Veerle Bogaert

Fat Mass Is Negatively Associated with Cortical Bone Size in Young Healthy Male Siblings

CONTEXT Body weight has been associated with bone mass and bone size through shared genetic determination and environmental influences. Whereas lean mass exerts a positive influence on bone size, the relationship between fat and bone remains unclear. OBJECTIVE The objective of the present study was to investigate the individual influence of fat mass and lean mass on volumetric bone density and size in young healthy male siblings at age of peak bone mass. DESIGN This was a cross-sectional, population-based sibling pair study. PARTICIPANTS A total of 677 men (25-45 yr) were included in this study with 296 independent pairs of brothers. MAIN OUTCOME MEASURES Areal and volumetric bone parameters were determined using dual-energy X-ray absorptiometry (DXA) and peripheral quantitative computed tomography (pQCT). Body composition was determined by DXA. Sex steroids, leptin, and adiponectin were determined by immunoassay. RESULTS Total and regional fat mass were found to be inversely associated with areal bone mass and bone size, independent from lean mass (radius periosteal circumference beta: -0.29 +/- 0.04; P < 0.001). Lean mass was positively associated with bone size but inversely with cortical density at both tibia and radius (P < 0.01). The negative association between total fat mass and bone size was independent from sex steroid concentrations. Leptin but not adiponectin was inversely associated with bone size, but this was no longer significant after adjustment for body fat. CONCLUSIONS Increased fat mass is associated with smaller bone size, challenging the view of a high bone mass index as a protective factor for osteoporosis, whereas lean mass was a consistent positive determinant of bone size.

Serum Estradiol Is Associated With Volumetric BMD and Modulates the Impact of Physical Activity on Bone Size at the Age of Peak Bone Mass: A Study in Healthy Male Siblings

This study investigates determinants of peak bone mass (PBM) in healthy men, focusing on effects and interactions of parameters reflecting mechanical loading and sex steroids. Healthy male siblings (n = 677; 25–45 yr) were recruited in a cross‐sectional, population‐based study. Physical activity score was assessed by a self‐reported questionnaire. Cross‐sectional muscle area (CSMA) and bone parameters of radius (4% and 66% site) and tibia (66% site) were assessed using pQCT. Peak torque of biceps and quadriceps muscles was assessed by isokinetic dynamometry. Serum testosterone (T) and estradiol (E2) levels were measured using immunoassays; free hormone fractions were calculated. Relations between indices of bone strength, CSMA, muscle strength, and sex steroids were studied using linear mixed‐effects modeling. Physical activity, CSMA, and muscle strength were positively associated with indices of bone strength, except for volumetric BMD (vBMD). After controlling for age, weight, and height, free E2 levels were positively associated with trabecular and cortical vBMD, negatively associated with endosteal circumference at the radius, and positively associated with cortical vBMD at the tibia. In addition, positive interactions between physical activity and serum E2 concentrations were observed for bone size at the tibia. No associations between free T levels and pQCT bone parameters were found. In this population of healthy men at the age of PBM, parameters reflecting mechanical loading are confirmed as important determinants of bone size. E2, but not T, levels are positively associated with vBMD and modulate the impact of physical activity on bone size at the tibia.

Heritability of blood concentrations of sex-steroids in relation to body composition in young adult male siblings

Objective  Sex steroid concentrations in men are related to body composition and both are determined by genetic and environmental factors. This study investigates heritability estimates of sex steroid serum concentrations and body composition as well as the genetic and environmental components of their interrelation.

Adenoviral gene transfer of ABIN‐1 protects mice from TNF/galactosamine‐induced acute liver failure and lethality

