ABSTRACT
The effects of soluble TNF-alpha receptor, etanercept, on bone metabolism were investigated in patients with rheumatoid arthritis (RA). Thirty RA patients were administered etanercept once or twice a week for more than 6 months. We evaluated clinical and laboratory parameters and measured urinary excretion levels of pyridinoline (PYD), deoxypyridinoline (DPD), cross-linked N-telopeptides of type I collagen (NTX), and serum levels of bone alkaline phosphatase (BAP), osteoprotegerin (OPG), and soluble receptor activator of NFkappaB ligand (sRANKL) at the baseline and at 3 and 6 months after initial treatment with etanercept. Etanercept treatment resulted in an improvement of symptoms due to RA and in a reduction of urinary excretion levels of PYD and DPD as well as serum sRANKL levels, with a significant difference at 6 months, and an increase of serum BAP levels at 3 and 6 months after the initial treatment with etanercept. Urinary NTX and serum OPG levels did not show a significant change at 3 and 6 months after the initial treatment, but serum OPG levels did show a reverse correlation with serum CRP levels, suggesting that the regulation of inflammation in RA may result in an induction of OPG production. Etanercept may have the ability to reduce the levels of bone resorption markers and to increase the levels of a bone formation marker while reducing sRANKL formation in RA patients.
