Relationship between α₁-antichymotrypsin microsatellite and apolipoprotein E in Alzheimer's disease

The amyloid associated proteins apolipoprotein E (apoE) and α₁-antichymotrypsin (ACT) have been shown to enhance the formation of β-amyloid filaments in vitro. Amyloid deposits are present in the brain of Alzheimer's disease (AD) patients and of elderly individuals. Genetic studies in AD have identified the allele ε4 of apoE as a major risk factor for AD, however this allele is neither necessary nor sufficient for the manifestation of the disease. A bi-allele polymorphism in the signal region of the ACT gene and a repeat microsatellite region at the start of the ACT gene have been postulated to be associated with AD. Our investigation, carried out in post-mortem brain tissue from 56 histologically confirmed AD patients and 70 histologically confirmed controls, showed an association between the apoE ε4 allele and AD but no association between the ACT bi-allele polymorphism. Previous results showing an increased risk for AD in individuals possessing apoE ε4 and allele 10 of the ACT microsatellite was not found in the present study and this could be explained by the non-random association of the ACT A10 allele with apoE ε4 in both the control and AD groups. It was not possible, therefore, to separate the effects of each of the two alleles.