Increased levels of circulating islet amyloid polypeptide in patients with chronic renal failure have no effect on insulin secretion.

To elucidate the metabolism of islet amyloid polypeptide (IAPP) with respect to a possible renal elimination we investigated IAPP levels in 20 lean, nondiabetic patients with renal failure maintained on chronic hemodialysis (HD) and in 20 healthy controls. The basal levels of IAPP were significantly higher in uremic patients than in controls (15.1 +/- 3.2 vs. 3.2 +/- 0.2 pM, P < 0.001) suggesting renal excretion of IAPP. To investigate the impact of chronically elevated levels of endogenous IAPP on insulin secretion and insulin sensitivity, a frequently sampled intravenous glucose tolerance test (FSIGT) was performed in a subset of patients on hemodialysis and in age-matched healthy controls (C) and obese patients with normal (NGT) and with impaired glucose tolerance (IGT). Insulin sensitivity index (SI) was 8.7 +/- 1.5 in C (P < 0.05 vs. NGT, P < 0.01 vs. IGT), 5.4 +/- 0.9 in HD (P < 0.05 vs. IGT), 3.1 +/- 1.0 in NGT, and 2.0 +/- 0.5 in IGT. First phase insulin secretion was increased in patients on HD compared with those of several control groups. The results of this study therefore indicate a renal route of metabolism of IAPP. Increased endogenous circulating IAPP levels over a long period of time do not lead to a decrease in insulin release in patients on HD and do not cause the insulin resistance commonly seen in obesity and diabetes. Increased levels of circulating IAPP therefore are not likely to be a pathogenetic factor in the development of non-insulin-dependent diabetes mellitus (NIDDM).

Decrease of stimulated amylin release precedes impairment of insulin secretion in type II diabetes.

Amylin, a 37-amino acid polypeptide, has been identified as the major protein component of pancreatic amyloid deposits in patients with non-insulin-dependent (type II) diabetes mellitus. Amylin is stored and released together with insulin and has been proposed to play a major role in the pathogenesis of type II diabetes. To compare amylin release and its proportion to insulin secretion under different metabolic conditions, oral and intravenous glucose tolerance tests (OGTT and IVGTT, respectively) were performed in healthy, lean control subjects, obese patients with normal and impaired glucose tolerance (NGT and IGT, respectively), and obese type II diabetic patients. Compared with control subjects, basal and stimulated amylin secretion during OGTT was significantly higher in obese patients with NGT and IGT but not in type II diabetic patients. The integrated amylin response was significantly higher in obese patients with NGT than lean control subjects and type II diabetic patients matched for degree of obesity. The amylin-insulin ratio decreased slightly in obese subjects with NGT and IGT and significantly in type II diabetic patients. Amylin secretion was significantly stimulated during IVGTT in control subjects and obese patients with NGT and IGT but not in type II diabetic patients. These findings suggest that amylin is physiologically released by pancreatic beta-cells in a constant ratio to insulin in nondiabetic subjects. Glucose-stimulated amylin secretion is increased in obese subjects with NGT and IGT. In type II diabetes mellitus, amylin secretion relative to that of insulin is decreased, and amylin is not stimulated by IVGTT.

Prognostic impact of big endothelin-1 plasma concentrations compared with invasive hemodynamic evaluation in severe heart failure.

OBJECTIVES: This study sought to test the hypothesis that big endothelin-1 plasma levels in advanced heart failure are related to survival. BACKGROUND: In heart failure, production of the potent vasoconstrictor endothelin-1 is increased. Because elevation of immunoreactive endothelin-1 in severe heart failure is primarily related to the precursor "big" endothelin-1, increased big endothelin-1 levels may be associated with a poor prognosis. METHODS: Plasma big endothelin-1 concentrations, in addition to 16 clinical, hemodynamic and neurohumoral variables, were obtained from 113 patients (mean age -=/[SEM] 53 +/- 1 years) with left ventricular ejection fraction <20% and were related to 1-year mortality by a stepwise Cox regression multivariate analysis. RESULTS: Plasma big endothelin-1 concentrations were significantly higher in patients with moderate and severe heart failure than in those with mild heart failure (4.5 +/- 0.4 and 6.0 +/- 0.1 vs. 2.7 +/- 0.1 fmol/ml, p = 0.0001, respectively) and lower in 58 one-year survivors than in 29 nonsurvivors (2.6 +/- 0.1 vs. 5.9 +/- .04 fmol/ml, p = 0.0001) and 26 heart transplant recipients. By univariate analysis, big endothelin-1 plasma concentrations (p < 0.0001), functional class, daily furosemide dose, left ventricular ejection fraction, most hemodynamic variables and plasma atrial natriuretic peptide, sodium renin activity and aldosterone levels were all related to mortality, but only functional class provided additional prognostic information when big endothelin-1 plasma levels were entered into the multivariate model. CONCLUSIONS: In advanced heart failure, plasma big endothelin-1 is strongly related to survival and appears to predict 1-year mortality better than hemodynamic variables and levels of atrial natriuretic peptide, an established neurohumoral prognostic marker in chronic heart failure.

