Oxidative stress markers such as increased oxidized proteins, glycosylated products, elevated levels of lipid peroxidation, formation of aldehydes, alcohols, ketones, free carbonyls, and cholestenone, as well as oxidative modifications in ribonucleic acid (RNA) and mitochondrial and nuclear DNA were observed in postmortem brain tissue and in peripheral systems such as cells and isolated mitochondria from initial phases of AD and APOE4 carriers [34–51]. The gene discussed is APOE; the disease is Alzheimer disease.