SIRT1 and endothelial dysfunction: Sirtuin 1 (SIRT1) acts as a key regulator of vascular endothelial homeostasis, angiogenesis, and endothelial dysfunction and SIRT1 acts as an intrinsic negative modulator of Notch signaling in endothelial cells, which may be at the basis of the osteoclastogenesis vs. osteoblastogenesis in osteosarcoma [39, 40].