Kisspeptin Administration Research Articles

Changes in the Responsiveness of the Hypothalamic-Pituitary-Gonadal Axis to Kisspeptin-10 Administration during Pubertal Transition in Boys.

In human, no studies are available regarding changes in kisspeptin1 receptor (KISS1R) sensitivity during pubertal transition. In this study, healthy boys were classified into 5 Tanner stages of puberty (n = 5/stage). Human kisspeptin-10 was administered to boys at each Tanner stage and to adult men (n = 5) as an IV bolus for comparison. Serial blood samples were collected for 30 min pre- and 120 min post-kisspeptin injection periods at 30 min interval for measuring plasma LH and testosterone levels. There was insignificant effect of kisspeptin on LH and testosterone levels in boys of Tanner stages I–III. At Tanner stage IV, the effect of kisspeptin on plasma LH was insignificant. However, a paired t-test on a log-transformed data showed a significant (P < 0.05) increase in mean peak post-kisspeptin testosterone level. In Tanner stage V, a significant (P < 0.05) increase was observed in mean post-kisspeptin peak LH level as compared to the mean basal LH value. Post-kisspeptin plasma testosterone levels were also significantly (P < 0.05) increased as compared to the pre-kisspeptin level in Tanner stage V. Our data suggest that sensitivity of KISS1R on GnRH neurons with reference to LH stimulation in boys develops during the later part of puberty reaching to adult level at Tanner stage V. This trial is registered with WHO International Clinical Trial Registration ID NCT03286517.

Conspecific odor exposure predominantly activates non-kisspeptin cells in the medial nucleus of the amygdala

A small neuronal subpopulation in the medial nucleus of the amygdala (MeA), expressing the Kiss1 gene, is now considered an important mediator that integrates socio-sexual behavior and odor information in order to modulate the Hypothalamic-Pituitary-Gonadal (HPG) axis. Previous studies demonstrated that exogenous kisspeptin administration or selective activation of Kiss1-expressing neurons in the MeA modulates the onset of puberty, LH secretion and sexual behavior. These functions are supported by the known MeA neuronal connections. In the MeA, as well as in the hypothalamus, Kiss1 mRNA expression mostly depends on sex steroids levels. However, the percentage of Kiss1-expressing cells that co-express estrogen receptor α (ERα) in the MeA is currently unknown. Additionally, whether MeA kisspeptin neurons show Fos expression due to pheromone exposure is still undisclosed. In the present study, we used adult male and female mice that express a reporter protein under the Kiss1 promoters to determine the percentage of Kiss1-expressing neurons that co-express the ERα in the MeA and, whether those cells are activated by olfactory cues. We found a high percentage of Kiss1-expressing neurons in the MeA co-expressing the ERα. The proportion of co-expression was similar between male and female mice in diestrus. Interestingly, a low percentage of Kiss1-expressing neurons in the MeA co-express Fos after conspecific odor exposure, despite a significant increase of Fos positive cells in the MeA. Additionally, odor exposition leads to a sexually dimorphic change in Kiss1 expression in the posterior subdivision of the MeA. Our findings suggest that olfactory signals predominantly activate non-kisspeptin cells in the MeA to modulate responses to pheromones and therefore the HPG axis.

New insights on the neuroendocrine control of puberty and seasonal breeding in female sheep

Timing of puberty has a great influence on animal productivity. For example, reproduction in sheep can be affected by seasonality, leading to fluctuations in availability of animal products. Therefore, optimization of birth dates would improve reproductive success in sheep. Since the discovery of the major role of kisspeptin and Kiss1R, its cognate receptor, in reproductive function, there are new opportunities for interventions. Repeated or continuous administration of native kisspeptin are able to hasten puberty and induce ovulation during breeding and non-breeding seasons of sheep. However, due to the short half-life of kisspeptin, protocols involving native kisspeptin are usually proof of concept, but not practical under field conditions. Consequently, there are efforts to develop kisspeptin analogues capable of replicating effects of repeated/continuous administration of native kisspeptin. In this review, we intended to provide a comprehensive summary of the neuroendocrine requirements for puberty onset and ovulation in adult ewes, focusing on kisspeptin, its physiological effects and responses to its analogues on reproductive function in ewes.

Intergenerational Influence of Paternal Obesity on Metabolic and Reproductive Health Parameters of the Offspring: Male-Preferential Impact and Involvement of Kiss1-Mediated Pathways.

