Changes in pituitary gonadotropin subunits and hypothalamic Kiss-1 gene expression by administration of sex steroids in ovary-intact female rats.

OBJECTIVE: We examined how the sex steroids influence the synthesis of gonadotropins. MATERIALS AND METHODS: The effects of sex steroids estradiol (E2), progesterone (P4), and dihydrotestosterone (DHT) in pituitary gonadotroph cell model (LßT2 cells) in vitro and ovary-intact rats in vivo were examined. The effects of sex steroids on Kiss1 gene expression in the hypothalamus were also examined in ovary-intact rats. RESULTS: In LßT2 cells, E2 increased common glycoprotein alpha (Cga) and luteinizing hormone beta (Lhb) subunit promoter activity as well as their mRNA expression. Although gonadotropin subunit promoter activity was not modulated by P4, Cga and Lhb mRNA expression was increased by P4. DHT inhibited Cga and Lhb mRNA expression with a concomitant decrease in their promoter activity. During the 2-week administration of exogenous E2 to ovary-intact rats, the estrous cycle determined by vaginal smears was disrupted. P4 or DHT administration completely eliminated the estrous cycle. Protein expression of all three gonadotropin subunits within the pituitary gland was inhibited by E2 or P4 treatment in vivo; however, DHT reduced Cga expression but did not modulate Lhb or follicle-stimulating hormone beta subunit expression. E2 administration significantly repressed Kiss1 mRNA expression in a posterior hypothalamic region that included the arcuate nucleus. P4 and DHT did not modulate Kiss1 mRNA expression in this region. In contrast, P4 administration significantly inhibited Kiss1 mRNA expression in the anterior region of the hypothalamus that included the anteroventral periventricular nucleus. The expression of gonadotropin-releasing hormone (Gnrh) mRNA in the anterior hypothalamic region, where the preoptic area is located, appeared to be decreased by treatment with E2 and P4. CONCLUSION: Our findings suggest that sex steroids have different effects in the hypothalamus and pituitary gland.

Endocrine patterns associated with ovarian development in female Pacific halibut (Hippoglossus stenolepis).

The Pacific halibut (Hippoglossus stenolepis) is a large migratory demersal flatfish species that occupies a top trophic role in the North Pacific Ocean and Bering Sea ecosystems, where it also supports various fisheries. As a first attempt to characterize the endocrine mechanisms driving sexual maturation in this important species, we collected pituitary, ovarian and blood samples from Pacific halibut females captured in the wild that were classified histologically into various female developmental stages. We conducted gene expression analyses of gonadotropin beta subunits in the pituitary and observed that mRNA expression levels of fshb gradually increased throughout vitellogenesis, remained elevated until before ovulation and declined after spawning. In contrast, the mRNA expression levels of lhb markedly increased during oocyte maturation and remained elevated until after spawning. Ovarian mRNA expression levels of the gonadotropin receptor genes fshr and lhr peaked during oocyte maturation and before spawning, respectively, immediately following the developmental stage at which pituitary fshb and lhb mRNA expression first reached maximum levels. The ovarian gene expression patterns of steroidogenic enzyme genes cyp19a1 and hsd20b2 paralleled those of fshr and lhr, respectively. Testosterone and 17ß-estradiol (E2) plasma levels increased concomitantly with fshr and cyp19a1 mRNA expression levels, and vitellogenin plasma levels increased throughout vitellogenesis and reached maximum levels prior to spawning. These results are consistent with the notion that in female Pacific halibut, as in other teleosts, vitellogenesis and oocyte maturation and ovulation are likely under the control of pituitary gonadotropic hormones Fsh and Lh, respectively.

Consumption of soy isoflavones during the prepubertal phase delays puberty and causes hypergonadotropic hypogonadism with disruption of hypothalamic-pituitary gonadotropins regulation in male rats.

