Neuroendocrine control of growth hormone secretion

Functional characterization of growth hormone releasing hormone and its receptor in amphioxus with implication for origin of hypothalamic-pituitary axis

Growth hormone-releasing hormone (GHRH) has been widely shown to stimulate growth hormone (GH) production via binding to GHRH receptor GHRHR in various species of vertebrates, but information regarding the functional roles of GHRH and GHRHR in the protochordate amphioxus remains rather scarce. We showed here that two mature peptides, BjGHRH-1 and BjGHRH-2, encoded by BjGHRH precursor, and a single BjGHRHR protein were identified in the amphioxus Branchiostoma. japonicum. Like the distribution profiles of vertebrate GHRHs and GHRHRs, both the genes Bjghrh and Bjghrhr were widely expressed in the different tissues of amphioxus, including in the cerebral vesicle, Hatschek's pit, neural tube, gill, hepatic caecum, notochord, testis and ovary. Moreover, both BjGHRH-1 and BjGHRH-2 interacted with BjGHRHR, and triggered the cAMP/PKA signal pathway in a dose-dependent manner. Importantly, BjGHRH-1 and BjGHRH-2 were both able to activate the expression of GH-like gene in the cells of Hatschek's pit. These indicate that a functional vertebrate-like GHRH-GHRHR axis had already emerged in amphioxus, which is a seminal innovation making physiological divergence including reproduction, growth, metabolism, stress and osmoregulation possible during the early evolution of vertebrates.

Growth hormone promotes myelin repair after chronic hypoxia via triggering pericyte-dependent angiogenesis

White matter injury (WMI) causes oligodendrocyte precursor cell (OPC) differentiation arrest and functional deficits, with no effective therapies to date. Here, we report increased expression of growth hormone (GH) in the hypoxic neonatal mouse brain, a model of WMI. GH treatment during or post hypoxic exposure rescues hypoxia-induced hypomyelination and promotes functional recovery in adolescent mice. Single-cell sequencing reveals that Ghr mRNA expression is highly enriched in vascular cells. Cell-lineage labeling and tracing identify the GHR-expressing vascular cells as a subpopulation of pericytes. These cells display tip-cell-like morphology with kinetic polarized filopodia revealed by two-photon live imaging and seemingly direct blood vessel branching and bridging. Gain-of-function and loss-of-function experiments indicate that GHR signaling in pericytes is sufficient to modulate angiogenesis in neonatal brains, which enhances OPC differentiation and myelination indirectly. These findings demonstrate that targeting GHR and/or downstream effectors may represent a promising therapeutic strategy for WMI.

Pathogenesis, clinical features, and treatment of plurihormonal pituitary adenoma

Plurihormonal pituitary adenoma (PPA) is a type of pituitary tumor capable of producing two or more hormones and usually presents as an aggressive, large adenoma. As yet, its pathogenesis remains unclear. This is the first study to systematically summarize the underlying pathogenesis of PPA. The pathogenesis is related to plurihormonal primordial stem cells, co-transcription factors, hormone co-expression, differential gene expression, and cell transdifferentiation. We conducted a literature review of PPA and analyzed its clinical characteristics. We found that the average age of patients with PPA was approximately 40 years, and most showed only one clinical symptom. The most common manifestation was acromegaly. Currently, PPA is treated with surgical resection. However, recent studies suggest that immunotherapy may be a potentially effective treatment.

Short Stature due to Bioinactive Growth Hormone (Kowarski Syndrome)

OBJECTIVE

Bioinactive growth hormone (BGH) is a structurally abnormal, biologically inactive, but immunoreactive form of growth hormone encoded by pathogenic growth hormone 1 gene variants. The underlying cause of the defective physiology is decreased BGH binding affinity to both growth hormone binding proteins and growth hormone receptors (GHRs). GHR cannot dimerize when it is in a quiescent state because BGH cannot activate it. Nondimerized GHR is unable to activate intracytoplasmic signaling pathway molecules such as Janus kinase 2 and signal transducer and activator of transcription, which initiate insulin-like growth factor-1 (IGF-1) transcription. IGF-1 cannot therefore be synthesized and IGF-1 levels in the circulation decrease. In contrast to children with growth hormone insensitivity, children with short stature due to BGH, known as Kowarski syndrome, exhibit an outstanding linear growth response to recombinant growth hormone therapy. For a number of reasons, differential diagnosis presents some difficulties. Similar diseases caused by genetic abnormalities that cause short stature range in severity from minor to severe clinical spectrum. Furthermore, some patients with Kowarski syndrome have previously been diagnosed with familial short stature, constitutional delayed puberty, and idiopathic short stature. This paper aims to review the particular clinical and laboratory findings of BGH.

METHODS

This study collected clinical and laboratory data from KS cases reported in the literature.

RESULTS

This review reports that KS cases have lower SDSs for height and IGF-1 compared to growth hormone deficiency.

CONCLUSION

The diversity of genetic defects underlying Kowarski syndrome (KS) will provide new insights into growth hormone insensitivity. As the availability of genetic analysis, including functional investigations expands, researchers will identify new underlying genetic pathways.

Role of Estrogen and Estrogen Receptor in GH-Secreting Adenomas

Acromegaly is a rare disease with several systemic complications that may lead to increased overall morbidity and mortality. Despite several available treatments, ranging from transsphenoidal resection of GH-producing adenomas to different medical therapies, complete hormonal control is not achieved in some cases. Some decades ago, estrogens were first used to treat acromegaly, resulting in a significant decrease in IGF1 levels. However, due to the consequent side effects of the high dose utilized, this treatment was later abandoned. The evidence that estrogens are able to blunt GH activity also derives from the evidence that women with GH deficiency taking oral estro-progestins pills need higher doses of GH replacement therapy. In recent years, the role of estrogens and Selective Estrogens Receptor Modulators (SERMs) in acromegaly treatment has been re-evaluated, especially considering poor control of the disease under first- and second-line medical treatment. In this review, we analyze the state of the art concerning the impact of estrogen and SERMs on the GH/IGF1 axis, focusing on molecular pathways and the possible implications for acromegaly treatment.

The multiple roles of GH in neural ageing and injury

Advanced age is typically associated with a decrease in cognitive function including impairment in the formation and retention of new memories. The hippocampus is critical for learning and memory, especially spatial learning, and is particularly affected by ageing. With advanced age, multiple neural components can be detrimentally affected including a reduction in the number of neural stem and precursor cells, a decrease in the formation of adult born neurons (neurogenesis), and deficits in neural circuitry, all of which ultimately contribute to impaired cognitive function. Importantly, physical exercise has been shown to ameliorate many of these impairments and is able to improve learning and memory. Relevantly, growth hormone (GH) is an important protein hormone that decreases with ageing and increases following physical exercise. Originally described due to its role in longitudinal growth, GH has now been identified to play several additional key roles, especially in relation to the brain. Indeed, the regular decrease in GH levels following puberty is one of the most well documented components of neuroendocrine ageing. Growth hormone deficiency (GHD) has been described to have adverse effects on brain function, which can be ameliorated via GH replacement therapy. Physical exercise has been shown to increase circulating GH levels. Furthermore, we recently demonstrated the increase in exercise-mediated GH is critical for improved cognitive function in the aged mouse. Here we examine the multiple roles that GH plays, particularly in the aged brain and following trauma, irradiation and stroke, and how increasing GH levels can ameliorate deficits in cognition.

