Serum sclerostin levels positively correlate with lumbar spinal bone mineral density in postmenopausal women--the six-month effect of risedronate and teriparatide

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.

Relationship of Dickkopf1 (DKK1) with cardiovascular disease and bone metabolism in Caucasian type 2 diabetes mellitus

Objectives

Dickkopf-1 (DKK1) is a potent inhibitor of Wnt signalling, which exerts anabolic effects on bone and also takes part in the regulation of vascular cells. Our aims were to evaluate serum DKK1 in type 2 diabetes (T2DM) patients and to analyze its relationships with cardiovascular disease (CVD). We also evaluated the relationship between DKK1 and bone metabolism.

Design

We conducted a cross-sectional study in which we measured serum DKK1 (ELISA, Biomedica) in 126 subjects: 72 patients with T2DM and 54 non-diabetic subjects. We analysed its relationship with clinical CVD, preclinical CVD expressed as carotid intima media thickness (IMT), and bone metabolism.

Results

T2DM patients with CVD (P = 0,026) and abnormal carotid IMT (P = 0,038) had higher DKK1 concentrations. DKK1 was related to the presence of CVD in T2DM, independently of the presence of risk factors for atherosclerosis. Therefore, for each increase of 28 pg/ml of serum DKK1 there was a 6,2% increase in the risk of CVD in T2DM patients. The ROC curve analysis to evaluate the usefulness of DKK1 as a marker for high risk of CVD showed an area under the curve of 0,667 (95% CI: 0,538–0,795; P = 0,016). In addition, there was a positive correlation between serum DKK1 and spine bone mineral density in the total sample (r = 0,183; P = 0,048).

Conclusion

In summary, circulating DKK1 levels are higher in T2DM with CVD and are associated with an abnormal carotid IMT in this cross-sectional study. DKK1 may be involved in vascular disease of T2DM patients.

Early effects of tumor necrosis factor inhibition on bone homeostasis after soluble tumor necrosis factor receptor use

BACKGROUND/AIMS

Our aim was to assess whether short-term treatment with soluble tumor necrosis factor (TNF) receptor affects circulating markers of bone metabolism in rheumatoid arthritis (RA) patients.

METHODS

Thirty-three active RA patients, treated with oral disease-modifying antirheumatic drugs (DMARDs) and glucocorticoids for > 6 months, were administered etanercept for 12 weeks. Serum levels of bone metabolism markers were compared among patients treated with DMARDs at baseline and after etanercept treatment, normal controls and naive RA patients not previously treated with DMARDs (both age- and gender-matched).

RESULTS

Bone-specific alkaline phosphatase (BSALP) and serum c-telopeptide (CTX)-1 levels were lower in RA patients treated with DMARDs than in DMARD-naive RA patients. After 12 weeks of etanercept treatment, serum CTX-1 and sclerostin levels increased. In patients whose DAS28 improved, the sclerostin level increased from 1.67 ± 2.12 pg/mL at baseline to 2.51 ± 3.03 pg/mL, which was statistically significant (p = 0.021). Increases in sclerostin levels after etanercept treatment were positively correlated with those of serum CTX-1 (r = 0.775), as were those of BSALP (r = 0.755).

CONCLUSIONS

RA patients treated with DMARDs showed depressed bone metabolism compared to naive RA patients. Increases in serum CTX-1 and sclerostin levels after short-term etanercept treatment suggest reconstitution of bone metabolism homeostasis.

Serum sclerostin in high-activity adult patients with juvenile idiopathic arthritis

Introduction

Juvenile idiopathic arthritis (JIA) is a disease associated with loss of bone mass, deterioration in bone mass quality and an increased risk of fractures. The objective of this study was to evaluate factors that predict bone mineral density (BMD) alterations in young adult patients with active JIA before and during therapy with tumour necrosis factor α (TNFα) inhibitors.

Methods

Thirty-one patients (twelve males and nineteen females; mean age =25.1 ± 6.1 years) with active JIA (mean Disease Activity Score in 28 joints (DAS28) =6.36 ± 0.64; mean high-sensitivity C-reactive protein (hsCRP) =18.36 ± 16.95 mg/L) were investigated. The control group consisted of 84 healthy individuals matched by sex and age. BMD, bone turnover markers and serum concentrations of soluble receptor activator of nuclear factor κB ligand, osteoprotegerin, dickkopf Wnt signalling pathway inhibitor 1 (Dkk1) and sclerostin were evaluated.

Results

Baseline BMD values in the lumbar spine, proximal femur, femoral neck and distal radius were significantly lower in patients with JIA compared to healthy control participants. Baseline sclerostin serum concentrations were significantly higher in patients with JIA compared to control participants. After 2 years of treatment with TNFα inhibitors, BMD was significantly increased in the lumbar spine. This increase correlated with a drop in DAS28 score. A statistically significant correlation between hsCRP and Dkk1 was found at baseline, as well as during the 2-year follow-up period. A significant reduction in serum sclerostin after 1 year of therapy was predictive of a drop in DAS28 score observed with a 1-year delay after reduction of serum sclerostin.

Conclusion

A significant correlation between the sclerostin serum concentration and the number of tender and swollen joints, but not BMD, supports the hypothesis that chondrocytes and cells of the subchondral bone may contribute to circulating sclerostin in JIA.

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.

Elevated circulating Sclerostin concentrations in individuals with high bone mass, with and without LRP5 mutations

CONTEXT

The role and importance of circulating sclerostin is poorly understood. High bone mass (HBM) caused by activating LRP5 mutations has been reported to be associated with increased plasma sclerostin concentrations; whether the same applies to HBM due to other causes is unknown.

OBJECTIVE

Our objective was to determine circulating sclerostin concentrations in HBM.

DESIGN AND PARTICIPANTS

In this case-control study, 406 HBM index cases were identified by screening dual-energy x-ray absorptiometry (DXA) databases from 4 United Kingdom centers (n = 219 088), excluding significant osteoarthritis/artifact. Controls comprised unaffected relatives and spouses.

MAIN MEASURES

Plasma sclerostin; lumbar spine L1, total hip, and total body DXA; and radial and tibial peripheral quantitative computed tomography (subgroup only) were evaluated.

