Background and aims <p>Endothelial dysfunction is critical in diabetic angiopathy. While our previous study established role of FOXO1 in mediating advanced glycation end products (AGEs)-induced autophagic apoptosis in human aortic endothelial cells (HAECs), the potential mechanism of N6-methyladenosine (m⁶A) modification in this process remains unknown.</p> Methods <p>RNA-m⁶A methylation and methyltransferase-like 3 (METTL3) / YTH domain containing 1 (YTHDC1) expression in carotid plaques of diabetic patients and aortic plaques of diabetic apoe^−/− mice induced by STZ were detected by quantitative kit, immunohistochemical staining and immunofluorescence co-localization respectively. METTL3 and YTHDC1 were knocked down to observe changes in the m⁶A methylation status and expression of FOXO1. FOXO1 was overexpressed in METTL3-deficient HAECs to assess autophagic flux and apoptosis. Finally, the effect of METTL3 on atherosclerotic plaque formation was validated using endothelial cell-specific METTL3 knockout diabetic mice.</p> Results <p>RNA m⁶A modification levels and the expression of the METTL3/YTHDC1 were upregulated in human diabetic carotid plaques, mouse aortic plaques, and AGEs-treated HAECs, accompanied by increased m⁶A methylation of <i>Foxo1</i> mRNA. METTL3 mediates the AGEs-induced increase in m⁶A modification of <i>Foxo1</i> mRNA, which is subsequently recognized by the YTHDC1 at a specific site in the 3’-UTR-3. This mechanism synergistically enhances FOXO1 expression and blocks autophagic flux leading to apoptosis in endothelial cells. In vivo, endothelial-specific METTL3 knockout attenuated aortic plaque formation in diabetic atherosclerotic mice and reduced FOXO1 expression along with autophagic apoptosis related proteins.</p> Conclusions <p>The METTL3/YTHDC1 axis-mediated m⁶A modification of <i>Foxo1</i> mRNA promotes endothelial autophagic apoptosis in diabetic atherosclerosis, revealing a promising therapeutic target.</p>