Relationship between weight loss in obese knee osteoarthritis patients and serum biomarkers of cartilage breakdown: secondary analyses of a randomised trial.

OBJECTIVE: To explore effects of weight loss and maintenance on serum cartilage biomarkers denaturation neoepitope for Collagen2 (Coll2-1) and Fibulin3 fragment (Fib3-2), as well as correlations between Coll2-1 and Fib3-2 and symptomatic improvement, in a knee osteoarthritis (KOA) population. DESIGN: 192 obese KOA patients followed a 16 week weight loss intervention and 52 weeks weight maintenance (ClinicalTrials.gov identifier: NCT00655941). Assessments were at 0, 8, 16 and 68 weeks. Serum Coll2-1 and Fib3-2 were determined with ELISA, and symptoms by the Knee Osteoarthritis Outcome Score (KOOS) questionnaire. Changes from week 0 and association between changes from baseline in body weight and Coll2-1, Fib3-2, and the 5 KOOS domains were assessed at all time points. RESULTS: Coll2-1 changes from baseline showed a decrease at week 8 (P = 0.0002), no change at week 16 (P = 0.49), and an increase at week 68 (P = 0.036). Fib3-2 showed an increase from baseline at week 8 (P = 0.0015) and 16 (P < 0.0001), but none at week 68 (P = 0.23). No statistically significant correlations were found between changes in body weight and Coll2-1 and Fib3-2 at any time point (r < 0.05; P > 0.49). At all time-points there were significant positive correlations between changes from baseline in Coll2-1 and in KOOSSports/Recreation (week 8, 16, 68: r = 0.17; P = 0.03; r = 0.16; P = 0.04; and r = 0.17; P = 0.04, respectively). CONCLUSION: The clinical improvement after a substantial weight loss and weight maintenance in KOA patients was not associated with decrease in markers of cartilage breakdown Coll2-1 or Fib3-2, even with indications of a slightly negative effect.