkers [including total immunoglobulin (Ig)G, total IgM, interleukin (IL)-7, anti‑phosphatidylserine (aPS)-IgG immune complexes (IC), and IL-15], a novel early prediction model was constructed, which achieved superior predictive value [area under the curve (AUC) and 95% confidence interval (CI) 0.906 (0.840-0.971), with a sensitivity of 75% and a specificity of 94.7%] for GDM development. The eXtreme Gradient Boosting (XGBoost) model achieved an AUC of 0.995 (95% CI: 0.995-1.000, P < 0.001) for the training set and 0.867 (95% CI: 0.789-0.952, P < 0.001) for the test set in predicting GDM.

CONCLUSIONS

We identified a set of novel first‑trimester serum cytokines and immune-related biomarkers and constructed an efficient first‑trimester prediction model for GDM in IVF population. These findings are expected to aid in the development of early predictive strategies for GDM and offer immunological insights for further mechanistic studies of GDM.

Variation of Leptin During Menstrual Cycle and Its Relation to the Hypothalamic-Pituitary-Gonadal (HPG) Axis: A Systematic Review

Recently, adipose tissue has been identified as endocrine organ in addition to its action as energy store; it produces a large number of biologically active mediators known as adipocytokines. Significantly, adipocytokines were found to be involved in the physiology of many body functions, including reproduction. The role of body weight, body fat compositions, and nutrition has been largely investigated using animal models and human studies. Malnutrition and/or abnormal body weight may induce disturbances in fertility, puberty, pregnancy, and menstrual cycles. Leptin was the first discovered adipocytokine, and a large body of data over the last 25 years has shown that leptin is not only a molecule that reflects energy stores in the body, but is also an important cytokine involved in many physiological functions, such as inflammatory response, insulin sensitivity, bone metabolism, immunity, and most importantly, reproductive function. Leptin controls the normal physiology of the female reproductive system; it interacts with the hypothalamic–pituitary–gonadal (HPG) axis by a complex mechanism that connects energy homeostasis with reproduction. However, observational studies have demonstrated inconsistent results about leptin variation during normal menstrual cycle, and the mechanisms involved in the interplay between leptin and the hormones of the HPG axis are largely unknown. This review focuses on leptin variation during normal menstrual cycles and its relation to the hypothalamic–pituitary–gonadal axis, and the effect of overweight/obesity on leptin during menstrual cycle is further reviewed.

Serum leptin levels and reproductive function during the menstrual cycle

OBJECTIVE

The purpose of this study was to investigate the role of leptin on reproductive hormones and ovulation.

STUDY DESIGN

The BioCycle Study (2005-2007) followed 259 healthy premenopausal women not using hormonal contraceptives for ≤2 menstrual cycles (n = 509 cycles). Serum leptin, estradiol, progesterone, luteinizing hormone (LH), follicle-stimulating hormone, and testosterone were measured ≤8 times per cycle. The association of time-varying leptin and reproductive hormones over the cycle was estimated with the use of linear mixed models that were adjusted for percent body fat and age with inverse probability weighting for time-varying physical activity, caloric intake, and other reproductive hormones. The odds ratio for sporadic anovulation (n = 42 cycles) was estimated with the use of generalized linear models that were adjusted for percent body fat and age.

RESULTS

Geometric mean serum leptin levels increased from menses to the late luteal phase (16.7-20.4 ng/mL; P < .01), with a mid-cycle peak (21.7 ng/mL) at the time of the LH surge (P < .01). A 10% higher leptin level across the menstrual cycle was associated with higher estradiol levels (2.2%; 95% CI, 1.5-3.0), luteal progesterone levels (2.1%; 95% CI, 0.5-3.7), ovulatory LH levels (1.2%; 95% CI, 0-2.3), testosterone levels (0.6%; 95% CI, 0.3-0.9), and lower follicle-stimulating hormone levels (-0.7%; 95% CI, -1.1 to -0.4). Leptin at the time of the expected LH surge was moderately inversely associated with sporadic anovulation (per log increase in leptin; adjusted odds ratio, 0.58; 95% CI, 0.28-1.22).

CONCLUSION

The association that was observed between leptin level and reproductive function points to a possible relationship between serum leptin level and enhanced fertility.

Changes in serum leptin during phases of menstrual cycle of fertile women: relationship to age groups and fertility

BACKGROUND

It is established that serum level of leptin is affected by transitional phases of reproduction. It is also reported that the puberty is triggered when body fat and circulating levels of leptin exceed the critical thresholds, butthere is less focus on the serum level of leptin and its relationship with different phases of menstrual cycle and the fertility.

OBJECTIVES

The present study try to determines the serum concentration of leptin and fertility hormonesin the various phases of normal menstrual cycle of fertile women and compare any difference in serum concentration between age groups of 18-30 years and 31-41 years It is a well known fact that fertility start to decrease from age 31 years.

PATIENTS AND METHODS

A total of 118 healthy fertile women with normal menstrual cycle aged between 18-40, were divided into two age groups (n = 65) 18-30 years and (n = 53) 31-40 years. Serum concentrations of leptin, estradiol, progesterone, luteinising hormone (LH) and follicle-stimulating hormone (FSH) were measured on day1 (menstrual phase), day7 (proliferative/follicular phase), day14 (ovulatory phase), day21 (luteal phase) and day 28(secretory phase) of the menstrual cycle.

RESULTS

There was a significant increase (P < 0.05) in leptin levels on day 14 (12.75 + 5.8 ng/mL) and day 21 (12.91 + 3.2 ng/mL) for age group 18-30 years compared to day 14 (11.60 + 3.2 ng/mL) and day 21 (11.60 + 3.2 ng/mL) for age group 31-40 years. Leptin was positively correlated with FSH on day 14, with LH on day 7 and day 21; likewise, with progesterone on day 21 and day 28 and with estradiol on day 7 and day 14 for both age groups.

CONCLUSIONS

The serum leptin level was at the lowest level during the menstrual and secretory phase and the highest level was around the luteal phase. The significant increase ofleptin in the younger age group raise this question whether circulating leptin has any role to play in the age of pregnancy and fertility. Data in this study shows that leptin level was affected with increase in age; therefore changes in leptin level will affect fertility in this study suggest that there may be a relation between leptin levels and fertility.

Characterization of a distinctive pattern of periovulatory leptin secretion and its relationship with ovulation rate and luteal function in swine with obesity/leptin resistance

Patterns of leptin secretion during the estrous cycle and the possible relationship of changes in circulating leptin during the periovulatory period with ovarian function in sows of obese (Iberian breed) and lean genotype (Large White x Landrace) were evaluated in two consecutive experiments. Plasma leptin concentrations throughout the estrous cycle in lean sows remain unchanged, but Iberian females showed a periovulatory increase in circulating leptin levels without associated changes in body condition and fatness. In these sows, plasma leptin concentrations at Days -1 and 0 of the cycle were found to be positively correlated with the ovulation rate (r=0.943 and r=0.987, respectively; P<0.05 for both), but the levels of leptin at Day 0 were negatively correlated with the progesterone release from Day 3 (r=-0.557; P<0.05) and, became more evident at Day 5 of the estrous cycle (r=-0.924; P<0.005). Such relationships were not observed in the females of the lean genotype. In conclusion, the present study indicates the existence of a distinctive pattern in the periovulatory leptin secretion in swine with obesity and leptin resistance, which is associated with the number and functionality of the corpora lutea present in the subsequent cycle.

Effects of estradiol and FSH on leptin levels in women with suppressed pituitary

BACKGROUND

Female fertility depends on adequate nutrition and energy reserves, suggesting a correlation between the metabolic reserve and reproductive capacity. Leptin regulates body weight and energy homeostasis. The aim of this study was to investigate whether estradiol or FSH alone has a direct effect on the production of leptin.

METHODS

A total of 64 patients submitted to controlled ovarian hyperstimulation with recombinant FSH for assisted reproduction and 20 patients using estradiol valerate for endometrial preparation for oocyte donation treatment were included in the study. All patients used GnRH analogues before starting treatment to achieve pituitary suppression. Blood samples for hormonal measurements were collected before starting and after completing the respective treatments. Data were analyzed statistically by the chi-square test, Student's t-test and Pearson's correlation test.

RESULTS

We observed an elevation of serum leptin levels secondary to the increase in estradiol, in the absence of influence of any other ovarian or pituitary hormone. The rising rate of leptin levels was higher in women treated with recombinant FSH, which also had higher levels of estradiol, than in those treated with estradiol valerate.

CONCLUSIONS

This study demonstrates a correlation between serum levels of estradiol and leptin, suggesting that estradiol is an important regulator of leptin production and that its effects can be amplified by its association with FSH.

The effects of GnRH analogs on serum and follicular fluid leptin levels and pregnancy outcomes in short protocols of assisted reproductive technology

OBJECTIVE

To determine serum and follicular leptin levels in patients using gonadotropin releasing hormone agonist and antagonist in Assisted Reproductive Technology short protocol cycles and to evaluate pregnancy outcomes.

