Protein-bound uremic toxins: a long overlooked culprit in cardiorenal syndrome

Protein-bound uremic toxins (PBUTs) accumulate once renal excretory function declines and are not cleared by dialysis. There is increasing evidence that PBUTs exert toxic effects on many vital organs, including the kidney, blood vessels, and heart. It has been suggested that PBUTs are likely to be a potential missing link in cardiorenal syndrome, based on the high incidence of cardiovascular events and mortality in the dialysis population, which are dramatically reduced in successful kidney transplant recipients. These data have led the call for more effective dialysis or additional adjunctive therapy to eradicate these toxins and their adverse biological effects. Indoxyl sulfate and p-cresyl sulfate are the two most problematic PBUTs, conferring renal and cardiovascular toxicity, and are derived from dietary amino acid metabolites by colonic microbial organisms. Therefore, targeting the colon where these toxins are initially produced appears to be a potential therapeutic alternative for patients with chronic kidney disease. This strategy, if approved, is likely to be applicable to predialysis patients, thereby potentially preventing progression of chronic kidney disease to end-stage renal disease as well as preventing the development of cardiorenal syndrome.

Avoiding collateral damage in the war on hypertension

When performed by experienced clinicians, renal nerve denervation (RND) can be done with very low risk of complication and/or acute renal injury Renal function seems to remain unchanged in this small series over 3 years More studies are needed to establish the role of renal biomarkers in assessment of acute renal injury in this setting and larger series of RND in azotemic patients should be done before the procedure indications can be expanded.

Paracellular epithelial sodium transport maximizes energy efficiency in the kidney

Efficient oxygen utilization in the kidney may be supported by paracellular epithelial transport, a form of passive diffusion that is driven by preexisting transepithelial electrochemical gradients. Claudins are tight-junction transmembrane proteins that act as paracellular ion channels in epithelial cells. In the proximal tubule (PT) of the kidney, claudin-2 mediates paracellular sodium reabsorption. Here, we used murine models to investigate the role of claudin-2 in maintaining energy efficiency in the kidney. We found that claudin-2-null mice conserve sodium to the same extent as WT mice, even during profound dietary sodium depletion, as a result of the upregulation of transcellular Na-K-2Cl transport activity in the thick ascending limb of Henle. We hypothesized that shifting sodium transport to transcellular pathways would lead to increased whole-kidney oxygen consumption. Indeed, compared with control animals, oxygen consumption in the kidneys of claudin-2-null mice was markedly increased, resulting in medullary hypoxia. Furthermore, tubular injury in kidneys subjected to bilateral renal ischemia-reperfusion injury was more severe in the absence of claudin-2. Our results indicate that paracellular transport in the PT is required for efficient utilization of oxygen in the service of sodium transport. We speculate that paracellular permeability may have evolved as a general strategy in epithelial tissues to maximize energy efficiency.

Kidney Injury Molecule Levels in Type 2 Diabetes Mellitus

BACKGROUND

This study was designed to determine the diagnostic role of urinary kidney injury molecule (KIM)-1 levels in renal damage in patients with type 2 diabetes mellitus according to the urinary albumin/creatinine ratio.

METHODS

Patients with type 2 diabetes mellitus admitted to different polyclinics in our hospital enrolled in the study and were subdivided into three groups according to albumin/creatinine ratio - normalbuminuric (n: 20); microalbuminuric (n: 20); albuminuric (n: 18) - and compared with the control group. Urine albumin was analyzed using the immunoturbidimetric method (Architect C16000, Abbott Diagnostics). uKIM-1 was determined using a commercially available enzyme-linked immunosorbent assay test kit (USCN Life Science, Hankou, Wuhan, China). One-sample Kolmogorov-Smirnov test, Spearman correlation and Kruskal-Wallis non-parametric tests were performed. Post hoc comparisons were made using Bonferroni-corrected Mann-Whitney U tests.

RESULTS

The differences between the controls and normalbuminuric, microalbuminuric and albuminuric groups were highly significant for KIM-1. Positive correlation was found between KIM-1 and urine microalbumin-urine microalbumin/creatinine (r = 0.479 P < 0.001; r = 0. 400, P < 0.001; respectively).

CONCLUSION

In our study, KIM-1 levels were significantly different suggesting that urinary KIM-1 levels may be an early marker in patients with diabetic nephropathy. J. Clin. Lab. Anal. 00:1-6, 2016.

Pentraxin 3 Is Closely Associated With Tubulointerstitial Injury in Lupus Nephritis: A Large Multicenter Cross-Sectional Study

Lupus nephritis always elicits immune inflammatory tissue damages in kidney. Pentraxin 3 (PTX3), mainly produced at inflammatory sites, is known to be involved in the regulation of the innate immunity system. The aim of this study was to investigate the serum and urine levels of PTX3, and the expression of PTX3 in renal tissues in lupus nephritis patients from a large Chinese cohort.The study used cross-sectional survey and 288 active lupus nephritis patients, including discovery cohort and validation cohort, 115 systemic lupus erythematosus (SLE) patients without clinical renal involvement and 46 healthy controls were enrolled. Serum and urine PTX3 were screened by enzyme-linked immunosorbent assay (ELISA). The renal deposition of PTX3 was detected by immunohistochemistry and immunofluorescence.The average level of serum PTX3 in the discovery cohort of lupus nephritis was significantly higher than that in nonrenal involvement SLE group and normal controls (P < 0.001, P < 0.001, respectively), which was confirmed by the validation cohort. Serum PTX3 levels of 15 lupus nephritis patients in remission decreased significantly compared with that in active phase. Serum PTX3 levels were significantly higher in patients with hematuria (P = 0.014), leucocyturia (P = 0.002), acute renal failure (P = 0.001), and nephrotic syndrome (P = 0.036). There were significant correlations between serum PTX3 levels and Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) scores, serum creatinine value, renal pathological activity indices, and serum complement 3 (C3) in active lupus nephritis patients. The urinary PTX3 levels were significantly higher in active lupus nephritis patients compared with patients in remission and normal controls (P = 0.011, P = 0.008, respectively). There were significant associations between urinary PTX3 levels and multiple indices of tubulointerstitial lesions, including urinary KIM-1 (r = 0.368, P = 0.016), neutrophil gelatinase-associated lipocalin (NGAL) (r = 0.320, P = 0.039), microalbumin (r = 0.621, P = 0.003), transferring (r = 0.451, P = 0.040) levels and renal pathological indices scores, especially interstitial inflammation (r = 0.349, P = 0.025) in active lupus nephritis patients. A significant correlation was found between serum and urine PTX3 levels (r = 0.431, P = 0.006). PTX3 staining was mainly observed in tubulointerstitial areas of patients with lupus nephritis, and immunofluorescence study showed that PTX3 could colocalize with fibroblast in interstitium.Circulating and local PTX3 levels were significantly increased in patients with active lupus nephritis and might be a biomarker for the disease progression, especially of tubulointerstitial injury.

Effect of genetic and environmental factors on protein biomarkers for common non-communicable disease and use of personally normalized plasma protein profiles (PNPPP)

OBJECTIVE

To study the impact of genetic and lifestyle factors on protein biomarkers and develop personally normalized plasma protein profiles (PNPPP) controlling for non-disease-related variance.

MATERIALS AND METHODS

Proximity extension assays were used to measure 145 proteins in 632 controls and 344 cases with non-communicable diseases.

