For instance, the MFN-1 level is decreased in AD patients with a mean age of 88.5 years (Yin et al., 2020), while the levels of MFN-1, MFN-2, and OPA1 are increased in the hippocampus of patients with AD with the age range from 60 to 89 years, in which the mean age is lower (Wang et al., 2009). The gene discussed is OPA1; the disease is Alzheimer disease.