Time course of exercise-induced decline in malonyl-CoA in different muscle types.
Malonyl-CoA is a potent inhibitor of carnitine palmitoyltransferase I (CPT-I), the rate-limiting enzyme for fatty acid oxidation in mitochondria from liver of fed rats. Malonyl-CoA has also been demonstrated to inhibit skeletal muscle CPT-I. This study was designed to determine the rate of decline in malonyl-CoA in muscle during the course of a prolonged exercise bout. Adult male rats were anesthetized (pentobarbital sodium, intravenously) at rest or after running for 5, 10, 20, 30, 60, or 120 min on a treadmill (21 m/min, 15% grade). Malonyl-CoA was then quantitated in the soleus (type I fibers) and in the superficial white (type IIB) and deep red (type IIA) regions of the quadriceps. Malonyl-CoA decreased in red quadriceps from 2.8 +/- 0.2 to 1.4 +/- 0.2 pmol/mg after 5 min and to 0.9 +/- 0.1 pmol/mg after 20 min of exercise. The concentration of malonyl-CoA remained at this level for the duration of the exercise bout (120 min). In white quadriceps, resting values of malonyl-CoA were lower than in red quadriceps, and a significant decline was not observed until 30 min of exercise. A significant decrease in the soleus was observed after 20 min of exercise. This decline in muscle malonyl-CoA may be an important signal for allowing increased fatty acid oxidation during long-term exercise.
Winder
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WW
Zoology Department, Brigham Young University, Provo, Utah 84602.
Arogyasami
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J
Elayan
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IM
Cartmill
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D000214:Acyl Coenzyme A / Q000378:metabolism*; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D002334:Carnitine O-Palmitoyltransferase / Q000378:metabolism; D003576:Electron Transport Complex IV / Q000378:metabolism; D005230:Fatty Acids, Nonesterified / Q000097:blood; D006003:Glycogen / Q000378:metabolism; D007700:Kinetics; D008297:Male; D008316:Malonyl Coenzyme A / Q000378:metabolism*; D008931:Mitochondria, Muscle / Q000201:enzymology; D009132:Muscles / Q000378:metabolism / Q000502:physiology*; D009928:Organ Specificity; D005082:Physical Exertion; D051381:Rats; D011919:Rats, Inbred Strains; D012420:Running; D013997:Time Factors
D000214:Acyl Coenzyme A; D001786:Blood Glucose; D005230:Fatty Acids, Nonesterified; D008316:Malonyl Coenzyme A; D006003:Glycogen; D003576:Electron Transport Complex IV; D002334:Carnitine O-Palmitoyltransferase