Urinary hepcidin: an inverse biomarker of acute kidney injury after cardiopulmonary bypass?

Protective effect of MiR-146 on renal injury following cardiopulmonary bypass in rats through mediating NF-κB signaling pathway

The mechanism of renal injury after cardiopulmonary bypass is not clear, and the protective effect of microRNA-146 through mediating NF KB signaling pathway needs to be verified. The study intends to establish a rat model of cardiopulmonary bypass (CPB). MiR-146 is silenced or overexpressed by lentivirus transfection. It is divided into miR-146 inhibitors group (inhibitors), miR-146 mimics group (mimics) and sham group. It is found that the contents of Cr, bun and MDA in blood = , serum IL-1, IL-6 and TNF in mimics group are higher than those in the other two groups- α Content, apoptosis rate, ICAM-1, TNF- α, NF- κ B mRNA and NF- κ B protein decreased significantly (P < 0.05), while the content of SOD in kidney increased significantly (P < 0.05). In the inhibitors group, the above indicators showed the opposite results. Double luciferase assay showed that NF-kB was the target gene of miR-146. It can be seen that the expression of miR-146 inhibits inflammatory factors, apoptosis, oxidative stress and NF- κ the activation of B pathway promotes the repair of renal injury in CPB rats.

Combination of hepcidin with neutrophil gelatinase-associated lipocalin for prediction of the development of sepsis-induced acute kidney injury

BACKGROUND AND AIMS

The early prediction of the development of acute kidney injury (AKI) in critically ill patients with sepsis would facilitate early effective intervention. Recently, interest has focused on the biomarkers for AKI-linked iron metabolism. This study aimed to assess the early predictive values of hepcidin, neutrophil gelatinase-associated lipocalin (NGAL), and their combination for secondary AKI in patients with sepsis.

MATERIALS AND METHODS

A prospective cohort study was performed in septic patients. Serum and urine hepcidin, and urine NGAL were analyzed at admission. The primary outcome measure was occurrence of sepsis-induced AKI based on 2011 Kidney Disease: Improving Global Outcomes (KDIGO) criteria during the first week of ICU stay.

RESULTS

Of the 90 patients analyzed finally in the study, 44 (48.9%) patients developed AKI. Patients with AKI occurrence were more likely than those without AKI to have higher serum hepcidin and urine NGAL levels at admission (P < 0.01). Higher concentrations of these biomarkers were each independent predictor of the development of AKI in critically septic patients within the first week of their ICU stay. Serum hepcidin and urine NGAL (AUROC 0.787, 95% CI 0.688 to 0.8660 and AUROC 0.729, 95% CI 0.625 to 0.818, respectively) were comparable predictive indicators of AKI occurrence (P = 0.43 for DeLong's test). Combining both biomarkers increased the AUROC to 0.828(95% CI 0.733 to 0.899), and this performance was statistically significantly better than urine NGAL alone (P = 0.03 for DeLong's test).

CONCLUSION

Serum hepcidin measured at admission predicts the development of AKI similarly to urine NGAL. However, serum hepcidin adds significant accuracy to this prediction in combination with urine NGAL alone and has a good predictive value in patients with sepsis. Larger studies are needed to validate and explain these findings.

Effect of atorvastatin on iron metabolism regulation in patients with chronic kidney disease - a randomized double blind crossover study

INTRODUCTION

To determine the effect of 6-month administration of atorvastatin on hepcidin and hemojuvelin levels, inflammatory parameters and iron metabolism in patients with chronic kidney disease (CKD) stages 3 and 4.

METHODS

Thirty six statin- and erythropoiesis-stimulating agent-naive patients with CKD stages 3 and 4 and LDL cholesterol ≥100 mg/dl received atorvastatin or placebo for two 6-month periods in a double blind, randomized crossover study. Hepcidin, hemojuvelin, hsCRP, IL-6, hemoglobin, red blood cell distribution width, iron, total iron binding capacity (TIBC), and unsaturated iron binding capacity (UIBC) were measured before and after each treatment period.

RESULTS

Hepcidin decreased (from 102 [307] to 63 [170] pg/ml (p > .001)) in the course of statin therapy but remained unchanged after placebo administration (173 [256] to 153 [204] pg/ml, respectively). Hemojuvelin did not change after either part of the study. Both IL-6 and hsCRP decreased following statin therapy (from 8.7 [12.0] to 8.1 [13.9] pg/ml; p = .04 and from 4.7 [4.0] to 4.0 [3.6] mg/l; p = .4, respectively), but did not change after placebo administration. Blood hemoglobin increased slightly but significantly after 6-month statin therapy (from 11.6 ± 1.6 to 11.9 ± 1.5 g/dl, p = .002), and was unchanged after placebo treatment. TIBC and UIBC increased significantly after 6-month statin therapy, and serum iron also tended to increase. The change of eGFR during the study did not differ between the two treatment periods.

