Wesley Jongbloed

Clusterin Levels in Plasma Predict Cognitive Decline and Progression to Alzheimer’s Disease

BACKGROUND Increased clusterin levels have been reported in brain, cerebrospinal fluid (CSF), and plasma of Alzheimers disease (AD) patients. Because changes are also observed in mild cognitive impairment (MCI), a possible relationship between clusterin levels and early neurodegenerative changes in AD was suggested. OBJECTIVES To determine whether clusterin concentrations could 1) serve as a diagnostic marker for AD, 2) predict disease progression in MCI, and 3) correlate with AD-biomarkers. METHODS Clusterin levels in CSF and plasma, as well as AD biomarker levels of Aβ42, Tau, and pTau in CSF and Mini-Mental State Examination scores (MMSE) were determined in 67 controls, 50 MCI, and 107 AD patients. Repeated MMSE was obtained for 44 MCI and 72 AD patients after, on average, 2.7 years. RESULTS Elevated clusterin concentrations in plasma, but not in CSF, were a risk factor for AD (HR 18.6; 95% CI 2.8-122), and related to cognitive decline in MCI (r =-0.38; p <  0.01). An inverse relation between plasma clusterin levels and cognitive decline was observed in AD patients (r = 0.23; p≤0.05). In CSF, but not in plasma, clusterin levels correlated with Tau and pTau in all groups. CONCLUSION Elevated plasma clusterin levels in MCI confer an increased risk for progression to AD, and more rapid cognitive decline. We speculate that clusterin levels in CSF may reflect its involvement in the earliest neurodegenerative processes associated with AD pathology. Whereas neither clusterin levels in CSF nor in plasma had diagnostic value, plasma clusterin levels may serve as a prognostic marker for AD.

Amyloid-beta Oligomers Relate to Cognitive Decline in Alzheimer's Disease

BACKGROUND Amyloid-β (Aβ)-oligomers are neurotoxic isoforms of Aβ and are a potential diagnostic biomarker for Alzheimers disease (AD). OBJECTIVES 1) Analyze the potential of Aβ-oligomer concentrations in cerebrospinal fluid (CSF) to diagnose and predict progression to AD in a large clinical study sample. 2) Monitor Aβ-oligomer concentrations over-time, both in early and advanced stages of AD. 3) Examine the relation between Aβ-oligomer levels in CSF and cognitive functioning. METHODS 24 non-demented, 61 mild cognitive impairment (MCI), and 64 AD patients who underwent lumbar puncture and cognitive testing at baseline and follow-up were selected from the memory clinic based Amsterdam Dementia Cohort. CSF samples were analyzed for standard AD-biomarkers and Aβ-oligomer levels using a validated in-house Aβ-oligomer specific enzyme-linked immunosorbent assay. Aβ-oligomer levels were analyzed as indicators of disease progression (follow-up AD diagnosis) and cognitive decline, respectively. RESULTS Patient groups did not differ in Aβ-oligomer concentrations at baseline or follow-up. Baseline CSF Aβ-oligomer levels were similar in MCI patients that develop AD as in stable MCI patients. MCI and AD patients showed an annual decrease in Aβ-oligomer levels of 9.4% and 6.8%, respectively. A decrease in Aβ-oligomer levels over time was strongly associated with more severe cognitive decline in AD patients. CONCLUSION Despite the limited diagnostic potential of Aβ-oligomer levels in CSF to differentiate between patient groups, and between MCI-AD and MCI-stable patients, changes in CSF Aβ-oligomer levels were related to cognitive decline. Therefore, CSF Aβ-oligomers may aid in the selection of patients with a more aggressive disease course.

Discriminatory and predictive capabilities of enzyme-linked immunosorbent assay and multiplex platforms in a longitudinal Alzheimer’s disease study

Multiplex assays such as xMAP have been proposed for the assessment of Alzheimers disease (AD) biomarkers amyloid β 42 (Aβ42), tau (Tau), and phosphorylated tau (pTau) in cerebrospinal fluid (CSF). Here, we compared the traditional enzyme‐linked immunosorbent assay (ELISA) and xMAP with respect to their: (1) absolute biomarker concentration, (2) ability to distinguish AD from nondemented subjects, (3) ability to monitor AD longitudinally, and (4) ability to predict progression from mild cognitive impairment (MCI) to AD.

