Administration of equol-producing bacteria alters the equol production status in the Simulator of the Gastrointestinal Microbial Ecosystem (SHIME)

Exploring substrate-microbe interactions: a metabiotic approach toward developing targeted synbiotic compositions

Gut microbiota is an important modulator of human health and contributes to high inter-individual variation in response to food and pharmaceutical ingredients. The clinical outcomes of interventions with prebiotics, probiotics, and synbiotics have been mixed and often unpredictable, arguing for novel approaches for developing microbiome-targeted therapeutics. Here, we review how the gut microbiota determines the fate of and individual responses to dietary and xenobiotic compounds via its immense metabolic potential. We highlight that microbial metabolites play a crucial role as targetable mediators in the microbiota-host health relationship. With this in mind, we expand the concept of synbiotics beyond prebiotics' role in facilitating growth and engraftment of probiotics, by focusing on microbial metabolism as a vital mode of action thereof. Consequently, we discuss synbiotic compositions that enable the guided metabolism of dietary or co-formulated ingredients by specific microbes leading to target molecules with beneficial functions. A workflow to develop novel synbiotics is presented, including the selection of promising target metabolites (e.g. equol, urolithin A, spermidine, indole-3 derivatives), identification of suitable substrates and producer strains applying bioinformatic tools, gut models, and eventually human trials.In conclusion, we propose that discovering and enabling specific substrate-microbe interactions is a valuable strategy to rationally design synbiotics that could establish a new category of hybrid nutra-/pharmaceuticals.

Dietary Polyphenol, Gut Microbiota, and Health Benefits

Polyphenols, which are probably the most important secondary metabolites produced by plants, have attracted tremendous attention due to their health-promoting effects, including their antioxidant, anti-inflammatory, antibacterial, anti-adipogenic, and neuro-protective activities, as well as health properties. However, due to their complicated structures and high molecular weights, a large proportion of dietary polyphenols remain unabsorbed along the gastrointestinal tract, while in the large intestine they are biotransformed into bioactive, low-molecular-weight phenolic metabolites through the residing gut microbiota. Dietary polyphenols can modulate the composition of intestinal microbes, and in turn, gut microbes catabolize polyphenols to release bioactive metabolites. To better investigate the health benefits of dietary polyphenols, this review provides a summary of their modulation through in vitro and in vivo evidence (animal models and humans), as well as their possible actions through intestinal barrier function and gut microbes. This review aims to provide a basis for better understanding the relationship between dietary polyphenols, gut microbiota, and host health.

Maternal Supplementation With Different Probiotic Mixture From Late Pregnancy to Day 21 Postpartum: Consequences for Litter Size, Plasma and Colostrum Parameters, and Fecal Microbiota and Metabolites in Sows

The present study determined the effects of different probiotic mixture supplementation to sows from late pregnancy to day 21 postpartum on reproductive performance, colostrum composition, plasma biochemical parameters, and fecal microbiota and metabolites. A total of 80 pregnant sows were randomly assigned to one of four groups (20 sows per group). The sows in the control group (CON group) were fed a basal diet, and those in the BS-A+B, BS-A+BL, and BS-B+BL groups were fed basal diets supplemented with 250 g/t of different probiotic mixture containing either 125 g/t of Bacillus subtilis A (BS-A), Bacillus subtilis B (BS-B), and/or Bacillus licheniformis (BL), respectively. The trial period was from day 85 of pregnancy to day 21 postpartum. The results showed that different dietary probiotic mixture supplementation increased (P < 0.05) the average weaning weight and average daily gain of piglets, while dietary BS-A+BL supplementation increased the number of weaned piglets (P < 0.05), litter weight (P = 0.06), litter weight gain (P = 0.06), and litter daily gain (P = 0.06) at weaning compared with the CON group. Different dietary probiotic mixture supplementation improved (P < 0.05) the colostrum quality by increasing the fat and dry matter concentrations, as well as the protein and urea nitrogen concentrations in the BS-A+BL group. Dietary probiotic mixture BS-B+BL increased the plasma total protein on days 1 and 21 postpartum while decreased the plasma albumin on day 1 postpartum (P < 0.05). In addition, the plasma high-density lipoprotein-cholesterol was increased in the BS-A+B and BS-B+BL groups on day 21 postpartum, while plasma ammonia was decreased in the BS-A+B and BS-A+BL groups on day 1 and in the three probiotic mixtures groups on day 21 postpartum (P < 0.05). Dietary supplementation with different probiotic mixture also modified the fecal microbiota composition and metabolic activity in sows during pregnancy and postpartum stages. Collectively, these findings suggest that maternal supplementation with Bacillus subtilis in combination with Bacillus licheniformis are promising strategies for improving the reproductive performance and the overall health indicators in sows, as well as the growth of their offspring.

Dietary Supplementation With Xylo-oligosaccharides Modifies the Intestinal Epithelial Morphology, Barrier Function and the Fecal Microbiota Composition and Activity in Weaned Piglets

The present study determined the effects of dietary xylo-oligosaccharides (XOS) supplementation on the morphology of jejunum and ileum epithelium, fecal microbiota composition, metabolic activity, and expression of genes related to colon barrier function. A total of 150 piglets were randomly assigned to one of five groups: a blank control group (receiving a basal diet), three XOS groups (receiving the basal diet supplemented with 100, 250, and 500 g/t XOS, respectively), as well as a positive control group, used as a matter of comparison, that received the basal diet supplemented with 0.04 kg/t virginiamycin, 0.2 kg/t colistin, and 3,000 mg/kg ZnO. The trial was carried out for 56 days. The results showed that the lowest dose tested (100 g/t XOS) increased (P < 0.05) the ileal villus height, the relative amount of Lactobacillus and Bifidobacterium spp., and the concentration of acetic acid and short-chain fatty acid in feces when compared with the blank control group. In conclusion, dietary 100 g/t XOS supplementation modifies the intestinal ecosystem in weaned piglets in an apparently overall beneficial way.