Tumor necrosis factor (TNF) is a proinflammatory cytokine that plays a central role in acute and chronic hepatitis B and C infection and alcoholic liver disease as well as fulminant liver failure. TNF‐induced liver failure is characterized by parenchymal cell apoptosis and inflammation leading to liver cell necrosis. The transcription factor NF‐κB is believed to mediate at least part of the proinflammatory effects of TNF, and is therefore a favorite drug target. However, NF‐κB also suppresses TNF‐mediated hepatocyte apoptosis, implicating a potential cytotoxic effect of NF‐κB inhibitors in the liver. This dual function of NF‐κB emphasizes the need for therapeutics that can inhibit both TNF‐induced NF‐κB activation and cell death. Here we describe that adenoviral expression of the NF‐κB inhibitory protein ABIN‐1, but not an IκBα superrepressor (IκBαs), completely prevents lethality in the TNF/D‐(+)‐galactosamine–induced model of liver failure. Protection was associated with a significant decrease in TNF‐induced leukocyte infiltration as well as hepatocyte apoptosis. The differential effects of ABIN‐1 and IκBαs suggest a role for an NF‐κB independent function of ABIN‐1. Indeed, ABIN‐1 was found to prevent not only NF‐κB activation, but also apoptosis of cultured hepatocytes in response to TNF, explaining its protective effect against TNF‐induced liver failure. In conclusion, ABIN‐1 has a dual NF‐κB inhibitory and anti‐apoptotic activity in the liver, which might be of considerable interest for the treatment of inflammatory liver diseases. (HEPATOLOGY 2005;42:381–389.)

Early smoking is associated with peak bone mass and prevalent fractures in young, healthy men

Smoking is associated with lower areal bone mineral density (aBMD) and higher fracture risk, although most evidence has been derived from studies in elderly subjects. This study investigates smoking habits in relation to areal and volumetric bone parameters and fracture prevalence in young, healthy males at peak bone mass. Healthy male siblings (n = 677) at the age of peak bone mass (25 to 45 years) were recruited in a cross‐sectional population‐based study. Trabecular and cortical bone parameters of the radius and cortical bone parameters of the tibia were assessed using peripheral quantitative computed tomography (pQCT). Areal bone mass was determined using dual energy X‐ray absorptiometry (DXA). Sex steroids and bone markers were determined using immunoassays. Prevalent fractures and smoking habits were assessed using questionnaires. Self‐reported fractures were more prevalent in the current and early smokers than in the never smokers (p < .05), with a fracture prevalence odds ratio for early smokers of 1.96 (95% confidence interval 1.18–3.24) after adjustment for age, weight, educational level, and alcohol use and exclusion of childhood fractures. Current smoking was associated with a larger endosteal circumference (β = 0.027 ± 0.009, p = .016) and a decreased cortical thickness (β = −0.034 ± 0.01, p = .020) at the tibia. In particular, early smokers (≤16 years) had a high fracture risk and lower areal BMD, together with a lower cortical bone area at the tibia and lower trabecular and cortical bone density at the radius. An interaction between free estradiol and current smoking was observed in statistical models predicting cortical area and thickness (β = 0.29 ± 0.11, p = .01). In conclusion, smoking at a young age is associated with unfavorable bone geometry and density and is associated with increased fracture prevalence, providing arguments for a disturbed acquisition of peak bone mass during puberty by smoking, possibly owing to an interaction with sex steroid action.

Polymorphisms of the SHBG gene contribute to the interindividual variation of sex steroid hormone blood levels in young, middle-aged and elderly men

Objective  In men there is a large interindividual variation of SHBG levels and consequently of testosterone (T) and E2 levels. Family and twin studies suggested a strong genetic contribution, besides metabolic and hormonal influences. The aim of this study was to examine the influence of a missense mutation in exon 8 (Asp327Asn) and a (TAAAA)n‐repeat in the promoter region of the SHBG gene, on SHBG and sex steroid serum concentrations in a population of healthy men.

Birth Weight in Relation to Sex Steroid Status and Body Composition in Young Healthy Male Siblings

