Lipid peroxidation and platelet membrane fluidity--implications for Alzheimer's disease?

In humans, the fluidity of cell membranes generally decreases with age. Unexpectedly, several laboratories have found increased fluidity of platelet membranes (mainly endoplasmic reticulum) in patients with Alzheimer's disease (AD) compared with controls. In the present study, free radical induced lipid peroxidation was found to increase the fluidity of platelet membranes. Hydroxyl radicals were generated in the presence of Fe2+ and EDTA at low concentrations of ascorbate. It is hypothesised that platelet membranes are unable to restore their microviscosity by incorporating cholesterol. There may be a link between the result obtained in this study, the recently discovered decreased cholesterol content of affected AD neuronal membranes, and the increased frequency of epsilon 4 apolipoprotein E (a cholesterol carrier) found in AD patients.