Effects of human growth hormone in men over 60 years old

Growth Hormone Improves Ovarian Follicle Health in Premature Ovarian Failure Mice by Reducing Apoptosis : (GH Improves Ovarian Follicle Health in POF Mice by Reducing Apoptosis)

Premature ovarian failure (POF) is a perplexing condition in women characterized by cessation of oocyte production in the ovaries. Despite numerous proposed causes for the development of POF, the actual cause of the most POF cases remains unknown. Given that POF significantly affects fertility and is a devastating diagnosis for women, there is an urgent need for the development of new therapies aimed at reducing the long-term health consequences associated with POF. To explore the functions and potential mechanisms of growth hormone (GH) in ovarian development, follicle formation, and oocyte production, we created a mouse model of premature ovarian failure (POF) by administering cisplatin via intraperitoneal injection. Subsequently, we investigated the role of GH in attenuating the POF-induced effects. Our findings demonstrate that GH effectively improves the ovarian coefficient, promotes follicular development, and increases the quantity of oocytes. To explore the functions and potential mechanisms of growth hormone (GH) in ovarian development, follicle formation, and oocyte production, we created a mouse model of premature ovarian failure (POF) by administering cisplatin via intraperitoneal injection. Subsequently, we investigated the role of GH in attenuating the POF-induced effects. Our findings demonstrate that GH effectively improves the ovarian coefficient, promotes follicular development, and increases the quantity of oocytes.

Growth hormone and aging: a clinical review

Aging is a complex biological process characterized by functional decline, reduced quality of life, and increased vulnerability to diseases such as type 2 diabetes, cardiovascular conditions, neurodegeneration, and cancer. Advances in medical technology have introduced the concept of aging therapies, with growth hormone (GH) and its primary mediator, insulin-like growth factor 1 (IGF-1), receiving considerable attention for their potential to counteract age-related physiological and metabolic changes. GH plays a multifaceted role in the human body, primarily influencing body composition by increasing muscle mass, reducing fat tissue, promoting bone formation, and regulating the metabolism of proteins, lipids, and glucose. Additional effects have been noted on endothelial function, cognitive performance, and circadian rhythms. This review examines the molecular mechanisms of GH in aging, its potential as an anti-aging therapy, and findings from clinical trials involving these hormones for this purpose. It also addresses the associated adverse effects, limitations, and controversies. While some studies report significant benefits, these therapies' long-term safety and efficacy in promoting healthy aging remain uncertain, highlighting the need for further research.

Weight loss-independent changes in human growth hormone during water-only fasting: a secondary evaluation of a randomized controlled trial

Introduction

Water-only fasting for one day or more may provide health benefits independent of weight loss. Human growth hormone (HGH) may play a key role in multiple fasting-triggered mechanisms. Whether HGH changes during fasting are independent of weight loss and how basal HGH and HGH change relate to other fasting-induced changes are unknown.

Methods

Apparently healthy individuals (N=30) were randomized by Latin square to begin two days with either 24-hour water-only fasting or a control of 24-hour ad libitum eating. On day 2, subjects were crossed over to control (if day 1 was fasting) or fasting (if they ate on day 1). HGH, weight, and other parameters were measured at baseline and at the end of the first and second days.

Results

Baseline HGH had median 0.50 ng/mL for females (n=20) and 0.04 ng/mL for males (n=10), and correlated inversely with weight, glucose, insulin, and triglycerides and positively with changes in insulin and HOMA-IR. The 24-hour fasting-induced HGH change was uncorrelated with weight loss (r= 0.01, p=0.98), but correlated with changes in glucose, HGB, and IGF-1. The percent increase in HGH was greater (p<0.001) for lower (females ≤0.15 ng/mL, males ≤0.05 ng/mL) vs. higher baseline HGH (median: 1,225% vs. 50.3%, respectively). Subjects with lower baseline HGH had a trend to greater reduction of HOMA-IR (median: -6.15 vs. -1.35 for lower vs. higher HGH, respectively, p=0.08).

Conclusions

Fasting increased HGH and the HGH changes were independent of weight loss. Basal HGH and fasting-induced HGH changes correlated inversely with cardiometabolic risk factors.Clinical Trial Registration: clinicaltrials.gov, identifier NCT01059760.

Update on regulation of GHRH and its actions on GH secretion in health and disease

This review focuses on our current understanding of how growth hormone releasing hormone (GHRH): 1) stimulates GH release and synthesis from pituitary growth hormone (GH)-producing cells (somatotropes), 2) drives somatotrope proliferation, 3) is negatively regulated by somatostatin (SST), GH and IGF1, 4) is altered throughout lifespan and in response to metabolic challenges, and 5) analogues can be used clinically to treat conditions of GH excess or deficiency. Although a large body of early work provides an underpinning for our current understanding of GHRH, this review specifically highlights more recent work that was made possible by state-of-the-art analytical tools, receptor-specific agonists and antagonists, high-resolution in vivo and ex vivo imaging and the development of tissue (cell) -specific ablation mouse models, to paint a more detailed picture of the regulation and actions of GHRH.

Targeting Cell Senescence and Senolytics: Novel Interventions for Age-Related Endocrine Dysfunction

Multiple changes occur in hormonal regulation with aging and across various endocrine organs. These changes are associated with multiple age-related disorders and diseases. A better understanding of responsible underling biological mechanisms could help in the management of multiple endocrine disorders over and above hormone replacement therapy (HRT). Cellular senescence is involved in multiple biological aging processes and pathologies common in elderly individuals. Cellular senescence, which occurs in many older individuals but also across the lifespan in association with tissue damage, acute and chronic diseases, certain drugs, and genetic syndromes, may contribute to such endocrine disorders as osteoporosis, metabolic syndrome, and type 2 diabetes mellitus. Drugs that selectively induce senescent cell removal, "senolytics,", and drugs that attenuate the tissue-destructive secretory state of certain senescent cells, "senomorphics," appear to delay the onset of or alleviate multiple diseases, including but not limited to endocrine disorders such as diabetes, complications of obesity, age-related osteoporosis, and cancers as well as atherosclerosis, chronic kidney disease, neurodegenerative disorders, and many others. More than 30 clinical trials of senolytic and senomorphic agents have already been completed, are underway, or are planned for a variety of indications. Targeting senescent cells is a novel strategy that is distinct from conventional therapies such as HRT, and thus might address unmet medical needs and can potentially amplify effects of established endocrine drug regimens, perhaps allowing for dose decreases and reducing side effects.

Candidate molecular targets uncovered in mouse lifespan extension studies

INTRODUCTION

Multiple interventions have demonstrated an increase in mouse lifespan. However, non-standardized controls, sex or strain-specific factors, and insufficient focus on targets, hinder the translation of these findings into clinical applications.

AREAS COVERED

We examined the effects of genetic and drug-based interventions on mice from databases DrugAge, GenAge, the Mouse Phenome Database, and publications from PubMed that led to a lifespan extension of more than 10%, identifying specific molecular targets that were manipulated to achieve the maximum lifespan in mice. Subsequently, we characterized 10 molecular targets influenced by these interventions, with particular attention given to clinical trials and potential indications for each.

