VAMP-2 Is a Surrogate Cerebrospinal Fluid Marker of Alzheimer-related Cognitive Impairment in Adults With Down Syndrome

doi:10.21203/rs.3.rs-340117/v1

Download PDF

Research

VAMP-2 Is a Surrogate Cerebrospinal Fluid Marker of Alzheimer-related Cognitive Impairment in Adults With Down Syndrome

https://doi.org/10.21203/rs.3.rs-340117/v1

This work is licensed under a CC BY 4.0 License

You are reading this latest preprint version

Background. There is an urgent need for objective markers of Alzheimer’s disease (AD)-related cognitive impairment in people with Down syndrome (DS) to improve diagnosis, monitor disease progression and assess response to disease-modifying therapies. Previously, GluA4 and Neuronal Pentraxin 2 (NPTX2) showed limited potential as cerebrospinal fluid (CSF) markers of cognitive impairment in adults with DS. Here we compare the CSF profile of a panel of synaptic proteins (Calsyntenin-1, Neuroligin-2, Neurexin-2A, Neurexin-3A, Syntaxin-1B, Thy-1, VAMP-2) to that of NPTX2 and GluA4 in a large cohort of subjects with DS across the preclinical and clinical AD continuum and explore their correlation with cognitive impairment.

Methods. We quantified the synaptic panel proteins by selected reaction monitoring in CSF from 20 non-trisomic cognitively normal controls (mean age 44) and 80 adults with DS grouped according to clinical AD diagnosis (asymptomatic, prodromal AD or AD dementia). We used regression analyses to determine CSF changes across the AD continuum and explored correlations with age, global cognitive performance (CAMCOG), episodic memory (modified cued-recall test; mCRT) and CSF AD biomarkers, CSF Aβ_42:40 ratio, CSF Aβ_1-42 and CSF p-tau. P-values were adjusted for multiple testing.

Results. In adults with DS, VAMP-2 was the only synaptic protein to correlate with episodic memory (delayed recall adj.p=.04) and age (adj.p=.0008) and was the best correlate of CSF Aβ_42:40(adj.p=.0001) and CSF p-tau (adj.p<.0001). Compared to controls, mean VAMP-2 levels were lower in asymptomatic adults with DS only (adj.p=.02). CSF levels of Neurexin-3A, Thy-1, Neurexin-2A, Calysntenin-1, Neuroligin-2, GluA4 and Syntaxin-1B all strongly correlated with NPTX2 (p<.0001), which was the only synaptic protein to show reduced CSF levels in DS at all AD stages compared to controls (adj.p<.002).

Conclusion. CSF VAMP-2 represents a promising objective surrogate marker of cognitive failure in DS. VAMP-2 also has potential for use in AD clinical trials as a measure of synapse engagement and therapeutic response that does not directly measure the drug target (typically Aβ and tau).

Cognitive Neuroscience

Down syndrome

Alzheimer’s disease

synapse

biomarker

cognitive decline

Alzheimer’s disease (AD) is the leading cause of death in adults with Down syndrome (DS), with a cumulative incidence that exceeds 90% in the seventh decade (1–4). Current standard cerebrospinal fluid (CSF) markers for AD in the DS population are restricted to surrogate markers of amyloidosis (Aβ_42:40 ratio, Aβ₁₋₄₂) and tau-mediated neurodegeneration (p-tau) and neurofilament light chain combined with neuropsychological assessment. However neuropsychological assessment can be confounded by substantial inter-individual variation in intellectual disability. Therefore, there is an urgent need for objective markers of AD-related cognitive impairment in people with DS to improve diagnosis, monitor disease progression and assess response to disease-modifying therapies.

Synapse loss is an early event in AD (5) and one of the best pathological correlates of cognitive dysfunction (6–9). As such, synaptic proteins that show AD-associated changes in biofluids are rapidly gaining attention as potential surrogate markers of AD-related synapse loss and may be informative markers of early AD-related cognitive dysfunction in adults with DS.

Neuronal Pentraxin-2 (NPTX2), a protein involved in inhibitory circuit dysfunction (10) is a promising biofluid surrogate marker of inhibitory circuit dysfunction and cognitive decline in sporadic AD (11–13), vascular dementia (14), genetic frontotemporal dementia (15) and Lewy body dementia (16). We recently reported low CSF NPTX2 concentrations in adults with DS across the AD continuum, which correlated with cortical atrophy and reduced glucose metabolism. However, CSF NPTX2 levels did not correlate with measures of cognitive decline in our DS cohort (17). In the same study, we also evaluated the glutamatergic receptor, GluA4, and found no association with cognitive measures.