Cerebrospinal fluid and plasma clusterin levels in Parkinson's disease

Clusterin is a multifunctional chaperone protein that has repeatedly been linked to Alzheimers disease (AD) pathogenesis and, more recently, also to Parkinsons disease (PD) by both genetic and proteomic analyses. Although clusterin is detectable in cerebrospinal fluid (CSF) and plasma, studies comparing clusterin levels in PD patients and controls have been scarce and yielded conflicting data. The aim of the present study was to determine whether CSF and/or plasma clusterin levels differ between PD patients and controls and are related to disease severity. We measured CSF and plasma clusterin levels in a group of 52 PD patients and in 50 age-matched neurologically healthy controls and found that clusterin levels in CSF and plasma were not different between the two groups. Furthermore, clusterin levels in CSF and plasma were not associated with disease duration, stage or severity. CSF clusterin levels did, however, correlate with CSF levels of total tau, phospho-tau and amyloid-β-42. We elaborate on the identified correlations between levels of clusterin and AD related proteins and on possible explanations for the discrepant findings in clusterin studies in PD so far.

Apolipoprotein A1 in Cerebrospinal Fluid and Plasma and Progression to Alzheimer’s Disease in Non-Demented Elderly

BACKGROUND HDL-cholesterol transporter Apolipoprotein A1 (ApoA1) holds neuroprotective properties, such as inhibition of amyloid-β aggregation. Low plasma ApoA1 concentrations are associated with Alzheimers disease (AD). Little is known about ApoA1 levels in the pre-dementia stages of AD. OBJECTIVE To investigate associations between cerebrospinal fluid (CSF) and plasma ApoA1 levels and clinical progression toward AD in non-demented elderly. METHODS From the Amsterdam Dementia Cohort, we included 429 non-demented elderly with subjective cognitive decline (SCD; n = 206, 61±9 years, Mini-Mental State Exam (MMSE) 28±2) and mild cognitive impairment (MCI; n = 223, 67±8 years, MMSE 27±2), with a mean follow-up of 2.5±1.6 years. We used Cox proportional hazard models to investigate relations between CSF and plasma ApoA1 concentrations and clinical progression, defined as progression to MCI or AD for SCD, and progression to AD for MCI. Analyses were adjusted for age, gender, MMSE, and plasma cholesterol levels. Analyses were stratified for diagnosis and APOEɛ4 carriership. RESULTS 117 patients (27%) showed clinical progression. One standard deviation increase of CSF ApoA1 was associated with a 30% increased risk of clinical progression (hazard ratio (HR) (95% CI)  = 1.3(1.0-1.6)). The effect appeared to be attributable to the APOEɛ4 carriers with SCD (HR 3.3(1.0-10.9)). Lower plasma ApoA1 levels were associated with an increased risk of clinical progression in APOEɛ4 carriers with SCD (HR 5.0(1.3-18.9)). CONCLUSION Higher CSF and lower plasma ApoA1 levels were associated with an increased risk of clinical progression in APOEɛ4 carriers with SCD; suggesting that ApoA1 may be involved in the earliest stages of AD.

Facilitating the Validation of Novel Protein Biomarkers for Dementia: An Optimal Workflow for the Development of Sandwich Immunoassays.

