YKL-40 is a CSF biomarker of intrathecal inflammation in secondary progressive multiple sclerosis.

YKL-40 (CHI3L1) is a glycoprotein predominantly produced by reactive astrocytes in chronic active MS lesions, which are common in secondary progressive MS. In this study, YKL-40 was investigated in different stages of MS and in relation to MRI findings. YKL-40 levels in CSF samples from two independent patient cohorts of MS patients were determined with ELISA. CSF YKL-40 was increased in patients with active relapsing-remitting MS and correlated with the number of gadolinium enhancing lesions. Patients with secondary progressive MS had similar high levels of YKL-40, whereas not active relapsing-remitting MS patients had YKL-40 levels comparable to healthy controls.

Cerebrospinal Fluid Markers of Alzheimer's Disease Pathology and Microglial Activation are Associated with Altered White Matter Microstructure in Asymptomatic Adults at Risk for Alzheimer's Disease.

BACKGROUND: The immune response in Alzheimer's disease (AD) involves activation of microglia which may remove amyloid-ß (Aß). However, overproduction of inflammatory compounds may exacerbate neural damage in AD. AD pathology accumulates years before diagnosis, yet the extent to which neuroinflammation is involved in the earliest disease stages is unknown. OBJECTIVE: To determine whether neuroinflammation exacerbates neural damage in preclinical AD. METHODS: We utilized cerebrospinal fluid (CSF) and magnetic resonance imaging collected in 192 asymptomatic late-middle-aged adults (mean age = 60.98 years). Neuroinflammatory markers chitinase-3-like protein 1 (YKL-40) and monocyte chemoattractant protein-1 (MCP-1) in CSF were utilized as markers of neuroinflammation. Neural cell damage was assessed using CSF neurofilament light chain protein (NFL), CSF total tau (T-Tau), and neural microstructure assessed with diffusion tensor imaging (DTI). With regard to AD pathology, CSF Aß42 and tau phosphorylated at threonine 181 (P-Tau181) were used as markers of amyloid and tau pathology, respectively. We hypothesized that higher YKL-40 and MCP-1 in the presence of AD pathology would be associated with higher NFL, T-Tau, and altered microstructure on DTI. RESULTS: Neuroinflammation was associated with markers of neural damage. Higher CSF YKL-40 was associated with both higher CSF NFL and T-Tau. Inflammation interacted with AD pathology, such that greater MCP-1 and lower Aß42 was associated with altered microstructure in bilateral frontal and right temporal lobe and that greater MCP-1 and greater P-Tau181 was associated with altered microstructure in precuneus. CONCLUSION: Inflammation may play a role in neural damage in preclinical AD.

Protein-Based Classifier to Predict Conversion from Clinically Isolated Syndrome to Multiple Sclerosis.

Multiple sclerosis is an inflammatory, demyelinating, and neurodegenerative disease of the central nervous system. In most patients, the disease initiates with an episode of neurological disturbance referred to as clinically isolated syndrome, but not all patients with this syndrome develop multiple sclerosis over time, and currently, there is no clinical test that can conclusively establish whether a patient with a clinically isolated syndrome will eventually develop clinically defined multiple sclerosis. Here, we took advantage of the capabilities of targeted mass spectrometry to establish a diagnostic molecular classifier with high sensitivity and specificity able to differentiate between clinically isolated syndrome patients with a high and a low risk of developing multiple sclerosis. Based on the combination of abundances of proteins chitinase 3-like 1 and ala-ß-his-dipeptidase in cerebrospinal fluid, we built a statistical model able to assign to each patient a precise probability of conversion to clinically defined multiple sclerosis. Our results are of special relevance for patients affected by multiple sclerosis as early treatment can prevent brain damage and slow down the disease progression.

Neurogranin and YKL-40: independent markers of synaptic degeneration and neuroinflammation in Alzheimer's disease.

