CHAT and Alzheimer disease: The cholinergic system including choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) is essential in carrying out cognitive functions, as evidenced by the decrease in neurotransmitter signaling in line with the progression of cognitive impairment that occurs in various neurodegenerative diseases such as Alzheimer’s disease, even though the systems affected are usually complex and involve several pathways [164,165].