Search

Semaphorin molecules regulate cell adhesion and motility in a wide variety of cell types and are therefore involved in numerous processes including axon guidance, angiogenesis, cardiogenesis, tumor growth, and immune response. Increasing evidence points to a role of transmembrane, membrane-associated and soluble semaphorins during bone development as well as in the control of normal bone homeostasis. Within bone, semaphorins are implicated in the communication between different cell types by relaying signals in an autocrine or paracrine way. Semaphorins are not only involved in bone resorption but also in bone formation. Therefore, targeting semaphorin-induced signaling in bone may constitute an interesting new therapeutic strategy in osteoporosis. However, all the pioneering research on semaphorins is performed in mice and it remains to be established to what extent semaphorin signaling pathways are conserved between mice and men. In addition, knowledge of semaphorin signaling in bone mostly arises from loss/gain of function studies of one single semaphorin and/or receptor. However, different semaphorin molecules are co-expressed in bone and their signaling pathways are likely to interact in a complex and coherent way that needs proper understanding before targeting semaphorin signaling can be therapeutically exploited. [ABSTRACT FROM AUTHOR]

Background Aromatase inhibitors (AIs) frequently induce or enhance musculoskeletal problems (AI-induced musculoskeletal syndrome (AIMSS)) which sometimes are debilitating. Apart from low oestrogen levels, underlying mechanisms are unknown and likely multiple. We previously hypothesised a role for the growth hormone/insulin like growth factor-I (IGF-I) axis. Here, we report the effect of tamoxifen and AI on IGF-I, IGF binding protein-3 (IGFBP-3) and oestrogen levels from a prospective study. Materials and methods Postmenopausal women with an early breast cancer scheduled to start adjuvant endocrine therapy with an AI or tamoxifen were recruited. A rheumatologic questionnaire was completed and serum was collected for assessment of IGF-I, IGFBP-3 and oestrogen levels. Re-evaluation was done after 3, 6 and 12 months of therapy. Results 84 patients started on tamoxifen ( n = 42) or an AI ( n = 42). 66% of the latter group experienced worsening of pre-existing or de novo complaints in joint and/or muscle, compared to 29% of tamoxifen-treated patients. AI therapy resulted in elevated IGF-I levels with a statistically significant increase at 6 months ( p = 0.0088), whereas tamoxifen users were characterised by a decrease in IGF-I levels at all follow-up times ( p < 0.0004). No effect on IGFBP-3 was seen in the latter group. AI-users, however, showed decreased IGFBP-3 levels at 12 months ( p = 0.0467). AIMSS was characterised by a decrease in IGFBP-3 levels ( p = 0.0007) and a trend towards increased IGF-I/IGFBP-3 ratio ( p = 0.0710). Conclusion These findings provide preliminary evidence that AI-induced musculoskeletal symptoms are associated with changes in the growth hormone (GH)/IGF-I axis. [ABSTRACT FROM AUTHOR]

Osteoporosis remains underrecognized and undertreated but more so in men, adding considerably to fracture burden and costs. Fracture-related morbidity and mortality is higher in men, partly due to greater frailty. Improved peak bone mass, geometry and turn-over contribute to lower fracture incidence in men. Bioavailable androgens and oestrogens regulate these aspects of musculoskeletal sexual dimorphism, yet the direct cellular and molecular targets of sex steroids in bone remain incompletely understood. Screening with clinical risk factors and dual energy X-ray absorptiometry are advised in men from age 70 (or 50 with additional risk factors). We now have compelling evidence that osteoporosis drugs are equally effective in men and women, not only to increase bone density but also to prevent osteoporotic fractures. The use of testosterone or selective androgen receptor modulators for osteoporosis, sarcopenia, frailty and falls in men with late-onset hypogonadism requires further investigation. [Copyright &y& Elsevier]

Abstract: The region between the DNA-binding domain and the ligand-binding domain of nuclear receptors is termed the hinge region. Although this flexible linker is poorly conserved, diverse functions have been ascribed to it. For the androgen receptor (AR), the hinge region and in particular the 629RKLKKL634 motif, plays a central role in controlling AR activity, not only because it acts as the main part of the nuclear translocation signal, but also because it regulates the transactivation potential and intranuclear mobility of the receptor. It is also a target site for acetylation, ubiquitylation and methylation. The interplay between these different modifications as well as the phosphorylation at serine 650 will be discussed here. The hinge also has an important function in AR binding to classical versus selective androgen response elements. In addition, the number of coactivators/corepressors that might act via interaction with the hinge region is still growing. The importance of the hinge region is further illustrated by the different somatic mutations described in patients with androgen insensitivity syndrome and prostate cancer. In conclusion, the hinge region serves as an integrator for signals coming from different pathways that provide feedback to the control of AR activity. [Copyright &y& Elsevier]

