The Growth Hormone Receptor: Mechanism of Receptor Activation, Cell Signaling, and Physiological Aspects

Small molecules to regulate the GH/IGF1 axis by inhibiting the growth hormone receptor synthesis

Growth hormone (GH) and insulin-like growth factor-1 (IGF1) play an important role in mammalian development, cell proliferation and lifespan. Especially in cases of tumor growth there is an urgent need to control the GH/IGF1 axis. In this study we screened a 38,480-compound library, and in two consecutive rounds of analogues selection, we identified active lead compounds based on the following criteria: inhibition the GH receptor (GHR) activity and its downstream effectors Jak2 and STAT5, and inhibition of growth of breast and colon cancer cells. The most active small molecule (BM001) inhibited both the GH/IGF1 axis and cell proliferation with an IC50 of 10-30 nM of human cancer cells. BM001 depleted GHR in human lymphoblasts. In preclinical xenografted experiments, BM001 showed a strong decrease in tumor volume in mice transplanted with MDA-MB-231 breast cancer cells. Mechanistically, the drug acts on the synthesis of the GHR. Our findings open the possibility to inhibit the GH/IGF1 axis with a small molecule.

Gene expression analysis on growth, development and toxicity pathways of male Nile tilapia (Oreochromis niloticus), after acute and sub-chronic benzo (α) pyrene exposures

Benzo[α]pyrene (BaP), a lipophilic polycyclic aromatic hydrocarbon (PAH), is a contaminant widely distributed in aquatic systems. Its presence in freshwater organisms is of great concern; particularly in Nile tilapia (Oreochromis niloticus), due to its economic relevance. The aim of this study is to evaluate the effects of acute and sub-chronic BaP exposures on molecular growth/development responses, toxicity to DNA pathways and xenobiotic metabolism. Negative morphometric changes (the growth condition factor, hepatosomatic and gonadosomatic indices), the fluorescent aromatic compounds (FACs) in bile were also studied in order to understand the mechanisms of action of BaP. Genes involved in the growth hormone GH/insulin-like growth factor 1 (IGF-1) were measured, such as IGF1-2 with the growth hormone receptor gene expression GHR1-2, and the endocrine disruption biomarker vitellogenin (VTG). Acute exposure elicited changes in the GH/IGF axis, mainly in the GHR1 and in IGF1 mRNA levels without affecting the GHR2 expression. While sub-chronic exposure had less effect on both GHR and IGF genes. The most notable tissue-specific effects and morphometric endpoints were observed upon sub-chronic exposure, such as changes in key genes involved in detoxification, DNA damage, and altered reproductive morphological endpoints; showing that sub-chronic BaP doses have longer-lasting toxic effects. This study shows that sub-chronic BaP exposure may compromise the health of Nile tilapia and sheds light on the changes of the GH/IGF axis and the biotransformation of the xenobiotics due to the presence of this contaminant.

Beta-Sitosterol Promotes Milk Protein and Fat Syntheses-Related Genes in Bovine Mammary Epithelial Cells

Simple Summary

The levels of milk fats and proteins are important indexes used to evaluate milk quality. Generally, feed additives are used to improve milk quality. This study aimed to investigate the effect of β-sitosterol on milk fat and protein gene expression in bovine mammary epithelial cells. β-sitosterol increased the β-casein levels in bovine mammary epithelial cells and promoted the expression of milk fat and protein synthesis-related genes, suggesting the use of β-sitosterol as a potential feed additive to improve milk quality in dairy cows.

Abstract

β-sitosterol, a phytosterol with multiple biological activities, has been used in the pharmaceutical industry. However, there are only a few reports on the use of β-sitosterol in improving milk synthesis in dairy cows. This study aimed to investigate the effects of β-sitosterol on milk fat and protein syntheses in bovine mammary epithelial cells (MAC-T) and its regulatory mechanism. MAC-T cells were treated with different concentrations (0.01, 0.1, 1, 5, 10, 20, 30, or 40 μM) of β-sitosterol, and the expression levels of milk protein and fat synthesis-related genes and proteins were analyzed. β-sitosterol at 0.1, 1, and 10 μM concentrations promoted the mRNA and protein expression of β-casein. β-sitosterol (0.1, 1, 10 μM) increased the mRNA and protein expression levels of signal transducer activator of transcription 5 (STAT5), mammalian target of rapamycin (mTOR), and ribosomal protein S6 kinase beta-1 (S6K1) of the JAK2/STAT5 and mTOR signaling pathways. It also stimulated the milk fat synthesis-related factors, including sterol regulatory element-binding protein 1 (SREBP1), peroxisome proliferator-activated receptor-gamma (PPARγ), acetyl-CoA carboxylase (ACC), lipoprotein lipase (LPL), and stearyl CoA desaturase (SCD). β-sitosterol (0.1, 1, 10 μM) also significantly increased the expression of growth hormone/insulin-like growth factor-1 (GH/IGF-1) axis and hypoxia-inducible factor-1α (HIF-1α)-related genes. Notably, the compound inhibited the expression of the negative regulator, the suppressor of cytokine signaling 2 (SOCS2) at the two lower concentrations (0.1, 1 μM), but significantly promoted the expression at the highest concentration (30 μM). These results highlight the role of β-sitosterol at concentrations ranging from 0.1 to 10 μM in improving milk protein and fat syntheses, regulating milk quality. Therefore, β-sitosterol can be used as a potential feed additive to improve milk quality in dairy cows.

Mel1b and Mel1c melatonin receptors mediate green light-induced secretion of growth hormone in chick adenohypophysis cells via the AC/PKA and ERK1/2 signalling pathways

A previous study showed that melatonin (MEL) membrane receptors 1b (Mel1b) and Mel1c promoted the secretion of growth hormone (GH) in chick adenohypophysis cells under monochromatic green light. However, the intracellular signalling pathways of these two receptors are unclear. Therefore, cultured adenohypophysis cells derived from chickens exposed to monochromatic green light were treated with MEL, Mel1b- and Mel1c-specific blockers, protein kinase A (PKA) inhibitors and adenylate cyclase (AC), or AC activator in vitro to explore the signal transduction mechanism that promote the secretion of GH. The results showed that Mel1b and Mel1c participate in MEL-mediated green light-induced secretion of GH in chick adenohypophysis cells. However, MEL increased cyclic adenosine monophosphate (cAMP) levels, and p-PKA protein levels were blocked by a Mel1b-specific antagonist but not a Mel1c-specific antagonist, which indicated that Mel1b affected the secretion of GH via the AC/cAMP/PKA signalling pathway. Moreover, Mel1b and Mel1c both activated ERK1/2 to regulate the secretion of GH. In addition, intracellular and extracellular Ca²⁺ channels were also involved in secretion of GH in chick adenohypophysis cells. These results demonstrate that the MEL mediated green light-induced secretion of GH in chick adenohypophysis via the Mel1b/AC/PKA/ERK1/2, Mel1c/ERK1/2, and intracellular and extracellular Ca2⁺ channel signalling pathways.

Dysregulated expression levels of APH1B in peripheral blood are associated with brain atrophy and amyloid-β deposition in Alzheimer's disease

BACKGROUND

The interaction between the brain and periphery might play a crucial role in the development of Alzheimer's disease (AD).

METHODS

Using blood transcriptomic profile data from two independent AD cohorts, we performed expression quantitative trait locus (cis-eQTL) analysis of 29 significant genetic loci from a recent large-scale genome-wide association study to investigate the effects of the AD genetic variants on gene expression levels and identify their potential target genes. We then performed differential gene expression analysis of identified AD target genes and linear regression analysis to evaluate the association of differentially expressed genes with neuroimaging biomarkers.