Obesity and its comorbidities are reaching epidemic proportions worldwide. Maternal obesity is known to predispose the offspring to metabolic disorders, independently of genetic inheritance. This intergenerational transmission has also been suggested for paternal obesity, with a potential negative impact on the metabolic and, eventually, reproductive health of the offspring, likely via epigenetic changes in spermatozoa. However, the neuroendocrine component of such phenomenon and whether paternal obesity sensitizes the offspring to the disturbances induced by high-fat diet (HFD) remain poorly defined. We report in this work the metabolic and reproductive impact of HFD in the offspring from obese fathers, with attention to potential sex differences and alterations of hypothalamic Kiss1 system. Lean and obese male rats were mated with lean virgin female rats; male and female offspring were fed HFD from weaning onward and analyzed at adulthood. The increases in body weight and leptin levels, but not glucose intolerance, induced by HFD were significantly augmented in the male, but not female, offspring from obese fathers. Paternal obesity caused a decrease in luteinizing hormone (LH) levels and exacerbated the drop in circulating testosterone and gene expression of its key biosynthetic enzymes caused by HFD in the male offspring. LH responses to central kisspeptin-10 administration were also suppressed in HFD males from obese fathers. In contrast, paternal obesity did not significantly alter gonadotropin levels in the female offspring fed HFD, although these females displayed reduced LH responses to kisspeptin-10. Our findings suggest that HFD-induced metabolic and reproductive disturbances are exacerbated by paternal obesity preferentially in males, whereas kisspeptin effects are affected in both sexes.

Evolutionally Conserved Function of Kisspeptin Neuronal System Is Nonreproductive Regulation as Revealed by Nonmammalian Study.

The kisspeptin neuronal system, which consists of a neuropeptide kisspeptin and its receptor Gpr54, is considered in mammals a key factor of reproductive regulation, the so-called hypothalamic-pituitary-gonadal (HPG) axis. However, in nonmammalian vertebrates, especially in teleosts, existence of kisspeptin regulation on the HPG axis is still controversial. In this study, we applied multidisciplinary techniques to a teleost fish, medaka, and examined possible kisspeptin regulation on the HPG axis. First, we generated knockout medaka for kisspeptin-related genes and found that they show normal fertility, gonadal maturation, and expression of gonadotropins. Moreover, the firing activity of GnRH1 neurons recorded by the patch clamp technique was not altered by kisspeptin application. Furthermore, in goldfish, in vivo kisspeptin administration did not show any positive effect on HPG axis regulation. However, as kisspeptin genes are completely conserved among vertebrates except birds, we surmised that kisspeptin should have some important nonreproductive functions in vertebrates. Therefore, to discover novel functions of kisspeptin, we generated a gpr54-1:enhanced green fluorescent protein (EGFP) transgenic medaka, whose gpr54-1-expressing cells are specifically labeled by EGFP. Analysis of neuronal projection of gpr54-1:EGFP-expressing neurons showed that these neurons in the ventrolateral preoptic area project to the pituitary and are probably involved in endocrine regulation other than gonadotropin release. Furthermore, combination of deep sequencing, histological, and electrophysiological analyses revealed various novel neural systems that are under control of kisspeptin neurons-that is, those expressing neuropeptide Yb, cholecystokinin, isotocin, vasotocin, and neuropeptide B. Thus, our new strategy to genetically label receptor-expressing neurons gives insights into various kisspeptin-dependent neuronal systems that may be conserved in vertebrates.

Towards new strategies to manage livestock reproduction using kisspeptin analogs

The discovery of the hypothalamic neuropeptide kisspeptin and its receptor (KISS1R) have dramatically improved our knowledge about the central mechanisms controlling reproduction. Kisspeptin neurons could be considered the hub where internal and external information controlling reproduction converge. The information is here elaborated and the command dispatched to GnRH neurons, the final output of the brain system controlling reproduction. Several studies have shown that in mammals administration of kisspeptin could finely modulate many aspects of reproduction from puberty to ovulation. For example in ewes kisspeptin infusion triggered ovulation during the non-breeding season and in prepubertal rat repeated injections advanced puberty onset. However, especially in livestock, the suboptimal pharmacological properties of endogenous kisspeptin, notably it short half-life and consequently its poor pharmacodynamics, fetters its use to experimental setting. To overcome this issue synthetic KISS1R agonists, mainly based on kisspeptin backbone, were created. Their more favorable pharmacological profile, longer half-life and duration of action, allowed to perform promising initial experiments for controlling ovulation and puberty. Additional experiments and further refinement of analogs would still be necessary to exploit fully the potential of targeting the kisspeptin system. Nevertheless, it is already clear that this new strategy may represent a breakthrough in the field of reproduction control.

