Proteomic identification of early urinary-biomarkers of acute kidney injury in preterm infants

Abstract

The immature preterm kidney is likely to be vulnerable to acute kidney injury (AKI). However, the biomarkers currently used for AKI are not sensitive or specific and are also inadequate for the timely detection of AKI in preterm infants. The objectives of this study were to identify novel urinary biomarkers of AKI using proteomic techniques, and to verify and validate that the candidates can serve as early predictive biomarkers for AKI. In total, 1,810 proteins were identified in the discovery phase. Among those proteins, 174 were selected as the 1^st targeted proteins. A total of 168 proteins were quantified, and the levels of 6 were significantly increased in the AKI group in the verification phase. Using a clinical assay, the results were confirmed and validated using samples of the first urine after birth from the biorepository. Finally, enzyme-linked immunosorbent assays revealed that the levels of annexin A5, neutrophil gelatinase-associated lipocalin (NGAL), and protein S100-P were significantly higher in the samples of the first urine from patients with AKI than in those from patients without AKI. In conclusion, urinary annexin A5, NGAL and protein S100-P levels are promising biomarkers for early, accurate prediction of AKI in preterm infants.

Figure 1

Work flow in proteomic biomarker discovery experiments. LC MS/MS, liquid chromatography-tandem mass spectrometry; DDA, data-dependent acquisition; DIA, data-independent acquisition; ELISA, enzyme-linked immunosorbent assays.

Figure 2

Schematic representation of the target protein selection process in the discovery phase.

Figure 3

Box and whisker plots of urine values of NGAL, annexin A5, S100P, 6-PGLS, and galectin 3 in preterm infants with AKI and infants without AKI during the first day of life. *p-value <0.05, data are presented as box and whisker plots NGAL, neutrophil gelatinase-associated lipocalin; 6-PGLS, 6-phosphogluconolactonase; AKI, acute kidney injury.

Figure 4

ROC AUC values for combined urinary biomarkers; their predictive abilities to detect AKI in preterm infants. ROC, receiver operating characteristic; AUC, area under the curve; NGAL, neutrophil gelatinase-associated lipocalin; AKI, acute kidney injury.