Serum Levels of Albumin–β-Amyloid Complex in Patients with Depression

Abstract

Epidemiologic studies have demonstrated that suffering from depression may be a risk for Alzheimer disease (AD). As a possible biologic mechanism underlying the transition from depression to AD, it has been speculated that pathologic changes in β-amyloid (Aβ) metabolism are involved. To further understand the peripheral kinetics of amyloid in patients with depression, we investigated serum levels of free Aβ and albumin-bound Aβ. Seventy inpatients with DSM-IV major depressive disorder (MDD) and 81 healthy individuals (the comparison group) were recruited between June 2012 and February 2014. Serum Aβ40 and Aβ42 levels, Aβ40/Aβ42 ratio, and serum levels of albumin-Aβ complexes (SLAACs) were compared between the comparison group and patients in two age groups comprising younger (<60 years) and elderly (≥60 years) people. SLAAC was decreased in older patients with MDD but not in younger patients. The serum-free Aβ40/Aβ42 ratio was higher in patients with depression, even in younger patients. Our findings suggest that free Aβ and the albumin-bound Aβ reflect a different serum amyloid kinetics in depression. We speculate that serum-free Aβ reflects changes in amyloid metabolism in patients suffering from depression and albumin-bound Aβ reflects AD pathology and may be a potential predictor of the prodromal stage of AD.