Hypogonadotropic hypogonadism in mice lacking a functional Kiss1 gene

The ticking clock sets the pace for female fertility

At a time when an increasing number of men and women face fertility issues, it is necessary to understand the basic mechanisms involved in mammalian reproductive activity in order to propose adapted therapeutic tools. This review describes how endogenous circadian clocks take part in the timing of reproductive cycles in female mammals and, consequently, how exposure to circadian disruption may impair female fertility. In female mammals, the master circadian clock, located in the hypothalamic suprachiasmatic nuclei (SCN), uses a vasopressinergic output to knock on preoptic kisspeptin (Kp) neurons each day at the onset of the active period. Kp is a potent activator of neurons producing the gonadotropin-releasing hormone (GnRH) controlling the release of the pituitary gonadotropins luteinizing (LH) and follicle-stimulating (FSH) hormones, which in turn promote ovarian gameto- and steroido-genesis. Estradiol, produced as oocytes mature, exerts positive feedback on Kp neurons. This dual control of Kp neuronal activity by the clock-driven vasopressin output and the elevated circulating estradiol allows a large increase in GnRH-induced LH release at the onset of the waking period, at the end of the follicular phase, triggering the release of mature oocytes. Additionally, different parts of the reproductive axis also host secondary circadian clocks that participate in the daily and ovarian regulation of female reproductive cycles. Different experiments revealed the functional significance of the circadian regulation of female reproduction. Indeed, exposure of female rodents to different protocols of circadian disruption impairs estrous cycle robustness, LH surge timing, and gestational success. Additionally, epidemiological studies indicate that women working non-standard schedules face increased risks of reproductive issues. Therefore, when women seek medical assistance for infertility, lifestyle factors, including work schedule organization, should be assessed. Chronotherapeutic interventions could then be considered to enhance the robustness of female reproductive cycles and, as a result, improve their reproductive health.

Kisspeptins Regulating Fertility: Potential Future Therapeutic Approach in Infertility Treatment

Kisspeptins play a crucial role in the normal functioning of the reproductive axis in both humans and animals by stimulating the secretion of gonadotropin-releasing hormone (GnRH) from the hypothalamus. Recent studies have investigated the association of kisspeptins to infertility of diverse causes and the therapeutic potential of kisspeptins in infertility. Exogenous administration of kisspeptins appears to hold significant promise in restoring fertility, with ongoing studies in their application in ovarian stimulation protocols and as cryoprotectants during vitrification. This review provides a comprehensive analysis of the role of kisspeptins in reproductive physiology and their potential as therapeutic agents for infertility, highlighting their advantages over conventional treatments and their future prospects in clinical practice.

Dietary availability acutely influences puberty onset via a hypothalamic neural circuit

Reproduction poses a substantial burden, especially for mammalian females. Puberty onset serves as a vital checkpoint, regulated based on the body's energy state, to prevent inappropriate reproductive activity under malnutrition. However, the neural basis of this puberty checkpoint remains poorly understood. Here, we demonstrate that peripubertal malnutrition in female mice reduces the synchronous activity episodes of arcuate kisspeptin neurons, which are critical regulators of the gonadotropin axis. Improved dietary availability increased the frequency of this pulsatile activity, facilitating puberty onset. Using a viral-genetic approach, we show that the activity of agouti-related protein neurons in the arcuate nucleus, a hunger center, can bidirectionally regulate the pulsatile activity of kisspeptin neurons and follicular maturation in the ovaries. Collectively, a neural circuit connecting feeding to reproductive centers acts as an adjuster of the frequency of pulsatile kisspeptin neuron activity based on dietary availability, contributing to the neural basis of the puberty checkpoint.

Kisspeptin and neurokinin B: roles in reproductive health

Kisspeptin and neurokinin B (NKB) play a key role in several physiological processes including in puberty, adult reproductive function including the menstrual cycle, as well as mediating the symptoms of menopause. Infundibular kisspeptin neurons, which coexpress NKB, regulate the activity of gonadotropin-releasing hormone (GnRH) neurons and thus the physiological pulsatile secretion of GnRH from the hypothalamus. Outside of their hypothalamic reproductive roles, these peptides are implicated in several physiological functions including sexual behavior and attraction, placental function, and bone health. Over the last two decades, research findings have considerably enhanced our understanding of the physiological regulation of the hypothalamic-pituitary-gonadal (HPG) axis and identified potential therapeutic applications. For example, recognition of the role of kisspeptin as the natural inductor of ovulation has led to research investigating its use as a safer, more physiological trigger of oocyte maturation in in vitro fertilization (IVF) treatment. Moreover, the key role of NKB in the pathophysiology of menopausal hot flashes has led to the development of pharmacological antagonism of this pathway. Indeed, fezolinetant, a neurokinin 3 receptor antagonist, has recently received Food and Drug Administration (FDA) approval for clinical use to treat menopausal vasomotor symptoms. Here, we discuss the roles of kisspeptin and NKB in human physiology, including in the regulation of puberty, menstrual cyclicity, reproductive behavior, pregnancy, menopause, and bone homeostasis. We describe how perturbations of these key physiological processes can result in disease states and consider how kisspeptin and NKB could be exploited diagnostically as well as therapeutically to treat reproductive disorders.

Metabolomics and transcriptomics analyses reveal the complex molecular mechanisms by which the hypothalamus regulates sexual development in female goats

BACKGROUND

The hypothalamus is a critical organ that regulates sexual development in animals. However, current research on the hypothalamic regulation of sexual maturation in female goats remains limited. In this study, we conducted metabolomic and transcriptomic analyses on the hypothalamic tissues of female Jining grey goats at different stages of sexual development (1 day old (neonatal, D1, n = 5), 2 months old (prepuberty, M2, n = 5), 4 months old (sexual maturity, M4, n = 5), and 6 months old (breeding period, M6, n = 5)).

RESULTS

A total of 418 differential metabolites (DAMs) were identified in this study, among which the abundance of metabolites such as anserine, L-histidine, carnosine, taurine, and 4-aminobutyric gradually increased with the progression of sexual development. These metabolites may regulate neuronal development and hormone secretion processes by influencing the metabolism of histidine and phenylalanine. Through combined transcriptomic and metabolomic analyses, we identified that differentially expressed genes such as mitogen-activated protein kinase kinase kinase 9 (MAP3K9), prune homolog 2 with BCH domain (PRUNE2), and potassium voltage-gated channel interacting protein 4(KCNIP4) may jointly regulate the development and energy metabolism of hypothalamic Gonadotropin-releasing hormone neurons in conjunction with DAMs, including LPC22:5, 2-Arachidonyl Glycerol ether, LPE22:5, and Lysops22:5. Additionally, we elucidated the molecular mechanism through which glutathione metabolism regulates sexual maturation in goats.

CONCLUSIONS

In summary, this study illustrates the dynamic changes in metabolites and mRNA within hypothalamic tissue during postnatal sexual maturation in female Jining grey goats. This research may provide significant scientific insights for future animal breeding.

Regulatory Involvement of Kisspeptin in Energy Balance and Reproduction

The hypothalamic-pituitary-gonadal axis, which regulates steroidogenesis and germ cell formation, closely regulates the reproduction process. Nonetheless, other chemical mediators, such as kisspeptin, influence this axis. Kisspeptin is a hypothalamic neuropeptide that modulates the function of this axis and also plays a central role in energy balance. The present study reviews the impact and associated mechanisms of kisspeptin on male and female reproduction based on available evidence in the literature. Kisspeptin and its neurons exert anorexigenic activity, thus maintaining adequate energy balance for optimal reproductive function. Also, they stimulate the release of GnRH, resulting in the optimal performance of gonadal physiological processes viz. production of steroid sex hormones and germ cells. However, studies linking kisspeptin to reproduction are yet scanty. Hence, studies exploring the upstream and downstream signaling pathways activated by kisspeptin concerning reproduction in an attempt to better understand the associated mechanisms of the regulatory activities of kisspeptin on reproduction are recommended. In addition, potential factors that may modulate kisspeptin activities may be useful in the management of infertility and perhaps, in the development of contraceptives for those who do not intend to achieve conception.

Estrogen-Regulated Lateral Septal Kisspeptin Neurons Abundantly Project to GnRH Neurons and the Hypothalamic Supramammillary Nucleus

While hypothalamic kisspeptin (KP) neurons play well-established roles in the estrogen-dependent regulation of reproduction, little is known about extrahypothalamic KP-producing (KPLS) neurons of the lateral septum. As established previously, Kiss1 expression in this region is low and regulated by estrogen receptor- and GABAB receptor-dependent mechanisms. Our present experiments on Kiss1-Cre/ZsGreen knock-in mice revealed that transgene expression in the LS begins at Postnatal Day (P)33-36 in females and P40-45 in males and is stimulated by estrogen receptor signaling. Fluorescent cell numbers continue to increase in adulthood and are higher in females. Viral tracing uncovered that the bulk of KPLS fibers joins the medial forebrain bundle and terminates in the hypothalamic supramammillary nucleus. Smaller subsets innervate the medial amygdala or project to other limbic structures. One-quarter of gonadotropin-releasing hormone (GnRH)-immunoreactive perikarya in the preoptic area and their dendrites receive appositions from KPLS axons. OVX adult Kiss1-Cre/ZsGreen mice treated for 4 d with 17β-estradiol or vehicle were used for RNA sequencing studies of laser-microdissected KPLS neurons. The transcriptome included markers of GABAergic and neuropeptidergic (Penk, Cartpt, Vgf) cotransmission and 571 estrogen-regulated transcripts. Estrogen treatment upregulated the acetylcholine receptor transcript Chrm2 and, in slice electrophysiology experiments, caused enhanced muscarinic inhibition of KPLS neurons. Finally, we provided immunohistochemical evidence for homologous neurons in the postmortem human brain, suggesting that KPLS neurons may contribute to evolutionarily conserved regulatory mechanisms. Future studies will need to investigate the putative roles of KPLS neurons in the estrogen-dependent control of GnRH neurons and/or various hypothalamic/limbic functions.

