Intramuscular fatty acid metabolism in contracting and non-contracting human skeletal muscle

• Published in: The Journal of physiology Vol. 540; no. 1; pp. 387 - 395
• Main Authors: Sacchetti, M., Saltin, B., Osada, T., Hall, G.
• Format: Journal Article
• Language: English
• Published: Oxford, UK The Physiological Society 01.04.2002; Blackwell Publishing Ltd; Blackwell Science Inc
• Subjects: Adult; Carbon Isotopes; Energy Metabolism - physiology; Fatty Acids, Nonesterified - blood; Fatty Acids, Nonesterified - pharmacokinetics; Humans; Male; Muscle Contraction - physiology; Muscle, Skeletal - metabolism; Original; Oxidation-Reduction; Palmitates - blood; Palmitates - pharmacokinetics; Physical Exertion - physiology; Triglycerides - metabolism
• ISSN: 0022-3751; 1469-7793
• DOI: 10.1113/jphysiol.2001.013912

The present study was undertaken to investigate the fate of blood-borne non-esterified fatty acids (NEFA) entering contracting and non-contracting knee extensor muscles of healthy young individuals. [U- 13 C]-palmitate was infused into a forearm vein during 5 h of one-legged knee extensor exercise at 40 % of maximal work capacity and the NEFA kinetics, oxidation and rate of incorporation into intramuscular triacylglycerol (mTAG) were determined for the exercising and the non-exercising legs. During 4 h of one-legged knee extensor exercise, m tag content decreased by 30 % ( P < 0.05) in the contracting muscle, whereas it was unchanged in the non-contracting muscle. The uptake of plasma NEFA, as well as the proportion directed towards oxidation, was higher in the exercising compared to the non-exercising leg, whereas the rate of palmitate incorporation into m tag was fourfold lower (0.70 ± 0.14 vs. 0.17 ± 0.04 μmol (g dry wt) −1 h −1 ; P lt; 0.05), resulting in fractional synthesis rates of 1.0 ± 0.2 and 3.8 ± 0.9 % h −1 ( P lt; 0.01) for the contracting and non-contracting muscle, respectively. These findings demonstrate that mTAG in human skeletal muscle is continuously synthesised and degraded and that the metabolic fate of plasma NEFA entering the muscle is influenced by muscle contraction, so that a higher proportion is directed towards oxidation at the expense of storage in mTAG.