Testosterone deficiency, insulin resistance and the metabolic syndrome

Total testosterone is the most valuable indicator of metabolic syndrome among various testosterone values in middle-aged Japanese men

Endogenous testosterone is known to be protective against metabolic syndrome (MetS) in men. While various markers of testosterone status including serum total testosterone (TT), free testosterone (measured using analogue ligand RIA [aFT]), calculated FT (cFT), calculated bioavailable testosterone (cbT), and sex-hormone binding globulin (SHBG) are recognized, it is unclear which of these markers are the most appropriate ones for the detection of MetS. We measured various testosterone values and metabolic markers in 249 healthy Japanese males (mean age 52.7 ± 7.4 yr) and analyzed which testosterone value is most associated with various metabolic parameters, including MetS as diagnosed according to the International Diabetes Federation (IDF, 2009 version) or with the Japanese criteria. Age had no effect on the TT level but significantly decreased aFT, cFT, and cbT levels and significantly increased the SHBG level. All testosterone values and SHBG showed weak inverse relationships with the metabolic markers BMI, waist circumference, insulin, HOMA-R, and HOMA-β, with the strongest relationship being to TT. TT and SHBG were significantly lower in men with MetS than in men without MetS. All testosterone values gradually decreased as the number of MetS components increased. Multivariate analysis revealed that the TT median value of <4.0 ng/mL was the only significant marker for the detection of MetS. These results were essentially the same regardless of whether the diagnosis of MetS was based on the IDF or the Japanese criteria. In conclusion, among various testosterone values, TT is the most reliable indicator of MetS in middle-aged Japanese men.

Sex Hormones and Their Receptors Regulate Liver Energy Homeostasis

The liver is one of the most essential organs involved in the regulation of energy homeostasis. Hepatic steatosis, a major manifestation of metabolic syndrome, is associated with imbalance between lipid formation and breakdown, glucose production and catabolism, and cholesterol synthesis and secretion. Epidemiological studies show sex difference in the prevalence in fatty liver disease and suggest that sex hormones may play vital roles in regulating hepatic steatosis. In this review, we summarize current literature and discuss the role of estrogens and androgens and the mechanisms through which estrogen receptors and androgen receptors regulate lipid and glucose metabolism in the liver. In females, estradiol regulates liver metabolism via estrogen receptors by decreasing lipogenesis, gluconeogenesis, and fatty acid uptake, while enhancing lipolysis, cholesterol secretion, and glucose catabolism. In males, testosterone works via androgen receptors to increase insulin receptor expression and glycogen synthesis, decrease glucose uptake and lipogenesis, and promote cholesterol storage in the liver. These recent integrated concepts suggest that sex hormone receptors could be potential promising targets for the prevention of hepatic steatosis.

Diet-induced obesity and low testosterone increase neuroinflammation and impair neural function

BACKGROUND

Low testosterone and obesity are independent risk factors for dysfunction of the nervous system including neurodegenerative disorders such as Alzheimer's disease (AD). In this study, we investigate the independent and cooperative interactions of testosterone and diet-induced obesity on metabolic, inflammatory, and neural health indices in the central and peripheral nervous systems.

METHODS

Male C57B6/J mice were maintained on normal or high-fat diet under varying testosterone conditions for a four-month treatment period, after which metabolic indices were measured and RNA isolated from cerebral cortex and sciatic nerve. Cortices were used to generate mixed glial cultures, upon which embryonic cerebrocortical neurons were co-cultured for assessment of neuron survival and neurite outgrowth. Peripheral nerve damage was determined using paw-withdrawal assay, myelin sheath protein expression levels, and Na+,K+-ATPase activity levels.

RESULTS

Our results demonstrate that detrimental effects on both metabolic (blood glucose, insulin sensitivity) and proinflammatory (cytokine expression) responses caused by diet-induced obesity are exacerbated by testosterone depletion. Mixed glial cultures generated from obese mice retain elevated cytokine expression, although low testosterone effects do not persist ex vivo. Primary neurons co-cultured with glial cultures generated from high-fat fed animals exhibit reduced survival and poorer neurite outgrowth. In addition, low testosterone and diet-induced obesity combine to increase inflammation and evidence of nerve damage in the peripheral nervous system.

CONCLUSIONS

Testosterone and diet-induced obesity independently and cooperatively regulate neuroinflammation in central and peripheral nervous systems, which may contribute to observed impairments in neural health. Together, our findings suggest that low testosterone and obesity are interactive regulators of neuroinflammation that, in combination with adipose-derived inflammatory pathways and other factors, increase the risk of downstream disorders including type 2 diabetes and Alzheimer's disease.

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.

Association of serum androgen concentrations with cardiovascular risk factors in elderly male patients with chronic systolic heart failure in China

OBJECTIVE

To survey the serum androgen concentrations and investigate the relationship between androgen levels and cardiovascular risk factors in elderly male patients with chronic systolic heart failure (HF) in China.

METHODS

106 consecutive male patients hospitalized for chronic systolic HF aged from 60 to 87 were enrolled. About 400 healthy age-matched men were compared as a control group. Total testosterone (TT), free testosterone (FT), dehydroepiandrosterone sulfate (DHEAS) and sex hormone binding globulin (SHBG) were measured. Differences of androgen levels between HF patients and healthy men were determined by t-test and associations of androgen with cardiovascular risk factors were evaluated by partial correlations analyses.

RESULTS

Compared with healthy men, TT, FT and DHEAS levels in patients with HF decreased, whereas SHBG level increased significantly (both p < 0.01). TT was negatively correlated with TC, TG and DBP (p < 0.05), FT was negatively correlated with TC, LDL-C and DBP (p < 0.05). SHBG correlated with BMI and smoking history positively (p < 0.05).

CONCLUSIONS

Level of bio-available testosterone decreased with advancing age, especially in men with HF. Men with low levels of bio-available testosterone had worse profiles of cardiovascular risk factors. Treatment of HF is still challenging and testosterone supplementation therapy may be an effective therapeutic option.

Testosterone replacement increases aged pulmonary vein and left atrium arrhythmogenesis with enhanced adrenergic activity

BACKGROUND

Aging and testosterone deficiency contribute to the pathogenesis of atrial fibrillation (AF). We determine the effects of testosterone replacement on the electrophysiology and arrhythmogenesis of pulmonary vein (PV) and left atrium (LA) in aged rabbits.

METHODS

Electrocardiography, heart rate variability, echocardiography, Western blot and conventional microelectrodes were used in aged rabbits (age, >2 years) with and without (control) testosterone treatment (10mg/kg, 12 weeks).

RESULTS

Testosterone-treated aged rabbits had longer corrected QT interval, higher low frequency/high frequency, greater left ventricle (LV) mass but lower LA total emptying fraction and LV ejection fraction than control rabbits. In tissue preparations, the spontaneous rate was faster for testosterone-treated PVs than for control PVs. Angiotensin II concentration-dependently increased the amplitude of delayed afterdepolarizations (DADs) in testosterone-treated PVs but only did so at the highest angiotensin II concentration (100 nM) in control PVs. Isoproterenol increased the incidence of early afterdepolarizations (EADs) and DADs in testosterone-treated PVs but not in control PVs. Testosterone-treated PVs had more H2O2-induced burst firing and EADs than control PVs. Testosterone-treated LAs had more isoproterenol-induced DADs and spontaneous activity than did control LAs. However, acetylcholine infusion and rapid atrial pacing (10-20 Hz) induced AF in control LAs but not in testosterone-treated LAs. In addition, as compared with control LAs, testosterone-treated LAs expressed more androgen receptor, β1-adrenergic receptor, and Cav 1.2 and less G protein-coupled receptor kinase-2 and Kv 4.2.