MATERIAL AND METHODS

Patients randomly selected to join assisted reproductive technology cycles during February 2004-July 2004 were enrolled in this study. Group 1 consisted of 21 patients receiving r FSH+ GnRH agonists, whereas Group 2 consisted of 34 patients who received r FSH +GnRH antagonists. During the ovulation induction period 5 serum samples were collected (induction day 1, day 3 or antagonist starting day, human chorionic hormone day, oocyte pickup day, and twelfth day of embryo transfer). Follicular fluid samples were collected to be evaluated for leptin, estradiol, prolactin and luteinizing hormone.

RESULTS

There was no difference in age, basal FSH, basal LH, and basal E2 between groups. Serum leptin levels were similar in both groups. Also, when each group's serum leptin levels were evaluated according to the presence of pregnancy, there was no significant difference in both groups. When follicle leptin levels were evaluated according to the existence of pregnancy, in both groups the follicle leptin levels were lower in pregnant participants but this difference was not statistically significant. When obesity is defined as body mass index over 26.5, there is a correlation between obesity and leptin levels in Group 2.

CONCLUSION

Our results have shown that both agonists and antagonists have similar efficacy and effect in poor responder women. Leptin levels in either groups, whether pregnant or non-pregnant were not statistically different. This result shows the need for more studies on leptin in infertility.

Intrafollicular and serum levels of leptin during in vitro fertilization cycles: comparison between the effects of recombinant follicle-stimulating hormones and human menopausal gonadotrophin

OBJECTIVES

To compare the effect of recombinant follicle-stimulating hormones (r-FSH) and human menopausal gonadotrophin (hMG) on leptin levels in serum and follicular fluid (FF) during in vitro fertilization IVF/ET treatment, and to investigate whether leptin levels in the follicular fluid and/or serum are correlated with IVF success.

METHODS

Sixty-three patients undergoing IVF cycle were subdivided into two groups. r-FSH was used to for controlled ovarian hyperstimulation in 29 patients (Group A) while, hMG was used in 34 patients (Group B). Our main outcomes were serum and FF leptin on the day of oocyte collection.

RESULT(S)

The two groups were comparable in age, body mass index (BMI), indications for IVF/ET, E2 level on human chorionic gonadotrophin day, number of retrieved oocytes, fertilization rate, number of transferred embryos and pregnancy rate. Serum and FF leptin levels were similar between the two study groups. Additionally, no correlation was found between levels of leptin in either serum or FF and cycle results such as: number of retrieved oocytes, fertilization rate and pregnancy rate.

CONCLUSIONS

r-FSH and hMG have been found to have comparable effects on leptin levels in the serum and the FF of patients undergoing IVF/ET. Additionally, leptin levels in both serum and FF on day of retrieval have no correlation to IVF/ET outcome.

Plasma levels of C-reactive protein, leptin and glycosaminoglycans during spontaneous menstrual cycle: differences between ovulatory and anovulatory cycles

PURPOSE

To assess the plasma levels of the inflammatory markers such as C-reactive protein (CRP), leptin, and glycosaminoglycans (GAGs) during the menstrual cycle.

METHODS

Eighteen healthy volunteers were divided into two groups according to the presence of ovulatory or anovulatory menstrual cycles. Blood samples were collected at different time points: at the menstrual phase (days 2-3), periovulatory phase (days 12-13), and luteal phase (days 23-24). CRP and leptin concentrations were measured by enzyme immunoassay. GAGs were isolated using ion-exchange chromatography on DEAE-Sephacel and quantified as hexuronate. The structural characterization of chondroitin sulfate (CS) isomers was performed by fluorophore-assisted carbohydrate electrophoresis (FACE).

RESULTS

In the women with ovulatory cycles, plasma GAG levels differed significantly during menstrual cycle, with increased values at the periovulatory with respect to the menstrual phase. No significant differences in CRP and leptin concentrations were observed through the menstrual cycle in both the examined cycles, but inter-group analysis revealed significant differences of CRP and leptin levels between the ovulatory and anovulatory cycles with higher values at periovulatory phase in the ovulatory cycles.

CONCLUSIONS

There are no fluctuations of both total GAG concentration and CS isomer content during menstrual cycle in the anovulatory cycles. A significant correlation between CRP and gonadotrophins was found. There is no significant difference in CRP across the menstrual cycle among ovulatory cycles, but there is a trend toward higher CRP at the periovulatory than the other phases, consistent with the significant difference in CRP between ovulatory and anovulatory cycles at the periovulatory phase. Both the trend and the significant result suggest an elevation in CRP with ovulation. These observations provide additional evidences to the hypothesis that the ovulation is an inflammatory-like phenomenon.

Hyperandrogenism alters intraovarian parameters during early folliculogenesis in mice

This study aimed to investigate how hyperandrogenism affects early folliculogenesis. Hyperandrogenism was induced in prepuberal female BALB/c mice by daily s.c. injection of dehydroepiandrosterone (60 mg/kg body weight in 0.1 ml sesame oil) for 10 consecutive days. Although hyperandrogenism increased the growth rate of primary follicles, it also increased ovarian oxidative stress (evaluated by the increase in lipid peroxidation, the decrease in superoxide dismutase activity and the fact that glutathione content was not modified). By using the annexin V/cytometry assay it was found that the excess of androgens decreased viable ovarian cells and increased early apoptotic ones. The increased lipid peroxidation induced enhanced ovarian prostaglandin E production. In addition, hyperandrogenism increased the number of T lymphocytes that infiltrate ovarian tissue and modified their phenotype (decreased CD4+ or helper and increased the suppressor/cytotoxic CD8+). The excess of androgens decreased the ovarian expression of the long isoform of leptin receptor (Ob-Rb, the only isoform expressed in the ovarian tissue) when compared with controls. All these alterations increased serum concentrations of oestradiol, a pro-apoptotic agent. It is concluded that the excess of androgens impairs early follicular development by modulating some endocrine and immune parameters that are either directly or indirectly related to follicular atresia.

Leptin levels in relation to marital status and neuroendocrine function in Iraqi females with polycystic ovary syndrome

The present study was designed to evaluate the relationship between serum leptin levels and the hormones related to fertility in Iraqi females with polycystic ovary syndrome (PCOS) and marital status. This study was conducted during the period from July to December 2007. Twenty-four women (12 married and 12 unmarried) with PCOS and not maintained on any type of therapy were included in the study. Twelve healthy and normal ovulatory women with an age range matched with that of PCOS women were included. After an overnight fasting, blood samples were drawn from all women at random days. While in those with regular menstrual cycles, blood samples were obtained during the follicular phase of the cycle, except for samples utilized for the assay of progesterone that performed in the day 21 of the cycle (luteal phase). After preparation of serum, the levels of leptin, luteinizing hormone (LH), follicle-stimulation hormone (FSH), progesterone, testosterone and prolactin were analyzed. Both groups of PCOS patients showed significantly lower levels of serum leptin, while prolactin, LH and FSH and testosterone were significantly elevated compared to controls. No significant differences were reported among PCOS patients with different marital status. In conclusion, impaired plasma leptin levels in PCOS women were associated with impaired endocrinological parameters related to fertility.

Modulating effect of leptin on basal and follicle stimulating hormone stimulated steroidogenesis in cultured human lutein granulosa cells

BACKGROUND

In vitro data have shown conflicting results in terms of the effect of leptin on granulosa cells steroidogenesis.

AIM

The aim of the present study was to investigate the effect of low and high doses of leptin on basal and FSH-induced steroids secretion by human luteinized granulosa cells in culture.

MATERIALS AND METHODS

Granulosa cells were obtained from normal women undergoing in vitro fertilization (IVF) treatment and were cultured in serum-free conditions for 72 h. A one-way analysis of variance design was set to study the effect of leptin on basal and FSH-induced steroidogenesis.

RESULTS

Leptin affected basal estradiol and progesterone secretion in a dose-related manner. In particular, leptin at low concentrations stimulated the secretion of estradiol (1 and 10 ng/ml) and progesterone (10 ng/ml), while at a high concentration (100 ng/ml) it suppressed the secretion of both steroids. A dose-related effect of leptin on FSH-induced steroidogenesis was not evident, since only the suppressive effect of the high concentration of leptin (100 ng/ml) reached statistical significance for both steroids.

CONCLUSIONS

These results demonstrate that leptin affects the secretion of steroids in luteinized granulosa cells in a dose-dependent manner. Although a physiological role for leptin is possible, it is suggested that this protein is a mediator of negative rather than positive influential interactions on ovarian function that may compromise fertility.

Serum leptin levels in women with uterine leiomyomas

OBJECTIVE

The purpose of this study was to examine the influence of leptin in women with uterine myoma.

