Conjugated equine estrogens alone, but not in combination with medroxyprogesterone acetate, inhibit aortic connective tissue remodeling after plasma lipid lowering in female monkeys

Ovariectomy-Induced Arterial Stiffening Differs from Vascular Aging and is Reversed by GPER Activation

Arterial stiffness is a cardiovascular risk factor and dramatically increases as women transition through menopause. The current study assessed whether a mouse model of menopause increases arterial stiffness in a similar manner to aging, and whether activation of the G protein-coupled estrogen receptor (GPER) could reverse stiffness. Female C57Bl/6J mice were ovariectomized (OVX) at 10 weeks of age or aged to 52 weeks, and some mice were treated with GPER agonists. OVX and aging increased pulse wave velocity to a similar extent independent of changes in blood pressure. Aging increased carotid wall thickness, while OVX increased material stiffness without altering vascular geometry. RNA-Seq analysis revealed that OVX downregulated smooth muscle contractile genes. The enantiomerically pure GPER agonist, LNS8801, reversed stiffness in OVX mice to a greater degree than the racemic agonist G-1. In summary, OVX and aging induced arterial stiffening via potentially different mechanisms. Aging was associated with inward remodeling while OVX induced material stiffness independent of geometry and a loss of the contractile phenotype. This study helps to further our understanding of the impact of menopause on vascular health and identifies LNS8801 as a potential therapy to counteract this detrimental process in women.

Aromatase and estrogen receptor immunoreactivity in the coronary arteries of monkeys and human subjects

OBJECTIVE

The objective of this study was to determine whether estrogen could be formed locally in the coronary arteries.

DESIGN

Coronary arteries were examined from monkeys (Macaca fascicularis, one male and one female) and human subjects (one premenopausal woman, one postmenopausal woman, and one man) by immunocytochemistry, using purified antisera against human placental estrogen synthetase (aromatase) and ER α. The arteries were graded for the amount of atherosclerosis.

RESULTS

There was clear immunopositivity for both aromatase and estrogen receptors in all arteries studied. Although all endothelial cells (CD31 positive) stained for both antigens, the staining in macrophages, fibroblasts, and smooth muscle cells was irregular.

CONCLUSION

The present results provide the first evidence for the local formation of estrogen in the coronary arteries. In addition to complementing the evidence of a cardioprotective effect of estrogen on the coronary circulation, our results highlight the potential importance of local regulation of estrogen formation and the role of available precursor androgens in maintaining the cardiovascular system.

Atherosclerosis and Vascular Biologic Responses to Estrogens: Histologic, Immunohistochemical, Biochemical, and Molecular Methods

Atherogenesis is a multifactorial pathologic process influenced by genetics and environmental factors such as diet, exercise, stress, and other exposures. Estrogen receptors (ER) are expressed in cells of the arterial wall, suggesting that estrogen receptor ligands (estradiol, natural and pharmacologic ligands) may directly affect arterial biology and atherogenesis. Ligand bound estrogen receptor alpha and beta (ERα, ERβ) can influence physiology through direct binding to estrogen response elements in the DNA, through interactions with other transcription factors such as NF-κB, or through rapid effects not dependent on gene expression changes but instead through non-nuclear membrane sites involving ERα, ERβ, or G-coupled protein ER (GPER1). Elucidation of potential direct effects of estrogens on the artery wall requires careful evaluation of arterial biologic responses to estrogens. We have developed a comprehensive approach to understand the mechanisms of estrogen action which employs histologic measures of the size and other characteristics of atherosclerotic lesions, immunohistochemical assessments of cellular composition, evaluation of chemical, molecular, and genomic changes in the arterial environment, and determination of the relationships between arterial estrogen receptor expression and atherogenesis. This approach can provide important insights into the mechanisms of action of estrogen and other mediators of atherogenesis.

Why primate models matter

Research involving nonhuman primates (NHPs) has played a vital role in many of the medical and scientific advances of the past century. NHPs are used because of their similarity to humans in physiology, neuroanatomy, reproduction, development, cognition, and social complexity-yet it is these very similarities that make the use of NHPs in biomedical research a considered decision. As primate researchers, we feel an obligation and responsibility to present the facts concerning why primates are used in various areas of biomedical research. Recent decisions in the United States, including the phasing out of chimpanzees in research by the National Institutes of Health and the pending closure of the New England Primate Research Center, illustrate to us the critical importance of conveying why continued research with primates is needed. Here, we review key areas in biomedicine where primate models have been, and continue to be, essential for advancing fundamental knowledge in biomedical and biological research.

Sex hormone replacement therapy and modulation of vascular function in cardiovascular disease

Epidemiological and experimental studies suggest vascular protective effects of estrogen. Cardiovascular disease (CVD) is less common in premenopausal women than in men and postmenopausal women. Cytosolic/nuclear estrogen receptors (ERs) have been shown to mediate genomic effects that stimulate endothelial cell growth but inhibit vascular smooth muscle proliferation. However, the Heart and Estrogen/Progestin Replacement Study (HERS), HERS-II and Women's Health Initiative clinical trials demonstrated that hormone replacement therapy (HRT) may not provide vascular benefits in postmenopausal women and may instead trigger adverse cardiovascular events. HRT may not provide vascular benefits because of the type of hormone used. Oral estrogens are biologically transformed by first-pass metabolism in the liver. By contrast, transdermal preparations avoid first pass metabolism. Also, natural estrogens and phytoestrogens may provide alternatives to synthetic estrogens. Furthermore, specific ER modulators could minimize the adverse effects of HRT, including breast cancer. HRT failure in CVD could also be related to changes in vascular ERs. Genetic polymorphism and postmenopausal decrease in vascular ERs or the downstream signaling mechanisms may reduce the effects of HRT. HRT in the late postmenopausal period may not be as effective as during menopausal transition. Additionally, while HRT may aggravate pre-existing CVD, it may thwart its development if used in a timely fashion. Lastly, the vascular effects of progesterone and testosterone, as well as modulators of their receptors, may modify the effects of estrogen and thereby provide alternative HRT strategies. Thus, the beneficial effects of HRT in postmenopausal CVD can be enhanced by customizing the HRT type, dose, route of administration and timing depending on the subject's age and cardiovascular condition.

Differential effects of estradiol on carotid artery inflammation when administered early versus late after surgical menopause

OBJECTIVE

The aim of this study was to determine the effects of estrogen therapy (ET) on carotid artery inflammation when initiated early and late relative to surgical menopause.

METHODS

Female cynomolgus macaques consuming atherogenic diets were ovariectomized and randomized to control or oral estradiol (E2; human equivalent dose of 1 mg/d micronized E2) initiated at 1 month (early menopause, n = 24) or 54 months (late menopause, n = 40) after ovariectomy. The treatment period was 8 months. Carotid artery expression of the markers of monocyte/macrophages (CD68 and CD163), dendritic cells (CD83), natural killer cells (neural cell adhesion molecule-1), and interferon-γ was significantly lower in E2-treated animals in the early menopause group but not in the late menopause group (P < 0.05). In contrast, carotid artery transcripts for T-cell markers (CD3, CD4, CD8, and CD25), interleukin-10, type I collagen, monocyte chemoattractant protein-1, matrix metalloproteinase-9, and tumor necrosis factor-α were lower in E2-treated monkeys regardless of menopausal stage (P < 0.05).

CONCLUSIONS

ET initiated soon after menopause inhibits macrophage accumulation in the carotid artery, an effect that is not observed when E2 is administered after several years of estrogen deficiency. No evidence for pro-inflammatory effects of late ET is observed. The results provide support for the timing hypothesis of postmenopausal ET with implications for the interpretation of outcomes in the Women's Health Initiative.

