Sclerostin measurement in human disease: Validity and current limitations

Associations of serum sclerostin levels with body composition, pulmonary function, and exacerbations in COPD patients

BACKGROUND

In COPD, the bronchial epithelium shows a pathologically activated Wnt pathway. Sclerostin (SOST) is a secreted glycoprotein that is associated with bone metabolism and blocks the Wnt pathway. We hypothesized that low sclerostin levels might be associated with lung function and COPD exacerbations in patients.

METHODS

We studied 139 outpatients with stable COPD and normal kidney function. We assessed the serum levels of SOST and bone metabolism parameters, body composition, clinical characteristics and lung function at baseline. We followed the patients prospectively for 12 months after enrolment. Moderate exacerbations and hospital admissions were recorded during follow-up.

RESULTS

The serum SOST levels were 23.98±7.6 pmol/l (men: 25.5±7.7 pmol/l, women: 20.3±5.9 pmol/l (p < 0.001)). SOST showed correlations with age (r = 0.36), FFMI (r = 0.38), FEV1 (r = 0.27), DLCO (r = 0.39), 6MWD (r = 0.19) and CAT (r = -0.24). In multivariate linear regression analysis, only age (beta=0.264) and FFMI (beta=1.241) remained significant. SOST showed a significant negative correlation with serum phosphorus (r = -0.29). Cox proportional risk analysis indicated that patients in the lower tertile of SOST levels were at higher risk of moderate COPD exacerbation (HR 2.015, CI95% 1.136-3.577, p = 0.017) and hospital admission due to COPD (HR 5.142, CI95% 1.380-19.158, p = 0.015) than the rest of the patients.

CONCLUSIONS

SOST levels are associated with body composition and lung function in patients with COPD. Furthermore, lower SOST levels predict a higher risk of exacerbations and hospitalization.

Low Levels of Serum Sclerostin in Adult Patients With Tumor-Induced Osteomalacia Compared With X-linked Hypophosphatemia

CONTEXT

Sclerostin inhibits Wnt-β-catenin signaling, regulating bone formation. Circulating sclerostin was reported to be elevated in X-linked hypophosphatemia (XLH) patients, and sclerostin antibody (Scl-Ab) increased bone mass and normalized circulating phosphate in Hyp mice. However, circulating sclerostin levels in patients with acquired hypophosphatemia due to tumor-induced osteomalacia (TIO) are rarely reported.

OBJECTIVE

This study was designed to evaluate serum sclerostin levels in TIO patients compared with age- and sex-matched healthy controls and XLH patients to analyze correlations with bone mineral density (BMD) and laboratory parameters.

METHODS

This cross-sectional study determined serum sclerostin levels in 190 individuals, comprising 83 adult TIO patients, 83 adult healthy controls and 24 adult XLH patients.

RESULTS

TIO patients (43 male, 40 female) aged 44.3 ± 8.7 (mean ± SD) years had lower levels of circulating sclerostin than controls (94.2 ± 45.8 vs 108.4 ± 42.3 pg/mL, P = 0.01), adjusted for age, gender, BMI, and diabetes rate. Sclerostin levels were positively associated with age (r = 0.238, P = 0.030). Male patients had higher sclerostin than female patients (104.7 ± 47.3 vs 83.0 ± 41.8 pg/mL, P = 0.014). Sclerostin levels were positively associated with L1-4 BMD (r = 0.255, P = 0.028), femoral neck BMD (r = 0.242, P = 0.039), and serum calcium (r = 0.231, P = 0.043). Comparison of sclerostin levels in TIO patients (n = 24, age 35.9 ± 7.3 years) vs XLH patients vs healthy controls revealed significant differences (respectively, 68.4 ± 31.3, 132.0 ± 68.8, and 98.6 ± 41.1 pg/mL, P < 0.001).

CONCLUSION

Circulating sclerostin was decreased in TIO patients but increased in XLH patients, possibly due to histological abnormality and bone mass.

Impaired Bone Microarchitecture in Premenopausal Women With Acromegaly: The Possible Role of Wnt Signaling

CONTEXT

Acromegaly can impair bone integrity, increasing the risk of vertebral fractures (VFs).