Differential response patterns of kisspeptin and RFamide-related peptide to photoperiod and sex steroid feedback in the Djungarian hamster (Phodopus sungorus).

Many animals synchronise their reproductive activity with the seasons to optimise the survival of their offspring. This synchronisation involves switching on and off their gonadotrophic axis. Ever since their discovery as key regulators of gonadotrophin-releasing hormone (GnRH) neurones, the hypothalamic RF-amide peptides kisspeptin and RFamide-related peptide (RFRP) have been a major focus of research on the seasonal regulation of the gonadotrophic axis. In the present study, we investigated the regulation of both neuropeptides in the Djungarian hamster, a major animal model for the study of seasonal reproduction. During the long-day breeding period, kisspeptin neurones in the anteroventral periventricular area are solely controlled by a positive sex steroid feedback and, in the arcuate nucleus, they are subject to a very strong negative sex steroid feedback associated with a minor photoperiodic effect. During short-day sexual quiescence, the disappearance of this hormonal feedback leads to high levels of kisspeptin in arcuate neurones. Notably, chronic central administration of kisspeptin is able to over-ride the photoperiodic inhibition of the gonadotrophic axis and reactivate the reproductive function. Therefore, our data suggest that kisspeptin secretion by arcuate neurones during sexual quiescence is inhibited by mechanisms upstream of kisspeptin neurones. RFRP expression is solely controlled by photoperiod, being strongly reduced in short days independently of the sex steroid feedback. Thus, kisspeptin and RFRP display contrasting patterns of expression and regulation. Upstream mechanisms controlling these neurones should be the focus of further studies on the roles of these RFamide neuropeptides in the seasonal control of reproduction.

The effect of oxytocin and Kisspeptin-10 in ovary and uterus of ischemia-reperfusion injured rats

ObjectiveIschemia/reperfusion (I/R) injuries result in damage to endothelial and parenchymal cells. Oxytocin (OXY) stimulates uterine contraction during parturition and myoepithelial cells during suckling. OXY has been used as a protective antioxidant. Kisspeptin plays a key role in the central control of reproductive functions and onset of puberty. Recent studies show that these reproductive hormones have protective potential as antioxidant. The aim of this study is to investigate the potential protective effects of Kisspeptin and OXY as antioxidants on I/R injured ovary and uterus of female rats. Materials and methodsRats were separated into five groups. Group 1, is control group; Group 2, rats were subjected to ischemia followed by reperfusion. Group 3, OXY administration 30 min prior to I/R applied rats; Group 4, Kisspeptin administration 30 min prior to I/R applied rats; Group 5, OXY and Kisspeptin administration 30 min prior to I/R. Ovary and uterus were removed for histopathological and biochemical observations. Malondialdehyde, glutathione levels, and superoxide dismutase activities were analyzed in order to observe antioxidant potential of OXY and Kisspeptin. Hematoxylin and Eosin staining was applied for histopathologic scoring. ResultsStromal and granulosa cells in ovary, endometrial cells in uterus were damaged in I/R group. The cellular damage of ovary and uterus were reduced in OXY and Kisspeptin administered I/R group when compared to only Kisspeptin injected I/R group and I/R group. There is no significant difference between OXY and OXY + Kisspeptin injected I/R groups. MDA levels were decreased in Kisspeptin and/or Oxytocin applied I/R group compared to I/R group. SOD activity and GSH levels were increased in Kisspeptin and/or OXY applied I/R group compared to I/R group. ConclusionsThe present results suggest that exogenous application of oxytocin and kisspeptin can have antioxidant effects on the uterus and ovary.

