Beta-blockers and lipid metabolism

The use of diuretics in modern antihypertensive therapy

A review is made to sum up the indications when diuretics may be the drug of choice in the treatment of hypertension. Advantages from the combined treatment of thiazide diuretics and other antihypertensive agents are also emphasized. Adverse effects from diuretic treatment, i.e. hypokalemia, hyperuricemia, impaired glucose tolerance and risks associated with unfavourable serum lipoprotein patterns are discussed. It is concluded that from a hemodynamic point of view thiazide diuretics can be a good therapeutic alternative for most patients, excepting those with hyperkinetic circulation. It is recommended to use lower doses of thiazide diuretics than previously and the monitoring of S-potassium is necessary in all patients.

Do antihypertensive drugs precipitate diabetes in predisposed men?

OBJECTIVE

To evaluate the influence of antihypertensive treatment and metabolic characteristics on the development of diabetes mellitus in middle aged men.

DESIGN

Prospective study over an average of nine years.

SETTING

Community based health survey of middle aged men carried out at the University of Uppsala.

SUBJECTS

Seventy three hypertensive men aged 49-54 and 65 normotensive controls matched for body mass index, glucose disappearance rate (k value) at an intravenous glucose tolerance test, and serum triglyceride and cholesterol concentrations.

INTERVENTIONS

Hypertensive group was treated with beta blockers, thiazides, hydralazine, or combinations of these drugs. Treatment was not randomised.

MEASUREMENTS AND MAIN RESULTS

Intravenous glucose tolerance, fasting blood glucose and serum lipid and insulin concentrations, body weight and height, three skinfold measurements, and blood pressure were recorded both during an initial health screening survey in 1970-3 and at a follow up survey in 1980-3. In the period between the two surveys 12 hypertensive men and two controls developed diabetes. Review of values obtained at the initial survey showed that the hypertensive men who developed diabetes or impaired glucose tolerance could be distinguished from those hypertensive men who did not by virtue of a higher fasting serum insulin concentration (26.1 v 15.2 mU/l (confidence interval of difference -15.2 to -6.2)), a lower peak serum insulin concentration (78.9 v 94.3 mU/l (confidence interval of difference -1.1 to 41.1)), and a lower k value (1.29 v 1.68 (confidence interval of difference -0.02 to 0.68)). The insulin index (peak insulin concentration divided by fasting insulin concentration), however, decreased significantly in the hypertensive men over time irrespective of whether they developed diabetes but did not change in the controls. Furthermore, the serum triglyceride concentration increased in the treated group and decreased in the controls.

CONCLUSION

A severalfold difference in the incidence of diabetes between treated hypertensive and non-treated, normotensive men may be a consequence of the treatment, which may be particularly deleterious in men predisposed to diabetes.

Inhibition of purified human postheparin lipoprotein lipase by beta-adrenergic blockers in vitro

We examined the effects of five beta-adrenergic blockers on the hydrolysis of phosphatidylcholine-stabilized triolein particles by purified human postheparin lipoprotein lipase (PHLpL) in order to evaluate the possible role of direct inhibition as a mechanism of drug-induced hypertriglyceridemia. The relative inhibitory potencies were observed in the following order: propranolol much greater than pindolol greater than metoprolol greater than atenolol greater than nadolol. There was a positive correlation between the octanol/water partition coefficients of these agents and their inhibition of lipoprotein lipase, suggesting that hydrophobicity may be one of the major determinants for PHLpL inhibition. The amount of the beta-adrenergic blockers required to produce 50% inhibition of human PHLpL was much greater than that required to inhibit purified bovine lipoprotein lipase.

Effects of adrenoceptor-blocking drugs on plasma lipoprotein concentrations

Evidence from numerous clinical trials has indicated that beta-adrenoceptor blocking agents without intrinsic sympathomimetic activity increase plasma triglycerides and decrease high density lipoprotein cholesterol in patients with hypertension or coronary artery disease. There appears to be little or no difference between the nonselective and cardioselective drugs in this regard. In contrast, beta blockers with intrinsic sympathomimetic activity and alpha 1 blockers appear not to have these effects. The changes induced by adrenoceptor-blocking agents in lipid and lipoprotein metabolism and their possible significance in relation to the pathogenesis of coronary artery disease are discussed.