RESULTS

A cis-eQTL analysis identified and replicated significant associations in seven genes (APH1B, BIN1, FCER1G, GATS, MS4A6A, RABEP1, TRIM4). APH1B expression levels in the blood increased in AD and were associated with entorhinal cortical thickness and global cortical amyloid-β deposition.

CONCLUSION

An integrative analysis of genetics, blood-based transcriptomic profiles, and imaging biomarkers suggests that APH1B expression levels in the blood might play a role in the pathogenesis of AD.

Emerging role of signal transducer and activator of transcription 3 (STAT3) in pituitary adenomas

Pituitary adenomas are benign tumours that can cause an individual various clinical manifestations including tumour mass effects and/or the diverse effects of abnormal pituitary hormone secretion. Given the morbidity and limited treatment options for pituitary adenomas, there is a need for better biomarkers and treatment options. One molecule that is of specific interest is the signal transducer and activator of transcription 3 (STAT3), a transcription factor that plays a critical role in mediating cytokine-induced changes in gene expression. In addition, STAT3 controls cell proliferation by regulating mitochondrial activity. Not only does activation of STAT3 play a crucial role in tumorigenesis, including pituitary tumorigenesis, but a number of studies also demonstrate pharmacological STAT3 inhibition as a promising treatment approach for many types of tumours, including pituitary tumours. This review will focus on the role of STAT3 in different pituitary adenomas, in particular, growth hormone-producing adenomas and null cell adenomas. Furthermore, how STAT3 is involved in the cell proliferation and hormone regulation in pituitary adenomas and its potential role as a molecular therapeutic target in pituitary adenomas will be summarized.

Advances in differential diagnosis and management of growth hormone deficiency in children

Growth hormone (GH) deficiency (GHD) in children is defined as impaired production of GH by the pituitary gland that results in growth failure. This disease might be congenital or acquired, and occurs in isolation or in the setting of multiple pituitary hormone deficiency. Isolated GHD has an estimated prevalence of 1 patient per 4000-10,000 live births and can be due to multiple causes, some of which are yet to be determined. Establishing the correct diagnosis remains key in children with short stature, as initiating treatment with recombinant human GH can help them attain their genetically determined adult height. During the past two decades, our understanding of the benefits of continuing GH therapy throughout the transition period from childhood to adulthood has increased. Improvements in transitional care will help alleviate the consequent physical and psychological problems that can arise from adult GHD, although the consequences of a lack of hormone replacement are less severe in adults than in children. In this Review, we discuss the differential diagnosis in children with GHD, including details of clinical presentation, neuroimaging and genetic testing. Furthermore, we highlight advances and issues in the management of GHD, including details of transitional care.

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.

Effects of Growth Hormone Receptor Ablation in Corticotropin-Releasing Hormone Cells

Corticotropin-releasing hormone (CRH) cells are the dominant neuronal population responsive to the growth hormone (GH) in the paraventricular nucleus of the hypothalamus (PVH). However, the physiological importance of GH receptor (GHR) signaling in CRH neurons is currently unknown. Thus, the main objective of the present study was to investigate the consequences of GHR ablation in CRH-expressing cells of male and female mice. GHR ablation in CRH cells did not cause significant changes in body weight, body composition, food intake, substrate oxidation, locomotor activity, glucose tolerance, insulin sensitivity, counterregulatory response to 2-deoxy-D-glucose and ghrelin-induced food intake. However, reduced energy expenditure was observed in female mice carrying GHR ablation in CRH cells. The absence of GHR in CRH cells did not affect anxiety, circadian glucocorticoid levels or restraint-stress-induced corticosterone secretion and activation of PVH neurons in both male and female mice. In summary, GHR ablation, specifically in CRH-expressing neurons, does not lead to major alterations in metabolism, hypothalamic-pituitary-adrenal axis, acute stress response or anxiety in mice. Considering the previous studies showing that central GHR signaling regulates homeostasis in situations of metabolic stress, future studies are still necessary to identify the potential physiological importance of GH action on CRH neurons.

CISH attenuates homeostatic cytokine signaling to promote lung-specific macrophage programming and function

[Figure: see text].

Renal effects of growth hormone in health and in kidney disease

Growth hormone (GH) and its mediator insulin-like growth factor-1 (IGF-1) have manifold effects on the kidneys. GH and IGF receptors are abundantly expressed in the kidney, including the glomerular and tubular cells. GH can act either directly on the kidneys or via circulating or paracrine-synthesized IGF-1. The GH/IGF-1 system regulates glomerular hemodynamics, renal gluconeogenesis, tubular sodium and water, phosphate, and calcium handling, as well as renal synthesis of 1,25 (OH)2 vitamin D3 and the antiaging hormone Klotho. The latter also acts as a coreceptor of the phosphaturic hormone fibroblast-growth factor 23 in the proximal tubule. Recombinant human GH (rhGH) is widely used in the treatment of short stature in children, including those with chronic kidney disease (CKD). Animal studies and observations in acromegalic patients demonstrate that GH-excess can have deleterious effects on kidney health, including glomerular hyperfiltration, renal hypertrophy, and glomerulosclerosis. In addition, elevated GH in patients with poorly controlled type 1 diabetes mellitus was thought to induce podocyte injury and thereby contribute to the development of diabetic nephropathy. This manuscript gives an overview of the physiological actions of GH/IGF-1 on the kidneys and the multiple alterations of the GH/IGF-1 system and its consequences in patients with acromegaly, CKD, nephrotic syndrome, and type 1 diabetes mellitus. Finally, the impact of short- and long-term treatment with rhGH/rhIGF-1 on kidney function in patients with kidney diseases will be discussed.

Insulin-like growth factor signalling and its significance as a biomarker in fish and shellfish research

The insulin-like growth factor signalling system comprises insulin-like growth factors, insulin-like growth factor receptors and insulin-like growth factor-binding proteins. Along with the growth hormones, insulin-like growth factor signalling is very pivotal in the growth and development of all vertebrates. In fishes, insulin-like growth factors play an important role in osmoregulation, besides the neuroendocrine regulation of growth. Insulin-like growth factor concentration in plasma can assess the growth in fishes and shellfishes and therefore widely applied in nutritional research as an indicator to evaluate the performance of selected nutrients. The present review summarizes the role of insulin-like growth factor signalling in fishes and shellfishes, its significance in aquaculture and in evaluating growth, reproduction and development, and discusses the utility of this system as biomarkers for early indication of growth in aquaculture.

Growth hormone receptor disrupts glucose homeostasis via promoting and stabilizing retinol binding protein 4

Rationale: The molecular mechanisms underlying the pathogenesis of systemic insulin resistance in type 2 diabetes remain elusive. Growth hormone receptor (GHR) deficiency has long been known to improved insulin sensitivity. However, whether hepatic GHR overexpression or activation is a cause of insulin resistance is still unknown. The aim of this study was to identify the new role of GHR in systemic insulin resistance and explore the underlying mechanism.

Method: Different samples obtained from obese humans, ob/ob mice, db/db mice, high-fat diet (HFD)-fed mice and primary mouse hepatocytes were used to evaluate the correlations between GHR and metabolic disorders. Recombinant adeno-associated viruses encoding GHR and STAT5 and GHR knockout mice were used to investigate the roles of hepatic GHR in glucose homeostasis. Tissue H&E, Oil Red O and PAS staining were performed for histomorphological analysis. Gel filtration chromatography was employed for the separation of serum RBP4-TTR complexes. Plasmids (related to GHR, STAT5 and HIF1α), siRNA oligos (siGHR and siSTAT5), luciferase activity and ChIP assays were used to explore the potential mechanism of hepatic GHR.

