Kisspeptins: regulators of metastasis and the hypothalamic-pituitary-gonadal axis

Nasal application of kisspeptin-54 mitigates motor deficits by reducing nigrostriatal dopamine loss in hemiparkinsonian rats

Parkinson's Disease is a progressive neurodegenerative disorder characterized by motor symptoms resulting from the loss of nigrostriatal dopaminergic neurons. Kisspeptins (KPs) are a family of neuropeptides that are encoded by the Kiss-1 gene, which exert their physiological effects through interaction with the GPR54 receptor. In the current investigation, we investigated the prospective protective effects of central KP-54 treatments on nigrostriatal dopaminergic neurons and consequent motor performance correlates in 6-hydroxydopamine (6-OHDA)-lesioned rats. Male adult Sprague Dawley rats underwent stereotaxic injection of 6-OHDA into the right medial forebrain bundle to induce hemiparkinsonism. Following surgery, rats received chronic central treatments of nasal or intracerebroventricular KP-54 (logarithmically increasing doses) for seven consecutive days. Motor performance was evaluated seven days post-surgery utilizing the open field test and catalepsy test. The levels of dopamine in the striatum were determined with mass spectrometry. Immunohistochemical analysis was conducted to assess the immunoreactivities of tyrosine hydroxylase (TH) and the GPR54 in the substantia nigra. The dose-response curve revealed a median effective dose value of ≈3 nmol/kg for both central injections. Due to its non-invasive and effective nature, nasal administration was utilized in the second phase of our study. Chronic administration of KP-54 (3nmol/kg, nasally) significantly protected 6-OHDA-induced motor deficits. Nasal KP-54 attenuated the loss of nigrostriatal dopaminergic neurons induced by 6-OHDA. Additionally, significant correlations were observed between motor performance and nigrostriatal dopamine levels. Immunohistochemical analysis demonstrated the localization of the GPR54 within TH-positive nigral cells. These findings suggest the potential efficacy of central KP-54 on motor impairments in hemiparkinsonism.

Dapagliflozin partially restores reproductive function in MC4R KO obese female mice

Obese women often have certain degree of reproductive dysfunction with infertility. Although the clinical impact of obesity on female infertility has been extensively studied, the effective and targeted treatment is still lacking. Melanocortin-4-receptor knock-out (MC4R KO) mouse is an over-eating obese model with hyperphagia, hyperinsulinemia, reduced growth hormone (GH), and insulin resistance. Dapagliflozin improved the metabolic and hormonal parameters in MC4R KO mice. MC4R KO female mice were treated with dapagliflozin for 14 weeks from 14-week age. Age-matched WT littermates and non-treated MC4R KO mice were used as control groups. Food intake was measured daily. Body weight was measured twice a week. Estrous cycles, GH, and luteinizing hormone (LH) profiles were measured. Selected tissues were collected at the end of experiments for gene expression profiles and hematoxylin-eosin staining. Regularity and mode of hormonal profiles were restored by the dapagliflozin treatment. Estrous cycle was partially normalized, number of CL was significantly increased, and the expression of Kiss1 and Gnrh1 in the hypothalamus and LH in the pituitary was markedly increased by the dapagliflozin treatment. It is conclsuded that dapagliflozin may recover LH and GH profiles partially through modification of relevant gene expression in the hypothalamus and pituitary, and result in an improved ovulation rate in obese mouse model. Dapagliflozin may therefore improve fertility in obese patients.

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

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

Neuropeptides as regulators of the hypothalamus-pituitary-gonadal (HPG) axis activity and their putative roles in stress-induced fertility disorders

Neuropeptides being regulators of the hypothalamus-pituitary-adrenal (HPA) axis activity, also affect the function of the hypothalamus-pituitary-gonadal (HPG) axis by regulating gonadotrophin-releasing hormone (GnRH) secretion from hypothalamic neurons. Here, we review the available data on how neuropeptides affect HPG axis activity directly or indirectly via their influence on the HPA axis. The putative role of neuropeptides in stress-induced infertility, such as polycystic ovary syndrome, is also described. This review discusses both well-known neuropeptides (i.e., kisspeptin, Kp; oxytocin, OT; arginine-vasopressin, AVP) and more recently discovered peptides (i.e., relaxin-3, RLN-3; nesfatin-1, NEFA; phoenixin, PNX; spexin, SPX). For the first time, we present an up-to-date review of all published data regarding interactions between the aforementioned neuropeptide systems. The reviewed literature suggest new pathophysiological mechanisms leading to fertility disturbances that are induced by stress.

Kisspeptin-54 attenuates oxidative stress and neuronal apoptosis in early brain injury after subarachnoid hemorrhage in rats via GPR54/ARRB2/AKT/GSK3β signaling pathway

Oxidative stress-induced neuron apoptosis plays a crucial role in the early brain injury (EBI) after subarachnoid hemorrhage (SAH). Kisspeptin has been reported as antioxidant to reduce oxidative stress-induced neuronal cell death through G protein-coupled receptor 54 (GPR54). The goal of this study was to determine the neuroprotection of the Kisspeptin/GRP54 signaling pathway against EBI after SAH. Two hundred and ninety-two Sprague Dawley male rats were used and SAH was induced by the endovascular perforation. Exogenous Kisspeptin 54 (KP54) was delivered intranasally. Small interfering ribonucleic acid (siRNA) for endogenous KISS1, a selective GPR54 antagonist kisspeptin 234, or β-arrestin 2 siRNA for ARRB2 (a functional adaptor of GPR54) were administered intracerebroventricularly. Post-SAH evaluations included neurobehavioral tests, SAH grade, Western blot, immunofluorescence, Fluoro-Jade C, TUNEL, and Nissl staining. The results showed that endogenous KISS1 knockdown aggravated but exogenous KP54 (1.0 nmol/kg) treatment attenuated neurological deficits, brain oxidative stress, and neuronal apoptosis at 24 h after SAH. The benefits of KP54 persisted to 28 days after SAH, which significantly improved cognitive function in SAH rats. The GPR54 blockade or the ARRB2 knockout offset the neuroprotective effects of KP54 in SAH rats. In conclusion, our results suggested that administration of KP54 attenuated oxidative stress, neuronal apoptosis and neurobehavioral impairments through GPR54/ARRB2/AKT/GSK3β signaling pathway after SAH in rat. Thus, KP54 may provide an effective treatment strategy for SAH patients.

