Isoflavones improve vascular reactivity in post-menopausal women with hypercholesterolemia

Soy Isoflavones Inhibit Endothelial Cell Dysfunction and Prevent Cardiovascular Disease

Soybeans are among the most popular foods worldwide, and intake of soy-containing foods has been associated with many health benefits in part because of it structure similar to estrogen. Epidemiologic studies have demonstrated that soy consumption improves serum profiles of hypercholesterolemic patients. Several studies have also indicated an inverse relationship between the consumption of soy isoflavones and the incidence of cardiovascular diseases (CVD). Soy is a rich dietary source of isoflavones. The main soy isoflavones are daidzein and genistein; equol, another isoflavone and a major intestinal bacterial metabolite of daidzein, is generated by enterobacterial effects. Many isoflavones have antioxidative effects and anti-inflammatory actions, as well as induce nitric oxide production to maintain a healthy endothelium and prevent endothelial cell dysfunction. These effects may limit the development of atherosclerosis and CVD and restore healthy endothelial function in altered endothelia. Although the evidence supporting the benefits of soy isoflavones in CVD prevention continues to increase, the association between soy isoflavones and disease is not fully understood. This review summarized recent progress in identifying the preventive mechanisms of action of dietary soybean isoflavones on vascular endothelial cells. Furthermore, it describes the beneficial roles that these isoflavones may have on endothelial dysfunction-related atherosclerosis.

Effects of Drugs, Phytoestrogens, Nutrients and Probiotics on Endothelial Dysfunction in the Estrogen-Deficient State

BACKGROUND

Endothelial dysfunction is commonly present in estrogen-deficient states, e.g., after menopause. In the search for alternatives to hormone replacement therapy (HRT), treatments based on phytoestrogens or in non-hormonal mechanisms have been under evaluation.

OBJECTIVE

Here we aim to present an overview of innovative potential treatments for endothelial dysfunction in estrogen-deficient states, introducing our own preliminary data about the probiotic kefir.

METHODS

We conducted a review based on a PubMed database search for keywords of interest (Menopause, Ovariectomy, Vascular dysfunction, Hot flashes, Metformin, Statins, Phytoestrogens, Omega-3, Vitamin D, Probiotics).

RESULTS

Vascular parameters were found to be improved by both metformin and statins through pleiotropic effects, being related to a decrease in oxidative stress and restoration of the nitric oxide pathway. Phytoestrogens such as genistein and resveratrol have also been shown to improve vascular dysfunction, which seems to involve their estrogenic-like actions. Omega-3, vitamin D and its analogues, as well as probiotics, have shown similar vascular beneficial effects in both postmenopausal women and an animal model of ovariectomy (OVX), which could be related to antioxidant and/or anti-inflammatory effects. Moreover, our preliminary data on the probiotic kefir treatment in OVX rats suggested a vascular antioxidant effect. In particular, some evidence points to statins and vitamin D having anti-atherogenic effects.

CONCLUSION

Pleiotropic effects of common medications and natural compounds could have therapeutic potential for endothelial dysfunction in estrogen-deficient states. They could, therefore, work as future complementary or alternative treatments to HRT.

Sagunja-Tang Improves Lipid Related Disease in a Postmenopausal Rat Model and HepG2 Cells

The present study was conducted to investigate the effect of Sagunja-tang on the lipid related disease in a rat model of menopausal hyperlipidemia and lipid accumulation in methyl-β-cyclodextrin-induced HepG2 cells. In in vivo study using menopausal hyperlipidemia rats, Sagunja-tang reduced retroperitoneal and perirenal fat, serum lipids, atherogenic index, cardiac risk factor, media thickness, and nonalcoholic steatohepatitis score, when compared to menopausal hyperlipidemia control rats. In HepG2 cells, Sagunja-tang significantly decreased the lipid accumulation, total cholesterol levels, and low-density/very-low-density lipoprotein levels. Moreover, Sagunja-tang reversed the methyl-β-cyclodextrin-induced decrease in the protein levels of critical molecule involved in cholesterol synthesis, sterol regulatory element binding protein-2, and low-density lipoprotein receptor and inhibited protein levels of 3-hydroxy-3-methylglutaryl coenzyme A reductase as well as activity. Phosphorylation level of AMP-activated protein kinase was stimulated by Sagunja-tang. These results suggest that Sagunja-tang has effect on inhibiting hepatic lipid accumulation through regulation of cholesterol synthesis and AMPK activity in vitro. These observations support the idea that Sagunja-tang is bioavailable both in vivo and in vitro and could be developed as a preventive and therapeutic agent of hyperlipidemia in postmenopausal females.

Palmiwon attenuates hepatic lipid accumulation and hyperlipidemia in a menopausal rat model

OBJECTIVE

We examined the phytoestrogenic effects of palmiwon on breast carcinoma, lipid accumulation in methyl-β-cyclodextrin-induced HepG2 cells, and lipid-related diseases in a rat model of menopausal hyperlipidemia.

METHODS

E-Screen assay was used to screen for phytoestrogens, especially those with antiestrogenic activity, in MCF-7 cells. Oil Red O staining and intracellular cholesterol analyses were used to quantify cellular cholesterol levels. 3-Hydroxy-3-methyl glutaryl coenzyme A reductase assay was used to measure enzyme activity. The levels of phosphorylated adenosine monophosphate-activated protein kinases and products of genes involved in cholesterol synthesis were measured by Western blot analysis. Thirty rats were either ovariectomized or sham-operated and randomly assigned to four groups (n = 5)-Sham, OVX, OVX-SV, or OVX-PMW (50, 150, or 450 mg/kg) group-for 8 weeks. A number of targets associated with lipid-related diseases were examined to confirm the estrogenic effects of palmiwon.

RESULTS

Palmiwon showed antiestrogenic activity in MCF-7 cells. Palmiwon decreased lipid accumulation, total cholesterol levels, and low-density lipoprotein/very-low-density lipoprotein levels in HepG2 cells. Moreover, palmiwon reversed the effects of methyl-β-cyclodextrin on cholesterol synthesis regulators and inhibited the activity of 3-hydroxy-3-methyl glutaryl coenzyme A reductase. Phosphorylation of adenosine monophosphate-activated protein kinase was stimulated by palmiwon. In ovariectomized rats, palmiwon reduced retroperitoneal and perirenal fat accumulation, serum lipids, atherogenic index, cardiac risk factor score, intima-media thickness, and nonalcoholic steatohepatitis scores.