EXPERT OPINION

To increase the translational potential of mice life-extension studies to clinical research several factors are crucial: standardization of mice lifespan research approaches, the development of clear criteria for control and experimental groups, the establishment of criteria for potential geroprotectors, and focusing on targets and their clinical application. Pinpointing the targets affected by geroprotectors helps in understanding species-specific differences and identifying potential side effects, ensuring the safety and effectiveness of clinical trials. Additionally, target review facilitates the optimization of treatment protocols and the evaluation of the clinical feasibility of translating research findings into practical therapies for humans.

The Potential of Exercise on Lifestyle and Skin Function: Narrative Review

BACKGROUND

The skin is an important organ of the human body and has moisturizing and barrier functions. Factors such as sunlight and lifestyle significantly affect these skin functions, with sunlight being extremely damaging. The effects of lifestyle habits such as smoking, diet, and sleep have been studied extensively. It has been found that smoking increases the risk of wrinkles, while excessive fat and sugar intake leads to skin aging. Lack of sleep and stress are also dangerous for the skin's barrier function. In recent years, the impact of exercise habits on skin function has been a focus of study. Regular exercise is associated with increased blood flow to the skin, elevated skin temperature, and improved skin moisture. Furthermore, it has been shown to improve skin structure and rejuvenate its appearance, possibly through promoting mitochondrial biosynthesis and affecting hormone secretion. Further research is needed to understand the effects of different amounts and content of exercise on the skin.

OBJECTIVE

This study aims to briefly summarize the relationship between lifestyle and skin function and the mechanisms that have been elucidated so far and introduce the expected effects of exercise on skin function.

METHODS

We conducted a review of the literature using PubMed and Google Scholar repositories for relevant literature published between 2000 and 2022 with the following keywords: exercise, skin, and life habits.

RESULTS

Exercise augments the total spectrum power density of cutaneous blood perfusion by a factor of approximately 8, and vasodilation demonstrates an enhancement of approximately 1.5-fold. Regular exercise can also mitigate age-related skin changes by promoting mitochondrial biosynthesis. However, not all exercise impacts are positive; for instance, swimming in chlorinated pools may harm the skin barrier function. Hence, the exercise environment should be considered for its potential effects on the skin.

CONCLUSIONS

This review demonstrates that exercise can potentially enhance skin function retention.

[Growth hormone - 30 years of clinical practice: past, present, future]

The recombinant technologies era, which began in the second half of the XX century, made it possible to produce recombinant growth hormone (rGH) necessary for the treatment of stunting of various genesis. The time of practically unlimited possibilities of rGH production has come, which served as a stimulus for studying the efficacy and safety of rGH application, searching for optimal ways of its use and dosing regimes. Many years of experience in the use of somatropin in clinical practice allowed us to obtain data on its effectiveness primarily in somatotropic insufficiency in children, to study its effect on the functional state of various organs and systems, and to expand the indications for the use of RGR.

Antiaging Strategies and Remedies: A Landscape of Research Progress and Promise

Aging is typified by a gradual loss of physiological fitness and accumulation of cellular damage, leading to deteriorated functions and enhanced vulnerability to diseases. Antiaging research has a long history throughout civilization, with many efforts put forth to understand and prevent the effects of aging. Multiple strategies aiming to promote healthy aging and extend the lifespan have been developed including lifestyle adjustments, medical treatments, and social programs. A multitude of antiaging medicines and remedies have also been explored. Here, we use data from the CAS Content Collection to analyze the publication landscape of recent research related to antiaging strategies and treatments. We review the recent advances and delineate trends in research headway of antiaging knowledge and practice across time, geography, and development pipelines. We further assess the state-of-the-art antiaging approaches and explore their correlations with age-related diseases. The landscape of antiaging drugs has been outlined and explored. Well-recognized and novel, currently evaluated antiaging agents have also been summarized. Finally, we review clinical applications of antiaging products with their development pipelines. The objective of this review is to summarize current knowledge on preventive strategies and treatment remedies in the field of aging, to outline challenges and evaluate growth opportunities, in order to further efforts to solve the problems that remain.

Growth Hormone, Atherosclerosis and Peripheral Arterial Disease: Exploring the Spectrum from Acromegaly to Growth Hormone Deficiency

Growth hormone (GH) and insulin-like growth factor 1 (IGF-1) are increasingly recognised for their role in cardiovascular (CV) physiology. The GH-IGF-1 axis plays an essential role in the development of the CV system as well as in the complex molecular network that regulates cardiac and endothelial structure and function. A considerable correlation between GH levels and CV mortality exists even among individuals in the general population without a notable deviation in the GHIGF- 1 axis functioning. In addition, over the last decades, evidence has demonstrated that pathologic conditions involving the GH-IGF-1 axis, as seen in GH excess to GH deficiency, are associated with an increased risk for CV morbidity and mortality. A significant part of that risk can be attributed to several accompanying comorbidities. In both conditions, disease control is associated with a consistent improvement of CV risk factors, reduction of CV mortality, and achievement of standardised mortality ratio similar to that of the general population. Data on the prevalence of peripheral arterial disease in patients with acromegaly or growth hormone deficiency and the effects of GH and IGF-1 levels on the disease progression is limited. In this review, we will consider the pivotal role of the GH-IGF-1 axis on CV system function, as well as the far-reaching consequences that arise when disorders within this axis occur, particularly in relation to the atherosclerosis process.

Current and investigational medications for the treatment of sarcopenia

Sarcopenia, defined as the loss of muscle mass and function, is a widely prevalent and severe condition in older adults. Since 2016, it is recognized as a disease. Strength exercise training and nutritional support are the frontline treatment of sarcopenia, with no drug currently approved for this indication. However, new therapeutic options are emerging. In this review, we evidenced that only very few trials have focused on sarcopenia/sarcopenic patients. Most drug trials were performed in different clinical older populations (e.g., men with hypogonadism, post-menopausal women at risk for osteoporosis), and their efficacy were tested separately on the components of sarcopenia (muscle mass, muscle strength and physical performances). Results from trials testing the effects of Testosterone, Selective Androgen Receptor Modulators (SARMs), Estrogen, Dehydroepiandrosterone (DHEA), Insulin-like Growth Factor-1 (IGF-1), Growth Hormone (GH), GH Secretagogue (GHS), drug targeting Myostatin and Activin receptor pathway, Vitamin D, Angiotensin Converting Enzyme inhibitors (ACEi) and Angiotensin Receptor Blockers (ARBs), or β-blockers, were compiled. Although some drugs have been effective in improving muscle mass and/or strength, this was not translated into clinically relevant improvements on physical performance. Finally, some promising molecules investigated in on-going clinical trials and in pre-clinical phase were summarized, including apelin and irisin.

