Kisspeptin and KISS1R: a critical pathway in the reproductive system

Intraperitoneal administration of kisspeptin-10 modulates follicle maturation, gonadal steroids, calcium and metabolites in Sterlet sturgeon, Acipenser ruthenus

Kisspeptin is a multifunctional neurohormone, primarily involved in the regulation of reproduction. We tested whether peripheral administration of kisspeptin10 (KP-10) via intraperitoneal injection or slow release affects reproductive hormones and metabolites in Sterlet sturgeon (Acipenser ruthenus). Plasma and mucus 17β-estradiol (E2), and testosterone (T), plasma and follicular vitellogenin (VTG) and calcium (Ca) as well as glucose and lipids were determined. Mature Sterlet sturgeon were grouped into six groups: saline i.p injection (control), human kisspeptin (hKP-10) i.p injection; acipenser kisspeptin (aKP-10) i.p injection; hKP-10 (slow release); aKP-10 (slow-release) and no treatment control. No effect for KP-10 on sturgeon body weight was found after 4 weeks of treatment. Multivariate analysis revealed a significant disparity in plasma E2 levels. It was significantly different between groups (time, P = 0.0022). E2 in epithelia mucosa showed significant difference between and within groups in the acute group (time, P = 0.0252; treatment, P = 0.0423; time × treatment, P = 0.0429). T levels were unaffected by treatments (P > 0.05). The presence of synthetic aKP-10 led to an elevation in oocyte and plasma VTG levels (P < 0.05). Prolonged exposure to this peptide resulted in an increase in plasma calcium levels. Simultaneously, there was an augmentation in the number of mature follicles. Regardless of the duration of exposure, aKP-10 significantly elevated plasma glucose levels in Sterlet (P < 0.0). Additionally, KP-10 led to an increase in plasma lipids and cholesterol in Sterlet. Overall, our data support an involvement for KP-10 in the regulation of gonadal steroid hormones, oocyte maturation and metabolite levels in sturgeon, suggesting a positive role for this peptide in the reproductive physiology of this species.

The Hypothalamic-Pituitary-Gonadal Axis in Men with Schizophrenia

Schizophrenia is a severe mental disorder with a chronic, progressive course. The etiology of this condition is linked to the interactions of multiple genes and environmental factors. The earlier age of onset of schizophrenia, the higher frequency of negative symptoms in the clinical presentation, and the poorer response to antipsychotic treatment in men compared to women suggests the involvement of sex hormones in these processes. This article aims to draw attention to the possible relationship between testosterone and some clinical features in male schizophrenic patients and discuss the complex nature of these phenomena based on data from the literature. PubMed, Web of Science, and Google Scholar databases were searched to select the papers without limiting the time of the publications. Hormone levels in the body are regulated by many organs and systems, and take place through the neuroendocrine, hormonal, neural, and metabolic pathways. Sex hormones play an important role in the development and function of the organism. Besides their impact on secondary sex characteristics, they influence brain development and function, mood, and cognition. In men with schizophrenia, altered testosterone levels were noted. In many cases, evidence from available single studies gave contradictory results. However, it seems that the testosterone level in men affected by schizophrenia may differ depending on the phase of the disease, types of clinical symptoms, and administered therapy. The etiology of testosterone level disturbances may be very complex. Besides the impact of the illness (schizophrenia), stress, and antipsychotic drug-induced hyperprolactinemia, testosterone levels may be influenced by, i.a., obesity, substances of abuse (e.g., ethanol), or liver damage.

