Studies of the in vitro intestinal metabolism of isoflavones aid in the identification of their urinary metabolites

Biotransformation analysis of daidzin in vitro based on fecal bacteria and probiotics

Daidzin, as one of isoflavone glycosides, has been reported to have multiple activities with few absorbed into body. However, the metabolic behavior of daidzin by intestinal flora has not been researched, that this defect severely constrains its applications. In this study, daidzin and its metabolites were qualitatively and quantitatively analyzed by HPLC and ultra-high performance liquid chromatography coupled to high-resolution mass spectrometry (UHPLC-HRMS) in the fermentation system for daidzin and fecal bacteria. Meanwhile, the alterations of intestinal flora with daidzin were detected by 16S rRNA sequencing technology. Based on the results of intestinal flora, the daidzin and its metabolites transformed by the screened probiotics were quantified and qualified, which the results would corroborate the transformation of daidzin and fecal bacteria. Eventually, daidzin was decreased from 0.30158 mg/mL at 0 h to 0.01176 mg/mL at 48 h, daidzein, as the aglycone of daidzin, was increased from 0.02963 mg/mL at 0 h to 0.04682 mg/mL at 48 h, suggesting the presence of other metabolites. Next, 31 metabolites including the products of ketone removal, Retro-Diels-Alder (RDA) fragmentation, hydroxylation, methylation, C ring cracking and sulfation were identified. The results of 16S rRNA sequencing showed that the intestinal flora, especially Bifidobacterium, was dramatically altered after incubation with daidzin (p < 0.05). Hereby, the fermentation systems of five probiotics (Lactobacillus 3044, Bifidobacterium adolescentis 1.2190, Bifidobacterium longum 25033, Lactobacillus plantarum F1 and Lactobacillus plantarum B2) and daidzin were approved, and these results showed that most metabolites of daidzin were able to be identified with the identical transformation reactions. The study revealed the rationality of daidzin biotransformation at the new perspective, and constructs a new model for fecal metabolites of compounds. These results will also broaden the continued research on daidzin.

Distribution and metabolism of daidzein and its benzene sulfonates in vivo (in mice) based on MALDI-TOF MSI

Daidzein (D1) has been proved to be of great benefit to human health. More and more attention was paid to the metabolic process of D1. Most studies focused on the metabolites of D1 and analogs were determined through the excretion of animals and humans by traditional HPLC-MS, while their in situ distribution and metabolism in organs in vivo has not been reported. In our group, novel daidzein sulfonate derivatives were synthesized and confirmed to have excellent pharmaceutical properties. They exhibited good anti-inflammatory, inhibitory activities on human vascular smooth muscle cell proliferation and other bioactivities. Compared with traditional analytical methods, matrix-assisted laser desorption ionization time-of-flight mass spectrometry imaging (MALDI-TOF MSI) can directly analyze the distribution of compounds in tissues and organs. In this study, we investigate the in situ distribution and metabolism of D1 and its derivatives (DD2, DD3) in the organs of mice based on MALDI-TOF MSI for the first time. Trace prototype compounds were detected in the plasma 4 h after the intravenous injection of D1, DD2, and DD3. Seven phase I metabolites and seven phase II metabolites were detected. D1 sulfates were found in the plasma and in organs except the heart. The presence of D1 and DD3 monosulfates in the brain indicated that they could penetrate the blood–brain barrier. DD2 and DD3 could be hydrolyzed into D1 and their metabolic pathways were similar to those of D1. In addition, a ligand-receptor docking of D1 and DD2 with mitogen-activated protein kinase 8 (JNK1) was performed because of their significant anti-inflammatory activities through the JNK signaling pathway. It showed that the binding energy of DD2 with JNK1 was obviously lower than that of D1 which was consistent with their anti-inflammatory activities. It provided a theoretical basis for further validation of their anti-inflammatory mechanism at the protein level. In summary, the research will provide beneficial guidance for further pharmacological, toxicological studies and the clinical-use research of these compounds.