NPFF signalling is critical for thermosensory and dietary regulation of thermogenesis

Thermogenesis is a centrally regulated physiological process integral for thermoregulation and energy homeostasis. However, the mechanisms and pathways involved remain poorly understood. Importantly, in this study we uncovered that in an environment of 28 °C that is within the mouse thermoneutral zone, lack of NPFF signalling leads to significant increases in energy expenditure, resting metabolic rate and brown adipose tissue (BAT) thermogenesis, which is associated with decreased body weight gain and lean tissue mass. Interestingly, when exposed to a high-fat diet (HFD) at 28 °C, Npff^-/- mice lost the high energy expenditure phenotype observed under chow condition and exhibited an impaired diet-induced thermogenesis. On the other hand, under conditions of increasing levels of thermal demands, Npff^-/- mice exhibited an elevated BAT thermogenesis at mild cold condition (22 °C), but initiated comparable BAT thermogenic responses as WT mice when thermal demand increased, such as an exposure to 4 °C. Together, these results reveal NPFF signalling as a novel and critical player in the control of thermogenesis, where it regulates thermosensory thermogenesis at warm condition and adjusts thermoregulation under positive energy balance to regulate diet-induced thermogenesis.

Increased GH Secretion and Body Growth in Mice Carrying Ablation of IGF-1 Receptor in GH-releasing Hormone Cells

Growth hormone (GH) secretion is controlled by short and long negative feedback loops. In this regard, both GH (short-loop feedback) and insulin-like growth factor 1 (IGF-1; long-loop feedback) can target somatotropic cells of the pituitary gland and neuroendocrine hypothalamic neurons to regulate the GH/IGF-1 axis. GH-releasing hormone (GHRH)-expressing neurons play a fundamental role in stimulating pituitary GH secretion. However, it is currently unknown whether IGF-1 action on GHRH-expressing cells is required for the control of the GH/IGF-1/growth axis. In the present study, we investigated the phenotype of male and female mice carrying ablation of IGF-1 receptor (IGF1R) exclusively in GHRH cells. After weaning, both male and female GHRHΔIGF1R mice exhibited increases in body weight, lean body mass, linear growth, and length of long bones (tibia, femur, humerus, and radius). In contrast, the percentage of body fat was similar between control and GHRHΔIGF1R mice. The higher body growth of GHRHΔIGF1R mice can be explained by increases in mean GH levels, GH pulse amplitude, and pulse frequency, calculated from 36 blood samples collected from each animal at 10-minute intervals. GHRHΔIGF1R mice also showed increased hypothalamic Ghrh mRNA levels, pituitary Gh mRNA expression, hepatic Igf1 expression, and serum IGF-1 levels compared with control animals. Furthermore, GHRHΔIGF1R mice displayed significant alterations in the sexually dimorphic hepatic gene expression profile, with a prevailing feminization in most genes analyzed. In conclusion, our findings indicate that GHRH neurons represent a key and necessary site for the long-loop negative feedback that controls the GH/IGF-1 axis and body growth.

The Effect of Diurnal Variation on Laboratory Tests

Objective: Commonly used biochemical tests in blood samples may be measured at any time of day. This study investigated the existence and clinical significance of diurnal variations in some of routine parameters to facilitate accurate and reliable decision-making in diagnosis and follow-up. Materials and Methods: Blood samples were collected from 17 healthy volunteers who were 18-50 years of age (11 men, 6 women) on the same day at 9:00 am, 12:00 am, 3:00 pm, 6:00 pm, and 12:00 pm. Samples collected at 9:00 am were regarded as baseline. The results of 19 biochemical parameters in blood samples obtained at 12.00 am, 3.00 pm, 6.00 pm and 12.00 pm were statistically and clinically compared with the results at 9.00 am baseline sample. Results: Total protein, creatinine, aspartate transaminase, alanine transaminase, alkaline phosphatase and gamma glutamyl transferase showed no clinically significant variation within the day, but clinically significant changes were observed in levels of glucose, total cholesterol, HDL-cholesterol, triglyceride, total bilirubin (TBIL), direct bilirubin (DBIL), albumin, blood urea nitrogen, uric acid, sodium, potassium, chloride and amylase. Especially, BUN changed by maximum 20-30%, TBIL, DBIL and triglyceride maximum 40-50% within the day. Conclusion: The results of our study suggest that clinicians should consider the timing of blood sampling and the diurnal variations in BUN, TBIL, DBIL and triglyceride parameters during diagnosis and treatment follow-up. Sampling throughout the day seems to pose no problem for other tests with limited diurnal variation.

Ablation of Growth Hormone Receptor in GABAergic Neurons Leads to Increased Pulsatile Growth Hormone Secretion

Growth hormone (GH) acts in several hypothalamic neuronal populations to modulate metabolism and the autoregulation of GH secretion via negative-feedback loops. However, few studies have investigated whether GH receptor (GHR) expression in specific neuronal populations is required for the homeostatic control of GH secretion and energy homeostasis. In the present study, we investigated the consequences of the specific GHR ablation in GABAergic (VGAT-expressing) or glutamatergic (VGLUT2-expressing) cells. GHR ablation in GABAergic neurons led to increased GH secretion, lean mass, and body growth in male and female mice. VGAT-specific GHR knockout (KO) male mice also showed increased serum insulin-like growth factor-1, hypothalamic Ghrh, and hepatic Igf1 messenger RNA levels. In contrast, normal GH secretion, but reduced lean body mass, was observed in mice carrying GHR ablation in glutamatergic neurons. GHR ablation in GABAergic cells increased weight loss and led to decreased blood glucose levels during food restriction, whereas VGLUT2-specific GHR KO mice showed blunted feeding response to 2-deoxy-D-glucose both in males and females, and increased relative food intake, oxygen consumption, and serum leptin levels in male mice. Of note, VGLUT2-cre female mice, independently of GHR ablation, exhibited a previously unreported phenotype of mild reduction in body weight without further metabolic alterations. The autoregulation of GH secretion via negative-feedback loops requires GHR expression in GABAergic cells. Furthermore, GHR ablation in GABAergic and glutamatergic neuronal populations leads to distinct metabolic alterations. These findings contribute to the understanding of the neuronal populations responsible for mediating the neuroendocrine and metabolic effects of GH.

Circadian clock, diurnal glucose metabolic rhythm, and dawn phenomenon

The circadian clock provides cue-independent anticipatory signals for diurnal rhythms of baseline glucose levels and glucose tolerance. The central circadian clock is located in the hypothalamic suprachiasmatic nucleus (SCN), which comprises primarily GABAergic neurons. The SCN clock regulates physiological diurnal rhythms of endogenous glucose production (EGP) and hepatic insulin sensitivity through neurohumoral mechanisms. Disruption of the molecular circadian clock is associated with the extended dawn phenomenon (DP) in type 2 diabetes (T2D), referring to hyperglycemia in the early morning without nocturnal hypoglycemia. The DP affects nearly half of patients with diabetes, with poorly defined etiology and a lack of targeted therapy. Here we review neural and secreted factors in physiological diurnal rhythms of glucose metabolism and their pathological implications for the DP.

Effects of the Isolated and Combined Ablation of Growth Hormone and IGF-1 Receptors in Somatostatin Neurons

Hypophysiotropic somatostatin (SST) neurons in the periventricular hypothalamic area express growth hormone (GH) receptor (GHR) and are frequently considered as the key neuronal population that mediates the negative feedback loop controlling the hypothalamic-GH axis. Additionally, insulin-like growth factor-1 (IGF-1) may also act at the hypothalamic level to control pituitary GH secretion via long-loop negative feedback. However, to the best of our knowledge, no study so far has tested whether GHR or IGF-1 receptor (IGF1R) signaling specifically in SST neurons is required for the homeostatic control of GH secretion. Here we show that GHR ablation in SST neurons did not impact the negative feedback mechanisms that control pulsatile GH secretion or body growth in male and female mice. The sex difference in hepatic gene expression profile was only mildly affected by GHR ablation in SST neurons. Similarly, IGF1R ablation in SST neurons did not affect pulsatile GH secretion, body growth, or hepatic gene expression. In contrast, simultaneous ablation of both GHR and IGF1R in SST-expressing cells increased mean GH levels and pulse amplitude in male and female mice, and partially disrupted the sex differences in hepatic gene expression. Despite the increased GH secretion in double knockout mice, no alterations in body growth and serum or liver IGF-1 levels were observed. In summary, GHR and IGF1R signaling in SST neurons play a redundant role in the control of GH secretion. Furthermore, our results reveal the importance of GH/IGF-1 negative feedback mechanisms on SST neurons for the establishment of sex differences in hepatic gene expression profile.

