Plasma β-amyloid peptides levels: a pilot study in bipolar depressed patients

Patients with mood disorders present a great risk for dementia and generally for cognitive decline. Low levels of β-amyloid peptide 1-42 (Aβ42) and high Aβ40/Aβ42 ratio have been associated with this risk and have been reported also in geriatric patients suffering from depression. The aim of the present study was to compare the plasma levels of Aβ40 and Aβ42 in patients with bipolar depression and healthy subjects, and to correlate them with the characteristics of clinical course.

Levels of Aβ40 and Aβ42 were measured by using specific ELISA kits in 16 patients with bipolar depression and in 16 control subjects with a negative history for somatic, psychiatric, neurological and substance abuse disorders.

Patients presented significantly lower plasma Aβ42 levels and higher Aβ40/Aβ42 ratio, as compared with control subjects. Moreover, a significant negative correlation was found between Aβ42 plasma levels and the duration of the illness, while a positive correlation was detected between the Aβ40/Aβ42 ratio and the number of affective episodes.

The major limitations of the study are the small sample size, the scanty characterization of the illness episodes and the fact that all the patients were under psychopharmacological treatment.

Although further research is necessary to establish firm conclusions, the present data would suggest that changes in plasma levels of different Aβ peptides might represent a useful tool to identify the risk for cognitive decline in bipolar patients.