Results: Here, we found that hepatic GHR expression was elevated during metabolic disorder. Accordingly, hepatic GHR overexpression disrupted systemic glucose homeostasis by promoting gluconeogenesis and disturbing insulin responsiveness in the liver. Meanwhile, hepatic GHR overexpression promoted lipolysis in white adipose tissue and repressed glucose utilization in skeletal muscle by promoting the circulating level of RBP4, which contributed to impaired systemic insulin action. A mechanistic study revealed that hepatic GHR disrupted systemic insulin sensitivity by increasing RBP4 transcription by activating STAT5. Additionally, overexpression of hepatic GHR promoted TTR transcriptional levels by enhancing the expression of HIF1α, which not only increased the protein stability of RBP4 but also inhibited renal clearance of RBP4 in serum.

Conclusions: Hepatic GHR overexpression and activation accelerated systemic insulin resistance by increasing hepatic RBP4 production and maintaining circulating RBP4 homeostasis. Our current study provides novel insights into the pathogenesis of type 2 diabetes and its associated metabolic complications.

Obesity and its impact on COVID-19

The severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) pandemic has proven a challenge to healthcare systems since its first appearance in late 2019. The global spread and devastating effects of coronavirus disease 2019 (COVID-19) on patients have resulted in countless studies on risk factors and disease progression. Overweight and obesity emerged as one of the major risk factors for developing severe COVID-19. Here we review the biology of coronavirus infections in relation to obesity. In particular, we review literature about the impact of adiposity-related systemic inflammation on the COVID-19 disease severity, involving cytokine, chemokine, leptin, and growth hormone signaling, and we discuss the involvement of hyperactivation of the renin-angiotensin-aldosterone system (RAAS). Due to the sheer number of publications on COVID-19, we cannot be completed, and therefore, we apologize for all the publications that we do not cite.

Dual Characters of GH-IGF1 Signaling Pathways in Radiotherapy and Post-radiotherapy Repair of Cancers

Radiotherapy remains one of the most important cancer treatment modalities. In the course of radiotherapy for tumor treatment, the incidental irradiation of adjacent tissues could not be completely avoided. DNA damage is one of the main factors of cell death caused by ionizing radiation, including single-strand (SSBs) and double-strand breaks (DSBs). The growth hormone-Insulin-like growth factor 1 (GH-IGF1) axis plays numerous roles in various systems by promoting cell proliferation and inhibiting apoptosis, supporting its effects in inducing the development of multiple cancers. Meanwhile, the GH-IGF1 signaling involved in DNA damage response (DDR) and DNA damage repair determines the radio-resistance of cancer cells subjected to radiotherapy and repair of adjacent tissues damaged by radiotherapy. In the present review, we firstly summarized the studies on GH-IGF1 signaling in the development of cancers. Then we discussed the adverse effect of GH-IGF1 signaling in radiotherapy to cancer cells and the favorable impact of GH-IGF1 signaling on radiation damage repair to adjacent tissues after irradiation. This review further summarized recent advances on research into the molecular mechanism of GH-IGF1 signaling pathway in these effects, expecting to specify the dual characters of GH-IGF1 signaling pathways in radiotherapy and post-radiotherapy repair of cancers, subsequently providing theoretical basis of their roles in increasing radiation sensitivity during cancer radiotherapy and repairing damage after radiotherapy.

Regulation of GH and GH Signaling by Nutrients

Growth hormone (GH) and insulin-like growth factor-1 (IGF-I) are pleiotropic hormones with important roles in lifespan. They promote growth, anabolic actions, and body maintenance, and in conditions of energy deprivation, favor catabolic feedback mechanisms switching from carbohydrate oxidation to lipolysis, with the aim to preserve protein storages and survival. IGF-I/insulin signaling was also the first one identified in the regulation of lifespan in relation to the nutrient-sensing. Indeed, nutrients are crucial modifiers of the GH/IGF-I axis, and these hormones also regulate the complex orchestration of utilization of nutrients in cell and tissues. The aim of this review is to summarize current knowledge on the reciprocal feedback among the GH/IGF-I axis, macro and micronutrients, and dietary regimens, including caloric restriction. Expanding the depth of information on this topic could open perspectives in nutrition management, prevention, and treatment of GH/IGF-I deficiency or excess during life.

Growth Hormone Modulation of Hepatic Epidermal Growth Factor Receptor Signaling

Epidermal growth factor receptor (EGFR) signaling has a central role in the regenerative response of the liver upon injury and is involved in cellular transformation linked to chronic damage. Hepatic EGFR expression, trafficking, and signaling are regulated by growth hormone (GH). Chronically elevated GH levels are associated with liver cancer development and progression in mice. Studies in different in vivo experimental models indicate that EGF and GH mutually crossregulate in a complex manner. Several factors, such as the extent of exposure to supraphysiological GH levels and the pattern of GH administration, are important variables to be considered in exploring the interplay between the two hormones in connection with the progression of hepatic tumors.

Mesenchymal growth hormone receptor deficiency leads to failure of alveolar progenitor cell function and severe pulmonary fibrosis

Recent studies have identified impaired type 2 alveolar epithelial cell (ATII) renewal in idiopathic pulmonary fibrosis (IPF) human organoids and severe fibrosis when ATII is defective in mice. ATIIs function as progenitor cells and require supportive signals from the surrounding mesenchymal cells. The mechanisms by which mesenchymal cells promote ATII progenitor functions in lung fibrosis are incompletely understood. We identified growth hormone receptor (GHR) is mainly expressed in mesenchymal cells, and its expression is substantially decreased in IPF lungs. Higher levels of GHR expression correlated with better lung function in patients with IPF. Profibrotic mesenchymal cells retarded ATII growth and were associated with suppressed vesicular GHR expression. Vesicles enriched with Ghr promote ATII proliferation and diminished pulmonary fibrosis in mesenchymal Ghr-deficient mice. Our findings demonstrate a previously unidentified mesenchymal paracrine signaling coordinated by GHR that is capable of supporting ATII progenitor cell renewal and limiting the severity of lung fibrosis.

Evaluation of the anticonvulsant and neuroprotective effect of intracerebral administration of growth hormone in rats

INTRODUCTION

The growth hormone (GH) has been reported as a crucial neuronal survival factor in the hippocampus against insults of diverse nature. Status epilepticus (SE) is a prolonged seizure that produces extensive neuronal cell death. The goal of this study was to evaluate the effect of intracerebroventricular administration of GH on seizure severity and SE-induced hippocampal neurodegeneration.

METHODOLOGY

Adult male rats were implanted with a guide cannula in the left ventricle and different amounts of GH (70, 120 or 220ng/3μl) were microinjected for 5 days; artificial cerebrospinal fluid was used as the vehicle. Seizures were induced by the lithium-pilocarpine model (3mEq/kg LiCl and 30mg/kg pilocarpine hydrochloride) one day after the last GH administration. Neuronal injury was assessed by Fluoro-Jade B (F-JB) staining.

RESULTS

Rats injected with 120ng of GH did not had SE after 30mg/kg pilocarpine, they required a higher number of pilocarpine injections to develop SE than the rats pretreated with the vehicle, 70ng or 220ng GH. Prefrontal and parietal cortex EEG recordings confirmed that latency to generalized seizures and SE was also significantly higher in the 120ng group when compared with all the experimental groups. FJ-B positive cells were detected in the hippocampus after SE in all rats, and no significant differences in the number of F-JB cells in the CA1 area and the hilus was observed between experimental groups.

CONCLUSION

Our results indicate that, although GH has an anticonvulsive effect in the lithium-pilocarpine model of SE, it does not exert hippocampal neuroprotection after SE.

