Catherine Tunnard

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.

Multivariate analysis of MRI data for Alzheimer's disease, mild cognitive impairment and healthy controls.

We have used multivariate data analysis, more specifically orthogonal partial least squares to latent structures (OPLS) analysis, to discriminate between Alzheimers disease (AD), mild cognitive impairment (MCI) and elderly control subjects combining both regional and global magnetic resonance imaging (MRI) volumetric measures. In this study, 117 AD patients, 122 MCI patients and 112 control subjects (from the AddNeuroMed study) were included. High-resolution sagittal 3D MP-RAGE datasets were acquired from each subject. Automated regional segmentation and manual outlining of the hippocampus were performed for each image. Altogether this yielded volumes of 24 different anatomically defined structures which were used for OPLS analysis. 17 randomly selected AD patients, 12 randomly selected control subjects and the 22 MCI subjects who converted to AD at 1-year follow up were excluded from the initial OPLS analysis to provide a small external test set for model validation. Comparing AD with controls we found a sensitivity of 87% and a specificity of 90% using hippocampal measures alone. Combining both global and regional measures resulted in a sensitivity of 90% and a specificity of 94%. This increase in sensitivity and specificity resulted in an increase of the positive likelihood ratio from 9 to 15. From the external test set, the model predicted 82% of the AD patients and 83% of the control subjects correctly. Finally, 73% of the MCI subjects which converted to AD at 1 year follow-up were shown to resemble AD patients more closely than controls. This method shows potential for distinguishing between different patient groups. Combining the different MRI measures together resulted in a significantly better classification than using them separately. OPLS also shows potential for predicting conversion from MCI to AD.

Analysis of regional MRI volumes and thicknesses as predictors of conversion from mild cognitive impairment to Alzheimer's disease

We determined predictors of conversion to Alzheimers disease (AD) from mild cognitive impairment (MCI) with automated magnetic resonance imaging (MRI) regional cortical volume and thickness measures. One hundred amnestic MCI subjects, 118 AD patients, and 94 age-matched healthy controls were selected from AddNeuroMed study. Twenty-four regional cortical volumes and 34 cortical thicknesses were measured with automated image processing software at baseline. Twenty-one subjects converted from MCI to AD determined with the cognitive tests at baseline and 1 year later. The hippocampus, amygdala, and caudate volumes were significantly smaller in progressive MCI subjects than in controls and stable MCI subjects. The cortical volumes achieved higher predictive accuracy than did cognitive tests or cortical thickness. Combining the volumes, thicknesses, and cognitive tests did not improve the accuracy. The volume of amygdala and caudate were independent variables in predicting conversion from MCI to AD. We conclude that regional cortical volume measures are more powerful than those common cognitive tests we used in identifying AD patients at the very earliest stage of the disease.

Insight, cognition and quality of life in Alzheimer's disease

Background The detrimental impact of dementia upon patient health-related quality of life (HRQL) is well established, as is the importance of improving HRQL. However, relatively little is known about the natural history of HRQL in dementia and those factors influencing it. This limited knowledge potentially restricts the evaluation of the efficacy of interventions designed to improve HRQL. One such area concerns the relationship between HRQL and patient insight. It remains unclear what impact, if any, impaired insight has upon a patients HRQL. The present study aimed to investigate the relationship between insight and HRQL in a sample of patients with Alzheimers disease (AD) and their carers. Methods 256 patients with AD were recruited as part of AddNeuroMed, a multicentre European AD biomarkers study. Of these, 174 completed a quality-of-life measure in addition to a comprehensive battery of clinical and neuropsychological assessments. Results Insight was found to be differentially related to patient perceptions of HRQL in mild and moderate dementia. Within moderate dementia, impaired insight was associated with better perceived HRQL. Conversely, cognition, but not insight, was associated with impaired HRQL in mild dementia. Insight was not found to be associated with carer perceptions of patient HRQL. Conclusion Impairment of insight is associated with better HRQL in moderate dementia. This finding has implications for interventions which focus on increasing patient awareness and orientation, as impairment of insight appears to have a positive impact upon HRQL.

Apathy and cortical atrophy in Alzheimer's disease

Apathy has been reported as the most prevalent behavioural symptom experienced in Alzheimers disease (AD), associated with greater functional decline and caregiver distress. The aim of the current study was to investigate structural correlates of apathy in AD using magnetic resonance imaging (MRI) regional volume and regional cortical thickness measures.

Effect of APOE ε4 allele on cortical thicknesses and volumes: the AddNeuroMed study.

The apolipoprotein E (APOE) ε4 allele is a risk factor for Alzheimers disease (AD), but its effect on brain volumes is controversial. We explored the effect of the ε4 allele on regional cortical thickness and volume measurements using an automated pipeline in 111 subjects with mild cognitive impairment (MCI), 115 AD patients, and 107 age-matched healthy controls. The clinical data were used as covariates in the thickness and volume comparisons. The ε4 carriers had significantly smaller volume than non-carriers in caudate (p=0.028) in controls; in amygdala and caudate in the MCI group (p <or= 0.049); and in hippocampus and amygdala in the AD group (p <or= 0.001). In the female subjects, the ε4 carriers had significantly thinner cortical thickness or smaller volume than non-carriers in medial orbitofrontal gyrus and caudate in controls (p <or= 0.014); in amygdala in MCI subjects (p=0.047) and in hippocampus and amygdala in AD patients (p <or= 0.024). However, in the male subjects, there were significant differences in cortical thickness and volume between ε4 carriers and non-carriers in several structures in the MCI group, but no differences in the controls and AD patients. Compared to the non-carriers, the homozygous ε4 carriers showed significant volume loss in hippocampus, deep nuclei, and caudal anterior cingulate cortex in MCI. In the AD group, the homozygous ε4 carriers had significant volume loss in hippocampus and amygdala. We conclude that the APOE ε4 allele modulates regional cortical thickness and volume in relation to diagnostic group and gender. The ε4 allele has a dose-dependent and regionally specific effect on brain structures.

