The value of phytoestrogens as a possible therapeutic option in postmenopausal women with coronary heart disease

Improved yeast-screening assay for phytoestrogens

A yeast estrogen screening (YES) assay was improved to increase sensitivity for detection of phytoestrogens. New yeast strains minus one or the other of transporters Pdr5 or Snq2 and harboring yEGFP as a reporter gene were developed. The new strains showed 2-100-fold improvement in sensitivity for detection of standard estrogens and antiestrogens. In addition, the assay time (1 h) using the newly developed strains was shorter than that (4 h) previously reported. Furthermore, the snq2-minus strains were most effective for detection of estrogenic activity while the pdr5-minus strains were most effective for detection of antiestrogenic activity. The efficacy of the new methods was evaluated and confirmed by testing with 23 Thai medicinal plant species. The new strains were also tested for detection of xenoestrogens. The results revealed that the newly developed YES methods were specific and rapid and suitable for simple high-throughput screening or detection of estrogen-like compounds.

Haemostatic effects of phytoestrogen genistein in postmenopausal women

INTRODUCTION

Genistein is an isoflavone phytoestrogen derived from the soybean which acts as natural selective estrogen receptor modulator. Various studies have pointed out its cardioprotective role. The aim of the study was to evaluate the haemostatic effects of genistein in postmenopausal women.

MATERIAL AND METHODS

In this double-blind placebo-controlled trial we enrolled 104 healthy postmenopausal women with osteopenia. 53 patients (mean age 54.9+/-4.2 yr; BMI 23.4+/-3.2 Kg/m(2)) received genistein (54 mg/day) and 51 patients (mean age 55.4+/-4.3 yr; BMI 23.6+/-3.6 Kg/m(2)) received an identical placebo-tablet. Both groups received a calcium and vitamin D supplement. Plasma levels of D-dimer (DD), plasminogen activator inhibitor-1 (PAI-1) and prothrombin fragment 1+2 (F1+2) were measured at baseline and after 6 and 12 months of treatment.

RESULTS

Baseline characteristics of the two groups were similar. Compared with placebo, genistein decreased significantly DD (p<0.001), but did not affect PAI-1 and F 1+2 plasma levels.

CONCLUSION

The results of our study do not confirm effects of genistein on activation of the haemostatic system, but on the contrary the significant decrease of DD could indicate a possible cardioprotective role of genistein in postmenopausal women.

Safety, tolerability, and pharmacokinetics of single ascending doses of synthetic genistein (Bonistein) in healthy volunteers

Genistein, an isoflavone and phytoestrogen predominantly found in soy, is considered a potentially safe therapeutic option to prevent postmenopausal bone loss. A novel purified product consisting of 99.4% synthetic genistein aglycone was investigated in a phase 1 clinical study to assess safety and tolerability in healthy volunteers as well as to obtain pharmacokinetic data. Single oral doses of 30, 60, 150, or 300 mg were administered to 40 healthy volunteers in this prospective, randomized, open-label and sequential-group study. Tolerability of the different genistein doses was very good. No clinically significant effects on vital signs, ECG, and clinical laboratory parameters were observed. Genistein was rapidly absorbed and the kinetic profiles revealed a one-peak plasma concentration-time course. Mean Cmax values of 252.0, 605.0, 1518.0, and 1808.0 ng/mL were observed after 4.0 to 6.0 hours. The mean terminal elimination half-lives were calculated to be 7.7, 7.5, 8.1, and 10.2 hours resulting in mean AUCs(0-infinity) of 2761.8, 8022.3, 21655.0, and 27537.8 ngxhr/mL. Linear regression of the dose-normalized AUCs(0-infinity) was not significantly different from zero, whereas the analysis for Cmax showed significance. Based on consecutive administration of single oral doses of genistein, dose linearity was assumed for extent of absorption [AUC(0-infinity)] for all doses (30-300 mg) and for rate of absorption (Cmax) up to 150 mg. At the highest dose the intestinal rate of absorption of genistein seemed to be limited. Genistein was safe and well tolerated in the dose range investigated and showed nearly dose-linear pharmacokinetic characteristics.

Effects of genistein and hormone-replacement therapy on bone loss in early postmenopausal women: a randomized double-blind placebo-controlled study

