Circulating sclerostin levels and markers of bone turnover in Chinese-American and white women

Evaluating the correlation of sclerostin levels with obesity and type 2 diabetes in a multiethnic population living in Kuwait

Obesity and Type 2 Diabetes Mellitus (T2DM) are intricate metabolic disorders with a multifactorial etiology, often leading to a spectrum of complications. Recent research has highlighted the impact of these conditions on bone health, with a particular focus on the role of sclerostin (SOST), a protein molecule integral to bone metabolism. Elevated circulating levels of SOST have been observed in patients with T2DM compared to healthy individuals. This study aims to examine the circulating levels of SOST in a multiethnic population living in Kuwait and to elucidate the relationship between SOST levels, obesity, T2DM, and ethnic background. The study is a cross-sectional analysis of a large cohort of 2083 individuals living in Kuwait. The plasma level of SOST was measured using a bone panel multiplex assay. The study found a significant increase in SOST levels in individuals with T2DM (1008.3 pg/mL, IQR-648) compared to non-diabetic individuals (710.6 pg/mL, IQR-479). There was a significant gender difference in median SOST levels, with males exhibiting higher levels than females across various covariates (diabetes, IR, age, weight, and ethnicity). Notably, SOST levels varied significantly with ethnicity: Arabs (677.4 pg/mL, IQR-481.7), South Asians (914.6 pg/mL, IQR-515), and Southeast Asians (695.2 pg/mL, IQR-436.8). Furthermore, SOST levels showed a significant positive correlation with gender, age, waist circumference, systolic and diastolic blood pressure, fasting blood glucose, HbA1c, insulin, total cholesterol, triglycerides, HDL, LDL, ALT, and AST (p-Value ≥0.05). South Asian participants, who exhibited the highest SOST levels, demonstrated the most pronounced associations, even after adjusting for age, gender, BMI, and diabetes status (p-Value ≥0.05). The observed correlations of SOST with various clinical parameters suggest its significant role in the diabetic milieu, particularly pronounced in the South Asian population compared to other ethnic groups.

Osteoporosis and Fracture Risk among Older US Asian Adults

PURPOSE OF REVIEW

This review summarizes the current knowledge regarding osteoporosis and fracture among older US Asian adults.

RECENT FINDINGS

Asian adults have lower (areal) bone density than non-Hispanic White adults and thus are more likely to be diagnosed and treated for osteoporosis, despite their lower risk of hip fracture. The latter may relate to favorable characteristics in hip geometry, volumetric bone density, and bone microarchitecture; lower risk of falls; and other clinical factors. The fracture risk calculator FRAX accounts for the lower risk of hip fracture among US Asian adults. However, data on major osteoporotic fracture risk remain limited. Fracture rates also vary by Asian subgroup, which may have implications for fracture risk assessment. Furthermore, among women receiving bisphosphonate drugs, Asian race is a risk factor for atypical femur fracture, an uncommon complication associated with treatment duration. Recent clinical trial efficacy data pertaining to lower bisphosphonate doses and longer dosing intervals may be relevant for Asian adults. More research is needed to inform osteoporosis care of US Asian adults, including risk-benefit considerations and the optimal duration of bisphosphonate treatment. Greater evidence-based guidance for primary fracture prevention among US Asian adults will ensure health equity in the prevention of osteoporotic fractures.

New Emerging Biomarkers for Bone Disease: Sclerostin and Dickkopf-1 (DKK1)

A healthy skeleton depends on a continuous renewal and maintenance of the bone tissue. The process of bone remodeling is highly controlled and consists of a fine-tuned balance between bone formation and bone resorption. Biochemical markers of bone turnover are already in use for monitoring diseases and treatment involving the skeletal system, but novel biomarkers reflecting specific biological processes in bone and interacting tissues may prove useful for diagnostic, prognostic, and monitoring purposes. The Wnt-signaling pathway is one of the most important pathways controlling bone metabolism and consequently the action of inhibitors of the pathway such as sclerostin and Dickkopf-related protein 1 (DKK1) have crucial roles in controlling bone formation and resorption. Thus, they might be potential markers for clinical use as they reflect a number of physiological and pathophysiological events in bone and in the cross-talk with other tissues in the human body. This review focuses on the clinical utility of measurements of circulating sclerostin and DKK1 levels based on preanalytical and analytical considerations and on evidence obtained from published clinical studies. While accumulating evidence points to clear associations with a number of disease states for the two markers, and thus, the potential for especially sclerostin as a biochemical marker that may be used clinically, the lack of standardization or harmonization of the assays still hampers the clinical utility of the markers.

