Enhancement of a robust arcuate GABAergic input to gonadotropin-releasing hormone neurons in a model of polycystic ovarian syndrome

Neuroendocrine mechanisms responsible for elevated gonadotrophin-releasing hormone and luteinising hormone pulses in polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is the leading cause of anovulatory infertility in premenopausal individuals with ovaries worldwide. Despite the diagnostic features of anovulation, ovarian cysts, and hyperandrogenemia, which indicate that ovary dysfunction is the cause of the syndrome, changes in central neuroendocrine circuits are a significant cause of PCOS pathology. Specifically, cells in the hypothalamus have a diminished ability to transmit negative feedback signals from gonadal sex steroid hormones to gonadotropin-releasing hormone (GnRH) neurons. This results in an elevated frequency of pulsatile hypothalamic GnRH and pituitary luteinizing hormone (LH) secretion, leading to ovarian hyperandrogenism and ovulatory dysfunction. In recent years, preclinical research in animal models has rapidly advanced our understanding of the neural mechanisms underlying GnRH pulse generation with the identification of KNDy cells-a unique cell population in the hypothalamus expressing the neuropeptides kisspeptin, neurokinin B and dynorphin. As a result, therapeutics targeting KNDy cell signaling have emerged as a promising avenue for treating GnRH/LH hypersecretion in PCOS patients. However, the precise central changes underpinning impaired negative feedback regulation of GnRH pulse generation in PCOS patients are still unclear. Evidence from both the clinic and animal models suggests that changes in the regulation of KNDy cells may be directly responsible for elevated GnRH and LH pulse frequency in PCOS. However, other cell populations regulating GnRH secretion may also be involved. This review provides an overview of our current understanding of the aetiology and contribution of neuroendocrine dysfunction in PCOS pathology. It also examines the evidence for neural mechanisms underlying GnRH/LH hypersecretion, which may serve as central targets in developing novel treatments. Finally, this review highlights key knowledge gaps that are hindering the development of preventive and curative interventions.

Women with polycystic ovary syndrome (PCOS): Likelihood of cooccurring neuropsychiatric conditions and the dual hit hypothesis

Polycystic Ovary Syndrome (PCOS) is the most common endocrine-metabolic disorder in women of reproductive age. Hyperandrogenism has been proposed as its main pathophysiological feature. PCOS is associated with co-occurring conditions, including psychiatric disorders such as anxiety, depression, and neurodevelopmental conditions such as autism. Exposure to hyperandrogenism during prenatal life and adolescence may explain this association. PCOS women exhibit hyperandrogenism during pregnancy, and up to 70% of their daughters will present a similar phenotype from puberty onwards. The 'dual hit hypothesis' proposes that stressors during prenatal life and adolescence can synergistically lead to co-occurring conditions in adulthood. PCOS has been recently proposed as an independent likelihood factor for the development of neuropsychiatric conditions. However, the specific mechanisms require further research to develop effective interventions. This review discusses how hyperandrogenism can affect neurodevelopment during two key periods of brain development, which may explain the long-term impact of PCOS on mental health.

The impact of GABA and GABAergic pathway in polycystic ovary syndrome: a systematic review

Emerging evidence indicates that dysfunction of the gamma-aminobutyric acid (GABA)ergic pathway may contribute to the pathophysiology of polycystic ovary syndrome (PCOS), and GABA demonstrates potential in the management of PCOS symptoms. This systematic review aimed to determine the role of the GABAergic pathway in PCOS and evaluate the impact of GABA on improving the condition. Web of Science, Embase, Scopus, Cochrane, and PubMed databases were systematically searched for experimental studies, clinical trials, animal studies, and cellular investigations. The search was conducted for relevant English-language manuscripts, published up to February 2024, using keywords, such as "polycystic ovary syndrome", PCOS, "gamma-aminobutyric acid" and GABA. Quality assessment of the included studies was performed using the Cochrane Collaboration's tool and the Newcastle-Ottawa scale. The results indicate that GABAergic dysfunction adversely affects gonadotrophin-releasing hormone neuronal activity, leading to hormonal imbalances and reproductive issues. Prenatal androgen exposure and kisspeptin signaling influence GABAergic transmission to GnRH neurons, thereby linking GABA to the pathogenesis of PCOS. Additionally, GABAergic signaling affects peripheral tissues relevant to PCOS, including the immune system, gut-brain axis, and ovaries. GABA supplementation has demonstrated potential benefits in enhancing metabolic and reproductive health, such as reducing insulin resistance and modulating sex hormone levels, as supported by animal models and clinical studies involving females with PCOS. The GABAergic signaling pathway may represent a promising therapeutic target for the management of PCOS. Nevertheless, further studies are required to validate these findings and deepen our understanding of the role of GABA in the pathogenesis and treatment of PCOS.

Multiple effects of kisspeptin on neuroendocrine, reproduction, and metabolism in polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is a highly prevalent and heterogeneous disease characterized by a combination of reproductive and endocrine abnormalities, often associated with metabolic and mental health disorders. The etiology and pathogenesis of PCOS remain unclear, but recent research has increasingly focused on the upstream mechanisms underlying its development. Among these, kisspeptin (KISS) signaling has emerged as a pivotal component in the regulation of the hypothalamic-pituitary-gonadal axis, with significant roles in reproductive function, energy regulation, and metabolism. Women with PCOS commonly exhibit disruptions in gonadotropin secretion, including elevated luteinizing hormone (LH) levels, imbalanced LH/follicle-stimulating hormone (FSH) ratios, and increased androgen levels, all of which are usually parallel with abnormal KISS signaling. Furthermore, alterations in the KISS/KISS1R system within the central and circulatory systems, as well as peripheral tissues, have been implicated in the development of PCOS. These changes affect multiple pathophysiological domains, including reproductive function, energy regulation, metabolic homeostasis, inflammatory response, and emotional disorders, and are further influenced by lifestyle and environmental factors. This review aims to comprehensively summarize the existing experimental and clinical evidence supporting these roles of KISS in PCOS, with the goal of establishing a foundation for future research and potential clinical applications.

The Hypothalamus and Pituitary Gland Regulate Reproduction and Are Involved in the Development of Polycystic Ovary Syndrome

BACKGROUND

Polycystic ovary syndrome (PCOS) is a complex condition with unclear mechanisms, posing a challenge for prevention and treatment of PCOS. The role of the hypothalamus and pituitary gland in regulating female reproduction is critical. Abnormalities in the hypothalamus and pituitary can impair reproductive function. It is important to study hypothalamic and pituitary changes in patients with PCOS.

SUMMARY

This article reviews articles on the hypothalamus and PCOS with the goal of summarizing what abnormalities of the hypothalamic-pituitary-ovarian axis are present in patients with PCOS and to clarify the pathogenesis of PCOS. We find that the mechanisms by which the hypothalamus and pituitary regulate reproduction in girls are complex and are associated with altered sex hormone levels, obesity, and insulin resistance. Different animal models of PCOS are characterized by different alterations in the hypothalamus and pituitary and respond differently to different treatments, which correspond to the complex pathogenesis of patients with PCOS.

KEY MESSAGES

Arcuate nucleus (ARC) is associated with luteinizing hormone (LH) surges. Suprachiasmatic nucleus, ARC, and RP3V are associated with LH surges. Animal models of PCOS have different characteristics.

Altered GnRH neuron-glia networks close to interface of polycystic ovary syndrome: Molecular mechanism and clinical perspectives

Polycystic ovary syndrome (PCOS) has been noticed as a neuroendocrine syndrome manifested by reproductive hormone dysregulation involving increased luteinizing hormone (LH) pulse frequency and an increased LH to follicle-stimulating hormone ratio, yet theory is just beginning to be established. Neuroglia located in the arcuate nucleus and median eminence (ARC-ME) that are close to gonadotropin-releasing hormone (GnRH) axon terminals, comprise the blood-brain barrier and fenestrated vessels implying their putative roles in the modulation of the abnormal GnRH pulse in PCOS. This review outlines the disturbances of neuron-glia networks that underlie hypothetically the deregulation of GnRH-LH release and impaired sex hormone negative feedback in PCOS. We then discuss chronic and low-grade inflammatory status together with gut dysbiosis and how the detriments may intrude the hypothalamus by virtue of violating interfaces between the brain and periphery, which might contribute to the etiology of the impaired neural circuits in the ARC-ME to induce PCOS.

GnRH pulse generator activity in mouse models of polycystic ovary syndrome

One in ten women in their reproductive age suffer from polycystic ovary syndrome (PCOS) that, alongside subfertility and hyperandrogenism, typically presents with increased luteinizing hormone (LH) pulsatility. As such, it is suspected that the arcuate kisspeptin (ARNKISS) neurons that represent the GnRH pulse generator are dysfunctional in PCOS. We used here in vivo GCaMP fiber photometry and other approaches to examine the behavior of the GnRH pulse generator in two mouse models of PCOS. We began with the peripubertal androgen (PPA) mouse model of PCOS but found that it had a reduction in the frequency of ARNKISS neuron synchronization events (SEs) that drive LH pulses. Examining the prenatal androgen (PNA) model of PCOS, we observed highly variable patterns of pulse generator activity with no significant differences detected in ARNKISS neuron SEs, pulsatile LH secretion, or serum testosterone, estradiol, and progesterone concentrations. However, a machine learning approach identified that the ARNKISS neurons of acyclic PNA mice continued to exhibit cyclical patterns of activity similar to that of normal mice. The frequency of ARNKISS neuron SEs was significantly increased in algorithm-identified 'diestrous stage' PNA mice compared to controls. In addition, ARNKISS neurons exhibited reduced feedback suppression to progesterone in PNA mice and their gonadotrophs were also less sensitive to GnRH. These observations demonstrate the importance of understanding GnRH pulse generator activity in mouse models of PCOS. The existence of cyclical GnRH pulse generator activity in the acyclic PNA mouse indicates the presence of a complex phenotype with deficits at multiple levels of the hypothalamo-pituitary-gonadal axis.

