Preliminary insights on the daily rhythm of CRP and IL-6 in athletic horses.
Authors: Aragona F, Rizzo M, Arfuso F, Arrigo F, Fazio F, Giudice E, Faggio C, Piccione G, Giannetto C
Journal: Journal of equine veterinary science
Summary
# Editorial Summary: Daily Inflammatory Rhythms in Athletic Horses Understanding how inflammatory markers fluctuate throughout the day is crucial for accurate interpretation of diagnostic bloodwork in horses, yet circadian patterns in equine inflammatory biomarkers remain poorly characterised. Aragona and colleagues monitored eight clinically healthy saddle geldings housed on a natural 12-hour light/dark cycle, collecting blood samples every 4 hours over 48 hours to track C-reactive protein (CRP) and Interleukin-6 (IL-6) concentrations and their temporal relationships. Both inflammatory markers displayed significant daily rhythms: CRP peaked mid-darkness (scotophase) whilst IL-6 reached maximum levels at the start of the light phase, and both showed robust cyclical patterns (>75% robustness), with a positive correlation between the two parameters across both monitoring days. These findings suggest that sampling time meaningfully influences inflammatory marker values and must be standardised in clinical practice to avoid misinterpretation; however, the authors appropriately acknowledge that environmental factors, management practices, and exercise intensity—all variables in real-world athletic settings—may substantially alter these rhythms and require investigation in future work. For equine practitioners, this research underscores the importance of documenting blood collection times and establishing reference ranges that account for circadian variation, particularly when serial monitoring informs decisions about training load, recovery protocols, or inflammatory pathology.
Read the full abstract on PubMed
Practical Takeaways
- •Blood sampling timing matters: CRP and IL-6 levels vary predictably throughout the day, so serial sampling or standardized collection times are needed for meaningful clinical interpretation in horses
- •Inflammation markers peak at different times (CRP nocturnal, IL-6 early morning), which could affect clinical decision-making and require consideration when interpreting results from single time-point samples
- •This baseline data in healthy horses provides a foundation for future studies on how exercise, stress, and management alter inflammatory rhythms—understanding these normal patterns helps identify true pathological changes
Key Findings
- •CRP and IL-6 showed positive correlation in healthy horses over 48-hour monitoring period
- •CRP peaked in the middle of the dark phase (scotophase) with >75% robustness
- •IL-6 peaked at the beginning of the light phase with >75% robustness
- •Both inflammatory biomarkers demonstrated significant daily rhythmicity driven by circadian clock