CSF Levels Research Articles

Diffusion MRI tracks cortical microstructural changes during the early stages of Alzheimer's disease.

There is increased interest in developing markers reflecting microstructural changes that could serve as outcome measures in clinical trials. This is especially important after unexpected results in trials evaluating disease-modifying therapies targeting amyloid-β (Aβ), where morphological metrics from MRI showed increased volume loss despite promising clinical treatment effects. In this study, changes over time in cortical mean diffusivity, derived using diffusion tensor imaging, were investigated in a large cohort (n = 424) of non-demented participants from the Swedish BioFINDER study. Participants were stratified following the Aβ/tau (AT) framework. The results revealed a widespread increase in mean diffusivity over time, including both temporal and parietal cortical regions, in Aβ-positive but still tau-negative individuals. These increases were steeper in Aβ-positive and tau-positive individuals and robust to the inclusion of cortical thickness in the model. A steeper increase in mean diffusivity was also associated with both changes over time in fluid markers reflecting astrocytic activity (i.e. plasma level of glial fibrillary acidic protein and CSF levels of YKL-40) and worsening of cognitive performance (all P < 0.01). By tracking cortical microstructural changes over time and possibly reflecting variations related to the astrocytic response, cortical mean diffusivity emerges as a promising marker for tracking treatments-induced microstructural changes in clinical trials.

Mass spectrometry in cerebrospinal fluid uncovers association of glycolysis biomarkers with Alzheimer’s disease in a large clinical sample

Alzheimer’s disease (AD) is a complex and heterogeneous neurodegenerative disorder with contributions from multiple pathophysiological pathways. One of the long-recognized and important features of AD is disrupted cerebral glucose metabolism, but the underlying molecular basis remains unclear. In this study, unbiased mass spectrometry was used to survey CSF from a large clinical cohort, comparing patients who are either cognitively unimpaired (CU; n = 68), suffering from mild-cognitive impairment or dementia from AD (MCI-AD, n = 95; DEM-AD, n = 72), or other causes (MCI-other, n = 77; DEM-other, n = 23), or Normal Pressure Hydrocephalus (NPH, n = 57). The results revealed changes related to altered glucose metabolism. In particular, two glycolytic enzymes, pyruvate kinase (PKM) and aldolase A (ALDOA), were found to be upregulated in CSF from patients with AD compared to those with other neurological conditions. Increases in full-length PKM and ALDOA levels in CSF were confirmed with immunoblotting. Levels of these enzymes furthermore correlated negatively with CSF glucose in matching CSF samples. PKM levels were also found to be increased in AD in publicly available brain-tissue data. These results indicate that ALDOA and PKM may act as technically-robust potential biomarkers of glucose metabolism dysregulation in AD.

Extracellular vesicle proteome unveils cathepsin B connection to Alzheimer's disease pathogenesis.

Extracellular vesicles (EVs) are membrane vesicles that are released extracellularly and considered to be implicated in the pathogenesis of neurodegenerative diseases including Alzheimer's disease. Here, CSF EVs of 16 ATN-classified cases were subjected to quantitative proteome analysis. In these CSF EVs, levels of 11 proteins were significantly altered during the ATN stage transitions (P < 0.05 and fold-change > 2.0). These proteins were thought to be associated with Alzheimer's disease pathogenesis and represent candidate biomarkers for pathogenic stage classification. Enzyme-linked immunosorbent assay analysis of CSF and plasma EVs revealed altered levels of cathepsin B (CatB) during the ATN transition (seven ATN groups in validation set, n = 136). The CSF and plasma EV CatB levels showed a negative correlation with CSF amyloid-β42 concentrations. This proteomic landscape of CSF EVs in ATN classifications can depict the molecular framework of Alzheimer's disease progression, and CatB may be considered a promising candidate biomarker and therapeutic target in Alzheimer's disease amyloid pathology.

Correlations of p‐tau217, p‐tau181 and tau levels between CSF and plasma that are measured by fully automated immunoassay platform

AbstractBackgroundCerebrospinal fluid (CSF)‐based ATN classification (A: β‐amyloid (Aβ) deposition, T: pathogenic tau accumulation, N: neurodegeneration) is being widely accepted for the characterization of Alzheimer’s disease (AD). However, for the implementation of ATN classification in clinical practice, blood‐based biomarker is preferable in terms of specimen collection ease. Therefore, we have developed the blood‐based biomarker assays that correlate well with CSF levels. We have previously demonstrated that the plasma tau and phosphorylated tau at threonine‐181 (p‐tau181) immunoassays can significantly differentiate between AD, mild cognitive impairment (MCI), and cognitively normal (CN) groups. Here, we evaluated the correlation of biomarker levels between CSF and plasma utilizing the biomarker panel with addition of phosphorylated tau at threonine‐217 (p‐tau217) immunoassay.MethodWe have measured p‐tau217, p‐tau181 and tau using commercially available specimens on a fully automated immunoassay platform, HISCLTM analyzer. The platform can achieve high degree of sensitivity, requires only 30 µl of sample and 17 minutes to complete the measurement per assay. The bio‐analytical performance for the immunoassays was evaluated by measuring lower limit of quantification (LLOQ). The developed immunoassays were used to measure the paired CSF and plasma specimens from AD (n = 10), MCI (n = 35) and CN (n = 9) groups.ResultThe quantitative sensitivity for p‐tau217, p‐tau181 and tau were sufficient to measure plasma specimens in all groups. The plasma biomarker levels were significantly different between the AD and CN groups for all the biomarkers. We have found good correlations of biomarker levels between CSF and plasma for p‐tau217 (rs = 0.594, p &lt; 0.01), p‐tau181 (rs = 0.453, p &lt; 0.01) and tau (rs = 0.326, p &lt; 0.05).ConclusionOur results indicated the possibility of detecting plasma p‐tau217, p‐tau181 and tau levels which may reflect the CSF levels. In addition to these assays, we have also developed plasma Ab and neurofilament light chain assays that had demonstrated good correlation with CSF levels. Thus, all the plasma assays developed on the HISCL analyzer could assess ATN classification. The blood‐based biomarker panel using our fully automated assay will accelerate research in the dementia field and may help in appropriate diagnosis of patients with dementia in routine clinical practice.

