Effects of dietary supplementation with isoflavones from red clover on ambulatory blood pressure and endothelial function in postmenopausal type 2 diabetes

Short-Term Supplementation With Fermented Red Clover Extract Reduces Vascular Inflammation in Early Post-menopausal Women

The decline in estrogen at menopause poses a critical challenge to cardiovascular and metabolic health. Recently, a growing interest in the role of phytoestrogens, with a particular focus on isoflavones, has emerged as they can bind to estrogen receptors and may mimic the roles of endogenous estrogen. Fermented red clover extract (RC) contains isoflavones with superior bioavailability compared to non-fermented isoflavones, however little is known regarding the impact of isoflavones on cardiovascular and metabolic health. We assessed markers of vascular health in plasma and skeletal muscle samples obtained from healthy but sedentary early post-menopausal women (n = 10; 54 ± 4 years) following 2 weeks of twice daily treatment with placebo (PLA) or RC (60 mg isoflavones per day). The two interventions were administered using a randomized, double-blind, crossover design with a two-week washout period. Plasma samples were utilized for assessment of markers of vascular inflammation. There was a statistically significant reduction (~5.4%) in vascular cell adhesion molecule 1 (VCAM-1) following 2 weeks of RC supplementation compared to PLA (p = 0.03). In contrast, there was no effect of RC supplementation compared to PLA on skeletal muscle estrogen receptor content and enzymes related to vascular function, and angiogenesis. Supplementation with RC reduces vascular inflammation in early post-menopausal women and future studies should address the long-term impact of daily supplementation with RC after menopause.

A Graded Approach for Evaluating Health Claims about Plant-Based Food Supplements: Application of a Case Study Methodology

The implementation of REGULATION (EC) No 1924/2006 has led to the formation of a list of health claims that can be used in food supplements (EU 432/2012). However, such supplements are often composed of plant preparations with claims omitted from this list. The peculiarity of plants is related to their long history of use, that could allow claims based on traditionally recognized health effects. In addition, the scientific literature has been enriched over the years through clinical studies that have assessed the bioavailability and efficacy of bioactive components, and investigated their mechanisms of action. Based on existing recognized models which aim to classify research according to the level of scientific evidence, Synadiet developed a three-grade model (A, B or C) for assessing plants health claims. In this paper, the applicability of the model is illustrated through an example for which a Grade B health claim attesting the possible contribution of red clover isoflavones to the improvement of blood lipid levels in postmenopausal women has been attributed. The model appears able to be easily extrapolated to claims pertaining to other plants. If adopted by consensus at European level, this model could initiate the implementation of a positive list of health claims on plant preparations.

The Vascular Effects of Isolated Isoflavones-A Focus on the Determinants of Blood Pressure Regulation

Isoflavones are phytoestrogen compounds with important biological activities, including improvement of cardiovascular health. This activity is most evident in populations with a high isoflavone dietary intake, essentially from soybean-based products. The major isoflavones known to display the most important cardiovascular effects are genistein, daidzein, glycitein, formononetin, and biochanin A, although the closely related metabolite equol is also relevant. Most clinical studies have been focused on the impact of dietary intake or supplementation with mixtures of compounds, with only a few addressing the effect of isolated compounds. This paper reviews the main actions of isolated isoflavones on the vasculature, with particular focus given to their effect on the determinants of blood pressure regulation. Isoflavones exert vasorelaxation due to a multitude of pathways in different vascular beds. They can act in the endothelium to potentiate the release of NO and endothelium-derived hyperpolarization factors. In the vascular smooth muscle, isoflavones modulate calcium and potassium channels, leading to hyperpolarization and relaxation. Some of these effects are influenced by the binding of isoflavones to estrogen receptors and to the inhibition of specific kinase enzymes. The vasorelaxation effects of isoflavones are mostly obtained with plasma concentrations in the micromolar range, which are only attained through supplementation. This paper highlights isolated isoflavones as potentially suitable alternatives to soy-based foodstuffs and supplements and which could enlarge the current therapeutic arsenal. Nonetheless, more studies are needed to better establish their safety profile and elect the most useful applications.

