Cerebrospinal fluid phosphorylated tau,visinin-like protein-1,and chitinase-3-like protein 1 in mild cognitive impairment and Alzheimer’s disease

Background:Visinin-like protein-1(VILIP-1)and chitinase-3-like protein 1(CHI3L1 or YKL-40)in cerebrospinal fluid(CSF)are newly discovered markers indicating neuronal damage and microglial activation,respectively.Phosphorylated tau(p-tau)reflects the neuropathology of Alzheimer’s disease(AD)and is useful as diagnostic markers for AD.However,it is unknown whether these biomarkers have similar or complementary information in AD.Methods:We stratified 121 participants from the Alzheimer’s Disease Neuroimaging Initiative(ADNI)database into cognitively normal(CN),stable mild cognitive impairment(sMCI),progressive MCI(pMCI),and dementia due to AD.Analysis of covariance(ANOVA)and chi-square analyses,Spearman correlation,and logistic regression models were performed to test the demographic,associations between biomarkers,and diagnostic accuracies,respectively.Linear mixed-effects models were used to evaluate the effects of CSF amyloid-β(Aβ)on above biomarkers within diagnostic groups,the combination of diagnostic group and Aβstatus as predictor,and CSF biomarkers as predictors of AD features,including cognition measured by Mini–Mental State Examination(MMSE)and brain structure and white matter hyperintensity(WMH)measured by magnetic resonance imaging(MRI).Results:P-tau,VILIP-1,and YKL-40 were all predictors of AD diagnosis,but combinations of biomarkers did not improve the diagnostic accuracy(AUC 0.924 for p-tau,VILIP-1,and YKL-40)compared to p-tau(AUC 0.922).P-tau and VILIP-1 were highly correlated(r=0.639,p<0.001)and strongly associated with Aβpathology across clinical stages of AD,while YKL-40 was correlated with Aβpathology in CN and AD groups.VILIP-1 was associated with acceleration of cognitive decline,hippocampal atrophy,and expansion of ventricles in longitudinal analyses.YKL-40 was associated with hippocampal atrophy at baseline and follow-up,while p-tau was only associated with worsening WMH at baseline.Conclusions:CSF levels of p-tau,VILIP-1,and YKL-40 may have utility for discriminating between cognitively normal subjects and patients with AD.Increased levels of both VILIP-1 and YKL-40 may be associated with disease degeneration.These CSF biomarkers should be considered for future assessment in the characterization of the natural history of AD.

Neuropsychiatric symptoms are early indicators of an upcoming metabolic decline in Alzheimer's disease

Background:Neuropsychiatric symptoms(NPS)are increasingly recognized as early non-cognitive manifestations in the Alzheimer's disease(AD)continuum.However,the role of NPS as an early marker of pathophysiological progression in AD remains unclear.Dominantly inherited AD(DIAD)mutation carriers are young individuals who are destined to develop AD in future due to the full penetrance of the genetic mutation.Hence,the study of DIAD mutation carriers enables the evaluation of the associations between pure AD pathophysiology and metabolic correlates of NPS without the confounding effects of co-existing pathologies.In this longitudinal study,we aimed to identify regional brain metabolic dysfunctions associated with NPS in cognitively intact DIAD mutation carriers.Methods:We stratified 221 cognitively intact participants from the Dominantly Inherited Alzheimer's Network according to their mutation carrier status.The interactions of NPS measured by the Neuropsychiatric Inventory-Questionnaire(NPI-Q),age,and estimated years to symptom onset(EYO)as a function of metabolism measured by[^(18)F]flurodeoxyglucose([^(18)F]FDG)positron emission tomography,were evaluated by the mixed-effects regression model with family-level random effects in DIAD mutation carriers and non-carriers.Exploratory factor analysis was performed to identify the neuropsychiatric subsyndromes in DIAD mutation carriers using the NPI-Q subcomponents.Then the effects of interactions between specific neuropsychiatric subsyndromes and EYO on metabolism were evaluated with the mixed-effects regression model.Results:A total of 119 mutation carriers and 102 non-carriers were studied.The interaction of higher NPI-Q and shorter EYO was associated with more rapid declines of global and regional[18F]FDG uptake in the posterior cingulate and ventromedial prefrontal cortices,the bilateral parietal lobes and the right insula in DIAD mutation carriers.The neuropsychiatric subsyndromes of agitation,disinhibition,irritability and depression interacted with the EYO to drive the[^(18)F]FDG uptake decline in the DIAD mutation carriers.The interaction of NPI and EYO was not associated with[^(18)F]FDG uptake in DIAD mutation non-carriers.Conclusions:The NPS in cognitively intact DIAD mutation carriers may be a clinical indicator of subsequent metabolic decline in brain networks vulnerable to AD,which supports the emerging conceptual framework that NPS represent early manifestations of neuronal injury in AD.Further studies using different methodological approaches to identify NPS in predinical AD are needed to validate our findings.