Hypothalamic Growth Hormone Research Articles

Quantitative measures of the vascular and neural components of the retina in adult individuals with congenital and untreated growth hormone deficiency

BackgroundThe somatotrophic axis, including hypothalamic growth hormone (GH)-releasing hormone (GHRH), pituitary GH and circulating IGF-I, is critical for body size. However, the local production of GH/IGF-I (and IGF-II) and other peptides is relevant for other body functions, such as vascular, brain, and retinal function. The consequences of GH deficiency (GHD) on the retinal structure are still unclear, possibly reflecting the heterogeneity of patients and the different types of assessment in previous publications. Our purpose was to assess quantitative measures of the vascular and neural components of the retina in subjects with severe congenital isolated GHD (IGHD).MethodsA cross-sectional study was carried out in 25 adult IGHD subjects and 25 age- and gender-matched controls. Interview, physical examination, laboratory data, optical coherence tomography (OCT) and OCT angiography (OCTA) were performed.ResultsOCT revealed no difference in the areas of the nerve fiber layer average, nor in the areas of superior, inferior, or nasal quadrants, between the two groups. However, areas of the temporal quadrant (p = 0.041), the optical disc (p = 0.042), the cup (p < 0.0001), as well as the cup/disc ratio (p < 0.0001), were higher in IGHD subjects than controls. The rim area was smaller (p = 0.002), although still normal. In OCTA, there was no difference in the minimum foveal thickness, central fovea, foveal avascular zone, and retinal density in any assessed area.ConclusionsIn conclusion, congenital IGHD does not affect quantitative measures of the vascular and neural retina, and it is associated with increased optical disc in this genetically homogeneous cohort.

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.

Changes in energy metabolism and respiration in different\xa0tracheal narrowing in rats

Why obstructive sleep apnea (OSA) treatment does not completely restore healthy metabolic physiology is unclear. In rats, the need for respiratory homeostasis maintenance following airway obstruction (AO) is associated with a loss of thermoregulation and abnormal metabolic physiology that persists following successful obstruction removal. Here, we explored the effect of two different types of tracheal narrowing, i.e., AO and mild airway obstruction (mAO), and its removal on respiratory homeostasis and metabolic physiology. We show that after ten weeks, mAO vs. AO consumes sufficient energy that is required to maintain respiratory homeostasis and thermoregulation. Obstruction removal was associated with largely irreversible increased feeding associated with elevated serum ghrelin, hypothalamic growth hormone secretagogue receptor 1a, and a phosphorylated Akt/Akt ratio, despite normalization of breathing and energy requirements. Our study supports the need for lifestyle eating behavior management, in addition to endocrine support, in order to attain healthy metabolic physiology in OSA patients.

IGF-1 and IGFBP-3 in Inflammatory Cachexia.

Inflammation induces a wide response of the neuroendocrine system, which leads to modifications in all the endocrine axes. The hypothalamic–growth hormone (GH)–insulin-like growth factor-1 (IGF-1) axis is deeply affected by inflammation, its response being characterized by GH resistance and a decrease in circulating levels of IGF-1. The endocrine and metabolic responses to inflammation allow the organism to survive. However, in chronic inflammatory conditions, the inhibition of the hypothalamic–GH–IGF-1 axis contributes to the catabolic process, with skeletal muscle atrophy and cachexia. Here, we review the changes in pituitary GH secretion, IGF-1, and IGF-1 binding protein-3 (IGFBP-3), as well as the mechanism that mediated those responses. The contribution of GH and IGF-1 to muscle wasting during inflammation has also been analyzed.