Effects of red clover on perimenopausal and postmenopausal women's blood lipid profile: A meta-analysis

The study aimed to perform a systematic review with meta-analysis of randomized controlled trials (RCTs) to access the effects of red clover isoflavones on the blood lipid profile of both perimenopausal and postmenopausal women. PubMed, Web of Science, Scopus, SciELO, and Cochrane Library were searched for the terms 'red clover', 'Trifolium pratense', and 'randomized controlled trial' during November 2017. Summary measures were reported as weighted mean differences (WMD) with 95% confidence interval (CI). Fixed or random effects models were used for meta-analyses, according to heterogeneity. Risk of bias was measured with the Cochrane tool. Twelve RCTs (totalizing 1284 perimenopausal and postmenopausal women receiving red clover isoflavones for 4 weeks-18 months) resulted in a significant decrease in total cholesterol (WMD = -12.34 mg/dl; 95% CI: -18.21, -6.48), low-density lipoprotein cholesterol (WMD = -10.61 mg/dl; 95% CI: -15.51, -5.72), and triglycerides (WMD = -10.18 mg/dl; 95% CI: -16.23, -4.13) together with a significant increase in high-density lipoprotein cholesterol (WMD = 1.60 mg/dl; 95% CI: 0.17, 3.03). In conclusion, the results demonstrate that the ingestion of red clover may have a beneficial effect on the lipid profile of perimenopausal and postmenopausal women.

Beneficial effects of cherry consumption as a dietary intervention for metabolic, hepatic and vascular complications in type 2 diabetic rats

Background

Oxidative stress (OS) plays an important role in type 2 diabetes (T2D) pathogenesis and its complications. New therapies target natural antioxidants as an alternative and/or supplemental strategy to prevent and control them. Our previous chemical and biological studies highlighted the important antioxidant activities of cherries, among other fruits and vegetables, thus we aimed to determine in vivo effects of 2-month long cherry consumption using a high-fat/high-fructose (HFHF) model of diabetic-rats (Lozano et al. in Nutr Metab 13:15, 2016).

Methods

After 2 months of HFHF, male Wistar rats were divided into: HFHF and HFHF enriched in cherry (nutritional approach) or standard diet ND (lifestyle measures) and ND plus cherry during 2 months. Metabolic, lipidic, oxidative parameters were quantified. Tissues (liver, pancreas and vessels) OS were assessed and hepatic (steatosis, fibrosis, inflammation) and vascular (endothelial dysfunction) complications were characterized.

Results

T2D was induced after 2 months of HFHF diet, characterized by systemic hyperglycaemia, hyperinsulinemia, glucose intolerance, dyslipidaemia, hyperleptinemia, and oxidative stress associated with endothelial dysfunction and hepatic complications. Cherry consumption for 2 months, in addition to lifestyle measures, in T2D-rats decreased and normalized the systemic disturbances, including oxidative stress complications. Moreover, in the vessel, cherry consumption decreased oxidative stress and increased endothelial nitric oxide (NO) synthase levels, thus increasing NO bioavailability, ensuring vascular homeostasis. In the liver, cherry consumption decreased oxidative stress by inhibiting NADPH oxidase subunit p22phox expression, nuclear factor erythroid-2 related factor 2 (Nrf2) degradation and the formation of reactive oxygen species. It inhibited the activation of sterol regulatory element-binding proteins (1c and 2) and carbohydrate-responsive element-binding protein, and thus decreased steatosis as observed in T2D rats. This led to the improvement of metabolic profiles, together with endothelial and hepatic function improvements.

Conclusion

Cherry consumption normalized vascular function and controlled hepatic complications, thus reduced the risk of diabetic metabolic disorders. These results demonstrate that a nutritional intervention with a focus on OS could prevent and/or delay the onset of vascular and hepatic complications related to T2D.

Electronic supplementary material

The online version of this article (10.1186/s12933-018-0744-6) contains supplementary material, which is available to authorized users.

Antidiabetic phytoconstituents and their mode of action on metabolic pathways

Diabetes Mellitus, characterized by persistent hyperglycaemia, is a heterogeneous group of disorders of multiple aetiologies. It affects the human body at multiple organ levels thus making it difficult to follow a particular line of the treatment protocol and requires a multimodal approach. The increasing medical burden on patients with diabetes-related complications results in an enormous economic burden, which could severely impair global economic growth in the near future. This shows that today's healthcare system has conventionally been poorly equipped towards confronting the mounting impact of diabetes on a global scale and demands an urgent need for newer and better options. The overall challenge of this field of diabetes treatment is to identify the individualized factors that can lead to improved glycaemic control. Plants are traditionally used worldwide as remedies for diabetes healing. They synthesize a diverse array of biologically active compounds having antidiabetic properties. This review is an endeavour to document the present armamentarium of antidiabetic herbal drug discovery and developments, highlighting mechanism-based antidiabetic properties of over 300 different phytoconstituents of various chemical categories from about 100 different plants modulating different metabolic pathways such as glycolysis, Krebs cycle, gluconeogenesis, glycogen synthesis and degradation, cholesterol synthesis, carbohydrate metabolism as well as peroxisome proliferator activated receptor activation, dipeptidyl peptidase inhibition and free radical scavenging action. The aim is to provide a rich reservoir of pharmacologically established antidiabetic phytoconstituents with specific references to the novel, cost-effective interventions, which might be of relevance to other low-income and middle-income countries of the world.

