Effect of angiotensin-converting enzyme inhibition on plasma brain natriuretic peptide levels in patients with heart failure

Radioimmunometric assay of natriuretic peptide type-B (BNP) in heart failure

The aim of this study was to assess the value of the radioimmunometric determination of natriuretic peptide type-B (brain natriuretic peptide, BNP) in the diagnosis and prognosis of heart failure, and to study the association between BNP and the clinical, analytical and echocardiographic variables associated with the evolution of heart failure. The study group included 169 patients (74 women and 95 men; mean, 66 years) with heart failure of different causes, admitted consecutively to our hospital. BNP levels were measured with a radioimmunometric assay (Shionora BNP Cis ) after day 3 of admission. Patients were also studied by echocardiography. A significant association between the cause of heart failure and the BNP concentration was found (patients with ischaemic disease had the highest BNP values). Systolic function was worse in patients with ischaemic disease or dilated cardiomyopathy. High BNP values were also associated with advanced functional class and male sex. Plasma creatinine correlated positively with plasma BNP. However, we found no significant association with the other clinical variables evaluated. Of the echocardiographic variables analysed, BNP correlated positively with the ventricular diameter and pulmonary artery systolic pressure, and inversely with the shortening fraction; patients with severely impaired systolic function had the highest BNP values. It can be concluded that BNP levels (by radioimmunometric assay) are increased in patients with heart failure, and increase in relation to left ventricular dysfunction and the severity of heart failure. The strong independent association of plasma BNP with the left ventricular ejection fraction, its stability and the low cost of measurement suggest that plasma BNP assay could become a routine test. BNP assay could be included as an important factor in clinical and therapeutic decision making, as it complements the information provided by other variables used in the diagnosis of heart failure.

Ventricular production of natriuretic peptides and ventricular structural remodeling in hypertensive heart failure

OBJECTIVES

Brain natriuretic peptide (BNP) is a strong predictor of left ventricular (LV) hypertrophy (LVH) and dysfunction. However, our recent studies suggested that LVH is not necessarily associated with enhanced production of BNP in hypertension. This study aimed to clarify the relation of the characteristics of hypertrophy with the degree of gene expression of BNP in the developmental process of hypertensive heart failure.

METHODS

Serial changes in LV geometry, histology and atrial natriuretic peptide (ANP) and BNP mRNA levels, were assessed in a hypertensive heart failure model using Dahl salt-sensitive rats (n = 24). We further studied effects of alpha1-receptor antagonist (doxazosin: 1 mg/kg per day, n = 5) and angiotensin II type 1 receptor (AT1R) antagonist (candesartan cilexetil: 1 mg/kg per day, n = 5).

RESULTS

The BNP mRNA level was not elevated at the compensatory hypertrophic stage when ANP mRNA level was elevated. BNP mRNA level was increased with further progression of hypertrophy and development of fibrosis. AT1R blockade prevented such fibrosis and further progression of hypertrophy with normalization of BNP mRNA levels. Compensatory hypertrophy was not suppressed; therefore, ANP mRNA level, although decreased, was still beyond the normal level. The alpha1-receptor blockade slightly attenuated LV hypertrophy with a slight decrease in ANP mRNA levels. LV fibrosis was not prevented, and the BNP mRNA level was not decreased.

CONCLUSIONS

BNP gene expression is not enhanced by initial compensatory hypertrophy, but is enhanced by LV fibrosis and late stage progression of hypertrophy dependent on AT1R-mediated signaling pathway.

Acute hyperglycaemia causes elevation in plasma atrial natriuretic peptide concentrations in Type 1 diabetes mellitus

AIMS

To examine the effect of acute hyperglycaemia on atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) concentrations in Type 1 diabetes.

METHODS

The study was two limb, randomized, and single-blind. Eight Type 1 diabetes subjects were clamped at euglycaemia by intravenous infusion of insulin. When euglycaemia was established, the insulin infusion rate was left unaltered for the remainder of the protocol, and an intravenous infusion of either 500 ml 0.9% saline or 500 ml 10% dextrose was administered over 1 h. Blood was collected for estimation of plasma glucose, ANP and BNP concentrations at 30 min intervals for 2 h from the start of the infusion period. One week later, each subject received the alternate infusion. Results are expressed as mean +/- standard deviation, and were analysed by ANOVA.

RESULTS

Baseline plasma glucose (P = 0.8), ANP (P = 0.8) and BNP (P = 0.8) concentrations were similar on the study days. Plasma glucose rose with dextrose (6.1 + 0.5-15.1 + 2.8 mmol/l, P = 0.9). Plasma ANP concentrations were unaltered by saline infusion (76.5 +/- 14.7-77.7 +/- 15.2 pg/ml, P = 0.9), but increased with dextrose infusion (79 +/- 14-134 +/- 17.1 pg/ml, P < 0.0001), and were higher with dextrose than saline infusion (P < 0.0001). Plasma concentrations of BNP were not significantly altered by infusion of either dextrose (5.1 +/- 3.9-9.3 +/- 5.4 pg/ml, P = 0.63) or saline (4.3 +/- 3.5-6 +/- 5.2 pg/ml, P = 0.84).

CONCLUSIONS

Plasma concentrations of ANP, but not BNP, rise in response to acute hyperglycaemia in Type 1 diabetes.

