Effect of Training on PPARGC1A and FNDC5 Gene Expression in Thoroughbred Horses

Abstract

IntroductionPGC‐1α and irisin, encoded by the PPARGC1A and FNDC5 genes, play key roles in mediating the beneficial effects of exercise. PPARGC1A gene expression is induced by exercise and has been shown to upregulate FNDC5 expression. Higher levels of FNDC5 have been observed in young male human athletes compared to sedentary controls. FNDC5 gene expression has also been shown in some species to be modulated by myostatin (MSTN), a growth factor that limits muscle hypertrophy. In horses MSTN variation (g.66493737C>T) affects gene expression and racing performance. Thoroughbreds homozygous for the C‐allele have significantly higher levels of MSTN mRNA than homozygous T : T horses. The aim of this study was to investigate the responses of PPARGC1A and FNDC5 in skeletal muscle to exercise and investigate the relationship with MSTN genotype.MethodsSkeletal muscle (gluteus medius) biopsies were taken from untrained yearling Thoroughbreds (n = 27) at rest and after a ten month period of training at two‐years‐old. Skeletal muscle gene expression was measured using real‐time qRT‐PCR assays and data was analysed using qBase software.ResultsA significant increase in both PPARGC1A (P = 0.0001, FC = 1.82) and FNDC5 (P = 0.039, FC = 1.72) was observed post‐training. A significant positive correlation was found between FNDC5 and PPARGC1A expression levels post training (P = 0.01, R2 = 0.22). There was no relationship between PPARGC1A or FNDC5 gene expression and MSTN genotype.ConclusionsThese data indicate a coordinated role for PGC‐1α and irisin in the skeletal muscle response to exercise in Thoroughbred horses. Their known roles in mitochondrial biogenesis and brown fat metabolism suggest important roles in the adaptive response to exercise, which is independent of MSTN‐determined muscle type.Ethical Animal ResearchInstitutional Animal Research Ethics Committee approval was obtained. Explicit owner informed consent for participation in this study is not stated. Sources of funding: Science Foundation Ireland under Grant Number 11/PI/1166. Competing interests: Dr Hill is a co‐founder and Chairman of Equinome Ltd.