CONCLUSIONS

These results indicate that palmiwon inhibits lipid accumulation without estrogenic activity in the breast. Therefore, palmiwon may have potential as a therapeutic agent for the treatment of hyperlipidemia in postmenopausal women.

A select review reporting the quality of studies measuring endothelial dysfunction in randomised diet intervention trials

A quality assessment of the primary studies reported in the literature carried out using select dietary ingredients (DI) purported to affect vascular endothelial function was conducted through a systematic PubMed search from January 2000 to August 2012. A total of seventy randomised controlled trials with defined DI (folic acid (fifteen), n-3 fatty acids (twenty), cocoa (fifteen) and isoflavones (twenty)) and standardised measures of vascular endothelial function were evaluated. Jadad scores, quality scoring parameters for DI and flow-mediated dilation (FMD) methodology used were ascertained. A total of 3959 randomised subjects, mean age 51 (se 0·21) years (range 9-79 years), were represented in the dataset. The mean Jadad scores did not differ statistically among the DI studies, with the majority of the studies being of good quality. Higher DI quality scores were achieved by studies using the botanical ingredients cocoa and isoflavones than by those using the nutrient ingredients folic acid and n-3 fatty acids. The mean DI quality scores were 4·13 (se 0·34), 5·20 (se 0·47), 6·13 (se 0·41) and 6·00 (se 0·59) for the folic acid, n-3 fatty acid, cocoa and isoflavone intervention studies, respectively (and significantly different). The mean Corretti FMD scores were 7·27 (se 0·56), 7·46 (se 0·79), 6·29 (se 0·61) and 7·11 (se 0·56) for the folic acid, n-3 fatty acid, cocoa and isoflavone intervention studies, respectively (NS). FMD studies failed to adequately describe the equipment used and more than half failed to provide an adequate description of the procedures used for vascular image acquisition and measurement. DI can be utilised for dietary intervention studies; however, the methodology should be clearly reported using the guidelines for assessment for both DI and FMD.

Ethanolic extract of rhizome of Ligusticum chuanxiong Hort. (chuanxiong) enhances endothelium-dependent vascular reactivity in ovariectomized rats fed with high-fat diet

Rhizome of Ligusticum chuanxiong Hort. (LC), also known as chuanxiong, is a very common herb widely used to treat cardiovascular and cerebrovascular diseases.

Effect of soy isoflavone supplementation on nitric oxide metabolism and blood pressure in menopausal women

BACKGROUND

Isoflavones, having chemical structures similar to estrogens, are believed to stimulate nitric oxide production and thus lower blood pressure. The efficacy of soy isoflavone supplementation to stimulate nitric oxide production and lower blood pressure in menopausal women with high normal blood pressure remains unknown.

OBJECTIVE

The objective was to test the effect of soy isoflavone supplementation on nitric oxide production and blood pressure in menopausal women with high normal blood pressure.

DESIGN

A randomized, double-blind, parallel, placebo-controlled 6-wk trial was conducted to assess the effects of daily supplementation with 80 mg soy hypocotyl isoflavones (in aglycone units) on nitric oxide metabolism and blood pressure in 24 menopausal women with 12 women per group. Changes in nitric oxide metabolism were assessed via a primed, constant-infusion protocol with [15N]arginine and [13C]- and [2H]citrulline. Changes in blood pressure and associated vascular hemodynamics were assessed via office and 24-h ambulatory blood pressure monitoring, forearm blood flow, and indexes of arterial compliance.

RESULTS

When compared with placebo and after control for pretreatment values, soy isoflavone supplementation had no effect on arginine flux, citrulline flux, nitric oxide synthesis, blood pressure, forearm blood flow, or estimates of arterial stiffness.

CONCLUSION

Daily supplementation with 80 mg soy hypocotyl isoflavones over a 6-wk period had no effect on nitric oxide metabolism or blood pressure and associated vascular hemodynamics in menopausal women with high normal blood pressure.

Exposure to isoflavone-containing soy products and endothelial function: a Bayesian meta-analysis of randomized controlled trials

BACKGROUND AND AIMS

To determine whether and to what degree exposure to isoflavone-containing soy products affects EF. Endothelial dysfunction has been identified as an independent coronary heart disease risk factor and a strong predictor of long-term cardiovascular morbidity and mortality. Data on the effects of exposure to isoflavone-containing soy products on EF are conflicting.

METHODS AND RESULTS

A comprehensive literature search was conducted using the PUBMED database (National Library of Medicine, Bethesda, MD) inclusively through August 21, 2009 on RCTs using the keywords: soy, isoflavone, phytoestrogen, EF, flow mediated vasodilation, and FMD. A Bayesian meta-analysis was conducted to provide a comprehensive account of the effect of isoflavone-containing soy products on EF, as measured by FMD. A total of 17 RCTs were selected as having sufficient data for study inclusion. The overall mean absolute change in FMD (95% Bayesian CI) for isoflavone-containing soy product interventions was 1.15% (-0.52, 2.75). When the effects of separate interventions were considered, the treatment effect for isolated isoflavones was 1.98% (0.07, 3.97) compared to 0.72% (-1.39, 2.90) for isoflavone-containing soy protein. The models were not improved when considering study-specific effects such as cuff measurement location, prescribed dietary modification, and impaired baseline FMD.

CONCLUSIONS

Cumulative evidence from the RCTs included in this meta-analysis indicates that exposure to soy isoflavones can modestly, but significantly, improve EF as measured by FMD. Therefore, exposure to isoflavone supplements may beneficially influence vascular health.

