A. Clerico

Circulating levels of cardiac natriuretic peptides (ANP and BNP) measured by highly sensitive and specific immunoradiometric assays in normal subjects and in patients with different degrees of heart failure

Plasma atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) levels increase in patients with heart failure with the progression of clinical symptoms and with the deterioration of hemodynamics; consequently, assay methods for these peptides may be useful in the follow-up of cardiac patients. Non-competitive immunoradiometric assay (IRMA) methods for ANP or BNP do not generally require preliminary extraction and/or purification of the plasma sample, and so may be more suitable than competitive immunoradiometric assay (RIA) methods for the routinary assay of plasma peptide concentrations. We evaluated the analytical characteristics and clinical usefulness of two IRMAs for plasma ANP and BNP, to verify whether these methods may be considered suitable for the follow-up of patients with heart failure. Both methods are based on the solid-phase sandwich IRMA system, which uses two monoclonal antibodies prepared against two sterically remote epitopes of peptide molecule; the first antibody was coated on the beads solid-phase and the second was radiolabeled with 125I. Blood samples were collected from a brachial vein in ice-chilled disposable polypropylene tubes containing aprotinin and EDTA after the patient had rested for at least 20 min in the recumbent position. Plasma samples were immediately separated by centrifugation and stored at −20 C until assay. The IRMA methods showed a better sensitivity and a wider working range sensitivity (about 2 ng/l) than those of RIA methods. Moreover, the normal range found with these methods (ANP= 16.1±8.6 ng/l, 5.2±2.8 pmol/l, BNP= 8.6±8.2 ng/l, 2.5±2.4 pmol/l) was similar to that generally reported using the most accurate methods, such as the other IRMAs or RIAs, using a preliminary extraction and purification of plasma samples with chromatographic procedures. Our results obtained in patients with different degrees of heart failure indicate that plasma ANP and BNP increase with the progression of clinical symptoms (NYHA class) (ANOVA p<0.0001). Indeed, circulating levels of ANP (R=− 0.701, no.=86) and BNP (R=−0.745, no.=55) were significantly (p<0.0001) and negatively correlated with the left ventricular ejection fraction values. Furthermore, a close curvilinear regression (R= 0.960, no.= 215) was found between ANP and BNP values, because plasma BNP progressively increases more than plasma ANP in patients with different stages of heart failure. In conclusion, IRMA methods are preferable for the measurement of plasma ANP and BNP for experimental studies and routine assay because they are more practicable, sensitive and accurate than RIA procedures. Finally, BNP assay appears to be better than ANP for discriminating between normal subjects and patients with different degrees of heart failure.

Endothelial nitric oxide synthase gene polymorphisms and risk of coronary artery disease

BACKGROUND Endothelial nitric oxide synthase (eNOS) could be a candidate gene for coronary artery disease (CAD). This study investigated the relationship of the eNOS Glu(298)-->Asp and T(786)-->C polymorphisms with the presence and severity of CAD in the Italian population. METHODS We enrolled 415 unrelated individuals who underwent coronary angiography. The severity of CAD was expressed by means of the Duke score. The eNOS Glu(298)-->Asp and T(786)-->C variants were analyzed by PCR. RESULTS There was significant linkage disequilibrium between the two eNOS polymorphisms (P <0.0001). Both variants were significantly associated with the occurrence and severity of CAD (P = 0.01 and 0.004 for Glu(298)-->Asp and T(786)-->C, respectively). The risk of CAD was increased among individuals homozygous for the C allele of the T(786)-->C polymorphism compared with individuals homozygous for the T allele (odds ratio = 2.5; P <0.01) and was independent of the other common risk factors (P = 0.04). Moreover, individuals with both the Asp/Asp genotype of the Glu(298)-->Asp polymorphism and at least one C allele of the T(786)-->C variant in the promoter region of the eNOS gene had an increased risk of CAD (odds ratio = 4.0; P <0.001) and a significantly higher mean Duke score (26.2 +/- 2.9 vs 45.2 +/- 3.7; P = 0.002) compared with individuals with the TT genotype and the Glu allele. CONCLUSIONS The present study provides evidence that the Glu(298)-->Asp and T(786)-->C polymorphisms of the eNOS gene are associated with the presence and severity of angiographically defined CAD in the Italian population and that those individuals carrying both eNOS variants simultaneously might have a higher risk of developing CAD.

