GH improves spatial memory and reverses certain anabolic androgenic steroid-induced effects in intact rats

Chronic high-dose testosterone impairs economic decision making, but has no effect on memory in male rats

The goal is to understand consequences of anabolic-androgenic steroid (AAS) abuse on cognitive function, using rats as a model. Economic decision making was evaluated in an operant test of effort value discounting, where subjects choose between 2 levers that deliver large and small rewards differing in maximum value and reward contrast. The hypothesis is that chronic high-dose testosterone increases preference for large rewards. Male rats were treated chronically with testosterone (7.5 mg/kg) or vehicle. Initially, all rats preferred the large reward lever when large and small rewards remained fixed at 3 and 1 sugar pellets, respectively. When different reward values were introduced, and with increasing response requirements, testosterone-treated rats made fewer responses for the large reward, and increased omissions. They earned fewer rewards overall. To determine if testosterone impairs memory, rats were tested for recognition memory with the novel object recognition and social transmission of food preference tasks, and for spatial memory with the radial arm maze and Morris water maze. There was not effect of chronic high-dose testosterone on any memory task. These results suggest that testosterone shifts economic decision making towards larger rewards even when they are disadvantageous, but does not alter memory in rats.

The decanoate esters of nandrolone, testosterone, and trenbolone induce steroid specific memory impairment and somatic effects in the male rat

Long-term use of anabolic androgenic steroids (AAS) in supratherapeutic doses is associated with severe adverse effects, including physical, mental, and behavioral alterations. When used for recreational purposes several AAS are often combined, and in scientific studies of the physiological impact of AAS either a single compound or a cocktail of several steroids is often used. Because of this, steroid-specific effects have been difficult to define and are not fully elucidated. The present study used male Wistar rats to evaluate potential somatic and behavioral effects of three different AAS; the decanoate esters of nandrolone, testosterone, and trenbolone. The rats were exposed to 15 mg/kg of nandrolone decanoate, testosterone decanoate, or trenbolone decanoate every third day for 24 days. Body weight gain and organ weights (thymus, liver, kidney, testis, and heart) were measured together with the corticosterone plasma levels. Behavioral effects were studied in the novel object recognition-test (NOR-test) and the multivariate concentric square field-test (MCSF-test). The results conclude that nandrolone decanoate, but neither testosterone decanoate nor trenbolone decanoate, caused impaired recognition memory in the NOR-test, indicating an altered cognitive function. The behavioral profile and stress hormone level of the rats were not affected by the AAS treatments. Furthermore, the study revealed diverse AAS-induced somatic effects i.e., reduced body weight development and changes in organ weights. Of the three AAS included in the study, nandrolone decanoate was identified to cause the most prominent impact on the male rat, as it affected body weight development, the weights of multiple organs, and caused an impaired memory function.

Nandrolone decanoate and testosterone undecanoate differently affect stress hormones, neurotransmitter systems, and general activity in the male rat

Anabolic androgenic steroids (AAS) are frequently used to improve physical appearance and strength. AAS are known to affect muscle growth, but many AAS-users also experience psychiatric and behavioral changes after long-term use. The AAS-induced effects on the brain seem to depend on the type of steroid used, but the rationale behind the observed effect is still not clear. The present study investigated and compared the impact of nandrolone decanoate and testosterone undecanoate on body weight gain, levels of stress hormones, brain gene expression, and behavioral profiles in the male rat. The behavioral profile was determined using the multivariate concentric squared field test (MCSF-test). Blood plasma and brains were collected for further analysis using ELISA and qPCR. Nandrolone decanoate caused a reduction in body weight gain in comparison with both testosterone undecanoate and control. Rats receiving nandrolone decanoate also demonstrated decreased general activity in the MCSF. In addition, nandrolone decanoate reduced the plasma levels of ACTH in comparison with the control and increased the levels of corticosterone in comparison with testosterone undecanoate. The qPCR analysis revealed brain region-dependent changes in mRNA expression, where the hypothalamus was identified as the region most affected by the AAS. Alterations in neurotransmitter systems and stress hormones may contribute to the changes in behavior detected in the MCSF. In conclusion, both AAS affect the male rat, although, nandrolone decanoate has more pronounced impact on the physiological and the behavioral parameters measured.

