Abstract
Glycogen-synthase kinase-3 (GSK-3) plays a central role in Alzheimer's disease (AD). It is involved in the hyper-phosphorylation of Tau and the increased production of beta-amyloid. Despite its eminent role, only one study has been published so far in AD blood samples, reporting an increase of GSK-3alpha and -3beta levels in white blood cells. In this study, we measured GSK-3alpha and -3beta by quantitative ELISA in peripheral blood mononuclear cells of patients with mild cognitive impairment (MCI), AD and depression in comparison to healthy subjects. In contrast to the previous study, we observed a significant reduction of GSK-3beta levels in MCI patients and less pronounced in AD but not in depression. The data indicate that high GSK-3 brain activity is not reflected in peripheral blood mononuclear cells. Therefore, we conclude that more longitudinal studies have to be performed to clarify whether GSK-3 blood levels may qualify as disease specific biological markers.