MATERIALS AND METHODS

In this study, 38 women with myoma uteri and 30 normal women who applied to the Dr Zekai Tahir Burak Woman Health Research and Education Hospital's gynecology clinic were enrolled. Uterine leiomyomas were proved by pathology postoperatively. In all subjects, FSH, LH, E2, prolactin, hemoglobin, hematocrit, blood urea nitrogen, creatinine, fasting glucose, CA125, and leptin were examined, and body mass index (BMI) was calculated. Data were analyzed by Student's t test and Mann-Whitney U test.

RESULTS

Although leptin level was higher in the myomatic women (5.73 +/- 4.08 ng/mL) than in the normal women, there was no statistically significant difference (p = 0.303). Also, no statistical difference in the ratios of leptin/BMI was found in both groups. A significant correlation was found between high E2 level and myoma uteri (p = 0.021). Hemoglobin levels were significantly lower in the myomatic women (p = 0.044). When we compared the leptin levels according to BMI, leptin levels were higher in patients who had BMI > 30 (p = 0.02).

CONCLUSION

We did not find any significant difference in serum leptin levels between the two groups. But leptin may have an indirect role in the pathogenesis of uterine leiomyoma. So further research is needed to reveal the role of leptin in myoma uteri pathogenesis.

Anterior pituitary leptin expression changes in different reproductive states: in vitro stimulation by gonadotropin-releasing hormone

This study was designed to learn more about the changes in expression of rat anterior pituitary (AP) leptin during the estrous cycle. QRT-PCR assays of cycling rat AP leptin mRNA showed 2-fold increases from metestrus to diestrus followed by an 86% decrease on the morning of proestrus. Percentages of leptin cells increased in proestrus and pregnancy to 55-60% of AP cells. Dual labeling for leptin proteins and growth hormone (GH) or gonadotropins showed that the rise in leptin protein-bearing cells from diestrus to proestrus was mainly in GH cells. Only 10-20% of leptin cells in male or cycling female rats coexpress gonadotropins. In contrast, 50-73% of leptin cells from pregnant or lactating females coexpress gonadotropins and only 19% coexpress GH, indicating plasticity in the distribution of leptin. Leptin cells expressed GnRH receptors, and estrogen and GnRH together increased the coexpression of leptin mRNA and gonadotropins. GnRH increased cellular leptin proteins three to four times and mRNA 9.8 times in proestrous rats and stimulated leptin secretion in cultures from diestrous, proestrous, and pregnant rats. These regulatory influences, and the high expression of AP leptin during proestrus and pregnancy, suggest a supportive role for leptin during key events involved with reproduction.

Intra-follicular leptin concentration as a predictive factor for in vitro oocyte fertilization in assisted reproductive techniques

BACKGROUND

Granulosa-cells are able to produce and store leptin, suggesting that this hormone is locally involved in the regulation of follicular growth. In this study, the role of follicular fluid (FF) leptin concentration in predicting oocyte fertilization and embryo quality was evaluated in 35 normogonadotrophic women undergoing controlled ovarian stimulation (COS) for assisted reproductive techniques.

MATERIALS AND METHODS

Leptin concentration was measured in 47 consecutively collected FF in which a mature oocyte had been found during the ovum pick-up. Embryos deriving from fertilized oocytes were submitted to quality scoring systems.

RESULTS

Mean leptin concentration was significantly higher in FF whose oocytes showed 2 pronuclei (no. 25) when compared with those with no evidence of fertilization (no. 22) at the 16-18 h check (26.0+/-6.1 vs 15.3+/-10.6 ng/ml, respectively, p<0.01). Follicular mean diameters were similar in the two groups (21.4+/-3.4 and 21.0+/-5.1 mm, respectively). Logistic regression analysis identified FF leptin levels as the best predictive parameter for oocyte fertilization (p<0.001). When receiving operating characteristics curve was employed, a FF leptin concentration of 20.25 ng/ml was the most reliable cut-off in predicting fertilization of oocytes. FF with leptin concentrations higher than this value (no. 27) had an oocyte fertilization rate of 85.7%. In contrast, FF levels < or =20.25 ng/ml (no. 20) were associated with a rate of 16.7% (p<0.05). No correlation emerged between FF leptin and the score attributed to 15 valuable embryos at the zygote stage (r=-0.01) and at 48 h after insemination (r=0.1).

CONCLUSIONS

FF leptin levels are a better predictor of oocyte fertilization success rates than follicular diameter. These results underline the relevance of FF variables in developing methods for oocyte selection.

Effects of oral continuous 17beta-estradiol plus norethisterone acetate replacement therapy on abdominal subcutaneous fat, serum leptin levels and body composition

AIM

To evaluate the effects of oral continuous 17beta-estradiol plus norethisterone acetate (E2/NETA) replacement therapy on abdominal subcutaneous fat, serum leptin level (SLL) and body composition in postmenopausal women.

MATERIALS AND METHODS

A 6-month, prospective, randomized, double-blind and placebo-controlled study was conducted. Forty-three healthy naturally postmenopausal women aged 43-65 years were randomly assigned to receive E2/NETA (2 mg E2 plus 1 mg NETA, n = 22) or placebo (n = 21). Fasting SLL by enzyme-linked immunosorbent assay, subcutaneous abdominal fat thickness (STh) by ultrasound and the anthropometric indices of body weight (BW), body mass index (BMI), waist and hip circumference (WC, HC) and waist-to-hip ratio (WHR) were recorded at the beginning and the end of the study.

RESULTS

After 6 months of therapy, BW and SLL increased in the placebo group (p = 0.043 and 0.033, respectively). WC, HC and STh decreased significantly in the E2/NETA group (p = 0.002, 0.006 and 0.000, respectively) and they were also significantly lower in women receiving E2/NETA than in women taking placebo (p = 0.000, 0.034 and 0.000, respectively). At baseline, SLL and STh were positively correlated with all anthropometric indices except WHR.

CONCLUSION

Oral continuous combined regimen of E2/NETA significantly reduced central fat accumulation as assessed by WC and STh, and attenuated the increase in SLL. The observed changes in SLL were highly and positively related to changes in STh. The oral continuous combined E2/NETA regimen appears to have protective effects on cardiovascular function and probably on metabolic diseases by its slimming effect upon WC in postmenopausal women.

Interactions of the hormones leptin, ghrelin, adiponectin, resistin, and PYY3-36 with the reproductive system

OBJECTIVE

To summarize the effects of novel hormones (leptin, ghrelin, adiponectin, resistin, and PYY3-36) secreted from adipose tissue and the gastrointestinal tract that have been discovered to exert different effects on several reproductive functions, such as the hypothalamic-pituitary-gonadal axis, embryo development, implantation physiology, and clinically relevant conditions.

DESIGN

A MEDLINE computer search was performed to identify relevant articles.

RESULT(S)

Leptin and ghrelin exert important roles on body weight regulation, eating behavior, and reproduction, acting on the central nervous system and target reproductive organs. As a marker of adequate nutritional stores, these hormones may act on the central nervous system to initiate the complex process of puberty and maintain normal reproductive function. In addition, leptin and ghrelin and their receptors are involved in reproductive events such as gonadal function, embryo development, and embryo-endometrial interaction.

CONCLUSION(S)

Leptin and ghrelin and other adipose tissue-secreted hormones have significant effects on reproduction. Acting through the brain, these hormones may serve as links between adipose tissue and the reproductive system to supply and regulate energy needs for normal reproduction and pregnancy. Future studies are needed to further clarify the role of these hormones in reproductive events and other related gynecological conditions.

Correlation of leptin and sex hormones with endocrine changes in healthy Saudi women of different body weights

BACKGROUND

A relationship between estrogen and leptin has been described during the follicular phase of both spontaneous menstrual cycles and cycles stimulated with exogenous follicle-stimulating hormone (FSH), which suggest that leptin has either a direct effect on or is regulated by gonadal steroids in the human ovary. To examine the changes in plasma leptin levels during the menstrual cycle, we studied the association between plasma leptin and reproductive hormones in young, healthy Saudi women.

SUBJECTS AND METHODS

Sixty-five young women between 19 to 39 years of age, with a normal menstrual cycle, were grouped into 33 overweight and obese females of BMI >25 kg/m2, and 32 lean females of BMI <25 kg/m2. Anthropometrics measurements were made at the time of the collection. Samples were analyzed for leptin, progesterone, estradiol (E2), FSH, luteinizing hormone (LH), cortisol, and testosterone concentrations.

RESULTS

Overweight and obese women, compared with lean, tended to have a significantly higher plasma leptin levels (11.38 +/- 4.06 vs. 6.22 +/- 2.87 ng/mL; P=0.05). In overweight and obese subjects, circulating leptin concentrations showed a directcorrelation with BMI (r=0.53; P=0.002), hip circumference (r=0.32; P=0.005), waist-hip ratio (r=0.37; P=0.042), weight (r=0.41; P=0.021), and E2 on day 3 (r=0.35; P=0.048). In all correlation analyses, leptin levels did not correlate with cortisol or testosterone. In lean subjects, a bivariate correlation analysis showed that plasma leptin concentrations were directly correlated to hip circumference (r=0.43; P=0.012). Moreover, a direct correlation was found with progesterone on day 10 (r=0.43; P=0.014) and E2 on day 24 (r=0.47; P=0.007).

