Urinary Neutrophil Gelatinase-associated Lipocalin Research Articles

Oxidative stress: A driving force in CKD induced heart failure

Background: Several clinical investigations have shown that individuals with renal impairment are more likely to experience heart failure. Cardiac remodeling happens relatively early in the course of kidney injury, yet research into identification of common markers of cardiorenal signaling remains insuffcient. This may be because studies conducted in small animal models do not accurately reflect the complexity of the disease. To bridge the translational gap, we developed a swine model for chronic kidney disease (CKD) Aim: We employed proteome studies to clarify the pathophysiological impact of chronic kidney disease (CKD) on the heart and correlate to cardiac function and perfusion in order to offer mechanistic insights. Methods: We used microspheres to embolise both kidneys of swine at 10-12 weeks of age while sham operated swine served as controls. Post 6 months, we performed pressure volume loops to assess cardiac function, while coronary flow reserve (CFR) was measured by intracoronary infusion of adenosine in control and CKD. (LC-MS-MS based proteomic analyses of left ventricular tissue was performed. Paraffn embedded myocardium and kidney tissues were histologically examined for interstitial fibrosis and oxidative stress. Results: Renal embolization resulted in mild chronic kidney injury as evidenced by increased fibrosis staining and urinary NGAL (24±4 vs 48±9 pg/ml). Hemodynamic parameters showed increased wall stress (20±3 vs 40±7 ml*mmHg/g) as well as increase of end diastolic volume (1.5±0.1 vs 1.9±0.1 ml/kg) indicating dilation of the left ventricle in CKD. Quantitative proteomic analysis detected significant differences in the left ventricle of the controls when compared to those with CKD and STRING pre-ranked functional analysis showed enrichments in pathways related to reactive oxygen species. Furthermore, we detected alterations of pathways associated with remodeling of the extracellular matrix (ECM), Oxidative stress and ECM remodeling were confirmed histologically. Interestingly, in CKD we found that mitochondrial proteins like cytochrome oxidase (MT-CO2) and ATP5 synthase subunit were downregulated suggesting mitochondrial dysfunction which was associated with higher basal coronary blood flow (0.48±0.05 vs 0.87±0.11 ml/min/g). Conclusions: Our proteomic data in swine model provides strong evidence that mild CKD can induce early alterations in mitochondrial function along with oxidative stress and ECM remodeling. Thus, we aim to further our understanding by applying our proteomic findings in conjunction with functional hemodynamic data in this swine model of cardiorenal disease. German Center for Cardiovascular Research (DZHK81Z0600207 to D.M. and P.S.). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Combination of Urinary Neutrophil Gelatinase-associated Lipocalin, Kidney Injury Molecular-1, and Angiotensinogen for the Early Diagnosis and Mortality Prediction of Septic Acute Kidney Injury.

Acute kidney injury (AKI) is one of the most severe complications of sepsis. This study was conducted to analyze the role of urinary neutrophil gelatinase-associated lipocalin (uNGAL), urinary kidney injury molecular-1 (uKIM-1), and urinary angiotensinogen (uAGT) in the early diagnosis and mortality prediction of septic AKI. The prospective study enrolled 80 sepsis patients in the ICU and 100 healthy individuals and divided patients into an AKI group and a non-AKI group. uNGAL, uKIM-1, uAGT, serum creatinine/procalcitonin/C-reaction protein, and other indicators were determined, and clinical prediction scores were recorded. The sensitivity and specificity of uNGAL, uKIM-1, and uAGT in diagnosis and mortality prediction were analyzed by the receiver operator characteristic (ROC) curve and the area under the curve (AUC). uNGAL, uKIM-1, and uAGT levels were higher in sepsis patients than healthy controls, higher in AKI patients than non-AKI patients, and higher in AKI-2 and AKI-3 patients than AKI-1 patients. At 0 h after admission, the combined efficacy of three indicators in septic AKI diagnosis (ROC-AUC: 0.770; sensitivity: 82.5%; specificity: 70.0%) was better than a single indicator. At 24 h, uNGAL, uKIM-1, and uAGT levels were higher in sepsis non-survivals than survivals and higher in septic AKI non-survivals than septic AKI survivals. The combined efficacy of three indicators in the prediction of sepsis/septic AKI mortality (ROC-AUC: 0.828/0.847; sensitivity: 71.4%/100.0%; specificity: 82.7%/66.7%) was better than a single indicator. uNGAL, uKIM-1, and uAGT levels were increased in septic AKI, and their combination helped the early diagnosis and mortality prediction.

