Growth hormone and cognitive function

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.

Effects of growth hormone in the central nervous system

Growth hormone (GH) is best known for its effect stimulating tissue and somatic growth through the regulation of cell division, regeneration and proliferation. However, GH-responsive neurons are spread over the entire central nervous system, suggesting that they have important roles in the brain. The objective of the present review is to summarize and discuss the potential physiological importance of GH action in the central nervous system. We provide evidence that GH signaling in the brain regulates the physiology of numerous functions such as cognition, behavior, neuroendocrine changes and metabolism. Data obtained from experimental animal models have shown that disruptions in GH signaling in specific neuronal populations can affect the reproductive axis and impair food intake during glucoprivic conditions, neuroendocrine adaptions during food restriction, and counter-regulatory responses to hypoglycemia, and they can modify gestational metabolic adaptions. Therefore, the brain is an important target tissue of GH, and changes in GH action in the central nervous system can explain some dysfunctions presented by individuals with excessive or deficient GH secretion. Furthermore, GH acts in specific neuronal populations during situations of metabolic stress to promote appropriate physiological adjustments that restore homeostasis. Arch Endocrinol Metab. 2019;63(6):549-56.

Regenerative Effect of Growth Hormone (GH) in the Retina after Kainic Acid Excitotoxic Damage

In addition to its role as an endocrine messenger, growth hormone (GH) also acts as a neurotrophic factor in the central nervous system (CNS), whose effects are involved in neuroprotection, axonal growth, and synaptogenic modulation. An increasing amount of clinical evidence shows a beneficial effect of GH treatment in patients with brain trauma, stroke, spinal cord injury, impaired cognitive function, and neurodegenerative processes. In response to injury, Müller cells transdifferentiate into neural progenitors and proliferate, which constitutes an early regenerative process in the chicken retina. In this work, we studied the long-term protective effect of GH after causing severe excitotoxic damage in the retina. Thus, an acute neural injury was induced via the intravitreal injection of kainic acid (KA, 20 µg), which was followed by chronic administration of GH (10 injections [300 ng] over 21 days). Damage provoked a severe disruption of several retinal layers. However, in KA-damaged retinas treated with GH, we observed a significant restoration of the inner plexiform layer (IPL, 2.4-fold) and inner nuclear layer (INL, 1.5-fold) thickness and a general improvement of the retinal structure. In addition, we also observed an increase in the expression of several genes involved in important regenerative pathways, including: synaptogenic markers (DLG1, NRXN1, GAP43); glutamate receptor subunits (NR1 and GRIK4); pro-survival factors (BDNF, Bcl-2 and TNF-R2); and Notch signaling proteins (Notch1 and Hes5). Interestingly, Müller cell transdifferentiation markers (Sox2 and FGF2) were upregulated by this long-term chronic GH treatment. These results are consistent with a significant increase in the number of BrdU-positive cells observed in the KA-damaged retina, which was induced by GH administration. Our data suggest that GH is able to facilitate the early proliferative response of the injured retina and enhance the regeneration of neurite interconnections.

Intellectual functioning in Silver-Russell syndrome: First study in adults

Silver-Russell syndrome (SRS) is a rare genetic disorder (estimated incidence 1/30,000 to 100,000 live births). So far, only a few studies have focused on the cognitive profile of individuals with SRS, and these were conducted some time ago, concentrated on pediatric cohorts, and included patients who had been diagnosed using a variety of clinical diagnostic systems. There has yet to be any research on the intellectual functioning of adults with SRS. This study sought to establish the intelligence, strengths and weaknesses within intellectual profile of adults with SRS, compared with normative data. Ten individuals with 11p15 epimutation aged 18-39 years completed the Wechsler Adult Intelligence Scale-Fourth Edition. Measures of interest included participants' intelligence (Full Scale Intelligence Quotient [FSIQ]) and four domains of cognitive functioning: verbal comprehension, perceptual reasoning, working memory and processing speed. Discrepancy scores were calculated, and descriptive statistical and linear correlations were used to investigate factors associated with IQ outcome. Clinical and medical information such as rehabilitation, and perceived difficulties in daily life were collected by interviews and questionnaires. Results showed that the mean FSIQ score was in the average range (M = 95.40, SD = 18.55) and they performed best on verbal comprehension. Frequent daily difficulties were reported by patients and/or their families: learning disabilities and low self-esteem were perceived by 60% of adults. Early intervention and multidisciplinary care from childhood to adulthood are important in SRS for care potential medical, cognitive and psychosocial problems. This is the first study to document the intellectual functioning of adults with SRS.

Traumatic brain injury: neuropathological, neurocognitive and neurobehavioral sequelae

Traumatic brain injury (TBI) causes substantial neurological disabilities and mental distress. Annual TBI incidence is in magnitude of millions, making it a global health challenge. Categorization of TBI into severe, moderate and mild by scores on the Glasgow coma scale (GCS) is based on clinical grounds and standard brain imaging (CT). Recent research focused on repeated mild TBI (sport and non-sport concussions) suggests that a considerable number of patients have long-term disabling neurocognitive and neurobehavioral sequelae. These relate to subtle neuronal injury (diffuse axonal injury) visible only by using advanced neuroimaging distinguishing microstructural tissue damage. With advanced MRI protocols better characterization of TBI is achievable. Diffusion tensor imaging (DTI) visualizes white matter pathology, susceptibility weight imaging (SWI) detects microscopic bleeding while functional magnetic resonance imaging (fMRI) provides closer understanding of cognitive disorders etc. However, advanced imaging is still not integrated in the clinical care of patients with TBI. Patients with chronic TBI may experience many somatic disorders, cognitive disturbances and mental complaints. The underlying pathophysiological mechanisms occurring in TBI are complex, brain injuries are highly heterogeneous and include neuroendocrine dysfunctions. Post-traumatic neuroendocrine dysfunctions received attention since the year 2000. Occurrence of TBI-related hypopituitarism does not correlate to severity of the GCS scores. Complete or partial hypopituitarism (isolated growth hormone (GH) deficiency as most frequent) may occur after mild TBI equally as after moderate-to-severe TBI. Many symptoms of hypopituitarism overlap with symptoms occurring in patients with chronic TBI, i.e. they have lower scores on neuropsychological examinations (cognitive disability) and have more symptoms of mental distress (depression and fatigue). The great challenges for the endocrinologist are: (1) detection of hypopituitarism in patients with TBI prospectively (in the acute phase and months to years after TBI), (2) assessment of the extent of cognitive impairment at baseline, and (3) monitoring of treatment effects (alteration of cognitive functioning and mental distress with hormone replacement therapy). Only few studies recently suggest that with growth hormone (rhGH) replacement in patients with chronic TBI and with abnormal GH secretion, cognitive performance may not change while symptoms related to depression and fatigue improve. Stagnation in post-TBI rehabilitation progress is recommended as a signal for clinical suspicion of neuroendocrine dysfunction. This remains a challenging area for more research.

