Leptin on peritoneal macrophages of patients with endometriosis

Endometriosis: Future Biological Perspectives for Diagnosis and Treatment

Endometriosis is an oestrogen-dependent inflammatory disease affecting menstruating women, with varying levels of severity. Oestrogen dysregulation is responsible for chronic inflammation, angiogenesis, endometrial lesion development, progression, and infertility during menarche in afflicted women. The inflammatory mediators associated with this chronic painful disease have been established, with research also indicating the relationship between dysbiosis and disease manifestation. Endometriosis is also present with several painful comorbidities, including endometrial cancer, cardiovascular disease, and autoimmunity. The lack of specific and sensitive non-invasive diagnostic procedures, coupled with poor response to current therapeutic approaches, means that treatment needs remain unmet. Surgical procedures are performed to remove endometriosis ectopic lesions, for which the recurrence rate of disease is up to 50%, with certain patients exhibiting no alleviation of symptoms. This review aims to outline the aetiology of endometriosis, detailing novel diagnostic approaches and potential therapeutic approaches, namely advanced therapeutic medical products (ATMPs), including stem cell therapy and clustered regularly interspaced short palindromic repeats (CRISPR) gene editing. This timely review also provides novel insights into the important recent modalities which may be applied for the diagnosis and therapeutic response of endometriosis, including biomarkers, microfluidic platforms, and organoid systems. Undoubtedly, reliable, reproducible, sensitive, and specific models of endometriosis in humans are urgently needed to investigate and detail the aetiology of this debilitating disease.

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.

Mental stress promotes the proliferation of endometriotic lesions in mice

Endometriosis is a condition in which tissue similar to the womb lining begins to grow in other sites, such as the ovaries or fallopian tubes. Endometriosis can cause pelvic pain, adhesion formation, and infertility. Here, we investigated the relationship between deterioration of endometriosis and inflammation of intraperitoneal adipose tissue in mice. We created a mouse model of endometriosis, then subjected these mice to stress loading. In the experimental mice, we measured protein expression levels of prostaglandin-E2, monocyte chemoattractant protein-1, and tumor necrosis factor-α using ELISA kits. We used quantitative real-time polymerase chain reaction to measure mRNA expression levels of inflammation-related enzymes and cytokines in lesions and adipose tissues. This study sugest that endometriotic lesions may progress in the presence of psychological stress in the presence of endometriosis. In addition, inflammation of the adipose tissue around the uterus may be involved in the development of endometriosis. However, this needs further consideration. Reducing or avoiding stress as much as possible may prevent the progression of endometriosis.

Effect of maternal body mass index on neonatal outcomes in women with endometriosis undergoing IVF

RESEARCH QUESTION

Does preconception body mass index (BMI) affect neonatal outcomes in women with endometriosis who conceive with IVF?

DESIGN

This retrospective study included 7086 women who delivered a singleton live birth through IVF between December 2006 and December 2017. Of these, 1111 women were diagnosed with endometriosis by laparoscopy or laparotomy, while 5975 women received IVF treatment due to tubal factor or male factor infertility. Women were categorized according to predefined BMI groups (<18.5 kg/m², BMI 18.5-24.9 kg/m², ≥25 kg/m²). All comparisons performed were between women undergoing cryopreserved embryo transfer.

RESULTS

After stratification by BMI, underweight women with endometriosis showed higher preterm birth (PTB) rates compared with controls (14.61% versus 3.28%, P < 0.001), whereas normal weight and overweight/obese endometriotic women had similar PTB rates to controls. There was a significant interactive effect of endometriosis and maternal BMI on preterm delivery (P for interaction <0.05). After adjustment for potential confounding factors, the PTB rate remained consistently higher in the low BMI subgroup of women with endometriosis (adjusted odds ratio 4.66, 95% confidence interval 2.54-8.57), whereas this difference was not observed for the other BMI categories. Additionally, we noted no differences in the rate of early PTB, low birthweight, macrosomia, small for gestational age and large for gestational age between women with endometriosis and controls with respect to any preconception category of BMI.

