Exercise influences circadian gene expression in equine skeletal muscle

Vet J. 2014 Jul;201(1):39-45. doi: 10.1016/j.tvjl.2014.03.028. Epub 2014 Mar 31.


Circadian rhythms are endogenously generated 24-h oscillations that coordinate numerous aspects of mammalian physiology, metabolism and behaviour. The existence of a molecular circadian clock in equine skeletal muscle has previously been demonstrated. This study investigates how the circadian 24-h expression of exercise-relevant genes in skeletal muscle is influenced by a regular exercise regime. Mid-gluteal, percutaneous muscle biopsies were obtained over a 24-h period from six Thoroughbred mares before and after an 8-week exercise programme. Real-time qPCR assays were used to assess the expression patterns of core clock genes ARNTL, PER2, NR1D1, clock-controlled gene DBP, and muscle genes MYF6, UCP3, VEGFA, FOXO1, MYOD1, PPARGC1A, PPARGC1B, FBXO32 and PDK4. Two-way repeated measures ANOVA revealed a significant interaction between circadian time and exercise for muscle genes MYF6, UCP3, MYOD1 and PDK4. A significant effect of time was observed for all genes with the exception of VEGFA, where a main effect of exercise was observed. By cosinor analysis, the core clock genes, ARNTL (P <0.01) and NR1D1 (P <0.05), showed 24-h rhythmicity both pre- and post-exercise, while PER2 expression was rhythmic post-exercise (P <0.05) but not pre-exercise. The expression profiles of muscle genes MYOD1 and MYF6 showed significant fits to a 24-h cosine waveform indicative of circadian rhythmicity post-exercise only (P <0.01). This study suggests that the metabolic capacity of muscle is influenced by scheduled exercise and that optimal athletic performance may be achieved when exercise times and competition times coincide.

Keywords: Circadian; Equine; Exercise; Gene expression; Skeletal muscle.

MeSH terms

  • Animals
  • Circadian Rhythm*
  • Female
  • Gene Expression Regulation*
  • Horses / genetics
  • Horses / injuries
  • Horses / physiology*
  • Muscle, Skeletal / injuries
  • Muscle, Skeletal / physiology*
  • Physical Conditioning, Animal / physiology*
  • Real-Time Polymerase Chain Reaction / veterinary
  • Species Specificity