Cerebral microbleeds and amyloid pathology

AbstractBackgroundCerebral microbleeds (CMBs) are common in the elderly population and are associated with cognitive decline. The aim of the current study was to examine the association between CMBs and cerebral amyloid pathology in cognitively unimpaired (CU) and cognitively impaired (CI) individuals included in the Amyloid Biomarker Study.MethodWe included 2550 CU and 1002 CI participants from 12 cohorts of the Amyloid Biomarker Study. Presence of amyloid pathology was determined based on Aß42 levels in CSF (n = 2873) or amyloid‐PET (n = 679) using data‐driven or center‐specific cutoffs. CMBs were assessed on in vivo MRI and were classified as present (≥1) or absent. The association of amyloid pathology with CMBs and its dependency on age, sex, APOE‐e4 carriership and hypertension was assessed using generalized‐estimating‐equations.ResultThirty‐seven percent of participants were amyloid positive, 38% were APOE‐e4 carrier, 54% were female, 30% had hypertension and 17% had CMBs (20% of the amyloid positive and 16% of the amyloid negative group, respectively). The mean age was 66.7 years (SD9.2). In CU participants, there was no association between amyloid pathology and CMBs. In CI individuals, CMB prevalence was associated with amyloid pathology depending on age (p = 0.044). At younger ages (&lt;75 years), CMBs were more common in amyloid positive rather than amyloid negative participants while at older ages, amyloid negative participants had CMBs more often. However, the interaction between amyloid status and age became insignificant when hypertension was considered. CMB prevalence was associated with amyloid pathology depending on hypertension (p = 0.006). In CI participants without hypertension, CMBs were more common in those that were amyloid positive rather than amyloid negative. In CI participants with hypertension, there was no significant difference in CMB prevalence between the amyloid positive and negative groups (Figure 1). Sex and APOE‐e4 status did not affect the observed associations between amyloid pathology and CMBs in participants with CI.ConclusionCMB prevalence is associated with amyloid pathology and this association is dependent on hypertension. Knowledge on the background prevalence of CMBs considering AD biomarker and vascular risk factor status is needed to inform clinical trial design and safety evaluation of AD therapies.

CSF ADAM10 levels in AD patients in relationship to ADAM10 gene variants

AbstractBackgroundThe disintegrin metalloproteinase 10 (ADAM10) is the main α‐secretase acting in the non‐amyloidogenic processing of APP. Some ADAM10 gene variants (Q170H, R181G) have been associated with higher susceptibility to develop late‐onset AD and have been shown to promote AD‐type changes in mice models. We tested the hypothesis that some ADAM10 rare variants could increase the risk for AD through conferring an earlier age‐related downregulation of a‐secretase activity.Method ADAM10 gene was sequenced in 103 AD cases (78% with family history) with positive CSF biomarkers, and 96 cognitively preserved nonagenarians. ADAM10 in CSF of the AD cases was analyzed by means of ELISA (total levels) and western blot (segregated by isoforms of 50 kDa, 55 kDa, and 80 kDa) in comparison with controls and non‐AD dementia cases. We examined whether there was an increase of rare gene variants (MAF &lt; 0.01) in the AD group and their potential association with lowers CSF protein levels.ResultRare variants were found in 15,5% of AD cases (in 23% of early‐onset versus 7,8% in late‐onset, p = 0.058) and in 12,5% of nonagenarians, and several of them were exclusive of the group. However, all were intronic variants except the Q170H change found in three AD cases and one nonagenarian. The SNP rs74016945 (3’UTR), with MAF close to 0.01, was found in 6% of the nonagenarians (OR 0.146, Fisher exact test p = 0.057). ELISA ADAM10 levels were not significantly different comparing AD cases with controls, carriers of rare variants versus non‐carriers, and did not differ consistently according to age at onset or APOE genotype. The three ADAM10 species were also similar in AD cases and controls, and did not differ according to genetic variants or age at onset.ConclusionRare ADAM10 exonic variants are uncommon in AD cases and the presence of rare intronic variants (more frequent in early versus late‐onset cases) is not associated with decreased ADAM10 levels in CSF.

