Does hormone replacement therapy inhibit coronary artery calcification?

Anti-osteoporotic drugs and vascular calcification: the bidirectional calcium traffic

During the last years, numerous epidemiological studies have demonstrated a direct relationship between vascular calcification and low bone mineral density. This observation is in line with experimental data demonstrating the osteogenic characteristics of calcified arteries. Various common risk factors have been suggested to link vascular calcification and bone loss, including aging, estrogen deficiency, vitamin D and K deficiency, diabetes mellitus, renal failure, smoking, chronic inflammation and oxidative stress. Although the underlying pathogenetic mechanisms are not yet clear, current research is focusing on anti-osteoporotic agents that could potentially affect the deposition of calcium in the arterial wall and thus provide an additional therapeutic strategy in elderly osteoporotic women prone to calcific cardiovascular disease.

Response to hormonal treatment of young females with primary or very premature ovarian failure

The aim of this study was to evaluate the impact of hormone treatment (HT) on several endocrinologic, metabolic and bone parameters in young women with primary or very premature ovarian failure. The study included 40 phenotypically females of 14-20 years old with primary or secondary amenorrhoea and female external genitalia. Study subjects were categorised in three groups: Group A included 12 subjects with Turner syndrome, Group B included 19 subjects with Swyer syndrome and Group C included 9 subjects with very premature ovarian failure. HT was administered for 24 months and included conjugated oestrogens and medroxyprogesterone acetate. In all groups, HT provided a beneficial hormonal profile and resulted in safe and adequate serum oestrogens levels. In Group A, no adverse effects on metabolic or coagulation parameters were noted; significant increases in high-density lipoprotein cholesterol (HDL) levels and bone density were observed. Similar positive effects of HT were observed in Group B. Finally, in Group C, no adverse effects of HT were noted, but the favourable increase in HDL was absent; bone density kept significantly increasing until the 12-month evaluation. In conclusion, the administration of HT is remarkably beneficial for young women with primary or very premature ovarian failure.

Post menopausal hormones and measures of subclinical atherosclerosis: the multi-ethnic study of atherosclerosis

OBJECTIVE

To evaluate whether post menopausal hormones are associated with atherosclerosis.

METHODS

We studied the relation of hormone use to coronary calcification and carotid intima-media thickness in a cross-sectional sample of 3245 post menopausal women, of whom 1620 had used hormones for various periods. Adjusted associations with three measures of hormone use (ever use, duration, and type of hormone) were estimated by multivariable regression.

RESULTS

The prevalence of coronary calcification was only 4 percentage points lower in women who had ever used hormones than in women who had not (40% versus 44%), and was not monotonically related to longer use: <2 years: 38%; 2-6 years: 36%; 6-13 years: 41%; >13 years: 48%. Similarly, duration of hormone use did not show a monotonic dose-response relation with the calcium score. Mean differences in carotid intima-media thickness according to categories of years of hormone use and type of hormone ranged from -0.10 mm to +0.08 mm, with no consistent patterns. Most adjusted associations were weak and sometimes contrary to our expectation.

CONCLUSIONS

We did not find meaningful associations between hormone use and subclinical atherosclerosis-neither to support benefit or harm, nor to support the prevailing theory of "healthy user" bias (namely, inverse associations due to residual confounding).

Differential effects of 17beta-estradiol and raloxifene on VSMC phenotype and expression of osteoblast-associated proteins

Several studies demonstrate an association between osteoporosis and arterial calcific disease, both of which being common in elderly women. Estradiol and raloxifene, a selective estrogen receptor modulator, prevent bone loss in postmenopausal women. Little is known regarding how these agents affect arterial calcification. The aim of this study was to determine whether or not 17beta-estradiol and raloxifene reduced vascular smooth muscle cell (VSMC) differentiation and expression of bone-associated proteins during phosphate-induced calcification in vitro. Aortic VSMC were cultured from adult, gonadally intact, and ovariectomized (OVX) female pigs. Calcifying medium was added, and cells were treated with solvent (control), 17beta-estradiol (E(2)), or raloxifene. Extent of calcification and phenotypic expression of bone-associated proteins [matrix gla protein (MGP), osteoprotegerin (OPG), and bone sialoprotein (BSP)] were examined at 3-day intervals over 2 wk. Calcium content increased in all groups but was greater in VSMC derived from intact compared with OVX animals. E(2) reduced calcification and preserved a contractile phenotype. Expression of OPG significantly decreased with time; this decrease was significantly greater in VSMC derived from OVX compared with gonadally intact pigs. E(2) and raloxifene preserved expression of OPG only in VSMC from intact pigs. Expression of MGP increased significantly with time and was not affected by E(2) or raloxifene treatments. E(2) treatment significantly inhibited synthesis of BSP in cells from both groups. In conclusion, E(2) slows differentiation of VSMC induced by excess phosphate. Effectiveness of raloxifene to preserve expression of bone cell-associated proteins depends on the hormonal status of the tissue donor.

