Responses of HDL subclasses, Lp(A-I) and Lp(A-I:A-II) levels and lipolytic enzyme activities to continuous oral estrogen-progestin and transdermal estrogen with cyclic progestin regimens in postmenopausal women

An Essential Role for Liver ERα in Coupling Hepatic Metabolism to the Reproductive Cycle

Lipoprotein synthesis is controlled by estrogens, but the exact mechanisms underpinning this regulation and the role of the hepatic estrogen receptor α (ERα) in cholesterol physiology are unclear. Utilizing a mouse model involving selective ablation of ERα in the liver, we demonstrate that hepatic ERα couples lipid metabolism to the reproductive cycle. We show that this receptor regulates the synthesis of cholesterol transport proteins, enzymes for lipoprotein remodeling, and receptors for cholesterol uptake. Additionally, ERα is indispensable during proestrus for the generation of high-density lipoproteins efficient in eliciting cholesterol efflux from macrophages. We propose that a specific interaction with liver X receptor α (LXRα) mediates the broad effects of ERα on the hepatic lipid metabolism.

Post-menopausal hormone therapy reduces autoantibodies to oxidized apolipoprotein B100

The aim of the study was to verify whether post-menopausal hormone replacement therapy (HRT) modifies autoantibody titers against oxidized low-density lipoprotein (LDL) (anti-LDLoxi), against epitopes of oxidized apolipoprotein B100 and common carotid intima-media thickness (IMT) in these women. Sixty-eight women in pre-menopause (PMW) and 216 in post-menopause (POMW) were recruited; eighty-three had undergone HRT for at least 12 months, where 48 received conjugated estrogens alone (EHRT) and 35 received conjugated estrogen and medroxyprogesterone acetate (CHRT). ELISA was used to determine autoantibodies. Lipoprotein lipase (LPL), hepatic lipase (HL), cholesterol ester transfer protein (CETP) and phospholipid transfer protein (PLTP) activities were assayed by radiometric methods. IMT was measured using Doppler ultrasound. Anti-oxidized LDL and anti-D antibodies increased by 40% (p ≤ 0.003) and 42% (p ≤ 0.006), respectively, with menopause. There was a surprising and significant 7% reduction in anti-D2 antibody titers with HRT (p ≤ 0.050), indicating a positive effect of treatment on the immune response to oxidized LDL. Combined HRT decreased activities of HL and LPL. HRT did not change common carotid IMT, which was increased by 32% as expected after menopause (p ≤ 0.030). This study describes, for the first time, the protective effect of HRT on decreasing autoantibody titers against oxidized apolipoprotein B in LDL.

Changes in remnant and high-density lipoproteins associated with hormone therapy and progression of coronary artery disease in postmenopausal women

OBJECTIVE

This study examined the effect of hormone therapy (HT) on the plasma concentration of remnant lipoprotein cholesterol (RLP-C) and high-density lipoprotein (HDL) subpopulations and the contribution of HT-related changes in these lipoproteins to the progression of coronary heart disease (CHD) in postmenopausal women.

METHODS

Study participants were 256 women who completed the Estrogen Replacement and Atherosclerosis (ERA) trial, a placebo-controlled, randomized trial that examined the effects of 3.2 years of conjugated equine estrogen (CEE, 0.625 mg/day) or CEE (0.625 mg/day) plus medroxyprogesterone acetate (MPA, 2.5mg/day) on postmenopausal women with established coronary atherosclerosis. Quantitative coronary angiography and plasma RLP-C and HDL subpopulations were assessed at baseline and at follow-up.

RESULTS

Relative to placebo, both CEE and CEE+MPA caused a significant reduction in plasma RLP-C concentrations and a significant increase in alpha1 and alpha2 HDL subpopulations. However, in the HT-treated subjects, faster progression of coronary atherosclerosis was observed in women who experienced the greatest reductions in RLP-C and in prebeta1 HDL subpopulations.

CONCLUSIONS

Our data suggest that individual variability in RLP-C and HDL subpopulation response to HT is a predictor of CHD progression. Lipoprotein response to HT may be an indirect marker of susceptibility to other harmful effect of HT in postmenopausal women with established CHD or an indication of formation of dysfunctional lipoproteins.

