Effect of circulating forms of soy isoflavones on the oxidation of low density lipoprotein

Soy isoflavones are thought to have a cardioprotective effect that is partly mediated by an inhibitory influence on the oxidation of low density lipoprotein (LDL). However, the aglycone forms investigated in many previous studies do not circulate in appreciable quantities because they are metabolised in the gut and liver. We investigated effects of various isoflavone metabolites, including for the first time the sulphated conjugates formed in the liver and the mucosa of the small intestine, on copper-induced LDL oxidation. The parent aglycones inhibited oxidation, although only 5% as well as quercetin. Metabolism increased or decreased their effectiveness. Equol inhibited 2.65-fold better than its parent compound daidzein and 8-hydroxydaidzein, not previously assessed, was 12.5-fold better than daidzein. However, monosulphated conjugates of genistein, daidzein and equol were much less effective and disulphates completely ineffective. Since almost all isoflavones circulate as conjugates, these data suggest that despite the increased potency produced by some metabolic changes, isoflavones may not be effective antioxidants in vivo unless they are deconjugated again.

Savory peptides present in Moromi obtained from soy sauce fermentation of yellow soybean

The presence of savory peptides in moromi has been investigated. Moromi was prepared by fermenting yellow soybean using Aspergillus oryzae as the starter at the first step (mold fermentation) and 20% brine solution at the next step (brine fermentation). The moromi was then ultrafiltered stepwise using membranes with MW cut-offs of 10,000, 3,000, and 500 Da, respectively. The fraction with MW < 500 Da was chromatographed using Sephadex G-25 SF to yield four fractions, 1-4. Analysis of soluble peptides, NaCl content, alpha-amino nitrogen, amino acid composition, peptide profile using CE coupled with DAD, taste profile and free glutamic acid content, were performed for each fraction. Fraction 2 contained a relatively high total glutamic acid content, but a relatively low free glutamic acid content and had the highest umami taste. This fraction also had more peptides containing non-aromatic amino acids than the other fractions. The peptides present in fraction 2 may play a role, at least in part, in its intense umami taste.

Soy isoflavones increase preprandial peptide YY (PYY), but have no effect on ghrelin and body weight in healthy postmenopausal women

Background: Soy isoflavones show structural and functional similarities to estradiol. Available data indicate that estradiol and estradiol-like components may interact with gut "satiety hormones" such as peptide YY (PYY) and ghrelin, and thus influence body weight. In a randomized, double-blind, placebo-controlled, cross-over trial with 34 healthy postmenopausal women (59 ± 6 years, BMI: 24.7 ± 2.8 kg/m2), isoflavone-enriched cereal bars (50 mg isoflavones/day; genistein to daidzein ratio 2:1) or non-isoflavone-enriched control bars were consumed for 8 weeks (wash-out period: 8-weeks). Seventeen of the subjects were classified as equol producers. Plasma concentrations of ghrelin and PYY, as well as energy intake and body weight were measured at baseline and after four and eight weeks of each intervention arm. Results: Body weight increased in both treatment periods (isoflavone: 0.40 ± 0.94 kg, P < 0.001; placebo: 0.66 ± 0.87 kg, P = 0.018), with no significant difference between treatments. No significant differences in energy intake were observed (P = 0.634). PYY significantly increased during isoflavone treatment (51 ± 2 pmol/L vs. 55 ± 2 pmol/L), but not during placebo (52 ± 3 pmol/L vs. 50 ± 2 pmol/L), (P = 0.010 for treatment differences, independent of equol production). Baseline plasma ghrelin was significantly lower in equol producers (110 ± 16 pmol/L) than in equol non-producers (162 ± 17 pmol/L; P = 0.025). Conclusion: Soy isoflavone supplementation for eight weeks did not significantly reduce energy intake or body weight, even though plasma PYY increased during isoflavone treatment. Ghrelin remained unaffected by isoflavone treatment. A larger and more rigorous appetite experiment might detect smaller differences in energy intake after isoflavone consumption. However, the results of the present study do not indicate that increased PYY has a major role in the regulation of body weight, at least in healthy postmenopausal women.