The effects of antihypertensive drugs on serum lipids and lipoproteins. II. Non-diuretic drugs

This review examines the effects of various antihypertensive drugs on blood lipids, lipoproteins, and apolipoproteins. A large number of studies have documented the elevation of total cholesterol, triglycerides, low density lipoprotein (LDL) cholesterol, and very-low density lipoprotein (VLDL) cholesterol with many thiazide-type diuretic drugs, albeit mainly in short term studies. When added to thiazide diuretics, both beta 1-selective and non-selective beta-blocking drugs elevate total triglycerides and VLDL triglycerides, lower high density lipoprotein (HDL) cholesterol and raise the ratio of total cholesterol to HDL cholesterol ratio. Most non-selective beta-blockers have similar effects when used as monotherapy, but the beta 1-selective agents appear not to affect HDL cholesterol in monotherapy. Prazosin appears free of adverse lipid effects and has improved lipid-lipoprotein concentrations in many studies. Preliminary data on several other drugs also suggest a favourable lipid profile and additional study is warranted - among these are guanabenz, clonidine, pindolol, labetalol, indapamide, and guanfacine. Elevations in serum triglycerides are often ignored on various counts, but triglycerides have been found to be a strong risk factor in European studies and in women over the age of 50 years in the Framingham study. Despite the unfavourable short term effects of diuretics, the theoretical risk of the lipid-lipoprotein changes remains unclear because HDL cholesterol and the total cholesterol to HDL cholesterol ratio are often unchanged. For this and other reasons, a long term trial comparing thiazide-type diuretics with drugs with the most favourable lipid-lipoprotein profile is needed. Until this is accomplished, in most settings diuretic-based regimens are still preferred initially since they are of proven, if limited, efficacy against the cardiovascular complications of hypertension.

Effects of guanfacine on growth hormone, prolactin, renin, lipoproteins and glucose in essential hypertension

The effect of single-dose, short-term (6 weeks) and long-term (7 years) guanfacine therapy on various endocrine and metabolic parameters was evaluated in patients with moderate essential hypertension (WHO phase I and II). A single oral dose (2 mg) of guanfacine did not affect the secretion of growth hormone but produced a prompt decrease in blood pressure (BP) levels. Short-term treatment decreased BP and heart rate, and also produced a marked (p less than 0.001) fall in urinary excretion of norepinephrine and serum prolactin levels. Short-term therapy did not affect growth hormone or renin levels. A mean daily dose of 2.8 mg of guanfacine maintained normal BP levels in 22 patients during the long-term follow-up study. In addition, treatment produced a progressive decrease in prolactin, renin, total cholesterol and triglyceride levels, but did not change growth hormone values or oral glucose tolerance test results. The cumulative incidence of cardiovascular complications was significantly lower (p less than 0.001) in guanfacine-treated patients than in a matched control group. The most significant difference was the absence of fatal complications in the guanfacine-treated patients. The present results support the theory that decreased morbidity and mortality in patients treated with guanfacine may depend not only on its important antihypertensive activity, but also on its beneficial effect on known cardiovascular risk factors.

Effect of chronic treatment of propranolol on lipid metabolism in spontaneously hypertensive rats (SHR)

The effects of propranolol on lipid metabolism were studied in spontaneously hypertensive rats (SHR). Male SHR and corresponding Wistar Kyoto rats (WKY) were used at 5 weeks of age. The SHR were given 10 mg/kg/day of dl-propranolol . HCl by gavage for 10 weeks. Body weight gain in untreated SHR and propranolol-treated SHR (SHR-P) groups were low, as compared with those of the WKY group. Total cholesterol, phospholipid and total lipid of the serum and liver in the SHR-P group were higher than in the SHR group. In the early weeks of treatment, serum triglyceride and non-esterified fatty acid levels in the SHR-P group were slightly lower than those in the SHR group. Aortic lipid levels in the SHR-P group were lower than those in the SHR group. During the later weeks of treatment, blood glucose level in the SHR-P group was higher than in the SHR group. The serum immunoreactive insulin value in the SHR-P group was slightly lower than in the SHR group. These results may suggest that propranolol inhibits hormone-sensitive lipase activity in the early weeks of treatment and influences cholesterol biosynthesis and/or catabolism.

