Symmetry and spatial distribution of muscle glucose uptake in the lower limbs during walking measured using FDG-PET

PLoS One. 2019 Apr 29;14(4):e0215276. doi: 10.1371/journal.pone.0215276. eCollection 2019.

Abstract

Purpose: This study aimed to elucidate whether muscle activity (in terms of glucose uptake) between the legs can be considered symmetrical during walking. Furthermore, we aimed to determine whether the [18F]-fluorodeoxyglucose was distributed heterogeneously throughout each muscle, and if so, whether areas of high uptake would be clustered.

Methods: Ten healthy participants walked on a treadmill at self-selected comfortable walking speed for a total of 90 minutes, 60 minutes before and 30 minutes after intravenous injection of 50 MBq [18F]-fluorodeoxyglucose. Thereafter, a positron emission tomography/computed tomography scan of the lower limb was acquired. Three-dimensional muscle contours of 78 (= 39x2) muscles of the left and right lower limb were semi-automatically determined from magnetic resonance imaging scans. After non-rigid registration, those muscle contours were used to extract [18F]-fluorodeoxyglucose uptake from the positron emission tomography scans.

Results: Large asymmetries were observed in the lower leg muscles (e.g. median absolute asymmetry index of 42% in the gastrocnemius medialis) and in the gluteus minimus (30% asymmetry) and gluteus medius (15% asymmetry), whereas the uptake in the thighs was relatively symmetrical between the limbs (<6% asymmetry). These were not related to limb-dominance nor to inter-limb differences in muscle volume. The [18F]-fluorodeoxyglucose distribution was not distributed normally; most voxels had a relatively low standardized uptake value, and a minority of voxels had a relatively high standardized uptake value. The voxels with higher [18F]-fluorodeoxyglucose uptake were distributed heterogeneously; they were clustered in virtually all muscles.

Conclusion: The findings in this study challenge the common assumption of symmetry in muscle activity between the limbs in healthy subjects. The clustering of voxels with high uptake suggests that even in this prolonged repetitive task, different spatial regions of muscles contribute differently to walking than others.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Biological Transport, Active
  • Female
  • Fluorodeoxyglucose F18 / pharmacokinetics
  • Glucose / metabolism*
  • Healthy Volunteers
  • Humans
  • Imaging, Three-Dimensional
  • Lower Extremity / diagnostic imaging
  • Male
  • Middle Aged
  • Models, Biological
  • Muscle, Skeletal / diagnostic imaging*
  • Muscle, Skeletal / metabolism*
  • Positron Emission Tomography Computed Tomography
  • Radiopharmaceuticals / pharmacokinetics
  • Walking / physiology*
  • Young Adult

Substances

  • Radiopharmaceuticals
  • Fluorodeoxyglucose F18
  • Glucose

Grant support

We gratefully acknowledge financial support by the Seventh Framework Programme of the European Union for the TLEMsafe project (grant FP7-ICT-247860 to NV, http://www.tlemsafe.eu). The funder provided support in the form of salaries for authors SK, JS, NV, VW, but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of these authors are articulated in the ‘author contributions’ section.