MRI of carriers of the apolipoprotein E e4 allele–evidence for structural differences in normal‐appearing brain tissue in e4+ relative to e4– young adults. (31st January 2013)

• Record Type: Journal Article
• Authors: Dowell, Nicholas G.; Ruest, Torsten; Evans, Simon L.; King, Sarah L.; Tabet, Naji; Tofts, Paul S.; Rusted, Jennifer M.
• Is Part Of: NMR in biomedicine. Volume 26:Number 6(2013:Jun.)
• Page Start: 674
• Page End: 682
• Publication Date: 2013-01-31
• Subjects: apolipoprotein E e4 -- diffusion tensor imaging -- quantitative magnetisation transfer -- tract‐based spatial statistics -- voxel‐based morphometry -- cognition -- neural efficiency; Nuclear magnetic resonance -- Periodicals; Magnetic Resonance Spectroscopy -- Periodicals; 574
• DOI: 10.1002/nbm.2912
• Languages: English
• ISSNs: 0952-3480

Abstract

Abstract : Apolipoprotein E is a protein involved in cholesterol and lipid transport. The gene coding for this protein has three different alleles: e2, e3 and e4. The e4 allele is recognised as a significant risk factor for the development of Alzheimer's disease in later life. Paradoxically, behavioural and functional evidence has demonstrated that the e4 allele may confer a cognitive advantage to the carrier in youth. In this article, a range of sophisticated and novel structural imaging techniques were used to identify subtle differences in the brain tissue of groups of young e4 and homozygous e3 carriers that might support this paradox. Using voxel‐based morphometry of high‐resolution structural MR images, we identified a higher white matter volume ratio in e4 relative to homozygous e3 carriers. Furthermore, diffusion tensor imaging and tract‐based spatial statistics studies identified increases in axial diffusivity and mode of anisotropy in carriers of the e4 allele. In addition, quantitative magnetisation transfer data were analysed using tract‐based spatial statistics. Evidence of a trend towards an increased transverse relaxation time of the bound proton pool was detected in e4 carriers, indicative of altered white matter composition. These changes were found to correlate with indices of cognitive performance across the two groups, supporting the notion that such subtle differences in white matter integrity may confer neural advantages that contribute to cognitive outcomes and, potentially, to performance differences, such as observed here in a test of verbal fluency and reported previously by other researchers. Copyright © 2013 John Wiley & Sons, Ltd. Abstract : We present the first study to show subtle differences in the brains of young healthy adult e4+ and e4– subpopulations. These differences were detected in normal‐appearing brain tissue using a range of sophisticated and novel structural imaging techniques. We suggest that such subtle differences in white matter integrity may confer neural efficiency advantages, and hence give rise to the performance differences in tests of verbal fluency.