Hormone replacement therapy in the geriatric patient: current state of the evidence and questions for the future. Estrogen, progesterone, testosterone, and thyroid hormone augmentation in geriatric clinical practice: part 1

This article presents an up-to-date review of the literature on hormone augmentation in the elderly to help primary care physicians better evaluate and utilize hormone replacement and optimization strategies to benefit their patients. The scientific literature suggests that hormone supplementation with estrogen, progesterone, testosterone, growth hormone, and thyroid hormone has the potential to improve quality of life and to prevent, or reverse, the many symptoms and conditions associated with aging, including fatigue, depression, weight gain,frailty, osteoporosis, loss of libido, and heart disease. Possible long-term side effects are also considered.

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.

Timing of the vascular actions of estrogens in experimental and human studies: why protective early, and not when delayed?

Estrogens, and in particular 17β-estradiol (E2), play a pivotal role in sexual development and reproduction and are also implicated in a large number of physiological processes including the cardiovascular system. Although epidemiological studies and Nurses' Health Study suggested, and all animal models of early atheroma clearly demonstrated a vasculoprotective action of both endogenous and exogenous estrogens, the Women's Health Initiative did not confirm the preventive action of estrogens against coronary heart disease (CHD). However, women who initiated hormone therapy closer to menopause tended to have reduced CHD risk compared with increased CHD risk among women more distant from menopause. Thus, it is now mandatory to try to understand the mechanisms that could have influenced the actions of estrogens at various stages of atherosclerosis and/or of life. In this current review, we will summarize our understanding of the potential cellular targets and mechanisms of the vasculoprotective actions of estrogens, as well as of the lack of action of estrogens when administered after a period of hormonal deprivation. The mechanisms of the aggravating role of progestogens such as medroxyprogesterone acetate will be considered. Finally, we will analyze the possibilities to uncouple some beneficial from other undesirable actions following the partial/selective activation of estrogen receptors.

A new approach to menopausal therapy: the tissue selective estrogen complex

A new approach to menopausal therapy is the tissue selective estrogen complex or the pairing of a selective estrogen receptor modulator with estrogens. The clinical profile of a tissue selective estrogen complex will result from the blended tissue-selective activities of its components. An appropriate tissue selective estrogen complex may provide the therapeutic benefits of estrogens and selective estrogen receptor modulators with better tolerability and safety than either therapy alone. An ideal menopausal therapy would reduce the number and severity of hot flashes, effectively treat vulvar-vaginal atrophy and its symptoms, prevent and treat menopausal osteoporosis, and have favorable effects on lipoprotein profiles, while at the same time would not stimulate the endometrium, not cause uterine bleeding, not increase the risk of vascular events, not be associated with breast pain or tenderness, and potentially reduce breast cancer incidence. Here, we introduce the concept of a tissue selective estrogen complex and the rationale for its development as a next generation menopausal therapy.

Alteration of vaginal elastin metabolism in women with pelvic organ prolapse

OBJECTIVE

To compare elastin metabolism in the vagina of women with and without pelvic organ prolapse and to define the regulation of this process by hormone therapy (HT).

METHODS

Eighty-seven histologically confirmed full-thickness vaginal biopsies were procured from study participants at time of surgery. Premenopausal women with no prolapse served as controls. Women with prolapse were divided into three groups: premenopausal, postmenopausal not on HT, and postmenopausal on HT. The epithelium was excised leaving the subepithelium, muscularis, and adventitia for analyses. The elastin precursor, tropoelastin, was measured by immunoblotting and mature elastin protein via a desmosine cross-link radioimmunoassay. Matrix metalloproteinases (MMPs)-2 and -9 were quantitated by gelatin zymography. Data were analyzed using Kruskal-Wallis test and post hoc analysis using the Mann-Whitney U test.

RESULTS

Tropoelastin (432%), mature elastin (55%), proMMP-9 (90%), and active MMP-9 (106%) were increased in women with prolapse relative to those in the control group while active MMP-2 (41%) was decreased. Comparison of tropoelastin and mature elastin values obtained from the same women showed them to be independently regulated (r=0.19). Interestingly, the highest amount of both proteins occurred in postmenopausal patients not on HT.

CONCLUSION

Elastin metabolism is altered in the vagina of women with prolapse relative to those in the control group, suggesting that vaginal tissue is rapidly remodeling in response to mechanical stretch. We found that elastin levels are highest in the absence of hormones.

Research into Specific Modulators of Vascular Sex Hormone Receptors in the Management of Postmenopausal Cardiovascular Disease

Cardiovascular disease (CVD) is more common in men and postmenopausal women than premenopausal women, suggesting vascular benefits of female sex hormones. Studies on the vasculature have identified estrogen receptors ERα, ERβ and a novel estrogen binding membrane protein GPR30, that mediate genomic and/or non-genomic effects. Estrogen promotes endothelium-dependent relaxation by inducing the production/activity of nitric oxide, prostacyclin, and hyperpolarizing factor, and inhibits the mechanisms of vascular smooth muscle contraction including [Ca(2+)](i), protein kinase C, Rho kinase and mitogen-activated protein kinase. Additional effects of estrogen on the cytoskeleton, matrix metalloproteinases and inflammatory factors contribute to vascular remodeling. However, the experimental evidence did not translate into vascular benefits of menopausal hormone therapy (MHT), and the HERS, HERS-II and WHI clinical trials demonstrated adverse cardiovascular events. The discrepancy has been partly related to delayed MHT and potential changes in the vascular ER amount, integrity, affinity, and downstream signaling pathways due to the subjects' age and preexisting CVD. The adverse vascular effects of MHT also highlighted the need of specific modulators of vascular sex hormone receptors. The effectiveness of MHT can be improved by delineating the differences in phramcokinetics and pharmacodynamics of natural, synthetic, and conjugated equine estrogens. Estriol, "hormone bioidenticals" and phytoestrogens are potential estradiol substitutes. The benefits of low dose MHT, and transdermal or vaginal estrogens over oral preparations are being evaluated. Specific ER modulators (SERMs) and ER agonists are being developed to maximize the effects on vascular ERs. Also, the effects of estrogen are being examined in the context of the whole body hormonal environment and the levels of progesterone and androgens. Thus, the experimental vascular benefits of estrogen can be translated to the outcome of MHT in postmenopausal CVD, as more specific modulators of sex hormone receptors become available and are used at the right dose, route of administration and timing, depending on the subject's age and preexisting cardiovascular condition.

Could transdermal estradiol + progesterone be a safer postmenopausal HRT? A review

Hormone replacement therapy (HRT) in young postmenopausal women is a safe and effective tool to counteract climacteric symptoms and to prevent long-term degenerative diseases, such as osteoporotic fractures, cardiovascular disease, diabetes mellitus and possibly cognitive impairment. The different types of HRT offer to many extent comparable efficacies on symptoms control; however, the expert selection of specific compounds, doses or routes of administration can provide significant clinical advantages. This paper reviews the role of the non-oral route of administration of sex steroids in the clinical management of postmenopausal women. Non-orally administered estrogens, minimizing the hepatic induction of clotting factors and others proteins associated with the first-pass effect, are associated with potential advantages on the cardiovascular system. In particular, the risk of developing deep vein thrombosis or pulmonary thromboembolism is negligible in comparison to that associated with oral estrogens. In addition, recent indications suggest potential advantages for blood pressure control with non-oral estrogens. To the same extent, a growing literature suggests that the progestins used in association with estrogens may not be equivalent. Recent evidence indeed shows that natural progesterone displays a favorable action on the vessels and on the brain, while this might not be true for some synthetic progestins. Compelling indications also exist that differences might also be present for the risk of developing breast cancer, with recent trials indicating that the association of natural progesterone with estrogens confers less or even no risk of breast cancer as opposed to the use of other synthetic progestins. In conclusion, while all types of hormone replacement therapies are safe and effective and confer significant benefits in the long-term when initiated in young postmenopausal women, in specific clinical settings the choice of the transdermal route of administration of estrogens and the use of natural progesterone might offer significant benefits and added safety.

