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TREM2 is an innate immune receptor expressed on the surface of microglia. Loss‐of‐function mutations of TREM2 are associated with increased risk of Alzheimer's disease (AD). TREM2 is a type‐1 protein with an ectodomain that is proteolytically cleaved and released into the extracellular space as a soluble variant (sTREM2), which can be measured in the cerebrospinal fluid (CSF). In this cross‐sectional multicenter study, we investigated whether CSF levels of sTREM2 are changed during the clinical course of AD, and in cognitively normal individuals with suspected non‐AD pathology (SNAP). CSF sTREM2 levels were higher in mild cognitive impairment due to AD than in all other AD groups and controls. SNAP individuals also had significantly increased CSF sTREM2 compared to controls. Moreover, increased CSF sTREM2 levels were associated with higher CSF total tau and phospho‐tau 181P , which are markers of neuronal degeneration and tau pathology. Our data demonstrate that CSF sTREM2 levels are increased in the early symptomatic phase of AD, probably reflecting a corresponding change of the microglia activation status in response to neuronal degeneration. Synopsis TREM2 is an innate immune receptor selectively expressed by microglia in the brain. Measuring its soluble variant in the CSF (sTREM2) may be a candidate as a marker of microglial activity. This study aimed to investigate how CSF sTREM2 levels change during the course of Alzheimer's disease (AD). CSF sTREM2 levels are increased in the mild cognitive impairment (MCI) stage of AD compared to controls ( P  = 0.002), and to the preclinical (trend level, P  = 0.062), and dementia stage of AD ( P  = 0.013). CSF sTREM2 levels are increased in individuals with suspected non‐AD pathology (SNAP) compared to controls ( P  = 0.0004). CSF sTREM2 levels increase with aging. Increased CSF sTREM2 levels are associated with higher levels of T‐tau and P‐tau 181P , markers of neuronal cell injury, and neurofibrillary tangles. Graphical Abstract TREM2 is an innate immune receptor selectively expressed by microglia in the brain. Measuring its soluble variant in the CSF (sTREM2) may be a candidate as a marker of microglial activity. This study aimed to investigate how CSF sTREM2 levels change during the course of Alzheimer's disease (AD).

Background Recently developed blood markers for Alzheimer's disease (AD) detection have high accuracy but usually require ultra-sensitive analytic tools not commonly available in clinical laboratories, and their performance in clinical practice is unknown. Methods We analyzed plasma samples from 290 consecutive participants that underwent lumbar puncture in routine clinical practice in a specialized memory clinic (66 cognitively unimpaired, 130 participants with mild cognitive impairment, and 94 with dementia). Participants were classified as amyloid positive (A +) or negative (A-) according to CSF Aβ 1–42 /Aβ 1–40 ratio. Plasma pTau 217 , pTau 181 , Aβ 1–42 and Aβ 1–40 were measured in the fully-automated LUMIPULSE platform. We used linear regression to compare plasma biomarkers concentrations between A + and A- groups, evaluated Spearman’s correlation between plasma and CSF and performed ROC analyses to assess their diagnostic accuracy to detect brain amyloidosis as determined by CSF Aβ 1–42 /Aβ 1–40 ratio. We analyzed the concordance of pTau 217 with CSF amyloidosis. Results Plasma pTau 217 and pTau 181 concentration were higher in A + than A- while the plasma Aβ 1–42 /Aβ 1–40 ratio was lower in A + compared to A-. pTau 181 and the Aβ 1–42 /Aβ 1–40 ratio showed moderate correlation between plasma and CSF (Rho = 0.66 and 0.69, respectively). The areas under the ROC curve to discriminate A + from A- participants were 0.94 (95% CI 0.92–0.97) for pTau 217 , and 0.88 (95% CI 0.84–0.92) for both pTau 181 and Aβ 1–42 /Aβ 1–40 . Chronic kidney disease (CKD) was related to increased plasma biomarker concentrations, but ratios were less affected. Plasma pTau 217 had the highest fold change (× 3.2) and showed high predictive capability in discriminating A + from A-, having 4–7% misclassification rate. The global accuracy of plasma pTau 217 using a two-threshold approach was robust in symptomatic groups, exceeding 90%. Conclusion The evaluation of blood biomarkers on an automated platform exhibited high diagnostic accuracy for AD pathophysiology, and pTau 217 showed excellent diagnostic accuracy to identify participants with AD in a consecutive sample representing the routine clinical practice in a specialized memory unit.