Thirty years of the heart as an endocrine organ: physiological role and clinical utility of cardiac natriuretic hormones

Thirty years ago, De Bold et al. (20) reported that atrial extracts contain some biologically active peptides, which promote a rapid and massive diuresis and natriuresis when injected in rats. It is now clear that the heart also exerts an endocrine function and in this way plays a key role in the regulation of cardiovascular and renal systems. The aim of this review is to discuss some recent insights and still-debated findings regarding the cardiac natriuretic hormones (CNHs) produced and secreted by cardiomyocytes (i.e., atrial natriuretic peptide and B-type natriuretic peptide). The functional status of the CNH system depends not only on the production/secretion of CNHs by cardiomyocytes but also on both the peripheral activation of circulating inactive precursor of natriuretic hormones and the transduction of the hormone signal by specific receptors. In this review, we will discuss the data supporting the hypothesis that the production and secretion of CNHs is the result of a complex integration among mechanical, chemical, hemodynamic, humoral, ischemic, and inflammatory inputs. The cross talk among endocrine function, adipose tissue, and sex steroid hormones will be discussed more in detail, considering the clinically relevant relationships linking together cardiovascular risk, sex, and body fat development and distribution. Finally, we will review the pathophysiological role and the clinical relevance of both peripheral maturation of the precursor of B-type natriuretic peptides and hormone signal transduction.

The Circulating Levels of Cardiac Natriuretic Hormones in Healthy Adults: Effects of Age and Sex

Abstract In order to study the relationships between sex hormones, aging, and circulating levels of cardiac natriuretic peptides and to define reference values for atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) assays, we measured the plasma levels of cardiac natriuretic peptides in a large group of healthy adults divided according to age and sex. We studied 216 healthy subjects of both sexes (109 men and 107 women) with age ranging from 20 to 77 years (mean 43.2±14.8 years). All subjects were non-obese and had normal arterial blood pressure; they were free from acute diseases, including asymptomatic heart disease. Highly sensitive and specific IRMA methods were used to measure plasma ANP and BNP. The mean ANP value in healthy adult subjects of both sexes was 17.8±10.9 pg/ml with no significant difference between men (16.7±10.0 pg/ml) and women (18.8±11.7 pg/ml). The mean BNP value in healthy adult subjects of both sexes was 9.9±9.0 pg/ml with a significant difference (p<0.0001) between men (7.7±7.1 pg/ml) and women (12.2±10.2 pg/ml). There was a weak linear relationship between age and either ANP (r=0.350, p<0.0001) or BNP (r=0.254, p=0.0002) values. When the circulating levels of cardiac natriuretic hormones, and age and sex were analyzed by multiple stepwise regression analysis, both age and sex significantly and independently contributed to the regression. Our study indicates independent positive effects of aging and female sex hormones on ANP and BNP levels in healthy adult subjects. These effects should be taken into account in the calculation of appropriate reference values for cardiac natriuretic hormones.

Evidence for association of a common variant of the endothelial nitric oxide synthase gene (Glu298→Asp polymorphism) to the presence, extent, and severity of coronary artery disease

Background: Genetic variants of endothelial nitric oxide synthase (eNOS) could influence individual susceptibility to coronary artery disease. Objective: To assess whether Glu298→Asp polymorphism of the eNOS gene is associated with the occurrence and severity of angiographically defined coronary artery disease in the Italian population. Methods: Polymerase chain reaction/restriction fragment length polymorphism analysis was done to detect the Glu298→Asp variant of the eNOS gene in 201 patients with coronary artery disease and 114 controls. The severity of coronary artery disease was expressed by the number of affected vessels and by the Duke scoring system. Results: The frequencies of the eNOS Glu/Glu, Glu/Asp, and Asp/Asp genotypes in the coronary artery disease group were significantly different from those of controls (45.3%, 38.8%, and 15.9% v 42.1%, 51.8%, and 6.1%, respectively; χ2 = 8.589, p = 0.0136). In comparison with subjects who had a Glu298 allele in the eNOS gene, the risk of coronary artery disease was increased among Asp/Asp carriers (odds ratio 2.9, 95% confidence interval 1.2 to 6.8, p = 0.01) and was independent of the other common risk factors (p = 0.04). There was a significant association between the eNOS Glu298→Asp variant and both the number of stenosed vessels (mean (SEM), 2.3 (0.1) for Asp/Asp v 1.9 (0.1) and 1.8 (0.1) for Glu/Glu and Glu/Asp, respectively; p = 0.01) and the Duke score (56.1 (3.1) for Asp/Asp v 46.7 (2.0) and 46.1 (1.9) for Glu/Glu and Glu/Asp, respectively; p = 0.02). Conclusions: Glu298→Asp polymorphism of the eNOS gene appears to be associated with the presence, extent, and severity of angiographically assessed coronary artery disease.

