Presynaptic membrane protein dysfunction occurs prior to neurodegeneration and predicts faster cognitive decline.

Abstract

Although presynaptic loss measured by cerebrospinal fluid (CSF) growth-associated protein-43 (GAP-43) is significantly involved in Alzheimer's disease (AD), the sequential association between CSF GAP-43 and AD-typical neurodegeneration is poorly understood. We compared baseline CSF GAP-43 levels (n=730) and longitudinal CSF GAP-43 changes (n=327) in various biological stages of AD, and investigated their relationships with cross-sectional and longitudinal measures of residual hippocampal volume, 18 F-fluorodeoxyglucose PET, regional gray matter volume and cortical thickness, and cognition. Elevated CSF GAP43 levels were significantly associated with faster rates of hippocampal atrophy, AD-signature hypometabolism and cortical thinning, and middle temporal gray matter atrophy-related and AD-signature hypometabolism-related cognitive decline. In contrast, baseline levels of all these neurodegeneration biomarkers did not predict longitudinal CSF GAP-43 increases. These findings suggest that presynaptic loss may occur prior to neurodegeneration, highlighting the importance of lowing tau aggregation and tau-related synaptic dysfunction in elderly adults and AD patients.