Gonadotropin-releasing Hormone Secretion Research Articles

Gonadotropin-releasing hormone-secreting neuron development and function: an update.

The coordinated and pulsatile secretion of gonadotropin-releasing hormone (GnRH) plays a central role in vertebrate reproductive function. The development of the hypothalamo-pituitary-gonadal (HPG) axis is characterized by a complex network of molecular signals that controls, at first, migration of the GnRH neurons along the nose, through the cribriform plate, up to the frontal lobe. This migratory process is orchestrated by several factors including anosmin-1, polysialylated form of the neural cell adhesion molecule, γ-amino butyric acid, hepatocyte growth factor, chemokines, cytokines and semaphorins. Moreover, antimüllerian hormone, growth hormone and insulin-like growth factor-1 were recently reported to modulate immature GnRH neuron migration in vitro. Once arrived in the forebrain, GnRH neurons mainly localize in the medial preoptic area and their axon elongation, mediated by fibroblast growth factor receptor 1 and semaphorin 7A signaling, is essential for GnRH secretion. The physiological pulsatile release of GnRH is controlled by central and peripheral factors, including kisspeptin, neurokinin B and dynorphin from KNDy neurons, and sex steroids and leptin, respectively. GnRH pulsatile release into the hypothalamus-pituitary blood portal system stimulates luteinizing hormone and follicle-stimulating hormone secretion into the general circulation. Such knowledge also results crucial for understanding of the molecular bases of congenital and acquired dysfunction of the HPG axis, which imply severe pathological consequences, such as GnRH deficiency or congenital hypogonadotropic hypogonadism, characterized by incomplete or absent puberty and infertility.

The role of gonadotropin-releasing hormone neurons in polycystic ovary syndrome.

Given the critical central role of gonadotropin‐releasing hormone (GnRH) neurons in fertility, it is not surprising that the GnRH neural network is implicated in the pathology of polycystic ovary syndrome (PCOS), the most common cause of anovulatory infertility. Although many symptoms of PCOS relate most proximately to ovarian dysfunction, the central reproductive neuroendocrine system ultimately drives ovarian function through its regulation of anterior pituitary gonadotropin release. The typical cyclical changes in frequency of GnRH release are often absent in women with PCOS, resulting in a persistent high‐frequency drive promoting gonadotropin changes (i.e., relatively high luteinizing hormone and relatively low follicle‐stimulating hormone concentrations) that contribute to ovarian hyperandrogenemia and ovulatory dysfunction. However, the specific mechanisms underpinning GnRH neuron dysfunction in PCOS remain unclear. Here, we summarize several preclinical and clinical studies that explore the causes of aberrant GnRH secretion in PCOS and the role of disordered GnRH secretion in PCOS pathophysiology.

The Effect of Photoperiodic Conditions on GnRH/LH Secretion in Ewes.

Simple SummaryDuring the course of evolution, animals have evolved biological rhythms that are associated with changes in the lighting and temperature of their environment. Females in most breeds of sheep are seasonal breeders, with ovulatory cycles occurring in the autumn and winter and anovulation in the spring and summer. Secretion of gonadotropin releasing hormone and luteinizing hormone, the main hormones regulating reproduction in females, displays a circadian pattern; however, data concerning the day/night differences in their secretion in ewes are incomplete. The aim of the undertaken study was to determine the day/night differences in the secretion of gonadotropin releasing hormone and luteinizing hormone in follicular phase and anestrous ewes. It was demonstrated that secretion of investigated hormones is subject to diurnal and seasonal changes. The observed reduction in luteinizing hormone release, a few hours after the sunset, seems to be universal for both the anestrus and follicular phase. It could be concluded that the nocturnal suppression of luteinizing hormone secretion in follicular phase ewes may be a mechanism moving this hormone surge to the early morning.Secretion of gonadotropin releasing hormone (GnRH) and luteinizing hormone (LH) displays a circadian pattern. Data concerning differences in daily GnRH/LH secretion during different seasons in sheep are fragmentary. The aim of the study was to determine day/night differences in GnRH/LH secretion in the follicular phase and in the anestrous ewes. The studies were performed on Blackhead ewes (n = 24). Ewes from each season were divided into two groups of six animals (day and night group). The animals were euthanized 5 h after sunset or 5 h after sunrise and blood was taken to determine LH and melatonin concentrations. In the hypothalamus, the expression of GnRH and gonadotropin releasing hormone receptor (GnRHR) was determined. In the anterior pituitary, the expression of mRNA encoding subunit β of LH (LHβ) and GnRHR was assayed. Our study showed that GnRH/LH secretion is subject to diurnal and seasonal changes. The observed reduction in LH release, a few hours after the sunset, seems to be universal for both the anestrus and follicular phase, when the processes occurring at the hypothalamus are more equivocal. It could be concluded that the nocturnal suppression of LH secretion in follicular phase ewes may be a mechanism moving the LH surge to the early morning.