The Effect of Hypothalamic Involvement and Growth Hormone Treatment on Cardiovascular Risk Factors in Patients With Childhood-Onset Craniopharyngioma

Background: We evaluated cardiovascular risk factors at the time of growth hormone (GH) retesting after completion of linear growth in patients with childhood-onset craniopharyngioma (CP). We also investigated the effects of postoperative hypothalamic involvement (HI) and GH discontinuation during transition period on cardiovascular risk factors. Methods: Forty-two CP patients (24 males, mean age 17.7 years) who reached final adult height after GH therapy between 1995 and 2012 from a tertiary center were included. We measured anthropometric data and components of the metabolic syndrome at the time of GH retesting. The period of GH discontinuation was classified as < 6 months vs. ≥ 6 months. The extent of HI was categorized into “no”, “mild”, and “extensive” HI according to Puget grading system. Results: The mean age of initial operation after CP diagnosis was 7.5 ± 3.6 years, and 23 (54.8%) patients showed extensive HI. All patients were treated with GH during childhood for median 5.8 years (range 2.4-8.2years). Duration of GH discontinuation was median 1.5 years (range 0.5-3.2 years), and 32 (76.2%) had GH discontinuation ≥ 6 months. At the time of GH retesting, 13 (31.0%) were obese, and the proportion of patients with impaired fasting glucose (≥ 100 mg/dL), high triglycerides (≥ 150 mg/dL), low high-density lipoprotein (HDL) cholesterol (male, < 40 mg/dL; female, < 50 mg/dL), and hypertension (systolic blood pressure ≥ 130mmHg or diastolic blood pressure ≥ 85mmHg) was 5 (11.9%), 18 (42.9%), 24 (57.1%), and 5 (11.9%), respectively. When multivariate-adjusted models were constructed including age, sex, postoperative duration, extent of HI, duration of GH discontinuation, and family history of cardiovascular disease, the extent of HI was significantly predictive for increased body mass index z-score (β = 1.27, P = 0.017), fasting insulin levels (β = 7.1, P = 0.049), HOMA-IR (β = 1.61, P = 0.020), and decreased HDL cholesterol levels (β = -9.9, P = 0.012). GH discontinuation more than 6 months was significantly associated with decreasedHDL cholesterol levels (β = -10.23, P = 0.026). Conclusion: In this study, impaired fasting glucose or hypertension accounted for one-tenth, and dyslipidemia was detected in more than half of childhood-onset CP patients with GH deficiency at the time of GH retesting. The more extensive HI and the longer duration of GH discontinuation were associated with increased risk of metabolic disturbance during the transition period.

A Body Weight Sensor Regulates Prepubertal Growth via the Somatotropic Axis in Male Rats.

In healthy conditions, prepubertal growth follows an individual specific growth channel. Growth hormone (GH) is undoubtedly the major regulator of growth. However, the homeostatic regulation to maintain the individual specific growth channel during growth is unclear. We recently hypothesized a body weight sensing homeostatic regulation of body weight during adulthood, the gravitostat. We now investigated if sensing of body weight also contributes to the strict homeostatic regulation to maintain the individual specific growth channel during prepubertal growth. To evaluate the effect of increased artificial loading on prepubertal growth, we implanted heavy (20% of body weight) or light (2% of the body weight) capsules into the abdomen of 26-day-old male rats. The body growth, as determined by change in biological body weight and growth of the long bones and the axial skeleton, was reduced in rats bearing a heavy load compared with light load. Removal of the increased load resulted in a catch-up growth and a normalization of body weight. Loading decreased hypothalamic growth hormone releasing hormone mRNA, liver insulin-like growth factor (IGF)-1 mRNA, and serum IGF-1, suggesting that the reduced body growth was caused by a negative feedback regulation on the somatotropic axis and this notion was supported by the fact that increased loading did not reduce body growth in GH-treated rats. Based on these data, we propose the gravitostat hypothesis for the regulation of prepubertal growth. This states that there is a homeostatic regulation to maintain the individual specific growth channel via body weight sensing, regulating the somatotropic axis and explaining catch-up growth.

