Effects of estrogen replacement with and without medroxyprogesterone acetate on brachial flow-mediated vasodilator responses in postmenopausal women with coronary artery disease

Estrogen and the Vascular Endothelium: The Unanswered Questions

Premenopausal women have a lower incidence of cardiovascular disease (CVD) compared with their age-matched male counterparts; however, this discrepancy is abolished following the transition to menopause or during low estrogen states. This, combined with a large amount of basic and preclinical data indicating that estrogen is vasculoprotective, supports the concept that hormone therapy could improve cardiovascular health. However, clinical outcomes in individuals undergoing estrogen treatment have been highly variable, challenging the current paradigm regarding the role of estrogen in the fight against heart disease. Increased risk for CVD correlates with long-term oral contraceptive use, hormone replacement therapy in older, postmenopausal cisgender females, and gender affirmation treatment for transgender females. Vascular endothelial dysfunction serves as a nidus for the development of many cardiovascular diseases and is highly predictive of future CVD risk. Despite preclinical studies indicating that estrogen promotes a quiescent, functional endothelium, it still remains unclear why these observations do not translate to improved CVD outcomes. The goal of this review is to explore our current understanding of the effect of estrogen on the vasculature, with a focus on endothelial health. Following a discussion regarding the influence of estrogen on large and small artery function, critical knowledge gaps are identified. Finally, novel mechanisms and hypotheses are presented that may explain the lack of cardiovascular benefit in unique patient populations.

Coronary Artery Disease and Endothelial Dysfunction: Novel Diagnostic and Therapeutic Approaches

Coronary artery disease is the leading cause of morbidity and mortality worldwide. The most common pathophysiologic substrate is atherosclerosis which is an inflammatory procedure that starts at childhood and develops throughout life. Endothelial dysfunction is associated with the initiation and progression of atherosclerosis and is characterized by the impaired production of nitric oxide. In general, endothelial dysfunction is linked to poor cardiovascular prognosis and different methods, both invasive and non-invasive, have been developed for its evaluation. Ultrasound evaluation of flow mediated dilatation of the branchial artery is the most commonly used method to assessed endothelial function while intracoronary administration of vasoactive agents may be also be used to test directly endothelial properties of the coronary vasculature. Endothelial dysfunction has also been the subject of therapeutic interventions. This review article summarizes the knowledge about evaluation of endothelial function in acute coronary syndromes and stable coronary artery disease and demonstrates the current therapeutic approaches against endothelial dysfunction.

Total brachial artery reactivity and first time incident coronary heart disease events in a longitudinal cohort study: The multi-ethnic study of atherosclerosis

Background

Brachial artery reactivity (BAR) is usually determined as the maximum brachial artery diameter (BAD) following release of an occluding pressure cuff compared to a BAD before cuff inflation. BAD early after cuff deflation can also serve as baseline for estimating total brachial artery reactivity (TBAR). We investigate whether TBAR is associated with first time coronary heart disease events.

Methods

Participants of the Multi-Ethnic Study of Atherosclerosis (n = 5499) consisting of whites, African-Americans, Chinese and Hispanics were followed longitudinally for a mean of 12.5 years. Brachial artery ultrasound was performed following five minutes of cuff occlusion at the forearm. TBAR was estimated from BAD following cuff release as the difference between maximum and minimum brachial artery diameters divided by the minimum diameter multiplied by 100%. TBAR was added to multivariable Cox proportional hazards models with Framingham risk factors as predictors and time to first coronary heart disease event as outcome.

Results

Average TBAR was 9.7% (9.7 SD). Mean age was 61.7 years, 50.9% women. Increased TBAR was associated with lower risk of CHD events with a hazard rate of 0.78 per SD increase (95% C.I. 0.67, 0.91; p = 0.001). A TBAR below the median of 7.87% (Inter Quartile Range: 4.16%, 13.0%) was associated with a 31% lower risk of coronary heart disease event (Hazard Ratio: 0.69; 95% C.I.: 0.55, 0.87).