The aim of this study was to evaluate a comprehensive panel of alternative synaptic proteins (Calsyntenin-1, Neuroligin-2, Neurexin-2A, Neurexin-3A, Syntaxin-1B, Thy-1, VAMP-2) as surrogate markers of early AD-related cognitive decline in non-trisomic cognitively normal controls (n = 20) and a large cohort of adults with DS (n = 80) from across the preclinical and clinical AD continuum, exploring their relationship to cognitive performance. The panel comprises 8 proteins that were shown to be specifically expressed at the synapse in human frontal cortex postmortem tissue and show CSF alterations that precede clinical symptoms and markers of neurodegeneration in sporadic AD (18). We also compare the CSF profile of the synaptic panel proteins in adults with DS to that of previously published data on NPTX2 and GluA4 in the same cohort (17).

Objectives

The primary objective of this study was to evaluate a comprehensive panel of synaptic proteins as surrogate markers of early AD-related cognitive decline in adults with DS from across the preclinical and clinical AD continuum, specifically exploring their relationship to cognitive performance and AD biomarkers.

Study design

This is a single-centre, cross-sectional study of CSF levels of synaptic markers in adults with DS, sporadic AD patients and cognitively normal controls. The study (IIBSP-BMS-2018-103) was approved by the local ethics committee (Comité Ètic d’Investigació Clínica, Fundació de Gestió Sanitària de l’Hospital de la Santa Creu i Sant Pau) and was conducted in accordance with the Declaration of Helsinki. All participants gave their written informed consent to participate in the study. Non-trisomic controls were selected from the Sant Pau Initiative in Neurodegeneration (SPIN) cohort, a prospective longitudinal cohort at Hospital Sant Pau, Barcelona, Spain (19). Adults with DS were selected from the Down Alzheimer Barcelona Neuroimaging Initiative (DABNI), a prospective longitudinal cohort, linked to a population-based health plan in Catalonia, Spain, led by the Fundació Catalana Síndrome de Down and Hospital de Sant Pau (20). Inclusion criteria for controls required the absence of a cognitive or neurological disorders and normal CSF core AD biomarker (Aβ_1-42, Aβ_42/40 ratio, t-tau, p-tau) concentrations using our validated cut-offs for sporadic AD (21). For adults with DS, inclusion criteria for participation in the study required that all participants were over 18 years of age. Where consent was given, participants received a comprehensive neurological and neuropsychological evaluation (22) and underwent a lumbar puncture to assess CSF biomarkers (20). As in previous studies (4, 20), participants with DS were classified by neurologists and neuropsychologists, blind to biomarker data in a consensus meeting into asymptomatic AD (aDS), prodromal AD (pDS) and AD dementia (dDS) according to previously published criteria (20).

Neuropsychological assessment

The level of intellectual disability in adults with DS was categorized according to the Diagnostic and Statistical Manual of Mental Disorders (DSM), Fifth Edition as mild, moderate, severe, or profound intellectual disability, based on caregivers’ reports of the individuals’ best-ever level of functioning and the Kaufmann Brief Intelligence Test (KBIT) (23). As previously described (20, 22), neurological and neuropsychological examination of the full range of cognitive impairment included a semi-structured health questionnaire (Cambridge Examination for Mental Disorders of Older People with Down Syndrome and others with intellectual disabilities [CAMDEX-DS]) (24) and a neuropsychological battery including the Cambridge Cognition Examination (CAMCOG) adapted for intellectual disabilities in DS participants and was restricted to those with mild and moderate intellectual disability. The Spanish version of the cued recall test modified for use in people with intellectual disability (mCRT) (25) was used to evaluate episodic memory as previously described (26). The total mCRT scores for immediate recall were calculated as free recall score + cued recall score.

CSF collection, biomarker assessment

CSF samples were collected following international consensus recommendations (27) as previously described (28). Samples had been previously stored at -80°C and had not been thawed prior to analysis. Commercially available fully-automated immunoassays were used to determine levels of CSF Aβ_1-42,Aβ_1-40, total tau and p-tau at threonine residue 181 (Lumipulse Aβ_{1-42 ,}Aβ_1-40, total tau G, p-tau 181, Fujirebio-Europe) (21).

Targeted Liquid Chromatography Mass Spectrometry (LC-SRM)

We monitored a set of 20 proteotypic peptides corresponding to 8 panel proteins identified in our previous study (Calsyntenin-1, GluA2, Neurexin-2A, Neurexin-3A, Neuroligin-2, Syntaxin-1B, Thy-1 and VAMP-2) by Selected Reaction Monitoring (SRM) as previously described (18). Briefly, we digested individual CSF samples overnight and spiked isotopically-labeled peptides (Pepotech SRM custom peptides, grade 2, Thermo Fisher Scientific) into each sample. We analyzed an equivalent of 5µl of each sample in a randomized order over a 120-min gradient (0-35% ACN+0.1% FA) in SRM mode using a triple quadrupole-Qtrap mass spectrometer (5500 QTrap, Sciex, Massachussetts) coupled to a nano-LC chromatography column (300 µl/min, 25-cm C18 column, 75 µm I.d., 2 µm particle size). We ran BSA technical controls between each sample. We used isotopically-labeled peptides as internal standards. We visualized and analyzed transitions using Skyline 3.5 as previously described (18). Injection of a pool of all the samples over the duration of the mass spectrometric measurements and monitoring the peak area of the standard peptides was used to evaluate the stability of the peptides over the course of the experiment and resulted in the exclusion of GluA2 from the study. We processed the SRM transitions using the dataProcess function of MSstats v3.5 package in R (29) and removed transitions with between-run interference (betweenRunInterferenceScore<0.8). Censored missing values were samples with log base-2 endogenous log2 intensities under the cut-off designated by the MSstats package (8.49). We used the EqualizeMedians function to normalize the transitions and Tukey’s Median Polish to generate a summarized value of transitions for each protein.

