Platelet monoamine oxidase molecular activity in demented patients

Blood platelet monoamine oxidase activity, as well as other platelet enzyme activities, have been studied in several neuropsychiatric disorders in an attempt to identify biochemical markers of altered brain function. In this study, we determined both total and molecular monoamine oxidase activity in platelets derived from demented patients, which showed significantly greater enzyme activity than those of the controls. It therefore seems that the high degree of monoamine oxidase activity depends on the increased intrinsic activity of individual enzyme molecules. A significant positive correlation was found between monoamine oxidase activity and the severity of illness, which suggests that monoamine oxidase activity may be a state-dependent marker of neurodegeneration. These findings are discussed with reference to the central nervous system biochemical abnormalities of demented subjects: it may be that Alzheimer-type dementia involves some central biochemical changes that are reflected in certain peripheral tissues (e.g. platelets), or a systemic derangement that also affects the brain.