Evidence of a metabolic reserve in the skeletal muscle of elderly people.
The purpose of the present study was to determine whether mitochondrial function is limited by O2availability 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 O2availability 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 O2delivery (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 O2availability enhanced mitochondrial function thus indicating a skeletal muscle metabolic reserve despite advancing age and low level of physical activity.
Department of Medicine, Division of Geriatrics, University of Utah, Salt Lake City, UT 84112, USA.|Geriatric Research, Education, and Clinical Center, George E. Whalen VA Medical Center, Salt Lake City, UT 84112, USA.
Gwenael
G
Layec
Department of Medicine, Division of Geriatrics, University of Utah, Salt Lake City, UT 84112, USA.|Geriatric Research, Education, and Clinical Center, George E. Whalen VA Medical Center, Salt Lake City, UT 84112, USA.
Joel D
JD
Trinity
Geriatric Research, Education, and Clinical Center, George E. Whalen VA Medical Center, Salt Lake City, UT 84112, USA.|Department of Exercise and Sport Science, University of Utah, Salt Lake City, UT 84112, USA.
Corey R
CR
Hart
CRMBM, Aix-Marseille Universite, CNRS 7339, Marseille, France.
Yann
Y
Le Fur
Geriatric Research, Education, and Clinical Center, George E. Whalen VA Medical Center, Salt Lake City, UT 84112, USA.|Department of Exercise and Sport Science, University of Utah, Salt Lake City, UT 84112, USA.
Jacob R
JR
Sorensen
Department of Radiology and Utah Center for Advanced Imaging Research, University of Utah, Salt Lake City, UT 84112, USA.
Eun-Kee
EK
Jeong
Department of Medicine, Division of Geriatrics, University of Utah, Salt Lake City, UT 84112, USA.|Geriatric Research, Education, and Clinical Center, George E. Whalen VA Medical Center, Salt Lake City, UT 84112, USA.|Department of Exercise and Sport Science, University of Utah, Salt Lake City, UT 84112, USA.
Russell S
RS
Richardson
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000368:Aged; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008875:Middle Aged; D008931:Mitochondria, Muscle / Q000378:metabolism*; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000098:blood supply / Q000378:metabolism*; D010101:Oxygen Consumption / Q000502:physiology*; D012039:Regional Blood Flow / Q000502:physiology
D000255:Adenosine Triphosphate
O availability 2; P-MRS 31; PCr recovery kinetics; aging; mitochondrial ATP synthesis