ENDURANCE TRAINING ATTENUATES THE DECREASE IN SKELETAL-MUSCLE MALONYL-COA WITH EXERCISE

Muscle malonyl-CoA has been postulated to regulate fatty acid metaboli sm by inhibiting carnitine palmitoyltransferase 1. In nontrained rats, malonyl-CoA decreases in working muscle during exercise. Endurance tr aining is known to increase a muscle's reliance on fatty acids as a su bstrate. This study was designed to investigate whether the decline in malonyl-CoA with exercise would be greater in trained than in nontrai ned muscle, thereby allowing increased fatty acid oxidation. After 6-1 0 wk of endurance training (2 h/day) or treadmill habituation (5-10 mi n/day), rats were killed at rest or after running up a 15% grade at 21 m/min for 5, 20, or 60 min. Training attenuated the exercise-induced drop in malonyl-CoA and prevented the exercise-induced increase in the constant for citrate activation of acetyl-CoA carboxylase in the red quadriceps muscle of rats run for 20 and 60 min. Hence, contrary to ex pectations, the decrease in malonyl-CoA was less in trained than in no ntrained muscle during a single bout of prolonged submaximal exercise.