Sulfhydryl angiotensin-converting enzyme inhibition induces sustained reduction of systemic oxidative stress and improves the nitric oxide pathway in patients with essential hypertension

Background

Essential hypertension is associated with enhanced LDL oxidation and impaired endothelium-dependent vasodilation. The antioxidant status is linked to the nitric oxide (NO) pathway. Sulfhydryl angiotensin-converting enzyme (ACE) inhibitors inhibit oxidative stress and atherogenesis in experimental models; therefore we tested whether this beneficial antioxidant activity could be also clinically relevant in patients with essential hypertension.

Methods

Plasma LDL oxidizability was investigated initially in untreated normocholesterolemic patients with moderate essential hypertension without clinically evident target organ damage (n = 96) and in control normotensive subjects (n = 46). Patients were then randomly assigned into two age- and sex-matched groups to receive the new sulfhydryl ACE inhibitor zofenopril (15 to 30 mg/d; n = 48) or enalapril (20 mg/d, n = 48). LDL oxidizability was evaluated (generation of malondialdehyde, MDA) and systemic oxidative stress was evaluated by isoprostanes (8-isoPGF_2α). Asymmetrical dimethyl-l-arginine (ADMA), a competitive inhibitor of endothelial NO synthase, and plasma nitrite and nitrates (NOx) were also measured.

Results

LDL from hypertensive subjects had enhanced susceptibility to oxidation in vitro compared with that in control subjects (P < .05). Similarly, isoprostanes were significantly increased (P < .01) in hypertensive subjects versus control subjects. After 12-week treatment, MDA levels were significantly reduced by zofenopril (P < .05) but not enalapril treatment (P = not significant). Isoprostanes were normalized after zofenopril treatment (P < .03), whereas enalapril was ineffective. After treatment with both ACE inhibitors, plasma NOx concentrations were significantly reduced (P < .05). Similarly, hypertension increased ADMA concentration compared with the normotensive state, whereas ACE inihibition elicited a significant decrease. However, the reduction of ADMA concentration was significantly higher in patients receiving sulfhydryl ACE inhibition (P < .05 vs enalapril).

Conclusions

The sulfhydryl ACE inhibitor zofenopril reduces oxidative stress and improves the NO pathway in patients with essential hypertension. If confirmed in a large multicenter clinical trial, our data suggest a possible vasculoprotective effect of the compound in retarding vascular dysfunction and atherogenesis that often develops rapidly in hypertensive patients.     

Prevention of nitrate tolerance with angiotension converting enzyme inhibitors

BACKGROUND. Activation of neurohumoral hormones or sulfhydryl group depletion may contribute to the development of nitroglycerin tolerance. In an attempt to prevent nitrate tolerance, this study evaluated the interaction of nitroglycerin with angiotensin converting enzyme (ACE) inhibitors with and without a sulfhydryl group. METHODS AND RESULTS. Thirty-four subjects were randomized to a 7-day regimen of enalapril 10 mg b.i.d., captopril 25 mg t.i.d., or placebo. Venodilator response to nitroglycerin was assessed with forearm plethysmography by measuring the change in venous volume after administration of 0.4 mg sublingual nitroglycerin. Plethysmographic measurements were obtained serially 1) at baseline, 2) after 4 days of ACE inhibitor or placebo, 3) 2 hours after application of a 10 mg/24 hr nitroglycerin patch, and 4) 74 hours after continuous nitropatch application. ACE inhibition alone caused no significant change in the response to sublingual nitroglycerin. Nitrate response remained unchanged after 2 hours ("acute") of nitropatch exposure in all three groups. After 74 hours ("chronic") of continuous nitropatch application, the venodilator response to sublingual nitroglycerin was reduced by 40% in the placebo group, 10% in the enalapril group, and 2% in the captopril group. This attenuation was significant only in the placebo group (p less than 0.01). Pairwise comparison of nitrate response between groups was significantly different between the captopril and placebo groups (p less than 0.01) and between the placebo and enalapril groups (p less than 0.05). Plasma renin levels increased equally in the enalapril and captopril groups. Body weight increased only in the placebo group, suggesting prevention of nitrate-induced volume expansion in the ACE inhibitor groups. CONCLUSIONS. This study demonstrates that ACE inhibitors may prevent nitrate tolerance to long-term nitrate therapy.     

