Alzheimer's Disease Cerebrospinal Fluid Research Articles

The cerebrospinal fluid soluble TREM‐1 concentration in Alzheimer’s Disease (AD) and Mild Cognitive Impairment (MCI)

AbstractBackgroundThe most prevalent form of dementia in the world is Alzheimer Disease (AD), a common neurodegenerative condition. Amyloid peptides, phosphorylated tau proteins, and neuroinflammation are the disease’s hallmarks. Finding new biomarkers that can assist in early AD detection is crucial due to the late appearance of the disease symptoms. Triggering receptor expressed on myeloid cell 1 (TREM‐1) is hypothesized that may contribute to the development of AD by causing neuroinflammation. Due of its significance in inflammatory responses, it has been regarded as a promising biomarker. Literature data indicate that TREM‐1 could be potential biomarker of AD severity. Therefore the purpose of our research was to measure the concentration of soluble TREM‐1 in cerebrospinal fluid of AD and MCI patients and non‐demented controls and compare it with classical AD biomarkers.MethodThe concentrations of TREM‐1 were measured in cerebrospinal fluid (CSF) of 20 AD patients and 15 MCI patients as well as 11 non‐demented controls using multiplexing method. Classical biomarkers, such as Aβ‐42, Aβ‐42/Aβ‐40, tau and pTau181 were assessed by immunoenzyme assays.ResultTREM‐1 concentrations were significantly higher in AD and MCI patients in comparison to non‐demented controls. Moreover, in MCI patients, the levels of this protein were significantly higher than in AD patients. Additionally, increased CSF levels of TREM‐1 correlated positively with Tau, pTau181 in the whole study group.ConclusionFindings of our research suggest that TREM‐1 could be early indicator of AD pathology. However, follow‐up studies on larger study group are needed.

Single domain antibodies as promising tools for the selective detection and neutralization of neurotoxic Aβ42 oligomers in the cerebrospinal fluid of Alzheimer’s disease patients

AbstractBackgroundExtracellular amyloid β (Aβ) plaques and intracellular neurofibrillary tangles of the hyperphosphorylated tau protein are the main hallmarks of Alzheimer’s disease (AD). Small, soluble oligomers, rather than mature fibrils, are the major neurotoxic agents. The heterogeneous structures and the transient nature of these oligomers make their isolation and characterization very challenging. Single domain Abs (sdAbs), composed only of a variable domain of the heavy chain with high specificity and affinity, appear as promising tools for an early diagnosis and therapy for AD.MethodsPerforming an in vitro and in vivo screening of different sdAbs, we selected those targeting Aβ42 oligomers or fibrils with high specificity using dot‐blot, ELISA assay and the super resolution stimulated emission depletion (STED) microscopy. The potential of sdAbs was also investigated in preventing Aβ42 oligomer‐induced cytotoxicity in cultured neuronal cells. Then, the sdAbs were used to selectively detect Aβ42 species in the cerebrospinal fluid (CSF) of AD patients and control subjects and to neutralize their associated harmful effects following cell exposure to CSF samples.ResultssdAbs can selectively detect Aβ42 oligomers or fibrils both in vitro and in cultured cells, preventing the neurotoxicity induced by small oligomers. Moreover, sdAbs can significantly identify Aβ42 oligomers in the CSF of AD patients counteracting their induced toxicity in our cell models.ConclusionsAll these data provide a solid foundation for the development of sdAbs‐based immunodiagnostic tools that can selectively detect toxic aggregates in human body fluids for an early differential diagnosis of protein deposition diseases, such as AD. Furthermore, our results contribute to the improvement of the current therapeutic approaches against AD.The study was supported by Airalzh (AGYR 2020 to R.C.).

Blood proteomics to identify AD CSF molecular subtypes

AbstractBackgroundWe identified three distinct molecular subtypes in Alzheimer’s disease (AD) using cerebrospinal fluid (CSF) proteomics: one subtype was characterised by neuronal hyperplasticity with increased amyloid metabolism, the second subtype was characterised by innate immune activation and the third subtype by a disrupted blood‐brain barrier. Each subtype will likely need specific treatment, but for patient selection CSF proteomics might be impractical. Here we investigated if AD molecular subtypes can also be detected in blood.MethodWe selected from EMIF‐AD MBD 149 individuals with AD across the clinical spectrum who had plasma proteomics as well as a CSF subtype definition available. We compared CSF subtypes on plasma levels using general linear models. We selected a subset of proteins that best predicted AD subtype by trying a random forest classifier on 70% of the patient sample, and computed prediction accuracy statistics on patients that were left out.ResultPlasma levels of 407 (13%) proteins differed between AD subtypes (figure). The plasma profiles specific to AD subtype showed altered levels for corresponding molecular processes: The CSF hyperplasticity subtype (n = 53) showed low plasma levels of 76 proteins associated with neuron development and axon guidance. The CSF innate immune activation subtype (n = 48) showed low plasma levels of 142 proteins related to regulation of immune response. The CSF blood‐brain barrier subtype (n = 48) showed the low plasma levels of 189 proteins associated with blood vessel morphogenesis. The random forest could classify subtypes with an overall accuracy of 77% (range 70%‐85%), and the top 5 contributing proteins were FGF10, CTCF, TCN2, PLXNA1, and EMILIN3.ConclusionIt is possible to detect distinct AD CSF molecular subtypes in blood. The next step is to validate this in independent cohorts, and to test if subtypes are related to different treatment responses.