Different effects of isoflavones on vascular function in premenopausal and postmenopausal smokers and nonsmokers: NYMPH study

Isoflavone intake has been associated with a reduction in the risk of cardiovascular disease in postmenopausal women. The aim of the present study was to determine if the effects of isoflavones on vascular function differ between premenopausal and postmenopausal women and between women who smoke and those who do not. Women smokers and nonsmokers who consumed 50 mg of isoflavone/day as black soybean tea for a period of 2 months (n = 55, mean age 39) were enrolled in the present study. We examined endothelial function, which was assessed by the percent change in flow-mediated dilation (%FMD) and arterial wall stiffness using the cardio-ankle vascular index (CAVI), as well as by biochemical parameters of the blood. Neither premenopausal (p = 0.697) nor postmenopausal (p = 0.389) smokers experienced an increase in %FMD after daily consumption of isoflavones. However, both premenopausal (p = 0.004) and postmenopausal (p = 0.019) nonsmokers exhibited a marked elevation in %FMD. By contrast, isoflavone intake effectively reduced CAVI among both premenopausal smokers (p = 0.027) and nonsmokers (p = 0.013), but had no effect on CAVI among postmenopausal smokers (p = 0.169) or nonsmokers (p = 0.128). The women smokers and nonsmokers did not differ in age or %FMD at the time of enrollment in the study. Thus, isoflavones have different effects on vascular endothelial function and arterial wall stiffness in premenopausal and postmenopausal smokers and nonsmokers.

The lipid-lowering effects of 4 weeks of daily soymilk or dairy milk ingestion in a postmenopausal female population

Alterations in plasma cholesterol concentrations, especially increases in low-density lipoprotein (LDL), are well-known risk factors in the development of atherosclerosis. Numerous studies have examined the lipid-lowering effects of functional soy-containing foods, but few have specifically examined soymilk, with equivocal findings reported. In September 2008, a single-blind, randomized, controlled trial was conducted on 32 postmenopausal women at Baylor University, Waco, TX, USA. After a 2-week run-in period, subjects were randomly assigned to consume three servings of vanilla soy (n = 16) or reduced-fat dairy (n = 16) milk per day for 4 weeks. Plasma lipid profiles were obtained pre- and post-supplementation. Plasma high-density lipoprotein, LDL, and triglycerides were not significantly different between groups post-intervention (P = .45) or from baseline (P = .83). Separate analysis of plasma total cholesterol levels yielded similar results (P = .19 and P = .92, respectively). Furthermore, subanalyses controlling for dyslipidemia (n = 23) and lipid-lowering medication usage (n = 28) did not significantly alter results. Despite good dietary compliance, our study failed to show a significant hypocholesterolemic effect of soymilk consumption in this postmenopausal female population. Potential reasons for this nonsignificant finding are discussed, and future research directions are presented.

Equol: pharmacokinetics and biological actions

Equol [7-hydroxy-3-(4'-hydroxyphenyl)-chroman], an isoflavan produced by intestinal bacteria in response to soy isoflavone intake in some but not all humans, exhibits a wide range of biological properties. It exists as the diastereoisomers S-(-)equol and R-(+)equol. Intestinal bacteria produce exclusively S-(-)equol, which has selective affinity for estrogen receptor (ER)-beta. The evidence is conflicting on whether there is an advantage to producing S-(-)equol in response to soy isoflavone intakes, but the ability to now synthesize these diastereoisomers opens the way for future clinical trials to directly examine their potential in a number of hormone-dependent conditions. In this review, the plasma and urinary pharmacokinetics of S-(-)equol and R-(+)equol are reviewed and summarized, and some of the more recent evidence supporting potential biological effects of S-(-)equol is considered.

Effect of high soy diet on the cerebrovasculature and endothelial nitric oxide synthase in the ovariectomized rat

High soy (HS) diets are neuroprotective and promote vascular dilatation in the periphery. We hypothesized that an HS diet would promote vascular dilatation in the cerebrovasculature by mimicking estradiol's actions on the endothelial nitric oxide synthase (eNOS) system including increasing eNOS expression and decreasing caveolin-1 expression to increase nitric oxide (NO) production. Ovariectomized rats were fed HS or a soy-free diet (SF)+/-low physiological estradiol (E2) for 4weeks. Neither E2 nor HS altered middle cerebral artery (MCA) structure or vascular responses to acetylcholine, serotonin, or phenylephrine. Estradiol enhanced bradykinin-induced relaxation in an eNOS-dependent manner. Although E2 and HS increased eNOS mRNA expression in the brain and cerebrovasculature, they had no effect on eNOS protein expression or phosphorylation in the MCA. However, E2 decreased caveolin-1 protein in the MCA. In MCAs neither E2 nor HS altered estrogen receptor (ER) alpha expression, but E2 did reduce ER beta levels. These data suggest that HS diets have no effect on vascular NO production, and that E2 may modulate basal NO production by reducing the expression of caveolin-1, an allosteric inhibitor of NOS activity. However, the effects of E2 and HS on the cerebrovasculature are small and may not underlie their protective actions in pathological states.

Potential health-modulating effects of isoflavones and metabolites via activation of PPAR and AhR

Isoflavones have multiple actions on cell functions. The most prominent one is the activation of estrogen receptors. Other functions are often overlooked, but are equally important and explain the beneficial health effects of isoflavones. Isoflavones are potent dual PPARα/γ agonists and exert anti-inflammatory activity, which may contribute to the prevention of metabolic syndrome, atherosclerosis and various other inflammatory diseases. Some isoflavones are potent aryl hydrocarbon receptor (AhR) agonists and induce cell cycle arrest, chemoprevention and modulate xenobiotic metabolism. This review discusses effects mediated by the activation of AhR and PPARs and casts a light on the concerted action of isoflavones.

Bioactivity of isoflavones: assessment through a theoretical model as a way to obtain a "Theoretical Efficacy Related to Estradiol (TERE)"

The increase of human life span will have profound implications in Public Health in decades to come. By 2030, there will be an estimated 1.2 billion women in post-menopause. Hormone Replacement Therapy with synthetic hormones is still full of risks and according to the latest developments, should be used for the shortest time possible. Searching for alternative drugs is inevitable in this scenario and science must provide physicians with other substances that can be used to treat the same symptoms with less side effects. Systematic research carried out on this field of study is focusing now on isoflavones but the randomised controlled trials and reviews of meta-analysis concerning post-menopause therapy, that could have an important impact on human health, are very controversial. The aim of the present work was to establish a theoretical calculation suitable for use as a way to estimate the “Theoretical Efficacy (TE)” of a mixture with different bioactive compounds as a way to obtain a “Theoretical Efficacy Related to Estradiol (TERE)”. The theoretical calculation that we propose in this paper integrates different knowledge about this subject and sets methodological boundaries that can be used to analyse already published data. The outcome should set some consensus for new clinical trials using isoflavones (isolated or included in mixtures) that will be evaluated to assess their therapeutically activity. This theoretical method for evaluation of a possible efficacy could probably also be applied to other herbal drug extracts when a synergistic or contradictory bio-effect is not verified. In this way, it we may contribute to enlighten and to the development of new therapeutic approaches.