Developmental expression patterns of gonadal hormone receptors in arcuate kisspeptin and GABA neurons of the postnatal female mouse

The arcuate nucleus of the hypothalamus (ARC) is central in the neuronal regulation of fertility and reproduction through translating gonadal steroid hormone cues into the GnRH signaling pathway in the brain. Evidence suggests that circulating gonadal steroids play an important role in modulating female reproduction via kisspeptin and γ-aminobutyric acid (GABA) neurons in the ARC in both development and adulthood. However, the temporal onset of these ARC neurons' sensitivity to gonadal steroids is unknown. Using RNAscope® in situ hybridization, we localized androgen receptor (Ar), estrogen receptor alpha (Esr1), and progesterone receptor (Pgr) expression in ARC kisspeptin or GABA neurons of female mice at postnatal day (P)4, P8, P12, P20, and P60. A probe that binds to kiss1 mRNA or vGat mRNA was used to produce signal in kisspeptin or GABA neurons, respectively. In adult, we identified that the vast majority of kisspeptin neurons coexpressed Esr1 (95%) and Pgr (93%), while a smaller proportion coexpressed Ar (66%). Similar proportions of Ar- or Esr1-positive kisspeptin neurons were seen from P4, suggesting that kisspeptin neurons develop adult-like sensitivity to androgen and estrogen in early postnatal life. In contrast, the proportion of Pgr-positive kisspeptin cells in early life was significantly lower than in adulthood, suggesting that progesterone sensitivity develops over time in the ARC kisspeptin population. ARC GABA neurons also colocalized with Ar (70%), Esr1 (64%), or Pgr (85%) in adulthood. GABA neurons continuously expressed Esr1 or Pgr from the postnatal stages to adulthood, while the proportion of Ar-positive GABA neurons gradually increased from P4 (24%) to P20 (59%). These results suggest that while ARC GABA neurons can respond to circulating estrogen and progesterone from early postnatal ages, this same population may become more sensitive to androgens during later postnatal life. Our findings identified the expression patterns of Ar, Esr1, and Pgr by ARC kisspeptin and GABA neurons during early postnatal life. These data provide the understanding for the hormone sensitivity of these populations during early postnatal life, the critical time for the formation and regulation of female reproductive physiology.Esr1 (95%) and Pgr (93%), while a smaller proportion coexpressed Ar (66%). Similar proportions of Ar- or Esr1-positive kisspeptin neurons were seen from P4, suggesting that kisspeptin neurons develop adult-like sensitivity to androgen and estrogen in early postnatal life. In contrast, the proportion of Pgr-positive kisspeptin cells in early life was significantly lower than in adulthood, suggesting that progesterone sensitivity develops over time in the ARC kisspeptin population. ARC GABA neurons also colocalized with Ar (70%), Esr1 (64%), or Pgr (85%) in adulthood. GABA neurons continuously expressed Esr1 or Pgr from the postnatal stages to adulthood, while the proportion of Ar-positive GABA neurons gradually increased from P4 (24%) to P20 (59%). These results suggest that while ARC GABA neurons can respond to circulating estrogen and progesterone from early postnatal ages, this same population may become more sensitive to androgens during later postnatal life. Our findings identified the expression patterns of Ar, Esr1, and Pgr by ARC kisspeptin and GABA neurons during early postnatal life. These data provide the understanding for the hormone sensitivity of these populations during early postnatal life, the critical time for the formation and regulation of female reproductive physiology.

Targeted inhibition of kisspeptin neurons reverses hyperandrogenemia and abnormal hyperactive LH secretion in a preclinical mouse model of polycystic ovary syndrome

STUDY QUESTION

Do hyperactive kisspeptin neurons contribute to abnormally high LH secretion and downstream hyperandrogenemia in polycystic ovary syndrome (PCOS)-like conditions and can inhibition of kisspeptin neurons rescue such endocrine impairments?

SUMMARY ANSWER

Targeted inhibition of endogenous kisspeptin neuron activity in a mouse model of PCOS reduced the abnormally hyperactive LH pulse secretion and hyperandrogenemia to healthy control levels.

WHAT IS KNOWN ALREADY

PCOS is a reproductive disorder characterized by hyperandrogenemia, anovulation, and/or polycystic ovaries, along with a hallmark feature of abnormal LH hyper-pulsatility, but the mechanisms underlying the endocrine impairments remain unclear. A chronic letrozole (LET; aromatase inhibitor) mouse model recapitulates PCOS phenotypes, including polycystic ovaries, anovulation, high testosterone, and hyperactive LH pulses. LET PCOS-like females also have increased hypothalamic kisspeptin neuronal activation which may drive their hyperactive LH secretion and hyperandrogenemia, but this has not been tested.

STUDY DESIGN, SIZE, DURATION

Transgenic KissCRE+/hM4Di female mice or littermates Cre- controls were treated with placebo, or chronic LET (50 µg/day) to induce a PCOS-like phenotype, followed by acute (once) or chronic (2 weeks) clozapine-N-oxide (CNO) exposure to chemogenetically inhibit kisspeptin cells (n = 6 to 10 mice/group).

PARTICIPANTS/MATERIALS, SETTING, METHODS

Key endocrine measures, including in vivo LH pulse secretion patterns and circulating testosterone levels, were assessed before and after selective kisspeptin neuron inhibition and compared between PCOS groups and healthy controls. Alterations in body weights were measured and pituitary and ovarian gene expression was determined by qRT-PCR.

MAIN RESULTS AND THE ROLE OF CHANCE

Acute targeted inhibition of kisspeptin neurons in PCOS mice successfully lowered the abnormally hyperactive LH pulse secretion (P < 0.05). Likewise, chronic selective suppression of kisspeptin neuron activity reversed the previously high LH and testosterone levels (P < 0.05) down to healthy control levels and rescued reproductive gene expression (P < 0. 05).

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

Ovarian morphology was not assessed in this study. Additionally, mouse models can offer mechanistic insights into neuroendocrine processes in PCOS-like conditions but may not perfectly mirror PCOS in women.

WIDER IMPLICATIONS OF THE FINDINGS

These data support the hypothesis that overactive kisspeptin neurons can drive neuroendocrine PCOS-like impairments, and this may occur in PCOS women. Our findings complement recent clinical investigations using NKB receptor antagonists to lower LH in PCOS women and suggest that pharmacological dose-dependent modulation of kisspeptin neuron activity may be a valuable future therapeutic target to clinically treat hyperandrogenism and lower elevated LH in PCOS women.

STUDY FUNDING/COMPETING INTEREST(S)

This research was supported by NIH grants R01 HD111650, R01 HD090161, R01 HD100580, P50 HD012303, R01 AG078185, and NIH R24 HD102061, and a pilot project award from the British Society for Neuroendocrinology. There are no competing interests.

Deletion of Nuclear Progesterone Receptors From Kisspeptin Cells Does Not Impair Negative Feedback in Female Mice

Reproductive function in mammals depends on the ability of progesterone (P4) to suppress pulsatile gonadotrophin-releasing hormone (GnRH) and luteinizing hormone (LH) secretion in a homeostatic-negative feedback loop. Previous research identified that cells upstream from GnRH neurons expressing the nuclear progesterone receptor (PGR) are required for P4-negative feedback. However, the identity of these cells and the mechanism by which they reduce GnRH/LH pulsatile secretion is unknown. We aimed to address the hypothesis that PGR expressed by a neural population in the arcuate nucleus recently identified as the GnRH pulse generator, cells expressing kisspeptin, neurokinin B, and dynorphin (KNDy cells), mediate P4-negative feedback. To achieve this, we used female mice with the PGR gene conditionally deleted from kisspeptin cells (KPRKO mice) and observed a substantial decrease in the percentage of KNDy neurons coexpressing PGR messenger RNA (mRNA) (11% in KPRKO mice vs 86% in wild-type [WT] mice). However, KPRKO mice did not display changes in the frequency or amplitude of LH pulses in diestrus or estrus, nor in the ability of exogenous P4 to blunt a postcastration increase in LH. Further, mRNA expression of arcuate kisspeptin and dynorphin, which are excitatory and inhibitory to GnRH secretion, respectively, remained unaltered in KPRKO mice compared to WT controls. Together, these findings show that the near-complete loss of PGR signaling from KNDy cells does not affect negative feedback regulation of GnRH pulse generation in mice, suggesting that feedback through this receptor can occur via a small number of KNDy cells or a yet unidentified cell population.

Investigating GABA Neuron-Specific Androgen Receptor Knockout in two Hyperandrogenic Models of PCOS

Androgen excess is a hallmark feature of polycystic ovary syndrome (PCOS), the most common form of anovulatory infertility. Clinical and preclinical evidence links developmental or chronic exposure to hyperandrogenism with programming and evoking the reproductive and metabolic traits of PCOS. While critical androgen targets remain to be determined, central GABAergic neurons are postulated to be involved. Here, we tested the hypothesis that androgen signaling in GABAergic neurons is critical in PCOS pathogenesis in 2 well-characterized hyperandrogenic mouse models of PCOS. Using cre-lox transgenics, GABA-specific androgen receptor knockout (GABARKO) mice were generated and exposed to either acute prenatal androgen excess (PNA) or chronic peripubertal androgen excess (PPA). Females were phenotyped for reproductive and metabolic features associated with each model and brains of PNA mice were assessed for elevated GABAergic input to gonadotropin-releasing hormone (GnRH) neurons. Reproductive and metabolic dysfunction induced by PPA, including acyclicity, absence of corpora lutea, obesity, adipocyte hypertrophy, and impaired glucose homeostasis, was not different between GABARKO and wild-type (WT) mice. In PNA mice, acyclicity remained in GABARKO mice while ovarian morphology and luteinizing hormone secretion was not significantly impacted by PNA or genotype. However, PNA predictably increased the density of putative GABAergic synapses to GnRH neurons in adult WT mice, and this PNA-induced plasticity was absent in GABARKO mice. Together, these findings suggest that while direct androgen signaling in GABA neurons is largely not required for the development of PCOS-like traits in androgenized models of PCOS, developmental programming of GnRH neuron innervation is dependent upon androgen signaling in GABA neurons.

