PGC-1α encoded by the PPARGC1A gene regulates oxidative energy metabolism in equine skeletal muscle during exercise

Peroxisome proliferator-activated receptor-? coactivator 1a (PGC-1a) has emerged as a critical control factor in skeletal muscle adaptation to exercise, acting via transcriptional control of genes responsible for angiogenesis, fatty acid oxidation, oxidative phosphorylation, mitochondrial biogenesis and muscle fibre type composition. In a previous study, we demonstrated a significant increase in mRNA expression for the gene encoding PGC-1a (PPARGC1A) in Thoroughbred horse skeletal muscle following a single bout of endurance exercise. In this study, we investigated mRNA expression changes in genes encoding transcriptional coactivators of PGC-1a and genes that function upstream and downstream of PGC-1a in known canonical pathways. We used linear regression to determine the associations between PPARGC1A mRNA expression and expression of the selected panel of genes. Biopsy samples were obtained from the gluteus medius pre-exercise (T0), immediately post-exercise (T1) and 4 h post-exercise (T2). Significant (P < 0.05) expression fold change differences relative to T0 were detected for genes functioning in angiogenesis (ANGP2 and VEGFA); Ca2+-dependent signalling pathway (PPP3CA); carbohydrate/glucose metabolism (PDK4); fatty acid metabolism/mitochondrial biogenesis (PPPARGC1B); haem biosynthetic process (ALAS1); insulin signalling (FOXO1, PPPARGC1A and SLC2A4); mitogen-activated protein kinase signalling (MAPK14 and MEF2A); and myogenesis (HDAC9). Gene expression associations were identified between PPARGC1A and genes involved in angiogenesis, mitochondrial respiration, glucose transport, insulin signalling and transcriptional regulation. These results suggest that PGC-1a and genes regulated by PGC-1a play significant roles in the skeletal muscle response to exercise and therefore may contribute to performance potential in Thoroughbred horses.