Mouse models to study polycystic ovary syndrome: A possible link between metabolism and ovarian function?

Polycystic ovary syndrome (PCOS) is the most common cause of female infertility affecting 6–8% of women worldwide. PCOS is characterized by two of the following three criteria: clinical or biochemical hyperandrogenism, oligo- or amenorrhea, and polycystic ovaries (PCO). In addition, women with PCOS are often obese and insulin resistant, and are at risk for type 2 diabetes and cardiovascular disease. The etiology of PCOS remains unknown. Therefore, several animal models for PCOS have been generated to gain insight into the etiology and development of the PCOS-associated phenotypes. Androgens are considered the main culprit of PCOS, and therefore, androgenization of animals is the most frequently used approach to induce symptoms that resemble PCOS. Prenatal or prepubertal androgen treatment results in many characteristics of human PCOS, including anovulation, cyst-like follicles, elevated luteinizing hormone (LH) levels, increased adiposity, and insulin insensitivity. However, PCOS has a heterogeneous presentation, and therefore it is difficult to generate a model that exactly reproduces the reproductive and metabolic phenotypes observed in women with PCOS. In this review, we discuss several mouse models for PCOS, and compare the reproductive and/or metabolic phenotypes observed in several androgen-induced models as well as in several genetic models.     

Calpain-10 genetic polymorphisms and polycystic ovary syndrome risk: A meta-analysis and meta-regression

Recent evidences suggest that common functional polymorphisms in the promoter region of the Calpain-10 gene may have an impact on an individual's susceptibility to polycystic ovary syndrome (PCOS), but individually published results are inconclusive. Our meta-analysis is aimed to provide a more precise estimation of the relationships between Calpain-10 genetic polymorphisms and PCOS risk. An extensive literature search for relevant studies was conducted on PubMed, Embase, Web of Science, Cochrane Library, and CBM databases from inception through April 1st, 2013. This meta-analysis was performed using the STATA 12.0 software. The crude odds ratio (OR) with 95% confidence interval (CI) was calculated. Fourteen case–control studies were included with a total of 2123 PCOS patients and 3612 healthy controls. Nine common SNPs in the Calpain-10 gene were addressed. Our meta-analysis indicated that UCSNP-19, UCSNP-63 and UCSNP-45 polymorphisms in the Calpain-10 gene might be associated with increased PCOS risk. However, no statistically significant association was observed in UCSNP-43, UCSNP-22, UCSNP-43, UCSNP-45, UCSNP-56, UCSNP-58, and UCSNP-110 polymorphisms. Further subgroup analysis by ethnicity revealed that UCSNP-19, UCSNP-63 and UCSNP-45 polymorphisms might decrease the risk of PCOS among Asian populations, but not among Caucasian populations. The current meta-analysis indicates that UCSNP-19, UCSNP-63 and UCSNP-45 polymorphisms in the Calpain-10 gene may be risk factors for PCOS, especially among Asian populations.     

Association of angiotensin converting enzyme (ACE) gene I/D polymorphism and polycystic ovary syndrome (PCOS)

This study was conducted in Turkish patients with polycystic ovary syndrome to determine the frequency of I/D polymorphism genotypes of angiotensin converting enzyme gene, and to examine the role of this polymorphism in polycystic ovary syndrome development. Genomic DNA obtained from 200 persons (100 patients with polycystic ovary syndrome and 100 healthy controls) was used in the study. DNA was multiplied by polymerase chain reaction using I and D allele-specific primers. Polymerase chain reaction products were assessed with a charge coupled device (CCD) camera by being exposed to 2% agarose gel electrophoresis. There was statistically significant difference between the groups with respect to genotype distribution (p < 0.001). The D allele frequency was indicated as 68% and I allele was as 32% in the patients, whereas it was 51.5-48.5% respectively in the control group. As a result of our study we may assert that angiotensin converting enzyme gene I/D polymorphism DD genotype should be considered as a genetic marker in polycystic ovary syndrome development in this Turkish study population.     

