Hormone Replacement Therapy and Cardiovascular Disease: Lessons from a Monkey Model of Postmenopausal Women

Menopausal hormone therapy and coronary heart disease: the roller-coaster history

In the USA it is estimated that more than one million women become menopausal each year. Coronary heart disease (CHD) is the leading cause of mortality in menopausal woman globally. The majority of perimenopausal to postmenopausal women experience bothersome symptoms including hot flashes, night sweats, mood liability, sleep disturbances, irregular bleeding and sexual dysfunction. While menopausal hormone therapy (HT) effectively treats most of these symptoms, use of HT has become confusing, especially related to CHD risk. Despite years of observational and retrospective studies supporting a CHD benefit and improved survival among HT users, the Heart and Estrogen/Progestin Replacement Study (HERS) and the Women's Health Initiative (WHI) raised doubts about this long-held premise. The timing hypothesis has since emerged and states that when HT is initiated in younger women, soon after menopause onset, there may be cardiovascular benefit. The following review discusses the roller-coaster history of HT use as it pertains to CHD in postmenopausal women. Studies that highlight HT's CHD benefit are reviewed and provide reassurance that HT utilized in appropriately selected younger postmenopausal women close to the onset of menopause is safe from a cardiovascular perspective, in line with consensus recommendations.

The Effect of Vitamin E Supplementation in Postmenopausal Women-A Systematic Review

Menopause is a physiological change in any woman. Nevertheless, its symptoms could be difficult to accept, and hormone therapy can be sometimes unattractive or contraindicated. Vitamin E components are phytoestrogens, so they are believed to be useful in some indications including menopause. This review aimed to assess the available evidence on the effectiveness of vitamin E in alleviating menopausal symptoms. The Pubmed/MEDLINE, Cochrane Library and Scopus databases were screened. All types of studies that assessed the effectiveness of vitamin E in alleviating menopausal symptoms were included. The PICO question was: "How does vitamin E supplementation affect menopausal symptom occurrence?" The PROSPERO ID number of this review is CRD42022328830. After quality assessment, 16 studies were included in the analysis. The studies were divided into three groups in which the influence of vitamin E on the genital syndrome of menopause, vasomotor symptoms and vascular and metabolic changes were assessed. Vitamin E influences postmenopausal hot flashes, vascular modulation, plasma lipid profile level and vaginal changes. Compared to vitamin E, estrogen administration leads to better clinical effects. Nevertheless, vitamin E might serve as additive to hormone therapy and its alternative in women with contraindications to estrogens. More quality data are necessary to draw final conclusions.

Standard Morphologic Evaluation of the Heart in the Laboratory Dog and Monkey

The nonrodent species most commonly utilized in preclinical safety studies are the purpose-bred beagle dog and cynomolgus macaque ( Macaca fascicularis). Potential effects of a new chemical entity (NCE) on the heart pose serious concerns; consequently in vivo testing is focused on detection of functional alterations as well as morphological changes. Macroscopic and microscopic evaluation of the heart is based on a standard survey of key structures to properly assess presence of spontaneous and potential drug-induced lesions. Evaluation of historical controls to determine type and frequency of background change is valuable, as studies with non-rodent species generally have a small sample size. Archived control dog and monkey data were retrospectively reviewed, including terminal body weight (BW), heart weight (HW), and archival glass slides of heart. Control dogs had minimal background changes that included myxomatous or cartilagenous change in the cardiac skeleton and a variable degree of vacuolation in Purkinje fibers. Control monkey hearts commonly contained inflammatory cell infiltrates, myocyte anisokaryosis, and handling artifacts, while myocyte degeneration, squamous plaques, pigment, and intimal plaques were occasionally observed. These findings highlight the utility of consistently recorded and readily accessible archived control data when attempting to discern background spontaneous changes and artifacts from test-article induced changes.

Cardiovascular risk assessment with oxidised LDL measurement in postmenopausal women receiving intranasal estrogen replacement therapy

OBJECTIVE

To investigate the effect of intranasal estrogen replacement therapy administered to postmenopausal women alone or in combination with progesterone on markers of cardiovascular risk.

METHODS

The study was conducted with 44 voluntary postmenopausal women. In group I (n = 15), the patients were treated with only intranasal estradiol (300 μg/day estradiol hemihydrate). In group II (n = 11), the patients received cyclic progesterone (200 mg/day micronized progesterone) for 12 days in each cycle in addition to continuous intranasal estradiol. Group III (n = 18) was the controls. Serum lipid profiles, oxidised low-density lipoprotein (LDL) and other markers of cardiovascular risk were assessed at baseline and at the 3rd month of the treatment.

