Kisspeptin System Research Articles

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.

Bone marrow mesenchymal stem cells expressing Neat-1, Hotair-1, miR-21, miR-644, and miR-144 subsided cyclophosphamide-induced ovarian insufficiency by remodeling the IGF-1–kisspeptin system, ovarian apoptosis, and angiogenesis

Ovarian insufficiency is one of the common reproductive disorders affecting women with limited therapeutic aids. Mesenchymal stem cells have been investigated in such disorders before yet, the exact mechanism of MSCs in ovarian regeneration regarding their epigenetic regulation remains elusive. The current study is to investigate the role of the bone marrow-derived mesenchymal stem cells (BM-MSCs) lncRNA (Neat-1 and Hotair1) and miRNA (mir-21-5p, mir-144-5p, and mir-664-5p) in mitigating ovarian granulosa cell apoptosis as well as searching BM-MSCs in altering the expression of ovarian and hypothalamic IGF-1 – kisspeptin system in connection to HPG axis in a cyclophosphamide-induced ovarian failure rat model. Sixty mature female Sprague Dawley rats were divided into 3 equal groups; control group, premature ovarian insufficiency (POI) group, and POI + BM-MSCs. POI female rat model was established with cyclophosphamide. The result revealed that BM-MSCs and their conditioned media displayed a significant expression level of Neat-1, Hotair-1, mir-21-5p, mir-144-5p, and mir-664-5p. Moreover, BM-MSCs transplantation in POI rats improves; the ovarian and hypothalamic IGF-1 – kisspeptin, HPG axis, ovarian granulosa cell apoptosis, steroidogenesis, angiogenesis, energy balance, and oxidative stress. BM-MSCs expressed higher levels of antiapoptotic lncRNAs and microRNAs that mitigate ovarian insufficiency.

Social isolation and aggression training lead to escalated aggression and hypothalamus-pituitary-gonad axis hyperfunction in mice

Although the participation of sex hormones and sex hormone-responsive neurons in aggressive behavior has been extensively studied, the role of other systems within the hypothalamus-pituitary-gonadal (HPG) axis remains elusive. Here we assessed how the gonadotropin-releasing hormone (GnRH) and kisspeptin systems are impacted by escalated aggression in male mice. We used a combination of social isolation and aggression training (IST) to exacerbate mice’s aggressive behavior. Next, low-aggressive (group-housed, GH) and highly aggressive (IST) mice were compared regarding neuronal activity in the target populations and hormonal levels, using immunohistochemistry and ELISA, respectively. Finally, we used pharmacological and viral approaches to manipulate neuropeptide signaling and expression, subsequently evaluating its effects on behavior. IST mice exhibited enhanced aggressive behavior compared to GH controls, which was accompanied by elevated neuronal activity in GnRH neurons and arcuate nucleus kisspeptin neurons. Remarkably, IST mice presented an increased number of kisspeptin neurons in the anteroventral periventricular nucleus (AVPV). In addition, IST mice exhibited elevated levels of luteinizing hormone (LH) in serum. Accordingly, activation and blockade of GnRH receptors (GnRHR) exacerbated and reduced aggression, respectively. Surprisingly, kisspeptin had intricate effects on aggression, i.e., viral ablation of AVPV-kisspeptin neurons impaired the training-induced rise in aggressive behavior whereas kisspeptin itself strongly reduced aggression in IST mice. Our results indicate that IST enhances aggressive behavior in male mice by exacerbating HPG-axis activity. Particularly, increased GnRH neuron activity and GnRHR signaling were found to underlie aggression whereas the relationship with kisspeptin remains puzzling.

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

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

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

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. 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. 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. 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.