Targeting GNAQ in hypothalamic nerve cells to regulate seasonal estrus in sheep

Kazakh sheep are typical seasonal estrus animals. Their reproductive system regulation mainly involves the complex regulation of the hypothalamic–pituitary–gonadal axis (HPGA), which is also closely related to reproductive hormone secretion. Gonadotropin-releasing hormone (GnRH), synthesized and secreted by the hypothalamus, is the key to controlling sheep reproductive activity. We studied how GNAQ (G protein subunit alpha q) regulates estrus in sheep by controlling GnRH expression and secretion. We used hypothalamic nerve cells as the research model. GNAQ overexpression and RNA interference vectors were constructed and transfected into the hypothalamic nerve cells of fetal Kazakh sheep. qPCR, western blotting, and enzyme-linked immunosorbent assay were used to detect GNAQ gene expression in Kazakh ewe tissues and analyze its regulatory effect on GnRH expression in the hypothalamic nerve cells. The fetal sheep hypothalamic nerve cells were successfully isolated and cultured. qPCR and cell immunofluorescence showed that the purity of positive cells was >95%. The tissue expression profile showed that there were different degrees of GNAQ gene expression in the Kazakh ewe tissue. Expression levels were relatively higher in the hypothalamus, pituitary, brain, and uterine tissues. When GNAQ expression was downregulated in the hypothalamic nerve cells, the upstream genes KISS1 (kisspeptin), GPR54 (KISS1 receptor), and ER (estrogen receptor) were all upregulated, as were the downstream genes PLCB1 (phospholipase C beta 1), PRKCB (protein kinase C beta), and GNRH. At the same time, GnRH secretion levels were also upregulated. GNAQ regulated its downstream gene PLCB1 in the hypothalamic nerve cells, and directly regulated GnRH expression and secretion through the calcium and PRKC signaling pathways. GNAQ also regulated kisspeptin expression, subsequently regulating GnRH expression and secretion indirectly through the kisspeptin–GPR54 signaling pathway. Our results are of great importance for improving the reproductive performance of seasonal-estrus sheep.

Kiss1 expression in the hypothalamic arcuate nucleus is lower in dairy cows of reduced fertility†.

We tested the hypothesis that divergent genetic merit for fertility of dairy cows is due to aberrant reproductive neuroendocrine function. The kisspeptin status of non-pregnant cows of either positive (POS) or negative (NEG) breeding values (BVs) for fertility was studied in three groups (n = 8), based on their previous post-partum period: POS cows, which had spontaneous ovarian cycles (POS-CYC) and NEG cows, which either cycled (NEG-CYC) or did not cycle (NEG-NONCYC). Ovarian cycles were synchronized, blood samples were taken to define endocrine status, and the animals were slaughtered in an artificial follicular phase. The brains and the pituitary glands were collected for quantitative polymerase chain reaction (qPCR) and in situ hybridization of hypothalamic GNRH1, Kiss1, TAC3, and PDYN and pituitary expression of LHB and FSHB. Gonadotropin releasing hormone (GnRH) and kisspeptin levels were quantified in snap frozen median eminence (ME). GNRH1 expression and GnRH levels in the ME were similar across groups. Kiss1 expression in the preoptic area of the hypothalamus was also similar across groups, but Kiss1 in the arcuate nucleus was almost 2-fold higher in POS-CYC cows than in NEG groups. TAC3 expression was higher in POS-CYC cows. The number of pituitary gonadotropes and the level of expression of LHB and FSHB were similar across groups. We conclude that the lower levels of Kiss1 and TAC3 in NEG cows with low fertility status and may lead to deficient GnRH and gonadotropin secretion.

