Sex hormones and lipoprotein metabolism

HDL Particle Subspecies and Their Association With Incident Type 2 Diabetes: The PREVEND Study

CONTEXT

High-density lipoproteins (HDL) may be protective against type 2 diabetes (T2D) development, but HDL particles vary in size and function, which could lead to differential associations with incident T2D. A newly developed nuclear magnetic resonance (NMR)-derived algorithm provides concentrations for 7 HDL subspecies.

OBJECTIVE

We aimed to investigate the association of HDL particle subspecies with incident T2D in the general population.

METHODS

Among 4828 subjects of the Prevention of Renal and Vascular End-Stage Disease (PREVEND) study without T2D at baseline, HDL subspecies with increasing size from H1P to H7P were measured by NMR (LP4 algorithm of the Vantera NMR platform).

RESULTS

A total of 265 individuals developed T2D (median follow-up of 7.3 years). In Cox regression models, HDL size and H4P (hazard ratio [HR] per 1 SD increase 0.83 [95% CI, 0.69-0.99] and 0.85 [95% CI, 0.75-0.95], respectively) were inversely associated with incident T2D, after adjustment for relevant covariates. In contrast, levels of H2P were positively associated with incident T2D (HR 1.15 [95% CI, 1.01-1.32]). In secondary analyses, associations with large HDL particles and H6P were modified by body mass index (BMI) in such a way that they were particularly associated with a lower risk of incident T2D, in subjects with BMI < 30 kg/m2.

CONCLUSION

Greater HDL size and lower levels of H4P were associated with a lower risk, whereas higher levels of H2P were associated with a higher risk of developing T2D. In addition, large HDL particles and H6P were inversely associated with T2D in nonobese subjects.

Changes in serum lipid levels during pregnancy in women with gestational diabetes. A narrative review

We review current knowledge on lipid metabolism changes during pregnancy with special focus on changes in gestational diabetes. In physiological pregnancy, total plasma cholesterol, triglyceride and HDL-cholesterol level rises, the atherogenic index (LDL-cholesterol / HDL-cholesterol remains unchanged. Compared with healthy women, women with GDM show more pronounced signs of mixed dyslipidaemia - increased levels of triglyceride, changes in cholesterol and lipoprotein concentrations with a shift towards greater small dense LDL subtractions, which is typical for insulin resistance states. Dyslipidaemia, particularly hypertriglyceridemia, is thought to be one of the key drivers of foetal macrosomia and that is why measurements of plasma lipids may be valuable in detecting the metabolic abnormality in GDM and in predicting foetal outcome. Dyslipidaemia in GDM is seen as proatherogenic and potentially harmful for the baby and therefore it should be monitored more carefully.

Metabolomics reveals the sex-specific effects of the SORT1 low-density lipoprotein cholesterol locus in healthy young adults

Metabolite profiles of individuals possessing either the cardiovascular risk or protective variants of the low-density lipoprotein cholesterol (LDL-C) associated 1p13.3 locus of the SORT1 gene (rs646776) were analyzed. Serum metabolites and lipids were assessed using LC-MS-based metabolomics in a healthy young population (n = 138: 95 males, 43 females). Although no significant differences were observed in the combined cohort, divergent sex effects were identified. Females carrying the protective allele showed increased phosphatidylcholines, very long chain fatty acids (>C20), and unsaturated fatty acids. Unsaturated fatty acids are considered to be protective against cardiovascular disease. In contrast, males carrying the protective allele exhibited decreased long-chain fatty acids (≤C20) and sphingomyelins, which is similarly considered to decrease cardiovascular disease risk. No significant changes in clinically assessed lipids such as LDL-C, high-density lipoprotein (HDL-C), total cholesterol, or triglycerides were observed in females, whereas only LDL-C was significantly changed in males. This indicates that, apart from reducing LDL-C, other mechanisms may contribute to the protective effect of the SORT1 locus. Thus, the analysis of metabolic biomarkers might reveal early disease development that may be overlooked by relying on standard clinical parameters.

Endogenous oestradiol but not testosterone is related to coronary artery disease in men

OBJECTIVES

Men die of coronary artery disease (CAD) more often than women. There is evidence that testosterone either is neutral or has a beneficial effect on male cardiovascular disease. The role of oestrogens in male CAD has been less studied. This study was carried out with the purpose of evaluating the relationship between sex hormone levels and CAD.

DESIGN

Case-control study.

PARTICIPANTS

Men (aged 40-70) submitted to coronary angiography. A 70% occlusion of at least one major coronary artery defined the cases; subjects with ≤ 50% occlusion constituted the control group.

MEASUREMENTS

Blood samples were collected for total testosterone (TT), oestradiol, luteinizing hormone, follicle-stimulating hormone, sex hormone-binding globulin, lipid profile and albumin measurements. Bioavailable and free testosterone, free androgen index (FAI) and free oestrogen index (FEI) were calculated. Oestradiol and TT levels were examined as terciles, based on the whole study population.

RESULTS

Of the 140 patients included, 72 were cases and 68 were controls. The baseline characteristics of the two groups were similar, except for the older age and lower LDL-C in the cases. Oestradiol and FEI but not total, bioavailable and free testosterone and FAI correlated positively with CAD. After adjustments for potential confounders, oestradiol remained statistically significant. The prevalence of CAD was significantly higher in the 3rd than in the 1st tercile of oestradiol.

CONCLUSION

In this study, men with CAD had higher oestradiol and FEI levels. Additional studies are needed to clarify the direction of causality and possible underlying mechanisms.

Estrogen deficiency after menopause does not result in male very-low-density lipoprotein metabolism phenotype

CONTEXT

Sex differences in lipid metabolism result in a less proatherogenic plasma lipid profile in premenopausal women than men. The mechanisms responsible for this are unclear but are thought to be related to differences in the sex hormone milieu in men and women.

OBJECTIVE

Our objective was to evaluate the effect of endogenous sex hormones on very-low-density lipoprotein (VLDL) triglyceride (TG) and apolipoprotein B-100 (apoB-100) metabolism. EXPERIMENTAL DESIGN AND MAIN OUTCOME MEASURES: We measured basal VLDL-TG and VLDL-apoB-100 concentrations and kinetics by using stable isotope-labeled tracers.

SETTING AND PARTICIPANTS

Eight premenopausal women [age, 43 + or - 8 yr; body mass index (BMI), 35 + or - 4 kg/m(2); mean + or - sd], eight postmenopausal women (age, 55 + or - 4 yr; BMI, 34 + or - 4 kg/m(2)), and eight men (age, 41 + or - 13 yr; BMI, 34 + or - 4 kg/m(2)) were studied at Washington University School of Medicine, St. Louis, MO.

RESULTS

VLDL-TG secretion rate was approximately double (P < 0.05) in postmenopausal women and men compared with premenopausal women but not different in postmenopausal women and men. The secretion rate of VLDL-apoB-100 was not different in pre- and postmenopausal women but was greater (P < 0.05) in men than in women.

CONCLUSIONS

Endogenous ovarian sex steroids are responsible for sexual dimorphism in VLDL-TG secretion, whereas VLDL-apoB-100 secretion is not regulated by female reproductive hormones.

Maternal metabolism and obesity: modifiable determinants of pregnancy outcome

BACKGROUND

Obesity among pregnant women is highly prevalent worldwide and is associated in a linear manner with markedly increased risk of adverse outcome for mother and infant. Obesity in the mother may also independently confer risk of obesity to her child. The role of maternal metabolism in determining these outcomes and the potential for lifestyle modification are largely unknown.

METHODS

Relevant studies were identified by searching PubMed, the metaRegister of clinical trials and Google Scholar without limitations. Sensitive search strategies were combined with relevant medical subject headings and text words.

RESULTS

Maternal obesity and gestational weight gain have a significant impact on maternal metabolism and offspring development. Insulin resistance, glucose homeostasis, fat oxidation and amino acid synthesis are all disrupted by maternal obesity and contribute to adverse outcomes. Modification of lifestyle is an effective intervention strategy for improvement of maternal metabolism and the prevention of type 2 diabetes and, potentially, gestational diabetes.

