Factors modifying collagen catabolism in patients with ankylosing spondylitis

Objective: We quantified the total excretion of the collagen crosslinks (CL) pyridinofine (PYD) and deoxypyridinoline (DPD) in 108 ankylosing spondylitis (AS) patients (29 f, 79 in) in correlation to different characteristics of disease to evaluate different mechanism contributing to development of osteoporosis in AS. Methods: PYD and DPD were measured by HPLC. Results: AS patients show a highly significant positive correlation between PYD and inflammatory activity In cases involving peripheral joints, significantly higher CL levels in urine were found. Patients with syndesmophytes excreted significantly more CL vs. those without. In the more advanced stages of sacroiliitis (stage III and IV), CL levels tended to be higher. Among those patients treated with NSAIDs, a tendency to decreased levels of DPD and consecutive raised levels of the quotient PYD/DPD were observed. No significant correlation was found between restricted spine mobility or duration of disease and amount of excreted CL. Conclusions: Our investigations show that the inflammatory process, the involvement of the peripheral joints, the presence of syndesmophytes and the stage of sacroiliitis all have an influence on the extent of collagen degradation in AS patients. NSAIDs do not increase but appear to reduce collagen I catabolism.