Reduced trabecular bone mineral density and thinner cortices in men with distal forearm fractures

Men with distal forearm fractures have reduced bone density, an increased risk of osteoporosis and of further fractures. The aim of the study was to investigate the structural determinants of these observations using quantitative CT (qCT). Ninety six men with low-trauma distal forearm fracture and 101 age-matched healthy control subjects were recruited. All subjects underwent a quantitative CT on a standard 64-slice whole body CT scanner. These were analysed on Mindways QCT PRO™ Software to generate volumetric and geometric data at the lumbar spine, femoral neck and total hip, ultra-distal and distal 33 % radius. Biochemical investigations, health questionnaires and measurements of bone turnover were made. Men with fracture had significantly lower total and trabecular vBMD at all sites. The greatest percentage reduction was at the ultra-distal radius (13.5 % total and 11.7 % trabecular vBMD). In the fracture group cortical vBMD was significantly higher in the femoral neck (p < 0.001) and maintained at the ultra-distal radius compared with control subjects. However, cortical cross-sectional area (CSA) and thickness were significantly reduced at the femoral neck (p < 0.001 and p = 0.002 respectively) and forearm sites (CSA ultradistal radius p = 0.001, cortical thickness p = 0.002, CSA distal one third radius p = 0.045 and cortical thickness p = 0.005). Cross sectional moment of inertia (CSMI) and section moduli were significantly reduced at the femoral neck (CSMI1 p = 0.002, CSMI2 p = 0.012 and section moduli Z1 p < 0.001, Z2 p = 0.004) and the ultra-distal radius (CSMI1 p = 0.008 and section moduli Z1 p = 0.018, Z2 p = 0.007). In stepwise logistic regression analysis distal forearm fracture showed the strongest association with a model comprising ultra-distal forearm trabecular vBMD (negative), procollagen type I N-terminal propeptide (PINP, positive) and sex hormone binding globulin (SHBG, negative). In conclusion, these observations explain the structural reasons for the increased fracture risk in men with distal forearm fractures.

Serum Sclerostin and Its Association with Bone Turnover Marker in Metabolic Bone Diseases

Sclerostin is a secreted inhibitor of Wnt/β-catenin signaling that is mainly produced by osteocytes and is an important regulator of bone remodeling. Some studies have evaluated serum sclerostin levels in metabolic bone diseases, but the results have been contradictory. The profile of serum sclerostin levels in patients with osteogenesis imperfecta (OI), X-linked hypophosphatemia (XLH), and Paget's disease of bone (PDB) was obtained to determine their association with bone turnover marker. Serum sclerostin levels, biochemical parameters, and the bone turnover marker, β-CrossLaps of type 1 collagen containing cross-linked C-telopeptide (β-CTX), were measured in 278 individuals, comprising 71 patients with OI, 51 patients with XLH, 17 patients with PDB, and 139 age- and sex-matched healthy controls. A correlation analysis was performed between sclerostin and β-CTX concentration. The univariate logistic regression analysis was used to analyze factors associated with OI, XLH, and PDB. Patients with PDB (11 male 6 female), aged 44.47 ± 14.75 years; XLH (17 male, 34 female), aged 19.29 ± 15.65 years; and OI (43 male, 28 female), aged 19.57 ± 16.45 years, had higher sclerostin level than age- and sex-matched healthy controls [median(interquartile range): 291.60 (153.42, 357.35) vs. 38.00 (27.06, 68.52) pmol/L, 163.40 (125.10, 238.20) vs. 31.13 (20.37, 45.84) pmol/L, and 130.50 (96.12, 160.80) vs. 119.00 (98.89, 194.80) pmol/L, respectively; P < 0.001]. Patients with PDB had the highest level of serum sclerostin, followed by those with XLH and OI (P < 0.05). Sclerostin was positively correlated with β-CTX in OI and XLH (r = 0.541 and r = 0.661, respectively; P < 0.001). Higher β-CTX and sclerostin levels were associated with a higher risk of OI, XLH, and PBD. Sclerostin may be a biomarker of OI, XLH, and PDB. Whether sclerostin inhibitors can be used in these patients requires further analysis using additional cohorts.

