Study protocol on Alzheimer's disease and related disorders: focus on clinical and imaging predictive markers in co-existing lesions

BACKGROUND

One of the crucial challenges for the future of therapeutic approaches to Alzheimer's disease (AD) is to target the main pathological processes responsible for disability and dependency. However, a progressive cognitive impairment occurring after the age of 70, the main population affected by dementia, is often related to mixed lesions of neurodegenerative and vascular origins. Whereas young patients are mostly affected by pure lesions, ageing favours the occurrence of co-lesions of AD, cerebrovascular disease (CVD) and Lewy body dementia (LBD). Most of clinical studies report on functional and clinical disabilities in patients with presumed pure pathologies. But, the weight of co-morbid processes involved in the transition from an independent functional status to disability in the elderly with co-lesions still remains to be elucidated. Neuropathological examination often performed at late stages cannot answer this question at mild or moderate stages of cognitive disorders. Brain MRI, Single Photon Emission Computed Tomography (SPECT) with DaTscan®, amyloid Positron Emission Tomography (PET) and CerebroSpinal Fluid (CSF) AD biomarkers routinely help in performing the diagnosis of underlying lesions. The combination of these measures seems to be of incremental value for the diagnosis of mixed profiles of AD, CVD and LBD. The aim is to determine the clinical, neuropsychological, neuroradiological and biological features the most predictive of cognitive, behavioral and functional impairment at 2 years in patients with co-existing lesions.

METHODS

A multicentre and prospective cohort study with clinical, neuro-imaging and biological markers assessment will recruit 214 patients over 70 years old with a cognitive disorder of AD, cerebrovascular and Lewy body type or with coexisting lesions of two or three of these pathologies and fulfilling the diagnostic criteria for dementia at a mild to moderate stage. Patients will be followed every 6 months (clinical, neuropsychological and imaging examination and collection of cognitive, behavioural and functional impairment) for 24 months.

DISCUSSION

This study aims at identifying the best combination of markers (clinical, neuropsychological, MRI, SPECT-DaTscan®, PET and CSF) to predict disability progression in elderly patients presenting coexisting patterns.

TRIAL REGISTRATION

NCT02052947 .

Two novel blood-based biomarker candidates measuring degradation of tau are associated with dementia: A prospective study

BACKGROUND

Truncated tau appears to be specifically related to disease pathology and recent studies have shown the presence and elevation of several truncated tau species in Cerebrospinal fluid (CSF) of subjects with Alzheimer's disease (AD); however, the relevance of truncated Tau measurements in blood is still being studied.

OBJECTIVE

The aim of the current study was to assess the longitudinal associations between baseline levels of two novel blood biomarker candidates measuring truncated tau, Tau-A and Tau-C, and the risk of incident dementia and AD in elderly women.

METHODS

Using solid phase competitive ELISA, two tau fragments were detected in serum of 5,309 women from the Prospective Epidemiological Risk Factor study. The study was an observational, prospective study of Danish postmenopausal women. Subjects were followed with registry-linkage for up to 15 years (median follow-up time 13.7 years). Cox regression was used to assess the utility of the biomarker candidates in relation to dementia and AD.

RESULTS

High levels of Tau-A and Tau-C (above the median) in blood were associated with lower risk of dementia and AD (Tau-A: Dementia HR[95% CI] = 0.85[0.70-1.04]; AD 0.71[0.52-0.98] and Tau-C: Dementia 0.84[0.70-1.00]; AD 0.78[0.60-1.03]). Tau-C gave a very modest increase in the AUC in a 5-year prediction horizon as compared to a reference model with age and education, while a combination of the two did not improve their predictive capacity.

CONCLUSIONS

Measurement of tau in serum is feasible. The serological tau turnover profile may be related to the diagnosis and development of dementia and AD. The exact processing and profile in serum in relation to cognitive disorders remains to be further assessed to provide simple non-invasive tests to identify subjects with progressive cognitive disorders.

Change of Amyloid-β 1-42 Toxic Conformer Ratio After Cerebrospinal Fluid Diversion Predicts Long-Term Cognitive Outcome in Patients with Idiopathic Normal Pressure Hydrocephalus

BACKGROUND

Alzheimer's disease (AD) pathology in idiopathic normal pressure hydrocephalus (iNPH) contributes to poor shunt responses. Amyloid-β 1- 42 (Aβ42) toxic conformer was recently identified with features of rapid oligomerization, strong neurotoxicity and synaptotoxicity.

OBJECTIVE

This observational study points to Aβ42 toxic conformer as a biomarker for AD pathology and for poor postoperative prognosis in patients with iNPH.

METHODS

The first cohort consisted of patients with AD (n = 17) and iNPH (n = 17), and cognitively normal individuals (CN, n = 12). The second cohort, consisted of 51 patients with iNPH, was divided into two groups according to phosphorylated Tau (pTau) level (low- and high-pTau groups); the low-pTau group was further subdivided according to one-year postoperative change in Aβ42 toxic conformer ratio (%) [Aβ42 toxic conformer/Aβ42×100] (decreased- and increased-conformer subgroups). Enzyme-linked immunosorbent assay was used to measure pTau, Aβ42, and Aβ42 toxic conformer in cerebrospinal fluid. Outcomes were evaluated using neuropsychological tests one- and two-years postoperatively.

RESULTS

In the first cohort, Aβ42 toxic conformer ratio in the iNPH group (10.8%) was significantly higher than that in the CN group (6.3%) and significantly lower than that in the AD group (17.2%). In the second cohort, the high-pTau group showed cognitive decline two-years postoperatively compared to baseline. However, the low-pTau group showed favorable outcomes one-year postoperatively; furthermore, the increased-conformer subgroup showed cognitive decline two-years postoperatively while the decreased-conformer subgroup maintained the improvement.

CONCLUSIONS

Change in Aβ42 toxic conformer ratio predicts long-term cognitive outcome in iNPH, even in the low-pTau group.

Impact of High-Dose Multi-Strain Probiotic Supplementation on Neurocognitive Performance and Central Nervous System Immune Activation of HIV-1 Infected Individuals

Background: Gut microbiota has metabolic activity which influences mucosal homeostasis, local and systemic immune responses, and other anatomical systems (i.e., brain). The effects of dysbiosis are still poorly studied in Human Immunodeficiency Virus-1 (HIV-1) positive subjects and insufficient data are available on the impairment of the gut-brain axis, despite neurocognitive disorders being commonly diagnosed in these patients. This study evaluated the impact of a probiotic supplementation strategy on intrathecal immune activation and cognitive performance in combined antiretroviral therapy (cART) treated HIV-1 infected subjects. Methods: Thirty-five HIV-1 infected individuals were included in this study. At baseline (T0) a battery of tests was administered, to evaluate neurocognitive function and a lumbar puncture was performed to determine neopterin concentration in cerebrospinal fluid (CSF), as a marker of Central Nervous System (CNS) immune activation. Subsequently, a subgroup of participants underwent a 6-month course of multi-strain probiotics supplementation; this intervention group was evaluated, after probiotic treatment, with a second lumbar puncture and with repeated neurocognitive tests. Results: At T0, all participants showed impaired results in at least one neurocognitive test and elevated neopterin concentrations in CSF. After supplementation with probiotics (T6), the interventional group presented a significant decrease in neopterin concentration and a significant improvement in several neurocognitive tests. In contrast, no significant modifications were observed in the neurocognitive performance of controls between T0 and T6. The CNS Penetration Effectiveness Score of antiretroviral therapy did not show an influence from any of the investigated variables. Conclusions: Multi-strain probiotic supplementation seems to exert a positive effect on neuroinflammation and neurocognitive impairment in HIV-1 infected subjects, but large trials are needed to support the concept that modulation of the gut microbiota can provide specific neurological benefits in these patients.

High prevalence of neuronal surface autoantibodies associated with cognitive deficits in cancer patients

The recent discovery of neuronal cell-surface antibodies profoundly expanded the clinical spectrum of paraneoplastic neurological syndromes. Many of these syndromes are associated with impaired cognitive function, a clinical symptom that is of increasing concern in cancer patients. However, the frequency of these antibodies in cancer patients and their relation to clinical syndromes is currently unknown. Here, we investigated the prevalence of neuronal cell-surface antibodies and associated paraneoplastic neurological syndromes in 323 patients with different cancer types and in 105 controls. Cerebrospinal fluid and serum samples were analysed for a large panel of anti-neuronal antibodies and all patients were screened for cognitive deficits. Blood-brain barrier integrity was assessed using the age-normalized albumin cerebrospinal fluid/serum ratio. Anti-neuronal autoantibodies were observed in 24.5% of cancer patients (in contrast to 3.1% in neurological control patients without cancer and 2.5% in healthy controls) and were almost exclusively detected in serum. The majority of antibodies were directed against cell-surface antigens (75.9%), most frequently IgA/IgM isotypes targeting the N-methyl-D-aspartate (NMDA) receptor. Cognitive deficits and cerebellar syndromes were significantly more prevalent in antibody-positive in comparison with antibody-negative patients (21 vs. 7%, p = 2.7 × 10^-4; 11 vs. 2%, p = 3.0 × 10^-3). Antibody-positive patients with cognitive deficits had a significantly increased albumin cerebrospinal fluid/serum ratio in comparison with antibody-positive patients with other neurological deficits, indicating blood-brain barrier dysfunction (49.1 × 10^-3 vs. 12.0 × 10^-3; p = 0.036). Our results show that anti-neuronal antibodies have a high prevalence in a wide range of different tumour types and are associated with distinct neurological deficits. Specifically, the results suggest a so far undefined cognitive paraneoplastic syndrome in patients with antibodies targeting neuronal surface antigens and concurrent blood-brain barrier dysfunction. Anti-neuronal antibodies might thus serve as a biomarker for potentially treatment-responsive cognitive impairments in cancer patients.