CONCLUSIONS

Maternal obesity requires the development of effective interventions to improve pregnancy outcome. Strategies that incorporate a detailed understanding of the maternal metabolic environment and its consequences for the health of the mother and the growth of the child are likely to identify the best approach.

Effect of anastrozole and tamoxifen on lipid metabolism in Japanese postmenopausal women with early breast cancer

Endocrine therapies that profoundly decrease estrogen levels potentially have a detrimental effect on the cardiovascular system. This study evaluated the effect on lipid metabolism of one such agent, the new generation aromatase inhibitor anastrozole, compared with tamoxifen, when used as adjuvant treatment in postmenopausal Japanese women with early breast cancer. All patients had completed primary surgery and were randomized to anastrozole 1 mg once daily (n=22) or tamoxifen 20 mg once daily (n=22). Anastrozole significantly reduced levels of triglycerides and remnant-like particle cholesterol, whereas tamoxifen significantly increased these. Activity of lipoprotein lipase and levels of high-density lipoprotein cholesterol significantly increased after anastrozole treatment. In contrast, activity of hepatic triglyceride lipase, also a key enzyme of triglyceride metabolism, significantly decreased following treatment with tamoxifen. We thus conclude that in our study anastrozole had a beneficial effect on lipid profiles of postmenopausal women with early breast cancer after 12 weeks of treatment.

Transdermal hormone therapy in postmenopausal women: a review of metabolic effects and drug delivery technologies

Vasomotor symptoms (VMS) associated with menopause can cause significant discomfort and decrease the quality of life for women in the peri-menopausal and post-menopausal stages of life. Hormone therapy (HT) is the mainstay of treatment for menopausal symptoms and is currently the only therapy proven effective for VMS. Numerous HT options are available to treat VMS, including estrogen-only and estrogen-progestogen combination products to meet the needs of both hysterectomized and nonhysterectomized women. In addition to selecting an appropriate estrogen or estrogen-progestogen combination, consideration should be given to the route of administration to best suit the needs of the patient. Delivery systems for hormone therapy include oral tablets, transdermal patches, transdermal topical (nonpatch) products, and intravaginal preparations. Oral is currently the most commonly utilized route of administration in the United States. However, evidence suggests that oral delivery may lead to some undesirable physiologic effects caused by significant gut and hepatic metabolism. Transdermal drug delivery may mitigate some of these effects by avoiding gut and hepatic first-pass metabolism. Advantages of transdermal delivery include the ability to administer unmetabolized estradiol directly to the blood stream, administration of lower doses compared to oral products, and minimal stimulation of hepatic protein production. Several estradiol transdermal delivery technologies are available, including various types of patches, topical gels, and a transdermal spray.

Lifestyle and the Risk of Cardiovascular Disease in Women: Is Physical Activity an Equal Opportunity Benefactor?

Cardiovascular disease is the number one killer of women in the United States. It is estimated that 36.6% of women older than age 20 have some form of cardiovascular disease. In 2004, an estimated 459 100 women died from cardiovascular disease, more than 10 times the number of women who died from breast cancer that same year. Regular physical activity of moderate intensity, such as brisk walking, reduces the risk of cardiovascular disease and mortality in women. The benefits of more vigorous exercise are not clear, but the apparent lack of a dose-response relationship between exercise intensity and cardiovascular benefit may be the result of the design of many epidemiologic and interventional studies. Studies examining the benefits of greater cardiorespiratory fitness for women are limited, but the data suggest that they are similar to that of men. Women may require greater caloric expenditure than men for weight reduction, but this issue may be confounded by other variables such as caloric intake and spontaneous physical activity. The risk of cardiovascular disease associated with type 2 diabetes is much greater in women than in men. Regular physical activity and greater cardiorespiratory fitness are associated with a lower incidence and prevalence of type 2 diabetes in women. Greater cardiorespiratory fitness has also been found to be protective of the metabolic syndrome, but the benefit of physical activity is unclear. Limited evidence suggests that moderate-intensity activities can lower systolic blood pressure in women. There is a pressing need for more research into the health benefits of regular physical activity in women.

No effect of menstrual cycle phase on basal very-low-density lipoprotein triglyceride and apolipoprotein B-100 kinetics

Dyslipidemia, manifested by increased plasma triglyceride (TG), increased total and LDL-cholesterol concentrations and decreased HDL-cholesterol concentration, is an important risk factor for cardiovascular disease. Premenopausal women have a less atherogenic plasma lipid profile and a lower risk of cardiovascular disease than men, but this female advantage disappears after menopause. This suggests that female sex steroids affect lipoprotein metabolism. The impact of variations in the availability of ovarian hormones during the menstrual cycle on lipoprotein metabolism is not known. We therefore investigated whether very-low-density lipoprotein (VLDL)-TG and VLDL-apolipoprotein B-100 (apoB-100) kinetics are different during the follicular (FP) and luteal phases (LP) of the menstrual cycle. We studied seven healthy, premenopausal women (age 27 +/- 2 yr, BMI 25 +/- 2 kg/m(2)) once during FP and once during LP. We measured VLDL-TG, VLDL-apoB-100, and plasma free fatty acid (FFA) kinetics by using stable isotope-labeled tracers, VLDL subclass profile by nuclear magnetic resonance spectroscopy, whole body fat oxidation by indirect calorimetry, and the plasma concentrations of lipoprotein lipase (LPL) and hepatic lipase (HL) by ELISA. VLDL-TG and VLDL-apoB-100 concentrations in plasma, VLDL-TG and VLDL-apoB-100 secretion rates and mean residence times, VLDL subclass distribution, FFA concentration and rate of appearance in plasma, whole body substrate oxidation, and LPL and HL concentrations in plasma were not different during the FP and the LP. We conclude that VLDL-TG and VLDL-apoB-100 metabolism is not affected by menstrual cycle phase.

ApoO, a novel apolipoprotein, is an original glycoprotein up-regulated by diabetes in human heart

Obesity is an independent risk factor for cardiac failure. Obesity promotes excessive deposition of fat in adipose and nonadipose tissues. Intramyocardial lipid overload is a relatively common finding in nonischemic heart failure, especially in obese and diabetic patients, and promotes lipoapoptosis that contributes to the alteration of cardiac function. Lipoprotein production has been proposed as a heart-protective mechanism through the unloading of surplus cellular lipids. We previously analyzed the heart transcriptome in a dog nutritional model of obesity, and we identified a new apolipoprotein, regulated by obesity in heart, which is the subject of this study. We detected this new protein in the following lipoproteins: high density lipoprotein, low density lipoprotein, and very low density lipoprotein. We designated it apolipoprotein O. Apolipoprotein O is a 198-amino acid protein that contains a 23-amino acidlong signal peptide. The apolipoprotein O gene is expressed in a set of human tissues. Confocal immunofluorescence microscopy colocalized apolipoprotein O and perilipins, a cellular marker of the lipid droplet. Chondroitinase ABC deglycosylation analysis or cell incubation with p-nitrophenyl-beta-d-xyloside indicated that apolipoprotein O belongs to the proteoglycan family. Naringenin or CP-346086 treatments indicated that apolipoprotein O secretion requires microsomal triglyceride transfer protein activity. Apolipoprotein O gene expression is up-regulated in the human diabetic heart. Apolipoprotein O promoted cholesterol efflux from macrophage cells. To our knowledge, apolipoprotein O is the first chondroitin sulfate chain containing apolipoprotein. Apolipoprotein O may be involved in myocardium-protective mechanisms against lipid accumulation, or it may have specific properties mediated by its unique glycosylation pattern.

