Effect of exercise intensity on skeletal muscle malonyl-CoA and acetyl-CoA carboxylase.
Malonyl-CoA is synthesized by acetyl-CoA carboxylase (ACC) and is an inhibitor of fatty acid oxidation. Exercise induces a decline in skeletal muscle malonyl-CoA, which is accompanied by inactivation of ACC and increased activity of AMP-activated protein kinase (AMPK). This study was designed to determine the effect of exercise intensity on the enzyme kinetics of ACC, malonyl-CoA levels, and AMPK activity in skeletal muscle. Male Sprague-Dawley rats were killed (pentobarbital sodium anesthesia) at rest or after 5 min of exercise (10, 20, 30, or 40 m/min at 5% grade). The fast-twitch red and white regions of the quadriceps muscle were excised and frozen in liquid nitrogen. A progressive decrease in red quadriceps ACC maximal velocity (from 28.6 +/- 1.5 to 14.3 +/- 0.7 nmol . g-1 . min-1, P < 0.05), an increase in activation constant for citrate, and a decrease in malonyl-CoA (from 1.9 +/- 0.2 to 0.9 +/- 0.1 nmol/g, P < 0.05) were seen with the increase in exercise intensity from rest to 40 m/min. AMPK activity increased more than twofold. White quadriceps ACC activity decreased only during intense exercise. We conclude that the extent of ACC inactivation during short-term exercise is dependent on exercise intensity.
Rasmussen
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BB
Department of Zoology, Brigham Young University, Provo, Utah 84602, USA.
Winder
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WW
D055372:AMP-Activated Protein Kinases; D000103:Acetyl-CoA Carboxylase / Q000378:metabolism*; D000818:Animals; D007700:Kinetics; D008297:Male; D008316:Malonyl Coenzyme A / Q000378:metabolism*; D009097:Multienzyme Complexes / Q000378:metabolism; D018656:Muscle Fibers, Fast-Twitch / Q000201:enzymology; D018482:Muscle, Skeletal / Q000201:enzymology*; D005082:Physical Exertion / Q000502:physiology*; D011494:Protein Kinases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases; D051381:Rats; D017207:Rats, Sprague-Dawley
D009097:Multienzyme Complexes; D008316:Malonyl Coenzyme A; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; D055372:AMP-Activated Protein Kinases; D000103:Acetyl-CoA Carboxylase