Association between nandrolone and behavioral alterations: A systematic review of preclinical studies

BACKGROUND AND AIM

In recent years the expanding misuse of Nandrolone among non-athletes, particularly adolescent males is a prevalent global concern due to its adverse effects. This article provides a summary of the experimental studies to clarify the relationship between Nandrolone exposure and behavioral and cognitive performances.

MATERIALS AND METHODS

The present systematic review was conducted using PubMed, Embase and ScienceDirect databases, from 2000 to 2020, using the following key terms: Nandrolone AND Cognition, Nandrolone AND Learning, Nandrolone AND Memory, Nandrolone AND (Synaptic plasticity or Hippocampal synaptic plasticity), Nandrolone AND (Aggression or Aggressive-like behavior), Nandrolone AND (Anxiety or Anxiety-like behavior), Nandrolone AND (Depression or Depressive-like behavior).

RESULTS

33 qualified papers were selected from the 2498 sources found. Of the 33 cases, 32 (96.97%) were males while only 1 (3.03%) was female and male. From 33 selected articles 8 reported studies were related to spatial memory, 2 reported studies were related to avoidance memory, 11 studies reported information on synaptic plasticity, 11 reported studies were related to aggressive behavior, 8 reported studies were related to aggressive behavior and 6 reported studies were related to depression.

CONCLUSION

Nandrolone can change spatial ability, avoidance memory and hippocampal synaptic plasticity. Also, Nandrolone exposure produces variable effects on behavioral function such as aggression, depression and anxiety. This despite the fact that the results are contradictory. These discrepancies might be due to the differences in sex, age, dosage and treatment duration, and administration route. However, the negative results are more common than the published positive ones.

Structurally different anabolic androgenic steroids reduce neurite outgrowth and neuronal viability in primary rat cortical cell cultures

The illicit use of anabolic androgenic steroids (AAS) among adolescents and young adults is a major concern due to the unknown and unpredictable impact of AAS on the developing brain and the consequences of this on mental health, cognitive function and behaviour. The present study aimed to investigate the effects of supra-physiological doses of four structurally different AAS (testosterone, nandrolone, stanozolol and trenbolone) on neurite development and cell viability using an in vitro model of immature primary rat cortical cell cultures. A high-throughput screening image-based approach, measuring the neurite length and number of neurons, was used for the analysis of neurite outgrowth. In addition, cell viability and expression of the Tubb3 gene (encoding the protein beta-III tubulin) were investigated. Testosterone, nandrolone, and trenbolone elicited adverse effects on neurite outgrowth as deduced from an observed reduced neurite length per neuron. Trenbolone was the only AAS that reduced the cell viability as indicated by a decreased number of neurons and declined mitochondrial function. Moreover, trenbolone downregulated the Tubb3 mRNA expression. The adverse impact on neurite development was neither inhibited nor supressed by the selective androgen receptor (AR) antagonist, flutamide, suggesting that the observed effects result from another mechanism or mechanisms of action that are operating apart from AR activation. The results demonstrate a possible AAS-induced detrimental effect on neuronal development and regenerative functions. An impact on these events, that are essential mechanisms for maintaining normal brain function, could possibly contribute to behavioural alterations seen in AAS users.

Growth hormone increases dendritic spine density in primary hippocampal cell cultures

OBJECTIVE

Growth hormone (GH) is widely known for its peripheral effects during growth and development. However, numerous reports also suggest that GH exert pro-cognitive, restorative, and protective properties in the brain. In in vitro studies, the detection of dendritic spines, small protrusions extending from axons, can act as a marker for cognition-related function as spine formation is considered to be associated with learning and memory. Here we show that an acute 24-hour treatment of GH can increase dendritic spine density in primary hippocampal cell cultures.