1768-P: The Role of Hypothalamic Growth Hormone Receptor–Expressing Neurons in Glucose Metabolism and Energy Homeostasis

GH and the GH receptor (GHR) are present in regions known to participate in the regulation of feeding, energy balance and glucose metabolism, including the hypothalamus. We have previously demonstrated that GHR signals in nutrient-sensing neurons is critical for hepatic glucose production and lipid metabolism. Given the high expression pattern of GHR in the arcuate nucleus (ARC) of the hypothalamus, we aimed to define the specific role of the ARC GHR-expressing neurons in energy homeostasis and glucose metabolism. For this purpose, we have developed a novel GHR cell-specific molecular tool (GHRcre) using CRISPR/Cas9 gene editing technology. We show that GHR+ neurons in the ARC are mostly co-localized with AgRP, GHRH, and SST neurons and rapidly respond to fasting. Specific chemogenetic activation of GHR+ neurons in the ARC (ARCGHR+) by the DREADDs technique impaired glucose metabolism, suggesting the role of these neurons in metabolic homeostasis. Additionally, while activation of ARCGHR+ neurons increased energy homeostasis (RER, VO2) under metabolic resting phase, the responses to fasting were significantly attenuated, demonstrating the inhibitory role of GHR+ neurons in the ARC for fasting responses. Sirtuin 1 (SIRT1) is highly expressed in the ARC and had been associated with hypothalamic responses to fasting. The majority of ARCGHR+ neurons express SIRT1 and respond to fasting by upregulating the SIRT1 expression. Importantly, hypothalamic upregulation of SIRT1 in response to fasting is blunted in mice lacking GHR in AgRP neurons (AgRPEYFP∆GHR mice), suggesting a novel role of SIRT1 within the hypothalamic GH axis and providing evidence for a link between the somatotropic system and SIRT1 function in responses to fasting. Disclosure J. Lima: None. L.K. Debarba: None. I.T. Ayyar: None. C. Ubah: None. M. Khan: None. H. AlRomdhan: None. M. Alysofi: None. M. Sadagurski: None. Funding American Diabetes Association (1-18-JDF-063 to M.S.); Wayne State University

Hypothalamic lipoma and growth hormone deficiency

BackgroundIntracranial lipomas are rare, congenital lesions, most often located at the midline. Most hypothalamic lipomas are asymptomatic, but some cases have been associated with precocious puberty, hypothermia, headache and/or obesity.Case presentationA 7-year-old boy was referred for short stature and proved to be partially growth-hormone deficient. Magnetic resonance imaging (MRI) revealed a lipoma in the paramedian hypothalamus. Growth hormone treatment resulted in swift and uncomplicated catch-up growth.ConclusionsThe present case appears to be the first to link hypothalamic lipoma to GH deficiency. The neuro-endocrine pathophysiology underpinning this link remains to be explored.

1819-P: Growth Hormone Receptor (GHR) in AgRP Neurons Modulates Energy Balance and Metabolic Adaptation to Fasting via Sirtuin 1 (SIRT1)

We are facing a worldwide public health emergency due to the increasing epidemic of diabetes. In the central nervous system, the hypothalamus is the primary site of integration of the neuroendocrine and autonomic responses which maintain glucose and energy homeostasis. Main physiological effects of growth hormone (GH) in adult brain - is the inhibition of its own secretion, especially critical under fasting states. While the importance of hypothalamic GH receptor (GHR) in GH feedback inhibition is well established, the direct involvement of neuronal GHR signals in the regulation of whole-body homeostasis has not been studied. Previously, we have identified a unique population of hypothalamic leptin receptor (LepRb)-GHR expressing neurons that regulate hepatic glucose production, suggesting a crucial role for these neurons in GHR-neurocircuitry. To characterize hypothalamic GHR-expressing neurons, we have developed GHRcre mice using CRISPR/Cas9 technology. Approximately 60% of GHR+ neurons in the arcuate nucleus (ARC) co-localize with AgRP-expressing neurons and about 25% with GHRH neurons, basically representing most of ARCGHR neurons. By manipulating neuronal activity of neurochemically-defined GHR neurons, we demonstrate that ARCGHR neurons represent distinct neuronal population in glycemic control. Despite similarity in responses in both sexes, only female mice selectively lacking GHR in AgRP neurons showed impaired energy homeostasis and heat production, accompanied by alterations in metabolic adaptation to fasting. Fasting increased the abundance of sirtuin 1 (SIRT1) within ARCGHR+ neurons, while this pattern was diminished in the fasted AgRPEYFP∆GHR female mice. Our data suggests a role of SIRT1 within somatotropic signaling in the AgRPGHR+ neurons in response to alterations in nutritional status and demonstrates the role of AgRP-GHR neurons in assisting the organism in recruiting its resources for survival purposes. Disclosure L.K. Debarba: None. I.T. Ayyar: None. M.C. Koch: None. G. Cady: None. M. Sadagurski: None. Funding American Diabetes Association (1-18-JDF-063 to M.S.)