Effect of kisspeptin-10, LH and hCG on serum testosterone concentrations in stallions, donkeys and mules

This study was conducted to determine the response of serum testosterone (T) in male equines (stallions, donkeys and mules) after administering intravenous doses of kisspeptin-10 (KP-10), human chorionic gonadotropin (hCG) and luteinizing hormone (LH) and saline as a control. The animals were divided into four groups of three each: Group I, 3 ml of 0.95% saline; Group II, 50 μg KP-10; Group III, 2500 IU hCG and group IV, 400 μg LH. The administration of KP-10 and hCG to stallions resulted in a significant increase in serum T concentration at 240 min; whereas it was significantly higher at 30, 60, 120, and 240 min with LH treatment as compared to pre-dose concentrations. Both KP-10 and hCG significantly elevated the T concentrations in donkeys at 120 and 240 min, respectively; whereas it was significantly higher at 60, 120, and 240 min with LH treatment as compared to pre-dose concentration. Both KP-10 and LH elevated T in donkeys at 240 min as compared to the control and hCG concentrations. After 120 and 240 min, T concentrations in mules were higher (p < 0.05) with administration of KP-10, hCG and LH as compared to the control. In conclusion, the administration of KP-10, hCG and LH elevate the serum T concentration in normal male equines. It is suggested that KP-10 may be useful in situations where an increase in T is desired. Further work is required to determine the effect of KP-10 on T in male equids with reproductive abnormalities before it can be used in clinical situations.

Potential clinical application of Kisspeptin in reproductive endocrinology

Gonadotropin-releasing hormone (GnRH) plays an important role in the process of reproduction. Studies have shown that a family of peptides Kisspeptin can act on GnRH-related neurons, stimulating the secretion of GnRH, and activating the hypothalamic-pituitary-gonadal axis. Both animal experiments and clinical studies have shown that exogenous administration of Kisspeptin is able to induce physiological GnRH release in healthy individuals and those with endocrine-disorders, which brings great hope for treatment of reproductive endocrine diseases. The effect of Kisspeptin is similar to the physiological process in induction of ovulation and ovum maturation, leading to high security and efficiency for women receiving in vitro fertilization. Kisspeptin is involved in trophoblast invasion, so it may be useful for predicting pregnancy outcomes. In addition, Kisspeptin is the key hormone in the onset of puberty acting as a signal transducer in metabolism and reproduction, so it provides some directions for studies of polycystic ovary syndrome, hyperprolactinemia, and other metabolic-related reproductive endocrine diseases. This article reviews the character of Kisspeptin and the prospect of its application in treatment of reproductive endocrine diseases.

Kiss 1 and GPR54 mRNA expression, endocrine profile, follicular development and onset of estrus following kisspeptin administration in pre-pubertal mithun heifers

Present study was undertaken to find out the effect of exogenous kisspeptin administration on Kiss1 and GPR54 mRNA expression, plasma endocrine profile and follicular development in pre-pubertal mithun heifers. Mithun heifers (20), age between 22–26 months, were selected and divided randomly into two groups (n=10). Before starting the experiment, all animals were examined by rectal palpation as well as through ultrasonography to ascertain the pre-pubertal status and blood samples were collected. All the animals in group A (treatment) were injected with kisspeptin (Metastin) @ 1.3 μg/kg body wt. at every 3 days interval up to day 20 while in group B (control), normal saline was injected as placebo. Blood samples were collected on the day of injection and on the day of estrus in control as well as treatment group. Trans-rectal ultrasonography was also conducted at every 3 days interval till day 20 and at estrus to study the follicular development. Results revealed significant increase in Kiss1 and GPR54 mRNA expression following kisspeptin administration as compared to control. Level of FSH and Estradiol 17β was higher in treatment group while no difference was reported in plasma progesterone in control and treatment group. Increased numbers of medium and large follicle were recorded in treatment group while control group showed only small and medium follicles. Early onset of estrus was reported in treatment group than in control. It may be concluded that exogenous administration of kisspeptin increased expression of Kiss1 and GPR54 mRNA; peripheral FSH and estradiol concentration, increased follicular growth and early onset of estrus in treated heifers than in control.

Continuous Kisspeptin Administration in Postmenopausal Women: Impact of Estradiol on Luteinizing Hormone Secretion.

