Low-dose sustained release nicotinic acid (Tri-B3) and lipoprotein (a)

Does the beneficial effect of HRT on endothelial function depend on lipid changes

OBJECTIVES

To determine whether improvement in endothelial function of the brachial artery observed in women treated with hormone replacement therapy (HRT) may be explained by changes in lipid profile or blood pressure, information was used obtained in a single-centre, randomised, double blind, placebo-controlled trial.

METHODS

Hundred-and-five healthy postmenopausal women, aged 50-65 years, were treated with 0.625 mg conjugated equine estrogens (CEE) combined with 2.5 mg medroxyprogesterone acetate (MPA) (CEE+MPA), 2.5 mg tibolone or placebo for 3 months. At baseline and after 3 months, endothelial function was assessed using flow-mediated dilatation (FMD) and nitro glycerine-mediated dilatation (NMD). Furthermore, lipids were measured. Multivariate linear regression analysis was applied to address the research question.

RESULTS

Treatment with CEE+MPA resulted in an improvement in FMD of 2.0% (95% CI: -0.1; 4.1). CEE/MPA reduced total cholesterol with 13% (95% CI: -18%; -7%), LDL-cholesterol with 23% (95% CI: -30%; -15%) and lipoprotein(a) (Lp(a)) with 14% (95% CI: -26%; -2%). The magnitude of the relation of CEE/MPA with endothelial function was attenuated to from 2.0 to 1.6% when change in Lp(a) was taken into account. Adjustments for other lipids or blood pressure did not attenuate the association.

CONCLUSIONS

The improvement in endothelial function in postmenopausal women treated with CEE+MPA appears to be partially mediated by change in Lp(a), and apparently not by changes in other lipids.

Effect of hormone replacement therapy on lipids in perimenopausal and early postmenopausal women

OBJECTIVE

To determine the effects of oral sequential hormone replacement therapy (HRT) on lipid-profile in perimenopausal and early postmenopausal women.

METHODS

We performed a single-center, randomized, placebo-controlled trial. The trial was double blind with respect to 17beta-estradiol/desogestrel (17beta-E-D) and placebo and open with respect to conjugated estrogens/norgestrel (CEE-N). A total of 125 healthy perimenopausal and early postmenopausal women, aged 43-58 years, were recruited from the general population in Zoetermeer, the Netherlands. The intervention consisted of 6 months treatment with 1.5 mg 17beta-estradiol/0.15 mg desogestrel (n=53), 0.625 mg conjugated estrogens/0.15 mg norgestrel (n=36) or placebo (n=36). At baseline, cycle 1, 3 and 6, overnight fasting blood samples were obtained in which lipids were determined. We used linear regression analysis to calculate differences in mean change from baseline in lipids in the active treatment groups compared to placebo.

RESULTS

In both treatment groups significant (P<0.05) falls in low-density-lipoprotein (LDL)-cholesterol (17beta-E-D: -7.8% and CEE-N: -8.4%) and lipoprotein(a) (17beta-E-D: -11.7% and CEE-N: -28.3%) were found compared to placebo. Apolipoprotein A1 (17beta-E-D: 6.8% and CEE-N: 7.3%) and HDL-cholesterol (17beta-E-D: 6.4% and CEE-N: 8.0%) significantly increased compared to placebo. No significant changes were found in the other lipids. Mean changes from baseline in total cholesterol, LDL-cholesterol and apolipoprotein B were significantly more pronounced in postmenopausal women compared to perimenopausal women, adjustment for age-differences did not change the results.

CONCLUSION

Treatment of perimenopausal and early postmenopausal women with 17beta-E-D or CEE-N changes their lipid-profile in a potentially anti-atherogenic direction. Changes appear to be more pronounced in postmenopausal women compared to perimenopausal women.

Effect of gemfibrozil versus lovastatin on increased serum lipoprotein(a) levels of patients with hypercholesterolemia

The aim of this study was to determine the effect of gemfibrozil, compared with lovastatin, in patients with high levels of lipoprotein(a) and on plasma lipid profile. Twenty-seven nondiabetic patients with high levels of plasma lipids and lipoprotein(a), 19 male and eight female, aged 37-68 (mean +/- S.D. 54.2 +/- 7.5) years, were randomly assigned to 2 weeks of treatment with gemfibrozil 600 mg twice daily (14 pts.) or lovastatin 40-80 mg once daily (13 pts.). Patients had fasting plasma total cholesterol levels > or = 6.2 mmol/l, low-density lipoprotein > 4.14 mmol/l and lipoprotein(a) > 0.62 mmol/l. All patients but one had triglycerides > 2.82 mmol/l. There were no statistical differences between both groups in terms of age, sex, clinical diagnosis and previous medication. After 3 months of treatment, gemfibrozil reduced triglycerides (47.9% vs. 24.5%; P < 0.001), very low density lipoprotein (43.9% vs. 24.6%; P < 0.05), lipoprotein(a) (25.3% vs. 4.9%; P < 0.05) and increased high-density lipoprotein (34.4% vs. 11%; P < 0.01) more than lovastatin. Gemfibrozil and lovastatin reduced comparably total cholesterol (21.4% vs. 29.0%; P = NS) and low-density lipoprotein (26.5% vs. 37.3%; P = NS). The plasma levels of high-density lipoprotein and lipoprotein(a) were unchanged significantly by lovastatin. In conclusion, besides well-known efficacy in hyperlipidemia treatment, gemfibrozil also increased high-density lipoprotein and reduced lipoprotein(a), which may have important epidemiologic implications.

