Bone Abstracts

Vaspin (visceral adipose tissue-derived serine protease inhibitor) is a newly discovered adipokine that widely participates in diabetes mellitus, polycystic ovarian syndrome and other disorders of metabolism. However, the effect of vaspin on the regulation of osteogenesis and the mechanism responsible are still unclear. Here, we found that vaspin could attenuate the ALP activities, osteocalcin secretion and Runx2 expression in the preosteoblast cell line MC3T3-E1 in a dose-dependent way, which suggested vaspin inhibit the osteogenic differentiation of MC3T3-E1 cells; also, during this process, the expression of miRNA-34c (miR-34c) was significantly increased confirmed by miRNA microarray and real-time PCR. Down-regulation of the expression of miR-34c in MC3T3-E1 cells diminished the osteogenic inhibitory effect of vaspin, while the up-regulation of miR-34c increased this effect. Using luciferase reporter assays, we confirmed Runx2 is the target of miR-34c. Meanwhile, we found that vaspin could up-regulation of miR-34c through activate the PI3K-Akt signalling pathway. Blocking the PI3K-Akt signalling pathway with specific inhibitors could decrease the expression level of miR-34c, meanwhile the osteogenic inhibitory effect of vaspin also decreased. Furthermore, knock-down of miR-34c could promote the activation of Akt, which was realised by decreased c-met expression, which was the target of miR-34c and the upstream of Akt. Thus, PI3K-Akt, miR-34c and c-met constituted a modulation loop and controlled the expression of each other. Taken together, our study showed that vaspin could inhibit the osteogenic differentiation in vitro, and the PI3K-Akt/miR-34c and miR-34c/c-met loop might be the underlying mechanism.