Potential urinary biomarkers of disease activity in Crohn's disease

Abstract

Objective. Measurement of the immunoreactive urinary albumin (ir-uAlb) concentration by immunological methods was found to be an effective method to identify disease activity in Crohn's disease (CD). Recently a size-exclusion (SE) high performance liquid chromatography (HPLC) method was developed to measure both ir-uAlb and non-immunoreactive urinary albumin (total, t-uAlb). We aimed to follow-up one of our CD patients with frequent remissions and exacerbation phases comparing the changes of disease activity parameters and the concentration of ir-uAlb and t-uAlb. The surprising results led us to perform measurements in greater depth. Material and methods. Concentration of ir-uAlb was measured by immunoturbidimetry (IT) and t-uAlb by SE-HPLC. Albumin peak of SE-HPLC was collected and applied to a reversed-phase (RP) HPLC and to gel-electrophoresis. Eluted peaks of RP-HPLC and identified bands of gel-electrophoresis were analyzed using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF/MS). Results. The concentration of t-uAlb was 15 times higher than that of the ir-uAlb during active state. The RP-HPLC and the gel-electrophoresis separation proved that albumin peak by size-exclusion consists of three different peaks. MALDI-TOF/MS measurements identified α1-acid-glycoprotein and Zn-α2-glycoprotein as major, and albumin as minor protein. Conclusions. Peak of albumin of SE-HPLC contains a significant amount of glycoprotein during the active phase of CD, which could not be detected in remission. Urinary α1-acid-glycoprotein and/or Zn-α2-glycoprotein could be an ideal disease activity biomarker of CD.

Key Words::

• Alpha-1-acid-glycoprotein
• biomarker
• Crohn's disease
• zinc-alpha-2-glycoprotein

Acknowledgements

This work was supported by grants PD 76395 (ZSz) and PD 78599 (AT) of the Hungarian Scientific Research Fund (OTKA). The technical assistance of Sámikné Varga Ilona and Erzsébet Györgyi is highly appreciated.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.