The effects of reproductive hormones on serum lipoproteins: unresolved issues in biology and clinical practice

Antibiotic treatment triggers gut dysbiosis and modulates metabolism in a chicken model of gastro-intestinal infection

Background

Infection of the digestive track by gastro-intestinal pathogens results in the development of symptoms ranging from mild diarrhea to more severe clinical signs such as dysentery, severe dehydration and potentially death. Although, antibiotics are efficient to tackle infections, they also trigger dysbiosis that has been suggested to result in variation in weight gain in animal production systems.

Results

Here is the first study demonstrating the metabolic impact of infection by a gastro-intestinal pathogen (Brachyspira pilosicoli) and its resolution by antibiotic treatment (tiamulin) on the host (chicken) systemic metabolism and gut microbiota composition using high-resolution ¹H nuclear magnetic resonance (NMR) spectroscopy and 16S rDNA next generation sequencing (NGS). Clear systemic metabolic markers of infections such as glycerol and betaine were identified. Weight loss in untreated animals was in part explained by the observation of a modification of systemic host energy metabolism characterized by the utilization of glycerol as a glucose precursor. However, antibiotic treatment triggered an increased VLDL/HDL ratio in plasma that may contribute to reducing weight loss observed in treated birds. All metabolic responses co-occurred with significant shift of the microbiota upon infection or antibiotic treatment.

Conclusion

This study indicates that infection and antibiotic treatment trigger dysbiosis that may impact host systemic energy metabolism and cause phenotypic and health modifications.

Electronic supplementary material

The online version of this article (10.1186/s12917-018-1761-0) contains supplementary material, which is available to authorized users.

Effects of hormone replacement therapy on serum lipids and phospholipids in postmenopausal women

Hormone replacement therapy (HRT) has been shown to reduce the risk of cardiovascular disease and the beneficial effects may be mediated in part by favourable changes in plasma lipid levels. Evidence exists concerning the effect of combined oestrogen and progestogen on lipids, nevertheless no such evidence can be found on the phospholipid profile, which is important the lipid metabolic pathways. In the present study, involving the serum lipids and lipoproteins, we observed an increase in the concentration of total cholesterol (P < 0.001), HDL-C (P < 0.001), HDL-C (P < 0.001), 2 HDL-C (P < 0.001) and a decrease in the ratio LDL-C/ 3 HDL-C (P < 0.001) in the subjects of Group B (oestrogen plus progestogens) compared with controls (baseline). Also, we found an increased in triglycerides (P < 0.01) and ApoA-1 (P < 0.01) concentrations in the subjects of Group A (oestrogen alone) compared with controls (baseline). With regard to the phospholipids, the main changes observed in their concentrations were: an increase in phosphatidyl choline (P < 0.001) and a decrease in phosphatidyl serine (P < 0.01) for both groups compared with controls. Also, a decrease in phosphatidylinositol (P < 0.01) in Group B compared with controls (baseline). The significance of these results are discussed.

Analysis of Gender Difference of Cardiac Risk Biomarkers Using hGH-Transgenic Mice

We investigated gender difference in the effects of chronic exposure to human growth hormone (hGH) on cardiac risk biomarkers using transgenic mice with non-pulsatile circulating hGH. Blood plasma was obtained from transgenic and control mice at 8, 12, and 16 weeks of age, and was used for the measurement of hGH and the following cardiac risk biomarkers: total cholesterol (CHO), triglyceride (TG), HDL cholesterol (HDL), LDL cholesterol (LDL), non esterified free fatty acids (NEFA), and lipid peroxides (LPO). The hearts and the livers of transgenic mice were weighed and histopathologically examined, and the results were compared with those of control mice. Transgenic males exhibited higher levels of LDL at 8 and 12 weeks of age and higher levels of LPO at every week of age examined, as compared to those of the control males, while transgenic females exhibited somewhat lower levels of LDL and LPO from 8 to 16 weeks of age, as compared to the control females. The relative heart weight in males increased with aging and was significantly higher in the 16-week-old transgenic males compared to those of the control mice. The present results demonstrate that transgenic males had cardiac risk potential caused by chronic-exposure to hGH as compared to females. The results also show that the present transgenic mouse line is a useful model for the study of gender difference in cardiac disorders caused by hGH.

Expression of iNOS gene in macrophages stimulated with 17β-estradiol is regulated by free intracellular Ca2+

17β-Estradiol has potent Ca2+ ionophore capability and its signaling in macrophages is mediated through binding to surface and genomic receptors, resulting in transient nitric oxide (NO) elaboration. We decided to examine if the transient release of NO is due to Ca2+ influx pattern or the quenching effect of superoxide (·O2–) through peroxynitrite formation. Differential chelation of intracellular Ca2+ ([Ca2+]i) showed that NO generation was favored by [Ca2+]i concentration of 237 nM. Application of an estrogen receptor antagonist ICI 182 780 resulted in attenuation of estradiol mediated NO release. Studies directed at identifying the possible role of ·O2– in the attenuation of NO showed no supportive evidence. Inhibition of extracellular Ca2+ channel or extracellular and intracellular Ca2+ channels showed data consistent with a case for optimum Ca2+ influx signal favoring iNOS gene expression, accompanied by an elevation in iNOS protein. These data show that Ca2+ influx pattern determines macrophage NO elaboration.Key words: optimum Ca2+ signals, activation of iNOS gene, estradiol signaling.

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.

