AUTHOR=Castellano Christian-Alexandre , Hudon Carol , Croteau Etienne , Fortier Mélanie , St-Pierre Valérie , Vandenberghe Camille , Nugent Scott , Tremblay Sébastien , Paquet Nancy , Lepage Martin , Fülöp Tamàs , Turcotte Éric E. , Dionne Isabelle J. , Potvin Olivier , Duchesne Simon , Cunnane Stephen C. 

TITLE=Links Between Metabolic and Structural Changes in the Brain of Cognitively Normal Older Adults: A 4-Year Longitudinal Follow-Up

JOURNAL=Frontiers in Aging Neuroscience

VOLUME=11

YEAR=2019

URL=https://www.frontiersin.org/journals/aging-neuroscience/articles/10.3389/fnagi.2019.00015

DOI=10.3389/fnagi.2019.00015

ISSN=1663-4365

ABSTRACT=<p>We aimed to longitudinally assess the relationship between changing brain energy metabolism (glucose and acetoacetate) and cognition during healthy aging. Participants aged 71 ± 5 year underwent cognitive evaluation and quantitative positron emission tomography (PET) and magnetic resonance imaging (MRI) scans at baseline (<italic>N</italic> = 25) and two (<italic>N</italic> = 25) and four (<italic>N</italic> = 16) years later. During the follow-up, the rate constant for brain extraction of glucose (K<sub>glc</sub>) declined by 6%–12% mainly in the temporo-parietal lobes and cingulate gyri (<italic>p</italic> ≤ 0.05), whereas brain acetoacetate extraction (Kacac) and utilization remained unchanged in all brain regions (<italic>p</italic> ≥ 0.06). Over the 4 years, cognitive results remained within the normal age range but an age-related decline was observed in processing speed. K<sub>glc</sub> in the caudate was directly related to performance on several cognitive tests (<italic>r</italic> = +0.41 to +0.43, <italic>all</italic><italic>p</italic> ≤ 0.04). Peripheral insulin resistance assessed by the homeostasis model assessment of insulin resistance (HOMA-IR) was significantly inversely related to K<sub>glc</sub> in the thalamus (<italic>r</italic> = −0.44, <italic>p</italic> = 0.04) and in the caudate (<italic>r</italic> = −0.43, <italic>p</italic> = 0.05), and also inversely related to executive function, attention and processing speed (<italic>r</italic> = −0.45 to −0.53, all <italic>p</italic> ≤ 0.03). We confirm in a longitudinal setting that the age-related decline in K<sub>glc</sub> is directly associated with declining performance on some tests of cognition but does not significantly affect Kacac.</p>