Role of Sclerostin in Cardiovascular Disease

Sclerostin is most recognized for its role in controlling bone formation but is also expressed in the heart, aorta, coronary, and peripheral arteries. This review summarizes research on sclerostin's role in cardiovascular disease. Rodent studies have found sclerostin to be expressed at sites of arterial calcification. In contrast, aortic sclerostin was reported to be downregulated in a mouse model of abdominal aortic aneurysm, and transgenic upregulation or administration of sclerostin was found to prevent abdominal aortic aneurysm and atherosclerosis formation. Sclerostin deficiency was reported to stimulate cardiac rupture in one rodent model. In humans, 7 of 11 studies reported a significant association between high serum sclerostin and high carotid intima media thickness. Ten of 15 studies reported a significant association between high serum sclerostin and severe arterial calcification. Twelve of 14 studies reported a significant association between high serum sclerostin and high arterial stiffness or atherosclerosis severity. Four of 9 studies reported a significant association between high serum sclerostin and high risk of cardiovascular events. A meta-analysis of randomized controlled trials suggested that administration of the sclerostin blocking antibody romosozumab did not significantly increase the risk of major adverse cardiovascular events (risk ratio, 1.14 [95% CI, 0.83-1.57]; P=0.54) or cardiovascular death (risk ratio, 0.92 [95% CI, 0.53-1.59]; P=0.71). Human genetic studies reported variants predisposing to low arterial sclerostin expression were associated with a high risk of cardiovascular events. Overall, past research suggests a cardiovascular protective role of sclerostin but findings have been inconsistent, possibly due to variations in study design, the unique populations and models studied, and the heterogeneous methods used.

Circulating SIRT1 and Sclerostin Correlates with Bone Status in Young Women with Different Degrees of Adiposity

Sirtuin1 (SIRT1) and sclerostin play important roles in adipose tissue and bone metabolism. We evaluated the circulating SIRT1 and sclerostin relationship with mass and quality of bone while considering the degree of adiposity. Sixty-six premenopausal women (16 underweight, 25 normal weight and 25 with obesity), aged <50 years, were enrolled. Plasma SIRT1, sclerostin and DXA body composition (total fat mass (FM), abdominal visceral adipose tissue, lean mass, trabecular bone score (TBS) and lumbar spine and femoral neck (FN) bone mineral density (BMD)) were assessed. The patients with obesity showed the lowest SIRT1 and TBS values and the highest sclerostin concentrations; BMD increased with FM and BMI and had an inverse association with SIRT1. Sclerostin was negatively correlated with SIRT1 (ρ = −0.37, p = 0.002). When spine BMD, FN BMD and TBS were standardized for BMI, a positive correlation with SIRT1 and a negative correlation with sclerostin were seen (p < 0.005). In the regression analysis, sclerostin was the best independent, negative predictor for BMD and TBS, while SIRT1 directly predicted TBS (p < 0.05). In conclusion, blood measurement of SIRT1 and sclerostin could represent a snapshot of the bone status that, taking into account the degree of adiposity, may reduce the interference of confounding factors in the interpretation of bone health parameters.

The association of circulating sclerostin level with markers of bone metabolism in patients with thyroid dysfunction

Background

The aim of this study was to compare serum sclerostin concentrations in patients with thyroid dysfunction with euthyroid control subjects and to assess the relationship between sclerostin and markers of bone metabolism (osteocalcin and beta-cross-laps).

Methods

The study included 30 patients with thyroid dysfunction (hypothyroidism, hyperthyroidism and subclinical hyperthyroidism) and ten euthyroid controls. Free thyroxine (FT4) was measured by radioimmunoassay, while thyroid stimulating hormone (TSH) concentration was determined immunoradiometrically. We used an ELISA kit to determine the sclerostin level. The electrochemiluminescence method was applied for measuring the bone markers.

Results

Sclerostin levels were significantly lower in hypothyroid patients (p=0.009) and significantly elevated in hyperthyroid patients (p=0.008) compared to control values. Hyperthyroid patients also had higher sclerostin than patients with subclinical hyperthyroidism (p=0.013). Sclerostin concentrations were negatively correlated with TSH levels (r=-0.746, p<0.001), but positively with FT4 (r=0.696, p < 0.001). Moreover, sclerostin was positively associated with osteocalcin (r=0.605, p=0.005) and beta-cross-laps levels (r=0.573, p=0.008) in all thyroid patients.

Conclusions

Serum sclerostin is significantly affected in subjects with thyroid dysfunction. Both sclerostin and thyroid status affect bone homeostasis, which is reflected through the significant correlations with osteocalcin and beta-cross-laps.

Circulating sclerostin is associated with bone mineral density independent of HIV-serostatus

Background

Low bone mineral density (BMD) is commonly observed in people living with HIV (PLWH), however the cause for this BMD loss remains unclear. Sclerostin, a bone-derived antagonist to the Wnt/β-catenin-pathway, suppresses bone remodeling and is positively associated with BMD. The goal of the current study was to investigate associations between sclerostin and BMD in a cohort of HIV-seropositive and demographically-matched seronegative women.

Methods

This cross-sectional analysis used a subset of early postmenopausal women enrolled in the Women's Interagency HIV Study (WIHS). BMD was assessed at the lumbar spine, total hip, femoral neck, and distal and ultradistal radius via dual energy x-ray absorptiometry (DXA). Circulating sclerostin was assessed via commercial ELISAs. Univariate and multivariate linear regression modeling tested associations between sclerostin and BMD after adjusting for a variety of BMD-modifying variables.