OBJECTIVE

To evaluate the impact of isolated GH/IGF-I hypersecretion on bone turnover markers, Wnt inhibitors, bone mineral density (BMD), microarchitecture, bone strength and vertebral fractures in female patients with acromegaly (Acro), compared with healthy control group (HC).

DESIGN, SETTING, AND PATIENTS

Cross-sectional study including 83 premenopausal women without any pituitary deficiency:18 acromegaly in remission (AcroR), 12 in group with active acromegaly (AcroA), and 53 HC. Serum procollagen type 1 N-terminal propeptide, β-carboxy-terminal crosslinked telopeptide of type 1 collagen, osteocalcin, sclerostin, and DKK1 were measured in blood samples. dual-energy X-ray absorptiometry, high-resolution peripheral quantitative computed tomography (HR-pQCT) and vertebral fractures evaluation were also assessed simultaneously.

MAIN OUTCOME AND RESULTS

AcroA showed significantly lower sclerostin and higher DKK1 compared with HC. On HR-pQCT of tibia and radius, Acro showed impairment of trabecular (area and trabecular number), increased cortical porosity, and increased cortical area and cortical thickness compared with HC. The only significant correlation found with HR-pQCT parameters was a positive correlation between cortical porosity and serum DKK1 (R = 0.45, P = 0.044). Mild VFs were present in approximately 30% of patients.

CONCLUSIONS

Eugonadal women with acromegaly without any pituitary deficiency showed increased cortical BMD, impairment of trabecular bone microstructure, and increased VF. Sclerostin was not correlated with any HR-pQCT parameters; however, DKK1 was correlated with cortical porosity in tibia (P = 0.027). Additional studies are needed to clarify the role of Wnt inhibitors on bone microarchitecture impairment in acromegaly.

Sclerostin and its role as a bone modifying agent in periodontal disease

BACKGROUND

Periodontitis is a highly prevalent inflammatory disease affecting the periodontium that results from an imbalance between periodontopathogens and host mechanisms. Continuous progression of the disease may lead to tissue and bone destruction, eventually resulting in tooth loss. The extent of bone loss depends on the dysregulated host immune response. Various host-elicited molecules play a major role in disease progression. The discovery of the glycoprotein sclerostin and its role as a regulator of bone mass has led to a better understanding of bone metabolism.

HIGHLIGHT

Sclerostin, which is primarily expressed by osteocytes, is a negative regulator of bone formation. It is a potent antagonist of the canonical Wingless-related integration site (Wnt) pathway, which is actively involved in bone homeostasis. Sclerostin is known to stimulate bone resorption by altering the osteoprotegerin (OPG)/receptor activator of nuclear factor kappa- β ligand (RANKL) balance. Additionally, in periodontitis, activation of the inflammatory cascade also increases the synthesis of sclerostin.

CONCLUSION

The recently discovered sclerostin antibody has emerged as a positive therapeutic tool for the treatment of metabolic bone diseases. It has been reported to improve bone strength, bone formation, osseointegration around implants and lower the risk of bone fractures in various animal and human models. This review describes the properties and action of sclerostin, its role in periodontal diseases, and the advent and efficacy of sclerostin antibodies.

Therapeutic Effect of Calcimimetics on Osteoclast-Osteoblast Crosslink in Chronic Kidney Disease and Mineral Bone Disease