Lipoprotein(A): physiologic function, association with atherosclerosis, and effects of lipid-lowering drug therapy

OBJECTIVE

To review the structure and physiologic function of lipoprotein(a) [Lp(a)], review the association of Lp(a) with the development of atherosclerosis, and to critically evaluate the current literature regarding the effects of lipid-lowering drug therapy on Lp(a) serum concentrations.

DATA SOURCES

English language clinical and animal studies, abstracts, and review articles pertaining to Lp(a).

STUDY SELECTION AND DATA EXTRACTION

Relevant human and animal studies examining Lp(a)'s role in atherosclerosis and the effect of drug therapy on Lp(a) serum concentrations.

DATA SYNTHESIS

Possible physiologic functions and potential atherogenic mechanisms of Lp(a) are discussed. Evidence supporting the association of Lp(a) with atherosclerosis is presented. Studies evaluating the effects of lipid-lowering drug therapy on Lp(a) concentrations are reviewed and critiqued.

CONCLUSIONS

Lp(a) concentrations are correlated with the risk of atherosclerotic vascular disease (AVD) in both animals models and human studies. Drug therapies that have produced a consistent reduction in Lp(a) concentration include niacin alone or in combination with a bile acid sequestrant or neomycin. However, additional, larger studies are needed to evaluate the ability of drug therapies to specifically reduce elevated Lp(a) concentrations. Preliminary information suggests that reduction in Lp(a) concentrations may be associated with atherosclerotic plaque regression. Although drugs are available to lower Lp(a), one cannot conclude that lowering of Lp(a) is warranted until clinical trials demonstrating beneficial effects have been published.

Effects of hormone replacement therapy on lipoprotein(a) and lipids in postmenopausal women

High concentrations of lipoprotein(a) [Lp(a)], an independent risk factor for atherosclerosis, cannot be managed by the usual lipid-lowering agents. It has been suggested that Lp(a) levels are related to female sex hormones. Estrogen replacement therapy makes the lipid profiles favorable for delaying atherosclerosis in postmenopausal women. The effects of the combination therapy of estrogen and progesterone on lipids are controversial. This study was designed to evaluate the effect of female sex hormones on the concentration of Lp(a) and to clarify the influence of progesterone on the effect of estrogen in postmenopausal women. Postmenopausal women (n = 184) were divided into four groups: control; 0.625 mg conjugated equine estrogen (CEE) plus 10 mg medroxyprogesterone acetate (MPA); 0.625 mg CEE plus 5 mg MPA; and 0.625 mg CEE only. Medication for 2 months lowered the concentrations of Lp(a) by 20% in all treated groups. The decrease was more pronounced in subjects with a relatively higher basal Lp(a) concentration. Estrogen replacement therapy raised the concentration of high-density lipoprotein cholesterol and decreased low-density lipoprotein cholesterol without changing total cholesterol. The combination therapy of estrogen and progesterone abolished the effect of estrogen on high-density lipoprotein cholesterol. Hormone replacement therapy lowered Lp(a) levels in postmenopausal women. The effect was prominent in subjects with high basal Lp(a) levels. This decrease may be one of the mechanisms of the cardioprotective effects of estrogen. The cardioprotective effect of estrogen cannot be applied to the combination therapy due to the adverse effect of progesterone on high-density lipoprotein cholesterol.

Effects of age, sex, and menopausal status on plasma lipoprotein(a) levels. The Framingham Offspring Study

BACKGROUND

Lipoprotein(a) [Lp(a)] is an atherogenic particle that structurally resembles a low density lipoprotein (LDL) particle but contains a molecule of apolipoprotein(a) attached to apolipoprotein B-100 by a disulfide bond. Because elevated plasma levels of Lp(a) have been shown to be an independent risk factor for coronary artery disease, it is important to define normal ranges for this lipoprotein.

METHODS AND RESULTS

We have measured Lp(a) in 1,284 men (mean age, 48 +/- 10 years) and 1,394 women (mean age, 48 +/- 10 years) free of cardiovascular and cerebrovascular disease and not on medications known to affect lipids who were seen at the third examination cycle of the Framingham Offspring Study. Plasma Lp(a) levels were measured by an enzyme-linked immunosorbent assay, which uses a "capture" monoclonal anti-apo(a) antibody that does not cross-react with plasminogen, and a polyclonal anti-apo(a) antibody conjugated to horseradish peroxidase. The assay was calibrated to total Lp(a) mass. The Lp(a) frequency distribution was highly skewed to the right, with 56% of the values in the 0-10-mg/dL range. Mean plasma Lp(a) concentrations were 14 +/- 17 mg/dL in men and 15 +/- 17 mg/dL in women. Values of more than 38 mg/dL were above the 90th percentile and values of more than 22 mg/dL were above the 75th percentile in both men and women.

CONCLUSIONS

We have determined mean Lp(a) levels for men and women participating in the Framingham Offspring Study. In this population, there was an inverse association between plasma levels of Lp(a) and triglycerides for both sexes (p < 0.006), but triglycerides accounted for only approximately 0.5% of the variation in Lp(a) levels. Associations of Lp(a) levels with total and LDL cholesterol levels were not significant after correction for the estimated contribution of Lp(a) cholesterol to total and LDL cholesterol. After controlling for age, Lp(a) values were 8% greater in postmenopausal women than in premenopausal women, but this difference was not statistically significant. Body mass index, alcohol consumption, cigarette smoking, use of beta-blockers or cholesterol-lowering medications, and use of drugs for the treatment of diabetes and hypertension were not correlated with Lp(a) levels.