Short-term Estrogen Treatment Research Articles

History of Previous Midlife Estradiol Treatment Permanently Alters Interactions of Brain Insulin-like Growth Factor-1 Signaling and Hippocampal Estrogen Synthesis to Enhance Cognitive Aging in a Rat Model of Menopause.

Across species, including humans, elevated levels of brain estrogen receptor (ER) α are associated with enhanced cognitive aging, even in the absence of circulating estrogens. In rodents, short-term estrogen treatment, such as that commonly used in the menopausal transition, results in long-term increases in ERα levels in the hippocampus, leading to enhanced memory long after termination of estrogen treatment. However, mechanisms by which increased levels of brain ERα enhances cognitive aging remain unclear. Here we demonstrate in aging female rats that insulin-like growth factor-1 (IGF-1), which can activate ER via ligand-independent mechanisms, requires concomitant synthesis of brain-derived neuroestrogens to phosphorylate ERα via MAPK signaling, ultimately resulting in enhanced memory. In a rat model of menopause involving long-term ovarian hormone deprivation, hippocampal neuroestrogen activity decreases, altering IGF-1 activity and resulting in impaired memory. However, this process is reversed by short-term estradiol treatment. Forty days of estradiol exposure following ovariectomy results in maintenance of neuroestrogen levels that persist beyond the period of hormone treatment, allowing for continued interactions between IGF-1 and neuroestrogen signaling, elevated levels of hippocampal ERα, and ultimately enhanced memory. Collectively, results demonstrate that short-term estradiol use following loss of ovarian function has long-lasting effects on hippocampal function and memory by dynamically regulating cellular mechanisms that promote activity of ERα in the absence of circulating estrogens. Translational impacts of these findings suggest lasting cognitive benefits of short-term estrogen use near menopause and highlight the importance of hippocampal ERα, independent from the role of circulating estrogens, in regulating memory in aging females.SIGNIFICANCE STATEMENT Declines in ovarian hormones following menopause coincide with increased risk of cognitive decline. Because of potential health risks, current recommendations are that menopausal estrogen therapy be limited to a few years. Long-term consequences for the brain and memory of this short-term midlife estrogen therapy are unclear. Here, in a rodent model of menopause, we determined mechanisms by which short-term midlife estrogen exposure can enhance hippocampal function and memory with cognitive benefits and molecular changes enduring long after termination of estrogen exposure. Our model indicates long-lasting benefits of maintaining hippocampal estrogen receptor function in the absence of ongoing estrogen exposure and suggests potential strategies for combating age-related cognitive decline.

P763Ovariectomy increases epinephrine-induced mortality in a rat takotsubo cardiomyopathy model: the effects of estrogen supplementation

Background: Takotsubo cardiomyopathy (TCM) is an acute heart failure syndrome that can occur after a period of intense emotional stress, characterised by a hypokinetic apex and a hyperkinetic base. We have previously shown that a single IV injection of epinephrine can recapitulate the syndrome in male rats. As TCM usually occurs in post-menopausal females we gave the same epinephrine dose to normal female and ovariectomised (OVX) rats with or without short or long-term (2 weeks) estrogen replacement. Methods: OVX rats were anaesthetised with 2% isoflurane in 100% O2 and a parasternal long-axis echocardiograph was acquired. For short-term estrogen treatment, 600ng 17β-estradiol was infused IV 5 minutes before epinephrine injection (4.3x10-8mol.100g-1). For 2-week replacement, osmotic minipumps were implanted containing 17β-estradiol (238μg.day-1) in 50:50 glycerol:DMSO. Fractional shortening was measured before and at 5 minute intervals after epinephrine using M-mode images from the apex and base of the left ventricle. QTc was calculated using the LabChart 7 ECG Analysis Module from a Lead II ECG. Results: Compared to males, female non-OVX rats had reduced mortality and did not exhibit TCM-like contraction patterns when given the same epinephrine bolus (6.25% vs. 46% mortality; P<0.01). OVX rats showed increased mortality compared to non-OVX females (75% vs. 6.25%; P<0.001, n=12-16); death was typically due to VF. Two-week E2 supplementation (n=10) reduced mortality compared to OVX (no minipump) (10% vs. 75% mortality; P=0.007). Vehicle minipump (n=10) had a similar but non-significant trend to reduce mortality (40% vs. 75%; P=0.38) with the result that E2 vs. vehicle was not significantly different (P=0.30, n=10). Acute estrogen supplementation did not significantly reduce mortality (75% vs. 50%; P=0.4, n=12 per group). Vehicle and E2 minipump groups had significantly (P<0.0001 and P<0.01, respectively) shorter QTc intervals compared to OVX (no minipump) (OVX=200±2.36ms, n=12; E2=158±8.86ms, n=11; Vehicle=173±4.61 ms, n=11). The difference in QTc interval between E2 and vehicle groups was not significant. Conclusion: Female rats are protected from epinephrine-induced sudden death. Loss of ovarian function predisposes rats to epinephrine-mediated death; acute estrogen infusion did not reverse this but 2 week E2 treatment did. There appeared to be an interacting effect of the DMSO vehicle on this reduction, as well as the decrease in QTc interval: we suggest this may be a result of its effect to reduce ROS.

