Background A possible link between obesity, adipocytokines (leptin) and pain severity in osteoarthritis (OA) has been suggested. Synovial leptin levels are increased in OA, particularly in women and in obese patients. OA pain severity is strongly associated with elevated synovial leptin concentrations in weight bearing joints . This finding has led to the hypothesis that the increased OA pain severity observed in women and in obese patients might be mediated by leptin levels. However, the influence of leptin on OA pain severity in non-weight bearing joints is unknown.
Objectives To evaluate whether high serum leptin concentrations also correlate with pain severity in hand OA.
Methods We carried out a cross-sectional study including all patients with symptomatic hand OA enrolled in a placebo-controlled, double-blind, clinical trial . We included all available frozen serum samples and assessed serum leptin concentrations using an ELISA kit (R&D, Abingdon, UK). Primary outcome was severity of joint pain assessed with a VAS scale in the most symptomatic hand. Exposure of interest was serum leptin levels. We analyzed 1) the crude correlations between severity of joint pain and serum leptin levels, 2) the independent contribution of leptin to the severity of joint pain using multivariate linear regression models, adjusting for potential confounders (sex, obesity, functional status, RCT’s treatment groups).
Results Serum from 106/160 patients with symptomatic hand OA were available for analysis. 77% of patients were women, mean age was 63 (±8) years, mean BMI was 25.4 kg/m2 (±3.7), mean hand pain severity was 46 (± 23) mm on a VAS, and median leptin concentration was 19 (IQR: 9 – 37) ng/ml. Serum leptin levels significantly correlated with BMI (r=0.52, p<0.001) and with female sex (+16 ng/ml, p=0.03). The association between joint pain and leptin levels was non-linear (p=0.25); only the elevated leptin concentrations (highest quintile, >66 ng/ml) were significantly associated with increased pain levels (+13 mm, (95%CI: 0.02; 26.3), Figure). The association remained after adjusting for presence of obesity and female sex (adjusted VAS pain +12 mm (95%CI: 0.1 – 24)).
There were weaker associations between increased joint pain and (1) female sex (+6.2 mm (95% CI: -4.2; 16.6)) and (2) obesity (+7.2 mm (95% CI: -6.6; 20.9)), as previously reported for weight bearing OA joints . These associations were substantially weakened (decreased ∼1/3) after adjusting for leptin concentrations, suggesting that the established association between OA joint pain and obesity and gender is partially mediated by leptin levels also in OA of the hands.
Conclusions Severe joint pain in hand OA is significantly associated with high serum leptin concentrations, similar to what has previously been reported in weight-bearing joints.
Lübbeke A, Finckh A, Puskas G et al. “Synovial Fluid Leptin Levels and Joint Pain in End-Stage Osteoarthritis: A Potential Explanation for Increased Pain in Women and in Obese Patients” Arthritis & Rheum, 2011, Vol 63 (10 Suppl), S421 (N° 1081)
Gabay C, Medinger-Sadowski C, Gascon D et al. Symptomatic Effect of Chondroitin Sulfate in Hand Osteoarthritis: The Finger OsteoArthritis Chondroitin Treatment Study (FACTS). A Randomized Double-Blind Placebo Controlled Clinical Trial. Arthritis Rheum. 2011 Nov;63(11):3383-91
Disclosure of Interest None Declared