Peptides in Plasma, Urine, and Dialysate: Toward Unravelling Renal Peptide Handling

Abstract

Purpose: The peptidomes of spent hemodialysate, urine, and plasma are investigated, to shed light on peptide handling in the kidney. Experimental Design: Fifteen plasma, 15 urine, and 13 spent hemodialysate samples are collected from age-and sex-matched subjects with chronic kidney disease. Peptide identification and quantification are performed with capillary electrophoresis-coupled mass spectrometry. Results: A total of 6278 urinary peptides, 1743 plasma peptides, and 1727 peptides from spent hemodialysate are detected. Of these, sequences can be assigned to 1580, 419, and 352 peptides, respectively. A strong correlation in peptide abundance between urine and spent hemodialysate (p = 3 × 10 −21 , Rho = 0.52), a moderately strong correlation between spent hemodialysate and plasma (p = 4.5 × 10 −5 , Rho = 0.30), and no significant correlation between urine and plasma (p = 0.11, Rho = 0.094) are found. Collagen and fibrinogen alpha peptides are highly abundant in all three body fluids. In spent hemodialysate, thymosin ß4 is one of the most abundant peptides, which is shown to be negatively associated with the estimated glomerular filtration rate (Rho = −0.39, p-value = 3.9 × 10 −81). Conclusion and Clinical Relevance: The correlation of peptide abundance in these three body fluids is lower than expected, supporting the hypothesis that tubular reabsorption has a major impact on urinary peptide content. Further investigation of thymosin ß4 in hemodialysis is thus warranted.

Urinary Protein and Peptide Markers in Chronic Kidney Disease

“…Harald Mischak's group is the leader in MS studies on the urinary peptidome and proteome. This group described 1580 native urinary peptides, showing that 73% were unique for urine and proving the clinical value of native urinary peptide markers for diagnosing several diseases, including those associated with kidney damage [14,77,78].…”

Proteomics in Kidney and Cardiovascular Clinical Research

“…[7] Several urinary peptidomics/proteomics studies using mass spectrometry (MS) technologies, like robust capillary electrophoresis coupled to MS (CE-MS) [8] or complementary liquid chromatography-based MS (LC-MS), [9] to investigate urinary peptides to improve diagnostic and prognostic assessment in various kidney diseases. [10][11][12][13][14][15] In an explorative study, He et al [16] used respective CE-MS technique to compare the distribution of the peptidome in plasma, urine, and dialysate to increase the knowledge of filtration and reabsorption processes in the kidney.…”

“…[20] However, sample handling is a major issue for the body fluid-based MS analyses regarding preanalytical variations and harmonization of sample processing protocols. [16,[21][22][23][24] Besides body fluids, proteomics analysis directly off affected tissues is a highly promising strategy to unravel disease mechanism in kidney and cardiovascular disorders. Label-free quantification LC-MS was integrated in a multi-omics workflow to investigate the proteome dynamics during cardiac remodeling.…”

“…[ 10–15 ] In an explorative study, He et al. [ 16 ] used respective CE‐MS technique to compare the distribution of the peptidome in plasma, urine, and dialysate to increase the knowledge of filtration and reabsorption processes in the kidney.…”

“…[ 20 ] However, sample handling is a major issue for the body fluid‐based MS analyses regarding pre‐analytical variations and harmonization of sample processing protocols. [ 16,21–24 ]…”