title: Long- and medium-chain fatty acid oxidation is increased in exercise-trained human skeletal muscle.
abstract: The purpose of this study was to test the hypothesis that skeletal muscle fatty acid oxidation is enhanced by increased entry into the mitochondria with exercise training. Muscle was obtained from young ( approximately 24 years) sedentary (n = 13) and endurance-trained (n = 10) volunteers and oxidation studied by measuring (14)CO(2) production from labeled medium-chain (MCFA) or long-chain (LCFA) fatty acids in muscle homogenate preparations. LCFA (palmitate) oxidation was (P <.05) approximately 34% higher in the trained than sedentary subjects (26.9 +/- 3.0 v 17.8 +/- 1.3 nmol CO(2)/g x h). MCFA (octanoate) oxidation was also about 26% higher (P <.05) in the trained subjects (21.7 +/- 2.1 v 16.1 +/- 2.0 nmol CO(2)/g x h). To examine the roles of carnitine-mediated transport and mitochondrial content, we also measured carnitine palmitoyltransferase I (CPT1), carnitine octanoyl transferase (COT), and citrate synthase (CS) activities. CPT1 and CS activity were significantly (P <.05) higher (approximately 25%) in the endurance-trained subjects; there was no difference in COT activity. These data suggest that adaptations at the level of CPT1 and processes distal to this step may contribute to increases in LCFA or MFCA oxidation with exercise training. In contrast, carnitine-mediated transport (COT) does not appear to contribute to an enhancement in MCFA oxidation with exercise training.
authors.affiliation: Department of Biochemistry, Diabetes/Obesity Center, East Carolina University, Greenville, NC 27858, USA.
authors.forename: Kim
authors.initials: K
authors.lastname: Jong-Yeon
authors.forename: Robert C
authors.initials: RC
authors.lastname: Hickner
authors.forename: G Lynis
authors.initials: GL
authors.lastname: Dohm
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Houmard
mesh_terms: D000328:Adult; D002210:Caprylates / Q000378:metabolism; D002245:Carbon Dioxide / Q000032:analysis; D002331:Carnitine / Q000494:pharmacology; D002333:Carnitine Acyltransferases / Q000378:metabolism; D002334:Carnitine O-Palmitoyltransferase / Q000378:metabolism; D002950:Citrate (si)-Synthase / Q000378:metabolism; D015444:Exercise / Q000502:physiology*; D005230:Fatty Acids, Nonesterified / Q000378:metabolism*; D005260:Female; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism*; D010084:Oxidation-Reduction; D019308:Palmitic Acid / Q000378:metabolism; D012044:Regression Analysis
chemical_list: D002210:Caprylates; D005230:Fatty Acids, Nonesterified; D002245:Carbon Dioxide; D019308:Palmitic Acid; D002333:Carnitine Acyltransferases; C030162:carnitine octanoyltransferase; D002334:Carnitine O-Palmitoyltransferase; D002950:Citrate (si)-Synthase; C031492:octanoic acid; D002331:Carnitine