Prenatal Testosterone Treatment Leads to Changes in the Morphology of KNDy Neurons, Their Inputs, and Projections to GnRH Cells in Female Sheep

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

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

Placental mRNA Expression of Neurokinin B Is Increased in PCOS Pregnancies with Female Offspring

Current research suggests that polycystic ovary syndrome (PCOS) might originate in utero and implicates the placenta in its pathogenesis. Kisspeptin (KISS1) and neurokinin B (NKB) are produced by the placenta in high amounts, and they have been implicated in several pregnancy complications associated with placental dysfunction. However, their placental expression has not been studied in PCOS. We isolated mRNA after delivery from the placentae of 31 PCOS and 37 control women with term, uncomplicated, singleton pregnancies. The expression of KISS1, NKB, and neurokinin receptors 1, 2, and 3 was analyzed with real-time polymerase chain reaction, using β-actin as the reference gene. Maternal serum and umbilical cord levels of total testosterone, sex hormone-binding globulin (SHBG), free androgen index (FAI), androstenedione, dehydroepiandrosterone sulfate (DHEAS), Anti-Mullerian hormone (AMH), and estradiol were also assessed. NKB placental mRNA expression was higher in PCOS women versus controls in pregnancies with female offspring. NKB expression depended on fetal gender, being higher in pregnancies with male fetuses, regardless of PCOS. NKB was positively correlated with umbilical cord FAI and AMH, and KISS1 was positively correlated with cord testosterone and FAI; there was also a strong positive correlation between NKB and KISS1 expression. Women with PCOS had higher serum AMH and FAI and lower SHBG than controls. Our findings indicate that NKB might be involved in the PCOS-related placental dysfunction and warrant further investigation. Studies assessing the placental expression of NKB should take fetal gender into consideration.

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.

Prenatal Origins of Endometriosis Pathology and Pain: Reviewing the Evidence of a Role for Low Testosterone

Endometriosis is a polygenic, estrogen-dependent, inflammatory disorder of uncertain aetiology associated with pain, infertility and reduced quality of life. While the positive association between endometriosis and estrogen is established, a suite of recent studies has demonstrated an inverse association between the presence of endometriosis lesions and levels of testosterone both prenatally and postnatally. The following narrative review provides new insights into the roles of testosterone in the aetiology, diagnosis, and management of endometriosis and associated symptoms, especially pain. A relatively short anogenital distance (AGD) is indicative of lower levels of testosterone during fetal development. A shorter AGD has recently been correlated with both a higher risk of developing endometriosis in adult life, and with known correlates of endometriosis including earlier onset of reproductive cycling, lower ovarian follicle number, lower postnatal testosterone, and premature ovarian insufficiency. During adult life, lower levels of testosterone are positively associated with key comorbidities of endometriosis, including days per month of pelvic pain and increased pain sensitivity. Biochemically, lower levels of testosterone are associated with higher levels of pro-inflammatory IL-1β and lower levels of β-endorphin. In rodents, prenatal administration of testosterone to females reduces their pain sensitivity in adulthood. The emerging convergent links of endometriosis with low prenatal and postnatal testosterone provide evidence of a centrally mediated effect beginning in early prenatal development, and persisting through adult life, with notable effects on pain sensitivity. They generate a novel conceptual framework for understanding, studying and treating this disorder, whereby endometriosis is mediated by a combination of high estrogen in endometrial tissue with low systemic and ovarian testosterone.

Prenatal kisspeptin antagonist exposure prevents polycystic ovary syndrome development in prenatally-androgenized rats in adulthood: An experimental study

Background

Increased levels of kisspeptin are associated with hypothalamus-pituitary-ovary axis dysfunction. It may lead to the development of polycystic ovary syndrome (PCOS).

Objective

We aimed to investigate the effect of prenatal kisspeptin antagonist exposure on the development of PCOS in prenatally androgenized rats in adulthood.

Materials and Methods

In this experimental study, pregnant rats were injected with free testosterone (T, 5 mg/day) or T+P271 (kisspeptin antagonist) on the 20 th day of the pregnancy period (n = 5 in each group), while rats in the control group received solvent. Female offspring were examined in terms of anogenital distance (AGD), anovaginal distance (AVD), vaginal opening, serum total testosterone (TT) levels, ovarian follicles, and the regularity of estrous cycles in adulthood. AGD and AVD were measured using a vernier caliper. TT levels were measured using the enzyme-linked immunosorbent assay method. Ovaries were fixed in 10% formalin, tissue processing was done by a standard protocol, and then ovaries embedded in paraffin. 5 μm-thickness ovarian sections mounted on a glass slide, deparaffinized, and stained using Harris's Hematoxylin and Eosin Y.

Results

AGD, AVD (p < 0.001), TT levels (p = 0.02), and the numbers of preantral and antral follicles (p < 0.001) in the ovaries were significantly decreased in prenatally T-P271-exposed rats compared to prenatally T-exposed rats. The age of vaginal opening was early in T-P271-exposed rats compared to prenatally T-exposed rats (p < 0.001). The number of corpora lutea was significantly increased in T-P271-exposed rats (p < 0.001). No cystic follicles were observed in the ovaries of prenatally T-P271-exposed rats. Prenatally T-P271-exposed rats had regular estrous cycles compared to prenatally T-exposed rats.

Conclusion

Prenatal exposure to kisspeptin antagonist can prevent PCOS development in prenatally androgenized rats in adulthood.

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.

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.

Kisspeptin neuron electrophysiology: Intrinsic properties, hormonal modulation, and regulation of homeostatic circuits

The obligatory role of kisspeptin (KISS1) and its receptor (KISS1R) in regulating the hypothalamic-pituitary-gonadal axis, puberty and fertility was uncovered in 2003. In the few years that followed, an impressive body of work undertaken in many species established that neurons producing kisspeptin orchestrate gonadotropin-releasing hormone (GnRH) neuron activity and subsequent GnRH and gonadotropin hormone secretory patterns, through kisspeptin-KISS1R signaling, and mediate many aspects of gonadal steroid hormone feedback regulation of GnRH neurons. Here, we review knowledge accrued over the past decade, mainly in genetically modified mouse models, of the electrophysiological properties of kisspeptin neurons and their regulation by hormonal feedback. We also discuss recent progress in our understanding of the role of these cells within neuronal circuits that control GnRH neuron activity and GnRH secretion, energy balance and, potentially, other homeostatic and reproductive functions.