Statistical Analysis

All statistical analyses were performed in R version 3.4.3 (30). Extreme outliers were excluded using the 3 × interquartile range rule. Group comparisons were performed using χ² test, t-test or linear regression and we used Pearson’s coefficients to assess correlations. Where residuals deviated from a Gaussian distribution (Shapiro-Wilk p<0.05), tests were performed on square root transformed values. When comparing the association of multiple synaptic proteins, p-values were adjusted for multiple testing using the Benjamini-Hochberg method.

Demographics

The Table shows the demographic and clinical data for the participants included in the study, which included 20 controls and 80 adults with DS from across the AD continuum (40 aDS, 19 pDS and 21 dDS). The mean age-at-analysis across the whole study was 44.5 years (standard deviation; SD = 11.2). Compared to controls, the mean age was comparable in pDS (+ 5 years, p = .20) and dDS (+ 5 years, p = .13) but lower in aDS (-12 years, p < .0001). The male:female proportion was comparable across clinical groups (p = .45). The level of intellectual disability in the adults with DS was classified as either mild/moderate (78% of cases) or severe/profound (22% of cases), a proportion that was comparable across clinical groups (p = .37). Cognitive tests were restricted to individuals with mild or moderate intellectual disability. As would be expected, cognitive scores were sequentially lower in pDS (CAMCOG; -11, p = .02, mCRT immediate; -15, p < .0001, mCRT delayed; -5, p < .0001) and dDS (CAMCOG − 21 p < .0001, mCRT immediate; -20. p < .0001, mCRT delayed; -7, p < .0001) compared to aDS. As previously reported (20), the mean Aβ_42:40 ratio (all p < .0001) was lower in all DS groups compared to controls, while mean CSF p-tau and t-tau levels were higher in pDS and dDS compared to controls (all p < .0001).

CSF VAMP-2 levels show a distinct profile to other synaptic proteins in adults with DS

We first sought to determine the degree of correlation between CSF levels of the 7 synaptic panel proteins as well as with previously published data for CSF NPTX2 and GluA4. Figure 1 shows that in adults with DS, synaptic proteins, including Neurexin-3A, Thy-1, Neurexin-2A, Calysntenin-1, Neuroligin-2, GluA4 and Syntaxin-1B, were all correlated (pair-wise r = .74 to .93, p < .0001). They also all correlated with NPTX2 (pair-wise r = .54 to .79, p < .0001). VAMP-2 showed the weakest correlation with all other proteins (r = .35 to.63, p < .0001). In controls, all proteins showed weaker pair-wise correlations than in the DS group, although NPTX2, Neurexin-3A, Thy-1, Neurexin-2A, Calysntenin-1, Neuroligin-2, GluA4 and Syntaxin-1B were moderately correlated in at least one pair-wise combination (pair-wise r = .45 to .84, p < .04). VAMP-2 did not correlate with any other protein in controls (pair-wise r = − .31 to .34, p > .15). We took VAMP-2 forward for further analyses due to its relative independence from NPTX2.

Table. Demographics and clinical data for study participants.

	Controls	aDS	pDS	dDS
N	20	40	19	21
Age-at-analysis, years	47 (11, 24–64)	35 (9, 22–57)^b	52 (4, 45–60)	52 (5, 42–62)
% Female	60%	40%	42%	38%
% Mild or moderate ID	0%	83%	79%	67%
CAMCOG score^a	NA	80/107 (11, 55–96, n = 31)	70/107 (13.8, 41–92, n = 11)^c	59/107 (13.9, 39–87, n = 10)^c
mCRT score (immediate)^a	NA	35/36 (1.5, 30–36, n = 30)	20/36 (11.2, 0–36, n = 12)^c	15/36 (7.9, 0–32, n = 11)^c
mCRT score (delayed)^a	NA	12/12 (0.9, 8–12, n = 31)	6/12 (3.8, 0–12, n = 13)^c	4/12 (3.3, 0–12, n = 11)^c
CSF Aβ_42:40 ratio	0.11 (0.01, 0.08–0.12)	0.09 (0.02, 0.04–0.12)^b	0.05 (0.01, 0.03–0.08)^b	0.05 (0.01, 0.04–0.08)^b
CSF p-tau pg/ml	36 (8, 22–54)	35 (24, 10–122)	145 (86, 22–304)^b	158 (82, 31–323)^b
CSF t-tau pg/ml	243 (57, 167–366)	295 (166, 86–671)	936 (658, 118–2565) ^b	959 (500, 212–1988) ^b

Mean values (standard deviation, range) are given for each variable across clinical groups. NA; not available. ^aIn individuals with mild/moderate intellectual disability (ID) only. ^bp<0.05 compared to controls. ^cp<0.05 compared to aDS.

