Growth hormone and aging

Exercise training restores IGFIR survival signaling in d-galactose induced-aging rats to suppress cardiac apoptosis

Introduction

Insulin-like growth factor-I receptor (IGF1R) mediated survival signaling is a crucial mechanism for cellular endurance and a potential indicator of recuperation in deteriorating hearts.

Objective

This study evaluates the impact of long-term exercise training in enhancing cardiac survival mechanism in D-galactose-induced toxicity associated aging rats.

Methods

Forty-eight male SD-rats were segregated into 4 groups (n=9) and were named as control, exercise training groups, aging group and aging group with exercise training. Aging was induced by intraperitoneal (IP) D-galactose (150 mL/kg) injection for 8 weeks and for exercise training, the rats were left to swim in warm water for 60 min every day and 5 times/week. Western blotting of proteins from the left ventricles was performed to identify the modulations in the survival signaling. Tissue sections were analyzed to determine the extent of fibrosis and apoptosis.

Results

Western-blot analysis performed on the excised left ventricles (LV) showed that proteins of the cardiac survival pathway including IGF1R and Akt and the pro-survival Bcl-2 showed significant decrease in the aging group, whereas the levels were restored in the aging rats subjected to exercise training. In addition, aging groups showed increased interstitial space and collagen accumulation. Further, TUNEL assay showed higher number of apoptotic cells in the LV of aging group, which was correlated with increase in the proteins involved in FAS-FADD-dependent apoptosis. However, these aging associated effects were ameliorated upon exercise training in the D-galactose-induced aging rats that showed elevated IGF1R/Akt signaling.

Conclusion

The results suggest that IGFIR survival signaling cascadeis elevated in following long-term exercise training and thereby provide cardio-protective benefits in D-galactose induced aging rats.

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.

Influence of aging and growth hormone on different members of the NFkB family and IkB expression in the heart from a murine model of senescence-accelerated aging

Inflammation is related to several pathological processes. The aim of this study was to investigate the protein expression of the different subunits of the nuclear factor Kappa b (NFkBp65, p50, p105, p52, p100) and the protein expressions of IkB beta and alpha in the hearts from a murine model of accelerated aging (SAM model) by Western blot. In addition, the translocation of some isoforms of NFkB from cytosol to nuclei (NFkBp65, p50, p52) and ATP level content was studied. In addition we investigated the effect of the chronic administration of growth hormone (GH) on these age-related parameters. SAMP8 and SAMR1 mice of 2 and 10 months of age were used (n = 30). Animals were divided into five experimental groups: 2 old untreated (SAMP8/SAMR1), 2 young control (SAMP8/SAMR1) and one GH treated-old groups (SAMP8). Age-related changes were found in the studied parameters. We were able to see decreases of ATP level contents and the translocation of the nuclear factor kappa B p50, p52 and p65 from cytosol to nuclei in old SAMP8 mice together with a decrease of IKB proteins. However p100 and p105 did not show differences with aging. No significant changes were recorded in SAMR1 animals. GH treatment showed beneficial effects in old SAMP8 mice inducing an increase in ATP levels and inhibiting the translocation of some NFkB subunits such as p52. Our results supported the relation of NFkB activation with enhanced apoptosis and pro-inflammatory status in old SAMP8 mice and suggested a selective beneficial effect of the GH treatment, which was able to partially reduce the incidence of some deleterious changes in the heart of those mice.

Cortical ablation induces time-dependent changes in rat pituitary somatotrophs and upregulates growth hormone receptor expression in the injured cortex

The pituitary appears to be vulnerable to brain trauma, and its dysfunction is a common feature after traumatic brain injury. The role of pituitary growth hormone (GH) in brain repair after injury has been envisaged, but more studies must be performed to understand completely the importance of GH in these processes. Because some of the neuroprotective effects of GH are mediated directly through the GH receptor (GHR), we examined GHR expression in the rat cerebral cortex after sensorimotor cortex ablation. RT-PCR, immunohistochemistry, and double immunofluorescence had been performed to analyze the correlation between GHR expression in the injured cortex and activity of GH cells in the pituitary. Our results showed that the volume of GH-immunopositive cells was reduced at days 2 and 7 postsurgery (dps), and volume density of GH cells was significantly decreased at 14 dps, all compared with appropriate sham controls. At 30 dps all investigated parameters had returned to control level. In the injured cortex, GHR expression was transiently upregulated. Increased GHR immunoreactivity was observed in reactive astrocytes at 7 and particularly at 14 dps. In neuronal cells, an increase of GHR immunoreactivity was seen in neuronal cell bodies and well-defined primary dendrites at 14 and especially at 30 dps. The results presented here suggest that, during recovery from brain injury, changes in activity of pituitary GH cells result in upregulation of GHR that may have a role in neuronal arborization and glial proliferation in the injured cortex.

