Physiological effects of phyto-oestrogens in relation to cancer and other human health risks

Effect of soy isoflavones supplementation on migraine characteristics, mental status and calcitonin gene-related peptide (CGRP) levels in women with migraine: results of randomised controlled trial

Background

Literature suggests a relationship between estrogen levels and migraine headache pathogenesis. However, the effect of soy isoflavones on migraine characteristic remains unclear. This study aimed to investigate the effect of soy isoflavones on migraine characteristics and calcitonin gene-related peptide (CGRP) levels in women with migraine.

Methods

Eighty-three participants completed a randomized double-blind controlled trial, receiving 50 mg per day soy isoflavones or placebo supplementation for 8 weeks. Migraine severity, migraine days per month, frequency and duration of attacks, mental status, quality of life and serum CGRP levels were measured at baseline and the end of the intervention. Bivariate comparison and intention-to-treat (ITT) were used for analysis.

Results

Soy isoflavones intake resulted in a significant decrease in mean frequency (-2.36 vs -0.43, P < 0.001), duration (-2.50 vs -0.02, P < 0.001) of migraine attacks and CGRP level (-12.18 ng/l vs -8.62, P = 0.002) in compared to placebo group. Also, a significant improvement was found in quality of life (16.76 vs 2.52, P < 0.001). Although, reduction in the migraine severity and mental status did not reach a statistically significant level (P > 0.05).

Conclusion

soy isoflavones supplementation may be considered as a complementary treatment for women with migraine to improve migraine characteristics and reduce the burden of disease.

Prunetin Protects Against Dexamethasone-Induced Pancreatic Β-Cell Apoptosis via Modulation of p53 Signaling Pathway

Long-term administration of dexamethasone results in insulin resistance and pancreatic β-cell apoptosis. Prunetin (an O-methylated isoflavone, a type of flavonoid) is demonstrated to protect diabetes, but the molecular mechanism of this protection is still unclear. This study thus aims to investigate how prunetin protects against dexamethasone-induced pancreatic β-cell apoptosis. Rat insulinoma (INS-1) cells were cultured in medium with or without dexamethasone in the presence or absence of prunetin or pifithrin-α, a p53 inhibitor. Cell apoptosis was measured by Annexin V/propidium iodide staining. Dexamethasone significantly induced INS-1 apoptosis but dexamethasone plus prunetin significantly reduced INS-1 apoptosis. Dexamethasone-treated INS-1 upregulated p53 protein expression; the induction of p53 was also reduced in the presence of RU486, a glucocorticoid receptor (GR) inhibitor. This suggested that dexamethasone induced P53 via GR. Dexamethasone-treated INS-1 significantly increased p53, Bax, and Rb protein expressions, whereas treatments of dexamethasone plus prunetin or pifithrin-α significantly decreased these protein expressions. In addition, dexamethasone significantly decreased B-cell lymphoma 2 (Bcl2), while dexamethasone plus prunetin or pifithrin-α significantly increased Bcl2. Dexamethasone significantly increased caspase-3 activity while co-treatment of dexamethasone plus prunetin or pifithrin-α significantly decreased caspase-3 activity to the control level. Taken together, our results revealed that prunetin protected against dexamethasone-induced pancreatic β-cells apoptosis via modulation of the p53 signaling pathway.

Oral Exposure to Genistein during Conception and Lactation Period Affects the Testicular Development of Male Offspring Mice

Simple Summary

Spermatogenesis and hormones secretions are important life-threating and complicated process, which can be affected by environmental estrogens. Genistein, a type of isoflavones, widely exists in the soybean products diet, which exerts a controversial role in reproductive regulation for its special structures or functions. The results of the study revealed that low-dose genistein treatment increased the level of testosterone in the mice serum, and positively regulated expression of spermatogenesis-related genes, which enhanced spermatogenesis and testicular development. However, High-dose genistein treatment induced apoptosis of germ cells and inhibited proliferation of germ cells during spermatogenesis. Reproductive alterations in the structures and functions of testis were dose-dependent in different genistein treatments.

Abstract

Sexual hormones are essential for the process of spermatogenesis in the testis. However, the effect of maternal genistein (GEN) on the pups’ testicular development remain-unclear. Our present study evaluated the effects of supplementing GEN for parental and offspring mice on the reproductive function and growth performance of the male pups. Mothers during gestation and lactation period were assigned to a control diet (CON group), low dose GEN (LGE group) diet (control diet +40 mg/kg GEN), and high dose of GEN (HGE group) diet (control diet +800 mg/kg GEN). Their male offspring underwent the same treatment of GEN after weaning. LGE treatment (40 mg/kg GEN) significantly increased body weights (p < 0.001), testes weights (p < 0.05), diameters of seminiferous tubule (p < 0.001) and heights of seminiferous epithelium (p < 0.05) of offspring mice. LGE treatment also increased serum testosterone (T) levels and spermatogenesis scoring (p < 0.05). However, HGE treatment (800mg/kg GEN) significantly decreased body weights (p < 0.001), testes weights (p < 0.05) and testis sizes (p < 0.001). Furthermore, mRNA expressions of ESR2 (p < 0.05), CYP19A1 (p < 0.001), SOX9 (p < 0.001) and BRD7 (p < 0.001) in testis of mice were increased in the LGE group. Similarly, HGE treatment increased mRNA expressions of ESR2 (p < 0.05) and CYP19A1 (p < 0.001). However, mRNA expressions of SOX9 and BRD7 were decreased significantly in the HGE group (p < 0.001). Meanwhile, higher ratio apoptotic germ cells and abnormal sperms were detected in the HGE group (p < 0.001). In conclusion, exposure to a low dose of GEN during fetal and neonatal life could improve testicular development of offspring mice, whereas, unfavorable adverse effects were induced by a high dose of GEN.