CONCLUSION

There is a link between plasma leptin and progesterone concentrations during the menstrual cycle, and the variation in circulating estradiol concentrations may have an influence on circulating leptin in female subjects.

Simultaneous increases of leptin and gonadotropin-releasing hormone following exogenous estrogen administration in women with normally menstrual cycle

The aim of this study was to investigate whether administration of exogenous estrogen affects the changes of leptin and GnRH levels in women with normal menstrual cycle. A total of 18 women received a bolus intravenous injection of 20 mg conjugated estrogen (premarin group) at 0800 during the fifth day of menstrual cycle, while another 18 women were administered 20 mL of normal saline as the control group. Fasting blood samples were collected at 0, 4, 8, 24, 28, 32, 48, 56, 72 and 96 hours after injection for analyses of leptin, GnRH, estrone (E(1)), estradiol (E(2)), LH and FSH. Both the mean plasma levels of E(1) and E(2) were significantly increased from 4 hours and significantly sustained elevated levels up to 72 hours after injection of premarin. Simultaneous significant increases of leptin and GnRH levels were observed at 28, 32 and 48 hours after injection, while the controls remained constant. The mean LH and FSH levels were initially suppressed and then significantly increased at 56 and 72 hours after premarin administration. Leptin appears to be involved in the regulation of positive feedback mechanism of estrogen by conveyance of metabolic signal to affect the release of GnRH in hypothalamus, while its participation in the modulation of negative feedback remains unknown.

Feeding-unrelated factors influencing the plasma leptin level in ruminants

The triglyceride content of lipid depots associated with the current feeding level is the primary determinant of leptin gene expression and the circulating leptin level. In laboratory rodents and primates the plasma leptin is influenced also by the age, gender and physiological status (puberty, pregnancy, lactation, postpartum period), and by the health condition such as sepsis due to Gram-negative (GN) bacteria. Some pathologic conditions with intensive cytokine release evoke an increase in plasma leptin, which is thought to depress the subsequent feed intake. However, the effect of these secondary factors may be species-dependent, with still unknown clinical relevance in ruminants. In our ovine and bovine models plasma leptin increased after castration and dexamethasone treatment, decreased after experimental administration of synthetic androgens in castrated rams, but remained unchanged throughout the ovarian cycle and after ovariectomy. The circulating leptin level increased temporarily during synthetic progestin (fluorogestone) treatment in ewes, but similar changes were not seen in progesterone-supplemented ewes and norgestomet-treated cows. In a second trial on dairy cows we wanted to study whether elevated plasma leptin levels are induced by experimental endotoxin mastitis, or by natural outbreak of GN mastitis and puerperal metritis. Experimental endotoxin mastitis resulted in some-hour elevation in cortisol and insulin, with a simultaneous decrease in IGF-I and thyroid hormones. In the first 14 days of lactation GN mastitis induced the same endocrine alterations as the experimental endotoxin challenge, but in natural cases these changes varied within a wider range, and were more protracted and robust. Cows with puerperal metritis had more obvious catabolic changes in the early weeks of lactation, than their healthy counterparts. However, both mastitis and puerperal metritis failed to increase the circulating leptin level, showing that in cows the plasma leptin is not responsible for the anorexia associated with these inflammatory diseases.

The relation of serum and follicular fluid leptin and ovarian steroid levels in response to induction of ovulation in in vitro fertilization cycles

OBJECTIVE

Leptin restores energy homeostasis and regulates appetite and body weight by communicating the energy status to the central nervous system. Although there is strong evidence that leptin affects reproduction, its role in the control of reproductive physiology is little understood.

STUDY DESIGN

We studied leptin concentrations in the serum and follicular fluid of 65 women undergoing ovarian hyperstimulation for in vitro fertilization (IVF). Fasting serum samples were collected (1) on the 3rd day of the cycle before IVF and (2) at the time of oocyte retrieval. Serum concentrations of leptin, estradiol (E2), progesterone, FSH, LH, prolactin, total testosterone, DHEA-SO4, and TSH and follicular fluid concentrations of leptin, E2, and progesterone were measured.

RESULTS

Serum leptin values increased on average by 66.4% over basal leptin levels on the day of oocyte pick-up (OPU). A positive correlation between leptin increase and body mass index was observed. The serum leptin level was similar to that in follicular fluid o the day of OPU. E2 levels increased 34.5-fold with controlled ovarian hyperstimulation. There was a negative correlation between the increase in leptin levels and in E2 levels (P <0.05) and in the number of oocytes harvested (P <0.05).

CONCLUSION

The significant increase in serum leptin levels during controlled ovarian hyperstimulation indicates a possible role of leptin in reproductive function. The increase in leptin levels is negatively correlated with ovarian response evaluated by E2 production and number of oocytes retrieved. This might be due to the reduced ovarian response through negative feedback of leptin to the ovaries at high levels.

Serum leptin concentrations in patients with severe ovarian hyperstimulation syndrome during in vitro fertilization–embryo transfer treatment

OBJECTIVE

To investigate the changes in serum leptin concentration in the conception cycle of severe ovarian hyperstimulation syndrome (OHSS).

DESIGN

Prospective longitudinal study of 66 IVF-ET cycles between May 2000 and June 2002.

SETTING

Infertility outpatient clinic at a Japanese medical school.

PATIENT(S)

Infertile patients undergoing IVF-ET cycles at the infertility outpatient clinic were divided into three groups consisting of group 1 (conception-cycle patients with severe OHSS, n = 9), and group 2 (conception cycle, non-OHSS, n = 28), and group 3 (nonconception cycle, non-OHSS, n = 29).

INTERVENTION(S)

Blood samples were collected at five different periods. Period I, on the first day of ovarian stimulation with FSH; period II, at hCG administration before oocyte retrieval; period III, 7 days after oocyte retrieval; period IV, 14 days after oocyte retrieval; and period V, 21 days after oocyte retrieval.

MAIN OUTCOME MEASURE(S)

Serum leptin concentration.

RESULT(S)

The serum leptin concentration was low in the OHSS group compared with that of the non-OHSS groups in all serum samples, with significant levels at periods III (vs. groups 2 and 3; P<.05) and IV (vs. group 3; P<.01). A twofold increase of leptin concentration from period I to period II (P<.05) was observed in all groups.

CONCLUSION(S)

The change pattern in serum leptin concentration might provide a great contribution to the pathophysiology development of OHSS patients during assisted reproductive treatment.

Leptin and its association with polycystic ovary syndrome: a twin study

Polycystic ovary syndrome (PCOS) is a common endocrinopathy with symptoms such as obesity, insulin resistance and hyperandrogenemia. PCOS might be the result of a genetic disorder. Genetic discrepancy in the production of leptin, a product of the obesity gene, may lead to various endocrinopathies such as PCOS. The objective of this study was first, to ascertain the incidence of PCOS, using the gold standard; second, to ascertain the genetic property of leptin; and third, to evaluate the association between leptin concentration and PCOS. A total of 154 Tehran-resident female-female twins were studied. They included 48 pairs of monozygotic (MZ) and 29 pairs of dyzygotic (DZ) twins, aged 15-45 years. Clinical, ultrasound and biochemical findings were used to diagnose PCOS. The incidence of PCOS using biochemical and clinical features was 16.2%. The correlation coefficient between serum leptin levels of MZ twins was higher than that of the DZ twins. The serum level of leptin was similar between subjects with or without PCOS, irrespective of their zygosity. It was concluded that the incidence of PCOS is high among twins, and that leptin is likely to be genetically determined, although the effect of environmental factors cannot be denied. This study did not find any association between the diagnosis of PCOS and leptin level. However, the link between the two may lie with other entities such as eating disorders and/or obesity.

Positive correlation of serum leptin with estradiol levels in patients with polycystic ovary syndrome

Patients with polycystic ovary syndrome (PCOS) usually are obese, insulin resistant and hyperinsulinemic. The known association between leptin, obesity and insulin action suggests that leptin may have a role in PCOS but this has only been addressed peripherally. This study was designed to assess the relationship between serum leptin and the anthropometric, metabolic and endocrine variables of obese (body mass index, BMI (3)30 kg/m(2)) and non-obese (BMI <30 kg/m(2)) PCOS patients. Twenty-eight PCOS patients and 24 control women subdivided into obese and non-obese groups were evaluated. Leptin, androgens, lipids, gonadotrophins and insulin-glucose response to the oral glucose tolerance test were measured by radioimmunoassay in all participants. The assays were done all in one time. The areas under the insulin curve (AUC-I) and the glycemia curve were calculated to identify patients with insulin resistance. Mean leptin levels were not significantly higher in patients with PCOS compared to the control group (21.2 +/- 10.2 vs 27.3 +/- 12.4 ng/ml). Leptin levels were found to be significantly higher in the obese subgroups both in patients with PCOS (26.9 +/- 9.3 vs 14.1 +/- 7.0 ng/ml) and in the control group (37.3 +/- 15.5 vs 12.9 +/- 5.8 ng/ml). The leptin of the PCOS group was correlated with BMI (r = 0.74; P < 0.0001) and estradiol (r = 0.48; P < 0.008) and tended to be correlated with the AUC-I (r = 0.36; P = 0.05). Of the parameters which showed a correlation with leptin in PCOS, only estradiol and probably insulinemia (AUC-I) did not show a significant correlation with BMI, suggesting that the other parameters were correlated with leptin due to their correlation with BMI. Estradiol correlated with leptin in PCOS patients regardless of their weight.

