Urinary Liver-Type Fatty Acid-Binding Protein Level as a Predictive Biomarker of Acute Kidney Injury in Patients with Acute Decompensated Heart Failure

Toward Precision Medicine: Exploring the Landscape of Biomarkers in Acute Kidney Injury

Acute kidney injury (AKI) remains a complex challenge with diverse underlying pathological mechanisms and etiologies. Current detection methods predominantly rely on serum creatinine, which exhibits substantial limitations in specificity and poses the issue of late-stage detection of kidney injury. In this review, we propose an up-to-date and comprehensive summary of advancements that identified novel biomarker candidates in blood and urine and ideal criteria for AKI biomarkers such as renal injury specificity, mechanistic insight, prognostic capacity, and affordability. Recently identified biomarkers not only indicate injury location but also offer valuable insights into a range of pathological processes, encompassing reduced glomerular filtration rate, tubular function, inflammation, and adaptive response to injury. The clinical applications of AKI biomarkers are becoming extensive and serving as relevant tools in distinguishing acute tubular necrosis from other acute renal conditions. Also, these biomarkers can offer significant insights into the risk of progression to chronic kidney disease CKD and in the context of kidney transplantation. Integration of these biomarkers into clinical practice has the potential to improve early diagnosis of AKI and revolutionize the design of clinical trials, offering valuable endpoints for therapeutic interventions and enhancing patient care and outcomes.

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

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.

Utility of urinary liver-type fatty acid-binding protein as a prognostic marker in adult congenital heart patients hospitalized for acute heart failure

Progression to acute kidney injury (AKI) under treatment in adult congenital heart disease (ACHD) patients with heart failure is associated with poor prognosis, early detection and interventions are necessary. We aimed to explore the utility of urinary liver-type fatty acid binding protein (L-FABP) in ACHD patients hospitalized for acute decompensated heart failure (ADHF). We prospectively evaluated hemodynamic, biochemical data, and urinary biomarkers including urinary L-FABP in ACHD patients hospitalized in our institution from June 2019 to March 2022. The primary outcomes were the development of AKI and death. AKI was defined as serum creatinine level increased by 0.3 mg/dl or more within 5 days after hospitalization. A total of 104 ADHF patients aged 31 (36-51) years were enrolled. 26 cases (25% of ADHF patients) developed AKI during hospitalization and 4 died after hospital discharge. Serum creatinine (sCr), serum total bilirubin, brain natriuretic peptide (BNP), and urinary L-FABP in AKI patients were significantly higher than in non-AKI patients, whereas systemic oxygen saturation of the peripheral artery (SpO₂) and estimated glomerular filtration ratio in AKI patients were lower than non-AKI patients. There was no difference in the intravenous diuretic dose on admission and during hospitalization between the two groups. In the receiver operating characteristic (ROC) analysis, the maximum area under the curve (AUC) of urinary biomarkers in AKI patients was urinary L-FABP (AUC = 0.769, p < 0.001) with a cutoff value of 4.86 µg/gCr. Urinary L-FABP level on admission was associated with a predictor for AKI development during hospitalization after adjusting for sCr, BNP and SpO₂. Urinary L-FABP was a useful predictor for the development of AKI in ACHD patients hospitalized for ADHF. Monitoring of urinary L-FABP allows us to detect a high-risk patient earlier than the conventional biomarkers.

Cardiorenal syndrome: Pathophysiology as a key to the therapeutic approach in an under-diagnosed disease

Cardiorenal syndrome is a clinical condition that impacts both the heart and the kidneys. One organ's chronic or acute impairment can lead to the other's chronic or acute dysregulation. The cardiorenal syndrome has been grouped into five subcategories that describe the etiology, pathophysiology, duration, and pattern of cardiac and renal dysfunction. This classification reflects the large spectrum of interrelated dysfunctions and underlines the bidirectional nature of heart-kidney interactions. However, more evidence is needed to apply these early findings in medical practice. Understanding the relationship between these two organs during each organ's impairment has significant clinical implications that are relevant for therapy in both chronic and acute conditions. The epidemiology, definition, classification, pathophysiology, therapy, and outcome of each form of cardiorenal syndrome are all examined in this review.

