The cerebrospinal fluid (CSF) biochemical markers (biomarkers) Amyloidβ 42 (Aβ
), total Tau (T-tau) and Tau phosphorylated at threonine 181 (P-tau
) have proven diagnostic accuracy for mild cognitive ...impairment and dementia due to Alzheimer's Disease (AD). In an effort to improve the accuracy of an AD diagnosis, it is important to be able to distinguish between AD and other types of dementia (non-AD). The concentration ratio of Aβ
to Aβ
(Aβ
Ratio) has been suggested to be superior to the concentration of Aβ
alone when identifying patients with AD. This article reviews the available evidence on the use of the CSF Aβ
ratio in the diagnosis of AD. Based on the body of evidence presented herein, it is the conclusion of the current working group that the CSF Aβ
ratio, rather than the absolute value of CSF Aβ
, should be used when analysing CSF AD biomarkers to improve the percentage of appropriately diagnosed patients.
A growing body of evidence suggests that the plasma concentration of the neurofilament light chain (NfL) might be considered a plasma biomarker for the screening of neurodegeneration in Alzheimer's ...disease (AD).
With a single molecule array method (Simoa, Quanterix), plasma NfL concentrations were measured in 99 subjects with AD at the stage of mild cognitive impairment (MCI-AD; n = 25) or at the stage of early dementia (ADD; n = 33), and in nondemented controls (n = 41); in all patients, the clinical diagnoses were in accordance with the results of the four core cerebrospinal fluid (CSF) biomarkers (amyloid β (Aβ)1-42, Aβ42/40, Tau, and pTau181), interpreted according to the Erlangen Score algorithm. The influence of preanalytical storage procedures on the NfL in plasma was tested on samples exposed to six different conditions.
NfL concentrations significantly increased in the samples exposed to more than one freezing/thawing cycle, and in those stored for 5 days at room temperature or at 4 °C. Compared with the control group of nondemented subjects (22.0 ± 12.4 pg/mL), the unadjusted plasma NfL concentration was highly significantly higher in the MCI-AD group (38.1 ± 15.9 pg/mL, p < 0.005) and even further elevated in the ADD group (49.1 ± 28.4 pg/mL; p < 0.001). A significant association between NfL and age (ρ = 0.65, p < 0.001) was observed; after correcting for age, the difference in NfL concentrations between AD and controls remained significant (p = 0.044). At the cutoff value of 25.7 pg/mL, unconditional sensitivity, specificity, and accuracy were 0.84, 0.78, and 0.82, respectively. Unadjusted correlation between plasma NfL and Mini Mental State Examination (MMSE) across all patients was moderate but significant (r = -0.49, p < 0.001). We observed an overall significant correlation between plasma NfL and the CSF biomarkers, but this correlation was not observed within the diagnostic groups.
This study confirms increased concentrations of plasma NfL in patients with Alzheimer's disease compared with nondemented controls.
Abstract Several potential disease-modifying drugs for Alzheimer's disease (AD) have failed to show any effect on disease progression in clinical trials, conceivably because the AD subjects are ...already too advanced to derive clinical benefit from treatment and because diagnosis based on clinical criteria alone introduces a high misdiagnosis rate. Thus, well-validated biomarkers for early detection and accurate diagnosis are crucial. Low cerebrospinal fluid (CSF) concentrations of the amyloid-β (Aβ1-42 ) peptide, in combination with high total tau and phosphorylated tau, are sensitive and specific biomarkers highly predictive of progression to AD dementia in patients with mild cognitive impairment. However, interlaboratory variations in the results seen with currently available immunoassays are of concern. Recent worldwide standardization efforts and quality control programs include standard operating procedures for both preanalytical (e.g., lumbar puncture and sample handling) and analytical (e.g., preparation of calibration curve) procedures. Efforts are also ongoing to develop highly reproducible assays on fully automated instruments. These global standardization and harmonization measures will provide the basis for the generalized international application of CSF biomarkers for both clinical trials and routine clinical diagnosis of AD.