Serum pattern of circulating free leptin, bound leptin, and soluble leptin receptor in the physiological menstrual cycle

OBJECTIVE

To investigate the serum pattern of free leptin, bound leptin, and soluble leptin receptor throughout the physiological menstrual cycle.

DESIGN

Prospective observational study.

SETTING

Tertiary care center for gynecological endocrinology and reproductive medicine and a university research laboratory.

PATIENT(S)

Thirty regularly cycling volunteers (age, 29 +/- 4.2 years).

INTERVENTION(S)

Blood sampling was performed at different phases (early and mid follicular phase, preovulatory phase, and early and late luteal phase) of three consecutive menstrual cycles; each phase of the menstrual cycle was investigated twice.

MAIN OUTCOME MEASURE(S)

Free leptin, bound leptin, soluble leptin receptor, LH, E(2), P, vaginal ultrasound.

RESULT(S)

A peak of serum free leptin levels was found in the late luteal phase followed by a significant drop in the early follicular phase and again by a continuous increase up to the next luteal peak. There were no significant alterations in serum bound leptin and soluble leptin receptor levels.

CONCLUSION(S)

The present study shows that there are significant circacyclic fluctuations of free leptin levels with the highest concentrations in the late luteal phase and the lowest levels in the early follicular phase, which suggests that circulating free leptin is up-regulated by the C(21)-steroid (P). Circulating bound leptin and soluble leptin receptor are not altered by the cyclic hormone status. The significant rise of the leptin bioequivalent, free leptin, in the late luteal phase might be of importance for the luteal-follicular and the luteal-preimplantatory functional shift.

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.

Leptin in pregnancy

Leptin is a 16-kDa polypeptide, encoded in humans by the LEP gene. This protein is probably involved in the regulation of ovarian function, oocyte maturation and embryo development, and in the implantation process. During pregnancy, leptin is produced in the placenta; its values increase in the maternal blood particularly in the second trimester and decline postpartum. Leptin levels may be abnormally high in pregnancies complicated by conditions such as diabetes mellitus and pre-eclampsia. The role of leptin in fetal physiology has not been clarified, although cord blood values correlate significantly with birth weight. It is expected that further research will provide new insight into the physiological importance of leptin in the pregnant woman and fetus.

Leptin affects pregnancy outcome of in vitro fertilization and steroidogenesis of human granulosa cells

PURPOSE

This study was to examine the serum leptin levels in the prediction of pregnancy outcomes in women receiving ovarian hyperstimulation. Effect of leptin on the steroidogenesis was evaluated for granulosa cell (GC) culture in vitro.

METHOD

Serum levels of leptin and estradiol were measured on Day 2, the time of hCG administration and oocyte retrieval in 50 women undergoing long-course GnRH agonist ovarian hyperstimulation. The production of estrogen and progesterone in granulosa cell culture were detected after administration of leptin at the absence or presence of FSH 1 mIU.

RESULTS

Leptin levels at the time of hCG injection were significantly lower in the pregnant women than in those without pregnancy. Estradiol concentrations were not correlated with leptin levels during the time of hCG injection and oocyte retrieval. High leptin concentration suppressed both basal estradiol and progesterone productions in GC. Leptin in high doses suppressed estradiol production, but did not alter progesterone production of GC in the presence of FSH.

CONCLUSIONS

Serum leptin levels may be predictive of IVF pregnancy outcome with the effect on intraovarian progesterone/estradiol ratio during the follicular phase. Significantly low serum leptin levels were noted in the pregnant women than in the nonpregnant women.

Leptin and reproduction: a review

OBJECTIVE

To review recent advances in understanding the role of leptin in the physiology and pathophysiology of reproduction, with a focus on relevant clinical situations.

DESIGN

A MEDLINE computer search was performed to identify relevant articles.

RESULT(S)

Leptin, an adipocyte hormone important in regulating energy homeostasis, interacts with the reproductive axis at multiple sites, with stimulatory effects at the hypothalamus and pituitary and inhibitory actions at the gonads. More recently, leptin has been shown to play a role in other target reproductive organs, such as the endometrium, placenta, and mammary gland, with corresponding influences on important physiologic processes such as menstruation, pregnancy, and lactation. As a marker of whether nutritional stores are adequate, leptin may act in concert with gonadotropins and the growth hormone axis to initiate the complex process of puberty. Conditions in which nutritional status is suboptimal, such as eating disorders, exercise-induced amenorrhea, and functional hypothalamic amenorrhea, are associated with low serum leptin levels; and conditions with excess energy stores or metabolic disturbances, such as obesity and polycystic ovarian syndrome, often have elevated serum or follicular fluid leptin levels, raising the possibility that relative leptin deficiency or resistance may be at least partly responsible for the reproductive abnormalities that occur with these conditions.

CONCLUSION(S)

Leptin may act as the critical link between adipose tissue and the reproductive system, indicating whether adequate energy reserves are present for normal reproductive function. Future interventional studies involving leptin administration are expected to further clarify this role of leptin and may provide new therapeutic options for the reproductive dysfunction associated with states of relative leptin deficiency or resistance.

Leptin and reproduction

Since the cloning of leptin by Friedman's laboratory in 1994, over 3000 papers have been published on leptin, making it one of the most active research areas in all of science. Leptin appears to be a pleiotrophic hormone affecting many different tissues in the body. This review focuses on the role of leptin in reproduction. Evidence is accumulating that leptin potentially has roles in the regulation of GnRH and LH secretion, puberty, pregnancy, and lactation. Reciprocal regulation of leptin and its receptors by gonadal hormones and the implications and controversies thereof are also discussed in the review. Signaling pathways utilized by leptin are starting to become more clear, particularly JAK/STAT, MAPK, and SOCS3 have been implicated as mediators/modulators of leptin effects at the cellular level. At the hypothalamic level, there is also evidence that CART (cocaine and amphetamine-related transcript) is involved as a downstream mediator of leptin effects, especially with regards to control of GnRH secretion. While leptin clearly has many effects upon the reproductive axis, defining its precise roles is not without controversies. This review presents both pro and con findings, thereby demarking controversial areas that undoubtedly will be fertile ground for future investigation.

The acute leptin response to GH

The effect of an acute bolus of GH on serum leptin in normal individuals and the factors affecting this response have not previously been studied. Seventeen healthy volunteers with normal body mass index, with ages ranging from 20.5-78.2 yr were studied. Each subject received three single doses of GH in random order at least 4 wk apart. Bioimpedence analysis was performed to provide estimates of fat and lean masses. Serum samples for leptin, insulin, and IGF-I were taken 0, 18, 24, 48, 72, and 120 h after each dose of GH. Leptin levels changed significantly after the 0.67- and 7-mg doses of GH, but not after the 0.27-mg dose. Compared with baseline, there was a significant elevation (P < 0.001) in serum leptin levels at 24 h, followed by a significant decrease (P < 0.01) at 72 h. Baseline and peak leptin levels were significantly determined by gender, fat mass, and log(10) insulin. Nadir leptin levels were significantly determined by gender and fat mass. In contrast, the increment in leptin levels was significantly determined by age, although this only accounted for 24% of the variability in the increment in leptin levels. We have demonstrated that administration of a single bolus dose of GH significantly increases serum leptin levels, followed by a significant nadir. This occurs not only after a supraphysiological dose of GH, but also after 0.67 mg, a dose within the physiological replacement range. The increment in leptin increases with advancing age, suggesting that at the level of the adipocyte, aging increases responsiveness to GH. However, this only partially explains the changes seen, and it is likely that another factor(s) is involved in the acute impact of GH on circulating leptin levels. The presence of a significant nadir after the peak in leptin levels supports the existence of a negative feedback loop, linking circulating leptin to its own biosynthesis in adipose tissue, mediated by peripheral leptin receptors. These data provide unequivocal evidence that GH can affect serum leptin levels in the absence of a change in body composition.

Oestradiol plus progesterone treatment increases serum leptin concentrations in normal women

BACKGROUND

Previous studies have alluded to a role for both oestradiol and progesterone in the secretion of leptin from fat cells in the human, although direct evidence has yet to be obtained. The study aim was to assess serum leptin concentrations in normally cycling women receiving exogenous oestradiol and progesterone.

