Urinary liver-type fatty acid binding protein is a biomarker reflecting renal damage and the ameliorative effect of drugs at an early stage of histone-induced acute kidney injury.

AIM: Circulated histones play a crucial role in the pathogenesis of infectious diseases and severe trauma, and it is one of the potential molecular targets for therapeutics. Recently, we reported that histone is one of the causative agents for urinary L-FABP increase. However, the mechanism is still unclear, especially in severe cases. We further investigated the mechanism of urinary L-FABP increase using a more severe mouse model with histone-induced kidney injury. This study also aims to evaluate the therapeutic responsiveness of urinary L-FABP as a preliminary study. METHODS: Human L-FABP chromosomal transgenic mice were administrated 30 mg/kg histone from a tail vein with a single dose. We also performed a comparative study in LPS administration model. For the evaluation of the therapeutic responsiveness of urinary L-FABP, we used heparin and rolipram. RESULTS: The histological change with cast formation as a characteristic of the models was observed in proximal tubules. Urinary L-FABP levels were significantly elevated and these levels tended to be higher in those with more cast formation. Heparin and rolipram had the ameliorative effect of the cast formation induced by histone and urinary L-FABP levels significantly decreased. CONCLUSION: Histone is one of the causative agents for the increase of urinary L-FABP at an early stage of AKI. In addition, it suggested that urinary L-FABP may be useful as a subclinical AKI marker reflecting kidney damage induced by histone. Furthermore, urinary L-FABP reflected the degree of the damage after the administration of therapeutic agents such as heparin and PDE4 inhibitor.

Urinary L-FABP as an Early Biomarker for Pediatric Acute Kidney Injury Following Cardiac Surgery with Cardiopulmonary Bypass: A Systematic Review and Meta-Analysis.

Acute kidney injury (AKI) following surgery with cardiopulmonary bypass (CPB-AKI) is common in pediatrics. Urinary liver-type fatty acid binding protein (uL-FABP) increases in some kidney diseases and may indicate CPB-AKI earlier than current methods. The aim of this systematic review with meta-analysis was to evaluate the potential role of uL-FABP in the early diagnosis and prediction of CPB-AKI. Databases Pubmed/MEDLINE, Scopus, and Web of Science were searched on 12 November 2023, using the MeSH terms "Children", "CPB", "L-FABP", and "Acute Kidney Injury". Included papers were revised. AUC values from similar studies were pooled by meta-analysis, performed using random- and fixed-effect models, with p < 0.05. Of 508 studies assessed, nine were included, comprising 1658 children, of whom 561 (33.8%) developed CPB-AKI. Significantly higher uL-FABP levels in AKI versus non-AKI patients first manifested at baseline to 6 h post-CPB. At 6 h, uL-FABP correlated with CPB duration (r = 0.498, p = 0.036), postoperative serum creatinine (r = 0.567, p < 0.010), and length of hospital stay (r = 0.722, p < 0.0001). Importantly, uL-FABP at baseline (AUC = 0.77, 95% CI: 0.64-0.89, n = 365), 2 h (AUC = 0.71, 95% CI: 0.52-0.90, n = 509), and 6 h (AUC = 0.76, 95% CI: 0.72-0.80, n = 509) diagnosed CPB-AKI earlier. Hence, higher uL-FABP levels associate with worse clinical parameters and may diagnose and predict CPB-AKI earlier.

Urinary liver-type fatty acid binding protein is increased in the early stages of the disease with a risk of acute kidney injury induced by histone.