Comparison of Antiobesity Effects Between Gochujangs Produced Using Different Koji Products and Tabasco Hot Sauce in Rats Fed a High-Fat Diet

In this study, we compared the antiobesity effects between gochujangs prepared using different koji products and Tabasco hot sauce in rats fed a high-fat diet (HFD). Male Sprague-Dawley rats were fed HFD containing four different types of 10% gochujang powder or 0.25% commercial Tabasco sauce powder for 8 weeks. The body weight gain, liver and epididymal and mesenteric fat pad weights, serum leptin levels, and lipogenesis-related mRNA levels of HFD-gochujang supplementation groups were significantly decreased compared with those of the HFD group. In addition, gochujang supplement significantly reduced adipocyte size; hepatic triglyceride and total cholesterol levels; the occurrence of fatty liver deposits and steatosis by inhibiting lipogenesis through downregulation of fatty acid synthase, acetly-CoA carboxylase, and glucose-6-phosphate-dehydrogenase. These effects were greater in the gochujang-supplemented groups than the Tabasco hot sauce-supplemented group. The gochujang prepared by nutritious giant embryo rice koji and soybean koji was most effective in terms of antiobesity effects, compared with the other tested gochujangs. In gochujangs, the antiobesity effects are mediated by high levels of secondary metabolites such as isoflavone, soyasaponin, capsaicin, and lysophosphatidylcholine. The current results indicated that the gochujang products have the potential to reduce fat accumulation and obesity.

Antioxidant and hypolipidemic effects of soymilk fermented via Lactococcus acidophilus MF204

Previous studies have shown that fermentations can enhance the bioactivity and absorption rate of soybean products. Fermented soybean products can alleviate hyperlipidemia and decrease risks of atherosclerosis and cardiovascular diseases. This study aimed to investigate the effects and mechanisms of soymilk fermented by Lactococcus acidophilus on blood lipids and antioxidant enzyme activities of rats fed with a high fat diet. Sixty rats were randomly assigned to six groups: normal control group (NC), high-fat control group (HFC), positive control group (cholestyramine, PC), Lactococcus acidophilus group (LA), soymilk group (SM), and fermented soymilk group (FSM), respectively. The NC group was fed with a basic diet, while the other groups were fed with a high-fat diet. After the experimental period (6 W), rats were sacrificed by decapitation. Blood and liver were collected to measure the concentrations of lipids and antioxidant enzyme activities. Results demonstrated that fermented soymilk could regulate lipid levels, restore HDL-c and TG to normal levels, and lower the concentrations of LDL-c than hypolipidemic drugs in hyperlipidemia rats. More importantly, fermented soymilk caused significant reduction in arteriosclerosis index and coronary risk index. Fermented soymilk also improved antioxidant capacities of hyperlipidemia rats. The increase of aglycone isoflavones in fermented soymilk could explain the above phenomena. In conclusion, soymilk fermented by Lactococcus acidophilus reduced risks of arteriosclerosis and coronary heart disease by regulating lipid levels and improving the antioxidant capacities of hyperlipidemia rats.

Compared with feeding infants breast milk or cow-milk formula, soy formula feeding does not affect subsequent reproductive organ size at 5 years of age

BACKGROUND

Literature reports suggest that phytochemicals, such as isoflavones found in soybeans, impair reproductive function in animals and raise the possibility that consuming soy infant formula could alter hormonally sensitive organ development in children.

OBJECTIVE

This study compared reproductive organs volumes and structural characteristics in children at age 5 y who were enrolled in the Beginnings study long-term cohort.

METHODS

Breast bud, uterus, ovaries, prostate, and testes volumes and characteristics were assessed by ultrasonography in 101 children (50 boys and 51 girls) aged 5 y who were breastfed (n = 35) or fed cow-milk formula (n = 32) or soy formula (n = 34) as infants. Analyses were adjusted for race, gestational age, and birth weight.

RESULTS

Among girls, no significant differences were found in breast bud, ovarian, or uterine volumes; counts of ovaries with cysts; ovarian cysts numbers; ovarian cyst size; and uterine shape between the diet groups. Among boys, no significant differences were found in breast bud, testes, or prostate volumes or structural characteristics between the diet groups.

CONCLUSIONS

In this cohort, no early infant feeding effects were found on reproductive organs volumes and structural characteristics in children age 5 y. The follow-up of these children through puberty is planned and should help delineate potential early infant feeding effect on reproductive function later in life.

Effect of Phellinus baumii-Biotransformed Soybean Powder on Lipid Metabolism in Rats

In this study, we evaluated the hypolipidemic and antioxidative effects of biotransformed soybean powder (BTS; Phellinus baumii-fermented soybean) on lipid metabolism in rats. Sprague-Dawley (SD) male rats were divided into basal diet group (BA), high fat diet group (HF), high fat diet containing 10% BTS group (10 BTS), and high fat diet containing 20% BTS group (20 BTS). Changes in the content of various isoflavones, including daidzein and genistein, within the soybean after fermentation to BTS were investigated. The levels of daidzein and genistein were 149.28 μg/g and 364.31 μg/g, respectively. After six weeks experimental period, Food efficiency ratio in the 10 and 20 BTS group was significantly lower than the HF group (P<0.05). Total serum levels of cholesterol, triglycerides, low-density lipoprotein cholesterol, and atherogenic index ratio in the 10 or 20 BTS group were significantly lower than the HF group. The levels of alanine aminotransferase, aspartate aminotransferase and thiobarbituric acid reactive substance were significantly lower in the groups that received 10% and 20% BTS than the HF. The activities of SOD and CAT were significantly higher in the 10 and 20 BTS group than the HF group. The activity of XO in the 10 and 20 BTS group was significantly lower than in the HF group by 20% and 23%, respectively. In conclusion, these data suggest that BTS is an effective agent in improving lipid metabolism and antioxidant enzyme system.

