Plasma Neuregulin 1 as a Synaptic Biomarker in Alzheimer’s Disease.

doi:10.21203/rs.3.rs-1353170/v1

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Research Article

Plasma Neuregulin 1 as a Synaptic Biomarker in Alzheimer’s Disease.

https://doi.org/10.21203/rs.3.rs-1353170/v1

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Background:Synaptic dysfunction is an early core feature of Alzheimer’s disease (AD), closely associatedwith cognitive symptoms. Neuregulin 1 (NRG1) is a growth and differentiation factor with a key role in the development and maintenance of synaptic transmission. Previous reports have shown that changes in cerebrospinal fluid (CSF) NRG1 concentrationare associated with cognitive status and biomarker evidence of AD pathology. Plasma biomarkers reflecting synaptic impairment would be of great clinical interest.

Objective: To measure plasma NRG1 concentration in AD patientsin comparison with other neurodegenerative disorders and neurological controls (NC)and to study its association with cerebrospinal fluid (CSF) core AD and synaptic biomarkers.

Methods: This retrospective study enrolled 127 participants including patients with AD at mild cognitive impairment stage (AD-MCI, n=27) and at dementia stage (n=35), non-AD dementia (n=26, Aβ-negative), non-AD MCI (n=19) and neurological controls (n=20). Plasma and CSF NRG1, as well as CSF core AD biomarkers (Aβ 42/Aβ 40 ratio, phospho-tau and total tau), were measured using ELISA. CSF synaptic markers were measured using ELISA for GAP-43 and neurogranin and through immunoprecipitation mass spectrometry for SNAP-25.

Results: Plasma NRG1 concentration was higher in AD-MCI and AD dementia patients compared with neurological controls (respectively P=0.005 and P<0.001). Plasma NRG1 differentiated AD MCI patients from neurological controls with an area under the curve of 88.3%, and AD dementia patients from NC with an area under the curve of 87.3%. Plasma NRG1 correlated with CSF NRG1 (β=0.372, P=0.0056, adjusted on age and sex). Plasma NRG1 was associated with AD CSF core biomarkers in the whole cohort and in Aβ-positive patients (β=-0.197- 0.423). Plasma NRG1 correlated with CSF GAP-43, neurogranin and SNAP-25 (β=0.278-0.355). Plasma NRG1 concentration correlated inversely with MMSE in the whole cohort and in Aβ-positive patients (all, β=-0.188, P=0.038; Aβ+: β=-0.255, P=0.038).

Conclusion: Plasma NRG1concentration is increased in AD patients and correlates with CSF core AD and synaptic biomarkers, and cognitive status. Thus, plasma NRG1 is a promising non-invasive biomarker to monitor synaptic impairment in AD.

Alzheimer’s disease

NRG1

synaptic pathology

plasma biomarker

Synaptic impairmentisa core feature of Alzheimer’s disease (AD) and one of the earliest detectable changes(1,2).Neuropathological examination has demonstrated that synaptic demise shows higher association to cognitive decline than amyloid plaques load or neurofibrillary tangles pathology(3,4).Positron emission tomography (PET) imaging using synaptic tracers indicates that synaptic density is significantly reduced in the hippocampus in AD patients, especially in its early symptomatic stages(5,6).The evaluation of several synaptic proteins has been achieved in the cerebrospinal fluid (CSF)(7–10).Presynaptic synaptosomal‐associated protein 25 (SNAP-25),synaptotagmin or(GAP-43) growth-associated protein-43 as well as post-synaptic neurogranin levels are altered in AD CSF and are reliable biomarkers of synaptic impairment, as early as in the preclinical stage of the disease(11,12). In blood, the presynaptic betasynuclein measured using quantitative mass spectrometry could discriminate AD and CJD from controls and other neurodegenerative disorders (13). Other synaptic markers have been explored in blood but so far, due to the existence of peripheral expression or of other factors of variability, there is no validated reliable biomarker of synaptic pathology (14).

