Cerebrospinal fluid tau, neurogranin, and neurofilament light in Alzheimer's disease

Added value of cerebrospinal fluid multimarker analysis in diagnosis and progression of dementia

BACKGROUND AND PURPOSE

Recently, some emerging cerebrospinal fluid (CSF) markers have been proposed as diagnostic tools for Alzheimer disease (AD) that can have an effect on disease progression. We analyze the accuracy of these CSF markers for diagnosis of AD in reference to brain amyloid positron emission tomography (PET). We also investigated whether they help in differentiating AD from other dementias and examined their influence in tracing the progression to dementia.

METHODS

Amyloid-β (Aβ) 1-42, total tau (t-tau), phosphorylated tau, Aβ₄₀ , Aβ₃₈ , beta-site amyloid precursor protein cleaving enzyme 1 (BACE-1), neurogranin (ng), phosphorylated neurofilament heavy-chain, and α-synuclein (α-syn) CSF levels were analyzed in 319 subjects, among whom 57 also underwent an amyloid PET scan. We also analyzed longitudinal clinical data from 239 subjects.

RESULTS

Emerging CSF markers, especially ng/BACE-1 ratio (area under the curve = 0.77) and their combinations with core AD CSF markers (all AUCs >0.85), showed high accuracy to discriminate amyloid PET positivity. Subjects with AD had higher CSF BACE-1, ng, and α-syn levels than those with non-AD dementia. CSF t-tau/α-syn ratio was higher in subjects with dementia with Lewy bodies than in those with frontotemporal dementia. Most emerging/core AD ratios predicted a faster conversion from mild cognitive impairment (MCI) stage to AD and appeared to be helpful when core AD CSF markers were discordant. In addition, the rate of cognitive decline was associated with all CSF core AD markers, several emerging/core AD two-marker ratios, and CSF ng levels.

CONCLUSIONS

These results suggest that emerging biomarkers in conjunction with core AD markers improve diagnosis of AD, are associated with the conversion from MCI into AD, and predict a faster progression of dementia.

Blood TDP-43 Combined with Demographics Information Predicts Dementia Occurrence in Community Non-Dementia Elderly

BACKGROUND

TAR DNA-binding protein-43 (TDP-43) and neurofilament light chain (NfL) are promising fluid biomarkers of disease progression for various dementia.

OBJECTIVE

We would explore whether blood levels of NfL and TDP-43 could predict the long-term progression to dementia, and the relationship of TDP-43 levels between cerebrospinal fluid (CSF) and blood.

METHODS

A total of 86 non-dementia elderly received 7-year follow-up, and were divided into 49 stable normal control (NC)/mild cognitive impairment (MCI) subjects, 19 subjects progressing from NC to MCI, and 18 subjects progressing from NC/MCI to dementia. Blood TDP-43 and NfL levels, and cognitive functions were measured in all subjects. Furthermore, another cohort of 23 dementia patients, including 13 AD and 10 non-AD patients received blood and CSF measurements of TDP-43.

RESULTS

In cohort 1, compared to stable NC/MCI group, there were higher levels of blood TDP-43 at baseline in subjects progressing from NC/MCI to dementia. The combination of baseline blood TDP-43 levels with demographics including age, education, and diabetes had the detection for dementia occurrence. Baseline blood levels of NfL are negatively associated with cognitive function at 7-year follow-up. In cohort 2, we found there were no relationship between CSF and blood levels of TDP-43. Moreover, the levels of TDP-43 in CSF was positively associated with the age of patients, especially in AD group.

CONCLUSION

Single blood TDP-43 could not estimate dementia occurrence; however, TDP-43 combined with demographics has the predictive effect for dementia occurrence and NfL level is associated with a decrease of cognitive function.

Biomarkers: Our Path Towards a Cure for Alzheimer Disease

Over the last decade, biomarkers have significantly improved our understanding of the pathophysiology of Alzheimer disease (AD) and provided valuable tools to examine different disease mechanisms and their progression over time. While several markers of amyloid, tau, neuronal, synaptic, and axonal injury, inflammation, and immune dysregulation in AD have been identified, there is a relative paucity of biomarkers which reflect other disease mechanisms such as oxidative stress, mitochondrial injury, vascular or endothelial injury, and calcium-mediated excitotoxicity. Importantly, there is an urgent need to standardize methods for biomarker assessments across different centers, and to identify dynamic biomarkers which can monitor disease progression over time and/or response to potential disease-modifying treatments. The updated research framework for AD, proposed by the National Institute of Aging- Alzheimer’s Association (NIA-AA) Work Group, emphasizes the importance of incorporating biomarkers in AD research and defines AD as a biological construct consisting of amyloid, tau, and neurodegeneration which spans pre-symptomatic and symptomatic stages. As results of clinical trials of AD therapeutics have been disappointing, it has become increasingly clear that the success of future AD trials will require the incorporation of biomarkers in participant selection, prognostication, monitoring disease progression, and assessing response to treatments. We here review the current state of fluid AD biomarkers, and discuss the advantages and limitations of the updated NIA-AA research framework. Importantly, the integration of biomarker data with clinical, cognitive, and imaging domains through a systems biology approach will be essential to adequately capture the molecular, genetic, and pathological heterogeneity of AD and its spatiotemporal evolution over time.

The relationship between neurofilament light chain and cognition in neurological disorders: A scoping review

Neurofilament light chain (NfL) is an emerging biomarker of neural degeneration. NfL is an integral component of axons and is released into the bloodstream and cerebrospinal fluid during neurodegeneration; hence it can be used to monitor disease progression. Given that several neurological disorders are accompanied by cognitive decline, recent literature has investigated the relationship between NfL levels and cognition. The objective of this scoping review was to determine whether a consistent relationship between NfL and cognition exists in the context of variable degrees of neurodegeneration present across several neurological disorders. Four electronic databases were searched for relevant articles and 160 articles were initially identified. After article screening, 37 studies met the final inclusion criteria. Studies were then qualitatively synthesized to determine the relationship between NfL and cognition across a variety of neurological disorders. The large majority of studies found that NfL levels are inversely correlated with cognition, such that higher NfL levels are associated with poorer cognition. This relationship was not universal, however, and this discrepancy was speculated to be due to the nature of the neurological disorder, individual differences between participants, or methodological inconsistencies. Further study is required, and associated recommendations were proposed for the design of future investigations.

Are neuropsychiatric symptoms in dementia linked to CSF biomarkers of synaptic and axonal degeneration?

Background

The underlying disease mechanism of neuropsychiatric symptoms (NPS) in dementia remains unclear. Cerebrospinal fluid (CSF) biomarkers for synaptic and axonal degeneration may provide novel neuropathological information for their occurrence. The aim was to investigate the relationship between NPS and CSF biomarkers for synaptic (neurogranin [Ng], growth-associated protein 43 [GAP-43]) and axonal (neurofilament light [NFL]) injury in patients with dementia.

Methods

A total of 151 patients (mean age ± SD, 73.5 ± 11.0, females n = 92 [61%]) were included, of which 64 had Alzheimer’s disease (AD) (34 with high NPS, i.e., Neuropsychiatric Inventory (NPI) score > 10 and 30 with low levels of NPS) and 18 were diagnosed with vascular dementia (VaD), 27 with mixed dementia (MIX), 12 with mild cognitive impairment (MCI), and 30 with subjective cognitive impairment (SCI). NPS were primarily assessed using the NPI. CSF samples were analyzed using enzyme-linked immunosorbent assays (ELISAs) for T-tau, P-tau, Aβ1–42, Ng, NFL, and GAP-43.

Results

No significant differences were seen in the CSF levels of Ng, GAP-43, and NFL between AD patients with high vs low levels of NPS (but almost significantly decreased for Ng in AD patients < 70 years with high NPS, p = 0.06). No significant associations between NPS and CSF biomarkers were seen in AD patients. In VaD (n = 17), negative correlations were found between GAP-43, Ng, NFL, and NPS.

Conclusion

Our results could suggest that low levels of Ng may be associated with higher severity of NPS early in the AD continuum (age < 70). Furthermore, our data may indicate a potential relationship between the presence of NPS and synaptic as well as axonal degeneration in the setting of VaD pathology.

Clinical Utility of the Pathogenesis-Related Proteins in Alzheimer's Disease

Research on the Aβ cascade and alternations of biomarkers in neuro-inflammation, synaptic dysfunction, and neuronal injury followed by Aβ have progressed. But the question is how to use the biomarkers. Here, we examine the evidence and pathogenic implications of protein interactions and the time order of alternation. After the deposition of Aβ, the change of tau, neurofilament light chain (NFL), and neurogranin (Ng) is the main alternation and connection to others. Neuro-inflammation, synaptic dysfunction, and neuronal injury function is exhibited prior to the structural and metabolic changes in the brain following Aβ deposition. The time order of such biomarkers compared to the tau protein is not clear. Despite the close relationship between biomarkers and plaque Aβ deposition, several factors favor one or the other. There is an interaction between some proteins that can predict the brain amyloid burden. The Aβ cascade hypothesis could be the pathway, but not all subjects suffer from Alzheimer's disease (AD) within a long follow-up, even with very elevated Aβ. The interaction of biomarkers and the time order of change require further research to identify the right subjects and right molecular target for precision medicine therapies.

Cerebrospinal Fluid Biomarkers for the Diagnosis and Classification of Alzheimer's Disease Spectrum

BACKGROUND

Cerebrospinal fluid (CSF) biomarkers are increasingly used in clinical practice for the diagnosis of Alzheimer's disease (AD). We aimed to 1) determine cutoff values of CSF biomarkers for AD, 2) investigate their clinical utility by estimating a concordance with amyloid positron emission tomography (PET), and 3) apply ATN (amyloid/tau/neurodegeneration) classification based on CSF results.