Catch-up growth and behavioral development among preterm, small-for-gestational-age children: A nationwide Japanese population-based study

OBJECTIVE

To examine the relationship between the catch-up growth of preterm, SGA children and their behavioral development.

METHODS

We analyzed data from a large Japanese, nationwide, population-based, longitudinal survey that started in 2001. We restricted the study participants to preterm children with information on height at 2 years of age (n = 1667). Catch-up growth for SGA infants was defined as achieving a height at 2 years of age above -2.0 standard deviations for chronological age. We then used logistic regression to estimate odds ratios (ORs) and 95% confidence intervals (95% CIs) for the associations of SGA/catch-up status with neurobehavioral development both at 5.5 and 8 years of age, adjusting for potential infant- and parent-related confounding factors.

RESULTS

Twenty-six percent of preterm SGA infants failed to catch up. SGA children without catch-up growth were more likely to be unable to listen without fidgeting (OR 2.51, 95% CI: 1.06-5.93) and unable to focus on one task (OR 2.66, 95% CI: 1.09-6.48) compared with non-SGA children at 5.5 years of age. Furthermore, SGA children without catch-up growth were at significant risk for inattention at 8 years of age.

CONCLUSIONS

SGA infants with poor postnatal growth were at risk for attention problems throughout preschool-age to school-age among preterm infants. Early detection and intervention for attention problems among these infants is warranted.

The interplay between neuroendocrine and sleep alterations following traumatic brain injury

BACKGROUND

Sleep and endocrine disruptions are prevalent after traumatic brain injury (TBI) and are likely to contribute to morbidity.

OBJECTIVE

To describe the interaction between sleep and hormonal regulation following TBI and elucidate the impact that alterations of these systems have on cognitive responses during the posttraumatic chronic period.

METHODS

Review of preclinical and clinical literature describing long-lasting endocrine dysregulation and sleep alterations following TBI. The bidirectional relationship between sleep and hormones is described. Literature describing co-occurrence between sleep-wake disturbances and hormonal dysregulation will be presented. Review of literature describing cognitive effects of seep and hormones. The cognitive and functional impact of sleep disturbances and hormonal dysregulation is discussed within the context of TBI.

RESULTS/CONCLUSIONS

Sleep and hormonal alterations impact cognitive and functional outcome after TBI. Diagnosis and treatment of these disturbances will impact recovery following TBI and should be considered in the post-acute rehabilitative setting.

Childhood-onset growth hormone deficiency and the transition to adulthood: current perspective

Childhood-onset growth hormone deficiency (CO-GHD) is an endocrine condition associated with a broad range of health issues from childhood through to adulthood, which requires particular attention during the transition period from adolescence to young adulthood. There is uncertainty in the clinical practice of the management of CO-GHD during transition regarding the clinical assessment and management of individual patients during and after transition to obtain optimal follow-up and improved health outcomes. Despite the availability of clinical guidelines providing the framework for transition of young adults with CO-GHD, there remains substantial variation in approaching transitional care among pediatric and adult services. A well-structured and coordinated transitional plan with clear communication and direct collaboration between pediatric and adult health care to ensure optimal management of adolescents with CO-GHD during transition is needed.

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.

Tissue regeneration: Impact of sleep on stem cell regenerative capacity

The circadian rhythm orchestrates many cellular functions, such as cell division, cell migration, metabolism and numerous intracellular biological processes. The physiological changes during sleep are believed to promote a suitable microenvironment for stem cells to proliferate, migrate and differentiate. These effects are mediated either directly by circadian clock genes or indirectly via hormones and cytokines. Hormones, such as melatonin and cortisol, are secreted in response to neural optic signals and act in harmony to regulate many biological functions during sleep. Herein, we correlate the effects of the main circadian genes on the expression of certain stem cell genes responsible for the regeneration of different tissues, including bone, cartilage, skin, and intestine. We also review the effects of different hormones and cytokines on stem cell activation or suppression and their relationship to the day/night cycle. The correlation of circadian rhythm with tissue regeneration could have implications in understanding the biology of sleep and tissue regeneration and in enhancing the efficacy and timing of surgical procedures.

Strengthening the Brain-Is Resistance Training with Blood Flow Restriction an Effective Strategy for Cognitive Improvement?

Aging is accompanied by a decrease in physical capabilities (e.g., strength loss) and cognitive decline. The observed bidirectional relationship between physical activity and brain health suggests that physical activities could be beneficial to maintain and improve brain functioning (e.g., cognitive performance). However, the exercise type (e.g., resistance training, endurance training) and their exercise variables (e.g., load, duration, frequency) for an effective physical activity that optimally enhance cognitive performance are still unknown. There is growing evidence that resistance training induces substantial brain changes which contribute to improved cognitive functions. A relative new method in the field of resistance training is blood flow restriction training (BFR). While resistance training with BFR is widely studied in the context of muscular performance, this training strategy also induces an activation of signaling pathways associated with neuroplasticity and cognitive functions. Based on this, it seems reasonable to hypothesize that resistance training with BFR is a promising new strategy to boost the effectiveness of resistance training interventions regarding cognitive performance. To support our hypothesis, we provide rationales of possible adaptation processes induced by resistance training with BFR. Furthermore, we outline recommendations for future studies planning to investigate the effects of resistance training with BFR on cognition.

Improved Mental and Motor Development During 3 Years of GH Treatment in Very Young Children With Prader-Willi Syndrome

CONTEXT

Infants and toddlers with Prader-Willi syndrome (PWS) have mental and motor developmental delay. Short-term data suggest a positive effect of GH on mental and motor development in infants and children with PWS. There are, however, no longer-term results about the effects of GH treatment on mental and motor development.

OBJECTIVE

To investigate the longer-term effects of GH on psychomotor development in infants and toddlers with PWS and the effect of age at start of GH treatment on psychomotor development.

DESIGN

Prospective cohort study during 3 years of GH treatment.