Nutritional intervention and impact of polyphenol on glycohemoglobin (HbA1c) in non-diabetic and type 2 diabetic subjects: Systematic review and meta-analysis

Polyphenols have been extensively studied for their antioxidant and anti-inflammatory properties. Recently, their antiglycative actions by oxidative stress modulation have been linked to the prevention of diabetes and associated complications. This article assesses the evidence for polyphenol interventions on glycohemoglobin (HbA1c) in non-diabetic, pre-diabetic, and type 2 diabetes mellitus (T2DM) subjects. A systematic review of polyphenols' clinical trials on HbA1c in humans was performed according to the Preferred Reporting Items for Systematic Review and Meta-Analysis. Thirty-six controlled randomized trials with HbA1c values were included. Polyphenols (extracts, supplements, and foods) were supplemented (28 mg to 1.5 g) for 0.7 to 12 months. Combining all subjects (n = 1954, mean baseline HbA1c = 7.03%, 53 mmol/mol), polyphenol supplementation significantly (P < 0.001) lowered HbA1c% by -0.53 ± 0.12 units (-5.79 ± 0.13 mmol/mol). This reduction was significant (P < 0.001) in T2DM subjects, specifically (n = 1426, mean baseline HbA1c = 7.44%, 58 mmol/mol), with HbA1c% lowered by -0.21 ± 0.04 units (-2.29 ± 0.4 mmol/mol). Polyphenol supplementation had no significant effect (P > 0.21) in the non-diabetic (n = 258, mean baseline HbA1c = 5.47%, 36 mmol/mol) and the pre-diabetic subjects (n = 270, mean baseline HbA1c = 6.06%, 43 mmol/mol) strata: -0.39 ± 0.27 HbA1c% units (-4.3 ± 0.3 mmol/mol), and -0.38 ± 0.31 units (-4.2 ± 0.31 mmol/mol), respectively. In conclusion, polyphenols can successfully reduce HbA1c in T2DM without any intervention at glycemia, and could contribute to the prevention of diabetes complications.

Role of phytoestrogens in prevention and management of type 2 diabetes

Type 2 diabetes (T2D) has become a major public health threat across the globe. It has been widely acknowledged that diet plays an important role in the development and management of T2D. Phytoestrogens are polyphenols that are structurally similar to endogenous estrogen and have weak estrogenic properties. Emerging evidence from pre-clinical models has suggested that phytoestrogens may have anti-diabetic function via both estrogen-dependent and estrogen-independent pathways. In the current review, we have summarized the evidence linking two major types of phytoestrogens, isoflavones and lignans, and T2D from epidemiological studies and clinical trials. The cross-sectional and prospective cohort studies have reported inconsistent results, which may due to the large variations in different populations and measurement errors in dietary intakes. Long-term intervention studies

using isoflavone supplements have reported potential beneficial effects on glycemic parameters in postmenopausal women, while results from short-term small-size clinical trials are conflicting. Taken together, the current evidence from different study designs is complex and inconsistent. Although the widespread use of phytoestrogens could not be recommended yet, habitual consumption of phytoestrogens, particularly their intact food sources like soy and whole flaxseed, could be considered as a component of overall healthy dietary pattern for prevention and management of T2D.

Red clover isoflavones enriched with formononetin lower serum LDL cholesterol-a randomized, double-blind, placebo-controlled study

BACKGROUND

Although postmenopausal combined hormone replacement therapy reduces the risk of hip fracture, long-term use may be associated with an increased risk of breast cancer, and in women more than 10 years after menopause it is associated with an increased risk of cardiovascular disease. Isoflavones, because of preferential binding to estrogen receptor beta, may retain the beneficial effects on bone but lessen the adverse effects on the breast.

OBJECTIVE

The objective of this study was to study the effects of an isoflavone obtained from red clover (Rimostil) on bone mineral density, and on low-density lipoprotein (LDL) cholesterol.

