GPR54 Research Articles

Clinical and Genetic Mechanisms in Patients with MC2R Deficiency Presenting with Early Puberty.

Melanocortin receptor 2 (MC2R) in the adrenal cortex controls the hypothalamic-pituitary-adrenal axis. The melanocortin system, influenced by leptin, regulates GnRH neurons, crucial for puberty onset and fertility. This study evaluates early puberty in primary adrenal insufficiency (PAI) patients due to MC2R gene alterations. Seven patients with PAI (P1-P7) from five unrelated families, all presenting with early or precocious puberty, were included. MC2R deficiency diagnosis ranged from 1 day to 11 months. MKRN3, DLK1, KISS1, and KISS1R genes were analyzed using Sanger sequencing in four cases (P2,P4,P6 and P7). All clinical data were obtained retrospectively. Puberty onset mean age was 8.6 years (7.4-9.5) in boys (P1, P2, P3, P7) and 8.5 years (7.4-9.5) in girls (P4, P5, P6). Tumor markers were negative; no adrenal rest or tumors were found. GnRH analogs were used for rapid puberty in P2, P3, P6. Final height in P1 and P2 was below target (-2.6 SDS, -0.7 SDS). Menarche occurred at 11 and 11.3 years in P4 and P5. No pathogenic variants were found. Genetic causes of early puberty were not identified. Elevated ACTH may stimulate kisspeptin neurons, triggering puberty. Close monitoring of these patients for pubertal development is recommended.

Kisspeptin Alleviates Human Hepatic Fibrogenesis by Inhibiting TGFβ Signaling in Hepatic Stellate Cells.

The peptide hormone kisspeptin attenuates liver steatosis, metabolic dysfunction-associated steatohepatitis (MASH), and fibrosis in mouse models by signaling via the kisspeptin 1 receptor (KISS1R). However, whether kisspeptin impacts fibrogenesis in the human liver is not known. We investigated the impact of a potent kisspeptin analog (KPA) on fibrogenesis using human precision-cut liver slices (hPCLS) from fibrotic livers from male patients, in human hepatic stellate cells (HSCs), LX-2, and in primary mouse HSCs. In hPCLS, 48 h and 72 h of KPA (3 nM, 100 nM) treatment decreased collagen secretion and lowered the expression of fibrogenic and inflammatory markers. Immunohistochemical studies revealed that KISS1R is expressed and localized to HSCs in MASH/fibrotic livers. In HSCs, KPA treatment reduced transforming growth factor b (TGFβ)-the induced expression of fibrogenic and inflammatory markers, in addition to decreasing TGFβ-induced collagen secretion, cell migration, proliferation, and colony formation. Mechanistically, KISS1R signaling downregulated TGFβ signaling by decreasing SMAD2/3 phosphorylation via the activation of protein phosphatases, PP2A, which dephosphorylates SMAD 2/3. This study revealed for the first time that kisspeptin reverses human hepatic fibrogenesis, thus identifying it as a new therapeutic target to treat hepatic fibrosis.

Screening of MKRN3, DLK1, KISS1, KISS1R, and PROKR2 genes sequences in related girls with precocious puberty for a personalized management

Screening of MKRN3, DLK1, KISS1, KISS1R, and PROKR2 genes sequences in related girls with precocious puberty for a personalized management

Abstract C111: Characterization of kisspeptin receptor signaling pathways in cervical cancer: Unveiling novel mechanisms and therapeutic potentials

