Increased expression of the leptin receptor in human ovaries affected by endometrioma and detection of high levels of leptin in the ovarian endometriomal fluid

Is the leptin/BMI ratio a reliable biomarker for endometriosis?

Background

The aim of this study was to analyze the concentration of leptin in peritoneal fluid and plasma and to assess their role as potential biomarkers in the diagnosis of endometriosis.

Materials & methods

Leptin adjusted for BMI (leptin/BMI ratio) was measured using surface plasmon resonance imaging (SPRI) biosensors. Patients with suspected endometriosis were included in the study. Plasma was collected from 70 cases, and peritoneal fluid from 67 cases. Based on the presence of endometriosis lesions detected during laparoscopy, patients were divided into a study group and a control group (patients without endometriosis).

Results

Leptin/BMI ratio in plasma did not differ between women with endometriosis and the control group (0.7159 ± 0.259 vs 0.6992 ± 0.273, p= 0,7988). No significant differences were observed in peritoneal leptin/BMI ratio levels in patients with and without endometriosis (0.6206 ± 0.258 vs 0.6215 ± 0.264, p= 0,9896). Plasma and peritoneal leptin/BMI ratios were significantly lower in women with endometriosis - related primary infertility compared to women with endometriosis without primary infertility (0.640 ± 0.502 vs 0.878 ± 0.623, p < 0.05). The difference was observed in case of primary infertility, but not in terms of the secondary one. No significant differences were noted between leptin/BMI ratio in the proliferative phase and the secretory phase (0.716 ± 0.252 vs 0.697 ± 0.288, p= 0,7785).

Conclusion

The results of present study do not support the relevance of leptin concentration determination as a biomarker of the endometriosis. Due to the limited number of samples in the tested group, further studies are needed to confirm its role.

Metabolic hormones are integral regulators of female reproductive health and function

The female reproductive system is strongly influenced by nutrition and energy balance. It is well known that food restriction or energy depletion can induce suppression of reproductive processes, while overnutrition is associated with reproductive dysfunction. However, the intricate mechanisms through which nutritional inputs and metabolic health are integrated into the coordination of reproduction are still being defined. In this review, we describe evidence for essential contributions by hormones that are responsive to food intake or fuel stores. Key metabolic hormones-including insulin, the incretins (glucose-dependent insulinotropic polypeptide and glucagon-like peptide-1), growth hormone, ghrelin, leptin, and adiponectin-signal throughout the hypothalamic-pituitary-gonadal axis to support or suppress reproduction. We synthesize current knowledge on how these multifaceted hormones interact with the brain, pituitary, and ovaries to regulate functioning of the female reproductive system, incorporating in vitro and in vivo data from animal models and humans. Metabolic hormones are involved in orchestrating reproductive processes in healthy states, but some also play a significant role in the pathophysiology or treatment strategies of female reproductive disorders. Further understanding of the complex interrelationships between metabolic health and female reproductive function has important implications for improving women's health overall.

What is the link between endometriosis and adiposity?

Endometriosis is defined by the presence of extrauterine endometrial tissue and presents with symptoms of dysmenorrhea, chronic pelvic pain, and impaired fertility. This condition often follows a chronic progressive course with favorable recurrence, even after surgical or medical treatment. The etiology or exact pathophysiology of endometriosis remains to be clarified, although it is thought to be a complex and multifactorial disease. Prior epidemiological or population-based studies have reported several risk factors related to endometriosis, such as environmental, menstrual, habitual, and lifestyle factors. Moreover, anthropometry has been found to be significantly associated with the diagnosis of endometriosis, as a lower body mass index is associated with an elevated risk of endometriosis. Here, we review studies that have examined the association between body size and the risk of endometriosis and discuss the clinical and biological significance of the relationship between adiposity and endometriosis.