Neuregulin 1 (NRG1), a protein encoded by the NRG1 gene, isa member of the epithelial growth factor (EGF) family.Theyconstitute ligands with high affinity for ErbB tyrosine kinase receptors. NRG1 is implicated in many processes during neural development including proliferation of neuronal progenitors, neuron migration and survival, axon guidance, glial development and myelination, as well as synaptogenesis(15,16). In the adult brain, NRG1 is expressed in multiple regions and regulates neurotransmission and synaptic plasticity(17). Membrane-bound, NRG1 requires processing by a protease to initiate release and signaling. Among implicated proteases, NRG1 can undergo cleavage by the β-site amyloid precursor protein cleaving enzyme 1 (BACE1)at multiple sites(18–20). Proteolytic processing results in the secretionof soluble forms that will further activate ErbB receptors, mainly at the post-synaptic level. NRG1 andits receptor ErbB4 levels have been found altered in human AD brain, both in hippocampus and cortex(21,22).In CSF, two studies including our prior work have reportedmodified NRG1levels in AD patients compared with controlsand to patients with non-ADrelated cognitive decline (23,24).

The purpose of our study was to investigateplasma NRG1 levels in a cohort of patients with cognitive decline du to AD, non-AD related cognitive decline and neurological controls and to assess its association with core AD CSF biomarkers, CSF synaptic markers and cognitive status.

Cohort

A total of 127 patientsfrom the Cognitive Neurology Center, Lariboisière Fernand Widal Hospital, Université de Pariswas retrospectively included in our study. Patients had undergoneCSF biomarkers analysis from 2012 to 2015 including Aβ 42/Aβ 40 ratio, tau phosphorylated on threonine 181 (p-tau) and totaltau (t-tau)measurements,in the context of the diagnostic workup of a cognitive complaint. We had a two-fold clinical and biological approach. Patients were first studied in relation to diagnosis, comprising patients with AD at the stage of mild cognitive impairment (AD-MCI, n=27) and at the stage of dementia(n = 35), non-AD related mild cognitive decline (non-AD MCI, n = 19), non-ADdementia (n=26) and neurological controls (NC, n = 20). Patients were then dichotomized according to their amyloid status defined by the CSF amyloid-β 42/ amyloid-β 40 (Aβ42/Aβ40) ratio (Aβ-positive: n=62; Aβ-negative: n=65).

Consensus diagnoses were made by neurologists, geriatricians, neuropsychologists, neuroradiologistsand biologists after comprehensive neurological examination, neuropsychological assessment, brain imaging and CSF biomarkers analysis, according to current diagnostic criteria(25–29). All AD patients met the NIA-AA research framework criteria and displayed a CSF profile on the AD continuum(26).AD-MCI patients followed Albert et al. definition of MCI due to AD (25). Non-AD MCI group comprised subjects with cognitive decline unrelated to AD, encompassing diagnosis of psychiatric disorders, systemic disorders or non-neurodegenerative disorders. Non-AD dementia group included patients withdementia with Lewy bodies (DLB, n = 6), behavioral variant frontotemporal dementia (FTD, n = 9)and vascular dementia (VD, n = 7). Non-AD MCI and non-AD dementia patients had normal amyloid ratio Aβ 42/40and normal or abnormal p-tau and t-tau. NC included patients with subjective cognitive decline, anxiety, depression, or sleep apnea syndrome, presenting with normative or sub-normative cognitive scores, normal CSF biomarkers and an absence of cognitive decline at follow-up.

CSF Biomarkers

CSF was obtained through a lumbar puncture; the second and third milliliterswere collected and centrifuged to prevent blood contamination. The supernatant was stored at − 80 °C until further analysis.

CSF core AD biomarkers (Aβ 42, Aβ 40, p-tau and t-tau) were analyzed at the Department of Biochemistry at Lariboisiere University Hospital Paris, France, using commercially available INNOTEST^® kits (Fujirebio Europe NV, Gent, Belgium). CSF profiles were analyzed according to the following cut-offs: A+: Aβ42/Aβ40 ratio <0.076; T+: p-tau > 58 pg/mL;N+:t-tau >340 pg/mL(26). Patients were classified as Aβ-positive and Aβ-negative according to the Aβ42/Aβ40 ratio.