Effects of Transdermal Estrogen Replacement Therapy on Cardiovascular Risk Factors

The prevalence of hypertension and cardiovascular disease increases dramatically after menopause in women, implicating estrogen as having a protective role in the cardiovascular system. However, recent large clinical trials have failed to show cardiovascular benefit, and have even demonstrated possible harmful effects, of opposed and unopposed estrogen in postmenopausal women. While these findings have led to a revision of guidelines such that they discourage the use of estrogen for primary or secondary prevention of heart disease in postmenopausal women, many investigators have attributed the negative results in clinical trials to several flaws in study design, including the older age of study participants and the initiation of estrogen late after menopause.Because almost all clinical trials use oral estrogen as the primary form of hormone supplementation, another question that has arisen is the importance of the route of estrogen administration with regards to the cardiovascular outcomes. During oral estrogen administration, the concentration of estradiol in the liver sinusoids is four to five times higher than that in the systemic circulation. This supraphysiologic concentration of estrogen in the liver can modulate the expression of many hepatic-derived proteins, which are not observed in premenopausal women. In contrast, transdermal estrogen delivers the hormone directly into the systemic circulation and, thus, avoids the first-pass hepatic effect.Although oral estrogen exerts a more favorable influence than transdermal estrogen on traditional cardiovascular risk factors such as high- and low-density lipoprotein-cholesterol levels, recent studies have indicated that oral estrogen adversely influences many emerging risk factors in ways that are not seen with transdermal estrogen. Oral estrogen significantly increases levels of acute-phase proteins such as C-reactive protein and serum amyloid A; procoagulant factors such as prothrombin fragments 1+2; and several key enzymes involved in plaque disruption, while transdermal estrogen does not have these adverse effects.Whether the advantages of transdermal estrogen with regards to these risk factors will translate into improved clinical outcomes remains to be determined. Two ongoing clinical trials, KEEPS (Kronos Early Estrogen Prevention Study) and ELITE (Early versus Late Intervention Trial with Estradiol) are likely to provide invaluable information regarding the role of oral versus transdermal estrogen in younger postmenopausal women.

Perspectives on Dyslipidemia and Coronary Heart Disease in Women

Coronary heart disease (CHD) remains the leading cause of death among American women. Numerous differences exist between younger and older women and between women and men with respect to the pathology of CHD and its incidence and prevalence over the life cycle. Differences in lipoprotein levels and lipid fractions play an important role in CHD risk. Hormonal influences on lipoprotein levels in women are complex, change throughout the life span, and are influenced by the administration of oral contraceptives and hormone replacement therapy. Women with obesity, metabolic syndrome, or diabetes have lipid profiles that adversely affect CHD risk. To date, no randomized trials testing the impact of lifestyle changes on lipoprotein levels and subsequent CHD events in non-institutionalized women have been performed, and women have not been well represented in clinical end point trials of pharmacologic lipid-lowering therapy. Available evidence suggests that lipid-lowering therapy with statins does provide benefit in reducing the risk of coronary events in women; however, women remain undertreated, and more data are needed to determine optimal cardiovascular prevention and treatment in this population.

Progesterone abolishes estrogen and/or atorvastatin endothelium dependent vasodilatory effects

This double blind randomized placebo controlled study assessed the effects of atorvastatin, estradiol and norethisterone, isolated and in combination, on the lipid profile and on vascular reactivity, in post-menopausal women with hypercholesterolemia and arterial hypertension. Ninety-four women aged 50-65 were selected. All have received dietary counseling (4 weeks), placebo (4 weeks), and drug therapy (12 weeks): 17-beta estradiol 2mg/day (E) (n=17); E + norethisterone acetate 1mg/day (P) (n=18); Atorvastatin 10mg/day (A) (n=20); E + A (n=21) and E + P + A (n=18). All treatment modalities have significantly reduced total cholesterol (TC) (E=8.8%, E + P=10.1%, A=27.9%, A + E=29.4% and E + P + A=35.7%) and LDL-cholesterol (LDL-c) levels (E + P + A=46.6%, E + A=45.9%, A=40.2%, E=20.3%, and E + P=12.1%). As concerns HDL-cholesterol (HDL-c), Groups E and E + A had increases of 15.5% and 13.1%, respectively. The addition of a progesterone compound reduced its concentration (Group E + P=-9.1%, and Group E + P + A=-9.5%). By random, approximately half of the patients in each group were designated to the endothelial function evaluation (brachial artery ultrasound). We observed that in Group A (n=10), in Group E (n=10) and with the association (Group E + A) (n=7), there was a significant increase in the flow-mediated vasodilatation as compared to basal measurements. The addition of a progestin has annulled these benefits.

CONCLUSIONS

Atorvastatin has promoted more beneficial effects on TC and LDL-c, whereas estradiol was responsible for an increase in HDL-c. The addition of a progesterone derivative abolished these benefits. Atorvastatin, estradiol or both together improved endothelial function, an effect suppressed by the addition of norethisterone.

Estrogen regulation of growth hormone action

GH plays a pivotal role in regulating body growth and development, which is modulated by sex steroids. A close interplay between estrogen and GH leads to attainment of gender-specific body composition during puberty. The physiological basis of the interaction is not well understood. Most previous studies have focused on the effects of estrogen on GH secretion. There is also strong evidence that estrogen modulates GH action independent of secretion. Oral but not transdermal administration of estrogen impairs the metabolic action of GH in the liver, causing a fall in IGF-I production and fat oxidation. This results in a loss of lean tissue and a gain of body fat in postmenopausal women and an impairment of GH effect in hypopituitary women on GH replacement. The negative metabolic sequelae are potentially important because of the widespread use of oral estrogen and estrogen-related compounds. Estrogen affects GH action at the level of receptor expression and signaling. More recently, estrogen has been shown to inhibit Janus kinase/signal transducer and activator of transcription signaling by GH via the induction of suppressor of cytokine signaling-2, a protein inhibitor for cytokine signaling. This represents a novel paradigm of steroid regulation of cytokine receptors and is likely to have significance for a diverse range of cytokine function.

Sex steroids and plasma lipoprotein levels in healthy women: The importance of androgens in the estrogen-deficient state

The role of endogenous estrogens and androgens and their potential interaction in atherosclerosis is not well understood. Therefore, we investigated the effects of natural menopause and endogenous sex steroids on triglycerides (TG), a major risk factor for cardiovascular disease in women. Fasting lipid and lipoprotein concentrations, postheparin lipase activities, kinetic indicators of triglyceride lipolysis, and various hormone levels, including dehydroepiandrostenedione-sulfate (DHEA-S), (bioavailable) testosterone, and androstenedione, were determined in 18 premenopausal and 18 postmenopausal women, matched for age and body composition. Fasting plasma TG were 0.69 +/- 0.29 mmol/L in postmenopausal women and 0.73 +/- 0.33 mmol/L in premenopausal women (difference not significant [NS]). Approximately 30% of all plasma TG were present in the very-low-density lipoproteins (VLDLs) in both groups. No differences were found between groups in plasma lipolytic potential of TG-rich lipoproteins. Univariate analysis revealed that VLDL-TG concentrations were strongly related to insulin (r = 0.84, P =.0001) and androstenedione (r = 0.65, P =.004) in postmenopausal women. Multivariate analysis of potential determinants of VLDL-TG showed that insulin, androstenedione, and bioavailable testosterone were independent variables, explaining 87% of the variability (r = 0.93, P =.0001) in postmenopausal women. In contrast, in premenopausal women, the only identified predictor of fasting VLDL-TG in univariate and multivariate analysis was insulin (r = 0.72, P =.001). Our results show that the association of androgens with TG varied depending on androgen concentrations, the relative androgenic potential, and most importantly on hormonal milieu. Endogenous androgens were only related to plasma VLDL-TG in the estrogen-deficient state.