Sex-Specific Temporal Trends in Overweight and Obese Among Schoolchildren From 2009 to 2018: An Age Period Cohort Analysis

Background: Our study examined the age, period, and cohort effects on overweight and obesity in children using a 10-year dataset collected from schoolchildren in Hualien, Taiwan. Methods: We used data from the annual health checkup of a total of 94,661 schoolchildren in primary schools and junior high schools in Hualien from 2009 to 2018. Children were defined as overweight or obese by the gender- and age-specific norm of the body mass index. We conducted the age-period-cohort (APC) analysis in boys and girls separately. Results: From 2009 to 2018, the rates of children overweight and obese were 12.78 and 14.23%, respectively. Boys had higher rates of overweight and obesity than girls (29.73 vs. 24.03%, P < 0.001). Based on APC analysis results, positive age effect existed regardless of gender. The risk of overweight or obesity of children aged 9 or 12 years was significantly higher compared to the average rate. As for period effect, a fluctuating downward trend in overweight was evident in 2016, and a similar trend in obesity was seen in 2017 across gender groups. The birth cohort of 2007 to 2009 had a significant higher proportion of overweight and obese than other birth cohorts. This indicated that the proportion of children overweight and obese in the young generation is higher than that in the old generation. Conclusion: An increased risk of children overweight or obese was associated with age and later birth cohort. For the period effect, the trend in the prevalence of overweight and obesity fluctuated downward slowly from 2016 to 2017.

Effects of a Mixture of Humulus japonicus on Longitudinal Bone Growth in Hypophysectomized Rats

Previously, we reported that the administration of a mixture of Humulus japonicus (MH) increased the longitudinal bone growth rate in Sprague Dawley rats. In this study, we investigated the effects of the dietary administration of MH on longitudinal bone growth in growth hormone (GH)-deficient hypophysectomized male and female rats to determine whether the effect of MH was similar to that of GH. We measured the nose-to-anus and nose-to-tail length gain, femur and tibia lengths, growth plate zones, and expression of insulin-like growth factor-1 (IGF-1) and IGF-binding protein-3 (IGFBP-3) after the dietary administration of MH or the injection of GH into hypophysectomized rats for 4 weeks. Results demonstrated that the dietary administration of MH had no effect on longitudinal bone growth, whereas the injection of GH increased the nose-to-tail length gain and femur and tibia lengths in hypophysectomized rats. In addition, MH did not affect the growth plate, bone mineralization, and expression of IGF-1 and IGFBP-3. These findings indicate that MH does not exert a GH-like effect and that the effects of MH and GH on longitudinal bone growth involve different pathways.

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.

The Role of MicroRNAs in Influencing Body Growth and Development

Body growth and development are regulated among others by genetic and epigenetic factors. MicroRNAs (miRNAs) are epigenetic regulators of gene expression that act at the post-transcriptional level, thereby exerting a strong influence on regulatory gene networks. Increasing studies suggest the importance of miRNAs in the regulation of the growth plate and growth hormone (GH)-insulin-like growth factor (IGF) axis during the life course in a broad spectrum of animal species, contributing to longitudinal growth. This review summarizes the role of miRNAs in regulating growth in different in vitro and in vivo models acting on GH, GH receptor (GHR), IGFs, and IGF1R genes besides current knowledge in humans, and highlights that this regulatory system is of importance for growth.

Growth Hormone Releasing Hormone Reduces Circulating Markers of Immune Activation in Parallel with Effects on Hepatic Immune Pathways in Individuals with HIV-Infection and Nonalcoholic Fatty Liver Disease

BACKGROUND

The growth hormone (GH)/insulin-like growth factor-1 (IGF-1) axis modulates critical metabolic pathways; however, little is known regarding effects of augmenting pulsatile GH secretion on immune function in humans. This study used proteomics and gene set enrichment analysis to assess effects of a GH releasing hormone (GHRH) analog, tesamorelin, on circulating immune markers and liver tissue in people with HIV (PWH) and NAFLD.

METHODS

92 biomarkers associated with immunity, chemotaxis, and metabolism were measured in plasma samples from 61 PWH with NAFLD who participated in a double-blind, randomized trial of tesamorelin versus placebo for 12 months. Gene set enrichment analysis was performed on serial liver biopsies targeted to immune pathways.

RESULTS

Tesamorelin, compared to placebo, decreased interconnected proteins related to cytotoxic T-cell and monocyte activation. Circulating concentrations of 13 proteins were significantly decreased, and no proteins increased, by tesamorelin. These included four chemokines (CCL3, CCL4, CCL13 [MCP4], IL8 [CXCL8]), two cytokines (IL-10 and CSF-1), and four T-cell associated molecules (CD8A, CRTAM, GZMA, ADGRG1), as well as ARG1, Gal-9, and HGF. Network analysis indicated close interaction among the gene pathways responsible for these proteins, with imputational analyses suggesting down regulation of a closely related cluster of immune pathways. Targeted transcriptomics using liver tissue confirmed a significant end-organ signal of down-regulated immune activation pathways.

CONCLUSIONS

Long-term treatment with a GHRH analog reduced markers of T-cell and monocyte/macrophage activity, suggesting that augmentation of the GH axis may ameliorate immune activation in an HIV population with metabolic dysregulation, systemic and end organ inflammation.

Significant down-regulation of growth hormone receptor expression revealed as a new unfavorable prognostic factor in hepatitis C virus-related hepatocellular carcinoma

BACKGROUND/AIMS

Growth hormone (GH) is the main regulator of somatic growth, metabolism, and gender dimorphism in the liver. GH receptor (GHR) signaling in cancer is derived from a large body of evidence, although the GHR signaling pathway involved in the prognosis of hepatocellular carcinoma (HCC) in patients with hepatitis C virus (HCV)-related HCC, remains unclear. We aimed to explore the expression of GHR and analyze its association with clinicopathologic features and prognosis of patients with chronic hepatitis C and HCC.

METHODS

The expression of GHR mRNA was investigated by quantitative real-time polymerase chain reaction in paired tumors and adjacent non-tumorous (ANT) liver tissues of 200 patients with chronic hepatitis C and HCC. Western blotting and immunofluorescence assays using the HCV-infected Huh7.5.1 cell model was performed.

RESULTS

GHR mRNA was significantly lower in HCV-HCC tissues than in corresponding ANT liver tissues. GHR mRNA and protein levels also decreased in the HCV-infected Huh7.5.1 cell model. Notably, lower GHR expression was associated with age of >60 years (P=0.0111) and worse clinicopathologic characteristics, including alpha-fetoprotein >100 ng/mL (P=0.0403), cirrhosis (P=0.0075), vascular invasion (P=0.0052), pathological stage II-IV (P=0.0002), and albumin ≤4.0 g/dL (P=0.0055), which were linked with poor prognosis of HCC. Most importantly, the high incidence of recurrence and poor survival rates in patients with a low ratio of tumor/ANT GHR (≤0.1) were observed, indicating that low expression levels of GHR had great risk for development of HCC in patients with chronic hepatitis C.

CONCLUSION

Our study demonstrates a significant down-regulation of GHR expression as a new unfavorable independent prognostic factor in patients with chronic hepatitis C and HCC.

A novel peptide antagonist of the human growth hormone receptor

Excess circulating human growth hormone (hGH) in vivo is linked to metabolic and growth disorders such as cancer, diabetes, and acromegaly. Consequently, there is considerable interest in developing antagonists of hGH action. Here, we present the design, synthesis, and characterization of a 16-residue peptide (site 1-binding helix [S1H]) that inhibits hGH-mediated STAT5 phosphorylation in cultured cells. S1H was designed as a direct sequence mimetic of the site 1 mini-helix (residues 36-51) of wild-type hGH and acts by inhibiting the interaction of hGH with the human growth hormone receptor (hGHR). In vitro studies indicated that S1H is stable in human serum and can adopt an α-helix in solution. Our results also show that S1H mitigates phosphorylation of STAT5 in cells co-treated with hGH, reducing intracellular STAT5 phosphorylation levels to those observed in untreated controls. Furthermore, S1H was found to attenuate the activity of the hGHR and the human prolactin receptor, suggesting that this peptide acts as an antagonist of both lactogenic and somatotrophic hGH actions. Finally, we used alanine scanning to determine how discrete amino acids within the S1H sequence contribute to its structural organization and biological activity. We observed a strong correlation between helical propensity and inhibitory effect, indicating that S1H-mediated antagonism of the hGHR is largely dependent on the ability for S1H to adopt an α-helix. Taken together, these results show that S1H not only acts as a novel peptide-based antagonist of the hGHR but can also be applied as a chemical tool to study the molecular nature of hGH-hGHR interactions.