Orobol from enzyme biotransformation attenuates Dermatophagoides farinae-induced atopic dermatitis-like symptoms in NC/Nga mice

Orobol, a metabolite of genistein, is rare in natural soybean. Several studies have revealed the immune-controlling effects of orobol on inflammatory diseases. Furthermore, a few studies have demonstrated that orobol decreases pro-inflammatory compounds resulting in the alleviation of allergic reactions. However, the relationship between orobol and atopic dermatitis (AD) in animal models has not been revealed. Therefore, we sought to investigate the effects of orobol on AD-like symptoms. AD-like symptoms and skin lesions were induced by repeated topical application of Dermatophagoides farinae extract (DFE) on the skin of NC/Nga mice. Topical application of orobol attenuated DFE-induced AD-like symptoms and transepidermal water loss and increased skin hydration. Histopathological analysis revealed that orobol alleviated DFE-induced eosinophil and mast cell infiltration into the skin. These observations occurred concomitantly with the downregulation of inflammatory markers including serum TARC, MDC, and IgE. In addition, orobol alleviated dorsal Th2 cytokines such as IL-4 and IL-13. Pre-treatment of orobol decreased the activity of the MAPKs and NF-κB signalling cascade in the TNFα/IFNγ-induced HaCaT cell line. These results suggest that orobol, a natural dietary isoflavone, has therapeutic efficacy for the prevention and treatment of AD.

Isoflavones in Animals: Metabolism and Effects in Livestock and Occurrence in Feed

Soybeans are a common ingredient of animal feed. They contain isoflavones, which are known to act as phytoestrogens in animals. Isoflavones were described to have beneficial effects on farm animals. However, there are also reports of negative outcomes after the consumption of isoflavones. This review summarizes the current knowledge of metabolization of isoflavones (including the influence of the microbiome, phase I and phase II metabolism), as well as the distribution of isoflavones and their metabolites in tissues. Furthermore, published studies on effects of isoflavones in livestock species (pigs, poultry, ruminants, fish) are reviewed. Moreover, published studies on occurrence of isoflavones in feed materials and co-occurrence with zearalenone are presented and are supplemented with our own survey data.

Impact of Short-Term Isoflavone Intervention in Polycystic Ovary Syndrome (PCOS) Patients on Microbiota Composition and Metagenomics

BACKGROUND

Polycystic ovary syndrome (PCOS) affects 5-20% of women of reproductive age worldwide and is associated with disorders of glucose metabolism. Hormone and metabolic signaling may be influenced by phytoestrogens, such as isoflavones. Their endocrine effects may modify symptom penetrance in PCOS. Equol is one of the most active isoflavone metabolites, produced by intestinal bacteria, and acts as a selective estrogen receptor modulator.

METHOD

In this interventional study of clinical and biochemical characterization, urine isoflavone levels were measured in PCOS and control women before and three days after a defined isoflavone intervention via soy milk. In this interventional study, bacterial equol production was evaluated using the log(equol: daidzein ratio) and microbiome, metabolic, and predicted metagenome analyses were performed.

RESULTS

After isoflavone intervention, predicted stool metagenomic pathways, microbial alpha diversity, and glucose homeostasis in PCOS improved resembling the profile of the control group at baseline. In the whole cohort, larger equol production was associated with lower androgen as well as fertility markers.

CONCLUSION

The dynamics in our metabolic, microbiome, and predicted metagenomic profiles underline the importance of external phytohormones on PCOS characteristics and a potential therapeutic approach or prebiotic in the future.

Dietary Flavonoids for Immunoregulation and Cancer: Food Design for Targeting Disease

Flavonoids, one of the most abundant phytochemicals in a diet rich in fruits and vegetables, have been recognized as possessing anti-proliferative, antioxidant, anti-inflammatory, and estrogenic activities. Numerous cellular and animal-based studies show that flavonoids can function as antioxidants by preventing DNA damage and scavenging reactive oxygen radicals, inhibiting formation of DNA adducts, enhancing DNA repair, interfering with chemical damage by induction of Phase II enzymes, and modifying signaling pathways. Recent evidence also shows their ability to regulate the immune system. However, findings from clinical trials have been mixed with no clear consensus on dose, frequency, or type of flavonoids best suited to elicit many of the beneficial effects. Delivery of these bioactive compounds to their biological targets through "targeted designed" food processing strategies is critical to reach effective concentration in vivo. Thus, the identification of novel approaches that optimize flavonoid bioavailability is essential for their successful clinical application. In this review, we discuss the relevance of increasing flavonoid bioavailability, by agricultural engineering and "targeted food design" in the context of the immune system and cancer.