Kisspeptin Modulation of Reproductive Function

Kisspeptin is a peptide expressed mainly in the infundibular nucleus of the hypothalamus. Kisspeptin plays a crucial role in the regulation of reproductive functions. It is regarded as the most important factor responsible for the control of the hypothalamic–pituitary–gonadal axis, the onset of puberty, and the regulation of menstruation and fertility. Kisspeptin activity influences numerous processes such as steroidogenesis, follicular maturation, ovulation, and ovarian senescence. The identification of kisspeptin receptor mutations that cause hypogonadotropic hypogonadism has initiated studies on the role of kisspeptin in puberty. Pathologies affecting the neurons secreting kisspeptin play a major role in the development of PCOS, functional hypothalamic amenorrhea, and perimenopausal vasomotor symptoms. Kisspeptin analogs (both agonists and antagonists), therefore, may be beneficial as therapy in those afflicted with such pathologies. The aim of this review is to summarize the influence of kisspeptin in the physiology and pathology of the reproductive system in humans, as well as its potential use in therapy.

Early programming of reproductive health and fertility: novel neuroendocrine mechanisms and implications in reproductive medicine

BACKGROUND

According to the Developmental Origins of Health and Disease (DOHaD) hypothesis, environmental changes taking place during early maturational periods may alter normal development and predispose to the occurrence of diverse pathologies later in life. Indeed, adverse conditions during these critical developmental windows of high plasticity have been reported to alter the offspring developmental trajectory, causing permanent functional and structural perturbations that in the long term may enhance disease susceptibility. However, while solid evidence has documented that fluctuations in environmental factors, ranging from nutrient availability to chemicals, in early developmental stages (including the peri-conceptional period) have discernible programming effects that increase vulnerability to develop metabolic perturbations, the impact and eventual mechanisms involved, of such developmental alterations on the reproductive phenotype of offspring have received less attention.

OBJECTIVE AND RATIONALE

This review will summarize recent advances in basic and clinical research that support the concept of DOHaD in the context of the impact of nutritional and hormonal perturbations, occurring during the periconceptional, fetal and early postnatal stages, on different aspects of reproductive function in both sexes. Special emphasis will be given to the effects of early nutritional stress on the timing of puberty and adult gonadotropic function, and to address the underlying neuroendocrine pathways, with particular attention to involvement of the Kiss1 system in these reproductive perturbations. The implications of such phenomena in terms of reproductive medicine will also be considered.

SEARCH METHODS

A comprehensive MEDLINE search, using PubMed as main interface, of research articles and reviews, published mainly between 2006 and 2021, has been carried out. Search was implemented using multiple terms, focusing on clinical and preclinical data from DOHaD studies, addressing periconceptional, gestational and perinatal programming of reproduction. Selected studies addressing early programming of metabolic function have also been considered, when relevant.

OUTCOMES

A solid body of evidence, from clinical and preclinical studies, has documented the impact of nutritional and hormonal fluctuations during the periconceptional, prenatal and early postnatal periods on pubertal maturation, as well as adult gonadotropic function and fertility. Furthermore, exposure to environmental chemicals, such as bisphenol A, and maternal stress has been shown to negatively influence pubertal development and gonadotropic function in adulthood. The underlying neuroendocrine pathways and mechanisms involved have been also addressed, mainly by preclinical studies, which have identified an, as yet incomplete, array of molecular and neurohormonal effectors. These include, prominently, epigenetic regulatory mechanisms and the hypothalamic Kiss1 system, which likely contribute to the generation of reproductive alterations in conditions of early nutritional and/or metabolic stress. In addition to the Kiss1 system, other major hypothalamic regulators of GnRH neurosecretion, such as γ-aminobutyric acid and glutamate, may be targets of developmental programming.

WIDER IMPLICATIONS

This review addresses an underdeveloped area of reproductive biology and medicine that may help to improve our understanding of human reproductive disorders and stresses the importance, and eventual pathogenic impact, of early determinants of puberty, adult reproductive function and fertility.

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.

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.

Prenatal Androgen Exposure Alters KNDy Neurons and Their Afferent Network in a Model of Polycystic Ovarian Syndrome

Polycystic ovarian syndrome (PCOS), the most common endocrinopathy affecting women worldwide, is characterized by elevated luteinizing hormone (LH) pulse frequency due to the impaired suppression of gonadotrophin-releasing hormone (GnRH) release by steroid hormone negative feedback. Although neurons that co-express kisspeptin, neurokinin B, and dynorphin (KNDy cells) were recently defined as the GnRH/LH pulse generator, little is understood about their role in the pathogenesis of PCOS. We used a prenatal androgen-treated (PNA) mouse model of PCOS to determine whether changes in KNDy neurons or their afferent network underlie altered negative feedback. First, we identified elevated androgen receptor gene expression in KNDy cells of PNA mice, whereas progesterone receptor and dynorphin gene expression was significantly reduced, suggesting elevated androgens in PCOS disrupt progesterone negative feedback via direct actions upon KNDy cells. Second, we discovered GABAergic and glutamatergic synaptic input to KNDy neurons was reduced in PNA mice. Retrograde monosynaptic tract-tracing revealed a dramatic reduction in input originates from sexually dimorphic afferents in the preoptic area, anteroventral periventricular nucleus, anterior hypothalamic area and lateral hypothalamus. These results reveal 2 sites of neuronal alterations potentially responsible for defects in negative feedback in PCOS: changes in gene expression within KNDy neurons, and changes in synaptic inputs from steroid hormone-responsive hypothalamic regions. How each of these changes contribute to the neuroendocrine phenotype seen in in PCOS, and the role of specific sets of upstream KNDy afferents in the process, remains to be determined.

Prenatal Androgen Treatment Does Not Alter the Firing Activity of Hypothalamic Arcuate Kisspeptin Neurons in Female Mice

Neuroendocrine control of reproduction is disrupted in many individuals with polycystic ovary syndrome (PCOS), who present with increased luteinizing hormone (LH), and presumably gonadotropin-releasing hormone (GnRH), release frequency, and high androgen levels. Prenatal androgenization (PNA) recapitulates these phenotypes in primates and rodents. Female offspring of mice injected with dihydrotestosterone (DHT) on gestational days 16-18 exhibit disrupted estrous cyclicity, increased LH and testosterone, and increased GnRH neuron firing rate as adults. PNA also alters the developmental trajectory of GnRH neuron firing rates, markedly blunting the prepubertal peak in firing that occurs in three-week (3wk)-old controls. GnRH neurons do not express detectable androgen receptors and are thus probably not the direct target of DHT. Rather, PNA likely alters GnRH neuronal activity by modulating upstream neurons, such as hypothalamic arcuate neurons co-expressing kisspeptin, neurokinin B (gene Tac2), and dynorphin, also known as KNDy neurons. We hypothesized PNA treatment changes firing rates of KNDy neurons in a similar age-dependent manner as GnRH neurons. We conducted targeted extracellular recordings (0.5-2 h) of Tac2-identified KNDy neurons from control and PNA mice at 3wks of age and in adulthood. About half of neurons were quiescent (<0.005 Hz). Long-term firing rates of active cells varied, suggestive of episodic activity, but were not different among groups. Short-term burst firing was also similar. We thus reject the hypothesis that PNA alters the firing rate of KNDy neurons. This does not preclude altered neurosecretory output of KNDy neurons, involvement of other neuronal populations, or in vivo networks as critical drivers of altered GnRH firing rates in PNA mice.