The Effects of the New Therapeutic Treatments for Diabetes Mellitus on the Male Reproductive Axis

One of the complications of chronic hyperglycemia and insulin resistance due to type 2 diabetes mellitus (T2DM) on the hypothalamic-pituitary-gonadal axis in men, is the high prevalence of hypogonadotropic hypogonadism, which has been recently defined as functional hypogonadism, characterized by low testosterone associated with inappropriately normal gonadotropin levels. Although the pathophysiology of this hormonal imbalance may be related to several factors, including glycemic control, concomitant sleep apnea, insulin resistance, the main role is determined by the degree of central or visceral obesity and the consequent inflammatory state. Several drugs have been developed to treat T2DM such as glucagon-like peptide-1 receptor agonists, dipeptidyl peptidase 4 inhibitors, and sodium-glucose co-transporter 2 inhibitors. All appear to be effective in ameliorating blood glucose control, by lowering inflammation and body weight, and most seem to reduce the risk of micro- and macrovascular damage as a consequence of uncontrolled diabetes. A few studies have evaluated the impact of these drugs on gonadal function in T2DM patients with hypogonadism, with promising results. This review summarizes the main current knowledge of the effects of these new antidiabetic drugs on the hypothalamus-pituitary-gonadal axis, showing their potential future application in addition to glucose control in dysmetabolic male patients.

Genetic polymorphisms of reproductive hormones and their receptors in assisted reproduction technology for patients with polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is one of the most common endocrinopathies in women of childbearing, which is defined by the accumulation of multiple, small fluid-filled ovarian cysts without the selection of a single dominant follicle. Most PCOS phenotypes are characterized by the absence of spontaneous ovulation, resistance toward ovulation inductors, the production of a large immature oocytes number, and the high prevalence of ovarian hyperstimulation syndrome, resulting in reduced assisted reproductive technologies (ART) programs effectiveness. The review analyses current data about the relationship between polymorphism genotypes of KISS genes, follicle stimulating hormone (FSH), luteinizing hormone (LH), anti-Müllerian hormone (AMH) and their receptors genes, gonadotropin-releasing hormone (GnRH), estrogen, and progesterone receptors genes, the PCOS risk and the features of ovarian response to stimulation during ART cycles. The use of single nucleotide polymorphisms (SNPs) as prognostic markers of ART programs outcomes would provide a personalized approach to the drugs and doses choice for ovarian stimulation and significantly increase the chance of pregnancy.

The Therapeutic Effect of Shugan Xiehuo Formula in the Female Rat Model with Central Precocious Puberty

Central precocious puberty (CPP) severely affects children's physical and mental health and needs to be treated promptly and effectively. This article aimed to research the therapeutic effect of Shugan Xiehuo Formula (SXF) on CPP. A female CPP rat model was established and then treated with leuprolide and different doses of SXF. Sex organ volume and index were measured. Ovaries and uteri were visualized by hematoxylin-eosin staining. The concentrations of follicle-stimulating hormone (FSH), luteinizing hormone (LH), prolactin (PRL), and estradiol (E2) in peripheral blood were determined. The expression levels of gonadotropin-releasing hormone (GnRH), gonadotropin-releasing hormone receptor (GnRHR), estrogen receptor alpha (ERα), and G protein-coupled receptor 30 (GPR30) in the hypophysis were investigated by Real-Time Quantitative Reverse Transcription PCR and western blot. GnRH expression in the hypothalamus and GnRHR expression in the ovary were detected by immunohistochemistry. SXF reduced the volume of the bilateral ovaries, as well as the volumes of the uterus, hypothalamus, and hypophysis in the female CPP rats and diminished the index of the ovary, uterus, hypothalamus, and hypophysis in the female CPP rats (P < 0.05 or P < 0.01). SXF treatment inhibited follicle maturation and uterine wall thickening in the female CPP rats. SXF decreased the concentrations of FSH, LH, PRL, and E2 in the peripheral blood in the female CPP rats (P < 0.01 or P < 0.001). SXF suppressed the expressions of GnRH, GnRHR, ERα, and GPR30 in the hypophysis (P < 0.05), the expression of GnRH in the hypothalamus (P < 0.01), and the expression of GnRHR in the ovaries (P < 0.001) of the female CPP rats. Overall, our study revealed that SXF had therapeutic effects on CPP in female rats. This is worthy of promoting clinically.

