Lack of effects of angiotensin-converting enzyme (ACE)-inhibitors on glucose metabolism in type 1 diabetes

Renal Denervation Reverses Hepatic Insulin Resistance Induced by High-Fat Diet

Activation of the sympathetic nervous system (SNS) constitutes a putative mechanism of obesity-induced insulin resistance. Thus, we hypothesized that inhibiting the SNS by using renal denervation (RDN) will improve insulin sensitivity (S_I) in a nonhypertensive obese canine model. S_I was measured using euglycemic-hyperinsulinemic clamp (EGC), before (week 0 [w0]) and after 6 weeks of high-fat diet (w6-HFD) feeding and after either RDN (HFD + RDN) or sham surgery (HFD + sham). As expected, HFD induced insulin resistance in the liver (sham 2.5 ± 0.6 vs. 0.7 ± 0.6 × 10^-4 dL ⋅ kg^-1 ⋅ min^-1 ⋅ pmol/L^-1 at w0 vs. w6-HFD [P < 0.05], respectively; HFD + RDN 1.6 ± 0.3 vs. 0.5 ± 0.3 × 10^-4 dL ⋅ kg^-1 ⋅ min^-1 ⋅ pmol/L^-1 at w0 vs. w6-HFD [P < 0.001], respectively). In sham animals, this insulin resistance persisted, yet RDN completely normalized hepatic S_I in HFD-fed animals (1.8 ± 0.3 × 10^-4 dL ⋅ kg^-1 ⋅ min^-1 ⋅ pmol/L^-1 at HFD + RDN [P < 0.001] vs. w6-HFD, [P not significant] vs. w0) by reducing hepatic gluconeogenic genes, including G6Pase, PEPCK, and FOXO1. The data suggest that RDN downregulated hepatic gluconeogenesis primarily by upregulating liver X receptor α through the natriuretic peptide pathway. In conclusion, bilateral RDN completely normalizes hepatic S_I in obese canines. These preclinical data implicate a novel mechanistic role for the renal nerves in the regulation of insulin action specifically at the level of the liver and show that the renal nerves constitute a new therapeutic target to counteract insulin resistance.

Blocking the renin-angiotensin-aldosterone system to prevent diabetes mellitus

Type 2 diabetes mellitus (DM) is increasing around the world, and the public health impact of DM, driven largely by cardiovascular disease complications, underpins the importance of continued efforts toward primary prevention of DM. Only a few interventions have been shown to prevent DM, with none of them yet proven to improve cardiovascular risk commensurately. Accumulating evidence suggest that drugs that block the renin-angiotensin-aldosterone system (RAAS), many of which have proven cardiovascular disease (CVD) benefit, also have favourable effects on parameters of glucose metabolism and incident diabetes. Here we review the evidence accumulated to date from animal studies, clinical mechanistic studies and clinical trials regarding the effect of RAAS inhibition and incident DM.

Skeletal muscle capillary responses to insulin are abnormal in late-stage diabetes and are restored by angiotensin-converting enzyme inhibition

Acute physiological hyperinsulinemia increases skeletal muscle capillary blood volume (CBV), presumably to augment glucose and insulin delivery. We hypothesized that insulin-mediated changes in CBV are impaired in type 2 diabetes mellitus (DM) and are improved by angiotensin-converting enzyme inhibition (ACE-I). Zucker obese diabetic rats (ZDF, n = 18) and control rats (n = 9) were studied at 20 wk of age. One-half of the ZDF rats were treated with quinapril (ZDF-Q) for 15 wk prior to study. CBV and capillary flow in hindlimb skeletal muscle were measured by contrast-enhanced ultrasound (CEU) at baseline and at 30 and 120 min after initiation of a euglycemic hyperinsulinemic clamp (3 mU.min(-1).kg(-1)). At baseline, ZDF and ZDF-Q rats were hyperglycemic and hyperinsulinemic vs. controls. Glucose utilization in ZDF rats was 60-70% lower (P < 0.05) than in controls after 30 and 120 min of hyperinsulinemia. In ZDF-Q rats, glucose utilization was impaired at 30 min but similar to controls at 120 min. Basal CBV was lower in ZDF and ZDF-Q rats compared with controls (13 +/- 4, 7 +/- 3, and 9 +/- 2 U, respectively). With hyperinsulinemia, CBV increased by about twofold in control animals at 30 and 120 min, did not change in ZDF animals, and increased in ZDF-Q animals only at 120 min to a level similar to controls. Anatomic capillary density on immunohistology was not different between groups. We conclude that insulin-mediated capillary recruitment in skeletal muscle, which participates in glucose utilization, is impaired in animals with DM and can be partially reversed by chronic ACE-I therapy.

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.