CONCLUSIONS

Testosterone replacement increased arrhythmogenesis in PV and LA by enhancing adrenergic activity in aged rabbits.

Effect of testosterone on markers of mitochondrial oxidative phosphorylation and lipid metabolism in muscle of aging men with subnormal bioavailable testosterone

OBJECTIVE

Recent studies have indicated that serum testosterone in aging men is associated with insulin sensitivity and expression of genes involved in oxidative phosphorylation (OxPhos), and that testosterone treatment increases lipid oxidation. Herein, we investigated the effect of testosterone therapy on regulators of mitochondrial biogenesis and markers of OxPhos and lipid metabolism in the skeletal muscle of aging men with subnormal bioavailable testosterone levels.

METHODS

Skeletal muscle biopsies were obtained before and after treatment with either testosterone gel (n=12) or placebo (n=13) for 6 months. Insulin sensitivity and substrate oxidation were assessed by euglycemic-hyperinsulinemic clamp and indirect calorimetry. Muscle mRNA levels and protein abundance and phosphorylation of enzymes involved in mitochondrial biogenesis, OxPhos, and lipid metabolism were examined by quantitative real-time PCR and western blotting.

RESULTS

Despite an increase in lipid oxidation (P<0.05), testosterone therapy had no effect on insulin sensitivity or mRNA levels of genes involved in mitochondrial biogenesis (PPARGC1A, PRKAA2, and PRKAG3), OxPhos (NDUFS1, ETFA, SDHA, UQCRC1, and COX5B), or lipid metabolism (ACADVL, CD36, CPT1B, HADH, and PDK4). Consistently, protein abundance of OxPhos subunits encoded by both nuclear (SDHA and UQCRC1) and mitochondrial DNA (ND6) and protein abundance and phosphorylation of AMP-activated protein kinase and p38 MAPK were unaffected by testosterone therapy.

CONCLUSION

The beneficial effect of testosterone treatment on lipid oxidation is not explained by increased abundance or phosphorylation-dependent activity of enzymes known to regulate mitochondrial biogenesis or markers of OxPhos and lipid metabolism in the skeletal muscle of aging men with subnormal bioavailable testosterone levels.

Synthetic therapeutic gene circuits in mammalian cells

In the emerging field of synthetic biology, scientists are focusing on designing and creating functional devices, systems, and organisms with novel functions by engineering and assembling standardised biological building blocks. The progress of synthetic biology has significantly advanced the design of functional gene networks that can reprogram metabolic activities in mammalian cells and provide new therapeutic opportunities for future gene- and cell-based therapies. In this review, we describe the most recent advances in synthetic mammalian gene networks designed for biomedical applications, including how these synthetic therapeutic gene circuits can be assembled to control signalling networks and applied to treat metabolic disorders, cancer, and immune diseases. We conclude by discussing the various challenges and future prospects of using synthetic mammalian gene networks for disease therapy.

Alzheimer's disease and type 2 diabetes: multiple mechanisms contribute to interactions

Obesity, metabolic syndrome, and type 2 diabetes (T2D) are related disorders with widespread deleterious effects throughout the body. One important target of damage is the brain. Persons with metabolic disorders are at significantly increased risk for cognitive decline and the development of vascular dementia and Alzheimer's disease. Our review of available evidence from epidemiologic, clinical, and basic research suggests that neural dysfunction from T2D-related disease results from several underlying mechanisms, including metabolic, inflammatory, vascular, and oxidative changes. The relationships between T2D and neural dysfunction are regulated by several modifiers. We emphasize 2 such modifiers, the genetic risk factor apolipoprotein E and an age-related endocrine change, low testosterone. Both factors are independent risk factors for Alzheimer's disease that may also cooperatively regulate pathologic interactions between T2D and dementia. Continued elucidation of the links between metabolic disorders and neural dysfunction promises to foster the development of effective therapeutic strategies.

The role of hypogonadism in Klinefelter syndrome

Klinefelter syndrome (KS) (47, XXY) is the most abundant sex-chromosome disorder, and is a common cause of infertility and hypogonadism in men. Most men with KS go through life without knowing the diagnosis, as only 25% are diagnosed and only a few of these before puberty. Apart from hypogonadism and azoospermia, most men with KS suffer from some degree of learning disability and may have various kinds of psychiatric problems. The effects of long-term hypogonadism may be diffi cult to discern from the gene dose effect of the extra X-chromosome. Whatever the cause, alterations in body composition, with more fat and less muscle mass and diminished bone mineral mass, as well as increased risk of metabolic consequences, such as type 2 diabetes and the metabolic syndrome are all common in KS. These findings should be a concern as they are not simply laboratory findings; epidemiological studies in KS populations show an increased risk of both hospitalization and death from various diseases. Testosterone treatment should be offered to KS patients from early puberty, to secure a proper masculine development, nonetheless the evidence is weak or nonexisting, since no randomized controlled trials have ever been published. Here, we will review the current knowledge of hypogonadism in KS and the rationale for testosterone treatment and try to give our best recommendations for surveillance of this rather common, but often ignored, syndrome.

Association of bone turnover markers with mortality in women referred to coronary angiography: the Ludwigshafen Risk and Cardiovascular Health (LURIC) study

We examined the association of fatal events with beta-crosslaps (β-CTX) and osteocalcin (OC) concentrations in women. We observed an independent association of β-CTX and OC concentrations with fatal events in women at high to intermediate cardiovascular risk.

INTRODUCTION

There is some evidence suggesting an association of β-CTX and OC with fatal events in men and frail elderly subjects. We aimed to examine the association of fatal events with β-CTX and OC in women.

METHODS

We measured β-CTX and OC in 986 women aged 65 (58-72) years referred to coronary angiography.

RESULTS

Compared to the first β-CTX quartile, the crude hazard ratios (HRs) for all-cause and cardiovascular mortality in the highest β-CTX quartile were 2.50 (1.65-3.81) and 3.28 (1.82-5.91), respectively. In multivariate adjusted models, HRs for all-cause and cardiovascular mortality in the highest β-CTX quartile were 1.72 (1.09-2.70) and 2.31 (1.24-4.32), respectively. The lowest 25-hydroxyvitamin D [25(OH)D] quartile was significantly associated with increased risk of all-cause and cardiovascular mortality in multivariate adjusted models. In those models, the highest β-CTX quartile was associated with an increased risk of all-cause and cardiovascular mortality. For OC concentrations, we found a reverse J-shaped association with noncardiovascular mortality. Using the first quartile as reference, crude and multivariate adjusted HRs for noncardiovascular mortality in the second and third OC quartile were 0.41 (0.19-0.90) [multivariate: 0.40 (0.18-0.88)] and 0.51 (0.25-1.06) [multivariate: 0.43 (0.20-0.94)], respectively. The lowest 25(OH)D quartile was associated with a trend towards increased risk of noncardiovascular mortality in multivariate analysis. In that analysis, OC quartile 2 and 3 were significantly associated with lower risk of noncardiovascular mortality.