Results

HIV-seropositive women had significantly reduced BMD at all skeletal sites compared to HIV-seronegative women. There was no difference in sclerostin levels according to HIV-serostatus (0.25 vs 0.27 ng/mL in HIV-seronegative and HIV-seropositive, respectively, p = 0.71). Circulating sclerostin was positively associated with BMD at all sites in both univariate and multivariate models adjusting for HIV status, age, BMI, and race, although the coefficients of association were attenuated in HIV-seropositive women. The positive association between sclerostin and BMD among seropositive women remained statistically significant after adjusting for ART or tenofovir disoproxil fumarate (TDF) use.

Conclusions

The current study suggests that circulating sclerostin is a biomarker for bone mass for both HIV seronegative and seropositive women using and not using ART. The lower coefficients of association between sclerostin and BMD by HIV status may suggest HIV-induced alternation in osteocyte function.

Sclerostin and Its Associations With Bone Metabolism Markers and Sex Hormones in Healthy Community-Dwelling Elderly Individuals and Adolescents

Sclerostin is an important regulator of bone mass involving Wnt/β-catenin signaling pathway. We aimed to obtain the profile of serum sclerostin level and explore its associations with bone metabolism markers and sex hormones in healthy community-dwelling Chinese elderly individuals and adolescents. A cross-sectional study was performed in three communities in Shanghai. In all, 861 participants, including 574 healthy elderly individuals, and 287 healthy adolescents, were recruited. The levels of serum sclerostin, procollagen type 1 N-terminal propeptide (P1NP), β-CrossLaps of type I collagen containing cross-linked C-telopeptide (β-CTX), parathyroid hormone (PTH), 25-hydroxyvitamin D [25(OH)D], estradiol (E₂), testosterone (T), and sex hormone-binding globulin (SHBG) were measured in blood samples from all participants. Median sclerostin level was higher in males than in females and in elderly individuals than in adolescents (elderly males: 54.89 pmol/L, elderly females: 39.95 pmol/L, adolescent males: 36.58 pmol/L, adolescent females: 27.06 pmol/L; both P < 0.05). In elderly individuals, serum sclerostin was positively correlated with age (β = 0.176, P < 0.001) and T (β = 0.248, P = 0.001), but negatively associated to P1NP (β = −0.140, P = 0.001). In adolescents, circulating sclerostin was significantly and positively associated with P1NP (β = 0.192, P = 0.003). The directions of the association between sclerostin and P1NP were opposite in Chinese elderly individuals and adolescents, which may reflect that sclerostin plays distinct roles in different functional states of the skeleton. Our findings revealed the rough profile of circulating sclerostin level in general healthy Chinese population and its associations with bone metabolism markers and sex hormones, which may provide a clue to further elucidate the cross action of sclerostin in bone metabolism and sexual development.

Effects of High-Intensity Interval Running Versus Cycling on Sclerostin, and Markers of Bone Turnover and Oxidative Stress in Young Men

This study compared sclerostin's response to impact versus no-impact high-intensity interval exercise in young men and examined the association between exercise-induced changes in sclerostin and markers of bone turnover and oxidative stress. Twenty healthy men (22.3 ± 2.3 years) performed two high-intensity interval exercise trials (crossover design); running on treadmill and cycling on cycle ergometer. Trials consisted of eight 1 min running or cycling intervals at ≥ 90% of maximal heart rate, separated by 1 min passive recovery intervals. Blood samples were collected at rest (pre-exercise), and 5 min, 1 h, 24 h, and 48 h following each trial. Serum levels of sclerostin, cross-linked telopeptide of type I collagen (CTXI), procollagen type I amino-terminal propeptide (PINP), thiobarbituric acid reactive substances (TBARS), and protein carbonyls (PC) were measured. There was no significant time or exercise mode effect for PINP and PC. A significant time effect was found for sclerostin, CTXI, and TBARS with no significant exercise mode effect and no significant time-by-mode interaction. Sclerostin increased from pre- to 5 min post-exercise (47%, p < 0.05) and returned to baseline within 1 h following the exercise. CTXI increased from pre- to 5 min post-exercise (28%, p < 0.05), then gradually returned to baseline by 48 h. TBARS did not increase significantly from pre- to 5 min post-exercise but significantly decreased from 5 min to 48 h post-exercise. There were no significant correlations between exercise-induced changes in sclerostin and any other marker. In young men, sclerostin's response to high-intensity interval exercise is independent of impact and is not related to changes in bone turnover and oxidative stress markers.

Response of Sclerostin and Bone Turnover Markers to High Intensity Interval Exercise in Young Women: Does Impact Matter?