Colonization Potential to Reconstitute a Microbe Community in Pseudo Germ-Free Mice After Fecal Microbe Transplant From Equol Producer

Human intestinal microbiota plays a crucial role in the conversion of isoflavones into equol. Usually, human microbiota-associated (HMA) animal models are used, since it is difficult to establish the mechanism and causal relationship between equol and microbiota in human studies. Currently, several groups have successfully established HMA animal models that produce equol through germ-free mice or rats; however, the HMA model of producing equol through pseudo germ-free mice has not been established. The objective of this study is to establish an HMA mice model for equol production through pseudo germ-free mice, mimicking the gut microbiota of an adult human equol producer. First, a higher female equol producer was screened as a donor from 15 volunteers. Then, mice were exposed to vancomycin, neomycin sulfate, metronidazole, and ampicillin for 3 weeks to obtain pseudo germ-free mice. Finally, pseudo germ-free mice were inoculated with fecal microbiota of the equol producer for 3 weeks to establish HMA mice of producing equol. The results showed that (i) the ability to produce equol was partially transferred from the donor to the HMA mice. (ii) Most of the original intestinal microbiota of mice were eliminated after broad-spectrum antibiotic administration. (iii) The taxonomy data from HMA mice revealed similar taxa to the donor sample, and the species richness returned to the level close to the donor. (iv) The family Coriobacteriaceae and genera Collinsella were successfully transferred from the donor to HMA mice. In conclusion, the HMA mice model for equol production, based on pseudo germ-free mice, can replace the model established by germ-free mice. The model also provides a basis for studying microbiota during the conversion from isoflavones into equol.

The Role of the Gut Microbiota in Colorectal Cancer Causation

Here, we reviewed emerging evidence on the role of the microbial community in colorectal carcinogenesis. A healthy gut microbiota promotes intestinal homeostasis and can exert anti-cancer effects; however, this microbiota also produces a variety of metabolites that are genotoxic and which can negatively influence epithelial cell behaviour. Disturbances in the normal microbial balance, known as dysbiosis, are frequently observed in colorectal cancer (CRC) patients. Microbial species linked to CRC include certain strains of Bacteroides fragilis, Escherichia coli, Streptococcus gallolyticus, Enterococcus faecalis and Fusobacterium nucleatum, amongst others. Whether these microbes are merely passive dwellers exploiting the tumour environment, or rather, active protagonists in the carcinogenic process is the subject of much research. The incidence of chemically-induced tumours in mice models varies, depending upon the presence or absence of these microorganisms, thus strongly suggesting influences on disease causation. Putative mechanistic explanations differentially link these strains to DNA damage, inflammation, aberrant cell behaviour and immune suppression. In the future, modulating the composition and metabolic activity of this microbial community may have a role in prevention and therapy.

Equol: A Bacterial Metabolite from The Daidzein Isoflavone and Its Presumed Beneficial Health Effects

Epidemiological data suggest that regular intake of isoflavones from soy reduces the incidence of estrogen-dependent and aging-associated disorders, such as menopause symptoms in women, osteoporosis, cardiovascular diseases and cancer. Equol, produced from daidzein, is the isoflavone-derived metabolite with the greatest estrogenic and antioxidant activity. Consequently, equol has been endorsed as having many beneficial effects on human health. The conversion of daidzein into equol takes place in the intestine via the action of reductase enzymes belonging to incompletely characterized members of the gut microbiota. While all animal species analyzed so far produce equol, only between one third and one half of human subjects (depending on the community) are able to do so, ostensibly those that harbor equol-producing microbes. Conceivably, these subjects might be the only ones who can fully benefit from soy or isoflavone consumption. This review summarizes current knowledge on the microorganisms involved in, the genetic background to, and the biochemical pathways of, equol biosynthesis. It also outlines the results of recent clinical trials and meta-analyses on the effects of equol on different areas of human health and discusses briefly its presumptive mode of action.

Dietary Supplementation With Chinese Herbal Residues or Their Fermented Products Modifies the Colonic Microbiota, Bacterial Metabolites, and Expression of Genes Related to Colon Barrier Function in Weaned Piglets

To explore the feasibility of dietary Chinese herbal residue (CHR) supplementation in swine production with the objective of valorization, we examined the effects of dietary supplementation with CHR or fermented CHR products on the colonic ecosystem (i.e., microbiota composition, luminal bacterial metabolites, and expression of genes related to the intestinal barrier function in weaned piglets). We randomly assigned 120 piglets to one of four dietary treatment groups: a blank control group, CHR group (dose of supplement 4 kg/t), fermented CHR group (dose of supplement 4 kg/t), and a positive control group (supplemented with 0.04 kg/t virginiamycin, 0.2 kg/t colistin, and 3000 mg/kg zinc 0.04 kg/t virginiamycin, 0.2 kg/t colistin, and 3000 mg/kg zinc oxide). Our results indicate that dietary supplementation with CHR increased (P < 0.05) the mRNA level corresponding to E-cadherin compared with that observed in the other three groups, increased (P < 0.05) the mRNA level corresponding to zonula occludens-1, and decreased (P < 0.05) the quantity of Bifidobacterium spp. When compared with the blank control group. Dietary supplementation with fermented CHR decreased (P < 0.05) the concentration of indole when compared to the positive control group; increased (P < 0.05) the concentrations of short-chain fatty acids compared with the values measured in the CHR group, as well as the mRNA levels corresponding to interleukin 1 alpha, interleukin 2, and tumor necrosis factor alpha. However, supplementation with fermented CHR decreased (P < 0.05) interleukin 12 levels when compared with the blank control group. Collectively, these findings suggest that dietary supplementation with CHR or fermented CHR modifies the gut environment of weaned piglets.

