Yen Ying Lim1, Robert Williamson1, Simon M Laws2,3,4, Victor L Villemagne1,5,6, Pierrick Bourgeat7, Christopher Fowler1, Stephanie Rainey-Smith2, Olivier Salvado7, Ralph N Martins2, Christopher C Rowe5,6, Colin L Masters1, Paul Maruff1,8. 1. The Florey Institute of Neuroscience and Mental Health, The University of Melbourne, Parkville, VIC, Australia. 2. Centre of Excellence for Alzheimer's Disease Research and Care, Edith Cowan University, Joondalup, Western Australia, Australia. 3. Co-operative Research Centre for Mental Health, http://www.mentalhealthcrc.com. 4. School of Biomedical Sciences, Faculty of Health Sciences, Curtin Health Innovation Research Institute, Curtin University, Perth, Western Australia, Australia. 5. Department of Nuclear Medicine and Centre for PET, Austin Health, Heidelberg, VIC, Australia. 6. Department of Medicine, Austin Health, The University of Melbourne, Heidelberg, VIC, Australia. 7. CSIRO Preventative Health National Research Flagship, Australian e-Health Research Centre-BiaMedIA, Brisbane, Queensland, Australia. 8. Cogstate Ltd., Melbourne, VIC, Australia.
Abstract
BACKGROUND: The association between the apolipoprotein E (APOE) ɛ4 allele and high risk of developing Alzheimer's disease (AD) dementia before the age of 80 has been recognized for over 30 years. However, the timing and mode of action of APOE is not understood, nor has there been a detailed analysis of the effect of APOE genotype on memory, hippocampal volume, and amyloid-β (Aβ) levels in cognitively normal adults. OBJECTIVE: Examine the effect of APOE allelic genotype on the relationship between Aβ levels, hippocampal volume, and memory in cognitively normal adults. METHODS: This is a cross-sectional study of 989 cognitively normal older adults enrolled in the Australian Imaging, Biomarkers and Lifestyle (AIBL) study, all of whom underwent APOE genotyping and memory assessment. A subset of this group underwent PET neuroimaging for Aβ (n = 585) and MRI for hippocampal volume (n = 303). RESULTS: APOEɛ4 homozygotes (ɛ4/ɛ4) showed significantly worse episodic memory and higher Aβ levels than ɛ4 heterozygotes. The relationship between increasing Aβ levels and worse episodic memory was significant for ɛ3 homozygotes (ɛ3/ɛ3), ɛ4 heterozygotes, and strongest for ɛ4 homozygotes. There were no differences in hippocampal volume between APOE groups; the relationship between smaller hippocampal volume and worse episodic memory was significant only for ɛ4 homozygotes. CONCLUSION: APOE acts in a co-dominant fashion on Aβ levels, episodic memory, and hippocampal volume in cognitively normal older adults. APOEɛ4 is central to the events that lead to AD in cognitively normal older adults, likely through a quantitative role in the disruption of Aβ clearance.
BACKGROUND: The association between the apolipoprotein E (APOE) ɛ4 allele and high risk of developing Alzheimer's disease (AD) dementia before the age of 80 has been recognized for over 30 years. However, the timing and mode of action of APOE is not understood, nor has there been a detailed analysis of the effect of APOE genotype on memory, hippocampal volume, and amyloid-β (Aβ) levels in cognitively normal adults. OBJECTIVE: Examine the effect of APOE allelic genotype on the relationship between Aβ levels, hippocampal volume, and memory in cognitively normal adults. METHODS: This is a cross-sectional study of 989 cognitively normal older adults enrolled in the Australian Imaging, Biomarkers and Lifestyle (AIBL) study, all of whom underwent APOE genotyping and memory assessment. A subset of this group underwent PET neuroimaging for Aβ (n = 585) and MRI for hippocampal volume (n = 303). RESULTS:APOEɛ4 homozygotes (ɛ4/ɛ4) showed significantly worse episodic memory and higher Aβ levels than ɛ4 heterozygotes. The relationship between increasing Aβ levels and worse episodic memory was significant for ɛ3 homozygotes (ɛ3/ɛ3), ɛ4 heterozygotes, and strongest for ɛ4 homozygotes. There were no differences in hippocampal volume between APOE groups; the relationship between smaller hippocampal volume and worse episodic memory was significant only for ɛ4 homozygotes. CONCLUSION:APOE acts in a co-dominant fashion on Aβ levels, episodic memory, and hippocampal volume in cognitively normal older adults. APOEɛ4 is central to the events that lead to AD in cognitively normal older adults, likely through a quantitative role in the disruption of Aβ clearance.
Authors: Laura B Zahodne; Elizabeth Rose Mayeda; Timothy J Hohman; Evan Fletcher; Annie M Racine; Brandon Gavett; Jennifer J Manly; Nicole Schupf; Richard Mayeux; Adam M Brickman; Dan Mungas Journal: Neurobiol Aging Date: 2019-08-14 Impact factor: 4.673
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Authors: Christopher Fowler; Stephanie R Rainey-Smith; Sabine Bird; Julia Bomke; Pierrick Bourgeat; Belinda M Brown; Samantha C Burnham; Ashley I Bush; Carolyn Chadunow; Steven Collins; James Doecke; Vincent Doré; Kathryn A Ellis; Lis Evered; Amir Fazlollahi; Jurgen Fripp; Samantha L Gardener; Simon Gibson; Robert Grenfell; Elise Harrison; Richard Head; Liang Jin; Adrian Kamer; Fiona Lamb; Nicola T Lautenschlager; Simon M Laws; Qiao-Xin Li; Lucy Lim; Yen Ying Lim; Andrea Louey; S Lance Macaulay; Lucy Mackintosh; Ralph N Martins; Paul Maruff; Colin L Masters; Simon McBride; Lidija Milicic; Madeline Peretti; Kelly Pertile; Tenielle Porter; Morgan Radler; Alan Rembach; Joanne Robertson; Mark Rodrigues; Christopher C Rowe; Rebecca Rumble; Olivier Salvado; Greg Savage; Brendan Silbert; Magdalene Soh; Hamid R Sohrabi; Kevin Taddei; Tania Taddei; Christine Thai; Brett Trounson; Regan Tyrrell; Michael Vacher; Shiji Varghese; Victor L Villemagne; Michael Weinborn; Michael Woodward; Ying Xia; David Ames Journal: J Alzheimers Dis Rep Date: 2021-06-03
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