Moderate and high intensity sprint exercise induce differential responses in COX4I2 and PDK4 gene expression in Thoroughbred horse skeletal muscle
Article first published online: 8 NOV 2010
© 2010 EVJ Ltd
Equine Veterinary Journal
Special Issue: Proceedings of the 8th International Conference on Equine Exercise Physiology
Volume 42, Issue Supplement s38, pages 576–581, November 2010
How to Cite
HILL, E. W., EIVERS, S. S., McGIVNEY, B. A., FONSECA, R. G., GU, J., SMITH, N. A., BROWNE, J. A., MacHUGH, D. E. and KATZ, L. M. (2010), Moderate and high intensity sprint exercise induce differential responses in COX4I2 and PDK4 gene expression in Thoroughbred horse skeletal muscle. Equine Veterinary Journal, 42: 576–581. doi: 10.1111/j.2042-3306.2010.00206.x
- Issue published online: 8 NOV 2010
- Article first published online: 8 NOV 2010
- [Paper received for publication 08.01.10; Accepted 30.06.10]
- gene expression;
Reasons for performing study: The role of molecular signalling pathways in the phenotypic adaptation of skeletal muscle to different exercise stimuli in the Thoroughbred horse has not been reported previously.
Objective: To examine CKM, COX4I1, COX4I2 and PDK4 gene expression following high intensity sprint and moderate intensity treadmill exercise stimuli in skeletal muscle of Thoroughbred horses.
Materials and methods: Two groups of trained 3-year-old Thoroughbred horses participated. Group A (n = 6 females, n = 3 males) participated in an incremental step test (moderate intensity) to fatigue or HRmax on a Sato high speed treadmill (distance = 5418.67m ± 343.21). Group B (n = 8 females) participated in routine ‘work’ (sprint) on an all-weather gallop (distance = 812.83 m ± 12.53). Biopsy samples were obtained from the gluteus medius pre-exercise (T0), immediately post exercise (T1) and 4 h post exercise (T2). For physiological relevance venous blood samples were collected to measure plasma lactate and creatine kinase concentrations. Changes in mRNA expression were determined by quantitative real-time RT-PCR for creatine kinase muscle (CKM), cytochrome c oxidase subunit IV isoform 1 (COX4I1), cytochrome c oxidase subunit IV isoform 2 (COX4I2) and pyruvate dehydrogenase kinase, isozyme 4 (PDK4) genes. Statistical significance (α<0.05) was determined using Student's t tests.
Results:COX4I2 mRNA expression decreased significantly in Group A and remained unchanged in Group B between T0 vs. T2 (−1.7-fold, P = 0.017; −1.0-fold, P = 0.859). PDK4 mRNA expression increased significantly in Group B but not in Group A between T0 vs. T1 (3.8-fold, P = 0.039; 1.4-fold, P = 0.591). There were no significant changes in the expression in CKM or COX4I1 mRNA abundance in either group.
Conclusions: Different exercise protocols elicit variable transcriptional responses in key exercise relevant genes in equine skeletal muscle due to variation in metabolic demand.