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Research Paper|Volume 9, Issue 1|pp 52—67

Evidence of a metabolic reserve in the skeletal muscle of elderly people

Gwenael Layec1,2, Joel D. Trinity1,2, Corey R. Hart2,3, Yann Le Fur5, Jacob R. Sorensen2,3, Eun-Kee Jeong4, Russell S. Richardson1,2,3
  • 1Department of Medicine, Division of Geriatrics, University of Utah, Salt Lake City, UT 84112, USA
  • 2Geriatric Research, Education, and Clinical Center, George E. Whalen VA Medical Center, Salt Lake City, UT 84112, USA
  • 3Department of Exercise and Sport Science, University of Utah, Salt Lake City, UT 84112, USA
  • 4Department of Radiology and Utah Center for Advanced Imaging Research, University of Utah, Salt Lake City, UT 84112, USA
  • 5CRMBM, Aix-Marseille Universite, CNRS 7339, Marseille, France
Received: June 1, 2016Accepted: October 20, 2016Published: November 6, 2016
https://doi.org/10.18632/aging.101079

Copyright: © 2016 Layec et al. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Abstract

The purpose of the present study was to determine whether mitochondrial function is limited by O2 availability or the intrinsic capacity of mitochondria to synthesize ATP in elderly individuals. To this aim, we examined, in comparison to free-flow conditions (FF), the effect of superimposing reactive hyperemia (RH), induced by a period of brief ischemia during the last min of exercise, on O2 availability and mitochondrial function in the calf muscle. 12 healthy, untrained, elderly subjects performed dynamic plantar flexion exercise and phosphorus magnetic resonance spectroscopy (31P-MRS), near-infrared spectroscopy (NIRS), and Doppler ultrasound were used to assess muscle metabolism and peripheral hemodynamics. Limb blood flow [area under the curve (AUC), FF: 1.5±0.5L; RH: 3.2±1.1L, P<0.01] and convective O2 delivery (AUC, FF: 0.30±0.13L; RH: 0.64±0.29L, P<0.01) were significantly increased in RH in comparison to FF. RH was also associated with significantly higher capillary blood flow (P<0.05) and this resulted in a 33% increase in estimated peak mitochondrial ATP synthesis rate (FF: 24±11 mM.min-1; RH: 31±7 mM.min-1, P<0.05). These results document a hemodynamic reserve in the contracting calf muscle of the elderly accessible by superimposing reactive hyperemia. Furthermore, this increase in O2 availability enhanced mitochondrial function thus indicating a skeletal muscle metabolic reserve despite advancing age and low level of physical activity.