METHODS

We performed CSF analysis in 51 normal controls (NC), 23 mild cognitive impairment (MCI) and 65 AD dementia (ADD) patients at the Samsung Medical Center in Korea. We attempted to develop cutoff of CSF biomarkers for differentiating ADD from NC using receiver operating characteristic analysis. We also investigated a concordance between CSF and amyloid PET results and applied ATN classification scheme based on CSF biomarker abnormalities to characterize our participants.

RESULTS

CSF Aβ42, total tau (t-tau) and phosphorylated tau (p-tau) significantly differed across the three groups. The area under curve for the differentiation between NC and ADD was highest in t-tau/Aβ42 (0.994) followed by p-tau/Aβ42 (0.963), Aβ42 (0.960), t-tau (0.918), and p-tau (0.684). The concordance rate between CSF Aβ42 and amyloid PET results was 92%. Finally, ATN classification based on CSF biomarker abnormalities led to a majority of NC categorized into A-T-N-(73%), MCI as A+T-N-(30%)/A+T+N+(26%), and ADD as A+T+N+(57%).

CONCLUSION

CSF biomarkers had high sensitivity and specificity in differentiating ADD from NC and were as accurate as amyloid PET. The ATN subtypes based on CSF biomarkers may further serve to predict the prognosis.

Fluid Candidate Biomarkers for Alzheimer's Disease: A Precision Medicine Approach

A plethora of dynamic pathophysiological mechanisms underpins highly heterogeneous phenotypes in the field of dementia, particularly in Alzheimer's disease (AD). In such a faceted scenario, a biomarker-guided approach, through the implementation of specific fluid biomarkers individually reflecting distinct molecular pathways in the brain, may help establish a proper clinical diagnosis, even in its preclinical stages. Recently, ultrasensitive assays may detect different neurodegenerative mechanisms in blood earlier. ß-amyloid (Aß) peptides, phosphorylated-tau (p-tau), and neurofilament light chain (NFL) measured in blood are gaining momentum as candidate biomarkers for AD. P-tau is currently the more convincing plasma biomarker for the diagnostic workup of AD. The clinical role of plasma Aβ peptides should be better elucidated with further studies that also compare the accuracy of the different ultrasensitive techniques. Blood NFL is promising as a proxy of neurodegeneration process tout court. Protein misfolding amplification assays can accurately detect α-synuclein in cerebrospinal fluid (CSF), thus representing advancement in the pathologic stratification of AD. In CSF, neurogranin and YKL-40 are further candidate biomarkers tracking synaptic disruption and neuroinflammation, which are additional key pathophysiological pathways related to AD genesis. Advanced statistical analysis using clinical scores and biomarker data to bring together individuals with AD from large heterogeneous cohorts into consistent clusters may promote the discovery of pathophysiological causes and detection of tailored treatments.

Plasma tau predicts cerebral vulnerability in aging

Identifying cerebral vulnerability in late life may help prevent or slow the progression of aging-related chronic diseases. However, non-invasive biomarkers aimed at detecting subclinical cerebral changes in the elderly are lacking. Here, we have examined the potential of plasma total tau (t-tau) for identifying cerebral and cognitive deficits in normal elderly subjects. Patterns of cortical thickness and cortical glucose metabolism were used as outcomes of cerebral vulnerability. We found that increased plasma t-tau levels were associated with widespread reductions of cortical glucose uptake, thinning of the temporal lobe, and memory deficits. Importantly, tau-related reductions of glucose consumption in the orbitofrontal cortex emerged as a determining factor of the relationship between cortical thinning and memory loss. Together, these results support the view that plasma t-tau may serve to identify subclinical cerebral and cognitive deficits in normal aging, allowing detection of individuals at risk for developing aging-related neurodegenerative conditions.

CSF and Blood Biomarkers in Neuroinflammatory and Neurodegenerative Diseases: Implications for Treatment

Neuroinflammatory and neurodegenerative diseases are characterized by the interplay of a number of molecular pathways that can be assessed through biofluids, especially cerebrospinal fluid and blood. Accordingly, the definition and classification of these disorders will move from clinical and pathological to biological criteria. The consequences of this biomarker-based diagnostic and prognostic approach are highly relevant to the field of drug development. Indeed, in view of the availability of disease-modifying drugs, fluid biomarkers offer a unique opportunity for improving the quality and applicability of results from clinical trials. Herein, we discuss the benefits of using fluid biomarkers for patient stratification, target engagement, and outcome assessment, as well as the most recent developments in neuroinflammatory and neurodegenerative diseases.

The role of synaptic biomarkers in the spectrum of neurodegenerative diseases

INTRODUCTION

The quest for reliable fluid biomarkers tracking synaptic disruption is supported by the evidence of a tight association between synaptic density and cognitive performance in neurodegenerative diseases (NDD), especially Alzheimer's disease (AD).

AREAS COVERED

Neurogranin (Ng) is a post-synaptic protein largely expressed in neurons involved in the memory networks. Currently, Ng measured in CSF is the most promising synaptic biomarker. Several studies show Ng elevated in AD dementia with a hippocampal phenotype as well as in MCI individuals who progress to AD. Ng concentrations are also increased in Creutzfeldt Jacob Disease where widespread and massive synaptic disintegration takes place. Ng does not discriminate Parkinson's disease from atypical parkinsonisms, nor is it altered in Huntington disease. CSF synaptosomal-associated protein 25 (SNAP-25) and synaptotagmin-1 (SYT-1) are emerging candidates.

EXPERT OPINION

CSF Ng revealed a role as a diagnostic and prognostic biomarker in NDD. Ng increase seems to be very specific for typical AD phenotype, probably for a prevalent hippocampal involvement. Synaptic biomarkers may serve different context-of-use in AD and other NDD including prognosis, diagnosis, and tracking synaptic damage - a critical pathophysiological mechanism in NDD - thus representing reliable tools for a precision medicine-oriented approach to NDD.

Calmodulin Binding Proteins and Alzheimer's Disease: Biomarkers, Regulatory Enzymes and Receptors That Are Regulated by Calmodulin

The integral role of calmodulin in the amyloid pathway and neurofibrillary tangle formation in Alzheimer’s disease was first established leading to the “Calmodulin Hypothesis”. Continued research has extended our insight into the central function of the small calcium sensor and effector calmodulin and its target proteins in a multitude of other events associated with the onset and progression of this devastating neurodegenerative disease. Calmodulin’s involvement in the contrasting roles of calcium/CaM-dependent kinase II (CaMKII) and calcineurin (CaN) in long term potentiation and depression, respectively, and memory impairment and neurodegeneration are updated. The functions of the proposed neuronal biomarker neurogranin, a calmodulin binding protein also involved in long term potentiation and depression, is detailed. In addition, new discoveries into calmodulin’s role in regulating glutamate receptors (mGluR, NMDAR) are overviewed. The interplay between calmodulin and amyloid beta in the regulation of PMCA and ryanodine receptors are prime examples of how the buildup of classic biomarkers can underly the signs and symptoms of Alzheimer’s. The role of calmodulin in the function of stromal interaction molecule 2 (STIM2) and adenosine A2A receptor, two other proteins linked to neurodegenerative events, is discussed. Prior to concluding, an analysis of how targeting calmodulin and its binding proteins are viable routes for Alzheimer’s therapy is presented. In total, calmodulin and its binding proteins are further revealed to be central to the onset and progression of Alzheimer’s disease.

Interrelations of Alzheimer´s disease candidate biomarkers neurogranin, fatty acid-binding protein 3 and ferritin to neurodegeneration and neuroinflammation

There is growing evidence that promising biomarkers of inflammation in Alzheimer´s disease (AD) and other neurodegenerative diseases correlate strongest to levels of tau or neurofilament, indicating an inflammatory response to neuronal damage or death. To test this hypothesis, we investigated three AD candidate markers (ferritin, fatty acid binding protein 3 (FABP-3), and neurogranin) in interrelation to established AD and inflammatory protein markers. We further aimed to determine if such interrelations would be evident in pathological subjects only or also under non-pathological circumstances. Cerebrospinal fluid levels of the three proteins were quantified in samples from the University Clinic of Bonn (UKB) Department of Neurodegenerative Diseases & Geriatric Psychiatry, Germany. Data were analyzed based on clinical or biomarker-defined stratification of subjects with adjustment for covariates age, sex, and APOE status. Levels of ferritin, FABP-3 and neurogranin were elevated in subjects with pathological levels of t-tau independent of beta-amyloid status. The three markers correlated with each other, tau isoforms, age, and those inflammatory markers previously described as related to neurodegeneration, predominantly sTREM2, macrophage migration inhibitory factor, soluble vascular endothelial growth factor receptor, soluble vascular cell adhesion molecule 1 (sVCAM-1), and C1q. These interrelations existed in subjects with pathological and sub-pathological tau levels, in particular for FABP-3 and neurogranin. Relations to ferritin were independent of absolute levels of tau, too, but showed differing trajectories between pathological and non-pathological subjects. A specific set of inflammatory markers is highly related to markers of neuronal damage such as tau, neurogranin, or FABP-3. These proteins could be used as readouts of the inflammatory response during the neurodegeneration phase of AD.