RESULTS

Lipid profile, LDL apolipoprotein B, lipoprotein a, homocysteine, oxidised LDL values and oxidised LDL/LDL cholesterol ratio were not observed to change after 3 months compared to baseline values within each group (p > 0.016). In comparison to changes between the groups after the treatment, only oxidised LDL levels and oxidised LDL/LDL cholesterol ratios of group II were increased compared to control group (p < 0.05).

CONCLUSIONS

Intranasal estradiol alone did not appear to have an effect on markers of cardiovascular risk in healthy postmenopausal women. However, the addition of cyclic oral micronized progesterone to intranasal estradiol influenced the markers of cardiovascular risk negatively in comparison to non-users in healthy postmenopausal women.

Estrogen receptor alpha and beta are both involved in the cerebral VEGF/Akt/NO pathway and cerebral angiogenesis in female mice

We have previously demonstrated that vascular endothelial growth factor (VEGF) is critical for cerebral angiogenesis in middle-aged female rats and may play a role in the flow-preserving neuroprotective actions of estrogen through its angiogenic and antiapoptotic properties. Here, we attempt to elucidate the effects of estrogen and the specific estrogen receptor (ER) subtype in cerebral VEGF/Akt/NO pathways and cerebral angiogenesis using 15-week old female mice that are either wild-type (WT), lack estrogen receptor α (ERαKO) or β (ERβKO). Protein levels of VEGF and basic signaling molecules of VEGF angiogenic pathway in the frontal cortex were expressed as follows, as revealed by ELISA and immunoblotting : a) VEGF; WT: ERαKO: ERβKO, 47 ± 15: 27 ± 5: 28 ± 5 pg/mg, respectively (P < 0.01); b) KDR decreased about 40% in both ERαKO and ERβKO compared to WT; c) Akt was significantly down-regulated in both ERαKO and ERβKO compared to WT; d) phosphorylated Akt (pAkt); WT: ERαKO: ERβKO, 0.6 ± 0.2: 0.3 ± 0.01: 0.3 ± 0.1 units/mg, respectively; e) phosphorylated eNOS significantly decreased about 45% in both ERαKO and ERβKO compared to WT. Cerebral capillary density decreased in both ERαKO and ERβKO compared to WT. Thus, it can be concluded that in female mice, VEGF/Akt/eNOS pathway plays an important role in cerebral angiogenesis and that both ER subtypes are involved in the regulation of VEGF and its signaling molecule expression in the frontal cortex.

Isoflavones--safe food additives or dangerous drugs?

The sales volume of products containing isoflavone has increased since the publication of the Women's Health Initiative. The many apparently contradictory results published on the effects of isoflavones on a variety of estrogen-regulated organs point to both beneficial as well as adverse effects on human health. It is of particular importance that psychovegetative climacteric complaints such as hot flushes are, if at all, only slightly influenced by isoflavones. The substances appear to have weak anti-osteoporotic effect. Their anti-atherosclerotic action is debatable, as not all authors find any beneficial effect on lipids. Most importantly, there is dispute as to whether isoflavones derived from soy or red clover have negative, positive or any effect at all on the mammary gland or endometrium. It is beyond any doubt that soy products may have cancer preventing properties in a variety of organs including the mammary gland. However, these properties may only be exerted if the developing organ was under the influence of isoflavones during childhood and puberty. This may also explain the often quoted "Japanese Phenomenon", the fact that breast cancer occurs to a lesser extent in Japanese women. When administered to isoflavone "inexperienced" women at the time of menopause, the phytoestrogens appear to share the same effects as estrogen used in classical preparations for hormone replacement therapy, i.e. they may stimulate the proliferation of endometrial and mammary gland tissue with at present unknown and unpredictable risk to these organs. Therefore, the following question arises for the clinician: Why should soy or red clover products containing isoflavone be recommended, if the positive effects are only negligible but the adverse effects serious?

The enhanced endothelin-1-induced contraction in cultured coronary arteries from mature female pigs is not antagonized by 17beta-estradiol

We have previously reported that organ cultured coronary arteries from market-age pigs (6-9 months of age) exhibit an enhanced contraction to the atherosclerotic-associated peptide, endothelin-1 (ET-1). The objective of this study was to investigate the interaction of 17beta-estradiol with ET-1 in organ cultured coronary arteries from older female pigs (3-4 years old). A cumulative concentration-response relationship (1 x 10(-9) M to 3 x 10(-7) M) was generated to ET-1, and the isometric tension measured in fresh and organ cultured (4 days at 37 degrees C) arterial rings that were each pre-incubated for 50 min in different concentrations (1 x 10(-9) M to 1 x 10(-5) M) of 17beta-estradiol. Compared to freshly used arteries, culturing induced a 2-fold increase in tension development to ET-1 (3 x 10(-7) M). Although 17beta-estradiol previously relaxed pre-constricted (with a 60 mM KCl solution) arteries, it did not affect the constrictive response to ET-1. Also, using an ET-1 ELISA we found that 17beta-estradiol did not effect ET-1 production in intact arteries. Our results indicate that 17beta-estradiol does not attenuate the production and constrictive properties of ET-1 in coronary arteries demonstrating a dedifferentiated cell phenotype.