Advances in the study of subclinical AKI biomarkers

Acute kidney injury (AKI) is a prevalent and serious illness in all clinical departments, with a high morbidity and death rate, particularly in intensive care units, where prevention and treatment are crucial. As a result, active prevention, early detection, and timely intervention for acute kidney injury are critical. The current diagnostic criteria for acute kidney injury are an increase in serum creatinine concentration and/or a decrease in urine output, although creatinine and urine output merely reflect changes in kidney function, and AKI suggests injury or damage, but not necessarily dysfunction. The human kidney plays a crucial functional reserve role, and dysfunction is only visible when more than half of the renal mass is impaired. Tubular damage markers can be used to detect AKI before filtration function is lost, and new biomarkers have shown a new subset of AKI patients known as “subclinical AKI.” Furthermore, creatinine and urine volume are only marginally effective for detecting subclinical AKI. As a result, the search for new biomarkers not only identifies deterioration of renal function but also allows for the early detection of structural kidney damage. Several biomarkers have been identified and validated. This study discusses some of the most promising novel biomarkers of AKI, including CysC, NGAL, KIM-1, lL-18, L-FABP, IGFBP7, TIMP-2, Clusterin, and Penkid. We examine their performance in the diagnosis of subclinical AKI, limitations, and future clinical practice directions.

Novel Biomarkers of Kidney Disease in Advanced Heart Failure: Beyond GFR and Proteinuria

PURPOSE

Kidney disease is a common finding in patients with heart failure and can significantly impact treatment decisions and outcomes. Abnormal kidney function is currently determined in clinical practice using filtration markers in the blood to estimate glomerular filtration rate, but the manifestations of kidney disease in the setting of heart failure are much more complex than this. In this manuscript, we review novel biomarkers that may provide a more well-rounded assessment of kidney disease in patients with heart failure.

RECENT FINDINGS

Galectin-3, ST2, FGF-23, suPAR, miRNA, GDF-15, and NAG may be prognostic of kidney disease progression. L-FABP and suPAR may help predict acute kidney injury (AKI). ST2 and NAG may be helpful in diuretic resistance. Several biomarkers may be useful in determining prognosis of long-term kidney disease progression, prediction of AKI, and development of diuretic resistance. Further research into the mechanisms of kidney disease in heart failure utilizing many of these biomarkers may lead to the identification of therapeutic targets.

Identifying Candidate Protein Markers of Acute Kidney Injury in Acute Decompensated Heart Failure

One-quarter of patients with acute decompensated heart failure (ADHF) experience acute kidney injury (AKI)—an abrupt reduction or loss of kidney function associated with increased long-term mortality. There is a critical need to identify early and real-time markers of AKI in ADHF; however, to date, no protein biomarkers have exhibited sufficient diagnostic or prognostic performance for widespread clinical uptake. We aimed to identify novel protein biomarkers of AKI associated with ADHF by quantifying changes in protein abundance in the kidneys that occur during ADHF development and recovery in an ovine model. Relative quantitative protein profiling was performed using sequential window acquisition of all theoretical fragment ion spectra–mass spectrometry (SWATH–MS) in kidney cortices from control sheep (n = 5), sheep with established rapid-pacing-induced ADHF (n = 8), and sheep after ~4 weeks recovery from ADHF (n = 7). Of the 790 proteins quantified, we identified 17 candidate kidney injury markers in ADHF, 1 potential kidney marker of ADHF recovery, and 2 potential markers of long-term renal impairment (differential abundance between groups of 1.2–2.6-fold, adjusted p < 0.05). Among these 20 candidate protein markers of kidney injury were 6 candidates supported by existing evidence and 14 novel candidates not previously implicated in AKI. Proteins of differential abundance were enriched in pro-inflammatory signalling pathways: glycoprotein VI (activated during ADHF development; adjusted p < 0.01) and acute phase response (repressed during recovery from ADHF; adjusted p < 0.01). New biomarkers for the early detection of AKI in ADHF may help us to evaluate effective treatment strategies to prevent mortality and improve outcomes for patients.

Cardiorenal Syndrome: New Pathways and Novel Biomarkers

Cardiorenal syndrome (CRS) is a multi-organ disease characterized by the complex interaction between heart and kidney during acute or chronic injury. The pathogenesis of CRS involves metabolic, hemodynamic, neurohormonal, and inflammatory mechanisms, and atherosclerotic degeneration. In the process of better understanding the bi-directional pathophysiological aspects of CRS, the need to find precise and easy-to-use markers has also evolved. Based on the new pathophysiological standpoints and an overall vision of the CRS, the literature on renal, cardiac, metabolic, oxidative, and vascular circulating biomarkers was evaluated. Though the effectiveness of different extensively applied biomarkers remains controversial, evidence for several indicators, particularly when combined, has increased in recent years. From new aspects of classic biomarkers to microRNAs, this review aimed at a 360-degree analysis of the pathways that balance the kidney and the heart physiologies. In this delicate system, different markers and their combination can shed light on the diagnosis, risk, and prognosis of CRS.