CSF VAMP2 changes over the course of AD and with age in adults with DS

Figure 2a shows that mean CSF VAMP-2 SRM intensities were lower in individuals with DS compared to controls (.84-fold, p = .04). Mean CSF VAMP-2 intensities were lower in the aDS group compared to controls (.73-fold, p = .005) and compared to the symptomatic group (pDS and dDS combined; .67-fold, p = .01). CSF VAMP-2 intensities were comparable to controls in pDS (.98-fold, p = .26) and dDS (.93-fold, p = .47). This relative increase in CSF VAMP-2 at late AD stages in adults with DS is supported by Fig. 2b, which shows that CSF VAMP-2 directly correlated with age in DS (r = .43, p < .0001). Conversely, CSF VAMP-2 inversely correlated with age in controls (r=-.51, p = .02). The control and DS regression lines for VAMP-2 were non-overlapping at the earliest age included in the study (22 years old) and did not intercept until the age of 42. Figure 2c shows the correlation between CSF VAMP-2 and CSF biomarkers of brain amyloid and tau pathology in adults with DS. VAMP-2 inversely correlated with the Aβ_42:40 ratio (r=-.47, p < .0001) and directly correlated with p-tau, (r = .56, p < .0001). To determine whether low CSF VAMP-2 is related to AD biomarker positivity in asymptomatic DS, we compared CSF VAMP-2 SRM intensities in the aDS group stratified by positivity for CSF Aβ₁₋₄₂ using our validated in-house cut-offs for sporadic AD. Compared to controls, CSF VAMP-2 SRM intensities were lower in individuals positive for CSF Aβ₁₋₄₂ (0.67-fold, p = .009) but not in individuals negative for CSF Aβ₁₋₄₂ (0.78-fold, p = .30). Thus, low CSF VAMP-2 is related to AD biomarker positivity and changes over the course of AD and with age in adults with DS.

CSF VAMP2 is associated with cognitive performance in adults with DS

Figure 3 shows the relationship between CSF VAMP-2 and measures of intellectual and cognitive impairment in adults with DS. Mean CSF VAMP-2 SRM intensities were comparable across individuals with, mild, moderate and severe intellectual disability (Fig. 3a; p = .76) and were not associated with K-bit score (Fig. 3b; r = .21, p = .16). While Fig. 3c shows a similar regression line for VAMP-2 with CAMCOG and mCRT scores, correlation analyses showed that VAMP-2 SRM intensities were associated with immediate (r = − .35, p = .01) and delayed (r = − .38, p = .005) recall in the mCRT test but not with CAMCOG scores (r = − .25, p = .07). However, linear regression analysis including level of intellectual disability as a covariate, showed that both intellectual disability (t= -3.90, p = .0003) and VAMP-2 (t= -2.02, p = .05) were associated with CAMCOG score (model adj.r² = .25, F = 9.7, p = .0003), while VAMP-2 (t= -2.20, p = .03) but not intellectual disability (t= -0.89, p = .38) was associated with immediate recall in the mCRT test. We observed a similar association with delayed recall (VAMP-2; t= -2.81, p = .007, intellectual disability t= -1.11, p = .27). Therefore, VAMP-2 was associated with both CAMCOG (when controlling for level of intellectual disability) and mCRT score in adults with DS.

Compared to other synaptic proteins, VAMP-2 is the best correlate of cognitive performance, age and AD biomarkers in adults with DS

Finally, we compared these findings for VAMP-2 to the other synaptic panel proteins and to NPTX2 and applied a strict adjustment of p-values to account for multiple testing. The correlation of VAMP-2 with immediate recall (adj.p = .09) and association with CAMCOG (adj.p = .44) did not survive adjustment for multiple testing. Variables associated with at least one synaptic protein (adj.p < .05) in DS are shown in Fig. 4. VAMP-2 was the only protein to correlate with mCRT delayed recall (adj.p = .04) and age (adj.p = .0008) and was the best correlate of CSF Aβ_42:40 (adj.p = .0001) and CSF p-tau (adj.p < .0001). On the other hand, NPTX2 was the best correlate of CSF Aβ₁₋₄₂ (r = .58, adj.p < .0001), showed the greatest fold-change across all AD stages (0.34 to 0.55-fold, adj.p < .002) and was the only synaptic protein to show changes in pDS (0.47-fold, adj.p = .002).

