The above experiment was repeated five times

and that Runx2 might be a substrate for Sirt-1 deacetylation. Furthermore, our data demonstrate that nicotinamide treatment induced Runx2 acetylation and this was decreased and attenuated in the pretreatment cultures with resveratrol, suggesting that Sirt-1 activity is increased in these cultures. This data suggest that resveratrol suppresses nicotinamide-induced Runx2 acetylation through Sirt1 activation and at the same time through inhibition of NCoR/ PPAR-c complex. Our study suggests that nicotinamide induces Runx2 acetylation in MSCs during osteogenesis in vitro. Runx2 acetylation was reversed by resveratrol, resulting in the suppression of nicotinamide-induced PPAR-c transcriptional activity including adipogenesis. Resveratrol activates the deacetylase Sirt-1, but it can also inhibit a number of other signaling pathways. Therefore, we used a specific gene knockdown approach to investigate whether the ability of resveratrol to reverse Runx2 acetylation operates via Sirt-1. Knockdown of Sirt-1 protein levels inhibited the effects of resveratrol, suggesting that it was not operating via other signaling pathways. Furthermore, immunoprecipitation and western blotting demonstrated functional and physical interactions between Runx2 and Sirt-1, suggesting that Sirt-1 directly deacetylates Runx2. This is the first description of Runx2-Sirt-1 interactions; Sirt-1 mediated MRT-67307 site deacetylation of Runx2 suggests that this may play an important role in regulating resveratrol-activated Sirt-1 during osteogenesis. Additionally, the transcription factor Runx2 is modified by acetylation/deacetylation like other transcription factors such as p53, NF-kB, MyoD, HMG I, E2F and FOXO. In summary, this study identified Runx2 acetylation as an important event in osteogenesis in vitro. Resveratrol-mediated inhibition of adipogenesis in MSCs was attributed to Sirt-1 activation, which deacetylated Runx2 and suppressed the nicotinamide-induced adipogenesis. Thus, prevention or reversal of Runx2 acetylation may represent a new therapeutic strategy for suppression of osteoporosis. Chirality is a quite common feature for both biomacromolecules and small-molecules in nature and in our daily life. Biomacromolecules have the potential to stereoselectively recognize and dispose the ligands. For example, it has been shown that S-verapamil is significantly different from R-verapamil in plasma protein binding and systemic clearance. On the other hand, small-molecules also stereoselectively take their biological actions. Taking propoxyphene as an example, dextropropoxyphene is an analgesic, whereas levopropoxyphene is an antitussive agent. Warfarin is another example. At physiological concentrations, R-warfarin interacts with pregnane X receptor and significantly induces CYP3A4 and CYP2C9 mRNAs, while S-warfarin does not show such effects. As mentioned above, it is interesting and important to explore the interactions between chiral small molecules and stereoselective biomacromolecules, with pre-clinical and clinical significances. Ginsenosides, the main effective constituents of ginseng, have a broad range of therapeutic applications. The basic structure of ginsenoside is tetracyclic triterpenoid, with many chiral carbones in the molecule. Particularly, the chirality of carbon-20 contributes to the two stereoisomers of each ginsenoside. They are called epimers. It is very likely that the two epimers of ginsenoside have different biological characteristics. 20-ginsenoside R