A Balanced Act: The Effects of GH-GHR-IGF1 Axis on Mitochondrial Function

Mitochondrial function is multifaceted in response to cellular energy homeostasis and metabolism, with the generation of adenosine triphosphate (ATP) through the oxidative phosphorylation (OXPHOS) being one of their main functions. Selective elimination of mitochondria by mitophagy, in conjunction with mitochondrial biogenesis, regulates mitochondrial function that is required to meet metabolic demand or stress response. Growth hormone (GH) binds to the GH receptor (GHR) and induces the JAK2/STAT5 pathway to activate the synthesis of insulin-like growth factor 1 (IGF1). The GH–GHR–IGF1 axis has been recognized to play significant roles in somatic growth, including cell proliferation, differentiation, division, and survival. In this review, we describe recent discoveries providing evidence for the contribution of the GH–GHR–IGF1 axis on mitochondrial biogenesis, mitophagy (or autophagy), and mitochondrial function under multiple physiological conditions. This may further improve our understanding of the effects of the GH–GHR–IGF1 axis on mitochondrial function, which may be controlled by the delicate balance between mitochondrial biogenesis and mitophagy. Specifically, we also highlight the challenges that remain in this field.

The Attenuated Secretion of Hyaluronan by UVA-Exposed Human Fibroblasts Is Associated with Up- and Downregulation of HYBID and HAS2 Expression via Activated and Inactivated Signaling of the p38/ATF2 and JAK2/STAT3 Cascades

Little is known about the effects on hyaluronan (HA) metabolism of UVA radiation. This study demonstrates that the secretion of HA by human dermal fibroblasts (HDFs) is downregulated by UVA, accompanied by the down- and upregulation of mRNA and protein levels of the HA-synthesizing enzyme (HAS2) and the HA-degrading protein, HYaluronan Binding protein Involved in HA Depolymerization(HYBID), respectively. Signaling analysis revealed that the exposure distinctly elicits activation of the p38/MSK1/CREB/c-Fos/AP-1 axis, the JNK/c-Jun axis, and the p38/ATF-2 axis, but downregulates the phosphorylation of NF-kB and JAK/STAT3. A signal inhibition study demonstrated that the inhibition of p38 significantly abrogates the UVA-accentuated mRNA level of HYBID. Furthermore, the inhibition of STAT3 significantly downregulates the level of HAS2 mRNA in non-UVA exposed HDFs. Analysis using siRNAs demonstrated that transfection of ATF-2 siRNA but not c-Fos siRNA abrogates the increased protein level of HYBID in UVA-exposed HDFs. An inhibitor of protein tyrosine phosphatase but not of protein serine/threonine phosphatase restored the diminished phosphorylation level of STAT3 at Tyr 705, accompanied by a significant abolishing effect on the decreased mRNA expression level of HAS2. Silencing with a protein tyrosine phosphatase PTP-Meg2 siRNA revealed that it abrogates the decreased phosphorylation of STAT3 at Tyr 705 in UVA-exposed HDFs. These findings suggest that the UVA-induced decrease in HA secretion by HDFs is attributable to the down- and upregulation of HAS2 and HYBID expression, respectively, changes that are mainly ascribed to the inactivated signaling of the STAT3 axis due to the activated tyrosine protein phosphatase PTP-Meg2 and the activated signaling of the p38/ATF2 axis, respectively.

GWAS of three molecular traits highlights core genes and pathways alongside a highly polygenic background

Genome-wide association studies (GWAS) have been used to study the genetic basis of a wide variety of complex diseases and other traits. We describe UK Biobank GWAS results for three molecular traits-urate, IGF-1, and testosterone-with better-understood biology than most other complex traits. We find that many of the most significant hits are readily interpretable. We observe huge enrichment of associations near genes involved in the relevant biosynthesis, transport, or signaling pathways. We show how GWAS data illuminate the biology of each trait, including differences in testosterone regulation between females and males. At the same time, even these molecular traits are highly polygenic, with many thousands of variants spread across the genome contributing to trait variance. In summary, for these three molecular traits we identify strong enrichment of signal in putative core gene sets, even while most of the SNP-based heritability is driven by a massively polygenic background.

Comparison of Growth Velocity Among School Age Children With Different Body Mass Index From Childhood Into Early Adolescence in Hualien County, Taiwan: A Retrospective Cohort Study

Objective: This study aimed to investigate the contribution of high body mass index (BMI) to growth velocity among school-aged children who remained in the same BMI categories for a 6-year period. Methods: This retrospective cohort study included children who enrolled in the school year 2009 and remained in the same BMI categories during their 1st, 4th, and 7th grades (6-7, 9-10, 12-13 years of age). Annual linear growth velocity and weight gain were calculated and compared between sexes, BMI groups, and different times. Risk analysis and repeated measures analysis of variance were performed to identify the impact of BMI on growth velocity. Results: Of the 1,637 subjects, 53.0% were male, and 2.5% and 10.9% belonged to BMI groups of overweight and obese, respectively. In students between 6 and 13 years of age, obesity was associated with higher annual weight gain and height gain. Risk analysis showed that obese subjects had higher linear growth velocity than normal BMI groups of both sexes between 6 and 9 years of age. Unexpectedly, overweight and obese girls between 9 and 13 years of age had less linear growth velocity than underweight girls at the same interval. Repeated measures analysis of variance in both sexes showed a significant statistical association between BMI and different times of growth. However, the effect was less in girls between 9 and 13 years of age. Conclusion: Puberty may dominate over BMI as the main contributor to high growth velocity in girls with underweight BMI emerging into pubertal age.

Assessing the effects of genotype-by-environment interaction on epigenetic, transcriptomic, and phenotypic response in a Pacific salmon

Genotype-by-environment (GxE) interactions are non-parallel reaction norms among individuals with different genotypes in response to different environmental conditions. GxE interactions are an extension of phenotypic plasticity and consequently studying such interactions improves our ability to predict effects of different environments on phenotype as well as the fitness of genetically distinct organisms and their capacity to interact with ecosystems. Growth hormone transgenic coho salmon grow much faster than non-transgenics when raised in tank environments, but show little difference in growth when reared in nature-like streams. We used this model system to evaluate potential mechanisms underlying this growth rate GxE interaction, performing RNA-seq to measure gene transcription and whole-genome bisulfite sequencing to measure gene methylation in liver tissue. Gene ontology (GO) term analysis revealed stress as an important biological process potentially influencing growth rate GxE interactions. While few genes with transcription differences also had methylation differences, in promoter or gene regions, many genes were differentially methylated between tank and stream environments. A GO term analysis of differentially methylated genes between tank and stream environments revealed increased methylation in the stream environment of more than 95% of the differentially methylated genes, many with biological processes unrelated to liver function. The lower nutritional condition of the stream environment may cause increased negative regulation of genes less vital for liver tissue function than when fish are reared in tanks with unlimited food availability. These data show a large effect of rearing environment both on gene expression and methylation, but it is less clear that the detected epigenetic marks are responsible for the observed altered growth and physiological responses.

