Regional differences in blood flow, glucose uptake and fatty acid uptake within quadriceps femoris muscle during dynamic
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ORIGINAL ARTICLE
Regional differences in blood flow, glucose uptake and fatty acid uptake within quadriceps femoris muscle during dynamic knee-extension exercise M. S. Laaksonen • J. Kemppainen • H. Kyro¨la¨inen J. Knuuti • P. Nuutila • K. K. Kalliokoski
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Received: 26 August 2012 / Accepted: 6 February 2013 / Published online: 17 February 2013 Ó Springer-Verlag Berlin Heidelberg 2013
Abstract The purpose of the present study was to investigate the regional differences in glucose and fatty acid uptake within skeletal muscle during exercise. Blood flow (BF), glucose uptake (GU) and free fatty acid uptake (FFAU) were measured in four different regions (vastus lateralis, VL; rectus femoris, RF; vastus intermedius, VI; and vastus medialis, VM) of the quadriceps femoris (QF) muscle during low-intensity, knee-extension exercise using positron emission tomography. BF was higher in VI than in VL, RF and VM (P \ 0.05). FFAU was higher in VI (P \ 0.001) but also in VM (P \ 0.05) compared with VL and RF. In contrast, GU was higher in RF compared with VL (P \ 0.05) but was not significantly different to VM or VI (both P = NS). FFAU within these four muscle regions correlated significantly with BF (r = 0.951, P \ 0.05), whereas no significant relationship was observed between GU and BF (r = 0.352, P = NS). Therefore, skeletal
Communicated by David C. Poole. M. S. Laaksonen (&) Department of Health Sciences, Swedish Winter Sports Research ¨ stersund, Sweden Centre, Mid Sweden University, SE-831 25 O e-mail: [email protected] J. Kemppainen J. Knuuti P. Nuutila K. K. Kalliokoski Turku PET Centre, University of Turku, Turku, Finland J. Kemppainen K. K. Kalliokoski Department of Clinical Physiology and Nuclear Medicine, University of Turku, Turku, Finland H. Kyro¨la¨inen Department of Biology of Physical Activity, Neuromuscular Research Centre, University of Jyva¨skyla¨, Jyva¨skyla¨, Finland P. Nuutila Department of Medicine, University of Turku, Turku, Finland
muscle FFAU, but not GU, appears to be associated with BF during low-intensity exercise. The present results also indicate considerable regional differences in substrate use within working QF muscle. As such, an important methodological outcome from these results is that one sample from a specific part of the QF muscle does not represent the response in the entire QF muscle group. Keywords Skeletal muscle Perfusion Energy metabolism Heterogeneity
Introduction The use and uptake of different energy substrates in skeletal muscle during exercise are regulated by several different factors and complex systems. In general, glucose uptake (GU) and plasma free fatty acid uptake (FFAU) are dependent on exercise intensity (Romijn et al. 1993) and duration (Ahlborg et al. 1974; Wolfe et al. 1990), but also on the level of substrate delivery (i.e. blood flow, BF) (Ahlborg et al. 1974) and transport capacities across the vascular endothelium and plasma membrane (Holloway et al. 2008). During exercise, the muscle BF increases markedly (Andersen and Saltin 1985), th
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