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

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

Absence of mating behaviors in the female dogs neonatally treated with estrogen and progesterone

This study aimed to develop a non-surgical method to neutralize reproduction in female dogs. Female Beagle puppies, aged 6 days, were treated with pellets designed to release estradiol benzoate (EB; 1.0 mg) and progesterone (P4; 5.0 mg) over approximately 3 weeks. Their estrous cycles were monitored from 6 to 34 months of age by examining their vulvas daily and measuring their serum P4 levels once a month. Vulvar edema and discharge, followed by a serum P4 level above 5 ng/ml, indicated the potential estrus. Each time a dog showed these signs, breeding was attempted by housing with a proven male Beagle. All the treated dogs displayed cyclic progesterone surges with 5 to 6-month-long anestrous intervals. Surprisingly, none exhibited sexual behaviors, and no mating occurred (i.e., no intromission and copulatory tie), resulting in no pups being born. This phenomenon was further explored in laboratory animals. Neonatal female rats were treated with microspheres containing smaller doses of the same steroids (0.3 mg EB + 3.0 mg P4) at 1 or 2 days old. At 3 months old, the rats were ovariectomized, chemically stimulated to exhibit estrus behaviors using a standard protocol and tested for receptivity to proven male rats. Untreated control rats showed normal receptivity (i.e., lordosis) and allowed males to mate. However, rats treated with EB+P4 did not exhibit lordosis or allow mating. These results indicate that the combined use of estrogen and progesterone could be an effective non-surgical method for inhibiting mating behavior and, consequently, neutralizing female dog reproduction.

Human-specific epigenomic states in spermatogenesis

Infertility is becoming increasingly common, affecting one in six people globally. Half of these cases can be attributed to male factors, many driven by abnormalities in the process of sperm development. Emerging evidence from genome-wide association studies, genetic screening of patient cohorts, and animal models highlights an important genetic contribution to spermatogenic defects, but comprehensive identification and characterization of the genes critical for male fertility remain lacking. High divergence of gene regulation in spermatogenic cells across species poses challenges for delineating the genetic pathways required for human spermatogenesis using common model organisms. In this study, we leveraged post-translational histone modification and gene transcription data for 15,491 genes in four mammalian species (human, rhesus macaque, mouse, and opossum), to identify human-specific patterns of gene regulation during spermatogenesis. We combined H3K27me3 ChIP-seq, H3K4me3 ChIP-seq, and RNA-seq data to define epigenetic states for each gene at two stages of spermatogenesis, pachytene spermatocytes and round spermatids, in each species. We identified 239 genes that are uniquely active, poised, or dynamically regulated in human spermatogenic cells distinct from the other three species. While some of these genes have been implicated in reproductive functions, many more have not yet been associated with human infertility and may be candidates for further molecular and epidemiologic studies. Our analysis offers an example of the opportunities provided by evolutionary and epigenomic data for broadly screening candidate genes implicated in reproduction, which might lead to discoveries of novel genetic targets for diagnosis and management of male infertility and male contraception.

Development of KISS1 knockout pigs is characterized by hypogonadotropic hypogonadism, normal growth, and reduced skatole†

Kisspeptin is a major regulator of gonadotropin secretion in pigs. Previously, CRISPR/Cas9 knockout of KISS1 was used to develop a mosaic parental line of pigs to generate offspring that would not need castration due to loss of kisspeptin. The current goal was to characterize growth and reproductive development of F1 pigs from this parental line. Body weights, gonadotropin concentrations and gonadal development were measured from birth through development (boars to 220 days of age, n = 42; gilts to 160 days of age, n = 36). Testosterone, skatole, and androstenone were also measured in boars. Blood samples were collected by jugular venipuncture for quantification of serum hormones, gonadal tissues were collected for gross morphology and histology, and a fat biopsy was collected (boars) for skatole and androstenone analysis. Body weight did not differ with genotype. There were no differences between KISS1+/+ and heterozygote KISS1+/- animals for most parameters measured. Gonadotropin concentrations were reduced in KISS1-/- boars and gilts compared with KISS1+/+ and KISS1+/- animals (P < 0.05). Concentrations of testosterone in serum and both androstenone and skatole in adipose were less in KISS1-/- boars than in KISS1+/+ and KISS1+/- boars (P < 0.05). Hypogonadism was present in all KISS1-/- gilts and boars. These data indicate that knocking out KISS1 causes hypogonadotropic hypogonadism but does not negatively affect growth in pigs. Only one KISS1 allele is needed for normal gonadotropin secretion and gonadal development, and accumulation of compounds in adipose leading to boar taint.

Neuropeptides and receptors in the cephalochordate: A crucial model for understanding the origin and evolution of vertebrate neuropeptide systems

Genomes and transcriptomes from diverse organisms are providing a wealth of data to explore the evolution and origin of neuropeptides and their receptors in metazoans. While most neuropeptide-receptor systems have been extensively studied in vertebrates, there is still a considerable lack of understanding regarding their functions in invertebrates, an extraordinarily diverse group that account for the majority of animal species on Earth. Cephalochordates, commonly known as amphioxus or lancelets, serve as the evolutionary proxy of the chordate ancestor. Their key evolutionary position, bridging the invertebrate to vertebrate transition, has been explored to uncover the origin, evolution, and function of vertebrate neuropeptide systems. Amphioxus genomes exhibit a high degree of sequence and structural conservation with vertebrates, and sequence and functional homologues of several vertebrate neuropeptide families are present in cephalochordates. This review aims to provide a comprehensively overview of the recent findings on neuropeptides and their receptors in cephalochordates, highlighting their significance as a model for understanding the complex evolution of neuropeptide signaling in vertebrates.

Impact of Dietary Isoflavones in Standard Chow on Reproductive Development in Juvenile and Adult Female Mice with Different Metabolic Phenotypes

Two factors influencing female reproduction have been repeatedly studied in different animal species and humans, namely, 1. secondary plant compounds, especially phytoestrogens (mainly isoflavones (IFs)), and 2. the physical constitution/metabolic phenotype (e.g., obesity). So far, these research results have only been considered separately. In this study, we investigated the influence on reproduction of both phytochemicals, mainly dietary IFs, and the metabolic phenotype represented by three mouse models considered as three distinct genetic groups (a control group, a mouse model with high metabolic activity, and a mouse line with obese body weight). The IF content in different investigated standard chows with similar macronutrient profiles varied significantly (p < 0.005), leading to high mean total plasma IF levels of up to 5.8 µmol/L in juvenile and 6.7 µmol/L in adult female mice. Reproductive performance was only slightly affected; only an IF dose-dependent effect on gestation length was observed in all genetic groups, as well as an effect on pregnancy rate in obese mice. Dietary IF exposure, however, caused earlier onset of vaginal opening by 4-10 days in juvenile mice (p < 0.05), dependent on the genetic group, resulting in a slight acceleration of sexual maturation in the already precocious obese model and to a strong earlier maturation in the otherwise late-maturing sporty model, bred for high treadmill performance. Therefore, our results may help to draw the missing line between the effect of dietary secondary plant constituents, such as IFs, and metabolic phenotype on sexual development.

The evolutionary conserved miR-137/325 tandem mediates obesity-induced hypogonadism and metabolic comorbidities by repressing hypothalamic kisspeptin

BACKGROUND

Obesity-induced hypogonadism (OIH) is a prevalent, but often neglected condition in men, which aggravates the metabolic complications of overweight. While hypothalamic suppression of Kiss1-encoded kisspeptin has been suggested to contribute to OIH, the molecular mechanisms for such repression in obesity, and the therapeutic implications thereof, remain unknown.

METHODS

A combination of bioinformatic, expression and functional analyses was implemented, assessing the role of the evolutionary-conserved miRNAs, miR-137 and miR-325, in mediating obesity-induced suppression of hypothalamic kisspeptin, as putative mechanism of central hypogonadism and metabolic comorbidities. The implications of such miR-137/325-kisspeptin interplay for therapeutic intervention in obesity were also explored using preclinical OIH models.