Serotonin Receptors of 5-HT2 Type in the Hypothalamic Arcuate Nuclei Positively Regulate Liver Cytochrome P450 via Stimulation of the Growth Hormone-Releasing Hormone/Growth Hormone Hormonal Pathway.

Our recent study carried out after local injection of the serotonergic neurotoxin 5,7-dihydroxytryptamine into the arcuate nucleus (ARC) of the hypothalamus suggested a positive influence of the serotonergic innervation of the ARC on growth hormone (GH) secretion and GH-dependent expression of cytochrome P450. The aim of our present study was to determine the effect of the activation of the serotonin (5-HT)-type receptors, 5-HT1 or 5-HT2, in the ARC on the expression and activity of cytochrome P450 in the liver of male rats. The serotonergic agonist 5-carboxyamidotryptamine [(5-CT), a 5-HT1-type receptor agonist] or 2,5-dimethoxy-4-iodoamphetamine [(DOI), a 5-HT2-type receptor agonist] was injected into the ARC for 5 days. The activity and expression of cytochrome P450 isoenzymes and the levels of serum and pituitary hormones were estimated. DOI significantly increased the activity and expression (both mRNA and protein levels) of CYP2C11, CYP3A1/23, and CYP3A2, which positively correlated with an increase in the pituitary growth hormone-releasing hormone (GHRH) and serum GH level. The injection of 5-CT into the ARC did not affect the activity of liver P450 enzymes or hormone levels. The obtained results indicate that 5-HT2, but not the 5-HT1-type receptors in the ARC, are engaged in the positive neuroendocrine regulation of cytochrome P450, possibly by the stimulation of hypothalamic GHRH release and pituitary GH secretion, and an increase in the serum GH concentration. Further studies are going to identify which of the 5-HT2 receptor subtypes (5-HT2A, 5-HT2B, or 5-HT2C) is responsible for the observed neuroendocrine regulation of cytochrome P450.

In-ovo green light photostimulation during different embryonic stages affect somatotropic axis.

Previous studies demonstrated that in-ovo photostimulation with monochromatic green light increased the somatotropic axis expression in broilers embryos. The objective of the current study was to detect the critical period for in-ovo GL photostimulation, in order to find the optimal targeted photostimulation period during the incubation process. Three hundred thirty-six fertile broiler eggs were divided into 4 groups. The first group was incubated under dark conditions as a negative control. The second incubated under intermittent monochromatic green light using light-emitting diode (LED) lamps with an intensity of 0.1 W\m2 at shell level from d 0 of the incubation as a positive control. The third group incubated under intermittent monochromatic green light from d 10 of the incubation. The last group incubated under intermittent monochromatic green light from d 15 of the incubation. In-ovo green light photostimulation from embryonic d 0 (ED0) increased plasma growth hormone (GH), as well as hypothalamic growth hormone releasing hormone (GHRH) and liver growth hormone receptor (GHR) and insulin-like growth factor-1 (IGF-1) mRNA levels. In-ovo green light photostimulation from ED10 increased the GH plasma levels compared to the negative control group, without affecting somatotropic axis mRNA genes expressions of GHRH, GHR, and IGF-1. In-ovo green light photostimulation from ED15 caused an increase in both the plasma GH levels and the somatotropic axis mRNA genes expressions of GHRH, GHR, and IGF-1, compared to the negative control group. These results suggest that the critical period of somatotropic axis acceleration by GL photostimulation start at 15 d of incubation.