Apolipoprotein E kinetics: influence of insulin resistance and type 2 diabetes

BACKGROUNDS AND AIMS: Insulin resistance related to obesity and diabetes is characterized by an increase in plasma TG-rich lipoprotein concentrations. Apolipoprotein (apo) E plays a crucial role in the metabolism of these lipoproteins and particularly in the hepatic clearance of their remnants. The aim of this study was to explore apoE kinetics of obese subjects and to determine what parameters could influence its metabolism. METHODS: Using stable-isotope labelling technique ([(2)H(3)]-leucine-primed constant infusion) and monocompartmental model (SAAM II computer software), we have studied the plasma kinetics of very-low-density lipoprotein (VLDL) and high-density lipoprotein (HDL) apoE in 12 obese subjects (body mass index (BMI) 27.4-36.6 kg/m(2)): Seven were type 2 diabetics (age 47-65 y; HbA1c 7.1-10.2%) and five were non-diabetics (age 40-51 y, HbA1c: 4.9-5.3%). Six of the diabetic subjects were insulin resistant as assessed by insulin sensitivity index (HOMA 2.6-10.0), while non-diabetic subjects were all insulin sensitive (HOMA 1.2-2.1). RESULTS: Plasma VLDL and HDL apoE concentrations were significantly higher in diabetic than in non-diabetic subjects (5.74+/-1.60 vs 1.46+/-1.74 mg/l, P<0.01 and 17.81+/-6.67 vs 9.97+/-3.32 mg/l, P<0.05). These increased levels were associated with significantly higher absolute production rate (APR) of VLDL and HDL apoE (0.714+/-0.343 vs 0.130+/-0.200 mg/kg/day, P<0.01, and 0.197+/-0.087 vs 0.080+/-0.060 mg/kg/day, P<0.05, respectively) while no significant difference was found for fractional catabolic rate (FCR) of VLDL and HDL apoE (3.44+/-1.64 vs 1.97+/-0.84/day and 0.30+/-0.12 vs 0.19+/-0.09/day, respectively). In the whole population, BMI was not correlated with any of apoE kinetic data. HOMA was positively correlated with FCR of VLDL apoE (r=0.64, P<0.05) and tended to be correlated with APR of VLDL apoE (r=0.58, P=0.06). HbA1c was positively correlated with APR and FCR of both VLDL apoE (r=0.91 and 0.78, P<0.01, respectively) and HDL apoE (r=0.66 and 0.69, P<0.05, respectively). CONCLUSION: Obese diabetics are characterized by elevated VLDL and HDL apoE levels associated with enhancement of VLDL and HDL apoE production rates. Whereas obesity did not influence apoE kinetic parameters in itself, insulin resistance may lead to an increase in VLDL apoE production and fractional catabolic rates. Diabetes and the glycemic control may also specifically influence the kinetics of both VLDL and HDL apoE. All together, these disorders should explain at least part of the increase in VLDL and HDL apoE observed in diabetes.     

Effect of beta 1 blockade with atenolol on progression of heart failure in patients pretreated with high-dose enalapril

BACKGROUND: The survival benefit of beta-blocker treatment in patients with heart failure has been established in recent trials. Yet, the impact of beta-blockers added on high dose angiotensin converting enzyme inhibitors has not been reported. AIMS: To investigate the effect of atenolol, a hydrophilic, selective beta1-adrenergic antagonist, added on enalapril 40 mg/day in patients with advanced left ventricular dysfunction in a double-blind placebo-controlled trial. METHODS: One hundred and nineteen patients with class II or III heart failure, left ventricular ejection fraction < or = 25% and treatment with 40 mg enalapril daily were given an initial challenge dose of atenolol 12. 5 mg. One hundred patients (54 with idiopathic, 28 with ischemic, 18 with other dilated cardiomyopathy) tolerated challenge and were randomized to atenolol (maintenance dose 89+/-11 mg/day, range 50-100 mg/day) or placebo. The primary endpoint was combined worsening heart failure or death within 2 years, the secondary endpoint was hospitalization for cardiac events. RESULTS: After 395+/-266 days interim analysis revealed a significant difference between the atenolol and placebo group (log rank P<0.01) and the trial was concluded. Twenty-seven patients had developed worsening heart failure (8 in the atenolol group vs. 19 in the placebo group) and 13 patients had died (5 in the atenolol vs. 8 in the placebo group). Overall there were 23 hospitalizations for cardiac events (6 in the atenolol group vs. 21 in the placebo group, P=0.07); 17 hospitalizations were due to worsening heart failure (5 in the atenolol group, 12 in the placebo-group, P=0.05) and 10 due to arrhythmias (1 in the atenolol group vs. 9 in the placebo group, P<0.01) CONCLUSIONS: The data suggest that in patients with advanced left ventricular dysfunction, beta-blockers can provide substantial benefits supplementary to that already achieved with high dose enalapril treatment.     

