m6A demethylase FTO/ALKBH5 promotes diabetes-induced endothelial cell dysfunction by negatively regulating lncRNA H19

Endothelial cell dysfunction induced by glucose is the most important cause of diabetic vascular complications, which are the leading causes of blindness, disability, renal failure, heart failure, stroke, and even death in diabetic patients. RNA m6A modification is involved in the pathogenesis of human disease. However, the role and underlying mechanism of RNA m6A modification in high glucose-induced endothelial cell dysfunction is not well understood. Herein, this study first demonstrated that m6A levels were decreased and that the demethylases FTO and ALKBH5 were upregulated in diabetic patients and an STZ-induced diabetic mouse model. This study revealed that high glucose induced decreased m6A levels and increased expression of FTO and ALKBH5, and silencing of FTO and ALKBH5 restored high glucose-induced decreases in m6A levels and dysfunction of HUVECs. Next, this study systematically screened differentially expressed lncRNAs, including H19, in HUVECs under high glucose conditions. This study revealed that FTO-ALKBH5 inhibited H19 expression by decreasing m6A modification in H19 transcripts. In addition, this study demonstrated the role of the FTO/ALKBH5/H19 pathway in high glucose-induced cellular dysfunction of HUVECs. Ultimately, this study uncovered that silencing of H19 promoted the expression of cell cycle-related genes, including PTEN, p21 and p27 via interacting with EZH2 and affecting the H3K27me3 histone modification. Overall, this study is the first to dissect the regulation of lncRNA by m6A modification in hyperglycaemia, identifying a new regulatory pathway in high glucose-induced cellular dysfunction and providing biomarkers with the potential to serve as therapeutic targets for high glucose-induced cellular dysfunction.