A novel fluid biomarker for TDP‐43 loss of function

AbstractBackgroundTDP‐43 nuclear clearance and cytoplasmic aggregation occur in multiple neurodegenerative diseases, including amyotrophic lateral sclerosis‐frontotemporal dementia (ALS‐FTD), Alzheimer’s disease (AD), and limbic‐predominant age‐related TDP‐43 encephalopathy (LATE). Nuclear clearance of TDP‐43 leads to its failure to repress splicing of nonconserved cryptic exons. This loss of TDP‐43 splicing repression is well‐documented in postmortem tissues, but there is currently no method of detecting TDP‐43 dysfunction in living patients. As some cryptic exons are spliced in‐frame and translated into proteins carrying novel epitopes, we hypothesize that these “cryptic peptides” may be found in patient CSF as biomarkers of TDP‐43 dysfunction.MethodWe generated novel monoclonal antibodies against several TDP‐43 cryptic exon targets and then developed a sandwich ELISA using the Meso Scale Discovery (MSD) platform, which we validated in cells deficient in TDP‐43 for the cryptic exon target in HDGFL2. We then screened CSF samples of C9ORF72‐mutation carriers with or at risk of ALS‐FTD and control individuals for the presence of this cryptic peptide.ResultThe MSD signal for cryptic HDGFL2 was elevated in CSF of C9ORF72‐mutation carriers with ALS (n = 5, mean = 1601) compared to those of controls (n = 5, mean = ‐64.10; p&lt;0.013), so we examined a larger cohort of C9ORF72‐mutation carriers. In symptomatic individuals (n = 27), cryptic peptide levels showed a correlation nearing significance with symptom duration (r = ‐0.368, p = 0.059), suggesting that levels of the cryptic peptide tend to be higher during the earlier symptomatic phase. We also found elevated cryptic peptide levels in CSF of several pre‐symptomatic individuals. To clarify cryptic peptide dynamics during disease progression, we began to assess longitudinal CSF samples and found that in 82.35% (14/17) of symptomatic individuals, levels of the cryptic peptide decreased with disease progression.ConclusionOur findings indicate that loss of TDP‐43 splicing repression occurs early in disease progression in ALS‐FTD, even pre‐symptomatically, and that detection of HDGFL2’s cryptic neoepitope may facilitate earlier diagnosis of TDP‐43‐related diseases. Further efforts linking the presence of cryptic HGDFL2 to TDP‐43 co‐pathology in AD may help expand biomarker development in AD. Additionally, evaluating dynamics of these biomarkers could provide a way of measuring target engagement for new therapeutics aimed at restoring TDP‐43 function.

Cerebral amyloid angiopathy (CAA) in dementia cohort‐ biomarkers

AbstractBackgroundCerebral amyloid angiopathy (CAA) defined as deposition of amyloid β‐protein (Aβ) in brain vessels, leads to hemorrhagic phenomena and cognitive impairment. As a disease with Aβ deposition, CAA is commonly compared to Alzheimer’s disease (AD). Imaging‐based Boston criteria allow a diagnosis of probable CAA in vivo, but cannot predict the development of CAA thus development of reliable biomarkers is necessary.Recognizing the potential risks of CAA in patients with dementia is of great importance in the context of emerging accessibility of anti‐Aβ immunotherapy. Clinicians will be balancing the risks and benefits of such therapy for their Patients with Alzheimer’s disease on daily basis. This situation calls for developing better biomarkers of cerebral amyloid angiopathy.MethodPresented here a retrospective cohort study of 463 bio‐banked patients with cognitive disorders. De‐identified parameters like sex, age, MOCA, APOE; CSF levels: Aβ 1‐40, Aβ 1‐42, p and t Tau were correlated with the signs of CAA (as assessed by MRI).ResultsCAA was present in 53 out of 463 (11.5%) of the examined population with different types of dementia. 33% of those with CAA were diagnosed with Alzheimer’s disease; 38% with Vascular dementia;23% with MCI‐amnestic; 4% with MCI‐non‐amnestic; 2% with Lewy Body Dementia. Age and level of Amyloid beta 1‐40 were significantly associated with the occurrence of CAA, . An increase in age will increase the odds of developing CAA. From all the other parameters analyzed, the odds of CAA were linked to the low CSF level of Amyloid beta 1‐40.ConclusionLow CSF level of Amyloid beta 1‐40 may be considered a biomarker of CAA in dementia.

Tissue inhibitor of matrix metalloproteinases 4: a novel marker associated with CAA

AbstractBackgroundWe have previously shown that matrix metalloproteinase 9 (MMP9) and tissue inhibitor of proteinases 3 (TIMP3) are specifically expressed in the vasculature of patients with cerebral amyloid angiopathy (CAA). Moreover, we have demonstrated increased MMP9 and decreased TIMP3 levels, as well as an altered MMP9:TIMP3 ratio in the vasculature of CAA patients that suffered from intracerebral haemorrhages (CAA‐ICH) compared to CAA patients without ICH (CAA‐nonICH). We now extended our studies to investigate whether TIMP4 may have a similar role in CAA, as this has not been studied before.MethodUsing immunohistochemistry, we studied occipital lobe tissue of 44 controls (mean age 78.4 years; 50% female) and 58 CAA patients (77.5 years; 55% female; 40 CAA‐nonICH and 18 CAA‐ICH). Vascular TIMP4 staining was scored in a semiquantitative manner. Using ELISA, we measured TIMP4 CSF levels of 33 CAA patients (mean age 72.2 years; 47% female) and 35 controls (mean age 71.2 years; 51% female). For a subset of CSF samples (11 CAA samples and 14 controls), the levels of MMP2, MMP9, and MMP14 have been determined previously, and now their ratios to TIMP4 were calculated. Differences between CAA patients and controls were assessed using (ordinal) linear regression analysis.ResultIn brain tissue, CAA cases had increased vascular TIMP4 expression when compared to controls (p = 0.00002, figure 1). TIMP4 expression did not differ between CAA‐nonICH and CAA‐ICH cases. In the absence of vascular TIMP4 staining, we often observed perivascular staining. Decreased levels of perivascular TIMP4 staining were observed in CAA‐ICH cases when compared to CAA‐nonICH cases (p = 0.045) and to controls (p = 0.035). CSF levels of TIMP4 were decreased in CAA patients compared to controls (p = 0.03, figure 2). In addition, the ratios of MMP2 (p = 0.038), MMP9 (p = 0.005), and MMP14 (p = 0.025) to TIMP4 were increased in CAA patients compared to controls.ConclusionWe demonstrated increased TIMP4 expression in vessel walls of CAA patients compared to controls. In contrast, TIMP4 CSF levels were decreased in CAA patients compared to controls, whereas MMP:TIMP4 ratios were increased, indicating a disbalance of MMP/TIMP4 levels in CAA pathophysiology.Funding: BIONIC project (no. 733050822, ZonMW) and CAFÉ project (no. 5R01NS104147‐02, NIH).