Peripheral action of kisspeptin at reproductive tissues-role in ovarian function and embryo implantation and relevance to assisted reproductive technology in livestock: a review

Kisspeptin (KISS1) is encoded by the KISS1 gene and was initially found to be a repressor of metastasis. Natural mutations in the KISS1 receptor gene (KISS1R) were subsequently shown to be associated with idiopathic hypothalamic hypogonadism and impaired puberty. This led to interest in the role of KISS1 in reproduction. It was established that KISS1 had a fundamental role in the control of gonadotropin releasing hormone (GnRH) secretion. KISS1 neurons have receptors for leptin and estrogen receptor α (ERα), which places KISS1 at the gateway of metabolic (leptin) and gonadal (ERα) regulation of GnRH secretion. More recently, KISS1 has been shown to act at peripheral reproductive tissues. KISS1 and KISS1R genes are expressed in follicles (granulosa, theca, oocyte), trophoblast, and uterus. KISS1 and KISS1R proteins are found in the same tissues. KISS1 appears to have autocrine and paracrine actions in follicle and oocyte maturation, trophoblast development, and implantation and placentation. In some studies, KISS1 was beneficial to in vitro oocyte maturation and blastocyst development. The next phase of KISS1 research will explore potential benefits on embryo survival and pregnancy. This will likely involve longer-term KISS1 treatments during proestrus, early embryo development, trophoblast attachment, and implantation and pregnancy. A deeper understanding of the direct action of KISS1 at reproductive tissues could help to achieve the next step change in embryo survival and improvement in the efficiency of assisted reproductive technology.

Expression of the anti-Mullerian hormone, kisspeptin 1, and kisspeptin 1 receptor in polycystic ovary syndrome and controlled ovarian stimulation rat models

Polycystic ovary syndrome represents a significant cause of female infertility. The aim of this study was to investigate the expression of anti-Mul-lerian hormone (AMH), kisspeptin 1 (KISS-1), and kisspeptin 1 receptor (KISS1r) in rat models of polycystic ovary syndrome (PCOS) and controlled ovarian stimulation (COS). For this purpose, 28 rats were assigned into four groups. Estrus and Diestrus groups consisted of rats in estrus and diestrus phases, respectively, while COS and PCOS groups consisted of rats with induced COS and PCOS, respectively. The serum AMH, KISS-1, and estradiol levels, and ovarian KISS1r levels were analyzed by enzyme-linked immunosorbent assay. Furthermore, histopathological analysis of the ovary tissue was done and ovarian KISS-1 expression was determined by immunohistochemical assay. The results revealed that ovarian KISS1r levels were higher in the Estrus (1271.43±51.98 pg/mL) and COS (1191.43±85.67 pg/mL) groups, compared to Diestrus and PCOS groups. The highest level of AMH was found in the Estrus group (16.91±2.12 ng/mL). The results indicate that AMH had no effect on the development of COS and PCOS, while KISS-1 was found to affect the development of COS in rats.

Effects of Ovarian Transplant on Anti-Müllerian Hormone, Kisspeptin-1, and Kisspeptin-1 Receptor Levels in Rats

OBJECTIVES

Information is scarce on levels of kisspeptin-1 and the kisspeptin-1 receptorin females after ovarian transplant. In this study, our aim was to explore serum estradiol, anti-Müllerian hormone, kisspeptin-1, and kisspeptin receptor levels, along with kisspeptin-1-positive cell density, in ovaries from rats after ovarian transplant.

MATERIALS AND METHODS

For this study, 28 female Sprague Dawley rats were divided into 4 groups, with sham surgery performed on rats in group 1 (control group). Group 2 rats had ovaries transplanted under the peritoneum, and group 3 rats had their own ovaries transplanted subcutaneously. Group 4 rats were maintained in an estrous state. Serum anti-Müllerian hormone, kisspeptin-1, estradiol, and ovarian kisspeptin receptor levels were determined using commercial enzyme-linked immunosorbent assay kits. Kisspeptin-1-positive cell densities in the ovaries were determined immunohistochemically.The ovaries were also examined histopathologically.

RESULTS

Our statistical analyses showed that levels of kisspeptin receptors in the ovaries were lowest in the subcutaneously transplanted group (group 3; 628.57 ± 35.69 pg/mL). The highest serum anti-Müllerian hormone levels were found in the estrous group (group 4; 16.91 ± 2.12 ng/mL). Differences between groups in terms of serum kisspeptin-1 and estradiol concentrations were not statistically significant.

CONCLUSIONS

Our findings suggest that, in rats, results were better in the peritoneum transplant group than in the subcutaneous transplant group. We also found that serum anti-Müllerian hormone levels were lower in the transplant groups than in the estrous group, although levels were not completely decreased to zero. These results support the finding that ovarian activities continue after transplant.

Testosterone therapy for women with low sexual desire: a position statement from the Brazilian Society of Endocrinology and Metabolism

OBJECTIVE

To summarize current evidence regarding testosterone treatment for women with low sexual desire.

MATERIALS AND METHODS

The Female Endocrinology and Andrology Department of the Brazilian Society of Endocrinology and Metabolism invited nine experts to review the physiology of testosterone secretion and the use, misuse, and side effects of exogenous testosterone therapy in women, based on the available literature and guidelines and statements from international societies.

RESULTS

Low sexual desire is a common complaint in clinical practice, especially in postmenopausal women, and may negatively interfere with quality of life. Testosterone seems to exert a positive effect on sexual desire in women with sexual dysfunction, despite a small magnitude of effect, a lack of long-term safety data, and insufficient evidence to make a broad recommendation for testosterone therapy. Furthermore, there are currently no testosterone formulations approved for women by the relevant regulatory agencies in the United States, Brazil, and most other countries, and testosterone formulations approved for men are not recommended for use by women.

CONCLUSION

Therefore, testosterone therapy might be considered if other strategies fail, but the risks and benefits must be discussed with the patient before prescription. Arch Endocrinol Metab. 2019;63(3):190-8.