Neurofilament light chain level in traumatic brain injury: A system review and meta-analysis

BACKGROUND

Neurofilament light (NfL) level was obviously increased in traumatic brain injury (TBI) individuals. But, no comprehensive meta-analysis has ever been conducted to assess the diagnostic performance of NfL. This study aims to evaluate the relationship between NfL level and TBI through a meta-analysis.

METHODS

Studies were selected from Pubmed, Web of science, Embase, Google Scholar, PMC and Chinese National Knowledge Infrastructure (CNKI), and the Chinese Biomedical Literature Database (CBM) through inclusion and exclusion criteria. The standard mean difference (SMD) and 95% confidence interval (CI) were calculated using the random-effect model or fixed-effect model to assess the association between NfL level and TBI. Subgroup analysis according to sample collection time, sample type and detection method was performed. The influence analysis and publication bias was also conducted. All analyses were performed using the RevMan 5.3 and Stata 12 software.

RESULTS

A total of 9 studies were included. Results indicated that TBI individuals had a higher NfL expression level compared with the non-TBI individuals (SMD = 2.48, 95% CI = 1.52-3.43, I = 96%, P < .01). Similar NfL increasing was also observed in Caucasian population, 0-48 hour and 6-10 days sample collection time, as well as cerebrospinal fluid (CSF), serum, plasma sample subgroup analysis. Moreover, the NfL increasing still existed no matter the NfL expression level was detected by ELISA or Simoa assay.

CONCLUSION

NfL expression level was increased in TBI individuals, which indicated that NfL could be a potential biomarker in the diagnosis of TBI and other neurodegenerative diseases.

Neurofilament light chain in the vitreous humor of the eye

BACKGROUND

Neurofilament light chain (NfL) is a promising biomarker of neurodegeneration in the cerebrospinal fluid and blood. This study investigated the presence of NfL in the vitreous humor and its associations with amyloid beta, tau, inflammatory cytokines and vascular proteins, apolipoprotein E (APOE) genotypes, Mini-Mental State Examination (MMSE) scores, systemic disease, and ophthalmic diseases.

METHODS

This is a single-site, prospective, cross-sectional cohort study. Undiluted vitreous fluid (0.5-1.0 mL) was aspirated during vitrectomy, and whole blood was drawn for APOE genotyping. NfL, amyloid beta (Aβ), total Tau (t-Tau), phosphorylated Tau (p-Tau181), inflammatory cytokines, chemokines, and vascular proteins in the vitreous were quantitatively measured by immunoassay. The main outcome measures were the detection of NfL levels in the vitreous humor and its associations with the aforementioned proteins. Linear regression was used to test the associations of NfL with other proteins, APOE genotypes, MMSE scores, and ophthalmic and systemic diseases after adjustment for age, sex, education level, and other eye diseases.

RESULTS

NfL was detected in all 77 vitreous samples. NfL was not found to be associated with ophthalmic conditions, APOE genotypes, MMSE scores, or systemic disease (p > 0.05). NfL levels were positively associated with increased vitreous levels of Aβ40 (p = 7.7 × 10-5), Aβ42 (p = 2.8 × 10-4), and t-tau (p = 5.5 × 10-7), but not with p-tau181 (p = 0.53). NfL also had significant associations with inflammatory cytokines such as interleukin-15 (IL-15, p = 5.3 × 10-4), IL-16 (p = 2.2 × 10-4), monocyte chemoattractant protein-1 (MCP1, p = 4.1 × 10-4), and vascular proteins such as vascular endothelial growth factor receptor-1 (VEGFR1, p = 2.9 × 10-6), Vegf-C (p = 8.6 × 10-6), vascular cell adhesion molecule-1 (VCAM-1, p = 5.0 × 10-4), Tie-2 (p = 6.3 × 10-4), and intracellular adhesion molecular-1 (ICAM-1, p = 1.6 × 10-4).

CONCLUSION

NfL is detectable in the vitreous humor of the eye and significantly associated with amyloid beta, t-tau, and select inflammatory and vascular proteins in the vitreous. Additionally, NfL was not associated with patients' clinical eye condition. Our results serve as a foundation for further investigation of NfL in the ocular fluids to inform us about the potential utility of its presence in the eye.

Neurogranin as a Novel Biomarker in Alzheimer's Disease

BACKGROUND

In this study, we investigated the possible role of 2 novel biomarkers of synaptic damage, namely, neurogranin and α-synuclein, in Alzheimer disease (AD).

METHODS

The study was performed in a cohort consisting of patients with AD and those without AD, including individuals with other neurological diseases. Cerebrospinal fluid (CSF) neurogranin and α-synuclein levels were measured by sensitive enzyme-linked immunosorbent assays (ELISAs).

RESULTS

We found significantly increased levels of CSF neurogranin and α-synuclein in patients with AD than those without AD. Neurogranin was correlated with total tau (tTau) and phosphorylated tau (pTau), as well as with cognitive decline, in patients with AD. Receiver operating characteristic (ROC) curve analysis showed good diagnostic accuracy of neurogranin for AD at a cutoff point of 306 pg per mL with an area under the curve (AUC) of 0.872 and sensitivity and specificity of 84.2% and 78%, respectively.

CONCLUSIONS

Our findings support the use of CSF neurogranin as a biomarker of synapsis damage in patients with AD.

Amyloid, tau and risk of Alzheimer's disease: a Mendelian randomization study

This study was carried out to assess the effect of amyloid and tau on Alzheimer's disease using two-sample Mendelian randomization design. Genetic associations with plasma amyloid species (amyloid precursor protein, amyloid-like protein 2, serum amyloid P-component, amyloid beta peptide), cerebrospinal fluid (CSF) amyloid beta, total tau, and phosphorylated tau₁₈₁ were extracted from the largest genome-wide association study (GWAS) available. Genetic associations with Alzheimer's disease were obtained from a GWAS of proxy-cases based on family history of Alzheimer's disease with 314,278 participants from the UK Biobank and a GWAS with clinically diagnosed Alzheimer's disease from the International Genomics of Alzheimer's Project (IGAP) with 21,982 cases and 41,944 controls. Estimates were obtained using inverse variance weighting with sensitivity analyses including MR-Egger, weighted median and MR-PRESSO. Presence of bias due to selective survival and competing risk was also considered. Plasma amyloid species, CSF total tau and phosphorylated tau₁₈₁ were not associated with Alzheimer's disease. For CSF Aβ₄₂, no association was found using the proxy-cases but an inverse association was found after removing outliers with MR-PRESSO using IGAP. Higher genetically predicted (p < 1 × 10^-5) plasma amyloid species, CSF total tau and phosphorylated tau₁₈₁ (based on sample sizes ~ 3300) were not associated with Alzheimer's disease using family history or clinically diagnosed cases while effects of CSF Aβ₄₂ were inconsistent between the family history and IGAP GWAS.

Association of glial and neuronal degeneration markers with Alzheimer's disease cerebrospinal fluid profile and cognitive functions

BACKGROUND

Neuroinflammation has gained increasing attention as a potential contributing factor in the onset and progression of Alzheimer's disease (AD). The objective of this study was to examine the association of selected cerebrospinal fluid (CSF) inflammatory and neuronal degeneration markers with signature CSF AD profile and cognitive functions among subjects at the symptomatic pre- and early dementia stages.

METHODS

In this cross-sectional study, 52 subjects were selected from an Icelandic memory clinic cohort. Subjects were classified as having AD (n = 28, age = 70, 39% female, Mini-Mental State Examination [MMSE] = 27) or non-AD (n = 24, age = 67, 33% female, MMSE = 28) profile based on the ratio between CSF total-tau (T-tau) and amyloid-β_1-42 (Aβ₄₂) values (cut-off point chosen as 0.52). Novel CSF biomarkers included neurofilament light (NFL), YKL-40, S100 calcium-binding protein B (S100B) and glial fibrillary acidic protein (GFAP), measured with enzyme-linked immunosorbent assays (ELISAs). Subjects underwent neuropsychological assessment for evaluation of different cognitive domains, including verbal episodic memory, non-verbal episodic memory, language, processing speed, and executive functions.

RESULTS

Accuracy coefficient for distinguishing between the two CSF profiles was calculated for each CSF marker and test. Novel CSF markers performed poorly (area under curve [AUC] coefficients ranging from 0.61 to 0.64) compared to tests reflecting verbal episodic memory, which all performed fair (AUC > 70). LASSO regression with a stability approach was applied for the selection of CSF markers and demographic variables predicting performance on each cognitive domain, both among all subjects and only those with a CSF AD profile. Relationships between CSF markers and cognitive domains, where the CSF marker reached stability selection criteria of > 75%, were visualized with scatter plots. Before calculations of corresponding Pearson's correlations coefficients, composite scores for cognitive domains were adjusted for age and education. GFAP correlated with executive functions (r = - 0.37, p = 0.01) overall, while GFAP correlated with processing speed (r = - 0.68, p < 0.001) and NFL with verbal episodic memory (r = - 0.43, p = 0.02) among subjects with a CSF AD profile.

CONCLUSIONS

The novel CSF markers NFL and GFAP show potential as markers for cognitive decline among individuals with core AD pathology at the symptomatic pre- and early stages of dementia.