RESULTS

MiR-137/325 repressed human KISS1 3'-UTR in-vitro and inhibited hypothalamic kisspeptin content in male rats, while miR-137/325 expression was up-regulated, and Kiss1/kisspeptin decreased, in the medio-basal hypothalamus of obese rats. Selective over-expression of miR-137 in Kiss1 neurons reduced Kiss1/ kisspeptin and partially replicated reproductive and metabolic alterations of OIH in lean mice. Conversely, interference of the repressive actions of miR-137/325 selectively on Kiss1 3'-UTR in vivo, using target-site blockers (TSB), enhanced kisspeptin content and reversed central hypogonadism in obese rats, together with improvement of glucose intolerance, insulin resistance and cardiovascular and inflammatory markers, despite persistent exposure to obesogenic diet. Reversal of OIH by TSB miR-137/325 was more effective than chronic kisspeptin or testosterone treatments in obese rats.

CONCLUSIONS

Our data disclose that the miR-137/325-Kisspeptin repressive interaction is a major player in the pathogenesis of obesity-induced hypogonadism and a putative druggable target for improved management of this condition and its metabolic comorbidities in men suffering obesity.

SIGNIFICANCE STATEMENT

Up to half of the men suffering obesity display also central hypogonadism, an often neglected complication of overweight that can aggravate the clinical course of obesity and its complications. The mechanisms for such obesity-induced hypogonadism remain poorly defined. We show here that the evolutionary conserved miR137/miR325 tandem centrally mediates obesity-induced hypogonadism via repression of the reproductive-stimulatory signal, kisspeptin; this may represent an amenable druggable target for improved management of hypogonadism and other metabolic complications of obesity.

Phenytoin causes behavioral abnormalities and suppresses kisspeptin expression, reducing reproductive performance in Japanese medaka

Phenytoin, an antiepileptic drug, induces neurotoxicity and abnormal embryonic development and reduces spontaneous locomotor activity in fish. However, its effects on other endpoints remain unclear. Therefore, we investigated the effects of phenytoin on the swimming behavior and reproductive ability of Japanese medaka. Abnormalities in swimming behavior, such as imbalance, rotation, rollover, and vertical swimming, were observed. However, when phenytoin exposure was discontinued, the behavioral abnormality rates decreased. Phenytoin exposure also significantly reduced reproductive ability. By investigating reproduction-related gene expression of gnrh1, gnrh2, fshb, and lhb remained unchanged in males and females. In contrast, kiss1 expression was significantly suppressed due to phenytoin exposure in males and females. kiss2 expression was also significantly suppressed in females but not in males. We filmed videos to examine phenytoin exposure effects on sexual behavior. Females showed no interest in the male's courtship. As the kisspeptin 1 system controls sexual behavior in Japanese medaka, phenytoin exposure may have decreased kiss1 expression, which decreased female reproductive motivation; hence, they did not spawn eggs. This is the first study to show that phenytoin exposure induces behavioral abnormalities, and suppresses kiss1 expression and reproductive performance in Japanese medaka.

Structural basis for hormone recognition and distinctive Gq protein coupling by the kisspeptin receptor

Kisspeptin signaling through its G protein-coupled receptor, KISS1R, plays an indispensable role in regulating reproduction via the hypothalamic-pituitary-gonadal axis. Dysregulation of this pathway underlies severe disorders like infertility and precocious puberty. Here, we present cryo-EM structures of KISS1R bound to the endogenous agonist kisspeptin-10 and a synthetic analog TAK-448. These structures reveal pivotal interactions between peptide ligands and KISS1R extracellular loops for receptor activation. Both peptides exhibit a conserved binding mode, unveiling their common activation mechanism. Intriguingly, KISS1R displays a distinct 40° angular deviation in its intracellular TM6 region compared to other Gq-coupled receptors, enabling distinct interactions with Gq. This study reveals the molecular intricacies governing ligand binding and activation of KISS1R, while highlighting its exceptional ability to couple with Gq. Our findings pave the way for structure-guided design of therapeutics targeting this physiologically indispensable receptor.

Male animal sterilization: history, current practices, and potential methods for replacing castration

Sterilization and castration have been synonyms for thousands of years. Making an animal sterile meant to render them incapable of producing offspring. Castration or the physical removal of the testes was discovered to be the most simple but reliable method for managing reproduction and sexual behavior in the male. Today, there continues to be global utilization of castration in domestic animals. More than six hundred million pigs are castrated every year, and surgical removal of testes in dogs and cats is a routine practice in veterinary medicine. However, modern biological research has extended the meaning of sterilization to include methods that spare testis removal and involve a variety of options, from chemical castration and immunocastration to various methods of vasectomy. This review begins with the history of sterilization, showing a direct link between its practice in man and animals. Then, it traces the evolution of concepts for inducing sterility, where research has overlapped with basic studies of reproductive hormones and the discovery of testicular toxicants, some of which serve as sterilizing agents in rodent pests. Finally, the most recent efforts to use the immune system and gene editing to block hormonal stimulation of testis function are discussed. As we respond to the crisis of animal overpopulation and strive for better animal welfare, these novel methods provide optimism for replacing surgical castration in some species.

Kisspeptin signaling in astrocytes modulates the reproductive axis

Reproduction is safeguarded by multiple, often cooperative, regulatory networks. Kisspeptin signaling, via KISS1R, plays a fundamental role in reproductive control, primarily by regulation of hypothalamic GnRH neurons. We disclose herein a pathway for direct kisspeptin actions in astrocytes that contributes to central reproductive modulation. Protein-protein interaction and ontology analyses of hypothalamic proteomic profiles after kisspeptin stimulation revealed that glial/astrocyte markers are regulated by kisspeptin in mice. This glial-kisspeptin pathway was validated by the demonstrated expression of Kiss1r in mouse astrocytes in vivo and astrocyte cultures from humans, rats, and mice, where kisspeptin activated canonical intracellular signaling-pathways. Cellular coexpression of Kiss1r with the astrocyte markers GFAP and S100-β occurred in different brain regions, with higher percentage in Kiss1- and GnRH-enriched areas. Conditional ablation of Kiss1r in GFAP-positive cells in the G-KiR-KO mouse altered gene expression of key factors in PGE2 synthesis in astrocytes and perturbed astrocyte-GnRH neuronal appositions, as well as LH responses to kisspeptin and LH pulsatility, as surrogate marker of GnRH secretion. G-KiR-KO mice also displayed changes in reproductive responses to metabolic stress induced by high-fat diet, affecting female pubertal onset, estrous cyclicity, and LH-secretory profiles. Our data unveil a nonneuronal pathway for kisspeptin actions in astrocytes, which cooperates in fine-tuning the reproductive axis and its responses to metabolic stress.

Early adversity causes sex-specific deficits in perforant pathway connectivity and contextual memory in adolescent mice

BACKGROUND

Early life adversity impairs hippocampal development and function across diverse species. While initial evidence indicated potential variations between males and females, further research is required to validate these observations and better understand the underlying mechanisms contributing to these sex differences. Furthermore, most of the preclinical work in rodents was performed in adult males, with only few studies examining sex differences during adolescence when such differences appear more pronounced. To address these concerns, we investigated the impact of limited bedding (LB), a mouse model of early adversity, on hippocampal development in prepubescent and adolescent male and female mice.

METHODS

RNA sequencing, confocal microscopy, and electron microscopy were used to evaluate the impact of LB and sex on hippocampal development in prepubescent postnatal day 17 (P17) mice. Additional studies were conducted on adolescent mice aged P29-36, which included contextual fear conditioning, retrograde tracing, and ex vivo diffusion magnetic resonance imaging (dMRI).

RESULTS

More severe deficits in axonal innervation and myelination were found in the perforant pathway of prepubescent and adolescent LB males compared to LB female littermates. These sex differences were due to a failure of reelin-positive neurons located in the lateral entorhinal cortex (LEC) to innervate the dorsal hippocampus via the perforant pathway in males, but not LB females, and were strongly correlated with deficits in contextual fear conditioning.

CONCLUSIONS

LB impairs the capacity of reelin-positive cells located in the LEC to project and innervate the dorsal hippocampus in LB males but not female LB littermates. Given the critical role that these projections play in supporting normal hippocampal function, a failure to establish proper connectivity between the LEC and the dorsal hippocampus provides a compelling and novel mechanism to explain the more severe deficits in myelination and contextual freezing found in adolescent LB males.

Male reproductive phenotypes of genetically altered laboratory mice (Mus musculus): a review based on pertinent literature from the last three decades

Laboratory mice (Mus musculus) are preferred animals for biomedical research due to the close relationship with humans in several aspects. Therefore, mice with diverse genetic traits have been generated to mimic human characteristics of interest. Some genetically altered mouse strains, on purpose or by accident, have reproductive phenotypes and/or fertility deviating from wild-type mice. The distinct reproductive phenotypes of genetically altered male mice mentioned in this paper are grouped based on reproductive organs, beginning with the brain (i.e., the hypothalamus and anterior pituitary) that regulates sexual maturity and development, the testis where male gametes and sex steroid hormones are produced, the epididymis, the accessory sex glands, and the penis which involve in sperm maturation, storage, and ejaculation. Also, distinct characteristics of mature sperm from genetically altered mice are described here. This repository will hopefully be a valuable resource for both humans, in terms of future biomedical research, and mice, in the aspect of the establishment of optimal sperm preservation protocols for individual mouse strains.