Insulin sensitivity in hypertensive Type 2 diabetic patients after 1 and 19 days' treatment with trandolapril

AIMS

The aims of this study were to examine the effects of trandolapril, a long acting angiotensin converting enzyme (ACE) inhibitor with high tissue uptake, on insulin sensitivity and lipid concentrations in hypertensive patients with Type 2 diabetes mellitus.

METHODS

Insulin sensitivity was assessed after an acute dose (day 3) and 19 days continuous treatment (days 3-21) using the isoglycaemic, hyperinsulinaemic glucose clamp with D[3-3H] labelled glucose, a variable D[3-3H] priming dose and a 'hot' glucose infusion. Rates of glucose appearance (Ra) and glucose disappearance (Rd) were isotopically determined during the basal and insulin stimulated periods of the clamp. Twenty-four (5 female) hypertensive (blood pressure >75th centile for age and sex) patients with Type 2 diabetes mellitus were studied. Patients were randomized, in a double-blind manner, to either trandolapril 4 mg daily (T) or placebo (P).

RESULTS

Baseline (day 1) systolic (mean +/- SD; P 164+/-14 and T 168+/-13 mm Hg) and diastolic (P 93+/-6, and T 98+/-10 mm Hg) blood pressures were comparable. On days 3 and 21, significant reductions were observed in both groups (P<0.001). In the trandolapril-treated group, serum trandolapril concentrations were >200 pg/ml on days 3 and 21, in all patients apart from one subject at a single visit, while trandolapril was undetectable in the placebo group. Body mass index (BMI) was greater in T compared with P (32.2+/-5.4 v. 28.3+/-4.6, P = 0.07). After correcting for BMI, basal hepatic glucose output (HGO) P 2.6 (95% CI 2.23-3.13) and T 1.91 (1.33-2.51) mg x kg(-1) x min(-1) and clamped HGO P 0.32 (-0.44-1.09) and T 0.87 (0.40-1.34) mg x kg(-1) x min(-1) were similar in both groups. The insulin sensitivity index was comparable in both groups on all days. Total cholesterol concentrations were similar in both groups throughout the study. Triglyceride concentrations were significantly lower in group P 1.38 (1.07-1.68); T 2.14 (1.70-2.58) mmol/l, P<0.01), no significant treatment effect being observed.

CONCLUSIONS

An acute dose and 19 days' continuous treatment with trandolapril resulted in no change in insulin sensitivity or plasma lipid profiles in patients with Type 2 diabetes mellitus and hypertension. These data support the metabolic neutrality of trandolapril in patients with Type 2 diabetes mellitus and hypertension.

Antihypertensive drug therapy and hypoglycemia in elderly diabetic patients treated with insulin and/or sulfonylureas. Gruppo Italiano di Farmacovigilanza nell'Anziano (GIFA)

We performed this case control study to evaluate the risk of hypoglycemia associated with the use of antihypertensive drugs in older hospitalized diabetic patients treated with sulfonylureas and/or insulin. All diabetic patients admitted during 4 months in 1988, month in 1991, 4 months in 1993 and 4 months in 1995 (n = 3477, mean age 71.4 +/- 0.2 years, 1542 males and 1935 females) were enrolled in the study. During the four annual surveys 86 patients (mean age 71.1 +/- 1.4 years, 33 males and 53 females) presented hypoglycemia during hospital stay. The patients who presented hypoglycemia were less frequently users of sulfonylureas and more frequently users of a combination of insulin and sulfonylureas. Use of antihypertensive drugs was similar in the two groups studied, and among potentially interacting drugs considered in the analysis, sulfonamides were more frequently used in patients who experienced hypoglycemia. Moreover, patients with hypoglycemia used a higher number of drugs, had a longer length of stay and had a greater prevalence of hypoglycemia as admission problem. Finally, although not significant, liver and renal diseases were more frequent among patients with hypoglycemia. In the multivariate analysis, contemporary use of insulin and sulfonylureas, liver disease and length of stay were significantly associated with hypoglycemia, while none of the antihypertensive drugs showed a significant association with the occurrence of hypoglycemia during hospital stay. Our results indicate that antihypertensive drugs do not increase the risk of hypoglycemia in elderly diabetic patients.

Controlled study of the effect of angiotensin converting enzyme inhibition versus calcium-entry blockade on insulin sensitivity in overweight hypertensive patients: Trandolapril Italian Study (TRIS)

OBJECTIVE

The aim of this study was to evaluate the effect of trandolapril, an angiotensin converting enzyme inhibitor, on blood pressure, forearm blood flow and insulin sensitivity in comparison with nifedipine gastrointestinal therapeutic system.

PATIENTS AND METHODS

This is a multicentre, two-way parallel-group, open-label comparative study in 90 overweight hypertensive patients, who were randomly assigned to treatment for 8 weeks with either trandolapril or nifedipine. At baseline and after treatment, all patients underwent an oral glucose tolerance test, an evaluation of their metabolic profiles and a euglycaemic hyperinsulinaemic clamp test. In a subgroup of 18 patients, a forearm study was carried out.

