Effect of endurance training on lipid metabolism in women: a potential role for PPAR alpha in the metabolic response to training

Endurance training increases fatty acid oxidation (FAO) and skeletal muscle oxidative capacity. However, the source of the additional fat and the mech anisms for increasing FAO capacity in muscle are not clear. We measured who le body and regional lipolytic activity and whole body and plasma FAO in si x lean women during 90 min of bicycling exercise (50% pretraining peak O-2 consumption) before and after 12 wk of endurance training. We also assessed skeletal muscle content of peroxisome proliferator-activated receptor-alph a (PPAR alpha) and its target proteins that regulate FAO [medium-chain and very long chain acyl-CoA dehydrogenase (MCAD and VLCAD)]. Despite a 25% inc rease in whole body FAO during exercise after training (P < 0.05), training did not alter regional adipose tissue lipolysis (abdominal: 0.56 +/- 0.26 and 0.57 +/- 0.10 mmol . 100 g(-1) . min(-1); femoral: 0.13 +/- 0.07 and 0. 09 +/- 0.02 mmol . 100 g(-1) . min(-1)), whole body palmitate rate of appea rance in plasma (168 +/- 18 and 150 +/- 25 mu mol/ min), and plasma FAO (55 4 +/- 61 and 601 +/- 45 mu mol/ min). However, training doubled the levels of muscle PPAR alpha, MCAD, and VLCAD. We conclude that training increases the use of nonplasma fatty acids and may enhance skeletal muscle oxidative capacity by PPAR alpha regulation of gene expression.