Fast and reliable class-selective isoflavone index determination on carbon nanotube press-transferred electrodes using microfluidic chips

Direct microfluidic electrochemical sensing of class-isoflavones in complex soy samples on press-transferred carbon nanotubes.

Plasma pharmacokinetics and urinary excretion of isoflavones after ingestion of soy products with different aglycone/glucoside ratios in South Korean women

Asian populations are thought to receive significant health benefits from traditional diets rich in soybeans due to high isoflavone contents. However, available epidemiologic data only weakly support this hypothesis. The present study was carried out to assess the pharmacokinetics of isoflavones in South Korean women after ingestion of soy-based foods. Twenty-six healthy female volunteers (20-30 y old) consumed three different soy products (i.e., isogen, soymilk, and fermented soybeans) with different aglycone/glucoside ratios. Plasma and urine isoflavone concentrations were measured by high-performance liquid chromatography (HPLC) after ingestion of one of the soy products. Pharmacokinetic parameters were determined using the WinNonlin program. The area under the curve (AUC) for plasma daidzein levels of the soymilk group (2,101 ± 352 ng · h/mL) was significantly smaller than those of the isogen (2,628 ± 573 ng · h/mL) and fermented soybean (2,593 ± 465 ng · h/mL) groups. The maximum plasma concentration (C_max) of daidzein for the soymilk group (231 ± 44 ng/mL) was significantly higher than those of the isogen (160 ± 32 ng/mL) and fermented soybean (195 ± 35 ng/mL) groups. The half-lives of daidzein and genistein in the soymilk group (5.9 and 5.6 h, respectively) were significantly shorter than those in the individuals given isogen (9.6 and 8.5 h, respectively) or fermented soybean (9.5 and 8.2 h, respectively). The urinary recovery rates of daidzein and genistein were 42% and 17% for the isogen group, 46% and 23% for the fermented soybean group, and 33% and 22% for the soymilk group. In conclusion, our data indicated that soy products containing high levels of isoflavone aglycone are more effective for maintaining plasma isoflavone concentrations. Additional dose-response, durational, and interventional studies are required to evaluate the ability of soy-based foods to increase the bioavailability of isoflavones that positively affect human health.

Isoflavones: estrogenic activity, biological effect and bioavailability

Isoflavones are phytoestrogens with potent estrogenic activity; genistein, daidzein and glycitein are the most active isoflavones found in soy beans. Phytoestrogens have similarity in structure with the human female hormone 17-β-estradiol, which can bind to both alpha and beta estrogen receptors, and mimic the action of estrogens on target organs, thereby exerting many health benefits when used in some hormone-dependent diseases. Numerous clinical studies claim benefits of genistein and daidzein in chemoprevention of breast and prostate cancer, cardiovascular disease and osteoporosis as well as in relieving postmenopausal symptoms. The ability of isoflavones to prevent cancer and other chronic diseases largely depends on pharmacokinetic properties of these compounds, in particular absorption and distribution to the target tissue. The chemical form in which isoflavones occur is important because it influences their bioavailability and, therefore, their biological activity. Glucose-conjugated isoflavones are highly polar, water-soluble compounds. They are hardly absorbed by the intestinal epithelium and have weaker biological activities than the corresponding aglycone. Different microbial families of colon can transform glycosylated isoflavones into aglycones. Clinical studies show important differences between the aglycone and conjugated forms of genistein and daidzein. The evaluation of isoflavone metabolism and bioavailability is crucial to understanding their biological effects. Lipid-based formulations such as drug incorporation into oils, emulsions and self-microemulsifying formulations have been introduced to increase bioavailability. Complexation with cyclodextrin also represent a valid method to improve the physicochemical characteristics of these substances in order to be absorbed and distributed to target tissues. We review and discuss pharmacokinetic issues that critically influence the biological activity of isoflavones.

Development of an updated phytoestrogen database for use with the SWAN food frequency questionnaire: intakes and food sources in a community-based, multiethnic cohort study

Phytoestrogens, heterocyclic phenols found in plants, may benefit several health outcomes. However, epidemiologic studies of the health effects of dietary phytoestrogens have yielded mixed results, in part due to challenges inherent in estimating dietary intakes. The goal of this study was to improve the estimates of dietary phytoestrogen consumption using a modified Block Food Frequency Questionnaire (FFQ), a 137-item FFQ created for the Study of Women's Health Across the Nation (SWAN) in 1994. To expand the database of sources from which phytonutrient intakes were computed, we conducted a comprehensive PubMed/Medline search covering January 1994 through September 2008. The expanded database included 4 isoflavones, coumestrol, and 4 lignans. The new database estimated isoflavone content of 105 food items (76.6%) vs. 14 (10.2%) in the 1994 version and computed coumestrol content of 52 food items (38.0%), compared to 1 (0.7%) in the original version. Newly added were lignans; values for 104 FFQ food items (75.9%) were calculated. In addition, we report here the phytonutrient intakes for each racial and language group in the SWAN sample and present major food sources from which the phytonutrients came. This enhanced ascertainment of phytoestrogens will permit improved studies of their health effects.

