Invited review: Pharmacogenetics of estrogen replacement therapy

Pharmacogenomics and health disparities, are we helping?

Pharmacogenomics has been at the forefront of precision medicine during the last few decades. Precision medicine carries the potential of improving health outcomes at both the individual as well as population levels. To harness the benefits of its initiatives, careful dissection of existing health disparities as they relate to precision medicine is of paramount importance. Attempting to address the existing disparities at the early stages of design and implementation of these efforts is the only guarantee of a successful just outcome. In this review, we glance at a few determinants of existing health disparities as they intersect with pharmacogenomics research and implementation. In our opinion, highlighting these disparities is imperative for the purpose of researching meaningful solutions. Failing to identify, and hence address, these disparities in the context of the current and future precision medicine initiatives would leave an already strained health system, even more inundated with inequality.

Menopause as a potential cause for higher prevalence of low back pain in women than in age-matched men

Female sex hormones play an important role in the aetiology and pathophysiology of a variety of musculoskeletal degenerative diseases. Postmenopausal women show accelerated disc degeneration due to relative oestrogen deficiency, resulting in narrower intervertebral disc space in women than age-matched men, increased prevalence of spondylolisthesis, and increased prevalence of facet joint osteoarthritis. Postmenopausal women also show higher osteoporosis related spine fracture rate, particularly at the thoracic-lumbar junction site. I propose the concept that low back pain (LBP) is more prevalent in postmenopausal women than age-matched men and is associated with the physiological changes caused by the relatively lower level of sex hormones after menopause in women. Considering hormone replacement treatment (HRT)'s consistent efficacy reported with menopause-associated osteoarthritis, an in-depth understanding of the role of the gonadal hormones in LBP modulation warrants further study. HRT initiated at early postmenopausal phase may be protective for recurring LBP. If this is the case, further cost-benefit analysis should be performed for optimal HRT regimen in cases of women with high risk of recurring severe LBP.

Pharmacogenetics: Policy needs for personal prescribing

Pharmacogenetics involves genetic testing of individual patients to guide drug treatment. Proponents argue that pharmacogenetics will achieve major gains in drug safety and efficacy, and revolutionise marketing. Pharmacogenetics also raises several policy concerns, including the need for sound information for clinical decision-making on drug-genetic test combinations. Currently, the pharmacogenetics science base and the rate of emergence of clinical applications are uncertain. Most commentary on pharmacogenetics focuses on new compounds, yet older drugs cause most adverse events. Test regulation in the USA appears fundamentally different from Europe, where evidence of safety or efficacy may not be required. Genetics research is needed as part of postmarketing surveillance systems. In routine clinical practice, computer-based health records with relevant decision support systems will also be needed. Without health policy action, pharmacogenetics could produce a new generation of poorly evaluated tests and drugs, with medicine becoming significantly less evidence-based, leading to rising costs, patient hazard and exclusions of drug-related ‘genetic minorities’ from evaluated treatments.

Increased low back pain prevalence in females than in males after menopause age: evidences based on synthetic literature review

Female sex hormones play an important role in the etiology and pathophysiology of a variety of musculoskeletal degenerative diseases. Postmenopausal women show accelerated disc degeneration due to relative estrogen deficiency. This literature review aims to validate or falsify this hypothesis, i.e., while overall females have higher prevalence of low back pain (LBP) across all age groups, this male vs. female difference in LBP prevalence further increases after female menopause age. The literature search was performed on PubMed on January 2, 2016. The search word combination was (low back pain) AND prevalence AND [(males OR men) AND (females OR women)]. The following criteria were taken to include the papers for synthetic analysis: (I) only English primary literatures on nonspecific pain; (II) only prospective studies on general population, but not population with occupational LBP causes, of both males and female subjects studied using the same LBP criterion, ages-specific information available, and males and female subjects were age-matched; (III) studies without major quality flaws. In total 98 studies with 772,927 subjects were analyzed. According to the information in the literature, participant subjects were divided into four age groups: (I) school age children group: 6-19 years; (II) young and middle aged group: 20-50 years; (III) mixed age group: data from studies did not differentiate age groups; (IV) elderly group: ≥50 years old. When individual studies were not weighted by participant number and each individual study is represented as one entry regardless of their sample size, the median LBP prevalence ratio of female vs. males was 1.310, 1.140, 1.220, and 1.270 respectively for the four age groups. When individual studies were weighted by participant number, the LBP prevalence ratio of female vs. males was 1.360, 1.127, 1.185, and 1.280 respectively for the four groups. The higher LBP prevalence in school age girls than in school age boys is likely due to psychological factors, female hormone fluctuation, and menstruation. Compared with young and middle aged subjects, a further increased LBP prevalence in females than in males was noted after menopause age.