INTRODUCTION: Neuroinflammation and synaptic degeneration are major neuropathological hallmarks in Alzheimer's disease (AD). Neurogranin and YKL-40 in cerebrospinal fluid (CSF) are newly discovered markers indicating synaptic damage and microglial activation, respectively. METHODS: CSF samples from 95 individuals including 39 patients with AD dementia (AD-D), 13 with mild cognitive impairment (MCI) due to AD (MCI-AD), 29 with MCI not due to AD (MCI-o) and 14 patients with non-AD dementias (non-AD-D) were analyzed for neurogranin and YKL-40. RESULTS: Patients with dementia or MCI due to AD showed elevated levels of CSF neurogranin (p < 0.001 for AD-D and p < 0.05 for MCI-AD) and YKL-40 (p < 0.05 for AD-D and p = 0.15 for MCI-AD) compared to mildly cognitively impaired subjects not diagnosed with AD. CSF levels of neurogranin and YKL-40 did not differ between MCI not due to AD and non-AD dementias. In AD subjects no correlation between YKL-40 and neurogranin was found. The CSF neurogranin levels correlated moderately with tau and p-tau but not with Aß42 or the MMSE in AD samples. No relevant associations between YKL-40 and MMSE or the core AD biomarkers, Aß42, t-tau and p-tau were found in AD subjects. CONCLUSIONS: Neurogranin and YKL-40 are promising AD biomarkers, independent of and complementary to the established core AD biomarkers, reflecting additional pathological changes in the course of AD.

Cerebrospinal fluid VILIP-1 and YKL-40, candidate biomarkers to diagnose, predict and monitor Alzheimer's disease in a memory clinic cohort.

INTRODUCTION: We examined the utility of cerebrospinal fluid (CSF) proteins, Chitinase-3-like protein 1 (CHI3L1 or YKL-40), a putative marker of inflammation, and Visinin-like protein-1 (VILIP-1), a marker for neuronal injury, for diagnostic classification and monitoring of disease progression in a memory clinic cohort. METHODS: CSF levels of YKL-40 and VILIP-1 were measured in 37 cognitively normal, 61 Mild Cognitive Impairment (MCI) and 65 Alzheimer's disease (AD) patients from the memory clinic-based Amsterdam Dementia Cohort who underwent two lumbar punctures, with minimum interval of 6 months and a mean (SE) interval of 2.0(0.1) years. Mean(SE) cognitive follow-up was 3.8 (0.2) years. ANOVA was used to compare baseline differences of log-transformed CSF measures. Cox proportional hazard models were used to evaluate disease progression as a function of CSF tertiles. Linear mixed models were used to evaluate longitudinal change over time. All analyses were sex and age adjusted. RESULTS: Baseline levels of YKL-40, but not VILIP-1, were higher in MCI and AD patients compared to cognitively normal individuals (mean (SE) pg/mL, 304 (16) and 288 (12) vs. 231 (16), p = 0.03 and p = 0.006). Baseline levels of both YKL-40 and VILIP-1 in MCI predicted progression to AD (HR 95% CI = 3.0 (1.1-7.9) and 4.4 (1.5-13.0), respectively, for highest vs. lowest tertile). YKL-40 increased longitudinally in patients with MCI and AD (mean (SE) pg/mL per year, 8.9 (3.0) and 7.1 (3.1), respectively), but not in cognitively normal individuals, whereas levels of VILIP-1 increased only in MCI (mean (SE), 10.7 (2.6) pg/mL per year). CONCLUSIONS: CSF levels of YKL-40 may have utility for discriminating between cognitively normal individuals and patients with MCI or AD. Increased levels of both YKL-40 and VILIP-1 may be associated with disease progression. These CSF biomarkers should be considered for future evaluation in the characterization of the natural history of AD.

The Inflammatory Marker YKL-40 Is Elevated in Cerebrospinal Fluid from Patients with Alzheimer's but Not Parkinson's Disease or Dementia with Lewy Bodies.

