Fetuin-a and secondary osteoporosis in patients with rheumatoid arthritis

Aim. To study the level of fetuin-A (FA), bone mineral density (BMD) and certain markers of bone remodeling in patients with rheumatoid arthritis (RA).

Materials and Methods. 110 Patients with RA and 30 conventionally healthy patients were examined. In both groups the levels of FA and BMD were determined. In the group of patients with RA the levels of C-telopeptide of type I collagen, N-terminal propeptide of procollagen I, 25-hydroxy-cholecalciferol, total alkaline phosphatase, total calcium of blood were determined.

Results. The mean concentration of FA in blood serum of patients with RA was 765.67±120.66 µg/mL, which was below the respective parameter in donors – 812.95±76.21 µg/mL (p=0.0437). In the group of patients with RA with osteoporosis (n=52) the mean level of FA was 733.65±135.84 µg/mL, and in the group without osteoporosis – 794.37±97.7 µg/mL (p=0.0044). The level of FA was also reduced in patients with osteoporotic fractures (n=24) – 694.79±110.47 µg/mL against 785.45±116.43 µg/mL in patients without osteoporotic fractures (n=86; p=0.00091). A positive correlation relationship was found between the level of FA and BMD of L1-L4 (r=0.194; p=0.042), femoral neck (r=0.328; p<0.0001) and proximal femur (r=0.293; p=0.002), and the level of 25-hydroxy-cholecalciferol (r=0.259; p=0.006), and the negative correlation relationship – with C-telopeptide of type I collagen (r=-0.203; p=0.033).

Conclusions. Patients with RA with reduced FA level were characterized by a higher detection rate of osteoporosis and of osteoporotic fractures, and by a lower BMD of L2-L4, femoral bone and proximal femur. Besides, a lower level of FA was associated with a lower level of 25-hydroxy-cholecalciferol and with a higher level of C-telopeptide of type I collagen which permits to suggest existence of osteoprotective function in this glycoprotein.