For example, Zhong et al. showed that retinal superoxide dismutase gene (SOD2) was epigenetically regulated in diabetes through methylation/acetylation of H4K20me3, acetyl H3K9, and NF-kB p65 on the histones at the promoter/enhancer location of retinal SOD2 in diabetes (36). This evidence concerns the gene SOD2 and diabetes mellitus.