Apolipoprotein E (Apo E) is one of the most major apolipoproteins in the central nervous system, with functions of neurons repair. Apo E genetic variants showed significant associations with the risks of nervous system degenerative diseases, including Alzheimer's disease, vascular dementia, and cerebrovascular disease [48, 49]. Apo E gene as a receptor-binding ligand mediating the clearance of chylomicron and remnants of very-low-density lipoprotein cholesterol from plasma also plays a major role in the metabolisms of cholesterol and triglyceride. Here, APOE is linked to Alzheimer disease.