Isoflavones are phytoestrogens with recognized estrogenic activity but may also affect testosterone, corticosterone and thyroid hormone levels in experimental models. However, the molecular mechanisms involved in these alterations are still unclear. Isoflavones are present in soy-based infant formula, in breast milk after the consumption of soy by the mother and are widely used for the preparation of beverages consumed by toddlers and teenagers. In this sense, we proposed to investigate the effects of soy isoflavone exposure during the prepubertal period, a recognized window of sensitivity for endocrine disruption, over the hypothalamic-pituitary-testicular (HPT) axis. For this, 42 3-week-old male Wistar rats were exposed to 0.5, 5 or 50 mg of soy isoflavones/kg from postnatal day (PND) 23 to PND60. We evaluated body growth, age at puberty, serum concentrations of LH, FSH, testosterone and estradiol, and the expression of the transcripts (mRNA) of genes encoding key genes controlling the hypothalamic-pituitary-testicular (HPT) axis. In the hypothalamus, we observed an increase in Esr1 mRNA expression (0.5 and 5 mg). In the pituitary, we observed an increase in Gnrhr mRNA expression (50 mg), a reduction in Lhb mRNA expression (0.5 mg), and a reduction in Ar mRNA expression. In the testis, we observed an increase in Lhcgr mRNA expression (50 mg) and a reduction in Star mRNA expression (0.5 and 5 mg). The serum levels of LH (5 and 50 mg) and FSH (0.5 mg) were increased, while testosterone and estradiol were reduced. Puberty was delayed in all groups. Taken together, these results suggest that prepubertal consumption of relevant levels of soy isoflavones disrupts the HPT axis, causing hypergonadotropic hypogonadism and altered expression levels of key genes regulating the axis.

Copper deposition in Wilson's disease causes male fertility decline by impairing reproductive hormone release through inducing apoptosis and inhibiting ERK signal in hypothalamic-pituitary of mice.

Wilson's disease (WD) is an autosomal recessive disorder of copper metabolism characterized by liver and central nervous system dysfunction. Considerable evidence suggests that infertility is also very common in male patients with WD, but the exact molecular mechanisms involved remain unknown. In order to further investigate the pathological changes in the hypothalamic-pituitary-testicular (HPT) axis and its mechanisms, mice were divided into the normal control group (NC), WD model TX mice group (WD), dimercaptosuccinic acid-treated TX mice group (DMSA), and pregnant horse serum gonadotropin-treated TX mice group (PMSG). The copper content and morphology of hypothalamus and pituitary tissues, the ultrastructure and apoptosis of hypothalamus neurons and pituitary gonadotropin cells, the serum levels of reproductive hormones, and the pregnancy rate and litter size of the female mice were studied. The expression of apoptosis-related proteins and the phosphorylation of extracellular regulatory protein kinase (ERK) 1/2 in the hypothalamus and pituitary were detected. The results showed that the copper content was significantly increased in the WD group, and the histopathological morphology and ultrastructure of the hypothalamus and pituitary were damaged. The levels of the gonadotropin-releasing hormone, the follicle-stimulating hormone, the luteinizing hormone, and testosterone were significantly decreased. The apoptosis rate in the hypothalamus and pituitary was significantly increased. The expressions of proapoptotic proteins Bax and Caspase-3 were significantly increased, the expression of the anti-apoptotic protein Bcl-2 was significantly decreased, and the phosphorylation level of ERK1/2 was significantly decreased. Fertility is significantly reduced. After DMSA intervention, the hypothalamus tissue copper content decreased, the hypothalamus and pituitary tissue morphology and ultrastructure were improved, cell apoptosis was alleviated, the expression of Bax and Caspase-3 was significantly decreased, the expression of Bcl-2 was significantly increased, and the reproductive hormone level, phosphorylation level, and fertility were increased. Fertility was preserved after treatment with PMSG in male TX mice. These results suggest that copper deposition in WD causes male fertility decline by impairing reproductive neuroendocrine hormone release through inducing apoptosis and inhibiting the ERK signal in the hypothalamic-pituitary region. This study can also provide reference for the damage of copper pollution to the male reproductive system.

Changes in hormones after apneic hypoxia/hypercapnia - An investigation in voluntary apnea divers.

BACKGROUND: Prolonged apnea is characterized by hypoxia/hypercapnia. Hypoxia can be associated with hormonal dysfunction. We raised the question as to whether steroid hormonal and gonadotropin levels could be influenced by short-term hypoxia/hypercapnia in a model of dry apnea in trained apnea divers. METHODS: Adrenal, sex steroid and pituitary hormones were measured in ten trained voluntary apnea divers before, immediately after, 0.5 h and 4 h after a maximal breath-hold. Apnea was carried out under dry conditions. RESULTS: Corticosterone, progesterone, cortisol, 17-OH-progesterone, dehydroepiandrosterone and androstenedione showed a significant continuous increase with a maximum at 0.5 h after apnea, followed by a decrease back to or below baseline at 4 h after apnea. Testosterone, estradiol, cortisone and dihydrotestosterone showed a decrease 4 h after apnea. Dehydroepiandrosteronesulfate, luteinizing hormone (LH) and follicle stimulating hormone (FSH) showed no significant changes. CONCLUSION: Even a single apnea resulted in two different patterns of hormone response to apnea, with increased adrenal and reduced sex steroid levels, while LH/FSH showed no clear kinetic reaction. Apnea divers might be a suitable clinical model for hypoxic disease.