Chronic treatment with nitric oxide-releasing aspirin reduces plasma low-density lipoprotein oxidation and oxidative stress,arterial oxidation-specific epitopes,and atherogenesis in hypercholesterolemic mice

The effects of chronic treatment with nitric oxide-containing aspirin (NO-aspirin, NCX-4016) in comparison with regular aspirin or placebo on the development of a chronic disease such as atherosclerosis were investigated in hypercholesterolemic low-density lipoprotein (LDL)-receptor-deficient mice. Male mice were assigned randomly to receive in a volume of 10 ml/kg either placebo (n = 10), 30 mg/kg/day NO-aspirin (n = 10), or 18 mg/kg/day of regular aspirin (n = 10). After 12 weeks of treatment, the computer-assisted imaging analysis revealed that NO-aspirin reduced the aortic cumulative lesion area by 39.8 +/- 12.3% compared with that of the placebo (P < 0.001). Regular aspirin did not reduce significantly aortic lesions (-5.1 +/- 2.3%) compared with the placebo [P = 0.867, not significant (NS)]. Furthermore, NO-aspirin reduced significantly plasma LDL oxidation compared with aspirin and placebo, as shown by the significant reduction of malondialdehyde content (P < 0.001) as well as by the prolongation of lag-time (P < 0.01). Similarly, systemic oxidative stress, measured by plasma isoprostanes, was significantly reduced by treatment with NCX-4016 (P < 0.05). More importantly, mice treated with NO-aspirin revealed by immunohistochemical analysis of aortic serial sections a significant decrease in the intimal presence of oxidation-specific epitopes of oxLDL (E06 monoclonal antibody, P < 0.01), and macrophages-derived foam cells (F4/80 monoclonal antibody, P < 0.05), compared with placebo or aspirin. These data indicate that enhanced NO release by chronic treatment with the NO-containing aspirin has antiatherosclerotic and antioxidant effects in the arterial wall of hypercholesterolemic mice.     

Differentiation of angiotensin-converting enzyme (ACE) inhibitors by their selective inhibition of ACE in physiologically important target organs

Seven ACE inhibitors were studied for possible differences in distribution to aorta, brain, heart, lung, and kidney after administration of single oral doses to spontaneously hypertensive rats (SHR). Doses, normalized for differences in inhibitory potency and molecular weight, were expected to deliver equivalent levels of ACE-inhibitory activity to the circulation, and this was confirmed by preliminary dose-response studies. The relative potencies of the active moieties of the seven drugs and the normalized oral doses used were: SQ 29,852 (1.0), 100 mg/kg; captopril (3.5), 30 mg/kg; enalapril (12), 20 mg/kg; fosinopril (13), 25 mg/kg; zofenopril (20), 10 mg/kg; lisinopril (24), 10 mg/kg; and ramipril (51), 5 mg/kg. In these ex vivo studies, ACE activities were determined fluorometrically in SHR sera and in uncentrifuged homogenates of the solid tissues at various times after oral dosing with the ACE inhibitors. As expected, the normalized oral doses of the seven inhibitors had equivalent effects on serum ACE. In lung, where ACE has a vascular endothelial localization, and in aorta, where ACE inhibition correlates with antihypertensive action, ramipril, lisinopril, and zofenopril were distinguished by the magnitude and duration (three to four days) of their effects. In the brain, where ACE may affect central regulation of blood pressure and participate in the degradation of certain neuropeptides, ramipril and enalapril had no effect; captopril and zofenopril had modest, short-lasting effects, and fosinopril, lisinopril, and SQ 29,852 had delayed but long-lasting inhibitory actions. In the kidney, where ACE inhibition may have positive or negative effects on renal function, ramipril and fosinopril could be distinguished by their weak actions, perhaps associated with biliary routes of excretion. In the heart, where ACE inhibitors may prevent ischemic damage to the myocardium, single oral doses of captopril, fosinopril, and particularly zofenopril produced striking and long-lasting inhibition, whereas equivalent doses of ramipril and enalapril produced barely detectable inhibition.     

Vasopeptidase inhibition exhibits endothelial protection in salt-induced hypertension

