Plasma neuregulin 1 as a synaptic biomarker in Alzheimer's disease: a discovery cohort study

BACKGROUND: Synaptic dysfunction is an early core feature of Alzheimer's disease (AD), closely associated with 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 concentration are 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 patients in 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 NRG1 concentration 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

N-terminal and mid-region tau fragments as fluid biomarkers in neurological diseases

Brain-derived tau secreted into CSF and blood consists of different N-terminal and mid-domain fragments, which may have a differential temporal course and thus, biomarker potential across the Alzheimer's disease continuum or in other neurological diseases. While current clinically validated total-tau (t-tau) assays target mid-domain epitopes, comparison of these assays with new biomarkers targeting N-terminal epitopes using the same analytical platform may be important to increase the understanding of tau pathophysiology. We developed three t-tau immunoassays targeting specific N-terminal (NTA and NTB t-tau) or mid-region (MR t-tau) epitopes, using single molecule array technology. After analytical validation, the diagnostic performance of these biomarkers was evaluated in CSF and compared with the Innotest t-tau (and as proof of concept, with N-p-tau181 and N-p-tau217) in three clinical cohorts (n = 342 total). The cohorts included participants across the Alzheimer's disease continuum (n = 276), other dementia (n = 22), Creutzfeldt-Jakob disease (n = 24), acute neurological disorders (n = 18) and progressive supranuclear palsy (n = 22). Furthermore, we evaluated all three new t-tau biomarkers in plasma (n = 44) and replicated promising findings with NTA t-tau in another clinical cohort (n = 50). In CSF, all t-tau biomarkers were increased in Alzheimer's disease compared with controls (P < 0.0001) and correlated with each other (rs = 0.53-0.95). NTA and NTB t-tau, but not other t-tau assays, distinguished amyloid-positive and amyloid-negative mild cognitive impairment with high accuracies (AUCs 84% and 82%, P < 0.001) matching N-p-tau217 (AUC 83%; DeLong test P = 0.93 and 0.88). All t-tau assays were excellent in differentiating Alzheimer's disease from other dementias (P < 0.001, AUCs 89-100%). In Creutzfeldt-Jakob disease and acute neurological disorders, N-terminal t-tau biomarkers had significantly higher fold changes versus controls in CSF (45-133-fold increase) than Innotest or MR t-tau (11-42-fold increase, P < 0.0001 for all). In progressive supranuclear palsy, CSF concentrations of all t-tau biomarkers were similar to those in controls. Plasma NTA t-tau concentrations were increased in Alzheimer's disease compared with controls in two independent cohorts (P = 0.0056 and 0.0033) while Quanterix t-tau performed poorly (P = 0.55 and 0.44). Taken together, N-terminal-directed CSF t-tau biomarkers increase ahead of standard t-tau alternatives in the Alzheimer's disease continuum, increase to higher degrees in Creutzfeldt-Jakob disease and acute neurological diseases and show better potential than Quanterix t-tau as Alzheimer's disease blood biomarkers. For progressive supranuclear palsy, other tau biomarkers should still be investigated

N-terminal and mid-region tau fragments as fluid biomarkers in neurological diseases

Brain-derived tau secreted into CSF and blood consists of different N-terminal and mid-domain fragments, which may have a differential temporal course and thus, biomarker potential across the Alzheimer’s disease continuum or in other neurological diseases. While current clinically validated total tau assays target mid-domain epitopes, comparison of these assays with new biomarkers targeting N-terminal epitopes using the same analytical platform may be important to increase the understanding of tau pathophysiology. We developed three total tau immunoassays targeting specific N-terminal (NTA and NTB total tau) or mid-region (MR total tau) epitopes, using single molecule array technology. After analytical validation, the diagnostic performance of these biomarkers was evaluated in CSF and compared with the Innotest total tau (and as proof of concept, with N-p-tau181 and N-p-tau217) in three clinical cohorts (n = 342 total). The cohorts included participants across the Alzheimer’s disease continuum (n = 276), other dementias (n = 22), Creutzfeldt–Jakob disease (n = 24), acute neurological disorders (n = 18) and progressive supranuclear palsy (n = 22). Furthermore, we evaluated all three new total tau biomarkers in plasma (n = 44) and replicated promising findings with NTA total tau in another clinical cohort (n = 50). In CSF, all total tau biomarkers were increased in Alzheimer’s disease compared with controls (P </p