RESULTS

Genetic and lifestyle factors explained 20-88% of the variation in healthy controls. Adjusting for these factors reduced the number of candidate biomarkers by 63%.

CONCLUSION

PNPPP efficiently controls for non-disease-related variance, allowing both for efficient discovery of novel biomarkers and for covariate-independent linear cut-offs suitable for clinical use.

Mammalian Target of Rapamycin Mediates Kidney Injury Molecule 1-Dependent Tubule Injury in a Surrogate Model

Kidney injury molecule 1 (KIM-1), an epithelial phagocytic receptor, is markedly upregulated in the proximal tubule in various forms of acute and chronic kidney injury in humans and many other species. Whereas acute expression of KIM-1 has adaptive anti-inflammatory effects, chronic expression may be maladaptive in mice. Here, we characterized the zebrafish Kim family, consisting of Kim-1, Kim-3, and Kim-4. Kim-1 was markedly upregulated in kidney after gentamicin-induced injury and had conserved phagocytic activity in zebrafish. Both constitutive and tamoxifen-induced expression of Kim-1 in zebrafish kidney tubules resulted in loss of the tubule brush border, reduced GFR, pericardial edema, and increased mortality. Kim-1-induced kidney injury was associated with reduction of growth of adult fish. Kim-1 expression led to activation of the mammalian target of rapamycin (mTOR) pathway, and inhibition of this pathway with rapamycin increased survival. mTOR pathway inhibition in KIM-1-overexpressing transgenic mice also significantly ameliorated serum creatinine level, proteinuria, tubular injury, and kidney inflammation. In conclusion, persistent Kim-1 expression results in chronic kidney damage in zebrafish through a mechanism involving mTOR. This observation predicted the role of the mTOR pathway and the therapeutic efficacy of mTOR-targeted agents in KIM-1-mediated kidney injury and fibrosis in mice, demonstrating the utility of the Kim-1 renal tubule zebrafish models.

Nanostar Clustering Improves the Sensitivity of Plasmonic Assays

Star-shaped Au nanoparticles (Au nanostars, AuNS) have been developed to improve the plasmonic sensitivity, but their application has largely been limited to single-particle probes. We herein describe a AuNS clustering assay based on nanoscale self-assembly of multiple AuNS and which further increases detection sensitivity. We show that each cluster contains multiple nanogaps to concentrate electric fields, thereby amplifying the signal via plasmon coupling. Numerical simulation indicated that AuNS clusters assume up to 460-fold higher field density than Au nanosphere clusters of similar mass. The results were validated in model assays of protein biomarker detection. The AuNS clustering assay showed higher sensitivity than Au nanosphere. Minimizing the size of affinity ligand was found important to tightly confine electric fields and improve the sensitivity. The resulting assay is simple and fast and can be readily applied to point-of-care molecular detection schemes.

No increase in Kidney Injury Molecule-1 and Neutrophil Gelatinase-Associated Lipocalin excretion following intravenous contrast enhanced-CT

Objectives

To analyze kidney injury molecule-1 (KIM-1) and neutrophil gelatinase-associated lipocalin (N-GAL) excretion post-intravenous contrast enhanced-CT (CE-CT) in patients with chronic kidney disease (CKD).

Methods

Patients were enrolled in a trial on hydration regimes to prevent contrast-induced acute kidney injury (CI-AKI). Blood and urine samples were taken at baseline, 4 – 6, and 48 – 96 h post CE-CT. Urinary KIM-1 and N-GAL values were normalized for urinary creatinine levels, presented as medians with 2.5 – 97.5 percentiles.

Results

Of the enrolled 511 patients, 10 (2 %) were lost to follow-up. CI-AKI occurred in 3.9 % of patients (20/501). Median KIM-1 values were 1.2 (0.1 – 7.7) at baseline, 1.3 (0.1 – 8.6) at 4 – 6 h, and 1.3 ng/mg (0.1 – 8.1) at 48 – 96 h post CE-CT (P = 0.39). Median N-GAL values were 41.0 (4.4 – 3,174.4), 48.9 (5.7 – 3,406.1), and 37.8 μg/mg (3.5 – 3,200.4), respectively (P = 0.07). The amount of KIM-1 and N-GAL excretion in follow-up was similar for patients with and without CI-AKI (P-value KIM-1 0.08, P-value N-GAL 0.73). Neither patient characteristics at baseline including severe CKD, medication use, nor contrast dose were associated with increased excretion of KIM-1 or N-GAL during follow-up.

Conclusion

KIM-1 and N-GAL excretion were unaffected by CE-CT both in patients with and without CI-AKI, suggesting that CI-AKI was not accompanied by tubular injury.

Key Points

• KIM-1 and N-GAL excretion were unaffected by intravenous contrast-enhanced CT (CE-CT).

• Patient or procedure characteristics were not associated with increased KIM-1 or N-GAL excretion.

• Performance of CE-CT in CKD patients is likely to be safe.

Elevated Urinary Connective Tissue Growth Factor in Diabetic Nephropathy Is Caused by Local Production and Tubular Dysfunction

Connective tissue growth factor (CTGF; CCN2) plays a role in the development of diabetic nephropathy (DN). Urinary CTGF (uCTGF) is elevated in DN patients and has been proposed as a biomarker for disease progression, but it is unknown which pathophysiological factors contribute to elevated uCTGF. We studied renal handling of CTGF by infusion of recombinant CTGF in diabetic mice. In addition, uCTGF was measured in type 1 DN patients and compared with glomerular and tubular dysfunction and damage markers. In diabetic mice, uCTGF was increased and fractional excretion (FE) of recombinant CTGF was substantially elevated indicating reduced tubular reabsorption. FE of recombinant CTGF correlated with excretion of endogenous CTGF. CTGF mRNA was mainly localized in glomeruli and medullary tubules. Comparison of FE of endogenous and recombinant CTGF indicated that 60% of uCTGF had a direct renal source, while 40% originated from plasma CTGF. In DN patients, uCTGF was independently associated with markers of proximal and distal tubular dysfunction and damage. In conclusion, uCTGF in DN is elevated as a result of both increased local production and reduced reabsorption due to tubular dysfunction. We submit that uCTGF is a biomarker reflecting both glomerular and tubulointerstitial hallmarks of diabetic kidney disease.

Urinary β2-Microglobulin Is a Good Indicator of Proximal Tubule Injury: A Correlative Study with Renal Biopsies

Objective. After filtration through glomeruli, β2-microglobulin is reabsorbed in proximal tubules. Increased urinary β2-microglobulin indicates proximal tubule injury and measurement of β2-microglobulin in urine is useful to determine the source of renal injury. Kidney injury molecule-1 (KIM-1) has been characterized as a selective proximal tubule injury marker. This study was designed to evaluate the correlation of urinary β2-microglobulin concentration and KIM-1 expression as evidence of proximal tubule injury. Methods. Between 2009 and 2012, 46 patients with urine β2-microglobulin (RenalVysion) had follow-up kidney biopsy. Diagnoses included glomerular and tubule-interstitial disease. Immunohistochemical staining for KIM-1 was performed and the intensity was graded from 0 to 3+. Linear regression analysis was applied to correlate the values of urinary β2-microglobulin and KIM-1 staining scores. P < 0.05 was considered statistically significant. Results. Thirty patients had elevated urinary β2-microglobulin. KIM-1 staining was positive in 35 kidney biopsies. There was a significant correlation between urinary β2-microglobulin and KIM-1 staining (P < 0.05). Sensitivity was 86.6%, specificity was 43.7%, positive predictive value was 74.2%, and negative predictive value was 63.6%. Conclusion. Increased urinary β2-microglobulin is significantly correlated with KIM-1 staining in injured proximal tubules. Measurement of urine β2-microglobulin is a sensitive assay for proximal tubule injury.

