Obesity Alters POMC and Kisspeptin Neuron Cross Talk Leading to Reduced Luteinizing Hormone in Male Mice.

Obesity is associated with hypogonadism in males, characterized by low testosterone and sperm number. Previous studies determined that these stem from dysregulation of hypothalamic circuitry that regulates reproduction, by unknown mechanisms. Herein, we used mice fed chronic high-fat diet, which mimics human obesity, to determine mechanisms of impairment at the level of the hypothalamus, in particular gonadotropin-releasing hormone (GnRH) neurons that regulate luteinizing hormone (LH), which then regulates testosterone. Consistent with obese humans, we demonstrated lower LH, and lower pulse frequency of LH secretion, but unchanged pituitary responsiveness to GnRH. LH pulse frequency is regulated by pulsatile GnRH secretion, which is controlled by kisspeptin. Peripheral and central kisspeptin injections, and DREADD-mediated activation of kisspeptin neurons, demonstrated that kisspeptin neurons were suppressed in obese mice. Thus, we investigated regulators of kisspeptin secretion. We determined that the LH response to NMDA was lower in obese mice, corresponding to fewer glutamate receptors in kisspeptin neurons, which may be critical for kisspeptin synchronization. Given that kisspeptin neurons also interact with anorexigenic POMC neurons, which are affected by obesity, we examined their cross talk, and determined that the LH response to either DREADD-mediated activation of POMC neurons or central injection of αMSH, a product of POMC, is abolished in obese mice. This was accompanied by diminished levels of αMSH receptor, MC4R, in kisspeptin neurons. Together, our studies determined that obesity leads to the downregulation of receptors that regulate kisspeptin neurons, which is associated with lower LH pulse frequency, leading to lower LH and hypogonadism.

Androgen signalling in the ovaries and endometrium.

Currently, our understanding of hormonal regulation within the female reproductive system is largely based on our knowledge of estrogen and progesterone signalling. However, while the important functions of androgens in male physiology are well known, it is also recognized that androgens play critical roles in the female reproductive system. Further, androgen signalling is altered in a variety of gynaecological conditions, including endometriosis and polycystic ovary syndrome, indicative of regulatory roles in endometrial and ovarian function. Co-regulatory mechanisms exist between different androgens, estrogens, and progesterone, resulting in a complex network of steroid hormone interactions. Evidence from animal knockout studies, in vitro experiments, and human data indicate that androgen receptor expression is cell-specific and menstrual cycle stage-dependent, with important regulatory roles in the menstrual cycle, endometrial biology, and follicular development in the ovaries. This review will discuss the expression and co-regulatory interactions of androgen receptors, highlighting the complexity of the androgen signalling pathway in the endometrium and ovaries, and the synthesis of androgens from additional alternative pathways previously disregarded as male-specific. Moreover, it will illustrate the challenges faced when studying androgens in female biology, and the need for a more in-depth, integrative view of androgen metabolism and signalling in the female reproductive system.

Microglia: sculptors of the polycystic ovary syndrome (PCOS)-like brain?

In brief: Neuroendocrine dysfunction and transgenerational susceptibility associated with polycystic ovary syndrome (PCOS) suggest that programmed changes within the brain contribute to adult development of the syndrome. This review discusses a potentially important role for microglia in mediating prenatal androgen-programmed changes in the female brain that contribute to PCOS-like features. Abstract: Several lines of evidence support a role for the brain in both the development and maintenance of polycystic ovary syndrome (PCOS), the most common cause of anovulatory infertility worldwide. Persistently elevated luteinizing hormone secretion and impaired gonadal steroid hormone feedback in PCOS patients suggest impairments within the neuronal networks that regulate the reproductive axis. Evidence from preclinical models has linked androgen excess during prenatal life with altered structure and function of the developing female brain that might underpin syndrome development in adulthood. Studies investigating the mechanisms by which excess androgens program changes in the female brain have highlighted an important role for microglia. This review discusses how these non-neuronal cells shape the developing female brain in response to excess androgens and focuses on how microglia may be involved in the development of the neuroendocrine dysfunctions associated with PCOS.