Conclusion

TBAR is an independent predictor of first time coronary heart disease events and is exclusively measured after release of a blood pressure occlusion cuff.

Menopausal hormone therapy: examining cardiovascular and clinical impacts of treatment

Postmenopausal women have reduced levels of female sex hormones and this may play a significant role in the onset of cardiovascular disease. Menopausal hormone therapy (MHT), which is primarily prescribed for the treatment of perimenopausal symptoms, has been associated with risk of coronary heart disease, hypertension and stroke in women. This review will summarize the outcomes of observational studies and randomized clinical trials that have investigated the influence of MHT use on the cardiovascular system. In addition, it will explore how the timing of MHT prescription relative to menopause, dosage and route of administration may alter the impact of MHT on cardiovascular health.

Experimental benefits of sex hormones on vascular function and the outcome of hormone therapy in cardiovascular disease

Cardiovascular disease (CVD) is more common in men and postmenopausal women than premenopausal women, suggesting vascular benefits of female sex hormones. Experimental data have shown beneficial vascular effects of estrogen including stimulation of endothelium-dependent nitric oxide, prostacyclin and hyperpolarizing factor-mediated vascular relaxation. However, the experimental evidence did not translate into vascular benefits of hormone replacement therapy (HRT) in postmenopausal women, and HERS, HERS-II and WHI clinical trials demonstrated adverse cardiovascular events with HRT. The lack of vascular benefits of HRT could be related to the hormone used, the vascular estrogen receptor (ER), and the subject’s age and preexisting cardiovascular condition. Natural and phytoestrogens in small doses may be more beneficial than synthetic estrogen. Specific estrogen receptor modulators (SERMs) could maximize the vascular benefits, with little side effects on breast cancer. Transdermal estrogens avoid the first-pass liver metabolism associated with the oral route. Postmenopausal decrease and genetic polymorphism in vascular ER and post-receptor signaling mechanisms could also modify the effects of HRT. Variants of cytosolic/nuclear ER mediate transcriptional genomic effects that stimulate endothelial cell growth, but inhibit vascular smooth muscle (VSM) proliferation. Also, plasma membrane ERs trigger not only non-genomic stimulation of endothelium-dependent vascular relaxation, but also inhibition of [Ca²⁺]i, protein kinase C and Rho kinase-dependent VSM contraction. HRT could also be more effective in the perimenopausal period than in older postmenopausal women, and may prevent the development, while worsening preexisting CVD. Lastly, progesterone may modify the vascular effects of estrogen, and modulators of estrogen/testosterone ratio could provide alternative HRT combinations. Thus, the type, dose, route of administration and the timing/duration of HRT should be customized depending on the subject’s age and preexisting cardiovascular condition, and thereby make it possible to translate the beneficial vascular effects of sex hormones to the outcome of HRT in postmenopausal CVD.

Effect of conjugated estrogen versus conjugated estrogen associated with medroxyprogesterone acetate in postmenopausal women on internal carotid artery pulsatility index: a randomized pilot study

AIM

To compare the effect of conjugated estrogen (CEE) versus conjugated estrogen and medroxyprogesterone acetate (MPA) therapy on internal carotid artery pulsatility index (PI) in postmenopausal women.

MATERIAL & METHODS

In the prospective, randomized, single-blinded comparative study, postmenopausal women meeting the inclusion criteria were randomized into one of two groups: CEE group (CEE 0.625 mg/day), or CEE + MPA group (CEE 0.625 mg/day plus MPA 2.5 mg/day). Patients were submitted to blood tests (total cholesterol, high-density lipoprotein cholesterol, triglycerides and total glucose) and to color Doppler ultrasound of the internal carotid artery to assess PI at the beginning of the study. Ultrasound was repeated after 16 weeks of treatment. Statistical analysis was performed using Student's t-test or two-way analysis of variance for repeated measures. Data were considered to be significant at P < 0.05.