RESULTS

Sclerostin concentrations were significantly higher in both LRP5 HBM and non-LRP5 HBM cases compared with controls: mean (SD) 130.1 (61.7) and 88.0 (39.3) vs 66.4 (32.3) pmol/L (both P < .001, which persisted after adjustment for a priori confounders). In combined adjusted analyses of cases and controls, sclerostin concentrations were positively related to all bone parameters found to be increased in HBM cases (ie, L1, total hip, and total body DXA bone mineral density and radial/tibial cortical area, cortical bone mineral density, and trabecular density). Although these relationships were broadly equivalent in HBM cases and controls, there was some evidence that associations between sclerostin and trabecular phenotypes were stronger in HBM cases, particularly for radial trabecular density (interaction P < .01).

CONCLUSIONS

Circulating plasma sclerostin concentrations are increased in both LRP5 and non-LRP5 HBM compared with controls. In addition to the general positive relationship between sclerostin and DXA/peripheral quantitative computed tomography parameters, genetic factors predisposing to HBM may contribute to increased sclerostin levels.

Bone mineral density and serum biochemical predictors of bone loss in patients with CKD on dialysis

BACKGROUND AND OBJECTIVES

Use of bone mineral density (BMD) by dual-energy x-ray absorptiometry (DXA) is controversial for diagnosing bone loss in CKD patients on dialysis. The alternative quantitative computed tomography (QCT) is expensive and requires high radiation exposure. This study compared the two techniques and evaluated serum biochemical parameters for prediction of bone loss.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This prospective study enrolled patients from dialysis centers throughout Kentucky. BMD of the spine and hip was measured at baseline and after 1 year by DXA and QCT. Customary and novel serum biochemical parameters were obtained at the same times, including calcium, phosphorus, whole and intact parathyroid hormone, bone-specific alkaline phosphatase, procollagen type 1 N-terminal propeptide, tartrate-resistant acid phosphatase-5b, Dickkopf-1, fibroblast growth factor, and sclerostin. Rates of detection of osteoporosis by DXA and QCT were compared. Correlations were calculated between baseline biochemical parameters and BMD at baseline and changes over 1 year. Multivariable regression was performed to adjust for age, sex, body mass index, and race.

RESULTS

Eighty-one patients completed the study (mean age=52.6 ± 12.3 years, 56% men, 53% African American, and median dialysis vintage=41 months). At baseline, QCT and DXA of the spine identified similar rates of osteoporosis (13.6% and 13.6%), but at the hip, DXA identified more osteoporosis (22.2% versus 13.6%). At any site and by either method, 33.3% of the patients were osteoporotic. Baseline BMD correlated with sclerostin, intact parathyroid hormone, bone-specific alkaline phosphatase, tartrate-resistant acid phosphatase-5b, and fibroblast growth factor. At 1 year, hip QCT identified a higher number of patients experiencing bone loss (51.3%) than DXA (38.5%). After multivariable adjustment, baseline sclerostin and tartrate-resistant acid phosphatase-5b predicted bone loss measured by QCT of the hip; procollagen type 1 N-terminal propeptide predicted cortical spine bone gain by QCT.

CONCLUSIONS

QCT identified prospectively more bone loss at the hip than DXA. The baseline serum biochemical parameters sclerostin and tartrate-resistant acid phosphatase-5b were noninvasive independent predictors of bone loss in CKD patients on dialysis.

Expression of fibroblast growth factor 23, vitamin D receptor, and sclerostin in bone tissue from hypercalciuric stone formers

BACKGROUND AND OBJECTIVES

Increased bone resorption, low bone formation, and abnormal mineralization have been described in stone formers with idiopathic hypercalciuria. It has been previously shown that the receptor activator of NF-κB ligand mediates bone resorption in idiopathic hypercalciuria (IH). The present study aimed to determine the expression of fibroblast growth factor 23 (FGF-23), vitamin D receptor (VDR), and sclerostin in bone tissue from IH stone formers.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Immunohistochemical analysis was performed in undecalcified bone samples previously obtained for histomorphometry from 30 transiliac bone biopsies of idiopathic hypercalciuria stone-forming patients between 1992 and 2002 and 33 healthy individuals (controls). Serum parameters were obtained from their medical records.

RESULTS

Histomorphometry disclosed 21 IH patients with high and 9 IH patients with normal bone resorption. Importantly, eroded surfaces (ES/BS) from IH patients but not controls were significantly correlated with VDR immunostaining in osteoblasts (r=0.51; P=0.004), sclerostin immunostaining in osteocytes (r=0.41; P=0.02), and serum 1,25-dihydroxyvitamin D (r=0.55; P<0.01). Of note, both VDR and sclerostin immunostaining were significantly correlated with serum 1,25-dihydroxyvitamin D in IH patients (r=0.52; P=0.01 and r=0.53; P=0.02, respectively), although VDR and sclerostin expression did not differ between IH and controls. IH patients with high bone resorption exhibited a significantly stronger sclerostin immunostaining than IH patients with normal bone resorption. FGF-23 expression in osteocytes from IH patients did not differ from controls and was not correlated with any histomorphometric parameter.

CONCLUSIONS

These findings suggest the contribution of VDR and sclerostin, as well as 1,25-dihydroxyvitamin D, to increase bone resorption in idiopathic hypercalciuria but do not implicate FGF-23 in the bone alterations seen in these patients.

Teriparatide increases bone formation and bone mineral density in adult women with anorexia nervosa

CONTEXT

Anorexia nervosa (AN), a prevalent psychiatric disorder predominantly affecting women, is characterized by self-induced starvation and low body weight. Increased clinical fractures are common, and most women have low bone mineral density (BMD). Previously investigated treatments have led to no or modest increases in BMD in AN.

OBJECTIVE

Our objective was to investigate the effect of teriparatide (TPT; human PTH[1-34]), an anabolic agent, on low bone mass in women with AN.

DESIGN, SETTING, AND PATIENTS

This randomized, placebo-controlled trial at a clinical research center included 21 women with AN: 10 (mean age ± SEM, 47 ± 2.7 years) treated with TPT and 11 (47.1 ± 2.3 years) treated with placebo.

INTERVENTIONS

TPT (20 μg s.c.) or placebo was administered for 6 months.

MAIN OUTCOME MEASURES

Our primary outcome measure was change in BMD of the spine and hip by dual-energy x-ray absorptiometry. Secondary outcome measures included changes in serum N-terminal propeptide of type 1 procollagen (P1NP), C-terminal collagen cross-links, sclerostin, and IGF-1 levels.

