It is assumed that an increased influx of 27OH-Chinto the brain and/or increased extrusion of 24OH-Ch from the brain mayunderlie the association between a high level of cholesterol in the plasma and AD[11, 19].Studies of organo-typical brain slices from adult animalshave shown that 27OH-Ch increases the levels of Aβ and phosphorylated tau,whereas 24OH-Ch promotes nonamyloidogenic APP processing. This evidence concerns the gene APP and Alzheimer disease.