METHODS

Normally cycling women were investigated in an untreated spontaneous cycle (control, n = 10), a cycle treated with oestradiol (oestradiol cycle, n = 10) and a cycle treated with oestradiol plus progesterone (oestradiol+progesterone cycle, n = 6). Oestradiol was given to the women through skin patches on cycle days 2, 3 and 4, and progesterone intravaginally on cycle days 3, 4 and 5. Serum concentrations of leptin, oestradiol, progesterone, FSH and LH were measured in daily blood samples.

RESULTS

During the treatment, serum oestradiol and progesterone concentrations increased significantly. In the oestradiol cycles, leptin concentrations were not affected by treatment and did not differ from those in controls. In the oestradiol+progesterone cycles, leptin concentrations (mean +/- SEM) increased in all women from cycle day 3 (8.6 +/- 1.1 ng/ml) to days 5 (12.2 +/- 1.8 ng/ml, P < 0.01) and 6 (11.9 +/- 2.0, P < 0.05), and were at these points significantly higher than in the control cycles (P < 0.05). The mean percentage increase from day 3 to the peak concentration on days 5 or 6 was 62.6 +/- 6.8%. Leptin concentrations returned to the pretreatment value on day 7, together with the concentrations of oestradiol and progesterone. In the oestradiol+progesterone cycles, leptin concentrations correlated significantly with oestradiol and progesterone concentrations, but not with FSH and LH concentrations.

CONCLUSIONS

These results show, for the first time, that leptin secretion can be stimulated in women by the administration of oestradiol plus progesterone. This may explain the increased concentrations of leptin during the luteal phase of the normal menstrual cycle.

Lack of effect of isoflavonic phytoestrogen intake on leptin concentrations in premenopausal and postmenopausal women

OBJECTIVE

To assess the effect of soy isoflavone ingestion on plasma leptin concentrations in premenopausal and postmenopausal women.

DESIGN

Randomized, crossover studies, with blinding of participants and laboratory personnel.

SETTING

Procedures involving free-living individuals were carried out at the University of Minnesota General Clinical Research Center.

PATIENT(S)

Fourteen regularly cycling premenopausal women, and 18 postmenopausal women.

INTERVENTION(S)

Each premenopausal participant consumed, on a daily basis, each of three soy protein powders containing different levels of isoflavones for three menstrual cycles plus 9 days, with plasma samples collected every other day the last 6 weeks of each diet period. Similarly, each postmenopausal participant consumed each of the three powders for 93 days, with plasma samples collected daily on days 64 to 66 and 92 to 94 of each diet period. The powders, dosed on a per-kilogram body weight basis, provided mean isoflavone intakes of 8, 65, and 130 mg/day, for the control, low-isoflavone, and high-isoflavone diet periods, respectively.

MAIN OUTCOME MEASURE(S)

Plasma leptin concentrations.

RESULT(S)

Isoflavone intake had essentially no effect on leptin concentrations in either premenopausal or postmenopausal participants. Concentrations in the premenopausal women were higher during the periovulatory and midluteal phases as compared to the early follicular and midfollicular phases.

CONCLUSION(S)

Despite the well-documented effect of estrogens to enhance leptin production, even high levels of isoflavone consumption do not alter leptin concentrations in women. Further studies are needed to more precisely delineate the nature of estrogenic and/or antiestrogenic effects of isoflavones in humans.

Loss of gender difference in serum leptin levels and its slow recovery after successful surgery for Leydig cell tumours in two virilized females

One of the factors that predicts serum leptin levels is gender. It has been shown that sex steroid hormones, in particular testosterone, play an important role in the regulation of serum leptin levels. We had the opportunity to examine the effects of acute and chronic changes in serum testosterone levels on serum leptin concentrations in two virilized females harbouring testosterone-secreting ovarian tumours, before and after curative surgery. Chronically elevated basal testosterone levels (46 nmol/l) were associated with suppressed serum leptin levels (1.46 microg/l and 2.56 microg/l) vs. 12 age- and BMI-matched healthy subjects 9.89 +/- 0.64 microg/l. Leptin levels were determined from pooled serum samples assayed by commercial radioimmunoassay. High testosterone levels abolished the well known sexual dimorphism of serum leptin levels. Two weeks after curative resection of these tumours serum leptin levels were unaltered and started to increase progressively after one month. One patient received parenteral conjugated oestrogens while the other resumed spontaneous menstrual cycles. Three months after curative surgery obvious changes in body composition were registered (DEXA). Six months later further rise in serum leptin concentrations occurred without further changes in body composition. In conclusion, leptin levels did not change in spite of rapid changes in the steroid milieu, but in the long term increase in body fat stores, new steroid milieu and maybe other factors are important determining factors of serum leptin levels.

Leptin in obstetrics and gynecology: a review

Leptin, a recently described type-1 cytokine, is involved in cellular maturation and growth and appears to have a relationship to some obstetrical and gynecologic diseases. The MEDLINE database was accessed, and leptin-related articles published during the past 6 years were reviewed for their relevance to gynecologic and obstetrical diseases. The relationships between this cytokine and obesity, puberty, polycystic ovary syndrome, endometriosis, assisted fertility, and menopause are discussed. The role of leptin in fetal physiology and in normal and abnormal fetal growth as well as its role in diabetes, pregnancy, and pregnancy-induced hypertension are reviewed.

Leptin during assisted reproductive cycles: the effect of ovarian stimulation and of very early pregnancy

Leptin may have a role in human reproduction. The impact of IVF and of very early pregnancy on serum leptin concentrations was studied in 66 infertile patients, of whom 19 became pregnant. Ovarian suppression was accompanied by a fall in leptin concentrations (21 +/- 4%, mean +/- SE; P < 0.01) from the mid-luteal phase, and ovarian stimulation by a rise (76 +/- 8%; P < 0.0001) from suppression. The mid-luteal concentration of leptin after stimulation was 28 +/- 7% higher than that during the preceding normal cycle (P < 0.001). Concentrations of leptin and oestradiol were related before treatment, at ovarian suppression and at 8 days after oocyte retrieval. In addition, the rises in leptin and oestradiol concentrations during stimulation were correlated, but only in those patients who became pregnant (r = 0.69; P = 0.001). Women with a successful pregnancy had higher concentrations of leptin (18.7 +/- 4.8 microg/l) at 12 days after embryo transfer than those who had miscarriages (10.0 +/- 1.9 microg/l; P < 0.001), or those failing to become pregnant (11.6 +/- 1.2 microg/l; P < 0.0001). We concluded that leptin concentrations are influenced by ovarian function and that the relationship between leptin and oestrogen (but not a single leptin concentration), may be an important factor for the outcome of IVF.

Neuroendocrine effects of leptin

Leptin, the product of the obesity gene, is a cytokine-like circulating protein acting as a peripheral satiety signal to the hypothalamus. It was initially described as a secreted product of white adipose cells, but more recent data have demonstrated its expression by endocrine and neuroendocrine tissues like the ovary and the hypothalamus, as well as several anterior pituitary cell types. The effects of leptin on body weight homeostasis are mediated via different hypothalamic neurotransmitters regulating appetite and energy expenditure. In addition, leptin participates to the modulation of the activity of the neuroendocrine thyrotrope, somatotrope, corticotrope and gonadotrope axes. These endocrine effects of leptin have progressively emerged as important physiological functions of this molecule. Its role as a permissive factor for puberty and normal reproductive function in adulthood is becoming widely recognized. In addition, leptin participates in the fine tuning of the corticotrope axis. Thus, by signalling body fat stores to the hypothalamus and other endocrine organs, leptin serves as a metabolic integrator of several neuroendocrine functions. The precise site of action and mode of regulation of the gonadotrope and somatotrope axes by leptin are reviewed.

The in vivo and in vitro effects of exogenous leptin on ovulation in the rat

Leptin, a hormonal product of the Lep gene, is expressed by adipocytes and is thought to play a role in regulating food intake and reproduction. The leptin protein has been localized in many reproductive tissues, including the ovary. Several publications indicate that the ovary is directly affected by leptin and that leptin may be a factor linking obesity and reproductive dysfunction. In this study, the effect of systemic leptin administration on ovulation in the rat ovary, both in vivo and in vitro, was investigated. Ip administration of leptin (30 microg at 3 hourly intervals for 15 h) to immature gonadotropin-primed rats caused a decline in ovulation in vivo, from 15.9+/-2.0 oocytes in the control animals to 5.3+/-1.6 oocytes in the leptin-treated animals (P < 0.001). Plasma progesterone and estradiol levels were analyzed immediately before ovulation, and neither was altered significantly in animals receiving the leptin treatment. Food consumption and body weight decreased following leptin treatment; however, a loss in body weight alone (pair-fed controls) was insufficient to explain the decrease in ovulation observed in the leptin-treated animals. In vitro perfusion of FSH-primed whole ovaries showed that treatment with leptin in combination with LH significantly decreased ovulations from 5.7+/-1.6 per ovary perfused with LH alone to 1.3+/-0.6 in those with LH and 1 microg/ml leptin (P < 0.05). Progesterone and estradiol levels in the samples taken during the perfusion period were unaffected by leptin treatment. In summary, leptin administration resulted in fewer ovulations, both in vivo and in vitro, but did not influence steroid levels. Systemic leptin administration at these doses can therefore inhibit ovulation, a process that occurs through a direct effect on the ovary.

