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

Effect of soy isoflavone supplementation on blood pressure: a meta-analysis of randomized controlled trials

BACKGROUND

Previous experimental studies have suggested that the consumption of soy isoflavones may have a potential impact on lowering blood pressure. Nevertheless, epidemiological studies have presented conflicting outcomes concerning the correlation between soy isoflavone consumption and blood pressure levels. Consequently, a comprehensive meta-analysis of all eligible randomized controlled trials (RCTs) was conducted to explore the influence of soy isoflavones on systolic blood pressure (SBP) and diastolic blood pressure (DBP) in adults.

METHODS

A thorough search of PubMed, Embase, and the Cochrane Library for relevant literature up to April 30, 2023 was conducted. RCTs involving adults that compared soy isoflavone supplementation with a placebo (the same matrix devoid of soy isoflavone) were included. The combined effect size was presented as the weighted mean difference (WMD) along with 95% confidence interval (CI), employing a fixed-effects model.

RESULTS

Our meta-analysis included a total of 24 studies involving 1945 participants. The results revealed a significant reduction in both SBP and DBP with soy isoflavone supplementation. Subgroup analyses suggested more pronounced reductions in SBP and DBP for interventions lasting ≥6 months, in individuals receiving mixed-type soy isoflavone, and among patients with metabolic syndrome or prehypertension. However, we did not detect significant nonlinear associations between supplementation dosage and intervention duration concerning both SBP and DBP. The overall quality of evidence was deemed moderate.

CONCLUSIONS

The current meta-analysis revealed that supplementation with soy isoflavones alone effectively reduces blood pressure. Additional high-quality studies are required to investigate the efficacy of blood pressure reduction through supplementation with an optimal quantity and proportion of soy isoflavone.

Collectrin (Tmem27) deficiency in proximal tubules causes hypertension in mice and a TMEM27 variant associates with blood pressure in males in a Latino cohort

Collectrin (Tmem27), an angiotensin-converting enzyme 2 homologue, is a chaperone of amino acid transporters in the kidney and endothelium. Global collectrin knockout (KO) mice have hypertension, endothelial dysfunction, exaggerated salt sensitivity, and diminished renal blood flow. This phenotype is associated with altered nitric oxide and superoxide balance and increased proximal tubule (PT) Na+/H+ exchanger isoform 3 (NHE3) expression. Collectrin is located on the X chromosome where genome-wide association population studies have largely been excluded. In the present study, we generated PT-specific collectrin KO (PT KO) mice to determine the precise contribution of PT collectrin in blood pressure homeostasis. We also examined the association of human TMEM27 single-nucleotide polymorphisms with blood pressure traits in 11,926 Hispanic Community Health Study/Study of Latinos (HCHS/SOL) Hispanic/Latino participants. PT KO mice exhibited hypertension, and this was associated with increased baseline NHE3 expression and diminished lithium excretion. However, PT KO mice did not display exaggerated salt sensitivity or a reduction in renal blood flow compared with control mice. Furthermore, PT KO mice exhibited enhanced endothelium-mediated dilation, suggesting a compensatory response to systemic hypertension induced by deficiency of collectrin in the PT. In HCHS/SOL participants, we observed sex-specific single-nucleotide polymorphism associations with diastolic blood pressure. In conclusion, loss of collectrin in the PT is sufficient to induce hypertension, at least in part, through activation of NHE3. Importantly, our model supports the notion that altered renal blood flow may be a determining factor for salt sensitivity. Further studies are needed to investigate the role of the TMEM27 locus on blood pressure and salt sensitivity in humans.NEW & NOTEWORTHY The findings of our study are significant in several ways: 1) loss of an amino acid chaperone in the proximal tubule is sufficient to cause hypertension, 2) the results in global and proximal tubule-specific collectrin knockout mice support the notion that vascular dysfunction is required for salt sensitivity or that impaired renal tubule function causes hypertension but is not sufficient to cause salt sensitivity, and 3) our study is the first to implicate a role of collectrin in human hypertension.

