Synovial/serum leptin ratio in rheumatoid arthritis: the association with activity and erosion

Reports suggest leptin, which was initially described as a hormone that regulates food intake and energy balance, has an intimate relationship, and interacts with the immune system. Leptin consumption in the synovial cavity in patients with rheumatoid arthritis (RA) reported to have protective effect against erosion. To determine the difference in serum leptin and synovial/serum leptin ratio between RA and control and to assess whether these parameters correlate with systemic inflammation in RA. Also, the hypothesis that synovial/serum leptin ratio could be linked to joint erosion in RA was evaluated. The study subjects consisted of 40 consecutive patients with RA, 30 patients of them had knee effusion, and 30 controls. Ten of these controls had acute knee injury and their synovial fluid was obtained for comparison of synovial/serum leptin ratio with patients with RA. The mean serum leptin in patients with RA was significantly higher than controls. Also, the synovial leptin and synovial/serum leptin ratio in the RA patients with effusion was significantly higher than in the 10 control subjects with traumatic effusion. Serum leptin in the 30 RA patients with effusion was higher than the matched synovial leptin. In RA patients with effusion, synovial/serum leptin ratio was also significantly higher in RA patients with erosion than RA patients without erosion. Serum leptin level and synovial/serum leptin ratio are significantly correlated with the RA duration, DAS28, ESR, CRP, TNF-α, and IL-6. Finally, in regression analysis, only the synovial/serum leptin ratio was positively associated with erosion in patients with RA. In RA, there is a significant increase in circulating leptin levels and synovial/serum leptin ratio compared to non-RA controls. Serum leptin and synovial/serum leptin ratio are significantly in erosive RA than non-erosive RA. Both parameters are correlated with disease duration and parameters of RA activity. In regression analysis, only the synovial/serum leptin ratio was positively associated with erosion in patients with RA. These results indicate that local consumption of leptin in the joint cavity has a protective role against the destructive course of RA.