Evaluation of Weight Gain, Clinicopathological and Radiographic Changes after Early Diagnosis and Treatment of Congenital Hypothyroidism in Cats

Congenital hypothyroidism is uncommon in cats. This case report describes weight gain, clinicopathological and radiographic changes after early diagnosis and treatment of congenital hypothyroidism in three British shorthair cats’ siblings. Data were assessed at 53 (diagnosis), 83, 185 and 365 days of age. Correlations between serum insulin-like growth factor-1 (IGF-1) and body weight, levothyroxine dose, total thyroxine, and thyroid-stimulating hormone concentrations were evaluated. The body weights of the congenital hypothyroid kittens were compared with those of their two healthy siblings and British shorthair kittens of the same age. At diagnosis, the congenital hypothyroid kittens showed a significantly lower body weight compared to the healthy siblings (p = 0.03). After diagnosis, oral levothyroxine supplementation was started. The difference in body weight was no longer observed after one month of treatment. The clinical signs, clinicopathological and radiographic abnormalities ameliorated after one month of treatment. IGF-1 concentration was significantly positively correlated with body weight (rs = 0.80, p < 0.002). In conclusion, resolution of the clinical signs, achieving a consistent within-breed weight, and improvement of the clinicopathological and radiographic parameters demonstrated the importance of the early diagnosis and treatment of feline congenital hypothyroidism.

Antidepressants as Endocrine Disrupting Compounds in Fish

As antidepressant usage by the global population continues to increase, their persistent detection in aquatic habitats from municipal wastewater effluent release has led to concerns of possible impacts on non-target organisms, including fish. These pharmaceuticals have been marketed as mood-altering drugs, specifically targeting the monoaminergic signaling in the brain of humans. However, the monoaminergic systems are highly conserved and involved in the modulation of a multitude of endocrine functions in vertebrates. While most studies exploring possible impact of antidepressants on fish have focused on behavioural perturbations, a smaller spotlight has been placed on the endocrine functions, especially related to reproduction, growth, and the stress response. The purpose of this review is to highlight the possible role of antidepressants as endocrine disruptors in fish. While studies linking the effects of environmentally relevant levels of antidepressant on the endocrine system in fish are sparse, the emerging evidence suggests that early-life exposure to these compounds have the potential to alter the developmental programming of the endocrine system, which could persist as long-term and multigenerational effects in teleosts.

Effects of growth hormone-releasing hormone receptor antagonist MIA-602 in mice with emotional disorders: a potential treatment for PTSD

Anxiety and depression have been suggested to increase the risk for post-traumatic stress disorders (PTSD). A link between all these mental illnesses, inflammation and oxidative stress is also well established. Recent behavior studies by our group clearly demonstrate a powerful anxiolytic and antidepressant-like effects of a novel growth hormone releasing hormone (GHRH) antagonist of MIAMI class, MIA-690, probably related to modulatory effects on the inflammatory and oxidative status. In the present work we investigated the potential beneficial effects of MIA-602, another recently developed GHRH antagonist, in mood disorders, as anxiety and depression, and the possible brain pathways involved in its protective activity, in adult mice. MIA-602 exhibited antinflammatory and antioxidant effects in ex vivo and in vivo experimental models, inducing anxiolytic and antidepressant-like behavior in mice subcutaneously treated for 4 weeks. The beneficial effect of MIA-602 on inflammatory and oxidative status and synaptogenesis resulting in anxiolytic and antidepressant-like effects could be related by increases of nuclear factor erythroid 2-related factor 2 (Nrf2) and of brain-derived neurotrophic factor (BDNF) signaling pathways in the hippocampus and prefrontal cortex. These results strongly suggest that GHRH analogs should be tried clinically for the treatment of mood disorders including PTSD.

Cysteamine administration in lambs grazing on mountain pastures: Effects on the body weight, antioxidant capacity, thyroid hormones and growth hormone secretion

This study aimed to evaluate the effects of intravenous injection of cysteamine (CS) on body weight (BW), growth hormone (GH), thyroid hormones (TH) secretion, and antioxidant status of growing lambs grazing on mountain pastures. Fifteen lambs (3-4 months of age) were randomly allocated into three experimental groups which received different dosages of CS: 0, 20, and 50 mg/kg BW^-1 . The CS was injected on the 1st, 10th^, and 20th days of the experiment to the lambs through the jugular vein. Assessment of plasma concentration of GH and TH hormones was carried out at days 0 (a day before the start of CS injections), 15, and 30 of the experiment. The antioxidant enzymes were measured at the end of the experiment. Lambs were weighed at days 0, 10, 20, and 30 of the experiment. The results showed that treatment and time affected the BW, GH, triiodothyronine (T₃ ), and tetraiodothyronine (T₄ ) secretion. The intravenous injection of CS increased the BW of growing lambs (p < 0.01) and increased the plasma concentration of GH, T3, and T4 (p < 0.01). The treatment also enhanced glutathione peroxidase (GSH-Px; p < 0.05) and reduced malondialdehyde concentrations (MDA; p < 0.01). Total antioxidant capacity (T-AOC) level reduced in CS-1 treatment compared to GC and CS-2 treatments (p < 0.01). The levels of superoxide dismutase (SOD) and catalase (CAT) were not affected by CS. In conclusion, intravenous injection of CS improved BW, GH, and TH concentrations and antioxidant capacity in growing lambs grazing on mountain pastures.

Insulin-like Growth Factor 1 Signaling in Mammalian Hearing

Insulin-like growth factor 1 (IGF-1) is a peptide hormone belonging to the insulin family of proteins. Almost all of the biological effects of IGF-1 are mediated through binding to its high-affinity tyrosine kinase receptor (IGF1R), a transmembrane receptor belonging to the insulin receptor family. Factors, receptors and IGF-binding proteins form the IGF system, which has multiple roles in mammalian development, adult tissue homeostasis, and aging. Consequently, mutations in genes of the IGF system, including downstream intracellular targets, underlie multiple common pathologies and are associated with multiple rare human diseases. Here we review the contribution of the IGF system to our understanding of the molecular and genetic basis of human hearing loss by describing, (i) the expression patterns of the IGF system in the mammalian inner ear; (ii) downstream signaling of IGF-1 in the hearing organ; (iii) mouse mutations in the IGF system, including upstream regulators and downstream targets of IGF-1 that inform cochlear pathophysiology; and (iv) human mutations in these genes causing hearing loss.

Dietary selenium promotes the growth performance through growth hormone-insulin-like growth factor and hypothalamic-pituitary-thyroid axes in grass carp (Ctenopharyngodon idella)

Selenium (Se), an essential component of deiodinases (DIOs), regulates the contents of thyroid hormones and thus improves animal growth. To explore the influences of selenium supplementation on fish growth metabolism, a total of 270 healthy grass carp (Ctenopharyngodon idella) were divided into three groups and feed three graded dietary selenium (0.141, 0.562, and 1.044 mg Se/kg) levels. The results showed that after 60-day feeding, dietary selenium improved the final body weight and specific growth rate (SGR) of grass carp. The hepatic DIO activities in selenium-supplemented groups were higher than those in control group. A significant increase in triiodothyronine (T3), free triiodothyronine (FT3), and thyroid-stimulating hormone (TSH) levels was accompanied by a decrease in the contents of thyroxine (T4) and free thyroxine (FT4) in selenium-supplemented groups. The histopathological observation of thyroid suggested that selenium deficiency resulted in hypertrophy of follicular epithelial cells. Moreover, the gene relative expression levels of dio1, dio2, and dio3 showed an increasing trend with the rising concentration of dietary selenium. The transcription levels of HPT axis-related genes (crh, tsh-β, ttr, tr-s, tpo, nis) and GH/IGF1-related genes (gh, ghr, igf1, igf1r) were significantly upregulated in selenium-supplemented groups. No significant differences in the above indicators were observed between 0.562 and 1.044 mg Se/kg diet group except T3 content and dio1 relative expression ratio. These results indicate that dietary selenium supplementation improves the hepatic DIO activities and thyroid hormone metabolism and regulates the transcription levels of HPT and GH/IGF axis-related genes, which may be responsible for the growth promotion in grass carp.