Plasma melatonin night‐time peak levels and 24‐hour area under the curve profile seem higher in AD patients with epileptiform activity than in those without

AbstractBackgroundPlasma melatonin levels drop in elderly, which might become more pronounced in Alzheimer’s disease (AD) as compared to controls.(1) Melatonin can serve as a potential biomarker for AD, given the inverse correlation between cerebrospinal fluid (CSF) melatonin levels and severity of neuropathology (Braak stages).(2) Due to suggested antiepileptic effects(6), melatonin can potentially slow down disease progression as epileptiform activity may contribute to AD disease progression.(3‐5). We here present a preliminary interim analysis of an ongoing study.Aims1. To evaluate melatonin’s potential as biomarker for AD by comparing blood melatonin levels between patients with mild cognitive impairment (MCI) and dementia due to AD and preclinical AD subjects.2. To study the link between melatonin levels and epileptiform activity in AD.MethodsAll subjects underwent a neuropsychological examination, and lumbar puncture for analysis of core AD CSF biomarkers or amyloid brain PET. Subjects belonging to the AD continuum (dementia [n = 7]; MCI [n = 4]; preclinical AD [n = 1]) were diagnosed according to the NIA‐AA research criteria. A subset of subjects (n = 6) underwent 50‐minute magnetoencephalography to detect epileptiform activity. Blood samples were taken multiple times during a 24‐hour period, in in‐hospital controlled circumstances, and were analysed by use of liquid chromatography‐mass spectrometry.ResultsAD patients with epileptiform activity (n = 2) tended to have a higher melatonin 24‐hour area under the curve (AUC) and peak concentration (AUC 517.9pg/ml.h [+/‐140.1pg/ml.h] versus 204.5pg/ml.h [+/‐115.5pg/ml.h]; peak 65.4pg/ml [+/‐14.6pg/ml] versus 25.8pg/ml [+/‐17.5pg/ml]) than AD patients without (n = 4) (p = 0.064 for both; MWU test). There was no statistical difference regarding the melatonin 24‐hour plasma AUC or peak levels between patients with dementia, MCI, preclinical AD subjects (p = 0.760 for both; Kruskall‐Wallis test). We have to interpret these data with caution since sample sizes are still small and more patients are being recruited.ConclusionOn the basis of very preliminary data, 24‐hour plasma melatonin profile and peak plasma melatonin concentration tended to be higher in AD patients with epileptiform activity than in those without. Whether this could be a potential compensatory mechanism against epileptiform activity in AD or whether melatonin could rather have pro‐epileptic effects, remains to be elucidated in future research.

Levels of nicastrin species are increased in Alzheimer’s disease cerebrospinal fluid

AbstractBackgroundPrevious studies demonstrated that presenilin‐1 (PS1), the active component of the intramembrane γ‐secretase complex, can be detected as soluble heteromeric aggregates in cerebrospinal fluid (CSF). The γ‐secretase components, APH‐1 (anterior pharynx‐defective 1) and PEN‐2 (presenilin enhancer 2), co‐exist within these CSF complexes, while nicastrin is not detected. Nicastrin plays a role in the complex regulation, and substrate recognition, being the unique γ‐secretase component that is a Type I, single‐pass transmembrane protein. Here, we aim to characterize and compare the levels of CSF nicastrin in Alzheimer’s disease (AD) and non‐AD control patients.MethodNicastrin levels were analyzed in the CSF by western blotting using antibodies against the ectodomain and the intracellular domain to identify the different species of the protein that are present in human CSF. Core AD CSF biomarkers (Aβ1‐42, T‐tau, and p‐Tau) were determined. We also assessed whether CSF nicastrin and PS1 are present in extracellular vesicles (EVs).ResultWe show that nicastrin is present in CSF as full‐length species of 130, 110, and 105 kDa. We demonstrated that nicastrin full‐length species are increased in AD patients (n = 21) in comparison with non‐AD controls (n = 21), and that the levels of the three species positively correlated with T‐tau and p‐Tau levels in AD patients. Nicastrin was also found to be present in EVs, different from PS1.ConclusionThe increased levels of nicastrin in the CSF of AD patients confirmed the potential alteration of γ‐secretase subunits during pathology progression. Further studies are required to evaluate whether these proteins could act as biomarkers to facilitate AD diagnosis and/or prognosis.