Effects of Hormone Replacement on Progression of Coronary Calcium as Measured by Electron Beam Tomography

PURPOSE

The recent Women's Health Initiative (WHI) results have demonstrated that combined estrogen plus progestin imparts a small but significant increase in cardiovascular risk and breast cancer among asymptomatic women. However, the effect and potential benefit of unopposed estrogen is not as clear. We sought to evaluate the progression of subclinical atherosclerosis in postmenopausal women using no hormone replacement therapy (HRT), combined therapy, and estrogen alone in an observational study.

METHODS

Postmenopausal women without symptoms or known coronary heart disease (CHD) were evaluated at our center for follow-up of coronary calcification. Patients were physician referred and underwent two consecutive electron beam tomography scans at least 1 year apart. All women fitting the study criteria were asked to participate, and those who consented were included. Demographic data, risk factors for CHD, HRT, and other medication use were collected by interview.

RESULTS

The study included 177 asymptomatic women. Calcium progression was 14.6%+/-21% in women taking any hormone therapy (n=97). Annual calcium progression rates in nonusers (n=80) was 22.3%+/-32%. Relative to the nonuser group, HRT treatment inhibited the progression of atherosclerosis by 35% (p=0.01). This effect was independent of age, risk, cardiovascular factors, statin use, or baseline CAC score. Thirty-five of the 97 women (36%) were taking estrogen plus progestin, with an annual increase in calcium scores of 24%+/-23%, similar to the non-HRT women (22%). Those women taking estrogen replacement only (n=62) was 63% lower (9%+/-22%).

CONCLUSIONS

This is an observational study, and the results are in accordance with the recently published WHI study, demonstrating no benefit of estrogen plus progestin compared with no therapy. However, women taking unopposed estrogen demonstrated a significant slowing of subclinical atherosclerosis compared with non-HRT and estrogen plus progestin.

Hormone therapy and coronary artery calcification in asymptomatic postmenopausal women: the Rancho Bernardo Study

OBJECTIVE

To determine (1) whether past or current hormone therapy (HT) in postmenopausal women is associated with subclinical coronary artery plaque burden, (2) whether any association is independent of age, body size, blood pressure, lipids, fasting plasma glucose, cigarette smoking, leisure time physical activity, alcohol intake, use of lipid-lowering medications, and socioeconomic status, and (3) whether any association varies by duration of HT or by the use of combined versus unopposed HT.

DESIGN

An observational study, with HT validated and coronary heart disease risk factors determined between 1997 and 1999 in a research clinic, and coronary artery calcium score (CACS) evaluated by electron beam computed tomography in 2001 through 2002. Participants were 204 community-dwelling postmenopausal women from the Rancho Bernardo cohort aged 55 to 78 years with no history of heart disease.

RESULTS

The odds of severe CACS in current estrogen users (n = 127) was 0.40 (95% CI 0.19, 0.82), controlling for all covariates. Past users (n = 40) had intermediate odds (multiply adjusted OR = 0.66, 95% CI = 0.28, 1.58). In subgroup analyses, age-adjusted associations did not differ between the 68 women using unopposed estrogen versus the 59 using an estrogen-progestin regimen. Women who had used HT for at least 10 years (n = 86) had significantly less (P = 0.01) plaque burden than shorter term users (n = 41).

CONCLUSIONS

Both the strong association and the duration of use effect independent of lifestyle and social class suggest an antiatherogenic effect of postmenopausal estrogen. Only a clinical trial can completely exclude confounding by social class, lifestyle, and unmeasured covariates.