RESULTS

At 6 months, spine BMD increased significantly more with TPT (posteroanterior spine, 6.0% ± 1.4%; lateral spine, 10.5% ± 2.5%) compared with placebo (posteroanterior spine, 0.2% ± 0.7%, P < .01; lateral spine, -0.6% ± 1.0%; P < .01). The results remained significant after controlling for baseline body mass index, P1NP, and IGF-1. Changes in femoral neck (P = .4) and total hip (P = 0.8) BMD were comparable in both groups, as were changes in weight. Serum P1NP levels increased after 3 months of TPT treatment and remained at this higher level at 6 months, whereas P1NP levels were unchanged in the placebo group (P = .02). TPT was well-tolerated by all subjects.

CONCLUSIONS

This study demonstrates that TPT administration increases spine BMD substantially after only 6 months of therapy in women with AN.

The role of Wnt signaling and sclerostin in the pathogenesis of glucocorticoid-induced osteoporosis

Bone formation is suppressed in glucocorticoid-induced osteoporosis. One of the mechanisms by which glucocorticoids depress bone formation is through their effects on the Wnt/β-catenin signaling pathway, a critical regulator of osteoblastogenesis. Thus, Wnt signaling induces the differentiation of osteoblast precursors toward mature osteoblasts and prevents osteoblast and osteocyte apoptosis. Glucocorticoids increase the expression of Wnt signaling antagonists (sclerostin and Dkk-1) in experimental studies in rodents and cell cultures. However, the scarce data of their effects in humans are somewhat contradictory, probably due to the dose and duration of treatment as well as the characteristics of the patients. A progressive decrease in Dkk-1 serum levels and an increase in circulating sclerostin levels at long-term follow-up have recently been reported in patients treated with high doses of glucocorticoids. This review describes the most recent data on the effects of glucocorticoids on the Wnt signaling pathway, especially on their antagonists, sclerostin and Dkk-1.

Serum sclerostin in hepatitis C virus infected patients

Background

Sclerostin inhibits osteoblast functions, differentiations, and survival rates. As an endogenous inhibitor of the Wnt/β-catenin pathway, the sclerostin should be related to decreased bone masses, although several studies indicate opposite results. In addition, it may be related to insulin resistances and carbohydrate metabolisms, a relation shared with other markers of bone metabolisms, such as osteocalcin. Hepatitis C virus (HCV) infected patients may present osteoporosis, and frequently show liver steatosis, which is a consequence of insulin resistance. The behaviour of sclerostin in these patients is yet unknown. The aim of this work is to analyse the relationships between serum sclerostin and osteocalcin levels and bone mineral density (BMD), liver functions, the intensity of liver steatosis and biochemical markers of bone homeostasis and insulin resistance in HCV-infected patients.

Methods

Forty HCV patients with 20 years of age and gender-matching controls were included in this study and underwent bone densitometry. Serum sclerostin, osteocalcin, collagen telopeptide, adiponectin, leptin, insulin, resistin, tumor necrosis factor (TNF)-α, and interleukin (IL)-6 were determined. Liver fat was histomorphometrically assessed.

Results

Sclerostin levels were slightly higher in patients than in controls, and were directly related to BMD at different parts of the skeleton, also to the serum telopeptide, and to the liver steatosis and TNF-α. On the contrary, osteocalcin showed a significant direct relationship with serum adiponectin, and an inverse one with IL-6.

Conclusions

Serum sclerostin levels were within the normal range in HCV patients, and correlated directly with BMD and serum telopeptide. In addition, the relationships of sclerostin and osteocalcin with variables associated with insulin resistance suggested the role of bones for intermediary metabolisms.

Serum sclerostin levels are decreased in adult patients with different types of osteogenesis imperfecta

CONTEXT

There are no specific biochemical bone markers available for osteogenesis imperfecta (OI), and the role of sclerostin as a key regulator of bone formation in OI is unknown.

OBJECTIVES

We aimed to evaluate the role of sclerostin and its association with bone turnover markers as well as body composition parameters in adult patients with different types of OI.

DESIGN, SETTING, AND PARTICIPANTS

This was a case-control study in 27 adult patients and 50 healthy age- and gender-matched controls.

MAIN OUTCOME MEASURES

Serum sclerostin levels and bone turnover markers including serum osteocalcin, amino terminal propeptide of type I procollagen, and CrossLaps as well as body composition parameters were determined in mild OI stage I (OI-I) and moderate-severe OI stages III-IV (OI-III-IV), according to Sillence classification. Data were compared with healthy controls.

RESULTS

Sclerostin levels were significantly lower in OI-I (19.9 ± 10.9 pmol/L; P < .001) and OI-III-IV (13.3 ± 10.0 pmol/L; P < .001) compared with healthy adults (45.3 ± 14.9 pmol/L), even after adjustment for age, sex, bone mineral content, and body mass index. CrossLaps and PTH were significantly lower in OI-I (0.197 ± 0.15 ng/L; P = .007 and 33.7 ± 19.1 pg/L; P = .033, respectively) and OI-III-IV (0.221 ± 0.18 ng/L; P = .039, and 27.9 ± 14.7 pg/L; P = .001, respectively) than in healthy controls (0.322 ± 0.15 ng/L and 45.0 ± 16.6 pg/L). Amino-terminal propeptide of type I procollagen was below the reference range for OI-I and OI-III-IV. Patients with OI were shorter and lighter and had a decreased bone mineral content (P < .001) but similar fat distribution and lean body mass, compared with controls. Serum sclerostin levels were not related to any bone marker except osteocalcin, the number of prevalent fractures, or body composition readings.

CONCLUSION

Decreased sclerostin levels in OI might reflect a down-regulation or negative feedback mechanism to prevent further bone loss.

Role of sclerostin in the bone loss of postmenopausal chinese women with type 2 diabetes

OBJECTIVE

To evaluate the role of sclerostin in bone loss of postmenopausal Chinese women with type 2 diabetes mellitus.

METHODS

The postmenopausal patients suffering from type 2 diabetes mellitus and age, body mass index, and duration of menopause matched healthy controls were enrolled into this cross-sectional study according to criteria of inclusion and exclusion. The serum sclerostin level and bone mineral density of the anterior-posterior lumbar spine (L1-L4), femoral neck, and total hip were determined by using a quantitative sandwich ELISA kit and dual X-ray absorptiometry, respectively. Meanwhile, the clinical and laboratory indexes of bone mineral metabolism were analyzed. Associations between serum sclerostin level and bone mineral density as well as bone turnover markers were evaluated by linear regression analysis.

