Effects of a growth hormone-releasing hormone antagonist on telomerase activity, oxidative stress, longevity, and aging in mice

Growth Hormone and Aging

Growth hormone (GH) secretion declines with aging (somatopause). One of the most controversial issues in aging is GH treatment of older adults without evidence of pituitary pathology. Although some clinicians have proposed reversing the GH decline in the older population, most information comes from not placebo-controlled studies. Although most animal studies reported an association between decreased GH levels (or GH resistance) and increased lifespan, human models have shown contradictory reports on the consequences of GH deficiency (GHD) on longevity. Currently, GH treatment in adults is only indicated for individuals with childhood-onset GHD transitioning to adulthood or new-onset GHD due to hypothalamic or pituitary pathologic processes.

Mechanisms of ageing: growth hormone, dietary restriction, and metformin

Tackling the mechanisms underlying ageing is desirable to help to extend the duration and improve the quality of life. Life extension has been achieved in animal models by suppressing the growth hormone-insulin-like growth factor 1 (IGF-1) axis and also via dietary restriction. Metformin has become the focus of increased interest as a possible anti-ageing drug. There is some overlap in the postulated mechanisms of how these three approaches could produce anti-ageing effects, with convergence on common downstream pathways. In this Review, we draw on evidence from both animal models and human studies to assess the effects of suppression of the growth hormone-IGF-1 axis, dietary restriction, and metformin on ageing.

Protective effects of GHRH antagonists against hydrogen peroxide-induced lung endothelial barrier disruption

PURPOSE

Growth hormone-releasing hormone (GHRH) is a hypothalamic hormone, which regulates growth hormone release from the anterior pituitary gland. GHRH antagonists (GHRHAnt) are anticancer agents, which also exert robust anti-inflammatory activities in malignancies. GHRHAnt exhibit anti-oxidative and anti-inflammatory effects in vascular endothelial cells, indicating their potential use against disorders related to barrier dysfunction (e.g. sepsis). Herein, we aim to investigate the effects of GHRHAnt against lung endothelial hyperpermeability.

METHODS

The in vitro effects of GHRHAnt in H₂O₂-induced endothelial barrier dysfunction were investigated in bovine pulmonary artery endothelial cells (BPAEC). Electric cell-substrate impedance sensing (ECIS) was utilized to measure transendothelial resistance, an indicator of barrier function.

RESULTS

Our results demonstrate that GHRHAnt protect against H₂O₂-induced endothelial barrier disruption via P53 and cofilin modulation. Both proteins are crucial modulators of vascular integrity. Moreover, GHRHAnt prevent H₂O₂ - induced decrease in transendothelial resistance.

CONCLUSIONS

GHRHAnt represent a promising therapeutic intervention towards diseases related to lung endothelial hyperpermeability, such as acute respiratory distress syndrome - related or not to COVID-19 - and sepsis. Targeted medicine for those potentially lethal disorders does not exist.

Therapeutic effects of growth hormone in a rat model of total sleep deprivation: Evaluating behavioral, hormonal, biochemical and electrophysiological parameters

OBJECTIVE

Total sleep deprivation (TSD) causes several harmful changes in the brain, including memory impairment, increased stress and depression levels, as well as reduced antioxidant activity. Growth hormone (GH) has been shown to boost antioxidant levels while improving memory and depression. The present study was conducted to explain the possible effects of exogenous GH against behavioral and biochemical disorders caused by TSD and the possible mechanisms involved.

MAIN METHODS

To induce TSD, rats were housed in homemade special cages equipped with stainless steel wire conductors to induce general and inconsistent TSD. They received a mild repetitive electric shock to their paws every 10 min for 21 days. GH (1 ml/kg, sc) was administered to rats during induction of TSD for 21 days. Memory retrieval, anxiety, depression-like behaviors, pain behaviors, antioxidant activity, hippocampal level of BDNF, and simultaneously brain electrical activity were measured at scheduled times after TSD.

KEY FINDINGS

The results showed that GH treatment improved memory (p < 0.001) in the PAT test of rats exposed to TSD. These beneficial effects were associated with lowering the level of anxiety and depression-like behavior (p < 0.001), rising the pain threshold (p < 0.01), increasing the activity of antioxidants (p < 0.01), hippocampal BDNF (p < 0.001), and regular brain electrical activity.

SIGNIFICANCE

Our findings show that GH plays a key role in modulating memory, anxiety and depression behaviors, as well as reducing oxidative stress and improve hippocampal single-unit activity in the brain during TSD.

Growth Hormone-Releasing Hormone in Endothelial Inflammation

The discovery of hypothalamic hormones propelled exciting advances in pharmacotherapy and improved life quality worldwide. Growth hormone-releasing hormone (GHRH) is a crucial element in homeostasis maintenance, and regulates the release of growth hormone from the anterior pituitary gland. Accumulating evidence suggests that this neuropeptide can also promote malignancies, as well as inflammation. Our review is focused on the role of that 44 - amino acid peptide (GHRH) and its antagonists in inflammation and vascular function, summarizing recent findings in the corresponding field. Preclinical studies demonstrate the protective role of GHRH antagonists against endothelial barrier dysfunction, suggesting that the development of those peptides may lead to new therapies against pathologies related to vascular remodeling (eg, sepsis, acute respiratory distress syndrome). Targeted therapies for those diseases do not exist.