SETTING

The PWS Reference Center in the Netherlands.

INTERVENTION

All children were treated with GH 1 mg/m2/d (≈0.035 mg/kg/d).

MAIN OUTCOME MEASURES

Mental and motor developmental age assessed with Bayleys Scales of Infant Development II and expressed as percentage of the expected development (100%).

RESULTS

During 3 years of GH, mean (SEM) mental development increased from 58.1% (2.8) at baseline to 79.6% (3.7), and motor development increased from 41.9% (2.9) to 78.2% (3.9; both P < 0.01). A lower baseline psychomotor development and a younger age at start of GH treatment were associated with a higher increase in mental and motor development (P < 0.01).

CONCLUSIONS

Mental and motor development increased significantly during 3 years of GH treatment, reducing the gap between infants with PWS and healthy peers. A younger age at start of GH treatment leads to greater improvement in psychomotor development.

Gut microbiota regulates mouse behaviors through glucocorticoid receptor pathway genes in the hippocampus

Gut microbiota has an important role in the immune system, metabolism, and digestion, and has a significant effect on the nervous system. Recent studies have revealed that abnormal gut microbiota induces abnormal behaviors, which may be associated with the hypothalamic-pituitary-adrenal (HPA) axis. Therefore, we investigated the behavioral changes in germ-free (GF) mice by behavioral tests, quantified the basal serum cortisol levels, and examined glucocorticoid receptor pathway genes in hippocampus using microarray analysis followed by real-time PCR validation, to explore the molecular mechanisms by which the gut microbiota influences the host's behaviors and brain function. Moreover, we quantified the basal serum cortisol levels and validated the differential genes in an Escherichia coli-derived lipopolysaccharide (LPS) treatment mouse model and fecal "depression microbiota" transplantation mouse model by real-time PCR. We found that GF mice showed antianxiety- and antidepressant-like behaviors, whereas E. coli LPS-treated mice showed antidepressant-like behavior, but did not show antianxiety-like behavior. However, "depression microbiota" recipient mice exhibited anxiety- and depressive-like behaviors. In addition, six glucocorticoid receptor pathway genes (Slc22a5, Aqp1, Stat5a, Ampd3, Plekhf1, and Cyb561) were upregulated in GF mice, and of these only two (Stat5a and Ampd3) were upregulated in LPS-treated mice, whereas the shared gene, Stat5a, was downregulated in "depression microbiota" recipient mice. Furthermore, basal serum cortisol levels were decreased in E. coli LPS-treated mice but not in GF mice and "depression microbiota" recipient mice. These results indicated that the gut microbiota may lead to behavioral abnormalities in mice through the downstream pathway of the glucocorticoid receptor. Herein, we proposed a new insight into the molecular mechanisms by which gut microbiota influence depressive-like behavior.

Growth hormone promotes synaptogenesis and protects neuroretinal dendrites against kainic acid (KA) induced damage

There is increasing evidence that suggests a possible role for GH in retinal development and synaptogenesis. While our previous studies have focused largely on embryonic retinal ganglion cells (RGCs), our current study demonstrates that GH has a synaptogenic effect in retinal primary cell cultures, increasing the abundance of both pre- (SNAP25) and post- (PSD95) synaptic proteins. In the neonatal chick, kainate (KA) treatment was found to damage retinal synapses and abrogate GH expression. In response to damage, an increase in Cy3-GH internalization into RGCs was observed when administered shortly before or after damage. This increase in internalization also correlated with increase in PSD95 expression, suggesting a neuroprotective effect on the dendritic trees of RGCs and the inner plexiform layer (IPL). In addition, we observed the presence of PSD95 positive Müller glia, which may suggest GH is having a neuroregenerative effect in the kainate-damaged retina. This work puts forth further evidence that GH acts as a synaptogenic modulator in the chick retina and opens a new possibility for the use of GH in retinal regeneration research.

Treatment with Growth Hormone (GH) Increased the Metabolic Activity of the Brain in an Elder Patient, Not GH-Deficient, Who Suffered Mild Cognitive Alterations and Had an ApoE 4/3 Genotype

(1) Background: We analyzed, using PET-SCAN and cognitive tests, how growth hormone (GH) could act in the brain of an older woman, not deficient in GH, who showed mild cognitive alterations (MCI) and had a genotype of ApoE 4/3 and familial dyslipidemia. (2) Methods: After performing a first psychometric study (TAVEC verbal learning test), the metabolic activity of brain structures related to knowledge, memory, and behavior was analyzed using 18-F fluorodeoxyglucose PET-SCAN. The patient was then treated with GH (0.4 mg/day, subcutaneous) for three weeks and on the last day under this treatment, a new PET-SCAN was performed. One month after beginning treatment with GH, a new TAVEC test was performed. (3) Results: GH administration normalized the cognitive deficits observed in the first psychometric test and significantly (p < 0.025) increased the metabolic activity in practically all brain cortical areas, specifically in the left hippocampus and left amygdala, although not in the left parahippocampus. (4) Conclusions: This study demonstrates for the first time the positive effects of GH on cerebral metabolism in a patient without GH deficiency, recovering the function of affected areas related to knowledge, memory, and behavior in an elderly patient with MCI.

Effect of low-normal and high-normal IGF-1 levels on memory and wellbeing during growth hormone replacement therapy: a randomized clinical trial in adult growth hormone deficiency

Background

The aim of the present study was to investigate the effect of low-normal and high-normal levels of IGF-1 in growth hormone (GH) deficient adults on cognition and wellbeing during GH treatment.

Methods

A randomized, open-label, clinical trial including 32 subjects receiving GH therapy for at least 1 year. Subjects were randomized to receive either a decrease (IGF-1 target level of − 2 to − 1 SDS) or an increase of their daily GH dose (IGF-1 target level of 1 to 2 SDS) for a period of 24 weeks. Memory was measured by the Cambridge Neuropsychological Test Automated Battery, selecting the Pattern Recognition Memory task and the Spatial Working Memory. Wellbeing was measured as mood by the Profile of Moods States questionnaire, and quality of life by the Nottingham Health Profile and QoL Assessment in GH Deficiency in Adults questionnaires.

Results

Data from 30 subjects (65.6% male, mean age 46.6 (9.9 SD) years), who fulfilled the target levels, were analyzed. Females in the low dose treatment arm were found to have a better working memory and a better strategic memory control after 24 weeks as opposed to the females in the high treatment arm. With respect to mood, the decrease in IGF-1 levels in females within the low treatment arm was associated with more fatigue and less vigor.