Mechanisms for Sex Differences in Energy Homeostasis

Sex differences exist in the regulation of energy homeostasis. Better understanding of the underlying mechanisms for sexual dimorphism in energy balance may facilitate development of gender-specific therapies for human diseases, e.g. obesity. Multiple organs, including the brain, liver, fat and muscle, play important roles in the regulations of feeding behavior, energy expenditure and physical activity, which therefore contribute to the maintenance of energy balance. It has been increasingly appreciated that this multi-organ system is under different regulations in male vs. female animals. Much of effort has been focused on roles of sex hormones (including androgens, estrogens and progesterone) and sex chromosomes in this sex-specific regulation of energy balance. Emerging evidence also indicates that other factors (not sex hormones/receptors and not encoded by the sex chromosomes) exist to regulate energy homeostasis differentially in males vs. females. In this review, we summarize factors and signals that have been shown to regulate energy homeostasis in a sexually dimorphic fashion and propose a framework where these factors and signals may be integrated to mediate sex differences in energy homeostasis.

Impact of Triclosan on Female Reproduction through Reducing Thyroid Hormones to Suppress Hypothalamic Kisspeptin Neurons in Mice

Triclosan (TCS), a broad-spectrum antimicrobial agent, is widely used in clinical settings and various personal care products. The aim of this study was to evaluate the influence of TCS on reproductive endocrine and function. Here, we show that the exposure of adult female mice to 10 or 100 mg/kg/day TCS caused prolongation of diestrus, and decreases in antral follicles and corpora lutea within 2 weeks. TCS mice showed decreases in the levels of serum luteinizing hormone (LH), follicle-stimulating hormone (FSH) and progesterone, and gonadotrophin-releasing hormone (GnRH) mRNA with the lack of LH surge and elevation of prolactin (PRL). TCS mice had lower kisspeptin immunoreactivity and kiss1 mRNA in anteroventral periventricular nucleus (AVPV) and arcuate nucleus (ARC). Moreover, the estrogen (E2)-enhanced AVPV-kisspeptin expression was reduced in TCS mice. In addition, the serum thyroid hormones (triiodothyronine (T3) and thyroxine (T4)) in TCS mice were reduced with increases in levels of thyroid stimulating hormone (TSH) and thyroid releasing hormone (TRH). In TCS mice, the treatment with Levothyroxine (L-T4) corrected the increases in PRL, TSH and TRH; the administration of L-T4 or type-2 dopamine receptors agonist quinpirole inhibiting PRL release could rescue the decline of kisspeptin expression in AVPV and ARC; the treatment with L-T4, quinpirole or the GPR45 agonist kisspeptin-10 recovered the levels of serum LH and FSH and progesterone, and GnRH mRNA. Furthermore, TCS mice treated with L-T4 or quinpirole resumed regular estrous cycling, follicular development and ovulation. Together, these results indicate that exposing adult female mice to TCS (≥10 mg/kg) reduces thyroid hormones causing hyperprolactinemia that then suppresses hypothalamic kisspeptin expression, leading to deficits in reproductive endocrine and function.

Immunocytochemical localization of kisspeptin and kisspeptin receptor in the primate testis

BACKGROUND

Hypothalamic kisspeptin-kisspeptin receptor signalling in primates ensures the successful progression into puberty during development and maintenance of reproductive capacity during adulthood. Human testis has been shown to express high-to-moderate levels of kisspeptin and kisspeptin receptor gene expression. In this study, we aimed at characterizing the localization of kisspeptin and kisspeptin receptor in adult primate testis tissue.

METHODS

Immunocytochemistry was performed on paraffin-embedded testicular sections from adult rhesus monkeys and from common marmoset monkeys.

RESULTS

Kisspeptin receptor was detected in Sertoli cells in the periphery of the seminiferous tubules in adult testes of both species. In contrast, kisspeptin was not localized in the seminiferous epithelium and was detected only in the interstitial compartment of the adult rhesus monkey testis.

CONCLUSION

Kisspeptin receptor and kisspeptin are localized in the testis of Old World and New World primates.

A clinicopathological analysis of KISS1 and KISS1R expression in colorectal cancer

Kisspeptins, the products of the KISS1 gene have tumor suppressing and antimetastatic properties. We aimed to study KISS1 and KISS1R expression in colorectal cancer. We analyzed KISS1 and KISS1R expression using immunohistochemistry and image analysis in normal and malignant tissue samples from 111 patients with colorectal adenocarcinoma. KISS1 expression was much higher in the normal than in the malignant colonic mucosa. Regarding malignant tissues, KISS1 levels were higher in larger tumors, in stage III and IV cancers, in cancers with lymph node metastasis and in tumors located in the distal part of the large intestine. Patients with greater KISS1 levels had worse prognosis. No KISS1R expression was detected in normal or malignant tissues or in liver metastases. KISS1 expression is reduced during the malignant transformation of the colonic mucosa. However, larger and advanced colorectal cancers express more KISS1, without reaching the former normal levels, and increased KISS1 levels are associated with worse prognosis. Finally, neither the normal nor the malignant colonic epithelial cells produce KISS1R.

Epigenetic regulation in biopsychosocial pathways

Theory and empirical evidence suggest that psychological stress and other adverse psychosocial experiences can contribute to cancer progression. Research has begun to explore the potential role of epigenetic changes in these pathways. In basic, animal and human models, exposure to stressors or to the products of the physiological stress response (e.g., cortisol) has been associated with epigenetic changes, such as DNA methylation and microRNA (miR) expression, which may influence tumor growth, progression, metastasis, or chemoresistance. However, the specific biological pathways linking stress, epigenetic changes, and cancer outcomes remain unclear. Numerous opportunities exist to extend the preliminary evidence for the role of epigenetic mechanisms in the biopsychosocial pathways contributing to cancer progression. Such work will improve our understanding of how the psychosocial environment influences cancer risk and survival, potentially leading to improved prevention and treatment strategies.

Luteal phase dynamics of follicle-stimulating and luteinizing hormones in obese and normal weight women

OBJECTIVES

Female obesity is a state of relative hypogonadotrophic hypogonadism. The aim of this study is to examine gonadotrophin secretion and response to gonadotrophin-releasing hormone (GnRH) in the luteal phase of the menstrual cycle and to investigate the pharmacodynamics and pharmacokinetics of endogenous and exogenous luteinizing hormone (LH) in obese women.

