|Ahead of print publication
Serum sclerostin levels in rheumatoid arthritis and correlation with disease activity and bone mineral density
Urmila Dhakad, Rasmi Ranjan Sahoo, Akhil Pawan Goel, Sourav Pradhan, Ragini Srivastava, Siddharth Kumar Das
Department of Rheumatology, King George's Medical University, Lucknow, Uttar Pradesh, India
Rasmi Ranjan Sahoo,
King George's Medical University, Lucknow - 226 003, Uttar Pradesh
Source of Support: None, Conflict of Interest: None
Background: This study aims to assess serum sclerostin, an inhibitor of the Wnt/β-catenin signaling pathway, in rheumatoid arthritis (RA) and its correlation with disease activity and bone mineral density (BMD).
Methods: RA patients (>18 years) fulfilling the ACR/EULAR (2010) criteria for RA were included. Postmenopausal women, those with other autoimmune diseases, secondary causes of osteoporosis, severe vitamin D deficiency, chronic liver disease, chronic kidney disease stage 3 and above, and those patients on anticonvulsants were excluded. Rheumatoid factor, anticitrullinated protein antibody, 25-OH Vitamin D estimation, plain radiographs of hands, and BMD measurement by dual-energy X-ray absorpiometry were done in patients. Disease activity was assessed by clinical disease activity index (CDAI). Serum sclerostin levels in RA patients and controls (age and sex matched) were measured by commercial enzyme-linked immunosorbent assay (ELISA) and the relationship of sclerostin with low BMD, ESR, CDAI, and erosion were explored.
Results: The mean age of patients (n = 47) was 32.7 ± 6.8 years and mean disease duration was 4.2 ± 2 years. All patients were women, mean body mass index was 22.38±4.4 and mean vitamin D level was 27.9±16.4 ng/ml. 25.5% of RA patients had low BMD at least one site (Z-score: −2 or less). Serum sclerostin was significantly higher in patients compared to controls (8422 ± 3655 pg/ml vs. 6479 ± 1510 pg/ml, P = 0.002). Serum sclerostin levels did not correlate significantly with ESR (r = −0.31 and P = 0.048), CDAI (r = −0.11 and P = 0.45), BMD at lumbar spine (L1–L4, r = 0.14, and P = 0.35), femur neck (r = 0.06 and P = 0.67), and wrist (r = 0.12 and P = 0.41).
Conclusion: Serum sclerostin levels were elevated in RA patients but did not correlate with disease activity and BMD.
Keywords: Antisclerostin, osteoporosis, premenopausal rheumatoid arthritis, Wnt signaling
|How to cite this URL:|
Dhakad U, Sahoo RR, Goel AP, Pradhan S, Srivastava R, Das SK. Serum sclerostin levels in rheumatoid arthritis and correlation with disease activity and bone mineral density. Indian J Rheumatol [Epub ahead of print] [cited 2019 Jan 18]. Available from: http://www.indianjrheumatol.com/preprintarticle.asp?id=249617
| Introduction|| |
Osteoporosis is a common but underrecognized problem in rheumatoid arthritis (RA). In the Korean observational study network for arthritis cohort, 90.8% RA patients had osteopenia and osteoporosis. There is an increased risk of vertebral fractures in patients with long-standing RA resulting in huge socioeconomic impact. Besides traditional risk factors of osteoporosis, physical disability, uncontrolled disease, and glucocorticoid use are additional contributing factors for bone loss in RA., Long-standing disease and seropositivity have also been shown to be associated with osteoporosis in RA.,
The hallmark of RA is increased bone resorption without an increase in bone formation. The Wnt/β-catenin signaling is important for osteoblast differentiation and proliferation leading to bone formation. Wnt pathway is inhibited by antagonists such as sclerostin and Dickkopf-related protein 1. Sclerostin, encoded by the SOST gene, is secreted from osteocytes. It binds to low-density lipoprotein receptor-related protein 5/6 (LRP5/6) and displaces the Wnt proteins, leading to the dissociation of the LRP5/6 and frizzled receptor complex. Thus, sclerostin inhibits differentiation and proliferation of osteoblasts. Sclerostin also stimulates receptor activator of nuclear factor κB ligand secretion from osteocytes to activate osteoclasts, leading to bone resorption. Overall, sclerostin is involved in the prevention of bone formation.