Local kisspeptin excitation of rat oxytocin neurones in late pregnancy.

The hormone, oxytocin, is synthesised by magnocellular neurones of the supraoptic and paraventricular nuclei and is released from the posterior pituitary gland into the circulation to trigger uterine contractions during parturition. Kisspeptin fibre density increases around the supraoptic nucleus over pregnancy and intracerebroventricular kisspeptin excites oxytocin neurones only in late pregnancy. However, the mechanism of this excitation is unknown. Here, we found that microdialysis administration of kisspeptin into the supraoptic nucleus consistently increased the action potential (spike) firing rate of oxytocin neurones in urethane-anaesthetised late-pregnant rats (gestation day 18-21) but not in non-pregnant rats. Hazard analysis of action potential firing showed that kisspeptin specifically increased the probability of another action potential firing immediately after each action potential (post-spike excitability) in late-pregnant rats. Patch-clamp electrophysiology in hypothalamic slices showed that bath application of kisspeptin did not affect action potential frequency or baseline membrane potential in supraoptic nucleus neurones. Moreover, kisspeptin superfusion did not affect the frequency or amplitude of excitatory postsynaptic currents or inhibitory postsynaptic currents in supraoptic nucleus neurones. Taken together, these studies suggest that kisspeptin directly activates oxytocin neurones in late pregnancy, at least in part, via increased post-spike excitability. KEY POINTS: Oxytocin secretion is triggered by action potential firing in magnocellular neurones of the hypothalamic supraoptic and paraventricular nuclei to induce uterine contractions during birth. In late pregnancy, kisspeptin expression increases in rat periventricular nucleus neurones that project to the oxytocin system. Here, we show that intra-supraoptic nucleus administration of kisspeptin increases the action potential firing rate of oxytocin neurones in anaesthetised late-pregnant rats, and that the increased firing rate is associated with increased oxytocin neurone excitability immediately after each action potential. By contrast, kisspeptin superfusion of hypothalamic slices did not affect the activity of supraoptic nucleus neurones or the strength of local synaptic inputs to supraoptic nucleus neurones. Hence, kisspeptin might activate oxytocin neurons in late pregnancy by transiently increasing oxytocin neuron excitability after each action potential.

Activation of a Classic Hunger Circuit Slows Luteinizing Hormone Pulsatility.

INTRODUCTION: The central regulation of fertility is carefully coordinated with energy homeostasis, and infertility is frequently the outcome of energy imbalance. Neurons in the hypothalamus expressing neuropeptide Y and agouti-related peptide (NPY/AgRP neurons) are strongly implicated in linking metabolic cues with fertility regulation. OBJECTIVE: We aimed here to determine the impact of selectively activating NPY/AgRP neurons, critical regulators of metabolism, on the activity of luteinizing hormone (LH) pulse generation. METHODS: We employed a suite of in vivo optogenetic and chemogenetic approaches with serial measurements of LH to determine the impact of selectively activating NPY/AgRP neurons on dynamic LH secretion. In addition, electrophysiological studies in ex vivo brain slices were employed to ascertain the functional impact of activating NPY/AgRP neurons on gonadotropin-releasing hormone (GnRH) neurons. RESULTS: Selective activation of NPY/AgRP neurons significantly decreased post-castration LH secretion. This was observed in males and females, as well as in prenatally androgenized females that recapitulate the persistently elevated LH pulse frequency characteristic of polycystic ovary syndrome (PCOS). Reduced LH pulse frequency was also observed when optogenetic stimulation was restricted to NPY/AgRP fiber projections surrounding GnRH neuron cell bodies in the rostral preoptic area. However, electrophysiological studies in ex vivo brain slices indicated these effects were likely to be indirect. CONCLUSIONS: These data demonstrate the ability of NPY/AgRP neuronal signaling to modulate and, specifically, reduce GnRH/LH pulse generation. The findings suggest a mechanism by which increased activity of this hunger circuit, in response to negative energy balance, mediates impaired fertility in otherwise reproductively fit states, and highlight a potential mechanism to slow LH pulsatility in female infertility disorders, such as PCOS, that are associated with hyperactive LH secretion.

