Testosterone replacement therapy restores normal ghrelin in hypogonadal men

Ghrelin deficiency sex-dependently affects food intake, locomotor activity, and adipose and hepatic gene expression in a binge-eating mouse model

Binge-eating disorder is the most prevalent eating disorder diagnosed, affecting three times more women than men. Ghrelin stimulates appetite and reward signaling, and loss of its receptor reduces binge-eating behavior in male mice. Here, we examined the influence of ghrelin itself on binge-eating behavior in both male and female mice. Five-wk-old wild-type (WT) and ghrelin-deficient (Ghrl^-/-) mice were housed individually in indirect calorimetry cages for 9 wks. Binge-like eating was induced by giving mice ad libitum chow, but time-restricted access to a Western-style diet (WD; 2 h access, 3 days/wk) in the light phase (BE); control groups received ad libitum chow (CO), or ad libitum access to both diets (CW). All groups of BE mice showed binge-eating behavior, eating up to 60% of their 24-h intake during the WD access period. Subsequent dark phase chow intake was decreased in Ghrl^-/- mice and remained decreased in Ghrl^-/- females on nonbinge days. Also, nonbinge day locomotor activity was lower in Ghrl^-/- than in WT BE females. Upon euthanasia, Ghrl^-/- BE mice weighed less and had a lower lean body mass percentage than WT BE mice. In BE and CW groups, ghrelin and sex altered the expression of genes involved in lipid processing, thermogenesis, and aging in white adipose tissue and livers. We conclude that, although ghrelin deficiency does not hamper the development of binge-like eating, it sex-dependently alters food intake timing, locomotor activity, and metabolism. These results add to the growing body of evidence that ghrelin signaling is sexually dimorphic.NEW & NOTEWORTHY Ghrelin, a peptide hormone secreted from the gut, is involved in hunger and reward signaling, which are altered in binge-eating disorder. Although sex differences have been described in both binge-eating and ghrelin signaling, this interaction has not been fully elucidated. Here, we show that ghrelin deficiency affects the behavior and metabolism of mice in a binge-like eating paradigm, and that the sex of the mice impacts the magnitude and direction of these effects.

Obesity and male infertility: multifaceted reproductive disruption

Background

The global prevalence of obesity has soared to a concerning height in the past few decades. Interestingly, the global decline in semen quality is a parallel occurrence that urges researchers to evaluate if obesity is among the most essential causatives of male infertility or subfertility.

Main body

Obesity may alter the synchronized working of the reproductive-endocrine milieu, mainly the hypothalamic-pituitary-gonadal (HPG) axis along with its crosstalks with other reproductive hormones. Obesity-mediated impairment in semen parameters may include several intermediate factors, which include physical factors, essentially increased scrotal temperature due to heavy adipose tissue deposits, and systemic inflammation and oxidative stress (OS) initiated by various adipose tissue-derived pro-inflammatory mediators. Obesity, via its multifaceted mechanisms, may modulate sperm genetic and epigenetic conformation, which severely disrupt sperm functions. Paternal obesity reportedly has significant adverse effects upon the outcome of assisted reproductive techniques (ARTs) and the overall health of offspring. Given the complexity of the underlying mechanisms and rapid emergence of new evidence-based hypotheses, the concept of obesity-mediated male infertility needs timely updates and pristine understanding.

Conclusions

The present review comprehensively explains the possible obesity-mediated mechanisms, especially via physical factors, OS induction, endocrine modulation, immune alterations, and genetic and epigenetic changes, which may culminate in perturbed spermatogenesis, disrupted sperm DNA integrity, compromised sperm functions, and diminished semen quality, leading to impaired male reproductive functions.

The Role of the Gastric Hormones Ghrelin and Nesfatin-1 in Reproduction

Ghrelin and nesfatin-1 are enteroendocrine peptide hormones expressed in rat X/A-like and human P/D1cells of the gastric mucosa. Besides their effect on food intake, both peptides are also implicated in various other physiological systems. One of these is the reproductive system. This present review illustrates the distribution of ghrelin and nesfatin-1 along the hypothalamus–pituitary–gonadal (HPG) axis, their modulation by reproductive hormones, and effects on reproductive functions as well as highlighting gaps in current knowledge to foster further research.

The Role of the Gastric Hormones Ghrelin and Nesfatin-1 in Reproduction

Ghrelin and nesfatin-1 are enteroendocrine peptide hormones expressed in rat X/A-like and human P/D1cells of the gastric mucosa. Besides their effect on food intake, both peptides are also implicated in various other physiological systems. One of these is the reproductive system. This present review illustrates the distribution of ghrelin and nesfatin-1 along the hypothalamus-pituitary-gonadal (HPG) axis, their modulation by reproductive hormones, and effects on reproductive functions as well as highlighting gaps in current knowledge to foster further research.

The Role of the Gastric Hormones Ghrelin and Nesfatin-1 in Reproduction

Ghrelin and nesfatin-1 are enteroendocrine peptide hormones expressed in rat X/A-like and human P/D1cells of the gastric mucosa. Besides their effect on food intake, both peptides are also implicated in various other physiological systems. One of these is the reproductive system. This present review illustrates the distribution of ghrelin and nesfatin-1 along the hypothalamus–pituitary–gonadal (HPG) axis, their modulation by reproductive hormones, and effects on reproductive functions as well as highlighting gaps in current knowledge to foster further research.

Distribution and effect of ghrelin genotype on plasma lipid and apolipoprotein profiles in obese and nonobese Chinese subjects

PURPOSE

The hormone ghrelin has an important role in a wide range of metabolic and nonmetabolic processes. Ghrelin gene polymorphisms have been reported to influence obesity or lipid abnormalities in some ethnic groups. This study was conducted mainly to examine the possible association of ghrelin - 604 G > A and Leu72Met polymorphisms with obesity and related traits in a Southwest Chinese population.

METHODS

Three hundred and eighty-six Han Chinese individuals (118 obese and 268 normal weight control subjects) in the Chengdu area were studied using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis. Clinical and biochemical parameters were also analyzed.

RESULTS

The genotype and allele frequencies of ghrelin gene polymorphisms in participants with obesity showed no significant difference compared to those in nonobese controls. However, in the nonobese control group, carriers of genotype Met/Met at the Leu72Met site had higher serum TC and LDL-C concentrations than those of the Leu/Leu genotype (P < 0.05). When nonobese subjects were stratified by sex, the genotype-dependent effects on TC and LDL-C were more evident, although this was observed only in females. In addition, genotype-related effects on these lipid parameters at this site were observed in male obese subjects only.

CONCLUSIONS

The Leu72Met polymorphism of the ghrelin gene is associated with altered plasma TC and LDL-C concentrations, and the effects on TC and LDL-C levels are sex-dependent in both nonobese and obese subjects in the Chinese population of the Chengdu area.

