Natriuretic peptides for guiding heart failure therapy

Use of natriuretic peptide to guide heart failure therapy represents a promising option. Although natriuretic peptides provide accurate diagnostic and independent incremental prognostic information, their use to gauge and titrate therapy is not yet fully realized.

Natriuretic peptides and therapeutic applications

Since the discovery of atrial natriuretic factor by de Bold et al., there has been tremendous progress in our understanding of the physiologic, diagnostic and therapeutic roles of the natriuretic peptides (NPs) in health and disease. Natriuretic peptides are endogenous hormones that are released by the heart in response to myocardial stretch and overload. Three mammalian NPs have been identified and characterized, including atrial natriuretic peptide (ANP or atrial natriuretic factor), B-type natriuretic peptide (BNP), and C-type natriuretic peptide (CNP). In addition, Dendroaspis natriuretic peptide (DNP) has been isolated from the venom of Dendroaspis angusticeps (the green mamba snake), and urodilatin from human urine. These peptides are structurally similar and they consist of a 17-amino-acid core ring and a cysteine bridge. Both ANP and BNP bind to natriuretic peptide receptor A (NPR-A) that are expressed in the heart and other organs. Activation of NPR-A generates an increase in cyclic guanosine monophosphate, which mediates natriuresis, inhibition of renin and aldosterone, as well as vasorelaxant, anti-fibrotic, anti-hypertrophic, and lusitropic effects. The NP system thus serves as an important compensatory mechanism against neurohumoral activation in heart failure. This provides a strong rationale for the use of exogenous NPs in the management of acutely decompensated heart failure. In this article, the therapeutic applications of NPs in the acute heart failure syndromes are reviewed. Emerging therapeutic agents and areas for future research are discussed.

[Natriuretic peptides: their role in diagnosis and therapy]

Cardiac natriuretic peptide hormones, atrial natriuretic peptide (ANP) and B-type natriuretic peptide (BNP), are synthesized and secreted by the heart, producing several biological effects, such as natriuresis, vasorelaxation and hypotension. During the last decade these peptides, especially BNP, have received increasing attention as potential markers of cardiovascular disease. Their measurements can be used to diagnose heart failure, including diastolic dysfunction, and using them has been shown to save money. BNP levels can enable the differentiation between dyspnoic patients secondary to ventricular dysfunction and subjects with primary respiratory disorders. Moreover, there is good evidence that natriuretic peptides may have a diagnostic role in arterial hypertension, acute coronary syndromes, pulmonary hypertension, some valvular heart disease and some disorders affecting other systems (diabetes or thyroid disorders). In this paper we discuss the clinical utility of assessment of natriuretic peptide hormones in the diagnosis of various clinical conditions and their use as pharmacological agents.

Guanylin peptides and colorectal cancer (CRC)

Agonists of guanylyl-C receptor, such as guanylin/uroguanylin, are correlated not only with the intestinal cell epithelial physiology but also with the colorectal cancer tumorigenesis. Activation of the second intracellular messenger cyclic guanosine monophosphate by guanylyl cyclase-C receptor results in a complex intracellular signalling cascade involving the phosphodiesterase, the ion channels and the protein kinase. After an analytical review of relevant new knowledge, new diagnostic and therapeutic approaches for colorectal cancer are discussed.

Emerging drugs for acute and chronic heart failure: current and future developments

Heart failure continues to be a major public health issue. Although angiotensin-converting enzyme inhibitors and beta-adrenergic blockers have been broadly used as evidence-based therapies in heart failure, morbidity and mortality remains high. Furthermore, treatment for acute decompensated heart failure and diastolic heart failure (or 'heart failure with preserved ejection fraction') is far from perfect. This review provides a broad overview of some of the novel compounds under investigation for the treatment of heart failure. Novel strategies include drugs that aim to alleviate congestion and improve hemodynamics, drugs that preserve renal function, drugs that reduce arterial and myocardial stiffness, drugs that module myocardial contractility, drugs that affect metabolic and hormonal balance, and drugs that act on existing and novel physiologic targets.

Effect of nesiritide infusion duration on renal function in acutely decompensated heart failure patients

BACKGROUND

Nesiritide, a synthetic B-type natriuretic peptide, is used for the treatment of patients with acutely decompensated heart failure. Although nesiritide has been reported to worsen renal function, as reflected by significant elevations in serum creatinine (SCr), the impact of infusion duration on renal function has not been evaluated.

OBJECTIVE

To investigate the effect of nesiritide infusion duration (< 24 h vs > or = 24 h) on worsening renal function in patients with acutely decompensated heart failure.