We have previously demonstrated calcimimetics optimize the balance between osteoclastic bone resorption and osteoblastic mineralization through upregulating Wingless and int-1 (Wnt) signaling pathways in the mouse and cell model. Nonetheless, definitive human data are unavailable concerning therapeutic effects of Cinacalcet on chronic kidney disease and mineral bone disease (CKD-MBD) and osteoclast-osteoblast interaction. We aim to investigate whether Cinacalcet therapy improves bone mineral density (BMD) through optimizing osteocytic homeostasis in a human model. Hemodialysis patients with persistently high intact parathyroid hormone (iPTH) levels > 300 pg/mL for more than 3 months were included and received fixed dose Cinacalcet (25 mg/day, orally) for 6 months. Bone markers presenting osteoclast-osteoblast communication were evaluated at baseline, the 3rd and the 6th month. Eighty percent of study patients were responding to Cinacalcet treatment, capable of improving BMD, T score and Z score (16.4%, 20.7% and 11.1%, respectively). A significant correlation between BMD improvement and iPTH changes was noted (r = -0.26, p < 0.01). Nonetheless, baseline lower iPTH level was associated with better responsiveness to Cinacalcet therapy. Sclerostin, an inhibitor of canonical Wnt/β-catenin signaling, was decreased from 127.3 ± 102.3 pg/mL to 57.9 ± 33.6 pg/mL. Furthermore, Wnt-10b/Wnt 16 expressions were increased from 12.4 ± 24.2/166.6 ± 73.3 pg/mL to 33.8 ± 2.1/217.3 ± 62.6 pg/mL. Notably, procollagen type I amino-terminal propeptide (PINP), a marker of bone formation and osteoblastic activity, was increased from baseline 0.9 ± 0.4 pg/mL to 91.4 ± 42.3 pg/mL. In contrast, tartrate-resistant acid phosphatase isoform 5b (TRACP-5b), a marker of osteoclast activity, was decreased from baseline 16.5 ± 0.4 mIU/mL to 7.7 ± 2.2 mIU/mL. Moreover, C-reactive protein levels were suppressed from 2.5 ± 0.6 to 0.8 ± 0.5 mg/L, suggesting the systemic inflammatory burden may be benefited after optimizing the parathyroid-bone axis. In conclusion, beyond iPTH suppression, our human model suggests Cinacalcet intensifies BMD through inhibiting sclerostin expression and upregulating Wnt-10b/Wnt 16 signaling that activates osteoblastic bone formation and inhibits osteoclastic bone resorption and inflammation. From the perspective of translation to humans, this research trial brings a meaningful insight into the osteoblast-osteoclast homeostasis in Cinacalcet therapy for CKD-MBD.

Effects of progesterone therapy on serum sclerostin levels in healthy menopausal women: a 3-month randomized, placebo-controlled clinical trial

Sclerostin, a natural hormone made in bone, suppresses bone formation. Sclerostin is also decreased by estrogen. Progesterone, estrogen's menstrual partner, stimulates bone formation. It is unclear whether progesterone influences sclerostin. This study showed that progesterone did not change sclerostin using serum remaining from a randomized progesterone hot flush therapy trial.

INTRODUCTION

Progesterone and sclerostin are both endogenous hormones acting through osteoblast-origin cells and promote or suppress bone formation, respectively. Estradiol suppresses sclerostin, but progesterone, its menstrual cycle partner hormone, has unclear sclerostin relationships. We postulated that progesterone therapy would influence serum sclerostin levels.

METHODS

We obtained sclerostin levels for an ethics-approved post hoc analysis. Fasting sclerostin was measured in all remaining sera from a previous 12-week randomized controlled trial (RCT) of oral micronized progesterone (progesterone) for menopausal (> 1 year after last flow) vasomotor symptoms (VMS). Women in the RCT took 300 mg progesterone at bedtime or placebo (1:1) in a trial showing progesterone significantly decreased VMS.

RESULTS

Participants were healthy menopausal, primarily Caucasian (91.2%) community-dwelling women (± SD), 55.2 ± 4.6 years old with BMI 24.9 ± 2.9 kg/m². The baseline sclerostin level in 60 women was 28.41 ± 10.47 pmol/L. Baseline sclerostin was not correlated with the run-in VMS score (r = 0.143, P = 0.294). Paired baseline and 12-week RCT data for 52 women showed serum sclerostin levels did not change related to experimental therapy (P = 0.504). Changes in final sclerostin values adjusted for baseline were progesterone (- 1.07 ± 7.96 pmol/L) and placebo (- 2.64 ± 8.70 pmol/L). In observational data (n = 60), baseline sclerostin levels correlated with the General Framingham Cardiovascular (CVD) Risk score (r = - 0.398, P = 0.003) and self-reported health by SF-36 quality of life instrument (QoL, r = - 0.331, P = 0.016).