CSF NRG1 concentrationwasmeasured using the Human NRG1 DuoSet ELISA kit (R&D Systems, Minneapolis, MN) as reported in Mouton-Liger et al(24).

All the CSF synaptic markerswere assessedat the Clinical Neurochemistry Laboratory at the Sahlgrenska University Hospital (Mölndal, Sweden). CSF neurograninand CSF GAP-43 concentrations were measured using in-house developed ELISAs(8,10).CSF SNAP-25concentration was measured by immunoprecipitation mass spectrometry according to a validated method(9,11).

Plasma NRG1 Measurement

Blood samples were obtainedthrough venipuncture under fasting condition and collected into ethylenediaminetetraacetic acid (EDTA) tubes. Samples were centrifuged at 2000xg for 20 minutes at 4◦C. Plasma supernatant was collected and frozen at −80◦C until further use. Prior to analysis, samples were centrifuged at 2000g for 10 minutes after thawing at room temperature. Plasma NRG1 wasassessed using the Human NRG1 DuoSet ELISA kit (R&D Systems)in Mölndal, Sweden following the manufacturer’s protocol. This assay has been shown to be highly sensitive to human NRG1 alpha-subunit with a sensitivity of 125–4,000 pg/mL(24,30,31). Plasma samples from study participants were analyzed in duplicates. Intra-plate and inter-plate coefficients of variation were respectively 5.9% and 7.4%.Ten samples (7.9% of samples total) were below the detection limit of the assays, including 4 NC, 3 AD, 2 non-AD dementia and one non-AD MCI other patients. For those samples, plasma NRG1 levels were interpolated from the standard curve or if this was not possible due to the very low signal the values were imputed to the lowest interpolated value. One outlier sample (plasma NRG1 value > mean+5SD) was excluded from analysis.

Statistical Analysis

Participants’ characteristics were examined in 5groups: NC, AD-MCI patients, AD dementia, non-AD MCI and non-AD dementia. Patients were also divided in Aβ-positive and Aβ-negative groups according to their CSF Aβ42/Aβ40 ratio using the clinically validated cut-off. Data are expressed as mean (standard deviation) for continuous variables or percentage (%) for categorical variables. We used Kruskal Wallis test to compare age and mini-mental state examination (MMSE)scores between groups and Pearson’s chi-square for sex. Fluid biomarkers levels were log-transformed prior to analysis and compared usinga one-way ANCOVAadjusted on age and sex followed by a post hoc least significant difference (LSD) test for pairwise group comparisons, adjusted for multiple comparisons (Bonferroni).Linear regression adjusted on age and sex was used to explore the association between CSF and plasma NRG1.Receiver operator curve (ROC) analysis was performed to study the accuracy of plasma NRG1 in differentiating the different groups.The association ofplasma NRG1 with core AD CSF biomarkers, CSF synaptic markers and with MMSE were explored by linear regression adjusted on age and sex in the whole cohort and in regard to Aβ status.

A p-value (P)< 0.05 was overall considered significant.Statistical analyses were performed using SPSS IBM 27.0 (IBM, Armonk, NY), and GraphPad Prism 9 (GraphPad Software, San Diego, CA, USA).

Data Availability

The datasets analyzed during the current study are available from the corresponding authors on a reasonable request.

Ethics and Consent

This study was approved by the Bichat Hospital Ethics Committee of Paris Diderot University(N°10–037, 18/03/2010) and all the participants have given their written consent.

Cohort

Demographics and biomarkers values in our cohort are reported Table 1.Detailed description of non-AD dementia patients is reportedin Supplemental Table 1and description of the cohort dichotomized by Aβ ratio in Supplemental Table 2.AD-MCI,AD dementia and non-AD dementia patients were older than NC and non-AD MCI patients (P= 0.003 – P<0.001). There was no difference regarding sex between groups (P =0.155). All further analysis was adjusted on age and sex, unless otherwise specified. AD-MCI and AD dementia patients displayed decreased CSF Aβ42/Aβ40 ratio and increased p-tau and t-tau levels compared with other groups. CSF synaptic markers neurogranin, GAP-43 and SNAP-25 were significantly higher in AD patients compared to NC. AD-MCI, non-AD MCI, AD dementia and non-AD dementia patients had decreased MMSE compared to NC.

