Scientific BackgroundApolipoprotein E (ApoE) is a lipoprotein involved in fat metabolism and acts as cholesterol carrier between cells and across tissues. On a genetic level, three APOE alleles are described, APOE2, APOE3 and APOE4. These alleles give rise to six APOE isoforms, which are differentially implicated in various diseases. In the peripheral system, APOE4 is linked to increased risk of atherosclerosis. In the CNS, the ability of APOE4 in clearing beta-amyloid is impaired, while APOE3 and APOE2 are more efficient in performing this task. The APOE4 genotype in particular has been linked to increased risk for developing Alzheimer's Disease.