Omapatrilat represents a new class of drugs capable of inhibiting both ACE and neutral endopeptidase 24.11, the so-called vasopeptidase inhibitors. It therefore contributes to neurohumoral modulation, which might improve endothelial function in cardiovascular diseases. This study investigated the effect of omapatrilat in comparison to the ACE inhibitor captopril on systolic blood pressure and endothelial function in salt-induced hypertension. Dahl salt-sensitive rats (n=6/group) on standard or salt-enriched (4% NaCl) chow were treated for 8 weeks with either omapatrilat (36+/-4 mg/kg per day), captopril (94+/-2 mg/kg per day), or placebo. Aortic rings were then isolated and suspended in organ chambers for isometric tension recording. Systolic blood pressure of salt-fed, placebo-treated animals increased to 196+/-6 mm Hg, which was prevented by omapatrilat (162+/-5 mm Hg, P<0.05) and captopril (164+/-7 mm Hg, P<0.05) to a comparable degree. In control rats, acetylcholine (10(-10) to 10(-5) mol/L) induced endothelium-dependent relaxation (97+/-4%), which was reduced by high-salt diet to 30+/-5% (P<0.005; n=6). Omapatrilat improved relaxation to a greater extent (86+/-5%) than did captopril (57+/-6%; P<0.05). eNOS protein expression and aortic nitrite/nitrate content were reduced in hypertensive rats and improved by both omapatrilat and captopril. Aortic endothelin-1 levels were increased in salt-fed animals and unaffected by omapatrilat or captopril. These data suggest that despite comparable blood pressure, omapatrilat is superior to captopril in improving endothelium-dependent relaxation in salt-sensitive hypertension.     

Double-blind comparison of captopril and enalapril in mild to moderate hypertension

To compare the antihypertensive and humoral effects of the angiotensin-converting enzyme inhibitors captopril and enalapril, 20 patients with essential hypertension, not receiving treatment for 2 weeks and consuming a prescribed sodium ion intake, were randomly assigned to two parallel, double-blind treatment groups with stratification based on race and untreated seated diastolic blood pressure. These groups received a placebo (day -1) followed by either captopril, 200 mg every 12 hours (n = 9), or enalapril maleate, 20 mg every 12 hours (n = 11), alone (days 1 to 14) and then with hydrochlorothiazide, 25 mg every 12 hours (days 16 to 28). Captopril and enalapril were coadministered alone (day 15) and with hydrochlorothiazide (day 29) to assess whether further decreases in blood pressure would occur. Captopril and enalapril alone caused comparable decreases (p less than 0.05) in the mean 12 hour time-averaged seated diastolic blood pressure from values on day -1 (placebo), on day 1 (11 and 9 mm Hg, respectively) and day 14 (8 and 7 mm Hg, respectively). The addition of hydrochlorothiazide further decreased (p less than 0.05) blood pressure in each group (7 and 8 mm Hg, respectively) from values on day 14. Combined use of captopril and enalapril did not result in further reduction. Coupled with the comparable changes observed in each treatment group in serum angiotensin-converting enzyme activity, plasma renin activity and plasma aldosterone concentration, these data support the view that captopril and enalapril have similar antihypertensive effects and mechanisms.     

Herbal ephedra/caffeine for weight loss: a 6-month randomized safety and efficacy trial

OBJECTIVE: To examine long-term safety and efficacy for weight loss of an herbal Ma Huang and Kola nut supplement (90/192 mg/day ephedrine alkaloids/caffeine). DESIGN: Six-month randomized, double-blind placebo controlled trial. SUBJECTS: A total of 167 subjects (body mass index (BMI) 31.8+/-4.1 kg/m(2)) randomized to placebo (n=84) or herbal treatment (n=83) at two outpatient weight control research units. MEASUREMENTS: Primary outcome measurements were changes in blood pressure, heart function and body weight. Secondary variables included body composition and metabolic changes. RESULTS: By last observation carried forward analysis, herbal vs placebo treatment decreased body weight (-5.3+/-5.0 vs. -2.6+/-3.2 kg, P<0.001), body fat (-4.3+/-3.3 vs. -2.7+/-2.8 kg, P=0.020) and LDL-cholesterol (-8+/-20 vs. 0+/-17 mg/dl, P=0.013), and increased HDL-cholesterol (+2.7+/-5.7 vs. -0.3+/-6.7 mg/dl, P=0.004). Herbal treatment produced small changes in blood pressure variables (+3 to -5 mm Hg, P< or =0.05), and increased heart rate (4+/-9 vs. -3+/-9 bpm, P<0.001), but cardiac arrhythmias were not increased (P>0.05). By self-report, dry mouth (P<0.01), heartburn (P<0.05), and insomnia (P<0.01) were increased and diarrhea decreased (P<0.05). Irritability, nausea, chest pain and palpitations did not differ, nor did numbers of subjects who withdrew. CONCLUSIONS: In this 6-month placebo-controlled trial, herbal ephedra/caffeine (90/192 mg/day) promoted body weight and body fat reduction and improved blood lipids without significant adverse events.     