CSF Biomarkers and [18F]flutemetamol PET‐Derived Centiloids in Patients with SCD or MCI

AbstractBackgroundCSF biomarkers are well characterised as surrogate markers for amyloid deposition and neurofibrillary tau tangles reflecting pathological features of Alzheimer’s disease. Amyloid PET images provide a visual and quantitative assessment of brain amyloid burden. In diagnostic workup these biomarkers are considered interchangeable, however their relationship is not fully understood.MethodCentiloid (CL) values for 387 [18F]flutemetamol images from the Swedish BioFINDER I study were derived following the methods of Klunk et.al. (Alzheimer’s &amp; Dementia, 2015). Subjects, comprising Controls, SCD and MCI (Table 1), were ranked by Centiloid values (lowest to highest) and the average for each consecutive group of 30 subjects calculated. Corresponding CSF biomarker values (Aß42/40 and pTau181) were plotted for each group.ResultSubjects in groups averaging ‐7.7 CL to 29.0 CL had a mean(±SD) Aß 42/40 ratio of 0.144 (±0.033, range 0.051 to 0.236, n = 240) with no statistically significant differences between groups (Fig. 1A). A statistically significant fall in CSF Aß42/40 ratio between the 29.0 CL and 47.3 CL groups (from 0.134 (+0.041, 0.066 to 0.236) to 0.088(+0.031, 0.045 to 0.183), p&lt;0.0001) was observed. The average CSF Aß42/40 ratio value for all subjects ranging from 66.3 Cl to129.8 CL was 0.072 (±0.017, 0.030 to 0.127, n = 117) with no statistically significant difference in CSF levels across these CL bands. Subjects in the groups averaging ‐7.7 CL to 29.0 CL had a mean(±SD) pTau181 value of 48.9 pg/mL (±15.9, 22 to 138) with no statistically significant difference between groups (Fig. 1B). A statistically significant (p&lt;0.05) increase between 29.0 CL (47.3±19.3, 24 to 116 pg/mL) and 47.3 CL groups (67.8±29.4, 24 to 175 pg/mL) was observed. For all Subjects from 66.3 CL to129.8 CL mean pTau181 levels were 79.6 (±30.3, 32 to 209 pg/mL) with no statistically significant difference across these CL bands.ConclusionComparison of [18F]flutemetamol image quantitation and CSF biomarkers indicates CSF Aß42/40 and pTau181 starts to show amyloid positivity at approximately 30‐40 CL units. Recent comparisons between visual rating and Centiloids from PET imaging indicate visual positivity from approximately 20 CL units indicating sensitivity of amyloid PET imaging for the detection of early amyloid deposition.

Biomarkers - Part 1.

The CSF amyloid to tau ratio can isolate cognitively healthy participants into normal Aβ42/tau (CH-NAT) or a pathological Aβ42/tau (CH-PAT) with a low or high risk of cognitive decline, respectively. We aim to determine if plasma Aβ42/tau ratios can differentiate CH-NAT from CH-PAT participants. Study participants (> 65 years of age) were recruited, and demographic, neurological, and neuropsychological data were obtained in an ongoing HMRI Brain Aging study. Overnight fasting plasma and CSF were collected within a month of examination, and the levels of Aβ38, Aβ40, Aβ42 (MSD 6E10 kit), and total tau were quantified using the MSD electrochemiluminescence platform. Differences in fluid biomarker levels and the plasma ratios (n = 55) and CSF ratios (Aβ42/Aβ40, n = 41, Aβ42/tau, n = 55) were determined using nonparametric student t-test and correlations using a Spearman test. Aβ40 and Aβ42 levels were higher (15-18-fold, and 10-14-fold, respectively), while tau levels are 8-13-fold higher in CSF than in plasma. Plasma and CSF Aβ40 were not distinct in CH-NAT compared with CH-PAT. In contrast, Aβ42 levels were 30.9% lower in CH-PAT (16.3 ± 18.3 pg/ml) compared with CH-NAT plasma (23.6 ± 26.4 pg/mL) (p < 0.05). CSF Aβ42 levels in CH-PAT (171.6 ± 124.6 pg/mL) were lower by 47.6% compared with CH-NAT (327.6 ± 182.6 pg/ml) (p < 0.0001). The Aβ42/Aβ40 ratio was significantly lower in both plasma and CSF (Table 1A). Similarly, the Aβ42/tau ratio was significantly lower in plasma and CSF (Table 1B). Individually, plasma levels of Aβ42 and tau did not correlate with CSF levels. However, the ratio of Aβ42 to total tau in plasma significantly correlated with the CSF ratios (Spearman r = 0.36, p = 0.0071). Finally, CSF Aβ42/Aβ40 ratio correlated with Aβ42/tau ratio for all samples, CH (n = 100) and MCI (n = 35) (Fig. 1). While not as robust as CSF ratios, plasma Aβ42/Aβ40 and Aβ42/tau ratios can isolate cognitively healthy participants with lower risk from participants with a higher risk of cognitive decline. Thus, plasma represents a less invasive medium for the biomarker classification of aging participants.