Cholinergic Control of GnRH Neuron Physiology and Luteinizing Hormone Secretion in Male Mice: Involvement of ACh/GABA Cotransmission

Gonadotropin-releasing hormone (GnRH)-synthesizing neurons orchestrate reproduction centrally. Early studies have proposed the contribution of acetylcholine (ACh) to hypothalamic control of reproduction, although the causal mechanisms have not been clarified. Here, we report that in vivo pharmacogenetic activation of the cholinergic system increased the secretion of luteinizing hormone (LH) in orchidectomized mice. 3DISCO immunocytochemistry and electron microscopy revealed the innervation of GnRH neurons by cholinergic axons. Retrograde viral labeling initiated from GnRH-Cre neurons identified the medial septum and the diagonal band of Broca as exclusive sites of origin for cholinergic afferents of GnRH neurons. In acute brain slices, ACh and carbachol evoked a biphasic effect on the firing rate in GnRH neurons, first increasing and then diminishing it. In the presence of tetrodotoxin, carbachol induced an inward current, followed by a decline in the frequency of miniature postsynaptic currents (mPSCs), indicating a direct influence on GnRH cells. RT-PCR and whole-cell patch-clamp studies revealed that GnRH neurons expressed both nicotinic (α4β2, α3β4, and α7) and muscarinic (M1-M5) AChRs. The nicotinic AChRs contributed to the nicotine-elicited inward current and the rise in firing rate. Muscarine via M1 and M3 receptors increased, while via M2 and M4 reduced the frequency of both mPSCs and firing. Optogenetic activation of channelrhodopsin-2-tagged cholinergic axons modified GnRH neuronal activity and evoked cotransmission of ACh and GABA from a subpopulation of boutons. These findings confirm that the central cholinergic system regulates GnRH neurons and activates the pituitary-gonadal axis via ACh and ACh/GABA neurotransmissions in male mice.

Development and prenatal exposure to androgens alter potassium currents in gonadotropin-releasing hormone neurons from female mice

Pulsatile gonadotropin-releasing hormone (GnRH) release is critical for reproduction. Disruptions to GnRH secretion patterns may contribute to polycystic ovary syndrome (PCOS). Prenatally androgenized (PNA) female mice recapitulate many neuroendocrine abnormalities observed in PCOS patients. PNA and development induce changes in spontaneous GnRH neuron firing rate, response to synaptic input, and the afterhyperpolarization potential of the action potential. We hypothesized potassium currents are altered by PNA treatment and/or development. Whole-cell patch-clamp recordings were made of transient and residual potassium currents of GnRH neurons in brain slices from 3-week-old and adult control and PNA females. At 3 weeks of age, PNA treatment increased transient current density versus controls. Development and PNA altered voltage-dependent activation and inactivation of the transient current. In controls, transient current activation and inactivation were depolarized at 3 weeks of age versus in adulthood. In GnRH neurons from 3-week-old mice, transient current activation and inactivation were more depolarized in control than PNA mice. Development and PNA treatment interacted to shift the time-dependence of inactivation and recovery from inactivation. Notably, in cells from adult PNA females, recovery was prolonged compared to all other groups. Activation of the residual current occurred at more depolarized membrane potentials in 3-week-old than adult controls. PNA depolarized activation of the residual current in adults. These findings demonstrate the properties of GnRH neuron potassium currents change during typical development, potentially contributing to puberty, and further suggest PNA treatment may both alter some typical developmental changes and induce additional modifications, which together may underlie aspects of the PNA phenotype. There was not any clinical trial involved in this work.

Androgen receptor actions on AgRP neurons are not a major cause of reproductive and metabolic impairments in peripubertally androgenized mice

Excess levels of circulating androgens during prenatal or peripubertal development are an important cause of polycystic ovary syndrome (PCOS), with the brain being a key target. Approximately half of the women diagnosed with PCOS also experience metabolic syndrome; common features including obesity, insulin resistance and hyperinsulinemia. Although a large amount of clinical and preclinical evidence has confirmed this relationship between androgens and the reproductive and metabolic features of PCOS, the mechanisms by which androgens cause this dysregulation are unknown. Neuron-specific androgen receptor knockout alleviates some PCOS-like features in a peripubertal dihydrotestosterone (DHT) mouse model, but the specific neuronal populations mediating these effects are undefined. A candidate population is the agouti-related peptide (AgRP)-expressing neurons, which are important for both reproductive and metabolic function. We used a well-characterised peripubertal androgenized mouse model and Cre-loxP transgenics to investigate whether deleting androgen receptors specifically from AgRP neurons can alleviate the induced reproductive and metabolic dysregulation. Androgen receptors were co-expressed in 66% of AgRP neurons in control mice, but only in <2% of AgRP neurons in knockout mice. The number of AgRP neurons was not altered by the treatments. Only 20% of androgen receptor knockout mice showed rescue of DHT-induced androgen-induced anovulation and acyclicity. Furthermore, androgen receptor knockout did not rescue metabolic dysfunction (body weight, adiposity or glucose and insulin tolerance). While we cannot rule out developmental compensation in our model, these results suggest peripubertal androgen excess does not markedly influence Agrp expression and does not dysregulate reproductive and metabolic function through direct actions of androgens onto AgRP neurons.

Molecular Mechanisms in the Etiology of Polycystic Ovary Syndrome (PCOS): A Multifaceted Hypothesis Towards the Disease with Potential Therapeutics

Among the premenopausal women, Polycystic Ovary Syndrome (PCOS) is the most prevalent endocrinopathy affecting the reproductive system and metabolic rhythms leading to disrupted menstrual cycle. Being heterogeneous in nature it is characterized by complex symptomology of oligomennorhoea, excess of androgens triggering masculine phenotypic appearance and/or multiple follicular ovaries. The etiology of this complex disorder remains somewhat doubtful and the researchers hypothesize multisystem links in the pathogenesis of this disease. In this review, we attempt to present several hypotheses that tend to contribute to the etiology of PCOS. Metabolic inflexibility, aberrant pattern of gonadotropin signaling along with the evolutionary, genetic and environmental factors have been discussed. Considered a lifelong endocrinological implication, no universal treatment is available for PCOS so far however; multiple drug therapy is often advised along with simple life style intervention is mainly advised to manage its cardinal symptoms. Here we aimed to present a summarized view of pathophysiological links of PCOS with potential therapeutic strategies.

Impose of KNDy/GnRH neural circuit in PCOS, ageing, cancer and Alzheimer's disease: StAR actions in prevention of neuroendocrine dysfunction

The Kisspeptin1 (KISS1)/neurokinin B (NKB)/Dynorphin (Dyn) [KNDy] neurons in the hypothalamus regulate the reproduction stage in human beings and rodents. KNDy neurons co-expressed all KISS1, NKB, and Dyn peptides, and hence commonly regarded as KISS1 neurons. KNDy neurons contribute to the "GnRH pulse generator" and are implicated in the regulation of pulsatile GnRH release. The estradiol (E2)-estrogen receptor (ER) interactions over GnRH neurons in the hypothalamus cause nitric oxide (NO) discharge, in addition to presynaptic GABA and glutamate discharge from respective neurons. The released GABA and glutamate facilitate the activity of GnRH neurons via GABAA-R and AMPA/kainate-R. The KISS1 stimulates MAPK/ERK1/2 signaling and cause the release of Ca2+ from intracellular store, which contribute to neuroendocrine function, increase apoptosis and decrease cell proliferation and metastasis. The ageing in women deteriorates KISS1/KISS1R interaction in the hypothalamus which causes lower levels of GnRH. Because examining the human brain is so challenging, decades of clinical research have failed to find the causes of KNDy/GnRH dysfunction. The KISS1/KISS1R interactions in the brain have a neuroprotective effect against Alzheimer's disease (AD). These findings modulate the pathophysiological role of the KNDy/GnRH neural network in polycystic ovarian syndrome (PCOS) associated with ageing and, its protective role in cancer and AD. This review concludes with protecting effect of the steroid-derived acute regulatory enzyme (StAR) against neurotoxicity in the hippocampus, and hypothalamus, and these measures are fundamental for delaying ageing with PCOS. StAR could serve as novel diagnostic marker and therapeutic target for the most prevalent hormone-sensitive breast cancers (BCs).

[Neuroendocrine features of the pathogenesis of polycystic ovary syndrome (literature review)]

Polycystic ovary syndrome (PCOS) is one of the most pressing problems in endocrine gynecology. The main signs of the disease are hyperandrogenism, menstrual and/or ovulatory dysfunction, and polycystic ovarian structure according to ultrasound. Women with PCOS are at risk for developing metabolic syndrome, type 2 diabetes, cardiovascular disease, and endometrial cancer. In this connection, the pathogenetic mechanisms of the occurrence of this syndrome are continuously studied and new methods of treatment are being sought. PCOS is characterized by a wide range of various disorders of the neuroendocrine regulation of the reproductive system. The main focus of the review is aimed at summarizing information about the etiological role of neuropeptides and neurotransmitters, such as phoenixin, galanins, orexins, GABA, in the pathophysiology of PCOS and about the possibility of their use for diagnostic and therapeutic purposes. In recent decades, the interest of scientists has been focused on the study of KNDy neurons, because it is the kisspeptin synthesized by them that is one of the main regulators of the hypothalamic-pituitary-ovarian axis. This article discusses data on the significance of KNDy neurons in the pathogenesis of the syndrome. Information is provided on the effect of elevated levels of androgens and anti-Müllerian hormone on GnRH neurons. Also analyzed are studies on functional and structural disorders in the hypothalamus in PCOS. Literature search was carried out in national (eLibrary, CyberLeninka.ru) and international (PubMed, Cochrane Library) databases in Russian and English. The priority was free access to the full text of articles. The choice of sources was prioritized for the period from 2018 to 2023.However, taking into account the insufficient knowledge of the chosen topic, the choice of sources dates back to 1998.

