A soy protein isolate rich in genistein and daidzein and its effects on plasma isoflavone concentrations, platelet aggregation, blood lipids and fatty acid composition of plasma phospholipid in normal men

Estrogenic in vitro evaluation of zearalenone and its phase I and II metabolites in combination with soy isoflavones

Humans and animals are exposed to multiple substances in their food and feed that might have a negative health impact. Among these substances, the Fusarium mycoestrogen zearalenone (ZEN) and its metabolites α-zearalenol (α-ZEL) and α-zearalanol (α-ZAL) are known to possess endocrine disruptive properties. In a mixed diet or especially animal feed, these potential contaminants might be ingested together with naturally occurring phytoestrogens such as soy isoflavones. So far, risk assessment of potential endocrine disruptors is usually based on adverse effects of single compounds whereas studies investigating combinatorial effects are scarce. In the present study, we investigated the estrogenic potential of mycoestrogens and the isoflavones genistein (GEN), daidzein (DAI) and glycitein (GLY) as well as equol (EQ), the gut microbial metabolite of DAI, in vitro alone or in combination, using the alkaline phosphatase (ALP) assay in Ishikawa cells. In the case of mycoestrogens, the tested concentration range included 0.001 to 10 nM with multiplication steps of 10 in between, while for the isoflavones 1000 times higher concentrations were investigated. For the individual substances the following order of estrogenicity was obtained: α-ZEL > α-ZAL > ZEN > GEN > EQ > DAI > GLY. Most combinations of isoflavones with mycoestrogens enhanced the estrogenic response in the investigated concentrations. Especially lower concentrations of ZEN, α-ZEL and α-ZAL (0.001—0.01 nM) in combination with low concentrations of GEN, DAI and EQ (0.001—0.1 µM) strongly increased the estrogenic response compared to the single substances.

Soy Consumption, but Not Dairy Consumption, Is Inversely Associated with Fatty Acid Desaturase Activity in Young Adults

Past research using hepatic rat microsomes showed that soy protein suppressed delta-6 desaturase activity (D6D) compared to casein (a dairy protein). The effects of soy and dairy on desaturase pathway activity in humans remain poorly investigated. The objective of this analysis was to investigate the association between soy and dairy consumption with plasma fatty acids and estimate the desaturase pathway activity in a multiethnic Canadian population of young adults. We analyzed data from men (n = 319) and women (n = 764) previously collected for the Toronto Nutrigenomics and Health Study. Food frequency questionnaires and plasma fatty acids were assessed. Relationships between soy and dairy beverages and food consumption with estimated desaturase activities were assessed by regression models and by grouping participants according to beverage and food intake data. Weak inverse associations (p ≤ 0.05) were found between soy consumption and the overall desaturation pathway activity, specifically D6D activity. When participants were grouped based on soy and dairy consumption habits, omega-6 LC-PUFAs, as well as various estimates of the desaturase pathway activity, were significantly lower in individuals consuming soy (with or without dairy) compared to individuals consuming only fluid milk and dairy products. In conclusion, soy consumption, not dairy consumption, appears to suppress desaturase pathway activity.

Platelet Responses in Cardiovascular Disease: Sex-Related Differences in Nutritional and Pharmacological Interventions

Cardiovascular diseases (CVD) represent one of the biggest causes of death globally, and their prevalence, aetiology, and outcome are related to genetic, metabolic, and environmental factors, among which sex- and age-dependent differences may play a key role. Among CVD risk factors, platelet hyperactivity deserves particular mention, as it is involved in the pathophysiology of main cardiovascular events (including stroke, myocardial infarction, and peripheral vascular injury) and is closely related to sex/age differences. Several determinants (e.g., hormonal status and traditional cardiovascular risk factors), together with platelet-related factors (e.g., plasma membrane composition, receptor signaling, and platelet-derived microparticles) can elucidate sex-related disparity in platelet functionality and CVD onset and outcome, especially in relation to efficacy of current primary and secondary interventional strategies. Here, we examined the state of the art concerning sex differences in platelet biology and their relationship with specific cardiovascular events and responses to common antiplatelet therapies. Moreover, as healthy nutrition is widely recognized to play a key role in CVD, we also focused our attention on specific dietary components (especially polyunsaturated fatty acids and flavonoids) and patterns (such as Mediterranean diet), which also emerged to impact platelet functions in a sex-dependent manner. These results highlight that full understanding of gender-related differences will be useful for designing personalized strategies, in order to prevent and/or treat platelet-mediated vascular damage.

