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PubMed2002

Bone growth stimulators. New tools for treating bone loss and mending fractures.

In the new millennium, humans will be traveling to Mars and eventually beyond with skeletons that respond to microgravity by self-destructing. Meanwhile in Earth's aging populations growing numbers of men and many more women are suffering from crippling bone loss. During the first decade after menopause all women suffer an accelerating loss of bone, which in some of them is severe enough to result in "spontaneous" crushing of vertebrae and fracturing of hips by ordinary body movements. This is osteoporosis, which all too often requires prolonged and expensive care, the physical and mental stress of which may even kill the patient. Osteoporosis in postmenopausal women is caused by the loss of estrogen. The slower development of osteoporosis in aging men is also due at least in part to a loss of the estrogen made in ever smaller amounts in bone cells from the declining level of circulating testosterone and is needed for bone maintenance as it is in women. The loss of estrogen increases the generation, longevity, and activity of bone-resorbing osteoclasts. The destructive osteoclast surge can be blocked by estrogens and selective estrogen receptor modulators (SERMs) as well as antiosteoclast agents such as bisphosphonates and calcitonin. But these agents stimulate only a limited amount of bone growth as the unaffected osteoblasts fill in the holes that were dug by the now suppressed osteoclasts. They do not stimulate osteoblasts to make bone--they are antiresorptives not bone anabolic agents. (However, certain estrogen analogs and bisphosphates may stimulate bone growth to some extent by lengthening osteoblast working lives.) To grow new bone and restore bone strength lost in space and on Earth we must know what controls bone growth and destruction. Here we discuss the newest bone controllers and how they might operate. These include leptin from adipocytes and osteoblasts and the statins that are widely used to reduce blood cholesterol and cardiovascular damage. But the main focus of this article is necessarily the currently most promising of the anabolic agents, the potent parathyroid hormone (PTH) and certain of its 31- to 38-aminoacid fragments, which are either in or about to be in clinical trial or in the case of Lilly's Forteo [hPTH-(1-34)] tentatively approved by the Food and Drug Administration for treating osteoporosis and mending fractures.

Animals↗
PubMed2006

Genomic alterations identified by array comparative genomic hybridization as prognostic markers in tamoxifen-treated estrogen receptor-positive breast cancer.

BACKGROUND: A considerable proportion of estrogen receptor (ER)-positive breast cancer recurs despite tamoxifen treatment, which is a serious problem commonly encountered in clinical practice. We tried to find novel prognostic markers in this subtype of breast cancer. METHODS: We performed array comparative genomic hybridization (CGH) with 1,440 human bacterial artificial chromosome (BAC) clones to assess copy number changes in 28 fresh-frozen ER-positive breast cancer tissues. All of the patients included had received at least 1 year of tamoxifen treatment. Nine patients had distant recurrence within 5 years (Recurrence group) of diagnosis and 19 patients were alive without disease at least 5 years after diagnosis (Non-recurrence group). RESULTS: Potential prognostic variables were comparable between the two groups. In an unsupervised clustering analysis, samples from each group were well separated. The most common regions of gain in all samples were 1q32.1, 17q23.3, 8q24.11, 17q12-q21.1, and 8p11.21, and the most common regions of loss were 6q14.1-q16.3, 11q21-q24.3, and 13q13.2-q14.3, as called by CGH-Explorer software. The average frequency of copy number changes was similar between the two groups. The most significant chromosomal alterations found more often in the Recurrence group using two different statistical methods were loss of 11p15.5-p15.4, 1p36.33, 11q13.1, and 11p11.2 (adjusted p values < 0.001). In subgroup analysis according to lymph node status, loss of 11p15 and 1p36 were found more often in Recurrence group with borderline significance within the lymph node positive patients (adjusted p = 0.052). CONCLUSION: Our array CGH analysis with BAC clones could detect various genomic alterations in ER-positive breast cancers, and Recurrence group samples showed a significantly different pattern of DNA copy number changes than did Non-recurrence group samples.