A higher aneurysmal subarachnoid hemorrhage incidence in women prior to menopause: a retrospective analysis of 4,895 cases from eight hospitals in China

BACKGROUND

Subarachnoid hemorrhage (SAH) from a ruptured cerebral aneurysm is a devastating disease. Despite the risk factors, including hypertension, cigarette smoking and alcohol use, are more common in men, aneurysmal SAH belongs to a few diseases which the incidence is higher in women than in men. Sex hormones, especially estrogen, might be protective against this condition. Hormone replacement therapy (HRT) seems to be associated with a reduced risk for aneurysmal SAH. This study aims to know the prevalence of aneurysmal SAH of men and women at different ages.

METHODS

The age and gender information of 4,895 case of aneurysmal SAH (3,016 females, 1,879 males) were collected retrospectively from eight institutions in mainland China. The prevalence of aneurysmal SAH of men and women at different ages was analyzed.

RESULTS

The data showed women had a higher incidence of aneurysmal SAH than men starting at late thirties, and men might have a higher incidence of aneurysmal SAH than women only before 37-year-old.

CONCLUSIONS

Menopause may not be the only dominant factor causing higher incidence of aneurysmal SAH in women than in men.

Lessons from the dissection of the activation functions (AF-1 and AF-2) of the estrogen receptor alpha in vivo

Estrogens influence most of the physiological processes in mammals, including but not limited to reproduction, cognition, behavior, vascular system, metabolism and bone integrity. Given this widespread role for estrogen in human physiology, it is not surprising that estrogen influence the pathophysiology of numerous diseases, including cancer (of the reproductive tract as breast, endometrial but also colorectal, prostate,…), as well as neurodegenerative, inflammatory-immune, cardiovascular and metabolic diseases, and osteoporosis. These actions are mediated by the activation of estrogen receptors (ER) alpha (ERα) and beta (ERβ), which regulate target gene transcription (genomic action) through two independent activation functions (AF)-1 and AF-2, but can also elicit rapid membrane initiated steroid signals (MISS). Targeted ER gene inactivation has shown that although ERβ plays an important role in the central nervous system and in the heart, ERα appears to play a prominent role in most of the other tissues. Pharmacological activation or inhibition of ERα and/or ERβ provides already the basis for many therapeutic interventions, from hormone replacement at menopause to prevention of the recurrence of breast cancer. However, the use of these estrogens or selective estrogen receptors modulators (SERMs) have also induced undesired effects. Thus, an important challenge consists now to uncouple the beneficial actions from other deleterious ones. The in vivo molecular "dissection" of ERα represents both a molecular and integrated approach that already allowed to delineate in mouse the role of the main "subfunctions" of the receptor and that could pave the way to an optimization of the ER modulation.

Structure-function relationship of estrogen receptors in cardiovascular pathophysiological models

