Cerebrospinal fluid tau and beta-amyloid(1-42) in dementia disorders

Particulate matter exposure from motorized traffic and risk of conversion from mild cognitive impairment to dementia: An Italian prospective cohort study

BACKGROUND

Based on epidemiologic and laboratory studies, exposure to air pollutants has been linked to many adverse health effects including a higher risk of dementia. In this study, we aimed to evaluate the effect of long-term exposure to outdoor air pollution on risk of conversion to dementia in a cohort of subjects with mild cognitive impairment (MCI).

METHODS

We recruited 53 Italian subjects newly-diagnosed with MCI. Within a geographical information system, we assessed recent outdoor air pollutant exposure, by modeling air levels of particulate matter with equivalent aerodynamic diameter ≤10 μm (PM₁₀) from motorized traffic at participants' residence. We investigated the relation of PM₁₀ concentrations to subsequent conversion from MCI to any type of dementia. Using a Cox-proportional hazards model combined with a restricted cubic spline model, we computed the hazard ratio (HR) of dementia with its 95% confidence interval (CI) according to increasing PM₁₀ exposure, adjusting for sex, age, and educational attainment.

RESULTS

During a median follow up of 47.3 months, 34 participants developed dementia, in 26 cases diagnosed as Alzheimer's dementia. In non-linear restricted spline regression analysis, mean and maximum annual PM₁₀ levels positively correlated with cerebrospinal fluid total and phosphorylated tau proteins concentrations, while they were inversely associated with β-amyloid. Concerning the risk of dementia, we found a positive association starting from above 10 μg/m³ for mean PM₁₀ levels and above 35 μg/m³ for maximum PM₁₀ levels. Specific estimates for Alzheimer's dementia were substantially similar. Adding other potential confounders to the multivariable model or removing early cases of dementia onset during the follow-up had little effect on the estimates.

CONCLUSIONS

Our findings suggest that exposure to outdoor air pollutants, PM₁₀ in particular, may non-linearly increase conversion from MCI to dementia above a certain ambient air concentration.

Accumulation of Cerebrospinal Fluid Glycerophospholipids and Sphingolipids in Cognitively Healthy Participants With Alzheimer's Biomarkers Precedes Lipolysis in the Dementia Stage

Insight into lipids' roles in Alzheimer's disease (AD) pathophysiology is limited because brain membrane lipids have not been characterized in cognitively healthy (CH) individuals. Since age is a significant risk factor of AD, we hypothesize that aging renders the amyloid precursor protein (APP) more susceptible to abnormal processing because of deteriorating membrane lipids. To reflect brain membranes, we studied their lipid components in cerebrospinal fluid (CSF) and brain-derived CSF nanoparticle membranes. Based on CSF Aβ42/Tau levels established biomarkers of AD, we define a subset of CH participants with normal Aβ42/Tau (CH-NAT) and another group with abnormal or pathological Aβ42/Tau (CH-PAT). We report that glycerophospholipids are differentially metabolized in the CSF supernatant fluid and nanoparticle membrane fractions from CH-NAT, CH-PAT, and AD participants. Phosphatidylcholine molecular species from the supernatant fraction of CH-PAT were higher than in the CH-NAT and AD participants. Sphingomyelin levels in the supernatant fraction were lower in the CH-PAT and AD than in the CH-NAT group. The decrease in sphingomyelin corresponded with an increase in ceramide and dihydroceramide and an increase in the ceramide to sphingomyelin ratio in AD. In contrast to the supernatant fraction, sphingomyelin is higher in the nanoparticle fraction from the CH-PAT group, accompanied by lower ceramide and dihydroceramide and a decrease in the ratio of ceramide to sphingomyelin in CH-PAT compared with CH-NAT. On investigating the mechanism for the lipid changes in AD, we observed that phospholipase A2 (PLA2) activity was higher in the AD group than the CH groups. Paradoxically, acid and neutral sphingomyelinase (SMase) activities were lower in AD compared to the CH groups. Considering external influences on lipids, the clinical groups did not differ in their fasting blood lipids or dietary lipids, consistent with the CSF lipid changes originating from brain pathophysiology. The lipid accumulation in a prodromal AD biomarker positive stage identifies perturbation of lipid metabolism and disturbances in APP/Amyloid beta (Aβ) as early events in AD pathophysiology. Our results identify increased lipid turnover in CH participants with AD biomarkers, switching to a predominantly lipolytic state in dementia. This knowledge may be useful for targeting and testing new AD treatments.