Sex steroids and vascular responses in hypertension and aging

BACKGROUND

Sex hormones play a significant role in human physiology. Estrogen may have protective effects in the cardiovascular system, as evidenced by the decreased incidence of cardiovascular disease (CVD) in premenopausal compared with postmenopausal women.

OBJECTIVE

This review highlights the acute and long-term effects of sex hormones on the vascular endothelium and vascular smooth muscle (VSM) in adults. Changes in the sex hormone mix, their receptors, and their effects on vascular function in hypertension and aging are also discussed.

METHODS

Literature collected from the National Centers for Biotechnology Information as identified by a PubMed database search, as well as our experimental work, was used to highlight current knowledge regarding vascular responses to sex hormones in hypertension and in aging.

RESULTS

Experiments in adult female animals have shown that estrogen induces endothelium-dependent vascular relaxation via the nitric oxide (NO), prostacyclin, and hyperpolarization pathways. Also, surface membrane estrogen receptors (ERs) decrease intracellular free Ca2+ concentration and perhaps protein kinase C-dependent VSM contraction. However, clinical trials such as the Heart and Estrogen/progestin Replacement Study (HERS), HERS-II, and the Women's Health Initiative did not support the experimental findings and demonstrated adverse cardiovascular events of hormone therapy (HT) in aging women. The lack of vascular benefits of HT may be related to the hormone used, the ER, or the patient's cardiovascular condition or age. Experiments on vascular strips from aging (16-month-old) female spontaneously hypertensive rats have shown reduced ER-mediated NO production from endothelial cells and decreased inhibitory effects of estrogen on Ca2+ entry mechanisms of VSM contraction. The age-related decrease in ER-mediated vascular relaxation may explain the decreased effectiveness of HT on CVD in aging women.

CONCLUSIONS

New HT strategies should further examine the benefits of natural estrogens and phytoestrogens. Transdermal estrogen may be more effective than the oral form, and specific ER modulators may maximize the vascular benefits and reduce the risk of invasive breast cancer. Variants of vascular ERs should be screened for genetic polymorphisms and postmenopausal decrease in the amount of downstream signaling mechanisms. HT may be more effective during the menopausal transition than in late menopause. Progesterone, testosterone, or their specific modulators may be combined with estrogen to provide alternative HT strategies. Thus, HT type, dose, route of administration, and timing should be customized, depending on the patient's cardiovascular condition and age, thereby enhancing the vascular benefits of HT in aging women.

Timing of estrogen replacement influences atherosclerosis progression and plaque leukocyte populations in ApoE-/- mice

Studies of the effects of estrogen replacement therapy on coronary heart disease risk have produced conflicting results. We hypothesize that this may be explained by differences in the length of estrogen deficiency prior to initiation of treatment and associated variation in plaque inflammation or stage of progression. The goal of this study was to determine whether estrogen administered after a period of deficiency affects plaque progression and leukocyte populations. Ovariectomized ApoE-/- mice were treated as follows: group 1: continuous estrogen for 90 days (E+/+); group 2: placebo for 45 days followed by estrogen for 45 days (E-/+); group 3: estrogen for 45 days followed by placebo for 45 days (E+/-); and group 4: placebo for 90 days (E-/-). Serum lipoprotein concentrations, plaque size and inflammatory cell (macrophage, CD3+, CD4+, CD8+, dendritic cell, and NK cell) densities were quantified. Plaque size was smaller in groups receiving early estrogen therapy. CD3+ and total inflammatory cell densities were lower in late estrogen therapy groups. The CD8 to dendritic cell ratio was significantly lower in the E-/+ group only. These results suggest that a period of estrogen deficiency followed by reintroduction alters the immunologic environment of atherosclerotic lesions as well as plaque progression.

Comparative effects of dydrogesterone and medroxyprogesterone acetate in critical areas: the brain and the vessels

Several epidemiological and observational studies have investigated the role of hormone replacement therapy (HRT) in postmenopausal women. Within a few years, clinicians shifted from considering HRT as the panacea for everything to considering it a venomous poison with which women, in search of the fountain of eternal youth, could instead harm themselves. This debate is not yet settled and the unexplained discrepancy between basic science and some of the clinical trials has fueled the discussion. One of the hottest areas of discussion remains the role of progestins. For many years, progestins were considered only as necessary additions to estrogen to protect the endometrium. However, we now know that every progestin has its own specific activities on different tissues, which can vary significantly between progestins of different classes and even within the same class. Indeed, different progestins may support or oppose the effects of estrogen depending on the tissue, thereby supporting the concept that the clinical selection of progestins for HRT is critical in determining potential positive or detrimental effects. Newer progestins, such as dydrogesterone, show effects that are remarkably different from those of other agents; these actions might be particularly relevant in the central nervous system and the cardiovascular system. The aim of the present paper is to review the comparative effects of dydrogesterone and other progestins at these sites, supporting the idea that the progestin has to be clinically selected.

Medroxyprogesterone acetate prevents the cardioprotective and anti-inflammatory effects of 17β-estradiol in an in vivo model of myocardial ischemia and reperfusion

Previous studies demonstrated the protective effects of estrogen administration in models of cardiovascular disease. However, there is a discrepancy between these data and those from the recent clinical trials with hormone replacement therapy in menopausal women. One possible explanation for the divergent results is the addition of progestin to the hormone regimen in the Women's Health Initiative and the Heart and Estrogen/Progestin Replacement Study trials. The aim of the present study was to examine the effects of a combination of 17β-estradiol (E2, 20 μg) and medroxyprogesterone acetate (MPA, 80 μg) on infarct size in New Zealand White rabbits. Infarct size as a percentage of the area at risk was significantly reduced by administration of E2 30 min before induction of myocardial ischemia compared with vehicle (19.5 ± 3.1 vs. 55.7 ± 2.6%, P < 0.001). However, E2 + MPA failed to elicit a reduction in infarct size (52.5 ± 4.6%), and MPA had no effect (50.8 ± 2.6%). E2 also reduced serum levels of cardiac troponin I, immune complex deposition in myocardial tissue, activation of the complement system, and lipid peroxidation. All these effects were reversed by MPA. The results suggest that MPA antagonizes the infarct-sparing effects of E2, possibly through modulation of the immune response after ischemia and reperfusion.

The impact of hormone replacement therapy on the pathophysiology of peripheral arterial disease

BACKGROUND

Hormone replacement therapy (HRT) is recommended to post-menopausal women to control menopausal symptoms and prevent osteoporosis. The management of women with peripheral arterial disease (PAD) and who are taking HRT is controversial.

AIM

To summarise what is known about HRT and its effect on the natural progression of PAD and its subsequent treatment.

METHODS

A MEDLINE (1966-2004) and Cochrane library search for articles relating to HRT and PAD was undertaken.

RESULTS

The potential benefits of unopposed estrogen therapy on atherosclerotic progression and limb microcirculation are outweighed by the increased risk of endometrial dysplasia and thrombotic complications. Only one major study (Rotterdam) specifically assessed the impact of HRT on the clinical course of PAD. The findings suggested a decreased risk of PAD among healthy post-menopausal women taking HRT which contrasts with the sub-group analyses of other major studies (HERS/HERS II). HRT appears to reduce the primary success rates of both endovascular and open surgical revascularisation in patients with PAD.

