AUTHOR=Rudroff Thorsten , Kindred John H. , Benson John-Michael , Tracy Brian L. , Kalliokoski Kari K. 

TITLE=Greater glucose uptake heterogeneity in knee muscles of old compared to young men during isometric contractions detected by [18F]-FDG PET/CT

JOURNAL=Frontiers in Physiology

VOLUME=Volume 5 - 2014

YEAR=2014

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2014.00198

DOI=10.3389/fphys.2014.00198

ISSN=1664-042X

ABSTRACT=We used positron emission tomography/computed tomography (PET/CT) and [18F]-FDG to test the hypothesis that glucose uptake (GU) heterogeneity in skeletal muscles as a measure of heterogeneity in muscle activity is greater in old than young men when they perform isometric contractions.  Six young (26 ± 6 yrs) and six old (77 ± 6 yrs) men performed two types of submaximal isometric contractions that required either force or position control.  [18F]-FDG was injected during the task and PET/CT scans were performed immediately after the task.  Within-muscle heterogeneity of knee muscles was determined by calculating the coefficient of variation (CV) of GU in PET image voxels within the muscles of interest.  The average GU heterogeneity (mean ± SD) for knee extensors and flexors was greater for the old (35.3 ± 3.3 %) than the young (28.6 ± 2.4 %) (P = 0.006).  Muscle volume of the knee extensors were greater for the young compared to the old men (1016 ± 163 vs. 598 ± 70 cm3, P= 0.004).  In a multiple regression model, knee extensor muscle volume was a predictor (partial r = - 0.87; P = 0.001) of GU heterogeneity for old men (R2 = 0.78; P < 0.001), and MVC force predicted GU heterogeneity for young men (partial r = - 0.95, P < 0.001).  The findings demonstrate that glucose uptake is more spatially variable for old than young men and especially so for old men who exhibit greater muscle atrophy.