APOE and Alzheimer disease: Such studies have provided insight into the role of specific molecules and lipid fractions, such as HDL-4, which is positively associated with AD pathophysiology (46), VLDL-C, and intermediate-density lipoprotein cholesterol; have demonstrated that coregulated serum lipids are associated with AD pathophysiology (47); and have examined the mechanistic relationship between AD risk conferred by APOE genetic status and blood lipid species.