Skeletal muscle: Energy metabolism, fiber types, fatigue and adaptability |
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Authors: | Håkan Westerblad Joseph D Bruton Abram Katz |
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Institution: | Department of Physiology and Pharmacology, Karolinska Institutet, 171 77 Stockholm, Sweden |
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Abstract: | Skeletal muscles cope with a large range of activities, from being able to support the body weight during long periods of upright standing to perform explosive movements in response to an unexpected threat. This requires systems for energy metabolism that can provide energy during long periods of moderately increased energy consumption as well as being able to rapidly increasing the rate of energy production more than 100-fold in response to explosive contractions. In this short review we discuss how muscles can deal with these divergent demands. We first outline the major energy metabolism pathways in skeletal muscle. Next we describe metabolic differences between different muscle fiber types. Contractile performance declines during intense activation, i.e. fatigue develops, and we discuss likely underlying mechanisms. Finally, we discuss the ability of muscle fibers to adapt to altered demands, and mechanisms behind these adaptations. The accumulated experimental evidence forces us to conclude that most aspects of energy metabolism involve multiple and overlapping signaling pathways, which indicates that the control of energy metabolism is too important to depend on one single molecule or mechanism. |
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Keywords: | AMPK AMP-dependent protein kinase [Ca2+]i cytosolic free Ca2+ concentration Cr creatine MAPK mitogen-activated protein kinase MHC myosin heavy chain PCr phosphocreatine PGC-1α peroxisome proliferator-activated receptor gamma coactivator 1α Pi inorganic phosphate ions ROS reactive oxygen species SERCA sarcoplasmic reticulum Ca2+ pump SR sarcoplasmic reticulum |
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