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Butyrylcholinesterase K (BCHE-K) is associated with increased risk of developing Alzheimer's disease (AD) in apolipoprotein ℇ (APOE4) carriers, while among APOE4 non-carriers BCHE-K appears to be protective. Nonetheless, pure pharmacogenetic reports have provided conflicting results. To provide insights about these controversies, we combined BCHE-K pharmacogenetic observations in AD patients (n = 179) with proteomic and enzymatic analysis of plasma, cerebrospinal fluid (CSF), or both samples. We found that BCHE-K genotype was overrepresented among the AD patients (χ2 = 14.21, p < 0.0001). Plasma BuChE activity was gene dose-dependently 20-50% less among K-carriers (p < 0.001). CSF BuChE activity did not show such robust K-gene dosage-dependency, because K homozygotes (n = 9) had 30-40% less activity compared to both non-carriers (n = 78, p < 0.01) and heterozygotes (n = 42, p < 0.09). CSF ApoE protein expression was also altered by presence of K-allele (p < 0.001, n = 129). Mutually, APOE4 altered phenotypic display of BuChE variants in CSF (p < 0.01, n = 129). In absence of APOE4, CSF BuChE activity was essentially indistinguishable among K-carriers (n = 16) and non-carriers (n = 17, p < 0.8) although the K-carriers had 24-39% less circulating BuChE protein. In contrast in presence of APOE4, the K-carriers (n = 35) had K allele dose-dependently a BuChE phenotype with 14-46% reduced activity compared to K non-carriers (p < 0.001, n = 59), despite an essentially identical BChE concentration in CSF (1 ± 4%, p < 0.8). Pattern of the patients' cognitive performance in MMSE closely resembled the APOE4-derived phenotypic display of BuChE variants. APOE4-dependent outcome of BCHE-K genotype as AD risk factor arises through a differential phenotypic modulation of BuChE. Future pharmacogenetic studies should include assessment of the subjects' true phenotypic display of BuChE. [ABSTRACT FROM AUTHOR]

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by the accumulation and aggregation of amyloid-β peptide and loss of forebrain cholinergic neurons, resulting in progressive loss of memory and irreversible impairment of higher cognitive functions. Several studies have accounted for the close relationship between AD and the central cholinergic system, suggesting that a dysfunction of acetylcholine containing neurons in the brain contributes significantly to the cognitive deficit of individuals with AD. The aim of the present review is to survey current literature on this topic in order to provide a clear understanding of the role of the cholinergic system in the development and neurodegenerative process of AD. The implications for anesthesia are also discussed. This knowledge could be valuable to improve anesthesia performance and patient safety. [ABSTRACT FROM AUTHOR]