title: Optimizing Urine Processing Protocols for Protein and Metabolite Detection.
abstract: BACKGROUND
  In urine, factors such as timing of voids, and duration at room temperature (RT) may affect the quality of recovered protein and metabolite data. Additives may aid with detection, but can add more complexity in sample collection or analysis. We aimed to identify the optimal urine processing protocol for clinically-obtained urine samples that allows for the highest protein and metabolite yields with minimal degradation.
  
  
  METHODS
  Healthy women provided multiple urine samples during the same day. Women collected their first morning (1stAM) void and another "random void". Random voids were aliquotted with: 1) no additive; 2) boric acid (BA); 3) protease inhibitor (PI); or 4) both BA + PI. Of these aliquots, some were immediately stored at 4°C, and some were left at RT for 4 hours. Proteins and individual metabolites were quantified, normalized to creatinine concentrations, and compared across processing conditions. Sample pools corresponding to each processing condition were analyzed using mass spectrometry to assess protein degradation.
  
  
  RESULTS
  Ten Caucasian women between 35-65 years of age provided paired 1stmorning and random voided urine samples. Normalized protein concentrations were slightly higher in 1stAM compared to random "spot" voids. The addition of BA did not significantly change proteins, while PI significantly improved normalized protein concentrations, regardless of whether samples were immediately cooled or left at RT for 4 hours. In pooled samples, there were minimal differences in protein degradation under the various conditions we tested. In metabolite analyses, there were significant differences in individual amino acids based on the timing of the void.
  
  
  CONCLUSIONS
  For comparative translational research using urine, information about void timing should be collected and standardized. For urine samples processed in the same day, BA does not appear to be necessary while the addition of PI enhances protein yields, regardless of 4°C or RT storage temperature.
authors.affiliation: Division of Urogynecology & Reconstructive Pelvic Surgery; Department of Obstetrics & Gynecology, Duke University, Durham, NC, USA.
authors.forename: Nazema Y
authors.initials: NY
authors.lastname: Siddiqui
authors.affiliation: Center for Genomic & Computational Biology; Duke University, Durham, NC, USA.
authors.forename: Laura G
authors.initials: LG
authors.lastname: DuBois
authors.affiliation: Center for Genomic & Computational Biology; Duke University, Durham, NC, USA.
authors.forename: Lisa
authors.initials: L
authors.lastname: St John-Williams
authors.affiliation: Center for Genomic & Computational Biology; Duke University, Durham, NC, USA.
authors.forename: Thompson J
authors.initials: TJ
authors.lastname: Will
authors.affiliation: Division of Gynecologic Oncology; Department of Obstetrics & Gynecology, Duke University, Durham, NC, USA.
authors.forename: Carole
authors.initials: C
authors.lastname: Grenier
authors.affiliation: Department of Biostatistics and Bioinformatics, Duke University, Durham, NC, USA.
authors.forename: Emily
authors.initials: E
authors.lastname: Burke
authors.affiliation: Division of Urology; Department of Surgery, Duke University, Durham, NC, USA.
authors.forename: Matthew O
authors.initials: MO
authors.lastname: Fraser
authors.affiliation: Division of Urogynecology & Reconstructive Pelvic Surgery; Department of Obstetrics & Gynecology, Duke University, Durham, NC, USA.
authors.forename: Cindy L
authors.initials: CL
authors.lastname: Amundsen
authors.affiliation: Division of Gynecologic Oncology; Department of Obstetrics & Gynecology, Duke University, Durham, NC, USA.
authors.forename: Susan K
authors.initials: SK
authors.lastname: Murphy
keywords: Boric acid; First morning void; Metabolomics; Protease inhibitors; Proteomics; Random void; Urine; Urine protein degradation