Background The innate immune system is known to be involved early in the pathogenesis of Alzheimer’s disease (AD) and other neurodegenerative disorders. The inflammatory response in the central nervous system can be measured postmortem or through a series of inflammatory mediator surrogates. YKL-40 (also named Chitinase-3-like I) has been frequently investigated in body fluids as a surrogate marker of neuroinflammation in AD and other neurological disorders. However, the expression pattern of YKL-40 in the human brain with neurodegenerative pathology remains poorly investigated. Our aim was to study the cellular expression pattern of YKL-40 in the brain of patients with clinical and neuropathological criteria for AD ( n  = 11); three non-AD tauopathies: Pick’s disease (PiD; n  = 8), corticobasal degeneration (CBD; n  = 8) and progressive supranuclear palsy (PSP; n  = 9) and a group of neurologically healthy controls ( n  = 6). Methods Semiquantitative neuropathological evaluation and quantitative confocal triple immunofluorescence studies were performed. An in-house algorithm was used to detect and quantify pathology burden of random regions of interest on a full tissue-section scan. Kruskal-Wallis and Dunn’s multiple comparison tests were performed for colocalization and quantification analyses. Results We found that brain YKL-40 immunoreactivity was observed in a subset of astrocytes in all four diseases and in controls. There was a strong colocalization between YKL-40 and the astroglial marker GFAP but not with neuronal nor microglial markers. Intriguingly, YKL-40-positive astrocytes were tau-negative in PSP, CBD and PiD. The number of YKL-40-positive astrocytes was increased in tauopathies compared with that in controls. A positive correlation was found between YKL-40 and tau immunoreactivities. Conclusions This study confirms that YKL-40 is expressed by a subset of astrocytes in AD and other tauopathies. YKL-40 expression is elevated in several neurodegenerative conditions and correlates with tau pathology.

Physician burnout has a negative impact on both physicians and patients. Limited information is available on professional burnout of neurologists. The aim of this study was to assess the presence of burnout among neurologists caring for patients with cognitive disorders and to identify associated factors. An online, cross-sectional study was conducted in collaboration with the Spanish Society of Neurology. Neurologists involved in the care of patients with cognitive disorders answered a survey composed of demographic characteristics, professional background, clinical practice setting, and behavioral factors. Burnout was assessed using a single-item measure from the Physician Work Life Study. A multivariate logistic regression analysis was conducted to determine the association between neurologists' characteristics and burnout. A total of 188 neurologists answered the survey. The mean age (standard deviation-SD) was 40.6 (11.3) years and 52.7% were male. The majority of participants were general neurologists (60.6%) who attending a median of 20 patients with cognitive disorders (interquartile range 10.0-30.0) weekly. Thirty-nine participants (20.7%) reported burnout. Participants with burnout had greater experiences of regret associated with past clinical decisions than their counterparts (mean Regret Intensity Scale scores of 2.3 and 1.9, respectively; p = 0.003). Burnout was associated with non-academic practice (OR = 3.02 [95% CI 1.18, 7.73], p = 0.021) and care-related regret (OR = 2.53 [95% CI 1.13, 5.64], p = 0.023) in the multivariate analysis after adjustment for confounders. Professional burnout was a common phenomenon among neurologists managing cognitive disorders. Identifying physician burnout and its associated factors may be critical for implementing preventive intervention strategies.

Physician burnout has a negative impact on both physicians and patients. Limited information is available on professional burnout of neurologists. The aim of this study was to assess the presence of burnout among neurologists caring for patients with cognitive disorders and to identify associated factors. An online, cross-sectional study was conducted in collaboration with the Spanish Society of Neurology. Neurologists involved in the care of patients with cognitive disorders answered a survey composed of demographic characteristics, professional background, clinical practice setting, and behavioral factors. Burnout was assessed using a single-item measure from the Physician Work Life Study. A multivariate logistic regression analysis was conducted to determine the association between neurologists' characteristics and burnout. A total of 188 neurologists answered the survey. The mean age (standard deviation-SD) was 40.6 (11.3) years and 52.7% were male. The majority of participants were general neurologists (60.6%) who attending a median of 20 patients with cognitive disorders (interquartile range 10.0-30.0) weekly. Thirty-nine participants (20.7%) reported burnout. Participants with burnout had greater experiences of regret associated with past clinical decisions than their counterparts (mean Regret Intensity Scale scores of 2.3 and 1.9, respectively; p = 0.003). Burnout was associated with non-academic practice (OR = 3.02 [95% CI 1.18, 7.73], p = 0.021) and care-related regret (OR = 2.53 [95% CI 1.13, 5.64], p = 0.023) in the multivariate analysis after adjustment for confounders. Professional burnout was a common phenomenon among neurologists managing cognitive disorders. Identifying physician burnout and its associated factors may be critical for implementing preventive intervention strategies.

Trisomy 21 (T21) causes Down syndrome (DS), affecting immune and neurological function by ill-defined mechanisms. Here we report a large metabolomics study of plasma and cerebrospinal fluid, showing in independent cohorts that people with DS produce elevated levels of kynurenine and quinolinic acid, two tryptophan catabolites with potent immunosuppressive and neurotoxic properties, respectively. Immune cells of people with DS overexpress IDO1 , the rate-limiting enzyme in the kynurenine pathway (KP) and a known interferon (IFN)-stimulated gene. Furthermore, the levels of IFN-inducible cytokines positively correlate with KP dysregulation. Using metabolic tracing assays, we show that overexpression of IFN receptors encoded on chromosome 21 contribute to enhanced IFN stimulation, thereby causing IDO1 overexpression and kynurenine overproduction in cells with T21. Finally, a mouse model of DS carrying triplication of IFN receptors exhibits KP dysregulation. Together, our results reveal a mechanism by which T21 could drive immunosuppression and neurotoxicity in DS. Down syndrome (DS) is caused by trisomy 21 (T21), but the underlying etiology of the related immune and neurological dysfunction is unclear. Here, the authors show that T21 activates the kynurenine pathway via increased interferon receptor copy number, which could contribute to DS pathophysiology.