Plasma tau, neurofilament light chain and amyloid-β levels and risk of dementia; a population-based cohort study

CSF biomarkers, including total-tau, neurofilament light chain (NfL) and amyloid-β, are increasingly being used to define and stage Alzheimer’s disease. These biomarkers can be measured more quickly and less invasively in plasma and may provide important information for early diagnosis of Alzheimer’s disease. We used stored plasma samples and clinical data obtained from 4444 non-demented participants in the Rotterdam study at baseline (between 2002 and 2005) and during follow-up until January 2016. Plasma concentrations of total-tau, NfL, amyloid-β₄₀ and amyloid-β₄₂ were measured using the Simoa NF-light^® and N3PA assays. Associations between biomarker plasma levels and incident all-cause and Alzheimer’s disease dementia during follow-up were assessed using Cox proportional-hazard regression models adjusted for age, sex, education, cardiovascular risk factors and APOE ε4 status. Moreover, biomarker plasma levels and rates of change over time of participants who developed Alzheimer’s disease dementia during follow-up were compared with age and sex-matched dementia-free control subjects. During up to 14 years follow-up, 549 participants developed dementia, including 374 cases with Alzheimer’s disease dementia. A log₂ higher baseline amyloid-β₄₂ plasma level was associated with a lower risk of developing all-cause or Alzheimer’s disease dementia, adjusted hazard ratio (HR) 0.61 [95% confidence interval (CI), 0.47–0.78; P < 0.0001] and 0.59 (95% CI, 0.43–0.79; P = 0.0006), respectively. Conversely, a log₂ higher baseline plasma NfL level was associated with a higher risk of all-cause dementia [adjusted HR 1.59 (95% CI, 1.38–1.83); P < 0.0001] or Alzheimer’s disease [adjusted HR 1.50 (95% CI, 1.26–1.78); P < 0.0001]. Combining the lowest quartile group of amyloid-β₄₂ with the highest of NfL resulted in a stronger association with all-cause dementia [adjusted HR 9.5 (95% CI, 2.3–40.4); P < 0.002] and with Alzheimer’s disease [adjusted HR 15.7 (95% CI, 2.1–117.4); P < 0.0001], compared to the highest quartile group of amyloid-β₄₂ and lowest of NfL. Total-tau and amyloid-β₄₀ levels were not associated with all-cause or Alzheimer’s disease dementia risk. Trajectory analyses of biomarkers revealed that mean NfL plasma levels increased 3.4 times faster in participants who developed Alzheimer’s disease compared to those who remained dementia-free (P < 0.0001), plasma values for cases diverged from controls 9.6 years before Alzheimer’s disease diagnosis. Amyloid-β₄₂ levels began to decrease in Alzheimer’s disease cases a few years before diagnosis, although the decline did not reach significance compared to dementia-free participants. In conclusion, our study shows that low amyloid-β₄₂ and high NfL plasma levels are each independently and in combination strongly associated with risk of all-cause and Alzheimer’s disease dementia. These data indicate that plasma NfL and amyloid-β₄₂ levels can be used to assess the risk of developing dementia in a non-demented population. Plasma NfL levels, although not specific, may also be useful in monitoring progression of Alzheimer’s disease dementia.

The effect of lumbar puncture on the neurodegeneration biomarker neurofilament light in macaque monkeys

INTRODUCTION

Neurofilament light (NFL) in cerebrospinal fluid (CSF) is elevated in neurodegenerative disease patients, and may track disease progression and treatment. Macaque monkeys are emerging as important translational models of neurodegeneration, and NFL may be a useful biomarker.

METHODS

To determine the influence of a previous lumbar puncture (LP) on NFL, we collected CSF at multiple time points in macaque monkeys via LP or cisterna magna puncture. NFL, amyloid beta (Aβ40, Aβ42), and tau (tTau, pTau) in CSF were measured by standard enzyme-linked immunosorbent assay and multiplex.

RESULTS

NFL was significantly elevated at 14 to 23 days after an LP (median increase: 162%). Aβ and tau biomarkers remained stable. NFL peaked and decayed over 1 to 2 months after LP. NFL was not elevated after cisterna magna puncture.

DISCUSSION

Results suggest damage of the cauda equina during LP may increase NFL. Caution should be taken in interpreting NFL concentration in studies in which repeat LPs are performed.

Cerebrospinal fluid biomarkers of Alzheimer's disease in a cohort of adults with Down syndrome

INTRODUCTION

Virtually all individuals with Down syndrome (DS) will develop Alzheimer's disease (AD) pathology by age 40. Cerebrospinal fluid (CSF) biomarkers have characterized AD pathology in cohorts of late-onset AD (LOAD) and autosomal-dominant AD (ADAD). Few studies have evaluated such biomarkers in adults with DS.

METHODS

CSF concentrations of amyloid beta (Aβ)40, Aβ42, tau, phospho-tau181 (p-tau), neurofilament light chain (NfL), soluble triggering receptor expressed on myeloid cells 2 (sTREM2), chitinase-3-like protein 1 (YKL-40), alpha synuclein (αSyn), neurogranin (Ng), synaptosomal-associated protein 25 (SNAP-25), and visinin-like protein 1 (VILIP-1) were assessed in CSF from 44 adults with DS from the Alzheimer's Biomarker Consortium-Down Syndrome study. Biomarker levels were evaluated by cognitive status, age, and apolipoprotein E gene (APOE) ε4 carrier status.

RESULTS

Biomarker abnormalities indicative of amyloid deposition, tauopathy, neurodegeneration, synaptic dysfunction, and neuroinflammation were associated with increased cognitive impairment. Age and APOE ε4 status influenced some biomarkers.

DISCUSSION

The profile of many established and emerging CSF biomarkers of AD in a cohort of adults with DS was similar to that reported in LOAD and ADAD, while some differences were observed.

Dissection of synaptic pathways through the CSF biomarkers for predicting Alzheimer disease

OBJECTIVE

To assess the ability of a combination of synaptic CSF biomarkers to separate Alzheimer disease (AD) and non-AD disorders and to help in the differential diagnosis between neurocognitive diseases.

METHODS

This was a retrospective cross-sectional monocentric study. All participants explored with CSF assessments for neurocognitive decline were invited to participate. After complete clinical and imaging evaluations, 243 patients were included. CSF synaptic (GAP-43, neurogranin, SNAP-25 total, SNAP-25aa40, synaptotagmin-1) and AD biomarkers were blindly quantified with ELISA or mass spectrometry. Statistical analysis compared CSF levels between the various groups of AD dementias (n = 81), mild cognitive impairment (MCI)-AD (n = 30), other MCI (n = 49), other dementias (OD) (n = 49), and neurologic controls (n = 35) and their discriminatory powers.

RESULTS

All synaptic biomarkers were significantly increased in patients with MCI-AD and AD-dementia compared to the other groups. All synaptic biomarkers could efficiently discriminate AD dementias from OD (AUC ≥0.80). All but synaptotagmin were also able to discriminate patients with MCI-AD from controls (area under the curve [AUC] ≥0.85) and those with AD dementias from controls (AUC ≥0.80). Overall, CSF SNAP-25aa40 had the highest discriminative power (AUC 0.93 between patients with AD dementias and controls or OD, AUC 0.90 between those with MCI-AD and controls). Higher levels were associated with 2 alleles of APOE ε4.

CONCLUSION

All synaptic biomarkers tested had a good discriminatory power to distinguish patients with AD abnormal CSF from those with non-AD disorders. SNAP25aa40 demonstrated the highest power to discriminate AD CSF-positive patients from patients without AD and neurologic controls in this cohort.

CLASSIFICATION OF EVIDENCE

This retrospective study provides Class II evidence that CSF synaptic biomarkers discriminate patients with AD from those without AD.

Amyloid beta, tau, synaptic, neurodegeneration, and glial biomarkers in the preclinical stage of the Alzheimer's continuum

Introduction

The biological pathways involved in the preclinical stage of the Alzheimer's continuum are not well understood.

Methods

We used NeuroToolKit and Elecsys^® immunoassays to measure cerebrospinal fluid (CSF) amyloid‐β (Aβ)42, Aβ40, phosphorylated tau (p‐tau), total tau (t‐tau), neurofilament light (NfL), neurogranin, sTREM2, YKL40, GFAP, IL6, S100, and α‐synuclein in cognitively unimpaired participants of the ALFA+ study, many within the Alzheimer's continuum.

Results

CSF t‐tau, p‐tau, and neurogranin increase throughout aging only in Aβ‐positive individuals, whereas NfL and glial biomarkers increase with aging regardless of Aβ status. We modelled biomarker changes as a function of CSF Aβ42/40, p‐tau and p‐tau/Aβ42 as proxies of disease progression. The first change observed in the Alzheimer's continuum was a decrease in the CSF Aβ42/40 ratio. This is followed by a steep increase in CSF p‐tau; t‐tau; neurogranin; and, to a lesser extent, in NfL and glial biomarkers.

Discussion

Multiple biological pathways are altered and could be targeted very early in the Alzheimer's continuum.

Serum neurofilament light chain in FTLD: association with C9orf72, clinical phenotype, and prognosis

Objective

The aim of the present study was to compare the levels of serum neurofilament light chain (sNfL) in frontotemporal lobar degeneration (FTLD) patients of different clinical subtypes (bvFTD, PPA, and FTLD‐MND) and with or without the C9orf72 repeat expansion, and to correlate sNfL levels to disease progression, assessed by the brain atrophy rate and survival time.

Methods

The sNfL levels were determined from 78 FTLD patients (C9orf72 repeat expansion carriers [n = 26] and non‐carriers [n = 52]) with Single Molecule Array (SIMOA). The progression of brain atrophy was evaluated using repeated T1‐weighted MRI scans and the survival time from medical records.