Neutrophil gelatinase-associated lipocalin (NGAL) as biomarker of acute kidney injury: a review of the laboratory characteristics and clinical evidences

Abstract Acute kidney injury (AKI) is a common and serious condition, currently diagnosed by functional biomarkers, such as serum creatinine measurements. Unfortunately, creatinine increase is a delayed and unreliable indicator of AKI. The lack of early biomarkers of structural kidney injury has hampered our ability to translate promising experimental therapies to human AKI. The recent discovery, translation and validation of neutrophil gelatinase-associated lipocalin (NGAL), possibly the most promising novel AKI biomarker, is reviewed here. NGAL may be measured by several methods both in plasma and urine for the early diagnosis of AKI and for the prediction of clinical outcomes, such as dialysis requirement and mortality, in several common clinical scenarios, including in the intensive care unit, cardiac surgery and renal damage due the exposition to toxic agent and drugs, and renal transplantation. Furthermore, the predictive properties of NGAL, may play a critical role in expediting the drug development process. A systematic review of literature data indicates that further studies are necessary to establish accurate reference population values according to age, gender and ethnicity, as well as reliable and specific decisional values concerning the more common clinical settings related to AKI. Furthermore, proper randomized clinical trials on renal and systemic outcomes comparing the use of NGAL vs. standard clinical practice are still lacking and accurate cost-benefit and/or cost-utility analyses for NGAL as biomarker of AKI are also needed. However, it is important to note that NGAL, in the absence of diagnostic increases in serum creatinine, is able to detect some patients affected by subclinical AKI who have an increased risk of adverse outcomes. These results also suggest that the concept and definition of AKI might need to be reassessed.

Analytical performance and diagnostic accuracy of a fully-automated electrochemiluminescent assay for the N-terminal fragment of the pro-peptide of brain natriuretic peptide in patients with cardiomyopathy: comparison with immunoradiometric assay methods for brain natriuretic peptide and atrial natriuretic peptide

Abstract We evaluated the analytical performance of a fully-automated electrochemiluminescence “sandwich” immunoassay method for the N-terminal fragment of the pro-peptide of brain natriuretic peptide (BNP). We then compared the diagnostic accuracy of this method in discriminating between normal subjects and patients with cardiomyopathy with that found with two previously described immunoradiometric assay methods for the assay of atrial natriuretic peptide (ANP) and BNP. We studied 193 consecutive patients (mean age 64.4±12.3 years, range 20–89 years, including 56 women and 137 men) with chronic cardiomyopathy and a group of 85 healthy subjects (mean age 52.3±12.0 years, 42 women and 43 men, range 20–79 years). N-terminal fragment of proBNP1–76 (NT-proBNP) was measured with a fully-automated “sandwich” electrochemiluminescence method using an Elecsys® 2010 analyzer, while ANP and BNP were measured with immunoradiometric assay methods. The low detection limit of the NTproBNP assay was 4.2 pg/ml (0.50 pmol/l), while the functional sensitivity was 22 pg/ml (2.60 pmol/l) with a working range (imprecision profile ≤ 10% coefficient of variation) extended up to about 30 000 pg/ml (3540 pmol/l). Healthy women (64.3±41.6 pg/ml, 7.59±4.91 pmol/l) showed significantly higher values than men (46.9±30.9 pg/ml, 5.53±3.64 pmol/l, p=0.0118). Moreover, age and sex were significantly and independently related to the NT-proBNP values in healthy subjects, as assessed by a multiple linear regression analysis (R=0.389, F-value=7.316, P-value=0.0012). As expected, the NT-proBNP values of patients with cardiomyopathy were significantly higher than those of normal subjects and progressively increased with the severity of heart failure. The respective diagnostic accuracy of the ANP, BNP and NT-proBNP assays in discriminating between the group of normal subjects and that of patients with cardiomyopathy was tested by the response operating characteristic curve analysis. Our data indicated that the NT-proBNP assay is significantly better than either of the ANP or BNP immunoradiometric assays in discriminating affected patients from healthy subjects, especially when only patients with mild disease severity (New York Heart Association class I and II) are considered.