Abstract Introduction: This study delves into the complex signaling mechanisms of the kisspeptin system in cervical cancer, aiming to unravel the intricate interactions between kisspeptin and its receptor, as well as their roles in modulating cancer progression. Given the emerging significance of the kisspeptin system in tumor biology, our research seeks to illuminate how kisspeptin signaling influences cellular behaviors critical to cancer development, such as proliferation and migration. By exploring the nuanced effects of kisspeptin receptor activation, this study contributes to a deeper understanding of its therapeutic potential and underscores the importance of kisspeptin pathways in the broader context of cancer research. Methods: Was employed Bioluminiscence Resonance Energy Transfer (BRET) assays to explore the activation of the kisspeptin receptor in cervical cancer cell lines, using synthesized analogs of kisspeptin-10 for detailed signaling analysis. Functional effects were assessed through proliferation and migration assays. Additionally, we evaluated the activation or reduction in phosphorylation of specific kinases involved in tumoral processes, providing a nuanced understanding of the signaling mechanisms at play. Results: Our data demonstrate that activation of the kisspeptin receptor substantially modulates cellular proliferation and motility in cervical cancer cell lines. We uncovered novel activation of the Gz protein by kisspeptin-10, which is integral to the kisspeptin receptor function, and identified an upregulation of signaling pathways critical for cell survival and metastasis. Importantly, we observed activation of kinases such as Chk2, c-Jun, p70 S6 kinase, and RSK 1/2/3, as well as members of the STAT family, following kisspeptin-10 stimulation. This kinase activation underscores the multifaceted role of kisspeptin in tumor progression, suggesting its involvement in both pro-oncogenic and tumor-suppressive pathways, and provides direct insights into the mechanistic underpinnings of kisspeptin effect on cancer cell behavior. Conclusion: In conclusion, our study elucidates the complex role of kisspeptin-10 in cervical cancer, demonstrating its ability to modulate cellular proliferation and motility through activation of the kisspeptin receptor. The novel activation of the Gz protein and subsequent upregulation of signaling pathways associated with cell survival and metastasis highlight the intricate involvement of kisspeptin in cancer progression. Furthermore, the activation of key kinases such as Chk2, c-Jun, p70 S6 kinase, RSK 1/2/3, and STAT family members upon kisspeptin-10 stimulation reveals a dual-faceted influence on tumor dynamics, promoting both pro-oncogenic and tumor-suppressive mechanisms. These findings provide significant insights into the molecular actions of kisspeptin in cervical cancer, offering potential targets for therapeutic intervention and a deeper understanding of its role in tumor biology. Citation Format: Deisy Y. Rodríguez-Sarmiento, Pedro H. Scarpelli-Pereira, Michel Bouvier. Characterization of kisspeptin receptor signaling pathways in cervical cancer: Unveiling novel mechanisms and therapeutic potentials [abstract]. In: Proceedings of the 17th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2024 Sep 21-24; Los Angeles, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2024;33(9 Suppl):Abstract nr C111.

Structural basis for the ligand recognition and G protein subtype selectivity of kisspeptin receptor.

Kisspeptin receptor (KISS1R), belonging to the class A peptide-GPCR family, plays a key role in the regulation of reproductive physiology after stimulation by kisspeptin and is regarded as an attractive drug target for reproductive diseases. Here, we demonstrated that KISS1R can couple to the Gi/o pathway besides the well-known Gq/11 pathway. We further resolved the cryo-electron microscopy (cryo-EM) structure of KISS1R-Gq and KISS1R-Gi complexes bound to the synthetic agonist TAK448 and structure of KISS1R-Gq complex bound to the endogenous agonist KP54. The high-resolution structures provided clear insights into mechanism of KISS1R recognition by its ligand and can facilitate the design of targeted drugs with high affinity to improve treatment effects. Moreover, the structural and functional analyses indicated that conformational differences in the extracellular loops (ECLs), intracellular loops (ICLs) of the receptor, and the "wavy hook" of the Gα subunit may account for the specificity of G protein coupling for KISS1R signaling.

Astrocytes: a star emerges in the control of reproductive hormones.

Kisspeptin is an essential neuropeptide sitting at the apex of the hypothalamo-pituitary-gonadal (HPG) endocrine axis to regulate gonadotropin-releasing hormone (GnRH) neurons and downstream reproductive hormones. Kisspeptin neurons integrate feedback from sex steroids facilitating regulation of the menstrual cycle and mediate the effects of metabolic stressors on the reproductive axis. In this issue of the JCI, Torres and colleagues describe another pathway for kisspeptin signaling in astrocytes to influence GnRH neuronal output. Astrocytes had kisspeptin receptors that activated canonical intracellular signaling pathways to constrain the magnitude of kisspeptin-induced GnRH neuronal stimulation. Additionally, the appositions between kisspeptin and GnRH neurons were dynamic during the ovarian cycle, with astrocyte kisspeptin signaling proposed as a putative modulator of this neuroplasticity. Importantly, astrocyte kisspeptin signaling also mediated susceptibility to metabolic stressors and the development of obesity-induced hypogonadism, underscoring the physiological and pathological importance of this pathway and revealing the importance of nonneuronal signaling in reproductive health.

