Evaluation of selected bone metabolism markers in rheumatoid arthritis patients

Rheumatoid arthritis (RA) is a chronic systemic disease of connective tissue characterized by progressive destructive arthritis associated with deformation and impairment of the function of the motor system. RA patients more often present secondary osteoporosis and increased risk of fractures. The aetiology of the process remains not fully understood. A significant role is played by proinflammatory cytokines being common mediators of both inflammatory processes and bone remodelling.

The purpose of the study was to evaluate the effect of activity of the inflammation and of applied therapy on osteogenesis marker concentrations in RA patients.

Thirty six female patients with RA, confirmed according to ACR criteria, aged from 35 to 77 years were qualified into the study. A control group included 45 healthy women aged between 34 and 78 years. Clinical evaluation (number of painful and swollen joints, DAS 28) and evaluation of RA laboratory activity (ESR, CRP, blood cell count) and levels of selected bone metabolism markers (osteocalcin, PICP) and serum interleukin 1 levels were performed to carry out the study. X-rays of hands and densitometric scanning of the femoral bone neck and spine were completed in order to assess the advancement of lesions in the bones.

Osteocalcin and PICP levels were significantly lower in the RA groups compared to the control group (2.51 ± 0.22 pg/mL vs. 18.65 ± 12.84 pg/mL, p < 0.0001; 0.292 ± 0.047 pg/mL vs. 0.829 ± 0.263 pg/mL, p < 0.0001 respectively). A statistically significant difference was also observed between the levels of osteocalcin and PICP in both sub-groups of RA patients (DAS28 ≤ 5.1 and DAS28 > 5.1) and the control (osteocalcin 2.48 ± 0.23 pg/mL vs. 18.65 ± 12.84 pg/mL, p < 0.0001; 2.52 ± 0.22 pg/mL vs. 18.65 ± 12.84 pg/mL, p < 0.0001 respectively and PICP 0.281 ± 0.053 pg/mL vs. 0.829 ± 0.263 pg/mL, p < 0.0001; 0.298 ± 0.044 pg/mL vs. 0.829 ± 0.263 pg/mL, p < 0.0001 respectively). No correlation was demonstrated between the levels of selected bone metabolism markers and the therapy with methotrexate or cyclosporine.

Analysis of the obtained results confirms the presence of disorders of bone metabolism in RA patients. A chronic inflammatory process favors the development of osteoporosis in RA patients. Reduced levels of bone metabolism markers (osteocalcin, PICP) in the study group, compared to the control, may indicate a reduced pace of osteogenesis in RA patients. No effect of therapy with methotrexate and cyclosporine on bone metabolism in that group of patients was found.