Polycystic ovary syndrome: Understanding the role of the brain.

Polycystic ovary syndrome (PCOS) is a prevalent endocrine disorder and the leading cause of anovulatory infertility. Characterised by hyperandrogenism, menstrual dysfunction and polycystic ovaries, PCOS is a broad-spectrum disorder unlikely to stem from a single common origin. Although commonly considered an ovarian disease, the brain is now a prime suspect in both the ontogeny and pathology of PCOS. We discuss here the neuroendocrine impairments present in PCOS that implicate involvement of the brain and review evidence gained from pre-clinical models of the syndrome about the specific brain circuitry involved. In particular, we focus on the impact that developmental androgen excess and adult hyperandrogenemia have in programming and regulating brain circuits important in the central regulation of fertility. The studies discussed here provide compelling support for the importance of the brain in PCOS ontogeny and pathophysiology and highlight the need for a better understanding of the underlying mechanisms involved.

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

Polycystic ovarian syndrome (PCOS), the leading cause of female infertility, is associated with an increase in luteinizing hormone (LH) pulse frequency, implicating abnormal steroid hormone feedback to gonadotropin-releasing hormone (GnRH) neurons. This study investigated whether modifications in the synaptically connected neuronal network of GnRH neurons could account for this pathology. The PCOS phenotype was induced in mice following prenatal androgen (PNA) exposure. Serial blood sampling confirmed that PNA elicits increased LH pulse frequency and impaired progesterone negative feedback in adult females, mimicking the neuroendocrine abnormalities of the clinical syndrome. Imaging of GnRH neurons revealed greater dendritic spine density that correlated with increased putative GABAergic but not glutamatergic inputs in PNA mice. Mapping of steroid hormone receptor expression revealed that PNA mice had 59% fewer progesterone receptor-expressing cells in the arcuate nucleus of the hypothalamus (ARN). To address whether increased GABA innervation to GnRH neurons originates in the ARN, a viral-mediated Cre-lox approach was taken to trace the projections of ARN GABA neurons in vivo. Remarkably, projections from ARN GABAergic neurons heavily contacted and even bundled with GnRH neuron dendrites, and the density of fibers apposing GnRH neurons was even greater in PNA mice (56%). Additionally, this ARN GABA population showed significantly less colocalization with progesterone receptor in PNA animals compared with controls. Together, these data describe a robust GABAergic circuit originating in the ARN that is enhanced in a model of PCOS and may underpin the neuroendocrine pathophysiology of the syndrome.

Development of an excitatory kisspeptin projection to the oxytocin system in late pregnancy.

KEY POINTS: Oxytocin release from the posterior pituitary gland stimulates uterine contraction during birth but the central mechanisms that activate oxytocin neurones for birth are not well characterized. We found that that kisspeptin fibre density around oxytocin neurones increases in late-pregnant rats. These kisspeptin fibres originated from hypothalamic periventricular nucleus neurones that upregulated kisspeptin expression in late pregnancy. Oxytocin neurones were excited by central kisspeptin administration in late-pregnant rats but not in non-pregnant rats or early- to mid-pregnant rats. Our results reveal the emergence of a new excitatory kisspeptin projection to the oxytocin system in late pregnancy that might contribute to oxytocin neurone activation for birth. ABSTRACT: The hormone oxytocin promotes uterine contraction during parturition. Oxytocin is synthesized by magnocellular neurones in the hypothalamic supraoptic and paraventricular nuclei and is released into the circulation from the posterior pituitary gland in response to action potential firing. Systemic kisspeptin administration increases oxytocin neurone activity to elevate plasma oxytocin levels. Here, immunohistochemistry revealed that rats on the expected day of parturition (day 21 of gestation) had a higher density of kisspeptin-positive fibres in the perinuclear zone surrounding the supraoptic nucleus (which provides dense glutamatergic and GABAergic innervation to the supraoptic nucleus) than was evident in non-pregnant rats. Retrograde tracing showed the kisspeptin projections to the perinuclear zone originated from the hypothalamic periventricular nucleus. Quantitative RT-PCR showed that kisspeptin receptor mRNA, Kiss1R mRNA, was expressed in the perinuclear zone-supraoptic nucleus and that the relative Kiss1R mRNA expression does not change over the course of pregnancy. Finally, intracerebroventricular administration of kisspeptin increased the firing rate of oxytocin neurones in anaesthetized late-pregnant rats (days 18-21 of gestation) but not in non-pregnant rats, or in early- or mid-pregnant rats. Taken together, these results suggest that kisspeptin expression is upregulated in the periventricular nucleus projection to the perinuclear zone of the supraoptic nucleus towards the end of pregnancy. Hence, this input might activate oxytocin neurones during parturition.