CONCLUSIONS

Statin may have a small but potentially beneficial effect on serum hepcidin, which may lead to improvement of anemia control in CKD patients.

Prospective Assessment of Hepcidin in Relation to Delayed or Immediate Graft Function in Patients Undergoing Kidney Transplantation

BACKGROUND

Hepcidin is a peptide hormone that regulates iron homeostasis. Hepcidin may represent an early, predictive biomarker of acute kidney injury, another model of ischemia-reperfusion injury. Urinary hepcidin-25 has been shown to be elevated in patients who do not develop acute kidney injury. Creatinine is an unreliable indicator during acute changes in kidney; therefore, the aim of the study was to assess whether hepcidin could predict renal outcome in 31 consecutive patients undergoing kidney allograft transplantation. Serum hepcidin was evaluated before and after 1, 3, 6, and 10 days after kidney transplantation, using commercially available kits. Serum creatinine was assessed at the same time.

METHODS

We found a significant decrease in serum hepcidin, as early as after 1 day after kidney transplantation. Before transplantation, serum hepcidin was related to creatinine. In patients with delayed graft function, there was no decrease in serum hepcidin.

RESULTS

Our findings may have important implications for the clinical treatment of patients undergoing kidney transplantation. The "window of opportunity" is narrow in delayed graft function to distinguish between acute rejection and calcineurin inhibitors nephrotoxicity, and time is limited to introduce proper treatment after initiating insult.

CONCLUSIONS

Hepcidin must be investigated as a potential early marker for delayed graft function, especially in the upcoming setting of early dialysis treatment or anti-rejection therapy and might contribute to early patient risk stratification.

Hepcidin on 24-hour urine collection: preanalytical aspects and correlation with ferritin levels

BACKGROUND

Urine hepcidin measurement is a potential non-invasive tool for assessing iron stores. However, hepcidin, due to its amphipathic structure, tends to aggregate and to adhere to surfaces in a protein-poor environment. In this study, we assessed the effect of solid bovine serum albumin (BSA) at different final concentrations (0, 2.5 or 5 g/L) in limiting the loss of hepcidin in spot urine samples. We also explored how hepcidin measured on plasma, spot or 24-hour urine collections can identify iron deficiency.

METHODS

Hepcidin levels were quantified on plasma, spot (with or without BSA) or 24-h urine collections for 33 volunteers. Hematological and iron status parameters were measured for each individual. The ability to detect iron deficiency (defined as a ferritin level <30 μg/L) based on plasma, spot or 24-h urine collections hepcidin levels was assessed by the means of receiver operator curves analysis.

RESULTS

The addition of BSA into urine prior to sample collection prevented hepcidin loss by 13.3% (mean) in spot urine samples whatever the amount. The areas under the receiver operator curves obtained for detecting iron deficiency were respectively 0.94 and 0.93 for hepcidin levels obtained on plasma and 24-h urine collections.

CONCLUSION

In this study, we showed that the addition of solid BSA into urine sample collection containers could prevent aggregation of hepcidin and that 24-h urine hepcidin levels could be as efficient as plasma concentrations for identifying iron deficiency.

Combination of biomarkers for diagnosis of acute kidney injury after cardiopulmonary bypass

Novel acute kidney injury (AKI) biomarkers offer promise of earlier diagnosis and risk stratification, but have yet to find widespread clinical application. We measured urinary α and π glutathione S-transferases (α-GST and π-GST), urinary l-type fatty acid-binding protein (l-FABP), urinary neutrophil gelatinase-associated lipocalin (NGAL), urinary hepcidin and serum cystatin c (CysC) before surgery, post-operatively and at 24 h after surgery in 93 high risk patient undergoing cardiopulmonary bypass (CPB) and assessed the ability of these biomarkers alone and in combination to predict RIFLE-R defined AKI in the first 5 post-operative days. Twenty-five patients developed AKI. π-GST (ROCAUC = 0.75), lower urine Hepcidin:Creatine ratio at 24 h (0.77), greater urine NGAL:Cr ratio post-op (0.73) and greater serum CysC at 24 h (0.72) best predicted AKI. Linear combinations with significant improvement in AUC were: Hepcidin:Cr 24 h + post-operative π-GST (AUC = 0.86, p = 0.01), Hepcidin:Cr 24 h + NGAL:Cr post-op (0.84, p = 0.03) and CysC 24 h + post-operative π-GST (0.83, p = 0.03), notably these significant biomarkers combinations all involved a tubular injury and a glomerular filtration biomarker. Despite statistical significance in receiver-operator characteristic (ROC) analysis, when assessed by ability to define patients to two groups at high and low risk of AKI, combinations failed to significantly improve classification of risk compared to the best single biomarkers. In an alternative approach using Classification and Regression Tree (CART) analysis a model involving NGAL:Cr measurement post-op followed by Hepcidin:Cr at 24 h was developed which identified high, intermediate and low risk groups for AKI. Regression tree analysis has the potential produce models with greater clinical utility than single combined scores.