Results

In the total FTLD cohort, sNfL levels were significantly higher in C9orf72 repeat expansion carriers compared to non‐carriers. Considering clinical phenotypes, sNfL levels were higher in the C9orf72 repeat expansion carriers than in the non‐carriers in bvFTD and PPA groups. Furthermore, sNfL levels were the highest in the FTLD‐MND group (median 105 pg/mL) and the lowest in the bvFTD group (median 27 pg/mL). Higher sNfL levels significantly correlated with frontal cortical atrophy rate and subcortical grey matter atrophy rate. The higher sNfL levels also associated with shorter survival time.

Interpretation

Our results indicate that the C9orf72 repeat expansion carriers show elevated sNFL levels compared to non‐carriers and that the levels differ among different clinical phenotypes of FTLD. Higher sNfL levels correlated with a shorter survival time and cortical and subcortical atrophy rates. Thus, sNfL could prove as a potential prognostic biomarker in FTLD.

Association of cerebrospinal fluid neurogranin levels with cognition and neurodegeneration in Alzheimer's disease

Accumulating data suggest cerebrospinal fluid (CSF) neurogranin (Ng) as a potential biomarker for cognitive decline and neurodegeneration in Alzheimer disease (AD). To investigate whether the CSF Ng can be used for diagnosis, prognosis, and monitoring of AD, we examined 111 cognitively normal (CN) controls, 193 mild cognitive impairment (MCI) patients and 95 AD patients in the Alzheimer's Disease Neuroimaging Initiative (ADNI) cohort. Correlations were tested between baseline CSF Ng levels and baseline core AD biomarkers and longitudinal glucose metabolism, brain atrophy and cognitive decline. We detected that CSF Ng levels increased with disease severity, and correlated with phosphorylated tau and total tau levels within each diagnostic group. High baseline CSF Ng levels correlated with longitudinal reductions in cortical glucose metabolism within each diagnostic group and hippocampal volume within MCI group during follow-up. In addition, high baseline CSF Ng levels correlated with cognitive decline as reflected by decreased cognitive scale scores. The CSF Ng levels predicted future cognitive impairment (adjusted hazard ratio:3.66, 95%CI: 1.74-7.70, P = 0.001) in CN controls. These data demonstrate that CSF Ng offers diagnostic utility for AD and predicts future cognitive impairment in CN individuals and, therefore, may be a useful addition to the current AD biomarkers.

Cerebrospinal Fluid Biomarkers to Differentiate Idiopathic Normal Pressure Hydrocephalus from Subcortical Ischemic Vascular Disease

BACKGROUND

Idiopathic normal pressure hydrocephalus (iNPH) remains a challenge to differentiate from subcortical ischemic vascular disease (SIVD). Despite major research efforts, the cerebrospinal fluid (CSF) biomarker profiles of the two diseases are still not known in detail.

OBJECTIVE

To determine if novel CSF biomarkers, neurofilament light (NFL) reflecting axonal damage, the synaptic protein neurogranin (NG), and the astroglial marker chitinase-3-like protein 1 (YKL-40), and the core Alzheimer's disease (AD) biomarkers, amyloid-β 42 (Aβ42), total tau (t-tau), phosphorylated tau (p-tau), can differentiate iNPH from SIVD. Patients with AD and healthy controls (HC) were included for comparison purposes.

METHODS

Patients with iNPH (n = 28), SIVD (n = 30), AD (n = 57), and HC (n = 33) were retrospectively included from the Danish Dementia Biobank. All patients with iNPH had effect of shunt surgery with a follow-up period of 4 to 69 months. CSF biomarkers were measured using immunoassays.

RESULTS

Lower levels of NFL, NG, Aβ42, and t-tau were found in patients with iNPH versus SIVD, while YKL-40 and p-tau were similar in the two diseases. NFL and Aβ42 were the most reliable biomarkers to differentiate iNPH from SIVD with an area under the curve (AUC) on 0.82 and 0.80, respectively. Combining NFL with Aβ42, t-tau, and p-tau resulted in an AUC of 0.90, which was equivalent to the diagnostic accuracy of all six biomarkers combined.

CONCLUSION

An addition of NFL to the CSF panel of Aβ42, t-tau, and p-tau may improve the differentiation of iNPH from SIVD.

Cerebrospinal fluid biomarkers of neurodegeneration, synaptic dysfunction, and axonal injury relate to atrophy in structural brain regions specific to Alzheimer's disease

INTRODUCTION

Patterns of atrophy can distinguish normal cognition from Alzheimer's disease (AD), but neuropathological drivers of this pattern are unknown. This study examined associations between cerebrospinal fluid biomarkers of AD pathology, synaptic dysfunction, and neuroaxonal injury with two AD imaging signatures.

METHODS

Signatures were calculated using published guidelines. Linear regressions related each biomarker to both signatures, adjusting for demographic factors. Bootstrapped analyses tested if associations were stronger with one signature versus the other.

RESULTS

Increased phosphorylated tau (p-tau), total tau, and neurofilament light (P-values <.045) related to smaller signatures (indicating greater atrophy). Diagnosis and sex modified associations between p-tau and neurogranin (P-values<.05) and signatures, such that associations were stronger among participants with mild cognitive impairment and female participants. The strength of associations did not differ between signatures.

DISCUSSION

Increased evidence of neurodegeneration, axonopathy, and tau phosphorylation relate to greater AD-related atrophy. Tau phosphorylation and synaptic dysfunction may be more prominent in AD-affected regions in females.

Association of serum biomarker neurofilament light concentration with post-stroke depression: A preliminary study

OBJECTIVE

To investigate serum neurofilament light (sNfL) levels in acute ischemic stroke and to assess whether sNfL are related to the severity of disease and a potential prognostic marker of post-stroke depression (PSD) during a 3-month follow-up period.

METHODS

This was a single-center prospective cohort study. The sNfL concentration was measured in baseline samples using the Simoa platform- Single Molecule Array technology. A psychiatrist administered the Structural Clinical Interview for Diagnostic and Statistical Manual IV to all patients and made a diagnosis of PSD 3 months after stroke. The logistic regression was used to examine the association between sNfL and PSD.

RESULTS

In total, 236 ischemic stroke cases were included and finished the follow-up. In the follow-up, 55 patients were defined as PSD, thus the incidence rate was 23.3% (95% confidence intervals [CI]: 17.9%-28.7%). Significant differences were observed between the sNfL levels in patients with PSD (124.8 pg/ml [interquartile range {IQR}: 59.6-159.2]) and in patients without PSD (35.9 pg/ml [IQR: 18.2-60.4]) levels (P < 0.001). After adjusting for age, family history of depression, marital status, National Institutes of Health and Stroke Scale score, C-reactive protein and homocysteine levels, sNfL levels independently predicted the development of post-stroke depression. The crude and adjusted odds ratios [OR] (and 95%CI) of PSD associated with an IQR increase for sNfL were 3.38(2.29, 4.98) and 2.65(1.59, 4.04), respectively. According to receiver operating characteristic curves (ROC) curves, the cut-off value of sNfL to predict PSD was 111.4 pg/ml with an area under the curve (AUC) of 0.84(95% CI, 0.78-0.90) and with the highest sensitivity (61.8%) and specificity (95.4%).

CONCLUSIONS

In this study, elevated level of sNfL is associated with higher risk of 3-month depression in patients with ischemic stroke and makes early diagnoses of depression. The study needs replication to ensure the validity of our preliminary results.

Utility of Animal Models to Understand Human Alzheimer's Disease, Using the Mastermind Research Approach to Avoid Unnecessary Further Sacrifices of Animals

To diagnose and treat early-stage (preclinical) Alzheimer’s disease (AD) patients, we need body-fluid-based biomarkers that reflect the processes that occur in this stage, but current knowledge on associated processes is lacking. As human studies on (possible) onset and early-stage AD would be extremely expensive and time-consuming, we investigate the potential value of animal AD models to help to fill this knowledge gap. We provide a comprehensive overview of processes associated with AD pathogenesis and biomarkers, current knowledge on AD-related biomarkers derived from on human and animal brains and body fluids, comparisons of biomarkers obtained in human AD and frequently used animal AD models, and emerging body-fluid-based biomarkers. In human studies, amyloid beta (Aβ), hyperphosphorylated tau (P-tau), total tau (T-tau), neurogranin, SNAP-25, glial fibrillary acidic protein (GFAP), YKL-40, and especially neurofilament light (NfL) are frequently measured. In animal studies, the emphasis has been mostly on Aβ. Although a direct comparison between human (familial and sporadic) AD and (mostly genetic) animal AD models cannot be made, still, in brain, cerebrospinal fluid (CSF), and blood, a majority of similar trends are observed for human AD stage and animal AD model life stage. This indicates the potential value of animal AD models in understanding of the onset and early stage of AD. Moreover, animal studies can be smartly designed to provide mechanistic information on the interrelationships between the different AD processes in a longitudinal fashion and may also include the combinations of different conditions that may reflect comorbidities in human AD, according to the Mastermind Research approach.

Biomarker profiling beyond amyloid and tau: cerebrospinal fluid markers, hippocampal atrophy, and memory change in cognitively unimpaired older adults

Brain changes occurring in aging can be indexed by biomarkers. We used cluster analysis to identify subgroups of cognitively unimpaired individuals (n = 99, 64-93 years) with different profiles of the cerebrospinal fluid biomarkers beta amyloid 1-42 (Aβ42), phosphorylated tau (P-tau), total tau, chitinase-3-like protein 1 (YKL-40), fatty acid binding protein 3 (FABP3), and neurofilament light (NFL). Hippocampal volume and memory were assessed across multiple follow-up examinations covering up to 6.8 years. Clustering revealed one group (39%) with more pathological concentrations of all biomarkers, which could further be divided into one group (20%) characterized by tauopathy and high FABP3 and one (19%) by brain β-amyloidosis, high NFL, and slightly higher YKL-40. The clustering approach clearly outperformed classification based on Aβ42 and P-tau alone in prediction of memory decline, with the individuals with most tauopathy and FABP3 showing more memory decline, but not more hippocampal volume change. The results demonstrate that older adults can be classified based on biomarkers beyond amyloid and tau, with improved prediction of memory decline.

