Background Obesity and especially body fat content appears to play a role in the development and especially in the progression of osteoarthritis (OA). Leptin is an adipokine involved in body weight regulation and usually shows higher levels in obese patients. Leptin has proinflammatory effects and has been implicated in OA physiopathology.
Objectives To evaluate the relationship between body fat content with the amount of synovial fluid as a surrogate marker of inflammation and with levels of synovial fluid leptin in knee OA.
Methods Cross-sectional study including patients aged 50 years or more with symptomatic osteoarthritis of the knee and joint effusion, Kellgren-Lawrence II-III. Demographics, disease duration and percentage of body fat (%BF) were assessed. Percentage of body fat was determined by bio-electrical impedance. Knee ultrasound (US) was performed evaluating and measuring the presence of effusion and at the suprapatellar midline. After US measurement joint aspiration was performed. Synoval leptin levels were analyzed using a Human leptin ELISA kit (Biocompare, California, USA). All patients were evaluated in fasting conditions approximately at the same time of the day.
Results Seventy consecutive female patients with symptomatic knee OA and Kellgren-Lawrence II-III were included, age 65±7.8 years, disease duration of symptoms 66±49.5 mo (12-200). Mean %BF was 42.34±5.11%. Patients were categorized into two groups based on %BF so that those with levels above the mean and median values (n=36) were compared with the rest of the sample (n=34). Mean synovial fluid measurement was 9.59±2.79 mm. Mean level of leptin in synovial fluid was 76.76±38.66 ng/mL. Patients in the higher %BF group had similar amount of synovial effusion compared with those without such a high percentage (9.4±2.4 vs. 9.75±3.2 mm). However, patients with %BF above the mean and median values showed significantly higher synovial leptin levels than those with values below (88.47±46.8 vs. 60.24±19.5 ng/mL, p<0.005).
Conclusions In this study higher synovial leptin levels were observed in patients with the highest body fat percentage as measured by bio-electrical impedance. On the other hand, synovial effusion did not appear to be linked to body fat content, indicating that body fat could be more related to metabolic abnormalities than to clinical signs of inflammation.
Disclosure of Interest None declared