P-tau235: a novel biomarker for staging preclinical Alzheimer's disease

Alzheimer's disease (AD) is characterised by a long preclinical phase. Although phosphorylated tau (p-tau) species such as p-tau217 and p-tau231 provide accurate detection of early pathological changes, other biomarkers capable of staging disease progression during preclinical AD are still needed. Combining exploratory and targeted mass spectrometry methods in neuropathologically confirmed brain tissue, we observed that p-tau235 is a prominent feature of AD pathology. In addition, p-tau235 seemed to be preceded by p-tau231, in what appeared to be a sequential phosphorylation event. To exploit its biomarker potential in cerebrospinal fluid (CSF), we developed and validated a new p-tau235 Simoa assay. Using three clinical cohorts, we demonstrated that (i) CSF p-235 increases early in AD continuum, and (ii) changes in CSF p-tau235 and p-tau231 levels during preclinical AD are consistent with the sequential phosphorylation evidence in AD brain. In conclusion, CSF p-tau235 appears to be not only a highly specific biomarker of AD but also a promising staging biomarker for the preclinical phase. Thus, it could prove useful tracking disease progression and help enriching clinical trial recruitment

Évolution et facteurs prédictifs à court terme des dyskinésies après stimulation cérébrale profonde du noyau sous-thalamique dans la maladie de Parkinson

Introduction: deep brain stimulation of the subthalamic nucleus (STN-DBS) improves motor state in advanced Parkinson's disease (PD). Dyskinesia is among the symptoms that reduce the most the quality of life at the stage of motor fluctuations. The aims of our study were to i) assess the evolution of dyskinesia at one year after STN-DBS, ii) identify predictors of the outcome and iii) identify an optimal location of active contacts to obtain improvement of dyskinesia. Materials and methods: we included 269 patients from the Predi-Stim multicenter prospective cohort, who underwent STN-DBS and had had evaluation at one year post-surgery. The primary endpoint was the UPDRS IV dyskinesia sub-scores 4.1 + 4.2 + 4.6 (UPDRS DSK) scored at baseline and at one year follow-up. Motor and neuropsychiatric clinical data were collected pre-operatively and at one year. Pre-surgery cerebral MRI and post-surgery CT-scan were collected and treated to locate active contacts. Logistic regression analysis was performed to identify independent predictors of outcome. An analysis by ROC curve was made in order to establish a threshold of UPDRS IV DSK at inclusion allowing to determine outcome. Results: dyskinesia was improved at one-year follow-up in 82,4% of patients: the UPDRS DSK mean score decreased from 3.26 +-2.31 to 1.3 +-1.73 (p <0.001 ). This improvement concerned all subtypes of dyskinesia. Only the severity of the dyskinesia was predictive of the outcome at one year: the UPDRS DSK score at baseline was positively correlated with its decrease at one year post-surgery (r = -0.5654, p < 0.0001). A UPDRS DSK score of less than 3 at baseline allowed to identify with a specificity of 77.0% and a sensitivity of 81.4% the patients with an pejorative evolution of dyskinesia at one year. A more favorable evolution of dyskinesia was associated with a dorsal position of the active contacts (r = 0.2238, p= 0.0350) and the location of at least one active contact in the sensorimotor territory (p = 0.0303) in 89 patients for whom the location of active contacts was available. Conclusion: in a homogeneous cohort of patients with advanced PD, we showed that i) STNDBS improved dyskinesia, ii) initial severity of dyskinesia was predictive of improvement and iii) improvement correlated with a posterior location of active contacts.Introduction : la Stimulation Cérébrale Profonde (SCP) du Noyau Sous-Thalamique (NST) améliore l’état moteur dans la Maladie de Parkinson (MP) évoluée. Les dyskinésies sont parmi les symptômes réduisant le plus la qualité de vie au stade des fluctuations motrices. Les objectifs de notre étude étaient i) d’évaluer l’évolution des dyskinésies à un an de la SCP du NST, ii) d’identifier des facteurs prédictifs de leur évolution et iii) d’identifier une localisation optimale des contacts actifs pour leur amélioration. Matériels et méthodes : nous avons inclus 269 patients de la cohorte prospective multicentrique Prédi-Stim ayant eu le bilan d’évaluation à un an de la SCP du NST. Le critère de jugement principal était le score UPDRS IV sous-scores 4,1+4,2+4,6 (UPDRS DSK) évalué à l’inclusion et à un an de la SCP. Les données cliniques motrices et neuropsychiatriques étaient recueillies en pré-opératoire et à un an. L’IRM cérébrale pré-opératoire et le scanner postopératoire étaient collectés et traités pour localiser les contacts actifs. Une analyse de régression logistique était effectuée pour identifier des facteurs prédictifs indépendants. Une analyse par courbe ROC permettait d’établir un seuil de score UPDRS DSK à l’inclusion permettant de discriminer les patients selon leur évolution. Résultats : les dyskinésies étaient améliorées à un an chez 82,4% des patients : le score UPDRS DSK moyen passait de 3,26 +- 2,31 à 1,3+-1,73 (p<0,001). Cette amélioration portait sur tous les sous-types de dyskinésies. Seule la sévérité des dyskinésies était prédictive de l’évolution à un an : le score UPDRS DSK à l’inclusion était positivement corrélé à sa diminution à un an post-opératoire (r=-0,5654, p<0,0001). Un score UPDRS DSK inférieur à 3 à l’inclusion permettait d’identifier avec une spécificité de 77,0% et une sensibilité de 81,4% les patients avec une évolution défavorable des dyskinésies à un an. Une évolution plus favorable des dyskinésies était associée à une position postérieure des contacts actifs (r=0,2238, p=0,0350) et à la présence d’au moins un contact actif dans le territoire sensorimoteur (p=0,0303) chez 89 patients pour lesquels la localisation des contacts actifs était disponible. Conclusion : dans une cohorte homogène de patients avec une MP évoluée, nous avons montré que i) la SCP des NST améliorait les dyskinésies, ii) la sévérité initiale des dyskinésies était prédictive de leur amélioration et iii) l’amélioration était corrélée à une position plus postérieure des contacts actifs