Effect of oral isoflavone supplementation on vascular endothelial function in postmenopausal women: a meta-analysis of randomized placebo-controlled trials

BACKGROUND

The effect of isoflavone on endothelial function in postmenopausal women is controversial.

OBJECTIVE

The objective of this study was to evaluate the effect of oral isoflavone supplementation on endothelial function, as measured by flow-mediated dilation (FMD), in postmenopausal women.

DESIGN

A meta-analysis of randomized placebo-controlled trials was conducted to evaluate the effect of oral isoflavone supplementation on endothelial function in postmenopausal women. Trials were searched in PubMed, Embase, the Cochrane Library database, and reviews and reference lists of relevant articles. Summary estimates of weighted mean differences (WMDs) and 95% CIs were obtained by using random-effects models. Meta-regression and subgroup analyses were performed to identify the source of heterogeneity.

RESULTS

A total of 9 trials were reviewed in the present meta-analysis. Overall, the results of the 9 trials showed that isoflavone significantly increased FMD (WMD: 1.75%; 95% CI: 0.83%, 2.67%; P = 0.0002). Meta-regression analysis indicated that the age-adjusted baseline FMD was inversely related to effect size. Subgroup analysis showed that oral supplementation of isoflavone had no influence on FMD if the age-adjusted baseline FMD was > or = 5.2% (4 trials; WMD: 0.24%; 95% CI: -0.94%, 1.42%; P = 0.69). This improvement seemed to be significant when the age-adjusted baseline FMD levels were <5.2% (5 trials; WMD: 2.22%; 95% CI: 1.15%, 3.30%; P < 0.0001), although significant heterogeneity was still detected in this low-baseline-FMD subgroup.

CONCLUSIONS

Oral isoflavone supplementation does not improve endothelial function in postmenopausal women with high baseline FMD levels but leads to significant improvement in women with low baseline FMD levels.

Daidzein relaxes rat cerebral basilar artery via activation of large-conductance Ca2+-activated K+ channels in vascular smooth muscle cells

Daidzein, a phytoestrogen, has been reported to produce vasodilation via inhibition of Ca(2+) inflow. However, the involvement of large-conductance Ca(2+)-activated K(+) (BK(Ca)) channels in the effect of daidzein is debated. Therefore, the present study was designed to investigate the effect of daidzein on the rat cerebral basilar artery and the underlying molecular mechanisms. Isolated cerebral basilar artery rings and single vascular smooth muscle cells (VSMCs) were used for vascular reactivity and electrophysiology measurements, to investigate the effect of daidzein on BK(Ca) channels in cerebral basilar artery smooth muscle. In addition, the human BK(Ca) channel alpha-subunit gene (hslo) was transfected into HEK293 cells, to directly assess whether daidzein activates BK(Ca) channels. The results showed that daidzein produced a concentration-dependent but endothelium-independent relaxation in rat cerebral basilar arteries. Paxilline, a selective BK(Ca) channel blocker, significantly inhibited the daidzein-induced vasodilation, whereas NS1619, a selective BK(Ca) channel opener, enhanced the vasodilation. In the whole-cell configuration, daidzein increased noisy oscillation currents in cerebral basilar artery VSMCs in a concentration-dependent manner, and washout of daidzein or blockade of BK(Ca) channels with paxilline fully reversed the increase. However, daidzein did not substantially affect hSlo currents in HEK293 cells when applied to the outside of the cell membrane. In conclusion, these results indicate that the activation of BK(Ca) channels in VSMCs at least partly contributes to the daidzein-induced vasodilation of the rat cerebral basilar artery. The beta1-subunit of BK(Ca) channels plays a critical role in the activation of BK(Ca) currents by daidzein.

Analytical and compositional aspects of isoflavones in food and their biological effects

This paper provides an overview of analytical techniques used to determine isoflavones (IFs) in foods and biological fluids with main emphasis on sample preparation methods. Factors influencing the content of IFs in food including processing and natural variability are summarized and an insight into IF databases is given. Comparisons of dietary intake of IFs in Asian and Western populations, in special subgroups like vegetarians, vegans, and infants are made and our knowledge on their absorption, distribution, metabolism, and excretion by the human body is presented. The influences of the gut microflora, age, gender, background diet, food matrix, and the chemical nature of the IFs on the metabolism of IFs are described. Potential mechanisms by which IFs may exert their actions are reviewed, and genetic polymorphism as determinants of biological response to soy IFs is discussed. The effects of IFs on a range of health outcomes including atherosclerosis, breast, intestinal, and prostate cancers, menopausal symptoms, bone health, and cognition are reviewed on the basis of the available in vitro, in vivo animal and human data.

The differential effect of the phytoestrogen genistein on cardiovascular risk factors in postmenopausal women: relationship with the metabolic status

CONTEXT

The wide family of the phytoestrogens has become an alternative to the classical hormonal therapy in menopause; nevertheless, some findings are still conflicting.

OBJECTIVE

To examine the effect of genistein administration on metabolic parameters and vascular reactivity considering the basal endocrine status of the patients.

DESIGN AND SETTING

A randomized placebo controlled study was conducted at a university hospital.

PARTICIPANTS

Fifty postmenopausal women participated.

INTERVENTIONS

Thirty subjects (group A) were randomized to receive 54 mg/d genistein while 20 subjects (group B) were treated with the placebo for 24 wk. In group A, we distinguish two subgroups: 14 normoinsulinemic and 12 hyperinsulinemic patients.

MAIN OUTCOME MEASURES

Anthropometric measures, hormonal and lipid assays, oral glucose tolerance test with glycemic, insulin, and C-peptide evaluation, indexes of insulin sensitivity and endothelial function, and euglycemic-hyperinsulinemic clamps were performed.

