Fig. 3

Angiotensin-converting enzyme 2 (ACE-2) activity is inversely correlated with ACE-1 activity, and the ACE-1/ACE-2 ratio is increased, in Alzheimer’s disease (AD). a Scatterplot showing a strong inverse relationship between ACE-1 and ACE-2 activity in mid-frontal cortex (r = −.453, P < 0.0001). The inner solid line indicates the best-fit linear regression and the outer lines the 95% confidence intervals. Each dot represents an individual brain. b Bar chart showing elevated ACE-1/ACE-2 ratio in AD (P < 0.0001). c and d Scatterplots showing positive correlation between the ACE-1/ACE-2 ratio and insoluble amyloid-β (Aβ) load (r = 0.199, P = 0.059) and p-tau load (r = 0.252, P < 0.05). e Bar chart showing a trend towards increased ACE-1/ACE-2 ratio in individuals who possessed an apolipoprotein E (APOE) ε4 allele. f Bar chart showing lower ACE:ACE-2 ratio in individuals who were homozygous DD for the ACE1 (rs1799752) indel polymorphism compared with II (P < 0.01) and ID (P < 0.05). The bars indicate the mean value and SEM. *P < 0.05, **P < 0.01, ****P < 0.0001. rfu Relative fluorescence units