High serum isoflavone concentrations are associated with the risk of precocious puberty in Korean girls

OBJECTIVE

The gradual decrease in the age of onset of puberty raises concerns about the contribution of phytoestrogen intake on sexual maturation. However, no data are available on the association between serum isoflavone (genistein, daidzein) concentration and central precocious puberty (CPP). The aim of the study was to test the association between serum isoflavone concentrations and the risk of CPP in Korean girls.

STUDY DESIGN

A case-control study was conducted at Inje University Hospital in Korea. One-hundred and eight girls with CPP (aged 8·6 ± 0·8 year) and 91 age-matched controls (aged 8·5 ± 0·8 year) were examined.

RESULTS

Serum concentrations of daidzein (P = 0·0202), genistein (P = 0·0021) and total isoflavones (P = 0·0009) were higher in children with CPP than in normal children. When the children were categorized into three groups according to total serum isoflavone as follows: <30, 30-70 and ≥70 nmol/l, serum concentrations of daidzein, genistein and total isoflavones significantly increased across three categories of serum isoflavone (P < 0·0001). The prevalence of CPP was significantly higher in children with serum isoflavone level of ≥30 nmol/l than those with serum level of <30 nmol/l (P = 0·0008). The adjusted OR for precocious puberty increased significantly across a range of total serum isoflavone (OR = 4·39; 95% CI: 1·83-10·51 vs OR = 5·22; 95% CI: 2·07-13·20; P = 0·001).

CONCLUSION

These results suggest that elevated serum isoflavones may be associated with the risk of CPP in Korean girls.

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.

Urinary isoflavones and their metabolites validate the dietary isoflavone intakes in US adults

BACKGROUND

Isoflavones are derived from dietary sources and considered to promote health by preventing the onset of such chronic diseases as cardiovascular disease, cancer, and osteoporosis. Valid and reliable estimation of isoflavone intake is a prerequisite to establishing biological functions of isoflavones on health risks.

OBJECTIVE

This study aimed to validate the approach of estimating dietary isoflavone intake with respective urinary isoflavone concentrations in US adults.

DESIGN

Data from the US Department of Agriculture isoflavone database and dietary recalls of 2,908 US adults with urinary isoflavone data in the 1999-2002 National Health and Nutrition Examination Survey were used.

RESULTS

Dietary isoflavone was consumed by only 35% of adults in a day with an average intake of 3.1 mg/day, which resulted in a mean intake of 1.0 mg/day for all US adults. The isoflavone intakes were from genistein (55%), diadzein (35%), glycitein (7%), biochanin A (2%), and formononetin (2%). Both daily total and energy adjusted isoflavone intake differed by race/ethnicity subgroups (P<0.05) and was associated positively with income (P<0.01) and inversely with body mass index (P<0.05). Geometric mean urinary isoflavone concentration was 5.0 ng/mL among isoflavone consumers and the urinary genistein and daidzein excretion correlated with their isoflavone intake levels (P<0.01).

CONCLUSIONS

In large population-based studies, estimated dietary isoflavone intake can be validated by urinary isoflavones. Further studies are needed at an individual level to validate dietary isoflavone intake by urinary isoflavone concentration.

Effect of frequency and duration of ultrasonication on the extraction efficiency of selected isoflavones and trans-resveratrol from peanuts (Arachis hypogaea)

Plant derived phytochemicals have been the focus of recent research due to their health promoting effects. Previous studies to estimate the levels of these bioactive compounds made use of traditional solvent extraction procedures such as homogenization and soxhlet (reflux) methods. Recently, the ultrasonication technique has been shown to be an efficient non-thermal extraction method. The objective of this study was to investigate the effect of frequency and duration (time) of sonication on the extraction efficiency of selected phytochemicals from peanuts and to determine optimal conditions (sample-to-solvent ratio, frequency, and time) for their extraction. The results obtained showed that sample-to-solvent ratio, frequency, and duration of sonication had significant effect on the extraction efficiency of the phytochemicals from peanut. Sonication at 80 kHz facilitated the extraction of biochanin A and trans-resveratrol while 25 kHz was effective in the extraction of daidzein and genistein. Multi-frequency extractions were more efficient than single frequency.

Risk assessment of soybean-based phytoestrogens

Koreans generally consume high quantities of soybean-based foods that contain a variety of phytoestrogens, such as, daidzein, zenistein, and biochalin A. However, phytoestrogens are considered to be potential endocrine-disrupting chemicals (EDC), which interfere with the normal function of the hormonal and reproductive systems. Therefore, dietary exposure to soybean-based phytoestrogens is of concern for Koreans, and comparative dietary risk assessments are required between Japanese (high consumers) versus Americans (low consumers). In this study, a relative risk assessment was conducted based upon daily intake levels of soybean-based foods and phytoestrogens in a Korean cohort, and the risks of photoestrogens were compared with those posed by estradiol and other EDC. Koreans approximately 30-49 yr of age consume on average a total of 135.2 g/d of soy-based foods including soybean, soybean sauce, soybean paste, and soybean oil, and 0.51 mg/kg body weight (bw)/d of phytoestrogens such as daidzein and genistein. Using estimated daily intakes (EDI) and estrogenic potencies (EP), margins of safety (MOS) were calculated where 0.05 is for estradiol (MOS value <1, considered to exert a positive estrogenic effect); thus, MOS values of 1.89 for Japanese, 1.96 for Koreans, and 5.55 for Americans indicate that consumption of soybean-based foods exerted no apparent estrogenic effects, as all MOS values were all higher than 1. For other synthetic EDC used as reference values, MOS values were dieldrin 27, nonylphenol 250, butyl benzyl phthalate 321, bisphenol A 1000, biochanin A 2203, and coumesterol 2898. These results suggest that dietary exposure to phytoestrogens, such as daidzein and genistein, poses a relatively higher health risk for humans than synthetic EDC, although MOS values were all greater than 1.