AIM: Urinary liver-type fatty acid binding protein (L-FABP) has potential utility as an early prognostic biomarker ahead of traditional severity scores in coronavirus disease 2019 and sepsis, however, the mechanism of elevated urinary L-FABP in the disease has not been clearly elucidated. We investigated the background mechanisms of urinary L-FABP excretion through non-clinical animal model focusing on histone, which is one of the aggravating factors in these infectious diseases. METHODS: Male Sprague-Dawley rats were placed in central intravenous catheters, and these rats were given a continuous intravenous infusion of 0.25 or 0.5 mg/kg/min calf thymus histones for 240 min from caudal vena cava. RESULTS: After the administration of histone, urinary L-FABP and gene expression of an oxidative stress marker in the kidney increased in a histone dose-dependent manner before increased serum creatinine. Upon further investigation, fibrin deposition in the glomerulus was observed and it tended to be remarkable in the high dose administrated groups. The levels of coagulation factor were significantly changed after the administration of histone, and these were significantly correlated with the levels of urinary L-FABP. CONCLUSIONS: Firstly, it was suggested that histone is one of the causative agents for the urinary L-FABP increase at an early stage of the disease with a risk of acute kidney injury. Secondly, urinary L-FABP could be a marker reflecting the changes of coagulation system and microthrombus caused by histone in the early stage of acute kidney injury before becoming severely ill and maybe a guide to early treatment initiation.

Plasma levels and tissue expression of liver-type fatty acid-binding protein in patients with breast cancer.

BACKGROUND: Liver-type fatty acid-binding protein (L-FABP) is widely expressed in hepatocytes and plays a role in lipid metabolism. It has been demonstrated to be overexpressed in different types of cancer; however, few studies have investigated the association between L-FABP and breast cancer. The aim of this study was to assess the association between plasma concentrations of L-FABP in breast cancer patients and the expression of L-FABP in breast cancer tissue. METHOD: A total of 196 patients with breast cancer and 57 age-matched control subjects were studied. Plasma L-FABP concentrations were measured using ELISA in both groups. The expression of L-FABP in breast cancer tissue was examined using immunohistochemistry. RESULT: The patients had higher plasma L-FABP levels than the controls (7.6 ng/mL (interquartile range 5.2-12.1) vs. 6.3 ng/mL (interquartile range 5.3-8.5), p = 0.008). Multiple logistic regression analysis showed an independent association between L-FABP and breast cancer, even after adjusting for known biomarkers. Moreover, the rates of pathologic stage T2+T3+T4, clinical stage III, positive HER-2 receptor status, and negative estrogen receptor status were significantly higher in the patients with an L-FABP level greater than the median. Furthermore, the L-FABP level gradually increased with the increasing stage. In addition, L-FABP was detected in the cytoplasm, nuclear, or both cytoplasm and nuclear of all breast cancer tissue examined, not in the normal tissue. CONCLUSIONS: Plasma L-FABP levels were significantly higher in the patients with breast cancer than in the controls. In addition, L-FABP was expressed in breast cancer tissue, which suggests that L-FABP may be involved in the pathogenesis of breast cancer.

Pathogenesis and prognosis of intrarenal reflux.

Scar development in the children's renal cortex with vesicoureteral reflux (VUR) is one of the most important parameters of prognosis. It can develop regardless of the chosen treatment, even after the regression of VUR. The shape of the renal papillae, the ascending urinary tract infection, the greater than third-degree VUR, and finally the increased intra-calyceal pressure, induce the formation of renal scarring in the renal parenchyma. Renal scarring may complicate VUR independently of the therapeutic strategy (conservative or operative) and its regression. For restitution of this entity, many scientific terms have been used and the most common of them is intrarenal reflux (IRR). The effects of VUR on future renal function result from the limited ability of the affected kidney to grow (failure of renal growth) due to the existence of scars in the renal cortex, the worsening of these scars, or finally the creation of new scars. With the present study, we intend to clarify the etiology and the pathophysiology of IRR and the relation of VUR prognosis to newer biomarkers such as N-acetyl-beta-glycosaminidase, beta-2 microglobulin, Pen- traxin- 3 and Liver-type fatty-acid-binding protein.

Admission free-fatty acid level is a predictor of the mid-term worsening renal function in patients with ST-segment elevation myocardial infarction.

