Liver fatty acid-binding protein as a biomarker of acute kidney injury after cardiac surgery.

Acute kidney injury (AKI) is a major complication of cardiac bypass surgery. We examined whether levels of liver fatty acid-binding protein (L-FABP) can be an early biomarker for ischemic injury by measuring this protein in the urine of 40 pediatric patients prior to and following cardiopulmonary bypass surgery. AKI was defined as a 50% increase in the serum creatinine from baseline, which was normally not seen until 24-72 h after surgery. Enzyme-linked immunosorbent assay analysis showed increased L-FABP levels (factored for creatinine excretion) of about 94- and 45-fold at 4 and 12 h, respectively, following surgery in the 21 patients who developed AKI with western blot analysis, confirming L-FABP identity. Univariate logistic regression analyses showed that both bypass time and urinary L-FABP were significant independent risk indicators for AKI. After excluding bypass time from the model and using a stepwise multivariate logistic regression analysis, urinary L-FABP levels at 4 h after surgery were an independent risk indicator with the area under the receiver-operating characteristic curve 0.810, sensitivity 0.714, and specificity 0.684 for a 24-fold increase in urinary L-FABP. Our study shows that urinary L-FABP levels represent a sensitive and predictive early biomarker of AKI after cardiac surgery.

A role of liver fatty acid-binding protein in cisplatin-induced acute renal failure.

Previous studies from our laboratory showed that increased fatty acid oxidation by the kidney is cytoprotective during cisplatin (CP)-mediated nephrotoxicity. In this study, we determined the effects of CP and fibrates on peroxisome proliferation and the expression of liver fatty acid-binding protein (L-FABP) in normal mice, and in mice transgenically overexpressing human L-FABP (h-L-FABP). Labeling of peroxisomes demonstrated reduced peroxisomal staining in the proximal tubule of CP-treated mice compared with control mice. There was increased peroxisomal labeling in the proximal tubules of both control and CP-treated mice when either was treated with fibrate; a known peroxisome proliferator-activated receptor-alpha ligand. L-FABP protein expression, not detected in control or CP-treated mice, was significantly increased in the proximal tubules of fibrate-treated mice of either group. In the transgenic mice, CP increased the shedding of h-L-FABP in the urine, which was decreased by fibrate as was the acute renal failure. A cytosolic pattern of h-L-FABP expression was found in the proximal tubules of untreated transgenic mice with a nuclear presence in CP-treated mice. Fibrate pretreatment restored the cytosolic expression pattern in CP-treated mice. Our study shows that fibrate may improve CP-induced acute renal failure due to both peroxisome proliferation and increased L-FABP in the cytosol of the proximal tubule.

Metabolomic study of cisplatin-induced nephrotoxicity.

We have shown that cisplatin inhibits fatty acid oxidation, and that fibrate treatment ameliorates renal function by preventing the inhibition of fatty acid oxidation and proximal tubule cell death. Urine samples of mice treated with single injection of cisplatin (20 mg/kg body weight) were collected for 3 days and analyzed by 1H-nuclear magnetic resonance (NMR) spectroscopy. In a separate group, urine samples of mice treated with peroxisome proliferator-activated receptor-alpha (PPARalpha) ligand WY were also analyzed by NMR after 2 days of cisplatin exposure. Biochemical analysis of endogenous metabolites was performed in serum, urine, and kidney tissue. Electron microscopic studies were carried out to examine the effects of PPARalpha ligand and cisplatin. Principal component analysis demonstrated the presence of glucose, amino acids, and trichloacetic acid cycle metabolites in the urine after 48 h of cisplatin administration. These metabolic alterations precede changes in serum creatinine. Biochemical studies confirmed the presence of glucosuria, but also demonstrated the accumulation of nonesterified fatty acids, and triglycerides in serum, urine, and kidney tissue, in spite of increased levels of plasma insulin. These metabolic alterations were ameliorated by the use of PPARalpha ligand. Electron microscopic analysis confirmed the protective effect of the fibrate on preventing cisplatin-mediated necrosis of the S3 segment of the proximal tubule. Our study shows that cisplatin-induces a unique NMR metabolic profile in urine of mice that developed acute renal failure, and confirms the protective effect of a fibrate class of PPARalpha ligands. We propose that the injury-induced metabolic profile may be used as a biomarker of cisplatin-induced nephrotoxicity.

Expression of ERRP in normal and neoplastic pancreata and its relationship to clinicopathologic parameters in pancreatic adenocarcinoma.

INTRODUCTION AND AIMS: Epidermal growth factor (EGF) and its receptor (EGFR) play crucial roles in cellular signaling in many malignancies, including pancreatic neoplasia. Attenuation of EGFR signaling has been considered novel strategy for the management of human malignancies in several ongoing clinical trials. We recently isolated a novel negative regulator of EGFR, termed EGF receptor related protein (ERRP), whose expression appears to attenuate EGFR activation. In the current study, the expression of ERRP in normal and neoplastic pancreas was investigated and correlated with the clinicopathologic parameters in pancreatic ductal adenocarcinoma (DA). METHODOLOGY: Using rabbit polyclonal antibody that specifically interacts with ERRP, immunohistochemical staining was performed on 45 benign pancreata and 106 cases of DA. The intensity and percentage of cells with cytoplasmic and membranous staining were scored as 0, 1, 2, or 3. A combined score was calculated as intensity x percent/3, and for comparative analysis, the data were arbitrarily divided into three groups: <20, 20-49, and > or =50. The expression of ERRP was correlated with patient age, gender, race, tumor size, stage, grade, and survival. RESULTS: ERRP was expressed in most benign ductal epithelium and islet cells, but not in normal acinar cells. In pancreatic ductal adenocarcinoma, ERRP expression frequency decreased progressively from well (WD) to moderate (MD) to poorly differentiated (PD) carcinoma (58%, 43%, and 15% respectively, < 0.001). ERRP expression was correlated with survival in DA showing decreased median survival with decreased ERRP score ( = 0.0035). Median survival of the lower intensity (0 or 1) group was less than that of the higher intensity (2 or 3) group (8 14 months, = 0.002). The higher expressing group (> or =50% of cells) had longer median survival (17 months) than the lower expressing (<50% of cells) group (10 months, = 0.003). Stepwise multiple regression analyses revealed that ERRP expression score and tumor grade are the significant predictors of survival in pancreatic ductal carcinomas ( < 0.03). CONCLUSION: ERRP is usually expressed in benign ductal epithelium, but not in ductal adenocarcinoma. Its expression decreases with decreasing tumor differentiation. Low levels of ERRP are associated with poor clinical outcome, suggesting that progressive loss of ERRP, a negative regulator of EGFR, may partly stimulate aggressive tumor cell growth in pancreatic adenocarcinoma.