A major daidzin metabolite 7,8,4'-trihydroxyisoflavone found in the plasma of soybean extract-fed rats attenuates monocyte-endothelial cell adhesion

Among many functional foods and their phytochemicals, ingestion of soybean (Glycine max) is highly correlated to reduced risk of cardiovascular diseases. Validation of potential health benefits of functional foods requires information about the bioavailability and metabolism of bioactive compounds. In this context, several phase I and II metabolites of isoflavones were target-analyzed in the plasma of rats acutely supplemented with soybean embryo extract. A daidzein metabolite, 7,8,4'-trihydroxyisoflavone (7,8,4'-THI), was found to have the highest average area under curve value (574.3±112.8). Therefore, its potential prevention effect on atherosclerosis was investigated using monocyte-endothelial cell adhesion assay. Different from its precursor daidzein or daidzin, 7,8,4'-THI attenuated adhesion of THP-1 monocytes to tumor necrosis factor-alpha (TNF-α) stimulated human umbilical vein endothelial cells (HUVECs). In addition, 7,8,4'-THI significantly downregulated TNF-α stimulated the expression of vascular cell adhesion molecule-1 and monocyte chemotactic protein-1 and phosphorylation of IκB kinase and IκBα involved in the initiation of atherosclerosis in HUVECs. Therefore, 7,8,4'-THI, a highly bioavailable hydroxylated isoflavone metabolite, has potential anti-atherosclerotic effect via inhibiting monocyte-endothelial adhesion.

Dietary flavonoid aglycones and their glycosides: Which show better biological significance?

The dietary flavonoids, especially their glycosides, are the most vital phytochemicals in diets and are of great general interest due to their diverse bioactivity. The natural flavonoids almost all exist as their O-glycoside or C-glycoside forms in plants. In this review, we summarized the existing knowledge on the different biological benefits and pharmacokinetic behaviors between flavonoid aglycones and their glycosides. Due to various conclusions from different flavonoid types and health/disease conditions, it is very difficult to draw general or universally applicable comments regarding the impact of glycosylation on the biological benefits of flavonoids. It seems as though O-glycosylation generally reduces the bioactivity of these compounds - this has been observed for diverse properties including antioxidant activity, antidiabetes activity, anti-inflammation activity, antibacterial, antifungal activity, antitumor activity, anticoagulant activity, antiplatelet activity, antidegranulating activity, antitrypanosomal activity, influenza virus neuraminidase inhibition, aldehyde oxidase inhibition, immunomodulatory, and antitubercular activity. However, O-glycosylation can enhance certain types of biological benefits including anti-HIV activity, tyrosinase inhibition, antirotavirus activity, antistress activity, antiobesity activity, anticholinesterase potential, antiadipogenic activity, and antiallergic activity. However, there is a lack of data for most flavonoids, and their structures vary widely. There is also a profound lack of data on the impact of C-glycosylation on flavonoid biological benefits, although it has been demonstrated that in at least some cases C-glycosylation has positive effects on properties that may be useful in human healthcare such as antioxidant and antidiabetes activity. Furthermore, there is a lack of in vivo data that would make it possible to make broad generalizations concerning the influence of glycosylation on the benefits of flavonoids for human health. It is possible that the effects of glycosylation on flavonoid bioactivity in vitro may differ from that seen in vivo. With in vivo (oral) treatment, flavonoid glycosides showed similar or even higher antidiabetes, anti-inflammatory, antidegranulating, antistress, and antiallergic activity than their flavonoid aglycones. Flavonoid glycosides keep higher plasma levels and have a longer mean residence time than those of aglycones. We should pay more attention to in vivo benefits of flavonoid glycosides, especially C-glycosides.