The key importance of soy isoflavone bioavailability to understanding health benefits

Research over the past two decades has provided significant epidemiological and other evidence for the health benefits of the consumption of soy-based foods. A large number of dietary intervention studies have examined the effects of soy isoflavones on risk factors for cardiovascular disease and hormone-dependent cancers. However, these report large variability in outcome measures, very limited reproducibility between studies, and in some cases, controversy between the results of clinical trials using dietary soy or soy protein and isoflavone supplementation. This highlights a major gap in our understanding of soy isoflavone uptake, metabolism, distribution, and overall bioavailability. There are many potential factors that may influence bioavailability and a better knowledge is necessary to rationalize the inconsistencies in the intervention and clinical studies. This review focuses attention on our current state of knowledge in this area and highlights the importance of metabolism of the parent soy isoflavones and the critical role of gut microbiota on the bioavailability of these compounds and their metabolites.

Endogenous β-glucosidase and β-galactosidase activities from selected probiotic micro-organisms and their role in isoflavone biotransformation in soymilk

AIM

To compare endogenous beta-glucosidases and beta-galactosidases for hydrolysis of the predominant isoflavone glycosides into isoflavone aglycones in order to improve biological activity of soymilk.

METHODS AND RESULTS

beta-glucosidase and beta-galactosidase activities of probiotic organisms including Lactobacillus acidophilus ATCC 4461, Lactobacillus casei 2607 and Bifidobacterium animalis ssp. lactis Bb12 in soymilk were evaluated and correlated with the increase in concentration of isoflavone aglycones during fermentation. The concentrations of isoflavone compounds in soymilk were monitored using a Varian model high-performance liquid chromatography (HPLC) with an amperometric electrochemical detector. In all micro-organisms, beta-glucosidase activity was found greater than that of beta-galactosidase. There was an increase in the aglycone concentration with incubation time because of the apparent hydrolytic action on isoflavone glycosides. Aglycone concentration in the soymilk with L. acidophilus 4461, L. casei 2607 and B. animalis ssp. lactis Bb12, increased by 5.37-, 5.52- and 6.10-fold, respectively, after 15 h of fermentation at 37 degrees C. The maximum hydrolytic potential was also observed at 15 h of fermentation for the three micro-organims coinciding with peak activities of the two enzymes.

CONCLUSIONS

beta-glucosidase activity was more than 15 times higher than beta-galactosidase activity in soymilk for each of the micro-organisms during fermentation. beta-glucosidase played a greater role in isoflavone glycoside hydrolysis.

SIGNIFICANCE AND IMPACT OF THE STUDY

Screening for beta-glucosidase and beta-galactosidase activities among probiotics in soymilk is important for the improvement of biological activity of soymilk and in the selection of micro-organisms for use in the growing industry of functional foods and beverages.

A comparison of changes in the transformation of isoflavones in soymilk using varying concentrations of exogenous and probiotic-derived endogenous ?-glucosidases

AIMS

To compare endogenous and exogenous beta-glucosidases for the hydrolysis of the predominant isoflavone glucosides in soymilk in order to improve the biological activity.

METHODS AND RESULTS

beta-glucosidase activity of probiotic organisms, including Bifidobacterium animalis ssp. lactis Bb12, Lactobacillus acidophilus ATCC 4461 and Lactobacillus casei 2607 in soymilk, was evaluated and was related to the increase in the concentration of isoflavone aglycones during fermentation. The concentrations of isoflavone compounds in soymilk were monitored using a Varian model HPLC with an Amperometric electrochemical detector. The aglycone composition, also known as aglycone equivalent ratio, has been considered to be important for the delivery of health benefits of isoflavones, and was monitored during the fermentation of soymilk. Comparison of the hydrolytic effectiveness of both exogenous and endogenous enzyme during 4-h incubation in soymilk was conducted using the Otieno-Shah (O-S) index. Results showed that exogenous enzyme exhibited faster rate of isoflavone glucoside hydrolysis than that by endogenous enzyme. Highest O-S indices were obtained after 4, 3 and 2 h of incubation with enzyme solution having beta-glucosidase activity of 0.288 U ml(-1), 0.359 U ml(-1) and 0.575 U ml(-1), resulting into aglycone concentration increments of 5.87-, 6.07- and 5.94-fold, respectively. Conversely, aglycone concentration in the soymilk with B. animalis ssp. lactis Bb12, L. casei 2607 and L. acidophilus 4461 increased by 3.43-, 2.72- and 3.03-fold, respectively, after 4 h of fermentation at 37 degrees C. In addition, the O-S index of endogenous enzyme was much lower than that of the exogenous enzyme over the same 4-h incubation period. Optimum aglycone equivalent ratios coincided with highest O-S indices and highest aglycone concentrations in soymilk hydrolysed with exogenous enzyme. The same correlation of O-S indices and highest aglycone concentrations occurred for endogenous enzyme during the 24 h of fermentation.

CONCLUSIONS

Obtaining highest aglycone concentration and optimum aglycone equivalent ratio could provide a critical beginning point in clinical trials for the realization of unique health benefits of soy isoflavones.