CD8+ T cells mediate kidney fibrosis in diet-induced obese mice

Diet-induced obesity (DIO) is an epidemic in the United States and globally. Obesity is well known to exacerbate and/or promote kidney disease. Inflammation is a major factor in DIO and kidney disease. Utilizing a 20-week DIO mouse model (45% fat) and a normal diet (ND; 10% fat), our lab previously showed greater kidney medullary interstitial fibrosis as well as increased kidney medullary CD3+ T cells in DIO mice when compared to ND mice. Specifically, we found increased kidney CD8+ T cells, but similar CD4+ T cells, in DIO mice compared to ND mice. We hypothesized that CD8+ T cells in DIO mice are a primary factor in promoting kidney interstitial fibrosis. DIO mice were treated with anti-CD8 antibody or control anti-IgG antibody and ND mice were treated with control anti-IgG antibody for the final two weeks of the DIO protocol (n=7-9). DIO/anti-IgG and DIO/anti-CD8 mice had significantly higher body weight than ND/anti-IgG mice as expected (one-way ANOVA; p<0.0001). Administration of anti-CD8 treatment in DIO mice had null effects on body weight (one-way ANOVA, p=0.509) and kidney weight (one-way ANOVA; p=0.067). Utilizing flow cytometry, we verified that anti-CD8 treatment significantly reduced CD8+ T cells compared to anti-IgG in the kidney (one-way ANOVA; p=0.0077; DIO/anti-IgG vs DIO/anti-CD8, p=0.0066) and in the blood (one-way ANOVA; p=0.0034; DIO/anti-IgG vs DIO/anti-CD8, p=0.0048). Using Picrosirius Red histological staining to assess kidney fibrosis, we found that anti-CD8 treatment significantly blunted kidney medullary fibrosis (one-way ANOVA, p=0.0177, ND/anti-IgG vs DIO/anti-IgG, p=0.0329; DIO/anti-IgG vs DIO/anti-CD8, p=0.0318), whereas glomerular fibrosis was not affected by anti-CD8 treatment in DIO mice (one-way ANOVA, p=0.31). Urine was collected in 12-hour increments and analyzed for markers of kidney damage. All groups of mice showed similar urinary KIM-1 excretion (one-way ANOVA; p=0.62) and protein excretion (one-way ANOVA; p=0.69). DIO mice with anti-CD8 or anti-IgG treatment had significantly increased urinary NGAL excretion compared to ND mice (one-way ANOVA; p=0.0203). In summary, anti-CD8 treatment reduced circulating and kidney CD8+ T cells, as well as kidney medullary interstitial fibrosis but not urinary NGAL excretion. These results indicate that CD8+ T cells mediate kidney medullary interstitial fibrosis in a 20 week DIO mouse model. Funding: R01 DK134562, R25 DK115353, F31HL167626. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

The Human Phospholipase B-II Precursor (HPLBII-P) in Urine as a Novel Biomarker of Increased Glomerular Production or Permeability in Diabetes Mellitus?

Background: A previous report showed that the urine output of HPLBII-P in patients with diabetes mellitus and SARS-CoV-2 infection was increased as a sign of glomerular dysfunction. The aim of this report was to investigate the relation of the urine output of HPLBII-P to diabetes mellitus in two large community-based elderly populations, i.e., the ULSAM and PIVUS cohorts. Methods: HPLBII-P was measured by an ELISA in the urine of a community-based cohort of 839 men (ULSAM) collected at 77 years of age and in the urine of a community-based cohort of 75-year-old men, n = 387, and women, n = 401 (PIVUS). KIM-1, NGAL, and albumin were measured in urine and cathepsin S and cystatin C in serum. Results: HPLBII-P was significantly raised among males with diabetes in the ULSAM (p < 0.0001) and PIVUS cohorts (p ≤ 0.02), but not in the female cohort of PIVUS. In the female subpopulation of insulin-treated diabetes, HPLBII-P was raised (p = 0.02) as compared to women treated with oral antidiabetics only. In the ULSAM cohort, HPLBII-P was correlated to NGAL, KIM-1, and albumin in urine both in non-DM (all three biomarkers; p < 0.0001) and in DM (NGAL; p = 0.002, KIM-1; p = 0.02 and albumin; p = 0.01). Plasma glucose and HbA1c in blood showed correlations to U-HPLBII-P (r = 0.58, p < 0.001 and r = 0.42, p = 0.004, respectively). U-HPLBII-P and cathepsin S were correlated in the ULSAM group (r = 0.50, p < 0.001). No correlations were observed between U-HPLBII-P and serum creatinine or cystatin C. Conclusions: The urine measurement of HPLBII-P has the potential to become a novel and useful biomarker in the monitoring of glomerular activity in diabetes mellitus.

