Background Obesity is one of the main risk factors for knee osteoarthritis (OA). Fat tissue produces systemic inflammatory mediators, adipokines, which have a critical role in the development of OA. Chemerin is a chemokine that, through the engagement of its counter-receptor, ChemR23, attracts pro-inflammatory cells and IL-1β, along with other adipokines and glucocorticoids, is able to modulate the expression of this adipokine. Furthermore, stimulation of ChemR23 increases the production of pro-catabolic cytokines and matrix metalloproteinases.
Objectives To determine serum chemerin levels and to evaluate the association of chemerin with inflammation and disease severity in older adults with knee OA.
Methods 184 patients with clinical and radiographic criteria of primary knee OA diagnosed according to the criteria of the American College of Rheumatology and 96 age-sex-body mass index (BMI) matched healthy volunteers were recruited in this study. Disease severity assessment was performed using the Kellgren and Lawrence (KL) grading system. OA patients were defined as having radiographic knee OA of KL grade ≥2 in at least one knee. Controls were defined as having no radiographic knee OA as indicated by KL grades of 0 for both knees. The grading of the worst affected knee in each patient was used for data analysis. All participants underwent a full clinical examination including BMI calculation. Serum samples were obtained and levels of Chemerin, MMP-1, MMP-3, IL-1 and IL-6 were measured using commercial enzyme-linked immunosorbent assay (ELISA). Levels of C-reactive protein (CRP) and tumour necrosis factor (TNF)-alpha were also assessed.
Results Chemerin levels in serum were significantly higher in patients compared to controls, p < 0.01. Chemerin levels in knee OA patients correlated with disease severity as assessed by KL grading criteria. Chemerin levels correlated positively with biomarkers of OA, that is, MMP-1 (r = 0.555, p< 0.01) and MMP-3 (r = 0.347, < 0.01), IL-1 (r = 0.413, p< 0.001), IL-6 (r = 0.432, P < 0.01) and TNF-alpha (r = 0.537, p< 0.05) respectively. Furthermore, there was a positive correlation between chemerin and BMI (r = 0.575, p< 0.01).
Conclusions The findings of this study show that in patients with knee OA, chemerin is associated with obesity, disease severity, inflammation and cartilage destruction. The implication of these findings is that chemerin may be a novel molecule involved in the pathogenesis and progression of OA. Chemerin may be regarded as a surrogate biomarker for severity of OA. Further studies targeting this adipokine may offer new hope for patients with knee OA.
Disclosure of Interest None Declared