Transcriptional control, but not subcellular location, of PGC-1α is altered following exercise in a hot environment

The purpose of this study was to determine mitochondrial biogenesisrelated mRNA expression, binding of transcription factors to the peroxisome proliferator-activated receptor- coactivator 1- (PGC-1) promoter, and subcellular location of PGC-1 protein in human skeletal muscle following exercise in a hot environment compared with a room temperature environment. Recreationally trained males (n 11) completed two trials in a temperature-and humiditycontrolled environmental chamber. Each trial consisted of cycling in either a hot (H) or room temperature (C) environment (33 and 20C, respectively) for 1 h at 60% of maximum wattage (Wmax) followed by 3 h of supine recovery at room temperature. Muscle biopsies were taken from the vastus lateralis pre-, post-, and 3 h postexercise. PGC-1 mRNA increased post (P 0.039)-and 3 h postexercise in C (P 0.002). PGC-1, estrogen-related receptor- (ERR), and nuclear respiratory factor 1 (NRF-1) mRNA was all lower in H than C post (P 0.038, P<0.001, and P 0.030, respectively)-and 3 h postexercise (P 0.035, P 0.007, and P<0.001, respectively). Binding of cAMP response element-binding protein (CREB) (P 0.005), myocyte enhancer factor 2 (MEF2) (P 0.047), and FoxO forkhead box class-O1 (FoxO1) (P 0.010) to the promoter region of the PGC-1 gene was lower in H than C. Nuclear PGC-1 protein increased postexercise in both H and C (P 0.029) but was not different between trials (P 0.602). These data indicate that acute exercise in a hot environment blunts expression of mitochondrial biogenesis-related mRNA, due to decreased binding of CREB, MEF2, and FoxO1 to the PGC-1 promoter.