Here we report a comprehensive evaluation of synaptic proteins in CSF from adults with DS across the whole clinical continuum of AD. We show that of the 9 synaptic proteins evaluated, VAMP-2 is the only correlate of cognitive performance and age in this relatively understudied population. We also show that while mean CSF VAMP-2 levels were lower in asymptomatic adults with DS compared to cognitively normal controls, mean VAMP-2 levels were elevated at advanced AD stages. Increased CSF VAMP-2 correlated with low CSF Aβ_42/40, increased CSF p-tau and worse cognitive performance. Thus, changes in CSF VAMP-2 are closely related to CSF AD biomarkers and cognitive measures in adults with DS.

In controls, CSF VAMP-2 levels decreased with age and when compared across similar ages, VAMP-2 levels were lower in adults with DS compared to controls from the earliest age included in the study (22 years old) and did not converge until the age of 42. This finding suggests a distinct CSF profile of VAMP-2, and potentially a different mechanism of synaptic pruning, between healthy aging and the presence of AD pathology and/or triplication of chromosome 21. It is possible that the relatively lower CSF VAMP-2 levels in younger adults with DS compared to controls is a result of reduced VAMP-2 expression from birth. However, several lines of evidence suggest that CSF VAMP-2 levels change as a function of AD as opposed to intellectual disability; (a) CSF VAMP-2 was comparable to controls in adults with DS negative for the amyloid marker, (b) the findings reported here for this genetically determined form of AD replicate the nonlinear CSF profile of the 8 synaptic panel proteins previously reported across disease stages in sporadic AD (18) and (c) CSF VAMP-2 did not correlate with K-bit score and was comparable between individuals classified as having mild, moderate, severe or profound intellectual impairment but did correlate with age, AD biomarkers and episodic memory performance. Based on these findings, we propose that low VAMP-2 levels in these individuals may at least partially reflect changes related to the preclinical phase of AD, similar to that previously report in sporadic AD where CSF VAMP-2 levels were nominally reduced in preclinical AD and significantly elevated in prodromal and dementia stages compared to cognitively normal controls (18).

We have previously evaluated NPTX2 as a synaptic marker in the same cohort reported here (17). Similar to VAMP-2, CSF NPTX2 levels were lower in DS compared to controls, albeit that NPTX2 was reduced at all AD stages. In fact, here we report that compared to the other 8 synaptic proteins, NPTX2 was the only protein to be reduced at all AD stages compared to controls. However, unlike VAMP-2, CSF NPTX2 did not correlate with cognition or age. The distinct expression and function of these two proteins could explain their distinct CSF profiles in adults with DS. VAMP-2 is expressed at the human cortical synapse with increased enrichment compared not only to the other 7 synaptic panel proteins evaluated here but also to the widely-used pre-synaptic marker, synaptophysin (18). This high synapse specificity supports other studies that have shown that VAMP-2 is predominantly found at glutamatergic synapses (31) as part of the synaptic exocytosis core vesicular complex (32) where it is necessary for regulating the releasable pool of glutamate at the pre-synapse (33) and is also critical for post-synaptic trafficking of glutamate receptor subunits, particularly in the CA1 region of the hippocampus (34). Reduced VAMP-2 brain expression has been reported in AD (35). NPTX2 is specifically expressed by pyramidal neurons where it mediates activity-dependent strengthening of pyramidal neuron excitatory synapses on GABAergic parvalbumin interneurons (10). Therefore, both VAMP-2 and NPTX2 are specifically expressed at distinct populations of synapses where they have distinct functions that are critical for synaptic transmission. We therefore propose that CSF levels of these 2 synaptic proteins may reflect degeneration of distinct synapse populations. While, NPTX2 remains a promising surrogate marker of inhibitory circuit dysfunction in AD, DS and other neurodegenerative diseases, VAMP-2 may be a better surrogate marker of cognitive performance in adults with DS.

A previous study reported that CSF NPTX2 correlates well CSF levels of two other synaptic proteins, SNAP-25 and neurogranin in sporadic AD CSF (12). In this study, we report that, with the exception of VAMP-2, CSF levels of synaptic proteins were highly inter-correlated in adults with DS and that VAMP-2 was the only synaptic protein not to correlate with at least one other synaptic protein in controls.

The novelty of VAMP-2 is that it was the only synaptic protein evaluated here to correlate with age (a surrogate measure of disease progression in DS) and mCRT in the DS population. Similar to our previous study, we found that intellectual disability had a greater impact on CAMCOG score than on mCRT (22) such that the association of VAMP-2 with mCRT score was evident without the need to control for level of intellectual disability. The mCRT test is a version of the CRT modified for use in DS and discriminates well between DS adults with and without dementia (26). The CRT test is considered a clinical marker of episodic memory disorders due to medial temporal damage, especially in the CA1 field of the hippocampus (36), which is consistent with the functional role of VAMP-2 at CA1 synapses (34). It should be noted that while tau markers remain the best CSF correlates of cognition in this population, as tau is fast becoming a common drug target in AD clinical trials, an alternative surrogate measure of cognitive performance that does not directly measure the target levels would be a useful addition to the biomarker arsenal to monitor synapse engagement and therapeutic response.