In-ovo monochromatic green light photostimulation enhances embryonic somatotropic axis activity

Previous studies demonstrated that in ovo photostimulation with monochromatic green light increases body weight and accelerates muscle development in broilers. The mechanism in which in ovo photostimulation accelerates growth and muscle development is not clearly understood. The objective of the current study was to define development of the somatotropic axis in the broiler embryo associated with in ovo green light photostimulation. Two-hundred-forty fertile broiler eggs were divided into 2 groups. The first group was incubated under intermittent monochromatic green light using light-emitting diode (LED) lamps with an intensity of 0.1 W\m2 at shell level, and the second group was incubated under dark conditions and served as control. In ovo green light photostimulation increased plasma growth hormone (GH) and prolactin (PRL) levels, as well as hypothalamic growth hormone releasing hormone (GHRH), liver growth hormone receptor (GHR), and insulin-like growth factor-1 (IGF-1) mRNA levels. The in ovo photostimulation did not, however, increase embryo's body weight, breast muscle weight, or liver weight. The results of this study suggest that stimulation with monochromatic green light during incubation increases somatotropic axis expression, as well as plasma prolactin levels, during embryonic development.

Development of ghrelin resistance in a cancer cachexia rat model using human gastric cancer-derived 85As2 cells and the palliative effects of the Kampo medicine rikkunshito on the model.

Cancer cachexia (CC) is a multifactorial disease characterized by decreased food intake and loss of body weight due to reduced musculature with or without loss of fat mass. Patients with gastric cancer have a high incidence of cachexia. We previously established a novel CC rat model induced by human gastric cancer-derived 85As2 cells in order to examine the pathophysiology of CC and identify potential therapeutics. In patients with CC, anorexia is often observed, despite elevation of ghrelin, suggesting that ghrelin resistance may develop in these patients. In this study, we aimed to clarify the occurrence of ghrelin resistance in CC rats accompanied by anorexia and we investigated whether rikkunshito (RKT), a traditional Japanese Kampo medicine that potentiates ghrelin signaling, ameliorated CC-related anorexia through alleviation of ghrelin resistance. 85As2-tumor-bearing rats developed severe CC symptoms, including anorexia and loss of body weight/musculature, with the latter symptoms being greater in cachectic rats than in non-tumor-bearing or pair-fed rats. CC rats showed poor responses to intraperitoneal injection of ghrelin. In CC rats, plasma ghrelin levels were elevated and hypothalamic anorexigenic peptide mRNA levels were decreased, whereas hypothalamic growth hormone secretagogue receptor (GHS-R) mRNA was not affected. In vitro, RKT directly enhanced ghrelin-induced GHS-R activation. RKT administrated orally for 7 days partly alleviated the poor response to ghrelin and ameliorated anorexia without affecting the elevation of plasma ghrelin levels in CC rats. The expression of hypothalamic orexigenic neuropeptide Y mRNA but not hypothalamic GHS-R mRNA was increased by RKT. Thus, the 85As2 cell-induced CC rat model developed ghrelin resistance, possibly contributing to anorexia and body weight loss. The mechanism through which RKT ameliorated anorexia in the CC rat model may involve alleviation of ghrelin resistance by enhancement of ghrelin signaling. These findings suggest that RKT may be a promising agent for the treatment of CC.

Growth hormone/IGF-1 axis longitudinal evaluation in clinically isolated syndrome patients on interferon β-1b therapy: stimulation tests and correlations with clinical and radiological conversion to multiple sclerosis.

