Perspectives on a collaborative Canada-China research program on diagnostic biomarkers for pre-dementia stages of Alzheimer’s disease

As biomarkers are important in the early diagnosis ofAlzheimer’s disease （AD）, the frst collab-orative work of recruiting early-onset familial AD （EO-FAD） families in Canada and China was initiated in 2012. The registration networks have collected hundreds of pedigrees, for which genetic screening, neuropsycholog-ical tests and amyloid and tau imaging was used to study diagnostic biomarkers for preclinical and mild cognitive impairment （MCI） stages of AD. Besides identifying ped-igrees with novel mutations in presenilins （PSENs）/amy-loid precursor protein （APP）, the program has benefted training of Chinese research fellows, AD clinical trials forprevention,the ethical concernsfor clinical fndings, and other collaborative projects with Chinese investiga-tors. Further research of the collaborative program may facilitate the testing and clinical use of novel treatments for EOFAD and late onset AD and contribute to dementia prevention strategies in Canada and China.

Alzheimer’s disease: current status and perspective

Aging is an undeniable fact of life and the global population is aging to a historically unprecedented degree. The population aged65 years or older comprises 750 million people, representing nearly 10%of the global population. As a result of prolonged life expectancy and falling mortality rates, China has become one of the most rapidly aging countries in the world, even surpassing several high-income countries in North America and Europe.

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.

Associations of AT(N) biomarkers with neuropsychiatric symptoms in prechnical Alzheimer’s disease and cognitively unimpaired individuals

The development of in vivo biomarkers of Alzheimer's disease(AD)has advanced the diagnosis of AD from a clinical syndrome to a biological construct.The preclinical stage of AD continuum is defined by the identification of AD biomarkers crossing the pathological threshold in cognitively unimpaired individuals.While neuropsychiatric symptoms(NPS)are non-cognitive symptoms that are increasingly recognized as early manifestations of AD,the associations of NPS with AD pathophysiology in preclinical AD remain unclear.Here,we review the associations between NPS and AD biomarkers amyloid-(3(Aβ),tau and neurodegeneration in preclinical AD and cognitivelyunimpaired individuals in 19 eligible English-language publications(8 cross-sectional studies,10 longitudinal,1 both cross-sectional and longitudinal).The cross-sectional studies have consistently shown that NPS,particularly depressive and anxiety symptoms,are associated with higher Aβ.The longitudinal studies have suggested that greater NPS are associated with higher Aβ and cognitive decline in cognitively unimpaired subjects over time.However,most of the studies have either cross-sectionally or longitudinally shown no association between NPS and tau pathology.For the association of NPS and neurodegeneration,two studies have shown that the cerebrospinal fluid total-tau is linked to longitudinal increase in NPS and that the NPS may predict longitudinal metabolic decline in preclinical AD,respectively.However,evidence for the association between atrophy and NPS in preclinical AD is less consistent.Therefore,future longitudinal studies with well-designed methodologies and NPS measurements are required not only to determine the relationship among AT(N)biomarkers,NPS and cognitive decline,but also to elucidate the contribution of comorbid pathology to preclinical AD.

Is ApoE ɛ 4 a good biomarker for amyloid pathology in late onset Alzheimer’s disease?

Amyloid plaques are pathological hallmarks of Alzheimer’s Disease(AD)and biomarkers such as cerebrospinal fluid(CSF)β-amyloid 1–42(Aβ1-42)and amyloid positron emission tomographic(PET)imaging are important in diagnosing amyloid pathology in vivo.ɛ4 allele of the Apolipoprotein E gene(ApoEɛ4),which is a major genetic risk factor for late onset AD,is an important genetic biomarker for AD pathophysiology.It has been shown that ApoEɛ4 is involved in Aβdeposition and formation of amyloid plaques.Studies have suggested the utility of peripheral blood ApoEɛ4 in AD diagnosis and risk assessment.However it is still a matter of debate whether ApoEɛ4 status would improve prediction of amyloid pathology and represent a cost-effective alternative to amyloid PET or CSF Aβin resource-limited settings in late onset AD.Recent research suggest that the mean prevalence of PET amyloid-positivity is 95%in ApoEɛ4-positive AD patients.This short review aims to provide an updated information on the relationship between ApoEɛ4 and amyloid biomarkers.

Prevention strategies for Alzheimer’s disease

Symptomatic treatment during the dementia stage of Alzheimer’s disease(AD)cannot delay or halt the progression of this disease.Therefore,prevention in the preclinical stage is likely the most effective way to decrease the incidence of this age-associated neurodegenerative condition,and its associated burden for individuals and society.Age,gender,family history,ApoE4,systolic blood pressure,body mass index,total cholesterol level and physical activity are all used as component of dementia risk score.There have been numerous challenges in conducting primary prevention trials in AD.Enrichment strategies for prevention studies include studying those subjects with more risk factors for AD,such as older age,those with a positive family history of late onset AD,and those who are ApoE4 positive.Each of these strategies is designed to increase the probability of developing AD thereby decreasing the sample size or the duration of follow up.Another strategy would be to target directly the pathophysiology of AD in its preclinical stages and use the biomarkers in prevention trial as surrogate markers.This will be done first in carriers of dominantly inherited early onset AD.As this research takes place networks of memory clinics must prepare to transfer new knowledge to persons interested in a preventive approach to AD.

Expert Consensus on Clinical Diagnostic Criteria for Fatal Familial Insomnia

INTRODUCTION Fatal familial insomnia （FFI） is a serious and rare prion disease, which was first reported by Lugaresi et al. in 1986.Early diagnosis of FFI might be important for early and sufficient counseling of patients and their relatives, also concerning the risk of inheritance, and potentially also for treatment studies. However, the diagnosis of FFI might be difficult because of the heterogeneity of clinical features, low sensitivity of diagnostic tests, and absence of family history. The aim of the present study was to develop a clinical scheme and diagnostic criteria for FFI based on our research and expert consensus.

In vivo tracking of tau pathology using positron emission tomography (PET) molecular imaging in small animals

Hyperphosphorylation of the tau protein leading to the formation of neurofibrillary tangles(NFTs)is a common feature in a wide range of neurodegenerative diseases known as tauopathies,which include Alzheimer’s disease(AD)and the frontotemporal dementias(FTDs).Although heavily investigated,the mechanisms underlying the pathogenesis and progression of tauopathies have yet to be fully understood.In this context,several rodent models have been developed that successfully recapitulate the behavioral and neurochemical features of tau pathology,aiming to achieve a better understanding of the link between tau and neurodegeneration.To date,behavioral and biochemical parameters assessed using these models have been conducted using a combination of memory tasks and invasive methods such as cerebrospinal fluid(CSF)sampling or post-mortem analysis.Recently,several novel positron emission tomography(PET)radiopharmaceuticals targeting tau tangles have been developed,allowing for non-invasive in vivo quantification of tau pathology.Combined with tau transgenic models and micro-PET,these tracers hold the promise of advancing the development of theoretical models and advancing our understanding of the natural history of AD and non-AD tauopathies.In this review,we briefly describe some of the most important insights for understanding the biological basis of tau pathology,and shed light on the opportunity for improved modeling of tau pathology using a combination of tau-radiopharmaceuticals and animal models.

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.