Defining Subpopulations of Arcuate Nucleus GABA Neurons in Male, Female, and Prenatally Androgenized Female Mice.

BACKGROUND/AIMS: Arcuate nucleus (ARN) γ-aminobutyric acid (GABA) neurons are implicated in many critical homeostatic mechanisms, from food intake to fertility. To determine the functional relevance of ARN GABA neurons, it is essential to define the neurotransmitters co-expressed with and potentially co-released from ARN GABA neurons. METHODS: The present study investigated the expression of markers of specific signaling molecules by ARN GABA neurons in brain sections from male, female, and, in some cases, prenatally androgen-treated (PNA) female, vesicular GABA transporter (VGaT)-ires-Cre/tdTomato reporter mice. Immunofluorescence for kisspeptin, ß-endorphin, neuropeptide Y (NPY), tyrosine hydroxylase (TH) and neuronal nitric oxide synthase (nNOS) was detected by confocal microscopy, and co-localization with tdTomato VGaT reporter expression throughout the ARN was quantified. RESULTS: GABA neurons rarely co-localized with kisspeptin (<2%) or ß-endorphin (<1%), and only a small proportion of kisspeptin (∼10%) or ß-endorphin (∼3%) neurons co-localized with VGaT in male and female mice. In contrast, one-third of ARN GABA neurons co-localized with NPY, and nearly all NPY neurons (>95%) co-localized with VGaT across groups. Both TH and nNOS labeling was co-localized with ∼10% of ARN GABA neurons. The proportion of TH neurons co-localized with VGaT was significantly greater in males than either control or PNA females, and the proportion of nNOS neurons co-localizing VGaT was higher in control and PNA females compared with males. CONCLUSION: These data highlight NPY as a significant subpopulation of ARN GABA neurons, demonstrate no significant impact of PNA on signal co-expression, and, for the first time, show sexually dimorphic co-expression patterns of TH and nNOS with ARN GABA neurons.

Systemic metabolic benefits of 17α-estradiol are not exclusively mediated by ERα in glutamatergic or GABAergic neurons.

17α-Estradiol (17αE2), a less-feminising enantiomer of 17ß-estradiol, has been shown to prolong lifespan and improve metabolic health in a sex-specific manner in male, but not in female mice. Recent studies have demonstrated the pivotal role of estrogen receptor α (ERα) in mediating the effects of 17αE2 on metabolic health. However, the specific tissues and/or neuronal signalling pathways that 17αE2 acts through remain to be elucidated. ERα expression in glutamatergic and GABAergic neurons (principal excitatory and inhibitory neurons respectively) in the hypothalamus is essential for estradiol signalling. Therefore, we hypothesised that knocking out ERα from one of these neuronal populations would attenuate the established beneficial metabolic effects of 17αE2 in male mice exposed to a high fat diet. To test this hypothesis we used two established brain specific ERα KO models, targeting either glutamatergic or GABAergic neurons (Vglut2/Vgat-ERαKO). We show that both of these ERα KO models exhibit a strong reduction in ERα expression in the arcuate nucleus of the hypothalamus, a control centre for metabolic regulation. Deletion of ERα from GABAergic neurons significantly diminished the effect of 17αE2 on body weight relative to controls, although these animals still show metabolic benefits with 17αE2 treatment. The response to 17αE2 was unaffected by ERα deletion in glutamatergic neurons. Our results support a benefit of 17αE2 treatment in protection against metabolic dysfunction, but these effects do not depend on exclusive ERα expression in glutamatergic and GABAergic neurons and persist when ERα expression is strongly reduced in the arcuate nucleus of the hypothalamus.