Soy intake is associated with lowering blood pressure in adults: A systematic review and meta-analysis of randomized double-blind placebo-controlled trials

BACKGROUND

Soy has several beneficial effects on cardiovascular disease (CVD); however, results of clinical trial studies are equivocal. Thus, the present study sought to discern the efficacy of soy intake on blood pressure.

METHODS

The search process was conducted in PubMed, Scopus, Web of Science, and Cochrane Library, to ascertain studies investigating the efficacy of soy intake on blood pressure in adults, published up to June 2020. A random-effects model was applied to pool mean difference and 95 % confidence interval (CI). Begg's and Egger's methods were conducted to assess publication bias.

RESULTS

Pooled effects from 17 effect sizes revealed a significant improvement in systolic blood pressure (SBP) (-1.70; -3.34 to -0.06 mmHg; I² = 45.4 %) and diastolic blood pressure (DBP) (-1.27; -2.36 to -0.19 mmHg, I² = 43.9 %) following soy consumption, in comparison with controls. Subgroup analysis demonstrated a reduction in both SBP and DBP in younger participants with lower baseline DBP and intervention durations of <16 weeks.

CONCLUSION

Our results suggest that soy intake is associated with an ameliorating effect on blood pressure in adults.

Effect of S-equol and Soy Isoflavones on Heart and Brain

BACKGROUND

Observational studies in Asia show that dietary intake of soy isoflavones had a significant inverse association with coronary heart disease (CHD). A recent randomized controlled trial (RCT) of soy isoflavones on atherosclerosis in the US, however, failed to show their benefit. The discrepancy may be due to the much lower prevalence of S-equol producers in Westerners: Only 20-30% of Westerners produce S-equol in contrast to 50-70% in Asians. S-equol is a metabolite of dietary soy isoflavone daidzein by gut microbiome and possesses the most antiatherogenic properties among all isoflavones. Several short-duration RCTs documented that soy isoflavones improves arterial stiffness. Accumulating evidence shows that both atherosclerosis and arterial stiffness are positively associated with cognitive decline/dementia. Therefore, potentially, soy isoflavones, especially S-equol, are protective against cognitive decline/dementia.

METHODS/RESULTS

This narrative review of clinical and epidemiological studies provides an overview of the health benefits of soy isoflavones and introduces S-equol. Second, we review recent evidence on the association of soy isoflavones and S-equol with CHD, atherosclerosis, and arterial stiffness as well as the association of atherosclerosis and arterial stiffness with cognitive decline/ dementia. Third, we highlight recent studies that report the association of soy isoflavones and S-equol with cognitive decline/dementia. Lastly, we discuss the future directions of clinical and epidemiological research on the relationship of S-equol and CHD and dementia.

CONCLUSIONS

Evidence from observational studies and short-term RCTs suggests that S-equol is anti-atherogenic and improves arterial stiffness and may prevent CHD and cognitive impairment/ dementia. Well-designed long-term (≥ 2years) RCTs should be pursued.

Metabolic enzymes dysregulation in heart failure: the prospective therapy

The heart failure accounts for the highest mortality rate all over the world. The development of preventive therapeutic approaches is still in their infancy. Owing to the extremely high energy demand of the heart, the bioenergetics pathways need to respond efficiently based on substrate availability. The metabolic regulation of such heart bioenergetics is mediated by various rate limiting enzymes involved in energy metabolism. Although all the pertinent mechanisms are not clearly understood, the progressive decline in the activity of metabolic enzymes leading to diminished ATP production is known to cause progression of the heart failure. Therefore, metabolic therapy that can maintain the appropriate activities of metabolic enzymes can be a promising approach for the prevention and treatment of the heart failure. The flavonoids that constitute various human dietary ingredients also effectively offer a variety of health benefits. The flavonoids target a variety of metabolic enzymes and facilitate effective management of the equilibrium between production and utilization of energy in the heart. This review discusses the broad impact of metabolic enzymes in the heart functions and explains how the dysregulated enzyme activity causes the heart failure. In addition, the prospects of targeting dysregulated metabolic enzymes by developing flavonoid-based metabolic approaches are discussed.