Microbial species involved in production of 1,2-sn-diacylglycerol and effects of phosphatidylcholine on human fecal microbiota

1,2-sn-Diacylglycerols (DAGs) are activators of protein kinase C (PKQ, which is involved in the regulation of colonic mucosal proliferation. Extracellular DAG has been shown to stimulate the growth of cancer cell lines in vitro and may therefore play an important role in tumor promotion. DAG has been detected in human fecal extracts and is thought to be of microbial origin. Hitherto, no attempts have been made to identify the predominant fecal bacterial species involved in its production. We therefore used anaerobic batch culture systems to determine whether fecal bacteria could utilize phosphatidylcholine (0.5% [wt/vol]) to produce DAG. Production was found to be dependent upon the presence of the substrate and was enhanced in the presence of high concentrations of deoxycholate (5 and 10 mM) in the growth medium. Moreover, its production increased with the pH, and large inter- and intraindividual variations were observed between cultures seeded with inocula from different individuals. Clostridia and Escherichia coli multiplied in the fermentation systems, indicating their involvement in phosphatidylcholine metabolism. On the other hand, there was a significant decrease in the number of Bifidobacterium spp. in the presence of phosphatidylcholine. Pure-culture experiments showed that 10 of the 12 strains yielding the highest DAG levels (>50 nmol/ml) were isolated from batch culture enrichments run at pH 8.5. We found that the strains capable of producing large amounts of DAG were predominantly Clostridium bifermentans (8 of 12), followed by Escherichia coli (2 of 12). Interestingly, one DAG-producing strain was Bifidobacterium infantis, which is often considered a beneficial gut microorganism. Our results have provided further evidence that fecal bacteria can produce DAG and that specific bacterial groups are involved in this process. Future strategies to reduce DAG formation in the gut should target these species.

In vitro effects of phosphatidylcholine and transgalactooligosaccharides on the production of 1,2-sn-diacylglycerol by Bifidobacterium longum biovar infantis

Aims: To investigate the production of the tumour promoter 1,2-sn-diacylglycerol (DAG) by a human gut isolate of Bifidobacterium longum biovar infantis. Methods and Results: Bifidobacterium longum biovar infantis was grown in vitro using anaerobic static batch cultures in the presence of phosphatidylcholine (PC) and trans-galactooligosaccharides (TOS). Production of DAG was found to be dependent upon the presence of PC, while TOS had a reducing effect. Considerable differences in morphology, growth and metabolic end products from the micro-organism were observed under the different culture conditions. Conclusions: Our results have provided evidence that B. longum biovar infantis can produce DAG in vitro and that a prebiotic exerted a reducing effect upon this production. Significance and Impact of the Study: The results presented in this study demonstrate an ability of ostensibly beneficial member of the colonic environment to produce unwanted compounds under certain conditions. Therefore, it may be important that a combination of substrates and other factors are assessed when studying the behaviour of any bacterial group or species, especially when designing the dietary interventions.

Effect of circulating forms of soy isoflavones on the oxidation of low density lipoprotein

Soy isoflavones are thought to have a cardioprotective effect that is partly mediated by an inhibitory influence on the oxidation of low density lipoprotein (LDL). However, the aglycone forms investigated in many previous studies do not circulate in appreciable quantities because they are metabolised in the gut and liver. We investigated effects of various isoflavone metabolites, including for the first time the sulphated conjugates formed in the liver and the mucosa of the small intestine, on copper-induced LDL oxidation. The parent aglycones inhibited oxidation, although only 5% as well as quercetin. Metabolism increased or decreased their effectiveness. Equol inhibited 2.65-fold better than its parent compound daidzein and 8-hydroxydaidzein, not previously assessed, was 12.5-fold better than daidzein. However, monosulphated conjugates of genistein, daidzein and equol were much less effective and disulphates completely ineffective. Since almost all isoflavones circulate as conjugates, these data suggest that despite the increased potency produced by some metabolic changes, isoflavones may not be effective antioxidants in vivo unless they are deconjugated again.

Effects of high pressure on functional properties of soy protein

Simultaneous measurement of the effects of low soy protein concentration, pH and high pressure treatment at room temperature on solubility, emulsifying properties and rheological properties (loss modulus, G '') of soy protein isolate (SPI) were evaluated. Central composite rotatable designs (2(3)) were employed over two pH ranges (2.66-4.34 and 5.16-6.84) with SPI concentration (0.32-3.68%) and pressure (198-702 MPa) as the other independent variables. The surface responses were obtained for protein solubility, emulsifying activity index (EAI) and G ''. The samples with the highest effect on protein solubility, EAI and G '' values were evaluated, as well, by electrophoresis and free sulphydryl determination. The pH was the main factor that affected protein solubility, with solubility at a maximum at pH < 3 or pH > 6. Increasing SPI concentration and decreasing/increasing the pH away from the isoelectric point both caused a reduction in EAI. Loss modulus (G '') was found to increase with SPI concentration in both pH ranges. (c) 2006 Elsevier Ltd. All rights reserved.

