Peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1 alpha) is considered to play a pivotal role in the exercise-induced metabolic adaptation of skeletal muscle. Although the oxidized form of nicotinamide adenine dinucloetide (NAD(+))-dependent histone deacetylase SIRT1 has been shown to mediate PGC-1 alpha-induced metabolic adaptation, the effect of endurance exercise on the SIRT1 protein remains to be elucidated. The purposes of this study were (1) to investigate the distribution of SIRT1 and PGC-1 alpha proteins in skeletal muscle and (2) to examine the effects of acute endurance exercise and low- or high-intensity exercise training on SIRT1 and PGC-1 alpha protein expressions and on the metabolic components in rat skeletal muscle. Both the SIRT1 and PGC-1 alpha proteins preferentially accumulate in red oxidative muscles. Acute endurance exercise on a motor-driven treadmill (20 m/min, 18.5% incline, 45 minutes) increases the PGC-1 alpha protein expression at 18 hours after,exercise and the SIRT1 protein expression at 2 hours after exercise in the soleus muscle. In the training experiment, the rats were divided into control, low-intensity (20 m/min, 18.5% incline, 90 min/d), and high-intensity (30 m/min, 18.5% incline, 60 min/d)training groups. After 14 days of training, the SIRT1 and PGC-1 alpha proteins, hexokinase activity, mitochondrial proteins and enzyme activities, and glucose transporter 4 protein in the soleus muscle were increased by both trainings. In the plantaris muscle, SIRT1, hexokinase activity, mitochondrial proteins and enzyme activities, and glucose transporter 4 were increased by high-intensity training whereas the PGC-1 alpha was not. These results suggest that endurance exercise increases the skeletal muscle SIRT1 protein content. In addition, the findings also raise the possibility that the SIRT1 protein expression may play a potentially important role in such adaptations, whereas an increase in the PGC-1 alpha protein expression is not necessary for such adaptations. (C) 2008 Elsevier Inc. All rights reserved.