Andrew P. Keegan

Cross validation of the Montreal Cognitive Assessment in community dwelling older adults residing in the Southeastern US

Cross validation study of the MoCA for the detection of Alzheimers disease (AD) and Mild Cognitive Impairment (MCI) in a community‐based cohort residing in the Southeastern United States.

The influence of diagnosis, intra- and inter-person variability on serum and plasma Aβ levels

Evidence suggests that high peripheral beta-amyloid (Abeta)(1-40) levels and low ratios of Abeta(1-42)/Abeta(1-40) are associated with increased risk for Alzheimers disease (AD). In this cross-sectional design, serum and plasma samples from 67 AD patients and 146 controls (similar in age and gender) were evaluated using Abeta(1-40) and Abeta(1-42) ELISA. Coefficient of variance was calculated for intra- and inter-person variability of Abeta(1-40) and Abeta(1-42). Abeta(1-40) correlated with age, MMSE and their Abeta(1-42)/Abeta(1-40) ratios (p<0.05). Significantly higher Abeta(1-40) levels were observed in AD patients than controls (p<0.05) but no difference was observed for Abeta(1-42) (p>0.05). Serum Abeta(1-42)/Abeta(1-40) ratios were also significantly lower in AD patients than controls (p<0.05). Lower intra-person than inter-person variability was observed for serum and plasma Abeta(1-40) and Abeta(1-42) and these were higher in controls than in AD patients. The intra-person variability of serum Abeta(1-40) did not influence the group differences observed between AD patients and controls. Significant interaction was observed between diagnosis and intra-person variability for serum Abeta(1-40) levels (p<0.05) and was supported by our finding of higher intra-person variability for serum Abeta(1-40) in controls (26.97%) than in AD patients (18.35%). We confirm the previously observed differences in blood Abeta levels between AD and control groups. In addition, we now report the presence of high intra- and inter-person variability possibly due to factors that influence peripheral Abeta levels and warrant further investigation before the potential use of Abeta as an AD biomarker can be fully exploited.

Diagnostic utility of APOE, soluble CD40, CD40L, and Aβ1–40 levels in plasma in Alzheimer’s disease

A continuous inflammatory state is associated with Alzheimers disease (AD) evidenced by an increase in proinflammatory cytokines around beta-amyloid (Abeta) deposits. In addition, functional loss of CD40L is shown to result in diminished Amyloid precursor proton (APP) processing and microglial activation, supporting a prominent role of CD40-CD40L in AD etiology. We therefore hypothesize that a peripheral increase in Abeta may result in corresponding increase of sCD40 and sCD40L further contributing to AD pathogenesis. We measured plasma Abeta, sCD40 and sCD40L levels in 73 AD patients and compared to 102 controls matched on general demographics. We demonstrated that Abeta(1-40), levels of sCD40 and sCD40L are increased in AD and declining MMSE scores correlated with increasing sCD40L, which in turn, correlated positively with Abeta(1-42). We then combined sCD40, sCD40L, Abeta and APOE and found that this biomarker panel has high sensitivity and specificity (>90%) as a predictor of clinical AD diagnosis. Given the imminent availability of potentially disease modifying therapies for AD, a great need exists for peripheral diagnostic markers of AD. Thus, we present preliminary evidence for potential usefulness for combination of plasma sCD40, sCD40L along with Abeta(1-40) and APOE epsilon4 in improving the clinical diagnosis of AD.

Serum Aβ Levels as Predictors of Conversion to Mild Cognitive Impairment/Alzheimer Disease in an ADAPT Subcohort