Neuroimaging Correlates of Alzheimer’s Disease biomarkers in a mid‐life, racially diverse high‐risk cohort

AbstractBackgroundClinicians and researchers utilize neuroimaging (NI) biomarkers of Alzheimer’s disease (AD) at an increasing rate. It is crucial that we determine whether these biomarkers generalize to underrepresented populations, particularly Black Americans (BAs), as they are 64% more likely as white individuals to develop AD. BAs may exhibit unique AD biomarker profiles across disease states, including NI biomarkers. Investigating biomarkers in at‐risk individuals may allow for early identification and intervention. Here we analyze comprehensive NI biomarkers including resting state fMRI, white matter lesions, and hippocampal volumes in conjunction with cerebrospinal fluid (CSF) markers in a midlife, racially diverse, cognitively normal cohort with a parental history of AD.MethodData included 57 cognitively normal, middle‐aged individuals, 14 BAs and 43 white. CSF was acquired via lumbar puncture to determine CSF t‐tau and Aβ1‐42 concentrations. Using resting state fMRI data, we analyzed default mode network connectivity between the posterior cingulate & precuneus, parrahippocampal gyrus (PHG), temporal pole, hippocampus, and lateral temporal cortex. We obtained regional WMH data from FLAIR images using an in‐house algorithm, and hippocampal volumes from Freesurfer. In our multivariate model, outcome variables were connectivity values, regional WMH and hippocampal volumes, with race and CSF t‐tau and Aβ1‐42 as our independent variables with a race X CSF interaction term.ResultWe identified a significant race X t‐tau and race X Aβ1‐42 interaction term for temporal and parietal WMH volumes and connectivity between PHG and temporal pole. Higher AD CSF biomarkers negatively correlated with brain connectivity (p = 0.01), and positively with WMH volume (p<0.001) in BAs.ConclusionWe extend our previous work to a middle‐aged cohort to show that DMN connectivity may be a predictor of AD risk in middle‐age, particularly for BAs, and that BAs may exhibit earlier vulnerability to vascular lesions. We support previous work that the temporal lobe is the first region to experience AD‐related connectivity changes, and that WMHs may predispose this region to AD vulnerability. This study emphasizes the need for recruitment of diverse cohorts in NI studies of AD.

Area Deprivation Index is associated with biomarkers of inflammation cross‐sectionally and longitudinally over a 9‐year follow‐up period

AbstractBackgroundLiving in a socioeconomically disadvantaged neighborhood has a negative impact on health outcomes, including increased risk for Alzheimer’s disease (AD). The biological mechanisms underlying this risk are poorly understood. We examined how neighborhood disadvantage relates to core AD pathology, neurodegeneration, and inflammatory biomarkers in community‐dwelling older adultsMethodVanderbilt Memory and Aging Project participants (n = 327, 73±8 years, 41% female) underwent fasting blood and cerebrospinal fluid (CSF) acquisition serially over a 9‐year follow‐up period (mean follow‐up = 5.8 years). Area Deprivation Index (ADI), representing neighborhood disadvantage, was quantified at baseline based on 17 components [e.g., housing, income, education, and household characteristics (Kind & Buckingham, 2018)]. Ordinary least squares regressions cross‐sectionally related ADI to plasma and CSF biomarkers adjusting for age, sex, race/ethnicity, education, modified Framingham Stroke Risk Profile score, apolipoprotein E‐e4 status, and cognitive status. Linear mixed‐effects regression models related baseline ADI to longitudinal biomarkers with identical baseline covariates plus follow‐up time. Outcomes included CSF chitinase‐3‐like protein 1 (YKL‐40), CSF soluble triggering receptor expressed on myeloid cells 2 (sTREM2), CSF amyloid‐b40 (Ab40), CSF amyloid‐b42 (Ab42), CSF Ab40/Ab42 ratio, CSF tau, CSF phosphorylated tau (ptau), plasma high sensitivity C‐reactive protein (CRP), and plasma and CSF neurofilament light chain (NfL).ResultOn average, the sample was from relatively less disadvantaged neighborhoods (ADI national decile = 35.4±25.0, range = 1‐98). Greater neighborhood disadvantage at study entry was cross‐sectionally associated with elevated CSF YKL‐40 (β = ‐0.733, p = 0.003), sTREM2 (β = 19.74, p = 0.04), Aβ40 (β = 35.96, p = 0.01), tau (β = 2.31, p = 0.02), and ptau (β = 0.33, p = 0.03). Greater neighborhood disadvantage at study entry related to longitudinal increases in CRP (β = 0.012, p<0.001) and decreases in plasma NfL (β = ‐0.025, p = 0.04) over the follow‐up period.ConclusionAmong community‐dwelling older adults, greater neighborhood disadvantage was associated with elevated inflammatory and AD CSF biomarkers cross‐sectionally, and longitudinal increases in a non‐specific inflammatory blood biomarker. Collectively, findings suggest that neighborhood disadvantage confers immediate risk for systemic neuroinflammation and AD and future risk for non‐specific inflammation, providing valuable evidence of a sociobiological mechanism underlying health disparities in aging adults based on geographic location. Funding. R01‐AG034962, K24‐AG046373, T32‐AG058524, P20‐AG068082