Oral but not transdermal estrogen replacement therapy changes the composition of plasma lipoproteins

The role of hormone replacement therapy and estrogen replacement therapy (ERT) in cardiovascular disease prevention has not been unambiguously defined yet. The metabolic effects of estrogens may vary depending upon the route of administration. Therefore, we compared the impact of unopposed oral or transdermal ERT on plasma lipids and lipoproteins in 41 hysterectomized women. This was an open-label, randomized, crossover study (with 2 treatments and 2 periods). The 41 hysterectomized women were randomized to receive oral or transdermal 17beta-estradiol in the first or second of two 12-week study periods. Plasma lipid and lipoprotein levels were assayed before and after each treatment using standard automated methods. Lipid content of lipoprotein subclasses was assessed by sequential ultracentrifugation. The atherogenic index of plasma (AIP) was calculated as log(triglyceride [TG]/high-density lipoprotein [HDL] cholesterol). The difference between the 2 forms of administration was tested using a linear mixed model. The change from baseline for each of the forms was tested using paired t test. Oral ERT resulted in a significant increase in HDL cholesterol and apolipoprotein A-I levels, whereas it significantly decreased total and low-density lipoprotein (LDL) cholesterol and increased TG concentrations. Transdermal ERT had no such effect. Oral ERT led to a significant TG enrichment of HDL (0.19 +/- 0.06 vs 0.27 +/- 0.07 mmol/L, P < .001) and LDL particles (0.23 +/- 0.08 vs 0.26 +/- 0.10 mmol/L, P < .001) compared with baseline, whereas transdermal therapy did not have any effect on lipoprotein subclasses composition. The difference between the 2 treatments was statistically significant for HDL-TG and LDL-TG (0.27 +/- 0.07 vs 0.19 +/- 0.05 mmol/L, P < .001 and 0.26 +/- 0.10 vs 0.22 +/- 0.07 mmol/L, P< .001, respectively). The transdermal but not oral ERT significantly reduced the AIP compared with baseline (-0.17 +/- 0.26 vs -0.23 +/- 0.25, P = .023), making the difference between the therapies statistically significant (-0.23 +/- 0.25 vs -0.18 +/- 0.22, P = .017). Oral administration of ERT resulted in TG enrichment of LDL and HDL particles. Transdermal ERT did not change the composition of the lipoproteins and produced a significant improvement of AIP. Compared with transdermal ERT, orally administered ERT changes negatively the composition of plasma lipoproteins.

Atherosclerosis is enhanced by testosterone deficiency and attenuated by CETP expression in transgenic mice

In this work, we investigated the impact of testosterone deficiency and cholesteryl ester transfer protein (CETP) expression on lipoprotein metabolism and diet-induced atherosclerosis. CETP transgenic mice and nontransgenic (nTg) littermates were studied 4 weeks after bilateral orchidectomy or sham operation. Castrated mice had an increase in the LDL fraction (+36% for CETP and +79% for nTg mice), whereas the HDL fraction was reduced (-30% for CETP and -11% for nTg mice). Castrated mice presented 1.7-fold higher titers of anti-oxidized LDL (Ox-LDL) antibodies than sham-operated controls. Plasma levels of CETP, lipoprotein lipase, and hepatic lipase were not changed by castration. Kinetic studies showed no differences in VLDL secretion rate, VLDL-LDL conversion rate, or number of LDL and HDL receptors. Competition experiments showed lower affinity of LDL from castrated mice for tissue receptors. Diet-induced atherosclerosis studies showed that testosterone deficiency increased by 100%, and CETP expression reduced by 44%, the size of aortic lesion area in castrated mice. In summary, testosterone deficiency increased plasma levels of apolipoprotein B-containing lipoproteins (apoB-LPs) and anti-OxLDL antibodies, decreased LDL receptor affinity, and doubled the size of diet-induced atherosclerotic lesions. The expression of CETP led to a milder increase of apoB-LPs and reduced atherosclerotic lesion size in testosterone-deficient mice.

Role of progestogen in hormone therapy for postmenopausal women: position statement of The North American Menopause Society

OBJECTIVE

To create an evidence-based position statement regarding the role of progestogen in postmenopausal hormone therapy (estrogen plus a progestogen, or EPT) for the management of menopause-related symptoms.

