[Show abstract][Hide abstract] ABSTRACT: Background: Alzheimer’s disease is a common debilitating dementia with known heritability, for which 20 late onset susceptibility loci have been identified, but more remain to be discovered. This study sought to identify new susceptibility genes, using an alternative gene-wide analytical approach which tests for patterns of association within genes, in the powerful genome-wide association dataset of the International Genomics of Alzheimer’s Project Consortium, comprising over 7 m genotypes from 25,580 Alzheimer’s cases and 48,466 controls.
Principal Findings: In addition to earlier reported genes, we detected genome-wide significant loci on chromosomes 8 (TP53INP1, p=1.461026) and 14 (IGHV1-67 p=7.961028) which indexed novel susceptibility loci.
Significance: The additional genes identified in this study, have an array of functions previously implicated in Alzheimer’s disease, including aspects of energy metabolism, protein degradation and the immune system and add further weight to these pathways as potential therapeutic targets in Alzheimer’s disease
PLoS ONE 06/2014; 9(6):e94661. · 3.73 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Disease-, age- and gender-associated changes in brain copper, iron and zinc were assessed in post-mortem neocortical tissue (Brodmann area 7) from patients with moderate Alzheimer’s disease (AD) (n=14), severe AD (n=28), dementia with Lewy Bodies (DLB) (n=15) and normal age-matched control subjects (n=26). Copper was lower (20%; P<0.001) and iron higher (10-16%; P<0.001) in severe AD compared with Control. Intriguingly significant Group*Age interactions were observed for both copper and iron, suggesting gradual age-associated decline of these metals in healthy non-cognitively impaired individuals. Zinc was unaffected in any disease pathologies and no age-associated changes were apparent. Age-associated changes in brain elements warrant further investigation.
Journal of Alzheimer's disease: JAD 05/2014; · 4.17 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Alzheimer's disease (AD) is the most common and complex neurodegenerative disease in the elderly individuals. Recently, genome-wide association studies (GWAS) have been used to investigate AD pathogenesis. These GWAS have yielded important new insights into the genetic mechanisms of AD. However, these newly identified AD susceptibility loci exert only very small risk effects and cannot fully explain the underlying AD genetic risk. We hypothesize that combining the findings from different AD GWAS may have greater power than genetic analysis alone. To identify new AD risk factors, we integrated findings from 3 previous large-scale AD GWAS (n = 14,138) using a gene-based meta-analysis and subsequently conducted a pathway analysis using the kyoto encyclopedia of genes and genomes and gene ontology databases. Interestingly, we not only confirmed previous findings, but also highlighted, for the first time, the involvement of cardiovascular disease-related pathways in AD. Our results provided the clues as to the link between these diseases using pathway analysis methods. We believe that these findings will be very useful for future genetic studies of AD.
[Show abstract][Hide abstract] ABSTRACT: Aim: Substantial evidence links atherosclerosis and Alzheimer's disease (AD). Apolipoproteins, such as apolipoprotein E, have a causal relationship with both diseases. The rs1113600 SNP within the CLU gene, which encodes clusterin (apolipoprotein J), is also associated with increased AD risk. The aim of this study was to investigate the relationship between plasma clusterin and the rs11136000 genotype in mild cognitive impairment (MCI) and AD. Methods: Plasma and DNA samples were collected from control, MCI and AD subjects (n=142, 111, 154, respectively). Plasma clusterin was determined by ELISA and DNA samples were genotyped for rs11136000 by TaqMan assay. Results: Plasma clusterin levels were higher in MCI and AD subjects vs. controls (222.3±61.3 and 193.6±58.2 vs. 178.6±52.3 µg/ml, respectively; p<0.001 for both comparisons), and in MCI vs. AD (p<0.05). Plasma clusterin was not influenced by genotype in the MCI and AD subjects, although in control subjects plasma clusterin was lower in the TT vs. TC genotypes (157.6±53.4 vs. 188.6±30.5 µg/ml; p<0.05). Conclusion: This study examined control, MCI and AD subjects, identifying for the first time that plasma clusterin levels were influenced, not only by the presence of AD, but also the transitional stage of MCI, while rs11136000 genotype only influenced plasma clusterin levels in the control group. The increase in plasma clusterin in MCI and AD subjects may occur in response to the disease process and would be predicted to increase binding capacity for amyloid-beta peptides in plasma, enhancing their removal from the brain.
