The leptin receptor in human osteoblasts and the direct effect of leptin on bone metabolism.

It is important to elucidate whether the leptin receptor, especially the long signal-transducing form of the leptin receptor (OB-Rb) is expressed in human osteoblasts. We detected the expression of human OB-Rb in cultured commercially available human osteoblasts (NHOst cells) using real-time quantitative reverse transcriptase polymerase chain reaction (RT-PCR). After confirming the expression of OB-Rb, we investigated the effect of leptin on NHOst cells. Leptin enhanced cell proliferation of the cells shown by the MTT assay. Furthermore, leptin changed the copy numbers of Bax and Bcl-2 mRNAs in the cultured cells as shown by real-time quantitative RT-PCR, although the effect was not consistent. Leptin did not change the production of osteocalcin and osteopontin by the cells. Leptin did not change the expression of OB-Rb mRNA in the cells. In conclusion, OB-Rb mRNA is expressed in cultured commercially available human osteoblasts. Leptin may have some effects on bone metabolism by directly modulating cell proliferation and apoptosis of osteoblasts in humans.