CLU and Alzheimer disease: In an early study on the role of cerebrospinal fluid HDL on the development of AD, the HDL1 subclass was found to have increased soluble amyloid β (sAβ) and increased apolipoprotein in the AD group compared to age-matched aging normal human subjects, and that sAβ molecules were associated with ApoE and apolipoprotein J in the HDL2 and HDL3 subclasses [112].