Tris(1,3-dichloro-2-propyl)phosphate Reduces Growth Hormone Expression via Binding to Growth Hormone Releasing Hormone Receptors and Inhibits the Growth of Crucian Carp

Tris(1,3-dichloro-2-propyl)phosphate (TDCIPP) has commonly been used as an additive flame retardant and frequently detected in the aquatic environment and in biological samples worldwide. Recently, it was found that exposure to TDCIPP inhibited the growth of zebrafish, but the relevant molecular mechanisms remained unclear. In this study, 5 day-old crucian carp (Carassius auratus) larvae were treated with 0.5, 5, or 50 μg/L TDCIPP for 90 days; the effect on growth was evaluated; and related molecular mechanisms were explored. Results demonstrated that 5 or 50 μg/L TDCIPP treatment significantly inhibited the growth of crucian carp and downregulated the expression of growth hormones (ghs), growth hormone receptor (ghr), and insulin-like growth factor 1 (igf1). Molecular docking, dual-luciferase reporter gene assay, and in vitro experiments demonstrated that TDCIPP could bind to the growth hormone releasing hormone receptor protein of crucian carp and disturb the stimulation of growth hormone releasing hormone to the expression of ghs, resulting in the decrease of the mRNA level of gh1 and gh2 in pituitary cells. Our findings provide new perceptions into the molecular mechanisms of developmental toxicity of TDCIPP in fish.

The Roles of Neuropeptide Y (Npy) and Peptide YY (Pyy) in Teleost Food Intake: A Mini Review

Neuropeptide Y family (NPY) is a potent orexigenic peptide and pancreatic polypeptide family comprising neuropeptide Y (Npy), peptide YYa (Pyya), and peptide YYb (Pyyb), which was previously known as peptide Y (PY), and tetrapod pancreatic polypeptide (PP), but has not been exhaustively documented in fish. Nonetheless, Npy and Pyy to date have been the key focus of countless research studies categorizing their copious characteristics in the body, which, among other things, include the mechanism of feeding behavior, cortical neural activity, heart activity, and the regulation of emotions in teleost. In this review, we focused on the role of neuropeptide Y gene (Npy) and peptide YY gene (Pyy) in teleost food intake. Feeding is essential in fish to ensure growth and perpetuation, being indispensable in the aquaculture settings where growth is prioritized. Therefore, a better understanding of the roles of these genes in food intake in teleost could help determine their feeding regime, regulation, growth, and development, which will possibly be fundamental in fish culture.

Early Life Nociception is Influenced by Peripheral Growth Hormone Signaling

A number of cellular systems work in concert to modulate nociceptive processing in the periphery, but the mechanisms that regulate neonatal nociception may be distinct compared with adults. Our previous work indicated a relationship between neonatal hypersensitivity and growth hormone (GH) signaling. Here, we explored the peripheral mechanisms by which GH modulated neonatal nociception under normal and injury conditions (incision) in male and female mice. We found that GH receptor (GHr) signaling in primary afferents maintains a tonic inhibition of peripheral hypersensitivity. After injury, a macrophage dependent displacement of injury-site GH was found to modulate neuronal transcription at least in part via serum response factor (SRF) regulation. A single GH injection into the injured hindpaw muscle effectively restored available GH signaling to neurons and prevented acute pain-like behaviors, primary afferent sensitization, and neuronal gene expression changes. GH treatment also inhibited long-term somatosensory changes observed after repeated peripheral insult. Results may indicate a novel mechanism of neonatal nociception.SIGNIFICANCE STATEMENT Although it is noted that mechanisms of pain development in early life are unique compared with adults, little research focuses on neonatal-specific peripheral mechanisms of nociception. This gap is evident in the lack of specialized care for infants following an injury including surgeries. This report evaluates how distinct cellular systems in the periphery including the endocrine, immune and nervous systems work together to modulate neonatal-specific nociception. We uncovered a novel mechanism by which muscle injury induces a macrophage-dependent sequestration of peripheral growth hormone (GH) that effectively removes its normal tonic inhibition of neonatal nociceptors to promote acute pain-like behaviors. Results indicate a possible new strategy for treatment of neonatal postsurgical pain.

Morphological and Functional Changes of Pituitary GH and PRL Cells Following Prolonged Exposure of Female Rats to Constant Light

Light regulates numerous physiological functions including secretion of different hormones. Our aim was to determine morphological and functional changes of the pituitary growth hormone (GH) and prolactin (PRL) producing cells in female rats exposed to constant light regime from the peripubertal to adult period of life. Starting from the thirtieth postnatal day, female Wistar rats were exposed to constant light (600 lx) for the following 95 days. Controls were maintained under the regular laboratory lighting conditions. The GH and PRL cells were immunohistochemically visualized. Changes in cell volumes and volume densities were evaluated by stereology. Concentrations of PRL and GH in circulation were also determined. We detected significant decrease of the GH cell volume and volume density, followed by reduced the GH blood concentration in comparison to the controls. In contrast, PRL cells were larger in size and their volume density was significantly increased when compared to the controls. Accordingly, PRL concentration was elevated. It can be concluded that exposure of female rats to constant light regime, from peripubertal to adult period of life, causes inhibition of the pituitary GH and stimulation of PRL cells.

The prevalence of silent acromegaly in prolactinomas is very low

PURPOSE

The aim of this study was to evaluate the somatotroph axis in a large series of patients with prolactinoma to verify the prevalence of silent acromegaly in this population.

METHODS

A hundred and forty-four patients were enrolled in a multicenter study: 90 were already on cabergoline (CAB) and enrolled in a cross-sectional arm (group A) with random PRL, GH and IGF-I determination on treatment (≥ 3 months), whereas 54 untreated patients were enrolled at diagnosis in a prospective arm (group B) with PRL, GH and IGF-I measurement before and after 6 and 12 months of treatment. In the presence of high IGF-I, CAB was withdrawn for 3 months and GH, IGF-I, PRL and GH during an oral Glucose Tolerance Test (OGTT) were obtained.

RESULTS

High IGF-I levels (ULN 1.01-1.56) were observed in 9 patients (6.25%, 5F). After CAB withdrawal, IGF-I levels normalized in 5/9 patients, GH was < 0.4 ng/ml after OGTT in 7/9 cases or at random GH determination in one case. After CAB re-introduction, IGF-I levels re-increased in a single case. Overall, a single young female patient harboring a macroadenoma in group A was diagnosed with silent acromegaly and underwent successful transsphenoidal removal of a GH/PRL-secreting adenoma.

CONCLUSION

The prevalence of silent acromegaly in prolactinomas (0.7%) is lower than previously reported and OGTT is helpful to recognize silent acromegaly. We suggest that the somatotroph axis should be evaluated at diagnosis in all cases and not systematically during follow-up.

