Plasma metabolomic profiling of healthy pregnant mares and mares with experimentally induced placentitis.
Authors: Beachler Theresa M, Gracz Hanna S, Morgan David R, Bembenek Bailey Stasia A, Borst Luke, Ellis Katey E, Von Dollen Karen A, Lyle Sara K, Nebel Amber, Andrews Natalie C, Koipalli Joanna, Gadsby John E, Bailey Christopher S
Journal: Equine veterinary journal
Summary
# Plasma Metabolomic Profiling in Equine Placentitis Ascending placentitis represents a significant threat to late-term pregnancy in mares, yet early diagnosis remains challenging; metabolomic profiling of blood plasma may offer a novel diagnostic avenue by identifying biochemical fingerprints of infection before clinical signs become apparent. Researchers induced ascending placentitis in five late-term pregnant pony mares using *Streptococcal equi* subsp. *zooepidemicus* inoculation whilst five mares served as healthy controls, collecting plasma samples and ultrasound measurements (combined thickness of uterus and placenta, CTUP) at multiple time points for nuclear magnetic resonance (NMR) spectroscopy analysis. Two distinct metabolic phases emerged: within four hours of inoculation, ten metabolites involved in energy and amino acid metabolism (including alanine, phenylalanine, histidine, pyruvate, citrate, lactate and glucose) showed significant elevation before normalising by 12 hours; by day four, when placentitis was confirmed ultrasonographically, these same metabolites demonstrated marked reduction compared with controls. The biphasic metabolomic response—initial acute spike followed by sustained depression—may reflect the innate immune response and energy depletion associated with systemic infection, suggesting potential value for early detection if validated in larger cohorts without therapeutic intervention. Whilst sample size limitations and the use of treated animals warrant cautious interpretation, these findings provide a mechanistic foundation for developing metabolomic biomarkers that could enable diagnosis of placentitis before CTUP thickening becomes detectable and before clinical deterioration compromises pregnancy salvage.
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Practical Takeaways
- •Plasma metabolomic profiling using NMR spectroscopy may offer a diagnostic tool for early detection of ascending placentitis in late-term pregnant mares, with specific metabolite patterns emerging within hours of infection.
- •The two-phase metabolite response pattern suggests potential for developing non-invasive blood-based screening protocols to complement or potentially precede ultrasound diagnosis of placentitis.
- •Early intervention within the 4-12 hour window after infection may be critical, as metabolite changes normalize quickly; future research should explore whether identifying these early metabolite shifts could enable treatment before ultrasonographic changes are evident.
Key Findings
- •Four hours post-inoculation with Streptococcal equi subsp. zooepidemicus, plasma concentrations of alanine, phenylalanine, histidine, pyruvate, citrate, glucose, creatine, glycolate, lactate and 3-hydroxyisobutyrate significantly increased, returning to baseline by 12 hours.
- •By day 4, infected mares showed significant reductions in alanine, phenylalanine, histidine, tyrosine, pyruvate, citrate, glycolate, lactate and dimethylsulfone compared with controls.
- •Two distinct metabolomic phases were identified: immediate elevation in energy and nitrogen metabolism metabolites (4 hours) followed by metabolite reduction (4 days) coinciding with ultrasonographic diagnosis of placentitis.