The ancestral status of estrogen receptor (ER) in the family of the steroid receptors has probably contributed to the pleiotropic actions of estrogens, and in particular of 17β-estradiol (E2). Indeed, in addition to their well described role in sexual development and reproduction, they influence most of the physiological processes. The pathophysiological counterpart of these actions includes several highly beneficial effects such as prevention of osteoporosis, atheroma and type 2 diabetes,… However, estrogens also promotes two deleterious actions : the stimulation of the proliferation of the epithelium of two sex targets : uterus and breast, favoring an increase in risk of epithelial cancer in these two tissues. These actions are mediated by the activation of ER alpha (ERα) and beta (ERβ), which regulate target gene transcription (genomic action) through two independent activation functions AF-1 and AF-2, but can also elicit rapid membrane initiated steroid signals. Although ERβ plays an important role in the central nervous system and in the heart, ERα appears to play a prominent role in most of the other tissues. One major challenge consists in uncoupling some beneficial actions from other deleterious ones, i.e. selective ER modulation. Tamoxifen and raloxifen are beneficial to prevent the recurrence of breast cancer, and mimic estrogen action mainly on bone, but their effets on atheroma and on type 2 diabetes are if any marginal. These last years, several labs, and in particular our lab, have attempted: 1) To perform an in vivo molecular "dissection" of ER alpha, allowing the uncoupling of some of its actions, and potentially paving the way to optimized selective ER modulators. (reviewed in Arnal JF, et al. Br J Pharmacol. 2012;165:57-66). 2) To describe an unexpected action of E2 treatment at the level of platelet responses in mice, that protects the animals from thromboembolism through the haematopoietic ER alpha. (Valéra MC et al. Blood. 2012, in press).

Genetic polymorphisms associated with carotid artery intima-media thickness and coronary artery calcification in women of the Kronos Early Estrogen Prevention Study

Menopausal hormone treatment (MHT) may limit progression of cardiovascular disease (CVD) but poses a thrombosis risk. To test targeted candidate gene variation for association with subclinical CVD defined by carotid artery intima-media thickness (CIMT) and coronary artery calcification (CAC), 610 women participating in the Kronos Early Estrogen Prevention Study (KEEPS), a clinical trial of MHT to prevent progression of CVD, were genotyped for 13,229 single nucleotide polymorphisms (SNPs) within 764 genes from anticoagulant, procoagulant, fibrinolytic, or innate immunity pathways. According to linear regression, proportion of European ancestry correlated negatively, but age at enrollment and pulse pressure correlated positively with CIMT. Adjusting for these variables, two SNPs, one on chromosome 2 for MAP4K4 gene (rs2236935, β = 0.037, P value = 2.36 × 10(-06)) and one on chromosome 5 for IL5 gene (rs739318, β = 0.051, P value = 5.02 × 10(-05)), associated positively with CIMT; two SNPs on chromosome 17 for CCL5 (rs4796119, β = -0.043, P value = 3.59 × 10(-05); rs2291299, β = -0.032, P value = 5.59 × 10(-05)) correlated negatively with CIMT; only rs2236935 remained significant after correcting for multiple testing. Using logistic regression, when we adjusted for waist circumference, two SNPs (rs11465886, IRAK2, chromosome 3, OR = 3.91, P value = 1.10 × 10(-04); and rs17751769, SERPINA1, chromosome 14, OR = 1.96, P value = 2.42 × 10(-04)) associated positively with a CAC score of >0 Agatston unit; one SNP (rs630014, ABO, OR = 0.51, P value = 2.51 × 10(-04)) associated negatively; none remained significant after correcting for multiple testing. Whether these SNPs associate with CIMT and CAC in women randomized to MHT remains to be determined.

Are polymorphisms in oestrogen receptors genes associated with lipid levels in response to hormone therapy?

BACKGROUND

Polymorphisms in the oestrogen receptor 1 (ESR1) and oestrogen receptor 2 (ESR2) genes are associated with intermediate or endpoint markers of cardiovascular disease and with the efficacy of postmenopausal hormone therapy (HT). Contradictory findings have been described in the past and the role of these genetics variants remains unclear.

METHODS

A cross-sectional study was carried out with 266 postmenopausal women, of whom 115 received oral HT (HT+) and 151 did not receive any HT (HT-). We analysed three single-nucleotide polymorphisms (SNPs) in ESR1 (rs1801132, rs7757956 and rs2813544) and two in ESR2 (rs3020450 and rs7154455) and derived haplotypes with three additional polymorphisms that had been previously investigated by our group (ESR1 rs2234693 and ESR2 rs1256049 and rs4986938).

RESULTS

The ESR1 rs2813544 polymorphism was associated with low-density lipoprotein cholesterol (LDL-C) in HT+ postmenopausal women (p = 0.044; pC = 0.388), while one ESR2 gene haplotype was associated with total cholesterol (T-chol) (p = 0.015; pC = 0.090) and LDL-C in HT+ postmenopausal women (p = 0.021; pC = 0.126).