Neuroendocrine mechanisms of reproductive dysfunctions in undernourished condition.

It is well known that undernourished conditions disturb female reproductive functions in many species, including humans. These alterations are mainly caused by a reduction in gonadotrophin-releasing hormone (GnRH) secretion from the hypothalamus. Evidence from the literature suggests that some hypothalamic factors play pivotal roles in the coordination of reproductive functions and energy homeostasis in response to environmental cues and internal nutritional status. Generally, anorexigenic/satiety-related factors, such as leptin, alpha-melanocyte-stimulating hormone, and proopiomelanocortin, promote GnRH secretion, whereas orexigenic factors, such as neuropeptide Y, agouti-related protein, orexin, and ghrelin, attenuate GnRH secretion. Conversely, gonadotrophin-inhibitory hormone, which exerts anti-GnRH and gonadotrophic effects, promotes feeding behavior in many species. In addition, the activity of kisspeptin, which is a potent stimulator of GnRH, is reduced by undernourished conditions. Under normal nutritional conditions, these factors are coordinated to maintain both feeding behavior and reproductive functions. However, in undernourished conditions their activity levels are markedly altered to promote feeding behavior and temporarily suppress reproductive functions, in order to prioritize the survival of the individual over that of the species.

Effects of undernutrition and low energy availability on reproductive functions and their underlying neuroendocrine mechanisms.

It has been well established that undernutrition and low energy availability disturb female reproductive functions in humans and many animal species. These reproductive dysfunctions are mainly caused by alterations of some hypothalamic factors, and consequent reduction of gonadotrophin-releasing hormone (GnRH) secretion. Evidence from literature suggests that increased activity of orexigenic factors and decreased activity of anorexigenic/satiety-related factors in undernourished conditions attenuate GnRH secretion in an integrated manner. Likewise, the activity of kisspeptin neurons, which is a potent stimulator of GnRH, is also reduced in undernourished conditions. In addition, it has been suggested that gonadotrophin-inhibitory hormone, which has anti-GnRH and gonadotrophic effects, may be involved in reproductive dysfunctions under several kinds of stress conditions. It should be remembered that these alterations, i.e., promotion of feeding behavior and temporary suppression of reproductive functions, are induced to prioritize the survival of individual over that of species, and that improvements in metabolic and nutritional conditions should be considered with the highest priority.

Dose-Dependent Degeneration of Leydig Cells Following Kisspeptin-10 Administration: An Ultrastructural Study.

The discovery of kisspeptin signaling as a key regulator of gonadotropin- releasing hormone (GnRH) secretion from the hypothalamus enhanced our understanding of the neuroendocrine regulation of mammalian reproduction. Effects of central and peripheral administration of kisspeptin on plasma gonadotropins, testosterone, and spermatogenesis are studied in detail. The present study was conducted to check the ultrastructure of Leydig cells in prepubertal male rats in response to the administration of a range of kisspeptin doses. We administered a range of kisspeptin-10 doses (1 μg, 1 ηg, and 10 ρg) intraperitoneally to prepubertal male Sprague-Dawley rats (PND 35) twice daily after every 12 hours. Control rats were injected with physiological saline in parallel. At the end of the treatment, plasma concentrations of testosterone were measured by competitive binding radioimmunoassay, and small pieces of rat testicular tissue were processed for electron microscopy to examine the ultrastructure of Leydig cells. Plasma testosterone concentration was reduced significantly at 1ηg (P<0.05) and 1μg (P<0.01) doses as compared to control. Distinct ultrastructural changes categorized as dilatation of cytoplasmic organelles, irregularly shaped nuclei with nuclear membrane invaginations, reduced nuclear sizes, degeneration, and vacuolation were observed in the kisspeptin-10 treated Leydig cells as compared to control. Quantification of the data showed reduced Leydig cell indices and hyperplasia of the interstitial cells. It is concluded that chronic intermittent administration of kisspeptin-10 has a dose-dependent degenerative effect on the plasma testosterone levels and Leydig cells ultrastructure in prepubertal male rats.

