Department of Primary Care Medicine, National Taiwan University College of Medicine, Taipei, Taiwan.
J Bone Miner Res. 2011 Oct;26(10):2552-63. doi: 10.1002/jbmr.460.
Reports of the bone-protective effects of resveratrol, a naturally occurring phytoestrogen and agonist for the longevity gene SIRT1, have highlighted this compound as a candidate for therapy of osteoporosis. Moreover, SIRT1 antagonism enhances adipogenesis. There has been speculation that resveratrol can promote osteogenesis through SIRT1, but the mechanism remains unclear. In this study we investigated the molecular mechanism of how resveratrol can modulate the lineage commitment of human mesenchymal stem cells to osteogenesis other than adipogenesis. We found that resveratrol promoted spontaneous osteogenesis but prevented adipogenesis in human embryonic stem cell-derived mesenchymal progenitors. Resveratrol upregulated the expression of osteo-lineage genes RUNX2 and osteocalcin while suppressing adipo-lineage genes PPARγ2 and LEPTIN in adipogenic medium. Furthermore, we found that the osteogenic effect of resveratrol was mediated mainly through SIRT1/FOXO3A with a smaller contribution from the estrogenic pathway. Resveratrol activated SIRT1 activity and enhanced FOXO3A protein expression, a known target of SIRT1, in an independent manner. As a result, resveratrol increased the amount of the SIRT1-FOXO3A complex and enhanced FOXO3A-dependent transcriptional activity. Ectopic overexpression or silencing of SIRT1/FOXO3A expression regulated RUNX2 promoter activity, suggesting an important role for SIRT1-FOXO3A complex in regulating resveratrol-induced RUNX2 gene transcription. Further mutational RUNX2 promoter analysis and chromatin immunoprecipitation assay revealed that resveratrol-induced SIRT1-FOXO3A complex bound to a distal FOXO response element (-1269/-1263), an action that transactivated RUNX2 promoter activity in vivo. Taken together, our results describe a novel mechanism of resveratrol in promoting osteogenesis of human mesenchymal stem cells by upregulating RUNX2 gene expression via the SIRT1/FOXO3A axis.
白藜芦醇是一种天然存在的植物雌激素，也是长寿基因 SIRT1 的激动剂，其具有骨保护作用的报告使其成为骨质疏松症治疗的候选药物。此外，SIRT1 拮抗剂可增强脂肪生成。有人推测白藜芦醇可以通过 SIRT1 促进成骨，但机制尚不清楚。在这项研究中，我们研究了白藜芦醇调节人间充质干细胞向成骨而不是向脂肪生成分化的分子机制。我们发现，白藜芦醇可促进人胚胎干细胞衍生的间充质祖细胞自发成骨，但防止其向脂肪生成分化。在脂肪生成培养基中，白藜芦醇上调成骨谱系基因 RUNX2 和骨钙素的表达，同时抑制脂肪谱系基因 PPARγ2 和 LEPTIN 的表达。此外，我们发现白藜芦醇的成骨作用主要通过 SIRT1/FOXO3A 介导，而雌激素途径的贡献较小。白藜芦醇以独立的方式激活 SIRT1 活性并增强 SIRT1 的已知靶标 FOXO3A 蛋白表达。结果，白藜芦醇增加了 SIRT1-FOXO3A 复合物的数量，并增强了 FOXO3A 依赖性转录活性。SIRT1/FOXO3A 表达的异位过表达或沉默调节 RUNX2 启动子活性，表明 SIRT1-FOXO3A 复合物在调节白藜芦醇诱导的 RUNX2 基因转录中起重要作用。进一步的 RUNX2 启动子突变分析和染色质免疫沉淀实验表明，白藜芦醇诱导的 SIRT1-FOXO3A 复合物结合到一个远端 FOXO 反应元件（-1269/-1263），该作用在体内反式激活 RUNX2 启动子活性。总之，我们的结果描述了白藜芦醇通过 SIRT1/FOXO3A 轴上调 RUNX2 基因表达促进人骨髓间充质干细胞成骨的新机制。