WITHDRAWN: Flavonoid glycosylation and biological benefits

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Dietary (poly)phenolics in human health: structures, bioavailability, and evidence of protective effects against chronic diseases

Human intervention trials have provided evidence for protective effects of various (poly)phenol-rich foods against chronic disease, including cardiovascular disease, neurodegeneration, and cancer. While there are considerable data suggesting benefits of (poly)phenol intake, conclusions regarding their preventive potential remain unresolved due to several limitations in existing studies. Bioactivity investigations using cell lines have made an extensive use of both (poly)phenolic aglycones and sugar conjugates, these being the typical forms that exist in planta, at concentrations in the low-μM-to-mM range. However, after ingestion, dietary (poly)phenolics appear in the circulatory system not as the parent compounds, but as phase II metabolites, and their presence in plasma after dietary intake rarely exceeds nM concentrations. Substantial quantities of both the parent compounds and their metabolites pass to the colon where they are degraded by the action of the local microbiota, giving rise principally to small phenolic acid and aromatic catabolites that are absorbed into the circulatory system. This comprehensive review describes the different groups of compounds that have been reported to be involved in human nutrition, their fate in the body as they pass through the gastrointestinal tract and are absorbed into the circulatory system, the evidence of their impact on human chronic diseases, and the possible mechanisms of action through which (poly)phenol metabolites and catabolites may exert these protective actions. It is concluded that better performed in vivo intervention and in vitro mechanistic studies are needed to fully understand how these molecules interact with human physiological and pathological processes.

The isoflavone metabolite 6-methoxyequol inhibits angiogenesis and suppresses tumor growth

BACKGROUND

Increased consumption of plant-based diets has been linked to the presence of certain phytochemicals, including polyphenols such as flavonoids. Several of these compounds exert their protective effect via inhibition of tumor angiogenesis. Identification of additional phytochemicals with potential antiangiogenic activity is important not only for understanding the mechanism of the preventive effect, but also for developing novel therapeutic interventions.

RESULTS

In an attempt to identify phytochemicals contributing to the well-documented preventive effect of plant-based diets on cancer incidence and mortality, we have screened a set of hitherto untested phytoestrogen metabolites concerning their anti-angiogenic effect, using endothelial cell proliferation as an end point. Here, we show that a novel phytoestrogen, 6-methoxyequol (6-ME), inhibited VEGF-induced proliferation of human umbilical vein endothelial cells (HUVE) cells, whereas VEGF-induced migration and survival of HUVE cells remained unaffected. In addition, 6-ME inhibited FGF-2-induced proliferation of bovine brain capillary endothelial (BBCE) cells. In line with its role in cell proliferation, 6-ME inhibited VEGF-induced phosphorylation of ERK1/2 MAPK, the key cascade responsible for VEGF-induced proliferation of endothelial cells. In this context, 6-ME inhibited in a dose dependent manner the phosphorylation of MEK1/2, the only known upstream activator of ERK1/2. 6-ME did not alter VEGF-induced phosphorylation of p38 MAPK or AKT, compatible with the lack of effect on VEGF-induced migration and survival of endothelial cells. Peri-tumor injection of 6-ME in A-431 xenograft tumors resulted in reduced tumor growth with suppressed neovasularization compared to vehicle controls (P < 0.01).

CONCLUSIONS

6-ME inhibits VEGF- and FGF2-induced proliferation of ECs by targeting the phosphorylation of MEK1/2 and it downstream substrate ERK1/2, both key components of the mitogenic MAPK pathway. Injection of 6-ME in mouse A-431 xenograft tumors results to tumors with decreased neovascularization and reduced tumor volume suggesting that 6-ME may be developed to a novel anti-angiogenic agent in cancer treatment.

Improving bioavailability and stability of genistein by complexation with high-amylose corn starch

Genistein, like other phytochemicals, has beneficial health effects, but its bioavailability is limited. This research studied the effect of complexation of genistein with starch on genistein bioavailability. Genistein release from these complexes was tested in vitro under simulated intestinal conditions and in vivo in rats fed high-amylose corn starch (HACS)-genistein complexes (experimental group) as compared to those fed a physical mixture of HACS and genistein (controls). In vitro results showed that genistein release is sustained and fits the normal transit time of food in the intestine. The genistein concentration in the plasma was twice as high in the experimental group versus controls; the genistein concentration in the urine was also higher in the experimental group but lower in the feces. These results indicate that starch-genistein complexes increase genistein bioavailability and suggest that starch can affect the bioavailability of additional food components.

