title: Resting-state functional connectivity changes in aging apoE4 and apoE-KO mice.
abstract: It is well established that the cholesterol-transporter apolipoprotein ε (APOE) genotype is associated with the risk of developing neurodegenerative diseases. Recently, brain functional connectivity (FC) in apoE-ε4 carriers has been investigated by means of resting-state fMRI, showing a marked differentiation in several functional networks at different ages compared with carriers of other apoE isoforms. The causes of such hampered FC are not understood. We hypothesize that vascular function and synaptic repair processes, which are both impaired in carriers of ε4, are the major contributors to the loss of FC during aging. To test this hypothesis, we integrated several different MRI techniques with immunohistochemistry and investigated FC changes in relation with perfusion, diffusion, and synaptic density in apoE4 and apoE-knock-out (KO) mice at 12 (adult) and 18 months of age. Compared with wild-type mice, we detected FC deficits in both adult and old apoE4 and apoE-KO mice. In apoE4 mice, these changes occurred concomitant with increased mean diffusivity in the hippocampus, whereas perfusion deficits appear only later in life, together with reduced postsynaptic density levels. Instead, in apoE-KO mice FC deficits were mirrored by strongly reduced brain perfusion since adulthood. In conclusion, we provide new evidence for a relation between apoE and brain connectivity, possibly mediated by vascular risk factors and by the efficiency of APOE as synaptic modulator in the brain. Our results show that multimodal MR neuroimaging is an excellent tool to assess brain function and to investigate early neuropathology and aging effects in translational research.
authors.affiliation: Departments of Anatomy, Donders Institute for Brain Cognition and Behaviour, Radiology.
authors.forename: Valerio
authors.initials: V
authors.lastname: Zerbi
authors.affiliation: Departments of Anatomy, Donders Institute for Brain Cognition and Behaviour, Geriatric Medicine, and.
authors.forename: Maximilian
authors.initials: M
authors.lastname: Wiesmann
authors.affiliation: Departments of Anatomy, Donders Institute for Brain Cognition and Behaviour.
authors.forename: Tim L
authors.initials: TL
authors.lastname: Emmerzaal
authors.affiliation: Departments of Anatomy, Donders Institute for Brain Cognition and Behaviour.
authors.forename: Diane
authors.initials: D
authors.lastname: Jansen
authors.affiliation: Departments of Anatomy, Donders Institute for Brain Cognition and Behaviour.
authors.forename: Maarten
authors.initials: M
authors.lastname: Van Beek
authors.affiliation: Departments of Anatomy, Donders Institute for Brain Cognition and Behaviour.
authors.forename: Martina P C
authors.identifier: http://orcid.org/0000-0001-8196-2137
authors.initials: MP
authors.lastname: Mutsaers
authors.affiliation: Donders Centre for Cognitive Neuroimaging, Radboud university medical center, 6525 EZ Nijmegen, The Netherlands, and MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, 7500 AE Enschede, The Netherlands.
authors.forename: Christian F
authors.initials: CF
authors.lastname: Beckmann
authors.affiliation: Radiology.
authors.forename: Arend
authors.initials: A
authors.lastname: Heerschap
authors.affiliation: Departments of Anatomy, Donders Institute for Brain Cognition and Behaviour, Amanda.Kiliaan@radboudumc.nl.
authors.forename: Amanda J
authors.initials: AJ
authors.lastname: Kiliaan
mesh_terms: D000375:Aging / Q000378:metabolism* / Q000473:pathology; D000818:Animals; D053327:Apolipoprotein E4 / Q000172:deficiency*; D001057:Apolipoproteins E / Q000172:deficiency; D001921:Brain / Q000378:metabolism* / Q000473:pathology; D002478:Cells, Cultured; D005260:Female; D006801:Humans; D008297:Male; D051379:Mice; D057507:Mice, 129 Strain; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D009415:Nerve Net / Q000378:metabolism* / Q000473:pathology; D012146:Rest / Q000502:physiology*
chemical_list: D053327:Apolipoprotein E4; D001057:Apolipoproteins E
keywords: apoE; apoE4 mice; cerebral blood flow; diffusion tensor imaging; functional connectivity; resting-state fMRI