DESIGN

NAMS followed the general principles established for evidence-based guidelines to create this document. Clinicians and researchers acknowledged to be experts in the field of postmenopausal hormone therapy were enlisted to review the evidence obtained from the medical literature and develop a position statement for approval by the NAMS Board of Trustees.

RESULTS

The primary role of progestogen in postmenopausal hormone therapy is endometrial protection. Unopposed estrogen therapy (ET) is associated with a significantly increased risk of endometrial hyperplasia and adenocarcinoma. Adding the appropriate dose and duration of progestogen to ET has been shown to lower that risk to the level found in never-users of ET. The clinical goal of progestogen in EPT is to provide endometrial protection while maintaining estrogen benefits and minimizing progestogen-induced side effects, particularly uterine bleeding. EPT discontinuance correlates with uterine bleeding-women with more days of amenorrhea have higher rates of continuance. All US Food and Drug Administration-approved progestogen formulations will provide endometrial protection if the dose and duration are adequate. Progestogens may diminish the beneficial effects of ET on cardiovascular risk factors. However, no EPT (or ET) regimen should be initiated for the primary or secondary prevention of cardiovascular heart disease. Some progestogens may negatively affect mood. Adding progestogen to ET does not decrease the breast cancer risk, although it does not seem to increase mortality. Progestogen increases mammographic density, which is reversed after discontinuation of use. Progestogen has limited effect on the bone-enhancing action of ET. In general, the side effects of added progestogen are mild, although they may be severe in a small percentage of women.

CONCLUSIONS

Progestogen should be added to ET for all postmenopausal women with an intact uterus to prevent the elevated risk of estrogen-induced endometrial hyperplasia and adenocarcinoma. There is no consensus on a preferred regimen for all women. By changing the progestogen type, route, or regimen, clinicians can individualize therapy to minimize side effects, especially uterine bleeding, and limit any effects on ET benefits while providing adequate endometrial protection.

Cholesteryl ester transfer protein expression attenuates atherosclerosis in ovariectomized mice

Reduced estrogen levels result in loss of protection from coronary heart disease in postmenopausal women. Enhanced and diminished atherosclerosis have been associated with plasma levels of cholesteryl ester transfer protein (CETP); however, little is known about the role of CETP-ovarian hormone interactions in atherogenesis. We assessed the severity of diet-induced atherosclerosis in ovariectomized (OV) CETP transgenic mice crossbred with LDL receptor knockout mice. Compared with OV CETP expressing ((+)), OV CETP non-expressing ((-)) mice had higher plasma levels of total, VLDL-, LDL-, and HDL-cholesterol, as well as higher antibodies titers against oxidized LDL. The mean aortic lesion area was 2-fold larger in OV CETP(-) than in OV CETP(+) mice (147 +/- 90 vs. 73 +/- 42 x 10(3) micro m(2), respectively). Estrogen therapy in OV mice blunted the CETP dependent differences in plasma lipoproteins, oxLDL antibodies, and atherosclerosis severity. Macrophages from OV CETP(+) mice took up less labeled cholesteryl ether (CEt) from acetyl-LDL than macrophages from OV CETP(-) mice. Estrogen replacement induced a further reduction in CEt uptake and an elevation in HDL mediated cholesterol efflux from pre-loaded OV CETP(+) as compared with OV CETP(-) macrophages. These findings support the proposed anti-atherogenic role of CETP in specific metabolic settings.

Relationship of phospholipid transfer protein activity to HDL and apolipoprotein B-containing lipoproteins in subjects with and without type 1 diabetes