SIGNIFICANCE AND IMPACT OF THE STUDY

Screening for beta-glucosidase activities of probiotics in soymilk and comparing their hydrolytic potentials with that of exogenous beta-glucosidase could find wide applications in the development of different aglycone-rich functional soy beverages.

Bioavailability of isoflavone phytoestrogens in postmenopausal women consuming soya milk fermented with probiotic bifidobacteria

We investigated the effects of consuming an isoflavone aglycone-enriched soya milk containing viable bifidobacteria on urinary isoflavone excretion and percentage recovery. Sixteen postmenopausal women were randomly divided into two groups to consume either fermented or non-fermented soya milk. Each group participated in a double-blind, crossover study with three 14 d supplementation periods, separated by a 14 d washout. Subjects ingested three daily dosages of isoflavone via the soya milk and collected four 24 h pooled urine specimens per supplementation period. Soya milks were prepared with soya protein isolate and soya germ, followed by fermentation with bifidobacteria. Isoflavone levels were quantified using HPLC. Non-fermented soya milks at 20, 40 and 80 mg isoflavone/200 ml contained 10 %, 9 % and 7 % aglycone, respectively, with their fermented counterparts containing 69 %, 57 % and 36 % aglycone (P<0·001). A trend to a greater percentage urinary recovery of daidzein and glycitein was observed among women consuming fermented soya milk at a dosage of 40 mg isoflavone (P=0·13). A distinct linear dose response for the fermented soya milk group (R2=0·9993) compared with the non-fermented group (R2=0·8865) suggested less interindividual variation in isoflavone absorption. However, total urinary isoflavone excretion was similar for both groups (P>0·05), with urinary isoflavone recovery at approximately 31 %. Increasing the isoflavone dosage correlated positively with its urinary excretion, but urinary percentage recovery of isoflavone was inversely related to dosage level. Hence, a modest dosage ranging from 20 to 30 mg/d may provide the most bioavailable source of isoflavone, regardless of whether it is via an aglycone-rich fermented soya milk or a glucoside-rich soya milk.

Impact of genetic variation on metabolic response of bone to diet

There is compelling evidence to suggest that both the development of bone to peak bone mass at maturity and subsequent loss depend on the interaction between genetic, hormonal, environmental and nutritional factors. The major part (≤80%) of the age-specific variation in bone turnover and bone density is genetically determined. However, the notion of genetic determinant is of little value unless the specific genes that are involved can be identified. Most work in this area of osteoporosis research has focused on the candidate gene approach, which has identified several candidate genes for osteoporosis, including genes encoding the vitamin D receptor (VDR), oestrogen receptors (α and β), apolipoprotein E, collagen type I α 1 and methylenetetrahydrofolate reductase, amongst many others. However, in general, findings from numerous studies of the association between such genes and various bone variables have been inconsistent. In addition to possible gene—gene interactions it is likely that there are interactions between these genes and certain environmental factors, especially nutrition, that may mediate expression of bone-related phenotypes. While these potential interactions add a level of complexity to our understanding of these apparent genetic effects on bone, identification of a role for genetic factors without knowledge of their interaction with nutrients can do little to advance prevention and treatment of osteoporosis. This information is especially important because, unlike genotype, diet and nutrition can be modified. The aim of the present review is to critically evaluate current knowledge relating to candidate genes for osteoporosis, with particular emphasis on their interaction with nutrients and dietary factors in determining bone health.

Importance of insoluble-bound phenolics to antioxidant properties of wheat

Two commercial samples of soft (70% Canadian Eastern soft red spring and 30% Canadian Eastern soft white winter) and hard (90% Canadian western hard red spring and 10% Canadian Eastern hard red winter) wheats were used to obtain different milling fractions. Phenolics extracted belonged to free, soluble esters and insoluble-bound fractions. Soluble esters of phenolics and insoluble-bound phenolics were extracted into diethyl ether after alkaline hydrolysis of samples. The content of phenolics was determined using Folin-Ciocalteu's reagent and expressed as ferulic acid equivalents (FAE). The antioxidant activity of phenolic fractions was evaluated using Trolox equivalent antioxidant capacity, 2,2-diphenyl-1-picrylhydrazyl radical scavenging, reducing power, oxygen radical absorbance capacity, inhibition of oxidation of human low-density lipoprotein cholesterol and DNA, Rancimat, inhibition of photochemilumenescence, and iron(II) chelation activity. The bound phenolic content in the bran fraction was 11.3 +/- 0.13 and 12.2 +/- 0.15 mg FAE/g defatted material for hard and soft wheats, respectively. The corresponding values for flour were 0.33 +/- 0.01 and 0.46 +/- 0.02 mg FAE/g defatted sample. The bound phenolic content of hard and soft whole wheats was 2.1 (+/-0.004 or +/-0.005) mg FAE/g defatted material. The free phenolic content ranged from 0.14 +/- 0.004 to 0.98 +/- 0.05 mg FAE/g defatted milling fractions of hard and soft wheats examined. The contribution of bound phenolics to the total phenolic content was significantly higher than that of free and esterified fractions. In wheat, phenolic compounds were concentrated mainly in the bran tissues. In the numerous in vitro antioxidant assays carried out, the bound phenolic fraction demonstrated a significantly higher antioxidant capacity than free and esterified phenolics. Thus, inclusion of bound phenolics in studies related to quantification and antioxidant activity evaluation of grains and cereals is essential.