RESULTS

Seventy-five postmenopausal women (age 53.3 ± 5.5 years) were included in the study. There was a statistically significant reduction in PI in both groups after 16 weeks of hormonal treatment. However, there was no difference between the two groups (group 1: 0.8960 to 0.8450; group 2: 0.9048 to 0.8426).

CONCLUSION

The use of CEE and CEE associated with MPA during 16 weeks led to an improvement in internal carotid flow as measured by PI, with no difference between the treatments.

Submaximal exercise coronary artery flow increases in postmenopausal women without coronary artery disease after estrogen and atorvastatin

OBJECTIVE

The aim of this study was to determine the effect of statins and hormone therapy on submaximal exercise-induced coronary artery blood flow in postmenopausal women without a history of coronary artery disease. Hormone therapy or statin therapy in early postmenopausal women without coronary artery disease has been shown to enhance arterial endothelial function; we hypothesized that these agents would improve submaximal exercise-induced coronary artery blood flow.

METHODS

Sixty-four postmenopausal women, aged 50 to 65 years without documented coronary artery disease, were randomized in a double-blind, crossover fashion to receive 8 weeks of hormone therapy versus placebo, with or without 80 mg/day of atorvastatin. Before receipt of any therapy and after each treatment period, each woman underwent measures of coronary artery blood flow at rest and stress.

RESULTS

The combination of hormone therapy and atorvastatin increased submaximal exercise-induced coronary artery blood flow (P = 0.04). In the subgroups of women compliant with treatment, resting coronary artery blood flow increased in those receiving hormone therapy (P = 0.03) or statin therapy (P = 0.02).

CONCLUSIONS

In postmenopausal women aged 50 to 65 years without documented coronary artery disease, resting and submaximal exercise-induced coronary artery blood flow improves after receipt of high-dose atorvastatin and conjugated estrogens therapy.

Effect of hot flushes on vascular function: a randomized controlled trial

OBJECTIVE

To compare the vascular responses to hormone therapy in women with and without hot flushes.

METHODS

We randomly assigned 143 healthy, recently postmenopausal women (mean age 52.4+/-0.2 years, time since menopause 19.5+/-0.9 months) with intolerable hot flushes (more than seven moderate/severe episodes per day) or tolerable hot flushes (fewer than three mild episodes per day) to receive 1 mg of transdermal estradiol gel, oral estradiol (2 mg) with and without daily medroxyprogesterone acetate, or placebo for 6 months. Vascular function was assessed by pulse-wave analysis and endothelial function testing with nitroglycerin and salbutamol challenges.

RESULTS

Hot flushes did not affect the changes in arterial or aortic stiffness or endothelial function in response to various forms of hormone therapy. However, in women with tolerable hot flushes, oral estradiol caused a decrease of 13.2% (P=.028) in the time to the first systolic peak (dependent on the rapid phase of ventricular ejection) after nitroglycerin. In addition, the time to the reflected wave (dependent on pulse-wave velocity) after nitroglycerin was decreased by 8.4% (P=.018). These effects were not seen in women with intolerable hot flushes or with the other treatment regimens.

CONCLUSION

Women without troublesome hot flushes are susceptible to unfavorable vascular effects after oral estrogen treatment, resulting in less compliant vasculature.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov, www.clinicaltrials.gov, NCT00668603.

LEVEL OF EVIDENCE

I.

Membrane-initiated actions of estrogen on the endothelium

Estrogen-induced rapid, membrane-initiated activation of numerous signal transduction cascades has been shown in animal, cellular and molecular vascular studies, which support the favorable effects of estrogen on vascular structure and function. These effects are mediated by distinct forms of estrogen receptor (ER) alpha. This includes estrogen-stimulated, rapid activation of endothelial nitric oxide synthase (eNOS), resulting in elaboration of the athero-protective, angiogenesis-promoting product nitric oxide (NO). An N-terminus truncated short isoform of ERalpha, ER46, plays a critical role in membrane-initiated, rapid responses to 17beta-estradiol (E2) in human endothelial cells (ECs). We have proposed a ER46-centered, eNOS-activating molecular complex in human EC caveolar membranes, containing c-Src, phosphatidylinositol 3-kinase (PI3K), Akt and eNOS. In this review, we describe estrogen-induced, rapid, non-genomic actions in the endothelium.

