Effect on biochemical vasoactive markers during postmenopausal hormone replacement therapy: estradiol versus estradiol/dienogest

Late Onset of Estrogen Therapy Impairs Carotid Function of Senescent Females in Association with Altered Prostanoid Balance and Upregulation of the Variant ERα36

Recent analysis of clinical trials on estrogen therapy proposes the existence of a therapeutic window of opportunity for the cardiovascular benefits of estrogens, which depend on women's age and the onset of therapy initiation. In this study, we aimed to determine how vascular senescence and the onset of estrogen treatment influence the common carotid artery (CCA) function in senescent and non-senescent females. Ovariectomized female senescence-accelerated (SAMP8) or non-senescent (SAMR1) mice were treated with vehicle (OVX) or 17β-estradiol starting at the day of ovariectomy (early-onset, E₂E) or 45 days after surgery (late-onset, E₂L). In SAMR1, both treatments, E₂E and E₂L, reduced constriction to phenylephrine (Phe) in CCA [(AUC) OVX: 193.8 ± 15.5; E₂E: 128.1 ± 11.6; E₂L: 130.2 ± 15.8, p = 0.004] in association with positive regulation of NO/O2- ratio and increased prostacyclin production. In contrast, E₂E treatment did not modify vasoconstrictor responses to Phe in OVX-SAMP8 and, yet, E₂L increased Phe vasoconstriction [(AUC) OVX: 165.3 ± 10; E₂E: 183.3 ± 11.1; E₂L: 256.3 ± 30.4, p = 0.005]. Increased vasoconstriction in E₂L-SAMP8 was associated with augmented thromboxane A2 and reduced NO production. Analysis of wild-type receptor alpha (ERα66) expression and its variants revealed an increased expression of ERα36 in E₂L-SAMP8 in correlation with unfavorable effects of estrogen in those animals. In conclusion, estrogen exerts beneficial effects in non-senescent CCA, regardless of the initiation of the therapy. In senescent CCA, however, estrogen loses its beneficial action even when administered shortly after ovariectomy and may become detrimental when given late after ovariectomy. Aging and onset of estrogen treatment are two critical factors in the mechanism of action of this hormone in CCA.

cGMP-dependent protein kinase-2 regulates bone mass and prevents diabetic bone loss

NO/cGMP signaling is important for bone remodeling in response to mechanical and hormonal stimuli, but the downstream mediator(s) regulating skeletal homeostasis are incompletely defined. We generated transgenic mice expressing a partly-activated, mutant cGMP-dependent protein kinase type 2 (PKG2R242Q) under control of the osteoblast-specific Col1a1 promoter to characterize the role of PKG2 in post-natal bone formation. Primary osteoblasts from these mice showed a two- to three-fold increase in basal and total PKG2 activity; they proliferated faster and were resistant to apoptosis compared to cells from WT mice. Male Col1a1-Prkg2R242Q transgenic mice had increased osteoblast numbers, bone formation rates and Wnt/β-catenin-related gene expression in bone and a higher trabecular bone mass compared to their WT littermates. Streptozotocin-induced type 1 diabetes suppressed bone formation and caused rapid bone loss in WT mice, but male transgenic mice were protected from these effects. Surprisingly, we found no significant difference in bone micro-architecture or Wnt/β-catenin-related gene expression between female WT and transgenic mice; female mice of both genotypes showed higher systemic and osteoblastic NO/cGMP generation compared to their male counterparts, and a higher level of endogenous PKG2 activity may be responsible for masking effects of the PKG2R242Q transgene in females. Our data support sexual dimorphism in Wnt/β-catenin signaling and PKG2 regulation of this crucial pathway in bone homeostasis. This work establishes PKG2 as a key regulator of osteoblast proliferation and post-natal bone formation.