Analytical performance of reagent for assaying tau protein in human plasma and feasibility study screening neurodegenerative diseases

Immunomagnetic reduction (IMR), which involves the use of antibody-functionalized magnetic nanoparticles to specifically label target biomarkers, was utilized to develop an assay for total tau protein in human plasma. The analytic properties of the IMR assay on tau protein were investigated. The limit of detection was found to be 0.026 pg/ml. Other properties such as Hook effect, assay linearity, dilution recovery range, reagent stability, interference test, and spiked recovery were also characterized. The ultra-sensitive IMR assay was applied to detect the plasma tau protein levels of subjects with prevalent neurodegenerative diseases, such as Alzheimer's disease (AD), mild cognitive impairment (MCI) due to AD, Parkinson's disease (PD), frontotemporal dementia (FTD) and vascular dementia (VD). The concentrations of plasma tau protein in patients with VD, PD, MCI due to AD, FTD, and AD patients were higher than that of healthy controls. Using an ROC curve analysis, the cutoff value for discriminating dementia patients from healthy controls was 17.43 pg/ml, resulting in 0.856 and 0.727 for clinical sensitivity and specificity, respectively. The area under the ROC curve was 0.908. These results imply that the IMR plasma tau assay would be useful to screen for prevalent neurodegenerative diseases.

Associations between TOMM40 Poly-T Repeat Variants and Dementia in Cases with Parkinsonism

BACKGROUND

Mitochondrial dysfunction has been implicated in the pathophysiology of Parkinson's disease (PD)-related pathologies.

OBJECTIVE

To investigate the role of the Translocase of the Outer Mitochondrial Membrane 40 homolog (TOMM40) variants in PD without dementia (PDND), PD with dementia (PDD) and in Dementia with Lewy bodies (DLB).

METHODS

248 individuals, including 92 PDND, 55 PDD, and 101 DLB, were included. The rs10524523 locus in the TOMM40 gene (TOMM40 poly-T repeat) is characterized by a variable number of T residues that were classified into three groups based on length; short (S), long (L), and very long (VL). We tested log-additive genetic model of association with dementia and adjusted for age, sex, and APOEɛ4 carrier status. We analyzed cerebrospinal fluid (CSF) levels of Aβ42 and Tau, biomarkers related to Alzheimer's disease (AD).

RESULTS

PDD/DBL status and abnormal CSF AD biomarkers (Aβ42 and Aβ42/Tau ratio) were both associated with the APOEɛ4 allele (p <  0.014) and the L allele of TOMM40 poly-T repeat (p <  0.008). The VL allele was less frequently observed in the PDD/DLB group (p = 0.013). In APOE-ɛ4 adjusted analyses, the relationships between the L and VL alleles and dementia status as well as CSF AD biomarkers were not significant. When adjusting for APOE-ɛ4, however, there were associations between S carrier status and PDD/DLB (p = 0.019) and abnormal CSF levels of Aβ42/Tau ratio (p = 0.037) although these were not significant after adjustment for multiple comparisons.

CONCLUSION

Our results do not support the notion that TOMM40 poly-T repeat variants have independent effects on PDD and DLB pathology. This relationship seems to be driven by APOE-ɛ4.

A network model of genomic hormone interactions underlying dementia and its translational validation through serendipitous off-target effect

BACKGROUND

While the majority of studies have focused on the association between sex hormones and dementia, emerging evidence supports the role of other hormone signals in increasing dementia risk. However, due to the lack of an integrated view on mechanistic interactions of hormone signaling pathways associated with dementia, molecular mechanisms through which hormones contribute to the increased risk of dementia has remained unclear and capacity of translating hormone signals to potential therapeutic and diagnostic applications in relation to dementia has been undervalued.

METHODS

Using an integrative knowledge- and data-driven approach, a global hormone interaction network in the context of dementia was constructed, which was further filtered down to a model of convergent hormone signaling pathways. This model was evaluated for its biological and clinical relevance through pathway recovery test, evidence-based analysis, and biomarker-guided analysis. Translational validation of the model was performed using the proposed novel mechanism discovery approach based on 'serendipitous off-target effects'.

RESULTS

Our results reveal the existence of a well-connected hormone interaction network underlying dementia. Seven hormone signaling pathways converge at the core of the hormone interaction network, which are shown to be mechanistically linked to the risk of dementia. Amongst these pathways, estrogen signaling pathway takes the major part in the model and insulin signaling pathway is analyzed for its association to learning and memory functions. Validation of the model through serendipitous off-target effects suggests that hormone signaling pathways substantially contribute to the pathogenesis of dementia.