While DS and autosomal dominant cohorts with available CSF are scarce, further replication of the findings reported here in independent genetic AD and DS cohorts would be valuable. A limitation of this study is the cross-sectional design. Longitudinal studies are needed to fully establish the prognostic value of VAMP-2 in DS cohorts.

VAMP-2 represents a new addition to the DS biomarker arsenal that may be used to detect and monitor AD-related synaptic dysfunction and cognitive decline, independent of intellectual disability, in this relatively under-studied population. VAMP-2 also has potential for use in AD clinical trials as an alternative surrogate measure of cognitive performance that does not directly measure the drug target (typically Aβ and tau). This work opens the door to future studies exploring the prognostic capacity of CSF VAMP-2 in adults with DS and sporadic AD.

AD; Alzheimer’s disease

aDS; asymptomatic Alzheimer’s disease in Down syndrome

CAMCOG; Cambridge Cognition Examination

CSF; cerebrospinal fluid

DABNI; Down Alzheimer Barcelona Neuroimaging Initiative

dDS; Dementia due to Alzheimer’s disease in Down syndrome

DS; Down syndrome

DSM; Diagnostic and Statistical Manual of Mental Disorders

KBIT; Kaufmann Brief Intelligence Test

ID; intellectual disability

mCRT; Modified cued recall test

NPTX2; Neuronal Pentraxin-2

pDS; prodromal Alzheimer’s disease in Down syndrome

SD; standard deviation

SPIN; Sant Pau Initiative in Neurodegeneration

SRM; Selected Reaction Monitoring

VAMP-2; Vesicle-associated membrane protein-2

Availability of data and materials

The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.

Acknowledgements

We thank the participants and their families for their generosity. We also acknowledge the Fundació Catalana Síndrome de Down for global support; Shaima El Bounasri, Soraya Torres, and Laia Muñoz for laboratory and sample handling and Judit Reyes Vilasalo for nursing management.

Funding

This work was supported by the Fundació Catalana Síndrome de Down and Fundació Víctor Grífols i Lucas and research grants from Institute of Health Carlos III (ISCIII), Spain (PI18/00327 to OB, PI18/00435 to DA, INT19/00016 to DA, PI17/01019 to JF; PI16/01825 to RB; PI17/01895 to AL and PI18/0335 to MC-I and CIBERNED Program 1, Alzheimer Disease to AL and SIGNAL study, www.signal.es) and the National Institutes of Health, US (NIA grants R01AG056850-01A1, R21AG056974 and R01AG061566 to JF). This work has also been supported by the Fundació La Marató de TV3 (20141210 to JF and 044412 to RB), the Fundació Bancaria Obra Social La Caixa (DABNI project to RB), Fundación BBVA (to AL) and by the Department of Health, Generalitat de Catalunya PERIS (SLT006/17/125 to DA, SLT002/16/00099 to RNL, SLT006/17/00119 to JF 2017) and SGR (2017 SGR 547 to JC) programs and partly funded by Fondo Europeo de Desarrollo Regional (FEDER), Unión Europea, “Una manera de hacer Europa”. OB is funded by the Miguel Servet Fellowhsip grant from the Institute of Health Carlos III (ISCIII), Spain and M.F I is supported by the Jérôme Lejeune Foundation, France. PW, DS and MX were supported by R35NS097966.

Author contributions

OB, MC-I, LV, SF, BB, JP, IB, MA, SV, RN-L, AB, MFI, MX, DX, MQ-A, SS and DA contributed to the acquisition and analysis of data. AL, DA, JC, JF, RB, PW drafted a significant portion of the manuscript and figures. All authors read and approved the final manuscript.

Ethics declarations

Ethics approval and consent to participate

The study (IIBSP-BMS-2018-103) was approved by the local ethics committee (Comité Ètic d’Investigació Clínica, Fundació de Gestió Sanitària de l’Hospital de la Santa Creu i Sant Pau) and was conducted in accordance with the Declaration of Helsinki. All participants gave their written informed consent to participate in the study.

Consent for publication

Not applicable.

Competing interests

Drs Belbin, Lleó, Fortea and Alcolea declare a filed patent application (WO2019175379 A1 Markers of synaptopathy in neurodegenerative disease) that includes the 9 synaptic proteins evaluated in this study. D.A. participated in advisory boards from Fujirebio-Europe and Roche Diagnostics and received speaker honoraria from Fujirebio-Europe, Nutricia and from Krka Farmacéutica S.L. J.F participated in advisory boards from AC-Inmune and was consultant to Novartis. MX, DX and PW are co-founders of CogNext.