This study examined potential exercise-induced changes in sclerostin and in bone turnover markers in young women following two modes of high intensity interval exercise that involve impact (running) or no-impact (cycling). Healthy, recreationally active, females (n=20; 22.5±2.7 years) performed two exercise trials in random order: high intensity interval running (HIIR) on a treadmill and high intensity interval cycling (HIIC) on a cycle ergometer. Trials consisted of eight 1 min running or cycling intervals at ≥90% of maximal heart rate, separated by 1 min passive recovery intervals. Blood samples were collected at rest (pre-exercise) and 5 min, 1h, 24h, and 48h following each exercise trial. Serum was analyzed for sclerostin, cross linked telopeptide of type I collagen (CTXI), and procollagen type I amino-terminal propeptide (PINP). A significant time effect was found for sclerostin, which increased from pre-exercise to 5 min after exercise in both trials (100.2 to 131.6 pg/ml in HIIR; 102.3 to 135.8 pg/ml in HIIC, p<0.001) and returned to baseline levels by 1h, with no difference between exercise modes and no exercise mode-by-time interaction. CTXI did not significantly change following either trial. PINP showed an overall time effect following HIIR, but none of the post hoc pairwise comparisons were statistically significant. In young women, a single bout of high intensity exercise induces an increase in serum sclerostin, irrespective of exercise mode (impact versus no-impact), but this response is not accompanied by a response in either bone formation or resorption markers.

24-hour profile of serum sclerostin and its association with bone biomarkers in men

The osteocyte's role in orchestrating diurnal variations in bone turnover markers (BTMs) is unclear. We identified no rhythm in serum sclerostin (osteocyte protein). These results suggest that serum sclerostin can be measured at any time of day and the osteocyte does not direct the rhythmicity of other BTMs in men.

INTRODUCTION

The osteocyte exerts important effects on bone remodeling, but its rhythmicity and effect on the rhythms of other bone cells are not fully characterized. The purpose of this study was to determine if serum sclerostin displays rhythmicity over a 24-h interval, similar to that of other bone biomarkers.

METHODS

Serum sclerostin, FGF-23, CTX, and P1NP were measured every 2 h over a 24-h interval in ten healthy men aged 20-65 years. Maximum likelihood estimates of the parameters in a repeated measures model were used to determine if these biomarkers displayed a diurnal, sinusoidal rhythm.

RESULTS

No discernible 24-h rhythm was identified for sclerostin (p = 0.99) or P1NP (p = 0.65). CTX rhythmicity was confirmed (p < 0.001), peaking at 05:30 (range 01:30-07:30). FGF-23 levels were also rhythmic (p < 0.001), but time of peak was variable (range 02:30-11:30). The only significant association identified between these four bone biomarkers was for CTX and P1NP mean 24-h metabolite levels (r = 0.65, p = 0.04).

CONCLUSIONS

Sclerostin levels do not appear to be rhythmic in men. This suggests that in contrast to CTX, serum sclerostin could be measured at any time of day. The 24-h profiles of FGF-23 suggest that a component of osteocyte function is rhythmic, but its timing is variable. Our results do not support the hypothesis that osteocytes direct the rhythmicity of other bone turnover markers (CTX), at least not via a sclerostin-mediated mechanism.

Sclerostin measurement in human disease: Validity and current limitations

Sclerostin a potent regulator of bone formation, is an antagonist of the Wnt-signaling pathway. The advent of assays to measure circulating sclerostin has enabled research to be performed with the aim to understand the potential role of circulating sclerostin as a pathophysiological marker in a variety of clinical settings. At this time, however, assays to measure circulating sclerostin are still relatively new and have not demonstrated consistent internal agreement in addition to which there are differences between serum and plasma levels. Nevertheless, measurement of sclerostin in the circulation has the potential to reflect the dynamics of bone formation with particular reference to situations in which osteocytes, the major source of circulating sclerostin, may be perturbed. Because of technical uncertainties regarding sclerostin assays that are currently available, circulating sclerostin measurements should be interpreted cautiously with attention to reference ranges for each assay and whether or not the measurement is made in serum or plasma.

Changes of serum sclerostin and Dickkopf-1 levels during the menstrual cycle. A pilot study