Rapid and complete dehalogenation of halonitromethanes in simulated gastrointestinal tract and its influence on toxicity

Halonitromethanes (HNMs) as one typical class of nitrogenous disinfection byproducts in drinking water and wastewater are receiving attentions due to their high toxicity. This study applied a simulator of the human gastrointestinal tract to determine the dehalogenation processes of trichloronitromethane, bromonitromethane and bromochloronitromethane for the first time. Influence of digestion process of HNMs on gut microbiota and hepatotoxicity was further analyzed. Results showed that the three HNMs were rapidly and completely dehalogenated in the gastrointestinal tract, especially in the stomach (2 h retention Time) and small intestine (4 h retention Time). Mucin, cysteine, pancreatin and bile salts in the digestive juice played major roles in the dehalogenation process. HNMs and their dehalogenation products in the resulting fluids of stomach induced the highest toxicity followed by those in intestine and colon, exhibiting dose-dependent effects. Although most HNMs were degraded in the stomach and small intestine, residual HNMs entered into colon changed the microbial community. Abundance of several genera, such as Bacteroides, Lachnospiraceae_unassigned and Lactobacillus had high correlation with exposure concentration of HNMs. This study sheds new light on dehalogenation and toxic processes of HNMs by oral exposure, which provides basic data for their human health risk assessment.

Anti-obesity molecular mechanism of soy isoflavones: weaving the way to new therapeutic routes

Obesity is ringing alarm bells globally. Advances in food science and nutrition research have been devoted to identifying food components that exert anti-obesity effects, as well as investigating the molecular mechanisms by which they modulate the progression of obesity. Soy foods have attracted much interest as high-protein components of the human diet and as unique sources of isoflavones. As they have similar chemical structures to endogenous estrogens, isoflavones are believed to interact with intracellular estrogen receptors, which results in reductions in the accumulation of lipids and the distribution of adipose tissue. Both in vitro and in vivo studies have revealed other signaling pathways in which isoflavones are involved in the inhibition of adipogenesis and lipogenesis by interacting with various transcription factors and upstream signaling molecules. Although the biological mechanisms that cause the biphasic effects of isoflavones and various controversial results remain unknown, it is noteworthy that isoflavones exhibit pleiotropic effects in the human body to regulate metabolism and balance, which may potentially prevent and treat obesity.

Systematic review of the effects of the intestinal microbiota on selected nutrients and non-nutrients

PURPOSE

There is considerable interest in the effects of the intestinal microbiota (IM) composition, its activities in relation with the metabolism of dietary substrates and the impact these effects may have in the development and prevention of certain non-communicable diseases. It is acknowledged that a complex interdependence exists between the IM and the mammalian host and that the IM possesses a far greater diversity of genes and repertoire of metabolic and enzymatic capabilities than their hosts. However, full knowledge of the metabolic activities and interactions of the IM and the functional redundancy that may exist are lacking. Thus, the current review aims to assess recent literature relating to the role played by the IM in the absorption and metabolism of key nutrients and non-nutrients.

METHODS

A systematic review (PROSPERO registration: CRD42015019087) was carried out focussing on energy and the following candidate dietary substrates: protein, carbohydrate, fat, fibre, resistant starch (RS), and polyphenols to further understand the effect of the IM on the dietary substrates and the resulting by-products and host impacts. Particular attention was paid to the characterisation of the IM which are predominantly implicated in each case, changes in metabolites, and indirect markers and any potential impacts on the host.

RESULTS

Studies show that the IM plays a key role in the metabolism of the substrates studied. However, with the exception of studies focusing on fibre and polyphenols, there have been relatively few recent human studies specifically evaluating microbial metabolism. In addition, comparison of the effects of the IM across studies was difficult due to lack of specific analysis/description of the bacteria involved. Considerable animal-derived data exist, but experience suggests that care must be taken when extrapolating these results to humans. Nevertheless, it appears that the IM plays a role in energy homeostasis and that protein microbial breakdown and fermentation produced ammonia, amines, phenols and branch chain fatty acids, and a greater diversity in the microbes present. Few recent studies appear to have evaluated the effect of the IM composition and metabolism per se in relation with digestible dietary carbohydrate or fat in humans. Intakes of RS and prebiotics altered levels of specific taxa that selectively metabolised specific prebiotic/carbohydrate-type substances and levels of bifidobacteria and lactobacilli were observed to increase. In controlled human studies, consistent data exist that show a correlation between the intake of fibre and an increase in bifidobacteria and short-chain fatty acids, in particular butyrate, which leads to lower intestinal pH. Dietary polyphenols rely on modification either by host digestive enzymes or those derived from the IM for absorption to occur. In the polyphenol-related studies, a large amount of inter-individual variation was observed in the microbial metabolism and absorption of certain polyphenols.

CONCLUSIONS

The systematic review demonstrates that the IM plays a major role in the breakdown and transformation of the dietary substrates examined. However, recent human data are limited with the exception of data from studies examining fibres and polyphenols. Results observed in relation with dietary substrates were not always consistent or coherent across studies and methodological limitations and differences in IM analyses made comparisons difficult. Moreover, non-digestible components likely to reach the colon are often not well defined or characterised in studies making comparisons between studies difficult if not impossible. Going forward, further rigorously controlled randomised human trials with well-defined dietary substrates and utilizing omic-based technologies to characterise and measure the IM and their functional activities will advance the field. Current evidence suggests that more detailed knowledge of the metabolic activities and interactions of the IM hold considerable promise in relation with host health.

