In vivo butyrylcholinesterase activity is not increased in Alzheimer's disease synapses.
OBJECTIVE
We tested the premise that cholinesterase inhibitor therapy should target butyrylcholinesterase (BuChE) in Alzheimer's disease (AD), not acetylcholinesterase (AChE) alone, because both enzymes hydrolyze acetylcholine, and BuChE is increased in AD cerebral cortex.


METHODS
To examine this issue in vivo, we quantified human cerebral cortical BuChE activity using tracer kinetic estimates (k(3)) of 1-[(11)C]methyl-4-piperidinyl n-butyrate ([(11)C]BMP) hydrolysis determined by positron emission tomography. Validation of the putative positron emission tomography method included regional distribution, positive correlation with age, and attenuation by the nonselective cholinesterase inhibitor physostigmine, but no attenuation by the AChE-selective inhibitor donepezil. Positron emission tomography scans in AD patients (n = 15) and control subjects (n = 12) measured both BuChE (using [(11)C]BMP) and AChE activity (using N-[(11)C] methylpiperidin-4-yl propionate, an established method).


RESULTS
As expected, AChE activity in AD cerebral cortex was decreased to 75 +/- 13% of normal (p = 0.00001). Contrary to prediction, accompanying BuChE activity also was decreased to 82 +/- 14% of normal (p = 0.001).


CONCLUSIONS
Failure to observe increased [(11)C]BMP hydrolysis in vivo makes it less likely that incremental BuChE contributes importantly to acetylcholine hydrolysis in AD. The findings do not support the premise that inhibitor therapy should target BuChE so as to prevent increased levels of BuChE from hydrolyzing acetylcholine in AD cerebral cortex.
Kuhl
David E
DE
Division of Nuclear Medicine, Department of Radiology, University of Michigan Medical Center, 1500 East Medical Center Drive, Ann Arbor, MI 48109, USA. dkuhl@umich.edu
Koeppe
Robert A
RA
Snyder
Scott E
SE
Minoshima
Satoshi
S
Frey
Kirk A
KA
Kilbourn
Michael R
MR
D000110:Acetylcholinesterase / Q000378:metabolism; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000188:drug therapy / Q000201:enzymology* / Q000473:pathology; D002091:Butyrylcholinesterase / Q000378:metabolism*; D002250:Carbon Radioisotopes / Q000378:metabolism; D002540:Cerebral Cortex / Q000201:enzymology; D002800:Cholinesterase Inhibitors / Q000378:metabolism / Q000627:therapeutic use; D000077265:Donepezil; D005260:Female; D006801:Humans; D007189:Indans / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D010830:Physostigmine / Q000378:metabolism; D010880:Piperidines / Q000378:metabolism; D049268:Positron-Emission Tomography; D015203:Reproducibility of Results; D013569:Synapses / Q000201:enzymology*
D002250:Carbon Radioisotopes; D002800:Cholinesterase Inhibitors; D007189:Indans; D010880:Piperidines; D000077265:Donepezil; D010830:Physostigmine; D000110:Acetylcholinesterase; D002091:Butyrylcholinesterase