Associations between serum 25-hydroxyvitamin D and disease activity, inflammatory cytokines and bone loss in patients with rheumatoid arthritis

Objective. The aim of this study was to describe the associations between serum levels of 25-hydroxyvitamin D [25(OH)D] and disease activity, inflammatory cytokines and bone loss/erosions in patients with RA. Methods. The study included 130 patients with RA and 80 healthy controls. Serum 25(OH) D, IL-17 and IL-23 levels were detected by ELISA. Radiographic bone erosion was assessed using the van der Heijde modified Sharp score and BMD was measured using DXA. Results. There were no significant differences in age, gender and BMI between the RA and control groups. Serum level of 25(OH) D was markedly lower in the RA group than in the control group [43.12 nmol/l (S.D. 15.59) vs 57.93 (15.95), P < 0.01]. In RA patients, 25(OH)D levels were significantly and negatively associated with clinical parameters of disease activity including swollen joint count, tender joint count, joint pain degree, morning stiffness time and HAQ score and laboratory measures including platelets and ESR after adjustment for gender, age and BMI. They were also negatively associated with serum levels of IL-17 and IL-23. While 25(OH) D levels were not associated with radiographic bone erosions of RA, they were significantly lower in those with osteopenia and osteoporosis than in those with normal BMD (P < 0.01). Conclusion. 25(OH)D levels were reduced in patients with RA and were negatively associated with disease activity, IL-17/IL-23 and bone loss in RA. These suggest that vitamin D deficiency may play a role in the aetiology of RA.