Involvement of the kisspeptin system in regulation of sexual behaviors in medaka

In mammals, kisspeptin (Kiss1) neurons are generally considered as a sex steroid-dependent key regulator of hypothalamic-pituitary-gonadal (HPG) axis. In contrast, previous studies in non-mammalian species, especially in teleosts, propose that Kiss1 is not directly involved in the HPG axis regulation, which suggests some sex-steroid-dependent functions of kisspeptin(s) other than the HPG axis regulation in non-mammals. Here, we used knockout (KO) medaka of kisspeptin receptor-coding genes (gpr54-1 and gpr54-2) and examined possible roles of kisspeptin in the regulation of sexual behaviors. We found that the KO pairs of gpr54-1, but not gpr54-2, spawned fewer eggs and exhibited delayed spawning than wild type pairs. Detailed behavior analysis suggested that the KO females are responsible for the delayed spawning and that the KO males showed hyper-motivation for courtship. Taken together, the present finding suggests that one of the reproductive-state-dependent functions of the Kiss1 may be the control of successful sexual behaviors.

The effect of NK3-Saporin injection within the arcuate nucleus on puberty, the LH surge, and the response to Senktide in female sheep†

The timing of puberty onset is reliant on increased gonadotropin-releasing hormone (GnRH). This elicits a corresponding increase in luteinizing hormone (LH) due to a lessening of sensitivity to the inhibitory actions of estradiol (E2). The mechanisms underlying the increase in GnRH release likely involve a subset of neurons within the arcuate (ARC) nucleus of the hypothalamus that contain kisspeptin, neurokinin B (NKB), and dynorphin (KNDy neurons). We aimed to determine if KNDy neurons in female sheep are critical for: timely puberty onset; the LH surge; and the response to an intravenous injection of the neurokinin-3 receptor (NK3R) agonist, senktide. Prepubertal ewes received injections aimed at the ARC containing blank-saporin (control, n = 5) or NK3-saporin (NK3-SAP, n = 6) to ablate neurons expressing NK3R. Blood samples taken 3/week for 65 days following surgery were assessed for progesterone to determine onset of puberty. Control ewes exhibited onset of puberty at 33.2 ± 3.9 days post sampling initiation, whereas 5/6 NK3-SAP treated ewes didn't display an increase in progesterone. After an artificial LH surge protocol, surge amplitude was lower in NK3-SAP ewes. Finally, ewes were treated with senktide to determine if an LH response was elicited. LH pulses were evident in both groups in the absence of injections, but the response to senktide vs saline was similar between groups. These results show that KNDy cells are necessary for timely puberty onset and for full expresson of the LH surge. The occurrence of LH pulses in NK3-SAP treated ewes may indicate a recovery from an apulsatile state.

Postweaning Social Isolation Alters Puberty Onset by Suppressing Electrical Activity of Arcuate Kisspeptin Neurons

INTRODUCTION

Postweaning social isolation (PWSI) in rodents is an advanced psychosocial stress model in early life. Some psychosocial stress, such as restrain and isolation, disrupts reproductive physiology in young and adult periods. Mechanisms of early-life stress effects on central regulation of reproduction need to be elucidated. We have investigated the effects of PWSI on function of arcuate kisspeptin (ARCKISS1) neurons by using electrophysiological techniques combining with monitoring of puberty onset and estrous cycle in male and female Kiss1-Cre mice.

METHODS

Female mice were monitored for puberty onset with vaginal opening examination during social isolation. After isolation, the estrous cycle of female mice was monitored with vaginal cytology. Anxiety-like behavior of mice was determined by an elevated plus maze test. Effects of PWSI on electrophysiology of ARCKISS1 neurons were investigated by the patch clamp method after intracranial injection of AAV-GFP virus into arcuate nucleus of Kiss1-Cre mice after the isolation period.

RESULTS

We found that both male and female isolated mice showed anxiety-like behavior. PWSI caused delay in vaginal opening and extension in estrous cycle length. Spontaneous-firing rates of ARCKISS1 neurons were significantly lower in the isolated male and female mice. The peak amplitude of inhibitory postsynaptic currents to ARCKISS1 neurons was higher in the isolated mice, while frequency of excitatory postsynaptic currents was higher in group-housed mice.

CONCLUSION

These findings demonstrate that PWSI alters pre- and postpubertal reproductive physiology through metabolic and electrophysiological pathways.

The Emerging Therapeutic Potential of Kisspeptin and Neurokinin B

Kisspeptin (KP) and neurokinin B (NKB) are neuropeptides that govern the reproductive endocrine axis through regulating hypothalamic gonadotropin-releasing hormone (GnRH) neuronal activity and pulsatile GnRH secretion. Their critical role in reproductive health was first identified after inactivating variants in genes encoding for KP or NKB signaling were shown to result in congenital hypogonadotropic hypogonadism and a failure of pubertal development. Over the past 2 decades since their discovery, a wealth of evidence from both basic and translational research has laid the foundation for potential therapeutic applications. Beyond KP's function in the hypothalamus, it is also expressed in the placenta, liver, pancreas, adipose tissue, bone, and limbic regions, giving rise to several avenues of research for use in the diagnosis and treatment of pregnancy, metabolic, liver, bone, and behavioral disorders. The role played by NKB in stimulating the hypothalamic thermoregulatory center to mediate menopausal hot flashes has led to the development of medications that antagonize its action as a novel nonsteroidal therapeutic agent for this indication. Furthermore, the ability of NKB antagonism to partially suppress (but not abolish) the reproductive endocrine axis has supported its potential use for the treatment of various reproductive disorders including polycystic ovary syndrome, uterine fibroids, and endometriosis. This review will provide a comprehensive up-to-date overview of the preclinical and clinical data that have paved the way for the development of diagnostic and therapeutic applications of KP and NKB.

Sex difference in developmental changes in visualized Kiss1 neurons in newly generated Kiss1-Cre rats

Hypothalamic kisspeptin neurons are master regulators of mammalian reproduction via direct stimulation of gonadotropin-releasing hormone and consequent gonadotropin release. Here, we generated novel Kiss1 (kisspeptin gene)-Cre rats and investigated the developmental changes and sex differences in visualized Kiss1 neurons of Kiss1-Cre-activated tdTomato reporter rats. First, we validated Kiss1-Cre rats by generating Kiss1-expressing cell-specific Kiss1 knockout (Kiss1-KpKO) rats, which were obtained by crossing the current Kiss1-Cre rats with Kiss1-floxed rats. The resulting male Kiss1-KpKO rats lacked Kiss1 expression in the brain and exhibited hypogonadotropic hypogonadism, similar to the hypogonadal phenotype of global Kiss1 KO rats. Histological analysis of Kiss1 neurons in Kiss1-Cre-activated tdTomato reporter rats revealed that tdTomato signals in the anteroventral periventricular nucleus (AVPV) and arcuate nucleus (ARC) were not affected by estrogen, and that tdTomato signals in the ARC, AVPV, and medial amygdala (MeA) were sexually dimorphic. Notably, neonatal AVPV tdTomato signals were detected only in males, but a larger number of tdTomato-expressing cells were detected in the AVPV and ARC, and a smaller number of cells in the MeA was detected in females than in males at postpuberty. These findings suggest that Kiss1-visualized rats can be used to examine the effect of estrogen feedback mechanisms on Kiss1 expression in the AVPV and ARC. Moreover, the Kiss1-Cre and Kiss1-visualized rats could be valuable tools for further detailed analyses of sexual differentiation in the brain and the physiological role of kisspeptin neurons across the brain in rats.

The interplay between kisspeptin and endocannabinoid systems modulates male hypothalamic and gonadic control of reproduction in vivo

Introduction

Male reproduction is under the control of the hypothalamus-pituitary-gonadal (HPG) axis. The endocannabinoid system (ECS) and the kisspeptin system (KS) are two major signaling systems in the central and peripheral control of reproduction, but their possible interaction has been poorly investigated in mammals. This manuscript analyzes their possible reciprocal modulation in the control of the HPG axis.

Materials and methods

Adolescent male rats were treated with kisspeptin-10 (Kp10) and endocannabinoid anandamide (AEA), the latter alone or in combination with the type 1 cannabinoid receptor (CB1) antagonist rimonabant (SR141716A). The hypothalamic KS system and GnRH expression, circulating sex steroids and kisspeptin (Kiss1) levels, and intratesticular KS and ECS were evaluated by immunohistochemical and molecular methods. Non-coding RNAs (i.e., miR145-5p, miR-132-3p, let7a-5p, let7b-5p) were also considered.

