Heart-kidney biomarkers in patients undergoing cardiac stress testing

Increased susceptibility to structural acute kidney injury in a mouse model of presymptomatic cardiomyopathy

The early events that signal renal dysfunction in presymptomatic heart failure are unclear. We tested the hypothesis that functional and mechanistic changes occur in the kidney that precede the development of symptomatic heart failure. We employed a transgenic mouse model with cardiomyocyte-specific overexpression of mutant α-B-crystallin that develops slowly progressive cardiomyopathy. Presymptomatic transgenic mice displayed an increase in serum creatinine (1.17 ± 0.34 vs. wild type 0.65 ± 0.16 mg/dl, P < 0.05) and in urinary neutrophil gelatinase-associated lipocalin (NGAL; 278.92 ± 176.24 vs. wild type 49.11 ± 22.79 ng/ml, P < 0.05) but no renal fibrosis. Presymptomatic transgenic mouse kidneys exhibited a twofold upregulation of the Ren1 gene, marked overexpression of renin protein in the tubules, and a worsened response to ischemia-reperfusion injury based on serum creatinine (2.77 ± 0.66 in transgenic mice vs. 2.01 ± 0.58 mg/dl in wild type, P < 0.05), urine NGAL (9,198.79 ± 3,799.52 in transgenic mice vs. 3,252.94 ± 2,420.36 ng/ml in wild type, P < 0.05), tubule dilation score (3.4 ± 0.5 in transgenic mice vs. 2.6 ± 0.5 in wild type, P < 0.05), tubule cast score (3.2 ± 0.4 in transgenic mice vs. 2.5 ± 0.5 in wild type, P < 0.05), and TdT-mediated dUTP nick-end labeling (TUNEL)-positive nuclei (10.1 ± 2.1 in the transgenic group vs. 5.7 ± 1.6 per 100 cells counted in wild type, P < 0.01). Our findings indicate functional renal impairment, urinary biomarker elevations, and induction of renin gene and protein expression in the kidney that occur in early presymptomatic heart failure, which increase the susceptibility to subsequent acute kidney injury.

Renal biomarkers for the prediction of cardiovascular disease

PURPOSE OF REVIEW

Chronic kidney disease (CKD) is a well-known risk factor for cardiovascular disease (CVD). Renal biomarkers might be valuable in predicting CVD. Investigation of these biomarkers may uncover some of the poorly understood mechanisms that link renal and CVD as well as aid in the modification of disease and serve as a useful tool in diagnosing early disease and monitoring therapeutic responses. In this review we discuss the clinical utility of emerging and known renal biomarkers in predicting CVD.

RECENT FINDINGS

Prior to adopting a biomarker into routine clinical practice, evidence-based laboratory medicine requires optimal technical and analytical performance, which is a prerequisite to have confidence in the result. Furthermore, an ideal biomarker should have evidence of its utility in predicting clinical, therapeutic and other health outcomes as well as proving its organizational impact and cost-effectiveness. The renal biomarkers that have been associated with CVD include cystatin C as a better marker of glomerular filtration than creatinine, albuminuria, neutrophil gelatinase associated lipocalin, a marker of acute kidney injury, fibroblast growth factor-23 and parathyroid hormone. Only urine albumin has been adopted into routine clinical practice.

SUMMARY

Of all the renal biomarkers, only albumin is clearly associated with CVD. The other biomarkers are earlier in clinical development and the evidence base for their clinical utility needs to be expanded substantially before they can be adopted into routine practice.

Cardiorenal syndrome: new developments in the understanding and pharmacologic management

Cardiorenal syndromes (CRSs) with bidirectional heart-kidney signaling are increasingly being recognized for their association with increased morbidity and mortality. In acute CRS, recognition of the importance of worsening kidney function complicating management of acute decompensated heart failure has led to the examination of this specific outcome in the context of acute heart failure clinical trials. In particular, the role of fluid overload and venous congestion has focused interest in the most effective use of diuretic therapy to relieve symptoms of heart failure while at the same time preserving kidney function. Additionally, many novel vasoactive therapies have been studied in recent years with the hopes of augmenting cardiac function, improving symptoms and patient outcomes, while maintaining or improving kidney function. Similarly, recent advances in our understanding of the pathophysiology of chronic CRS have led to reanalysis of kidney outcomes in pivotal trials in chronic congestive heart failure, and newer trials are including changes in kidney function as well as kidney injury biomarkers as prospectively monitored and adjudicated outcomes. This paper provides an overview of some new developments in the pharmacologic management of acute and chronic CRS, examines several reports that illustrate a key management principle for each subtype, and discusses opportunities for future research.

Role of the NT-proBNP level in the diagnosis of pediatric heart failure and investigation of novel combined diagnostic criteria

The aim of this study was to investigate the modified Ross criteria score and the diagnostic cut-off level for plasmatic amino-terminal pro-brain natriuretic peptide (NT-proBNP) in the diagnosis of pediatric heart failure, by analyzing the receiver operating characteristic (ROC) curve. The plasma NT-proBNP level was measured in 80 children diagnosed with heart failure according to the modified Ross criteria, 80 children with non-cardiogenic dyspnea and 80 healthy children. The NT-proBNP levels were then compared using an F-test. The cut-off score for heart failure in the modified Ross criteria and the diagnostic cut-off level for plasmatic NT-proBNP in pediatric heart failure were determined by ROC curve analysis. The results demonstrated that the NT-proBNP level was markedly increased in 76 of the 80 children with heart failure, and the correlation with the modified Ross criteria was 95%. Based on ROC curve analysis, the diagnosis of pediatric heart failure was most accurate when the modified Ross criteria score was ≥4 and the plasmatic NT-proBNP level was ≥598 ng/l. The NT-proBNP level was normal (0–300 ng/l) in the children with non-cardiogenic dyspnea and the healthy children. Significant differences were observed in the comparison of the three groups (P<0.01). In conclusion, a NT-proBNP level of ≥598 ng/l, combined with a modified Ross criteria score ≥4, is highly diagnostic of heart failure in children.

Neutrophil gelatinase-associated lipocalin as a biomarker of cardiovascular disease: a systematic review

BACKGROUND

Neutrophil gelatinase-associated lipocalin (NGAL) is a biomarker of acute kidney injury (AKI). Recently, elevated NGAL levels have also been reported in heart failure, coronary heart disease, and stroke. Other studies demonstrate that NGAL is upregulated in failing myocardium and in atherosclerotic plaque. Our aim was to synthesize the current evidence on NGAL and cardiovascular disease (CVD), and to clarify the prognostic significance of systemic NGAL levels in CVD.

METHODS

We performed a systematic review to identify experimental and human studies on NGAL and CVD. We excluded articles which specifically dealt with AKI or renal endpoints.

RESULTS

We identified 22 studies, including both animal and human data. NGAL is highly expressed in the heart, both in failing myocardium and myocarditis, and is also expressed in atherosclerotic plaques. Areas of co-localization of NGAL and matrix metalloproteinase (MMP)-9 exhibited increased MMP-9 proteolytic activity. Systemic NGAL levels correlated with renal function and severity of CVD in several, but not all, studies. An association between elevated systemic NGAL levels and clinical outcomes (e.g., death, hospital readmissions) were reported in six CVD studies, but these had limited adjustment for potential confounders.

CONCLUSIONS

There is ample literature to support a putative role of NGAL in the pathophysiology of CVD, but at present there is insufficient data regarding the clinical utility of systemic NGAL levels in the management of CVD. Available evidence regarding NGAL as a predictor of outcomes in CVD is very limited.