Aging Reduces the Efficacy of Estrogen Substitution to Attenuate Cardiac Hypertrophy in Female Spontaneously Hypertensive Rats

Clinical trials failed to show a beneficial effect of postmenopausal hormone replacement therapy, whereas experimental studies in young animals reported a protective function of estrogen replacement in cardiovascular disease. Because these diverging results could in part be explained by aging effects, we compared the efficacy of estrogen substitution to modulate cardiac hypertrophy and cardiac gene expression among young (age 3 months) and senescent (age 24 months) spontaneously hypertensive rats (SHRs), which were sham operated or ovariectomized and injected with placebo or identical doses of 17beta-estradiol (E2; 2 microg/kg body weight per day) for 6 weeks (n=10/group). Blood pressure was comparable among sham-operated senescent and young SHRs and not altered by ovariectomy or E2 treatment among young or among senescent rats. Estrogen substitution inhibited uterus atrophy and gain of body weight in young and senescent ovariectomized SHRs, but cardiac hypertrophy was attenuated only in young rats. Cardiac estrogen receptor-alpha expression was lower in intact and in ovariectomized senescent compared with young SHRs and increased with estradiol substitution in aged rats. Plasma estradiol and estrone levels were lower not only in sham-operated but surprisingly also in E2-substituted senescent SHRs and associated with a reduction of hepatic 17beta-hydroxysteroid dehydrogenase type 1 enzyme activity, which converts weak (ie, estrone) into potent estrogens, such as E2. Aging attenuates the antihypertrophic effect of estradiol in female SHRs and is associated with profound alterations in cardiac estrogen receptor-alpha expression and estradiol metabolism. These observations contribute to explain the lower efficiency of estrogen substitution in senescent SHRs.

Destruction of primordial ovarian follicles in adult cynomolgus macaques after exposure to 4-vinylcyclohexene diepoxide: a nonhuman primate model of the menopausal transition

OBJECTIVE

To determine whether the 4-vinylcyclohexene diepoxide (VCD)-treated mouse menopause model, which involves accelerated atresia of primordial follicles and induces gradual ovarian failure (while sparing the ovarian stroma), can be adapted to nonhuman primates.

DESIGN

Controlled periclinical trial (nonhuman primates).

SETTING

Comparative Medicine Clinical Research Center.

ANIMAL(S)

Four adult female cynomolgus monkeys.

INTERVENTION(S)

Once-daily i.m. injections for 15 days as follows: vehicle or VCD doses of 80 mg/kg, 160 mg/kg, 250 mg/kg. Ovaries were removed 27 days after treatment, and pathological determinations were made at necropsy.

MAIN OUTCOME MEASURE(S)

Baseline and interim hematologic and biochemical measures, physical exams, and body weights. Follicle counts and organ evaluation at necropsy.

RESULT(S)

A nearly complete elimination of primordial, intermediate, primary and secondary follicles was achieved with 250 mg/kg VCD. A 50% reduction in primordial and primary follicles was observed with 160 mg/kg VCD. No effect of 80 mg/kg VCD per day was observed. Clinical health measures remained within normal range except for transient, mild increases in liver enzymes and an inflammatory response at the injection site with 250 mg/kg. Postmortem evaluations (9 months) revealed no gross or histological lesions in the organs studied.

CONCLUSION(S)

These results demonstrate that the monkey ovary is susceptible to VCD and that as in rodents, primordial and primary follicles are targeted selectively.

Clinical study comparing the effects of sequential hormone replacement therapy with oestradiol/dydrogesterone and conjugated equine oestrogen/norgestrel on lipids and symptoms

A clinical study comparing the effects of sequential hormone replacement therapy with oestradiol/dydrogesterone and conjugated equine oestrogen/norgestrel on lipids and symptoms.

OBJECTIVE

The objective of the study was to compare the effects of sequential 17beta-oestradiol/dydrogesterone and conjugated equine oestrogens (CEE)/norgestrel on lipid parameters, climacteric symptoms, bleeding patterns and tolerability.

STUDY DESIGN

This double-blind study was conducted in 193 peri- and post-menopausal women randomised to receive six, 28-day cycles of oral sequential oestradiol 1 mg/dydrogesterone 10 mg or CEE 0.625 mg/norgestrel 0.15 mg. The change from baseline in serum lipids and hot flushes was analysed using a two-way analysis of variance.