Predictive usefulness of urinary biomarkers for the identification of cyclosporine A-induced nephrotoxicity in a rat model

The main side effect of cyclosporine A (CsA), a widely used immunosuppressive drug, is nephrotoxicity. Early detection of CsA-induced acute nephrotoxicity is essential for stop or minimize kidney injury, and timely detection of chronic nephrotoxicity is critical for halting the drug and preventing irreversible kidney injury. This study aimed to identify urinary biomarkers for the detection of CsA-induced nephrotoxicity. We allocated salt-depleted rats to receive CsA or vehicle for 7, 14 or 21 days and evaluated renal function and hemodynamics, microalbuminuria, renal macrophage infiltration, tubulointerstitial fibrosis and renal tissue and urinary biomarkers for kidney injury. Kidney injury molecule-1 (KIM-1), tumor necrosis factor-alpha (TNF-α), interleukin 6 (IL-6), fibronectin, neutrophil gelatinase-associated lipocalin (NGAL), TGF-β, osteopontin, and podocin were assessed in urine. TNF-α, IL-6, fibronectin, osteopontin, TGF-β, collagen IV, alpha smooth muscle actin (α -SMA) and vimentin were assessed in renal tissue. CsA caused early functional renal dysfunction and microalbuminuria, followed by macrophage infiltration and late tubulointerstitial fibrosis. Urinary TNF-α, KIM-1 and fibronectin increased in the early phase, and urinary TGF-β and osteopontin increased in the late phase of CsA nephrotoxicity. Urinary biomarkers correlated consistently with renal tissue cytokine expression. In conclusion, early increases in urinary KIM-1, TNF-α, and fibronectin and elevated microalbuminuria indicate acute CsA nephrotoxicity. Late increases in urinary osteopontin and TGF-β indicate chronic CsA nephrotoxicity. These urinary kidney injury biomarkers correlated well with the renal tissue expression of injury markers and with the temporal development of CsA nephrotoxicity.

Assessment of kidney function in diabetic patients. Is there a role for new biomarkers NGAL, cystatin C and KIM-1?

PURPOSE

Assessment of kidney injury early detection in diabetic patients has great importance for therapy and prognosis. The aim of this study was to assess whether neutrophil gelatinase-associated lipocalin (NGAL), cystatin C, and kidney injury molecule-1 (KIM-1) could represent sensitive markers of kidney function/injury in patients with coronary heart disease and diabetes.

MATERIALS AND METHODS

The study comprised 121 consecutive patients with diabetes referred for coronary angiography due to coronary heart disease and a reference group consisting of 64 patients without diabetes.

RESULTS

Cystatin C, serum and urinary NGAL values were significantly higher in diabetics than in non-diabetics. There was no significant difference in KIM-1 levels in both groups. Serum NGAL in diabetic group was associated with serum creatinine, fibrinogen, urinary NGAL, cystatin C and inversely related to kidney function assessed with 4 equations. After analysing levels of studied biomarkers in both groups, no significant difference in patients with estimated glomerular filtration rate (eGFR) below 60 ml/min/1.73m² was found. The analysis of patients with eGFR over 60 ml/min/1.73m² showed significant differences in cystatin C and urinary NGAL levels. The area under the curve for serum NGAL, urinary NGAL and cystatin C was 0.60 (95% CI, 0.51 to 0.69), 0.59 (95% CI, 0.5 to 0.68), 0.62 (95% CI, 0.54 to 0.71), respectively, good cut-off values of studied biomarkers to detect diabetes were not found.

CONCLUSION

NGAL, cystatin C and KIM-1 are not more useful than eGFR in the assessment of kidney function in diabetic patients with coronary heart disease.

Urinary kidney injury molecule-1 and the risk of cardiovascular mortality in elderly men

BACKGROUND AND OBJECTIVES

Kidney injury molecule-1 (KIM-1) has been suggested as a clinically relevant highly specific biomarker of acute kidney tubular damage. However, community-based data on the association between urinary levels of KIM-1 and the risk for cardiovascular mortality are lacking. This study aimed to investigate the association between urinary KIM-1 and cardiovascular mortality.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This was a prospective study, using the community-based Uppsala Longitudinal Study of Adult Men (N=590; mean age 77 years; baseline period, 1997-2001; median follow-up 8.1 years; end of follow-up, 2008).

RESULTS

During follow-up, 89 participants died of cardiovascular causes (incidence rate, 2.07 per 100 person-years at risk). Models were adjusted for cardiovascular risk factors (age, systolic BP, diabetes, smoking, body mass index, total cholesterol, HDL cholesterol, antihypertensive treatment, lipid-lowering treatment, aspirin treatment, and history of cardiovascular disease) and for markers of kidney dysfunction and damage (cystatin C-based eGFR and urinary albumin/creatinine ratio). Higher urinary KIM-1/creatinine (from 24-hour urine collections) was associated with a higher risk for cardiovascular mortality (hazard ratio per SD increase, 1.27; 95% confidence interval [95% CI], 1.05 to 1.54; P=0.01). Participants with a combination of high KIM-1/creatinine (upper quintile, ≥175 ng/mmol), low eGFR (≤60 ml/min per 1.73 m(2)), and microalbuminuria/macroalbuminuria (albumin/creatinine ratio≥3 g/mol) had a >8-fold increased risk compared with participants with low KIM-1/creatinine (<175 ng/mmol), normal eGFR (>60 ml/min per 1.73 m(2)), and normoalbuminuria (albumin/creatinine ratio<3 g/mol) (hazard ratio, 8.56; 95% CI, 4.17 to 17.56; P<0.001).

CONCLUSIONS

These findings suggest that higher urinary KIM-1 may predispose to a higher risk of cardiovascular mortality independently of established cardiovascular risk factors, eGFR, and albuminuria. Additional studies are needed to further assess the utility of measuring KIM-1 in the clinical setting.

Emerging biomarkers and metabolomics for assessing toxic nephropathy and acute kidney injury (AKI) in neonatology

Identification of novel drug-induced toxic nephropathy and acute kidney injury (AKI) biomarkers has been designated as a top priority by the American Society of Nephrology. Increasing knowledge in the science of biology and medicine is leading to the discovery of still more new biomarkers and of their roles in molecular pathways triggered by physiological and pathological conditions. Concomitantly, the development of the so-called "omics" allows the progressive clinical utilization of a multitude of information, from those related to the human genome (genomics) and proteome (proteomics), including the emerging epigenomics, to those related to metabolites (metabolomics). In preterm newborns, one of the most important factors causing the pathogenesis and the progression of AKI is the interaction between the individual genetic code, the environment, the gestational age, and the disease. By analyzing a small urine sample, metabolomics allows to identify instantly any change in phenotype, including changes due to genetic modifications. The role of liquid chromatography-mass spectrometry (LC-MS), proton nuclear magnetic resonance (1H NMR), and other emerging technologies is strategic, contributing basically to the sudden development of new biochemical and molecular tests. Urine neutrophil gelatinase-associated lipocalin (uNGAL) and kidney injury molecule-1 (KIM-1) are closely correlated with the severity of kidney injury, representing noninvasive sensitive surrogate biomarkers for diagnosing, monitoring, and quantifying kidney damage. To become routine tests, uNGAL and KIM-1 should be carefully tested in multicenter clinical trials and should be measured in biological fluids by robust, standardized analytical methods.