Growth hormone and cognitive function

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

Melatonin, and to a lesser extent growth hormone, restores colonic smooth muscle physiology in old rats

There is increasing evidence that aging is associated with oxidative damage, inflammation, and apoptosis in different cell types. However, there is limited information regarding aging mechanisms in colon smooth muscle. Old male Wistar rats (22 months) were treated for 10 wks with melatonin or growth hormone (GH). Animals were sacrificed at 24 months of age by decapitation. The colon was dissected and the smooth muscle homogenized. H(2)O(2) and malonyl dialdehyde (MDA) content and catalase and glutathione peroxidase (GPX) activities were determined using colorimetric kits. Expression of nuclear factor kappa B (NF-κB), cyclooxygenase 2 (COX-2), caspase-3, and caspase-9 were determined by Western blot. Aging of colon smooth muscle correlated with an increase in H(2)O(2) and MDA levels when compared with young animals in both proximal and distal segments; these changes were associated with a decrease in the catalase activity in the distal colon. Oxidative stress correlated with an increase in COX-2 and NF-κB expression, which were accompanied by an enhanced expression of the pro-apoptotic enzyme caspase-3 and its upstream enzyme, caspase-9. Melatonin treatment normalized the oxidative, inflammatory, and apoptotic patterns, whereas GH replacement, although effective in reducing oxidative stress in distal colon, did not reverse the age-related inflammation or apoptosis. These results suggest that melatonin should be the treatment of choice to most effectively recover physiological functions in aged colonic smooth muscle.

Effect of growth hormone and melatonin on the brain: from molecular mechanisms to structural changes

Aging of the brain causes important reductions in quality of life and has wide socio-economic consequences. An increase in oxidative stress, and the associated inflammation and apoptosis, could be responsible for the pathogenesis of aging associated brain lesions. Melatonin has neuroprotective effects, by limiting the negative effects of oxygen and nitrogen free radicals. Growth hormone (GH) might exert additional neuro-protective and or neurogenic effects on the brain. The molecular mechanisms of the protective effects of GH and melatonin on the aging brain have been investigated in young and old Wistar rats. A reduction in the total number of neurons in the hilus of the dentate gyrus was evident at 24 months of age and was associated with a significant increase in inflammation markers as well as in pro-apoptotic parameters, confirming the role of apoptosis in its reduction. Melatonin treatment was able to enhance neurogenesis in old rats without modification of the total number of neurons, whereas GH treatment increased the total number of neurons without enhancing neurogenesis. Both GH and melatonin were able to reduce inflammation and apoptosis in the hippocampus. In conclusion, neuroprotective effects demonstrated by GH and melatonin in the hippocampus were exerted by decreasing inflammation and apoptosis.

Cardiological aging in SAM model: effect of chronic treatment with growth hormone

The purpose of this study was to investigate the effect of aging on different parameters related to inflammation, oxidative stress and apoptosis in hearts from two types of male mice models: senescence-accelerated mice (SAM-P8) and senescence-accelerated-resistant (SAM-R1), and the influence of chronic administration of Growth Hormone (GH) on old SAM-P8 mice. Forty male mice were used. Animals were divided into five experimental groups: two 10 month old untreated groups (SAM-P8/SAM-R1), two 2 month old young groups (SAM-P8/SAM-R1) and one 10 month old group (SAM-P8) treated with GH for 30 days. The expression of tumor necrosis factor-alpha, interleukin 1, interleukin 10, heme oxygenases 1 and 2, endothelial and inducible nitric oxide synthases, NFkB, Bad, Bax and Bcl-2 were determined by real-time reverse transcription polymerase chain reaction (RT-PCR). Results were submitted to a two way ANOVA statistical evaluation using the Statgraphics program. Inflammation, as well as, oxidative stress and apoptosis markers were increased in the heart of old SAM-P8 males, as compared to young controls and this situation was not observed in the old SAM-R1 mice. Exogenous GH administration reverted the effect of aging in the described parameters of old SAM-P8 mice. Our results suggest that inflammation, apoptosis and oxidative stress could play an important role in the observed cardiovascular alterations related to aging of SAM-P8 mice and that GH may play a potential protective effect on the cardiovascular system of these animals.