Overactivation of GnRH neurons is sufficient to trigger polycystic ovary syndrome-like traits in female mice

BACKGROUND

Polycystic ovary syndrome (PCOS) is the most common endocrine disorder leading to anovulatory infertility. Abnormalities in the central neuroendocrine system governed by gonadotropin-releasing hormone (GnRH) neurons might be related to ovarian dysfunction in PCOS, although the link in this disordered brain-to-ovary communication remains unclear. Here, we manipulated GnRH neurons using chemogenetics in adult female mice to unveil whether chronic overaction of these neurons would trigger PCOS-like hormonal and reproductive impairments.

METHODS

We used adult Gnrh1cre female mice to selectively target and express the designer receptors exclusively activated by designer drugs (DREADD)-based chemogenetic tool hM3D(Gq) in hypophysiotropic GnRH neurons. Chronic chemogenetic activation protocol was carried out with clozapine N-oxide (CNO) i.p. injections every 48 h over a month. We evaluated the reproductive and hormonal profile before, during, and two months after chemogenetic manipulations.

FINDINGS

We discovered that the overactivation of GnRH neurons was sufficient to disrupt reproductive cycles, promote hyperandrogenism, and induce ovarian dysfunction. These PCOS features were detected with a long-lasting neuroendocrine dysfunction through abnormally high luteinizing hormone (LH) pulse secretion. Additionally, the GnRH-R blockade prevented the establishment of long-term neuroendocrine dysfunction and androgen excess in these animals.

INTERPRETATION

Taken together, our results show that hyperactivity of hypothalamic GnRH neurons is a major driver of reproductive and hormonal impairments in PCOS and suggest that antagonizing the aberrant GnRH signaling could be an efficient therapeutic venue for the treatment of PCOS.

FUNDING

European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (grant agreement n◦ 725149).

Hormone-mediated neural remodeling orchestrates parenting onset during pregnancy

During pregnancy, physiological adaptations prepare the female body for the challenges of motherhood. Becoming a parent also requires behavioral adaptations. Such adaptations can occur as early as during pregnancy, but how pregnancy hormones remodel parenting circuits to instruct preparatory behavioral changes remains unknown. We found that action of estradiol and progesterone on galanin (Gal)-expressing neurons in the mouse medial preoptic area (MPOA) is critical for pregnancy-induced parental behavior. Whereas estradiol silences MPOAGal neurons and paradoxically increases their excitability, progesterone permanently rewires this circuit node by promoting dendritic spine formation and recruitment of excitatory synaptic inputs. This MPOAGal-specific neural remodeling sparsens population activity in vivo and results in persistently stronger, more selective responses to pup stimuli. Pregnancy hormones thus remodel parenting circuits in anticipation of future behavioral need.

Unkeito promotes follicle development by restoring reduced follicle-stimulating hormone responsiveness in rats with polycystic ovary syndrome

Background

Polycystic ovary syndrome (PCOS) is a common disorder resulting in irregular menstruation and infertility due to improper follicular development and ovulation. PCOS pathogenesis is mediated by downregulated follicle-stimulating hormone receptor (FSHR) expression in granulosa cells (GCs); however, the underlying mechanism remains elusive. Unkeito (UKT) is a traditional Japanese medicine used to treat irregular menstruation in patients with PCOS. In this study, we aimed to confirm the effectiveness of UKT in PCOS by focusing on follicle-stimulating hormone (FSH) responsiveness.

Methods

A rat model of PCOS was generated by prenatal treatment with 5α-dihydrotestosterone. Female offspring (3-week-old) rats were fed a UKT mixed diet or a normal diet daily. To compare the PCOS phenotype in rats, the estrous cycle, hormone profiles, and ovarian morphology were evaluated. To further examine the role of FSH, molecular, genetic, and immunohistological analyses were performed using ovarian tissues and primary cultured GCs from normal and PCOS model rats.

Results

UKT increased the number of antral and preovulatory follicles and restored the irregular estrous cycle in PCOS rats. The gene expression levels of FSHR and bone morphogenetic protein (BMP)-2 and BMP-6 were significantly decreased in the ovarian GCs of PCOS rats compared to those in normal rats. UKT treatment increased FSHR staining in the small antral follicles and upregulated Fshr and Bmps expression in the ovary and GCs of PCOS rats. There was no change in serum gonadotropin levels. In primary cultured GCs stimulated by FSH, UKT enhanced estradiol production, accompanied by increased intracellular cyclic adenosine monophosphate levels, and upregulated the expression of genes encoding the enzymes involved in local estradiol synthesis, namely Cyp19a1 and Hsd17b. Furthermore, UKT elevated the expression of Star and Cyp11a1, involved in progesterone production in cultured GCs in the presence of FSH.

Conclusions

UKT stimulates ovarian follicle development by potentiating FSH responsiveness by upregulating BMP-2 and BMP-6 expression, resulting in the recovery of estrous cycle abnormalities in PCOS rats. Restoring the FSHR dysfunction in the small antral follicles may alleviate the PCOS phenotype.

Potential for NPY receptor-related therapies for polycystic ovary syndrome: an updated review

Polycystic ovary syndrome (PCOS) is a complex endocrine disease that can cause female infertility and bring economic burden to families and to society. The clinical and/or biochemical manifestations include hyperandrogenism, persistent anovulation, and polycystic ovarian changes, often accompanied by insulin resistance and obesity. Although its pathogenesis is unclear, PCOS involves the abnormal regulation of the hypothalamic-pituitary-ovarian axis and the abnormal activation of GnRH neurons. Neuropeptide Y (NPY) is widely distributed in the arcuate nucleus of the hypothalamus and functions as the physiological integrator of two neuroendocrine systems, one governing feeding and the other controlling reproduction. In recent years, an increasing number of studies have focused on the improvement of the reproductive and metabolic status of PCOS through the therapeutic application of NPY and its receptors. In this review, we summarize the central and peripheral regulation of NPY and its receptors in the development of PCOS and discuss the potential for NPY receptor-related therapies for PCOS.

Validation of a new Custom Polyclonal Progesterone Receptor Antibody for Immunohistochemistry in the Female Mouse Brain

Immunohistochemical visualization of progesterone receptor (PR)-expressing cells in the brain is a powerful technique to investigate the role of progesterone in the neuroendocrine regulation of fertility. A major obstacle to the immunohistochemical visualization of progesterone-sensitive cells in the rodent brain has been the discontinuation of the commercially produced A0098 rabbit polyclonal PR antibody by DAKO. To address the unavailability of this widely used PR antibody, we optimized and evaluated 4 alternative commercial PR antibodies and found that each lacked the specificity and/or sensitivity to immunohistochemically label PR-expressing cells in paraformaldehyde-fixed female mouse brain sections. As a result, we developed and validated a new custom RC269 PR antibody, directed against the same 533-547 amino acid sequence of the human PR as the discontinued A0098 DAKO PR antibody. Immunohistochemical application of the RC269 PR antibody on paraformaldehyde-fixed mouse brain sections resulted in nuclear PR labeling that was highly distinguishable from background, specific to its antigen, highly regulated by estradiol, matched the known distribution of PR protein expression in the female mouse hypothalamus, and nearly identical to that of the discontinued A0098 DAKO PR antibody. In summary, the RC269 PR antibody is a specific and sensitive antibody to immunohistochemically visualize PR-expressing cells in the mouse brain.

Alteration of the N6-methyladenosine methylation landscape in a mouse model of polycystic ovary syndrome

OBJECTIVE

To explore the N6-methyladenosine (m6A) methylation abnormality of mRNAs and its potential roles in the mouse model of polycystic ovary syndrome (PCOS).

METHODS

The mouse model of PCOS were induced by injecting dehydroepiandrosterone (DHEA), and confirmed by observing the morphological structures of ovarian follicles. Subsequently, m6A-tagged mRNAs were identified via m6A epitranscriptomic microarray and its potential functional pathways were predicted in KEGG database. The expression and modification levels of key mRNAs in the most enriched pathway were evaluated and compared using western blot and methylated RNA immunoprecipitation-quantitative PCR (MeRIP-qPCR).

RESULTS

Compared with the control group, 415 hypermethylated and downregulated mRNAs, 8 hypomethylated and upregulated mRNAs, and 14 hypermethylated and upregulated mRNAs were identified in the PCOS group (Fold change ≥ 1.5). Those mRNAs were mainly involved in insulin signaling pathway, type II diabetes mellitus, Fc epsilon RI signaling pathway, inositol phosphate metabolism, and GnRH secretion. In insulin signaling pathway, the expression levels of phosphorylated protein kinase B (p-AKT) were decreased, whereas that of upstream phosphorylated phosphatidylinositol 3-kinase (p-PI3K) were increased in PCOS group. Moreover, skeletal muscle and kidney-enriched inositol polyphosphate 5-phosphatease (SKIP), one of PIP3 phosphatases, was verified to be overexpressed, and Skip mRNAs were hypermethylated in PCOS group.

CONCLUSION

The altered m6A modification of mRNAs might play a critical role in PCOS process. The PI3K/AKT pathway is inhibited in the mouse model of PCOS. Whether it is caused by the m6A modification of Skip mRNAs is worthy of further exploration.