CONCLUSIONS

The integrated network model of hormone interactions underlying dementia may serve as an initial translational platform for identifying potential therapeutic targets and candidate biomarkers for dementia-spectrum disorders such as Alzheimer's disease.

A prediction model to calculate probability of Alzheimer's disease using cerebrospinal fluid biomarkers

BACKGROUND

We aimed to develop a prediction model based on cerebrospinal fluid (CSF) biomarkers, that would yield a single estimate representing the probability that dementia in a memory clinic patient is due to Alzheimer's disease (AD).

METHODS

All patients suspected of dementia in whom the CSF biomarkers had been analyzed were selected from a memory clinic database. Clinical diagnosis was AD (n = 272) or non-AD (n = 289). The prediction model was developed with logistic regression analysis and included CSF amyloid β42, CSF phosphorylated tau181, and sex. Validation was performed on an independent data set from another memory clinic, containing 334 AD and 157 non-AD patients.

RESULTS

The prediction model estimated the probability that AD is present as follows: p(AD) = 1/(1 + e (- [-0.3315 + score])), where score is calculated from -1.9486 × ln(amyloid β42) + 2.7915 × ln(phosphorylated tau181) + 0.9178 × sex (male = 0, female = 1). When applied to the validation data set, the discriminative ability of the model was very good (area under the receiver operating characteristic curve: 0.85). The agreement between the probability of AD predicted by the model and the observed frequency of AD diagnoses was very good after taking into account the difference in AD prevalence between the two memory clinics.

CONCLUSIONS

We developed a prediction model that can accurately predict the probability of AD in a memory clinic population suspected of dementia based on CSF amyloid β42, CSF phosphorylated tau181, and sex.

CSF tau and β-amyloid as biomarkers for mild cognitive impairment

Early diagnosis of Alzheimer s disease (AD) is relevant in order to initiate symptomatic treatment with antidementia drugs. This will be of greater significance if the drugs aimed at slowing down the degenerative process (secondary prevention) prove to affect AD pathology and are clinically effective, such as γ-secretase inhibitors. However, there is currently no clinical assessment to differentiate the patients with mild cognitive impairment (MCI) who will progress to AD from those with a benign form of memory impairment that is part of the normal aging process. Thus, there is great clinical need for diagnostic and predictive biomarkers, as well as biomarkers for classification purposes, to identify incipient AD in MCI subjects. The most promising cerebrospinal fluid (CSF) biomarker candidates are total tau protein (T-tau), phosphorylated tau protein (P-tau), and the 42-andno acid form offi-amyloid (Aβ42), which may, if used in the right clinical context, prove to have sufficient diagnostic accuracy and predictive power to resolve this diagnostic challenge.

Biomarkers in dementia with Lewy bodies: a review

BACKGROUND

Dementia with Lewy bodies (DLB) shares common clinical, neuropsychological and pathological features with other dementia subtypes, such as Alzheimer's disease (AD), making it difficult to differentiate in clinical practice. Despite the development of consensus diagnostic criteria, many cases are missed, and biomarkers to assist with diagnosis would represent important advances. Our aim was to review the literature to identify potential biomarkers that may distinguish DLB from other dementia subtypes, especially AD.

METHOD

The literature search was performed using Medline up to October 2010 for imaging studies [single-photon emission computed tomography (SPECT), positron emission tomography (PET), magnetic resonance imaging (MRI) and amyloid imaging] and cerebrospinal fluid (CSF) markers in DLB. Individual articles were examined for additional references. The abstracts of the identified articles were read to determine the most relevant papers, which became the basis for this review.

RESULTS

The most robust evidence available was for striatal dopamine transporter activity visualised by (123) I-labelled N-(3-fluoropropyl)-2β-carbomethoxy-3β-(4-iodophenyl)nortropane ((123) I-FP-CIT) SPECT. Several other imaging techniques have also reported promising results, such as [(18) F]fluorodopa PET, which assesses nigrostriatal integrity; [(18) F]fluorodeoxyglucose PET, which assesses metabolic deficits; and meta-iodobenzylguanidine imaging, which assesses sympathetic cardiac denervation. Data from studies using CSF measures of amyloid and tau, occipital hypoperfusion on SPECT and preservation of medial temporal lobe structures on MRI suggest that they may offer less diagnostic discrimination.

