Lipids and lipoproteins during antihypertensive drug therapy. Comparison of doxazosin and atenolol in a randomized, double-blind trial: the Alpha Beta Canada Study

Association between dyslipidemia and antihypertensive and antidiabetic treatments in a China multicenter study

Dyslipidemia is an emerging disease in China, especially in the presence of hypertension and diabetes mellitus. We investigated the association of dyslipidemia with the use of antihypertensive and antidiabetic agents. The study participants (n = 2423) were hypertensive and diabetic patients enrolled in a China nationwide registry. Serum mean ± (SD, except for serum triglycerides, median [interquatile range]) concentrations were 1.38 (0.97‐2.02) mmol/L, 4.85 ± 1.12 mmol/L, 1.30 ± 0.36 mmol/L, and 2.89 ± 0.92 mmol/L for triglycerides and total, high‐density lipoprotein (HDL), and low‐density lipoprotein (LDL) cholesterol, respectively. The prevalence of dyslipidemia was 18.9%, 13.5%, 16.6%, and 37.7% for hypertriglyceridemia (serum triglycerides ≥2.3 mmol/L), hypercholesterolemia (total cholesterol ≥6.2 mmol/L or LDL cholesterol ≥4.1 mmol/L), low HDL cholesterol (HDL cholesterol <1.0 mmol/L), and any of the three lipid disorders, respectively. Treated (n = 1647), compared with untreated hypertensive patients (n = 303), had a significantly (P ≤ .0006) lower serum total, LDL, and HDL cholesterol, but similar serum triglycerides (P = .20). Treated (n = 1325), compared with untreated diabetic patients (n = 238), had a significantly (P ≤ .004) lower serum triglycerides, and total and LDL cholesterol, but similar serum HDL cholesterol (P = .81). After adjustment, the odds ratios (OR) were significant for hypercholesterolemia (OR 0.76, 95% confidence interval [CI] 0.58‐0.997, P = .048) and low HDL cholesterol (OR 1.56, CI 1.19‐2.03, P = .001) in treated versus untreated hypertension, and for low HDL cholesterol (OR 1.50, CI 1.18‐1.89, P = .0008) in treated versus untreated diabetes. In conclusion, the prevalence of dyslipidemia differed between treated and untreated hypertension and diabetes.

The impact of carvedilol and metoprolol on serum lipid concentrations and symptoms in patients with hyperthyroidism

BACKGROUND

Hyperthyroidism is associated with unpleasant symptoms and hypertension due to increased adrenergic tone. Therefore, beta-blockers are often used in hyperthyroid patients. While some beta-blockers (such as propronolol and metoprolol) may have unwanted effects on lipid profile, carvedilol, a new alpha- and beta-blocker, has been suggested to have some metabolic advantages with respect to lipid profiles in hypertensive patients. However, this has not been shown in hyperthyroid patients.

OBJECTIVE

We aimed to compare the effects of two beta-blockers (metoprolol and carvedilol) on the lipid profiles of hyperthyroid patients with hypertension.

METHODS

Thirty patients with hyperthyroidism and hypertension were randomly assigned to receive either carvedilol (n = 15) or metoprolol (n = 15). Thyroid-stimulating hormone (TSH), free T3, free T4, low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), triglyceride, and total cholesterol levels were measured before and following 3 months of treatment.

RESULTS

Systolic and diastolic blood pressure, heart rate, TSH, and free T4 improved significantly in both treatment groups. There were no statistically significant changes in the lipid parameters in either of the two treatment groups; however, triglyceride levels slightly decreased with carvedilol treatment. There were also no differences between the two groups in terms of the typical symptoms of hyperthyroidism.

CONCLUSION

Carvedilol might be a preferred agent to treat hyperthyroid patients who have hypertension and dyslipidemia. This is likely due to the possible beneficial effect of carvedilol on lipid parameters, especially on triglyceride levels.

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.

ATP-Binding Cassette Transporter A1 Gene Transcription Is Downregulated by Activator Protein 2α