Comprehensive Analysis of Kisspeptin Signaling: Effects on Cellular Dynamics in Cervical Cancer.

Kisspeptin, a key neuropeptide derived from the KISS1R gene, is renowned for its critical role in regulating the hypothalamic-pituitary-gonadal axis and reproductive hormone secretion. Beyond its primary function in reproductive biology, emerging research has illuminated its influence in various cancers, mediating significant effects through its interaction with the G protein-coupled receptor, kisspeptin receptor. This interaction has been implicated in modulating cellular processes such as proliferation and metastasis, making it a potential target for therapeutic intervention. Our study initially screened ten kisspeptin-10 analogs through cytotoxic effects of kisspeptin-10 (KP10) and its analogs in several cancer types, including cervical, prostate, breast, and gastric cancers, with a particular focus on cervical cancer, where the most profound effects were observed. Further exploration using kinase array assays revealed that these analogs specifically alter key kinases involved in cancer progression. Migration assays demonstrated a substantial decrease in cell motility, and Bioluminescence Resonance Energy Transfer assays confirmed these analogs' strong interactions with the kisspeptin receptor. Overall, our results indicate that these KP10 analogs not only hinder cervical cancer cell proliferation but also curtail migration through targeted modulation of kinase signaling, suggesting their potential as therapeutic agents in managing cervical cancer progression. This comprehensive approach underscores the therapeutic promise of exploiting kisspeptin signaling in cancer treatment strategies.

Changes in the Bile Acid Pool and Timing of Female Puberty: Potential Novel Role of Hypothalamic TGR5.

The regulation of pubertal timing and reproductive axis maturation is influenced by a myriad of physiologic and environmental inputs yet remains incompletely understood. To contrast differences in bile acid isoform profiles across defined stages of reproductive maturity in humans and a rat model of puberty and to characterize the role of bile acid signaling via hypothalamic expression of bile acid receptor populations in the rodent model. Secondary analysis and pilot studies of clinical cohorts, rodent models, ex vivo analyses of rodent hypothalamic tissues. Bile acid concentrations is the main outcome measure. Lower circulatory conjugated:deconjugated bile acid concentrations and higher total secondary bile acids were observed in postmenarcheal vs pre-/early pubertal adolescents, with similar shifts observed in infantile (postnatal day [PN]14) vs early juvenile (PN21) rats alongside increased tgr5 receptor mRNA expression within the mediobasal hypothalamus of female rats. 16S rRNA gene sequencing of the rodent gut microbiome across postnatal life revealed changes in the gut microbial composition predicted to have bile salt hydrolase activity, which was observed in parallel with the increased deconjugated and increased concentrations of secondary bile acids. We show that TGR5-stimulated GnRH release from hypothalamic explants is mediated through kisspeptin receptors and that early overexpression of human-TGR5 within the arcuate nucleus accelerates pubertal onset in female rats. Bile acid isoform shifts along stages of reproductive maturation are conserved across rodents and humans, with preclinical models providing mechanistic insight for the neuroendocrine-hepatic-gut microbiome axis as a potential moderator of pubertal timing in females.

Sex Differences in the Brain Transcriptomes of Adult Blue Gourami Fish (Trichogaster trichopterus)