CONCLUSION

Our findings suggest that, in HT+ postmenopausal women, the rs2813544 polymorphism may influence LDL-C levels and, as previously described, ESR2 rs1256049 is associated with T-chol and LDL-C. No previous study has investigated the association of this SNP set with lipoprotein levels in women while taking into account the hormonal status of the patients.

From in vivo gene targeting of oestrogen receptors to optimization of their modulation in menopause

The ancestral status of oestrogen receptor (ER) in the family of the steroid receptors has probably contributed to the pleiotropic actions of oestrogens, and in particular, that of 17β-oestradiol (E2). Indeed, in addition to their well-described role in sexual development and reproduction, they influence most of the physiological processes. The pathophysiological counterpart of these actions includes prevention of osteoporosis, atheroma and type 2 diabetes, and also the promotion of uterus and breast cancer growth. Thus, the major challenge consists in uncoupling some beneficial actions from other deleterious ones, that is, selective ER modulation. Tamoxifen and raloxifene are already used, as they prevent the recurrence of breast cancer and mimic oestrogen action mainly on bone. Both E2 and tamoxifen exhibit a proliferative and, thus, a protumoural action on the endometrium. Activation of ERα and ERβ regulates target gene transcription (genomic action) through two independent activation functions, AF-1 and AF-2, but can also elicit rapid membrane-initiated steroid signals. In the present review, we attempted to summarize recent advances provided by the in vivo molecular 'dissection' of ERα, allowing the uncoupling of some of its actions and potentially paving the way to optimized selective ER modulators.

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.

Estrogen Receptors and Endothelium

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. Both acetylcholine-induced and flow-dependent vasodilation are preserved or potentiated by estrogen treatment in both animal models and humans. Indeed, E2 increases the endothelial production of nitric oxide and prostacyclin and prevents early atheroma through endothelial-mediated mechanisms. Furthermore, whereas it prevents endothelial activation, E2 potentiates the ability of several subpopulations of the circulating or resident immune cells to produce proinflammatory cytokines. The balance between these 2 actions could determine the final effect in a given pathophysiological process. E2 also promotes endothelial healing, as well as angiogenesis. Estrogen actions are essentially mediated by 2 molecular targets: estrogen receptor-α (ERα) and ERβ. The analysis of mouse models targeted for ERα or ERβ demonstrated a prominent role of ERα in vascular biology. ERα directly modulates transcription of target genes through 2 activation functions (AFs), AF-1 and AF-2. Interestingly, an AF-1-deficient ERα isoform can be physiologically expressed in the endothelium and appears sufficient to mediate most of the vasculoprotective actions of E2. In contrast, AF-1 is necessary for the E2 actions in reproductive targets. Thus, it appears conceivable to uncouple the vasculoprotective and sexual actions with appropriate selective ER modulators.

Hormone replacement therapy may prevent the development of isolated pulmonary hypertension in patients with systemic sclerosis and limited cutaneous involvement

BACKGROUND

Isolated pulmonary hypertension (iPHT) is a near-fatal consequence of systemic sclerosis (SSc); in female patients, the risk of its development is increased during the post-menopausal period, when the protective effects of oestrogens on the endothelium decrease. In many animal and human models, hormone replacement therapy (HRT) and oestrogen administration proved efficacious in counteracting many mechanisms that might be implicated in the pathogenesis of iPHT. Accordingly, it has been hypothesized that HRT might help to prevent the development of iPHT.

METHODS

A retrospective cohort study was conducted on 61 SSc patients with the limited cutaneous form of the disease and no sign of pulmonary hypertension on echocardiogram (pulmonary artery pressure, PAP > 35 mmHg) at the time of menopause. All the patients had to be stably treated with calcium-channel blockers and not to have risk factors for secondary PHT throughout the duration of the observational period.

RESULTS

Twenty patients (32.8%) received HRT for a mean of 6.7 +/- 3.7 years. None of these patients developed iPHT after a mean of 7.2 +/- 3.5 years from menopause, whereas eight out of 41 patients not receiving HRT (19.5%) developed iPHT after a similar time period (7.5 +/- 3.9 years, p = 0.032). These rates were not explained by differences between the two groups with respect to autoantibodies, age, age at onset of SSc, diffusing capacity of the lung for carbon monoxide (DLCO) at menopause, or duration of therapy with calcium-channel blockers.