CONCLUSIONS

Further studies are required to investigate the effects of HRT on the progression of PAD and its management.

A simulation using data from a primary care practice database closely replicated the women's health initiative trial

OBJECTIVE

In contrast to prior observational studies, hormone replacement therapy (HRT) did not prevent coronary heart disease in the Women's Health Initiative Randomized Controlled Trial (WHI RCT). To assess the validity of a novel observational study design, we compared the WHI RCT with a simulation using data from the United Kingdom General Practice Research Database (GPRD).

STUDY DESIGN AND SETTING

A cohort from GPRD was used to simulate the WHI RCT by replicating, to the extent possible, all aspects of the RCT except randomization. The study included 37,730 Unexposed and 13,658 Exposed women treated with estrogen and norgestrel.

RESULTS

Myocardial infarction (adjusted hazard ratio 0.95 [0.78-1.16]) was not decreased significantly in the GPRD Exposed group. Similar to the WHI RCT, stroke, venous thromboembolic events, and breast cancer were increased; and colorectal cancer was decreased. Although death appeared to decrease in the total cohort, it was unaltered in a subset of subjects without missing data on baseline covariates.

CONCLUSION

A structured comparison using data from GPRD was largely concordant with the WHI RCT and did not show a cardioprotective effect of HRT. These findings further generalize the results of WHI and reinforce the potential utility of this analytic approach.

Sex hormones, vascular function and the outcome of hormone replacement therapy in cardiovascular disease

Cardiovascular disease is more common in men and post-menopausal women than premenopausal women, suggesting that female sex hormones have vascular benefits. Cytosolic/nuclear estrogen and progesterone receptors mediate genomic transcriptional effects that stimulate endothelial cell growth and inhibit smooth muscle proliferation. Sex hormone receptors on the plasma membrane trigger nongenomic stimulation of endothelium-dependent nitric oxide–cyclic (c)GMP, prostacyclin–cAMP and hyperpolarizing vascular relaxation pathways, as well as inhibition of [Ca2+]i, protein kinase C and Rho-kinase-dependent mechanisms of smooth muscle contraction. Despite the vasodilator effects of sex hormones, the Heart and Estrogen/progestin Replacement Study (HERS), HERS-II and Women’s Health Initiative clinical trials have shown minimal benefits of hormone replacement therapy (HRT) in post-menopausal cardiovascular disease. The prospect of HRT relies on further mechanistic analysis of the vascular effects of natural sex hormones and phytoestrogens, and the identification of specific estrogen receptor modulators. Androgens have vascular effects, and modulators of the estrogen/testosterone ratio could provide better HRT combinations. The timing/duration and the type, dose and route of administration of HRT should be customized according to the subject’s age and pre-existing cardiovascular condition, thereby enhancing the outcome of HRT in cardiovascular disease.

Drospirenone and its antialdosterone properties

Drospirenone is a unique progestogen derived from 17alpha-spirolactone, with a pharmacologic profile very similar to that of endogenous progesterone. In contrast with other available progestins, drospirenone is a progestogen with aldosterone receptor antagonism (PARA) through its affinity for the mineralocorticoid receptor. It is thus able to act on the renin-angiotensin-aldosterone system (RAAS), which prevents excessive sodium loss and regulates blood pressure. Estrogen acts on the RAAS to stimulate the synthesis of angiotensinogen, which increases aldosterone levels and promotes sodium and water retention. When these effects are unopposed, for example during estrogen replacement therapy, they can lead to increases in weight and blood pressure. The antialdosterone properties exhibited by drospirenone promote sodium excretion and prevent water retention, conferring potential blood pressure benefits. In addition to its effects on the kidney, aldosterone has effects on the vasculature, myocardium and central nervous system, which may elicit a variety of pathophysiologic processes associated with cardiovascular disease. The antialdosterone properties of drospirenone may therefore confer additional cardiovascular benefits beyond the RAAS system. The combined actions of drospirenone on sodium and water retention and cardiovascular parameters make it a more attractive therapeutic option as a component of hormone replacement therapy than other synthetic progestins.

Estrogen affects post-menopausal women differently than estrogen plus progestin replacement therapy

BACKGROUND

In the Women's Health Initiative Randomized Controlled Trial (WHI RCT), estrogen-only treatment compared with combined estrogen-progestin treatment resulted in less coronary artery disease, no increase in breast cancer and no reduction in colorectal cancer. Since we previously reasonably replicated the combined estrogen-progestin WHI RCT using the UK General Practice Research Database (GPRD), estrogen-only treatment was investigated using a similar methodology.

METHODS

This GPRD study simulated the estrogen-only WHI RCT of women who had undergone a hysterectomy except for randomization. The primary analysis examined 11 572 unexposed and 6890 Exposed women (aged 55-79) treated with conjugated equine estrogen and was compared with the combined estrogen-progestin GPRD study.

RESULTS

At baseline, women with a hysterectomy exhibited more cardiovascular disease than those with an intact uterus. In the estrogen-only GPRD study, adjusted hazard ratios (HRs) were 0.50 (0.38-0.67) for myocardial infarction (MI), 1.13 (0.91-1.41) for breast cancer, and 1.18 (0.72-1.92) for colorectal cancer. Compared to the HRs in the estrogen-progestin GPRD study, the estrogen-only results are significantly lower for MI and breast cancer and higher for colon cancer, a pattern similar to the WHI RCT study comparisons.

CONCLUSIONS

This study confirms that post-menopausal women in the overall population respond differently to estrogen-only treatment compared with estrogen-progestin treatment, due to different hormone regimens and/or increased cardiovascular disease in hysterectomized women.

Effects of dydrogesterone and of its stable metabolite, 20-α-dihydrodydrogesterone, on nitric oxide synthesis in human endothelial cells

OBJECTIVE

To investigate the effects of P, medroxyprogesterone acetate (MPA), and dydrogesterone (DYD) and its metabolite, 20-alpha-dihydrodydrogesterone (DHD) on endothelial synthesis of nitric oxide (NO) and characterize the signaling events recruited by these compounds. The Women's Health Initiative trial reports an excess of heart disease in postmenopausal women receiving MPA.

DESIGN

Cell culture.

SETTING

Research laboratory.

PATIENT(S)

Human endothelial cells from umbilical vein.

INTERVENTION(S)

Treatments with P, MPA, DYD, or DHD.

MAIN OUTCOME MEASURE(S)

Measure of NO release, endothelial nitric oxide synthase (eNOS) activity and expression, and activation of ERK 1/2 and Akt.

RESULT(S)

The administration of DYD alone or in combination with estrogen to endothelial cells results in neutral effects on NO synthesis and on the activity and expression of eNOS. In parallel, the stable metabolite DHD acts similarly to natural P, enhancing the expression of eNOS and inducing rapid activation of the enzyme through the regulation of the ERK 1/2 mitogen-activated protein kinase cascade. 20-Alpha-dihydrodydrogesterone and P also potentiate eNOS induction by E2. On the contrary, MPA does not trigger eNOS enzymatic activation and decreases the extent of eNOS induction by E2.

CONCLUSION(S)

These findings support the concept that synthetic progestins act differently on vascular cells and that hormonal preparations may differ as to their cardiovascular effects.

Activation of Nitric Oxide Synthesis in Human Endothelial Cells Using Nomegestrol Acetate

OBJECTIVE

Recent clinical trials indicate that synthetic progestins may be unexpectedly relevant for the development of cardiovascular disease. The aim of this study was to establish whether nomegestrol acetate induces signaling events in human endothelial cells that differ from those of other progestins, such as natural progesterone or medroxyprogesterone acetate.