Patients with type 1 diabetes have greatly increased phospholipid transfer protein (PLTP) activity and have an altered HDL subclass distribution. In 195 patients with type 1 diabetes and in 194 men and women aged 30-55 years, we examined the relationship of PLTP activity to HDL and examined whether PLTP activity contributes to differences in HDL found in type 1 diabetes. PLTP activity was measured using an exogenous substrate assay. Average HDL particle size and HDL subclasses were measured using nuclear magnetic resonance spectroscopy. Apolipoprotein AI (apoAI) and apoAII were measured by immunoturbidimetry. The amount of apoAI present in LpAI was measured using a differential electroimmunoassay, and the amount of apoAI in LpAIAII was inferred from the apoAI and LpAI data. Higher PLTP activity was associated with more large HDL (P < 0.001) and less small HDL (P < 0.01), more apoAI and apoAII (both at P < 0.001), and more apoAI in both LpAI and LpAIAII (P = 0.02 and P < 0.001, respectively). These associations were independent of other lipids and enzyme activities. Adjusting for PLTP activity halved the difference between subjects with and without diabetes in apoA1 (from 10.1 mg/dl higher in subjects with diabetes to 4.6 mg/dl higher) and large HDL (2.4 micro mol/l higher to 1.2 micro mol/l higher) and reduced the difference in HDL size (from 0.31 nm higher to 0.26 nm higher). PLTP activity was also positively associated with apoB, total VLDL and LDL particle number, and IDL level in subjects with diabetes. These data support the idea that PLTP is a major factor in HDL conversion and remodeling in humans and that higher PLTP activity makes an important contribution to the higher apoAI levels and altered HDL subclass distribution in type 1 diabetes. They also support a role for PLTP in the metabolism of apoB-containing lipoproteins.

National differences in lipid response to postmenopausal hormone replacement therapy

OBJECTIVE

To compare the response of serum lipids and lipoproteins to the transdermal hormone replacement therapy (HRT) in five European countries.

METHODS

Five-hundred and sixty-seven healthy postmenopausal women from Belgium, Finland, the Netherlands, Sweden, and the UK received transdermal estradiol 50 microg daily for 12 months. In addition, two groups received transdermally norethisterone acetate (NETA) continuously, two groups sequentially (170 or 350 microg/day); one group received sequentially oral NETA (1 mg/day), and one group dydrogestrone (20 mg/day). Serum total cholesterol, HDL-, HDL2-, LDL-cholesterol, lipoprotein(a) (Lp(a)), and triglycerides were assessed before and at the end of treatment.

RESULTS

No significant national differences existed in the pretreatment levels of lipids and lipoproteins. Mean cholesterol, LDL, Lp(a), and triglycerides decreased during HRT, and HDL and HDL2 increased. Individual changes in responses to HRT were strongly dependent on pretreatment values. In this regard, British women differed from the others: their cholesterol, HDL, HDL2, and Lp(a) responses, when related to the pretreatment levels, were smaller than those of the others.

CONCLUSION

A national difference discovered in response of serum lipids to HRT calls for caution in generalization of lipid data from one nation to another during HRT.

A common mutation in cholesteryl ester transfer protein gene and plasma HDL cholesterol level before and after hormone replacement therapy in Korean postmenopausal women

BACKGROUND

Plasma cholesteryl ester transfer protein (CETP) functions to transfer cholesteryl ester from HDL to triglyceride-rich lipoproteins and regulates plasma HDL cholesterol level. A common mutation, the exon 15 A to G substitution at codon 442 (D442G) results in reduced plasma CETP activity and increased plasma HDL cholesterol level. Meanwhile, hormone replacement therapy (HRT) in postmenopausal women increases plasma HDL cholesterol level.

METHODS

We investigated the frequency of D442G mutation and its effect on plasma HDL cholesterol level in Korean women. We also examined if the mutation has any effect on an increase in plasma HDL cholesterol level during HRT.

RESULTS

Two hundred and twenty eight women aged over 40 years were recruited in this study. Of 228 women, 22 (9.6%) were identified as having the D442G mutation; 21 heterozygotes and 1 homozygote. The subjects with the mutation had higher plasma HDL cholesterol levels than those without the mutation (61.6 +/- 17.3 vs. 55.1 +/- 14.0 mg/dL, p < 0.05). After 12 month HRT, HDL cholesterol increased by 6.4% (3.6 +/- 13.2 mg/dL, p < 0.05) and D442G mutation did not have any significant effect on the change of plasma HDL cholesterol level.

CONCLUSION

D442G mutation is common in Korean postmenopausal women and it is associated with increased plasma HDL cholesterol level. HRT for postmenopausal women increased plasma HDL cholesterol level in similar amounts regardless of the presence or absence of D442G mutation.

Relationship between endogenous estrogen concentrations and serum cholesteryl ester transfer protein concentrations in Chinese women

BACKGROUND

CETP plays an important role in HDL metabolism and in the reverse cholesterol transport pathway.

