Molecular Signatures of Exercise Adaptation in Arabian Racing Horses: Transcriptomic Insights from Blood and Muscle

<b>Background/Objectives:</b> Human-driven selection has shaped modern horse breeds into highly specialized athletes, particularly in racing. Arabian horses, renowned for their endurance, provide an excellent model for studying molecular adaptations to exercise. This study aimed to identify genes commonly influenced by physical exertion in the gluteus medius muscle and whole blood of Arabian horses during their first year of race training. <b>Methods:</b> RNA sequencing of sixteen pure-breed Arabian horses was used to analyze transcriptomic changes at three key training stages. Differentially expressed genes (DEGs) were identified to explore their role in endurance and metabolic adaptation. <b>Results:</b> Seven genes-<i>RCHY1</i>, <i>PIH1D1</i>, <i>IVD</i>, <i>FABP3</i>, <i>ANKRD2</i>, <i>USP13</i>, and <i>CRYAB</i>-were consistently deregulated across tissues and training periods. These genes are involved in muscle remodeling, metabolism, oxidative stress response, and protein turnover. <i>ANKRD2</i> was associated with mechanosensing and muscle adaptation, <i>FABP3</i> with fatty acid metabolism, and <i>USP13</i> with ubiquitination-related pathways crucial for muscle recovery and energy regulation. The transcriptomic overlap between muscle and blood suggests potential systemic biomarkers for athletic performance and endurance. <b>Conclusions:</b> Our findings highlight the importance of multi-tissue transcriptomic profiling in understanding exercise-induced molecular adaptations. The identified genes warrant further investigation as potential molecular markers for monitoring training progression and athletic potential in endurance horses. This study contributes to the growing field of equine sports genetics and may offer translational insights into human sports performance.