DESIGN

In a double-blind, randomized, placebo-controlled trial, 50 mg of Rimostil was given to women who were menopausal for at least 1 year. Bone mineral density of the spine, femoral neck and forearm and serum LDL cholesterol were measured at baseline and at 6-month intervals. The duration of follow-up was 2 years.

RESULTS

There was no beneficial effect of Rimostil on bone density at any site. There was a 12% fall in serum LDL cholesterol in the Rimostil-treated arm, which was significantly greater than the 2% drop seen in the control arm (P=0.005).

Dietary polyphenols as potential nutraceuticals in management of diabetes: a review

In recent years, there is growing evidence that plant-foods polyphenols, due to their biological properties, may be unique nutraceuticals and supplementary treatments for various aspects of type 2 diabetes mellitus. In this article we have reviewed the potential efficacies of polyphenols, including phenolic acids, flavonoids, stilbenes, lignans and polymeric lignans, on metabolic disorders and complications induced by diabetes. Based on several in vitro, animal models and some human studies, dietary plant polyphenols and polyphenol-rich products modulate carbohydrate and lipid metabolism, attenuate hyperglycemia, dyslipidemia and insulin resistance, improve adipose tissue metabolism, and alleviate oxidative stress and stress-sensitive signaling pathways and inflammatory processes. Polyphenolic compounds can also prevent the development of long-term diabetes complications including cardiovascular disease, neuropathy, nephropathy and retinopathy. Further investigations as human clinical studies are needed to obtain the optimum dose and duration of supplementation with polyphenolic compounds in diabetic patients.

Trifolium species-derived substances and extracts--biological activity and prospects for medicinal applications

BACKGROUND

Despite of the fact that clovers (family: Fabaceae; genus: Trifolium) have been known for many centuries as important forage plants and valuable herbs in folk medicine, their phytochemical characteristics and biological activity remain only partly established.

AIM OF THE STUDY

The presentation of the current knowledge of physiological effects, therapeutic action, new trends in the investigation of Trifolium plants and suggestions for the future applications of these herbs in therapy of various disorders.

METHODS

A critical review of literature on the biological activity of Trifolium plants, with the indication on important gaps, was performed. The compilation of existing information on physiological effects and medicinal value of clovers, derived from both traditional medicine recommendations and scientific reports, is presented.

RESULTS

The available data indicate on the abundance of biologically active substances in Trifolium plants, including numerous flavonoids, saponins, clovamides and phenolic acids. The best known clover - Trifolium pratense L. (red clover) - is used for the production of herbal medicines, an alternative to the conventional hormonal replacement therapy. The biological activity and potential therapeutic effects of other Trifolium species have gained a considerable scientific interest; extracts obtained from various clovers have been shown to possess antioxidative and antiinflammatory activities, inhibiting angiogenesis and displaying anti-cancer properties.

CONCLUSIONS

Clovers other than T. pratense also seem to be a promising source of valuable phytochemicals, such as isoflavones and various flavonoids. However, the therapeutic use of these Trifolium species is significantly limited by the lack of clinical evidence; thus further studies are needed.

Chronic ingestion of flavan-3-ols and isoflavones improves insulin sensitivity and lipoprotein status and attenuates estimated 10-year CVD risk in medicated postmenopausal women with type 2 diabetes: a 1-year, double-blind, randomized, controlled trial

OBJECTIVE

To assess the effect of dietary flavonoids on cardiovascular disease (CVD) risk in postmenopausal women with type 2 diabetes on established statin and hypoglycemic therapy.

RESEARCH DESIGN AND METHODS

Despite being medicated, patients with type 2 diabetes have elevated CVD risk, particularly postmenopausal women. Although dietary flavonoids have been shown to reduce CVD risk factors in healthy participants, no long-term trials have examined the additional benefits of flavonoids to CVD risk in medicated postmenopausal women with type 2 diabetes. We conducted a parallel-design, placebo-controlled trial with type 2 diabetic patients randomized to consume 27 g/day (split dose) flavonoid-enriched chocolate (containing 850 mg flavan-3-ols [90 mg epicatechin] and 100 mg isoflavones [aglycone equivalents)]/day) or matched placebo for 1 year.

