Kinetics of intramuscular triglyceride fatty acids in exercising humans.
A pulse ([(14)C]palmitate)-chase ([(3)H]palmitate) approach was used to study intramuscular triglyceride (imTG) fatty acid and plasma free fatty acid (FFA) kinetics during exercise at approximately 45% peak O(2) consumption in 12 adults. Vastus lateralis muscle was biopsied before and after 90 min of bicycle exercise; (3)H(2)O production, breath (14)CO(2) excretion and lipid oxidation (indirect calorimetry) rates were measured during exercise.


RESULTS
during exercise, 8.2+/-1.2 and 8.4+/-0.7 micromol x kg(-1) x min(-1) of imTG fatty acids and plasma FFA, respectively, were oxidized according to isotopic measurements. The sum of these two values was not different (P = 0.6) from lipid oxidation by indirect calorimetry (15.4 +/-1.6 micromol x kg(-1) x min(-1)); the isotopic and indirect calorimetry values were correlated (r = 0.79, P<0.005). During exercise, imTG turnover rate was 0.32+/-0.07%/min (6.0+/-2.0 micromol of imTG x kg wet muscle(-1) x min(-1)) and plasma FFA were incorporated into imTG at a rate of 0.7+/-0.1 micromol x kg wet muscle(-1) x min(-1). The imTG pool size did not change during exercise. This pulse-chase, dual tracer appears to be a reasonable approach to measure oxidation and synthesis kinetics of imTG.
Guo
Z
Z
Endocrine Research Unit, Mayo Clinic, Rochester, Minnesota 55905, USA.
Burguera
B
B
Jensen
M D
MD
D000328:Adult; D002153:Calorimetry, Indirect; D002250:Carbon Radioisotopes; D004734:Energy Metabolism / Q000502:physiology; D015444:Exercise / Q000502:physiology*; D005230:Fatty Acids, Nonesterified / Q000097:blood / Q000493:pharmacokinetics*; D005260:Female; D006801:Humans; D007866:Leg; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism*; D010084:Oxidation-Reduction; D019308:Palmitic Acid / Q000493:pharmacokinetics; D004856:Postural Balance; D014280:Triglycerides / Q000097:blood / Q000493:pharmacokinetics*; D014316:Tritium
D002250:Carbon Radioisotopes; D005230:Fatty Acids, Nonesterified; D014280:Triglycerides; D014316:Tritium; D019308:Palmitic Acid