The Role of Kisspeptin in Female Reproduction

[Neuroendocrine features of the pathogenesis of polycystic ovary syndrome (literature review)]

Polycystic ovary syndrome (PCOS) is one of the most pressing problems in endocrine gynecology. The main signs of the disease are hyperandrogenism, menstrual and/or ovulatory dysfunction, and polycystic ovarian structure according to ultrasound. Women with PCOS are at risk for developing metabolic syndrome, type 2 diabetes, cardiovascular disease, and endometrial cancer. In this connection, the pathogenetic mechanisms of the occurrence of this syndrome are continuously studied and new methods of treatment are being sought. PCOS is characterized by a wide range of various disorders of the neuroendocrine regulation of the reproductive system. The main focus of the review is aimed at summarizing information about the etiological role of neuropeptides and neurotransmitters, such as phoenixin, galanins, orexins, GABA, in the pathophysiology of PCOS and about the possibility of their use for diagnostic and therapeutic purposes. In recent decades, the interest of scientists has been focused on the study of KNDy neurons, because it is the kisspeptin synthesized by them that is one of the main regulators of the hypothalamic-pituitary-ovarian axis. This article discusses data on the significance of KNDy neurons in the pathogenesis of the syndrome. Information is provided on the effect of elevated levels of androgens and anti-Müllerian hormone on GnRH neurons. Also analyzed are studies on functional and structural disorders in the hypothalamus in PCOS. Literature search was carried out in national (eLibrary, CyberLeninka.ru) and international (PubMed, Cochrane Library) databases in Russian and English. The priority was free access to the full text of articles. The choice of sources was prioritized for the period from 2018 to 2023.However, taking into account the insufficient knowledge of the chosen topic, the choice of sources dates back to 1998.

Role of leptin, adiponectin, and kisspeptin in polycystic ovarian syndrome pathogenesis

INTRODUCTION

Polycystic ovarian syndrome (PCOS) affects 5-20% of females and is the most common cause of anovulatory infertility. Leptin seems to have an important role in reproduction. Many reproductive pathologies such as preeclampsia, PCOS, and endometriosis are associated to plasma adiponectin levels. Kisspeptin levels are increased in PCOS women.

EVIDENCE ACQUISITION

A review of the literature was completed through the PubMed database aiming to find articles regarding leptin, adiponectin and kisspeptin and if they are related to PCOS pathogenesis.

EVIDENCE SYNTHESIS

Even today it is not clear what is the role of leptin in women with PCOS, although most of the researchers found increased levels of leptin as well as leptin resistance in PCOS (both obese and lean individuals). Many more longitudinal studies should be done to discover the usefulness of measuring adiponectin in prepubertal women who apparently have a possibility to develop PCOS to find out if they finally develop PCOS. Most of the researchers found that PCOS women have decreased levels of adiponectin unrelated to BMI levels. Nevertheless, not all studies had the same result. Moreover, it is necessary more studies to be made to investigate the connection between kisspeptin and other metabolic factors such as LH and insulin resistance.

CONCLUSIONS

In general, it remains inconclusive whether leptin, adiponectin, and kisspeptin can be used as clinical and/or biochemical markers of PCOS. Therefore, it is essential to review the current data with regards to the association between PCOS and circulating leptin, adiponectin, and kisspeptin in women with PCOS.

Is There an Association Between Circulating Kisspeptin Levels and Ovarian Reserve in Women of Reproductive Age?

BACKGROUND/AIM

To investigate the possible association of kisspeptin levels with the ovarian reserves of women of reproductive age.

PATIENTS AND METHODS

Eighty women aged 19-40 participated after signing an informed consent. Of these, 74 were finally included as in 6 women the blood samples were considered inappropriate due to hemolysis. They were divided into three main groups according to their ovarian reserve patterns: women with adequate ovarian reserves (Group A - AOR) (n=30), women with increased ovarian reserves (Group B - PCOS) (n=31), and women with diminished ovarian reserves (Group C - DOR) (n=13).

RESULTS

Women with diminished ovarian reserves had statistically significantly increased age and FSH compared to the other two groups. No statistically significant difference was found between the three groups for estradiol and thyroid stimulating hormone. Moreover, body mass index, luteinizing hormone, total testosterone, 17-hydroxyprogesterone, dehydroepiandrosterone, anti-Mullerian hormone (AMH), and antral follicle count (AFC) were increased in group B compared to the other two groups. AMH and AFC were decreased in women with diminished ovarian reserves compared to the other two groups, as expected. The comparison of kisspeptin levels between the three groups showed that kisspeptin levels were increased in women with diminished ovarian reserves, compared to the other two groups, but without a statistically significant difference. However, kisspeptin levels in group C were statistically significantly higher than those in group A.

