Even though there are multiple protein complexes involved in the mitochondrial fission/fusion dynamics and Ca2+ buffering, we selected key players that are essential for these processes (DRP1, MFN2, and MCU) to investigate the effects of melatonin in hyperglycemia-caused changes in mitochondrial function, as well as the protective effect of melatonin in STZ-induced diabetic retinas. This evidence concerns the gene MFN2 and diabetes mellitus.