Fig. 1

Angiotensin-converting enzyme 2 (ACE-2) activity is reduced in Alzheimer’s disease (AD). a Bar chart showing reduced ACE-2 activity in the mid-frontal cortex in AD (n = 90) compared with age-matched controls (n = 59) (P < 0.0001). b Bar chart showing reduced ACE-2 activity in relation to disease severity when all cases were combined and grouped according to Braak stage (0–II, II–IV, and V–VI) (P < 0.0001). Post hoc analysis revealed that ACE-2 activity was reduced in Braak tangle stages V–VI compared with stages 0–II and III-IV (P < 0.0001 and P < 0.05 respectively) and in Braak tangle stages III–IV compared with stages 0–II, but the difference was not statistically different. The bars indicate the mean value and SEM. c and d Scatterplots showing that ACE-2 activity was inversely correlated with insoluble amyloid-β (Aβ) load (measured by enzyme-linked immunosorbent assay) (r = −0.267, P < 0.01) and phosphorylated tau (p-tau) load (measured by field fraction analysis) (r = −0.327, P < 0.001). The solid inner line indicates the best-fit linear regression and the outer lines the 95% confidence intervals. *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001. rfu Relative fluorescence units