CONCLUSION

There are no strong indications that kisspeptin levels are associated with the ovarian reserve in women of reproductive age.

Prenatal kisspeptin antagonist exposure prevents polycystic ovary syndrome development in prenatally-androgenized rats in adulthood: An experimental study

Background

Increased levels of kisspeptin are associated with hypothalamus-pituitary-ovary axis dysfunction. It may lead to the development of polycystic ovary syndrome (PCOS).

Objective

We aimed to investigate the effect of prenatal kisspeptin antagonist exposure on the development of PCOS in prenatally androgenized rats in adulthood.

Materials and Methods

In this experimental study, pregnant rats were injected with free testosterone (T, 5 mg/day) or T+P271 (kisspeptin antagonist) on the 20 th day of the pregnancy period (n = 5 in each group), while rats in the control group received solvent. Female offspring were examined in terms of anogenital distance (AGD), anovaginal distance (AVD), vaginal opening, serum total testosterone (TT) levels, ovarian follicles, and the regularity of estrous cycles in adulthood. AGD and AVD were measured using a vernier caliper. TT levels were measured using the enzyme-linked immunosorbent assay method. Ovaries were fixed in 10% formalin, tissue processing was done by a standard protocol, and then ovaries embedded in paraffin. 5 μm-thickness ovarian sections mounted on a glass slide, deparaffinized, and stained using Harris's Hematoxylin and Eosin Y.

Results

AGD, AVD (p < 0.001), TT levels (p = 0.02), and the numbers of preantral and antral follicles (p < 0.001) in the ovaries were significantly decreased in prenatally T-P271-exposed rats compared to prenatally T-exposed rats. The age of vaginal opening was early in T-P271-exposed rats compared to prenatally T-exposed rats (p < 0.001). The number of corpora lutea was significantly increased in T-P271-exposed rats (p < 0.001). No cystic follicles were observed in the ovaries of prenatally T-P271-exposed rats. Prenatally T-P271-exposed rats had regular estrous cycles compared to prenatally T-exposed rats.

Conclusion

Prenatal exposure to kisspeptin antagonist can prevent PCOS development in prenatally androgenized rats in adulthood.

The role of kisspeptin in the pathogenesis of a polycystic ovary syndrome

Hypothalamic-pituitary gonadal (HPG) axis is responsible for the development and regulation of the female reproductive system. In polycystic ovary syndrome (PCOS), there is a disturbance in the HPG axis. Kisspeptin, a neuropeptide produced by the KISS1 gene, plays a vital role in the regulation of HPG axis by binding with its receptors KISS1R/GPR54, and stimulates gonadotropin secretion from the hypothalamus into pituitary to release luteinizing hormone (LH) and follicle stimulating hormone (FSH). Polymorphisms or mutations in the KISS1 gene can cause disturbance in the kisspeptin signaling pathway and is thought to disrupt HPG axis. Altered signaling of kisspeptin can cause abnormal secretion of GnRH pulse, which leads to increased LH/FSH ratio, thereby affecting androgen levels and ovulation. The increased levels of androgen worsen the symptoms of PCOS. In the present article, we review the molecular physiology and pathology of kisspeptin and how it is responsible for the development of PCOS. The goal of this review article is to provide an overview and metabolic profile of kisspeptin in PCOS patients and the expression of kisspeptin in PCOS animal models. In the present article, we also review the molecular physiology and pathology of kisspeptin and how it is responsible for the development of PCOS.

Serum kisspeptin and proopiomelanocortin in cystic fibrosis: a single study

The determination of hormonal biomarkers is of increasing interest in many diseases, including cystic fibrosis (CF). Hormones that have not been estimated and described so far in CF include kisspeptin (KISS) and proopiomelanocortin (POMC), which are involved in the regulation of many processes, including appetite and fertility. Therefore, the aim of our study was to estimate the level of KISS and POMC in sera from CF patients and to determine the correlation between these hormones and clinical parameters. For this purpose, we estimated the levels of KISS and POMC in 38 CF patients and 16 healthy participants with enzyme-linked immunosorbent assay. We found significantly reduced levels of KISS and POMC in people with CF compared to healthy subjects (1.76 ± 0.46 vs. 2.27 ± 0.56 ng/mL, p < 0.05 and 6.25 ± 4.36 vs. 14.74 ± 6.24 ng/mL, p < 0.001, respectively). Furthermore, the level of both hormones was negatively correlated with age. The hormones studied did not correlate with the results of spirometry and each other. Thus, decreased KISS and POMC levels may be associated with lower body weight and delayed puberty in patients with CF.