Consumption of soy isoflavones does not affect plasma total homocysteine or asymmetric dimethylarginine concentrations in healthy postmenopausal women

Postmenopausal women are at increased risk for cardiovascular disease because many risk factors are aggravated by menopause. Phytoestrogens may modulate risk factors favorably, involving mechanisms similar to estrogen. The effect of phytoestrogens on the atherogenic amino acids homocysteine and asymmetric dimethylarginine (ADMA) was investigated in a controlled intervention study in healthy postmenopausal women. A multicenter, double-blind, crossover intervention trial in 89 postmenopausal women from Denmark, Germany, and the UK was performed. Subjects consumed fruit cereal bars with or without soy isoflavones (50 mg/d) for 8 wk each with an 8-wk washout period in between. Urinary phytoestrogens increased significantly after isoflavone intervention (P < 0.001). lsoflavone supplementation did not affect plasma total homocysteine or ADMA. For homocysteine, changes from baseline were 0.32 mu mol/L (range: -0.31-0.92; 95% Cl 0.13-0.72), and 0.29 mu mol/L (range: 0.45-1.09;95% Cl 0.01-0.63, P = 0.286) for isoflavone treatment and placebo, respectively. For ADMA concentrations, changes from baseline were -0.02 mu mol/L (range: -0.08-0.03; 95% Cl -0.04-0.01, and 0.00 mu mol/L (range: 0,05-0.03: 95% Cl -0.03-0.01, P = 0.397) for isoflavone treatment and placebo, respectively, There was no association between plasma total homocysteine and ADMA. Changes from baseline in plasma ADMA and folate were negatively correlated (r= -0.18, P = 0.017). These results challenge the overall health effect of isoflavone supplementation in healthy postmenopausal women.

Effects of calcium-chelating agents and pasteurisation on certain properties of calcium-fortified soy milk

Addition of 25 mM calcium chloride to soy milk reduced pH, increased ionic calcium and caused it to coagulate. The effects of different chelating agents were investigated on selected physicochemical properties of soy milk and on preventing coagulation. The soy milks were then pasteurised to examine how heat treatment changed some of these properties as well as to evaluate their effects on heat stability. Sediment formation and susceptibility to coagulation could be reduced by decreasing ionic calcium and increasing pH. To achieve this, the most effective chelating agents were tri-sodium citrate and disodium hydrogen phosphate. These chelating agents also reduce absolute viscosity and particle size. Sodium hexa meta phosphate was also effective, but less so; it reduced ionic calcium but had a less noticeable effect on pH. The disodium salt of ethylenediamine tetraacetic acid was not effective, as it decreased the pH of soy milk. Ionic calcium and pH are useful indicators of heat stability of calcium-fortified soy beverages. (C) 2009 Elsevier Ltd. All rights reserved.

Soy-isoflavone-enriched foods and markers of lipid and glucose metabolism in postmenopausal women: interactions with genotype and equol production

Background: The hypocholesterolemic effects of soy foods are well established, and it has been suggested that isoflavones are responsible for this effect. However, beneficial effects of isolated isoflavones on lipid biomarkers of cardiovascular disease risk have not yet been shown. Objective: The objective was to investigate the effects of isolated soy isoflavones on metabolic biomarkers of cardiovascular disease risk, including plasma total, HDL, and LDL cholesterol; triacylglycerols; lipoprotein(a); the percentage of small dense LDL; glucose; nonesterified fatty acids; insulin; and the homeostasis model assessment of insulin resistance. Differences with respect to single nucleotide polymorphisms in selected genes [ie, estrogen receptor a (Xbal and PvuII), estrogen receptor beta (AluI), and estrogen receptor beta(cx) (Tsp5091), endothelial nitric oxide synthase (Glu298Asp), apolipoprotein E (Apo E2, E3, and E4), cholesteryl ester transfer protein (TaqIB), and leptin receptor (Gln223Arg)] and with respect to equol production were investigated. Design: Healthy postmenopausal women (n = 117) participated in a randomized, double-blind, placebo-controlled, crossover dietary intervention trial. Isoflavone-enriched (genistein-to-daidzein ratio of 2: 1; 50 mg/d) or placebo cereal bars were consumed for 8 wk, with a wash-out period of 8 wk before the crossover. Results: Isoflavones did not have a significant beneficial effect on plasma concentrations of lipids, glucose, or insulin. A significant difference between the responses of HDL cholesterol to isoflavones and to placebo was found with estrogen receptor 0(cx) Tsp5091 genotype AA, but not GG or GA. Conclusions: Isoflavone supplementation, when provided in the form and dose used in this study, had no effect on lipid or other metabolic biomarkers of cardiovascular disease risk in postmenopausal women but may increase HDL cholesterol in an estrogen receptor P gene-polymorphic subgroup.