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.

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.

Recent advances in emerging PCOS therapies.

Polycystic ovary syndrome is a prevalent endocrinopathy involving androgen excess, and anovulatory infertility. The disorder is also associated with many comorbidities such as obesity and hyperinsulinemia, and an increased risk of cardiovascular complications. Reproductive, endocrine, and metabolic symptoms are highly variable, with heterogenous phenotypes adding complexity to clinical management of symptoms. This review highlights recent findings regarding emerging therapies for treating polycystic ovary syndrome, including i) pharmacological agents to target androgen excess, ii) modulation of kisspeptin signalling to target central neuroendocrine dysregulation, and iii) novel insulin sensitisers to combat peripheral metabolic dysfunction.

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.

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.

Comparing Literature- and Subreddit-Derived Laboratory Values in Polycystic Ovary Syndrome (PCOS): Validation of Clinical Data Posted on PCOS Reddit Forums.

BACKGROUND: Polycystic ovary syndrome (PCOS) is a heterogeneous condition that affects 4% to 21% of people with ovaries. Inaccessibility or dissatisfaction with clinical treatment for PCOS has led to some individuals with the condition discussing their experiences in specialized web-based forums. OBJECTIVE: This study explores the feasibility of using such web-based forums for clinical research purposes by gathering and analyzing laboratory test results posted in an active PCOS forum, specifically the PCOS subreddit hosted on Reddit. METHODS: We gathered around 45,000 posts from the PCOS subreddit. A random subset of 5000 posts was manually read, and the presence of laboratory test results was labeled. These labeled posts were used to train a machine learning model to identify which of the remaining posts contained laboratory results. The laboratory results were extracted manually from the identified posts. These self-reported laboratory test results were compared with values in the published literature to assess whether the results were concordant with researcher-published values for PCOS cohorts. A total of 10 papers were chosen to represent published PCOS literature, with selection criteria including the Rotterdam diagnostic criteria for PCOS, a publication date within the last 20 years, and at least 50 participants with PCOS. RESULTS: Overall, the general trends observed in the laboratory test results from the PCOS web-based forum were consistent with clinically reported PCOS. A number of results, such as follicle stimulating hormone, fasting insulin, and anti-Mullerian hormone, were concordant with published values for patients with PCOS. The high consistency of these results among the literature and when compared to the subreddit suggests that follicle stimulating hormone, fasting insulin, and anti-Mullerian hormone are more consistent across PCOS phenotypes than other test results. Some results, such as testosterone, sex hormone-binding globulin, and homeostasis model assessment-estimated insulin resistance index, were between those of PCOS literature values and normal values, as defined by clinical testing limits. Interestingly, other results, including dehydroepiandrosterone sulfate, luteinizing hormone, and fasting glucose, appeared to be slightly more dysregulated than those reported in the literature. CONCLUSIONS: The differences between the forum-posted results and those published in the literature may be due to the selection process in clinical studies and the possibility that the forum disproportionally describes PCOS phenotypes that are less likely to be alleviated with medical intervention. However, the degree of concordance in most laboratory test values implied that the PCOS web-based forum participants were representative of research-identified PCOS cohorts. This validation of the PCOS subreddit grants the possibility for more research into the contents of the subreddit and the idea of undertaking similar research using the contents of other medical internet forums.

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.

Deletion of Androgen Receptors From Kisspeptin Neurons Prevents PCOS Features in a Letrozole Mouse Model.