Endothelin ET(B) receptors contribute to sex differences in blood pressure elevation in angiotensin II hypertensive rats on a high-salt diet

Female rats are more resistant to blood pressure increases induced by high salt (HS) intake or angiotensin (Ang) II infusion. Because endothelin ET(B) receptors on endothelial and epithelial cells mediate tonic vasodilation and sodium excretion, we hypothesized that ET(B) receptors limit the hypertensive response and renal injury induced by HS diet alone or with chronic AngII infusion (AngII/HS) in female compared with male rats. A 4 week HS diet (4% NaCl) did not significantly change blood pressure (measured by telemetry) in either male or female Sprague-Dawley rats. Administration of the ET(B) receptor antagonist A-192621 (1, 3 and 10 mg/kg per day in food) during HS feeding caused a dose-dependent increase in blood pressure in both sexes. In AngII/HS rats, males had a larger increase in blood pressure than females. The increase in blood pressure produced by ET(B) receptor blockade in male AngII/HS rats was not significant. However, A-192621 treatment resulted in a significant further increase in blood pressure in female AngII/HS rats. Male rats had consistently higher protein excretion rates before and during AngII/HS, but this was not significantly affected by ET(B) receptor blockade in either sex. In conclusion, ET(B) receptors play a significantly greater beneficial role in protecting female compared with male rats against AngII-induced hypertension and may contribute to the sex differences in AngII-induced hypertension.

Kidney injury molecule (KIM)-1 is associated with insulin resistance: results from two community-based studies of elderly individuals

BACKGROUND AND OBJECTIVES

Insulin resistance has been shown to be closely associated with glomerular filtration rate and urinary albumin/creatinine ratio, even prior to the development of diabetes. Urinary kidney injury molecule 1 (KIM-1) is a novel, highly specific marker of kidney tubular damage. The role of insulin resistance in the development of kidney tubular damage is not previously reported. Thus, we aimed to investigate the associations between insulin sensitivity (assessed by HOMA) and urinary KIM-1.

DESIGN, SETTING, PARTICIPANTS AND MEASUREMENTS

Two community-based cohorts of elderly individuals were investigated: Prospective Investigation of the vasculature in Uppsala seniors (PIVUS, n=701; mean age 75 years, 52% women); and Uppsala Longitudinal Study of adult men (ULSAM, n=533; mean age 78 years).

RESULTS

Lower insulin sensitivity was associated with higher urinary KIM-1 in both cohorts after adjustments for age, BMI, blood pressure, antihypertensive treatment, glomerular filtration rate, and urinary albumin-creatinine ratio (PIVUS: regression coefficient for 1-SD higher HOMA-IR 0.11, 95% CI 0.03-0.20, p=0.009, and ULSAM: 0.13, 95% CI 0.04-0.22, p=0.007). Results were similar in individuals without diabetes, with normal kidney function and normo-albuminuria.

CONCLUSIONS

Our findings in elderly individuals support the notion that the interplay between an impaired glucose metabolism and renal tubular damage is evident even prior to the development of diabetes and overt kidney disease.

Diagnostic value of urinary kidney injury molecule 1 for acute kidney injury: a meta-analysis

Background

Urinary Kidney Injury Molecule 1 (KIM-1) is a proximal tubular injury biomarker for early detection of acute kidney injury (AKI), with variable performance characteristics depending on clinical and population settings.

Methods

Meta-analysis was performed to assess the diagnostic value of urinary KIM-1 in AKI. Relevant studies were searched from MEDLINE, EMBASE, Pubmed, Elsevier Science Direct, Scopus, Web of Science, Google Scholar and Cochrane Library. Meta-analysis methods were used to pool sensitivity and specificity and to construct summary receiver operating characteristic (SROC) curves.

Results

A total of 2979 patients from 11 eligible studies were enrolled in the analysis. Five prospective cohorts, two cross-sectional and four case-control studies were identified for meta-analysis. The estimated sensitivity of urinary KIM-1 for the diagnosis of AKI was 74.0% (95% CI, 61.0%–84.0%), and specificity was 86.0% (95% CI, 74.0%–93.0%). The SROC analysis showed an area under the curve of 0.86(0.83–0.89). Subgroup analysis suggested that population settings and detection time were the key factors affecting the efficiency of KIM-1 for AKI diagnosis.

Limitation

Various population settings, different definition of AKI and Serum creatinine level used as the standard might have influence on AKI diagnosis. The relatively small number of studies and heterogeneity between them also affected the evaluation.

Conclusion

Urinary KIM-1 may be a promising biomarker for early detection of AKI with considerable predictive value, especially for cardiac surgery patients, and its potential value needs to be validated in large studies and across a broader scope of clinical settings.

Tissue kidney injury molecule-1 expression in the prediction of renal function for several years after kidney biopsy

Objectives. Retrospective study was designed to examine the importance of tissue kidney injury molecule-1 (KIM-1) expression in predicting kidney function in sixty patients (27 males) aged 34.15 ± 12.23 years with different kidney diseases over three years after kidney biopsy. Materials and Methods. Tissue KIM-1 expression was determined immunohistochemically and KIM-1 staining was scored semiquantitatively, as well as tubulointerstitialis (TIN), inflammation, atrophy, and fibrosis. Kidney function (MDRD formula) and proteinuria/day were evaluated at the time of biopsy (GFR0) and 6, 12, 24, and 36 months later. Results. Significantly positive correlations between tissue KIM-1 expression and age (r = 0.313), TIN inflammation (r = 0.456), fibrosis (r = 0.317), and proteinuria at 6 months (r = 0.394) as well as negative correlations with GFR0 (r = −0.572), GFR6 (r = −0.442), GFR24 (r = −0.398), and GFR36 (r = −0.412) were found. Meanwhile, TIN inflammation was the best predictor of all measured kidney functions during three years, while tissue KIM-1 expression (P = 0.016) was a predictor only at 6 months after biopsy. Conclusion. Tissue KIM-1 expression significantly predicts kidney function solely at 6 months after biopsy, when the effects of immune and nonimmune treatments are the strongest.

Kidney injury molecule-1

PURPOSE OF REVIEW

To review the new findings about the physiological roles of kidney injury molecule-1 (KIM-1) and the rapidly expanding evidence for this molecule as a promising biomarker in preclinical kidney toxicity evaluation and various human kidney diseases.

RECENT FINDINGS

KIM-1 has attracted increasing interest because of its possible pathophysiological role in modulating tubular damage and repair. There is rapidly accumulating evidence from both animal models and clinical studies that urinary KIM-1 is a sensitive and specific urinary biomarker for various forms of nephrotoxic injury, cardiac surgery-induced kidney injury, transplant rejection, and chronic kidney diseases.

SUMMARY

KIM-1 mediates epithelial phagocytosis in the injured kidney converting the proximal epithelial cell into a phagocyte, with potentially important pathophysiological implications for modulation of the immune response and repair process after injury. KIM-1 serves as a highly sensitive and specific urinary biomarker for kidney injury and may also be a therapeutic target for various kidney diseases.