Current Alzheimer research 10/2013; · 4.97 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Eleven susceptibility loci for late-onset Alzheimer's disease (LOAD) were identified by previous studies; however, a large portion of the genetic risk for this disease remains unexplained. We conducted a large, two-stage meta-analysis of genome-wide association studies (GWAS) in individuals of European ancestry. In stage 1, we used genotyped and imputed data (7,055,881 SNPs) to perform meta-analysis on 4 previously published GWAS data sets consisting of 17,008 Alzheimer's disease cases and 37,154 controls. In stage 2, 11,632 SNPs were genotyped and tested for association in an independent set of 8,572 Alzheimer's disease cases and 11,312 controls. In addition to the APOE locus (encoding apolipoprotein E), 19 loci reached genome-wide significance (P < 5 × 10(-8)) in the combined stage 1 and stage 2 analysis, of which 11 are newly associated with Alzheimer's disease.
[Show abstract][Hide abstract] ABSTRACT: We undertook a two-stage genome-wide association study (GWAS) of Alzheimer's disease (AD) involving over 16,000 individuals, the most powerful AD GWAS to date. In stage 1 (3,941 cases and 7,848 controls), we replicated the established association with the apolipoprotein E (APOE) locus (most significant SNP, rs2075650, P = 1.8 × 10−157) and observed genome-wide significant association with SNPs at two loci not previously associated with the disease: at the CLU (also known as APOJ) gene (rs11136000, P = 1.4 × 10−9) and 5′ to the PICALM gene (rs3851179, P = 1.9 × 10−8). These associations were replicated in stage 2 (2,023 cases and 2,340 controls), producing compelling evidence for association with Alzheimer's disease in the combined dataset (rs11136000, P = 8.5 × 10−10, odds ratio = 0.86; rs3851179, P = 1.3 × 10−9, odds ratio = 0.86).
[Show abstract][Hide abstract] ABSTRACT: Objectives: A healthy lifestyle may help maintain cognitive function and reduce the risk of developing dementia. This study employed a focus group approach in order to gain insight into opinions of mild cognitive impairment (MCI) patients, caregivers (CG) and health professionals (HP) regarding lifestyle and its relationship with cognition. The qualitative data were used to design, develop and pilot test educational material (EM) to help encourage lifestyle behaviour change. Method: Data gathering phase: structured interviews were conducted with HP (n = 10), and focus groups with MCI patients (n = 24) and CG (n = 12). EM was developed and pilot tested with a new group of MCI patients (n = 21) and CG (n = 6). Results: HP alluded to the lack of clinical trial evidence for a lifestyle and MCI risk link. Although they felt that lifestyle modifications should be recommended to MCI patients, they appeared hesitant in communicating this information and discussions were often patient-driven. MCI patients lacked awareness of the lifestyle cognition link. Participants preferred EM to be concise, eye-catching and in written format, with personal delivery of information favoured. Most pilot testers approved of the EM but were heterogeneous in terms of lifestyle, willingness to change and support needed to change. Conclusion: MCI patients need to be made more aware of the importance of lifestyle for cognition. EM such as those developed here, which are specifically tailored for this population would be valuable for HP who, currently, appear reticent in initiating lifestyle-related discussions. Following further evaluation, the EM could be used in health promotion activities targeting MCI patients.
Aging and Mental Health 02/2013; · 1.68 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: BACKGROUND: Vascular dementia represents the second most common type of dementia after Alzheimer's disease. In older patients, in particular, the combination of vascular dementia and Alzheimer's disease is common, and is referred to as mixed dementia. The classification of vascular dementia broadly follows three clinico-pathological processes: multi-infarct dementia, single strategic infarct dementia and subcortical dementia. Not all victims fulfil strict criteria for dementia and may be significantly cognitively impaired without memory loss, when the term vascular cognitive impairment (VCI) is more useful. Currently, no established standard treatment for VCI exists. Reductions in acetylcholine and acetyltransferase activity are common to both Alzheimer's disease and VCI, raising the possibility that cholinesterase inhibitors - such as rivastigmine - which are beneficial in Alzheimer's disease, may also be beneficial for VCI. OBJECTIVES: To assess the efficacy of rivastigmine compared with placebo in the treatment of people with vascular cognitive impairment (VCI), vascular dementia or mixed dementia. SEARCH METHODS: We searched ALOIS (the Cochrane Dementia and Cognitive Improvement Group's Specialized Register) on 12 February 2013 using the terms: rivastigmine, exelon, "SDZ ENA 713". ALOIS contains records of clinical trials identified from monthly searches of a number of major healthcare databases (The Cochrane Library, MEDLINE, EMBASE, CINAHL, PsycINFO, LILACS), numerous trial registries and grey literature sources. SELECTION CRITERIA: All unconfounded randomized double-blind trials comparing rivastigmine with placebo in the treatment of people with VCI, vascular dementia or mixed dementia were eligible for inclusion. DATA COLLECTION AND ANALYSIS: Two reviewers extracted and assessed data independently, and agreement was reached after discussion. They noted results concerning adverse effects. MAIN RESULTS: Three trials, with a total of 800 participants, were identified