A Critical Analysis of the FDA's Omics-Driven Pharmacodynamic Biomarkers to Establish Biosimilarity

Demonstrating biosimilarity entails comprehensive analytical assessment, clinical pharmacology profiling, and efficacy testing in patients for at least one medical indication, as required by the U.S. Biologics Price Competition and Innovation Act (BPCIA). The efficacy testing can be waived if the drug has known pharmacodynamic (PD) markers, leaving most therapeutic proteins out of this concession. To overcome this, the FDA suggests that biosimilar developers discover PD biomarkers using omics technologies such as proteomics, glycomics, transcriptomics, genomics, epigenomics, and metabolomics. This approach is redundant since the mode-action-action biomarkers of approved therapeutic proteins are already available, as compiled in this paper for the first time. Other potential biomarkers are receptor binding and pharmacokinetic profiling, which can be made more relevant to ensure biosimilarity without requiring biosimilar developers to conduct extensive research, for which they are rarely qualified.

Growth hormone proteoformics atlas created to promote predictive, preventive, and personalized approach in overall management of pituitary neuroendocrine tumors

Human growth hormone (GH) is the indispensable hormone for the maintenance of normal physiological functions of the human body, including the growth, development, metabolism, and even immunoregulation. The GH is synthesized, secreted, and stored by somatotroph cells in adenohypophysis. Abnormal GH is associated with various GH-related diseases, such as acromegaly, dwarfism, diabetes, and cancer. Currently, some studies found there are dozens or even hundreds of GH proteoforms in tissue and serum as well as a series of GH-binding protein (GHBP) proteoforms and GH receptor (GHR) proteoforms were also identified. The structure-function relationship of protein hormone proteoforms is significantly important to reveal their overall physiological and pathophysiological mechanisms. We propose the use of proteoformics to study the relationship between every GH proteoform and different physiological/pathophysiological states to clarify the pathogenic mechanism of GH-related disease such as pituitary neuroendocrine tumor and conduct precise molecular classification to promote predictive preventive personalized medicine (PPPM / 3P medicine). This article reviews GH proteoformics in GH-related disease such as pituitary neuroendocrine tumor, which has the potential role to provide novel insight into pathogenic mechanism, discover novel therapeutic targets, identify effective GH proteoform biomarker for patient stratification, predictive diagnosis, and prognostic assessment, improve therapy method, and further accelerate the development of 3P medicine.

Augmentation of Growth Hormone by Chewing in Females

Sarcopenia is an age-related condition characterized by progressive loss of muscle mass and strength. Age-related decline in the secretion of growth hormone (GH), a condition called somatopause, is thought to play a role in sarcopenia. As pharmacological GH has adverse effects, we attempted to increase physiological GH. While the relationship between chewing and ghrelin levels has been studied, there are no reports on the relationship between chewing and GH. The aim of this study was to clarify the effects of chewing on the muscle anabolic hormones serum GH and plasma ghrelin. Thirteen healthy adults ingested a chewy nutrition bar containing 5.56 g of protein, 12.71 g of carbohydrate, and 0.09 g of fat on two different days, chewing before swallowing in one trial and swallowing without chewing in the other. Blood samples were taken before and after ingestion (0, 15, 30, and 60 min); GH, acylated ghrelin, glucose, insulin, amino acids, and lactate were measured. Two-way repeated ANOVA revealed a significant difference in the GH concentrations between the "Chew trial" and "Swallow trial" in females (p = 0.0054). However, post-hoc analyses found no statistically significant difference at each time point. The area under the curve of the percentage increase in GH was significantly increased in the "Chew trial" compared with the "Swallow trial" in females (12,203 ± 15,402% min vs. 3735 ± 988% min, p = 0.0488). Chewing had no effect on glucose, insulin, amino acids, or lactate concentrations. Thus, we found that chewing a protein supplement rather than swallowing it without chewing elevates the blood GH concentration. These results serve as a rationale for larger research and longitudinal studies to confirm the impacts of chewing on GH secretion.

Aging under endocrine hormone regulation

Aging is a biological process in which the environment interacts with the body to cause a progressive decline in effective physiological function. Aging in the human body can lead to a dysfunction of the vital organ systems, resulting in the onset of age-related diseases, such as neurodegenerative and cardiovascular diseases, which can seriously affect an individual's quality of life. The endocrine system acts on specific targets through hormones and related major functional factors in its pathways, which play biological roles in coordinating cellular interactions, metabolism, growth, and aging. Aging is the result of a combination of many pathological, physiological, and psychological processes, among which the endocrine system can achieve a bidirectional effect on the aging process by regulating the hormone levels in the body. In this paper, we explored the mechanisms of growth hormone, thyroid hormone, and estrogen in the aging process to provide a reference for the exploration of endocrine mechanisms related to aging.

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.

Oral Supplementation and Systemic Drugs for Skin Aging: A Narrative Review

Skin aging is influenced by intrinsic and extrinsic factors and involves multiple pathogenic mechanisms. The most widely used treatments are topical products and minimally invasive procedures. Evidence on the benefits of systemic therapy is limited for several reasons: Reliance on mostly small and predominantly female samples, short study durations, methodologic heterogeneity, and a lack of consensus on which outcome measures are clinically relevant. Furthermore, systemic drugs and oral supplements are not without adverse effects. Oral hydrolyzed collagen and oral hyaluronic acid are well tolerated, and numerous clinical trials show they can mitigate some signs of skin aging. Low-dose oral isotretinoin is another option, but it has a higher risk of adverse effects. Evidence is lacking on the effects of the many dietary supplements on offer, such as vitamins, flavonoids, plant extracts, and trace elements. The future of skin aging management would appear to lie in the use of senolytic and senomorphic agents targeting senescent cells in the skin.

[Translated article] Oral Supplementation and Systemic Drugs for Skin Aging: A Narrative Review

Skin aging is influenced by intrinsic and extrinsic factors and involves multiple pathogenic mechanisms. The most widely used treatments are topical products and minimally invasive procedures. Evidence on the benefits of systemic therapy is limited for several reasons: reliance on mostly small and predominantly female samples, short study durations, methodologic heterogeneity, and a lack of consensus on which outcome measures are clinically relevant. Furthermore, systemic drugs and oral supplements are not without adverse effects. Oral hydrolyzed collagen and oral hyaluronic acid are well tolerated, and numerous clinical trials show they can mitigate some signs of skin aging. Low-dose oral isotretinoin is another option, but it has a higher risk of adverse effects. Evidence is lacking on the effects of the many dietary supplements on offer, such as vitamins, flavonoids, plant extracts, and trace elements. The future of skin aging management would appear to lie in the use of senolytic and senomorphic agents targeting senescent cells in the skin.

Growth Hormone Response to L-Arginine Alone and Combined with Different Doses of Growth Hormone-Releasing Hormone: A Systematic Review and Meta-Analysis

Background

Arginine (ARG) can modulate growth hormone (GH) release by suppressing its endogenous inhibitory regulator, somatostatin. ARG also induces the release of the GH-releasing hormone (GHRH). This study aims to review the effects of L-arginine supplementation alone and combined with GHRH in different doses on GH secretion.