Pathophysiology of NAFLD and NASH in Experimental Models: The Role of Food Intake Regulating Peptides

Obesity, diabetes, insulin resistance, sedentary lifestyle, and Western diet are the key factors underlying non-alcoholic fatty liver disease (NAFLD), one of the most common liver diseases in developed countries. In many cases, NAFLD further progresses to non-alcoholic steatohepatitis (NASH), fibrosis, cirrhosis, and to hepatocellular carcinoma. The hepatic lipotoxicity and non-liver factors, such as adipose tissue inflammation and gastrointestinal imbalances were linked to evolution of NAFLD. Nowadays, the degree of adipose tissue inflammation was shown to directly correlate with the severity of NAFLD. Consumption of higher caloric intake is increasingly emerging as a fuel of metabolic inflammation not only in obesity-related disorders but also NAFLD. However, multiple causes of NAFLD are the reason why the mechanisms of NAFLD progression to NASH are still not well understood. In this review, we explore the role of food intake regulating peptides in NAFLD and NASH mouse models. Leptin, an anorexigenic peptide, is involved in hepatic metabolism, and has an effect on NAFLD experimental models. Glucagon-like peptide-1 (GLP-1), another anorexigenic peptide, and GLP-1 receptor agonists (GLP-1R), represent potential therapeutic agents to prevent NAFLD progression to NASH. On the other hand, the deletion of ghrelin, an orexigenic peptide, prevents age-associated hepatic steatosis in mice. Because of the increasing incidence of NAFLD and NASH worldwide, the selection of appropriate animal models is important to clarify aspects of pathogenesis and progression in this field.

Effects of Testosterone Supplementation on Ghrelin and Appetite During and After Severe Energy Deficit in Healthy Men

Background

Severe energy deficits cause interrelated reductions in testosterone and fat free mass. Testosterone supplementation may mitigate those decrements, but could also reduce circulating concentrations of the orexigenic hormone ghrelin, thereby exacerbating energy deficit by suppressing appetite.

Objective

To determine whether testosterone supplementation during severe energy deficit influences fasting and postprandial ghrelin concentrations and appetite.

Design and methods

Secondary analysis of a randomized, double-blind trial that determined the effects of testosterone supplementation on body composition changes during and following severe energy deficit in nonobese, eugonadal men. Phase 1 (PRE-ED): 14-day run-in; phase 2: 28 days, 55% energy deficit with 200 mg testosterone enanthate weekly (TEST; n = 24) or placebo (PLA; n = 26); phase 3: free-living until body mass recovered (end-of-study; EOS). Fasting and postprandial acyl ghrelin and des-acyl ghrelin concentrations and appetite were secondary outcomes measured during the final week of each phase.

Results

Fasting acyl ghrelin concentrations, and postprandial acyl and des-acyl ghrelin concentrations increased in PLA during energy deficit then returned to PRE-ED values by EOS, but did not change in TEST (phase-by-group, P < 0.05). Correlations between changes in free testosterone and changes in fasting acyl ghrelin concentrations during energy deficit (ρ = -0.42, P = 0.003) and body mass recovery (ρ = -0.38; P = 0.01) were not mediated by changes in body mass or body composition. Transient increases in appetite during energy deficit were not affected by testosterone treatment.

Conclusions

Testosterone supplementation during short-term, severe energy deficit in healthy men prevents deficit-induced increases in circulating ghrelin without blunting concomitant increases in appetite.

Clinical Trials Registration

www.clinicaltrials.gov NCT02734238 (registered 12 April 2016).

Physiological Effect of Ghrelin on Body Systems

Ghrelin is a relatively novel multifaceted hormone that has been found to exert a plethora of physiological effects. In this review, we found/confirmed that ghrelin has effect on all body systems. It induces appetite; promotes the use of carbohydrates as a source of fuel while sparing fat; inhibits lipid oxidation and promotes lipogenesis; stimulates the gastric acid secretion and motility; improves cardiac performance; decreases blood pressure; and protects the kidneys, heart, and brain. Ghrelin is important for learning, memory, cognition, reward, sleep, taste sensation, olfaction, and sniffing. It has sympatholytic, analgesic, antimicrobial, antifibrotic, and osteogenic effects. Moreover, ghrelin makes the skeletal muscle more excitable and stimulates its regeneration following injury; delays puberty; promotes fetal lung development; decreases thyroid hormone and testosterone; stimulates release of growth hormone, prolactin, glucagon, adrenocorticotropic hormone, cortisol, vasopressin, and oxytocin; inhibits insulin release; and promotes wound healing. Ghrelin protects the body by different mechanisms including inhibition of unwanted inflammation and induction of autophagy. Having a clear understanding of the ghrelin effect in each system has therapeutic implications. Future studies are necessary to elucidate the molecular mechanisms of ghrelin actions as well as its application as a GHSR agonist to treat most common diseases in each system without any paradoxical outcomes on the other systems.

The Mouse Microbiome Is Required for Sex-Specific Diurnal Rhythms of Gene Expression and Metabolism

The circadian clock and associated feeding rhythms have a profound impact on metabolism and the gut microbiome. To what extent microbiota reciprocally affect daily rhythms of physiology in the host remains elusive. Here, we analyzed transcriptome and metabolome profiles of male and female germ-free mice. While mRNA expression of circadian clock genes revealed subtle changes in liver, intestine, and white adipose tissue, germ-free mice showed considerably altered expression of genes associated with rhythmic physiology. Strikingly, the absence of the microbiome attenuated liver sexual dimorphism and sex-specific rhythmicity. The resulting feminization of male and masculinization of female germ-free animals is likely caused by altered sexual development and growth hormone secretion, associated with differential activation of xenobiotic receptors. This defines a novel mechanism by which the microbiome regulates host metabolism.

Klinefelter Syndrome: Integrating Genetics, Neuropsychology, and Endocrinology

Although first identified over 70 years ago, Klinefelter syndrome (KS) continues to pose substantial diagnostic challenges, as many patients are still misdiagnosed, or remain undiagnosed. In fact, as few as 25% of patients with KS are accurately diagnosed and most of these diagnoses are not made until adulthood. Classic characteristics of KS include small testes, infertility, hypergonadothropic hypogonadism, and cognitive impairment. However, the pathophysiology behind KS is not well understood, although genetic effects are also thought to play a role. For example, recent developments in genetics and genomics point to a fundamental change in our understanding of KS, with global epigenetic and RNA expression changes playing a central role for the phenotype. KS is also associated with more general health markers, including higher morbidity and mortality rates and lower socioeconomic status (which likely affect both morbidity and mortality). In addition, hypogonadism is associated with greater risk of metabolic syndrome, type 2 diabetes, cardiovascular disease, breast cancer, and extragonadal germ cell tumors. Medical treatment typically focuses on testosterone replacement therapy (TRT), although the effects of this therapy have not been studied rigorously, and future studies need to evaluate the effects of TRT on metabolic risk and neurocognitive outcomes. This review presents a comprehensive interdisciplinary examination of recent developments in genetic, endocrine, and neurocognitive science, including the study of animal models. It provides a number of recommendations for improving the effectiveness of research and clinical practice, including neonatal KS screening programs, and a multidisciplinary approach to KS treatment from childhood until senescence.

Benefits and Health Implications of Testosterone Therapy in Men With Testosterone Deficiency

INTRODUCTION

Testosterone (T) deficiency (TD; hypogonadism) has deleterious effects on men's health; negatively affects glycometabolic and cardiometabolic functions, body composition, and bone mineral density; contributes to anemia and sexual dysfunction; and lowers quality of life. T therapy (TTh) has been used for the past 8 decades to treat TD, with positive effects on signs and symptoms of TD.

AIM

To summarize the health benefits of TTh in men with TD.