LHCGR and ALMS1 defects likely cooperate in the development of polycystic ovary syndrome indicated by double-mutant mice

Polycystic ovary syndrome(PCOS) is a heterogeneous disorder with evidence of polygenetic components,and obesity may be a risk factor for hyperandrogen ism.Previous studies have shown that LHCGR is en riched in the ovary and LHCGR deficiency causes infertility without typical PCOS phenotypes.ALMS1 is implicated in obesity and hyperandrogenism,the common phenotypes among PCOS patients.Through whole-exome sequencing of 22 PCOS families and targeted candidate gene sequencing of additional 65 sporadic PCOS patients,we identified potential causative mutations in LHCGR and ALMS1 in a sibling-pair PCOS family and three sporadic PCOS patients.The expression of LHCGRL638 P in granulosa-like tumor cell line(KGN) cells promoted cyclic adenosine monophosphate production and granulosa cell proliferation,indicating that LHCGRL638 P is an activating mutation.Lhcgr~(L642 P/L642 P) mice showed an irregular estrous cycle,reduced follicles with dynamic folliculogenesis,and increased testosterone(T),estradiol(E2),and dehydroepiandrosterone.Lhcgr~(+/L642 P) AIms1~(+/PB) mice displayed increased T and E2 but decreased late secondary and preovulatory follicles.We showed that activating mutation of LHCGR likely plays important roles in the pathophysiology of PCOS involving abnormal reproductive physiology,whereas ALMS1 deficiency may promote anovulatory infertility via elevated androgens,suggesting that the disturbed LHCGR and ALMS1 cooperatively induce PCOS phenotypes,characterized as anovulation and hyperandrogenemia frequently observed in PCOS patients with obesity.     

Polymorphism T→C of gene CYP17 promoter and polycystic ovary syndrome risk: a meta-analysis

The T → C polymorphism of CYP17 gene has been inconsistently associated with polycystic ovary syndrome (PCOS) risk. We examined the association by performing a meta-analysis. Two investigators independently searched the Medline, Embase, CNKI, and Chinese Biomedicine Databases. Summary odds ratios (ORs) and 95% confidence intervals (95% CIs) for CYP17 polymorphism and PCOS were calculated in a fixed-effects model and a random-effects model when appropriate. The pooled ORs were performed for co-dominant model (CC vs. TT, TC vs. TT), dominant model (CC + TC vs. TT), and recessive model (CC vs. TC + TT). Subgroup analyses were performed by ethnicity, country, Hardy-Weinberg equilibrium (HWE) in controls and study sample size. This meta-analysis included 10 case-control studies, which included 1321 PCOS cases and 1017 controls. Overall, the variant genotypes (CC and TC) were not associated with PCOS risk, compared with the wild-type TT homozygote. Similarly, no associations were found in the dominant and recessive models. Stratified analyses by ethnicity/country also detected no significant association. However, limiting the analysis to the studies within HWE, a significantly increased risk was observed (TC vs. TT, OR = 1.44, 95% CI = 1.10-1.88; dominant model, OR = 1.41, 95% CI = 1.10-1.81). Moreover, when stratifying by study sample size, a significantly elevated risk was found among small sample studies (≤ 200 subjects), but not among large sample studies (> 200 subjects). This meta-analysis suggests that the CYP17 T/C polymorphism may be not associated with PCOS risk, while the observed increase in risk of PCOS may be due to small-study bias.     

Plasma level of calcitonin gene-related peptide in patients with polycystic ovary syndrome and its relationship to hormonal and metabolic parameters

The aim of the study was to evaluate the plasma level of calcitonin gene-related peptide (CGRP) in patients with polycystic ovary syndrome (PCOS) and its relationship to hormonal and metabolic parameters. We also observed the effect of CGRP on testosterone (T) and estradiol (E(2)) release in cultured human granulosa cells. PCOS subjects (n=215) and matched healthy control women (n=103) at age of 22-38 years were enrolled in this study. We analyzed plasma CGRP concentrations, relationship of plasma CGRP with insulin resistance (IR), body mass index (BMI), luteinizing hormone/follicle-stimulating hormone (LH/FSH) ratio and T. The T and E(2) release levels of cultured human granulosa cells treated by CGRP were also measured. The results showed that plasma CGRP concentrations were significantly higher in women with PCOS than those of control subjects. In women with PCOS, there was a strong positive correlation between the plasma CGRP level with HOMA-IR, AUC-insulin, AUC-glucose, the ratio of LH/FSH and plasma T concentration. Human granulosa cells expressed CGRP receptor. Exogenous CGRP caused an elevation of T and E(2) released from the human granulosa cells. These findings suggest that CGRP may participate in the pathophysiological process of PCOS.     