Neurokinin 3 Receptor Antagonism Ameliorates Key Metabolic Features in a Hyperandrogenic PCOS Mouse Model

Polycystic ovary syndrome (PCOS) is a prevalent endocrine condition characterized by a range of endocrine, reproductive, and metabolic abnormalities. At present, management of women with PCOS is suboptimal as treatment is only symptomatic. Clinical and experimental advances in our understanding of PCOS etiology support a pivotal role for androgen neuroendocrine actions in PCOS pathogenesis. Hyperandrogenism is a key PCOS trait and androgen actions play a role in regulating the kisspeptin-/neurokinin B-/dynorphin (KNDy) system. This study aimed to investigate if targeted antagonism of neurokinin B signaling through the neurokinin 3 receptor (NK3R) would reverse PCOS traits in a dihydrotestosterone (DHT)-induced mouse model of PCOS. After 3 months, DHT exposure induced key reproductive PCOS traits of cycle irregularity and ovulatory dysfunction, and PCOS-like metabolic traits including increased body weight; white and brown fat pad weights; fasting serum triglyceride and glucose levels, and blood glucose incremental area under the curve. Treatment with a NK3R antagonist (MLE4901) did not impact the observed reproductive defects. In contrast, following NK3R antagonist treatment, PCOS-like females displayed decreased total body weight, adiposity, and adipocyte hypertrophy, but increased respiratory exchange ratio, suggesting NK3R antagonism altered the metabolic status of the PCOS-like females. NK3R antagonism did not improve circulating serum triglyceride or fasted glucose levels. Collectively, these findings demonstrate that NK3R antagonism may be beneficial in the treatment of adverse metabolic features associated with PCOS and support neuroendocrine targeting in the development of novel therapeutic strategies for PCOS.

Evidence that synaptic plasticity of glutamatergic inputs onto KNDy neurones during the ovine follicular phase is dependent on increasing levels of oestradiol

Neurones in the arcuate nucleus co-expressing kisspeptin, neurokinin B (NKB) and dynorphin (KNDy) play a critical role in the control of gonadotrophin-releasing hormone (GnRH) and luteinising hormone (LH) secretion. In sheep, KNDy neurones mediate both steroid-negative- and -positive-feedback during pulsatile and preovulatory surge secretions of GnRH/LH, respectively. In addition, KNDy neurones receive glutamatergic inputs expressing vGlut2, a glutamate transporter that serves as a marker for those terminals, from both KNDy neurones and other populations of glutamatergic neurones. Previous work reported higher numbers of vGlut2-positive axonal inputs onto KNDy neurones during the LH surge than in luteal phase ewes. In the present study, we further examined the effects of the ovarian steroids progesterone (P) and oestradiol (E₂ ) on glutamatergic inputs to KNDy neurones. Ovariectomised (OVX) ewes received either no further treatment (OVX) or steroid treatments that mimicked the luteal phase (low E₂  + P), and early (low E₂ ) or late follicular (high E₂ ) phases of the oestrous cycle (n = 4 or 5 per group). Brain sections were processed for triple-label immunofluorescent detection of NKB/vGlut2/synaptophysin and analysed using confocal microscopy. We found higher numbers of vGlut2 inputs onto KNDy neurones in high E₂ compared to the other three treatment groups. These results suggest that synaptic plasticity of glutamatergic inputs onto KNDy neurones during the ovine follicular phase depend on increasing levels of E₂ required for the preovulatory GnRH/surge. These synaptic changes likely contribute to the positive-feedback action of oestrogen on GnRH/LH secretion and thus the generation of the preovulatory surge in the sheep.

Clinical Applications of Serum Anti-Müllerian Hormone Measurements in Both Males and Females: An Update

Infertility is one of the most common non-communicable diseases, affecting both men and women equally. Ovarian reserve, the number of primordial follicles in the ovaries is believed to be the most important determinants for female fertility. Anti-Müllerian hormone (AMH) secreted from granulosa cells of growing follicles is recognized as the most important biomarker for ovarian reserve. Ovarian reserve models have been developed using AMH and other hormonal indicators, thus childbearing plans and reproductive choices could be arranged by women. In assisted reproductive technology cycles, measurement of AMH helps to predict ovarian response and guide recombinant follicle-stimulating hormone dosing in women. Serum AMH level is increasingly being recognized as a potential surrogate marker for polycystic ovarian morphology, one of the criteria for diagnosis of polycystic ovarian syndrome. AMH is also secreted by Sertoli cells of testes in men, and AMH measurements in the prediction of surgical sperm recovery rate in men have also been investigated. AMH levels are significantly higher in boys than in girls before puberty. Therefore, serum levels of AMH in combination with testosterone is used for the differential diagnosis of disorders of sex development, anorchia, non-obstructive azoospermia, and persistent Müllerian duct syndrome. Recently, serum AMH measurements have also been used in fertility preservation programs in oncofertility, screening for granulosa cell tumors, and prediction of menopause applications. In this review, we will focus on clinical application of AMH in fertility assessments for healthy men and women, as well as for cancer patients.

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Anti-Müllerian hormone (AMH) plays a key role in models assessing ovarian reserve

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AMH is used for the differential diagnosis of disorders of sex development

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AMH provides a molecular marker for related fertility and infertility disorders

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An international standard will aid in the development of various AMH assays

Developmental programming: gestational testosterone excess disrupts LH secretion in the female sheep fetus

BACKGROUND

Prenatal testosterone (T) excess results in reproductive and metabolic perturbations in female sheep that closely recapitulate those seen in women with polycystic ovary syndrome (PCOS). At the neuroendocrine level, prenatal T-treated sheep manifest increased pituitary sensitivity to GnRH and subsequent LH hypersecretion. In this study, we investigated the early effects of gestational T-treatment on LH secretion and pituitary function in the female sheep fetus. Additionally, because prenatal T effects can be mediated via the androgen receptor or due to changes in insulin homeostasis, prenatal co-treatment with an androgen antagonist (flutamide) or an insulin sensitizer (rosiglitazone) were tested.

