ABSTRACT
Objective To investigate the mechanisms of action of adiponectin on receptor activator of NF-Kb ligand(Rankl) and osteoprotegerin (OPG)expressions in human osteoblasts.Methods Real-time PCR was used to detect the expressions of RANKL and OPG mRNA in cultured human osteoblasts. The phosphorylations of JNK, p38 mitogen-activated protein kinase (MAPK) , ERK1/2 were assayed by Western blot. RNA interference for adiponectin receptor, MAPK inhibitors SB203580 and SP600125 were used for elucidating the mechanism of the action of adiponectin in regulating OPG and RANKL expressions. Results Suppression of adiponectin receptor-1 (AdR1) expression with siRNA abolished the adiponectin-regulated expressions of OPG and RANKL mRNA in human osteoblasts. Furthermore, pretreatment of osteoblasts with MAPK inhibitor SB203580 abolished the expressions of adiponectin-regulated RANKL and OPG mRNA, but SP600125 did not show the effect. Conclusion Adiponectin induces the expression of RANKL and inhibits the expression of OPG in human osteoblasts through AdR1/p38 MAPK pathways.