Adiposity and Endometriosis Severity and Typology

The kisspeptin system in and beyond reproduction: exploring intricate pathways and potential links between endometriosis and polycystic ovary syndrome

Endometriosis and polycystic ovary syndrome (PCOS) are two common female reproductive disorders with a significant impact on the health and quality of life of women affected. A novel hypothesis by evolutionary biologists suggested that these two diseases are inversely related to one another, representing a pair of diametrical diseases in terms of opposite alterations in reproductive physiological processes but also contrasting phenotypic traits. However, to fully explain the phenotypic features observed in women with these conditions, we need to establish a potential nexus system between the reproductive system and general biological functions. The recent discovery of kisspeptin as pivotal mediator of internal and external inputs on the hypothalamic-pituitary-gonadal axis has led to a new understanding of the neuroendocrine upstream regulation of the human reproductive system. In this review, we summarize the current knowledge on the physiological roles of kisspeptin in human reproduction, as well as its involvement in complex biological functions such as metabolism, inflammation and pain sensitivity. Importantly, these functions are known to be dysregulated in both PCOS and endometriosis. Within the evolving scientific field of "kisspeptinology", we critically discuss the clinical relevance of these discoveries and their potential translational applications in endometriosis and PCOS. By exploring the possibilities of manipulating this complex signaling system, we aim to pave the way for novel targeted therapies in these reproductive diseases.

An artificial intelligence approach for investigating multifactorial pain-related features of endometriosis

Endometriosis is a debilitating, chronic disease that is estimated to affect 11% of reproductive-age women. Diagnosis of endometriosis is difficult with diagnostic delays of up to 12 years reported. These delays can negatively impact health and quality of life. Vague, nonspecific symptoms, like pain, with multiple differential diagnoses contribute to the difficulty of diagnosis. By investigating previously imprecise symptoms of pain, we sought to clarify distinct pain symptoms indicative of endometriosis, using an artificial intelligence-based approach. We used data from 473 women undergoing laparoscopy or laparotomy for a variety of surgical indications. Multiple anatomical pain locations were clustered based on the associations across samples to increase the power in the probability calculations. A Bayesian network was developed using pain-related features, subfertility, and diagnoses. Univariable and multivariable analyses were performed by querying the network for the relative risk of a postoperative diagnosis, given the presence of different symptoms. Performance and sensitivity analyses demonstrated the advantages of Bayesian network analysis over traditional statistical techniques. Clustering grouped the 155 anatomical sites of pain into 15 pain locations. After pruning, the final Bayesian network included 18 nodes. The presence of any pain-related feature increased the relative risk of endometriosis (p-value < 0.001). The constellation of chronic pelvic pain, subfertility, and dyspareunia resulted in the greatest increase in the relative risk of endometriosis. The performance and sensitivity analyses demonstrated that the Bayesian network could identify and analyze more significant associations with endometriosis than traditional statistical techniques. Pelvic pain, frequently associated with endometriosis, is a common and vague symptom. Our Bayesian network for the study of pain-related features of endometriosis revealed specific pain locations and pain types that potentially forecast the diagnosis of endometriosis.

Examining the co-occurrence of endometriosis and polycystic ovarian syndrome

BACKGROUND

Polycystic ovarian syndrome and endometriosis are 2 of the most common reproductive disorders among women but are thought to be unrelated.

OBJECTIVE

This study aimed to examine the overlap and common symptoms of polycystic ovarian syndrome and endometriosis.

STUDY DESIGN

The study population included the Endometriosis, Natural History, Diagnosis, and Outcomes Study (2007-2009) operative cohort: 473 women, aged 18 to 44 years, who underwent a diagnostic and/or therapeutic laparoscopy or laparotomy at 1 of 14 surgical centers located in Salt Lake City, Utah, or San Francisco, California, in addition to a population cohort composed of 127 women from the surgical centers' catchment areas. Age and site-adjusted multinomial regression models were used to estimate adjusted prevalence ratios and 95% confidence intervals of reproductive history characteristics among women with endometriosis only, women with polycystic ovarian syndrome only, and women with both endometriosis and polycystic ovarian syndrome.