Transcriptomic Profiling Revealed Signaling Pathways Associated with the Spawning of Female Zebrafish under Cold Stress

As one of the critical abiotic factors, temperature controls fish development and reproduction. However, the effects of low temperature on the transcriptional regulation of zebrafish reproduction remain largely unclear. In this study, the fecundity of zebrafish was examined after exposure to cold temperatures at 19.5 °C, 19 °C, 18.5 °C, or 18 °C. The temperature at 19 °C showed no significant influence on the fecundity of zebrafish, but temperature at 18.5 °C or 18 °C significantly blocked the spawning of females, suggesting the existence of a low temperature critical point for the spawning of zebrafish females. Based on these observations, the brains of anesthetized fish under cold stress at different cold temperatures were collected for high-throughput RNA-seq assays. Key genes, hub pathways and important biological processes responding to cold temperatures during the spawning of zebrafish were identified through bioinformatic analysis. The number of down-regulated and up-regulated genes during the temperature reduction from egg-spawning temperatures at 19.5 °C and 19 °C to non-spawning temperatures at 18.5 °C and 18 °C were 2588 and 2527 (fold change ≥ 1.5 and p-value ≤ 0.01), respectively. Venn analysis was performed to identify up- and down-regulated key genes. KEGG enrichment analysis indicated that the hub pathways overrepresented among down-regulated key genes included the GnRH signaling pathway, vascular smooth muscle contraction, C-type lectin receptor signaling pathway, phosphatidylinositol signaling system and insulin signaling pathway. GO enrichment analysis of down-regulated key genes revealed the most important biological processes inhibited under non-spawning temperatures at 18.5 °C and 18 °C were photoreceptor cell outer segment organization, circadian regulation of gene expression and photoreceptor cell maintenance. Furthermore, 99 hormone-related genes were found in the brain tissues of non-spawning and spawning groups, and GnRH signaling pathway and insulin signaling pathway were enriched from down-regulated genes related to hormones at 18.5 °C and 18 °C. Thus, these findings uncovered crucial hormone-related genes and signaling pathways controlling the spawning of female zebrafish under cold stress.

The Role of Kisspeptin in the Control of the Hypothalamic-Pituitary-Gonadal Axis and Reproduction

The discovery of kisspeptin as a critical central regulatory factor of GnRH release has given people a novel understanding of the neuroendocrine regulation in human reproduction. Kisspeptin activates the signaling pathway by binding to its receptor kisspeptin receptor (KISS1R) to promote GnRH secretion, thereby regulating the hypothalamic-pituitary-gonadal axis (HPG) axis. Recent studies have shown that kisspeptin neurons located in arcuate nucleus (ARC) co-express neurokinin B (NKB) and dynorphin (Dyn). Such neurons are called KNDy neurons. KNDy neurons participate in the positive and negative feedback of estrogen to GnRH secretion. In addition, kisspeptin is a key factor in the initiation of puberty, and also regulates the processes of female follicle development, oocyte maturation, and ovulation through the HPG axis. In male reproduction, kisspeptin also plays an important role, getting involved in the regulation of Leydig cells, spermatogenesis, sperm functions and reproductive behaviors. Mutations in the KISS1 gene or disorders of the kisspeptin/KISS1R system may lead to clinical symptoms such as idiopathic hypogonadotropic hypogonadism (iHH), central precocious puberty (CPP) and female infertility. Understanding the influence of kisspeptin on the reproductive axis and related mechanisms will help the future application of kisspeptin in disease diagnosis and treatment. In this review, we critically appraise the role of kisspeptin in the HPG axis, including its signaling pathways, negative and positive feedback mechanisms, and its control on female and male reproduction.

Kisspeptin as autocrine/paracrine regulator of human ovarian cell functions: Possible interrelationships with FSH and its receptor