New fluid biomarkers tracking non-amyloid-β and non-tau pathology in Alzheimer's disease

Cerebrospinal fluid (CSF) biomarkers based on the core pathological proteins associated with Alzheimer’s disease (AD), i.e., amyloid-β (Aβ) and tau protein, are widely regarded as useful diagnostic biomarkers. However, a lack of biomarkers for monitoring the treatment response and indexing clinical severity has proven to be problematic in drug trials targeting Aβ. Therefore, new biomarkers are needed to track non-Aβ and non-tau pathology. Many proteins involved in the pathophysiological progression of AD have shown promise as new biomarkers. Neurodegeneration- and synapse-related biomarkers in CSF (e.g., neurofilament light polypeptide [NFL], neurogranin, and visinin-like protein 1) and blood (e.g., NFL) aid prediction of AD progress, as well as early diagnosis. Neuroinflammation, lipid dysmetabolism, and impaired protein clearance are considered important components of AD pathophysiology. Inflammation-related proteins in the CSF, such as progranulin, intercellular adhesion molecule 1, and chitinase-3-like protein 1 (YKL-40), are useful for the early detection of AD and can represent clinical severity. Several lipid metabolism-associated biomarkers and protein clearance-linked markers have also been suggested as candidate AD biomarkers. Combinations of subsets of new biomarkers enhance their utility in terms of broadly characterizing AD-associated pathological changes, thereby facilitating precise selection of susceptible patients and comprehensive monitoring of the treatment response. This approach could facilitate the development of effective treatments for AD.

Finding new biomarkers for Alzheimer’s disease (AD) may help in tracking disease progression and identifying optimal patient-specific treatments. Although useful markers are available for diagnosis of AD, they are unreliable for tracking disease progression. Looking for better ways to track disease progression, Sun Ah Park at the Ajou University School of Medicine, Suwon, South Korea, and coworkers have reviewed alternative AD markers. They report that several markers for axonal degeneration, synaptic loss, brain inflammation and lipid metabolism show promise for tracking AD. Some of these markers can be obtained from blood samples, which are minimally invasive to collect. Use of combinations of markers is especially promising for estimating a patient’s disease stage. These results will contribute to developing tailored treatments for this common cause of dementia.

Neurofilaments in disease: what do we know?

Neurofilaments are proteins selectively expressed in the cytoskeleton of neurons, and increased levels are a marker of damage. Elevated neurofilament levels can serve as a marker of ongoing disease activity as well as a tool to measure response to therapeutic intervention. The potential utility of neurofilaments has drastically increased as recent advances have made it possible to measure levels in both the cerebrospinal fluid and blood. There is mounting evidence that neurofilament light chain (NfL) and phosphorylated neurofilament heavy chain (NfH) are abnormal in a host of neurodegenerative diseases. In this review we examine how both of these proteins behave across diseases and what we know about how these biomarkers relate to in vivo white matter pathology and each other.

The Influence of Baseline Alzheimer's Disease Severity on Cognitive Decline and CSF Biomarkers in the NILVAD Trial

We examined the effects of a dihydropyridine calcium channel blocker nilvadipine with anti-inflammatory properties on cognition and cerebrospinal fluid (CSF) biomarkers by baseline Alzheimer's disease (AD) severity. Exploratory analyses were performed on the dataset (n = 497) of a phase III randomized placebo-controlled trial to examine the response to nilvadipine in AD subjects stratified by baseline AD severity into very mild (MMSE ≥ 25), mild (MMSE 20-24) and moderate AD (MMSE < 20). The outcome measures included total and subscale scores of the Alzheimer's Disease Assessment Scale Cognitive 12 (ADAS-Cog 12), the Clinical Dementia Rating Scale sum of boxes (CDR-sb) and the AD composite score (ADCOMS). Cerebrospinal fluid biomarkers Aβ38, Aβ40, Aβ42, neurofilament light chain (NFL), neurogranin, YKL-40, total tau and P181 tau (ptau) were measured in a subset of samples (n = 55). Regression analyses were adjusted for confounders to specifically examine the influence of nilvadipine and baseline AD severity on cognitive outcomes over 78-weeks. Compared to their respective placebo-controls, nilvadipine-treated, very mild AD subjects showed less decline, whereas moderate AD subjects showed a greater cognitive decline on the ADAS-Cog 12 test and the ADCOMS. A lower decline was observed after nilvadipine treatment for a composite memory trait in very mild AD subjects and a composite language trait in mild AD subjects. Cerebrospinal fluid Aβ42/Aβ40 ratios were increased in mild AD and decreased in moderate AD patients treated with nilvadipine, compared to their respective controls. Among moderate AD subjects, levels of ptau, total tau, neurogranin and YKL-40 increased in subjects treated with nilvadipine compared to placebo. These studies suggest that baseline AD severity influenced the treatment outcome in the NILVAD trial and that future clinical trials of nilvadipine should be restricted to mild and very mild AD patients.

Trial Registration: NCT02017340 Registered 20 December 2013, https://clinicaltrials.gov/ct2/show/NCT02017340

EUDRACT Reference Number 2012-002764-27 Registered 04 February 2013, https://www.clinicaltrialsregister.eu/ctr-search/search?query=2012-002764-27

Improved Differential Diagnosis of Alzheimer's Disease by Integrating ELISA and Mass Spectrometry-Based Cerebrospinal Fluid Biomarkers

Background:

Alzheimer’s disease (AD) is diagnosed based on a clinical evaluation as well as analyses of classical biomarkers: Aβ₄₂, total tau (t-tau), and phosphorylated tau (p-tau) in cerebrospinal fluid (CSF). Although the sensitivities and specificities of the classical biomarkers are fairly good for detection of AD, there is still a need to develop novel biochemical markers for early detection of AD.

Objective:

We explored if integration of novel proteins with classical biomarkers in CSF can better discriminate AD from non-AD subjects.

Methods:

We applied ELISA, mass spectrometry, and multivariate modeling to investigate classical biomarkers and the CSF proteome in subjects (n = 206) with 76 AD patients, 74 mild cognitive impairment (MCI) patients, 11 frontotemporal dementia (FTD) patients, and 45 non-dementia controls. The MCI patients were followed for 4–9 years and 21 of these converted to AD, whereas 53 remained stable.

Results:

By combining classical CSF biomarkers with twelve novel markers, the area of the ROC curves (AUROCS) of distinguishing AD and MCI/AD converters from non-AD were 93% and 96%, respectively. The FTDs and non-dementia controls were identified versus all other groups with AUROCS of 96% and 87%, respectively.

Conclusions:

Integration of new and classical CSF biomarkers in a model-based approach can improve the identification of AD, FTD, and non-dementia control subjects.

Cerebrospinal fluid neurofilament light concentration predicts brain atrophy and cognition in Alzheimer's disease

INTRODUCTION

This study assessed the utility of cerebrospinal fluid (CSF) neurofilament light (NfL) in Alzheimer's disease (AD) diagnosis, its association with amyloid and tau pathology, as well as its potential to predict brain atrophy, cognition, and amyloid accumulation.

METHODS

CSF NfL concentration was measured in 221 participants from the Australian Imaging, Biomarkers & Lifestyle Flagship Study of Ageing (AIBL).

RESULTS

CSF NfL levels as well as NfL/amyloid β (Aβ42) were significantly elevated in AD compared to healthy controls (HC; P < .001), and in mild cognitive impairment (MCI) compared to HC (P = .008 NfL; P < .001 NfL/Aβ42). CSF NfL and NfL/Aβ42 differentiated AD from HC with an area under the receiver operating characteristic (ROC) curve (AUC) of 0.84 and 0.90, respectively. CSF NfL and NfL/Aβ42 predicted cortical amyloid load, brain atrophy, and cognition.

DISCUSSION

CSF NfL is a biomarker of neurodegeneration, correlating with cognitive impairment and brain neuropathology.

Plasma neurofilament light as a longitudinal biomarker of neurodegeneration in Alzheimer’s disease

Objective:

To examine whether plasma neurofilament light (NFL) might be a potential longitudinal biomarker for Alzheimer’s disease (AD).

Methods:

A total of 835 individuals from the Alzheimer’s Disease Neuroimaging Initiative were involved. Correlations of the rate of change in plasma NFL with cerebrospinal fluid biomarkers, cognition, and brain structure were investigated. Cox proportional hazards models were used to assess the associations between quartiles of plasma NFL and the risk of AD conversion.

Results:

Participants were further divided into β amyloid-positive (Aβ+) versus β amyloid-negative (Aβ−), resulting in five biomarker group combinations, which are CN Aβ−, CN Aβ+, MCI Aβ−, MCI Aβ+ and AD Aβ+. Plasma NFL concentration markedly increased in the five groups longitudinally ( p < 0.001) with the greatest rate of change in AD Aβ+ group. The rate of change in plasma NFL was associated with cognitive deficits and neuroimaging hallmarks of AD over time ( p < 0.005). Compared with the bottom quartile, the top quartile of change rate was associated with a 5.41-fold increased risk of AD (95% CI = 1.83−16.01) in the multivariate model.

Conclusion:

Our finding implies the potential of plasma NFL as a longitudinal noninvasive biomarker in AD.