CircAgtpbp1 Acts as a Molecular Sponge of miR-543-5p to Regulate the Secretion of GH in Rat Pituitary Cells

CircRNAs have been identified to be expressed differently and stably in numerous species and tissues, but their functions in growth hormone (GH) secretion are still largely unknown. In summary, we have revealed a circRNA-miRNA-mRNA network that may play a biological role in the rat pituitary gland. First, we verified the chromosome location information of circAgtpbp1 according to sequencing analysis. The circAgtpbp1 characteristics were authenticated through PCR, qRT-PCR, treating with RNase and fluorescent in situ hybridization (FISH). Second, we detected the expression pattern of circAgtpbp1 in the rat anterior pituitary by qRT-PCR. We also designed circAgtpbp1 siRNA and constructed overexpression plasmid to evaluate the effect of circAgtpbp1 function on GH secretion by qRT-PCR, ELISA and Western blot. CircAgtpbp1 is a stable, truly circular molecule. We found that circAgtpbp1 interacted with miR-543-5p and can regulate GH secretion in pituitary cells through a circAgtpbp1-miR-543-5p-GH axis. Overall, the evidence generated by our study suggests that circAgtpbp1 can act as a sponge of miR-543-5p to reduce the inhibitory effect of miR-543-5p on Gh1 and further promote GH secretion. These findings expand our existing knowledge on the mechanisms of hormone regulation in the pituitary gland.

Mice with an RGS-insensitive Gαi2 protein show growth hormone axis dysfunction

Mice carrying an RGS-insensitive Gαi2 mutation display growth retardation early after birth. Although the growth hormone (GH)-axis is a key endocrine modulator of postnatal growth, its functional state in these mice has not been characterized. The present study was undertaken to address this issue. Results revealed that pituitary mRNA levels for GH, prolactin (PRL), somatostatin (SST), GH-releasing-hormone receptor (GHRH-R) and GH secretagogue receptor (GHS-R) were decreased in mutants compared to controls. These changes were reflected by a significant decrease in plasma levels of GH, IGF-1 and IGF-binding protein-3 (IGFBP-3). Mutants were also less responsive to GHRH and ghrelin (GhL) on GH stimulation of release from pituitary primary cell cultures. In contrast, they were more sensitive to the inhibitory effect of SST. These data provide the first evidence for an alteration of the functional state of the GH-axis in Gαi2G184S mice that likely contributes to their growth retardation.

Molecular cloning and functional characterization of growth hormone-releasing hormone in Mastacembelus armatus

Growth hormone-releasing hormone (GHRH) is a neuropeptide that controls growth hormone (GH) synthesis and release. In this study, the full-length cDNA of Mastacembelus armatus ghrh was obtained by rapid amplification of cDNA ends method. Sequence analysis showed that the cloned sequence is 1090 bp in length, containing an open reading frame (ORF) of 429 bp that encodes a precursor protein of 142 amino acids. Sequence alignment revealed that the 27-amino acid mature peptide of Ghrh in M. armatus is conserved. Real-time PCR showed that ghrh is highly expressed in the brain, with very low or no expression in other tissues. During embryonic and larval development, ghrh expression was low in embryos but increased gradually in the stages of larval development. The biological function of Ghrh peptide was further investigated in vivo. Ghrh injection could significantly upregulate the mRNA expression of growth hormone (gh) and insulin-like growth factor-1/2 (igf-1/2) in M. armatus. Our data indicate that Ghrh is able to activate the GH-IGFs axis in M. armatus.

The impact of endocrine-disrupting chemical exposure in the mammalian hypothalamic-pituitary axis

The hypothalamic-pituitary axis (HP axis) plays a critical and integrative role in the endocrine system control to maintain homeostasis. The HP axis is responsible for the hormonal events necessary to regulate the thyroid, adrenal glands, gonads, somatic growth, among other functions. Endocrine-disrupting chemicals (EDCs) are a worldwide public health concern. There is growing evidence that exposure to EDCs such as bisphenol A (BPA), some phthalates, polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs) and biphenyls (PBBs), dichlorodiphenyltrichloroethane (DDT), tributyltin (TBT), and atrazine (ATR), is associated with HP axis abnormalities. EDCs act on hormone receptors and their downstream signaling pathways and can interfere with hormone synthesis, metabolism, and actions. Because the HP axis function is particularly sensitive to endogenous hormonal changes, disruptions by EDCs can alter HP axis proper function, leading to important endocrine irregularities. Here, we review the evidence that EDCs could directly affect the mammalian HP axis function.

Circulating LEAP-2 is associated with puberty in girls

BACKGROUND/OBJECTIVES

Liver-expressed antimicrobial peptide 2 (LEAP-2) was recently identified as an endogenous non-competitive allosteric antagonist of the growth hormone secretagogue receptor 1a (GHSR1a). LEAP-2 blunts ghrelin-induced feeding and its plasma levels are modulated in response to nutritional status in humans. Despite the relevant role of ghrelin in childhood, puberty, and childhood obesity, the potential implication of LEAP-2 in these aspects remains totally unknown. We aimed to investigate the regulation of circulating plasma LEAP-2 in childhood and adolescent either lean or obese.

METHODS AND RESULTS

Plasma levels of LEAP-2 were analyzed in a cross-sectional study with lean and obese children and adolescents (n = 150). Circulating LEAP-2 levels were significantly higher in girls than in boys independently of whether they were obese or lean. In addition, LEAP-2 was significantly increased (p < 0.001) in pubertal than in prepubertal girls, while no changes were found in boys between both developmental stages. Moreover, in girls LEAP-2 was positively correlated with insulin, IGF-1, HOMA-IR and triglycerides and negatively with ghrelin. In boys, LEAP-2 was positively correlated with leptin and negatively with vitamin D levels.

CONCLUSION

This study reveals a sexual dimorphism in LEAP-2 levels in children and adolescents. These changes and the higher levels during puberty imply that LEAP-2 may contribute to some of the biological adaptations occurring during pubertal development in terms of food intake, energy balance, growth rate, and puberty onset. Future studies assessing LEAP-2 levels in longitudinal studies and its implications in growth rate, puberty onset, and reproductive hormones will help to understand the relevance of this hormone in this stage of life.

Crosstalk between the growth hormone/insulin-like growth factor-1 axis and the gut microbiome: A new frontier for microbial endocrinology

Both the GH/IGF-1 axis and the gut microbiota independently play an important role in host growth, metabolism, and intestinal homeostasis. Inversely, abnormalities in GH action and microbial dysbiosis (or a lack of diversity) in the gut have been implicated in restricted growth, metabolic disorders (such as chronic undernutrition, anorexia nervosa, obesity, and diabetes), and intestinal dysfunction (such as pediatric Crohn's disease, colonic polyps, and colon cancer). Over the last decade, studies have demonstrated that the microbial impact on growth may be mediated through the GH/IGF-1 axis, pointing toward a potential relationship between GH and the gut microbiota. This review covers current research on the GH/IGF-1 axis and the gut microbiome and its influence on overall host growth, metabolism, and intestinal health, proposing a bidirectional relationship between GH and the gut microbiome.

Physiological and metabolic features of mice with CRISPR/Cas9-mediated loss-of-function in growth hormone-releasing hormone

Our previous study demonstrated that the loss of growth hormone releasing hormone (GHRH) results in increased lifespan and improved metabolic homeostasis in the mouse model generated by classical embryonic stem cell-based gene-targeting method. In this study, we targeted the GHRH gene using the CRISPR/Cas9 technology to avoid passenger alleles/mutations and performed in-depth physiological and metabolic characterization. In agreement with our previous observations, male and female GHRH-/- mice have significantly reduced body weight and enhanced insulin sensitivity when compared to wild type littermates. Dual-energy X-ray absorptiometry showed that there were significant decreases in lean mass, bone mineral content and density, and a dramatic increase in fat mass of GHRH-/- mice when compared to wild type littermates. Indirect calorimetry measurements showed dramatic reductions in oxygen consumption, carbon dioxide production and energy expenditure in GHRH-/- mice compared to wild type mice in both light and dark cycles. Respiratory exchange ratio was significantly lower in GHRH-/- mice during the light cycle, but not during the dark cycle, indicating a circadian related metabolic shift towards fat utilization in the growth hormone deficient mice. The novel CRISPR/Cas9 GHRH-/- mice are exhibiting the consistent and unique physiological and metabolic characteristics, which might mediate the longevity effects of growth hormone deficiency in mice.

