Evidence against altered excitatory/inhibitory balance in the posteromedial cortex of young adult APOE E4 carriers: A resting state 1H-MRS study

A strategy to gain insight into early changes that may predispose people to Alzheimer's disease (AD) is to study the brains of younger cognitively healthy people that are at increased genetic risk of AD. The Apolipoprotein (APOE) E4 allele is the strongest genetic risk factor for AD, and severa...

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Autores principales:	A.G. Costigan, K. Umla-Runge, C.J. Evans, R. Raybould, K.S. Graham, A.D. Lawrence
Formato:	article
Lenguaje:	EN
Publicado:	Elsevier 2021
Materias:	Alzheimer's disease APOE E4 Default network Glutamate GABA 1H-MRS Neurosciences. Biological psychiatry. Neuropsychiatry RC321-571
Acceso en línea:	https://doaj.org/article/a56bd27418a444c58765ccebaeabfe5a
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spelling	oai:doaj.org-article:a56bd27418a444c58765ccebaeabfe5a2021-11-12T04:49:31ZEvidence against altered excitatory/inhibitory balance in the posteromedial cortex of young adult APOE E4 carriers: A resting state 1H-MRS study2666-956010.1016/j.ynirp.2021.100059https://doaj.org/article/a56bd27418a444c58765ccebaeabfe5a2021-12-01T00:00:00Zhttp://www.sciencedirect.com/science/article/pii/S266695602100057Xhttps://doaj.org/toc/2666-9560A strategy to gain insight into early changes that may predispose people to Alzheimer's disease (AD) is to study the brains of younger cognitively healthy people that are at increased genetic risk of AD. The Apolipoprotein (APOE) E4 allele is the strongest genetic risk factor for AD, and several neuroimaging studies comparing APOE E4 carriers with non-carriers at age ∼20–30 years have detected hyperactivity (or reduced deactivation) in posteromedial cortex (PMC), a key hub of the default network (DN), which has a high susceptibility to early amyloid deposition in AD. Transgenic mouse models suggest such early network activity alterations may result from altered excitatory/inhibitory (E/I) balance, but this is yet to be examined in humans. Here we test the hypothesis that PMC fMRI hyperactivity could be underpinned by altered levels of excitatory (glutamate) and/or inhibitory (GABA) neurotransmitters in this brain region. Forty-seven participants (20 APOE E4 carriers and 27 non-carriers) aged 18–25 years underwent resting-state proton magnetic resonance spectroscopy (1H-MRS), a non-invasive neuroimaging technique to measure glutamate and GABA in vivo. Metabolites were measured in a PMC voxel of interest and in a comparison voxel in the occipital cortex (OCC). There was no difference in either glutamate or GABA between the E4 carriers and non-carriers in either MRS voxel, or in the ratio of glutamate to GABA, a measure of E/I balance. Default Bayesian t-tests revealed evidence in support of this null finding. Our findings suggest that PMC hyperactivity in APOE E4 carriers is unlikely to be associated with, or possibly may precede, alterations in local resting-state PMC neurotransmitters, thus informing our understanding of the spatio-temporal sequence of early network alterations underlying APOE E4 related AD risk.A.G. CostiganK. Umla-RungeC.J. EvansR. RaybouldK.S. GrahamA.D. LawrenceElsevierarticleAlzheimer's diseaseAPOE E4Default networkGlutamateGABA1H-MRSNeurosciences. Biological psychiatry. NeuropsychiatryRC321-571ENNeuroimage: Reports, Vol 1, Iss 4, Pp 100059- (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	Alzheimer's disease APOE E4 Default network Glutamate GABA 1H-MRS Neurosciences. Biological psychiatry. Neuropsychiatry RC321-571
spellingShingle	Alzheimer's disease APOE E4 Default network Glutamate GABA 1H-MRS Neurosciences. Biological psychiatry. Neuropsychiatry RC321-571 A.G. Costigan K. Umla-Runge C.J. Evans R. Raybould K.S. Graham A.D. Lawrence Evidence against altered excitatory/inhibitory balance in the posteromedial cortex of young adult APOE E4 carriers: A resting state 1H-MRS study
description	A strategy to gain insight into early changes that may predispose people to Alzheimer's disease (AD) is to study the brains of younger cognitively healthy people that are at increased genetic risk of AD. The Apolipoprotein (APOE) E4 allele is the strongest genetic risk factor for AD, and several neuroimaging studies comparing APOE E4 carriers with non-carriers at age ∼20–30 years have detected hyperactivity (or reduced deactivation) in posteromedial cortex (PMC), a key hub of the default network (DN), which has a high susceptibility to early amyloid deposition in AD. Transgenic mouse models suggest such early network activity alterations may result from altered excitatory/inhibitory (E/I) balance, but this is yet to be examined in humans. Here we test the hypothesis that PMC fMRI hyperactivity could be underpinned by altered levels of excitatory (glutamate) and/or inhibitory (GABA) neurotransmitters in this brain region. Forty-seven participants (20 APOE E4 carriers and 27 non-carriers) aged 18–25 years underwent resting-state proton magnetic resonance spectroscopy (1H-MRS), a non-invasive neuroimaging technique to measure glutamate and GABA in vivo. Metabolites were measured in a PMC voxel of interest and in a comparison voxel in the occipital cortex (OCC). There was no difference in either glutamate or GABA between the E4 carriers and non-carriers in either MRS voxel, or in the ratio of glutamate to GABA, a measure of E/I balance. Default Bayesian t-tests revealed evidence in support of this null finding. Our findings suggest that PMC hyperactivity in APOE E4 carriers is unlikely to be associated with, or possibly may precede, alterations in local resting-state PMC neurotransmitters, thus informing our understanding of the spatio-temporal sequence of early network alterations underlying APOE E4 related AD risk.
format	article
author	A.G. Costigan K. Umla-Runge C.J. Evans R. Raybould K.S. Graham A.D. Lawrence
author_facet	A.G. Costigan K. Umla-Runge C.J. Evans R. Raybould K.S. Graham A.D. Lawrence
author_sort	A.G. Costigan
title	Evidence against altered excitatory/inhibitory balance in the posteromedial cortex of young adult APOE E4 carriers: A resting state 1H-MRS study
title_short	Evidence against altered excitatory/inhibitory balance in the posteromedial cortex of young adult APOE E4 carriers: A resting state 1H-MRS study
title_full	Evidence against altered excitatory/inhibitory balance in the posteromedial cortex of young adult APOE E4 carriers: A resting state 1H-MRS study
title_fullStr	Evidence against altered excitatory/inhibitory balance in the posteromedial cortex of young adult APOE E4 carriers: A resting state 1H-MRS study
title_full_unstemmed	Evidence against altered excitatory/inhibitory balance in the posteromedial cortex of young adult APOE E4 carriers: A resting state 1H-MRS study
title_sort	evidence against altered excitatory/inhibitory balance in the posteromedial cortex of young adult apoe e4 carriers: a resting state 1h-mrs study
publisher	Elsevier
publishDate	2021
url	https://doaj.org/article/a56bd27418a444c58765ccebaeabfe5a
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Evidence against altered excitatory/inhibitory balance in the posteromedial cortex of young adult APOE E4 carriers: A resting state 1H-MRS study

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