Different neurodegenerative disorders, such as Alzheimer’s disease (AD) and frontotemporal dementia (FTD), lead to dementia syndromes. Dementia will pose a huge impact on society and thus it is essential to develop novel tools that are able to detect the earliest, most sensitive, discriminative, and dynamic biomarkers for each of the disorders. To date, the most common assays used in large-scale protein biomarker analysis are enzyme-linked immunosorbent assays (ELISA), such as the sandwich immunoassays, which are sensitive, practical, and easily implemented. However, due to the novelty of many candidate biomarkers identified during proteomics screening, such assays or the antibodies that specifically recognize the desired marker are often not available. The development and optimization of a new ELISA should be carried out with considerable caution since a poor planning can be costly, ineffective, time consuming, and it may lead to a misinterpretation of the findings. Previous guidelines described either the overall biomarker development in more general terms (i.e., the process from biomarker discovery to validation) or the specific steps of performing an ELISA procedure. However, a workflow describing and guiding the main issues in the development of a novel ELISA is missing. Here, we describe a specific and detailed workflow to develop and validate new ELISA for a successful and reliable validation of novel dementia biomarkers. The proposed workflow highlights the main issues in the development of an ELISA and covers several critical aspects, including production, screening, and selection of specific antibodies until optimal fine-tuning of the assay. Although these recommendations are designed to analyze novel biomarkers for dementia in cerebrospinal fluid, they are generally applicable for the development of immunoassays for biomarkers in other human body fluids or tissues. This workflow is designed to maximize the quality of the developed ELISA using a time- and cost-efficient strategy. This will facilitate the validation of the dementia biomarker candidates ultimately allowing accurate diagnostic conclusions.

Quantification of clusterin in paired cerebrospinal fluid and plasma samples

Background Clusterin (ApoJ) is an amyloid-associated protein and plays an important role in Alzheimer’s disease (AD) pathology. Recent genome-wide association studies have indicated that certain genetic variants increase the risk of developing AD. To determine if the expression of clusterin is different in AD patients, both systemically and locally in the brain, differs between (subgroups of) AD patients and non-AD cases, an assay available that detects clusterin in both plasma and cerebrospinal fluid (CSF) with equal sensitivity would be helpful. Methods We compared four different commercially available antibodies in their ability to detect recombinant clusterin and immune-purified human clusterin. Specificity was tested on western blot and in ELISA systems, and selection was based on the ability to detect clusterin in CSF and plasma. A sandwich ELISA was developed and validated with monoclonal antibody G7 as capture, and rabbit polyclonal (Alexis) antibodies for detection. Results Our ELISA measured clusterin concentrations in plasma and CSF with dynamic ranges of 2–70 mg/L and 0.5–40 mg/L, respectively. The assays showed 99.8% recovery in CSF and 97% recovery in plasma. Intra-assay coefficient of variation was 1.4% and inter-assay 8.8%. The assay shows no cross-reactivity with related apolipoproteins. Clusterin quantification is dependent on the type of storage for plasma samples. A single freeze/thaw cycle caused fluctuations of clusterin concentrations in plasma, while clusterin in CSF is stable for up to five cycles. Conclusions We have successfully developed a clusterin ELISA that reliably measures CSF and plasma clusterin concentrations. In a pilot study, all samples gave results that were well within the dynamic range of the assay, with low variations. Freshly stored plasma samples are crucial for accurate clusterin quantification.

Beta-amyloid oligomer detection in cerebrospinal fluid and brain tissue

major health and social care challenges for the 21st century worldwide. The global number of people with dementia was calculated at 36 million by 2010 and is estimated to increase to 66 million by 2030 and 115 million by 2050 (World Alzheimer Report 2009). The global cost is estimated at US

CSF ApoE predicts clinical progression in nondemented APOEε4 carriers

604 billion by 2010 (World Alzheimer Report 2010). Governments and societies are not prepared to these challenges. Therefore Alzheimer’s Disease International (ADI), the global federation of Alzheimer associations is campaigning to make dementia a global health priority with programs of World Health Organization (WHO) and United Nations (UN). Methods: ADI has started an advocacy program towards WHO and UN meetings including training of national advocates, creating an international network and visiting international and regional meetings and make statements, contact country representatives and produce data on prevalence and cost of illness. Results: Dementia was included in the Mental Health Global Action Programme of WHO as a priority area. The UN High Level Meeting on Non-Communicable Diseases in September 2011 adopted a paragraph on the importance of mental health and Alzheimer’s disease. The WHO is going to release a report Dementia: A Public Health Priority by April 2012. A resolution on ageing will be put forward at the annual WHO assembly in May 2012. Conclusions: Alzheimer’s disease and dementia have become part of the international health agenda. This needs to be implemented in national and subnational action plans. This has happened in a few countries like Australia, Korea, France and England. A plan for the USA is on its way. Monitoring and evaluation of those plans will be crucial as well as securing the funding. Countries without a plan need to be encouraged to develop.