METHODS

The relationship between the changes of endogenous estrogen and the concentration of cholesteryl ester transfer protein (CETP) in the serum of Chinese women was investigated. Serum concentrations of estradiol (E(2)), follicle-stimulating hormone (FSH), CETP and lipid profile were determined in 196 Chinese women (52 premenopausal with ages ranging from 18 to 40 years, 57 perimenopausal from 41 to 60 years, and 87 postmenopausal from 61 to 81 years).

RESULTS

Serum CETP concentration was significantly lower in postmenopausal women compared with those in perimenopausal and premenopausal women (1.39+/-1.06, 2.36+/-1.50 and 2.31+/-1.25 mg/l, respectively, P<0.0001). Even in the women around the menopausal, CETP concentration in postmenopause was significantly lower than that in premenopause (1.93+/-1.33 vs. 3.42+/-1.35 mg/l, P<0.01). In addition, CETP concentration had a highly positive correlation with serum concentration of E(2) (r=0.243, P<0.001), while negative correlation of CETP concentration with serum concentration of FSH was found (r=-0.273, P<0.001).

CONCLUSIONS

Estrogen may affect the concentration of CETP.

Differing associations of lipid and lipoprotein disturbances with the macrovascular and microvascular complications of type 1 diabetes

OBJECTIVE

Cardiovascular disease (CVD) is increased in patients with type 1 diabetes, but lipid and lipoprotein patterns remain favorable. In contrast, nephropathy is associated with an adverse distribution. We compared the associations and predictive power of lipid and lipoprotein disturbances with these complications.

RESEARCH DESIGN AND METHODS

A nested case-control study from the EURODIAB cohort of 140 case subjects with evidence of at least one complication and 84 control subjects with no complications were analyzed. Conventional and unconventional lipid and lipoprotein fractions, including apolipoprotein (apo)-A1, lipoprotein (Lp)-A1, LpA1/A2, apoB, and LDL particle size were measured centrally.

RESULTS

CVD was only associated with increased LDL cholesterol (3.6 vs. 3.0 mmol/l, P = 0.02). In contrast, albuminuria was associated with elevated cholesterol, triglyceride, LDL, and apoB and with diminished LDL particle size. No disturbances in HDL and related lipoproteins were noted. In normoalbuminuric patients, CVD was not associated with any significant changes in lipids. CVD in macroalbuminuric patients was associated with increased triglyceride level (2.37 vs. 1.07 mmol/l, P = 0.001; P = 0.02 for CVD/albuminuria interaction) and LDL cholesterol (5.4 vs. 3.3 mmol/l, P = 0.005; P = 0.004 for interaction). Independent associations were observed for total cholesterol and for LDL particle size and albuminuria.

CONCLUSIONS

Abnormalities in lipid and lipoprotein disturbances are more closely related to albuminuria than to CVD in patients with type 1 diabetes. Measurement of conventional parameters provide sufficient risk information. ApoB and LDL particle size offer limited extra information. HDL metabolism remains undisturbed in the presence of complications. These changes reflect associations with glycemic control, which is the key to understanding lipid and lipoprotein disturbances.

Effects of postmenopausal hormone replacement therapy on lipid, lipoprotein, and apolipoprotein (a) concentrations: analysis of studies published from 1974-2000

OBJECTIVE

To establish reference estimates of the effects of different hormone replacement therapy (HRT) regimens on lipid and lipoprotein levels.

DESIGN

Review and pooled analysis of prospective studies published up until the year 2000.

SETTING

Clinical trials centers, hospitals, menopause clinics.

PATIENT(S)

Healthy postmenopausal women.

INTERVENTION(S)

Estrogen alone, estrogen plus progestogen, tibolone, or raloxifene in the treatment of menopausal symptoms.

MAIN OUTCOME MEASURE(S)

Serum high- and low-density lipoprotein (HDL and LDL) cholesterol, total cholesterol, triglycerides, and lipoprotein (a).

