Plasma Levels of amyloid β proteins Aβ1–40 and Aβ1–42(43) are elevated in Down's syndrome

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Abstract
To investigate the effect of the overexpression of β-amyloid precursor protein (APP) on the production of two major amyloid β protein (Aβ) species, Aβ40 and Aβ42(43), we measured amounts of Aβ1–40 and Aβ1–42(43) in the plasma from 44 patients with Down's syndrome (DS) (age, 19–61 years) and 66 age-matched normal controls using enzyme-linked immunosorbent assays. Plasma concentrations of both Aβ1–40 and Aβ1–42(43) were increased about 3-fold and 2-fold, respectively, in DS patients compared with normal controls. Especially, the increases in plasma Aβ1–40 in DS Patients were statistically higher than the 1.5-fold increase one might predict based on the gene dose of APP in DS. These findings showed that both Aβ1–40 and Aβ1–42(43) are increased in plasma in DS patients, the former more than the latter, suggesting that overexpression of APP and/or other genes may have different effects on the production of these two Aβ species in DS.