Structural analysis and cytotoxic evaluation of kisspeptin10 and analogs in types of cancer

The Kisspeptin system is a peptidergic system that plays a crucial role in regulating of reproduction and hormonal function. Kisspeptin is a peptide synthesized from the KiSS-1 gene and has been identified as the endogenous ligand of the kisspeptin receptor (KISS1R or GPR54 receptor). This system plays a key role in activating sex hormone secretion and puberty. In addition to its function in the regulation of reproduction, the Kisspeptin system has been found to play a role in other physiological processes, such as the regulation of appetite, energy metabolism, cardiovascular function, and cancer. In this study, several Kisspeptin analogs with structural modifications were designed and synthesized. The Kisspeptin analogs were evaluated by in vitro cytotoxicity tests on cancer cells of different cancer types. Cell viability assays were performed, and the concentrations that inhibited cell growth by a significant percentage were determined. The results showed that certain Kisspeptin analogs exhibited increased selective cytotoxicity in cancer cells compared to healthy cells. In conclusion, this study demonstrates that structurally modified Kisspeptin analogs have the potential to be therapeutic agents against some types of cancer. Understanding the structure-activity relationship of these analogs and their evaluation of their selective toxicity on cancer cells will be of great importance. Keywords: Kisspeptins Analogs, GPR54, Cancer, Cytotoxicity, Molecular Docking, Structure-activity relationship, Anticancer therapy, Drug Design.

Beyond reproduction: Exploring the Non-Canonical roles of the Kisspeptin System in Diverse Biological Systems

G protein-coupled receptors are integral membrane proteins in cell signaling processes. Activation of G protein-coupled receptors by specific agonists promotes the activation of different G-proteins, activating different intracellular signaling pathways, including adenylate cyclase activation and intracellular calcium release. One of the G protein-coupled receptors studied is the kisspeptin receptor, which regulates reproduction and gonadotropin secretion. However, recent studies have shown that kisspeptin and its receptor have non-canonical roles in cell signaling and several biological systems. In the present review, we will present these different functions exerted by the kisspeptin system in different biological systems, such as the central nervous system, the cardiovascular system, and the immune system, as well as the role of this system in pathologies such as preeclampsia, diabetes, and cancer. Understanding their non-canonical roles in cell signaling may have important implications in developing new therapies for various diseases. Keywords: Kisspeptin-1 Receptor, Kisspeptins, G-protein coupled receptor, Signal Transduction, Cancer, Diabetes Mellitus, Preeclampsia.

The kiss2/kiss2r system directly modulates the activity of the pituitary gland in largemouth bass (Micropterus salmoides)

The kisspeptin system, which involves hypothalamic neuropeptides, plays pivotal roles in the regulation of teleost reproduction. A previous study suggested that the kiss2/kissr2 system in largemouth bass (Micropterus salmoides) was involved in regulating gonadal development through the hypothalamus-pituitary-gonad (HPG) axis. However, whether the kiss2/kiss2r system directly regulates the activity of pituitary gland were not studied. This study aimed to elucidate the detailed mechanism of kisspeptin-induced effects on gonadotropin hormone-producing cells in vivo and in vitro. In situ hybridization analysis revealed very widespread expression of kiss2r mRNA in the optic tectum, hypothalamus and pituitary. In the pituitary, kiss2r-expressing cells were mainly located in the proximal pars distalis and pars intermedia, among which the fshβ- and lhβ-positive cells exhibited expression of kiss2r messengers. Furthermore, primary culture of pituitary cells and peptide administration experiments revealed that the Kiss2-10 peptide stimulates the expression of fshβ and lhβ and the secretion of FSH and LH in 24 h. In addition, histology analysis revealed that three injections of the Kiss2-10 peptide promoted ovary development and increased oocyte size but had little effect on testis development. These results suggested that the intrapituitary kisspeptinergic system, as a hypophysiotropic neuropeptide factor, directly modulates of gonadotroph function. This study will help uncover the reproductive endocrinology network and improve artificial breeding technology for largemouth bass.

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

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

Food deprivation differentially modulates gene expression of LPXRFa and kisspeptin systems in the brain-pituitary axis of half-smooth tongue sole (Cynoglossus semilaevis).

