Untargeted Sweat Metabolomics and Targeted Plasma Amino Acid Profiling Reveal Dynamic Metabolic Remodeling During Conditioning in Yili Horses.

Overview

• This study investigates how training changes horse sweat types and plasma amino acid levels, revealing underlying metabolic adaptations during conditioning in Yili horses.
• The research combines untargeted metabolomics of sweat and targeted analysis of plasma amino acids to understand systemic metabolic changes associated with different sweat phenotypes.

Background and Purpose

• Horses exhibit different sweat types during training: muddy sweat (MS), foamy sweat (FS), and clear sweat (CS), which are thought to indicate physiological adaptation stages.
• The metabolic processes linking these sweat changes to systemic amino acid dynamics and overall metabolism were previously unclear.
• The study aims to connect sweat metabolite profiles with plasma amino acid concentrations, observing how these relate to conditioning progress in horses.

Methods

• Subjects: Six 2-year-old stallions of the Yili horse breed were monitored through a 10-week training program.
• Sampling: Both plasma and sweat samples were collected before and after races at three time points reflecting distinct sweat types (MS, FS, CS).
• Analytical Techniques:
  • Sweat samples underwent untargeted metabolomics using Liquid Chromatography-Mass Spectrometry/Mass Spectrometry (LC-MS/MS).
  • Plasma amino acids were profiled using targeted Ultra High Performance Liquid Chromatography-Tandem Mass Spectrometry (UHPLC-MS/MS).
• Data Analysis:
  • Multivariate statistical methods were used to identify significant metabolite differences across sweat types.
  • Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis determined key metabolic pathways involved.
  • Correlation network (CNet) analysis examined relationships between plasma amino acids and sweat metabolites.

Key Findings

• Metabolite Changes:
  • The number of differential sweat metabolites varied between stages: 45 between MS and FS, 127 between MS and CS, and 38 between FS and CS, indicating dynamic metabolic remodeling.
• Plasma Amino Acid Dynamics:
  • Before races, branched-chain amino acids (BCAAs) were higher in the MS stage compared to FS and CS stages, suggesting a role in early stress response.
  • Glycine concentration was lower pre-race in MS compared to FS and CS.
  • After races, valine, histidine, and aspartate increased only in the MS stage, signifying acute metabolic response during early conditioning.
• Correlation Patterns:
  • Pre-race plasma amino acid levels showed positive correlations with sweat lipids and organic acids, indicative of coordinated systemic metabolism.
  • Post-race, these correlations shifted to negative, reflecting changes in metabolic state due to exercise stress.
• Pathway Insights:
  • ABC transporters and mTOR signaling pathways, as well as BCAA metabolism, emerged as key regulators coordinating metabolic remodeling between sweat and plasma.

Interpretation and Implications

• The transition from muddy sweat to clear sweat mirrors a metabolic shift from acute physiological stress responses towards a more stable, homeostatic condition as horses adapt to training.
• Elevated plasma BCAAs and sweat cortisol could serve as biomarkers for monitoring training status and metabolic adaptation in horses.
• mTOR signaling and ABC transporter activity are likely mediators of the interplay between sweat composition and systemic amino acid metabolism during exercise adaptation.
• Understanding these metabolic networks can inform more effective conditioning programs and health monitoring practices for athletic horses.

Conclusion

• This integrative metabolomic analysis demonstrates dynamic and coordinated metabolic remodeling in Yili horses during conditioning, linking sweat phenotype changes with plasma amino acid shifts.
• The findings highlight potential biomarkers and molecular pathways that underpin physiological adaptation to training stress in equine athletes.