AIM:To explore the effect of miR-1246 on high glucose-induced retinal microvascular endothelial cells(RMECs)injury by regulating methyltransferase like 3(METTL3)mediated sirtuin 1(SIRT1)N6-methyladenosine(m6A)modification.METHODS:Dual luciferase assay was used to detect miR-1246 regulation of METTL3 expression; RMECs cells were divided into control group, high glucose(HG)group, high glucose+knocking down control(HG+anti-miR-NC)group, high glucose+knocking down miR-1246 expression(HG+anti-miR-1246)group, high glucose+overexpression control(HG+NC)group, high glucose+overexpression METTL3(HG+METTL3)group, high glucose+overexpression miR-1246+control(HG+miR-1246+NC)group, and high glucose+overexpression miR-1246+METTL3(HG+miR-1246+METTL3)group. After induction of high glucose for 48 h, CCK-8 method was used to detect cell survival; Annexin V-FITC/PI method was used to detect cell apoptosis; Transwell experiment was used to detect cell migration and invasion; ELISA method was used to detect cell oxidative stress and inflammation levels; Colorimetric method was used to detect m6A methylation level in total RNA; MeRIP-qPCR method was used to detect SIRT1 m6A methylation level; Real-time quantitative PCR was used to detect miR-1246, METTL3, SIRT1 mRNA expression in cells; Western blot was used to detect METTL3, SIRT1 and endothelial mesenchymal transition(EndMT)markers protein expression in cells.RESULTS: The MiR-1246 regulated METTL3 expression. Compared with the control group, cell survival rate was decreased in the HG group, apoptosis rate was increased, and the number of migrating and invading cells were increased, lactate dehydrogenase(LDH)activity, tumor necrosis factor-α(TNF-α), and interleukin(IL)-6 levels in cell culture supernatant were increased, IL-10 level was decreased, malondialdehyde(MDA)level was increased, superoxide dismutase(SOD)activity was decreased, miR-1246 expression was increased, total RNA m6A level and SIRT1 m6A level were decreased, METTL3, SIRT1, cluster of differentiation 31(CD31)and vascular endothelial cadherin(VE-cadherin)expression were decreased, while Vimentin and Snail1 expression were increased(all P<0.05); compared with the HG+anti-miR-NC group, cell survival rate was increased in the HG+anti-miR-1246 group, apoptosis rate was decreased, and the number of migrating and invading cells were decreased, LDH activity, TNF-α, and IL-6 levels in cell culture supernatant were decreased, IL-10 level was increased, MDA level was decreased, SOD activity was increased, miR-1246 expression was decreased, total RNA m6A level and SIRT1 m6A level were increased, METTL3, SIRT1, CD31 and VE-cadherin expression were increased, while Vimentin and Snail1 expression were decreased(all P<0.05); compared with the HG+NC group, cell survival rate was increased in the HG+METTL3 group, apoptosis rate was decreased, and the number of migrating and invading cells were decreased, LDH activity, TNF-α, and IL-6 levels in cell culture supernatant were decreased, IL-10 level was increased, MDA level was decreased, SOD activity was increased, miR-1246 expression was decreased, total RNA m6A level and SIRT1 m6A level were increased, METTL3, SIRT1, CD31 and VE-cadherin expression were increased, while Vimentin and Snail1 expression were decreased(all P<0.05); compared with the HG+miR-1246+NC group, cell survival rate was increased in the HG+miR-1246+METTL3 group, apoptosis rate was decreased, and the number of migrating and invading cells were decreased, LDH activity, TNF-α, and IL-6 levels in cell culture supernatant were decreased, IL-10 level was increased, MDA level was decreased, SOD activity was increased, miR-1246 expression was decreased, total RNA m6A level and SIRT1 m6A level were increased, METTL3, SIRT1, CD31 and VE-cadherin expression were increased, while Vimentin and Snail1 expression were decreased(all P<0.05).CONCLUSION:The miR-1246 promotes high glucose-induced apoptosis, invasion and metastasis, oxidative stress, inflammatory response, and EndMT process in RMECs cells by regulating METTL3 mediated SIRT1 m6A modification.