Modification of blood pressure in postmenopausal women: role of hormone replacement therapy

The rate of hypertension increases after menopause. Whether estrogen and progesterone deficiency associated with menopause play a role in determining a worst blood pressure (BP) control is still controversial. Also, studies dealing with the administration of estrogens or hormone therapy (HT) have reported conflicting evidence. In general it seems that, despite some negative data on subgroups of later postmenopausal women obtained with oral estrogens, in particular conjugated equine estrogens (CEE), most of the data indicate neutral or beneficial effects of estrogen or HT administration on BP control of both normotensive and hypertensive women. Data obtained with ambulatory BP monitoring and with transdermal estrogens are more convincing and concordant in defining positive effect on BP control of both normotensive and hypertensive postmenopausal women. Overall progestin adjunct does not hamper the effect of estrogens. Among progestins, drospirenone, a spironolactone-derived molecule, appears to be the molecule with the best antihypertensive properties.

Why use of dienogest for the first contraceptive pill with estradiol?

Dienogest (DNG) has the essential properties of an effective progestogen for use in a new contraceptive pill using estradiol valerate as estrogenic component -- it inhibits ovulation and protects against endometrial proliferation. DNG is a derivative of norethisterone (NET), but has a cyanomethyl- instead of an ethinyl-group in C17 position which may offer a variety of benefits regarding hepatic effects. The similarity to NET is reflected in the high endometriotropy and in similar pharmacokinetics like short plasma half-live and high bioavailability. However, DNG also elicits properties of progesterone derivatives like neutrality in metabolic and cardiovascular system and considerable antiandrogenic activity, the latter increased by lack of binding to SHBG as specific property of DNG. It has no glucocorticoid and antimineralocorticoid activity and has no antiestrogenic activity with the consequence that possible beneficial estradiol effects should not be antagonized. This may be of special importance for the tolerability and safety of the first pill with estradiol valerate instead of ethinylestradiol, although well-designed postmarketing studies are still ongoing to demonstrate what can be expected on the basis of pharmacology.

Progestin effects in endometriosis treatment: new research on mechanisms

New research on mechanisms of progestin effects in endometriosis treatment has been performed with dienogest (DNG), which has recently been launched in this regard. It is effective in the same low dosage of 2 mg/day, similar to the use of contraception and hormone therapy, whereas other progestogens (with the exception of dydrogesterone) must be given in much higher dosages to treat typical symptoms of endometriosis. This short review summarizes experimental studies on DNG. They demonstrate strong antiproliferative effects in endometrial and endometriotic cells or experimental endometriosis, as well as anti-inflammatory and antiangiogenic actions. By direct action on the ovarian folliculogenesis DNG lead to only modest suppression of estradiol production in contrast to the high-dosed progestogens or to gonadotropin releasing hormone (GnRH) agonists. These effects add to the well-known tolerability because DNG is very neutral regarding cardiovascular, metabolic or central action which also makes it suitable for long-term therapy.

Low-dose continuous combinations of hormone therapy and biochemical surrogate markers for vascular tone and inflammation: transdermal versus oral application

OBJECTIVE

To compare the effects of low-dose transdermal estradiol (E2)/norethisterone acetate (NETA) patches (Estalis 25/125) with low-dose oral E2/NETA (Activelle) on cardiovascular biochemical markers after 12 and 52 weeks of treatment in postmenopausal women with intact uteri.

DESIGN

Participants were randomly assigned to receive either transdermal E2/NETA (delivering daily doses of 25 microg E2 and 125 microg NETA, applied every 3-4 d) or oral E2/NETA (1 mg E2 and 0.5 mg NETA, given daily) in this open-label study. The following markers or their stable metabolites in serum or urine were assessed: P-selectin, intercellular adhesion molecule-1, vascular cell adhesion molecule-1, monocyte chemoattractant protein-1, matrix metalloproteinase-9, homocysteine, cyclic guanosine monophosphate, serotonin, prostacyclin, thromboxane, and urodilatin.