RESULTS

The insulin basal values significantly decreased in group A, whereas the homeostasis model index of insulin sensitivity and the fasting glucose levels significantly improved compared with placebo group. The genistein administration decreased fasting glucose and area under the curve glucose levels in the normoinsulinemic patients after treatment. In the hyperinsulinemic patients, a significant reduction in fasting insulin, fasting C-peptide, and area under the curve insulin levels as well as an increase in fractional hepatic insulin extraction was shown. In these patients, high-density lipoprotein cholesterol levels were significantly improved. The endothelium-dependent and -independent dilatation improved in the treated group. Normoinsulinemic patients showed both a significantly enhanced flow-mediated and nitrate-mediated dilatation, whereas no significant changes were found in the hyperinsulinemic group.

CONCLUSIONS

The glycoinsulinemic metabolism and the endothelial function were significantly influenced by genistein. In particular, normoinsulinemic patients showed an improvement in glycemic and vascular reactivity indexes. Conversely, an improvement in the insulin sensitivity indexes was noted in hyperinsulinemic patients.

Effects of extracted soy isoflavones alone on blood total and LDL cholesterol: Meta-analysis of randomized controlled trials

When provided concurrently with soy protein for 1-3 months, soy isoflavones exert synergistic or additive cholesterol-lowering effects. This meta-analysis was performed to evaluate the effects of extracted soy isoflavones alone (not ingested concurrently with soy protein) on total and low density lipoprotein (LDL) cholesterol. MEDLINE (1966-2007), EMBASE (1966-2007), CENTRAL (1966-2007), ICHUSHI (1983-2008), and CNKI (1979-2007) were searched for randomized placebo-controlled trials published in English, Japanese, and Chinese, describing the changes in lipid profiles in adult humans resulting from ingestion of extracted soy isoflavones for 1-3 months. Reference lists of relevant systematic reviews and meta-analyses were hand-searched. Meta-analysis of 10 and 9 trials with usable information using REVMAN found that an average of 70 mg soy isoflavones/day (27-132 mg, as the aglycone form) alone had a nonsignificant effect on total (0.01 mmol/L [95% CI: -0.12, 0.14]; P = 0.86) and LDL (0.03 mmol/L [95% CI: -0.11, 0.16]; P = 0.71) cholesterol in menopausal women, respectively. It is concluded that ingestion of about 70 mg extracted soy isoflavones/day alone for 1-3 months does not improve total and LDL cholesterol levels in normocholesterolemic menopausal women; further studies are needed to verify the effects of extracted soy isoflavones.

Investigating the Optimal Soy Protein and Isoflavone Intakes for Women: A Perspective

Traditional soyfoods have been consumed for centuries throughout much of East Asia and, recently, these foods have also become popular in the West. Soyfoods and specific soybean components, such as the protein and isoflavones, have attracted attention for their possible health benefits. Isoflavones are classified as phytoestrogens and have been postulated to be natural alternatives to hormone therapy for menopausal women. To provide guidance on optimal soy intake, this article evaluates Asian soy consumption and both clinical and Asian epidemiologic studies that examined the relationship between soy intake and a variety of health outcomes. On the basis of these data and the standard principles of dietary practice the author suggests that optimal soy protein and isoflavone intakes are 15–20 g/day and 50–90 mg/day, respectively. In addition, an intake of 25 g/day soy protein can be specifically used as the recommendation for cholesterol reduction.

A meal enriched with soy isoflavones increases nitric oxide-mediated vasodilation in healthy postmenopausal women

Evidence from infusion studies suggests that soy isoflavones influence nitric oxide-dependent vasorelaxation. It is uncertain whether orally consumed isoflavones have similar effects. Healthy postmenopausal women (n = 22) consumed 2 low-fat test meals in random order 1 wk apart, with 80 mg isoflavones (ISO) or without isoflavones (CON). Endothelium-dependent vasodilation, assessed by brachial artery flow-mediated dilatation (FMD), was measured in fasting subjects, and 4 and 6 h following the test meal, in addition to blood pressure and pulse wave analysis to derive the peripheral augmentation index (pAIx). Blood samples were taken after fasting, and 5 and 7 h following the test meal for serum isoflavone, plasma 8-isoprostane F(2alpha), nitric oxide metabolites (NOx), glucose, and triacylglycerol analysis. Serum genistein and daidzein concentrations (geometric mean, 95% CI) reached 1.49 (1.20-1.84) micromol/L and 0.95 (0.70-1.30) micromol/L, respectively, following ISO (7 h). FMD and plasma NOx concentrations were greater following ISO compared with CON, indicating better postprandial endothelial function. FMD values (%, mean +/- SD) were: CON, 5.49 +/- 2.32, 4.35 +/- 2.32, 4.40 +/- 2.26; ISO, 5.38 +/- 1.91, 5.08 +/- 1.74, 6.11 +/- 2.60, at baseline, 4 h, and 6 h, respectively (P < 0.01). Plasma NOx concentrations (micromol/L, mean +/- SD) were: CON, 20.0 +/- 5.1, 16.8 +/- 5.1, 23.1 +/- 6.0; ISO, 18.6 +/- 6.3, 19.5 +/- 5.1, 21.3 +/- 10.1, at baseline, 5 h, and 7 h, respectively (P < 0.005). Treatment did not affect pAIx, blood pressure, or plasma 8-isoprostane F(2alpha) concentrations. In conclusion, consuming an isoflavone-enriched low-fat meal acutely increases endothelium-dependent vasodilation in postmenopausal women. Regular consumption of soy isoflavones may protect against endothelial dysfunction.