CSF Biomarkers and [18F]flutemetamol PET‐Derived Centiloids in Patients with SCD or MCI

AbstractBackgroundCSF biomarkers are well characterised as surrogate markers for amyloid deposition and neurofibrillary tau tangles reflecting pathological features of Alzheimer’s disease. Amyloid PET images provide a visual and quantitative assessment of brain amyloid burden. In diagnostic workup these biomarkers are considered interchangeable, however their relationship is not fully understood.MethodsCentiloid (CL) values for 387 [18F]flutemetamol images from the Swedish BioFINDER I study were derived following the methods of Klunk et.al. (Alzheimer’s &amp; Dementia, 2015). Subjects, comprising Controls, SCD and MCI (Table 1), were ranked by Centiloid values (lowest to highest) and the average for each consecutive group of 30 subjects calculated. Corresponding CSF biomarker values (Aβ42/40 and pTau181) were plotted for each group.ResultsSubjects in groups averaging ‐7.7 CL to 29.0 CL had a mean(±SD) Aβ 42/40 ratio of 0.144 (±0.033, range 0.051 to 0.236, n = 240) with no statistically significant differences between groups (Fig. 1A). A statistically significant fall in CSF Aβ42/40 ratio between the 29.0 CL and 47.3 CL groups (from 0.134 (±0.041, 0.066 to 0.236) to 0.088(±0.031, 0.045 to 0.183), p&lt;0.0001) was observed. The average CSF Aβ42/40 ratio value for all subjects ranging from 66.3 Cl to129.8 CL was 0.072 (±0.017, 0.030 to 0.127, n = 117) with no statistically significant difference in CSF levels across these CL bands.Subjects in the groups averaging ‐7.7 CL to 29.0 CL had a mean(±SD) pTau181 value of 48.9 pg/mL (±15.9, 22 to 138) with no statistically significant difference between groups (Fig. 1B). A statistically significant (p&lt;0.05) increase between 29.0 CL (47.3±19.3, 24 to 116 pg/mL) and 47.3 CL groups (67.8±29.4, 24 to 175 pg/mL) was observed. For all Subjects from 66.3 CL to129.8 CL mean pTau181 levels were 79.6 (±30.3, 32 to 209 pg/mL) with no statistically significant difference across these CL bands.ConclusionsComparison of [18F]flutemetamol image quantitation and CSF biomarkers indicates CSF Aβ42/40 and pTau181 starts to show amyloid positivity at approximately 30‐40 CL units. Recent comparisons between visual rating and Centiloids from PET imaging indicate visual positivity from approximately 20 CL units indicating sensitivity of amyloid PET imaging for the detection of early amyloid deposition.

Refinement of Neurofilament light Dynamics in CSF and Blood for familial Alzheimer’s Disease

AbstractBackgroundDisease‐modifying therapies for Alzheimer’s Disease (AD) are likely most beneficial when initiated in the pre‐symptomatic phase. To track success of such interventions fluid biomarkers became instrumental, with neurofilament light chain (NfL) showing particular promise. We previously reported that serum NfL increases in pre‐symptomatic phases of familial (autosomal‐dominantly inherited) AD (fAD) and that within‐person rate‐of‐change in NfL is an earlier predictor of fAD symptom onset compared to cross‐sectional levels. The aim of the study at hand was to extend these initial findings in a larger cohort.MethodParticipants enrolled in the Dominantly Inherited Alzheimer Network (DIAN) with matched cross‐sectional and longitudinal cerebrospinal fluid (CSF; n = 962) as well as plasma (n = 1294) samples were used. NfL measurements have been performed on the SIMOA platform using commercially available assay‐kits. To investigate the influence of physiological factors independent from AD, we first analyzed whether age and body mass index (BMI) could account for observed variation in inter‐individual CSF and plasma NfL levels considering non‐carrier family‐members (NC) as a healthy control group. Next, utilizing estimated years to symptom onset (EYO) and previously published methods (Preische et al., 2019), we determined the point in disease course when baseline and longitudinal CSF and plasma NfL concentrations started to increase in mutation carriers (MC) relative to NC, after adjusting for age and BMI.ResultOur results reveal a tight correlation of CSF and blood NfL values within MC as well as NC (figure 1A‐B). However, within NC, after correction for age and BMI, some unexplained variability remained (figure 1C). Further, a decrease of the NfL plasma/CSF ratio over age was found after correcting for BMI (figure 1D). The discrimination of MC from NC was equally good for plasma compared to CSF, being possible on the group level as early as around ‐15 to almost ‐20 EYO depending on the modelling (figure 2).ConclusionOur results support plasma equivalently to CSF NfL as a clinically useful biomarker to longitudinally track neurodegeneration in fAD. The systemic factors influencing physiological NfL values in blood should be investigated in future studies to further improve interpretation of this biomarker.