METHODS

We used human endothelial cells to study the action of nomegestrol acetate (either alone or in the presence of estradiol [E2]) on the synthesis of nitric oxide (NO) and on the activity or expression of endothelial nitric oxide synthase (eNOS). We compared the effects of nomegestrol acetate with those of progesterone or medroxyprogesterone acetate. In addition, we characterized the signaling events recruited by these compounds.

RESULTS

Progesterone and nomegestrol acetate increase NO synthesis by transcriptional and nontranscriptional mechanisms, whereas medroxyprogesterone acetate lacks such effects. When used together with physiological E2 concentrations, progesterone and nomegestrol acetate do not interfere with (or even enhance) E2 effects, whereas medroxyprogesterone acetate impairs E2 signaling. A marked difference in the recruitment of mitogen-activated protein kinase and phosphatidylinositol-3 kinase explains the divergent effects of the three gestagens.

CONCLUSION

Our findings show significant differences in the signal transduction pathways recruited by progesterone, nomegestrol acetate, and medroxyprogesterone acetate in human endothelial cells that may have relevant clinical implications.

A critique of the Women's Health Initiative hormone therapy study

OBJECTIVE

This review critiques The Women's Health Initiative (WHI) study, focusing on aspects of the study design contributing to the adverse events resulting in the study's discontinuation.

CONCLUSION(S)

Two aspects of the design contributed to the adverse events: [1] The decision to administer continuous combined conjugated equine estrogen (CEE)/medroxyprogesterone acetate (MPA) or E alone as a standard regimen to a population with little previous hormonal treatment, ranging in age from 50-79 years, who, because of their age, were predisposed to coronary and cerebral atherosclerosis. [2] Selection of an untested regimen of continuous combined CEE plus MPA, which we hypothesize, negated the protective effect of E on the cardiovascular and cerebrovascular systems. Multiple observational studies that preceded the WHI study concluded that the use of E alone and E plus cyclic (not daily) progestin combination treatments initiated in early menopause had beneficial effects. The therapeutic regimens resulted in prevention of atherosclerosis and reductions in coronary artery disease mortality. It is our conclusion that the WHI hormonal replacement study had major design flaws that led to adverse conclusions about the positive effects of hormone therapy. An alternative hormonal regimen is proposed that, on the basis of data supporting its beneficial cardiovascular effects, when initiated appropriately in a population of younger, more recently menopausal women, has promise to yield a more favorable risk/benefit outcome.

Pharmaceutical prospects of phytoestrogens

Interest in the physiologic and pharmacologic role of bioactive compounds present in plants has increased dramatically over the last decade. Of particular interest in relation to human health are the classes of compounds known as the phytoestrogens, which embody several groups of non-steroidal estrogens, including isoflavones and lignans that are widely distributed within nature. The impact of dietary phytoestrogens on normal biologic processes was first recognized in sheep. Observations of sheep grazing on fields rich in clover and cheetahs fed high soy diets in zoos suggested that flavonoids and related phytochemicals can affect mammalian health. Endogenous estrogens have an important role not only in the hypothalamic-pituitary-gonadal axis, but also in various non-gonadal systems, such as cardiovascular systems, bone, and central nervous systems, and lipid metabolism. There have been several clinical studies of hormone replacement therapy (HRT) in post-menopausal women to examine whether HRT has beneficial effects on the cardiovascular system, bone fractures, lipid metabolism, and Alzheimer's disease. In addition, estrogen contributes to the development of some estrogen-dependent cancers, such as breast cancer and prostate cancer and the number of patients with these cancers is increasing in developed countries. Although recent mega-studies showed negative results for classical HRT in the prevention of some of these diseases, the molecules that interact with estrogen receptors are candidate drugs for various diseases, including hormone-dependent cancers. This review focuses on the molecular properties and pharmaceutical potential of phytoestrogens.

Allelic genes involved in artery compliance and susceptibility to sporadic abdominal aortic aneurysm

Vascular smooth muscle cells (VSMCs) synthesize elastin (ELN), major protein of aortic tunica media which confers strength and elasticity to aortic wall. Protein loss or distortion is typical in aneurysm tunica media. Transforming growth factor beta1 (TGFbeta1) inhibits growth and connective protein expression of abdominal VSMCs cultures. Also, in atherogenic studies, estrogen (but not estrogen plus progestin) treatments inhibit aortic collagen accumulation and elastic loss, risk factors to subsequent aortic enlargement. Therefore, polymorphisms of ELN, estrogen receptor alpha (ERalpha) and beta (ERbeta), progesterone receptor (PR) and TGFbeta1 genes and their products may be involved in the abdominal aortic aneurysm (AAA) development. Using PCR-RFLP method, we analyzed ELN RmaI (exon 16), ERalphaPvuII-XbaI (intron 1), ERbetaAluI (exon 8), PR TaqI (intron 7) and TGFbeta1 Bsu36I (-509 bp, promoter) polymorphisms in 324 Caucasian male subjects: 225 healthy controls (mean age 71.20 +/- 6.85 years) and 99 unrelated AAA patients (mean age 69.8 +/- 7.1 years). No difference in ELN, ERalpha, PR and TGFbeta1 allele frequencies was observed in AAA patients versus controls (P > 0.05). However, because possessing at least an ERbetaAluI restriction site was statistically associated to AAA onset (chi(2) = 5.220; OR = 1.82, P < 0.05), ERbeta polymorphism was proposed as genetic determinant in the AAA susceptibility.

Differential signal transduction of progesterone and medroxyprogesterone acetate in human endothelial cells

The conjugated equine estrogens-only arm of the Women's Health Initiative trial, showing a trend toward protection from heart disease as opposed to women receiving also medroxyprogesterone acetate (MPA), strengthens the debate on the cardiovascular effects of progestins. We compared the effects of progesterone (P) or MPA on the synthesis of nitric oxide and on the expression of leukocyte adhesion molecules, characterizing the signaling events recruited by these compounds. Although P significantly increases nitric oxide synthesis via transcriptional and nontranscriptional mechanisms, MPA is devoid of such effects. Moreover, when used together with physiological estradiol (E2) concentrations, P potentiates E2 effects, whereas MPA impairs E2 signaling. These findings are observed both in isolated human endothelial cells as well as in vivo, in ovariectomized rat aortas. A marked difference in the recruitment of MAPK and phosphatidylinositol-3 kinase explains the divergent effects of the two gestagens. In addition, both P and MPA decrease the adhesiveness of endothelial cells for leukocytes when given alone or with estrogen. MPA is more potent than P in inhibiting the expression of vascular cell adhesion molecule-1 and intercellular adhesion molecule-1. However, when administered together with physiological amounts of glucocorticoids, MPA (which also binds glucocorticoid receptor) markedly interferes with the hydrocortisone-dependent stabilization of the transcription factor nuclear factor kappaB and with the expression of adhesion molecules, acting as a partial glucocorticoid receptor antagonist. Our findings show significant differences in the signal transduction pathways recruited by P and MPA in endothelial cells, which may have relevant clinical implications.

Normal genetic variation, cognition, and aging

This article reviews the modulation of cognitive function by normal genetic variation. Although the heritability of "g" is well established, the genes that modulate specific cognitive functions are largely unidentified. Application of the allelic association approach to individual differences in cognition has begun to reveal the effects of single nucleotide polymorphisms on specific and general cognitive functions. This article proposes a framework for relating genotype to cognitive phenotype by considering the effect of genetic variation on the protein product of specific genes within the context of the neural basis of particular cognitive domains. Specificity of effects is considered, from genes controlling part of one receptor type to genes controlling agents of neuronal repair, and evidence is reviewed of cognitive modulation by polymorphisms in dopaminergic and cholinergic receptor genes, dopaminergic enzyme genes, and neurotrophic genes. Although allelic variation in certain genes can be reliably linked to cognition--specifically to components of attention, working memory, and executive function in healthy adults--the specificity, generality, and replicability of the effects are not fully known.

