Michele Emdin

Gamma-Glutamyltransferase, Atherosclerosis, and Cardiovascular Disease Triggering Oxidative Stress Within the Plaque

The serum determination of gamma-glutamyltransferase (γ-GT) activity is a low-cost, highly sensitive and accurate, and frequently used laboratory test. Although it is considered to be an index of hepatobiliary dysfunction and alcohol abuse,1 recent epidemiology and pathology studies have suggested its independent role in the pathogenesis and clinical evolution of cardiovascular diseases brought on by atherosclerosis.1,2 Article p 2130 The prospective study by Ruttman and colleagues in 163 944 Austrian adults studied for 17 years shows that γ-GT is independently associated with cardiovascular mortality.3 Serum γ-GT activity had a prognostic impact on fatal events of chronic forms of coronary heart disease, congestive heart failure, and ischemic or hemorrhagic stroke. This was found to be true in both sexes, with a clear dose-response relationship, and with a stronger prognostic significance of γ-GT in younger participants. These findings from a large unselected cohort unequivocally confirm previous observations that γ-GT is associated with overall mortality and cardiovascular events, in both unselected populations4–7 and patients with ascertained coronary artery disease, independent of all confounders including liver function and alcohol use.8,9 γ-GT is the enzyme responsible for the extracellular catabolism of glutathione (GSH, γ-glutamyl-cisteinyl-glycine), the main thiol intracellular antioxidant agent in mammalian cells.1 It is present, linked through a small lipophilic sequence of its larger subunit, on the cell surface membrane of most cell types; although the same protein is produced in all tissues, differences in the sugar moieties allow that only the liver γ-GT is detectable in serum.10 Most serum γ-GT is bound to carriers, such as α- and β-lipoproteins and albumin.1 This association is likely to occur within hepatocytes, before γ-GT releases in serum, through still-unknown mechanisms. Serum γ-GT activity is affected by genetic and environmental factors, with heritability estimated at 0.52.11 Within its …

Predictive value of elevated neutrophil–lymphocyte ratio on cardiac mortality in patients with stable coronary artery disease

BACKGROUND An association between white blood cell count (WBC), severity of coronary artery disease (CAD) and survival has been described in patients with acute coronary syndrome. Our aim was to analyze the predictive ability for cardiac events of differential WBC, which is still not well characterized, against established risk factors in angiographically proven CAD patients. METHODS We prospectively evaluated complete blood count, biomarkers of inflammation [(C-reactive protein (CRP) and serum iron (SI)], glucose/lipid metabolism [(fasting glucose (FG), total, high-density lipoprotein (HDL) and low-density lipoprotein cholesterol] and established risk factors in 422 consecutive ischemic patients with angiographically documented stable CAD. On a 3-year follow-up, cardiac death and non-fatal myocardial infarction (MI) were considered as end-points. RESULTS At multivariate analysis neutrophil to lymphocyte ratio (N/L) emerged as independent predictor of cardiac death (HR 8.13; p=0.02) together with CRP, left ventricular ejection fraction (LVEF), FG, HDL and SI. CRP, LVEF, and HDL showed an independent prognostic value for cardiac death and non-fatal MI. Event-free survival according to N/L tertiles was 99% for the first tertile (1.23+/-0.26), 96.5% for the second (2.05+/-0.29), and 88.8% for the third one (5.19+/-3.81). CONCLUSIONS N/L is an independent predictor of cardiac mortality in stable CAD patients.

Hyperinsulinemia and Autonomic Nervous System Dysfunction in Obesity Effects of Weight Loss

Background —Because hyperinsulinemia acutely stimulates adrenergic activity, it has been postulated that chronic hyperinsulinemia may lead to enhanced sympathetic tone and cardiovascular risk. Methods and Results —In 21 obese (body mass index, 35±1 kg/m2) and 17 lean subjects, we measured resting cardiac output (by 2-dimensional echocardiography), plasma concentrations and timed (diurnal versus nocturnal) urinary excretion of catecholamines, and 24-hour heart rate variability (by spectral analysis of ECG). In the obese versus lean subjects, cardiac output was increased by 22% (P <0.03), and the nocturnal drop in urinary norepinephrine output was blunted (P =0.01). Spectral power in the low-frequency range was depressed throughout 24 hours (P <0.04). During the afternoon and early night, ie, the postprandial phase, high-frequency power was lower, heart rate was higher; and the ratio of low to high frequency, an index of sympathovagal balance, was increased in direct proportion to the degree of hyperinsulinemia independent of body mass index (partial r =0.43, P =0.01). In 9 obese subjects who lost 10% to 18% of their body weight, cardiac output decreased and low-frequency power returned toward normal (P <0.05). Conclusions —In free-living subjects with uncomplicated obesity, chronic hyperinsulinemia is associated with a high-output, low-resistance hemodynamic state, persistent baroreflex downregulation, and episodic (postprandial) sympathetic dominance. Reversal of these changes by weight loss suggests a causal role for insulin.

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.