Cumulative Meta-Analysis of the Soy Effect Over Time

Background

Soy protein foods have attracted attention as useful plant protein foods with mild cholesterol‐lowering effects that are suitable for inclusion in therapeutic diets. But on the basis of the lack of consistency in significant cholesterol reduction by soy in 46 randomized controlled trials, the US Food and Drug Administration (FDA) is reassessing whether the 1999 heart health claim for soy protein should be revoked.

Methods and Results

We have, therefore, performed a cumulative meta‐analysis on the 46 soy trials identified by the FDA to determine if at any time, since the 1999 FDA final rule that established the soy heart health claim, the soy effect on serum cholesterol lost significance. The cumulative meta‐analysis for both total cholesterol and low‐density lipoprotein cholesterol demonstrated preservation of the small, but significant, reductions seen both before and during the subsequent 14 years since the health claim was originally approved. For low‐density lipoprotein cholesterol, the mean reduction in 1999 was −6.3 mg/dL (95% CI, −8.7 to −3.9 mg/dL; P=0.00001) and remained in the range of −4.2 to −6.7 mg/dL (P=0.0006 to P=0.0002, respectively) in the years after 1999. At no time point did the total cholesterol or low‐density lipoprotein cholesterol reductions lose significance or were the differences at individual time points in the cumulative meta‐analysis significantly different from those seen in 1999 when the health claim was approved.

Conclusions

A cumulative meta‐analysis of the data selected by the FDA indicates continued significance of total cholesterol and low‐density lipoprotein cholesterol reduction after soy consumption and supports the rationale behind the original soy FDA heart health claim.

See Editorial Petersen and Kris‐Etherton

A Meta-Analysis of 46 Studies Identified by the FDA Demonstrates that Soy Protein Decreases Circulating LDL and Total Cholesterol Concentrations in Adults

BACKGROUND

Certain plant foods (nuts and soy protein) and food components (viscous fibers and plant sterols) have been permitted by the FDA to carry a heart health claim based on their cholesterol-lowering ability. The FDA is currently considering revoking the heart health claim for soy protein due to a perceived lack of consistent LDL cholesterol reduction in randomized controlled trials.

OBJECTIVE

We performed a meta-analysis of the 46 controlled trials on which the FDA will base its decision to revoke the heart health claim for soy protein.

METHODS

We included the 46 trials on adult men and women, with baseline circulating LDL cholesterol concentrations ranging from 110 to 201 mg/dL, as identified by the FDA, that studied the effects of soy protein on LDL cholesterol and total cholesterol (TC) compared with non-soy protein. Two independent reviewers extracted relevant data. Data were pooled by the generic inverse variance method with a random effects model and expressed as mean differences with 95% CI. Heterogeneity was assessed and quantified.

RESULTS

Of the 46 trials identified by the FDA, 43 provided data for meta-analyses. Of these, 41 provided data for LDL cholesterol, and all 43 provided data for TC. Soy protein at a median dose of 25 g/d during a median follow-up of 6 wk decreased LDL cholesterol by 4.76 mg/dL (95% CI: -6.71, -2.80 mg/dL, P < 0.0001; I2 = 55%, P < 0.0001) and decreased TC by 6.41 mg/dL (95% CI: -9.30, -3.52 mg/dL, P < 0.0001; I2 = 74%, P < 0.0001) compared with non-soy protein controls. There was no dose-response effect or evidence of publication bias for either outcome. Inspection of the individual trial estimates indicated most trials (∼75%) showed a reduction in LDL cholesterol (range: -0.77 to -58.60 mg/dL), although only a minority of these were individually statistically significant.