Prognostic evaluation of neurohumoral plasma levels before and during beta-blocker therapy in advanced left ventricular dysfunction.

OBJECTIVES: The study assessed the relative predictive potency of neurohumoral factors in patients with advanced left ventricular (LV) dysfunction during neurohumoral blocking therapy. BACKGROUND: The course of heart failure is characterized by progressive LV deterioration associated with an increase in cardiac (natriuretic peptides) and predominantly extracardiac (norepinephrine, big endothelin [big ET]) hormone plasma levels. METHODS: Plasma hormones were measured at baseline and months 3, 6, 12 and 24 in 91 patients with heart failure (left ventricular ejection fraction [LVEF] <25%) receiving 40 mg enalapril/day and double-blind atenolol (50 to 100 mg/day) or placebo. After the double-blind study phase, patients were followed up to four years. Stepwise multivariate regression analyses were performed with 10 variables (age, etiology, LVEF, symptom class, atenolol/placebo, norepinephrine, big ET, log aminoterminal atrial natriuretic peptide, log aminoterminal B-type natriuretic peptide [N-BNP] and log B-type natriuretic peptide [BNP]). During the study, the last values prior to patient death were used, and in survivors the last hormone level, New York Heart Association class and LVEF at month 24 were used. RESULTS: Thirty-one patients died from a cardiovascular cause during follow-up. At baseline, log BNP plasma level (x2 = 13.9, p = 0.0002), treatment allocation (x2 = 9.5, p = 0.002) and LVEF (x2 = 5.6, p = 0.017) were independently related to mortality. During the study, log BNP plasma level (x2 = 21.3, p = 0.0001) remained the strongest predictive marker, with LVEF (x2 = 11.2, p = 0.0008) log N-BNP plasma level (x2 = 8.9, p = 0.0027) and treatment allocation (x2 = 6.4, p = 0.0109) providing additional independent information. CONCLUSIONS: In patients with advanced LV dysfunction receiving high-dose angiotensin-converting enzyme inhibitors and beta-blocker therapy BNP and N-BNP plasma levels are both independently related to mortality. This observation highlights the importance of these hormones and implies that they will likely emerge as a very useful blood test for detection of the progression of heart failure, even in the face of neurohumoral blocking therapy.

Plasma big endothelin-1 concentrations in congestive heart failure patients with or without systemic hypertension.

Plasma endothelin concentrations were evaluated in 53 chronic, congestive heart failure (CHF) patients with or without history of systemic hypertension, as well as in 9 with hypertension only and in 22 healthy control subjects. Plasma renin, aldosterone and atrial natriuretic peptide, as well as clinical and hemodynamic data were determined. In patients with CHF, big endothelin-1 was, independent of hypertension history, significantly greater than in hypertensive patients with normal cardiac function and in control subjects (both p < 0.0001). Patients with severe CHF had significantly greater big endothelin-1 values than did those with moderate CHF. During 12-month follow-up, 11 patients with CHF underwent heart transplantation, and 9 died; these patients had significantly greater big endothelin-1 concentrations than did the 33 clinically stable patients (p < 0.001). Big endothelin-1 and atrial natriuretic peptide correlated with right atrial pressure, pulmonary capillary wedge pressure, left ventricular ejection fraction, effort capacity and severity of CHF (New York Heart Association functional class).

Human atrial natriuretic peptide secretion in precapillary pulmonary hypertension. Clinical study in patients with COPD and interstitial fibrosis.

Human atrial natriuretic peptide (hANP) is stored by granules of both human atria. Atrial distension appears to be a major stimulus for hANP secretion. Precapillary pulmonary hypertension increases right ventricular afterload and may thus cause right atrial distension. We therefore hypothesized that hANP plasma concentrations (1) are higher in the right atrium than in the peripheral vein, (2) are increased in patients with precapillary pulmonary hypertension, and (3) correlate with right atrial pressure. Thirty-three adult patients with chronic obstructive pulmonary disease (COPD) or interstitial fibrosis were examined by right heart catheterization. Mean pressures were measured in the right atrium, pulmonary artery, and pulmonary capillary wedge position, and blood was drawn from the right atrium and from a peripheral vein for determination of hANP levels. In general, hANP plasma levels in the right atrium were significantly higher than in a peripheral vein. Seventeen out of 33 patients had pulmonary hypertension, whereas 16 patients exhibited normal pulmonary artery mean pressures. In all patients, pulmonary arterial wedge pressure was normal. Plasma hANP concentrations were significantly higher in patients with pulmonary hypertension than in patients with normal pulmonary artery pressure. A strong correlation between central or peripheral hANP plasma levels (or both) and mean right atrial pressure could be observed (r = 0.75; p less than 0.001). From these data, we conclude that the increased secretion of hANP in our patients with precapillary pulmonary hypertension appears to be mediated by right atrial distension.