Results

Circulating hormonal values were not significantly affected by Kp10 or AEA; in the hypothalamus, Kp10 significantly increased GnRH mRNA and aromatase Cyp19, Kiss1, and Kiss1 receptor (Kiss1R) proteins. By contrast, AEA treatment affected the hypothalamic KS at the protein levels, with opposite effects on the ligand and receptor, and SR141716A was capable of attenuating the AEA effects. Among the considered non-coding RNA, only the expression of miR145-5p was positively affected by AEA but not by Kp10 treatment. Localization of Kiss1+/Kiss1R+ neurons in the arcuate nucleus revealed an increase of Kiss1R-expressing neurons in Kp10- and AEA-treated animals associated with enlargement of the lateral ventricles in Kp10-treated animals. In the brain and testis, the selected non-coding RNA was differently modulated by Kp10 or AEA. Lastly, in the testis, AEA treatment affected the KS at the protein levels, whereas Kp10 affected the intragonadal levels of CB1 and FAAH, the main modulator of the AEA tone. Changes in pubertal transition-related miRNAs and the intratesticular distribution of Kiss1, Kiss1R, CB1, and CB2 following KP and AEA treatment corroborate the KS-ECS crosstalk also showing that the CB1 receptor is involved in this interplay.

Conclusion

For the first time in mammals, we report the modulation of the KS in both the hypothalamus and testis by AEA and revealed the KP-dependent modulation of CB1 and FAAH in the testis. KP involvement in the progression of spermatogenesis is also suggested.

Fasting Modulates GABAergic Synaptic Transmission to Arcuate Kisspeptin Neurons in Female Mice

It is well-established that the hypothalamic-pituitary-gonadal (HPG) axis is suppressed due to negative energy balance. However, less information is available on whether kisspeptin neuronal activity contributes to fasting-induced responses. In the present study, female and male mice were fasted for 24 hours or provided food ad libitum (fed group) to determine whether acute fasting is sufficient to modulate kisspeptin neuronal activity. In female mice, fasting attenuated luteinizing hormone (LH) and prolactin (PRL) serum levels and increased follicle-stimulating hormone levels compared with the fed group. In contrast, fasting did not affect gonadotropin or PRL secretion in male mice. By measuring genes related to LH pulse generation in micropunches obtained from the arcuate nucleus of the hypothalamus (ARH), we observed that fasting reduced Kiss1 mRNA levels in female and male mice. In contrast, Pdyn expression was upregulated only in fasted female mice, whereas no changes in the Tac2 mRNA levels were observed in both sexes. Interestingly, the frequency and amplitude of the GABAergic postsynaptic currents recorded from ARH kisspeptin neurons (ARHKisspeptin) were reduced in 24-hour fasted female mice but not in males. Additionally, neuropeptide Y induced a hyperpolarization in the resting membrane potential of ARHKisspeptin neurons of fed female mice but not in males. Thus, the response of ARHKisspeptin neurons to fasting is sexually dependent with a female bias, associated with changes in gonadotropins and PRL secretion. Our findings suggest that GABAergic transmission to ARHKisspeptin neurons modulates the activity of the HPG axis during situations of negative energy balance.

KNDy neurones and GnRH/LH pulse generation: Current understanding and future aspects

Uncovering the central mechanism underlying mammalian reproduction is warranted to develop new therapeutic approaches for reproductive disorders in humans and domestic animals. The present study focused on the role of arcuate kisspeptin neurones (also known as KNDy neurones) as an intrinsic gonadotropin-releasing hormone (GnRH) pulse generator, which plays a fundamental role in mammalian reproduction via the stimulation of pituitary gonadotropin synthesis and release and thereby in gametogenesis and steroidogenesis in the gonads of mammals. We also discuss the mechanism that inhibits pulsatile GnRH/gonadotropin release under a negative energy balance, considering that reproductive disorders often occur during malnutrition in humans and livestock.

Kisspeptin and lactational anestrus: Current understanding and future prospects

Lactational anestrus, characterized by the suppression of pulsatile gonadotropin-releasing hormone (GnRH)/luteinizing hormone (LH) release, would be a strategic adaptation to ensure survival by avoiding pregnancy during lactation in mammals. In the present article, we first provide a current understanding of the central regulation of reproduction in mammals, i.e., a fundamental role of arcuate kisspeptin neurons in mammalian reproduction by driving GnRH/LH pulses. Second, we discuss the central mechanism inhibiting arcuate Kiss1 (encoding kisspeptin) expression and GnRH/LH pulses during lactation with a focus on suckling stimulus, negative energy balance due to milk production, and the role of circulating estrogen in rats. We also discuss upper regulators that control arcuate kisspeptin neurons in rats during the early and late lactation periods based on the findings obtained by a lactating rat model. Finally, we discuss potential reproductive technology for the improvement of reproductive performance in milking cows.

Current insight into the transient X-zone in the adrenal gland cortex

Mouse models have been widely used in the study of adrenal gland development and diseases. The X-zone is a unique structure of the mouse adrenal gland and lineage-tracing studies show that the X-zone is a remnant of the fetal adrenal cortex. Although the X-zone is considered analogous to the fetal zone in the human adrenal cortex, the functional significance of the X-zone has remained comparatively more obscure. The X-zone forms during the early postnatal stages of adrenal development and regresses later in a remarkable sexually dimorphic fashion. The formation and regression of the X-zone can be different in mice with different genetic backgrounds. Mouse models with gene mutations, hormone/chemical treatments, and/or gonadectomy can also display an aberrant development of the X-zone or alternatively a dysregulated X-zone regression. These models have shed light on the molecular mechanisms regulating the development and regression of these unique adrenocortical cells. This review paper briefly describes the development of the adrenal gland including the formation and regression processes of the X-zone. It also summarizes and lists mouse models that demonstrate different X-zone phenotypes.

The sex-dependent and enduring impact of pubertal stress on health and disease

Illness is often predicated long before the manifestation of its symptoms. Exposure to stressful experiences particularly during critical periods of development, such as puberty and adolescence, can induce various physical and mental illnesses. Puberty is a critical period of maturation for neuroendocrine systems, such as the hypothalamic-pituitary-gonadal (HPG) and hypothalamic-pituitary-adrenal (HPA) axes. Exposure to adverse experiences during puberty can impede normal brain reorganizing and remodelling and result in enduring consequences on brain functioning and behaviour. Stress responsivity differs between the sexes during the pubertal period. This sex difference is partly due to differences in circulating sex hormones between males and females, impacting stress and immune responses differently. The effects of stress during puberty on physical and mental health remains under-examined. The purpose of this review is to summarize the most recent findings pertaining to age and sex differences in HPA axis, HPG axis, and immune system development, and describe how disruption in the functioning of these systems can propagate disease. Lastly, we delve into the notable neuroimmune contributions, sex differences, and the mediating role of the gut microbiome on stress and health outcomes. Understanding the enduring consequences of adverse experiences during puberty on physical and mental health will allow a greater proficiency in treating and preventing stress-related diseases early in development.

Single neonatal estrogen implant sterilizes female animals by decreasing hypothalamic KISS1 expression

Reproductive sterilization by surgical gonadectomy is strongly advocated to help manage animal populations, especially domesticated pets, and to prevent reproductive behaviors and diseases. This study explored the use of a single-injection method to induce sterility in female animals as an alternative to surgical ovariohysterectomy. The idea was based on our recent finding that repetitive daily injection of estrogen into neonatal rats disrupted hypothalamic expression of Kisspeptin (KISS1), the neuropeptide that triggers and regulates pulsatile secretion of GnRH. Neonatal female rats were dosed with estradiol benzoate (EB) either by daily injections for 11 days or by subcutaneous implantation of an EB-containing silicone capsule designed to release EB over 2-3 weeks. Rats treated by either method did not exhibit estrous cyclicity, were anovulatory, and became infertile. The EB-treated rats had fewer hypothalamic Kisspeptin neurons, but the GnRH-LH axis remained responsive to Kisspeptin stimulation. Because it would be desirable to use a biodegradable carrier that is also easier to handle, an injectable EB carrier was developed from PLGA microspheres to provide pharmacokinetics comparable to the EB-containing silicone capsule. A single neonatal injection of EB-microspheres at an equivalent dosage resulted in sterility in the female rat. In neonatal female Beagle dogs, implantation of an EB-containing silicone capsule also reduced ovarian follicle development and significantly inhibited KISS1 expression in the hypothalamus. None of the treatments produced any concerning health effects, other than infertility. Therefore, further development of this technology for sterilization in domestic female animals, such as dogs and cats is worthy of investigation.

Dynamics of pulsatile activities of arcuate kisspeptin neurons in aging female mice

Reproductive senescence is broadly observed across mammalian females, including humans, eventually leading to a loss of fertility. The pulsatile secretion of gonadotropin-releasing hormone (GnRH), which is essential for gonad function, is primarily controlled by kisspeptin neurons in the hypothalamic arcuate nucleus (ARC^kiss), the pulse generator of GnRH. The pulsatility of GnRH release, as assessed by the amount of circulating gonadotropin, is markedly reduced in aged animals, suggesting that the malfunctions of ARC^kiss may be responsible for reproductive aging and menopause-related disorders. However, the activity dynamics of ARC^kiss during the natural transition to reproductive senescence remain unclear. Herein, we introduce chronic in vivo Ca²⁺ imaging of ARC^kiss in female mice by fiber photometry to monitor the synchronous episodes of ARC^kiss (SEs^kiss), a known hallmark of GnRH pulse generator activity, from the fully reproductive to acyclic phase over 1 year. During the reproductive phase, we find that not only the frequency, but also the intensities and waveforms of individual SEs^kiss, vary depending on the stage of the estrus cycle. During the transition to reproductive senescence, the integrity of SEs^kiss patterns, including the frequency and waveforms, remains mostly unchanged, whereas the intensities tend to decline. These data illuminate the temporal dynamics of ARC^kiss activities in aging female mice. More generally, our findings demonstrate the utility of fiber-photometry-based chronic imaging of neuroendocrine regulators in the brain to characterize aging-associated malfunction.