Gender-related differences in proliferative responses of vascular smooth muscle cells to endothelin-1

Endothelin-1 is an endothelium-derived factor which alters tone and proliferation of vascular smooth muscle and has been implicated in the development of atherosclerosis. Estrogen modulates production of and contractile responses to endothelin-1. Since atherosclerosis is less in estrogen-replete women compared to men, experiments were designed to determine whether or not there were gender-associated differences in proliferative responses to endothelin-1 and effect of estrogen status on those responses. Proliferation of smooth muscle cells derived from coronary arteries of sexually mature, gondally intact male and female and oophorectomized female pigs was determined by thymidine incorporation in the absence and presence of endothelin-1 with and without 17beta-estradiol. Endothelin-1 (10(-9) M to 10(-7) M) significantly inhibited proliferation only in coronary smooth muscle cells from intact female pigs. Addition of beta-estradiol inhibited proliferation of cells from intact females but there was not a synergistic effect with endothelin-1. Gender associated inhibition of smooth muscle proliferation by endothelin-1 may contribute, in part, to cardioprotection noted in estrogen-replete states.

Alternations in hepatic expression of fatty-acid metabolizing enzymes in ArKO mice and their reversal by the treatment with 17beta-estradiol or a peroxisome proliferator

We generated aromatase gene knockout mice (ArKO mice) by targeting disruption of Cyp19, which encodes an enzyme responsible for conversion of androgens to estrogens. We found that ArKO males developed hepatic steatosis spontaneously with aging, indicating that the function of Cyp19 is required to maintain constitutive lipid metabolism in male mice. Plasma lipoprotein analysis using a gel permeation chromatography revealed that high density lipoprotein (HDL)-cholesterol levels were slightly higher in ArKO males than in wild-type males, whereas no other obvious alternations in the profiles were detected. Nevertheless, analysis of lipoprotein compositions by SDS-polyacrylamide gel electrophoresis demonstrated apparent reduction in the amounts of apolipoprotein E, functioning in receptor-mediated clearance of lipoproteins in the liver, in the IDL/LDL fraction of ArKO males as compared with that of wild-type males. Biochemical analysis on the ArKO livers revealed suppression of mRNA expression and activity of enzymes involved in fatty acid beta-oxidation. The impairment was reversed to the wild-type levels by treatment with 17beta-estradiol or bezafibrate, the latter is a synthetic peroxisome proliferator. These findings indicated a pivotal role of estrogen in supporting constitutive hepatic expression of genes involved in fatty acid beta-oxidation and in maintaining lipid homeostasis.

A comparison of continuous combined hormone replacement therapy, HMG-CoA reductase inhibitor and combined treatment for the management of hypercholesterolemia in postmenopausal women

OBJECTIVE

To compare the lipid-altering effects of hormone replacement therapy alone and in combination with HMG-CoA reductase inhibitor in postmenopausal women with hypercholesterolemia.

METHODS

This was a prospective randomized controlled trial with 3 parallel groups. The patients (n = 35) were randomly assigned to receive pravastatin 20 mg/day (n = 12); continuous combined hormone replacement therapy (0.625 mg conjugated estrogen/day combined with medroxyprogesterone 5 mg/day) (n = 12); continuous combined hormone replacement therapy plus pravastatin (n = 11) for 16 weeks.

RESULTS

Among patients treated with continuous combined hormone replacement therapy levels of total cholesterol (10.7%) and LDL cholesterol (12.6%) decreased significantly (p < 0.05), while levels of high density lipoprotein cholesterol (5%) and triglycerides (6.2%) increased insignificantly (p > 0.05). Patients in the pravastatin group achieved significant reductions of 18.8 and 21.4% in total cholesterol and low density lipoprotein cholesterol levels, respectively (p < 0.05). Among patients treated with a combination of continuous combined hormone replacement therapy plus pravastatin, levels of total cholesterol (20.5%) and low density lipoprotein cholesterol (23.8%) decreased the most, while levels of triglycerides (2.1%) decreased lower than the pravastatin-only group. The mean percentage of the differences between the baseline and treatment levels of the lipids and lipoproteins were not significant between the 3 study groups (p > 0.05).

CONCLUSION

No significant difference between hormone replacement therapy alone and in combination with HMG-CoA reductase inhibitor in the treatment of postmenopausal women with hypercholesterolemia was noted in this study. The combination of hormone replacement therapy not only does not adversely affect the lipid-lowering effect of pravastatin alone, but hormone replacement therapy also offers additional benefits in the treatment of hypoestrogenic hypercholesterolemia in postmenopausal women.

Metabolism of chylomicron cholesterol is delayed by estrogen. An in vivo study in the rat

In order to test the effects of estrogen on the clearance of cholesterol of dietary origin from the blood and its elimination from the body via the bile in an in vivo animal model, the fate of radioactivity from intravenously injected [3H]cholesterol-labeled chylomicrons was investigated in the rat. The labeled lipoproteins were administered intrajugularly to male rats previously given 17alpha ethinyl estradiol or the vehicle only, and the removal of the radioactivity from the blood and its uptake by the liver and secretion into bile was determined. Experiments were carried out in animals with or without prior drainage (20 hr) of the pool of bile acids in the enterohepatic circulation, to take account of the different demands of the liver for cholesterol in the two conditions. In rats without biliary drainage, estrogen treatment decreased the rate of removal of radioactivity from the blood by about 30% and the recovery of cholesterol in the liver by about 50% in the first 30 min after injection of the labeled chylomicrons. After biliary drainage, however, the recovery of label in the liver after 90 min was similar in estrogen-treated and control animals, although its secretion into bile was markedly reduced in the estrogen-treated group (total biliary secretion in 90 min was 26% of the value found in control rats). In addition, the apolipoprotein E (aopE) content of the serum total lipoproteins was markedly reduced by estrogen. These results provide direct evidence indicating that estrogen retards the elimination of dietary cholesterol from the body via the bile in the rat, and this is likely to be mainly due to a reduced level of apoE in chylomicrons. In view of this, we suggest that the hypothesis that estrogen increases the hepatic uptake of chylomicron cholesterol, and its excretion in the bile during contraceptive and hormone replacement therapy should be re-examined.