DESIGN

Participants underwent a luteal phase frequent blood sampling study. Endogenous LH pulsatility was observed, gonadotrophin-releasing hormone (GnRH) was given in two weight-based doses, and GnRH antagonist was administered followed by recombinant LH.

PATIENTS

Regularly menstruating obese (n = 10) and normal weight (n = 10) women.

MEASUREMENTS

Endogenous hypothalamic-pituitary function (as measured by LH pulsatility), pituitary sensitivity (GnRH-induced LH secretion), pharmacodynamics of endogenous LH and pharmacokinetics of exogenous LH were compared between the obese and normal weight groups.

RESULTS

There were no statistically significant differences in endogenous LH pulsatility or pituitary responses to two weight-based doses of GnRH between the obese and normal weight women. There were no differences in the pharmacodynamics of endogenous LH or the pharmacokinetics of exogenous LH between the groups. FSH dynamics did not differ between the groups throughout the study.

CONCLUSIONS

The relative hypogonadotrophic hypogonadism of obesity cannot be explained by differences in LH and FSH luteal phase dynamics or differences in endogenous LH pharmacodynamics or exogenous LH pharmacokinetics.

Sustained exposure to the investigational Kisspeptin analog, TAK-448, down-regulates testosterone into the castration range in healthy males and in patients with prostate cancer: results from two phase 1 studies

BACKGROUND/OBJECTIVE

Kisspeptin-54, an endogenous naturally occurring ligand of the G protein-coupled receptor-54, stimulates GnRH-gonadotropin secretion and suppresses metastases in animal models of cancer but is subject to rapid degradation and inactivation. TAK-448 is an investigational oligopeptide analog of the fully active 10-amino acid C terminus of kisspeptin-54. This phase 1 study evaluated the safety, pharmacokinetics, and pharmacodynamics of TAK-448 in healthy subjects and patients with prostate cancer (PC).

DESIGN

Healthy subjects aged 50 years or older received TAK-448 sc as a single-bolus or 2-hour infusion (0.01-6 mg/d; part A) and as a 14-day sc administration (0.01-1 mg/d; part B). In a subsequent, open-label, phase 1 study in PC patients aged 40-78 years, TAK-448 was given as a 1-month depot formulation.

RESULTS

Eighty-two healthy subjects received TAK-448; 30 received placebo. Grades 1-2 adverse events were reported in 26% of subjects during TAK-448 treatment. All dosing regimens resulted in dose-proportional exposures. The maximum observed plasma concentration occurred after 0.25-0.5 hours, and median terminal elimination half-life was 1.4-5.3 hours. T increased approximately 1.3- to 2-fold by 48 hours after a single bolus or 2 hour injections, whereas during the 14-day infusion, at doses above 0.1 mg/d, T dropped to below-baseline values by 60 hours and reached a subsequently sustained below-castration level by day 8. In PC patients, T decreased to less than 20 ng/dL in four of five patients dosed with 12 or 24 mg TAK-448 sc-depot injections. The prostate-specific antigen decreased greater than 50% in all patients dosed with 24 mg.

CONCLUSIONS

Continuous TAK-448 infusion was well tolerated by healthy males and resulted in sustained T suppression. Depot injection in patients with PC similarly reduced T and resulted in prostate-specific antigen responses.

Design and synthesis of fluorescent probes for GPR54

Kisspeptins are neuropeptides that induce the secretion of gonadotropin-releasing hormone via the activation of the cognate receptor, G-protein coupled receptor 54 (GPR54). The kisspeptin-GPR54 axis is associated with the onset of puberty and the maintenance of the reproductive system. In this study, several fluorescent probes have been designed and synthesized for rat GPR54 through the modification of the N-terminus of rat kisspeptins to allow for the visualization of the expression and localization of kisspeptin receptor(s) in living cells and native tissues. The tetramethylrhodamine (TMR) and rhodamine green (RG)-labeled kisspeptins exhibited good binding and agonistic activities towards GPR54, and the results of the application studies demonstrated that these fluorescent probes could be used effectively for the detection of GPR54 receptors in flow cytometry and confocal microscopy experiments.

Effect of vehicle and route of administration of letrozole on ovarian function in a bovine model

The objective of this study was to determine the effects of vehicle and route of administration of letrozole on ovarian function in sexually mature beef heifers. On Day 3 (Day 0 = ovulation), heifers were assigned randomly to four treatment groups and given 1 mg kg–1 letrozole intravenously (iv, n = 10) or intramuscularly (im, n = 10) or given a placebo iv (control iv, n = 5) or im (control im, n = 5). The interwave interval was longer in heifers treated with letrozole im than in im and iv controls (11.7 ± 0.30 vs 9.5 ± 0.50 and 10 ± 0.43, respectively; P < 0.05). Corpus luteum diameter profiles and plasma progesterone concentrations were greater (P < 0.03 and P < 0.05, respectively) in heifers treated with letrozole im compared with control im. Plasma oestradiol concentrations were lower in both letrozole-treated groups compared with controls (P ≤ 0.03). Plasma LH concentrations tended to be elevated at the time of wave emergence in heifers treated with letrozole im compared with other groups (group-by-day interaction, P = 0.06) and plasma FSH concentrations tended to be greater (P < 0.09) in heifers treated with letrozole by either route compared with a single control group. We conclude that intramuscular administration of letrozole in oil is a feasible route and vehicle for the development of a letrozole-based treatment protocol for herd synchronisation in cattle.

KISS1 expression in colorectal cancer

Kisspeptins, the products of the KISS1 gene, are involved in cancer invasion, migration, metastasis and angiogenesis, while they induce apoptosis in various cancers. Herein, we studied KISS1 expression in colorectal cancer. We analyzed KISS1 expression using immunohistochemistry and image analysis in normal and malignant tissue samples from 60 patients with colorectal adenocarcinoma. The results correlated with various clinicopathological parameters. The expression of KISS1 was much higher in normal than in malignant colonic mucosa. However, among malignant tissues, KISS1 expression was higher in larger tumors (>4 cm) than in smaller ones (≤4 cm) and in stages III and IV than in stages I and II. In addition, it was higher in patients with lymph node metastases. Moreover, KISS1 levels in the normal mucosa and their difference from those in the malignant mucosa were higher in the right part of the large intestine than in the left one. KISS1 expression is reduced during the malignant transformation of the colonic mucosa and there is a difference in the expression pattern between the right and the left part of the large intestine. However, larger and advanced colorectal tumors express higher KISS1 levels than smaller and localized ones.