Do some viruses use growth hormone, prolactin and their receptors to facilitate entry into cells?: Episodic evolution of hormones and receptors suggests host-virus arms races; related placental lactogens may provide protective viral decoys

The molecular evolution of pituitary growth hormone and prolactin in mammals shows two unusual features: episodes of markedly accelerated evolution and, in some species, complex families of related proteins expressed in placenta and resulting from multiple gene duplications. Explanations of these phenomena in terms of physiological adaptations seem unconvincing. Here, I propose an alternative explanation, namely that these evolutionary features reflect the use of the hormones (and their receptors) as viral receptors. Episodes of rapid evolution can then be explained as due to "arms races" in which changes in the hormone lead to reduced interaction with the virus, and subsequent changes in the virus counteract this. Placental paralogues of the hormones could provide decoys that bind viruses, and protect the foetus against infection. The hypothesis implies that the extensive changes introduced into growth hormone, prolactin and their receptors during the course of mammalian evolution reflect viral interactions, not endocrine adaptations.

Chronic inflammation and the growth hormone/insulin-like growth factor-1 axis

Interactions between growth hormone (GH), insulin-like growth factor-1 (IGF-1), and the immune system are complex, bidirectional, but not fully explained. Current reviews based on numerous studies have indicated that chronic inflammation could suppress the GH/IGF-1 axis via several mechanisms such as relative GH and/or IGF-1 insufficiency, peripheral resistance to GH and/or IGF-1 resulting from down-regulation of GH and IGF-1 receptors, disruption in the GH/IGF-1 signalling pathways, dysregulation of IGF binding proteins (IGFBPs), reduced IGF bioavailability, and modified gene regulation due to changes in the microRNA system. It is well-known that relationships between the immune system and the GH/IGF-1 axis are mutual and GH as well as IGF-1 could modulate inflammatory response and the activity of systemic inflammation. Available data indicate that the GH/IGF-1 axis exerts both pro-inflammatory and anti-inflammatory effects. Pro-inflammatory cytokines such as interleukin-6 (IL-6), tumour necrosis factor-a (TNF-α), and interleukin-1b (IL-b) are some of the most significant factors, besides malnutrition, chronic stress, and prolonged use of glucocorticoids, which impair the activity of the GH/IGF-1 axis, and consequently lead to growth retardation in children suffering from childhood-onset chronic inflammatory diseases. In this review, we discuss the mechanisms underlying the impact of chronic inflammation on the GH/IGF-1 axis and growth processes during childhood and adolescence, based on a number of experimental and human studies.

GHR signalling: Receptor activation and degradation mechanisms

Growth hormone (GH) actions via initiating cell signalling through the GH receptor (GHR) are important for many physiological processes, in addition to its well-known role in regulating growth. The activation of JAK-STAT signalling by GH is well characterized, however knowledge on GH activation of SRC family kinases (SFKs) is still limited. In this review we summarise the collective knowledge on the activation, regulation, and downstream signalling of GHR. We highlight studies on GH activation of SFKs and the important outcome of this signalling pathway with a focus on the different degradation mechanisms that can regulate GHR availability since this is an area that warrants further study considering its role in tumour progression.

Integrative Analyses of mRNA Expression Profile Reveal SOCS2 and CISH Play Important Roles in GHR Mutation-Induced Excessive Abdominal Fat Deposition in the Sex-Linked Dwarf Chicken

Sex-linked dwarf (SLD) chicken, which is caused by a recessive mutation of the growth hormone receptor (GHR), has been widely used in the Chinese broiler industry. However, it has been found that the SLD chicken has more abdominal fat deposition than normal chicken. Excessive fat deposition not only reduced the carcass quality of the broilers but also reduced the immunity of broilers to diseases. To find out the key genes and the precise regulatory pathways that were involved in the GHR mutation-induced excessive fat deposition, we used high-fat diet (HFD) and normal diet to feed the SLD chicken and normal chicken and analyzed the differentially expressed genes (DEGs) among the four groups. Results showed that the SLD chicken had more abdominal fat deposition and larger adipocytes size than normal chicken and HFD can promote abdominal fat deposition and induce adipocyte hypertrophy. RNA sequencing results of the livers and abdominal fats from the above chickens revealed that many DEGs between the SLD and normal chickens were enriched in fat metabolic pathways, such as peroxisome proliferator-activated receptor (PPAR) signaling, extracellular matrix (ECM)-receptor pathway, and fatty acid metabolism. Importantly, by constructing and analyzing the GHR-downstream regulatory network, we found that suppressor of cytokine signaling 2 (SOCS2) and cytokine-inducible SH2-containing protein (CISH) may involve in the GHR mutation-induced abdominal fat deposition in chicken. The ectopic expression of SOCS2 and CISH in liver-related cell line leghorn strain M chicken hepatoma (LMH) cell and immortalized chicken preadipocytes (ICP) revealed that these two genes can regulate fatty acid metabolism, adipocyte differentiation, and lipid droplet accumulation. Notably, overexpression of SOCS2 and CISH can rescue the hyperactive lipid metabolism and excessive lipid droplet accumulation of primary liver cell and preadipocytes that were isolated from the SLD chicken. This study found some genes and pathways involved in abdominal fat deposition of the SLD chicken and reveals that SOCS2 and CISH are two key genes involved in the GHR mutation-induced excessive fat deposition of the SLD chicken.

GH directly inhibits steatosis and liver injury in a sex-dependent and IGF1-independent manner

A reduction in hepatocyte growth hormone (GH)-signaling promotes non-alcoholic fatty liver disease (NAFLD). However, debate remains as to the relative contribution of the direct effects of GH on hepatocyte function vs indirect effects, via alterations in insulin-like growth factor 1 (IGF1). To isolate the role of hepatocyte GH receptor (GHR) signaling, independent of changes in IGF1, mice with adult-onset, hepatocyte-specific GHR knockdown (aHepGHRkd) were treated with a vector expressing rat IGF1 targeted specifically to hepatocytes. Compared to GHR-intact mice, aHepGHRkd reduced circulating IGF1 and elevated GH. In male aHepGHRkd, the shift in IGF1/GH did not alter plasma glucose or non-esterified fatty acids (NEFA), but was associated with increased insulin, enhanced systemic lipid oxidation and reduced white adipose tissue (WAT) mass. Livers of male aHepGHRkd exhibited steatosis associated with increased de novo lipogenesis, hepatocyte ballooning and inflammation. In female aHepGHRkd, hepatic GHR protein levels were not detectable, but moderate levels of IGF1 were maintained, with minimal alterations in systemic metabolism and no evidence of steatosis. Reconstitution of hepatocyte IGF1 in male aHepGHRkd lowered GH and normalized insulin, whole body lipid utilization and WAT mass. However, IGF1 reconstitution did not reduce steatosis or eliminate liver injury. RNAseq analysis showed IGF1 reconstitution did not impact aHepGHRkd-induced changes in liver gene expression, despite changes in systemic metabolism. These results demonstrate the impact of aHepGHRkd is sexually dimorphic and the steatosis and liver injury observed in male aHepGHRkd mice is autonomous of IGF1, suggesting GH acts directly on the adult hepatocyte to control NAFLD progression.

Enhanced Bioactivity of a Human GHR Antagonist Generated by Solid-Phase Site-Specific PEGylation

Growth hormone (GH) has been implicated in cancer progression andis a potential target for anticancer therapy. Currently, pegvisomant is the only GH receptor (GHR) antagonist approved for clinical use. Pegvisomant is a mutated GH molecule (B2036) which is PEGylated on amine groups to extend serum half-life. However, PEGylation significantly reduces the bioactivity of the antagonist in mice. To improve bioactivity, we generated a series of B2036 conjugates with the site-specific attachment of 20, 30, or 40 kDa methoxyPEG maleimide (mPEG maleimide) by introduction of a cysteine residue at amino acid 144 (S144C). Recombinant B2036-S144C was expressed in Escherichia coli, purified, and then PEGylated using cysteine-specific conjugation chemistry. To avoid issues with dimerization due to the introduced cysteine, B2036-S144C was PEGylated while immobilized on an Ni-nitrilotriacetic (Ni-NTA) acid column, which effectively reduced disulfide-mediated dimer formation and allowed efficient conjugation to mPEG maleimide. Following PEGylation, the IC₅₀ values for the 20, 30, and 40 kDa mPEG maleimide B2036-S144C conjugates were 66.2 ± 3.8, 106.1 ± 7.1, and 127.4 ± 3.6 nM, respectively. The circulating half-life of the 40 kDa mPEG conjugate was 58.3 h in mice. Subcutaneous administration of the 40 kDa mPEG conjugate (10 mg/kg/day) reduced serum insulin-like growth factor I (IGF-I) concentrations by 50.6%. This in vivo reduction in serum IGF-I was at a considerably lower dose compared to the higher doses required to observe comparable activity in studies with pegvisomant. In conclusion, we have generated a novel PEGylated GHR antagonist by the solid-phase site-specific attachment of mPEG maleimide at an introduced cysteine residue, which effectively reduces serum IGF-I in vivo.