[Antihypertensive therapy and lipid metabolism]

Hypertension, hyperlipidaemia and cigarette smoking are major risk factors in coronary heart disease. Since many antihypertensive drugs alter plasma lipid levels it is a subject of current discussion that these agents may increase associated coronary risk and therefore offset the beneficial effects of lowering blood pressure. The purpose of this paper is to review clinical and experimental data in the literature on the influence of data in the literature on the influence of antihypertensive drugs on lipid metabolism. The thiazides hydrochlorothiazide and chlorthalidone cause an elevation of plasma triglycerides and very low density lipoprotein (VLDL) but have little effect on total cholesterol, low density lipoprotein (LDL) and high density lipoprotein (HDL). The unspecific beta-blockers, e.g. propranolol, do not affect total cholesterol and LDL but increase total triglycerides and VLDL and decrease HDL. The changes of plasma lipids and lipoproteins caused by cardio-selective beta-blockers, e.g. atenolol and metoprolol, and unspecific beta-blockers with intrinsic sympathomimetic activity (ISA), e.g. oxprenolol and pindolol, appear to be qualitatively similar but less pronounced. The alpha 1-blocker prazosin reduces total triglycerides and slightly lowers total cholesterol. The concentration of VLDL plus LDL decreases while HDL may increase. Only very few studies have been reported on the effects of other antihypertensive drugs, e.g. clonidine, hydralazine, on plasma lipids. Several experimental studies reveal that antihypertensive agents exert direct effects on triglyceride and cholesterol metabolism. Although the pathophysiological mechanisms and the significance of the alterations of lipid metabolism induced by antihypertensive drugs are not yet clear, the following guidelines for the clinical use of these agents are recommended: (1) before initiating drug treatment in hypertensive patients, blood lipid levels should be measured to exclude a preexisting hyperlipidaemia, (2) during long-term therapy with antihypertensive agents, lipoprotein fractions should be controlled in order to reconsider the therapeutic regime if major alterations of blood lipid levels are observed.

Oxprenolol, methyldopa and lipids in diabetes mellitus

1 Twelve-week courses of oxprenolol and methyldopa were administered in a randomised, double-blind cross over study to ten insulin dependent hypertensive diabetics. 2 Prior to treatment, and at the end of each period of drug administration, fasting levels of high density lipoprotein, triglycerides, free fatty acids and cholesterol were measured. 3 Neither preparation altered levels of high density lipoprotein and cholesterol, but both drugs significantly reduced the free fatty acids. 4 Whereas oxprenolol did not alter triglyceride levels, methyldopa significantly elevated triglycerides above pre-treatment values. 5 Oxprenolol does not appear to influence lipoprotein fractions affecting the relative risks of coronary heart disease, but methyldopa seems to have potentially detrimental effects of triglyceride levels.

Reversal or prevention of diuretic-induced alterations in serum lipoproteins with betablockers

In 18 patients with essential hypertension serum low density lipoprotein cholesterol (LDL-C) was significantly (P less than 0.001) increased following short-term chlorthalidone therapy, but not during combination therapy with chlorthalidone and a betablocker. This tendency was similar in two subgroups which were studied with an inverse sequence of drug administration. In Group I (11 men), a 22% increase (P less than 0.01) in LDL-C during chlorthalidone monotherapy was restored to normal 6 weeks after addition to a betablocker to the diuretic; in Group II (5 men, 2 postmenopausal women) LDL-C levels were increased by 41% (P less than 0.05) 6 weeks after withdrawal of the betablocker from the combination therapy. No significant changes occurred during either the treatment phase in high density lipoprotein cholesterol or apoprotein B levels. It is concluded that combination therapy with a betablocker may prevent or reverse an increase in serum LDL-C associated with short-term chlorthalidone monotherapy.