RESULTS

Finally, 265 postmenopausal women with type 2 diabetes and 225 non-diabetic women were recruited in the diabetic group and control group, respectively. Serum sclerostin level of the diabetic group was significantly higher than that of the control group (48.2±19.4 vs. 37.2±18.6 pmol/L, P<0.001) and was increased with age in both groups (diabetic group, r=0.374, P<0.001; control group, r=0.312, P<0.001). In type 2 diabetes patients, serum sclerostin concentration was positively correlated with hemoglobin A1c level (r=0.237; P=0.021). Biochemical bone turnover markers, intact parathyroid hormone and bone-specific alkaline phosphatase, were negatively associated with serum sclerostin level (r=-0.138, P=0.078 and r=-0.265, P<0.001). Conversely, the positive correlation between sclerostin and C-terminal cross-linking telopeptide of type I collagen was found in diabetic patients (r=0.354, P<0.001). Serum sclerostin levels of the diabetic group were positively correlated with bone mineral density of the lumbar spine, femoral neck, and total hip (r=0.324, 0.367, and 0.416, respectively; all P<0.001).

CONCLUSIONS

Sclerostin might participate in the pathogenesis of bone loss of type 2 diabetes. The high sclerostin level might serve as a marker of increased osteocyte activity in postmenopausal patients with type 2 diabetes mellitus.

Effect of glucocorticoid treatment on Wnt signalling antagonists (sclerostin and Dkk-1) and their relationship with bone turnover

The aim of this study was to analyse the effect of glucocorticoid therapy (GCCT) on Wnt signalling antagonists (sclerostin and Dkk-1) and their relationship with bone turnover. 25 patients (8 M/17 F, aged 48±19yrs) recently initiating GCCT (≥7.5mg/day, ≤6months) were prospectively included. Bone turnover markers (bone formation: P1NP, osteocalcin [OC], bone ALP; bone resorption: sCTx) and Wnt antagonists (serum sclerostin and Dkk-1) were assessed in all patients (short-term and 12months after initiating GCCT). Bone mineral density (BMD) was performed to assess osteoporosis. The results were compared with 60 healthy controls. At short-term patients on GCCT showed a significant decrease in bone formation markers versus controls (P1NP: 19±9 vs. 43±16ng/mL, p<0.001; OC: 7.4±2.4 vs. 18.4±5.2ng/mL, p=0.001) and in Dkk-1 levels (24.5±20.1 vs. 36.8±13.7pmol/L, p=0.008) with similar sclerostin values (41.8±21.8 vs. 42.1±13.9pmol/L, p=0.950). Sclerostin correlated positively with GCCT doses (r=0.449, p=0.024) and lumbar BMD (r=0.424, p=0.035), and negatively with bone ALP (r=-0.398, p=0.049). A progressive decrease in Dkk-1 levels was observed at 12months, (19.1±14.9, p=0.001), whereas sclerostin increased compared to controls (48.9±11.6, p=0.045). In conclusion, the effect of GCCT on the serum levels of the Wnt signalling parameters differs depending on the antagonist evaluated. Whereas sclerostin values increased and showed a relationship with the dose and bone AP, Dkk-1 levels decreased throughout the study suggesting a counter-regulatory mechanism of this factor thereby reducing the deleterious effect of GCCT in the bone.

Traditional and novel bone remodeling markers in premenopausal and postmenopausal women

CONTEXT

Bone turnover markers (BTMs) may identify changes in bone remodeling within a relatively short time interval before changes in bone mineral density can be detected. New markers such as osteoprotegerin, receptor activator of nuclear factor-κB ligand, and sclerostin have emerged, but there is little information about their potential use in clinical practice.

OBJECTIVES

The aim of this study was to analyze the ability of several BTMs to predict bone loss in pre- and postmenopausal women and to monitor the efficacy of treatment in osteoporotic women.

DESIGN, PATIENTS, AND SETTING

We performed an observational prospective study in pre- and postmenopausal ambulatory women (n = 72 and n = 152, respectively).

INTERVENTION

Postmenopausal women with osteoporosis (n = 18) were treated with risedronate and calcium. Women filled out a questionnaire and underwent bone mineral density measurement using dual-energy x-ray absorptiometry at the time of enrollment and after 1 year of follow-up. BTMs were measured at baseline, at 6 months, and after 1 year.

RESULTS

Increased levels of N-terminal propeptide of type 1 procollagen (P1NP) and β-type I collagen telopeptides (CTXs) were associated with low bone mineral density in the premenopausal (P = .02 and P = .04, respectively) and postmenopausal (P = .03 and P = .02) groups. The best analytical performance to diagnose osteoporosis was for β-CTX, osteocalcin, and P1NP, with areas under the curve of 0.70 (P = .005), 0.64 (P = .048), and 0.71 (P = .003). A significant decrease was found in P1NP, osteocalcin, tartrate-resistant acid phosphatase-5b, β-CTX, and bone alkaline phosphatase after 1 year of treatment (all P < .05).

CONCLUSIONS

Our data suggest that measurement of β-CTX and P1NP shows adequate analytical performance and could potentially be included in algorithms for the screening of osteoporosis. Furthermore, these two markers, along with osteocalcin and tartrate-resistant acid phosphatase-5b, are useful to monitor the response to risedronate.

Sclerostin and bone strength in women in their 10th decade of life

Sclerostin is a potent inhibitor of bone formation but has been shown to correlate positively with areal bone mineral density (aBMD). Little is known about its relationship to parameters of bone strength and volumetric BMD (vBMD) as measured by peripheral quantitative computed tomography (pQCT). We measured both serum sclerostin and parameters of tibial bone size and strength by pQCT to characterize this relationship. Our study population consisted of 223 white and 35 African American women (mean age 87 years) from the Study of Osteoporotic Fractures (SOF) cohort, who had usable pQCT scans of the tibia at sites 4% (T4%), 33% (T33%), and 66% (T66%) from the ankle. Analysis of covariance was used to test for differences in age-adjusted means of aBMD, pQCT variables, and serum biomarkers across sclerostin quartiles. African American women had significantly lower median sclerostin (34.3 pmol/L) than white women (48.5 pmol/L) (p = 0.05). Women in the highest sclerostin quartile had 7% to 14.5% higher hip aBMD and pQCT parameters of vBMD and bone size than those in the lowest quartile in multivariate models adjusting for age, race, weight, height, and diabetes status. The association of sclerostin with parameters of bone strength differed dramatically between T33% and T66% sites. At T66%, women in the highest sclerostin quartile had pQCT strength parameters 9.4% to 15.3% greater than the lowest quartile, whereas no trend was found for the T33% site. Our results suggest paradoxical associations between circulating sclerostin and bone size, density, and strength.