Lack of dose-responsive effect of dietary phyto-oestrogens on transepithelial calcium transport in human intestinal-like Caco-2 cells

Ca absorption has been shown to be unaffected by high luminal concentrations of two commonly consumed soyabean phyto-oestrogens (PO) (genistein and daidzein) in Caco-2 cells grown under oestrogen-depleted conditions. However, these compounds exhibit dose-dependent biphasic effects in some tissues, such as reproductive tissue and bone. Thus, in light of this biphasic activity, the effect of lower concentrations of genistein and daidzein on Ca absorption requires further investigation. Therefore, the aim of the present study was to investigate the effect of a range of concentrations of genistein and daidzein on Ca absorption in the human Caco-2 intestinal-like cell model. Caco-2 cells were seeded onto permeable filter supports and allowed to differentiate into monolayers. On day 21, the Caco-2 monolayers (n 12 per treatment), grown in oestrogen-deplete media, were then exposed to 10 nm-1,25-dihydroxycholecalciferol (1,25 (OH)2D3), or 1, 10 and 50 microm-genistein or -daidzein for 24 h. After exposure, transepithelial and transcellular transport of (45)Ca and fluorescein transport were measured. As expected, 1,25 (OH)2D3 stimulated Ca absorption in Caco-2 cells, by up regulating transcellular transport. Ca absorption was unaffected by either PO at luminal concentrations of 1, 10 or 50 microm, typical of intakes by Western and Asian populations as well as supplemental levels, respectively. The results of this model suggest that the proposed beneficial effects of supplemental levels of these PO compounds on bone mass in postmenopausal women more probably arise from direct effects on bone cells, and not by an indirect effect of these compounds on Ca absorption.

Inhibition of reactive nitrogen species effects in vitro and in vivo by isoflavones and soy-based food extracts

Recent studies have shown that soy isoflavone inhibits inducible nitric oxide (NO) synthase activities and is reported to have peroxynitrite scavenging ability. Consequently, we investigated whether isoflavones (daidzein and genistein) and extracts from soy-based products (miso, soymilk, tofu, soy sprout, black soybean, soybean, and yuba) would inhibit the reactive nitrogen species (RNS) effect in vitro and in vivo. In the in vitro experiments [including the protection of cellular DNA from peroxynitrite or sodium nitroprusside damage, an inhibitory effect on nitric oxide production from lipopolysaccharide (LPS)-induced RAW 264.7 cells, and nitric oxide scavenging ability], extracts from soy-based foods showed a potent antioxidant activity and an inhibiting effect on RNS activity. These effects were correlated with total isoflavone content. In the in vivo experiments, rats were given isoflavones (4.0 mg/kg bw) or soy-based product extracts (1.0 g/kg bw) orally for 1 week and were injected with vehicle H(2)O (1 mL/kg bw) or LPS (10 mg/kg bw) on the day 7. Twelve hours after treatment, the rats were killed, and blood serum was collected for analysis. The intraperitoneal administration of LPS resulted in an increase in serum nitrite, nitrate, and nitrotyrosine concentrations. These are stable metabolite end products of nitric oxide, to 4-, 16-, and 5-fold levels, (4, 10 microM and 58 +/- 14 pmol/mL), of the placebo control, respectively. Results showed that oral administration of isoflavones and extracts from soy-based products significantly decreased serum nitrite, nitrate, and nitrotyrosine levels in LPS-induced rats. This study demonstrates that soy isoflavone supplementation may inhibit RNS-induced oxidation both in vitro and in vivo.

Metabolism of the soy isoflavones daidzein, genistein and glycitein in human subjects. Identification of new metabolites having an intact isoflavonoid skeleton

Epidemiological studies have associated high soy intake with a lowered risk for certain hormone-dependent diseases. Soy and soy foods are rich sources of isoflavones, which have been shown to possess several biological activities. In this study, the metabolism of soy isoflavones daidzein, genistein and glycitein was investigated in human subjects. The aim was to find and identify urinary phase I metabolites of isoflavones, which have an intact isoflavonoid skeleton, and which might possess some bioactivity. Six volunteers included three soy bars per day into their normal western diet for a 2-week period. Daily urine samples were collected before, and after the supplementation period. Urine samples were hydrolyzed with Helix pomatia, extracted with diethyl ether, purified with Sephadex LH-20 chromatography, and analyzed as trimethylsilyl derivatives using gas chromatography-mass spectrometry (GC-MS). The structures of the isoflavone metabolites were identified using authentic reference compounds. The metabolites, for which authentic reference compounds were not available, were identified by the interpretation of mass spectra. Several new isoflavone metabolites were identified, and the presence of previously reported metabolites confirmed. The metabolic pathways of daidzein, genistein and glycitein are presented on the basis of the identification of the metabolites in human urine after soy supplementation.