Plasma NRG1Levels Across Groups

Higher concentration of plasma NRG1 was found in AD dementia patients compared to NCafter adjustment on age and sex (940.3 versus378.9 pg/mL, P<0.001, Figure 1A). AD-MCI patients also displayed higher concentrations compared to NC (707.6 versus 378.9 pg/mL, P =0.005). Non-AD dementia had higher levels compared to NC (615.5versus 378.9 pg/mL, P =0.014). Plasma NRG1 concentration did not differ significantly between NC and non-AD MCI patients.Participants were then dichotomizedaccording to their Aβ status defined by CSF Aβ42/Aβ40 ratio (Supplemental Table 2).Aβ-positivepatients displayed higherplasma NRG1concentration thanAβ-negativepatients (774.0 versus 538.4pg/mL,P = 0.023, Figure 1B).

Plasma NRG1 Accuracy in Identifying AD

We studied plasma NRG1 accuracy in discriminating AD patients from other diagnosis groups (Figure 1C). Plasma NRG1 showed good performance in differentiating AD patients from NC both at MCI stage (AUC = 88.3%, 95% CI: 77.2%-0.99.6%)and at dementia stage (AUC =87.6%, 95% CI: 76.9%- 98.2%). When comparing AD-MCI to non-AD MCIpatients, plasma NRG1 showed similar accuracy (AUC =86.4%, 95% CI: 74.7%- 98.3%). However, its discriminating power was lower between AD patients and non-AD dementia patients (AUC = 69.3%, 95% CI: 55.7% - 82.3%).

Correlation to CSF NRG1

Plasma and CSF NRG1 concentrations correlated in the overall cohort (β = 0.372, P= 0.0056, adjusted on age and sex) (Figure 2A). This correlation was also detected in the Aβ-positive group (β = 0.292, P= 0.034). No correlation was observed between plasma and CSF NRG1 in the Aβ-negative group (β = 0.156, P= 0.305).

Correlation to AD Biomarkers

Plasma NRG1 displayed a weak inverse correlation with CSF Aβ42/Aβ40 ratio in the whole cohort (β=-0.197, P= 0.043, adjusted on age and sex, Figure 2B). This correlation was stronger in the Aβ-positive group (β=-0.372, P= 0.003). CSF p-tau and CSF t-tau displayed a stronger correlation with plasma NRG1 in the whole population (respectively: β=0.361, P< 0.001 and β=0.423, P< 0.001)(Figure 2 C-D). These correlations were both sustained in the Aβ-positive patients (CSF p-tau: β=0.430, P< 0.001; CSF t-tau: β=0.209, P< 0.001). There was no correlationbetween plasma NRG1 and CSF Aβ42/Aβ40 ratio, p-tau and t-tau in Aβ-negativepatients.

Association to Synaptic Biomarkers and to Cognition

We studied the association of plasma NRG1 with three CSF synaptic biomarkers, neurogranin, GAP-43 and SNAP-25, after adjustment on age and sex (Figure 3). Plasma NRG1 levels were overall associated with CSF GAP-43 levels (β= 0.355, P< 0.001) (Figure 3A). This association remained significant in Aβ-positive patients (β= 0.434, P< 0.001) but not in the Aβ-negative group. Similarly, plasma NRG1 levels were associated with CSF neurogranin levels, in the whole cohort (β= 0.278, P = 0.002) and in the Aβ-positive patients (β= 0.322, P= 0.007) (Figure 3B). CSF SNAP-25 levels were associated with plasma NRG1 in the whole cohort (β= 0.327, P= 0.001) as in the Aβ-positive (β = 0.375, P = 0.004) and in Aβ-negative group (β = 0.339, P= 0.026, Figure 3C).

MMSE scores were significantly associated with plasma NRG1 levels after adjustment on age and sex (β= -0.188, P=0.038, Figure 3D). This association was sustained in the Aβ-positive group (β= -0.255, P=0.037) but not in the Aβ-negative group.

