Association of Platelet Serotonin Levels in Alzheimer’s Disease with Clinical and Cerebrospinal Fluid Markers

Abstract

Introduction: Serotonin (5-HT) is involved in the pathology of Alzheimer’s disease (AD). Objective: We aimed to measure 5-HT level in platelets in AD and explore its association with cerebrospinal fluid (CSF), AD biomarkers (amyloid- 1-42 (A42), total tau (t-tau), and phosphorylated tau (p-tau)), and clinical symptoms. Methods: 15 patients with AD and 20 patients with subjective cognitive impairment (SCI) were included. 5-HT metabolites

were measured, in a specific fraction, using high performance liquid chromatography with electrochemical detection (HPLC- ECD).

Results: Significantly lower 5-HT concentrations were observed in AD patients compared to SCI patients both after normal- ization against total protein (p = 0.008) or platelet count (p = 0.019). SCI patients with lower 5-HT level have higher AD CSF

biomarkers, total tau (p = 0.026) and tau/A42 ratio (p = 0.001), compared to those with high 5-HT levels. Conclusion: AD patients have reduced platelet 5-HT levels. In SCI, lower 5-HT content was associated with a higher AD-CSF biomarker burden.