Parity and Short-Term Estradiol Treatment Utilizes Similar Cellular Mechanisms to Confer Protection Against Breast Cancer

Background: Protective effect of early pregnancy and short-term estrogen treatment (STET), against breast cancer is well established. The underlying mechanisms are not well understood. In this study, we compared the mammary gland cellular microenvironment influenced/induced by parity and STET alongside age-matched controls. Methods: Parous, STET, and control rats were injected with N-methyl-N-nitrosourea at 15 weeks and monitored for the development of mammary cancer. A subset of 4 rats were killed five weeks post carcinogen treatment and mammary gland samples were isolated and subjected to molecular analysis. Results: Our results demonstrated a reduction in cell survival, extracellular matrix associated proliferation, hormonal and growth factor receptor pathways in the experimental groups compared to control rats. Moreover, concomitant reductions in the EMT markers along with cell migration regulators were also observed in parous and STET groups. Hormonal receptor such as GHR, PR, ERα and growth factor receptors IGFR, EGFR and erbB2 were down regulated in the treatment groups. Further analysis revealed that parity and STET drastically reduced the expression, activation of JAK2 and nuclear localization of STATs. Conclusion: Parity and STET by targeting major cell signaling pathways involved in cell survival, cell migration and cell death reduces the mammary tumor promoting environment.

Effects of Estrogen on Bone mRNA Levels of Sclerostin and Other Genes Relevant to Bone Metabolism in Postmenopausal Women

Studies in postmenopausal women have shown that estrogen reduces circulating sclerostin levels, but effects of estrogen on skeletal sclerostin mRNA levels are unknown. The objective of the study was to evaluate the effects of short-term estrogen treatment on bone mRNA levels of sclerostin and other genes relevant to bone metabolism. Needle bone biopsies were obtained from 20 postmenopausal women treated with transdermal estrogen for 3 weeks and 20 untreated controls. Quantitative PCR analyses were used to examine the expression of sclerostin and other genes related to bone metabolism, including 71 additional genes linked to bone density/fracture from genome-wide association studies. Estrogen treatment was associated with lower bone sclerostin mRNA levels (by 48%, P<.05) and with lower (by 54%, P<.01) mRNA levels of the sclerostin-related protein, sclerostin domain-containing protein 1 (SOSTDC1), which is also a Wnt/bone morphogenetic protein inhibitor. Consistent with studies in mice showing that ovariectomy increased nuclear factor-κB (NF-κB) activation, we found that estrogen treatment was associated with a significant reduction in inflammatory genes as a group (P=.028), with bone mRNA levels of NFKB2 and RELB (both encoding proteins in the NF-κB transcription factor complex) being significantly reduced individual genes. Eight of the 71 genome-wide association study-related genes examined were modulated by estrogen (P<.05, false discovery rate<0.10). In humans, estrogen-induced decreases in two key inhibitors of Wnt/bone morphogenetic protein signaling, sclerostin and SOSTDC1, along with reductions in NF-κB signaling, may be responsible for at least part of the protective effects of estrogen on bone.

Abstract PD01-07: High throughput sequencing following cross-linked immune-precipitation (HITS-CLIP) of Argonaute protein reveals novel miRNA regulatory pathways of Estrogen Receptor in breast cancer.

