Objectives: To determine whether circulating osteopontin (OPN) levels in patients with ankylosing spondylitis (AS) undergoing TNF-α antagonist-infliximab-therapy are increased compared with controls and to establish whether disease activity, systemic inflammation, metabolic syndrome, adipokines and biomarkers of atherosclerosis are potential determinants of circulating OPN levels in these patients.
Methods: We assessed OPN serum concentrations in a series of 30 non-diabetic AS patients without cardiovascular disease undergoing TNF-α antagonist-infliximab therapy and 48 matched controls. OPN levels were measured immediately before and after an infliximab infusion, at time 0 and at time 120 minutes respectively. Correlations of OPN serum levels with clinical features, disease activity, systemic inflammation, metabolic syndrome and several biomarkers of atherosclerosis were assessed. Potential changes in OPN concentration following an infusion of anti-TNF-α monoclonal antibody-infliximab were also analysed.
Results: At the time of the study AS patients undergoing anti-TNF-α therapy had low disease activity (mean BASDAI 2.94) and they showed similar OPN serum levels to healthy controls. No differences in OPN levels according to the specific clinical features of the disease were seen. Also, no correlation between OPN concentration and insulin resistance and adipokines was observed. However, a positive correlation between OPN and angiopoietin-2 (Angpt-2) serum levels was found (r=0.397; p=0.04). In addition, a single infliximab infusion led to a marginal statistically significant reduction in OPN levels (24112.19±14608.73 pg/ml at time 0 versus 21806.62±11390.83 pg/ml at time 120'; p=0.05).
Conclusions: OPN and Angpt-2 serum levels are correlated in non-diabetic AS patients undergoing TNF-α antagonist therapy.