Studies in postmenopausal women have identified sclerostin as a strong candidate for mediating estrogen effects on the skeleton. The effects of estradiol on sclerostin and Dickkopf-1 in younger women remain unclear. The main purpose of this study is to investigate the impact of estradiol and gonadotrophins fluctuations during the menstrual cycle on circulating sclerostin and Dickkopf-1 levels and the possible relationship of sclerostin and Dickkopf-1 with changes in N-terminal propeptide of type 1 collagen and C-telopeptide of collagen cross-links. Fourteen healthy premenopausal Caucasian women, with regular menses, aged 33.6 ± 4.5 years participated. After the first day of menstruation and every-other-day up to the next menses, fasting serum estradiol, luteinizing hormone, follicle-stimulating hormone, sclerostin, Dickkopf-1, N-terminal propeptide of type 1 collagen, and C-telopeptide of collagen cross-links levels were measured in peripheral blood. Participants completed dietary questionnaires and the International physical activity questionnaire during the cycle. Neither sclerostin nor Dickkopf-1 levels changed significantly across the menstrual cycle (p = 0.18 and p = 0.39, respectively), while N-terminal propeptide of type 1 collagen and C-telopeptide of collagen cross-links levels presented cyclic variation (p < 0.001 and p = 0.004, respectively). Baseline sclerostin (29.23 ± 10.62 pmol/L) positively correlated with N-terminal propeptide of type 1 collagen (r = 0.71, p < 0.01) and C-telopeptide of collagen cross-links (r = 0.63, p < 0.05), while Dickkopf-1 (4.82 ± 2.23 pmol/L) correlated positively with N-terminal propeptide of type 1 collagen (r = 0.56, p < 0.05). Mid-cycle E2 levels presented significant negative association with the percent decrease of C-telopeptide of collagen cross-links at all-time points during the luteal period (r = -0.60 to -0.68, p < 0.05-0.01). Circulating sclerostin and Dickkopf-1 levels do not change across the menstrual cycle and do not demonstrate any relationship with estradiol in premenopausal women. Further investigation is needed concerning the role of sclerostin and Dickkopf-1 on bone turnover in young estrogen-sufficient women.

Decreased Plasma Levels of Sclerostin But Not Dickkopf-1 are Associated with an Increased Prevalence of Osteoporotic Fracture and Lower Bone Mineral Density in Postmenopausal Korean Women

Although sclerostin (SOST) and Dickkopf-related protein 1 (DKK1) are major regulators in bone metabolism, their associations with osteoporotic fracture (OF) in Asians are inconclusive. Furthermore, there have been no clinical studies separately considering non-vertebral and vertebral fractures in terms of the blood levels of SOST and DKK1. Among 513 consecutive postmenopausal Korean women, we identified 103 cases defined as subjects with OF (i.e., non-vertebral and/or vertebral fractures). The controls were randomly selected from the remaining 410 subjects and matched 1:1 to cases according to both age and body mass index. Non-vertebral and morphological vertebral fractures were identified by an interviewer-assisted questionnaire and lateral thoracolumbar radiographs, respectively. Bone mineral density (BMD) and plasma levels of SOST and DKK1 were measured. Plasma SOST levels were lower in subjects with OF than in the control group. Each standard deviation decrement of plasma SOST concentration was associated with a multivariable-adjusted odds ratio of 1.77 for any prevalent OF type. The odds for OF was 2.97-fold higher in subjects in the lowest SOST tertile compared with subjects in the highest SOST tertile. These associations remained significant when the non-vertebral and vertebral fractures were analyzed separately. However, prevalent OF was not associated with plasma DKK1 levels, regardless of the type of fracture and the adjustment model employed. Consistently, plasma SOST levels were positively related with BMD values at all measured skeletal sites, although this was not observed for DKK1. Circulating SOST but not DKK1 may be a potential biomarker for predicting bone health in Asians.

The potential use of antisclerostin therapy in chronic kidney disease-mineral and bone disorder

PURPOSE OF REVIEW

Sclerostin is a regulator of the osteoanabolic canonical Wnt signaling pathway, and thus helps to govern rates of bone formation. The Wnt pathway is also recognized as playing an important role in the pathophysiology of the chronic kidney disease-mineral and bone disorder (CKD-MBD). It also may serve as an interface between bone and the vascular system. Pharmacological inhibition of sclerostin has shown promise as an osteoanabolic approach to the treatment of osteoporosis. Inhibition of sclerostin is a potentially useful but unproven strategy in the management of CKD-MBD.

RECENT FINDINGS

Clinical trials with humanized monoclonal sclerostin antibodies (Scl-Ab) have shown a rapid initial increase in bone formation and a marked increase in bone mineral density. Although clinical data, to this point, in CKD are not available, animal models of low bone turnover CKD show that Scl-Ab improves trabecular bone volume and mineralization without affecting biochemical indices.

SUMMARY

Targeted clinical trials are needed to evaluate the potential effectiveness of Scl-Ab in CKD. Based upon the available data, there is potential not only for this new therapeutic class to improve skeletal health but perhaps also to have substantial cardiovascular benefits in CKD.

Increase in circulating sclerostin at the early stage of menopausal transition in Japanese women

OBJECTIVE

We examined the change in circulating sclerostin level during the menopausal transition and we investigated the associations of sclerositin with hormones and bone turnover markers according to each menopausal stage in cross-sectional and longitudinal studies.

