Raloxifene, conjugated oestrogen and endothelial function in postmenopausal women

The effects of different hormone treatment on endothelial function in healthy postmenopausal women

We aimed to compare the effects of different types of hormone treatment (HT) on endothelial function by means of brachial artery ultrasonographic examination in postmenopausal women. Sixty-two healthy postmenopausal women were included in this study. Subjects were assigned to one of the five groups receiving 6 months of treatment [estrogen (conjugated estrogen), estrogen (conjugated estrogen) plus progesterone (medroxyprogesterone acetate; MPA), raloxifene, tibolone or control]. Endothelial function was assessed by measurement of flow-mediated dilatation (FMD) and nitrate-dependent dilatation in the brachial artery. At the end of 6 months, FMD values were found to be significantly increased in women with HT use than the control group (p = 0.001). In subgroups, FMD increased significantly in the estrogen [12 ± 7 versus 25 ± 8, p = 0.001] and raloxifene groups [7 ± 5 versus 11 ± 3, p < 0.01] compared to tibolone and estrogen plus progesterone groups. In conclusion, endothelial function is impaired in postmenopausal women. Both estrogen and raloxifene regimens may improve endothelial functions in healthy postmenopausal women. The direct protective effects of these HT on the healthy endothelium may be more remarkable than the favorable effects on lipid profile.

Raloxifene: a selective estrogen-receptor modulator for postmenopausal osteoporosis - a clinical update on efficacy and safety

Selective estrogen-receptor modulators are molecules with specific estrogen-receptor binding affinity. Each selective estrogen-receptor modulator induces a unique conformation in the ligand-receptor complex, which leads to transcriptional activation and/or inhibition. Raloxifene 60 mg/day, a benzothiophene selective estrogen-receptor modulator, is approved for the prevention and treatment of postmenopausal osteoporosis. This article provides an update on new studies and further analyses of clinical trial data for raloxifene. The Multiple Outcomes of Raloxifene Evaluation (MORE) trial of women with osteoporosis has described the efficacy of raloxifene in decreasing vertebral fracture risk over 4 years. The Continuing Outcomes Relevant to Evista((R)) (CORE) trial, designed to assess the effects of raloxifene on breast cancer prevention, is a 4-year continuation of MORE. The skeletal and cardiovascular effects of raloxifene in the CORE study were similar to those observed in MORE. The relative risk of developing breast cancer was significantly decreased in women treated with raloxifene, compared with placebo, after 4 years in MORE and 8 years in the CORE trial. The incidence of uterine bleeding, endometrial hyperplasia and endometrial cancer was similar between raloxifene and placebo after 8 years of treatment. Raloxifene use is associated with a higher incidence of hot flashes and leg cramps, and an increased risk of venous thromboembolic events.

Morphologic effects of epithelial ion channels on the mouse uterus: differences between raloxifene analog (LY117018) and estradiol treatments

OBJECTIVE

Estrogen regulates the expression of epithelial Na(+) channel (ENaC) and cystic fibrosis transmembrane conductance regulator (CFTR). Our purpose was to assess the effects of raloxifene analog LY117018 on the expression of ENaC and CFTR in ovariectomized mice.

STUDY DESIGN

Three groups of 5 female ovariectomized mice were treated with 17beta-estradiol benzoate (E2), LY117018 (LY), or vehicle, respectively, for 4-12 weeks. Effects on the messenger ribonucleic acid expression levels of ENaC and CFTR channels in the uterus were studied using real-time reverse transcriptase-polymerase chain reaction.

RESULTS

E2 treatment induced CFTR expression, repressed ENaC expression and resulted in fluid accumulation in the uterus. In contrast, LY induced CFTR expression, did not repress ENaC expression, and caused no fluid accumulation.

CONCLUSION

Estradiol and LY117018 differentially regulate the expression of CFTR and ENaC in ovariectomized mouse uterus. This finding suggests that uterine fluid accumulation can be controlled mainly by targeting the ENaC.

Differential impact of conventional-dose and low-dose postmenopausal hormone therapy, tibolone and raloxifene on C-reactive protein and other inflammatory markers

BACKGROUND

Postmenopausal hormone therapy (HT) is associated with an increased risk for arterial and venous thrombosis.

OBJECTIVES

To compare the impact of HT, tibolone, and raloxifene on C-reactive protein (CRP) and other inflammatory markers, and to investigate possible underlying mechanisms for changes in CRP and D-dimer.

METHODS

Two hundred and two healthy women were randomly assigned to treatment for 12 weeks with either low-dose HT containing 1 mg of 17beta-estradiol and 0.5 mg of norethisterone acetate (NETA) (n = 50), conventional-dose HT containing 2 mg of 17beta-estradiol and 1 mg of NETA (n = 50), 2.5 mg of tibolone (n = 51), or 60 mg of raloxifene (n = 51).

RESULTS

CRP increased in the conventional-dose HT and low-dose HT groups. These changes were significantly more pronounced in the conventional-dose HT group (RMANOVA, P = 0.02). Also, tibolone was associated with an increase in CRP, in contrast to raloxifene, which reduced CRP. Reductions in levels of Lp(a), intercellular adhesion molecule-1 (ICAM-1), P-selectin, E-selectin, monocyte chemotactic protein 1 (MCP-1) and interleukin-6 (IL-6) were observed in all treatment groups. The changes were most pronounced for the conventional-dose HT group, and least pronounced for the raloxifene group, whereas the changes in those allocated to tibolone and low-dose HT were intermediary. Increased levels of tumor necrosis factor (TNF)-alpha and von Willebrand factor (VWF) were seen in the raloxifene group. We observed positive associations between changes in IL-6, VWF, MCP-1, and CRP.

