Association of angiotensin-converting enzyme functional gene I/D polymorphism with amnestic mild cognitive impairment

The relationship between angiotensin-converting enzyme (ACE) gene insertion/deletion (I/D) polymorphism and serum ACE activity, as well as amnestic mild cognitive impairment (aMCI), was investigated. The study recruited 90 aMCI patients and 90 matched healthy controls. All subjects underwent an extensive assessment of cognitive function. The ACE gene I/D genotype was determined by polymerase chain reaction. Serum ACE activity was measured using a spectrophotometric technique. The scores obtained by the aMCI patients on the neuropsychological tests were significantly lower than those of the control subjects (all p<0.01). The genotype (χ(2)=11.510) and allele (χ(2)=6.945) frequencies of the ACE gene were significantly different between the aMCI and the control groups (all p<0.01). The DD genotype (23%) and D-allele (57%) frequencies in the aMCI patients were higher than those in the controls (16% vs. 43%). ACE genotype was correlated with delayed recall in Auditory Verbal Memory Test, delayed recall in Complex Figure Test, Category Fluency Test, and Symbol Digit Modalities Test in all subjects, in which the carriers of the DD and DI genotypes obtained lower scores than those of the II genotype (p<0.05). A significant difference in the serum ACE level was observed among the three genotypes (DD>DI>II) in both the aMCI and the control groups (all p<0.01). D-allele may be a genetic risk factor for the development of aMCI to Alzheimer's disease. A high serum ACE level possibly plays an important role in the incidence of aMCI.