Soy Improves Cardiometabolic Health and Cecal Microbiota in Female Low-Fit Rats

Phytoestrogen-rich soy is known to ameliorate menopause-associated obesity and metabolic dysfunction for reasons that are unclear. The gut microbiota have been linked with the development of obesity and metabolic dysfunction. We aimed to determine the impact of soy on cardiometabolic health, adipose tissue inflammation, and the cecal microbiota in ovariectomized (OVX) rats bred for low-running capacity (LCR), a model that has been previously shown to mimic human menopause compared to sham-operated (SHM) intact control LCR rats. In this study, soy consumption, without affecting energy intake or physical activity, significantly improved insulin sensitivity and body composition of OVX rats bred for low-running capacity. Furthermore, soy significantly improved blood lipid profile, adipose tissue inflammation, and aortic stiffness of LCR rats. Compared to a soy-free control diet, soy significantly shifted the cecal microbial community of LCR rats, resulting in a lower Firmicutes:Bacteroidetes ratio. Correlations among metabolic parameters and cecal bacterial taxa identified in this study suggest that taxa Prevotella, Dorea, and Phascolarctobacterium may be taxa of interest. Our results suggest that dietary soy ameliorates adiposity, insulin sensitivity, adipose tissue inflammation, and arterial stiffness and exerts a beneficial shift in gut microbial communities in a rat model that mimics human menopause.

Understanding the Molecular Mechanisms of the Interplay Between Herbal Medicines and Gut Microbiota

Herbal medicines (HMs) are much appreciated for their significant contribution to human survival and reproduction by remedial and prophylactic management of diseases. Defining the scientific basis of HMs will substantiate their value and promote their modernization. Ever-increasing evidence suggests that gut microbiota plays a crucial role in HM therapy by complicated interplay with HM components. This interplay includes such activities as: gut microbiota biotransforming HM chemicals into metabolites that harbor different bioavailability and bioactivity/toxicity from their precursors; HM chemicals improving the composition of gut microbiota, consequently ameliorating its dysfunction as well as associated pathological conditions; and gut microbiota mediating the interactions (synergistic and antagonistic) between the multiple chemicals in HMs. More advanced experimental designs are recommended for future study, such as overall chemical characterization of gut microbiota-metabolized HMs, direct microbial analysis of HM-targeted gut microbiota, and precise gut microbiota research model development. The outcomes of such research can further elucidate the interactions between HMs and gut microbiota, thereby opening a new window for defining the scientific basis of HMs and for guiding HM-based drug discovery.

Bioactivation of Phytoestrogens: Intestinal Bacteria and Health

Phytoestrogens are polyphenols similar to human estrogens found in plants or derived from plant precursors. Phytoestrogens are found in high concentration in soya, flaxseed and other seeds, fruits, vegetables, cereals, tea, chocolate, etc. They comprise several classes of chemical compounds (stilbenes, coumestans, isoflavones, ellagitannins, and lignans) which are structurally similar to endogenous estrogens but which can have both estrogenic and antiestrogenic effects. Although epidemiological and experimental evidence indicates that intake of phytoestrogens in foods may be protective against certain chronic diseases, discrepancies have been observed between in vivo and in vitro experiments. The microbial transformations have not been reported so far in stilbenes and coumestans. However, isoflavones, ellagitanins, and lignans are metabolized by intestinal bacteria to produce equol, urolithins, and enterolignans, respectively. Equol, urolithin, and enterolignans are more bioavailable, and have more estrogenic/antiestrogenic and antioxidant activity than their precursors. Moreover, equol, urolithins and enterolignans have anti-inflammatory effects and induce antiproliferative and apoptosis-inducing activities. The transformation of isoflavones, ellagitanins, and lignans by intestinal microbiota is essential to be protective against certain chronic diseases, as cancer, cardiovascular disease, osteoporosis, and menopausal symptoms. Bioavailability, bioactivity, and health effects of dietary phytoestrogens are strongly determined by the intestinal bacteria of each individual.

Fecal bacterial community changes associated with isoflavone metabolites in postmenopausal women after soy bar consumption

Soy isoflavones and their metabolism by intestinal microbiota have gained attention because of potential health benefits, such as the alleviation of estrogen/hormone-related conditions in postmenopausal women, associated with some of these compounds. However, overall changes in gut bacterial community structure and composition in response to addition of soy isoflavones to diets and their association with excreted isoflavone metabolites in postmenopausal women has not been studied. The aim of this study was to determine fecal bacterial community changes in 17 postmenopausal women after a week of diet supplementation with soy bars containing isoflavones, and to determine correlations between microbial community changes and excreted isoflavone metabolites. Using DGGE profiles of PCR amplified 16S rRNA genes (V3 region) to compare microbial communities in fecal samples collected one week before and one week during soy supplementation revealed significant differences (ANOSIM p<0.03) before and after soy supplementation in all subjects. However, between subjects comparisons showed high inter-individual variation that resulted in clustering of profiles by subjects. Urinary excretion of isoflavone (daidzein) metabolites indicated four subjects were equol producers and all subjects produced O-desmethylangolensin (ODMA). Comparison of relative proportions of 16S rRNA genes from 454 pyrosequencing of the last fecal samples of each treatment session revealed significant increases in average proportions of Bifidobacterium after soy consumption, and Bifidobacterium and Eubacterium were significantly greater in equol vs non-S-(-)equol producers. This is the first in vivo study using pyrosequencing to characterize significant differences in fecal community structure and composition in postmenopausal women after a week of soy diet-supplementation, and relate these changes to differences in soy isoflavones and isoflavone metabolites.

Trial Registration

Clinicaltrials.gov NCT00244907

Gut metabotypes govern health effects of dietary polyphenols

Polyphenols are thought to be responsible for some of the health effects conferred by a diet rich in fruit and vegetables. Both the formation of bioactive polyphenol-derived metabolites and the modulation of colonic microbiota contribute to these health benefits. Therefore, one cannot infer biological responses from dietary intake records without considering polyphenol-microbiota interactions. However, the latter are complex and subject to large interindividual variability, leading to different polyphenol-metabolizing phenotypes or 'metabotypes'. Based on accurate measurements of intake, exposure and effect on carefully selected samples, the physiological relevance of dietary polyphenols can be evaluated for each metabotype. Ultimately, this will lead to predictive modeling and the development of (personalized) functional foods and other nutraceuticals with maximized health benefits.

