The effects of growth hormone and sex steroid on lean body mass, fat mass, muscle strength, cardiovascular endurance and adverse events in healthy elderly women and men

In the land of not-unhappiness: On the state-of-the-art of targeting aging and age-related diseases by biomedical research

The concept of the Land of Not-Unhappiness refers to the potential achievement of eliminating the pathologies of the aging process. To inform of how close we are to settling in the land, we summarize and review the achievements of research on anti-aging interventions over the last hundred years with a specific focus on strategies that slow down metabolism, compensate for aging-related losses, and target a broad range of age-related diseases. We critically evaluate the existing interventions labeled as "anti-aging," such as calorie restriction, exercise, stem cell administration, and senolytics, to provide a down-to-earth evaluation of their current applicability in counteracting aging. Throughout the text, we have maintained a light tone to make it accessible to non-experts in biogerontology, and provide a broad overview for those considering conducting studies, research, or seeking to understand the scientific basis of anti-aging medicine.

High Cardiorespiratory Fitness Protects against Molecular Impairments of Metabolism, Heart, and Brain with Higher Efficacy in Obesity-Induced Premature Aging

BACKGRUOUND

High cardiorespiratory fitness (CRF) protects against age-related diseases. However, the mechanisms mediating the protective effect of high intrinsic CRF against metabolic, cardiac, and brain impairments in non-obese versus obese conditions remain incompletely understood. We aimed to identify the mechanisms through which high intrinsic CRF protects against metabolic, cardiac, and brain impairments in non-obese versus obese untrained rats.

METHODS

Seven-week-old male Wistar rats were divided into two groups (n=8 per group) to receive either a normal diet or a highfat diet (HFD). At weeks 12 and 28, CRF, carbohydrate and fatty acid oxidation, cardiac function, and metabolic parameters were evaluated. At week 28, behavior tests were performed. At the end of week 28, rats were euthanized to collect heart and brain samples for molecular studies.

RESULTS

The obese rats exhibited higher values for aging-related parameters than the non-obese rats, indicating that they experienced obesity-induced premature aging. High baseline CRF levels were positively correlated with several favorable metabolic, cardiac, and brain parameters at follow-up. Specifically, the protective effects of high CRF against metabolic, cardiac, and brain impairments were mediated by the modulation of body weight and composition, the lipid profile, substrate oxidation, mitochondrial function, insulin signaling, autophagy, apoptosis, inflammation, oxidative stress, cardiac function, neurogenesis, blood-brain barrier, synaptic function, accumulation of Alzheimer's disease-related proteins, and cognition. Interestingly, this effect was more obvious in HFD-fed rats.

CONCLUSION

The protective effect of high CRF is mediated by the modulation of several mechanisms. These effects exhibit greater efficacy under conditions of obesity-induced premature aging.

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.

Alterations in Body Uneasiness, Eating Attitudes, and Psychopathology Before and After Cross-Sex Hormonal Treatment in Patients with Female-to-Male Gender Dysphoria

Body dissatisfaction plays an important role in the development of psychiatric problems such as eating disorders as well as gender dysphoria (GD). Cross-sex hormonal treatment (CHT) alleviates the dissatisfaction by making various changes in the body. We examined the alteration of body uneasiness, eating attitudes and behaviors, and psychological symptoms longitudinally in Turkish participants with female-to-male gender dysphoria (FtM GD) after CHT. Thirty-seven participants with FtM GD and 40 female controls were asked to complete the Body Uneasiness Test to explore different areas of body-related psychopathology, the Eating Attitudes Test to assess eating disturbances, and the Symptom Checklist-90 Revised to measure psychological state, both before CHT and after 6 months of CHT administration. The baseline mean body weight, BMI scores, body uneasiness scores, and general psychopathological symptoms of participants with FtM GD were significantly higher than female controls, whereas baseline eating attitudes and behaviors were not significantly different. Over time, FtM GD participants' mean body weight and BMI scores increased, body uneasiness and general psychopathological symptoms decreased, and eating attitudes and behaviors had not changed at 24th weeks following CHT administration compared to baseline. CHT may have a positive impact on body uneasiness and general psychopathological symptoms in participants with FtM GD. However, CHT does not have an impact on eating attitudes and behaviors.