Growth Hormone-Releasing Hormone Antagonist JV-1-36 Suppresses Reactive Oxygen Species Generation in A549 Lung Cancer Cells

Growth hormone-releasing hormone (GHRH) and its receptors are expressed in a variety of human cancers, and have been involved in malignancies. GHRH antagonists (GHRHAnt) were developed to suppress tumor progression and metastasis. Previous studies demonstrate the involvement of reactive oxygen species (ROS) in cancer progression. Herein, we investigate the effect of a commercially available GHRH antagonist, namely JV-1-36, in the redox status of the A549 human cancer cell line. Our results suggest that this peptide significantly reduces ROS production in those cells in a time-dependent manner and counteracts H2O2-induced ROS. Our study supports the anti-oxidative effects of JV-1-36 and contributes in our knowledge towards the in vitro effects of GHRHAnt in cancers.

Genetic architecture and heritability of early-life telomere length in a wild passerine

Early-life telomere length (TL) is associated with fitness in a range of organisms. Little is known about the genetic basis of variation in TL in wild animal populations, but to understand the evolutionary and ecological significance of TL it is important to quantify the relative importance of genetic and environmental variation in TL. In this study, we measured TL in 2746 house sparrow nestlings sampled across 20 years and used an animal model to show that there is a small heritable component of early-life TL (h²  = 0.04). Variation in TL among individuals was mainly driven by environmental (annual) variance, but also brood and parental effects. Parent-offspring regressions showed a large maternal inheritance component in TL ( h maternal 2  = 0.44), but no paternal inheritance. We did not find evidence for a negative genetic correlation underlying the observed negative phenotypic correlation between TL and structural body size. Thus, TL may evolve independently of body size and the negative phenotypic correlation is likely to be caused by nongenetic environmental effects. We further used genome-wide association analysis to identify genomic regions associated with TL variation. We identified several putative genes underlying TL variation; these have been inferred to be involved in oxidative stress, cellular growth, skeletal development, cell differentiation and tumorigenesis in other species. Together, our results show that TL has a low heritability and is a polygenic trait strongly affected by environmental conditions in a free-living bird.

Adropin transgenesis improves recognition memory in diet-induced obese LDLR-deficient C57BL/6J mice

Obesity-related metabolic dysregulation causes mild cognitive impairment and increased risk for dementia. We used an LDLR-deficient C57BL/6J mouse model (LDLRKO) to investigate whether adropin, a neuropeptide linked to neurodegenerative diseases, improves cognitive function in situations of metabolic dysregulation. Adropin transgenic mice (AdrTG) were crossed with LDLRKO; male and female progeny were fed a high fat diet for 3-months. Male chow-fed wild type (WT) mice were used as controls. Diet-induced obesity and LDLR-deficiency caused severe dyslipidemia, irrespective of sex. The AdrTG prevented reduced adropin protein levels in LDLRKO cortex. In males, metabolic dysregulation and AdrTG genotype significantly and bi-directionally affected performance in the novel object recognition (NOR) test, a declarative hippocampal memory task (discrimination index mean ± SE for WT, 0.02 ± 0.088; LDLRKO, -0.115 ± 0.077; AdrTG;LDLRKO, 0.265 ± 0.078; genotype effect, p = 0.009; LDLRKO vs. AdrTG;LDLRKO, P < 0.05). A 2-way ANOVA (fixed variables: sex, AdrTG genotype) indicated a highly significant effect of AdrTG (P = 0.003). The impact of the diet-genotype interaction on the male mouse brain was investigated using RNA-seq. Gene-ontology analysis of transcripts showing fold-changes of>1.3 or <-1.3 (P < 0.05) indicated metabolic dysregulation affected gene networks involved in intercellular/neuronal signaling, immune processes, angiogenesis, and extracellular matrix organization. The AdrTG selectively attenuated the impact of metabolic dysregulation on intercellular/neuronal signaling pathways. Intercellular/neuronal signaling pathways were also the predominant processes overrepresented when directly comparing AdrTG;LDLRKO with LDRKO. In summary, adropin overexpression improves cognitive function in severe metabolic dysregulation through pathways related to cell-cell communication and neuronal processes, and independently of preventing inflammatory responses.