Urine peptidome analysis in cardiorenal syndrome reflects molecular processes

The cardiorenal syndrome (CRS) is defined as the confluence of heart-kidney dysfunction. This study investigates the molecular differences at the level of the urinary peptidome between CRS patients and controls and their association to disease pathophysiology. The urinary peptidome of CRS patients (n = 353) was matched for age and sex with controls (n = 356) at a 1:1 ratio. Changes in the CRS peptidome versus controls were identified after applying the Mann-Whitney test, followed by correction for multiple testing. Proteasix tool was applied to investigate predicted proteases involved in CRS-associated peptide generation. Overall, 559 differentially excreted urinary peptides were associated with CRS patients. Of these, 193 peptides were specifically found in CRS when comparing with heart failure and chronic kidney disease urinary peptide profiles. Proteasix predicted 18 proteases involved in > 1% of proteolytic cleavage events including multiple forms of MMPs, proprotein convertases, cathepsins and kallikrein 4. Forty-four percent of the cleavage events were produced by 3 proteases including MMP13, MMP9 and MMP2. Pathway enrichment analysis supported that ECM-related pathways, fibrosis and inflammation were represented. Collectively, our study describes the changes in urinary peptides of CRS patients and potential proteases involved in their generation, laying the basis for further validation.

Urinary biomarkers of kidney tubule injury, risk of acute kidney injury, and mortality in patients with acute ischaemic stroke treated at a stroke care unit

BACKGROUND AND PURPOSE

Urinary liver-type fatty-acid binding protein (L-FABP), which is a biomarker of kidney tubule injury, has been studied extensively and established as a risk marker of acute kidney injury (AKI). The aim of this study was to investigate whether kidney tubule injury is associated with the development of AKI and mortality in patients with acute ischaemic stroke.

METHODS

Acute ischaemic stroke patients hospitalized in the stroke care unit (SCU) within 24 h after symptom onset were prospectively investigated. AKI was defined on the basis of Kidney Disease: Improving Global Outcomes (KDIGO) criteria. Baseline urinary L-FABP was measured on admission. We evaluated the associations among urinary L-FABP, incidence of AKI, and 90-day mortality adjusted for renal function, albuminuria and other potentially predictive variables, using multivariable analysis.

RESULTS

In total, 527 acute ischaemic stroke patients (342 men, median age 74 years) were enrolled in the study. Twenty-seven patients (5.1%) experienced AKI within 7 days of admission. In the univariate analysis, high urinary L-FABP level had positive associations with AKI [53.8 μg/g creatinine (Cr) vs. 3.9 μg/g Cr; P < 0.001] and 90-day mortality (15.5 μg/g Cr vs. 4.0 μg/g Cr; P < 0.001). In the multivariate analysis, elevated urinary L-FABP level (per 10-μg/g Cr increase) was independently associated with AKI (odds ratio 1.225, 95% confidence interval (CI) 1.083-1.454; P = 0.003) and 90-day mortality (hazard ratio 1.091, 95% CI 1.045-1.138; P < 0.001).

CONCLUSION

Urinary biomarkers of kidney tubule injury are independently associated with the development of AKI and 90-day mortality in patients with acute ischaemic stroke treated at the SCU.

Implication of Acute Kidney Injury in Heart Failure

Patients with acute or chronic decompensated heart failure (ADHF) present with various degrees of heart and kidney dysfunction characterizing cardiorenal syndrome (CRS). CRS can be generally defined as a pathophysiologic disorder of the heart and kidneys whereby acute or chronic dysfunction of 1 organ may induce acute or chronic dysfunction of the other. ADHF is a challenge in the management of heart failure. This review provides an overview the pathophysiology of type 1 CRS together with new approaches to treatment in patients with heart failure with worsening renal function or acute kidney disease.

Protein-based cardiogenic shock patient classifier

Aims

Cardiogenic shock (CS) is associated with high short-term mortality and a precise CS risk stratification could guide interventions to improve patient outcome. Here, we developed a circulating protein-based score to predict short-term mortality risk among patients with CS.

Methods and results

Mass spectrometry analysis of 2654 proteins was used for screening in the Barcelona discovery cohort (n = 48). Targeted quantitative proteomics analyses (n = 51 proteins) were used in the independent CardShock cohort (n = 97) to derive and cross-validate the protein classifier. The combination of four circulating proteins (Cardiogenic Shock 4 proteins—CS4P), discriminated patients with low and high 90-day risk of mortality. CS4P comprises the abundances of liver-type fatty acid-binding protein, beta-2-microglobulin, fructose-bisphosphate aldolase B, and SerpinG1. Within the CardShock cohort used for internal validation, the C-statistic was 0.78 for the CardShock risk score, 0.83 for the CS4P model, and 0.84 (P = 0.033 vs. CardShock risk score) for the combination of CardShock risk score with the CS4P model. The CardShock risk score with the CS4P model showed a marked benefit in patient reclassification, with a net reclassification improvement (NRI) of 0.49 (P = 0.020) compared with CardShock risk score. Similar reclassification metrics were observed in the IABP-SHOCK II risk score combined with CS4P (NRI =0.57; P = 0.032). The CS4P patient classification power was confirmed by enzyme-linked immunosorbent assay (ELISA).