A comparison of the neuroendocrine mechanisms underlying the initiation of the preovulatory LH surge in the human, Old World monkey and rodent

As recognized for decades, the role of the rodent hypothalamus in timing the LH surge is deterministic and mediated by a GnRH discharge that is generated by an obligatory interaction in the preoptic area (POA) between a threshold level of estradiol and a circadian neural signal: a view consistent with contemporary kisspeptinocentric models of the estrous cycle. In higher primates, generation of the LH surge is emancipated from control by the POA. Woman represents the exemplar of the system in higher primates, as the LH surge appears to unfold in the absence of a midcycle GnRH discharge being generated instead by facilitatory interaction between a pulsatile GnRH input to the pituitary and an action of ovarian estradiol. The neurobiology of GnRH pulse generation is only beginning to emerge but from a translational perspective this aspect of hypothalamic function is critical for understanding the human menstrual cycle and how it may be perturbed.

Novel potential regulators of maternal adaptations during lactation: tuberoinfundibular peptide 39 and amylin

Maternal adaptations during lactation include milk synthesis and ejection, the appearance of maternal behaviours, reduced stress response, suppression of the ovarian cycle, and increased food and fluid intake. Several recently identified neuropeptides may participate in these adaptations, and we focus on two of them in the present study: tuberoinfundibular peptide of 39 residues (TIP39) and amylin. TIP39 is the ligand of the parathyroid hormone 2 receptor (PTH2 receptor) is induced in the posterior intralaminar complex of the thalamus (PIL) during lactation. TIP39 neurones in the PIL are activated in mother rats in response to pup exposure and project to preoptic, periventricular, paraventricular, arcuate and dorsomedial regions of the hypothalamus. Furthermore, an antagonist of the PTH2 receptor reduced suckling induced prolactin release. On the basis of their projections, TIP39 neurones might interact with additional neurones involved in maternal adaptations, including kisspeptin neurones participating in the control of gonadotrophin-releasing hormone function. TIP39 fibres might also interact with amylin, a peptide that we recently identified to appear in the preoptic area of rat dams. On the basis of its distribution, preoptic amylin could play a role in the control of maternal behaviours. We hypothesise that TIP39 neurones mediate the effects of suckling on different hypothalamic systems to affect maternal adaptations.

Molecular characterization, tissue distribution, and mRNA expression profiles of two Kiss genes in the adult male and female chub mackerel (Scomber japonicus) during different gonadal stages

Kisspeptins, encoded by the Kiss1 gene, have emerged as key modulators of reproduction in mammals. In contrast to the placental mammals, some teleosts express two Kiss genes, Kiss1 and Kiss2. In the present study, full-length cDNAs of Kiss1 and Kiss2 in the chub mackerel were cloned and sequenced. Chub mackerel Kiss1 and Kiss2 cDNAs encode 105 and 123 amino acids, respectively. A comparison of the deduced amino acid sequences of chub mackerel Kiss1 and Kiss2 with those of other vertebrate species showed a high degree of conservation only in the kisspeptin-10 region (Kp-10). The Kp-10 of chub mackerel Kiss1 (YNFNSFGLRY) and Kiss2 (FNFNPFGLRF) showed variations at three amino acids. Tissue distribution analysis using quantitative real-time PCR (qRT-PCR) revealed that the Kiss1 and Kiss2 transcripts were expressed in different tissues of adult chub mackerel. In addition, their levels in the adipose tissue exhibited sexually dimorphic expression. Further, to have a basic understanding on the involvement of Kiss1 and Kiss2 in the seasonal gonadal development, their relative mRNA expression profiles in the brain, pituitary, and gonads at different gonadal stages were analyzed using qRT-PCR. Kiss1 and Kiss2 levels in the brain showed a differential expression profile between male and female fish. In males, Kiss1 and Kiss2 levels gradually decreased from the immature stage to spermiation and reached a minimal level during the post-spawning period. In contrast, Kiss1 levels in the brain of females did not vary significantly among the different gonadal stages. However, Kiss2 levels fluctuated as that of males, gradually declining from the immature stage to the post-spawning period. The pituitary Kiss1 levels did not show significant fluctuations. However, Kiss1 levels in the gonads were highly elevated during spermiation and late vitellogenesis compared to the immature and post-spawning period. These results suggest the possible involvement of two Kiss genes in the brain and Kiss1 in the gonads of chub mackerel during seasonal gonadal development.

Co-expression of leptin and oestrogen receptors in the preoptic-hypothalamic area

The interaction between the reproductive axis and energy balance suggests that leptin acts as a possible mediator. This hormone acts in the regulation of metabolism, feeding behaviour and reproduction. Animals homozygous for the gene 'ob' (ob/ob) are obese and infertile, and these effects are reversed after systemic administration of leptin. Thus, the present study aimed to determine: (i) whether cells that express leptin also express oestrogen receptors of type-alpha (ER-alpha) or -beta (ER-beta) in the medial preoptic area (MPOA) and in the arcuate (ARC), dorsomedial (DMH) and ventromedial hypothalamic nucleus and (ii) whether there is change in the gene and protein expression of leptin in these brain areas in ovariectomised (OVX) animals when oestrogen-primed. Wistar female rats with normal oestrous cycles or ovariectomised oestrogen-primed or vehicle (oil)-primed were utilised. To determine whether there was a co-expression, immunofluorescence was utilised for double staining. Confocal microscopy was used to confirm the co-expression. The technique of real-time polymerase chain reaction and western blotting were employed to analyse gene and protein expression, respectively. The results obtained showed co-expression of leptin and ER-alpha in the MPOA and in the DMH, as well as leptin and ER-beta in the MPOA, DMH and ARC. However, we did not detect leptin in the MPOA, ARC and DMH using western blotting and there was no statistical difference in leptin gene expression in the MPOA, DMH, ARC, pituitary or adipose tissue between OVX rats treated with oestrogen or vehicle. In conclusion, the results obtained in the present study confirm that the brain is also a source of leptin and reveal co-expression of oestrogen receptors and leptin in the same cells from areas related to reproductive function and feeding behaviour. Although these data corroborate the previous evidence obtained concerning the interaction between the action of brain leptin and reproductive function, the physiological relevance of this interaction remains uncertain and additional studies are necessary to elucidate the exact role of central leptin.