Conclusions

The adjustment of GH dose in female patients seems to have a narrow window. A dose too high may impair prefrontal cognitive functioning, while a dose too low may result in decreased vigor.

Trial registration

This study is registered with ClinicalTrials.gov, number NCT01877512.

Slow-Wave Activity Enhancement to Improve Cognition

Slow-wave activity (SWA), and its coupling with other sleep features, reorganizes cortical circuitry, supporting cognition. This raises the question: can cognition be improved through SWA enhancement? SWA enhancement techniques range from behavioral interventions (such as exercise), which have high feasibility but low specificity, to laboratory-based techniques (such as transcranial stimulation), which have high specificity but are less feasible for widespread use. In this review we describe the pathways through which SWA is enhanced. Pathways encompass enhanced neural activity, increased energy metabolism, and endocrine signaling during wakefulness; also direct enhancement during sleep. We evaluate the robustness and practicality of SWA-enhancement techniques, discuss approaches for determining a causal role of SWA on cognition, and present questions to clarify the mechanisms of SWA-dependent cognitive improvements.

Increasing use of cognitive measures in the operational definition of frailty-A systematic review

Ageing is associated both with frailty and cognitive decline. The quest for a unifying approach has led to a new concept: cognitive frailty. This systematic review explores the contribution of cognitive assessment in frailty operationalization. PubMed, Web of Knowledge and PsycINFO were searched until December 2016 using the keywords aged; frail elderly; aged, 80 and over; frailty; diagnosis; risk assessment and classification, yielding 2863 hits. Seventy-nine articles were included, describing 94 frailty instruments. Two instruments were not sufficiently specified and excluded. 46% of the identified frailty instruments included cognition. Of these, 85% were published after 2010, with a significant difference for publication date (X² = 8.45, p < .05), indicating increasing awareness of the contribution of cognitive deficits to functional decline. This review identified 7 methods of cognitive assessment: dementia as co-morbidity; objective cognitive-screening instruments; self-reported; specific signs and symptoms; delirium/clouding of consciousness; non-specific cognitive terms and mixed assessments. Although cognitive assessment has been increasingly integrated in recently published frailty instruments, this has been heterogeneously operationalized. Once the domains most strongly linked to functional decline will have been identified and operationalized, this will be the groundwork for the identification of reversible components, and for the development of preventive interventional strategies.

MECHANISMS IN ENDOCRINOLOGY: Lessons from growth hormone receptor gene-disrupted mice: are there benefits of endocrine defects?

Growth hormone (GH) is produced primarily by anterior pituitary somatotroph cells. Numerous acute human (h) GH treatment and long-term follow-up studies and extensive use of animal models of GH action have shaped the body of GH research over the past 70 years. Work on the GH receptor (R)-knockout (GHRKO) mice and results of studies on GH-resistant Laron Syndrome (LS) patients have helped define many physiological actions of GH including those dealing with metabolism, obesity, cancer, diabetes, cognition and aging/longevity. In this review, we have discussed several issues dealing with these biological effects of GH and attempt to answer the question of whether decreased GH action may be beneficial.

Growth Hormone Improves Cognitive Function After Experimental Stroke

BACKGROUND AND PURPOSE

Cognitive impairment is a common outcome for stroke survivors. Growth hormone (GH) could represent a potential therapeutic option as this peptide hormone has been shown to improve cognition in various clinical conditions. In this study, we evaluated the effects of peripheral administration of GH at 48 hours poststroke for 28 days on cognitive function and the underlying mechanisms.

METHODS

Experimental stroke was induced by photothrombotic occlusion in young adult mice. We assessed the associative memory cognitive domain using mouse touchscreen platform for paired-associate learning task. We also evaluated neural tissue loss, neurotrophic factors, and markers of neuroplasticity and cerebrovascular remodeling using biochemical and histology analyses.

RESULTS

Our results show that GH-treated stroked mice made a significant improvement on the paired-associate learning task relative to non-GH-treated mice at the end of the study. Furthermore, we observed reduction of neural tissue loss in GH-treated stroked mice. We identified that GH treatment resulted in significantly higher levels of neurotrophic factors (IGF-1 [insulin-like growth factor-1] and VEGF [vascular endothelial growth factor]) in both the circulatory and peri-infarct regions. GH treatment in stroked mice not only promoted protein levels and density of presynaptic marker (SYN-1 [synapsin-1]) and marker of myelination (MBP [myelin basic protein]) but also increased the density and area coverage of 2 major vasculature markers (CD31 and collagen-IV), within the peri-infarct region.

CONCLUSIONS

These findings provide compelling preclinical evidence for the usage of GH as a potential therapeutic tool in the recovery phase of patients after stroke.

The Involvement of PPARs in the Selective Regulation of Brain CYP2D by Growth Hormone

Brain CYP2D is responsible for the synthesis of endogenous neurotransmitters such as dopamine and serotonin. This study is to investigate the effects of cerebral CYP2D on mouse behavior and the mechanism whereby growth hormone regulates brain CYP2D. The inhibition of cerebellar CYP2D significantly affected the spatial learning and exploratory behavior of mice. CYP2D expression was lower in the brain in GHR-/- mice than that in WT mice; however, hepatic CYP2D levels were similar. Brain PPARα expression in male GHR-/- mice were markedly higher than those in WT mice, while brain PPARγ levels were decreased or unchanged in different regions. However, both hepatic PPARα and PPARγ in male GHR-/- mice were markedly higher than those in WT mice. Pulsatile GH decreased the PPARα mRNA level and increased the mRNA levels of CYP2D6 and PPARγ in SH-SY5Y cells. A luciferase assay showed that PPARγ activated the CYP2D6 gene promoter while PPARα inhibited its function. Pulsatile GH decreased the binding of PPARα to the CYP2D6 promoter by 40% and promoted the binding of PPARγ to the CYP2D6 promoter by approximately 60%. The male GH secretory pattern altered PPAR expression and the binding of PPARs to the CYP2D promoter, leading to the elevation of brain CYP2D in a tissue-specific manner. Growth hormone may alter the learning and memory functions in patients receiving GH replacement therapy via brain CYP2D.