An Isolated Hypogonadotropic Hypogonadism due to a L102P Inactivating Mutation of KISS1R/GPR54 in a Large Family

KISS1R (GPR54) mutations have been reported in several patients with congenital normosmic idiopathic hypogonadotropic hypogonadism (nIHH). We aim to describe in detail nIHH patients with KISS1R (GPR54) mutations belonging to one related extended family and to review the literature. A homozygous mutation (T305C) leading to a leucine substitution with proline (L102P) was found in three affected kindred (2 males and 1 female) from a consanguineous Saudi Arabian family. This residue is localized within the first exoloop of the receptor, affects a highly conserved amino acid, perturbs the conformation of the transmembrane segment, and impairs its function. In the affected female, a combined gonadotropin administration restored regular period and ovulation and she conceived with a healthy baby boy after 4 years of marriage. We showed that a loss-of-function mutation (p.Tyr305C) in the KISS1R gene can cause (L102P) KISS1 receptor dysfunction and familial nIHH, revealing the crucial role of this amino acid in KISS1R function. The observed restoration of periods and later on pregnancy by an exogenous gonadotropin administration further support, in humans, that the KISS1R mutation has no other harmful effects on the patients apart from the gonadotropin secretion impairment.

The role of kisspeptin system in cancer biology

Kisspeptins are a family of neuropeptides that are known to be critical in puberty initiation and ovulation. Apart from that kisspeptin derived peptides (KPs) are also known for their antimetastatic activities in several malignancies. Herein we report recent evidence of the role of kisspeptins in cancer biology and we examine the prospective of targeting the kisspeptin pathways leading to a better prognosis in patients with malignant diseases.

Effect of kisspeptin on the proliferation and apoptosis of bovine granulosa cells

Previous studies have shown that kisspeptin (Kp-10) is expressed in mammalian ovaries; however, the expression and role of Kp-10 in bovine ovarian granulosa cells are still unclear. In this study, we assessed the expression of Kp-10 and its effects on the proliferation and apoptosis of bovine granulosa cells. Immunohistochemical analysis showed that Kp-10 was expressed in the cytoplasm of bovine ovarian granulosa cells. Moreover, MTT assays showed that 100nM Kp-10 significantly inhibited the viability of granulosa cells (P<0.05). Flow cytometry analysis showed that Kp-10 could significantly increase accumulation of cells in the G₁ phase, decrease accumulation of cells in the S phase, and promote apoptosis in bovine granulosa cells (P<0.05). Additionally, Kp-10 decreased the mRNA levels of Bcl-2, an anti-apoptotic gene; increased the mRNA levels of caspase-3, a pro-apoptotic gene; and increased the mRNA levels of Fas and Fasl (P< 0.05). Thus, our findings demonstrated for the first time that Kp-10 inhibited proliferation and promoted apoptosis in bovine ovarian granulosa cells. These findings provide insights into our understanding of the role of Kp-10 in mediating the proliferation of bovine granulosa cells.

Obesity in pregnancy: a novel concept on the roles of adipokines in uterine contractility

Obesity is a global health problem even among pregnant women. Obesity alters quality of labor, such as preterm labor, prolonged labor, and higher oxytocin requirements in pregnant women. The most important factors to play a role in the altered gestational period and serve as drug targets to treat the consequences are female sexual hormones, calcium channels, adrenergic system, oxytocin, and prostaglandins. However, we have limited information about the impact of obesity on the pregnant uterine contractility and gestation time. Adipose tissue, which is the largest endocrine and paracrine organ, especially in obesity, is responsible for the production of adipokines and various cytokines and chemokines, and there are no reliable data available describing the relation between body mass index, glucose intolerance, and adipokines during pregnancy. Recent data suggest that the dysregulation of leptin, adiponectin, and kisspeptin during pregnancy contributes to gestational diabetes mellitus and pre-eclampsia. A preclinical method for obese pregnancy should be developed to clarify the action of adipokines and assess their impact in obesity. The deeper understanding of the adipokines-induced processes in obese pregnancy may be a step closer to the prevention and therapy of preterm delivery or prolonged pregnancy. Gestational weight gain is one of the factors that could influence the prenatal development, birth weight, and adiposity of newborn.