Early Recovery of Height Velocity in Prepubertal Children With Acute Lymphoblastic Leukemia Treated by a Short Intensive Phase Without Cranial Radiation Therapy

PURPOSE

There have been few reports on height disturbance in childhood acute lymphoblastic leukemia (ALL) patients treated without cranial radiation therapy (CRT). Our study aimed to clarify the critical period of growth in pediatric patients who were treated by the Japan Childhood Leukemia Study (JACLS) ALL-02 protocol, which involved short-term intensive treatment without CRT.

PATIENTS AND METHODS

A retrospective, cohort study was conducted for prepubertal children with B-precursor ALL who were diagnosed from July 2002 to November 2011 and treated by the JACLS ALL-02 protocol at Oita University Hospital. The heights were chronologically measured at pretreatment, after the intensive phase (INT), at the end of treatment (END), and at 1 to 5 year(s) posttreatment (POST 1 to 5).

RESULTS

Nine boys and 4 girls were enrolled. Z score of the height was reduced at INT and END. Delta Z scores of the height and Z score of height velocity were reduced from pretreatment to INT, and they demonstrated an early recovery during maintenance treatment in INT to END.

CONCLUSIONS

Early recovery of delta Z scores of the height and Z score of height velocity was observed during the INT to END period. The shortened intensive phase without CRT may result in an adequate height in prepubertal ALL patients.

Proteomic analysis reveals sex-specific biomarker signature in postural orthostatic tachycardia syndrome

Background

Postural orthostatic tachycardia syndrome (POTS) is a variant of cardiovascular (CV) autonomic disorder of unknown etiology characterized by an excessive heart rate increase on standing and orthostatic intolerance. In this study we sought to identify novel CV biomarkers potentially implicated in POTS pathophysiology.

Methods

We conducted a nested case-control study within the Syncope Study of Unselected Population in Malmö (SYSTEMA) cohort including 396 patients (age range, 15–50 years) with either POTS (n = 113) or normal hemodynamic response during passive head-up-tilt test (n = 283). We used a targeted approach to explore changes in cardiovascular proteomics associated with POTS through a sequential two-stage process including supervised principal component analysis and univariate ANOVA with Bonferroni correction.

Results

POTS patients were younger (26 vs. 31 years; p < 0.001) and had lower BMI than controls. The discovery algorithm identified growth hormone (GH) and myoglobin (MB) as the most specific biomarker fingerprint for POTS. Plasma level of GH was higher (9.37 vs 8.37 of normalised protein expression units (NPX); p = 0.002), whereas MB was lower (4.86 vs 5.14 NPX; p = 0.002) in POTS compared with controls. In multivariate regression analysis, adjusted for age and BMI, and stratified by sex, lower MB level in men and higher GH level in women remained independently associated with POTS.

Conclusions

Cardiovascular proteomics analysis revealed sex-specific biomarker signature in POTS featured by higher plasma level of GH in women and lower plasma level of MB in men. These findings point to sex-specific immune-neuroendocrine dysregulation and deconditioning as potentially key pathophysiological traits underlying POTS.

Growth hormone-releasing hormone promotes therapeutic effects of peripheral blood endothelial progenitor cells in ischemic repair

PURPOSE

In peripheral artery disease, blockage of the blood supply to the limbs leads to blood flow attenuation and tissue ischemia. We investigated whether growth hormone-releasing hormone (GHRH) could enhance the biological functions and therapeutic effects of endothelial progenitor cells (EPCs) derived from adult human peripheral blood (PB).

METHODS

EPCs were isolated from human PB (PB-EPCs) and cord blood and expanded in vitro. PB-EPCs incubated with or without GHRH were evaluated for proliferation, migration, and angiogenesis capacity and apoptosis rates under oxidative stress conditions. Activation of STAT3 and Akt pathways was evaluated using Western blot. A hind-limb ischemia (HLI) mouse model was used to study the efficacy of GHRH in improving EPC therapy in vivo.

RESULTS

GHRH enhanced the proliferation, migration, and angiogenesis capacity of PB-EPCs and reduced apoptosis under H₂O₂ stimulation. These beneficial effects were GHRH receptor-dependent and were paralleled by increased phosphorylation of STAT3 and Akt. Transplantation of GHRH-preconditioned EPCs into HLI model mice enhanced blood flow recovery by increasing vascular formation density and enhanced tissue regeneration at the lesion site.

CONCLUSION

Our studies demonstrate a novel role for GHRH in dramatically improving therapeutic angiogenesis in HLI by enhancing the biological functions of EPCs. These findings support additional studies to explore the full potential of GHRH in augmenting cell therapy for the management of ischemia.

How treatments with endocrine and metabolic drugs influence pituitary cell function

A variety of endocrine and metabolic signals regulate pituitary cell function acting through the hypothalamus-pituitary neuroendocrine axes or directly at the pituitary level. The underlying intracellular transduction mechanisms in pituitary cells are still debated. AMP-activated protein kinase (AMPK) functions as a cellular sensor of low energy stores in all mammalian cells and promotes adaptive changes in response to calorie restriction. It is also regarded as a target for therapy of proliferative disorders. Various hormones and drugs can promote tissue-specific activation or inhibition of AMPK by enhancing or inhibiting AMPK phosphorylation, respectively. This review explores the preclinical studies published in the last decade that investigate the role of AMP-activated protein kinase in the intracellular transduction pathways downstream of endocrine and metabolic signals or drugs affecting pituitary cell function, and its role as a target for drug therapy of pituitary proliferative disorders. The effects of the hypoglycemic agent metformin, which is an indirect AMPK activator, are discussed. The multiple effects of metformin on cell metabolism and cell signalling and ultimately on cell function may be either dependent or independent of AMPK. The in vitro effects of metformin may also help highlighting differences in metabolic requirements between pituitary adenomatous cells and normal cells.

Antinflammatory, antioxidant, and behavioral effects induced by administration of growth hormone-releasing hormone analogs in mice

Growth hormone-releasing hormone (GHRH) antagonist MIA-690 and GHRH agonist MR-409, previously synthesized and developed by us have demonstrated potent antitumor effects. However, little is known about the effects of these analogs on brain functions. We investigated the potential antinflammatory and antioxidant effects of GHRH antagonist MIA-690 and GHRH agonist MR-409, on isolated mouse prefrontal cortex specimens treated with lipopolysaccharide (LPS). Additionally, we studied their effects on emotional behavior after chronic in vivo treatment. Ex vivo, MIA-690 and MR-409 inhibited LPS-induced inflammatory and pro-oxidative markers. In vivo, both MIA-690 and MR-409 induced anxiolytic and antidepressant-like effects, increased norepinephrine and serotonin levels and decreased nuclear factor-kB, tumor necrosis factor-α and interleukin-6 gene expression in prefrontal cortex. Increased nuclear factor erythroid 2–related factor 2 expression was also found in mice treated with MIA-690 and MR-409. MIA-690 showed higher efficacy in inhibiting all tested inflammatory and oxidative markers. In addition, MR-409 induced a down regulation of the gene and protein expression of pituitary-type GHRH-receptor in prefrontal cortex of mice after 4 weeks of treatment at 5 µg/day. In conclusion, our results demonstrate anxiolytic and antidepressant-like effects of GHRH analogs that could involve modulatory effects on monoaminergic signaling, inflammatory and oxidative status.

