Acute kidney injury in critically ill infants: the role of urine Neutrophil Gelatinase-Associated Lipocalin (NGAL)

Effectiveness and Renal Functions Safety of Treatments Used for Neonates with Patent Ductus Arteriosus: A Prospective Cohort Study

Background

Neutrophil gelatinase-associated lipocalin plays an important role in renal dysfunctions. The objective of this study was to test the hypothesis that indomethacin used in treating patent ductus arteriosus protects infants from renal dysfunction.

Material/Methods

This prospective cohort study assessed data on urine prostaglandin metabolites, urinary neutrophil gelatinase-associated lipocalin, and the renal functions of preterm infants with confirmed patent ductus arteriosus who had been injected with indomethacin (n=144, ID group) or acetaminophen (n=144, AP group).

Results

A reduction of neutrophil gelatinase-associated lipocalin in urine samples was found in the ID group (993±48 μG/L vs. 103±5 μG/L, p<0.0001). The reduction in prostaglandin (673±32 pg/mL vs. 139±7 pg/mL, p<0.0001) and the closure of ductus (2.64±0.89 mm vs. 2.31±0.81 mm, p=0.001) were found in the ID group after the first dose of indomethacin, but the closure of ductus (2.47±0.54 mm vs. 2.32±0.55 mm, p=0.02) and prostaglandin reduction (667±31 pg/mL vs. 129±7 pg/mL, p<0.0001) were found after the second dose of acetaminophen. Indomethacin had greater effect in reducing the risk of acute kidney injury than did acetaminophen (p=0.042).

Conclusions

Indomethacin treatment used in treating patent ductus arteriosus protects infants from renal dysfunction.

Urinary Neutrophil Gelatinase-associated Lipocalin in the evaluation of Patent Ductus Arteriosus and AKI in Very Preterm Neonates: a cohort study

Background

A patent ductus arteriosus (PDA) is frequently found in very preterm neonates and is associated with increased risk of morbidity and mortality. A shunt across a PDA can result in an unfavorable distribution of the cardiac output and may in turn result in poor renal perfusion. Urinary Neutrophil Gelatinase-associated Lipocalin (U-NGAL) is a marker of renal ischemia and may add to the evaluation of PDA. Our primary aim was to investigate if U-NGAL is associated with PDA in very preterm neonates. Secondary, to investigate whether U-NGAL and PDA are associated with AKI and renal dysfunction evaluated by fractional excretion of sodium (FENa) and urine albumin in a cohort of very preterm neonates.

Methods

A cohort of 146 neonates born at a gestational age less than 32 weeks were consecutively examined with echocardiography for PDA and serum sodium, and urine albumin and sodium were measured on postnatal day 3 and U-NGAL and serum creatinine day 3 and 6. AKI was defined according to modified neonatal Acute Kidney Injury Network (AKIN) criteria. The association between U-NGAL and PDA was investigated. And secondly we investigated if PDA and U-NGAL was associated with AKI and renal dysfunction.

Results

U-NGAL was not associated with a PDA day 3 when adjusted for gestational age and gender. A PDA day 3 was not associated with AKI when adjusted for gestational age and gender; however, it was associated with urine albumin. U-NGAL was not associated with AKI, but was found to be associated with urine albumin and FENa.

Conclusions

Based on our study U-NGAL is not considered useful as a diagnostic marker to identify very preterm neonates with a PDA causing hemodynamic changes resulting in early renal morbidity. The interpretation of NGAL in preterm neonates remains to be fully elucidated.

Renal function and novel urinary biomarkers in infants with neonatal encephalopathy

AIM

Perinatal asphyxia is associated with multi-organ injury including acute kidney injury (AKI). New urinary biomarkers may detect more subtle renal injury.

METHODS

Urinary biomarkers (albumin, beta-2 microglobulin, cystatin-C, epidermal growth factor, neutrophil gelatinase-associated lipocalin, osteopontin, uromodulin) were serially measured from days 1 to 7 in term infants with perinatal asphyxia and controls and compared to 'Kidney Disease Improving Global Outcome' scoring of renal injury and to encephalopathy grade.

RESULTS

A total of 255 urine samples were taken from infants exposed to perinatal asphyxia (n = 82) and term controls (n = 10). Thirty-nine infants underwent therapeutic hypothermia, four died and 30 infants had acute kidney injury. Infants with acute kidney injury had significantly higher levels of urinary albumin (day 2), cystatin-C (days 1, 2, 3 and 7), neutrophil gelatinase-associated lipocalin (days 2, 3 and 7) and osteopontin (days 2, 3 and 7) and lower epidermal growth factor and uromodulin (day 1) compared to those without AKI. Day 2 cystatin-C predicted AKI with an area under receiver operating characteristic curve of 0.89, p < 0.001, cut-off 9.8 × 10⁴  pg/mL. NE grade II/III infants had significantly elevated levels of urinary cystatin-C, neutrophil gelatinase-associated lipocalin and decreased EGF compared to grade 0/I infants.

CONCLUSION

Asphyxiated infants who develop acute kidney injury have significantly altered urinary biomarkers postnatally. Validation of neonatal AKI urinary biomarkers in a large prospective study is required. Long-term follow-up of infants post-asphyxial insult for chronic renal injury is advised.

Urinary markers of acute kidney injury in newborns with perinatal asphyxia (.)