Étude clinique de nouveaux biomarqueurs liquidiens dans la maladie d'Alzheimer et autres maladies neurodégénératives

Alzheimer's disease (AD) is the most common cause of dementia worldwide. Diagnosis during life can be made using imaging and fluid biomarkers reflecting the hallmark lesions including amyloid and tau pathologies, and neurodegeneration. 'Core AD' cerebrospinal fluid (CSF) biomarkers, including measurements of amyloid beta 1-42 (Aß42) and of phosphorylated tau (p-tau) and total tau (t-tau), are now being used in the routine clinical work up of cognitive impairment. However, those biomarkers present with limited availability, invasiveness and high financial costs. Moreover, they do not reflect the other processes underlying AD, such as synaptic demise, axonal damage or neuroinflammation. Recently developed novel blood-based biomarkers appear to be very promising for AD diagnosis. Additionally, new markers tracking non-amyloid and tau mechanisms are now available, showing potential for AD and non-AD dementia exploration. The aim of this thesis was to investigate novel CSF and blood candidate biomarkers in patients from clinical settings, including amyloid and tau specific and'''unspecific markers, for positive and differential diagnosis of AD. We studied a memory clinic cohort issued from the Center of Cognitive Neurology, Paris University, France, including cognitively impaired patients and neurological controls who had undergone CSF and plasma sampling for exploration of a cognitive complaint. Firstly, we explored plasma neuregulin 1, a presynaptic protein member of the epidermal growth factor family. Plasma neuregulin 1 levels were increased in AD patients compared with control subjects. These levels were associated with CSF synaptic markers and cognitive status, showing potential to easily monitor synaptic impairment. Secondly, we performed a paired CSF and plasma comparison of two neurofilament markers, neurofilament's light chain (NfL) and phosphorylated heavy chains (pNfH), both axonal damage markers. Plasma NfL, the most studied plasma marker in neurodegenerative disorders, performed as well as its CSF counterparts and was associated with cognition and cerebral atrophy. Thirdly, we explored plasma glial acidic fibrillary protein (GFAP), a marker of astrocytic activation. Plasma GFAP levels had high potential to identify amyloid positive status at an early stage in AD in two selected cohorts but also in our memory clinic patients. Fourthly, we explored Galectin-3, a marker of microglial activation in AD brain and CSF. An increased expression of Gal-3 was associated with amyloid plaques at neuropathological examination. CSF Galectin-3 levels were increased in AD and clustered with other neuroinflammation CSF biomarkers. Finally, we compared a series of plasma biomarkers for AD diagnosis: we showed that plasma p-tau measurements including p-tau181 (Thr181 phosphorylation) and p-tau231 (Thr231 phosphorylation), and plasma GFAP displayed a higher specificity to AD, compared with plasma amyloid Aß42/Aß40 ratio, total tau and NfL. Combinations of plasma biomarkers improved positive and differential diagnosis of AD. Our plasma biomarkers were also associated with cognition and mediotemporal atrophy and cerebral white matter lesions. In conclusion, the work included in this thesis demonstrates that novel CSF and blood-based biomarkers show potential to contribute to AD diagnosis in clinical settings, and to monitor amyloid and tau lesions, synaptic impairment, axonal damage and neuroinflammation processes. However, their exact interpretation and the conditions of their use in clinical routine still warrant further study.La maladie d'Alzheimer (MA) est la plus fréquente des pathologies neurodégénératives. Des biomarqueurs d'imagerie et liquidiens sont