METHODS

Pregnant sheep were treated from gestational day (GD) 30 to 90 with either: 1) vehicle (control); 2) T-propionate (~ 1.2 mg/kg); 3) T-propionate and flutamide (15 mg/kg/day); and 4) T-propionate and rosiglitazone (8 mg/day). At GD 90, LH concentrations were determined in the uterine artery (maternal) and umbilical artery (fetal), and female fetuses were euthanized. Pituitary glands were collected, weighed, and protein level of several key regulators of LH secretion was determined.

RESULTS

Fetal pituitary weight was significantly reduced by prenatal T-treatment. Flutamide completely prevented the reduction in pituitary weight, while rosiglitazone only partially prevented this reduction. Prenatal T markedly reduced fetal LH concentrations and flutamide co-treatment partially restored LH to control levels. Prenatal T resulted in a marked reduction in LH-β protein level, which was associated with a reduction in GnRH receptor and estrogen receptor-α levels and an increase in androgen receptor. With the exception of androgen receptor, flutamide co-treatment completely prevented these alterations in the fetal pituitary, while rosiglitazone largely failed to prevent these changes. Prenatal T-treatment did not alter the protein levels of insulin receptor-β and activation (phosphorylation) of the insulin signaling pathways.

CONCLUSIONS

These findings demonstrate that prenatal T-treatment results in reduced fetal LH secretion, reduced fetal pituitary weight, and altered protein levels of several regulators of gonadotropin secretion. The observations that flutamide co-treatment prevented these changes suggest that programming during fetal development likely occurs via direct androgen actions.

Arcuate nucleus kisspeptin response to increased nutrition in rams

Rams respond to acute nutritional supplementation by increasing the frequency of gonadotrophin-releasing hormone (GnRH) pulses. Kisspeptin neurons may mediate the effect of environmental cues on GnRH secretion, so we tested whether the ram response to nutrition involves activation of kisspeptin neurons in the arcuate nucleus (ARC), namely kisspeptin, neurokin B, dynorphin (KNDy) neurons. Rams were given extra lupin grain with their normal ration. Blood was sampled before feeding, and continued until animals were killed for collection of brain tissue at 2 or 11h after supplementation. In supplemented rams, LH pulse frequency increased after feeding, whereas control animals showed no change. Within the caudal ARC, there were more kisspeptin neurons in supplemented rams than in controls and a higher proportion of kisspeptin cells coexpressed Fos, regardless of the time the rams were killed. There were more Fos cells in the mid-ARC and mid-dorsomedial hypothalamus of the supplemented compared with control rams. No effect of nutrition was found on kisspeptin expression in the rostral or mid-ARC, or on GnRH expression in the preoptic area. Kisspeptin neurons in the caudal ARC appear to mediate the increase in GnRH and LH production due to acute nutritional supplementation, supporting the hypothesised role of the KNDy neurons as the pulse generator for GnRH.

Animal Models to Understand the Etiology and Pathophysiology of Polycystic Ovary Syndrome

More than 1 out of 10 women worldwide are diagnosed with polycystic ovary syndrome (PCOS), the leading cause of female reproductive and metabolic dysfunction. Despite its high prevalence, PCOS and its accompanying morbidities are likely underdiagnosed, averaging > 2 years and 3 physicians before women are diagnosed. Although it has been intensively researched, the underlying cause(s) of PCOS have yet to be defined. In order to understand PCOS pathophysiology, its developmental origins, and how to predict and prevent PCOS onset, there is an urgent need for safe and effective markers and treatments. In this review, we detail which animal models are more suitable for contributing to our understanding of the etiology and pathophysiology of PCOS. We summarize and highlight advantages and limitations of hormonal or genetic manipulation of animal models, as well as of naturally occurring PCOS-like females.

Morphological and functional evidence for sexual dimorphism in neurokinin B signalling in the retrochiasmatic area of sheep

Neurokinin B (NKB) is critical for fertility in humans and stimulates gonadotrophin-releasing hormone/luteinising hormone (LH) secretion in several species, including sheep. There is increasing evidence that the actions of NKB in the retrochiasmatic area (RCh) contribute to the induction of the preovulatory LH surge in sheep. In the present study, we determined whether there are sex differences in the response to RCh administration of senktide, an agonist to the NKB receptor (neurokinin receptor-3 [NK3R]), and in NKB and NK3R expression in the RCh of sheep. To normalise endogenous hormone concentrations, animals were gonadectomised and given implants to mimic the pattern of ovarian steroids seen in the oestrous cycle. In females, senktide microimplants in the RCh produced an increase in LH concentrations that lasted for at least 8 hours after the start of treatment, whereas a much shorter increment (approximately 2 hours) was seen in males. We next collected tissue from gonadectomised lambs 18 hours after the insertion of oestradiol implants that produce an LH surge in female, but not male, sheep for immunohistochemical analysis of NKB and NK3R expression. As expected, there were more NKB-containing neurones in the arcuate nucleus of females than males. Interestingly, there was a similar sexual dimorphism in NK3R-containing neurones in the RCh, NKB-containing close contacts onto these RCh NK3R neurones, and overall NKB-positive fibres in this region. These data demonstrate that there are both functional and morphological sex differences in NKB-NK3R signalling in the RCh and raise the possibility that this dimorphism contributes to the sex-dependent ability of oestradiol to induce an LH surge in female sheep.

Abnormal GnRH Pulsatility in Polycystic Ovary Syndrome: Recent Insights

Although the fundamental symptoms of polycystic ovary syndrome (PCOS) relate most directly to ovarian dysfunction, central neuroendocrine systems play a prominent role in its pathophysiology. Gonadotropin-releasing hormone (GnRH) pulse generator resistance to negative feedback contributes to rapid GnRH pulse secretion, which promotes gonadotropin abnormalities that foster ovarian hyperandrogenemia and ovulatory dysfunction. The causes of GnRH neuron dysfunction, however, have remained enigmatic. In this review, we highlight a number of recent preclinical and clinical studies pertinent to the neuroendocrine abnormalities of PCOS, including those that have provided important insights into the relevance of animal models with PCOS-like features, the potential roles of kisspeptin and γ-aminobutyric acid (GABA)-ergic neurons, and the potential role of anti-Müllerian hormone.

Metabolic dysfunction in polycystic ovary syndrome: Pathogenic role of androgen excess and potential therapeutic strategies

Background

Polycystic ovary syndrome (PCOS) is the most common endocrinopathy among reproductive age women. Although its cardinal manifestations include hyperandrogenism, oligo/anovulation, and/or polycystic ovarian morphology, PCOS women often display also notable metabolic comorbidities. An array of pathogenic mechanisms have been implicated in the etiology of this heterogeneous endocrine disorder; hyperandrogenism at various developmental periods is proposed as a major driver of the metabolic and reproductive perturbations associated with PCOS. However, the current understanding of the pathophysiology of PCOS-associated metabolic disease is incomplete, and therapeutic strategies used to manage this syndrome's metabolic complications remain limited.