辛伐他汀消退老年载脂蛋白E基因敲除小鼠动脉粥样硬化斑块的观察

目的观察辛伐他汀对高脂喂养的老年载脂蛋白E(apoE)基因敲除小鼠动脉粥样硬化(AS)斑块的作用。方法选取高脂喂养的60周龄雄性aopE基因敲除小鼠30只,随机分为辛伐他汀高剂量组、辛伐他汀低剂量组和模型组,每组10只,分别每天予以辛伐他汀20mg/kg、辛伐他汀5mg/kg和等量生理盐水灌胃,连续灌胃8周后,取主动脉窦部做病理检测。冷冻切片光镜下观察AS斑块病理情况,免疫组织化学染色观察骨桥蛋白、α肌动蛋白的表达。vonkossa染色观察斑块钙化情况。结果与模型组比较,辛伐他汀高、低剂量组apoE基因敲除小鼠的血清TC和LDL-C水平明显降低(P<0.05),斑块面积占管腔面积比、斑块内钙化染色面积明显减少(P<0.05)。结论辛伐他汀可明显降低老年apoE基因敲除小鼠的血清TC和LDL-C水平,消退AS斑块的大小及其钙化。     

Comparison of enalapril versus captopril on left ventricular function and survival three months after acute myocardial infarction (the “practical” Study)

Left ventricular (LV) function and survival can be improved with captopril when initiated later than 24 hours after acute myocardial infarction. Animal studies suggest additional benefits may be obtained with earlier initiation of angiotensinconverting enzyme (ACE) inhibitors. The effects on LV function of captopril and enalapril initiated within 24 hours of myocardial infarction were studied. Two hundred twenty-five patients with acute myocardial infarction were enrolled within 24 hours of the onset of chest pain. They were randomized to receive either captopril 25 mg three times daily, enalapril 5 mg three times daily, or placebo. LV ejection fraction (EF) and volumes were measured by radionuclide ventriculography at baseline during treatment and at 3 months after a 3-day withdrawal from therapy. The ACE inhibitor group had a significant increase in EF (45 ± 1 to 47 ± 1%; P = 0.005) and significantly attenuated LV dilatation compared with results in the placebo group (175 ± 6 to 189 ± 7 ml in the placebo group vs 168 ± 4 to 172 ± 4 ml in the ACE inhibitor group; P = 0.051 for LV end-diastolic volume; and 99 ± 6 to 108 ± 7 ml in the placebo group vs 94 ± 3 to 94 ± 4 ml; P = 0.026 for LV end-systolic volume). The beneficial effects of ACE inhibitor therapy on LV function were observed irrespective of the degree of initial LV dysfunction and were comparable in both the captopril and enalapril groups. Survival at 90 days and 12 months was significantly improved in the enalapril group (7 placebo, 9 captopril, 1 enalapril [p = 0.038] and 12 placebo, 10 captopril, 2 enalapril [p = 0.022]; deaths at 90 days and 12 months, respectively). Immediate administration of captopril and enalapril improved LV function and prevented LV dilatation after acute myocardial infarction. The benefit was similar with both ACE inhibitors and was in excess of the benefits of optimal conventional therapy.     

Quality of life and cough on antihypertensive treatment: a randomised trial of eprosartan, enalapril and placebo.

The objective of this study was to compare the quality of life and incidence of dry cough with the angiotensin II antagonist eprosartan, the ACE-inhibitor enalapril, and placebo, in hypertensive patients with a history of ACE-inhibitor cough. The study was a multicentre, randomised, double-blind, parallel group controlled trial. A total of 136 patients judged to have ACE-inhibitor cough during single-blind enalapril treatment which was lost during a subsequent placebo washout phase, were randomised to receive either eprosartan 300 mg twice daily, or enalapril 20 mg once daily, or placebo for 6 weeks. Self-completion questionnaires assessing quality of life and cough were examined at baseline and end of study. At study end point 23% of patients in the enalapril group and 5% in the eprosartan and placebo groups reported cough (which included definite, probable and possible coughs) (P = 0.02). After adjusting for multiple comparisons, the eprosartan group was not significantly different from either placebo or enalapril. There were no significant differences in the Psychological General Wellbeing Index (PGWB). In conclusion the incidence of self-reported cough on eprosartan was similar to that on placebo, and lower than on enalapril but this difference was not significant when adjustments were made for multiple comparisons. There were no differences in quality of life.     