Urinary Epidermal Growth Factor Level as a Noninvasive Indicator of Tubular Repair in Patients with Acute Kidney Injury.

Epidermal growth factor (EGF), an essential factor for the proliferation and survival of renal tubular cells, is expressed by distal tubules and normally excreted via urine. Previous studies in rats demonstrated that acute tubular injury reduces urinary EGF levels. However, it is unclear whether urinary EGF is a suitable monitoring marker of tubular repair status after acute kidney injury (AKI) in humans. To address this question, we measured serum and urinary EGF in patients with AKI (n = 99) using ELISA and investigated whether urinary EGF levels were associated with the severity of tubular injury and renal prognosis. Urinary EGF was abundant in healthy controls but showed a significant decrease in AKI patients (14,522 ± 2190 pg/mL vs. 3201 ± 459.7 pg/mL, p < 0.05). The urinary EGF level in patients with renal AKI was notably lower than that in patients with pre-renal AKI. Furthermore, the urinary EGF level in patients with AKI stage 3 was significantly lower than that in patients with AKI stage 1. Urinary EGF levels were negatively correlated with urinary β-2MG and serum creatinine levels but positively correlated with hemoglobin levels and eGFR. Urinary EGF was not significantly correlated with urinary NAG, α-1MG, L-FABP, NGAL, KIM-1, or urinary protein concentrations. No significant correlation was observed between serum and urinary EGF levels, suggesting that urinary EGF is derived from the renal tubules rather than the blood. In living renal transplantation donors, the urinary EGF/Cr ratio was approximately half the preoperative urinary EGF/Cr ratio after unilateral nephrectomy. Collectively, these data suggest that urinary EGF is a suitable noninvasive indicator of not only the volume of functional normal renal tubules but also the status of tubular repair after AKI.

Obesity aggravates acute kidney injury resulting from ischemia and reperfusion in mice

In critically ill patients, overweight and obesity are associated with acute respiratory distress syndrome and acute kidney injury (AKI). However, the effect of obesity on ischemia–reperfusion injury (IRI)-induced AKI is unknown. We hypothesized that obesity would aggravate renal IRI in mice. We fed mice a standard or high-fat diet for eight weeks. The mice were divided into four groups and submitted to sham surgery or IRI: obese, normal, normal + IRI, obese, and obese + IRI. All studies were performed 48 h after the procedures. Serum glucose, cholesterol, and creatinine clearance did not differ among the groups. Survival and urinary osmolality were lower in the obese + IRI group than in the normal + IRI group, whereas urinary neutrophil gelatinase-associated lipocalin levels, tubular injury scores, and caspase 3 expression were higher. Proliferating cell nuclear antigen expression was highest in the obese + IRI group, as were the levels of oxidative stress (urinary levels of thiobarbituric acid-reactive substances and renal heme oxygenase-1 protein expression), whereas renal Klotho protein expression was lowest in that group. Expression of glutathione peroxidase 4 and peroxiredoxin 6, proteins that induce lipid peroxidation, a hallmark of ferroptosis, was lower in the obese + IRI group. Notably, among the mice not induced to AKI, macrophage infiltration was greater in the obese group. In conclusion, greater oxidative stress and ferroptosis might aggravate IRI in obese individuals, and Klotho could be a therapeutic target in those with AKI.

Assessment of Urinary and Serum Neutrophil Gelatinase-Associated Lipocalin (NGAL) Levels as Novel Predictors for Vesicoureteral Reflux Diagnosis in Children with Febrile Urinary Tract Infection.