A major difference in the revised diagnostic criteria for Alzheimer's disease (AD) is the incorporation of biomarkers to support a clinical diagnosis and allow the identification of preclinical AD due to AD neuropathological processes. However, AD-specific fluid biomarkers which specifically distinguish clinical AD dementia from other dementia disorders are still missing. Here we aimed to evaluate the disease-specificity of increased YKL-40 levels in cerebrospinal fluid (CSF) from AD patients with mild to moderate dementia (n = 49) versus Parkinson's disease (PD) (n = 61) and dementia with Lewy bodies (DLB) patients (n = 36), and non-demented controls (n = 44). Second we aimed to investigate whether altered YKL-40 levels are associated with CSF levels of other inflammation-associated molecules. When correcting for age, AD patients exhibited 21.3%, 27.7% and 38.8% higher YKL-40 levels compared to non-demented controls (p = 0.0283), DLB (p = 0.0027) and PD patients (p<0.0001). The AD-associated increase in YKL-40 was not associated with CSF P-tau, T-tau or Aß42. No relationship between increased YKL-40 and levels of the astrocytic marker glial-fibrillary acidic protein (GFAP), interleukin-8 (IL-8), monocyte chemoattractant protein-1 (MCP-1) and interferon gamma-induced protein 10 (IP-10) could be identified. Our results confirm previous reports of an age-associated increased in CSF YKL-40 levels and further demonstrate increased CSF YKL-40 in AD patients versus non-demented controls and patients with DLB or PD. The increase in YKL-40 levels in the AD patients was unrelated to the established CSF AD biomarkers and the inflammatory markers GFAP, MCP-1, IP-10 and IL-8, proposing YKL-40 as a marker of yet to be identified AD-related pathological processes.

Longitudinal Cerebrospinal Fluid Biomarker Changes in Preclinical Alzheimer Disease During Middle Age.

IMPORTANCE: Individuals in the presymptomatic stage of Alzheimer disease (AD) are increasingly being targeted for AD secondary prevention trials. How early during the normal life span underlying AD pathologies begin to develop, their patterns of change over time, and their relationship with future cognitive decline remain to be determined. OBJECTIVE: To characterize the within-person trajectories of cerebrospinal fluid (CSF) biomarkers of AD over time and their association with changes in brain amyloid deposition and cognitive decline in cognitively normal middle-aged individuals. DESIGN, SETTING, AND PARTICIPANTS: As part of a cohort study, cognitively normal (Clinical Dementia Rating [CDR] of 0) middle-aged research volunteers (n = 169) enrolled in the Adult Children Study at Washington University, St Louis, Missouri, had undergone serial CSF collection and longitudinal clinical assessment (mean, 6 years; range, 0.91-11.3 years) at 3-year intervals at the time of analysis, between January 2003 and November 2013. A subset (n = 74) had also undergone longitudinal amyloid positron emission tomographic imaging with Pittsburgh compound B (PiB) in the same period. Serial CSF samples were analyzed for ß-amyloid 40 (Aß40), Aß42, total tau, tau phosphorylated at threonine 181 (P-tau181), visinin-like protein 1 (VILIP-1), and chitinase-3-like protein 1 (YKL-40). Within-person measures were plotted according to age and AD risk defined by APOE genotype (ε4 carriers vs noncarriers). Linear mixed models were used to compare estimated biomarker slopes among middle-age bins at baseline (early, 45-54 years; mid, 55-64 years; late, 65-74 years) and between risk groups. Within-person changes in CSF biomarkers were also compared with changes in cortical PiB binding and progression to a CDR higher than 0 at follow-up. MAIN OUTCOMES AND MEASURES: Changes in Aß40, Aß42, total tau, P-tau181, VILIP-1, and YKL-40 and, in a subset of participants, changes in cortical PiB binding. RESULTS: While there were no consistent longitudinal patterns in Aß40 (P = .001-.97), longitudinal reductions in Aß42 were observed in some individuals as early as early middle age (P ≤ .05) and low Aß42 levels were associated with the development of cortical PiB-positive amyloid plaques (area under receiver operating characteristic curve = 0.9352; 95% CI, 0.8895-0.9808), especially in mid middle age (P < .001). Markers of neuronal injury (total tau, P-tau181, and VILIP-1) dramatically increased in some individuals in mid and late middle age (P ≤ .02), whereas the neuroinflammation marker YKL-40 increased consistently throughout middle age (P ≤ .003). These patterns were more apparent in at-risk ε4 carriers (Aß42 in an allele dose-dependent manner) and appeared to be associated with future cognitive deficits as determined by CDR. CONCLUSIONS AND RELEVANCE: Longitudinal CSF biomarker patterns consistent with AD are first detectable during early middle age and are associated with later amyloid positivity and cognitive decline. Such measures may be useful for targeting middle-aged, asymptomatic individuals for therapeutic trials designed to prevent cognitive decline.