LPXRFa, also known as gonadotropin-inhibitory hormone (GnIH), and kisspeptin (Kiss) are two major hypothalamic peptides that modulate the reproductive axis of vertebrates, including teleosts. However, little information is available regarding the actions of nutritional status on the regulation of these two neuroendocrine systems in fish. Herein, we assessed the effects of starvation and refeeding on the expression of lpxrfa, kiss2 and their receptors (lpxrfa-r and kiss2r respectively) at the brain-pituitary level of half-smooth tongue sole (Cynoglossus semilaevis). Food deprivation for 4 weeks induced a rise in brain lpxrfa as well as brain and pituitary lpxrfa-r mRNA levels, and refeeding restored brain lpxrfa and lpxrfa-r expression back to normal. However, pituitary lpxrfa-r mRNA levels still remained high after 1 week of refeeding. Neither lpxrfa nor kiss2 transcripts in the pituitary were altered by fasting, but their mRNA levels increased significantly after 1 week of refeeding, and declined back to the control levels after 2 weeks of refeeding. None of brain kiss2 and kiss2r along with pituitary kiss2r transcripts were modified by the nutritional status. In summary, our results revealed an interaction between energy status and the elements of LPXRFa and Kiss systems in the brain-pituitary axis of half-smooth tongue sole. Food deprivation and refeeding differentially regulated the two systems, which provided additional evidence for the involvement of the LPXRFa and Kiss systems in the regulation of reproduction by energy balance in non-mammalian species.

Deletion of GABAB receptors from Kiss1 cells affects glucose homeostasis without altering reproduction in male mice.

Kisspeptin and γ-amino butyric acid (GABA), synthesized in the central nervous system, are critical for reproduction. Both are also expressed in peripheral organs/tissues critical to metabolic control (liver/pancreas/adipose). Many kisspeptin neurons coexpress GABAB receptors (GABABR) and GABA controls kisspeptin expression and secretion. We developed a unique mouse lacking GABABR exclusively from kisspeptin cells/neurons (Kiss1-GABAB1KO) to evaluate the impact on metabolism/reproduction. We confirmed selective deletion of GABABR from Kiss1 cells in the anteroventral periventricular nucleus/periventricular nucleus continuum (AVPV/PeN; immunofluorescence and PCR) and arcuate nucleus (ARC), medial amygdala (MeA), pituitary, liver, and testes (PCR). Young Kiss1-GABAB1KO males were fertile, with normal LH and testosterone. Kiss1 expression was similar between genotypes in AVPV/PeN, ARC, MeA, bed nucleus of the stria terminalis (BNST), and peripheral organs (testis, liver, pituitary). Kiss1-GABAB1KO males presented higher fasted glycemia and insulin levels, an impaired response to a glucose overload, reduced insulin sensitivity, and marked insulin resistance. Interestingly, when Kiss1-GABAB1KO males got older (9 mo old) their body weight (BW) increased, in part due to an increase in white adipose tissue (WAT). Old Kiss1-GABAB1KO males showed higher fasted insulin, increased pancreatic insulin content, insulin resistance, and significantly decreased pancreatic kisspeptin levels. In sum, lack of GABABR specifically in Kiss1 cells severely impacts glucose homeostasis in male mice, reinforcing kisspeptin involvement in metabolic regulation. These alterations in glucose homeostasis worsened with aging. We highlight the impact of GABA through GABABR in the regulation of the pancreas kisspeptin system in contrast to liver kisspeptin that was not affected.NEW & NOTEWORTHY We developed a unique mouse lacking GABAB receptors specifically in Kiss1 cells to evaluate the impact on reproduction and metabolism. Knockout males showed a severe impact on glucose homeostasis, which worsened with aging. These results reinforce the proposed kisspeptin involvement in metabolic regulation and highlight the impact of GABA through GABABR in the regulation of the peripheral pancreas kisspeptin system.

DNA hypermethylation of Kiss1r promoter and reduction of hepatic Kiss1r in female rats with type 2 diabetes

ABSTRACT Kisspeptin, produced from the brain and peripheral tissues, may constitute an important link in metabolic regulation in response to external cues, such as diet. The kisspeptin system is well described in the brain. However, its function and regulation in the peripheral tissues, especially in relation to metabolic disease and sex differences, remain to be elucidated. As Kiss1 and Kiss1r, encoding for kisspeptin and kisspeptin receptors, respectively, are altered by overnutrition/fasting and regulated by DNA methylation during puberty and cancer, epigenetic mechanisms in metabolic disorders are highly probable. In the present study, we experimentally induced type 2 diabetes mellitus (DM2) in female Wistar rats using high-fat diet/streptozocin. We analysed expression and DNA methylation of Kiss1 and Kiss1r in the peripheral tissues, using quantitative-reverse-transcription PCR (qRT-PCR) and pyrosequencing. We discovered differential expression of Kiss1 and Kiss1r in peripheral organs in DM2 females, as compared with healthy controls, and the profile differed from patterns reported earlier in males. DM2 in females was linked to the increased Kiss1 mRNA in the liver and increased Kiss1r mRNA in the liver and adipose tissue. However, Kiss1r promoter was hypermethylated in the liver, suggesting gene silencing. Indeed, the increase in DNA methylation of Kiss1r promoter was accompanied by a reduction in Kiss1r protein, implying epigenetic or translational gene repression. Our results deliver novel evidence for tissue-specific differences in Kiss1 and Kiss1r expression in peripheral organs in DM2 females and suggest DNA methylation as a player in regulation of the hepatic kisspeptin system in DM2.