Dietary Total Isoflavone Intake Is Associated With Lower Systolic Blood Pressure: The Coronary Artery Risk Development in Young Adults (CARDIA) Study

The effect of dietary isoflavone intake on systolic blood pressure (SBP) has not been studied in a large community-based cohort inclusive of African Americans. The authors analyzed data from the year 20 examination of the Coronary Artery Risk Development in Young Adults (CARDIA) study, including medical history, physical examination, and dietary intake surveys for 3142 participants. Multivariable linear regression models controlled for age, sex, body mass index, smoking, physical activity, and intakes of alcohol and total energy. Effect modification by race was tested. Overall, patients with hypertension had a lower daily intake of total dietary isoflavones (2.2±5.2 mg/d vs 4.1±11.7 mg/d; P<.001). In fully adjusted models, the highest quartile of dietary isoflavone intake was associated with a 4.4 mm Hg lower SBP on average compared with SBP for the lowest quartile. The relationship between dietary isoflavone intake and SBP was more pronounced among African Americans compared with Caucasians (P for interaction <.001). Greater dietary intake of isoflavones was independently associated with a lower SBP.

The impact of equol-producing status in modifying the effect of soya isoflavones on risk factors for CHD: a systematic review of randomised controlled trials

Recent studies suggest that the ability to produce equol, a metabolite of the soya isoflavone daidzein, is beneficial to coronary health. Equol, generated by bacterial action on isoflavones in the human gut, is biologically more potent than dietary sources of isoflavones. Not all humans are equol producers. We investigated whether equol-producing status is favourably associated with risk factors for CHD following an intervention by dietary soya isoflavones. We systematically reviewed randomised controlled trials (RCT) that evaluated the effect of soya isoflavones on risk factors for CHD and that reported equol-producing status. We searched PubMed, EMBASE, Ovid Medline and the Cochrane Central Register for Controlled Trials published up to April 2015 and hand-searched bibliographies to identify the RCT. Characteristics of participants and outcomes measurements were extracted and qualitatively analysed. From a total of 1671 studies, we identified forty-two articles that satisfied our search criteria. The effects of equol on risk factors for CHD were mainly based on secondary analyses in these studies, thus with inadequate statistical power. Although fourteen out of the forty-two studies found that equol production after a soya isoflavone intervention significantly improved a range of risk factors including cholesterol and other lipids, inflammation and blood pressure variables, these results need further verification by sufficiently powered studies. The other twenty-eight studies primarily reported null results. RCT of equol, which has recently become available as a dietary supplement, on CHD and its risk factors are awaited.

High-cholesterol diet enriched with onion affects endothelium-dependent relaxation and NADPH oxidase activity in mesenteric microvessels from Wistar rats

BACKGROUND

The aim of the present study was to examine the effects of onion as functional ingredient on the oxidative status, lipoprotein levels (total cholesterol-TC, HDL-C, LDL-C), triacylglycerides (TAG) and vascular reactivity of mesenteric arteries in hypercholesterolemic Wistar rats.

METHODS

Twenty-four animals were fed with three different diets [control, high-cholesterol diet (HC) and high-cholesterol enriched with onion diet (HCO)]. After seven weeks of experimental feeding the rats were euthanized for blood and tissues collection. TC, HDL-C, LDL-C and TAG were measured, and 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) radical cation (ABTS(•+)) scavenging capacity and ferric reducing antioxidant power (FRAP) were determined in plasma. Superoxide dismutase (SOD) and glutathione peroxidase (GPx) enzyme activities were assayed in erythrocyte lysates. Endothelium-dependent vasodilation to acetylcholine was evaluated in mesenteric arterial segments. NADPH oxidase (NOX) was also measured by lucigenin-derived chemiluminiscence.