Male osteoporosis is an increasingly important public health problem: from age 50 onward, one in three osteoporotic fractures occurs in men and fracture-related morbidity and mortality are even higher than in women. In 50% of osteoporotic men, an underlying cause can be identified (secondary osteoporosis). In the absence of an identifiable etiology, male osteoporosis is referred to as ‘idiopathic osteoporosis’ in men aged 30–70 years and as ‘age-related osteoporosis’ in older men. As in women, estrogen, not testosterone, appears the most important sex steroid regulating male skeletal status. Diagnosis and treatment recommendations are still largely based on bone mineral density (BMD), with osteoporosis defined as a T-score of 2.5 standard deviations below young adult values. However, there is ongoing discussion as to whether male or female reference ranges should be used and, like in women, treatment decisions are increasingly based on absolute fracture risk estimations rather than on BMD alone. In men, evidence-based data on the efficacy of pharmacologic interventions in reducing fracture risk are convincing but not conclusive. In particular, bisphosphonates and teriparatide seem to be as effective in men as in women. [ABSTRACT FROM AUTHOR]

Age is a major determinant of osteoporosis, but the elderly are rarely assessed and often remain untreated for this condition. Falls, co-morbidities and co-medications compound the risk of fracture in senile osteoporosis. The prevalence of osteoporosis is expected to increase with increasing life expectancy, and the associated fractures – particularly hip fractures – will lead to significant demands on health resources. Treatment of senile osteoporosis can include pharmacological and non-pharmacological intervention. Calcium and vitamin D dietary supplementation is a relatively low-cost way of reducing the risk of fracture. Pharmacological interventions with risedronate, zoledronic acid, or teriparatide have been shown to reduce vertebral fracture risk in osteoporosis patients over the age of 75. Zoledronic acid has been shown to reduce fracture risk in frail patients with recent hip fracture. In the oldest old (patients over 80), strontium ranelate is the first agent with documented anti-fracture efficacy for both non-vertebral and vertebral fracture and documented sustained efficacy over 5 years. Falls prevention is an essential component of any strategy for decreasing fracture risk in old age. Currently, senile osteoporosis is under-diagnosed and under-treated, but age should not be a barrier to intervention. [Copyright &y& Elsevier]

Abstract: Dual energy X-ray absorptiometry (DXA) measurements from different manufacturers provide different bone mineral density (BMD) values and derived T-scores and Z-scores. These differences result partly from technical differences in the algorithms for the determination of bone mineral content and bone area and partly from the use of different manufacturer-derived reference databases. The present study was to implement a uniform expression of BMD in all male patients by using standardized BMD (sBMD) values and referring to a newly established national male reference sample. In 8 bone densitometry centers throughout Belgium 229 young healthy men were measured on Hologic (Bedford, MA) or GE-Lunar (Madison, WI) bone densitometers. Quality control procedures were implemented and site cross-calibration performed using the European Spine Phantom. Absolute BMD values were converted to standardized values by validated formulas (sBMD). Clinically acceptable between-center differences were noted. No discrepancy was observed in terms of mean sBMD and standard deviations at the lumbar spine and proximal femur between the Belgian and the US reference populations. Region-specific sBMD thresholds for the diagnosis of male osteoporosis were calculated. The current data provide a basis to implement a nation-wide, uniform expression of BMD in male patients and allow harmonization of the BMD-based diagnosis and treatment of osteoporosis in men. [Copyright &y& Elsevier]

: ObjectiveThis study tests the hypothesis that IUI treatment in cases with isolated teratozoospermia (<10% normal forms using strict criteria, normal motility and normal count), results in a lower cumulative live birth rate compared to cases with normozoospermia.: DesignA retrospective cohort study.: SettingAn academic fertility center.: Patient(s)Eight hundred seventy-two IUI cycles in 440 couples were analyzed.: Intervention(s)Couples (n = 440) were classified in three groups: normozoospermia (n = 213), isolated teratozoospermia (n = 104), and male factor infertility (n = 123).: Main outcome measure(s)Live birth rate per cycle and cumulative live birth rate (CLBR).: Result(s)The three groups were similar with regard to female age, female infertility factors, and ovarian response after hormonal stimulation. The overall CLBR after four cycles was 41.5%, and was significantly increased in the normozoospermic group (52.8%) when compared to the isolated teratozoospermia group (33.4%) and the male factor infertility group (31.4%).: Conclusion(s)This study documents for the first time that the CLBR after four IUI cycles is significantly and similarly reduced in couples with isolated teratozoospermia as in couples with other sperm defects, when compared to couples with normozoospermia. As with couples with male factor infertility, couples with isolated teratozoospermia should be counseled about other treatment options such as IVF, as the CLBR after three IVF cycles is 70%–80% in our program. [Copyright &y& Elsevier]