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

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

Suppression of reactive oxygen species in endothelial cells by an antagonist of growth hormone-releasing hormone

Growth hormone-releasing hormone (GHRH) is a hypothalamic hormone, which regulates the secretion of growth hormone (GH) from the anterior pituitary gland. The effects of GHRH extend beyond the GH-insulin-like growth factor I axis, and that neuropeptide has been involved in the potentiation of several malignancies and other inflammatory disorders. The development of GHRH antagonists (GHRHAnt) delivers an exciting possibility to counteract the pathogenesis of the GHRH-related effects in human pathophysiology, especially when considered that GHRHAnt support endothelial barrier integrity. Those GHRHAnt-mediated effects are exerted at least in part due to the suppression of major inflammatory pathways, and the modulation of major cytoskeletal components. In the present study, we measured the production of reactive oxygen species (ROS) in bovine pulmonary artery endothelial cells, human cerebral microvascular endothelial cells, and human lung microvascular endothelial cells exposed to GHRH or a commercially available GHRHAnt. Our findings reveal the antioxidative effects of GHRHAnt in all three cell lines, which express GHRH receptors. The redox status of NIH/3T3 cells, which do not produce GHRH receptors, was not significantly affected by GHRH or GHRHAnt. Hence, the application of GHRHAnt in pathologies related to increased ROS production should be further investigated.

Antagonists of Growth Hormone-Releasing Hormone Inhibit the Growth of Pituitary Adenoma Cells by Hampering Oncogenic Pathways and Promoting Apoptotic Signaling

Simple Summary

Many studies have demonstrated that the antagonists of growth hormone-releasing hormone (GHRH) exert inhibitory activities in a variety of experimental cancers; however, their potential antitumor role in pituitary adenomas (PAs) remains largely unknown. Here, we show that GHRH antagonists of Miami (MIA) class, MIA-602 and MIA-690, are able to reduce the growth and promote cell death in hormone-secreting PA cell lines, through the inhibition of mechanisms implicated in tumorigenesis and cancer progression. MIA-602 and MIA-690 also decreased the viability of tumor cells derived from human pituitary tumors. Overall, these findings suggest that GHRH antagonists may represent new therapeutic tools for the treatment of PAs, both alone or in combination with standard pharmacological treatments.

Abstract

Pituitary adenomas (PAs) are intracranial tumors, often associated with excessive hormonal secretion and severe comorbidities. Some patients are resistant to medical therapies; therefore, novel treatment options are needed. Antagonists of growth hormone-releasing hormone (GHRH) exert potent anticancer effects, and early GHRH antagonists were found to inhibit GHRH-induced secretion of pituitary GH in vitro and in vivo. However, the antitumor role of GHRH antagonists in PAs is largely unknown. Here, we show that the GHRH antagonists of MIAMI class, MIA-602 and MIA-690, inhibited cell viability and growth and promoted apoptosis in GH/prolactin-secreting GH3 PA cells transfected with human GHRH receptor (GH3-GHRHR), and in adrenocorticotropic hormone ACTH-secreting AtT20 PA cells. GHRH antagonists also reduced the expression of proteins involved in tumorigenesis and cancer progression, upregulated proapoptotic molecules, and lowered GHRH receptor levels. The combination of MIA-690 with temozolomide synergistically blunted the viability of GH3-GHRHR and AtT20 cells. Moreover, MIA-690 reduced both basal and GHRH-induced secretion of GH and intracellular cAMP levels. Finally, GHRH antagonists inhibited cell viability in human primary GH- and ACTH-PA cell cultures. Overall, our results suggest that GHRH antagonists, either alone or in combination with pharmacological treatments, may be considered for further development as therapy for PAs.

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

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

Effects of somatotropic axis on cognitive dysfunction of obstructive sleep apnea

PURPOSE

Obstructive sleep apnea (OSA) is associated with a variety of neuroendocrine disorders and may lead to many complications, including cognitive dysfunction. The aim of this study was to assess the change of somatotropic axis and to detect the relation between somatotropic axis hormone and cognitive dysfunction.

METHODS

Sixty-six patients with OSA and 16 healthy controls were enrolled in this cross-sectional study. Cognitive function assessment using the Mini-Mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA) and polysomnography were performed on all individuals. Blood samples were taken the next morning following the polysomnography and the level of serum growth hormone-releasing hormone (GHRH) and growth hormone (GH) were analyzed by enzyme-linked immunosorbent assay.

RESULTS

Compared with the control group, OSA patients showed significantly lower serum GH level (p < 0.05), whereas no statistical significance of GHRH level was found. In addition, lower MMSE and MoCA scores were found only in the severe OSA patients when compared with the controls. Furthermore, in severe OSA patients with cognitive dysfunction (MMSE score < 27 and MoCA score < 26), serum GHRH and GH levels were significantly lower than those without cognitive dysfunction. Logistic analysis revealed that cognitive dysfunction in severe OSA patients was associated with micro-arousal index and the level of serum GHRH and GH.

CONCLUSION

Decreased serum GH and GHRH levels were found among severe OSA patients with cognitive dysfunction who were overweight, which might promote the occurrence of cognitive dysfunction.