CONCLUSION

Physiological oral micronized progesterone did not stimulate nor suppress serum sclerostin levels based on post hoc analysis of RCT data. Exploratory results, however, showed sclerostin negatively correlated with CVD risk and QoL. ClinicalTrials.gov #NCT0146469.

Sclerostin and Vascular Pathophysiology

There is cumulating evidence for a contribution of Wnt signaling pathways in multiple processes involved in atherosclerosis and vascular aging. Wnt signaling plays a role in endothelial dysfunction, in the proliferation and migration of vascular smooth muscle cells (VSMCs) and intimal thickening. Moreover, it interferes with inflammation processes, monocyte adhesion and migration, as well as with foam cell formation and vascular calcification progression. Sclerostin is a negative regulator of the canonical Wnt signaling pathway and, accordingly, the consequence of increased sclerostin availability can be disruption of the Wnt signalling cascade. Sclerostin is becoming a marker for clinical and subclinical vascular diseases and several lines of evidence illustrate its role in the pathophysiology of the vascular system. Sclerostin levels increase with aging and persist higher in some diseases (e.g., diabetes, chronic kidney disease) that are known to precipitate atherosclerosis and enhance cardiovascular risk. Current knowledge on the association between sclerostin and vascular diseases is summarized in this review.

The Osteocyte as the New Discovery of Therapeutic Options in Rare Bone Diseases

Osteocytes are the most abundant (~95%) cells in bone with the longest half-life (~25 years) in humans. In the past osteocytes have been regarded as vestigial cells in bone, since they are buried inside the tough bone matrix. However, during the last 30 years it has become clear that osteocytes are as important as bone forming osteoblasts and bone resorbing osteoclasts in maintaining bone homeostasis. The osteocyte cell body and dendritic processes reside in bone in a complex lacuno-canalicular system, which allows the direct networking of osteocytes to their neighboring osteocytes, osteoblasts, osteoclasts, bone marrow, blood vessels, and nerves. Mechanosensing of osteocytes translates the applied mechanical force on bone to cellular signaling and regulation of bone adaptation. The osteocyte lacuno-canalicular system is highly efficient in transferring external mechanical force on bone to the osteocyte cell body and dendritic processes via displacement of fluid in the lacuno-canalicular space. Osteocyte mechanotransduction regulates the formation and function of the osteoblasts and osteoclasts to maintain bone homeostasis. Osteocytes produce a variety of proteins and signaling molecules such as sclerostin, cathepsin K, Wnts, DKK1, DMP1, IGF1, and RANKL/OPG to regulate osteoblast and osteoclast activity. Various genetic abnormality-associated rare bone diseases are related to disrupted osteocyte functions, including sclerosteosis, van Buchem disease, hypophosphatemic rickets, and WNT1 and plastin3 mutation-related disorders. Meticulous studies during the last 15 years on disrupted osteocyte function in rare bone diseases guided for the development of various novel therapeutic agents to treat bone diseases. Studies on genetic, molecular, and cellular mechanisms of sclerosteosis and van Buchem disease revealed a role for sclerostin in bone homeostasis, which led to the development of the sclerostin antibody to treat osteoporosis and other bone degenerative diseases. The mechanism of many other rare bone diseases and the role of the osteocyte in the development of such conditions still needs to be investigated. In this review, we mainly discuss the knowledge obtained during the last 30 years on the role of the osteocyte in rare bone diseases. We speculate about future research directions to develop novel therapeutic drugs targeting osteocyte functions to treat both common and rare bone diseases.