Serum sclerostin levels in healthy men over 50 years of age

The aim of this study is to evaluate the relationship of serum sclerostin levels with age, cystatin C, bone mineral density (BMD) and biochemical markers of bone turnover in healthy Hungarian men >50 years of age. We determined serum levels of sclerostin and examined its relationship to age, cystatin C, osteocalcin, C-terminal telopeptides of type-I collagen, procollagen type 1 amino-terminal propeptide, 25-hydroxyvitamin D, parathyroid hormone, and L1-L4 (LS) and femur neck (FN) BMD data available from 194 randomly selected ambulatory men belonging to the HunMen cohort. In the study population as a whole [n = 194; age (median, range) 59 (51-81) years], statistically significant correlation was found between sclerostin and age (r = 0.211; p = 0.003), cystatin C (r = 0.246; p = 0.001), FN BMD (r = 0.147; p = 0.041) and LS BMD (r = 0.169; p = 0.019). Compared to middle-aged men (age ≤59 years, n = 98), elderly men (age >59 years, n = 96) had significantly higher serum sclerostin levels (67.8 ± 15.9 vs 63.5 ± 14 pmol/L; p = 0.047). Among men with normal (T score >-1.0) FN BMD, the elderly had significantly higher serum sclerostin levels compared to the middle-aged men (70.4 ± 17 vs 63.9 ± 11.5 pmol/L; p = 0.019). Furthermore, among the elderly men cystatin C was the only significant predictor of serum sclerostin levels (standardized regression coefficient (β) = 0.487; p < 0.001). In the studied healthy elderly cohort, this study reports a significant increase in sclerostin levels with increasing age and deteriorating kidney function as determined by plasma cystatin C levels.

The clinical utility of bone marker measurements in osteoporosis

Osteoporosis is characterised by low bone mass and structural deterioration of bone tissue, resulting in increased fragility and susceptibility to fracture. Osteoporotic fractures are a significant cause of morbidity and mortality. Direct medical costs from such fractures in the UK are currently estimated at over two billion pounds per year, resulting in a substantial healthcare burden that is expected to rise exponentially due to increasing life expectancy. Currently bone mineral density is the WHO standard for diagnosis of osteoporosis, but poor sensitivity means that potential fractures will be missed if it is used alone. During the past decade considerable progress has been made in the identification and characterisation of specific biomarkers to aid the management of metabolic bone disease. Technological developments have greatly enhanced assay performance producing reliable, rapid, non-invasive cost effective assays with improved sensitivity and specificity. We now have a greater understanding of the need to regulate pre-analytical sample collection to minimise the effects of biological variation. However, bone turnover markers (BTMs) still have limited clinical utility. It is not routinely recommended to use BTMs to select those at risk of fractures, but baseline measurements of resorption markers are useful before commencement of anti-resorptive treatment and can be checked 3–6 months later to monitor response and adherence to treatment. Similarly, formation markers can be used to monitor bone forming agents. BTMs may also be useful when monitoring patients during treatment holidays and aid in the decision as to when therapy should be recommenced. Recent recommendations by the Bone Marker Standards Working Group propose to standardise research and include a specific marker of bone resorption (CTX) and bone formation (P1NP) in all future studies. It is hoped that improved research in turn will lead to optimised markers for the clinical management of osteoporosis and other bone diseases.

Involvement of WNT/β-catenin signaling in the treatment of osteoporosis

Osteoblast differentiation is predominantly regulated by the WNT/β-catenin signaling (canonical WNT pathway), which, together with bone morphogenetic proteins, acts as the master regulator of osteogenesis. The recent characterization of the canonical WNT pathway in the regulation of bone modeling and remodeling provided important insights for our understanding of the pathophysiology of a number of conditions and of the mechanism of action of hormones or drugs with important effect on bone metabolism. This review is mainly focused on the growing therapeutic implications of these new findings. WNT/β-catenin signaling plays a key role in bone tissue by determining the differentiation of stem cells into mature osteoblasts rather than into chondrocytes and adipocytes. Its regulation is predominantly driven by the production of two WNT signaling antagonists: sclerostin (SOST) and Dickkopf-related protein 1 (DKK1). The most proximate regulator of SOST expression by osteocytes and its serum levels is bone mechanical load. SOST expression is increased with advancing age, by glucocorticoid treatment and during treatment with antiresorptive agents such as bisphosphonates and denosumab, while it is decreased by parathyroid hormone excess or administration of estrogens. Correlation between DKK1 serum levels and bone formation in various pathological conditions or during osteoporosis treatment has been reported. Inhibitors of the negative regulators of WNT/β-catenin signaling ("inhibiting the endogenous inhibitors") are potential candidates for the prevention and treatment of bone loss. Inactivating monoclonal antibodies against SOST appears to be the most attractive strategy because SOST is the only component of the WNT pathway expressed almost exclusively by osteocytes.

Combination therapy with risedronate and teriparatide in male osteoporosis

Most studies of combination therapy with teriparatide and a bisphosphonate have not shown greater efficacy over monotherapy. The bisphosphonate risedronate, has not been studied in this context. The purpose of this proof-of-concept study was to assess whether combination risedronate and teriparatide increases bone mineral density (BMD) more than monotherapy with either drug alone. This was a randomized, double-blinded study of risedronate (35 mg weekly plus placebo injection), teriparatide (20 μg subcutaneously daily plus placebo tablet), or both risedronate plus teriparatide (combination) for 18 months in 29 men with low BMD. The primary endpoint was percentage change in lumbar spine (LS) BMD at 18 months. Secondary outcomes included changes in bone markers and BMD at other sites and interim time-points. All therapies increased LS BMD as compared with baseline (p < 0.05), but there were no between-group differences at 18 months. Total hip (TH) BMD increased to a greater extent in the combination group (mean ± SEM, 3.86 ± 1.1 %) versus teriparatide (0.29 ± 0.95 %) or risedronate (0.82 ± 0.95 %; p < 0.05 for both). Femoral neck (FN) BMD also increased more in the combination group (8.45 ± 1.8 %) versus risedronate (0.50 ± 1.7 %; p = 0.002), but was not different from teriparatide alone. In the combination group, P1NP and CTX increased rapidly, mirroring the teriparatide-alone arm. There were no between-group differences in adverse events. Combination teriparatide and risedronate increased BMD at the LS, TH as well as the FN and provided greater BMD increases at the TH than monotherapy. The results suggest combination risedronate and teriparatide therapy holds promise as a treatment for osteoporosis.