The GnRH Antagonist Degarelix Suppresses Gonadotropin Secretion and Pituitary Sensitivity in Midgestation Sheep Fetuses.

The specific role of gonadotropin-releasing hormone (GnRH) on brain sexual differentiation remains unclear. To investigate whether gonadotropin and, in turn, testosterone (T) secretion is regulated by GnRH during the critical period for brain differentiation in sheep fetuses, we attempted to selectively suppress pituitary-testicular activation during midgestation with the long-acting GnRH antagonist degarelix. Fetuses received subcutaneous injections of the antagonist or vehicle on day 62 of gestation. After 2 to 3 weeks we examined consequences of the intervention on baseline and GnRH-stimulated plasma luteinizing hormone (LH) and T levels. In addition, we measured the effect of degarelix-treatment on messenger RNA (mRNA) expression for the pituitary gonadotropins and key gonadal steroidogenic enzymes. Baseline and GnRH-stimulated plasma LH levels were significantly suppressed in degarelix-treated male and female fetuses compared to control values. Similarly, T concentrations were suppressed in degarelix-treated males. The percentage of LHß-immunoreactive cells colocalizing c-fos was significantly reduced by degarelix treatment indicating that pituitary sensitivity was inhibited. Degarelix treatment also led to the significant suppression of mRNA expression coding for the pituitary gonadotropin subunits and for the gonadal enzymes involved in androgen synthesis. These findings demonstrate that pharmacologic inhibition of GnRH early in gestation results in suppression of LH secretion and deficits in the plasma T levels of male lamb fetuses. We conclude that GnRH signaling plays a pivotal role for regulating T exposure during the critical period of sheep gestation when the brain is masculinized. Thus, disturbance to gonadotropin secretion during this phase of gestation could have long-term consequence on adult sexual behaviors and fertility.

Acupuncture regulates the autophagy of ovarian granulosa cells in polycystic ovarian syndrome ovulation disorder by inhibiting the PI3K/AKT/mTOR pathway through LncMEG3.

The main features of polycystic ovary syndrome (PCOS) are abnormal follicular development and ovulation dysfunction, which are caused by the excessive autophagy of ovarian granulosa cells. Acupuncture has been shown to improve ovulation dysfunction and abnormal follicular development in PCOS patients, but its mechanism is unclear. This study hypothesized that the beneficial effects of acupuncture are the result of LncMEG3-mediated effects on the PI3K/AKT/mTOR pathway. Acupuncture (CV-4, RN-3, CV-6, SP-6 and EX-CA 1) was used to treat a rat model of polycystic ovary syndrome. Hematoxylin-eosin staining was used to observe ovarian morphology and enzyme-linked immunosorbent assay, western blotting, immunohistochemistry and real-time PCR were used to detect LH, E2, FSH, T, AMH, LncMEG3, PI3K, AKT, mTOR, P62 and LC3II/I expression. The ovarian morphology of 90% of the rats in the acupuncture treatment group was significantly improved after 11 consecutive days of therapy. Acupuncture also resulted in a significant decrease in serum LH, FSH, T and AMH levels and a significant increase in E2 level (P<0.01). LncMEG3, PI3K, AKT, mTOR, P62 and LC3II/I expression was decreased in ovarian granulosa cells after acupuncture compared with PCOS and lentiviral Intervention Group (P<0.05), while the expression of follicle stimulating hormone receptor was increased (P<0.05). These results indicate that acupuncture can down-regulate the expression of LncMEG3 and thereby inhibit the PI3K/AKT/mTOR pathway, reducing granulosa cell autophagy and normalizing their proliferation. These factors ultimately remedy abnormal follicular development. These findings suggest that acupuncture has clinical potential as a safe treatment for PCOS ovulatory dysfunction.

ENDOCRINE TUMOURS: Thyrotropin-secreting pituitary adenoma: a structured review of 535 adult cases.