Biomarkers of Contrast-Induced Nephropathy: Which Ones and What Is Their Clinical Relevance?

Contrast-induced nephropathy, or contrast-induced acute kidney injury (AKI), is an acute impairment of renal function as manifested by an increase in serum creatinine. Different urinary and serum proteins have been intensively investigated as possible biomarkers for the early diagnosis of AKI. Promising candidate biomarkers have the ability to detect an early and graded increase in tubular epithelial cell injury and to distinguish prerenal causes of AKI from acute tubular necrosis. In this article new, emerging biomarkers of contrast-induced AKI are presented and described, of which serum neutrophil gelatinase-associated lipocalin appears to be the most promising.

Hepcidin-minireview

Iron related disorders are encountered in daily clinical settings. Maintenance of stable extracellular iron concentrations requires the coordinate regulation of iron transport into plasma from dietary sources in the duodenum, from recycled senescent red cells in macrophages and from storage in hepatocytes. Hepcidin acts as a systemic iron-regulatory hormone. Many human diseases are associated with alterations in hepcidin concentrations. This review has focused on hepcidin structure, kinetics and function, its correlation with iron metabolism disorders, the therapeutic potential for modulating hepcidin expression and the diagnostic potential of hepcidin measurements in clinical practice.

Acute kidney injury following cardiac surgery

Acute kidney injury (AKI), a recognized complication of cardiac surgery with cardiopulmonary bypass (CPB) is associated with increased morbidity and mortality (15-30%) with approximately 1% of all the affected patients requiring dialysis. Early detection of AKI would enable intervention before occurrence of irreversible injury and might minimize the morbidity and mortality. Recently developed biomarkers of AKI facilitate its earlier discovery and help assessment of its severity and prognosis. In this article, we review the causes of well-known yet inexplicable association between CPB and AKI, the advances in pathophysiologic basis, the diagnostics and the management options.

Urinary hepcidin-25 and risk of acute kidney injury following cardiopulmonary bypass

BACKGROUND AND OBJECTIVES

Acute kidney injury (AKI) complicating cardiopulmonary bypass (CPB) results in increased morbidity and mortality. Urinary hepcidin-25 has been shown to be elevated in patients who do not develop AKI after CPB using semiquantitative mass spectrometry (SELDI TOF-MS). The goals of this study were to quantitatively validate these findings with ELISA and evaluate the diagnostic performance of hepcidin-25 for AKI.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

A nested, case-control analysis of urinary hepcidin-25 in AKI (n = 22) and non-AKI (n = 22) patients was conducted to validate the SELDI TOF-MS data at the following times: preoperatively; the start of CPB; 1 hour on CPB; on arrival to the intensive care unit; and postoperative days (POD) 1 and 3 to 5. The diagnostic performance of hepcidin-25 was then evaluated in the entire prospective observational cohort (n = 338) at POD 1. AKI was defined as Cr >50% from baseline, within 72 hours postoperatively.

RESULTS

Urinary hepcidin-25/Cr ratio was significantly elevated in all patients at POD 1 compared with baseline (P < 0.0005) and was also significantly elevated in non-AKI versus AKI patients at POD 1 (P < 0.0005). Increased log(10) hepcidin-25/Cr ratio was strongly associated with avoidance of AKI on univariate analysis. On multivariate analysis, the log(10) hepcidin-25/Cr ratio (P < 0.0001) was associated with avoidance of AKI with an area under the curve of 0.80, sensitivity 0.68, specificity 0.68, and negative predictive value 0.96.

CONCLUSIONS

Elevated urinary hepcidin-25 on POD 1 is a strong predictor of avoidance of AKI beyond postoperative day 1.