Nitrate Promotes the Survival of Diabetic Skin Flaps by Enhancing Autophagy Through the AMPK Signaling Pathway

Random skin flap is commonly used for the repair of craniofacial defects. However, ischemic necrosis is frequently detected postoperatively, which severely affects patients' prognosis and quality of life, especially for those with diabetes. Although nitrate has been found to protect against the development of ischemic diseases, its effects on ischemic injury in diabetic skin flaps remains to be thoroughly explored. This study investigated the effects of nitrate on the survival of diabetic skin flaps and the associated mechanisms. The results showed that nitrate increased blood perfusion in diabetic skin flaps and decreased the area of ischemic necrosis. It also promoted angiogenesis, reduced apoptosis, and oxidative stress, while upregulating autophagy levels in the ischemic regions. These protective effects were reversed by the autophagy inhibitor, 3-MA, indicating that autophagy mediated the protective effects of nitrate on diabetic flaps. RNA-seq analysis revealed that nitrate activated the Adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) signaling pathway in diabetic skin flaps. Inhibition of the AMPK phosphorylation by compound C reduced autophagy levels and reversed the protective effects. In conclusion, this study demonstrates that nitrate can promote the survival of diabetic skin flaps by improving angiogenesis, inhibiting apoptosis, and reducing oxidative stress. These beneficial effects are mediated by the enhancement of autophagy through the AMPK signaling pathway.