Growth hormone (GH)/insulin-like growth factor 1 (IGF-1) axis abnormalities in multiple sclerosis (MS) suggest their role in its pathogenesis. Interferon β (IFN-β) efficacy could be mediated also by an increase of IGF-1 levels. A 2-year longitudinal study was performed to estimate the prevalence of GH and/or IGF-1 deficiency in clinically isolated syndrome (CIS) patients and their correlation with conversion to MS in IFN treated patients. Clinical and demographic features of CIS patients were collected before the start of IFN-β-1b. IGF-1 levels and GH response after arginine and GH releasing hormone + arginine stimulation tests were assessed. Clinical and magnetic resonance imaging evaluations were performed at baseline, 1 year and 2 years. Thirty CIS patients (24 female) were enrolled. At baseline, four patients (13%) showed a hypothalamic GH deficiency (GHD), whilst no one had a pituitary GHD. Baseline demographic, clinical and radiological data were not related to GHD, whilst IGF-1 levels were inversely related to age (P < 0.001) and GH levels (P = 0.03). GH and IGF-1 serum mean levels were not significantly modified after 1 and 2 years of treatment in the whole group, although 3/4 GHD patients experienced a normalization of GH levels, whilst one dropped out. After 2 years of treatment 13/28 (46%) patients converted to MS. The presence of GHD and GH and IGF-1 levels were not predictive of relapses, new T2 lesions or conversion occurrence. Growth hormone/IGF-1 axis function was found to be frequently altered in CIS patients, but this was not related to MS conversion. Patients experienced an improvement of GHD during IFN therapy. Longer follow-up is necessary to assess its impact on disease progression.

Effect of preduodenal lipase inhibition in suckling rats on dietary octanoic acid (C8:0) gastric absorption and plasma octanoylated ghrelin concentration

Part of medium chain fatty acids (MCFAs) coming from dietary triglycerides (TGs) can be directly absorbed through the gastric mucosa after the action of preduodenal lipase (lingual lipase in the rat). MCFA gastric absorption, particularly that of octanoic acid (C8:0), may have a physiological importance in the octanoylation of ghrelin, the orexigenic gastric peptide acting as an endogenous ligand of the hypothalamic growth hormone secretagogue receptor 1a (GHSR-1a). However, the amount of C8:0 absorbed in the stomach and its metabolic fate still haven't been clearly characterized. The purpose of the present study was to further characterize and quantify the importance of preduodenal lipase activity on the release and gastric absorption of dietary C8:0 and on the subsequent ghrelin octanoylation in the stomach mucosa. Fifteen days old rats received fat emulsions containing triolein or [1,1,1-13C]-Tri-C8:0 and a specific inhibitor of preduodenal lipase, 5-(2-(benzyloxy)ethoxy)-3-(3-phenoxyphenyl)-1,3,4-oxadiazol-2(3H)-one or BemPPOX. The fate of the 13C-C8:0 was followed in rat tissues after 30 and 120min of digestion and octanoylated ghrelin was measured in the plasma. This work (1) demonstrates that part of C8:0 coming from Tri-C8:0 is directly absorbed at the gastric level, (2) allows the estimation of C8:0 gastric absorption level (1.3% of the 13C-C8:0 in sn-3 position after 30min of digestion), as well as (3) the contribution of rat lingual lipase to total lipolysis and to duodenal absorption of dietary FAs (at least 30%), (4) shows no short-term effect of dietary Tri-C8:0 consumption and subsequent increase of C8:0 gastric tissue content on plasma octanoylated ghrelin concentration.

Surgical castration but not immuncastration is associated with reduced hypothalamic GnIH and GHRH/GH/IGF-I axis function in male rats

Gonadotropin-inhibitory hormone (GnIH) is a potent positive regulator of the growth axis. The present study was aimed to comparatively investigate the effects of surgical and immunologic castration on hypothalamic GnIH expression and endocrine function of the growth axis. Thirty-six prepubertal male rats were randomly allocated into three groups (n = 12): control, surgically castrated or immunized against 100-μg D-Lys6-GnRH-tandem peptide conjugated to ovalbumin in Specol adjuvant at 6 weeks of age (with a booster 8 weeks later). Blood samples were collected (for hormone and urea nitrogen concentrations) at 2-week intervals, and growth performance was evaluated. Compared to intact controls, surgical castration reduced (P < 0.05) messenger RNA (mRNA) expressions of hypothalamic GnIH and growth hormone–releasing hormone (GHRH), pituitary growth hormone (GH), and liver insulin-like growth factor-1 (IGF-1), reduced (P < 0.05) serum concentrations of GH and IGF-1 and increased (P < 0.05) serum concentrations of urea nitrogen. In contrast, immunocastration did not alter messenger RNA expressions of hypothalamic GnIH, GHRH and pituitary GH, and the serum concentrations of GH (P > 0.05). Moreover, serum concentrations of IGF-1 and urea nitrogen in immunocastrates were substantially higher and lower than those in surgical castrates, respectively (P < 0.05). Compared to surgical castrates, immuncastrates had superior feed conversion efficiency and faster daily weight gain (P < 0.05). We concluded that surgical castration but not immunocastration is associated with reduced hypothalamic GnIH and GHRH/GH/IGF-I axis function in male rats.

