title: Lipid oxidation is reduced in obese human skeletal muscle.
abstract: The purpose of this study was to discern cellular mechanisms that contribute to the suppression of lipid oxidation in the skeletal muscle of obese individuals. Muscle was obtained from obese [body mass index (BMI), 38.3 +/- 3.1 kg/m(2)] and lean (BMI, 23.8 +/- 0.9 kg/m(2)) women, and fatty acid oxidation was studied by measuring (14)CO(2) production from (14)C-labeled fatty acids. Palmitate oxidation, which is at least partially dependent on carnitine palmitoyltransferase-1 (CPT-1) activity, was depressed (P < 0.05) by approximately 50% with obesity (6.8 +/- 2.2 vs. 13.7 +/- 1.4 nmole CO(2).g(-1).h(-1)). The CPT-1-independent event of palmitoyl carnitine oxidation was also depressed (P < 0.01) by approximately 45%. There were significant negative relationships (P < 0.05) for adiposity with palmitate (r = -0.76) and palmitoyl carnitine (r = -0.82) oxidation. Muscle CPT-1 and citrate synthase activity, an index of mitochondrial content, were also significantly (P < 0.05) reduced ( approximately 35%) with obesity. CPT-1 (r = -0.48) and citrate synthase (r = -0.65) activities were significantly (P < 0.05) related to adiposity. These data suggest that lesions at CPT-1 and post-CPT-1 events, such as mitochondrial content, contribute to the reduced reliance on fat oxidation evident in human skeletal muscle with obesity.
authors.affiliation: Department of Biochemistry, East Carolina University, Greenville, North Carolina 27858, USA.
authors.forename: J Y
authors.initials: JY
authors.lastname: Kim
authors.forename: R C
authors.initials: RC
authors.lastname: Hickner
authors.forename: R L
authors.initials: RL
authors.lastname: Cortright
authors.forename: G L
authors.initials: GL
authors.lastname: Dohm
authors.forename: J A
authors.initials: JA
authors.lastname: Houmard
mesh_terms: D000328:Adult; D015992:Body Mass Index; D002210:Caprylates / Q000378:metabolism; D002247:Carbon Isotopes; D002331:Carnitine / Q000378:metabolism; D002334:Carnitine O-Palmitoyltransferase / Q000378:metabolism; D002950:Citrate (si)-Synthase / Q000378:metabolism; D005227:Fatty Acids / Q000378:metabolism; D005260:Female; D006801:Humans; D015227:Lipid Peroxidation; D018482:Muscle, Skeletal / Q000378:metabolism*; D009765:Obesity / Q000378:metabolism*; D010084:Oxidation-Reduction; D019308:Palmitic Acid / Q000378:metabolism; D010732:Phosphofructokinase-1 / Q000378:metabolism
chemical_list: D002210:Caprylates; D002247:Carbon Isotopes; D005227:Fatty Acids; D019308:Palmitic Acid; D002334:Carnitine O-Palmitoyltransferase; D002950:Citrate (si)-Synthase; D010732:Phosphofructokinase-1; C031492:octanoic acid; D002331:Carnitine