CONCLUSION

HRT administration may be effective in SSc post-menopausal women, preventing the development of iPHT.

Do Estrogen Receptor beta Polymorphisms Play A Role in the Pharmacogenetics of Estrogen Signaling?

Estrogen hormones play critical roles in the regulation of many tissue functions. The effects of estrogens are primarily mediated by the estrogen receptors (ER) alpha and beta. ERs are ligand-activated transcription factors that regulate a complex array of genomic events that orchestrate cellular growth, differentiation and death. Although many factors contribute to their etiology, estrogens are thought to be the primary agents for the development and/or progression of target tissue malignancies. Many of the current modalities for the treatment of estrogen target tissue malignancies are based on agents with diverse pharmacology that alter or prevent ER functions by acting as estrogen competitors. Although these compounds have been successfully used in clinical settings, the efficacy of treatment shows variability. An increasing body of evidence implicates ERalpha polymorphisms as one of the contributory factors for differential responses to estrogen competitors. This review aims to highlight the recent findings on polymorphisms of the lately identified ERbeta in order to provide a functional perspective with potential pharmacogenomic implications.

Steroid hormone receptor gene polymorphisms and osteoporosis: a pharmacogenomic review

Osteoporosis is a common skeletal disorder with a strong genetic component. In recent years, significant progress has been made in understanding the genetic basis of osteoporosis. Given the biological significance of signalling through steroid hormone receptors, bone biology and calcium homeostasis, alleles of steroid hormone receptor genes have been postulated to contribute to the well-documented genetic predisposition to osteoporosis; and in different studies, these alleles have been associated with variation in bone mass and fracture risk. Even though results are still conflicting and the molecular mechanisms by which these polymorphisms influence receptor activity remain, in part, to be investigated, an additional important issue is represented by potential pharmacogenomic (the investigation of variations of DNA or RNA characteristics as related to drug response) or pharmacogenetic (the influence of variations of DNA sequence on drug response) implications. In fact, steroid hormone receptors actually mediate the action of several compounds known to positively or negatively affect bone homeostasis, such as vitamin D, estrogen and glucocorticoids. This review analyses major pharmacogenetic studies of polymorphisms in steroid hormone receptor genes.

Estrogen therapy and thrombotic risk

Post-menopausal hormone therapy increases the risk for venous thrombosis, and possibly myocardial infarction (MI) and ischemic stroke. However, most women using hormone therapy do not suffer thrombosis, and to date our ability to identify women at risk is limited. Thrombosis, arterial or venous, has 2 requisites: a vascular anomaly and a response of the hemostasis system to the anomaly. Consequently, experimental approaches to understand the pathophysiology of thrombosis require definition of vascular anatomy and function as well as characteristics of the blood within the context of genetic background, lifestyle choices and environmental exposures, which influence gene expression. Defining interactions among factors that affect individual propensity to thrombosis will allow physicians to better identify at-risk individuals, for example a woman contemplating estrogen therapy for symptoms of menopause, and prevent adverse thrombotic events.

Factor V Leiden, prothrombin G20210A substitution and hormone therapy: indications for molecular screening

Venous thromboembolism is a well-known complication of oral contraception and hormonal replacement therapy. Inherited thrombophilia is viewed as an important determinant in modulating the effects of estrogens on thrombotic risk. An increasing number of kits for thrombophilic mutations [factor V Leiden, G20210A prothrombin and methylenetetrahydrofolate reductase (MTHFR) C677T genes] are becoming commercially available, and screening for inherited thrombotic risk is among the most requested genetic tests in molecular diagnostic laboratories. However, the question of routine genetic screening for thrombophilia before prescribing hormones is still a matter of debate. The purpose of this article is to discuss the usefulness and practical applications of thrombotic genetic testing to identify which women should be tested to improve both the safety and efficacy of individualized estrogen therapy.