Prognostic value of hemodynamic vs big endothelin measurements during long-term IV therapy in advanced heart failure patients.

STUDY OBJECTIVE: To compare hemodynamics and plasma big endothelin levels in patients awaiting heart transplantation who are receiving continuous IV therapy, and to establish their respective potency for predicting future cardiac events. DESIGN: A randomized, prospective trial of ambulatory continuous treatment with IV prostaglandin E(1) (PGE(1)) vs dobutamine. A subanalysis was conducted of all patients who completed 4 weeks of follow-up in regard to treatment effects on hemodynamics and big endothelin plasma levels. PATIENTS: Thirty-two listed heart transplant candidates who were refractory to oral treatment, 21 patients who were receiving PGE(1), and 11 patients receiving dobutamine. MEASUREMENTS AND RESULTS: Hemodynamics and plasma big endothelin levels were measured at baseline and after 4 weeks. The cardiac index increased significantly (PGE(1) group, 1.7 +/- 0.4 vs 2.5 +/- 0.6 L/min/m(2); dobutamine group, 1.8 +/- 0.3 vs 2.3 +/- 0.6 L/min/m(2); p < 0.05), whereas the systemic vascular resistance index (SVRI) decreased significantly only in the PGE(1) group (3,352 +/- 954 vs 2,178 +/- 519 dyne. s. cm(-5)/m(2); p < 0. 05). The plasma big endothelin level decreased significantly (PGE(1) group, 7.6 +/- 3.1 vs 4.7 +/- 2.6 fmol/mL; dobutamine group, 6.5 +/- 3.7 vs 5.0 +/- 2.6 fmol/mL; p < 0.01 for the time effect). Plasma big endothelin (beta = 0.393; chi(2) = 10.8; p = 0.001) and SVRI (beta = 0.003; chi(2) = 6.9; p < 0.01), both measured after 4 weeks of continuous treatment, were the only independent predictors of future outcome. CONCLUSION: Continuous treatment over 4 weeks with either PGE(1) or dobutamine in patients awaiting heart transplantation yields an improved hemodynamic state accompanied by a reduction of increased big endothelin levels. Plasma big endothelin measured after 4 weeks of continuous therapy provides prognostic information about future outcome.

Hemodynamic and neurohumoral effects of long-term prostaglandin E1 infusions in outpatients with severe congestive heart failure.

BACKGROUND: Prostaglandins of the E type are potent endogenous vasodilators that also interfere with the activity of the sympathetic nervous system. Thus treating patients with end-stage heart failure with prostaglandin E1 (PGE1) infusions seems to accord well with the hypothesis that neurohumoral imbalance rather than hemodynamic derangements should be the priority in the treatment of heart failure. METHODS: We sought to investigate neurohumoral in addition to hemodynamic changes during long-term PGE1 infusion and determined plasma renin activity, atrial natriuretic peptide, norepinephrine, and big endothelin plasma levels in 13 male patients with heart failure whose symptoms remained severe in spite of optimized oral therapy with digitalis, nitrates, furosemide (185 +/- 72 mg/d) and enalapril (33 +/- 3 mg/d). PGE1 infusion rate was started with 2.5 ng/kg/min and stepwise increased to the maximum tolerated dose (26 +/- 4 ng/kg/min), which was halved for continuous infusion through the following 12 hours and further stepwise reduced to an average dose of 8 +/- 1 ng/kg/min. Right heart catheterization was performed for acute hemodynamic studies and after 4 weeks. All patients were discharged with a catheter that was connected to a portable pump for home therapy. RESULTS: Acute effects of PGE1 were reductions in systemic blood pressure, (p < 0.05), right atrial pressure (p < 0.001), pulmonary artery pressure (p < 0.05), pulmonary capillary wedge pressure (p < 0.01), systemic and pulmonary vascular resistance index (both p < 0.01) and an increase in cardiac and stroke volume index (both p < 0.001) without a change in heart rate. After 4 weeks a persistent increase from baseline in cardiac index (from 1.9 +/- 0.1 to 2.5 +/- 0.2 L/min/m2; p < 0.01) and in pulmonary vascular resistance index (from 479 +/- 50 to 331 +/- 29 dynes x sec/cm5 x m2; p < 0.05) was observed. Atrial natriuretic peptide (p < 0.05) decreased, and norepinephrine and big endothelin showed a tendency to a lower level. Concomitantly, New York Heart Association functional class changed (p = 0.0001), with one patient's condition remaining class IV, the conditions of seven patients decreasing to class II, and the conditions of five patients decreasing to class III. CONCLUSION: Thus long-term parenteral home therapy with PGE1 infusions in patients with severe end-stage heart failure elicited beneficial clinical and hemodynamic effects without activating neurohumoral counterregulatory systems.