Methods

In this systematic review and meta-analysis, an electronic literature search was conducted on Medline database (PubMed), Scopus, and Web of Science databases. All eligible studies were randomized clinical trials that reported the effects of ARG supplementation alone or with GHRH on GH levels. Mean difference (MD) and 95% confidence intervals (CI) were computed as the effect size.

Results

Meta-analyses showed significant effects of ARG alone on GH release (MD = 10.07, 95% CI: 7.87, 12.28). Moreover, the response of GH was greater with ARG in combination with GHRH (MD = 24.96, 95% CI: 17.51, 32.42). There was no significant difference between the patients and healthy individuals and between oral and injection use of ARG. The systematic review revealed the important role of ARG in combination with other amino acids on GH secretion in patients with GH deficiency.

Conclusion

This study revealed that in GH-deficient individuals, high doses of ARG supplementation in combination with GHRH and/or other amino acids might have potential therapeutic effects on increasing GH concentrations. These findings propose that ARG supplementation can be considered as a potential stimulator in management of GH deficiency.

Effects of GH on the Aging Process in Several Organs: Mechanisms of Action

In order to investigate the possible beneficial effects of GH administration on the aging process, 24-month-old rats of both sexes and 10-month-old SAMP8 mice were used. Male rats showed increased fat content and decreased lean body mass together with enhanced vasoconstriction and reduced vasodilation of their aortic rings compared to young adult animals. Chronic GH treatment for 10 weeks increased lean body mass and reduced fat weight together with inducing an enhancement of the vasodilatory response by increasing eNOS and a reduction of the constrictory responses. Old SAMP8 male mice also showed insulin resistance together with a decrease in insulin production by the endocrine pancreas and a reduced expression of differentiation parameters. GH treatment decreased plasma levels and increased pancreatic production of insulin and restored differentiation parameters in these animals. Ovariectomy plus low calcium diet in rabbits induced osteoporosis Titanium implants inserted into these rabbit tibiae showed after one month lesser bone to implant (BIC) surface and bone mineral density (BMD). Local application of GH in the surgical opening was able to increase BIC in the osteoporotic group. The hippocampus of old rats showed a reduction in the number of neurons and also in neurogenesis compared to young ones, together with an increase of caspases and a reduction of Bcl-2. GH treatment was able to enhance significantly only the total number of neurons. In conclusion, GH treatment was able to show beneficial effects in old animals on all the different organs and metabolic functions studied.

Progerin modulates the IGF-1R/Akt signaling involved in aging

Progerin, a product of LMNA mutation, leads to multiple nuclear abnormalities in patients with Hutchinson-Gilford progeria syndrome (HGPS), a devastating premature aging disorder. Progerin also accumulates during physiological aging. Here, we demonstrate that impaired insulin-like growth factor 1 receptor (IGF-1R)/Akt signaling pathway results in severe growth retardation and premature aging in Zmpste24^-/- mice, a mouse model of progeria. Mechanistically, progerin mislocalizes outside of the nucleus, interacts with the IGF-1R, and down-regulates its expression, leading to inhibited mitochondrial respiration, retarded cell growth, and accelerated cellular senescence. Pharmacological treatment with the PTEN (phosphatase and tensin homolog deleted on chromosome 10) inhibitor bpV (HOpic) increases Akt activity and improves multiple abnormalities in Zmpste24-deficient mice. These findings provide previously unidentified insights into the role of progerin in regulating the IGF-1R/Akt signaling in HGPS and might be useful for treating LMNA-associated progeroid disorders.

Advances in Our Understanding of the Mechanism of Action of Drugs (including Traditional Chinese Medicines) for the Intervention and Treatment of Osteoporosis

Osteoporosis (OP) is known as a silent disease in which the loss of bone mass and bone density does not cause obvious symptoms, resulting in insufficient treatment and preventive measures. The losses of bone mass and bone density become more severe over time and an only small percentage of patients are diagnosed when OP-related fractures occur. The high disability and mortality rates of OP-related fractures cause great psychological and physical damage and impose a heavy economic burden on individuals and society. Therefore, early intervention and treatment must be emphasized to achieve the overall goal of reducing the fracture risk. Anti-OP drugs are currently divided into three classes: antiresorptive agents, anabolic agents, and drugs with other mechanisms. In this review, research progress related to common anti-OP drugs in these three classes as well as targeted therapies is summarized to help researchers and clinicians understand their mechanisms of action and to promote pharmacological research and novel drug development.

Nutrient-Response Pathways in Healthspan and Lifespan Regulation

Cellular, small invertebrate and vertebrate models are a driving force in biogerontology studies. Using various models, such as yeasts, appropriate tissue culture cells, Drosophila, the nematode Caenorhabditis elegans and the mouse, has tremendously increased our knowledge around the relationship between diet, nutrient-response signaling pathways and lifespan regulation. In recent years, combinatorial drug treatments combined with mutagenesis, high-throughput screens, as well as multi-omics approaches, have provided unprecedented insights in cellular metabolism, development, differentiation, and aging. Scientists are, therefore, moving towards characterizing the fine architecture and cross-talks of growth and stress pathways towards identifying possible interventions that could lead to healthy aging and the amelioration of age-related diseases in humans. In this short review, we briefly examine recently uncovered knowledge around nutrient-response pathways, such as the Insulin Growth Factor (IGF) and the mechanistic Target of Rapamycin signaling pathways, as well as specific GWAS and some EWAS studies on lifespan and age-related disease that have enhanced our current understanding within the aging and biogerontology fields. We discuss what is learned from the rich and diverse generated data, as well as challenges and next frontiers in these scientific disciplines.

Protocols aiming to increase muscle mass in persons with motor complete spinal cord injury: a systematic review

PURPOSE

The purpose of this review was to compare all intervention modalities aimed at increasing skeletal muscle mass (SMM) in the paralysed limbs of persons with chronic (>1-year post-injury), motor complete spinal cord injury (SCI).

MATERIALS AND METHODS

A systematic review of EMBASE, MEDLINE, Scopus, and SPORTDiscus databases was conducted from inception until December 2021. Published intervention studies aimed to increase SMM (measured by magnetic resonance imaging, computed tomography, ultrasound, muscle biopsy, or lean soft tissue mass by dual X-ray absorptiometry) in the paralysed limbs of adults (>18 years) with SCI were included.

RESULTS

Fifty articles were included that, overall, demonstrated a high risk of bias. Studies were categorised into six groups: neuromuscular electrical stimulation (NMES) with and without external resistance, functional electrical stimulation cycling, walking- and standing-based interventions, pharmacological treatments, and studies that compared or combined intervention modalities. Resistance training (RT) using NMES on the quadriceps produced the largest and most consistent increases in SMM of all intervention modalities.