Polycystic ovarian syndrome (PCOS) is the leading cause of anovulatory infertility and is a heterogenous condition associated with a range of reproductive and metabolic impairments. While its etiology remains unclear, hyperandrogenism and impaired steroid negative feedback have been identified as key factors underpinning the development of PCOS-like features both clinically and in animal models. We tested the hypothesis that androgen signaling in kisspeptin-expressing neurons, which are key drivers of the neuroendocrine reproductive axis, is critically involved in PCOS pathogenesis. To this end, we used a previously validated letrozole (LET)-induced hyperandrogenic mouse model of PCOS in conjunction with Cre-lox technology to generate female mice exhibiting kisspeptin-specific deletion of androgen receptor (KARKO mice) to test whether LET-treated KARKO females are protected from the development of reproductive and metabolic PCOS-like features. LET-treated mice exhibited hyperandrogenism, and KARKO mice exhibited a significant reduction in the coexpression of kisspeptin and androgen receptor mRNA compared to controls. In support of our hypothesis, LET-treated KARKO mice exhibited improved estrous cyclicity, ovarian morphology, and insulin sensitivity in comparison to LET-treated control females. However, KARKO mice were not fully protected from the effects of LET-induced hyperandrogenism and still exhibited reduced corpora lutea numbers and increased body weight gain. These data indicate that increased androgen signaling in kisspeptin-expressing neurons plays a critical role in PCOS pathogenesis but highlight that other mechanisms are also involved.

Dendro-dendritic bundling and shared synapses between gonadotropin-releasing hormone neurons.

The pulsatile release of gonadotropin-releasing hormone (GnRH) is critical for mammalian fertility, but the mechanisms underlying the synchronization of GnRH neurons are unknown. In the present study, the full extent of the GnRH neuron dendritic tree was visualized by patching and filling individual GnRH neurons with biocytin in acute brain slices from adult GnRH-green fluorescent protein (GFP) transgenic mice. Confocal analysis of 42 filled GnRH neurons from male and female adult mice revealed that the dendrites of the great majority of GnRH neurons (86%) formed multiple close appositions with dendrites of other GnRH neurons. Two types of interactions were encountered; the predominant interaction was one of vertical dendritic bundling where dendrites were found to wrap around each other in the same axis. The other interaction was one in which a GnRH neuron dendrite intercepted other GnRH neuron dendrites in a perpendicular fashion. Electron microscopy using pre-embedded, silver-enhanced immunogold labeling for both GnRH and GFP peptides in GnRH-GFP transgenic mice, confirmed that GnRH neuron dendrites were often immediately juxtaposed. Membrane specializations, including punctae and zonula adherens, were found connecting adjacent dendritic elements of GnRH neurons. Remarkably, individual afferent axon terminals were found to synapse with multiple GnRH neuron dendrites at sites of bundling. Together, these data demonstrate that GnRH neurons are not isolated from one another but, rather, interconnected via their long dendritic extensions. The observation of shared synaptic input to bundled GnRH neuron dendrites suggests a mechanism of GnRH neuron synchronization.

Physiological regulation of leptin as an integrative signal of reproductive readiness.

Reproductive function is tightly regulated by both environmental and physiological factors. The adipose-derived hormone leptin has been identified as one such critical factor that relays information about peripheral energy availability to the centrally-governed HPG axis to ensure there is sufficient energy availability to support the high energy demands of mammalian reproduction. In the absence of adequate central leptin signaling, reproductive function is suppressed. While leptin levels are predominantly regulated by adiposity, circulating leptin levels are also under the modulatory influence of other factors, such as stress system activation, circadian rhythmicity, and immune activation and the inflammatory response. Furthermore, changes in leptin sensitivity can affect the degree to which leptin exerts its influence on the neuroendocrine reproductive axis. This review will discuss the different mechanisms by which leptin serves to integrate and relay information about metabolic, psychological, environmental and immune conditions to the central neuronal network that governs reproductive function.