Male Idiopathic Hypogonadotropic Hypogonadism: Serum Insulin-like Growth Factor-1 and Oestradiol Levels.

Idiopathic hypogonadotropic hypogonadism (IHH) is a form of male infertility caused by a congenital defect in the secretion or action of gonadotropin-releasing hormone from the hypothalamus. Oestradiol emerged as the main sex steroid in the regulation of the hypothalamic-pituitary-testicular axis, reproductive function and growth hormone/insulin-like growth factor-1 (GH/IGF-1) axis in men. Moreover, GH/IGF-1 axis has been suggested to play a role in IHH. This study evaluated serum IGF-1 in IHH men and controls. Furthermore, we evaluated the association between serum total oestradiol (TE2) and IGF-1 levels in patients and controls. Parameters including age, body mass index and fertility history were analysed. This prospective study was conducted at the Royan institute. In 20 men with IHH and 20 controls, serum IGF-1 levels were estimated using chemiluminescence immunoassay and serum E2 levels were assessed by means of the electrochemiluminescence method. Kolmogorov-Smirnov test, parametric t-test or the Mann-Whitney and the Pearson correlation coefficient were performed. SPSS version 22 was used for the analysis of data. There was a significant decrease in serum IGF-1 levels in IHH patients compared with controls (145.1 ± 8.9 ng/ml vs. 229.6 ± 7.3 ng/ml P < 0.001, respectively). Furthermore, a significant decrease was observed in TE2 levels in IHH male patients (12.3 ± 2.5 pg/ml) compared with controls (31.9 ± 5.3 pg/ml P < 0.001). A positive correlation was observed between serum IGF-1 and TE2 levels in the total number of participants, suggesting that E2 deficiency in IHH cases can explain the lower levels of serum IGF-1. These findings suggest that the reduction in IGF-1 levels may be associated with the influence of E2 on the GH/IGF-1 axis, and may confirm the role of the GH/IGF-1 axis in IHH. Further investigations will be required to determine the exact mechanisms by which E2 and IGF-1 affect the reproductive neuroendocrine function.

Clock Genes - A New Perspective on Pregnancy Complications-

The circadian rhythm is controlled by clock genes, which is crucial for development, reproduction and pregnancy. The precise timing of kisspeptin, gonadotropin-releasing hormone, and gonadotropin secretion in the hypothalamic-pituitary-gonadal axis determines fertility. Additionally, the mouse uterus demonstrated the circadian rhythm regulated by circadian clock genes. The expression level of aryl hydrocarbon receptor nuclear translocator-like protein (Bmal1), a core component of circadian oscillation, was shown to be lower in the endometrium of women who experienced recurrent miscarriages. Bmal1 participates in a variety of physiological processes. It is known that Bmal1-deficient mice were sterile and had damaged gametes and reproductive systems. In addition, hormone secretion is disrupted in Bmal1-deficient mice. Recently, we discovered that uterus-specific Bmal1-deficient mice had impaired placental development and were unable to sustain pregnancy. Additionally, we revealed that time-restricted feeding controlled the uterine clock's circadian rhythm. In humans, we found a higher incidence of hypertensive disorders of pregnancy in pregnant women who had dysmenorrhea in the past at a younger age. These findings suggest that the uterine clock system is a candidate for the new perspective on pregnancy complications.