Multivariate analyses of serum apolipoproteins and risk factors in relation to acute myocardial infarction

In 25 middle-aged infarction survivors and 76 corresponding controls, representative for a well-defined community, multivariate analysis was used to evaluate whether serum apolipoproteins were better discriminators of infarction survivors than serum lipids and other risk factors. Levels of serum cholesterol and triglycerides, alphalipoprotein cholesterol, apolipoproteins A-I, A-II, B, and D, as well as tobacco smoking and other risk factors, were included. In descending order, serum apo A-II levels (t(b) = -3.12, p = 0.002), tobacco consumption (t(b) = 2.64, p = 0.010), and serum triglycerides (t(b) = 2.06, p = 0.042) contributed significantly to the multiple regression on myocardial infarction (R = 0.53, p = 0.00001). When entered into ka discriminant function, these three variables gave a good separation between survivors and controls. Of the survivors, 50% were above the 90th percentile inthe control group. The relative prevalence of infarction increased continuously with increasing values of the function from zero to more than 6 times the average. Serum apo A-II levels alone were almost as good in separating cases and controls. From this study, we concluded that, among apolipoproteins, apo A-II seems to be a more sensitive discriminator of infarction survivors than other risk factors.

Serum lipoprotein changes during atenolol treatment of essential hypertension

Serum lipoproteins were determined in 15 patients before and during antihypertensive treatment with atenolol (0.1-0.2 g/day for a mean of 8 months. The mean blood pressure fell from 171/103 to 154/93 mm Hg (p less than 0.05). Significant lipoprotein changes were an increase in very low density triglycerides (VLDL-TG) from 1.21 +/- 0.95 (SD) to 1.62 +/- 1.24 mmol/l (p less than 0.01) and in low density (LDL) TG from 0.46 +/- 0.12 to 0.51 +/- 0.12 mmol/l (p less than 0.05). Together, these TG increases resulted in development of hypertriglyceridaemia in 7/15 patients during atenolol treatment. No effect on whole serum cholesterol or on the high density lipoprotein cholesterol concentrations were found. Thus, some patients on long term treatment with atenolol seem to received the benefit of normotension at the cost of hypertriglyceridaemia. This may have practical implications, since hypertriglyceridaemia, constitutes an important risk factor for atherosclerosis.

Treatment of mild hypertension: a five year controlled drug trial. The Oslo study

In 1972--1973, 785 symptom-free men, aged 40 to 49 years, without target organ damage, with systolic blood pressures between 150 and 179 mm Hg and diastolic blood pressure below 110 mm Hg, were assigned at random to one of two groups: (406 to a drug treatment group and 379 to a control group) for a five-year controlled drug treatment trial to evaluate the effect of therapy on cardiovascular complications. Drug treatment started with hydrochlorothiazide. If systolic blood pressure remained above 140 mm Hg and/or diastolic blood pressure above 90 mm Hg, alphamethyldopa was added. If there were side effects, methyldopa was replaced with propranolol. The control group was not given a placebo. The mean observation time was 66 months (range 60 to 78 months). A difference in blood pressure between groups of about 17 mm Hg systolic and 10 mm Hg diastolic was maintained throughout the study. The study protocol had a rather low "ethical" blood pressure roof, 180 mm Hg systolic and/or 110 mm Hg diastolic. Seventeen percent of the control group had an increase in blood pressure above this level during the trial, and drug treatment was started. There was no effect on major cardiovascular morbidity comparing groups as established by randomization, with 18 events in the treatment group and 20 events in the control group. There was no difference between the groups in total mortality and mortality from cardiovascular events. However, in the subgroups with diastolic blood pressure greater than or equal to 100 mm Hg before randomization, there was a probable reduction in total morbidity from cardiovascular events in favor or the group receiving drug therapy, 7.6 and 16.4 percent events in the treated and control groups, respectively. Cerebrovascular events occurred only in the control group, 7 versus 0. Two cases of fatal aortic aneurysms also occurred in the control group. Other "pressure" complications, such as marked left ventricular hypertrophy in the electrocardiogram and left ventricular failure, occurred only in the control group. However, regarding coronary heart disease, including sudden death, the incidence tended to be higher in the treated group, although it was not statistically significant. Only 13 men (1.7 percent) failed to meet for regular examinations. At the end of the study these men were also followed up with regard to possible cardiovascular events.