RESULTS

Significant decreases were found for P-selectin, intercellular adhesion molecule-1, monocyte chemoattractant protein-1, and homocysteine for both hormone therapy (HT) regimens compared with baseline. Matrix metalloproteinase-9 was increased only by oral HT. The urinary concentrations of cyclic guanosine monophosphate, the ratio of prostacyclin to thromboxane metabolite, and the serotonin metabolite were significantly increased for both HT application modes, although the oral treatment showed a significantly greater increase than the transdermal one with respect to baseline. Urodilatin excretion was increased only by the oral regimen.

CONCLUSIONS

Low-dose transdermal and oral HTs using E2 and NETA elicit favorable effects on cardiovascular biochemical markers. For most markers the magnitude of changes found were similar with respect to baseline; however, in some cases oral HT led to a significantly greater change, whereas in other cases the transdermal formulations seemed to provide greater benefits. Whether these differences may be attributed to the different administration routes or to different pharmacokinetic properties remains an open question. Overall low-dose transdermal HT seems to provoke the same benefit on the cardiovascular system as oral HT, as suggested by the results on vascular markers.

[Hormone replacement therapy for internal risk patients]

Using hormone replacement therapy (HRT), absolute and relative contradictions have to be considered, which are primarily classified according to a "worst case" scenario on the assumption of group effects, in order to satisfy forensic demands. However, in patients with severe complaints it make sense to apply HRT even at increased risk. To minimize the risk, a differentiated choice of the preparation especially in terms of progestin component and application mode is feasible apart from a general dose reduction. For internal risk patients, transdermal estradiol in a patch or gel and neutral progestins like progesterone and dydrogesterone or combination patches for a completely transdermal HRT are to be preferred. In the Women's Health Initiative, a study investigating a population strongly burdened with cardiovascular risks, the most important risks were venous thromboses and strokes, in old age also myocardial infarctions. In this context, the risk groups with diabetes, hypertension and dyslipoproteinemia as well as smokers in general are of particular importance. Other common internal risk groups comprise women with thyroid and hepatobiliary diseases. Rare but prognostically important diseases such as porphyria and lupus erythematosus are considered as relative contraindications. The available data on these risk groups are described and practical recommendations are given.

Biochemical markers surrogating on vascular effects of sex steroid hormones

The main mechanism of possible cardioprotection by estrogens appears to be a direct effect on the vasculature, resulting in an improvement of endothelial function and inhibition of atherogenesis. Numerous observational and experimental studies have demonstrated a positive correlation between estrogens and various biochemical markers surrogating direct vascular effects. In general, most markers are influenced in a similar way by oral and transdermal hormone therapy, although oral therapy may have a faster and more pronounced effect. The main difference between oral and transdermal administration may be confined to markers that are mainly or exclusively produced in the liver. Clinical studies demonstrate that progestogen addition can have an impact on the beneficial estrogen-induced changes of biochemical markers. Concerning the effects of tibolone, inconsistent data have been found. Overall, tibolone-induced beneficial changes on the various biochemical markers appear to be less marked compared with those of hormone therapy. The few data available on the direct effects of androgens on the vascular wall indicate a less favorable action of androgens on biochemical markers than of estrogens. The practical relevance of marker measurements is currently under discussion. Although evidence strongly supports some of these markers as predictors of acute events, it remains to be established whether modifying circulating levels of these markers will influence outcomes.

Role of progestins with partial antiandrogenic effects

An experts' meeting on the 'Role of progestins with partial antiandrogenic effects' was held in Berlin from January 19 to 22, 2001. The meeting was chaired by Dr R. Sitruk-Ware (New York, USA) and participants included Ms F. Fruzzetti (Pisa, Italy), J. Hanker (Trier, Germany), J. Huber (Vienna, Austria), F. Husmann (Bad Sassendorf, Germany), S. O. Skouby (Copenhagen, Denmark), J. H. H. Thijssen (Utrecht, The Netherlands), and R. Druckmann (Nice, France). The present paper reports the conclusions of the meeting. However, the publication of the Women's Health Initiative study, which appeared after the meeting, led to additional comments and revisions.