The relationship between serum IGF-1, handgrip strength, physical performance and falls in elderly men and women

OBJECTIVE

Human aging is accompanied by a decrease in growth hormone secretion and serum insulin-like growth factor (IGF)-1 levels. Also, loss of muscle mass and strength and impairment of physical performance, ending in a state of frailty, are seen in elderly. We aimed to investigate whether handgrip strength, physical performance and recurrent falls are related to serum IGF-1 levels in community-dwelling elderly.

DESIGN

Observational cohort study (cross-sectional and prospective).

METHODS

We studied the association between IGF-1 and handgrip strength, physical performance and falls in participants of the Longitudinal Aging Study Amsterdam. A total of 1292 participants were included (633 men, 659 women). Serum IGF-1 levels were divided into quartiles (IGF-1-Q1 to IGF-1-Q4). Data on falls were collected prospectively for a period of 3 years. All analyses were stratified for age and physical activity and adjusted for relevant confounders.

RESULTS

Men with a low physical activity score in IGF-1-Q1 and IGF-1-Q2 of the younger age group had a lower handgrip strength compared to IGF-1-Q4. In younger more active males in IGF-1-Q2 physical performance was worse. Recurrent fallers were less prevalent in older, low active males with low IGF-1 levels. In females, recurrent fallers were more prevalent in older, more active females in IGF-1-Q2. IGF-1 quartile may predict changes in handgrip strength and physical performance in men and women.

CONCLUSIONS

Our results indicate that lower IGF-1 levels are associated with lower handgrip strength and worse physical performance, but less recurrent fallers especially in men. Associations were often more robust in IGF-1-Q2. Future studies on this topic are desirable.

Diet and body fat in adolescence and early adulthood: a systematic review of longitudinal studies

Adipose tissue is a vital component of the human body, but in excess, it represents a risk to health. According to the World Health Organization, one of the main factors determining excessive body adiposity is the dietary habit. This systematic review investigated longitudinal studies that assessed the association between diet and body fat in adolescents and young adults. Twenty-one relevant papers published between 2001 and 2015 were selected. The most used method for estimating body fat was the body mass index (15 studies). Diet was most commonly assessed by estimating the consumption of food groups (cereals, milk and dairy products) and specific foods (sugar-sweetened beverages, soft drinks, fast foods, milk, etc.). Ten studies found a direct association between diet and quantity of body fat. During adolescence, adhering to a dietary pattern characterized by high consumption of energy-dense food, fast foods, sugar-sweetened beverages and soft drinks, as well as low fiber intake, appears to contribute to an increase in body fat in early adulthood. The findings of the present study suggest that the frequent consumption of unhealthy foods and food groups (higher energy density and lower nutrient content) in adolescence is associated with higher quantity of body fat in early adulthood.

Effects of dietary soy protein on skeletal muscle volume and strength in humans with various physical activities

BACKGROUND

In recent years, the number of bedridden people is rapidly increasing due to aging or lack of exercise in Japan. This problem is becoming more serious, since there is no countermeasure against it. In the present study, we designed to investigate whether dietary proteins, especially soy, had beneficial effects on skeletal muscle in 59 volunteers with various physical activities.

METHODS

We subjected 59 volunteers with various physical activities to meal intervention examination. Persons with low and high physical activities were divided into two dietary groups, the casein diet group and the soy diet group. They ate daily meals supplemented with 7.8 g of powdered casein or soy protein isolate every day for 30 days. Bedridden patients in hospitals were further divided into three dietary groups: the no supplementation diet group, the casein diet group and the soy diet group. They were also subjected to a blood test, a urinalysis, magnetic resonance imaging analysis and muscle strength test of the knee before and after the meal intervention study.