METHODS

A comprehensive literature search was carried out using PubMed, articles relevant to TTh were accessed and evaluated, and a comprehensive summary was synthesized.

MAIN OUTCOME MEASURES

Improvements in signs and symptoms of TD reported in observational studies, registries, clinical trials, and meta-analyses were reviewed and summarized.

RESULTS

A large body of evidence provides significant valuable information pertaining to the therapeutic value of TTh in men with TD. TTh in men with TD provides real health benefits for bone mineral density, anemia, sexual function, glycometabolic and cardiometabolic function, and improvements in body composition, anthropometric parameters, and quality of life.

CONCLUSION

TTh in the physiologic range for men with TD is a safe and effective therapeutic modality and imparts great benefits on men's health and quality of life. Traish AM. Benefits and Health Implications of Testosterone Therapy in Men With Testosterone Deficiency. Sex Med Rev 2018;6:86-105.

Effect of Testosterone Treatment on Adipokines and Gut Hormones in Obese Men on a Hypocaloric Diet

Context

In obese men with lowered testosterone levels, testosterone treatment augments diet-associated loss of body fat.

Objective

We hypothesized that testosterone treatment modulates circulating concentrations of hormonal mediators of fat mass and energy homeostasis in obese men undergoing a weight loss program.

Design

Prespecified secondary analysis of a randomized, double-blind, placebo-controlled trial.

Setting

Tertiary referral center.

Participants

Obese men (body mass index ≥30 kg/m²) with a repeated total testosterone level ≤12 nmol/L.

Intervention

One hundred participants mean age 53 years (interquartile range 47 to 60 years) receiving 10 weeks of a very low-energy diet followed by 46 weeks of weight maintenance were randomly assigned at baseline to 56 weeks of intramuscular testosterone undecanoate (cases, n = 49) or matching placebo (controls, n = 51). Eighty-two men completed the study.

Main outcomes

Between-group differences in leptin, adiponectin, ghrelin, glucagon like peptide-1, gastric inhibitory polypeptide, peptide YY, pancreatic polypeptide, and amylin levels.

Results

At study end, compared with controls, cases had greater reductions in leptin [mean adjusted difference (MAD), -3.6 ng/mL (95% CI, -5.3 to -1.9); P < 0.001]. The change in leptin levels between cases and controls was dependent on baseline fat mass, as the between-group difference progressively increased with increasing fat mass [MAD, -0.26 ng/mL (95% CI, -0.31 to -0.26); P = 0.001 per 1 kg of baseline fat mass]. Weight loss-associated changes in other hormones persisted during the weight maintenance phase but were not modified by testosterone treatment.

Conclusions

Testosterone treatment led to reductions in leptin beyond those achieved by diet-associated weight loss. Testosterone treatment may reduce leptin resistance in obese men.

Estradiol and testosterone modulate the tissue-specific expression of ghrelin, ghs-r, goat and nucb2 in goldfish

Ghrelin, and nesfatin-1 (encoded by nucleobindin2/nucb2) are two metabolic peptides with multiple biological effects in vertebrates. While sex steroids are known to regulate endogenous ghrelin and NUCB2 in mammals, such actions by steroids in fish remain unknown. This study aimed to determine whether estradiol (E2) and testosterone (T) affects the expression of preproghrelin, ghrelin/growth hormone secretagogue receptor (GHS-R), ghrelin O-acyl transferase (GOAT) and NUCB2 in goldfish (Carassius auratus). First, a dose-response assay was performed in which fish were intraperitoneally (ip) implanted with pellets containing 25, 50 or 100 μg/g body weight (BW) of E2 or T. It was found that sex steroids (100 μg/g BW) administered for 2.5 days achieved the highest E2 or T in circulation. In a second experiment, fish were ip implanted with pellets containing 100 μg/g BW of E2, T or without hormone (control). RT-qPCR analyses at 2.5 days post-administration show that gut preproghrelin and GOAT expression was upregulated by both E2 and T treatments, while the same effect was observed for GHS-R only in the pituitary. Both treatments also reduced hypothalamic preproghrelin mRNA expression. NUCB2 expression was increased in the forebrain of T treated group and reduced in the gut and pituitary under both treatments. These results show for the first time a modulation of preproghrelin and nucb2/nesfatin-1 by sex steroids in fish. The interaction between sex steroids and genes implicated in both metabolism and reproduction might help meeting the reproduction dependent energy demands in fish.

The imbalance of sex-hormones related to depressive symptoms in obese men

Obese men may present hypogonadothrofic hypogonadism, mainly related to higher insulinemia and aromatase activity. Our objectives were to evaluate the relationship of sex-hormones profiles and frequency of depressive symptoms in 43 obese men, in a cross-sectional study. They had 19-60 years, and body mass index 30-50 kg/m(2). LH, total and free testosterone (TT and FT), estradiol (E2), sex hormone binding globulin, estradiol/total testosterone ratio (E2/T) were analyzed. Depressive symptoms were evaluated by "beck depression inventory" (BDI), and significant depression was considered if BDI ≥ 16.Thirty-four (80%) presented low TT levels, but only 4 (14%) had low free testosterone and hypogonadism symptoms; 12 of 43 (28%) presented increased E2. Forty five (56%) presented depressive symptoms, but 16 (28% of the 45) had significant depression. BDI correlated positively with E2 (r = 0.407; p = 0.001) and E2/T (r = 0.473; p = 0.001), but not TT or FT. Patients with significant depressive showed higher levels of estradiol (136 ± 48 versus 103 ± 48 pg/ml, p = 0.02) and E2/T (16.0 ± 9.9 versus 9.8 ± 4.6; p = 0.002) (mean ± SD).In conclusion, obese men may present relatively excess of estradiol and deficiency in testosterone, leading to an imbalance between these two hormones. The greater this imbalance, the more depressive symptoms had our patients.

Hormonal 'minipuberty' influences the somatic development of boys but not of girls up to the age of 6 years

OBJECTIVE

Hormonal 'minipuberty' refers to a transient sex-specific surge of LH, FSH, testosterone (T) and estradiol (E2) in the first few months of life. We hypothesized a potential long-term effect of this hormonal surge on somatic parameters in the following years and therefore designed this longitudinal study.

DESIGN

A hierarchical multiple regression analysis was used to analyse the potential influence of hormone concentrations during minipuberty on anthropometric measurements conducted in the first 6 years of life.

PATIENTS

Thirty-five healthy babies (17 male, 18 female) were the participants.

MEASUREMENTS

Testosterone, E2, SHBG, LH and FSH were measured at the ages of four, eight and 20 weeks. Anthropometric measurements were taken eight times in the first 12 months, then every 6 months up to the age of 6 years.

RESULTS

A significant negative effect was found in boys between testosterone and LH levels at 8 weeks and body weight up to the age of 6 years and BMI up to 6 years (LH) and 3 years (T), respectively. A further negative effect was found between E2 levels at the age of 20 weeks and body weight as well as body length in the years that followed. A positive effect was observed between E2 at the age of 4 weeks and skinfold thickness up to the age of 6 years in boys. No significant effects were found in girls.

CONCLUSIONS

The findings seem to reflect an up to now unknown long-term influence of the physiological early hormonal surge on the subsequent male but not female somatic development.