disponibles, reflétant les lésions caractéristiques de la maladie, à savoir l'accumulation anormale des protéines amyloïdes et tau, et la neurodégénérescence. Les biomarqueurs du liquide cérébrospinal (LCS), mesurant les niveaux de peptide béta-amyloïde 1-42 (Aß42) et de protéine tau (forme phosphorylée phospho-tau, et forme totale), sont utilisés en pratique clinique pour l'exploration des troubles cognitifs. Cependant, ils restent peu disponibles, invasifs, coûteux et ne reflètent pas les autres processus sous-jacents de la maladie, tels que la perte synaptique, les dommages axonaux et la neuro-inflammation. De nouveaux biomarqueurs prometteurs ont récemment été développés, incluant des biomarqueurs sanguins, moins invasifs, et des marqueurs des mécanismes non amyloïdes et tau de la MA. L'objectif de cette thèse était d'étudier de nouveaux biomarqueurs candidats de la MA, incluant des marqueurs du LCS et du plasma, spécifiques ou non des lésions amyloïdes et tau, dans une cohorte clinique de centre mémoire. À cette fin, des patients atteints de troubles cognitifs ainsi que des sujets témoins ayant eu un prélèvement de LCS et plasmatique pour l'exploration d'une plainte cognitive, ont été inclus au Centre de Neurologie Cognitive, Université de Paris Cité, France. Dans une première étude, nous nous sommes intéressés à une protéine présynaptique, neuréguline 1, et avons montré que ses taux plasmatiques étaient plus élevés chez les patients MA que ceux retrouvés chez les témoins. Ils étaient associés aux marqueurs synaptiques du LCS et à l'état cognitif, démontrant leur potentiel pour le suivi de l'atteinte synaptique. Nous avons ensuite comparé les taux cérébrospinaux et plasmatiques de deux marqueurs de dommages axonaux : les taux de neurofilaments à chaîne légère (NfL) et à chaîne lourde phosphorylée (pNfH). Nous avons mis en évidence que le dosage des NfL dans le plasma, marqueur le plus étudié dans les troubles neurocognitifs, était aussi performant que leur mesure dans le LCS et qu'il était corrélé aux troubles cognitifs et à l'atrophie cérébrale. Troisièmement, nous avons étudié deux marqueurs de neuro-inflammation. Nous avons démontré que les concentrations plasmatiques de la protéine acide fibrillaire gliale (GFAP), un marqueur d'activation astrocytaire, identifiaient les individus amyloïde-positifs dès les stades précoces de la maladie, dans deux cohortes de recherche, mais également chez nos patients de centre mémoire. Ensuite, nous avons exploré galectine-3 (Gal-3), une protéine microgliale. En analyse neuropathologique, une expression accrue de Gal-3 était observée autour des plaques amyloïdes dans le tissu cérébral. Nous avons démontré que Gal-3 était mesurable dans le LCS et que ses niveaux étaient augmentés dans la MA et corrélaient à d'autres marqueurs neuro-inflammatoires du LCS, ce qui en fait un potentiel marqueur microglial. Finalement, nous avons comparé une série de biomarqueurs plasmatiques pour le diagnostic positif et différentiel de la MA : les mesures plasmatiques de protéine phospho-tau et de GFAP discriminaient correctement les patients avec une MA de ceux atteints d'autres pathologies neurodégénératives, comparés aux niveaux plasmatiques d'Aß42, de tau totale et des NfL. De plus, la combinaison de ces biomarqueurs plasmatiques améliorait leur performance diagnostique dans la MA. En conclusion, les travaux réalisés dans le cadre de cette thèse démontrent que les nouveaux biomarqueurs cérébrospinaux et plasmatiques ont le potentiel de contribuer au diagnostic de la MA. Bien que leur interprétation et les conditions de leur utilisation en pratique clinique doivent encore être précisées, ils permettent de suivre les lésions amyloïdes et tau de manière moins invasive, mais également la perte synaptique, les dommages axonaux et la neuro-inflammation

