The results presented here clearly demonstrate that MALAT1-mediated DNA methylation plays a significant role in the downregulation of Mfn2 in diabetes in both endothelial cells and Müller cells, leading to mitochondrial damage/dysfunction, and inhibiting MALAT1 upregulation by its siRNA protects their mitochondria from undergoing accelerated fission damage. The gene discussed is MFN2; the disease is diabetes mellitus.