Effect of hormone therapy on BP in normotensive and hypertensive postmenopausal women

High blood pressure (BP) ranks as the greatest risk factor for cardiovascular disease. The increased cardiovascular risk determined in recent interventional studies has led the health authorities in some countries to re-ignite the discussion about whether hypertension should be listed as a contraindication for hormone replacement therapy (HRT). We reviewed papers published since 1960 and listed in MEDLINE, EMBASE and Biosis, on studies that monitored the course of BP during HRT. We found that both primarily normotensive and hypertensive postmenopausal women actually run only a very low risk of BP increase during HRT, indeed, BP was often lowered. In one of our own studies 1397 hypertensive women with BP diastolic >95 mmHg received transdermal HRT regimens; BP was lowered by an average of 7 mmHg systolic and 9 mmHg diastolic. The results of the more recent 24-h ambulatory BP studies are particularly conclusive. At least 19 such studies have been performed, 13 placebo-controlled and 10 cross-over; 5 found no effect on BP and 14 studies demonstrated BP reductions. BP was lowered by treatment with transdermal estradiol in 11 of 13 studies and by oral estrogen in 4 of 11 studies. The effects were not consistent with regard to systolic or diastolic BP nor to action on day- and night-time BP. It cannot be ruled out that some women with a particular predisposition exhibit an abnormal reaction to the vasoactive effects of HRT, and there is a paucity of long-term data on risk populations, specifically on the progestogenic effects in patients with pre-existing arteriosclerotic lesions. In conclusion, the risk of developing hypertension during HRT is very low, but hormone therapy should always be appropriately indicated and during therapy BP should be checked regularly.

New Progestogens

The progestins have different pharmacological properties depending upon the parent molecule, usually testosterone or progesterone, from which they are derived. Very small structural changes in the parent molecule may induce considerable differences in the activity of the derivative. In postmenopausal women with an intact uterus, progestins are used in combination with estrogen as hormone-replacement therapy (HRT). The development of new generations of progestins with improved selectivity profiles has been a great challenge. Steroidal and nonsteroidal progesterone-receptor (PR) agonists have been synthesised as well, although the latter are still in a very early stage of development. Several new progestins, which have been synthesised in the last 2 decades, may be considered fourth-generation progestins. These include dienogest, drospirenone, Nestorone (Population Council, New York, NY, USA), nomegestrol acetate and trimegestone. The fourth-generation progestins have been designed to have no androgenic or estrogenic actions and to be closer in activity to the physiological hormone progesterone. Drospirenone differs from the classic progestins as it is derived from spirolactone. It is essentially an antimineralocorticoid steroid with no androgenic effect but a partial antiandrogenic effect. The antiovulatory potency of the different progestins varies. Trimegestone and Nestorone are the most potent progestins synthesised to date, followed by two of the older progestins, 3-keto-desogestrel and levonorgestrel. The new molecules trimegestone, drospirenone and dienogest also have antiandrogenic activity. Following the publication of the results of the Women's Health Initiative study, the role of progestins in HRT became controversial. Unfortunately, this concern has been directed towards progestins as a class, although striking differences exist among the progestins. Natural progesterone and some of its derivatives, such as the 19-norprogesterone molecules, and the new molecules drospirenone and dienogest are not androgenic and, therefore, have no negative effect on the lipid profile. The effects of progestins on breast tissue remain controversial as well. However, depending on the progestin and the duration of application, breast cell differentiation and apoptosis may predominate over proliferation. It is still unclear if the currently available progestins are able to bind specifically to the PR isoforms PR-A or PR-B and whether this is of clinical relevance to breast cell proliferation is also unclear. Although it is likely that the new progestins may have neutral effects on the risk of coronary heart disease or breast cancer in younger postmenopausal women, this hypothesis must be confirmed in large randomised, well controlled clinical trials.

