Association of a salivary acetylcholinesterase with Alzheimerʹs disease and response to cholinesterase inhibitors

Objectives: A decrease in cholinergic activity is a key event in the biochemistry of Alzheimerʹs disease (AD). The aim of the study was to investigate the expression levels of markers of cholinergic function in saliva, which is a readily accessible body fluid that can be obtained from subjects with minimal distress. Design and methods: Salivary samples were obtained from people with NINCDS-ARDRA “probable” Alzheimerʹs disease and age- and sex-matched controls. Salivary acetylcholinesterase enzyme (AChE) activity was determined colorometrically. Results: Robust AChE catalytic activity was detected in the saliva samples that was stable for up to 6 h at room temperature following the provision of the salivary sample. The activity of the enzyme was significantly lower in people with AD than in age-matched controls. In addition, there were significant differences in activity between those who responded to acetylcholinesterase inhibitor (AChE-I) therapy and those who did not. Conclusions: Salivary enzyme activity may therefore prove to be a useful marker of central cholinergic activity.