A Pilot Study on the Urine Proteome of Cats Fed a High-Protein Complete Diet, Supplemented with or without Arginine, Ornithine or Zeolite

SIMPLE SUMMARY: The number and kind of proteins in the urine are of increasing scientific interest, as they might provide information on the health status of an organism. Besides diseases, however, further factors could influence the so-called “urine proteome”, such as dietary intake. In the present investigation, the urine of four healthy adult cats was analyzed. Each cat received a high-protein diet without or with supplements that could affect the protein metabolism: arginine, ornithine or zeolite. At the end of the feeding periods, the urine of the animals was collected. We found a huge number of proteins in the urine of the cats (means between 399 and 516 urinary proteins). According to an on-line database search, these proteins are associated with several biological processes. When the feeding groups were compared, a higher or lower abundance of some urinary proteins could be observed in the cats receiving the dietary supplements than the control treatment. Overall, our study provides basic data on the urine proteome of healthy adult cats. The huge number of urinary proteins implies the potential to identify biomarkers for health and disease, as well as for metabolic processes, which should be further investigated in future studies. ABSTRACT: Proteome analyses can be used to detect biomarkers for the healthy and diseased organism. However, data in cats are scarce, and no information is available on the potential impact of nutritional interventions on the feline urine proteome. In the present study, a label-free shotgun proteomics approach was performed to investigate the urinary proteins of four healthy adult cats. Each animal received a high-protein complete diet without (w/o) or with supplements that could affect the protein metabolism: arginine (+100% compared to the arginine concentration in the w/o diet), ornithine (+200% compared to the arginine concentration in the w/o diet) or zeolite (0.375 g/kg body weight/day). Our results demonstrate a huge number of proteins in the urine of cats (516 ± 49, 512 ± 39, 399 ± 149 and 455 ± 134 in the w/o, arginine, ornithine and zeolite group, respectively), which are associated with several biological processes. In addition, up- and downregulated urinary proteins could be detected in the dietary supplementation periods. Overall, the present pilot study provides basic data on the urine proteome of healthy adult cats. With increasing information, the numerousness of urinary proteins implies the potential to identify biomarkers and metabolic pathways in the feline organism.