A hypothesis for a possible synergy between ghrelin and exercise in patients with cachexia: Biochemical and physiological bases

This article reviews the biochemical and physiological observations underpinning the synergism between ghrelin and ghrelin agonists with exercise, especially progressive resistance training that has been shown to increase muscle mass. The synergy of ghrelin agonists and physical exercise could be beneficial in conditions where muscle wasting is present, such as that found in patients with advanced cancer. The principal mechanism that controls muscle anabolism following the activation of the ghrelin receptor in the central nervous system involves the release of growth hormone/insulin-like growth factor-1 (GH/IGF-1). GH/IGF-1 axis has a dual pathway of action on muscle growth: (a) a direct action on muscle, bone and fat tissue and (b) an indirect action via the production of both muscle-restricted mIGF-1 and anti-cachectic cytokines. Progressive resistance training is a potent inducer of the secretion the muscle-restricted IGF-1 (mIGF-1) that enhances protein synthesis, increases lean body mass and eventually leads to the improvement of muscle strength. Thus, the combination of ghrelin administration with progressive resistance training may serve to circumvent ghrelin resistance and further reduce muscle wasting, which are commonly associated with cachexia.

Ghrelin - Physiological Functions and Regulation

Ghrelin is an orexigenic peptide predominantly secreted from the stomach and stimulates appetite and growth hormone (GH) release. Studies have provided evidence that ghrelin exercises a wide range of functions, including regulation of food intake and energy metabolism, modulation of cardiovascular function, stimulation of osteoblast proliferation and bone formation and stimulation of neurogenesis and myogenesis. In the gastrointestinal system, ghrelin affects multiple functions, including secretion of gastric acid, gastric motility and pancreatic protein output. Most of these functions have been attributed to the actions of acylated ghrelin. The balance among its secretion rate, degradation rate and clearance rate determines the circulating level of ghrelin. This review explains what ghrelin is, its physiological functions and the factors that influence its level.

Sex-related difference in food-anticipatory activity of mice

The expression of food-anticipatory activity (FAA) is induced by restricted feeding (RF), and its entrainment requires food-entrainable oscillators, the neuroanatomical basis of which is currently unclear. Although RF impacts various hormones, sex-related differences in FAA are unclear. 'Here, we report significantly more food-anticipatory wheel-running activity in male than in female mice during RF. In parallel with the sex-related difference in FAA, male and female mice display different food intake and body weight in response to RF. Since gonadal hormones could be involved in the sex-specific difference in FAA, we compared sham and gonadectomized male and female wild-type mice. In gonadectomized mice, the sex difference in FAA was abolished, indicating a role for gonadal hormones in FAA. Further, plasma concentrations of the hormone ghrelin were higher in female than in male mice during ad libitum (AL) feeding, and RF induced a temporal advance in its peak in both sexes. RF also shifted the expression peak of the circadian gene mPer1 in the hippocampus and liver, although no sex difference was found in either the level or the cyclic phase of its expression. Per1(Brdm1) mutant mice were still sexually dimorphic for FAA, but diminished FAA was noted in both male and female Per2(Brdm1) mutant mice. In summary, our results imply that gonadal hormones contribute to the sex difference in FAA, possibly through modulating ghrelin activity.

The regulation of circulating ghrelin - with recent updates from cell-based assays

Ghrelin is a stomach-derived orexigenic hormone with a wide range of physiological functions. Elucidation of the regulation of the circulating ghrelin level would lead to a better understanding of appetite control in body energy homeostasis. Earlier studies revealed that circulating ghrelin levels are under the control of both acute and chronic energy status: at the acute scale, ghrelin levels are increased by fasting and decreased by feeding, whereas at the chronic scale, they are high in obese subjects and low in lean subjects. Subsequent studies revealed that nutrients, hormones, or neural activities can influence circulating ghrelin levels in vivo. Recently developed in vitro assay systems for ghrelin secretion can assess whether and how individual factors affect ghrelin secretion from cells. In this review, on the basis of numerous human, animal, and cell-based studies, we summarize current knowledge on the regulation of circulating ghrelin levels and enumerate the factors that influence ghrelin levels.

Outcomes of testosterone therapy in men with testosterone deficiency (TD): part II

Testosterone (T) deficiency (TD) is a common clinical condition, which contributes to co-morbidities including loss of muscle mass, increased fat mass, increased inflammation, insulin resistance, risk of vascular disease, sexual dysfunction, fatigue, depressed mood and reduced quality of life. T therapy attenuates inflammation, increases insulin sensitivity, muscle mass and reduces fat mass and adiposity. T therapy improves lipid profiles and endothelial function and reduces systolic and diastolic blood pressure. In addition, T therapy may reduce risk of vascular disease and mortality. T therapy improves bone mineral density and increases energy and vitality and improves mood and sexual function and overall quality of life. T therapy appears to be safe if treatment and monitoring are appropriately executed. The evidence available to date does not support alleged concerns regarding risk of cardiovascular disease and prostate cancer. Indeed, T therapy remains controversial. The data in the contemporary literature suggest that T therapy reduces cardiovascular risk and fears promoted by some recent studies should be re-evaluated. The cardiovascular risk and mortality with T therapy must await large prospective controlled clinical trials, which depend on many complex factors. Such studies may be prohibitive in the current environment due to logistical challenges, such as recruiting large number of men to be treated for long-durations with appropriate follow-up, requiring astronomical cost.

Adverse health effects of testosterone deficiency (TD) in men

Testosterone and its metabolite, 5α-dihydrotestosterone are critical metabolic and vascular hormones, which regulate a host of biochemical pathways including carbohydrate, lipid and protein metabolism and modulate vascular function. Testosterone deficiency (TD) is a well-recognized medical condition with important health implications. TD is associated with a number of co-morbidities including increased body weight, adiposity and increased waist circumference, insulin resistance (IR) and type 2 diabetes mellitus (T2DM), hypertension, inflammation, atherosclerosis and cardiovascular disease, erectile dysfunction (ED) and increased incidence of mortality. In this review, we summarize the data in the literature on the prevalence of TD and its association with the various co-morbidities and suggest that T therapy is necessary to improve health outcomes in men with TD.

Association between testosterone levels and the metabolic syndrome in adult men

OBJECTIVE

To evaluate the relationship between testosterone levels and the metabolic syndrome (MS) in men older than 45 years.

METHODS

Six hundred and sixty men (45-70 years) selected from 2906 participants of a population screening for prostate cancer were included in this study. Testosterone and the components of MS were assessed in all men. MS was diagnosed according to NCEP-ATP III criteria. Triglycerides (TG)/HDL-cholesterol (chol) index was calculated.

RESULTS

The presence of MS was inversely associated with testosterone (χ2, p < 0.001), independently of age (OR 0.802, CI 95%: 0.724-0.887, p < 0.0001). Hypertension was the most frequent abnormality observed followed by elevated TG and waist circumference (WC). Testosterone correlated positively with HDL-chol (r: 0.14, p < 0.0001) and negatively with body mass index (BMI)(r: -0.29, p < 0.0001), WC (r: -0.26, p < 0.0001), TG (r: -0.20, p < 0.0001), TG/HDL-chol (r: -0.20, p < 0.0001), glucose (r: -0.11, p = 0.005) and MS score (r: -0.23, p < 0.0001).