Background To assess a patient’s vitamin D status the precursor metabolite 25-hydroxyvitamin D can be determined. However, measurement of 1,25-dihydroxyvitamin D is required when disorders of 1a-hydroxylation, extrarenal 1a-hydroxylation, or vitamin D receptor defects are suspected. Methods The aim of this study was to determine reference values for 1,25-dihydroxyvitamin D 3 and D 2 using a 2D ID-UPLC–MS/MS method. Results The LC–MS/MS method, able to measure picomolar concentrations of both 1,25-dihydroxyvitamin D 3 and D 2 in human serum, was extensively validated. Intra-assay variations were <5% and 8.5% and <7.5% and 11%, for 1,25-dihydroxyvitamin D 3 and D 2 , respectively, over the whole dynamic range (3.1–376 and 3.1–652 pmol/L). Limit of quantitation was 3.4 pmol/L for both compounds. Our method correlated well with a published LC–MS/MS method ( r = 0.87) and with the average 1,25-dihydroxyvitamin D 3 results of the vitamin D External Quality Assessment Scheme (DEQAS) determined with LC–MS/MS ( r = 0.93). Reference ranges, determined in 96 plasma samples of healthy volunteers were 59–159 pmol/L and <17 pmol/L for respectively 1,25-dihydroxyvitamin D 3 and D 2 . The female part of the reference group showed a statistically significant decrease of 1,25-dihydroxyvitamin D 3 concentrations with age. The presence of significantly higher average 1,25-dihydroxyvitamin D 3 levels in premenopausal women taking oral contraceptive pills compared to postmenopausal women suggests that this effect is estrogen-related, as estrogens lead to a higher vitamin D binding protein. Conclusions The major finding of the present study is a reference interval of 59–159 pmol/L for 1,25-dihydroxyvitamin D 3 determined with a highly sensitive and precise LC–MS/MS method. [ABSTRACT FROM AUTHOR]

Traditionally, the stronger male skeleton was considered to result from higher androgen levels in men compared to women. However, the regulation of male bone growth by sex steroids appears more complex than originally anticipated. Based on clinical observations and studies in animal models, not only androgens and androgen receptor (AR), but also estrogens and estrogen receptor-α (not ERβ) are required for optimal bone mineral acquisition during male growth. In addition, both sex steroids are involved in the maintenance of male skeletal health. In fact, bone loss and fracture risk have been associated with estrogen exposure in elderly men. Overall, a compelling body of evidence suggests that both androgens and estrogens are crucial for male skeletal growth and maintenance. [Copyright &y& Elsevier]

Osteocyte lacunae are small cavities within the bone matrix. Their dimensions and spatial arrangement affect bone mechanical properties. Furthermore, their size and shape affect the strain in bone tissue close to the lacunae; hence, they are supposed to affect the mechanosensory function of the osteocytes residing in the lacunae. It was the purpose of this study to quantify the morphological features of osteocyte lacunae, whether these are affected by aging and whether these vary among different anatomical location. In addition, we aimed at quantifying the vascular canals as these affect bone's microporosity too. We quantified the microporosity in the fibular midshaft of young-adult and old female C57BL/6 mice. Using micro-computed tomography (μCT), we found that advanced age was associated with a significantly decreased vascular canal number and volume density. In aged mice, the mean volume of the lacuna was significantly smaller than in young animals and they were more round. Lacuna number density close to the neutral axis of the fibula was higher in older mice than in young ones. The characterization of bone microporosity presents a first step in further unraveling their potential role in age-related reductions in bone strength. [ABSTRACT FROM AUTHOR]