Does equol production determine soy endocrine effects?

Isoflavones, a group of phytoestrogens, are selective oestrogen receptor (ER) modulators. They may positively impact endocrine-related conditions but the current evidence is sparse. Equol, a non-steroidal oestrogen, is produced by the metabolism of the isoflavone daidzein by intestinal bacteria. In Western countries, 30-50% of individuals metabolize daidzein into equol and are known as equol producers. Equol production may be the source of benefit from isoflavones in endocrine disease.

Emerging evidence of the health benefits of S-equol, an estrogen receptor β agonist

Many clinical studies have been carried out to determine the health benefits of soy protein and the isoflavones contained in soy. S-equol is not present in soybeans but is produced naturally in the gut of certain individuals, particularly Asians, by the bacterial biotransformation of daidzein, a soy isoflavone. In those intervention studies in which plasma S-equol levels were determined, a concentration of >5-10 ng/mL has been associated with a positive outcome for vasomotor symptoms, osteoporosis (as measured by an increase in bone mineral density), prostate cancer, and the cardiovascular risk biomarkers low-density lipoprotein cholesterol and C-reactive protein. These studies suggest that S-equol may provide therapeutic benefits for a number of medical needs.

Synthesis of isoflavone aglycones and equol in soy milks fermented by food-related lactic acid bacteria and their effect on human intestinal Caco-2 cells

One hundred and three strains of lactic acid bacteria, isolated from various food ecosystems, were assayed for β-glucosidase activity toward p-nitrophenyl-β-D-glucopyranoside substrate. Lactobacillus plantarum DPPMA24W and DPPMASL33, Lactobacillus fermentum DPPMA114, and Lactobacillus rhamnosus DPPMAAZ1 showed the highest activities and were selected as the mixed starter to ferment various soy milk preparations, which mainly differed for chemical composition, protein dispersibility index, and size dimension. The soy milk made with organically farmed soybeans (OFS) was selected as the best preparation. All selected strains grew well in OFS soy milk, reaching almost the same values of cell density (ca. 8.5 log cfu/mL). After 96 h of fermentation with the selected mixed starter, OFS soy milk contained 57.0 μM daidzein, 140.3 μM genistein, 20.4 μM glycitein, and 37.3 μM equol. Fermented and nonfermented OFS soy milks were used for the in vitro assays on intestinal human Caco-2/TC7 cells. Fermented OFS soy milk markedly inhibited the inflammatory status of Caco-2/TC7 cells as induced by treatment with interferon-γ (IFN-γ) (1000 U/mL) and lipopolysaccharide (LPS) (100 ng/mL), maintained the integrity of the tight junctions, even if subjected to negative stimulation by IFN-γ, and markedly inhibited the synthesis of IL-8, after treatment with interleukin-1β (2 ng/mL). As shown by using chemical standards, these effects were due to the concomitant activities of isoflavone aglycones and, especially, equol, which were synthesized in the fermented OFS soy milk preparation.

The intestinal microbiome: a separate organ inside the body with the metabolic potential to influence the bioactivity of botanicals

For many years, it was believed that the main function of the large intestine was the resorption of water and salt and the facilitated disposal of waste materials. However, this task definition was far from complete, as it did not consider the activity of the microbial content of the large intestine. Nowadays it is clear that the complex microbial ecosystem in our intestines should be considered as a separate organ within the body, with a metabolic capacity which exceeds the liver with a factor 100. The intestinal microbiome is therefore closely involved in the first-pass metabolism of dietary compounds. This is especially true for botanical supplements, which are now marketed for various health applications. Being of natural origin, their structural building blocks, such as polyphenols, are often highly recognized by the human and especially the intestinal microbial metabolism machinery. Intensive metabolism results in often low circulating levels of the original products, with the consequence that final health effects of botanicals are often related to specific active metabolites which are produced in the body rather than being related to the product's original composition. Understanding how such metabolic processes contribute to the in situ exposure is therefore crucial for the proper interpretation of biological responses. A multidisciplinary approach, characterizing the food and phytochemical intake as well as the metabolic potency of the gut microbiota, while measuring biomarkers of both exposure and response in target tissues, is therefore of critical importance. With polyphenol metabolism as example, this review describes how the incorporation of microbial metabolism as an important variable in the evaluation of the final bioactivity of botanicals strongly increases the relevance and predictive value of the outcome. Moreover, knowledge about intestinal processes may offer innovative strategies for targeted product development.

Dietary equol and bone metabolism in postmenopausal Japanese women and osteoporotic mice

Equol binds to the estrogen receptor with greater affinity than its precursor, daidzein, an isoflavone found in soybeans. Inter-individual differences in the ability to produce equol may lead to differential effects of isoflavone intervention on human health. Here, we review previously published work from our laboratory on equol producer status and bone health in humans and in a mouse model of osteoporosis. We performed a 1-y, double-blind, randomized trial to compare the effects of isoflavone (75 mg of isoflavone conjugates/d; equivalent to 47 mg/d of the aglycone form) with those of placebo on bone mineral density (BMD), fat mass, and serum isoflavone concentrations in 54 early postmenopausal Japanese women classified by their equol-producer phenotype. Isoflavone intervention increased the serum equol concentration in equol producers but not in nonproducers (P < 0.04). The annualized changes in BMD in the total hip and intertrochanteric regions in the isoflavone-treated equol producers (-0.46 and -0.04%, respectively) were less than in the nonproducers (-2.28 and -2.61%, respectively). The annualized change in fat mass was lower in the equol producers compared with the nonproducers in the isoflavone group. The annualized changes in BMD and fat mass did not differ between the equol producers and nonproducers in the placebo group. Equol also inhibited bone loss and fat accumulation in estrogen-deficient osteoporotic mice. Our data suggest that prevention of bone loss and fat accumulation in early postmenopausal women by isoflavones may depend on an individual's equol-producing capacity.