Heterogeneity of neuroanatomical patterns in prodromal Alzheimer's disease: links to cognition, progression and biomarkers

See Coulthard and Knight (doi:10.1093/aww335) for a scientific commentary on this article.Individuals with mild cognitive impairment and Alzheimer's disease clinical diagnoses can display significant phenotypic heterogeneity. This variability likely reflects underlying genetic, environmental and neuropathological differences. Characterizing this heterogeneity is important for precision diagnostics, personalized predictions, and recruitment of relatively homogeneous sets of patients into clinical trials. In this study, we apply state-of-the-art semi-supervised machine learning methods to the Alzheimer's disease Neuroimaging cohort (ADNI) to elucidate the heterogeneity of neuroanatomical differences between subjects with mild cognitive impairment (n = 530) and Alzheimer's disease (n = 314) and cognitively normal individuals (n = 399), thereby adding to an increasing literature aiming to establish neuroanatomical and neuropathological (e.g. amyloid and tau deposition) dimensions in Alzheimer's disease and its prodromal stages. These dimensional approaches aim to provide surrogate measures of heterogeneous underlying pathologic processes leading to cognitive impairment. We relate these neuroimaging patterns to cerebrospinal fluid biomarkers, white matter hyperintensities, cognitive and clinical measures, and longitudinal trajectories. We identified four such atrophy patterns: (i) individuals with largely normal neuroanatomical profiles, who also turned out to have the least abnormal cognitive and cerebrospinal fluid biomarker profiles and the slowest clinical progression during follow-up; (ii) individuals with classical Alzheimer's disease neuroanatomical, cognitive, cerebrospinal fluid biomarkers and clinical profile, who presented the fastest clinical progression; (iii) individuals with a diffuse pattern of atrophy with relatively less pronounced involvement of the medial temporal lobe, abnormal cerebrospinal fluid amyloid-β1-42 values, and proportionally greater executive impairment; and (iv) individuals with notably focal involvement of the medial temporal lobe and a slow steady progression, likely representing in early Alzheimer's disease stages. These four atrophy patterns effectively define a 4-dimensional categorization of neuroanatomical alterations in mild cognitive impairment and Alzheimer's disease that can complement existing dimensional approaches for staging Alzheimer's disease using a variety of biomarkers, which offer the potential for enabling precision diagnostics and prognostics, as well as targeted patient recruitment of relatively homogeneous subgroups of subjects for clinical trials.

Clinical variables and biomarkers in prediction of cognitive impairment in patients with newly diagnosed Parkinson's disease: a cohort study

BACKGROUND

Parkinson's disease is associated with an increased incidence of cognitive impairment and dementia. Predicting who is at risk of cognitive decline early in the disease course has implications for clinical prognosis and for stratification of participants in clinical trials. We assessed the use of clinical information and biomarkers as predictive factors for cognitive decline in patients with newly diagnosed Parkinson's disease.

METHODS

The Parkinson's Progression Markers Initiative (PPMI) study is a cohort study in patients with newly diagnosed Parkinson's disease. We evaluated cognitive performance (Montreal Cognitive Assessment [MoCA] scores), demographic and clinical data, APOE status, and biomarkers (CSF and dopamine transporter [DAT] imaging results). Using change in MoCA scores over 2 years, MoCA scores at 2 years' follow-up, and a diagnosis of cognitive impairment (combined mild cognitive impairment or dementia) at 2 years as outcome measures, we assessed the predictive values of baseline clinical variables and separate or combined additions of APOE status, DAT imaging, and CSF biomarkers. We did univariate and multivariate linear analyses with MoCA change scores between baseline and 2 years, and with MoCA scores at 2 years as dependent variables, using backwards linear regression analysis. Additionally, we constructed a prediction model for diagnosis of cognitive impairment using logistic regression analysis.

FINDINGS

390 patients with Parkinson's disease recruited between July 1, 2010, and May 31, 2013, and for whom data on MoCA scores at baseline and 2 years were available. In multivariate analyses, baseline age, University of Pennsylvania Smell Inventory Test (UPSIT) scores, CSF amyloid - (Aβ42) to t-tau ratio, and APOE status were associated with change in MoCA scores over time. Baseline age, MoCA and UPSIT scores, and CSF Aβ42 to t-tau ratio were associated with MoCA score at 2 years (using a backwards p-removal threshold of 0·1). Accuracy of prediction of cognitive impairment using age alone (area under the curve 0·68, 95% CI 0·60-0·76) significantly improved by addition of clinical scores (UPSIT, Rapid Eye Movement Sleep Behaviour Disorder Screening Questionnaire [RBDSQ], Geriatric Depression Scale, and Movement Disorder Society Unified Parkinson's Disease Rating Scale motor scores; 0·76, 0·68-0·83), CSF variables (0·74, 0·68-0·81), or DAT imaging results (0·76, 0·68-0·83). In combination, the five variables showing the most significant associations with cognitive impairment (age, UPSIT, RBDSQ, CSF Aβ42, and caudate uptake on DAT imaging) allowed prediction of cognitive impairment at 2 years (0·80, 0·74-0·87; p=0·0003 compared to age alone).

INTERPRETATION

In newly diagnosed Parkinson's disease, the occurrence of cognitive impairment at 2 year follow-up can be predicted with good accuracy using a model combining information on age, non-motor assessments, DAT imaging, and CSF biomarkers.

FUNDING

None.

(1→3)-β-D-Glucan Levels Correlate With Neurocognitive Functioning in HIV-Infected Persons on Suppressive Antiretroviral Therapy: A Cohort Study

Microbial translocation from the gut is associated with immune dysfunction, persistent inflammation, and likely plays a role in the pathogenesis of neurocognitive dysfunction during HIV infection. (1→3)-β-D-Glucan (BDG) is a component of most fungal cell walls and might be a useful indicator of gut mucosal barrier impairment. The objective of this study was to evaluate whether higher blood BDG levels correlate with impaired neurocognitive functioning in a cohort of HIV-infected adults with suppressed levels of HIV RNA in blood plasma. In this cross-sectional cohort study, we measured levels of BDG in blood plasma and cerebrospinal fluid (CSF) supernatant samples in a cohort of adults with acute/early HIV infection, who initiated antiretroviral therapy (ART) during the earliest phase of infection and achieved suppressed levels of HIV RNA in blood plasma (<50 copies/mL) thereafter. We compared BDG with established biomarkers of microbial translocation, immune activation, and cognitive dysfunction (evaluated by global deficit score). We found that higher blood BDG levels were significantly related to higher global deficit scores, reflecting worse neurocognitive performance (Spearman r = 0.47; P = 0.042) among HIV-infected adults with suppressed viral loads who initiated ART early in infection. Two CSF samples presented elevated BDG levels. Interestingly, these 2 samples originated from the 2 subjects with the highest global deficit scores of the cohort. BDG may be a promising independent biomarker associated with neurocognitive functioning in virologically suppressed HIV-infected individuals.

Do CSF Biomarkers Predict Progression to Cognitive Impairment in Parkinson's disease patients? A Systematic Review

Many patients with Parkinson's disease (PD) will develop cognitive impairment. Cross-sectional studies have shown that certain protein levels are altered in the cerebrospinal fluid (CSF) of PD patients with dementia and are thought to represent potential biomarkers of underlying pathogenesis. Recent studies suggest that CSF biomarker levels may be predictive of future risk of cognitive decline in non-demented PD patients. However, the strength of this evidence and difference between specific CSF biomarkers is not well delineated. We therefore performed a systematic review to assess if levels of specific CSF protein biomarkers are predictive of progression to cognitive impairment. Nine articles were identified that met inclusion criteria for the review. Findings from the review suggest a convergence of evidence that a low baseline Aβ42 in the CSF of non-demented PD patients predicts development of cognitive impairment over time. Conversely, there is limited evidence that CSF levels of tau, either total tau or phosphorylated tau, is a useful predictive biomarker. There are mixed results for other CSF biomarkers such as α-synuclein, Neurofilament light chain, and Heart fatty acid-binding protein. Overall the results of this review show that certain CSF biomarkers have better predictive ability to identify PD patients who are at risk for developing cognitive impairment. Given the interest in developing disease-modifying therapies, identifying this group will be important for clinical trials as initiation of therapy prior to the onset of cognitive decline is likely to be more efficacious.