Acute effects of estradiol and progesterone on insulin, lipids and lipoproteins in postmenopausal women: a pilot study

OBJECTIVES

To examine the acute effects of estradiol-17beta (E(2)) and progesterone (P) on serum levels of insulin, lipids and lipoproteins in estrogen-deficient postmenopausal women, whereby, a direct cause-effect relationship could be established without the influence of lifestyle changes.

MATERIALS AND METHODS

Nine postmenopausal women were given oral E(2) (Estrace) 2 mg/day for 28 days and oral micronized P (Prometrium) 200 mg/day in the last 14 days of E(2) treatment. Fasting blood samples were obtained before starting E(2) (day 1) and P (day 15) and on day 29. Serum levels of insulin, triglycerides (TG), total cholesterol (TC), low density lipoprotein (LDL), high density lipoprotein (HDL) and lipoprotein (a) (Lp(a)) at the three time points were compared by Friedman analysis of variance (ANOVA). Corresponding levels of glucose, the apolipoproteins (Apo) A1 and B and serum androgen levels were also evaluated.

RESULTS

E(2) decreased while P increased fasting levels of insulin (32.45+/-3.57, 26.36+/-2.90 and 37.36+/-3.67 pmol/l on day 1, 15 and 29 respectively; P<0.01). Fasting glucose to insulin ratios changed inversely (P<0.01). E(2) increased HDL from 1.07+/-0.05 mmol/l on day 1 to 1.17+/-0.07 mmol/l on day 29 but decreased corresponding levels of Lp(a) from 261+/-93 to 211+/-83 U/l (P=0.03 for both). TC and LDL levels fell significantly after 14 days of E(2) treatment with no further decrease when P was added. Androgen levels remained unchanged during hormone treatment.

CONCLUSION

The sequential, acute effects of E(2) and micronized P on insulin and lipids confirm a direct cause-effect relationship. The acute effects of P on insulin in particular, highlights the importance of standardizing the medication days according to estrogen and progestin in the clinical evaluation of their true metabolic impact in longer-term studies and may influence the choice of progestin type, dose and duration in hormone replacement.

Estrogen and progesterone reduce lipid accumulation in human monocyte-derived macrophages: a sex-specific effect

BACKGROUND

Males have an earlier onset and greater prevalence of clinical atherosclerosis than age-matched females, which is consistent with an atheroprotective effect of the female sex steroids, estrogen and progesterone. We therefore examined the effects of estrogen and progesterone on human foam cell formation, a key early event in atherogenesis.

METHODS AND RESULTS

Monocytes from healthy female and male donors were obtained from white cell concentrates and allowed to differentiate into macrophages over 10 days. These human monocyte-derived macrophages (MDMs) were exposed to either control (0.1% vol/vol ethanol) or estrogen or progesterone treatment on days 3 through 10. Lipid loading was achieved on days 8 through 10 by incubation with acetylated LDL. Lipid from the MDMs was then extracted for analysis of cholesteryl ester (CE) content. 17beta-Estradiol at both physiological (2 nmol/L) and supraphysiological (20 and 200 nmol/L) concentrations produced a significant reduction in macrophage CE content (88+/-3%, 88+/-2%, and 85+/-4%, respectively; P<0.02 compared with control). Physiological and supraphysiological levels of progesterone (2, 10, and 200 nmol/L) produced an even more dramatic reduction in CE content (74+/-9%, 56+/-10%, and 65+/-8%, respectively; P<0.002 compared with control). This effect could be abrogated by coincubation with the progesterone receptor antagonist RU486. Neither estrogen nor progesterone produced a reduction in lipid loading in male-donor-derived MDMs. Detailed lipid trafficking studies demonstrated that both estrogen and progesterone altered macrophage uptake and/or processing of modified LDL.

CONCLUSIONS

Physiological levels of estrogen and progesterone are associated with a female-sex-specific reduction in human macrophage lipid loading, which is consistent with an atheroprotective effect.

Comparison of the effects of triphasic oral contraceptives with desogestrel or levonorgestrel on apolipoprotein A-I-containing high-density lipoprotein particles