Androgens and coronary artery disease

A significant and independent association between endogenous testosterone (T) levels and coronary events in men and women has not been confirmed in large prospective studies, although cross-sectional data have suggested coronary heart disease can be associated with low T in men. Hypoandrogenemia in men and hyperandrogenemia in women are associated with visceral obesity; insulin resistance; low high-density lipoprotein (HDL) cholesterol (HDL-C); and elevated triglycerides, low-density lipoprotein cholesterol, and plasminogen activator type 1. These gender differences and confounders render the precise role of endogenous T in atherosclerosis unclear. Observational studies do not support the hypothesis that dehydroepiandrosterone sulfate deficiency is a risk factor for coronary artery disease. The effects of exogenous T on cardiovascular mortality or morbidity have not been extensively investigated in prospective controlled studies; preliminary data suggest there may be short-term improvements in electrocardiographic changes in men with coronary artery disease. In the majority of animal experiments, exogenous T exerts either neutral or beneficial effects on the development of atherosclerosis. Exogenous androgens induce both apparently beneficial and deleterious effects on cardiovascular risk factors by decreasing serum levels of HDL-C, plasminogen activator type 1 (apparently deleterious), lipoprotein (a), fibrinogen, insulin, leptin, and visceral fat mass (apparently beneficial) in men as well as women. However, androgen-induced declines in circulating HDL-C should not automatically be assumed to be proatherogenic, because these declines may instead reflect accelerated reverse cholesterol transport. Supraphysiological concentrations of T stimulate vasorelaxation; but at physiological concentrations, beneficial, neutral, and detrimental effects on vascular reactivity have been observed. T exerts proatherogenic effects on macrophage function by facilitating the uptake of modified lipoproteins and an antiatherogenic effect by stimulating efflux of cellular cholesterol to HDL. In conclusion, the inconsistent data, which can only be partly explained by differences in dose and source of androgens, militate against a meaningful assessment of the net effect of T on atherosclerosis. Based on current evidence, the therapeutic use of T in men need not be restricted by concerns regarding cardiovascular side effects. Available data also do not justify the uncontrolled use of T or dehydroepiandrosterone for the prevention or treatment of coronary heart disease.

Statins and menopause

During the reproductive period, women generally have lower low-density lipoprotein (LDL) cholesterol and higher high-density lipoprotein cholesterol than age- and diet-matched men. However, these possibly antiatherogenic characteristics of lipoproteins are changed to a potentially atherogenic profile after menopause. Menopause-related changes in lipoprotein profile can be corrected by the administration of hormone replacement therapy (HRT). However, the results of recent studies did not show definite benefits of HRT on coronary heart disease-related mortality rates. On the other hand, several large-scale, long-term clinical trials provide evidence for efficacy and safety of HMG-CoA reductase inhibitors (statins) in both men and women. The results of 19 short-term clinical trials using simvastatin, pravastatin, fluvastatin or lovastatin in postmenopausal women are summarised and discussed. All these investigations reported significant reductions in both total and LDL cholesterol levels. The question of whether statin therapy results in a significant decrease in cardiovascular-related mortality rates along with a better quality of life in postmenopausal women remains to be investigated in large-scale, randomised, double-blind, placebo-controlled clinical trials.

Health status of users of hormone replacement therapy by hysterectomy status in Western Australia

STUDY OBJECTIVES

To compare the demographic, behavioural, and biological correlates of use of hormone replacement therapy (HRT) in women with an intact uterus and women who have undergone hysterectomy.

DESIGN

Cross sectional analysis of data from the Busselton Health Study and the 1994 Healthway-National Heart Foundation Risk Factor Survey.

SETTING

Busselton and Perth, Western Australia, 1994.

PARTICIPANTS

2540 women aged 35-79 years.

MAIN OUTCOME MEASURES

Demographic, behavioural, and biological correlates of use of HRT by hysterectomy status.

RESULTS

In women with an intact uterus, after adjustment for age and place of residence, current use of HRT was significantly associated with having a professional level of occupation, ever use of alcohol, having a history of smoking, and a lower body mass index. Current users of HRT had significantly lower levels of total cholesterol and higher levels of triglycerides than non-users. In women who had undergone hysterectomy, the only non-biological characteristic associated with use of HRT was having a history of smoking. Current users of HRT had lower levels of systolic blood pressure, lower levels of LDL cholesterol, higher levels of HDL cholesterol, and higher levels of triglycerides. The association between use of HRT and participation in exercise, level of systolic blood pressure, level of HDL cholesterol, and total/HDL cholesterol ratio varied significantly by hysterectomy status. After adjustment for age and place of residence, the mean levels of systolic and diastolic blood pressure, body mass index, waist/hip ratio, LDL cholesterol, and total/HDL cholesterol ratio were highest in women who had undergone hysterectomy and were not using HRT.

CONCLUSIONS

Demographic/behavioural and biological correlates of use of HRT varied depending on hysterectomy status. Demographic and behavioural characteristics were more important as selection factors for use of HRT in women with an intact uterus than in women who had undergone hysterectomy. Women who had undergone hysterectomy and were not using HRT had a significantly worse profile for CHD than did women with an intact uterus. These results indicate that any bias in estimates of the protective effect of HRT on risk of CHD in observational studies is likely to depend on the prevalence of hysterectomy within the study population. Hysterectomy status needs to be taken into account in any studies that investigate the effect of HRT on risk of CHD.

Update on clinical role of tamoxifen

PURPOSE OF REVIEW

Breast cancer is the most common malignancy amongst women in the United States and decreased mortality over the past decade has been attributed to a combination of screening and adjuvant therapies. There has been a resurgence of interest in hormonal therapies and this article discusses the clinical status of tamoxifen in the context of emerging alternative agents for treatment and prevention of breast cancer.

RECENT FINDINGS

Tamoxifen has served as a prototype for the development of selective estrogen receptor modulators at the laboratory-clinical interface. Molecular technologies have permitted elucidation of mechanisms for tissue specific action and led to newer selective estrogen receptor modulators with potentially greater antitumour efficacy and attenuated uterotrophic profile. Publications over the past 12 months have emphasized the risks of thromboembolism and endometrial carcinoma associated with tamoxifen use which has accelerated application of other hormonal agents for treatment of advanced disease and as neoadjuvant therapy. This article reviews the current role of tamoxifen in the treatment of early and advanced breast cancer together with its potential for chemoprevention. Models for quantitative risk assessment are being developed to identify women for whom chemoprotection is justified.

SUMMARY

Recent data showing a survival advantage for the aromatase inhibitor letrozole compared with tamoxifen in the advanced setting and improvement in disease-free survival for the aromatase inhibitor anastrozole versus tamoxifen as adjuvant treatment may herald a major shift in standard first-line endocrine therapies for both advanced and early disease and ultimately chemoprevention of breast cancer. Other agents including newer SERMs and pure antiestrogens are undergoing phase III clinical trials and future endocrine and biological therapies are likely to include more selective and targeted therapies, which may be efficacious in both hormone-sensitive and receptor-negative disease.

Lipoprotein abnormalities related to women's health

Although women have a greater life expectancy than men and tend to develop coronary artery disease (CAD) 10 to 20 years later than men, the burden of CAD in women is high, with a lifetime risk >20%. Beginning at puberty, women have more favorable lipoprotein profiles than men. High-density lipoprotein (HDL) cholesterol levels remain higher in women than men throughout their lifetime. Low-density lipoprotein (LDL) cholesterol levels in women exceed those in men after middle age, but despite a shift toward smaller, denser LDL particles at the time of menopause, LDL particle number remains lower in women than in men throughout the lifespan. Lipoprotein levels strongly predict incident and recurrent CAD events in both sexes, and LDL particle size may be a better predictor of premature CAD in women than of CAD associated with advanced age. The effects of postmenopausal hormonal therapy on lipoprotein levels are complex, and the benefits of such therapy are not established. In contrast, lifestyle changes and pharmacological lipid-lowering therapy have been shown to favorably influence the natural course of atherosclerotic disease and reduce cardiovascular events in men and women.

Effects of resistance training and detraining on muscle strength and blood lipid profiles in postmenopausal women

OBJECTIVES

To study the effects of eight weeks of supervised, low intensity resistance training (80% of 10 repetition maximum (10RM)) and eight weeks of detraining on muscle strength and blood lipid profiles in healthy, sedentary postmenopausal women.

SUBJECTS

Fifteen postmenopausal women, aged 49-62 years, took part in the study. Subjects were assigned to either a control (n = 7) or training (n = 8) group. The training regimen consisted of three sets of eight repetitions of leg press, bench press, knee extension, knee flexion, and lat pull-down, three days a week at 80% of 10RM. Dynamic leg strength, 10RM, and blood lipid profiles (total cholesterol (TC), low and high density lipoprotein cholesterol (LDL-C, HDL-C), triglycerides, and very low density lipoprotein cholesterol (VLDL-C)) were measured at baseline, after eight weeks of training, and after a further eight weeks of detraining.