RESULTS

Thirty-day soy protein supplementation significantly increased skeletal muscle volume in participants with low physical activity, compared with 30-day casein protein supplementation. Both casein and soy protein supplementation increased the volume of quadriceps femoris muscle in bedridden patients. Consistently, soy protein significantly increased their extension power of the knee, compared with casein protein. Although casein protein increased skeletal muscle volume more than soy protein in bedridden patients, their muscle strength changes by soy protein supplementation were bigger than those by casein protein supplementation.

CONCLUSIONS

The supplementation of soy protein would be one of the effective foods which prevent the skeletal muscle atrophy caused by immobilization or unloading.

Testosterone deficiency increases hospital readmission and mortality rates in male patients with heart failure

Background

Testosterone deficiency in patients with heart failure (HF) is associated with decreased exercise capacity and mortality; however, its impact on hospital readmission rate is uncertain. Furthermore, the relationship between testosterone deficiency and sympathetic activation is unknown.

Objective

We investigated the role of testosterone level on hospital readmission and mortality rates as well as sympathetic nerve activity in patients with HF.

Methods

Total testosterone (TT) and free testosterone (FT) were measured in 110 hospitalized male patients with a left ventricular ejection fraction < 45% and New York Heart Association classification IV. The patients were placed into low testosterone (LT; n = 66) and normal testosterone (NT; n = 44) groups. Hypogonadism was defined as TT < 300 ng/dL and FT < 131 pmol/L. Muscle sympathetic nerve activity (MSNA) was recorded by microneurography in a subpopulation of 27 patients.

Results

Length of hospital stay was longer in the LT group compared to in the NT group (37 ± 4 vs. 25 ± 4 days; p = 0.008). Similarly, the cumulative hazard of readmission within 1 year was greater in the LT group compared to in the NT group (44% vs. 22%, p = 0.001). In the single-predictor analysis, TT (hazard ratio [HR], 2.77; 95% confidence interval [CI], 1.58–4.85; p = 0.02) predicted hospital readmission within 90 days. In addition, TT (HR, 4.65; 95% CI, 2.67–8.10; p = 0.009) and readmission within 90 days (HR, 3.27; 95% CI, 1.23–8.69; p = 0.02) predicted increased mortality. Neurohumoral activation, as estimated by MSNA, was significantly higher in the LT group compared to in the NT group (65 ± 3 vs. 51 ± 4 bursts/100 heart beats; p < 0.001).

Conclusion

These results support the concept that LT is an independent risk factor for hospital readmission within 90 days and increased mortality in patients with HF. Furthermore, increased MSNA was observed in patients with LT.

Soy Glycinin Contains a Functional Inhibitory Sequence against Muscle-Atrophy-Associated Ubiquitin Ligase Cbl-b

Background. Unloading stress induces skeletal muscle atrophy. We have reported that Cbl-b ubiquitin ligase is a master regulator of unloading-associated muscle atrophy. The present study was designed to elucidate whether dietary soy glycinin protein prevents denervation-mediated muscle atrophy, based on the presence of inhibitory peptides against Cbl-b ubiquitin ligase in soy glycinin protein. Methods. Mice were fed either 20% casein diet, 20% soy protein isolate diet, 10% glycinin diet containing 10% casein, or 20% glycinin diet. One week later, the right sciatic nerve was cut. The wet weight, cross sectional area (CSA), IGF-1 signaling, and atrogene expression in hindlimb muscles were examined at 1, 3, 3.5, or 4 days after denervation. Results. 20% soy glycinin diet significantly prevented denervation-induced decreases in muscle wet weight and myofiber CSA. Furthermore, dietary soy protein inhibited denervation-induced ubiquitination and degradation of IRS-1 in tibialis anterior muscle. Dietary soy glycinin partially suppressed the denervation-mediated expression of atrogenes, such as MAFbx/atrogin-1 and MuRF-1, through the protection of IGF-1 signaling estimated by phosphorylation of Akt-1. Conclusions. Soy glycinin contains a functional inhibitory sequence against muscle-atrophy-associated ubiquitin ligase Cbl-b. Dietary soy glycinin protein significantly prevented muscle atrophy after denervation in mice.

