Comprehensive Analysis of Individual Variation in the Urinary Proteome Revealed Significant Gender Differences.

Disease biomarkers are the measurable changes associated with a pathophysiological process. Without homeostatic control, urine accumulates systematic changes in the body. Thus, urine is an attractive biological material for the discovery of disease biomarkers. One of the major bottlenecks in urinary biomarker discovery is that the concentration and composition of urinary proteins are influenced by many physiological factors. To elucidate the individual variation and related factors influencing the urinary proteome, we comprehensively analyzed the urine samples from healthy adult donors (aged 20-69 years). Co-expression network analysis revealed protein clusters representing the metabolic status, gender-related differences and age-related differences in urinary proteins. In particular, we demonstrated that gender is a crucial factor contributing to individual variation. Proteins that were increased in the male urine samples include prostate-secreted proteins and TIMP1, a protein whose abundance alters under various cancers and renal diseases; however, the proteins that were increased in the female urine samples have known functions in the immune system. Nine gender-related proteins were validated on 85 independent samples by multiple reaction monitoring. Five of these proteins were further used to build a model that could accurately distinguish male and female urine samples with an area under curve value of 0.94. Based on the above results, we strongly suggest that future biomarker investigations should consider gender as a crucial factor in experimental design and data analysis. Finally, reference intervals of each urinary protein were estimated, providing a baseline for the discovery of abnormalities.

Dynamic changes of urinary proteins in focal segmental glomerulosclerosis model.

Compare to blood, which has mechanisms to maintain homeostasis, urine is more likely to reflect changes in the body. As urine accumulates all types of changes, identifying the precise cause of changes in the urine proteome is challenging and crucial in biomarker discovery. To reduce the confounding factors to minimal, some studies used animal model resembling human diseases. This chapter highlights the importance of animal models and introduces a strategic research which focused on adriamycin-induced nephropathy. In this study, urine samples were collected at before adriamycin administration and days 3, 7, 11, 15, and 23 after, urinary proteins were profiled by LC-MS/MS. Of 23 changed proteins with disease development, 13 proteins were identified as stable in normal human urine, meaning that changes in these proteins are more likely to reflect disease. We think this stage-dependent dynamic changes of urine proteome in animal models will help to support the role of urine as key source in biomarker discovery especially in kidney diseases and help to identify corresponding biomarkers for clinical validation.

Dynamic changes of urinary proteins in a focal segmental glomerulosclerosis rat model.

BACKGROUND: In contrast to blood, which has mechanisms to maintain a homeostatic internal environment, urine is more likely to reflect changes in the body. As urine accumulates all types of changes, identifying the precise cause of changes in the urine proteome is challenging and crucial in biomarker discovery. To reduce the effects of both genetic and environmental factors on the urinary proteome, this study used a rat model of adriamycin-induced nephropathy resembling human focal segmental glomerulosclerosis (FSGS) development. RESULTS: Urine samples were collected at before adriamycin administration and day3, 7, 11, 15 and 23 after. Urinary proteins were profiled by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). Of 23 changed proteins with disease development, 20 have human orthologs, and 13 proteins were identified as stable in normal human urine, meaning that changes in these proteins are more likely to reflect disease. Fifteen of the identified proteins have not been established to function in FSGS development. Seven proteins were selected for verification in ten more rats as markers closely associated with disease severity by western blot. CONCLUSION: We identified proteins changed in different stages of FSGS in rat models, which may aid in biomarker development and the understanding of FSGS pathogenesis.

Early urinary candidate biomarkers and clinical outcomes of intervention in a rat model of experimental autoimmune encephalomyelitis.

Multiple sclerosis is a chronic autoimmune demyelinating disease of the central nervous system and is difficult to diagnose in early stages. Without homeostatic control, urine was reported to have the ability to accumulate early changes in the body. We expect that urinary proteome can reflect early changes in the nervous system. The early urinary proteome changes in a most employed multiple sclerosis rat model (experimental autoimmune encephalomyelitis) were analysed to explore early urinary candidate biomarkers, and early treatment of methylprednisolone was used to evaluate the therapeutic effect. Twenty-five urinary proteins were altered at day 7 when there were no clinical symptoms and obvious histological changes. Fourteen were reported to be differently expressed in the serum/cerebrospinal fluid/brain tissues of multiple sclerosis patients or animals such as angiotensinogen and matrix metallopeptidase 8. Functional analysis showed that the dysregulated proteins were associated with asparagine degradation, neuroinflammation and lipid metabolism. After the early treatment of methylprednisolone, the incidence of encephalomyelitis in the intervention group was only 1/13. This study demonstrates that urine may be a good source of biomarkers for the early detection of multiple sclerosis. These findings may provide important information for early diagnosis and intervention of multiple sclerosis in the future.