RESULTS

Blood pressure fell by the second week of treatment and remained significantly reduced compared with baseline in both treatment groups. Plasma triglyceride levels were also significantly reduced after trandolapril therapy, but no significant changes occurred in the other metabolic parameters during treatment with either drug. During the euglycaemic hyperinsulinaemic clamp, whole-body glucose use was similar in the two treatment groups at baseline, and a moderate but statistically significant increase in insulin sensitivity was observed after trandolapril treatment (trandolapril: 5.0 +/- 0.2 versus 4.5 +/- 0.2 mg/kg per min; nifedipine: 4.1 +/- 0.3 versus 4.2 +/- 0.3 mg/kg per min; P < 0.05, versus baseline and trandolapril versus nifedipine treatment). Skeletal muscle glucose uptake was significantly higher after trandolapril than after nifedipine therapy (5.0 +/- 0.7 and 3.0 +/- 0.4 mg/min, respectively; P < 0.01). As forearm blood flow was similar in the two treatment groups at baseline and was unchanged after 8 weeks of therapy, skeletal muscle glucose extraction was significantly greater in the ACE inhibitor treated-group than in the nifedipine comparative group (trandolapril: baseline 21 +/- 2, treatment 24 +/- 3 mg/dl; nifedipine: baseline 18 +/- 3, treatment 16 +/- 2 mg/dl; P < 0.05, trandolapril versus nifedipine treatment).

CONCLUSIONS

During short-term treatment, ACE inhibition with trandolapril was able to moderately improve insulin sensitivity, in comparison with calcium blockade, and this effect appeared to be independent of the haemodynamic action of the drug.

Role of angiotensin-converting enzyme inhibition in glucose metabolism and renal injury in diabetes

The role of angiotensin-converting enzyme (ACE) inhibition in glucose metabolism and renal injury in diabetes has been extensively investigated in diabetic humans, as well as in animal models of diabetes. Accumulated data indicate that ACE inhibitors have either no adverse effect on glucose control or insulin sensitivity or may even improve them. ACE inhibitors also appear to have neutral or positive effects on lipid metabolism. The variability of results between studies may relate to differences in experimental design, the degree of glycemia or insulin resistance, potassium balance, and dose or duration of ACE inhibitor treatment, among others. In contrast, ACE inhibitors have proved effective in limiting proteinuria and retarding renal function loss in insulin-dependent diabetes mellitus (IDDM) or non-insulin-dependent diabetes mellitus (NIDDM) patients. In rats with experimental or spontaneous diabetes, ACE inhibitors also reduce proteinuria and limit glomerular as well as tubulointerstitial damage, independent of their effects on systemic arterial pressure. How ACE inhibitors limit renal injury in diabetes is not entirely clear, but hemodynamic and nonhemodynamic mechanisms may be involved. Increasing evidence suggests that the intrarenal renin-angiotensin system (RAS) may be altered or activated in the diabetic kidney. Such activation may be specifically inhibited by ACE inhibitors and may explain the superiority of this class of agents over other antihypertensive agents in reducing proteinuria and slowing the progression of diabetic nephropathy.

Long-term effects of perindopril on metabolic parameters and the heart in the spontaneously hypertensive/NIH-corpulent rat with non-insulin-dependent diabetes mellitus and hypertension

The spontaneously hypertensive/NIH-corpulent (SHR/N-cp) rat is a genetic model that exhibits both non-insulin-dependent diabetes mellitus (NIDDM) and hypertension. To determine the impact of long-term treatment with the long-acting angiotensin-converting enzyme (ACE) inhibitor perindopril (PE) on the glucose metabolism, lipid levels, and heart in this model, studies were performed in three groups of SHR/N-cp rats maintained on a diet containing 54% carbohydrate with 18% sucrose and 36% starch. One group of obese rats received PE (0.5 to 1.0 mg/kg body weight/d) for 3 to 4 months, a second group of obese rats received no treatment, and a third group of lean rats were used as controls. The mean systolic blood pressure (SBP) increased gradually in both untreated obese and lean rats, with lean animals showing slightly higher levels compared with untreated obese rats. By contrast, SBP was reduced to normal levels in PE-treated obese rats throughout the treatment period. Compared with lean rats, obese rats showed significantly higher body weight and fasting serum levels of glucose, insulin, total cholesterol (TC), and triglyceride (TG). However, no significant differences were observed in these metabolic parameters between PE-treated and untreated obese rats. Plasma renin activity measured at the end of the treatment period was significantly higher in PE-treated rats compared with untreated obese and untreated lean rats. The mean heart weight and left ventricular weight, expressed in absolute terms or indexed to body weight, were significantly lower in PE-treated versus untreated obese and untreated lean rats. To further determine whether glucose metabolism is directly affected by PE treatment, in vitro glycogen synthesis was evaluated in isolated soleus muscles obtained from three additional groups of animals. The basal rate of muscle glycogen synthesis was significantly lower in obese compared with lean rats (P < .05), but did not differ between PE-treated and untreated obese rats. Maximal insulin-stimulated glycogen synthesis increased threefold in PE-treated obese rats, but this increase did not differ from the increases observed in untreated obese and lean rats. In conclusion, the present study shows that long-term PE treatment in obese SHR/N-cp rats with NIDDM and hypertension effectively controlled systemic arterial pressure and resulted in a significant reduction in left ventricular weight. However, these favorable effects of PE were not associated with significant improvement in glucose tolerance, hyperinsulinemia, and hyperlipidemia in this model. PE also had no direct stimulatory effects on either basal or insulin-mediated glycogen synthesis in the isolated soleus muscle of obese rats, perhaps because of the severe insulin-resistant state of the animals. Our results support the clinical observations that antihypertensive therapy with ACE inhibitors has neutral effects on glucose metabolism and insulin sensitivity in patients with combined hypertension and NIDDM.