The invasive, expensive, and time-consuming nature of radiological examinations for vesicoureteral reflux (VUR) has compelled researchers to search for new markers to predict VUR. This study was designed to evaluate the usefulness of serum and urine concentrations of neutrophil gelatinase-associated lipocalin (NGAL) in predicting the existence of VUR. This cross-sectional study involved all patients with a first febrile urinary tract infection (UTI) referred to Ali Asghar Children's Hospital. Each patient included in the study had clinical symptoms of pyelonephritis and a positive urine culture. The patients were divided into 2 groups: VUR and non-VUR. The serum and urinary NGAL levels were calculated in both groups. The receiver operating characteristic (ROC) curve was used to look for serum and urinary NGAL cut-points that differentiated the VUR group from the non-VUR group. Among the 40 children in the study, 23 belonged to the VUR group. The median age was 2.5 years (range, 0.3-8 years), and 35 patients were girls. ROC curve analysis showed that only the urinary NGAL level was significantly related to VUR. There was no association between serum NGAL levels and VUR. According to the ROC curve, a urinary NGAL level cut-off value of 15 ng/mL was likely to be diagnostic of VUR with 82.6% sensitivity and 58.8% specificity. The urinary NGAL level, specifically with a cut-off value of 15 ng/mL, can indicate the existence of VUR in patients with UTI with near-acceptable levels of sensitivity and specificity.

The ability of tidal volume challenge test to predict early post-operative acute kidney injury and intra-operative hypotension in laparoscopic abdominal surgeries

ABSTRACT Background Improper management and late detection of complications, especially peri-operative acute kidney injury (AKI), could result in higher morbidity and mortality rates. This work was aimed at confirming the tidal volume challenge (TVC) test’s predictability while performing laparoscopic abdominal surgery for early postoperative AKI and intra-operative hypotension. Methods Our prospective observational study involved 70 cases whose age ranged between 18 and 65 years, American Society of Anesthesiologists (ASA) I and ASA II going through general anesthesia (GA) for laparoscopic abdominal elective surgery. Patients went through a categorization into AKI or Non-AKI according to the worst Kidney Disease: Improving Global Outcomes (KDIGO) classification according to serum creatinine and urine output that are measured at 0, 24 and 48h. Results TVC exhibited significant correlation with the AKI development with the OR of 2.3, 95% CI, p = 0.052, while the exposure index was deemed to be an AKI development risk factor with the OR of 1.0, 95% CI, p = 0.034. However, baseline neutrophil gelatinase-associated lipocalin in urine (UNGAL) showed insignificant association with the AKI development with the OR 1.04 and p = 0.366. The relationship between TVC and hypotension frequency was estimated using linear regression. The regression showed that there exists a positive significant relation between these two parameters; as hypotension frequency increases, TVC increases as well with a coefficient estimate of 0.5. Conclusions AKI represents complication after laparoscopic abdominal surgery. To avoid peri-operative renal impairment, the limiting exposure index should be considered. Our work introduces the TVC test for AKI prediction in laparoscopic abdominal surgeries.

Pharmacokinetics and Nephrotoxicity of Polymyxin MRX-8 in Rats: A Novel Agent against Resistant Gram-Negative Bacteria.

MRX-8 is a novel polymyxin for carbapenem-resistant Gram-negative infections that has been recently evaluated in Phase I clinical trials. Herein, its pharmacokinetics (PK) and nephrotoxicity in rats are reported for the first time. This study aimed at pre-clinical PK and safety assessments. An LC-MS/MS method was developed to determine concentrations of MRX-8 and its major deacylation metabolite, MRX-8039, in rat plasma. Animals were administered a single dose of MRX-8 (2, 4, 6, and 8 mg/kg) or comparator polymyxin B (PMB) (4 and 8 mg/kg) to compare the kidney injury known for the polymyxin drug class. Nephrotoxicity was evaluated using serum creatinine, blood urea nitrogen (BUN) biomarkers, and renal histopathology. In rats, MRX-8 displayed linear PK within the range of 2-8 mg/kg, with approximately 4% of MRX-8 converted to MRX-8039. MRX-8 induced only mild increases in serum creatinine and BUN levels, with an apparent decrease in nephrotoxicity within 24 h, in contrast to PMB, which exhibited a significant and more persistent toxicity. Additional nephrotoxicity biomarkers (plasma NGAL and urinary NGAL, KIM-1, and TIMP-1) have confirmed attenuated MRX-8 kidney injury. Histopathology has revealed significantly greater cellular/tissue toxicity for PMB as compared to MRX-8 (variances of p = 0.008 and p = 0.048 vs. saline control, respectively). Thus, MRX-8 induces a mild and reversible kidney injury in rats compared to PMB. These data support a continued evaluation of the novel polymyxin in human trials.