CONCLUSION

Several potential biomarkers have shown good diagnostic accuracy for DLB, but apart from FP-CIT SPECT, there is now a need for larger clinical multi-site studies, as well as for studies with pathological verification of diagnosis, before their use could be recommended for routine clinical practice.

Changes in CSF acetyl- and butyrylcholinesterase activity after long-term treatment with AChE inhibitors in Alzheimer's disease

OBJECTIVES

  To measure cerebrospinal fluid (CSF) activity of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) in patients with Alzheimer's disease (AD) participating in randomized clinical trials from three European centers, before and after long-term treatment with different AChE inhibitors (AChEIs).

MATERIALS AND METHODS

  Of the 144 patients included in the study, 104 were treated with donepezil, 15 with galantamine, 16 with rivastigmine, and nine with placebo. CSF AChE and BChE activities were measured at baseline and after 1- year treatment.

RESULTS

Donepezil and galantamine groups showed a significant increase in CSF AChE activity at follow-up, while no changes for BChE activity were observed; in donepezil group, a positive correlation between plasma concentration and AChE activity was documented. Conversely, in rivastigmine group, a decrease in CSF activity of both enzymes was observed. CSF AChE and BChE activities were not correlated with the clinical outcome in any group considered. CSF biomarkers did not show any change after treatment.

CONCLUSIONS

  AChEIs differently influence the activity of target enzymes in CSF independent of their pharmacodynamic effects.

Tau and p-tau as CSF biomarkers in dementia: a meta-analysis

BACKGROUND

To evaluate the value of total tau (tau) and phosphorylated tau (p-tau) in cerebrospinal fluid (CSF) in the differential diagnosis of dementia, more specifically: dementia with Lewy Bodies (DLB), frontotemporal lobar degeneration (FTLD), vascular dementia (VaD), and Creutzfeldt-Jacob disease (CJD).

METHODS

A systematic literature search was performed to identify studies on tau and p-tau in DLB, FTLD, VaD and CJD. Tau concentrations were compared to healthy controls and to subjects with Alzheimer's disease (AD) using random effect meta-analysis. Outcome measures were Cohen's delta, sensitivity and specificity.

RESULTS

Compared to controls, tau concentrations are moderately elevated in DLB, FTLD and VaD, while p-tau concentrations are only slightly elevated in DLB and not elevated in FTLD and VaD. Compared to AD, lower tau concentrations differentiated DLB with a sensitivity of 73% and a specificity of 90%, FTLD with sensitivity and specificity of 74%, and VaD with a sensitivity of 73% and a specificity of 86%. Relative to AD, lower p-tau values differentiated FTLD with a sensitivity of 79% and specificity of 83%, and VaD with a sensitivity of 88% and a specificity of 78%. CJD is characterized by extremely elevated tau concentrations with a sensitivity of 91% and a specificity of 98% vs. AD.

CONCLUSIONS

CSF tau concentrations in DLB, FTLD and VaD are intermediate between controls and AD patients. Overlap with both controls and AD patients results in insufficient diagnostic accuracy, and the development of more specific biomarkers for these disorders is needed. CJD is characterized by extremely increased tau values, resulting in a sensitivity and specificity that exceeds 90%.

Biochemistry of Tau in Alzheimer's disease and related neurological disorders

Microtubule-associated Tau proteins belong to a family of factors that polymerize tubulin dimers and stabilize microtubules. Tau is strongly expressed in neurons, localized in the axon and is essential for neuronal plasticity and network. From the very beginning of Tau discovery, proteomics methods have been essential to the knowledge of Tau biochemistry and biology. In this review, we have summarized the main contributions of several proteomic methods in the understanding of Tau, including expression, post-translational modifications and structure, in both physiological and pathophysiological aspects. Finally, recent advances in proteomics technology are essential to develop further therapeutic targets and early predictive and discriminative diagnostic assays for Alzheimer's disease and related disorders.