RESULTS

Among the operative cohort, 35% had endometriosis only, 9% had polycystic ovarian syndrome only, and 5% had endometriosis and polycystic ovarian syndrome. Among the population cohort, 10% had endometriosis only, 8% had polycystic ovarian syndrome only, and 2% had endometriosis and polycystic ovarian syndrome. In the operative cohort, a history of subfertility was associated with a higher adjusted probability of having both conditions (adjusted prevalence ratio, 10.33; 95% confidence interval, 3.94-27.08), followed by having endometriosis only (adjusted prevalence ratio, 2.45; 95% confidence interval, 1.56-3.84) or polycystic ovarian syndrome only (adjusted prevalence ratio, 1.15; 95% confidence interval, 0.51-2.61), than having neither condition. In addition, experiencing chronic pelvic pain within the past 12 months was associated with a higher probability of having both conditions (adjusted prevalence ratio, 2.53; 95% confidence interval, 1.07-6.00) than having neither condition.

CONCLUSION

Among a cohort of women undergoing gynecologic laparoscopy or laparotomy, our study found that nearly 1 in 20 women had both an incident endometriosis diagnosis and symptoms consistent with polycystic ovarian syndrome. Among a population cohort of women not seeking gynecologic care, polycystic ovarian syndrome and endometriosis overlap prevalence was approximately 1 in 50 women.

Is There a Correlation between the Second-to-Four Digit Ratio (2D:4D) and Endometriosis? Results of a Case-Control Study

The second-to-four digit ratio (2D:4D) has been proposed as a marker of prenatal hormonal exposure. It is suggested that prenatal exposure to androgens results in a shorter 2D:4D ratio, whereas a prenatal oestrogenic environment results in a longer one. In addition, previous research has shown an association between exposure to endocrine-disrupting chemicals and 2D:4D in animals and humans. On the endometriosis side, hypothetically, a longer 2D:4D ratio, reflecting a lower androgenic intrauterine milieu, could represent an indicator of the presence of the disease. In this light, we have designed a case-control study to compare 2D:4D measurements between women with and without endometriosis. Exclusion criteria included the presence of PCOS and previous trauma on the hand that could impact the measurement of the digit ratio. The 2D:4D ratio of the right hand was measured using a digital calliper. A total of 424 participants (endometriosis n = 212; controls n = 212) were recruited. The group of cases included 114 women with endometriomas and 98 patients with deep infiltrating endometriosis. The 2D:4D ratio was significantly higher in women with endometriosis compared to controls (p = 0.002). There is an association between a higher 2D:4D ratio and the presence of endometriosis. Our results support the hypothesis claiming potential influences of intrauterine hormonal and endocrine disruptors exposure on the onset of the disease.

A Pilot Study on the Co-existence of Diabetes and Endometriosis in Reproductive-Age Women: Potential for Endometriosis Progression

Endometriosis (ENDO) is a chronic estrogen-dependent gynecological condition that affects reproductive-age women, causing pelvic pain, infertility, and increased risk for ovarian cancer. Diabetes mellitus (DM) is a metabolic disease with significant morbidity and mortality and rising incidence worldwide. The occurrence of DM among ENDO patients remains understudied, despite commonalities in these conditions' immune, inflammatory, and metabolic dysfunctions. This pilot study evaluated whether a subset of women with ENDO manifests DM co-morbidity and if so, whether DM promotes ENDO status. Archived ectopic lesions obtained at ENDO surgery from non-diabetic (ENDO-N; n = 11) and diabetic (ENDO-DM; n = 15) patients were identified by a search of an electronic health database. Retrieved samples were analyzed by immunohistochemistry for markers of proliferation (Ki67, PTEN), steroid receptor signaling (ESR, PGR) and macrophage infiltration (CD68). Immunostaining data were expressed as percentages of immune-positive cells in lesion stroma and epithelium. In lesion stroma, the percentages of nuclear immune-positive cells were higher for ESR2 and lower for PGR-T, in ENDO-DM than ENDO-N patients. The percentages of nuclear immune-positive cells for ESR1 and PTEN tended to be higher and lower, respectively, in ENDO-DM than ENDO-N groups. In lesion glandular epithelium, the percentages of nuclear immune-positive cells were higher for ESR1 and ESR2, in ENDO-DM than ENDO-N groups. ENDO-N lesions had lower percentages of stromal CD68 immune-positive cells than ENDO-DM Type 1 lesions. Findings demonstrate DM in a subset of women with ENDO, which was associated with significant changes in lesion stromal and epithelial nuclear steroid hormone receptor levels, suggestive of disease progression.

