Urinary Level of Liver-Type Fatty Acid Binding Protein Reflects the Degree of Tubulointerstitial Damage in Polycystic Kidney Disease

Background/Aims: Polycystic kidney disease (PKD) is a common, progressive, and heritable type of kidney disease. Although certain imaging modalities are useful for the diagnosis and staging of PKD, they cannot adequately monitor the severity of interstitial inflammation and fibrosis. Therefore, the present study evaluated the urinary level of liver-type fatty acid binding protein (L-FABP) as a marker of interstitial inflammation and fibrosis in PKD. Methods: Male PCK/CrljCrl-Pkhd1pck/Crl (PCK) rats (n = 34) were used as an animal model of the PKD. Age-and sex-matched Sprague–Dawley rats (SD) (n = 34) were used as controls. Urine samples were obtained from the rats at 8, 12, 16, 20, and 24 weeks of age, and the sera and kidney tissues were obtained at 8, 16, 20, and 24 weeks of age. Results: All PCK rats developed cysts, and the degrees of tubular epithelial cell proliferation and interstitial inflammation increased linearly with age in these model rats relative to the controls. Interstitial fibrosis tended to increase in the PCK rats from 8 to 20 weeks of age, and revealed a peak level at 20 weeks. The urinary L-FABP levels increased linearly with age in the PCK rats, and the levels at 12, 16, 20, and 24 weeks were significantly higher than those in the controls. The urinary levels of L-FABP in the PCK rats correlated significantly with the severity of tubulointerstitial damage; specifically, we observed a significant correlation of the urinary levels at 16 weeks of age with the total kidney volume at 20 weeks. In contrast, both PCK and SD rats exhibited similar serum levels of L-FABP. Conclusion: Urinary L-FABP reflects the progression of tubulointerstitial damage, and therefore, may be a useful marker for monitoring the progression of PKD

Clinical usefulness of urinary biomarkers for early prediction of acute kidney injury in patients undergoing transaortic valve implantation

Abstract This study aimed to reveal the clinical usefulness of urinary biomarkers for the early prediction of AKI onset after transcatheter aortic valve implantation (TAVI) (n = 173). In this study, 22 (12.7%) patients had AKI, of which 21 had mild AKI and 1 had moderate AKI. Higher levels of urinary liver-type fatty acid binding protein (L-FABP), [tissue inhibitor of metalloproteinases-2] × [insulin-like growth factor-binding protein 7], clusterin and urinary albumin before, after and 4 h after TAVI were associated with AKI onset. However, the time point of higher urinary N-acetyl-β-d-glucosaminidase levels related to AKI onset was only before TAVI. No significant differences were found in the area under the receiver-operator characteristic curves (AUC) for predicting AKI onset between urinary biomarkers before TAVI. After TAVI, the AUC (0.81) of urinary albumin was significantly higher than those of any other urinary biomarkers. The sensitivity (0.86) in urinary albumin after TAVI and specificity (0.98) in urinary L-FABP before TAVI were the highest among urinary biomarkers. In conclusion, urinary biomarkers may be clinically useful for early differentiation of patients with a higher or lower risk for AKI onset or early prediction of post-TAVI onset of AKI

Urinary Excretion of Liver Type Fatty Acid Binding Protein Accurately Reflects the Degree of Tubulointerstitial Damage

To investigate the relationship between liver-type fatty acid-binding protein (L-FABP), a biomarker of chronic kidney disease, in the kidney and the degree of tubulointerstitial damage, folic acid (FA)-induced nephropathy was studied in a mouse model system. As renal L-FABP is not expressed in wild-type mice, human L-FABP (hL-FABP) transgenic mice were used in this study. hL-FABP is expressed in the renal proximal tubules of the transgenic mice that were injected intraperitoneally with FA in NaHCO3 (the FA group) or only NaHCO3 (the control group) and oral saline solution daily during the experimental period. The FA group developed severe tubulointerstitial damage with the infiltration of macrophages and the deposition of type I collagen on days 3 and 7 and recovered to the control level on day 14. The gene and protein expression levels of hL-FABP in the kidney were significantly enhanced on days 3 and 7. Urinary hL-FABP in the FA group was elevated on days 3 and 7 and decreased to the control level on day 14. The protein expression levels of hL-FABP in both the kidney and urine significantly correlated with the degree of tubulointerstitial damage, the infiltration of macrophages, and the deposition of type I collagen. In conclusion, renal expression and urinary excretion of hL-FABP significantly reflected the severity of tubulointerstitial damage in FA-induced nephropathy

Urinary excretion of liver-type fatty acid-binding protein reflects the severity of sepsis

Abstract Sepsis due to microbial invasion often causes multiple organ failure (MOF), including acute kidney injury (AKI), with high mortality rates in serious cases. Hence, there is an urgent need for diagnostic biomarkers that can be used to rapidly, accurately, and easily detect sepsis to identify the condition early and guide the selection of appropriate treatment. Liver-type fatty acid-binding protein (L-FABP), which localizes in renal proximal tubules, is excreted into the urine in response to oxidative stress-induced tubular injury. Because of this mechanism, L-FABP has been reported to be a useful urinary biomarker not only for renal disease but also for the severity of sepsis. Based on this concept, we developed a new L-FABP point-of-care (POC) assay kit that can be used to rapidly measure human L-FABP in the urine to further improve the usefulness of this biomarker in clinical settings. In this review, we describe the molecular mechanisms of L-FABP, its clinical usefulness, and the performance of the POC assay kit

Independent predictors of urinary L-FABP^* in multivariate linear regression models.

<p>^*Log-transformed variables.</p><p>ACR, albumin-to-creatinine ratio; eGFR, estimated glomerular filtration rate; ACE/ARB, angiotensin-converting enzyme/angiotensin-receptor blocker.</p><p>Independent predictors of urinary L-FABP<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0126990#t003fn001" target="_blank">^*</a> in multivariate linear regression models.</p

Urinary L-FABP levels and anemia.

<p>Patients with anemia had significantly higher urinary L-FABP levels than patients without anemia (5.6 μg/gCr [2.3–20.2] vs. 3.3 μg/gCr [0.2–7.4], P = 0.002).</p

Urinary L-FABP levels and albuminuria.

<p>Patients with albuminuria had significantly higher urinary L-FABP levels than patients without albuminuria (7.9 μg/gCr [2.0–21.2] vs. 2.8 μg/gCr [0.3–6.1], P < 0.001).</p

Baseline patient characteristics.

<p>Data are mean (SD), median (IQR), or number of patients (%). ACR, albumin-to-creatinine ratio; ACE/ARB, angiotensin-converting enzyme/angiotensin-receptor blocker; HDL, high-density lipoprotein; eGFR, estimated glomerular filtration rate.</p><p>Baseline patient characteristics.</p