RESUMO
INTRODUCTION: Cerebrospinal fluid analysis and other measurements of amyloidosis, such as amyloid-binding positron emission tomography studies, are limited by cost and availability. There is a need for a more practical amyloid ß (Aß) biomarker for central nervous system amyloid deposition. METHODS: We adapted our previously reported stable isotope labeling kinetics protocol to analyze the turnover kinetics and concentrations of Aß38, Aß40, and Aß42 in human plasma. RESULTS: Aß isoforms have a half-life of approximately 3 hours in plasma. Aß38 demonstrated faster turnover kinetics compared with Aß40 and Aß42. Faster fractional turnover of Aß42 relative to Aß40 and lower Aß42 and Aß42/Aß40 concentrations in amyloid-positive participants were observed. DISCUSSION: Blood plasma Aß42 shows similar amyloid-associated alterations as we have previously reported in cerebrospinal fluid, suggesting a blood-brain transportation mechanism of Aß. The stability and sensitivity of plasma Aß measurements suggest this may be a useful screening test for central nervous system amyloidosis.