Distribution of kisspeptin system and its relation with gonadotropin-releasing hormone in the hypothalamus of the South American plains vizcacha, Lagostomus maximus

Kisspeptin (KISS), a key hormone involved in the regulation of the hypothalamic-pituitary-ovarian (HPO) axis, has been localized in the anteroventral periventricular (AVPV) nucleus and the neighboring rostral periventricular nucleus (PeVN), and in the arcuate (ARC) nucleus of the mammalian hypothalamus. In the ARC, the KISS neurons that co-express neurokinin B (NKB) and dynorphin A (Dyn) are named KNDy cells. The South American plains vizcacha is a rodent with peculiar reproductive traits. Around mid-pregnancy, vizcacha shows the reactivation of its HPO axis with the pulsatile release of gonadotropin-releasing hormone (GnRH) and luteinizing hormone (LH), an essential event for the success of gestation. Considering the role of KISS system in GnRH modulation, the aim of this work was to study their neuroanatomical distribution in adult vizcachas. AVPV showed sexual dimorphism with a significant smaller area in males (t-Test, p < 0.05), and KISS immunoreactivity was detected in somas and varicosities homogenously distributed in the AVPV with a concordant sex-related expression pattern. NKB and Dyn expression was also observed in cytoplasm of neurons scattered in the AVPV. Three subpopulations of neurons were detected in the AVPV: neurons expressing Dyn and NKB (DyNK cells), neurons expressing KISS and NKB (KiNK cells), and single NKB expressing neurons. Strikingly, KISS and Dyn were always expressed in different cells. In addition, in the ARC nucleus, KNDy cells were detected. On the other hand, KISS and GnRH expression was detected in different subpopulations of neurons, GnRH cells showed KISS receptor (KISSR or GPR-54) expression, and KISS immunoreactive afferent contacts were detected making close appositions onto somas and dendrites of GnRH cells. These results show similarities and differences between the KISS system in the hypothalamus of the vizcacha and other mammals, and constitute crucial observations about KISS and GnRH relation. Considering the peculiarity of HPO axis regulation in this species, the present work provides a neuroanatomical framework for the further elucidation of molecular mechanisms underlying GnRH expression and secretion.

The roles of kisspeptin and neurokinin B in GnRH pulse generation in humans, and their potential clinical application.

The delivery of gonadotropin-releasing hormone (GnRH) in a pulsatile mode to the gonadotropes has long been known to be essential for normal reproductive function. There have been numerous studies aimed at dissecting out the mechanisms underlying GnRH pulse generation. The discovery of kisspeptin as an upstream regulator of GnRH attracted the possibility that pulsatile kisspeptin governed the pulsatile secretion of GnRH. Subsequent studies have shown the importance of the neurokinin B (NKB) system in modulating kisspeptin secretion and this GnRH. A number of studies in laboratory rodents have supported this notion. By contrast, we present data from clinical studies in men and women, in a range of contexts, showing that continuous infusion of kisspeptin 10 at receptor-saturating levels gives rise to an increase in luteinizing hormone (LH) (GnRH) pulse frequency. This has been demonstrated in normal healthy and hypogonadal men, in normal women during the mid-cycle LH surge, in men and women with mutations in the genes encoding NKB or its receptor, neurokinin 3 receptor (NK3R), in women with polycystic ovary syndrome treated with NK3R antagonist, and in women treated with NK3R antagonist during the LH surge. These finds indicate that pulsatile secretion and action of kisspeptin on GnRH neurons is not required for the generation of LH (GnRH) pulses in humans. We also report that there is an absence of desensitization in humans exposed to continuous infusion of kisspeptin-10 at receptor-saturating concentrations over 22h and briefly review GnRH, kisspeptin and NKB analogs and their clinical application.

