Neutrophil gelatinase-associated lipocalin as a predictor of pre-eclampsia: A systematic review and meta-analysis

BACKGROUND

Protein neutrophil gelatinase-associated lipocalin (NGAL) has been associated with kidney injury and inflammatory conditions. In particular, several studies have found an association between maternal blood and urine levels and the development of pre-eclampsia.

OBJECTIVES

To examine whether maternal blood and urine levels of NGAL are good predictors of pre-eclampsia.

SEARCH STRATEGY

The authors searched MEDLINE databases via PubMed, Embase, Scopus, Scielo, Google Scholar, PROSPERO International Prospective Register of Systematic Reviews, and the Cochrane Central Register of Controlled Trials.

SELECTION CRITERIA

The authors included case-control observational clinical studies comparing protein levels of NGAL in serum and urine in women with pre-eclampsia with uncomplicated pregnancies. Only studies where the collection of blood or urine was peformed before the occurrence of pre-eclampsia were selected.

DATA COLLECTION AND ANALYSIS

The primary outcome was the difference in NGAL levels in blood or urine between women with and without pre-eclampsia.

RESULTS

Seven studies in total were included: five studies measuring NGAL in blood and two in urine. Regarding the serum studies, 315 patients were included as cases and 540 as controls. Higher NGAL in maternal blood during all three trimesters together was associated with pre-eclampsia; the standardized mean difference was 1.15 ng/mL (95% confidence interval, 0.92-1.39; P < 0.01). Regarding the urine studies, 39 patients were included as cases and 220 as controls. There was no statistically significant difference between patients with pre-eclampsia and controls regarding urine NGAL.

CONCLUSIONS

NGAL in maternal blood is higher in patients who later develop pre-eclampsia compared with controls and could be used as a potential predicting test in the routine clinical setting.

Innate Immune Cells and Toll-like Receptor-Dependent Responses at the Maternal-Fetal Interface

During pregnancy, the placenta, the mother and the fetus exploit several mechanisms in order to avoid fetal rejection and to maintain an immunotolerant environment throughout nine months. During this time, immune cells from the fetal and maternal compartments interact to provide an adequate defense in case of an infection and to promote a tolerogenic milieu for the fetus to develop peacefully. Trophoblasts and decidual cells, together with resident natural killer cells, dendritic cells, Hofbauer cells and other macrophages, among other cell types, contribute to the modulation of the uterine environment to sustain a successful pregnancy. In this review, the authors outlined some of the various roles that the innate immune system plays at the maternal-fetal interface. First, the cell populations that are recruited into gestational tissues and their immune mechanisms were examined. In the second part, the Toll-like receptor (TLR)-dependent immune responses at the maternal-fetal interface was summarized, in terms of their specific cytokine/chemokine/antimicrobial peptide expression profiles throughout pregnancy.

Subclinical First Trimester Renal Abnormalities Are Associated With Preeclampsia in Normoalbuminuric Women With Type 1 Diabetes

OBJECTIVE

This study was conducted to determine the utility of tubular (urinary/plasma neutrophil gelatinase-associated lipocalin [NGAL] and urinary kidney injury molecule 1 [KIM-1]) and glomerular (estimated glomerular filtration rate [eGFR]) biomarkers in predicting preeclampsia (PE) in pregnant women with type 1 diabetes mellitus (T1DM) who were free of microalbuminuria and hypertension at the first trimester.

RESEARCH DESIGN AND METHODS

This was a prospective study of T1DM pregnancy. Maternal urinary and plasma NGAL, urinary KIM-1 (ELISA of frozen samples), and eGFR (Chronic Kidney Disease Epidemiology Collaboration equation) were determined at three study visits (V1: 12.4 ± 1.8; V2: 21.7 ± 1.4; V3: 31.4 ± 1.5 weeks' gestation [mean ± SD]) in 23 women with T1DM with subsequent PE (DM+PE+), 24 who remained normotensive (DM+PE-), and, for reference, in 19 normotensive pregnant women without diabetes (DM-). The groups with diabetes were matched for age, diabetes duration, and parity. All subjects were normotensive and free of microalbuminuria or albuminuria at V1. All study visits preceded the onset of PE.

RESULTS

Urinary creatinine-corrected NGAL (uNGALcc, ng/mg) was significantly elevated at V1 in DM+PE+ vs. DM+PE- women (P = 0.01); this remained significant after exclusion of leukocyte-positive samples (5 DM+PE+ and 2 DM+PE-) (P = 0.02). Accounting for BMI, HbA_1c, and total daily insulin dose, a doubling of uNGALcc at V1 conferred a sevenfold increase in risk for PE (P = 0.026). In contrast, neither plasma NGAL nor urinary KIM-1 predicted PE. Also at V1, eGFR was elevated in DM+PE+ vs. DM+PE- (P = 0.04).

CONCLUSIONS

Early tubular and glomerular dysfunction may predict PE in first trimester women with T1DM, even if free of microalbuminuria. These data suggest that subclinical renal tubular and glomerular injury, if present early in pregnancy, may predispose women with T1DM to PE.

Second-trimester urinary neutrophil gelatinase-associated lipocalin levels in gestational diabetes: preliminary results

OBJECTIVE

The objective of this study is to investigate the urinary neutrophil gelatinase-associated lipocalin (uNGAL) levels in the second trimester of pregnant patients at the time of gestational diabetes mellitus (GDM) screening.

MATERIALS AND METHODS

Urinary samples from 88 pregnant women who underwent gestational diabetes screening test were collected in late second trimester (24-28 weeks) prospectively. After an overnight fasting, 75 g GTT was performed. The blood samples were drawn for measurement of glucose, insulin, and HbA1c. The urinary and blood parameters were compared for pregnant women with or without gestational diabetes.

