Exploratory Metabolomic Fingerprinting of Aqueous Humor in Healthy Horses and Donkeys, and in Horses with Ocular Pathologies

This study aims to generate foundational metabolomic data of aqueous humor (AH) in healthy horses and donkeys, and to investigate potential changes or trends in the metabolomic profile associated with age, sex or ocular pathology in horses. The AH metabolomic fingerprint from 5 donkeys and 35 equine eyes (17 controls, 8 with cataracts, 6 with retinal disease and 4 with anterior chamber disease (ACD)) were analyzed using nuclear magnetic resonance (NMR) spectroscopy. A linear mixed-effects model, with individual horse as a random effect and group as a fixed effect, with multiple testing correction using the Benjamini-Hochberg false discovery rate (FDR) method was used to compare groups. The metabolomic profile of the donkeys and horse's AH is very similar to that of other mammals. Threonine was higher in young horses (<i>p</i> = 0.04), and creatinine was elevated in males (<i>p</i> = 0.04). Compared with control groups, dimethyl sulfone was higher in the retina (<i>p</i> < 0.00) and cataract (<i>p</i> = 0.05) groups. Arginine (<i>p</i> = 0.05) and valine (<i>p</i> = 0.03) were lower in the retina group compared to controls. This study successfully characterized the AH metabolomic profile in healthy horses and donkeys and identified several metabolites that could be associated with ocular pathology, warranting further investigation to determine their potential as biomarkers of ocular disease.