Ovariectomy induces abdominal fat accumulation by improving gonadotropin-releasing hormone secretion in mouse

The ovariectomy would induce the occurrence of obesity, but its regulatory mechanism is not clear. This study aimed to elucidate the regulation on fat accumulation for ovariectomy in mouse. In the current study, the abdominal fat mass dramatically increased in OVX mice compared with sham mice at eighth week after ovariectomy, accompanied with the higher GnRH level in blood and abdominal fat tissue. Also, a decrease of the abdominal fat mass was occurred in OVX mice with a GnRH-antagonist injection. Furthermore, the results in vivo and in vitro confirmed that GnRH promoted the transition of G1/S phase by upregulating CCND1 and CCNE1 mRNA levels by the mediation of GnRHR via the PKA-CREB pathway. Meanwhile, the higher FSH secretion was induced by increase GnRH and accelerate fat deposition in abdominal fat tissue. Our findings are the first to elucidate the effect mechanism of ovariectomy on obesity in mouse. GnRH stimulates fat accumulation in adipocytes via PKA-CREB pathway by directly promoting cell proliferation for driving the cell cycle and simultaneously accelerating differentiation for improving the FSH secretion.

Vasoactive intestinal peptide exerts an excitatory effect on hypothalamic kisspeptin neurons during estrogen negative feedback

Hypothalamic kisspeptin neurons are the primary modulators of gonadotropin-releasing hormone (GnRH) neurons. It has been shown that circadian rhythms driven by the suprachiasmatic nucleus (SCN) contribute to GnRH secretion. Kisspeptin neurons are potential targets of SCN neurons due to reciprocal connections with the anteroventral periventricular and rostral periventricular nuclei (AVPV/PeN) and the arcuate nucleus of the hypothalamus (ARH). Vasoactive intestinal peptide (VIP), a notable SCN neurotransmitter, modulates GnRH secretion depending on serum estradiol levels, aging or time of the day. Considering that kisspeptin neurons may act as interneurons and mediate VIP's effects on the reproductive axis, we investigated the effects of VIP on hypothalamic kisspeptin neurons in female mice during estrogen negative feedback. Our findings indicate that VIP induces a TTX-independent depolarization of approximately 30% of AVPV/PeN kisspeptin neurons in gonad-intact (diestrus) and ovariectomized (OVX) mice. In the ARH, the percentage of kisspeptin neurons that were depolarized by VIP was even higher (approximately 90%). An intracerebroventricular infusion of VIP leds to an increased percentage of kisspeptin neurons expressing the phosphoSer133 cAMP-response-element-binding protein (pCREB) in the AVPV/PeN. On the other hand, pCREB expression in ARH kisspeptin neurons was similar between saline- and VIP-injected mice. Thus, VIP can recruit different signaling pathways to modulate AVPV/PeN or ARH kisspeptin neurons, resulting in distinct cellular responses. The expression of VIP receptors (VPACR) was upregulated in the AVPV/PeN, but not in the ARH, of OVX mice compared to mice on diestrus and estradiol-primed OVX mice. Our findings indicate that VIP directly influences distinct cellular aspects of the AVPV/PeN and ARH kisspeptin neurons during estrogen negative feedback, possibly to influence pulsatile LH secretion.

Deletion of Gαq/11 or Gαs Proteins in Gonadotropes Differentially Affects Gonadotropin Production and Secretion in Mice.

Gonadotropin-releasing hormone (GnRH) regulates gonadal function via its stimulatory effects on gonadotropin production by pituitary gonadotrope cells. GnRH is released from the hypothalamus in pulses and GnRH pulse frequency differentially regulates follicle-stimulating hormone (FSH) and luteinizing hormone (LH) synthesis and secretion. The GnRH receptor (GnRHR) is a G protein-coupled receptor that canonically activates Gα q/11-dependent signaling on ligand binding. However, the receptor can also couple to Gα s and in vitro data suggest that toggling between different G proteins may contribute to GnRH pulse frequency decoding. For example, as we show here, knockdown of Gα s impairs GnRH-stimulated FSH synthesis at low- but not high-pulse frequency in a model gonadotrope-derived cell line. We next used a Cre-lox conditional knockout approach to interrogate the relative roles of Gα q/11 and Gα s proteins in gonadotrope function in mice. Gonadotrope-specific Gα q/11 knockouts exhibit hypogonadotropic hypogonadism and infertility, akin to the phenotypes seen in GnRH- or GnRHR-deficient mice. In contrast, under standard conditions, gonadotrope-specific Gα s knockouts produce gonadotropins at normal levels and are fertile. However, the LH surge amplitude is blunted in Gα s knockout females and postgonadectomy increases in FSH and LH are reduced both in males and females. These data suggest that GnRH may signal principally via Gα q/11 to stimulate gonadotropin production, but that Gα s plays important roles in gonadotrope function in vivo when GnRH secretion is enhanced.