CONCLUSIONS

Soy protein significantly reduced LDL cholesterol by approximately 3-4% in adults. Our data support the advice given to the general public internationally to increase plant protein intake. This trial was registered at clinicaltrials.gov as NCT03468127.

Biomarkers of legume intake in human intervention and observational studies: a systematic review

There is a growing interest in assessing dietary intake more accurately across different population groups, and biomarkers have emerged as a complementary tool to replace traditional dietary assessment methods. The purpose of this study was to conduct a systematic review of the literature available and evaluate the applicability and validity of biomarkers of legume intake reported across various observational and intervention studies. A systematic search in PubMed, Scopus, and ISI Web of Knowledge identified 44 studies which met the inclusion criteria for the review. Results from observational studies focused on soy or soy-based foods and demonstrated positive correlations between soy intake and urinary, plasma or serum isoflavonoid levels in different population groups. Similarly, intervention studies demonstrated increased genistein and daidzein levels in urine and plasma following soy intake. Both genistein and daidzein exhibited dose-response relationships. Other isoflavonoid levels such as O-desmethylangolensin (O-DMA) and equol were also reported to increase following soy consumption. Using a developed scoring system, genistein and daidzein can be considered as promising candidate markers for soy consumption. Furthermore, genistein and daidzein also served as good estimates of soy intake as evidenced from long-term exposure studies marking their status as validated biomarkers. On the contrary, only few studies indicated proposed biomarkers for pulses intake, with pipecolic acid and S-methylcysteine reported as markers reflecting dry bean consumption, unsaturated aliphatic, hydroxyl-dicarboxylic acid related to green beans intake and trigonelline reported as marker of peas consumption. However, data regarding criteria such as specificity, dose-response and time-response relationship, reliability, and feasibility to evaluate the validity of these markers is lacking. In conclusion, despite many studies suggesting proposed biomarkers for soy, there is a lack of information on markers of other different subtypes of legumes. Further discovery and validation studies are needed in order to identify reliable biomarkers of legume intake.

Inhibition of Kv4.3 by genistein via a tyrosine phosphorylation-independent mechanism

The effects of genistein, a protein tyrosine kinase (PTK) inhibitor, on voltage-dependent K(+) (Kv) 4.3 channel were examined using the whole cell patch-clamp techniques. Genistein inhibited Kv4.3 in a reversible, concentration-dependent manner with an IC(50) of 124.78 μM. Other PTK inhibitors (tyrphostin 23, tyrphostin 25, lavendustin A) had no effect on genistein-induced inhibition of Kv4.3. Orthovanadate, an inhibitor of protein phosphatases, did not reverse the inhibition of Kv4.3 by genistein. We also tested the effects of two inactive structural analogs: genistin and daidzein. Whereas Kv4.3 was unaffected by genistin, daidzein inhibited Kv4.3, albeit with a lower potency. Genistein did not affect the activation and inactivation kinetics of Kv4.3. Genistein-induced inhibition of Kv4.3 was voltage dependent with a steep increase over the channel opening voltage range. In the full-activation voltage range positive to +20 mV, no voltage-dependent inhibition was found. Genistein had no significant effect on steady-state activation, but shifted the voltage dependence of the steady-state inactivation of Kv4.3 in the hyperpolarizing direction in a concentration-dependent manner. The K(i) for the interaction between genistein and the inactivated state of Kv4.3, which was estimated from the concentration-dependent shift in the steady-state inactivation curve, was 1.17 μM. Under control conditions, closed-state inactivation was fitted to a single exponential function, and genistein accelerated closed-state inactivation. Genistein induced a weak use-dependent inhibition. These results suggest that genistein directly inhibits Kv4.3 by interacting with the closed-inactivated state of Kv4.3 channels. This effect is not mediated via inhibition of the PTK activity, because other types of PTK inhibitors could not prevent the inhibitory action of genistein.