Stroke risk interacts with Alzheimer's disease biomarkers on brain aging outcomes

Alzheimer's disease (AD) biomarkers and stroke risk factors independently predict cognitive impairment, likely through independent disease pathways. However, limited work has sought to describe the dynamic interplay between these important risk factors. This article evaluated the interaction between stroke risk and AD biomarkers on hippocampal volume and cognitive performance. We first evaluated the interaction between stroke risk factors and AD biomarkers using data from the Alzheimer's Disease Neuroimaging Initiative (ADNI, n = 1202). We then extended our findings to an independent autopsy data set from the National Alzheimer's Coordinating Center (NACC, n = 1122) using measures of AD pathology. Stroke risk was quantified using the Framingham Stroke Risk Profile. In ADNI, stroke risk interacted with tau and amyloid levels in relation to baseline and longitudinal cognitive performance. Similarly, in NACC, stroke risk interacted with amyloid and tau positivity on cognitive performance. The effect of stroke risk factors on cognition was strongest in the absence of AD biomarkers or neuropathology, providing additional evidence that AD biomarkers and stroke risk factors relate to cognition through independent pathways.

How does additional diagnostic testing influence the initial diagnosis in patients with cognitive complaints in a memory clinic setting?

BACKGROUND

patients suspected of dementia frequently undergo additional diagnostic testing (e.g. brain imaging or neuropsychological assessment) after standard clinical assessment at a memory clinic. This study investigates the use of additional testing in an academic outpatient memory clinic and how it influences the initial diagnosis.

METHODS

the initial diagnosis after standard clinical assessment (history, laboratory tests, cognitive screening and physical and neurological examination) and the final diagnosis after additional testing of 752 memory clinic patients were collected. We specifically registered if, and what type of, additional testing was requested.

RESULTS

additional testing was performed in 518 patients (69%), 67% of whom underwent magnetic resonance imaging, 45% had neuropsychological assessment, 14% had cerebrospinal fluid analysis and 49% had (combinations of) other tests. This led to a modification of the initial diagnosis in 17% of the patients. The frequency of change was highest in patients with an initial non-Alzheimer's disease (AD) dementia diagnosis (54%, compared with 11 and 14% in patients with AD and 'no dementia'; P < 0.01). Finally, after additional testing 44% was diagnosed with AD, 9% with non-AD dementia and 47% with 'no dementia'.

CONCLUSION

additional testing should especially be considered in non-AD patients. In the large group of patients with an initial AD or 'no dementia' diagnosis, additional tests have little diagnostic impact and may perhaps be used with more restraint.

Interleukin 10 Level in the Cerebrospinal Fluid as a Possible Biomarker for Lymphomatosis Cerebri

A 71-year-old immunocompetent man developed cognitive decline and gait disturbance. Brain magnetic resonance imaging (MRI) revealed bilateral diffuse leukoencephalopathy without a mass lesion. An analysis of the cerebrospinal fluid (CSF) showed elevated levels of interleukin (IL)-10. The condition of the patient progressively deteriorated, and intravenous high-dose steroids proved ineffective. Detection of non-destructive, diffusely infiltrating, large B-cell lymphoma in biopsy and autopsy specimens led to a diagnosis of lymphomatosis cerebri (LC). On serial MRI, the basal ganglia and white matter lesions increased in parallel with the levels of IL-10. These findings suggest that the IL-10 level in the CSF may represent a potentially useful biomarker for the early diagnosis and monitoring of the disease progression in LC.

Prognostic classification of mild cognitive impairment and Alzheimer's disease: MRI independent component analysis

Identifying predictors of mild cognitive impairment (MCI) and Alzheimer's disease (AD) can lead to more accurate diagnosis and facilitate clinical trial participation. We identified 320 participants (93 cognitively normal or CN, 162 MCI, 65 AD) with baseline magnetic resonance imaging (MRI) data, cerebrospinal fluid biomarkers, and cognition data in the Alzheimer's Disease Neuroimaging Initiative database. We used independent component analysis (ICA) on structural MR images to derive 30 matter covariance patterns (ICs) across all participants. These ICs were used in iterative and stepwise discriminant classifier analyses to predict diagnostic classification at 24 months for CN vs. MCI, CN vs. AD, MCI vs. AD, and stable MCI (MCI-S) vs. MCI progression to AD (MCI-P). Models were cross-validated with a "leave-10-out" procedure. For CN vs. MCI, 84.7% accuracy was achieved based on cognitive performance measures, ICs, p-tau(181p), and ApoE ε4 status. For CN vs. AD, 94.8% accuracy was achieved based on cognitive performance measures, ICs, and p-tau(181p). For MCI vs. AD and MCI-S vs. MCI-P, models achieved 83.1% and 80.3% accuracy, respectively, based on cognitive performance measures, ICs, and p-tau(181p). ICA-derived MRI biomarkers achieve excellent diagnostic accuracy for MCI conversion, which is little improved by CSF biomarkers and ApoE ε4 status.

Intracellular Aβ pathology and early cognitive impairments in a transgenic rat overexpressing human amyloid precursor protein: a multidimensional study

Numerous studies have implicated the abnormal accumulation of intraneuronal amyloid-β (Aβ) as an important contributor to Alzheimer's disease (AD) pathology, capable of triggering neuroinflammation, tau hyperphosphorylation and cognitive deficits. However, the occurrence and pathological relevance of intracellular Aβ remain a matter of controversial debate. In this study, we have used a multidimensional approach including high-magnification and super-resolution microscopy, cerebro-spinal fluid (CSF) mass spectrometry analysis and ELISA to investigate the Aβ pathology and its associated cognitive impairments, in a novel transgenic rat model overexpressing human APP. Our microscopy studies with quantitative co-localization analysis revealed the presence of intraneuronal Aβ in transgenic rats, with an immunological signal that was clearly distinguished from that of the amyloid precursor protein (APP) and its C-terminal fragments (CTFs). The early intraneuronal pathology was accompanied by a significant elevation of soluble Aβ42 peptides that paralleled the presence and progression of early cognitive deficits, several months prior to amyloid plaque deposition. Aβ38, Aβ39, Aβ40 and Aβ42 peptides were detected in the rat CSF by MALDI-MS analysis even at the plaque-free stages; suggesting that a combination of intracellular and soluble extracellular Aβ may be responsible for impairing cognition at early time points. Taken together, our results demonstrate that the intraneuronal development of AD-like amyloid pathology includes a mixture of molecular species (Aβ, APP and CTFs) of which a considerable component is Aβ; and that the early presence of these species within neurons has deleterious effects in the CNS, even before the development of full-blown AD-like pathology.

Biomarker evidence of axonal injury in neuroasymptomatic HIV-1 patients

BACKGROUND

Prevalence of neurocognitive impairment in HIV-1 infected patients is reported to be high. Whether this is a result of active HIV-related neurodegeneration is unclear. We examined axonal injury in HIV-1 patients by measuring the light subunit of neurofilament protein (NFL) in CSF with a novel, sensitive method.

METHODS

With a cross-sectional design, CSF concentrations of neurofilament protein light (NFL) (marker of neuronal injury), neopterin (intrathecal immunoactivation) and CSF/Plasma albumin ratio (blood-brain barrier integrity) were analyzed on CSF from 252 HIV-infected patients, subdivided into untreated neuroasymptomatics (n = 200), HIV-associated dementia (HAD) (n = 14) and on combinations antiretroviral treatment (cART) (n = 85), and healthy controls (n = 204). 46 HIV-infected patients were included in both treated and untreated groups, but sampled at different timepoints. Furthermore, 78 neuroasymptomatic patients were analyzed before and after treatment initiation.

RESULTS

While HAD patients had the highest NFL concentrations, elevated CSF NFL was also found in 33% of untreated neuroasymptomatic patients, mainly in those with blood CD4+ cell counts below 250 cells/μL. CSF NFL concentrations in the untreated neuroasymptomatics and treated groups were equivalent to controls 18.5 and 3.9 years older, respectively. Neopterin correlated with NFL levels in untreated groups while the albumin ratio correlated with NFL in both untreated and treated groups.

CONCLUSIONS

Increased CSF NFL indicates ongoing axonal injury in many neuroasymptomatic patients. Treatment decreases NFL, but treated patients retain higher levels than controls, indicating either continued virus-related injury or an aging-like effect of HIV infection. NFL correlates with neopterin and albumin ratio, suggesting an association between axonal injury, neuroinflammation and blood-brain barrier permeability. NFL appears to be a sensitive biomarker of subclinical and clinical brain injury in HIV and warrants further assessment for broader clinical use.