Effects of enalapril, losartan, and verapamil on blood pressure and glucose metabolism in the Cohen-Rosenthal diabetic hypertensive rat

We undertook the present study to examine the effect of the angiotensin-converting enzyme inhibitor enalapril, the angiotensin II antagonist losartan, and calcium antagonist verapamil on systolic pressure and spontaneous blood glucose levels in rats from the Cohen-Rosenthal diabetic hypertensive strain. Genetic hypertension and diabetes developed in this strain after crossbreeding of Cohen diabetic and spontaneously hypertensive rats. The new rat strain was fed their usual copper-poor sucrose diet, which is essential for the development of this model, and for 4 weeks received either enalapril, losartan, or verapamil. Systolic pressure was reduced significantly compared with controls in all treated groups. Chronic treatment with enalapril or verapamil, but not with losartan, succeeded in lowering spontaneous blood glucose, indicating improved diabetic control. Data suggest that angiotensin-converting enzyme inhibition by enalapril, but not angiotensin II antagonism by losartan, can improve glucose metabolism in addition to its hypotensive effect in a genetic diabetic hypertensive rat strain. This confirms that the drop in glucose with converting enzyme inhibition is highly dependent on bradykinin accumulation. Data further suggest that calcium channel blockade by verapamil can also improve glucose metabolism. The question remains whether the reduction in glucose by verapamil was a result of inhibition of glucogenesis.

Metabolic manifestations of low-dose diuretics

Hypertension has been defined and treated as a disease of abnormal systolic and diastolic blood pressure. Recent data have, however, demonstrated that effective blood-pressure control has not resulted in the expected decrease in coronary artery disease. These findings are probably a result of hypertension being a complex inherited syndrome of cardiovascular risk factors, all of which are genetically linked and all of which contribute to the development of cardiovascular disease in these patients. Included in the hypertension syndrome are abnormalities of lipid profile, insulin resistance, changes in renal function, left ventricular hypertrophy and reduced arterial compliance. In many patients, high blood pressure is a late manifestation of this disease process. Since all cardiovascular risk factors contribute to heart disease in these patients, they should all be considered in the management of this disease process. Diuretics and beta blockers, when used at high doses, negatively impact lipid metabolism and insulin sensitivity, while angiotensin converting enzyme (ACE) inhibitors and calcium antagonists tend to have a neutral effect on these metabolic risk factors. These findings have resulted in decreased use of diuretics and beta blockers in favor of newer agents such as ACE inhibitors and calcium antagonists. However, recent data have demonstrated that when used at low doses (6.25 or 12.5 mg of hydrochlorothiazide), diuretics lack significant metabolic side effects while bringing about significant reductions in blood pressure. Thus, at these doses, hydrochlorothiazide is a useful drug in the treatment of hypertension, both as monotherapy and in combination therapy.

Enalapril improves glucose tolerance in two rat models: a new hypertensive diabetic strain and a fructose-induced hyperinsulinaemic rat

1. The present study was undertaken to examine the effect of the angiotensin converting enzyme (ACE) inhibitor, enalapril, on blood pressure and spontaneous blood glucose levels in two rat models: our new diabetic hypertensive rat in which genetic hypertension and diabetes develop following cross-breeding of Cohen diabetic rat (CDR) and spontaneous hypertensive rats (SHR); and a rat in which hypertension, hyperinsulinaemia and hyperlipidaemia were induced by fructose diet. 2. The new strain of animal was fed the usual copper-poor sucrose diet, and for 4 weeks received enalapril. The fructose-induced hyperinsulinaemic animals were fed a fructose-enriched diet for 3 weeks, and enalapril 20 mg per kg per day was added to the drinking water for 2 more weeks. 3. The new strain of diabetic-hypertensive rats that received enalapril showed a significant decrease in blood pressure level. The fructose-fed animals showed a fall in insulin and blood pressure following the introduction of enalapril to their diet. 4. The present study confirms the advantage of the ACE inhibitor enalapril in improving the metabolic parameters of hypertensive diabetic rats, including insulin sensitivity.