for inclusion. The participants in one trial did not have dementia, while the other two studies included participants with dementia of different severities. The dose of rivastigmine was different in each study. No pooling of study results was attempted because of these differences between the studies.One trial included 40 participants with subcortical vascular dementia (age range 40 to 90 years) with a mean mini-mental state examination (MMSE) score of 13.0 and 13.4 in the rivastigmine and placebo arms, respectively. Treatment over 26 weeks was limited to 3 mg rivastigmine twice daily, or placebo. No significant difference was found on any outcome measure relevant to cognition, neuropsychiatric symptoms, function or global rating, or in the number of withdrawals before the end of treatment.Another trial included 710 participants with vascular dementia, including subcortical and cortical forms (age range 50 to 85 years). Over 24 weeks, a mean dose of rivastigmine of 9.4 mg/day was achieved versus placebo. Baseline MMSE was identical for both groups, at 19.1. Statistically significant advantage in cognitive response (but not with global impression of change or non-cognitive measures) was seen with rivastigmine treatment at 24 weeks (MMSE change from baseline MD 0.6, 95% CI 0.11 to 1.09, P value 0.02; Vascular Dementia Assessment Scale (VaDAS) change from baseline MD -1.3, 95% CI-2.62 to 0.02, P value 0.05 ). Significantly higher rates of vomiting, nausea, diarrhoea and anorexia and withdrawals from treatment were noted in the participants randomized to rivastigmine compared with placebo (withdrawals rivastigmine 90/365, placebo 48/345, OR 2.02, 95% CI 1.38 to 2.98) (withdrawals due to an adverse event rivastigmine 49/365, placebo 19/345, OR 2.66, 95% CI 1.53 to 4.62, P value 0.0005).The third study included 50 participants (age range 48 to 84 years) with mean MMSE scores of 23.7 and 23.9 in the rivastigmine and placebo arms, respectively. Over a 24-week period, participants labelled as having cognitive impairment but no dementia (CIND) following ischaemic stroke were given up to 4.5 mg rivastigmine twice daily, or placebo. Primary and secondary outcome measures showed no statistically significant difference when considering neurocognitive abilities, function, neuropsychiatric symptoms and global performance. One participant in the rivastigmine group and two in the placebo group discontinued their medication because of an adverse effect. AUTHORS' CONCLUSIONS: There is some evidence of benefit of rivastigmine in VCI from trial data from three studies. However, this conclusion is based on one large study. Rivastigmine is capable of inducing side effects that lead to withdrawal in a significant proportion of patients.
[Show abstract][Hide abstract] ABSTRACT: Alzheimer's disease (AD) and age-related macular degeneration (AMD) are both neurodegenerative disorders which share common pathological and biochemical features of the complement pathway. The aim of this study was to investigate whether there is an association between well replicated AMD genetic risk factors and AD. A large cohort of AD (n = 3898) patients and controls were genotyped for single nucleotide polymorphisms (SNPs) in the complement factor H (CFH), the Age-related maculopathy susceptibility protein 2 (ARMS2) the complement component 2 (C2), the complement factor B (CFB), and the complement component 3 (C3) genes. While significant but modest associations were identified between the complement factor H, the age-related maculopathy susceptibility protein 2, and the complement component 3 single nucleotide polymorphisms and AD, these were different in direction or genetic model to that observed in AMD. In addition the multilocus genetic model that predicts around a half of the sibling risk for AMD does not predict risk for AD. Our study provides further support to the hypothesis that while activation of the alternative complement pathway is central to AMD pathogenesis, it is less involved in AD.
Neurobiology of aging 01/2012; 33(8):1843.e9-17. · 5.94 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Neprilysin (NEP), also known as membrane metalloendopeptidase (MME), is considered amongst the most important β-amyloid (Aβ)-degrading enzymes with regard to prevention of Alzheimer's disease (AD) pathology. Variation in the NEP gene (MME) has been suggested as a risk factor for AD. We conducted a genetic association study of 7MME SNPs - rs1836914, rs989692, rs9827586, rs6797911, rs61760379, rs3736187, rs701109 - with respect to AD risk in a cohort of 1057 probable and confirmed AD cases and 424 age-matched non-demented controls from the United Kingdom, Italy and Sweden. We also examined the association of these MME SNPs with NEP protein level and enzyme activity, and on biochemical measures of Aβ accumulation in frontal cortex - levels of total soluble Aβ, oligomeric Aβ(1-42), and guanidine-extractable (insoluble) Aβ - in a sub-group of AD and control cases with post-mortem brain tissue. On multivariate logistic regression analysis one of the MME variants (rs6797911) was associated with AD risk (P = 0.00052, Odds Ratio (O.R. = 1.40, 95% confidence interval (1.16-1.70)). None of the SNPs had any association with Aβ levels; however, rs9827586 was significantly associated with NEP protein level (p=0.014) and enzyme activity (p=0.006). Association was also found between rs701109 and NEP protein level (p=0.026) and a marginally non-significant association was found for rs989692 (p=0.055). These data suggest that MME variation may be associated with AD risk but we have not found evidence that this is mediated through modification of NEP protein level or activity.
