Anna Kinsey

Association of Plasma Clusterin Concentration With Severity, Pathology, and Progression in Alzheimer Disease

CONTEXT Blood-based analytes may be indicators of pathological processes in Alzheimer disease (AD). OBJECTIVE To identify plasma proteins associated with AD pathology using a combined proteomic and neuroimaging approach. DESIGN Discovery-phase proteomics to identify plasma proteins associated with correlates of AD pathology. Confirmation and validation using immunodetection in a replication set and an animal model. SETTING A multicenter European study (AddNeuroMed) and the Baltimore Longitudinal Study of Aging. PARTICIPANTS Patients with AD, subjects with mild cognitive impairment, and healthy controls with standardized clinical assessments and structural neuroimaging. MAIN OUTCOME MEASURES Association of plasma proteins with brain atrophy, disease severity, and rate of clinical progression. Extension studies in humans and transgenic mice tested the association between plasma proteins and brain amyloid. RESULTS Clusterin/apolipoprotein J was associated with atrophy of the entorhinal cortex, baseline disease severity, and rapid clinical progression in AD. Increased plasma concentration of clusterin was predictive of greater fibrillar amyloid-beta burden in the medial temporal lobe. Subjects with AD had increased clusterin messenger RNA in blood, but there was no effect of single-nucleotide polymorphisms in the gene encoding clusterin with gene or protein expression. APP/PS1 transgenic mice showed increased plasma clusterin, age-dependent increase in brain clusterin, as well as amyloid and clusterin colocalization in plaques. CONCLUSIONS These results demonstrate an important role of clusterin in the pathogenesis of AD and suggest that alterations in amyloid chaperone proteins may be a biologically relevant peripheral signature of AD.

Plasma clusterin concentration is associated with longitudinal brain atrophy in mild cognitive impairment

Recent genetic and proteomic studies demonstrate that clusterin/apolipoprotein-J is associated with risk, pathology, and progression of Alzheimers disease (AD). Our main aim was to examine associations between plasma clusterin concentration and longitudinal changes in brain volume in normal aging and mild cognitive impairment (MCI). A secondary objective was to examine associations between peripheral concentration of clusterin and its concentration in the brain within regions that undergo neuropathological changes in AD. Non-demented individuals (N=139; mean baseline age 70.5 years) received annual volumetric MRI (912 MRI scans in total) over a mean six-year interval. Sixteen participants (92 MRI scans in total) were diagnosed during the course of the study with amnestic MCI. Clusterin concentration was assayed by ELISA in plasma samples collected within a year of the baseline MRI. Mixed effects regression models investigated whether plasma clusterin concentration was associated with rates of brain atrophy for control and MCI groups and whether these associations differed between groups. In a separate autopsy sample of individuals with AD (N=17) and healthy controls (N=4), we examined the association between antemortem clusterin concentration in plasma and postmortem levels in the superior temporal gyrus, hippocampus and cerebellum. The associations of plasma clusterin concentration with rates of change in brain volume were significantly different between MCI and control groups in several volumes including whole brain, ventricular CSF, temporal gray matter as well as parahippocampal, superior temporal and cingulate gyri. Within the MCI but not control group, higher baseline concentration of plasma clusterin was associated with slower rates of brain atrophy in these regions. In the combined autopsy sample of AD and control cases, representing a range of severity in AD pathology, we observed a significant association between clusterin concentration in the plasma and that in the superior temporal gyrus. Our findings suggest that clusterin, a plasma protein with roles in amyloid clearance, complement inhibition and apoptosis, is associated with rate of brain atrophy in MCI. Furthermore, peripheral concentration of clusterin also appears to reflect its concentration within brain regions vulnerable to AD pathology. These findings in combination suggest an influence of this multi-functional protein on early stages of progression in AD pathology.

Minocycline reduces the development of abnormal tau species in models of Alzheimer’s disease

Alzheimers disease (AD) is characterized by the presence of neurofibrillary tangles of hyperphosphorylated, aggregated tau protein and extracellular deposits of β‐amyloid peptide. Increased β‐amyloid levels are thought to precede tangle formation, but tau pathology is more closely related to neuronal death. Minocycline, a tetracycline derivative, has potent antiinflammatory, antiapoptotic, and neuroprotective effects in several models of neurodegenerative disease, including models of AD with amyloid pathology. We have used both in vitro and in vivo models of AD to determine whether minocycline may have therapeutic efficacy against tau pathology. In primary cortical neurons, minocycline prevents β‐amyloid‐induced neuronal death, reduces caspase‐3 activation, and lowers generation of caspase‐3‐cleaved tau fragments. Treatment of tangle‐forming transgenic mice (htau line) with minocycline results in reduced levels of tau phosphorylation and insoluble tau aggregates. The in vivo effects of minocycline are also associated with reduced caspase‐3 activation and lowered tau cleavage by caspase‐3. In tau mice, we find that conformational changes in tau are susceptible to minocycline treatment, but are not directly associated with the amount of tau fragments produced, highlighting a dissociation between the development of these pathological tau species. These results suggest a possible novel therapeutic role for minocycline in the treatment of AD and related tauopathies.— Noble, W., Garwood, C., Stephenson, J., Kinsey, A. M., Hanger, D. P., Anderton, B. H. Minocycline reduces the development of abnormal tau species in models of Alzheimers disease. FASEB J. 23, 739–750 (2009)