Sclerostin and parathyroid hormone responses to acute whole-body vibration and resistance exercise in young women

Whole-body vibration (WBV) has been shown to improve bone mineral density, and muscle strength and power. No studies to date have examined sclerostin and parathyroid hormone (PTH) responses to WBV combined with resistance exercise (RE). This randomized crossover study compared acute serum sclerostin and PTH responses to RE and WBV + RE in young women (n = 9) taking oral contraceptives. Participants were exposed to 5 1-min bouts of vibration (20 Hz, 3.38 peak-peak displacement, separated by 1 min of rest) before high intensity resistance exercise. Fasting blood samples were obtained before (PRE), immediately after WBV (POSTWBV), immediately post RE (IP) and 30 min post RE (30P). Pre-exercise sclerostin and PTH levels were not significantly different between conditions. Sclerostin levels significantly (p < 0.05) increased from PRE to IP for the WBV + RE condition, then decreased back to the pre-exercise level. PTH significantly decreased from PRE to 30P (p < 0.05) and IP to 30P (p < 0.01) for both conditions. Correcting for hemoconcentration eliminated the significant sclerostin responses, but the significant decrease in PTH remained (p < 0.05). There were no significant relationships found between sclerostin and PTH. In conclusion, sclerostin concentrations increased in response to the WBV + RE condition, which may have been mediated by plasma volume shifts. There was no transient PTH increase, but it showed a large decrease at 30P for both conditions. Based on these findings, the addition of WBV exposures prior to high intensity RE did not alter sclerostin and PTH responses to RE in young women.

Sclerostin rather than Dickkopf-1 is associated with mSASSS but not with disease activity score in patients with ankylosing spondylitis

OBJECTIVE

To determine the serum levels of Dickkopf-1 (DKK-1) and sclerostin, as well as their correlations with the structural damage assessed by modified stoke ankylosing spondylitis spine score (mSASSS) and the disease activity evaluated by ankylosing spondylitis disease activity score (ASDAS) in patients with ankylosing spondylitis (AS).

METHODS

Eighty-eight AS patients, 26 rheumatoid arthritis (RA) patients, and 26 age- and gender-matched healthy controls (HC) were collected from rheumatic clinic of the Second Affiliated Hospital of Zhejiang University, School of Medicine, between March 2015 and July 2015. Demographic data, parameters of ASDAS, and image evaluations of spine (i.e., mSASSS) were collected. The serum levels of DKK-1 and sclerostin were measured using commercially available ELISA kits.

RESULTS

Both DKK-1 and sclerostin were significantly higher in the AS patients than in the controls (1855 ± 84.58 vs. 1406 ± 99.76 pg/ml and 106 ± 6.75 vs. 62.78 ± 6.39 pmol/l, respectively, P < 0.05). The correlation analysis suggested a negative correlation between serum sclerostin and mSASSS (P = 0.019, r² = 0.062). DKK-1 had a trend of positive correlation with mSASSS, but was not statistically significant (P > 0.05). There was no association between the serum levels of DKK-1 or sclerostin and disease activity assessed by ASDAS (P > 0.05). DKK-1 and sclerostin had a negative correlation (P = 0.013, r² = 0.07).

CONCLUSION

In the present study, the expressions of serum DKK-1 and sclerostin were independent of disease activity. Sclerostin was negatively correlated with the mSASSS, which suggests that sclerostin may be a potential marker indicating the spine ossification process in AS. The specific mechanism remains to be investigated.

Validation of a novel, rapid, high precision sclerostin assay not confounded by sclerostin fragments

Sclerostin is a 190 amino acid protein secreted primarily by osteocytes. It was initially identified due to mutations in the SOST gene associated with high bone mass phenotypes. Much recent work has sought to determine the importance of sclerostin across an array of conditions which affect the human skeleton. However, accurate measurement of sclerostin from serum and plasma sources remains a significant impediment, with currently available commercial assays showing marked differences in measured sclerostin values. Accordingly, sclerostin assay standardization remains an important but unmet need before sclerostin measurements can be used for the clinical management of bone disease. Here we characterize a novel automated chemiluminescent sclerostin assay (LIAISON®, DiaSorin) which overcomes many of these limitations. Important assay characteristics include: a wide dynamic range (50-6500pg/mL); high intra- (<2.5%) and inter- (<5%) assay precision; matched serum and plasma equivalence (<10% difference); specificity for the intact sclerostin molecule; and rapid assay results. Serum sclerostin levels measured with the LIAISON® assay in a population-based sample of adult men (n=278) and women (n=348) demonstrated that sclerostin levels were significantly higher in men as compared to women and were positively associated with age in both sexes, consistent with previously published work. In postmenopausal women, serum sclerostin levels measured with the LIAISON® assay were reduced in response to treatment with either estrogen or teriparatide, again consistent with previous findings. Collectively, the above data demonstrate that the LIAISON® sclerostin assay provides a reliable tool for more confident assessment of emergent mechanisms wherein sclerostin may impact a number of bone related pathologies.

