Leptin effect on RANKL and OPG expression in MC3T3-E1 osteoblasts

Recent studies have suggested that leptin hormone may play a pivotal role on bone remodeling through a direct effect by modulating positively the OPG/RANKL balance. Here, we investigate the effect of leptin hormone on RANKL and OPG expression in MC3T3‐E1 osteoblasts using RT‐PCR and ELISA measurements. We have at first identified the expression of Ob‐Rb and Ob‐Ra leptin receptor isoforms in MC3T3‐E1 and observed that these cells respond to mrleptin treatments. We then investigated the effect of mrleptin on RANKL and OPG expression. We show that mrleptin dose‐dependently regulated the expression of RANKL mRNA with complete inhibition observed at concentrations higher than 12 ng/ml. This effect was confirmed with sRANKL protein measurements. However, the exposure of MC3T3‐E1 to mrleptin had no effect on OPG mRNA. Taken together, these results suggest that leptin modulates positively OPG/RANKL balance by inhibiting the expression of RANKL gene. J. Cell. Biochem. 98: 1123–1129, 2006. © 2006 Wiley‐Liss, Inc.