Abstract Micro RNAs (miRNAs) are a class of small non-coding RNAs with well-known regulatory roles in normal physiological processes and cancer. Conventionally their study has been based on defining single miRNA-mRNA target interactions using a combination of miRNA expression arrays and bioinformatic predictions of binding to the 3′ untranslated regions of genes, followed by miRNA over-expression in the relevant cell type. These approaches present circumstantial evidence for binding of a particular miRNA to its target but do not allow the study of global interactions nor provide direct evidence of binding. In order to study the genome wide impact of miRNA regulation in breast cancer we chose to use a recently described biochemical technique called Cross-Linked Immune-Precipitation of Argonaute (AGO) protein followed by high throughput sequencing (HITS-CLIP). Cross-linking of RNA to adjacent protein moieties by ultraviolet (UV) light allows for stringent isolation of the miRNA-mRNA-AGO complexes by immune precipitation (IP); miRNA-mRNA interaction within the RNA-induced silencing complex (RISC) is known to occur within the folds of AGO. The isolated miRNA-mRNA-AGO complexes are then analyzed with next generation sequencing (NGS) to determine the miRNA-mRNA interactome. We performed HITS-CLIP on three well characterized breast cancer cell lines that represent ER+, Her2+ and triple negative (TN) disease (MCF7, BT474 and MDA231). To determine the role of miRNAs in coordinating the response to the estrogen receptor axis, MCF7 and BT474 cells were analyzed with or without short term (24 hour) estrogen treatment. Analysis of sequencing data revealed several novel miRNA-mRNA interactions that target the ER pathway. For example, miR-9 directly regulates ER expression and miR-193a is involved in regulating expression of the ER co-activator NCOA3. We confirmed the biological relevance of these results using functional in vitro studies where manipulation of both miR-193a and miR-9 altered the responsiveness of breast cancer cells to tamoxifen. These results were further validated by quantitation of both transcript (RT-PCR) and protein (Western Blot) levels after transfection of miRNA precursors. Functional binding between these miRNAs and putative binding targets in the 3′ Untranslated Regions (3′ UTRs) were also validated by luciferase-based reporter assays. Finally, we performed global analysis of miRNAs and their targets (as predicted by the HITS-CLIP datasets across all cell lines); this predicted regulation of core cellular processes such as cell proliferation, DNA repair and metabolism as being targeted by highly abundant miRNAs such as miR-27a and miR-21. In addition, our datasets confirmed previous reports of miRNA regulation of ER pathway such as miR-221 regulation of ER itself and miR-34a regulation of Myc. In summary, genome-wide biochemical approaches like HITS-CLIP allow for defining novel and clinically relevant miRNA-based regulatory pathways of endocrine responsiveness and resistance in breast cancer. In addition, breast cancer subtype specific biological pathways targeted by individual miRNAs can be predicted by this approach. Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr PD01-07.

Abstract 285: Cardiac Inflammation and Fibrosis Induced by Heart Failure Are Reversed by Short-Duration Estrogen Therapy

Heart failure is generally characterized by increased fibrosis and inflammation, which leads to functional and contractile defects. We have previously shown that short-term estrogen (E2) treatment can rescue pressure overload-induced decompensated heart failure (HF) in mice. Here, we investigate the anti-inflammatory and anti-fibrotic effects of E2 on reversing the adverse remodeling of the left ventricle which occurs during the progression to heart failure. Trans-aortic constriction procedure was used to induce HF. Once the ejection fraction reached ∼30%, one group of mice was sacrificed and the other group was treated with E2 (30 αg/kg/day) for 10 days. In vitro, co-cultured neonatal rat ventricular myocytes and fibroblasts were treated with Angiotensin II (AngII) to simulate cardiac stress, both in the presence or absence of E2. In vivo RT-PCR showed that the transcript levels of the pro-fibrotic markers Collagen I, TGFβ, Fibrosin 1 (FBRS) and Lysil Oxidase (LOX) were significantly upregulated in HF (from 1.00±0.16 to 1.83±0.11 for Collagen 1, 1±0.86 to 4.33±0.59 for TGFβ, 1±0.52 to 3.61±0.22 for FBRS and 1.00±0.33 to 2.88±0.32 for LOX) and were reduced with E2 treatment to levels similar to CTRL. E2 also restored in vitro AngII-induced upregulation of LOX, TGFβ and Collagen 1 (LOX:1±0.23 in CTRL, 6.87±0.26 in AngII and 2.80±1.5 in AngII+E2; TGFβ: 1±0.08 in CTRL, 3.30±0.25 in AngII and 1.59±0.21 in AngII+E2; Collagen 1: 1±0.05 in CTRL.2±0.01 in AngII and 0.65±0.02 (p&lt;0.05, values normalized to CTRL)). Furthermore, the pro-inflammatory interleukins IL-1β and IL-6 were upregulated from 1±0.19 to 1.90±0.09 and 1±0.30 to 5.29±0.77 in the in vivo model of HF, respectively, and reversed to CTRL levels with E2 therapy. In vitro, IL-1β was also significantly increased ∼ 4 fold from 1±0.63 in CTRL to 3.86±0.14 with AngII treatment and restored to 1.29±0.77 with Ang+E2 treatment. Lastly, the anti-inflammatory interleukin IL-10 was downregulated from 1.00±0.17 to 0.49±0.03 in HF and reversed to 0.67±0.09 in vivo with E2 therapy (all values normalized to CTRL). This data strongly suggests that one of the mechanisms for the beneficial action of estrogen on left ventricular heart failure is through reversal of inflammation and fibrosis.