Effects of isoflavones (soy phyto-estrogens) on serum lipids: a meta-analysis of randomized controlled trials

Objectives

To determine the effects of isoflavones (soy phyto-estrogens) on serum total cholesterol (TC), low density lipoprotein cholesterol (LDL), high density lipoprotein cholesterol (HDL) and triglyceride (TG).

Methods

We searched electronic databases and included randomized trials with isoflavones interventions in the forms of tablets, isolated soy protein or soy diets. Review Manager 4.2 was used to calculate the pooled risk differences with fixed effects model.

Results

Seventeen studies (21 comparisons) with 853 subjects were included in this meta-analysis. Isoflavones tablets had insignificant effects on serum TC, 0.01 mmol/L (95% CI: -0.17 to 0.18, heterogeneity p = 1.0); LDL, 0.00 mmol/L (95% CI: -0.14 to 0.15, heterogeneity p = 0.9); HDL, 0.01 mmol/L (95% CI: -0.05 to 0.06, heterogeneity p = 1.0); and triglyceride, 0.03 mmol/L (95% CI: -0.06 to 0.12, heterogeneity p = 0.9). Isoflavones interventions in the forms of isolated soy protein (ISP), soy diets or soy protein capsule were heterogeneous to combine.

Conclusions

Isoflavones tablets, isolated or mixtures with up to 150 mg per day, seemed to have no overall statistical and clinical benefits on serum lipids. Isoflavones interventions in the forms of soy proteins may need further investigations to resolve whether synergistic effects are necessary with other soy components.

Soya phytoestrogens, genistein and daidzein, decrease apolipoprotein B secretion from HepG2 cells through multiple mechanisms

Diets containing the soya-derived phytoestrogens, genistein and daidzein, decrease plasma cholesterol in humans and experimental animals. The mechanisms responsible for the hypocholesterolaemic effects of these isoflavones are unknown. The present study was conducted to determine if genistein and daidzein regulate hepatocyte cholesterol metabolism and apolipoprotein (apo) B secretion in cultured human hepatoma (HepG2) cells. ApoB secretion was decreased dose-dependently by up to 63% and 71% by genistein and daidzein (100 microM; P<0.0001) respectively. In contrast, no effect on apoAI secretion was observed. Cellular cholesterol synthesis was inhibited 41% by genistein (100 microM; P<0.005) and 18% by daidzein (100 microM; P<0.05), which was associated with significant increases in 3-hydroxy-3-methylglutaryl-CoA reductase mRNA. Cellular cholesterol esterification was decreased 56% by genistein (100 microM; P<0.04) and 29% by daidzein (100 microM; P<0.04); however, mRNA levels for acyl-CoA:cholesterol acyltransferase (ACAT) 1 and ACAT2 were unaffected. At 100 microM, both isoflavones equally inhibited the activities of both forms of ACAT in cells transfected with either ACAT1 or ACAT2. Genistein (100 microM) and daidzein (100 microM) significantly decreased the activity of microsomal triacylglycerol transfer protein (MTP) by 30% and 24% respectively, and significantly decreased MTP mRNA levels by 35% and 55%. Both isoflavones increased low-density lipoprotein (LDL)-receptor mRNA levels by 3- to 6-fold (100 microM; P<0.03) and significantly increased the binding, uptake and degradation of (125)I-labelled LDL, suggesting that enhanced reuptake of newly secreted apoB-containing lipoproteins contributed to the net decrease in apoB secretion. These results indicate that genistein and daidzein inhibit hepatocyte apoB secretion through several mechanisms, including inhibition of cholesterol synthesis and esterification, inhibition of MTP activity and expression and increased expression of the LDL-receptor.