Up-regulation of cyclinD1 and Bcl2A1 by insulin is involved in osteoclast proliferation.
AIMS
Insulin receptor signaling in osteoblasts has been well established, but the effects of insulin on osteoclast proliferation are poorly explored. The objective of this study was to investigate the roles and the mechanisms of insulin on osteoclast proliferation.


MAIN METHODS
After insulin treatment to primary osteoclast precursors, BrdU incorporation assay was performed and the expression of cell cycle- and apoptosis-related genes was determined by real-time PCR and immunoblotting. Apoptosis was analyzed using a FACScan flow cytometer.


KEY FINDINGS
Insulin activated insulin receptor and promoted the proliferation of osteoclast precursors in time- and dose-dependent manners. However, the expression of insulin receptor was not changed by it during that time. Insulin remarkably induced the expression of cyclinD1, a cell cycle marker, and Bcl2A1, an anti-apoptotic oncogene, whereas cdk1 and cdk4 were not affected by it. The expression of Bcl2l11 and Bax, both apoptotic markers, was reduced or not changed in osteoclast precursors. Bcl2A1/Bax ratio was also increased in protein levels. Treatment with obatoclax, a Bcl2 family inhibitor, significantly induced the apoptosis of osteoclast precursors in the presence of insulin. These results demonstrate that insulin promotes osteoclast proliferation by increasing cell cycle and suppressing apoptosis through specific gene regulation.


SIGNIFICANCE
These data provide a basis for understanding and ultimately treating several bone-related metabolic diseases.
['Lee|Jae Yoon|JY|', 'Lee|Na Kyung|NK|']
D017209:Apoptosis D015153:Blotting, Western D001973:Bromodeoxyuridine D049109:Cell Proliferation D019938:Cyclin D1 D005434:Flow Cytometry D007328:Insulin D015778:Minor Histocompatibility Antigens D010010:Osteoclasts D019253:Proto-Oncogene Proteins c-bcl-2 D060888:Real-Time Polymerase Chain Reaction D015854:Up-Regulation
CyclinD1 Bcl2A1 Insulin Osteoclast Proliferation