RESULT(S)

Two-hundred forty-eight studies provided information on the effects of 42 different HRT regimens. All estrogen alone regimens raised HDL cholesterol and lowered LDL and total cholesterol. Oral estrogens raised triglycerides. Transdermal estradiol 17-beta lowered triglycerides. Progestogens had little effect on estrogen-induced reductions in LDL and total cholesterol. Estrogen-induced increases in HDL and triglycerides were opposed according to type of progestogen, in the order from least to greatest effect: dydrogesterone and medrogestone, progesterone, cyproterone acetate, medroxyprogesterone acetate, transdermal norethindrone acetate, norgestrel, and oral norethindrone acetate. Tibolone decreased HDL cholesterol and triglyceride levels. Raloxifene reduced LDL cholesterol levels. In 41 studies of 20 different formulations, HRT generally lowered lipoprotein (a).

CONCLUSION(S)

Route of estrogen administration and type of progestogen determined differential effects of HRT on lipid and lipoprotein levels. Future work will focus on the interpretation of the clinical significance of these changes.

Resistance of pelvic arteries and plasma lipids in postmenopausal women: comparative study of tibolone and continuous combined estradiol and norethindrone acetate replacement therapy

OBJECTIVE

We sought to compare vascular resistance and plasma lipids in postmenopausal women assigned to tibolone (a synthetic estrogen replacement steroid) therapy or continuous combined hormone replacement therapy.

STUDY DESIGN

Pulsatility and resistance indexes in pelvic arteries (color Doppler transvaginal ultrasonography) and lipids were monitored in this double-blind 1-year trial of 100 women randomized to either 2.5 mg tibolone or 2 mg 17beta-estradiol plus 1 mg norethindrone acetate daily.

RESULTS

Both indexes of the arcuate arteries (uterine arteries) were significantly reduced beyond 3 and 6 months (12 months) from baseline, respectively, by the combined regimen compared with tibolone alone. Tibolone increased the resistance index of arcuate arteries but did not affect uterine arteries. There was no effect of either regimen on the internal iliac arteries. The medians of the percentage changes from baseline of high-density lipoprotein cholesterol (triglycerides) were significant between groups after 1 year, as follows: -17% (-16%) in the tibolone group and -4% (+15%) in the combined group, respectively. Both regimens similarly reduced total and low-density lipoprotein cholesterol and lipoprotein Lp(a).

CONCLUSION

Hormone replacement therapy may induce different or opposite changes of both vascular resistance and lipids. It is unknown whether these findings may modify cardiovascular risk.

Effects of menopause and hormone replacement therapy on plasma lipids, lipoproteins and LDL-receptor activity

A cross-sectional study of ninety six women was conducted to examine the effect of menopause and hormone replacement therapy (HRT) on plasma lipids, lipoproteins and oxidation of low density lipoproteins. The sample consisted of 26 premenopausal women, 26 postmenopausal women taking no replacement hormones and 43 postmenopausal women on hormone replacement therapy. Postmenopausal women not taking replacement hormones had significantly higher plasma cholesterol, low density lipoprotein (LDL) cholesterol and lipoprotein[a] (Lp[a]) levels compared to premenopausal women or postmenopausal women on HRT [6.00 +/- 0.15, 5.36 +/- 0.17 (P < 0.01), 5.63 +/- 0.13 (P < 0.05) mmol/l, respectively for total cholesterol; 4.13 +/- 0.15, 3.64 +/- 0.15 (P < 0.05), 3.82 +/- 0.12 (P < 0.05) mmol/l, respectively for LDL-cholesterol; 48.19 +/- 9.90, 26.59 +/- 5.53 (P < 0.03), 25.12 +/- 4.62 (P < 0.03) mg/dl, respectively for Lp[a]]. The differences in LDL cholesterol concentrations were inversely related to changes in LDL receptor activity (r = -0.27, P < 0.01). HRT use was found to be associated with a significantly smaller LDL particle size. Plasma triglyceride was significantly higher in women on HRT (1.16 +/- 0.07 mmol/l) than in the premenopausal group (0.96 +/- 0.07) or postmenopausal group not using HRT (0.87 +/- 0.06). There were no differences in LDL oxidation between the groups when LDL was oxidised in the presence of copper. Nor was there any difference in the uptake of copper-oxidised or macrophage-modified LDL into J774 macrophages. These results confirm the effect of menopause and exogenous hormones on plasma lipids and lipoproteins, and suggest that HRT modifies the activity of the LDL receptor. Hormone replacement did not appear to protect LDL from oxidation.