CONTEXT Sex steroid concentrations have a strong genetic determination, but environmental factors and body composition play an important role. From studies in children with intrauterine growth restriction, low birth weight has been associated with altered gonadotropin concentrations. OBJECTIVE We aim to investigate sex steroid concentrations in healthy young brothers in relation to birth weight (normal gestational age), body composition, and parental steroid concentrations. DESIGN AND SETTING We conducted a cross-sectional, population-based sibling pair study with inclusion of parental data. PARTICIPANTS A total of 677 men (25-45 yr old) were included in this study, with 296 independent pairs of brothers and 122 fathers. MAIN OUTCOMES We measured testosterone, estradiol, leptin, adiponectin, IGF-I (immunoassays), and free steroid hormones (calculated) in relation to birth weight and changes in body composition (dual-energy x-ray absorptiometry). RESULTS Birth weight was associated with serum testosterone (P = 0.0004) and SHBG (P = 0.0001), independent from weight, age, or fat mass, whereas no association with (free) estradiol, LH, or FSH was found. Paternal testosterone (P = 0.02), estradiol (P = 0.04), and SHBG (P = 0.0004) were associated with the respective sex steroid concentrations in the brothers. Weight increase (population rank) during life, was associated with lower testosterone (-15%; P < 0.001), independent from current weight and with higher free estradiol concentrations (+8%; P = 0.002), whereas weight decrease was associated with higher testosterone (+13%; P < 0.001). CONCLUSION Birth weight and paternal steroid concentrations are associated with testosterone concentrations, independent from adult weight. These findings support the concept of in utero programming across the range of birth weight.

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.

Small effect of the androgen receptor gene GGN repeat polymorphism on serum testosterone levels in healthy men

OBJECTIVE The human androgen receptor (AR) contains a polyglutamine and a polyglycine stretch which are highly polymorphic and are coded respectively by a CAG and GGN repeat in exon 1 of the AR gene. Although the in vitro studies indicated a possible effect of the GGN repeat polymorphism on the AR gene transcription and clinical observations suggest that it might modulate the androgen action, its functional significance remains unclear. We wanted to assess whether the GGN repeat affects the serum testosterone levels in healthy men, which is the expected outcome through feedback regulation if it influences androgen action as has been shown to be the case for the CAG repeat. DESIGN AND PATIENTS A population based cross-sectional cohort study including 1476 healthy young, middle-aged, and elderly men. MEASUREMENT Testosterone and LH levels were determined by immunoassay; free testosterone (FT) levels were calculated. Genotyping of the GGN repeat was performed using the sequencing technique. RESULTS The GGN repeat number was significantly associated with circulating testosterone and FT levels (P=0.017 and P=0.013 respectively). However, taking into account that age, body mass index, and CAG are already in the regression model, the GGN repeat could explain only a small part of the variation of both testosterone and FT. CONCLUSION To our knowledge, this study is the first to demonstrate a significant positive association between the GGN repeat and androgen levels in a large cohort of healthy men. Although the present study thus adds credence to the view that the polyglycine tract in the AR can modulate AR action, this effect appears to be only small so that its clinical relevance remains questionable.

Development and validation of a high-performance liquid chromatography (HPLC) method for the determination of human serum albumin (HSA) in medical devices

Because of its nutritional, anti-oxidative, and cryoprotective properties, human serum albumin (HSA) is an important ingredient of the culture and cryopreservation media for assisted reproductive techniques (ART) such as in vitrofertilization (IVF) and intracytoplasmic sperm injection (ICSI) procedures. Several tools are available for the determination of this serum protein in biological samples and pharmaceutical preparations, including colorimetric, electrophoretic, and immunological assays. However, because of inter-assay variability and accuracy problems of the above-mentioned assays, we have chosen to develop and validate a reverse phase (RP) high-performance liquid chromatography (HPLC) method to assess HSA content in ART-related media. Briefly, a gradient elution (a combination of acetonitrile/water, supplemented with 0.1% (v/v) trifluoroacetic acid) was used to separate samples on a C4 (n-butyl-coated silica) column. Two main peaks were observed at 4.970 and 8.715 min, representing the stabilizer N-acetyl-tryptophan (N-Ac-Trp) and HSA respectively. Validation of the method demonstrated that HSA can be determined in an accurate and precise manner, in a range between 0.4 and 25 mg ml−1, without interference of matrix ingredients. The limit of detection (LOD) and lower limit of quantification (LLOQ) values were 0.128 and 0.386 mg ml−1, respectively. In summary, this RP-HPLC method serves as a quality control for ART product release and stability studies. If required, the method can be easily adapted for assessment of HSA in biological samples and pharmaceutical preparations.