Negative Association Between Sclerostin and INSL3 in Isolated Human Osteocytes and in Klinefelter Syndrome: New Hints for Testis-Bone Crosstalk

CONTEXT

The regulation of bone mass by the testis is a well-recognized mechanism, but the role of Leydig-specific marker insulin-like 3 peptide (INSL3) on the most abundant bone cell population, osteocytes, is unknown. In this study, we aimed to investigate the relationship between INSL3 and sclerostin, an osteocyte-specific protein that negatively regulates bone formation.

DESIGN

Serum sclerostin and INSL3 levels were evaluated in Klinefelter syndrome (KS) and healthy controls. In vitro effect of INSL3 on sclerostin production was evaluated in human cultured osteocytes.

PATIENTS

A total of 103 KS patients and 60 age- and sex-matched controls were recruited.

MAIN OUTCOME MEASURES

Serum sclerostin and INSL3 levels were assessed by enzyme-linked immunosorbent assay. Osteocytes were isolated by fluorescence-assisted cell sorting. Sclerostin expression was evaluated by western blot, immunofluorescence, and reverse transcription polymerase chain reaction. Measurement of bone mineral density was done by dual-energy X-ray absorptiometry at lumbar spine (L1-L4) and femoral neck.

RESULTS

Sclerostin levels were significantly increased in KS subjects, and negatively correlated with INSL3 levels in both cohorts and with bone mineral density in the KS group. Stimulation of cultured osteocytes with INSL3 at 10-7 M significantly decreased both sclerostin messenger RNA and protein expression.

CONCLUSIONS

We report a negative association between the testicular hormone INSL3 and the osteocytic negative regulator of bone formation, sclerostin. We further explored this association in vitro and showed that INSL3 was able to reduce sclerostin expression. These results add further knowledge on the emerging role of sclerostin as a therapeutic target for osteoporosis treatment.

Targeted inhibition of sclerostin for post-menopausal osteoporosis therapy: A critical assessment of the mechanism of action

Promising news in the treatment of osteoporosis is that sequestering sclerostin from circulation with antibodies stimulates robust bone formation. Pre-clinical studies on rodents and monkeys have confirmed that treatment with anti-sclerostin monoclonal antibody (Scl-Ab) increases bone mass, improves bone strength and enhances fracture repair. Clinical trials show that bone gain (anabolic effect) is transient and are primarily at central (spine and hips) than peripheral (wrist) sites. Interestingly Scl-Ab also inhibited bone resorption. Thus Scl-Ab is being regarded as the pharmacologic agent with dual properties - stimulating bone formation and decreasing bone resorption. Sclerostin neutralization transiently increases bone formation markers in post-menopausal women and like parathyroid hormone (PTH) activates osteoblasts and lining cells resulting in bone anabolic effect. However, unlike PTH, sclerostin antibody also decreases bone resorption (anti-catabolic). Although, the U.S. Food and Drug Administration have accepted the Biologics License Application for one of the monoclonal antibodies against sclerostin (romosozumab) for review, many questions remain before romosozumab can be introduced as a skeletal anabolic agent to clinical practice. For example, neutralizing sclerostin alters calcium homeostasis and increases PTH. In addition, sclerostin depletion in preclinical studies has been reported to severely compromises B cell depletion in bone marrow. We have reviewed the currently available evidences that support the use of sclerostin antibody in treating osteoporosis and compare its efficacy and mechanism of action with the currently available anabolic drug, human PTH.