Growth Hormone Upregulates Mediators of Melanoma Drug Efflux and Epithelial-to-Mesenchymal Transition In Vitro and In Vivo

Simple Summary

Growth hormone (GH) action is strongly implicated in the progression and therapy resistance in several types of solid tumors which overexpress the GH receptor (GHR). The aim of our study was to characterize the effects of GH and its downstream effector insulin-like growth factor 1 (IGF-1) on melanoma using in vitro and in vivo models. We confirmed an IGF-1-independent role of elevated circulating GH in upregulating key mechanisms of therapy resistance and malignancy with analyses conducted at the molecular and cellular level. We identified that GH upregulates key mechanisms of therapy resistance and metastases in melanoma tumors in an IGF-1 dependent and independent manner by upregulating multidrug efflux pumps and EMT transcription factors. Our study reveals that GH action renders an intrinsic drug resistance phenotype to the melanoma tumors—a clinically crucial property of GH verifiable in other human cancers with GHR expression.

Abstract

Growth hormone (GH) and the GH receptor (GHR) are expressed in a wide range of malignant tumors including melanoma. However, the effect of GH/insulin-like growth factor (IGF) on melanoma in vivo has not yet been elucidated. Here we assessed the physical and molecular effects of GH on mouse melanoma B16-F10 and human melanoma SK-MEL-30 cells in vitro. We then corroborated these observations with syngeneic B16-F10 tumors in two mouse lines with different levels of GH/IGF: bovine GH transgenic mice (bGH; high GH, high IGF-1) and GHR gene-disrupted or knockout mice (GHRKO; high GH, low IGF-1). In vitro, GH treatment enhanced mouse and human melanoma cell growth, drug retention and cell invasion. While the in vivo tumor size was unaffected in both bGH and GHRKO mouse lines, multiple drug-efflux pumps were up regulated. This intrinsic capacity of therapy resistance appears to be GH dependent. Additionally, epithelial-to-mesenchymal transition (EMT) gene transcription markers were significantly upregulated in vivo supporting our current and recent in vitro observations. These syngeneic mouse melanoma models of differential GH/IGF action can be valuable tools in screening for therapeutic options where lowering GH/IGF-1 action is important.

Classical and novel GH receptor signaling pathways

In this review, I summarize historical and recent features of the classical pathways activated by growth hormone (GH) through the cell surface GH receptor (GHR). GHR is a cytokine receptor superfamily member that signals by activating the non-receptor tyrosine kinase, JAK2, and members of the Src family kinases. Activation of the GHR engages STATs, PI3K, and ERK pathways, among others, and details of these now-classical pathways are presented. Modulating elements, including the SOCS proteins, phosphatases, and regulated GHR metalloproteolysis, are discussed. In addition, a novel physical and functional interaction of GHR with IGF-1R is summarized and discussed in terms of its mechanisms, consequences, and physiological and therapeutic implications.

Role of the GH-IGF1 system in progression of cancer

Emerging evidence links the growth hormone (GH)-insulin-like growth factor-1 (IGF1) endocrine axis to cancer development. While this putative correlation is of major translational relevance, most clinical and epidemiological reports to date found no causal linkage between GH therapy and enhanced cancer risk. Thus, it is generally agreed that GH therapy constitutes a safe pharmacological intervention. The present review focuses on a number of issues in the area of GH-IGF1 action in cancer development. Emphasis is given to the idea that GH and IGF1 do not conform to the definition of oncogenic factors. Specifically, these hormones, even at high pharmacological doses, are unable to induce malignant transformation. However, the GH-IGF1 axis is capable of 'pushing' already transformed cells through the various phases of the cell cycle. Viral and cellular oncogenes require an intact IGF1 signaling pathway in order to elicit transformation; in other words, oncogenic agents adopt the IGF1 pathway. This universal mechanism of action of oncogenes has broad implications in oncology. Our review provides an in-depth analysis of the interplay between the GH-IGF1 axis and cancer genes, including tumor suppressors p53 and BRCA1. Finally, the safety of GH therapy in both children and adults needs further long-term follow-up studies.

Healthful aging mediated by inhibition of oxidative stress

The progressive increase in lifespan over the past century carries with it some adversity related to the accompanying burden of debilitating diseases prevalent in the older population. This review focuses on oxidative stress as a major mechanism limiting longevity in general, and healthful aging, in particular. Accordingly, the first goal of this review is to discuss the role of oxidative stress in limiting longevity, and compare healthful aging and its mechanisms in different longevity models. Secondly, we discuss common signaling pathways involved in protection against oxidative stress in aging and in the associated diseases of aging, e.g., neurological, cardiovascular and metabolic diseases, and cancer. Much of the literature has focused on murine models of longevity, which will be discussed first, followed by a comparison with human models of longevity and their relationship to oxidative stress protection. Finally, we discuss the extent to which the different longevity models exhibit the healthful aging features through physiological protective mechanisms related to exercise tolerance and increased β-adrenergic signaling and also protection against diabetes and other metabolic diseases, obesity, cancer, neurological diseases, aging-induced cardiomyopathy, cardiac stress and osteoporosis.

Luzhong mutton sheep: inbreeding and selection signatures

Intense artificial selection has been imposed to Luzhong mutton sheep population in the past years. Improvements on growth and reproductive performance are two breeding goals in the present herd. Although some progresses were phenotypically observed possibly due to inbreeding induced by strong selection in terms of these traits, the genomic evaluation was poorly understood. Therefore, a high-density SNP array was used to characterize the pattern of runs of homozygosity (ROH), estimate inbreeding and inbreeding depressions on early growth performance and litter size based upon ROH, and scan positive selection signatures of recent population. Consequently, a low inbreeding level was observed which had negative effects on litter size, but not on early growth performance. And 160 genes were under selection, of which some were reported to be linked to several traits of sheep including body weight, litter size, carcass and meat quality, milk yield and composition, fiber quality and health, and the top genes were associated with growth (growth hormone [GH]- growth hormone receptor [GHR]- Insulin-like growth factor 1 [IGF1] axis) and litter size (bone morphogenic proteins [BMPs]-associated). The effectiveness of previous breeding measures was highlighted, but purging selection was proposed to alleviate the inbreeding depression on litter size, providing some genomic insights to breeding management of Luzhong mutton sheep.