242 Divergent Selection for Early Puberty Impacts KNDy Neuron Gene Expression in Gilts

Abstract Advancing gilt puberty onset is financially desirable for swine production. Neurons in the hypothalamic arcuate nucleus (ARC) that co-express kisspeptin, neurokinin B (NKB), and dynorphin (i.e. KNDy cells) are believed to control gonadotropin-releasing hormone (GnRH) and luteinizing hormone (LH) secretion, but their role in gilt pubertal development is unknown. We hypothesized that puberty onset in gilts would coincide with greater expression of mRNA for kisspeptin and NKB, and less expression of dynorphin. Using fluorescent in situ hybridization (RNAscope), we examined expression of kisspeptin, NKB, and dynorphin in pre- and postpubertal gilts from two genetic lines divergently selected for age at puberty. Prepubertal (n = 6/line) and postpubertal (n = 6/line) gilts were used, and postpubertal animals all received Matrix (0.22% altrenogest) orally for 14 days with tissue collection two days after the final dose. Gilts were euthanized and heads were perfused with 8 L of 4% paraformaldehyde (PFA). Hypothalamic brain tissue was removed, placed in 4% PFA for 24 hrs, and then in 20% sucrose until sectioning (50 µm). Sectioned tissue was stored in cryopreservative at -20°C until RNAscope. Data were analyzed using SAS software (Version 9.4, SAS Institute, Cary NC) with significance declared at P &amp;lt; 0.05. We determined mRNA expression for kisspeptin was not different between groups (P &amp;gt; 0.05). In addition, we found that mRNA expression for NKB was higher in prepubertal gilts compared to postpubertal gilts (P &amp;lt; 0.05) but was not different between lines; mRNA expression was lowest in postpubertal late puberty gilts. Furthermore, total number of dynorphin cells were higher in prepubertal gilts compared to postpubertal gilts (P &amp;lt; 0.05), while individual cell mRNA expression for dynorphin was greatest in postpubertal early puberty gilts (P &amp;lt; 0.05). Taken together, we suggest puberty onset in gilts is more dependent on NKB and dynorphin than kisspeptin.

Kisspeptin, Neurokinin B, and Dynorphin Expression during Pubertal Development in Female Sheep.

Simple SummaryMistiming of puberty onset has negative consequences for humans and livestock. Puberty depends on increased brain secretion of gonadotrophin-releasing hormone (GnRH), which causes pituitary luteinizing hormone (LH) release. Luteinizing hormone then stimulates estrogen release from the ovary and, eventually, the first ovulation. The brain neural systems that control the pubertal increase in GnRH and LH are not completely known. Neurons co-expressing kisspeptin, neurokinin B (NKB), and dynorphin (called KNDy neurons) are critical for puberty, with kisspeptin and NKB stimulating and dynorphin inhibiting LH secretion. Herein, we used female sheep at prepubertal, peripubertal, and postpubertal ages and hypothesized that kisspeptin and NKB would increase, and dynorphin decrease, during the pubertal increase in LH secretion. We observed that kisspeptin and NKB protein and mRNA expression were evident well before the pubertal increase in LH secretion and did not change with age. We saw no change in numbers of dynorphin neurons, but actually saw an increase in the amount of mRNA per neuron at a postpubertal age. We conclude that puberty-associated increases in GnRH and LH secretion occur without significant changes in KNDy peptide expression and suggest that, while critical, KNDy neurons await inputs from other neural systems to trigger puberty onset.The neural mechanisms underlying increases in gonadotropin-releasing hormone (GnRH) and luteinizing hormone (LH) secretion that drive puberty onset are unknown. Neurons coexpressing kisspeptin, neurokinin B (NKB), and dynorphin, i.e., KNDy neurons, are important as kisspeptin and NKB are stimulatory, and dynorphin inhibitory, to GnRH secretion. Given this, we hypothesized that kisspeptin and NKB expression would increase, but that dynorphin expression would decrease, with puberty. We collected blood and hypothalamic tissue from ovariectomized lambs implanted with estradiol at five, six, seven, eight (puberty), and ten months of age. Mean LH values and LH pulse frequency were the lowest at five to seven months, intermediate at eight months, and highest at ten months. Kisspeptin and NKB immunopositive cell numbers did not change with age. Numbers of cells expressing mRNA for kisspeptin, NKB, or dynorphin were similar at five, eight, and ten months of age. Age did not affect mRNA expression per cell for kisspeptin or NKB, but dynorphin mRNA expression per cell was elevated at ten months versus five months. Thus, neither KNDy protein nor mRNA expression changed in a predictable manner during pubertal development. These data raise the possibility that KNDy neurons, while critical, may await other inputs for the initiation of puberty.