McCarron M, McCallion P, Reilly E, Mulryan N. A prospective 14-year longitudinal follow-up of dementia in persons with Down syndrome. J Intellect Disabil Res. 2014;58(1):61-70.
Sinai A, Mokrysz C, Bernal J, Bohnen I, Bonell S, Courtenay K, et al. Predictors of Age of Diagnosis and Survival of Alzheimer's Disease in Down Syndrome. J Alzheimers Dis. 2018;61(2):717-28.
Hithersay R, Startin CM, Hamburg S, Mok KY, Hardy J, Fisher EMC, et al. Association of Dementia With Mortality Among Adults With Down Syndrome Older Than 35 Years. JAMA Neurol. 2018.
Fortea J, Vilaplana E, Carmona-Iragui M, Benejam B, Videla L, Barroeta I, et al. Clinical and biomarker changes of Alzheimer´s Disease in adults with Down Syndrome: a cross-sectional study. The Lancet. (in press 2020).
Selkoe DJ. Alzheimer's disease is a synaptic failure. Science. 2002;298(5594):789-91.
Terry RD, Masliah E, Salmon DP, Butters N, DeTeresa R, Hill R, et al. Physical basis of cognitive alterations in Alzheimer's disease: synapse loss is the major correlate of cognitive impairment. Annals of Neurology. 1991;30(4):572-80.
Henstridge CM, Sideris DI, Carroll E, Rotariu S, Salomonsson S, Tzioras M, et al. Synapse loss in the prefrontal cortex is associated with cognitive decline in amyotrophic lateral sclerosis. Acta Neuropathol. 2018;135(2):213-26.
Koffie RM, Hyman BT, Spires-Jones TL. Alzheimer's disease: synapses gone cold. Mol Neurodegener. 2011;6(1):63.
Robinson JL, Molina-Porcel L, Corrada MM, Raible K, Lee EB, Lee VM, et al. Perforant path synaptic loss correlates with cognitive impairment and Alzheimer's disease in the oldest-old. Brain. 2014;137(Pt 9):2578-87.
Chang MC, Park JM, Pelkey KA, Grabenstatter HL, Xu D, Linden DJ, et al. Narp regulates homeostatic scaling of excitatory synapses on parvalbumin-expressing interneurons. Nat Neurosci. 2010;13(9):1090-7.
Xiao MF, Xu D, Craig MT, Pelkey KA, Chien CC, Shi Y, et al. NPTX2 and cognitive dysfunction in Alzheimer's Disease. Elife. 2017;6.
Galasko DR, Xiao M, Xu D, Smirnov D, Salmon DP, Dewit N, et al. Synaptic biomarkers in CSF aid in diagnosis, correlate with cognition and predict progression in MCI and Alzheimer's disease. Alzheimer's & Dementia: Translational Research & Clinical Interventions. 2019;5:871-82.
Swanson A, Willette AA. Neuronal Pentraxin 2 predicts medial temporal atrophy and memory decline across the Alzheimer's disease spectrum. Brain Behav Immun. 2016;58:201-8.
Shao K, Shan S, Ru W, Ma C. Association between serum NPTX2 and cognitive function in patients with vascular dementia. Brain Behav. 2020:e01779.
van der Ende EL, Xiao M, Xu D, Poos JM, Panman JL, Jiskoot LC, et al. Neuronal pentraxin 2: a synapse-derived CSF biomarker in genetic frontotemporal dementia. J Neurol Neurosurg Psychiatry. 2020;91(6):612-21.
van Steenoven I, Koel-Simmelink MJA, Vergouw LJM, Tijms BM, Piersma SR, Pham TV, et al. Identification of novel cerebrospinal fluid biomarker candidates for dementia with Lewy bodies: a proteomic approach. Mol Neurodegener. 2020;15(1):36.
Belbin O, Xiao MF, Xu D, Carmona-Iragui M, Pegueroles J, Benejam B, et al. Cerebrospinal fluid profile of NPTX2 supports role of Alzheimer's disease-related inhibitory circuit dysfunction in adults with Down syndrome. Mol Neurodegener. 2020;15(1):46.
Lleo A, Nunez-Llaves R, Alcolea D, Chiva C, Balateu-Panos D, Colom-Cadena M, et al. Changes in Synaptic Proteins Precede Neurodegeneration Markers in Preclinical Alzheimer's Disease Cerebrospinal Fluid. Mol Cell Proteomics. 2019;18(3):546-60.
Alcolea D, Clarimon J, Carmona-Iragui M, Illan-Gala I, Morenas-Rodriguez E, Barroeta I, et al. The Sant Pau Initiative on Neurodegeneration (SPIN) cohort: A data set for biomarker discovery and validation in neurodegenerative disorders. Alzheimers Dement (N Y). 2019;5:597-609.
Fortea J, Carmona-Iragui M, Benejam B, Fernandez S, Videla L, Barroeta I, et al. Plasma and CSF biomarkers for the diagnosis of Alzheimer's disease in adults with Down syndrome: a cross-sectional study. Lancet Neurol. 2018.