Adult↗
PubMed2000

A comparison of the effects of raloxifene and estrogen on bone in postmenopausal women.

Raloxifene HCl, a selective estrogen receptor modulator, has been shown to increase bone mineral density (BMD) and decrease biochemical markers of bone turnover in postmenopausal women without stimulatory effects on the breast and uterus. However, it is not known whether the changes in BMD and bone turnover are associated with changes at the tissue level, nor how changes with raloxifene compare with estrogen. In this randomized, double blind study, we evaluated the effects of raloxifene (Evista, 60 mg/day) or conjugated equine estrogens (CEE; Premarin, 0.625 mg/day) on bone architecture, bone turnover, and BMD. Iliac crest bone biopsies were obtained at baseline and at the end of the study after double tetracycline labeling and were analyzed for standard histomorphometric indexes. Serum and urinary biochemical markers of bone turnover were measured at baseline and at 4, 10, 18, and 24 weeks of treatment. Total body, lumbar spine, and hip BMD were measured at baseline and at the end of the study by dual energy x-ray absorptiometry. Activation frequency and bone formation rate/bone volume were significantly decreased from baseline in the CEE, but not in the raloxifene, group. Bone mineralization did not change in either group. Most markers of bone resorption and formation decreased in both groups, but to a greater degree in the CEE group (P < .05). Total body and lumbar spine BMD increased from baseline in both groups, with a greater increase in the CEE group (P < 0.05). Hip BMD significantly increased from baseline in the raloxifene group, but the change was not different from that in the CEE group. These results suggest that raloxifene reduces bone turnover and increases bone density, although to a lesser extent than CEE. Thus, raloxifene is an alternative to CEE for the prevention and treatment of osteoporosis in postmenopausal women.

Aged↗
PubMed2001

Modulation of aromatase expression in human breast tissue.

Aromatase plays an important role in breast cancer development through its role in the synthesis of estrogen. Aromatase expression in breast tissue can be regulated by several mechanisms. The major promoter usage for aromatase expression in breast tumors (i.e. cAMP-stimulated promoters I.3 and II) is different from that in normal breast tissue (i.e. glucocorticoid-stimulated promoter I.4). Recent characterization of transcription factors that interact with the two important regulatory elements near promoters I.3 and II, i.e. S1 and CREaro, helps us better understand the mechanism of the switch of promoter usage between normal breast tissue and cancer tissue. It is thought that in normal breast tissue, the function of promoters I.3 and II is suppressed through the binding of EAR-2, COUP-TFI, and EARgamma to S1, and through the binding of Snail/Slug proteins to their binding site that quenchs the CREaro activity. In cancer tissue, the expression levels of EAR-2, COUP-TFI, EARgamma, Snail, and Slug decrease, and aromatase expression is then up regulated through the binding of ERRalpha-1 to S1 and the binding of CREB or related factors to CREaro. Results from this and other laboratories reveal that aromatase activity in aromatase expressing cells can also be modified by treatment with aromatase inhibitors and the antiestrogen ICI 182, 780. While aromatase inhibitors are used to treat breast cancer, the treatment has been found to increase the level of aromatase in the breast tissue of some patients. The enhancement of aromatase activity by aromatase inhibitors is thought to be due to a decrease of aromatase protein degradation by enzyme-inhibitor complex formation, up-regulation of the aromatase gene transcription through a cAMP-mediated mechanism, and an induction of aromatase expression by gonadtropins that are released from the pituitary in response to a reduction of estrogen levels in circulation in premenopausal women. Antiestrogen ICI 182, 780 has been found to suppress aromatase expression, but the mechanism has not yet been determined. In addition, aromatase activity and expression can be affected by environmental chemicals. A detailed structure-function study has revealed that flavones, but not isoflavones, are inhibitors of aromatase. It was found that flavones bind to the active site of aromatase in an orientation in which their rings-A and -C mimic rings-D and -C of the androgen substrate. The modulation of aromatase expression by endocrine disrupting chemicals is exemplified by two organochlorine pesticides (i.e. toxaphene and chlordane) that have been found to be antagonists of ERRalpha-1 orphan receptor. These compounds reduce ERRalpha-1 activity, resulting in a suppression of aromatase expression.