Scope of review

This study is a systematic review of the potential etiopathogenic mechanisms of metabolic dysfunction frequently associated with PCOS, with special emphasis on the metabolic impact of androgen excess on different metabolic tissues and the brain. We also briefly summarize the therapeutic approaches currently available to manage metabolic perturbations linked to PCOS, highlighting current weaknesses and future directions.

Major conclusions

Androgen excess plays a prominent role in the development of metabolic disturbances associated with PCOS, with a discernible impact on key peripheral metabolic tissues, including the adipose, liver, pancreas, and muscle, and very prominently the brain, contributing to the constellation of metabolic complications of PCOS, from obesity to insulin resistance. However, the current understanding of the pathogenic roles of hyperandrogenism in metabolic dysfunction of PCOS and the underlying mechanisms remain largely incomplete. In addition, the development of more efficient, even personalized therapeutic strategies for the metabolic management of PCOS patients persists as an unmet need that will certainly benefit from a better comprehension of the molecular basis of this heterogeneous syndrome.

Pathological pulses in PCOS

Polycystic ovary syndrome (PCOS) is a highly prevalent endocrine disorder associated with hyperandrogenism and anovulation. Although a spectrum disorder, many women with PCOS exhibit elevated luteinizing hormone (LH) pulse frequency and an elevated LH to follicle stimulating hormone ratio. This aberrant pattern of gonadotrophin signalling drives many of the downstream ovarian features of PCOS, including increased androgen synthesis, and indicates neuroendocrine impairments upstream. Decreased responsiveness to gonadal steroid hormone negative feedback in PCOS patients points toward dysfunction within the gonadotropin-releasing hormone (GnRH) neuronal network in the brain. Excessive androgen exposure during development or over pubertal onset can recapitulate the neuroendocrine pathology of PCOS in pre-clinical models, and these models have been fundamental in beginning to pick apart the specific central mechanisms involved. This mini-review will briefly describe the pathology of PCOS associated with high frequency GnRH/LH pulses and then highlight what is currently known, and yet to be discovered, about the central mechanisms involved.

Prenatal Testosterone Exposure Alters GABAergic Synaptic Inputs to GnRH and KNDy Neurons in a Sheep Model of Polycystic Ovarian Syndrome

Prenatal testosterone (T)-treated female sheep display reproductive deficits similar to women with polycystic ovarian syndrome (PCOS), including an increase in LH pulse frequency due to actions of the central GnRH pulse generator. In this study, we used multiple-label immunocytochemistry to investigate the possibility of changes in the γ-aminobutyric acid (GABA) neurotransmitter system at two key components of the GnRH pulse generator in prenatal T-treated sheep: kisspeptin/neurokinin B/dynorphin (KNDy) neurons of the arcuate nucleus, and GnRH neurons in the preoptic area (POA) and mediobasal hypothalamus (MBH). We observed a significant decrease and increase, respectively, in the number of GABAergic synapses onto POA and MBH GnRH neurons in prenatal T-treated ewes; additionally, there was a significant increase in the number of GABAergic inputs onto KNDy neurons. To determine the actions of GABA on GnRH and KNDy neurons, we examined colocalization with the chloride transporters NKCC1 and KCC2, which indicate stimulatory or inhibitory activation of neurons by GABA, respectively. Most GnRH neurons in both POA and MBH colocalized NKCC1 cotransporter whereas none contained the KCC2 cotransporter. Most KNDy neurons colocalized either NKCC1 or KCC2, and 28% of the KNDy population contained NKCC1 alone. Therefore, we suggest that, as in the mouse, GABA in the sheep is stimulatory to GnRH neurons, as well as to a subset of KNDy neurons. Increased numbers of stimulatory GABAergic inputs to both MBH GnRH and KNDy neurons in prenatal T-treated animals may contribute to alterations in steroid feedback control and increased GnRH/LH pulse frequency seen in this animal model of PCOS.

Neuroendocrine Impairments of Polycystic Ovary Syndrome

Polycystic ovary syndrome (PCOS) is a prevalent and distressing disorder of largely unknown etiology. Although PCOS defined by ovarian dysfunction, accumulating evidence supports a critical role for the brain in the ontogeny and pathophysiology of PCOS. A critical pathological feature of PCOS is impaired gonadal steroid hormone negative feedback to the GnRH neuronal network in the brain that regulates fertility. This impairment is associated with androgen excess, a cardinal feature of PCOS. Impaired steroid hormone feedback to GnRH neurons is thought to drive hyperactivity of the neuroendocrine axis controlling fertility, leading to a vicious cycle of androgen excess and reproductive dysfunction. Decades of clinical research have been unable to uncover the mechanisms underlying this impairment, because of the extreme difficulty in studying the brain in humans. It is only recently, with the development of preclinical models of PCOS, that we have begun to unravel the role of the brain in the development and progression of PCOS. Here, we provide a succinct overview of what is known about alterations in the steroid hormone-sensitive GnRH neuronal network that may underlie the neuroendocrine defects in clinical PCOS, with a particular focus on those that may contribute to impaired progesterone negative feedback, and the likely role of androgens in driving this impairment.

The Mechanism of Androgen Actions in PCOS Etiology

Polycystic ovary syndrome (PCOS) is the most common endocrine condition in reproductive-age women. By comprising reproductive, endocrine, metabolic and psychological features—the cause of PCOS is still unknown. Consequently, there is no cure, and management is persistently suboptimal as it depends on the ad hoc management of symptoms only. Recently it has been revealed that androgens have an important role in regulating female fertility. Androgen actions are facilitated via the androgen receptor (AR) and transgenic Ar knockout mouse models have established that AR-mediated androgen actions have a part in regulating female fertility and ovarian function. Considerable evidence from human and animal studies currently reinforces the hypothesis that androgens in excess, working via the AR, play a key role in the origins of polycystic ovary syndrome (PCOS). Identifying and confirming the locations of AR-mediated actions and the molecular mechanisms involved in the development of PCOS is critical to provide the knowledge required for the future development of innovative, mechanism-based interventions for the treatment of PCOS. This review summarises fundamental scientific discoveries that have improved our knowledge of androgen actions in PCOS etiology and how this may form the future development of effective methods to reduce symptoms in patients with PCOS.