Timing of Maternal Exposure and Foetal Sex Determine the Effects of Low-level Chemical Mixture Exposure on the Foetal Neuroendocrine System in Sheep

We have shown that continuous maternal exposure to the complex mixture of environmental chemicals (ECs) found in human biosolids (sewage sludge), disrupts mRNA expression of genes crucial for development and long-term regulation of hypothalamic-pituitary gonadal (HPG) function in sheep. The present study investigated whether exposure to ECs only during preconceptional period or only during pregnancy perturbed key regulatory genes within the hypothalamus and pituitary gland and whether these effects were different from chronic (life-long) exposure to biosolid ECs. The findings demonstrate that the timing and duration of maternal EC exposure influences the subsequent effects on the foetal neuroendocrine system in a sex-specific manner. Maternal exposure prior to conception, or during pregnancy only, altered the expression of key foetal neuroendocrine regulatory systems such as gonadotrophin-releasing hormone and kisspeptin to a greater extent than when maternal exposure was 'life-long'. Furthermore, hypothalamic gene expression was affected to a greater extent in males than in females and, following EC exposure, male foetuses expressed more 'female-like' mRNA levels for some key neuroendocrine genes. This is the first study to show that 'real-life' maternal exposure to low levels of a complex cocktail of chemicals prior to conception can subsequently affect the developing foetal neuroendocrine system. These findings demonstrate that the developing neuroendocrine system is sensitive to EC mixtures in a sex-dimorphic manner likely to predispose to reproductive dysfunction in later life.

Double-blind, randomized, placebo-controlled study of safety, tolerability, pharmacokinetics and pharmacodynamics of TAK-683, an investigational metastin analogue in healthy men

AIMS

Two randomized, double-blind, placebo-controlled studies were performed to characterize the safety, tolerability, pharmacokinetics (PK) and pharmacodynamics (PD) of the investigational metastin analogue, TAK-683, in healthy men.

METHODS

We first investigated a single subcutaneous (s.c.) dose of TAK-683 (0.01-2.0 mg) in 60 subjects (TAK-683, n = 42; placebo, n = 18). We then assessed a single s.c. bolus of 0.03-1.0 mg TAK-683 on day 1, followed by a 0.01-2.0 mg day(-1) continuous infusion on days 2-13, to simulate a depot formulation, in 30 subjects (TAK-683, n = 25; placebo, n = 5) for 14 days.

RESULTS

TAK-683 was well tolerated up to a dose of 2.0 mg day(-1) by continuous s.c. infusion for 14 days. Adverse events were similar between TAK-683 and placebo subjects at all dose levels. TAK-683 plasma concentrations generally increased in proportion to dose with single and continuous dosing, with steady-state concentrations achieved by day 2 of continuous dosing. TAK-683 at 2.0 mg day(-1) suppressed testosterone below castration level (<50 ng dl(-1)) in four of five subjects by day 7 of continuous dosing. Luteinizing hormone and follicle stimulating hormone concentrations were suppressed with TAK-683 continuous dosing compared with placebo by up to 70 and 43%, respectively, but this was not consistently dose-dependent.

CONCLUSIONS

In healthy men, s.c. administration of TAK-683 was well tolerated at all dose levels. The PK profile of TAK-683 was favourable, and TAK-683 suppressed testosterone profoundly during continuous dosing. Further investigation of metastin analogues is warranted for the treatment of castration-resistant prostate cancer.