Comparison of effects of combined ACE inhibitor and low-dose thiazide diuretic with ACE inhibitor alone on insulin action in patients with hypertension and Type 2 diabetes: a double-blind crossover study

Aims To establish the safety in terms of insulin sensitivity of a low dose thiazide/ACE inhibitor combination. Methods We examined the effects on insulin sensitivity of captopril either alone or in combination with low-dose bendroflumethiazide (1.25 mg) in 15 hypertensive Type 2 diabetic patients. Insulin action was assessed using an isoglycaemic hyperinsulinaemic clamp in a double-blind, randomised, crossover study after a 6-week placebo run-in and following two 12-week treatment periods with captopril (C) (100 mg) alone or in combination with bendroflumethiazide (CB) (1.25 mg). Results Blood pressure was lower following CB compare to C (138/83 vs. 144/85 mmHg; P < 0.05) and both were lower than baseline (153/92 mmHg; P < 0.01). CB resulted in a significant increase in fasting plasma glucose compared to C (9.6 ± 2.6 vs. 8.5 ± 1.6 mmol/l; P < 0.05). Exogenous glucose infusion rates required to maintain isoglycaemia during hyperinsulinaemia were lower after CB compared to C (25.1 ± 13.3 vs. 34.2 ± 16.8 µmol/kg/min; P < 0.01) as were isotopically determined glucose utilisation rates (29.0 ± 12.4 vs. 36.6 ± 17.3 µmol/kg/min; P < 0.05). There was no significant difference in fasting endogenous glucose production between treatments (CB 9.3 ± 3.3 vs. C 8.6 ± 1.6 µmol/kg/min), nor between suppression following insulin (CB 4.0 ± 2.1 vs. C 4.3 ± 3.1 µmol/kg/min). Conclusions Combination of low-dose bendroflumethiazide with captopril lowered blood pressure but resulted in deleterious effects on insulin action compared to captopril alone.     

Reversal of cardiac hypertrophy and fibrosis by S21402, a dual inhibitor of neutral endopeptidase and angiotensin converting enzyme in SHRs

OBJECTIVE: The major advantage of dual inhibitors of neutral endopeptidase (NEP) and angiotensin converting enzyme (ACE) is their ability to lower blood pressure irrespective of renin or volume status. The aim of this study was to determine whether dual NEP/ACE inhibition produces different effects on cardiovascular structure and fibrosis, hormonal parameters and inhibition of tissue enzymes compared with selective inhibition of ACE and NEP in the spontaneously hypertensive rat (SHR). METHODS: Male SHRs received the dual NEP/ACE inhibitor (S21402, 100 mg/kg per day), the ACE inhibitor (captopril, 50 mg/kg per day), the NEP inhibitor (SCH42495, 60 mg/kg per day) or vehicle for 2 weeks. RESULTS: S21402 produced equivalent blood pressure lowering effects to captopril (vehicle, 220 +/- 1 mmHg; S21402, 189 +/- 2 mmHg; captopril, 187 +/- 3 mmHg), but was a more effective antihypertensive agent than SCH42495 (214 +/- 2 mmHg, P< 0.01). All treatments reduced left ventricular mass (P< 0.05) and cardiac fibrosis (P< 0.01). S21402 inhibited renal NEP and ACE (P< 0.01), SCH42495 inhibited renal NEP (P < 0.01), and captopril inhibited renal ACE (P< 0.01). Captopril and S21402 increased plasma renin activity (P< 0.05), but the rise with S21402 was attenuated compared with that caused by captopril (P< 0.01). All treatments reduced plasma aldosterone levels (P< 0.01), and NEP inhibition with SCH42495 and S21402 increased plasma atrial natriuretic peptide (ANP; P< 0.05). CONCLUSIONS: These results indicate that selective NEP inhibition has major benefits in the regression of cardiac hypertrophy and reduction of fibrosis but has limited antihypertensive effects. The dual NEP/ACE inhibitor S21402 offered no advantage over the selective ACE inhibitor in terms of blood pressure reduction, or attenuation of cardiac hypertrophy and fibrosis, but did increase plasma ANP and blunted the reactive rise in renin with ACE inhibition. Further studies are needed to determine whether more complete blockade of the renin-angiotensin system with dual NEP/ACE inhibition results in additional benefits in terms of morbidity and mortality in cardiovascular disease.     

Enhancement of blood glucose lowering effect of a sulfonylurea when coadministered with an ACE inhibitor: results of a glucose-clamp study