BACKGROUND AND AIMS: Thyrotropin-secreting pituitary adenomas (TSHomas) are a rare entity, occurring in one per million people. We performed a systematic review of 535 adult cases summarizing the clinical, biochemical, hormonal and radiological characteristics of TSHoma. Furthermore, we discussed the current guidelines for diagnosis and treatment. METHODS: A structured research was conducted using Pubmed and Web of Science with the following MeSH terms: 'thyrotropin secreting pituitary adenoma' OR 'TSHoma' OR 'thyrotropinoma.' RESULTS: Our analysis included 535 cases originating from 18 case series, 5 cohort studies and 91 case reports. The mean age at diagnosis was 46 years. At presentation, 75% had symptoms of hyperthyroidism, 55.5% presented with a goitre and 24.9% had visual field defects. The median TSH at diagnosis was 5.16 (3.20-7.43) mU/L with a mean FT4 of 41.5 ± 15.3 pmol/L. The majority (76.9%) of the TSHomas were macroadenoma. Plurihormonality was seen in 37.4% of the adenoma with a higher incidence in macroadenoma. Surgical resection of the adenoma was performed in 87.7% of patients of which 33.5% had residual pituitary adenoma. Post-operative treatment with a somatostatin analogue (SSA) led to a stable disease in 81.3% of the cases with residual tumour. We noticed a significant correlation between the diameter of the adenoma and residual pituitary adenoma (r = 0.490, P < 0.001). However, in patients preoperatively treated with an SSA, this correlation was absent. CONCLUSION: TSHomas are a rare cause of hyperthyroidism and are frequently misdiagnosed. Based on our structured analysis of case series, cohort studies and case reports, we conclude that the majority of TSHomas are macroadenoma being diagnosed in the fifth to sixth decade of life and presenting with symptoms of hyperthyroidism. Plurihormonalitiy is observed in one-third of TSHomas. Treatment consists of neurosurgical resection and SSA in case of surgical failure.

Generation and use of recombinant gonadotropins in fish.

Understanding the differential roles of the pituitary gonadotropins Fsh and Lh in gonad maturation is crucial for a successful manipulation of the reproductive process in fish, and requires species-specific tools and appropriate active hormones. With the increasing availability of fish cDNAs coding for gonadotropin subunits, the production of recombinant hormones in heterologous systems has gradually substituted the approach of isolating native hormones. These recombinant hormones can be continually produced without depending on the fish as starting material and no cross-contamination with other pituitary glycoproteins is assured. Recombinant gonadotropins should be produced in eukaryotic cells, which have glycosylation capacity, but this post-translational modification varies greatly depending on the cell system, influencing hormone activity and stability. The production of recombinant gonadotropin beta-subunits to be used as antigens for antibody production has allowed the development of immunoassays for quantification of gonadotropins in some fish species. The administration in vivo of dimeric homologous recombinant gonadotropins has been used in basic studies and as a biotechnological approach to induce gametogenesis. In addition, gene-based therapies using somatic transfer of the gonadotropin genes have been tested as an alternative for hormone delivery in vivo. In summary, the use of homologous hormonal treatments can open new strategies in aquaculture to solve reproductive problems or develop out-of-season breeding programs.

Chronic exposure of adult male Wistar rats to bisphenol A causes testicular oxidative stress: Role of gallic acid.

OBJECTIVES: Bisphenol A (BPA) has been reported that among other male reproductive dys-functions, it can cause marked estrogenic effects including alteration in serum hormones as well as testicular lesions in exposed animals. This work sought to study the role of gallic acid (GA), a known antioxidant, on the BPA-induced testicular oxidative stress in adult male Wistar rats using serum hormone analysis, histopathology, and biochemical assays. METHODS: Adult male rats were divided into four groups (n=10) including control (0.2 ml of corn oil), GA (20 mg/kg/day), BPA (10 mg/kg/day), BPA+GA (BPA, 10 mg/kg/day + GA, 20 mg/kg/day). All medications were given by oral gavage for 45 consecutive days. The body and testicular weights were measured. Blood and organ samples were collected for the serum hormonal assay: testosterone (T), luteinizing hormone (LH), follicle stimulating hormone (FSH) and prolactin (PRL), and tissue biochemistry analysis: superoxide dismutase (SOD), reduced glutathione (GSH), glutathione-S-transferase (GST), malondialdehyde (MDA), hydrogen peroxide (H2O2), respectively. RESULTS: The BPA-treated rats showed significant reduction in the gonadosomatic index. BPA also caused significant decrease in the levels of the serum testosterone and prolactin. Furthermore, BPA induced testicular oxidative stress by decreasing the activities of antioxidant enzymes and increasing reactive oxygen species. However, co-treatment with GA protected against these alterations. CONCLUSION: Findings from the present study confirmed the previously reported data and show that the ability of GA, as a potent antioxidant, may protect against BPA-induced alterations in the male reproductive function. Hence, GA protects against testicular oxidative stress in adult male Wistar rats following chronic exposure to BPA.