Cell-transforming activity and mutagenicity of 5 phytoestrogens in cultured mammalian cells

For the simultaneous assessment of in vitro carcinogenicity and mutagenicity of phytoestrogens, the abilities of 5 phytoestrogens, daidzein, genistein, biochanin A, prunetin, and coumestrol, to induce cell transformation and genetic effects were examined using the Syrian hamster embryo (SHE) cell model. Cellular growth was inhibited by all phytoestrogens in a concentration-related manner. The growth inhibitory effect of the compounds was ranked: genistein, prunetin > coumestrol > biochanin A > daidzein, which did not correspond to their apoptosis-inducing abilities. Morphological transformation in SHE cells was elicited by all phytoestrogens, except, prunetin. The transforming activities were ranked as follows: genistein > coumestrol > daidzein > biochanin A. Somatic mutations in SHE cells at the Na(+)/K(+) ATPase and hprt loci were induced only by genistein, coumestrol, or daidzein. Chromosome aberrations were induced by genistein or coumestrol, and aneuploidy in the near diploid range was occurred by genistein or biochanin A. Genistein, biochanin A or daidzein induced DNA adduct formation in SHE cells with the abilities: genistein > biochanin A > daidzein. Prunetin was negative for any of these genetic endpoints. Our results provide evidence that genistein, coumestrol, daidzein and biochanin A induce cell transformation in SHE cells and that the transforming activities of these phytoestrogens correspond to at least 2 of the mutagenic effects by each phytoestrogen, i.e., gene mutations, chromosome aberrations, aneuploidy or DNA adduct formation, suggesting the possible involvement of mutagenicity in the initiation of phytoestrogen-induced carcinogenesis.

The effect of oestrogen and dietary phyto-oestrogens on transepithelial calcium transport in human intestinal-like Caco-2 cells

Recently, dietary phyto-oestrogens (PO) have been suggested as possible alternatives to oestrogen therapy (hormone replacement therapy) as a means of preventing bone loss associated with ovarian hormone deficiency. While PO, which exhibit oestrogen-like activity, act directly on bone cells, their protective effect on bone may be partly due to their ability to enhance Ca absorption. Therefore, the aim of the present study was to investigate the effect of 17beta-oestradiol and two commonly consumed soyabean PO (genistein and daidzein) on Ca absorption in the human Caco-2 intestinal-like cell model. Caco-2 cells were seeded onto permeable filter supports and allowed to differentiate into monolayers. On day 21, the Caco-2 monolayers (n 8-18 per treatment), grown in oestrogen-replete or -deplete media, were then exposed to 10 nm-17beta-oestradiol, 1 nm-1,25-dihydroxycholecalciferol, or 50 micro m-genistein or -daidzein for 24 h. After exposure, transepithelial and transcellular transport of 45Ca and fluorescein transport (a marker of paracellular diffusion) were measured. As expected, 1,25-dihydroxycholecalciferol stimulated Ca absorption in Caco-2 cells, by up-regulating transcellular transport, whereas 17beta-oestradiol had no effect on Ca absorption. Unexpectedly, both PO decreased Ca absorption (by about 17-19 % compared with control, P<0.05), by reducing transcellular Ca transport in Caco-2 cells grown in oestrogen-replete media. This inhibitory effect disappeared when monolayers were grown in oestrogen-deplete media. In conclusion, PO at high luminal concentrations either had no effect or reduced Ca absorption in Caco-2 cells, dependent on oestrogen status. The effect of lower concentrations of these compounds needs to be investigated.

The clinical importance of the metabolite equol-a clue to the effectiveness of soy and its isoflavones

Equol [7-hydroxy-3-(4'-hydroxyphenyl)-chroman] is a nonsteroidal estrogen of the isoflavone class. It is exclusively a product of intestinal bacterial metabolism of dietary isoflavones and it possesses estrogenic activity, having affinity for both estrogen receptors, ERalpha and ERbeta. Equol is superior to all other isoflavones in its antioxidant activity. It is the end product of the biotransformation of the phytoestrogen daidzein, one of the two main isoflavones found in abundance in soybeans and most soy foods. Once formed, it is relatively stable; however, equol is not produced in all healthy adults in response to dietary challenge with soy or daidzein. Several recent dietary intervention studies examining the health effects of soy isoflavones allude to the potential importance of equol by establishing that maximal clinical responses to soy protein diets are observed in people who are good "equol-producers." It is now apparent that there are two distinct subpopulations of people and that "bacterio-typing" individuals for their ability to make equol may hold the clue to the effectiveness of soy protein diets in the treatment or prevention of hormone-dependent conditions. In reviewing the history of equol, its biological properties, factors influencing its formation and clinical data, we propose a new paradigm. The clinical effectiveness of soy protein in cardiovascular, bone and menopausal health may be a function of the ability to biotransform soy isoflavones to the more potent estrogenic isoflavone, equol. The failure to distinguish those subjects who are "equol-producers" from "nonequol producers" in previous clinical studies could plausibly explain the variance in reported data on the health benefits of soy.

Quantitative analysis of urinary daidzein and equol by gas chromatography after solid-phase extraction and high-performance liquid chromatography

Daidzein and its main metabolite equol are isoflavone phytoestrogens. Several studies have suggested that intake of an isoflavone-rich diet may prevent hormone-related cancer and estrogen-related disorders (cardiovascular disease, osteoporosis and menopausal symptoms). To better understand the role of isoflavones in preventing such severe disease, several methods have been developed to measure these compounds in biological fluids. However, the analytical procedures to measure isoflavones are often time-consuming and require highly skilled technicians. In this paper we describe a method for urinary daidzein and equol measurement that combines solid phase extraction and HPLC purification before gas chromatographic determination. The specificity of the method was confirmed by the gas chromatography-mass spectrometry technique. The mean recovery of daidzein and equol was 94.6% and 97.0%, respectively. The repeatability of the method was in the range of 2.0-7.4% for daidzein and 1.3-4.9% for equol. A linear relationship between observed and expected values was found in the dilution (r2=0.9983 for daidzein; r2=0.9982 for equol) and addition (r2=0.9984 for daidzein; r2=0.9989 for equol) assays. The method is suitable to measure changes in the urinary excretion of isoflavones and to investigate urinary isoflavonoids as biomarkers of isoflavone exposure.