RESULTS

After 24 weeks there was a statistically significant increase in high-density lipoprotein (HDL) cholesterol in the oestradiol/dydrogesterone group and a significant reduction in the CEE/norgestrel group. The difference between the groups was significant (P=0.001). The number of hot flushes was reduced by 86% in both groups; this improvement was supported by the Greene Climacteric Symptom Scale score, the patients' opinion and quality of life assessments. The percentage of women experiencing cyclic bleeding was greater with CEE/norgestrel, as was the mean duration and severity of bleeding. Both treatments were well tolerated.

CONCLUSION

Oestradiol/dydrogesterone and CEE/norgestrel were equally effective in treating climacteric symptoms, but oestradiol/dydrogesterone showed some advantages in terms of lipid profile and incidence of bleeding.

Effects of Surgical Menopause and Estrogen Replacement Therapy on Serum Paraoxonase Activity and Plasma Malondialdehyde Concentration

BACKGROUND

We have investigated the effects of surgical menopause and estrogen replacement therapy (ERT) on serum paraoxonase 1 (PON1) activity and plasma malondialdehyde (MDA) levels in surgically postmenopausal women.

METHODS

Thirty-six healthy perimenopausal women who underwent total abdominal hysterectomy and bilateral salpingo-oopherectomy for uterine myoma were enrolled in this study. Blood samples were taken from the subjects 1 day before surgery, 1 day before starting ERT (30 days after the operation) and on the 30th day after the start of therapy.

RESULTS

After surgical menopause, there were significant increases in plasma MDA levels (p < 0.05) and a decrease in serum PON1 activity (p < 0.05). ERT significantly increased the PON1 activity (p < 0.05) and reduced MDA levels (p < 0.05). There was a positive correlation between serum high-density lipoprotein cholesterol and PON1 activity (r = 0.7, p < 0.001, n = 36) and a negative correlation between serum PON1 activity and plasma MDA levels (r = -0.63, p < 0.006, n = 36).

CONCLUSIONS

The present study suggests that postmenopausal women tend to have high levels of plasma MDA and reduced PON1 activity, and ERT reverses these effects. The effect of ERT on lipid peroxidation seems to be associated with serum PON1 activity.

Role of the nonhuman primate for research related to women's health

This overview of the current status of medical problems that affect women is related to current studies on pathophysiology and therapeutic interventions using nonhuman primates to demonstrate the utility of the primate model for the study of disease processes in women. The current medical literature on women's health is compared with the literature on nonhuman primate research. The findings reviewed in the articles of ILAR Journal Volume 45 Issue 2 of 2004 are evaluated in the context of the scope and problems associated with disease entities in women. Nonhuman primate research with known information regarding women's disease is discussed, and the utility of the animal model for the study of human disease is highlighted, based on its significant relevance due to similarities of nonhuman primate and human subjects' physiology, metabolism, and responses to therapeutic interventions. Additional advantages of the animal model include the ability to control the experimental environment and the capacity to perform chronic study procedures. These findings allow us to utilize the nonhuman primate as the most relevant model in the animal world for the study of human disease processes.

Usefulness of the Monkey Model to Investigate the Role of Soy in Postmenopausal Women's Health

Some of the important health issues for postmenopausal women include cardiovascular disease, osteoporosis, breast cancer, and relief of menopausal symptoms. Ovariectomized cynomolgus monkeys (Macaca fascicularis) have many strengths as models for research in this area including a close phylogenetic relationship to humans, similarities in lipid/lipoprotein metabolism and coronary artery anatomy, similar skeletal anatomical and morphological characteristics, mammary glands with similar pathophysiological characteristics, and a 28-day menstrual cycle with similar hormonal fluctuations. Monkeys (macaques) also experience declining ovarian function and irregular menstrual cycles (natural menopause) when they approach 24 to 29 yr of age. However, because of their very short life span after natural menopause, ovariectomized macaques are used to model postmenopausal women. The cynomolgus monkey model has been useful in defining the potential cardiovascular benefits of soy foods and soy supplements; however, it remains unclear whether the observations are generalizable to all women or only to those who, like cynomolgus monkeys, convert the soy isoflavone daidzein to the metabolite equol. Particularly important has been the use of the cynomolgus monkey model to understand the effects of soy on breast health. There is evidence from a cynomolgus monkey trial to suggest that soy/soy phytoestrogens have no estrogen agonist effects for breast. Finally, soy/soy phytoestrogens do not appear to be an adequate alternative to postmenopausal hormone therapy. Nevertheless, important attributes of soy have been identified, and it may have potential as a complementary component to hormone therapy.