Accessible biomarkers monitoring synaptic dysfunction and loss would be of great clinical use in AD for early diagnosis, prediction and monitoring of cognitive decline, and for drug evaluation. In this study, we report that plasma synaptic marker NRG1 i/ was increased in AD patients already at MCI stage ii/ had a promising AUC to discriminate AD patients both at MCI and dementia stage, from NC, iii/was associated with CSF AD biomarkers in Aβ-positive individuals and iv/ correlated with CSF synaptic markers and v/ was inversely correlated with cognition.

NRG1 is expressed at the synapse in multiple brain regions, including those preferentially affected in AD, as hippocampus and entorhinal cortex(32–34).Post-mortem studies have reported NRG1 accumulation in neuritic plaques in association with dystrophic neurites, activated astrocytes, and microglia in human AD brains(21,22). NRG1 and ErbB4 directed immunoreactivity was observed in the hippocampus located in neuronal cell bodies and dendrites (22). Interestingly, NRG1 can be measured in human fluids(17,23,24,30,31,35,36). Increased levels of CSF NRG1 in AD compared with controls and with non-AD related cognitive decline, have been reported in the literature, including our prior work (23,24). In Pankonin et al., CSF NRG1 was increased in AD patients from an early stage of the disease. More recently, in a larger cohort using the most recent AD diagnosis criteria including CSF biomarkers, we have confirmed those results(24). CSF NRG1 was significantly associated with CSF AD core biomarkers, suggesting a possible implicationin AD pathophysiological processes. Moreover,CSF NRG1 levels correlated with other CSF synaptic markers, also suggesting that NRG1 was mainly originating from the synapse.

A previous study has already reported increased levels of plasma NRG1 in AD patients, with higher levels in advanced disease(35). However, in this work, AD was clinically diagnosedwith no biomarker to confirm underlying AD pathophysiological process andcorrelation with CSF NRG1 levels was not studied.Our study brings evidence that plasma NRG1 is increased in patients with confirmed underlying amyloid pathology, already at MCI stage.It is interesting to noteas APP, at the origin of Aβ, and NRG1 are both cleaved by BACE1 in the brain(18,20).

Plasma NRG1 levels were significantly correlated with CSF levels in the whole cohort and this association was sustained in the Aβ-positive patients group.The existence of extra cerebral expression of NRG1 is known but the significant correlation between plasma and CSF levels indicates that plasma level modifications substantially arise from the central nervous system (37). Thus, this flags plasma NRG1 levels as a potential surrogate for brain NRG1 modifications in AD.Correlation to CSF synaptic markers GAP-43, neurogranin and SNAP-25 in the Aβ-positive patients tends to indicate that detected NRG1 changes are related to synaptic modifications.

There was a significant association between plasma NRG1 levelsand MMSE in our whole cohort as well as in the Aβ-positive patients.This finding is in agreement with the previous studies in plasma and CSF again showing that NRG1 levels associate with cognition already at early stages of the disease (23,24,35).

Plasma NRG1 also displayed increased levels in non-AD dementia compared to NC and its accuracy in identifying AD at dementia stage was moderate. In a study on vascular dementia, plasma NRG1 levels were found to be increased and inversely correlated to cognitive severity(38).Neuropathological studies and synaptic CSF biomarkers results have highlighted the fact that synapse dysfunction is a prominent feature in AD but that it is not entirely specific to it(39,40). It can also be observed in non-AD dementia, although to a much lesser extentthan in AD, a finding in line with our results (41).

An underlying mechanistic question to this marker iswhether alterations in NRG1 levels are related to a general process of synaptic degeneration and clearance or whether these changes occur as a response, positive or negative, to the development of AD pathology, or to an increase in synaptic synthesis and release.