RESULTS

Ninety-three patients completed the trial, and adherence was high (flavonoid 91.3%; placebo 91.6%). Compared with the placebo group, the combined flavonoid intervention resulted in a significant reduction in estimated peripheral insulin resistance (homeostasis model assessment of insulin resistance [HOMA-IR] -0.3 ± 0.2; P = 0.004) and improvement in insulin sensitivity (quantitative insulin sensitivity index [QUICKI] 0.003 ± 0.00; P = 0.04) as a result of a significant decrease in insulin levels (-0.8 ± 0.5 mU/L; P = 0.02). Significant reductions in total cholesterol:HDL-cholesterol (HDL-C) ratio (-0.2 ± 0.1; P = 0.01) and LDL-cholesterol (LDL-C) (-0.1 ± 0.1 mmol/L; P = 0.04) were also observed. Estimated 10-year total coronary heart disease risk (derived from UK Prospective Diabetes Study algorithm) was attenuated after flavonoid intervention (flavonoid +0.1 ± 0.3 vs. placebo 1.1 ± 0.3; P = 0.02). No effect on blood pressure, HbA(1c), or glucose was observed.

CONCLUSIONS

One-year intervention with flavan-3-ols and isoflavones improved biomarkers of CVD risk, highlighting the additional benefit of flavonoids to standard drug therapy in managing CVD risk in postmenopausal type 2 diabetic patients.

Red clover extract: a source for substances that activate peroxisome proliferator-activated receptor alpha and ameliorate the cytokine secretion profile of lipopolysaccharide-stimulated macrophages

OBJECTIVE

Inflammation and hyperlipidemia or dyslipidemia contribute to an increased risk of atherosclerosis and cardiovascular disease. Cardiovascular disease represents one of the major causes of premature death worldwide. The activation of peroxisome proliferator-activated receptor (PPAR) alpha, a drug target for hyperlipidemia and dyslipidemia, leads to an improved blood lipid profile. In this study, we determined the putative anti-inflammatory and PPARalpha stimulatory activities of red clover, an alternative to the classic hormone therapy used currently to treat menopausal symptoms.

METHODS

Lipopolysaccharide-induced macrophages were used as a model for anti-inflammatory activity, and a chimeric GAL4-PPARalpha system was used as a model for putative hypolipidemic activity.

RESULTS

Red clover extract and the isoflavones genistein and biochanin A were moderate PPARalpha activators. Daidzein only slightly activated PPARalpha, but its metabolite 6-hydroxydaidzein exerted a much higher PPARalpha activity. Similarly, the metabolite 3'-hydroxygenistein achieved higher activation efficiency than its precursor, genistein, did. In lipopolysaccharide-stimulated macrophages, red clover extract and its compounds reduced the secretion of proinflammatory cytokines, interleukin-6 and tumor necrosis factor alpha, increased the secretion of the anti-inflammatory interleukin-10, and/or reduced the expression of nuclear factor-kappaB, inducible nitric oxide synthase, and/or cyclooxygenase 2. Tumor necrosis factor alpha production was most efficiently reduced by biochanin A and genistein. Interleukin-6 levels were most efficiently reduced by genistein and equol.

CONCLUSIONS

Owing to its PPARalpha activation and modulation of the secreted cytokine profile, red clover extract is a putative candidate for preventing atherosclerosis and, thus, cardiovascular disease.

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.

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.

Dietary phyto-oestrogens: molecular mechanisms, bioavailability and importance to menopausal health

Following the high-profile studies on hormone replacement therapy which provided little evidence in support of the drug therapy improving future health, there remains a growing demand for dietary solutions for maintaining health and preventing disease as women age. Although interest in the relative importance of phyto-oestrogens to human health has increased dramatically over the last decade, the effective dose for health benefits and hypothetical issues on safety remain to be resolved. Plausible mechanisms and epidemiological data are available to support the concept that phyto-oestrogen-rich diets exert physiological effects, but optimal doses and sources of these compounds have still not been elucidated for specific health benefits. In addition, much of the current mechanistic data are difficult to interpret as the experiments have incorporated levels of phyto-oestrogens that may not be achievable in vivo and have to date only used aglycones and glycosides of the pure compounds rather than examining the biological effects of gut and liver metabolites. The present review will concentrate on the isoflavone subclass of phyto-oestrogens, as, to date, these compounds have received most attention from both a commercial and research perspective.