The present study aims to examine the role of kisspeptin (KP), FSH, and its receptor (FSHR), and their interrelationships in the control of basic human ovarian granulosa cells functions. We investigated: (1) the ability of granulosa cells to produce KP and FSHR, (2) the role of KP in the control of ovarian functions, and (3) the ability of KP to affect FSHR and to modify the FSH action on ovarian functions. The effects of KP alone (0, 10 and 100 ng/mL); or of KP (10 and 100 ng/mL) in combination with FSH (10 ng/mL) on cultured human granulosa cells were assessed. Viability, markers of proliferation (PCNA and cyclin B1) and apoptosis (bax and caspase 3), as well as accumulation of KP, FSHR, and steroid hormones, IGF-I, oxytocin (OT), and prostaglandin E2 (PGE2) release were analyzed by the Trypan blue exclusion test, quantitative immunocytochemistry, and ELISA. KP given at a low dose (10 ng/mL) stimulated viability, proliferation, inhibited apoptosis, promoted the release of progesterone (P4), estradiol (E2), IGF-I, OT, and PGE2, the accumulation of FSHR, but not testosterone (T) release. KP given at a high dose (100 ng/mL) had the opposite, inhibitory effect. FSH stimulated cell viability, proliferation and inhibited apoptosis, promoted P4, T, E2, IGF-I, and OT, but not PGE2 release. Furthermore, KP at a low dose promoted the stimulatory effect of FSH on viability, proliferation, P4, E2, and OT release, promoted its inhibitory action on apoptosis, but did not modify its action on T, IGF-I, and PGE2 output. KP at a high dose prevented and inverted FSH action. These results suggest an intra-ovarian production and a functional interrelationship between KP and FSH/FSHR in direct regulation of basic ovarian cell functions (viability, proliferation, apoptosis, and hormones release). The capability of KP to stimulate FSHR, the ability of FSH to promote ovarian functions, as well as the similarity of KP (10 ng/mL) and FSH action on granulosa cells' viability, proliferation, apoptosis, steroid hormones, IGF-I, OT, and PGE2 release, suggest that FSH influence these cells could be mediated by KP. Moreover, the capability of KP (100 ng/mL) to decrease FSHR accumulation, basal and FSH-induced ovarian parameters, suggest that KP can suppress some ovarian granulosa cell functions via down-regulation of FSHR. These observations propose the existence of the FSH-KP axis up-regulating human ovarian cell functions.

RFamide peptides, the novel regulators of mammalian HPG axis: A review

The RFamide-related peptides (RFRPs) are the group of neuropeptides synthesized predominantly from the hypothalamus that negatively affects the hypothalamo-hypophyseal-gonadal (hypothalamic–pituitary–gonadal [HPG]) axis. These peptides are first identified in quail brains and emerged as the mammalian orthologs of avian gonadotropin inhibitory hormones. The RFRP-3 neurons in the hypothalamus are present in several mammalian species. The action of RFRP-3 is mediated through a G-protein-coupled receptor called OT7T022. The predominant role of RFRP-3 is the inhibition of HPG axis with several other effects such as the regulation of metabolic activity, stress regulation, controlling of non-sexual motivated behavior, and sexual photoperiodicity in concert with other neuropeptides such as kisspeptin, neuropeptide-Y (NPY), pro-opiomelanocortin, orexin, and melanin. RFamide peptides synthesized in the granulosa cells, interstitial cells, and seminiferous tubule regulate steroidogenesis and gametogenesis in the gonads. The present review is intended to provide the recent findings that explore the role of RFRP-3 in regulating HPG axis and its potential applications in the synchronization of reproduction and its therapeutic interventions to prevent stress-induced amenorrhea.

Role of Kisspeptin on Hypothalamic-Pituitary-Gonadal Pathology and Its Effect on Reproduction

Kisspeptin is a neuropeptide that plays a significant role in human reproduction by its action on the hypothalamic-pituitary-gonadal (HPG) axis and functions through a G-protein-coupled receptor called G-protein-coupled receptor 54/kisspeptin 1 receptor (GPR54/KISS1R). It is encoded by the kisspeptin 1 (KISS1) gene that is mainly expressed in the hypothalamus. Kisspeptins are also recognized as vital aspects of maturation and proper function of the reproductive system in both males and females. It also plays its role in the onset of puberty, sexual patterns, desires, ovum development in women, sperm quality in men, feedback mechanisms, pregnancy, and lactation. Studies proved the pathological role of kisspeptin dysregulation in disorders like polycystic ovarian syndrome (PCOS) and infertility. Mutations in the KISS1 gene also contribute to precocious puberty or hypogonadotropic hypogonadism, depending upon the nature of mutations. Levels of kisspeptin also aid in the identification of a few pregnancy-related complications like preeclampsia, intrauterine growth restriction, and act as a marker of miscarriage. Due to the wide range of effects that kisspeptin has on the reproductive axis, investigations are being carried out to develop it as a diagnostic marker, treat diseases like hypogonadism and PCOS, and solve infertility issues.