RESULTS

Eight weeks of resistance training produced significant increases in knee extension (F(1,13) = 12.60; p<0.01), bench press (F(1,13) = 13.79; p<0.01), leg press (F(1,13) = 15.65; p<0.01), and lat pull-down (F(1,13) = 16.60; p<0.005) 10RM strength tests. Although 10RM strength decreased after eight weeks of detraining, the results remained significantly elevated from baseline measures. Eight weeks of training did not result in any significant alterations in blood lipid profiles, body composition, or dynamic isokinetic leg strength. There were no significant differences in any of the variables investigated over the 16 week period in the control group.

CONCLUSIONS

These data suggest that a short, low intensity resistance training programme produces substantial improvements in muscle strength. Training of this intensity and duration was not sufficient to produce significant alterations in blood lipid concentrations.

Age-related changes in fatty acids in obese offspring of streptozotocin-induced diabetic rats

OBJECTIVE

The long-term effects of fetal hyperinsulinemia, time course of changes in liver and very-low-density lipoprotein (VLDL) lipid levels and fatty acid compositions were investigated in obese offspring of streptozotocin-induced mildly diabetic rats.

RESEARCH METHODS AND PROCEDURES

Mild hyperglycemia in pregnant rats was induced by intraperitoneal injection of streptozotocin on day 5 of gestation. Control pregnant rats were injected with citrate buffer. Liver and VLDL lipids and fatty acids were analyzed in offspring at different ages.

RESULTS

At birth, obese pups had higher VLDL triglyceride levels, saturated fatty acids, and C20:4n-6. They also had lower C18:2n-6 proportions in VLDL triglycerides, phospholipids, and cholesteryl esters than controls pups. In 1-month-old male and female obese rats, VLDL and liver lipid amounts were similar to those in their respective controls; however, high levels of C18:2n-6 and C20:4n-6 were noted in liver and VLDL lipids. At the age of 2 months, liver and VLDL triglyceride levels were higher in obese females than in control females. Fatty acid abnormalities seen in obese rats included low C18:3n-3 and high C22:6n-3 proportions in liver triglycerides and phospholipids. At the age of 3 months, obese rats, both males and females, compared with control animals, had higher VLDL and hepatic lipids with reduced C20:4n-6 levels and polyunsaturated/saturated fatty acids ratios in hepatic and VLDL triglycerides and phospholipids.

DISCUSSION

Fetal obesity, associated with alterations in VLDL lipid fatty acid composition, represents an important risk factor for adult obesity and diabetes.

The effect of tibolone on the lipoprotein profile of postmenopausal women with type III hyperlipoproteinemia

OBJECTIVE

To investigate the short-term effect of treatment with tibolone on plasma lipid and lipoprotein levels in postmenopausal women with type III hyperlipoproteinemia (HLP).

DESIGN AND INTERVENTION

Patients were randomized to receive, in a double-blind cross-over fashion, a fixed dose of tibolone, 2.5 mg once daily or placebo for 8 weeks. The two treatment periods were separated by a wash-out period of 6 weeks. At each visit body weight and blood pressure were determined. Before and after each treatment period, fasting venous blood samples were obtained from the patients for biochemical measurements.

SETTING

The Leiden University Medical Center.

SUBJECTS

Postmenopausal women with type III HLP (aged < or = 65 years) were recruited from the Lipid Clinics of the Leiden University Medical Center, the Amsterdam Medical Center, the Utrecht Medical Center and the University Hospital Rotterdam. Five out of 25 women with type III HLP were eligible to be included in the study. Four of the five included patients completed the study according to the protocol. One patient was excluded from blinded therapy because total cholesterol levels increased above 20 mmol L(-1).

MAIN OUTCOME MEASURES

A significant reduction of plasma triglyceride, total cholesterol, VLDL cholesterol and VLDL triglyceride levels.

RESULTS

Plasma triglyceride and total cholesterol levels decreased from 6.82 +/- 3.58 to 2.45 +/- 1.36 mmol L(-1) and from 13.53 +/- 3.64 to 6.61 +/- 2.03 mmol L(-1), respectively (both P < 0.05). The body mass index remained unchanged. The glycated haemoglobin percentage decreased significantly from 5.8 to 5.3%. Treatment with tibolone resulted in a profound reduction in plasma apolipoprotein E, VLDL cholesterol and VLDL triglyceride levels (mean reductions of 66, 77 and 70%, respectively, P < 0.05).

CONCLUSIONS

Tibolone is a valuable adjuvant to current therapy in postmenopausal women with type III HLP.

The influence of apo E phenotypes on the plasma triglycerides response to hormonal replacement therapy during the menopause

OBJECTIVE

To study the influence of apo E phenotype in plasma lipids, especially in triglycerides levels, in menopausal women receiving hormonal replacement therapy (HRT).

METHODS

One hundred and ten postmenopausal women were studied. Plasma total cholesterol (TC), HDL-C and triglycerides (TG) were measured before and after 3 months of HRT and the apo E phenotype was determined. According to the apo E phenotype the sample was divided into three groups: E2/E3 (n=28), E3/E3 (n=96) and E4/E3 (n=25).

RESULTS

In the pre-treatment state, higher plasma levels of TC and TC/HDL-C ratio were observed in women with phenotype E3/E4 (P<0.0001 and P<0.02, respectively), while higher plasma TG levels were found in the apo E2/E3 group (P<0.0001). After HRT, women with phenotype E3/E4 showed higher levels of TC and TC/HDL-C ratio (P<0.0001 and P<0.006, respectively). The apo E2/E3 phenotype group showed increased levels of TG (P<0.0001). In the multivariant analysis the changes of TG after HRT were related to the type of treatment used (P<0.001), age (P=0.05) and the apo E phenotype (E2/E3).

CONCLUSION

Women with phenotype E2/E3 have higher plasma TG levels and show a significant post HRT increase compared with the other phenotypes. Other factors with a lower impact on TG levels are age and progestagen association.

Comparison of the long-term effects of oral estriol with the effects of conjugated estrogen on serum lipid profile in early menopausal women

OBJECTIVE

We investigated the long-term effects of oral estriol (E(3)) on serum levels of total cholesterol (t-Cho), high-density lipoprotein cholesterol (HDL-Cho), low-density lipoprotein cholesterol (LDL-Cho), and triglycerides in early menopausal women.

METHODS

We studied 67 healthy early menopausal women who were treated for 48 months with 2.0 mg of E(3) plus 2.5 mg of medroxyprogesterone acetate daily (E(3) group, n=21), 0.625 mg of conjugated estrogen plus 2.5 mg of medroxyprogesterone acetate daily (CE group, n=19), or 1.0 microg of 1alpha-hydroxyvitamin D(3) daily or 1.8 g of calcium lactate containing 250 mg of elemental calcium daily (control group, n=27). The serum levels of t-Cho, HDL-Cho, LDL-Cho, and triglycerides were evaluated at baseline and every 6 months.

RESULTS

After 48 months of treatment, the t-Cho decreased significantly by 4.3+/-2.1% (mean+/-SE) from baseline in the E(3) group, did not change in the CE group (-1.9+/-2.1%), and significantly increased (5.4+/-3.4%) in the control group. The HDL-Cho significantly increased in the CE group (10.7+/-2.4%), but not in the E(3) group (3.8+/-3.3%) or in the control group (-3.6+/-3. 0%). The LDL-Cho significantly decreased in the CE group (-11.4+/-4. 0%), did not change in the E(3) group (-5.2+/-3.6%), and significantly increased in the control group (11.8+/-6.3%). The triglyceride level decreased significantly in the E(3) group (-6. 7+/-4.9%), whereas it significantly increased in the CE group (17. 6+/-11.4%), and did not change in the control group (6.1+/-6.4%).

CONCLUSIONS

Oral E(3) prevented a postmenopausal rise in the t-Cho. Oral estriol did not induce the hypertriglyceridemia that was seen after treatment with conjugated estrogen. Oral E(3) may be a useful alternative therapy in women with hypertriglyceridemia and in women who are reluctant to continue conventional hormone replacement therapy because of uterine bleeding.