BACKGROUND: To investigate if coadministration of enalapril alters the metabolic effect of glibenclamide by employing an euglycemic glucose-clamp technique in healthy volunteers. METHODS: A double-blind crossover study with nine healthy normotensive volunteers (age 27 +/- 3 y, BMI 23.3 +/- 2.0 kg m(-2); mean +/- SD)-randomly assigned to a 3-day treatment of either 5 mg enalapril or placebo. In the morning of the fourth day, volunteers orally received 3.5 mg glibenclamide together with either 10 mg enalapril or placebo. Blood glucose levels of volunteers were allowed to fall by 10% from fasting levels and were kept constant thereafter by employing a Biostator-based euglycemic glucose clamp. RESULTS: Coadministration of enalapril-compared with placebo-resulted in a temporarily higher metabolic effect of glibenclamide (AUC GIR(0-120)229 +/- 173 vs 137 +/- 44 mg kg(-1), p < 0.01; mean +/- SD), which lasted from 120 min to 240 min after enalapril administration. In parallel, the maximal metabolic effect of glibenclamide tended to be higher with enalapril (GIR(max)5.2 +/- 1.9 vs 4.1 +/- 1.3 mg kg(-1) min(-1); p = 0.19). However, the total metabolic effect of glibenclamide was almost identical between volunteers taking enalapril or placebo (AUC GIR(0-600)1267 +/- 334 vs 1286 +/- 249 mg kg(-1), ns). In contrast, serum insulin levels, C-peptide levels, and serum glibenclamide profiles were not significantly different between enalapril and placebo. CONCLUSIONS: The results of this study may explain the higher incidence of hypoglycemic episodes observed in patients with type 2 diabetes when taking ACE inhibitors together with sulfonylureas or insulin. ACE inhibitors may cause a temporary increase of the insulin sensitivity, which leads to an increased risk of hypoglycemia under these conditions.     

Effect of captopril and enalapril on left ventricular geometry, function and collagen during healing after anterior and inferior myocardial infarction in a dog model

Objectives. This study compared the effects of captopril and enalapril on left ventricular geometry, function and mass and on scar collagen and topography during healing after anterior and inferior myocardial infarction in a canine model.

Background. The beneficial effect of prolonged angiotensin-converting enzyme inhibitor therapy on remodeling during healing after myocardial infarction might be greater in anterior than inferior infarcts and more effective with captopril than enalapril therapy.

Methods. The effects of 6 weeks of therapy with captopril (50 mg twice a day), enalapril (2.5 mg twice a day) or placebo on in vivo variables of left ventricular remodeling, function and mass (by echocardiography), hemodynamic function, postmortem topography (by planimetry) and collagen (hydroxyproline levels) were studied in 36 instrumented dogs randomized to receive therapy 48 h after left anterior descending or left circumflex coronary artery occlusion.

Results. Compared with placebo therapy, both captopril and enalapril decreased infarct expansion and thinning, progressive ventricular dilation, ventricular mass and asynergy and infarct collagen levels in anterior and inferior infarcts. Despite similar small scar sizes, the effects on remodeling and dysfunction were greater in anterior than inferior infarcts. In addition, captopril produced greater attenuation of infarct expansion and ventricular enlargement, greater improvement in volume ejection fraction and less decrease in infarct collagen levels than enalapril.

Conclusions. On balance, captopril and enalapril attenuated left ventricular remodeling and preserved function in small anterior and inferior infarcts despite differences in the effects of the drugs on individual remodeling variables. Further studies will be needed to determine whether inhibition of infarct collagen might be harmful, or differences between captopril and enalapril therapy important, in large transmural infarctions.     

The pharmacokinetics, pharmacodynamics, safety and tolerability following 7 days daily oral treatment with NN703 in healthy male subjects.

The aim of the present study was to assess the safety, pharmacokinetics and pharmacodynamics (including specificity) of NN703 (tabimorelin), a growth hormone (GH) secretagogue, in healthy male subjects following treatment for 7 days once-daily. This was a randomized, double-blind and placebo-controlled study with four active dose levels: 1.71, 3.0, 4.5 and 6.86 mg/kg body weight. There was a dose-related increase for GH area under the curve (AUC) (0-12 h) and GH C(max)(0--12 h); these were significantly higher on both days 1 and 7 as compared with placebo treatment (P = 0.04 to P< 0.0001); however, an overall significant decrease in GH release was found from day 1 to day 7 (P< 0.001). Insulin-like growth factor-I (IGF-I) and IGF binding protein 3 (IGFBP-3) increased at all dose levels (including placebo); however, a significantly higher increase as compared with placebo treatment was observed at the three highest dose levels for IGF-I (P = 0.04--0.0006) and at the highest dose level for IGFBP-3 (P = 0.03). There was no statistically significant increase in AUC (0-5 h) for follicle-stimulating hormone, luteinizing hormone and cortisol between active and placebo treatment for day 1 or 7. On day 1 only, a statistically significant increase in AUC (0--5 h) was found for prolactin at 1.71 and 6.86 mg/kg (P< 0.05), for thyroid-stimulating hormone (TSH) at 3.0 mg/kg (P< 0.01) and for adrenocorticotrophic hormone (ACTH) at 4.5 mg/kg (P< 0.05); however, no dose--response relationship was observed for TSH or ACTH. In addition, a statistically significant decrease in AUC (0--5 h) for ACTH (3.0 and 6.86 mg/kg) and cortisol (1.71 mg/kg) was observed on day 7 (P< 0.05). Thus, NN703 is a promising candidate for treatment of absolute or relative GH deficiency.     