Whether free fatty acids (FFAs), which are generators of reactive oxygen species and substrates of cytotoxic lipid peroxidation products in proximal tubules of the kidney, can be a predictor of worsening renal function (WRF) is not fully elucidated. A total of 110 patients with ST-segment elevation myocardial infarction (STEMI) who underwent primary percutaneous coronary intervention within 24 h after symptom onset were included. The exclusion criteria were out-of-hospital cardiac arrest, vasospastic angina, hemodialysis, and/or lack of data. FFAs and serum cystatin C were measured on admission, and urinary liver-type fatty acid-binding protein (L-FABP) was measured 3 h after admission. WRF, defined as an increase in serum creatinine by ≥ 0.3 mg/dL for 2-year follow-up, was observed in 16 patients (15%). A multivariate logistic regression analysis (a stepwise algorithm) revealed that the FFA level was an independent predictor of WRF (P = 0.024). The FFA level was associated with WRF adjusted after serum cystatin C (odds ratio [OR]: 1.378 per 1 mEq/L, P = 0.017), L-FABP (OR: 1.370 per 1 mEq/L, P = 0.016), or the Mehran contrast-induced nephropathy (CIN) risk score (OR: 1.362 per 1 mEq/L, P = 0.021). The FFA level was inversely associated with the change in estimated glomerular filtration rate level for 2 years (R2 = 0.051, P = 0.018). The FFA level on admission was associated with the mid-term WRF in patients with STEMI.

The Role of Elevated Liver-Type Fatty Acid-Binding Proteins in Liver Diseases.

Liver-type fatty acid-binding protein (L-FABP) is mainly expressed in the liver as well as the proximal tubular epithelial cells in the kidney. In general, the proteins and enzymes existing within the hepatocytes have the potential to become biomarkers, for instance alanine aminotransferase, which reflects hepatocellular damage. However, due to reduced hepatocellular function in late stage of chronic liver diseases (e.g. cirrhosis), proteins and enzymes relating to hepatocellular damage are not always accurate measures of disease progression. Recently, several publications have demonstrated elevated serum L-FABP levels during the progression of human liver diseases, including hepatocellular carcinoma (HCC), and were a prognostic factor for survival in acute and chronic liver disease patients. However, the study regarding serum L-FABP levels and hepatic L-FABP expression in liver diseases is not sufficient to understand the molecular mechanism of L-FABP during the progression of these disease states. In this review, we focus on the use of serum and/or hepatic L-FABP expression as a biomarker in human liver diseases, including mechanistic potential in HCC.

Elevated Serum Liver-Type Fatty Acid Binding Protein Levels in Non-acetaminophen Acute Liver Failure Patients with Organ Dysfunction.

BACKGROUND: Liver-type fatty acid binding protein (FABP1) has previously been demonstrated to improve prognostic discrimination in acetaminophen (APAP)-induced ALF but has not been investigated in other etiologies of ALF. AIM: To determine whether FABP1 levels (early: admission or late: days 3-5) are associated with 21-day transplant-free survival in non-APAP ALF. METHODS: FABP1 was measured in serum samples from 384 ALF patients (n = 88 transplant-free survivors (TFS), n = 296 died/LT-NTFS) using solid-phase enzyme-linked immunosorbent assay and analyzed with US ALFSG registry data. RESULTS: Of 384 ALF patients (autoimmune hepatitis n = 125, drug-induced liver injury n = 141, Hepatitis B n = 118), 177 (46%) patients received LT. Early FABP1 levels were significantly higher in ALF patients requiring vasopressor support (203.4 vs. 76.3 ng/mL) and renal replacement therapy (203.4 vs. 78.8 ng/mL; p < 0.001 for both). Late FABP1 levels were significantly higher in patients requiring mechanical ventilation (77.5 vs. 53.3 ng/mL), vasopressor support (116.4 vs. 53.3 ng/mL) and in patients with grade 3/4 hepatic encephalopathy (71.4 vs. 51.4 ng/mL; p = 0.03 for all). Late FABP1 levels were significantly lower in TFS patients (TFS 54 vs. NTFS 66 ng/mL; p = 0.049) but not admission (TFS 96 vs. NTFS 87 ng/mL; p = 0.67). After adjusting for significant covariates, serum FABP1 did not discriminate significantly between TFS and patients who died/received LT at day 21 either on admission (p = 0.29) or late (days 3-5, p = 0.087) time points. CONCLUSION: In this first report of FABP1 in non-APAP ALF, FABP1 levels at late time points (days 3-5) were significantly lower in ALF patients who were alive without transplant at day 21 but not after adjusting for covariates reflecting severity of illness. Higher FABP1 levels were associated with the presence of increased organ failure.