Hormone replacement therapy and cardioprotection: a new dawn? A statement of the Study Group on Cardiovascular Disease in Women of the Italian Society of Cardiology on hormone replacement therapy in postmenopausal women

Cardiovascular disease is the leading cause of death in women in Western countries. Despite preventive strategies, in the past decades the incidence of cardiovascular events has shown a decline in men but a rise in women, matching the growth of the population of postmenopausal women. Several epidemiological findings suggest the causative pathophysiological role of ovarian hormone deficiency in the development of cardiovascular disease in women. Observational and randomized studies have suggested that hormone replacement therapy in early postmenopause could be beneficial from a cardiovascular point of view. Conversely, aging, time since menopause and presence of cardiovascular risk factors or cardiovascular disease may decrease its efficacy and increase the risk of cardiovascular events. It is plausible that the unfavorable effects of the estrogen/progestin combination used in the randomized studies are not related to the hormone preparation per se but rather to the use of hormones in the less receptive group of women, older and with cardiovascular risk factors. Clinical judgment, choice of the right dose and estrogen/progestin combination are of pivotal importance to maximize the beneficial effect of estrogen replacement therapy/hormone replacement therapy, especially if given within a reasonable time after the menopause to women who need the therapy for the relief of menopausal symptoms.

Sex/gender medicine. The biological basis for personalized care in cardiovascular medicine

Sex differences in morbidity and mortality associated with cardiovascular disease have been recognized by the medical community for decades. Investigation into the underlying biological basis of these differences was largely neglected by the scientific community until a report released by the Institute of Medicine in the United States in 2001 "Exploring the Biological Contributions to Human Health: Does Sex Matter?" Recommendations from this report included the need for more accurate use of the terms "sex" and "gender", better tools and resources to study the biological basis of sex differences, integration of findings from different levels of biological organization and continued synergy between basic and clinical researchers. Ten years after the Institute's report, this review evaluates some of the sex differences in cardiovascular disease, reviews new approaches to study sex differences and emphasizes areas where further research is required. In the era of personalized medicine, the study of the biological basis of sex differences promises to optimize preventive, diagnostic and therapeutic strategies for cardiovascular disease in men and women, but will require diligence by the scientific and medical communities to remember that sex does matter.

Cardiovascular disease in older women: a challenge in diagnosis and treatment

Cardiovascular disease is the leading cause of death in women and more heart disease is present in elderly women than men. Risk factors for heart disease affect men and women differently, with a greater impact of diabetes, hyperlipidemia and smoking in women. Diagnosis of heart disease can be more challenging in women, especially when elderly, as symptoms may be vague. Understanding the appropriate use of diagnostic testing and appropriate treatment is essential, given the high burden of disease in elderly women. This article will discuss the current guidelines for diagnosis and therapy of heart disease in women and will discuss the appropriate role of prevention strategies.

Effects of hormone therapy on soluble cell adhesion molecules in postmenopausal women with coronary artery disease

OBJECTIVE

Although observational studies showed an apparent lower ischemic coronary disease risk in postmenopausal women receiving hormone therapy (HT), randomized clinical trials in postmenopausal women showed an increase in ischemic cardiovascular events. Soluble cell adhesion molecules have been associated with cardiovascular risk factors and events. HT reduces circulating levels of soluble cell adhesion molecules in healthy postmenopausal women, but its effects in postmenopausal women with coronary artery disease are less clear. We assessed the effect of HT on soluble cell adhesion molecules in the Estrogen Replacement and Atherosclerosis trial.

