Androgen receptor splice variants and polycystic ovary syndrome: cause or effect?

Beyond Prostate Cancer: An Androgen Receptor Splice Variant Expression in Multiple Malignancies, Non-Cancer Pathologies, and Development

Multiple studies have demonstrated the importance of androgen receptor (AR) splice variants (SVs) in the progression of prostate cancer to the castration-resistant phenotype and their utility as a diagnostic. However, studies on AR expression in non-prostatic malignancies uncovered that AR-SVs are expressed in glioblastoma, breast, salivary, bladder, kidney, and liver cancers, where they have diverse roles in tumorigenesis. AR-SVs also have roles in non-cancer pathologies. In granulosa cells from women with polycystic ovarian syndrome, unique AR-SVs lead to an increase in androgen production. In patients with nonobstructive azoospermia, testicular Sertoli cells exhibit differential expression of AR-SVs, which is associated with impaired spermatogenesis. Moreover, AR-SVs have been identified in normal cells, including blood mononuclear cells, neuronal lipid rafts, and the placenta. The detection and characterization of AR-SVs in mammalian and non-mammalian species argue that AR-SV expression is evolutionarily conserved and that AR-SV-dependent signaling is a fundamental regulatory feature in multiple cellular contexts. These discoveries argue that alternative splicing of the AR transcript is a commonly used mechanism that leads to an expansion in the repertoire of signaling molecules needed in certain tissues. Various malignancies appropriate this mechanism of alternative AR splicing to acquire a proliferative and survival advantage.

Deconstructing a Syndrome: Genomic Insights Into PCOS Causal Mechanisms and Classification

Polycystic ovary syndrome (PCOS) is among the most common disorders in women of reproductive age, affecting up to 15% worldwide, depending on the diagnostic criteria. PCOS is characterized by a constellation of interrelated reproductive abnormalities, including disordered gonadotropin secretion, increased androgen production, chronic anovulation, and polycystic ovarian morphology. It is frequently associated with insulin resistance and obesity. These reproductive and metabolic derangements cause major morbidities across the lifespan, including anovulatory infertility and type 2 diabetes (T2D). Despite decades of investigative effort, the etiology of PCOS remains unknown. Familial clustering of PCOS cases has indicated a genetic contribution to PCOS. There are rare Mendelian forms of PCOS associated with extreme phenotypes, but PCOS typically follows a non-Mendelian pattern of inheritance consistent with a complex genetic architecture, analogous to T2D and obesity, that reflects the interaction of susceptibility genes and environmental factors. Genomic studies of PCOS have provided important insights into disease pathways and have indicated that current diagnostic criteria do not capture underlying differences in biology associated with different forms of PCOS. We provide a state-of-the-science review of genetic analyses of PCOS, including an overview of genomic methodologies aimed at a general audience of non-geneticists and clinicians. Applications in PCOS will be discussed, including strengths and limitations of each study. The contributions of environmental factors, including developmental origins, will be reviewed. Insights into the pathogenesis and genetic architecture of PCOS will be summarized. Future directions for PCOS genetic studies will be outlined.

Polycystic ovary syndrome and reproductive health of women: a curious association

Reproductive health is a broad concept that encompasses mortality, morbidity, and quality of life associated with the reproductive system, mechanism, and incidents encountered at all ages by men and women. Orthodox Indian society finds the conversation on reproductive health to be a taboo and discourages open conversations about it. Polycystic ovary syndrome (PCOS) is a reproductive-age metabolic endocrine disorder found in females. Females suffering from PCOS are prone to reproductive, metabolic, and cardiovascular disorders. In this paper, we will systematically review about effect of PCOS on Reproductive Health of Women. The numerous electronic databases such as: BMJ, LANCET, PUBMED, Unicef Website, WHO Website and Google Scholar have been comprehensively searched for studies linked to PCOS, its various effects and effect on women's reproductive health. For additional analyses, we have reviewed reference lists of reviews and collected papers. The effects of PCOS on women's reproductive health have been verified by several scientific reports worldwide. PCOS is a hormonal condition, as per multiple reports, with the ability to lead to different outcomes. It still appears to be a common cause among females of infertility. An integral aspect of the treatment of this disease is the early diagnosis of long-term morbidities by effective screening tests. In the future, studies must concentrate on the missing holes in our growing perception of this disease. Several studies have confirmed that reproductive morbidity, including irregular uterine bleeding, abortion, miscarriage, and other risk of pregnancy during reproductive years, is associated with PCOS. PCOS is an amalgam of physiological and psychosocial dysfunction, not just an endocrine disorder.