Calcium and phosphate are vital for the organism and constitute essential components of the skeleton. Serum levels are tightly hormonally regulated and maintained by exchange with three major sources: the intestines, the kidney and the bone. The effects of sex steroids on the bone have been extensively studied and it is well known that sex steroid deficiency induces bone loss, indirectly influencing renal calcium and phosphate homeostasis. However, it is unknown whether sex steroids also directly regulate renal calcium and phosphate handling, hereby potentially indirectly impacting on bone. The presence of androgen receptors (AR) and estrogen receptors (ER) in both human and rodent kidney, although their exact localization within the kidney remains debated, supports direct effects. Estrogens stimulate renal calcium reabsorption as well as phosphate excretion, while the effects of androgens are less clear. Many of the studies performed with regard to renal calcium and/or phosphate homeostasis do not correct for the calcium and phosphate fluxes from the bone and intestines, which complicates the differentiation between the direct effects of sex steroids on renal calcium and phosphate handling and the indirect effects via the bone and intestines. The objective of this study is to review the literature and current insight of the role of sex steroids in calcium and phosphate handling in the kidney. [ABSTRACT FROM AUTHOR]

Background The measurement of 1α,25(OH) 2 D 3 in human serum poses a true challenge as concentrations are very low and structurally similar metabolites can interfere. Materials and methods During optimization of our in-house LC–MSMS method for serum 1α,25(OH) 2 D 3 a previously co-eluting isobaric interference was separated. The isobar was identified as 1β,25(OH) 2 D 3 by comparing retention time and fragmentation spectra to standards (other isobaric dihydroxylated vitamin D 3 analogs). 1β,25(OH) 2 D 3 showed specific cluster formation (water), not present in 1α,25(OH) 2 D 3 . 1β,25(OH) 2 D 3 was measured in serum of apparently healthy human volunteers (n = 20), patients with high serum 25-hydroxyvitamin D [25(OH)D] concentrations (>50 ng/mL) (n = 33 among which 4 with very high levels (>150 ng/mL)) and patients with kidney failure (n = 68; 39 stage 1–3, 29 stage 4–5). Pearson’s r was calculated for correlations and Mann-Whitney statistic to compare group medians. Results Median serum 1β,25(OH) 2 D 3 was 11 pg/mL in apparently healthy volunteers and increased to 20 pg/mL for serum 25(OH)D concentrations above 80 ng/mL (n = 22) (p < 0.0001). 1β,25(OH) 2 D 3 concentrations were significantly correlated to serum 25(OH)D concentrations (r = 0.85) for the combined results from healthy volunteers and patient sera (n = 53) (p < 0.0001). For patients with kidney failure, median serum 1β,25(OH) 2 D 3 was 7 pg/mL and not different from the median level in healthy volunteers (p = 0.06). The median concentration did not vary with different stages. Conclusions We present evidence for the widespread presence of 1β,25(OH) 2 D 3 , a new vitamin D metabolite, in human serum. The level increases with rising serum 25(OH)D concentrations and is particularly high in patients with very high 25(OH)D levels. We previously demonstrated that 1β,25(OH) 2 D 3 is a poor genomic agonist but a potent non-genomic antagonist of 1α,25(OH) 2 D 3. The clinical implications of the presence of this analog therefore require further exploration. [ABSTRACT FROM AUTHOR]

The selective estrogen receptor modulator tamoxifen exerts estrogen agonistic or antagonistic actions on several tissues, including bone. The off-target effects of tamoxifen are one of the most widely recognized pitfalls of tamoxifen-inducible Cre recombinases (CreERs), potentially confounding the phenotypic findings. Still, the validation of tamoxifen induction schemes that minimize the side effects of the drug has not been addressed. Here, we compared the side effects on the skeleton and other androgen-responsive targets of a shortened tamoxifen regimen (2 doses of 190 mg/kg body weight by oral gavage) to a standard protocol (4 doses) and determined their efficiency in inducing CreER-mediated gene deletion. In addition, both a vehicle- and a 10-dose group, which served as a positive control for tamoxifen side effects, were also included. For this purpose, we generated male mice with a floxed androgen receptor (AR) and a neuron-specifically expressed CreER. Treatment with two doses of tamoxifen was the only regimen that did not diminish androgenic bioactivity, as assessed by both seminal vesicles and levator ani/bulbocavernosus muscle weights and serum testosterone concentrations. Similarly, trabecular and cortical femoral bone structure were dramatically altered by both the standard and high-dose protocols but not by the shortened version. Serum osteocalcin and bone-gene expression analyses confirmed the absence of effects on bone by 2 doses of tamoxifen. This protocol decreased AR mRNA levels efficiently and specifically in the nervous system. Thus, we optimized a protocol for tamoxifen-induced CreER gene deletion in mice without off-target effects on bone and male reproductive organs. [ABSTRACT FROM AUTHOR]