METHODS

Medical records of hospitalized patients receiving nesiritide were retrospectively reviewed, and 84 consecutive charts of patients with acute decompensated heart failure and available renal function tests were identified for the study. SCr and blood urea nitrogen (BUN) were documented at baseline and during infusion. Worsening renal function was defined as an increase in SCr of 0.5 mg/dL or more or BUN 10 mg/dL or more from baseline.

RESULTS

Univariate analysis showed a significant association between nesiritide infusion duration of 24 hours or more (26.1% vs 2.6%; p = 0.003), high diuretic doses (61.5% vs 32.4%; p = 0.045), and baseline SCr (2.0 +/- 0.8 vs 1.5 +/- 0.7 mg/dL; p = 0.04) with increases in SCr of 0.5 mg/dL or more. However, only infusion duration of 24 hours or more was statistically significant on multivariate analysis, after adjusting for baseline SCr (OR 10.46; 95% CI 1.26 to 86.72; p = 0.03). Longer duration of infusion was also a consistent variable in both univariate and multivariate analysis when elevated BUN was evaluated (34.8 vs 2.6%; p < 0.001 and OR 19.73; 95% CI 2.47 to 157.46; p = 0.005, respectively).

CONCLUSIONS

Nesiritide infusion of 24 hours or more appears to be significantly associated with elevated markers of worsening renal function in patients with acutely decompensated heart failure compared with infusion of less than 24 hours; however, prospective studies are needed to corroborate this finding.

Prevention of Acute Renal Failure

Acute renal failure (ARF) comprises a family of syndromes that is characterized by an abrupt and sustained decrease in the glomerular filtration rate. In the ICU, ARF is most often due to sepsis and other systemic inflammatory states. ARF is common among the critically ill and injured and significantly adds to morbidity and mortality of these patients. Despite many advances in medical technology, the mortality and morbidity of ARF in the ICU continue to remain high and have not improved significantly over the past 2 decades. Primary strategies to prevent ARF still include adequate hydration, maintenance of mean arterial pressure, and minimizing nephrotoxin exposure. Diuretics and dopamine have been shown to be ineffective in the prevention of ARF or improving outcomes once ARF occurs. Increasing insight into mechanisms leading to ARF and the importance of facilitating renal recovery has prompted investigators to evaluate the role of newer therapeutic agents in the prevention of ARF.

Current and novel pharmacological approaches to renal insufficiency in heart failure

Renal insufficiency is becoming an increasingly common and devastating comorbidity in both acute and chronic heart failure settings. Part of the problem is due to the lack of insight into the underlying pathophysiology of salt and water balance leading to the congestive states. This review summarizes our current understanding regarding the cause and consequences of renal insufficiency in patients with heart failure, and addresses some of the limitations of current therapeutic strategies. Based on these limitations, this paper will explore the ongoing efforts to develop novel drug therapeutics to prevent or ameliorate renal impairment in patients with heart failure. These include natriuretic peptides and other vasodilators, adenosine receptor antagonists, and vasopressin receptor antagonists all currently undergoing late-stage clinical trials.

Novel therapeutic directions for the natriuretic peptides in cardiovascular diseases: what's on the horizon

Remarkable advances have occurred since the discovery of ANP. The field of the natriuretic peptides has moved beyond their role as regulators of renal function. Growing evidence has now established the natriuretic peptides as regulators of myocardial structure and function as well as in cardiovascular regulation. Further, they emerge as being products not only of the cardiomyocyte but also of the cardiac fibroblast. Studies in vitro and in vivo have clearly established these cardiac hormones as antihypertrophic and antifibrotic. Further, indications such as cardioprotection for acute myocardial infarction, chronic therapy with oral BNP for hypertension and next generation peptides such as DNP-like peptides for acute heart failure may be in the near future. Novel therapeutic strategies to be tested in clinical trials in humans with cardiovascular disease are clearly on the horizon.

[Natriuretic peptides: anything new in cardiology?]

Twenty-five years after the first publication of the strong natriuretic effect of rat cardiac atria extract, natriuretic peptides play an important part in everyday, not only cardiological, practice. In the current review the authors briefly describe the role of natriuretic peptides (ANP, BNP, and CNP) in clinical practice, concentrating on the possibilities of their therapeutic use. They also summarize their role in the mechanisms of endogenous cardioprotection and regulation of LVH, which is the endpoint of many cardiovascular pathologies.

