Genetic variations in the androgen receptor are associated with steroid concentrations and anthropometrics but not with muscle mass in healthy young men

OBJECTIVE: The relationship between serum testosterone (T) levels, muscle mass and muscle force in eugonadal men is incompletely understood. As polymorphisms in the androgen receptor (AR) gene cause differences in androgen sensitivity, no straightforward correlation can be observed between the interindividual variation in T levels and different phenotypes. Therefore, we aim to investigate the relationship between genetic variations in the AR, circulating androgens and muscle mass and function in young healthy male siblings. DESIGN: 677 men (25-45 years) were recruited in a cross-sectional, population-based sibling pair study. METHODS: Relations between genetic variation in the AR gene (CAGn, GGNn, SNPs), sex steroid levels (by LC-MS/MS), body composition (by DXA), muscle cross-sectional area (CSA) (by pQCT), muscle force (isokinetic peak torque, grip strength) and anthropometrics were studied using linear mixed-effect modelling. RESULTS: Muscle mass and force were highly heritable and related to age, physical activity, body composition and anthropometrics. Total T (TT) and free T (FT) levels were positively related to muscle CSA, whereas estradiol (E2) and free E2 (FE2) concentrations were negatively associated with muscle force. Subjects with longer CAG repeat length had higher circulating TT, FT, and higher E2 and FE2 concentrations. Weak associations with TT and FT were found for the rs5965433 and rs5919392 SNP in the AR, whereas no association between GGN repeat polymorphism and T concentrations were found. Arm span and 2D:4D finger length ratio were inversely associated, whereas muscle mass and force were not associated with the number of CAG repeats. CONCLUSIONS: Age, physical activity, body composition, sex steroid levels and anthropometrics are determinants of muscle mass and function in young men. Although the number of CAG repeats of the AR are related to sex steroid levels and anthropometrics, we have no evidence that these variations in the AR gene also affect muscle mass or function

Health promotion intervention in mental health care : design and baseline findings of a cluster preference randomized controlled trial

Background : Growing attention is given to the effects of health promotion programs targeting physical activity and healthy eating in individuals with mental disorders. The design of evaluation studies of public health interventions poses several problems and the current literature appears to provide only limited evidence on the effectiveness of such programs. The aim of the study is to examine the effectiveness and cost-effectiveness of a health promotion intervention targeting physical activity and healthy eating in individuals with mental disorders living in sheltered housing. In this paper, the design of the study and baseline findings are described. Methods/design : The design consists of a cluster preference randomized controlled trial. All sheltered housing organisations in the Flanders region (Belgium) were asked if they were interested to participate in the study and if they were having a preference to serve as intervention or control group. Those without a preference were randomly assigned to the intervention or control group. Individuals in the intervention group receive a 10-week health promotion intervention above their treatment as usual. Outcome assessments occur at baseline, at 10 and at 36 weeks. The primary outcomes include body weight, Body Mass Index, waist circumference, and fat mass. Secondary outcomes consist of physical activity levels, eating habits, health-related quality of life and psychiatric symptom severity. Cost-effectiveness of the intervention will be examined by calculating the Cost-Effectiveness ratio and through economic modeling. Twenty-five sheltered housing organisations agreed to participate. On the individual level 324 patients were willing to participate, including 225 individuals in the intervention group and 99 individuals in the control group. At baseline, no statistical significant differences between the two groups were found for the primary outcome variables. Discussion : This is the first trial evaluating both the effectiveness and cost-effectiveness of a health promotion intervention targeting physical activity and health eating in mental health care using a cluster preference randomized controlled design. The baseline characteristics already demonstrate the unhealthy condition of the study population

On line graphs and road networks

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Sex hormone-binding globulin as an independent determinant of cortical bone status in men at the age of peak bone mass

Context: Sex steroids are important determinants of the skeletal development, growth, and maintenance after achievement of peak bone mass. A large fraction of these hormones are bound by SHBG, and previous studies have shown that SHBG could be a determinant of bone characteristics. Objective: We investigated associations of serum SHBG levels with cortical and trabecular bone characteristics in young healthy men. Design and Settings: A total of 677 healthy male siblings aged 25-45 yr were recruited in a cross-sectional, population-based study. Main Outcomes: Areal bone parameters were assessed using dual-energy x-ray absorptiometry. Cortical bone parameters at the tibia and radius and trabecular vBMD at the radius were assessed using peripheral quantitative computed tomography. Serum testosterone, estradiol, and SHBG levels were measured using immunoassays. Results: Regression models including age, height, and weight showed that SHBG levels were positively associated with bone area at the hip and the whole body, but not with areal bone mineral density (BMD). Higher SHBG levels were associated with a larger cortical bone area and periosteal and endosteal circumferences at both the tibia and the radius, whereas trabecular volumetric BMD at the radius was negatively associated with SHBG levels. Associations persisted after adjustment for (free) sex steroid levels. No associations were found with cortical volumetric BMD or cortical thickness. Conclusion: In this population of healthy adult men at the age of peak bone mass, SHBG levels were positively associated with cortical bone size, independently from sex-steroid levels. This suggests a possible independent role of SHBG in the determination of adult bone size. (J Clin Endocrinol Metab 95: 1579-1586, 2010