MFN1 and obesity due to melanocortin 4 receptor deficiency: Although a direct comparison is difficult due to the lack of studies on the link between obesity and mitochondrial dynamics in the brain, Axelrod et al.39 reported that exercise may control mitochondrial fusion and fission in human muscle and thus induce post-translational modifications in mitochondria, and Konopka et al.40 reported that 12 weeks of aerobic exercise training led to a similar increase in the expressions of MFN1 and MFN2 in skeletal muscle of both the young and elderly subjects.