Activation of AMP-activated protein kinase decreases receptor activator of NF-kappa B ligand expression and increases sclerostin expression by inhibiting the mevalonate pathway in osteocytic MLO-Y4 cells

作者：Yokomoto Umakoshi Maki; Kanazawa Ippei^*; Takeno Ayumu; Tanaka Ken ichiro; Notsu Masakazu; Sugimoto Toshitsugu

来源：Biochemical and Biophysical Research Communications, 2016, 469(4): 791-796.

DOI：10.1016/j.bbrc.2015.12.072

• AMP-activated protein kinase
• Osteocyte
• RANKL
• Sclerostin
• Mevalonate pathway

Background: AMP-activated protein kinase (AMPK) plays important roles in bone metabolism; however, little is known about its role in osteocytes. This study investigated the effects of AMPK activation on the expression of receptor activator of NF-kappa B ligand (RANKL) and sclerostin in osteocytes.
Results: Real-time PCR showed that AMPK activation by 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR) significantly decreased the expression of Rankl in a dose- and time-dependent manner and significantly increased the expression of Sost, the gene encoding sclerostin, in osteocytic MLO-Y4 cells. Western blotting confirmed that AICAR decreased RANKL protein levels and increased sclerostin levels. In addition, suppression of AMPK alpha 1 by siRNA significantly increased the expression of Rankl on 4 days after the transfection of siRNA, while Sost expression was not changed. Simvastatin, an inhibitor of HMG-CoA reductase, significantly decreased Rankl expression and increased Sost expression in MLO-Y4 cells. Supplementation with mevalonate or geranylgeranyl pyrophosphate, which are downstream metabolites of HMG-CoA reductase, significantly reversed the effects of AICAR.
Conclusion: These findings indicated that AMPK regulated RANKL and sclerostin expression through the mevalonate pathway in osteocytes.

• 出版日期2016-1-22