BACKGROUND

Acute kidney injury (AKI) affects up to 60% of severely asphyxiated neonates. The diagnosis of AKI can be and is further challenged by a lack of good biomarkers. We studied the role of novel markers for AKI, neutrophil gelatinase-associated lipocalin (NGAL), interleukin-8 (IL-18), Netrin-1 (NTN-1), and sodium hydrogen exchanger isoform 3 (NHE3) on development and early diagnosis of AKI in newborns with perinatal asphyxia (PA).

METHODS

Forty-one newborns with a diagnosis of PA (15 with AKI and 26 without AKI) and 20 healthy matched controls were involved to the study. Urinary samples were obtained on postnatal days 1 and 4 for patients with PA and on postnatal day 1 for the control subjects. AKI was defined using a serum creatinine-based modification of the acute kidney injury network criteria.

RESULTS

The levels of NGAL, NTN-1, NHE3, and IL-18 on the first postnatal day urine samples were higher in patients compared to controls (p < 0.001, p <0.001, p  <0.02, p  <0.001, respectively). In patients with AKI, the levels of NGAL and IL-18 were higher when compared to patients without AKI (p = 0.002, p  <0.001, respectively). The levels of NTN-1 and NHE3 were similar in both groups. For the samples obtained on postnatal day 4, only NGAL levels were significantly higher in patients with AKI (p = 0.004) compared to those without AKI.

CONCLUSION

To our knowledge, this is the largest study, which evaluated the utility of urinary biomarkers in the diagnosis of AKI in newborns with PA. First day, urine NGAL and IL-18 levels have an important diagnostic power in such patients.

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.

Neonatal RIFLE

A standardized classification of acute kidney injury (AKI) has recently been proposed with the RIFLE (Risk, Injury, Failure, Loss of function, End-stage kidney disease) score. Such definition/classification has been applied both in adult and in paediatric patients. Neonatal definition of AKI likely results as a challenging task due to the peculiar renal pathophysiology of newborn critically ill patients. Their so-called 'immature kidneys' require careful management and neonatal AKI is frequently complicated by unfavourable outcomes. A recent attempt to implement the RIFLE score with a neonatal modification might lead to improvement on the knowledge of AKI incidence and epidemiology.

Biomarkers of acute kidney injury in neonatal encephalopathy

Acute kidney injury (AKI) is a common complication of neonatal encephalopathy (NE). The accurate diagnosis of neonatal AKI, irrespective of the cause, relies on suboptimal methods such as identification of rising serum creatinine, decreased urinary output and glomerular filtration rate. Studies of AKI biomarkers in adults and children have shown that biomarkers can improve the early diagnosis of AKI. Hypoxia-ischaemia is the proposed aetiological basis of AKI in both NE and cardiopulmonary bypass (CPB). However, there is a paucity of studies examining the role of AKI biomarkers specifically in NE. Urinary cystatin C (CysC), neutrophil gelatinase-associated lipocalin (NGAL), interleukin-18, kidney injury molecule-1, liver-type fatty acid-binding protein, serum CysC and serum NGAL all show good ability to predict early AKI in a heterogeneous critically ill neonatal population including infants post-CPB. Moreover, serum and urinary NGAL and urinary CysC are early predictors of AKI secondary to NE. These findings are promising and open up the possibility of biomarkers playing a significant role in the early diagnosis and treatment of NE-related AKI. There is an urgent need to explore the role of AKI biomarkers in infants with NE as establishing the diagnosis of AKI earlier may allow more timely intervention with potential for improving long-term outcome.

The multifaceted roles of neutrophil gelatinase associated lipocalin (NGAL) in inflammation and cancer

Neutrophil gelatinase associated lipocalin (NGAL), also known as oncogene 24p3, uterocalin, siderocalin or lipocalin 2, is a 24kDa secreted glycoprotein originally purified from a culture of mouse kidney cells infected with simian virus 40 (SV-40). Subsequent investigations have revealed that it is a member of the lipocalin family of proteins that transport small, hydrophobic ligands. Since then, NGAL expression has been reported in several normal tissues where it serves to provide protection against bacterial infection and modulate oxidative stress. Its expression is also dysregulated in several benign and malignant diseases. Its small size, secreted nature and relative stability have led to it being investigated as a diagnostic and prognostic biomarker in numerous diseases including inflammation and cancer. Functional studies, conducted primarily on lipocalin 2 (Lcn2), the mouse homologue of human NGAL have revealed that Lcn2 has a strong affinity for iron complexed to both bacterial siderophores (iron-binding proteins) and certain human proteins like norepinephrine. By sequestering iron-laden siderophores, Lcn2 deprives bacteria of a vital nutrient and thus inhibits their growth (bacteriostatic effect). In malignant cells, its proposed functions range from inhibiting apoptosis (in thyroid cancer cells), invasion and angiogenesis (in pancreatic cancer) to increasing proliferation and metastasis (in breast and colon cancer). Ectopic expression of Lcn2 also promotes BCR-ABL induced chronic myelogenous leukemia in murine models. By transporting iron into and out of the cell, NGAL also regulates iron responsive genes. Further, it stabilizes the proteolytic enzyme matrix metalloprotease-9 (MMP-9) by forming a complex with it, and thereby prevents its autodegradation. The factors regulating NGAL expression are numerous and range from pro-inflammatory cytokines like interleukins, tumor necrosis factor-α and interferons to vitamins like retinoic acid. The purpose of this review article is to examine the expression, structure, regulation and biological role of NGAL and critically assess its potential as a novel diagnostic and prognostic marker in both benign and malignant human diseases.