Cerebrospinal fluid apolipoprotein E concentration and severity of cognitive impairment in patients with newly diagnosed Alzheimer's disease

BACKGROUND/OBJECTIVE

Apolipoprotein E (apoE) plays an important role in the pathogenesis of Alzheimer's disease (AD). Altered cerebrospinal fluid (CSF) and plasma levels have been previously reported in patients with AD. We hypothesized that CSF apoE levels of patients with newly diagnosed AD might be associated with their cognitive performance.

METHODS

Patients with AD (N = 71) enrolled into an observational study underwent neuropsychological testing (Consortium to Establish a Registry for AD [CERAD] plus) at time of diagnosis. The CSF was obtained, and apoE concentrations were determined. Generalized linear models were constructed to assess the associations of apoE and neuropsychological measures while adjusting for important potential confounders.

RESULTS

No association of CSF apoE levels and cognitive function could be demonstrated. Still, the use of neuroleptic drugs, female gender, preprogression time, and lower education were linked to worse cognitive function in some domains.

CONCLUSION

The CSF apoE appears not to be suitable as a biochemical surrogate of cognitive function in AD under the given circumstances. By means of longitudinal analyses, potential associations with the velocity of decline will be investigated in the near future.

Neurodegenerative and inflammatory biomarkers in cerebrospinal fluid in patients with Cushing's syndrome in remission

OBJECTIVE

Patients with Cushing's syndrome (CS) in long-term remission have impaired cognitive function. Cerebrospinal fluid (CSF) biomarkers are important diagnostic tools in the work-up of patients with cognitive impairment. The aim of this study was to analyze neurodegenerative and inflammatory biomarkers in the CSF of patients with CS in remission.

DESIGN

A cross-sectional, single-center study.

PATIENTS

Twelve women previously treated for CS and six healthy subjects.

MEASUREMENTS

Neurodegenerative CSF markers: total tau, hyperphosphorylated tau, amyloid beta peptides, soluble amyloid precursor protein alpha and beta, neurofilament light proteins, glial fibrillary acidic protein, and monocyte chemoattractant protein 1; and inflammatory CSF markers: interferon gamma, interleukin (IL) 1B, IL2, IL4, IL5, IL8, IL10, IL12p70, IL13, and tumor necrosis factor alpha.

RESULTS

The mean age (mean±S.D.) was similar in patients with CS in remission (44.9±14 years) and healthy subjects (42.3±15.7 years; P=0.726). No differences were observed in the concentrations of any neurodegenerative biomarkers between the patients and healthy subjects. Nor were the concentrations of inflammatory biomarkers different between the groups.

CONCLUSIONS

The pattern of neurodegenerative and inflammatory biomarkers in the CSF of patients with CS in remission does not differ from that of the healthy subjects. The underlying mechanisms of the cognitive deficits in patients with CS in remission are different from those observed in patients with neurodegenerative disorders and remain to be explained.

Cytokines in CSF correlate with HIV-associated neurocognitive disorders in the post-HAART era in China

In the current era of highly active antiretroviral therapy (HAART), the incidence of HIV dementia has declined, but the prevalence of HIV-associated neurocognitive disorder (HAND) remains high. HIV-induced systemic and localized inflammation is considered to be one of the mechanisms of HAND. Changes in cytokine levels in the cerebrospinal fluid (CSF) during HIV infection might help to identify HAND. To investigate whether the cytokine profile of the CSF during HIV infection could be used as a biomarker of HAND, we compared cytokine levels in the CSF of HIV-infected cases with and without neurocognitive impairment. Cytokine concentrations in the CSF were measured by quantification bioassays (Luminex xMAP). HIV-infected cases with neurocognitive impairment demonstrated higher levels of interleukin (IL)-8, monocyte chemotactic protein (MCP)-1, induced protein (IP)-10, and granulocyte colony-stimulating factor (G-CSF) in the CSF than those without neurocognitive impairment (G-CSF (p = 0.0003), IL-8 (p = 0.0046), IP-10 (p < 0.0001), and MCP-1 (p < 0.0001)). There was no significant impact of HAART on cytokine levels in the CSF, except for IP-10, which was higher in HAART-treated patients with impaired cognition (p = 0.0182). Findings from this preliminary study suggest that elevated levels of the cytokines IL-8, MCP-1, G-CSF, and IP-10 in the CSF are associated with neurocognitive impairment in HIV infection, and these cytokines likely represent a biomarker profile for HAND.

[Use of cerebrospinal fluid (CSF) biomarkers for Alzheimer's type dementia: diagnosis in mild cognitive impairment]

An increasing number of people with mild cognitive impairment (MCI) visits a memory clinic to find out whether their symptoms indicate Alzheimer's disease (AD). Markers in cerebrospinal fluid are increasingly used for the diagnosis of Alzheimer's disease. In the short term, CSF biomarkers are more accurate in ruling out progression to AD-type dementia than demonstrating progression. The predictive value of the CSF biomarkers increases with longer-duration follow-up and declines with age. The added value of CSF biomarkers is not yet clear in MCI patients in whom extensive clinical, neuropsychological examination or imaging have already been performed.

Comparison of brief cognitive tests and CSF biomarkers in predicting Alzheimer's disease in mild cognitive impairment: six-year follow-up study

INTRODUCTION

Early identification of Alzheimer's disease (AD) is needed both for clinical trials and in clinical practice. In this study, we compared brief cognitive tests and cerebrospinal fluid (CSF) biomarkers in predicting conversion from mild cognitive impairment (MCI) to AD.

METHODS

At a memory clinic, 133 patients with MCI were followed until development of dementia or until they had been stable over a mean period of 5.9 years (range 3.2-8.8 years). The Mini-Mental State Examination (MMSE), the clock drawing test, total tau, tau phosphorylated at Thr(181) (P-tau) and amyloid-β(1-42) (Aβ(42)) were assessed at baseline.

RESULTS

During clinical follow-up, 47% remained cognitively stable and 53% developed dementia, with an incidence of 13.8%/year. In the group that developed dementia the prevalence of AD was 73.2%, vascular dementia 14.1%, dementia with Lewy bodies (DLB) 5.6%, progressive supranuclear palsy (PSP) 4.2%, semantic dementia 1.4% and dementia due to brain tumour 1.4%. When predicting subsequent development of AD among patients with MCI, the cognitive tests classified 81% of the cases correctly (AUC, 0.85; 95% CI, 0.77-0.90) and CSF biomarkers 83% (AUC, 0.89; 95% CI, 0.82-0.94). The combination of cognitive tests and CSF (AUC, 0.93; 95% CI 0.87 to 0.96) was significantly better than the cognitive tests (p = 0.01) and the CSF biomarkers (p = 0.04) alone when predicting AD.

CONCLUSIONS

The MMSE and the clock drawing test were as accurate as CSF biomarkers in predicting future development of AD in patients with MCI. Combining both instruments provided significantly greater accuracy than cognitive tests or CSF biomarkers alone in predicting AD.

CCL2 is associated with a faster rate of cognitive decline during early stages of Alzheimer's disease

Chemokine (C-C motif) receptor 2 (CCR2)-signaling can mediate accumulation of microglia at sites affected by neuroinflammation. CCR2 and its main ligand CCL2 (MCP-1) might also be involved in the altered metabolism of beta-amyloid (Aβ) underlying Alzheimer's disease (AD). We therefore measured the levels of CCL2 and three other CCR2 ligands, i.e. CCL11 (eotaxin), CCL13 (MCP-4) and CCL26 (eotaxin-3), in the cerebrospinal fluid (CSF) and plasma of 30 controls and 119 patients with mild cognitive impairment (MCI) at baseline. During clinical follow-up 52 MCI patients were clinically stable for five years, 47 developed AD (i.e. cases with prodromal AD at baseline) and 20 developed other dementias. Only CSF CCL26 was statistically significantly elevated in patients with prodromal AD when compared to controls (p = 0.002). However, in patients with prodromal AD, the CCL2 levels in CSF at baseline correlated with a faster cognitive decline during follow-up (r(s) = 0.42, p = 0.004). Furthermore, prodromal AD patients in the highest tertile of CSF CCL2 exhibited a significantly faster cognitive decline (p<0.001) and developed AD dementia within a shorter time period (p<0.003) compared to those in the lowest tertile. Finally, in the entire MCI cohort, CSF CCL2 could be combined with CSF Tau, P-tau and Aβ42 to predict both future conversion to AD and the rate of cognitive decline. If these results are corroborated in future studies, CCL2 in CSF could be a candidate biomarker for prediction of future disease progression rate in prodromal AD. Moreover, CCR2-related signaling pathways might be new therapeutic targets for therapies aiming at slowing down the disease progression rate of AD.