Biochemical assessments of androgen status (hyper- or hypoandrogenism) are usually based on serum testosterone concentrations. According to the free hormone hypothesis, sex hormone-binding globulin (SHBG) determines free and bioavailable testosterone concentrations. Previous studies have suggested that in vitro androgen bioassay results may also be influenced by SHBG and correlate with free or bioavailable testosterone concentrations. To test this hypothesis, we established a stable HEK293 cell line with high expression of the human androgen receptor (AR) and a luciferase reporter downstream of a classical androgen response element. Importantly, we demonstrate that bioassay results are sensitive to dilution effects which increase apparent bioactivity in an SHBG-dependent manner. We therefore adopted a method using undiluted serum, which reduced cell proliferation but did not significantly affect the luciferase signal, cell viability or cytotoxicity. To correct for serum matrix effects, we applied signal correction based on internal controls with AR agonists or antagonists. Using this method, we provide direct evidence that in vitro androgen bioactivity reflects the inhibitory effects of SHBG, and correlates with free or bioavailable testosterone concentrations in adult hypogonadal men receiving androgen replacement therapy. In men receiving anti-androgens, serum bioactivity decreased tenfold while serum testosterone concentrations decreased only four-fold. Further pilot results in prostate cancer patients showed that androgen synthesis inhibitors result in more complete inhibition of androgen bioactivity than gonadorelin-based androgen deprivation therapy, even in patients whose testosterone concentrations were undetectable by mass spectrometry. We conclude that in vitro androgen reporter bioassays are useful tools to study how androgen bioactivity in serum is determined by androgens, anti-androgens as well as SHBG, provided that dilution and matrix effects are accounted for. [ABSTRACT FROM AUTHOR]

Aging hypogonadal men are at increased risk of osteoporosis and sarcopenia. Testosterone is a potentially appealing strategy to prevent simultaneous bone and muscle loss. The androgen receptor (AR) mediates antiresorptive effects on trabecular bone via osteoblast-lineage cells, as well as muscle-anabolic actions. Sex steroids also modify the skeletal response to mechanical loading. However, it is unclear whether the effects of androgens on bone remain effective independent of mechanical stimulation or rather require indirect androgen effects via muscle. This study aims to characterize the effects and underlying mechanisms of androgens on disuse osteosarcopenia. Adult male mice received a unilateral botulinum toxin (BTx) injection, and underwent sham surgery or orchidectomy (ORX) without or with testosterone (ORX + T) or dihydrotestosterone (ORX + DHT) replacement. Compared to the contralateral internal control hindlimb, acute trabecular number and bone volume loss was increased by ORX and partially prevented DHT. T was more efficient and increased BV/TV in both hindlimbs over sham values, although it did not reduce the detrimental effect of BTx. Both androgens and BTx regulated trabecular osteoclast surface as well as tartrate-resistant acid phosphatase expression. Androgens also prevented BTx-induced body weight loss but did not significantly influence paralysis or muscle atrophy. BTx and ORX both reduced cortical thickness via endosteal expansion, which was prevented by T but not DHT. In long-term follow-up, the residual trabecular bone volume deficit in sham-BTx hindlimbs was prevented by DHT but T restored it more efficiently to pre-treatment levels. Conditional AR deletion in late osteoblasts and osteocytes or in the satellite cell lineage increased age-related trabecular bone loss in both hindlimbs without influencing the effect of BTx on trabecular osteopenia. We conclude that androgens have antiresorptive effects on trabecular disuse osteopenia which do not require AR actions on bone via muscle or via osteocytes. [ABSTRACT FROM AUTHOR]