Androgen receptor gene mutations in 258 Han Chinese patients with polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) affects 8-13% of reproductive-age females worldwide and mutations or aberrant expression of androgen receptor (AR) may cause the onset of this disease. In the present study, 258 samples from Han Chinese patients with PCOS were analyzed for the presence of AR mutations via sequencing of all coding exons of the AR gene. A total of five heterozygous missense mutations, namely p.V3M, p.Q72R, p.S158L, p.S176R and p.G396R, were identified in five of the patients. Among these, p.S158L was a novel mutation that, to the best of our knowledge, has not been reported previously. Although the remaining four mutations have been reported previously, they existed at low frequencies or were absent in the control subjects and in the Exome Aggregation Consortium database. The results of evolutionary conservation and in silico analysis revealed that the p.V3M, p.S158L and p.S176R mutations were pathogenic, whereas the p.Q72R and p.G396R mutations were benign. Compared with the patients with PCOS without AR mutations or with benign AR mutations, markedly lower estrogen levels on the day of human chorionic gonadotropin injection were observed in the three patients with PCOS with potentially pathogenic mutations. In addition, patients with PCOS with pathogenic mutations had lower numbers of oocytes; however, the difference was not statistically significant. Of note, these observations should be interpreted with caution due to the relatively small sample size in the present study. Therefore, a larger number of samples should be collected to validate the results of the present study in future studies. In summary, the present study identified three potential pathogenic mutations in 258 Han Chinese patients with PCOS and these mutations may have an implication in the pathogenesis of PCOS.

Current concepts of polycystic ovary syndrome pathogenesis

PURPOSE OF REVIEW

This review provides a model for understanding polycystic ovary syndrome (PCOS) pathophysiology and updates the evidence on which it is based. Then, it highlights complimentary molecular genetic and epigenetic advances in understanding PCOS cause.

RECENT FINDINGS

Important studies into PCOS cause built on the 2014 discovery of a novel regulatory protein variant that underlies the typical PCOS steroidogenic abnormalities: DENND1A.V2 (differentially expressed in normal and neoplastic development, isoform 1A, variant 2). Over 30 DENND1A gene variants have been found, the vast majority upstream of the coding sequence and potentially regulatory. These variants are individually uncommon but collectively plausibly cause 50% of PCOS. Anti-Müllerian hormone (AMH)/AMH receptor variants with decreased function possibly cause 6.7% of PCOS. DENNND1A was recently reported to belong to a signaling network that upregulates luteinizing hormone receptor expression and insulin mitogenic signaling. Prenatal androgen administration has proven to be a potent epigenetic regulator that causes transgenerational epigenomic changes in a mouse PCOS model with similarities to those in human PCOS and PCOS daughters.

SUMMARY

In addition to finding how gene variants contribute to PCOS pathogenesis, better understanding of androgen epigenetic mechanisms of action in diverse tissues can be expected to expand our understanding of PCOS pathogenesis.

Role of androgens in the ovary

It has been well established for decades that androgens, namely testosterone (T) plays an important role in female reproductive physiology as the precursor for oestradiol (E₂). However, in the last decade a direct role for androgens, acting via the androgen receptor (AR), in female reproductive function has been confirmed. Deciphering the specific roles of androgens in ovarian function has been hindered as complete androgen resistant females cannot be generated by natural breeding. In addition, androgens can be converted into estrogens which has caused confusion when interpreting findings from pharmacological studies, as observed effects could have been mediated via the AR or estrogen receptor. The creation and analysis of genetic mouse models with global and cell-specific disruption of the Ar gene, the sole mediator of pure androgenic action, has now allowed the elucidation of a role for AR-mediated androgen actions in the regulation of normal and pathological ovarian function. This review aims to summarize findings from clinical, animal, pharmacological and novel genetic AR mouse models to provide an understanding of the important roles androgens play in the ovary, as well as providing insights into the human implications of these roles.

High level of C-type natriuretic peptide induced by hyperandrogen-mediated anovulation in polycystic ovary syndrome mice

Polycystic ovary syndrome (PCOS), which is characterized by hyperandrogenism, is a complex endocrinopathy that affects the fertility of 9-18% of reproductive-aged women. However, the exact mechanism of PCOS, especially hyperandrogen-induced anovulation, is largely unknown to date. Physiologically, the natriuretic peptide type C/natriuretic peptide receptor 2 (CNP/NPR2) system is essential for sustaining oocyte meiotic arrest until the preovulatory luteinizing hormone (LH) surge. We therefore hypothesized that the CNP/NPR2 system is also involved in PCOS and contributes to arresting oocyte meiosis and ovulation. Here, based on a dehydroepiandrosterone (DHEA)-induced PCOS-like mouse model, persistent high levels of CNP/NPR2 were detected in anovulation ovaries. Meanwhile, oocytes arrested at the germinal vesicle stage correlated with persistent high levels of androgen and estrogen. We further showed that ovulation failure in these mice could be a result of elevated Nppc/Npr2 gene transcription that was directly increased by androgen (AR) and estrogen (ER) receptor signaling. Consistent with this, anovulation was alleviated by administration of either exogenous human chorionic gonadotropin (hCG) or inhibitors of AR or ER to reduce the level of CNP/NPR2. Additionally, the CNP/NPR2 expression pattern in the anovulated follicles was, to some extent, consistent with the clinical expression in PCOS patients. Therefore, our study highlights the important role an overactive CNP/NPR2 system caused by hyperandrogenism in preventing oocytes from maturation and ovulation in PCOS mice. Our findings provide insight into potential mechanisms responsible for infertility in women with PCOS.