CONCLUSIONS

Current evidence suggests that clinical practise aiming to increase SMM in the paralysed limbs of persons with motor complete SCI should perform NMES-RT. However, more high-quality randomised control trials are needed to determine how training variables, such as exercise volume and intensity, can be optimised for increasing SMM. Implications for rehabilitationPersons with spinal cord injury (SCI) experience severe reductions in skeletal muscle mass (SMM) post-injury, which may exacerbate their risk of obesity and metabolic disease.Out of all exercise and non-exercise-based interventions, this systematic review shows that neuromuscular electrical stimulation-based resistance training demonstrates the most robust and consistent evidence for increasing skeletal muscle mass in the paralysed limbs of adults with motor complete spinal cord injury.The findings from this review can be used to inform evidence-based practise for exercise practitioners, as well as direct future research focused on increasing muscle mass in this population.

Sex Hormones, Growth Hormone, and the Cornea

The growth and maintenance of nearly every tissue in the body is influenced by systemic hormones during embryonic development through puberty and into adulthood. Of the ~130 different hormones expressed in the human body, steroid hormones and peptide hormones are highly abundant in circulation and are known to regulate anabolic processes and wound healing in a tissue-dependent manner. Of interest, differential levels of sex hormones have been associated with ocular pathologies, including dry eye disease and keratoconus. In this review, we discuss key studies that have revealed a role for androgens and estrogens in the cornea with focus on ocular surface homeostasis, wound healing, and stromal thickness. We also review studies of human growth hormone and insulin growth factor-1 in influencing ocular growth and epithelial regeneration. While it is unclear if endogenous hormones contribute to differential corneal wound healing in common animal models, the abundance of evidence suggests that systemic hormone levels, as a function of age, should be considered as an experimental variable in studies of corneal health and disease.

Growth hormone/IGF-I-dependent signaling restores decreased expression of the myokine SPARC in aged skeletal muscle

Skeletal muscle exerts many beneficial effects on the human body including the contraction-dependent secretion of peptides termed myokines. We have recently connected the myokine secreted protein acidic and rich in cysteine (SPARC) to the formation of intramuscular adipose tissue (IMAT) in skeletal muscle from aged mice and humans. Here, we searched for inducers of SPARC in order to uncover novel treatment approaches for IMAT. Endurance exercise in mice as well as forskolin treatment in vitro only modestly activated SPARC levels. However, through pharmacological treatments in vitro, we identified IGF-I as a potent inducer of SPARC expression in muscle cells, likely through a direct activation of its promoter via phosphatidylinositol 4,5-bisphospate 3-kinase (PI3K)-dependent signaling. We employed two different mouse models of growth hormone (GH)/IGF-I deficiency to solidify our understanding of the relationship between IGF-I and SPARC in vivo. GH administration robustly increased intramuscular SPARC levels (3.5-fold) in GH releasing hormone receptor-deficient mice and restored low intramuscular SPARC expression in skeletal muscle from aged mice. Intramuscular glycerol injections induced higher levels of adipocyte markers (adiponectin, perilipin) in aged compared to young mice, which was not prevented by GH treatment. Our study provides a roadmap for the study of myokine regulation during aging and demonstrates that the GH/IGF-I axis is critical for SPARC expression in skeletal muscle. Although GH treatment did not prevent IMAT formation in the glycerol model, targeting SPARC by exercise or by activation of IGF-I signaling might offer a novel therapeutic strategy against IMAT formation during aging. KEY MESSAGES : IGF-I regulates the myokine SPARC in muscle cells directly at the promoter level. GH/IGF-I is able to restore the decreased SPARC levels in aged skeletal muscle. The glycerol model induces higher adipocyte markers in aged compared to young muscle. GH treatment does not prevent IMAT formation in the glycerol model.

Growth Hormone and the Human Hair Follicle

Ever since the discoveries that human hair follicles (HFs) display the functional peripheral equivalent of the hypothalamic-pituitary-adrenal axis, exhibit elements of the hypothalamic-pituitary-thyroid axis, and even generate melatonin and prolactin, human hair research has proven to be a treasure chest for the exploration of neurohormone functions. However, growth hormone (GH), one of the dominant neurohormones of human neuroendocrine physiology, remains to be fully explored in this context. This is interesting since it has long been appreciated clinically that excessive GH serum levels induce distinct human skin pathology. Acromegaly, or GH excess, is associated with hypertrichosis, excessive androgen-independent growth of body hair, and hirsutism in females, while dysfunctional GH receptor-mediated signaling (Laron syndrome) is associated with alopecia and prominent HF defects. The outer root sheath keratinocytes have recently been shown to express functional GH receptors. Furthermore, and contrary to its name, recombinant human GH is known to inhibit female human scalp HFs’ growth ex vivo, likely via stimulating the expression of the catagen-inducing growth factor, TGF-β2. These limited available data encourage one to systematically explore the largely uncharted role of GH in human HF biology to uncover nonclassical functions of this core neurohormone in human skin physiology.

Induction of somatopause in adult mice compromises bone morphology and exacerbates bone loss during aging

Somatopause refers to the gradual declines in growth hormone (GH) and insulin‐like growth factor‐1 throughout aging. To define how induced somatopause affects skeletal integrity, we used an inducible GH receptor knockout (iGHRKO) mouse model. Somatopause, induced globally at 6 months of age, resulted in significantly more slender bones in both male and female iGHRKO mice. In males, induced somatopause was associated with progressive expansion of the marrow cavity leading to significant thinning of the cortices, which compromised bone strength. We report progressive declines in osteocyte lacunar number, and increases in lacunar volume, in iGHRKO males, and reductions in lacunar number accompanied by ~20% loss of overall canalicular connectivity in iGHRKO females by 30 months of age. Induced somatopause did not affect mineral/matrix ratio assessed by Raman microspectroscopy. We found significant increases in bone marrow adiposity and high levels of sclerostin, a negative regulator of bone formation in iGHRKO mice. Surprisingly, however, despite compromised bone morphology, osteocyte senescence was reduced in the iGHRKO mice. In this study, we avoided the confounded effects of constitutive deficiency in the GH/IGF‐1 axis on the skeleton during growth, and specifically dissected its effects on the aging skeleton. We show here, for the first time, that induced somatopause compromises bone morphology and the bone marrow environment.

Rodent diet aids and the fallacy of caloric restriction

Understanding the molecular mechanisms of normal aging is a prerequisite to significantly improving human health span. Caloric restriction (CR) can delay aging and has served as a yardstick to evaluate interventions extending life span. However, mice given unlimited access to food suffer severe obesity. Health gains from CR depend on control mice being sufficiently overweight and less obese mouse strains benefit far less from CR. Pharmacologic interventions that increase life span, including resveratrol, rapamycin, nicotinamide mononucleotide and metformin, also reduce body weight. In primates, CR does not delay aging unless the control group is eating enough to suffer from obesity-related disease. Human survival is optimal at a body mass index achievable without CR, and the above interventions are merely diet aids that shouldn't slow aging in healthy weight individuals. CR in humans of optimal weight can safely be declared useless, since there is overwhelming evidence that hunger, underweight and starvation reduce fitness, survival, and quality of life. Against an obese control, CR does, however, truly delay aging through a mechanism laid out in the following tumor suppression theory of aging.