Mitophagy biomarkers are changed in the continuum of Alzheimer’s disease

AbstractBackgroundAutophagy is a cellular self “garbage clearance ”system through which cells eliminate and recycle dysfunctional cytoplasmatic components, such as defective organelles and misfolded protein aggregates. Mitophagy is the sub‐type of autophagy that recognizes and degrades damaged or superfluous mitochondria to maintain cellular homeostasis. Emerging evidence demonstrates that autophagy and mitophagy are impaired in Alzheimer’s disease (AD); its upregulation ameliorates Aß pathology and slows down the cognitive decline in animal models of AD, thus representing a potentially treatable target. The change in the mitophagy biomarkers in individuals with AD needs to be clarified. We aimed to explore the changes of mitophagy biomarkers in biomarkers‐defined individuals in various stages of AD and compare them to cognitively unimpaired individuals (CU).MethodWe included 228 biomarker‐defined individuals from the Czech Brain Aging Study:98 AD dementia (ADD), 88 mild cognitive impairment due to AD (MCI‐AD), and 42 CU individuals. They underwent clinical examination, complex neuropsychological assessment, and brain MRI. Commercial ELISA kits were used to measure standard AD biomarkers in CSF (Aß42, Aß40, pTau, tTau), a biomarker of neurodegeneration (neurofilament light chain – NfL), synaptic dysfunction (neurogranin, Ng), and mitophagy biomarkers in CSF (PINK1‐ mitochondrial kinase crucial for mitophagy) and in serum (BNIP3L‐ mitophagy receptor, TFEB‐ transcription factor critical for lysosomal degradation).ResultWe found a significant increase in PINK1 CSF and BNIP3L serum levels in ADD compared to MCI‐AD and CU (ps&lt;.001). TFEB serum levels were decreased in ADD compared to MCI‐AD and CU (ps&lt;.05). Additionally, in ADD, PINK1 correlated with NfL (r = 0.27) and Ng (r = 0.47). In MCI‐AD, there was a correlation between PINK1 and Ng (r = 0.51), but not with NfL. There was no correlation in CU individuals with NfL or Ng.ConclusionWe identified candidate proteins of mitophagy that are changed in various cognitive stages of AD. In the ADD stage, there is an upregulation of the mitophagy inducers, PINK1 and BNIP3L, together with decreased levels of TFEB, a master regulator of lysosomal biogenesis. One of the possible explanations is that these findings reflect impairment in the final stage of autophagy–lysosomal degradation. Further research is needed to clarify its pathophysiological importance in the AD cascade.

Value of blood‐based biomarkers for differential diagnosis of Alzheimer’s disease: the ActiGliA cohort

AbstractBackgroundCerebrospinal fluid (CSF) and positron emission tomography (PET) biomarkers of Alzheimer’s disease (AD), ß‐amyloid (Aß) and tau, can identify early disease stages with high accuracy. However, this approach is not suitable for routine clinical care because of the high costs and invasiveness. Implementation of blood‐based biomarkers (BBBM) in the diagnostic process may facilitate the identification of persons with AD in the earliest stage possible and may reliably differentiate AD from healthy aging and other non‐AD dementias like corticobasal syndrome (CBS).MethodFrom the prospective ActiGliA study we included 27 participants with probable AD (including participants with mild cognitive impairment [n = 16] and AD‐related dementia [n = 11]), 17 age‐matched controls with subjective cognitive impairment, 9 participants with corticobasal syndrome and underlying Aß‐pathology (Aß[+]CBS), and 26 participants with Aß[‐]negative CBS. The diagnostic value of different BBBMs in differentiating amyloid‐positive from ‐negative cases was examined. All participants underwent a thorough diagnostic work‐up, including CSF and blood sampling, neuropsychological tests, amyloid‐PET, and magnetic resonance imaging. Blood biomarkers (Aß1‐40, Aβ1‐42, apolipoprotein E4 [ApoE4], glial fibrillary acidic protein [GFAP], neurofilament light chain [NfL], and phosphorylated‐tau181 [pTau181]) were measured using Elecsys® plasma prototype immunoassays.ResultIn amyloid‐positive cases, plasma concentrations of Aβ1‐42/1‐40 ratio were decreased while ApoE, GFAP, and pTau181 levels were elevated. In the entire cohort, blood and CSF levels of both Aß1‐42/Aß1‐40 ratio and pTau181 were significantly positively correlated. ApoE4, GFAP, and particularly pTau181 levels showed a strong negative association with neuropsychological performance. A positive association between NfL levels and hippocampal atrophy was demonstrated. pTau181 levels revealed an are under the curve (AUC) of 0.885 in the discrimination between amyloid‐positive and ‐negative cases, plasma ApoE4 levels and Aß1‐42/Aß1‐40 ratio showed an AUC of 0.774 resp. 0.815. Regarding differentiation of AD from healthy aging and other dementias, elevated NfL levels were associated with a diagnosis of CBS and Aß[+]CBS, while elevated pTau181 and ApoE4 levels indicated a diagnosis of AD.ConclusionBBBMs may be useful in differentiating amyloid PET‐positive from amyloid PET‐negative cases and in differentiating AD from healthy aging and non‐Alzheimer dementias. These results must be validated in a larger cohort.

