To examine how high Mn intake increased amyloidogenic APP processing, qRT-PCR and Western blot analyses were performed to detect and quantify the key enzymes in APP processing including BACE1 (β-secretase activity producing Aβ), ADAM10 (a key component of α-secretase activity), presenilin 1 (PS1, a key component of α-secretase activity producing Aβ), and APP cleavage fragments including C99 and C83, in the cortex and hippocampus of control and Mn-treated 3×Tg-AD mice. Here, BACE1 is linked to Alzheimer disease.