ATP-binding cassette transporter A1 (ABCA1) is a rate-limiting factor for high-density lipoprotein (HDL) biogenesis. The ABCA1 gene expression is known to be upregulated by various transcriptional factors. However, negative regulation factors would be better targets for pharmacological modulation of HDL biogenesis. Doxazosin, an α 1 -adrenoceptor blocker, increased ABCA1 mRNA, its protein, and apolipoprotein A-I–mediated HDL biogenesis in THP-1 macrophages and CHO-K1 cells, independent of α 1 -adrenoceptor blockade. Analysis of the human ABCA1 promoter indicated that the region between the positions −368 and −147 that contains an activator protein (AP)2-binding site responsible for the effects of doxazosin. Overexpression of AP2α inhibited ABCA1 transcription in a dose-dependent fashion. Mutation in the AP2-binding site caused increase of the basal promoter activity and canceling both the transactivation by doxazosin and the trans-repression by AP2α. Doxazosin had no effect on ABCA1 mRNA level in HepG2 cells, which lack endogenous AP2α, and it reversed the inhibitory effect of AP2α expression in this type of cells. Chromatin immunoprecipitation and gel shift assays revealed that doxazosin reduced specific binding of AP2α to the ABCA1 promoter, as it suppressed phosphorylation of AP2α. Finally, doxazosin increased ABCA1 expression and plasma HDL in mice. We thus concluded that AP2α negatively regulates the ABCA1 gene transcription. Doxazosin inhibits AP2α activity independent of α 1 -adrenoceptor blockade and increases the ABCA1 expression and HDL biogenesis. AP2α is a potent pharmacological target for the increase of HDL.

Combining beta-adrenergic and peroxisome proliferator-activated receptor gamma stimulation improves lipoprotein composition in healthy moderately obese subjects

Current pharmacological regimens for hypertriglyceridemia and low high-density lipoprotein (HDL) are limited to the peroxisome proliferator-activated receptor (PPAR) alpha activating fibrates, niacin, and statins. This pilot study examined the impact of simultaneous stimulation of cyclic adenosine monophosphate with a beta-adrenergic agonist and PPARgamma with pioglitazone (PIO) on lipoprotein composition in moderately obese, healthy subjects. Subjects were treated with PIO (45 mg) to stimulate PPARgamma or a combination of ephedrine (25 mg TID), a beta-agonist, with caffeine (200 mg TID), a phosphodiesterase inhibitor (ephedrine plus caffeine), or both for 16 weeks. Lipoproteins were separated by gradient ultracentrifugation into very low-density lipoprotein (VLDL), intermediate-density lipoprotein, low-density lipoprotein (LDL), and 3 HDL (L, M, and D) subfractions. Apolipoproteins were measured by high-performance liquid chromatography. PIO alone reduced the core triglyceride (TG) content relative to cholesterol ester (CE) in VLDL (-40%), IDL (-25%), and HDL-M (-38%). Ephedrine plus caffeine alone reduced LDL CE (-13%), phospholipids (-9%), and apolipoprotein (apo) B (-13%); increased HDL-M LpA-I (HDL containing apoA-I without apoA-II, 28%), CE/TG (23%), and CE/apoA-I (8%) while reducing apoA-II (-10%); and increased HDL-L LpA-I (29%). Combination therapy reduced total plasma TG (-28%), LDL cholesterol (LDL-C, -10%), apoB (-16%), apoB/apoA-I ratio (-21%) while increasing HDL cholesterol (HDL-C, 21%), total plasma apoA-I (12%), LpA-I (43%), and apoC-I (26%). It also reduced VLDL total mass (-34%) and apoC-III (-39%), LDL CE (-13%), apoB (-13%), and total mass (-11%). Combination therapy increased HDL-L CE/TG (32%), apoC-I (30%), apoA-I (56%), and LpA-I (70%), as well as HDL-M CE (35%), phospholipids (24%), total mass (19%), apoC-I (25%), apoA-I (18%), and LpA-I (56%). In conclusion, simultaneous beta-adrenergic and PPARgamma activation produced beneficial effects on VLDL, LDL, HDL-L, and HDL-M. Perhaps the most important impact of combination therapy was dramatic increases in LpA-I and apoC-I in HDL-L and HDL-M, which were much greater than the sum of the monotherapies. Because LpA-I appears to be the most efficient mediator of reverse-cholesterol transport and a major negative risk factor for cardiovascular disease, this combination therapy may provide very effective treatment of atherosclerosis.