Estrogen-metabolizing gene polymorphisms and lipid levels in women with different hormonal status

Endogenous and exogenous sex steroid hormones have multiple effects on lipid and lipoprotein metabolism. It is also known that estrogen has antiatherogenic actions, therefore we considered examining whether there was any association between polymorphisms in estrogen-metabolizing genes and lipid levels in women. We investigated the association between variants in genes related to estrogen biosynthesis (CYP19-TTTA(n)) and estrogen catabolism (CYP1A1*2A, CYP1A1*2C, CYP1A2-Asn516Asn, CYP3A4*1B, and COMT-Val158Met) with serum lipid levels in a cross-sectional study with 472 Brazilian women of European descent. They were divided into three subgroups according to their hormonal status: premenopausal women (n=187), postmenopausal women exposed to hormonal replacement therapy (HRT) (n=118), and postmenopausal women unexposed to HRT (n=167). The postmenopausal women receiving HRT who were carriers of the CYP3A4*1B variant showed lower low-density lipoprotein cholesterol levels than wild-type homozygotes. Premenopausal women homozygous for the CYP1A1*2C allele had higher high-density lipoprotein cholesterol levels than heterozygotes. While the CYP1A1*2C variant probably has a higher catalytic activity, the functional implications of the CYP3A4 polymorphism are still uncertain. These data are the first attempt to associate estrogen metabolism genes to lipid levels in women.

Applications of polymorphisms and pharmacogenomics in obstetrics and gynecology

The number of reports investigating disease susceptibility based on the carriage of low-penetrance, high-frequency polymorphisms has steadily increased over the last years. Evidence based on meta-analyses of individual case-control studies is accumulating, defining specific individual variations in disease susceptibility. For example, genetic variations of the estradiol metabolism have been described as significant contributors to disease susceptibility with variations depending on ethnic background. In the field of obstetrics and gynecology, the genetic contribution of polymorphic markers to a series of disorders has been characterized. These disorders include recurrent pregnancy loss, pre-eclampsia, endometriosis, breast cancer, and hormone replacement therapy (HRT)-related complications such as thrombosis. Among other genetic markers, thrombophilic genetic variants, such as the Factor V Leiden and prothrombin G20210A polymorphisms, as well as genetic variants of cytochrome P450 (CYP) enzymes, for example, CYP19 and CYP1B1, have been established as genetic risk markers and disease modifiers of recurrent and sporadic pregnancy loss and HRT-independent and -dependent breast cancer, respectively. In addition, meta-analyses of data in the literature established the TGFBR1*6A, GSTP I105V, and TP53 R72P polymorphisms, as well as the GSTM1 gene deletion as low-penetrance genetic risk factors of sporadic breast cancer. With respect to genetic modulation of therapeutic effects, beneficial effects of estrogen replacement therapy and HRT are modulated by the carriage of single nucleotide polymorphisms, for example, osteoprotection and blood lipid changes by the estrogen receptor-alpha (ER-a) PvuII polymorphism. Polymorphisms of the catechol-O-methyltransferase (COMT), ER-alpha, IL-1 receptor antagonist, and Factor V genes have been demonstrated to modulate the timing of natural menopause. Lastly, a strong genetic contribution of polymorphisms to the development and the clinical course of endometriosis has been established with data pointing to polymorphisms of the COMT, GST, NAT-2, and ER-alpha genes as susceptibility markers. In summary, the available evidence points to a number of polymorphisms of a wide variety of genes as strong hereditary determinants of the susceptibility to benign and malignant gynecologic and obstetric conditions.

Thoughts on Individualizing Hormone Replacement Therapy Based on the Postmenopausal Health Disparities Study Data

BACKGROUND

This study presents an approach that can be used to address the controversy about the long-term risks and benefits of hormone replacement therapy (HRT).

METHODS

Categories of estradiol (E(2)) levels based on the mean and standard deviation (SD) in postmenopausal women not treated with HRT were created. E(2) levels achieved in women treated with oral or patch replacement therapy were examined. In the application of this method, data from the Postmenopausal Health Disparities Study were used because identical E(2) assay methods were used for all postmenopausal women in the study population.