The Long Intron 1 of Growth Hormone Gene from Reeves' Turtle (Chinemys reevesii) Correlates with Negatively Regulated GH Expression in Four Cell Lines

Turtles grow slowly and have a long lifespan. Ultrastructural studies of the pituitary gland in Reeves’ turtle (Chinemys reevesii) have revealed that the species possesses a higher nucleoplasmic ratio and fewer secretory granules in growth hormone (GH) cells than other animal species in summer and winter. C. reevesii GH gene was cloned and species-specific similarities and differences were investigated. The full GH gene sequence in C. reevesii contains 8517 base pairs (bp), comprising five exons and four introns. Intron 1 was found to be much longer in C. reevesii than in other species. The coding sequence (CDS) of the turtle’s GH gene, with and without the inclusion of intron 1, was transfected into four cell lines, including DF-1 chicken embryo fibroblasts, Chinese hamster ovary (CHO) cells, human embryonic kidney 293FT cells, and GH4C1 rat pituitary cells; the turtle growth hormone (tGH) gene mRNA and protein expression levels decreased significantly in the intron-containing CDS in these cell lines, compared with that of the corresponding intronless CDS. Thus, the long intron 1 of GH gene in Reeves’ turtle might correlate with downregulated gene expression.

Integrative neurobiology of metabolic diseases, neuroinflammation, and neurodegeneration

Alzheimer's disease (AD) is a complex, multifactorial disease with a number of leading mechanisms, including neuroinflammation, processing of amyloid precursor protein (APP) to amyloid β peptide, tau protein hyperphosphorylation, relocalization, and deposition. These mechanisms are propagated by obesity, the metabolic syndrome and type-2 diabetes mellitus. Stress, sedentariness, dietary overconsumption of saturated fat and refined sugars, and circadian derangements/disturbed sleep contribute to obesity and related metabolic diseases, but also accelerate age-related damage and senescence that all feed the risk of developing AD too. The complex and interacting mechanisms are not yet completely understood and will require further analysis. Instead of investigating AD as a mono- or oligocausal disease we should address the disease by understanding the multiple underlying mechanisms and how these interact. Future research therefore might concentrate on integrating these by “systems biology” approaches, but also to regard them from an evolutionary medicine point of view. The current review addresses several of these interacting mechanisms in animal models and compares them with clinical data giving an overview about our current knowledge and puts them into an integrated framework.

β-Hydroxybutyric acid inhibits growth hormone-releasing hormone synthesis and secretion through the GPR109A/extracellular signal-regulated 1/2 signalling pathway in the hypothalamus

β-Hydroxybutyric acid (BHBA) has recently been shown to regulate hormone synthesis and secretion in the hypothalamus. However, little is known about the effects of BHBA-mediated hormone regulation or the detailed mechanisms by which BHBA regulates growth hormone-releasing hormone (GHRH) synthesis and secretion. In the present study, we examined the expression of the BHBA receptor GPR109A in primary hypothalamic cell cultures. We hypothesised that BHBA regulates GHRH via GPR109A and its downstream signals. Initial in vivo studies conducted in rats demonstrated that GHRH mRNA expression in the hypothalamus was strongly inversely correlated with BHBA levels in the cerebrospinal fluid during postnatal development (r = -0.89, P < 0.01). Furthermore, i.c.v. administration of BHBA acutely decreased GHRH mRNA expression in rats. Further in vitro studies revealed a decrease in GHRH synthesis and secretion in primary hypothalamic cells after treatment with BHBA; this effect was inhibited when hypothalamic cells were pretreated with pertussis toxin (PTX). BHBA had no effect on GHRH synthesis and secretion in GT1-7 cells, which do not exhibit cell surface expression of GPR109A. Furthermore, BHBA acutely decreased the transcription of the homeobox gene for Gsh-1 in the hypothalamus in both in vivo and in vitro, and this effect was also inhibited by PTX in vitro. In primary hypothalamic cells, BHBA activated the extracellular signal-regulated kinase (ERK)1/2, p38 and c-Jun N-terminal kinase mitogen-activated protein kinase (MAPK) kinases, as shown by western blot analysis. Moreover, inhibition of ERK1/2 with U0126 attenuated the BHBA-mediated reduction in Gsh-1 expression and GHRH synthesis and secretion. These results strongly suggest that BHBA directly regulates GHRH synthesis and secretion via the GPR109A/ERK1/2 MAPK pathway, and also that Gsh-1 is essential for this function.

Antagonist of GH-releasing hormone receptors alleviates experimental ocular inflammation

Disruptions in immunity and occurrence of inflammation cause many eye diseases. The growth hormone-releasing hormone-growth hormone-insulin-like growth factor-1 (GHRH-GH-IGF1) axis exerts regulatory effects on the immune system. Its involvement in ocular inflammation remains to be investigated. Here we studied this signaling in endotoxin-induced uveitis (EIU) generated by LPS. The increase in GHRH receptor (GHRH-R) protein levels was parallel to the increase in mRNA levels of pituitary-specific transcription factor-1, GHRH-R splice variant 1, GHRH, and GH following LPS insult. Elevation of GHRH-R and GH receptor was localized on the epithelium of the iris and ciliary body, and GHRH-R was confined to the infiltrating macrophages and leukocytes in aqueous humor but not to those in stroma. Treatment with GHRH-R antagonist decreased LPS-stimulated surges of GH and IGF1 in aqueous humor and alleviated inflammation by reducing the infiltration of macrophages and leukocytes and the production of TNF-α, IL-1β, and monocyte chemotactic protein-1. Our results indicate that inflammation in the iris and ciliary body involves the activation of GHRH signaling, which affects the recruitment of immune cells and the production of proinflammatory mediators that contribute to EIU pathogenesis. Moreover, the results suggest that GHRH-R antagonists are potential therapeutic agents for the treatment of acute ocular inflammation.

