Nicotinamide riboside promotes skin flap survival by enhancing autophagy associated with the NAD⁺/SIRT1-FOXO1 signaling axis.

Flap transplantation is a widely used clinical approach for wound repair, organ reconstruction, and aesthetic restoration. However, ischemic flap necrosis remains a serious postoperative complication, driven by multiple factors, including inadequate blood perfusion, oxidative stress, and cell death. Nicotinamide riboside (NR), a bioavailable precursor of NAD⁺, can increase intracellular NAD⁺ levels following supplementation. This study aimed to investigate the protective effects of NR against ischemic flap injury. In vitro, NR attenuated oxygen-glucose deprivation/reperfusion (OGD/R)-induced injury in HUVECs. Co-immunoprecipitation (Co-IP) assays showed an association between sirtuin-1 (SIRT1) and forkhead box O1 (FOXO1). FOXO1 knockdown partially impaired NR-associated autophagic responses, whereas FOXO1 overexpression partially restored autophagic responses following SIRT1 silencing. NR supplementation increased intracellular NAD⁺ levels and enhanced autophagic activity in OGD/R-treated HUVECs, accompanied by changes in SIRT1, FOXO1, and Ac-FOXO1. In a rat model of ischemic skin flaps, NR administration improved flap survival and was accompanied by enhanced angiogenic responses, autophagy-associated changes, and reduced ferroptosis-related alterations. Collectively, these findings indicate that NR exerts protective effects against ischemic flap injury in rats and support the involvement of NAD⁺/SIRT1-FOXO1 signaling in NR-associated autophagic responses.