Plasma oligomer βeta‐amyloid and white matter microstructural integrity in cognitively normal older adults according to cerebral amyloid deposition

AbstractBackgroundMultimer detection system‐oligomeric amyloid‐ß (MDS‐OAß) measures plasma OAß level, which is associated with earlier pathology of Alzheimer’s disease (AD). Previous studies showed that plasma levels of MDS‐OAβ were higher in patients with dementia due to AD than in cognitive normal older adults (CN), and they correlated well with conventional AD biomarkers including standardized uptake value ratio (SUVR) of Pittsburgh compound B (PiB) and CSF level of Aβ42, p‐Tau, and t‐Tau. However, no previous study investigated MDS‐OAβ difference in CN with or without cerebral Aβ burden. In addition, associations among MDS‐OAß, cerebral Aß deposition, aberrance of white matter integrity, and cortical thickness in CN is not elucidated.MethodWe studied 34 CN with amyloid‐PET negative and 23 CN with amyloid‐PET positive results who received MDS‐OAβ, structural MRI, and diffusion tensor imaging (DTI).ResultAmyloid‐PET positive group showed higher MDS‐OAß level than amyloid‐PET negative group, but two groups did not differ in WM integrity or cortical thickness. MDS‐OAβ level was significantly higher in amyloid‐PET positive group than in amyloid‐PET negative group. MDS‐OAβ positive group had significantly higher cerebral AB deposition, or mean global SUVR values, than MDS‐OAβ negative group. There was a positive correlation between MDS‐OAβ level and PET‐SUVR. In terms of DTI analysis, MDS‐OAβ positive group had significantly lower FA in the left forceps minor of corpus callosum and right superior longitudinal fasciculus than in lower MDS‐OAβ negative group. In addition, the FA values were negatively correlated with MDS‐OAβ level (figure 1). MDS‐OAB positive group showed a significant reduction in the cortical thickness in the left fusiform when compared with the MDS‐OAB negative groupConclusionPlasma MDS‐OAβ value might reflect cerebral amyloid status and global cerebral Aß retention in CN. We elucidated toxic role of OAβ by showing that the plasma OAβ value were associated with decrement of WM microstructural integrity in the early pathological process of AD. Cortical thickness did not differ according to cerebral Aβ burden but rather was associated with higher plasma OAβ level. Thus, MDS‐OAβ value might reflect earlier, and different, pathology than cerebral Aß retention measured using amyloid PET scan in CN with AD continuum.

CSF Plasminogen inhibitor 1(PAI‐1) levels are associated with dementia symptoms in Alzheimer disease

AbstractBackgroundThere are currently excellent fluid biomarkers of brain amyloidosis, including CSF Aβ42/Aβ40 and CSF pT217/T217 (%). However, many individuals with brain amyloidosis do not have symptoms of Alzheimer disease (AD). Biomarkers that are strongly associated not only with brain amyloidosis but also with symptomatic AD would be invaluable tool in clinical trials and clinical diagnosis. We evaluated whether CSF biomarkers in an immunoassay panel added value to existing biomarkers in prediction of cognitive impairment.MethodAn immunoassay panel from Rules Based Medicine was used to measure CSF levels of 52 proteins including plasminogen inhibitor 1 (PAI1). CSF Aβ42/Aβ40 was measured by Lumipulse, and CSF pT217/T217 (%) was measured by an immunoprecipitation‐mass spectrometry assay. Logistic regression and linear models were used to evaluate the association between biomarkers and cognitive status (cognitively unimpaired or symptomatic AD as defined by a Clinical Dementia Rating [CDR] of 0.5 or greater), the Mini‐Mental State Exam [MMSE] score, and CDR Sum of Boxes [CDR‐SB]. Models included the covariates of age, self‐identified gender, and years of education.ResultThe cohort included n = 179 older research participants (average age 73.0 years, standard deviation 6.6 years), of which 47 (26%) had cognitive impairment (CDR&gt;0). Cognitively impaired individuals had higher levels of PAI1 (p = 1.18e‐05) (Fig. 1A). PAI1 levels predicted cognitive status in the entire cohort (p = 4e10−3) and the sub‐cohort with CSF Aβ42/Aβ40 levels consistent with brain amyloidosis (Aβ42/Aβ40&lt;0.0673; p = 0.003). Even when CSF pT217/T217 (%) was included in the model of cognitive status, PAI1 was a significant independent predictor of cognitive status in both the entire cohort (p = 0.005) and the sub‐cohort with brain amyloidosis (p = 0.008) (Fig. 1B). Both the MMSE and CDR‐SB were associated with PAI1 in the entire cohort (p = 1.86e‐07 and p = 5.45e‐07), and the sub‐cohort with brain amyloidosis (p = 2.44e‐05 and p = 4.77E‐05) (Fig. 1C‐D). When CSF pT217/T217 (%) was included in the model, both the MMSE and CDR‐SB remained associated with PAI1 in the entire cohort (p = 8.85e‐06 and p = 3.02e‐05) and the sub‐cohort with brain amyloidosis (p = 0.0001 and p = 0.0003).ConclusionThese results demonstrate that CSF PAI1 is associated with symptomatic AD and adds value to CSF pT217/T217 in predicting AD symptoms.