Amyloid precursor protein metabolism and inflammation markers in preclinical Alzheimer disease.

OBJECTIVE: To investigate CSF markers involved in amyloid precursor protein processing, neuronal damage, and neuroinflammation in the preclinical stages of Alzheimer disease (AD) and participants with suspected non-Alzheimer pathology (SNAP). METHODS: We collected CSF from 266 cognitively normal volunteers participating in a cross-sectional multicenter study (the SIGNAL study) to investigate markers involved in amyloid precursor protein processing (Aß42, sAPPß, ß-secretase activity), neuronal damage (total-tau [t-tau], phospho-tau [p-tau]), and neuroinflammation (YKL-40). We analyzed the relationship among biomarkers, clinical variables, and the APOE genotype, and compared biomarker levels across the preclinical stages of the National Institute on Aging-Alzheimer's Association classification: stage 0, 1, 2, 3, and SNAP. RESULTS: The median age in the whole cohort was 58.8 years (range 39.8-81.6). Participants in stages 2-3 and SNAP had higher levels of YKL-40 than those in stages 0 and 1. Participants with SNAP had higher levels of sAPPß than participants in stage 0 and 1. No differences were found between stages 0, 1, and 2-3 in sAPPß and ß-secretase activity in CSF. Age correlated with t-tau, p-tau, and YKL-40. It also correlated with Aß42, but only in APOE ε4 carriers. Aß42 correlated positively with t-tau, sAPPß, and YKL-40 in participants with normal Aß42. CONCLUSIONS: Our findings suggest that inflammation in the CNS increases in normal aging and is intimately related to markers of neurodegeneration in the preclinical stages of AD and SNAP. sAPPß and ß-secretase activity are not useful diagnostic or staging markers in preclinical AD.

CSF neuroinflammatory biomarkers in bipolar disorder are associated with cognitive impairment.

Persistent cognitive impairment in the euthymic state of bipolar disorder is increasingly recognized. Mounting evidence also suggests an association between neuroinflammation and cognitive dysfunction. The purpose of this study was to test if cerebrospinal fluid (CSF) markers of neuroinflammation could account for cognitive impairment in bipolar disorder. Hierarchical linear regression models were applied to account for performance in five cognitive domains using CSF neuroinflammatory biomarkers as predictors in patients with bipolar disorder type I and II (N=78). The associations between these biomarkers and cognition were further tested in healthy age- and sex-matched controls (N=86). In patients with bipolar disorder, the CSF biomarkers accounted for a significant proportion of the variance in executive functions (42.8%, p=<.0005) independently of age, medication, disease status, and bipolar subtype. The microglial marker YKL-40 had a high impact (beta=-.99), and was the only biomarker that contributed individually. CSF biomarkers were not associated with cognitive performance in healthy controls. The CSF neuroinflammation biomarker YKL-40 is associated with executive performance in euthymic bipolar disorder, but not in healthy controls.

Relationship between cortical thickness and cerebrospinal fluid YKL-40 in predementia stages of Alzheimer's disease.