Body weight and leukocyte infiltration after an acute exercise-related muscle injury in ovariectomized mice treated with estrogen and progesterone

In both rats and mice, an acute skeletal muscle injury leads to leukocyte infiltration in which the leukocytes remove dead fibers and cellular debris, induce a secondary injury, and/or promote myofiber regeneration. Short-term exogenous estrogen treatment attenuates this leukocyte infiltration and prevents body weight gain in rat exercise-induced skeletal muscle injury models. But these estrogen effects may not occur in mice because body weight gain does not consistently occur in ovariectomized mice treated with estrogen. Additionally, progesterone may also attenuate this leukocyte infiltration without affecting body weight [13]. The aim of the current study was to compare body weight and leukocyte infiltration in exercise-injured skeletal muscle of ovariectomized mice treated with exogenous estrogen and progesterone for the short period of 17days with that of ovariectomized-placebo-treated mice and gonadal-intact male and female mice. There was no significant difference in body weight between the ovariectomized-estrogen-treated and the ovariectomized-placebo-treated mice. The amount of intramuscular leukocyte infiltration of ovariectomized mice treated with estrogen or progesterone was not significantly different from that of ovariectomized-placebo-treated mice. However, in the injured muscle, the mean area of the leukocyte antigen, 7/4, of the ovariectomized-estrogen-treated group was 2–3-fold greater than that of the ovariectomized-placebo-treated, ovariectomized-estrogen-progesterone-treated, and intact male groups (p<.05), suggesting that the 7/4-positive leukocytes of the ovariectomized-estrogen-treated group were larger or had more antigen. In conclusion, ovariectomized mice demonstrate a different body weight and leukocyte response to short-term estrogen treatment than that of ovariectomized rats, and short-term estrogen treatment modulates leukocyte phenotype. These data broaden our understanding of estrogen’s effects on body weight and leukocyte infiltration, and may aid in increasing our understanding of how males and females differ in response to acute muscle injury.

Abstract P130: Estrogen Receptor β Mediates the Rescue of Cardiac Function in Advanced Heart Failure by Promoting Neoangiogenesis and Reducing Fibrosis

Estrogen can act via the estrogen receptor alpha (ERa) or estrogen receptor beta (ERb) to exert its biological effects, and both of these receptors are present in the heart. We have previously shown that short-term estrogen (E2) treatment can rescue pressure overload-induced decompensated heart failure (HF) in mice, and that this rescue is achieved mainly through the ERb. Furthermore, E2 has been shown to regulate angiogenesis in different tissues. Because HF has been associated with decreased angiogenesis and increased fibrosis, here we investigated whether the E2-induced rescue of HF by the selective ERb agonist DPN can regulate cardiac fibrosis and neoangiogenesis. We used transaortic constriction to induce HF, and once the ejection fraction (EF) reached ∼30%, one group of animals was sacrificed (HF group), and the other three groups received either 17b-estradiol via a subcutaneous pellet implant (0.012mg/pellet, n=16), selective ERa agonist (PPT, 0.625mg/kg/day), or selective ERb agonist (DPN, 0.625mg/kg/day) for 10 days. Serial echocardiography was performed to monitor cardiac structure and function. As expected, E2 rescued HF by restoring EF from 33.17±1.12% to 53.05±1.29%. Mice treated with DPN had a significant EF improvement from 33.17±1.12% to 45.25±2.1% (n=7), while the EF of PPT-treated mice did not improve (31.09±2.3%, n=6). Similarly, only the fractional shortening of DPN-treated mice improved from 15.7±0.58% in HF to 21.95±1.65% with DPN treatment vs. 14.72±1.24% with PPT. Next, we examined whether promotion of cardiac neoangiogenesis and suppression of fibrosis by the selective ERb agonist are possible mechanisms in the rescue action of HF by DPN. DPN treatment was able to reverse the interstitial and perivascular fibrosis observed in HF, while PPT had no effect. The selective ERb agonist also stimulated neoangiogenesis, as the capillary density was increased from 0.46±0.04 microvessels/cardiomyocyte in HF to 0.67±0.07 with DPN treatment, whereas PPT treatment had no effect (0.43±0.03). Our data strongly suggests that upregulation of cardiac neoangiogenesis and reversal of fibrosis are pivotal mechanisms in rescuing advanced HF by the estrogen receptor beta agonist DPN.