DESIGN

Primary hippocampal cells were harvested from embryonic Wistar rats and cultured for 14 days. Cells were treated with supra-physiological doses of GH (10-1000 nM) and subjected to a high-throughput screening protocol. Images were acquired and analyzed using automated image analysis and the number of spines, spines per neurite length, neurite length, and mean area of spines, was reported.

RESULTS

GH treatment (1000 nM) increased the number of dendritic spines by 83% and spines per neurite length by 82% when compared to control. For comparison BDNF, a known inducer of spine densities, produced statistically non-significant increase in this setting.

CONCLUSION

The results was found significant using the highest supra-physiological dose of GH, and the present study further confirms a potential role of the hormone in the treatment of cognitive dysfunction.

The role of serum growth hormone and insulin-like growth factor-1 in adult humans brain morphology

Growth hormone (GH) and its anabolic mediator, insulin-like growth factor-1 (IGF-1), have a critical role in the central nervous system. However, their detailed roles in the adult human brain are not clear. In this study, structural MRIs of 48 patients with GH-secreting pituitary adenoma (GH-PA), 48 sex- and age-matched clinical Non-Functional pituitary adenoma patients (NonFun-PA) and healthy controls (HCs) were assessed using voxel-based morphometry (VBM) and region-based morphometry (RBM). Correlation analyses helped determine the relationships between serum hormone levels and brain structure. The whole-brain gray matter volume (GMV) and white matter volume (WMV) significantly increased at the expense of cerebrospinal fluid volume (CSFV) in GH-PA (Bonferroni corrected, p<0.01). The increase in GMV and reduction in CSFV were significantly correlated with serum GH/IGF-1 levels (p<0.05). VBM showed significant correlations of the GMV/WMV alteration pattern between GH-PA vs HCs and GH-PA vs NonFun-PA and widespread bilateral clusters of significantly increased GMV and WMV in GH-PA (pFDR<0.05). RBM showed obviously increased GMV/WMV in 54 of 68 brain regions (p<0.05) in GH-PA compared to HCs. Our results provide imaging evidence that serum GH/IGF-1 contributes to brain growth, which may be a potential treatment option for neurodegenerative disorders and brain injury in humans.

Hippocampal growth hormone modulates relational memory and the dendritic spine density in CA1

Growth hormone (GH) deficiency is associated with cognitive decline which occur both in normal aging and in endocrine disorders. Several brain areas express receptors for GH although their functional role is unclear. To determine how GH affects the capacity for learning and memory by specific actions in one of the key areas, the hippocampus, we injected recombinant adeno-associated viruses (rAAVs) in male rats to express green fluorescent protein (GFP) combined with either GH, antagonizing GH (aGH), or no hormone, in the dorsal CA1. We found that aGH disrupted memory in the Morris water maze task, and that aGH treated animals needed more training to relearn a novel goal location. In a one-trial spontaneous location recognition test, the GH treated rats had better memory performance for object locations than the two other groups. Histological examinations revealed that GH increased the dendritic spine density on apical dendrites of CA1, while aGH reduced the spine density. GH increased the relative amount of immature spines, while aGH decreased the same amount. Our results imply that GH is a neuromodulator with strong influence over hippocampal plasticity and relational memory by mechanisms involving modulation of dendritic spines. The findings are significant to the increasing aging population and GH deficiency patients.

Anabolic androgenic steroids exert a selective remodeling of the plasma lipidome that mirrors the decrease of the de novo lipogenesis in the liver

INTRODUCTION

The abuse of anabolic androgenic steroids (AASs) is a source of public concern because of their adverse effects. Supratherapeutic doses of AASs are known to be hepatotoxic and regulate the lipoproteins in plasma by modifying the metabolism of lipids in the liver, which is associated with metabolic diseases. However, the effect of AASs on the profile of lipids in plasma is unknown.

OBJECTIVES

To describe the changes in the plasma lipidome exerted by AASs and to discuss these changes in the light of previous research about AASs and de novo lipogenesis in the liver.

METHODS

We treated male Wistar rats with supratherapeutic doses of nandrolone decanoate and testosterone undecanoate. Subsequently, we isolated the blood plasma and performed lipidomics analysis by liquid chromatography-high resolution mass spectrometry.