Chronic epithelial kidney injury molecule-1 expression causes murine kidney fibrosis

Acute kidney injury predisposes patients to the development of both chronic kidney disease and end-stage renal failure, but the molecular details underlying this important clinical association remain obscure. We report that kidney injury molecule-1 (KIM-1), an epithelial phosphatidylserine receptor expressed transiently after acute injury and chronically in fibrotic renal disease, promotes kidney fibrosis. Conditional expression of KIM-1 in renal epithelial cells (Kim1(RECtg)) in the absence of an injury stimulus resulted in focal epithelial vacuolization at birth, but otherwise normal tubule histology and kidney function. By 4 weeks of age, Kim1(RECtg) mice developed spontaneous and progressive interstitial kidney inflammation with fibrosis, leading to renal failure with anemia, proteinuria, hyperphosphatemia, hypertension, cardiac hypertrophy, and death, analogous to progressive kidney disease in humans. Kim1(RECtg) kidneys had elevated expression of proinflammatory monocyte chemotactic protein-1 (MCP-1) at early time points. Heterologous expression of KIM-1 in an immortalized proximal tubule cell line triggered MCP-1 secretion and increased MCP-1-dependent macrophage chemotaxis. In mice expressing a mutant, truncated KIM-1 polypeptide, experimental kidney fibrosis was ameliorated with reduced levels of MCP-1, consistent with a profibrotic role for native KIM-1. Thus, sustained KIM-1 expression promotes kidney fibrosis and provides a link between acute and recurrent injury with progressive chronic kidney disease.

[Biomarkers of acute kidney injury: a « trending topic » in cirrhosis]

Acute kidney injury (AKI) is an ominous event in the natural history of cirrhosis. The differential diagnosis of this entity is hampered by the absence of specific biomarkers of tubular damage in cirrhosis. The clinical usefulness of such biomarkers is determined by their effectiveness in the diagnosis of AKI and their ability to provide critical information to ameliorate clinical outcomes and survival. The lack of biomarkers has hindered the development of interventions aimed to improve the prognosis of kidney impairment in cirrhosis. Currently, biomarkers are an area of intense research in nephrology. Emerging genomic and proteomic technologies have revealed novel plasma and urinary biomarkers of AKI. The present article discusses the most promising candidate biomarkers with potential application in cirrhosis, such as NGAL, KIM-1, cystatin-C, IL-18, L-FABP, N-acetyl glucosaminidase and netrin-1, are discussed below.

urinary biomarkers in relapsing antineutrophil cytoplasmic antibody-associated vasculitis

OBJECTIVE

Glomerulonephritis (GN) is common in antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV), but tools for early detection of renal involvement are imperfect. We investigated 4 urinary proteins as markers of active renal AAV: alpha-1 acid glycoprotein (AGP), kidney injury molecule-1 (KIM-1), monocyte chemoattractant protein-1 (MCP-1), and neutrophil gelatinase-associated lipocalin (NGAL).

METHODS

Patients with active renal AAV (n = 20), active nonrenal AAV (n = 16), and AAV in longterm remission (n = 14) were identified within a longitudinal cohort. Urinary biomarker concentrations (by ELISA) were normalized for urine creatinine. Marker levels during active AAV were compared to baseline remission levels (from 1-4 visits) for each patient. Areas under receiver-operating characteristic curves (AUC), sensitivities, specificities, and likelihood ratios (LR) comparing disease states were calculated.

RESULTS

Baseline biomarker levels varied among patients. All 4 markers increased during renal flares (p < 0.05). MCP-1 discriminated best between active renal disease and remission: a 1.3-fold increase in MCP-1 had 94% sensitivity and 89% specificity for active renal disease (AUC = 0.93, positive LR 8.5, negative LR 0.07). Increased MCP-1 also characterized 50% of apparently nonrenal flares. Change in AGP, KIM-1, or NGAL showed more modest ability to distinguish active renal disease from remission (AUC 0.71-0.75). Hematuria was noted in 83% of active renal episodes, but also 43% of nonrenal flares and 25% of remission samples.

CONCLUSION

Either urinary MCP-1 is not specific for GN in AAV, or it identifies early GN not detected by standard assessment and thus has potential to improve care. A followup study with kidney biopsy as the gold standard is needed.

Glomerular and tubular damage markers in individuals with progressive albuminuria

BACKGROUND AND OBJECTIVES

Albuminuria is associated with risk for renal and cardiovascular disease. It is difficult to predict which persons will progress in albuminuria. This study investigated whether assessment of urinary markers associated with damage to different parts of the nephron may help identify individuals that will progress in albuminuria.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Individuals were selected from a prospective community-based cohort study with serial follow-up and defined as "progressors" if they belonged to the quintile of participants with the most rapid annual increase in albuminuria, and reached an albuminuria ≥150 mg/d during follow-up. Patients with known renal disease or macroalbuminuria at baseline were excluded. Each progressor was matched to two control participants, based on baseline albuminuria, age, and sex. Furthermore, damage markers were measured in a separate set of healthy individuals.

RESULTS

After a median follow-up of 8.6 years, 183 of 8394 participants met the criteria for progressive albuminuria. Baseline clinical characteristics were comparable between progressors and matched controls (n=366). Both had higher baseline albuminuria than the overall population. Urinary excretion of the glomerular damage marker IgG was significantly higher in progressors, whereas urinary excretion of proximal tubular damage markers and inflammatory markers was lower in these individuals compared with controls. Healthy individuals (n=109) had the lowest values for all urinary damage markers measured.

CONCLUSIONS

These data suggest that albuminuria associated with markers of glomerular damage is more likely to progress, whereas albuminuria associated with markers of tubulointerstitial damage is more likely to remain stable.

Selenium inhibits renal oxidation and inflammation but not acute kidney injury in an animal model of rhabdomyolysis

Acute kidney injury (AKI) is a manifestation of rhabdomyolysis (RM). Extracellular myoglobin accumulating in the kidney after RM promotes oxidative damage, which is implicated in AKI.

AIM

To test whether selenium (Se) supplementation diminishes AKI and improves renal function.

RESULTS

Dietary selenite increased Se in the renal cortex, as demonstrated by X-ray fluorescence microscopy. Experimental RM-stimulated AKI as judged by increased urinary protein/creatinine, clusterin, and kidney injury molecule-1 (KIM-1), decreased creatinine clearance (CCr), increased plasma urea, and damage to renal tubules. Concentrations of cholesterylester (hydro)peroxides and F₂-isoprostanes increased in plasma and renal tissues after RM, while aortic and renal cyclic guanidine monophosphate (cGMP; marker of nitric oxide (NO) bioavailability) decreased. Renal superoxide dismutase-1, phospho-P65, TNFα gene, MCP-1 protein, and the 3-chloro-tyrosine/tyrosine ratio (Cl-Tyr/Tyr; marker of neutrophil activation) all increased after RM. Dietary Se significantly decreased renal lipid oxidation, phospho-P65, TNFα gene expression, MCP-1 and Cl-Tyr/Tyr, improved NO bioavailability in aorta but not in the renal microvasculature, and inhibited proteinuria. However, CCr, plasma urea and creatinine, urinary clusterin, and histopathological assessment of AKI remained unchanged. Except for the Se++ group, renal angiotensin-receptor-1/2 gene/protein expression increased after RM with parallel increases in MEK1/2 inhibitor-sensitive MAPkinase (ERK) activity.

INNOVATION

We employed synchrotron radiation to identify Se distribution in kidneys, in addition to assessing reno-protection after RM.