Neuroendocrine control of the transition to reproductive senescence: lessons learned from the female rodent model

The natural transition to reproductive senescence is an important physiological process that occurs with aging, resulting in menopause in women and diminished or lost fertility in most mammalian species. This review focuses on how rodent models have informed our knowledge of age-related changes in gonadotropin-releasing hormone (GnRH) neurosecretory function and the subsequent loss of reproductive capacity. Studies in rats and mice have shown molecular, morphological and functional changes in GnRH cells. Furthermore, during reproductive aging altered sex steroid feedback to the hypothalamus contributes to a decrease of stimulatory signaling and increase in inhibitory tone onto GnRH neurons. At the site of the GnRH terminals where the peptide is released into the portal vasculature, the cytoarchitecture of the median eminence becomes disorganized with aging, and mechanisms of glial-GnRH neuronal communication may be disrupted. These changes can result in the dysregulation of GnRH secretion with reproductive decline. Interestingly, reproductive aging effects on the GnRH circuitry are observed in middle age even prior to any obvious physiological changes in cyclicity. We speculate that the hypothalamus may play a critical role in this mid-life transition. Because there are substantial species differences in these aging processes, we also compare and contrast rodent aging to that in primates. Work discussed herein shows that in order to understand neuroendocrine mechanisms of reproductive senescence, further research needs to be conducted in ovarian-intact models.

Ablation of neurons expressing agouti-related protein, but not melanin concentrating hormone, in leptin-deficient mice restores metabolic functions and fertility

Leptin-deficient (Lep(ob/ob)) mice are obese, diabetic, and infertile. Ablation of neurons that make agouti-related protein (AgRP) in moderately obese adult Lep(ob/ob) mice caused severe anorexia. The mice stopped eating for 2 wk and then gradually recovered. Their body weight fell to within a normal range for WT mice, at which point food intake and glucose tolerance were restored to that of WT mice. Remarkably, both male and female Lep(ob/ob) mice became fertile. Ablation of neurons that express melanin-concentrating hormone (MCH) in adult Lep(ob/ob) mice had no effect on food intake, body weight, or fertility, but resulted in improved glucose tolerance. We conclude that AgRP-expressing neurons play a critical role in mediating the metabolic syndrome and infertility of Lep(ob/ob) mice, whereas MCH-expressing neurons have only a minor role.

Metastasis suppressor genes at the interface between the environment and tumor cell growth

The molecular mechanisms and genetic programs required for cancer metastasis are sometimes overlapping, but components are clearly distinct from those promoting growth of a primary tumor. Every sequential, rate-limiting step in the sequence of events leading to metastasis requires coordinated expression of multiple genes, necessary signaling events, and favorable environmental conditions or the ability to escape negative selection pressures. Metastasis suppressors are molecules that inhibit the process of metastasis without preventing growth of the primary tumor. The cellular processes regulated by metastasis suppressors are diverse and function at every step in the metastatic cascade. As we gain knowledge into the molecular mechanisms of metastasis suppressors and cofactors with which they interact, we learn more about the process, including appreciation that some are potential targets for therapy of metastasis, the most lethal aspect of cancer. Until now, metastasis suppressors have been described largely by their function. With greater appreciation of their biochemical mechanisms of action, the importance of context is increasingly recognized especially since tumor cells exist in myriad microenvironments. In this chapter, we assemble the evidence that selected molecules are indeed suppressors of metastasis, collate the data defining the biochemical mechanisms of action, and glean insights regarding how metastasis suppressors regulate tumor cell communication to-from microenvironments.

International Union of Basic and Clinical Pharmacology. LXXVII. Kisspeptin receptor nomenclature, distribution, and function