CONCLUSIONS

We observed an independent association of high β-CTX with all-cause and cardiovascular mortality and a reverse J-shaped association of OC with noncardiovascular mortality.

Opposite effects of tamoxifen on metabolic syndrome-induced bladder and prostate alterations: a role for GPR30/GPER?

BACKGROUND

BPH and LUTS have been associated to obesity, hypogonadism, and metabolic syndrome (MetS). MetS-induced prostate and bladder alterations, including inflammation and tissue remodeling, have been related to a low-testosterone and high-estrogen milieu. In addition to ERs, GPR30/GPER is able to mediate several estrogenic non-genomic actions.

METHODS

Supplementing a subgroup of MetS rabbits with tamoxifen, we analyzed the in vivo effects on MetS-induced prostate and bladder alterations. The effects of selective ER/GPER ligands and GPER silencing on prostate inflammation were also studied in vitro using hBPH cells.

RESULTS

ERα, ERβ, and PR expression was upregulated in MetS bladder, where tamoxifen decreased ERα and PR expression, further stimulating ERβ. In addition, tamoxifen-dosing decreased MetS-induced overexpression of inflammatory and tissue remodeling genes. In prostate, sex steroid receptors, pro-inflammatory and pro-fibrotic genes were upregulated in MetS. However, tamoxifen did not affect them and even increased COX-2. In hBPH cells, 17β-estradiol increased IL-8 secretion, an effect blunted by co-treatment with GPER antagonist G15 but not by ER antagonist ICI 182,780, which further increased it. GPER agonist G1 dose-dependently (IC50  = 1.6 nM) induced IL-8 secretion. In vitro analysis demonstrated that GPER silencing reverted these stimulatory effects.

CONCLUSIONS

GPER can be considered the main mediator of estrogen action in prostate, whereas in bladder the mechanism appears to rely on ERα, as indicated by in vivo experiments with tamoxifen dosing. Limiting the effects of the MetS-induced estrogen action via GPER could offer new perspectives in the management of BPH/LUTS, whereas tamoxifen dosing showed potential benefits in bladder.

Testosterone levels and type 2 diabetes in men: current knowledge and clinical implications

The relationship between testosterone and diabetes is an important issue, given the fact that diabetes is becoming a fast-growing epidemic, the morbidity associated with which is more disabling than the disease itself. Various studies have demonstrated the increasing prevalence of hypogonadism in diabetic subjects, but whether this is a cause or effect is still an area of active research. The past couple of decades have witnessed an increasing rate of testosterone prescriptions, even though the relationship between testosterone therapy and cardiovascular effects is still not conclusive. The studies done in this regard have shown conflicting results, and there is still a dearth of long-term, follow-up studies in this field. This paper reviews in brief the postulated mechanisms, observational studies, and interventional data regarding the adverse effects of testosterone therapy in type 2 diabetes mellitus, stressing the cardiovascular risks.

Screening for hypopituitarism in 509 patients with traumatic brain injury or subarachnoid hemorrhage

We performed a screening on patients with traumatic brain injury (TBI) or subarachnoid hemorrhage (SAH) to determine the prevalence of post-traumatic hypopituitarism in neurorehabilitation in a cross-sectional, observational single-center study. In addition, the therapeutic consequences of our screening were analyzed retrospectively. From February 2006 to August 2009, patients between 18 and 65 years (n=509) with the diagnosis of TBI (n=340) or SAH (n=169) were screened within two weeks of admittance to neurorehabilitation as clinical routine. Blood was drawn to determine fasting cortisol, free thyroxine (fT4), prolactin, testosterone or estradiol, and insulin-like growth factor I (IGF-I). Patients with abnormalities in the screening or clinical signs of hypopituitarism received further stimulation tests: growth hormone releasing hormone -L-arginine-test and adrenocorticotrophic hormone (ACTH)-test (n=36); ACTH-test alone (n=26); or insulin tolerance test (n=56). In our screening of 509 patients, 28.5% showed lowered values in at least one hormone of the hypothalamus-pituitary axis and 4.5% in two or more axes. The most common disturbance was a decrease of testosterone in 40.7% of all men (in the following 13/131 men were given substitution therapy). Low fT4 was detected in 5.9% (n=3 were given substitution therapy). Low IGF-I was detected in 5.8%, low cortisol in 1.4%, and low prolactin in 0.2%; none were given substitution therapy. Further stimulation tests revealed growth hormone deficiency in 20.7% (n=19/92) and hypocortisolism in 23.7% (n=28/118). Laboratory values possibly indicating hypopituitarism (33%) were common but did not always implicate post-traumatic hypopituitarism. Laboratory values possibly indicating hypopituitarism were common in our screening but most patients were clinically not diagnosed as pituitary insufficient and did not receive hormone replacement therapy. A routine screening of all patients in neurorehabilitation without considering the time since injury, the severity of illness and therapeutic consequences seems not useful.

Activation of FGF2-FGFR signaling in the castrated mouse prostate stimulates the proliferation of basal epithelial cells

The prostate gland is unique in that it undergoes rapid regression following castration but regenerates completely once androgens are replaced. Residual ductal components play an important role in the regeneration of a fully functional prostate. In this study, to examine how androgen status affects prostate structure and components, we conducted histopathological studies of the involuted and regenerated mouse dorsolateral prostate (DLP). In the castrated mouse DLP, the number of luminal epithelial cells decreased in a time-dependent manner. On Day 14 postandrogen replacement, the number of luminal epithelial cells was completely restored to the baseline level. In contrast, the number of basal epithelial cells gradually increased in the castrated mouse prostate. The Ki67-labeling index of prostate basal epithelial cells was significantly increased after castration. The number of basal epithelial cells decreased to baseline after androgen replacement. After castration, mRNA expression levels of specific growth factors, such as Fgf2, Fgf7, Hgf, Tgfa, and Tgfb, were relatively abundant in whole mouse DLPs. In organ culture experiments, basal epithelial proliferation was recapitulated in the absence of dihydrotestosterone (DHT). The proliferation of basal epithelial cells in the absence of DHT was suppressed by treatment with an FGF receptor inhibitor (PD173074). Moreover, FGF2 treatment directly stimulated the proliferation of basal epithelial cells. Taken together, these data indicated that the FGF2-FGF receptor signal cascade in the prostate gland may be one of the pathways stimulating the proliferation of basal epithelial cells in the absence of androgens.

