Clock Genes Expression in Peripheral Leukocytes and Plasma Melatonin Daily Rhythm in Horses.
Authors: Giannetto Claudia, Fazio Francesco, Alberghina Daniela, Giudice Elisabetta, Piccione Giuseppe
Journal: Journal of equine veterinary science
Summary
# Editorial Summary Circadian rhythms coordinate critical physiological and behavioural processes in horses, yet the peripheral clock gene expression underlying these 24-hour cycles remains poorly characterised in equine species. Researchers sampled blood from ten mature geldings at four-hourly intervals over 48 hours under natural light and temperature conditions, measuring melatonin concentration via radioimmunoassay and quantifying expression of five key clock genes (Bmal1, Cry1, Per1, Per2, and Per3) in peripheral leukocytes using real-time qPCR. Melatonin displayed a robust nocturnal peak around 21:30–21:40, whilst four of the five clock genes examined showed clear daily rhythmicity; notably, Bmal1 and Per2 expression oscillations were significantly correlated with melatonin levels, with melatonin peaks preceding both gene acrophases by approximately three hours. These findings confirm that peripheral blood leukocytes maintain autonomous circadian clock gene expression in horses, suggesting that timed blood sampling could provide a practical biomarker for circadian phase assessment in clinical or performance contexts. For practitioners managing stabled horses or those undergoing intensive training, understanding these peripheral clock rhythms may have implications for optimising the timing of therapeutic interventions, nutritional protocols, and recovery strategies aligned with individual circadian physiology.
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Practical Takeaways
- •Understanding equine circadian clock gene expression may inform optimal timing for diagnostic blood sampling and therapeutic interventions that depend on immune function
- •The strong correlation between melatonin and Bmal1/Per2 expression suggests melatonin could be a useful marker for circadian phase in horses, with potential applications in managing sleep-related or stress-related conditions
- •Natural photoperiod and housing conditions significantly influence equine circadian gene expression; standardized sampling times are important for consistent laboratory results
Key Findings
- •Melatonin showed a consistent daily rhythm with nocturnal acrophase around 21:30-21:40 in horses
- •Five of six clock genes tested (Bmal1, Cry1, Per1, Per2, Per3) demonstrated daily rhythmicity in peripheral blood leukocytes, while Clock gene showed no rhythmicity
- •Bmal1 and Per2 oscillations were correlated with melatonin concentration, with melatonin peaks preceding Bmal1 and Per2 acrophases by approximately 3 hours
- •Cyclic transcription of clock genes in equine peripheral leukocytes confirms presence of circadian regulation in horses