Serum extracellular secreted antagonists of the canonical Wnt/β-catenin signaling pathway in patients with Cushing's syndrome

Patients with endogenous hypercortisolism have higher sclerostin, but do not differ in Dickkopf 1 (Dkk1) or secreted frizzled-related protein 1 (SFRP1) levels as compared to healthy control.

INTRODUCTION

Endogenous Cushing's syndrome (CS), usually affecting young and otherwise healthy patients, is a good model to validate the effects of supraphysiological levels of glucocorticoids in humans. This study evaluates circulating levels of extracellular antagonists of the Wnt/β-catenin signaling pathway (sclerostin, Dkk1, SFRP1) in patients with CS versus healthy individuals.

METHODS

Forty patients with clinically and biochemically evident CS and 40 sex-, age-, and body mass index-matched healthy subjects provided fasting serum samples for sclerostin, SFRP1 and Dkk1, along with bone turnover markers.

RESULTS

Patients with CS had higher sclerostin levels (34.5 (30.3-37.1) pmol/L) versus healthy individuals (29.9 (24.3-36.8) pmol/L) (p = 0.032). Differences in sclerostin were due to the lack of lower sclerostin values rather than an increase in protein levels above the upper limits of the healthy control. The odds of sclerostin levels being higher than 30 pmol/L were greater in patients with CS as compared with the odds in healthy subjects (odds ratio = 3.81 95 % confidence interval 1.45-10.02) (p = 0.01). It coexisted with suppressed bone formation and unchanged bone resorption markers. Dkk1, SFRP1 did not differ from the control group.

CONCLUSIONS

Of all the tested proteins (sclerostin, Dkk1, SFRP1), only sclerostin showed a significant difference when contrasting CS with healthy subjects. Hypercortisolism might prevent the down-regulation of sclerostin. Targeting sclerostin seems to be a promising therapeutic approach to treating osteoporosis in patients with CS.

Association of serum sclerostin with bone mineral density, bone turnover, steroid and parathyroid hormones, and fracture risk in postmenopausal women: the OFELY study

SUMMARY

Sclerostin is a key regulator of bone formation. In a population of 572 postmenopausal women (mean age, 67 years) followed prospectively for a median of 6 years, there was no significant association between baseline levels of serum sclerostin and incidence of all fractures which occurred in 64 subjects.

INTRODUCTION

Sclerostin, an osteocyte soluble factor, is a major negative regulator of osteoblastic activity. Circulating sclerostin levels were reported to increase with age and to be modestly associated with bone mineral density (BMD) and bone turnover, but there are no data on the association with fracture risk.

METHODS

We investigated 572 postmenopausal women (mean age, 67 ± 8.5 years) from the OFELY population-based cohort. The associations of serum sclerostin measured with a new two-site ELISA and spine and hip BMD by DXA, serum β-isomerized C-terminal crosslinking of type I collagen (CTX), intact N-terminal propeptide of type I collagen (PINP), intact PTH, 25-hydroxyvitamin D [25(OH)D], estradiol, testosterone, and fracture risk were analyzed. At the time of sclerostin measurements, 98 postmenopausal women had prevalent fractures. After a median of 6 years (interquartile range, 5-7 years) follow-up, 64 postmenopausal sustained an incident fracture.

RESULTS

Serum sclerostin correlated positively with spine (r = 0.35, p < 0.0001) and total hip (r = 0.25, <0.0001) BMD. Conversely, serum sclerostin was weakly negatively associated with the bone markers PINP (r = -0.10, p = 0.014) and CTX (r = -0.13, p = 0.0026) and with intact PTH (r = -0.13, p = 0.0064). There was no significant association of serum sclerostin with 25(OH)D, estradiol, free estradiol index, or testosterone. Serum sclerostin considered as a continuous variable or in quartiles was not significantly associated with the risk of prevalent or incident fracture.

CONCLUSION

Serum sclerostin is weakly correlated with BMD, bone turnover, and PTH in postmenopausal women. It was not significantly associated with the risk of all fractures, although the number of incident fractures recorded may not allow detecting a modest association.

Low sclerostin levels: a predictive marker of persistent inflammation in ankylosing spondylitis during anti-tumor necrosis factor therapy?

Introduction

Sclerostin levels have been reported to be low in ankylosing spondylitis (AS), but there is no data regarding the possible role of this Wnt inhibitor during anti-tumor necrosis factor (TNF) therapy. The present study longitudinally evaluated sclerostin levels, inflammatory markers and bone mineral density (BMD) in AS patients under anti-TNF therapy.

Methods

Thirty active AS patients were assessed at baseline, 6 and 12 months after anti-TNF therapy regarding clinical parameters, inflammatory markers, BMD and baseline radiographic damage (mSASSS). Thirty age- and sex-matched healthy individuals comprised the control group. Patients' sclerostin levels, sclerostin binding low-density lipoprotein receptor-related protein 6 (LRP6) and BMD were evaluated at the same time points and compared to controls.

Results

At baseline, AS patients had lower sclerostin levels (60.5 ± 32.7 vs. 96.7 ± 52.9 pmol/L, P = 0.002) and comparable sclerostin binding to LRP6 (P = 0.387) than controls. Improvement of Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), Bath Ankylosing Spondylitis Functional Index (BASFI), Bath Ankylosing Spondylitis Metrology Index (BASMI), Ankylosing Spondylitis quality of life (ASQoL) was observed at baseline vs. 6 vs. 12 months (P < 0.01). Concomitantly, a gradual increase in spine BMD (P < 0.001) and a positive correlation between baseline mSASSS and spine BMD was found (r = 0.468, P < 0.01). Inflammatory parameters reduction was observed comparing baseline vs. 6 vs. 12 months (P <0.01). Sclerostin levels progressively increased [baseline (60.5 ± 32.7) vs. 6 months (67.1 ± 31.9) vs. 12 months (72.7 ± 32.3) pmol/L, P <0.001]. At 12 months, the sclerostin levels remained significantly lower in patients compared to controls (72.7 ± 32.3 vs. 96.70 ± 52.85 pmol/L, P = 0.038). Moreover, sclerostin serum levels at 12 months were lower in the 10 patients with high C reactive protein (CRP) (≥ 5 mg/l) compared to the other 20 patients with normal CRP (P = 0.004). Of note, these 10 patients with persistent inflammation also had lower sclerostin serum levels at baseline compared to the other patients (P = 0.023). Univariate logistic regression analysis demonstrated that AS patients with lower sclerostin serum levels had an increased risk to have high CRP at 12 months (odds ratio = 7.43, 95% CI 1.23 to 45.01, P = 0.020) than those with higher sclerostin values.