The spermatogenic effect of yacon extract and its constituents and their inhibition effect of testosterone metabolism

We screened the pharmacological effects of a 50% ethanol extract of Yacon tubers and leaves on spermatogenesis in rats. As a result, we found that Yacon tuber extracts increased sperm number and serum testosterone level in rats. It has been reported that the crude extract of Yacon tubers and leaves contain phenolic acids, such as, chlorogenic acid, ferulic acid and caffeic acid by HPLC/MS analysis. We were interested in the contributions made by phenolic acid, particularly chlorogenic acid of Yacon tuber extract to the spermatogenic activity. After administering Yacon tuber extract or chlorogenic acid to rats for 5 weeks, numbers of sperm in epididymis were increased by 34% and 20%, respectively. We also administered ferulic acid, which has been reported to be a metabolite of chlorogenic acid and a constituent of Yacon tuber extract to investigate its spermatogenic activity in rats. Yacon tuber extract and ferulic acid increased sperm numbers by 43% and 37%, respectively. And, Yacon tuber extract, and chlorogenic acid showed significantly inhibition effect of testoeterone degradation in rat liver homogenate. We considered that the spermatogenic effect of Yacon tuber extract might be related to phenolic compounds and their inhibitory effect of testosterone degradation. Yacon showed the possibility as ameliorable agents of infertility by sperm deficiency and late onset hypogonadism syndrome with low level of testosterone.

Relationship between Testicular Volume and Conventional or Nonconventional Sperm Parameters

Background. Reduced testicular volume (TV) (<12 cm(3)) is associated with lower testicular function. Several studies explored the conventional sperm parameters (concentration, motility, and morphology) and the endocrine function (gonadotropins and testosterone serum concentrations) in the patients with reduction of TV. No other parameters have been examined. Aim. This study aims at evaluating some biofunctional sperm parameters by flow cytometry in the semen of men with reduced TV compared with that of subjects with normal TV. Methods. 78 patients without primary scrotal disease were submitted to ultrasound evaluation of the testis. They were divided into two groups according to testicular volume: A Group, including 40 patients with normal testicular volume (TV > 15 cm(3)) and B Group, including 38 patients with reduced testicular volume (TV ≤ 12 cm(3)). All patients underwent serum hormone concentration, conventional and biofunctional (flow cytometry) sperm parameters evaluation. Results. With regard to biofunctional sperm parameters, all values (mitochondrial membrane potential, phosphatidylserine externalization, chromatin compactness, and DNA fragmentation) were strongly negatively correlated with testicular volume (P < 0.0001). Conclusions. This study for the first time in the literature states that the biofunctional sperm parameters worsen and with near linear correlation, with decreasing testicular volume.

Effects of age on male fertility

Later parenting is considered by many to have advantages, parents-to-be may feel themselves more stable to rear children. In addition, many men start a second family later in life. Thus, paternal age becomes an emerging issue. Aging affects male fertility by a scope of factors, which are not fully understood to date. Generally, the amount of produced sperm cells as well as their motility decreases with age, as testicular histological architecture deteriorates. Decreased fecundity and an increased risk for disturbed pregnancies occur with advancing paternal age. Some rare autosomal dominant pathologies are clearly related to paternal age. Altered patterns of epigenetics/gene expression in aging sperm seem to affect a range of neurocognitive disorders and also metabolic dyshomeostasis across generations. Such effects refer to men older than 40 years and may have impact on socio-economic issues. Nevertheless, councelling of older men seeking paternity should be patient-oriented and weigh statistical probabilities against the right for individual life-planning.

Metabolic syndrome--from the neurotrophic hypothesis to a theory

Metabolic syndrome (MetS) is a complex and heterogeneous disease characterized by central obesity, impaired glucose metabolism, dyslipidemia, arterial hypertension, insulin resistance and high-sensitivity C-reactive protein. In 2006, a neurotrophic hypothesis of the etiopathogenesis of MetS was launched. This hypothesis considered the neurotrophins a key factor in MetS development. Chronic inflammatory and/or psychoemotional distress provoke a series of neuroimmunoendocrine interactions such as increased tissue and plasma levels of proinflammatory cytokines and neurotrophins, vegetodystonia, disbalance of neurotransmitters, hormones and immunity markers, activation of the hypothalamo-pituitary-adrenal axis, insulin resistance, and atherosclerosis. An early and a late clinical stage in the course of MetS are defined. Meanwhile, evidence of supporting results from the world literature accumulates. This enables the transformation of the definition of the neurotrophic hypothesis into a neurotrophic theory of MetS. The important role of two neurotrophic factors, i.e. the nerve growth factor and brain-derived neurotrophic factor as well as of the proinflammatory cytokines, neurotransmitters, adipokines and, especially, of leptin for the development of MetS, obesity and type 2 diabetes mellitus is illustrated. There are reliable scientific arguments that the metabotrophic deficit due to reduced neurotrophins could be implicated in the pathogenesis of MetS, type 2 diabetes mellitus, and atherosclerosis as well. A special attention is paid to the activity of the hypothalamo-pituitary-adrenal axis after stress. The application of the neurotrophic theory of MetS could contribute to the etiological diagnosis and individualized management of MetS by eliminating the chronic distress, hyponeurotrophinemia and consequent pathology. It helps estimating the risk, defining the prognosis and implementing the effective prevention of this socially significant disease as evidenced by the dramatic recent growth of the world publication output on this interdisciplinary topic.

Testosterone: a metabolic hormone in health and disease

Testosterone is a hormone that plays a key role in carbohydrate, fat and protein metabolism. It has been known for some time that testosterone has a major influence on body fat composition and muscle mass in the male. Testosterone deficiency is associated with an increased fat mass (in particular central adiposity), reduced insulin sensitivity, impaired glucose tolerance, elevated triglycerides and cholesterol and low HDL-cholesterol. All these factors are found in the metabolic syndrome (MetS) and type 2 diabetes, contributing to cardiovascular risk. Clinical trials demonstrate that testosterone replacement therapy improves the insulin resistance found in these conditions as well as glycaemic control and also reduces body fat mass, in particular truncal adiposity, cholesterol and triglycerides. The mechanisms by which testosterone acts on pathways to control metabolism are not fully clear. There is, however, an increasing body of evidence from animal, cell and clinical studies that testosterone at the molecular level controls the expression of important regulatory proteins involved in glycolysis, glycogen synthesis and lipid and cholesterol metabolism. The effects of testosterone differ in the major tissues involved in insulin action, which include liver, muscle and fat, suggesting a complex regulatory influence on metabolism. The cumulative effects of testosterone on these biochemical pathways would account for the overall benefit on insulin sensitivity observed in clinical trials. This review discusses the current knowledge of the metabolic actions of testosterone and how testosterone deficiency contributes to the clinical disease states of obesity, MetS and type 2 diabetes and the role of testosterone replacement.

Fat boosts, while androgen receptor activation counteracts, BPH-associated prostate inflammation

BACKGROUND

Metabolic syndrome (MetS) and benign prostate hyperplasia (BPH) are often comorbid. Chronic inflammation, a determinant pathogenic factor for BPH, is a putative link between the two conditions.

METHODS

In a multi-center cohort of BPH patients (n = 244) who underwent prostatectomy, we evaluated whether MetS is associated with prostatic inflammation in BPH specimens. In addition, we investigated the in vitro inflammatory effects of metabolic insults on human prostatic myofibroblastic cells (hBPH).

