DNMT1 and diabetes mellitus: Here, our novel results show that, in both retinal vascular and nonvascular cells, the upregulation of MALAT1 in diabetes downregulates Mfn2 by hypermethylating its promoter DNA, and the mechanism for this MALAT1-mediated hypermethylation appears to be via increasing MALAT1–Dnmt1 interactions, leading to the increased binding of Dnmt1 at the Mfn2 promoter.