The natural isoflavone phytoestrogen genistein has been shown to stimulate osteoblastic bone formation, inhibit osteoclastic bone resorption, and prevent bone loss in ovariectomized rats. However, no controlled clinical trial has been performed so far to evaluate the effects of the phytoestrogen on bone loss in postmenopausal women. We performed a randomized double-blind placebo-controlled study to evaluate and compare with hormone-replacement therapy (HRT) the effect of the phytoestrogen genistein on bone metabolism and bone mineral density (BMD) in postmenopausal women. Participants were 90 healthy ambulatory women who were 47-57 years of age, with a BMD at the femoral neck of <0.795 g/cm2. After a 4-week stabilization on a standard fat-reduced diet, participants of the study were randomly assigned to receive continuous HRT for 1 year (n = 30; 1 mg of 17beta-estradiol [E2] combined with 0.5 mg of norethisterone acetate), the phytoestrogen genistein (n = 30; 54 mg/day), or placebo (n = 30). Urinary excretion of pyridinoline (PYR) and deoxypyridinoline (DPYR) was not significantly modified by placebo administration either at 6 months or at 12 months. Genistein treatment significantly reduced the excretion of pyridinium cross-links at 6 months (PYR = -54 +/- 10%; DPYR = -55 +/- 13%; p < 0.001) and 12 months (PYR = -42 +/- 12%; DPYR = -44 +/- 16%; p < 0.001). A similar and not statistically different decrease in excretion of pyridinium cross-links was also observed in the postmenopausal women randomized to receive HRT. Placebo administration did not change the serum levels of the bone-specific ALP (B-ALP) and osteocalcin (bone Gla protein [BGP]). In contrast, administration of genistein markedly increased serum B-ALP and BGP either at 6 months (B-ALP = 23 +/- 4%; BGP = 29 +/- 11%; p < 0.005) or at 12 months (B-ALP = 25 +/- 7%; BGP = 37 +/- 16%; p < 0.05). Postmenopausal women treated with HRT had, in contrast, decreased serum B-ALP and BGP levels either at 6 months (B-ALP = -17 +/- 6%; BGP = -20 +/- 9%; p < 0.001) or 12 months (B-ALP = -20 +/- 5%; BGP = -22 +/- 10%; p < 0.001). Furthermore, at the end of the experimental period, genistein and HRT significantly increased BMD in the femur (femoral neck: genistein = 3.6 +/- 3%, HRT = 2.4 +/- 2%, placebo = -0.65 +/- 0.1%, and p < 0.001) and lumbar spine (genistein = 3 +/- 2%, HRT = 3.8 +/- 2.7%, placebo = -1.6 +/- 0.3%, and p < 0.001). This study confirms the genistein-positive effects on bone loss already observed in the experimental models of osteoporosis and indicates that the phytoestrogen reduces bone resorption and increases bone formation in postmenopausal women.

Reduction of post injury neointima formation due to 17beta-estradiol and phytoestrogen treatment is not influenced by the pure synthetic estrogen receptor antagonist ICI 182,780 in vitro

BACKGROUND

Animal and organ culture experiments have shown beneficial inhibitory estrogen effects on post injury neointima development. The purpose of this study was to investigate whether such estrogen effects are influenced by the estrogen receptor antagonist ICI 182,780. Different concentrations of 17beta-estradiol and the phytoestrogens genistein and daidzein were tested.

METHODS

Female New Zealand White rabbits were benumbed. In situ vascular injury of the thoracic and abdominal aorta was performed by a 3F Fogarty catheter. Segments of 5 mm were randomised and held in culture for 21 days. Three test series were performed: 1) control group--20 microM ICI--30 microM ICI--40 microM ICI. 2) control group--20 microM ICI--40 microM 17beta-estradiol--40 microM 17beta-estradiol + 20 microM ICI. 3) control group--20 microM ICI--40 microM daidzein--40 microM daidzein + 20 microM ICI--20 microM genistein--20 microM genistein + 20 microM ICI. After 21 days the neointima-media-ratio was evaluated.

RESULTS

1) Treatment with ICI 182,780 did not reduce neointima formation significantly (p = 0.05). 2) 40 microM 17beta-estradiol alone (p < 0.0001) and in combination with 20 microM ICI (p < 0.0001) reduced neointima formation significantly. 3) 20 microM genistein alone (p = 0.0083) and combined with 20 microM ICI (p = 0.0053) reduced neointima formation significantly. 40 microM daidzein did not have a significant (p = 0.0637) effect.

CONCLUSIONS

The estrogen receptor antagonist ICI 182,780 did not modulate the inhibitory estrogen effects on post injury neointima formation. These results do not support the idea that such effects are mediated by vascular estrogen receptors.

The effect of the phytoestrogen genistein on plasma nitric oxide concentrations, endothelin-1 levels and endothelium dependent vasodilation in postmenopausal women

The phytoestrogen genistein improves endothelial dysfunction in ovariectomized rats through a nitric oxide-dependent mechanism. We investigated whether genistein alters the balance between the nitric oxide products and endothelin-1 and influences endothelium-dependent vasodilation in postmenopausal women. Sixty healthy postmenopausal women were enrolled in the study. A double-blind, placebo controlled, randomized design was employed. After a 4-week stabilization on a standard fat-reduced diet, participants to the study were randomly assigned to receive either genistein (n=30; 54 mg/day) or placebo (n=30). Flow-mediated, endothelium-dependent vasodilation of the brachial artery, plasma nitric oxide breakdown products and endothelin-1 levels were measured at baseline and after 6 months of genistein therapy. The mean baseline level of nitrites/nitrates was 22+/-10 micromol/l and increased to 41+/-10 micromol/ml after 6 months of treatment. The mean baseline plasma endothelin-1 level was 14+/-4 pg/ml and decreased to 7+/-1 pg/ml following 6 months of treatment with genistein. The mean baseline ratio of nitric oxide to endothelin also significantly increased at the end of treatment. Flow-mediated, endothelium-dependent vasodilation of the brachial artery was 3.9+/-0.8 mm at baseline and increased to 4.4+/-0.7 mm after 6 months of treatment. Placebo-treated women showed no changes in plasma nitrites/nitrates, endothelin-1 levels and flow-mediated vasodilation. Genistein therapy improves flow-mediated endothelium dependent vasodilation in healthy postmenopausal women. This improvement may be mediated by a direct effect of genistein on the vascular function and could be the result of an increased ratio of nitric oxide to endothelin.