Are Proteins Such as MMP2, IGF1, IL-13, and IL-1ra Valuable as Markers of Fitness Status in Racehorses? A Pilot Study

In a recent study, in which more than a thousand racehorses were evaluated, three potential blood markers were selected. It was concluded that insulin-like growth factor 1 (IGF1), interleukin-1 receptor antagonist (IL-1ra), and matrix metalloproteinase 2 (MMP2) may enable the early detection of horses at risk of injuries. However, in other studies, it was suggested that cytokine concentrations indicate the athlete’s status better than mRNA expression in blood cells. Thus, the purpose of this study was to evaluate changes in IGF1, MMP-2, and novel markers such as interleukin-13 (IL-13) after exercise in horses at different fitness levels as well as after different intensities of exercise. ELISA tests were performed on thirty-one racehorses [n = 31], who were divided into an inexperienced [beginner] group [n = 20] and an experienced [advanced] group [n = 6]. In addition, differences between race and training session were evaluated to see the influence of different intensities of exercise. Blood samples were taken before and after exercise. The basal IGF1 concentration was lower in an inexperienced group ( p < 0.01) as well as IL-13 ( p < 0.05) in comparison to the experienced group. There were no differences between pre- and post-exercise samples, changes in multiples or between training, and racing exercises. In conclusion, the basal values of some cytokines may appear to be more beneficial in forecasting horse fitness level.