Gene Expression of Adipocytokine Receptors during Osteoblastic Differentiation

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In order to elucidate the involvement of adipocytokine action in bone formation, we demonstrated the expression of adipocytokine receptors, leptin receptor (LepR) and adiponectin receptors (AdipoR1 and AdipoR2), in cultured pro-osteoblastic cells during osteoblastic differentiation.
The mRNA expression levels of osteocalcin and Runx2 were increased significantly by culture with differential medium. Both adiponectin receptors, AdipoR1 and AdipoR2, were also increased significantly during osteoblastic differentiation, though there were no significant changes in the leptin receptor, LepR, level. This indicated that adiponectin rather than leptin may be involved in osteoblastic differentiation.
Circulating adiponectin includes both a full-length type and a globular type. We also investigated the effect of globular adiponectin (gAN) on the induction of osteoblastic properties. gAN significantly suppressed the induced gene expression of osteocalcin and adiponectin receptors.
Our results indicate that the expressions of adiponectin receptors may be involved in osteoblastic differentiation without involvement of the serum globular type of adiponectin.