Isoflavones and endothelial function

Dietary isoflavones are thought to be cardioprotective due to their structural similarity to oestrogen. Oestrogen is believed to have beneficial effects on endothelial function and may be one of the mechanisms by which premenopausal women are protected against CVD. Decreased NO production and endothelial NO synthase activity, and increased endothelin-1 concentrations, impaired lipoprotein metabolism and increased circulating inflammatory factors result from oestrogen deficiency. Oestrogen acts by binding to oestrogen receptors α and β. Isoflavones have been shown to bind with greater affinity to the latter. Oestrogen replacement therapy is no longer thought to be a safe treatment for prevention of CVD; isoflavones are a possible alternative. Limited evidence from human intervention studies suggests that isoflavones may improve endothelial function, but the available data are not conclusive. Animal studies provide stronger support for a role of isoflavones in the vasculature, with increased vasodilation and endothelial NO synthase activity demonstrated. Cellular mechanisms underlying the effects of isoflavones on endothelial cell function are not yet clear. Possible oestrogen receptor-mediated pathways include modulation of gene transcription, and also non-genomic oestrogen receptor-mediated signalling pathways. Putative non-oestrogenic pathways include inhibition of reactive oxygen species production and up regulation of the protein kinase A pathway (increasing NO bioavailability). Further research is needed to unravel effects of isoflavones on intracellular regulation of the endothelial function. Moreover, there is an urgent need for adequately powered, robustly designed human intervention studies in order to clarify the present equivocal findings.

Pasta naturally enriched with isoflavone aglycons from soy germ reduces serum lipids and improves markers of cardiovascular risk

Most studies of soy and cholesterol have tested foods made from purified soy proteins containing mainly isoflavone glycosides. Fermented soy foods have mainly isoflavone aglycons and account for a high proportion of the soy protein source in Asia, where there is an inverse relationship between soy intake and serum cholesterol. The aim of this study was to compare a novel soy germ pasta, naturally enriched in isoflavone aglycons as a result of the manufacturing process, with conventional pasta for effects on serum lipids and other cardiovascular risk markers. In this randomized, controlled, parallel study design of 62 adults with hypercholesterolemia who consumed a Step II diet that included one 80-g serving/d of pasta, we measured serum lipids, high sensitivity C-reactive protein (hsCRP), urinary isoprostanes, and brachial artery flow-mediated vasodilatation at baseline and after 4 and 8 wk. The pasta delivered 33 mg of isoflavones and negligible soy protein and led to a serum isoflavone concentration of 222 +/- 21 nmol/L; 69% of subjects were equol producers. Soy germ pasta reduced serum total and LDL cholesterol by 0.47 +/- 0.13 mmol/L (P = 0.001) and 0.36 +/- 0.10 mmol/L (P = 0.002) more than conventional pasta, representing reductions from baseline of 7.3% (P = 0.001) and 8.6% (P = 0.002), respectively. Arterial stiffness (P = 0.003) and hsCRP (P = 0.03) decreased and improvements in all the above risk markers were greatest in equol producers. All measures returned to baseline when patients were switched to conventional pasta. In conclusion, pasta naturally enriched with isoflavone aglycons and lacking soy protein had a significant hypocholesterolemic effect beyond a Step II diet and improved other cardiovascular risk markers.

Effects of soy germ isoflavones and hormone therapy on nitric oxide derivatives, low-density lipoprotein oxidation, and vascular reactivity in hypercholesterolemic postmenopausal women

OBJECTIVE

To evaluate the effects of soy germ isoflavones and hormone therapy on vascular reactivity, the formation of nitric oxide derivatives, and lipid peroxidation in hypercholesterolemic postmenopausal women.

DESIGN

Women were treated with soy germ, 17beta-estradiol or 17beta-estradiol + noretisterone acetate for 3 months after taking placebo for 1 month. The plasma concentrations of nitrite + nitrate and S-nitrosothiols were evaluated by gaseous phase chemiluminescence; nitrotyrosine, electronegative low-density lipoprotein, and estradiol levels were determined by enzyme-linked immunosorbent assay; cholesterol oxides and isoflavones were determined by gas chromatography and high-performance liquid chromatography, respectively. Vascular reactivity was analyzed by high-resolution ultrasonography.

RESULTS

Soy germ isoflavones and hormone therapy induced a decrease in nitrite + nitrate, electronegative low-density lipoprotein, and cholesterol oxides, as well as an increase in S-nitrosothiols. Soy germ isoflavones lowered electronegative low-density lipoprotein, and cholesterol oxides more efficiently than did hormone therapy. Only soy isoflavones inhibited nitrotyrosine formation. A significant improvement of vascular reactivity was only seen in women treated with 17beta-estradiol.

CONCLUSIONS

The soy germ isoflavones and 17beta-estradiol, alone or associated with noretisterone acetate, in the doses and forms used here, have similar effects on the bioavailability of nitric oxide. Soy germ treatment inhibited lipid peroxidation more effectively than hormone therapy.

Soya isoflavone-enriched cereal bars affect markers of endothelial function in postmenopausal women

Soya isoflavones are thought to be cardioprotective due to their structural similarity to oestrogen. In order to investigate the effect of soya isoflavones on markers of endothelial function we conducted a randomised, double-blind, placebo-controlled, cross-over study with thirty healthy postmenopausal women. The women consumed cereal bars, with or without soya isoflavones (50 mg/d), for 8 weeks, separated by an 8-week washout period. Systemic arterial compliance (SAC), isobaric arterial compliance (IAC), flow-mediated endothelium-dependent vasodilation (FMD) and nitroglycerine-mediated endothelium-independent vasodilation (NMD) were measured at the beginning of the study and after each intervention period. Blood pressure (BP) and plasma concentrations of nitrite and nitrate (NOx) and endothelin-1 (ET-1) were measured at the beginning and end of each intervention period. NMD was 13.4 (SEM 2.0)% at baseline and 15.5 (SEM 1.1) % after isoflavone treatment compared with 12.4 (SEM 1.0)% after placebo treatment (P=0.03). NOx increased from 27.7 (SEM 2.7) to 31.1 (SEM 3.2) microM after isoflavones treatment compared with 25.4 (SEM 1.5) to 20.4 (SEM 1.1) microM after placebo treatment (P=0.003) and a significant increase in the NOx:ET-1 ratio (P=0.005) was observed after the isoflavone treatment compared with placebo. A significant difference in SAC after the isoflavone and placebo treatment was observed (P=0.04). No significant difference was found in FMD, IAC, BP and ET-1. In conclusion, 8 weeks' consumption of cereals bars enriched with 50 mg soya isoflavones/d increased plasma NOx concentrations and improved endothelium-independent vasodilation in healthy postmenopausal women.

