ABNORMAL PATTERN OF PLATELET APP ISOFORMS IN ALZHEIMER-DISEASE AND DOWN-SYNDROME

Objective: To determine if changes in levels of amyloid precursor prot ein (APP) isoforms in periphery are associated with Alzheimer disease and Down syndrome. Design: After subjects were grouped according to di agnosis, APP isoform levels in platelets were compared. Setting: Unive rsity medical center. Subjects: Ten patients who fulfilled diagnostic criteria for probable Alzheimer disease, 22 healthy volunteers, and 7 elderly (mean age, 42.7 years) and 7 young (mean age, 19.0 years) pati ents with Down syndrome. Main Outcome Measures: The levels of APP isof orms were evaluated by means of Western blot analysis and immunostaini ng of whole platelets. Results: The ratio between the 130- and the 106 - to 110-kd APP isoforms was markedly lower in patients with Alzheimer disease and in elderly patients with Down syndrome than in control su bjects. In young patients with Down syndrome, the ratio did not signif icantly differ from that in control subjects. Conclusions: A consisten t alteration in platelet APP isoforms has been found in Alzheimer dise ase and Down syndrome. Further studies will determine whether this alt eration could provide a peripheral biochemical marker of the disorder and whether it could intervene in the pathogenesis of Alzheimer diseas e.