CONCLUSION

Se treatment has some potential as a therapeutic for AKI as it inhibits oxidative damage and inflammation and decreases proteinuria, albeit histopathological changes to the kidney and some plasma and urinary markers of AKI remain unaffected after RM.

Urinary kidney injury molecule 1 and incidence of heart failure in elderly men

AIMS

There is growing recognition of the clinical importance of cardiorenal syndrome-the bidirectional interplay between kidney and cardiac dysfunction. Yet, the role of kidney tubular damage in the development of heart failure is less studied. The objective of this study was to investigate whether urinary kidney injury molecule (KIM)-1, a specific marker of tubular damage, predisposes to an increased heart failure risk.

METHODS AND RESULTS

This was a community-based cohort study [Uppsala Longitudinal study of Adult Men (ULSAM)] of 565, 77-year-old men free from heart failure at baseline. Heart failure hospitalizations were used as outcome. During follow-up (median 8.0 years), 73 participants were hospitalized for heart failure. In models adjusted for cardiovascular risk factors (age, systolic blood pressure, diabetes, smoking, body mass index, LDL/HDL ratio, antihypertensive treatment, lipid-lowering treatment, aspirin treatment, LV hypertrophy, and prevalent cardiovascular disease) and markers of kidney dysfunction and damage [cystatin C-based glomerular filtration rate (GFR) and urinary albumin/creatinine ratio], a higher urinary KIM-1/creatinine ratio was associated with higher risk for heart failure (hazard ratio upper vs. lower tertile, 1.81; 95% confidence interval 1.01-3.29; P < 0.05). Participants with a combination of low GFR (<60 mL/min/1.72 m(2)) and high KIM-1/creatinine (>128 ng/mmol) had a 3-fold increase in heart failure risk compared with participants with normal GFR and KIM-1 (P < 0.001).

CONCLUSION

Our findings suggest that kidney tubular damage predisposes to an increased risk for heart failure in the community. Further studies are needed to clarify the causal role of KIM-1 in the development of heart failure, and to evaluate the clinical utility of urinary KIM-1 measurements.

Pre-clinical markers for diagnosis of diabetic nephropathy in patients with type 1 diabetes mellitus

Due to progressive nature of diabetic nephropathy (DN) and limited effectiveness of therapeutic efforts at clinically overt stages, diagnosisof pre-clinical (and, therefore, potentially reversible) DN is especially important. To date, however, test for microalbuminuriaremains the only technique applicable for early diagnostics of DN. Current review addresses search for potential markers of pre-clinical stage of DN in patients with type 1 diabetes mellitus and embracesdata from latest experimental and clinical studies in this area.

Cardio-renal syndrome: new perspective in diagnostics

Chronic heart failure and chronic renal failure are at epidemic proportions. These patients have significantly altered cardiac, renal, and all-cause outcomes. Much of the current research has focused on treating these individual organs in isolation. Although there are positive data on outcomes with neurohormonal modulation, they, however, remain underused. At present, data lacks for novel treatment options, while evidence continues to point at significantly worsened prognosis. Current diagnostic tools that detect acute changes in renal function or renal injury appear retrospective, which often hinder meaningful diagnostic and therapeutic decisions. This review is aimed at exploring the importance of accurate assessment of renal function for the heart failure patient by providing a synopsis on cardio-renal physiology and establishing the possibility of novel approaches in bridging the divide.

[Kidney injury biomarkers]

Over the last few decades, prevalence of renal diseases has grown continuously in occidental societies due to life conditions (age, life style, chronic disease, etc.) or potential exposure to nephrotoxic agents (drugs and environmental chemicals). Today, the knowledge of the nephropatology mechanism is improving. Nevertheless, considering it is a complex and multifunctional structure, the clinical strategy of this issue (prognostic, diagnostic or therapy) keeps posing a major challenge for clinicians mostly because classical markers are not sensitive enough and require hours before reaching significant levels. Furthermore, most of these markers provide information on function and not on structural integrity of the tissue. Identification and development of new biomarkers share promise of improvement in the rapid diagnostic of kidney diseases and development of new cures in order to optimize the clinical strategy associated to the renal failure.

Distinct role of matrix metalloproteinase-3 in kidney injury molecule-1 shedding by kidney proximal tubular epithelial cells

Tubulointerstitial injury is a common pathway in progressive renal impairment and human proximal tubular epithelial cells (PTEC) play a crucial role in this process. Kidney injury molecule-1 (KIM-1) has received increasing attention due to its potential utility as the therapeutic target and biomarker for kidney injury. This study aims to explore the underlying mechanism regulating the release of KIM-1. Cultured primary human PTEC expressed and released KIM-1 from the apical surface through an ectodomain shedding process mediated by matrix metalloproteinase (MMP), independent of gene expression and protein synthesis. The constitutive KIM-1 shedding by PTEC was enhanced in a dose- and time-dependent manner by human serum albumin (HSA) or tumor necrosis factor-α (TNF-α), two important physiological stimuli found during kidney injury. Data from PCR array screening of MMPs gene expression in PTEC following activation by HSA or TNF-α, and from blocking experiments using either synthetic MMP inhibitors or MMP gene knockdown by siRNA, revealed that the constitutive and accelerated shedding of KIM-1 in cultured PTEC was mediated by MMP-3. Furthermore, the up-regulation of MMP-3 and KIM-1 release by PTEC was associated with generation of reactive oxygen species. In a mouse model of acute kidney injury induced by ischemia and reperfusion, increased expression of MMP-3 and KIM-1 as well as their co-localization were observed in kidney from ischemic but not in sham-operated mice. Taken together, these in vitro and in vivo evidences suggest that MMP-3 plays an inductive role in KIM-1 shedding by PTEC.

Increased prevalence of simple renal cysts in patients with gout

The aim of this study was to determine the prevalence of simple renal cysts in gout patients and evaluate associated risk factors for its development. Hundred and forty-six patients followed at our outpatient Gout Unit and 47 sex- and age-matched healthy kidney donors who had undergone routine renal ultrasonography, using a static gray scale and real-time B-mode units with a 3.5- or 5.0-MHz transducer, were evaluated for the presence of renal cysts. Demographic and clinical characteristics of gout patients were evaluated considering possible risk factors for the occurrence of simple renal cysts such as age, male gender, hypertension, and renal impairment. The prevalence of simple renal cyst was 26.0 % in gout patients and 10.6 % in control group (P = 0.045). Gout patients with simple renal cysts presented less renal lithiasis than those without this complication (5.2 vs 25.9 %; P = 0.003) in spite of an overall higher frequency of renal stones in gout patients compared to control group (20.5 vs. 6.3 %, P = 0.025). The presence of simple renal cyst in gout was not associated with previously reported factors such as age (P = 0.296), male predominance (P = 0.688), hypertension (P = 0.314), and renal impairment (P = 254). Moreover, no association with disease duration (P = 0.843) or tophi (P = 0.616) was observed. In conclusion, gout patients have an increased prevalence of simple renal cysts associated with a lower occurrence of nephrolithiasis. Whether renal cysts have any protective effect in the development of nephrolithiasis in gout remains to be determined.

Biomarkers for the prediction of acute kidney injury: a narrative review on current status and future challenges

Acute kidney injury (AKI) is strongly associated with increased morbidity and mortality in critically ill patients. Efforts to change its clinical course have failed because clinically available therapeutic measures are currently lacking, and early detection is impossible with serum creatinine (SCr). The demand for earlier markers has prompted the discovery of several candidates to serve this purpose. In this paper, we review available biomarker studies on the early predictive performance in developing AKI in adult critically ill patients. We make an effort to present the results from the perspective of possible clinical utility.