METHODS

We conducted a cross-sectional study in 200 healthy Japanese women and divided them into 4 stages (reproductive, menopausal transition, early postmenopause and late postmenopause) by menstrual regularity, follicle-stimulating hormone level and years since menopause. Serum levels of sclerostin, bone turnover markers and reproductive hormones were measured. In addition, we examined changes in sclerostin level from the reproductive stage to menopausal transition and from menopausal transition to early postmenopause in a longitudinal study.

RESULTS

In the cross-sectional study, sclerostin level gradually increased with progression of menopausal stages and showed a significant change during the menopausal transition. Sclerostin levels significantly increased from the reproductive stage to menopausal transition and from menopausal transition to early postmenopause in the longitudinal study. A negative correlation of sclerostin with estradiol was found in early postmenopause. Sclerostin levels were negatively correlated with bone-specific alkaline phosphatase levels in the reproductive stage and menopausal transition and with tartrate-resistant acid phosphatase-5b in menopausal transition.

CONCLUSION

The change in sclerostin has already occurred in the early stage of menopausal transition and sclerostin level increases with progression of menopausal stages. Elevated sclerostin levels during the menopausal transition may be involved in relative decline in bone formation against increase in bone resorption.

Circulating sclerostin and estradiol levels are associated with inadequate response to bisphosphonates in postmenopausal women with osteoporosis

INTRODUCTION

The biological mechanisms associated with an inadequate response to treatment with bisphosphonates are not well known. This study investigates the association between circulating levels of sclerostin and estradiol with an inadequate clinical outcome to bisphosphonate therapy in women with postmenopausal osteoporosis.

METHODS

This case-control study is based on 120 Spanish women with postmenopausal osteoporosis being treated with oral bisphosphonates. Patients were classified as adequate responders (ARs, n=66, mean age 68.2±8 years) without incident fractures during 5 years of treatment, or inadequate responders (IRs, n=54, mean age 67±9 years), with incident fractures between 1 and 5 years of treatment. Bone mineral density (DXA), structural analysis of the proximal femur and structural/fractal analysis of the distal radius were assessed. Sclerostin concentrations were measured by ELISA and 17β-estradiol levels by radioimmunoassay based on ultrasensitive methods.

RESULTS

In the ARs group, sclerostin serum levels were significantly lower (p=0.02) and estradiol concentrations significantly higher (p=0.023) than in the IRs group. A logistic regression analysis was performed, including as independent variables in the original model femoral fracture load, 25 hydroxyvitamin D, previus history of fragility fracture, sclerostin and estradiol. Only previous history of fragility fracture (OR 14.04, 95% CI 2.38-82.79, p=0.004) and sclerostin levels (OR 1.11, 95% CI 1.02-1.20, p=0.011), both adjusted by estradiol levels remained associated with IRs. Also, sclerostin concentrations were associated with the index of resistance to compression (IRC) in the fractal analysis of the distal radius, a parameter on bone microstructure.

CONCLUSIONS

Sclerostin and estradiol levels are associated with the response to bisphosphonate therapy in women with postmenopausal osteoporosis.

Mechanisms of Normalisation of Bone Metabolism during Recovery from Hyperthyroidism: Potential Role for Sclerostin and Parathyroid Hormone

Sclerostin, a protein expressed by osteocytes, is a negative regulator of bone formation. The aim of the study was to investigate the relationship between parathyroid hormone (PTH) and markers of bone metabolism and changes of sclerostin concentrations before and after treatment of hyperthyroidism. Patients and Methods. The study involved 33 patients (26 women), age (mean ± SD) 48 ± 15 years, with hyperthyroidism. Serum sclerostin, PTH, calcium, and bone markers [osteocalcin (OC) and collagen type I cross-linked C-telopeptide I (CTX)] were measured at diagnosis of hyperthyroidism and after treatment with thiamazole. Results. After treatment of hyperthyroidism a significant decrease in free T3 (FT3) and free T4 (FT4) concentrations was accompanied by marked decrease of serum sclerostin (from 43.7 ± 29.3 to 28.1 ± 18.4 pmol/L; p < 0.001), OC (from 35.6 ± 22.0 to 27.0 ± 14.3 ng/mL; p < 0.001), and CTX (from 0.49 ± 0.35 to 0.35 ± 0.23 ng/dL; p < 0.005), accompanied by an increase of PTH (from 29.3 ± 14.9 to 39.8 ± 19.8; p < 0.001). During hyperthyroidism there was a positive correlation between sclerostin and CTX (r s = 0.41, p < 0.05) and between OC and thyroid hormones (with FT3  r s = 0.42, with FT4  r s = 0.45, p < 0.05). Conclusions. Successful treatment of hyperthyroidism results in a significant decrease in serum sclerostin and bone markers concentrations, accompanied by an increase of PTH.

