Serum leptin levels correlate with interleukin-6 levels and disease activity in patients with ankylosing spondylitis

Objective: To determine whether serum leptin levels are elevated in men with ankylosing spondylitis (AS) and whether the levels correlate with serum cytokine profiles and disease activity of AS. Methods: Forty-two male patients with newly diagnosed AS were enrolled. Their Bath AS Disease Activity Index (BASDAI), body mass index (BMI), and acute phase reactants, such as erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) levels, were assessed. Serum leptin levels were determined using radioimmunoassay (RIA) and serum cytokine profiles, including tumour necrosis factor (TNF)-alpha, interleukin (IL)-6, and interferon (IFN)-gamma, were determined using enzyme-linked immunosorbent assay (ELISA). These results were compared with those from 42 age-matched healthy men. After a follow-up period of 31.0 +/- 20.1 months, clinical and biochemical variables were reassessed in the men with AS. Results: At baseline, patients with AS had significantly elevated serum levels of leptin, leptin adjusted for BMI (leptin/BMI), TNF alpha, and IL-6, but not IFN-gamma, as compared to the controls. Serum leptin/ BMI levels correlated well with IL-6 levels, and both leptin/BMI and IL-6 levels correlated well with BASDAI and CRP levels in patients with AS. The changes in leptin/BMI and IL-6 levels between the baseline and follow-up measurements correlated well with one another (p < 0.05) and both correlated well with the changes in BASDAI (p < 0.05). Conclusion: Serum leptin/BMI levels were increased and significantly associated with IL-6 levels and disease activity in men with AS, suggesting a possible role for leptin in the inflammatory reactions of AS.