Human Atherosclerotic Plaques Contain Gamma-Glutamyl Transpeptidase Enzyme Activity

During the last decade, growing evidence has shown that serum gamma-glutamyl transpeptidase (GGT) is an independent prognostic marker for cardiac death and reinfarction, both in unselected populations and in patients with coronary artery disease. Clinical and epidemiological evidence indicates that the prognostic value of GGT is largely independent of other risk factors for cardiovascular disease and alcohol consumption. The catalytic activity of GGT, which is present on the surface of cell membranes and in serum, is …

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.

γ-Glutamyltransferase activity in human atherosclerotic plaques—Biochemical similarities with the circulating enzyme

BACKGROUND AND PURPOSE Serum gamma-glutamyltransferase (GGT) activity has been identified as a predictor of complications of atherosclerosis, with a prognostic value for cardiovascular diseases and stroke. Human atherosclerotic lesions contain active GGT, which can give rise to pro-oxidant molecular species; thus a direct contribution of GGT to atherosclerosis progression is conceivable. The relationship between plaque and serum GGT is however unclear. METHODS AND RESULTS Human carotid plaques obtained from 18 consecutive patients undergoing carotid endoarteriectomy were analyzed, of which 6 were used for anion exchange and gel filtration chromatography/western blot studies, 7 for beta-lipoprotein precipitation, and 5 for RNA extraction and determination of low molecular weight thiols. Mean GGT activity in crude plaque homogenates was 60.9+/-21.5 (S.D.) mU/g tissue. The characteristics of GGT activity were compared in plaque homogenates and in serum obtained from controls (healthy blood donors). The methods employed (anion exchange and gel chromatography, western blot) showed the presence in plaque homogenates of two distinct complexes containing GGT activity, one of which comparable with plasma LDL/GGT complexes. Accordingly, precipitation of beta-lipoproteins from plaque homogenates resulted in removal of GGT activity. RT-PCR indicated in plaques the presence of GGT mRNA transcribed from GGT-I gene. Analysis of plaque extracts also revealed the presence of enzyme product cysteinyl-glycine both as free and protein-bound form, confirming that GGT-dependent pro-oxidant reactions may occur within the plaque environment. CONCLUSIONS The results obtained suggest the presence in plaques of a serum-like GGT protein, indicating that a direct contribution of serum GGT to enzyme activity found within atherosclerotic lesions is possible. Data also indicate the occurrence of GGT-mediated redox reactions within plaque environment, which might influence plaque progression.

Metabolic exercise test data combined with cardiac and kidney indexes, the MECKI score: A multiparametric approach to heart failure prognosis

OBJECTIVES We built and validated a new heart failure (HF) prognostic model which integrates cardiopulmonary exercise test (CPET) parameters with easy-to-obtain clinical, laboratory, and echocardiographic variables. BACKGROUND HF prognostication is a challenging medical judgment, constrained by a magnitude of uncertainty. METHODS Our risk model was derived from a cohort of 2716 systolic HF patients followed in 13 Italian centers. Median follow up was 1041days (range 4-5185). Cox proportional hazard regression analysis with stepwise selection of variables was used, followed by cross-validation procedure. The study end-point was a composite of cardiovascular death and urgent heart transplant. RESULTS Six variables (hemoglobin, Na(+), kidney function by means of MDRD, left ventricle ejection fraction [echocardiography], peak oxygen consumption [% pred] and VE/VCO2 slope) out of the several evaluated resulted independently related to prognosis. A score was built from Metabolic Exercise Cardiac Kidney Indexes, the MECKI score, which identified the risk of study end-point with AUC values of 0.804 (0.754-0.852) at 1year, 0.789 (0.750-0.828) at 2years, 0.762 (0.726-0.799) at 3years and 0.760 (0.724-0.796) at 4years. CONCLUSIONS This is the first large-scale multicenter study where a prognostic score, the MECKI score, has been built for systolic HF patients considering CPET data combined with clinical, laboratory and echocardiographic measurements. In the present population, the MECKI score has been successfully validated, performing very high AUC.

THE SIGNIFICANCE OF SERUM GAMMA-GLUTAMYLTRANSFERASE IN CARDIOVASCULAR DISEASES

Abstract Since early after the introduction of serum γ-glutamyltransferase (GGT) in clinical practice as a reliable and widely employed laboratory test, epidemiological and prospective studies have repeatedly shown that this activity possesses a prognostic value for morbidity and mortality. The association is independent of possibly concomitant conditions of liver disease, and notably, a significant independent correlation of serum GGT exists with the occurrence of cardiovascular diseases (myocardial infarction, stroke). Experimental work has documented that active GGT is present in atherosclerotic plaques of coronary as well as in cerebral arteries. These findings, and the recently recognized functions of GGT in the generation of reactive oxygen species, indicate that serum GGT represents a true marker of cardiovascular diseases and underlying atherosclerosis. Further insights into potential therapeutic interest will probably be derived from studies investigating the origin of GGT activity in plaque tissue.

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.