Vascular calcification: mechanisms and clinical ramifications

Vascular calcification, long thought to result from passive degeneration, involves a complex, regulated process of biomineralization resembling osteogenesis. Evidence indicates that proteins controlling bone mineralization are also involved in the regulation of vascular calcification. Artery wall cells grown in culture are induced to become osteogenic by inflammatory and atherogenic stimuli. Furthermore, osteoclast-like cells are found in calcified atherosclerotic plaques, and active resorption of ectopic vascular calcification has been demonstrated. In general, soft tissue calcification arises in areas of chronic inflammation, possibly functioning as a barrier limiting the spread of the inflammatory stimulus. Atherosclerotic calcification may be one example of this process, in which oxidized lipids are the inflammatory stimulus. Calcification is widely used as a clinical indicator of atherosclerosis. It progresses nonlinearly with time, following a sigmoid-shaped curve. The relationship between calcification and clinical events likely relates to mechanical instability introduced by calcified plaque at its interface with softer, noncalcified plaque. In general, as calcification proceeds, interface surface area increases initially, but eventually decreases as plaques coalesce. This phenomenon may account for reports of less calcification in unstable plaque. Vascular calcification is exacerbated in certain clinical entities, including diabetes, menopause, and osteoporosis. Mechanisms linking them must be considered in clinical decisions. For example, treatments for osteoporosis may have unanticipated effects on vascular calcification; the converse also applies. Further understanding of processes governing vascular calcification may yield new therapeutic options for vascular disease.

Pulse Pressure Is an Independent Predictor for the Progression of Aortic Wall Calcification in Patients With Controlled Hyperlipidemia

Recent epidemiological studies suggested that calcifications of the aorta and the coronary arteries are important predictors for cardiovascular morbidity and mortality. However, the relation between blood pressure components and the progression of vascular wall calcification has remained unclear. We quantified calcium deposits in the abdominal aorta as the percentage of aortic calcification volume (%ACV) using computed tomography in patients with hyperlipidemia. Those who had aortic calcification were treated with lipid-lowering agents and followed-up for >2 years (6.3+/-3.2 years). The relationship between the components of blood pressure and the increase in %ACV per year (Delta%ACV/year) was assessed in subjects in whom serum lipid levels were well controlled during the follow-up periods. An age- and sex-adjusted correlation analysis showed that Delta%ACV/year was significantly correlated to body mass index (r=0.229, P=0.015), systolic blood pressure (r=0.244, P=0.009), and pulse pressure (r=0.359, P<0.001). A multivariate regression analysis revealed that pulse pressure is an independent and the most sensitive predictor for Delta%ACV/year (beta=0.389, P<0.001) among the blood pressure components. These results suggested that increase in pulse pressure promotes the progression of vascular calcification.

Low bone mineral density in the hip as a marker of advanced atherosclerosis in elderly women

Previous studies indicate that low bone mineral density (BMD) in the hip is a useful predictor of cardiovascular mortality among the elderly. The objective of this study was to investigate whether low hip BMD is directly associated with the severity of atherosclerosis. The per-protocol population consisted of 963 women aged 60-85 years. Study variables were aortic calcification (AC) graded on lateral lumbar radiographs, BMD at various anatomic sites (distal radius, lumbar spine, proximal femur) measured by DXA, information on various risk factors, and medical history. After adjustment for age, BMD at the proximal femur, but not at the radius or spine BMD, showed statistically significant association with the severity of AC (r = -0.12-17, P < 0.001). Age, years since menopause, BMI, level of education, current and previous smoking, and weekly fitness activity were significant common risk factors (all P < 0.05) with contrasting influence on AC and hip BMD. In a multiple regression model, AC contributed significantly and independently to the variation in hip BMD (beta = -0.10, P = 0.004). Impaired blood flow represented by 40 women with documented history of intermittent claudication was not an independent contributor and did not alter the association between AC and hip BMD. However, AC and demineralization in the hip was particularly severe in women with intermittent claudication accompanied by a higher prevalence of coronary heart disease compared with age-matched controls (all P < 0.001). In conclusion, severe osteoporosis in the hip may indicate advanced atherosclerosis and thereby an increased risk for not only hip fractures but also for coronary heart disease. The results further emphasize that osteoporosis in the hip and peripheral vascular disease are linked by common risk factors and pathomechanisms.