Effects of short-term estrogen treatment on the progression of N-methyl-N-nitrosourea-induced premalignant mammary lesions in female Lewis rats

We studied the effects of short-term estrogen treatment (STET) on the progression of mammary lesions from ductal hyperplasia (DH) through ductal carcinoma in situ (DCIS) to invasive ductal carcinoma (IDC) in the N-methyl-N-nitrosourea (MNU)-induced rat mammary carcinogenesis model. Three-week-old female Lewis rats (n = 40) received an intraperitoneal injection of MNU (50 mg/kg). Three weeks later, a 3-week-release, 0.25-mg, 17β-estradiol pellet was subcutaneously implanted for 2 weeks in 20 rats (STET); the remaining 20 rats did not receive the estradiol pellets (age-matched control). All rats were killed at 12 weeks of age, and their abdominal-inguinal mammary glands were histologically examined. The incidence and multiplicity of DHs were similar between groups (STET, 90% and 3.9 ± 0.6 vs. age-matched controls, 80% and 3.0 ± 0.5). However, DCIS and IDC did not develop in STET rats, whereas DCIS (25% and 1.4 ± 0.2) and IDC (35% and 1.4 ± 0.3) developed in the age-matched controls. Immunoscores of estrogen and progesterone receptors and positive rate of proliferative cell nuclear antigen (PCNA) in DH were similar in both groups, while the positive rate of cyclin D1 was significantly reduced in the STET group (P < 0.05). Thus, STET blocked the progression from DH to DCIS in MNU-induced mammary carcinogenesis, and decreased expression of cyclin D1 may play an important role in the blockade of cell transition from DH to DCIS.

Parenteral 17beta-estradiol decreases fasting blood glucose levels in non-obese mice with short-term ovariectomy

Aims Long-term ovariectomy-induced metabolic changes such as insulin resistance and glucose intolerance might be caused directly by estrogen deficiency and may occur partly as secondary effects of obesity arising due to the orexigenic effects of estrogen deficiency. Long-term estrogen treatment prevented those by exerting anorexigenic and metabolic actions in ovariectomized mice. However, the effect of short-term estrogen treatment on glucose metabolism in mice with short-term ovariectomy, during which ovariectomy-induced obesity does not develop, is not yet clear. The aim of this study was to evaluate the effect of short-term parenteral 17beta-estradiol treatment on glucose metabolism and blood glucose levels in mice at 2 weeks after ovariectomy, a time period during which ovariectomy-induced obesity does not develop. Main methods We examined the effect of three 17beta-estradiol injections on fasting blood glucose levels, insulin resistance, components of the insulin signaling pathway, AMPK activation, and the expression of genes related to glucose metabolism in liver, skeletal muscle, and white adipose tissues of non-obese C57BL/6N mice with short-term ovariectomy. Key findings Three 17beta-estradiol injections decreased the fasting blood glucose levels, activated AMPK, and decreased the expression of gluconeogenic genes, phosphoenolpyruvate carboxykinase, glucose-6-phosphatase and peroxisome proliferator-activated receptor-γ coactivator-1α in the liver. But three 17beta-estradiol injections did not affect insulin sensitivity and the components of the insulin signaling pathway in the liver and skeletal muscle. Significance Short-term parenteral 17beta-estradiol treatment decreases the fasting blood glucose levels not via insulin sensitivity of the skeletal muscle in non-obese mice with short-term ovariectomy.

A Little Estrogen Goes a Long Way

Short-term estrogen treatment in "postmenopausal" rats benefits cognition comparably to long-term estrogen therapy.

