Dataset Information

Mechanisms Underlying Increased TIMP2 and IGFBP7 Urinary Excretion in Experimental AKI.

ABSTRACT:

Background

Recent clinical data support the utility/superiority of a new AKI biomarker ("NephroCheck"), the arithmetic product of urinary TIMP × IGFBP7 concentrations. However, the pathophysiologic basis for its utility remains ill defined.

Methods

To clarify this issue, CD-1 mice were subjected to either nephrotoxic (glycerol, maleate) or ischemic AKI. Urinary TIMP2/IGFBP7 concentrations were determined at 4 and 18 hours postinjury and compared with urinary albumin levels. Gene transcription was assessed by measuring renal cortical and/or medullary TIMP2/IGFBP7 mRNAs (4 and 18 hours after AKI induction). For comparison, the mRNAs of three renal "stress" biomarkers (NGAL, heme oxygenase 1, and p21) were assessed. Renal cortical TIMP2/IGFBP7 protein was gauged by ELISA. Proximal tubule-specific TIMP2/IGFBP7 was assessed by immunohistochemistry.

Results

Each AKI model induced prompt (4 hours) and marked urinary TIMP2/IGFBP7 increases without an increase in renal cortical concentrations. Furthermore, TIMP2/IGFBP7 mRNAs remained at normal levels. Endotoxemia also failed to increase TIMP2/IGFBP7 mRNAs. In contrast, each AKI model provoked massive NGAL, HO-1, and p21 mRNA increases, confirming that a renal "stress response" had occurred. Urinary albumin rose up to 100-fold and strongly correlated (r=0.87-0.91) with urinary TIMP2/IGFBP7 concentrations. Immunohistochemistry showed progressive TIMP2/IGFBP7 losses from injured proximal tubule cells. Competitive inhibition of endocytic protein reabsorption in normal mice tripled urinary TIMP2/IGFBP7 levels, confirming this pathway's role in determining urinary excretion.

Conclusions

AKI-induced urinary TIMP2/IGFBP7 elevations are not due to stress-induced gene transcription. Rather, increased filtration, decreased tubule reabsorption, and proximal tubule cell TIMP2/IGFBP7 urinary leakage seem to be the most likely mechanisms.

SUBMITTER: Johnson ACM

PROVIDER: S-EPMC6065093 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundTo examine whether the new urinary biomarkers TIMP2 and IGFBP7 can predict progression within 24 hours and 72 hours from mild and moderate (KDIGO 1 or 2) to severe (KDIGO 3) AKI in patients with septic shock.MethodsA prospective, multicenter observational study performed in three French ICUs. The urinary biomarkers TIMP2∗IGFBP7 were analyzed at the early phase (<6 hours) of patients admitted for septic shock with mild and moderate AKI.ResultsAmong the 112 patients included, 45 (40%) progressed to the KDIGO 3 level 24 hours after inclusion (KDIGO 3 H24) and 47 (42%) 72 hours after inclusion (KDIGO 3 H72). The median urinary TIMP2∗IGFBP7 at inclusion (baseline) were higher in the KDIGO 3 group than in the KDIGO<3 group at H24 and H72. All covariates with a p value < 0.1 in the univariate analysis were included in stepwise multiple logistic regression models to identify factors independently associated with the risk of KDIGO 3 at H24 and H72. TIMP2∗IGFBP7 remained independently associated with KDIGO 3 at H24 and H72. Baseline posology of norepinephrine, baseline urine output, and baseline serum creatinine remained also significantly associated with progression to KDIGO 3 at H24. Baseline TIMP2∗IGFBP7 and baseline urinary output had the best AUC ROC. A baseline TIMP2∗IGFBP7 > 2.0 (ng/ml)2/1,000 identified the population at high risk of KDIGO 3 H24 (relative risk 4.19 (1.7-10.4)) with a sensitivity of 76% (60-87) and a specificity of 81% (69-89). But the diagnostic performance at H72 of baseline TIMP2∗IGFBP7 was poor (AUC: 0.69 (0.59-0.77)).ConclusionThe urinary TIMP2∗IGFBP7 concentration and the urine output at the early phase of septic shock are independent factors to identify the population at high risk of progression from mild and moderate to severe AKI over the next 24 but not 72 hours. A TIMP2∗IGFBP7 concentration > 2.0 (ng/ml)2/1,000 quadruples the risk of KDIGO 3 AKI within 24 hours. This trial is registered with (NCT03547414).