Effects of Growth Hormone Administration on Muscle Strength in Men over 50 Years Old

Growth hormone (GH) use has been speculated to improve physical capacity in subjects without GH deficiency (GHD) through stimulation of collagen synthesis in the tendon and skeletal muscle, which leads to better exercise training and increased muscle strength. In this context, the use of GH in healthy elderly should be an option for increasing muscle strength. Our aim was to evaluate the effect of GH therapy on muscle strength in healthy men over 50 years old. Fourteen healthy men aged 50-70 years were evaluated at baseline for body composition and muscle strength (evaluated by leg press and bench press exercises, which focus primarily on quadriceps-lower body part and pectoralis major-upper body part-muscles, resp.). Subjects were randomised into 2 groups: GH therapy (7 subjects) and placebo (7 subjects) and reevaluated after 6 months of therapy. Thirteen subjects completed the study (6 subjects in the placebo group and 7 subjects in the GH group). Subjects of both groups were not different at baseline. After 6 months of therapy, muscle strength in the bench press responsive muscles did not increase in both groups and showed a statistically significant increase in the leg press responsive muscles in the GH group. Our study demonstrated an increase in muscle strength in the lower body part after GH therapy in healthy men. This finding must be considered and tested in frail older populations, whose physical incapacity is primarily caused by proximal muscle weakness. The trial was registered with NCT01853566.

The role of androgens and estrogens on healthy aging and longevity

Aging is associated with a loss of sex hormone in both men (andropause) and women (menopause). In men, reductions in testosterone can trigger declines in muscle mass, bone mass, and in physical function. In women, the impact of the loss of sex hormones, such as estradiol, on bone is well elucidated, but evidence is limited on whether the loss of estradiol negatively affects muscle mass and physical function. However, deficiencies in multiple anabolic hormones have been shown to predict health status and longevity in older persons. Thus, consideration should be given as to whether targeted hormone replacement therapies may prove effective at treating clinical conditions, such as age-related sarcopenia, cancer cachexia, and/or acute or chronic illnesses. If initiated carefully in the appropriate clinical population, hormone replacement therapies in men and women may prevent and reverse muscle and bone loss and functional declines and perhaps promote healthy aging and longevity.

Late-onset hypogonadism

Late-onset hypogonadism is a clinical and biological syndrome associated with advancing age and characterized by typical symptoms and a deficiency in serum testosterone levels. It is a common condition but often underdiagnosed and undertreated. The main symptoms of hypogonadism are reduced libido/erectile dysfunction, reduced muscle mass and strength, increased adiposity, osteoporosis/low bone mass, depressed mood, and fatigue. Testosterone replacement therapy is only warranted in the presence of both clinical symptoms suggesting hormone deficiency and decreased hormone levels. It improves libido and sexual function, bone density, muscle mass, body composition, mood, erythropoiesis, cognition, quality of life, and cardiovascular disease.

Acute gonadotroph and somatotroph hormonal suppression after traumatic brain injury

Hormonal dysfunction is a known consequence of moderate and severe traumatic brain injury (TBI). In this study we determined the incidence, time course, and clinical correlates of acute post-TBI gonadotroph and somatotroph dysfunction. Patients had daily measurement of serum luteinizing hormone (LH), follicle-stimulating hormone (FSH), testosterone, estradiol, growth hormone, and insulin-like growth factor-1 (IGF-1) for up to 10 days post-injury. Values below the fifth percentile of a healthy cohort were considered abnormal, as were non-measurable growth hormone (GH) values. Outcome measures were frequency and time course of hormonal suppression, injury characteristics, and Glasgow Outcome Scale (GOS) score. The cohort consisted of 101 patients (82% males; mean age 35 years; Glasgow Coma Scale [GCS] score <or=8 in 87%). In men, 100% had at least one low testosterone value, and 93% of all values were low; in premenopausal women, 43% had at least one low estradiol value, and 39% of all values were low. Non-measurable GH levels occurred in 38% of patients, while low IGF-1 levels were observed in 77% of patients, but tended to normalize within 10 days. Multivariate analysis revealed associations of younger age with low FSH and low IGF-1, acute anemia with low IGF-1, and older age and higher body mass index (BMI) with low GH. Hormonal suppression was not predictive of GOS score. These results indicate that within 10 days of complicated mild, moderate, and severe TBI, testosterone suppression occurs in all men and estrogen suppression occurs in over 40% of women. Transient somatotroph suppression occurs in over 75% of patients. Although this acute neuroendocrine dysfunction may not be TBI-specific, low gonadal steroids, IGF-1, and GH may be important given their putative neuroprotective functions.