Significance of urinary liver-type fatty acid-binding protein in patients with normal renal function after undergoing intestinal urinary diversion: a preliminary study.

BACKGROUND: Liver-type fatty acid-binding protein (L-FABP) in urine is one of the early diagnostic biomarkers for acute and chronic kidney injuries. Although this protein is also identified in the intestine, there is no verified reference value for patients with intestinal urinary diversion (UD). The aim of the present study was to measure L-FABP values in such patients and compare them with the results for patients without UD. METHODS: Spot urine specimens were collected from 41 patients with UD and 50 subjects without UD with estimated glomerular filtration rates of over 60 ml/min/1.73 m2, and the L-FABP values were measured. The normal upper cutoff value in healthy subjects without UD is considered to be 7.24 µg/g Cr. First, the median values of the two groups were compared. Next, the subjects with negative proteinuria and without comorbidities associated with renal function were further selected and the median values of the groups were compared. RESULTS: The mean age was significantly higher in the UD group. The types of UD were ileal conduit (38 patients) and ileal neobladder (three patients). The median L-FABP value in the UD group was significantly higher than that in the non-diversion group (89.1 µg/g Cr vs. 2.0 µg/g Cr, p < 0.0001). After adjustment for their backgrounds, the median value remained higher in the UD group. CONCLUSIONS: L-FABP values in subjects with UD are higher than in those without UD. By this result, to develop a reference value in patients with intestinal UD population, further studies are required.

Combined evaluation of plasma B-type natriuretic peptide and urinary liver-type fatty acid-binding protein/creatinine ratio is related to worsening renal function in patients undergoing elective percutaneous coronary intervention.

BACKGROUND: There are few reports on the significance for the combined evaluation of blood humoral factors and urinary biomarkers in terms of worsening renal function (WRF) after coronary angiography (CAG)/percutaneous coronary arterial intervention (PCI). METHOD AND RESULTS: Urinary liver type-fatty acid-binding protein (L-FABP), neutrophil gelatinase associated lipocalin (NGAL), and adrenomedullin (AM) were measured less than 24 h before and 3 h, 6 h, 1 day, and 2 days after CAG/PCI. WRF was defined as a > 20% decrease in the estimated GFR. WRF occurred in seven of 100 patients and the increase in L-FABP/creatinine (Cr) at 1 day after CAG/PCI was significantly higher in the WRF group than in the non-WRF group. Plasma B-type natriuretic peptide (BNP) before CAG/PCI and L-FABP/Cr at 1 day after CAG/PCI were independent predictors for WRF. The areas under the receiver-operating characteristic curves were as follows: 0.760 for BNP before CAG/PCI, 0.731 for L-FABP/Cr at 1 day after CAG/PCI, and 0.892 for BNP and L-FABP/Cr. Urinary AM levels after PCI/CAG were negatively correlated only to serum potassium levels. Gene expressions of AM and AM-receptor were detectable in renal tubule epithelial cells. AM increased intracellular second messenger levels in a dose-dependent manner. CONCLUSIONS: Our results suggest that combined evaluation of plasma BNP and urinary L-FABP/Cr is useful as a predictor of renal dysfunction in CAG/PCI patients.

Relationship of urinary liver-type fatty acid-binding protein with cardiovascular risk factors in the Japanese population without chronic kidney disease: Sasayama study.