Characterization and stability of transthyretin isoforms in cerebrospinal fluid examined by immunoprecipitation and high-resolution mass spectrometry of intact protein

Post-translational modifications (PTMs) contribute significantly to the complexity of proteins. PTMs may vary in certain patterns according to diseases and microenviroments making them potential markers for pathological processes. Human transthyretin (TTR) is a transporter of thyroxine and retinol in blood and cerebrospinal fluid (CSF). A single free cysteine thiol group in TTR possesses the ability to form mixed disulfides potentially related to diseases such as TTR amyloidosis and Alzheimer's disease (AD). Additionally, TTR-Cys10 S-thiolations might mirror the oxidative stress and redox balance of CSF. Here we describe a quick and gentle method for immunoprecipitating (IP) TTR from CSF with minimal introduction of sample-handling artifacts. A high-resolution mass spectrometer (LTQ-Orbitrap XL) was used in a simple setup with direct infusion that generates data suitable for confident assignment of TTR isoforms and validation of the protocol. Moreover, we demonstrate how simple storage of CSF at 4°C induces major oxidative modifications of TTR. Using the optimized method, we show data from a limited number of mild cognitive impairment (MCI) and AD patients. The protocol controls and minimizes the introduction of sample-handling artifacts during purification of TTR isoforms for high-resolution MS analysis.

Role of cerebrospinal fluid and plasma biomarkers in the diagnosis of neurodegenerative disorders and mild cognitive impairment

Biomarkers are one type of laboratory testing being developed in response to the therapeutic imperative for diseases that cause cognitive impairment and dementia. The role of biomarkers is already transforming the organization and conduct of clinical trials, and if successful will likely contribute in the future to the medical management of patients with these diseases. Despite the obvious utility of practicality of blood- or urine-based biomarkers, so far results from these fluid compartments have not been reproducible. In contrast, substantial progress has been made in cerebrospinal fluid biomarkers. Here we review the stages of cerebrospinal fluid biomarker development for several common and unusual diseases that cause cognitive impairment and dementia, stressing the distinction between diagnostic and mechanistic biomarkers. Future applications will likely focus on diagnosis of latent or early-stage disease, assessment of disease progression, mechanism of injury, and response to experimental therapeutics.

Diet intervention and cerebrospinal fluid biomarkers in amnestic mild cognitive impairment

OBJECTIVE

To compare the effects of a 4-week high-saturated fat/high-glycemic index (HIGH) diet with a low-saturated fat/low-glycemic index (LOW) diet on insulin and lipid metabolism, cerebrospinal fluid (CSF) markers of Alzheimer disease, and cognition for healthy adults and adults with amnestic mild cognitive impairment (aMCI).

DESIGN

Randomized controlled trial.

SETTING

Veterans Affairs Medical Center clinical research unit.

PARTICIPANTS

Forty-nine older adults (20 healthy adults with a mean [SD] age of 69.3 [7.4] years and 29 adults with aMCI with a mean [SD] age of 67.6 [6.8] years).

INTERVENTION

Participants received the HIGH diet (fat, 45% [saturated fat, > 25%]; carbohydrates, 35%-40% [glycemic index, > 70]; and protein, 15%-20%) or the LOW diet (fat, 25%; [saturated fat, < 7%]; carbohydrates, 55%-60% [glycemic index, < 55]; and protein, 15%-20%) for 4 weeks. Cognitive tests, an oral glucose tolerance test, and lumbar puncture were conducted at baseline and during the fourth week of the diet.

MAIN OUTCOME MEASURES

The CSF concentrations of β-amyloid (Aβ42 and Aβ40), tau protein, insulin, F2-isoprostanes, and apolipoprotein E, plasma lipids and insulin, and measures of cognition.

RESULTS

For the aMCI group, the LOW diet increased CSF Aβ42 concentrations, contrary to the pathologic pattern of lowered CSF Aβ42 typically observed in Alzheimer disease. The LOW diet had the opposite effect for healthy adults, ie, decreasing CSF Aβ42, whereas the HIGH diet increased CSF Aβ42. The CSF apolipoprotein E concentration was increased by the LOW diet and decreased by the HIGH diet for both groups. For the aMCI group, the CSF insulin concentration increased with the LOW diet, but the HIGH diet lowered the CSF insulin concentration for healthy adults. The HIGH diet increased and the LOW diet decreased plasma lipids, insulin, and CSF F2-isoprostane concentrations. Delayed visual memory improved for both groups after completion of 4 weeks of the LOW diet.

CONCLUSION

Our results suggest that diet may be a powerful environmental factor that modulates Alzheimer disease risk through its effects on central nervous system concentrations of Aβ42, lipoproteins, oxidative stress, and insulin.

Protein changes in CSF of HIV-infected patients: evidence for loss of neuroprotection

To begin to unravel the complexity of HIV-associated changes in the brain, broader, multifaceted analyses of cerebrospinal fluid (CSF) are needed that examine a wide range of proteins reflecting different functions. To provide the first broad profiles of protein changes in the CSF of HIV-infected patients, we used antibody arrays to measure 120 cytokines, chemokines, growth factors, and other proteins. CSF from HIV-infected patients with a range of cognitive deficits was compared to CSF from uninfected, cognitively normal patients to begin to identify protein changes associated with HIV infection and neurological disease progression. Uninfected patients showed relatively consistent patterns of protein expression. Highly expressed proteins in CSF included monocyte chemotactic protein-1, tissue inhibitors of metalloproteases, granulocyte colony-stimulating factor, adiponectin, soluble tumor necrosis factor receptor-1, urokinase-type plasminogen activator receptor, and insulin-like growth factor binding protein-2. Inflammatory and anti-inflammatory cytokines were expressed at low levels. HIV-infected patients showed increases in inflammatory proteins (interferon-gamma, tumor necrosis factor-alpha), anti-inflammatory proteins (IL-13), and chemokines but these correlated poorly with neurological status. The strongest correlation with increasing severity of neurological disease was a decline in growth factors, particularly, brain-derived neurotrophic factor and NT-3. These studies illustrate that HIV infection is associated with parallel changes in both inflammatory and neuroprotective proteins in the CSF. The inverse relationship between growth factors and neurological disease severity suggests that a loss of growth factor neuroprotection may contribute to the development of neural damage and may provide useful markers of disease progression.

Cognitive reserve and Alzheimer's disease biomarkers are independent determinants of cognition

The objective of this study was to investigate how a measure of educational and occupational attainment, a component of cognitive reserve, modifies the relationship between biomarkers of pathology and cognition in Alzheimer's disease. The biomarkers evaluated quantified neurodegeneration via atrophy on magnetic resonance images, neuronal injury via cerebral spinal fluid t-tau, brain amyloid-β load via cerebral spinal fluid amyloid-β1-42 and vascular disease via white matter hyperintensities on T2/proton density magnetic resonance images. We included 109 cognitively normal subjects, 192 amnestic patients with mild cognitive impairment and 98 patients with Alzheimer's disease, from the Alzheimer's Disease Neuroimaging Initiative study, who had undergone baseline lumbar puncture and magnetic resonance imaging. We combined patients with mild cognitive impairment and Alzheimer's disease in a group labelled 'cognitively impaired' subjects. Structural Abnormality Index scores, which reflect the degree of Alzheimer's disease-like anatomic features on magnetic resonance images, were computed for each subject. We assessed Alzheimer's Disease Assessment Scale (cognitive behaviour section) and mini-mental state examination scores as measures of general cognition and Auditory-Verbal Learning Test delayed recall, Boston naming and Trails B scores as measures of specific domains in both groups of subjects. The number of errors on the American National Adult Reading Test was used as a measure of environmental enrichment provided by educational and occupational attainment, a component of cognitive reserve. We found that in cognitively normal subjects, none of the biomarkers correlated with the measures of cognition, whereas American National Adult Reading Test scores were significantly correlated with Boston naming and mini-mental state examination results. In cognitively impaired subjects, the American National Adult Reading Test and all biomarkers of neuronal pathology and amyloid load were independently correlated with all cognitive measures. Exceptions to this general conclusion were absence of correlation between cerebral spinal fluid amyloid-β1-42 and Boston naming and Trails B. In contrast, white matter hyperintensities were only correlated with Boston naming and Trails B results in the cognitively impaired. When all subjects were included in a flexible ordinal regression model that allowed for non-linear effects and interactions, we found that the American National Adult Reading Test had an independent additive association such that better performance was associated with better cognitive performance across the biomarker distribution. Our main conclusions included: (i) that in cognitively normal subjects, the variability in cognitive performance is explained partly by the American National Adult Reading Test and not by biomarkers of Alzheimer's disease pathology; (ii) in cognitively impaired subjects, the American National Adult Reading Test, biomarkers of neuronal pathology (structural magnetic resonance imaging and cerebral spinal fluid t-tau) and amyloid load (cerebral spinal fluid amyloid-β1-42) all independently explain variability in general cognitive performance; and (iii) that the association between cognition and the American National Adult Reading Test was found to be additive rather than to interact with biomarkers of Alzheimer's disease pathology.