Alcolea D, Pegueroles J, Munoz L, Camacho V, Lopez-Mora D, Fernandez-Leon A, et al. Agreement of amyloid PET and CSF biomarkers for Alzheimer's disease on Lumipulse. Ann Clin Transl Neurol. 2019;6(9):1815-24.
Benejam B, Videla L, Vilaplana E, Barroeta I, Carmona-Iragui M, Altuna M, et al. Diagnosis of prodromal and Alzheimer's disease dementia in adults with Down syndrome using neuropsychological tests. Alzheimers Dement (Amst). 2020;12(1):e12047.
Kaufman AS, & Kaufman, N. L. Manual for the Kaufman Brief Intelligence Test. : Circle Pines, MN: American Guidance Service; 1990.
Esteba-Castillo S, Dalmau-Bueno A, Ribas-Vidal N, Vila-Alsina M, Novell-Alsina R, Garcia-Alba J. [Adaptation and validation of CAMDEX-DS (Cambridge Examination for Mental Disorders of Older People with Down's Syndrome and others with intellectual disabilities) in Spanish population with intellectual disabilities]. Rev Neurol. 2013;57(8):337-46.
Devenny DA, Zimmerli EJ, Kittler P, Krinsky-McHale SJ. Cued recall in early-stage dementia in adults with Down's syndrome. J Intellect Disabil Res. 2002;46(Pt 6):472-83.
Benejam B, Fortea J, Molina-Lopez R, Videla S. Patterns of Performance on the Modified Cued Recall Test in Spanish Adults With Down Syndrome With and Without Dementia. Am J Intellect Dev Disabil. 2015;120(6):481-9.
Teunissen CE, Tumani H, Bennett JL, Berven FS, Brundin L, Comabella M, et al. Consensus Guidelines for CSF and Blood Biobanking for CNS Biomarker Studies. Mult Scler Int. 2011;2011:246412.
Alcolea D, Martinez-Lage P, Sanchez-Juan P, Olazaran J, Antunez C, Izagirre A, et al. Amyloid precursor protein metabolism and inflammation markers in preclinical Alzheimer disease. Neurology. 2015;85(7):626-33.
Choi M, Chang CY, Clough T, Broudy D, Killeen T, MacLean B, et al. MSstats: an R package for statistical analysis of quantitative mass spectrometry-based proteomic experiments. Bioinformatics. 2014;30(17):2524-6.
R-Core-Team. R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria; 2018.
Benagiano V, Lorusso L, Flace P, Girolamo F, Rizzi A, Bosco L, et al. VAMP-2, SNAP-25A/B and syntaxin-1 in glutamatergic and GABAergic synapses of the rat cerebellar cortex. BMC Neurosci. 2011;12:118.
Lin RC, Scheller RH. Structural organization of the synaptic exocytosis core complex. Neuron. 1997;19(5):1087-94.
Gu Y, Chiu SL, Liu B, Wu PH, Delannoy M, Lin DT, et al. Differential vesicular sorting of AMPA and GABAA receptors. Proc Natl Acad Sci U S A. 2016.
Hussain S, Davanger S. Postsynaptic VAMP/Synaptobrevin Facilitates Differential Vesicle Trafficking of GluA1 and GluA2 AMPA Receptor Subunits. PLoS One. 2015;10(10):e0140868.
Berchtold NC, Coleman PD, Cribbs DH, Rogers J, Gillen DL, Cotman CW. Synaptic genes are extensively downregulated across multiple brain regions in normal human aging and Alzheimer's disease. Neurobiology of Aging. 2012;34(6):1653-61.
Sarazin M, Chauvire V, Gerardin E, Colliot O, Kinkingnehun S, de Souza LC, et al. The amnestic syndrome of hippocampal type in Alzheimer's disease: an MRI study. J Alzheimers Dis. 2010;22(1):285-94.

Download PDF

Review #1 received at journal
12 Apr, 2021
Editorial decision: Major Revision
12 Apr, 2021
Review #2 received at journal
04 Apr, 2021
Reviewer #2 agreed at journal
22 Mar, 2021
Reviewers invited by journal
20 Mar, 2021
Reviewer #1 agreed at journal
20 Mar, 2021
Reviews received at journal
20 Mar, 2021
Editor assigned by journal
17 Mar, 2021
Submission checks completed at journal
17 Mar, 2021
Editor invited by journal
17 Mar, 2021
First submitted to journal
17 Mar, 2021

You are reading this latest preprint version

VAMP-2 Is a Surrogate Cerebrospinal Fluid Marker of Alzheimer-related Cognitive Impairment in Adults With Down Syndrome

Status:

Version 1

Abstract

Figures

Introduction

Material And Methods

Results

Discussion

Study Limitations

Conclusion

Abbreviations

Declarations

References

Status:

Version 1