Differential regulation of cyclic AMP synthesis by estrogen in MCF7 cells

The classical view of the molecular actions of estrogen is described by its interaction with the intracellular estrogen receptor (ER), the binding of hormone receptor complex to the estrogen response element (ERE) on the DNA and followed by the alterations of gene expressions. Recently it has been reported that membrane estrogen receptor (mER) exist and it is suggested to be G protein linked receptor. In this report we show that under steroid-free culture conditions supplemented with low percentage of charcoal-stripped serum, differential estrogen treatments of human breast cancer MCF7 cells induce different responses of cyclic AMP (cAMP) productions. Treating [2- 3H]adenine-labeled MCF7 cells with 1 nM estrogen for 30 min stimulates cAMP production by measuring the ratio of [ 3H]cAMP:Total [ 3H]adenine nucleotides (ATP + ADP + cAMP), as determined by column chromatography, when compared with the control. This short-term estrogen treatment also significantly enhanced forskolin stimulated cAMP production when compared with the ratio of cAMP/Total measured in cells stimulated with forskolin alone. Pre-treating MCF7 cells with the same concentration of estrogen for 24 h before the assay, on the contrary, significantly decreased the basal cAMP level and it also suppressed cAMP production stimulated with forskolin when compared with its respective value under short-term estrogen treatment. Estrogen receptor antagonist ICI 182780 abolished both the stimulatory and suppressive effect of estrogen on cAMP synthesis indicating both effects were mediated through ER. Pre-treating cells with pertussis toxin relieved the suppression of cAMP synthesis by chronic estrogen treatment. Our data suggest that estrogen exerts differential effects on the cAMP production in MCF7 cells, involving the activations Gα i and Gα s family of G proteins, depending on the length of time of hormone treatment.

N-methyl-N-nitrosourea-induced mammary carcinogenesis is promoted by short-term treatment with estrogen and progesterone mimicking pregnancy in aged female Lewis rats

We examined the effects of short-term estrogen and progesterone treatment mimicking pregnancy in aged female Lewis rats on the development of N-methyl-N-nitrosourea (MNU)-induced mammary carcinoma. Rats were administered a single intraperitoneal injection of 20 mg/kg MNU at 7 weeks of age and half of those rats were administered a subcutaneously implanted 21-day release pellet containing 0.5 mg 17beta-estradiol and 32.5 mg progesterone (E/P) at 24 weeks of age. The rats were then monitored for the occurrence of mammary tumors. Rats were sacrificed when the largest mammary tumor became > or = 1 cm in diameter, or when the rat reached 48 weeks of age. Development of MNU-induced mammary carcinomas was accelerated after short-term E/P treatment, compared with E/P-untreated rats: the incidence of > or = 1-cm mammary carcinomas tended to increase (60 vs. 44%); the latency tended to shorten (28.7 vs. 34.6 weeks); and cancer multiplicity (number of all-sized carcinomas per rat) significantly increased (1.8 vs. 0.8). In E/P-treated rats, comedo necrosis was frequently seen and the incidence of estrogen receptor and/or progesterone receptor-negative mammary carcinomas was significantly increased. Early age at full-term pregnancy or short-term hormone treatment mimicking pregnancy may suppress the risk of breast cancer, but the age of hormone exposure is a crucial factor, because hormone exposure mimicking pregnancy in aged individuals may exert effects opposite of those exerted in younger individuals.

Effect of Estrogen Therapy on Insulin Resistance and Plasminogen Activator Inhibitor Type 1 Concentrations in Postmenopausal Women

Background/Aims: An elevated thrombotic risk due to abnormal fibrinolysis might be associated with insulin resistance in postmenopause. The aim of this study was to investigate the association of insulin resistance with a biochemical marker of fibrinolysis as well as the effect of transdermal estrogen treatment (ET) on this association. Methods: Thirty postmenopausal hysterectomized women received transdermal estradiol during 3 months. 17β-Estradiol, FSH, LH, plasminogen activator inhibitor type 1 (PAI-1), insulin and glucose were measured in blood samples before and after ET. Insulin resistance was calculated by the use of the homeostasis model assessment for insulin resistance (HOMA-IR).Results:ET induced a significant decrement in both PAI-1 levels and HOMA-IR values. The study also showed that HOMA-IR was a significant predictor for PAI-1 concentrations. Conclusion: Short-term ET improved HOMA-IR values in parallel with a decrease in PAI-1 levels.

A 3-day estrogen treatment improves prefrontal cortex-dependent cognitive function in postmenopausal women

