Urine Is An Ideal Source Of Disease Markers

The past decade witnessed a few biomarkers discovered and validated; however, biomarker research as a whole has not been fruitful as expected. Biomarker is the measurable change associated with a physiological or pathophysiological process. Biomarker studies commonly monitor the composition of plasma, which is under strict homeostatic control, while urine is not. Urine is a partial filtrate of blood; therefore, urine serves not only as an ideal source of biomarker discovery for diseases of the kidney and other tissues of the urogenital system but also as a potential source of information on diseases in other physiological systems. In the first part, we show that changes in the coagulation status of blood can be more sensitively detected in urine than in plasma. Plasma and urine protein composition was analysed by LC-MS/MS and Western blot in six SD female rats before and after treatment with heparin or argatroban. In argatroban treated group,62proteins changed in urine, only one of which changed in plasma. In heparin treated group,27proteins changed in urine but only three other proteins changed in plasma. LC-MS/MS and Western blot analyses demonstrated drug-induced increases in transferrin and hemopexin levels in urine but not in plasma. Our data indicates that urine may serve as a source for more sensitive detection of protein biomarkers than plasma.However, urinary biomarker research can be intimidating because changes in urine are very complicated, and determining which factors are associated with any particular pathophysiological condition, especially in human samples, is very difficult. As urine accumulates all types of changes, identifying the precise cause of changes in the urine proteome is challenging and crucial in biomarker discovery. Many factors which can influence urine proteome should be taken into consideration. Transient increase of blood glucose frequently occurs after the consumption of food and may be an interfering factor in biomarker studies. In the second part, a transient increase of blood glucose level was achieved by performing an oral glucose tolerance test on nine healthy human volunteers. Only one protein was increased in the urine after glucose intake. Thus, transient increase of blood glucose levels may not be a major interfering factor in biomarker studies, at least with current levels of detection sensitivity.Besides, the study of the human urinary proteome can provide significant insights into normal and disease physiology. A comprehensive map of the human urinary proteome can offer information which can be applied to various diseases. In the third part, we carried out a multi-dimensional fraction strategy coupled with high-resolution mass spectrometry to profile composition of normal human urinary proteome. In all, we identified4657proteins with less than1%false discovery rate. More analysis will be performed on this data and we aim to provide a comprehensive reference list for identification and characterization of urinary biomarkers of various diseases.On the other hand, liver perfusates exhibit theoretical advantages regarding the discovery of disease biomarkers because they contain proteins that readily enter the blood-stream, and perfusion preserves the disease state in its natural context. The purpose of the study is to explore the value of liver perfusate proteome in the biomarker discovery of liver diseases. In the fourth part,86differentially expressed proteins were identified in perfusates from isolated rat livers metastasized by Walker-256tumor cells. Among these proteins, three proteins were chosen for Western blot analysis. As a member of the14-3-3protein family, Ywhab may participate in liver metastasis and could be a potential biomarker for this disease. These results show that perfusate proteome can be used as an alternative initial resource for biomarker identification, which ultimately requires validation in serum.The study aimed to find a better source of biomarker discovery for diseases. We considered these interference factors in urine biomarker studies, carried out a comprehensive analysis of human urinary proteome and showed an alternative source for biomarker discovery. We believe all of that will offers considerable potential to contribute to biomarker analysis in the future.