NRG1-ErbB4 signaling is important in regulating synaptic function at both excitatory and inhibitory synapses (42). While loss of NRG1 signaling has been shown to be pejorative to synaptic transmission, excessive NRG1 activity is also associated with synaptic dysfunction resulting from alterationof LTP at glutamatergic synapses(34,43). NRG1 has also been identified as a major susceptibility gene in schizophrenia(Stefansson et al. 2002; Mei and Xiong 2008). Mutant NRG1 mice display both excitatory and inhibitory synaptic impairment and schizophrenia-like behavioral disorder(46).NRG1 function must be precisely balanced to maintain normal glutamatergic receptor functions at synapses and excitatory-inhibitory neurotransmission.In line with those findings, evidence suggests that NRG1 increase may specifically influence cognitive function and neuropathology in AD(47–49). Although not formally established,the mechanism of the increase of NRG1 could beexplained by the increased levels and activity of BACE1 observed in AD (47). Yet, its beneficial or detrimental effect is not solved. In experimental works, NRG1 overexpression could rescue APP induced toxicity in primary cortical neurons(48). In an AD mouse model, NRG1 treatment prevented Aβ-induced impairment of long-term potentiation in hippocampal slices via its receptor ErbB4(50).Conversely, other experimental works have suggested a negative effect of the NRG1-ErbB4 signaling in AD. Perfusion of NRG1 in hippocampus decreased LTP in AD mice model as well as in control mice (51). Further understandings of NRG1 responseupon amyloid pathology will allow to specify the exact synaptic eventsassociated with CSF and plasma NRG1 modifications observed in AD patients.

In addition to contributing to better understanding of AD mechanisms, our finding that plasma NRG1 levels could reflect synaptic impairment in AD may have major practical utility. Development of blood biomarkers measuring Aβ, tau and neurodegeneration processes has known great advancement recently, but, to date, there is no validated blood biomarkers reflecting synaptic pathology (14). Recent studies have reported that the measure of markers of AD hallmarksin plasma such as Aβ42, p-tau 181, p-tau217 and p-231can identify and monitor AD brain pathology with high accuracy, demonstratingthat they can be used as non-invasive toolsin AD diagnosis(52–54).As synaptic impairment is one of the earliestabnormal features in AD,already present at the preclinical phase, an accessible non-invasive synaptic marker would be of high added value for early diagnosis(12).

Moreover, synaptic markers hold important promise for monitoringthe effects of disease-modifying treatments on synaptic degeneration. Compared with CSF markers, validated blood-based synaptic AD biomarkers would provide a fast, acceptable and cost-effective method of early detection, diagnosis and follow-up as well as a screening and follow-up tool in therapeutic trials.Our work shows that plasma NRG1 levels could be one of these potential biomarkers.

Limitations

This study has several limitations. The correlation between plasma and CSF NRG1 remained moderate. Further studies will be needed to understand if this variability is related to the blood-brain barrier’s passage, NRG1 metabolism in plasma, matrix effects or interaction with peripheral NRG1. In our cohort, cognition was evaluated using MMSE, a general test. Study of plasma NRG1 relation to cognition using neuropsychological assessment with testsevaluating specifically episodic memory should give more robust evidence. We could not include measurements of AD‐specific blood biomarkers such as p-tau or Aβ. Finally,confirmation of our results in larger cohorts is needed, including larger samples of non-AD dementia patients. Study of plasma NRG1 at preclinical phase will also be needed to better characterize its kinetic on the whole AD spectrum.

Our results suggest that plasma NRG1 is a novel biomarker for synaptic dysfunction and degeneration in AD. Plasma NRG1 showed a significant increase in AD patients already at MCI stage, and correlated with biomarkers for AD pathology, as well as with established CSF biomarkers for synaptic dysfunction in AD. As a novel blood synaptic marker, plasma NRG1 may improve the diagnosis of neurodegenerative disorders and may also be useful to monitor clinical disease progression and therapeutic response in clinical trials of novel disease-modifying drug candidates.

AD, Alzheimer’s disease; Aβ40, amyloid beta 1–40; Aβ42, amyloid beta 1–42; APP, amyloid precursor protein; AUC, area under the curve; BACE1, beta-site amyloid precursor protein cleaving enzyme 1; CSF, cerebrospinal fluid; erbB4, receptor tyrosine-protein kinase erbB-4; GAP-43, growth-associated protein 43; MCI, mild cognitive impairment; MMSE, mini mental state examination; NRG1, neuregulin1; PET, Positron emission tomography; p-tau, phosphorylated tau; SNAP-25, synaptosomal associated protein 25; t-tau, total tau

Acknowledgements

The authors wish to sincerely thank all the patients that participated in this study as well as their relatives.

