Exercise influences circadian gene expression in equine skeletal muscle.
Authors: Murphy B A, Wagner A L, McGlynn O F, Kharazyan F, Browne J A, Elliott J A
Journal: Veterinary journal (London, England : 1997)
Summary
# Editorial Summary: Exercise and Circadian Gene Expression in Equine Muscle Horses possess intrinsic molecular clocks within skeletal muscle that regulate 24-hour cycles of gene expression controlling metabolism, energy production and muscle adaptation. Murphy and colleagues examined how an 8-week structured exercise programme altered these rhythmic patterns by sampling gluteal muscle from six Thoroughbred mares at regular intervals over 24 hours before and after training, using quantitative PCR to measure expression of 13 genes including core clock regulators and metabolically important muscle genes. Four muscle-relevant genes (MYF6, UCP3, MYOD1 and PDK4) demonstrated significant circadian rhythmicity only following exercise training, whilst the core clock genes ARNTL and NR1D1 remained rhythmic throughout, and PER2 only became rhythmic post-exercise. These findings indicate that regular exercise training entrains the peripheral circadian clock within muscle tissue, synchronising the temporal expression of genes governing muscle development, oxidative capacity and metabolic flexibility. The practical implication is that scheduling training and competition at consistent times of day may optimise athletic performance by aligning exercise stimuli with the horse's naturally synchronised muscle metabolic state—a consideration particularly relevant for competition planning and training programme design across all disciplines.
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Practical Takeaways
- •Scheduling training and competition at consistent times of day may optimize athletic performance by aligning exercise with the horse's circadian-regulated metabolic capacity
- •Regular exercise programs induce changes in the circadian expression patterns of muscle genes involved in metabolism and muscle remodeling, suggesting adaptation to training timing
- •Consider that a horse's response to exercise and recovery capacity may vary across the 24-h day based on circadian gene expression patterns
Key Findings
- •Core clock genes ARNTL and NR1D1 demonstrated 24-h rhythmicity both before and after exercise, while PER2 became rhythmic only post-exercise
- •Muscle genes MYOD1 and MYF6 showed significant circadian rhythmicity post-exercise only, indicating exercise-induced changes in gene expression patterns
- •Significant interactions between circadian time and exercise were observed for MYF6, UCP3, MYOD1 and PDK4, demonstrating exercise influences the temporal expression of metabolically relevant genes
- •All genes except VEGFA showed significant time effects, with exercise producing a main effect on VEGFA expression