Synaptic, axonal damage and inflammatory cerebrospinal fluid biomarkers in neurodegenerative dementias

INTRODUCTION

Synaptic damage, axonal neurodegeneration, and neuroinflammation are common features in Alzheimer's disease (AD), frontotemporal dementia (FTD), and Creutzfeldt-Jakob disease (CJD).

METHODS

Unicentric cohort of 353 participants included healthy control (HC) subjects, AD continuum stages, genetic AD and FTD, and FTD and CJD. We measured cerebrospinal fluid neurofilament light (NF-L), neurogranin (Ng), 14-3-3, and YKL-40 proteins.

RESULTS

Biomarkers showed differences in HC subjects versus AD, FTD, and CJD. Disease groups differed between them except AD versus FTD for YKL-40. Only NF-L differed between all stages within the AD continuum. AD and FTD symptomatic mutation carriers presented differences with respect to HC subjects. Applying the AT(N) system, 96% subjects were positive for neurodegeneration if 14-3-3 was used, 94% if NF-L was used, 62% if Ng was used, and 53% if YKL-40 was used.

DISCUSSION

Biomarkers of synapse and neurodegeneration differentiate HC subjects from neurodegenerative dementias and between AD, FTD, and CJD. NF-L and 14-3-3 performed similar to total tau when AT(N) system was applied.

Neurofilament Light Chain as a Biomarker, and Correlation with Magnetic Resonance Imaging in Diagnosis of CNS-Related Disorders

The search for diagnostic and prognostic biomarkers for neurodegenerative conditions is of high importance, since these disorders may present difficulties in differential diagnosis. Biomarkers with high sensitivity and specificity are required. Neurofilament light chain (NfL) is a unique biomarker related to axonal damage and neural cell death, which is elevated in a number of neurological disorders, and can be detected in cerebrospinal fluid (CSF), as well as blood, serum, or plasma samples. Although the NfL concentration in CSF is higher than that in blood, blood measurement may be easier in practice due to its lesser invasiveness, reproducibility, and convenience. Many studies have investigated NfL in both CSF and serum/plasma as a potential biomarker of neurodegenerative disorders. Neuroimaging biomarkers can also potentially improve detection of CNS-related disorders at an early stage. Magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI) are sensitive techniques to visualize neuroaxonal loss. Therefore, investigating the combination of NfL levels with indices extracted from MRI and DTI scans could potentially improve diagnosis of CNS-related disorders. This review summarizes the evidence for NfL being a reliable biomarker in the early detection and disease management in several CNS-related disorders. Moreover, we highlight the correlation between MRI and NfL and ask whether they can be combined.

Neurofilament Light Predicts Decline in Attention but Not Episodic Memory in Preclinical Alzheimer's Disease

BACKGROUND

Cerebrospinal fluid tau and neurofilament light (NfL) are two biomarkers of neurodegeneration in Alzheimer's disease. Previous reports have shown that the influence of tau on cognitive decline depends on levels of amyloid burden whereas NfL predicts decline independently of amyloid. Most studies use a global cognitive composite as the primary outcome, and it is unknown if critical cognitive domain scores are similarly sensitive to rates of decline due to neurodegeneration.

OBJECTIVE

To examine the unique contribution of amyloid, tau, and NfL to rates of cognitive decline in multiple cognitive composites in a cognitively healthy, middle-aged to older adult cohort.

METHODS

A total of 255 participants (55% female; mean age = 66.2 years, range = 42.5-86.7 years) completed CSF studies and serial cognitive assessments to measure global cognition, episodic memory, and attentional control. Linear mixed effects models were used to examine rates of change on each composite score as a function of baseline biomarker levels.

RESULTS

Total tau predicted decline in attention regardless of amyloid status, but the relationship to global cognition and episodic memory was dependent on amyloid, replicating prior literature. NfL predicted decline in attention and global cognition, but not memory, and this effect was independent of amyloid status.

CONCLUSIONS

These findings suggest that NfL can be used to monitor cognitive decline in aging and Alzheimer's disease and that an attentional control composite may be a better outcome for tracking general neurodegenerative effects on cognition.

CSF synaptic protein concentrations are raised in those with atypical Alzheimer's disease but not frontotemporal dementia

BACKGROUND

Increased CSF levels of a number of synaptic markers have been reported in Alzheimer's disease (AD), but little is known about their concentrations in frontotemporal dementia (FTD). We investigated this in three synaptic proteins, neurogranin, SNAP-25, and synaptotagmin-1.

METHODS

CSF samples were analysed from 66 patients with a disorder in the FTD spectrum and 19 healthy controls. Patients were stratified by their tau to Aβ42 ratio: those with a ratio of > 1 considered as having likely AD pathology, i.e. an atypical form of AD ('AD biomarker' group [n = 18]), and < 1 as likely FTD pathology ('FTD biomarker' group [n = 48]). A subgroup analysis compared those in the FTD group with likely tau (n = 7) and TDP-43 (n = 18) pathology. Concentrations of neurogranin were measured using two different ELISAs (Ng22 and Ng36), and concentrations of two SNAP-25 fragments (SNAP-25tot and SNAP-25aa40) and synaptotagmin-1 were measured via mass spectrometry.

RESULTS

The AD biomarker group had significantly higher concentrations of all synaptic proteins compared to controls except for synaptotagmin-1 where there was only a trend to increased levels-Ng22, AD mean 232.2 (standard deviation 138.9) pg/ml, controls 137.6 (95.9); Ng36, 225.5 (148.8) pg/ml, 130.0 (80.9); SNAP-25tot, 71.4 (27.9) pM, 53.5 (11.7); SNAP-25aa40, 14.0 (6.3), 7.9 (2.3) pM; and synaptotagmin-1, 287.7 (156.0) pM, 238.3 (71.4). All synaptic measures were significantly higher in the atypical AD group than the FTD biomarker group except for Ng36 where there was only a trend to increased levels-Ng22, 114.0 (117.5); Ng36, 171.1 (75.2); SNAP-25tot, 49.2 (16.7); SNAP-25aa40, 8.2 (3.4); and synaptotagmin-1, 197.1 (78.9). No markers were higher in the FTD biomarker group than controls. No significant differences were seen in the subgroup analysis, but there was a trend to increased levels in those with likely tau pathology.

CONCLUSIONS

No CSF synaptic proteins have been shown to be abnormal in those with likely FTD pathologically. Higher CSF synaptic protein concentrations of neurogranin, SNAP-25, and synaptotagmin-1 appear to be related to AD pathology.

Cerebrospinal fluid levels of neurogranin in Parkinsonian disorders

BACKGROUND

CSF concentration of neurogranin has been suggested as a biomarker for synapse dysfunction.

OBJECTIVES

To investigate CSF neurogranin in parkinsonian disorders compared to controls and Alzheimer's disease and the possible correlations between neurogranin and cognitive and motor impairment.

METHODS

We included 157 patients with PD, 29 with PD with dementia, 11 with dementia with Lewy bodies, 26 with MSA, 21 with PSP, 6 with corticobasal syndrome, 47 controls, and 124 with Alzheimer's disease. CSF neurogranin was measured using two enzyme-linked immunosorbent assays; from EUROIMMUN and the University of Gothenburg.

RESULTS

We found a strong correlation between CSF neurogranin-EI and CSF neurogranin-University of Gothenburg (R_s = 0.890; P < 0.001). Neurogranin was decreased in PD, PD with dementia, MSA, and PSP compared to controls and Alzheimer's disease. Neurogranin did not correlate with motor or cognitive impairment, longitudinal decline, or progression to dementia in PD.

CONCLUSIONS

CSF neurogranin is decreased in parkinsonian disorders compared to controls, emphasizing the importance of synaptic dysfunction in these disorders. © 2019 International Parkinson and Movement Disorder Society.

Synaptic biomarkers in CSF aid in diagnosis, correlate with cognition and predict progression in MCI and Alzheimer's disease

INTRODUCTION

Amyloid, Tau, and neurodegeneration biomarkers can stage Alzheimer's Disease (AD). Synaptic biomarkers may help track cognition.

METHODS

In cognitively normal controls, Mild Cognitive Impairment (MCI) and AD, we investigated CSF biomarkers in relation to cognitive measures and as predictors of cognitive and global decline.

RESULTS

There were 90 normal controls (mean age 73.0, 58% women), 57 MCI (mean age 74.3, 35% women), and 46 AD (mean age 70.7, 41% women). CSF Aβ1-42 and Neuronal Pentraxin 2 (NPTX2) were decreased, and CSF Tau, neurogranin, and SNAP25 increased in AD versus controls. Aβ1-42/Tau or NPTX2/Tau discriminated AD and controls best. NPTX2/Tau correlated strongly with cognition in AD and MCI and predicted a 2-3-year decline. We replicated findings in the ADNI cohort.

DISCUSSION

CSF synaptic biomarkers, particularly NPTX2, which regulates synaptic homeostasis, relate to cognition and predict progression in AD beyond Aβ1-42 and Tau. This is relevant for prognosis and clinical trials.