Kisspeptins are members of the Arg-Phe amide family of peptides, which have been identified as endogenous ligands for a G-protein-coupled receptor encoded by a gene originally called GPR54 (also known as AXOR12 or hOT7T175). After this pairing, the gene has been renamed KISS1R. The International Union of Basic and Clinical Pharmacology Committee on Receptor Nomenclature and Drug Classification recommends that the official name for the receptor is the kisspeptin receptor to follow the convention of naming the receptor protein after the endogenous ligand. The endogenous ligand was initially called metastin, after its role as a metastasis suppressor, and is now referred to as kisspeptin-54 (KP-54), a C-terminally amidated 54-amino acid peptide cleaved from the 145-amino acid gene product. Shorter C-terminal cleavage fragments [KP-14, KP-13 and KP-10 (the smallest active fragment)] are also biologically active. Both receptor and peptide are widely expressed in human, rat, and mouse; the receptor sequence shares more than 80% homology in these species. Activation of the kisspeptin receptor by kisspeptin is via coupling to G(q/11) and the phospholipase C pathway, causing Ca(2+) mobilization. Mutations in the KISS1R gene result in hypogonadotropic hypogonadotropism, and targeted disruption of Kiss1r in mice reproduces this phenotype, which led to the discovery of the remarkable ability of the kisspeptin receptor to act as a molecular switch for puberty. In addition to regulating the reproductive axis, the kisspeptin receptor is also implicated in cancer, placentation, diabetes, and the cardiovascular system.

Aromatase inhibition causes increased amplitude, but not frequency, of hypothalamic-pituitary output in normal women

OBJECTIVE

To better understand the site and mode of action of aromatase inhibitors.

DESIGN

Prospective study.

SETTING

Academic research environment.

PATIENT(S)

Five eumenorrheic (without polycystic ovary syndrome), early follicular phase women with a normal body mass index (mean: 20.47±0.68 kg/m2), and 12 normal weight, midreproductive aged, early follicular phase women with a normal body mass index (mean: 20.8±1.7 kg/m2) as historical controls.

INTERVENTION(S)

2.5 mg letrozole daily for 7 days, with daily urine collection (first morning void), thrice weekly blood sampling, and 4 hours of blood sampling every 10 minutes.

MAIN OUTCOME MEASURE(S)

Serum luteinizing hormone (LH) measured by a well-characterized immunofluorometric assay with LH pulse characteristics compared between treated and control groups using t tests.

RESULT(S)

Mean LH and LH pulse amplitude more than doubled in the women who had taken letrozole compared with the controls, but the LH pulse frequency did not differ between the women taking letrozole and the controls.

CONCLUSION(S)

These results indicate that the release of negative feedback inhibition of estradiol on the hypothalamic-pituitary axis in normal women by aromatase inhibitors creates an amplitude-related increase in endogenous hypothalamic-pituitary drive. The finding that the mean LH and LH pulse amplitude, but not the frequency, increased after letrozole suggests a possible pituitary site of action.

Plasma levels of kisspeptins in postmenopausal Chinese women do not show substantial elevation

The menopause, defined as the permanent cessation of menstruation resulting from ovarian failure, is characterized by elevated levels of serum gonadotropins. Recent studies have demonstrated that the gonadotropin hypersecretion in postmenopausal women is secondary to increase of KiSS-1 mRNA from the hypothalamus neurons, which encoded kisspeptin peptides. The present study was designed to determine whether plasma kisspeptins levels are altered in postmenopausal women. Blood samples were taken from 145 postmenopausal women, 35 young women and 30 pregnant women control in the first trimester. The plasma concentration of kisspeptins, follicle-stimulating hormone (FSH), luteinizing hormone (LH) and estradiol (E₂) was measured using immunoassay kits. Results indicated that plasma kisspeptins levels in postmenopausal women had higher than those in young women (5.25±0.36; 4.48±0.34 pmol/L), but no significant difference was found between the two groups (p=0.179). Plasma FSH and LH levels were significantly higher in postmenopausal women (124.67±12.78, 57.14±3.57 mIu/mL) than those in young women (9.23±2.78, 7.56±2.71 mIu/mL, p<0.001). However, Plasma kisspeptins levels were not significantly correlated to FSH and LH in postmenopausal women (r=-0.23, 0.324; p=0.927, 0.176, respectively), and also there was no any correlation between plasma kisspeptins and E₂ in postmenopausal women (r=-0.065; p=0.792). Collectively, there was no significant difference in plasma kisspeptins levels between postmenopausal and young women. Our result suggested that kisspeptins' role during menopause might mainly act in central rather than peripheral system and it could not be currently used as a clinical marker for menopause.