Defining potential targets of prenatal androgen excess: Expression analysis of androgen receptor on hypothalamic neurons in the fetal female mouse brain

Polycystic ovary syndrome (PCOS) is a female endocrine disorder that is associated with prenatal exposure to excess androgens. In prenatally androgenized (PNA) mice that model PCOS, GABAergic neural transmission to and innervation of GnRH neurons is increased. Evidence suggests that elevated GABAergic innervation originates in the arcuate nucleus (ARC). We hypothesized that GABA-GnRH circuit abnormalities are a direct consequence of PNA, resulting from DHT binding to androgen receptor (AR) in the prenatal brain. However, whether prenatal ARC neurons express AR at the time of PNA treatment is presently unknown. We used RNAScope in situ hybridization to localize AR mRNA (Ar)-expressing cells in healthy gestational day (GD) 17.5 female mouse brains and to assess coexpression levels in specific neuronal phenotypes. Our study revealed that less than 10% of ARC GABA cells expressed Ar. In contrast, we found that ARC kisspeptin neurons, critical regulators of GnRH neurons, were highly colocalized with Ar. Approximately 75% of ARC Kiss1-expressing cells also expressed Ar at GD17.5, suggesting that ARC kisspeptin neurons are potential targets of PNA. Investigating other neuronal populations in the ARC we found that ~50% of pro-opiomelanocortin (Pomc) cells, 22% of tyrosine hydroxylase (Th) cells, 8% of agouti-related protein (Agrp) cells and 8% of somatostatin (Sst) cells express Ar. Lastly, RNAscope in coronal sections showed Ar expression in the medial preoptic area (mPOA), and the ventral part of the lateral septum (vLS). These Ar-expressing regions were highly GABAergic, and 22% of GABA cells in the mPOA and 25% of GABA cells in the vLS also expressed Ar. Our findings identify specific neuronal phenotypes in the ARC, mPOA, and vLS that are androgen sensitive in late gestation. PNA-induced functional changes in these neurons may be related to the development of impaired central mechanisms associated with PCOS-like features.

Immunological and Metabolic Causes of Infertility in Polycystic Ovary Syndrome

Infertility has been recognized as a civilizational disease. One of the most common causes of infertility is polycystic ovary syndrome (PCOS). Closely interrelated immunometabolic mechanisms underlie the development of this complex syndrome and lead to infertility. The direct cause of infertility in PCOS is ovulation and implantation disorders caused by low-grade inflammation of ovarian tissue and endometrium which, in turn, result from immune and metabolic system disorders. The systemic immune response, in particular the inflammatory response, in conjunction with metabolic disorders, insulin resistance (IR), hyperadrenalism, insufficient secretion of progesterone, and oxidative stress lead not only to cardiovascular diseases, cancer, autoimmunity, and lipid metabolism disorders but also to infertility. Depending on the genetic and environmental conditions as well as certain cultural factors, some diseases may occur immediately, while others may become apparent years after an infertility diagnosis. Each of them alone can be a significant factor contributing to the development of PCOS and infertility. Further research will allow clinical management protocols to be established for PCOS patients experiencing infertility so that a targeted therapy approach can be applied to the factor underlying and driving the "vicious circle" alongside symptomatic treatment and ovulation stimulation. Hence, therapy of fertility for PCOS should be conducted by interdisciplinary teams of specialists as an in-depth understanding of the molecular relationships and clinical implications between the immunological and metabolic factors that trigger reproductive system disorders is necessary to restore the physiology and homeostasis of the body and, thus, fertility, among PCOS patients.

Successful Implementation of Menstrual Cycle Biomarkers in the Treatment of Infertility in Polycystic Ovary Syndrome-Case Report

Polycystic ovary syndrome (PCOS) is the most common cause of anovulatory infertility. Absent, impaired, or rare ovulation induces progesterone deficiency in the luteal phase, which is a critical problem in PCOS. A usual pattern of progesterone administration from a fixed and arbitrary pre-determined day of a menstrual cycle may preserve infertility but can easily be avoided. We present the case of a 29-year-old infertile woman who had been ineffectively treated for over two years. We introduced a line of therapy that was suited to her individual menstrual cycle by implementing biomarker recording. Supplementation based on a standardized observation of the basal body temperature (BBT) and cervical mucus stopped the vicious circle of absent ovulation and hyperandrogenism, restoring regular bleeding, ovulation cycles, and fertility. The implementation of a reliable fertility awareness method (FAM), accompanied by a standardized teaching methodology and periodic review of the observations recorded by the patient, validated through an ultrasound examination and plasma gonadotropins, estrogens, and progesterone concentrations, is key to achieving therapeutic success. The presented case is an example of a clinical vignette for many patients who have successfully managed to improve their fertility and pregnancy outcomes by applying the principles of a personalized treatment approach together with gestagens by recording their fertility biomarkers.

Transcriptomic survey of key reproductive and metabolic tissues in mouse models of polycystic ovary syndrome

Excessive androgen production and obesity are key to polycystic ovary syndrome (PCOS) pathogenesis. Prenatal androgenized (PNA), peripubertal androgenized, and overexpression of nerve growth factor in theca cells (17NF) are commonly used PCOS-like mouse models and diet-induced maternal obesity model is often included for comparsion. To reveal the molecular features of these models, we have performed transcriptome survey of the hypothalamus, adipose tissue, ovary and metaphase II (MII) oocytes. The largest number of differentially expressed genes (DEGs) is found in the ovaries of 17NF and in the adipose tissues of peripubertal androgenized models. In contrast, hypothalamus is most affected in PNA and maternal obesity models suggesting fetal programming effects. The Ms4a6e gene, membrane-spanning 4-domains subfamily A member 6E, a DEG identified in the adipose tissue in all mouse models is also differently expressed in adipose tissue of women with PCOS, highlighting a conserved disease function. Our comprehensive transcriptomic profiling of key target tissues involved in PCOS pathology highlights the effects of developmental windows for androgen exposure and maternal obesity, and provides unique resource to investigate molecular mechanisms underlying PCOS pathogenesis.

Deletion of Androgen Receptor in LepRb Cells Improves Estrous Cycles in Prenatally Androgenized Mice

Androgens are steroid hormones crucial for sexual differentiation of the brain and reproductive function. In excess, however, androgens may decrease fertility as observed in polycystic ovary syndrome, a common endocrine disorder characterized by oligo/anovulation and/or polycystic ovaries. Hyperandrogenism may also disrupt energy homeostasis, inducing higher central adiposity, insulin resistance, and glucose intolerance, which may exacerbate reproductive dysfunction. Androgens bind to androgen receptors (ARs), which are expressed in many reproductive and metabolic tissues, including brain sites that regulate the hypothalamo-pituitary-gonadal axis and energy homeostasis. The neuronal populations affected by androgen excess, however, have not been defined. We and others have shown that, in mice, AR is highly expressed in leptin receptor (LepRb) neurons, particularly in the arcuate (ARH) and the ventral premammillary nuclei (PMv). Here, we assessed if LepRb neurons, which are critical in the central regulation of energy homeostasis and exert permissive actions on puberty and fertility, have a role in the pathogenesis of female hyperandrogenism. Prenatally androgenized (PNA) mice lacking AR in LepRb cells (LepRbΔAR) show no changes in body mass, body composition, glucose homeostasis, or sexual maturation. They do show, however, a remarkable improvement of estrous cycles combined with normalization of ovary morphology compared to PNA controls. Our findings indicate that the prenatal androgenization effects on adult reproductive physiology (ie, anestrus and anovulation) are mediated by a subpopulation of LepRb neurons directly sensitive to androgens. They also suggest that the effects of hyperandrogenism on sexual maturation and reproductive function in adult females are controlled by distinct neural circuits.

Maternal androgen excess significantly impairs sexual behavior in male and female mouse offspring: Perspective for a biological origin of sexual dysfunction in PCOS

INTRODUCTION

Polycystic ovary syndrome (PCOS) is the most common infertility disorder worldwide, typically characterised by high circulating androgen levels, oligo- or anovulation, and polycystic ovarian morphology. Sexual dysfunction, including decreased sexual desire and increased sexual dissatisfaction, is also reported by women with PCOS. The origins of these sexual difficulties remain largely unidentified. To investigate potential biological origins of sexual dysfunction in PCOS patients, we asked whether the well-characterized, prenatally androgenized (PNA) mouse model of PCOS exhibits modified sex behaviours and whether central brain circuits associated with female sex behaviour are differentially regulated. As a male equivalent of PCOS is reported in the brothers of women with PCOS, we also investigated the impact of maternal androgen excess on the sex behaviour of male siblings.

METHODS

Adult male and female offspring of dams exposed to dihydrotestosterone (PNAM/PNAF) or an oil vehicle (VEH) from gestational days 16 to 18 were tested for a suite of sex-specific behaviours.

RESULTS

PNAM showed a reduction in their mounting capabilities, however, most of PNAM where able to reach ejaculation by the end of the test similar to the VEH control males. In contrast, PNAF exhibited a significant impairment in the female-typical sexual behaviour, lordosis. Interestingly, while neuronal activation was largely similar between PNAF and VEH females, impaired lordosis behaviour in PNAF was unexpectedly associated with decreased neuronal activation in the dorsomedial hypothalamic nucleus (DMH).

CONCLUSION

Taken together, these data link prenatal androgen exposure that drives a PCOS-like phenotype with altered sexual behaviours in both sexes.

GnRH Neuron Excitability and Action Potential Properties Change with Development But Are Not Affected by Prenatal Androgen Exposure

Gonadotropin-releasing hormone (GnRH) neurons produce the final output from the brain to control pituitary gonadotropin secretion and thus regulate reproduction. Disruptions to gonadotropin secretion contribute to infertility, including polycystic ovary syndrome (PCOS) and idiopathic hypogonadotropic hypogonadism. PCOS is the leading cause of infertility in women and symptoms resembling PCOS are observed in girls at or near the time of pubertal onset, suggesting that alterations to the system likely occurred by that developmental period. Prenatally androgenized (PNA) female mice recapitulate many of the neuroendocrine phenotypes observed in PCOS, including altered time of puberty, disrupted reproductive cycles, increased circulating levels of testosterone, and altered gonadotropin secretion patterns. We tested the hypotheses that the intrinsic properties of GnRH neurons change with puberty and with PNA treatment. Whole-cell current-clamp recordings were made from GnRH neurons in brain slices from control and PNA females before puberty at three weeks of age and in adulthood to measure GnRH neuron excitability and action potential (AP) properties. GnRH neurons from adult females were more excitable and required less current to initiate action potential firing compared with three-week-old females. Further, the afterhyperpolarization (AHP) potential of the first spike was larger and its peak was delayed in adulthood. These results indicate development, not PNA, is a primary driver of changes to GnRH neuron intrinsic properties and suggest there may be developmentally-induced changes to voltage-gated ion channels in GnRH neurons that alter how these cells respond to synaptic input.

