Optimizing Urine Processing Protocols for Protein and Metabolite Detection
- *Corresponding Author:
- Nazema Y Siddiqui, MD, MHSc
Assistant Professor, Department of Obstetrics & Gynecology
Duke University Medical Center; DUMC 3192
Durham, NC 27710, USA
Tel: (919) 401-1006
Fax: (919) 401-1033
E-mail: [email protected]
Received Date: August 16, 2015; Accepted Date: December 16, 2015; Published Date: December 21, 2015
Citation: Siddiqui NY, DuBois LG, John-Williams LS, Thompson WJ, Grenier C, et al. (2015) Optimizing Urine Processing Protocols for Protein and Metabolite Detection. J Proteomics Bioinform S14:003. doi:10.4172/jpb.S14-003
Copyright: © 2015 Siddiqui NY, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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 (1st AM) 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 1st morning and random voided urine samples. Normalized protein concentrations were slightly higher in 1st AM 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.