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Apolipoprotein E(apoE)is associated with Alzheimer's neurofibrillary tangles and B-amyloid protein in senile plaques.It also appears to play an important part in the redistribution of lipids that follows deafferentation and neurodegeneration in the brain.The gene for apoE is on chromosome 19,within the genomic region previously associated with late- onset familial Alzheimer's disease(AD).We have studied apoE phenotype expression and the corresponding allele frequencies(e2,e3,e4)in 91 patients with sporadic AD and 74 controls.There was a significant association between e4 and sporadic AD(e4 frequency 0.380 in AD and 0.122 in controls,p<0.01).Analysis of e4 allele frequency as a function of age revealed a bimodal distribution,with peaks at 65 and 75 years.In bearers of e4 in whom AD develops this tended to happen earlier in life than in those with e3 or e2.The e4/AD association was more pronounced in women. Octogenarians with AD had an e4 allele frequency that was 3 times higher than one reported,in a different study,in healthy octogenarians.ApoE may be an important susceptibility factor in the aetiopathology of sporadic AD. |
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