Serum ß-amyloid peptide levels spike in the early stage of Alzheimer-like plaque pathology in an APP/PS1 double transgenic mouse model.

ABSTRACT

Serum levels of ß-amyloid (Aß) peptides may represent an early biomarker in the diagnosis of Alzheimer's disease (AD). In the present study, we investigated the temporal kinetic changes in the levels of serum Aß 1-42 and 40 in an amyloid precursor protein (APP)/presenilin (PS)1 double transgenic mouse model of AD. Serum Aß peptide levels in 2-, 3-, 6-, 9- and 18-month old, and liver Aß 1-40 level in 6-month old mice were measured using enzyme-linked immunosorbent assay (ELISA) kits. Results revealed that serum Aß levels peaked in 3-month old transgenic mice, and the Aß level in non-transgenic and transgenic mice is comparable in liver. Compared to the 6-month old transgenic mice, Congo red staining showed that the 3-month old transgenic mice had minimum brain Aß plaques, corresponding to the early stage of Alzheimer-like plaque pathology, and confocal microscope images showed that the deposition of Aß in their cerebral vessels was minimal. Furthermore, results of the water maze test, showed that memory was normal for the 3- month old transgenic mice when compared to age-matched non-transgenic mice. These results suggest that serum Aß peptide levels may be peaked during the early stage of AD. Monitoring serum Aß peptide levels in the potential AD population may provide an early diagnosis of AD prior to the appearance of clinical symptoms.