Long-term combined therapy with an angiotensin type I receptor blocker and an angiotensin converting enzyme inhibitor prolongs survival in dilated cardiomyopathy

The efficacy of ACE inhibitors (ACEIs) in the treatment of chronic heart failures is well documented. However, ACEIs may provide incomplete blockade of the renin-angiotensin system (RAS) because of the alternative pathways for angiotensin II (All) production. We hypothesized that more complete blockade of RAS by adding an AT1 receptor blocker (ARB) may have greater potential to decrease mortality associated with heart failure and improve cardiac function than monotherapy with ACEIs. The objective of this study was to evaluate the effect of combined therapy on cardiac functions and survival in cardiomyopathic hamsters. Male cardiomyopathic hamsters (BIO TO2) were administered either placebo (group C), enalapril (30 mg/kg/day) (group E), or enalapril (30 mg/kg/day) + valsartan (500 mg/ kg/day) (group EV), starting at the age of 6 weeks. Kaplan-Meier analysis was performed to assess the differences in survival. Cardiac functions were evaluated by echocardiogram and cardiac catheterization. Group EV showed significant increases in fractional shortening, LV dP/dTmax, and deceleration time, and showed significant decreases in left ventricular diastolic dimension, LV dP/dTmin, and early diastolic mitral velocity/atrial systolic velocity. Treatment with enalapril resulted in longer survival compared with placebo. Moreover, life expectancy (median probability of survival: 433 days) increased significantly in group EV compared with group E (P<0.05) as well as group C (P<0.001). It is concluded that combined therapy improved cardiac function and survival compared to placebo or enalapril monotherapy.     

A nine-month, placebo-controlled study of the effects of growth hormone treatment on lipoproteins and LDL size in abdominally obese men.

Abdominal/visceral obesity is associated with blunted growth hormone (GH) secretion and an unfavourable lipoprotein pattern. In this study, the effect of GH treatment on LDL size and on serum lipoprotein concentrations was determined in abdominally obese men. Thirty men, aged 48-66 years, with a body mass index (BMI) of 25-35 kg/m(2)and a waist:hip ratio of >0.95, received treatment with GH (9. 5 microg/kg/day) or placebo for 9 months.Serum concentrations of total cholesterol (TC), low density lipoprotein-cholesterol (LDL-C) and apolipoprotein B (apoB) were reduced (P<0.05, P<0.05 and P<0.001 vs placebo, respectively). Serum lipoprotein(a) [Lp(a)] concentration increased (P<0.05 vs. placebo). Mean low density lipoprotein (LDL) particle diameter was marginally increased by active treatment as compared with placebo (P =0.08). No changes were observed in the serum concentrations of high density lipoprotein-cholesterol (HDL-C), apolipoprotein A-I (apoA-I) and apolipoprotein E (apoE).In conclusion, 9 months of GH treatment in abdominally obese men beneficially reduced serum concentrations of TC, LDL-C and apoB, and marginally increased mean LDL diameter, while serum Lp(a) increased. The ultimate effect of GH therapy on the cardiovascular risk remains, however, to be determined.     

Omapatrilat, a dual angiotensin-converting enzyme and neutral endopeptidase inhibitor, prevents fatty streak deposit in apolipoprotein E-deficient mice

Angiotensin-converting enzyme (ACE) is mainly responsible for converting angiotensin I (AI) to angiotensin II (AII), and ACE inhibitors prevent atherosclerosis in animal models. Neutral endopeptidase 24.11 (NEP) degrades substance P, kinins and atrial natriuretic peptide (ANP), and aortic wall NEP activity was found to be increased in atherosclerosis. In the present study, we have evaluated the effect of candoxatril, a NEP inhibitor, and of omapatrilat, a dual ACE and NEP inhibitor, on the development of fatty streak in apolipoprotein E (apoE)-deficient mice. Groups of ten male apoE-deficient mice were given either placebo, candoxatril 50 mg/kg per day, or omapatrilat 10, or 100 mg/kg per day for 4 months. None of the treatments influenced body weight, serum total or HDL-cholesterol. Compared with the placebo, candoxatril did not protect the mice from fatty streak deposit. In contrast, omapatrilat dose dependently inhibited the constitution of fatty streak in apoE-deficient mice. The precise advantages of the dual ACE and NEP inhibition versus the inhibition of only ACE should now be considered in the prevention of atherosclerosis as well as in the occurrence of its complications.