Adiponectin induces activation of mitogen-activated protein kinases in human primary chondrocytes. The effect of adiponectin (3 μg/ml) on mitogen-activated protein kinase (MAPK) phosphorylation in human primary chondrocytes obtained from patients with OA. The figure shows the results of a representative experiment which was repeated three times (that is, with cells from three donors) with similar results. MAPKs were determined by Western blot analysis at baseline and at 30 and 60 minutes after addition of adiponectin. Erk1/2 = extracellular signal-regulated kinase 1/2; JNK: c-Jun N-terminal kinase.