Predictive value for cerebrospinal fluid Alzheimer’s disease profile of different measures of verbal episodic memory in patients with mild cognitive impairment

AbstractBackgroundEpisodic memory deficits represent the typical manifestation of prodromal Alzheimer’s disease (AD), namely amnestic Mild Cognitive Impairment (a‐MCI). Current neuropsychological criteria for MCI recommend the use of at least two measures for each cognitive domain. Rey Auditory Verbal Learning Test (RAVLT) and Logical Memory (LM) are two widely used verbal episodic memory measures. Our aim was to investigate the value of these measures in predicting cerebrospinal fluid (CSF) AD biomarkers positivity in a retrospective fully characterized consecutive MCI cohort.MethodOne‐hundred and six MCI patients were included. All of them underwent a comprehensive neuropsychological assessment including RAVLT (sub‐measures: RAVLT‐imm, RAVLT‐del, RAVLT‐false_recognitions) and LM. All patients underwent lumbar puncture for the analysis of CSF core AD biomarkers (Aβ42/Aβ40 ratio, phospho‐tau, total tau). By applying the A/T/(N) classification model, patients were classified as AD (A+T+, MCI‐AD, n. 62) and non‐AD (A‐T*, MCI, n. 44). Pearson’s r correlation coefficient was used to assess the relationship of RAVLT and LM sub‐scores with diagnosis. WALD logistic regression model was used to find which memory sub‐measures show the best predictive value on biomarkers positivity. To evaluate the discriminatory power of different sub‐measures for CSF AD profile, receiver‐operating characteristic (ROC) curves were generated.ResultWith respect to non‐AD MCI, MCI‐AD patients showed worse scores on all RAVLT and LM sub‐measures. RAVLT‐del could predict both positivity of each biomarker (p<0.01) and CSF AD‐like profile (p<0.01). The combination of RAVLT‐del with other measures (RAVLT‐imm+RAVLT‐false_recognition+LM) discriminated these groups (AUC: 0.76, 95% CI: 0.67‐0‐85) with a sensitivity of 0.74 and a specificity of 0.66.ConclusionOur study shows that the combination of all RAVLT memory sub‐measures and LM reaches the higher diagnostic accuracy in discriminating non‐AD MCI from MCI‐AD patients. Since RAVLT and LM measure different aspects of verbal episodic memory, they should be considered as complementary, rather than interchangeable, tasks. Our findings support the use of different memory measures in the neuropsychological assessment of MCI patients.

Memory performance mediates subjective sleep quality associations with cerebrospinal fluid Alzheimer's disease biomarker levels and hippocampal volume among individuals with mild cognitive symptoms.

Sleep disturbances are prevalent in Alzheimer's disease (AD), affecting individuals during its early stages. We investigated associations between subjective sleep measures and cerebrospinal fluid (CSF) biomarkers of AD in adults with mild cognitive symptoms from the European Prevention of Alzheimer's Dementia Longitudinal Cohort Study, considering the influence of memory performance. A total of 442 participants aged >50 years with a Clinical Dementia Rating (CDR) score of 0.5 completed the Pittsburgh Sleep Quality Index questionnaire and underwent neuropsychological assessment, magnetic resonance imaging acquisition, and CSF sampling. We analysed the relationship of sleep quality with CSF AD biomarkers and cognitive performance in separated multivariate linear regression models, adjusting for covariates. Poorer cross-sectional sleep quality was associated with lower CSF levels of phosphorylated tau and total tau alongside better immediate and delayed memory performance. After adjustment for delayed memory scores, associations between CSF biomarkers and sleep quality became non-significant, and further analysis revealed that memory performance mediated this relationship. In post hoc analyses, poorer subjective sleep quality was associated with lesser hippocampal atrophy, with memory performance also mediating this association. In conclusion, worse subjective sleep quality is associated with less altered AD biomarkers in adults with mild cognitive symptoms (CDR score 0.5). These results could be explained by a systematic recall bias affecting subjective sleep assessment in individuals with incipient memory impairment. Caution should therefore be exercised when interpreting subjective sleep quality measures in memory-impaired populations, emphasising the importance of complementing subjective measures with objective assessments.

Understanding the Episodic Memory and Executive Functioning Axis Impairment in MCI Patients: A Multicenter Study in Comparison with CSF Biomarkers.