The red clover isoflavone irilone is largely resistant to degradation by the human gut microbiota

Intestinal bacteria may influence bioavailability and physiological activity of dietary isoflavones. We therefore investigated the ability of human intestinal microbiota to convert irilone and genistein in vitro. In contrast to genistein, irilone was largely resistant to transformation by fecal slurries of ten human subjects. The fecal microbiota converted genistein to dihydrogenistein, 6'-hydroxy-O-desmethylangolensin, and 2-(4-hydroxyphenyl)-propionic acid. However, considerable interindividual differences in the rate of genistein degradation and the pattern of metabolites formed from genistein were observed. Only one metabolite, namely dihydroirilone, was formed from irilone in minor amounts. In further experiments, Eubacterium ramulus, a prevalent flavonoid-degrading species of the human gut, was tested for transformation of irilone. In contrast to genistein, irilone was not converted by E. ramulus. Irilone only differs from genistein by a methylenedioxy group attached to the A-ring of the isoflavone skeleton. This substitution obviously restricts the degradability of irilone by human intestinal bacteria.

Identification and quantification of daidzein-7-glucuronide-4'-sulfate, genistein-7-glucuronide-4'-sulfate and genistein-4',7-diglucuronide as major metabolites in human plasma after administration of kinako

Much attention has been paid to the metabolism and disposition of isoflavones daidzein (Dein) and genistein (Gein) with regard to the prevention of several hormone-dependent diseases. Recent studies have reported that several conjugates as well as aglycones may be biologically active or may be activated within target cells. However, the disposition of Dein and Gein in plasma is still uncertain. This paper describes the identification and quantification of the highly polar metabolites, daidzein-7-glucuronide-4'-sulfate (D-7G-4'S), genistein-7-glucuronide-4'-sulfate (G-7G-4'S), daidzein-4',7-diglucuronide (D-4',7-diG), and genistein-4',7-diglucuronide (G-4',7-diG) in human plasma after dietary administration of kinako (baked soybean powder) to two healthy volunteers. The structure identification of these conjugated metabolites in plasma was performed in comparison to the LC-ESI-MS and 600 MHz (1)H-NMR spectral data of the chemically synthesized compounds. Furthermore, 16 isoflavone metabolites including D-7G-4'S, G-7G-4'S, D-4',7-diG, and G-4',7-diG in plasma were simultaneously measured by a high-performance liquid chromatography-UV-diode-array detector method combined with solid-phase extraction using an Oasis HLB cartridge. D-7G-4'S, G-7G-4'S and G-4',7-diG were found to be major metabolites of Dein and Gein in plasma, while intact aglycones were detected to be only ca. 2% in both subjects. The findings suggest that the conjugated metabolites could be the key compounds responsible for pharmacological and medicinal properties of isoflavones.

Metabolomics, a novel tool for studies of nutrition, metabolism and lipid dysfunction

AIMS

In this review metabolomics is introduced in historic perspective, with key platforms and bioinformatics methodologies described. An overview is provided covering recent applications of metabolomics and lipidomics in the context of human physiology, lipid metabolism and nutrition.

DATA SYNTHESIS

Global coverage of human metabolome requires application of multiple analytical platforms. The choice of a particular targeted or non-targeted analytical strategy depends on the hypothesis tested, state-of-the-art in the field, as well as on sample availability. Human metabolome has been shown to be sensitive to age, gut microbial composition, and lifestyle. Several studies have shown that, given the appropriate experimental design, subtle effects of interventions such as change of diet or weight loss can be detected by metabolomics and studied in the context of human physiology and health status.

CONCLUSION

Metabolome provides a sensitive intermediate phenotype linking the genotype, gut microbial composition and personal health status. Innovative experimental designs combined with novel computational tools for handling metabolomics data offer new opportunities for early disease detection as well as for characterization of dietary and therapeutic interventions in the context of human physiology.

