The Metabolomic Investigation of Urinary Biomarkers for Progestogenic and Dopaminergic Substance Misuse in Racehorses

Publication Type:
Thesis
Issue Date:
2025
Full metadata record
This thesis investigates progestogenic and dopaminergic substance misuse in racehorses, applying metabolomic analyses and machine learning to enhance biomarker discovery for anti-doping. Focused on altrenogest, a therapeutic progesterone analogue, the study examined differences between oral and intramuscular administration, noting distinct impurity excretion patterns for trendione and epitrenbolone. Samples from a ten-mare administration study revealed that impurities persisted longer after intramuscular dosing. Untargeted LC-HRMS analysis identified five sulfated steroids capable of distinguishing administration routes, achieving high classification accuracy (AUC = 0.965). For dopaminergic misuse, attention centred on levodopa-containing drugs, such as Stalevo, potentially used to manipulate race performance. Current 3-methoxytyramine thresholds detect large doses but miss micro-dosing or complex medication misuse. A validated LC-QTOF-MS method quantified key metabolites (3-methoxytyramine and tyramine), while metabolomic analysis identified conjugated catecholamines as potential novel biomarkers. Analysis of samples from a 12-horse administration study yielded metabolite profiles supporting extended detection windows via machine learning models. Overall, the work demonstrates integrated targeted/untargeted metabolomic strategies for detecting complex doping cases, proposing new biomarkers and predictive models to strengthen equine anti-doping efforts.
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