RESULTS

Inflammatory infiltrates score (IS) in prostatectomy specimens showed a step-wise association with the number of MetS factors present (P = 0.001). After adjusting for age, reduced HDL cholesterol, and elevated triglycerides were the only factors significantly associated with IS. Increased IS was also significantly associated with hypogonadism. In an age- and testosterone (T)-adjusted model, dyslipidemia was still associated with IS. To investigate whether metabolic factors could directly trigger prostate inflammation, we performed preliminary studies in myofibroblastic hBPH. Among the different factors, oxidized low-density lipoprotein (oxLDL) showed the highest secretion of IL-8 (>10-fold)-a surrogate marker of prostate inflammation--as well as IL-6, and bFGF. Co-treatment with DHT significantly inhibited oxLDL-induced secretion of IL-8, whilst an AR-antagonist, bicalutamide, reversed DHT effects. DHT suppresses oxLDL receptor (LOX-1) expression.

CONCLUSIONS

Our data suggest that fats and insulin could have a detrimental effect on prostate health, boosting inflammation, a key pathogenic factor in BPH. Conversely, beneficial effects of DHT in counteracting lipid- and insulin-induced prostatic alterations, suggest that T-via its conversion into DHT-may have unexpected beneficial effects on prostate health.

Erectile dysfunction may be the first clinical sign of insulin resistance and endothelial dysfunction in young men

OBJECTIVES

The purpose of this study is to investigate the possible underlying pathogenesis of erectile dysfunction (ED) without well-known etiology in young men under the age of 40 years.

METHODS

192 patients and 33 normal controls were enrolled. ED was evaluated by using the International Index of Erectile Function-5 (IIEF-5) questionnaire. Traditional cardiovascular risk factors, hormone levels, and vascular parameters were measured. Insulin resistance (IR) was measured by homeostasis model assessment (HOMA).

RESULTS

Patients with ED had significantly higher levels of systolic blood pressure (SBP), high-sensitivity C-reactive protein (Hs-CRP), high Insulin resistance index (HOMA-IR) and carotid intima-media thickness (IMT), compared with controls. The brachial artery endothelium-dependent flow-mediated vasodilation (FMD) values were significantly lower in ED patients. By multivariate logistic regression analysis, FMD, SBP, Hs-CRP and HOMA-IR were significantly associated with ED. In receiver-operating characteristic (ROC) analysis, FMD was a significant predictor of ED (area under the curve (AUC) 0.933, p < 0.001). The cutoff value of FMD <10.4 % had sensitivity of 81.3 % and specificity of 100 %. HOMA-IR was also proven to be predictor of ED (AUC of HOMA-IR 0.759, p < 0.001).

CONCLUSIONS

ED may be the first clinical sign of endothelial dysfunction and a clinical marker of cardiovascular and metabolic diseases. Subclinical endothelial dysfunction and insulin resistance may be the underlying pathogenesis of ED in young patients without well-known etiology. Measurement of FMD, HOMA-IR can improve our ability to predict and treat ED, as well as subclinical cardiovascular disease early in young men.

Anthropometric, penile and testis measures in post-pubertal Italian males

BACKGROUND

Relationships between anthropometric measures, body proportions, weight and penile dimensions in young adult males have not been previously analyzed. Furthermore, although male fertility has declined in last decades, no data on testicular volume (the best surrogate measure for spermatogenic potential) are available for the general population of young men in Italy.

AIM

To analyze anthropometric measures and proportions, testicular volumes, and penile dimensions in a large cohort from the general population of young Italian men aged 18-19 yr. MATERIALS/SUBJECTS: We analyzed 2019 students aged 18-19 years for height, weight, body mass index (BMI), waist circumference, arm span, pubis-to-floor and crown-to-pubis length, and penile dimensions. Testicular volumes were measured by ultrasound in 776 subjects.

RESULTS

Thirty-six percent of the subjects had a pathological arm span-height difference (>3 cm) and 44.7% had a pathological pubis-to-floor/ crown-to-pubis ratio (≤ 0.92). The mean penis length was 8.9 ± 1.4 cm and the penis circumference was 9.5 ± 1.0 cm. BMI was positively associated with arm span-height difference and negatively with penis length; 23.2% of the subjects had low mean testicular volume (<12 ml).

CONCLUSIONS

The findings highlight a strong influence of BMI on skeletal proportions and penis length, identify a large proportion of subjects with testicular hypotrophy at risk for future fertility, and suggest to consider worldwide studies to redefine normal values for arm span-height difference and upper/ lower body segment ratio.

Independent effects of testosterone on lipid oxidation and VLDL-TG production: a randomized, double-blind, placebo-controlled, crossover study

Low testosterone (T) levels in men have been shown to predict development of the metabolic syndrome, but the effects of T on lipid metabolism are incompletely understood. In a randomized, double-blind, placebo-controlled, crossover study, 12 healthy, young males received gonadotropin-releasing hormone agonist treatment 1 month prior to 3 of 4 trial days to induce castrate levels of T. On trial days, T gel was applied to the body containing either high or low physiological T dose or placebo. On the 4th trial day, participants constituted their own eugonadal controls. Each study comprised a 5-h basal period and a 3-h hyperinsulinemic-euglycemic clamp. Short-term hypogonadism did not affect VLDL triglyceride (TG) secretion, nor did it affect VLDL-TG concentrations. It was, however, characterized by lower total lipid oxidation. In addition, acute rescue with high physiological T increased VLDL-TG secretion during both basal and clamp conditions. These data show that T can act through fast nongenomic pathways in the liver. In addition, the early hypogonadal state is characterized by decreased total lipid oxidation, but whether these changes represent early hypogonadal metabolic dysfunction warrants further investigations. T is not a major determinant of resting VLDL-TG kinetics in men.

Similar reference intervals for total testosterone in healthy young and elderly men: results from the Odense Androgen Study

CONTEXT

Ageing in men is associated with changes in levels of sex hormones.

OBJECTIVE

To evaluate differences in sex hormones in young and elderly men and the significance of comorbidity and fat mass on sex hormones in elderly men.

DESIGN

Cross-sectional.

PATIENTS

Seven hundred and eighty-three men aged 20-29 years and 600 men aged 60-74 years randomly recruited from the background population.

MEASUREMENTS

Sex hormones and sex hormone-binding globulin (SHBG) were measured, and reference intervals were determined in healthy individuals in both groups and in elderly men stratified according to whether they were obese or lean (waist circumference ≥102 cm).

RESULTS

Sex hormones were lower and SHBG higher in elderly men compared with the young cohort. Lower cut-offs for total testosterone (TT) in healthy, young and elderly men were similar [Lower cut-off (95% CI): Young: 11·7 (11·2-12·1) vs elderly: 11·2 (10·3-12·1) nmol/l], but lower and higher cut-offs of bioavailable testosterone (BT) and free testosterone (FT) were higher in young men. Higher levels of androgens were found in healthy elderly men compared with those with a chronic disease or obesity. Androgens were inversely associated with central fat mass (CFM), whereas SHBG was inversely and directly associated with CFM and lower extremity fat mass, respectively, in both young and elderly men.

CONCLUSION

Reference intervals for TT were comparable in healthy young and elderly men, but reference intervals for FT and BT were lower in elderly men due to higher levels of SHBG. Androgens and SHBG were lower in elderly men with chronic disease and inversely associated with CFM.