We hypothesize that sclerostin also contributes to bone loss and osteoporosis in RA, and therefore, our aim was to assess its serum levels and correlate with disease activity and bone mineral density (BMD).
| Methods|| |
This was a cross-sectional study carried out from September 2015 to June 2016.
Patients aged 18 years and above who fulfilled the American College of Rheumatology/European League Against Rheumatism 2010 criteria for RA were recruited for this study. Those patients with other autoimmune diseases, secondary causes of osteoporosis (such as diabetes, celiac disease, and thyroid disease), severe Vitamin D deficiency, chronic liver disease, chronic kidney disease stage 3 and above, and those patients who were on medications that would possibly alter the BMD such as anticonvulsants were excluded from the study. Women in the postmenopausal age group were also excluded as postmenopausal osteoporosis is a potential confounder. Those patients who were on corticosteroid or had received corticosteroid in the past were not excluded, as treatment with corticosteroid is often an essential management strategy of RA.
Clinical history including duration of RA, medications, history suggestive of other autoimmune disorders, and relevant previous investigations was noted. Physical examination, including measurement of height, weight, body mass index (BMI), and musculoskeletal assessment, was done for all included patients.
Plain radiographs of the hands and wrists were taken to record the presence or absence of erosions. A complete blood count, erythrocyte sedimentation rate (ESR), kidney and liver function tests, rheumatoid factor, anticitrullinated protein antibody, and 25-OH Vitamin D estimation were done. RA disease was assessed by the clinical disease activity index (CDAI). A CDAI score ≤2.8 was considered to be disease remission, >2.8 and ≤10 as low disease activity, >10 and ≤22 as moderate disease activity, and >22 as high disease activity.
Paramedical personnel and patient visitors were enrolled as healthy controls. Venous blood was collected from patients and healthy controls; separated sera were stored for analysis of serum sclerostin at the end of participant recruitment. Serum sclerostin was assayed using commercially available enzyme-linked immunosorbent assay kits according to the manufacturer's instructions (Elabscience, China).
Bone mineral density measurement
All patients underwent BMD testing by dual-energy X-ray absorptiometry (DXA). The BMD was measured at the proximal femur, lumbar spine (L1–L4), and distal radius in RA patients (g/cm2) using DXA machine (GE, Lunar). For BMD measurement in premenopausal women, the international society for clinical densitometry recommendation was used with Z-scores of −2.0 or lower defined as either “low BMD for chronological age” or “below the expected range for age” and those above −2.0 being “within the expected range for age.” Quality control procedures were done as per the manufacturer's recommendations.
Statistical analysis was done by GraphPad Prism 5.01 (GraphPad Software, San Diego, CA, USA). Quantitative data were expressed as mean and standard deviation whereas qualitative data as frequency and percentage. Comparison of sclerostin levels between cases and controls was done by unpaired t-test. Spearman's correlation coefficient was used to test correlation between serum sclerostin and ESR and CDAI and BMD (g/cm2). P < 0.05 was considered statistically significant.
| Results|| |
Over a period of 9 months (September 2015 to June 2016), we included 47 RA patients and 28 healthy controls matched for gender and age. Incidentally, male patients were not encountered during the specified study period. Hence, all the patients included were premenopausal women, and all the controls were women too. Patients had a mean RA disease duration of 4.2 ± 2 years. The demographic and clinical characteristics of the patients are shown in [Table 1]. Four of 46 (8.7%) patients (CDAI was not available for one patient) were in remission, 17 (36.9%) had mild disease activity, 16 (34.8%) moderate disease activity, and 9 (19.6%) had severe disease. Low BMD at least one site was seen in 12 of 47 patients (25.5%) with wrist being the most common site [Table 1].