BACKGROUND: Urinary liver-type fatty acid-binding protein (L-FABP) is a well-known marker of proximal tubular impairment. We evaluated the relationship between cardiovascular disease (CVD) risk factors and levels of L-FABP in a cross-sectional community-based study. Participants with normoalbuminuria and normal estimated glomerular filtration rate (eGFR), that is, non-chronic kidney disease (non-CKD), were enrolled in this study. To the best of our knowledge, this is the first study to focus on the association between CVD risk factors and a proximal tubular marker in the Japanese general population with normoalbuminuria and normal eGFR. METHODS: The present study is part of the Sasayama study. The participants included 1000 community residents (447 men and 553 women) aged 40-64 years without a history of CVD or renal dysfunction. Out of these participants 375 men and 477 women, defined as non-CKD, were included for further analysis. In each sex, the highest quintile group was considered to have high-normal L-FABP levels. A multiple logistic regression model was used to evaluate the relationship between risk factors for CVD and high-normal L-FABP levels in the non-CKD participants. We performed a similar analysis using the high-normal urinary albumin to creatinine ratio (UACR) as a dependent variable instead of L-FABP. RESULTS: Among the non-CKD participants, in the highest quintile group (Q5, top 20%), L-FABP was ≥2.17 µg/gCre in men and ≥ 2.83 µg/gCre in women. In women, the multivariate odds ratio was 3.62 (1.45-9.00) for high-normal L-FABP in the presence of diabetes mellitus (DM) compared with that in the group without DM. However, the relationship between DM and the UACR level was not significant. In men, DM was significantly associated with high-normal UACR. However, the relationship with L-FABP levels was not significant. CONCLUSIONS: The presence of DM was more strongly related to high-normal L-FABP levels than to high-normal UACR in women even at the stage of normoalbuminuria and normal eGFR. Our results were also consistent with the findings of a previous study where women were more prone to nonalbuminuric renal impairment compared to men, although further studies are required to confirm the results.

Urinary liver-type fatty acid-binding protein variation as a predictive value of short-term mortality in intensive care unit patients.

BACKGROUND: Predicting the prognosis of intensive care unit (ICU) patients is crucial because it may lead to patient stratification that would in turn help in appropriately distributing limited medical resources. This study, therefore, aimed to investigate the use of the urinary liver-type fatty acid-binding protein (L-FABP) semi-quantitative kit in rapidly predicting the prognosis of patients admitted to the ICU. METHODS: We conducted a single-center, prospective, observational study wherein 100 consecutive patients admitted to the ICU with an indwelling bladder catheter were enrolled between April and October 2020. Urine specimens were collected at the time of admission (T1) and after 6 h (T2), and urinary L-FABP levels were semi-quantitatively measured. Based on the results, an L-FABP variation was defined as the change in L-FABP (negative, weakly positive, or strongly positive) from T1 to T2. Patients were divided into three groups (L-FABP decreased group, unchanged group, or increased group), following which we compared their 14-day mortality. RESULTS: Finally, a total of 79 patients were included in the analysis. In multivariate analysis, urinary L-FABP variation [Odds ratio (OR) = 14.327, 95% confidence interval (CI) = 1.819-112.868, p = 0.01] and lactate (OR = 1.234, 95%CI = 1.060-1.437, p = 0.01) were significantly associated with 14-day mortality. CONCLUSION: Urinary L-FABP variation at 6 h after admission was significantly associated with 14-day mortality.

Incremental short maximal exercise increases urinary liver-type fatty acid-binding protein in adults without CKD.

Exercise-induced redistribution of tissue blood flow decreases the renal blood flow in an exercise intensity-dependent manner. However, the acute effects of incremental short maximal exercise on renal tubular conditions remain unknown. The purpose of this study was to investigate the acute effects of incremental short maximal exercise on the urinary liver-type fatty acid-binding protein, which is a highly sensitive tubular biomarker that correlates excellently with peritubular capillary blood flow. A total of 116 adults (aged 24-83 years) without chronic kidney disease performed the incremental short maximal exercise using a cycling ergometer, wherein the exercise sequence consisted of commencing with a 2-min workout period at 20 W (as a warm-up period) and then followed by a 10-20 W increase every 1 minute until termination criteria were reached. Urinary samples were gathered before and immediately after the exercise to evaluate the concentrations of urinary creatinine, albumin, and liver-type fatty acid-binding protein. Urinary excretion levels of albumin and liver-type fatty acid-binding protein were significantly increased post-exercise (P < .001 and P = .008, respectively). Furthermore, the % change in urinary liver-type fatty acid-binding protein levels after exercise was found to correlate independently with age, estimated glomerular filtration rate at baseline, and the % change in urinary albumin (Model R2  = 0.451, P < .001). Our findings suggest that incremental short maximal exercise may lead to acute slightly adverse effects on tubular conditions, especially in young adults or adults with lower renal function, even without chronic kidney disease.

