HUMAN SKELETAL-MUSCLE MALONYL-COA AT REST AND DURING PROLONGED SUBMAXIMAL EXERCISE

Previous literature has indicated that contraction-induced decreases i n malonyl-CoA are instrumental in the regulation of fatty acid oxidati on during prolonged submaximal exercise. This study was designed to me asure malonyl-CoA in human vastus lateralis muscle at rest and during submaximal exercise. Eight males and one female cycled for 70 min (10 min at 40% and 60 min at 65% maximal O-2 uptake). Needle biopsies were obtained at rest and at 10 min, 20 min, and 70 min of exercise. Malon yl-CoA content in preexercise biopsy samples determined by highperform ance liquid chromatography (HPLC) was 1.53 +/- 0.18 mu mol/kg dry mass (dm). Malonyl-CoA content did not change significantly during exercis e (1.39 +/- 0.21 at 10 min, 1.46 +/- 0.14 at 20 min, and 1.22 +/- 0.15 mu mol/kg dm at 70 min). In contrast, malonyl-CoA content determined by HPLC in perfused rat red gastrocnemius muscle decreased significant ly during 20 min of stimulation at 0.7 Hz [3.44 +/- 0.54 to 1.64 +/- 0 .23 nmol/g dm, (n = 9)]. We conclude that human skeletal muscle malony l-CoA content 1) is less than reported in rat skeletal muscle at rest, 2) does not decrease with prolonged submaximal exercise, and 3) is no t predictive of increased fatty acid oxidation during exercise.