Urinary tubular biomarkers in short-term type 2 diabetes mellitus patients: a cross-sectional study

The purpose of this study was to investigate the prevalence of tubular damage in short-term (less than five years) type 2 diabetes mellitus (T2DM) patients and to explore the correlation between tubular markers and their relationship with renal indices at different stages of diabetic nephropathy. A group of 101 short-term T2DM patients and 28 control subjects were recruited. Tubular markers, such as neutrophil gelatinase-associated lipocalin (NGAL), N-acetyl-β-D: -glucosaminidase (NAG), and kidney injury molecule 1 (KIM-1), as well as urinary albumin excretion were measured in voided urine. Glomerular filtration rate (GFR) was estimated via Macisaac's formula. The patients were further categorized into three groups, namely, the normoalbuminuria, microalbuminuria, and macroalbuminuria groups, according to their urine albumin/creatinine ratio (UACR). Urinary tubular markers were compared and their correlations with renal indices [UACR and estimated GFR (eGFR)] were analyzed among the different diabetic groups. Compared with the control group, Urinary NGAL [median (IQR)][83.6(41.4-138.7) μg/gcr vs. 32.9(26.1-64.5) μg/gcr], NAG [13.5(8.7-17.9) U/gcr vs. 7.6(6.5-13.0) U/gcr] and KIM-1 [120.0(98.4-139.9) ng/gcr vs. 103.1(86.8-106.2) ng/gcr] in the T2DM were all markedly increased. For all patients, urinary NGAL had stronger positive correlations with UACR than NAG (R = 0.556 vs. 0.305, both P < 0.05). In addition, only urinary NGAL showed a negative correlation with eGFR (R = -0.215, P < 0.05). Urinary KIM-1, however, showed no significant difference among the three T2DM groups and did not correlate with either UACR or eGFR. As UACR increased from the normoalbuminuria to the last macroalbuminuria group, all of the markers increased. However, only the concentrations of NGAL were statistically different among the three diabetic groups. The correlation between the tubular markers and their relationships with the renal indices differed markedly among the three T2DM groups. In conclusion, these results suggest that tubular damage is common in short-term T2DM patients. Urinary NGAL may be a promising early marker for monitoring renal impairment in short-term T2DM patients.

Changes of the tubular markers in type 2 diabetes mellitus with glomerular hyperfiltration

AIM

To assess whether glomerular hyperfiltration (GHF) could result in renal tubular damage in type 2 diabetes mellitus (T2DM) patients.

METHODS

Reference value of estimated glomerular filtration rate (eGFR) was determined in 248 healthy individuals based on serum CysC levels. GHF was defined as an eGFR exceeding the sex-specific 97.5th percentile in non-diabetic individuals. In the present study, 30 with GHF, 58 with norm-GFR T2DM, and 24 healthy controls were recruited. Tubular markers, such as urinary N-acetyl-β-D-glucosaminidase (NAG) and kidney injury molecule 1 (KIM-1), as well as serum and urinary neutrophil gelatinase-associated lipocalin (NGAL), were measured and compared. The correlation of these markers with eGFR was analyzed in the GHF group.

RESULTS

The GHF group had higher urinary NGAL and KIM-1 levels but lower serum NGAL level than the norm-GFR and control groups. Slightly decreased serum NGAL and increased urinary NGAL levels were also noted in the norm-GFR group compared with those of the controls. There was no statistical difference in the urinary NAG values among the three groups. Correlation analysis showed that eGFR was positively related to fasting blood glucose (FBG), HbA1c, urinary NGAL, and KIM-1, but negatively with serum NGAL in the GHF group.

CONCLUSION

Higher urinary tubular damage markers were found in T2DM patients with GHF than the norm-GFR and control groups, probably a direct proof that GHF is a deleterious factor for diabetic nephropathy.

Enabling innovative translational research in acute kidney injury

Acute kidney injury (AKI) is a common, heterogeneous, and detrimental clinical condition that has significant attributable morbidity and mortality. Despite major advances in understanding the epidemiology, pathogenesis, and outcomes of AKI, preventive measures remain inadequate and therapeutic approaches (except for renal replacement therapy) have largely proven futile so far. Critical to the process of designing rational therapies is translational research, which involves the transition between the basic research discoveries and everyday clinical applications to prevent, diagnose, and treat human diseases. Progress in innovative approaches has been hampered due in part to the reliance on functional markers (serum creatinine and blood urea nitrogen) that are neither sensitive nor specific to diagnose AKI. This limitation has created a great deal of interest and intense investigation to identify a "troponin-like marker" that would facilitate recognition of AKI and allow for timely implementation of the precise therapeutic agent. The other major obstacle in this field is the diverse and complex nature of AKI that involves multiple independent and overlapping pathways, making it difficult to cure AKI with a single approach. In this review, we will summarize the advances, ongoing studies, and future perspectives in the field of translational research of AKI.

Acute-on-chronic liver failure: the kidneys

PURPOSE OF REVIEW

Acute-on-chronic liver failure (ACLF) is defined as an abrupt deterioration of liver function in patients with established liver disease. Kidney function is almost universally altered in patients with ACLF due to underlying circulatory abnormalities. We review current advances during the past year in the diagnosis and management of renal failure in ACLF.

RECENT FINDINGS

The adequate measurement of renal function by means of clearance methods remains the gold standard for estimation of the glomerular filtration rate in patients with cirrhosis. The new definition of acute kidney injury needs to be specifically studied in patients with cirrhosis. Alternative kidney biomarkers of renal function in cirrhosis are promising and need further investigation. The most common cause of renal failure in cirrhosis is that associated with infections followed by hypovolemia-induced renal failure, intrinsic renal diseases, hepatorenal syndrome, and drug-induced renal failure. Adrenal insufficiency commonly occurs in patients with cirrhosis and hemodynamic instability. The proper diagnosis relies on corticotropin stimulation testing and the role of hydrocortisone therapy in these patients merits further investigation. Hyponatremia in cirrhosis is a major risk factor for the development of hepatic encephalopathy and is associated with a poor outcome in patients with ACLF and also after deceased donor and living-related liver transplantation. Vasoconstrictor drugs, particularly terlipressin, are effective for the management of hepatorenal syndrome. Predictive factors of response to terlipressin include serum bilirubin levels and the presence of an early increase in mean arterial pressure.

SUMMARY

The ongoing advances in the diagnosis and management of patients with ACLF and renal failure will improve the diagnosis, therapy and outcome of these patients.

Albuminuria, proteinuria, and novel urine biomarkers as predictors of long-term allograft outcomes in kidney transplant recipients

BACKGROUND

Proteinuria is an established marker of decreased kidney function after kidney transplant. It recently has been suggested that albuminuria might be a more reliable marker. Although albuminuria often is regarded as a marker of glomerular damage, because chronic renal allograft damage is believed to be predominantly an interstitial process, albuminuria in this case might reflect tubular damage. Accordingly, we investigated the value of albuminuria, proteinuria, and tubular damage markers (KIM-1 [kidney injury molecule 1], NAG [N-acetyl-β-d-glucosaminidase], NGAL [neutrophil gelatinase-associated lipocalin], and H-FABP [heart fatty acid binding protein]) in predicting graft outcome in kidney transplant recipients.