Serum glucose and lipid changes during the course of clozapine treatment: the effect of concurrent beta-adrenergic antagonist treatment

We examined the effects of long-term clozapine treatment, concurrent treatment with beta-adrenergic antagonists, and clozapine-induced weight gain on serum glucose and lipid measures. Fifty subjects met the DSM-III-R criteria for schizophrenia or schizoaffective disorder, participated in a 10-week, double-blind comparison of haloperidol and clozapine and a 1-year, open-label clozapine trial, and had available serum glucose and lipid levels. Weight and glucose, and lipid laboratory values were measured at the baseline and throughout the double-blind and year-long study. There were significant increases in serum triglyceride, total cholesterol, and glucose levels during the course of clozapine treatment. There were no significant changes in high-density lipoprotein (HDL) or low-density lipoprotein (LDL). Propranolol and atenolol had additive effects on changes in the total cholesterol and triglycerides, with propranolol having the most pronounced effects. Propranolol and atenolol had no significant effect on the serum glucose levels. There were significant correlations between the triglyceride and HDL level changes and clozapine-associated weight gain during the study. There were no significant correlations between the change in serum total cholesterol, LDL, or glucose and weight gain. Clozapine therapy has adverse effects on glucose and lipid homeostasis, with clozapine-induced changes in serum glucose likely due to the inherent pharmacological properties of clozapine. Concurrent beta-adrenergic receptor antagonist treatment may have an additive effect on serum lipids, and clozapine-associated weight gain also plays a modest role in triglyceride increases.

Systemic adverse effects of beta-adrenergic blockers: an evidence-based assessment

PURPOSE

To present an evidence-based review of the systemic adverse effects of beta-adrenergic blockers and recommend safety guidelines for use of ophthalmic beta-adrenergic blockers.

DESIGN

Literature review of published articles in peer-reviewed journals and medical texts.

METHODS

Pre-MEDLINE and MEDLINE search of relevant English language articles from 1966 to the present. Cardiovascular, pulmonary, endocrine/metabolic, central nervous system, sexual, exercise, and neuromuscular effects of systemic or ophthalmic beta-adrenergic blockers were reviewed.

RESULTS

Systemic beta-adrenergic antagonists unequivocally reduce mortality in patients with mild, moderate, and even severe congestive heart failure. Development of symptomatic bradycardia on systemic or ophthalmic beta-adrenergic blockers alone likely indicates underlying cardiac conduction disturbances. Beta 2-adrenergic blockade, regardless of route of administration, may exacerbate or trigger bronchospasm in patients with asthma or pulmonary disease associated with hyper-reactive airways. This review identifies no scientific studies supporting the development of worsening claudication, depression, hypoglycemic unawareness, or prolonged hypoglycemia in non-insulin-dependent diabetes, sexual dysfunction, or impaired neuromuscular transmission with systemic or ophthalmic beta-adrenergic blockers.

CONCLUSIONS

Many commonly presumed adverse beta-adrenergic blocker effects observed via systemic or ocular administration are not supported by published randomized clinical trials. Wide acceptance of such traditionally purported side effects has been largely due to propagation of isolated case reports and short series as well as personal communication felt to reflect expert opinion. Many more patients may be eligible to use these drugs. Obtaining a careful medical history and checking pulse rate and rhythm in the office should identify the vast majority of patients with potential cardiopulmonary contraindications.

Beta-blockers in the management of hypertension in patients with type 2 diabetes mellitus: is there a role?

It has been conclusively established that treatment of hypertension in patients with type 2 (non-insulin-dependent) diabetes mellitus will significantly reduce the incidence of stroke, heart failure and progression of diabetic complications. Beta-blockers are effective antihypertensive agents which, in long term studies, have proven beneficial in reducing important clinical end-points. However nonselective beta-blockers may have a negative effect on lipid profiles and contribute to hypoglycaemic unawareness, thus preventing their use in some patients with diabetes mellitus. The development of newer and more selective beta-blockers has overcome many of these problems. In addition, some of the newer agents have novel properties such as release of nitric oxide, which theoretically would make them more attractive in patients with diabetes mellitus. Overall, the adverse metabolic effects of beta-blockers do not appear to be important in clinical practice and these agents should no longer be contraindicated in patients with type 2 diabetes mellitus. Their proven cardiovascular benefits would seem to easily tip the balance in favour of their use.

Apolipoprotein E polymorphisms and concentration in chronic diseases and drug responses

Apolipoprotein (apo) E is an important circulating and tissue protein involved in cholesterol homeostasis and many other functions. The common polymorphism in the coding region of the gene, four polymorphisms in the promoter region, other additional single nucleotide polymorphisms, as well as several apo E variants have been identified. The common coding polymorphism strongly influences the lipid metabolism and the circulating concentration of apo E itself. This polymorphism is at the origin of the implication of apo E in cardiovascular and neurodegenerative diseases, but also of the relation of apo E with longevity. Probably due to its many metabolic and functional consequences, apo E polymorphism has been shown to influence the responses of patients to several drugs (fibrates, statins, hormone replacement therapy, anti-Alzheimer drugs) or environmental interventions (black tea, alcohol, diet). Apo E genotyping may be clinically helpful in defining the risk of patients and their responses to therapeutics. Finally, circulating apo E concentration appears to be altered in diseases and can be modulated by some of the drugs cited above. This parameter can thus also give interesting clinical information and could be a therapeutic target, providing it is validated. At the present time, we cannot exclude that apo E concentration may be the most prominent apo E parameter to be considered in health and disease, while apo E polymorphisms would represent only secondary parameters influencing apo E concentration.