RESULTS

The dietary cholesterol content significantly affected plasma lipoprotein levels, increased superoxide generation from NOX, and caused impaired endothelium-dependent vasodilation in the rat mesenteric arteries. Onion ingredient improved antioxidant status in HCO group, as it was evidenced by ABTS(•+) and FRAP values and SOD and GPx enzyme activities compared to the HC-fed group, reduced the increment in NOX activity and reversed endothelial dysfunction promoted by the HC diet. Scavenging of superoxide with TEMPOL or inhibition of NOX with apocynin improved endothelium-dependent vasodilation only in HC-fed rats.

CONCLUSIONS

Enrichment of diet with onion as functional ingredient could be proposed as a complementary approach to prevent or partially modulate vascular dysfunction, reducing some of the risk indexes linked to initial development of atherosclerosis.

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.

Honey and cardiovascular risk factors, in normal individuals and in patients with diabetes mellitus or dyslipidemia

Diabetes mellitus, hypercholesteremia, hypertension (HTN), and obesity are well-known risk factors for cardiovascular diseases (CVD). Various medications are currently in use for management of these comorbidities. Undesirable side effects are unavoidable and the ultimate and ideal goal is hardly achieved. Honey and other bee products are widely used in traditional medicine for management of many diseases. Others and the authors have found potent biological activities of these products. Honey is now reintroduced in modern medicine as part of wound and burn management. Honey has antioxidant, anti-inflammatory, and antimicrobial activities. More studies are exploring other aspects of honey activity such as its effect on blood sugar, body weight, lipid profile, C-reactive protein, nitric oxide, proinflammatory prostaglandins, and homocysteine. Growing evidence and scientific data support the use of honey in patients with diabetes, HTN, dyslipidemia, obesity, and CVD. This review discusses clinical and preclinical studies on potential influence of honey on diabetes mellitus and cardiovascular risk factors, and emphasizes the importance of conducting more clinical and controlled studies.

Flavonoids and arterial stiffness: promising perspectives

BACKGROUND AND AIMS

Flavonoids are a group of polyphenol compounds, ubiquitously found in plants. Great emphasis has been given to their possible benefits for cardiovascular health. These beneficial effects may be mediated by a specific action on arterial walls. Arterial stiffness is a marker of vascular aging, increasingly used in the clinical setting and assessed by pulse wave velocity. It has shown to be a robust predictor of cardiovascular events and mortality. This review aims at providing a comprehensive evaluation of available intervention and observational studies examining the relationship between flavonoid consumption and arterial stiffness.

DATA SYNTHESIS

A Medline(®) literature search was performed using the keywords "arterial stiffness" and "flavonoids". As a result, 2 cross-sectional and 16 intervention studies assessing the relationship between flavonoids intake and arterial stiffness were retained. Four intervention trials reported a significant decrease of arterial stiffness after a flavonoid-based intervention, independently from blood pressure changes. The two observational studies reported significant associations between a higher flavonoid consumption and a lower arterial stiffness. In this review, isoflavones, anthocyanins and to a lesser extent cocoa flavan-3-ols appeared to be the more efficient to improve vascular function.

CONCLUSIONS

Despite their heterogeneity, preliminary data seem to support an improvement of the arterial stiffness related to flavonoid intake. However, further research on absorption and dose-response effects of the specific flavonoid subclasses on arterial structure is warranted.