Application of plasma metabolome for monitoring the effect of rivaroxaban in patients with nonvalvular atrial fibrillation.

Rivaroxaban, an oral factor Xa inhibitor, has been used to treating a series of thromboembolic disorders in clinical practice. Measurement of the anticoagulant effect of rivaroxaban is important to avoid serious bleeding events, thus ensuring the safety and efficacy of drug administration. Metabolomics could help to predict differences in the responses among patients by profiling metabolites in biosamples. In this study, plasma metabolomes before and 3 hours after rivaroxaban intake in 150 nonvalvular atrial fibrillation (NVAF) patients and 100 age/gender-matched controls were analyzed by liquid chromatography coupled with mass spectrometry (LC-MS/MS). When compared with controls, a total of thirteen plasma metabolites were differentially expressed in the NVAF patients. Pathway analysis revealed that purine and lipid metabolism were dysregulated. A panel of three metabolites (17a-ethynylestradiol, tryptophyl-glutamate and adenosine) showed good predictive ability to distinguish nonvalvular atrial fibrillation with an area under the receiver operating characteristic curve (AUC) of 1 for the discovery phase and 1 for validation. Under rivaroxaban treatment, a total of seven metabolites changed, the lipid and glycosylphosphatidylinositol biosynthesis pathways were altered and the panel consisting of avocadene, prenyl glucoside and phosphatidylethanolamine showed predictive ability with an AUC of 0.86 for the discovery dataset and 0.82 for the validation. The study showed that plasma metabolomic analyses hold the potential to differentiate nonvalvular atrial fibrillation and can help to monitor the effect of rivaroxaban anticoagulation.

Urinary proteomic analysis during pregnancy and its potential application in early prediction of gestational diabetes mellitus and spontaneous abortion.

Background: The maternal physiological changes which occur during gestation are complex and affect diverse systems in the body. Elucidating the various changes that occur during pregnancy may assist with understanding maternal health and the factors affecting pregnancy outcomes. Methods: A longitudinal cohort of 84 pregnant women was established. The urinary proteomes of women in different trimesters of pregnancy (6-8, 22-24, and 32-34 weeks) were characterized using data-independent acquisition tandem mass spectrometry. Gestational diabetes mellitus (GDM) was diagnosed at 24 to 28 weeks. Functional analysis of serial changed proteins was performed. Results: Fifteen women had GDM, 50 were healthy, and 19 experienced spontaneous abortion (SA). Functional analysis showed that the urinary proteome reflected physiological and pathological changes during pregnancy. Compared to those of women with a normal pregnancy, the urinary proteomes of women with GDM and SA showed significant disease-related changes in insulin secretion and estrogen receptor activity, respectively, during the first trimester. Urinary protein during the first trimester of pregnancy achieved an area under the curve of 0.91 and 0.81 for GDM and SA, respectively. Conclusions: The urinary proteome has the potential to reflect serial changes of pregnancy progression; therefore, its use might facilitate early diagnosis of pregnancy complications.

Global chemical modifications comparison of human plasma proteome from two different age groups.

In this study, two groups of human plasma proteome at different age groups (old and young) were used to perform a comparison of global chemical modifications, as determined by tandem mass spectrometry (MS/MS) combined with non-limiting modification identification algorithms. The sulfhydryl in the cysteine A total of 4 molecular modifications were found to have significant differences passing random grouping tests: the succinylation and phosphorylation modification of cysteine (Cys, C) and the modification of lysine (Lys, K) with threonine (Thr, T) were significantly higher in the old group than in the young group, while the carbamylation of lysine was lower in the young group. We speculate that there is an increase in certain modified proteins in the blood of the old people which, in turn, changes the function of those proteins. This change may be one of the reasons why old people are more likely than young people to be at risk for age-related diseases, such as metabolic diseases, cerebral and cardiovascular diseases, and cancer.

Evaluation of Urinary Proteome Library Generation Methods on Data-Independent Acquisition MS Analysis and its Application in Normal Urinary Proteome Analysis.