Recent highlights of research on androgen receptors in women

In this brief review we present an outline of the current state of research on examples of hyperandrogenism that can be strongly associated with diverse modifications in the androgen signaling pathway. We discuss the most prominent clinical features of androgen excess and correlate them with studies on androgen receptor (AR) alterations. For the first time we summarize the confirmed localizations of all known AR receptors in women. The knowledge of ARs may be the basis for AR-targeted therapies of androgenic disorders in women, including malignancy, as it has recently been demonstrated for triple-negative breast cancer. Moreover, we summarize the structure and characterization of key AR splice variants, which could be involved in the androgenization in women.

Neuroendocrine androgen action is a key extraovarian mediator in the development of polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is a complex hormonal disorder characterized by reproductive, endocrine, and metabolic abnormalities. As the origins of PCOS remain unknown, mechanism-based treatments are not feasible and current management relies on treatment of symptoms. Hyperandrogenism is the most consistent PCOS characteristic; however, it is unclear whether androgen excess, which is treatable, is a cause or a consequence of PCOS. As androgens mediate their actions via the androgen receptor (AR), we combined a mouse model of dihydrotestosterone (DHT)-induced PCOS with global and cell-specific AR-resistant (ARKO) mice to investigate the locus of androgen actions that mediate the development of the PCOS phenotype. Global loss of the AR reveals that AR signaling is required for all DHT-induced features of PCOS. Neuron-specific AR signaling was required for the development of dysfunctional ovulation, classic polycystic ovaries, reduced large antral follicle health, and several metabolic traits including obesity and dyslipidemia. In addition, ovariectomized ARKO hosts with wild-type ovary transplants displayed normal estrous cycles and corpora lutea, despite DHT treatment, implying extraovarian and not intraovarian AR actions are key loci of androgen action in generating the PCOS phenotype. These findings provide strong evidence that neuroendocrine genomic AR signaling is an important extraovarian mediator in the development of PCOS traits. Thus, targeting AR-driven mechanisms that initiate PCOS is a promising strategy for the development of novel treatments for PCOS.

The Pathogenesis of Polycystic Ovary Syndrome (PCOS): The Hypothesis of PCOS as Functional Ovarian Hyperandrogenism Revisited

Polycystic ovary syndrome (PCOS) was hypothesized to result from functional ovarian hyperandrogenism (FOH) due to dysregulation of androgen secretion in 1989-1995. Subsequent studies have supported and amplified this hypothesis. When defined as otherwise unexplained hyperandrogenic oligoanovulation, two-thirds of PCOS cases have functionally typical FOH, characterized by 17-hydroxyprogesterone hyperresponsiveness to gonadotropin stimulation. Two-thirds of the remaining PCOS have FOH detectable by testosterone elevation after suppression of adrenal androgen production. About 3% of PCOS have a related isolated functional adrenal hyperandrogenism. The remaining PCOS cases are mild and lack evidence of steroid secretory abnormalities; most of these are obese, which we postulate to account for their atypical PCOS. Approximately half of normal women with polycystic ovarian morphology (PCOM) have subclinical FOH-related steroidogenic defects. Theca cells from polycystic ovaries of classic PCOS patients in long-term culture have an intrinsic steroidogenic dysregulation that can account for the steroidogenic abnormalities typical of FOH. These cells overexpress most steroidogenic enzymes, particularly cytochrome P450c17. Overexpression of a protein identified by genome-wide association screening, differentially expressed in normal and neoplastic development 1A.V2, in normal theca cells has reproduced this PCOS phenotype in vitro. A metabolic syndrome of obesity-related and/or intrinsic insulin resistance occurs in about half of PCOS patients, and the compensatory hyperinsulinism has tissue-selective effects, which include aggravation of hyperandrogenism. PCOS seems to arise as a complex trait that results from the interaction of diverse genetic and environmental factors. Heritable factors include PCOM, hyperandrogenemia, insulin resistance, and insulin secretory defects. Environmental factors include prenatal androgen exposure and poor fetal growth, whereas acquired obesity is a major postnatal factor. The variety of pathways involved and lack of a common thread attests to the multifactorial nature and heterogeneity of the syndrome. Further research into the fundamental basis of the disorder will be necessary to optimally correct androgen levels, ovulation, and metabolic homeostasis.