Cerebrospinal fluid YKL-40 has been described as a marker of glial inflammation. We aimed to study the relationship between YKL-40 and brain structure and its interactions with core Alzheimer's disease (AD) biomarkers. We measured cortical thickness (CTh) and cerebrospinal fluid biomarkers (amyloid-ß 1-42 [Aß42], total tau, p-tau, and YKL-40) of 80 cognitively normal controls and 27 patients with amnestic mild cognitive impairment. Subjects were classified as Aß42+ (<550 pg/mL) or Aß42- (>550 pg/mL). CTh difference maps were derived from the interaction and correlation analyses in the whole sample and within clinical groups. There was a strong correlation between YKL-40 and markers of neurodegeneration (total tau and p-tau). In the whole sample, we found a negative correlation between YKL-40 and CTh in AD vulnerable areas in Aß42+ subjects but not in Aß42 participants. Our results suggest that YKL-40 could track the inflammatory processes associated to tau-related neurodegeneration in the presence of the AD pathophysiological process.

Monocyte and microglial activation in patients with mood-stabilized bipolar disorder.

BACKGROUND: Bipolar disorder is associated with medical comorbidities that have been linked to systemic inflammatory mechanisms. There is, however, limited evidence supporting a role of neuroinflammation in bipolar disorder. Here we tested whether microglial activation and associated tissue remodelling processes are related to bipolar disorder by analyzing markers in cerebrospinal fluid (CSF) and serum from patients and healthy controls. METHODS: Serum was sampled from euthymic patients with bipolar disorder and healthy controls, and CSF was sampled from a large subset of these individuals. The levels of monocyte chemoattractant protein-1 (MCP-1), YKL-40, soluble cluster of differentiation 14 (sCD14), tissue inhibitor of metalloproteinases-1 (TIMP-1) and tissue inhibitor of metalloproteinases-2 (TIMP-2), were measured, and we adjusted comparisons between patients and controls for confounding factors. RESULTS: We obtained serum samples from 221 patients and 112 controls and CSF samples from 125 patients and 87 controls. We found increased CSF levels of MCP-1 and YKL-40 and increased serum levels of sCD14 and YKL-40 in patients compared with controls; these differences remained after controlling for confounding factors, such as age, sex, smoking, blood-CSF barrier function, acute-phase proteins and body mass index. The CSF levels of MCP-1 and YKL-40 correlated with the serum levels, whereas the differences between patients and controls in CSF levels of MCP-1 and YKL-40 were independent of serum levels. LIMITATIONS: The cross-sectional study design precludes conclusions about causality. CONCLUSION: Our results suggest that both neuroinflammatory and systemic inflammatory processes are involved in the pathophysiology of bipolar disorder. Importantly, markers of immunological processes in the brain were independent of peripheral immunological activity.

Chitinase 3-like 1: prognostic biomarker in clinically isolated syndromes.

Chitinase 3-like 1 (CHI3L1) has been proposed as a biomarker associated with the conversion to clinically definite multiple sclerosis in patients with clinically isolated syndromes, based on the finding of increased cerebrospinal fluid CHI3L1 levels in clinically isolated syndrome patients who later converted to multiple sclerosis compared to those who remained as clinically isolated syndrome. Here, we aimed to validate CHI3L1 as a prognostic biomarker in a large cohort of patients with clinically isolated syndrome. This is a longitudinal cohort study of clinically isolated syndrome patients with clinical, magnetic resonance imaging, and cerebrospinal fluid data prospectively acquired. A total of 813 cerebrospinal fluid samples from patients with clinically isolated syndrome were recruited from 15 European multiple sclerosis centres. Cerebrospinal fluid CHI3L1 levels were measured by enzyme-linked immunosorbent assay. Multivariable Cox regression models were used to investigate the association between cerebrospinal fluid CHI3L1 levels and time to conversion to multiple sclerosis and time to reach Expanded Disability Status Scale 3.0. CHI3L1 levels were higher in patients who converted to clinically definite multiple sclerosis compared to patients who continued as clinically isolated syndrome (P = 8.1 × 10(-11)). In the Cox regression analysis, CHI3L1 levels were a risk factor for conversion to multiple sclerosis (hazard ratio = 1.7; P = 1.1 × 10(-5) using Poser criteria; hazard ratio = 1.6; P = 3.7 × 10(-6) for McDonald criteria) independent of other covariates such as brain magnetic resonance imaging abnormalities and presence of cerebrospinal fluid oligoclonal bands, and were the only significant independent risk factor associated with the development of disability (hazard ratio = 3.8; P = 2.5 × 10(-8)). High CHI3L1 levels were associated with shorter time to multiple sclerosis (P = 3.2 × 10(-9) using Poser criteria; P = 5.6 × 10(-11) for McDonald criteria) and more rapid development of disability (P = 1.8 × 10(-10)). These findings validate cerebrospinal fluid CHI3L1 as a biomarker associated with the conversion to multiple sclerosis and development of disability and reinforce the prognostic role of CHI3L1 in patients with clinically isolated syndrome. We propose that determining cerebrospinal fluid chitinase 3-like 1 levels at the time of a clinically isolated syndrome event will help identify those patients with worse disease prognosis.