Seasonal Related Multifactorial Control of Pituitary Gonadotropin and Growth Hormone in Female Goldfish: Influences of Neuropeptides and Thyroid Hormone.

Female reproduction is under multifactorial control of brain-pituitary-peripheral origin. The present study provides information on seasonal changes in circulating LH and GH concentrations, as well as transcript levels for a number of genes involved in the regulation of reproduction and growth in female goldfish. We also provide information on the effects of treatments with GnRH and/or GnIH, and their interaction with T3, at three stages of gonadal recrudescence. Maximum basal concentration of LH was observed at late recrudescence (Spring) while no seasonal changes in basal serum GH levels was detected. Serum LH and GH levels were stimulated by GnRH as expected, depending on the season. GnIH stimulated basal GH concentrations in gonadally regressed fish. GnIH inhibitory action on GnRH-induced LH response was observed in late, but not in mid recrudescence. T3 actions on basal and GnRH- or GnIH-induced GH secretion were generally inhibitory, depending on season. Administration of T3 attenuated GnRH-induced LH responses in mid and late stages of gonadal recrudescence, and the presence of GnIH abolished inhibitory actions of T3 in fish at mid recrudescence. Our results also demonstrated seasonal patterns in basal and GnRH- and/or GnIH-induced transcript levels for ERα, ERßI, FSHR, aromatase, TRαI, TRß, IGF-I, and Vtg in the liver and ovary. However, there were no clear correlations between changes in transcript levels and circulating levels of LH and GH. The results support the hypothesis that GnRH, GnIH, and T3 are contributing factors in complex reciprocal control of reproduction and growth in goldfish.

Post-photostimulation energy intake accelerated pubertal development in broiler breeder pullets.

The effect of ME intake (MEI) on the reproductive system was evaluated. Ross 308 broiler breeder pullets (n = 140) were assigned to 2 treatments from 22 to 26 wk of age: (1) Low-energy diet fed restricted (2,807 kcal/kg, low MEI) and (2) high-energy diet fed unrestricted (3,109 kcal/kg, high MEI). Daylength was increased from 8 to 14 h at 22 wk of age with a light intensity of 30 lux. Daily palpation was used to detect sexual maturity via the presence of a hard-shelled egg in the shell gland. Expression of gonadotropin releasing hormone-I (GnRH) and gonadotropin inhibitory hormone (GnIH) genes in the hypothalamus and GnRH receptor (GnRH-RI) and GnIH receptor (GnIH-R) genes in the anterior pituitary gland of each pullet was evaluated from 22 to 26 wk of age using quantitative real time-PCR. Blood samples were taken weekly and luteinizing hormone (LH), follicle stimulating-hormone (FSH), and 17-beta-estradiol (E2) determined using commercial ELISA kits. Carcass samples were used for determination of CP and fat content. Data were analyzed using the MIXED procedure in SAS, and differences were reported where P ≤ 0.05. High MEI treatment pullets had 2.3-fold higher GnRH and 1.8-fold higher GnRH-RI mRNA levels than low MEI pullets. MEI affected neither expression of GnIH and GnIH-R nor carcass protein content. For high MEI (489 kcal/D) and low MEI treatments (258 kcal/D), respectively, from 22 to 26 wk of age (P ≤ 0.05), LH concentration was 3.05 and 1.60 ng/mL; FSH concentration was 145 and 89.3 pg/mL; E2 concentration was 429 and 266 pg/mL, and carcass lipid was 13.9 and 10.3%. The onset of lay for pullets in the high MEI treatment advanced such that 100% had laid by 26 wk of age compared with 30% in the low MEI treatment. We concluded that higher MEI advanced the activation of the hypothalamic-pituitary-gonadal axis and also increased body lipid deposition, and moreover, stimulated reproductive hormone levels which overall accelerated puberty in broiler breeder pullets.

Effects of Qilin pills on spermatogenesis, reproductive hormones, oxidative stress, and the TSSK2 gene in a rat model of oligoasthenospermia.