Cerebrospinal fluid and plasma biomarker trajectories with increasing amyloid deposition in Alzheimer's disease

Failures in Alzheimer's disease (AD) drug trials highlight the need to further explore disease mechanisms and alterations of biomarkers during the development of AD. Using cross-sectional data from 377 participants in the BioFINDER study, we examined seven cerebrospinal fluid (CSF) and six plasma biomarkers in relation to β-amyloid (Aβ) PET uptake to understand their evolution during AD. In CSF, Aβ42 changed first, closely followed by Aβ42/Aβ40, phosphorylated-tau (P-tau), and total-tau (T-tau). CSF neurogranin, YKL-40, and neurofilament light increased after the point of Aβ PET positivity. The findings were replicated using Aβ42, Aβ40, P-tau, and T-tau assays from five different manufacturers. Changes were seen approximately simultaneously for CSF and plasma biomarkers. Overall, plasma biomarkers had smaller dynamic ranges, except for CSF and plasma P-tau which were similar. In conclusion, using state-of-the-art biomarkers, we identified the first changes in Aβ, closely followed by soluble tau. Only after Aβ PET became abnormal, biomarkers of neuroinflammation, synaptic dysfunction, and neurodegeneration were altered. These findings lend in vivo support of the amyloid cascade hypotheses in humans.

Association of Cerebrospinal Fluid Neurofilament Light Protein With Risk of Mild Cognitive Impairment Among Individuals Without Cognitive Impairment

Importance

Accumulating data suggest that elevated cerebrospinal fluid (CSF) neurofilament light (NfL) and neurogranin (Ng) levels are associated with cognitive decline and may be useful markers of neurodegeneration. However, to our knowledge, previous studies have not assessed these CSF markers in the community, evaluated them with regards to risk of mild cognitive impairment (MCI), or compared their prognostic value with CSF total tau (T-tau) or phosphorylated tau (P-tau).

Objective

To determine (1) whether CSF NfL and Ng levels were associated with risk of MCI, (2) the effect size of these markers compared with CSF T-tau or P-tau for risk of MCI, and (3) whether CSF amyloid-β (Aβ42) modified these associations.

Design, Setting and Participants

The analyses included 648 participants without cognitive impairment who were enrolled into the prospective population-based Mayo Clinic Study of Aging between January 2004 and December 2015 with available CSF data and at least 1 follow-up visit. Participants were followed up for a median of 3.8 years (interquartile range, 2.6-5.4 years). The CSF NfL and Ng levels were measured using an in-house sandwich enzyme-linked immunosorbent assay. The CSF Aβ42, T-tau, and P-tau levels were measured with automated electrochemiluminescence immunoassays. Cox proportional hazards models, with age as the timescale, were used to assess the association between CSF NfL, Ng, Aβ42, T-tau, or P-tau with risk of MCI after adjusting for sex, education, apolipoprotein E genotype, and the Charlson comorbidity index. To examine CSF Aβ42 as an effect modifier, it was categorized into tertiles; the bottom tertile was defined as having elevated brain amyloid.

Main Outcomes and Measures

Risk of MCI.

Results

At baseline, the median age of the 648 participants without cognitive impairment was 72.3 years (range, 50.7-95.3 years) and 366 (56.5%) were men; 96 (14.8%) developed incident MCI. Compared with the bottom quartile, the top quartile of CSF NfL was associated with a 3.1-fold increased risk of MCI (hazard ratio, 3.13; 95% CI, 1.36-7.18) in multivariate models. Neither CSF T-tau, P-tau, nor Ng was associated with risk of MCI. There was no interaction between Aβ42 and CSF NfL for risk of MCI.

Conclusions and Relevance

Elevated CSF NfL levels but not CSF T-tau, P-tau or Ng are a risk factor for MCI in a community population and are independent of brain amyloid.

Comparison of variables associated with cerebrospinal fluid neurofilament, total-tau, and neurogranin

INTRODUCTION

Three cerebrospinal fluid (CSF) markers of neurodegeneration (N) (neurofilament light [NfL], total-tau [T-tau], and neurogranin [Ng]) have been proposed under the AT(N) scheme of the National Institute on Aging-Alzheimer's Association Research Framework.

METHODS

We examined, in a community-based population (N = 777, aged 50-95) (1) what variables were associated with each of the CSF (N) markers, and (2) whether the variables associated with each marker differed by increased brain amyloid. CSF T-tau was measured with an automated electrochemiluminescence Elecsys immunoassay; NfL and Ng were measured with in-house enzyme-linked immunosorbent assays.

RESULTS

Multiple variables were differentially associated with CSF NfL and T-tau levels, but not Ng. Most associations were attenuated after adjustment for age and sex. T-tau had the strongest association with cognition in the presence of amyloidosis, followed by Ng. Variables associations with NfL did not differ by amyloid status.

DISCUSSION

Understanding factors that influence CSF (N) markers will assist in the interpretation and utility of these markers in clinical practice.

Biomarker-guided clustering of Alzheimer's disease clinical syndromes

Alzheimer's disease (AD) neuropathology is extremely heterogeneous, and the evolution from preclinical to mild cognitive impairment until dementia is driven by interacting genetic/biological mechanisms not fully captured by current clinical/research criteria. We characterized the heterogeneous "construct" of AD through a cerebrospinal fluid biomarker-guided stratification approach. We analyzed 5 validated pathophysiological cerebrospinal fluid biomarkers (Aβ_1-42, t-tau, p-tau₁₈₁, NFL, YKL-40) in 113 participants (healthy controls [N = 20], subjective memory complainers [N = 36], mild cognitive impairment [N = 20], and AD dementia [N = 37], age: 66.7 ± 10.4, 70.4 ± 7.7, 71.7 ± 8.4, 76.2 ± 3.5 years [mean ± SD], respectively) using Density-Based Spatial Clustering of Applications with Noise, which does not require a priori determination of the number of clusters. We found 5 distinct clusters (sizes: N = 38, 16, 24, 14, and 21) whose composition was independent of phenotypical groups. Two clusters showed biomarker profiles linked to neurodegenerative processes not associated with classical AD-related pathophysiology. One cluster was characterized by the neuroinflammation biomarker YKL-40. Combining nonlinear data aggregation with informative biomarkers can generate novel patient strata which are representative of cellular/molecular pathophysiology and may aid in predicting disease evolution and mechanistic drug response.

Potential Fluid Biomarkers for the Diagnosis of Mild Cognitive Impairment

Mild cognitive impairment (MCI) is characterized by a level of cognitive impairment that is lower than normal for a person’s age, but a higher function than that that observed in a demented person. MCI represents a transitional state between normal aging and dementia disorders, especially Alzheimer’s disease (AD). Much effort has been made towards determining the prognosis of a person with MCI who will convert to AD. It is now clear that cerebrospinal fluid (CSF) levels of Aβ40, Aβ42, total tau and phosphorylated tau are useful for predicting the risk of progression from MCI to AD. This review highlights the advantages of the current blood-based biomarkers in MCI, and discusses some of these challenges, with an emphasis on recent studies to provide an overview of the current state of MCI.

Neurofilament light chain as a biomarker in neurological disorders

In the management of neurological diseases, the identification and quantification of axonal damage could allow for the improvement of diagnostic accuracy and prognostic assessment. Neurofilament light chain (NfL) is a neuronal cytoplasmic protein highly expressed in large calibre myelinated axons. Its levels increase in cerebrospinal fluid (CSF) and blood proportionally to the degree of axonal damage in a variety of neurological disorders, including inflammatory, neurodegenerative, traumatic and cerebrovascular diseases. New immunoassays able to detect biomarkers at ultralow levels have allowed for the measurement of NfL in blood, thus making it possible to easily and repeatedly measure NfL for monitoring diseases' courses. Evidence that both CSF and blood NfL may serve as diagnostic, prognostic and monitoring biomarkers in neurological diseases is progressively increasing, and NfL is one of the most promising biomarkers to be used in clinical and research setting in the next future. Here we review the most important results on CSF and blood NfL and we discuss its potential applications and future directions.

CSF neurogranin as a neuronal damage marker in CJD: a comparative study with AD

OBJECTIVE

To investigate whether cerebrospinal fluid (CSF) neurogranin concentrations are altered in sporadic Creutzfeldt-Jakob disease (CJD), comparatively with Alzheimer's disease (AD), and associated with neuronal degeneration in brain tissue.

METHODS

CSF neurogranin, total tau, neurofilament light (NFL) and 14-3-3 protein were measured in neurological controls (NCs, n=64), AD (n=46) and CJD (n=81). The accuracy of neurogranin discriminating the three diagnostic groups was evaluated. Correlations between neurogranin and neurodegeneration biomarkers, demographic, genetic and clinical data were assessed. Additionally, neurogranin expression in postmortem brain tissue was studied.

RESULTS

Compared with NC, CSF neurogranin concentrations were increased in CJD (4.75 times of NC; p<0.001, area under curve (AUC), 0.96 (95% CI 0.93 to 0.99) and AD (1.94 times of NC; p<0.01, AUC 0.73, 95% CI 0.62 to 0.82), and were able to differentiate CJD from AD (p<0.001, AUC 0.85, 95% CI 0.78 to 0.92). CSF tau was increased in CJD (41 times of NC) and in AD (3.1 times of NC), both at p<0.001. In CJD, neurogranin positively correlated with tau (r=0.55, p<0.001) and was higher in 14-3-3-positivity (p<0.05), but showed no association with NFL (r=0.08, p=0.46). CJD-MM1/MV1 cases displayed higher neurogranin levels than VV2 cases. Neurogranin was increased at early CJD disease stages and was a good prognostic marker of survival time in CJD. In brain tissue, neurogranin was detected in the cytoplasm, membrane and postsynaptic density fractions of neurons, with reduced levels in AD, and more significantly in CJD, where they correlated with synaptic and axonal markers.

CONCLUSIONS

Neurogranin is a new biomarker of prion pathogenesis with diagnostic and prognostic abilities, which reflects the degree of neuronal damage in brain tissue in a CJD subtype manner.