Metabolic fate of polyphenols in the human superorganism

Dietary polyphenols are components of many foods such as tea, fruit, and vegetables and are associated with several beneficial health effects although, so far, largely based on epidemiological studies. The intact forms of complex dietary polyphenols have limited bioavailability, with low circulating levels in plasma. A major part of the polyphenols persists in the colon, where the resident microbiota produce metabolites that can undergo further metabolism upon entering systemic circulation. Unraveling the complex metabolic fate of polyphenols in this human superorganism requires joint deployment of in vitro and humanized mouse models and human intervention trials. Within these systems, the variation in diversity and functionality of the colonic microbiota can increasingly be captured by rapidly developing microbiomics and metabolomics technologies. Furthermore, metabolomics is coming to grips with the large biological variation superimposed on relatively subtle effects of dietary interventions. In particular when metabolomics is deployed in conjunction with a longitudinal study design, quantitative nutrikinetic signatures can be obtained. These signatures can be used to define nutritional phenotypes with different kinetic characteristics for the bioconversion capacity for polyphenols. Bottom-up as well as top-down approaches need to be pursued to link gut microbial diversity to functionality in nutritional phenotypes and, ultimately, to bioactivity of polyphenols. This approach will pave the way for personalization of nutrition based on gut microbial functionality of individuals or populations.

Lactobacillus collinoides JCM1123(T): effects on mouse plasma cholesterol and isoflavonoids in the caecum

The effects of Lactobacillus collinoides JCM1123(T) on plasma cholesterol levels, isoflavonoids in the caecum and faecal flora were assessed in adult mice. L. collinoides JCM1123(T) altered the equol production status in in vitro incubation of daidzein with faecal flora of mice. In in vivo investigation, mice were fed an AIN-93M purified diet for 13 days, and then randomly divided into two groups of seven animals each. All mice were fed an AIN-93M diet for 6 days; then the diet was replaced with a 0.05% daidzein diet, the mice received a 0.05% daidzein diet for 4 days. Two groups of mice were administered either L. collinoides JCM1123(T) (the experimental group) or a physiological saline solution (the control group) daily for 10 days and dissection was performed on the following day. The total plasma cholesterol concentration was significantly higher in the control group than in the experimental group. The amount of daidzein present in the caecum was significantly higher in the control group than in the experimental group. Significantly higher numbers of lactobacilli were observed in the experimental group than in the control group. Our data suggest that the administration of L. collinoides is likely to influence the metabolism of isoflavonoids and endogenous cholesterol via changes in the gastrointestinal environment.

The pharmacokinetic behavior of the soy isoflavone metabolite S-(-)equol and its diastereoisomer R-(+)equol in healthy adults determined by using stable-isotope-labeled tracers

BACKGROUND

The nonsteroidal estrogen equol occurs as diastereoisomers, S-(-)equol and R-(+)equol, both of which have significant biological actions. S-(-)equol, the naturally occurring enantiomer produced by 20-30% of adults consuming soy foods, has selective affinity for estrogen receptor-beta, whereas both enantiomers modulate androgen action. Little is known about the pharmacokinetics of the diastereoisomers, despite current interest in developing equol as a nutraceutical or pharmaceutical agent.

OBJECTIVE

The objective was to compare the pharmacokinetics of S-(-)equol and R-(+)equol by using [13C] stable-isotope-labeled tracers to facilitate the optimization of clinical studies aimed at evaluating the potential of these diastereoisomers in the prevention and treatment of estrogen- and androgen-dependent conditions.

DESIGN

A randomized, crossover, open-label study in 12 healthy adults (6 men and 6 women) compared the plasma and urinary pharmacokinetics of orally administered enantiomeric pure forms of S-(-)[2-13C]equol, R-(+)[2-13C]equol, and the racemic mixture. Plasma and urinary [13C]R-equol and [13C]S-equol concentrations were measured by tandem mass spectrometry.

RESULTS

Plasma [13C]equol concentration appearance and disappearance curves showed that both enantiomers were rapidly absorbed, attained high circulating concentrations, and had a similar terminal elimination half-life of 7-8 h. The systemic bioavailability and fractional absorption of R-(+)[2-13C]equol were higher than those of S-(-)[2-13C]equol or the racemate. The pharmacokinetics of racemic (+/-)[2-13C]equol were different from those of the individual enantiomers: slower absorption, lower peak plasma concentrations, and lower systemic bioavailability.

CONCLUSIONS

The high bioavailability of both diastereoisomers contrasts with previous findings for the soy isoflavones daidzein and genistein, both of which have relatively poor bioavailability, and suggests that low doses of equol taken twice daily may be sufficient to achieve biological effects.

Comparison of prebiotic effects of arabinoxylan oligosaccharides and inulin in a simulator of the human intestinal microbial ecosystem

In this study, the prebiotic potential of arabinoxylan oligosaccharides (AXOS) was compared with inulin in two simulators of the human intestinal microbial ecosystem. Microbial breakdown of both oligosaccharides and short-chain fatty acid production was colon compartment specific, with ascending and transverse colon being the predominant site of inulin and AXOS degradation, respectively. Lactate levels (+5.5 mM) increased in the ascending colon during AXOS supplementation, while propionate levels (+5.1 mM) increased in the transverse colon. The concomitant decrease in lactate in the transverse colon suggests that propionate was partially formed over the acrylate pathway. Furthermore, AXOS supplementation strongly decreased butyrate in the ascending colon, this in parallel with a decrease in Roseburia spp. and Bacteroides/Prevotella/Porphyromonas (-1.4 and -2.0 log CFU) levels. Inulin treatment had moderate effects on lactate, propionate and butyrate levels. Denaturing gradient gel electrophoresis analysis revealed that inulin changed microbial metabolism by modulating the microbial community composition. In contrast, AXOS primarily affected microbial metabolism by 'switching on' AXOS-degrading enzymes (xylanase, arabinofuranosidase and xylosidase), without significantly affecting microbial community composition. Our results demonstrate that AXOS has a higher potency than inulin to shift part of the sugar fermentation toward the distal colon parts. Furthermore, due to its stronger propionate-stimulating effect, AXOS is a candidate prebiotic capable of lowering cholesterol and beneficially affecting fat metabolism of the host.