Kisspeptin stimulates the reproductive endocrine cascade in both men and women. Circulating sex steroids are thought to modulate the ability of kisspeptin to stimulate gonadotropin-releasing hormone (GnRH)-induced luteinizing hormone (LH) release. To probe the effects of sex steroids on kisspeptin-stimulated GnRH-induced LH pulses. Eight healthy postmenopausal women. Subjects underwent every-10-minute blood sampling to measure GnRH-induced LH secretion at baseline and in response to a continuous kisspeptin infusion (12.5 µg/kg/h) over 24 hours. A subset of the participants also received kisspeptin (0.313 µg/kg) and GnRH (75 ng/kg) intravenous boluses. Postmenopausal women are resistant to the stimulatory effect of continuous kisspeptin on LH secretion. Postmenopausal women receiving estradiol replacement therapy are also resistant to kisspeptin initially, but they demonstrate a significant increase in LH pulse amplitude in direct proportion to the circulating estradiol concentration and duration of kisspeptin administration. Kisspeptin administration has complex effects on GnRH, and by extension, on LH secretion. The ability of kisspeptin to affect LH secretion can be modulated by the ambient sex-steroid milieu in a time- and dose-dependent manner.

Kisspeptin modulates sexual and emotional brain processing in humans.

BACKGROUND. Sex, emotion, and reproduction are fundamental and tightly entwined aspects of human behavior. At a population level in humans, both the desire for sexual stimulation and the desire to bond with a partner are important precursors to reproduction. However, the relationships between these processes are incompletely understood. The limbic brain system has key roles in sexual and emotional behaviors, and is a likely candidate system for the integration of behavior with the hormonal reproductive axis. We investigated the effects of kisspeptin, a recently identified key reproductive hormone, on limbic brain activity and behavior.METHODS. Using a combination of functional neuroimaging and hormonal and psychometric analyses, we compared the effects of kisspeptin versus vehicle administration in 29 healthy heterosexual young men.RESULTS. We demonstrated that kisspeptin administration enhanced limbic brain activity specifically in response to sexual and couple-bonding stimuli. Furthermore, kisspeptin’s enhancement of limbic brain structures correlated with psychometric measures of reward, drive, mood, and sexual aversion, providing functional significance. In addition, kisspeptin administration attenuated negative mood.CONCLUSIONS. Collectively, our data provide evidence of an undescribed role for kisspeptin in integrating sexual and emotional brain processing with reproduction in humans. These results have important implications for our understanding of reproductive biology and are highly relevant to the current pharmacological development of kisspeptin as a potential therapeutic agent for patients with common disorders of reproductive function.FUNDING. National Institute for Health Research (NIHR), Wellcome Trust (Ref 080268), and the Medical Research Council (MRC).

Kisspeptin and RFRP-3 differentially regulate food intake and metabolic neuropeptides in the female desert jerboa.

Jerboas are wild rodents exhibiting exceptional adaptation to their desert environment. Under harsh autumn conditions, they shut down reproduction, increase body weight and hibernate, while during spring they become sexually active even under negative energy-balance. We recently reported that these rhythms are associated with synchronized changes in genes expressing reproductive (Kiss1, Rfrp) and metabolic (Npy and Pomc) peptides, raising the hypothesis of coordinated seasonal regulation of both functions. Here we analyzed whether kisspeptin and RFRP-3 regulate food-intake in parallel to their established reproductive functions. Intracerebroventricular administration of kisspeptin inhibited food intake by 1.5-fold in fasted, but not ad-libitum fed, female jerboas captured in spring, an effect associated with an increase in Pomc and decrease in Rfrp mRNA levels. By contrast, intracerebroventricular injection of RFRP-3 induced a 4-fold increase in food-intake in ad-libitum female jerboas, together with a decrease in Pomc and increase in Npy mRNA levels. This orexigenic effect of RFRP-3 was observed in both spring and autumn, whereas kisspeptin’s anorexigenic effect was only observed in spring. Altogether, this study reports opposite metabolic effects of kisspeptin and RFRP-3 in the female jerboa and strengthens our hypothesis of a coordinated, season-dependent, regulation of reproductive activity and food intake through interactions of these hypothalamic peptides.