Recent evidence suggests an association of β-amyloid (Aβ) with vascular risk factors and the medications to treat them, which could potentially obfuscate the usefulness of Aβ for prediction of mild cognitive impairment (MCI) or Alzheimer disease (AD). In a subcohort from the Alzheimer’s Disease Anti-inflammatory Prevention Trial (enriched for family history of AD), we investigated whether systolic blood pressure, total cholesterol, triglycerides, serum creatinine, apolipoprotein E, and use of statins and antihypertensives influenced the predictive value of serum Aβ for MCI/AD during a 2-year period. We collected blood samples to quantify serum Aβ from cognitively normal participants (n = 203) at baseline and ascertained the outcome of MCI/AD (n = 24) for a period of approximately 2 years. In an unadjusted model, the lowest quartile of Aβ1–42 (hazard ratio (HR) = 2.93, 95% CI (1.02–8.32), P= 0.04) and of the Aβ1–42/Aβ1–40 ratio (HR = 3.53, 95% CI (1.24–10.07), P = 0.02), compared with the highest quartile, predicted conversion to MCI/AD, but no impact of Aβ1–40 was observed. No relationship between nonsteroidal antiinflammatory drug interventions and Aβ on MCI/AD risk was evident. Once data were adjusted for potential confounders (age, sex, and education), vascular risk factors, and the medications listed above, the lowest quartiles of Aβ1–42 (HR = 4.47, 95% CI (1.39–14.39), P= 0.01), and of the Aβ1–42/Aβ1–40 ratio (HR 4.87, 95% CI (1.50–15.87), P = 0.01) became strong predictors of conversion to MCI/AD. In this subcohort of individuals at risk for AD, the association of Aβ with vascular risk factors and medications to treat these conditions did not interfere with Aβ’s predictive value for MCI/AD.

Increased Plasma Beta-Secretase 1 May Predict Conversion to Alzheimer’s Disease Dementia in Individuals With Mild Cognitive Impairment

BACKGROUND Increased beta-secretase 1 (BACE1) activity has consistently been detected in brain tissue and cerebrospinal fluid of subjects with mild cognitive impairment (MCI) and probable Alzheimers disease (AD) compared with control subjects. The collection of cerebrospinal fluid by lumbar puncture is invasive. We sought to identify the presence of plasma BACE1 activity and determine potential alterations in subjects with MCI with clinical follow-up examinations for 3 years using patients with diagnosed probable AD dementia compared with healthy control subjects. METHODS Seventy-five patients with probable AD, 96 individuals with MCI, and 53 age-matched and sex-matched healthy control subjects were recruited from three independent international academic memory clinics and AD research expert centers. Plasma BACE1 activity was measured by a synthetic fluorescence substrate enzyme-linked immunosorbent assay. BACE1 protein expression was assessed by Western blotting using three different antibodies that recognize the epitopes of the N-terminus, C-terminus, and full-length BACE1. RESULTS Compared with healthy control subjects, plasma BACE1 activity (Vmax) significantly increased by 53.2% in subjects with MCI and by 68.9% in patients with probable AD. Subjects with MCI who converted to probable AD dementia at follow-up examinations exhibited significantly higher BACE1 activity compared with cognitively stable MCI nonconverters and showed higher levels of BACE1 activity than patients with AD. CONCLUSIONS Plasma BACE1 activity is significantly increased in MCI converters and patients with probable AD. The sensitivities and specificities of BACE1 activity for the patients were 84% and 88%, respectively. Our results indicate that plasma BACE1 activity may be a biomarker for AD risk and could predict progression from prodromal to probable AD dementia.

Feasibility of Predicting MCI/AD Using Neuropsychological Tests and Serum β-Amyloid

We examined the usefulness of brief neuropsychological tests and serum Aβ as a predictive test for detecting MCI/AD in older adults. Serum Aβ levels were measured from 208 subjects who were cognitively normal at enrollment and blood draw. Twenty-eight of the subjects subsequently developed MCI (n = 18) or AD (n = 10) over the follow-up period. Baseline measures of global cognition, memory, language fluency, and serum Aβ1–42 and the ratio of serum Aβ1–42/Aβ1–40 were significant predictors for future MCI/AD using Cox regression with demographic variables, APOE ε4, vascular risk factors, and specific medication as covariates. An optimal sensitivity of 85.2% and specificity of 86.5% for predicting MCI/AD was achieved using ROC analyses. Brief neuropsychological tests and measurements of Aβ1–42 obtained via blood warrants further study as a practical and cost effective method for wide-scale screening for identifying older adults who may be at-risk for pathological cognitive decline.

Plasma cytokine IL‐6 levels and subjective cognitive decline: preliminary findings

Detection of Alzheimers disease (AD) prior to clinical inception will be paramount for introducing disease modifying treatments. We have begun collecting baseline characteristics of a community cohort for longitudinal assessment and testing of antecedent blood‐based biomarkers. We describe the baseline visit from the first 131 subjects in relationship to a commonly described cytokine, interleukin 6 (IL‐6).