Amyloid beta peptide ratio 42/40 but not A beta 42 correlates with phospho-Tau in patients with low- and high-CSF A beta 40 load

Neurochemical dementia diagnostics (NDD) can significantly improve the clinically based categorization of patients with early dementia disorders, and the cerebrospinal fluid (CSF) concentrations of amyloid beta peptides ending at the amino acid position of 42 (A beta x-42 and A beta 1-42) are widely accepted biomarkers of Alzheimer's disease (AD). However, in subjects with constitutively high- or low-CSF concentrations of total A beta peptides (tA beta), the NDD interpretation might lead to erroneous conclusions as these biomarkers seem to correlate better with the total A beta load than with the pathological status of a given patient in such cases. In this multicenter study, we found significantly increased CSF concentrations of phosphorylated Tau (pTau181) and total Tau in the group of subjects with high CSF A beta x-40 concentrations and decreased A beta x-42/x-40 concentration ratio compared with the group of subjects with low CSF A beta x-40 and normal A beta ratio (p<0.001 in both cases). Furthermore, we observed significantly decreased A beta ratio (p<0.01) in the group of subjects with APOE epsilon 4 allele compared with the group of subjects without this allele. Surprisingly, patients with low-A beta x-40 and the decreased A beta ratio characterized with decreased pTau181 (p<0.05), and unaltered total Tau compared with the subjects with high A beta x-40 and the A beta ratio in the normal range. We conclude that the amyloid beta concentration ratio should replace the 'raw' concentrations of corresponding A beta peptides to improve reliability of the neurochemical dementia diagnosis.

Neuropsychological and behavioural correlates of CSF biomarkers in dementia

To improve clinical, neuropsychological and behavioural characterisation of the cerebrospinal fluid (CSF) biomarkers beta-amyloid((1-42)) protein (Abeta42), protein tau (tau) and tau phosphorylated at threonine 181 (P-tau181) across diagnostic dementia categories, a prospective study was set up. Patients with probable Alzheimer's disease (AD) (n=201), AD with cerebrovascular disease (CVD) (AD+CVD) (n=33), frontotemporal dementia (FTD) (n=27), dementia with Lewy bodies (DLB) (n=22) and healthy controls (n=148) were included. All patients underwent neuropsychological examination and behavioural assessment by means of a battery of behavioural assessment scales. CSF was obtained by lumbar puncture and levels of Abeta42, tau and P-tau181 were determined with commercially available ELISA kits. Negative correlations between CSF Abeta42 levels and aggressiveness (Spearman: r=-0.223; p=0.002) and positive correlations with age at inclusion (r=0.195; p=0.006), age at onset (r=0.205; p=0.003) and MMSE scores (r=0.198; p=0.005) were found in AD. In AD+CVD, CSF Abeta42 levels were correlated with MMSE (r=0.482; p=0.006), Hierarchic Dementia Scale (r=0.503; p=0.017) and Boston Naming Test (r=0.516; p=0.012) scores. In controls, age was positively correlated with CSF tau (r=0.465; p<0.001) and P-tau181 levels (r=0.312; p<0.001). CSF tau and P-tau181 levels correlated significantly in all groups, whereas CSF Abeta42 correlated with tau and P-tau181 levels in healthy controls only. Negative correlations between CSF Abeta42 levels and aggressiveness were found in AD patients. CSF Abeta42 seems to be a stage marker for AD (+/-CVD) given the positive correlations with neuropsychological test results suggesting that CSF Abeta42 might be of help for monitoring disease progression. Different correlations between age and CSF biomarker levels were obtained in healthy controls compared to AD patients, indicating that AD-induced pathophysiological processes change age-dependent regulation of CSF biomarker levels.

Neurochemical diagnosis of Alzheimer's dementia by CSF Abeta42, Abeta42/Abeta40 ratio and total tau

Cerebrospinal fluid (CSF) concentrations of amyloid beta peptides ending at positions 42 and 40 (Abeta42 and Abeta40, respectively), and total tau (tTau) protein were measured by ELISA in order to compare their accuracy in discriminating patients with Alzheimer's disease (AD, n = 22), non-Alzheimer dementia (nAD, n = 11) and control subjects (CON, n=35). As compared to the other groups, the concentrations of Abeta42 and tTau were decreased (P<0.001) and increased (P<0.001) in AD, respectively, while Abeta40 did not differ significantly among the groups. Receiver operating characteristic (ROC) analysis was performed to define cut-off values for maximized sensitivity and specificity. For all groups compared the Abeta peptide ratio 42/40 classified more patients correctly, as compared to the concentration of Abeta42 alone: AD versus controls, 94 and 86.7%; AD versus nAD, 90 and 85% and AD versus nAD plus controls, 90.8 and 87%, respectively. The percentage of correctly classified patients was further improved when the Abeta ratio was combined with the analysis of the tTau concentration. Presence of the apolipoprotein E 4 allele, age or degree of mental disability did not significantly influence the parameters studied.

