title: In Diabetic Kidney Disease Urinary Exosomes Better Represent Kidney Specific Protein Alterations Than Whole Urine.
abstract: BACKGROUND
  Predicting or diagnosing underlying kidney disease by analyzing whole urine remains the mainstay of nephrology practice. However, whole urine is a poor compartment to assess many structural changes in the kidney because whole urine contains only a few proteins derived from the kidney itself. Urinary exosomes, on the other hand, which are derived from the kidney, contain proteins secreted by the kidney. We experimentally tested the hypothesis that 'urinary exosomes more faithfully represent changes in the kidney tissue than whole urine'. A direct comparison between whole urine and urine exosomal levels of two chosen kidney disease markers, gelatinase and ceruloplasmin, was carried out on diabetic kidney disease patients.
  
  
  METHODS
  Urinary exosomes were separated from whole urine by sequential centrifugation including ultra-centrifugation. Gelatinase activity was measured using fluorosceinated gelatin as the substrate, and ceruloplasmin was measured by sandwich ELISA. A few kidney specimens from patients biopsied for atypical features were histochemically stained for validation of the biochemical results.
  
  
  RESULTS
  We found that changes in both, gelatinase (decreased activity) and ceruloplasmin (increased levels), in the urinary exosomes of diabetic kidney patients were in agreement with the alterations of these two proteins in the kidney tissue. In contrast, the levels of these two proteins in whole urine were highly variable and did not correlate with levels in the diabetic kidney tissue.
  
  
  CONCLUSIONS
  In conclusion, these results confirmed our hypothesis that protein markers in urinary exosomes better reflected the underlying protein changes in the kidney than in whole urine samples.
authors.affiliation: Division of Nephrology, John H. Stroger, Jr. Hospital of Cook County (JSH), Chicago, Ill., USA.
authors.forename: Krishnamurthy P
authors.initials: KP
authors.lastname: Gudehithlu
authors.forename: Ignacio
authors.initials: I
authors.lastname: Garcia-Gomez
authors.forename: Jane
authors.initials: J
authors.lastname: Vernik
authors.forename: Carolyn
authors.initials: C
authors.lastname: Brecklin
authors.forename: Mark
authors.initials: M
authors.lastname: Kraus
authors.forename: David J
authors.initials: DJ
authors.lastname: Cimbaluk
authors.forename: Peter
authors.initials: P
authors.lastname: Hart
authors.forename: George
authors.initials: G
authors.lastname: Dunea
authors.forename: Jose A L
authors.initials: JA
authors.lastname: Arruda
authors.forename: Ashok K
authors.initials: AK
authors.lastname: Singh
mesh_terms: D000328:Adult; D000418:Albumins / Q000737:chemistry; D015415:Biomarkers / Q000652:urine; D001706:Biopsy; D002570:Ceruloplasmin / Q000652:urine*; D003404:Creatinine / Q000652:urine; D003924:Diabetes Mellitus, Type 2 / Q000652:urine; D003928:Diabetic Nephropathies / Q000175:diagnosis* / Q000652:urine*; D004797:Enzyme-Linked Immunosorbent Assay; D055354:Exosomes / Q000737:chemistry*; D005260:Female; D019793:Fluorescein / Q000737:chemistry; D018093:Gelatinases / Q000652:urine*; D006801:Humans; D008297:Male; D008875:Middle Aged; D014461:Ultracentrifugation
chemical_list: D000418:Albumins; D015415:Biomarkers; D003404:Creatinine; D002570:Ceruloplasmin; D018093:Gelatinases; D019793:Fluorescein