High cholesterol affects platelet APP processing in controls and in AD patients

Alzheimer disease (AD) is characterised by a decrease of platelet Amyloid Precursor Protein forms ratio (APPr), which parallels symptoms' severity. Recent studies have suggested that cholesterol might play a role in the pathophysiology of AD by modulating Abeta production. Aim of this study was to evaluate the relationship between serum cholesterol levels and platelet APP processing in controls and AD. Sixty AD patients and 45 age-matched controls (CTRL) were investigated. Neuropsychological assessment, cholesterol dosage and APP forms' evaluation were performed on each subject. CTRL showed lower serum cholesterol levels compared to AD (P<0.01) and higher mean APPr scores (P<0.0001). Hypercholesterolaemic AD patients showed lower APPr scores compared to normocholesterolaemic AD patients matched for disease severity (0.31+/-0.16 versus 0.45+/-0.28; P<0.05), since the early stage of the disease. In AD, cholesterol levels influence APPr independently of disease severity. These findings confirm the association between cholesterol and AD, and suggest that in vivo cholesterol affects APP processing by interfering with its maturation.