CONCLUSIONS

Our results show that in men older than 45 years, as long as testosterone levels decline, the prevalence of MS increases, independently of age. The correlations found between testosterone and four of the five components of MS, as well as with BMI and TG/HDL-chol ratio, a surrogate marker of insulin resistance, suggest considering male hypogonadism as a determinant of developmental abnormalities typical of MS.

Preproghrelin gene polymorphisms in obese Japanese: Association with diabetes mellitus in men and with metabolic syndrome parameters in women

SUMMARY

Preproghrelin gene polymorphisms (SNPs) are possible predisposing factors to obesity and metabolic syndrome. We analysed SNPs in obese Japanese individuals and studied the correlation with diabetes and metabolic syndrome. We recruited 235 subjects (BMI > 28.3) from individuals undergoing periodic medical check-up at Saku Central Hospital. Their SNPs were genotyped using PCR-RFLP method. Frequencies of 5 SNPs in the preproghrelin gene -1500C>G (rs3755777), -1062G>C (rs26311), -994C>T (rs26312), Leu72Met (+408C>A) (rs696217), and +3056T>C (rs2075356) were compared with healthy individuals (data from HapMap Project or Asian population studies). Associations between these SNPs and clinical parameters were investigated. The phenotypes evidently differed between men and women. In men, higher fasting glucose and HbA1c values were observed in the +3056C/C minor homozygotes without leptin or insulin accumulation. The +408C -- +3056C haplotype was more frequent in the diabetic subgroup, in which diagnosis was based on fasting glucose, 75gOGTT, and HbA1c values, than normal subgroup. In contrast, in women, a significant correlation was observed between fat metabolism and obesity. The -1062C/C minor homozygotes had higher values of C-peptide, insulin, total and visceral fat area, waist circumference and BMI. The 72Met/Met minor homozygotes showed reduced leptin, total, HDL and LDL cholesterol concentrations and increased value of visceral fat area. Further, in the other SNPs, the minor homozygotes showed a similar trend, and the heterozygotes had intermediate values. Preproghrelin gene polymorphisms in obese Japanese may be predisposing factors to diabetes mellitus in men and to obesity via aberrant fat metabolism in women.:

Testosterone promotes glucose intolerance, lipid disorder and oxidative stress in type 1 diabetic rats

BACKGROUND

A bidirectional relationship has been established between testosterone deficiency (TD) and type 2 diabetes mellitus (T2DM). Low testosterone level has been reported to be a predisposing factor to T2DM, whereas recent clinical studies have shown a high prevalence of low testosterone in diabetic individuals. However, it is not known if any relationship exists between type 1 diabetes mellitus (T1DM) and testosterone level. This study was designed to investigate the effects of TD on T1DM. Twenty-four Sprague-Dawley rats were randomly divided into four groups designated as control, diabetic, orchiectomized and orchiectomized-diabetic.

METHODS

Diabetes was induced with an intravenous injection of alloxan, and orchiectomy was done under sterile conditions. Fasting blood glucose (FBG), insulin level, lipid and oxidative parameters were determined in all experimental rats.

RESULTS

The area under the curve during oral glucose tolerance test showed that the orchiectomized-diabetic group expressed an enhanced ability to metabolize glucose than the diabetic group. The malondialdehyde level in the diabetic group was significantly higher compared with that in the control and orchiectomized groups. Moreover, there was a significant decrease in glutathione (GSH) activity and an increase in superoxide dismutase activity in the diabetic group compared with control. Meanwhile, the activities of GSH and catalase were significantly reduced in the orchiectomized as well as the orchiectomized-diabetic group when compared with both control and diabetic groups.

CONCLUSIONS

These data indicate that TD attenuates glucose intolerance under diabetic conditions and is equally associated with a considerable reduction in oxidative stress, which implies that testosterone may be a pro-oxidant.

Sex differences in the physiology of eating

Hypothalamic-pituitary-gonadal (HPG) axis function fundamentally affects the physiology of eating. We review sex differences in the physiological and pathophysiological controls of amounts eaten in rats, mice, monkeys, and humans. These controls result from interactions among genetic effects, organizational effects of reproductive hormones (i.e., permanent early developmental effects), and activational effects of these hormones (i.e., effects dependent on hormone levels). Male-female sex differences in the physiology of eating involve both organizational and activational effects of androgens and estrogens. An activational effect of estrogens decreases eating 1) during the periovulatory period of the ovarian cycle in rats, mice, monkeys, and women and 2) tonically between puberty and reproductive senescence or ovariectomy in rats and monkeys, sometimes in mice, and possibly in women. Estrogens acting on estrogen receptor-α (ERα) in the caudal medial nucleus of the solitary tract appear to mediate these effects in rats. Androgens, prolactin, and other reproductive hormones also affect eating in rats. Sex differences in eating are mediated by alterations in orosensory capacity and hedonics, gastric mechanoreception, ghrelin, CCK, glucagon-like peptide-1 (GLP-1), glucagon, insulin, amylin, apolipoprotein A-IV, fatty-acid oxidation, and leptin. The control of eating by central neurochemical signaling via serotonin, MSH, neuropeptide Y, Agouti-related peptide (AgRP), melanin-concentrating hormone, and dopamine is modulated by HPG function. Finally, sex differences in the physiology of eating may contribute to human obesity, anorexia nervosa, and binge eating. The variety and physiological importance of what has been learned so far warrant intensifying basic, translational, and clinical research on sex differences in eating.

Serum sex steroid hormones and frailty in older American men of the Third National Health and Nutrition Examination Survey (NHANES III)

OBJECTIVE

To determine whether frailty is associated with circulating total and free testosterone, total and free estradiol, and sex hormone-binding globulin (SHBG) in older men.

METHODS

With NHANES III data of 461 men aged 60 years and older, we used logistic regression to analyze the associations between serum concentrations of sex steroid hormones, SHBG and frailty. Participants meeting any three or more of the five frailty criteria were classified as "frail", all others were considered as non-frail.

RESULTS

2.5% of men were frail. Men with SHBG ≥66 nmol/L had three times the odds of frailty (OR = 2.97; 95% CI 1.28-6.86) compared to men with SHBG <66 nmol/L. Men with free testosterone levels below 243 pmol/L had an increased odds of frailty (OR = 3.92; 95% CI 1.29-11.89). None of these associations was statistically significant after additionally adjusting for body mass index, smoking and history of cardiovascular diseases (CVD). Total testosterone, and total and free estradiol serum levels were not statistically significantly associated with frailty.

CONCLUSIONS

In this US nationally representative study of older men, low free testosterone and high SHBG serum levels were associated with a significantly increased odds of frailty after adjustment for age and race/ethnicity. These associations may, however, be explained by confounding due to obesity, smoking, and the higher prevalence of CVD in frail men or by low hormones or high SHBG mediating the association between obesity, smoking, CVD and frailty.

Acylated and unacylated ghrelin levels in normal weight and obese children: influence of puberty and relationship with insulin, leptin and adiponectin levels

BACKGROUND

Ghrelin circulates in blood as acylated (AG) and unacylated (UAG) ghrelin. The physiological role of the two forms is poorly understood, in particular in childhood. Aim of the study was to evaluate the AG and UAG levels in obese and normal weight (NW) children, pre-pubertal and pubertal, and their relationship with insulin, leptin and adiponectin levels.