Late-life onset hypogonadism: a review

Increased longevity and population aging will increase the number of men with late-onset hypogonadism, a common condition that is often under diagnosed and under treated. The indication of testosterone replacement therapy (TRT) treatment requires the presence of low testosterone level and symptoms and signs of hypogonadism. Although there is a lack of large-scale, long-term studies assessing the benefits and risks of TRT in men with hypogonadism, reports indicate that TRT may produce a wide range of benefits that include improvement in libido and sexual function, bone density, muscle mass, body composition, mood, erythropoiesis, cognition, quality of life, and cardiovascular disease. Perhaps the most controversial area is the issue of risk, especially the possible stimulation of prostate cancer by testosterone, even though there is no evidence to support this risk. Other possible risks include worsening symptoms of benign prostatic hypertrophy, liver toxicity, hyperviscosity, erythrocytosis, worsening untreated sleep apnea, or severe heart failure. Despite this controversy, testosterone supplementation in the United States has increased substantially in the past several years. The physician should discuss with the patient the potential benefits and risks of TRT. This review discusses the benefits and risks of TRT.

The influence of estrogen on skeletal muscle: sex matters

As women enter menopause, the concentration of estrogen and other female hormones declines. This hormonal decrease has been associated with a number of negative outcomes, including a greater incidence of injury as well as a delay in recovery from these injuries. Over the past two decades, our understanding of the protective effects of estrogen against various types of injury and disease states has grown immensely. In skeletal muscle, studies with animals have demonstrated that sex and estrogen may potentially influence muscle contractile properties and attenuate indices of post-exercise muscle damage, including the release of creatine kinase into the bloodstream and activity of the intramuscular lysosomal acid hydrolase, beta-glucuronidase. Furthermore, numerous studies have revealed an estrogen-mediated attenuation of infiltration of inflammatory cells such as neutrophils and macrophages into the skeletal muscles of rats following exercise or injury. Estrogen has also been shown to play a significant role in stimulating muscle repair and regenerative processes, including the activation and proliferation of satellite cells. Although the mechanisms by which estrogen exerts its influence upon indices of skeletal muscle damage, inflammation and repair have not been fully elucidated, it is thought that estrogen may potentially exert its protective effects by: (i) acting as an antioxidant, thus limiting oxidative damage; (ii) acting as a membrane stabilizer by intercalating within membrane phospholipids; and (iii) binding to estrogen receptors, thus governing the regulation of a number of downstream genes and molecular targets. In contrast to animal studies, studies with humans have not as clearly delineated an effect of estrogen on muscle contractile function or on indices of post-exercise muscle damage and inflammation. These inconsistencies have been attributed to a number of factors, including age and fitness level of subjects, the type and intensity of exercise protocols, and a focus on sex differences that typically involve factors and hormones in addition to estrogen. In recent years, hormone replacement therapy (HRT) or estrogen combined with exercise have been proposed as potentially therapeutic agents for postmenopausal women, as these agents may potentially limit muscle damage and inflammation and stimulate repair in this population. While the benefits and potential health risks of long-term HRT use have been widely debated, controlled studies using short-term HRT or other estrogen agonists may provide future new and valuable insights into understanding the effects of estrogen on skeletal muscle, and greatly benefit the aging female population. Recent studies with older females have begun to demonstrate their benefits.