The Role of the Brain in the Pathogenesis and Physiology of Polycystic Ovary Syndrome (PCOS)

Polycystic ovary syndrome (PCOS) is a common reproductive endocrine disorder, affecting at least 10% of women of reproductive age. PCOS is typically characterized by the presence of at least two of the three cardinal features of hyperandrogenemia (high circulating androgen levels), oligo- or anovulation, and cystic ovaries. Hyperandrogenemia increases the severity of the condition and is driven by increased luteinizing hormone (LH) pulse secretion from the pituitary. Indeed, PCOS women display both elevated mean LH levels, as well as an elevated frequency of LH pulsatile secretion. The abnormally high LH pulse frequency, reflective of a hyperactive gonadotropin-releasing hormone (GnRH) neural circuit, suggests a neuroendocrine basis to either the etiology or phenotype of PCOS. Several studies in preclinical animal models of PCOS have demonstrated alterations in GnRH neurons and their upstream afferent neuronal circuits. Some rodent PCOS models have demonstrated an increase in GnRH neuron activity that correlates with an increase in stimulatory GABAergic innervation and postsynaptic currents onto GnRH neurons. Additional studies have identified robust increases in hypothalamic levels of kisspeptin, another potent stimulator of GnRH neurons. This review outlines the different brain and neuroendocrine changes in the reproductive axis observed in PCOS animal models, discusses how they might contribute to either the etiology or adult phenotype of PCOS, and considers parallel findings in PCOS women.

New Perspectives on the Pathogenesis of PCOS: Neuroendocrine Origins

Polycystic ovary syndrome (PCOS) is the most common endocrine condition in reproductive-aged women. It is characterized by reproductive, endocrine, metabolic, and psychological features. The cause of PCOS is unknown, thus there is no cure and its management remains suboptimal because it relies on the ad hoc empirical management of symptoms only. We review here the strong support for PCOS having a neuroendocrine origin. In particular, we focus on the role of aberrant hypothalamic-pituitary function and associated hyperandrogenism, and their role as major drivers of the mechanisms underpinning the development of PCOS. This important information now provides a target site and a potential mechanism for the future development of novel, targeted, and mechanism-based effective therapies for the treatment of PCOS.

Kisspeptin and the regulation of the reproductive axis in domestic animals

The control of reproductive processes involves the integration of a number of factors from the internal and external environment, with the final output signal of these processes being the pulsatile secretion of gonadotrophin releasing hormone (GnRH) from the hypothalamus. These factors include the feedback actions of sex steroids, feed intake and nutritional status, season/photoperiod, pheromones, age and stress. Understanding these factors and how they influence GnRH secretion and hence reproduction is important for the management of farm animals. There is evidence that the RF-amide neuropeptide, kisspeptin, may be involved in relaying the effects of these factors to the GnRH neurons. This paper will review the evidence from the common domestic animals (sheep, goats, cattle, horses and pigs), that kisspeptin neurons are i) regulated by the factors listed above, ii) contact GnRH neurons, and iii) involved in the regulation of GnRH/gonadotrophin secretion.

KNDy Cells Revisited

In the past decade since kisspeptin/neurokinin B/dynorphin (KNDy) cells were first identified in the mammalian hypothalamus, a plethora of new research has emerged adding insights into the role of this neuronal population in reproductive neuroendocrine function, including the basis for GnRH pulse generation and the mechanisms underlying the steroid feedback control of GnRH secretion. In this mini-review, we provide an update of evidence regarding the roles of KNDy peptides and their postsynaptic receptors in producing episodic GnRH release and assess the relative contribution of KNDy neurons to the "GnRH pulse generator." In addition, we examine recent work investigating the role of KNDy neurons as mediators of steroid hormone negative feedback and review evidence for their involvement in the preovulatory GnRH/LH surge, taking into account species differences that exist among rodents, ruminants, and primates. Finally, we summarize emerging roles of KNDy neurons in other aspects of reproductive function and in nonreproductive functions and discuss critical unresolved questions in our understanding of KNDy neurobiology.

How to choose the suitable animal model of polycystic ovary syndrome?

Polycystic ovary syndrome (PCOS) is a gynecological metabolic and endocrine disorder with uncertain etiology. To understand the etiology of PCOS or the evaluation of various therapeutic agents, different animal models have been introduced. Considering this fact that is difficult to develop an animal model that mimics all aspects of this syndrome, but, similarity of biological, anatomical, and/or biochemical features of animal model to the human PCOS phenotypes can increase its application. This review paper evaluates the recently researched animal models and introduced the best models for different research purposes in PCOS studies. During January 2013 to January 2017, 162 studies were identified which applied various kinds of animal models of PCOS including rodent, primate, ruminant and fish. Between these models, prenatal and pre-pubertal androgen rat models and then prenatal androgen mouse model have been studied in detail than others. The comparison of main features of these models with women PCOS demonstrates higher similarity of these three models to human conditions. Thereafter, letrozole models can be recommended for the investigation of various aspects of PCOS. Interestingly, similarity of PCOS features of post-pubertal insulin and human chorionic gonadotropin rat models with women PCOS were considerable which can make it as a good choice for future investigations.

Enhancement of Melanocortin-4 Receptor (MC4R) and Constancy of Kiss1 mRNAs Expression in the Hypothalamic Arcuate Nucleus in a Model of Polycystic Ovary Syndrome Rat

Background:

Hypothalamic Melanocortin-4Receptor (MC4R) and kiss1/kisspeptin systems play roles in reproductive processes. This study was conducted to evaluate changes in MC4R and kiss1 genes expression in the arcuate nucleus (ARC) of the hypothalamus and its relationship with polycystic ovary syndrome (PCOS) in rats.

Materials and Methods:

In the current experimental study, 24 female rats were randomly and equally allocated into nulliparous and primiparous groups and then were divided into two subgroups of PCOS and control. PCOS was induced by exposure to continuous light. Sex-related hormones were evaluated by radioimmunoassay or immunoradiometric assay. Expressions of MC4R and kiss1 gene in the ARC of the hypothalamus of the rats were evaluated by real-time PCR. Histomorphometric alterations of ovaries were compared between groups.

Results:

Number of tertiary follicles and their size and number of atretic follicles in the PCOS subgroups were more than those in the controls (P<0.05) whereas the number of secondary follicles and corpus luteum in the PCOS subgroups were lower than those in the controls (P<0.05). Antrum and total diameters of tertiary follicles in the PCOS subgroups were greater and granulosa layer diameter was lower than those in the controls (P<0.05). The MC4R mRNA expression in the PCOS subgroups was 6.5-fold in nulliparous and 3.5-fold in primiparous groups more than their controls’ pairs (P<0.05). However, parity did not affect the expression of MC4R gene (P>0.05). The kiss1 mRNA expression in the PCOS and control subgroups was not significantly different (P>0.05).