GHRH expression plasmid improves osteoporosis and skin damage in aged mice

The hormone secretion of GHRH-GH-IGF-1 axis in animals was decreased as aging. These hormones play an important role in maintaining bone mass and bone structure, and also affect the normal structure and function of the skin. We used plasmid-based technology to deliver growth hormone releasing hormone (GHRH) to elderly mice. In the current study, 80 and 120 μg/kg pVAX-GHRH plasmid expression plasmid were injected into old mice, the serum GHRH and insulin-like growth factor-1(IGF-1) content were increased within three weeks (P < 0.05). In the groups of 80 and 120 μg/kg plasmid, the content of procollagen type I N-terminal pro-peptide (PINP) in the serum was increased(P < 0.05), and the content of C-terminal telopeptides of type I collagen (CTX-1) in the serum was reduced significantly (P < 0.05). Furthermore, the expression of osteoprotegerin (OPG) and osteocalcin (OCN) in the femur also was increased(P < 0.05). The bone mineral density(BMD)、trabecular bone volume (BV/TV) and trabecular number(Tb.N) of mouse femur were increased significantly (P < 0.05) and trabecular separation(Tb.Sp) was decreased(P < 0.05). There were more trabecular bones in the bone marrow cavity and the trabecular bones are thicker in the groups of 80 and 120 μg/kg plasmid relative to control. The superoxide dismutase (SOD) content in the skin was increased(P < 0.05), and the malondialdehyde (MDA) content was reduced significantly (P < 0.05). Meanwhile, the skin moisture content also increased significantly(P < 0.05). Moreover, the expression of matrix metalloproteinase 3(MMP3) and matrix metalloproteinase 9(MMP9) was decreased in the skin(P < 0.05). The thickness of the dermis and epidermis of the skin had increased significantly(P < 0.05). Skin structure is more dense and complete in the two groups. These results indicate that 80 and 120 μg/kg plasmid-mediated GHRH supplementation can improve osteoporosis and skin aging in aged mice.

Vascular Aging in Rodent Models: Contrasting Mechanisms Driving the Female and Male Vascular Senescence

Increasing scientific interest has been directed to sex as a biological and decisive factor on several diseases. Several different mechanisms orchestrate vascular function, as well as vascular dysfunction in cardiovascular and metabolic diseases in males and females. Certain vascular sex differences are present throughout life, while others are more evident before the menopause, suggesting two important and correlated drivers: genetic and hormonal factors. With the increasing life expectancy and aging population, studies on aging-related diseases and aging-related physiological changes have steeply grown and, with them, the use of aging animal models. Mouse and rat models of aging, the most studied laboratory animals in aging research, exhibit sex differences in many systems and physiological functions, as well as sex differences in the aging process and aging-associated cardiovascular changes. In the present review, we introduce the most common aging and senescence-accelerated animal models and emphasize that sex is a biological variable that should be considered in aging studies. Sex differences in the cardiovascular system, with a focus on sex differences in aging-associated vascular alterations (endothelial dysfunction, remodeling and oxidative and inflammatory processes) in these animal models are reviewed and discussed.

The prevalence of inorganic mercury in human cells increases during aging but decreases in the very old

Successful aging is likely to involve both genetic and environmental factors, but environmental toxicants that accelerate aging are not known. Human exposure to mercury is common, and mercury has genotoxic, autoimmune, and free radical effects which could contribute to age-related disorders. The presence of inorganic mercury was therefore assessed in the organs of 170 people aged 1-104 years to determine the prevalence of mercury in human tissues at different ages. Mercury was found commonly in cells of the brain, kidney, thyroid, anterior pituitary, adrenal medulla and pancreas. The prevalence of mercury in these organs increased during aging but decreased in people aged over 80 years. People with mercury in one organ usually also had mercury in several others. In conclusion, the prevalence of inorganic mercury in human organs increases with age. The relative lack of tissue mercury in the very old could account for the flattened mortality rate and reduced incidence of cancer in this advanced age group. Since mercury may accelerate aging, efforts to reduce atmospheric mercury pollution could improve the chances of future successful aging.

How to Overcome Anabolic Resistance in Dialysis-Treated Patients?

A current hypothesis is that dialysis-treated patients are "anabolic resistant" i. e., their muscle protein synthesis (MPS) response to anabolic stimuli is blunted, an effect which leads to muscle wasting and poor physical performance in aging and in several chronic diseases. The importance of maintaining muscle mass and MPS is often neglected in dialysis-treated patients; better than to describe mechanisms leading to energy-protein wasting, the aim of this narrative review is to suggest possible strategies to overcome anabolic resistance in this patient's category. Food intake, in particular dietary protein, and physical activity, are the two major anabolic stimuli. Unfortunately, dialysis patients are often aged and have a sedentary behavior, all conditions which per se may induce a state of "anabolic resistance." In addition, patients on dialysis are exposed to amino acid or protein deprivation during the dialysis sessions. Unfortunately, the optimal amount and formula of protein/amino acid composition in supplements to maximixe MPS is still unknown in dialysis patients. In young healthy subjects, 20 g whey protein maximally stimulate MPS. However, recent observations suggest that dialysis patients need greater amounts of proteins than healthy subjects to maximally stimulate MPS. Since unneccesary amounts of amino acids could stimulate ureagenesis, toxins and acid production, it is urgent to obtain information on the optimal dose of proteins or amino acids/ketoacids to maximize MPS in this patients' population. In the meantime, the issue of maintaining muscle mass and function in dialysis-treated CKD patients needs not to be overlooked by the kidney community.

Sexual dimorphic impact of adult-onset somatopause on life span and age-induced osteoarthritis

Osteoarthritis (OA), the most prevalent joint disease, is a major cause of disability worldwide. Growth hormone (GH) has been suggested to play significant roles in maintaining articular chondrocyte function and ultimately articular cartilage (AC) homeostasis. In humans, the age-associated decline in GH levels was hypothesized to play a role in the etiology of OA. We studied the impact of adult-onset isolated GH deficiency (AOiGHD) on the life span and skeletal integrity including the AC, in 23- to 30-month-old male and female mice on C57/BL6 genetic background. Reductions in GH during adulthood were associated with extended life span and reductions in body temperature in female mice only. However, end-of-life pathology revealed high levels of lymphomas in both sexes, independent of GH status. Skeletal characterization revealed increases in OA severity in AOiGHD mice, evidenced by AC degradation in both femur and tibia, and significantly increased osteophyte formation in AOiGHD females. AOiGHD males showed significant increases in the thickness of the synovial lining cell layer that was associated with increased markers of inflammation (IL-6, iNOS). Furthermore, male AOiGHD showed significant increases in matrix metalloproteinase-13 (MMP-13), p16, and β-galactosidase immunoreactivity in the AC as compared to controls, indicating increased cell senescence. In conclusion, while the life span of AOiGHD females increased, their health span was compromised by high-grade lymphomas and the development of severe OA. In contrast, AOiGHD males, which did not show extended life span, showed an overall low grade of lymphomas but exhibited significantly decreased health span, evidenced by increased OA severity.