Dissecting the KNDy hypothesis: KNDy neuron-derived kisspeptins are dispensable for puberty but essential for preserved female fertility and gonadotropin pulsatility

BACKGROUND

Kiss1 neurons in the hypothalamic arcuate-nucleus (ARC) play key roles in the control of GnRH pulsatility and fertility. A fraction of ARC Kiss1 neurons, termed KNDy, co-express neurokinin B (NKB; encoded by Tac2). Yet, NKB- and Kiss1-only neurons are also found in the ARC, while a second major Kiss1-neuronal population is present in the rostral hypothalamus. The specific contribution of different Kiss1 neuron sub-sets and kisspeptins originating from them to the control of reproduction and eventually other bodily functions remains to be fully determined.

METHODS

To tease apart the physiological roles of KNDy-born kisspeptins, conditional ablation of Kiss1 in Tac2-expressing cells was implemented in vivo. To this end, mice with Tac2 cell-specific Kiss1 KO (TaKKO) were generated and subjected to extensive reproductive and metabolic characterization.

RESULTS

TaKKO mice displayed reduced ARC kisspeptin content and Kiss1 expression, with greater suppression in females, which was detectable at infantile-pubertal age. In contrast, Tac2/NKB levels were fully preserved. Despite the drop of ARC Kiss1/kisspeptin, pubertal timing was normal in TaKKO mice of both sexes. However, young-adult TaKKO females displayed disturbed LH pulsatility and sex steroid levels, with suppressed basal LH and pre-ovulatory LH surges, early-onset subfertility and premature ovarian insufficiency. Conversely, testicular histology and fertility were grossly conserved in TaKKO males. Ablation of Kiss1 in Tac2-cells led also to sex-dependent alterations in body composition, glucose homeostasis, especially in males, and locomotor activity, specifically in females.

CONCLUSIONS

Our data document that KNDy-born kisspeptins are dispensable/compensable for puberty in both sexes, but required for maintenance of female gonadotropin pulsatility and fertility, as well as for adult metabolic homeostasis.

SIGNIFICANCE STATEMENT

Neurons in the hypothalamic arcuate nucleus (ARC) co-expressing kisspeptins and NKB, named KNDy, have been recently suggested to play a key role in pulsatile secretion of gonadotropins, and hence reproduction. However, the relative contribution of this Kiss1 neuronal-subset, vs. ARC Kiss1-only and NKB-only neurons, as well as other Kiss1 neuronal populations, has not been assessed in physiological settings. We report here findings in a novel mouse-model with elimination of KNDy-born kisspeptins, without altering other kisspeptin compartments. Our data highlights the heterogeneity of ARC Kiss1 populations and document that, while dispensable/compensable for puberty, KNDy-born kisspeptins are required for proper gonadotropin pulsatility and fertility, specifically in females, and adult metabolic homeostasis. Characterization of this functional diversity is especially relevant, considering the potential of kisspeptin-based therapies for management of human reproductive disorders.

Sexually dimorphic pubertal development and adipose tissue kisspeptin dysregulation in the obese and preeclamptic-like BPH/5 mouse model offspring

Preeclampsia (PE) is a devastating hypertensive disorder of pregnancy closely linked to obesity. Long-term adverse outcomes may occur in offspring from preeclamptic pregnancies. Accordingly, sex-specific changes in pubertal development have been described in children from preeclamptic women, but the underlying mechanisms remain vastly unexplored. Features of PE are spontaneously recapitulated by the blood pressure high subline 5 (BPH/5) mouse model, including obesity and dyslipidemia in females before and throughout pregnancy, superimposed hypertension from late gestation to parturition and fetal growth restriction. A sexually dimorphic cardiometabolic phenotype has been described in BPH/5 offspring: while females are hyperphagic, hyperleptinemic, and overweight, with increased reproductive white adipose tissue (rWAT), males have similar food intake, serum leptin concentration, body weight and rWAT mass as controls. Herein, pubertal development and adiposity were further investigated in BPH/5 progeny. Precocious onset of puberty occurs in BPH/5 females, but not in male offspring. When reaching adulthood, the obese BPH/5 females display hypoestrogenism and hyperandrogenism. Kisspeptins, a family of peptides closely linked to reproduction and metabolism, have been previously shown to induce lipolysis and inhibit adipogenesis. Interestingly, expression of kisspeptins (Kiss1) and their cognate receptor (Kiss1r) in the adipose tissue seem to be modulated by the sex steroid hormone milieu. To further understand the metabolic-reproductive crosstalk in the BPH/5 offspring, Kiss1/Kiss1r expression in male and female rWAT were investigated. Downregulation of Kiss1/Kiss1r occurs in BPH/5 females when compared to males. Interestingly, dietary weight loss attenuated circulating testosterone concentration and rWAT Kiss1 downregulation in BPH/5 females. Altogether, the studies demonstrate reproductive abnormalities in offspring gestated in a PE-like uterus, which appear to be closely associated to the sexually dimorphic metabolic phenotype of the BPH/5 mouse model.

Hypothalamic Kisspeptin Neurons: Integral Elements of the GnRH System

Highly sophisticated and synchronized interactions of various cells and hormonal signals are required to make organisms competent for reproduction. GnRH neurons act as a common pathway for multiple cues for the onset of puberty and attaining reproductive function. GnRH is not directly receptive to most of the signals required for the GnRH secretion during the various phases of the ovarian cycle. Kisspeptin neurons of the hypothalamus convey these signals required for the synchronized release of the GnRH. The steroid-sensitive anteroventral periventricular nucleus (AVPV) kisspeptin and arcuate nucleus (ARC) KNDy neurons convey steroid feedback during the reproductive cycle necessary for GnRH surge and pulse, respectively. AVPV region kisspeptin neurons also communicate with nNOS synthesizing neurons and suprachiasmatic nucleus (SCN) neurons to coordinate the process of the ovarian cycle. Neurokinin B (NKB) and dynorphin play roles in the GnRH pulse stimulation and inhibition, respectively. The loss of NKB and kisspeptin function results in the development of neuroendocrine disorders such as hypogonadotropic hypogonadism (HH) and infertility. Ca²⁺ signaling is essential for GnRH pulse generation, which is propagated through gap junctions between astrocytes-KNDy and KNDy-KNDy neurons. Impaired functioning of KNDy neurons could develop the characteristics associated with polycystic ovarian syndrome (PCOS) in rodents. Kisspeptin-increased synthesis led to excessive secretion of the LH associated with PCOS. This review provides the latest insights and understanding into the role of the KNDy and AVPV/POA kisspeptin neurons in GnRH secretion and PCOS.

CRISPR/Cas9-editing of KISS1 to generate pigs with hypogonadotropic hypogonadism as a castration free trait

Introduction: Most male pigs are surgically castrated to avoid puberty-derived boar taint and aggressiveness. However, this surgical intervention represents a welfare concern in swine production. Disrupting porcine KISS1 is hypothesized to delay or abolish puberty by inducing variable hypogonadotropism and thus preventing the need for castration. Methods: To test this hypothesis, we generated the first KISS1-edited large animal using CRISPR/Cas9-ribonucleoproteins and single-stranded donor oligonucleotides. The targeted region preceded the sequence encoding a conserved core motif of kisspeptin. Genome editors were intracytoplasmically injected into 684 swine zygotes and transferred to 19 hormonally synchronized surrogate sows. In nine litters, 49 American Yorkshire and 20 Duroc liveborn piglets were naturally farrowed. Results: Thirty-five of these pigs bore KISS1-disruptive alleles ranging in frequency from 5% to 97% and did not phenotypically differ from their wild-type counterparts. In contrast, four KISS1-edited pigs (two boars and two gilts) with disruptive allele frequencies of 96% and 100% demonstrated full hypogonadotropism, infantile reproductive tracts, and failed to reach sexual maturity. Change in body weight during development was unaffected by editing KISS1. Founder pigs partially carrying KISS1-disruptive alleles were bred resulting in a total of 53 KISS1 ^+/+, 60 KISS1 ^+/-, and 34 KISS1 ^-/- F1 liveborn piglets, confirming germline transmission. Discussion: Results demonstrate that a high proportion of KISS1 alleles in pigs must be disrupted before variation in gonadotropin secretion is observed, suggesting that even a small amount of kisspeptin ligand is sufficient to confer proper sexual development and puberty in pigs. Follow-on studies will evaluate fertility restoration in KISS1 KO breeding stock to fully realize the potential of KISS1 gene edits to eliminate the need for surgical castration.