Serum and peritoneal fluid leptin levels in endometriosis: a systematic review and meta-analysis

The role of leptin in the development of endometriosis has been investigated previously. However, researches on the change of leptin levels in endometriosis remains controversial. So, we aimed to clarify changes of leptin levels in patients with endometriosis and their association with the progression of endometriosis. We searched PubMed, Embase, Web of Science, and The Cochrane Library to identify relevant studies published before May 25, 2020. The detected levels of leptin in patients with endometriosis versus controls were evaluated in this meta-analysis. Eighteen studies met our inclusion criteria, five studies detected serum, nine detected peritoneal fluid and another four detected both serum and peritoneal fluid leptin levels. The overall results showed that peritoneal fluid leptin levels in patients with endometriosis was significantly higher than that in the control group, but the serum and corrected peritoneal fluid leptin levels were comparable in both groups. Subgroup analysis failed to eliminate the high degree of heterogeneity included in the studies and showed that peritoneal fluid leptin levels were significantly elevated in both early and advanced endometriosis. In conclusion, peritoneal fluid rather than serum leptin levels was elevated in patients with endometriosis, which did not seem to be related to the severity of endometriosis, but was related to body mass index.

Association of leptin and adiponectin levels with endometriosis: a systematic review and meta-analysis

BACKGROUND

We aimed to summarize the available data regarding the levels of leptin and adiponectin and the key modulators of endometriosis compared to the controls.

METHODS

The electronic databases such as MEDLINE, Embase, Scopus, Cochrane Library, and Web of Science were searched up to October 2020. The circulating and peritoneal levels of leptin and circulating levels of adiponectin were included. We used the Cochrane's Q test and the I² statistic in this study. These tests' weighted mean difference (WMD) and 95% CIs were considered as the summary effect size. They were then pooled using a random-effects model with the DerSimonian-Laird method.

RESULTS

Twenty eligible articles (or 25 studies) with 2645 participants (1362 women with endometriosis and 1283 controls) were included. Pooled results showed that women with endometriosis had significantly higher leptin levels (WMD = 4.45 mg/ml, 95%CI = 2.42-6.49, p < .01) and leptin/BMI ratio (WMD = 0.32 mg/ml, 95%CI = 0.23-0.42, p < .001) than the controls, whereas adiponectin levels (WMD = -0.24 mg/ml, 95%CI = -4.27 to -0.01, p = .038) were significantly lower. The pooled results also indicated significantly lower leptin levels in women with advanced-stage endometriosis (WMD = -8.07 mg/ml, 95%CI = -14.22 to -1.92, p = .01) than in the early stage. It was found, however, that there were no significant differences in adiponectin levels of women with advanced-stage endometriosis (WMD = -0.16 mg/ml, 95%CI = -0.64 to 0.32, p = .512) and the early-stage ones.

CONCLUSION

We showed that leptin levels and leptin/BMI ratio were significantly higher in women with endometriosis than the controls. Nonetheless, patients with endometriosis had significantly lower levels of adiponectin than the controls.

Leptin concentrations in endometriosis: A systematic review and meta-analysis

INTRODUCTION

Endometriosis is an inflammatory condition, affecting mainly women of reproductive age. Leptin is a regulator of food intake and energy expenditure, posing pleiotropic actions, and regulating immunity and fertility. The aim of this study was to systematically review the literature regarding leptin concentrations in biological fluids and tissues of women with endometriosis, and to investigate and propose a possible role of leptin in the pathophysiology of endometriosis.

MATERIALS AND METHODS

A systematic search of the literature was conducted in two electronic databases (MEDLINE, COCHRANE) and grey literature for original research articles on humans, published in any language.

RESULTS

Twenty-nine studies with 1291 women with endometriosis and 1664 controls were included in the systematic review. Peritoneal fluid and follicular fluid leptin concentrations were higher in endometriosis compared with control group [mean difference (MD) 7.10, 95 % confidence interval (CI) 4.76 to 9.44 ng/mL, 18 studies), (MD 1.35, 95 % CI 0.54-2.17 ng/ml, 2 studies) respectively. No differences were evident in serum (MD 0.92, 95 % CI -0.84 to 2.68 ng/mL, 12 studies) or plasma (MD -0.95, 95 % CI -4.63 to 2.72 ng/mL, 3 studies) between the groups. No meta-analysis was conducted for ovarian tissue leptin (2 studies).