Pattern of endothelin immunostaining during rejection episodes after kidney transplantation.

A pathophysiological role for endothelin (ET), one of the most potent vasoconstrictor peptides, has been suggested in ATN and during kidney allograft rejection. As ET is known to have predominantly local effects, we investigated intrarenal ET content in 82 kidney transplant biopsies and 10 normal control kidneys. ET-immunostaining, using a polyclonal anti-ET-1 antibody was investigated in 4 intrarenal vascular beds (glomeruli, capillaries, arterioles, arteries) and in tubular epithelium. Normal kidneys showed a strong staining of endothelial cells in all vessels and of tubular epithelium. In biopsies with signs for acute vascular rejection a marked decrease in ET staining intensity was seen. In contrast, normal staining similar to control kidneys was detected in interstitial rejection and in ATN. The presence of chronic CyA toxicity, however, lead to a significant reduction of endothelial ET staining. Neither mean doses nor trough levels of CyA correlated closely with the immunostaining findings. Plasma big-ET levels were elevated during vascular rejection, but not in interstitial rejection and ATN. This study demonstrates a significant reduction of ET immunostaining in intrarenal vascular endothelium of kidney transplant biopsies showing signs of endothelial damage. In vascular allograft rejection these changes are often associated with a concomitant rise in plasma ET levels. Our findings support a postulated role of ET in vascular rejection and during CyA toxicity and show that endothelial damage, independent of its genesis, can lead to a reduction of intrarenal ET content.

Increased levels of plasma amylin in advanced renal failure.

Amylin, a 37 amino acid polypeptide, has been suggested to play a prominent role in the pathogenesis of insulin resistance in type II diabetes mellitus. Various studies have demonstrated most recently that amylin is cosecreted with insulin. No data are available on the elimination of amylin from the circulation. We therefore tested plasma levels of amylin, insulin and C-peptide in 49 non-obese, non-diabetic patients (27 male/22 female) with various degree of renal impairment (Group A: CCr less than 20 ml/min, n = 20; Group B: CCr 20-89 ml/min, n = 18; and Group C: CCr greater than 80 ml/min, n = 9). We found a significant increase of plasma amylin when kidney function, expressed by creatinine clearance fell below 20 ml/min (17.9 +/- 1.7 vs. 12.2 +/- 0.8 vs. 8.8 +/- 1.2 pg/ml; p = 0.0005). Plasma amylin correlated closely with serum C-peptide (r = .764; p = 0.0001), and to a lesser extent with insulin (r = .595; p = 0.0001) underlining its postulated cosecretion with these peptides. The data indicate that amylin might be eliminated by renal mechanisms. Our data show that besides type II diabetes mellitus, advanced renal failure is another clinical situation with enhanced plasma amylin levels. Whether amylin plays any pathogenetic role in renal patients remains to be elucidated.

Determination of alpha-human atrial natriuretic peptide (alpha-hANP) in urine using combination HPLC with RIA strongly indicates non-immunoreactive metabolites.

Employing HPLC coupled with RIA, it was shown that alpha-human atrial natriuretic peptide is excreted in urine. Freshly collected urine had to be acidified to obtain reproducible results. When prepurified urine was subjected to HPLC (ion exchange and reversed phase) the subsequent quantification of alpha-hANP immunoreactive material in the eluate showed 10- to 30-fold greater amounts of alpha-hANP after treatment with HPLC; substances with the same elution parameters as synthetic alpha-hANP were detected, but they gave no response in the RIA.

Radioimmunological determination of arginine vasopressin and human atrial natriuretic peptide after simultaneous extraction from plasma.