Cardiovascular and metabolic effects of natriuretic peptides

Natriuretic peptides (NP) are essential in mammals to regulate blood volume and pressure. The functional roles of NP are not limited to natriuresis and diuresis. Several peripheral and central actions of the peptides have been characterized. Studies on transgenic mice have revealed their key function in the regulation of cardiomyocyte growth. Plasma NP levels increase in patients with cardiovascular disorders and heart failure. They represent useful clinical markers for clinicians to diagnose heart diseases. The recent discovery of their potent lipolytic action in adipose tissue is a breakthrough in cardiovascular medicine. This new function of NP in the regulation of lipid metabolism offers interesting questions in the field of obesity, diabetes and cardiovascular diseases. This review will briefly describe the effects of NP on the cardiovascular system and lipid metabolism.

The natriuretic peptide system: kidney and cardiovascular effects

PURPOSE OF REVIEW

The natriuretic peptide (NP) system is primarily an endocrine system that maintains fluid and pressure homeostasis by modulating cardiac and renal function. The physiologic functions of the NP system in healthy humans and in patients with cardiovascular disease are not fully understood. NP levels are elevated in patients with heart failure (HF) and other cardiac diseases; measurement of NPs may be used in the clinical setting to aid diagnosis and prognosis. In addition, synthetic NPs such as nesiritide are available for use in management of patients with acutely decompensated congestive HF.

RECENT FINDINGS

Not only do NPs modulate volume and pressure homeostasis, but they also exert important anti-proliferative, anti-fibrotic effects in the heart. Thus, NPs may prove useful for prevention of remodeling after myocardial infarction and in advanced HF. BNP is emerging as an important biomarker in patients with HF and other cardiovascular diseases, such as pulmonary hypertension and atherosclerotic vascular disease. Elevated NP levels may serve as an early warning system to help to identify patients at high risk for cardiac events. Recombinant human ANP (carperitide) and BNP (nesiritide) are useful for management of acutely decompensated HF; these drugs are also being investigated for myocardial and renal protection in the setting of cardiac surgery and for prevention of cardiac remodeling.

SUMMARY

The clinical application of NPs is expanding rapidly. Recent basic science and clinical research findings continue to improve our understanding of the NP system and guide use of ANP and BNP as biomarkers and as therapeutic agents.

Natriuretic peptides, their receptors, and cyclic guanosine monophosphate-dependent signaling functions

Natriuretic peptides are a family of structurally related but genetically distinct hormones/paracrine factors that regulate blood volume, blood pressure, ventricular hypertrophy, pulmonary hypertension, fat metabolism, and long bone growth. The mammalian members are atrial natriuretic peptide, B-type natriuretic peptide, C-type natriuretic peptide, and possibly osteocrin/musclin. Three single membrane-spanning natriuretic peptide receptors (NPRs) have been identified. Two, NPR-A/GC-A/NPR1 and NPR-B/GC-B/NPR2, are transmembrane guanylyl cyclases, enzymes that catalyze the synthesis of cGMP. One, NPR-C/NPR3, lacks intrinsic enzymatic activity and controls the local concentrations of natriuretic peptides through constitutive receptor-mediated internalization and degradation. Single allele-inactivating mutations in the promoter of human NPR-A are associated with hypertension and heart failure, whereas homozygous inactivating mutations in human NPR-B cause a form of short-limbed dwarfism known as acromesomelic dysplasia type Maroteaux. The physiological effects of natriuretic peptides are elicited through three classes of cGMP binding proteins: cGMP-dependent protein kinases, cGMP-regulated phosphodiesterases, and cyclic nucleotide-gated ion channels. In this comprehensive review, the structure, function, regulation, and biological consequences of natriuretic peptides and their associated signaling proteins are described.

Natriuretic peptides: novel therapeutic targets in heart failure

Since the discovery of the cardiac hormone atrial natriuretic peptide by de Bold and colleagues in 1981, the field of natriuretic peptides has significantly advanced with translation of new knowledge to the clinical practice of heart failure. This new knowledge builds on the importance of cardiorenal mechanisms that contribute to optimal cardiovascular regulation. Recent investigations by our group and others have also established the direct myocardial actions of the natriuretic peptides, broadening their therapeutic potential beyond renal mechanisms. Indeed, a potential therapeutic target is cardiac remodeling and fibrosis based on the unique cardiorenal and humoral protective properties that natriuretic peptides possess. We review new insights into the natriuretic peptide system and specifically focus on the possible role of natriuretic peptides as a new therapeutic strategy to limit cardiac remodeling and fibrosis to delay worsening of cardiac function and the progression of heart failure.

Four peptide hormones' specific decrease (up to 97%) of human prostate carcinoma cells

BACKGROUND

Mortality from prostate cancer remains a significant problem with current treatment(s), with an expected 30 350 deaths from prostate cancer in 2005. Long-acting natriuretic peptide, vessel dilator, kaliuretic peptide and atrial natriuretic peptide have significant anticancer effects in breast and pancreatic adenocarcinomas. Whether these effects are specific and whether they have anticancer effects in prostate adenocarcinoma cells has not been determined.