RESULTS

Lipid profiling revealed a decrease of sphingolipids and glycerolipids with palmitic, palmitoleic, stearic, and oleic acids. In addition, lipid profiling revealed an increase in free fatty acids and glycerophospholipids with odd-numbered chain fatty acids and/or arachidonic acid.

CONCLUSION

The lipid profile presented herein reports the imprint of AASs on the plasma lipidome, which mirrors the downregulation of de novo lipogenesis in the liver. In a broader perspective, this profile will help to understand the influence of androgens on the lipid metabolism in future studies of diseases with dysregulated lipogenesis (e.g. type 2 diabetes, fatty liver disease, and hepatocellular carcinoma).

Sleep and the GH/IGF-1 axis: Consequences and countermeasures of sleep loss/disorders

This article presents an up-to-date review of the state-of-the-art knowledge regarding the effect of sleep on the anabolic growth hormone/insulin-like growth factor-1 (GH/IGF-1) axis. This axis is involved in learning and memory and neuroprotection at the central level, and in the crosstalk between sleep and the immune system, with respect to its anti-inflammatory properties. We also aim to provide insight into the consequences of sleep loss on cognitive capacities in healthy individuals and patients with obstructive sleep apnea (OSA), regarding the mechanistic association with the GH/IGF-1 axis. Finally, this review examines the inflammatory/endocrine pathways that are affected by sleep loss, and which may consequently interact with the GH/IGF-1 axis. The deleterious effects of sleep loss include fatigue, and can cause several adverse age-dependent health outcomes. It is therefore important to improve our understanding of the fundamental physiology underlying these effects in order to better apply non-pharmacological countermeasures (e.g., sleep strategies, exercise training, continuous positive airway pressure therapy) as well as pharmacological solutions, so as to limit the deleterious consequences of sleep loss/disorders.

Toxic Impact of Anabolic Androgenic Steroids in Primary Rat Cortical Cell Cultures

The use of anabolic androgenic steroids (AASs) among non-athletes is a public health-problem, as abusers underestimate the negative effects associated with these drugs. The present study investigated the toxic effects of testosterone, nandrolone, stanozolol, and trenbolone, and aimed to understand how AAS abuse affects the brain. Mixed cortical cultures from embryonic rats were grown in vitro for 7 days and thereafter treated with increasing concentrations of AASs for 24 h (single-dose) or 3 days (repeated exposure). Cells were co-treated with the androgen-receptor (AR) antagonist flutamide, to determine whether the potential adverse effects observed were mediated by the AR. Cellular toxicity was determined by measuring mitochondrial activity, lactate dehydrogenase (LDH) release, and caspase-3/7 activity. Nandrolone, unlike the other AASs studied, indicated an effect on mitochondrial activity after 24 h. Furthermore, single-dose exposure with testosterone, nandrolone and trenbolone increased LDH release, while no effect was detected with stanozolol. However, all of the four steroids negatively affected mitochondrial function and resulted in LDH release after repeated exposure. Testosterone, nandrolone, and trenbolone caused their toxic effects by induction of apoptosis, unlike stanozolol that seemed to induce necrosis. Flutamide almost completely prevented AAS-induced toxicity by maintaining mitochondrial function, cellular integrity, and inhibition of apoptosis. Overall, we found that supra-physiological concentrations of AASs induce cell death in mixed primary cortical cultures, but to different extents, and possibly through various mechanisms. The data presented herein suggest that the molecular interactions of the AASs with the AR are primarily responsible for the toxic outcomes observed.