Rhythmic growth hormone secretion in physiological and pathological conditions: Lessons from rodent studies

Evolutionally conserved in all mammalians, the release of GH occurs in a rhythmic pattern, characterized by several dominant surges (pulsatile GH) with tonic low inter-pulse levels (tonic GH). Such pulsatile secretion pattern is essential for many physiological actions of GH on different tissues with defined gender dimorphism. Rhythmic release of pulsatile GH is tightly controlled by hypothalamic neurons as well as peripheral metabolic factors. Changes of GH pattern occur within a range of sophisticated physiological and pathological settings and significantly contribute to growth, ageing, survival and disease predispositions. Precise analysis of GH secretion pattern is vitally important for a comprehensive understanding of the function of GH and the components that regulate GH secretion pattern.

Actions and Potential Therapeutic Applications of Growth Hormone-Releasing Hormone Agonists

In this article, we briefly review the identification of GHRH, provide an abridged overview of GHRH antagonists, and focus on studies with GHRH agonists. Potent GHRH agonists of JI and MR class were synthesized and evaluated biologically. Besides the induction of the release of pituitary GH, GHRH analogs promote cell proliferation and exert stimulatory effects on various tissues, which express GHRH receptors (GHRH-Rs). A large body of work shows that GHRH agonists, such as MR-409, improve pancreatic β-cell proliferation and metabolic functions and facilitate engraftment of islets after transplantation in rodents. Accordingly, GHRH agonists offer a new therapeutic approach to treating diabetes. Various studies demonstrate that GHRH agonists promote repair of cardiac tissue, producing improvement of ejection fraction and reduction of infarct size in rats, reduction of infarct scar in swine, and attenuation of cardiac hypertrophy in mice, suggesting clinical applications. The presence of GHRH-Rs in ocular tissues and neuroprotective effects of GHRH analogs in experimental diabetic retinopathy indicates their possible therapeutic applications for eye diseases. Other effects of GHRH agonists, include acceleration of wound healing, activation of immune cells, and action on the central nervous system. As GHRH might function as a growth factor, we examined effects of GHRH agonists on tumors. In vitro, GHRH agonists stimulate growth of human cancer cells and upregulate GHRH-Rs. However, in vivo, GHRH agonists inhibit growth of human cancers xenografted into nude mice and downregulate pituitary and tumoral GHRH-Rs. Therapeutic applications of GHRH analogs are discussed. The development of GHRH analogs should lead to their clinical use.

Screening and evaluating of long non-coding RNAs in prenatal and postnatal pituitary gland of sheep

Long non-coding RNAs are transcribed into RNA molecules that are >200 nucleotides in length. However, the expression and function analysis of lncRNAs in the sheep pituitary gland are still lacking. In this study, we identified 1755 lncRNAs (545 annotated lncRNAs and 1210 novel lncRNAs) from RNA-seq data in the pituitary gland of embryonic and adult sheep. A total of 235 lncRNAs were differentially expressed between embryonic and adult group. We verified the presence of some lncRNAs using RT-PCR and DNA sequencing, and identified some differentially expressed lncRNAs using qPCR. We also investigated the role of cis-acting lncRNAs on target genes. GO and KEGG enrichment analysis revealed that the target genes of lncRNAs were involved in the regulation of hormones secretion and some signaling pathways in the sheep pituitary gland. Our study provides comprehensive expression profiles of lncRNAs and valuable resource for understanding their function in the pituitary gland.

Implantable multireservoir device with stimulus-responsive membrane for on-demand and pulsatile delivery of growth hormone

Implantable devices for on-demand and pulsatile drug delivery have attracted considerable attention; however, many devices in clinical use are embedded with the electronic units and battery inside, hence making them large and heavy for implantation. Therefore, we propose an implantable device with multiple drug reservoirs capped with a stimulus-responsive membrane (SRM) for on-demand and pulsatile drug delivery. The SRM is made of thermosensitive POSS(MEO₂MA-co-OEGMA) and photothermal nanoparticles of reduced graphene oxide (rGO), and each of the drug reservoirs is filled with the same amount of human growth hormone (hGH). Therefore, with noninvasive near-infrared (NIR) irradiation from the outside skin, the rGO nanoparticles generate heat to rupture the SRM in the implanted device, which can open a single selected drug reservoir to release hGH. Therefore, the device herein is shown to release hGH reproducibly only at the times of NIR irradiation without drug leakage during no irradiation. When implanted in rats with growth hormone deficiency and irradiated with an NIR light from the outside skin, the device exhibits profiles of hGH and IGF1 plasma concentrations, as well as body weight change, similar to those in animals treated with conventional s.c. hGH injections.

The Role of Insulin-Like Growth Factors and Insulin-Like Growth Factor-Binding Proteins in the Nervous System

The insulin-like growth factors (IGF-I and IGF-II) and their receptors are widely expressed in nervous tissue from early embryonic life. They also cross the blood brain barriers by active transport, and their regulation as endocrine factors therefore differs from other tissues. In brain, IGFs have paracrine and autocrine actions that are modulated by IGF-binding proteins and interact with other growth factor signalling pathways. The IGF system has roles in nervous system development and maintenance. There is substantial evidence for a specific role for this system in some neurodegenerative diseases, and neuroprotective actions make this system an attractive target for new therapeutic approaches. In developing new therapies, interaction with IGF-binding proteins and other growth factor signalling pathways should be considered. This evidence is reviewed, gaps in knowledge are highlighted, and recommendations are made for future research.

Comprehensive Expression Profiling Analysis of Pituitary Indicates that circRNA Participates in the Regulation of Sheep Estrus

The pituitary gland is the most important endocrine organ that mainly regulates animal estrus by controlling the hormones synthesis. There is a significant difference between the estrus state and anestrus state of sheep pituitary system. Here, we studied the circular RNA (circRNA) expression profiles of the anterior pituitary of estrus and anestrus sheep using RNA-seq technology. Through this study, we identified a total of 12,468 circRNAs and 9231 differentially expressed circRNAs in the estrus and anestrus pituitary system of sheep. We analyzed some differentially expressed circRNAs by reverse transcription quantitative-PCR (RT-qPCR), and some circRNAs were demonstrated using RNase-R+ resistance experiments. CircRNAs involving the regulation of estrus-related terms and pathways are enriched by using gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis. In addition, we also predicted partial microRNA-circRNA interaction network for circRNAs that regulate sheep estrus. Overall, this study explored a potential substantial role played by circRNAs involved in pituitary regulation on sheep estrus and proposed new questions for further study.

International Union of Basic and Clinical Pharmacology. CV. Somatostatin Receptors: Structure, Function, Ligands, and New Nomenclature

Somatostatin, also known as somatotropin-release inhibitory factor, is a cyclopeptide that exerts potent inhibitory actions on hormone secretion and neuronal excitability. Its physiologic functions are mediated by five G protein-coupled receptors (GPCRs) called somatostatin receptor (SST)1-5. These five receptors share common structural features and signaling mechanisms but differ in their cellular and subcellular localization and mode of regulation. SST₂ and SST₅ receptors have evolved as primary targets for pharmacological treatment of pituitary adenomas and neuroendocrine tumors. In addition, SST₂ is a prototypical GPCR for the development of peptide-based radiopharmaceuticals for diagnostic and therapeutic interventions. This review article summarizes findings published in the last 25 years on the physiology, pharmacology, and clinical applications related to SSTs. We also discuss potential future developments and propose a new nomenclature.