Soy protein isolate with isoflavones does not prevent estradiol-induced endometrial hyperplasia in postmenopausal women: a pilot trial

OBJECTIVE

To test the hypothesis that soy protein isolate (SPI) with isoflavones opposes the proliferative effects of exogenous estradiol (E2) on the endometrium after menopause.

DESIGN

Thirty-nine postmenopausal women were randomized to receive daily for 6 months either 0.5 mg E2 + placebo, 1.0 mg E2 + placebo, 0.5 mg E2 + 25 g SPI with 120 mg isoflavones, or 1.0 mg E2 + 25 g SPI with 120 mg isoflavones. Primary outcome measures were endometrial histology, ultrasound endometrial thickness, and Ki67 staining quantification, a marker of cellular proliferation. Secondary outcome measures were serum lipids and markers of bone resorption.

RESULTS

Endometrial hyperplasia, endometrial stromal and epithelial cellular proliferation, and sonographically measured endometrial thickness were similarly affected in all groups. SPI did not lessen the beneficial effects of E2 on lipids and markers of bone resorption.

CONCLUSION

In this pilot study, SPI with isoflavones did not protect the endometrium from E2-induced hyperplasia in postmenopausal women. If higher, long-term doses of isoflavone supplementation are found to be safe for postmenopausal women, then future studies combining E2 with isoflavones may be feasible as an alternative to traditional hormone replacement therapy.

Estrogens, homocysteine, vasodilatation and menopause: basic mechanisms, interactions and clinical implications

Estrogens influence the independent cardiovascular risk factor homocysteine as well as vasodilatation. Homocysteine alone also influences vasodilatation, indicating a relational triangle that seems important in interpreting the isolated effects of estrogens on homocysteine metabolism and vasoreactivity. This paper gives an overview of the current understanding regarding vasoreactivity, homocysteine metabolism and the role of estrogens. This is placed against the background of the clinical trials on the effect of postmenopausal hormone replacement therapy on homocysteine levels and addresses the importance of the interaction between homocysteine, estrogens and vasoreactivity.

Cholesterol-fed ovariectomized monkeys are good animal models for human atherosclerosis of postmenopausal women

Although it is well known that the incidence of atherosclerosis is markedly increased in postmenopausal women, antiatherosclerotic effects of estrogen replacement therapies are not clear. One of the reasons for this is due to the lack of appropriate animal models for atherosclerosis of postmenopausal women. Therefore, we attempted to develop an animal model for atherosclerosis of postmenopausal women and examined the antiatherosclerotic effects of estrogen replacement therapy. Adult ovariectomized Japanese monkeys were fed 2% cholesterol diet alone (C-group) or in combination with conjugated estrogen (CE-group) for 30 months. The serum estradiol-17beta levels of the CE-group were varied between 10 and 204.5 ng/dl during treatment. In the C-group, the serum total cholesterol levels were increased from 110 to 270 mg/dl, and atheroma was first observed after 3-months treatment with angioscopy. In the CE-group, the levels of the serum total cholesterol during treatment were 30% lower than those of the C-group, and the aortic lesions were first observed after 12-months treatment with angioscopy. The aortic intimal thickness of the CE-group was 58% of the C-group. This finding showed good agreement with the angioscopic observation. The aortic lesions were of a fibromuscular type in both groups. In conclusion, a cholesterol-fed ovariectomized monkey is an appropriate animal model for atherosclerosis of postmenopausal women. Furthermore, angiofiberscopic and histopathological observations suggested that estrogen replacement therapy was valid for atherosclerosis of postmenopausal women.

Blood pressure, arterial function, structure, and aging: the role of hormonal replacement therapy in postmenopausal women

The occurrence of natural menopause may indicate that a woman is entering a period of increased risk for cardiovascular disease, due to both chronologic aging and lower levels of estrogen. This brief review aims to demonstrate the relevance of changes in blood pressure and large artery structure and function occurring after menopause. These changes, i.e., thickening and stiffening of large arteries (which, in turn would also result in increased systolic and pulse pressures), were found to predict subsequent cardiovascular events, independently of other known cardiovascular risk. The benefits of early hormone replacement therapy on the life expectancy of women have dramatically lost consensus since publication of the Womens Health Initiative study results. However, the authors believe that those results should increase the attention paid by clinicians and public health researchers to the individualization of hormone replacement therapy prescription for postmenopausal women, and to a better characterization of those vascular parameters and profiles identifying postmenopausal women who are most likely to benefit from specific hormone replacement therapy in terms of cardiovascular protection.

Effects of tibolone and conventional hormone replacement therapies on arterial and hepatic cholesterol accumulation and on circulating endothelin-1, vascular cell adhesion molecule-1, and E-selectin in surgically menopausal monkeys

OBJECTIVE

Menopause and aging are associated with a marked increase in the incidence of coronary heart disease as well as reductions in circulating estrogen, progestogen, and androgen levels. The synthetic compound tibolone and its metabolites have estrogenic, progestogenic, and androgenic characteristics. In the present study, we compared the effects of tibolone, estrogen replacement therapy, and estrogen plus progestogen replacement therapy on arterial and hepatic lipid accumulation and on circulating soluble adhesion molecule and endothelin-1 concentrations in surgically postmenopausal cynomolgus monkeys.

DESIGN

Animals were fed an atherogenic diet for 2 years while receiving either no hormone treatment (control, n = 31) or the following treatments at doses designed to mimic the human dose on a daily caloric intake basis: tibolone at 2.5 mg/day (HiTib, n = 31), tibolone at 0.625 mg/day (LoTib, n = 29), conjugated equine estrogens (CEE) alone at 0.625 mg/day (CEE, n = 29), or CEE plus continuous medroxyprogesterone acetate (MPA) at 2.5 mg MPA/day (CEE + MPA, n = 30).

RESULTS

Relative to the control group, iliac artery total cholesterol content was not different in the HiTib, LoTib, and CEE + MPA groups but was significantly lower in the group receiving CEE only (P < 0.05). In contrast, hepatic free cholesterol content was reduced in all treatment groups [HiTib (P < 0.01), LoTib (P < 0.05), CEE (P < 0.01), and CEE + MPA (P < 0.05)], whereas hepatic total and esterified cholesterol content were reduced in the HiTib, CEE, and CEE + MPA groups (all P < 0.05). HiTib and CEE groups had lower hepatic triglyceride levels per milligram of protein (P < 0.05). Iliac arterial cholesterol content was highly correlated with hepatic cholesterol content and with previously published histomorphometrically determined coronary artery atherosclerosis, supporting the use of the iliac artery as a surrogate for the coronary artery in the monkey. Circulating levels of soluble vascular cell adhesion molecule-1 were significantly reduced in the HiTib (P < 0.02) and CEE (P < 0.05) groups, whereas soluble E-selectin was reduced in the CEE group only (P < 0.01). Plasma endothelin-1 was significantly reduced in the LoTib (P < 0.05), CEE (P < 0.01), and CEE + MPA (P < 0.01) groups.

CONCLUSIONS

These results suggest that while tibolone caused marked depression of high-density lipoprotein cholesterol and a resultant twofold increase in the total plasma cholesterol/high-density lipoprotein cholesterol ratio, those effects did not result in exacerbation of iliac artery atherosclerosis, perhaps because of beneficial effects on vascular biology or hepatic metabolism.