CONCLUSIONS

Endometriotic patients who were underweight before conception (BMI <18.5 kg/m²) had a higher rate of PTB than women without endometriosis, but the difference was not observed in the other BMI categories.

Hypoxia: The force of endometriosis

AIM

Summarize recent findings of how hypoxia regulates numerous important processes to facilitate the implantation, proliferation and progression of ectopic endometriotic lesions.

METHODS

Most up-to-date evidences about how hypoxia contributes to the disease pathogenesis of endometriosis and potential therapeutic approaches were collected by conducting a comprehensive search of medical literature electronic databases. Quality of data was analyzed by experienced experts including gynecologist and basic scientists.

RESULTS

Uterus is a highly vascularized organ, which makes endometrial cells constantly expose to high concentration of oxygen. When endometrial tissues shed off from the eutopic uterus and retrograde to the peritoneal cavity, they face severe hypoxic stress. Even with successful implantation to ovaries or peritoneum, the hypoxic stress remains as a critical issue because endometrial cells are used to live in the well-oxygenated environment. Under the hypoxia condition, cells undergo epigenetic modulation and evolve several survival processes including steroidogenesis, angiogenesis, inflammation and metabolic switch. The complex gene regulatory network driven by hypoxia ensures endometriotic cells can survive under the hostile peritoneal microenvironment.

CONCLUSION

Hypoxia plays critical roles in promoting pathological processes to facilitate the development of endometriosis. Targeting hypoxia-mediated gene network represents an alternative approach for the treatment of endometriosis.

Transforming Growth Factor-beta 1 Involved in the Pathogenesis of Endometriosis through Regulating Expression of Vascular Endothelial Growth Factor under Hypoxia

Background:

Endometriosis (EMs) is a common gynecological disorder characterized by endometrial-like tissue outside the uterus. Hypoxia induces the expression of many important downstream genes to regulate the implantation, survival, and maintenance of ectopic endometriotic lesions. Transforming growth factor-beta 1 (TGF-β1) plays a major role in the etiology of EMs. We aimed to determine whether TGF-β1 affects EMs development and progression and its related mechanisms in hypoxic conditions.

Methods:

Endometrial tissue was obtained from women with or without EMs undergoing surgery from October, 2015 to October, 2016. Endometrial cells were cultured and then exposed to hypoxia and TGF-β1 or TGF-β1 inhibitors. The messenger RNA (mRNA) and protein expression levels of TGF-β1, vascular endothelial growth factor (VEGF), and hypoxia-inducible factor-1α (HIF-1α) were measured. A Dual-Luciferase Reporter Assay was used to examine the effect of TGF-β1 and hypoxia on a VEGF promoter construct. Student's t-test was performed for comparison among groups (one-sided or two-sided) and a value of P < 0.05 was considered statistically significant.

Results:

TGF-β1, VEGF, HIF-1α mRNA, and protein expression were significantly higher in EMs tissue than that in normal endometrial tissue (t = 2.16, P = 0.042). EMs primary cultured cells exposed to hypoxia expressed 43.8% higher VEGF mRNA and protein (t = 6.84, P = 0.023). VEGF mRNA levels increased 12.5% in response to TGF-β, whereas the combined treatment of hypoxia/TGF-β1 resulted in a much higher production (87.5% increases) of VEGF. The luciferase activity of the VEGF promoter construct was increased in the presence of either TGF-β1 (2.6-fold, t = 6.08, P = 0.032) or hypoxia (11.2-fold, t = 32.70, P < 0.001), whereas the simultaneous presence of both stimuli resulted in a significant cooperative effect (18.5-fold, t = 33.50, P < 0.001).

Conclusions:

The data support the hypothesis that TGF-β1 is involved in the pathogenesis of EMs through regulating VEGF expression. An additive effect of TGF-β1 and hypoxia is taking place at the transcriptional level.