Sclerostin: recent advances and clinical implications

PURPOSE OF REVIEW

Discovery of the Wnt signaling pathway and understanding the central role of osteocyte in skeletal homeostasis have been the major advances in skeletal biology over the past decade. Sclerostin, secreted mainly (but not exclusively) by osteocytes, has emerged as a key player in skeletal homeostasis. This review highlights the most relevant recent advances.

RECENT FINDINGS

Sclerostin by inhibiting Wnt signaling pathway decreases bone formation and osteoblast differentiation and promotes osteoblast apoptosis. Ability to measure serum sclerostin levels better clarified the role of sclerostin in various physiologic and pathologic states. Early clinical trials with antibodies to sclerostin have produced robust increases in bone mineral density, and fracture prevention trials are underway.

SUMMARY

Since the discovery of Wnt signaling pathway and sclerostin's association with high bone mass, there has been a remarkable progress. Clinical trials with fracture endpoints, already underway, should expand osteoanabolic therapeutic horizon in the very near future. Measurement of sclerostin levels in a number of conditions has advanced our knowledge about pathophysiology of skeletal and nonskeletal disorders in an altogether new light.

New developments in biological markers of bone metabolism in osteoporosis

Over the last 15 years several biological markers of bone turnover have been developed with increased specificity and sensitivity. In osteoporosis clinical studies, the IOF and IFCC organizations have recently recommended the measurements of serum type I collagen N-propeptide (PINP) and the crosslinked C-terminal telopeptide (serum CTX) as markers of bone formation and bone resorption, respectively. However these markers have some limitations including a lack of specificity for bone tissue, their inability to reflect osteocyte activity or periosteal apposition. In addition they do not allow the investigation of bone tissue quality an important determinant of skeletal fragility. To address these limitations, new developments in markers of bone metabolism have been recently achieved. These include assays for periostin, a matricellular protein preferentially localized in the periosteal tissue, sphingosine 1-phosphate, a lipid mediator which acts mainly on osteoclastogenesis and the osteocyte factors such as sclerostin and FGF-23. Recent studies have shown an association between the circulating levels of these biological markers and fracture risk in postmenopausal women or elderly men, although data require confirmation in additional prospective studies. Finally, recent studies suggest that the measurements of circulating microRNAs may represent a novel class of early biological markers in osteoporosis. It is foreseen that with the use of genomics and proteomics, new markers will be developed to ultimately improve the management of patients with osteoporosis.

Osteoporosis in men: a review

Osteoporosis and consequent fracture are not limited to postmenopausal women. There is increasing attention being paid to osteoporosis in older men. Men suffer osteoporotic fractures about 10 years later in life than women, but life expectancy is increasing faster in men than women. Thus, men are living long enough to fracture, and when they do the consequences are greater than in women, with men having about twice the 1-year fatality rate after hip fracture, compared to women. Men at high risk for fracture include those men who have already had a fragility fracture, men on oral glucocorticoids or those men being treated for prostate cancer with androgen deprivation therapy. Beyond these high risk men, there are many other risk factors and secondary causes of osteoporosis in men. Evaluation includes careful history and physical examination to reveal potential secondary causes, including many medications, a short list of laboratory tests, and bone mineral density testing by dual energy X-ray absorptiometry (DXA) of spine and hip. Recently, international organizations have advocated a single normative database for interpreting DXA testing in men and women. The consequences of this change need to be determined. There are several choices of therapy for osteoporosis in men, with most fracture reduction estimation based on studies in women.

The Chinese skeleton: insights into microstructure that help to explain the epidemiology of fracture

Osteoporotic fractures are a major public health problem worldwide, but incidence varies greatly across racial groups and geographic regions. Recent work suggests that the incidence of osteoporotic fracture is rising among Asian populations. Studies comparing areal bone mineral density and fracture across races generally indicate lower bone mineral density in Asian individuals including the Chinese, but this does not reflect their relatively low risk of non-vertebral fractures. In contrast, the Chinese have relatively high vertebral fracture rates similar to that of Caucasians. The paradoxically low risk for some types of fractures among the Chinese despite their low areal bone mineral density has been elucidated in part by recent advances in skeletal imaging. New techniques for assessing bone quality non-invasively demonstrate that the Chinese compensate for smaller bone size by differences in hip geometry and microstructural skeletal organization. Studies evaluating factors influencing racial differences in bone remodeling, as well as bone acquisition and loss, may further elucidate racial variation in bone microstructure. Advances in understanding the microstructure of the Chinese skeleton have not only helped to explain the epidemiology of fracture in the Chinese, but may also provide insight into the epidemiology of fracture in other races as well.