Salt sensitivity: a review with a focus on non-Hispanic blacks and Hispanics

The purpose of this review is to summarize the available information regarding salt sensitivity particularly as it relates to non-Hispanic blacks and Hispanics and to clarify possible etiologies, especially those that might shed light on potential treatment options. In non-Hispanic blacks, there is evidence that endothelial dysfunction, reduced potassium intake, decreased urinary kallikrein excretion, upregulation of sodium channel activity, dysfunction in atrial natriuretic peptide (ANP) production, and APOL1 gene nephropathy risk variants may cause or contribute to salt sensitivity. Supported treatment avenues include diets high in potassium and soybean protein, the components of which stimulate nitric oxide production. Racial heterogeneity complicates the study of salt sensitivity in Hispanic populations. Caribbean Hispanics, who have a higher proportion of African ancestry, may respond to commonly prescribed anti-hypertensive agents in a way that is characteristic of non-Hispanic black hypertensives. The low-renin hypertensive phenotype commonly seen in non-Hispanic blacks has been linked to salt sensitivity and may indicate an increased risk for salt sensitivity in a portion of the Hispanic population. In conclusion, increased morbidity and mortality associated with salt sensitivity mandates further studies evaluating the efficacy of tailored dietary and pharmacologic treatment in non-Hispanic blacks and determining the prevalence of low renin hypertension and salt sensitivity within the various subgroups of Hispanic Americans.

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.

Polyphenols and human health: prevention of disease and mechanisms of action

Polyphenols are found ubiquitously in plants and their regular consumption has been associated with a reduced risk of a number of chronic diseases, including cancer, cardiovascular disease (CVD) and neurodegenerative disorders. Rather than exerting direct antioxidant effects, the mechanisms by which polyphenols express these beneficial properties appear to involve their interaction with cellular signaling pathways and related machinery that mediate cell function under both normal and pathological conditions. We illustrate that their interactions with two such pathways, the MAP kinase (ERK, JNK, p38) and PI3 kinase/Akt signaling cascades, allow them to impact upon normal and abnormal cell function, thus influencing the cellular processes involved in the initiation and progression of cancer, CVD and neurodegeneration. For example, their ability to activate ERK in neurons leads to a promotion of neuronal survival and cognitive enhancements, both of which influence the progression of Alzheimer’s disease, whilst ERK activation by polyphenols in vascular endothelial cells influences nitric oxide production, blood pressure and ultimately CVD risk. The main focus of this review is to provide an overview of the role that polyphenols play in the prevention of cancer, cardiovascular disease and neurodegeneration. We present epidemiological data, human intervention study findings, as well as animal and in vitro studies in support of these actions and in each case we consider how their actions at the cellular level may underpin their physiological effects.

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.

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.

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.

Proteomic biomarkers of peripheral blood mononuclear cells obtained from postmenopausal women undergoing an intervention with soy isoflavones

BACKGROUND

The incidence of cardiovascular diseases increases after menopause, and soy consumption is suggested to inhibit disease development.

OBJECTIVE

The objective was to identify biomarkers of response to a dietary supplementation with an isoflavone extract in postmenopausal women by proteome analysis of peripheral blood mononuclear cells.

DESIGN

The study with healthy postmenopausal woman was performed in a placebo-controlled sequential design. Peripheral mononuclear blood cells were collected from 10 volunteers after 8 wk of receiving daily 2 placebo cereal bars and after a subsequent 8 wk of intervention with 2 cereal bars each providing 25 mg of isoflavones. The proteome of the cells was visualized after 2-dimensional gel electrophoresis, and peptide mass fingerprinting served to identify proteins that by the intervention displayed altered protein concentrations.

RESULTS

Twenty-nine proteins were identified that showed significantly altered expression in the mononuclear blood cells under the soy-isoflavone intervention, including a variety of proteins involved in an antiinflammatory response. Heat shock protein 70 or a lymphocyte-specific protein phosphatase and proteins that promote increased fibrinolysis, such as alpha-enolase, were found at increased intensities, whereas those that mediate adhesion, migration, and proliferation of vascular smooth muscle cells, such as galectin-1, were found at reduced intensities after soy extract consumption.

CONCLUSION

Proteome analysis identified in vivo markers that respond to a dietary intervention with isoflavone-enriched soy extract in postmenopausal women. The nature of the proteins identified suggests that soy isoflavones may increase the antiinflammatory response in blood mononuclear cells that might contribute to the atherosclerosis-preventive activities of a soy-rich diet.