The association of hormone replacement therapy and coronary calcium as determined by electron beam tomography

BACKGROUND

Observational studies have shown that hormone replacement therapy (HRT) is associated with lower coronary heart disease (CHD), and animal studies demonstrate potent antiatherosclerotic estrogen effects. Paradoxically, recent clinical trials have not demonstrated a protective effect. This paradox may be explained by a healthy woman effect bias. Women using HRT have improved health outcomes unrelated to underlying atherosclerotic burden. Examination of the association between coronary calcium (CC), a marker of atherosclerotic plaque burden, and the use of HRT in postmenopausal women may help address this paradox.

METHODS

The study population comprised 641 asymptomatic postmenopausal women, 425 (66%) of whom were taking HRT. Data obtained from a self-administered questionnaire and blood samples were analyzed. Electron beam tomography (EBT) for CC was performed on each subject. Analysis of variance (ANOVA) was used to evaluate adjusted means.

RESULTS

Independent t tests found that age, low-density lipoproteins (LDL), high-density lipoproteins (HDL), body mass index (BMI), vitamin use, coronary calcium score (CCS), coronary calcified volume (CCV), and the number of coronary calcium lesions (CCL) were significantly different between the HRT group and the non-HRT group. However, after controlling for potential confounders, no significant differences were observed in CCS, CCV, or the number of CCL between the HRT and non-HRT groups. Stratifying by BMI shows that obese/overweight women taking HRT have lower adjusted CCS and fewer CCL than the obese/overweight women not taking HRT.

CONCLUSIONS

These findings demonstrate no association between HRT use and CCS, CCV, and CCL after adjusting for measurable confounders in postmenopausal women. Our failure to demonstrate an independent association between HRT use and a marker of atherosclerotic plaque burden suggests that a healthy woman effect may explain the beneficial association between HRT use and CHD in observational studies.

Hypertension in menopausal women--a special case, for special treatment?

After the menopause the consequences of hypertension in women change. Their risks of myocardial infarction and stroke rise steeply, a rise that has been blamed in part on the loss of estrogen and the onset of menopausal metabolic syndrome, with endothelial dysfunction, hyperlipidemia, insulin resistance and derangement in coagulation. Hypertensive menopausal women have not had optimum treatment. They have poorer prognoses than men of the same age. Their antihypertensive management therefore merits special attention. Hormone replacement, aspirin prophylaxis and lipid-lowering drugs have their place. The antihypertensive drug chosen should not worsen the metabolic syndrome: angiotensin-II converting enzyme (ACE) inhibitors are therefore among the first-line drugs. Few drugs have been specifically aimed at menopausal hypertension and these are reviewed here.

Arterial calcification: a review of mechanisms, animal models, and the prospects for therapy

The causes of arterial calcification are beginning to be elucidated. Macrophages, mast cells, and smooth muscle cells are the primary cells implicated in this process. The roles of a variety of bone-related proteins including bone morphogenetic protein-2 (BMP-2), matrix Gla protein (MGP), osteoprotegerin (OPG), osteopontin, and osteonectin in regulating arterial calcification are reviewed. Animals lacking MGP, OPG, smad6, carbonic anhydrase isoenzyme II, fibrillin-1, and klotho gene product develop varying extents of arterial calcification. Hyperlipidemia, vitamin D, nicotine, and warfarin, alone or in various combinations, produce arterial calcification in animal models. MGP has recently been discovered to be an inhibitor of bone morphogenetic protein-2, the principal osteogenic growth factor. Many of the forces that induce arterial calcification may act by disrupting the essential post-translational modification of MGP, allowing BMP-2 to induce mineralization. MGP requires gamma-carboxylation before it is functional, and this process uses vitamin K as an essential cofactor. Vitamin K deficiency, drugs that act as vitamin K antagonists, and oxidant stress are forces that could prevent the formation of GLA residues on MGP. The potential role of arterial apoptosis in calcification is discussed. Potential therapeutic options to limit the rate of arterial calcification are summarized.

Acoustic shadowing on B-mode ultrasound of the carotid artery predicts ischemic stroke: the Atherosclerosis Risk in Communities (ARIC) study

BACKGROUND AND PURPOSE

We examined the relationship of carotid artery lesions (CALs), with and without acoustic shadowing (AS), to incident ischemic stroke events in the Atherosclerosis Risk in Communities study cohort.

