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1 Animal Genomics Laboratory,
2 University Veterinary Hospital, University College Dublin School of Agriculture, Food Science and Veterinary Medicine;
3 University College Dublin Conway Institute of Biomolecular and Biomedical Research,
4 University College Dublin School of Medicine and Medical Science, University College Dublin, Belfield, Dublin, Ireland; and
5 Laboratory of Muscular Biopathology, Department of Comparative Anatomy and Pathological Anatomy, Faculty of Veterinary Sciences, University of Cordoba, Campus Rabanales, Crtra. Madrid-Cadiz, Cordoba, Spain
Intense selection for elite racing performance in the Thoroughbred horse ( Equus caballus ) has resulted in a number of adaptive physiological phenotypes relevant to exercise; however, the underlying molecular mechanisms responsible for these characteristics are not well understood. Adaptive changes in mRNA expression in equine skeletal muscle were investigated by real-time qRT-PCR for a panel of candidate exercise-response genes following a standardized incremental-step treadmill exercise test in eight untrained Thoroughbred horses. Biopsy samples were obtained from the gluteus medius before, immediately after, and 4 h after exercise. Significant ( P < 0.05) differences in gene expression were detected for six genes ( CKM , COX4I1, COX4I2, PDK4, PPARGC1A , and SLC2A4 ) 4 h after exercise. Investigation of relationships between mRNA and velocity at maximum heart rate (VHR max ) and peak postexercise plasma lactate concentration ([La]T 1 ) revealed significant ( P < 0.05) associations with postexercise COX4I1 and PPARCG1A expression and between [La]T 1 and basal COX4I1 expression. Gene expression changes were investigated in a second cohort of horses after a 10 mo period of training. In resting samples, COX4I1 gene expression had significantly increased following training, and, after exercise, significant differences were identified for COX4I2, PDK4 , and PPARGC1A . Significant relationships with VHR max and [La]T 1 were detected for PPARGC1A and COX4I1 . These data highlight the roles of genes responsible for the regulation of oxygen-dependent metabolism, glucose metabolism, and fatty acid utilization in equine skeletal muscle adaptation to exercise.
mRNA; physiology; performance