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

Oxytocin release from the posterior pituitary gland stimulates uterine contraction during birth but the central mechanisms that activate oxytocin neurones for birth are not well characterized. We found that that kisspeptin fibre density around oxytocin neurones increases in late-pregnant rats. These kisspeptin fibres originated from hypothalamic periventricular nucleus neurones that upregulated kisspeptin expression in late pregnancy. Oxytocin neurones were excited by central kisspeptin administration in late-pregnant rats but not in non-pregnant rats or early- to mid-pregnant rats. Our results reveal the emergence of a new excitatory kisspeptin projection to the oxytocin system in late pregnancy that might contribute to oxytocin neurone activation for birth. The hormone oxytocin promotes uterine contraction during parturition. Oxytocin is synthesized by magnocellular neurones in the hypothalamic supraoptic and paraventricular nuclei and is released into the circulation from the posterior pituitary gland in response to action potential firing. Systemic kisspeptin administration increases oxytocin neurone activity to elevate plasma oxytocin levels. Here, immunohistochemistry revealed that rats on the expected day of parturition (day21 of gestation) had a higher density of kisspeptin-positive fibres in the perinuclear zone surrounding the supraoptic nucleus (which provides dense glutamatergic and GABAergic innervation to the supraoptic nucleus) than was evident in non-pregnant rats. Retrograde tracing showed the kisspeptin projections to the perinuclear zone originated from the hypothalamic periventricular nucleus. Quantitative RT-PCR showed that kisspeptin receptor mRNA, Kiss1R mRNA, was expressed in the perinuclear zone-supraoptic nucleus and that the relative Kiss1R mRNA expression does not change over the course of pregnancy. Finally, intracerebroventricular administration of kisspeptin increased the firing rate of oxytocin neurones in anaesthetized late-pregnant rats (days 18-21 of gestation) but not in non-pregnant rats, or in early- or mid-pregnant rats. Taken together, these results suggest that kisspeptin expression is upregulated in the periventricular nucleus projection to the perinuclear zone of the supraoptic nucleus towards the end of pregnancy. Hence, this input might activate oxytocin neurones during parturition.

Kisspeptin-mediated regulation of testicular activity of rats under the effect of gold nanoparticles

There are a variety of biomedical applications of nanoparticles. They can be used as drug carriers, anti-tumor agents, biosensors and modulators of immune response. But full-scale real clinical application of nanomaterials requires a great deal of information on their safety and biotoxicity. Even traditionally harmless materials, like gold, can obtain toxic features when scaled to the nanosize. In vitro studies showed that nanoparticles can be geno- and cytotoxic, but their effects on the body as a whole remain largely a mystery. To shed some light on this, our study focused on the reproductive toxicity of nanomaterials. We synthesized 10–15 nm gold nanoparticles through the reduction of sodium tetrachloroaurate (III) in an alkaline medium with the addition of sodium polyphosphate as a stabilizing agent. Next, these particles were administered intraperitoneally to young and old rats for 10 days. To test functional capabilities of the testes, we injected kisspeptin-10 or its antagonist peptide-234 intracerebroventricularly. These substances are known to stimulate or inhibit the central component of the hypothalamic-pituitary-gonadal axis respectively. After the routine histological procedures, we measured the diameter of seminiferous tubules and the nuclear cross-sectional area of Sertoli cells as markers of testicular spermatogenic activity and a cross-sectional area of the Leydig cells’ nuclei as a marker of testicular steroidogenesis. We found that injections of nanogold caused no significant changes in the young animals. At the same time, morphometric parameters of adult animals were significantly lower compared to control, although we observed no pathological changes in the tissue. Combined administration of gold nanoparticles and kisspeptin showed that the stimulatory effect of the latter was not observed at all. This is a specific feature of toxicants called “endocrine disruptors”. Moreover, we found morphological signs of testicular degeneration, which are characteristic of the low-testosterone state. Simultaneous injections of gold and peptide-234 resulted in the highest degree of testicular functional downregulation, regardless of age. Taken as a whole, our data indicates that gold nanoparticles disrupt the regulatory network of the hypothalamic-pituitary-gonadal axis, possibly due to direct action on the interstitial cells and spermatogenic epithelium.

The F0F1 ATP Synthase Complex Localizes to Membrane Rafts in Gonadotrope Cells.