Aromatase↗
PubMed2001

An in vivo/in vitro model to assess endocrine disrupting activity of xenoestrogens in uterine leiomyoma.

Xenoestrogens with endocrine disrupting activity have been associated with the dysregulation of reproductive function and promotion of malignancies in experimental animals and human populations. The high incidence of uterine leiomyomas, a benign estrogen-responsive neoplasm of the uterine myometrium, calls into question the potential influence of xenoestrogens in the pathogenesis of these tumors. An in vivo/in vitro animal model, the Eker rat, that can be used to assess the estrogen-like agonist activity of potential endocrine disruptors in the uterine myometrium is discussed. Using this model, several in vitro assays are developed that demonstrate that compounds from three major classes of xenoestrogens can mimic the effect of estrogen on leiomyoma cells and act as estrogen receptor (ER) agonists: phytoestrogens, organochlorine pesticides and pharmacologic agents. These compounds can stimulate transcription via the ER and upregulate the expression of an estrogen-responsive gene in uterine leiomyoma cells. The use of these in vitro assays has also advanced our ability to predict the agonist activity of potential therapeutic agents in the uterine myometrium. Selective estrogen receptor modulators (SERMs), while able to act as agonists in some tissues such as the bone and uterine endometrium, act as antagonists in vivo in the uterine myometrium and in our in vitro assays. This antagonist activity in the uterine myometrium suggests that SERMs may be useful in the treatment of uterine leiomyoma.

Animals↗
PubMed2003

DT56a stimulates creatine kinase specific activity in vascular tissues of rats.

The novel natural product DT56a (Secure Pharmaceuticals, Yavne, Israel), derived from soybean, has been shown to relieve menopausal vasomotor symptoms and increase in bone mineral density with no effect on sex steroid hormone levels or endometrial thickness. In single injection, like 17beta-estradiol (E2), DT56a stimulated bone, cartilage and uterus in immature or ovariectomized female rats, by measuring the changes in the specific activity of the BB isozyme of creatine kinase (CK). When administered in multiple oral doses, DT56a stimulated skeletal tissues similarly to E2 but not uterine CK. The selective estrogen receptor modulator raloxifene blocked the stimulation of CK by either DT56a or by E2 in all tissues tested. In the present study we measured the effects of DT56a on vascular tissues i.e. aorta (Ao) and the left ventricle of the heart (Lv). Both types of animals responded to either single or multiple administration of DT56a like to E2. In the Ao from both animals and in the Lv from ovariectomized rats, raloxifene completely blocked CK activity induced by DT56a, whereas in the Lv of immature female rats the inhibition was partial. Our experimental findings suggest that DT56a acts as estrogen; it has beneficial effects not only on skeletal tissues, but also on vascular tissues, however contrary to estrogen DT56a, did not affect the uterus. These findings suggest that DT56a--which has similar beneficial effects on vascular tissues like that of E2--is probably mediated via common receptor(s).

Animals↗
PubMed2006

Improving bone health in patients with early breast cancer by adding bisphosphonates to letrozole: the Z-ZO-E-ZO-FAST program.