The behavioral, pathological and therapeutic features of the senescence-accelerated mouse prone 8 strain as an Alzheimer's disease animal model

Alzheimer's disease (AD) is a widespread and devastating progressive neurodegenerative disease. Disease-modifying treatments remain beyond reach, and the etiology of the disease is uncertain. Animal model are essential for identifying disease mechanisms and developing effective therapeutic strategies. Research on AD is currently being carried out in rodent models. The most common transgenic mouse model mimics familial AD, which accounts for a small percentage of cases. The senescence-accelerated mouse prone 8 (SAMP8) strain is a spontaneous animal model of accelerated aging. Many studies indicate that SAMP8 mice harbor the behavioral and histopathological signatures of AD, namely AD-like cognitive and behavioral alterations, neuropathological phenotypes (neuron and dendrite spine loss, spongiosis, gliosis and cholinergic deficits in the forebrain), β-amyloid deposits resembling senile plaques, and aberrant hyperphosphorylation of Tau-like neurofibrillary tangles. SAMP8 mice are useful in the development of novel therapies, and many pharmacological agents and approaches are effective in SAMP8 mice. SAMP8 mice are considered a robust model for exploring the etiopathogenesis of sporadic AD and a plausible experimental model for developing preventative and therapeutic treatments for late-onset/age-related AD, which accounts for the vast majority of cases.

Dietary resveratrol prevents Alzheimer's markers and increases life span in SAMP8

Resveratrol is a polyphenol that is mainly found in grapes and red wine and has been reported to be a caloric restriction (CR) mimetic driven by Sirtuin 1 (SIRT1) activation. Resveratrol increases metabolic rate, insulin sensitivity, mitochondrial biogenesis and physical endurance, and reduces fat accumulation in mice. In addition, resveratrol may be a powerful agent to prevent age-associated neurodegeneration and to improve cognitive deficits in Alzheimer's disease (AD). Moreover, different findings support the view that longevity in mice could be promoted by CR. In this study, we examined the role of dietary resveratrol in SAMP8 mice, a model of age-related AD. We found that resveratrol supplements increased mean life expectancy and maximal life span in SAMP8 and in their control, the related strain SAMR1. In addition, we examined the resveratrol-mediated neuroprotective effects on several specific hallmarks of AD. We found that long-term dietary resveratrol activates AMPK pathways and pro-survival routes such as SIRT1 in vivo. It also reduces cognitive impairment and has a neuroprotective role, decreasing the amyloid burden and reducing tau hyperphosphorylation.

Quantitative PCR analysis used to characterize physiological changes in brain tissue of senescent sockeye salmon

Senescence varies considerably among fishes, and understanding the evolutionary basis for this diversity has become an important area of study. For rapidly senescing species such as Pacific salmon, senescence is a complex process as these fish are initiating anorexia while migrating to natal spawning grounds, and die within days of reproduction. To better understand senescence in Pacific salmon we examined expression patterns for a suite of genes in brain tissue of pre-senescent and senescent sockeye salmon. Interestingly, a significant increase in expression of genes involved in telomere repair and immune activity was observed in senescent salmon. These data provide insight into physiological changes in salmon undergoing senescence and the factors contributing to variation in observed senescence rates among individuals and populations.

Growth hormone releasing hormone (GHRH) signaling modulates intermittent hypoxia-induced oxidative stress and cognitive deficits in mouse

Intermittent hypoxia (IH) during sleep, such as occurs in obstructive sleep apnea (OSA), leads to degenerative changes in the hippocampus, and is associated with spatial learning deficits in adult mice. In both patients and murine models of OSA, the disease is associated with suppression of growth hormone (GH) secretion, which is actively involved in the growth, development, and function of the central nervous system (CNS). Recent work showed that exogenous GH therapy attenuated neurocognitive deficits elicited by IH during sleep in rats. Here, we show that administration of the Growth Hormone Releasing Hormone (GHRH) agonist JI-34 attenuates IH-induced neurocognitive deficits, anxiety, and depression in mice along with reduction in oxidative stress markers such as MDA and 8-hydroxydeoxyguanosine, and increases in hypoxia inducible factor-1α DNA binding and up-regulation of insulin growth factor-1 and erythropoietin expression. In contrast, treatment with a GHRH antagonist (MIA-602) during intermittent hypoxia did not affect any of the IH-induced deleterious effects in mice. Thus, exogenous GHRH administered as the formulation of a GHRH agonist may provide a viable therapeutic intervention to protect IH-vulnerable brain regions from OSA-associated neurocognitive dysfunction. Sleep apnea, characterized by chronic intermittent hypoxia (IH), is associated with substantial cognitive and behavioral deficits. Here, we show that administration of a GHRH agonist (JI-34) reduces oxidative stress, increases both HIF-1α nuclear binding and downstream expression of IGF1 and erythropoietin (EPO) in hippocampus and cortex, and markedly attenuates water maze performance deficits in mice exposed to intermittent hypoxia during sleep.