Evaluation of Renal Function with Urinary NGAL and Doppler Ultrasonography in ICU Patients: A 1-Year Observational Pilot Study.

We estimated the diagnostic accuracy of urinary NGAL for the diagnosis of AKI. Urinary NGAL and Creatinine were measured daily for up to 3 days. Doppler ultrasonography was performed within 24 h of admission and for the following 3 days. Of the 21 patients, 44% had AKI during their ICU stay. The AKI group presented with higher values of serum Creatinine, renal length, MDRD as well as SAPS II already at admission. Urinary NGAL was significantly higher among patients with AKI and patients AKI-no at T0 (p < 0.0001) and increased steadily on T1 and T2. Urinary NGAL seemed to be a notable diagnostic marker for AKI from the first measurement (T0) with an area under the ROC of 0.93 (95% CI = 0.78-0.99) with a sensitivity of 99%. RRI levels were slightly higher in the AKI group at each time and increased gradually from T0 to T2 but reached statistical significance only at T2 (p = 0.02). Renal length and SAPS II at T0 showed high AuRoc and sensitivity. Urinary NGAL is a valuable marker for AKI in intensive care settings. It seemed that a pre-existing chronic renal disease, the SAPS II and the NGAL at admission represented the principal predictors of AKI.

Urine Liver-Type Fatty Acid Binding Protein; Biomarker for Diagnosing Acute Kidney Injury and Predicting Mortality in Cirrhotic Patients

Objective: To determine impact of urine liver-type fatty acid binding protein (uL-FABP) and urine neutrophil gelatinase-associated lipocalin (uNGAL), which were biomarkers linked to acute kidney injury (AKI), in AKI diagnosis and prediction of 28-day mortality among hospitalized cirrhotic patients. Materials and Methods: We prospectively enrolled hospitalized cirrhotic patients at a tertiary care university hospital between June 2018 and November 2019. The uL-FABP, uNGAL, and plasma NGAL (pNGAL) were collected within 48 hours of admission. Cutoff values of biomarkers for diagnosing AKI derived from receiver operating characteristic (ROC) curve. Logistic regression analysis was used to identify independent factors for 28-day mortality. Results: We enrolled 109 cirrhotic patients in derivative cohort, 41.3% had AKI. Median uL-FABP, uNGAL, and pNGAL levels in AKI group were higher than non-AKI group: 8.1 vs. 2.8 ng/mL (p=0.002), 40.5 vs. 10.1 ng/mL (p&lt;0.001), and 195.7 vs 81.4 ng/mL (p=0.001), respectively. Areas under the ROC curve of uL-FABP, uNGAL, and pNGAL for AKI diagnosis were 0.68, 0.73 and 0.68, respectively. Also, all biomarkers were significantly higher in mortality group. Multivariate analysis showed that the only independent predictor for 28-day mortality was uL-FABP ≥ 4.68 ng/mL (odd ratio 4.15, p=0.02). Conclusion: UL-FABP, uNGAL, and pNGAL are associated with AKI in hospitalized cirrhotic patients. Moreover, uL-FABP ≥ 4.68 ng/mL was a significant independent predictor for 28-day mortality.

Jiawei Shengjiangsan's Effect on Renal Injury in Diabetic Nephropathy Mice is Investigated via the PI3K/Akt/NF-κB Signaling Pathway.