RESULTS

uNGAL levels were significantly elevated in pregnant women with gesting compared with the control groups (p < .014). There was a positive correlation between uNGAL and HbA1c levels (p = .001).

CONCLUSIONS

In the second trimester, at the time of GDM screening, high levels of uNGAL indicate tubular injury in GDM cases which seems to be a result of hyperglycemia. uNGAL may correlate with an inflammatory renal involvement in GDM.

Diagnostic Value of Urine Tissue Inhibitor of Metalloproteinase-2 and Insulin-Like Growth Factor-Binding Protein 7 for Acute Kidney Injury: A Meta-Analysis

Background

Tissue inhibitor of metalloproteinase-2 (TIMP-2) and insulin-like growth factor-binding protein-7 (IGFBP7) are both involved in renal tubular epithelial cell cycle arrest in acute kidney injury (AKI). Several recent studies showed that urine TIMP-2 times IGFBP7 ([TIMP-2]*[IGFBP7]) is a promising biomarker to predict AKI.

Methods

The aim of this meta-analysis was to assess the diagnostic value of urine [TIMP-2]*[IGFBP7] for early diagnosis of AKI. Relevant studies were retrieved from the PubMed, EMBASE, and Cochrane Library databases. The sensitivity and specificity were determined, and summary receiver operating characteristic (SROC) curves were constructed.

Results

Ten full-text prospective studies were included in this meta-analysis. The estimated sensitivity of urine [TIMP-2]*[IGFBP7] for the early diagnosis of AKI was 0.84 (95% CI = 0.80–0.88) and the specificity was 0.57 (95%CI = 0.55–0.60). The SROC analysis showed an area under the curve of 0.8813.

Limitation

The limited number of included studies, small sample size, unpublished negative results and language limitation might have affected the evaluation.

Conclusion

Urine [TIMP-2]*[IGFBP7] is a promising candidate for early detection of AKI, especially in ruling-out AKI. However, the potential of this biomarker should be validated in larger studies with a broader spectrum of clinical settings.

Does maternal hydronephrosis have an impact on urinary neutrophil gelatinase-associated lipocalin (uNGAL) levels?

OBJECTIVE

To determine urinary neutrophil gelatinase-associated lipocalin (uNGAL) levels and creatinine clearance values in women with different degrees of asymptomatic hydronephrosis during pregnancy.

METHODS

A total of 44 pregnant women with different degrees of hydronephrosis and 46 without hydronephrosis were consecutively enrolled in this prospective study. Basic serum and urine parameters, uNGAL levels, and creatinine clearance values were evaluated. All results were compared between the two groups. Regression analysis was used to determine independent predictors, which were mostly related to hydronephrosis.

RESULTS

Demographic data, basal laboratory parameters, and creatinine clearance values were similar, whereas significantly higher uNGAL levels were detected in women with hydronephrosis compared to those without hydronephrosis (45.3 versus 33.2 ng/mL, respectively) (p = 0.004). An increasing trend in uNGAL levels was detected with increasing degrees of hydronephrosis; as it was not statistically significant (p = 0.163). Linear regression analysis revealed that the parameter of "pelvic diameter" was found as a significant independent factor influencing uNGAL concentrations (β = 0.289; 95% CI: 0.522-3.061; p = 0.006). Other independent variables were not found to influence uNGAL concentrations (p > 0.05).

CONCLUSION

The results obtained from this study indicate a significant increase of urinary concentration of NGAL in the presence of asymptomatic maternal hydronephrosis. This impact is likely to be more profound in those with severe hydronephrosis although this has not been specifically investigated. This theory needs to be validated in larger populations.

Increased urinary levels of podocyte glycoproteins, matrix metallopeptidases, inflammatory cytokines, and kidney injury biomarkers in women with preeclampsia

To investigate kidney injury in preeclampsia, we analyzed 14 biomarkers in urine specimen from 4 groups of pregnant women (normotensive pregnant women and those with pregnancy complicated with chronic hypertension or mild or severe preeclampsia). These biomarkers included 1) podocyte glycoproteins nephrin and podocalyxin, 2) matrix metallopeptidase (MMP)-2 and MMP-9 and their inhibitor tissue inhibitor of metalloproteinase-2, 3) inflammatory molecules and cytokines soluble VCAM-1, TNF-α, soluble TNF receptor receptor-1, IL-6, IL-8, IL-10, and IL-18, and 4) kidney injury biomarkers neutrophil gelatinase-associated lipocalin and kidney injury molecule-1. Postpartum urine specimens (6-8 wk) from normotensive women and those with severe preeclampsia were also evaluated. We found that, first, urine levels of nephrin, MMP-2, MMP-9, and kidney injury molecule-1 were significantly higher before delivery in severe preeclampsia than normotensive groups. The increased levels were all reduced to levels similar to those of the normotensive control group in postpartum specimens from the severe preeclampsia group. Second, soluble VCAM-1, soluble TNF receptor-1, and neutrophil gelatinase-associated lipocalin levels were significantly increased in the severe preeclampsia group compared with the normotensive control group before delivery, but levels of these molecules were significantly reduced in postpartum specimens in both groups. Third, IL-6 and IL-8 levels were not different between preeclampsia and normotensive groups but significantly increased in pregnancy complicated with chronic hypertension. Finally, tissue inhibitor of metalloproteinase-2 and IL-18 levels were not different among the study groups before delivery but were significantly reduced in postpartum specimens from normotensive controls. Our results indicate that the kidney experiences an increased inflammatory response during pregnancy. Most interestingly, tubular epithelial cell injury may also occur in severe preeclampsia. These biomarkers could be used to assess podocyte or tubular injury and kidney inflammatory responses during pregnancy and to evaluate postpartum kidney injury recovery in pregnancy-complicated disorders.