Multiplexed immunoassay panel identifies novel CSF biomarkers for Alzheimer's disease diagnosis and prognosis

BACKGROUND

Clinicopathological studies suggest that Alzheimer's disease (AD) pathology begins ∼10-15 years before the resulting cognitive impairment draws medical attention. Biomarkers that can detect AD pathology in its early stages and predict dementia onset would, therefore, be invaluable for patient care and efficient clinical trial design. We utilized a targeted proteomics approach to discover novel cerebrospinal fluid (CSF) biomarkers that can augment the diagnostic and prognostic accuracy of current leading CSF biomarkers (Aβ42, tau, p-tau181).

METHODS AND FINDINGS

Using a multiplexed Luminex platform, 190 analytes were measured in 333 CSF samples from cognitively normal (Clinical Dementia Rating [CDR] 0), very mildly demented (CDR 0.5), and mildly demented (CDR 1) individuals. Mean levels of 37 analytes (12 after Bonferroni correction) were found to differ between CDR 0 and CDR>0 groups. Receiver-operating characteristic curve analyses revealed that small combinations of a subset of these markers (cystatin C, VEGF, TRAIL-R3, PAI-1, PP, NT-proBNP, MMP-10, MIF, GRO-α, fibrinogen, FAS, eotaxin-3) enhanced the ability of the best-performing established CSF biomarker, the tau/Aβ42 ratio, to discriminate CDR>0 from CDR 0 individuals. Multiple machine learning algorithms likewise showed that the novel biomarker panels improved the diagnostic performance of the current leading biomarkers. Importantly, most of the markers that best discriminated CDR 0 from CDR>0 individuals in the more targeted ROC analyses were also identified as top predictors in the machine learning models, reconfirming their potential as biomarkers for early-stage AD. Cox proportional hazards models demonstrated that an optimal panel of markers for predicting risk of developing cognitive impairment (CDR 0 to CDR>0 conversion) consisted of calbindin, Aβ42, and age.

CONCLUSIONS/SIGNIFICANCE

Using a targeted proteomic screen, we identified novel candidate biomarkers that complement the best current CSF biomarkers for distinguishing very mildly/mildly demented from cognitively normal individuals. Additionally, we identified a novel biomarker (calbindin) with significant prognostic potential.

Surface-based TBM boosts power to detect disease effects on the brain: an N=804 ADNI study

Computational anatomy methods are now widely used in clinical neuroimaging to map the profile of disease effects on the brain and its clinical correlates. In Alzheimer's disease (AD), many research groups have modeled localized changes in hippocampal and lateral ventricular surfaces, to provide candidate biomarkers of disease progression for drug trials. We combined the power of parametric surface modeling and tensor-based morphometry to study hippocampal differences associated with AD and mild cognitive impairment (MCI) in 490 subjects (97 AD, 245 MCI, 148 controls) and ventricular differences in 804 subjects scanned as part of the Alzheimer's Disease Neuroimaging Initiative (ADNI; 184 AD, 391 MCI, 229 controls). We aimed to show that a new multivariate surface statistic based on multivariate tensor-based morphometry (mTBM) and radial distance provides a more powerful way to detect localized anatomical differences than conventional surface-based analysis. In our experiments, we studied correlations between hippocampal atrophy and ventricular enlargement and clinical measures and cerebrospinal fluid biomarkers. The new multivariate statistics gave better effect sizes for detecting morphometric differences, relative to other statistics including radial distance, analysis of the surface tensor and the Jacobian determinant. In empirical tests using false discovery rate curves, smaller sample sizes were needed to detect associations with diagnosis. The analysis pipeline is generic and automated. It may be applied to analyze other brain subcortical structures including the caudate nucleus and putamen. This publically available software may boost power for morphometric studies of subcortical structures in the brain.

Assessment of cerebrospinal fluid (CSF) beta-amyloid (1-42), phosphorylated tau (ptau-181) and total Tau protein in patients with Alzheimer's disease (AD) and other dementia at Siriraj Hospital, Thailand

BACKGROUND

The combination of decreased cerebrospinal fluid (CSF) levels of beta-amyloid (1-42) and increased levels of phosphorylated tau (ptau-181) or total tau protein are known to be biomarkers ofAlzheimer's disease (AD). These biomarkers can also be used as predictors of disease progression in persons with mild cognitive impairment. Utilizing biomarkers to differentiate Alzheimer's disease (AD) against non-Alzheimer dementia (non-AD) needs to be explored.

OBJECTIVE

To evaluate the clinical use ofCSF biomarker: beta-amyloid (1-42), phosphorylated tau (ptau-181) and total tau protein for distinguishing Alzheimer's disease (AD) from non-Alzheimer dementia (non-AD) in Thai patients.

MATERIAL AND METHOD

Thirty patients diagnosed of dementia during 2005-2007 at Siriraj hospital were offered CSF analysis for beta-amyloid (1-42), phosphorylated tau (ptau-181) and total tau protein. Diagnosis of dementia was performed by a concensus diagnostic group utilizing a standard criteria for diagnosis of AD and other dementia. All CSF testing was performed by Enzyme-Linked Immunoassay (ELISA) technique of the INNOTESTM to analyze these biomarkers.

RESULTS

Thirty demented patients were recruited in the study. Fourteen had AD and 16 had non-AD including 5 vascular dementia, 5 normal pressure hydrocephalus, 4 frontotemporal lobar degeneration and others. Mean age of the AD group was 67.79 (12.30) and that of non-AD group was 65.75 (15.04). Twelve AD had decreased levels of CSF /3-amyloid (1-42) (less than 487 pg/ml). Only one patient with AD had increased CSF phosphorylated tau (ptau-181) (more than 61 pg/ml). None of theAD patient had increased CSF total tau (more than 425 pg/ml). Eight patients with non-AD had decreased levels of CSF p-amyloid (1-42), one had increased CSF total tau protein, and none had increased CSF phosphorylated tau (ptau-181) protein. The sensitivity of decreased level of CSF beta-amyloid (1-42) in AD against non-AD dementia was 85.71%. Those of increased CSF total tau and phosphorylated tau (ptau-181) protein in AD against non-AD dementia were 7.14% and 0% consecutively. The specificity of decreased level of CSF beta-amyloid (1-42) in AD against non-AD dementia was 50%. The specificity of increased CSF total tau and phosphorylated tau (ptau-181) protein in AD against non-AD dementia were 100% and 93.75% sequentially. The combination of 2 biomarkers would increase specificity but decrease sensitivity.

CONCLUSION

CSF biomarker analysis should be encouraged to use as diagnostic aid in memory clinic especially to help diagnosis of atypical presentation of AD. The usefulness of longitudinal data needs to be explored.

Increased brain atrophy rates in cognitively normal older adults with low cerebrospinal fluid Aβ1-42

OBJECTIVE

To identify cognitively normal individuals at risk of Alzheimer disease (AD) based on cerebrospinal fluid (CSF) Aβ1-42, and to determine rates of cerebral atrophy.

METHODS

Control subjects from the Alzheimer's Disease Neuroimaging Initiative with CSF and serial magnetic resonance imaging (MRI) were dichotomized on CSF Aβ1-42 (normal control [NC]-high > 192 pg/ml; NC-low ≤ 192 pg/ml). Baseline and 1-year MRIs were registered, and brain, hippocampal, and ventricular volumes and annualized volume changes were calculated. Baseline characteristics, CSF profiles, neuropsychology, brain volumes and atrophy rates, and APOE, PICALM, CLU, and TOMM40 genotypes were compared. Sample sizes to power presymptomatic clinical trials based on rate of atrophy were calculated.

RESULTS

Forty of 105 (38%) were classified as NC-low, and 65 (62%) as NC-high. There were no differences in age (76.3 ± 5.1 vs 74.9 ± 5.1 years), gender, brain volumes, and all but 1 cognitive score (Trails B; p = 0.015). The NC-low group had higher tau (p = 0.005) and p-tau (p < 0.001), and was more likely to be APOE4 positive (48% vs 11%, p < 0.001). The NC-low group had significantly higher whole brain loss (9.3 vs 4.4 ml/yr, p < 0.001), ventricular expansion (2.04 vs 0.95 ml/yr, p = 0.002), and hippocampal atrophy rate (0.07 vs 0.03 ml/yr, p = 0.029). Baseline Aβ1-42 level was strongly correlated with rate of brain atrophy only in the NC-low group (p < 0.001). Using 141 (95% confidence interval, 86-287) patients per arm provides 80% power in a 1-year treatment trial to show 25% slowing of brain atrophy in the NC-low group.

INTERPRETATION

A significant percentage of healthy older adults have CSF profiles consistent with AD and increased rates of brain atrophy, suggesting that they may be in the earliest stages of neurodegeneration. Brain atrophy may be a feasible outcome measure for AD prevention studies.