Combined neutral endopeptidase and angiotensin-converting enzyme inhibition in heart failure: role of natriuretic peptides and angiotensin II

We examined for the first time the specific roles of angiotensin II and the natriuretic peptides during inhibition of angiotensin-converting enzyme (captopril, 25 mg bolus + 6 mg/3 h infusion) and endopeptidase 24.11 (SCH32615, 5 mg/kg bolus + 3 mg/kg/3 h infusion), both separately and in combination, in eight sheep with pacing-induced heart failure. Plasma atrial and brain natriuretic peptide levels were similarly increased by SCH32615 and to a lesser extent during combined inhibition but decreased with captopril. Captopril and combined inhibition induced identical increases in plasma renin activity and reductions in angiotensin II, whereas neither was changed by SCH32615 alone. Mean arterial pressure and peripheral resistance decreased during SCH32615 and further still during captopril and combined treatment. Left atrial pressure was reduced to a similar extent by SCH32615 and captopril alone and reduced further by combined inhibition. Cardiac output increased during all treatments. Urine volume and sodium excretion were significantly increased during SCH32615 and combined inhibition. Creatinine clearance increased during SCH32615, decreased during captopril, and was maintained during combined treatment. In conclusion, compared with captopril alone, cotreatment with an endopeptidase 24.11 inhibitor further improved filling pressures and induced a diuresis and natriuresis with preservation of renal glomerular filtration.

Effect of BNP on renal hemodynamics, tubular function and vasoactive hormones in humans

The effect of a continuous infusion of human brain natriuretic peptide (BNP) was studied in 48 healthy men. The study was randomized, placebo controlled, and single blind. BNP was given in doses of 1, 2, or 4 pmol.kg-1.min-1 for 60 min, and peak values of BNP in plasma were 38, 85, and 199 pmol/l, giving increments in plasma as seen in heart or renal failure. BNP infusion increased the urinary flow rate and the excretion of sodium in a dose-dependent way. The maximal effects were +65 and +156%, respectively. GFR increased and RPF decreased, the latter in a dose-dependent manner. Blood pressure, heart rate, angiotensin II, and aldosterone were all unaffected by infusion of BNP, whereas a direct inhibition of renin secretion was seen. With the use of the lithium clearance technique, we concluded that the tubular site of action is in both the proximal and distal segments, and the major effect on sodium handling is in the distal parts of the nephron.

Evidence for load-dependent and load-independent determinants of cardiac natriuretic peptide production

BACKGROUND

In hypertension with cardiac hypertrophy, the specific contributions to increased production of the cardiac natriuretic peptides (NP) atrial natriuretic factor (ANF) and brain natriuretic peptide (BNP) by load and the hypertrophic process are not known. In the present work we determine ANF and BNP synthesis and secretion in the aortic-banded rat treated with dosage schedules of the ACE inhibitor ramipril that result in the prevention or regression of both hypertension and hypertrophy (high dosage) or in the prevention or regression of hypertrophy alone with persistent hypertension (low dosage). Myosin heavy chain (MHC) isoform switch was studied as an indicator of ventricular cardiocyte hypertrophy as well as the levels of collagen III mRNA as a measure of changes in extracellular matrix.

METHODS AND RESULTS

Ramipril was administered for 6 weeks just after suprarenal aortic banding, or rats were banded for 6 weeks, after which ramipril was administered during the following 6 weeks. Banding caused an increase in blood pressure, left ventricular weight-to-body weight ratio, plasma and ventricular NP, ventricular NP mRNA, collagen III, and beta-MHC mRNA. Ramipril at 1 mg/kg normalized all these parameters while ramipril at 10 micrograms/kg normalized left ventricular weight-to-body weight ratio but not blood pressure. Plasma and ventricular NP content and mRNA levels were partially normalized by ramipril (10 micrograms/kg). Ramipril (10 micrograms/kg) prevented increased collagen III mRNA levels but did not affect beta-MHC mRNA levels.

CONCLUSIONS

(1) NP production and secretion in aortic-banded rats are independently related to increased blood pressure and hypertrophy. (2) A load-dependent component is more important than a load-independent component in regulating left ventricular NP production. (3) ANF production is more sensitive than BNP production to the load-independent component. (4) Low-dose ramipril treatment reverses hypertrophy and the increased collagen III expression but does not reverse the increased beta-MHC isoform expression, suggesting that these are independently regulated processes. (5) Aortic banding and ACE inhibition do not affect atrial NP production and content.

Plasma brain natriuretic peptide as an indicator for angiotensin-converting-enzyme inhibition after myocardial infarction

Brain natriuretic peptide (BNP) is a cardiac ventricular hormone that may be a sensitive and specific marker of changes in ventricular function. In a prospective, randomised open trial with 16 patients followed for 6 months after first Q wave anterior myocardial infarction we set out to determine: whether BNP concentrations are raised acutely, the effect on circulating BNP of angiotensin-converting enzyme (ACE) inhibition, how BNP and atrial natriuretic peptide (ANP) concentrations compared as correlates of left-ventricular ejection fraction, and whether plasma BNP concentrations could distinguish patients with low (< 40%) and relatively preserved (> 40%) ejection fractions. Plasma concentrations of BNP measured on days 2, 7, 8, 42, and 180 postinfarction were significantly raised in patients compared with normal controls and to a proportionately greater degree than ANP concentrations. Treatment with placebo (n = 8) or oral captopril (n = 8) from day 8 resulted in significantly lower BNP concentrations at days 42 (p = 0.05) and 180 (p < 0.05) in the captopril-treated group. Compared with ANP, BNP concentrations were much more strongly correlated with radionuclide-measured left-ventricular ejection fraction at days 2, 42, and 180. All 8 patients with baseline (day 2) ejection fractions of 40% or above had plasma BNP concentrations less than 10 pmol/L, whereas the 8 patients with ejection fractions less than 40% had BNP concentrations greater than 10 pmol/L. Our findings suggest that measurements of circulating BNP may identify those patients with significant left-ventricular dysfunction who have been highlighted by the Survival and Ventricular Enlargement study as likely to benefit from long-term ACE inhibition after myocardial infarction.