Effects of Prepubertal Exposure to Aroclor-1221 on Reproductive Development and Transcriptional Gene Expression in Female Rats

Polychlorinated biphenyls (PCBs), as persistent organic pollutants, are environmental endocrine-disrupting chemicals (EDCs). We aim to investigate the effects of prepubertal exposure to PCBs on the reproductive development and expression and regulation of related genes in rats. Female rats were treated with Aroclor-1221 (A-1221) (4 mg/kg/day, 0.4 mg/kg/day) or castor oil daily from postnatal day (PND) 28 for 2 weeks by gavage. Morphological, histological, hormonal, and biochemical parameters were studied. Lower weight and relative weight of hypothalamus, earlier puberty onset, a longer length of the estrous cycle, lower serum estradiol and progesterone levels, accelerated ovarian folliculogenesis, and higher apoptotic index in the ovary were found. The in vitro fertilization study showed a lower fertilization rate and cleavage rate. The genetic study revealed higher expression of Kiss-1 mRNA and lower expression of GnRH mRNA in the hypothalamus and higher expression of AMH mRNA and lower expression of C-myc mRNA in the ovary. These confirmed the reproductive damage of A-1221 in rats.

Role of Kisspeptin in Regulation of Reproductive and Immune Reactions

The work is focused on physiological role of the hormone kisspeptin produced by neurons of the hypothalamus anterior zone, which is a key regulator of reproduction processes. Role of the hormone in transmission of information on metabolic activity and induction of the secretion of gonadotropin-releasing hormone (GnRH) by the hypothalamus that determines gestation processes involving fertilization, placentation, fetal development, and child birth is considered. The literature data on molecular mechanisms and effects of kisspeptin on reproductive system including puberty initiation are summarized and analyzed. In addition, attention is paid to hormone-mediated changes in the cardiovascular system in pregnant women. For the first time, the review examines the effect of kisspeptin on functional activity of immune system cells presenting molecular mechanisms of the hormone signal transduction on the level of lymphoid cells that lead to the immune tolerance induction. In conclusion, a conceptual model is presented that determines the role of kisspeptin as an integrator of reproductive and immune functions during pregnancy.

Epigallocatechin gallate decreases plasma triglyceride, blood pressure, and serum kisspeptin in obese human subjects

Obesity is one of major risk factors increasing chronic diseases including type II diabetes, cardiovascular diseases, and hypertension. The effects of epigallocatechin gallate (EGCG), the major active compound in green tea, on reduced obesity and improved metabolic profiles are still controversial. Furthermore, the effects of EGCG on human adipocyte lipolysis and browning of white adipocytes have not been elucidated. This study aimed to investigate the effects of EGCG on obesity, lipolysis, and browning of human white adipocytes. The results showed that, when compared to the baseline values, EGCG significantly decreased fasting plasma triglyceride levels (P < 0.05), systolic blood pressure (P < 0.05), diastolic blood pressure (P < 0.05), and serum kisspeptin levels (P < 0.05) after 8 weeks of supplement. On the other hand, supplement of EGCG in obese human subjects for 4 or 8 weeks did not decrease body weight, body mass index, waist and hip circumferences, nor total body fat mass or percentage when compared to their baseline values. The study in human adipocytes showed that EGCG did not increase the glycerol release when compared to vehicle, suggesting that it had no lipolytic effect. Furthermore, treatment of EGCG did not enhance uncoupling protein 1 (UCP1) mRNA expression in human white adipocytes when compared with treatment of pioglitazone, the peroxisome proliferator-activated receptor γ (PPAR-γ) agonist, suggesting that EGCG did not augment the browning effect of PPAR-γ on white adipocytes. This study revealed that EGCG reduced 2 metabolic risk factors which are triglyceride and blood pressure in the human experiment. We also showed a novel evidence that EGCG decreased kisspeptin levels. However, EGCG had no effects on obesity reduction in humans, lipolysis, nor browning of human white adipocytes.

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.

STAT4 targets KISS1 to promote the apoptosis of ovarian granulosa cells

Background

In mammals, it is known that the estradiol-17β (E2) is mainly synthetized in ovarian granulosa cells (GCs), and the excessive apoptosis of GCs induces the follicular atresia. Many studies have implicated the essential role of KISS1, with the pro-synthetic effect of E2 and the anti-apoptotic effect on GCs, in the mammalian folliculogenesis, and several STAT4 potential binding sites were previously predicted on the promoter of KISS1 in pigs. However, the biological effects of STAT4 on GCs and the molecular regulation between STAT4 and KISS1 remained largely unknown.

Methods

Using the porcine GCs as the cellular model, the overexpression plasmid, small interfering RNA, 5′-deletion and luciferase assay were applied to investigate the molecular mechanisms for STAT4 regulating the expression of KISS1.