Social isolation reduces mammary development, tumor incidence, and expression of epigenetic regulators in wild-type and p53-heterozygotic mice

Chronic stress is associated with more rapid tumor progression, and recent evidence suggests that stress may contribute to social and ethnic disparities in the incidence and mortality of breast cancer. We evaluated the p53(+/-) FVB/N mouse as a model to investigate effects of chronic social stress on mammary gland development, gene expression, and tumorigenesis. We individually housed (IH) wild-type and p53(+/-) female FVB/N mice, starting at weaning. At 14 weeks of age, both wild-type and p53(+/-) IH mice showed strikingly reduced mammary development compared with group-housed (GH) controls, with IH mice having significantly fewer preterminal end buds. This morphologic difference was not reflected in levels of mammary transcripts for estrogen receptor-alpha or progestin receptor. However, IH increased levels of mRNA for the kisspeptin receptor in the medial preoptic area of the hypothalamus, associated with reduced duration of estrous cycles. Furthermore, IH altered mammary transcripts of genes associated with DNA methylation; transcripts for methyl-binding protein 2 and DNA methyltransferase 3b (DNMT3b), but not DNMT1 and DNMT3a, were reduced in IH compared with GH females. Interestingly, the glands of p53(+/-) females showed reduced expression of all these mediators compared with wild-type females. However, contrary to our initial hypothesis, IH did not increase mammary tumorigenesis. Rather, p53(+/-) GH females developed significantly more mammary tumors than IH mice. Together, these data suggest that social isolation initiated at puberty might confound studies of tumorigenesis by altering mammary development in mouse models.

The effects of Kisspeptin antibodies on delayed estrus in rats

In recent years, numerous studies have been conducted on the effects of Kisspeptin/GPR54 system on sexual cycle, which proved that this system regulated gonadotropin release through GnRH. This study aims to determine the effects of hyperimmune serum containing antibodies produced against Kisspeptin on the sexual cycle and GnRH receptors in rat pituitaries. To this end, five Wistar female rats were passively immunised using a hyperimmune serum obtained from two Wistar female rats against Kisspeptin 10. Another five rats were selected as the control group. Anti-Kisspeptin antibodies of the hyperimmunised rats in the serum were identified by ELISA. The sexual cycles of the rats were followed by the measurements of vaginal irrigations and the estradiol concentrations in their blood samples. The number of follicles and corpora lutea in their ovaries was determined through histopathological tests, and the GnRH receptors in their pituitaries were identified by immunohistochemistry. Consequently, strong seropositivity was detected in all passively immunised rats and the hyperimmune serum. However, no difference was found between the groups with regard to the number of estrous cycles observed, the interval between estrous periods, estradiol concentrations, the number of follicles and corpora lutea and immunohistochemical results.

Evidence for two distinct KiSS genes in non-placental vertebrates that encode kisspeptins with different gonadotropin-releasing activities in fish and mammals

Kisspeptins, the products of KiSS-1 gene, have recently emerged as fundamental regulators of reproductive function in different mammalian and, presumably, non-mammalian species. To date, a single form of KiSS-1 has been described in mammals, and recently, in several fish species and Xenopus. We report herein the cloning and characterization of two distinct KiSS-like genes, namely, KiSS-1 and KiSS-2, in the teleost sea bass. While KiSS-1 encodes a peptide identical to rodent kisspeptin-10, the predicted KiSS-2 decapeptide diverges at 4 amino acids (FNFNPFGLRF). Genome database searches showed that both genes are present in non-placental vertebrate genomes. Indeed, phylogenetic and genome mapping analyses suggest that KiSS-1 and KiSS-2 are paralogous genes that originated by duplication of an ancestral gene, although KiSS-2 is lost in placental mammals. KiSS-1 and KiSS-2 mRNAs are present in brain and gonads of sea bass, medaka and zebrafish. Comparative functional studies demonstrated that KiSS-2 decapeptide was significantly more potent than KiSS-1 peptide in inducing LH and FSH secretion in sea bass. In contrast, KiSS-2 decapeptide only weakly elicited LH secretion in rats, whereas KiSS-1 peptide was maximally effective. Our data are the first to provide conclusive evidence for the existence of a second KiSS gene, KiSS-2, in non-placental vertebrates, whose product is likely to play a dominant stimulatory role in the regulation of the gonadotropic axis at least in teleosts.

Modulation of angiogenic and inflammatory response in glioblastoma by hypoxia

Glioblastoma are rapidly proliferating brain tumors in which hypoxia is readily recognizable, as indicated by focal or extensive necrosis and vascular proliferation, two independent diagnostic criteria for glioblastoma. Gene expression profiling of glioblastoma revealed a gene expression signature associated with hypoxia-regulated genes. The correlated gene set emerging from unsupervised analysis comprised known hypoxia-inducible genes involved in angiogenesis and inflammation such as VEGF and BIRC3, respectively. The relationship between hypoxia-modulated angiogenic genes and inflammatory genes was associated with outcome in our cohort of glioblastoma patients treated within prospective clinical trials of combined chemoradiotherapy. The hypoxia regulation of several new genes comprised in this cluster including ZNF395, TNFAIP3, and TREM1 was experimentally confirmed in glioma cell lines and primary monocytes exposed to hypoxia in vitro. Interestingly, the cluster seems to characterize differential response of tumor cells, stromal cells and the macrophage/microglia compartment to hypoxic conditions. Most genes classically associated with the inflammatory compartment are part of the NF-kappaB signaling pathway including TNFAIP3 and BIRC3 that have been shown to be involved in resistance to chemotherapy.

Our results associate hypoxia-driven tumor response with inflammation in glioblastoma, hence underlining the importance of tumor-host interaction involving the inflammatory compartment.

Kisspeptin stimulation of insulin secretion: mechanisms of action in mouse islets and rats

AIMS/HYPOTHESIS

Kisspeptin is a novel peptide identified as an endogenous ligand of the G-protein-coupled receptor 54 (GPR-54), which plays a crucial role in puberty and reproductive function. High levels of GPR-54 and kisspeptin have been reported in the pancreas and we have previously shown that kisspeptin potentiates glucose-induced insulin release from isolated islets, although the mechanisms underlying this effect were unclear.