Insulin-like Growth Factor 1 (IGF-1) as a marker of cognitive decline in normal ageing: A review

Insulin-like Growth Factor 1 (IGF-1) and its signaling pathway play a primary role in normal growth and ageing, however serum IGF-1 is known to reduce with advancing age. Recent findings suggest IGF-1 is essential for neurogenesis in the adult brain, and this reduction of IGF-1 with ageing may contribute to age-related cognitive decline. Experimental studies have shown manipulation of the GH/GF-1 axis can slow rates of cognitive decline in animals, making IGF-1 a potential biomarker of cognition, and/or its signaling pathway a possible therapeutic target to prevent or slow age-related cognitive decline. A systematic literature review and qualitative narrative summary of current evidence for IGF-1 as a biomarker of cognitive decline in the ageing brain was undertaken. Results indicate IGF-1 concentrations do not confer additional diagnostic information for those with cognitive decline, and routine clinical measurement of IGF-1 is not currently justified. In cases of established cognitive impairment, it remains unclear whether increasing circulating or brain IGF-1 may reverse or slow down the rate of further decline. Advances in neuroimaging, genetics, neuroscience and the availability of large well characterized biobanks will facilitate research exploring the role of IGF-1 in both normal ageing and age-related cognitive decline.

Brain STAT5 signaling modulates learning and memory formation

The signal transducer and activator of transcription 5 (STAT5) is a transcription factor recruited by numerous cytokines. STAT5 is important for several physiological functions, including body and tissue growth, mammary gland development, immune system and lipid metabolism. However, the role of STAT5 signaling for brain functions is still poorly investigated, especially regarding cognitive aspects. Therefore, the objective of the present study was to investigate whether brain STAT5 signaling modulates learning and memory formation. For this purpose, brain-specific STAT5 knockout (STAT5 KO) mice were studied in well-established memory tests. Initially, we confirmed a robust reduction in STAT5a and STAT5b mRNA levels in different brain structures of STAT5 KO mice. STAT5 KO mice showed no significant alterations in metabolism, growth, somatotropic axis and spontaneous locomotor activity. In contrast, brain-specific STAT5 ablation impaired learning and memory formation in the novel object recognition, Barnes maze and contextual fear conditioning tests. To unravel possible mechanisms that might underlie the memory deficits of STAT5 KO mice, we assessed neurogenesis in the hippocampus, but no significant differences were observed between groups. On the other hand, reduced insulin-like growth factor-1 (IGF-1) mRNA expression was found in the hippocampus and hypothalamus of STAT5 KO mice. These findings collectively indicate that brain STAT5 signaling is required to attain normal learning and memory. Therefore, STAT5 is an important downstream cellular mechanism shared by several cytokines to regulate cognitive functions.

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.

Catch-Up Growth and Neurobehavioral Development among Full-Term, Small-for-Gestational-Age Children: A Nationwide Japanese Population-Based Study

OBJECTIVE

To examine the relationship between catch-up growth of full-term, small for gestational age (SGA) children and their neurobehavioral development.

STUDY DESIGN

Data were obtained from a population-based nationwide Japanese longitudinal survey that started in 2001. Study participants were full-term children with information on height at 2 years of age (n = 32 533). Catch-up growth for SGA infants was defined as achieving a height at 2 years of age of more than -2.0 standard deviations for chronological age. Logistic regression analyses were used to estimate ORs and 95% CIs for the associations of SGA and catch-up growth status with neurobehavioral development at 2.5 and 8 years of age, adjusting for potential infant- and parent-related confounding factors.

RESULTS

Fifteen percent of term SGA infants failed to catch up in height. At 2.5 years of age, SGA children without catch-up growth were more likely to be unable to climb stairs (OR, 10.42; 95% CI, 5.55-19.56) and unable to compose a 2-word sentence (OR, 3.58; 95% CI, 1.81-7.08) compared with children with normal growth at birth. Furthermore, SGA children without catch-up growth were at increased risk for aggressive behaviors (OR, 3.85; 95% CI, 1.19-12.47) at 8 years of age.

CONCLUSIONS

Continuous follow-up for full-term SGA infants with failure of catch-up growth or poor postnatal growth may be beneficial for early detection and intervention for behavioral problems.

Growth hormone protects against kainate excitotoxicity and induces BDNF and NT3 expression in chicken neuroretinal cells

There is increasing evidence to suggest a beneficial neuroprotective effect of growth hormone (GH) in the nervous system. While our previous studies have largely focused on retinal ganglion cells (RGCs), we have also found conclusive evidence of a pro-survival effect of GH in cells of the inner nuclear layer (INL) as well as a protective effect on the dendritic trees of the inner plexiform layer (IPL) in the retina. The administration of GH in primary neuroretinal cell cultures protected and induced neural outgrowths. Our results, both in vitro (embryo) and in vivo (postnatal), showed neuroprotective actions of GH against kainic acid (KA)-induced excitotoxicity in the chicken neuroretina. Intravitreal injections of GH restored brain derived neurotrophic factor (BDNF) expression in retinas treated with KA. In addition, we demonstrated that GH over-expression and exogenous administration increased BDNF and neurotrophin-3 (NT3) gene expression in embryonic neuroretinal cells. Thus, GH neuroprotective actions in neural tissues may be mediated by a complex cascade of neurotrophins and growth factors which have been classically related to damage prevention and neuroretinal tissue repair.

Serum insulin-like growth factor-I levels are associated with improved white matter recovery after traumatic brain injury

Objective

Traumatic brain injury (TBI) is a common disabling condition with limited treatment options. Diffusion tensor imaging measures recovery of axonal injury in white matter (WM) tracts after TBI. Growth hormone deficiency (GHD) after TBI may impair axonal and neuropsychological recovery, and serum insulin‐like growth factor‐I (IGF‐I) may mediate this effect. We conducted a longitudinal study to determine the effects of baseline serum IGF‐I concentrations on WM tract and neuropsychological recovery after TBI.

Methods

Thirty‐nine adults after TBI (84.6% male, median age = 30.5 years, 87.2% moderate–severe, median time since TBI = 16.3 months, n = 4 with GHD) were scanned twice, 13.3 months (range = 12.1–14.9) apart, and 35 healthy controls were scanned once. Symptom and quality of life questionnaires and cognitive assessments were completed at both visits (n = 33). Our main outcome measure was fractional anisotropy (FA), a measure of WM tract integrity, in a priori regions of interest: splenium of corpus callosum (SPCC) and posterior limb of internal capsule (PLIC).

