Serum levels of osteoprotegerin and RANKL in patients with rheumatoid arthritis and their relation to bone mineral density and disease activity

Aim of the workTo evaluate the levels of osteoprotegerin (OPG) and receptor activator of the nuclear factor κB ligand (RANKL), in patients with rheumatoid arthritis (RA) and to study the relation between these parameters and bone mineral density (BMD) and disease activity; thus, investigating the possible role of the OPG/RANKL system in RA related bone loss.Patients and methodsFifty patients with RA and 20 age and sex matched healthy controls were enrolled in the study. BMD of the non-dominant forearm, lumbar spine (L1–4) and proximal femur, including femoral neck, Wards triangle and greater trochanter was assessed using dual-energy X-ray absorptiometry (DEXA). The serum OPG and RANKL were measured by ELISA method.ResultsRheumatoid arthritis patients had a higher incidence of osteoporosis (23/50, 46%) than that in healthy controls (3/20, 15%). They displayed lower BMD values than controls at positions of all detected regions. Compared with healthy controls, RA group showed significantly higher serum levels of RANKL (4.7 ± 3.3 vs. 3.0 ± 3.1 ng/dl, p = 0.001), lower serum levels of OPG (331.2 ± 143.6 vs. 535.8 ± 229.1 pg/ml, p = 0.001) and OPG/RANKL ratio (531.6 ± 149.4 vs. 882.8 ± 148.6, p = 0.001).ConclusionsThese data suggest that, in RA patients, changes of the OPG/RANKL system resulting in increased RANKL and decreased OPG in peripheral blood could contribute to the bone loss characteristic and the generation of osteoporosis in these patients.