Amyloid beta peptides in cerebrospinal fluid as profiled with surface enhanced laser desorption/ionization time-of-flight mass spectrometry: evidence of novel biomarkers in Alzheimer's disease

BACKGROUND

The advent of new therapeutic avenues for Alzheimer's disease (AD) calls for an improved early and differential diagnosis.

METHODS

With surface enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF MS), cerebrospinal fluid from patients with AD (n = 10) and nondemented control subjects (n = 9) was studied.

RESULTS

Molecular mass signals were observed corresponding to three novel amyloid beta (Abeta) peptides that have not previously been described, in addition to those previously known, with molecular masses of 4525.1 d, 4846.8 d, and 7755.8 d. The signal-to-noise ratios (S/NR) of Abeta(4525.1) and Abeta(7758.8+2H) were significantly decreased in AD [Abeta(4525.1): median 2.2 and 4.3 in AD and control subjects, respectively, p <.01; Abeta(7758.8+2H): median 1.0 and 14.0 in AD and control subjects, respectively, p <.01], whereas the S/NR of Abeta(4846.8) was significantly increased in AD (median 3.6 and 2.5 in AD and control subjects, respectively, p <.05). The S/NR of two known AD biomarkers, Abeta1-42 and Abeta1-40, expectedly turned out to be significantly decreased (p <.01) and unaltered in AD, respectively. A moderate and highly significant correlation was observed between S/NR of Abeta1-42 and Abeta42 concentration as measured with enzyme-linked immunosorbent assay (R =.67, p <.01).

CONCLUSIONS

We report evidence of three novel amyloid beta peptides that might play an important role in the diagnosis and pathophysiology of Alzheimer's disease.

A prospective study of CSF markers in 250 patients with possible Creutzfeldt-Jakob disease

OBJECTIVE

To investigate various cerebrospinal fluid (CSF) markers that could assist in the clinical diagnosis of Creutzfeldt-Jakob disease (CJD).

METHODS

CSF samples were analysed for the presence of 14-3-3 protein, microtubule associated protein tau, and beta amyloid in 250 patients with possible CJD. Densitometric analysis was used to quantify the level of 14-3-3 in all patients.

RESULTS

Analysis of the clinical data showed that cerebellar signs or myoclonus combined with progressive dementia were the main features leading to a clinical suspicion of CJD. While 14-3-3 detection had a sensitivity of 100% and a specificity of 92%, tau determination using a threshold of 1300 pg/ml had a sensitivity of 87% and a specificity of 97%. If the protocol for the analysis of 14-3-3 was modified (using densitometric analysis) a higher specificity (97%) could be obtained, but with a lower sensitivity (96%). Maximum sensitivity, specificity, and positive predictive value were obtained with a combination of 14-3-3 and beta amyloid determinations. The concentrations of 14-3-3 and tau in the CSF were reduced in CJD patients with a long duration of disease (more than one year; p < 0.05). The concentrations of 14-3-3 or tau were lowest at the onset or at the end stage of the disease, while the beta amyloid concentration remained low throughout the course of the disease.

CONCLUSIONS

Both 14-3-3 and tau protein are sensitive and specific biomarkers for CJD. The combination of 14-3-3 and beta amyloid analysis resulted in the maximum sensitivity, specificity, and positive predictive value. When these biomarkers are used in the diagnosis of CJD, the phase of the disease in which the CSF sample was obtained should be taken into account. Disease duration, dependent on the PrP genotype, also has a significant influence on the level of 14-3-3 and tau in the CSF.

Advances in the development of biomarkers for Alzheimer's disease: from CSF total tau and Abeta(1-42) proteins to phosphorylated tau protein

Advances have been made to establish biological markers of Alzheimer's disease (AD). Measurement of total tau (t-tau) and beta-amyloid(1-42) (Abeta(1-42)) in the cerebrospinal fluid (CSF) seems useful to discriminate early and incipient AD from age-associated memory-impairment, depression, and some secondary dementias. New immunoassays to detect different phosphorylated tau epitopes (p-tau) have recently been developed. P-tau phosphorylated at threonine 231 (p-tau(231)) showed improvements compared to t-tau in the early detection of AD in subjects with mild cognitive impairment. As p-tau(231) declined during the course of AD, it may have potential to track disease progression. Additionally, p-tau(231) improved differential diagnosis between AD, frontotemporal dementia, and geriatric major depression. P-tau phosphorylated at threonine 181 improved diagnostic accuracy between AD and dementia with Lewy bodies. P-tau phosphorylated at serine 199 demonstrated high discriminative power between AD and non-Alzheimer's dementia. P-tau phosphorylated at serine 306/serine 404 improved differential diagnosis between AD and vascular dementia. A comparative study of the different p-tau epitopes is currently under way. In summary, first clinical multi-center studies suggest that measurement of phosphorylated tau proteins may significantly improve early and differential diagnosis and may come close to fulfilling proposed criteria of a biological marker for AD.

