Optimization and validation of metabolomics methods for feline urine and serum towards application in veterinary medicine

Abstract

BackgroundMetabolomics is an emerging and powerful technology that offers a comprehensive view of an organism's physiological status. Although widely applied in human medicine, it is only recently making its introduction in veterinary medicine. As a result, validated metabolomics protocols in feline medicine are lacking at the moment. Since biological interpretation of metabolomics data can be misled by the extraction method used, species and matrix-specific optimized and validated metabolomic protocols are sorely needed. ResultsSystematic optimization was performed using fractional factorial experiments for both serum (n=57) and urine (n=24), evaluating dilution for both matrices, and aliquot and solvent volume, protein precipitation time and temperature for serum. For the targeted (n=76) and untargeted (n=1,949) validation of serum respectively, excellent instrumental, intra-assay and inter-day precision were observed (CV≤ 15% or 30%, respectively). Linearity deemed sufficient both targeted and untargeted (R2≥0.99 or 0.90, respectively). An appropriate targeted recovery between 70 and 130% was achieved. For the targeted (n=69) and untargeted (n=2,348) validation of the urinary protocol, excellent instrumental and intra-assay precision were obtained (CV≤ 15% or 30%, respectively). Subsequently, the discriminative ability of our metabolomics methods was confirmed for feline chronic kidney disease (CKD) by univariate statistics (n=41 significant metabolites for serum, and n=55 for urine, p-value<0.05) and validated OPLS-DA models (R2(Y)>0.95, Q2(Y)>0.65, p-value<0.001 for both matrices). SignificanceThis study is the first to present an optimized and validated wholistic metabolomics methods for feline serum and urine using ultra-high performance liquid chromatography coupled to quadrupole-Orbitrap high-resolution mass spectrometry. This robust methodology opens avenues for biomarker panel selection and a deeper understanding of feline CKD pathophysiology and other feline applications.