Recent observations suggest that the risk of coronary artery disease (CAD) is associated with both the level and composition of the two major populations of apolipoprotein (apo)-defined high-density lipoprotein (HDL) particles: those containing both apo A-I and apo A-II [Lp(AI,AII)] and those containing apo A-I without apo A-II [Lp(AI)]. While sex hormones are known to affect HDL, their influence on these apo-defined HDL particles is not known. We have determined the effects of two triphasic oral contraceptive (OC) formulations on these HDL particles in healthy normolipidemic women aged 21 to 35 years. The formulations contain comparable quantities of ethinyl estradiol (EE) and either desogestrel (DG), a minimally androgenic progestin, or levonorgestrel (LN), a more androgenic progestin. Lipid and lipoprotein levels were measured during the third week of the normal menstrual cycle and the sixth month of OC use. The DG/EE formulation significantly increased total cholesterol (C) 15%, triglyceride (TG) 99%, phospholipid (PL) 17%, apo A-I 28%, apo A-II 34%, apo B 21%, very-low-density lipoprotein cholesterol (VLDL-C) 238%, HDL-C 20%, and HDL3-C 28% (P < .02 to .005, n = 11), but not low-density lipoprotein cholesterol (LDL-C). The LN/EE formulation also increased total C 15%, TG 33%, apo A-I 15%, HDL3-C 21% (P < .05, n = 10), apo B 30% (P < .005), and, additionally, LDL-C 19% (P < .05). Both formulations increased Lp(AI,AII) (DG/EE, 34%, P < .005; LN/EE, 24%, P < .01). These changes reflected comparable increases of small (7.0 to 8.2 nm) and medium (8.2 to 9.2 nm) particles in the LN/EE group and a predominant increase of medium-sized particles in the DG/EE group. Also, in the LN/EE group but not the DG/EE group, there were fewer large (9.2 to 11.2 nm) particles. Lp(AI) increased only in the DG/EE group (25%, P = .075) and was due to the presence of more large particles. The level of Lp(AI) did not change in the LN/EE group, but the lipid/A-I ratio of these particles was lower (P = .012) and there were more small particles. Thus, triphasic OC formulations with progestins of different androgenicity had different effects on VLDL, LDL, and the level and composition of HDL particles with and without apo A-II, possibly reflecting estrogen/progestin/androgen balance. Estrogen dominance increases both Lp(AI,AII) and Lp(AI) and favors large Lp(AI) particles, while progestin/androgen dominance increases only Lp(AI,AII) and favors small particles. Because of the importance of HDL in the arterial wall physiology, OC formulations with different estrogen and progestin content may affect arterial wall health to a different extent.

Effects of estrogen replacement therapy on the lipoprotein profile in postmenopausal women with ESRD

BACKGROUND

Patients with ESRD have excessive cardiovascular morbidity and mortality. In postmenopausal women with normal renal function, estrogen replacement therapy decreases cardiovascular mortality by 50%, in part because of their beneficial effects on the lipoprotein profile. Because of similarities in the lipoprotein profile between healthy, postmenopausal women, and women with ESRD, we examined the effects of estrogen replacement on lipoproteins in 11 postmenopausal women with ESRD.

METHODS

In a randomized, placebo-controlled crossover study (8 week treatment arms) using 2 mg daily of oral, micronized estradiol, 11 postmenopausal women with ESRD were treated. Neither baseline lipid nor lipoprotein abnormalities were used as entry criteria for study participation.

RESULTS

Blood estradiol levels were 19 +/- 4 with placebo and 194 +/- 67 pg/ml (P = 0.024) with estradiol treatment. Total HDL cholesterol concentrations increased from 52 +/- 19 mg/dl to 61 +/- 20 mg/dl (16%), with placebo and estradiol treatments, respectively (P = 0.002). Apolipoprotein A1 increased by 24.6% (P = 0.0002) with estradiol intervention. HDL2 concentrations were 19 +/- 13 with placebo and 24 +/- 16 with estradiol treatment (P = 0.046). There were no differences in total or LDL cholesterol, other lipoprotein fractions including Lp(a), and triglycerides with 2 mg daily estradiol treatment. No significant side effects were observed.

CONCLUSIONS

Therefore, using standard dosage regimens for estrogen replacement therapy in postmenopausal women with ESRD, HDL cholesterol is increased to an extent that would be expected to improve their cardiovascular risk profile. Further studies are needed to assess whether estrogen replacement therapy decreases the incidence or severity of cardiovascular disease in ESRD patients to a similar degree compared with other women.

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.

Effects of soya milk and Bifidobacterium-fermented soya milk on plasma and liver lipids, and faecal steroids in hamsters fed on a cholesterol-free or cholesterol-enriched diet

The effects of freeze-dried soya milk (SM) and Bifidobacterium-fermented soya milk (FSM) on plasma and liver lipids, and faecal steroid excretion were estimated in hamsters fed on a cholesterol-free or cholesterol-enriched diet. Hamsters fed on the cholesterol-free diet containing 300 g FSM/kg had lower levels of plasma VLDL + LDL cholesterol than the animals fed on the control diet. SM in the diet produced a similar pattern without significant differences. In the cholesterol-enriched diet group, SM and FSM decreased the levels of plasma total cholesterol and VLDL + LDL-cholesterol. SM and FSM decreased the plasma triacylglycerol level in both the cholesterol-free and -enriched diet groups. The liver total cholesterol contents in the SM and FSM groups were lower than that in the control group, for hamsters fed on the cholesterol-free diet. The liver triacylglycerol content was not modified by SM or FSM in hamsters fed on either the cholesterol-free or -enriched diet. SM and FSM increased the total bile acid excretion and the proportion of cholesterol entering the cholic acid biosynthesis pathway in both the cholesterol-free and -enriched diet groups. SM and FSM did not affect neutral steroid excretion in the cholesterol-free or -enriched diet group. There was an inverse relationship between VLDL + LDL-cholesterol and faecal bile acid excretion in hamsters fed on the cholesterol-free (r -0.670, P < 0.01) and cholesterol-enriched (r -0.761, P < 0.001) diets respectively. These results indicated that SM had an anti-atherogenic effect, and that this effect was not diminished by prior fermentation.

