The effect of chronic kidney disease on the urine proteome in the domestic cat (Felis catus)

Abstract

Chronic kidney disease (CKD) is a major cause of mortality in cats, but sensitive and specific biomarkers for early prediction and monitoring of CKD are currently lacking. The present study aimed to apply proteomic techniques to map the urine proteome of the healthy cat and compare it with the proteome of cats with CKD. Urine samples were collected by cystocentesis from 23 healthy young cats and 17 cats with CKD. One-dimensional sodium-dodecyl-sulfate polyacrylamide gel electrophoresis (1D-SDS-PAGE) was conducted on 4-12% gels. Two-dimensional electrophoresis (2DE) was applied to pooled urine samples from healthy cats (n = 4) and cats with CKD (n = 4), respectively. Sixteen protein bands and 36 spots were cut, trypsin-digested and identified by mass spectrometry. 1D-SDS-PAGE yielded an overall view of the protein profile and the separation of 32 ± 6 protein bands in the urine of healthy cats, while CKD cats showed significantly fewer bands (P < 0.01). 2-DE was essential in fractionation of the complex urine proteome, producing a reference map that included 20 proteins. Cauxin was the most abundant protein in urine of healthy cats. Several protease inhibitors and transport proteins that derive from plasma were also identified, including alpha-2-macroglobulin, albumin, transferrin, haemopexin and haptoglobin. There was differential expression of 27 spots between healthy and CKD samples (P < 0.05) and 13 proteins were unambiguously identified. In particular, increased expression of retinol-binding protein, cystatin M and apolipoprotein-H associated with decreased expression of uromodulin and cauxin confirmed tubular damage in CKD cats suggesting that these proteins are candidate biomarkers.

Dietary methionine restriction modulates renal response and attenuates kidney injury in mice

“…Clusterin has been shown to be a sensitive marker for the detection of drug‐induced nephrotoxicity (38, 39). Plasma A2M is used as a marker for chronic inflammation in cats and human subjects with kidney disease (40, 41). Cystastin C has been shown to be a more precise marker for monitoring kidney injury than creatinine in mice (42, 43).…”

Renal expression and urinary excretion of liver‐type fatty acid‐binding protein in cats with renal disease

“…For example, retinol binding protein and cystatin C levels are increased by dysfunction of proximal tubular reabsorption in cats. In contrast, Tamm‐Horsfall protein excretion decreases in cats associated with decreases in its production by damage to distal tubular cells . Carboxylesterase 5A (also known as cauxin), which produces a sex pheromone, is a major urinary protein in normal healthy cats and its excretion is decreased in cats with CKD due to decrease of number of proximal tubular cells expressing it .…”

“…In contrast, Tamm-Horsfall protein excretion decreases in cats associated with decreases in its production by damage to distal tubular cells. 11 Carboxylesterase 5A (also known as cauxin), which produces a sex pheromone, 12 is a major urinary protein in normal healthy cats 13 and its excretion is decreased in cats with CKD due to decrease of number of proximal tubular cells expressing it. [14][15][16][17] The increase of urinary excretion of these proteins usually results from functional, structural, or both damages in the glomerulus and renal tubules.…”

Top-Down Proteomics and Farm Animal and Aquatic Sciences

“…In fact, in these fields of research, two-dimensional gel electrophoresis (2DE) has been termed “the workhorse” for proteomics research [2]. Numerous examples may be found in the literature on AASP research using 2DE, including single stain gels [15,16,17,18] and 2DE-DIGE (difference gel electrophoresis) [19]. Additional alternative gel techniques such as blue native polyacrylamide (PAGE) gels, particularly suitable for membrane proteomics, and the study of protein complexes and protein–protein interactions [20], such as those in the mitochondria [21], have also been used.…”