Urinary Glycosylated IGF2 peptides in association with CKD

Chronic kidney disease (CKD) is prevalent in 10% of world’s adult population, with Estimated Glomerular filtration rate (eGFR) and albuminuria employed in diagnosis. Role of protein glycosylation in causal mechanisms of CKD progression is largely unknown. Aim of this study was to identify urinary O-linked glycopeptides in association to CKD for better characterization of CKD molecular manifestations. Urine samples from 2 healthy and 8 CKD subjects were analyzed by CE-MS/MS and glycopeptide analysis using Proteome Discoverer 1.4. Distribution of identi-fied glycopeptides and correlation with Age, eGFR and Albuminuria were evaluated in 3810 da-tasets. In total, 17 O-linked glycopeptides from 7 different proteins were identified, derived primarily from Insulin-like growth factor-II (IGF2). Glycosylation occurred at the surface ex-posed IGF2 Threonine 96 position. Three glycopeptides (DVStPPTVLPDNFPRYPVGKF, DVStPPTVLPDNFPRYPVG and DVStPPTVLPDNFPRYP) exhibited positive correlation with Age. Glycopeptide (tPPTVLPDNFPRYP) showed strong negative association with eGFR. These results suggest that with aging and deteriorating kidney function, alterations in IGF2 proteoforms take place; which may reflect changes in mature IGF2 protein. Our results corroborate this hypothesis as IGF2 increased plasma levels were observed in CKD patients. Protease predictions, consider-ing also available transcriptomics data, suggest activation of cathepsin S with CKD, meriting further investigation.