Lipoprotein kinetics in patients with analbuminemia. Evidence for the role of serum albumin in controlling lipoprotein metabolism

In vitro data suggested that albumin is a key factor controlling apolipoprotein (apo) synthesis by hepatocytes. Studies in analbuminemic rats have shown an increase in secretion of apoB-containing lipoprotein from the liver. We studied the kinetic aspects of apoB- and apoAI-containing lipoprotein metabolism in two sisters with analbuminemia using a constant 14-hour infusion of leucine labeled with stable isotopes. Compared with control subjects, total cholesterol was higher in the two patients (432 and 461 versus 155 +/- 14 mg/dL), as was apoB (257 and 230 versus 72 +/- 7 mg/dL). Triglycerides were slightly increased (134 and 105 versus 89 +/- 9 mg/dL), whereas apoAI was lower (109 and 105 versus 124 +/- 6 mg/dL). VLDL-apoB production was higher, as was the production of IDL-apoB and LDL-apoB (32.8 and 36.0 versus 24.8 +/- 5.9, 32.1 and 27.2 versus 16.4 +/- 2.3, and 14.1 and 17.6 versus 10.3 +/- 1.2 mg.kg-1.d-1, respectively). The fractional catabolic rate of all the apoB-containing lipoproteins was decreased (0.23 and 0.37 versus 0.48 +/- 0.05, 0.27 and 0.28 versus 0.62 +/- 0.08, and 0.012 and 0.009 versus 0.022 +/- 0.002.h-1, respectively). A similar mechanism could explain the dyslipidemia observed in other conditions associated with low albumin levels, such as nephrotic syndrome.

Arterial reactivity is enhanced in genetic males taking high dose estrogens

OBJECTIVES

We sought to assess whether high dose estrogen treatment is associated with enhanced arterial reactivity in genetic males.

BACKGROUND

Although estrogens have been shown to enhance arterial reactivity in women, and are thereby thought to confer cardiovascular benefit, the vascular effects of long-term estrogen therapy in genetic males is unknown.

METHODS

We studied the arterial physiology of 30 genetic males--15 male to female transsexuals receiving long-term high dose estrogen therapy and 15 healthy male control subjects matched for age, smoking history and vessel size. Using external vascular ultrasound, brachial artery diameter was measured at rest, after flow increase (causing endothelium-dependent dilation [EDD]) and after nitroglycerin (GTN), an endothelium-independent dilator. Blood pressure, cholesterol and testosterone levels were also measured in each subject.

RESULTS

Total testosterone and free testosterone index levels were lower in the transsexuals compared with the control subjects (p < 0.001). In contrast, EDD was significantly higher in the transsexuals than in the control males (mean [+/-SD] 7.1 +/- 3.1% vs. 3.2 +/- 2.8%, p = 0.001), as was the GTN response (21.2 +/- 6.7% vs. 14.6 +/- 3.3%, p = 0.002). Total and high density lipoprotein cholesterol, blood pressure levels and baseline vessel size were similar in the two groups. On multivariate analysis, enhanced EDD was associated independently with estrogen therapy (p = 0.02) and with low total cholesterol (p = 0.04). An enhanced GTN response was also significantly associated with estrogen therapy (p = 0.03).

CONCLUSIONS

Long-term treatment with high dose estrogens is associated with enhanced arterial reactivity in genetic males, which may be due to the effects of estrogen excess or androgen deprivation, or both.

Characterization of the ovariectomized rat model for the evaluation of estrogen effects on plasma cholesterol levels

Estrogens protect against cardiovascular disease in women through effects on the vascular wall and liver. Here we further characterize the rat as a model for the evaluation of estrogenic effects on plasma lipid levels vs. uterine wet weight. In adult ovariectomized female rats treated for 4 days s.c., 17alpha-ethinyl estradiol (EE) was the most potent agent to lower plasma total and high density lipoprotein cholesterol levels, followed by 17beta-estradiol and 17alpha-estradiol. However, 17alpha-estradiol had the greatest separation of uterotropic vs. cholesterol-lowering effects. EE had the same lipid-lowering potency whether administered s.c. or orally to adult rats. It had no effect on cholesterol levels in immature rats, even though the uterotropic response was dramatic. Testosterone propionate, dexamethasone, and progesterone did not significantly lower cholesterol levels. The antiestrogens tamoxifen and raloxifene lowered cholesterol levels, but with less efficacy and potency than the estrogens. ICI 182780 had no effect on cholesterol levels. When coadministered with EE, ICI 182780 inhibited the cholesterol-lowering and uterotropic activities of EE, suggesting that the estrogen receptor pathway is involved. In conclusion, although the information from the rat is limited as a model of the low density lipoprotein-lowering effects of estrogens in humans, it can be used to study the effects and mechanism of action of estrogen and antiestrogens on plasma cholesterol levels.

Association of hormone replacement therapy with hemostatic and other cardiovascular risk factors. The FINRISK Hemostasis Study

The risk of cardiovascular diseases in women is small until menopause but increases considerably afterwards. When all age groups are considered, cardiovascular diseases are responsible for approximately half of the total mortality in women. It has been suggested that hormone replacement therapy (HRT) in perimenopausal and postmenopausal women could be useful in the prevention of cardiovascular diseases, but its effects are insufficiently known. We performed a cross-sectional study on the associations of menopause and HRT with cardiovascular risk factors, in particular with hemostatic factors, on female participants of the FINRISK Hemostasis Study. The participants, aged 45 to 64 years, were recruited from the Finnish population register by random sampling from three geographically defined areas. The participation rate of women was 83.2%. Of the 1202 women included in the study, 29.2% were current users of HRT. Differences in cardiovascular risk factors by menopausal status and by HRT use were examined after adjustment for age, study area, current smoking, body mass index, self-reported diabetes, and years of education. Postmenopausal women not using exogenous sex hormones had on average a total cholesterol level 0.5 mmol/L (8.9%) higher and an LDL cholesterol level 0.4 mmol/L (11.4%) higher than premenopausal women. Women reporting irregular menstruation (presumably due to perimenopause) had higher adjusted plasma fibrinogen, factor VII coagulant activity, and factor VII antigen than women with regular menstruation or no menstrual periods.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of continuous combined hormone-replacement therapy on lipid levels in hypercholesterolemic postmenopausal women

PURPOSE

To test the lipid-lowering effects of continuous combined hormone-replacement therapy in hypercholesterolemic postmenopausal women.