The AppNL‐G‐F/MAPT mouse model of Alzheimer’s Disease demonstrates increased levels of ptau217 in CSF, changes that correlate with increased cerebral p‐tau depositions

AbstractBackgroundCerebrospinal fluid (CSF) biomarkers reflecting the neuropathological hallmarks of Alzheimer’s disease (AD) have during the two last decades been developed and are commonly used to diagnose patients with AD patients. Previous studies have shown that CSF p‐tau217 particularly well can separate AD patients from healthy controls and that CSF levels of ptau217 correlate significantly with the amyloid burden and tau pathology in the brain (determined by PET). However, more studies are needed to fully understand the temporal relationship between CSF p‐tau217 changes and the accumulation tau in the brain. In this current study, we aim to investigate these temporal associations by the use of a novel knock‐in mouse model, AppNL‐G‐F expressing all six isoforms of human MAPT.MethodCerebrospinal fluid (CSF) and brain tissue will be collected from 3‐22 months old AppNL‐G‐F /MAPT and MAPT knock‐in mice. A pilot study of a subset of mice at different ages has been performed where levels of CSF ptau217 were analyzed using Mesoscale Discovery developed by Eli Lilly and Company. Mouse brain sections were immunostained against Aß and ptau181/217/231 to determine the cerebral p‐tau distribution.ResultIn CSF from our AppNL‐G‐F /MAPT double knock‐in (dKi) mouse model, we found age‐related increases in ptau217 levels compared to MAPT Ki mice. These changes in CSF ptau217 were associated with an increase of cerebral accumulation of p‐tau positive inclusions in the cortex and hippocampus of these mice. Additionally, we also found temporal differences in co‐localization between Aß plaques and the investigated phosphorylation sites of tau.ConclusionOur preliminary results from the AppNL‐G‐F/MAPT double knock‐in model, show early alterations in CSF ptau217 levels, changes that correlate in time with cerebral p‐tau positive accumulation as well as formation of Aß plaques. These findings indicate that alterations in CSF and cerebral p‐tau occurs early in the disease, when Aß pathology is widespread but no tau tangles are present. Furthermore, our preliminary data suggest temporal differences in phosphorylation sites of tau associated with Aß pathology. Additional CSF analysis and immunostainings will be performed before the AAIC conference.

Locus coeruleus MRI contrast is associated with Complement factor C3b in cerebrospinal fluid

AbstractBackgroundDegeneration of the Locus coeruleus (LC) is associated with Alzheimer’s disease (AD) pathology and cognitive decline. Recent evidence from animal models indicates that this relationship may be mediated by neuroinflammation. Here we examined how LC MRI contrast is related to CSF biomarkers of neuroinflammation in humans.MethodThe LC as well as the Substantia nigra (SN) were visualized and segmented using neuromelanin‐sensitive T1‐weighted FLASH‐MRI images acquired at 3T and MRI contrast values were calculated as previously described (Betts et al., 2019b). A cohort of 65 participants with MRI contrast and CSF data from the DZNE longitudinal cognitive impairment and dementia (DELCODE) study (20 HC, 22 SCD, 16 MCI, 7 AD dementia; 53.8% female) were included in the analyses. We performed correlational analyses to test for associations between LC and SN contrast with a panel of 4 Principal Components (PC) created from a Principial Component Analysis on 16 individual inflammation‐related CSF biomarkers (Fig. 1). Both bivariate and partial correlation analyses were performed between PCs and MRI contrast values using sex, age, site and CSF levels of AD pathology, namely Aß42/40‐ratio and phosphorylated tau, as covariates (see Fig. 2).ResultWe found a significant positive association between LC MRI contrast and the inflammatory component PC4 including the proinflammatory complement factors C3 and C3b across the entire sample (r = 0.365, p = 0.003). Additional post‐hoc correlational analyses showed this association with LC MRI contrast was mainly due to a correlation with C3b (r = 0.349, p = 0.004). A significant positive association was still observed (r = 0.347, p = 0.008) in a subgroup of individuals comprising healthy older adults and individuals with a risk of AD dementia (HC, SCD and MCI) as shown in Fig. 2. In contrast, no significant associations between SN MRI contrast and any neurodegenerative or inflammatory measure were observed indicating effects were specific to the LC.ConclusionThe results demonstrate LC MRI contrast is associated with complement factors in CSF, in particular complement factor C3b in healthy older adults and individuals with a risk of AD dementia. Further analyses are required to determine if elevated complement factors may predict degeneration of the LC and subsequent cognitive decline.

CSF levels of the synaptic marker Cyclase‐associated protein CAP2 in Alzheimer disease across clinical stages

AbstractBackgroundSynaptic dysfunction represent a key event in cognitive decline in Alzheimer disease. There is evidence that Cyclase‐associated protein 2 (CAP2) is involved in synaptic plasticity in AD models but its role in clinical setting has never extensively assessed. Aim of this study was to evaluate CAP2 levels in cerebrospinal fluids of AD and other neurodegenerative diseases and their relationship with amyloid and tau related biomarkers.Methodone‐hundred ten AD patients (prodromal AD n = 70; mild to moderate AD n = 40), 20 Lewy Body Dementia (LBD), 20 frontotemporal dementia (FTD) and 40 healthy controls (HC) were investigated and clinically assessed following a standardized neurological and cognitive behavioral assessment. All subjects underwent CSF analyses for h‐tau, p‐tau and Aß42 (Lumipulse) while CAP2 levels were assessed by using standard ELISA. Between‐groups differences and correlations between CSF biomarkers were evaluated using non‐parametric comparisons and partial correlation analyses adjusted for the effect of age, sex and disease duration.ResultAD patients across severity stages showed higher CAP2 levels compared to controls and non‐AD patients (p = 0.001). CAP2 levels did not correlate with disease severity and were independent of APOE genotype. In AD patients, CAP2 levels showed a positive correlation with t‐tau and p‐tau (p&lt;0.001).ConclusionCSF levels of CAP2 were significantly increased in AD patients and correlated with t‐tau and p‐tau independently of amyloid pathology. Altogether, these findings support the hypothesis that AD is specifically associated with synaptic dysfunction since early stages and that amyloid‐related synaptic changes parallels tau‐related axonal degeneration.