Bone is a biomechanical tissue shaped by forces from muscles and gravitation. Simultaneous bone and muscle decay and dysfunction (osteosarcopenia or sarco-osteoporosis) is seen in ageing, numerous clinical situations including after stroke or paralysis, in neuromuscular dystrophies, glucocorticoid excess, or in association with vitamin D, growth hormone/insulin like growth factor or sex steroid deficiency, as well as in spaceflight. Physical exercise may be beneficial in these situations, but further work is still needed to translate acceptable and effective biomechanical interventions like vibration therapy from animal models to humans. Novel antiresorptive and anabolic therapies are emerging for osteoporosis as well as drugs for sarcopenia, cancer cachexia or muscle wasting disorders, including antibodies against myostatin or activin receptor type IIA and IIB (e.g. bimagrumab). Ideally, increasing muscle mass would increase muscle strength and restore bone loss from disuse. However, the classical view that muscle is unidirectionally dominant over bone via mechanical loading is overly simplistic. Indeed, recent studies indicate a role for neuronal regulation of not only muscle but also bone metabolism, bone signaling pathways like receptor activator of nuclear factor kappa-B ligand (RANKL) implicated in muscle biology, myokines affecting bone and possible bone-to-muscle communication. Moreover, pharmacological strategies inducing isolated myocyte hypertrophy may not translate into increased muscle power because tendons, connective tissue, neurons and energy metabolism need to adapt as well. We aim here to critically review key musculoskeletal molecular pathways involved in mechanoregulation and their effect on the bone-muscle unit as a whole, as well as preclinical and emerging clinical evidence regarding the effects of sarcopenia therapies on osteoporosis and vice versa. [ABSTRACT FROM AUTHOR]

• Sex steroid levels are proposed to be a modifiable risk factor for cognitive ageing • We tested this hypothesis in a large-scale study of middle-aged and older men • Steroid levels did not affect cognition after adjusting for health and lifestyle • Androgen CAG repeat length did not alter hormone-cognition relationships It has been proposed that endogenous sex hormone levels may present a modifiable risk factor for cognitive decline. However, the evidence for effects of sex steroids on cognitive ageing is conflicting. We therefore investigated associations between endogenous hormone levels, androgen receptor CAG repeat length, and cognitive domains including visuoconstructional abilities, visual memory, and processing speed in a large-scale longitudinal study of middle-aged and older men. Men aged 40-79 years from the European Male Ageing Study (EMAS) underwent cognitive assessments and measurements of hormone levels at baseline and follow-up (mean = 4.4 years, SD ± 0.3 years). Hormone levels measured included total and calculated free testosterone and estradiol, dihydrotestosterone, luteinizing hormone, follicle-stimulating hormone, dehydroepiandrosterone sulphate and sex hormone-binding globulin. Cognitive function was assessed using the Rey-Osterrieth Complex Figure Copy and Recall, the Camden Topographical Recognition Memory and the Digit Symbol Substitution Test. Multivariate linear regressions were used to examine associations between baseline and change hormone levels, androgen receptor CAG repeat length, and cognitive decline. Statistical analyses included 1,827 and 1,423 participants for models investigating relationships of cognition with hormone levels and CAG repeat length, respectively. In age-adjusted models, we found a significant association of higher baseline free testosterone (β=-0.001, p =0.005) and dihydrotestosterone levels (β=-0.065, p =0.003) with greater decline on Rey-Osterrieth Complex Figure Recall over time. However, these effects were no longer significant following adjustment for centre, health, and lifestyle factors. No relationships were observed between any other baseline hormone levels, change in hormone levels, or androgen receptor CAG repeat length with cognitive decline in the measured domains. In this large-scale prospective study there was no evidence for an association between endogenous sex hormone levels or CAG repeat length and cognitive ageing in men. These data suggest that sex steroid levels do not affect visuospatial function, visual memory, or processing speed in middle-aged and older men. [ABSTRACT FROM AUTHOR]

Androgen deficiency or androgen receptor knockout (ARKO) causes high-turnover osteopenia, but the target cells for this effect remain unclear. To examine whether AR in osteoclasts directly suppresses bone resorption, we crossed AR-floxed with cathepsin K-Cre mice. Osteoclast-specific ARKO (ocl-ARKO) mice showed no changes neither in osteoclast surface nor in bone microarchitecture nor in the response to orchidectomy and androgen replacement, indicating that the AR in osteoclasts is not critical for bone maintenance. In line with the lack of a bone phenotype, the levels of AR were very low in osteoclast-enriched cultures derived from bone marrow (BM) and undetectable in osteoclasts generated from spleen precursors. Since tibiae of ubiquitous ARKO mice displayed increased osteoclast counts, the role of AR was further explored using cell cultures from these animals. Osteoclast generation and activity in vitro were similar between ARKO and wildtype control (WT) mice. In co-culture experiments, BM stromal cells (BMSCs) were essential for the suppressive action of AR on osteoclastogenesis and osteoclast activity. Stimulation with 1,25(OH) 2 vitamin D 3 increased Rankl and decreased Tnfsf11 (osteoprotegerin, Opg ) gene expression in BMSCs more than in osteoblasts. This increase in the Rankl / Opg ratio following 1,25(OH) 2 D 3 stimulation was lower, not higher, in ARKO mice. Runx2 expression in BMSCs was however higher in ARKO vs. WT, suggesting that ARKO mice may more readily commit osteoprogenitor cells to osteoblastogenesis. In conclusion, the AR does not seem to suppress bone resorption through direct actions in osteoclasts. BMSCs may however represent an alternative AR target in the BM milieu. [ABSTRACT FROM AUTHOR]