SUBJECTS AND METHODS

A population based study in which AG, UAG, leptin, adiponectin, glucose, insulin, testosterone or estradiol levels, insulinemic indexes were evaluated in 82 NW and 58 obese (OB) children.

RESULTS

Both ghrelin forms in NW were higher (AG, p<0.02; UAG, p<0.0001) than in OB subjects, with similar ratio AG/UAG . While no differences were observed for gender, puberty AG (p<0.01) and UAG (p<0.0001) levels were higher in pre-pubertal than pubertal NW and OB subjects. Adiponectin levels in NW subjects were higher (p<0.001), while leptin and insulin levels were lower (p<0.0001) than in OB subjects. NW children showed homeostasis model assessment (HOMA) and HOMAβ indices lower than OB children (p<0.0001) with a higher a quantitative insulin sensitivity check index (p<0.0001). AG and UAG levels correlated to each other (p<0.0001), each showing a negative correlation to age, height, weight and body mass index. Both forms, but more strongly UAG, correlated with adiponectin, leptin, and insulin.

CONCLUSIONS

OB children show lower levels of both AG and UAG when compared to NW subjects, with lower levels during puberty. These results demonstrate a peculiar strong relationship between UAG levels and metabolic parameters in the pediatric population, suggesting a role for UAG in metabolic functions.

Acute testosterone deprivation reduces insulin sensitivity in men

OBJECTIVE

In men with prostate cancer, androgen deprivation reduces insulin sensitivity; however, the relative roles played by testosterone and estradiol are unknown. To investigate the respective effects of these hormones on insulin sensitivity in men, we employed a model of experimental hypogonadism with or without hormone replacement.

DESIGN

Placebo-controlled, randomized trial.

PARTICIPANTS

Twenty-two healthy male volunteers, 18-55 years old.

METHODS

Following screening, subjects received the gonadotrophin-releasing hormone antagonist acyline plus one of the following for 28 days: Group 1, placebo transdermal gel and placebo pills; Group 2, transdermal testosterone gel 10 g/day plus placebo pills; Group 3, transdermal testosterone gel 10 g/day plus the aromatase inhibitor anastrozole 1 mg/day to normalize testosterone while selectively reducing serum estradiol. Fasting insulin, glucose, adipokines and hormones were measured bi-weekly.

RESULTS

With acyline administration, serum testosterone was reduced by >90% in all subjects in Group 1. In these men, mean fasting insulin concentrations were significantly increased compared with baseline (P = 0·02) at 28 days, despite stable body weight and no changes in fasting glucose concentrations. Decreased insulin sensitivity was also apparent in the insulin sensitivity indices homeostasis model of insulin resistance (P = 0·03) and quantitative insulin sensitivity check index (P = 0·04). In contrast, in Groups 2 and 3, testosterone concentrations remained in the physiologic range, despite significant reduction in mean estradiol in Group 3. In these groups, no significant changes in insulin sensitivity were observed.

CONCLUSIONS

Acute testosterone withdrawal reduces insulin sensitivity in men independent of changes in body weight, whereas estradiol withdrawal has no effect. Testosterone appears to maintain insulin sensitivity in normal men.

Men's health in primary care: an emerging paradigm of sexual function and cardiometabolic risk

An office evaluation of men's health in primary care requires a thorough understanding of the implications of male sexual dysfunctions, hypogonadism, and cardiometabolic risk stratification and aggressive risk management. The paradigm of the men's health office visit in primary care is the recognition and assessment of male sexual dysfunction, specifically erectile dysfunction, and its value as a signal of overall cardiometabolic health, including the emerging evidence linking low testosterone and the metabolic syndrome. Indeed, erectile dysfunction may now be thought of as a harbinger of cardiovascular clinical events and other systemic vascular diseases in some men.

Influence of estrogens on GH-cell network dynamics in females: a live in situ imaging approach

The secretion of endocrine hormones from pituitary cells finely regulates a multitude of homeostatic processes. To dynamically adapt to changing physiological status and environmental stimuli, the pituitary gland must undergo marked structural and functional plasticity. Endocrine cell plasticity is thought to primarily rely on variations in cell proliferation and size. However, cell motility, a process commonly observed in a variety of tissues during development, may represent an additional mechanism to promote plasticity within the adult pituitary gland. To investigate this, we used multiphoton time-lapse imaging methods, GH-enhanced green fluorescent protein transgenic mice and sexual dimorphism of the GH axis as a model of divergent tissue demand. Using these methods to acutely (12 h) track cell dynamics, we report that ovariectomy induces a dramatic and dynamic increase in cell motility, which is associated with gross GH-cell network remodeling. These changes can be prevented by estradiol supplementation and are associated with enhanced network connectivity as evidenced by increased coordinated GH-cell activity during multicellular calcium recordings. Furthermore, cell motility appears to be sex-specific, because reciprocal alterations are not detected in males after castration. Therefore, GH-cell motility appears to play an important role in the structural and functional pituitary plasticity, which is evoked in response to changing estradiol concentrations in the female.

Onset of effects of testosterone treatment and time span until maximum effects are achieved

OBJECTIVE

Testosterone has a spectrum of effects on the male organism. This review attempts to determine, from published studies, the time-course of the effects induced by testosterone replacement therapy from their first manifestation until maximum effects are attained.

DESIGN

Literature data on testosterone replacement.

RESULTS

Effects on sexual interest appear after 3 weeks plateauing at 6 weeks, with no further increments expected beyond. Changes in erections/ejaculations may require up to 6 months. Effects on quality of life manifest within 3-4 weeks, but maximum benefits take longer. Effects on depressive mood become detectable after 3-6 weeks with a maximum after 18-30 weeks. Effects on erythropoiesis are evident at 3 months, peaking at 9-12 months. Prostate-specific antigen and volume rise, marginally, plateauing at 12 months; further increase should be related to aging rather than therapy. Effects on lipids appear after 4 weeks, maximal after 6-12 months. Insulin sensitivity may improve within few days, but effects on glycemic control become evident only after 3-12 months. Changes in fat mass, lean body mass, and muscle strength occur within 12-16 weeks, stabilize at 6-12 months, but can marginally continue over years. Effects on inflammation occur within 3-12 weeks. Effects on bone are detectable already after 6 months while continuing at least for 3 years.

CONCLUSION

The time-course of the spectrum of effects of testosterone shows considerable variation, probably related to pharmacodynamics of the testosterone preparation. Genomic and non-genomic effects, androgen receptor polymorphism and intracellular steroid metabolism further contribute to such diversity.

Ghrelin and reproductive disorders

Ghrelin is an important factor involved in most of the metabolic and hormonal signals which adapt the reproductive functions in conditions of altered energy balance. Moreover, the coordinated role of leptin and ghrelin appears in fact to have a specific role in the regulation of puberty. Systemic action of ghrelin on the reproductive axis involves the control of the hypothalamic-pituitary-gondal axis. In addition, it has been shown that ghrelin may directly act at a gonadal level in both females and males. Available data also demonstrate that sex steroid hormones and gonadotropins may in turn regulate the gonadal effect of ghrelin, as documented by studies performed in females with the polycystic ovary syndrome and in hypogonadal men. Notably, recent studies also confirm a potentially important role for ghrelin in fetal and neonatal energy balance, and specifically in allowing fetal adaptation to an adverse intrauterine environment.