Chitinase 3-like proteins as diagnostic and prognostic biomarkers of multiple sclerosis.

BACKGROUND: Despite sensitivity of MRI to diagnose multiple sclerosis (MS), prognostic biomarkers are still needed for optimized treatment. OBJECTIVE: The objective of this paper is to identify cerebrospinal fluid (CSF) diagnostic biomarkers of MS using quantitative proteomics and to analyze their expression at different disease stages. METHODS: We conducted differential analysis of the CSF proteome from control and relapsing-remitting MS (RRMS) patients followed by verification by ELISA of candidate biomarkers in CSF and serum in control, clinically isolated syndrome (CIS), RRMS and progressive MS (PMS) patients. RESULTS: Twenty-two of the 527 quantified proteins exhibited different abundances in control and RRMS CSF. These include chitinase 3-like protein 1 (CHI3L1) and 2 (CHI3L2), which showed a strong expression in brain of MS patients, especially in astrocytes and microglial cells from white matter plaques. CSF and serum CHI3L1 levels increased with the disease stage and CIS patients with high CSF (>189 ng/ml) and serum (>33 ng/ml) CHI3L1 converted more rapidly to RRMS (log rank test, p < 0.05 and p < 0.001, respectively). In contrast, CSF CHI3L2 levels were lower in PMS than in RRMS patients. Accordingly, CSF CHI3L1/CHI3L2 ratio accurately discriminated PMS from RRMS. CONCLUSIONS: CSF CHI3L1 and CHI3L2 and serum CHI3L1 might help to define MS disease stage and have a prognostic value in CIS.

Cerebrospinal fluid levels of chitinase 3-like 1 and neurofilament light chain predict multiple sclerosis development and disability after optic neuritis.

BACKGROUND: Cerebrospinal fluid (CSF) biomarkers have been suggested to predict multiple sclerosis (MS) after clinically isolated syndromes, but studies investigating long-term prognosis are needed. OBJECTIVE: To assess the predictive ability of CSF biomarkers with regard to MS development and long-term disability after optic neuritis (ON). METHODS: Eighty-six patients with ON as a first demyelinating event were included retrospectively. Magnetic resonance imaging (MRI), CSF leukocytes, immunoglobulin G index and oligoclonal bands were registered. CSF levels of chitinase-3-like-1, osteopontin, neurofilament light-chain, myelin basic protein, CCL2, CXCL10, CXCL13 and matrix metalloproteinase-9 were measured by enzyme-linked immunosorbent assay. Patients were followed up after 13.6 (range 9.6-19.4) years and 81.4% were examined, including Expanded Disability Status Scale and MS functional composite evaluation. 18.6% were interviewed by phone. Cox regression, multiple regression and Spearman correlation analyses were used. RESULTS: Forty-six (53.5%) developed clinically definite MS (CDMS) during follow-up. In a multivariate model MRI (p=0.0001), chitinase 3-like 1 (p=0.0033) and age (p=0.0194) combined predicted CDMS best. Neurofilament light-chain predicted long-term disability by the multiple sclerosis severity scale (p=0.0111) and nine-hole-peg-test (p=0.0202). Chitinase-3-like-1 predicted long-term cognitive impairment by the paced auditory serial addition test (p=0.0150). CONCLUSION: Neurofilament light-chain and chitinase-3-like-1 were significant predictors of long-term physical and cognitive disability. Furthermore, chitinase-3-like-1 predicted CDMS development. Thus, these molecules hold promise as clinically valuable biomarkers after ON as a first demyelinating event.