Androgen receptor agonism promotes an osteogenic gene program in preadipocytes

Androgens regulate body composition by interacting with the androgen receptor (AR) to control gene expression in a tissue-specific manner. To identify novel regulatory roles for AR in preadipocytes, we created a 3T3-L1 cell line stably expressing human AR. We found AR expression is required for androgen-mediated inhibition of 3T3-L1 adipogenesis. This inhibition is characterized by decreased lipid accumulation, reduced expression of adipogenic genes, and induction of genes associated with osteoblast differentiation. Collectively, our results suggest androgens promote an osteogenic gene program at the expense of adipocyte differentiation.

Circulating free testosterone in obese men after bariatric surgery increases in parallel with insulin sensitivity

BACKGROUND AND AIM

Male hypogonadism has been linked to obesity and diabetes. We aimed to study the association of changes in insulin sensitivity and testosterone levels in severe obese patients submitted to bariatric surgery.

SUBJECTS AND METHODS

Prospective intervention study with twenty consecutive patients who underwent bariatric surgery studied before and after significant weight loss. Serum testosterone, SHBG, fasting glucose, and insulin were measured among others. Free testosterone was calculated with the Vermeulen formula and insulin sensitivity with the homeostatic model assessment (HOMA).

RESULTS

At baseline, thirteen patients had low total testosterone levels, whereas eight of these patients also had free testosterone levels below the reference range obtained from the control group. After bariatric surgery total testosterone, SHBG, and free testosterone significantly increased and achieved normal values in all evaluated patients. Insulin sensitivity improved in all of them. Multivariate linear regression showed that changes in fasting glucose (β=-1.868, p=0.001), insulin (β=-3.782, p=0.001), weight (β=-0.622, p=0.002), and SHBG (β=-0.635, p=0.022) were associated with changes in free testosterone (adjusted R2=0.936, F=26.613, p=0.001). When insulin resistance calculated by HOMA was in the model instead of insulin and glucose, it also was associated (β=-3.488, p=0.008) with free testosterone (adjusted R2=0.821, F=11.111, p=0.005).

CONCLUSIONS

Circulating tes tos terone in obese men increases after bariatric surgery in parallel with an improvement in insulin sensitivity.

Pharmaceutically controlled designer circuit for the treatment of the metabolic syndrome

Synthetic biology has significantly advanced the design of genetic devices that can reprogram cellular activities and provide novel treatment strategies for future gene- and cell-based therapies. However, many metabolic disorders are functionally linked while developing distinct diseases that are difficult to treat using a classic one-drug-one-disease intervention scheme. For example, hypertension, hyperglycemia, obesity, and dyslipidemia are interdependent pathologies that are collectively known as the metabolic syndrome, the prime epidemic of the 21st century. We have designed a unique therapeutic strategy in which the clinically licensed antihypertensive drug guanabenz (Wytensin) activates a synthetic signal cascade that stimulates the secretion of metabolically active peptides GLP-1 and leptin. Therefore, the signal transduction of a chimeric trace-amine-associated receptor 1 (cTAAR1) was functionally rewired via cAMP and cAMP-dependent phosphokinase A (PKA)-mediated activation of the cAMP-response element binding protein (CREB1) to transcription of synthetic promoters containing CREB1-specific cAMP response elements. Based on this designer signaling cascade, it was possible to use guanabenz to dose-dependently control expression of GLP-1-Fc(mIgG)-Leptin, a bifunctional therapeutic peptide hormone that combines the glucagon-like peptide 1 (GLP-1) and leptin via an IgG-Fc linker. In mice developing symptoms of the metabolic syndrome, this three-in-one treatment strategy was able to simultaneously attenuate hypertension and hyperglycemia as well as obesity and dyslipidemia. Using a clinically licensed drug to coordinate expression of therapeutic transgenes combines drug- and gene-based therapies for coordinated treatment of functionally related metabolic disorders.

A randomized, double-blind, placebo-controlled trial of testosterone gel on body composition and health-related quality-of-life in men with hypogonadal to low-normal levels of serum testosterone and symptoms of androgen deficiency over 6 months with 12 months open-label follow-up

INTRODUCTION

The clinical significance of low to low-normal testosterone (T) levels in men remains debated.

AIM

To analyze the effects of raising serum T on lean body mass (LBM), fat mass (FM), total body mass, and health-related quality-of-life (HRQoL).

METHODS

Randomized, double-blind, placebo-controlled study. Men, aged 50-80 years, with serum total T<15 nmol/L and bioavailable T < 6.68 nmol/L, and a Aging Males' Symptoms (AMS) total score >36, received 6 months treatment with transdermal 1% T gel (5-7.5 mg/day; n =183) or placebo gel (n =179), followed by 12 months open-label with T in all.

RESULTS

After 6 months, LBM increased in T- treated patients by 1.28 ± 0.15 kg (mean ± SE) and FM decreased by 1.16 ± 0.16 kg, with minor changes with placebo (LBM +0.02 ± 0.10 kg and FM -0.14 ± 0.12 kg; all p < 0.001, T group vs. placebo). Changes were largely similar across subgroups of age, baseline total testosterone, and baseline BMI. Total HRQoL improved compared with placebo (p < 0.05, T group vs. placebo).

CONCLUSIONS

Six months 1% T gel improved body composition and HRQoL in symptomatic men with low to low-normal T, with further improvements over the following 12 months.

The androgen receptor in health and disease

Androgens play pivotal roles in the regulation of male development and physiological processes, particularly in the male reproductive system. Most biological effects of androgens are mediated by the action of nuclear androgen receptor (AR). AR acts as a master regulator of downstream androgen-dependent signaling pathway networks. This ligand-dependent transcriptional factor modulates gene expression through the recruitment of various coregulator complexes, the induction of chromatin reorganization, and epigenetic histone modifications at target genomic loci. Dysregulation of androgen/AR signaling perturbs normal reproductive development and accounts for a wide range of pathological conditions such as androgen-insensitive syndrome, prostate cancer, and spinal bulbar muscular atrophy. In this review we summarize recent advances in understanding of the epigenetic mechanisms of AR action as well as newly recognized aspects of AR-mediated androgen signaling in both men and women. In addition, we offer a perspective on the use of animal genetic model systems aimed at eventually developing novel therapeutic AR ligands.