Voluntary Wheel Running Reduces Vesicle Development in an Endometriosis Animal Model Through Modulation of Immune Parameters

Introduction

Endometriosis is a chronic gynecological disorder characterized by the growth of endometrial glands and stroma outside the endometrial cavity producing inflammation and pain. Previously we demonstrated that modulation of the hypothalamic pituitary adrenal (HPA) axis exacerbates the development and severity of this condition. A physically active lifestyle has been shown to confer health benefits in many chronic conditions by potentially acting as a stress buffer, thus we hypothesized that voluntary physical exercise can “realign/reset” the HPA axis resulting in reduced endometriosis symptoms in an animal model.

Methods

Endometriosis was induced in female Sprague Dawley rats by implanting uterine tissue next to the intestinal mesentery on day 0. Sham controls received sutures only. One group of endometriosis animals had access to a running wheel for 2 weeks prior to endometriosis induction until time of sacrifice at day 60. Sham and endometriosis controls received no exercise. All animals were examined for developed vesicles which were collected and measured. Uterine tissue was analyzed for cellular infiltration. Brain, liver, spleen, adrenal glands, leg muscles, and fat were collected, along with peritoneal fluid and blood.

Results

Endometriosis animals developed vesicles in 86.96% of the implants with significantly increased mesenteric fat compared to sham (p < 0.05). Exposure to exercise significantly decreased the size (p < 0.01) and number (p < 0.05) of vesicles that developed, as well as the mesenteric fat (p < 0.01). Exercised animals had higher levels of lactoferrin in peritoneal fluid, and decreased serum fractalkine and leptin. Exercise significantly increased estrogen alpha receptor expression levels (p < 0.01), while significantly decreasing estrogen receptor beta expression (p < 0.01) and macrophage infiltration (p < 0.05) in vesicles compared to non- exercised animals.

Conclusions

Our results suggest that voluntary physical activity might protect against endometriosis and alleviate the associated inflammation via immune modulation of the HPA axis. This offers the potential for further exploration of exercise as a complementary therapy in endometriosis patients.

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.

Lesion Genotype Modifies High-Fat Diet Effects on Endometriosis Development in Mice

Endometriosis is a chronic, estrogen-dependent gynecologic disorder that affects reproductive-aged women and to a lesser extent, post-menopausal women on hormone therapy. The condition is associated with systemic and local immune dysfunctions. While its underlying mechanisms remain poorly understood, endometriosis has a genetic component and propensity for the disease is subject to environmental, nutritional, and lifestyle influences. Previously, we showed that high-fat diet (HFD) increased ectopic lesion numbers, concurrent with systemic and peritoneal changes in inflammatory and oxidative stress status, in immunocompetent recipient mice ip administered with endometrial fragments null for Krüppel-like factor 9 gene. Herein, we determined whether HFD modifies lesion parameters, when recipient peritoneal environment is challenged with ectopic wild-type (WT) endometrial fragments, the latter simulating retrograde menstruation common in women during the menstrual period. WT endometrium-recipient mice fed HFD (45% kcal from fat) showed reduced lesion incidence, numbers, and volumes, in the absence of changes in systemic ovarian steroid hormone and insulin levels, relative to those fed the control diet (CD, 17% kcal from fat). Lesions from HFD- and CD-fed recipients demonstrated comparable gene expression for steroid hormone receptors (Esr and Pgr) and cytokines (Il-6, Il-8, and CxCL4) and similar levels of DNA oxidative biomarkers. HFD moderately altered serum (3-nitrotyrosine and methionine/homocysteine) and peritoneal (reduced glutathione/oxidized glutathione) pro-oxidative status but had no effect on peritoneal inflammatory (tumor necrosis factor α and tumor necrosis factor receptor 1) mediators. Results indicate that lesion genotype modifies dietary effects on disease establishment and/or progression and if translated, could be important for provision of nutritional guidelines to women with predisposition to, or affected by endometriosis.

Associations between body mass index and the surgical phenotype and location of endometriotic lesions

RESEARCH QUESTION

Is there a relationship between body mass index (BMI) and endometriotic lesions, specifically surgical phenotype and lesion location?