Globally, individuals with Down syndrome (DS) face profound inequities in social and health care access. These challenges are further compounded by racial disparities as well as a lack of awareness, research, and support, particularly in the Global South. This commentary discusses the multifaceted challenges and disparities encountered by people with DS in South Africa, highlighting the need for targeted interventions. The paper will summarise the proceedings and outcomes of an imbizo—a strategic gathering of stakeholders in South Africa. This event brought together a diverse group from the DS community, including individuals with DS, their families, healthcare providers, non-profit organizations, and representatives from the Gauteng Department of Health. The discussions at the imbizo were organized into five key thematic areas: Advocacy and Awareness, Inclusion and Engagement, Education, Data and Research, and Networking and Collaboration. Additionally, the paper will underscore the critical need for the establishment of a dedicated DS research network in South Africa. Such a network is envisioned to foster collaboration, facilitate knowledge sharing, and ensure that research initiatives are closely aligned with the needs of the DS community. Overcoming these inequities requires a holistic approach that encompasses policy reforms and the crafting of inclusive services. In its concluding sections, the paper will explore future avenues for creating a sustainable framework aimed at addressing the multifaceted needs of the DS community in South Africa. This initiative represents an effort towards amplifying the well-being, rights, and inclusion of people with DS. Highlighting the necessity of a collaborative and multifaceted approach, this paper proposes a path towards a more inclusive society, advocating for the mitigation of challenges faced by this marginalized community.

Alzheimer's disease (AD) is a neurodegenerative disease characterized by the presence of neurofibrillary tangles, constituted by tau protein, and plaques formed by amyloid-beta protein. The disease courses with high neural damage, which leads to memory loss and death. Here we analyzed the presence of CX3CL1, a chemokine expressed by neurons, in cerebrospinal fluid (CSF) samples from control subjects and patients with mild cognitive impairment and AD dementia. CX3CL1 was decreased in the CSF of AD dementia patients compared to control subjects. However, there was not difference in plasma samples from the same subjects.

This study assesses whether C-terminal fragments (CTF) of the amyloid precursor protein (APP) are present in cerebrospinal fluid (CSF) and their potential as biomarkers for Alzheimer’s disease (AD). Immunoprecipitation and simultaneous assay by Western blotting using multiplex fluorescence imaging with specific antibodies against particular domains served to characterize CTFs of APP in human CSF. We demonstrate that APP-CTFs are detectable in human CSF, being the most abundant a 25-kDa fragment, probably resulting from proteolytic processing by η-secretase. The level of the 25-kDa APP-CTF was evaluated in three independent CSF sample sets of patients and controls. The CSF level of this 25-kDa CTF is higher in subjects with autosomal dominant AD linked to PSEN1 mutations, in demented Down syndrome individuals and in sporadic AD subjects compared to age-matched controls. Our data suggest that APP-CTF could be a potential diagnostic biomarker for AD.

Objective To determine the cutoffs that optimized the agreement between 18F‐Florbetapir positron emission tomography (PET) and Aβ1‐42, Aβ1‐40, tTau, pTau and their ratios measured in cerebrospinal fluid (CSF) on the LUMIPULSE G600II instrument, we quantified the levels of these four biomarkers in 94 CSF samples from participants of the Sant Pau Initiative on Neurodegeneration (SPIN cohort) using the Lumipulse G System with available 18F‐Florbetapir imaging. Methods Participants had mild cognitive impairment (n = 35), AD dementia (n = 12), other dementias or neurodegenerative diseases (n = 41), or were cognitively normal controls (n = 6). Levels of Aβ1‐42 were standardized to certified reference material. Amyloid scans were assessed visually and through automated quantification. We determined the cutoffs of CSF biomarkers that optimized their agreement with 18F‐Florbetapir PET and evaluated concordance between markers of the amyloid category. Results Aβ1‐42, tTau and pTau (but not Aβ1‐40) and the ratios with Aβ1‐42 had good diagnostic agreement with 18F‐Florbetapir PET. As a marker of amyloid pathology, the Aβ1‐42/Aβ1‐40 ratio had higher agreement and better correlation with amyloid PET than Aβ1‐42 alone. Interpretation CSF biomarkers measured with the Lumipulse G System show good agreement with amyloid imaging in a clinical setting with heterogeneous presentations of neurological disorders. Combination of Aβ1‐42 with Aβ1‐40 increases the agreement between markers of amyloid pathology.