Effects of bunazosin and atenolol on serum lipids and apolipoproteins in a randomised trial

Effects of beta-blockers on glucose and lipid metabolism

BACKGROUND

Activation of the sympathetic nervous system (SNS) has been linked to hypertension. Beta-blockers, which decrease SNS activation via beta-adrenergic receptor antagonism, are effective in lowering blood pressure and reducing cardiovascular morbidity and mortality in several conditions, including post-myocardial infarction and heart failure. Despite these clinical benefits, many physicians are reluctant to prescribe beta-blockers because of perceived negative metabolic effects, including reduced glycemic control, masking of hypoglycemia, insulin resistance, and dyslipidemia.

OBJECTIVE

This article reviews the pathophysiology of hypertension and either insulin resistance or dyslipidemia as well as treatment effects from glucose- and lipid-lowering regimens on cardiovascular morbidity and mortality. Based on a PubMed literature search from January 1980 to December 2008, the effects of nonvasodilating (atenolol, metoprolol, and propranolol) and vasodilating beta-blockers (carvedilol, labetalol, and nebivolol) on parameters of glucose and lipid metabolism in hypertension are presented. Preference for clinical trial inclusion was given to randomized, controlled trials with at least 100 patients. Limitations of a drug class literature review may include trial inclusion bias with associated result skewing and underrepresentation of an individual agent, which may give different results.

RESULTS

Beta-blockers differ in terms of their mechanism of action and their effects on glucose and lipid metabolism. Nonvasodilating beta-blockers reduce blood pressure in association with a cardiac output reduction and may increase or have no appreciable effect on peripheral vascular resistance. As a result, nonvasodilating beta-blockers are associated with a worsening of glycemic and lipidic control. In contrast, vasodilating beta-blockers reduce peripheral vascular resistance but have little or no effect on cardiac output. Numerous studies have established that vasodilating beta-blockers are associated with more favorable effects on glucose and lipid profiles than nonvasodilating beta-blockers.

CONCLUSIONS

Improvements in glucose and lipid metabolism mediated by vasodilating beta-blockers may help reduce coronary artery disease risk among high-risk patients with hypertension.

New treatment strategies for patients with hypertension and insulin resistance

The metabolic syndrome is characterized by the clustering of insulin resistance, dyslipidemia, and hypertension and is associated with increased risk of cardiovascular disease and type 2 diabetes mellitus. However, older antihypertensive agents such as thiazide diuretics and beta-blockers have potentially adverse effects on glucose and lipid metabolism and may even the exacerbate the metabolic syndrome and increase risk of type 2 diabetes. Recent clinical trials have suggested that antihypertensive agents that inhibit the renin-angiotensin system may reduce risk for new-onset type 2 diabetes, but only a few of these studies were placebo controlled, and in most cases, the absolute antidiabetic effects were relatively modest. Evidence is accumulating that telmisartan, in addition to blocking the angiotensin II type 1 receptor, activates the peroxisome proliferator-activated receptor (PPAR)-gamma a well-known target for treatment of the metabolic syndrome and diabetes. By contrast, other angiotensin-receptor blockers are largely devoid of activity on PPAR-gamma. Telmisartan is a partial agonist of PPAR-gamma and has a superior tolerability profile without causing the fluid retention and edema associated with full agonists of PPAR-gamma such as pioglitazone and rosiglitazone. Recent studies have indicated that in addition to antidiabetic properties, PPAR-gamma activators may also provide protection against atherosclerosis and coronary events. Thus, the ability of telmisartan both to activate PPAR-gamma and to block the angiotensin receptor may provide added value not only in the treatment of the metabolic syndrome and prevention of type 2 diabetes but also in prevention and treatment of atherosclerotic cardiovascular disease.

Synergistic Effect of Doxazosin and Acarbose in Improving Metabolic Control in Patients with Impaired Glucose Tolerance

OBJECTIVE

The aim of this study was to evaluate if the expected improvement in glucose and lipid metabolism obtainable with doxazosin is or is not synergistic with standard antihyperglycaemic treatment using the alpha-glucosidase inhibitor acarbose.