Conclusion:

Overexpression of MC4R gene after PCOS induction in the ARC of the hypothalamus may link to metabolic disorders of induced PCOS in the rats. However, alteration in the kiss1 mRNA expression after PCOS induction was not observed in the rats.

Accelerated Episodic Luteinizing Hormone Release Accompanies Blunted Progesterone Regulation in PCOS-like Female Rhesus Monkeys (Macaca Mulatta) Exposed to Testosterone during Early-to-Mid Gestation

BACKGROUND/AIMS

Ovarian theca cell hyperandrogenism in women with polycystic ovary syndrome (PCOS) is compounded by androgen receptor-mediated impairment of estradiol and progesterone negative feedback regulation of episodic luteinizing hormone (LH) release. The resultant LH hypersecretion, likely the product of accelerated episodic release of gonadotropin-releasing hormone (GnRH) from the median eminence of the hypothalamus, hyperstimulates ovarian theca cell steroidogenesis, enabling testosterone (T) and androstenedione excess. Prenatally androgenized (PA) female monkeys exposed to fetal male levels of T during early-to-mid gestation, when adult, demonstrate PCOS-like traits, including high T and LH levels. This study tests the hypothesis that progesterone resistance-associated acceleration in episodic LH release contributes to PA monkey LH excess.

METHODS

A total of 4 PA and 3 regularly cycling, healthy control adult female rhesus monkeys of comparable age and body mass index underwent (1) a 10 h, frequent intravenous sampling assessment for LH episodic release, immediately followed by (2) IV infusion of exogenous GnRH to quantify continuing pituitary LH responsiveness, and subsequently (3) an SC injection of a progesterone receptor antagonist, mifepristone, to examine LH responses to blockade of progesterone-mediated action.

RESULTS

Compared to controls, the relatively hyperandrogenic PA females exhibited ~100% increase (p = 0.037) in LH pulse frequency, positive correlation of LH pulse amplitude (p = 0.017) with androstenedione, ~100% greater increase (p = 0.034) in acute (0-10 min) LH responses to exogenous GnRH, and an absence (p = 0.008) of modest LH elevation following acute progesterone receptor blockade suggestive of diminished progesterone negative feedback.

CONCLUSION

Such dysregulation of LH release in PCOS-like monkeys implicates impaired feedback control of episodic release of hypothalamic GnRH reminiscent of PCOS neuroendocrinopathy.

Is foetal hyperexposure to androgens a cause of PCOS?

BACKGROUND

Polycystic ovary syndrome (PCOS) is the most common endocrinopathy affecting reproductive-aged women. The pathophysiology of this syndrome is still not completely understood but recent evidence suggests that the intra-uterine environment may be a key factor in the pathogenesis of PCOS, in particular, hyperexposure of the foetus to androgens. High concentrations of maternal serum testosterone during pregnancy have been shown to influence behaviour during childhood, the prevalence of autism disorders and anti-Mullerian hormone (AMH) concentrations in adolescence. They are also thought to re-programme the female reproductive axis to induce the features of PCOS in later life: oligo/anovulation, polycystic ovaries, hyperandrogenism and insulin resistance (IR). Support for this developmental theory for the aetiology of PCOS is gathering momentum, following results from first animal studies and now human data, which lend credence to many aspects of this hypothesis.

OBJECTIVE AND RATIONALE

In this review the recent available evidence is presented to support the hypothesis that hyperandrogenic changes in the intra-uterine environment could play a major part in the aetiological basis of PCOS.

SEARCH METHODS

An extensive PubMED and MEDline database search was conducted. Relevant studies were identified using a combination of search terms: 'polycystic ovary syndrome', 'PCOS', 'aetiology', 'anti-Mullerian hormone', 'AMH', 'pathogenesis', 'kisspeptin', 'hyperandrogenism', 'insulin resistance', 'metabolic factors', 'placenta', 'developmental hypothesis', 'genetic and epigenetic origins'.

OUTCOMES

A total of 82 studies were finally included in this review. There is robust evidence that a hyperandrogenic intra-uterine environment 'programmes' the genes concerned with ovarian steroidogenesis, insulin metabolism, gonadotrophin secretion and ovarian follicle development resulting in the development of PCOS in adult life.

WIDER IMPLICATIONS

Once the evidence supporting this hypothesis has been expanded by additional studies, the door would be open to find innovative treatments and preventative measures for this very prevalent condition. Such measures could considerably ease the human and economic burden that PCOS creates.

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.

The Role of Kisspeptin in Female Reproduction

CONTEXT

Kisspeptin (KISS1), a recently discovered neuropeptide that acts upstream of gonadotropin-releasing hormone (GnRH) neurons, is critical for maturation and function of the reproductive axis. This review aimed at providing comprehensive and up-to-date information on Kisspeptin and its role in female reproduction.

EVIDENCE ACQUISITION

A literature review was performed using PubMed for all English language articles published between 1999 and 2016.

RESULTS

The kisspeptin system (KISS1/G protein-coupled receptor-54,GPR54) has recently been addressed as an essential gatekeeper of puberty onset and gonadotropin secretion. Compelling evidence has documented that hypothalamic Kisspeptin mediates steroid feedback and metabolic cues at different developmental stages throughout lifespan. Furthermore, in pre/postnatally androgenized animal models, which exhibit many of the characteristics of Polycystic Ovarian Syndrome (PCOS), the hypothalamic expression of KISS1 and GnRH is abnormal, which might lead to multiple tissue abnormalities observed in this disorder.

CONCLUSIONS

Kisspeptin, a principal activator of GnRH neurons and the target of endocrine and metabolic cues, is a prerequisite for the onset of puberty and maintenance of normal reproductive function, as abnormal KISS1/GPR54 system has been reported in both animal models and patients with certain forms of infertility, e.g. Idiopathic Hypogonadotropic hypogonadism (IHH) and PCOS. The information suggests that kisspeptin or its receptor represents a potential therapeutic target in the treatment of patients with fertility disorders.

Endogenous Opiates and Behavior: 2015

This paper is the thirty-eighth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2015 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia, stress and social status, tolerance and dependence, learning and memory, eating and drinking, drug abuse and alcohol, sexual activity and hormones, pregnancy, development and endocrinology, mental illness and mood, seizures and neurologic disorders, electrical-related activity and neurophysiology, general activity and locomotion, gastrointestinal, renal and hepatic functions, cardiovascular responses, respiration and thermoregulation, and immunological responses.