The Protective and Restorative Effects of Growth Hormone and Insulin-Like Growth Factor-1 on Methadone-Induced Toxicity In Vitro

Evidence to date suggests that opioids such as methadone may be associated with cognitive impairment. Growth hormone (GH) and insulin-like growth factor-1 (IGF-1) are suggested to be neuroprotective and procognitive in the brain and may therefore counteract these effects. This study aims to explore the protective and restorative effects of GH and IGF-1 in methadone-treated cell cultures. Primary cortical cell cultures were harvested from rat fetuses and grown for seven days in vitro. To examine the protective effects, methadone was co-treated with or without GH or IGF-1 for three consecutive days. To examine the restorative effects, methadone was added for the first 24 h, washed, and later treated with GH or IGF-1 for 48 h. At the end of each experiment, mitochondrial function and membrane integrity were evaluated. The results revealed that GH had protective effects in the membrane integrity assay and that both GH and IGF-1 effectively recovered mitochondrial function and membrane integrity in cells pretreated with methadone. The overall conclusion of the present study is that GH, but not IGF-1, protects primary cortical cells against methadone-induced toxicity, and that both GH and IGF-1 have a restorative effect on cells pretreated with methadone.

Growth Hormone (GH) and Gonadotropin-Releasing Hormone (GnRH) in the Central Nervous System: A Potential Neurological Combinatory Therapy?

This brief review of the neurological effects of growth hormone (GH) and gonadotropin-releasing hormone (GnRH) in the brain, particularly in the cerebral cortex, hypothalamus, hippocampus, cerebellum, spinal cord, neural retina, and brain tumors, summarizes recent information about their therapeutic potential as treatments for different neuropathologies and neurodegenerative processes. The effect of GH and GnRH (by independent administration) has been associated with beneficial impacts in patients with brain trauma and spinal cord injuries. Both GH and GnRH have demonstrated potent neurotrophic, neuroprotective, and neuroregenerative action. Positive behavioral and cognitive effects are also associated with GH and GnRH administration. Increasing evidence suggests the possibility of a multifactorial therapy that includes both GH and GnRH.

Effects of genistein and swimming exercise on spatial memory and expression of microRNA 132, BDNF, and IGF-1 genes in the hippocampus of ovariectomized rats

OBJECTIVES

The aim of the present study was to investigate the effects of genistein and exercise on the spatial memory and expression of microRNA-132, BDNF, and IGF-1 in the hippocampus of ovariectomized rats.

MATERIALS AND METHODS

Sixty animals were divided into six groups of control, sham, ovariectomy (OVX), ovariectomized with 8 weeks of genistein administration (OVX.G), with 8 weeks of swimming training (OVX.E), and with 8 weeks of both of them (OVX.G.E). The effect of genistein and/or exercise was evaluated by measuring microRNA-132, BDNF, and IGF-1 expression levels in the hippocampus tissue. Grafts were analyzed using Real-time polymerase chain reaction for microRNA-132, BDNF, IGF-1, and spatial memory via a Morris water maze (MWM).

RESULTS

Our findings showed that ovariectomy decreased the expression of microRNA-132, BDNF, and IGF-1 in the hippocampus (P<0.05) in comparison with the sham group as well as performance in the water maze (P<0.05). Also according to results ovariectomized groups that were treated with genistein/exercise or both of them showed significant difference in expression of microRNA-132, BDNF, and IGF-1 in the hippocampus (P<0.05) and decreased latency in MWM (P<0.05) compared with the OVX group but combination treatment was more effective in the OVX.G.E group in comparison with OVX.E and OVX.G groups.

CONCLUSION

Overall our results emphasized that combination treatment with genistein and exercise could improve microRNA-132, BDNF, and IGF-1 expression in the hippocampus as well as the spatial memory of ovariectomized rats. These effects may have beneficial impacts on the menopausal period.

The mRNA expression of insulin-like growth factor-1 (Igf1) is decreased in the rat frontal cortex following gamma-hydroxybutyrate (GHB) administration