It is estimated that Alzheimer’s disease (AD) affects tens of millions of people, comprising not only suffering patients, but also their relatives and caregivers. AD is one of age-related ...neurodegenerative diseases (NDs) characterized by progressive synaptic damage and neuronal loss, which result in gradual cognitive impairment leading to dementia. The cause of AD remains still unresolved, despite being studied for more than a century. The hallmark pathological features of this disease are senile plaques within patients’ brain composed of amyloid beta (Aβ) and neurofibrillary tangles (NFTs) of Tau protein. However, the roles of Aβ and Tau in AD pathology are being questioned and other causes of AD are postulated. One of the most interesting theories proposed is the causative role of amyloid β oligomers (AβOs) aggregation in the pathogenesis of AD. Moreover, binding of AβOs to cell membranes is probably mediated by certain proteins on the neuronal cell surface acting as AβO receptors. The aim of our paper is to describe alternative hypotheses of AD etiology, including genetic alterations and the role of misfolded proteins, especially Aβ oligomers, in Alzheimer's disease. Furthermore, in this review we present various putative cellular AβO receptors related to toxic activity of oligomers.
There is a paucity of empirical research on the use of non-pharmacological interventions to both treat and curb the spread of Alzheimer's disease (AD) across the globe. This paper examines the ...biochemical and clinical outlook and the social implications of the condition in relation to psychological aspects that may indicate a direction for further interventions. There is a scarcity of research on the effectiveness of using various psychological aspects of AD, a disease characterized by a process of transition from health and independence to a dependent state with a progressive loss of memory and functional skills. The paper investigates the biochemical and psychological aspects of AD and their significance for improving quality of life for patients with this disease. Psychological interventions based on, among other factors, biochemical studies, are conducted to improve the emotional wellbeing of AD patients and may assist in slowing down the progression of the disease. To date, however, no effective methods of AD treatment have been established.
Objective
Develop a cerebrospinal fluid biomarker signature for mild Alzheimer's disease (AD) in Alzheimer's Disease Neuroimaging Initiative (ADNI) subjects.
Methods
Amyloid‐β 1 to 42 peptide ...(Aβ1–42), total tau (t‐tau), and tau phosphorylated at the threonine 181 were measured in (1) cerebrospinal fluid (CSF) samples obtained during baseline evaluation of 100 mild AD, 196 mild cognitive impairment, and 114 elderly cognitively normal (NC) subjects in ADNI; and (2) independent 56 autopsy‐confirmed AD cases and 52 age‐matched elderly NCs using a multiplex immunoassay. Detection of an AD CSF profile for t‐tau and Aβ1–42 in ADNI subjects was achieved using receiver operating characteristic cut points and logistic regression models derived from the autopsy‐confirmed CSF data.
Results
CSF Aβ1–42 was the most sensitive biomarker for AD in the autopsy cohort of CSF samples: receiver operating characteristic area under the curve of 0.913 and sensitivity for AD detection of 96.4%. In the ADNI cohort, a logistic regression model for Aβ1–42, t‐tau, and APOε4 allele count provided the best assessment delineation of mild AD. An AD‐like baseline CSF profile for t‐tau/Aβ1–42 was detected in 33 of 37 ADNI mild cognitive impairment subjects who converted to probable AD during the first year of the study.
Interpretation
The CSF biomarker signature of AD defined by Aβ1–42 and t‐tau in the autopsy‐confirmed AD cohort and confirmed in the cohort followed in ADNI for 12 months detects mild AD in a large, multisite, prospective clinical investigation, and this signature appears to predict conversion from mild cognitive impairment to AD. Ann Neurol 2009
Alzheimer’s disease (AD) is a progressive condition and the most common cause of dementia worldwide. The neuropathological changes characteristic of the disorder can be successfully detected before ...the development of full-blown AD. Early diagnosis of the disease constitutes a formidable challenge for clinicians. CSF biomarkers are the in vivo evidence of neuropathological changes developing in the brain of dementia patients. Therefore, measurement of their concentrations allows for improved accuracy of clinical diagnosis. Moreover, AD biomarkers may provide an indication of disease stage. Importantly, the CSF biomarkers of AD play a pivotal role in the new diagnostic criteria for the disease, and in the recent biological definition of AD by the National Institute on Aging, NIH and Alzheimer’s Association. Due to the necessity of collecting CSF by lumbar puncture, the procedure seems to be an important issue not only from a medical, but also a legal, viewpoint. Furthermore, recent technological advances may contribute to the automation of AD biomarkers measurement and may result in the establishment of unified cut-off values and reference limits. Moreover, a group of international experts in the field of AD biomarkers have developed a consensus and guidelines on the interpretation of CSF biomarkers in the context of AD diagnosis. Thus, technological advancement and expert recommendations may contribute to a more widespread use of these diagnostic tests in clinical practice to support a diagnosis of mild cognitive impairment (MCI) or dementia due to AD. This review article presents up-to-date data regarding the usefulness of CSF biomarkers in routine clinical practice and in biomarkers research.
