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Kidney Week

Abstract: PO0245

Dicarbonyl L-Xylulose Reductase (DCXR) as Surrogate for "Muddy" Brown Granular Casts and Diagnostic Biomarker for Acute Tubular Injury

Session Information

Category: Acute Kidney Injury

  • 102 AKI: Clinical, Outcomes, and Trials

Authors

  • Varghese, Vipin, Department of Nephrology, Ochsner Clinic Foundation, New Orleans, Louisiana, United States
  • Ramanand, Akanksh, Department of Nephrology, Ochsner Clinic Foundation, New Orleans, Louisiana, United States
  • Abbruscato, Frank C., Department of Nephrology, Ochsner Clinic Foundation, New Orleans, Louisiana, United States
  • O'Reilly, Patrick Edward, Department of Biology, College of Charleston, Charleston, South Carolina, United States
  • Suplee, Colin, Department of Biology, College of Charleston, Charleston, South Carolina, United States
  • Bland, Alison, Department of Biology, College of Charleston, Charleston, South Carolina, United States
  • Neely, Benjamin A., National Institute for Standards and Technology, Charleston, South Carolina, United States
  • Matute Trochez, Luis A., Department of Nephrology, Ochsner Clinic Foundation, New Orleans, Louisiana, United States
  • Buckner, Lyndsey R., Biorepository Unit, Ochsner Clinic Foundation, New Orleans, Louisiana, United States
  • Janech, Michael G., Department of Biology, College of Charleston, Charleston, South Carolina, United States
  • Velez, Juan Carlos Q., Department of Nephrology, Ochsner Clinic Foundation, New Orleans, Louisiana, United States
Background

Detection of abundant “muddy” brown granular casts (MBGC) during microscopic examination of the urinary sediment (MicrExUrSed) is pathognomonic of acute tubular injury (ATI). Because hospital laboratories do not optimally report MBGC, nephrologists have to independently perform MicrExUrSed. Thus, a diagnostic test to identify MBGC without performance of MicrExUrSed could be clinically useful. Unlike most AKI biomarker discovery approaches, we hypothesized that MBGC-enriched urinary sediment (MBGC-sedi) contains unique proteins that could serve as biomarkers of ATI.

Methods

MicrExUrSed was performed in specimens from patients with acute kidney injury (AKI) seen for nephrology consultation with a suspected etiology of ATI. Specimens from 3 patients containing numerous MBGC (>10 per low power field in >50% of slide) were collected, subjected to low speed centrifugation (100g), proteolytically digested and analyzed by nano-LC tandem mass spectrometry. Identified proteins were quantified by normalized spectral abundance factor (NSAF). Proteins were identified by MASCOT and accepted at <1% false discovery. Presence of proteins in casts was verified by immunofluorescence (IF) and western blotting (WB).

Results

A total of 242 proteins were significantly more abundant in MBGC-sedi specimens respect to the supernatant (p<0.05). Among the identified proteins unique to the MBGC-sedi, we selected dicarbonyl L-xylulose reductase (DCXR) as a candidate ATI biomarker because it was the protein with the lowest p value for MBGC-sedi specificity (p=0.00012, per NSAF) and only identified in MBGC-sedi . To validate the proteomics, in a separate set of MBGC-sedi specimens from patients with AKI due to ATI (n = 10), presence of DCXR was probed by WB and detected in 6 of 7 cases, and DCXR localization within MBGC by IF was verified in 3 of 3 cases.

Conclusion

DCXR is abundant in MBGC-sedi and may be a biomarker of ATI as an etiology of AKI. DCXR is an enzyme expressed in the kidney, primarily localized in proximal tubuli, absent in glomeruli. At the cellular level, DCXR is involved in metabolic and osmotic stress detoxification. We conclude that urinary DCXR is a potential target molecule for ATI diagnosis.

Funding

  • Other NIH Support