Isoflavones and the prevention of breast and prostate cancer: new perspectives opened by nutrigenomics

Epidemiological evidence together with preclinical data from animal and in vitro studies strongly support a correlation between soy isoflavone consumption and protection towards breast and prostate cancers. The biological processes modulated by isoflavones, and especially by genistein, have been extensively studied, yet without leading to a clear understanding of the cellular and molecular mechanisms of action involved. This review discusses the existing gaps in our knowledge and evaluates the potential of the new nutrigenomic approaches to improve the study of the molecular effects of isoflavones. Several issues need to be taken into account for the proper interpretation of the results already published for isoflavones. Too often knowledge on isoflavone bioavailability is not taken into account; supra-physiological doses are frequently used. Characterization of the individual variability as defined by the gut microflora composition and gene polymorphisms may also help to explain the discrepancies observed so far in the clinical studies. Finally, the complex inter-relations existing between tissues and cell types as well as cross-talks between metabolic and signalling pathways have been insufficiently considered. By appraising critically the abundant literature with these considerations in mind, the mechanisms of action that are the more likely to play a role in the preventive effects of isoflavones towards breast and prostate cancers are reviewed. Furthermore, the new perspectives opened by the use of genetic, transcriptomic, proteomic and metabolomic approaches are highlighted.

Metabolism of dietary soy isoflavones to equol by human intestinal microflora--implications for health

Soy isoflavones have received considerable attention. Individuals with isoflavones-rich diets have significantly lower occurrences of cardiovascular disease, osteoporosis, and some cancers. The clinical effectiveness of soy isoflavones may be a function of the ability to biotransform soy isoflavones to the more potent estrogenic metabolite, equol, which may enhance the actions of soy isoflavones, owing to its greater affinity for estrogen receptors, unique antiandrogenic properties, and superior antioxidant activity. However, not all individuals consuming daidzein produce equol. Only approximately one-third to one-half of the population is able to metabolize daidzein to equol. This high variability in equol production is presumably attributable to interindividual differences in the composition of the intestinal microflora, which may play an important role in the mechanisms of action of isoflavones. But, the specific bacterial species in the colon involved in the production of equol are yet to be discovered. Therefore, future researches are aimed at identifying the specific bacterial species and strains that are capable of converting daidzein to equol or increasing equol production.

Isoflavone metabolites and their in vitro dual functions: they can act as an estrogenic agonist or antagonist depending on the estrogen concentration

The major soy isoflavones are daidzin and genistin, the glycoside conjugates of daidzein (DZ) and genistein (GTN). After ingestion, they are metabolized into diverse compounds in the gut. The marked inter-individual variation has been suggested in their metabolism. The clinical effects may be modulated by the metabolic ability to produce a more potent metabolite than the precursor. Our study was, therefore, designed to analyze and compare in vitro biologic activities of their metabolites: DZ, GTN, dihydrogenistein (DGTN), dihydrodaidzein (DDZ), tetrahydrodaidzein (TDZ), O-desmethylangolensin (ODMA), and equol (EQL). Furthermore, we investigated their modulatory effects in the presence of estrogen using several in vitro systems. The intermediate metabolites, such as DGTN, DDZ, and TDZ, bind much weakly to both ERs and induce less potently in transcriptional activity, gene expression, and mammary cell proliferation than their precursors. EQL has the strongest binding affinities and estrogenic activities especially for ERbeta among the daidzin metabolites and shows the ability to suppress osteoclast formation at high doses. The test isoflavonoids act like estrogen antagonists with the premenopausal dose of E2 and thus inhibit estrogenic actions by E2, whereas they exert estrogen agonist activity with the lower dose of estrogen close to the serum levels of postmenopausal women. Our results suggest that phytoestrogens such as isoflavones may exert their effects as estrogen antagonists in a high estrogen environment, or they may act as estrogen agonists in a low estrogen environment.

Application of coulometric electrode array detection to the analysis of isoflavonoids and lignans

A comprehensive review of the available methods for the analysis of isoflavonoids and lignans in biological matrices based on coulometric electrode array detection (CEAD) is presented. Different aspects such as sample extraction and purification procedures as well as instrumental settings and method validation are discussed. Comparisons with other available protocols using different detection techniques such as mass spectrometry or immunoassay are also reported to underline the versatility and reliability of the detector. Practical notes and tips for scientists working with CEAD are also provided.