Results

At baseline, FA was reduced in many WM tracts including SPCC and PLIC following TBI compared to controls, indicating axonal injury, with longitudinal increases indicating axonal recovery. There was a significantly greater increase in SPCC FA over time in patients with serum IGF‐I above versus below the median for age. Only the higher IGF‐I group had significant improvements in immediate verbal memory recall over time.

Interpretation

WM recovery and memory improvements after TBI were greater in patients with higher serum IGF‐I at baseline. These findings suggest that the growth hormone/IGF‐I system may be a potential therapeutic target following TBI. Ann Neurol 2017;82:30–43

Real-life GH dosing patterns in children with GHD, TS or born SGA: a report from the NordiNet® International Outcome Study

OBJECTIVE

To describe real-life dosing patterns in children with growth hormone deficiency (GHD), born small for gestational age (SGA) or with Turner syndrome (TS) receiving growth hormone (GH) and enrolled in the NordiNet International Outcome Study (IOS; Nbib960128) between 2006 and 2016.

DESIGN

This non-interventional, multicentre study included paediatric patients diagnosed with GHD (isolated (IGHD) or multiple pituitary hormone deficiency (MPHD)), born SGA or with TS and treated according to everyday clinical practice from the Czech Republic (IGHD/MPHD/SGA/TS: n = 425/61/316/119), France (n = 1404/188/970/206), Germany (n = 2603/351/1387/411) and the UK (n = 259/60/87/35).

METHODS

GH dosing was compared descriptively across countries and indications. Proportions of patients by GH dose group (low/medium/high) or GH dose change (decrease/increase/no change) during years 1 and 2 were also evaluated across countries and indications.

RESULTS

In the Czech Republic, GH dosing was generally within recommended levels. In France, average GH doses were higher for patients with IGHD, MPHD and SGA than in other countries. GH doses in TS tended to be at the lower end of the recommended label range, especially in Germany and the UK; the majority of patients were in the low-dose group. A significant inverse association between baseline height standard deviation score and GH dose was shown (P < 0.05); shorter patients received higher doses. Changes in GH dose, particularly increases, were more common in the second (40%) than in the first year (25%).

CONCLUSIONS

GH dosing varies considerably across countries and indications. In particular, almost half of girls with TS received GH doses below practice guidelines and label recommendations.

Spatial learning and memory in male mice with altered growth hormone action

Growth hormone (GH) has a significant influence on cognitive performance in humans and other mammals. To understand the influence of altered GH action on cognition, we assessed spatial learning and memory using a Barnes maze (BM) comparing twelve-month old, male, bovine GH (bGH) and GH receptor antagonist (GHA) transgenic mice and their corresponding wild type (WT) littermates. During the acquisition training period in the BM, bGH mice showed increased latency, traveled longer path lengths and made more errors to reach the target than WT mice, indicating significantly poorer learning. Short-term memory (STM) and long-term memory (LTM) trials showed significantly suppressed memory retention in bGH mice when compared to the WT group. Conversely, GHA mice showed significantly better learning parameters (latency, path length and errors) and increased use of an efficient search strategy than WT mice. Our study indicates a negative impact of GH excess and a beneficial effect of the inhibition of GH action on spatial learning and memory and, therefore, cognitive performance in male mice. Further research to elucidate GH's role in brain function will facilitate identifying therapeutic applications of GH or GHA for neuropathological and neurodegenerative conditions.

Mode of GH administration and gene expression in the female rat brain

The endogenous secretion of growth hormone (GH) is sexually dimorphic in rats with females having a more even and males a more pulsatile secretion and low trough levels. The mode of GH administration, mimicking the sexually dimorphic secretion, has different systemic effects. In the brains of male rats, we have previously found that the mode of GH administration differently affects neuron-haemoglobin beta (Hbb) expression whereas effects on other transcripts were moderate. The different modes of GH administration could have different effects on brain transcripts in female rats. Hypophysectomised female rats were given GH either as injections twice daily or as continuous infusion and GH-responsive transcripts were assessed by quantitative reverse transcription polymerase chain reaction in the hippocampus and parietal cortex (cortex). The different modes of GH-administration markedly increased Hbb and 5'-aminolevulinate synthase 2 (Alas2) in both brain regions. As other effects were relatively moderate, a mixed model analysis (MMA) was used to investigate general effects of the treatments. In the hippocampus, MMA showed that GH-infusion suppressed glia- and neuron-related transcript expression levels, whereas GH-injections increased expression levels. In the cortex, GH-infusion instead increased neuron-related transcripts, whereas GH-injections had no significant effect. Interestingly, this contrasts to previous results obtained from male rat cortex where GH-infusion generally decreased expression levels. In conclusion, the results indicate that there is a small but significant difference in response to mode of GH administration in the hippocampus as compared to the cortex. For both modes of GH administration, there was a robust effect on Hbb and Alas2.

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.

Peripheral insulin-like growth factor 1 in bipolar disorder

Bipolar disorder is a recurrent and highly incapacitating illness, related to inflammation and changes in the insulin-like growth factor 1 (IGF-1). The objective of this study was to evaluate serum levels of IGF-1 in bipolar disorder patients and its relation to inflammation. We included 31 patients with bipolar disorder and 33 healthy controls. Serum concentrations of IGF-1, growth hormone (GH), insulin and tumor necrosis factor α (TNF-α) were analyzed. The serum levels of IGF-1 seem to be increased in bipolar disorder patients (248.84±104.91ng/mL) compared to controls (169.18±74.16ng/mL). Comparing reference values of IGF serum concentrations between groups, we found that 32% of patients had increased IGF-1 serum concentrations while only 3% of subjects are above normal range. We did not find statistically significant differences between groups in the concentration of insulin, GH, and TNF-α. This study suggests an association between IGF-1 in the pathophysiology of bipolar disorder. It is possible that this peripheral increase is related to a central nervous system increased resistance to IGF-1, thus reducing its neuroprotective action.