Gestational exposure to bisphenol analogues and kisspeptin levels in pregnant women and their children: A pregnancy-birth cohort study

Gestational exposure to bisphenol analogues (BPs)，especially bisphenol A (BPA), has been associated with adverse pregnancy-related outcomes and altered reproductive development of offspring, but the underlying mechanisms are not well documented. Kisspeptin, a key regulator of reproductive health, could be the potential target for endocrine disrupting compounds like BPs. Among 528 mother-child pairs, we investigated the associations of gestational BPs exposure with kisspeptin levels in two critical life stages, pregnancy and pre-puberty. Maternal BPs and kisspeptin concentrations were measured in urine samples collected in the third trimester. Children's urine samples were collected at 6-year visit and analyzed for kisspeptin levels. Associations were observed between BPA and its alternatives and lower kisspeptin in pregnant women but higher kisspeptin in their children. In contrast, TCBPA was suggestively associated with higher kisspeptin in pregnant women but lower kisspeptin in children. Our study provides the first epidemiologic evidence that gestational exposure to selected BPs may be associated with altered kisspeptin system in both pregnant women and their children, sheds some light on the potential mechanisms underlying the various reproductive health outcomes following gestational BPA exposure, and suggests potential reproductive toxicities of other BPs in humans.

Sexually dimorphic distribution of kiss1 and kiss2 in the brain of yellowtail clownfish, Amphiprion clarkii.

Kisspeptin system was shown to be a key factor in mediating social stress and reproduction. Yellowtail clownfish, Amphiprion clarkii, is a hermaphrodite fish, whose sex determination and gonadal development are affected by the social status of individuals. The yellowtail clownfish is a fantastic animal model to explore sex determination, but the social status and precise distribution of kiss mRNAs in the brain of this species are unknown. Hererin, a novel in situ hybridization technique, RNAscope, was used to investigate the distribution of kiss1 and kiss2 expressions in the brain of yellowtail clownfish. The coronal planes of brain showed that the kiss1 signal was mainly present in dorsal habenular nucleus (NHd) and kiss2 mRNA was widely expressed in telencephalon, midbrain, and hypothalamus, especially in dorsal part of the nucleus of the lateral recess (NRLd). Additionally, kiss1 and kiss2 signals have sexually dimorphic distribution. The kiss1 mRNA was distributed in NHd, the telencephalon, and lateral part of the diffuse nucleus of the inferior lobe (NDLIl) of females but in NHd and NDLIl of males. kiss2 signals were stronger in females than that in males. The distribution of kiss1 and kiss2 neurons in NHd of habenula and NRLd of hypothalamus may suggest that kiss genes associate environmental signaling and reproductive function in yellowtail clownfish.

The role of Kisspeptin, KISS1 and KISS1R genes in primary female infertility: a case‐control study of a Nigerian population