Oestrogenicity of prenylflavonoids from hops: activation of pro-oestrogens by intestinal bacteria

For many centuries, hops (Humulus lupulus L.) have been used as essential ingredient in beers, providing the typical bitterness and hoppy flavour. However, the last few years the plant has gained increasing attention as a source of prenylflavonoids and in 1999, 8-prenylnaringenin (8-PN) was identified as the most potent phyto-oestrogen known so far. Hop extracts are therefore now marketed to reduce menopausal complaints. However, 8-PN concentrations in hops are very low, and variable efficiency of these extracts was observed. Yet, hops also contain isoxanthohumol (IX) in much higher amounts (IX/8-PN ratio in hop extracts is typically 10-20). This article reviews our recent findings on how the human intestinal microbiota may activate IX. Depending on inter-individual differences in the intestinal transformation potential, this conversion could easily increase the 8-PN exposure 10-fold. The variability in efficacy of hop extracts may therefore be explained by variable intestinal metabolism. Based on this scientific knowledge, an innovative strategy was developed to decrease this variability. First, Eubacterium limosum, capable of rapidly metabolizing all IX into 8-PN, was isolated from the complex intestinal ecosystem. This bacterium was then used to develop a new generation of hop products with increased reliability in effect. This strategy involves the use of the bacterium as probiotic, in which the bacterium is administered in combination with the original hop extract. This leads to efficient intestinal 8-PN production, also in individuals who originally did not harbour the appropriate bacteria. The findings presented in this review can therefore be considered as a typical example that good insight in the specific metabolic potential of complex microbial communities and individual bacterial species may offer important opportunities for the management and modulation of the microbial organization towards a certain metabolic function.

Arabinoxylan-oligosaccharides (AXOS) affect the protein/carbohydrate fermentation balance and microbial population dynamics of the Simulator of Human Intestinal Microbial Ecosystem

Arabinoxylan‐oligosaccharides (AXOS) are a recently newly discovered class of candidate prebiotics as – depending on their structure – they are fermented in different regions of gastrointestinal tract. This can have an impact on the protein/carbohydrate fermentation balance in the large intestine and, thus, affect the generation of potentially toxic metabolites in the colon originating from proteolytic activity. In this study, we screened different AXOS preparations for their impact on the in vitro intestinal fermentation activity and microbial community structure. Short‐term fermentation experiments with AXOS with an average degree of polymerization (avDP) of 29 allowed part of the oligosaccharides to reach the distal colon, and decreased the concentration of proteolytic markers, whereas AXOS with lower avDP were primarily fermented in the proximal colon. Additionally, prolonged supplementation of AXOS with avDP 29 to the Simulator of Human Intestinal Microbial Ecosystem (SHIME) reactor decreased levels of the toxic proteolytic markers phenol and p‐cresol in the two distal colon compartments and increased concentrations of beneficial short‐chain fatty acids (SCFA) in all colon vessels (25–48%). Denaturant gradient gel electrophoresis (DGGE) analysis indicated that AXOS supplementation only slightly modified the total microbial community, implying that the observed effects on fermentation markers are mainly caused by changes in fermentation activity. Finally, specific quantitative PCR (qPCR) analysis showed that AXOS supplementation significantly increased the amount of health‐promoting lactobacilli as well as of Bacteroides–Prevotella and Clostridium coccoides–Eubacterium rectale groups. These data allow concluding that AXOS are promising candidates to modulate the microbial metabolism in the distal colon.

Biotransformation of C-glucosylisoflavone puerarin to estrogenic (3S)-equol in co-culture of two human intestinal bacteria

Puerarin and daidzein are the major naturally occurring isoflavones in leguminous plants. These two compounds are metabolized to equol by human intestinal flora. Here we isolated two intestinal bacteria capable of metabolizing puerarin and daidzein, respectively, from human feces. One of them, strain PUE, converted puerarin to daidzein by cleaving a C-glucosyl bond, whereas the other, strain DZE, converted daidzein to equol by reducing a double bond in ring C followed by elimination of an oxo group. Based on the 16S ribosomal RNA gene sequence, strain DZE showed 85% similarity with Eggerthella lenta. Equol produced by strain DZE was identified as (3S)-equol through several analytical methods. Moreover, we obtained (3S)-equol from puerarin by co-incubation with strain PUE and DZE. In addition, 5-hydroxyequol was obtained from genistein by incubation with strain DZE.

