Abstract: FR-PO617

Uromodulin Proteolytic Processing Is Altered in Youth with Type 1 Diabetes

Session Information

Category: Diabetes

  • 501 Diabetes Mellitus and Obesity: Basic - Experimental

Authors

  • Van, Julie Anh Dung, University of Toronto, Toronto, Ontario, Canada
  • Hauschild, Anne-Christin, Princes Margaret Cancer Center, Toronto, Ontario, Ontario, Canada
  • Batruch, Ihor, Mount Sinai Hospital, Toronto, Ontario, Canada
  • Diamandis, Eleftherios P., Mount Sinai Hospital and University Health Network, Toronto, Alberta, Canada
  • Scholey, James W., University of Toronto, Toronto, Ontario, Canada
  • Konvalinka, Ana, University of Toronto, Toronto, Ontario, Canada
Background

Dysregulated proteolytic activity in the kidney may induce early functional and structural changes in type 1 diabetes, and this activity may be specific to some proteases and their protein substrates. Thus, peptides generated within kidney may be excreted into the urine and provide a footprint of intrarenal proteolysis. We aim to compare urinary peptidomes of youth with type 1 diabetes in relation to healthy peers and to infer protease activity in the kidney from differentially excreted peptides.

Methods

We obtained second-morning, midstream urines from 15 cases with type 1 diabetes and 15 age- and sex-matched healthy controls. Urine volumes normalized to creatinine were subjected to 10kDa ultrafiltration to isolate naturally occurring peptides. Peptides were then fractionated and analyzed on Q-Exactive mass spectrometer. MaxQuant software was used for peptide identification and label-free quantification. Proteasix, an online tool, was used to predict proteases responsible for generating differentially excreted peptides.

Results

A total of 6323 naturally occurring peptides were quantified. Of these, 163 peptides were consistently detected across all thirty urine samples. Five peptides from this subset were differentially excreted between the groups (FDR, q < 0.05), and they derived from regions near the C-terminus of uromodulin and clusterin. Peptide intensities strongly correlated with glycated hemoglobin and blood glucose, and only weakly so with albumin/creatinine ratio. Interestingly, urinary excretion of the uromodulin protein was not different between groups, suggesting an increase in proteolysis of uromodulin in the kidney. The top predicted proteases included hepsin, neutrophil elastase, and plasmin.

Conclusion

Our analysis of the urinary peptidome revealed early differences in the excretion rates of uromodulin peptides in adolescents with diabetes in the absence of microvascular complications, compared to healthy age-matched subjects. We conclude that sustained hyperglycemia is associated with early activation of proteolytic enzymes in the kidney before the onset of microalbuminuria.