This study aimed to investigate the intervention mechanism of Jiawei Shengjiangsan (JWSJS) on kidney injury in diabetic nephropathy mice. Thirty 8-week-old db/db mice were randomly divided into five groups: model group, Perindopril group, and JWSJS low-, medium-, and high-dose groups (n=6 per group) based on body weight. Additionally, a blank control group was established consisting of 6 db/m mice aged 8 weeks. The blank and model groups received daily intragastric administration of 7g/kg/d pure water. The remaining groups were assigned to JWSJS low (3.5g/kg/d), medium (7g/kg/d), high (14g/kg/d) dosage groups, and perindopril positive control group (0.48mg/kg/d) for 12 weeks. Post-experiment, serum creatinine (SCr) and blood urea nitrogen (BUN) were analyzed using an automatic biochemical analyzer. Enzyme-linked immunosorbent assay (ELISA) measured 24-hour urinary albumin, neutrophil gelatinase-associated lipocalin (NGAL), TNF-α, IL-1β, VCAM-1, MCP-1, and HbA1c. Western blot assessed the protein expressions of p-PI3K, p-Akt, and p-NF-κB p65, while pathological kidney changes were observed. Compared to the blank group, the model group exhibited increased SCr, BUN, 24-hour urinary albumin, serum NGAL, TNF-α, IL-1β, VCAM-1, MCP-1, HbA1c, p-PI3K, and p-Akt, alongside increased p-NF-κB p65 expression, indicating significant kidney pathology. After treatment, the JWSJS group showed decreased SCr, BUN, 24-hour urinary microalbumin, NGAL, HbA1c, TNF-α, IL-1β, VCAM-1, MCP-1 levels, increased p-PI3K and p-Akt expression (P<0.05), and reduced p-NF-κB p65 content (P<0.05). Histopathological analysis revealed that JWSJS ameliorated renal tubular epithelial cell damage, glomerular capillary and basement membrane injuries, and facilitated the repair of damaged podocytes in diabetic nephropathy mice. JWSJS demonstrated efficacy in reducing renal inflammation in diabetic nephropathy mice, with its mechanism likely associated with the inhibition of the PI3K/Akt/NF-κB signaling pathway.

Deceased Kidney Donor Biomarkers: Relationship between Delayed Kidney Function and Graft Function Three Years after Transplantation.

With an increasing number of marginal donors, additional methods for the evaluation of cadaveric kidney quality are required. This study aimed to evaluate pretransplant deceased donor serum (s) and urine (u) biomarkers, including neutrophil gelatinase-associated lipocalin (NGAL), kidney injury molecule-1 (KIM-1), interleukin-18, and C-X-C motif chemokine 10 (CXCL10) for predicting early and late graft function. In total, 43 deceased kidney donors and 76 corresponding recipients were enrolled. Delayed graft function (DGF) occurred in 27.6% of cases. sIL-18, sKIM-1, uNGAL, and uKIM-1 were predictors of DGF. A model incorporating sIL-18, uKIM-1, and clinical factors was developed to predict DGF (AUROC 0.863). Univariate analysis showed a negative association between uKIM and graft eGFR at 6, 12, 24, and 36 months, but this was not confirmed in the multivariate analysis. In conclusion, we report a superior performance of donor biomarkers for predicting DGF and later graft function over serum creatinine. Higher levels of donor sIL-18 and uKIM in conjunction with expanded-criteria donors and longer cold ischemia times predicted DGF. With no renal tubular damage in zero-time donor biopsies, higher pretransplant urine and serum NGAL levels were associated with better allograft function one year after transplantation, and sNGAL with graft function three years after transplantation.

Environmental exposure to melamine and its derivatives and kidney outcomes in children

Melamine caused acute nephrotoxicity in a past food adulteration incident, but it is unclear whether and how widespread ambient exposure to melamine and related compounds might affect pediatric kidney health. We assessed cross-sectional associations between childhood exposure to melamine and its derivatives and biomarkers of kidney injury and health and explored potential heterogeneity by sex suggested by sex-dependent differences in renal physiology. We measured melamine and its derivatives ammeline, ammelide, and cyanuric acid (CYA) in spot urine samples collected from 192 children from an urban site (Seattle, WA) and 187 children from a rural site (Yakima, WA) aged 4–8 years in the Global Alliance to Prevent Prematurity and Stillbirth (GAPPS) Study. In addition, biomarkers of kidney injury were measured in the same urine samples, including albumin, total protein, KIM-1, NAG, NGAL, and EGF. We utilized linear regressions to examine associations between individual chemical exposures and kidney biomarkers. Interaction terms examined association modification by sex, as well as potential interactions between melamine and CYA. Despite comparable exposures, girls had higher levels of many kidney injury biomarkers compared to boys. A ten-fold higher melamine concentration was associated with a 18% (95% CI: 5.6%, 31%) higher EGF in the full sample, while ten-fold higher melamine was associated with a 76% (14.1%, 173%) higher KIM-1 in boys but not in girls (−10.1% (−40.6%, 36.1%), interaction p = 0.026). Melamine exhibited significant negative interactions with CYA in association with total protein and NAG that appeared to be specific to girls. Our results suggest possible associations between melamine exposure and markers of kidney injury that may be more pronounced in boys. These findings provide novel insights into melamine and related derivative compound health effects at low levels of exposure in children and emphasize the role of sex in mediating the relationship between nephrotoxicant exposure and kidney injury.