Women undergoing treatment for breast cancer often have a number of pre-existing risk factors for bone loss, including existing or induced postmenopausal status. Long-term anticancer treatments may further augment this risk, inducing further bone-loss, increasing the incidence of bone fractures, associated morbidity and mortality, and healthcare costs. Long-term treatment with third-generation antiaromatase agents (AAAs) is used more and more instead of or after the selective estrogen-receptor modulator tamoxifen for the adjuvant treatment of postmenopausal women with breast cancer. These AAAs include anastrozole, letrozole, and exemestane, and all are superior to tamoxifen in both efficacy and safety. In particular, they reduce the incidence of serious adverse events such as thromboembolism and endometrial cancer that are associated with tamoxifen treatment. On the other hand, the AAAs lead to profound estrogen depletion and appear to have a pronounced effect on bone mineral density (BMD), and a significantly higher incidence of osteoporosis/osteopenia and bone fracture has been reported in some trials. Bisphosphonate therapies, including zoledronic acid (ZA), have emerged as a promising means of reducing bone loss associated with antiaromatase therapy. Several large, randomized, multicenter trials are underway to determine whether upfront or delayed ZA therapy can decrease BMD losses in patients undergoing treatment with the antiaromatase agent letrozole (Z-FAST; ZO-FAST, and E-ZO-FAST), and early results from the Zometa-Femara adjuvant synergy trial (Z-FAST) trial indicate a significant benefit of upfront ZA therapy compared with delayed ZA therapy. Forthcoming results from all these trials should determine whether ZA could be used to improve bone heath in women undergoing adjuvant therapy with AAAs for breast cancer.

Aromatase Inhibitors↗
PubMed1998

LY353381.HCl: a novel raloxifene analog with improved SERM potency and efficacy in vivo.

Body weight, uteri, serum cholesterol and bones were shown previously in vivo to be sensitive to circulating levels of estrogen, as well as to synthetic, nonsteroidal ligands termed selective estrogen receptor modulators (SERM). In this study, we examined the in vivo effects of a new potent SERM on these tissues in 6-month-old, ovariectomized rats that were orally dosed with 0.0001-10 mg/kg/day LY353381.HCl for 5 weeks. LY353381.HCl prevented the ovariectomy-induced increase in body weight and serum cholesterol levels of treated rats and lowered them to below sham levels in a dose dependent manner, with maximum efficacy similar to estrogen or raloxifene. However, LY353381.HCl was consistently more potent than raloxifene, with a half maximal efficacious dose of 0.001 mg/kg for the reduction of body weight and cholesterol. In the uterus, LY353381.HCl had marginal effects on uterine weight compared to ovariectomized controls (OVX) like raloxifene, but unlike estrogen. Histological examination of uterine epithelial cell height showed little to no stimulatory effect of LY353381.HCl on the endometrium. Quantitative computed tomographic analyses (pQCT) of tibiae showed that LY353381.HCl prevented loss of bone due to ovariectomy with an ED50 of about 0.01 mg/kg with maximal efficacy observed at 0.1-1 mg/kg/day. Maximally attainable bone mineral density and content with LY353381.HCl were not significantly different from Sham or ovariectomized rats treated with estrogen or raloxifene. Interestingly, assessment of bone quality by biomechanical analyses showed that LY353381.HCl preserved the strength of the femora neck and midshaft, while improving the Young's modulus of cortical bone to beyond estrogen, raloxifene or sham levels. In uteri of immature rats treated with estrogen, LY353381.HCl antagonized the estrogen-induced elevation in uterine weight down to vehicle-dosed control levels with ED50 of 0.03 mg/kg/day. Therefore, LY353381.HCl was 30-100 times more potent than raloxifene in preventing ovariectomy effects on body weight, serum cholesterol and bone, while maintaining estrogen antagonist effects on the uterus. These animal data suggest that LY353381.HCl may have advantages over estrogen or raloxifene in the prevention of bone loss and treatment of other tissues in postmenopausal women.

Animals↗
PubMed2004

Uterine effects of the phytoestrogen 6-(1,1-dimethylallyl)naringenin in rats.