Disturbance in cerebral spinal fluid sphingolipid content is associated with memory impairment in subjects infected with the human immunodeficiency virus

Despite widespread use of antiretroviral therapies to control replication of the human immunodeficiency virus (HIV), dysfunctions of cognition that are collectively termed HIV-associated neurocognitive disorders (HAND) still occur in approximately 50% of those infected by the virus. Currently there is not a biomarker that can identify HIV-infected people who are at risk for the development of HAND. Previous studies have identified particular sphingolipid species that are dysregulated in HAND, but the neurocognitive correlates of these biochemical findings are not currently understood. To address this question, we compared cerebrospinal fluid (CSF) levels of sphingomyelin, ceramide, and sterol species with performance on standard neurological tests designed to assess the function of multiple cognitive and motor domains in HIV-infected subjects. We found that sphingomyelin:ceramide ratios for acyl chain lengths of C16:0, C18:0, C22:0, and C24:0 were associated with worse performance on several indices of memory. The most striking finding was for the acyl chain of C18:0 that consistently associated with performance on multiple tests of memory. These findings suggest that the sphingomyelin:ceramide ratio for C18:0 may be a reasonable surrogate marker for memory dysfunction in HIV-infected subjects.

Requiring an amyloid-beta1-42 biomarker for prodromal Alzheimer's disease or mild cognitive impairment does not lead to more efficient clinical trials

BACKGROUND

Low cerebrospinal fluid (CSF) amyloid-beta(1-42) concentration and high total-tau/Abeta(1-42) ratio have been recommended to support the diagnosis of prodromal Alzheimer's disease (AD) in patients with amnestic mild cognitive impairment (aMCI) and also to select patients for clinical trials (Shaw et al, Ann Neurol 2009;65:403-13; Dubois et al, Lancet Neurol 2007;6:734-46).

METHODS

We tested this recommendation with clinical trials simulations using patients from the Alzheimer Disease Neuroimaging Initiative who fulfilled the following entry criteria: (1) aMCI, (2) aMCI with CSF Abeta(1-42) 0.39. For each criterion, we randomly resampled the database obtaining samples for 1000 trials for each trial scenario, planning for 1 or 2 year trials with samples from 50 to 400 patients per treatment or placebo group, with up to 40% dropouts, outcomes after using the AD assessment scale-cognitive subscale and clinical dementia rating scale with effect sizes ranging from 0.15 to 0.75, and calculated statistical power.

FINDINGS

Approximately 70% to 74% of aMCI patients with CSF measures met biomarker criteria. The addition of the low Abeta(1-42) or high tau/Abeta(1-42) requirement resulted in minimal or no increase in the power of the trials compared with enrolling aMCI without requiring the biomarker criteria. Slightly larger mean differences between the placebo and treatment groups fulfilling biomarker criteria were offset by increased outcome variability within the groups.

INTERPRETATIONS

Although patients with aMCI or patients with prodromal AD meeting CSF biomarkers criteria were slightly more cognitively impaired and showed greater decline than patients with aMCI diagnosed without considering the biomarkers, the requirement of biomarker-positive patients would most likely not result in more efficient clinical trials, and trials would take longer because fewer patients would be available. A CSF Abeta(1-42) marker, however, could be useful as an explanatory variable or covariate when warranted by the action of a drug.

Boosting power for clinical trials using classifiers based on multiple biomarkers

Machine learning methods pool diverse information to perform computer-assisted diagnosis and predict future clinical decline. We introduce a machine learning method to boost power in clinical trials. We created a Support Vector Machine algorithm that combines brain imaging and other biomarkers to classify 737 Alzheimer's disease Neuroimaging initiative (ADNI) subjects as having Alzheimer's disease (AD), mild cognitive impairment (MCI), or normal controls. We trained our classifiers based on example data including: MRI measures of hippocampal, ventricular, and temporal lobe volumes, a PET-FDG numerical summary, CSF biomarkers (t-tau, p-tau, and Abeta(42)), ApoE genotype, age, sex, and body mass index. MRI measures contributed most to Alzheimer's disease (AD) classification; PET-FDG and CSF biomarkers, particularly Abeta(42), contributed more to MCI classification. Using all biomarkers jointly, we used our classifier to select the one-third of the subjects most likely to decline. In this subsample, fewer than 40 AD and MCI subjects would be needed to detect a 25% slowing in temporal lobe atrophy rates with 80% power--a substantial boosting of power relative to standard imaging measures.

Update on the magnetic resonance imaging core of the Alzheimer's disease neuroimaging initiative

Functions of the Alzheimer's Disease Neuroimaging Initiative (ADNI) magnetic resonance imaging (MRI) core fall into three categories: (1) those of the central MRI core laboratory at Mayo Clinic, Rochester, Minnesota, needed to generate high quality MRI data in all subjects at each time point; (2) those of the funded ADNI MRI core imaging analysis groups responsible for analyzing the MRI data; and (3) the joint function of the entire MRI core in designing and problem solving MR image acquisition, pre-processing, and analyses methods. The primary objective of ADNI was and continues to be improving methods for clinical trials in Alzheimer's disease. Our approach to the present ("ADNI-GO") and future ("ADNI-2," if funded) MRI protocol will be to maintain MRI methodological consistency in the previously enrolled "ADNI-1" subjects who are followed up longitudinally in ADNI-GO and ADNI-2. We will modernize and expand the MRI protocol for all newly enrolled ADNI-GO and ADNI-2 subjects. All newly enrolled subjects will be scanned at 3T with a core set of three sequence types: 3D T1-weighted volume, FLAIR, and a long TE gradient echo volumetric acquisition for micro hemorrhage detection. In addition to this core ADNI-GO and ADNI-2 protocol, we will perform vendor-specific pilot sub-studies of arterial spin-labeling perfusion, resting state functional connectivity, and diffusion tensor imaging. One of these sequences will be added to the core protocol on systems from each MRI vendor. These experimental sub-studies are designed to demonstrate the feasibility of acquiring useful data in a multicenter (but single vendor) setting for these three emerging MRI applications.

[Biomarkers in the cerebrospinal fluid of patients with mild cognitive impairment: a meta-analysis of their predictive capacity for the diagnosis of Alzheimer's disease]

INTRODUCTION

Several studies have reported alterations in the cerebrospinal fluid biomarkers (Abeta-42, T-tau and P-tau proteins), both in Alzheimer's disease (AD) and in mild cognitive impairment (MCI).

AIM

To perform a meta-analysis of the diagnostic yield of this technique for the prediction of patients with MCI who are going to progress to AD.

MATERIALS AND METHODS

A search was conducted in PubMed and Embase of papers published between 1999 and September 2008, and as a result only prospective studies were included for the systematic review. The sensitivity and specificity for each biomarker were studied separately and also jointly.

RESULTS

Of the 12 studies that were included, 6 quantified the Abeta-42 protein, 11 the T-tau protein and seven the P-tau protein. In three of the studies data was obtained from the three biomarkers in combination. The sensitivity of the quantification of the T-tau and P-tau proteins is 82%, with a diagnostic odds ratio of 12.09 (confidence interval 95%, CI 95% = 7.71-18.99; p = 0.1) and 16.29 (CI 95% = 9.69-27.4; p = 0.9), respectively. Alteration of any of the three biomarkers has a specificity of 87%, with a diagnostic odds ratio of 35.97 (CI 95% = 7.8-164.6; p = 0.04).

CONCLUSIONS

The isolated alteration of T-tau or P-tau levels in cerebrospinal fluid is very sensitive for differentiating between patients with MCI who are going to develop AD and those who are going to remain stable. Normality of the three biomarkers is a very reliable way of ruling out the progression of AD in patients with MCI.

[Neurochemical markers of neurodegeneration in the early diagnosis of Alzheimer's disease, vascular and mixed dementia]

A study of 27 patients with dismnestic variant of moderate cognitive impairment (MCI) and 20 patients with neurodynamic-dysregulatory variant was carried out. The more intensive atrophic process supported by neuroimaging data and changed levels of neurodegeneration biomarkers - phosphorylated tau-protein 181 and beta-amyloid 42 - were found in patients with dismnestic MCI variant. The follow-up study showed that the large number of patients with progressive cognitive disorders associated with conversion to dementia was observed in this group. In conclusion, the determination of the neurochemical markers in the cerebrospinal fluid allows to detect the neurodegenerative process at early stages of the disease and assists in detection of cases with increased risk of Alzheimer's disease.

A case of progressive ataxia followed by cognitive and behavioral changes

The patient is a 60-year-old man who initially presented to his local hospital with complaints of gait difficulties that started suddenly after waking. Results of brain magnetic resonance imaging performed 1 week later were normal. Three weeks after that he developed blurred vision and he complained of a severe headache in the posterior head and neck regions at the onset of symptoms, which necessitated several visits to his local emergency room. The patient presented to our institution 1 month later, with progressive gait difficulty and truncal instability over a 2-week period.

