Abstract
Objective. To identify biomarkers for bone metabolism in patients with ankylosing spondylitis (AS) and to determine the relationship between these biomarkers and disease activity, back mobility, osteoproliferation, and bone mineral density (BMD).
Methods. Serum levels of Wingless protein (Wnt-3a), Dickkopf-1 (DKK-1), sclerostin, soluble receptor activator of nuclear factor-κB ligand (sRANKL), and osteoprotegerin were assessed using ELISA. Ankylosing Spondylitis Disease Activity Score-C reactive protein, Bath Ankylosing Spondylitis Disease Activity Index, Bath Ankylosing Spondylitis patient global score, and C-reactive protein (CRP) were used as disease activity measures, and Bath Ankylosing Spondylitis Metrology Index (BASMI) as a measure of spinal mobility. Lateral spine radiographs were scored for chronic AS-related changes (mSASSS). BMD was measured with dual-energy x-ray absorptiometry.
Results. Two hundred four patients with AS (NY criteria; 57% men), with a mean age of 50 ± 13 years and disease duration 15 ± 11 years, and 80 age and sex-matched controls were included. The patients with AS had significantly higher serum levels of Wnt-3a (p < 0.001) and lower levels of sclerostin (p = 0.014) and sRANKL (p = 0.047) compared with the controls. High CRP was associated with low sclerostin (rS = −0.21, p = 0.003) and DKK-1 (rS = −0.14, p = 0.045). In multiple linear regression analyses, increasing BASMI and mSASSS were independently associated with older age, male sex, high CRP, and elevated serum levels of Wnt-3a. In addition, mSASSS remained associated with a high number of smoking pack-years after adjusting for age. Low BMD of femoral neck was associated with high mSASSS after adjusting for age.
Conclusion. Serum levels of Wnt-3a are elevated in AS and associated with increased BASMI and mSASSS, independent of age, indicating that Wnt-3a could be a biomarker for the osteoproliferative process.
Footnotes
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Supported by grants from The Health and Medical Care Executive Board of the Västra Götaland, Rune and Ulla Amlövs foundation for Rheumatology Research, Göteborg’s Association Against Rheumatism, The Medical Society of Göteborg, the Medical Society of Göteborg and the Region Västra Götaland (agreement concerning research and education of doctors), COMBINE, the Margareta Rheuma research foundation, and the Inger Bendix foundation.
- Accepted for publication March 7, 2014.