BACKGROUND: Qilin pills (QLPs), a classic Traditional Chinese Medicine (TCM) formula for treating male infertility, effectively improve semen quality in clinical trials. This study was designed to evaluate the effects of QLPs on spermatogenesis, reproductive hormones, oxidative stress, and the testis-specific serinekinase-2 (TSSK2) gene in a rat model of oligoasthenospermia. METHODS: Forty adult male Sprague-Dawley (SD) rats were randomly divided into four groups. The rat model with oligoasthenospermia was generated by intragastric administration of tripterygium glycosides (TGs) once daily for 4 weeks. Then, two treatment groups were given different doses (1.62 g/kg and 3.24 g/kg) of QLPs once daily for 60 days. Sperm parameters, testicular histology and reproductive hormone measurements, oxidative stress tests, and TSSK2 expression tests were carried out. RESULTS: QLPs effectively improved semen parameters and testicular histology; restored the levels of FSH, LH, PRL, fT, and SHBG; reduced the levels of oxidative stress products (ROS and MDA); increased testicular SOD activity; and restored the expression of spermatogenesis-related gene TSSK2. CONCLUSION: QLPs have a therapeutic effect on a rat model of oligoasthenospermia, and this effect is manifested as improvement of semen quality and testis histology, gonadal axis stability, decreased oxidative stress, and the regulation of testis-specific spermatogenesis-related gene TSSK2.

Circulating Sex Hormone Levels and Risk of Esophageal Adenocarcinoma in a Prospective Study in Men.

OBJECTIVES: Sex hormones have been hypothesized to explain the strong male predominance in esophageal adenocarcinoma, but evidence is needed. This study examined how circulating sex hormone levels influence future risk of esophageal adenocarcinoma. METHODS: This case-control study was nested in a prospective Norwegian cohort (Janus Serum Bank Cohort), including 244 male patients with esophageal adenocarcinoma and 244 male age-matched control participants. Associations between prediagnostic circulating levels of 12 sex hormones and risk of esophageal adenocarcinoma were assessed using conditional logistic regression. In addition, a random-effect meta-analysis combined these data with a similar prospective study for 5 sex hormones. RESULTS: Decreased odds ratios (ORs) of esophageal adenocarcinoma were found comparing the highest with lowest quartiles of testosterone (OR = 0.44, 95% confidence interval [CI] 0.22-0.88), testosterone:estradiol ratio (OR = 0.37, 95% CI 0.19-0.72), and luteinizing hormone (OR = 0.50, 95% CI 0.30-0.98), after adjustment for tobacco smoking and physical activity. These associations were attenuated after further adjustment for body mass index (OR = 0.56, 95% CI 0.27-1.13 for testosterone; OR = 0.46, 95% CI 0.23-0.91 for testosterone:estradiol ratio; OR = 0.55, 95% CI 0.29-1.08 for luteinizing hormone). No associations were observed for sex hormone-binding globulin, dehydroepiandrosterone sulfate, follicle-stimulating hormone, prolactin, 17-OH progesterone, progesterone, androstenedione, or free testosterone index. The meta-analysis showed an inverse association between testosterone levels and risk of esophageal adenocarcinoma (pooled OR for the highest vs lowest quartile = 0.60, 95% CI 0.38-0.97), whereas no associations were identified for androstenedione, sex hormone-binding globulin, estradiol, or testosterone:estradiol ratio. DISCUSSION: Higher circulating testosterone levels may decrease the risk of esophageal adenocarcinoma in men.

Functional characterization of DLK1/MEG3 locus on chromosome 14q32.2 reveals the differentiation of pituitary neuroendocrine tumors.

Pituitary neuroendocrine tumors (PitNETs) represent the neoplastic proliferation of the anterior pituitary gland. Transcription factors play a key role in the differentiation of PitNETs. However, for a substantial proportion of PitNETs, the etiology is poorly understood. According to the transcription data of 172 patients, we found the imprinting disorders of the 14q32.2 region and DLK1/MEG3 locus associated with the differentiation of PitNETs. DLK1/MEG3 locus promoted somatotroph differentiation and inhibited tumor proliferation in PIT1(+) patients, furthermore, the level of DLK1 played a critical role in the trend of somatotroph or lactotroph differentiation. Anti-DLK1 monoclonal antibody blockade or siMEG3 both indicated that the DLK1/MEG3 significantly promoted the synthesis and secretion of GH/IGF-1 and inhibited cell proliferation. In addition, loss of DLK1 activated the mTOR signaling pathway in high DLK1-expressing and PIT1(+) GH3 cell lines, a mild effect in the low DLK1-expressing and PIT1(+) MMQ cell lines and no effect in the PIT1(-) ATT20 cell line. These findings emphasize that expression at the DLK1/MEG3 locus plays a key role in the differentiation of PitNETs, especially somatotroph adenomas, and provide potential molecular target data for patient stratification and treatment in the future.