Meta-analysis of CSF and MRI biomarkers for detecting preclinical Alzheimer's disease

BACKGROUND

Abnormal levels of biomarkers in cerebrospinal fluid (CSF) and atrophy of medial temporal lobe (MTL) structures on magnetic resonance imaging (MRI) are being used increasingly to diagnose early Alzheimer's disease (AD). We evaluated the claim that these biomarkers can detect preclinical AD before behavioural (i.e. memory) symptoms arise.

METHOD

We included all relevant longitudinal studies of CSF and MRI biomarkers published between January 2003 and November 2008. Subjects were not demented at baseline but some declined to mild cognitive impairment (MCI) or to AD during follow-up. Measures of tau and beta-amyloid in CSF, MTL atrophy on MRI, and performance on delayed memory tasks were extracted from the papers or obtained from the investigators.

RESULTS

Twenty-one MRI studies and 14 CSF studies were retrieved. The effect sizes of total tau (t-tau), phosphorylated tau (p-tau) and amyloid beta 42 (a beta 42) ranged from 0.91 to 1.11. The effect size of MTL atrophy was 0.75. Memory performance had an effect size of 1.06. MTL atrophy and memory impairment tended to increase when assessed closer to the moment of diagnosis, whereas effect sizes of CSF biomarkers tended to increase when assessed longer before the diagnosis.

CONCLUSIONS

Memory impairment is a more accurate predictor of early AD than atrophy of MTL on MRI, whereas CSF abnormalities and memory impairment are about equally predictive. Consequently, the CSF and MRI biomarkers are not very sensitive to preclinical AD. CSF markers remain promising, but studies with long follow-up periods in elderly subjects who are normal at baseline are needed to evaluate this promise.

Association of white matter lesions and lacunar infarcts with executive functioning: the SMART-MR study

The authors investigated the association of white matter lesions and lacunar infarcts with cognitive performance and whether brain atrophy mediates these associations. Within the Second Manifestations of Arterial Disease-Magnetic Resonance study (2001-2005, the Netherlands), cross-sectional analyses of 522 patients were performed (mean age, 57 years (standard deviation, 10); 76% male). Brain segmentation was used to quantify volumes of brain tissue, cerebrospinal fluid, and white matter lesions. Infarcts were rated visually. Brain volume, ventricular volume, and gray matter volume were divided by intracranial volume to obtain indicators of brain atrophy. Neuropsychological tests assessing executive functioning and memory were performed, and scores were transformed into z scores. The authors used linear regression analyses, adjusted for age, sex, education, intelligence, and vascular risk factors, to investigate the association of white matter lesions and number of lacunar infarcts with cognitive performance. A 1-standard-deviation higher volume of white matter lesions (beta = -0.12, 95% confidence interval: -0.20, -0.04) and the presence of >or=2 lacunar infarcts (beta = -0.48, 95% confidence interval: -0.87, -0.09) were associated with worse executive functioning. These associations remained after adjusting for brain atrophy. Both were not associated with worse memory. Results suggest that subcortical ischemic vascular lesions are associated with decreased executive functioning, but not with memory functioning, independent of brain atrophy.

CSF biomarker pathology correlates with a medial temporo-parietal network affected by very mild to moderate Alzheimer's disease but not a fronto-striatal network affected by healthy aging

It is suggested that reductions in a medial temporo-parietal episodic memory network characterize Alzheimer's disease (AD), while changes in a fronto-striatal executive network characterize healthy aging. In the present study, magnetic resonance imaging (MRI) was used to test this directly. MRI scans of 372 participants from two samples were analyzed: Sample 1 consisted of 96 very mild to moderate AD patients, 93 healthy elderly (HE), and 137 young (HY), all with available MR scans, while Sample 2 consisted of 46 MCI patients, with available MR scans and measures of CSF biomarkers Abeta42 and tau protein. Substantial morphometric reductions of the medial temporo-parietal network were found in AD, while the fronto-striatal network was less affected. Both networks were affected by healthy aging, but the fronto-striatal to a greater degree than the medial temporo-parietal. Further exploratory analyses of 49 cortical and subcortical structures indicated no overlap between predictors of AD vs. HE and predictors of HE vs. HY. CSF biomarker pathology correlated with the medial temporo-parietal but not fronto-striatal network. Likewise, the AD-prone structures from the exploratory analyses were related to CSF biomarkers, while the aging-prone structures were not. It is concluded that the pattern of macrostructural brain changes in very mild to moderate AD can be clearly delineated from that of healthy aging.

CSF biomarkers and incipient Alzheimer disease in patients with mild cognitive impairment

CONTEXT

Small single-center studies have shown that cerebrospinal fluid (CSF) biomarkers may be useful to identify incipient Alzheimer disease (AD) in patients with mild cognitive impairment (MCI), but large-scale multicenter studies have not been conducted.

OBJECTIVE

To determine the diagnostic accuracy of CSF beta-amyloid(1-42) (Abeta42), total tau protein (T-tau), and tau phosphorylated at position threonine 181 (P-tau) for predicting incipient AD in patients with MCI.

DESIGN, SETTING, AND PARTICIPANTS

The study had 2 parts: a cross-sectional study involving patients with AD and controls to identify cut points, followed by a prospective cohort study involving patients with MCI, conducted 1990-2007. A total of 750 individuals with MCI, 529 with AD, and 304 controls were recruited by 12 centers in Europe and the United States. Individuals with MCI were followed up for at least 2 years or until symptoms had progressed to clinical dementia.

MAIN OUTCOME MEASURES

Sensitivity, specificity, positive and negative likelihood ratios (LRs) of CSF Abeta42, T-tau, and P-tau for identifying incipient AD.

RESULTS

During follow-up, 271 participants with MCI were diagnosed with AD and 59 with other dementias. The Abeta42 assay in particular had considerable intersite variability. Patients who developed AD had lower median Abeta42 (356; range, 96-1075 ng/L) and higher P-tau (81; range, 15-183 ng/L) and T-tau (582; range, 83-2174 ng/L) levels than MCI patients who did not develop AD during follow-up (579; range, 121-1420 ng/L for Abeta42; 53; range, 15-163 ng/L for P-tau; and 294; range, 31-2483 ng/L for T-tau, P < .001). The area under the receiver operating characteristic curve was 0.78 (95% confidence interval [CI], 0.75-0.82) for Abeta42, 0.76 (95% CI, 0.72-0.80) for P-tau, and 0.79 (95% CI, 0.76-0.83) for T-tau. Cut-offs with sensitivity set to 85% were defined in the AD and control groups and tested in the MCI group, where the combination of Abeta42/P-tau ratio and T-tau identified incipient AD with a sensitivity of 83% (95% CI, 78%-88%), specificity 72% (95% CI, 68%-76%), positive LR, 3.0 (95% CI, 2.5-3.4), and negative LR, 0.24 (95% CI, 0.21-0.28). The positive predictive value was 62% and the negative predictive value was 88%.

CONCLUSIONS

This multicenter study found that CSF Abeta42, T-tau, and P-tau identify incipient AD with good accuracy, but less accurately than reported from single-center studies. Intersite assay variability highlights a need for standardization of analytical techniques and clinical procedures.

Enrichment of MCI and early Alzheimer's disease treatment trials using neurochemical and imaging candidate biomarkers

In the earliest clinical stages of Alzheimer's Disease (AD), when symptoms are mild, clinical diagnosis will still be difficult. AD related molecular mechanisms precede symptoms. Biological markers can serve as early diagnostic indicators, as markers of preclinical pathological change, e.g. underlying mechanisms of action (MoA). Hypothesis based candidates are derived from structural and functional neuroimaging as well as from cerebrospinal fluid (CSF) and plasma. Unbiased exploratory approaches e.g. proteome analysis or rater independent fully automated imaging post-processing methods yield novel candidates. Recent progress in the validation of core feasible imaging and neurochemical biomarkers for functions such as early detection, classification, progression and prediction of AD is summarized. Single core feasible biomarkers can already be used to enrich populations at risk for AD and may be further enhanced using distinct combinations. Some biomarkers are currently in the process of implementation as primary or secondary outcome variables into regulatory guideline documents, e.g. regarding phase II in drug development programs as outcome measures in proof of concept or dose finding studies. There are specific biomarkers available depending on the hypothesized mechanism of action of a medicinal product, e.g. impact on the amyloidogenic cascade or on tauhyperphosphorylation. Ongoing large-scale international controlled multi-center trials will provide further validation of selected core feasible imaging and CSF biomarker candidates as outcome measures in early AD for use in phase III clinical efficacy trials. There is a need of rigorous co-development of biological trait- and statemarker candidates facilitated through planned synergistic collaboration between academic, industrial and regulatory partners.