Subsequent correlated changes in complement component 3 and amyloid beta oligomers in the blood of patients with Alzheimer's disease

Abstract

INTRODUCTION: Alzheimer's disease (AD) involves the complement cascade, with complement component 3 (C3) playing a key role. However, the relationship between C3 and amyloid beta (A beta) in blood is limited. METHODS: Plasma C3 and A beta oligomerization tendency (A beta Ot) were measured in 35 AD patients and 62 healthy controls. Correlations with cerebrospinal fluid (CSF) biomarkers, cognitive impairment, and amyloid positron emission tomography (PET) were analyzed. Differences between biomarkers were compared in groups classified by concordances of biomarkers. RESULTS: Plasma C3 and A beta Ot were elevated in AD patients and in CSF or amyloid PET-positive groups. Weak positive correlation was found between C3 and A beta Ot, while both had strong negative correlations with CSF A beta 42 and cognitive performance. Abnormalities were observed for A beta Ot and CSF A beta 42 followed by C3 changes. DISCUSSION: Increased plasma C3 in AD are associated with amyloid pathology, possibly reflecting a defense response for A beta clearance. Further studies on A beta-binding proteins will enhance understanding of A beta mechanisms in blood.