Effect of angiotensin-converting enzyme inhibitors on fructose induced hypertension and hyperinsulinaemia in rats

1. The effect of angiotensin-converting enzyme inhibitors (ACEI) enalapril, lisinopril and ramipril was studied on fructose-induced hypertensive and hyperinsulinaemic rats. 2. 60 Sprague-Dawley rats were fed a fructose-enriched diet for 5 weeks, which produced hyperinsulinaemia, hypertriglyceridaemia and hypertension. Beginning with week 3 of the diet, lisinopril (10 and 20 mg per kg per day), ramipril (5 and 10 mg/kg per day) and enalapril (20 mg/kg per day) were given daily in drinking water for 2 weeks to 10 rats in each drug group. Ten rats fed only the fructose-enriched diet served as control. 3. Systolic blood pressure was measured weekly by the indirect tail-cuff method. Plasma insulin level was determined using RIA. 4. Data indicate that ACEI improve insulin resistance induced by high-fructose intake in rats; that despite their equal hypotensive effect, ACEI differ in their ability to improve insulin resistance; and that improvement of insulin resistance by ACEI is dose-dependent.

Normalization of insulin resistance in non-obese essential hypertension by cilazapril treatment

To determine whether ACE inhibitor other than captopril improves insulin sensitivity in patients with essential hypertension, we measured insulin sensitivity to glucose utilization using SSPG method in 10 lean hypertensive subjects before and after chronic cilazapril treatment (1.5 +/- 0.2 mg/day, 15.6 +/- 2.1 weeks). The results were compared with those obtained in 10 healthy control subjects. SSPG obtained by insulin sensitivity test was significantly higher in hypertensive subjects, indicating a lower insulin sensitivity than in controls. After cilazapril treatment, SSPG reduced significantly to the level which was statistically not different from control subjects. Hyperinsulinemia diminished after treatment, while no significant change of blood glucose was observed during oral glucose tolerance test in hypertensive subjects. Plasma HDL cholesterol increased by cilazapril treatment. Cilazapril treatment has beneficial effect in the reversal of insulin resistance in patients with essential hypertension.

Hypoglycaemia associated with use of inhibitors of angiotensin converting enzyme

The use of angiotensin-converting-enzyme (ACE) inhibitors has been associated with increased insulin sensitivity in diabetic patients. Although such an effect could be beneficial in the treatment of hypertension or congestive heart failure in diabetic patients, it might also precipitate severe hypoglycaemia. To test this hypothesis we carried out a nested case-control study, using data in the Dutch PHARMO system (1986-92), among diabetic patients treated with insulin or with oral antidiabetic drugs, who were admitted to hospital with hypoglycaemia. We identified 94 patients who had been admitted with hypoglycaemia and selected 654 controls from the same cohort. With adjustment for a wide range of potential confounding factors, hypoglycaemia was significantly associated with current use of ACE inhibitors (odds ratio 2.8 [95% CI 1.4-5.7]). Both among users of insulin and among users of oral antidiabetic drugs, use of ACE inhibitors was significantly associated with an increased risk of hospital admission for hypoglycaemia (2.8 [1.2-6.4] and 4.1 [1.4-12.2], respectively). Although ACE inhibitors have several advantages over other antihypertensive drugs in diabetes, the risk of hypoglycaemia should be taken into account. Further investigation of the mechanism is needed since as many as 13.8% of all hospital admissions for hypoglycaemia might be attributable to use of ACE inhibitors.

Effect on insulin sensitivity of angiotensin converting enzyme inhibitors with or without a sulphydryl group: bradykinin may improve insulin resistance in dogs and humans