International Journal of Molecular Epidemiology and Genetics 01/2012; 3(1):30-8.
[Show abstract][Hide abstract] ABSTRACT: Rare mutations in AβPP, PSEN1, and PSEN2 cause uncommon early onset forms of Alzheimer's disease (AD), and common variants in MAPT are associated with risk of other neurodegenerative disorders. We sought to establish whether common genetic variation in these genes confer risk to the common form of AD which occurs later in life (>65 years). We therefore tested single-nucleotide polymorphisms at these loci for association with late-onset AD (LOAD) in a large case-control sample consisting of 3,940 cases and 13,373 controls. Single-marker analysis did not identify any variants that reached genome-wide significance, a result which is supported by other recent genome-wide association studies. However, we did observe a significant association at the MAPT locus using a gene-wide approach (p = 0.009). We also observed suggestive association between AD and the marker rs9468, which defines the H1 haplotype, an extended haplotype that spans the MAPT gene and has previously been implicated in other neurodegenerative disorders including Parkinson's disease, progressive supranuclear palsy, and corticobasal degeneration. In summary common variants at AβPP, PSEN1, and PSEN2 and MAPT are unlikely to make strong contributions to susceptibility for LOAD. However, the gene-wide effect observed at MAPT indicates a possible contribution to disease risk which requires further study.
[Show abstract][Hide abstract] ABSTRACT: Psychotic symptoms occur in ∼40% of subjects with Alzheimer's disease (AD) and are associated with more rapid cognitive decline and increased functional deficits. They show heritability up to 61% and have been proposed as a marker for a disease subtype suitable for gene mapping efforts. We undertook a combined analysis of three genome-wide association studies (GWASs) to identify loci that (1) increase susceptibility to an AD and subsequent psychotic symptoms; or (2) modify risk of psychotic symptoms in the presence of neurodegeneration caused by AD. In all, 1299 AD cases with psychosis (AD+P), 735 AD cases without psychosis (AD-P) and 5659 controls were drawn from Genetic and Environmental Risk in AD Consortium 1 (GERAD1), the National Institute on Aging Late-Onset Alzheimer's Disease (NIA-LOAD) family study and the University of Pittsburgh Alzheimer Disease Research Center (ADRC) GWASs. Unobserved genotypes were imputed to provide data on >1.8 million single-nucleotide polymorphisms (SNPs). Analyses in each data set were completed comparing (1) AD+P to AD-P cases, and (2) AD+P cases with controls (GERAD1, ADRC only). Aside from the apolipoprotein E (APOE) locus, the strongest evidence for association was observed in an intergenic region on chromosome 4 (rs753129; 'AD+PvAD-P' P=2.85 × 10(-7); 'AD+PvControls' P=1.11 × 10(-4)). SNPs upstream of SLC2A9 (rs6834555, P=3.0 × 10(-7)) and within VSNL1 (rs4038131, P=5.9 × 10(-7)) showed strongest evidence for association with AD+P when compared with controls. These findings warrant further investigation in larger, appropriately powered samples in which the presence of psychotic symptoms in AD has been well characterized.Molecular Psychiatry advance online publication, 18 October 2011; doi:10.1038/mp.2011.125.
[Show abstract][Hide abstract] ABSTRACT: We sought to identify new susceptibility loci for Alzheimer's disease through a staged association study (GERAD+) and by testing suggestive loci reported by the Alzheimer's Disease Genetic Consortium (ADGC) in a companion paper. We undertook a combined analysis of four genome-wide association datasets (stage 1) and identified ten newly associated variants with P ≤ 1 × 10(-5). We tested these variants for association in an independent sample (stage 2). Three SNPs at two loci replicated and showed evidence for association in a further sample (stage 3). Meta-analyses of all data provided compelling evidence that ABCA7 (rs3764650, meta P = 4.5 × 10(-17); including ADGC data, meta P = 5.0 × 10(-21)) and the MS4A gene cluster (rs610932, meta P = 1.8 × 10(-14); including ADGC data, meta P = 1.2 × 10(-16)) are new Alzheimer's disease susceptibility loci. We also found independent evidence for association for three loci reported by the ADGC, which, when combined, showed genome-wide significance: CD2AP (GERAD+, P = 8.0 × 10(-4); including ADGC data, meta P = 8.6 × 10(-9)), CD33 (GERAD+, P = 2.2 × 10(-4); including ADGC data, meta P = 1.6 × 10(-9)) and EPHA1 (GERAD+, P = 3.4 × 10(-4); including ADGC data, meta P = 6.0 × 10(-10)).