Plasma Metallothioneins Are Potential Predictive Biomarkers of Acute Kidney Injury in Acute-on-chronic Liver Failure

Background and Aim: Acute kidney injury (AKI) is a central event in acute-on-chronic-liver failure (ACLF) and considerably increases the risk of short-term mortality. However, currently there are no biomarkers to predict AKI in ACLF. Our study aimed at de novo discovery of AKI biomarkers in ACLF. Methods: The study had two phases- (A) discovery phase in which quantitative plasma proteomics was carried out with day-of-admission samples collected from ACLF patients who presented with no-AKI but progressed to AKI (n=10) or did not progress to AKI(n=9) within 10 days of admission and, (B) Validation phase in which selected biomarkers were evaluated by ELISA in a larger cohort of ACLF plasma samples (n=93) followed by sub-group analyses. Results: Quantitative proteomics identified 56 differentially expressed plasma proteins in ACLF patients who progressed to AKI vs those who did not. The metallothionein family of proteins formed a prominent group among the upregulated proteins in ACLF patients who progressed to AKI. ELISA based validation showed significant upregulation of MT in ACLF-AKI vs no-AKI(p-value=0.0001) and in progression to AKI vs no-progression to AKI(p-value<0.001). AUROC for AKI vs no-AKI was 0.786(p-value <0.001) and for progression to AKI vs no-progression to AKI was 0.7888 (p-value=0.001). Kaplan-Meier analysis revealed that ACLF patients with plasma MT concentration >5.83 ng/mL had a high probability of developing AKI by day 7 (p-value=0.0001). PCR analysis showed high expression of metallothionein 1 and 2 genes in post-mortem liver biopsies from ACLF patients. We found that MT/ Albumin ratios were highly elevated in ACLF AKI vs no-AKI and in ACLF progression to AKI vs no-progression to AKI. Conclusions: Overall, our study led to the identification of plasma metallothionein as a potential day-of-admission biomarker for the prediction of AKI in ACLF patients and provided a basis to explore metallothionein in the pathogenesis of AKI in ACLF.