Mammalian puberty: a fly perspective

Mammalian puberty and Drosophila metamorphosis, despite their evolutionary distance, exhibit similar design principles and conservation of molecular components. In this Viewpoint, we review recent advances in this area and the similarities between both processes in terms of the signaling pathways and neuroendocrine circuits involved. We argue that the detection and uptake of peripheral fat by Drosophila prothoracic endocrine cells induces endomembrane remodeling and ribosomal maturation, leading to the acquisition of high biosynthetic and secretory capacity. The absence of this fat-neuroendocrine interorgan communication leads to giant, obese, non-pupating larvae. Importantly, human leptin is capable of signaling the pupariation process in Drosophila, and its expression prevents obesity and triggers maturation in mutants that do not pupate. This implies that insect metamorphosis can be used to address issues related to the biology of leptin and puberty.

Provocative tests with Kisspeptin-10 and GnRH set the scene for determining social status and environmental impacts on reproductive capacity in male African lions (Panthera leo)

Understanding the hypothalamic factors regulating reproduction facilitates maximising the reproductive success of breeding programmes and in the management and conservation of threatened species, including African lions. To provide insight into the physiology and pathophysiology of the hypothalamic-pituitary-gonadal reproductive axis in lions, we studied the luteinising hormone (LH) and steroid hormone responses to gonadotropin-releasing hormone (GnRH) and its upstream regulator, kisspeptin. Six young (13.3 ± 1.7 months, 56.2 ± 4.3 kg) and four adult (40.2 ± 1.4 months, 174 ± 6 kg) male lions (Ukutula Conservation Centre, South Africa) were used in this study. Lions were immobilised with a combination of medetomidine and ketamine and an intravenous catheter was placed in a jugular, cephalic or medial saphenous vein for blood sampling at 10-min intervals for 220 min. The ten-amino acid kisspeptin which has full intrinsic activity (KP-10, 1 µg/kg) and GnRH (1 µg/kg) were administered intravenously to study their effects on LH and steroid hormone plasma concentrations, measured subsequently by ELISA and liquid chromatography tandem mass spectrometry (LC-MS/MS), respectively. Basal LH levels were similarly low between the age groups, but testosterone and its precursor levels were higher in the adult animals. Adult lions showed a significant LH response to KP-10 (10-fold) and GnRH (11-fold) administration (p < 0.05 and P < 0.001, respectively) whereas in young lions LH increased significantly only in response to GnRH. In adults alone, testosterone and its precursors steadily increased in response to KP-10, with no significant further increase in response to GnRH. Plasma levels of glucocorticoids in response to KP-10 remained unchanged. We suggest that provocative testing of LH and steroid stimulation with kisspeptin provides a new and sensitive tool for determining reproductive status and possibly an index of exposure to stress, environmental insults such as disease, endocrine disruptors and nutritional status. 272 words.

Immune signaling in sex-specific neural and behavioral development: Adolescent opportunity

Sex differences in neural and behavioral development are integral to understanding neurodevelopmental, mental health, and neurodegenerative disorders. Much of the literature has focused on late prenatal and early postnatal life as a critical juncture for establishing sex-specific developmental trajectories, and data are now clear that immune signaling plays a central role in establishing sex differences early in life. Adolescence is another developmental period during which sex differences arise. However, we know far less about how immune signaling plays a role in establishing sex differences during adolescence. Herein, we review well-defined examples of sex differences during adolescence and then survey the literature to speculate how immune signaling might be playing a role in defining sex-specific adolescent outcomes. We discuss open questions in the literature and propose experimental design tenets that may assist in better understanding adolescent neurodevelopment.

Flexibility of neural circuits regulating mating behaviors in mice and flies

Mating is essential for the reproduction of animal species. As mating behaviors are high-risk and energy-consuming processes, it is critical for animals to make adaptive mating decisions. This includes not only finding a suitable mate, but also adapting mating behaviors to the animal's needs and environmental conditions. Internal needs include physical states (e.g., hunger) and emotional states (e.g., fear), while external conditions include both social cues (e.g., the existence of predators or rivals) and non-social factors (e.g., food availability). With recent advances in behavioral neuroscience, we are now beginning to understand the neural basis of mating behaviors, particularly in genetic model organisms such as mice and flies. However, how internal and external factors are integrated by the nervous system to enable adaptive mating-related decision-making in a state- and context-dependent manner is less well understood. In this article, we review recent knowledge regarding the neural basis of flexible mating behaviors from studies of flies and mice. By contrasting the knowledge derived from these two evolutionarily distant model organisms, we discuss potential conserved and divergent neural mechanisms involved in the control of flexible mating behaviors in invertebrate and vertebrate brains.

Invited review: Translating kisspeptin and neurokinin B biology into new therapies for reproductive health

The reproductive neuropeptide kisspeptin has emerged as the master regulator of mammalian reproduction due to its key roles in the initiation of puberty and the control of fertility. Alongside the tachykinin neurokinin B and the endogenous opioid dynorphin, these peptides are central to the hormonal control of reproduction. Building on the expanding body of experimental animal models, interest has flourished with human studies revealing that kisspeptin administration stimulates physiological reproductive hormone secretion in both healthy men and women, as well as patients with common reproductive disorders. In addition, emerging therapeutic roles based on neurokinin B for the management of menopausal flushing, endometriosis and uterine fibroids are increasingly recognised. In this review, we focus on kisspeptin and neurokinin B and their potential application as novel clinical strategies for the management of reproductive disorders.

Circadian Regulation of Hormonal Timing and the Pathophysiology of Circadian Dysregulation

Circadian rhythms are endogenously generated, daily patterns of behavior and physiology that are essential for optimal health and disease prevention. Disruptions to circadian timing are associated with a host of maladies, including metabolic disease and obesity, diabetes, heart disease, cancer, and mental health disturbances. The circadian timing system is hierarchically organized, with a master circadian clock located in the suprachiasmatic nucleus (SCN) of the anterior hypothalamus and subordinate clocks throughout the CNS and periphery. The SCN receives light information via a direct retinal pathway, synchronizing the master clock to environmental time. At the cellular level, circadian rhythms are ubiquitous, with rhythms generated by interlocking, autoregulatory transcription-translation feedback loops. At the level of the SCN, tight cellular coupling maintains rhythms even in the absence of environmental input. The SCN, in turn, communicates timing information via the autonomic nervous system and hormonal signaling. This signaling couples individual cellular oscillators at the tissue level in extra-SCN brain loci and the periphery and synchronizes subordinate clocks to external time. In the modern world, circadian disruption is widespread due to limited exposure to sunlight during the day, exposure to artificial light at night, and widespread use of light-emitting electronic devices, likely contributing to an increase in the prevalence, and the progression, of a host of disease states. The present overview focuses on the circadian control of endocrine secretions, the significance of rhythms within key endocrine axes for typical, homeostatic functioning, and implications for health and disease when dysregulated. © 2022 American Physiological Society. Compr Physiol 12: 1-30, 2022.

Receptor deorphanization in an echinoderm reveals kisspeptin evolution and relationship with SALMFamide neuropeptides

BACKGROUND

Kisspeptins are neuropeptides that regulate reproductive maturation in mammals via G-protein-coupled receptor-mediated stimulation of gonadotropin-releasing hormone secretion from the hypothalamus. Phylogenetic analysis of kisspeptin-type receptors indicates that this neuropeptide signaling system originated in a common ancestor of the Bilateria, but little is known about kisspeptin signaling in invertebrates.

RESULTS

Contrasting with the occurrence of a single kisspeptin receptor in mammalian species, here, we report the discovery of an expanded family of eleven kisspeptin-type receptors in a deuterostome invertebrate - the starfish Asterias rubens (phylum Echinodermata). Furthermore, neuropeptides derived from four precursor proteins were identified as ligands for six of these receptors. One or more kisspeptin-like neuropeptides derived from two precursor proteins (ArKPP1, ArKPP2) act as ligands for four A. rubens kisspeptin-type receptors (ArKPR1,3,8,9). Furthermore, a family of neuropeptides that act as muscle relaxants in echinoderms (SALMFamides) are ligands for two A. rubens kisspeptin-type receptors (ArKPR6,7). The SALMFamide neuropeptide S1 (or ArS1.4) and a 'cocktail' of the seven neuropeptides derived from the S1 precursor protein (ArS1.1-ArS1.7) act as ligands for ArKPR7. The SALMFamide neuropeptide S2 (or ArS2.3) and a 'cocktail' of the eight neuropeptides derived from the S2 precursor protein (ArS2.1-ArS2.8) act as ligands for ArKPR6.

CONCLUSIONS

Our findings reveal a remarkable diversity of neuropeptides that act as ligands for kisspeptin-type receptors in starfish and provide important new insights into the evolution of kisspeptin signaling. Furthermore, the discovery of the hitherto unknown relationship of kisspeptins with SALMFamides, neuropeptides that were discovered in starfish prior to the identification of kisspeptins in mammals, presents a radical change in perspective for research on kisspeptin signaling.

