CYP46A1 and early-onset autosomal dominant Alzheimer disease: Cholesterol and 24S-hydroxycholesterol, which is formed from cholesterol via the Cytochrome P450 46A1(CYP46-A1) enzyme [13,14], are involved in the neuropathology of Alzheimer’s disease, and the primary genetic risk factor for Alzheimer’s disease is apolipoprotein E-ε4 [6].