CONCLUSIONS

This meta-analysis provided evidence for increased leptin concentrations in both peritoneal fluid and follicular fluid of women with endometriosis compared with control; these differences were not present in the serum or plasma. The above results support a potential pathophysiologic role for leptin in the local microenvironment while declines its use as a blood diagnostic marker. Furthermore, we propose a possible role of leptin in the pathophysiology of endometriosis.

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.

The follicular levels of adipokines and their ratio as the prognostic markers of in vitro fertilization outcomes

INTRODUCTION

Adipokines are involved in the regulation of the female reproductive system. The purpose was to study the possibility of using adipokines levels in the follicular fluid to predict IVF efficiency.

MATERIALS AND METHODS

Four groups of women were studied: pregnant during IVF, with normal (PN, n = 9) and increased (BMI > 25 kg/m²) body weight (BW) (PI, n = 7), and nonpregnant during IVF, with normal (nPN, n = 16) and increased BW (nPI, n = 21).

RESULTS

In PN group, leptin level was higher than in nPN group (p < .05). In the PI and nPI groups, it did not differ, but was higher than in women with normal BW. In PN group, ghrelin level was lower than in nPN group (p < .05), while in the PI and nPI groups it was comparable. The leptin/ghrelin ratio in PN group was higher than in nPN group (18.10 ± 3.38 vs. 3.93 ± 0.60, p < .05), but lower than in the PI (31.70 ± 15.38) and nPI (24.30 ± 3.45) groups. The leptin/adiponectin ratio in PN group was also higher than in nPN group (6.97 ± 0.64 vs. 2.95 ± 0.39, p < .05), but lower than in the PI (13.60 ± 1.59) and nPI (10.86 ± 0.87) groups. Adiponectin levels differed only between the nPN and nPI groups. In women with normal BW, odds ratio showed that the leptin/ghrelin ratio has the greatest prognostic value for predicting the success of IVF outcomes (OR: 29.53; CI: 1.53-570.83, p =.025) among other indicators. In women with increased BW, none of the indicators had predictive value.

CONCLUSION

The follicular leptin/ghrelin ratio is a suitable indicator for predicting IVF outcomes in women with normal BW.

Serum Leptin as a Marker for Severity of Endometriosis

Background

Endometriosis a disease of theories, and one of the important causes of chronic pelvic pain, dysmenorrhea, dyspareunia, and subfertility. Surgery is the mainstay step for the diagnosis; noninvasive test is the goal in the future. Aim of Study. To test the role of serum leptin in determination of severity of endometriosis. Study Design. A cross-sectional study done in Al-Yarmouk Teaching Hospital from 1st of January 2018 to 1st of January 2019.

Methods

60 BMI-matched patients were involved in the study. A study group of 30 patients were operated either by laparoscopy or laparotomy for many reasons diagnosed as endometriosis by histopathology, and 30 normal women as a control group underwent elective surgery. Blood sample was taken from all patients in the theater room when laparoscopy finding went with endometriosis, and classifying according to surgical staging of endometriosis, the level of serum leptin was measured by ELISA using Human LEP (Leptin) ELISA Kit. The recording of finding of laparoscopy after conforming of diagnosis by histopathology was compared with the result of serum leptin.

Result

The result shows no significant difference between the two groups regarding parity and age; however, the level of serum leptin was significantly high in the endometriosis group than in the control group. The P value was less than 0.05. Also, the result shows no significant differences between serum leptin in both groups according to the symptom but there was a significant difference with surgical staging. The mean of the level of serum leptin in stage 1 was 214.8, while it was 340.3 in stage 4.

Conclusion

Serum leptin can be used as a marker of severity of endometriosis.