Clinical and subclinical acute kidney injury in multidrug-resistant septic patients treated with colistimethate sodium: Incidence and clinical outcomes.

AIM: Colistimethate sodium (CMS) has been postulated as the principal cause of high incidence of clinical acute kidney injury (AKI) in multidrug-resistance (MDR) septic patients with normal baseline serum creatinine (sCr) who were treated with CMS. This prospective observational study was conducted to examine the incidence and clinical outcomes of clinical and subclinical AKI in MDR septic patients receiving CMS. METHODS: Forty-two MDR septic patients with normal sCr who required CMS were included. Clinical AKI was diagnosed by increased sCr levels according to the KDIGO2012 criteria while subclinical AKI was identified by elevated levels of urinary neutrophil gelatinase-associated lipocalin (uNGAL > 150 ng/mL) or urinary liver-type fatty-acid-binding protein (uL-FABP > 10.5 ng/mL). RESULTS: Clinical AKI was noted in 47.6% of patients on day 5 and 38.1% on day 7 after initiating CMS. By using uL-FABP, subclinical AKI was observed in 45.2% and 54.8% on day 5 and 7, respectively. At baseline prior to CMS treatment, subclinical AKI was already present in 90%. The baseline uL-FABP was superior to the baseline uNGAL in early prediction of clinical AKI on day 5. The subclinical AKI patients had comparable worse outcomes as clinical AKI patients. CONCLUSION: The incidence of subclinical AKI in MDR septic patients before CMS treatment was extremely high. The baseline uL-FABP provided the best predictive capacity of clinical AKI. The causes of clinical AKI might include the persistence of sepsis process, subclinical AKI and CMS nephrotoxicity. Proper management of subclinical AKI patients before CMS initiation should be concerned to prevent further renal damage and improve patient and renal outcomes.

The Possibility of Urinary Liver-Type Fatty Acid-Binding Protein as a Biomarker of Renal Hypoxia in Spontaneously Diabetic Torii Fatty Rats.

BACKGROUND: Renal hypoxia is an aggravating factor for tubulointerstitial damage, which is strongly associated with renal prognosis in diabetic kidney disease (DKD). Therefore, urinary markers that can detect renal hypoxia are useful for monitoring DKD. OBJECTIVE: To determine the correlation between urinary liver-type fatty acid-binding protein (L-FABP) and renal hypoxia using a novel animal model of type 2 diabetes. METHODS: Male spontaneously diabetic Torii (SDT) fatty rats (n = 6) were used as an animal model of type 2 diabetes. Age- and sex-matched Sprague-Dawley (SD) rats (n = 8) were used as controls. Body weight, systolic blood pressure, and blood glucose levels were measured at 8, 12, 16, and 24 weeks of age. Urine samples and serum and kidney tissues were collected at 24 weeks of age. Microvascular blood flow index (BFI) was measured using diffuse correlation spectroscopy before sampling both the serum and kidneys for the evaluation of renal microcirculation at the corticomedullary junction. RESULTS: Obesity, hyperglycemia, and hypertension were observed in the SDT fatty rats. Focal glomerular sclerosis, moderate interstitial inflammation, and fibrosis were significantly more frequent in SDT fatty rats than in SD rats. While the frequency of peritubular endothelial cells and phosphoendothelial nitric oxide synthase levels were similar in both types of rats, the degree of renal hypoxia-inducible factor-1α (HIF-1α) expression was significantly higher (and with no change in renal vascular endothelial growth factor expression levels) in the SDT fatty rats. Urinary L-FABP levels were significantly higher and renal microvascular BFI was significantly lower in the SDT fatty rats than in the SD rats. Urinary L-FABP levels exhibited a significant positive correlation with renal HIF-1α expression and a significant negative correlation with renal microvascular BFI. CONCLUSIONS: Urinary L-FABP levels reflect the degree of renal hypoxia in DKD in a type 2 diabetic animal model. Urinary L-FABP may thus prove useful as a renal hypoxia marker for monitoring DKD in patients with type 2 diabetes in clinical practice.