Blue gourami (gourami, Trichogaster trichopterus) is a model for labyrinth fishes (Anabantoidei) adapted to partial air breathing. Its reproductive endocrinology has been extensively studied, and transcriptomic sex differences in the gonads were described. Nevertheless, sex differences in gene expression in non-gonadal tissues ostensibly affected by the sex-specific hormonal balance, e.g., the brain, are unknown. To assess such differences, we used bulk RNA-seq to assemble and compare polyA+ transcriptomes between whole brains of four adult male and five adult female gourami, in addition to other tissues (three dorsal fin and five ovary samples) from the same female group. While all nine brain transcriptomes clustered together relative to the other tissues, they showed separation according to sex. A total of 3568 genes were differentially expressed between male and female brains; of these, 1962 and 1606 showed lower and higher expression in males, respectively. Male brains showed stronger down-regulation of specific genes, which included hormone receptors, e.g., pituitary adenylate cyclase-activating polypeptide receptor (pacap-r1). Among the genes with lower expression in male brains, multiple pathways essential to brain function were over-represented, including GABA, acetylcholine and glutamate receptor signaling, calcium and potassium transmembrane transport, and neurogenesis. In contrast, genes with higher expression in male brains showed no significant over-representation of brain-specific functions. To measure the mRNA levels of specific hormone receptors known from prior studies to regulate reproductive function and behavior in gourami and to validate RNA-seq results for these specific genes, we performed RT-qPCR for five receptors, pacap-r1, gonadotropin-releasing hormone 2 receptor (gnrh2r), kisspeptin receptor 1 (gpαr1/kiss1), insulin-like growth factor 1 receptor (igf1r), and membrane progesterone receptor 1 (mpr1), in the brain RNA sample groups. Of these, pacap-r1 showed a significant, three-fold down-regulation, while gpαr1/kiss1 showed a significant two-fold down-regulation in male vs. female gourami brains. Our results are novel in describing the suppression of brain function-related gene expression in male, as compared to female, gourami brains. Further research is needed to assess the behavioral significance of this effect and its prevalence in other vertebrate groups.

The role of placental kisspeptin in trophoblast invasion and migration: an assessment in Kiss1r knockout mice, BeWo cell lines and human term placenta.

Context There is mounting evidence implicating kisspeptin signalling in placental development and function. Aims This study aimed to elucidate kisspeptin's role in trophoblast invasion and migration using three experimental models. Methods First, we examined the mouse fetus and placenta in a kisspeptin receptor (Kiss1r) knockout (KO) model. Fetal/placental weights and gene expression (quantitative polymerase chain reaction) were assessed. Second, we determined kisspeptin effects on a human trophoblast (BeWo) cell line in vitro . Third, we examined KISS1 and KISS1R gene expression in human placenta from term and pre-term pregnancies. Key results No difference was found in fetal or placental weight between Kiss1r KO and wildtype mice. However, expression of the trophoblast invasion marker, Mmp2 mRNA, was greater in the placental labyrinth zone of Kiss1r KO mice. BeWo cell models of villus cytotrophoblast and syncytiotrophoblast cells exhibited kisspeptin protein expression, with greater expression in syncytiotrophoblast, consistent with KISS1 mRNA. Kisspeptin treatment inhibited the migratory potential of cytotrophoblast-like cells. Finally, while no difference was seen in KISS1 and KISS1R mRNA between term and pre-term placentas, we saw a difference in the relative expression of each gene pre-term. We also observed a positive correlation between KISS1 expression and maternal body mass index. Conclusions Our results indicate that kisspeptin may inhibit trophoblast invasion. Implications Further investigation is required to clarify specific regulatory mechanisms.

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.

Genetic Variants in KNDy Pathway Lack Association with Premature Ovarian Insufficiency in Mexican Women: A Sequencing-Based Cohort Study.

Previous studies have demonstrated the essential role of the Kisspeptin/Neurokinin B/Dynorphin A (KNDy) pathway in female reproductive biology by regulating the activity of the hypothalamic-pituitary-gonadal axis. Identified loss-of-function mutations in these genes are linked to various reproductive disorders. This study investigated genetic disorders linked to mutations in the KNDy genes related to premature ovarian insufficiency (POI). A cohort of 14 Mexican POI patients underwent genetic screening using PCR-SSCP and Sanger sequencing, assessing the genetic variations' impact on protein function thereafter using multiple in silico tools. The PCR excluded extensive deletions, insertions, and duplications, while SSCP detected five genetic variants. Variations occurred in the KISS1 (c.58G>A and c.242C>G), KISS1R (c.1091A>T), PDYN (c.600C>T), and OPRK1 (c.36G>T) genes, whereas no genetic anomalies were found in NK3/NK3R genes. Each single-nucleotide variant underwent genotyping using PCR-SSCP in 100 POI-free subjects. Their allelic frequencies paralleled the patient group. These observations indicate that allelic variations in the KNDy genes may not contribute to POI etiology. Hence, screening for mutations in KNDy genes should not be a part of the diagnostic protocol for POI.