Performances of acute kidney injury biomarkers vary according to sex.

Before implementing individualized strategies to treat acute kidney injury (AKI), identifying clusters of patients with divergent pathophysiological mechanisms, diagnosis criteria or outcomes is of the utmost importance. Here we studied sex-related molecular mechanisms in cardiac bypass (CBP) surgery patients developing AKI. We compared the characteristics of 1170 patients referred for CBP surgery using multivariate logistic regression and propensity score-based analysis. Performances of the candidate urinary biomarkers at <4h post-surgery, urinary neutrophil gelatinase-associated lipocalin (uNGAL), [IGFBP7]·[TIMP-2] product (NephroCheck) and a recently developed AKI signature of 204 urinary peptides (AKI204) to predict AKI were compared in both sexes. Incidence (∼25%) and severity of AKI were similar in men and women, even after adjustment for the usual risk factors of AKI, including baseline estimated glomerular filtration rate, age, diabetes mellitus, length of CBP and red blood cell transfusion. However, at the molecular level, performances of uNGAL, NephroCheck and AKI204 to predict AKI strongly diverged between men and women. In the full cohort, as well as in subgroups of men and women, the multimarker AKI204 signature outperformed uNGAL and NephroCheck and predicted the development of AKI significantly better in women than in men. Analysis of AKI204 at the single-peptide level suggested divergences of AKI mechanisms between sexes due to increased kidney inflammation in women (increased abundance of urinary fragments of osteopontin and uromodulin). In patients referred for CBP surgery, significant clinical and biological differences between men and women as well as sexual dimorphism of AKI biomarker performances were identified. The urinary peptide signature points to sex-related molecular mechanisms underlying AKI.

Use of urine neutrophil gelatinase-associated lipocalin for nephrotoxic medication acute kidney injury screening in neonates.

Daily serum creatinine monitoring protocols for acute kidney injury (AKI) are invasive and may lead to surveillance resistance. We aimed to understand if use of urine neutrophil gelatinase-associated lipocalin (uNGAL) could increase high-risk nephrotoxic medication (NTMx) associated AKI screening adherence in neonates. Statistical process control methods prior to and post implementation were trended. The primary outcome, screening adherence, was defined as either daily serum creatinine or uNGAL assessment through 2 days post high-risk NTMx exposure. 1291 monitoring days from the pre-implementation era (4/2020-6/2021) were compared to1377 monitoring days from the post-era (6/2021-10/2022). AKI screening adherence increased (81 to 92%) following implementation of optional uNGAL screening. Urine NGAL accounted for 35% of screening obtained. Use of uNGAL resulted in a 40% reduction in blood sampling for serum creatinine. Incorporation of uNGAL as a complementary screening tool to serum creatinine demonstrated sustained increased AKI surveillance in our Baby NINJA monitoring program.

Systematic Review of Kidney Injury Biomarkers for the Evaluation of CKD of Uncertain Etiology

IntroductionChronic kidney disease of uncertain etiology (CKDu) is an incompletely defined phenotype of CKD affecting young individuals mostly in agricultural communities in Central America and South Asia. CKDu is a diagnosis of exclusion made in individuals from endemic regions. MethodsWe conducted a systematic review of the primary literature on urinary and plasma kidney injury biomarkers measured in the setting of CKDu (through February 2023). Literature was identified via a Web of Science search and hand search of the references of previously identified literature. Search terms included “CKDu,” “Mesoamerican Nephropathy,” “CKD of unknown etiology,” “Chronic Interstitial Nephritis in Agricultural Communities,” “biomarker,” “urin*,” and/or “plasma.” ResultsA total of 25 papers were included. The two most frequently measured biomarkers were urinary kidney injury molecule-1 and urinary neutrophil gelatinase-associated lipocalin. There was substantial variability in study design, laboratory assay methods, and statistical methodology which prohibited meta-analysis. ConclusionBiomarkers that identify tubulointerstitial disease early and accurately may substantially accelerate progress in the study of CKDu and facilitate public health approaches that eventually lead to its prevention and elimination. To date, the literature is limited by relatively small sample sizes and methodological limitations which should be addressed in future studies.

