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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 (R 2  ≥ 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 (R 2 (Y) > 0.95, Q 2 (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., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier B.V.)

Objectives: The objective of this study was to evaluate the presence of traces of thiamazole in the urine of owners of hyperthyroid cats treated with antithyroid drugs., Methods: Urine was collected from 24 owners of hyperthyroid cats, five human patients treated with thiamazole and five healthy humans without any contact with antithyroid drugs. All owners of hyperthyroid cats were asked to fill out a questionnaire. Urine of hyperthyroid cats was collected by spontaneous micturition. All urine samples were stored at -20°C until analysis by ultra-high-performance liquid chromatography coupled to high-resolution quadrupole Orbitrap mass spectrometry., Results: These owners were assessed to have a lot of contact with their cat. Adherence to antithyroid medication handling guidelines was rather poor. High concentrations of thiamazole were detected in all feline samples (median concentration 2818 ng/ml; range 104-15,127) and in the urine of all human patients treated with thiamazole (median concentration 4153 ng/ml; range 1826-5009). No thiamazole was detected in the urine of owners of hyperthyroid cats (limit of detection 3.88 ng/ml; limit of quantification 11.75 ng/ml)., Conclusions and Relevance: The results regarding the potential exposure of owners of hyperthyroid cats to antithyroid drugs are reassuring. Nevertheless, prudence is still warranted when administering antithyroid drugs. Whether these results can be extrapolated to the use of transdermal application requires further investigation.

The exact role of beta 2microglobulin (beta 2m) in dialysis amyloidosis is yet not known. Local release of beta 2m from the endothelial cells of the lung and other tissues as a consequence of acute-phase activation due to the contact of blood with membranes has still to be considered a possible pathogenetic factor in this syndrome. beta 2m kinetics and decrease of glutathione content in RBC were studied in 41 chronic hemodialysis patients during cuprophan dialysis. The latter test reflects the RBC scavenger function for free oxygen radicals. Only 30% of patients showed a clinically significant increase in beta 2m. The change in beta 2m in this group between the start and 180 minutes, corrected for plasma volume, was 23.1 +/- 3.6% and the change in gluthathione content between the start and 15 minutes was 4.5 +/- 3.4%. In these patients there was a significant correlation between beta 2m production and decrease of gluthathione (R = -0.61, p = 0.0299). It is possible that the production of free oxygen radicals during bioincompatible dialysis leads to cellular toxicity with release of beta 2m which may be prevented to some extent by the scavenger role of RBC.