DESIGN

The Estrogen Replacement and Atherosclerosis trial was a double-blind, placebo-controlled study that randomized 309 postmenopausal women (mean age, 65.8 y) to daily unopposed estrogen (conjugated estrogens 0.625 mg), estrogen plus 2.5 mg of medroxyprogesterone acetate, or placebo, with a mean follow-up period of 3.2 years. Soluble intercellular adhesion molecule-1, vascular cell adhesion molecule-1, and E-selectin were measured in serum obtained from participants at baseline and after 12 months of follow-up.

RESULTS

Of the 265 women with complete data, 87 women were assigned to unopposed estrogen, 88 women to estrogen plus medroxyprogesterone acetate, and 90 women to placebo. Compared with placebo, 12 months of HT (n = 175) was associated with reductions in soluble intercellular adhesion molecule-1 (25.6 +/- 4.7 vs 10.6 +/- 6.4 ng/mL, P = 0.06), soluble vascular cell adhesion molecule-1 (80.2+/- 10.6 vs 28.8 +/- 14.7 ng/mL, P = 0.005), and E-selectin (8.8 +/- 0.9 vs -1.1 +/- 1.2 ng/mL, P < 0.001).

CONCLUSIONS

Twelve months of HT in postmenopausal women with established coronary artery disease was associated with reductions in serum markers of endothelial cell activation/injury such as soluble intercellular adhesion molecule-1, vascular cell adhesion molecule-1, and E-selectin.

Estrogen and progestogen use in postmenopausal women: July 2008 position statement of The North American Menopause Society

OBJECTIVE

: To update for both clinicians and the lay public the evidence-based position statement published by The North American Menopause Society (NAMS) in March 2007 regarding its recommendations for menopausal hormone therapy (HT) for postmenopausal women, with consideration for the therapeutic benefit-risk ratio at various times through menopause and beyond.

DESIGN

: An Advisory Panel of clinicians and researchers expert in the field of women's health was enlisted to review the March 2007 NAMS position statement, evaluate new evidence through an evidence-based analysis, and reach consensus on recommendations. The Panel's recommendations were reviewed and approved by the NAMS Board of Trustees as an official NAMS position statement. The document was provided to other interested organizations to seek their endorsement.

RESULTS

: Current evidence supports a consensus regarding the role of HT in postmenopausal women, when potential therapeutic benefits and risks around the time of menopause are considered. This paper lists all these areas along with explanatory comments. Conclusions that vary from the 2007 position statement are highlighted. Addenda include a discussion of risk concepts, a new component not included in the 2007 paper, and a recommended list of areas for future HT research. A suggested reading list of key references is also provided.

CONCLUSIONS

: Recent data support the initiation of HT around the time of menopause to treat menopause-related symptoms; to treat or reduce the risk of certain disorders, such as osteoporosis or fractures in select postmenopausal women; or both. The benefit-risk ratio for menopausal HT is favorable close to menopause but decreases with aging and with time since menopause in previously untreated women.

New and emerging risk factors for CVD

Morphological and immunocytochemical studies have elucidated the complex processes involved in atherogenesis. The notion of plaque instability has emerged from this work and underscored the importance of inflammation in determining clinical complications associated with atherosclerosis, such as acute coronary syndrome. Cells of the immune system have been detected within atherosclerotic lesions and auto-antibodies directed against modified LDL and heat-shock proteins have been identified in the blood of individuals with atherosclerosis. The use of risk 'engines', e.g. the Framingham coronary risk score, has facilitated the identification of individuals at high risk, but the constituent classical risk factors used in these algorithms do not adequately differentiate individuals at moderate risk. As age is a major component of the equations used in these algorithms they are not particularly useful in young adults, and their applicability to non-Caucasian populations has been questioned. Biomarkers of early disease and plaque instability have therefore both been sought. Although some of these markers have been shown individually to be associated with a significant hazard ratio, no substantial improvement in discrimination has been demonstrated when they are incorporated into a risk 'engine'. The latter has generally been assessed by receiver operator characteristic curve analysis, although this approach has been criticised. Other modalities, including imaging and functional assessments of vascular function, are now being developed for clinical use.

