Plasma Amino Acids in Horses Suffering from Pituitary Pars Intermedia Dysfunction

Area of Science:

• Veterinary Medicine
• Equine Endocrinology
• Biochemistry

Background:

• Pituitary pars intermedia dysfunction (PPID) is a common endocrine disease in aged horses.
• Oxidative damage to dopaminergic pathways is implicated in both PPID and Parkinson's disease, suggesting potential biochemical links.
• Alterations in serum amino acid profiles have been observed in Parkinson's disease, prompting investigation in equine PPID.

Purpose of the Study:

• To investigate changes in the plasma amino acid profile of horses diagnosed with PPID.
• To identify potential amino acid biomarkers for PPID diagnosis.
• To explore the role of amino acid supplementation in managing PPID.

Main Methods:

• Collected EDTA plasma from horses presented for laboratory blood examinations.
• Measured basal ACTH concentrations to categorize horses into PPID (ACTH ≥ 100 pg/mL) and non-PPID (nPPID, ACTH < 30 pg/mL) groups.
• Further categorized horses based on pergolide treatment and ACTH levels (PPIDrr, PPIDarr).
• Determined plasma amino acid profiles for all included horses.

Main Results:

• Significant differences in plasma amino acid concentrations were observed between PPID and nPPID groups.
• Arginine levels were higher in PPIDrr horses compared to PPID and nPPID.
• Asparagine was significantly elevated in PPID, PPIDrr, and PPIDarr groups versus nPPID.
• Citrulline was higher in PPIDrr horses than in nPPID and PPID groups.
• Cysteine was lower in PPIDrr horses compared to other groups.
• Glutamine was higher in PPID and PPIDarr groups than in nPPID.

Conclusions:

• Plasma amino acid profiles differ significantly in horses with PPID compared to healthy controls.
• Asparagine, citrulline, and glutamine show promise as potential diagnostic markers for equine PPID.
• These findings suggest novel avenues for research into amino acid supplementation strategies for PPID management.