Conclusion

A new protein-based CS patient classifier, the CS4P, was developed for short-term mortality risk stratification. CS4P improved predictive metrics in combination with contemporary risk scores, which may guide clinicians in selecting patients for advanced therapies.

Protein biomarkers for cardiorenal syndrome

INTRODUCTION

The term cardiorenal syndrome (CRS) describes the progressive pathology and interactions that develop upon heart and kidney failure. The definition of CRS is not firmly established and has evolved gradually during the last decade. The main clinical challenges associated with CRS are the lack of tools for early disease diagnosis and the inability to predict the development of cardiorenal pathophysiology. Currently several biomarkers have been proposed for improving CRS patient management. However, validation studies are needed to implement these initial findings to the clinical setting. Areas covered: In this review the database PubMed was used for a literature search on the definition and classification of CRS as well as biomarkers for CRS diagnosis and prognosis. Expert opinion: A universally acceptable classification system for CRS is not available. Thus, acquiring mechanistic insights relative to the pathophysiology of the disease is challenging. Reported biomarkers include well-established markers for heart/renal dysfunction and inflammation. Some proteins expressed in both organs have also been associated with CRS, yet their link to disease pathophysiology and organ cross-talk is missing. Establishing the link between deregulated molecular pathways and CRS phenotypes is required to define biological relevance of existing findings and ultimately biology-driven markers and targets.

Paving the way for precision medicine v2.0 in intensive care by profiling necroinflammation in biofluids

Current clinical diagnosis is typically based on a combination of approaches including clinical examination of the patient, clinical experience, physiologic and/or genetic parameters, high-tech diagnostic medical imaging, and an extended list of laboratory values mostly determined in biofluids such as blood and urine. One could consider this as precision medicine v1.0. However, recent advances in technology and better understanding of molecular mechanisms underlying disease will allow us to better characterize patients in the future. These improvements will enable us to distinguish patients who have similar clinical presentations but different cellular and molecular responses. Treatments will be able to be chosen more “precisely”, resulting in more appropriate therapy, precision medicine v2.0. In this review, we will reflect on the potential added value of recent advances in technology and a better molecular understanding of necrosis and inflammation for improving diagnosis and treatment of critically ill patients. We give a brief overview on the mutual interplay between necrosis and inflammation, which are two crucial detrimental factors in organ and/or systemic dysfunction. One of the challenges for the future will thus be the cellular and molecular profiling of necroinflammation in biofluids. The huge amount of data generated by profiling biomolecules and single cells through, for example, different omic-approaches is needed for data mining methods to allow patient-clustering and identify novel biomarkers. The real-time monitoring of biomarkers will allow continuous (re)evaluation of treatment strategies using machine learning models. Ultimately, we may be able to offer precision therapies specifically designed to target the molecular set-up of an individual patient, as has begun to be done in cancer therapeutics.

Critical care mostly implies life-threatening situations involving systemic infection, inflammation and necrosis. Biofluids are an easily accessible source of liquid biopsies that can be used to monitor the evolution of the patient’s critical illness. The cellular and molecular profiling of necrosis and inflammation in biofluids using cutting-edge technologies such as realtime immunodiagnostics, next-generation sequencing and mass spectrometry will pave the way for precision medicine v2.0 in critical care. This is needed for data mining approaches to allow patientclustering, identify novel biomarkers and develop novel intervention strategies controlling necrosis and inflammation. The real-time monitoring of biomarkers will allow continued (re)evaluation of treatment strategies using machine learning models.

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.

Novel acute kidney injury biomarkers: their characteristics, utility and concerns

Acute kidney injury (AKI) consists of a rapid renal function decline which usually increases serum urea and creatinine levels. Since kidney injury begins by inducing biological and molecular changes which evolve to cellular damage, biomarkers could be used as tools for monitoring early AKI appearance, and predicting its recovery. Among the main AKI biomarkers the neutrophil gelatinase-associated lipocalin, cystatin C, kidney injury molecule-1, monocyte chemotactic peptide-1, N-acetyl-β-D-glucosaminidase, interleukin-18, liver-type fatty acid-binding protein, netrin-1, cycle arrest markers, endogenous ouabain, selenium-binding protein 1, and BPIFA2 marker, have been described. Even though novel biomarkers seem to be more helpful to early detect AKI and/or predict the need for renal replacement, and mortality compared to serum creatinine, more comprehensive studies are still required to determine their clinical utility.