PATIENTS AND METHODS

A total of 32 postmenopausal women identified through health fair and cholesterol screening records, whose ad libitum low-density lipoprotein (LDL) cholesterol level (mean of 2 measurements) was > 130 mg/dL, and whose fasting triglycerides were < 250 mg/dL, participated in a placebo-controlled, nonrandomized trial testing the lipid-lowering effect of continuous combined hormone-replacement therapy. Women with a history of uterine fibroids, thrombophlebitis, family or personal history of breast cancer, or recent hormone use were excluded. After a 1-month period to standardize baseline dietary intake (Hi-Sat), patients were taught a cholesterol-lowering, Step-One diet, which they followed for the remainder of the study. After 3 months, patients supplemented the Step-One diet with daily placebo tablets for 3 months, followed by supplementation with conjugated estrogens 0.625 mg/d plus medroxyprogesterone 2.5 mg/d for 3 months. The means of five fasting lipid and lipoprotein values at the end of each 3-month supplementation period were compared.

RESULTS

Total cholesterol fell from 261 mg/dL to 250 mg/dL to 233 mg/dL, with LDL reduction from 181 mg/dL to 173 mg/dL to 150 mg/dL, on diet and diet plus continuous combined hormone-replacement therapy, respectively (all P < 0.05). Whereas 26 of the 32 women had LDL values above 160 mg/dL during the Hi-Sat diet, only 10 of the 32 women remained with LDL values in this range during Step-One diet plus hormone therapy. Besides improving LDL cholesterol levels, continuous combined hormone-replacement therapy was associated with an increase in high density lipoprotein (HDL) cholesterol levels from 51 mg/dL to 54 mg/dL (P < 0.05). The 2 women whose HDL cholesterol levels were < 35 mg/dL during the Step-One diet plus placebo achieved HDL cholesterol levels > 35 mg/dL during hormone therapy. Nevertheless, continuous combined hormone-replacement therapy was associated with a high frequency of side effects, including breast tenderness and uterine bleeding. Most bothersome side effects dissipated after an initial adjustment period.

CONCLUSIONS

Continuous combined hormone-replacement therapy can produce significant and therapeutic reductions in LDL cholesterol levels in hypercholesterolemic postmenopausal women. After internists become familiar with the expected side effects and their time course, this regimen may provide an effective approach in the management of hypercholesterolemia in postmenopausal women who have not undergone hysterectomy.

Effects of acute and chronic estrogenic treatment on vasomotor responses of aortic rings from ovariectomized rats

The effects of either chronic or acute estrogenic treatment on the "in vitro" vasomotor responses to phenylephrine (10(-9)-10(-5) M) and to carbachol (10(-9)-10(-5) M) of aortic rings excised from ovariectomized rats were analyzed. Chronic estrogenic treatment consisted in a single subcutaneous dose of 1 mumol estradiol 17-stearate. Effects of acute estrogenic treatment were evaluated by recording the responses of aortic rings excised from untreated ovariectomized rats both before and after the addition of 17 beta-estradiol to the superfusing solutions. In order to identify the endothelium-dependent responses each experiment was performed simultaneously on pairs of rings from the same aorta, one with and the other without functional endothelium. The contractile responses to phenylephrine of endothelium-intact vessels were attenuated by chronic estrogenic treatment; this attenuation was further increased by preincubation of the vessels with indomethacin and was reverted by N omega-nitro-L-arginine methyl ester. Either chronic or acute estrogenic treatment enhanced the carbachol-induced endothelium dependent relaxation of phenylephrine-precontracted rings. The results may be explained by assuming that estrogens increase the basal release of both nitric oxide and a cyclooxygenase-dependent vasoconstricting prostanoid as well as the receptor-mediated release of nitric oxide from the endothelium of the rat aorta.

Postmenopausal hormone therapy and atherosclerotic disease

Several lines of evidence suggest that estrogen is an important determinant of cardiovascular risk in women. Epidemiologic data document low rates of coronary heart disease (CHD) in premenopausal women, a narrowing of the gender gap in CHD mortality after menopause, and elevated risk of CHD among young women with bilateral oophorectomy not treated with estrogen. Nearly all of the more than 30 observational studies of exogenous estrogen replacement therapy have indicated a reduced risk of CHD among women receiving estrogen therapy. In a meta-analysis comparing estrogen users and nonusers, the estimated reduction of CHD among users was 44%. In angiographic studies, women taking estrogen were less likely to have coronary artery stenosis. Estrogen is known to affect a wide range of physiologic processes that may have an impact on CHD risk. Use of oral estrogen has favorable effects on serum lipid profiles; it increases high-density lipoprotein cholesterol levels by 10% to 15% and decreases low-density lipoprotein cholesterol levels by a similar magnitude. Other proposed mechanisms include inhibition of endothelial hyperplasia, reduced arterial impedance, enhanced production of prostacyclin, increased insulin sensitivity, and inhibition of oxidation of low-density lipoprotein. Nevertheless, the role of hormone replacement therapy in preventing clinical atherosclerotic events in women remains inconclusive because of the absence of randomized trial data. The benefit-to-risk ratio must be reliably assessed, because estrogen has complex actions, including postulated benefits (CHD, osteoporosis, and menopausal symptoms) and postulated risks (endometrial cancer, breast cancer, and gallstones.(ABSTRACT TRUNCATED AT 250 WORDS)