The impact of childhood adversity on suicidality and clinical course in treatment-resistant depression

BACKGROUND Childhood adversity is a risk factor for the development of depression and can also affect clinical course. We investigated this specifically in treatment-resistant depression (TRD). METHODS One hundred and thirty-seven patients with TRD previously admitted to an inpatient affective disorders unit were included. Clinical, demographic and childhood adversity (physical, sexual, emotional abuse; bullying victimization, traumatic events) data were obtained during admission. Associations between childhood adversity, depressive symptoms and clinical course were investigated. RESULTS Most patients had experienced childhood adversity (62%), with traumatic events (35%) and bullying victimization (29%) most commonly reported. Childhood adversity was associated with poorer clinical course, including earlier age of onset, episode persistence and recurrence. Logistic regression analyses revealed childhood adversity predicted lifetime suicide attempts (OR 2.79; 95% CI 1.14, 6.84) and childhood physical abuse predicted lifetime psychosis (OR 3.42; 95% CI 1.00, 11.70). LIMITATIONS The cross-sectional design and retrospective measurement of childhood adversity are limitations of the study. CONCLUSIONS Childhood adversity was common amongst these TRD patients and was associated with poor clinical course, psychosis and suicide attempts. Routine assessment of early adversity may help identify at risk individuals and inform clinical intervention.

Combination analysis of neuropsychological tests and structural MRI measures in differentiating AD, MCI and control groups—The AddNeuroMed study

To study the ability of neuropsychological tests, manual MRI hippocampal volume measures, regional volume and cortical thickness measures to identify subjects with Alzheimers disease (AD), mild cognitive impairment (MCI), and healthy age-matched controls. Neuropsychological tests, manual hippocampal volume, automated regional volume and regional cortical thickness measures were performed in 120 AD patients, 120 MCI subjects, and 111 controls. The regional cortical thickness and volumes in MCI subjects were significantly decreased in limbic/paralimbic areas and temporal lobe compared to controls. Atrophy was much more extensive in the AD patients compared to MCI subjects and controls. The combination of neuropsychological tests and volumes revealed the highest accuracy (82% AD vs. MCI; 94% AD vs. control; 83% MCI vs. control). Adding regional cortical thicknesses into the discriminate analysis did not improve accuracy. We conclude that regional cortical thickness and volume measures provide a panoramic view of brain atrophy in AD and MCI subjects. A combination of neuropsychological tests and regional volumes are important when discriminating AD from healthy controls and MCI.

APOE ε2 Allele Is Associated with Larger Regional Cortical Thicknesses and Volumes

Background: The protective effect of the apolipoprotein E (APOE) Ε2 allele against Alzheimer’s disease (AD) is controversial. Objective: Our purpose was to clarify if the Ε2 allele affects regional cortical thicknesses and volumes. Methods: Regional cortical thicknesses and volumes were measured with an automated pipeline in 109 subjects with mild cognitive impairment, 114 AD patients and 105 age-matched healthy controls. Results: In the mild cognitive impairment group, the Ε2 carriers had thicker regional cortices at the transverse temporal cortex and parahippocampal gyrus than the subjects with Ε3/Ε3, and a larger cerebral gray matter and smaller lateral ventricles than the Ε3/Ε3 and Ε4 carriers. In the AD group, the Ε2 carriers had significantly thicker entorhinal and transverse temporal cortices, a larger whole cerebral gray matter, and smaller lateral ventricles than the subjects with the Ε3/Ε3 genotype, and a significantly thicker entorhinal cortex and larger cerebral gray matter than Ε4 carriers. No APOE2 effect was found in the control group. Conclusion: The APOE Ε2 allele is associated with larger regional cortical thicknesses and volumes in mild cognitive impairment and AD.

Frontotemporal atrophy associated with paranoid delusions in women with Alzheimer's disease.

BACKGROUND Paranoid delusions are a common and difficult-to-manage feature of Alzheimers disease (AD). We investigated the neuroanatomical correlates of paranoid delusions in a cohort of AD patients, using magnetic resonance imaging (MRI) to measure regional volume and regional cortical thickness. METHODS 113 participants with probable AD were assessed for severity of disease, cognitive and functional impairment. Presence and type of delusions were assessed using the Neuropsychiatric Inventory (NPI). Structural MRI images were acquired on a 1.5 T scanner, and were analyzed using an automated analysis pipeline. RESULTS Paranoid delusions were experienced by 23 (20.4%) of the participants. Female participants with paranoid delusions showed reduced cortical thickness in left medial orbitofrontal and left superior temporal regions, independently of cognitive decline. Male participants with delusions did not show any significant differences compared to males without delusions. An exploratory whole brain analysis of non-hypothesized regions showed reduced cortical thickness in the left insula for female participants only. CONCLUSION Frontotemporal atrophy is associated with paranoid delusions in females with AD. Evidence of sex differences in the neuroanatomical correlates of delusions as well as differences in regional involvement in different types of delusions may be informative in guiding management and treatment of delusions in AD.