Human atrial natriuretic peptide and arginine vasopressin were coextracted from EDTA-plasma with Sep-Pak C18 cartridges, and the hormones were coeluted from the cartridges by a solution containing 900 ml/l of methanol, 5 ml/l of trifluoroacetic acid and 95 ml/l of water. After volume reduction under nitrogen the eluates were lyophilized, dissolved in buffer and aliquots were used for radioimmunological determination of both hormones. Both procedures used delayed addition of [125I]-labelled tracer to enhance sensitivity. Recoveries were 95 +/- 2% for human atrial natriuretic peptide and 96 +/- 3% vor arginine vasopressin (mean +/- SD). Minimal detectable doses were 2 pg/tube of human atrial natriuretic peptide and 0.5 pg/tube of arginine vasopressin (Bo - 3 SD). Intra-assay variabilities were +/- 8% for both tests. Simultaneous extraction of both hormones with high recovery was achieved, thus increasing sensitivity and specificity, at the same time reducing sample volume requirements and technician time.

[Role of amylin in the pathogenesis of type II diabetes mellitus]. / Die Rolle von Amylin in der Pathogenese des Typ-II-Diabetes mellitus.

Amylin, a peptide, which was isolated from the islet amyloid of type II diabetics, might play a potential role in the pathogenesis of type II diabetes mellitus. In in vitro and in vivo studies it has been shown that amylin has an effect on insulin secretion as well as on insulin sensitivity. From measurements of plasma amylin levels it is known that amylin is cosecreted with insulin and patients with hyperinsulinemia have also elevated amylin levels. In patients with impaired glucose tolerance and type II diabetes amylin levels are decreased compared to insulin. A secretory defect of amylin and its local accumulation in the islets of type II diabetics might be a cause for the insulin secretory defect in type II diabetes. Additionally, amylin can induce peripheral insulin resistance, which might also be a cause for type II diabetes mellitus. Amylin is a new pancreatic peptide, which might play an important role in the pathogenesis of diabetes mellitus.

[Methodological problems in the radioimmunologic measurement of ANP (atrial natriuretic peptide)]. / Methodische Probleme der radioimmunologischen ANP-Messung.

Parameters influencing the measurement of hANP are designated and discussed on the basis of data from the literature and from our own results. Plasma hANP is dependent on the anatomical location of blood withdrawal, posture, state of hydration and salt load and medications. Interfering substances contained in plasma, management of samples and the type of assay used are of utmost importance. Direct RIA of hANP appears to be particularly sensitive to interferences. Preextraction of hANP from EDTA plasma by octadecylsilica cartridges, followed by RIA seems to be the most trustworthy method for measurement of hANP. Nevertheless, with this method too, we obtain different values for identical plasma samples if we use different antisera. Additionally, lipemia significantly lowers the ascertainable amount of endogenous, but not of exogenously added alpha-hANP. Therefore, it is reasonable to conclude that in preextracted samples too, hANP is not a homogeneous species. We observe a time-dependent increase in plasma hANP, reaching a final stable plateau value (about three times the initial values) after about 1.5 h, if EDTA blood samples are left on ice for prolonged time. Hemolysis interferes significantly with hANP determination. Readings of hANP values are reduced in dependence on plasma haemoglobin concentration. According to our experience, EDTA plasma can be stored for several months in either lyophilized form or deep frozen at -20 degrees C without the risk of reduction of hANP immunoreactivity. The data presented in this paper clearly show, that measurement of hANP is susceptible to faults in several details. Results should therefore be viewed critically.

[Effects of treatment of arrhythmias requiring therapy in dilated cardiomyopathy with amiodarone on alpha human atrial natriuretic peptide]. / Auswirkungen der Behandlung therapiepflichtiger Arrhythmien bei dilatativer CMP mit Amiodaron auf das alpha-humane atriale natriuretische Peptid (alpha-hANP).

In a longitudinal study comprising a total of 18 patients, the paradoxical time course of hANP plasma levels, i.e. the reproducibility of the low levels previously reported in cases of extreme cardiac insufficiency after administration of amiodarone, was investigated over a period of 9 months. At the same time, the effect of the degree of cardiac insufficiency and arrhythmia on the secretion of hANP was observed. The patients had been admitted to hospital because of the diagnoses "cardiac insufficiency secondary to cardiomyopathy" or "Grade IVb arrhythmia according to Lown's classification". During in-patient treatment, antiarrhythmic therapy was commenced in all patients. Clinical examinations and determinations of humoral parameters during therapy showed a substantial number of patients, who exhibited no increase in hANP levels despite massive cardiac decompensation. As far as drug therapy of patients with severe arrhythmias secondary to congestive (dilated) cardiomyopathy is concerned, amiodarone has proved to be the drug of choice in combination with digitalis, ACE inhibitors and diuretics. There is a close correlation between the degree of cardiac insufficiency and plasma hANP levels.