O242: Prolonged subnormothermic acellular machine perfusion of human kidneys

Abstract Introduction Prolonged periods of ex vivo perfusion are required to effectively deliver regenerative therapies directly to a kidney before transplantation. This provides time to start repair processes and reduce the likelihood of early graft dysfunction. The aim of this study was to assess the capability of extending the preservation interval using subnormothermic acelllular machine perfusion (SNAP). Methods After a period of static cold storage, 12 human kidneys declined for transplantation were perfused with an oxygenated human serum albumin-based solution at 32°C for 6, 12 or 24h (n=4 per group). After preservation all kidneys were reperfused with a red blood cell-based solution at 37°C for 4h for assessment. Results Functional parameters remained stable during SNAP in all kidneys. However, the perfusate flow rate was significantly lower in the 24h group (24h 166±45, 12h 266±45, 6h 214±36 mL/min/100g; P=0.008). After reperfusion, levels of urinary neutrophil gelatinase-associated lipocalin (uNGAL), insulin-like growth factor binding protein 7 (IGFBP7) and liver-type fatty acid-binding protein (L-FABP) were similar between groups (P&amp;gt;0.05). Levels of oxygen consumption were significantly lower in 24h kidneys compared to 12h (24h 1.45±0.86, 12h 4.3±1.78 mL/min/100g; P=0.0294). Histological evaluation showed a preserved renal morphology in all kidneys, except for the 24h group which showed a mild increase in tubular and endothelial damage. Conclusion This study demonstrated that human kidneys can be successfully preserved with SNAP for up to 12h. There was some evidence of additional ischaemic injury in the 24h SNAP kidneys which warrants further investigation.

Potential Utility of Urinary Follistatin as a Non-Invasive Indicator of Acute Tubular Damage in Patients with Acute Kidney Injury.

Activin A is known to impede tubular repair following renal ischemia, whereas exogenous follistatin, an activin A antagonist, has been shown to ameliorate kidney damage in rats. Despite these findings, the precise role of endogenous follistatin in the kidney has yet to be elucidated. In this study, we investigated the localization of follistatin in the normal human kidney and its potential utility as a marker for acute kidney injury (AKI). In a total of 118 AKI patients and 16 healthy adults, follistatin levels in serum and urine were quantified using ELISA, and correlations with clinical parameters were analyzed. Follistatin-producing cells were positive for Na-Cl co-transporter and uromodulin, but negative for aquaporin 1 and aquaporin 2. Unlike healthy adults, urinary follistatin significantly increased in AKI patients, correlating positively with AKI severity. Urinary follistatin levels were notably higher in patients needing renal replacement therapy. Significant correlations were observed with urinary protein, α1 microglobulin, and urinary NGAL, but not with urinary KIM-1, urinary L-FABP, urinary NAG, urinary β2 microglobulin, or serum creatinine. Interestingly, no correlation between urinary and serum follistatin levels was identified, indicating a renal origin for urinary follistatin. In conclusion, follistatin, produced by distal tubules, is detectable in the urine of AKI patients, suggesting its potential as a valuable marker for monitoring acute tubular damage severity in AKI.

Biomarkers for urinary tract infection: present and future perspectives.

A prompt diagnosis of urinary tract infection (UTI) is necessary to minimize its symptoms and limit sequelae. The current UTI screening by urine test strip analysis and microscopic examination has suboptimal diagnostic accuracy. A definitive diagnosis of UTI by urine culture takes two to three days for the results. These limitations necessitate a need for better biomarkers for the diagnosis and subsequent management of UTI in children. Here, we review the value of currently available UTI biomarkers and highlight the potential of emerging biomarkers that can facilitate a more rapid and accurate UTI diagnosis. Of the newer UTI biomarkers, the most promising are blood procalcitonin (PCT) and urinary neutrophil gelatinase-associated lipocalin (NGAL). PCT can provide diagnostic benefits and should be considered in patients who have a blood test for other reasons. NGAL, which is on the threshold of clinical care, needs more research to address its scope and utilization, including point-of-care application. Employment of these and other biomarkers may ultimately improve UTI diagnosis, guide UTI therapy, reduce antibiotic use, and mitigate UTI complications.