[Effects on health of soy in menopausic women]

Phystestrogens are organic compounds produced by a large variety of plants with protective function against the invasion of them by microorganisms. Phystestrogens, and among them isoflavones, have a great similarity with estradiol, principal endogenous estrogen. Those known most for their estrogenic activity are daidzeine and genisteine. Due to the existence of contradictory data on the effects of soy isoflavones on the most outstanding health disorders of menopause such as osteoporosis and hot flushes, and its ineffective role in the improvement of the lipid profile, it is recommendable to continue choosing hygienic-dietary and conventional drug treatments. However, we could introduce soy and soy derived products within a balanced, varied and adequate diet for these women.

Isoflavones made simple - genistein's agonist activity for the beta-type estrogen receptor mediates their health benefits

Soy isoflavones, the focus of much research and controversy, are often referred to as "weak estrogens". In fact, genistein is a relatively potent agonist for the recently characterized beta isoform of the estrogen receptor (ERbeta). The low nanomolar serum concentrations of unconjugated free genistein achieved with high-nutritional intakes of soy isoflavones are near the binding affinity of genistein for this receptor, but are about an order of magnitude lower than genistein's affinity for the "classical" alpha isoform of the estrogen receptor (ERalpha). Moreover, these concentrations are far too low to inhibit tyrosine kinases or topoisomerase II, in vitro activities of genistein often cited as potential mediators of its physiological effects. The thesis that these physiological effects are in fact mediated by ERbeta activation provides a satisfying rationale for genistein's clinical activities. Hepatocytes do not express ERbeta; this explains why soy isoflavones, unlike oral estrogen, neither modify serum lipids nor provoke the prothrombotic effects associated with increased risk for thromboembolic disorders. The lack of uterotrophic activity of soy isoflavones reflects the fact that ERalpha is the exclusive mediator of estrogen's impact in this regard. Vascular endothelium expresses both ERalpha and ERbeta, each of which has the potential to induce and activate nitric oxide synthase; this may account for the favorable influence of soy isoflavones on endothelial function in postmenopausal women and ovariectomized rats. The ERbeta expressed in osteoblasts may mediate the reported beneficial impact of soy isoflavones on bone metabolism. Suggestive evidence that soy-rich diets decrease prostate cancer risk, accords well with the observation that ERbeta appears to play an antiproliferative role in healthy prostate. In the breast, ERalpha promotes epithelial proliferation, whereas ERbeta has a restraining influence in this regard - consistent with the emerging view that soy isoflavones do not increase breast cancer risk, and possibly may diminish it. Premenopausal women enjoy a relative protection from kidney failure; since ERbeta is an antagonist of TGF-beta signaling in mesangial cells, soy isoflavones may have nephroprotective potential. Estrogen also appears to protect women from left ventricular hypertrophy, and recent evidence suggests that this effect is mediated by ERbeta. In conjunction with reports that isoflavones may have a modestly beneficial impact on menopausal symptoms - perhaps reflecting the presence of ERbeta in the hypothalamus - these considerations suggest that soy isoflavone regimens of sufficient potency may represent a safe and moderately effective alternative to HRT in postmenopausal women. Further clinical research is required to characterize the impact of optimal genistein intakes on endothelial and bone function in men. Studies with ERbeta-knockout mice could be helpful for clarifying whether ERbeta does indeed mediate the chief physiological effects of low nanomolar genistein. S-equol, a bacterial metabolite of daidzein, has an affinity for ERbeta nearly as high as that of genistein; whether this compound contributes meaningfully to the physiological efficacy of soy isoflavones in some individuals is still unclear.

Effects of soy or milk protein durign a high-fat feeding challenge on oxidative stress, inflammation, and lipids in healthy men

Soy isoflavones may impede atherogenic processes associated with cardiovascular disease. Research suggests that the postprandial generation of TG-rich remnants contributes to the development of atherosclerosis. The purpose of the current study was to determine if 39 g soy (85 mg aglycone isoflavones, treatment) compared with 40 g milk protein (0 mg aglycone isoflavones, control) in combination with a high-fat meal can modify postprandial, atherogenic-associated events and biomarkers for oxidative stress, inflammation, and thrombosis. Fifteen healthy men (20-47 yr) participated in a double-blind cross-over meal-challenge study occurring on two nonconsecutive days. The study meals consisted of two high-fat apple muffins consumed with either a soy or milk shake (229 mL, 41% fat, 41% carbohydrate, and 18% protein). Blood samples were obtained at baseline (fasted) and hours two, four, and six postprandial. Plasma TG significantly increased in both treatment and control meal challenges compared with baseline. There were no significant differences (P > 0.05) between treatment (soy) and control (milk) for ex vivo copper-induced LDL oxidation, serum C-reactive protein, serum interleukin-6 (IL-6), serum fibrinogen, or plasma lipids (total cholesterol, HDL, LDL, TG). IL-6-concentrations significantly decreased as a function of time during either meal challenge (P = 0.005). These data suggest that consumption of soy or milk protein in conjunction with a high-fat meal does not acutely modify postprandial oxidative stress, inflammation, or plasma lipid concentrations in young, healthy men.

Critical review of health effects of soyabean phyto-oestrogens in post-menopausal women

A consensus view of soyabean phyto-oestrogens in clinical interventions in post-menopausal women is presented that is based on data from the EU-funded project Phytohealth. The phyto-oestrogens, primarily genistein and daidzein, were given as soyabean-protein isolates, whole-soyabean foods or extracts, supplements or pure compounds. A comprehensive literature search was conducted with well-defined inclusion or exclusion criteria. For areas for which substantial research exists only placebo-controlled double-blind randomised controlled trials (RCT) conducted on healthy post-menopausal women were included. For emerging areas all available human studies in post-menopausal women were reviewed. In order to make cross comparisons between studies the doses of isoflavones were calculated as aglycone equivalents. There is a suggestion, but no conclusive evidence, that isoflavones from the sources studied so far have a beneficial effect on bone health. The consumption of whole-soyabean foods and soyabean-protein isolates has some beneficial effects on lipid markers of cardiovascular risk. The consumption of isolated isoflavones does not affect blood lipid levels or blood pressure, although it may improve endothelial function. For menopausal symptoms there is currently limited evidence that soyabean-protein isolates, soyabean foods or red-clover (Trifolium pratense L.) extract are effective but soyabean isoflavone extracts may be effective in reducing hot flushes. There are too few RCT studies to reach conclusions on the effects of isoflavones on breast cancer, colon cancer, diabetes or cognitive function. The health benefits of soyabean phyto-oestrogens in healthy post-menopausal women are subtle and even some well-designed studies do not show protective effects. Future studies should focus on high-risk post-menopausal women, especially in the areas of diabetes, CVD, breast cancer and bone health.

