Untargeted metabolomics profiling of 24-h ultramarathon runners: new insights into the biochemical alterations and the identification of performance biomarkers

Aims: Following our previous research experiences on the 24-h ultramarathon (UM) race - a highly demanding competition characterized by acute cardiorespiratory and metabolic responses - we herein explored for the first time the metabolic profile of UM runners (n = 17) participating in a 24-h race via an untargeted metabolomic approach to gain further insights into the biochemical changes induced by the ultra-endurance performance. Materials and methods: Metabolomics analysis was conducted on pre- and post-race plasma samples by high- resolution mass spectrometry in combination with reversed-phase chromatography. Key findings: The major metabolic changes induced by the 24-h running concerned lipid metabolism, with an increase in medium- and long-chain fatty acids as energy sources for muscle contraction during the prolonged physical activity. A significant accumulation of oxidized metabolites from linoleic and arachidonic acids was also detected, which are potent mediators of cellular responses associated with oxidative/inflammatory processes that could be of clinical relevance for athletes' health. Notably, some metabolites presented positive correlations with athletic performance. Higher pre-race levels of 5-methyltetrahydrofolic acid (5-MTHF), as well as higher post-race levels of 5-MTHF, β-alanine, and creatine, were associated with a greater distance covered in 24 h. This evidence may suggest that nutritional supplementation can play an important role before and during the race to sustain athletes' capacity and exercise efficiency throughout such challenging sporting events. Significance: Overall, this study confirms that the metabolomic approach could be a helpful tool to the sport and health management of athletes, and to the identification of possible biomarkers of performance.