Beneficial effects of novel antagonists of GHRH in different models of Alzheimer's disease

Alzheimer's disease is the most frequent debilitating disorder of the central nervous system. Neuroendocrine mechanisms appear to play an important role in this insidiously developing disease. In the present study, the effects of a recently developed growth hormone-releasing hormone (GHRH) antagonist (MIA-690) were evaluated in vivo observing the behavior of genetically modified "Alzheimer's" 5XFAD mice in a Morris water maze (MWM). The effects of the antagonist were also evaluated in vitro using HCN2 human cortical cell cultures treated with amyloid-β1-42. In vivo, the indices of cognitive performance (latency, cumulative index etc.) were followed up for 6 months. In vitro, the formation of reactive oxygen species, markers of inflammatory and neurohormonal signaling were measured by fluorescent detection, PCR, and ELISA. Accumulation of amyloid-β1-42 rafts and τ filaments in necropsied brain samples was verified with the help of ELISA. In the MWM experiments, MIA-690 decreased escape latency, and, in the brain samples, it inhibited the concentration of amyloid-β1-42 and τ filaments. In cell cultures, the GHRH analog showed anti-oxidative and neuro-protective properties and inhibited the GHRH-growth hormone-insulin like growth factor axis. Our data strongly suggest the merit of further studies with GHRH analogs in models of Alzheimer's disease and in elementary clinical trials.

Hypothalamic programming of systemic ageing involving IKK-β, NF-κB and GnRH

Ageing is a result of gradual and overall functional deteriorations across the body; however, it is unknown whether an individual tissue primarily works to mediate the ageing progress and control lifespan. Here we show that the hypothalamus is important for the development of whole-body ageing in mice, and that the underlying basis involves hypothalamic immunity mediated by IκB kinase-β (IKK-β), nuclear factor κB (NF-κB) and related microglia-neuron immune crosstalk. Several interventional models were developed showing that ageing retardation and lifespan extension are achieved in mice by preventing ageing-related hypothalamic or brain IKK-β and NF-κB activation. Mechanistic studies further revealed that IKK-β and NF-κB inhibit gonadotropin-releasing hormone (GnRH) to mediate ageing-related hypothalamic GnRH decline, and GnRH treatment amends ageing-impaired neurogenesis and decelerates ageing. In conclusion, the hypothalamus has a programmatic role in ageing development via immune-neuroendocrine integration, and immune inhibition or GnRH restoration in the hypothalamus/brain represent two potential strategies for optimizing lifespan and combating ageing-related health problems.

Paraoxonase is reduced in patients with growth hormone deficiency: A novel risk factor for atherosclerosis

BACKGROUND

Growth hormone deficiency (GHD) is associated with an increased cardiovascular mortality. Increased oxidative stress has been associated with development of cardiovascular and cerebrovascular diseases. In the present study, we aimed to evaluate oxidant and antioxidant status in patients with GHD by analyzing serum paraoxonase1 (PON1) activity, and malondialdehyde (MDA) and thiol levels.

MATERIALS AND METHODS

This study was a case-control study. Thirty patients with GHD were included in the study and compared with 20 healthy controls. Serum PON1 activity, and MDA and thiol levels were measured according to an enzymatic spectrophotometric method.

RESULTS

Serum MDA levels (2.8 ± 1.3 nmol/mL) were higher in GHD group than the controls (1.7 ± 0.5 nmol/mL) (P = 0.001). PON1 activity (149.9 ± 77.9 U/L) was lower in GHD group than the controls (286.3 ± 126.7 U/L) (P = 0.001). Thiol and high-density lipoprotein cholesterol (HDL-cholesterol) levels were lower in GHD group (218.6 ± 103.9 µmol/L and 32.6 ± 13.4 mg/dL, respectively) than the controls (289.6 ± 101.1 µmol/L and 54.3 ± 14.9 mg/dL, respectively) (P = 0.021 and P = 0.001, respectively). In GHD patients, serum MDA level was negatively correlated with serum HDL-cholesterol (r = -0.499, P = 0.001), and serum PON1 activity was positively correlated with serum thiol and HDL-cholesterol levels (r = 0.306, P = 0.032 and r = 0.303, P = 0.033, respectively).

CONCLUSION

These data support that GHD is characterized by an imbalance between oxidant and antioxidant factors. This abnormality may contribute to the increased atherogenic risk in patients with GHD.

