Characterization of rational biomarkers accompanying fever in yeast-induced pyrexia rats using urine metabolic footprint analysis

• A dynamic and continuous metabolic footprint analysis technique was developed.
• Potential biomarkers were figured out from three time-points with good clustering.
• Pearson correlation analysis was used to secondary screening biomarkers.
• ROC curve and metabolic network was introduced to validate the rationality.
• The study provides a strategy of selecting rational biomarkers in metabolomics.

Fever is a prominent feature of diseases and is an ongoing process that is always accompanied by metabolic changes in the body system. Despite the success of temperature regulation theory, the underlying biological process remains unclear. To truly understand the nature of the febrile response, it is crucial to confirm the biomarkers during the entire biological process. In the current study, a 73-h metabolic footprint analysis of the urine from yeast-induced pyrexia rats was performed using ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry. Potential biomarkers were selected using orthogonal partial least squares-discriminate analysis (OPLS-DA), the rational biomarkers were verified by Pearson correlation analysis, and the predictive power was evaluated using receiver operator characteristic (ROC) curves. A metabolic network constructed using traditional Chinese medicine (TCM) grammar systems was used to validate the rationality of the verified biomarkers. Finally, five biomarkers, including indoleacrylic acid, 3-methyluridine, tryptophan, nicotinuric acid and PI (37:3), were confirmed as rational biomarkers because their correlation coefficients were all greater than 0.87 and because all of the correlation coefficients between any pair of these biomarkers were higher than 0.75. The areas under the ROC curves were all greater than 0.84, and their combined predictive power was considered reliable because the greatest area under the ROC curve was 0.968. A metabolic network also demonstrated the rationality of these five biomarkers. Therefore, these five metabolites can be adopted as rational biomarkers to reflect the process of the febrile response in inflammation-induced pyrexia.

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