Atenolol v placebo in mild hypertension: renal metabolic and stress antipressor effects

1 The effects of 8 week treatment periods of atenolol and placebo on effective renal plasma flow (ERPF), glomerular filtration rate (GFR), plasma renin activity (PRA), oral glucose, fasting lipids and Achilles tendon reflex were compared in a double-blind crossover trial in ten subjects with mild hypertension.

2 Atenolol reduced resting blood pressure and pulse rate but did not prevent the rise in blood pressure and pulse rate in response to three kinds of stress.

3 Mean glomerular filtration rate and effective renal plasma flow were below the normal range during placebo (1.31 ml/s and 7.40 ml/s respectively) but were not significantly different on atenolol (1.23 ml/s and 7.18 ml/s). Serum urea was significantly (P < 0.01) higher on atenolol (6.7 mmol/l) than on placebo (5.6 mmol/l) but serum creatinine did not change. PRA was lower on atenolol (0.42 nmol l^-1 h^-1) than on placebo (1.01 nmol l^-1 h^-1).

4 The mean values of fasting cholesterol, triglycerides, ankle jerk contraction time, spirometry, weight, serum potassium, sodium and chloride were similar on atenolol and placebo.

5 Fasting blood sugar was a little higher (P < 0.05) on atenolol and the 1 and 2 h post-glucose serum insulin levels were a little lower (P < 0.01).

6 The cardioselectivity of atenolol does not impair its anti-hypertensive effect and may be associated with less effect on renal function. The metabolic effects of atenolol seem to differ from those of metoprolol.

Alphalipoprotein cholesterol levels in relation to acute myocardial infarction and its risk factors

During 1975-1977 twenty-nine males surviving acute myocardial infarction at an age between 40-44 years were registered in Gothenburg, Sweden. Twenty-five of these were studied and compared with two control groups. One group, the reference group (RG, n = 76), was randomly selected from the male population from which the acute myocardial infarction (AMI) group was derived. A second group, the matched control group (MC, n = 47), consisted of men with no history of coronary heart disease, matched with patients for age, serum cholesterol and body weight index. Serum triglyceride levels were higher and alphalipoprotein cholesterol lower in the AMI group than in RG. Prior to infarction, patients had a higher degree of physical activity at work and a higher tobacco consumption than RG. When AMI cases were compared with MC subjects lower alphalipoprotein cholesterol levels were found in AMI, and they also had a higher tobacco consumption prior to infarction. There was a negative correlation between alphalipoprotein cholesterol levels and tobacco consumption in the RG. The differences in alphalipoprotein cholesterol levels between AMI cases and controls could not attributed to smoking habits, but smoking may at least to some extent exert its effect as a risk factor through influence on alphalipoprotein cholesterol levels.

The effect of chlorthalidone on serum lipids and lipoproteins

The effect of chlorthalidone treatment on serum lipids and lipoproteins was investigated in 21 hypertensive patients. Chlorthalidone caused an increase in total serum and low density lipoprotein (LDL) cholesterol, but not in high density lipoprotein (HDL) cholesterol. Serum and lipoprotein triglycerides also increased. Our findings suggest that chlorthalidone increases serum concentrations of "atherogenic" lipoproteins (LDL and VLDL), and possibly decreases the levels of a "beneficial" lipoprotein, namely HDL. Thus, the use of this medication may increase a major atherosclerosis risk factor.