Cellular acidification as a new approach to cancer treatment and to the understanding and therapeutics of neurodegenerative diseases

During the last few years, the understanding of the dysregulated hydrogen ion dynamics and reversed proton gradient of cancer cells has resulted in a new and integral pH-centric paradigm in oncology, a translational model embracing from cancer etiopathogenesis to treatment. The abnormalities of intracellular alkalinization along with extracellular acidification of all types of solid tumors and leukemic cells have never been described in any other disease and now appear to be a specific hallmark of malignancy. As a consequence of this intracellular acid-base homeostatic failure, the attempt to induce cellular acidification using proton transport inhibitors and other intracellular acidifiers of different origins is becoming a new therapeutic concept and selective target of cancer treatment, both as a metabolic mediator of apoptosis and in the overcoming of multiple drug resistance (MDR). Importantly, there is increasing data showing that different ion channels contribute to mediate significant aspects of cancer pH regulation and etiopathogenesis. Finally, we discuss the extension of this new pH-centric oncological paradigm into the opposite metabolic and homeostatic acid-base situation found in human neurodegenerative diseases (HNDDs), which opens novel concepts in the prevention and treatment of HNDDs through the utilization of a cohort of neural and non-neural derived hormones and human growth factors.

Cognitive and adaptive advantages of growth hormone treatment in children with Prader-Willi syndrome

BACKGROUND

People with Prader-Willi syndrome (PWS) typically have mild to moderate intellectual deficits, compulsivity, hyperphagia, obesity, and growth hormone deficiencies. Growth hormone treatment (GHT) in PWS has well-established salutatory effects on linear growth and body composition, yet cognitive benefits of GHT, seen in other patient groups, have not been well studied in PWS.

METHODS

Study 1 included 96 children and youth with PWS aged 4-21 years who naturalistically varied in their exposures to GHT. Controlling for socioeconomic status, analyses compared cognitive and adaptive behavior test scores across age-matched treatment naïve versus growth hormone treated children. Study II assessed if age of treatment initiation or treatment duration was associated with subsequent cognition or adaptive behavior in 127, 4- to 21-year olds with PWS. Study III longitudinally examined cognitive and adaptive behavior in 168 participants who were either consistently on versus off GHT for up to 4-5 years.

RESULTS

Compared to the treatment naïve group, children receiving GHT had significantly higher Verbal and Composite IQs, and adaptive communication and daily living skills. Children who began treatment before 12 months of age had higher Nonverbal and Composite IQs than children who began treatment between 1 and 5 years of age. Longitudinally, the groups differed in their intercepts, but not slopes, with each group showing stable IQ and adaptive behavior scores over time.

CONCLUSIONS

Cognitive and adaptive advantages should be considered an ancillary benefit and additional justification for GHT in people with PWS. Future efforts need to target apparent socioeconomic inequities in accessing GHT in the PWS population.

The choroid plexus as a sex hormone target: Functional implications

The choroid plexuses (CPs) are highly vascularized branched structures that protrude into the ventricles of the brain, and form a unique interface between the blood and the cerebrospinal fluid (CSF). In recent years, novel functions have been attributed to this tissue such as in immune and chemical surveillance of the central nervous system, brain development, adult neurogenesis and circadian rhythm regulation. Sex hormones (SH) are widely recognized as modulators in several neurodegenerative diseases, and there is evidence that estrogens and androgens regulate several fundamental biological functions in the CPs. Therefore, SH are likely to affect the composition of the CSF impacting on brain homeostasis. This review will look at implications of the CPs' sex-related specificities.

Brain STAT5 signaling and behavioral control

Several growth factors and cytokines recruit the signal transducer and activator of transcription 5 (STAT5) signaling pathway to control cell proliferation, differentiation and apoptosis. Nonetheless, the importance of this transcription factor for brain functions is still poorly understood. Because some STAT5-inducing hormones, such as prolactin and leptin, act in the brain to regulate the expression of motivated behaviors, this signaling pathway is likely involved in behavioral modulation. Therefore, the objective of the present review was to summarize and discuss the available data regarding the possible role of central STAT5 signaling in the regulation of brain functions, especially on behavioral control. We discussed studies that investigated the importance of STAT5 signaling in the regulation of maternal and feeding behaviors. Additionally, we highlighted other behaviors that could be potentially affected by STAT5 signaling. This knowledge may help to understand how motivated behaviors are regulated at the cellular level.

Comparing the Behavioural Effects of Exogenous Growth Hormone and Melatonin in Young and Old Wistar Rats

Growth hormone (GH) and melatonin are two hormones with quite different physiological effects. Curiously, their secretion shows parallel and severe age-related reductions. This has promoted many reports for studying the therapeutic supplementation of both hormones in an attempt to avoid or delay the physical, physiological, and psychological decay observed in aged humans and in experimental animals. Interestingly, the effects of the external administration of low doses of GH and of melatonin were surprisingly similar, as both hormones caused significant improvements in the functional capabilities of aged subjects. The present report aims at discerning the eventual difference between cognitive and motor effects of the two hormones when administered to young and aged Wistar rats. The effects were tested in the radial maze, a test highly sensitive to the age-related impairments in working memory and also in the rotarod test, for evaluating the motor coordination. The results showed that both hormones caused clear improvements in both tasks. However, while GH improved the cognitive capacity and, most importantly, the physical stamina, the effects of melatonin should be attributed to its antioxidant, anxiolytic, and neuroprotective properties.

Treatment of autistic spectrum disorder with insulin-like growth factors

There are no treatments for the core symptoms of autistic spectrum disorder (ASD), but there is now more knowledge on emerging mechanisms and on mechanism-based therapies. In autism there are altered synapses: genes affected are commonly related to synaptic and immune function. Dysregulation of activity-dependent signaling networks may have a key role the etiology of autism. There is an over-activation of IGF-AKT-mTor in autism spectrum disorders. Morphological and electro-physiological defects of the cerebellum are linked to system-wide ASD-like behavior defects. The molecular basis for a cerebellar contribution has been demonstrated in a mouse model. These have led to a potential mechanism-based use of drug targets and mouse models. Neurotrophic factors are potential candidates for the treatment. Insulin-like growth factor-1 (IGF-1) is altered in autism. It reduces neuro-inflammation: by causing changes of cytokines such as IL-6 and microglial function. IGF-1 reduces the defects in the synapse. It alleviates NMDA-induced neurotoxicity via the IGF-AKT-mTor pathway in microglia. IGF-1 may rescue function in Rett syndrome and ASD caused by changes of the SCHANK3 gene. There are recently pilot studies of the treatment of Rett syndrome and of SCHANK3 gene deficiency syndromes. The FDA has granted Orphan drug designations for Fragile X syndrome, SCHANK3 gene deficiency syndrome and Rett syndrome.

