Association between angiotensin-converting enzyme gene polymorphism and Alzheimer's disease in a Chinese population

Angiotensin-converting enzyme has shown altered activity in patients with neurological diseases. An insertion/deletion (I/D) polymorphism of the DCP1 gene encoding angiotensin-converting enzyme has been reported to be associated with the risk for Alzheimer's disease (AD), but ambiguous results have also been presented. We conducted a case-control study in a sample composed of 192 sporadic AD patients and 195 age- and sex-matched controls from Chinese Han population in Beijing and Xi'an districts to investigate the possible effect of the polymorphism. Our data revealed no association between the DCP1 polymorphism and AD risk in the total sample. There was no significant difference in the DCP1 allele or genotype frequencies between cases and controls when stratified by gender and APOE epsilon4 status. However, the D allele and D/D genotype were more frequent among AD patients between 66 and 70 years compared with controls (D allele: OR=2.8, 95% CI=1.5-5.2, p=0.001; D/D genotype: OR=5.9, 95% CI=1.7-19.9, p=0.002). Our results provided new proof that the DCP1 D allele was a probable risk factor for late-onset AD. Its role was independent and was limited to the population at a certain age.