Plasma Amino Acids in Horses Suffering from Pituitary Pars Intermedia Dysfunction.
Authors: Stoeckle Sabita Diana, Timmermann Detlef, Merle Roswitha, Gehlen Heidrun
Journal: Animals : an open access journal from MDPI
Summary
Pituitary pars intermedia dysfunction remains highly prevalent in aged equine populations, yet our understanding of its biochemical signatures remains incomplete. Drawing parallels with Parkinson's disease—a condition similarly characterised by oxidative damage to dopaminergic pathways—researchers hypothesised that PPID might produce detectable alterations in plasma amino acid profiles; to test this, they measured basal ACTH concentrations and quantified 21 amino acids across 53 horses stratified into four groups: non-PPID controls (ACTH <30 pg/mL, n=25), untreated PPID cases (ACTH ≥100 pg/mL, n=20), and two treatment-responsive subgroups receiving pergolide (PPIDrr with controlled ACTH ≤30 pg/mL, n=5; PPIDarr with persistent elevation ≥100 pg/mL, n=3). Several amino acids showed significant dysregulation: asparagine, citrulline and glutamine were consistently elevated across PPID groups compared to controls, whilst arginine was notably raised in successfully treated horses and cysteine paradoxically decreased in the PPIDrr group. The most promising candidates for future investigation as potential biomarkers—asparagine, citrulline and glutamine—may help stratify disease severity or treatment responsiveness, whilst their dysregulation hints at underlying metabolic perturbations that could theoretically be addressed through targeted amino acid supplementation, though this remains speculative pending further mechanistic research.
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Practical Takeaways
- •Plasma amino acid profiling, particularly asparagine and citrulline levels, may offer a complementary diagnostic tool alongside ACTH testing for PPID diagnosis in aged horses
- •Amino acid supplementation warrants further investigation as a potential therapeutic adjunct in PPID management, particularly given the altered amino acid profiles observed
- •These findings provide a biochemical basis for understanding oxidative stress and metabolic dysfunction in equine PPID, similar to pathways implicated in Parkinson's disease
Key Findings
- •Asparagine, citrulline, and glutamine plasma levels were significantly elevated in PPID-affected horses compared to non-PPID controls
- •Arginine was significantly higher in pergolide-treated horses with controlled ACTH (PPIDrr) than in untreated PPID and control groups
- •Cysteine was significantly lower in PPIDrr horses compared to all other groups
- •Asparagine, citrulline, and glutamine show potential as diagnostic biomarkers for PPID in horses