Androgens and male aging: Current evidence of safety and efficacy

Many signs of aging, such as sexual dysfunction, visceral obesity, impaired bone and muscle strength, bear a close resemblance to features of hypogonadism in younger men. The statistical decline of serum testosterone in aging men is solidly documented. It has been presumed that the above features of aging are related to the concurrent decline of androgens, and that correction of the lower-than-normal circulating levels of testosterone will lead to improvement of symptoms of aging. But in essence, the pivotal question whether the age-related decline of testosterone must be viewed as hypogonadism, in the best case reversed by testosterone treatment, has not been definitively resolved. Studies in elderly men with lower-than-normal testosterone report improvement of features of the metabolic syndrome, bone mineral density, of mood and of sexual functioning. But as yet there is no definitive proof of the beneficial effects of restoring testosterone levels to normal in elderly men on clinical parameters. Few of these studies meet as yet rigorous standards of scientific enquiry: double-blind, placebo-controlled design of the study. The above applies also to the assessment of safety of testosterone administration to elderly men. There is so far no convincing evidence that testosterone is a main factor in the development of prostate cancer in elderly men and guidelines for monitoring the development of prostate disease have been developed. It is of note that there are presently no long-term safety data with regard to the prostate. Polycythemia is another potential complication of testosterone treatment. It is dose dependent and can be managed with dose adjustment.

Ubiquitin ligase Cbl-b is a negative regulator for insulin-like growth factor 1 signaling during muscle atrophy caused by unloading

Skeletal muscle atrophy caused by unloading is characterized by both decreased responsiveness to myogenic growth factors (e.g., insulin-like growth factor 1 [IGF-1] and insulin) and increased proteolysis. Here, we show that unloading stress resulted in skeletal muscle atrophy through the induction and activation of the ubiquitin ligase Cbl-b. Upon induction, Cbl-b interacted with and degraded the IGF-1 signaling intermediate IRS-1. In turn, the loss of IRS-1 activated the FOXO3-dependent induction of atrogin-1/MAFbx, a dominant mediator of proteolysis in atrophic muscle. Cbl-b-deficient mice were resistant to unloading-induced atrophy and the loss of muscle function. Furthermore, a pentapeptide mimetic of tyrosine(608)-phosphorylated IRS-1 inhibited Cbl-b-mediated IRS-1 ubiquitination and strongly decreased the Cbl-b-mediated induction of atrogin-1/MAFbx. Our results indicate that the Cbl-b-dependent destruction of IRS-1 is a critical dual mediator of both increased protein degradation and reduced protein synthesis observed in unloading-induced muscle atrophy. The inhibition of Cbl-b-mediated ubiquitination may be a new therapeutic strategy for unloading-mediated muscle atrophy.

The benefits and risks of testosterone replacement therapy: a review

Increased longevity and population aging will increase the number of men with late onset hypogonadism. It is a common condition, but often underdiagnosed and undertreated. The indication of testosterone-replacement therapy (TRT) treatment requires the presence of low testosterone level, and symptoms and signs of hypogonadism. Although controversy remains regarding indications for testosterone supplementation in aging men due to lack of large-scale, long-term studies assessing the benefits and risks of testosterone-replacement therapy in men, reports indicate that TRT may produce a wide range of benefits for men with hypogonadism that include improvement in libido and sexual function, bone density, muscle mass, body composition, mood, erythropoiesis, cognition, quality of life and cardiovascular disease. Perhaps the most controversial area is the issue of risk, especially possible stimulation of prostate cancer by testosterone, even though no evidence to support this risk exists. Other possible risks include worsening symptoms of benign prostatic hypertrophy, liver toxicity, hyperviscosity, erythrocytosis, worsening untreated sleep apnea or severe heart failure. Despite this controversy, testosterone supplementation in the United States has increased substantially over the past several years. The physician should discuss with the patient the potential benefits and risks of TRT. The purpose of this review is to discuss what is known and not known regarding the benefits and risks of TRT.

