SIRT1 and endothelial dysfunction: Therefore, the protective effect of NMN against IL-1β-mediated endothelial dysfunction is dependent on the NAD<sup>+</sup> <b>-</b>SIRT1 axis.<h4>Conclusions</h4>This <i>in vitro</i> mechanistic study suggests that the NAD+<b>-</b>SIRT1 axis contributes to IL-1β-induced endothelial barrier disruption, supporting further investigation of NMN in inflammatory vascular diseases.