Phytoestrogens are discussed as candidate substances to treat symptoms related to estrogen deficiency. In in vitro experiments, the naturally occurring flavonoid 6-(1,1-dimethylallyl)naringenin (6-DMAN) emerged as one of the most potent phytoestrogenic substances. 6-DMAN is not as well characterized as other flavonoids (8-prenylnaringenin) or isoflavones (genistein). We tested 6-DMAN for the first time in vivo, in a dose-dependent three-day uterotropic assay in ovariectomized Wistar rats, using 6-DMAN at three different concentrations (1.5 mg/kg; 7.5 mg/kg and 15 mg/kg BW/d). Estradiol (E2; 10 microg/kg BW/d) and the carrier castor oil were used as positive and negative controls. 6-DMAN did not have any effect on uterine wet weight, while the positive control E2 did. In contrast, 6-DMAN stimulated uterine mRNA expression of estrogen responsive genes in ovariectomized rats. Estrogen receptor alpha and beta mRNA were expressed in the uterus. They mediate the expression of genes with an estrogen responsive element in the promoter, e. g., complement C3 and the progesterone receptor. Therefore, we analyzed the expression of the above-mentioned genes in three different concentrations. 6-DMAN up-regulated progesterone receptor and particularly complement C3 mRNA expression however, less pronounced than E2. In conclusion, we demonstrated for the first time estrogenic activities of 6-DMAN in vivo. Surprisingly, although 6-DMAN regulated estrogen responsive gene expression, there was no uterine wet weight gain. These findings make 6-DMAN a very interesting candidate substance for further characterization, as it potentially represents a naturally occurring selective estrogen receptor modulator.

Animals↗
PubMed2004

Raloxifene improves coronary perfusion, cardiac contractility, and myocardial metabolism in the ischemic heart: role of phosphatidylinositol 3-kinase/Akt pathway.

The purpose of this study is to examine whether raloxifene, one of the selective estrogen receptor modulators, could improve myocardial ischemia and to assess the mechanisms involved. In open-chest beagle dogs anesthetized by intravenous infusion of sodium pentobarbital, the left anterior descending coronary artery (LAD) was perfused from the left carotid artery through an extracorporeal bypass tube. Raloxifene was infused into the LAD through the bypass tube under either ischemic or non-ischemic conditions. In the non-ischemic heart, raloxifene had no effect on coronary blood flow, fractional shortening, and myocardial metabolism. However, raloxifene caused an acute increase in both coronary blood flow and fractional shortening, and also improved myocardial anaerobic metabolism in the ischemic heart. These effects were partially attenuated by pretreatment with either L-NAME or wortmannin and were completely abolished by ICI182780 (an estrogen receptor antagonist) or L-NAME plus charybdotoxin (a blocker of Ca-activated K channels). Raloxifene also increased both Akt activity and the NO level, with these changes being completely abrogated by pretreatment with wortmannin. These results demonstrated that raloxifene improves coronary perfusion, cardiac contractility, and myocardial metabolism by release of NO and opening of Ca-activated K channels in the ischemic heart, and that NO production is mediated by the phosphatidylinositol 3-kinase/Akt pathway.

Animals↗
PubMed1999

Prevention of osteoporosis and fractures.

Osteoporosis and low bone density are associated with a risk of fracture as a result of even minimally traumatic events. The estimated lifetime risk of osteoporotic fracture is as high as 50 percent, especially in white and Asian women. The use of caffeine, tobacco and steroids is associated with a decrease in bone density. Cognitive impairment, vision problems and postural instability increase the risk of falling and sustaining a fracture. Medications such as long-acting sedative hypnotics, anticonvulsants and tricyclic antidepressants also increase this risk. Combinations of clinical and radiographic findings can predict fracture risk more effectively than bone densitometry, but often only after the first fracture has occurred. The addition of dietary calcium and/or vitamin D is clearly both cost-effective and significant in reducing the likelihood of fractures. Bisphosphonates reduce fracture risk but at a cost that may be prohibitive for some patients. Estrogen and estrogen-receptor modulators have not been well studied in randomized trials evaluating the reduction of fractures, but they are known to increase bone density. Pharmacologic therapy and the reduction of sensory and environmental hazards can prevent osteoporotic fractures in some patients.