Aging and liver regeneration

The loss of regenerative capacity is the most dramatic age-associated alteration in the liver. Although this phenomenon was reported over 50 years ago, the molecular basis for the loss of regenerative capacity of aged livers has not been fully elucidated. Aging causes alterations of several signal-transduction pathways and changes in the expression of CCAAT/enhancer-binding protein (C/EBP) and chromatin-remodeling proteins. Consequently, aging livers accumulate a multi-protein C/EBPalpha-Brm-HDAC1 complex that occupies and silences E2F-dependent promoters, reducing the regenerative capacity of livers in older mice. Recent studies have provided evidence for the crucial role of epigenetic silencing in the age-dependent inhibition of liver proliferation. This review focuses on mechanisms of age-dependent inhibition of liver proliferation and approaches for correcting liver regeneration in the elderly.

Estrogen supplementation selectively enhances hypothalamo-pituitary sensitivity to ghrelin in postmenopausal women

CONTEXT

Sex-steroid hormones amplify pulsatile GH secretion by unknown mechanisms. Ghrelin is the most potent natural GH secretagogue discovered to date. A plausible unifying postulate is that estradiol (E(2)) enhances hypothalamo-pituitary sensitivity to ghrelin (a physiological effect). The hypothesis is relevant to understanding the basis of hyposomatotropism in aging and other relatively hypogonadal states.

OBJECTIVE

Our objective was to test the hypothesis that E(2) supplementation potentiates ghrelin's stimulation of pulsatile GH secretion.

SETTING

The study was conducted at an academic medical center.

SUBJECTS

Healthy postmenopausal women (n = 20) were included in the study.

INTERVENTIONS

Separate-day iv infusions of saline vs. five graded doses of ghrelin were performed in volunteers prospectively randomly assigned to receive (n = 8) or not receive (n = 12) transdermal E(2) for 21 d were performed.

MEASURES

GH secretion was estimated by deconvolution analysis and abdominal visceral fat mass determined by computerized axial tomography were calculated.

RESULTS

E(2) supplementation augmented ghrelin's stimulation of basal (nonpulsatile) GH secretion by 3.6-fold (P = 0.022), increased GH responses to low-dose ghrelin by 2.9-fold (P = 0.035), did not alter ghrelin efficacy, and elicited more regular patterns of acylated ghrelin concentrations during saline infusion (P = 0.033). Abdominal visceral fat negatively determined responses to ghrelin (R = -0.346; P < 0.005).

CONCLUSIONS

Transdermal E(2) supplementation potentiates GH secretion stimulated by physiological but not pharmacological concentrations of acylated ghrelin, and concomitantly regularizes patterns of bioactive ghrelin secretion in postmenopausal women. Accordingly, the estrogen milieu appears to control sensitivity of the hypothalamopituitary unit to acylated ghrelin.

Testosterone and cardiovascular risk in men: a systematic review and meta-analysis of randomized placebo-controlled trials

OBJECTIVE

To conduct a systematic review and meta-analysis of randomized trials that assessed the effect of testosterone use on cardiovascular events and risk factors in men with different degrees of androgen deficiency.

METHODS

Librarian-designed search strategies were used to search the MEDLINE (1966 to October 2004), EMBASE (1988 to October 2004), and Cochrane CENTRAL (inception to October 2004) databases. The database search was performed again in March 2005. We also reviewed reference lists from included studies and content expert files. Eligible studies were randomized trials that compared any formulation of commercially available testosterone with placebo and that assessed cardiovascular risk factors (lipid fractions, blood pressure, blood glucose), cardiovascular events (cardiovascular death, nonfatal myocardial infarction, angina or claudication, revascularization, stroke), and cardiovascular surrogate end points (ie, laboratory tests indicative of cardiac or vascular disease). Using a standardized data extraction form, we collected data on participants, testosterone administration, and outcome measures. We assessed study quality with attention to allocation concealment, blinding, and loss to follow-up.

