Genes encoding for the subunits of mitochondrial ATP synthase (e.g., ATP5B, ATP5G3, ATP5J, and ATP5C1), cytochrome c oxidase (e.g., COX5A, COX5B, and COX6C), succinate dehydrogenase (e.g., SDHB, SDHC), NADH dehydrogenase (ubiquinone), (e.g., NDUFA8, NDUFA9, NDUFB5, and NDUFS1), and the ubiquinol-cytochrome c oxidoreductase (e.g., UQCRB, UQCRC1, and UQCRH) were deregulated in different datasets and highlighted KEGG pathways are involved in neurodegenerative diseases such as AD, HD, and PD. This evidence concerns the gene NDUFA9 and Alzheimer disease.