Improvement of cardiac and systemic function in old mice by agonist of growth hormone-releasing hormone

Age-related diseases such as cardiovascular diseases portend disability, increase health expenditures, and cause late-life mortality. Synthetic agonists of growth hormone-releasing hormone (GHRH) exhibit several favorable effects on heart function and remodeling. Here we assessed whether GHRH agonist MR409 can modulate heart function and systemic parameters in old mice. Starting at the age of 15 months, mice were injected subcutaneously with MR409 (10 µg/day, n = 8) or vehicle (n = 7) daily for 6 months. Mice treated with MR409 showed improvements in exercise activity, cardiac function, survival rate, immune function, and hair growth in comparison with the controls. More stem cell colonies were grown out of the bone marrow recovered from the MR409-treated mice. Mitochondrial functions of cardiomyocytes (CMs) from the MR409-treated mice were also significantly improved with more mitochondrial fusion. Fewer β-gal positive cells were observed in endothelial cells after 10 passages with MR409. In Doxorubicin-treated H9C2 cardiomyocytes, cell senescence marker p21 and reactive oxygen species were significantly reduced after cultured with MR409. MR409 also improved cellular ATP production and oxygen consumption rate in Doxorubicin-treated H9C2 cells. Mitochondrial protein OPA1 long isoform was significantly increased after treatment with MR409. The effects of MR409 were mediated by GHRH receptor and protein kinase A (PKA). In short, GHRH agonist MR409 reversed the aging-associated changes with respect of heart function, mobility, hair growth, cellular energy production, and senescence biomarkers. The improvement of heart function may be related to a better mitochondrial functions through GHRH receptor/cAMP/PKA/OPA1 signaling pathway and relieved cardiac inflammation.

Growth Hormone As Antiaging Factor in Old Bones

Aging induces changes in bone. Growth hormone (GH) is reduced by aging, and age-related changes observed in old bones might be due to a decrease in the GH/insulin-like growth factor-I (IGF-I) axis. GH administration on aged individuals is controversial. This study aimed to assess the effect of systemic GH treatment on bone properties, bone metabolism, and bone mineral density (BMD) in long bone of old rats. Aged Wistar rats were treated with GH at a dose of 2 mg/kg/day during 10 weeks. Plasma osteocalcin, IGF-I, and carboxy-terminal telopeptide of type I collagen levels were measured. Cross-sectional bone areas and BMD were measured by morphometric and densitometric analysis, respectively. Femora were analyzed by three point-bending testing. t-Test was used for statistical evaluation. p < 0.05 was considered to be significant. Significantly enhanced bone area, at the expense of the cortical area, was found in treated rats. The densitometric analysis showed 11% higher BMD in the experimental group. Significantly higher bone flexural modulus, stiffness, and ultimate load were observed in the treated rats. Plasma osteocalcin and IGF-I levels were significantly increased in the treated group, while the resorption marker concentration remained unchanged. Within the limitations of this experimental study, systemic GH administration has shown to enhance biomechanical properties, BMD, cortical mass, and plasma IGF-I and osteocalcin in old treated rats, compared to the control group; consequently, GH could be considered as an alternative therapy against age-related changes in the bone.

Clinical and biological impact of the exposome on the skin

The skin exposome is defined as the totality of environmental exposures over the life course that can induce or modify various skin conditions. Here, we review the impact on the skin of solar exposure, air pollution, hormones, nutrition and psychological factors. Photoageing, photocarcinogenesis and pigmentary changes are well-established consequences of chronic exposure of the skin to solar radiation. Exposure to traffic-related air pollution contributes to skin ageing. Particulate matter and nitrogen dioxide cause skin pigmentation/lentigines, while ozone causes wrinkles and has an impact on atopic eczema. Human skin is a major target of hormones, and they exhibit a wide range of biological activities on the skin. Hormones decline with advancing age influencing skin ageing. Nutrition has an impact on numerous biochemical processes, including oxidation, inflammation and glycation, which may result in clinical effects, including modification of the course of skin ageing and photoageing. Stress and lack of sleep are known to contribute to a pro-inflammatory state, which, in turn, affects the integrity of extracellular matrix proteins, in particular collagen. Hormone dysregulation, malnutrition and stress may contribute to inflammatory skin disorders, such as atopic dermatitis, psoriasis, acne and rosacea.

Management of skin thinning and aging: review of therapies for neocollagenesis; hormones and energy devices

BACKGROUND

Hormone replacement therapy and various devices exist to treat signs of aging, such as skin thinning, yet there are no reviews summarizing or evaluating their role in neocollagenesis and the associated increase in skin thickness.

OBJECTIVE

To review the literature regarding stimulation and generation of new collagen in the dermis in two parts. Part 2 reviews oral and topical hormone replacement therapy as well as energy-based devices.

METHODS

The PubMed database was searched for related literature. Studies involving the use of hormone supplements and energy devices with a resultant change in collagen production or skin thickness were obtained and reviewed for evidence.

RESULTS

Hormones, including estrogen, testosterone, and dehydroepiandrosterone, and human growth hormone have been reported with substantiating evidence for neocollagenesis and dermal thickening. Energy devices, including radiofrequency, ultrasound, and laser therapy, have also been reported to stimulate neocollagenesis.

LIMITATIONS

The results presented in certain literature are not based on randomized controlled trials.

CONCLUSION

Hormone deficient individuals can regain skin thickness with hormone replacement therapy. Dermal heating can provide a substantial amount of neocollagenesis; however, laser technology, specifically CO₂ , appears to be the most effective at increasing skin collagen and tightening.

Increased longevity due to sexual activity in mole-rats is associated with transcriptional changes in the HPA stress axis

Sexual activity and/or reproduction are associated with a doubling of life expectancy in the long-lived rodent genus Fukomys. To investigate the molecular mechanisms underlying this phenomenon, we analyzed 636 RNA-seq samples across 15 tissues. This analysis suggests that changes in the regulation of the hypothalamic–pituitary–adrenal stress axis play a key role regarding the extended life expectancy of reproductive vs. non-reproductive mole-rats. This is substantiated by a corpus of independent evidence. In accordance with previous studies, the up-regulation of the proteasome and so-called ‘anti-aging molecules’, for example, dehydroepiandrosterone, is linked with enhanced lifespan. On the other hand, several of our results are not consistent with knowledge about aging of short-lived model organisms. For example, we found the up-regulation of the insulin-like growth factor 1/growth hormone axis and several other anabolic processes to be compatible with a considerable lifespan prolongation. These contradictions question the extent to which findings from short-lived species can be transferred to longer-lived ones.