METHODS

Patients in this randomised, controlled, double-blind clinical trial were enrolled, evaluated and followed up at three Italian centres. We evaluated 107 patients (53 males and 54 females) with impaired glucose tolerance (IGT) as determined by oral glucose tolerance tests (OGTTs). All patients took a fixed dose of acarbose 150 mg/day for 3 months, after which they were titrated up to 300 mg/day for the next 3 months. In addition, patients were randomised to either placebo (53 patients: 27 males and 26 females, aged 50 +/- 4 [mean +/- SD] years) or doxazosin 4 mg/day (54 patients: 26 males and 28 females, aged 51 +/- 5 years) for the entire 6-month treatment period. Parameters evaluated during the 6-month treatment period included body mass index (BMI), glycaemic control (glycosylated haemoglobin [HbA(1c)], fasting plasma [FPG] and post-prandial plasma [PPG] glucose, fasting plasma [FPI] and post-prandial plasma [PPI] insulin levels, homeostasis model assessment [HOMA]-index [insulin resistance]), lipid profile (total cholesterol [TC], low-density lipoprotein cholesterol [LDL-C], high-density lipoprotein cholesterol [HDL-C], and triglycerides [TG]), and systolic (SBP) and diastolic (DBP) blood pressure.

RESULTS

Significant reductions in BMI, HbA(1c), FPG and PPG compared with baseline were observed after 6 months in both groups (p < 0.05). A significant decrease in FPI was obtained after 6 months (p < 0.05) in the doxazosin group compared with baseline, and this difference was also significant (p < 0.05) compared with the placebo group. Similarly, a significant decrease in HOMA-index was observed at 6 months (p < 0.05) compared with baseline in the doxazosin group, and this difference was also significant (p < 0.05) compared with the placebo group. Significant decreases in TC, LDL-C, HDL-C and TG (p < 0.05) were observed in the doxazosin group after 6 months compared with baseline values. Significant decreases in SBP and DBP were also observed at 3 months in the doxazosin group compared with baseline (p < 0.05), and these differences were significant (p < 0.05) compared with placebo. Furthermore, significant decreases in SBP and DBP were observed at 6 months (p < 0.01) in the doxazosin group compared with baseline, and these differences were also significant (p < 0.01) compared with placebo. All patients who completed an OGTT at 6 months (96 patients) were restored to normal glucose tolerance status.

CONCLUSION

In patients with IGT, doxazosin given in combination with acarbose seemed to improve glycaemic and lipid control compared with placebo, with the benefits observed appearing to extend beyond those expected from improvements in blood pressure. Patients in this study also benefited from acarbose therapy, which restored all patients from IGT to normal glucose tolerance status.

Comparison of the effects of telmisartan and nifedipine gastrointestinal therapeutic system on blood pressure control, glucose metabolism, and the lipid profile in patients with type 2 diabetes mellitus and mild hypertension: a 12-month, randomized, double-blind study

BACKGROUND

Angiotensin receptor blockers (ARBs) provide effective blood pressure control. Whereas none of the ARBs appear to affect glucose homeostasis, some ARBs have been associated with a decrease in cholesterolemia.

OBJECTIVE

This study was conducted to evaluate blood pressure control glucose homeostasis, and the plasma lipid profile in patients with type 2 diabetes mellitus and mild hypertension during 12 months of treatment with the ARB telmisartan or nifedipine gastrointestinal therapeutic system (GITS).

METHODS

In this double-blind trial, patients taking oral hypoglycemic agents were randomized to receive telmisartan 40 mg or nifedipine GITS 20 mg once daily for 12 months. At the time of enrollment, patients were given advice on diet (1400-1600 kcal/d) and exercise (stationary bicycle for > or =30 min, 4 d/wk). Assessments of systolic blood pressure (SBP), diastolic blood pressure, body mass index (BMI), fasting plasma glucose concentrations, glycosylated hemoglobin, fasting plasma insulin concentrations, the homeostasis model assessment of insulin resistance, and the lipid profile were performed at baseline and after 6 and 12 months of treatment.

RESULTS

One hundred sixteen patients were divided into 2 age- and sex-matched treatment groups (58 men, 58 women; mean [SD] age, 52.5 [5] years). All patients were in good general health at baseline; had achieved adequate glycemic control with diet and oral hypoglycemic agents; were taking antihypercholesterolemic drugs; and had no evidence of macroangiopathy, microalbuminuria, or neuropathy. There were significant reductions from baseline in seated trough SBP after 12 months of treatment with both telmisartan and nifedipine GITS (from 139 [4] to 132 [4] mm Hg and from 140 [4] to 130 [4] mm Hg, respectively; both, P < 0.01). No change in BMI or glucose metabolism was observed with either treatment. After 12 months, there were significant improvements in concentrations of total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) with telmisartan (-9% and -11.5%, respectively; both, P < 0.01) compared with nifedipine GITS (-2% and -1.5%).

CONCLUSIONS

In this selected sample of patients with type 2 diabetes and mild hypertension, both telmisartan and nifedipine GITS produced significant reductions in blood pressure. Telmisartan was associated with a slight but statistically significant improvement in plasma TC and LDL-C concentrations compared with nifedipine GITS.