Characterization of Kiss/Kissr system and expression profiling through developmental stages indicate kiss1 to be the active isotype in Clarias magur.

Kisspeptin (Kiss) and kisspeptin receptor (Kissr) system is a key regulator of GnRH expression in several vertebrates. The Indian catfish, Clarias magur, is popular in the Indian sub-continent, and a neo-type of the Asian catfish, C. batrachus. Catfish breeding is constrained as males do not release milt captivity with/without stimulation. Magur Kiss/Kissr system comprising of kiss1, kiss2, kissr1, and kissr2 genes was characterized for the first time. Full-length mRNA was sequenced using RACE PCR. Neighbor-joining tree of predicted proteins shows one clade of teleost orthologs. Magur whole genome (NCBI GenBank) has single copies of each gene, though yet unannotated/misannotated. Anomalies in the nomenclature of earlier sequences in GenBank were noted. Relative gene expression was profiled during various ontogenic stages, in six tissues including brain and gonads at maturity, and also in brains and gonads of premature and spent fish. Expression of gnrh1, gnrhr1, and gnrhr2 was estimated concomitantly. The kiss1 was the first to be twofold upregulated (P < 0.05) at 12h post fertilization. Kiss/Kissr genes expressed primarily in the brain, ovary, and testis. Though kiss2 was 10 times higher than kiss1, only kiss1 showed significant modulation across stages and appears to be the active isotype that regulates GnRH in magur.

Kisspeptin a potential therapeutic target in treatment of both metabolic and reproductive dysfunction.

Kisspeptins (KPs) are proteins that were first recognized to have antimetastatic action. Later, the critical role of this peptide in the regulation of reproduction was proved. In recent years, evidence has been accumulated supporting a role for KPs in regulating metabolic processes in a sexual dimorphic manner. It has been proposed that KPs regulate metabolism both indirectly via gonadal hormones and/or directly via the kisspeptin receptor in the brain, brown adipose tissue, and pancreas. The aim of the review is to provide both experimental and clinical evidence indicating that KPs are peptides linking metabolism and reproduction. We propose that KPs could be used as a potential target to treat both metabolic and reproductive abnormalities. Thus, we focus on the consequences of disruptions in KPs and their receptors in metabolic conditions such as diabetes, undernutrition, obesity, and reproductive disorders (hypogonadotropic hypogonadism and polycystic ovary syndrome). Data from both animal models and human subjects indicate that alterations in KPs in the case of metabolic imbalance lead also to disruptions in reproductive functions. Changes both in the hypothalamic and peripheral KP systems in animal models of the aforementioned disorders are discussed. Finally, an overview of current clinical studies involving KP in fertility and metabolism show fewer studies on metabolism (15%) and only one to date on both. Presented data indicate a dynamic and emerging field of KP studies as possible therapeutic targets in treatments of both reproductive and metabolic dysfunctions.

Treatment with Raloxifene Induces the Expression of Kisspeptin, Insulin, and Androgen Receptors in Bones of Castrated Adult Female Rats.

Objective To evaluate the effects of estrogen, raloxifene and genistein on the expression of KISS1 (kisspeptin), KISS1R (kisspeptin receptor), AR (androgen receptor) and INSR (insulin receptor) in the bones of ovariectomized rats. Methods Forty-eight adult rats were randomly divided into 6 groups, containing 8 animals each: G1-nonovariectomized control; G2-ovariectomized and treated with conjugated equine estrogens (50 µg/Kg/day); G3-ovariectomized and treated with raloxifene (0.75 mg/kg/day); G4-ovariectomized animal that received soy extract with genistein (300 mg/kg/day); G5-ovariectomized animal that received estrogen and genistein; and G6-ovariectomized animal that received estrogen and raloxifene. Three months after surgery, the castrated animals received the drugs orally daily for 120 days. All animals were sacrificed after this period, by deepening the anesthesia. The left tibia was removed for total RNA extraction and analysis of gene expression of KISS1 , KISS1R , AR and INSR , by quantitative real-time polymerase chain reaction (qRT-PCR). Results KISS1 was not detected in any of the treated groups. KISS1R , INSR and AR showed higher expression in the G3 group ( p < 0.001), while lower levels of transcripts for these genes were observed in G4 and G5. G2 animals showed hypoexpression of the evaluated genes. Conclusion The results indicate that raloxifene, alone or combined with estrogen, was able to induce the expression of genes associated with the recovery of bone tissue homeostasis in ovariectomized rats.