Soy-isoflavone-enriched foods and inflammatory biomarkers of cardiovascular disease risk in postmenopausal women: interactions with genotype and equol production

Background: Dietary isoflavones are thought to be cardioprotective because of their structural similarity to estrogen. The reduction of concentrations of circulating inflammatory markers by estrogen may be one of the mechanisms by which premenopausal women are protected against cardiovascular disease. Objective: Our aim was to investigate the effects of isolated soy isoflavones on inflammatory biomarkers [von Willebrand factor, intracellular adhesion molecule 1, vascular cell adhesion molecule 1 (VCAM-1), E-selectin, monocyte chemoattractant protein 1, C-reactive protein (CRP), and endothelin 1 concentrations]. Differences with respect to single-nucleotide polymorphisms in selected genes [estrogen receptor alpha (XbaI and PvuII), estrogen receptor beta [ER beta (AluI) and ER beta[cx] (Tsp5091), endothelial nitric oxide synthase (Glu298Asp), apolipoprotein E (Apo E2, E3, and E4), and cholesteryl ester transfer protein (TaqIB)] and equol production were investigated. Design: One hundred seventeen healthy European postmenopausal women participated in this randomized, double-blind, placebo-controlled, crossover dietary intervention trial. Isoflavone-enriched (genistein-to-daidzein ratio of 2:1;50 mg/d) or placebo cereal bars were consumed for 8 wk, with a washout period of 8 wk between the crossover. Plasma inflammatory factors were measured at 0 and 8 wk of each study arm. Results: Isoflavones improved CRP concentrations [odds ratio (95% Cl) for CRP values >1 mg/L for isoflavone compared with placebo: 0.43 (0.27, 0.69)]; no significant effects of isoflavone treatment on other plasma inflammatory markers were observed. No significant differences in the response to isoflavones were observed according to subgroups of equol production. Differences in the VCAM-1 response to isoflavones and to placebo were found with ER beta AluI genotypes. Conclusion: Isoflavones have beneficial effects on CRP concentrations, but not on other inflammatory biomarkers of cardiovascular disease risk in postmenopausal women, and may improve VCAM-1 in an ER beta gene polymorphic subgroup.

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

Background: The incidence of cardiovascular diseases increases after menopause, and soy consumption is suggested to inhibit disease development. Objective: The objective was to identify biomarkers of response to a dietary supplementation with an isoflavone extract in postmenopausal women by proteome analysis of peripheral blood mononuclear cells. Design: The study with healthy postmenopausal woman was performed in a placebo-controlled sequential design. Peripheral mononuclear blood cells were collected from 10 volunteers after 8 wk of receiving daily 2 placebo cereal bars and after a subsequent 8 wk of intervention with 2 cereal bars each providing 25 mg of isoflavones. The proteome of the cells was visualized after 2-dimensional gel electrophoresis, and peptide mass fingerprinting served to identify proteins that by the intervention displayed altered protein concentrations. Results: Twenty-nine proteins were identified that showed significantly altered expression in the mononuclear blood cells under the soy-isoflavone intervention, including a variety of proteins involved in an antiinflammatory response. Heat shock protein 70 or a lymphocyte-specific protein phosphatase and proteins that promote increased fibrinolysis, such as a-enolase, were found at increased intensities, whereas those that mediate adhesion, migration, and proliferation of vascular smooth muscle cells, such as galectin-1, were found at reduced intensities after soy extract consumption. Conclusion: Protcome analysis identified in vivo markers that respond to a dietary intervention with isoflavone-enriched soy extract in postmenopausal women. The nature of the proteins identified suggests that soy isoflavones may increase the anti inflammatory response in blood mononuclear cells that might contribute to the atherosclerosis-preventive activities of a soy-rich diet.

Some functional properties of fractionated soy protein isolates obtained by microfiltration

Five soy proteins isolate (SPI) fractions were produced using two microfiltration membranes with different pore sizes. Fractionation was carried out on SPI produced by isoelectric precipitation of a crude protein extract. The five fractions were two retentates and two permeates from the two membranes, the fifth fraction was obtained as the retentate on the smaller-po re- sized membrane fed with the permeate from the larger-pore-sized membrane. Solubility, foaming and emulsifying properties of the collected fractionates were investigated. It was observed that in the pH range 3-8 the retentates featured superior solubility compared with permeates. There was no significant difference (p > 0.0 1) in solubility between the retentates and SPI at pH >= 6. Foaming characteristics of the fractions followed the same trend as solubility with regard to foam expansion. There was, however, no particular trend observed with regards to foam stability. Emulsions stabilised by the retentates exhibited higher values (p<0.01) of emulsion stability index (ESI) and emulsifying activity index (EAI) than those stabilised with permeates. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) profiles indicated that the fractions exhibiting high functionality in terms of solubility, foaming and emulsifying properties were also richer in 7S globulin soy protein subunits. Isoelectric focussing (IEF) profiles showed that retentates were richer in species with isoelectric points (pl) between 5.2 and 5.6 while permeates featured more prominently at pis between 4.5 and 4.8. (C) 2006 Elsevier Ltd. All rights reserved.