Plasma endothelin in postmenopausal women with type 2 diabetes mellitus and metabolic syndrome: a comparison of oral combined and transdermal oestrogen-only replacement therapy

AIM

Type 2 diabetes and metabolic syndrome are major cardiovascular risk factors in postmenopausal women, but the role of vasoconstrictive endothelin-1 (ET-1) in these conditions is not known. We studied the levels of ET-1 and the effect of postmenopausal hormonal therapy on ET-1 levels in postmenopausal women.

METHODS

We compared plasma levels of ET-1 in 22 postmenopausal type 2 diabetic women and 14 postmenopausal women with metabolic syndrome with plasma levels in 10 healthy postmenopausal control women. The basal values for ET-1 were measured for all groups. These women were then randomised to receive in a double-dummy, crossover trial: either oral continuous oestradiol (2.0 mg) + norethisterone acetate (1.0 mg) per day or continuous transdermal oestrogen-only (50 mg/day) for 3 months. Between the active therapy there were 3-month wash-out periods. ET-1-values were measured again at the end of each treatment period.

RESULTS

The type 2 diabetic women had significantly (p < 0.003) elevated ET-1 levels (4.8+/-1.0 pg/ml) whereas those with metabolic syndrome (4.4+/-1.7 pg/ml]) had non-significantly (NS) elevated ET-1 levels compared to controls (3.6+/-0.3 pg/ml). Both oral and transdermal hormone replacement therapy (HRT) failed to affect plasma ET-1 except in 14 hypertensive women from the diabetes and metabolic syndrome groups who were on angiotensin convertase enzyme (ACE) inhibitors. These women's ET-1 levels before oral HRT (4.6+/-1.1 pg/ml) fell to 4.1+/-0.9 pg/ml (p < 0.05).

CONCLUSIONS

Type 2 diabetes in postmenopausal women is associated with elevated ET-1 levels. Oestrogen replacement therapy does not affect the levels of ET-1 in postmenopausal women with type 2 diabetes or metabolic syndrome.

Serum lipid levels during and after adjuvant toremifene or tamoxifen therapy for breast cancer

Tamoxifen decreases serum cholesterol (S-cholesterol) level about 10% and low-density lipoprotein cholesterol (S-LDL) 15-20%, but in most studies it has increased serum triglyceride levels and had little effect on serum high-density cholesterol (S-HDL). The effect of another antiestrogen, toremifene, on the serum lipid profile has not been completely studied. We monitored serum lipid levels longitudinally in 141 axillary node-positive postmenopausal breast cancer patients who received randomly either 40 mg toremifene or 20 mg tamoxifen as adjuvant therapy for 36 months, and in 34 postmenopausal women who received no adjuvant systemic therapy after surgery for axillary node-negative breast cancer. No significant differences were found between the drugs in their effects on S-cholesterol, LDL, HDL, or triglyceride levels, or on the cholesterol-to-HDL or LDL-to-HDL ratios. For both drugs the S-cholesterol and S-LDL absolute lowering effect was the greater the higher the pretreatment level. For a patient with a median pretreatment value, toremifene decreased S-cholesterol 6% and tamoxifen 13%, and S-LDL decreased by 13% and 23%, respectively, at 6 months of therapy. Six months after stopping three-year antiestrogen therapy S- cholesterol and S-LDL levels had returned to the pretreatment levels. In conclusion, we found no major differences between 40 mg toremifene and 20 mg of tamoxifen in their effect on the serum lipid levels, which return to the pretreatment levels within 6 months after cessation of therapy.

Biphasic effects of the natural estrogen 17beta-estradiol on hepatic cholesterol metabolism in intact female rats

The protective influence of estrogens in cardiovascular disease is believed to be partly due to beneficial effects on cholesterol metabolism. Much of the experimental data are based on models in which synthetic estrogens have been used in pharmacological doses, and therefore, the physiological role of estrogens in cholesterol metabolism is uncertain. To evaluate this important issue, we performed experiments in intact female rats with use of the natural estrogen 17beta-estradiol (E2) administered either subcutaneously or orally. After physiological doses of E2 (< or =0.04 mg. kg(-1). d(-1)) were administered, plasma levels of high density lipoprotein (HDL) cholesterol and apolipoprotein (apo) A-I were increased. In the liver, 3-hydroxy-3-methylglutaryl coenzyme A reductase and cholesterol 7alpha-hydroxylase activities were increased, as well as cholesterol 7alpha-hydroxylase mRNA levels. These effects were abolished during treatment with higher doses of E2, whereas apo A-I mRNA increased in a dose-dependent way. After treatment with pharmacological doses of E2 (> or =0.2 mg. kg(-1). d(-1)), the number of hepatic low density lipoprotein receptors increased and plasma cholesterol was reduced. These effects were similar after both oral and subcutaneous administration of E2. Our results show that the responses to E2 are biphasic: plasma HDL, apo A-I, and hepatic enzyme activities governing bile acid and cholesterol synthesis increased only at physiological doses of E2. At pharmacological doses of E2, hepatic low density lipoprotein receptors are stimulated and plasma cholesterol is reduced. Therefore, under physiological conditions, E2 exerts its major effects on hepatic cholesterol metabolism through mechanisms other than stimulation of low density lipoprotein receptor expression.

The EWA (estrogen in women with atherosclerosis) study: a randomized study of the use of hormone replacement therapy in women with angiographically verified coronary artery disease. Characteristics of the study population. Effects on lipids and lipoproteins

OBJECTIVES

To evaluate the effects of hormone replacement therapy (HRT) on lipids and lipoproteins in postmenopausal women with coronary artery disease.

SETTING

In this single-centre, controlled and randomized study taking place in a tertiary referral clinic, patients were examined at baseline, and after 3 and 12 months. All analyses were performed examiner-blind.

SUBJECTS

Postmenopausal women (n = 118) with angiographically verified coronary artery disease were recruited consecutively from patients referred for investigational procedures due to coronary artery disease.

INTERVENTIONS

The women were randomized to HRT, i.e. transdermal application of continuous 17-beta oestradiol with cyclic medroxyprogesterone actetate tablets every 3rd month for 14 days, or to a control group.

MAIN OUTCOMES

Effects on lipids and lipoproteins.

RESULTS

After 3 months of unopposed oestradiol, triglycerides decreased significantly compared to the control group (P = 0.006). Sequential administration of medroxyprogesterone caused a decrease in HDL cholesterol (P = 0.01), concomitantly with a decrease in ApoA1 lipoproteins (P = 0.007). No other changes in lipids or lipoproteins were observed. After 12 months of therapy, no significant differences were observed between the two groups in lipid or lipoprotein levels. Concomitant statin treatment did not alter the main findings.

CONCLUSIONS

In postmenopausal women with established coronary artery disease in whom the majority is treated with statins, no additional effect of HRT on lipids or lipoproteins could be observed except for a transient decrease in triglycerides in the initial unopposed oestradiol phase. No deleterious effect could be observed during medroxyprogesterone administration except for a small transient decrease in HDL cholesterol and ApoA1 lipoproteins.

A randomized trial on effects of hormone therapy on ambulatory blood pressure and lipoprotein levels in women with coronary artery disease

OBJECTIVE

To investigate 1-year effects of hormone replacement therapy (HRT) on ambulatory blood pressure (ABP) and lipoprotein levels in postmenopausal women with coronary artery disease (CAD).

METHODS

Sixty patients at a mean age (+/- SD) of 59 +/- 7 years were randomized into three groups: conjugated equine oestrogens (CEE) 0.625 mg daily (n = 20), 50 microg 17beta-oestradiol transdermally (TTSE) per 24 h (n = 20) or placebo (n = 20) for 18 days, then combined with medroxyprogesterone acetate 5 mg for 10 days. Each cycle of 28 days was repeated for one year.