Menopause: a review on the role of oxygen stress and favorable effects of dietary antioxidants

Menopause is often accompanied by hot flashes and degenerative processes such as arteriosclerosis and atrophic changes of the skin that suggest an acceleration of aging triggered by estrogen lack. Therefore, hormone replacement therapy (HRT) has been considered the most suitable treatment for the above symptoms and processes. However, because of the possible serious side effects of HRT (especially the increased risk of thrombo-embolic accidents and breast cancer) there is a growing demand for alternative treatments of the symptoms and pathological processes associated with menopause. In agreement with the above, we review research that supports the concept that oxygen stress contributes to menopause and that some of its physiopathological effects may be prevented and/or treated improving the antioxidant defense of menopausic and postmenopausic women. Accordingly, a selection of micronutrients may be useful as a dietary supplement for protection against the decline of physiological functions caused by age-related oxygen stress. Since aging is accompanied by a progressive oxidation of the physiological sulfur pool, we emphasize the role of the vitamins B that help to maintain the GSH/GSSG ratio in its normal reduced state. Nutritional supplements should also include the key antioxidant vitamins C and E, as well as beta-carotene and the mineral micronutrients found in the oxygen radical-detoxifying enzymes glutathione peroxidase and superoxide dismutase. Moreover, the reviewed data suport the concept that other antioxidants such as lipoic acid and the precursors of glutathione thioproline (TP) and l-2-oxothiazolidine-4-carboxylic acid (OTC), as well as the soy isoflavones and the "coantioxidants" of an hydroalcoholic extract of Curcuma longa may help to prevent antioxidant deficiency with resulting protection of mitochondria against premature oxidative damage with loss of ATP synthesis and especialized cellular functions. Therefore, the administration under medical advice of synergistic combinations of some of the above mentioned antioxidants in the diet as well as topically (for skin protection) may have favorable effects on the health and quality of life of women, especially of those who cannot be treated with HR, suffer high levels of oxygen stress, and do not consume a healthy diet that includes five daily rations of fresh fruit and vegetables.

Adjuvant strategies for prevention of glomerulosclerosis

The glomerulosclerosis which frequently complicates diabetes and severe hypertension is mediated primarily by increased mesangial production and activation of transforming growth factor-beta (TGF-beta), which acts on mesangial cells to boost their production of matrix proteins while suppressing extracellular proteolytic activity. Hyperglycemia and glomerular hypertension work in various complementary ways to stimulate superoxide production via NADPH oxidase in mesangial cells; the resulting oxidant stress results in the induction and activation of TFG-beta. Nitric oxide, generated by glomerular capillaries and by mesangial cells themselves, functions physiologically to oppose mesangial TGF-beta overproduction; however, NO bioactivity is compromised by oxidant stress. In addition to low-protein diets and drugs that suppress angiotensin II activity, a variety of other agents and measures may have potential for impeding the process of glomerulosclerosis. These include vitamin E, which blunts the rise in mesangial diacylglycerol levels induced by hyperglycemia; statins and (possibly) policosanol, which down-regulate NADPH oxidase activity by diminishing isoprenylation of Rac1; lipoic acid, whose potent antioxidant activity antagonizes the impact of oxidant stress on TGF-beta expression; pyridoxamine, which inhibits production of advanced glycation endproducts; arginine, high-dose folate, vitamin C, and salt restriction, which may support glomerular production of nitric oxide; and estrogen and soy isoflavones, which may induce nitric oxide synthase in glomerular capillaries while also interfering with TGF-beta signaling. Further research along these lines may enable the development of complex nutraceuticals which have important clinical utility for controlling and preventing glomerulosclerosis and renal failure. Most of these measures may likewise reduce risk for left ventricular hypertrophy in hypertensives, inasmuch as the signaling mechanisms which mediate this disorder appear similar to those involved in glomerulosclerosis.

Soy protein containing isoflavones reduces the size of atherosclerotic plaques without affecting coronary artery reactivity in adult male monkeys

The cardiovascular effects of dietary soy on men or adult male experimental animals have received little attention. We determined the effects of long-term (31 mo) consumption of a commercially available soy protein concentrate containing experimentally varied concentrations of isoflavones on the development of atherosclerosis and vascular reactivity in adult male monkeys. The monkeys were fed atherogenic diets that differed only in the source of protein: Control (n = 30), casein and lactalbumin; low-isoflavone soy (n = 30), a mixture of unmodified soy protein isolate and isoflavone-depleted soy protein isolate containing 0.94 mg of isoflavones/g protein; and high-isoflavone soy (n = 31), unmodified soy protein isolate containing 1.88 mg of isoflavone/g protein. Plasma LDL cholesterol was reduced, whereas HDL cholesterol and apolipoprotein A-1 (P < 0.05) were increased in both groups that consumed soy protein. Atherosclerosis (mean plaque size in the coronary arteries) was reduced by approximately 34% (P < 0.05) in both groups fed soy protein. There were no effects of dietary soy on endothelium-dependent or -independent reactivity of coronary arteries. The results indicate that long-term consumption of soy protein containing a modest amount of isoflavones inhibits the early progression of coronary artery atherosclerosis without affecting endothelium-dependent or -independent arterial function.

Allergenic Proteins in Soybean: Processing and Reduction of P34 Allergenicity

Soybean ranks among the "big 8" of the most allergenic foods, and with increasing consumption of soybean products, the incidence of soy-caused allergies is expected to escalate. Soybean and its derivatives have become ubiquitous in vegetarian and many meat-based food products, and as a result, dietary avoidance has become difficult. However, soybeans can be manipulated in a variety of ways to alter their allergenicity. Several studies have focused on reducing the allergenicity of soybeans by changing the structure of the immunodominant allergen P34 using food processing, agronomic, or genetic manipulation techniques. A review of the literature pertaining to these studies is presented here.