Conclusions

Persistent low sclerostin levels may underlie continuous inflammation in AS patients under anti-TNF therapy.

Serum sclerostin and risk of hip fracture in older Caucasian women

CONTEXT

Sclerostin, a protein secreted by osteocytes, inhibits bone formation. Individuals with genetic mutations that decrease the availability of sclerostin have very high bone mass.

OBJECTIVE

The aim of this study was to examine the hypothesis that elevated serum sclerostin levels are associated with increased risk of hip fracture in older women.

DESIGN, SETTING, AND PARTICIPANTS

This was a case-cohort study of a prospective, community-based cohort of 9704 women aged 65 yr or older. Sclerostin levels were measured in serum collected in 1989-1990 in 228 women with incident hip fractures and 227 women in a randomly selected sample; average follow-up time was 9.8 yr.

RESULTS

Serum sclerostin levels were correlated with total hip bone mineral density (BMD; r = 0.27, P < 0.001). The risk of hip fracture increased across quartiles of serum sclerostin (test for trend, P < 0.001) and was significantly elevated among those in the fourth quartile (hazard risk 3.4, 95% confidence interval 1.7-7.0) compared with women in the lowest quartile, after adjusting for age, body mass index, estrogen use, history of fracture since age 50 yr, and total hip BMD. When dividing the cohort into eight groups by sclerostin quartile and median hip BMD, women with lower total hip BMD in the highest sclerostin quartile had a 22.3-fold (95% confidence interval 5.8-86.3) increased risk of fracture compared with women with higher total hip BMD in the lowest sclerostin quartile.

CONCLUSIONS

We conclude that higher serum sclerostin levels are associated with a greater risk of hip fractures in older women. In addition, the risk of hip fracture is amplified when high sclerostin levels are combined with lower BMD.

Circulating sclerostin and Dickkopf-1 (DKK1) in predialysis chronic kidney disease (CKD): relationship with bone density and arterial stiffness

Abnormalities of bone metabolism and increased vascular calcification are common in chronic kidney disease (CKD) and important causes of morbidity and mortality. The Wnt signaling pathway may play a role in the bone and vascular disturbances seen in CKD, termed collectively "CKD-MBD." The aim of the study was to investigate the possible association of circulating concentrations of the secreted Wnt signaling inhibitors DKK1 and sclerostin with BMD and arterial stiffness in predialysis CKD. Seventy-seven patients (48 M, 29 F), mean age 57 (SD = 14) years with CKD stages 3B (n = 32) and 4 (n = 45) were studied. Sclerostin, DKK1, PTH, and 1,25(OH)(2)D were analyzed. BMD was measured at the lumbar spine (LS), femoral neck (FN), total hip (TH), and forearm (FARM). Arterial stiffness index was determined by contour analysis of digital volume pulse (SI(DVP)). There was a positive correlation between sclerostin and age (r = 0.47, p < 0.000). Sclerostin was higher in men than women (p = 0.013). Following correction for age and gender, there was a negative association between GFR and sclerostin (p = 0.002). We observed a positive association between sclerostin and BMD at the LS (p = 0.0001), FN (p = 0.004), and TH (p = 0.002). In contrast, DKK1 was negatively associated with BMD at the FN (p = 0.038). A negative association was seen between DKK1 and SI(DVP) (p = 0.027). Our data suggest that the Wnt pathway may play a role in CKD-MBD. Prospective studies are required to establish the clinical relevance of sclerostin and DKK1 as serological markers in CKD.

Serum sclerostin levels were positively correlated with fat mass and bone mineral density in central south Chinese postmenopausal women

OBJECTIVES

To investigate the relationship between serum sclerostin level, body composition, and bone mineral density (BMD) in central south Chinese postmenopausal women.

METHODS

A cross-sectional study was conducted on 260 healthy central southern Chinese postmenopausal women with vs without osteoporosis, aged 50-76 years old. Dual X-ray absorptiometry was used to measure the bone mineral content and BMD of the whole body, lumbar spine and left femur, and total body soft tissue composition. Serum sclerostin levels were measured by a quantitative sandwich enzyme-linked immunosorbent assay.

RESULTS

Compared with women without osteoporosis, osteoporotic women had a significantly lower level of serum sclerostin (P = 0.001). Serum sclerostin levels were positively correlated with body weight, Ponderal index and fat mass. There was a positive correlation with the BMD of both the whole body and at various sites (P < 0.05), even after controlling for age, age at menopause, height and body weight. Multiple linear stepwise regression analysis showed that serum sclerostin level was the most significant determinant of both whole-body and lumbar spine BMD, compared with age, age at menopause, fat mass and lean mass. Age had similar impact as serum sclerostin on hip BMD.

CONCLUSIONS

This study showed that in central south Chinese postmenopausal women, serum sclerostin is lower in women with osteoporosis than without. Serum sclerostin is positively correlated with fat mass and BMD for the whole body, lumbar spine and hip.