METHODS

The study population consisted of 13 123 men and women aged 45 to 64 years, and free of stroke, examined during 1986-1989. Over an average follow-up time of 8.0 years, 226 incident ischemic stroke cases (thromboembolic brain infarctions) were identified and classified by a standardized protocol. Three levels of exposure were defined on the basis of the presence of B-mode ultrasound-detected CALs and AS in a 3-cm segment of the carotid arteries centered at the bifurcation.

RESULTS

The hazard ratio for ischemic stroke adjusted for age, ethnicity, and study site for women with a CAL without AS, compared with those without a CAL, was 1.92 (95% CI, 1.23, 3.01), and the hazard ratio comparing those with a CAL with AS with those without a CAL was 4.01 (95% CI, 2.28, 7.06). The corresponding hazard ratios for men were 1.99 (95% CI, 1.36, 2.91) and 2.23 (95% CI, 1.32, 3.79). Although adjustment for diabetes, hypertension medication, systolic blood pressure, left ventricular hypertrophy score, fibrinogen, von Willebrand factor antigen, and smoking status attenuated these associations somewhat, when compared with no evidence of CALs, CALs with AS remained statistically significant predictors of ischemic stroke in women, while CALs without AS were predictive of ischemic stroke in men.

CONCLUSIONS

B-mode ultrasound-detected CALs and AS serve as markers of atherosclerosis and thus are predictive of ischemic stroke.

Evaluation of subsecond gated helical CT for quantification of coronary artery calcium and comparison with electron beam CT

OBJECTIVE

Since its introduction early in the 1990s, helical CT has become the predominant technology for obtaining CT images for medical applications. Recent improvements in the temporal resolution of helical CT (subsecond) and the addition of retrospective cardiac gating are combined in this report evaluating cardiac-gated helical CT for quantifying coronary artery calcium. We compare total calcium scores determined on subsecond gated helical CT with the current reference for coronary calcium evaluation, electron beam CT.

MATERIALS AND METHODS

We compared total calcium scores obtained using a general purpose, unmodified helical CT scanner with scores obtained using electron beam CT in 36 individuals who were 68+/-11 years old (age range, 41-85 years).

RESULTS

Correlation coefficients ranged from 0.97 to 0.98 (Pearson's product moment) and from 0.95 to 0.96 (Spearman's rank order), depending on the coronary calcium scoring method used. Agreement in the classification of participants as "healthy" or "diseased" at threshold total calcium scores of 10, 100, 160, 200, 400, and 680 was, respectively, 94%, 97%, 89%, 92%, 94%, and 100% using the conventional electron beam CT scoring method and an equivalent method with helical CT.

CONCLUSION

A general purpose, current generation helical CT scanner equipped for retrospective cardiac gating can accurately quantify coronary calcium, and the results are highly correlated to scores obtained with electron beam CT. As an alternative method for measuring coronary calcium, gated subsecond cardiac helical CT offers greater availability and lower cost, thereby making population-based screening for coronary artery calcium more feasible.

The role of osteoprogenitors in vascular calcification

Calcification is a component of vascular disease that usually occurs in concert with atheroma formation but through distinct pathophysiological processes. Vessel wall osteoprogenitor cells known as calcifying vascular cells can form bone matrix proteins and calcified nodules, analogous to osteoblastic differentiation in bone. These cells have been isolated from the tunica media of bovine and human arteries, and both in-vitro tissue culture models and mouse models of vascular calcification have been established. Studies of the effects of diabetes mellitus, hyperlipidemia, estrogens and glucocorticoids on calcifying vascular cell function provide insight into the relationship between common human disease states and vascular calcification.

Vascular calcification

Vascular calcification is an active and modifiable process involved in many disease entities, including atherosclerosis, cardiac valve disease and calcific uremic arteriolopathy. It occurs with distinct characteristics at different sites in the vessel wall. The mechanism by which calcification is induced remains uncertain; the roles of bone matrix and extracellular matrix proteins, estrogen and vitamin D are being further defined in animal models and clinical trials. Some risk factors for calcific uremic arteriolopathy and cardiac valve calcification, both disproportionately affecting chronic hemodialysis patients, have been identified in observational studies.