The choice of hormone replacement therapy or statin therapy in the treatment of hyperlipidemic postmenopausal women

Evidence based treatment of cardiovascular risk factors on outcome in women is still inconclusive given the very large numbers needed to achieve a significant difference in cardiovascular event. Although numerous studies of the effect of hormone replacement therapy (HRT) on risk factors have suggested benefit, the only data from a randomised control trial of HRT in secondary prevention was neutral. Coronary disease-primary prevention: (a) Statins: Air Force/Texas Coronary Atherosclerosis Prevention Study (AFCAPS/TEX CAPS). The only randomised controlled trial (RCT) to include women. There were fewer coronary heart disease (CHD) events in women but no difference in mortality. (b) HRT: no completed RCT-the results from Womens Health Initiative (WHI) and Women Intervention Study of Long Duration of Oestrogen in the Menopause (WISDOM) are awaited, the former likely to complete in 2004. There are numerous reports of positive observational epidemiological studies for HRT. There is little evidence for statin use in women who will probably not qualify for treatment on global CHD risk assessment, familial hypercholesterolemia and type 2 diabetes excepted. HRT is, therefore, not only appropriate for its multiple effects on lipoproteins, vascular function and insulin sensitivity but also for prevention of osteoporosis. Coronary disease-

SECONDARY PREVENTION

(a) Statins: the major measurable effect of these drugs is to reduce total and LDL cholesterol. In RCT trials, the Scandanavian Simvastatin Survival Study (4S), the Cholesterol and Recurrent Event (CARE) and Long-term Intervention with Pravastatin in Ischaemic Disease (LIPID), approximately 20% of subjects were female, in whom CHD events, but not CHD or total mortality were reduced. (b) HRT: there is data available from a single RCT of continuous combined premarin and medroxyprogesterone acetate (MPA) against placebo, The Heart Estrogen Replacement Study (HERS). A study of 2763 women and mean duration of 4.1 years. This study was neutral, with no reduction in CHD events or mortality. There were more events in the first year, and fewer in years 3-5. Other studies of HRT have been observational and positive for HRT. The effects of treatment on lipoproteins with statins, HRT and combination of statin and HRT have been investigated. In secondary prevention for hyperlipidemic women to achieve cholesterol <5, low density lipoprotein (LDL)<3 mmol/l statins will be first choice, possibly with HRT additionally for its other benefits on cardiovascular risk factors.

Angioscopic evaluation of the effect of estrogen on ovariectomized Japanese monkeys

Using angioscopy to study the atheroprotective effect of estrogen, atherosclerotic changes in surgically postmenopausal Japanese monkeys were observed for a long period. Changes in serum lipids and estradiol were also followed. About 3-6 months after the 2% cholesterol diet, serum cholesterol increased up to three times normal value, and atheroma was first found at the orifice of major branches of the abdominal aorta. However, in the other group of 2% cholesterol including an oral estrogen diet, the appearance of atheroma was inhibited until 12 months, although serum cholesterol increased gradually. The chronologic investigation was continued over 3 years. From these results we concluded that the most important atheroprotective effect of estrogen is the direct inhibition of atherosclerosis in the arterial wall, and improvement in lipid metabolism is of secondary importance.

Effects of postmenopausal hormone replacement therapy on lipid, lipoprotein, and apolipoprotein (a) concentrations: analysis of studies published from 1974-2000

OBJECTIVE

To establish reference estimates of the effects of different hormone replacement therapy (HRT) regimens on lipid and lipoprotein levels.

DESIGN

Review and pooled analysis of prospective studies published up until the year 2000.

SETTING

Clinical trials centers, hospitals, menopause clinics.

PATIENT(S)

Healthy postmenopausal women.

INTERVENTION(S)

Estrogen alone, estrogen plus progestogen, tibolone, or raloxifene in the treatment of menopausal symptoms.

MAIN OUTCOME MEASURE(S)

Serum high- and low-density lipoprotein (HDL and LDL) cholesterol, total cholesterol, triglycerides, and lipoprotein (a).

RESULT(S)

Two-hundred forty-eight studies provided information on the effects of 42 different HRT regimens. All estrogen alone regimens raised HDL cholesterol and lowered LDL and total cholesterol. Oral estrogens raised triglycerides. Transdermal estradiol 17-beta lowered triglycerides. Progestogens had little effect on estrogen-induced reductions in LDL and total cholesterol. Estrogen-induced increases in HDL and triglycerides were opposed according to type of progestogen, in the order from least to greatest effect: dydrogesterone and medrogestone, progesterone, cyproterone acetate, medroxyprogesterone acetate, transdermal norethindrone acetate, norgestrel, and oral norethindrone acetate. Tibolone decreased HDL cholesterol and triglyceride levels. Raloxifene reduced LDL cholesterol levels. In 41 studies of 20 different formulations, HRT generally lowered lipoprotein (a).

CONCLUSION(S)

Route of estrogen administration and type of progestogen determined differential effects of HRT on lipid and lipoprotein levels. Future work will focus on the interpretation of the clinical significance of these changes.

Postmenopausal oestrogen replacement therapy and atherosclerosis: can current compounds provide cardiovascular protection?

The natural oestrogen, 17 beta-oestradiol, has been implicated in protection from atherosclerosis, a chronic systemic vascular disease with an inflammatory component accounting for the majority of morbidity and mortality in Western countries. Despite the protective effects of 17 beta-oestradiol in premenopausal women and experimental evidence demonstrating inhibitory effects of oestrogen on atherosclerosis progression, it is currently unclear whether hormone replacement therapy can affect cardiovascular morbidity and mortality in postmenopausal women. The recent advances in understanding the mechanisms of oestrogen action demonstrated roles for different oestrogen receptors and oestrogen metabolites in the pathogenesis of vascular injury and endothelial cell dysfunction. However, their respective role in the process of atherogenesis remains yet to be elucidated. Moreover, the availability of novel drugs with tissue- and/or receptor-specific actions will help to understand the role of oestrogen in cardiovascular diseases. Several ongoing large-scale clinical trials using opposed or unopposed replacement therapy with natural or synthetic oestrogens, or selective oestrogen receptor modulators (SERMs) will resolve the question whether the drugs currently available have therapeutic potential to interfere with the progression of atherosclerosis and its complications.

Effect of estrogen and progestin replacement on arterial stiffness indices in postmenopausal women

Our objectives were to investigate whether long-term estrogen replacement therapy (ERT) is associated with a reduction in age-associated increases in arterial stiffness and blood pressure (BP), and whether the addition of progestin modifies the effects of estrogen. ERT has been found to have beneficial effects on cardiovascular risk. There are few data, however, delineating the effects of ERT on BP and arterial stiffness, and their age-associated changes. BP and aorto-femoral pulse wave velocity (PWV) were measured in 134 postmenopausal volunteers, aged 51 to 90 years, from the Baltimore Longitudinal Study of Aging, screened to exclude clinical and occult cardiovascular disease, and classified as ERT non-users (N=57) or ERT users (N=77). The latter group was further substratified according to the use of estrogen alone (N=32) or a combination of estrogen and progestins (N=45). ERT users showed similar body habitus, physical activity, and plasma lipids compared to non-ERT users. ERT was associated with an average 9.8 mmHg lower systolic BP (p<0.001), and a 6.3 mmHg lower pulse pressure (p<0.01) than in non-users. Multiple regression analysis showed that ERT was an independent predictor of lower SBP and PP (p<0.05). By analysis of covariance, ERT predicted a reduced age-associated increase in SBP, PP, and PWV (p<0.05). When systolic BP was >130 mmHg, the combination of ERT and progestins predicted a higher PWV than ERT alone. In conclusion, ERT in postmenopausal women can beneficially affect the vascular system, by reducing BP and the age-associated increase in arterial stiffness. The addition of progestins to ERT may reduce these beneficial effects.