Plasma Biomarkers of Brain Atrophy in Alzheimer's Disease

Peripheral biomarkers of Alzheimers disease (AD) reflecting early neuropathological change are critical to the development of treatments for this condition. The most widely used indicator of AD pathology in life at present is neuroimaging evidence of brain atrophy. We therefore performed a proteomic analysis of plasma to derive biomarkers associated with brain atrophy in AD. Using gel based proteomics we previously identified seven plasma proteins that were significantly associated with hippocampal volume in a combined cohort of subjects with AD (N = 27) and MCI (N = 17). In the current report, we validated this finding in a large independent cohort of AD (N = 79), MCI (N = 88) and control (N = 95) subjects using alternative complementary methods—quantitative immunoassays for protein concentrations and estimation of pathology by whole brain volume. We confirmed that plasma concentrations of five proteins, together with age and sex, explained more than 35% of variance in whole brain volume in AD patients. These proteins are complement components C3 and C3a, complement factor-I, γ-fibrinogen and alpha-1-microglobulin. Our findings suggest that these plasma proteins are strong predictors of in vivo AD pathology. Moreover, these proteins are involved in complement activation and coagulation, providing further evidence for an intrinsic role of these pathways in AD pathogenesis.

Proteome-based plasma markers of brain amyloid-β deposition in non-demented older individuals.

Blood-based markers reflecting core pathological features of Alzheimers disease (AD) in pre-symptomatic individuals are likely to accelerate the development of disease-modifying treatments. Our aim was to discover plasma proteins associated with brain amyloid-β (Aβ) burden in non-demented older individuals. We performed discovery-phase experiments using two dimensional gel electrophoresis (2DGE) and mass spectrometry-based proteomic analysis of plasma in combination with 11C-PiB PET imaging of the brain in samples collected 10 years prior to the PET scans. Confirmatory studies used ELISA assays in a separate set of blood samples obtained within a year of the PET scans. We observed that a panel of 18 2DGE plasma protein spots effectively discriminated between individuals with high and low brain Aβ. Mass spectrometry identified these proteins, many of which have established roles in Aβ clearance, including a strong signal from apolipoprotein-E (ApoE). In validation-phase studies, we observed a strong association between plasma ApoE concentration and Aβ burden in the medial temporal lobe. Targeted voxel-based analysis localized this association to the hippocampus and entorhinal cortex. APOE ε4 carriers also showed greater Aβ levels in several brain regions relative to ε4 non-carriers. These results suggest that both peripheral concentration of ApoE protein and APOE genotype are related to early neuropathological changes in brain regions vulnerable to AD pathology even in the non-demented elderly. Our strategy combining proteomics with in vivo brain amyloid imaging holds promise for the discovery of biologically relevant peripheral markers in those at risk for AD.

Plasma Transthyretin as a Candidate Marker for Alzheimer's Disease

Diagnosis of the progressive neurodegenerative disorder Alzheimers disease (AD) can only definitively be made postmortem. The most promising AD biomarkers identified to date are found in cerebrospinal fluid (CSF). Among these, one of the most interesting candidates is transthyretin (TTR), the carrier of thyroxine and retinol, which also binds with amyloid-β (Aβ), and it has been suggested that it protects against Aβ deposition. A biomarker detectable in plasma would have great diagnostic value and could be of use for determining disease progression and the monitoring of therapeutic efficacy due to its greater accessibility over CSF-based markers. We aimed to validate TTR as a prognostic marker in AD and to determine its relation with cognitive measures. We examined the plasma protein levels of TTR in 90 people with late-onset AD and 50 age-matched non-demented controls (NDC) by immunoblotting and found lower plasma TTR levels in AD compared to NDC (p = 0.004). We then quantified plasma TTR by enzyme-linked immunosorbent assays in a larger independent cohort (n = 270) including subjects with mild to severe AD. Plasma TTR levels were significantly lower in AD cases with rapid cognitive decline and with severe cognitive impairment. Regression analyses showed plasma TTR levels also predicted cognitive decline over the ensuing 6 months. These data indicate that plasma TTR is a strong candidate AD biomarker that should be included in the development of blood based biomarker panels for disease diagnosis and also suggests that plasma TTR is a marker of disease severity and progression.

P3-022: Correlation of plasma biomarkers with clinical measures of Alzheimer's disease

Anna M. Kinsey, Madhav Thambisetty , Abdul Hye , Mirsada Causevic, Richard Killick , Martin Broadstock , Thorsten Prinz, Catherine Tunnard , Nicola Dunlop , Andrew Simmons, Christian Spenger , Malcolm Ward , Paul Francis , Simon Lovestone, and on behalf of the AddNeuroMed Consortium, Institute of Psychiatry, London, United Kingdom; Proteome Sciences, London, United Kingdom; Wolfson CARD, London, United Kingdom; Proteome Sciences, Frankfurt, Germany; Karolinska Institutet, Stockholm, Sweden. Contact e-mail: a.kinsey@iop.kcl.ac.uk