LAUSR

OBJECTIVE Resistin acts as an endogenous ligand of Toll-like receptor (TLR)-4 that triggers major inflammatory pathways and mediates inflammatory processes. The role of resistin in osteoarthritis (OA) pathogenesis is unclear. The aim of this study is to describe the longitudinal associations of serum levels of resistin with knee synovitis measures and structural abnormalities in patients with knee OA. DESIGN A prospective cohort study. SETTING AND PARTICIPANTS Patients (n = 200) with symptomatic knee OA (mean age 63.1 years, range 49-79; female 46.5%) participated. MEASURES All measures were performed at baseline and 2 years later. Serum resistin was measured using enzyme-linked immunosorbent assay. Infrapatellar fat pad (IPFP) high signal intensity alteration and effusion synovitis were measured from magnetic resonance imaging (MRI). Knee structures including cartilage volume, cartilage defects, and bone marrow lesions (BMLs) were also assessed by MRI semiquantitatively or quantitatively. Linear or logistic mixed effects regression analyses were used in longitudinal analyses. RESULTS Serum resistin was positively associated with high signal intensity alteration measures of IPFP as well as the presence [relative risk = 1.06, 95% confidence interval (CI) 1.02, 1.10] and volume (β = 0.77, 95% CI 0.01, 1.53) of effusion synovitis in multivariable analyses. Serum levels of resistin were also positively associated with higher tibiofemoral cartilage defect (β = 1.98, 95% CI 0.34, 3.57) and BML scores (β = 3.18, 95% CI 0.99, 5.37) after adjustment for covariates. CONCLUSION AND IMPLICATIONS Higher serum levels of resistin are associated with knee synovitis surrogate measures and structural abnormalities, suggesting that obesity may promote OA not only by increasing weight loading on joints but also by triggering 1 or more inflammatory pathways.