Mean serum sclerostin level in patients was 8422 ± 3655 pg/ml which was significantly higher than the controls (6479 ± 1510 pg/ml, P = 0.002) [Figure 1]a. As depicted in [Figure 1]b, mean sclerostin level in the patients with low BMD was 8067 ± 3292 pg/ml, whereas in the group with normal BMD, sclerostin was 8554 ± 4241 pg/ml (P = 0.59). Furthermore, there was no difference in the sclerostin levels between those with and without erosion (8868 ± 4283 vs. 8816 ± 4430 pg/ml, respectively, P = 0.92).
|Figure 1: (a) Comparison of serum sclerostin levels among patients and controls: serum sclerostin levels were significantly higher in the patient group. (b) Comparison of serum sclerostin levels among patients with and without low bone mineral density: serum sclerostin levels did not differ in patients with and without low bone mineral density|
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Correlation analysis was performed between serum sclerostin and ESR, CDAI, BMD. As shown in [Table 2], there was no significant correlation of serum sclerostin with ESR, CDAI, and BMD at lumbar spine, neck of femur, and wrist. Further, sclerostin levels did not vary significantly among disease activity groups.
|Table 2: Correlation between serum sclerostin and erythrocyte sedimentation rate, clinical disease activity index and bone mineral density in patients (n = 47)|
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| Discussion|| |
In our study, we found that 25% of premenopausal RA patients had low BMD. The most common site was at the wrist followed by lumbar spine and neck of femur. Increased prevalence of osteoporosis in premenopausal RA has also been reported in studies. The study from India by Shankar et al. of 84 premenopausal women with RA reported osteopenia in 40% of patients at all the three sites and osteoporosis in 22% in at least one site. The factors contributing to low BMD in our patients could be uncontrolled disease as almost 54% had moderate-to-severe disease activity and steroid use. Measurement of wrist BMD is not routinely recommended but in the context of RA, Naumann et al. reported significant correlation between hand BMD and spine/femur BMD in RA patients depending on disease activity and disease duration and concluded that BMD measurement at wrist in addition to spine and femur in RA will quantify bone loss properly.
The major finding in our patients is that serum sclerostin levels were significantly higher in RA as compared to healthy controls. The study by Ibrahim et al. of 45 RA patients (35 females and 10 males) with the mean age of 49.47 ± 7.17 years also reported higher sclerostin levels in patients than healthy controls. Although Vis et al. found no difference in sclerostin levels between female RA patients (mean age of 57 ± 13 years) and healthy postmenopausal women, the levels were significantly higher when compared to healthy premenopausal women. Vargas-Muñoz et al. in their study of 48 postmenopausal RA patients (mean age: 50.81 ± 1.66 years) reported no difference in serum sclerostin levels between patients and healthy controls. They attributed the lack of increase of serum sclerostin levels in patients to low disease activity since 50.98% of their patients were in clinical remission (disease activity score <2.6) and disease-modifying antirheumatic drug treatment (72.55% were on methotrexate). This difference across studies may be further explained by the fact that serum sclerostin levels are influenced by many factors including age, sex, menopause, and inflammation. There is often a significant increase in serum sclerostin levels with advancing age and menopause which may contribute to increased fracture risk in postmenopausal women., In our study, we have excluded postmenopausal women and also other medical conditions that would contribute to osteoporosis, and hence, we believe that the higher sclerostin levels observed in RA could be due to high disease activity. Sclerostin known to be induced during inflammation that may contribute to low bone mass in RA patients.
We found no correlation between serum sclerostin and BMD, ESR, CDAI, or erosive disease, most likely because of small sample size. We did not power the study enough to detect meaningful differences in the subgroups of erosive disease and disease activity. Mehaney et al. studied 40 RA patients (28 females and 12 males) with the mean age of 48.9 ± 11.6 years and 40 healthy controls and reported no correlation between sclerostin levels and BMD, disease activity, radiographic grading. Although Ardawi et al. found significant negative correlation between serum sclerostin and BMD, it was not observed when adjusted for age and BMI., There are studies which also have reported positive correlations between serum sclerostin levels and BMD in RA. The variable results could be due to difference in characteristics of the study participants such as age, sex, ethnicity, and disease activity. Further, disease activity in RA fluctuates over time and might have a bearing on serum sclerostin levels.
Although from a mechanistic point of view, sclerostin can contribute to bone loss and bone erosions in RA patients; we did not find any correlation between serum sclerostin levels and BMD or disease activity for the obvious reasons stated above. The strength of our study is that we enrolled a relatively homogeneous group of patients with RA, without any other medical condition that would have caused osteoporosis, and also excluded postmenopausal women with RA which might have contributed to low BMD. The major limitation is small sample size of patients and controls. A larger prospective study may better address this issue. Second, the BMD was not measured in controls.
In conclusion, in our present study serum sclerostin levels were higher in RA as compared to controls, but there was no correlation with BMD and disease activity.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2]