CYP46A1 and Alzheimer disease: In the normal brain, this enzyme is expressed in both neurons and astrocytes, but in AD the levels of 24-OHC decrease mainly because of the neuronal damage; however, in AD there is an ectopic induction of CYP46A1 in astrocytes, especially around senile plaques, that leads to some 24-OHC production but without compensating for its decrease [148].