This study aimed to explore the association between a verbal learning task that evaluates the potential mutual dependency between memory and executive functions (i.e., the Test of Memory Strategies, TMS) and cerebrospinal fluid (CSF) Alzheimer's Disease (AD) biomarkers. A sample of 47 mild cognitive impairment (MCI) participants from Poland and Spain were classified according to the Erlangen Score Diagnostic Algorithm (ESA) into CSF- (n = 16) and CSF+ (n = 31) groups. Correlation analyses between TMS word-list conditions and CSF biomarkers were conducted. Additionally, an analysis of covariance was performed to define the effect on ESA classification in the sample, using as a covariable the country of origin of the participants. Significant associations between the TMS-3 condition and Aβ42, t-tau, and p-tau were observed for the whole sample. In addition, the CSF- participants obtained higher cognitive performance in TMS-3 compared to the CSF+ group. This outcome persisted if the groups were based on Aβ42 scores, but not t-tau or p-tau values. These findings could indicate that poor performance on verbal learning tests may be affected by executive dysfunctions. Therefore, future intervention plans focused on training executive functions would be of interest to improve the ability of MCI patients to encode and organize information.

Montreal Cognitive Assessment in Mild Cognitive Impairment: Relationship with Cerebrospinal Fluid Biomarkers and Conversion to Dementia.

Mild cognitive impairment (MCI) is considered a prodromal state of dementia. Abnormal values of cerebrospinal fluid Alzheimer's disease biomarkers (CSF-AD-b) have been associated with a higher risk of conversion to dementia (due to Alzheimer's disease), but studies evaluating the ability of Montreal Cognitive Assessment (MoCA) in this task are lacking. This study aims to investigate the relationship between MoCA and CSF-AD-b, as well as the ability of those tools to predict conversion to dementia. Taking advantage of our MCI cohort with biological characterization on longitudinal follow-up (180 patients followed for 62.6 months during which 41.3% converted), we computed MoCA and MMSE z-scores, using Portuguese normative data. The performance in MoCA z-score was correlated with CSF-AD-b and the relative time to conversion and risk according to baseline characteristics were analyzed using Kaplan-Meier analysis and Cox regression models. MoCA z-scores were correlated with Aβ42 (p = 0.026), t-tau (p = 0.033), and p-tau (p = 0.01). Impaired MMSE (p < 0.001) and MoCA z-scores (p = 0.019), decreased Aβ42 (p < 0.001) and increased t-tau (p < 0.001) and p-tau (p < 0.001) were associated with shorter estimated time of conversion. Aβ42 (p < 0.001) and MMSE z-scores (p = 0.029) were independent predictors of conversion. For those with at least 9 years of education, MoCA z-score (p = 0.004) (but not MMSE) was an independent predictor of conversion as well as Aβ42. This study confirms the role of CSF-AD-b, namely Aβ42, in predicting conversion from MCI to dementia and suggests the utility of MoCA in predicting conversion in highly educated subjects, supporting its use in the evaluation of MCI patients.

Changes of tRNA-Derived Fragments by Alzheimer's Disease in Cerebrospinal Fluid and Blood Serum.

Alzheimer's disease (AD) is the most common type of dementia, affecting individuals over 65. AD is also a multifactorial disease, with disease mechanisms incompletely characterized, and disease-modifying therapies are marginally effective. Biomarker signatures may shed light on the diagnosis, disease mechanisms, and the development of therapeutic targets. tRNA-derived RNA fragments (tRFs), a family of recently discovered small non-coding RNAs, have been found to be significantly enhanced in human AD hippocampus tissues. However, whether tRFs change in body fluids is unknown. To investigate whether tRFs in body fluids are impacted by AD. We first used T4 polynucleotide kinase-RNA-seq, a modified next-generation sequencing technique, to identify detectable tRFs in human cerebrospinal fluid and serum samples. The detectable tRFs were then compared in these fluids from control, AD, and mild cognitive impairment patients using tRF qRT-PCR. The stability of tRFs in serum was also investigated by checking the change in tRFs in response to protein digestion or exosome lysis. Among various tRFs, tRF5-ProAGG seemed to be impacted by AD in both cerebrospinal fluid and serum. AD-impacted serum tRF5-ProAGG showed a correlation with the AD stage. Putative targets of tRF5-ProAGG in the hippocampus were also predicted by a computational algorithm, with some targets being validated experimentally and one of them being in a negative correlation with tRF5-ProAGG even using a small size of samples. tRF5-ProAGG showed the potential as an AD biomarker and may play a role in disease progression.

96 The Proportion of Patients with Cerebrospinal Fluid Biomarkers Consistent with Alzheimer’s Disease in a Cohort with Suspected Normal Pressure Hydrocephalus