How alcohol affects insulin-like growth factor-1's influences on the onset of puberty: A critical review.

Alcohol (ALC) is capable of delaying signs associated with pubertal development in laboratory animals, as well as in humans. The normal onset of puberty results from a timely increase in gonadotropin‐releasing hormone (GnRH) secretion, which is associated with a gradual decline in prepubertal inhibitory influences, and the establishment of excitatory inputs that increase GnRH release, which together drive pubertal development. In recent years, insulin‐like growth factor‐1 (IGF‐1) has emerged as a pivotal contributor to prepubertal GnRH secretion and pubertal development, whose critical actions are interfered with by ALC abuse. Here we review the neuroendocrine research demonstrating the important role that IGF‐1 plays in pubertal development, and describe the detrimental effects and mechanisms of action of ALC on the onset and progression of pubertal maturation.

Effects of low energy availability on female reproductive function.

BackgroundIt is known that metabolic and nutritional disturbances induce reproductive dysfunction in females. The main cause of these alterations is reduced gonadotrophin‐releasing hormone (GnRH) secretion from the hypothalamus, and the underlying mechanisms have gradually been elucidated.MethodsThe present review summarizes current knowledge about the effects of nutrition/metabolism on reproductive functions, especially focusing on the GnRH regulation system.Main findingsVarious central and peripheral factors are involved in the regulation of GnRH secretion, and alterations in their activity combine to affect GnRH neurons. Satiety‐related factors, i.e., leptin, insulin, and alpha‐melanocyte‐stimulating hormone, directly and indirectly stimulate GnRH secretion, whereas orexigenic factors, i.e., neuropeptide Y, Agouti‐related protein, orexin, and ghrelin, attenuate GnRH secretion. In addition, kisspeptin, which is a potent positive regulator of GnRH, expression is reduced by metabolic and nutritional disturbances.ConclusionThese neuroendocrine systems may be defensive mechanisms, which help organisms to survive adverse conditions by temporarily suppressing reproduction.

Molecular genetics and phenotypic features of congenital isolated hypogonadotropic hypogonadism

Congenital isolated hypogonadotropic hypogonadism includes a group of diseases related to the defects of secretion and action of gonadotropin-releasing hormone (GNRH) and gonadotropins. In a half of cases congenital hypogonadism is associated with an impaired sense of smell. It's named Kallmann syndrome. Now 40 genes are known to be associated with function of hypothalamus pituitary gland and gonads. Phenotypic features of hypogonadism and therapy effectiveness are related to different molecular defects. However clinical signs may vary even within the same family with the same molecular genetic defect. Genotype phenotype correlation in patients with congenital malformations prioritizes the search for mutations in candidate genes. There are data of significant contribution of oligogenicity into the phenotype of the disease are presented in the review. Moreover, an issue of current isolated hypogonadotropic hypogonadism definition and classification revision is raised in the review due to hypogonadotropic hypogonadism development while there are mutations in genes not associated with GNRH neurons secretion and function.