Neuroendocrine mechanisms underlying estrogen positive feedback and the LH surge

A fundamental principle in reproductive neuroendocrinology is sex steroid feedback: steroid hormones secreted by the gonads circulate back to the brain to regulate the neural circuits governing the reproductive neuroendocrine axis. These regulatory feedback loops ultimately act to modulate gonadotropin-releasing hormone (GnRH) secretion, thereby affecting gonadotropin secretion from the anterior pituitary. In females, rising estradiol (E₂) during the middle of the menstrual (or estrous) cycle paradoxically "switch" from being inhibitory on GnRH secretion ("negative feedback") to stimulating GnRH release ("positive feedback"), resulting in a surge in GnRH secretion and a downstream LH surge that triggers ovulation. While upstream neural afferents of GnRH neurons, including kisspeptin neurons in the rostral hypothalamus, are proposed as critical loci of E₂ feedback action, the underlying mechanisms governing the shift between E₂ negative and positive feedback are still poorly understood. Indeed, the precise cell targets, neural signaling factors and receptors, hormonal pathways, and molecular mechanisms by which ovarian-derived E₂ indirectly stimulates GnRH surge secretion remain incompletely known. In many species, there is also a circadian component to the LH surge, restricting its occurrence to specific times of day, but how the circadian clock interacts with endocrine signals to ultimately time LH surge generation also remains a major gap in knowledge. Here, we focus on classic and recent data from rodent models and discuss the consensus knowledge of the neural players, including kisspeptin, the suprachiasmatic nucleus, and glia, as well as endocrine players, including estradiol and progesterone, in the complex regulation and generation of E₂-induced LH surges in females.

Effects of High-Fat Diet During Childhood on Precocious Puberty and Gut Microbiota in Mice

Precocious puberty mostly stems from endocrine disorders. However, more and more studies show that a high-fat diet (HFD) is closely related to precocious puberty, but its mechanism is unknown. Since gut microbiota is associated with hormone secretion and obesity, it inspires us to detect the mechanism of gut microbiota in triggering precocious puberty. The model of precocious puberty was established by feeding female mice with an HFD from 21 days old. After puberty, the serum hormone levels, gut microbiome sequencing, and metabolomics were collected. DNA was extracted from feces, and the V3–V4 region of the bacterial 16S rRNA gene was amplified, followed by microbial composition analysis. Subsequently, associations between precocious puberty and the microbiota were determined. We found that (1) HFD after weaning caused precocious puberty, increased serum estradiol, leptin, deoxycholic acid (DCA), and gonadotropin-releasing hormone (GnRH) in the hypothalamus; (2) Through correlation analysis, we found that GnRH was positively correlated with Desulfovibrio, Lachnoclostridium, GCA-900066575, Streptococcus, Anaerotruncus, and Bifidobacterium, suggesting that these bacteria may have a role in promoting sexual development. (3) “HFD-microbiota” transplantation promoted the precocious puberty of mice. (4) Estrogen changes the composition and proportion of gut microbiota and promotes precocious puberty. Therefore, the effect of HFD on precocious puberty is regulated by the interaction of gut microbiota and hormones.

Sexual Dimorphism in Adipose-Hypothalamic Crosstalk and the Contribution of Aryl Hydrocarbon Receptor to Regulate Energy Homeostasis

There are fundamental sex differences in the regulation of energy homeostasis. Better understanding of the underlying mechanisms of energy balance that account for this asymmetry will assist in developing sex-specific therapies for sexually dimorphic diseases such as obesity. Multiple organs, including the hypothalamus and adipose tissue, play vital roles in the regulation of energy homeostasis, which are regulated differently in males and females. Various neuronal populations, particularly within the hypothalamus, such as arcuate nucleus (ARC), can sense nutrient content of the body by the help of peripheral hormones such leptin, derived from adipocytes, to regulate energy homeostasis. This review summarizes how adipose tissue crosstalk with homeostatic network control systems in the brain, which includes energy regulatory regions and the hypothalamic–pituitary axis, contribute to energy regulation in a sex-specific manner. Moreover, development of obesity is contingent upon diet and environmental factors. Substances from diet and environmental contaminants can exert insidious effects on energy metabolism, acting peripherally through the aryl hydrocarbon receptor (AhR). Developmental AhR activation can impart permanent alterations of neuronal development that can manifest a number of sex-specific physiological changes, which sometimes become evident only in adulthood. AhR is currently being investigated as a potential target for treating obesity. The consensus is that impaired function of the receptor protects from obesity in mice. AhR also modulates sex steroid receptors, and hence, one of the objectives of this review is to explain why investigating sex differences while examining this receptor is crucial. Overall, this review summarizes sex differences in the regulation of energy homeostasis imparted by the adipose–hypothalamic axis and examines how this axis can be affected by xenobiotics that signal through AhR.

Kisspeptin Variations in Patients with Polycystic Ovary Syndrome-A Prospective Case Control Study

Background and objectives: Kisspeptin, also named metastin, showed important roles in initiating the secretion of gonadotropin-releasing hormone (GnRH) and is an essential factor in the development of polycystic ovaries syndrome (PCOS). Several research studies noticed associations between kisspeptin levels and patients with anovulatory cycles due to PCOS with an increased LH/FSH ratio. The aim of our study was to bring scientific evidence regarding the correlation between high kisspeptin and luteinizing hormone values in subfertile women due to PCOS. Materials and Methods: A prospective case-control study was conducted in “Elena Doamna” Hospital of Obstetrics and Gynecology between 4 January 2021 and 1 March 2022. All patients agreed to participate in our study, had ages between 18 and 45 years old, and had a body mass index between 18.5 and 30 kg/m². The study group consisted of subfertile patients with PCOS and menstrual disturbances, including amenorrhea or oligomenorrhea. The control group consisted of healthy patients with ovulatory cycles and no other reproductive or endocrinology pathologies. During the follicular phase of their menstrual cycle, patients had blood samples taken with the dosage of kisspeptin, LH, FSH, estradiol, insulin, glycemic levels, testosterone, and prolactin. Pelvic ultrasounds and clinical examinations were performed as well. Results: Significant differences were observed in kisspeptin, LH, FSH, and estradiol levels between patients with PCOS and the control group. After the univariate analysis, PCOS was significantly associated with increased kisspeptin, increased LH, and decreased FSH. There was no significant association between PCOS, estradiol, prolactin, and insulin. Conclusions: kisspeptin serum values are higher in subfertile PCOS patients, supporting the hypothesis that an over-stimulation of the KISS1 system might cause the hyper-stimulation of the HPG-axis.

Estrogenic regulation of reproduction and energy homeostasis by a triumvirate of hypothalamic arcuate neurons

Pregnancy is energetically demanding and therefore, by necessity, reproduction and energy balance are inextricably linked. With insufficient or excessive energy stores a female is liable to suffer complications during pregnancy or produce unhealthy offspring. Gonadotropin-releasing hormone neurons are responsible for initiating both the pulsatile and subsequent surge release of luteinizing hormone to control ovulation. Meticulous work has identified two hypothalamic populations of kisspeptin (Kiss1) neurons that are critical for this pattern of release. The involvement of the hypothalamus is unsurprising because its quintessential function is to couple the endocrine and nervous systems, coordinating energy balance and reproduction. Estrogens, more specifically 17β-estradiol (E₂ ), orchestrate the activity of a triumvirate of hypothalamic neurons within the arcuate nucleus (ARH) that govern the physiological underpinnings of these behavioral dynamics. Arising from a common progenitor pool, these cells differentiate into ARH kisspeptin, pro-opiomelanocortin (POMC), and agouti related peptide/neuropeptide Y (AgRP) neurons. Although the excitability of all these subpopulations is subject to genomic and rapid estrogenic regulation, Kiss1 neurons are the most sensitive, reflecting their integral function in female fertility. Based on the premise that E₂ coordinates autonomic functions around reproduction, we review recent findings on how Kiss1 neurons interact with gonadotropin-releasing hormone, AgRP and POMC neurons, as well as how the rapid membrane-initiated and intracellular signaling cascades activated by E₂ in these neurons are critical for control of homeostatic functions supporting reproduction. In particular, we highlight how Kiss1 and POMC neurons conspire to inhibit AgRP neurons and diminish food motivation in service of reproductive success.

The hypothalamus for whole-body physiology: from metabolism to aging

Obesity and aging are two important epidemic factors for metabolic syndrome and many other health issues, which contribute to devastating diseases such as cardiovascular diseases, stroke and cancers. The brain plays a central role in controlling metabolic physiology in that it integrates information from other metabolic organs, sends regulatory projections and orchestrates the whole-body function. Emerging studies suggest that brain dysfunction in sensing various internal cues or processing external cues may have profound effects on metabolic and other physiological functions. This review highlights brain dysfunction linked to genetic mutations, sex, brain inflammation, microbiota, stress as causes for whole-body pathophysiology, arguing brain dysfunction as a root cause for the epidemic of aging and obesity-related disorders. We also speculate key issues that need to be addressed on how to reveal relevant brain dysfunction that underlines the development of these disorders and diseases in order to develop new treatment strategies against these health problems.