Effects in postmenopausal women of estradiol and medroxyprogesterone alone and combined on resistance artery function and endothelial morphology and movement

CONTEXT

Endothelial dysfunction in resistance arteries after menopause is important for the development of high blood pressure and cardiovascular disease.

OBJECTIVES

Our objectives were to study the effects of different hormone replacement therapies on the function and morphology of isolated resistance arteries, and to look for their mechanistic basis.

DESIGN AND SETTING

This was a randomized, placebo-controlled double-blind study in a University hospital, along with laboratory based studies.

PATIENTS AND INTERVENTIONS

We isolated resistance arteries in sc biopsies from 55 postmenopausal women before and after 3-month therapy with estradiol (E2), medroxyprogesterone acetate (MPA), E2 plus MPA, or placebo. In addition, we studied isolated human endothelial cells.

MAIN OUTCOME MEASURES AND RESULTS

Artery flow-mediated dilatation was augmented after treatment with E2 or E2 plus MPA, whereas MPA or placebo had no effect. Pressure-induced myogenic tone was reduced by E2 plus MPA, whereas it was unchanged in the other groups. Scanning microscopy showed that E2 improved endothelial cell morphology and decreased signs of endothelial apoptosis, but the addition of MPA impaired these events. E2, MPA, or the combination all increased the expression and phosphorylation of the actin-binding protein, moesin and of the focal adhesion complex controller, focal adhesion kinase, and induced the rearrangement of cytoskeletal actin and vinculin fibers. All treatments promoted endothelial cell horizontal migration, with E2 inducing the strongest effect.

CONCLUSIONS

This study suggests that hormone replacement therapy with estrogens or in combination with MPA may benefit the function of resistance arteries and may preserve the morphological integrity of endothelial cells by regulatory actions on the cytoskeleton.

Effect of hyperbaric oxygen on flow-mediated vasodilation: an ultrasound study

OBJECTIVE

The purpose of this study was to investigate the effect of hyperbaric oxygen (HBO) treatment on flow-mediated vasodilation (FMD) by ultrasound examination.

METHODS

We studied 14 young patients without cardiovascular problems who underwent HBO treatment. The indications for HBO treatment were osteomyelitis (n = 8), Crohn disease (n = 2), perianal abscesses (n = 2), lingual artery embolization (n = 1), and aseptic necrosis (n = 1). The ultrasound evaluation for FMD was performed before HBO treatment, after 1 session of HBO treatment, and after 10 sessions of HBO treatment. The right brachial artery FMD response was evaluated by the mean of the baseline right brachial artery diameter, absolute change in the diameter before and after cuff inflation/deflation, and percent change in the diameter.

RESULTS

Statistical analysis showed a significant change in the preinflation right brachial artery diameter before (mean +/- SD, 3.6 +/- 0.54 mm) and after (3.76 +/- 0.56 mm) 10 sessions of HBO treatment (P < .05). The absolute changes in the right brachial artery diameter before and after cuff inflation/deflation (0.36 +/- 0.2 mm before HBO treatment, 0.37 +/- 0.22 mm after 1 session of HBO treatment, and 0.38 +/- 0.21 mm after 10 sessions) and percent change in FMD (10% +/- 5.8% before HBO treatment, 10.6% +/- 7.5% after 1 session of HBO treatment, and 10.6% +/- 7.7% after 10 sessions) after induction of a hyperemic response by cuff inflation were not statistically significant (P > .05).

CONCLUSIONS

Hyperbaric oxygen treatment did not have an immediate effect on FMD (absolute change in the right brachial artery diameter after cuff inflation/deflation); however, the right brachial artery diameter increased after 10 sessions of HBO treatment. This may suggest chronic stress on the vascular endothelium after HBO.