Estrogen secretion in young women follows a cyclic pattern characterized by a pronounced surge in estrogen around ovulation. The way in which this estrogen peak affects cognitive functioning is unclear. Short-term estrogen treatment for a few days mimicking normal pre-menopausal estrogen dynamics substantially enhanced cognitive functions in ovariectomized animals. Here, we provide evidence that inducing a single estrogen peak in postmenopausal women improves their cognitive abilities. Healthy women (51-64 yrs, n=14) received either 100 microg estrogen transdermally for 3 days or placebo in a double-blind within-subject design. The treatment caused a temporary rise in serum estrogen levels roughly comparable to the mid-cyclic changes in estrogen in young women. At the end of the treatment, the women completed two types of tests involving primarily hippocampus-dependent functions of memory retention or prefrontal cortex-dependent functions. Results revealed a clear beneficial effect of estrogen on tasks mainly involving the prefrontal cortex: performance on a digit-ordering task (p<0.05) and on a task requiring short-term memory of event sequences in an unfamiliar story (p<0.01) were improved, and susceptibility to interference in the Stroop test (p<0.05) was diminished after estrogen. On the other hand, estrogen did not affect hippocampus-dependent retention of a story, with delayed recall tested after 30 min or 1 week, although immediate recall was improved by estrogen. We conclude that in postmenopausal women, a transient increase in plasma estrogen concentration acutely improves prefrontal cortex-dependent cognitive functions, whereas hippocampus-dependent memory retention is less affected. Our results encourage future studies to investigate whether repeated induction of short-lasting estrogen peaks could enhance cognitive efficacy of hormonal replacement therapy.

Sex Steroids, Cardiovascular Disease, and Hypertension

The roles that both male and female sex steroids play in mediating or protecting against cardiovascular disease (CVD) and hypertension are controversial. For example, whereas animal studies have strongly implicated androgens as being mediators of CVD and hypertension, human epidemiological studies have shown that with chronic disease, including hypertension, serum testosterone levels are actually reduced.1 Thus, whether androgens are truly causative of CVD is not clear. However, premenopausal women are typically protected from CVD and hypertension compared with men, and this has been hypothesized to be because of the protective effects of estrogens. The negative findings of Heart and Estrogen/progestin Replacement Study (HERS) I and II2,3 and Women’s Health Initiative (WHI)4,5 studies on hormone replacement therapy (HRT) in postmenopausal women have shaken our previous ideas that HRT was protective against CVD. In this short review, the latest findings regarding the roles of sex steroids in hypertension and CVD are discussed, questions yet to be answered are suggested, and some speculations are made. In both males and females, the hypothalamus secretes gonadotropin-releasing hormone, which stimulates the anterior pituitary to release both luteinizing hormone and follicular-stimulating hormone. Luteinizing hormone binds to receptors on thecal cells in ovaries of females and Leydig cells in testes of males to cause testosterone to be synthesized. Follicular-stimulating hormone, however, binds to receptors on granulosa cells in females or Sertoli cells in males and stimulates the synthesis of aromatase, which converts testosterone to estradiol. There are 2 main types of estrogen receptors, ERα and ERβ, but several variants of both have also been identified. ERβ is present in a greater number of tissues than is ERα, but both isoforms are present in kidneys and the vasculature. ERβ has been found to be the predominant isoform in human vascular smooth muscle cells. The androgen receptor …

Short-term estrogen treatment in ovariectomized rats augments hippocampal acetylcholine release during place learning

Estrogen modulates learning and memory in ovariectomized and naturally cycling female rats, especially in tasks using spatial learning and navigation. Estrogen also modulates cholinergic function in various forebrain structures. Past studies have shown positive correlations between hippocampal ACh output and performance on hippocampus-dependent tasks. The present study examined whether estradiol replacement would potentiate hippocampal ACh release during place learning. In vivo microdialysis and HPLC were used to measure extracellular ACh levels in the hippocampus of ovariectomized female rats that had received s.c. injections of 17β-estradiol (10 μg) or sesame oil (vehicle treatment) 48 and 24 h prior to training on a place task. Estrogen did not alter baseline levels of extracellular ACh in the hippocampus. During training, hippocampal ACh increased in ovariectomized rats regardless of estrogen status. However, while estradiol did not enhance learning in this experiment, estradiol significantly potentiated the increase in hippocampal ACh release seen during place training. This represents the first demonstration of on-line assessment of ACh output in hippocampus during learning in female rats and suggests that estrogen-dependent modulation of ACh release during training might control activation of different neural systems used during learning.

Estrogen treatment of prostate cancer increases triglycerides in lipoproteins as demonstrated by HPLC and immunoseparation techniques