Testosterone and farnesoid X receptor agonist INT-747 counteract high fat diet-induced bladder alterations in a rabbit model of metabolic syndrome

In the male, metabolic syndrome (MetS) is associated to an increased risk of benign prostatic hyperplasia (BPH) and lower urinary tract symptoms (LUTS). A recently established rabbit model of high fat diet (HFD)-induced MetS showed hypogonadism and the presence of prostate gland alterations, including inflammation, hypoxia and fibrosis. The present study investigated whether HFD-induced MetS might also alter bladder structure and function. Testosterone and the farnesoid X receptor (FXR) agonist INT-747, were evaluated for possible effects on HFD bladder. MetS rabbits develop bladder alterations, including fibrosis (reduced muscle/fiber ratio), hypoxia [2-fold increase as compared to regular diet (RD) group], low-grade inflammation (increased leukocyte infiltration and inflammatory markers) and RhoA/ROCK hyperactivity. Bladder strips from HFD rabbits, pre-contracted with carbachol, showed an overactive response to the selective ROCK inhibitor Y-27632. All these HFD-induced bladder alterations were partially blunted by testosterone and almost completely reverted by INT-747. Both treatments prevented some MetS features (glucose intolerance and visceral fat increase), thus suggesting that their effects on bladder could be ascribed to an improvement of the metabolic and/or hypogonadal state. However, a pathogenetic role for hypogonadism has been ruled out as GnRH analog-induced hypogonadal rabbits, fed a regular diet, did not show any detectable bladder alterations. In addition, INT-747 did not revert the MetS-induced hypogonadal state. FXR mRNA was highly expressed in rabbit bladder and positively associated with visceral fat increase. A direct effect of INT-747 on bladder smooth muscle was further suggested by inhibition of RhoA/ROCK-mediated activity by in vitro experiments on isolated cells. In conclusion, HFD-related MetS features are associated to bladder derangements, which are ameliorated by testosterone or INT-747 administration. INT-747 showed the most marked effects in counteracting MetS-related RhoA/ROCK overactivity, thus opening novel therapeutic opportunities for this drug.

Feed-forward inhibition of androgen receptor activity by glucocorticoid action in human adipocytes

We compared transcriptomes of terminally differentiated mouse 3T3-L1 and human adipocytes to identify cell-specific differences. Gene expression and high content analysis (HCA) data identified the androgen receptor (AR) as both expressed and functional, exclusively during early human adipocyte differentiation. The AR agonist dihydrotestosterone (DHT) inhibited human adipocyte maturation by downregulation of adipocyte marker genes, but not in 3T3-L1. It is interesting that AR induction corresponded with dexamethasone activation of the glucocorticoid receptor (GR); however, when exposed to the differentiation cocktail required for adipocyte maturation, AR adopted an antagonist conformation and was transcriptionally repressed. To further explore effectors within the cocktail, we applied an image-based support vector machine (SVM) classification scheme to show that adipocyte differentiation components inhibit AR action. The results demonstrate human adipocyte differentiation, via GR activation, upregulates AR but also inhibits AR transcriptional activity.

Combination of low free testosterone and low vitamin D predicts mortality in older men referred for coronary angiography

CONTEXT

Low levels of 25-hydroxyvitamin D [25(OH)D] and free testosterone (FT) are both associated with increased mortality. Experimental studies show a complex interplay of vitamin D and androgen metabolism suggesting that a deficiency of both hormones may be associated with a particularly adverse clinical outcome.

OBJECTIVE

To evaluate the impact of parallel FT and 25(OH)D deficiency in a large cohort of older men.

DESIGN

We measured total testosterone (TT), sex hormone-binding globulin and 25(OH)D levels in 2069 men who were routinely referred for coronary angiography (1997-2000).

MAIN OUTCOME MEASURES

Cox proportional hazard ratios (HRs) (with 95% confidence intervals) for mortality from all causes, cardiovascular and noncardiovascular causes according to combined deficiency of FT and 25(OH)D.

RESULTS

In multivariate-adjusted analyses, we found an increased risk for all-cause mortality, cardiovascular and noncardiovascular mortality for men in the lowest FT [HR 1·26 (1·03-1·54), 1·24 (0·96-1·60) and 1·39 (1·00-1·93), respectively] and 25(OH)D quartile [HR 1·77 (1·47-2·13), 1·65 (1·29-2·10) and 1·89 (1·38-2·60) respectively] compared with men in higher FT and 25(OH)D quartiles. There was no independent association of TT levels with mortality. Multivariate-adjusted HRs progressively increased with the number of hormones (FT and 25(OH)D) in the lowest quartile [0 vs 2 hormone deficiencies: 2·11 (1·60-2·79) for all cause, 1·77 (1·23-2·55) for cardiovascular and 2·33 (1·45-3·47) for noncardiovascular mortality, respectively].

CONCLUSION

A combined deficiency of FT and 25(OH)D is significantly associated with fatal events in a large cohort of men referred for coronary angiography.

A potential role for insulin resistance in experimental pulmonary hypertension

Patients with pulmonary arterial hypertension have increased prevalence of insulin resistance. We aimed to determine whether metabolic defects are associated with bone morphogenic protein receptor type 2 (Bmpr2) mutations in mice, and whether these may contribute to pulmonary vascular disease development. Metabolic phenotyping was performed on transgenic mice with inducible expression of Bmpr2 mutation, R899X. Phenotypic penetrance in Bmpr2(R899X) was assessed in a high-fat diet model of insulin resistance. Alterations in glucocorticoid responses were assessed in murine pulmonary microvascular endothelial cells and Bmpr2(R899X) mice treated with dexamethasone. Compared to controls, Bmpr2(R899X) mice showed increased weight gain and demonstrated insulin resistance as assessed by the homeostatic model assessment insulin resistance (1.0 ± 0.4 versus 2.2 ± 1.8) and by fat accumulation in skeletal muscle and decreased oxygen consumption. Bmpr2(R899X) mice fed a high-fat diet had strong increases in pulmonary hypertension penetrance (seven out of 11 versus three out of 11). In cell culture and in vivo experiments, Bmpr2 mutation resulted in a combination of constitutive glucocorticoid receptor activation and insensitivity. Insulin resistance is present as an early feature of Bmpr2 mutation in mice. Exacerbated insulin resistance through high-fat diet worsened pulmonary phenotype, implying a possible causal role in disease. Impaired glucocorticoid responses may contribute to metabolic defects.

Impact of five nights of sleep restriction on glucose metabolism, leptin and testosterone in young adult men

BACKGROUND

Sleep restriction is associated with development of metabolic ill-health, and hormonal mechanisms may underlie these effects. The aim of this study was to determine the impact of short term sleep restriction on male health, particularly glucose metabolism, by examining adrenocorticotropic hormone (ACTH), cortisol, glucose, insulin, triglycerides, leptin, testosterone, and sex hormone binding globulin (SHBG).

METHODOLOGY/PRINCIPAL FINDINGS

N = 14 healthy men (aged 27.4±3.8, BMI 23.5±2.9) underwent a laboratory-based sleep restriction protocol consisting of 2 baseline nights of 10 h time in bed (TIB) (B1, B2; 22:00-08:00), followed by 5 nights of 4 h TIB (SR1-SR5; 04:00-08:00) and a recovery night of 10 h TIB (R1; 22:00-08:00). Subjects were allowed to move freely inside the laboratory; no strenuous activity was permitted during the study. Food intake was controlled, with subjects consuming an average 2000 kcal/day. Blood was sampled through an indwelling catheter on B1 and SR5, at 09:00 (fasting) and then every 2 hours from 10:00-20:00. On SR5 relative to B1, glucose (F(1,168) = 25.3, p<0.001) and insulin (F(1,168) = 12.2, p<0.001) were increased, triglycerides (F(1,168) = 7.5, p = 0.007) fell and there was no significant change in fasting homeostatic model assessment (HOMA) determined insulin resistance (F(1,168) = 1.3, p = 0.18). Also, cortisol (F(1,168) = 10.2, p = 0.002) and leptin (F(1,168) = 10.7, p = 0.001) increased, sex hormone binding globulin (F(1,167) = 12.1, p<0.001) fell and there were no significant changes in ACTH (F(1,168) = 0.3, p = 0.59) or total testosterone (F(1,168) = 2.8, p = 0.089).