IntroductionThere is growing evidence that genetic changes are present in as many as 10% of infertile females. The Kisspeptin system plays a critical regulatory role in female reproductive functions. However, the extent of its role is not yet evident in primary infertility.ObjectiveThis study investigated the relative gene expression levels of Kisspeptin, KISS1, and KISS1R in primary infertile and fertile Nigerian females.Materials and MethodsThis is a case‐control study of 50 fertile and 54 primary infertile Nigerian females (20 to 40 years) attending the gynecology and family planning clinics of University College Hospital, Nigeria, and met the study’s inclusion criteria between August and November 2020. Basic clinical and sociodemographic information was collected from each participant using a clinical proforma. Five ml of blood samples were also collected by venepuncture from both the cases and control subjects for Kisspeptin, KISS1, and KISS1R genes analysis, using ELISA and RT‐qPCR techniques.ResultsBMI of cases was significantly different from the study controls, though both are still in the overweight category (27.98±0.87 vs. 28.18±0.59; p=0.004). Menarcheal age was not significantly different (p=0.573) but shows a significant strong association with ovarian factor infertility (p=0.008, χ2=13.839, φc= 0.458) and tubal factor infertility (p=0.025, χ2=11.111; φc=0.527). There is no change in the relative expression of Kisspeptin, Kiss1, and Kiss1R genes (P>0.05). However, Kisspeptin levels in primary infertile women showed a weak negative correlation (r = ‐.305; p=0.039) and a good predictive model for Kiss1 gene expression (p=0.001; r=0.458).ConclusionFemales with primary infertility may present with overweight in no significantly different way than fertile females. Changes in the Kisspeptin levels and relative expressions of Kiss1 and Kiss1R may not be useful in diagnosing primary infertility. Menarcheal age should be investigated as an additional diagnostic indicator for tubal and ovarian factor infertility for primary infertile women.SignificanceChanges in the Kisspeptin system alone may not explain the primary female infertility due to the complexity of the disease. A look into the role of the Kisspeptin system in the specific causative factors of primary female infertility could be more revealing.

The Kisspeptin System in Male Reproduction

The kisspeptin system includes the cleavage products Kiss1 precursor and kisspeptin receptor (Kiss1R). It was originally discovered and studied in cancer metastasis, but the identification of KISS1/KISS1R gene mutations causing hypogonadotropic hypogonadism (HH) revealed unexpected effects in reproduction. Nowadays, the kisspeptin system is the main central gatekeeper of the reproductive axis at puberty and adulthood, but it also has a widespread functional role in the control of endocrine functions. At the periphery, Kiss1 and Kiss1R are expressed in the testes, but the need for kisspeptin signaling for spermatogenesis and sperm quality is still unclear and debated. This brief manuscript summarizes the main findings on kisspeptin and male reproduction; upcoming data on sperm maturation are also discussed.

A customized long acting formulation of the kisspeptin analog C6 triggers ovulation in anestrus ewe.

The modulation of the kisspeptin system holds promise as a treatment for human reproductive disorders and for managing livestock breeding. The design of analogs has overcome some unfavorable properties of the endogenous ligands. However, for applications requiring a prolongation of drug activity, such as ovulation induction in the ewe during the non-breeding season, additional improvement is required. To this aim, we designed and tested three formulations containing the kisspeptin analog C6. Two were based on polymeric nanoparticles (NP1 and NP2) and the third was based on hydrogels composed of a mixture of cyclodextrin polymers and dextran grafted with alkyl side chains (MD/pCD). Only the MD/pCD formulation prolonged C6 activity, as shown by monitoring luteinizing hormone (LH) plasma concentration (elevation duration 23.4 ± 6.1, 13.7 ± 4.7 and 12.0 ± 2.4h for MD/pCD, NP1 and NP2, respectively). When compared with the free C6 (15 nmol/ewe), the formulated (MD/pCD) doses of 10, 15 and 30 nmol/ewe, but not the 90 nmol/ewe dose, provided a more gradual release of C6 as shown by an attenuated LH release during the first 6h post-treatment. When tested during the non-breeding season without progestogen priming, only, the formulated 30 nmol/ewe dose triggered ovulation (50% of ewes). Hence, we showed that a formulation with an adapted action time would improve the efficacy of C6 with respect to inducing ovulation during the non-breeding season. This result suggests that formulations containing a kisspeptin analog might find applications in the management of livestock reproduction but also point to the possibility of their use for the treatment of some human reproductive pathologies.

Sexual Dimorphism in Kisspeptin Signaling.

