Decreased activities of thiamine diphosphatase in frontal and temporal cortex in Alzheimer's disease.

Thiamine diphosphatase (TDPase) activity was measured using a colorimetric assay in frontal and temporal cortex obtained at autopsy from eight patients with neuropathologically confirmed Alzheimer's disease (AD) and from an equal number of control patients matched for age and autopsy delay interval, free from neurological or psychiatric disorders. TDPase activities were significantly reduced in frontal cortex (by 28%, P < 0.05) and temporal cortex (by 62%, P < 0.01) of AD patients. These findings add to a growing body of evidence of altered thiamine neurochemistry in AD. Given the previous reports of an association of TDPase with cholinergic nerve terminals, loss of TDPase activities could reflect loss of cholinergic neurons in frontal and temporal cortex in AD.