APOE4-SPECIFIC IMBALANCE IN ARACHIDONIC ACID AND DOCOSAHEXAENOIC ACID IN SERUM PHOSPHOLIPIDS FROM INDIVIDUALS WITH PRECLINICAL MCI/AD

variants, and it has not been reported in the world. Methods: This study reports a novel S100A9 gene mutation in 5 Malaysian patient with AD. Direct sequencing of the S100A9 gene revealed a novel mis-sense mutation at codon 99 for predicting glucine to lysine substitution (E99K). Results: Additionally, dataset sequence of 60,706 unrelated individuals were screened, which could be used in the various disease-specific and population genetic studies. Conclusions: E99K is a novel S100A9 gene mutation responsible for AD in East Asia as well as in the world.

DETECTION AND DIFFERENTIATION OF MILD COGNITIVE IMPAIRMENT, ALZHEIMER'S AND PARKINSON’S DISEASES BY ANALYSIS OF BRAIN-ENRICHED MICRORNAS IN PLASMA

Background: Recent genome-wide association studies (GWAS) have identified around 20 variants as late-onset Alzheimer’s disease (LOAD) susceptibility loci in whites. In addition to these single loci tests, it is important to detect and understand combined effects of multiple associated genes on LOAD. We performed a preliminary network analysis incorporating human protein-protein interaction database mined from 12 different sites including BIND, BioGRID, IntAct etc. to the HapMap2-imputed combined ADGC data set. Post-GWAS, this helps researchers to prioritize functionally related genes and networks that are of the highest biological relevance underlying the pathogenesis of LOAD. Methods: We combined HapMap2-imputed data sets from 15 studies after performing strict quality control. We performed a case-control association for LOAD adjusting for population sub-structure and study sites on a set of 19,692 unrelated individuals using PLINK and those results were used to perform a gene-wide analysis using VEGAS. The gene-wide association results were then integrated into the human protein-protein interaction network using a dense module searching (DMS) method to identify candidate genes or sub-networks for LOAD. We then attempted to functionally validate candidate genes from this network in vivo using a transgenic C. elegans model of Ab 1-42 toxicity. Results: The network analysis identified several of the known LOAD risk loci as well as other genes such as ALB, BAG1 and UBC to be strongly associated with LOAD. RNAi knockdown of the C. elegans orthologs of UBC (ubq-1 or ubq-2) significantly accelerated the age-associated onset of Ab 1-42 toxicity. Conclusions:We were able to identify a set of significant modules and candidate genes, including some well-studied genes not detected in the single-marker analysis of GWA studies for LOAD, and to demonstrate a role for two of these genes as modifiers of Ab toxicity in C. elegans. This approach provides complementary data to a GWAS of a complex disease phenotype by incorporating biological knowledge derived from protein-protein interactions and allows for initial functional validation in vivo. Further functional enrichment analysis is needed to determine whether these novel loci may provide targets for interventions to ameliorate LOAD. THURSDAY, JULY 17, 2014 ORAL SESSIONS O5-05 BIOMARKERS: NOVEL MOLECULAR FLUID MARKERS

APOE ε4 specific imbalance of arachidonic acid and docosahexaenoic acid in serum phospholipids identifies individuals with preclinical Mild Cognitive Impairment/Alzheimer’s Disease

This study was designed to explore the influence of apolipoprotein E (APOE) on blood phospholipids (PL) in predicting preclinical Alzheimers disease (AD). Lipidomic analyses were also performed on blood from an AD mouse model expressing human APOE isoforms (EFAD) and five AD mutations and from 195 cognitively normal participants, 23 of who converted to mild cognitive impairment (MCI)/AD within 3 years. APOE ε4-carriers converting to MCI/AD had high arachidonic acid (AA)/docosahexaenoic acid (DHA) ratios in PL compared to cognitively normal ε4 and non-ε4 carriers. Arachidonic acid and DHA containing PL species, ε4-status and Aβ42/Aβ40 ratios provided 91% accuracy in detecting MCI/AD. Fish oil/omega-3 fatty acid consumption was associated with lower AA/DHA ratios even among ε4 carriers. High plasma AA/DHA ratios were observed in E4FAD compared to EFAD mice with other isoforms. In particular, alterations in plasma AA and DHA containing PL species were also observed in the brains of E4FAD mice compared to E3FAD mice. Despite the small sample size and a short follow-up, these results suggest that blood PL could potentially serve as biomarkers of preclinical MCI/AD.