Synaptic Marker NPTX2 Predicts Risk of MCI Clinical Symptom Onset

Background Neuronal pentraxin 2 (NPTX2) is a synaptic protein involved in the homeostatic regulation of cortical network dynamics and synaptic plasticity. Prior cross‐sectional studies suggest that NPTX2 levels decline across the spectrum of Alzheimer’s disease (AD), and that NPTX2 levels can distinguish individuals with normal cognition vs. mild cognitive impairment (MCI) and AD dementia. Less is known about how levels of NPTX2 among individuals with normal cognition relate to future clinical outcomes. To address this, we examined whether baseline levels of NPTX2 predicted time to onset of clinical symptoms of MCI, both alone and in combination with AD biomarkers, among individuals who were cognitively normal at baseline and have undergone 16.3y of follow‐up, on average. Method Cerebrospinal fluid (CSF) was collected at baseline from 269 cognitively normal BIOCARD Study participants (M baseline age = 57.7y), including 77 (29%) who subsequently progressed to MCI or dementia (Table 1). Baseline NPTX2 levels were measured from three highly correlated peptides using quantitative parallel reaction monitoring mass spectrometry. NPTX2 peptide levels were standardized and averaged to create an NPTX2 composite score. Baseline levels of Aβ42/Aβ40, p‐tau181, and t‐tau were measured using Lumipulse automated electrochemiluminescence assays. Result In Cox regression models, lower NPTX2 levels were significantly associated with earlier time to MCI clinical symptom onset (HR = 0.76, 95% CI (0.601, 0.962), p = 0.02; Figure 1a). After accounting for CSF AD biomarkers (i.e., Aβ42/Aβ40 and tau), the association between NPTX2 levels and MCI symptom onset appeared stronger (Table 2; Figure 1b). Importantly, NPTX2 did not interact with AD biomarker levels (all p > 0.11) or APOE‐ε4 genetic status (p = 0.71) in relation to MCI symptom onset. Conclusion CSF levels of the synaptic marker NPTX2 predict time to progress to MCI among individuals with normal cognition, suggesting that NPTX2 may be an early prognostic biomarker of synaptic dysfunction. Moreover, this association appears to be additive and independent of AD biomarker levels. Future work is underway to determine if NPTX2 provides resilience to cognitive impairment in the presence of AD pathology, and if there is a differential relationship with markers of amyloid vs. tau.