In recent years, growth hormone (GH), together with its secondary mediators insulin-like growth factor-1 (IGF-1) and insulin-like growth factor-2 (IGF-2), have been highlighted for their beneficial effects in the central nervous system (CNS), in particular as cognitive enhancers. Cognitive processes, such as learning and memory, are known to be impaired in individuals suffering from substance abuse. In the present study, we investigated the effect of gamma-hydroxybuturate (GHB), an illicit drug used for its sedating and euphoric properties, on genes associated with the somatotrophic axis in regions of the brain important for cognitive function. Sprague Dawley rats (n=36) were divided into three groups and administered either saline, GHB 50mg/kg or GHB 300mg/kg orally for seven days. The levels of Ghr, Igf1 and Igf2 gene transcripts were analyzed using qPCR in brain regions involved in cognition and dependence. The levels of IGF-1 in blood plasma were also determined using ELISA. The results demonstrated a significant down-regulation of Igf1 mRNA expression in the frontal cortex in high-dose treated rats. Moreover, a significant correlation between Igf1 and Ghr mRNA expression was found in the hippocampus, the frontal cortex, and the caudate putamen, indicating local regulation of the GH/IGF-1 axis. To summarize, the current study concludes that chronic GHB treatment influences gene expression of Ghr and Igf1 in brain regions involved in cognitive function.

Growth hormone is protective against acute methadone-induced toxicity by modulating the NMDA receptor complex

Human growth hormone (GH) displays promising protective effects in the central nervous system after damage caused by various insults. Current evidence suggests that these effects may involve N-methyl-d-aspartate (NMDA) receptor function, a receptor that also is believed to play a role in opioid-induced neurotoxicity. The aims of the present study were to examine the acute toxic effects of methadone, an opioid receptor agonist and NMDA receptor antagonist, as well as to evaluate the protective properties of recombinant human GH (rhGH) on methadone-induced toxicity. Primary cortical cell cultures from embryonic day 17 rats were grown for 7days in vitro. Cells were treated with methadone for 24h and the 50% lethal dose was calculated and later used for protection studies with rhGH. Cellular toxicity was determined by measuring mitochondrial activity, lactate dehydrogenase release, and caspase activation. Furthermore, the mRNA expression levels of NMDA receptor subunits were investigated following methadone and rhGH treatment using quantitative PCR (qPCR) analysis. A significant protective effect was observed with rhGH treatment on methadone-induced mitochondrial dysfunction and in methadone-induced LDH release. Furthermore, methadone significantly increased caspase-3 and -7 activation but rhGH was unable to inhibit this effect. The mRNA expression of the NMDA receptor subunit GluN1, GluN2a, and GluN2b increased following methadone treatment, as assessed by qPCR, and rhGH treatment effectively normalized this expression to control levels. We have demonstrated that rhGH can rescue cells from methadone-induced toxicity by maintaining mitochondrial function, cellular integrity, and NMDA receptor complex expression.

Growth Hormone Treatment Improves Cognitive Function in Short Children with Growth Hormone Deficiency

BACKGROUND/AIMS

We investigated the association between cognition and growth hormone (GH) status and GH treatment in short prepubertal children with broadly ranging GH secretion.

METHODS

A total of 99 children (age 3-11 years), 41 with GH deficiency (GHD) and 58 with idiopathic short stature (ISS), were randomized to a fixed dose (43 µg/kg/day) or a prediction model-guided individualized dose (17-100 µg/kg/day) and followed up for 24 months. In a longitudinal and mixed within- and between-subjects study, we examined clinical effect size changes, measured by Cohen's d, in full-scale IQ (FSIQ) and secondary IQ indices.

RESULTS

Significant increases giving medium effect size in FSIQ (p = 0.001, Cohen's d = 0.63), performance IQ (p = 0.001, Cohen's d = 0.65) and processing speed (p = 0.005, Cohen's d = 0.71) were found in the GH-deficient group. In contrast, perceptual organization only increased in the ISS group (p = 0.001, Cohen's d = 0.53). Baseline IQ was normally distributed with small but significant differences between the groups: GH-deficient children had lower FSIQ (p = 0.042) and lower performance IQ (p = 0.021). Using multiple regression analysis, 40% of the variance in delta processing speed scores (0-24 months) was explained by GHmax and IGF-ISDS at baseline.

CONCLUSION

IQ, specifically fluid intelligence, increased in the GH-deficient children. The pretreatment status of the GH/IGF-I axis was significantly predictive for these changes. © 2015 S. Karger AG, Basel.

