Potential urine biomarkers for the diagnosis of prediabetes and early diabetic nephropathy based on ISN CKHDP program.

BACKGROUND: Diabetic nephropathy (DN) is a major complication of diabetes mellitus (DM), and the most frequent cause of end-stage renal disease (ESRD) in many countries. Urinary extracellular vesicles (UEVs) are considered a rich non-invasive source of markers for renal diseases. In this study, UEV enrichment and analysis in diabetic nephropathy (DN) was performed in a community epidemiological survey supported through the ISN CKHDP program. MATERIALS AND METHODS: Patients were divided into five groups according to severity of kidney damage. A hydrostatic dialysis method was used for UEV enrichment followed by quantitation using Coomassie protein assays and subsequent adjustment using urinary creatinine levels. UEVs were then characterized by transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA), and Western blotting of tumor susceptibility gene product TSG101. Two-dimensional DIGE (2D-DIGE) was used to analyze differential protein expression in the UEVs. Mass spectrometry (MS) was conducted and MASCOT search engine was used to identify potential biomarkers. RESULTS: Bradford protein assay showed that protein concentration of UEVs in diabetics with kidney injury increased significantly as compared to normal controls. UEVs present a round, cup-shaped, membrane-encapsulated structure under TEM, and the main peak of UEVs show 55 - 110 nm nanoparticles with NTA. MS and MASCOT identified 22 differential proteins, and MASP2, CALB1, S100A8, and S100A9 were selected as potential biomarkers of early DN based on bioinformatic analysis. DISCUSSION: Our results show UEV proteome changes in different stages of DN. The results of this study show four unique proteins that undergo changes in early DN. These promising discoveries may prompt a new field of research focused on improving the diagnosis of DN.

Urine proteomic profiling in patients with nephrolithiasis and cystinuria.

PURPOSE: The purpose of the study was to assess the differences in the concentration and function of urinary proteins between patients with cystine stones (CYS) and healthy controls (HC). We postulated that CYS and HC groups would demonstrate different proteomic profiles. METHODS: A pilot study was performed comparing urinary proteomes of 10 patients with CYS and 10 age- and gender-matched HC, using liquid chromatography-mass spectrometry. Proteins which met the selection criteria (i) ≥ 2 unique peptide identifications; (ii) ≥ twofold difference in protein abundance; and (iii) ≤ 0.05 p value for the Fisher's Exact Test were analyzed using Gene Ontology classifications. RESULTS: Of the 2097 proteins identified by proteomic analysis, 398 proteins were significantly different between CYS and HC. Of those, 191 were involved in transport processes and 61 in inflammatory responses. The majority were vesicle-mediated transport proteins (78.5%), and 1/3 of them were down-regulated; of those, 12 proteins were involved in endosomal transport (including 6 charged multivesicular body proteins (CHMP) and 3 vacuolar sorting-associated proteins) and 9 in transmembrane transport. Myosin-2 and two actin-related proteins were significantly up-regulated in the vesicle-mediated transport group. CONCLUSION: We provide proteomic evidence of impaired endocytosis, dysregulation of actin and myosin cytoskeleton, and inflammation in CYS. Endosomal transport proteins were down-regulated mainly through defective CHMP. These findings may contribute to further understanding of the pathogenesis of CYS, potentially affecting its management.

Characterization of urinary exosomal release of aquaporin-1 and -2 after renal ischemia-reperfusion in rats.

Acute kidney injury (AKI) is an important risk factor for the development of chronic kidney disease (CKD), and an alteration in renal water handling has been observed during the transition of AKI to CKD. Urinary exosomal release of aquaporin-1 (AQP1) and AQP2, important proteins for renal water handling, has recently been reported to predict their levels of renal expression. Therefore, we examined the patterns of urinary exosomal release of AQP1 and AQP2, and the exosomal marker proteins tumor susceptibility 101 protein (TSG101) and ALG-2 interacting protein X (Alix), in the acute and chronic phases following induction of AKI by renal bilateral ischemia/reperfusion (I/R) in rats. Blood tests and histological examinations indicated that AKI occurred before at 7 days after renal I/R ( day 7) and that renal fibrosis developed progressively thereafter. Immunoblotting demonstrated significant decreases in the urinary exosomal release of AQP1 and AQP2 during severe AKI. Urinary exosomal release of Alix and TSG101 was significantly increased on day 7. These data were also confirmed in rats with unilateral renal I/R causing more serious AKI. Urinary exosomal release of either the Ser-256- or Ser-269-phosphorylated form of AQP2, both of which are involved in apical trafficking of AQP2, was positively correlated with that of total AQP2. These results suggest that urinary exosomal release of AQP1 and AQP2 is reduced in I/R-induced AKI, whereas that of Alix and TSG101 is increased in the initial phase of renal fibrosis. Furthermore, apical trafficking of AQP2 appears to be related to urinary exosomal release of AQP2.