Estrogen receptor alpha is a major mediator of 17beta-estradiol's atheroprotective effects on lesion size in Apoe-/- mice

The inhibitory effects of estrogen (17beta-estradiol) on atherosclerosis have been well documented in numerous animal models, and epidemiological evidence supports this protective effect in humans. The detailed mechanisms for this protection are not understood, but most are thought to be mediated through estrogen receptors (ERs), of which two are known (ERalpha and ERbeta). To investigate the role of ERalpha in the atheroprotective effect of 17beta-estradiol (E2), we ovariectomized female mice that lack apoE (AAee) or lack both apoE and ERalpha (alphaalphaee), and treated half of them with E2 for three months. E2 treatment of ovariectomized AAee females dramatically reduced the size of the lesions as well as their histological complexity. Plasma cholesterol was significantly reduced in this group, although the observed extent of protection by E2 was greater than could be explained solely by the change in lipid levels. In contrast, E2 treatment of ovariectomized alphaalphaee females caused minimal reduction in lesion size and no reduction in total plasma cholesterol compared with alphaalphaee mice without E2, demonstrating that ERalpha is a major mediator of the atheroprotective effect of E2. Nevertheless, E2 treatment significantly reduced the complexity of plaques in the alphaalphaee females, although not to the same degree as in AAee females, suggesting the existence of ERalpha-independent atheroprotective effects of E2.

Preserved forearm endothelial responses with acute exposure to progesterone: A randomized cross-over trial of 17-beta estradiol, progesterone, and 17-beta estradiol with progesterone in healthy menopausal women

Regularly menstruating women are relatively protected from cardiovascular disease. Epidemiological and endothelial function studies attribute this protection to estradiol (E(2)), but both progesterone (P) and E(2) are normally present. A range of vascular effects of added progestins have been described, from neutral to detrimental, but the effects of P per se on endothelial function in humans have not been reported. We therefore investigated the acute effects of E(2), P, and E(2) combined with P, on endothelium-dependent and -independent forearm blood flow responses. Using venous occlusion plethysmography, forearm blood flow (FBF) was measured during acute brachial artery infusions, achieving physiologic levels of 17-beta-E(2), P, and 17-beta-E(2) with P in healthy menopausal women with no cardiovascular disease risk factors. Vehicle or hormones were infused, in random order, on 4 days, 1 week apart. Flow responses were measured during coinfusions of hormone with the endothelium-dependent vasodilator acetylcholine and the endothelium-independent vasodilator sodium nitroprusside. Twenty-seven healthy menopausal women were studied, and all had normal baseline endothelial responses. Small ( approximately 15%), statistically nonsignificant increases in endothelium-dependent flow responses were seen after all acute hormone treatments. No impairment in response was seen with P alone or in combination with 17-beta-E(2). In healthy menopausal women without cardiovascular disease risk factors and without baseline defects in endothelial function, acute exposure to physiologic levels of 17-beta-E(2), P, and 17-beta-E(2) with P produced equivalent endothelium-dependent responses. These data suggest that P does not have detrimental vascular effects in humans.

Natural progesterone, but not medroxyprogesterone acetate, enhances the beneficial effect of estrogen on exercise-induced myocardial ischemia in postmenopausal women

OBJECTIVES

We sought to compare the effects of estrogen/transvaginal progesterone gel with estrogen/medroxyprogesterone acetate (MPA) on exercise-induced myocardial ischemia in postmenopausal women with coronary artery disease or previous myocardial infarction, or both.

BACKGROUND

Estrogen therapy beneficially affects exercise-induced myocardial ischemia in postmenopausal women; however, women with an intact uterus also take progestin to protect against uterine malignancies. The effects of combination estrogen/progestin therapy on myocardial ischemia are unknown.

METHODS

Eighteen postmenopausal women (mean +/- SD age 59+/-7 years) were given 17-beta-estradiol in single-blinded manner for four weeks (1 mg/day for three weeks then 2 mg/day for one week). Estradiol (2 mg/day) was then continued, and the patients were randomized (double-blind) for 12 days to either transvaginal progesterone gel (90 mg on alternate days) and oral MPA placebo (10 mg/day), or vice versa. After another two weeks on estradiol alone, the patients crossed over to progestin treatment and repeated the protocol on the opposite treatment. Patients underwent treadmill exercise testing after each estradiol phase and at day 10 of each progestin phase.

RESULTS

Exercise time to myocardial ischemia increased after the first estrogen phase as compared with baseline (mean difference with 95% confidence interval [CI]: 72 s [34 to 110], p = 0.001), and was increased by combination estradiol/progesterone therapy as compared with estradiol/MPA therapy (92 s [35 to 149], p = 0.001)). Two patients (11%) were withdrawn while taking estradiol/MPA owing to unstable angina.

CONCLUSIONS

Combination estrogen/transvaginal progesterone gel increases exercise time to myocardial ischemia, as compared with estrogen/MPA. These results imply that the choice of progestin in women at higher cardiovascular risk requires careful consideration.

The effect of hormone replacement therapy on arterial distensibility and compliance in perimenopausal women: a 2-year randomised trial

A single centre randomised placebo-controlled trial was performed to assess the 2-year effects of hormone replacement therapy compared to placebo on mechanical arterial properties in 99 perimenopausal women recruited from the general population. The trial was double-blind with respect to a sequential combined regimen of oral 17beta-oestradiol and desogestrel (17betaE(2)-D) and the placebo group and open with respect to combination of conjugated equine oestrogens and norgestrel (CEE-N). At baseline, distensibility and compliance of the common carotid artery were measured non-invasively with B-mode ultrasound and a vessel wall movement detector system, and the distensibility coefficient (DC) and compliance coefficient (CC) were calculated. Measurements were repeated after 6 and 24 months. Change in DC and CC in treatment groups was compared to placebo. After 24 months, changes for 17betaE(2)-D compared to placebo were -1.4x10(-3)/kPa (95% CI -4.4; 1.7, P=0.39) for DC and 0. 26 mm(2)/kPa (95% CI -0.01; 0.53, P=0.07) for CC. Changes for CEE-N compared to placebo were 0.4x10(-3)/kPa (95% CI -1.0; 1.9, P=0.79) and 0.11 mm(2)/kPa (95% CI -0.14; 0.37, P=0.40). For systolic blood pressure (SBP), diastolic blood pressure (DBP) and arterial lumen diameter no changes were found. In this study no significant differences in changes in distensibility and compliance were found between perimenopausal women using 17betaE(2)-D or CEE-N and women using placebo after 6 and 24 months.

Hormone replacement therapy in the prevention and treatment of atherosclerosis

As the population ages, the increasing number of women at risk for cardiovascular disease represents both a potential crisis and an opportunity in healthcare management. Although the overall death rate from cardiovascular disease in the general population is decreasing, the absolute numbers for women are increasing. A reduction in modifiable risk factors in women must be aggressively pursued by clinicians and health systems. Menopause is associated with many adverse effects on cardiovascular-disease risk factors in women. Estrogen replacement therapy has been shown to favorably influence many risk factors for cardiovascular disease. Despite this biologic plausibility and supporting evidence from epidemiologic studies, data from confirmatory clinical trials are lacking. Because of this, recommendations for hormone replacement therapy should be made on an individual basis.