Psychiatric symptoms in anti glutamic acid decarboxylase associated limbic encephalitis in adults: a systematic review

International audienceAutoimmune Limbic Encephalitis (LE) is a relatively new category of immune-mediated diseases with a wide range of neuropsychiatric symptoms. LE associated with Glutamic Acid Decarboxylase (GAD) antibodies is difficult to diagnose due to its possible atypical presentation with neuropsychiatric and behavioral features. We performed a systematic review of literature and retrieved 21 cases of anti GAD-associated LE with neuropsychiatric signs. Median age at onset was 27 years with a female predominance (81.0 %) and median diagnostic delay of 6 months. Clinical presentation included typical LE symptoms such as anterograde amnesia (95.2 %) and temporal lobe or tonico-clonic seizures (95.2 %). Psychiatric symptoms were described in 61.9 % of patients, presenting as anxiety, depressive symptoms, apathy and behavioral changes. Extra-limbic symptoms were present in 14.3 % of patients. No neoplasia associated was found. Some patients had poor epileptic, cognitive and psychiatric outcomes requiring prolonged immunosuppressive treatment. The description of the neuropsychiatric spectrum of anti-GAD LE and its specificities aims to improve our understanding of this entity, and may lead to earlier diagnosis as well as better outcome

Using virtual reality in lumbar puncture training improves students learning experience

International audienceBackground: Lumbar puncture (LP) is a commonly performed medical procedure in a wide range of indications. Virtual reality (VR) provides a stimulating, safe and efficient learning environment. We report the design and the evaluation of a three dimensions (3D) video for LP training.Methods: We recorded a stereoscopic 180-degrees 3D video from two LPs performed in clinical settings in Fernand Widal Lariboisière University Hospital, Paris, France. The video was administered to third-year medical students as well as to a residents and attendings group during LP simulation-based training sessions.Results: On 168 participants (108 novice third-year medical students, and 60 residents and attendings with prior LP experience), satisfaction after video exposure was high (rated 4.7 ± 0.6 on a 5-point scale). No significant discomfort was reported (comfort score graded 4.5 ± 0.8 on 5). LP-naive students displayed higher satisfaction and perceived benefit than users with prior LP experience (overall, P < 0.05). Trainees evaluated favorably the 3D feature and supported the development of similar tutorials for other medical procedures (respectively, 3.9 ± 1.1 and 4.4 ± 0.9 on 5).Conclusion: We report our experience with a 3D video for LP training. VR support could increase knowledge retention and skill acquisition in association to LP simulation training