Increased Urinary Liver-Type Fatty Acid-Binding Protein Level Predicts Worsening Renal Function in Patients With Acute Heart Failure.

BACKGROUND: Urinary liver-type fatty acid-binding protein (L-FABP) is a potential biomarker for acute kidney injury, and it in turn increases cardiovascular mortality. We tested whether the urinary L-FABP level predicted short- and mid-term outcomes in patients with acute heart failure. METHODS AND RESULTS: We enrolled consecutive patients with acute heart failure, and measured their urinary L-FABP levels before acute treatment. Worsening renal function (WRF), defined as both an absolute increase in the serum creatinine level of ≥0.3mg/dL and a ≥25% relative increase in its level from baseline, occurred in 37 (26.8%) of 138 patients. Patients with a urinary L-FABP level above the upper normal limit (8.4 µg/g creatinine) (n = 49; 35.5%) were more likely than those with a urinary L-FABP level within normal limits (n = 89; 64.5%) to develop WRF (n = 26 [53.1%] vs n = 11 [12.4%]; P < .001). A urinary L-FABP level above the upper limit was independently associated with WRF (hazard ratio 1.8; P = .01). During 1 year of follow-up, 12 patients (8.7%) died, and urinary L-FABP level had no association with all-cause mortality. There was, however, a tendency toward a higher readmission rate in patients with a urinary L-FABP level above the upper normal limit who survived the index hospitalization (n = 46) than in those without an abnormal L-FABP level (n = 88; n = 13 [28.3%] vs n = 13 [14.8%]; log-rank P = .06). CONCLUSIONS: Increased urinary L-FABP level before treatment may predict WRF in patients with acute heart failure. Further investigation is warranted for its predictive ability of adverse outcomes.

Predicting acute kidney injury using urinary liver-type fatty-acid binding protein and serum N-terminal pro-B-type natriuretic peptide levels in patients treated at medical cardiac intensive care units.

BACKGROUND: The early prediction of acute kidney injury (AKI) can facilitate timely intervention and prevent complications. We aimed to understand the predictive value of urinary liver-type fatty-acid binding protein (L-FABP) levels on admission to medical (non-surgical) cardiac intensive care units (CICUs) for AKI, both independently and in combination with serum N-terminal pro-B-type natriuretic peptide (NT-proBNP) levels. METHODS: We prospectively investigated the predictive value of L-FABP and NT-proBNP for AKI in a large, heterogeneous cohort of patients treated in medical CICUs. Baseline urinary L-FABP and serum NT-proBNP were measured on admission. AKI was diagnosed according to the Kidney Disease: Improving Global Outcomes criteria. We studied 1273 patients (mean age, 68 years), among whom 46% had acute coronary syndromes, 38% had acute decompensated heart failure, 5% had arrhythmia, 3% had pulmonary hypertension, 2% had acute aortic syndrome, 2% had infective endocarditis, and 1% had Takotsubo cardiomyopathy. RESULTS: Urinary L-FABP levels correlated with serum NT-proBNP levels (r = 0.17, p < 0.0001). AKI occurred in 224 patients (17.6%), including 48 patients with stage 2 or 3 disease. Patients who developed AKI had higher one-week and 6-month mortality than those who did not develop AKI (p = 0.0002 and p = 0.003, respectively). In the multivariate logistic analysis, both L-FABP (p < 0.0001) and NT-proBNP (p = 0.006) were independently associated with the development of AKI. Adding L-FABP and NT-proBNP to a baseline model that included established risk factors further improved reclassification (p < 0.001) and discrimination (p < 0.01) beyond that of the baseline model or any single biomarker individually. CONCLUSIONS: Urinary L-FABP and serum NT-proBNP levels on admission are independent predictors of AKI, and when used in combination, improve early prediction of AKI in patients hospitalized at medical CICUs.