Kisspeptin/KISS1R Signaling Modulates Human Airway Smooth Muscle Cell Migration.

Airway remodeling is a cardinal feature of asthma, associated with increased airway smooth muscle (ASM) cell mass and upregulation of extracellular matrix deposition. Exaggerated ASM cell migration contributes to excessive ASM mass. Previously, we demonstrated the alleviating role of Kp (kisspeptin) receptor (KISS1R) activation by Kp-10 in mitogen (PDGF [platelet-derived growth factor])-induced human ASM cell proliferation invitro and airway remodeling invivo in a mouse model of asthma. Here, we examined the mechanisms by which KISS1R activation regulates mitogen-induced ASM cell migration. KISS1R activation using Kp-10 significantly inhibited PDGF-induced ASM cell migration, further confirmed using KISS1R shRNA. Furthermore, KISS1R activation modulated F/G actin dynamics and the expression of promigration proteins like CDC42 (cell division control protein 42) and cofilin. Mechanistically, we observed reduced ASM RhoA-GTPAse with KISS1R activation. The antimigratory effect of KISS1R was abolished by PKA (protein kinase A)-inhibitory peptide. Conversely, KISS1R activation significantly increased cAMP and phosphorylation of CREB (cAMP-response element binding protein) in PDGF-exposed ASM cells. Overall, these results highlight the alleviating properties of Kp-10 in the context of airway remodeling.

Kisspeptin prevents pregnancy loss by modulating the immune microenvironment at the maternal-fetal interface in recurrent spontaneous abortion.

Immune factors are crucial in the development of recurrent spontaneous abortion (RSA). This study aimed to investigate whether kisspeptin regulates immune cells at the maternal-fetal interface and whether G protein-coupled receptor 54 (GPR54) is involved in this process, through which it contributes to the pathogenesis of RSA. Normal pregnancy (NP) (CBA/J × BALB/c) and RSA (CBA/J × DBA/2) mouse models were established. NP mice received tail vein injections of PBS and KP234 (blocker of kisspeptin receptor), whereas RSA mice received PBS and KP10 (active fragment of kisspeptin). The changes in immune cells in mouse spleen and uterus were assessed using flow cytometry and immunofluorescence. The expression of critical cytokines was examined by flow cytometry, ELISA, Western blotting, and qPCR. Immunofluorescence was employed to detect the coexpression of FOXP3 and GPR54. The findings revealed that the proportion of Treg cells, MDSCs, and M2 macrophages in RSA mice was lower than that in NP mice, but it increased following the tail vein injection of KP10. Conversely, the proportion of these cells was reduced in NP mice after the injection of KP234. However, the trend of γδT cell proportion change is contrary to these cells. Furthermore, FOXP3 and GPR54 were coexpressed in mouse spleen and uterus Treg cells as well as in the human decidua samples. Our results suggest that kisspeptin potentially participates in the pathogenesis of RSA by influencing immune cell subsets at the maternal-fetal interface, including Treg cells, MDSC cells, γδT cells, and M2 macrophages.

The role of KNDy neurons in human reproductive health.

In the early 2000s, metastin, an endogenous ligand for G protein-coupled receptor 54 (GPR54), was discovered in human placental extracts. In 2003, GPR54 receptor mutations were found in a family with congenital hypogonadotropic hypogonadism. Metastin was subsequently renamed kisspeptin after its coding gene, Kiss1. Since then, studies in mice and other animals have revealed that kisspeptin is located at the apex of the hypothalamic-pituitary-gonadal axis and regulates reproductive functions by modulating gonadotropin-releasing hormone (GnRH). In rodents, kisspeptin (Kiss1) neurons localize to two regions, the hypothalamic arcuate nucleus (ARC) and the anteroventral periventricular nucleus (AVPV). ARC Kiss1 neurons co-express neurokinin B (NKB) and dynorphin and are thus termed KNDy neurons. Kiss1 neurons in humans are concentrated in the infundibular nucleus (equivalent to the ARC), with few Kiss1 neurons localized to the preoptic area (equivalent to the AVPV), and the mechanisms underlying GnRH surge secretion in humans are poorly understood. However, peripheral administration of kisspeptin to humans promotes gonadotropin secretion, and administration of kisspeptin to patients with hypothalamic amenorrhea or congenital hypogonadotropic hypogonadism restores the pulsatile secretion of GnRH/luteinizing hormone. Thus, kisspeptin undoubtedly plays an important role in reproductive function in humans. Studies are currently underway to develop kisspeptin receptor agonists or antagonists for clinical application. Modification of KNDy neurons by NKB agonists/antagonists is also being attempted to develop therapeutic agents for various menstrual abnormalities, including polycystic ovary syndrome and menopausal hot flashes. Here, we review the role of kisspeptin in humans and its clinical applications.