Enhanced pup retrieval behaviour in a mouse model of polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is the most common endocrinopathy to affect women of reproductive-age world-wide. Hyperandrogenism is both a hallmark feature of PCOS, and is hypothesised to be an underlying mechanism driving the development of the condition in utero. With circulating hormones known to profoundly influence maternal responses in females, we aimed to determine whether maternal behaviour is altered in a well-described prenatally androgenised (PNA) mouse model of PCOS. Mouse dams were administered with dihydrotestosterone or vehicle on days 16, 17 and 18 of pregnancy. Maternal responses were assessed in both the dihydrotestosterone-injected dams following parturition and in their adult female PNA offspring. Exposure of dams to excess androgens during late pregnancy had no detrimental effects on pregnancy outcomes, including gestation length, pup survival and gestational weight gain, or on subsequent maternal behaviour following parturition. By contrast, PNA virgin females, modelling PCOS, exhibited enhanced maternal behaviour when tested in an anxiogenic novel cage environment, with females rapidly retrieving pups and nesting with them. In comparison, most control virgin females failed to complete this retrieval task in the anxiogenic environment. Assessment of progesterone receptor and oestrogen receptor α immunoreactivity in the brains of virgin PNA and control females revealed increased numbers of oestrogen receptor α positive cells in the brains of PNA females in regions well known to be important for maternal behaviour. This suggests that increased oestrogenic signalling in the neural circuit that underlies maternal behaviour may be a possible mechanism by which maternal behaviour is enhanced in PNA female mice.

A brief insight into the etiology, genetics, and immunology of polycystic ovarian syndrome (PCOS)

Polycystic ovarian syndrome (PCOS) is a prevailing endocrine and metabolic disorder occurring in about 6-20% of females in reproductive age. Most symptoms of PCOS arise early during puberty. Since PCOS involves a combination of signs and symptoms, thus it is considered as a heterogeneous disorderliness. The most accepted diagnostic criteria is Rotterdam criteria which involves two of the latter three features: (a) hyperandrogenism, (b) oligo- or an-ovulation, and (c) polycystic ovaries. The persistent hormonal imbalance leads to multiple small antral follicles formation and irregular menstrual cycle, ultimately causing infertility among females. Insulin resistance, cardiovascular diseases, abdominal obesity, psychological disorders, infertility, and cancer are also related to PCOS. These pathophysiologies associated with PCOS are interrelated with each other. Hyperandrogenism causes insulin resistance and hyperglycemia, leading to ROS formation, oxidative stress, and abdominal adiposity. In consequence, inflammation, ROS production, insulin resistance, and hyperandrogenemia also increase. Elevation of AGEs in the body either produced endogenously or consumed from diet exaggerates PCOS symptoms and is also related to ovarian dysfunction. This review summarizes how AGE formation, inflammation, and oxidative stress are significantly essential in PCOS progression. Alterations during prenatal development like exposure to excess AMH, androgens, or toxins (bisphenol-A, endocrine disruptors, etc.) may also be the etiologic mechanism behind PCOS. Although the etiology of this disorder is unclear, environmental and genetic factors are primarily involved. Physical inactivity, as well as unhealthy eating habits, has a vital role in the progression of PCOS. This review outlines a collection of specific genes phenotypically linked with PCOS. Furthermore, beneficial effect of metformin in maintaining endocrine abnormalities and ovarian function is also mentioned. Kisspeptin is a protein which helps in onset of puberty and increases GnRH pulsatile release during ovulation as well as role of KNDy neurons in GnRH pulsatile signal required for reproduction are also elaborated. This review also focuses on the immunology related to PCOS involving chronic low-grade inflammation, and how the alterations within the follicular microenvironment are intricated in the development of infertility in PCOS patients. How PCOS develops following antiepileptic and psychiatric medication is also expanded in this review. Initiation of antiandrogen treatment in early age (≤ 25 years) might be helpful in spontaneous conception in PCOS women. The role of BMP (bone morphogenetic proteins) in folliculogenesis and their expression in oocytes and granulosa cells are also explained. GDF8 and SERPINE1 expression in PCOS is given in detail.

Increased GABA transmission to GnRH neurons after intrahippocampal kainic acid injection in mice is sex-specific and associated with estrous cycle disruption

Patients with epilepsy develop reproductive endocrine comorbidities at a rate higher than that of the general population. Clinical studies have identified disrupted luteinizing hormone (LH) release patterns in patients of both sexes, suggesting potential epilepsy-associated changes in hypothalamic gonadotropin-releasing hormone (GnRH) neuron function. In previous work, we found that GnRH neuron firing is increased in diestrous females and males in the intrahippocampal kainic acid (IHKA) mouse model of temporal lobe epilepsy. Notably, GABA_A receptor activation is depolarizing in adult GnRH neurons. Therefore, here we tested the hypothesis that increased GnRH neuron firing in IHKA mice is associated with increased GABAergic drive to GnRH neurons. When ionotropic glutamate receptors (iGluRs) were blocked to isolate GABAergic postsynaptic currents (PSCs), no differences in PSC frequency were seen between GnRH neurons from control and IHKA diestrous females. In the absence of iGluR blockade, however, GABA PSC frequency was increased in GnRH neurons from IHKA females with disrupted estrous cycles, but not saline-injected controls nor IHKA females without estrous cycle disruption. GABA PSC amplitude was also increased in IHKA females with disrupted estrous cycles. These findings suggest the presence of an iGluR-dependent increase in feed-forward GABAergic transmission to GnRH neurons specific to IHKA females with comorbid cycle disruption. In males, GABA PSC frequency and amplitude were unchanged but PSC duration was reduced. Together, these findings suggest that increased GABA transmission helps drive elevated firing in IHKA females on diestrus and indicate the presence of a sex-specific hypothalamic mechanism underlying reproductive endocrine dysfunction in IHKA mice.

Daughters of polycystic ovary syndrome pregnancies and androgen levels in puberty: a Meta-analysis

Purpose: To provide an overview and critical analysis of the literature related to the circulating androgen levels of daughters of PCOS mothers during prepubertal and pubertal stage who have not yet been diagnosed with PCOS or precocious puberty. Methods: We critically considered and meta-analyzed observational studies comparing androgens concentration in daughters of PCOS mothers compared to daughters of mothers without PCOS. A literature search was conducted in MEDLINE, Scopus and other sources from 01/09/2021 until 01/12/2021. The study followed the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA). The primary outcome included total testosterone levels whereas the secondary outcomes included 17a-hydroxyprogesterone (17-OHP), androstenedione (Δ4Α) and Sex Hormone Binding Globulin (SHBG) levels respectively. Results: Our search yielded 1073 studies, 9 of which were included in our analysis. The results are presented differently according to pubertal stage. Pubertal daughters of PCOS mothers exhibited significantly higher total testosterone (pooled mean difference 14.95 (95%CI: 6.98 to 22.93), higher 17-OHP (pooled mean difference 0.11 (95%CI: 0.02 to 0.20) and lower SHBG levels (pooled mean difference -10.48 (95%CI: -16.46 to -4.61). Instead, prepubertal daughters of PCOS mothers presented greater SHBG levels (pooled mean difference 7.79 (95%CI: 0.03 to 15.54) compared to controls. No difference was found in Δ4Α levels in both groups. Conclusion: The onset of puberty is a critical point in the development of the disease and an early intervention may be imperative.

Key signalling pathways underlying the aetiology of polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is a common endocrine condition characterised by a range of reproductive, endocrine, metabolic and psychological abnormalities. Reports estimate that around 10% of women of reproductive age are affected by PCOS, representing a significant prevalence worldwide, which poses a high economic health burden. As the origin of PCOS remains largely unknown, there is neither a cure nor mechanism-based treatments leaving patient management suboptimal and focused solely on symptomatic treatment. However, if the underlying mechanisms underpinning the development of PCOS were uncovered then this would pave the way for the development of new interventions for PCOS. Recently, there have been significant advances in our understanding of the underlying pathways likely involved in PCOS pathogenesis. Key insights include the potential involvement of androgens, insulin, anti-Müllerian hormone and transforming growth factor beta in the development of PCOS. This review will summarise the significant scientific discoveries on these factors that have enhanced our knowledge of the mechanisms involved in the development of PCOS and discuss the impact these insights may have in shaping the future development of effective strategies for women with PCOS.

Impaired steroid hormone feedback in polycystic ovary syndrome: Evidence from preclinical models for abnormalities within central circuits controlling fertility

Polycystic ovary syndrome (PCOS) is the most common endocrinopathy and cause of infertility in women of reproductive age worldwide. Despite diagnostic features of anovulation, polycystic ovarian morphology, and high androgen secretion indicating the syndrome are the result of ovarian dysfunction, alterations to central neuroendocrine circuits that control reproductive capacity may drive PCOS symptoms. Resistance of gonadotrophin-releasing hormone (GnRH) neurons in the hypothalamus to inhibition by sex steroid hormone-negative feedback leads to a rapid frequency of pulsatile gonadotrophin secretion, which, in turn, drives the ovarian features of the disease. As GnRH neurons do not express steroid hormone receptors, impaired negative feedback is hypothesized to occur within an upstream network that controls GnRH pulse generation. This review will discuss the latest work from preclinical animal models of PCOS used to dissect the specific central mechanisms involved in impaired steroid hormone feedback. In particular, this review will focus on research that indicates neurons in the arcuate nucleus of the hypothalamus that express Kisspeptin, Neurokinin B and Dynorphin (KNDy cells) or γ-aminobutyric acid are targets of androgen-mediated impairment of steroid hormone feedback. Finally, this review will explore the development of therapeutic agents targeting neurons that control LH pulse frequency to resolve PCOS symptoms in the clinic.