PURPOSE: As an important part of the data-independent acquisition-mass spectrometry (DIA-MS) analysis approach, spectral library generation is closely related to the final protein identification and quantitation. EXPERIMENTAL DESIGN: In this study, an attempt is made to evaluate the influence of different sample separation methods (reversed-phase liquid chromatography (RPLC) linear gradient elution and spin column step gradient fractionation) and data acquisition modes (data-dependent acquisition (DDA) and DIA) on library generation of the human urine proteome. RESULTS: The RPLC separation method provides more proteins for generating the library than the spin column; however, the spin column library leads to identification of more proteins when used for the urine proteome analysis. The DDA mode can provide a larger spectral library than the DIA mode and the DDA-library leads to more protein identifications in the study. Use of a combined urinary protein library provides the most complete protein and peptide information, and the DIA approach can provide accurate protein quantitative information even for low-abundance proteins. CONCLUSIONS AND CLINICAL RELEVANCE: When the combined library is used to analyze the normal individual urine proteome (18 males and 18 females), gender-related and age-related proteins are discovered and functionally analyzed. This strategy may benefit urine proteome DIA analysis.

Urinary candidate biomarkers in an experimental autoimmune myocarditis rat model.

Urine is a better source than plasma for biomarker studies, as it can accumulate all changes in the body. Various candidate urinary biomarkers of physiological condition, kidney disease and even brain dysfunction, have been detected in urine; however, urine has rarely been used to reflect cardiac diseases. In this study, urine at day 0, 14, 21 and 28 were collected from the myosin-induced autoimmune myocarditis rat models. The candidate urinary biomarkers were then characterized using the isobaric tandem mass tag labeling approach coupled with offline two-dimensional reverse-phase liquid chromatography and high-resolution mass spectrometry. Compared with controls, forty-six urinary proteins were significantly changed in the myocarditis rats; among them, ten had previously been associated with myocarditis, twelve corresponding gene products had annotated as mainly cardiovascular network genes by the Ingenuity Pathway Analysis, four urinary proteins were validated by western blot, thirteen were reported in previous urine proteome studies of other diseases and twenty-six were reported the first time to be related to myocarditis. SIGNIFICANCE: This is the first study to use isobaric tandem mass tag labeling approach in the urine proteome analysis of experimental autoimmune myocarditis. These findings may provide clues for the pathogenesis of myocarditis. And the study showed that urine can be a good source of myocarditis biomarkers.

A Comparative Proteomics Analysis of Five Body Fluids: Plasma, Urine, Cerebrospinal Fluid, Amniotic Fluid, and Saliva.

PURPOSE: Body fluid is considered a rich source of disease biomarkers. Proteins in many body fluids have potential clinical applications for disease diagnostic and prognostic predictions. EXPERIMENTAL DESIGN: To determine differences in the protein components and functional features of body fluids, a proteomic comparison of five body fluids (plasma, urine, cerebrospinal fluid, saliva, and amniotic fluid) was conducted by high-resolution mass spectrometry. RESULTS: A total of 4717 nonredundant proteins were identified, and the concentrations of 3433 proteins were estimated by an intensity-based algorithm quantitation method. Among them, 564 proteins were shared among the five body fluids, with common functions in the coagulation/prothrombin system and inflammatory response. A total of 36.7% of the proteins were detected in only one body fluid and were closely related to their adjacent tissues by function. The functional analysis of the remaining 2986 proteins showed that similar functions might be shared among different body fluids, which highlighted intimate connection in the body. CONCLUSIONS AND CLINICAL RELEVANCE: The quantitative comparative functional analysis indicated that body fluids might reflect the diverse functions of the whole body rather than the characteristics of their adjacent tissues. The above data might indicate the potential application of body fluids for biomarker discovery.

Early Detection of Urinary Proteome Biomarkers for Effective Early Treatment of Pulmonary Fibrosis in a Rat Model.