Authors’ contributions

Concept and design: CP, FML, JH. Acquisition, analysis, and interpretation of the data: all authors.Statistical analysis: AV. Drafting the manuscript: AV, CP, FML, JH. Review & editing: all authors. All authors have read and agreed to the published version of themanuscript.Obtained funding: CP, JH, HZ, KB.

AV had full access to all the data in the study and takes full responsibility for the integrity of the data and the accuracy of the data analysis.

Competing interests

KB has served as a consultant or at advisory boards for Abcam, Axon, Biogen, JOMDD/Shimadzu, Lilly, MagQu, Prothena, Roche Diagnostics, and Siemens Healthineers, and as data monitoring committee for Julius Clinical and Novartis. KB is a co-founder of Brain Biomarker Solutions in Gothenburg AB (BBS), which is a part of the GU Ventures.HZ has served at scientific advisory boards and/or as a consultant for Abbvie, Alector, Annexon, Artery Therapeutics, AZTherapies, CogRx, Denali, Eisai, Nervgen, Pinteon Therapeutics, Red Abbey Labs, Passage Bio, Roche, Samumed, Siemens Healthineers, Triplet Therapeutics, and Wave, has given lectures in symposia sponsored by Cellectricon, Fujirebio, Alzecure, Biogen, and Roche, and is a co-founder of Brain Biomarker Solutions in Gothenburg AB (BBS), which is a part of the GU Ventures Incubator Program.CP is a member of the International Advisory Boards of Lilly; is a consultant for Fujirebio, Alzhois, Euroimmune, Ads Neuroscience, Roche, AgenT, and Gilead; and is involved as an investigator in several clinical trials for Roche, Esai, Lilly, Biogen, Astra-Zeneca, Lundbeck, and Neuroimmune.The other authors declare no competing interests.

Funding

AV was supported by Fondation Adolphe de Rothschild, Amicale des Anciens Internes des Hôpitaux de Paris, Fondation Philipe Chatrier and Fondation Vaincre Alzheimer. FML is supported by Fondation Planiol. HZ is a Wallenberg Scholar supported by grants from the Swedish Research Council (#2018–02532), the European Research Council (#681712), Swedish State Support for Clinical Research (#ALFGBG-720931), the Alzheimer Drug Discovery Foundation (ADDF), USA (#201809–2016862), the AD Strategic Fund and the Alzheimer’s Association (#ADSF-21-831376-C, #ADSF-21-831381-C and #ADSF-21-831377-C), the Olav Thon Foundation, the Erling-Persson Family Foundation, Stiftelsen för Gamla Tjänarinnor, Hjärnfonden, Sweden (#FO2019-0228), the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 860197 (MIRIADE), European Union Joint Program for Neurodegenerative Disorders (JPND2021-00694), and the UK Dementia Research Institute at UCL. KB is supported by the Swedish Research Council (#2017-00915), the Alzheimer Drug Discovery Foundation (ADDF), USA (#RDAPB-201809–2016615), the Swedish Alzheimer Foundation (#AF-742881), Hjärnfonden, Sweden (#FO2017-0243), the Swedish state under the agreement between the Swedish government and the County Councils, the ALF-agreement (#ALFGBG-715986), and European Union Joint Program for Neurodegenerative Disorders (JPND2019-466-236).

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Table 1, Demographics and biomarkers values