Serum Sclerostin Levels in Adults With Osteogenesis Imperfecta: Comparison With Normal Individuals and Response to Teriparatide Therapy

Sclerostin (SOST), a glycoprotein primarily derived from osteocytes, is an important regulator of bone remodeling. Osteogenesis imperfecta (OI) is a heritable disorder of bone characterized by low bone mass, bone fragility, recurrent fractures, and bone deformities. Altered SOST-mediated signaling may have a role in pathogenesis of type I collagen-related OI; however, this has not been evaluated in humans. We measured serum SOST levels in adults with OI who were enrolled in a randomized, placebo-controlled clinical trial that evaluated the effects of osteoanabolic therapy with teriparatide. Compared with age- and sex-matched control participants, mean SOST levels were lower in those with type I or types III/VI OI (p < 0.0001). Receiver operating curve analysis revealed that sclerostin alone or sclerostin plus bone mineral content discriminated patients with OI from controls (area under the curve 0.80 and 0.87, respectively). SOST levels increased in the group of patients with type I OI during therapy with teriparatide (compared with placebo, p = 0.01). The increase was significant at 6, 12, and 24 months of therapy (p ≤ 0.02) and was apparent as early as 3 months (p = 0.06). The magnitude of increases in SOST levels during therapy was inversely correlated with increases in vertebral volumetric bone mineral density (vBMD). Overall, these results suggest that: 1) SOST regulation is fundamentally altered in osteogenesis imperfecta; 2) serum SOST levels could be a biomarker of OI in adults; and 3) alterations in SOST may help predict the response to anabolic therapies in OI. © 2017 American Society for Bone and Mineral Research.

Novel skeletal effects of glucagon-like peptide-1 (GLP-1) receptor agonists

Type 2 diabetes mellitus (T2DM) leads to bone fragility and predisposes to increased risk of fracture, poor bone healing and other skeletal complications. In addition, some anti-diabetic therapies for T2DM can have notable detrimental skeletal effects. Thus, an appropriate therapeutic strategy for T2DM should not only be effective in re-establishing good glycaemic control but also in minimising skeletal complications. There is increasing evidence that glucagon-like peptide-1 receptor agonists (GLP-1RAs), now greatly prescribed for the treatment of T2DM, have beneficial skeletal effects although the underlying mechanisms are not completely understood. This review provides an overview of the direct and indirect effects of GLP-1RAs on bone physiology, focusing on bone quality and novel mechanisms of action on the vasculature and hormonal regulation. The overall experimental studies indicate significant positive skeletal effects of GLP-1RAs on bone quality and strength although their mechanisms of actions may differ according to various GLP-1RAs and clinical studies supporting their bone protective effects are still lacking. The possibility that GLP-1RAs could improve blood supply to bone, which is essential for skeletal health, is of major interest and suggests that GLP-1 anti-diabetic therapy could benefit the rising number of elderly T2DM patients with osteoporosis and high fracture risk.

Serum Sclerostin Levels in Patients with Ankylosing Spondylitis and Rheumatoid Arthritis: A Systematic Review and Meta-Analysis

Objective. Current studies of serum sclerostin levels in AS and RA patients are inconsistent. This meta-analysis was performed to identify the association of serum sclerostin level with AS and RA patients. Methods. Embase, PubMed, MEDLINE, and Cochrane Library databases (up to 25 January 2017) were used to collect all relevant published articles. Studies were pooled and standard mean difference (SMD) with 95% confidence interval (CI) was calculated. All data analyses were performed using RevMan 5.3. Results. Totally eight studies of AS including 420 AS patients and 317 healthy controls (HC) and three studies of RA including 145 RA patients and 127 HC were finally included in this meta-analysis. The results revealed that the serum sclerostin levels in both AS patients (SMD = −0.14; 95% CI = [−0.39,0.11]; P = 0.28) and RA patients (SMD = −0.10; 95% CI = [−0.34,0.15]; P = 0.43) were not significantly different from those in HC. Conclusion. The difference of serum sclerostin levels in AS and RA patients was not significantly different from HC, indicating that the sclerostin may not associate with the development of AS and RA.