RESULTS

The 30 trials included 1642 men, 808 of whom were treated with testosterone. Overall, the trials had limited reporting of methodological features that prevent biased results (only 6 trials reported allocation concealment), enrolled few patients, and were of brief duration (only 4 trials followed up patients for > 1 year). The median loss to follow-up across all 30 trials was 9%. Testosterone use in men with low testosterone levels led to inconsequential changes in blood pressure and glycemia and in all lipid fractions (total cholesterol: odds ratio [OR], -0.22; 95% confidence interval [CI], -0.71 to 0.27; high-density lipoprotein cholesterol: OR, -0.04; 95% CI, -0.39 to 0.30; low-density lipoprotein cholesterol: OR, 0.06; 95% CI, -0.30 to 0.42; and triglycerides: OR, -0.27; 95% CI, -0.61 to 0.08); results were similar in patients with low-normal to normal testosterone levels. The OR between testosterone use and any cardiovascular event pooled across trials that reported these events (n = 6) was 1.82 (95% CI, 0.78 to 4.23). Several trials failed to report data on measured outcomes. For reasons we could not explain statistically, the results were inconsistent across trials.

CONCLUSION

Currently available evidence weakly supports the inference that testosterone use in men is not associated with important cardiovascular effects. Patients and clinicians need large randomized trials of men at risk for cardiovascular disease to better inform the safety of long-term testosterone use.

Regulation of the pituitary growth hormone-releasing hormone receptor in ageing male and female LOU rats: new insights into healthy ageing

Ageing is characterised by a decrease of somatotroph functionality, involving growth hormone-releasing hormone receptor (GHRH-R). The present study was conducted in LOU/C/jall (LOU) rats, a strain described as a model of healthy ageing, which is characterised by a low adiposity and long life expectancy without developing severe pathologies. Effects of age and diet (chow versus self-selection), on levels of anterior pituitary GHRH-R mRNA transcripts, were assessed in male and female LOU rats. The effect of age on pituitary GHRH-R functionality was examined in the anterior pituitary of both males and females fed chow diet. Moreover, serum insulin-like growth factor-I (IGF-I), T4 and leptin were measured because changes in their concentration could affect GHRH-R expression. In the pituitary of 18-month-old male and female LOU/C/jall rats fed standard chow, the level of 2.5-kb GHRH-R mRNA transcript, coding for functional GHRH-R, was significantly decreased. In 24- to 34-month-old males and females, it progressively returned to the level of younger animals, suggesting an enrichment of the group with survivors maintaining functional GHRH-R. In males and females repeatedly submitted to self-selection, this phenomenon was not observed. Studies with the GHRH-R agonist, Fluo-GHRH, revealed that 73% of 16-18-month-old male and female rats studied did not show an increase of fluorescence density characteristic of receptor-mediated internalisation upon incubation at 37 degrees C. In the other 27%, the increase of fluorescence was identical to that observed in pituitaries of young rats, suggesting the presence of an optimal level of functional GHRH-R. Serum levels of leptin, free T4 and total IGF-I decreased more drastically in ageing males and in rats fed a self-selection diet. A positive correlation was demonstrated between leptin and IGF-I levels in ageing males and females fed standard chow and ageing females submitted to a self-selection regimen. In conclusion, healthy ageing in LOU rats fed chow diet appears to be associated with a maintenance of functional pituitary GHRH-R levels found in younger rats but not necessarily with those of serum leptin, T4 and IGF-I.

Emerging drugs for sarcopenia: age-related muscle wasting

Sarcopenia is the term widely used to describe the progressive loss of muscle mass with advancing age. Even before significant muscle wasting becomes apparent, ageing is associated with a slowing of movement and a gradual decline in muscle strength, factors that increase the risk of injury from sudden falls and the reliance of the frail elderly on assistance in accomplishing even basic tasks of independent living. Sarcopenia is recognised as one of the major public health problems now facing industrialised nations, and its effects are expected to place increasing demands on public healthcare systems worldwide. Although the effects of ageing on skeletal muscle are unlikely to be halted or reversed, the underlying mechanisms responsible for these deleterious changes present numerous targets for drug discovery with potential opportunities to attenuate muscle wasting, improve muscle function, and preserve functional independence. Very few drugs have been developed with sarcopenia specifically in mind. However, because many of the effects of ageing on skeletal muscle resemble those indicated in many neuromuscular disorders, drugs that target neurodegenerative diseases may also have important relevance for treating age-related muscle wasting and weakness. This review describes a selection of the emerging drugs that have been developed during the period 1997 - 2004, relevant to sarcopenia.