Platelet α and β secretase activities in mild cognitive impairment and Alzheimer’s disease

Abstract

Objective To investigate platelet α and β secretase activities and the amounts of platelet soluble fragment of APP (sAPPα) produced by α-secretase in patients with mild cognitive impairment (MCI) and Alzheimer’s disease (AD). Methods The neurological functions of 48 non-demented patients, 42 MCI and 40 AD patients were evaluated by neuropsychological examinations. The platelet α and β secretase activities and sAPPα production in each group were measured by fluorescence and Western blotting analysis respectively. Results The α secretase activities in non-demented, MCI and AD group were 100.0%±10.6%, 78.2%±9.4% and 61.8%±7.2% respectively. As compared with non-demented group, the α secretase activities in MCI and AD group were decreased (F=22.935, P=0.001). The α secretase activity in AD group was significantly lower than MCI group. The β secretase activities in non-demented, MCI and AD group were 100.0%±11.2%, 145.8%±12.7% and 189.8%±14.2% respectively. The β secretase activities in MCI and AD group were significantly higher than that in non-demented group (F=16.368, P=0.001). The β secretase activity in AD group was significantly decreased as compared with MCI group. The sAPPα amounts in MCI group and AD group were all decreased as compared with that in control group; the sAPPα amount in AD patients was significantly decreased as compared with that in MCI group. Conclusions The platelet α secretase activity and its production sAPPα in MCI and AD patients are decreased, while β secretase activity is increased, as compared with that in control group; the altered α and β secretase activities may participate in the pathogenesis of MCI and AD patients and may have diagnostic potential for them. Key words: Cognition disorders; Alzheimer disease; Amyloid precursor protein secretases