Soy protein reduces serum LDL cholesterol and the LDL cholesterol:HDL cholesterol and apolipoprotein B:apolipoprotein A-I ratios in adults with type 2 diabetes

Type 2 diabetes is highly prevalent in North America and is associated with increased risk of cardiovascular disease (CVD). Evidence supports a role for soy protein in the reduction of serum lipids related to CVD risk; however, few studies have focused on adults with type 2 diabetes who are not on lipid-lowering medications and/or do not have diabetic complications. The purpose of this study was to determine the effect of soy protein isolate (SPI) consumption on serum lipids in adults with diet-controlled type 2 diabetes. Using a double-blind, randomized, crossover, placebo-controlled intervention study design, adults with diet-controlled type 2 diabetes (n = 29) consumed SPI (80 mg/d aglycone isoflavones) or milk protein isolate (MPI) for 57 d each separated by a 28-d washout period. Twenty-four-hour urine samples were collected on d 54-56 of each treatment for analysis of isoflavones and blood was collected on d 1 and 57 of each treatment and analyzed for serum lipids and apolipoproteins. SPI consumption increased urinary isoflavones compared with MPI. SPI consumption reduced serum LDL cholesterol (P = 0.04), LDL cholesterol:HDL cholesterol (P = 0.02), and apolipoprotein B:apolipoprotein A-I (P = 0.05) compared with MPI. SPI did not affect serum total cholesterol, HDL cholesterol, triacylglycerol, apolipoprotein B, or apolipoprotein A-I. These data demonstrate that consumption of soy protein can modulate some serum lipids in a direction beneficial for CVD risk in adults with type 2 diabetes.

Soya protein does not affect glycaemic control in adults with type 2 diabetes

Evidence from observational, animal and human studies supports a role for soya protein and its isoflavones in the improvement of glycaemic control in type 2 diabetes. The objective of the present study was to determine the effect of isoflavone-rich soya protein on markers of glycaemic control in adults with type 2 diabetes. Using a randomised, crossover, double-blind, placebo-controlled design, adults with diet-controlled type 2 diabetes (n 29) consumed soya protein isolate (SPI) and milk protein isolate (MPI) for 57 d each separated by a 4-week washout. Blood was collected on days 1 and 57 of each treatment period for analysis of fasting HbA1C, and fasting and postprandial glucose, insulin and calculated indices of insulin sensitivity and resistance. Urine samples of 24 h were collected at the end of each treatment period for analysis of isoflavones. Urinary isoflavone excretion was significantly greater following consumption of SPI compared with MPI, and 20.7 % of the subjects (n 6) were classified as equol excretors. SPI consumption did not significantly affect fasting or postprandial glucose or insulin, fasting HbA1C, or indices of insulin sensitivity and resistance. These data do not support a role for soya protein in the improvement of glycaemic control in adults with diet-controlled type 2 diabetes and contribute to a limited literature of human studies on the effects of soya protein on the management of type 2 diabetes.

Clinical studies of red clover (Trifolium pratense) dietary supplements in menopause: a literature review

Red clover (Trifolium pratense L., Fabaceae) botanical dietary supplements have received much attention recently for their potential use in the treatment of menopause symptoms, maintenance/improvement of bone and cardiovascular health, and reported benign effects on the breast and endometrium. Literature searches of four computerized databases were run to identify clinical studies of red clover botanical dietary supplements. The manufacturer of the red clover products used in the majority of the studies was contacted for unpublished information and/or clarification regarding the chemical content of their products. Red clover studies were reviewed that pertained to women's health or menopause. Clinical evidence is presently lacking to support the efficacy of semipurified red clover isoflavone extracts for alleviation of climacteric vasomotor symptoms or reduction of low-density lipoprotein levels in the blood. Furthermore, the safety of use of red clover isoflavone supplements in patients with breast or endometrial cancer has not been established. Limited evidence suggests possible efficacy in maintenance of bone health and improvement of arterial compliance, a risk factor for atherosclerosis. This literature review covers red clover botanical dietary supplement clinical studies having a possible impact on the health care of mature and menopausal women, and provides historical perspective regarding the traditional uses of red clover.

NV-52

NV-52, a synthetic flavonoid derivative, is a selective thromboxane synthase (TXS) inhibitor that is being developed as a treatment for inflammatory bowel disease. NV-52 selectively inhibits TXS in vitro in physiological relevant concentrations, causing a reduction in thromboxane B(2) of </= 40% in association with an increase in prostaglandin E(2). NV-52 is effective in suppressing colonic inflammation in a murine model of inflammatory bowel disease. NV-52 has not demonstrated any toxicity in in vitro and animal toxicological studies, and has been administered to normal volunteers in a Phase I clinical trial without detectable adverse effects. NV-52 is well absorbed and a single dose of 400 mg p.o. produced a plasma concentration that is comparable with the concentrations that have been shown to produce significant TXS inhibition in vitro.