Cerebrospinal fluid level of YKL-40 protein in preclinical and prodromal Alzheimer's disease.

BACKGROUND: An increase in YKL-40 levels seems to correlate with disease severity and poor prognosis in many diseases, including several neurodegenerative diseases such as multiple sclerosis, amyotrophic lateral sclerosis, and Alzheimer's disease (AD). Specifically, YKL-40 protein is increased in mild AD with respect to controls, both in cerebrospinal fluid (CSF) and plasma. OBJECTIVE: We hypothesize that subjects in the preclinical (Pre-AD) and prodromal (Prod-AD) stage of AD could already present an increase in CSF YKL-40 levels with respect to healthy controls and idiopathic REM sleep behavior disorder (iRBD) subjects, included as a control group of a distinct neurological disease. METHODS: We measured CSF YKL-40 levels using a commercial ELISA kit in a cohort of 95 subjects, consisting of controls (n = 43), Pre-AD (n = 18), Prod-AD (n = 22), and iRBD (n = 12) subjects. We explored for possible correlations of YKL-40 levels with demographic characteristics, a wide battery of neuropsychological tests, and the AD CSF biomarkers: amyloid-ß42 (Aß42), total-tau protein (t-tau), and phosphorylated-tau protein (p-tau). RESULTS: We detected statistically significant differences between Prod-AD patients and controls. YKL-40 levels showed a significant correlation with t-tau and p-tau levels in the predementia AD continuum and the Pre-AD group. We also observed significant correlations with the MMSE, FCSRT, and M@T tests within the AD continuum, but not in iRBD subjects. CONCLUSION: Our data suggest that CSF YKL-40 levels, although not useful as a diagnostic marker for Prod-AD, may be a valuable marker to detect early physiopathological changes potentially linked with the neurodegenerative process.

Neurochemical evidence of potential neurotoxicity after prophylactic cranial irradiation.

PURPOSE: To examine whether cerebrospinal fluid biomarkers for neuroaxonal damage, neuroglial activation, and amyloid ß-related processes could characterize the neurochemical response to cranial radiation. METHODS AND MATERIALS: Before prophylactic cranial irradiation (PCI) of patients with small cell lung cancer, each patient underwent magnetic resonance imaging of the brain, lumbar puncture, and Mini-Mental State Examination of cognitive function. These examinations were repeated at approximately 3 and 12 months after radiation. RESULTS: The major findings were as follows. (1) Cerebrospinal fluid markers for neuronal and neuroglial injury were elevated during the subacute phase after PCI. Neurofilament and T-tau increased 120% and 50%, respectively, after PCI (P<.05). The same was seen for the neuroglial markers YKL-40 and glial fibrillary acidic protein, which increased 144% and 106%, respectively, after PCI (P<.05). (2) The levels of secreted amyloid precursor protein-α and -ß were reduced 44% and 46%, respectively, 3 months after PCI, and the levels continued to decrease as long as 1 year after treatment (P<.05). (3) Mini-Mental State Examination did not reveal any cognitive decline, indicating that a more sensitive test should be used in future studies. CONCLUSION: In conclusion, we were able to detect radiation therapy-induced changes in several markers reflecting neuronal injury, inflammatory/astroglial activation, and altered amyloid precursor protein/amyloid ß metabolism, despite the low number of patients and quite moderate radiation doses (20-30 Gy). These changes are hypothesis generating and could potentially be used to assess the individual risk of developing long-term symptoms of chronic encephalopathy after PCI. This has to be evaluated in large studies with extended clinical follow-up and more detailed neurocognitive assessments.

