Performance assessment of an equine metabolomics model for screening a range of anabolic agents

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

BACKGROUND

Metabolomics 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.

RESULTS

Systematic 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 = 1949) 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 = 2348) 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).

SIGNIFICANCE

This 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.

Sample Preparation Techniques for Growth-Promoting Agents in Various Mammalian Specimen Preceding MS-Analytics

The misuse of growth-promoting drugs such as beta-2 agonists and steroids is a known problem in farming and sports competitions. Prior to the analysis of biological samples via liquid chromatography (LC)-mass spectrometry (MS) or gas chromatography (GC)-MS, sufficient sample preparation is required to reliably identify or determine the residues of drugs. In practice, broad screening methods are often used to save time and analyze as many compounds as possible. This review was conceptualized to analyze the literature from 2018 until October 2023 for sample preparation procedures applied to animal specimens before LC- or GC-MS analysis. The animals were either used in farming or sports. In the present review, solid phase extraction (SPE) was observed as the dominant sample clean-up technique for beta-2 agonists and steroids, followed by protein precipitation. For the extraction of beta-2 agonists, mixed-mode cation exchanger-based SPE phases were preferably applied, while for the steroids, various types of SPE materials were reported. Furthermore, dispersive SPE-based QuEChERs were utilized. Combinatory use of SPE and liquid-liquid extraction (LLE) was observed to cover further drug classes in addition to beta-2 agonists in broader screening methods.