Androgens and Antiandrogens

The role of androgens in women's health has been generally neglected. Currently available assays are lacking in sensitivity and reliability at the lower ranges. Circulating androgens as prohormones for other steroids (e.g., androgens) have an ubiquitous role on diverse physiological and behavioral systems. Clinical assessment of both androgen production and androgen availability can be achieved by measurement of two or three essential values. These include either total T and sex-hormone binding globulin (SHBG), free T and SHBG, or free T and total T. The free testosterone index (total T/SHBG) correlates well with free or bioavailable T and can be used as a substitute. DHEA-S is the most useful measure of adrenal androgen production in women. Androgen insufficiency in women is not a specific consequence of natural menopause, but may occur secondarily to the age-related decline in both adrenal and ovarian androgen production. Since estrogen effects are also strongly linked to mood, psychological well-being, and sexual function in women, the diagnosis of androgen insufficiency should only be made in women who are adequately estrogenized. Before initiating a trial of androgen replacement therapy, a comprehensive clinical assessment should be performed in all cases. Approved androgen replacement therapy is not yet available in most countries for treatment of female sexual dysfunction. This would include T supplements or DHEA. Several new progestins have been synthesized in the last decade. Dienogest is a hybrid progestin that is derived from both the pregnane and the estrane groups with a 17alpha-cyanomethyl radical; drospirenone is derived from spirolactone. Somehow, the molecules available have demonstrated antiandrogenic properties. Cyproterone acetate (CPA) is the most potent antiandrogenic progestin, followed by dienogest, drosperinone, and chlormadinone acetate. Nomegestrol acetate and medrogestone also exert some antiandrogenic properties and are similar to chlormadinone acetate in antiandrogenic potency. While androgens act positively on libido in women, antiandrogenic properties in doses used in HRT do not appear to have a negative effect. Progestins used in HRT have varying pharmacological properties that are associated with different adverse effects. The new progestins with antiandrogenic properties avoid many of the androgenic side effects related to testosterone-derived progestins. They also have the potential of not counteracting beneficial estrogen effects, for example, on the cardiovascular system or mental tone.

Impact of hormone replacement therapy on endogenous estradiol metabolism in postmenopausal women

OBJECTIVES

Changes in estradiol metabolism may play a role in the pathophysiology of different diseases, of special interest being an increase in D-ring over A-ring metabolites for the risk of breast cancer. In the present work we investigated the effect of exogenous estradiol therapy on endogenous estradiol metabolism in postmenopausal women.

METHODS

Three different studies were carried out in 126 women: in study A the women were treated for 4 weeks either with oral or with transdermal 17beta-estradiol, in study B for 4 weeks with oral or transdermal 17beta-estradiol sequentially combined with oral or transdermal norethisterone acetate, and in study C for 12 weeks either with oral 17beta-estradiol or with an oral continuous combination of 17beta-estradiol with the new progestin dienogest. As main representatives of the A- and D-ring metabolism, 2-hydroxyestrone (2-OHE1) and 16 alpha-hydroxyestrone (16-OHE1), respectively, were measured in 8 h night urine using enzyme immunoassay technique.

RESULTS

Oral estradiol treatment resulted in a significant higher excretion of estradiol metabolites compared to transdermal treatment. Neither oral nor transdermal estradiol induced a significant change in the ratio of 16-OHE1 to 2-OHE1. The addition of oral or transdermal norethisterone acetate to estradiol did not alter on average the endogenous estradiol metabolism, although in individual patients a significant increase in 16-OHE1 metabolism was observed only with oral norethisterone. The continuous oral addition of dienogest did not lead to any significant change in estradiol metabolism.

CONCLUSIONS

These results indicate that oral estradiol replacement therapy enhances the quantity of circulating estradiol metabolites. This may have a more negative impact on estrogenic target cells as compared to transdermal application. Progestin addition to estradiol replacement therapy seems to have no major impact on endogenous estradiol metabolism. Further studies, however, are necessary to evaluate the progestin effect in possible pre-disposed patients.