METHODS

Insulin secretion from isolated mouse islets was measured to characterise the effects of kisspeptin. The effects of kisspeptin on both p42/44 mitogen-activated protein kinase (MAPK) phosphorylation and intracellular Ca(2+)([Ca(2+)](i)) in mouse islets were also investigated. Furthermore, kisspeptin was administered to rats in vivo and effects on plasma insulin levels measured.

RESULTS

In the current study, kisspeptin induced a concentration-dependent potentiation of glucose-induced (20 mmol/l) insulin secretion from mouse islets, with maximal effects at 1 micromol/l, but had no effect on insulin secretion at a substimulatory concentration of glucose (2 mmol/l). Activation of GPR-54 by kisspeptin also caused reversible increases in [Ca(2+)](i) in Fura-2 loaded dispersed islet cells. The kisspeptin-induced potentiation of glucose-induced insulin secretion was completely abolished by inhibitors of phospholipase C and p42/44 MAPK, but not by inhibitors of protein kinase C or p38 MAPK. Intravenous administration of kisspeptin into conscious, unrestrained rats caused an increase in circulating insulin levels, whilst central administration of kisspeptin had no effect, indicating a peripheral site of action.

CONCLUSIONS/INTERPRETATION

These observations suggest that neither typical protein kinase C isoforms nor p38 MAPK are involved in the potentiation of glucose-induced insulin release by kisspeptin, but intracellular signalling pathways involving phospholipase C, p42/44 MAPK and increased [Ca(2+)](i) are required for the stimulatory effects on insulin secretion. The observation that kisspeptin is also capable of stimulating insulin release in vivo supports the conclusion that kisspeptin is a regulator of beta cell function.

The kisspeptin (KiSS-1)/GPR54 system in cancer biology

Kisspeptin (KiSS-1) gene, initially described as a melanoma metastasis suppressor gene, encodes a number of peptides (kp-54, kp-14, kp-13, kp-10), which are endogenous ligands to a G protein-coupled receptor, referred as hOT7T175 or AXOR12 or GPR54. So far intensive investigation has provided substantiate evidence supporting the role of KiSS-1/GPR54 system in cancer biology as well as in the regulation of the reproductive function and trophoblast invasion. The precise mechanism by which KiSS-1/GPR54 system is affecting cancer cell growth and metastasis includes complex endocrine, paracrine and autocrine actions. Nevertheless, the detail mechanism of such actions is still under intensive investigation. Herein we review the evidence which support the role of KiSS-1/GPR54 system in cancer biology.

Neuroendocrine regulation of puberty in fish: insights from the grey mullet (Mugil cephalus) model

We investigated the molecular regulation of pubertal development in the grey mullet, Mugil cephalus, a relatively late-maturing teleost fish. We have isolated and characterized the cDNAs of key reproductive genes along the brain-pituitary-gonadal (BPG) axis as well as the promoters of genes that modulate the axis at multiple levels. Together with relevant findings from other model species, we propose a conceptual model of the neuroendocrine regulation of puberty in the female grey mullet. Research areas that warrant further investigation are identified in the model.

GPR54 and rGnRH I gene expression during the onset of puberty in Nile tilapia

The Kiss1/GPR54 system has recently been shown to play a key role in the onset of puberty in mammals. Growing evidence suggests that this system is also conserved across vertebrates although very few studies so far have been performed in lower vertebrates. The aims of this study were firstly in the teleost Nile tilapia to screen tissues for GPR54 expression levels, secondly to measure the expression patterns of GPR54 and GnRH I receptor (rGnRH I) in whole brains during the onset of puberty and finally to determine the effects of continuous illumination (LL) on receptor expression levels. Results confirmed that GPR54 was predominantly expressed in the brain and pituitary of adult tilapia. Furthermore, a significant increase of GPR54 gene expression was found in tilapia brains at 11 weeks post hatch (wph) followed by rGnRH I at 13 wph just prior to the histological observation of vitellogenic oocytes and active spermatogenesis in ova and testes at 17 wph. These results suggest a correlation between the increase of GPR54 expression in the brain and the onset of puberty. Finally, a significant effect of LL was observed on GPR54 expression levels which were characterized by a delayed surge with significantly lower levels than those of control fish. The current study not only suggests a link between the Kiss1/GPR54 system and the onset of puberty in a tropical batch spawning teleost that would be a highly conserved feature across vertebrates but also that the transcriptional mechanisms regulating GPR54 expression could be directly or indirectly influenced by light.

Fmoc-based solid-phase synthesis of GPR54-agonistic pentapeptide derivatives containing alkene- and fluoroalkene-dipeptide isosteres

Fmoc-protected Phe-Gly-type (Z)-alkene dipeptide isostere (ADI) and (E)-fluoroalkene dipeptide isostere (FADI) were synthesized and applied to Fmoc-based solid-phase peptide synthesis (SPPS). These cis-peptide bond mimetics were introduced into a bioactive pentapeptide [H-Amb-Phe-Gly-Leu-Arg-Trp-NH(2); Amb = 4-(aminomethyl) benzoic acid], which has potent GPR54 agonistic activity. The resulting pentapeptide derivatives showed low GPR54 agonistic activity, as compared with the parent peptide and (E)-ADI-containing derivative. This suggests that the trans-amide conformer of Phe-Gly peptide bond of the parent peptide would be significantly important for bioactivity. Contrary to our expectations, a (Z)-FADI-containing derivative exhibited essentially no activity, revealing the necessity of critical validation of FADI-bioisosterism.