Objective:Normal pressure hydrocephalus (NPH) is characterized by pathologically enlarged ventricles without elevated cerebrospinal fluid (CSF) pressure along with a triad of clinical symptoms including gait disturbances, urinary incontinence, and cognitive impairment. NPH is evaluated with lumbar drain trials (LDTs) where CSF is removed over several days to determine if patients would benefit from ventricular shunting. Candidate selection and success for these surgeries remains challenging because other diseases such as Alzheimer’s disease (AD) share common features with NPH in cognitive impairment and enlarged ventricles. Prior research has found that 20%-40% of presumed NPH cases have AD pathology as determined by brain biopsy or autopsy. CSF biomarkers of AD can be altered in NPH and are not always conclusive, complicating the interpretation of results when formulating diagnoses and prognoses. Studies to refine the analyses of AD CSF biomarkers in NPH are needed. We aimed to examine the frequency of CSF biomarker results among patients presenting for NPH evaluations with LDTs.Participants and Methods:62 patients presented for LDTs upon physician recommendations. CSF specimens were sent to Mayo Clinic Laboratories for Alzheimer Disease Evaluation (ADEVL) that utilizes Elecsys (Lenexa, KS) CSF electrochemiluminescence immunoassays (Roche Diagnostics, Basel, Switzerland) to measure levels of amyloid-beta 42 (Aβ42), total tau (t-tau), and phosphorylatedtau (p-tau), and p-tau:Aβ42 ratio. Results were classified based on interpretation through the Amyloid/Tau/Neurodegeneration (ATN) framework1: 1) AD - biomarker profile consistent with AD pathologic change, 2) non-AD profile - biomarker levels normal or inconsistent with AD pathologic change, or 3) indeterminate - biomarkers were incongruous with only one or two abnormal levels of Aβ42, t-tau, p-tau, or ptau: Aβ42. Indeterminate cases may represent altered protein levels due to CSF dynamics or AD-related pathologic change. In reviewing recent research on CSF dynamics and AD biomarkers in NPH2 a p-tau threshold of 15 pg/mL was derived and implemented such that cases with Aß42 &lt;=1026 pg/mL and p-tau &lt;15 pg/mL were designated as suspected non-AD, and those with Aß42 &lt;=1026 pg/mL and p-tau &gt;15 pg/mL were designated suspected AD.Results:Of the 62 LDT cases, 12 (19.35%) were classified as AD, 31 (50%) were indeterminate and 22 (35.48%) were non-AD. Of the 31 indeterminate cases, 21 (33.87% of the overall sample) were suspected non-AD and 7 (11.29% of the full sample) were categorized as suspected AD.Conclusions:Our findings show that 20%-30% of patients presenting for LDT showed evidence for AD-type pathologic change, consistent with prior reports of AD pathology in cases of possible NPH. Half of all LDT cases had indeterminate AD CSF biomarker results, the interpretations of which were confounded by the potential alterations of CSF biomarkers levels due to NPH independent of AD. Our findings emphasize the need to establish better approaches to interpreting CSF AD biomarkers in evaluating NPH. Future research should examine the discriminative utility of CSF AD biomarkers and the selected p-tau threshold in indeterminate cases for predicting response to LDT and shunting.

Agreement of cerebrospinal fluid biomarkers and amyloid-PET in a multicenter study.

Core Alzheimer's disease (AD) cerebrospinal fluid (CSF) biomarkers have shown incomplete agreement with amyloid-positron emission tomography (PET). Our goal was to analyze the agreement between AD CSF biomarkers and amyloid-PET in a multicenter study. Retrospective multicenter study (5 centers). Participants who underwent both CSF biomarkers and amyloid-PET scan within 18months were included. Clinical diagnoses were made according to latest diagnostic criteria by the attending clinicians. CSF Amyloid Beta1-42 (Aβ1-42, A), phosphorliated tau 181 (pTau181, T) and total tau (tTau, N) biomarkers were considered normal (-) or abnormal ( +) according to cutoffs of each center. Amyloid-PET was visually classified as positive/negative. Agreement between CSF biomarkers and amyloid-PET was analyzed by overall percent agreement (OPA). 236 participants were included (mean age 67.9years (SD 9.1), MMSE score 24.5 (SD 4.1)). Diagnoses were mild cognitive impairment or dementia due to AD (49%), Lewy body dementia (22%), frontotemporal dementia (10%) and others (19%). Mean time between tests was 5.1months (SD 4.1). OPA between single CSF biomarkers and amyloid-PET was 74% for Aβ1-42, 75% for pTau181, 73% for tTau. The use of biomarker ratios improved OPA: 87% for Aβ1-42/Aβ1-40 (n = 155), 88% for pTau181/Aβ1-42 (n = 94) and 82% for tTau/Aβ1-42 (n = 160). A + T + N + cases showed the highest agreement between CSF biomarkers and amyloid-PET (96%), followed by A-T-N- cases (89%). Aβ1-42/Aβ1-40 was a better marker of cerebral amyloid deposition, as identified by amyloid tracers, than Aβ1-42 alone. Combined biomarkers in CSF predicted amyloid-PET result better than single biomarkers.

Cerebrospinal Fluid Alzheimer's Disease Biomarker Patterns of Change Prior to the Onset of Mild Cognitive Impairment.