The present study compared the effect on insulin sensitivity of ACE inhibitors with a sulphydryl group (captopril) or those without a sulphydryl group (delapril and enalapril) during the hyperinsulinaemic euglycaemic clamp test in both animal and clinical experiments. A possible contribution of bradykinin to the improvement of insulin sensitivity by ACE-inhibition was also studied. In healthy control and depancreatized dog experiments, administration of captopril either intravenously (3.0 mmol.kg-1) or orally (5.0 mmol.kg-1) increased insulin sensitivity indices and plasma bradykinin concentrations. In comparison, intravenous administration of an active metabolite of delapril (3.0 mmol.kg-1) and oral administration of either delapril or enalapril (5.0 mmol.kg-1) showed slight, but not significant increases in insulin sensitivity indices and plasma bradykinin concentrations. Infusion of a bradykinin antagonist (N-alpha-adamantane-acetyl-D-Arg-[Hyp3,Thi5,8,D-Phe7]-b bradykinin) (0.5 nmol.kg-1 x min-1) abolished the effect of captopril on insulin sensitivity. Furthermore, intravenous administration of bradykinin (0.1 nmol.kg-1 x min-1) increased insulin sensitivity indices. In clinical experiments, insulin sensitivity indices decreased in the following order: normotensive healthy subjects, hypertensive non-diabetic patients, normotensive NIDDM patients and hypertensive NIDDM patients. In these four groups, oral administration of captopril (2.0 mmol.kg-1) significantly increased insulin sensitivity indices, and a concomitant increase in plasma bradykinin concentrations was observed. By contrast, oral administration of enalapril or delapril showed slight, but not significant effects on insulin sensitivity indices and plasma bradykinin concentrations. From these studies, it is concluded that ACE inhibitors with a sulphydryl group have more potent action on the improvement in insulin sensitivity than those without a sulphydryl group.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of chronic ACE inhibition on glucose tolerance and insulin sensitivity in hypertensive type 2 diabetic patients

The question, of whether long-term treatment of essential hypertension with angiotensin-converting enzyme (ACE) inhibitors is capable of modifying glucose tolerance or insulin sensitivity in Type 2 (non-insulin dependent) diabetes, is still unsolved. We studied 14 moderately overweight Type 2 diabetic patients with essential hypertension in stable metabolic control after a run-in period and again after 3 months of antihypertensive treatment with the ACE inhibitor, captopril. Glucose tolerance was tested with a 75-g oral glucose load and insulin sensitivity was measured by the insulin suppression test, while dietary and drug treatment of the diabetes remained constant. In the whole group, mean blood pressure (MBP) fell progressively over 3 months from a baseline value of 123 +/- 3 mmHg to a final value of 115 +/- 2 mmHg (p < 0.005); in six patients, the change in MBP was < 5 mmHg (non-responders), thus giving a clinical response rate of approximately 60%. After treatment, fasting plasma glucose, insulin, free fatty acid (FFA), potassium, and glycated haemoglobin concentrations were unchanged from baseline. During the oral glucose tolerance test, the incremental glucose area-under-curve was 0.75 +/- 0.05 mol 120 min l-1 before and 0.76 +/- 0.06 mol 120 min l-1 after treatment (p = ns). Endogenous insulin response and suppression of plasma FFA levels were superimposable on the two occasions. During the insulin suppression test, steady-state plasma glucose levels were 14.4 +/- 1.3 vs 14.2 +/- 1.1 mmol l-1 before and after chronic ACE inhibition, respectively, at comparable hyperinsulinaemic plateaux (291 +/- 21 vs 287 +/- 14 pmol l-1).(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of chronic angiotensin converting enzyme inhibition on glucose tolerance and insulin sensitivity in essential hypertension

The relation between the renin-angiotensin-aldosterone (RAA) system and carbohydrate metabolism and insulin sensitivity in essential hypertension has not been investigated systematically. Twenty nondiabetic patients (age, 49 +/- 1 years; body mass index (BMI), 26.1 +/- 0.4 kg/m2) with essential hypertension (blood pressure, 155 +/- 3/105 +/- 1 mm Hg) received an oral glucose tolerance test (OGTT) at the end of a 1-month placebo period and again monthly during 3 months of angiotensin converting enzyme (ACE) inhibition (cilazapril, 5 mg/day). Furthermore, a two-step euglycemic insulin clamp was performed after placebo and again at the end of treatment. Blood pressure fell by 7 +/- 4/10 +/- 3 mm Hg (p less than 0.001), while BMI remained stable. On the euglycemic clamp, insulin-mediated (plasma insulin, 470 pM) whole body glucose use averaged 42.5 +/- 1.6 mumol.min-1.kg-1 before and 43.6 +/- 1.9 after ACE inhibition (p = NS). Substrate concentrations and oxidative rates and energy expenditure (as estimated by indirect calorimetry) were not altered by ACE inhibition, either in the fasting state or in response to insulin. In contrast, oral glucose tolerance was significantly (p less than 0.05) improved after treatment (area under OGTT curve (AUC), 240 +/- 24 versus 282 +/- 23 mmol 2 hr.l-1). The latter change was associated with enhanced (+16%, p less than 0.05) insulin responsiveness to glucose (estimated as the insulin AUC divided by the glucose AUC) throughout the 3 months of ACE inhibition. At baseline, both the OGTT and the clamp had a marked hypokalemic effect (mean decrements in plasma potassium of 0.75 +/- 0.05 and 0.92 +/- 0.05 mmol/l, respectively) in association with plasma aldosterone reductions of 30% and 50%. Chronic ACE inhibition caused a further 20% (p less than 0.03) lowering of plasma aldosterone concentrations but attenuated insulin-induced hypokalemia. Plasma sodium, which was unaltered by the pretreatment tests, fell during the posttreatment tests (by 3 mmol/l, p less than 0.001). In the urine, the ratio of the fractional excretion of potassium to that of sodium was decreased by both oral glucose (-22%, p less than 0.01) and ACE inhibition (-21%, p less than 0.001). Higher plasma potassium levels before treatment predicted a better blood pressure response to ACE inhibition (r = 0.60, p less than 0.005).(ABSTRACT TRUNCATED AT 400 WORDS)

