Changes of bone metabolism, radiology and osteoprotegerin/receptor activator of nuclear factor-κB ligand serum levels in ankylosing spondylitis patients with the treatment of Etanercept

Abstract

Objective To evaluate bone metabolism, bone mineral density, radiology and osteoprotegerin/receptor activator of nuclear factor-κB ligand (OPG/RANKL) serum levels in patients with ankylosing spondylitis (AS) treated with etanercept compared with sulfasalazine (SSZ). Methods Sixty AS patients were randomly divided into 2 groups: the etanercept group (30 cases) treated with etanercept and SSZ group (27 cases, 3 cases) withdraw treated with SSZ. Serum samples from patients were obtained at baseline and 24 weeks after treatment. Disease activity indexes and serum levels of Osteocalcin (OC), β-collagen degradation products (CTX), RANKL, and OPG were measured before and after treatment respectively. Bone mineral density of lumbar spine and femoral neck were measured by dual energy X-ray and the X-ray images of pelvis were graded based on Bath AS radiology index (BASRI) before and after treatment. Paired t test, t' test, χ2 test were used for statistical analysis. Results After 24 weeks of treatment, the number of swelling and tender joints (0.7±1.2, 3.1±1.4), the Bath AS disease activity index (BASDAI) (2.9±1.1, 6.5±1.1), C reactive protein (CRP) [(1.8±0.9) mg/L, (28±20) mg/L], erythrocyte sedimentation rate (ESR) [(8±4) mm/1 h, (55±33) mm/1 h], CTX [(0.18 ±0.07) ng/ml, (0.27 ±0.11) ng/ml] and RANKL [(3.3 ±2.8) pg/ml, (6.7 ±2.9) pg/ml] levels were significantly decreased in the etanercept group (t=3.887, 7.642, 6.809, 7.264, 3.639, 6.248; P均 0.05). The indexes of BASDAI, CRP, ESR, CTX and RANKL in patients of the etanercept group were significantly decreased than patients of the SSZ group after treatment, while the indexes of OC, OPG and OPG/RANKL were significantly increased (P 0.05). After treatment, the BMD of lumbar spine and femoral neck in the etanercept group (30 cases) was negatively correlated with the indexes of BASDAI and RANKL (r=-0.432, -0.691, -0.522, -0.476; P<0.05), and was positively correlated with the indexes of OPG and OPG/RANKL (r=0.318, 0.392, 0.236, 0.370; P<0.05). Conclusion Secondary osteoporosis in AS patients is not rare. Compared with sulfasalazine, etanercept may be effective in reducing disease activity and improving bone metabolism via adjusting OPG system in patients with AS. Key words: Spondylitis, ankylosing; Bone density; Bone metabolism; Tumor necrosis factor-α; Radiology