MAPT and Alzheimer disease: Indeed, the levels of the aforementioned cholesterol metabolites in CSF have been proposed as potential AD biomarkers in combination with Aβ42, total tau, or phospho-tau [146], with 24-hydroxycholesterol being associated to increased APOE in astrocytes, as well as Aβ and tau levels in AD subjects, while 27-hydroxycholesterol has been linked to hypercholesterolemia and AD [152].