Identification of a cDNA encoding for Ghrelin in the testis of the frog Pelophylax esculentus and its involvement in spermatogenesis

GHRELIN (GHRL) is an acylated peptide that contains 28-amino acids prevalently expressed in the stomach of several species. Specifically, it contributes to energy balance, but some new evidence highlights its role in the regulation of reproductive functions. In fact, this protein has been detected at testicular level in the tubular and interstitial compartments of several vertebrate species, and previous research has demonstrated that GHRL affects various aspects of spermatogenesis and steroidogenesis. GHRL clearly plays an inhibitory role in mammalian reproduction, in contrast GHRL stimulates reproductive functions in non mammalian vertebrate. We have focused our attention on the comparative aspect of GHRL, thus studying its expression in an amphibian seasonal breeder, Pelophylax esculentus, to verify the presence and localization, of Ghrl transcript variations during the frog reproductive cycle, in order to demonstrate that Pelophylax esculentus may represent a useful animal model to assess the role of GHRL in male fertility.

Low free testosterone predicts frailty in older men: the health in men study

CONTEXT

The prevalence of frailty increases, whereas testosterone decreases, as men age. Low testosterone may be a risk factor for development of this syndrome.

OBJECTIVE

Our objective was to determine whether testosterone levels are associated with frailty.

DESIGN

We conducted a prospective cohort study.

SETTING AND PARTICIPANTS

Between 2001 and 2004, frailty was assessed in 3616 community-dwelling men aged 70-88 yr. Frailty was reassessed in 1586 men aged 76-93 yr in 2008-2009.

MAIN OUTCOME MEASURES

Frailty was assessed with the FRAIL scale, comprising five domains: fatigue, difficulty climbing a flight of stairs, difficulty walking more than 100 m, more than five illnesses present, or weight loss greater than 5%. Testosterone, SHBG, and LH were assayed at baseline. Free testosterone was calculated using mass action equations.

RESULTS

At baseline, 15.2% of men (n = 548) were frail (at least three deficits), increasing to 23.0% (n = 364) at follow-up. At baseline, each 1 sd decrease in total or free testosterone level was associated with increased odds of frailty [odds ratio (OR) = 1.23; 95% confidence interval (CI) = 1.11-1.38, and OR = 1.29; 95% CI = 1.15-1.44 for total and free testosterone, respectively]. Lower LH was associated with reduced odds of frailty (OR = 0.88; 95% CI = 0.81-0.95). Adjustments were made for age, body mass index, smoking, diabetes, social support, and other covariates. At follow-up, only lower free testosterone levels (OR = 1.22; 95% CI = 1.05-1.42) predicted frailty.

CONCLUSIONS

Lower free testosterone was independently associated with frailty at baseline and follow-up. Randomized trials should explore whether testosterone therapy can prevent the development of frailty.

Sex steroids deficiency impairs glucose transporter 4 expression and its translocation through defective Akt phosphorylation in target tissues of adult male rat

There is a substantial body of evidence suggesting that altered level of sex steroids in male is associated with insulin resistance and type 2 diabetes mellitus. However, the mechanism of this effect is not apparent. Our recent study indicated that testosterone deprivation decreases insulin receptor expression and glucose oxidation in insulin target tissues. The present study was designed to assess the impact of deficiency of testosterone and estradiol on Akt phosphorylation, glucose transporter expression, and glucose uptake in skeletal muscle, adipose tissue, and liver of adult male rat. Adult male albino rats of Wistar strain were orchidectomized and supplemented with testosterone (100 microg/100 g body weight per day), estradiol (5 microg/100 g body weight per day), and their combination (100 microg testosterone plus 5 microg estradiol per 100 g body weight per day) for 15 days from the 11th day postorchidectomy. On the day after the last treatment, animals were perfused; and blood was collected for the assay of plasma glucose, serum insulin, testosterone, and estradiol. Gastrocnemius muscle, adipose tissue, and liver were dissected out and used for the assay of various parameters such as Akt phosphorylation, glucose transporter (GLUT) 2 and 4 expression, glucose uptake, and glycogenic and glycogenolytic enzymes activity. Castration elevated the blood glucose level, which was accompanied by inhibitory effect on serum insulin, Akt phosphorylation, GLUT4 expression and its plasma membrane population, glucose uptake, glycogen and glycogen synthase activity, and stimulatory effect on GLUT2 expression and glycogen phosphorylase activity in tissues studied. After testosterone and its combination with estradiol supplementation to castrated rats, a normal pattern of all these parameters was restored. Estradiol administration to castrated rats increased the Akt phosphorylation without altering other parameters studied. It is concluded from the present study that sex steroids deficiency-induced defective glucose uptake in skeletal muscle and adipose tissue is mediated through defective Akt phosphorylation and GLUT4 expression in plasma membrane.

Relationship between ghrelin and the metabolic syndrome in the elderly: a longitudinal population-based study

CONTEXT

Ghrelin regulates energy homeostasis and may contribute to the development of the metabolic syndrome (MS) in the elderly.

OBJECTIVE

To study the relationship between ghrelin and the MS, IGF-I and life style factors over a 2-year follow-up.

DESIGN

Longitudinal population-based study, starting from 2002; 2 years follow-up.

PARTICIPANTS

Three hundred and thirteen (153 men/160 women) individuals living independently older than 70 years.

RESULTS

MS was found in 54.9% of men and 61% of women. In the 229 subjects available at follow-up, ghrelin was higher in men than in women at basal (P = 0.002) and 2-year follow-up (P = 0.004). Ghrelin decreased over time in both genders (P < 0.01). Ghrelin was lower in individuals showing MS compared to non-MS (P = 0.08), but this difference was more evident at 2-year follow-up (P = 0.016), mostly due to men with MS (P = 0.002) and even after adjustment for BMI, gender and age. Individuals with MS had an OR of 1.67 (95% CI: 1.0-2.78) for low ghrelin (< first tertile); when adjusting by BMI, gender and age, only high triglycerides with OR 1.8 (1.0-3.3), remained statistically significant among the MS components. IGF-I showed a positive correlation with ghrelin only in individuals without MS (r(s) 0.403, P < 0.001) with no gender differences; this relationship was not found in MS (r(s) 0.120, P = 0.129). A positive association of ghrelin was found with academic level, alcohol consumption and smoking.

CONCLUSIONS

Ghrelin is higher in old men in comparison to women and decreases over time with a steeper decline in subjects with MS; moreover, in these subjects ghrelin/IGF-I correlation is lost.

Estrogen elevates the peak overnight production rate of acylated ghrelin

CONTEXT

Acylated ghrelin is the putatively bioactive GH secretagogue.

HYPOTHESIS

Estradiol (E2) stimulates the synthesis rather than inhibits the metabolic clearance of acylated ghrelin.

SETTING

The study took place at an academic medical center.

SUBJECTS

Healthy postmenopausal women participated.

INTERVENTIONS

Interventions included prospectively randomized, double-blind separate-day iv infusions of saline or five graded doses of ghrelin in estrogen-deficient (n=12) and E2-supplemented (n=8) women.

OUTCOMES

Metabolic clearance rate (MCR), volume of distribution, half-life, and secretion rate of acylated ghrelin were assessed.