Results

In this study, the STAT4 negatively regulated the mRNA and protein levels of KISS1 in porcine GCs, and the mRNA level of STAT4 was observed to significantly decrease from immature to mature follicles, which was inversed with that of KISS1. The relative luciferase activity of KISS1 promoter was significantly increased with deletion of the fourth potential binding site (− 305/− 295), and ChIP further confirmed that the STAT4 bound at − 305/− 295 region of KISS1. Besides, the STAT4 significantly regulated the mRNA levels of PDK1, FOXO3 and TSC2 of PI3K signaling pathway to promote the cell apoptosis and the percentage of cells at G0/G1 phase of cell cycle in GCs. Alternatively, the STAT4 significantly decreased the mRNA levels of CYP17, 3B-HSD, 17B-33 HSD, ESR1, and ESR2, as well as the concentration of E2 in GCs. Furthermore, interfering with the expression of STAT4 was observed to significantly stimulate the pro-synthetic effect of E2 and anti-apoptotic effect of KISS1 in GCs.

Conclusions

Collectively, the STAT4 might directly target at − 305/− 295 region of KISS1 to negatively regulate the transcription of KISS1, promote the cell apoptosis via PI3K signaling pathway, suppress the synthesis of E2 through the estrogen signaling pathway in porcine GCs. These proposed works could provide useful insight in further investigations on the molecular functionalities of STAT4 and KISS1 in the folliculogenesis of mammals.

The effect of intracerebroventricular administration of neuropeptide Y on reproductive axis function in the male Wistar rats: Involvement of hypothalamic KiSS1/GPR54 system

Several studies have shown that neuropeptide Y (NPY) is considered to be one of the key regulators of the hypothalamic-pituitary-gonadal axis in the mammals. Also, kisspeptin is a powerful upstream regulator of gonadotropin-releasing hormone neurons in the hypothalamus. The present study aims to investigate the effects of the intracerebroventricular (ICV) injection of NPY and BIBP3226 (NPY receptor antagonist) on the reproductive axis (either hormonal or behavioral) of the male rats. Furthermore, to see whether NPY signals can be relayed through the pathway of KiSS1/GPR54, the gene expression of these peptides in the arcuate nucleus was measured. The ICV injection of NPY decreased the latencies and increased the frequencies of sexual parameters of the male rats in a significant way. Results obtained from LH and testosterone measurement showed that NPY had a significant increase in comparison with the control group. In this line, BIBP3226 antagonized the stimulative effects of NPY. Furthermore, data from real-time quantitative PCR showed that injection of NPY significantly increased the gene expression of KiSS1 and GPR54, while treatment with BIBP3226 controlled the stimulative effects of NPY on gene expression of KiSS1 and GPR54. Summing up, NPY can exert its impacts on the reproductive axis, this occurs at least partly through affecting KiSS1/GPR54 system.

Impact of serum and follicular fluid kisspeptin and estradiol on oocyte maturity and endometrial thickness among unexplained infertile females during ICSI

Objective

To relate serum and follicular fluid (FF) kisspeptin and estradiol levels in different stages of stimulation during Intracytoplasmic Sperm Injection (ICSI) with oocyte maturity and endometrial thickness among unexplained infertile females.

Methods

This cross-sectional study was carried out at the Australian Concept Infertility Medical Centre from March 2017 till March 2018. Fifty unexplained infertile females, booked for ICSI, were included in the study. Serum kisspeptin and estradiol were estimated by Enzyme-Linked Immunosorbent Assay in all four stages; 1: follicular stimulation, 2: ovulation induction, 3: oocyte pickup, and 4: embryo transfer. FF was aspirated during oocyte retrieval (stage 3) for the analysis of KP and estradiol. Pregnancy outcomes were categorized as non-pregnant, preclinical abortion, and clinical pregnancy.

Results

The age of the study subjects was 32.04 ± 2.29 (Mean±SD) years, with mean BMI of 28.51 ± 4.15 (Mean±SD) kg/m². Mean serum kisspeptin and estradiol levels increased in all subjects as the stimulation proceeded stages 1–3; however, the mean dropped after retrieval of the oocytes (stage 4). Out of 27 female subjects who completed the cycle, 17 remained non-pregnant, 4 had preclinical abortion, and 6 acquired clinical pregnancy. The FF kisspeptin concentration was significantly higher than serum concentrations and positively correlated with serum and FF estradiol concentrations. FF-kisspeptin correlated with serum kisspeptin in Stage 3 (r = 0.930, p<0.001), maturity of oocyte (r = 0.511, p = 0.006) and endometrial thickness (r = 0.522, p = 0.005). Kisspeptin in stage 3 was also found to correlate with endometrial thickness (r = 0.527, p = 0.005) and with estradiol (r = 0.624, p = 0.001) independently.