Lack of stimulatory effect of dienogest on the expression of intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 by endothelial cell as compared with other synthetic progestins

OBJECTIVES

Monocyte adhesion to endothelial cells is an important initial event at the onset of atherosclerosis. It is partially mediated by the expression of adhesion molecules on the endothelial cell surface. While estrogens inhibit the development of atherosclerosis, the effect of co-administered progestin remains controversial. We examined the effect of progestins on cytokine-stimulated human umbilical venous endothelial cell (HUVEC) expression of adhesion molecules.

METHODS

In HUVECs, mRNA expression of progesterone receptors (PRs) and androgen receptors (AR) was determined by RT-PCR. HUVECs were stimulated by interleukin-1beta (IL-1beta) for 24 h with or without various steroids, and then the cell-surface expression of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) was semiquantified by ELISA.

RESULTS

In all preparations of HUVECs used in this study, RT-PCR confirmed mRNA expression of both isoforms of PR, PR-A and PR-B, as well as AR. Addition of progesterone (10(-10)-10(-7) M) or dienogest (DNG) (10(-10)-10(-8) M) did not affect IL-1beta-stimulated ICAM-1 or VCAM-1 expression. In contrast, medroxyprogesterone acetate, norethindrone acetate and levonorgestrel (10(-10)-10(-8) M) dose-dependently increased cell adhesion molecules. The progestin-induced increase was blocked by the concomitant addition of mifepristone, a PR antagonist, but not by hydroxyflutamide, an AR antagonist, indicating that the progestin stimulation was mediated predominantly via PR.

CONCLUSIONS

These results suggest that DNG, unlike other synthetic progestins, lacks stimulation of cell adhesion molecules. For the prevention of atherosclerosis, estrogen in combination with DNG may be a suitable regimen in hormone replacement therapy in postmenopausal women.

Estradiol valerate/dienogest

Estradiol valerate 2mg/dienogest 2mg is an oral estrogen/ progestogen formulation that has been approved throughout the European Union for the treatment of climacteric symptoms in postmenopausal women. Dienogest is a progestogen that combines the properties of both progesterone and 19-nortestosterone derivatives. It has moderate affinity for the progesterone receptor, significant antiproliferative and antiandrogenic activity, and produces secretory transformation of the endometrium. Estradiol valerate is an esterified form of natural 17beta-estradiol, the most potent endogenous human ovarian estrogen, and is hydrolysed to estradiol soon after oral administration. Results from a randomised, double-blind, multicentre trial showed that oral estradiol valerate 2mg/dienogest 2mg and estradiol valerate 2mg/dienogest 3mg once daily for 1 year were each as effective as estradiol 2mg/estriol 1mg/norethisterone acetate 1mg in the treatment of climacteric symptoms in 581 postmenopausal women; reductions from baseline in Kupperman Index scores were 78.5, 74.5 and 75.0%, respectively. The number of days without any type of bleeding was lowest in patients treated with estradiol valerate 2mg/dienogest 2mg (8.7 days), and highest in the estradiol valerate 2mg/ dienogest 3mg group (12.1 days). During the twelfth month of treatment with estradiol valerate 2mg/dienogest 2mg, the percentage of patients who reported bleeding was 14.5%. Endometrial biopsy results were similar in patients treated with estradiol valerate 2mg/dienogest 2mg, estradiol valerate 2mg/dienogest 3mg or estradiol 2mg/estriol 1mg/norethisterone acetate 1mg once daily for 1 year; 90.8, 87.4 and 87.5% of samples, respectively, contained atrophic material. Proliferative material was found in 4.2, 2.5 and 4.4% of the biopsies, respectively; there was no incidence of hyperplasia in any of the treatment groups. A noncomparative multicentre study in 1501 postmenopausal women demonstrated that adverse events associated with estradiol valerate 2mg/dienogest 2mg once daily for 48 weeks included breakthrough bleeding, mastalgia, headache, abdominal pain, hypertension, thrush, migraine, weight gain, increase in endometrial thickness and metrorrhagia.