RESULTS

In pilot iv bolus ghrelin infusions, the median half-lives of acylated and total ghrelin were 21 and 36 min (P<0.01), MCRs 58 and 8.1 liters/kg.d (P<0.01), and volumes of distribution of 1.0 and 0.32 liters/kg (P<0.01), respectively. Transdermal E2 supplementation for 3 wk increased peak nighttime acylated ghrelin concentrations from 99+/-12 to 141+/-34 pg/ml (P=0.039). Exposure to E2 did not alter the linear relationships between 1) plasma acylated ghrelin concentration and ghrelin infusion rate (638+/-12 slope units), 2) MCR of acylated ghrelin and ghrelin infusion rate (10+/-2.5 slope units), and 3) MCR and plasma concentration of acylated ghrelin (0.017+/-0.004 slope units). These data predict peak nighttime production rates of acylated ghrelin of 3.8+/-0.9 (E2) and 1.9+/-0.2 (no E2) ng/kg.min (P=0.039).

CONCLUSION

Acylated ghrelin has a multifold larger distribution volume and MCR than total ghrelin. An estrogenic milieu augments synthesis and/or acylation of ghrelin peptide without altering its MCR.

Plasma ghrelin levels in males with idiopathic hypogonadotropic hypogonadism

It has recently been shown that ghrelin is a pleitropic modulator with effects on diverse biological functions, such as energy homeostasis and reproduction. In this study, ghrelin levels and its relationship between metabolic and biochemical parameters were investigated in male subjects with idiopathic hypogonadotropic hypogonadism (IHH). Patients in the study were composed of 33 men with IHH, and controls were composed of 36 healthy age-matched men. The patients' group had significantly higher waist/hip ratio (WHR), and lower testis volume, luteinizing hormone (LH), follicle stimuling hormone (FSH) and total testosterone (TT) levels when compared with controls. Plasma total ghrelin levels were significantly lower in patients than in controls (96.4 +/- 29.1 ng/ml vs. 146.1 +/- 28.9 ng/ml, P < 0.001, respectively). No correlation of ghrelin was found with body mass index, waist/hip ratio, homeostasis model assessment insulin resistance index, testis volume, LH, FSH and TT levels in both patients and controls. The present study showed that ghrelin levels were significantly lower in men with IHH than in controls. However, further studies are needed to better understand the relationships between ghrelin, and metabolic and reproductive systems.

Meal-related changes in ghrelin, peptide YY, and appetite in normal weight and overweight children

OBJECTIVE

Ghrelin and peptide YY (PYY) are two gut hormones that have effects on appetite. Our objectives were to characterize the patterns of secretion of these hormones in response to feeding in school-age children and determine whether there were differences between normal weight (NW) and overweight (OW) subjects.

METHODS AND PROCEDURES

This was a cross-sectional study at one tertiary care center. Subjects were 7- to 11-year-old healthy NW and OW volunteers recruited from local advertisements. Following an overnight fast, the subjects were given a standardized breakfast and lunch and had nine hourly blood samples for total ghrelin and total PYY. We assessed whether ghrelin and PYY levels changed from the preprandial to postprandial state and corresponded to reported hunger/satiety.

RESULTS

Hunger ratings were similar between the two groups throughout the study period. Ghrelin was not suppressed after eating, did not rise prior to the next meal, and did not correspond to hunger ratings in either group. PYY increased postprandially and decreased preprandially in the NW group, but OW children exhibited this pattern for only part of the day. PYY levels incompletely corresponded to reported satiety in the OW group.

DISCUSSION

Mixed meal consumption had little effect on ghrelin secretion and a variable effect on PYY secretion in young children in our study. Differences that were observed between the groups do not suggest that an abnormality in their secretion contributes to the development of obesity.

The prevalence of and risk factors for androgen deficiency in aging Taiwanese men

INTRODUCTION

Androgen deficiency in aging men has attracted much medical interest. Most studies on androgen deficiency have been conducted in Caucasian populations, and data from other ethnicities are lacking.

AIM

To evaluate the prevalence of and risk factors for androgen deficiency and symptomatic androgen deficiency in Taiwanese men over 40 years old.

METHODS

From August 2007 to April 2008, a free health screening was conducted by a medical center in Kaohsiung, Taiwan, and 819 men participated in this health screening. All participants completed a health questionnaire, received a detailed physical examination, and blood samples were drawn between 8:00 and 12:00 am.

MAIN OUTCOME MEASURES

Serum total testosterone (TT), albumin, and sex hormone-binding globulin levels were measured. The level of free testosterone (FT) was calculated. Clinical symptoms of androgen deficiency were assessed using the Androgen Deficiency in the Aging Male (ADAM) questionnaire.

RESULTS

Seven hundred thirty-four men who met the inclusion criteria (mean age 57.4 +/- 6.7 years; range: 43-87 years) were included in this study. The prevalence of androgen deficiency was 24.1% based on the criterion of TT level < 300 ng/dL, and 16.6% based on the criterion of both TT < 300 ng/dL and FT < 5 ng/dL. The prevalence of symptomatic androgen deficiency was 12.0%. Both prevalence of androgen deficiency and symptomatic androgen deficiency increased with age. Older age, obesity, and diabetes mellitus were independent risk factors for androgen deficiency and symptomatic androgen deficiency.

CONCLUSIONS

In a sample of aging Taiwanese men, a substantial proportion had androgen deficiency and symptomatic androgen deficiency, and the prevalence increased with age. Older age, obesity, and diabetes mellitus were independent risk factors for androgen deficiency and symptomatic androgen deficiency. Those potentially modifiable risk factors like obesity and diabetes mellitus should be prevented to maintain normal testosterone levels during aging in men.

Factors associated with fasting plasma ghrelin levels in children and adolescents

AIM: To measure plasma ghrelin levels in children and adolescents, analyze the associated factors, and investigate the role of ghrelin in obesity, insulin resistance and reproductive physiology.

METHODS: A total of 283 subjects aged 4.8-15.8 year were enrolled. Fasting blood samples were collected and plasma ghrelin levels were measured by radioimmunoassay. Fasting glucose (FG), fasting insulin (FI), baseline testosterone (T), estradiol (E2), prolactin (PRL), luteinizing hormone (LH), follicle-stimulating hormone (FSH), serum total cholesterol (TC), triglyceride (TG), alanine aminotransferase (ALT) and uric acid (UA) were measured. Body mass index (BMI), insulin resistance by homeostasis model (HOMA-IR) and beta cell function by homeostasis model (HOMA-β) were calculated.

RESULTS: The median ghrelin level was 290 ng/L (15.0-1325.0 ng/L). Bivariate correlation analysis showed that ghrelin levels were inversely correlated with BMI, ALT, TG, UA, LH, FI and HOMA-IR (all P < 0.05). No other significant correlation was found between ghrelin levels and age, gender, TC, E2, FSH, PRL, FG and HOMA-β. Stepwise multiple regression analysis showed that only BMI and FI were independent determinants of plasma ghrelin levels in these children and adolescents (P = 0.018 and P = 0.046, respectively), which explained 25.4% of the variance.

CONCLUSION: These data suggest that the lower ghrelin levels in obese subjects may be the result of obesity and hyperinsulinemia, which is very common in obese subjects. Moreover, ghrelin may regulate human reproductive physiology indirectly.