Differential effects of estrogen on low-density lipoprotein subclasses in healthy postmenopausal women

The use of estrogen by postmenopausal women decreases plasma low-density lipoprotein (LDL) cholesterol levels. To determine whether LDL subclass profiles influence this response, we studied 31 healthy postmenopausal women who were administered two doses (0.625 and 1.25 mg/d) of conjugated equine estrogen in a placebo-controlled double-blind crossover study. Lipid-stained gradient gels were used to categorize LDL subclass patterns. All women were classified as LDL subclass pattern A (predominant LDL peak > or = 260 A). Within the pattern A classification, there were 12 women during placebo treatment with LDL subclass I pattern (predominant LDL peak > 271 A) and 19 women with LDL subclass II pattern (predominant LDL peak < or = 271 and > or = 260 A). Postmenopausal women with LDL subclass I on placebo treatment had significantly lower LDL cholesterol levels compared with women having LDL subclass II (126 +/- 28 v 147 +/- 23 mg/dL, P < .03). Postmenopausal women with LDL subclass I also had significantly (P < .05) lower very-low-density lipoprotein (VLDL) cholesterol, VLDL triglyceride, and VLDL apo B levels and significantly higher (P < .05) high-density lipoprotein 2 (HDL2) cholesterol, HDL3 cholesterol, and HDL2 apo A-I levels. Estrogen replacement significantly (P < .05) decreased LDL cholesterol levels and increased VLDL and LDL triglyceride, HDL2 and HDL3 cholesterol and apo A-I, and HDL2 apo A-II levels to a similar extent in postmenopausal women with LDL I or II subclass patterns.(ABSTRACT TRUNCATED AT 250 WORDS)

Association of hormone-replacement therapy with various cardiovascular risk factors in postmenopausal women. The Atherosclerosis Risk in Communities Study Investigators

BACKGROUND

Most epidemiologic studies of cardiovascular disease in postmenopausal women suggest that estrogen-replacement therapy has a protective effect. The effects of the use of estrogen combined with progestin are less well studied.

METHODS

To examine the associations of hormone-replacement therapy with concentrations of plasma lipids and hemostatic factors, fasting serum concentrations of glucose and insulin, and blood pressure, we studied 4958 postmenopausal women participating in a population-based investigation. Using cross-sectional data, we classified the women into four groups according to their use of hormone-replacement therapy: current users of estrogen alone, current users of estrogen with progestin, nonusers who had formerly used these hormones, nonusers who had never used them.

RESULTS

Current users had higher mean levels of high-density lipoprotein cholesterol, its subfractions high-density lipoprotein2 and high-density lipoprotein3, and apolipoprotein A-I than nonusers and lower mean levels of low-density lipoprotein cholesterol, apolipoprotein B, lipoprotein(a), fibrinogen, antithrombin III, and fasting serum glucose and insulin. However, current users of estrogen alone had higher triglyceride, factor VII, and protein C levels than either nonusers or current users of estrogen with progestin. After making certain assumptions, we estimated that the findings, if causal, would translate into a reduction of 42 percent in the risk of coronary heart disease in users of hormones as compared with nonusers. Women using estrogen with progestin would have an even greater estimated benefit.

CONCLUSIONS

A randomized trial is needed to eliminate possible selection biases in our observational study that are related to the prescription of replacement hormones. Nevertheless, hormone-replacement therapy appears to be associated with a favorable physiologic profile, which probably mediates its protective effects on cardiovascular disease. The use of estrogen combined with progestin appears to be associated with a better profile than the use of estrogen alone.

Regulation of adrenal and hepatic alpha-tocopherol content by androgens and estrogens

Previous studies demonstrated that alpha-tocopherol concentrations were far greater in adrenal glands and in livers from female rats than in those from males. Studies were done to investigate the role of androgens and estrogens in the regulation of adrenal and hepatic alpha-tocopherol content. In males and females, adrenal concentrations of alpha-tocopherol were approx. 10-fold greater than those in liver and the highest concentrations of alpha-tocopherol were in the crude mitochondrial fractions in both organs. Castration of female rats decreased alpha-tocopherol concentrations in adrenals and in livers. Proportionately similar declines occurred in both organs and in all subcellular fractions. The effects of castration were prevented by estradiol replacement at the time of surgery. Gonadectomy in male rats had effects opposite to those in females, increasing adrenal and hepatic alpha-tocopherol concentrations. Testosterone administration to castrated males prevented the increases in adrenal and hepatic alpha-tocopherol content. Neither castration nor gonadal hormone replacement in either sex had any effect on plasma alpha-tocopherol levels or on cytosolic ascorbic acid concentrations in adrenals or livers. The results indicate a role for estrogens and androgens in the regulation of adrenal and hepatic concentrations of alpha-tocopherol. The opposing effects of androgens and estrogens fully account for the sex differences in tissue alpha-tocopherol levels in rats.