Abstract: The gene family of nuclear receptors is characterized by the presence of a typical, well conserved DNA-binding domain. In general, two zinc coordinating modules are folded such that an α-helix is inserted in the major groove of the DNA-helix displaying a sequence similar to one of two hexameric consensus motifs. Both zinc molecules coordinate four cysteines. Although the DNA-binding domains as well as the hormone response elements are very similar, each nuclear receptor will affect transcription of a specific set of target genes. This is in part due to some important receptor-specific variations on the general theme of DNA interaction. For most nuclear receptors, the DNA-binding domain dimerizes on DNA, which explains why most hormone response elements consist of a repeat of two hexamers. The hexamer dimers can be organized either as direct, inverted or everted repeats with spacers of varying lengths. The DNA can be bound by homodimers, heterodimers and for some orphan receptors, as monomer. Another key element for DNA binding by nuclear receptors is the carboxy-terminal extension of the DNA-binding domain extending into the hinge region. This part not only co-determines sequence specificity, but also affects other functions of the receptors like nuclear translocation, intranuclear mobility and transactivation potential. Moreover, allosteric signals passing through towards other receptor domains, explain why to some extent, the DNA elements can also be considered as controlling ligands. [Copyright &y& Elsevier]

Abstract: Introduction: Sex steroids have distinct effects on bone growth and maintenance in men and women, mediated through their respective steroid receptors. Though most evidence is derived from animal studies, several concepts have been confirmed in humans by detection of specific mutations. In this report we describe changes in bone size and volumetric bone density in a complete androgen insensitive subject (CAIS) due to a mutation in the androgen receptor during 5 years of estrogen treatment. Materials and methods: We present a case report of a 31 year old XY female with CAIS with a longitudinal follow-up for 5 years of areal and volumetric bone parameters. Areal and volumetric bone parameters were determined using dual-energy X-ray absorptiometry (DXA) and peripheral quantitative computed tomography (pQCT). Sex steroids, LH, FSH and IGF-I were determined by immunoassay. Results: Complete androgen insensitivity syndrome was genetically confirmed by detection of the mutation Asp767Tyr in the androgen receptor gene. Bone size at presentation was found to be intermediate between male and female reference values. Low areal and volumetric bone density (both trabecular and cortical) was observed at baseline and improved gradually with estrogen treatment (+2% to 6.5%). Upon estrogen treatment, endosteal contraction (−1%) was demonstrated, with increasing cortical thickness (+3%), cortical area (+5%) and unchanged periosteal circumference. Conclusions: During adult life, estrogens mediate endosteal bone apposition and volumetric bone density, without marked influence on periosteal bone apposition. The finding of a bone size intermediate between male and female supports testosterone as an essential mediator for periosteal bone expansion, but not as the sole stimulus for bone expansion during growth. [Copyright &y& Elsevier]

Abstract: This study reports the preclinical evaluation of the bone and muscle protective potential of the synthetic androgen 7α-methyl-19-nortestosterone (MENT™), as assessed in the aged orchidectomized rat model. Aged (13-month-old) orchidectomized Wistar rats were treated with different doses of MENT (4, 12 or 36 μg/day) subcutaneously for 16 weeks via mini-osmotic pumps. Analysis of the effects of androgen deficiency versus MENT replacement was performed using quantitative computed tomography (pQCT), dual energy X-ray absorptiometry (DEXA) and biochemical markers of bone turnover. At the end of the study period, prostate weight in orchidectomized rats treated with low- (4 μg/day) or mid-dose (12 μg/day) MENT remained significantly lower compared to the sham-operated animals (−47% and −25%, respectively). High-dose MENT (36 μg/day), on the other hand, induced prostate hypertrophy (+21% versus sham). Low-, mid- and high-dose MENT were found to be effective in suppressing the acceleration of bone remodeling following orchidectomy, as assessed by osteocalcin and deoxypyridinoline. In addition, low-, mid- and high-dose were able to prevent the orchidectomy-induced bone loss, as evaluated by DEXA at the femur and total-body and by pQCT at the femur. Compared to sham-operated animals, the low- and mid-dose MENT groups showed no decline in lean body mass and no muscle atrophy (as measured by m. quadriceps weight) at 16 weeks, whereas high-dose MENT was associated with a significant decline in lean body mass (−8.5% versus sham) and quadriceps weight (−10.6%). We conclude that, in the aged orchidectomized rat model, low- and mid-doses of the synthetic androgen MENT have bone and muscle protective effects and do not induce prostate hypertrophy. The bone protective action of high-dose MENT, however, occurs at the expense of muscle wasting and prostate hypertrophy. Our findings support the need for human studies to explore the potential of MENT as an option for androgen replacement in aging men. [Copyright &y& Elsevier]

