Identification of salivary peptidomic biomarkers in chronic kidney disease patients undergoing haemodialysis.

Chronic kidney disease (CKD) is a worldwide public health problem. To detect discriminating salivary peptide profiles between CKD patients undergoing haemodialysis (HD) and healthy controls (HCs) and to screen candidate biomarkers for CKD, we preliminarily explored the diagnostic potentiality of saliva. Saliva samples from 30 CKD HD patients and 35 HCs were analysed using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) combined with weak cation exchange magnetic beads. Ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was performed to identify the potential biomarkers. The HD group showed higher salivary pH. We chose 3 significantly different (p < 0.01) peptides to establish an effective discrimination model which was validated by a decision tree and ROC curve. Statistically significant correlations (p < 0.05) between the candidate salivary peptidomic biomarkers and serum parameters were found. Eight differentially expressed peptides were identified as segments of Histatin-1, Mucin-7, salivary acidic proline-rich phosphoprotein 1/2 (aPRP 1/2), submaxillary gland androgen-regulated protein 3B, and Histatin-3. Our findings substantiate the pivotal role of peptidomic methods in identifying biomarkers for CKD. Histatin-1, Mucin-7 and aPRP 1/2 are expected to be candidate salivary biomarkers of CKD HD patients. Furthermore, saliva might be a promising non-invasive diagnostic biofluid.