Conclusion

Increase in serum and FF-kisspeptin and estradiol levels from stages 1 to 3, resulted in an optimum endometrial thickness, probability of fertilization of oocytes and chances of clinical pregnancy in Assisted Reproductive Techniques /ICSI cycles of unexplained infertile females.

The Correlation between Hormonal Disturbance in PCOS Women and Serum Level of Kisspeptin

BACKGROUND

Kisspeptin is a neuropeptide that upregulates gonadotropin-releasing hormone (GnRH) secretion. It is an essential element for the luteinizing hormone (LH) surge and ovulation. Women with polycystic ovary syndrome (PCOS) expose alteration in both GnRH and LH secretion levels.

OBJECTIVE

This paper aims to evaluate serum kisspeptin levels in healthy and polycystic ovarian syndrome women. Furthermore, it investigates the effect of obesity and age on circulating kisspeptin levels in both normal and PCOS women. Moreover, it points out the correlation between kisspeptin and other hormonal parameters. Methods and Patients. One hundred women (60 are with PCOS and 40 are normal) were enrolled in the study. Five milliliter samples of blood from all the patients and control women were obtained twice during the menstrual cycle. All the study samples were classified depending on the age factor for several subgroups.

RESULTS

Kisspeptin levels were higher in PCOS patients than those in the normal group. Kisspeptin correlated with serum free testosterone level (r=0.26). In healthy women, preovulatory kisspeptin levels were higher than follicular kisspeptin levels (P < 0.05), while this difference was insignificant in PCOS patients. The variation in serum kisspeptin levels between overweight/obese and normal-weight women was insignificant. In normal women, serum kisspeptin levels were higher in women >35 years than those <24 years at (P=0.03).

CONCLUSION

The serum kisspeptin level is higher in PCOS women. Its levels fluctuate during the menstrual cycle, but these fluctuations are disturbed in PCOS women. The effect of BMI on serum kisspeptin levels is insignificant, and kisspeptin serum levels increase with age.

Reproductive enhancement in buffalo: looking at urinary pheromones and hormones

The success of conception in buffalo is greatly dependent on precise estrus detection and time of artificial insemination (AI). Various visual, behavioral, biochemical and gyneco-clinical parameters have been tracked closely and a cost-effective combinatorial model has been developed to detect estrus in buffaloes. Pheromones play pivotal roles in reproduction and behavior of mammals. Urine, an easily available biological material which reflects the internal status of an animal, was recruited for profiling the pheromone compounds during the various phases of estrous cycle using gas chromatography-mass spectrometry (GC-MS) analysis. Among the identified compounds, 4-methyl phenol (4-mp, p-Cresol) and 9-octadecenoic acid (Oleic acid) were found to be estrus-specific and would be promising estrus-indicators. Similarly, detection of luteinizing hormone (LH) in urine was also focused to predict the time of ovulation in buffaloes. Partial success has been obtained in the attempt to develop a cost-effective bioassay kit for estrus detection. The ongoing venture of the relevant research team is to develop a biosensor to identify estrus-specific pheromone compounds in urine. Development of a nanoparticle-based bioassay kit for detection of urinary LH for effective prediction of estrus or ovulation is also in progress.

Dysregulation of Kisspeptin and Leptin, as Anorexigenic Agents, Plays Role in the Development of Obesity in Postmenopausal Women

During the menopausal period, women have a higher tendency to develop obesity and any other metabolic syndromes. Dysregulation of leptin and kisspeptin signaling as anorexigenic agents is believed to be the connection between metabolic disorders and altered reproductive function. Therefore, this study aimed at investigating the association between leptin, soluble leptin receptor (sOBR), free leptin index, kisspeptin concentrations, and body mass index (BMI) in postmenopausal women. A cross-sectional study was carried out among 171 postmenopausal women aged 40-75 years from 2017 to 2018. Subjects were assigned into 2 groups according to their BMIs: obese group (84 subjects) and nonobese group (87 subjects). In addition to anthropometric measurement, blood sample was collected from each subject for leptin, sOBR, free leptin index (FLI), and kisspeptin evaluation. Bivariate and correlation analysis discovered that leptin and FLI were positively correlated with BMI, while sOBR and kisspeptin were negatively correlated with BMI. Among those variables, multivariate analysis found that leptin, sOBR, and kisspeptin were independently associated with obesity. Therefore, it can be concluded that higher serum leptin concentration and FLI, as well as lower serum sOBR and kisspeptin concentrations, are significantly associated with obesity in postmenopausal women.