CONCLUSIONS

The regimens had markedly different impacts on markers of inflammation. The average increase in CRP was not accompanied by increases in the average levels of IL-6, TNF-alpha or other markers, but women with large reductions in IL-6 had reduced increases in CRP.

Effect of estrogen-progestin hormonal replacement therapy on blood coagulation and fibrinolysis in postmenopausal women

OBJECTIVE

To evaluate antithrombin III (AT), thrombin (Fragment 1+2 [F1+2] and thrombin-antithrombin [TAT]) generation markers, as well as other coagulation parameters, such as prothrombin time, partial activated thromboplastin time, thrombin time, fibrinogen, euglobulin lysis time, and platelet count, in postmenopausal women after hormonal therapy.

STUDY DESIGN

Forty-five patients who received either 0.625 mg/day unopposed oral conjugated equine estrogen (CEE), 0.625 mg/day oral CEE plus medroxyprogesterone acetate (MP), or 50 microg/day transdermal 17beta-estradiol plus MP, were included. Tests were performed before (T0) and after 3 (T3), 6 (T6) and 12 (T12) months of treatment. AT was determined by an amidolytic method, whereas F1+2 and TAT complex were measured by ELISA.

RESULTS

There was a significant reduction in the AT level of patients who received oral CEE plus MP at T3. There was no AT reduction in patients taking either oral CEE alone or transdermal 17beta-estradiol plus MP. F1+2 increased in all patients, but it reached statistical significance only in patients receiving transdermal 17beta-estradiol MP at T3.

CONCLUSIONS

The CEE associated with MP treatment may reduce AT levels, whereas unopposed CEE or transdermal 17beta-estradiol plus MP does not change AT. These changes might not be clinically relevant in the general population; however, hormonal replacement therapy may increase the risk of thrombosis in women with congenital or acquired thrombophilia.

Raloxifene improves the ovariectomy-induced impairment in endothelium-dependent vasodilation

OBJECTIVE

To examine the effect of raloxifene on the endothelial dysfunction caused by surgical menopause.

DESIGN

Ten premenopausal women who underwent gynecological surgery with ovariectomy were divided into two groups. Five participants used raloxifene (60 mg/d) for 7 days staring 1 week after the surgery, and the other five participants did not use raloxifene. We examined the changes in flow-mediated dilatation (FMD) of the brachial artery using ultrasonography. Vasodilation in response to nitroglycerin was also studied. We also measured the brachial-ankle pulse wave velocity to examine the change in arterial stiffness in these participants before and after surgical menopause.

RESULTS

In both the raloxifene and control groups, a significant decrease in FMD was observed 1 week after the surgery. Although no further changes in FMD were observed in the control group at 2 weeks after surgery, FMD was significantly increased in the raloxifene group. No remarkable changes in nitroglycerin or brachial-ankle pulse wave velocity were observed after surgery in either group.

CONCLUSIONS

Raloxifene rapidly restored FMD that was impaired after surgical menopause. Therefore, raloxifene may be effective for ameliorating and maintaining endothelial function in premenopausal women who undergo ovariectomy.

Menopause, estrogens, and endothelial dysfunction: current concepts

Menopause is defined as the permanent cessation of menses. Cardiovascular disease is the leading cause of death among postmenopausal women in developed countries. The disparity between the incidence of cardiovascular disease among women in pre- and postmenopause has been ascribed to the actions of endogenous estrogen on the cardiovascular system and, particularly, on the vascular endothelium. The endothelium plays an important role in cardiovascular homeostasis, either through the vascular tonus and its regulation, or through coagulation and the inflammatory response. Endothelial dysfunction is implicated in the genesis of atherosclerosis and other chronic disorders, such as diabetes mellitus and hypertension. The pharmacological use of estrogen exerts influence on the circulating levels of markers of vascular tonus, and inflammation, as well as prothrombotic, and fibrinolytic markers, but the impact of these changes on the atherosclerotic disease is still uncertain.

Disposition mechanisms of raloxifene in the human intestinal Caco-2 model

The purpose of this study was to determine the mechanisms responsible for transport of raloxifene and its hydrophilic conjugates. Human intestinal Caco-2 cell culture model and Caco-2 cell lysate were used for the studies. The results indicated that absorptive permeability (PAB) of raloxifene was lower than its secretory permeability (PAB). As the concentration increased, the efflux ratio (PBA/PAB) decreased, but PBA increased. PAB was also increased in the presence of verapamil and cyclosporine A, two P-glycoprotein inhibitors. Raloxifene was extensively metabolized into sulfated and glucuronidated conjugates. The extent of metabolism or clearance was decreased as the concentration increased from 3.4 (96%) to 30 (22%) microM. Multidrug resistance-related protein inhibitors MK-571 (C26H26ClN2O3S2) and leukotriene C4 significantly decreased (maximal 80%) apical efflux of both conjugates. They also significantly decreased (maximal 85%) basolateral efflux of glucuronides but not sulfates. On the other hand, organic anion transporter (OAT) inhibitor estrone sulfate and estrone glucuronide significantly decreased (maximal 50%) the efflux of sulfate from both sides but had variable effects on glucuronide efflux. Inhibition of conjugate efflux with the OAT inhibitor estrone sulfate was concentration dependent, which resulted in increased transport of intact raloxifene (maximal 90%). This increase in raloxifene transport was also observed in the presence of another OAT inhibitor estrone glucuronide (70%). In conclusion, this is the first report that inhibition of an efflux transporter responsible for the transport of metabolites can result in increase in the transport of the intact compound. It also provides additional explanation why raloxifene has low bioavailability but a long half-life.