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Abstract: TH-PO878

Urinary Proteomics Identifies Signature of Early Type 1 Diabetes Linked to Keratan Sulfate Degradation and Lysosomal Enzymes

Session Information

Category: Diabetic Kidney Disease

  • 601 Diabetic Kidney Disease: Basic

Authors

  • Van, Julie Anh Dung, University of Toronto, Toronto, Ontario, Canada
  • Clotet Freixas, Sergi, University Health Network Toronto, Toronto, Ontario, Canada
  • Elia, Yesmino, The Hospital for Sick Children, Toronto, Alberta, Canada
  • Mahmud, Farid H., The Hospital for Sick Children, Toronto, Alberta, Canada
  • Scholey, James W., University of Toronto, Toronto, Ontario, Canada
  • Konvalinka, Ana, University Health Network Toronto, Toronto, Ontario, Canada
Background

Maladaptive changes have been described in the diabetic kidney long before the onset of microalbuminuria, in the form of renal hyperfiltration and hypertrophy. Our aim is to examine the urinary proteome of youths with early, uncomplicated type 1 diabetes and to examine the biological processes and pathways underlying early changes in the diabetic kidney.

Methods

We performed urinary proteomics on samples from 15 otherwise healthy youths with type 1 diabetes and 15 non-diabetic peers. All youths were < 19 years of age, free of comorbidity including microalbuminuria, and not using anti-hypertensive drugs. Urine volumes normalized to creatinine were subjected to 10-kDa ultrafiltration to isolate proteins. Proteins (200 micrograms) were digested with trypsin, fractionated using strong cation exchange chromatography, and analyzed on Q-Exactive mass spectrometer. MaxQuant software was used for peptide/protein identification and label-free quantification. The PathDIP database was searched to identify the top pathways associated with differentially excreted proteins. Proteins were validated in a second cohort of 30 youths with and without diabetes using enzyme-linked immunosorbent assays.

Results

Of the 2313 proteins quantified, 576 were detected across all thirty urine samples. Of these, 34 were differentially excreted between groups (Benjamini-Hochberg FDR, Q < 0.05). More than half of these differentially excreted proteins were lysosomal enzymes, and the dominant terms associated with these lysosomal enzymes include “hydrolase activity”, “glycosaminoglycan degradation”, and “keratan sulfate proteoglycan”. Increased urinary excretion rates of lumican and hexosaminidase A were validated in a second cohort, representing a core protein and an enzyme that degrades glycosidic bonds in keratan sulfate.

Conclusion

Lysosomal enzymes associated with keratan sulfate degradation were overrepresented in urines from youths with diabetes, suggesting that extracellular matrix remodeling may be an early response of the kidney to hyperglycemia.