GSK3β, CREB, and BDNF in peripheral blood of patients with Alzheimer's disease and depression

Background: Glycogen synthase kinase-3 beta (GSK3 beta), cAMP-response element-binding protein (CREB) and brain-derived neurotrophic factor (BDNF) play critical roles in neuronal survival, synaptic plasticity and memory and participate in the pathophysiology of both depressive disorder and Alzheimer's disease (AD). Methods: This study was designed to determine the association of GSK3 beta activity, CREB activity and BDNF concentration in peripheral blood of patients with AD with or without depressive symptoms and in depressive patients without AD. GSK3 beta activity in platelets, CREB activity in lymphocytes and BDNF concentration in plasma, platelet-rich plasma or platelets were measured in 85 AD patients (36 of whom displayed co-morbid depressive symptoms), 65 non-AD patients with depressive disorder and 96 healthy controls. AD patients were clinically assessed for stage of dementia, cognitive impairment and severity of depressive symptoms. Depressive patients were clinically assessed for severity of depression. Results: We observed increased CREB activity and GSK3 beta activity in AD with depressive symptoms or in AD at mild stage of dementia. Decreased BDNF concentration was found in platelet-rich plasma of AD patients at moderate to severe stages of dementia or in AD without depressive symptoms. An association was revealed of the severity of cognitive impairment with the increase of GSK3 beta in the platelets of AD patients with mild dementia. In depressive patients, a lower concentration of phosphorylated GSK3 beta was associated with a higher severity of depression. Association was confirmed between severity of depression, CREB activation, and BDNF concentration in drug-naive depressive patients. Conclusion: Our data demonstrated that AD is accompanied by increased CREB activity in lymphocytes and a decreased concentration of BDNF in platelet-rich plasma. The decreased BDNF concentration appears to correlate with moderate to severe stages of dementia in AD. Observation of decreased phosphorylation of GSK3 beta in platelets of both AD patients with depressive symptoms and depressive patients after treatment confirms the role of increased GSK3 beta activity in the pathophysiology of both AD and depressive disorder. Associations were confirmed between AD and platelet GSK3 beta activity, lymphocyte CREB activity and plasma BDNF. CREB activity and platelet BDNF concentration seems to be related to depressive disorder. (C) 2013 Elsevier Inc. All rights reserved.