DESIGN

An observational retrospective cohort study at the Royal Women's Hospital, Melbourne, Australia, including 471 histologically confirmed endometriosis patients. Statistical analyses included multivariate logistic regression and multivariate modelling, correcting for multiple testing. Outcomes were the presence or absence of surgically classified lesion phenotypes, as per revised American Society for Reproductive Medicine criteria including superficial or deep, peritoneal or ovarian, and adhesions (Study I); and lesions at specific anatomical locations (including pelvic side wall, uterosacral ligament, pouch of Douglas, ovarian, uterovesical fold, bladder, and pararectal endometriosis) (Study II).

RESULTS

In Study I, patients with higher BMI were more likely to have superficial peritoneal lesions (odds ratio [OR] 1.070, 95% confidence interval [CI] 1.004-1.144; P = 0.044), and less likely to have deep ovarian lesions (OR 0.928, 95% CI 0.864-0.993; P = 0.034). In Study II, patients with higher BMI were less likely to have uterovesical fold lesions (OR 0.927, 95% CI 0.867-0.985; P = 0.021) or anterior compartment lesions (OR 0.940, 95% CI 0.888-0.989; P = 0.023). After correcting for multiple testing, the relationship between BMI and lesion phenotypes did not persist (P > 0.01).

CONCLUSIONS

This analysis does not conclusively support an influence of BMI on endometriotic lesion phenotype based on surgical classification or location. Further investigation of the physiological disturbances underlying BMI and the promotion of endometriotic lesion phenotypes and their location is warranted, but any effect is likely to be small.

Endometriosis and polycystic ovary syndrome are diametric disorders

Evolutionary and comparative approaches can yield novel insights into human adaptation and disease. Endometriosis and polycystic ovary syndrome (PCOS) each affect up to 10% of women and significantly reduce the health, fertility, and quality of life of those affected. PCOS and endometriosis have yet to be considered as related to one another, although both conditions involve alterations to prenatal testosterone levels and atypical functioning of the hypothalamic-pituitary-gonadal (HPG) axis. Here, we propose and evaluate the novel hypothesis that endometriosis and PCOS represent extreme and diametric (opposite) outcomes of variation in HPG axis development and activity, with endometriosis mediated in notable part by low prenatal and postnatal testosterone, while PCOS is mediated by high prenatal testosterone. This diametric disorder hypothesis predicts that, for characteristics shaped by the HPG axis, including hormonal profiles, reproductive physiology, life-history traits, and body morphology, women with PCOS and women with endometriosis will manifest opposite phenotypes. To evaluate these predictions, we review and synthesize existing evidence from developmental biology, endocrinology, physiology, life history, and epidemiology. The hypothesis of diametric phenotypes between endometriosis and PCOS is strongly supported across these diverse fields of research. Furthermore, the contrasts between endometriosis and PCOS in humans parallel differences among nonhuman animals in effects of low versus high prenatal testosterone on female reproductive traits. These findings suggest that PCOS and endometriosis represent maladaptive extremes of both female life-history variation and expression of sexually dimorphic female reproductive traits. The diametric disorder hypothesis for endometriosis and PCOS provides novel, unifying, proximate, and evolutionary explanations for endometriosis risk, synthesizes diverse lines of research concerning the two most common female reproductive disorders, and generates future avenues of research for improving the quality of life and health of women.

The Formidable yet Unresolved Interplay between Endometriosis and Obesity

Obesity and endometriosis are two very common entities, yet there is uncertainty on their exact relationship. Observational studies have repeatedly shown an inverse correlation between endometriosis and a low body mass index (BMI). However, obesity does not protect against endometriosis and on the contrary an increased BMI may lead to more severe forms of the disease. Besides, BMI is not accurate in all cases of obesity. Consequently, other anthropometric and phenomic traits have been studied, including body adiposity content, as well as the effect of BMI early in life on the manifestation of endometriosis in adulthood. Some studies have shown that the phenotypic inverse correlation between the two entities has a genetic background; however, others have indicated that certain polymorphisms are linked with endometriosis in females with increased BMI. The advent of metabolic bariatric surgery and pertinent research have led to the emergence of biomolecules that may be pivotal in understanding the pathophysiological interaction of the two entities, especially in the context of angiogenesis and inflammation. Future research should focus on three objectives: detection and interpretation of obesity-related biomarkers in experimental models with endometriosis; integration of endometriosis-related queries into bariatric registries; and multidisciplinary approach and collaboration among specialists.