The KISS1 metastasis suppressor: a good night kiss for disseminated cancer cells

Re-expression of KISS1 in tumor cell lines allows all antecedent steps of metastasis, but prevents colonization of secondary sites. Because tumor cells have already disseminated by the time of cancer diagnosis, KISS1 may represent a new opportunity for therapeutic intervention. Moreover, numerous clinical reports demonstrate that a loss or reduction of KISS1 expression in different human cancers inversely correlates with tumor progression, metastasis, and survival. Taken together, these observations compel the hypothesis that KISS1 could be of tremendous utility in controlling metastasis in a therapeutic context. In this review, we highlight some key findings from preclinical and clinical studies and discuss strategies whereby KISS1 may be exploited clinically to treat metastases.

A comparison of knowledge about medicinal plants for three rural communities in the semi-arid region of northeast of Brazil

AIM

The aim of this research was to understand the importance of native and exotic plants in local medical systems in the Caatinga of the Brazilian northeast, and the influence of socio-economic factors on the acquisition of knowledge about these resources.

METHODS

A total of 55 people were interviewed in three rural communities using free list and semi-structured interviewes.

RESULTS

A total of 108 ethnospecies were reported, 99 of which were identified; 43 of these were preferred by informants. Most of the plants cited were exotic (51) but the difference in diversity among these plants and native plants (48) was not considered significant (p>0.05). The exotic plants were predominantly herbaceous and used to cure diseases that native plants did not seem to treat. There were no differences between men's and women's knowledge of the plants (p>0.05). However, for some communities, factors such as age and income were correlated with the number of citations and indications for plants, which suggested that older people and those with higher income levels had more knowledge about these properties.

CONCLUSION

The data presented in this study showed the importance of exotic species in the region studied and demonstrated that plant knowledge can be perceived as a way to diversify options for medical treatment in the area.

Kisspeptin signaling in the brain

Kisspeptin (a product of the Kiss1 gene) and its receptor (GPR54 or Kiss1r) have emerged as key players in the regulation of reproduction. Mutations in humans or genetically targeted deletions in mice of either Kiss1 or Kiss1r cause profound hypogonadotropic hypogonadism. Neurons that express Kiss1/kisspeptin are found in discrete nuclei in the hypothalamus, as well as other brain regions in many vertebrates, and their distribution, regulation, and function varies widely across species. Kisspeptin neurons directly innervate and stimulate GnRH neurons, which are the final common pathway through which the brain regulates reproduction. Kisspeptin neurons are sexually differentiated with respect to cell number and transcriptional activity in certain brain nuclei, and some kisspeptin neurons express other cotransmitters, including dynorphin and neurokinin B (whose physiological significance is unknown). Kisspeptin neurons express the estrogen receptor and the androgen receptor, and these cells are direct targets for the action of gonadal steroids in both male and female animals. Kisspeptin signaling in the brain has been implicated in mediating the negative feedback action of sex steroids on gonadotropin secretion, generating the preovulatory GnRH/LH surge, triggering and guiding the tempo of sexual maturation at puberty, controlling seasonal reproduction, and restraining reproductive activity during lactation. Kisspeptin signaling may also serve diverse functions outside of the classical realm of reproductive neuroendocrinology, including the regulation of metastasis in certain cancers, vascular dynamics, placental physiology, and perhaps even higher-order brain function.

Nuclear magnetic resonance and circular dichroism study of metastin (Kisspeptin-54) structure in solution

KISS1 was first discovered as a metastasis suppressor, but also plays crucial roles in the onset of puberty. The KISS1 gene encodes a secreted protein of 145 amino acids that exhibits no sequence similarity with any known proteins. KISS1 protein is proteolytically processed to generate a number of so-called kisspeptins (KP), the most well characterized is known as KP-54 or metastin. KP-54 is carboxy-terminally amidated and binds to and activates the KISS1 receptor (KISS1R). The current studies were undertaken in order to determine structure of KP-54 using nuclear magnetic resonance and circular dichroism. KP-54 is mostly disordered both in water and in trifluoroethanol/water mixed solvent, with no structural motifs. In sodium dodecyl sulfate micelles, KP-54 remains mostly disordered except for a small increase in helical propensity (from 3.7% in water to 9.9% in micelles). Despite this apparent lack of structure, KP-54 is biologically active. The intrinsic disorder of KP-54 may confer advantages in its ability to recognize and bind a wide range of target proteins.