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.

Urinary liver-type fatty acid binding protein is an independent predictor of stroke and mortality in individuals with type 1 diabetes.

AIMS/HYPOTHESIS: In type 1 diabetes, cardiovascular disease (CVD) and diabetic nephropathy progress in parallel, thereby potentiating the risk of premature death during their development. Since urinary liver-type fatty acid binding protein (L-FABP) predicts the progression of diabetic nephropathy, the aim of this study was to investigate whether urinary L-FABP also predicts cardiovascular outcomes and mortality. METHODS: We tested our hypothesis in a Finnish cohort of 2329 individuals with type 1 diabetes and a median follow-up of 14.1 years. The L-FABP to creatinine ratio was determined from baseline urine samples. The predictive value of urinary L-FABP was evaluated using Cox regression models, while its added predictive benefit for cardiovascular outcomes and mortality was evaluated using a panel of statistical indexes. RESULTS: Urinary L-FABP predicted incident stroke independently of traditional risk factors (HR 1.33 [95% CI 1.20, 1.49]) and after further adjustment for eGFR (HR 1.28 [95% CI 1.14, 1.44]) or AER (HR 1.24 [95% CI 1.06, 1.44]). In addition, it predicted mortality independently of traditional risk factors (HR 1.34 [95% CI 1.24, 1.45]), and after adjustment for eGFR (HR 1.29 [95% CI 1.18, 1.39]) or AER (HR 1.22 [95% CI 1.09, 1.36]). Urinary L-FABP was as good a predictor as eGFR or AER, and improved the AUC for both outcomes on top of traditional risk factors, with no reclassification benefit (integrated discrimination improvement/net reclassification improvement) for stroke or mortality when AER or eGFR were added to traditional risk factors. However, urinary L-FABP was not a predictor of other cardiovascular endpoints (coronary artery disease, peripheral vascular disease and overall CVD events) when adjusted for the AER. CONCLUSIONS/INTERPRETATION: Urinary L-FABP is an independent predictor of stroke and mortality in individuals with type 1 diabetes.

Renoprotective effect of the xanthine oxidoreductase inhibitor topiroxostat on adenine-induced renal injury.

The aim of the present study was to reveal the effect of a xanthine oxidoreductase (XOR) inhibitor, topiroxostat (Top), compared with another inhibitor, febuxostat (Feb), in an adenine-induced renal injury model. We used human liver-type fatty acid-binding protein (L-FABP) chromosomal transgenic mice, and urinary L-FABP, a biomarker of tubulointerstitial damage, was used to evaluate tubulointerstitial damage. Male transgenic mice (n = 24) were fed a 0.2% (wt/wt) adenine-containing diet. Two weeks after the start of this diet, renal dysfunction was confirmed, and the mice were divided into the following four groups: the adenine group was given only the diet containing adenine, and the Feb, high-dose Top (Top-H), and low-dose Top (Top-L) groups were given diets containing Feb (3 mg/kg), Top-H (3 mg/kg), and Top-L (1 mg/kg) in addition to adenine for another 2 wk. After withdrawal of the adenine diet, each medication was continued for 2 wk. Serum creatinine levels, the degree of macrophage infiltration, tubulointerstitial damage, renal fibrosis, urinary 15-F2t-isoprostane levels, and renal XOR activity were significantly attenuated in the kidneys of the Feb, Top-L, and Top-H groups compared with the adenine group. Serum creatinine levels in the Top-L and Top-H groups as well as renal XOR in the Top-H group were significantly lower than those in the Feb group. Urinary excretion of L-FABP in both the Top-H and Top-L groups was significantly lower than in the adenine and Feb groups. In conclusion, Top attenuated renal damage in an adenine-induced renal injury model.