Plasma leptin in female athletes: relationship with body fat, reproductive, nutritional, and endocrine factors

The relationship of leptin to thyroid and sex hormones, insulin, energy intake, exercise energy expenditure, and reproductive function was assessed in 39 female athletes. They comprised elite athletes who were either amenorrheic (EAA; n = 5) or cyclic (ECA; n = 8) and recreationally active women who were either cyclic (RCA; n = 13) or taking oral contraceptives (ROC; n = 13). Leptin was significantly lower in EAA (1.7 +/- 0.2 ng/ml) than in ECA (2.9 +/- 0.3 ng/ml), RCA (5.8 +/- 0.9 ng/ml), and ROC (7.4 +/- 1.3 ng/ml). Hypoleptinemia in EAA was paralleled by reductions (P < 0.05) in caloric intake, insulin, estradiol, and thyroid hormones. Leptin increased by 40-46% (P < 0.05) in the luteal phase of the menstrual cycle in RCA and ECA. Plasma leptin was similar in the placebo and active pill phases in ROC despite a significant increase in ethinylestradiol. Leptin correlated (P < 0.05) with triiodothyronine and insulin but not with estrogen, energy intake, or exercise energy expenditure. These data suggest that in female athletes 1) leptin may be a metabolic signal that provides a link between adipose tissue, energy availability, and the reproductive axis and 2) sex hormones do not directly regulate leptin secretion.

Antiestrogenic tamoxifen and toremifene increase serum leptin levels in postmenopausal breast cancer patients

OBJECTIVES

Because estrogens stimulate the synthesis and release of leptin in the adipocytes, the effect of antiestrogens on the circulating leptin levels were studied.

METHODS

Thirty postmenopausal patients with breast cancer were randomized to start either with tamoxifen (20 mg/day, n=15) or toremifene (40 mg/day, n=15), and the patients were examined and serum leptin concentrations measured before the study and at 6 and 12 months.

RESULTS

The baseline leptin concentrations ranged from 4.4 to 60.0 microg/l (15.3+/-13.1 microg/l, mean+/-S.D.), and it correlated positively with the body mass index (BMI) of the subjects (r=0.73, P=0.0001). Taking as a whole the antiestrogen regimen was associated with elevated leptin levels at 6 months (19.5+/-13.8 microg/l, P=0.0001) but no excess increase in leptin levels were seen at 12 months (20.9+/-13.5 microg/l, NS). Subgroup analysis showed no difference between the effects of tamoxifen or toremifene on leptin. BMI increased in 21 women (from 26.2+/-4.3 to 27.3+/-4.8 kg/m2, P=0.0001) at 6 months, but not after that; in nine women BMI did not change. There was no significant correlation between the change in leptin levels and the change in BMI in either group implying that antiestrogens may specifically stimulate leptin production.

CONCLUSIONS

Antiestrogens may stimulate the synthesis and release of leptin in the adipocytes. This effect of antiestrogens resembles the effect of estrogen and consequently stimulation of leptin production can be added to the estrogenic effects of antiestrogens.

Basal leptin concentrations in women with normal and dysfunctional ovarian conditions

OBJECTIVE

To determine whether leptin is involved in ovarian function.

METHODS

Fasting serum samples were obtained from 20 women with normal menstrual cycles who were either obese or non-obese: 12 non-obese patients with polycystic ovary syndrome (PCOS), 8 obese patients with PCOS, 10 patients with stress-related hypothalamic amenorrhea, and 8 patients with weight loss-related hypothalamic amenorrhea.

RESULTS

Serum leptin levels were strongly related to body mass index (BMI) in each group, but there was no difference in the mean serum leptin levels among the BMI-matched study groups. A significant difference in the mean serum leptin levels was found between the non-obese and obese control groups (P<0.001) and between the non-obese and obese PCOS groups (P<0.001).

CONCLUSIONS

These findings indicate that circulating leptin levels in women with normal menstrual cycles and those with ovarian dysfunction are strongly related to BMI. Leptin does not appear to be primarily involved in regulating ovarian function.

Circulating leptin levels during ovulation induction: relation to adiposity and ovarian morphology

OBJECTIVE

To assess serum leptin levels based on body habitus and ovarian morphology during controlled ovarian hyperstimulation.

DESIGN

Prospective analysis.

SETTING

University IVF program.

PATIENT(S)

Women undergoing IVF-ET were divided into two groups, obese ovulatory women (n = 6; mean (+/-SD) body mass index, 30.1 +/- 0.6 kg/m(2)) and lean ovulatory women (n = 20); mean (+/- SD) body mass index 22.0 +/- 0.2 kg/m(2)). Lean women were categorized further according to whether they had polycystic-appearing ovaries (n = 8) or normal-appearing ovaries (n = 12).

INTERVENTION(S)

Controlled ovarian hyperstimulation and IVF.

MAIN OUTCOME MEASURE(S)

Serum estradiol, testosterone, and leptin.

RESULT(S)

Mean (+/- SD) leptin levels were significantly higher before and after GnRH agonist down-regulation in obese women (41.7 +/- 5.2 pg/mL and 36.1 +/- 5.8 pg/mL, respectively) compared with lean women (8.4 +/- 1.0 pg/mL and 6.9 +/- 1.1 pg/mL, respectively). Mean (+/- SD) leptin levels increased significantly in both groups (54.5 +/- 5.1 pg/mL and 11.7 +/- 1.2 pg/mL, respectively), and the mean (+/-SD) percentage increase was similar (55% +/- 18% and 54.8% +/- 17%, respectively). Mean (+/-SD) leptin levels were similar in women with polycystic-appearing and normal-appearing ovaries before controlled ovarian hyperstimulation, but increased significantly in women with polycystic-appearing ovaries afterward (14.7 +/- 1.8 pg/mL and 9.3 +/- 1.0 pg/mL, respectively).

CONCLUSION(S)

Significant increases in leptin levels occur during controlled ovarian hyperstimulation, suggesting that leptin plays a role in follicular growth and maturation. The exaggerated response in women with polycystic-appearing ovaries reflects either a greater number of recruited follicles or a predisposition of adipocytes to leptin production.

Predictive value of serum and follicular fluid leptin concentrations during assisted reproductive cycles in normal women and in women with the polycystic ovarian syndrome

Leptin is an adipocyte-derived hormone which plays a central role in the regulation of body weight and energy homeostasis and in signalling to the brain that adequate energy stores are available for reproduction. Although leptin may affect reproduction by regulating the hypothalamic-pituitary-gonadal axis, recent in-vitro observations indicate that leptin may also have direct intra-ovarian actions. Leptin concentrations were measured in women who succeeded in becoming pregnant within three cycles of in-vitro fertilization (IVF) or gamete intra-fallopian transfer (n = 53), in women who failed to become pregnant within three cycles (n = 50), and in women with polycystic ovarian syndrome (PCOS) (n = 22). It was found that lower follicular fluid leptin concentrations were a marker of assisted reproduction treatment success in normal women. Women with PCOS had higher leptin concentrations than women without such a diagnosis, but this was due to their higher body mass index (BMI). After adjustment for age and BMI, women with PCOS who became pregnant tended to have lower mean follicular fluid leptin concentrations than women with PCOS who did not succeed at becoming pregnant. Further studies exploiting the strengths of the IVF model are needed to assess whether the prognostic role for follicular fluid leptin in human reproduction is independent of other factors, and to elucidate the underlying mechanisms.

Physiological roles of the leptin endocrine system: differences between mice and humans

Leptin is a 16-kDa cytokine secreted in humans primarily but not exclusively by adipose tissues. Its concentration in blood is usually proportional to body fat mass, but is higher in women than in men not only because of a different distribution of and greater fat mass in women, but also because testosterone reduces its level in men. Leptin features in different ways during the life span. It is synthesized in the ovary, transported in the oocyte, and made by both fetus and placenta, particularly during the last month of gestation. It is made by the lactating mammary gland and ingested by the newborn infant in its milk. The prime importance of leptin is realized at puberty when it is necessary for progression to a normal adult reproductive status in females. Fasting and chronic undernutrition result in a lower level of leptin in the blood. Lack of leptin results in hunger, ensuring that the individual eat to survive, and also inhibition of reproduction, until such time as food and fat stores are adequate to supply energy for pregnancy and lactation. Thus, leptin is important for survival of the individual and survival of the species. Although an extremely rare genetic absence of leptin induces hyperphagia and obesity in humans, as it does in mice, there appears to be little role for leptin in humans in ensuring that fat stores are not in excess of adequate, that is, in preventing obesity. The mouse differs from humans in many respects, in particular in the far more drastic ways it conserves energy when it very rapidly adapts to lack of food. These include not only suppression of reproduction but also lowering of its body temperature (torpor), suppressing its thyroid function, suppressing its growth, and increasing secretion of stress hormones (from the adrenal). This review concentrates on roles of leptin in human physiology and pathophysiology but also discusses why some observations on actions of leptin in mice are not applicable to humans.