RESULTS

Night-time systolic ABP had decreased by 9.6% (P= 0.0075) in 15 of 18 women in the CEE group and by 22% in 12 of 13 women (P = 0.0034) in the placebo group after 1 year. In the CEE group, a 4.6% rise in daytime systolic ABP (P< 0.05) and a 4.2% rise in night-time systolic ABP (P< 0.05) appeared from baseline to 6 months in 13 of 18 women. In the CEE group (14 women analysed), high-density lipoprotein levels showed a 15.8% increase (P= 0.0018) in 13 women, low-density lipoprotein levels a 15.2% decrease (P= 0.0129) in 12 women and total cholesterol levels a 7.5% decrease (P = 0.057) in 11 women after 1 year. Triglyceride levels showed no changes. In the TTSE group and in the placebo group, with 12 and 13 women analysed respectively, no significant changes appeared.

CONCLUSIONS

One year of HRT in patients with CAD does not influence ABP. Oral HRT induces beneficial effects on lipoprotein levels.

Understanding coronary heart disease as a consequence of defective regulation of apolipoprotein B metabolism

Further understanding of the causative link between plasma lipids and coronary heart disease will come from a deeper appreciation of the impact of lipoprotein heterogeneity on the processes of atherosclerosis and thrombosis. It is now widely appreciated that remnants of triglyceride-rich lipoproteins, IDL and specific LDL subfractions may have a role in atherogenesis disproportionate to the plasma concentrations of these species. Elucidation of the factors that control the distribution of subfractions within the spectrum of apolipoprotein B-containing lipoproteins is underway but far from complete. Important influences are the rate and nature of lipoproteins secreted from the liver, the extent of remodelling by lipid exchange and lipolysis in the circulation and the affinity of the various particles for cell surface receptors.

Oestrogen replacement therapy and coronary heart disease

This review highlights recent progress in our understanding of the beneficial effects of hormone replacement therapy (HRT) in cardiovascular disease (CVD). The fact that HRT is increasingly advocated has raised concern about possible adverse effects weighed against the potential benefits of HRT regimens. Both favourable and unfavourable effects of oestrogens and HRT regimens on CVD risk factors are increasingly recognized. Consequently, the picture on cardiovascular effects of oestrogen and HRT has become more complicated, and research in this field has extended to novel areas.

Estradiol stimulates apolipoprotein A-I- but not A-II-containing particle synthesis and secretion by stimulating mRNA transcription rate in Hep G2 cells

Estrogen therapy increases plasma HDL levels, which may reduce cardiovascular risk in postmenopausal women. The mechanism of action of estrogen in influencing various steps in hepatic HDL and apolipoprotein (apo) A-I synthesis and secretion are not fully understood. In this study, we have used the human hepatoblastoma cell line (Hep G2) as an in vitro model system to delineate the effect of estradiol on multiple regulatory steps involved in hepatic HDL metabolism. Incubation of Hep G2 cells with estradiol resulted in the following statistically significant findings: (1) increased accumulation of apoA-I in the medium without affecting uptake/removal of radiolabeled HDL-protein; (2) accelerated incorporation of [3H]leucine into apoA-I; (3) selective increase in [3H]leucine incorporation into lipoprotein (LP) A-I but not LP A-I+A-II HDL particles (HDL particles without and with apoA-II, respectively); (4) increased ability of apoA-I-containing particles to efflux cholesterol from fibroblasts; (5) stimulated steady state apoA-I but not apoA-II mRNA expression; and (6) increased newly transcribed apoA-I mRNA message without effect on apoA-I mRNA half-life. The data indicate that estradiol stimulates newly transcribed hepatic apoA-I mRNA, resulting in a selective increase in LP A-I, a subfraction of HDL that is associated with decreased atherosclerotic cardiovascular disease, especially in premenopausal women.

Cellular and molecular basis of estrogen's neuroprotection. Potential relevance for Alzheimer's disease

Alzheimer's disease (AD) is one of the most common types of dementia among the aged population, with a higher prevalence in women. The reason for this latter observation remained unsolved for years, but recent studies have provided evidence that a lack of circulating estrogen in postmenopausal women could be a relevant factor. Moreover, follow-up studies among postmenopausal women who had received estrogen-replacement therapy (ERT), suggested that they had a markedly reduced risk of developing AD. In addition, studies among older women who already had AD indeed confirmed that a decrease in estrogen levels was likely to be an important factor in triggering the pathogenesis of the disease. In this review article, we will discuss the evidence suggesting that estrogen may have a protective role against AD, mainly through its action as: a trophic factor for cholinergic neurons, a modulator for the expression of apolipoprotein E (ApoE) in the brain, an antioxidant compound decreasing the neuronal damage caused by oxidative stress, and a promoter of the physiological nonamyloidogenic processing of the amyloid precursor protein (APP), decreasing the production of the amyloid-beta-peptide (A beta), a key factor in the pathogenesis of AD.

Apolipoprotein E2 transgenic rabbits. Modulation of the type III hyperlipoproteinemic phenotype by estrogen and occurrence of spontaneous atherosclerosis

Transgenic rabbits were produced that expressed high plasma levels (30-70 mg/dl) of human apolipoprotein (apo) E2(Cys-158), an apoE variant associated with the human genetic disorder type III hyperlipoproteinemia (HLP). Male transgenic rabbits fed normal chow had up to 8-fold (289 +/- 148 mg/dl) and 15-fold (697 +/- 452 mg/dl) increases in plasma total cholesterol and triglycerides, respectively, compared with nontransgenic males. Female transgenic rabbits had only a modest hyperlipidemia (total cholesterol, 140 +/- 46 mg/dl; total triglycerides, 174 +/- 66 mg/dl). Both sexes displayed the hallmarks fo type III HLP: beta-migrating very low density lipoproteins (beta-VLDL) (intestinal and hepatic remnant lipoproteins) and significantly increased VLDL and intermediate density lipoproteins. Apolipoprotein E2-containing VLDL particles were cleared from teh circulation more slowly and were more resistant to lipoprotein lipase-mediated lipolysis than normal VLDL. Only females had increased high density lipoproteins (HDL) (40%), which were shifted from typical small HDL to larger HDL1. Plasma apoE2 was predominantly associated with beta-VLDL in males and with HDL in females. To ascertain reasons for the phenotypic gender difference, we treated male transgenic rabbits with 17alpha-ethinyl estradiol. Estrogen treatment for 10 days dramatically decreased total cholesterol (73%) and triglycerides (89%) and converted beta-VLDL to pre-beta-migrating VLDL. Concomitantly, lipoprotein lipase and hepatic lipase activities increased by 90%, low density lipoprotein receptor activity was stimulated significantly, apoE2 was redistributed to HDL, and HDL were converted to HDL1. Conversely, ovariectomy in female transgenic rabbits significantly increased total cholesterol (75%), triglycerides (117%), and beta-VLDL, while decreasing lipoprotein lipase and hepatic lipase activities by 35% and redistributing apoE2 to the beta-VLDL. Thus, estrogen status appears to be responsible for much of the gender difference of the lipoprotein phenotype, mainly by modulating both lipase and low density lipoprotein receptor activities. Furthermore, transgenic rabbits fed normal chow for 11 months developed fatty streaks, and some had more advanced atherosclerotic lesions, especially around the aortic arch and proximal abdominal aorta. The lesions were more extensive in males, roughly correlating with the magnitude of the hyperlipidemia. Therefore, high plasma levels of human apoE2 in transgenic rabbits result in a type III HLP phenotype, in which males have both more severe hyperlipidemia and more extensive atherosclerosis than females.

Serum lipids, lipoprotein lp(a), and plasminogen activator inhibitor-1 in patients with Turner's syndrome before and during growth hormone and estrogen therapy

OBJECTIVE

To evaluate whether girls with Turner's syndrome have an increased risk for cardiovascular disease due to alterations in their lipoprotein metabolism.

DESIGN

Controlled clinical study.

SETTING

Private academic hospital.

PATIENT(S)

Fifteen untreated girls with Turner's syndrome were studied initially; 11 of these patients were evaluated further while on therapy.

INTERVENTION(S)

Serum lipids, lipoprotein lp(a), and plasminogen activator (PA) inhibitor-1 were measured before and during 6 months of either GH or estrogen (E) treatment.

MAIN OUTCOME MEASURE(S)

Serum lipids, lipoprotein lp(a), and PA inhibitor-1 (PAI-1).