Somatotropic signaling: trade-offs between growth, reproductive development, and longevity

Growth hormone (GH) is a key determinant of postnatal growth and plays an important role in the control of metabolism and body composition. Surprisingly, deficiency in GH signaling delays aging and remarkably extends longevity in laboratory mice. In GH-deficient and GH-resistant animals, the "healthspan" is also extended with delays in cognitive decline and in the onset of age-related disease. The role of hormones homologous to insulin-like growth factor (IGF, an important mediator of GH actions) in the control of aging and lifespan is evolutionarily conserved from worms to mammals with some homologies extending to unicellular yeast. The combination of reduced GH, IGF-I, and insulin signaling likely contributes to extended longevity in GH or GH receptor-deficient organisms. Diminutive body size and reduced fecundity of GH-deficient and GH-resistant mice can be viewed as trade-offs for extended longevity. Mechanisms responsible for delayed aging of GH-related mutants include enhanced stress resistance and xenobiotic metabolism, reduced inflammation, improved insulin signaling, and various metabolic adjustments. Pathological excess of GH reduces life expectancy in men as well as in mice, and GH resistance or deficiency provides protection from major age-related diseases, including diabetes and cancer, in both species. However, there is yet no evidence of increased longevity in GH-resistant or GH-deficient humans, possibly due to non-age-related deaths. Results obtained in GH-related mutant mice provide striking examples of mutations of a single gene delaying aging, reducing age-related disease, and extending lifespan in a mammal and providing novel experimental systems for the study of mechanisms of aging.

Oxidative stress in growth hormone transgenic coho salmon with compressed lifespan--a model for addressing aging

Growth hormone (GH) transgenic fish have dramatically enhanced growth rates, increased oxygen demands and reactive oxygen species production. GH-transgenic coho salmon provide an opportunity to address effects of increased metabolism on physiological aging. The objective of this study was to compare oxidative stress in wild-type (WT) and GH-transgenic (T) coho salmon (Oncorhynchus kisutch) of different ages (1 and 2 years). Antioxidant enzyme activity, protein carbonyls (PC) and glutathione (GSH, GSSG) were measured. PC correlated to growth rates in individual fish. T fish exhibited lower antioxidant enzyme activities and GSH levels compared to the WT, while levels of PC and GSSG were higher. Age affects were observed in both WT and T fish; enzyme activities and GSH decreased while PC and GSSG increased. Our results support the metabolic rate theory of aging. This study aims to be a platform for continued studies of the theories of aging using fish as model organisms.

Involvement of neurotransmitters in the action of growth hormone-releasing hormone antagonist on passive avoidance learning

The antagonist MZ-4-71 of growth hormone-releasing hormone (GH-RH) has been shown to suppress the secretion of GH and insulin-like growth factor-1 (IGF-1), suggesting that this class of analogs could be used for the therapy of disorders characterized by excessive GH secretion. Numerous GH-RH antagonists has been synthetized and shown to suppress the growth of various tumors. MZ-4-71 facilitates the consolidation of passive avoidance learning. Beta-amyloid 25-35 impairs the consolidation of passive avoidance learning and MZ-4-71 fully blocks this impairment. However, little is known about the possible mechanism of action of GR-RH antagonists on these actions. In the present work, the possible effects of different neurotransmitters on the action of MZ-4-71 were studied in the memory consolidation of passive avoidance behavior. The involvement of cholinergic, serotonergic, dopaminergic, GABA-ergic, adrenergic and opiate receptors was tested. Mice were pretreated with a nonselective α-adrenergic receptor antagonist, phenoxybenzamine, a β-adrenergic receptor antagonist, propranolol, a mixed 5-HT1/5-HT2 serotonergic receptor antagonist, methysergide, a nonselective 5-HT2 serotonergic receptor antagonist, cyproheptadine, a nonselective muscarinic acetylcholine receptor antagonist, atropine, a D2, D3, D4 dopamine receptor antagonist, haloperidol, a γ-aminobutyric acid subunit A (GABA-A) receptor antagonist, bicuculline, or a nonselective opioid receptor antagonist, naloxone. Atropine, methysergide, cyproheptadine and naloxone prevented the effects of MZ-4-71 on passive avoidance learning, whereas haloperidol, phenoxybenzamine, propranolol and bicuculline did not change the effects of MZ-4-71. The results demonstrate that the muscarinic acetylcholine receptor, the 5-HT1/5-HT2 serotonergic receptor and opioid receptors are involved as mediators in the action of MZ-4-71 on the consolidation of passive avoidance learning.

Neurotransmitter-mediated action of an antagonist of growth hormone-releasing hormone on anxiolysis in mice

Antagonists of growth hormone-releasing hormone (GH-RH), such as MZ-4-71 suppress the secretion of GH. These findings suggest that GH-RH antagonists could be used for the therapy of disorders characterized by excessive GH secretion. It has been also demonstrated that MZ-4-71 displays antidepressant effects in a modified forced swimming test in mice, exerts anxiolytic effects in an elevated plus maze test, improves memory consolidation in passive avoidance learning, and corrects the impairment of memory consolidation caused by β-amyloid (25-35) in mice. However, little is known about the mechanisms of action of MZ-4-71 on brain functions. In the present work, the involvement of the adrenergic, serotonergic and GABA-ergic receptors in the anxiolytic action of MZ-4-71 was studied in an elevated plus maze. Mice were pretreated with a nonselective α-adrenergic receptor antagonist, phenoxybenzamine, an α1/α2β-adrenergic receptor antagonist, prazosin, an α2-adrenergic receptor antagonist, yohimbine, a mixed 5-HT1/5-HT2 serotonergic receptor antagonist, methysergide, a non-selective 5-HT2 serotonergic receptor antagonist, cyproheptadine, and a γ-aminobutyric acid subunit (GABA-A) receptor antagonist, bicuculline. Phenoxybenzamine, prazosin, yohimbine, methysergide, cyproheptadine and bicuculline prevented the effects of MZ-4-71 on the elevated plus maze revealing that the anxiolytic actions of MZ-4-71 in this test are mediated, at least in part, by the an interaction of the α1/α2-adrenergic, 5-HT1/5-HT2 serotonergic and GABA-A-ergic receptors.