A computational model for gonadotropin releasing cells in the teleost fish medaka.

Pituitary endocrine cells fire action potentials (APs) to regulate their cytosolic Ca2+ concentration and hormone secretion rate. Depending on animal species, cell type, and biological conditions, pituitary APs are generated either by TTX-sensitive Na+ currents (INa), high-voltage activated Ca2+ currents (ICa), or by a combination of the two. Previous computational models of pituitary cells have mainly been based on data from rats, where INa is largely inactivated at the resting potential, and spontaneous APs are predominantly mediated by ICa. Unlike in rats, spontaneous INa-mediated APs are consistently seen in pituitary cells of several other animal species, including several species of fish. In the current work we develop a computational model of gonadotropin releasing cells in the teleost fish medaka (Oryzias latipes). The model stands out from previous modeling efforts by being (1) the first model of a pituitary cell in teleosts, (2) the first pituitary cell model that fires sponateous APs that are predominantly mediated by INa, and (3) the first pituitary cell model where the kinetics of the depolarizing currents, INa and ICa, are directly fitted to voltage-clamp data. We explore the firing properties of the model, and compare it to the properties of previous models that fire ICa-based APs. We put a particular focus on how the big conductance K+ current (IBK) modulates the AP shape. Interestingly, we find that IBK can prolong AP duration in models that fire ICa-based APs, while it consistently shortens the duration of the predominantly INa-mediated APs in the medaka gonadotroph model. Although the model is constrained to experimental data from gonadotroph cells in medaka, it may likely provide insights also into other pituitary cell types that fire INa-mediated APs.

Activation of the brain-pituitary-gonadotropic axis in the black porgy Acanthopagrus schlegelii during gonadal differentiation and testis development and effect of estradiol treatment.

Previous studies revealed an estradiol (E2)-dependent peak in brain activity, including neurosteroidogenesis and neurogenesis in the black porgy during the gonadal differentiation period. The brain-pituitary-gonadotropic axis is a key regulator of reproduction and may also be involved in gonadal differentiation, but its activity and potential role in black porgy during the gonadal differentiation period is still unknown. The present study analyzed the expression of regulatory factors involved in the gonadotropic axis at the time of gonadal differentiation (90, 120, 150 days after hatching [dah]) and subsequent testicular development (180, 210, 300 dah). In agreement with previous studies, expression of brain aromatase cyp19a1b peaked at 120 dah, and this was followed by a gradual increase during testicular development. The expression of gonadotropin subunits increased slightly but not significantly during gonadal differentiation and then increased significantly at 300 dah. In contrast, the expression of brain gnrh1 and pituitary gnrh receptor 1 (gnrhr1) exhibited a pattern with two peaks, the first at 120 dah, during the period of gonadal differentiation, and the second peak during testicular development. Gonad fshr and lhcgr increased during gonadal differentiation period with highest transcript level in prespawning season during testicular development. This suggests that the early activation of brain gnrh1, pituitary gnrhr1 and gths, and gonad gthrs might be involved in the control of gonadal differentiation. E2 treatment increased brain cyp19a1b expression at each sampling time, in agreement with previous studies in black porgy and other teleosts. E2 also significantly stimulated the expression of pituitary gonadotropin subunits at all sampling times, indicating potential E2-mediated steroid feedback. In contrast, no significant effect of E2 was observed on gnrh1. Moreover, treatment of AI or E2 had no statistically significant effect on brain gnrh1 transcription levels during gonadal differentiation. This indicated that the early peak of gnrh1 expression during the gonadal differentiation period is E2-independent and therefore not directly related to the E2-dependent peak in brain neurosteroidogenesis and neurogenesis also occurring during this period in black porgy. Both E2-independent and E2-dependent mechanisms are thus involved in the peak expression of various genes in the brain of black porgy at the time of gonadal differentiation.

So similar and so different: Circulating androgens and androgen origin in bulimic women.