Identification of key genes involved in JAK/STAT pathway in colorectal cancer

JAK/STAT pathway has been well confirmed in the development of colorectal cancer (CRC), however, the exact mechanism is unclear. Therefore, we aimed to identify key genes involved in JAK/STAT pathway in CRC, as well as the potential mechanism. RT² profiler PCR arrays were performed to identify key genes of the JAK/STAT pathway. GO, KEGG pathway and PPI analyses were performed to screen the main functions of differentially expressed genes (DEGs). Moreover, the expression of DEGs was detected by GEPIA based on TCGA database and verified by qPCR and/or Western blot. Subsequently, the association between the two DEGs (CXCL9 and IL6ST) and clinicopathological features were determined by immunohistochemistry, and survival analysis was also conducted. Finally, the effects of IL6ST overexpression on STAT3 activation and HT29 cell functions were analyzed. A total of 14 DEGs were identified. Among the DEGs, GHR, NR3C1, IL6ST and A2M were confirmed to be statistically decreased, while CXCL9 was significantly increased in the CRC tissues. Furthermore, CXCL9 was significantly associated with differentiation, lymph node metastasis, distant metastasis and invasion, while IL6ST was related with tumor size, differentiation, stage and invasion. Patients with high expression of IL6ST presented significantly lower lifetime, however, CXCL9 showed the opposite results without significance. Additionally, we found that overexpression of IL6ST statistically elevated p-STAT3 level, cell viability, adhesion rate and migration, and decreased apoptosis, but had no effects on cell cycle. Our results suggest that IL6ST is a critical key gene involved in JAK/STAT signaling pathway in CRC.

Growth Hormone Receptor Regulation in Cancer and Chronic Diseases

The GHR signaling pathway plays important roles in growth, metabolism, cell cycle control, immunity, homeostatic processes, and chemoresistance via both the JAK/STAT and the SRC pathways. Dysregulation of GHR signaling is associated with various diseases and chronic conditions such as acromegaly, cancer, aging, metabolic disease, fibroses, inflammation and autoimmunity. Numerous studies entailing the GHR signaling pathway have been conducted for various cancers. Diverse factors mediate the up- or down-regulation of GHR signaling through post-translational modifications. Of the numerous modifications, ubiquitination and deubiquitination are prominent events. Ubiquitination by E3 ligase attaches ubiquitins to target proteins and induces proteasomal degradation or starts the sequence of events that leads to endocytosis and lysosomal degradation. In this review, we discuss the role of first line effectors that act directly on the GHR at the cell surface including ADAM17, JAK2, SRC family member Lyn, Ubc13/CHIP, proteasome, βTrCP, CK2, STAT5b, and SOCS2. Activity of all, except JAK2, Lyn and STAT5b, counteract GHR signaling. Loss of their function increases the GH-induced signaling in favor of aging and certain chronic diseases, exemplified by increased lung cancer risk in case of a mutation in the SOCS2-GHR interaction site. Insight in their roles in GHR signaling can be applied for cancer and other therapeutic strategies.

Molecular modeling, docking and dynamic simulations of growth hormone receptor (GHR) of Labeo rohita

Growth hormones (GH) have diverse functions like growth promotion, metabolism, appetite, reproduction and social behavior in vertebrates, which is mediated through the growth hormone receptor (GHR). This work was aimed to analyze structural features, homology modeling and molecular docking of Labeo rohita GHR protein. A physicochemical characteristic, like molecular weight was 67.2 kDa and hydropathicity was 0.336. Protein modeling and structure confirmation of L. rohita GHR protein showed 92.7% residues are in the favored region. Selection of ligands and molecular docking shown Melengestrol and Riboflavin ligand showed uppermost binding energy values -7.8 and -7.3 kcal/mol. Molecular interactions describe conventional hydrogen bonding of Melengestrol was observed with VAL94, GLU97, GLU95, TRP57, PHE33, THR34, PRO35, ASP36, PRO37, ARG49, GLY292, LYS291, ILE290, ALA287, LYS289 residues. Riboflavin hydrogen bonds interaction was at PRO37, ASP36, PRO35, THR34, ARG49, SER144, VAL443, GLN442, PRO284, ASP294, ILE285, PRO286, SER408, ALA287, GLY292, LYS291, ILE290, PRO288, LYS287. Molecular dynamics simulation outcomes revealed that complex 2 (Riboflavin and GHR protein) is better than complex1 (Melengestrol and GHR protein). Overall, the results of the present work lead identification of novel molecules that may be agonistic of growth hormone receptor protein and can be used to surge growth in fish. Communicated by Ramaswamy H. Sarma.

Growth hormone receptor knockout: Relevance to xenotransplantation

Xenotransplantation research has made considerable progress in recent years, largely through the increasing availability of pigs with multiple genetic modifications, effective immunosuppressive therapy, and anti-inflammatory therapy to protect pig tissues from the primate immune and inflammatory responses and correct molecular incompatibilities. Further study is required regarding identification and investigation of physiological incompatibilities. Although the exact cause remains uncertain, we and others have observed relatively rapid growth of kidney xenografts after transplantation into nonhuman primates (NHPs). There has also been some evidence of growth, or at least ventricular hypertrophy, of the pig heart after orthotopic transplantation into NHPs. Rapid growth could be problematic, particularly with regard to the heart within the relatively restricted confines of the chest. It has been suggested that the problem of rapid growth of the pig organ after transplantation could be resolved by growth hormone receptor (GHR) gene knockout in the pig. The GHR, although most well-known for regulating growth, has many other biological functions, including regulating metabolism and controlling physiological processes. Genetically modified GHRKO pigs have recently become available. We provide data on their growth compared to comparable pigs that do not include GHRKO, and we have reviewed the literature regarding the effect of GHRKO, and its relevance to xenotransplantation.

GHR knockdown enhances the sensitivity of HCC cells to sorafenib

Sorafenib is approved for treatment of advanced hepatocellular carcinoma (HCC) by the Drug Administration. However, the efficacy of sorafenib has become very limited because most tumors have developed resistance to this drug. In this study, we found that sorafenib stimulated GHR expression in HCC cell lines. Thus, GHR might be linked to sorafenib resistance. To verify this hypothesis, we researched the roles of GHR knockdown and sorafenib combination in cell viability, apoptosis, cycle, and migration. The results showed that GHR blockage enhanced sorafenib blocking of cell cycle progression, leading to inhibition of this drug on HCC cell viability, and the improved promoting ability of sorafenib on cell apoptosis. In addition, it was found that GHR knockdown enhanced sorafenib inhibition of cell migration. The synergistic antitumor effects of sorafenib and GHR knockdown combination may be attributed to inhibition of PI3K/AKT/ERK1/2 signaling pathway. In conclusion, the findings suggest that GHR knockdown enhances the sensitivity of HCC cells to sorafenib. and the inactivation of PI3K/AKT/ERK1/2 signaling pathway may be the underlying mechanisms. This highlights the absence of GHR as a promising way to enhance sorafenib efficacy in HCC.

Effects of 17β-Estradiol on growth-related genes expression in female and male spotted scat (Scatophagus argus)

Growth hormone (GH) is the most important endocrine factor to regulate somatic growth. Spotted scat (Scatophagus argus) is a famous marine aquaculture species in China with a typical sexual growth dimorphism in which females grow faster and larger than males. In this study, gh messenger RNA (gh mRNA) and GH protein expression were examined in the pituitary glands of female and male spotted scat. Based on qPCR analysis, gh mRNA was mainly expressed in the pituitary gland, and weakly in the gonads and hypothalamus. Furthermore, gh mRNA expression in the pituitary gland was significantly higher in females at stages II-IV than in males at stages III-V. In addition, gh mRNA was highly expressed in the ovary and testis during mature development stages. In this study, spotted scat GH polyclonal antibody was produced. Western blot analysis showed that the molecular weight of spotted scat GH was about 21 KDa. Immunohistochemistry (IHC) in pituitary glands showed that GH was mainly expressed in the proximal pars distal (PPD) and a few cells were distributed in the rostral pairs distal (RPD). After injecting 17β-Estradiol (E₂) in vivo, gh mRNA expression was significantly up-regulated in the pituitary gland, whereas igf1 and ghr1 mRNA levels were down-regulated in the liver, which might regulate gh mRNA expression in the pituitary gland. These results provide valuable insight into the molecular mechanisms of E₂ regulating gh expression in spotted scat.