n = 127	Neurologicalcontrols n = 20	Non-AD MCI n = 19	AD-MCI n = 25	ADdementia n = 37	Non-AD dementia n = 26	*P-value*
Age, years	60.6 (9.6)	61.1 (8.4)	70.3 (5.8)^#	67.7 (7.9)^#	68.1 (7.0)^#	<0.001
Female, n (%)	70% (14)	63% (12)	68% (17)	62% (23)	38% (10)	0.155
LoE, years	11.6 (3.8)	9.7 (2.5)	11.0 (3.9)	9.0 (3.5)^#	11.2 (3.4)	0.050
MMSE	27.42 (1.6)	25.0 (2.3)^#	25.1 (2.4)^#	18.2 (4.3)^#	22.8 (5.4)^#	<0.001
CSF biomarkers
CSF Aβ42, pg/mL	1041.6 (264.4)	987.2 (326.0)	516.4 (122.5)^#	548.3 (135.9)^#	919.3 (428.7)	<0.001
CSF Aβ42/Aβ40 ratio	0.129 (0.045)	0.092 (0.029)	0.051 (0.027)^#	0.045 (0.017)^#	0.104 (0.033)	<0.001
CSF p-tau, pg/mL	33.7 (10.7)	40.7 (17.2)	79.2 (22.9)^#	95.7 (32.5)^#	45.2 (20.5)^#	<0.001
CSF t-tau, pg/mL	196.0 (66.7)	223.0 (100.6)	501.7 (203.4)^#	703.9 (285.2)^#	305.2 (152.1)^#	<0.001
CSF NRG1, pg/mL	295.8 (107.1)	324.4 (137.5)	312.8 (157.8)	403.9 (155.1)^#	315.0 (134.4)	0.044
CSF neurogranin, pg/mL	208.1 (69.5)	213.6 (84.7)	364.4 (83.1)^#	351.4 (91.9)^#	230.2 (107.9)	<0.001
CSF GAP-43, pg/mL	1677.2 (616.2)	2004.8 (987.9)	3422.9 (1087.9)^#	3787.6 (1388.7)^#	2348.8 (1267.8)^#	<0.001
CSF SNAP-25, pg/mL	6.7 (2.2)	8.2 (3.5)	13.1 (3.7)^#	17.1 (5.3)^#	7.8 (3.9)	<0.001
Plasma biomarker
Plasma NRG1, pg/mL	378.9(400.7)	488.4 (392.2)	707.6 (562.7)^#	940.3 (737.5)^#	615.5 (486.3)^#	<0.001

Data shown as mean (SD) or n (%), as appropriate. Kruskall-Wallis test was used to compare age between groups and Pearson’s chi-square to compare sex. Fluid biomarkers levels and MMSE were compared with a one-way ANCOVA adjusted by age and sex followed by least square difference test adjusted for multiple comparisons.^#P < 0.05 compared to neurological controls.

Abbreviations: Aβ42, amyloid-beta 42; Aβ40, amyloid-beta 40; AD, Alzheimer’s disease; AD-MCI, MCI due to Alzheimer’s disease; CSF, cerebrospinal fluid; GAP-43, growth-associated protein 43; LoE, level of education; MCI, mild cognitive impairment; MMSE, Mini-Mental State Examination; NRG1, neuregulin1; p-tau, phosphorylated tau; SNAP-25, synaptosomal-associated protein 25; t-tau, total tau.

Competing interest reported. KB has served as a consultant or at advisory boards for Abcam, Axon, Biogen, JOMDD/Shimadzu, Lilly, MagQu, Prothena, Roche Diagnostics, and Siemens Healthineers, and as data monitoring committee for Julius Clinical and Novartis. KB is a co-founder of Brain Biomarker Solutions in Gothenburg AB (BBS), which is a part of the GU Ventures. HZ has served at scientific advisory boards and/or as a consultant for Abbvie, Alector, Annexon, Artery Therapeutics, AZTherapies, CogRx, Denali, Eisai, Nervgen, Pinteon Therapeutics, Red Abbey Labs, Passage Bio, Roche, Samumed, Siemens Healthineers, Triplet Therapeutics, and Wave, has given lectures in symposia sponsored by Cellectricon, Fujirebio, Alzecure, Biogen, and Roche, and is a co-founder of Brain Biomarker Solutions in Gothenburg AB (BBS), which is a part of the GU Ventures Incubator Program. CP is a member of the International Advisory Boards of Lilly; is a consultant for Fujirebio, Alzhois, Euroimmune, Ads Neuroscience, Roche, AgenT, and Gilead; and is involved as an investigator in several clinical trials for Roche, Esai, Lilly, Biogen, Astra-Zeneca, Lundbeck, and Neuroimmune. The other authors declare no competing interests.

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Plasma Neuregulin 1 as a Synaptic Biomarker in Alzheimer’s Disease.

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