MECHANISMS OF ENDOCRINOLOGY: Endocrinology of opioids

The use of opioids has grown substantially over the past two decades reaching the dimensions of a global epidemic. These drugs have effects on multiple levels of the endocrine system through mechanisms which are still not fully elucidated, and awareness of their endocrine sequelae is vital for all specialists prescribing or managing patients on them. Hypogonadism is the most well-recognised consequence of opioid use (prevalence 21–86%) which, however, may remain undiagnosed with potential adverse outcomes for the patients. Although less frequent, cortisol deficiency can also be found. Furthermore, there is a negative impact on bone health (with reduced bone mineral density and increased fracture risk) and occasionally hyperprolactinaemia, whereas the clinical significance of alterations in other hormones remains to be clarified. Discontinuation or reduction of the opioid and, in cases of chronic pain, consideration of alternative therapies for pain relief are potential management options. Hormonal replacement, especially when the above measures are not practically feasible, needs to be considered. Further studies are needed to clearly establish the prevalence of hormonal abnormalities with various regimes, doses and routes of opioids and to address reliably the long-term benefits and risks of hormonal treatment in patients on opioids. Until evidence-based, safe and cost-effective clinical guidelines become available, periodical assessment of the gonadal and adrenal function (particularly when relevant clinical manifestations are present) and evaluation of the bone health status are advised.

GH responses to whole body vibration alone or in combination with maximal voluntary contractions in obese male adolescents

BACKGROUND

The anabolic, lipolytic and anti-inflammatory effects of exercise-stimulated GH secretion could be usefully exploited in the multidisciplinary rehabilitative programs of obese patients, who are reported to suffer from hyposomatotropism. To date, evaluation of GH responses to whole body vibration (WBV) in combination with maximal voluntary contractions (MVC) has been performed in normal-weight subjects, but not obese patients. Thus, aim of the present study was to investigate the effects of WBV and MVC, alone and combined, on GH responsiveness in obese subjects.

METHODS

The acute effects of WBV or MVC alone and the combination of MVC with WBV (MVC + WBV) on serum GH, cortisol and IGF-I and blood lactate (LA) levels were evaluated in 8 obese male adolescents [mean age ± SD: 17.1 ± 3.3 yrs.; weight: 107.4 ± 17.8 kg; body mass index (BMI): 36.5 ± 6.6 kg/m²; BMI standard deviation score (SDS): 3.1 ± 0.6].

RESULTS

WBV and MVC (alone or combined) significantly stimulated GH secretion. In particular, GH peaks and net areas under the curve (nAUCs) were significantly higher after MVC + WBV and MVC than WBV, without any difference between MVC + WBV and MVC groups; anyway, an additive effect on GH levels immediately after the execution of MVC + WBV test was found in comparison with MVC test. LA peaks significantly increased after each exercise (vs. basal condition), being significantly higher after MVC + WBV and MVC than WBV, without any difference between MVC + WBV and MVC groups. Peak LA values were significantly correlated with GH peaks and nAUCs. In contrast to the unchanged IGF-I levels, MVC + WBV and MVC (but not WBV) significantly stimulated cortisol secretion.

CONCLUSIONS

The results of the present study confirm the ability of MVC and WBV to stimulate GH secretion in obese patients. Rehabilitative programs combining different types of exercise eliciting a potent GH response seem to be important to counteract the hyposomatotropism of obese patients. Due to its limited stress upon joints without provoking an excessive fatigue, WBV could be usefully employed in the initial stages of a weight loss program alone or in combination with more potent GH releasing stimuli, such as MVC.

Growth hormone-releasing hormone antagonists reduce prostatic enlargement and inflammation in carrageenan-induced chronic prostatitis

BACKGROUND

Inflammation plays a key role in the etiology of benign prostatic hyperplasia (BPH) through multiple pathways involving the stimulation of proliferation by cytokines and growth factors as well as the induction of the focal occurrence of epithelial-to-mesenchymal transition (EMT). We have previously reported that GHRH acts as a prostatic growth factor in experimental BPH and in autoimmune prostatitis models and its blockade with GHRH antagonists offer therapeutic approaches for these conditions. Our current study was aimed at the investigation of the beneficial effects of GHRH antagonists in λ-carrageenan-induced chronic prostatitis and at probing the downstream molecular pathways that are implicated in GHRH signaling.

METHODS

To demonstrate the complications triggered by recurrent/chronic prostatic inflammation in Sprague-Dawley rats, 50 μL 3% carrageenan was injected into both ventral prostate lobes two times, 3 weeks apart. GHRH antagonist, MIA-690, was administered 5 days after the second intraprostatic injection at 20 μg daily dose for 4 weeks. GHRH-induced signaling events were identified in BPH-1 and in primary prostate epithelial (PrEp) cells at 5, 15, 30, and 60 min with Western blot.

RESULTS

Inflammation induced prostatic enlargement and increased the area of the stromal compartment whereas treatment with the GHRH antagonist significantly reduced these effects. This beneficial activity was consistent with a decrease in prostatic GHRH, inflammatory marker COX-2, growth factor IGF-1 and inflammatory and EMT marker TGF-β1 protein levels and the expression of multiple genes related to EMT. In vitro, GHRH stimulated multiple pathways involved in inflammation and growth in both BPH-1 and PrEp cells including NFκB p65, AKT, ERK1/2, EGFR, STAT3 and increased the levels of TGF-β1 and Snail/Slug. Most interestingly, GHRH also stimulated the transactivation of the IGF receptor.

CONCLUSIONS

The study demonstrates that GHRH antagonists could be beneficial for the treatment of prostatic inflammation and BPH in part by inhibiting the growth-promoting and inflammatory effects of locally produced GHRH.

IGF-1 levels may increase paradoxically with dopamine agonist treatment for prolactinomas

OBJECTIVE

Hyperprolactinemia is common in acromegaly and in these patients, insulin-like growth factor (IGF)-1 level may decrease with dopamine agonist. We report a series of patients with prolactinoma and a paradoxical increase of IGF-1 levels during cabergoline treatment.

METHODS

Clinical characteristics and response to treatment of patients with prolactinomas, in whom normal or slightly elevated baseline IGF-1 levels increased with cabergoline.

RESULTS

The cohort consisted of ten prolactinoma patients (nine males, mean age 48 ± 14 years). Mean adenoma size was 23.8 ± 16.2 mm, with cavernous sinus invasion in eight. In five patients baseline IGF-1 levels were normal and in four levels were 1.2-1.5-fold the upper limit of the normal (ULN). One patient had IGF-1 measured shortly after initiating cabergoline and it was 1.4 × ULN. During cabergoline treatment (dose range 0.5-2 mg/week) PRL normalization was achieved in all and tumor shrinkage occurred in seven patients. The mean IGF-1 increase on cabergoline was 1.7 ± 0.4 × ULN. Cabergoline dose reduction or interruption was attempted in five patients and resulted in decreased IGF-1 levels in all, including normalization in two patients. Three patients were eventually diagnosed with acromegaly, one was referred for pituitary surgery followed by complete remission, another patient was switched to somatostatin analogue, and the third was treated by combination of somatostatin analogues with pegvisomant, with reduction of IGF-1 in all these patients.

CONCLUSION

IGF-1 levels may increase to clinically significant levels during cabergoline treatment for PRL-adenoma. We suggest IGF-1 monitoring in all patients treated with dopamine agonists and not only in those presenting symptoms of acromegaly.

Role of IGF1 and EFN-EPH signaling in skeletal metabolism

Insulin-like growth factor 1(IGF1) and ephrin ligand (EFN)-receptor (EPH) signaling are both crucial for bone cell function and skeletal development and maintenance. IGF1 signaling is the major mediator of growth hormone-induced bone growth, but a host of different signals and factors regulate IGF1 signaling at the systemic and local levels. Disruption of the Igf1 gene results in reduced peak bone mass in both experimental animal models and humans. Additionally, EFN-EPH signaling is a complex system which, particularly through cell-cell interactions, contributes to the development and differentiation of many bone cell types. Recent evidence has demonstrated several ways in which the IGF1 and EFN-EPH signaling pathways interact with and depend upon each other to regulate bone cell function. While much remains to be elucidated, the interaction between these two signaling pathways opens a vast array of new opportunities for investigation into the mechanisms of and potential therapies for skeletal conditions such as osteoporosis and fracture repair.