SCOPE: Pulmonary fibrosis (PF) is a progressive and devastating lung disease. With limited effective treatments available in the late stage, PF has a very poor prognosis. Molecular biomarkers are highly desired for PF, especially for its early phase. MATERIALS AND METHODS: Urine is a good biomarker source, and accumulates systemic changes in the body especially in the early-stage of diseases. In this study, a bleomycin (BLM)-induced rat model is used to mimic PF. Using labeled proteome quantitation, some urinary proteins are identified as candidate biomarkers of PF for early detection and disease monitoring. Then, prednisone treatment is administered at different phases of fibrosis. RESULTS: Our results suggested that urine proteins could enable early detection and monitoring of both disease progression and treatment efficacy in the BLM-induced PF model. Early prednisone treatment effectively inhibited pulmonary fibrosis, whereas the same treatment at a later phase had very limited effects. Meanwhile, five proteins showed the potential for monitoring therapeutic response. CONCLUSION: Urinary proteomics has been underutilized in respiratory diseases. These findings will improve our understanding of the pathogenesis of PF and accelerate biomarker discovery in respiratory diseases.

A comprehensive analysis and annotation of human normal urinary proteome.

Biomarkers are measurable changes associated with the disease. Urine can reflect the changes of the body while blood is under control of the homeostatic mechanisms; thus, urine is considered an important source for early and sensitive disease biomarker discovery. A comprehensive profile of the urinary proteome will provide a basic understanding of urinary proteins. In this paper, we present an in-depth analysis of the urinary proteome based on different separation strategies, including direct one dimensional liquid chromatography-tandem mass spectrometry (LC/MS/MS), two dimensional LC/MS/MS, and gel-eluted liquid fraction entrapment electrophoresis/liquid-phase isoelectric focusing followed by two dimensional LC/MS/MS. A total of 6085 proteins were identified in healthy urine, of which 2001 were not reported in previous studies and the concentrations of 2571 proteins were estimated (spanning a magnitude of 106) with an intensity-based absolute quantification algorithm. The urinary proteins were annotated by their tissue distribution. Detailed information can be accessed at the "Human Urine Proteome Database" (www.urimarker.com/urine).

The Specific α1-Adrenergic Receptor Antagonist Prazosin Influences the Urine Proteome.

Urine, reflecting many changes in the body, is a better source than blood for biomarker discovery. However, even under physiological conditions, the urine proteome often varies. Understanding how various regulating factors affect urine proteome helps link changes to urine proteome with urinary biomarkers of physiological conditions as well as corresponding diseases. To evaluate the possible impact of α1-adrenergic receptor on urine proteome, this study investigated effects of the specific inhibitor prazosin on the urine proteome in a rat model by using tandem mass tagging and two-dimensional liquid chromatography-tandem mass spectrometry. A total of 775 proteins were identified, approximately half of which were influenced by prazosin treatment, indicating that the sympathetic nervous system exerts a significant impact on urine proteome. Eight significantly changed proteins were previously annotated as urinary candidate biomarkers. Angiotensinogen, haptoglobin, and beta-2 microglobulin, which were reported to be associated with blood pressure, were validated via Western blot. Prazosin is widely used in clinical practice; thus, these protein changes should be considered when studying corresponding diseases such as hypertension, post-traumatic stress disorder and benign prostatic hyperplasia. The related physiological activities of α1-receptors, controlling blood pressure and fear response might significantly affect the urine proteome and warrant further biomarker studies.

Phosphoproteins with Stability Against All Urinary Phosphatases as Potential Biomarkers in Urine.

Urine, by accumulating all kinds of changes, was proposed to be a better source for biomarker discovery. As one of the most common post-translational modifications, phosphorylation plays a vital role in many biological activities. However, the urine phosphoproteome has been largely neglected due to the low abundance of phosphoproteins and the presence of various phosphatases in urine. The low level of background phosphorylation in urine is actually advantageous, as urinary phosphopeptides/proteins that are stable to the phosphatases present in urine have the potential to serve as valuable disease biomarkers. Using a TiO2 enrichment strategy, this study aimed to create a comprehensive proteomic profile of human urinary phosphoproteins and to characterize the changes in the urine phosphoproteome after incubation of urine with renal carcinoma cell lysates. In total, 106 urine phosphorylation sites corresponding to 64 proteins, including 80 previously unidentified human urine protein phosphorylation sites, were identified by mass spectrometry. Fifteen phosphopeptides, together averaging 47% of the total phosphopeptides, were found in samples from three individuals. Cellular proteins are potential source of biomarker in urine phosphorylated proteins. Addition of renal carcinoma cellular proteins to urine did not significantly change the phosphorylation level of urine proteins. But there were still a few phosphopeptides from cell lysates survived urinary phosphatases; such phosphopeptides represent potential biomarkers in urine.