Therapeutic regulation of endothelial dysfunction in type 2 diabetes mellitus

Endothelial dysfunction is universal in diabetes, being intimately involved with the development of cardiovascular disease. The pathogenesis of endothelial dysfunction in diabetes is complex. It is initially related to the effects of fatty acids and insulin resistance on 'uncoupling' of both endothelial nitric oxide synthase activity and mitochondrial function. Oxidative stress activates protein kinase C (PKC), polyol, hexosamine and nuclear factor kappa B pathways, thereby aggravating endothelial dysfunction. Improvements in endothelial function in the peripheral circulation in diabetes have been demonstrated with monotherapies, including statins, fibrates, angiotensin-converting enzyme (ACE) inhibitors, metformin and fish oils. These observations are supported by large clinical end point trials. Other studies show benefits with certain antioxidants, L-arginine, folate, PKC-inhibitors, peroxisome proliferator activated receptor (PPAR)-alpha and -gamma agonists and phosphodiesterase (PDE-5) inhibitors. However, the benefits of these agents remain to be shown in clinical end point trials. Combination treatments, for example, statins plus ACE inhibitors and statins plus fibrates, have also been demonstrated to have additive benefits on endothelial function in diabetes, but there are no clinical outcome data to date. Measurement of endothelial dysfunction in cardiovascular research can provide fresh opportunities for exploring the mechanism of benefit of new therapeutic regimens and for planning and designing large clinical trials.

Effects of dietary red clover on blood factors and cardiovascular fatty streak formation in hypercholesterolemic rabbits

Phytoestrogens with a biological activity like estradiol are naturally found in many plants. This study was designed to investigate the effect of red clover, a phytoestrogen-rich member of the legume family (Trifolium pratense) on the development of atherosclerosis in male hyperlipidemic rabbits. Twenty rabbits were semi-randomly distributed into four groups of five each. Two groups received either normal diet or normal diet supplemented with red clover. Two other groups received similar diets to both of which 1% cholesterol was added. Dietary use of red clover (RC) in hyperlipidemic rabbits significantly decreased C-reactive protein (CRP), triglyceride (TG), total cholesterol and LDL-cholesterol (LDL-C) whereas, HDL-cholesterol (HDL-C) was significantly increased in those animals (p < 0.05). Fatty streak formation was also significantly lower in aorta and left and right coronary arteries in the same animals due to use of dietary RC supplementation. These findings suggest that dietary RC may reduce cardiovascular risk factors.

Dietary antioxidants in preventing atherogenesis

Several naturally occurring constituents have received considerable attention because of their potential antioxidant activity. Consuming a diet rich in natural antioxidants has been associated with prevention from and/or treatment of atherosclerosis. Bioactive components of food, which are of special interest, include the Vitamins E and C, polyphenols, carotenoids-mainly lycopene and beta-carotene, and coenzyme Q10, featured by antioxidant properties. Antioxidant therapy is supposed to be effective in the early stages of atherosclerosis by preventing LDL oxidation and the oxidative lesion of endothelium. This review focuses on the effect of dietary antioxidants pertained to LDL oxidation and to the vascular endothelial dysfunction. Now that the human genome has been completely sequenced, genetic factors involved in oxidation may open new horizons to identify persons at risk for cardiovascular disease, allowing effective dietary intervention strategies to recover normal homeostasis and to prevent diet-related implications. On this basis, current studies on the action of selected antioxidant nutraceuticals on the activity of transcription factors, such as final targets in the signal transduction cascade and gene regulation, may emerge into new treatment concepts.

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.

The effect of red clover isoflavones on menopausal symptoms, lipids and vaginal cytology in menopausal women: a randomized, double-blind, placebo-controlled study

BACKGROUND

The unexpected results of the Women's Health Initiative study have decreased the use of conventional hormone therapy (HT), changing physicians' and patients' attitudes towards HT and increasing their interest in alternative options.

OBJECTIVE

The present study aimed to evaluate the effect of isoflavones contained in red clover extracts (Trifolium pratense) on menopausal symptoms, lipids and vaginal cytology in menopausal women.

METHODS

Sixty postmenopausal women aged >40 years, non-users of HT, with Kupperman index score 15, were double-blindly randomized to receive either a commercially available red clover isoflavone supplement (80 mg/day) or placebo for 90 days. Subsequently, after a 7-day washout period, subjects switched to receive the opposite treatment for a further 90 days. Kupperman index score was determined and fasting blood and vaginal cytologic sampling performed at baseline, 90 and 180 days.

