Blood β-synuclein is related to amyloid PET positivity in memory clinic patients

Introduction: beta-synuclein is an emerging blood biomarker to study synaptic degeneration in Alzheimert's disease (AD), but its relation to amyloid-beta (A beta) pathology is unclear. Methods: We investigated the association of plasma beta-synuclein levels with ([18F])flutemetamol positron emission tomography (PET) in patients with AD dementia (n = 51), mild cognitive impairment (MCI-A beta+ n = 18, MCI-A beta-n = 30), non-AD dementias (n = 22), and non-demented controls (n = 5). Results: Plasma beta-synuclein levels were higher in A beta+(AD dementia, MCI-A beta+) than in A beta-subjects (non-AD dementias, MCI-A beta-) with good discrimination of A beta+ from A beta-subjects and prediction of A beta status in MCI individuals. A positive correlation between plasma beta-synuclein and A beta PET was observed in multiple cortical regions across all lobes. Discussion: Plasma beta-synuclein demonstrated discriminative properties for A beta PET positive and negative subjects. Our data underline that beta-synuclein is not a direct marker of A beta pathology and suggest different longitudinal dynamics of synaptic degeneration versus amyloid deposition across the AD continuum.