Bone Mineral Density and Serum Levels of Bone Remodeling Markers in Ankylosing Spondylitis Treated with Anti TNF-α Agents

<b>Background:</b> Ankylosing spondylitis (AS) is a chronic autoinflammatory rheumatic disease mainly affecting the sacroiliac joints and spine, causing altered bone remodeling. Pro-inflammatory cytokines such as TNF-α and IL-17 contribute to bone loss by modulating pathways including Wnt/β-catenin, which is inhibited by proteins like Dickkopf-1 (DKK-1) and sclerostin (SOST). Bone morphogenetic protein-6 (BMP-6) promotes osteoblast differentiation and bone formation. This study evaluated the association between serum levels of DKK-1, SOST, BMP-6, and bone mineral density (BMD) in AS patients treated with anti-TNF agents and conventional synthetic DMARDs (csDMARDs). <b>Methods:</b> A cross-sectional study included 76 AS patients diagnosed by modified New York criteria and 30 healthy donors matched by age and sex. BMD at the lumbar spine and hips was assessed by DXA in all participants. Disease activity (BASDAI) and functional index (BASFI) were measured in AS patients. Serum levels of DKK-1, SOST, BMP-6, TNF-α, and IL-17 were quantified by ELISA in both groups. AS patients were divided into two treatment groups: combined anti-TNFα and csDMARD therapy (<i>n</i> = 38), and only csDMARDs (<i>n</i> = 38). <b>Results:</b> Bone mineral density showed no significant statistical differences between the spine (<i>p</i> = 0.930) and hips (<i>p</i> = 0.876) in AS patients compared to healthy controls. The activity (BASDAI) and functionality (BASFI) scores were similar in both treatment groups (<i>p</i> = 0.161 and <i>p</i> = 0.271, respectively). No significant differences were found in serum levels of DKK-1 (<i>p</i> = 0.815), SOST (<i>p</i> = 0.771), BMP-6 (<i>p</i> = 0.451), or IL-17 (<i>p</i> = 0.335) between combined anti-TNFα and csDMARD therapy versus monotherapy with csDMARD. <b>Conclusions:</b> The combination of anti-TNF bDMARD therapy and csDMARD therapy is not significantly associated with serum levels of DKK-1, SOST, BMP-6, and BMD compared to those treated with csDMARD monotherapy in patients with AS. This study provides novel and clinically relevant evidence on how anti-TNF bDMARDs and csDMARDs differentially affect bone turnover biomarkers and bone health in patients with AS, contributing to a better understanding of therapeutic strategies and guiding future research and clinical decision-making.