Endothelial Function and Carotid Intima-Media Thickness in Young Healthy Subjects Among Endothelial Nitric Oxide Synthase Glu298→Asp and T−786→C Polymorphisms

Background and Purpose— To assess the role of the endothelial nitric oxide synthase (eNOS) gene variants as risk factors for early atherosclerosis, we sought to investigate whether two polymorphisms located in the exon 7 (Glu298→Asp) and in the promoter region (T−786→C) of the eNOS gene were associated with functional changes in the endothelium and carotid intima-media thickness (IMT). Methods— Endothelium-dependent flow-mediated brachial artery dilation (FMD), endothelium-independent dilation response to glyceryl trinitrate (GTN), and carotid IMT were assessed by high-resolution ultrasound in 118 healthy young nonsmoker subjects (30.1±0.5 years) genotyped for the eNOS Glu298→Asp and T−786→C polymorphisms. Results— Carotid IMT was inversely related to FMD by univariate analysis (r= −0.28, P= 0.002) and after adjustment for possible confounders in all the subjects (P< 0.01). Asp homozygotes had a significantly lower FMD than Glu carriers (Glu/Glu: 15.0%±1.0%, Glu/Asp: 13.3%±0.7%, Asp/Asp: 9.6%±1.6%; P= 0.005), whereas FMD was unaffected by the T−786→C variant. Neither the Glu298→Asp nor the T−786→C polymorphisms influenced the GTN-mediated dilation. With respect to Glu carriers, Asp/Asp genotype displayed a significantly greater carotid IMT (Glu/Glu: 0.37±0.01 mm, Glu/Asp: 0.35±0.01 mm, Asp/Asp: 0.45±0.03 mm; P= 0.0002) and significant correlations between carotid IMT and FMD (r= −0.48, P= 0.04) and between carotid IMT and resting brachial artery diameter (r= 0.70, P= 0.001). No difference in IMT was found across the T−786→C genotypes. By multivariate regression analysis, Asp/Asp genotype was the only significant and independent predictor of flow-mediated brachial artery dilation (FMD) (P=0.04) and carotid intima-media thickness (IMT) (P=0.006). Conclusions— The eNOS Glu298→Asp polymorphism may be related to early atherogenesis.

Cardiac natriuretic hormones, neuro-hormones, thyroid hormones and cytokines in normal subjects and patients with heart failure

Abstract The derangement of neuro-endocrine control of circulation influences both disease evolution and response to treatment in patients with heart failure, but little data are available about the complex relationships between the degree of neuro-hormonal activation and clinical severity. We studied the relationships between cardiac natriuretic hormones (CNHs) and several neuro-hormones and immunological markers in a prospective cohort of 105 consecutive patients with cardiomyopathy (77 men and 28 women, mean age 66.7±12.4 years, range 33–89 years). We assayed the circulating levels of CNHs (atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP)), plasma renin activity (PRA), aldosterone, cortisol, adrenaline, noradrenaline, thyroid hormones and thyroid stimulating hormone (TSH), tumour necrosis factor-α (TNF-α) and interleukin-6 (IL-6). The concentrations of all CNHs and neuro-hormones were higher in patients with heart failure compared to normal subjects, except for free triiodothyronine (FT3), which was below normal values. ANP was positively related to NYHA class, IL-6, adrenaline, noradrenaline and cortisol, while negatively with ejection fraction and FT3. BNP was positively related to age, NYHA class, IL-6, TNF-α, adrenaline, noradrenaline and cortisol, while negatively with ejection fraction and FT3. A stepwise multiple linear regression indicated that plasma ANP depended only on ejection fraction, adrenaline and noradrenaline values, while for plasma BNP variation NYHA class contributed too. Our data confirm a progressive activation of hormonal and immunological systems in patients with heart failure. Furthermore, CNH circulating levels in heart failure are affected not only by cardiac function and disease severity, but also by activation of neuro-hormonal and stress-related cytokine systems, as well as by the thyroid hormones, even on usual medical treatment.

Genetic instability and atherosclerosis : Can somatic mutations account for the development of cardiovascular diseases?

Several observations suggest that cancer and atherosclerosis may entail fundamentally common biological mechanisms. The accumulation of lipids and the proliferation of smooth muscle cells (SMCs) are the main histological features of sclerotic plaque formation. The most prominent theory concerning the pathophysiological mechanisms of atherosclerotic plaque formation is the “inflammatory response to injury” hypothesis, which states that SMC proliferation is an inflammation‐fibroproliferative reaction to different insults to the artery wall. However, recent evidence suggests that alterations at the DNA level may contribute significantly to the development of the disease. In accordance with these findings, the “monoclonal” hypothesis of atherosclerosis has been suggested. This hypothesis proposes that atherosclerosis begins as a mutation or viral infection, transforming a single, isolated smooth muscle cell into the progenitor of a proliferative clone, as seen in carcinogenesis. Studies of DNA damage in atherosclerotic tissues are lacking. Biological evidence for the hypothesis that cancer and atherosclerosis may share pathological mechanisms is discussed, emphasizing the need to perform studies investigating the involvement of somatic mutations in heart diseases. Environ. Mol. Mutagen. 35:265–269, 2000