Efficacy and tolerability of doxazosin versus enalapril in the treatment of patients with mild-to-moderate hypertension

The effects of 4 weeks of treatment with doxazosin or enalapril on diastolic blood pressure (DBP) and plasma lipid levels were studied in 160 patients 18 to 50 years old with mild-to-moderate hypertension. Comparing baseline measurements with measurements taken after 4 weeks, DBP was significantly reduced by 6.8 +/- 7.4 (mean +/- SD) mm Hg and 12.0 +/- 7.1 mm Hg in the doxazosin and enalapril groups, respectively. Systolic blood pressure was significantly decreased from baseline to end of treatment in both groups. There were no significant changes in heart rate from baseline to end of treatment in the doxazosin group, but there was a statistically significant decrease in heart rate in the enalapril group. High-density lipoprotein cholesterol increased statistically significantly in the doxazosin group but not in the enalapril group. A decrease in triglycerides was statistically significant with respect to the doxazosin group and was close to significance for the enalapril group. Forty-nine (62%) patients in the doxazosin group and 43 (54%) patients in the enalapril group reported at least one adverse event. Significant reductions in DBP after 4 weeks of treatment were achieved by both drugs, each taken once daily. This reduction was more pronounced in the enalapril group 24 hours postdose, with a mean final daily dose of 2.8 mg of doxazosin and 12.6 mg of enalapril. However, even relatively short-term treatment with low-dose doxazosin showed a more favorable effect on lipids than did enalapril.

Review: the effects of antihypertensive agents on serum lipids

Because various antihypertensive drugs adversely affect lipid metabolism, these drugs may increase associated risks for coronary artery disease and thus offset some of the beneficial effects of blood pressure reduction. In this paper the current literature regarding the effects of antihypertensive agents on serum lipids is reviewed. Differing effects of various classes of antihypertensives are assessed to further our understanding of this very important subject.

Doxazosin. An update of its clinical pharmacology and therapeutic applications in hypertension and benign prostatic hyperplasia

Doxazosin is a long-acting alpha 1-adrenoceptor antagonist structurally related to prazosin and terazosin. Its antihypertensive effect is produced by a reduction in the smooth muscle tone of peripheral vascular beds resulting in a decrease in total peripheral resistance without significant effect on cardiac output or heart rate. In benign prostatic hyperplasia, doxazosin's effect of relieving bladder outflow obstruction is produced through a reduction in prostatic tone mediated via alpha 1-adrenoceptor blockade. In most comparative trials doxazosin has proven to be equally effective as the comparator drug in the treatment of mild to moderate hypertension. It has been used in a variety of patient populations including the elderly, Blacks, smokers, and patients with concomitant disease states such as renal dysfunction, hypercholesterolaemia, non-insulin dependent diabetes mellitus (NIDDM) and respiratory disease. Doxazosin has also been used successfully in combination with beta-adrenoceptor antagonists, diuretics, calcium channel antagonists, and angiotensin-converting enzyme inhibitors in patients with hypertension that is uncontrolled with monotherapy. Doxazosin has a beneficial effect on some of the risk factors associated with coronary heart disease including elevated serum lipid levels, impaired glucose metabolism, insulin resistance and left ventricular hypertrophy. Modest decreases in total cholesterol, low density lipoprotein cholesterol and triglycerides are seen with doxazosin therapy while small increases in high density lipoprotein cholesterol and the high density lipoprotein cholesterol/total cholesterol ratio are consistently reported. Some studies have reported an improvement in glucose tolerance although this effect has been more consistently seen in nondiabetic patients than in patients with NIDDM. Additionally, doxazosin produces a similar reduction in left ventricular hypertrophy to other antihypertensive agents. Modelling-based calculations suggest that doxazosin significantly reduces the risk of developing coronary heart disease in patients with mild to moderate hypertension, although this remains to be confirmed in long term prospective studies. Doxazosin appears to be a promising agent in the treatment of urinary symptoms associated with benign prostatic hyperplasia. Similar to other alpha 1-adrenoceptor antagonists, doxazosin treatment produces increases in peak and mean urinary flow rates and improves other objective and symptomatic measures.(ABSTRACT TRUNCATED AT 400 WORDS)