Treatments targeting neuroendocrine dysfunction in polycystic ovary syndrome (PCOS)

Polycystic ovary syndrome (PCOS) is the most common endocrine disorder in women of reproductive age and is the leading cause of anovulatory subfertility. Increased gonadotrophin releasing hormone (GnRH) pulsatility in the hypothalamus results in preferential luteinizing hormone (LH) secretion from the pituitary gland, leading to ovarian hyperandrogenism and oligo/anovulation. The resultant hyperandrogenism reduces negative feedback from sex steroids such as oestradiol and progesterone to the hypothalamus, and thus perpetuates the increase in GnRH pulsatility. GnRH neurons do not have receptors for oestrogen, progesterone, or androgens, and thus the disrupted feedback is hypothesized to occur via upstream neurons. Likely candidates for these upstream regulators of GnRH neuronal pulsatility are Kisspeptin, Neurokinin B (NKB), and Dynorphin neurons (termed KNDy neurons). Growing insight into the neuroendocrine dysfunction underpinning the heightened GnRH pulsatility seen in PCOS has led to research on the use of pharmaceutical agents that specifically target the activity of these KNDy neurons to attenuate symptoms of PCOS. This review aims to highlight the neuroendocrine abnormalities that lead to increased GnRH pulsatility in PCOS, and outline data on recent therapeutic advancements that could potentially be used to treat PCOS. Emerging evidence has investigated the use of neurokinin 3 receptor (NK3R) antagonists as a method of reducing GnRH pulsatility and alleviating features of PCOS such as hyperandrogenism. We also consider other potential mechanisms by which increased GnRH pulsatility is controlled, which could form the basis of future avenues of research.

Female sexual behavior is disrupted in a preclinical mouse model of PCOS via an attenuated hypothalamic nitric oxide pathway

Polycystic ovary syndrome (PCOS) is a major endocrine disorder leading to female infertility worldwide. Patients with PCOS also often experience sexual dysfunction; however, the developmental and central mechanisms mediating this behavioral derangement are unclear. Here, we show that prenatal excess of anti-Müllerian hormone triggers PCOS-like impairment in female sexual behavior in mice. Sexual dysfunction in PCOS-like mice is associated with decreased expression of progesterone-sensitive neuronal nitric oxide synthase (nNOS) neurons in the hypothalamus. Chemogenetic inhibition of nNOS neuronal activity in the ventromedial nucleus of the hypothalamus recapitulates PCOS-like sexual dysfunction. Of clinical relevance, administration of nitric oxide donor rescues normal sexual behavior in PCOS-like mice.

Women with polycystic ovary syndrome (PCOS) frequently experience decreased sexual arousal, desire, and sexual satisfaction. While the hypothalamus is known to regulate sexual behavior, the specific neuronal pathways affected in patients with PCOS are not known. To dissect the underlying neural circuitry, we capitalized on a robust preclinical animal model that reliably recapitulates all cardinal PCOS features. We discovered that female mice prenatally treated with anti-Müllerian hormone (PAMH) display impaired sexual behavior and sexual partner preference over the reproductive age. Blunted female sexual behavior was associated with increased sexual rejection and independent of sex steroid hormone status. Structurally, sexual dysfunction was associated with a substantial loss of neuronal nitric oxide synthase (nNOS)-expressing neurons in the ventromedial nucleus of the hypothalamus (VMH) and other areas of hypothalamic nuclei involved in social behaviors. Using in vivo chemogenetic manipulation, we show that nNOS^VMH neurons are required for the display of normal sexual behavior in female mice and that pharmacological replenishment of nitric oxide restores normal sexual performance in PAMH mice. Our data provide a framework to investigate facets of hypothalamic nNOS neuron biology with implications for sexual disturbances in PCOS.

Inhibition of Nicotinamide adenine dinucleotide phosphate oxidase 4 attenuates cell apoptosis and oxidative stress in a rat model of polycystic ovary syndrome through the activation of Nrf-2/HO-1 signaling pathway

Polycystic ovary syndrome (PCOS) is a common reproductive endocrine disorder in reproductive-aged women. In this study, a rat model of PCOS was established by subcutaneous injection of dehydroepiandrosterone (DHEA). NOX4 was highly expressed in PCOS rat ovaries, while its specific role in PCOS remains unclear. Lentivirus-mediated shRNA targeting NOX4 inhibited oxidative stress by reducing ROS, 4-HNE and MDA levels, and increasing SOD and GPX activities in rat ovaries. NOX4 deficiency increased Bcl-2 levels and decreased Bax, cleaved caspase-3 and cleaved caspase-9 levels and DHEA-induced cell apoptosis in rat ovaries. Similar to the in vivo results, NOX4 silencing inhibited oxidative stress and cell apoptosis in DHEA-treated rat granulosa cells. Moreover, NOX4 silencing promoted Nrf-2 translocation, and the expression of Nrf-2 and HO-1 both in vivo and in vitro. Thus, NOX4 deficiency may ameliorate PCOS in rats by reducing oxidative stress and cell apoptosis via activating the Nrf-2/HO-1 signal pathway.

Causality of anthropometric markers associated with polycystic ovarian syndrome: Findings of a Mendelian randomization study

Introduction

Using body mass index (BMI) as a proxy, previous Mendelian randomization (MR) studies found total causal effects of general obesity on polycystic ovarian syndrome (PCOS). Hitherto, total and direct causal effects of general- and central obesity on PCOS have not been comprehensively analyzed.

Objectives

To investigate the causality of central- and general obesity on PCOS using surrogate anthropometric markers.

Methods

Summary GWAS data of female-only, large-sample cohorts of European ancestry were retrieved for anthropometric markers of central obesity (waist circumference (WC), hip circumference (HC), waist-to-hip ratio (WHR)) and general obesity (BMI and its constituent variables–weight and height), from the IEU Open GWAS Project. As the outcome, we acquired summary data from a large-sample GWAS (118870 samples; 642 cases and 118228 controls) within the FinnGen cohort. Total causal effects were assessed via univariable two-sample Mendelian randomization (2SMR). Genetic architectures underlying causal associations were explored. Direct causal effects were analyzed by multivariable MR modelling.

Results

Instrumental variables demonstrated no weak instrument bias (F > 10). Four anthropometric exposures, namely, weight (2.69–77.05), BMI (OR: 2.90–4.06), WC (OR: 6.22–20.27), and HC (OR: 6.22–20.27) demonstrated total causal effects as per univariable 2SMR models. We uncovered shared and non-shared genetic architectures underlying causal associations. Direct causal effects of WC and HC on PCOS were revealed by two multivariable MR models containing exclusively the anthropometric markers of central obesity. Other multivariable MR models containing anthropometric markers of both central- and general obesity showed no direct causal effects on PCOS.

Conclusions

Both and general- and central obesity yield total causal effects on PCOS. Findings also indicated potential direct causal effects of normal weight-central obesity and more complex causal mechanisms when both central- and general obesity are present. Results underscore the importance of addressing both central- and general obesity for optimizing PCOS care.

Unusual suspects: Glial cells in fertility regulation and their suspected role in polycystic ovary syndrome

Gonadotropin-releasing-hormone (GnRH) neurons sitting within the hypothalamus control the production of gametes and sex steroids by the gonads, therefore ensuring survival of species. As orchestrators of reproductive function, GnRH neurons integrate information from external and internal cues. This occurs through an extensively studied neuronal network known as the "GnRH neuronal network." However, the brain is not simply composed of neurons. Evidence suggests a role for glial cells in controlling GnRH neuron activity, secretion and fertility outcomes, although numerous questions remain. Glial cells have historically been seen as support cells for neurons. This idea has been challenged by the discovery that some neurological diseases originate from glial dysfunction. The prevalence of infertility disorders is increasing worldwide, with one in four couples being affected; therefore, it remains essential to understand the mechanisms by which the brain controls fertility. The "GnRH glial network" could be a major player in infertility disorders and represent a potential therapeutic target. In polycystic ovary syndrome (PCOS), the most common infertility disorder of reproductive aged women worldwide, the brain is considered a prime suspect. Recent studies have demonstrated pathological neuronal wiring of the "GnRH neuronal network" in PCOS-like animal models. However, the role of the "GnRH glial network" remains to be elucidated. In this review, I aim to propose glial cells as unusual suspects in infertility disorders such as PCOS. In the first part, I state our current knowledge about the role of glia in the regulation of GnRH neurons and fertility. In the second part, based on our recent findings, I discuss how glial cells could be implicated in PCOS pathology.

Highlights of neuroanatomical discoveries of the mammalian gonadotropin-releasing hormone system

The anatomy and morphology of gonadotropin-releasing hormone (GnRH) neurons makes them both a joy and a challenge to investigate. They are a highly unique population of neurons given their developmental migration into the brain from the olfactory placode, their relatively small number, their largely scattered distribution within the rostral forebrain, and, in some species, their highly varied individual anatomical characteristics. These unique features have posed technological hurdles to overcome and promoted fertile ground for the establishment and use of creative approaches. Historical and more contemporary discoveries defining GnRH neuron anatomy remain critical in shaping and challenging our views of GnRH neuron function in the regulation of reproductive function. We begin this review with a historical overview of anatomical discoveries and developing methodologies that have shaped our understanding of the reproductive axis. We then highlight significant discoveries across specific groups of mammalian species to address some of the important comparative aspects of GnRH neuroanatomy. Lastly, we touch on unresolved questions and opportunities for future neuroanatomical research on this fascinating and important population of neurons.