Eubacterium limosum activates isoxanthohumol from hops (Humulus lupulus L.) into the potent phytoestrogen 8-prenylnaringenin in vitro and in rat intestine

Recently, it was shown that the exposure to the potent hop phytoestrogen 8-prenylnaringenin (8-PN) depends on intestinal bacterial activation of isoxanthohumol (IX), but this occurs in only one-third of tested individuals. As the butyrate-producing Eubacterium limosum can produce 8-PN from IX, a probiotic strategy was applied to investigate whether 8-PN production could be increased in low 8-PN producers, thus balancing phytoestrogen exposure. Using fecal samples from high (Hop +) and low (Hop -) 8-PN-producing individuals, a Hop + and Hop - dynamic intestinal model was developed. In parallel, Hop + and Hop - human microbiota-associated rats were developed, germ-free (GF) rats acting as negative controls. IX and then IX + E. limosum were administered in the intestinal model and to the rats, and changes in 8-PN production and exposure were assessed. After dosing IX, 80% was converted into 8-PN in the Hop + model and highest 8-PN production, plasma concentrations, and urinary and fecal excretion occurred in the Hop + rats. Administration of the bacterium triggered 8-PN production in the GF rats and increased 8-PN production in the Hop - model and Hop - rats. 8-PN excretion was similar in the feces (294.1 +/- 132.2 nmol/d) and urine (8.5 +/- 1.1 nmol/d ) of all rats (n = 18). In addition, butyrate production increased in all rats. In conclusion, intestinal microbiota determined 8-PN production and exposure after IX intake. Moreover, E. limosum administration increased 8-PN production in low producers, resulting in similar 8-PN production in all rats.

Metabolism of the lignan macromolecule into enterolignans in the gastrointestinal lumen as determined in the simulator of the human intestinal microbial ecosystem

Estrogenic plant compounds from the human diet such as the lignan secoisolariciresinol diglucoside (SDG, 1) can exert biological activity in the human body upon ingestion and bioactivation to enterodiol (END, 5) and enterolactone (ENL, 6). Bioavailability of lignans is influenced by the food matrix and gut microbial action, of which the latter is subject to a large interindividual variation. In this study, the fate of the lignan precursor SDG, present in the lignan macromolecule of flax seed ( Linum usitatissimum), was determined during an artificial stomach and small intestinal digestion and during metabolism by two different enterolignan phenotypes in a TWINSHIME environment (TWIN Simulator of the Human Intestinal Microbial Ecosystem). The lignan macromolecule acted as a delivery system of SDG in the large intestine. SDG was only hydrolyzed into secoisolariciresinol (SECO, 2) through microbial action in the ascending colon, after which it was bioactivated into enterolignans from the transverse colon onward. Single demethylation was a first step in the bioactivation, followed by dehydroxylation. Enterolignan phenotypes remained stable throughout the experimental period. The establishment of END and ENL production equilibria reflected the subdominance of ENL-producing bacteria in the gastrointestinal tract.

Probiotics: a critical review of their potential role as antihypertensives, immune modulators, hypocholesterolemics, and perimenopausal treatments

The conventional use of probiotics to modulate gastrointestinal health, such as in improving lactose intolerance, increasing natural resistance to infectious diseases in the gastrointestinal tract, suppressing traveler's diarrhea, and reducing bloating, has been well investigated and documented. Most of the mechanisms reported to date are mainly caused by the suppression of pathogenic bacteria. Currently, the potential applications of probiotics are being expanded beyond alleviating gastrointestinal disorders to include benefits involving antihypertension, immunomodulation, improving serum lipid profiles, and the alleviation of postmenopausal disorders. Although they seem promising, most of these postulated benefits are based on in vitro evaluations, and the lack of in vivo evidence and/or incompatible outcomes between in vitro experiments and in vivo trials has led to inconclusive claims. This present review highlights some of the previous roles of probiotics on gut health and addresses several potential roles currently being investigated.

Live encapsulated Lactobacillus acidophilus cells in yogurt for therapeutic oral delivery: preparation and in vitro analysis of alginate–chitosan microcapsulesThis article is one of a selection of papers published in this special issue (part 1 of 2) on the Safety and Efficacy of Natural Health Products

Targeted delivery of live microencapsulated bacterial cells has strong potential for application in treating various diseases, including diarrhea, kidney failure, liver failure, and high cholesterol, among others. This study investigates the potential of microcapsules composed of two natural polymers, alginate and chitosan (AC), and the use of these artificial cells in yogurt for delivery of probiotic Lactobacillus acidophilus bacterial live cells. Results show that the integrity of AC microcapsules was preserved after 76 h of mechanical shaking in MRS broth and after 12 h and 24 h in simulated gastric and intestinal fluids. Using an in vitro computer-controlled simulated human gastrointestinal (GI) model, we found 8.37 log CFU/mL of viable bacterial cells were present after 120 min of gastric exposure and 7.96 log CFU/mL after 360 min of intestinal exposure. In addition, AC microcapsules composed of chitosan 10 and 100 at various concentrations were subjected to 4-week storage in 2% milk fat yogurt or 0.85% physiological solution. It was found that 9.37 log CFU/mL of cells encapsulated with chitosan 10 and 8.24 log CFU/mL of cells encapsulated with chitosan 100 were alive after 4 weeks. The AC capsule composed of 0.5% chitosan 10 provided the highest bacterial survival of 9.11 log CFU/mL after 4 weeks. Finally, an investigation of bacterial viability over 72 h in different pH buffers yielded highest survival of 6.34 log CFU/mL and 10.34 log CFU/mL at pH 8 for free and AC-encapsulated cells, respectively. We conclude from these findings that encapsulation allows delivery of a higher number of bacteria to desired targets in the GI tract and that microcapsules containing bacterial cells are good candidates for oral artificial cells for bacterial cell therapy.

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.

Models for intestinal fermentation: association between food components, delivery systems, bioavailability and functional interactions in the gut

There is increasing interest in the human colonic microbiota and in the way its metabolic activities impact on host health and well-being. For most practical purposes, however, the large bowel is inaccessible for routine investigation, and a variety of animal and in vitro model systems have been developed to study the microbiota. In vitro models range from simple closed systems using pure or defined mixed populations of bacteria, or faecal material, to more sophisticated complex multistage continuous cultures that are able to simulate many of the spatial, temporal and environmental attributes that characterize microbiological events in different regions of the large gut. Recent developments using these systems have enabled modelling of surface colonisation and biofilm development, a hitherto neglected area of study.