Serum sRAGE, sRANKL and osteoprotegerin in subgroups of rheumatoid arthritis patients: biomarkers associated with iron and disease status

Abstract

Soluble receptors are important for the balance between ligands and their membrane receptors. Changes in the expression of soluble receptors are associated with human diseases. The aim of this study was to determine the serum levels of sRAGE, sRANKL and OPG in subgroups of rheumatoid arthritis (RA) patients according to the level of CRP and to assess the relationship of these parameters with markers of iron and disease status. The study involved 114 RA patients. The levels of sRAGE, sRANKL and OPG were higher in the subgroup with increased CRP level compared to the subgroup with normal CRP. sRAGE showed a significant positive correlation with sTfR (r = 0.435, p < 0.0001), prohepcidin (r = 0.232, p = 0.04), sRANKL (r = 0.636, p < 0.0001), RF (r = 0.363, p < 0.002), and antiCCP antibodies (r = 0.429, p = 0.003) in the subgroup with normal CRP. Serum sRANKL was positively associated with sRAGE (r = 0.636, p < 0.0001), sTfR (r = 0.513, p < 0.0001), CRP (r = 0.223, p = 0.048), DAS28 (r = 0.269, p = 0.016), RF (r = 0.390, p = 0.001) and antiCCP antibodies (r = 0.445, p = 0.002) also in the subgroup with normal CRP. Serum OPG was positively correlated with ferritin in the subgroup with normal CRP. The association of sRAGE, sRANKL and OPG with markers of iron and disease status in RA suggests a relationship between inflammatory state, osteoclast activation and impaired iron and immune status. Therefore, sRAGE, sRANKL and OPG can be useful markers for the assessment of early pathological changes in RA and can also assist in monitoring of the therapy.