Plasma Angiotensin-(1-7) is a Potential Biomarker for Alzheimer's Disease

Brain angiotensin-(1-7) (Ang-(1-7)) concentration has been shown to be reduced and inversely correlated with tau pathology in a mouse model of Alzheimer's disease (AD). In this study, to determine whether the concentration of Ang-(1-7) and the activity of its converting enzyme angiotensin-converting enzyme 2 were altered in plasma under AD context, the plasma samples from 110 AD patients and 128 age-and gender-matched controls were screened. In AD patients, the plasma concentration of Ang-(1-7) was significantly reduced (15.63 +/- 4.35pg/mL vs. 19.58 +/- 3.22pg/mL, P<0.001) and positively correlated with cognitive functions (R=0.66, P<0.001). Meanwhile, receiver-operating characteristic analysis showed that the Ang-(1-7) concentration in plasma could distinguish AD patients from controls with the sensitivity and specificity of 69.1% and 74.2%, respectively, when the optimal cut-off value (18.2 pg/mL) was chosen. These findings indicate that plasma Ang-(1-7) may represent a potential biomarker for AD diagnosis, and further suggest an involvement of this heptapeptide in the pathogenesis of this disease.