Defects in insulin signaling pathways in ovarian steroidogenesis and other tissues in polycystic ovary syndrome (PCOS)

The polycystic ovary syndrome (PCOS) is the most common endocrinopathy in women of reproductive age today. Women with PCOS often demonstrate defective ovarian steroid biosynthesis and present with hyperandrogenemia. Moreover, 50-70% of PCOS women are insulin resistant and hyperinsulinemic. Insulin acts on the ovary via its own receptor and interacts with gonadotrophins, modulating steroidogenesis. The precise role of insulin and the molecular mechanisms that take place are not yet completely explicated. This review will be focused on insulin's action on the ovary and other target tissues, describing the intracellular signaling pathways implicated in steroidogenesis and their defects in women with PCOS.     

Dehydroepiandrosterone stimulates inflammation and impairs ovarian functions of polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is one of the most common causes of infertility in child-bearing-age women. It is characterized by ovulation dysfunction, polycystic ovaries, and hyperandrogenism. Inflammation is likely to be a crucial contributor to the pathogenesis of PCOS. However, the association between the inflammatory cytokines and the development of PCOS has not been reported. To explore the relationship between the inflammatory cytokines and PCOS, alterations of serum proteins in dehydroepiandrosterone (DHEA)-induced PCOS rats were screened by protein array, and the concentration of IFN-γ was further measured by using enzyme-linked immunosorbent assay (ELISA). DHEA-induced PCOS rats had a decreased level of IFN-γ compared with the control rats, which was restored partly in flutamide (an androgen receptor antagonist)-treated rats. Moreover, the level of IFN-γ in serum of patients with PCOS was also lower than that in healthy women. Using the ovarian granulosa cells (KGN), we demonstrated that DHEA downregulated the expression and secretion of IFN-γ in dose- and time-dependent manners, which could be restored to some extent by treating with flutamide. Furthermore, flutamide ameliorated the inhibitory effect on cell proliferation and promotive effect on cell apoptosis by DHEA. The results also revealed that IFN-γ promoted the proliferation but inhibited the apoptosis of KGN cells, which was suppressed by DHEA via activating the downstream PI3K/AKT signaling pathway. Taken together, these results showed that DHEA inhibited the proliferation and promoted the apoptosis of ovarian granulosa cells through downregulating the expression of IFN-γ which could be restored by flutamide, and IFN-γ may serve as a potential inflammatory biomarker for PCOS detection.     

Immunohistochemical localization of advanced glycation end-products (AGEs) and their receptor (RAGE) in polycystic and normal ovaries

The aim of the present study was to investigate the localization/immunohistochemical distribution of AGEs and RAGE, as well as their putative signalling mediator NF-κB in ovaries of women with polycystic ovary syndrome (PCOS) compared to normal. Archival ovarian-tissue samples from biopsies of six women with PCOS and from six healthy of similar age women, were examined immunohistochemically with monoclonal anti-AGEs, anti-RAGE and anti-NF-κB(p50/p65) specific antibodies. In healthy women, AGE immunoreactivity was observed in follicular cell layers (granulosa and theca) and luteinized cells, but not in endothelial cells. PCOS specimens displayed AGE immunoexpression in theca interna and granulosa cells as well as in endothelial cells, but staining of granulosa cells was stronger than in that of normal ovaries. RAGE was highly expressed in normal and PCOS tissues. Normal tissue exhibited no staining differences between granulosa cell layer and theca interna. However, in PCOS ovaries, granulosa cells displayed stronger RAGE expression compared to theca interna cells in comparison to controls. NF-κB(p50/p65) was expressed in the cytoplasm of theca interna and granulosa cells of both normal and PCOS ovaries; whereas the NF-κB p65 subunit was only observed in granulosa cells nuclei in PCOS tissue. In conclusion, these findings demonstrate for the first time that RAGE and AGE-modified proteins with activated NF-κB are expressed in human ovarian tissue. Furthermore, a differential qualitative distribution of AGE, RAGE and NF-κB p65 subunit was observed in women with PCOS compared to healthy controls, where a stronger localization of both AGE and RAGE was observed in the granulosa cell layer of PCOS ovaries.