The Role Of Serum Angiotensin Converting Enzyme Activity In Alzheimer's Disease

Objective: To explore the association of serum angiotensin-converting enzyme(ACE) activity and cognition, and to determine the role of serum ACE activities in Alzheimer's disease(AD) and determine the severity of AD.Methods: One hundred sixty-seven subjects were included. Serum ACE activities and A?1-40/42 levels were measured in 62 moderate-severe AD, 21 mild AD, 45 amnestic mild cognitive impairment(a MCI) and 39 controls.Results: We found significant increase of ACE serum activities in AD patients compared with a MCI and controls when considering different stages of AD altogether(P=0.047 and P= 0.01, respectively), and moderate-severe AD stages significantly increased ACE activities in comparison to a MCI and controls(P=0.04 and P=0.01, respectively). We found an increased tendency of serum A? 1-40 in AD patients. Early stage of AD showed a weak and non-significant increase of A? 1-42 in comparison to a MCI and aged healthy controls, but moderate-severe AD showed a weak and non-significant decrease of A? 1-42 in comparison to a MCI and aged healthy controls. Logistic regression analysis showed that if ACE activities increased 200 U/L, the superiority of AD risk was 1.37 times higher than before compared with the control group(OR 1.37, 95% CI 1.00~1.87; P=0.05). And the superiority of AD risk increased 37%, when ACE activities increased 200 U/L. By means of multivariate linear regression analysis, we found that A?1-40 and A?1-42 significantly predicted ACE activities(P <0.00). Moreover, A?1-40 and A?1-42 were related to ACE activities in 92% total variation, and the effect of A?1-42 on ACE was more than A?1-40. ACE activities were found to be significantly negatively associated with measures of orientation and immediate recall among the AD patients(r <0, P < 0.05), whereas ACE activities were not associated with any MMSE scores among the non-AD groups(P > 0.05).Conclusions: ACE serum activity is likely to constitute a potential risk factor for the development of AD. ACE serum activity might be a useful biomarker for disease status with an increase from mild stage to moderate-severe stage. Moreover, patients with a MCI could take ACE inhibitor(ACEI) to decrease the incidence of AD, and patients with AD could take ACEI to retard cognitive decline in early AD.