Kisspeptin (KP) and kisspeptin receptor (KPR) are essential for the onset of puberty, development of gonads, and maintenance of gonadal function in both males and females. Hypothalamic KPs and KPR display a high degree of sexual dimorphism in expression and function. KPs act on KPR in gonadotropin releasing hormone (GnRH) neurons and induce distinct patterns of GnRH secretion in males and females. GnRH acts on the anterior pituitary to secrete gonadotropins, which are required for steroidogenesis and gametogenesis in testes and ovaries. Gonadal steroid hormones in turn regulate the KP neurons. Gonadal hormones inhibit the KP neurons within the arcuate nucleus and generate pulsatile GnRH mediated gonadotropin (GPN) secretion in both sexes. However, the numbers of KP neurons in the anteroventral periventricular nucleus and preoptic area are greater in females, which release a large amount of KPs in response to a high estrogen level and induce the preovulatory GPN surge. In addition to the hypothalamus, KPs and KPR are also expressed in various extrahypothalamic tissues including the liver, pancreas, fat, and gonads. There is a remarkable difference in circulating KP levels between males and females. An increased level of KPs in females can be linked to increased numbers of KP neurons in female hypothalamus and more KP production in the ovaries and adipose tissues. Although the sexually dimorphic features are well characterized for hypothalamic KPs, very little is known about the extrahypothalamic KPs. This review article summarizes current knowledge regarding the sexual dimorphism in hypothalamic as well as extrahypothalamic KP and KPR system in primates and rodents.

Overview and New Insights Into the Diversity, Evolution, Role, and Regulation of Kisspeptins and Their Receptors in Teleost Fish.

In the last two decades, kisspeptin (Kiss) has been identified as an important player in the regulation of reproduction and other physiological functions in vertebrates, including several fish species. To date, two ligands (Kiss1, Kiss2) and three kisspeptin receptors (Kissr1, Kissr2, Kissr3) have been identified in teleosts, likely due to whole-genome duplication and loss of genes that occurred early in teleost evolution. Recent results in zebrafish and medaka mutants have challenged the notion that the kisspeptin system is essential for reproduction in fish, in marked contrast to the situation in mammals. In this context, this review focuses on the role of kisspeptins at three levels of the reproductive, brain-pituitary-gonadal (BPG) axis in fish. In addition, this review compiled information on factors controlling the Kiss/Kissr system, such as photoperiod, temperature, nutritional status, sex steroids, neuropeptides, and others. In this article, we summarize the available information on the molecular diversity and evolution, tissue expression and neuroanatomical distribution, functional significance, signaling pathways, and gene regulation of Kiss and Kissr in teleost fishes. Of particular note are recent advances in understanding flatfish kisspeptin systems, which require further study to reveal their structural and functional diversity.

Kisspeptin stimulates oocyte maturation, and food deprivation modulates the abundance of kisspeptin system in zebrafish gonads

Kisspeptin is a hormone involved in the neuroendocrine control of reproduction in fish. We hypothesized that kisspeptin stimulates oocyte maturation and modulates other reproductive hormones in zebrafish; and the gonadal kisspeptin system in zebrafish is affected during energy unavailability. The main goals of this research were to test in vitro effects of kisspeptin on oocyte maturation and mRNA abundance in zebrafish ovarian follicles and determine how short-term feed restriction affects kisspeptin and its receptors in zebrafish testis and ovary. This study demonstrates the presence of kisspeptin and its receptors in zebrafish (Danio rerio) gonads and its direct action on ovarian follicles in vitro. Kisspeptin (10 ng/mL) induced oocyte maturation, as indicated by germinal vesicle break down at 18- and 24- hours post-treatment. Kisspeptin significantly increased the abundance of mRNAs encoding reproductive hormones and its receptors in zebrafish oocytes. This suggests that kisspeptin-10 affects ovarian functions by modulating other hormones. Reproduction is a process that requires energy. Therefore, whether energy availability affects the kisspeptin system in zebrafish gonads was determined. Food deprivation modulated kisspeptin expression differently in zebrafish testis and ovary. Kiss2 and kiss1ra were upregulated while kiss1rb was downregulated in the testis post-food deprivation. Meanwhile, no changes in kiss in the ovary were found after food deprivation. However, kiss1rb was downregulated in unfed fish at 3- and 7-days post-food deprivation. Overall, our results suggest sex- and tissue-specific changes in the gonadal abundance of the kisspeptin system in zebrafish. The fine tuning of reproduction during energy fluctuations in fish is likely mediated via changes in hormones, including kisspeptin as shown in this research.