Plasma Lipidomics and Proteomics Analyses Pre- and Post-5000 m Race in Yili Horses

The impact of exercise on human metabolism has been extensively studied, yet limited research exists on the effects of high-intensity racing on equine metabolism. The aim of this study was to screen the effect of a 5000 m race on lipids and proteins in the plasma of Yili horses for the breeding of racehorses. Blood samples were collected from the top three finishers, and lipidomics and proteomics analyses were performed. Lipidomic analysis identified 10 differential lipids. Compared to pre-race levels, phosphatidylethanolamine (18:0/16:0) (PE (18:0/16:0)) and phosphatidylcholine (18:0/18:2) (PC (18:0/18:2)) were significantly upregulated, while triglyceride (26:4/29:4) (TG (26:4/29:4)) and phosphatidylcholine (46:14CHO) (PC (46:14CHO)) were notably downregulated. These lipids were primarily associated with the regulation of lipolysis in adipocytes and glycerolipid metabolism pathways. Proteomic analysis revealed 79 differentially expressed proteins. Post-race, proteasome subunits (alpha type_2, alpha type_5 isoform X1, alpha type_6, and beta type_2), carboxypeptidase E, and S-phase kinase-associated protein 1 showed significant downregulation. These proteins were primarily involved in the cellular catabolic process (Gene Ontology term) and pathways related to the proteasome and type I diabetes mellitus (Kyoto Encyclopedia of Genes and Genomes terms). Correlation analysis indicated a significant positive correlation between proteasome subunits (alpha type_2 and beta type_2) and PC (18:0/18:2), while a significant negative correlation was found with PC (46:14CHO). Conversely, S-phase kinase-associated protein 1, along with proteasome subunits (alpha type_5 isoform X1 and alpha type_6), exhibited a significant negative correlation with PE (18:0/16:0) and a positive correlation with TG (26:4/29:4). In conclusion, Yili horses may sustain energy balance and physiological equilibrium during racing by suppressing protein degradation and optimizing lipid metabolism. The differentially expressed substances identified could serve as key biomarkers for assessing exercise load in horses.