Alendronate↗
PubMed2000

The treatment of osteoporosis. Antiresorptive therapy.

Antiresorptive pharmacologic interventions for the prevention and treatment of osteoporosis are discussed. These interventions include estrogen; calcitonin; biphosphonates; and selective estrogen receptor modulators and their use in postmenopausal osteoporosis, steroid-induced osteoporosis, and osteoporosis in men. The effects of antiresorptive therapy on bone mineral density, biomarkers of bone turnover, and fracture risk are discussed.

Bone Density↗
PubMed2002

Is there a role for estrogens in the maintenance of men's health?

This paper gives an overview of our own studies and the literature on the biosynthesis and metabolism of estrogens in elderly men, the estrogen action in the male, and the clinical usefulness of estrogen therapy, including the phytoestrogens. Finally, the paper includes a short review of our knowledge of xenoestrogens and men's sexual health. A strong estrogen-deficient status is seen in male patients with mutations of the estrogen receptors or in cases of deviations of the aromatase gene. On the other hand, there are no clear age-dependent changes in estrogen secretion. But, in men with disorders of glucose metabolism and also of increased body mass index, the serum estrogen concentrations are significantly elevated. There are also strong positive correlations between serum estrogen levels and bone density, including prevalence of fractures and mood in men. New fields of interest are natural fatty esters of endogenous estrogens, e.g. lipoprotein-associated estrogens, and the role and clinical significance of tissue-specific, local estrogen biosynthesis (e.g. different promoters of the aromatase gene). Exogenous estrogen treatment is focused today on patients with normal testosterone and low levels of circulating estrogens documented on several occasions and with clinical symptoms of hormone deficiency; male-to-female transsexuals; and selected patients with prostate cancer. Some clinical studies show the benefits of estrogen treatment on some cardiovascular parameters and for treating selected signs of mental stress. An indirect estrogen replacement can occur if dehydroepiandrosterone is given orally to men. The clinical usefulness of dissociated estrogens, including non-feminizing estrogens and selective estrogen receptor modulators, is still an open question. The beneficial action of phytoestrogens in lowering the clinical symptoms of benign prostatic hyperplasia is well documented. Finally, the question about the definitive influence of so-called endocrine disruptors (xenoestrogens) on sexual functions in men is also discussed.

Aged↗
PubMed2004

Soy isoflavone phyto-pharmaceuticals in interleukin-6 affections. Multi-purpose nutraceuticals at the crossroad of hormone replacement, anti-cancer and anti-inflammatory therapy.

Interleukin-6 is a pleiotropic cytokine which plays a crucial role in immune physiology and is tightly controlled by hormonal feedback mechanisms. After menopause or andropause, loss of the normally inhibiting sex steroids (estrogen, testosterone) results in elevated IL6 levels that are further progressively increasing with age. Interestingly, excessive IL6 production promotes tumorigenesis (breast, prostate, lung, colon, ovarian), and accounts for several disease-associated pathologies and phenotypical changes of advanced age, such as osteoporosis, rheumatoid arthritis, multiple myeloma, neurodegenerative diseases and frailty. In this respect, pharmacological modulation of IL6 gene expression levels may have therapeutical benefit in preventing cancer progression, ageing discomforts and restoring immune homeostasis. Although "plant extracts" are used in folk medicine within living memory, it is only since the 20th century that numerous scientific investigations have been performed to discover potential health-protective food compounds or "nutraceuticals" which might prevent cancer and ageing diseases. About 2000 years ago, Hippocrates already highlighted "Let food be your medicine and medicine be your food". Various nutrients in the diet play a crucial role in maintaining an "optimal" immune response, such that deficient or excessive intakes can have negative consequences on the organism's immune status and susceptibility to a variety of pathologies. Over the last few decades, various immune-modulating nutrients have been identified, which interfere with IL6 gene expression. Currently, a broad range of phyto-pharmaceuticals with a claimed hormonal activity, called "phyto-estrogens", is recommended for prevention of various diseases related to a disturbed hormonal balance (i.e. menopausal ailments and/or prostate/breast cancer). In this respect, there is a renewed interest in soy isoflavones (genistein, daidzein, biochanin) as potential superior alternatives to the synthetic selective estrogen receptor modulators (SERMs), which are currently applied in hormone replacement therapy (HRT). As phyto-chemicals integrate hormonal ligand activities and interference with signaling cascades, therapeutic use may not be restricted to hormonal ailments only, but may have applications in cancer chemoprevention and/or NF-kappaB-related inflammatory disorders as well.