STUDY DESIGN

Prospective observational cohort study.

SETTING & PARTICIPANTS

606 patients visiting our outpatient kidney transplant clinic in 2001-2003 were included and used in the analysis for death-censored graft failure. Median follow-up was 4.7 (25th-75th percentile, 3.8-5.2) years. 577 patients had follow-up longer than 1 year and were included in the analysis for estimated glomerular filtration rate (eGFR) decrease. Median follow-up was 3.2 (25th-75th percentile, 2.7-3.7) years.

PREDICTORS

Urine protein, albumin, and tubular damage markers in 24-hour urine samples.

OUTCOMES

Death-censored graft failure and decrease in eGFR.

RESULTS

There were 42 patients with graft failure; mean eGFR change was -0.46 ± 3.7 (standard deviation) mL/min/1.73 m(2)/y. The area under the receiver operating characteristic curve for death-censored graft failure showed that albuminuria (0.78; 95% CI, 0.59-0.76) was significantly higher than proteinuria (0.67; 95% CI, 0.59-0.76; P = 0.001), NGAL (0.63; 95% CI, 0.52-0.74; P = 0.02), and H-FABP (0.62; 95% CI, 0.53-0.73; P = 0.005) and not significantly different from KIM-1 (0.74; 95% CI, 0.66-0.82) and NAG (0.75; 95% CI, 0.67-0.83). Results were similar for the eGFR decrease outcome.

LIMITATIONS

Single-center observational study.

CONCLUSIONS

Measuring albuminuria may provide superior predictions for long-term renal outcomes after kidney transplant than total proteinuria. Additional assessment of urinary excretion of tubular damage markers may have limited value.

Post-transplant nuclear renal scans correlate with renal injury biomarkers and early allograft outcomes

BACKGROUND

Clinical- and histopathology-based scores are limited predictors of allograft outcome. In addition, more objective markers of early transplant function are needed to identify and validate biomarkers and predictive scores. We evaluated existing scores and transcriptome biomarkers of kidney injury as predictors of early transplant function measured by renal scan.

METHODS

Clinical, histopathologic and transcriptome data were collected in 143 consecutive kidney transplant recipients. A post-operative renal scan was performed within 48 h. Prediction scores for early outcomes were calculated.

RESULTS

Patients were stratified into three groups by renal scan: normal, mild-to-moderate or severe dysfunction. Kidneys with severe dysfunction were more often from deceased donors (P < 0.001), had greater HLA antigen mismatches (P < 0.001), were transplanted into older recipients (P = 0.040), had lower urine output during the first 8 h (P < 0.001), higher Day 7 serum creatinine (P < 0.001) and higher incidence of delayed graft function (P < 0.001). Clinical- and pathology-based scores did not discriminate between scan groups. In contrast, the overall transcriptome (P < 0.001) and transcripts of preselected acute kidney injury (AKI) genes were significantly different between the groups, with kidney injury molecule 1 (P = 0.001) and neutrophil gelatinase-associated lipocalin (P = 0.002) being most highly expressed and genes associated with glutathione metabolism (GSTA1, 3 and 4) most down-regulated in kidneys with subsequent severe dysfunction.

CONCLUSIONS

Renal scans reflect early transplant function and allow for a more objective assessment of scores predicting early outcome and for identification of biomarkers. The study shows that transcript levels of AKI genes correlate better with renal scans than clinical- or histopathology-based scores.

Association of urinary biomarkers with disease severity in patients with autosomal dominant polycystic kidney disease: a cross-sectional analysis

BACKGROUND

Disease monitoring of autosomal dominant polycystic kidney disease (ADPKD) will become more important with potential upcoming therapeutic interventions. Because serum creatinine level is considered of limited use and measurement of effective renal blood flow (ERBF) and total renal volume are time consuming and expensive, there is a need for other biomarkers. We aimed to investigate which urinary markers have increased levels in patients with ADPKD; whether these urinary markers are associated with measured glomerular filtration rate (mGFR), ERBF, and total renal volume; and whether these associations are independent of albuminuria (urine albumin excretion [UAE]).

STUDY DESIGN

Diagnostic test study.

SETTING & PARTICIPANTS

102 patients with ADPKD (Ravine criteria) and 102 age- and sex-matched healthy controls.

INDEX TEST

24-hour urinary excretion of glomerular (immunoglobulin G), proximal tubular (kidney injury molecule 1 [KIM-1], N-acetyl-β-d-glucosaminidase, neutrophil gelatinase-associated lipocalin [NGAL], and β(2)-microglobulin), and distal tubular (heart-type fatty acid binding protein [H-FABP]) damage markers and inflammatory markers (monocyte chemotactic protein 1 [MCP-1] and macrophage migration inhibitory factor).

REFERENCE TEST

Disease severity assessed using measures of kidney function (mGFR and ERBF, measured using clearance of iothalamate labeled with iodine 125 and hippuran labeled with iodine 131 during continuous infusion, respectively) and structure (total renal volume, measured using magnetic resonance imaging).

OTHER MEASUREMENTS

24-hour UAE.

RESULTS

In 102 patients with ADPKD (aged 40 ± 11 years; 58% men), levels of all measured urinary biomarkers were increased compared with healthy controls. Excretion of immunoglobulin G and albumin relatively were most increased. ERBF and mGFR values were associated with urinary excretion of β(2)-microglobulin, NGAL, and H-FABP independent of UAE, whereas total renal volume was associated with KIM-1, NGAL, and MCP-1 independent of UAE.

LIMITATIONS

Cross-sectional, single center.

CONCLUSIONS

Levels of markers for multiple parts of the nephron are increased in patients with ADPKD. In addition to measurement of UAE, measurement of urinary β(2)-microglobulin, KIM-1, H-FABP, MCP-1, and especially NGAL could be of value for determination of disease severity in patients with ADPKD.

TIM1 is an endogenous ligand for LMIR5/CD300b: LMIR5 deficiency ameliorates mouse kidney ischemia/reperfusion injury

Leukocyte mono-immunoglobulin (Ig)-like receptor 5 (LMIR5)/CD300b is a DAP12-coupled activating receptor predominantly expressed in myeloid cells. The ligands for LMIR have not been reported. We have identified T cell Ig mucin 1 (TIM1) as a possible ligand for LMIR5 by retrovirus-mediated expression cloning. TIM1 interacted only with LMIR5 among the LMIR family, whereas LMIR5 interacted with TIM4 as well as TIM1. The Ig-like domain of LMIR5 bound to TIM1 in the vicinity of the phosphatidylserine (PS)-binding site within the Ig-like domain of TIM1. Unlike its binding to TIM1 or TIM4, LMIR5 failed to bind to PS. LMIR5 binding did not affect TIM1- or TIM4-mediated phagocytosis of apoptotic cells, and stimulation with TIM1 or TIM4 induced LMIR5-mediated activation of mast cells. Notably, LMIR5 deficiency suppressed TIM1-Fc-induced recruitment of neutrophils in the dorsal air pouch, and LMIR5 deficiency attenuated neutrophil accumulation in a model of ischemia/reperfusion injury in the kidneys in which TIM1 expression is up-regulated. In that model, LMIR5 deficiency resulted in ameliorated tubular necrosis and cast formation in the acute phase. Collectively, our results indicate that TIM1 is an endogenous ligand for LMIR5 and that the TIM1-LMIR5 interaction plays a physiological role in immune regulation by myeloid cells.