Background: Estrogen administration is known to increase serum triglyceride concentrations. This study measured changes in lipoproteins of patients with prostate cancer treated with estrogen to determine whether the increased triglyceride concentrations are associated with atherogenic lipoprotein patterns. Methods: Fifteen patients (52–87 years) with histologically diagnosed prostate cancer received diethylstilbestrol diphosphate (250 mg/day). Serum samples were collected before and after 1 and 2 weeks of treatment. Cholesterol and triglyceride profiles of major lipoproteins were determined by HPLC, remnant-like particle cholesterol and triglyceride concentrations by an immunoseparation technique, and apolipoproteins by immunologic methods. Results: Estrogen treatment induced a 63.3% increase in total triglyceride concentrations, which occurred in all major lipoprotein classes with significant increases in HDL-triglycerides (130.4%), LDL-triglycerides (60.7%) and VLDL-triglycerides (56.2%). HDL-cholesterol increased significantly by 26.8%, while LDL-cholesterol decreased (15.6%). Remnant-like particle triglyceride concentrations also increased significantly by 77%, whereas remnant-like particle cholesterol concentrations remained unchanged. Apolipoproteins A-I and A-II increased; apolipoprotein E and Lp(a) decreased. Conclusions: The techniques used here conveniently demonstrated that short-term estrogen treatment in prostate cancer patients resulted in triglyceride enrichment of all major lipoprotein classes but did not induce changes in the lipoprotein profiles generally recognized as increasing risk for cardiovascular disease, except for the elevation of plasma triglyceride and remnant-like particle triglyceride.

Effects of estrogen therapy on well-being in postmenopausal women without vasomotor complaints

Objective: To establish whether estrogen treatment affects well-being in postmenopausal women without current or previous vasomotor symptoms. Design: Forty postmenopausal women, aged 45–59 years, without current or previous vasomotor complaints, were included. They were randomized to masked treatment with either transdermal 17β-estradiol 50 μg/24 h or to placebo. At baseline and after 12 and 14 weeks of treatment, the women completed a questionnaire which reflects well-being, the Psychological General Well-Being (PGWB) Index. Results: The women scored high on the PGWB Index, both at baseline and after 12 and 14 weeks of treatment. There was no significant difference in well-being according to PGWB Index between the groups treated with estrogen and placebo, neither at baseline, nor after therapy. Furthermore, there was no difference in change during therapy between the treatment groups. Conclusion: There is a gradual decline in estrogen during the climacteric, and it is controversial to which extent this affects women's mental health. The PGWB scores in this study were high before therapy, reflecting that these women without previous or current vasomotor complaints represented a selected sample. Neither short-term estrogen treatment over 12 weeks nor addition with medroxyprogesterone acetate during 2 weeks improved well-being in postmenopausal women without vasomotor symptoms who had high well-being at baseline.

Effects of short-term estrogen treatment on the neointimal response to balloon injury of rat carotid artery

Previous studies in our laboratory have demonstrated a sexual dimorphism in the response to balloon injury of the rat carotid artery, with marked attenuation in neointima formation in females compared with males. 1 Chen S.J. Li H. Durand J. Oparil S. Chen Y.F. Estrogen reduces myointimal proliferation after balloon injury of the rat carotid artery. Circulation. 1996; 93: 577-584 Crossref PubMed Scopus (221) Google Scholar Subsequent investigations established that this sexual dimorphism is estrogen dependent, because daily systemic administration of 17β-estradiol in a dose (20 μg/kg/day subcutaneously [SC]) that produced physiologic (20 to 50 pg/ml) levels of the circulating hormone attenuated neointima formation in gonadectomized rats of both sexes, whereas testosterone treatment had no effect. 2 Levine R.L. Chen S.J. Durand J. Chen Y.F. Oparil S. Medroxyprogesterone attenuates estrogen-mediated inhibition of neointima formation after balloon injury of the rat carotid artery. Circulation. 1996; 94: 2221-2227 Crossref PubMed Scopus (108) Google Scholar Many of the early molecular and/or cellular events in the vascular injury response exhibited sexual dimorphism and/or modulation by estrogen. For example, expression of the early response gene c-myc was increased >10-fold within 2 hours of balloon injury in the carotid artery of the male rat, but was minimally changed in the female. 1 Chen S.J. Li H. Durand J. Oparil S. Chen Y.F. Estrogen reduces myointimal proliferation after balloon injury of the rat carotid artery. Circulation. 1996; 93: 577-584 Crossref PubMed Scopus (221) Google Scholar More recent studies have shown that both vascular smooth muscle cells (VSMCs) and adventitial fibroblasts are activated and migrate toward the neointima within 24 to 72 hours of endoluminal injury of a rat carotid artery, and that these processes are modulated by estrogen. 3 Oparil S. Chen S.J. Chen Y.F. Durand J.N. Allen L. Thompson J.A. Estrogen attenuates the adventitial contribution to neointima formation in injured rat carotid arteries. Cardiovasc Res. 1999; 44: 608-614 Crossref PubMed Scopus (68) Google Scholar Based on these observations, we hypothesized that short-term systemic estrogen treatment beginning at the time of injury would attenuate the vascular injury response. The present study tested that hypothesis.