Profiles of mRNA expression of related genes in the duck hypothalamus–pituitary growth axis during embryonic and early post-hatch development

In this study, the ontogeny of body and liver weight and the pattern of related gene mRNA expression in the hypothalamus–pituitary growth axis (HPGA) of two different duck breeds (Anas platyrhynchos domestica) were compared during embryonic and post-hatch development. Duck hypothalamic growth hormone release hormone (GHRH), somatostatin (SS), pituitary growth hormone (GH), liver growth hormone receptor (GHR) and insulin-like growth factor-I (IGF-1) mRNA were first detected on the 13th embryonic day. During early duck development, SS maintained a lower expression status, whereas the other four genes exhibited highly significant variations in an age-specific manner. Highly significant breed specificity was observed with respect to hepatic IGF-1 mRNA expression, which showed a significant breed–age interaction effect. Compared with previous studies on chickens, significant species differences were observed regarding the mRNA expression of bird embryonic HPGA-related genes. During early development, highly significant breed and age specificity were observed with respect to developmental changes in body and liver weight, and varying degrees of significant linear correlation were found between these performances and the mRNA expression of HPGA-related genes in the duck HPGA. These results suggest that different genetic backgrounds may lead to differences in duck growth and HPGA-related gene mRNA expression, and the differential mRNA expression of related genes in the duck HPGA may be particularly important in the early growth of ducks. Furthermore, hepatic IGF-1 mRNA expression presented highly significant breed specificity, and evidence suggests the involvement of hepatic IGF-1 in mediating genetic effects on embryo and offspring growth in ducks.

Pancreatic Polypeptide Controls Energy Homeostasis via Npy6r Signaling in the Suprachiasmatic Nucleus in Mice

Y-receptors control energy homeostasis, but the role of Npy6 receptors (Npy6r) is largely unknown. Young Npy6r-deficient (Npy6r(-/-)) mice have reduced body weight, lean mass, and adiposity, while older and high-fat-fed Npy6r(-/-) mice have low lean mass with increased adiposity. Npy6r(-/-) mice showed reduced hypothalamic growth hormone releasing hormone (Ghrh) expression and serum insulin-like growth factor-1 (IGF-1) levels relative to WT. This is likely due to impaired vasoactive intestinal peptide (VIP) signaling in the suprachiasmatic nucleus (SCN), where we found Npy6r coexpressed in VIP neurons. Peripheral administration of pancreatic polypeptide (PP) increased Fos expression in the SCN, increased energy expenditure, and reduced food intake in WT, but not Npy6r(-/-), mice. Moreover, intraperitoneal (i.p.) PP injection increased hypothalamic Ghrh mRNA expression and serum IGF-1 levels in WT, but not Npy6r(-/-), mice, an effect blocked by intracerebroventricular (i.c.v.) Vasoactive Intestinal Peptide (VPAC) receptors antagonism. Thus, PP-initiated signaling through Npy6r in VIP neurons regulates the growth hormone axis and body composition.

The AlfpCre mouse revisited: Evidence for liver steatosis related to growth hormone deficiency