Evaluation of neuroendocrine status in longevity

It is well known that physiological changes in the neuroendocrine system may be related to the process of aging. To assess neuroendocrine status in aging humans we studied a group of 155 women including 78 extremely old women (centenarians) aged 100-115 years, 21 early elderly women aged 64-67 years, 21 postmenopausal women aged 50-60 years and 35 younger women aged 20-50 years. Plasma NPY, leptin, glucose, insulin and lipid profiles were evaluated, and serum concentrations of pituitary, adrenal and thyroid hormones were measured. Our data revealed several differences in the neuroendocrine and metabolic status of centenarians, compared with other age groups, including the lowest serum concentrations of leptin, insulin and T3, and the highest values for prolactin. We failed to find any significant differences in TSH and cortisol levels. On the other hand, LH and FSH levels were comparable with those in the elderly and postmenopausal groups, but they were significantly higher than in younger subjects. GH concentrations in centenarians were lower than in younger women. NPY values were highest in the elderly group and lowest in young subjects. We conclude that the neuroendocrine status in centenarians is markedly different from that found in early elderly or young women.

Effect of exogenous administration of melatonin and growth hormone on pro-antioxidant functions of the liver in aging male rats

Aging is accompanied by changes in the morphology and physiology of organs and tissues, such as the liver. This process might be due to the accumulation of oxidative damage induced by reactive oxygen (ROS) and reactive nitrogen species (RNS). Hepatocytes are very rich in mitochondria and have a high respiratory rate, so they are exposed to large amounts of ROS and permanent oxidative stress. Twenty-four male Wistar rats of 22 months of age were divided into three groups. One group remained untreated and acted as the control group. The second was treated with growth hormone (GH) (2 mg/kg/d sc) and the third was submitted to treatment wit 1 mg/kg/d of melatonin in the drinking water. A group of 2-months-old male rats was used as young controls. After 10 wk of treatment the rats were killed by decapitation, and the liver was dissected and homogenized. Mitochondrial, cytosolic and microsomal fractions were obtained and cytochrome C, glutathione peroxidase, s-transferase and nitric oxide (NO) were measured. Aging induced a significant increase in mitochondrial nitric oxide. An increase in cytochrome C in the cytosolic fraction and a reduction in the mitochondrial fraction with age was also observed. Both GH and melatonin treatments significantly reduced the enhanced measures and increased the reduced values. A reduction in glutathione peroxidase and glutathione S-transferase was found in old control rats when compared with the group of young animals. Treatment for 2.5 months of old rats with GH and melatonin were able to increase the enzymes reaching values similar to those found in young animals. In conclusion, GH and melatonin treatment seems to have beneficial effects against age-induced damage in the liver.

A complex dietary supplement extends longevity of mice

Key factors implicated in aging include reactive oxygen species, inflammatory processes, insulin resistance, and mitochondrial dysfunction. All are exaggerated in transgenic growth hormone mice (TGM), which display a syndrome resembling accelerated aging. We formulated a complex dietary supplement containing 31 ingredients known to ameliorate all of the above features. We previously showed that this supplement completely abolished the severe age-related cognitive decline expressed by untreated TGM. Here we report that longevity of both TGM and normal mice is extended by this supplement. Treated TGM showed a 28% increase (p < .00008) in mean longevity. An 11% increase in mean longevity was also significant (p < .002093) for treated normal mice, compared to untreated normal mice. These data support the hypothesis that TGM are a model of accelerated aging, and demonstrate that complex dietary supplements may be effective in ameliorating aging or age-related pathologies where simpler formulations have generally failed.

High level of orexin A observed in the phenylketonuria mouse brain is due to the abnormal expression of prepro-orexin

Orexins/hypocretins are recently discovered neuropeptides, synthesized mainly in the lateral hypothalamus of the brain. Orexins regulate various functions including sleep and apetite. We recently reported increased amount of orexin A in the phenylketonuria (PKU) mouse brain. Whether this is caused by overexpression of the precursor for orexins, prepro-orexin was studied in the PKU mouse brain. Microarray expression analysis revealed overexpression of orexin gene in the brain of PKU mouse. Quantitative real-time RT-PCR showed increased level of prepro-orexin mRNA in the PKU mouse brain. In addition, expression of genes associated with cell signal and growth regulation was also affected in the PKU mouse brain, as observed by microarray analysis. These data suggest that up-regulation of orexin mRNA expression is the possible factor for inducing high orexin A in the brain of PKU mouse. The metabolic environment in the brain of PKU mouse affects normal expression of other genes possibly to result in pathophysiology seen in the PKU mouse, if documented also in patients with PKU.