MATERIALS AND METHODS

These peptide hormones were evaluated to determine if they have specific anticancer effects in human prostate adenocarcinomas.

RESULTS

Dose-response curves revealed a significant (P < 0.05) decrease in human prostate cancer number with each tenfold increase in the concentration from 1 microM to 1000 microM (i.e. 1 mM) of these four peptide hormones. There was a 97.4%, 87%, 88% and 89% (P < 0.001 for each) decrease in prostate cancer cells secondary to vessel dilator, long-acting natriuretic peptide, kaliuretic peptide and atrial natriuretic peptide, respectively, at their 1-mM concentrations within 24 h, without any proliferation in the 3 days following this decrease. These same hormones decreased DNA synthesis from 68% to 89% (P < 0.001). When utilized with their respective antibodies their ability to decrease prostate adenocarcinoma cells or inhibit their DNA synthesis was completely blocked. Western blots revealed that for the first time natriuretic peptide receptors (NPR) A- and C- were present in prostate cancer cells.

CONCLUSIONS

These results indicate that these peptide hormones' anticancer effects are specific. Furthermore, they have very potent effects of eliminating up to 97% of prostate cancer cells within 24 h of treatment.

Natriuretic Peptides and the Dialysis Patient

The natriuretic peptide family consists of four structurally similar, but genetically distinct molecules with pronounced cardiovascular and renal actions. They are counterregulatory hormones playing an important role in fluid volume homeostasis. Atrial natriuretic peptide (ANP) and B-type natriuretic peptide (BNP) cause diuresis, natriuresis, and vasodilatation. C-type natriuretic peptide (CNP) has antimitogenic effects and causes vascular smooth muscle relaxation. Dendroaspis natriuretic peptide (DNP) shares many of the actions of ANP and BNP, but its function in humans is not yet fully understood. Natriuretic peptides have been extensively investigated as biochemical markers of the fluid state. Levels are elevated in disease conditions characterized by fluid overload and are closely related to survival in various cardiac disease states. In the dialysis population, BNP correlates significantly with cardiac function, whereas ANP is sensitive to volume changes during dialysis. However, changes in concentration do not predict achievement of euvolemia, and short half-life, combined with complicated assay techniques, make ANP a less than satisfactory tool for assessing hydration. BNP is a superior prognosticator for risk stratification in dialysis patients, and serial estimations will help in the identification of occult cardiac disease.

The emerging role of natriuretic peptides in the diagnosis and treatment of decompensated heart failure

B-type natriuretic peptide (BNP) is a cardiac neurohormone and is released as prepro BNP and then enzymatically cleaved to the N-terminal proBNP (NT-proBNP) and BNP upon ventricular myocyte stretch. Blood measurements of BNP and NT-proBNP have been used to identify patients with heart failure (HF). Clinical considerations for these tests include their half-lives in plasma, dependence on renal function for clearance, interpretation of their units of measure, and the rapid availability of the test results. The BNP assay is currently used as a diagnostic and prognostic aid in HF. In general, a BNP level below 100 pg/mL excludes acutely decompensated HF. Recombinant, human BNP (nesiritide) is an approved intravenous treatment for acute, decompensated HF. This paper reviews the literature concerning the use of this peptide as a diagnostic test and as an intravenous therapy.

[Acute dyspnea in the emergency room: the utility of troponin, natriuretic, procalcitonin and D-dimers]

In emergency, some "low cost" biological tests are too often systematically performed while others are not prescribed because they are considered "too expensive". Good practices for biological testing are in fact the real means for saving money. Here, in order to help for defining those good practices, we review emergency medical approach and, as an example, specify findings concerning the clinical utility of key blood analyses in patients with acute dyspnea. Emergency laboratory testing is usefull when it contributes to establish the diagnosis or to evaluate comorbidity or to stratify disease severity. In a given emergency context, clinical utility must be anticipated according to a bayesian approach with an estimation of the post-test probabilities using the likelihood ratios (estimated from literature) and the pretest probabilities (established by examination at the bedside). The likelihood ratio is the best criterion for diagnostic accuracy of a biological test. According to this criterion, troponin, natriuretic peptides, procalcitonin and D-dimers are four "costly" markers but which can significantly contribute to the etiologic diagnosis of an acute dyspnea. Troponin, natriuretic peptides and procalcitonin are also prognostic markers and are valuable parameters for stratifying disease severity according to their initial value and their plasmatic kinetic during the clinical course of the disease. In conclusion, it is not only the cost of the test but overall the potential impact of its result on the management of the patient's care which makes the decision of performing the test or not.