Growth Hormone and Aging: New Findings

Complex relationships between growth hormone (GH) signaling and mammalian aging continue to attract attention of many investigators. Recent results include evidence that the impact of GH on genome maintenance (DNA damage and repair) is drastically different in normal as compared to cancer cells, consistent with GH promoting aging and cancer progression. Impact of GH on DNA methylation was studied as a possible mechanism linking actions of GH during early life to the trajectory of aging. Animals with reduced or enhanced GH signaling and novel animals with adipocyte-specific deletion of GH receptors were used to elucidate the effects of GH on white and brown adipose tissue, including the impact of this hormone on lipolysis, fibrosis, and thermogenesis. Effects of GH on adipose tissue related to lipid and energy metabolism emerge as mechanistic links between GH, healthspan, and lifespan. Treatment of healthy men with a combination of GH, dehydroepiandrosterone, and metformin was reported to restore thymus function and reduce epigenetic age. Studies of human subjects with deficiency of GH or GH receptors and studies of mice with the same endocrine syndromes identified several phenotypic changes related (positively or negatively) to the previously reported predisposition to healthy aging. Results of these and other recent studies advance present understanding of the mechanisms by which GH influences aging and longevity and of the trade-offs involved.

Growth hormone and aging

Growth hormone (GH) actions impact growth, metabolism, and body composition and have been associated with aging and longevity. Lack of GH results in slower growth, delayed maturation, and reduced body size and can lead to delayed aging, increased healthspan, and a remarkable extension of longevity. Adult body size, which is a GH-dependent trait, has a negative association with longevity in several mammalian species. Mechanistic links between GH and aging include evolutionarily conserved insulin/insulin-like growth factors and mechanistic target of rapamycin signaling pathways in accordance with long-suspected trade-offs between anabolic/growth processes and longevity. Height and the rate and regulation of GH secretion have been related to human aging, but longevity is not extended in humans with syndromes of GH deficiency or resistance. However, the risk of age-related chronic disease is reduced in individuals affected by these syndromes and various indices of increased healthspan have been reported.

Hormonal and Metabolic Changes of Aging and the Influence of Lifestyle Modifications

Increased life expectancy combined with the aging baby boomer generation has resulted in an unprecedented global expansion of the elderly population. The growing population of older adults and increased rate of age-related chronic illness has caused a substantial socioeconomic burden. The gradual and progressive age-related decline in hormone production and action has a detrimental impact on human health by increasing risk for chronic disease and reducing life span. This article reviews the age-related decline in hormone production, as well as age-related biochemical and body composition changes that reduce the bioavailability and actions of some hormones. The impact of hormonal changes on various chronic conditions including frailty, diabetes, cardiovascular disease, and dementia are also discussed. Hormone replacement therapy has been attempted in many clinical trials to reverse and/or prevent the hormonal decline in aging to combat the progression of age-related diseases. Unfortunately, hormone replacement therapy is not a panacea, as it often results in various adverse events that outweigh its potential health benefits. Therefore, except in some specific individual cases, hormone replacement is not recommended. Rather, positive lifestyle modifications such as regular aerobic and resistance exercise programs and/or healthy calorically restricted diet can favorably affect endocrine and metabolic functions and act as countermeasures to various age-related diseases. We provide a critical review of the available data and offer recommendations that hopefully will form the groundwork for physicians/scientists to develop and optimize new endocrine-targeted therapies and lifestyle modifications that can better address age-related decline in heath.

Sirtuins and the prevention of immunosenescence

Aging of hematopoietic stem cells (HSCs) has been largely described as one underlying cause of senescence of the immune-hematopoietic system (immunosenescence). A set of well-defined hallmarks characterizes aged HSCs contributing to unbalanced hematopoiesis and aging-associated functional alterations of both branches of the immune system. In this chapter, the contribution of sirtuins, a family of conserved NAD⁺ dependent deacetylases with key roles in metabolism, genome integrity, aging and lifespan, to immunosenescence, will be addressed. In particular, the role of SIRT6 will be deeply analyzed highlighting a multifaceted part of this deacetylase in HSCs aging as well as in the immunosenescence of dendritic cells (DCs). These and other emerging data are currently paving the way for future design and development of rejuvenation means aiming at rescuing age-related changes in immune function in the elderly and combating age-associated hematopoietic diseases.

Is Adipose Tissue the Fountain of Youth? The Impact of Adipose Stem Cell Aging on Metabolic Homeostasis, Longevity, and Cell-Based Therapies

Aging is driven by four interlinked processes: (1) low-grade sterile inflammation; (2) macromolecular and organelle dysfunction, including DNA damage, telomere erosion, and mitochondrial dysfunction; (3) stem cell dysfunction; and (4) an accumulation of senescent cells in tissues. Adipose tissue is not immune to the effects of time, and all four of these processes contribute to a decline of adipose tissue function with advanced age. This decline is associated with an increase in metabolic disorders. Conversely, optimally functioning adipose tissue generates signals that promote longevity. As tissue-resident progenitor cells that actively participate in adipose tissue homeostasis and dysregulation, adipose stem cells (ASCs) have emerged as a key feature in the relationship between age and adipose tissue function. This review will give a mechanistic overview of the myriad ways in which age affects ASC function and, conversely, how ASC function contribute to healthspan and lifespan. A central mediator in this relationship is the degree of resilience of ASCs to maintain stemness into advanced age and the consequent preservation of adipose tissue function, in particular subcutaneous fat. The last sections of this review will discuss therapeutic options that target senescent ASCs to extend healthspan and lifespan, as well as ASC-based therapies that can be used to treat age-related pathologies, and collectively, these therapeutic applications may transform the way we age.

The endocrinology of sarcopenia and frailty

Sarcopenia describes low muscle mass and strength associated with ageing, whilst reduced physical performance indicates the severity of the condition. It can happen independently of other medical conditions and can be a key feature of the frailty phenotype. Frailty is a syndrome of increased vulnerability to incomplete resolution of homeostasis, following a stressor event. Researchers have described the implications of hypothalamic pituitary dysregulation in the pathogenesis of both entities. This review summarizes the recent evidence in this area as well as other endocrine factors such as insulin resistance and vitamin D status and outlines current research priorities. We conducted searches to PubMed and Embase databases for articles, reviews and studies reporting new data on the interaction between hormones of the endocrine system and frailty and/ or sarcopenia in the last 5 years. Interventional studies, cohort studies, case-control studies and animal studies were included. Clinical trials register was also searched to identify ongoing relevant studies. Studies have given us insights into the complex relationships between factors such as anabolic hormones, glucocorticoids and vitamin D on muscle strength and performance and their involvement in ageing phenotypes. However, robust randomized controlled trials are needed to consolidate existing evidence in humans and inform clinical practice. Current evidence supports hormone replacement in patients with confirmed deficiencies, to optimize health and prevent complications. Hormone replacement has limited use for age-related conditions. Current interest is focused on muscle/bone/fat interactions and health outcomes in "sarcopenic obesity." A life-course approach to improving 'health-span' is advocated. Lifestyle factors such as nutrition and physical activity have important interactions with body composition, physical function and metabolic outcomes. Large-scale clinical trials will determine the efficacy and long-term safety of hormone supplementation in the management of sarcopenia and frailty.