Validation of serum IGF-I as a biomarker to monitor the bioactivity of exogenous growth hormone agonists and antagonists in rabbits

The development of new growth hormone (GH) agonists and growth hormone antagonists (GHAs) requires animal models for pre-clinical testing. Ideally, the effects of treatment are monitored using the same pharmacodynamic marker that is later used in clinical practice. However, intact rodents are of limited value for this purpose because serum IGF-I, the most sensitive pharmacodynamic marker for the action of GH in humans, shows no response to treatment with recombinant human GH and there is little evidence for the effects of GHAs, except when administered at very high doses or when overexpressed. As an alternative, more suitable model, we explored pharmacodynamic markers of GH action in intact rabbits. We performed the first validation of an IGF-I assay for the analysis of rabbit serum and tested precision, sensitivity, linearity and recovery using an automated human IGF-I assay (IDS-iSYS). Furthermore, IGF-I was measured in rabbits of different strains, age groups and sexes, and we monitored IGF-I response to treatment with recombinant human GH or the GHA Pegvisomant. For a subset of samples, we used LC-MS/MS to measure IGF-I, and quantitative western ligand blot to analyze IGF-binding proteins (IGFBPs). Although recovery of recombinant rabbit IGF-I was only 50% in the human IGF-I assay, our results show that the sensitivity, precision (1.7–3.3% coefficient of variation) and linearity (90.4–105.6%) were excellent in rabbit samples. As expected, sex, age and genetic background were major determinants of IGF-I concentration in rabbits. IGF-I and IGFBP-2 levels increased after single and multiple injections of recombinant human GH (IGF-I: 286±22 versus 434±26 ng/ml; P<0.01) and were highly correlated (P<0.0001). Treatment with the GHA lowered IGF-I levels from the fourth injection onwards (P<0.01). In summary, we demonstrated that the IDS-iSYS IGF-I immunoassay can be used in rabbits. Similar to rodents, rabbits display variations in IGF-I depending on sex, age and genetic background. Unlike in rodents, the IGF-I response to treatment with recombinant human GH or a GHA closely mimics the pharmacodynamics seen in humans, suggesting that rabbits are a suitable new model to test human GH agonists and antagonists.

Expression and function of growth hormone in the nervous system: a brief review

There is increasing evidence that growth hormone (GH) expression is not confined exclusively to the pituitary somatotrophs as it is synthesized in many extrapituitary locations. The nervous system is one of those extrapituitary sites. In this brief review we summarize data that substantiate the expression, distribution and characterization of neural GH and detail its roles in neural function, including cellular growth, proliferation, differentiation, neuroprotection and survival, as well as its functional roles in behavior, cognition and neurotransmission. Although systemic GH may exert some of these effects, it is increasingly evident that locally expressed neural GH, acting through intracrine, autocrine or paracrine mechanisms, may also be causally involved as a neurotrophic factor.

Administration of growth hormone and nandrolone decanoate alters mRNA expression of the GABAB receptor subunits as well as of the GH receptor, IGF-1, and IGF-2 in rat brain

OBJECTIVE

The illicit use of anabolic androgenic steroids (AAS), especially among young adults, is of major concern. Among AAS users it is common to combine the AAS nandrolone decanoate (ND), with intake of growth hormone (GH) and a connection between gonadal steroids and the GH system has been suggested. Both AAS and GH affect functions in the brain, for example those associated with the hypothalamus and pituitary, and several GH actions are mediated by growth factors such as insulin-like growth factor 1 (IGF-1) and insulin-like growth factor 2 (IGF-2). The GABAergic system is implicated in actions induced by AAS and previous studies have provided evidence for a link between GH and GABAB receptors in the brain. Our aim was to examine the impact of AAS administration and a subsequent administration of GH, on the expression of GABAB receptors and important GH mediators in rat brain.

DESIGN

The aim was to investigate the CNS effects of a high-dose ND, and to study if a low, but physiological relevant, dose of GH could reverse the ND-induced effects. In the present study, male rats were administered a high dose of ND every third day during three weeks, and subsequently the rats were given recombinant human GH (rhGH) during ten days. Quantitative PCR (qPCR) was used to analyze gene expression in hypothalamus, anterior pituitary, caudate putamen, nucleus accumbens, and amygdala.

