Decreased levels of soluble amyloid β‐protein precursor are associated with Alzheimer's disease in concordant and discordant monozygous twin pairs

Abstract
We conducted immunochemical measurements of soluble amyloid β-protein precursor (βPP) in cerebrospinal fluid (CSF) from three monozygous twin pairs. Two of the twin pairs are discordant for Alzheimer's disease and one pair showed concordance for Alzheimer's disease, which was confirmed neuropathologically. All affected individuals displayed substantially lower levels of soluble βPP in CSF compared with the unaffected individuals. There were no differences in total protein levels in CSF samples from the affected twins compared with those of the unaffected twins. These studies suggest that decreased soluble βPP in CSF may reflect neuropathological processes in Alzheimer's disease involving βPP.