Effects of perindopril on insulin sensitivity and plasma lipid profile in hypertensive non-insulin-dependent diabetic patients

About 40% of patients with non-insulin-dependent diabetes (NIDDM) have hypertension, which in turn may contribute to their enhanced risk for cardiovascular diseases. However, a number of antihypertensive agents tend to cause a deterioration in the control of diabetes. The present study was designed to elucidate whether treatment with perindopril (a new angiotensin-converting enzyme [ACE] inhibitor) affects plasma lipid metabolism, glucose homeostasis, and insulin sensitivity. Ten patients with NIDDM and moderate hypertension were studied in a double-blind, placebo-controlled, crossover study encompassing 6 weeks of placebo treatment and 6 weeks of perindopril treatment given in random order. Mean systolic/diastolic blood pressure was 162/94 +/- 6/3 mm Hg during placebo treatment versus 157/91 +/- 5/2 mm Hg during perindopril therapy. Plasma levels of free fatty acids, triglycerides, high density lipoprotein (HDL) cholesterol, and total cholesterol were similar during placebo and perindopril treatment. Oral glucose tolerance tests showed similar responses of plasma glucose, serum insulin, and serum C peptide following placebo and perindopril treatment. Insulin sensitivity estimated with an intravenous insulin tolerance test (IVITT) was unchanged by perindopril therapy (KIVITT: 0.014 +/- 0.001 min-1 [placebo] versus 0.015 +/- 0.003 min-1 [perindopril], difference not significant. In conclusion, treatment with perindopril in NIDDM patients had no adverse effects on plasma lipids, glucose tolerance, or insulin sensitivity.

Effects of ACE inhibition supplementary to beta blockers and diuretics in early diabetic nephropathy

Angiotensin converting enzyme (ACE) inhibition has shown promising results in diabetic nephropathy, but long-term results on survival are not available. In a cohort of patients receiving antihypertensive treatment predominantly consisting of beta blockers in combination with diuretics, support for an improved survival has been presented. Addition of ACE inhibition to such a combination treatment may be favorable both due to the suggested renoprotective effects of ACE inhibitors and because diuretics activate the renin-angiotensin system. In 10 insulin-dependent diabetic patients with early diabetic nephropathy [urinary albumin excretion rate (UAE) less than 100o micrograms/min], who were receiving continuous therapy with metoprolol and bendroflumethiazide, a double-blind crossover study with four months addition of ramipril 5 mg (Ramace) and placebo was conducted. UAE (radioimmunoassay) and fractional albumin excretion were significantly reduced after the four months of ramipril administration [UAE: 114.1 x/divided by 1.3 (geometric mean x/divided by confidence factor] versus 174.6 x/divided by 1.2 micrograms/min, 2P less than 0.005). Renal plasma flow (clearance of 131I-hippuran) tended to increase [497 +/- 25 (mean +/- SE) vs. 464 +/- 28 ml/min/1.73 m2, 2P = 0.08], while GFR (125I-iothalamate) stayed unchanged (121 +/- 8 vs. 120 +/- 9 ml/min/1.73 m2). Mean arterial pressure during clearance studies fell moderately (95 +/- 3 vs. 101 +/- 1 mm Hg, 2P less than 0.05) and renal resistance was decreased (2P less than 0.03). ACE activity was suppressed in all patients. Twenty-four-hour ambulatory blood pressure measurements were not significantly different after the two periods (daytime averages: 91 +/- 2 vs. 93 +/- 2, nighttime 80 +/- 2 vs. 84 +/- 3 mm Hg).(ABSTRACT TRUNCATED AT 250 WORDS)

Enalapril. A reappraisal of its pharmacology and therapeutic use in hypertension

Enalapril, an angiotensin converting enzyme (ACE) inhibitor usually administered orally once daily, decreases blood pressure by lowering peripheral vascular resistance without increasing heart rate or output. It is effective in lowering blood pressure in all grades of essential and renovascular hypertension. Patients not responding adequately to enalapril monotherapy usually respond with the addition of a thiazide diuretic (or a calcium antagonist or beta-blocker), and rarely require a third antihypertensive agent. Enalapril is at least as effective as other established and newer ACE inhibitors, and members of other antihypertensive drug classes including diuretics, beta-blockers, calcium antagonists and alpha-blockers, but therapy with enalapril may be less frequently limited by serious adverse effects or treatment contraindications than with other drug classes. The most frequent adverse effect limiting all ACE inhibitor therapy in clinical practice is cough. This favourable profile of efficacy and tolerability, and the substantial weight of clinical experience, explain the increasing acceptance of enalapril as a major antihypertensive treatment and supports its use as logical first-line therapeutic option.