Animals↗
PubMedDate not supplied

mRNA expression of the type I growth factor receptors in the human breast cancer cells MCF-7: regulation by estradiol and tamoxifen.

BACKGROUND: We recently confirmed, in a series of 365 human breast cancers, that EGFR and c-erbB-2 were associated with estradiol receptors (ER) and/or progesterone receptors (PgR)-negative tumors. Conversely, we demonstrated that c-erbB-3 and c-erbB-4 were positively related to ER and PgR. In the present paper, we simultaneously quantified, for the first time, the mRNA expression of these four receptors in response to estradiol and 4-hydroxy-tamoxifen in the prototypical ER-positive human breast cancer cell line MCF-7. MATERIALS AND METHODS: The mRNA expression of the type I growth factor receptors was quantified with a one-step real-time RT-PCR assay. RESULTS: Estradiol down-regulates the mRNA expression of the four receptors. The EGFR decrease is maximal (30% under the control) for 10(-11) M estradiol. For the three other receptors, the decrease (50% under the control) in mRNA expression is maximal with 10(-9) M. These effects are completely abolished by 4-OH tamoxifen at 10(-6) M. CONCLUSION: In MCF-7 cells, we demonstrate that c-erbB-4 is down-regulated by estradiol and up-regulated by 4-OH tamoxifen, and confirm that the three other receptors followed the same pattern of expression.

Adenocarcinoma↗
PubMed2003

New markers for cardiovascular disease risk in women: impact of endogenous estrogen status and exogenous postmenopausal hormone therapy.

The role of estrogen in altering cardiovascular disease risk in women is contentious. Menopause is associated with increased risk for ischemic heart disease and cerebrovascular disease, which collectively are the main causes of morbidity and mortality in women of developed nations. Observational studies suggest a protective role of estrogen, whereas recent randomized controlled trials report a negative role for oral estrogen in primary and secondary prevention of cardiovascular events. Inflammatory mechanisms underlie the process of arterial thrombus formation following atheromatous plaque rupture, and as such modulation of the inflammatory process may be a potential means of reducing cardiovascular risk. Sex steroids may influence inflammatory processes and hence modify cardiovascular risk. The objective of the study was to review the current understanding of the relationships between C-reactive protein (CRP), homocysteine, IL-6, and lipoprotein (a) [Lp(a)] and endogenous estrogen status, exogenous estrogen treatment, and cardiovascular disease risk. The design was a review of all relevant published, peer- reviewed studies. Raised levels of CRP, homocysteine, Lp(a), IL-6, and CRP are each independently associated with increased risk for cardiovascular events in women. Changes in these parameters across the menopausal transition cannot clearly be attributed to hormonal changes. With respect to the effects of exogenous postmenopausal therapy, oral estrogen use is consistently associated with elevations in CRP, no change or a reduction in homocysteine, varied effects on IL-6, and a consistent reduction in Lp(a). Transdermal estradiol overall has no significant effect on any of these parameters. Progestin use appears to attenuate the effect of oral estrogen on CRP and is associated with a reduction in Lp(a). Like oral estrogen, tibolone use is associated with a rise in CRP, with no change in homocysteine and consistent lowering of Lp(a). Selective estrogen receptor modulators modestly lower homocysteine and Lp(a), have varied effects on CRP, and have no reported effects on IL-6. Despite these varied effects of postmenopausal hormone treatment on inflammatory markers, homocysteine, and Lp(a), there is no evidence that change in these markers results in modification of cardiovascular risk. Further studies are required to specifically investigate whether treatments that increase or decrease these markers in fact modulate the risk of cardiovascular events in women.