TAC3 and TACR3 mutations in familial hypogonadotropic hypogonadism reveal a key role for Neurokinin B in the central control of reproduction

The timely secretion of gonadal sex steroids is essential for the initiation of puberty, the postpubertal maintenance of secondary sexual characteristics and the normal perinatal development of male external genitalia. Normal gonadal steroid production requires the actions of the pituitary-derived gonadotropins, luteinizing hormone and follicle-stimulating hormone. We report four human pedigrees with severe congenital gonadotropin deficiency and pubertal failure in which all affected individuals are homozygous for loss-of-function mutations in TAC3 (encoding Neurokinin B) or its receptor TACR3 (encoding NK3R). Neurokinin B, a member of the substance P-related tachykinin family, is known to be highly expressed in hypothalamic neurons that also express kisspeptin, a recently identified regulator of gonadotropin-releasing hormone secretion. These findings implicate Neurokinin B as a critical central regulator of human gonadal function and suggest new approaches to the pharmacological control of human reproduction and sex hormone-related diseases.

Modulation of gonadotrophin-releasing hormone secretion by an endogenous circadian clock

The mechanisms mediating positive feedback effects of oestradiol on pre-ovulatory gonadotrophin releasing-hormone (GnRH) surge generation in female mammals, although well-explored, are still incompletely understood. In addition to binding to and signalling through classical nuclear receptor-mediated pathways in afferent hypothalamic neurones, recent evidence suggests that ovarian steroids may use membrane-bound receptors or nonclassical signalling pathways to directly influence cell function leading to the generation of GnRH surge secretion. We review recent investigations into the role of the endogenous molecular circadian clock on modulation of GnRH gene expression and neuropeptide secretion, and will explore potential molecular mechanisms by which ovarian steroids may directly induce secretory changes at the level of the GnRH neurone, examining closely whether circadian clock gene oscillations may be involved.

Association of prepubertal body composition in healthy girls and boys with the timing of early and late pubertal markers

BACKGROUND

It is controversial whether prepubertal body composition is implicated in the timing of puberty onset.

OBJECTIVE

The objective was to investigate whether body composition in the 2 y preceding the start of the pubertal growth spurt -- a marker of puberty onset -- is associated with the attainment of early and late pubertal markers in healthy German boys and girls.

DESIGN

Multivariate-adjusted regression analyses were performed in 215 participants of the DOrtmund Nutritional and Anthropometric Longitudinally Designed (DONALD) Study for whom body mass index (BMI) and its components fat mass/height(2) (FM/m(2)) and fat-free mass/height(2) (FFM/m(2)) 1 and 2 y before the onset of the pubertal growth spurt (age at takeoff; ATO) and information on early life exposures were available. In addition, age at peak height velocity (APHV) and menarche were examined.

RESULTS

Higher BMIs and FM/m(2) z scores 1 and 2 y before ATO showed modest associations with chronological age at ATO among girls only (girls: P for = trend 0.05-0.1, adjusted for early life factors; boys: P = 0.2-0.6). FFM/m(2) z scores were not related to age at ATO (P for trend = 0.5-0.8). Conversely, prepubertal BMI and FM/m(2) more clearly predicted APHV and puberty duration (APHV minus ATO) in both sexes and age at menarche in girls (girls: adjusted P for trend <0.0001-0.03; boys: P = 0.01-0.046).

CONCLUSION

This longitudinal study suggests that prepubertal body composition in healthy boys and girls may not be critical for the initiation of the pubertal growth spurt but instead affects the progression of pubertal development, which results in earlier attainment of later pubertal stages.