Abstract The last decade has seen a substantial increase in research focused on the identification of blood-based biomarkers that have utility in Alzheimer's disease (AD). Blood-based biomarkers have ...significant advantages of being time- and cost-efficient as well as reduced invasiveness and increased patient acceptance. Despite these advantages and increased research efforts, the field has been hampered by lack of reproducibility and an unclear path for moving basic discovery toward clinical utilization. Here we reviewed the recent literature on blood-based biomarkers in AD to provide a current state of the art. In addition, a collaborative model is proposed that leverages academic and industry strengths to facilitate the field in moving past discovery only work and toward clinical use. Key resources are provided. This new public-private partnership model is intended to circumvent the traditional handoff model and provide a clear and useful paradigm for the advancement of biomarker science in AD and other neurodegenerative diseases.
Biosynthesis of cholesterol: from lanosterol to cholesterol, and the conversion to 24S- and 27-hydroxycholesterol 24 DHCR=24-dehydrocholesterol reductase; Cyp 46A1=cytochrome P-450 46A1; and Cyp ...27A1=cytochrome P-450 27A1.
The disturbances of the cholesterol synthesis and metabolism described in Alzheimer's disease (AD) may be both a consequence of the neurodegenerative process and a contributor to the pathogenesis. These putative relationships and their underlying mechanisms are not well understood.
The aim of this study was to evaluate the relationship between the cerebral and extracerebral cholesterol synthesis and metabolism, and the AD pathology as reflected by CSF markers in humans.
We evaluated the relationships between the plasma and the cerebrospinal fluid (CSF) concentrations of cholesterol, the cholesterol precursors lanosterol, lathosterol and desmosterol, and the cholesterol elimination products 24S-hydroxycholesterol and 27-hydroxycholesterol, and the CSF markers for AD pathology Aβ1–42 and p-tau181 in 86 subjects with normal cognition and in 107 AD patients. CSF desmosterol, cholesterol and 24S-hydroxycholesterol in the AD group, and CSF 24S-hydroxycholesterol in the control group correlated with the p-tau181 levels. Neither CSF nor plasma concentrations of the included compounds correlated with the CSF Aβ1–42 levels. In multivariate regression tests including age, gender, albumin ratio, number of the APOEɛ4 alleles, and diagnosis, p-tau181 levels independently predicted the CSF desmosterol, cholesterol and 24S-hydroxycholesterol concentrations. The associations remained significant for CSF cholesterol and 24S-hydroxycholesterol when analyses were separately performed in the AD group.
The results suggest that alterations of CNS cholesterol de novo genesis and metabolism are related to neurodegeneration and in particular to the cerebral accumulation of phosphorylated tau.
Abstract Background Cerebrospinal fluid (CSF) biomarkers β-amyloid 1-42 (Aβ1-42 ), also expressed as Aβ1-42 :Aβ1-40 ratio, T-tau, and P-tau181P , have proven diagnostic accuracy for mild cognitive ...impairment and Alzheimer's disease (AD). How to use, interpret, and disclose biomarker results drives the need for standardization. Methods Previous Alzheimer's Biomarkers Standardization Initiative meetings discussed preanalytical issues affecting Aβ1-42 and tau in CSF. This second round of consensus meetings focused on issues related to clinical use of AD CSF biomarkers. Results Consensus was reached that lumbar puncture for AD CSF biomarker analysis be considered as a routine clinical test in patients with early-onset dementia, at the prodromal stage or with atypical AD. Moreover, consensus was reached on which biomarkers to use, how results should be interpreted, and potential confounding factors. Conclusions Changes in Aβ1-42 , T-tau, and P-tau181P allow diagnosis of AD in its prodromal stage. Conversely, having all three biomarkers in the normal range rules out AD. Intermediate conditions require further patient follow-up.
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