Mapping the effect of APOE epsilon4 on gray matter loss in Alzheimer's disease in vivo.

LENITEM Laboratory of Epidemiology, Neuroimaging and Telemedicine, IRCCS Centro San Giovanni di Dio - FBF, Brescia, Italy.
NeuroImage (Impact Factor: 6.25). 05/2009; 45(4):1090-8. DOI: 10.1016/j.neuroimage.2009.01.009
Source: PubMed

ABSTRACT Previous studies suggest that in Alzheimer's disease (AD) the Apolipoprotein E (APOE) epsilon4 allele is associated with greater vulnerability of medial temporal lobe structures. However, less is known about its effect on the whole cortical mantle. Here we aimed to identify APOE-related patterns of cortical atrophy in AD using an advanced computational anatomy technique. We studied 15 AD patients carriers (epsilon4+, age: 72+/-10 SD years, MMSE: 20+/-3 SD) and 14 non-carriers (epsilon4-, age: 69+/-9, MMSE: 20+/-5) of the epsilon4 allele and compared them to 29 age-and-sex matched controls (age: 70+/-9, MMSE: 28+/-1). Each subject underwent a clinical evaluation, a neuropsychological battery, and high-resolution MRI. UCLA's cortical pattern matching technique was used to identify regions of local cortical atrophy. epsilon4+ and epsilon4- patients showed similar performance on neuropsychological tests (p>.05, t-test). Diffuse cortical atrophy was detected for both epsilon4+ (p=.0001, permutation test) and epsilon4- patients (p=.0001, permutation test) relative to controls, and overall gray matter loss was about 15% in each patients group. Differences in gray matter loss between carriers and non-carriers mapped to the temporal cortex and right occipital pole (20% greater loss in carriers) and to the posterior cingulate, left orbitofrontal and dorsal fronto-parietal cortex (5-15% greater loss in non-carriers). APOE effect in AD was not significant (p>.74, ANOVA), but a significant APOE by region (temporal vs fronto-parietal cortex) interaction was detected (p=.002, ANOVA), in both early and late-onset patients (p<.05, ANOVA). We conclude that the epsilon4 allele modulates disease phenotype in AD, being associated with a pattern of differential temporal and fronto-parietal vulnerability.

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    ABSTRACT: Objectives To investigate whether APOE ε4 carriers have higher hippocampal atrophy rates than non-carriers in Alzheimer's disease (AD), mild cognitive impairment (MCI) and controls, and if so, whether higher hippocampal atrophy rates are still observed after adjusting for concurrent whole-brain atrophy rates. Methods MRI scans from all available visits in ADNI (148 AD, 307 MCI, 167 controls) were used. MCI subjects were divided into “progressors” (MCI-P) if diagnosed with AD within 36 months or “stable” (MCI-S) if a diagnosis of MCI was maintained. A joint multi-level mixed-effect linear regression model was used to analyse the effect of ε4 carrier-status on hippocampal and whole-brain atrophy rates, adjusting for age, gender, MMSE and brain-to-intracranial volume ratio. The difference in hippocampal rates between ε4 carriers and non-carriers after adjustment for concurrent whole-brain atrophy rate was then calculated. Results Mean adjusted hippocampal atrophy rates in ε4 carriers were significantly higher in AD, MCI-P and MCI-S (p≤0.011, all tests) compared with ε4 non-carriers. After adjustment for whole-brain atrophy rate, the difference in mean adjusted hippocampal atrophy rate between ε4 carriers and non-carriers was reduced but remained statistically significant in AD and MCI-P. Conclusions These results suggest that the APOE ε4 allele drives atrophy to the medial-temporal lobe region in AD.
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    ABSTRACT: Purpose To determine the effect of the apolipoprotein E (APOE) genotype on atrophy rates of specific brain gray matter regions hypothesized to be key components of cognitive networks disrupted in Alzheimer disease. Materials and Methods The Alzheimer's Disease Neuroimaging Initiative (ADNI) was approved by the institutional review boards of all participating sites. All subjects and their legal representatives gave written informed consent prior to data collection. The authors analyzed data from 237 subjects (mean age, 79.9 years; 40% female) with mild cognitive impairment (MCI) in the ADNI database and assessed the effect of the APOE ε4 and ε2 alleles on regional brain atrophy rates over a 12-48-month period. Brain regions were selected a priori: 15 experimental and five control regions were included. Regional atrophy rates were derived by using a fully automated algorithm applied to T1-weighted magnetic resonance (MR) imaging data. Analysis consisted of mixed-effects linear regression with repeated measures; results were adjusted for multiple testing with Bonferroni correction. Results Thirteen of 15 experimental regions showed a significant effect of ε4 for higher atrophy rates (P < .001 for all). Cohen d values ranged from 0.26 to 0.42, with the largest effects seen in the amygdalae and hippocampi. The transverse temporal cortex showed a trend (P = .02, but did not survive Bonferroni correction) for a protective effect (Cohen d value = 0.15) of ε2. No control region showed an APOE effect. Conclusion The APOE ε4 allele is associated with accelerated rates of atrophy in 13 distinct brain regions in limbic and neocortical areas. This suggests the possibility of a genotype-specific network of related brain regions that undergo faster atrophy in MCI and potentially contribute to cognitive decline. © RSNA, 2014 Online supplemental material is available for this article.
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    ABSTRACT: Background The genetic factors that determine the heterogeneity of cognitive impairment in Alzheimer’s disease (AD) patients have been rarely reported. We aimed to investigate the association between top hits of genome-wide association studies (GWAS) and specific cognitive domains in AD patients. Methods We investigated 86 single nucleotide polymorphisms (SNPs) selected from 12 genes (ABCA7, APOE, BIN1, CD2AP, CD33, CLU, CR1, EPHA1, LRAT, MS4A6A, PCDH11X, and PICALM) based on results of the recent GWAS and genotyped in 211 AD cases. We also analyzed results of comprehensive neuropsychological evaluations in all cases. We performed multiple regression analyses. Results There were four significant associations between genotypes and phenotypes of AD patients: CR1 SNP rs11803956 correlated with Mini-Mental State Examination (MMSE) score (β = 1.718, Pcorrected = 0.002); ABCA7 SNP rs3752232 correlated with Rey Complex Figure Test (RCFT) copy score (β = − 6.861, Pcorrected = 0.013); APOE SNP rs2075650 correlated with the percentile of RCFT copy score (β = 14.005, Pcorrected = 0.021) and the percentile of total score in phonemic fluency (β = 11.052, Pcorrected = 0.035). Conclusion Our results suggest that CR1, ABCA7, and APOE correlate with specific aspects of cognitive impairments in AD patients.
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