Beta-amyloid peptides in cerebrospinal fluid of patients with Creutzfeldt-Jakob disease

Decreased levels of beta-amyloid peptide 1-42 (Abeta1-42) in cerebrospinal fluid (CSF) are a characteristic feature of Alzheimer's disease (AD) but recently were also observed in Creutzfeldt-Jakob disease (CJD). We analyzed the CSF of patients with CJD, and AD and nondemented controls using a quantitative urea-based Abeta sodium dodecyl sulfate polyacrylamide gel electrophoresis immunoblot. Like in AD and nondemented controls, we found a highly conserved pattern of carboxyterminally truncated Abeta1-37/38/39 in addition to Abeta1-40/42 also in CJD patients. By the introduction of the ratio Abeta1-39 to Abeta1-42, CJD and AD can effectively be differentiated. We conclude that the immunoblot shows disease-specific CSF Abeta peptide patterns in CJD and AD and suppose that measurement of the Abeta peptide pattern seems to be a promising diagnostic tool in the differential diagnosis of dementias.

Modern proteomic strategies in the study of complex neuropsychiatric disorders

An insight into protein mechanisms involved in disease is critical to the discovery and design of new therapeutic tools. Direct protein analysis provides a method for studying the proteome of a tissue irrespective of an in-depth knowledge of its transcriptome. The development of a human central nervous system (CNS) proteome database ultimately will serve to accelerate the development of specific diagnostic and prognostic markers, neuropsychiatric disease markers, and the corresponding therapeutic tools. It may also reduce the uncertainties in in silico gene predictions by direct open reading frame verification and the ambiguities that experimental models of disease may provide. Advances in gel independent proteomic analyses by solid phase isotope tagging provide greater scope for the characterization of previously elusive membrane proteins; approximately half of all drug targets are key CNS membrane proteins. These advances hold great promise for improvements in the understanding, diagnosis, and therapy of central nervous system disorders.

Glycosylation of acetylcholinesterase and butyrylcholinesterase changes as a function of the duration of Alzheimer's disease

The identification of biochemical markers of Alzheimer's disease (AD) may help in the diagnosis of the disease. Previous studies have shown that Abeta(1-42) is decreased, and tau and phospho-tau are increased in AD cerebrospinal fluid (CSF). Our own studies have identified glycosylated isoforms of acetylcholinesterase (Glyc-AChE) and butyrylcholinesterase (Glyc-BuChE) that are increased in AD CSF. Glyc-AChE is increased in APP (SW) Tg2576 transgenic mice prior to amyloid plaque deposition, which suggests that Glyc-AChE may be an early marker of AD. The aim of this study was to determine whether Glyc-AChE or Glyc-BuChE is increased in CSF at early stages of AD and to compare the levels of these markers with those of Abeta(1-42), tau and phospho-tau. Lumbar CSF was obtained ante mortem from 106 non-AD patients, including 15 patients with mild cognitive impairment (MCI), and 102 patients with probable AD. Glyc-AChE, tau and phospho-tau were significantly increased in the CSF of AD patients compared to non-neurological disease (NND) controls. Abeta(1-42) was lower in the AD patients than in NND controls. A positive correlation was found between the levels of Glyc-AChE or Glyc-BuChE and disease duration. However, there was no clear correlation between the levels of tau, phospho-tau or Abeta(1-42) and disease duration. The results suggest that Glyc-AChE and Glyc-BuChE are unlikely to be early markers of AD, although they may have value as markers of disease progression.

Altered levels of cerebrospinal fluid reelin in frontotemporal dementia and Alzheimer's disease

Reelin is an essential glycoprotein for correct cytoarchitectonic organization during CNS development. Its function in the adult brain is far less well understood, but altered brain and blood reelin levels have been reported in some psychiatric disorders, and the possibility has been considered of an involvement of the reelin signaling pathway in neurodegeneration. Here we report, for the first time, the presence of detectable levels of reelin in rat and human cerebrospinal fluid (CSF) and show evidence for the involvement of a 180-kDa reelin fragment in two neurodegenerative disorders. This fragment was analyzed by Western blotting in CSF samples from 13 healthy control individuals and 14 frontotemporal dementia (FTD) and 20 Alzheimer's disease (AD) patients. Increased CSF 180-kDa reelin was found in FTD (161.7 +/- 6.7 arbitrary units; a.u.) and AD (151.4 +/- 3.8 a.u.) compared with control individuals (141.4 +/- 1.2 a.u., P < 0.05). Our results strongly suggest the involvement of reelin signaling in neurodegenerative pathologies.