Cerebrospinal fluid (CSF) biomarkers of Alzheimer's disease (AD) are altered many years before the onset of clinical symptoms of mild cognitive impairment (MCI). Incorporating clinical symptom onset time into biomarker modeling may enhance our understanding of changes preceding MCI. Using a new analytical approach, we examined patterns of biomarker change prior to MCI symptom onset among individuals who progressed from normal cognition to MCI, stratified based on the age of symptom onset. We also analyzed biomarker patterns of change among participants who remained cognitively normal, and examined potential modifiers of biomarker trajectories, including demographics and apolipoprotein E (APOE) status. Analyses included 93 participants who progressed from normal cognition to MCI and 186 participants who remained cognitively normal, over an average follow-up period of 16.2 years. CSF biomarkers, including Aβ42, Aβ40, total tau (t-tau), and phosphorylated tau181 (p-tau181), were measured using the fully automated Lumipulse assays. Among participants who progressed to MCI, Aβ42/Aβ40 decreased, and t-tau and p-tau181 increased. For participants who did not progress to MCI, CSF biomarkers showed relatively stable patterns. In both progressors and non-progressors, APOE4 carriers showed lower Aβ 42/Aβ40 levels (compared to non-carriers) at each point of the mean curves. Among non-progressors, APOE4 carriers had higher levels of p-tau181, p-tau181/(Aβ 42/Aβ40), and t-tau/(Aβ 42/Aβ 40). Additionally, among those who did not progress, female sex was associated with higher levels of t-tau, p-tau181, t-tau/(Aβ 42/Aβ 40), and p-tau181/(Aβ 42/Aβ 40). These findings suggest that this analytic approach may provide additional insights into biomarker changes during early phases of AD.

The Underestimated Relevance of Alzheimer's Disease Copathology in Amyotrophic Lateral Sclerosis.

Concomitant Alzheimer's disease (AD) pathology can be observed in approximately 10-15% of cases with amyotrophic lateral sclerosis (ALS). ALS-AD patients have a higher prevalence of amnestic cognitive disturbances, which may often precede motor symptoms. Cerebrospinal fluid (CSF) AD core biomarkers usually show no or slightly significant changes in ALS, whereas blood phosphorylated tau protein might be increased independently from AD copathology. Neurofilament proteins are consistently elevated in CSF and blood of ALS, but have been poorly investigated in ALS-AD. All these issues should be taken into account when using fluid biomarkers as inclusion criteria or secondary endpoints in clinical trials.

A microglial activity state biomarker panel differentiates FTD-granulin and Alzheimer’s disease patients from controls

BackgroundWith the emergence of microglia-modulating therapies there is an urgent need for reliable biomarkers to evaluate microglial activation states.MethodsUsing mouse models and human induced pluripotent stem cell-derived microglia (hiMGL), genetically modified to yield the most opposite homeostatic (TREM2-knockout) and disease-associated (GRN-knockout) states, we identified microglia activity-dependent markers. Non-targeted mass spectrometry was used to identify proteomic changes in microglia and cerebrospinal fluid (CSF) of Grn- and Trem2-knockout mice. Additionally, we analyzed the proteome of GRN- and TREM2-knockout hiMGL and their conditioned media. Candidate marker proteins were tested in two independent patient cohorts, the ALLFTD cohort (GRN mutation carriers versus non-carriers), as well as the proteomic data set available from the EMIF-AD MBD study.ResultsWe identified proteomic changes between the opposite activation states in mouse microglia and CSF, as well as in hiMGL cell lysates and conditioned media. For further verification, we analyzed the CSF proteome of heterozygous GRN mutation carriers suffering from frontotemporal dementia (FTD). We identified a panel of six proteins (FABP3, MDH1, GDI1, CAPG, CD44, GPNMB) as potential indicators for microglial activation. Moreover, we confirmed three of these proteins (FABP3, GDI1, MDH1) to be significantly elevated in the CSF of Alzheimer’s (AD) patients. Remarkably, each of these markers differentiated amyloid-positive cases with mild cognitive impairment (MCI) from amyloid-negative individuals.ConclusionsThe identified candidate proteins reflect microglia activity and may be relevant for monitoring the microglial response in clinical practice and clinical trials modulating microglial activity and amyloid deposition. Moreover, the finding that three of these markers differentiate amyloid-positive from amyloid-negative MCI cases in the AD cohort suggests that these proteins associate with a very early immune response to seeded amyloid. This is consistent with our previous findings in the Dominantly Inherited Alzheimer’s Disease Network (DIAN) cohort, where soluble TREM2 increases as early as 21 years before symptom onset. Moreover, in mouse models for amyloidogenesis, seeding of amyloid is limited by physiologically active microglia further supporting their early protective role. The biological functions of some of our main candidates (FABP3, CD44, GPNMB) also further emphasize that lipid dysmetabolism may be a common feature of neurodegenerative disorders.

Identification of Candidate Biomarkers of Alzheimer's Disease via Multiplex Cerebrospinal Fluid and Serum Proteomics.