Fertility in mammals requires appropriate communication within the hypothalamic-pituitary-gonadal axis and the GnRH receptor (GnRHR) is a central conduit for this communication. The GnRHR resides in discrete membrane rafts and raft occupancy is required for signaling by GnRH. The present studies use immunoprecipitation and mass spectrometry to define peptides present within the raft associated with the GnRHR and flotillin-1, a key raft marker. These studies revealed peptides from the F0F1 ATP synthase complex. The catalytic subunits of the F1 domain were validated by immunoprecipitation, flow cytometry, and cell surface biotinylation studies demonstrating that this complex was present at the plasma membrane associated with the GnRHR. The F1 catalytic domain faces the extracellular space and catalyzes ATP synthesis when presented with ADP in normal mouse pituitary explants and a gonadotrope cell line. Steady-state extracellular ATP accumulation was blunted by coadministration of inhibitory factor 1, limiting inorganic phosphate in the media, and by chronic stimulation of the GnRHR. Steady-state extracellular ATP accumulation was enhanced by pharmacological inhibition of ecto-nucleoside triphosphate diphosphohydrolases. Kisspeptin administration induced coincident GnRH and ATP release from the median eminence into the hypophyseal-portal vasculature in ovariectomized sheep. Elevated levels of extracellular ATP augmented GnRH-induced secretion of LH from pituitary cells in primary culture, which was blocked in media containing low inorganic phosphate supporting the importance of extracellular ATP levels to gonadotrope cell function. These studies indicate that gonadotropes have intrinsic ability to metabolize ATP in the extracellular space and extracellular ATP may serve as a modulator of GnRH-induced LH secretion.

Kisspeptin across the human lifespan:evidence from animal studies and beyond

Since its first description in 1996, the KISS1 gene and its peptide products, kisspeptins, have increasingly become recognised as key regulators of reproductive health. With kisspeptins acting as ligands for the kisspeptin receptor KISS1R (previously known as GPR54 or KPR54), recent work has consistently shown that administration of kisspeptin across a variety of species stimulates gonadotrophin release through influencing gonadotrophin-releasing hormone secretion. Evidence from both animal and human studies supports the finding that kisspeptins are crucial for ensuring healthy development, with knockout animal models, as well as proband genetic testing in human patients affected by abnormal pubertal development, corroborating the notion that a functional kisspeptin receptor is required for appropriate gonadotrophin secretion. Given the large body of evidence that exists surrounding the influence of kisspeptin in a variety of settings, this review summarises our physiological understanding of the role of these important peptides and their receptors, before proceeding to describe the varying role they play across the reproductive lifespan.

Insights into kisspeptin- and leptin-signalling on GnRH mRNA expression in hypothalamic organ cultures of immature pikeperch Sander lucioperca

Two types of gonadotropin-releasing hormones (GnRH) were identified as gnrh1 and gnrh2 in pikeperch Sander lucioperca. The administration of rodent leptin on hypothalamic organ cultures of immature pikeperch resulted in significantly elevated levels of gnrh2, but not in gnrh1 mRNA, whereas kisspeptin-10 administration did not affect gnrh1 or gnrh2 expression. These results represent preliminary insights into leptin-GnRH-signaling on a hypothalamic level in fish, potentially coupling fat metabolism and the activation of the reproductive axis during puberty. Mammalian leptin and kisspeptin-10, however, failed to initiate a consistent response in pikeperch and their use cannot be recommended.

Kisspeptin stimulates LH secretion but not ovulation in mares during vernal transition

Managing the return to regular cyclicity after the winter anestrous period in the mare has been a challenge for the equine breeding industry. Specifically, efforts have been made to shift or shorten the vernal transition period and to have it followed by a predictable first ovulation at the commencement of the breeding season. Intravenous administration of kisspeptin is known to stimulate an LH response in both reproductively active and inactive mares. This study examined the effects of a constant rate infusion (CRI) of kisspeptin on mares during vernal transition. Mares were given a 30 hours infusion of kisspeptin at a low and high rate (66 nmol [88 μg] and 100 nmol [130 μg] per hour, respectively) or saline, and the LH and follicular response tracked. Plasma samples were collected every 15 minutes for the first 6 hours to determine if there is an acute effect of kisspeptin infusion on LH secretion. Plasma samples were then collected every 3 hours for a total of 72 hours to examine the ability of kisspeptin to stimulate an LH surge. A CRI of kisspeptin increased LH secretion in these mares but was not able to stimulate an LH surge. To examine the effect of kisspeptin on ovarian activity, follicular measurements were collected ultrasonographically until ovulation occurred or the follicles regressed. CRI of kisspeptin at these rates was unable to induce ovulation earlier than controls.