Leptin levels vary significantly during the menstrual cycle, pregnancy, and in vitro fertilization treatment: possible relation to estradiol

OBJECTIVE

To evaluate the influence of sex steroids on leptin levels in patients with conditions in which the steroid levels are increased.

DESIGN

Prospective study.

SETTING

A hospital unit for reproductive medicine and a maternal care unit affiliated with the hospital and hospital staff.

PATIENT(S)

Thirteen women with regular menstrual cycles, 29 women with normal pregnancies, and 25 women undergoing IVF treatment.

INTERVENTION(S)

Blood samples were obtained during days 1-3, 6-8, 13-15, and 22-25 of the menstrual cycle in regularly cycling women and during gestational weeks 13, 20, 28, 32, and 36 and 7-13 weeks after birth in pregnant women. In women undergoing IVF treatment, blood samples were collected after E2 suppression, after ovarian stimulation, and at the time of ovum pickup.

MAIN OUTCOME MEASURE(S)

Serum levels of leptin, E2, and progesterone.

RESULT(S)

Leptin levels varied during the menstrual cycle and were elevated during pregnancy, with a peak during week 28. In the IVF group, leptin levels increased throughout the treatment cycle. Body mass index correlated positively with leptin levels in all three groups, and the maternal weight gain from weeks 13-32 tended to correlate with the rise in leptin levels. Estradiol levels correlated positively with leptin levels during E2 suppression. Negative correlations existed between the pregnancy-induced increases in E2 and leptin levels from weeks 13-32, and between the levels after birth. Leptin levels and progesterone levels did not correlate in any of the groups.

CONCLUSION(S)

Modest elevations of leptin levels were observed during IVF treatment and pregnancy. The increase in the IVF group indicates that factors other than body fat mass (possibly E2) also are of importance for the regulation of leptin levels.

Effects of short-term hormone replacement on serum leptin levels in postmenopausal women

OBJECTIVE

Leptin is a hormone which is secreted by adipocytes and appears to influence the reproductive axis. Previous studies have demonstrated higher leptin levels in relation to body fat mass in women compared to men, higher levels in normally cycling compared to postmenopausal women, and a decrease in leptin levels with increased age. The purpose of this study was to determine whether oestrogen replacement with or without progesterone increases serum leptin levels in postmenopausal women, independently of changes in body fat, and to determine if ageing affects leptin levels at baseline or in response to hormone replacement.

PATIENTS

Twenty-one healthy postmenopausal women on no hormone replacement were studied at baseline, after 1 month of oestrogen (E2: estraderm 50 microg/day) and after a further month of oestrogen and 7 days of progesterone (P: progesterone 100 mg per vagina bid) designed to achieve physiological hormone levels. Subjects included 11 younger (45-55 years) and 10 older (70-80 years) postmenopausal women.

RESULTS

The relationship between leptin and the absolute fat mass (% body fat x weight [kg]) at baseline was not different between the younger and older postmenopausal women. The adequacy of physiological hormone replacement was confirmed in all subjects. Despite the absence of an effect of hormone replacement on weight, body mass index (BMI), % and absolute fat mass (bioimpedance) or waist-hip ratio, there was an increase in serum leptin levels with hormone replacement (15.4 +/- 1.7, 17.6 +/- 1.7, and 18.1 +/- 1.6 microg/l; mean +/- SEM at baseline, with E2, and with E2 + P, respectively; P < 0.001 vs. baseline) for the group as a whole. An increase in leptin with hormonal treatment was seen in both the younger (15.1 +/- 2.1, 18.1 +/- 2.4, and 18.5 +/- 1.9 microg/l; P < 0.01) and the older (15.7 +/- 2.8, 17.0 +/- 2.5, 17.7 +/- 2.8 microg/l; P = 0.06) postmenopausal women.

CONCLUSIONS

(1) Short-term physiological oestrogen replacement increases serum leptin levels in postmenopausal women independently of changes in fat mass; and (2) physiological progesterone replacement does not influence leptin levels in postmenopausal women.

Serum and follicular fluid leptin during in vitro fertilization: relationship among leptin increase, body fat mass, and reduced ovarian response

The satiety factor leptin is expressed in several reproductive tissues, but its role in the control of reproductive physiology is not well understood. We studied leptin concentrations in the sera and follicle fluids of 52 women [body fat mass percentage (BFM%) range, 19.6-38.8%] undergoing pituitary down-regulation and ovarian hyperstimulation for in vitro fertilization (IVF) treatment. Fasting serum samples were collected 1) at maximal suppression before the initiation of gonadotropin treatment, 2) at maximal ovarian hyperstimulation, 3) at the time of oocyte retrieval, and 4) 16 days later when all subjects were under exogenous luteal support using 600 mg progesterone daily. Follicular fluid (FF) was obtained at oocyte retrieval from two representative preovulatory follicles in both ovaries. During ovarian hyperstimulation there was a significant 60% increase in serum leptin concentrations from 10.9 +/- 1.1 (SEM) to 15.7 +/- 1.5 ng/mL (P < 0.01) between suppression and maximal hyperstimulation, demonstrating that the ovarian functional state can affect serum leptin concentrations. A serum leptin increase of 22-198% during ovarian hyperstimulation was evident in 43 subjects, whereas in 9, leptin concentrations remained unchanged. A positive correlation between leptin change and BFM% (r = 0.55; P < 0.0005) was observed in the 43 leptin responders. The follicular fluid leptin level was similar to that in serum. In separate linear regression analysis, BFM% contributed to 59-64%, body mass index to 46-56%, and weight to 46-55% (all P < 0.001) of the variability in leptin concentrations at the 4 time points. The 20-fold increase in serum estradiol concentrations during IVF was not significantly correlated with changes in leptin concentrations. On the contrary, the relative serum leptin increase was negatively associated with the ovarian response to hyperstimulation, as revealed by the numbers of follicles (b = -0.28; r2 = 8.1%; P < 0.05) and oocytes retrieved (b = -0.39; r2 = 15.2%; P < 0.01). This relationship was further reflected in a positive correlation between the percent increases in leptin and FSH concentrations (r = 0.39; P < 0.01). The significant relationship of high leptin and reduced ovarian response was also maintained when the cumulative dose of FSH was used as a covariable. Reduced ovarian response was not a function of body mass index, BFM%, basal leptin levels, or insulin concentrations. Fasting serum insulin concentrations remained unchanged in response to IVF, but were positively correlated to serum leptin concentrations at all four time points. Our data suggest that leptin production may be influenced by the ovarian functional state. During IVF a high relative leptin increase is associated with adiposity and a reduced ovarian response. These observations support the possibility that high leptin concentrations might reduce ovarian responsiveness to gonadotropins. Hence, leptin might explain in part why obese individuals require higher amounts of gonadotropins than lean subjects to achieve ovarian hyperstimulation.

Are circulating leptin and luteinizing hormone synchronized in patients with polycystic ovary syndrome?

Animal and human studies suggest that leptin modulates hypothalamic-pituitary-gonadal axis functions. Leptin may stimulate gonadotrophin-releasing hormone (GnRH) release from the hypothalamus and luteinizing hormone (LH) and follicle stimulating hormone (FSH) secretion from the pituitary. A synchronicity of LH and leptin pulses has been described in healthy women, suggesting that leptin probably also regulates the episodic secretion of LH. In some pathological conditions, such as polycystic ovarian syndrome (PCOS), LH-leptin interactions are not known. The aim of the present investigation was to assess the episodic fluctuations of circulating LH and leptin in PCOS patients compared to regularly menstruating women. Six PCOS patients and six normal cycling (NC) women of similar age and body mass index (BMI) were studied. To assess episodic hormone secretion, blood samples were collected at 10-min intervals for 6 h. LH and leptin concentrations were measured in all samples. For pulse analysis the cluster algorithm was used. To detect an interaction between LH and leptin pulses, an analysis of copulsatility was employed. LH concentrations were significantly higher in the PCOS group in comparison to NC women, however serum leptin concentrations and leptin pulse characteristics for PCOS patients did not differ from NC women. A strong synchronicity between LH and leptin pulses was observed in NC women; 11 coincident leptin pulses were counted with a phase shift of 0 min (P = 0.027), 18 pulses with a phase shift of -1 (P = 0.025) and 24 pulses with a phase shift of -2 (P = 0.028). PCOS patients also exhibited a synchronicity between LH and leptin pulses but weaker (only 20 of 39 pulses) and with a phase shift greater than in normal women, leptin pulses preceding LH pulses by 20 min (P = 0.0163). These results demonstrate that circulating leptin and LH are synchronized in normal women and patients with PCOS. The real significance of the apparent copulsatility between LH and leptin must be elucidated, as well as the mechanisms that account for the ultradian leptin release.