Glucocorticoid may influence amyloid β metabolism in patients with depression.

Epidemiological studies have demonstrated that depression may be a risk factor for Alzheimer's disease (AD); however, the biological mechanisms of the transition from depression to AD are still not clear. Changes of amyloid β protein (Aβ) metabolism and increased glucocorticoid (GC) levels have been found in both depression and AD. Moreover, several studies in animal models have demonstrated that GC administration changes Aβ metabolism. To reveal whether GC affects amyloid metabolism in patients with depression, we evaluated serum levels of Aβ40, Aβ42 and cortisol at admission in 187 inpatients with major depressive disorder (MDD) and 224 healthy comparisons. Additionally, we re-evaluated the serum levels of Aβs in 27 patients with MDD 1 year later. The results of multiple regression analyses revealed that serum cortisol and Aβ levels are not correlated at the time of admission. However, serum cortisol levels at admission correlated with serum Aβ42 levels and Aβ40/Aβ42 ratio 1 year later. These findings suggest that increased cortisol in patients with MDD may influence the metabolism of Aβ over prolonged periods of time.