Epidemiological overview of oestrogen replacement and cardiovascular disease

In contrast to numerous epidemiological studies of prevention in men, there has been limited research into the prevention of cardiovascular disease in women. Nevertheless, sufficient data have accumulated showing that OeRT does protect against circulatory disease in women, although evidence regarding the true magnitude of that protection remains incomplete. The best estimates of the relationship between OeRT and CVD come from population-based prospective studies which are remarkably consistent: overall they indicate a 40% reduction in CVD with use of OeRT. However, because of the underlying better health of the postmenopausal women who use hormone replacement therapy, this result probably overestimates the benefit of OeRT by an unknown degree. Furthermore, details of OeRT formulation (especially the influence of regimens with an added progestin), dose, duration, and route of administration have not been adequately studied, and the evidence regarding the effect of OeRT on rates of stroke is equivocal and requires clarification. Oestrogen's cardioprotection appears to derive from favourable effects on serum lipoprotein profiles. There may also be a direct effect on the arterial system. Detrimental influences of OeRT on haemostatic function seem unlikely. Definitive information about the actual size of effects of commonly-used regimens of OeRT on cardiovascular disease and intermediate endpoints such as serum lipid concentrations can only be obtained through large-scale randomized controlled trials. Even if the reduction in CVD were modest, the mortality rates of CVD in our society are still so high that widespread use of oestrogen replacement therapy would result in substantial numbers of women's lives being saved.

Type of postmenopausal hormone use and risk of breast cancer: 12-year follow-up from the Nurses' Health Study

We prospectively examined the use of hormone replacement therapy in relation to breast cancer incidence in a cohort of women 30 to 55 years of age in 1976. During 12 years of follow-up (480,665 person-years) among postmenopausal women, 1,050 incident cases of breast cancer were documented. Overall, past users of replacement estrogen were not at increased risk. After adjustment for established risk factors, type of menopause, age at menopause, and current age, the rate ratio (RR) was 0.91, 95 percent confidence interval (CI) = 0.78-1.07. The risk of breast cancer was elevated significantly among current users (RR = 1.33, CI = 1.12-1.57); after adjusting for age, we observed no evidence of increasing risk with increasing duration of use among current users (P trend = 0.41), or among past users (P trend = 0.46). Women currently using unopposed estrogen (RR = 1.42, CI = 1.19-1.70), estrogen and progesterone (RR = 1.54, CI = 0.99-2.39), or progesterone alone (RR = 2.52, CI = 0.66-9.63), were all at increased risk of breast cancer compared with never users. These data suggest that long-term past use of estrogen replacement therapy is not related to risk, that current estrogen use increases risk of breast cancer to a modest degree, and that the addition of progesterone does not remove the increased risk observed with current use of unopposed estrogen.

Effects of postmenopausal estrogen replacement on the concentrations and metabolism of plasma lipoproteins

BACKGROUND

Postmenopausal estrogen-replacement therapy may reduce the risk of cardiovascular disease, and this beneficial effect may be mediated in part by favorable changes in plasma lipid levels. However, the effects on plasma lipoprotein levels of postmenopausal estrogens in the low doses currently used have not been precisely quantified, and the mechanism of these effects is unknown.

METHODS

We conducted two randomized, double-blind crossover studies in healthy postmenopausal women who had normal lipid values at base line. In study 1, 31 women received placebo and conjugated estrogens at two doses (0.625 mg and 1.25 mg per day), each treatment for three months. In study 2, nine women received placebo, oral micronized estradiol (2 mg per day), and transdermal estradiol (0.1 mg twice a week), each treatment for six weeks. The metabolism of very-low-density lipoprotein (VLDL) and low-density lipoprotein (LDL) was measured by endogenously labeling their protein component, apolipoprotein B.

RESULTS

In study 1, the conjugated estrogens at doses of 0.625 mg per day and 1.25 mg per day decreased the mean LDL cholesterol level by 15 percent (95 percent confidence interval, 11 to 19 percent; P less than 0.0001) and 19 percent (95 percent confidence interval, 15 to 23 percent; P less than 0.0001), respectively; increased the HDL cholesterol level by 16 percent (95 percent confidence interval, 12 to 20 percent; P less than 0.0001) and 18 percent (95 percent confidence interval, 14 to 22 percent; P less than 0.0001), respectively; and increased VLDL triglyceride levels by 24 percent (95 percent confidence interval, 8 to 40 percent; P less than 0.003) and 42 percent (95 percent confidence interval, 26 to 58 percent; P less than 0.0001), respectively. In study 2, oral estradiol increased the mean concentration of large VLDL apolipoprotein B by 30 +/- 10 percent (P = 0.05) by increasing its production rate by 82 +/- 18 percent (P less than 0.01). Most of this additional large VLDL was cleared directly from the circulation and was not converted to small VLDL or LDL. Oral estradiol reduced LDL cholesterol concentrations by 14 +/- 3 percent (P less than 0.005), because LDL catabolism increased by 36 +/- 7 percent (P less than 0.005). The oral estradiol increased the HDL cholesterol level by 15 +/- 2 percent (P less than 0.0001). Transdermal estradiol had no effect.

CONCLUSIONS

The postmenopausal use of oral estrogens in low doses favorably alters LDL and HDL levels that may protect women against atherosclerosis, while minimizing potentially adverse effects on triglyceride levels. The decrease in LDL levels results from accelerated LDL catabolism; the increase in triglyceride levels results from increased production of large, triglyceride-rich VLDL.