RESULT(S)

Total and low-density lipoprotein (LDL) cholesterol, triglycerides, lipoprotein lp(a), and PA inhibitor-1 levels were normal in Turner's syndrome patients compared with age-matched controls; HDL cholesterol was increased. During GH treatment, a significant decrease in total and LDL cholesterol was noted, whereas lipids, lipoprotein(a), and PA inhibitor-1 levels did not change with E therapy.

CONCLUSION(S)

The normal lipoproteins of untreated adolescents with Turner's syndrome, as well as the further decrease of total and LDL cholesterol during GH treatment, would seem to indicate that lipoproteins do not increase the cardiovascular risk of these girls.

Differences in erythrocyte membrane cholesterol to phospholipids ratio in postmenopausal women with and without hormone replacement

OBJECTIVES

To investigate the changes in the cholesterol:phospholipids (C/PL) ratio of erythrocyte membrane in post-menopausal women with and without hormone replacement therapy (HRT).

STUDY DESIGN

A cross-sectional study including 83 patients divided into three groups according to HRT (group 1, no HRT (n = 52); group 2, combined HRT (n = 16); and group 3, estrogen-only therapy (n = 15)).

RESULTS

The C/PL ratio was lower in group 2 with respect to group 1 and group 3 (P = 0.03). No difference was found in erythrocyte membrane cholesterol between the three groups; however, the phospholipid concentration was higher in group 2 with respect to the other groups (P < 0.05). In the control group, C/PL values correlated positively with plasma LDL levels (P < 0.005) and negatively with HDL levels (P < 0.005).

CONCLUSIONS

From our data the addition of progestogens in HRT appears to decrease the C/PL of the erythrocyte membrane possibly resulting in a beneficial effect on rheological properties of erythrocyte membrane. The results of our study thus suggest additional benefits from supplementation of progestogens in HRT, in addition to prevention of estrogen dependent endometrial hyperplasia and adenocarcinoma.

Astrocytes and microglia respond to estrogen with increased apoE mRNA in vivo and in vitro

This study examined the regulation of apolipoprotein E (apoE) by 17beta-estradiol (E2) in brain glia, using rats with regular ovulatory cycles as an in vivo model and cultured astrocytes and mixed glia as in vitro models. Two brain regions were examined which had demonstrated transient synaptic remodeling during the estrous cycle. In the hippocampal CA1 region and the hypothalamic arcuate nucleus, apoE mRNA was elevated at proestrus when plasma E2 was high and synaptic density was increasing. Both astrocytes and microglia contributed to this increase in apoE mRNA. In vitro, E2 treatment had no effect on apoE mRNA levels in monotypic cultures of either astrocytes or microglia. In contrast, mixed glial cultures responded to E2 with increased apoE mRNA and protein, suggesting that heterotypic cellular interactions are important in the brain response to estrogens. In situ hybridization in combination with cell-specific markers showed that E2 increased apoE mRNA levels in both astrocytes and microglia. These results, which are the first evidence of apoE mRNA localization to microglia in vivo and the control of apoE expression in brain cells by estrogens, are discussed in terms of the possible protective role of E2 in Alzheimer's disease and prior findings that emphasize the expression of apoE mRNA in astrocytes within the brain.

Hormone replacement therapy lowers plasma Lp(a) concentrations. Comparison of cyclic transdermal and continuous estrogen-progestin regimens

To study the responses of serum lipoproteins, apoproteins (apo's), and lipoprotein(a) (Lp[a]) to two frequently used hormone replacement therapies (HRTs), 120 postmenopausal women were randomly allocated to receive either transdermal therapy consisting of 28-day cycles with patches that delivered 17 beta-estradiol (50 micrograms/d) combined with cyclic oral medroxyprogesterone acetate (10 mg/d for 12 days per cycle) or continuous oral 17 beta-estradiol (2 mg/d) together with norethisterone acetate (1 mg/d) for 12 months. Blood samples were taken before and at 6 and 12 months of HRT. Concentrations of serum total, low density lipoprotein (LDL) and high density lipoprotein (HDL) cholesterol decreased by 14% (P < .001), 17% (P < .001), and 9% (P < .001) in the oral HRT group. Respective changes were 5.7% (P < .001), 4.8% (P < .05), and 4.7% (NS) in the transdermal group. Serum triglycerides remained unchanged in the oral group but decreased by 15.7% (P < .001) in the transdermal group. We observed only trivial changes in serum apo B levels. The changes in apo A-I levels paralleled those of HDL cholesterol in the oral HRT group. The concentration of serum Lp(a) decreased by 31% (P < .001) and 16% (P < .001) in the two groups. The combination of progestin and transdermal estrogen was not associated with any further change of Lp(a). The decrement in Lp(a) during therapy was positively associated with baseline Lp(a) levels in both groups (r = .96, P < .001 and r = .88, P < .001). Thus, both HRT regimens were highly effective in lowering elevated Lp(a) levels in postmenopausal women. The divergent responses of LDL and HDL cholesterol in the two HRT groups may influence the potential cardioprotective effects of the two HRT regimens. Prospective trials are needed to define the long-term effects with respect to coronary heart disease risk.

Serum lipid, lipoprotein and apolipoprotein changes in gestational diabetes mellitus: a cross-sectional and prospective study

AIMS

To compare serum lipid, lipoprotein and apolipoprotein concentrations during and six to 12 months after pregnancy in control and diabetic women.

METHODS

The serum lipid, lipoprotein and apolipoprotein concentrations were measured in 20 women with gestational diabetes mellitus (GDM) and 22 women with normal glucose tolerance (controls) during the third trimester of pregnancy and six to 12 months after delivery.

RESULTS

During pregnancy the women with GDM had higher serum triglyceride (mean (95% confidence interval (CI)), 2.91 (2.22-3.51) v 2.1 (1.75-2.52)) but lower low density lipoprotein (LDL) cholesterol concentrations compared with controls (mean (SD), 3.08 (1.2) v 4.01 (1.1). Total cholesterol, high density lipoprotein (HDL) cholesterol and apolipoprotein concentrations were not significantly different between the two groups. After pregnancy, total cholesterol, HDL cholesterol, triglyceride, and apolipoprotein A1 and B decreased in a parallel manner, resulting in lower concentrations, comparable between the two groups. LDL cholesterol concentrations decreased after pregnancy in the controls (mean (SD), 4.01 (1.1) v 2.69 (0.6)) but not in those with GDM (3.08 (1.2) v 2.72 (0.7)). The change in lipid concentrations was not related to change in weight.

CONCLUSION

Development of diabetes during pregnancy induces a state of dyslipidaemia characterised by elevated triglyceride concentrations, as seen in other insulin resistance states. However, GDM seems to blunt the increase in LDL cholesterol during pregnancy and this requires further investigation. Whether the changes in lipoprotein metabolism in GDM are significant for the health status of the mother and the foetus requires further study.

Cyclical variation of plasma lipids, apolipoproteins, and lipoprotein(a) during menstrual cycle of normal women

We report herein the effects of cyclical variations of endogenous sex steroids during the menstrual cycle on plasma lipids and apolipoproteins (apo) in normal women. We examined 16 normal women (age range 25-36 yr) with normal menstrual cycles of 28-31 days. The study covered the period from the 1st day of a menstrual phase (basal) until the 1st day of the following menstrual phase. During the study all women maintained a normolipidic diet (30% fat). Plasma total cholesterol and low-density-lipoprotein cholesterol were significantly higher than basal in the preovulatory phase until progesterone started to increase in the postovulatory phase [day +8 from luteinizing hormone (LH) surge]. High-density-lipoprotein cholesterol was significantly higher than basal from day -1 to the day after LH surge, whereas plasma apoAI levels were significantly higher from day -8 to day +8 (from LH surge). Plasma apo(a) increased significantly during the luteal phase in four women characterized by a single S4 band and lower basal plasma levels of apo(a). Our results indicate that endogenous female sex steroids have significant effects on the circulating levels of plasma lipids and apolipoproteins, including apo(a). More work needs to be done to elucidate the significance of the observed apo(a) changes, and the different phases of the menstrual cycle must be taken into account when evaluating the lipidic risk profile in premenopausal women.