Developmental Programming: Insulin Sensitizer Prevents the GnRH-Stimulated LH Hypersecretion in a Sheep Model of PCOS

Prenatal testosterone (T) treatment recapitulates the reproductive and metabolic phenotypes of polycystic ovary syndrome in female sheep. At the neuroendocrine level, prenatal T treatment results in disrupted steroid feedback on gonadotropin release, increased pituitary sensitivity to GnRH, and subsequent LH hypersecretion. Because prenatal T-treated sheep manifest functional hyperandrogenism and hyperinsulinemia, gonadal steroids and/or insulin may play a role in programming and/or maintaining these neuroendocrine defects. Here, we investigated the effects of prenatal and postnatal treatments with an androgen antagonist (flutamide [F]) or an insulin sensitizer (rosiglitazone [R]) on GnRH-stimulated LH secretion in prenatal T-treated sheep. As expected, prenatal T treatment increased the pituitary responsiveness to GnRH leading to LH hypersecretion. Neither prenatal interventions nor postnatal F treatment normalized the GnRH-stimulated LH secretion. Conversely, postnatal R treatment completely normalized the GnRH-stimulated LH secretion. At the tissue level, gestational T increased pituitary LHβ, androgen receptor, and insulin receptor-β, whereas it reduced estrogen receptor (ER)α protein levels. Although postnatal F normalized pituitary androgen receptor and insulin receptor-β, it failed to prevent an increase in LHβ expression. Contrarily, postnatal R treatment restored ERα and partially normalized LHβ pituitary levels. Immunohistochemical findings confirmed changes in pituitary ERα expression to be specific to gonadotropes. In conclusion, these findings indicate that increased pituitary responsiveness to GnRH in prenatal T-treated sheep is likely a function of reduced peripheral insulin sensitivity. Moreover, results suggest that restoration of ERα levels in the pituitary may be one mechanism by which R prevents GnRH-stimulated LH hypersecretion in this sheep model of polycystic ovary syndrome-like phenotype.

Prenatal testosterone exposure decreases colocalization of insulin receptors in kisspeptin/neurokinin B/dynorphin and agouti-related peptide neurons of the adult ewe

Insulin serves as a link between the metabolic and reproductive systems, communicating energy availability to the hypothalamus and enabling reproductive mechanisms. Adult Suffolk ewes prenatally exposed to testosterone (T) display an array of reproductive and metabolic dysfunctions similar to those seen in women with polycystic ovarian syndrome (PCOS), including insulin resistance. Moreover, prenatal T treatment alters neuropeptide expression in KNDy (co-expressing kisspeptin, neurokinin B/dynorphin) and agouti-related peptide (AgRP) neurons in the arcuate nucleus, two populations that play key roles in the control of reproduction and metabolism, respectively. In this study, we determined whether prenatal T treatment also altered insulin receptors in KNDy and AgRP neurons, as well as in preoptic area (POA) kisspeptin, pro-opiomelanocortin (POMC), and gonadotropin-releasing hormone (GnRH) neurons of the adult sheep brain. Immunofluorescent detection of the beta subunit of insulin receptor (IRβ) revealed that KNDy, AgRP and POMC neurons, but not GnRH or POA kisspeptin neurons, colocalize IRβ in control females. Moreover, prenatal T treatment decreased the percentage of KNDy and AgRP neurons that colocalized IRβ, consistent with reduced insulin sensitivity. Administration of the anti-androgen drug, Flutamide, during prenatal T treatment, prevented the reduction in IRβ colocalization in AgRP, but not in KNDy neurons, suggesting that these effects are programmed by androgenic and oestrogenic actions, respectively. These findings provide novel insight into the effects of prenatal T treatment on hypothalamic insulin sensitivity and raise the possibility that decreased insulin receptors, specifically within KNDy and AgRP neurons, may contribute to the PCOS-like phenotype of this animal model.

κ-Opioid Receptor Is Colocalized in GnRH and KNDy Cells in the Female Ovine and Rat Brain

Kisspeptin-neurokinin B-dynorphin (KNDy) cells of the hypothalamus are a key component in the neuroendocrine regulation of GnRH secretion. Evidence in sheep and other species suggests that dynorphin released by KNDy cells inhibits pulsatile GnRH secretion by acting upon κ-opioid receptors (KOR). However, the precise anatomical location and neurochemical phenotype of KOR-expressing cells in sheep remain unknown. To this end, we determined the distribution of KOR mRNA and protein in the brains of luteal phase ewes, using an ovine specific KOR mRNA probe for in situ hybridization and an antibody whose specificity we confirmed by Western blot analyses and blocking peptide controls. KOR cells were observed in a number of regions, including the preoptic area (POA); anterior hypothalamic area; supraoptic and paraventricular nuclei; ventromedial, dorsomedial, and lateral hypothalamus; and arcuate nucleus. Next, we determined whether KOR is colocalized in KNDy and/or GnRH cells. Dual-label immunofluorescence and confocal analysis of the KNDy population showed a high degree of colocalization, with greater than 90% of these neurons containing KOR. Surprisingly, GnRH cells also showed high levels of colocalization in sheep, ranging from 74.4% to 95.4% for GnRH cells in the POA and medial basal hypothalamus, respectively. Similarly, 97.4% of GnRH neurons in the POA of ovariectomized, steroid-primed female rats also contained immunoreactive KOR protein. These findings suggest that the inhibitory effects of dynorphin on pulsatile GnRH secretion may occur either indirectly by actions upon KOR within the KNDy population and/or directly via the activation of KOR on GnRH cells.

Prenatal programming of neuroendocrine reproductive function

It is now well recognized that the gestational environment can have long-lasting effects not only on the life span and health span of an individual but also, through potential epigenetic changes, on future generations. This article reviews the "prenatal programming" of the neuroendocrine systems that regulate reproduction, with a specific focus on the lessons learned using ovine models. The review examines the critical roles played by steroids in normal reproductive development before considering the effects of prenatal exposure to exogenous steroid hormones including androgens and estrogens, the effects of maternal nutrition and stress during gestation, and the effects of exogenous chemicals such as alcohol and environment chemicals. In so doing, it becomes evident that, to maximize fitness, the regulation of reproduction has evolved to be responsive to many different internal and external cues and that the GnRH neurosecretory system expresses a degree of plasticity throughout life. During fetal life, however, the system is particularly sensitive to change and at this time, the GnRH neurosecretory system can be "shaped" both to achieve normal sexually differentiated function but also in ways that may adversely affect or even prevent "normal function". The exact mechanisms through which these programmed changes are brought about remain largely uncharacterized but are likely to differ depending on the factor, the timing of exposure to that factor, and the species. It would appear, however, that some afferent systems to the GnRH neurons such as kisspeptin, may be critical in this regard as it would appear to be sensitive to a wide variety of factors that can program reproductive function. Finally, it has been noted that the prenatal programming of neuroendocrine reproductive function can be associated with epigenetic changes, which would suggest that in addition to direct effects on the exposed offspring, prenatal programming could have transgenerational effects on reproductive potential.