RESULTS

In the pituitary gland, the expression of GABAB receptor subunits was affected differently by the steroid treatment; the GABAB1 mRNA expression was decreased whereas a distinct elevation of the GABAB2 expression was found. Administration of ND also caused a decrease of GHR, IGF-1, and IGF-2 mRNA expression in the pituitary while the corresponding expression in the hypothalamus, caudate putamen, nucleus accumbens, and amygdala was unaffected. The rhGH administration did not alter the GABAB2 expression but increased the GABAB1 gene expression in the hypothalamus as compared to the AAS treated group.

CONCLUSIONS

These results provide new insights on the impact of ND and GH on the brain and highlight the interaction of these hormones with systems influencing GABAB receptor expression. The physiological significance of the observed effects of these hormones is discussed.

Generating new neurons to circumvent your fears: the role of IGF signaling

Extinction of fear memory is a particular form of cognitive function that is of special interest because of its involvement in the treatment of anxiety and mood disorders. Based on recent literature and our previous findings (EMBO J 30(19):4071-4083, 2011), we propose a new hypothesis that implies a tight relationship among IGF signaling, adult hippocampal neurogenesis and fear extinction. Our proposed model suggests that fear extinction-induced IGF2/IGFBP7 signaling promotes the survival of neurons at 2-4 weeks old that would participate in the discrimination between the original fear memory trace and the new safety memory generated during fear extinction. This is also called "pattern separation", or the ability to distinguish similar but different cues (e.g., context). To understand the molecular mechanisms underlying fear extinction is therefore of great clinical importance.

The impact of nandrolone decanoate and growth hormone on biosynthesis of steroids in rats

Growth hormone (GH) and anabolic androgenic steroids (AAS) are commonly used in sports communities. Several studies have suggested an association between GH and AAS. We have investigated the impact of GH in rats treated with nandrolone decanoate (ND). Male Wistar rats received ND (15 mg/kg) every third day during three weeks and were subsequently treated with recombinant human GH (1.0I U/kg) for ten consecutive days. Plasma samples were collected and peripheral organs (i.e. heart, liver, testis and thymus) were dissected and weighed. Concentration of thirteen endogenous steroids was measured in the rat plasma samples using high specificity LC-MS/MS methods. Seven steroids were detected and quantified, and concentrations of estrone, testosterone, and androstenedione were significantly different among the groups, while concentrations of pregnenolone, DHEA, 17-hydroxyprogesterone and corticosterone were not altered. Administration of rhGH alone altered the plasma steroid distribution, and the results demonstrated significantly increased concentrations of plasma estrone as well as decreased concentrations of testosterone and androstenedione in the ND-treated rats. Administration of rhGH to ND-pretreated rats did not reverse the alteration of the steroid distribution induced by ND. Administration of ND decreased the weight of the thymus, and addition of rhGH did not reverse this reduction. However, rhGH administration induced an enlargement of thymus. Taken together, the plasma steroid profile differed in the four groups, i.e. control, AAS, rhGH and the combination of AAS and rhGH treatment.

Growth hormone and cognitive function

Emerging data indicate that growth hormone (GH) therapy could have a role in improving cognitive function. GH replacement therapy in experimental animals and human patients counteracts the dysfunction of many behaviours related to the central nervous system (CNS). Various behaviours, such as cognitive behaviours related to learning and memory, are known to be induced by GH; the hormone might interact with specific receptors located in areas of the CNS that are associated with the functional anatomy of these behaviours. GH is believed to affect excitatory circuits involved in synaptic plasticity, which alters cognitive capacity. GH also has a protective effect on the CNS, as indicated by its beneficial effects in patients with spinal cord injury. Data collected from animal models indicates that GH might also stimulate neurogenesis. This Review discusses the mechanisms underlying the interactions between GH and the CNS, and the data emerging from animal and human studies on the relationship between GH and cognitive function. In this article, particular emphasis is given to the role of GH as a treatment for patients with cognitive impairment resulting from deficiency of the hormone.