Neurogranin, a synaptic protein, is associated with memory independent of Alzheimer biomarkers

Abstract

Objective: To determine the association between synaptic functioning as measured via neurogranin in CSF and cognition relative to established Alzheimer disease (AD) biomarkers in neurologically healthy older adults. Methods: We analyzed CSF concentrations of neurogranin, b-amyloid (Ab42), phosphorylated tau (p-tau), and total tau (t-tau) among 132 neurologically normal older adults (mean 64.5, range 55-85), along with bilateral hippocampal volumes and a measure of episodic memory (Auditory Verbal Learning Test, delayed recall). Univariable analyses examined the relationship between neurogranin and the other AD-related biomarkers. Multivariable regression models examined the relationship between neurogranin and delayed recall, adjusting for age and sex, and interaction terms (neurogranin 3 AD biomarkers). Results: Higher neurogranin concentrations were associated with older age (r 5 0.20, p 5 0.02), lower levels of p-tau and t-tau, and smaller hippocampal volumes (p>0.03), but not with CSF Ab42 (p 5 0.18). In addition, CSF neurogranin demonstrated a significant relationship with memory performance independent of the AD-related biomarkers; individuals with the lowest CSF neurogranin concentrations performed better on delayed recall than those with medium or high CSF neurogranin concentrations (p>0.01). Notably, CSF p-tau, t-tau, and Ab42 and hippocampal volumes were not significantly associated with delayed recall scores (p<0.40), and did not interact with neurogranin to predict memory (p<0.10).