CSF Abeta 42 levels correlate with amyloid-neuropathology in a population-based autopsy study

OBJECTIVE

To investigate the relationship of amyloid neuropathology to postmortem CSF Abeta 42 levels in an autopsy sample of Japanese American men from the population-based Honolulu-Asia Aging Study.

METHODS

In 1991, participants were assessed and diagnosed with dementia (including subtype) based on published criteria. At death CSF was obtained from the ventricles. Neuritic plaques (NP) and diffuse plaques in areas of the neocortex and hippocampus were examined using Bielschowsky silver stains. Cerebral amyloid angiopathy (CAA) was measured by immunostaining for beta4 amyloid in cerebral vessels in the neocortex. Neuropathologically confirmed AD was diagnosed using Consortium to Establish a Registry for Alzheimer's Disease criteria. In 155 autopsy samples, log transformed linear regression models were used to examine the association of NP and CAA to Abeta 42 levels, controlling for clinical dementia severity, time between diagnosis and death, age at death, brain weight, hours between death and collection of CSF, education, and APOE genotype.

RESULTS

Higher numbers of NP in the neocortex (p trend = 0.001) and in the hippocampus (p trend = 0.03) were strongly associated with lower levels of Abeta 42. Individuals with CAA had lower Abeta 42 levels (beta coefficient = -0.48; 95% CI -0.9, -0.1). Compared to participants with a diagnosis of clinical dementia, those with pathologically confirmed AD had lower Abeta 42 levels (beta coefficient = -0.74; 95% CI -1.4, -0.1).

CONCLUSION

The current study suggests that lower Abeta 42 levels reflect neuropathologic processes implicated in amyloid-related pathologies, such as NP and CAA.

The amyloid-beta (Abeta) peptide pattern in cerebrospinal fluid in Alzheimer's disease: evidence of a novel carboxyterminally elongated Abeta peptide

The patterns of amyloid beta (Abeta) peptides in human cerebrospinal fluid (CSF) and brain homogenates were studied by surface-enhanced laser desorption/ionization (SELDI) time-of-flight (TOF) mass spectrometry, and the results were compared with those obtained by Abeta-SDS-PAGE/immunoblot. Apart from the peptides known in the literature to occur in the CSF, we postulate the existence of a novel, previously not described peptide, either Abeta1-45 or Abeta2-46. This peptide was observed exclusively in a pool of samples originating from patients with AD, i.e. CSF and postmortem brain homogenates, but not in either the pooled CSF samples nor the pooled brain homogenates of the non-demented controls. Similarly to our previous results, Abeta1-42 was decreased in the CSF in AD. Expectedly, brain homogenates of the control subjects did not show the presence of Abeta peptides. Compared with Abeta-SDS-PAGE/immunoblot, SELDI-TOF enabled more precise analysis of Abeta peptides in the human material. We conclude that SELDI-TOF offers a promising tool for dementia expression pattern profiling using a minute amount of a biological sample.

Longitudinal cerebrospinal fluid tau load increases in mild cognitive impairment

Cross-sectional cerebrospinal fluid (CSF) levels of tau and amyloid (A) beta (beta) are of diagnostic importance for Alzheimer's disease (AD) and mild cognitive impairment (MCI). However, most longitudinal studies of tau fail to demonstrate progression. Because predominantly brain-derived proteins such as tau, have higher ventricle to lumbar ratios, we hypothesized that adjusting for the ventricular enlargement of AD would correct for the dilution of tau, and improve detection of longitudinal change. Abeta which is not exclusively brain derived, shows a ratio <1, and no benefit was expected from adjustment. In a 1 year longitudinal study of eight MCI and ten controls, we examined CSF levels of hyperphosphorylated (P) tau231, Abeta40, and Abeta42. In cross-section, MCI patients showed elevated Ptau231 and Abeta40 levels, and greater ventricular volumes. Longitudinally, only after adjusting for the ventricular volume and only for Ptau231, were increases seen in MCI. Further studies are warranted on mechanisms of tau clearance and on using imaging to interpret CSF studies.