Factors to consider in the verification of urinary biomarkers

Urine proteome changes in a chronic unpredictable mild stress (CUMS) mouse model of major depressive disorder

Major depressive disorder (MDD) is a prevalent complex psychiatric disorder, and there are no effective biomarkers for clinical diagnosis. Urine is not subjected to homeostatic control, allowing it to reflect the sensitive changes that occur in various diseases. In this study, we examined the urine proteome changes in a chronic unpredictable mild stress mouse model of MDD. Male C57BL/6 mice were subjected to chronic unpredictable mild stress for 5 weeks. The tail suspension test and sucrose consumption test were then applied to evaluate depression-like behaviors. The urine proteomes on day 0 and day 36 in the CUMS group were profiled by liquid chromatography coupled with tandem mass spectrometry (LCMS/MS). A total of 36 differential proteins were identified, 19 of which have been associated with the pathogenic mechanisms of MDD. There was an average of two differential proteins that were identified through 1,048,574 random combination statistical analyses, indicating that at least 95 % of the differential proteins were reliable. The differential proteins were mainly associated with blood coagulation, inflammatory responses and central nervous system development. Our preliminary results indicated that the urine proteome can reflect changes associated with MDD in the CUMS model, which provides potential clues for the diagnosis of MDD.

Identification of inflammatory markers suitable for non-invasive, repeated measurement studies in biobehavioral research: A feasibility study

Introduction

Studying the role of the immune system in the interaction between mental and physical health is challenging. To study individuals with an intensive, longitudinal study design that requires repetitive sampling in their daily life, non-invasive sampling techniques are a necessity. Urine can be collected in a non-invasive way, but this may be demanding for participants and little is known about fluctuation of inflammatory markers in urine over time. The aim of this study was to investigate the feasibility of non-invasive sampling, and to explore intra-individual differences in inflammatory markers in urine.

Materials & methods

Ten healthy individuals collected 24-hour urine for 63 consecutive days. In a pilot analysis, 39 inflammatory markers were examined for detectability in urine, stability over time and under storage conditions, and daily fluctuations. Multiplex analyses were used to quantify levels of eight selected markers: C-reactive protein (CRP), Fractalkine, Interleukin-1 receptor-antagonist (IL-1RA), interferon-α (IFNα), interferon-γ (IFNγ), Interferon gamma-induced protein 10 (IP10), Macrophage inflammatory protein-1β (MIP-1β), and Vascular Endothelial Growth Factor (VEGF). Cross-correlations were calculated between the overnight and 24-hour samples were calculated, to examine whether 24-hour urine could be replaced by the overnight portion for better feasibility. We examined intra- and interindividual differences in the levels of inflammatory markers in urine and the fluctuations thereof.

Results

This study showed that levels of selected inflammatory markers can be detected in urine. Cross-correlation analyses showed that correlations between levels of inflammatory markers in the night portion and the 24-hour urine sample varied widely between individuals. In addition, analyses of time series revealed striking inter- and intra-individual variation in levels of inflammatory markers and their fluctuations.

Conclusion

We show that the assessment of urinary inflammatory markers is feasible in an intensive day-to-day study in healthy individuals. However, 24-hour urine cannot be replaced by an overnight portion to alleviate the protocol burden. Levels of inflammatory markers show substantial variation between and within persons.