CONCLUSIONS/SIGNIFICANCE

Sleep restriction impaired glucose, but improved lipid metabolism. This was associated with an increase in afternoon cortisol, without significant changes in ACTH, suggesting enhanced adrenal reactivity. Increased cortisol and reduced sex hormone binding globulin (SHBG) are both consistent with development of insulin resistance, although hepatic insulin resistance calculated from fasting HOMA did not change significantly. Short term sleep curtailment leads to changes in glucose metabolism and adrenal reactivity, which when experienced repeatedly may increase the risk for type 2 diabetes.

A low level of serum total testosterone is independently associated with nonalcoholic fatty liver disease

BACKGROUND

The association between low serum testosterone levels, visceral adipose tissue (VAT), and metabolic syndrome is now well known. However, the relationship between hepatic steatosis and serum testosterone levels has not been extensively studied. Our aim was to investigate the association of serum total testosterone levels with nonalcoholic fatty liver disease (NAFLD), adjusting for the influence of VAT and insulin resistance.

METHODS

This study is a retrospective observational cross-sectional one of healthy Korean men and was conducted at the Seoul National University Hospital Healthcare System Gangnam Center. We used data obtained from 495 men who were at least 20 years of age and who had undergone blood testing, abdominal computed tomography, and ultrasonography. Multiple logistic regression analysis was used to explore the association of serum total testosterone levels with NAFLD.

RESULTS

Men in the low serum testosterone quintile were at a higher risk for NAFLD than men in the highest serum testosterone quintile. After adjusting for age, smoking, diabetes, exercise, BMI, triglycerides, and high-density-lipoprotein cholesterol, subjects with serum testosterone levels in the lowest quintile had an odds ratio (OR) (95% confidence interval (CI)) of 5.12 (2.43-10.77) for NAFLD (p value, 0.0004). The inverse association between serum testosterone and NAFLD was attenuated by further adjustment for variables including VAT; however, it remained statistically significant (OR (95% CI): 4.52 (2.09-9.80) in the lowest quintile; p value=0.004).

CONCLUSIONS

A low serum total testosterone level was independently associated with NAFLD. This report is the first one suggesting the association remains unchanged even after controlling for VAT and insulin resistance.

Multifaceted role of insulin-like growth factors and mammalian target of rapamycin in skeletal muscle

This review describes the current literature on the interaction between insulin-like growth factors, endocrine hormones, and branched-chain amino acids on muscle physiology in healthy young individuals and during select pathologic conditions. Emphasis is placed on the mechanism by which physical and hormonal signals are transduced at the cellular level to either grow or atrophy skeletal muscle. The key role of the mammalian target of rapamycin and its ability to respond to hypertrophic and atrophic signals informs our understanding how a combination of physical, nutritional, and pharmacologic therapies may be used in tandem to prevent or ameliorate reductions in muscle mass.

Vitamin D and fertility: a systematic review

BACKGROUND

Vitamin D has been well-known for its function in maintaining calcium and phosphorus homeostasis and promoting bone mineralization. There is some evidence that in addition to sex steroid hormones, the classic regulators of human reproduction, vitamin D also modulates reproductive processes in women and men.

AIM

The aim of this review was to assess the studies that evaluated the relationship between vitamin D and fertility in women and men as well as in animals.

METHODS

We performed a systematic literature search in Pubmed for relevant English language publications published until October 2011.

RESULTS AND DISCUSSION

The vitamin D receptor (VDR) and vitamin D metabolizing enzymes are found in reproductive tissues of women and men. Vdr knockout mice have significant gonadal insufficiency, decreased sperm count and motility, and histological abnormalities of testis, ovary and uterus. Moreover, we present evidence that vitamin D is involved in female reproduction including IVF outcome (clinical pregnancy rates) and polycystic ovary syndrome (PCOS). In PCOS women, low 25-hydroxyvitamin D (25(OH)D) levels are associated with obesity, metabolic, and endocrine disturbances and vitamin D supplementation might improve menstrual frequency and metabolic disturbances in those women. Moreover, vitamin D might influence steroidogenesis of sex hormones (estradiol and progesterone) in healthy women and high 25(OH)D levels might be associated with endometriosis. In men, vitamin D is positively associated with semen quality and androgen status. Moreover, vitamin D treatment might increase testosterone levels. Testiculopathic men show low CYP21R expression, low 25(OH)D levels, and osteoporosis despite normal testosterone levels.

Tissue- and cell-specific functions of the androgen receptor revealed through conditional knockout models in mice

This review aims to evaluate the contribution of individual cell-selective knockout models to our current understanding of androgen action. Cre/loxP technology has allowed the generation of cell-selective knockout models targeting the androgen receptor (AR) in distinct putative target cells in a wide variety of organs and tissues including: testis, ovary, accessory sex tissues, muscle, bone, fat, liver, skin and myeloid tissue. In some androgen-regulated processes such as spermatogenesis and folliculogenesis this approach has lead to the identification of a key cellular mediator of androgen action (Sertoli and granulosa cells, respectively). In many target tissues, however, the final response to androgens appears to be more complex. Here, cell-selective knockout technology offers a platform upon which we can begin to unravel the more complex interplay and signaling pathways of androgens. A prototypic example is the analysis of mesenchymal-epithelial interactions in many accessory sex glands. Furthermore, for some actions of testosterone, in which part of the effect is mediated by the active metabolite 17β-estradiol, conditional knockout technology offers a novel strategy to study the relative contribution of AR and estrogen receptor-mediated signaling. The latter approach has already resulted in a better understanding of androgen action in brain and bone. Finally, cell-selective knockout technology has generated valuable models to search for AR-controlled molecular mediators of androgen action, a strategy that has successfully been applied to the study of androgen action in the testis and in the epididymis. Although some conditional knockout models have provided clear answers to physiologic questions, it should be noted that others have pointed to unexpected complexities or technical limitations confounding interpretation of the results.

Control of adult stem cells in vivo by a dynamic physiological environment: diet-dependent systemic factors in Drosophila and beyond

Adult stem cells are inextricably linked to whole-body physiology and nutrient availability through complex systemic signaling networks. A full understanding of how stem cells sense and respond to dietary fluctuations will require identifying key systemic mediators, as well as elucidating how they are regulated and integrated with local and intrinsic factors across multiple tissues. Studies focused on the Drosophila germline have generated valuable insights into how stem cells are controlled by diet-dependent pathways, and increasing evidence suggests that diverse adult stem cell populations respond to nutrients through similar mechanisms. Systemic signals, including nutrients themselves and diet-regulated hormones such as Insulin/Insulin-like growth factor or steroid hormones, can directly or indirectly affect stem cell behavior by modifying local cell-cell communication or intrinsic factors. The physiological regulation of stem cells in response to nutritional status not only is a fascinating biological problem, but also has clinical implications, as research in this field holds the key to noninvasive approaches for manipulating stem cells in vivo. In addition, given the known associations between diet, stem cells, and cancer risk, this research may inspire novel anticancer therapies.