The role of gonadotropin-releasing hormone neurons in polycystic ovary syndrome

Given the critical central role of gonadotropin-releasing hormone (GnRH) neurons in fertility, it is not surprising that the GnRH neural network is implicated in the pathology of polycystic ovary syndrome (PCOS), the most common cause of anovulatory infertility. Although many symptoms of PCOS relate most proximately to ovarian dysfunction, the central reproductive neuroendocrine system ultimately drives ovarian function through its regulation of anterior pituitary gonadotropin release. The typical cyclical changes in frequency of GnRH release are often absent in women with PCOS, resulting in a persistent high-frequency drive promoting gonadotropin changes (i.e., relatively high luteinizing hormone and relatively low follicle-stimulating hormone concentrations) that contribute to ovarian hyperandrogenemia and ovulatory dysfunction. However, the specific mechanisms underpinning GnRH neuron dysfunction in PCOS remain unclear. Here, we summarize several preclinical and clinical studies that explore the causes of aberrant GnRH secretion in PCOS and the role of disordered GnRH secretion in PCOS pathophysiology.

The polygamous GnRH neuron: Astrocytic and tanycytic communication with a neuroendocrine neuronal population

To ensure the survival of the species, hypothalamic neuroendocrine circuits controlling fertility, which converge onto neurons producing gonadotropin-releasing hormone (GnRH), must respond to fluctuating physiological conditions by undergoing rapid and reversible structural and functional changes. However, GnRH neurons do not act alone, but through reciprocal interactions with multiple hypothalamic cell populations, including several glial and endothelial cell types. For instance, it has long been known that in the hypothalamic median eminence, where GnRH axons terminate and release their neurohormone into the pituitary portal blood circulation, morphological plasticity displayed by distal processes of tanycytes modifies their relationship with adjacent neurons as well as the spatial properties of the neurohemal junction. These alterations not only regulate the capacity of GnRH neurons to release their neurohormone, but also the activation of discrete non-neuronal pathways that mediate feedback by peripheral hormones onto the hypothalamus. Additionally, a recent breakthrough has demonstrated that GnRH neurons themselves orchestrate the establishment of their neuroendocrine circuitry during postnatal development by recruiting an entourage of newborn astrocytes that escort them into adulthood and, via signalling through gliotransmitters such as prostaglandin E2, modulate their activity and GnRH release. Intriguingly, several environmental and behavioural toxins perturb these neuron-glia interactions and consequently, reproductive maturation and fertility. Deciphering the communication between GnRH neurons and other neural cell types constituting hypothalamic neuroendocrine circuits is thus critical both to understanding physiological processes such as puberty, oestrous cyclicity and aging, and to developing novel therapeutic strategies for dysfunctions of these processes, including the effects of endocrine disruptors.

Chronic androgen excess in female mice does not impact luteinizing hormone pulse frequency or putative GABAergic inputs to GnRH neurons

Polycystic ovary syndrome (PCOS) is associated with androgen excess and, frequently, hyperactive pulsatile luteinizing hormone (LH) secretion. Although the origins of PCOS are unclear, evidence from pre-clinical models implicates androgen signalling in the brain in the development of PCOS pathophysiology. Chronic exposure of female mice to dihydrotestosterone (DHT) from 3 weeks of age drives both reproductive and metabolic impairments that are ameliorated by selective androgen receptor (AR) loss from the brain. This suggests centrally driven mechanisms in hyperandrogen-mediated PCOS-like pathophysiology that remain to be defined. Acute prenatal DHT exposure can also model the hyperandrogenism of PCOS, and this is accompanied by increased LH pulse frequency and increased GABAergic innervation of gonadotrophin-releasing hormone (GnRH) neurons. We aimed to determine the impact of chronic exposure of female mice to DHT, which models the hyperandrogenism of PCOS, on pulsatile LH secretion and putative GABAergic input to GnRH neurons. To do this, GnRH-green fluorescent protein (GFP) female mice received either DHT or blank capsules for 90 days from postnatal day 21 (n = 6 or 7 per group). Serial tail-tip blood sampling was used to measure LH dynamics and perfusion-fixed brains were collected and immunolabelled for vesicular GABA transporter (VGAT) to assess putative GABAergic terminals associated with GFP-labelled GnRH neurons. As expected, chronic DHT resulted in acyclicity and significantly increased body weight. However, no differences in LH pulse frequency or the density of VGAT appositions to GnRH neurons were identified between ovary-intact DHT-treated females and controls. Chronic DHT exposure significantly increased the number of AR expressing cells in the hypothalamus, whereas oestrogen receptor α-expressing neuron number was unchanged. Therefore, although chronic DHT exposure from 3 weeks of age increases AR expressing neurons in the brain, the GnRH neuronal network changes and hyperactive LH secretion associated with prenatal androgen excess are not evident. These findings suggest that unique central mechanisms are involved in the reproductive impairments driven by exposure to androgen excess at different developmental stages.

Pathology of hyperandrogenemia in the oocyte of polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is the most common ovulatory disorder in the world and is associated with multiple adverse outcomes. The phenotype is widely varied, with several pathologies contributing to the spectrum of the disease including insulin resistance, obesity and hyperandrogenemia. Of these, the role of hyperandrogenemia and the mechanism by which it causes dysfunction remains poorly understood. Early studies have shown that androgens may affect the metabolic pathways of a cell, and this may pose hazards at the level of the mitochondria. As mitochondria are strictly maternally inherited, this would provide an exciting explanation not only to the pathophysiology of PCOS as a disease, but also to the inheritance pattern. This review seeks to summarize what is known about PCOS and associated adverse outcomes with focus on the role of hyperandrogenemia and specific emphasis on the oocyte.

Polycystic Ovary Syndrome and the Neuroendocrine Consequences of Androgen Excess

Polycystic ovary syndrome (PCOS) is a major endocrine disorder strongly associated with androgen excess and frequently leading to female infertility. Although classically considered an ovarian disease, altered neuroendocrine control of gonadotropin-releasing hormone (GnRH) neurons in the brain and abnormal gonadotropin secretion may underpin PCOS presentation. Defective regulation of GnRH pulse generation in PCOS promotes high luteinizing hormone (LH) pulsatile secretion, which in turn overstimulates ovarian androgen production. Early and emerging evidence from preclinical models suggests that maternal androgen excess programs abnormalities in developing neuroendocrine circuits that are associated with PCOS pathology, and that these abnormalities are sustained by postpubertal elevation of endogenous androgen levels. This article will discuss experimental evidence, from the clinic and in preclinical animal models, that has significantly contributed to our understanding of how androgen excess influences the assembly and maintenance of neuroendocrine impairments in the female brain. Abnormal central gamma-aminobutyric acid (GABA) signaling has been identified in both patients and preclinical models as a possible link between androgen excess and elevated GnRH/LH secretion. Enhanced GABAergic innervation and drive to GnRH neurons is suspected to contribute to the pathogenesis and early manifestation of neuroendocrine derangement in PCOS. Accordingly, this article also provides an overview of GABA regulation of GnRH neuron function from prenatal development to adulthood to discuss possible avenues for future discovery research and therapeutic interventions. © 2022 American Physiological Society. Compr Physiol 12:3347-3369, 2022.

A review of the hormones involved in the endocrine dysfunctions of polycystic ovary syndrome and their interactions

Polycystic ovary syndrome (PCOS) affects up to 20% of women but remains poorly understood. It is a heterogeneous condition with many potential comorbidities. This review offers an overview of the dysregulation of the reproductive and metabolic systems associated with PCOS. Review of the literature informed the development of a comprehensive summarizing 'wiring' diagram of PCOS-related features. This review provides a justification for each diagram aspect from the relevant academic literature, and explores the interactions between the hypothalamus, ovarian follicles, adipose tissue, reproductive hormones and other organ systems. The diagram will provide an efficient and useful tool for those researching and treating PCOS to understand the current state of knowledge on the complexity and variability of PCOS.

Prenatal androgen treatment impairs the suprachiasmatic nucleus arginine-vasopressin to kisspeptin neuron circuit in female mice

Polycystic ovary syndrome (PCOS) is associated with elevated androgen and luteinizing hormone (LH) secretion and with oligo/anovulation. Evidence indicates that elevated androgens impair sex steroid hormone feedback regulation of pulsatile LH secretion. Hyperandrogenemia in PCOS may also disrupt the preovulatory LH surge. The mechanisms through which this might occur, however, are not fully understood. Kisspeptin (KISS1) neurons of the rostral periventricular area of the third ventricle (RP3V) convey hormonal cues to gonadotropin-releasing hormone (GnRH) neurons. In rodents, the preovulatory surge is triggered by these hormonal cues and coincident timing signals from the central circadian clock in the suprachiasmatic nucleus (SCN). Timing signals are relayed to GnRH neurons, in part, via projections from SCN arginine-vasopressin (AVP) neurons to RP3V^KISS1 neurons. Because rodent SCN cells express androgen receptors (AR), we hypothesized that these circuits are impaired by elevated androgens in a mouse model of PCOS. In prenatally androgen-treated (PNA) female mice, SCN Ar expression was significantly increased compared to that found in prenatally vehicle-treated mice. A similar trend was seen in the number of Avp-positive SCN cells expressing Ar. In the RP3V, the number of kisspeptin neurons was preserved. Anterograde tract-tracing, however, revealed reduced SCN^AVP neuron projections to the RP3V and a significantly lower proportion of RP3V^KISS1 neurons with close appositions from SCN^AVP fibers. Functional assessments showed, on the other hand, that RP3V^KISS1 neuron responses to AVP were maintained in PNA mice. These findings indicate that PNA changes some of the neural circuits that regulate the preovulatory surge. These impairments might contribute to ovulatory dysfunction in PNA mice modeling PCOS.