Discovery of BAY-298 and BAY-899: Tetrahydro-1,6-naphthyridine-Based, Potent, and Selective Antagonists of the Luteinizing Hormone Receptor Which Reduce Sex Hormone Levels in Vivo

The human luteinizing hormone receptor (hLH-R) is a member of the glycoprotein hormone family of G-protein-coupled receptors (GPCRs), activated by luteinizing hormone (hLH) and essentially involved in the regulation of sex hormone production. Thus, hLH-R represents a valid target for the treatment of sex hormone-dependent cancers and diseases (polycystic ovary syndrome, uterine fibroids, endometriosis) as well as contraception. Screening of the Bayer compound library led to the discovery of tetrahydrothienopyridine derivatives as novel, small-molecule (SMOL) hLH-R inhibitors and to the development of BAY-298, the first nanomolar hLH-R antagonist reducing sex hormone levels in vivo. Further optimization of physicochemical, pharmacokinetic, and safety parameters led to the identification of BAY-899 with an improved in vitro profile and proven efficacy in vivo. BAY-298 and BAY-899 serve as valuable tool compounds to study hLH-R signaling in vitro and to interfere with the production of sex hormones in vivo.

Kisspeptin/kisspeptin receptor system in pseudopregnant rabbit corpora lutea: presence and function

Kisspeptin (KiSS) and its related receptors (KiSS1R) have a critical role in the reproduction of mammals. The KiSS/KiSS1R system is expressed in numerous reproductive organs including the ovary. Here, we studied the expression of the KiSS/KiSS1R system and its functional role in rabbit corpora lutea (CL) at days 4 (early-), 9 (mid-), and 13 (late-stage) of pseudopregnancy. In vitro progesterone, prostaglandin (PG) F2α (PGF2α) and E2 (PGE2) productions and prostaglandin-endoperoxide synthase 1 (PTGS1) and 2 (PTGS2) activities were evaluated. Immune reactivity (IR) for KiSS and KiSS1R were detected in luteal cells at nuclear and cytoplasmic level at all luteal stage for KiSS and only at early- and mid-stage for KiSS1R; IR decreased from early- to later stages of pseudopregnancy. The KiSS-10 augmented progesterone and PGE2 and diminished PGF2α secretions by early- and mid-CL; KiSS-10 reduced PTGS2 activity at early- and mid-stages, but did not affect PTGS1 at any luteal stages. The antagonist KiSS-234 counteracted all KiSS-10 effects. This study shows that the KiSS/KiSS1R system is expressed in CL of pseudopregnant rabbits and exerts a luteotropic action by down-regulating PTGS2, which decreases PGF2α and increases PGE2 and progesterone.

Maternal high-fat diet impairs follicular development of offspring through intraovarian kisspeptin/GPR54 system

BACKGROUND

Excessive gestational weight gain (GWG), which is associated with adverse long-term effects on the health of the offspring, has become a major clinical problem. Accumulating evidence indicates that the ovary kisspeptin/GPR54 system directly participates in a series of physiological activities. We used a model of high-fat diet (HFD) during gestational to investigate offspring's ovarian function and whether kisspeptin/GPR54 system is involved.

METHODS

After introducing the male and confirmation of mating by checking a vaginal sperm plug, female rats were randomized into two groups: control diet called NCD group and high-fat diet called HFD group. After birth, all rats were changed into a control diet and litter size was adjusted to 12 pups per litter. Ovaries were collected for assessment at postnatal day (PND) 4 and PND 30. The timing of vaginal opening was recorded, and the estrous cyclicity was monitored for 2 consecutive weeks immediately. Primary granulosa cells and ovaries which were taken from PND 4 were collected for determination of the direct effect of kisspeptin-10 (kp-10) in vitro.

RESULTS

Neonatal rats exposed to HFD during gestation had a lower number of secondary follicles in the ovary. The expression of follicle-stimulating hormone receptor (FSHR) and kisspeptin was not altered. At prepuberty, the number of antral follicles and preovulatory follicles was elevated with decreased type III follicles in the HFD group. While the expression of ovulation-related genes was decreased, the expression levels of follicular growth-related genes and steroidogenesis synthesis related genes were elevated. A significant increase in kiss1 mRNA and kisspeptin protein was detected without changes in kiss1r mRNA and GPR54. Maternal high-fat diet during gestation resulted in a significant advanced puberty onset and an irregular estrous cycle in offspring rats. In addition, the administration of kp-10 produced an increase in viability of primary granulosa cells and enlarged the size of oocytes.

CONCLUSIONS

HFD exposure during maternal gestation had a long-term effect on reproductive function in the offspring and the increased ovarian kisspeptin/GPR54 system might be involved.