Hyper androgen state frequently can be diagnosed in bulimic women. Eating disorder not otherwise specified (EDNOS) recognized as a less severe form of bulimia nervosa (BN). The objective of the study was to determine whether androgen levels and androgen origin differs in bulimic women compared to control subjects. Forty-six women with bulimia nervosa (BN), 31 with eating disorder not otherwise specified, purging type (EDNOS P) and 56 matched healthy controls were studied with respect to serum testosterone (T), 5alpha-dihydrotestosterone (DHT), sex hormone-binding globulin (SHBG), deyhydroepiahndrosterone sulfate (DHEAS) and luteinizing hormone (LH) and to ovarian morphology. Despite all groups had almost identical androgen and SHBG levels; there were differences in the origin of circulating T and DHT. Correlation analysis suggest major differences in the formation of circulating testosterone (T) and 5α-dihydrotestosterone (DHT) with BN being more like the control subjects with peripheral formation from 4-androsterne-3,17-dione (A-4), dehydroepiandrosterone sulfate (DHEAS) and also from T. While in EDNOS group a possible direct ovarian T secretion and a DHEAS modulating action of androgens on pituitary gonadotropin secretion is present. The origin of circulating T and DHT differs between bulimics. Our findings do probably not reflect direct actions of circulating DHT on pituitary LH secretion in the women with EDNOS, but rather the effect of A-4, T via conversion to DHT in the central nervous system, indicating psych/endocrine differences between the two groups of bulimic women.

Advances in computational modeling approaches of pituitary gonadotropin signaling.

INTRODUCTION: Pituitary gonadotropins play an essential and pivotal role in the control of human and animal reproduction within the hypothalamic-pituitary-gonadal (HPG) axis. The computational modeling of pituitary gonadotropin signaling encompasses phenomena of different natures such as the dynamic encoding of gonadotropin secretion, and the intracellular cascades triggered by gonadotropin binding to their cognate receptors, resulting in a variety of biological outcomes. Areas covered: The authors provide an overview of the historical and ongoing issues in modeling and data analysis related to gonadotropin secretion in the field of both physiology and neuroendocrinology. They mention the different mathematical formalisms involved, their interest and limits. They also discuss open statistical questions in signal analysis associated with key endocrine issues and review recent advances in the modeling of the intracellular pathways activated by gonadotropins, which yields promising development for innovative approaches in drug discovery. Expert opinion: The greatest challenge to be tackled in computational modeling of pituitary gonadotropin signaling is the embedding of gonadotropin signaling within its natural multi-scale environment, from the single cell level, to the organic and whole HPG level. The development of modeling approaches of G protein-coupled receptor signaling, together with multicellular systems biology may lead to unexampled mechanistic understanding with critical expected fallouts in the therapeutic management of reproduction.

Resistin regulates reproductive hormone secretion from the ovine adenohypophysis depending on season.

Work in cattle and rodents has shown that resistin, in addition to its roles in insulin resistance and inflammation, is involved in the regulation of gonadal steroidogenesis. However, the role of resistin in the regulation of reproductive processes in other species, such as seasonally breeding sheep, is completely unknown. Herein, we tested the hypothesis that resistin can influence the secretion of anterior pituitary hormones and that its effect in ewes is dependent on the day length. Thirty Polish Longwool ewes, a breed that exhibits a strong seasonal reproductive pattern, were ovariectomized with estrogen replacement using subcutaneously inserted estradiol implants. Ewes were fed ad libitum and housed under a natural photoperiod (longitude: 19°57' E, latitude: 50° 04' N). Intravenous treatments consisted of control or recombinant bovine resistin (rbresistin) in saline: (1) control (saline; n = 10), (2) low resistin dose (1.0 µg/kg BW; n = 10), and (3) high resistin dose (10.0 µg/kg BW; n = 10). Experiments were conducted during both short-day (SD) and long-day (LD) seasons using 5 sheep per group within each season. Blood samples were collected every 10 min over 4 h. Blood plasma concentrations of FSH, LH, and prolactin (PRL) were assayed using RIA. A season × dose interaction was observed for all hormonal variables measured. Greater concentrations (P < 0.001) of LH and FSH were observed during SDs than during LDs in all groups. During SDs, the high dose (10 µg/kg BW) decreased (P < 0.001) basal LH levels and amplitude (P < 0.05) of LH pulses and increased (P < 0.001) circulating concentrations of FSH. However, the low dose of resistin decreased (P < 0.001) FSH concentrations compared to those of controls. During LDs, both the low and high resistin doses increased mean concentrations of LH (P < 0.001 and P < 0.05, respectively) and FSH (P < 0.001). A high dose of rbresistin increased (P < 0.001) the mean circulating concentrations of PRL during both seasons. However, in all groups, concentrations of PRL were greater during LDs than SDs. These results demonstrate for the first time that resistin is involved in the regulation of pituitary hormone secretion and that this effect is differentially mediated during LDs and SDs.