Association of serum AACT levels and AACT signal polymorphism with late-onset Alzheimer's disease in Northern Ireland

alpha 1-antichymotrypsin (AACT) is a serine protease inhibitor that has bee n associated with amyloid plaques in the brains of patients with Alzheimer' s disease (AD). It has been reported that AACT serum levels are higher in A D patients than in age and sex matched controls. In addition, polymorphisms in the signal peptide and 5' of the AACT gene have been reported to increa se the risk of developing AD, Serum AACT has also been suggested to be asso ciated with cognitive decline in elderly subjects. Our objective was to inv estigate whether a relationship existed between serum AACT levels, AACT gen otypes and risk for AD in a case control association study using 108 clinic ally well defined late onset AD cases and 108 age and sex matched controls from Northern Ireland. We also wished to determine whether higher serum AAC T affected levels of cognition as had been previously reported. Serum AACT levels were found to bet significantly raised in cases compared to controls (t = 3.8, df = 209, p < 0.001), However, we detected no relationship betwe en serum AACT levels and cognitive decline. We report allelic association o f the AACT signal polymorphism with AD (chi(2) = 3.70, df = 1,p = 0.04) but we failed to show any correlation between AACT serum levels and genotype. Copyright (C) 2000 John Wiley & Sons, Ltd.