Relationship between ß-Secretase, inflammation and core cerebrospinal fluid biomarkers for Alzheimer's disease.

BACKGROUND: Biomarkers in the cerebrospinal fluid (CSF) can track specific pathophysiological pathways underlying Alzheimer's disease (AD). The connection between these biomarkers remains unclear. OBJECTIVE: To study six CSF biomarkers in a clinical cohort of patients with different neurodegenerative conditions. METHODS: We measured markers of amyloid-ß protein precursor (AßPP) processing (Aß42, sAßPPß, ß-secretase activity), neuronal damage (total tau, p-tau), and inflammation (YKL-40) in CSF from 194 participants with the following diagnoses: subjective cognitive impairment or non-amnestic mild cognitive impairment (na-SCI, n = 44), amnestic mild cognitive impairment (aMCI, n = 45), dementia of the Alzheimer type (DAT, n = 59), frontotemporal dementia (FTD, n = 22), and 24 cognitively normal controls. We compared biomarkers between clinical groups and CSF-profile groups, and we analyzed the correlation between biomarkers. RESULTS: CSF levels of sAßPPß were decreased in FTD patients compared to the other groups. YKL-40 was elevated in DAT and FTD, and also in aMCI patients. CSF Aß42 correlated positively with ß-secretase activity (RS = 0.262) and sAßPPß (RS = 0.341). CSF YKL-40 correlated positively with total tau (RS = 0.467) and p-tau (RS = 0.429). CSF p-tau and sAßPPß contributed significantly to distinguish DAT from FTD. CONCLUSIONS: CSF biomarkers of AßPP processing correlate with each other and are decreased in FTD. The inflammatory marker YKL-40 is increased in different neurodegenerative diseases, even in early stages, and it correlates with biomarkers of neurodegeneration. This suggests that inflammation is a common feature in AD and FTD. A combination of CSF biomarkers tracking distinct pathophysiological processes may be useful to classify subjects with neurodegenerative conditions.

CSF levels of YKL-40 are increased in MS and replaces with immunosuppressive treatment.

The role of glial cells during different phases of multiple sclerosis (MS) is unclear. To monitor glial activation we analyzed the biomarkers YKL-40 and sCD14 in cerebrospinal fluid (CSF) from MS patients during different disease phases and in response to immunosuppressive treatment. CSF levels of YKL-40 were increased in MS during relapse, remission and secondary progression compared with healthy controls. Furthermore, YKL-40 levels in CSF decreased by mitoxantrone and natalizumab treatment. No differences were observed in CSF levels of sCD14. Thus, we can infer that glial activation is present in all MS phases and decreases by immunosuppressive treatment.

The glial marker YKL-40 is decreased in synucleinopathies.

BACKGROUND: Microglia are resident immunosurveillant cells in the central nervous system, and astrocytes are important for blood flow, plasticity, and neurotransmitter regulation. The aim of this study was to investigate whether astrocyte and microglial activation, estimated through markers in cerebrospinal fluid and serum, differed between synucleinopathies, tauopathies, and controls. METHODS: We analyzed the glial activation markers YKL-40 and soluble CD14 in serum and cerebrospinal fluid from 37 controls, 50 patients with Parkinson's disease (PD), and 79 P+ patients (those with progressive supranuclear palsy, corticobasal degeneration, and multiple system atrophy). RESULTS: Cerebrospinal fluid levels of YKL-40 were decreased significantly in patients who had PD compared with controls (P < 0.05), patients who had multiple system atrophy (P < 0.01), and patients who had tauopathies (P < 0.0001). In addition, cerebrospinal fluid levels of YKL-40 were significantly lower in patients who had synucleinopathies than in those who had tauopathies (P < 0.0001). CONCLUSIONS: The decreased cerebrospinal fluid levels of YKL-40 suggest that glial activation is reduced in the brains of patients who have Parkinson's disease and synucleinopathies compared with patients who have tauopathies and controls.