Kisspeptin stimulates sheep ovarian follicular development in vitro through homologous receptors.

The present study was conducted to elucidate (1) the influence of kisspeptin (KP) on the in vitro development of preantral follicles (PFs) and (2) evolution of KP receptor gene (KISS1R) expression during ovarian follicular development in sheep. Kisspeptin was supplemented (0-100 µg/ml) in the culture medium of PFs for 6 days. The cumulus-oocyte complexes (COCs) from cultured PFs were subsequently matured to metaphase II (MII) for an additional 24 h. The proportions of PFs exhibiting growth, antrum formation, average increase in diameter, and maturation of oocytes to MII stage were the indicators of follicular development in vitro. The expression of the kisspeptin receptor gene at each development stages of in vivo developed (preantral, early antral, antral, large antral and COCs from Graafian follicles) and in vitro cultured PFs supplemented with KP was assessed using a real-time polymerase chain reaction. The best development in all the parameters under study was elicited with 10 µg/ml of KP. Supplementation of KP (10 µg/ml) in a medium containing other growth factors (insulin-like growth factor-I) and hormones (growth hormone, thyroxine, follicle-stimulating hormone) resulted in better PF development. The KISS1R gene was expressed in follicular cells and oocytes at all the development stages of both in vivo developed and in vitro cultured follicles. Higher KISS1R gene expression was supported by culture medium containing KP along with other hormones and growth factors. Accordingly, it is suggested that one of the mechanisms through which KP and other growth factors and hormones influence the ovarian follicular development in mammals is through the upregulation of expression of the KP receptor gene.

Lunar Age-Dependent Oscillations in Expression of the Genes for Kisspeptin, GnIH, and Their Receptors in the Grass Puffer during the Spawning Season.

Grass puffer is a semilunar-synchronized spawner: spawning occurs on beaches only for several days of spring tide around new moon (lunar age 0) and full moon (lunar age 15) every 2 weeks from spring to early summer. To investigate the role of kisspeptin and gonadotropin-inhibitory hormone (GnIH) in the semilunar-synchronized spawning, lunar age-dependent expression of the genes encoding kisspeptin (kiss2), kisspeptin receptor (kissr2), GnIH (gnih), GnIH receptor (gnihr), gonadotropin-releasing hormone 1 (GnRH1) (gnrh1), and three gonadotropin (GTH) subunits (gpa, fshb, lhb) was examined in the male grass puffer, which was kept in an aquarium under natural light condition in a lunar month during the spawning period. In the brain, both kiss2 and kissr2 showed lunar variations with a peak at lunar age 10, while both gnih and gnihr showed semilunar variations with two peaks at lunar age 0 and 20. On the other hand, gnrh1 showed semilunar variation with two peaks at lunar age 0 and 15. In the pituitary, kiss2, kissr2, gnih, and gnihr showed similar variations to those shown in the brain. The fshb and lhb mRNA levels showed semilunar variations with two peaks at lunar age 0 and 15. The present study shows lunar and semilunar oscillations of kiss2/kissr2 and gnih/gnihr expressions, respectively, with their peaks around spring tide in the brain and pituitary along with the semilunar expressions of gnrh1 and the pituitary GTH subunit genes. These results suggest that the lunar age-dependent expressions of the kisspeptin, GnIH, and their receptor genes may be primarily important in the control of the precisely timed semilunar spawning of the grass puffer.