Alzheimer's disease (AD) is the most prevalent form of dementia among elderly people worldwide. Cerebrospinal fluid (CSF) is the optimal fluid source for AD biomarkers, while serum biomarkers are much more achievable. To search for novel diagnostic AD biomarkers, we performed a quantitative proteomic analysis of CSF and serum samples from AD and normal cognitive controls (NC). CSF and serum proteomes were analyzed via data-independent acquisition quantitative mass spectrometry. Our bioinformatic analysis was based on Gene Ontology (GO) functional annotation analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment. In comparison to the controls, 8 proteins were more abundant in AD CSF, and 60 were less abundant in AD CSF, whereas 55 proteins were more and 10 were less abundant in the serum samples. ATPase-associated activity for CSF and mitochondrial functions for CSF and serum were the most enriched GO terms of the DEPs. KEGG enrichment analysis showed that the most significant pathways for the differentially expressed proteins were the N-glycan biosynthesis pathways. The area under the curve (AUC) values for CSF sodium-/potassium-transporting ATPase subunit beta-1 (AT1B1), serglycin (SRGN), and thioredoxin-dependent peroxide reductase, mitochondrial (PRDX3) were 0.867 (p = 0.004), 0.833 (p = 0.008), and 0.783 (p = 0.025), respectively. A panel of the above three CSF proteins accurately differentiated AD (AUC = 0.933, p = 0.001) from NC. The AUC values for serum probable phospholipid-transporting ATPase IM (AT8B4) and SRGN were moderate. The AUC of the CSF SRGN + serum SRGN was 0.842 (p = 0.007). These novel AD biomarker candidates are mainly associated with inflammation, ATPase activity, oxidative stress, and mitochondrial dysfunction. Further studies are needed to investigate the molecular mechanisms by which these potential biomarkers are involved in AD.

Amyloid-Beta Co-Pathology Is a Major Determinant of the Elevated Plasma GFAP Values in Amyotrophic Lateral Sclerosis.

Recent studies reported increased plasma glial acidic fibrillary protein (GFAP) levels in amyotrophic lateral sclerosis (ALS) patients compared to controls. We expanded these findings in a larger cohort, including 156 ALS patients and 48 controls, and investigated the associations of plasma GFAP with clinical variables and other biofluid biomarkers. Plasma GFAP and Alzheimer's disease (AD) cerebrospinal fluid (CSF) biomarkers were assessed by the single molecule array and the Lumipulse platforms, respectively. In ALS patients, plasma GFAP was higher than in controls (p < 0.001) and associated with measures of cognitive decline. Twenty ALS patients (12.8%) showed a positive amyloid status (A+), of which nine also exhibited tau pathology (A+T+, namely ALS-AD). ALS-AD patients showed higher plasma GFAP than A- ALS participants (p < 0.001) and controls (p < 0.001), whereas the comparison between A- ALS and controls missed statistical significance (p = 0.07). Plasma GFAP distinguished ALS-AD subjects more accurately (area under the curve (AUC) 0.932 ± 0.027) than plasma p-tau181 (AUC 0.692 ± 0.058, p < 0.0001) and plasma neurofilament light chain protein (AUC, 0.548 ± 0.088, p < 0.0001). Cognitive measures differed between ALS-AD and other ALS patients. AD co-pathology deeply affects plasma GFAP values in ALS patients. Plasma GFAP is an accurate biomarker for identifying AD co-pathology in ALS, which can influence the cognitive phenotype.

A protein panel in cerebrospinal fluid for diagnostic and predictive assessment of Alzheimer's disease.

Alzheimer's disease (AD) is a neurodegenerative disease with heterogenous pathophysiological changes that develop years before the onset of clinical symptoms. These preclinical changes have generated considerable interest in identifying markers for the pathophysiological mechanisms linked to AD and AD-related disorders (ADRD). On the basis of our prior work integrating cerebrospinal fluid (CSF) and brain proteome networks, we developed a reliable and high-throughput mass spectrometry-selected reaction monitoring assay that targets 48 key proteins altered in CSF. To test the diagnostic utility of these proteins and compare them with existing AD biomarkers, CSF collected at baseline visits was assayed from 706 participants recruited from the Alzheimer's Disease Neuroimaging Initiative. We found that the targeted CSF panel of 48 proteins (CSF 48 panel) performed at least as well as existing AD CSF biomarkers (Aβ42, tTau, and pTau181) for predicting clinical diagnosis, FDG PET, hippocampal volume, and measures of cognitive and dementia severity. In addition, for each of those outcomes, the CSF 48 panel plus the existing AD CSF biomarkers significantly improved diagnostic performance. Furthermore, the CSF 48 panel plus existing AD CSF biomarkers significantly improved predictions for changes in FDG PET, hippocampal volume, and measures of cognitive decline and dementia severity compared with either measure alone. A potential reason for these improvements is that the CSF 48 panel reflects a range of altered biology observed in AD/ADRD. In conclusion, we show that the CSF 48 panel complements existing AD CSF biomarkers to improve diagnosis and predict future cognitive decline and dementia severity.