Serum leptin level across different phases of menstrual cycle in normal weight and overweight/obese females

We compared serum leptin levels during various phases of menstrual cycle and its correlation with serum estradiol between normal weight and overweight/obese young females. Fifty-six young females with normal menstrual cycle were grouped into 26 normal weight and 30 overweight/obese subjects. Serum leptin and estradiol levels were measured during early follicular, pre-ovulatory and luteal phases of menstrual cycle in both groups using ELISA technique. Serum leptin levels were significantly different across different phases of menstrual cycle with a steady increment from follicular phase (9.97 ± 5.48 ng/dl) through pre-ovulatory phase (11.58 ± 6.49 ng/dl) with their peaks in luteal phase (12.52 ± 6.39 ng/dl, p < .001). Same pattern of change during menstrual phases was observed when the normal weight and overweight/obese group were analyzed separately. Serum leptin levels were significantly higher in overweight/obese group compared to normal weight subjects. In any of the study groups, leptin levels were not found to be correlated with estradiol level during different phases of menstrual cycle.

Expression of leptin receptor in the oviduct of Chinese brown frog (Rana dybowskii)

The oviduct of Chinese brown frog ( Rana dybowskii) expands specifically during prehibernation instead of in the breeding period. In this study, we investigated the expression of leptin receptor (Ob-Rb) in Rana dybowskii oviduct during the breeding period and prehibernation. Histologically, the oviduct of Rana dybowskii consists of glandular cells, tubule lumen, and epithelial cells. The oviductal weight and pipe diameter also revealed significant differences, which were higher in prehibernation than that of the breeding period. Ob-Rb was observed in stromal cells of oviductal tissue in both the breeding period and prehibernation. The mean protein and mRNA levels of the Ob-Rb were significantly higher in prehibernation as compared with the breeding period. In addition, oviductal content of leptin was also higher in prehibernation than that of the breeding period. These results suggested that oviduct of Rana dybowskii might be a target organ of leptin, and leptin may play an autocrine/paracrine role mediated by Ob-Rb in regulating the oviductal hypertrophy during prehibernation.

Leptin, its receptor and aromatase expression in deep infiltrating endometriosis

Background

The aim of this study was to evaluate the leptin levels in the serum and peritoneal fluid (PF) and the protein expression in three different peritoneal ectopic implants in patients who underwent surgery for deep infiltrating endometriosis.

Methods

All patients had been treated at the Department of Gynecology of the Pedro Ernesto University Hospital, Rio de Janeiro. The study group consisted of 15 patients who underwent surgery for adnexal masses and infertility, while the control group consisted of ten women who underwent surgery for tubal ligation. Peritoneal fluid and samples tissues were collected during surgery. Serum samples were obtained before anesthesia. In this study, the leptin levels in the serum and peritoneal fluid (PF) were evaluated by ELISA. The protein expression of leptin and its receptors (ObR) and aromatase enzyme were evaluated by Western blot analysis of the intestine, uterosacral ligament and vaginal septum in the ectopic implants. The t-test and one-way ANOVA with Holm-Sìdak post-test were used, and p < 0.05 was considered to be statistically significant.

Results

Compared to the controls, the serum leptin levels (control = 14.7 ng/mL ± 2.63, endometriosis = 19.2 ng/mL ± 1.84, p < 0.0001) were increased, while in PF, there was no difference (control = 6.68 ng/mL ± 0.43, endometriosis = 7.71 ng/mL ± 0.59, p = 0.18). Comparing women with and without ovarian implants, the leptin levels in both the serum and PF were significantly higher in women without ovarian implants (serum: with ovarian implant = 15.85 ± 1.99; without ovarian implant = 23.14 ± 2.60; ng/mL, p = 0.04; PF: with ovarian implant = 4.28 ± 1.30; without ovarian implant = 11.18 ± 2.98;ng/mL, p = 0.048). The leptin, ObR and aromatase protein expression levels were increased in lesions in the vaginal septum and were decreased in the intestine lesions.

Conclusion

This study reports several interesting associations between the leptin levels in serum, peritoneal fluid, and tissue samples and the localization of the ectopic endometrium. Although this study does not provide a clear picture of the role of leptin in the development and progression of peritoneal implants, it contributed new data that might be useful to elucidating the enigma that is the role of leptin in endometriosis disease.