Elevated LRRK2 autophosphorylation in brain-derived and peripheral exosomes in LRRK2 mutation carriers.

Missense mutations in the leucine-rich repeat kinase 2 (LRRK2) gene can cause late-onset Parkinson disease (PD). LRRK2 mutations increase LRRK2 kinase activities that may increase levels of LRRK2 autophosphorylation at serine 1292 (pS1292) and neurotoxicity in model systems. pS1292-LRRK2 protein can be packaged into exosomes and measured in biobanked urine. Herein we provide evidence that pS1292-LRRK2 protein is robustly expressed in cerebral spinal fluid (CSF) exosomes. In a novel cohort of Norwegian subjects with and without the G2019S-LRRK2 mutation, with and without PD, we quantified levels of pS1292-LRRK2, total LRRK2, and other exosome proteins in urine from 132 subjects and in CSF from 82 subjects. CSF and urine were collected from the same morning clinic visit in 55 of the participants. We found that total LRRK2 protein concentration was similar in exosomes purified from either CSF or urine but the levels did not correlate. pS1292-LRRK2 levels were higher in urinary exosomes from male and female subjects with a LRRK2 mutation. Male LRRK2 mutation carriers without PD had intermediate pS1292-LRRK2 levels compared to male carriers with PD and controls. However, female LRRK2 mutation carriers without PD had the same pS1292-LRRK2 levels compared to female carriers with PD. pS1292-LRRK2 levels in CSF exosomes were near saturated in most subjects, ten-fold higher on average than pS1292-LRRK2 levels in urinary exosomes, irrespective of LRRK2 mutation status or PD diagnosis. These results provide insights into the effects of LRRK2 mutations in both the periphery and brain in a well-characterized clinical population and show that LRRK2 protein in brain exosomes may be much more active than in the periphery in most subjects.

Effect of pH on the isolation of urinary exosome.

PURPOSE: Urinary exosome is an ideal noninvasive, low-cost source of kidney diseases biomarkers. However, many factors effect the isolation of urine-derived exosome. The effect of pH on the yield of exosome isolation under different pH was explored. METHODS: The pH was adjusted for 4, 5, 6, 7 and 8 with hydrochloric acid and sodium hydroxide solution. All samples were incubated for 30 min before differential ultracentrifugation. Exosome-associated protein markers TSG101, ALIX and total concentration of RNA were evaluated by Western-blotting and micro-amount ultraviolet spectrophotometer, respectively. RESULTS: A major loss of urinary exosome was received at pH 8 compared with alkali medium or control group. There was no difference whether or not added EDTA-Na2. CONCLUSIONS: Acidic environment was likely to conducive to the isolation of exosome and maintain its stability and integrity that suggest pH medium needs to be carefully considered and also provide a methodology for future separation exosome.

Programmed cell death 6 interacting protein (PDCD6IP) and Rabenosyn-5 (ZFYVE20) are potential urinary biomarkers for upper gastrointestinal cancer.

PURPOSE: Cancer of the upper digestive tract (uGI) is a major contributor to cancer-related death worldwide. Due to a rise in occurrence, together with poor survival rates and a lack of diagnostic or prognostic clinical assays, there is a clear need to establish molecular biomarkers. EXPERIMENTAL DESIGN: Initial assessment was performed on urine samples from 60 control and 60 uGI cancer patients using MS to establish a peak pattern or fingerprint model, which was validated by a further set of 59 samples. RESULTS: We detected 86 cluster peaks by MS above frequency and detection thresholds. Statistical testing and model building resulted in a peak profiling model of five relevant peaks with 88% overall sensitivity and 91% specificity, and overall correctness of 90%. High-resolution MS of 40 samples in the 2-10 kDa range resulted in 646 identified proteins, and pattern matching identified four of the five model peaks within significant parameters, namely programmed cell death 6 interacting protein (PDCD6IP/Alix/AIP1), Rabenosyn-5 (ZFYVE20), protein S100A8, and protein S100A9, of which the first two were validated by Western blotting. CONCLUSIONS AND CLINICAL RELEVANCE: We demonstrate that MS analysis of human urine can identify lead biomarker candidates in uGI cancers, which makes this technique potentially useful in defining and consolidating biomarker patterns for uGI cancer screening.