Niclosamide As a Potential Nonsteroidal Therapy for Endometriosis That Preserves Reproductive Function in an Experimental Mouse Model

Endometriosis causes severe chronic pelvic pain and infertility. Because the standard medication and surgical treatments of endometriosis show high recurrence of symptoms, it is necessary to improve current treatment options. In the initial study, we examined whether niclosamide can be a useful drug for endometriosis in a preclinical setting. Endometriotic implants were induced using an established mouse model involving transimplantation of mouse endometrial fragments to the peritoneal wall of recipient mice. When the recipient mice were treated with niclosamide for 3 weeks, niclosamide reduced the size of endometriotic implants with inhibition of cell proliferation, and inflammatory signaling including RELA (NFKB) and STAT3 activation, but did not alter expression of steroid hormone receptors. To identify genes whose expression is regulated by niclosamide in endometriotic implants, RNA-sequencing was performed, and several genes downregulated by niclosamide were related to inflammatory responses, WNT and MAPK signaling. In a second study designed to assess whether niclosamide affects reproductive function, the recipient mice started receiving niclosamide after the induction of endometriosis. Then, the recipient mice were mated with wild type males, and treatments continued until the pups were born. Niclosamide treated recipient mice became pregnant and produced normal size and number of pups. These results suggest that niclosamide could be an effective therapeutic drug, and acts as an inhibitor of inflammatory signaling without disrupting normal reproductive function.

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.

Gene expression of leptin and long leptin receptor isoform in endometriosis: a case-control study

In this study, leptin/BMI ratio in serum and peritoneal fluid and gene expression of leptin and long form leptin receptor (OB-R_L) were assessed in eutopic and ectopic endometria of women with endometriosis and controls. Increased serum leptin/BMI ratio was found in endometriosis patients. Leptin and OB-R_L gene expression was significantly higher in ectopic versus eutopic endometrium of patients and controls. A positive, significant correlation was observed between leptin and OB-R_L transcripts in ectopic endometria and also in eutopic endometria in endometriosis and control groups. A negative and significant correlation was found between OB-R_L mRNA expression and peritoneal fluid leptin/BMI ratio only in endometriosis. These data suggest that, through a modulatory interaction with its active receptor, leptin might play a role in the development of endometrial implants.

Plasma adipokines and endometriosis risk: a prospective nested case-control investigation from the Nurses' Health Study II

STUDY QUESTION

Do higher leptin levels and lower adiponectin levels predict subsequent development of endometriosis?

SUMMARY ANSWER

Plasma leptin and adiponectin levels were not associated with laparoscopically confirmed endometriosis when collected prior to disease diagnosis.

WHAT IS KNOWN ALREADY

Case-control studies have identified altered levels of the inflammatory adipokines leptin and adiponectin in women with endometriosis, but it remains unclear whether inflammation results in endometriosis or whether the presence of endometriosis creates an inflammatory state.

STUDY DESIGN, SIZE, DURATION

Nested, matched, case-control study within the prospective Nurses' Health Study II (NHS II) cohort. Blood samples were collected between 1996 and 1999 from 29 611 female nurses within the cohort. Women who reported endometriosis before blood collection were excluded.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Plasma leptin and adiponectin levels were assayed by ELISA. Three hundred and fifty cases of laparoscopically confirmed endometriosis were matched 1:2 with 694 controls of comparable race, age, infertility history, menopausal status and time of blood draw. Relative risks (RRs) and 95% confidence intervals (CIs) were calculated using unconditional logistic regression models adjusting for matching factors and BMI.

MAIN RESULTS AND THE ROLE OF CHANCE

After adjusting for BMI, there were no statistically significant associations between endometriosis and leptin [RR = 1.2; 95% CI = 0.7-2.0; P-value, test for linear trend (P(trend)) = 0.72], adiponectin (RR = 0.8; 95% CI = 0.5-1.2; P(trend) = 0.48) or the leptin to adiponectin ratio (RR = 0.8; 95% CI = 0.4-1.4; P(trend) = 0.14) when comparing the upper with the lower quartile. Results were unaltered when analyses were stratified by BMI or restricted to cases diagnosed ≥ 4 years after blood draw. To evaluate statistical significance and limit the role of chance to the gold standard of 5%, we present 95% CIs about the RRs, and for P-values calculated for linear tests of trend and tests of heterogeneity, we have set the α-level to be 0.05 (i.e. <0.05 is considered to be statistically significant).