Renal calcium and phosphate handling is an important contributor to mineral homeostasis and bone health and the androgen receptor (AR) is highly expressed in the kidney. We investigated the short term effects of androgen deprivation on renal calcium and phosphate reabsorption, independent of their effects on bone. Two weeks following orchidectomy (ORX) of adult mice, bone loss occurred along with hypercalciuria, which was similarly prevented by testosterone and dihydrotestosterone supplementation. Treatment with bisphosphonates prior to ORX also inhibited hypercalciuria, indicating that the calcium flux originated from the bone. Renal calcium and phosphate transporter expression was increased post-ORX, independent of bisphosphonates. Furthermore, androgen deprivation appeared to stimulate local synthesis of 1,25(OH) 2 D 3. When bisphosphonate-treated mice were fed a low calcium diet, bone resorption was no longer blocked and secondary hyperparathyroidism developed, which was more pronounced in ORX mice than sham-operated mice. In conclusion, this study shows that androgen deprivation increased renal calcium and phosphate transporter expression, independent of bone, and underlines the importance of adequate intestinal calcium supply in circumstances of androgen deprivation and bisphosphonate treatment. • Two weeks after orchidectomy, acute trabecular bone loss is induced in adult male mice. • Androgens modulate renal calcium and phosphate handling. • Androgens modulate renal vitamin D metabolism. • Hypogonadism and low calcium diet decrease the efficiency of bisphosphonates. [ABSTRACT FROM AUTHOR]

Male infertility is associated with a higher long-term morbidity and mortality risk. However, it is not clear which diseases are contributing to this risk. Osteoporosis is a possible factor, as it is a frequent disease and sex steroids regulate both fertility and bone health. Furthermore, there are data indicating that high FSH levels in women are related to low bone mineral density (BMD), independent of estradiol levels. As infertile men often have increased FSH, already from a young age, this could be a risk factor for impaired bone health in later life. One hundred and thirty-seven men with a history of male factor infertility due to spermatogenic failure (SgF men) as well as a control group of 70 men from couples treated with IVF for female factor infertility (non-SgF men) were included in a long-term follow-up study. Men with explained infertility, including testosterone deficiency, were not included. Data from baseline fertility investigations were retrieved from the patient files of the SgF men. At follow-up hormonal and semen analysis were performed and axial, femoral and total body BMD was measured by dual X-ray absorptiometry in all men. Multiple linear regression was used to assess differences between SgF and non-SgF men and to study associations between FSH levels and BMD. Median follow-up time was 14.8 years (5th–95th percentile 11.3–18.2) after fertility assessment for SgF men and 15.6 years (12.1–18.5) for non-SgF men (p = 0.033). When comparing the two groups, no significant differences in total T, free T or E2 levels were apparent at follow-up. As expected, LH and FSH were higher in SgF men ((median (5th–95th percentile)) for LH (IU/L): 4.3 (2.2–13.6) for SgF men and 3.0 (1.4–5.8) for non-SgF men (p < 0.001); FSH (IU/L): 9.8 (2.8–35.5) versus 3.7 (1.6–8.7); p < 0.001), and inhibin B and semen parameters were lower in SgF men. There were no differences in BMD between the two groups at follow-up. Furthermore, both groups had median Z -scores close to zero at all sites, indicating that BMD is not different when compared to age-matched healthy men. In SgF men, neither baseline FSH, nor FSH at follow-up, was associated with BMD at the different sites at follow-up. Men with spermatogenic failure are not at increased risk for impaired bone health when middle aged. Furthermore, infertile men with high FSH levels do not have lower BMD. • Infertile men with high FSH levels do not have lower bone mineral density • Infertile men have similar bone mineral density 15 years after infertility work-up as fertile men • Follow-up of bone health is not necessary in men with primary spermatogenic failure and acceptable Leydig cell function [ABSTRACT FROM AUTHOR]