Temporal expression of G-protein-coupled receptor 54 (GPR54), gonadotropin-releasing hormones (GnRH), and dopamine receptor D2 (drd2) in pubertal female grey mullet, Mugil cephalus

The G-protein-coupled receptor 54 (muGPR54) cDNA was cloned from the brain of the grey mullet, and its expression level, as well as those of the gonadotropin-releasing hormones (GnRH1, GnRH2, GnRH3) and dopamine receptor D2 (drd2), in the brain, pituitary and ovary of pubertal fish (early, intermediate, advanced) were determined by real-time quantitative RT-PCR (QPCR). The muGPR54 cDNA has an open reading frame of 1140 bp with a predicted 380 amino acid peptide, containing seven putative transmembrane domains and putative N-glycosylation and protein kinase C phosphorylation sites. QPCR results showed that the early stage of puberty in grey mullet is characterized by significantly high levels of expression of GPR54, GnRH and drd2 in the brain relative to the intermediate and advanced stages, except for GnRH1 that increased at the advanced stage of puberty. In the pituitary, drd2 expression declined significantly at the advanced stage relative to levels at the intermediate stage. Ovarian expression of GPR54 significantly increased from the intermediate stage of puberty relative to the early stage while that of GnRH1 acutely increased at the advanced stage of puberty. The ovarian expression of drd2 decreased as puberty progressed, but the changes were not significant. The results suggest the possible role of GPR54 and GnRH in positively regulating pubertal development in grey mullet and the dopaminergic inhibition of reproductive function mediated by drd2.

Chronic subcutaneous administration of kisspeptin-54 causes testicular degeneration in adult male rats

The kisspeptins are KiSS-1 gene-derived peptides that signal through the G protein-coupled receptor-54 (GPR54) and have recently been shown to be critical regulators of reproduction. Acute intracerebroventricular or peripheral administration of kisspeptin stimulates the hypothalamic-pituitary-gonadal (HPG) axis. This effect is thought to be mediated via the hypothalamic gonadotropin-releasing hormone (GnRH) system. Chronic administration of GnRH agonists paradoxically suppresses the HPG axis after an initial agonistic stimulation. We investigated the effects of continuous peripheral kisspeptin administration in male rats by use of Alzet minipumps. Initially we compared the effects of acute subcutaneous administration of kisspeptin-10, -14, and -54 on the HPG axis. Kisspeptin-54 produced the greatest increase in plasma LH and total testosterone at 60 min postinjection and was used in the subsequent continuous administration experiments. Chronic subcutaneous long-term administration of 50 nmol kisspeptin-54/day for 13 days decreased testicular weight. Histological examination showed degeneration of the seminiferous tubules associated with a significant decrease in the circulating levels of the testes-derived hormone, inhibin B. Plasma free and total testosterone were also lower, although these changes did not reach statistical significance. Further studies examined the effects of shorter periods of continuous kisspeptin administration. Subcutaneous administration of 50 nmol kisspeptin-54 for 1 day increased plasma LH and testosterone. This effect was lost after 2 days of administration, suggesting a downregulation of the HPG axis response to kisspeptin following continuous administration. These findings indicate that kisspeptin may provide a novel tool for the manipulation of the HPG axis and spermatogenesis.

The role of KiSS-1 in the regulation of puberty in higher primates

Puberty in higher primates is triggered by resurgence in the pulsatile secretion of hypothalamic GnRH after a hiatus in the robust release of this hypophysiotropic signal during childhood and juvenile development. Interestingly, the prepubertal decline in GnRH release is not associated with a marked reduction in the expression of either the gene that codes for GnRH (GnRH-1) or the decapeptide itself, and the network of GnRH neurons in the hypothalamus of the juvenile may by activated prematurely and with surprising ease by intermittent neurochemical stimulation with N-methyl-d-aspartate (NMDA), a glutamate receptor agonist. KiSS-1, a gene that encodes for kisspeptin-121, which is proteolytically cleaved to a 54 amino acid peptide, metastin, was initially studied in the context of tumor suppression. In 2003, however, inactivating mutations in the metastin receptor, GPR54, were reported to be associated with hypogonadotropic hypogonadism and absent puberty in man. Subsequent studies in the rhesus monkey have shown that GPR54 and KiSS-1 are expressed in the mediobasal hypothalamus (MBH), KiSS-1 expression in the MBH increases at the time of the pubertal resurgence in GnRH release and pulsatile, but not continuous, i.v. administration of metastin 45-54 in the juvenile male monkey elicits sustained GnRH release precociously. The significance of these findings in the context of the initiation of the onset of puberty is discussed.

Kisspeptin Mediates the Photoperiodic Control of Reproduction in Hamsters

The KiSS-1 gene encodes kisspeptin, the endogenous ligand of the G-protein-coupled receptor GPR54. Recent data indicate that the KiSS-1/GPR54 system is critical for the regulation of reproduction and is required for puberty onset. In seasonal breeders, reproduction is tightly controlled by photoperiod (i.e., day length). The Syrian hamster is a seasonal model in which reproductive activity is promoted by long summer days (LD) and inhibited by short winter days (SD). Using in situ hybridization and immunohistochemistry, we show that KiSS-1 is expressed in the arcuate nucleus of LD hamsters. Importantly, the KiSS-1 mRNA level was lower in SD animals but not in SD-refractory animals, which spontaneously reactivated their sexual activity after several months in SD. These changes of expression are not secondary to the photoperiodic variations of gonadal steroids. In contrast, melatonin appears to be necessary for these seasonal changes because pineal-gland ablation prevented the SD-induced downregulation of KiSS-1 expression. Remarkably, a chronic administration of kisspeptin-10 restored the testicular activity of SD hamsters despite persisting photoinhibitory conditions. Overall, these findings are consistent with a role of KiSS-1/GPR54 in the seasonal control of reproduction. We propose that photoperiod, via melatonin, modulates KiSS-1 signaling to drive the reproductive axis.

Structure-activity relationship study on small peptidic GPR54 agonists

Metastin (kisspeptin-54) is an endogenous ligand that modulates gonadotropin-releasing hormone (GnRH) secretion through the interaction with a G protein-coupled receptor (GPCR), GPR54. The short-chain C-terminal decapeptide amide, metastin (45-54) (kisspeptin-10), exerts the identical bioactivities to metastin, such as metastasis suppression of cancer cells and inhibition of trophoblast migration and invasion. In order to understand the structural requirement for GPR54 agonistic activity, structure-activity relationship (SAR) study on pentapeptide-based C-terminal metastin analogues was carried out. As a result, H-Amb-Nal(2)-Gly-Leu-Arg-Trp-NH2 34 was identified as a novel GPR54 agonist that possessed the most potent GPR54 agonistic activity reported so far.

Postnatal and pubertal development of the rhesus monkey (Macaca mulatta) testis

This review examines the neurobiology, endocrinology, and cell biology underlying the development of the testis from birth until puberty in the rhesus monkey, a representative higher primate.