With great interest we read the article by Mueller et al. on the development of steatosis and hepatocellular carcinoma in mice by disrupting hepatic growth hormone (GH) and glucocorticoid receptor signaling.1 They demonstrate that abrogation of hepatic signal transducer and activator of transcription 5 (Stat5) signaling caused liver steatosis by up-regulation of genes involved in lipid uptake and synthesis. However, we have concerns regarding the use of AlfpCre+ transgenic mice to inactivate Stat5 in the liver. While generating the AlfpCre transgene, the entire human GH (hGH) gene was inserted for its introns and polyadenylation signal.2 As a consequence, a polycistronic messenger RNA (mRNA) transcript encoding Cre Recombinase and hGH was transcribed in the liver, hypothalamus, and pituitary (data not shown). However, hGH was only translated in the hypothalamus and pituitary (Fig. 1A). It has previously been described that targeted expression of hGH in the hypothalamus reduces expression of hypothalamic GH releasing hormone (GHRH), leading to GH deficiency (GHD).3 This is also the case in AlfpCre+ mice in a C57Bl6/J background, as shown by quantitative real-time polymerase chain reaction (qRT-PCR). In the hypothalamus, expression levels of GHRH were reduced by 70% (P < 0.01) and mouse GH messenger RNA (mRNA) in the adenopituitary by 61% (P < 0.05). AlfpCre+ mice also showed hypoplasia of the pituitary (Fig. 1B). Hepatic insulin-like growth factor 1 (Igf1) mRNA and Igf1 plasma protein levels were decreased by 71% (P < 0.001) and 60% (P < 0.001), respectively, and reduced phosphorylation of Stat5 in AlfpCre+ livers was shown by western blotting (Fig. 1C), confirming GHD in AlfpCre+ mice. Consequently, AlfpCre+ mice exhibit postnatal growth retardation (Fig. 1D), a finding that was also observed in AlfpCre+/−c-JunF/F mice.4 Downstream of the impaired GH signaling, AlfpCre+ livers showed increased levels of triglycerides (TGs), free fatty acids (FFAs), and cholesterol, indicating liver steatosis (Fig. 1E). Finally, genes involved in lipid uptake and synthesis, including CD36, very low-density lipoprotein receptor, and peroxisome proliferator-activated receptor gamma, were significantly up-regulated by 2.52- (P < 0.01), 5.44- (P < 0.01), and 2.09-fold (P < 0.001), respectively, an expression profile indicating liver steatosis (Fig. 1F). Altogether, AlfpCre+ mice show liver steatosis related to GHD, and therefore care should be taken to use the right controls (AlfpCre+ unfloxed mice instead of AlfpCre− floxed mice) while conditionally inactivating or overexpressing genes in livers of mice. Vincent P.E.G. Pruniau, M.Sc. Els Louagie, M.Sc., Ph.D. Bas Brouwers, M.Sc. Jeroen Declercq, M.Sc., Ph.D. John W.M. Creemers, Ph.D. Laboratory for Biochemical Neuroendocrinology Department for Human Genetics KU Leuven Leuven, Belgium Els Louagie is currently affiliated with the Laboratory for Molecular Immunology and Inflammation Department of Rheumatology Ghent University Hospital Ghent, Belgium

Neonatal xenoestrogen exposure alters growth hormone-dependent liver proteins and genes in adult female rats

The hypothalamic-growth hormone (GH)–liver axis represents a new concept in endocrine regulation of drug toxicity. Preponderant sex differences are found in liver gene expression, mostly dependent on the sexually dimorphic pattern of GH secretion which is set during the neonatal period by gonadal steroids. We tested if GH-dependent sexually dimorphic liver enzymes and proteins was perturbed by neonatal Bisphenol A (BPA) treatment in female rats. Female rats were sc injected with BPA (50 or 500μg/50μl) or castor oil vehicle from postnatal day 1 to 10. At five months serum prolactin, pituitary GH, and serum and liver insulin growth factor-I (IGF-I) were measured by RIA. Major urinary proteins (MUPs) were determined by electrophoresis. Liver Cyp2c11, Cyp2c12, Adh1, Hnf6, and Prlr mRNA levels were determined by real time PCR. Pituitary GH content and liver IGF-I concentration were increased by neonatal BPA treatment, indicating partial masculinization of the GH axis in treated females. GH-dependent female predominant liver enzyme genes (Cyp2c12 and Adh1) and a transcription factor (Hnf6) were downregulated or defeminized, while there were no changes in a male predominant gene (Cyp2c11) or protein (MUP). Our findings indicate that perinatal exposure to BPA may compromise the sexually dimorphic capacity of the liver to metabolize drugs and steroids.