Biomarkers↗
PubMed2003

Tamoxifen is a potent inhibitor of cholesterol esterification and prevents the formation of foam cells.

Tamoxifen is a selective estrogen receptor modulator (SERM) used for the treatment and prevention of breast cancer. Tamoxifen has been reported to protect against the progression of coronary artery diseases in human and different atherosclerosis animal models by blocking the appearance of the atheromatous plaque. However, the molecular mechanism of this effect remains unknown. Acyl-CoA:cholesterol acyl transferase (ACAT) catalyzes the biosynthesis of cholesteryl esters, which are the major lipids found in the atheromatous plaque. In this paper we have tested whether ACAT might be inhibited by tamoxifen. We show, using molecular modeling, that tamoxifen displays three-dimensional structural homology with Sah 58-035 (3-[decyldimethylsilyl]-N-[2-(4-methylphenyl)-1-phenylethyl]-propanamide), a prototypical inhibitor of ACAT. We report that tamoxifen inhibits ACAT in a concentration-dependent manner on rat liver microsomal extract. We show that the presence on estrogen receptor ligands of a backbone isosteric to the diphenyl ethane backbone of Sah 58-035 constitutes a pharmacophore for ACAT inhibition. More importantly, tamoxifen was able to inhibit ACAT on intact macrophages stimulated with acetylated low-density lipoproteins and blocked the formation of foam cells, a step that precedes the formation of the atheromatous plaque. This work constitutes the first evidence that tamoxifen is an inhibitor of ACAT and foam cell formation at therapeutic doses and that this may account for its atheroprotective action.

Animals↗
PubMed2003

Potentiation of human estrogen receptor alpha-mediated gene expression by steroid receptor coactivator-1 (SRC-1) in Saccharomyces cerevisiae.

The yeast Saccharomyces cerevisiae was used to reconstruct a human estrogen receptor alpha (ERalpha)-mediated transcription activation system. The level of reporter gene activation was dependent on both the position of the estrogen response element (ERE) relative to the translation start site and the number of EREs in the hybrid promoter. A G400V amino acid alteration in the ERalpha polypeptide decreased sensitivity to 17beta-estradiol (E(2)), demonstrating the hormone responsiveness of ERalpha to be qualitatively and quantitatively similar in yeast and mammalian cells. Coexpression of SRC-1a, a potent stimulator of ERalpha function in mammalian cells, potentiated ERalpha-mediated gene expression over fivefold in a E(2)-dependent manner. Deletion of 56 amino acids at the C-terminal end of SRC-1a resulted in a protein with enhanced ability to potentiate ERalpha-mediated gene expression, which mimics the activity of the same truncation in human SRC-1a as well as the SRC-1e isoform that has the 56 C-terminal residues replaced with a different 14 amino acid peptide. The selective estrogen receptor modulator tamoxifen acted as a weak agonist of ERalpha-mediated gene expression and this weak activity was potentiated by SRC-1. Tamoxifen had no effect on E(2)-induced gene activation in either the presence or absence of SRC-1. In contrast to previously reported yeast-based ERalpha-transactivation systems, the system reported here in which SRC-1 functions as a bona fide coactivator should permit a more thorough dissection of the factors involved in ERalpha-mediated transcriptional activation.

Estradiol↗