Neurotransmission of the antidepressant-like effects of the growth hormone-releasing hormone antagonist MZ-4-71

MZ-4-71 is an antagonist of growth hormone-releasing hormone (GH-RH) which suppresses the secretion of GH-RH. It has been shown that MZ-4-71 has antidepressive-like effects in a modified forced swimming test (FST) in mice, exerts anxiolytic effects in an elevated plus maze test, improves memory consolidation in passive avoidance learning, and corrects the impairment of memory consolidation caused by β-amyloid 25-35 in mice. However, little is known about the mechanisms of action of MZ-4-71 on brain functions. The involvement of the adrenergic, serotonergic, cholinergic, dopaminergic or GABA-ergic receptors in the antidepressant-like action of MZ-4-71 (1.0 μg/2 μl, intracerebroventricular (i.c.v.)) was studied in a modified mouse forced swimming test (FST). Mice were pretreated with a non-selective α-adrenergic receptor antagonist, phenoxybenzamine, an α1/α2β-adrenergic receptor antagonist prazosin, an α2-adrenergic receptor antagonist, yohimbine, a β-adrenergic receptor antagonist, propranolol, a mixed 5-HT1/5-HT2 serotonergic receptor antagonist methysergide, a non-selective 5-HT2 serotonergic receptor antagonist, cyproheptadine, a non-selective muscarinic acetylcholine receptor antagonist, atropine, a D2, D3, D4 dopamine receptor antagonist, haloperidol or a γ-aminobutyric acid subunit A (GABA-A) receptor antagonist bicuculline. Phenoxybenzamine, prazosin, methysergide, cyproheptadine and atropine prevented the effects of MZ-4-71 on the immobility, the climbing and the swimming times. Yohimbine, propranolol, haloperidol and bicuculline did not change the effects of MZ-4-71. The results demonstrated that the antidepressant-like effects of MZ-4-71 in this modified mouse FST are mediated, at least in part, by the an interaction of the α1-adrenergic, 5-HT1/5-HT2 serotonergic, and muscarinic acetylcholine receptors.

Pleiotropic effects of growth hormone signaling in aging

Growth hormone (GH) affects somatic growth, sexual maturation, body composition and metabolism, as well as aging and longevity. Mice lacking GH or GH receptor outlive their normal siblings and exhibit symptoms of delayed aging associated with improved insulin signaling and increased stress resistance. Beneficial effects of eliminating the actions of GH are counterintuitive but conform to the concept of antagonistic pleiotropy. Evolutionary selection for traits promoting early-life fitness and reproductive success could account for post-reproductive deficits. Reciprocal relationships between GH signaling and longevity discovered in mutant mice apply also to normal mice, other mammalian species, and perhaps humans. This review summarizes the present understanding of the multifaceted relationship between somatotropic signaling and mammalian aging.

Molecular regulation of telomerase activity in aging

The process of aging is mitigated by the maintenance and repair of chromosome ends (telomeres), resulting in extended lifespan. This review examines the molecular mechanisms underlying the actions and regulation of the enzyme telomerase reverse transcriptase (TERT), which functions as the primary mechanism of telomere maintenance and regulates cellular life expectancy. Underpinning increased cell proliferation, telomerase is also a key factor in facilitating cancer cell immortalization. The review focuses on aspects of hormonal regulations of telomerase, and the intracellular pathways that converge to regulate telomerase activity with an emphasis on molecular interactions at protein and gene levels. In addition, the basic structure and function of two key telomerase enzyme components-the catalytic subunit TERT and the template RNA (TERC) are discussed briefly.

Growth hormone-releasing hormone: not only a neurohormone

Growth hormone-releasing hormone (GHRH) is mostly thought to act by stimulating the production and release of growth hormone from the pituitary. However, this neuropeptide emerges as a rather pleiotropic hormone in view of the identification of various extrapituitary sources for GHRH production, as well as the demonstration of a direct action of GHRH on several tissues other than the pituitary. Non-pituitary GHRH has a wide spectrum of activity, exemplified by its ability to modulate cell proliferation, especially in malignant tissues, to regulate differentiation of some cell types, and to promote healing of skin wounds. These findings extend the role of GHRH and its analogs beyond its accepted regulation of somatotropic activity and indicate new possibilities for therapeutic intervention.