Weight loss in obese older adults increases serum sclerostin and impairs hip geometry but both are prevented by exercise training

We reported that weight loss induces bone loss which is prevented by exercise training; however, the mechanism for this observation remains unclear. Sclerostin, an inhibitor of bone formation, has been found to increase in states of unloading and may mediate the changes in bone metabolism associated with weight loss and exercise. The objective of the study was to determine the effect of lifestyle intervention in obese older adults on sclerostin levels, and on hip geometry parameters. A total of 107 obese (body mass index [BMI] ≥ 30 kg/m(2)) older (≥65 years) adults were randomly assigned to control, diet, exercise, and combined diet-exercise for 1 year. Sclerostin levels were measured by ELISA at baseline, 6 months, and 12 months, while hip geometry parameters were obtained from bone mineral density (BMD) images done by dual-energy X-ray absorptiometry using hip structure analysis at baseline and 12 months. Both the diet and diet-exercise groups had significant decreases in body weight (-9.6% and -9.4%, respectively), whereas weight was stable in the exercise and control groups. Sclerostin levels increased significantly and progressively in the diet group (6.6% ± 1.7% and 10.5% ± 1.9% at 6 and 12 months, respectively, all p < 0.05), whereas they were unchanged in the other groups; in particular, they were stable in the diet-exercise group (0.7% ± 1.6% and 0.4% ± 1.7% at 6 and 12 months, respectively, all p = 0.05). Hip geometry parameters showed significant decreases in cross-sectional area, cortical thickness, and BMD; and increases in buckling ratio at the narrow neck, intertrochanter, and femoral shaft. These negative changes on bone geometry were not observed in the diet-exercise group. Significant correlations between changes in sclerostin and changes in certain hip geometry parameters were also observed (p < 0.05). In conclusion, the increase in sclerostin levels with weight loss that was prevented by exercise may partly mediate the negative effects of weight loss on bone metabolism and the osteoprotective effect of exercise training.

Circulating sclerostin in disorders of parathyroid gland function

CONTEXT

Sclerostin, a protein encoded by the SOST gene in osteocytes and an antagonist of the Wnt signaling pathway, is down-regulated by PTH administration. Disorders of parathyroid function are useful clinical settings to study this relationship.

OBJECTIVE

The objective of the study was to evaluate sclerostin in two different disorders of parathyroid function, primary hyperparathyroidism and hypoparathyroidism, and to analyze the relationship between sclerostin and PTH, bone markers, and bone mineral density.

DESIGN

This is a cross-sectional study.

SETTING

The study was conducted at a clinical research center.

PATIENTS

Twenty hypoparathyroid and 20 hyperparathyroid patients were studied and compared to a reference control group.

RESULTS

Serum sclerostin was significantly higher in hypoparathyroid subjects than in hyperparathyroid subjects (P < 0.0001) and controls (P < 0.0001). PTH was negatively associated with sclerostin, achieving statistical significance in hypoparathyroidism (r = -0.545; P = 0.02). The bone turnover markers, cross-linked C-telopeptide of type I collagen (CTX) and amino-terminal propeptide of type I collagen (P1NP), were differently associated with sclerostin according to the parathyroid disorder. In primary hyperparathyroidism, bone turnover markers were associated negatively with sclerostin (for P1NP, r = -0.490; P = 0.03). In hypoparathyroidism, bone turnover markers were associated positively with sclerostin (for CTX, r = +0.571; P = 0.01). Although there was no significant correlation between bone mineral density and sclerostin in either parathyroid disorder, there was a significant positive relationship between sclerostin and bone mineral content in hypoparathyroidism.

CONCLUSIONS

The results are consistent with the hypothesis that PTH is a regulator of sclerostin in human disorders of parathyroid function. In addition, the results suggest that bone mineral content may be another factor that influences sclerostin.

Determinants of serum sclerostin in healthy pre- and postmenopausal women

Sclerostin is a secreted Wnt antagonist produced almost exclusively by osteocytes that regulates bone mass. However, there is currently limited information on the determinants of sclerostin in a large population-based study. The main objectives of the present study were to: (1) establish reference normative interval values for serum sclerostin in randomly selected healthy premenopausal women; (2) study the changes in serum sclerostin in relation to age in premenopausal and postmenopausal women and the factors that may influence bone turnover; and (3) determine the effect of menopausal status on serum sclerostin. A total of 1803 women were studied (including [n = 1235] premenopausal, and [n = 568] postmenopausal women, respectively, aged 20 to 79 years). A total of 443 healthy premenopausal women (aged 35 to 45 years) were used to establish reference normative intervals for serum sclerostin. All women studied were medically examined and had their bone mineral density values obtained for the lumbar spine (L(1) -L(4) ) and femoral neck according to a detailed inclusion criteria. In all women, values of serum sclerostin increased with increasing age up to the age of 45 years, and remained increased in postmenopausal women. Significant increases were evident in serum sclerostin in postmenopausal women with increasing years since menopause. Using stepwise multiple linear regression analysis, several variables were identified as determinants of serum sclerostin, including age, parathyroid hormone, estradiol (E(2)), and follicle-stimulating hormone (FSH) for premenopausal women; age, FSH, and E(2) for postmenopausal women; and age, serum osteocalcin, FSH, and E(2) in the entire sample studied. Further studies are needed to establish the potential role of this increase in mediating the known age-related impairment in bone formation.

Acute decline in serum sclerostin in response to PTH infusion in healthy men

CONTEXT

Animal models suggest that the osteoblast-stimulating actions of PTH are mediated by acute suppression of sclerostin, an inhibitor of the anabolic Wnt pathway. The immediate physiological changes in serum sclerostin in response to PTH infusion have not been reported in human studies.

OBJECTIVE

We sought to determine the acute physiological effects of PTH infusion on serum sclerostin and bone turnover markers in healthy adult men.

DESIGN, SETTING, AND PARTICIPANTS

Fifty-three healthy adult men underwent an 18-h iv infusion of human PTH(1-34) at a dose of 0.55 U/kg · h.

OUTCOMES

Serum levels of ionized calcium, sclerostin, and markers of bone formation (osteocalcin and amino-terminal propeptide of type I procollagen) and bone resorption (C-telopeptide and N-telopeptide) were obtained at 0, 6, 12, and 18 h.

RESULTS

Serum ionized calcium, C-telopeptide, and N-telopeptide increased, and osteocalcin and amino-terminal propeptide of type I procollagen fell linearly throughout the PTH infusion (P < 0.001 for all). Average ± sem sclerostin levels declined from 936 ± 65 to 813 ± 63 pg/ml at 6 h (P < 0.001) and remained stably suppressed for the duration of the PTH infusion. There were no significant correlations between change in sclerostin and change in bone markers.

CONCLUSIONS

Serum sclerostin declined in response to acute PTH infusion within 6 h in healthy adult men. The early plateau in sclerostin suppression may indicate that maximal stimulation of the Wnt pathway is achieved quickly after exposure to PTH. Our findings support the hypothesis that PTH may mediate its anabolic effects in part via suppression of sclerostin.