LIMITATIONS AND REASONS FOR CAUTION

A limitation of this study is the inability to differentiate the time of endometriosis 'diagnosis' from the time of disease 'onset' due to the impossibility in identifying a precise time point at which the disease process was first initiated at a molecular or cellular level. Additional limitations include lack of information regarding stage of endometriosis and the possibility of asymptomatic disease in the control population.

WIDER IMPLICATIONS OF THE FINDINGS

The mean age at diagnosis of endometriosis in the study population is 41.7, ≈ 10 years older than the mean age of diagnosis in the general population. While this may limit the generalizability of the results, there is no reason to suspect that the association between adipokines and endometriosis risk should differ at a younger age of diagnosis in an adult population.

Estrogen receptor expression affected by hypoxia inducible factor-1α in stromal cells from patients with endometriosis

OBJECTIVE

Endometriosis is an estrogen-dependent disease. The aim of this study was to evaluate the different expression of estrogen receptors (ER) and its relation to hypoxia inducible factor-1α (HIF-1α) in stromal cells from women with endometriosis.

MATERIALS AND METHODS

Paired eutopic endometrial and ectopic endometriotic stromal cells were isolated from women with endometriosis while they underwent laparoscopy. The expression of ERα and ERβ was measured by reverse transcription-polymerase chain reaction and Western blot. Regulation of ER expression was evaluated by HIF-1α knockdown via short interference RNA.

RESULTS

The expression of ERβ was significantly increased in ectopic stromal cells. Treatment of endometrial stromal cells with hypoxia induced ERβ expression. Knockdown of HIF-1α abolished hypoxia-induced ERβ expression and increased ERα expression.

CONCLUSION

The expression of ERβ is regulated by hypoxia. Results of this study will provide important information in the involvement of hypoxia factors in mediating estrogen action via different ER expression in endometriosis.

Deep infiltrating endometriosis is associated with markedly lower body mass index: a 476 case-control study

BACKGROUND

An inverse association between BMI and endometriosis has been reported but remains controversial. We decided to evaluate the association between BMI and the different types of endometriosis, classified as superficial endometriosis (SUP), deep infiltrating endometriosis (DIE) and ovarian endometrioma (OMA).

METHODS

From a prospective database of patients who underwent gynecological surgery between February 2005 and October 2008, we compared 238 patients with a histological diagnosis of endometriosis to 238 age- and smoking-status-matched controls using a prospective preoperative questionnaire and surgical data. Numerical variables means were compared for matched pairs, and non-parametric variables using Wilcoxon test. The Odds ratios for all types of endometriosis adjusted for confounding variables were computed according to predefined BMI groups [1(<18.5), 2 (≥18.5 and <22), 3(≥22 and <25), 4(≥25)], taking Group 3 as the reference population.

RESULTS

BMI was significantly lower for all 238 patients (21.70 ± 3.7 versus 23.29 ± 4.1, P < 0.001), for 101 OMA patients (21.88 ± 3.8 versus 22.99 ± 4, P < 0.038), and for 97 DIE patients (21.35 ± 3.4 versus 23.35 ± 3.8, P < 0.001) compared with their own controls, but not for the 40 SUP patients. Patients in Group 1 had adjusted odds ratios as high as 3.3 [95% confidence interval (CI): 1.6-6.8] for DIE and 2.7 (95% CI: 1.1-6.8) for OMA; in Group 2, the adjusted oddd ratios were 2.6 (95% CI: 1.3-5.5) for DIE and 2.9 (95% CI: 1.5-5.4) for OMA.

CONCLUSIONS

Endometriotic patients have lower BMI than age- and smoking-status-matched controls, independent of confounding variables. Patients with the lowest BMI (<18.5) are at a high risk of DIE.