Effect of transient blood glucose increases after oral glucose intake on the human urinary proteome.

PURPOSE: Unlike blood, which has mechanisms to maintain homeostasis, urine is more likely to reflect changes in the body. However, the urinary proteome is affected by many factors such as diet, medication, daily activities. Transient increase of blood glucose frequently occurs after the consumption of food and may be an interfering factor in biomarker studies. EXPERIMENTAL DESIGN: In this study, a transient increase of blood glucose level was achieved by performing an oral glucose tolerance test on nine healthy human volunteers. Urine samples before and after the test were collected and analyzed by LC-MS/MS. RESULTS: According to quantification using Progenesis LC-MS software, only the protein neutrophil defensin 1, which was reported to participate in reducing blood glucose levels, was increased in the urine after glucose intake; and almost all urinary proteins may not be affected. CONCLUSIONS AND CLINICAL RELEVANCE: Transient increase of blood glucose levels may not be a major interfering factor in biomarker studies, at least with current levels of identification and quantification.

Effects of anesthetics pentobarbital sodium and chloral hydrate on urine proteome.

Urine can be a better source than blood for biomarker discovery since it accumulates many changes. The urine proteome is susceptible to many factors, including anesthesia. Pentobarbital sodium and chloral hydrate are commonly used anesthetics in animal experiments. This study demonstrated the effects of these two anesthetics on the rat urine proteome using liquid chromatography-tandem mass spectrometry (LC-MS/MS). With anesthesia, the urinary protein-to-creatinine ratio of all rats increased twofold. The relative abundance of 22 and 23 urinary proteins were changed with pentobarbital sodium or chloral hydrate anesthesia, respectively, as determined by label-free quantification. Among these changed proteins, fifteen had been considered as candidate biomarkers such as uromodulin, and sixteen had been considered stable in healthy human urine, which are more likely to be considered as potential biomarkers when changed, such as transferrin. The pattern of changed urinary proteins provides clues to the discovery of urinary proteins regulatory mechanisms. When determining a candidate biomarker, anesthetic-related effects can be excluded from future biomarker discovery studies. Since anesthetics take effects via nervous system, this study is the first to provide clues that the protein handling function of the kidney may possibly be regulated by the nervous system.

Changes of proteins induced by anticoagulants can be more sensitively detected in urine than in plasma.

The most fundamental property of biomarkers is change. But changes are hard to maintain in plasma since it is strictly controlled by homeostatic mechanisms of the body. There is no homeostatic mechanism for urine. Besides, urine is partly a filtration of blood, and systematic information can be reflected in urine. We hypothesize that change of blood can be reflected in urine more sensitively. Here we introduce the interference into the blood by two anticoagulants heparin or argatroban. Plasma and urine proteins were profiled by LC-MS/MS and then validated by Western blot in totally six SD female rats before and after the drug treatments. In argatroban treated group, with exactly the same experimental procedure and the same cutoff value for both plasma and urine proteins, 62 proteins changed in urine, only one of which changed in plasma. In heparin treated group, 27 proteins changed in urine but only three other proteins changed in plasma. Both 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.

Effects of three commonly-used diuretics on the urinary proteome.

Biomarker is the measurable change associated with a physiological or pathophysiological process. Unlike blood which has mechanisms to keep the internal environment homeostatic, urine is more likely to reflect changes of the body. As a result, urine is likely to be a better biomarker source than blood. However, since the urinary proteome is affected by many factors, including diuretics, careful evaluation of those effects is necessary if urinary proteomics is used for biomarker discovery. Here, we evaluated the effects of three commonly-used diuretics (furosemide, F; hydrochlorothiazide, H; and spirolactone, S) on the urinary proteome in rats. Urine samples were collected before and after intragastric administration of diuretics at therapeutic doses and the proteomes were analyzed using label-free liquid chromatography-tandem mass spectrometry (LC-MS/MS). Based on the criteria of P≤0.05, a fold change ≥2, a spectral count ≥5, and false positive rate (FDR) ≤1%, 14 proteins (seven for F, five for H, and two for S) were identified by Progenesis LC-MS. The human orthologs of most of these 14 proteins are stable in the healthy human urinary proteome, and ten of them are reported as disease biomarkers. Thus, our results suggest that the effects of diuretics deserve more attention in future urinary protein biomarker studies. Moreover, the distinct effects of diuretics on the urinary proteome may provide clues to the mechanisms of diuretics.