RESULTS

Fifty-three women (88.3%) completed the trial. Mean age was 51.3 +/- 3.5 years, 69.7% of the women were aged 50 years or more. There was no significant effect on body mass index, weight or blood pressure after either treatment phase. Baseline Kupperman index score decreased significantly after each treatment phase, with the decrease more pronounced after the isoflavone phase (baseline: 27.2 +/- 7.7; after isoflavone: 5.9 +/- 3.9; after placebo: 20.9 +/- 5.3, p < 0.05). Red clover isoflavone supplementation significantly decreased the rate of menopausal symptoms and had a positive effect on vaginal cytology as expressed by improvement in karyopyknotic, cornification and basal cell maturation indices. Mean total cholesterol, low-density lipoprotein-cholesterol and triglyceride levels also decreased; however, only the latter was significantly lower compared with placebo.

CONCLUSIONS

Compared with placebo, red clover isoflavone supplementation in postmenopausal women significantly decreased menopausal symptoms and had a positive effect on vaginal cytology and triglyceride levels.

Activation of nitric oxide synthesis in human endothelial cells by red clover extracts

OBJECTIVE

The unexpected findings of the Women's Health Initiative trial, where surrogate cardiovascular risk markers have failed to predict the cardiovascular performance of hormone therapy, showing no reduction of cardiovascular disease in postmenopausal women receiving hormonal preparations inducing a favorable lipid profile, raise the interest on how molecules with hormone-like activity used for the treatment of menopausal symptoms act on vascular cells. This is particularly important for estrogen-like compounds such as phytoestrogens, whose mechanisms of action may significantly differ from those of other estrogenic compounds.

DESIGN

Because endothelial-derived nitric oxide (NO) is a key regulator of vascular tone and atherogenesis as well as a well-characterized estrogen-regulated molecule, we studied the regulation of NO synthesis in cultured human endothelial cells by phytoestrogens contained in red clover extracts.

RESULTS

We show that red clover extracts activate NO synthesis in endothelial cells by recruiting transcriptional pathways but are not capable of inducing rapid NO synthesis through nongenomic mechanisms. During prolonged exposures, red clover extracts enhance the expression as well as the activity of endothelial nitric oxide synthase. These effects are mediated by a recruitment of estrogen receptor-beta. Moreover, we show that red clover-derived isoflavones synergize with 17beta-estradiol in increasing endothelial nitric oxide synthase activity and expression, therefore being devoid of antiestrogenic effects in human endothelial cells.

CONCLUSIONS

These results help to understand the mechanisms of action of phytoestrogens on the cardiovascular system and have relevant clinical implications.

Phytoestrogenic isoflavones daidzein and genistein reduce glucose-toxicity-induced cardiac contractile dysfunction in ventricular myocytes

Epidemiological evidence suggests a reduction in the incidence of coronary heart disease, cancer and osteoporosis in populations with a high dietary intake of plant estrogen or phytoestrogen. The clinical benefit of phytoestrogens in cereals, vegetables and medicinal plants is attracting increasing attention for the general public. In the present study, we examined the effect of phytoestrogenic isoflavones daidzein and genistein on glucose toxicity-induced cardiac mechanical malfunction simulating diabetic cardiomyopathy. Adult rat ventricular myocytes were isolated and maintained for 24 hours in normal (NG, 5.5 mM) or high glucose (HG, 25.5 mM) medium in the absence or presence of isoflavones daidzein (50 microM) or genistein (20 microM). Cardiac contractile indices were evaluated using an IonOptix MyoCam system including peak shortening (PS), maximal velocity of shortening/relengthening (+/- dL/dt), time-to-PS (TPS) and time-to-90% relengthening (TR90). Myocytes maintained in HG medium displayed altered mechanical function simulating in vivo diabetes including reduced PS, +/- dL/dt and prolonged TR90 associated with normal TPS compared to those from NG myocytes. Interestingly, these HG-induced mechanical dysfunctions were abolished by co-incubation of daidzein or genistein. However, daidzein but not genistein itself depressed PS in NG myocytes. Neither daidzein nor genistein affected any other mechanical parameters tested in NG myocytes. Collectively, these data suggest that the phytoestrogenic isoflavones daidzein and genistein may reduce glucose toxicity-induced cardiac mechanical dysfunction and thus possess therapeutic potential against diabetes-associated cardiac defects.