Differential Metabolomics and Cardiac Function in Trained vs. Untrained Yili Performance Horses

This study aimed to investigate the effects of training on cardiac structure and function, as well as plasma metabolite profiles in horses, in order to uncover the molecular regulatory mechanisms and cardiac remodeling under long-term exercise. We hypothesize that long-term standardized training induces physiological cardiac remodeling and differential metabolomic changes in Yili horses, which correlate with improved athletic performance. The study focuses on physiological exercise-induced cardiac remodeling, characterized by increased left ventricular wall thickness and chamber size. A total of 18 Yili horses, a unique Chinese equine breed, were included in the study of equine exercise physiology. Twelve horses underwent six months of standardized training followed by three 1000 m performance tests. Based on final rankings, they were divided into an advanced group (AG, top six horses) and a habitual group (HG, bottom six horses). The remaining six untrained horses served as the untrained group (UG), with only free-range activity. Echocardiographic results revealed significant differences (<i>p</i> < 0.05) between the trained and untrained groups in cardiac parameters such as LVID, LVFW, LVM, AODd, IVSs, HR, EDV, ESV, LADs, LVLD, MVD, PADs, and SV. Further comparison between AG and HG showed significant differences in AODd, EESV, HR, IVSd, LVIDs, LVM, RVDd, and RVDs (<i>p</i> < 0.05). Metabolomic analysis identified 465 differential metabolites between AG and HG, 456 between AG and UG, and 379 between HG and UG, with 106 overlapping metabolites among all three groups. Plasma metabolomics revealed significant negative correlations between specific long-chain lysophosphatidylcholines (LPCs) and cardiac structural parameters (LVIDd, LVFWD, LVIDs, LVLD, MVD, and LADs), whereas LPC (O-18:2) showed an opposite trend. Key metabolites such as 3-hydroxybutanoic acid, carnitine C4:0, carnitine isoC4:0, hippuric acid, and uric acid were significantly lower in AG compared to HG and UG, with uric acid levels negatively correlated with LVID and LVM. Glycerophospholipid metabolism emerged as the core pathway differentiating exercise capacity among all groups. Notably, efferocytosis (vs. HG and UG) and tryptophan metabolism/aromatic amino acid biosynthesis (vs. HG) were specifically enriched in AG. These findings provide a novel theoretical basis and research perspective for optimizing racehorse training strategies and exploring the metabolic regulation of the athletic heart.