Effects of hyperglycaemia on kidney function, atrial natriuretic factor and plasma renin in patients with insulin-dependent diabetes mellitus

In normoalbuminuric patients with insulin-dependent diabetes mellitus, plasma atrial natriuretic factor (ANF), cyclic GMP and active renin and the renal clearances of [99Tcm]-diethylenetriaminepentaacetic acid (DTPA) lithium and sodium were studied on a hyperglycaemia day and a euglycaemia day. Baseline euglycaemia was achieved by an overnight variable insulin infusion, which during study days was fixed at the rate necessary to maintain euglycaemia in the morning. After a baseline euglycaemic clearance period of 90 min, measurements were repeated in a new 90-min period beginning 150 min later. On the hyperglycaemia day i.v. infusion of 20% glucose was started at the end of the euglycaemic baseline period, increasing blood glucose (5.3 +/- 1.3 vs 12.1 +/- 1.2 mmol l-1, p less than 0.01). On the euglycaemia day blood glucose declined (5.1 +/- 1.0 vs 4.2 +/- 1.0 mmol l-1, p less than 0.02). Glomerular filtration rate (GFR) was unchanged by acute hyperglycaemia (127 +/- 16 vs 129 +/- 24 ml min-1, NS), but nearly normalized during maintained euglycaemia on the euglycaemia day (124 +/- 17 vs 105 +/- 16 ml min-1, p less than 0.01). When comparing the hyperglycaemic study period with the similarly timed period on the euglycaemia day, GFR was elevated by hyperglycaemia (129 +/- 24 vs 105 +/- 16 ml min-1, p less than 0.01), while the renal clearances of lithium and sodium were similar. Consequently, the calculated absolute proximal reabsorption rate of sodium and water was elevated during hyperglycaemia. Hyperglycaemia reduced the slight decline in plasma concentrations of ANF and cyclic GMP observed on the euglycaemia day. Active renin, glucagon and plasma osmolality were unchanged. In conclusion, marked changes in glomerular filtration rate are induced by changes in blood glucose concentration, but the effect is delayed and thus not directly related to renal tubular transport of glucose. Hyperglycaemia does not affect renal clearances of lithium and sodium, while proximal tubular reabsorption is markedly stimulated. These changes are not related to changes in ANF, renin, glucagon or plasma osmolality.

ACE-inhibition increases hepatic and extrahepatic sensitivity to insulin in patients with type 2 (non-insulin-dependent) diabetes mellitus and arterial hypertension

To assess the effects of ACE-inhibition on insulin action in Type 2 (non-insulin-dependent) diabetes mellitus associated with essential hypertension, 12 patients with Type 2 diabetes (on diet and oral hypoglycaemic agents) and arterial hypertension were examined on two occasions, in a single blind, cross-over study after two days of treatment with either captopril or a placebo. The study consisted of a euglycaemic-hyperinsulinaemic clamp (two sequential steps of insulin infusion at the rates of 0.25 mU.kg-1.min-1 and 1 mU.kg-1.min-1, 2 h each step), combined with an infusion of 3-3H-glucose to measure the rate of hepatic glucose production and that of peripheral glucose utilization. The results show that blood pressure was lower after captopril (sitting, systolic 148 +/- 5 mm Hg, diastolic 89 +/- 2 mm Hg) compared to placebo (155 +/- 6 and 94 +/- 2 mm Hg) (p less than 0.05). Captopril treatment resulted in a more suppressed hepatic glucose production (2.7 +/- 0.4 vs 4.94 +/- 0.55 mumol.kg-1.min-1), and a lower plasma non-esterified fatty acid concentration (0.143 +/- 0.05 vs 0.200 +/- 0.05 mmol/l) (captopril vs placebo, p less than 0.05) at the end of the first step of insulin infusion (estimated portal plasma insulin concentration 305 +/- 28 pmol/l); and in a greater glucose utilization (36.5 +/- 5.1 vs 28 +/- 3.6 mumol.kg-1.min-1, p less than 0.001) at the end of the second step of insulin infusion (arterial plasma insulin concentration of 604 +/- 33 pmol/l).(ABSTRACT TRUNCATED AT 250 WORDS)