Exercise-specific plasma proteomic signatures in racehorses: Candidates for training adaptation and peak load monitoring.

This study identifies several plasma proteins as potential biomarkers for monitoring training adaptation and overload in racehorses.

Summary and findings

This study aimed to identify plasma biomarkers linked to training adaptation and peak load in racehorses undergoing high-intensity training. Forty-nine Arabian and Thoroughbred racehorses were assessed at different training phases, with plasma samples collected at rest, post-exercise, and after recovery. The study identified several proteins that were consistently modulated across training phases, indicating their potential as biomarkers.

Abstract

<h4>Background</h4>Racehorses undergo profound physiological changes with training and competition, but current biomarkers inadequately capture the complex molecular dynamics of exercise. This study aimed to identify novel plasma biomarkers of training adaptation and peak load using high-throughput proteomics.<h4>Objectives</h4>We hypothesised that systematic training and racing induce distinct plasma proteomic signatures, enabling the discovery of candidate biomarkers linked to training status, oxidative stress, inflammation and metabolic remodelling.<h4>Study design</h4>In vivo longitudinal study.<h4>Methods</h4>Forty-nine Arabian and Thoroughbred racehorses underwent standardised high-intensity training. Plasma samples were collected at rest, immediately post-exercise and after recovery during three phases: initial training (T1), mid-season conditioning (T2) and race-phase (R). In total, 314 samples were analysed using tandem mass tags based quantitative proteomics and Orbitrap mass spectrometry. Protein abundance changes were assessed with multiple-testing correction (q < 0.05), and pathway enrichment was performed using STRING and ShinyGO.<h4>Results</h4>Proteomic responses differed by phase. T1 showed broad activation of inflammatory (S100A8/A9), antioxidant (superoxide dismutase 1, catalase) and metabolic proteins (glucose-6-phosphate dehydrogenase, phosphoglycerate kinase 1). T2 displayed a more refined profile with remodelling and redox regulators (decorin, thymosin β4, glutathione S-transferase). Racing elicited the strongest response, with over 100 up-regulated proteins linked to energy metabolism, oxidative defense and cytoskeletal adaptation. Several proteins: including S100A8, thymosin β4, prothymosin-α, cofilin-1 and lipocalins, were consistently modulated across phases, highlighting their biomarker potential.<h4>Main limitations</h4>Breed imbalance and incomplete follow-up sampling may affect generalisability. Validation in larger, diverse cohorts with targeted assays is required.<h4>Conclusions</h4>This study identifies a panel of promising plasma proteins as candidate biomarkers of exercise adaptation and overload in racehorses. These findings may support improved monitoring of performance, training load and early detection of overtraining in equine athletes.

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