Functional Changes after Recombinant Human Growth Hormone Replacement in Patients with Chronic Traumatic Brain Injury and Abnormal Growth Hormone Secretion

We explored the effects of recombinant human growth hormone (rhGH) replacement on physical and cognitive functioning in subjects with a moderate-to-severe traumatic brain injury (TBI) with abnormal growth hormone (GH) secretion. Fifteen individuals who sustained a TBI at least 12 months prior to study enrollment were identified as having abnormal GH secretion by glucagon stimulation testing (maximum GH response less than 8 ng/mL). Peak cardiorespiratory capacity, body composition, and muscle force testing were assessed at baseline and one year after rhGH replacement. Additionally, standardized neuropsychological tests that assess memory, processing speed, and cognitive flexibility, as well as self-report inventories related to depression and fatigue, were administered at baseline and 1 year after rhGH replacement. Comparison tests were performed with proper post hoc analyses. All analyses were carried out at α < 0.05. Peak O₂ consumption, peak oxygen pulse (estimate of cardiac stroke volume), and peak ventilation all significantly increased (p < 0.05). Maximal isometric and isokinetic force production were not altered. Skeletal muscle fatigue did not change but the perceptual rating of fatigue was reduced by ∼25% (p = 0.06). Cognitive performance did not change significantly over time, whereas self-reported symptoms related to depression and fatigue significantly improved. The observed changes suggest that rhGH replacement has a positive impact on cardiorespiratory fitness and a positive impact on perceptual fatigue in survivors of TBI with altered GH secretion.

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.

Multiple Effects of Growth Hormone in the Body: Is it Really the Hormone for Growth?

In this review, we analyze the effects of growth hormone on a number of tissues and organs and its putative role in the longitudinal growth of an organism. We conclude that the hormone plays a very important role in maintaining the homogeneity of tissues and organs during the normal development of the human body or after an injury. Its effects on growth do not seem to take place during the fetal period or during the early infancy and are mediated by insulin-like growth factor I (IGF-I) during childhood and puberty. In turn, IGF-I transcription is dependent on an adequate GH secretion, and in many tissues, it occurs independent of GH. We propose that GH may be a prohormone, rather than a hormone, since in many tissues and organs, it is proteolytically cleaved in a tissue-specific manner giving origin to shorter GH forms whose activity is still unknown.

Homocysteine augments BK channel activity and decreases exocytosis of secretory granules in rat GH3 cells

In this study, we investigated the effects of L-homocysteine (Hcy) on maxi calcium-activated potassium (BK) channels and on exocytosis of secretory granules in GH3 rat pituitary-derived cells. A major finding of our study indicates that short-term application of Hcy increased the open probability of oxidized BK channels in inside-out recordings. Whole-cell recordings show that extracellular Hcy also augmented BK currents during long-term application. Furthermore, Hcy decreased the exocytosis of secretory granules. This decrease was partially prevented by the BK channel inhibitor paxilline and fully prevented by N-acetylcysteine, a reactive oxygen species scavenger. Taken together, our data show that elevation of cellular Hcy level induces oxidative stress, increases BK channel activity, and decreases exocytosis of secretory granules. These findings may provide insight into some of the developmental impairments and neurotoxicity associated with Hyperhomocysteinemia (HHcy), a disease arising due to abnormally elevated levels of Hcy in the plasma.

General intelligence is associated with subclinical inflammation in Nepalese children: A population-based plasma proteomics study

Improving child cognition in impoverished countries is a public health priority. Yet, biological pathways and associated biomarkers of impaired cognition remain poorly understood and largely unknown, respectively. This study aimed to explore and quantify associations between functional plasma protein biomarkers and childhood intellectual test performance. We applied proteomics to quantify proteins in plasma samples of 249 rural Nepalese children, 6-8years of age who, 1year later at 7-9years of age, were administered the Universal Nonverbal Intelligence Test (UNIT). Among 751 plasma proteins quantified, 22 were associated with UNIT scores, passing a false discovery rate threshold of 5.0% (q<0.05). UNIT scores were higher by 2.3-9.2 points for every 50% increase in relative abundance of two insulin-like growth factor binding proteins (IGFBPs), six subclasses of apolipoprotein (Apo) and transthyretin, and lower by 4.0-15.3 points for each 50% increase in relative abundance of 13 proteins predominantly involved in inflammation. Among them, IGFBP-acid labile subunit, orosomucoid 1 (ORM1), Apo C-I, and pyruvate kinase isoenzymes M1/M2 jointly explained 37% of the variance in UNIT scores. After additional adjustment for height-for-age Z-score and household socio-economic status as indicators of long-term nutritional and social stress, associations with 6 proteins involved in inflammation, including ORM1, α-1-antichymotrypsin, reticulocalbin 1, and 3 components of the complement cascade, remained significant (q<0.05). Using untargeted proteomics, stable, constitutive facets of subclinical inflammation were associated with lower developmental test performance in this rural South Asian child population. Plasma proteomics may offer opportunities to identify functional, antecedent biomarkers of child cognitive development.

The growth hormone receptor

Once thought to be present only in liver, muscle and adipose tissue, the GH receptor is now known to be ubiquitously distributed, in accord with the many pleiotropic actions of GH. These include the regulation of metabolism, postnatal growth, cognition, immune, cardiac and renal systems and gut function. GH exerts these actions primarily through alterations in gene expression, initiated by activation of its membrane receptor and the resultant activation of the associated JAK2 (Janus kinase 2) and Src family kinases. Receptor activation involves hormone initiated movements within a receptor homodimer, rather than simple receptor dimerization. We have shown that binding of the hormone realigns the orientation of the two receptors both by relative rotation and by closer apposition just above the cell membrane. This is a consequence of the asymmetric placement of the binding sites on the hormone. Binding results in a conversion of parallel receptor transmembrane domains into a rotated crossover orientation, which produces separation of the lower part of the transmembrane helices. Because the JAK2 is bound to the Box1 motif proximal to the inner membrane, receptor activation results in separation of the two associated JAK2s, and in particular the removal of the inhibitory pseudokinase domain from the kinase domain of the other JAK2 (and vice versa). This brings the two kinase domains into position for trans-activation and initiates tyrosine phosphorylation of the receptor cytoplasmic domain and other substrates such as STAT5, the key transcription factor mediating most genomic actions of GH. There are a limited number of genomic actions initiated by the Src kinase family member which also associates with the upper cytoplasmic domain of the receptor, including important immune regulatory actions to dampen exuberant innate immune activation of cells involved in transplant rejection. These findings offer insights for developing specific receptor antagonists which may be valuable in cancer therapy.