RESULTS

The findings demonstrated that approximately 42% of HRT-treated women had E(2) levels less than the mean E(2) level plus 1 SD in the controls (37 pg/ml). In contrast, approximately 11% had E(2) levels greater than the mean E(2) level plus 6 SD in the controls (126 pg/ml). Menopausal vasomotor and vaginal symptoms decreased ( p < 0.06) in increasing control-based E(2) categories. Levels of both follicle-stimulating hormone (FSH) and luteinizing hormone (LH) were significantly correlated with the E(2) control-based categories (both p = 0.000). When hormone variables and other variables (e.g., moderate alcoholic beverage consumption and bilateral ovariectomy) known to be determinants of E(2) levels in postmenopausal women not treated with HRT were included in the model for oral or patch HRT-treated women, 51.1% of the variability in the control-based E(2) categories was explained when menopause duration, use of oral as opposed to patch therapy, body mass index (BMI), scores for medical compliance, and being white entered the equation as statistically significant predictors.

CONCLUSIONS

First, there is substantial variability in E(2) concentrations achieved with conventional oral and patch HRT. Second, various factors that are statistically significant predictors of response categories have been identified. Third, race/ethnic group plays a role in the response to HRT. Finally, the demonstration of variable responses to HRT and the application of the categorization paradigm presented will be useful in resolving the controversy about the risks and benefits of conventional HRT.

Effects of estrogen on the vascular system

The cardiovascular protective actions of estrogen are partially mediated by a direct effect on the vessel wall. Estrogen is active both on vascular smooth muscle and endothelial cells where functionally competent estrogen receptors have been identified. Estrogen administration promotes vasodilation in humans and in experimental animals, in part by stimulating prostacyclin and nitric oxide synthesis, as well as by decreasing the production of vasoconstrictor agents such as cyclooxygenase-derived products, reactive oxygen species, angiotensin II, and endothelin-1. In vitro, estrogen exerts a direct inhibitory effect on smooth muscle by activating potassium efflux and by inhibiting calcium influx. In addition, estrogen inhibits vascular smooth muscle cell proliferation. In vivo, 17beta-estradiol prevents neointimal thickening after balloon injury and also ameliorates the lesions occurring in atherosclerotic conditions. As is the case for other steroids, the effect of estrogen on the vessel wall has a rapid non-genomic component involving membrane phenomena, such as alteration of membrane ionic permeability and activation of membrane-bound enzymes, as well as the classical genomic effect involving estrogen receptor activation and gene expression.

Role of endothelial dysfunction in insulin resistance

The endothelium regulates vascular tone through the release of vasodilating and vasoconstricting substances. The most important of these vasodilating substances is nitric oxide (NO), which is also vascular protective and inhibits inflammation, oxidation, vascular smooth muscle cell proliferation, and migration. Damage to the endothelium causes endothelial dysfunction with impaired release of NO and loss of its antiatherogenic protection. Traditional risk factors for coronary artery disease, including diabetes, hypercholesterolemia, hypertension, and low levels of high-density lipoprotein cholesterol, are associated with endothelial dysfunction and thus promote the atherogenic process. More recently, insulin resistance in the absence of overt diabetes or the metabolic syndrome has been associated with endothelial dysfunction. This association provides evidence that the atherosclerotic process may actually begin earlier in the spectrum of insulin resistance, ultimately resulting in a progression of the metabolic syndrome to prediabetes and then to type 2 diabetes. Aggressive treatment of dyslipidemia and hypertension, even before the onset of type 2 diabetes, would appear prudent in decreasing the progression of the atherosclerotic process. The thiazolidinediones are peroxisome proliferator-activated receptor-gamma agonists that improve glucose and lipid metabolism. These agents have recently been shown to improve endothelial function in the early stages of insulin resistance. Results from ongoing trials with thiazolidinediones will reveal whether they will also reduce cardiovascular end points.

The hunt for new genes and polymorphisms that can control the response to drugs

There has been a great increase in the knowledge of understanding the genetic basis for individual variation in response to drugs. The study of variation in gene structure (polymorphism) can now predict the likely metabolic behavior in an individual for a number of drugs. This review documents the different strategies that can be used to find new genes and polymorphisms within these genes. Candidate genes can be used in case-control studies or studies where the parents of the person having an adverse effect from the drug are used as controls. New genes are being discovered in the drug development process and the technological development in molecular biology is expected to greatly enhance knowledge of the genes that regulate drug metabolism.