Metabolism of isoflavones, lignans and prenylflavonoids by intestinal bacteria: producer phenotyping and relation with intestinal community

Urinary enterolignans and enterolignan-predicting microbial species are favourably associated with liver fat and other obesity markers

Aims: Plant-derived lignans may protect against obesity, while their bioactivity needs gut microbial conversion to enterolignans. We used repeated measures to identify enterolignan-predicting microbial species and investigate whether enterolignans and enterolignan-predicting microbial species are associated with obesity. Methods: Urinary enterolignans, fecal microbiota, body weight, height, and circumferences of the waist (WC) and hips (HC) were repeatedly measured at the baseline and after 1 year in 305 community-dwelling adults in Huoshan, China. Body composition and liver fat [indicated by the controlled attenuation parameter (CAP)] were measured after 1 year. Multivariate-adjusted linear models and linear mixed-effects models were used to analyze single and repeated measurements, respectively. Results: Enterolactone and enterodiol levels were both inversely associated with the waist-to-hip ratio, body fat mass (BFM), visceral fat level (VFL), and liver fat accumulation (all P < 0.05). Enterolactone levels were also associated with lower WC (β = -0.0035 and P = 0.013) and HC (β = -0.0028 and P = 0.044). We identified multiple bacterial genera whose relative abundance was positively associated with the levels of enterolactone (26 genera) and enterodiol (22 genera, all P false discovery rate < 0.05), and constructed the enterolactone-predicting microbial score and enterodiol-predicting microbial score to reflect the overall enterolignan-producing potential of the host gut microbiota. Both these scores were associated with lower body weight and CAP (all P < 0.05). The enterolactone-predicting microbial score was also inversely associated with the BFM (β = -0.1128 and P = 0.027) and VFL (β = -0.1265 and P = 0.044). Conclusion: Our findings support that modulating the host gut microbiome could be a potential strategy to prevent obesity by enhancing the production of enterolignans.

Enterolignans: from natural origins to cardiometabolic significance, including chemistry, dietary sources, bioavailability, and activity

The enterolignans, enterolactone and enterodiol, the main metabolites produced from plant lignans by the gut microbiota, have enhanced bioavailability and activity compared to their precursors, with beneficial effects on metabolic and cardiovascular health. Although extensively studied, the biosynthesis, cardiometabolic effects, and other therapeutic implications of mammalian lignans are still incompletely understood. The aim of this review is to provide a comprehensive overview of these phytoestrogen metabolites based on up-to-date information reported in studies from a wide range of disciplines. Established and novel synthetic strategies are described, as are the various lignan precursors, their dietary sources, and a proposed metabolic pathway for their conversion to enterolignans. The methodologies used for enterolignan analysis and the available data on pharmacokinetics and bioavailability are summarized and their cardiometabolic bioactivity is explored in detail. The special focus given to research on the health benefits of microbial-derived lignan metabolites underscores the critical role of lignan-rich diets in promoting cardiovascular health.

Successful Outcome of a Patient with Concomitant Pancreatic and Renal Carcinoma Receiving Secoisolariciresinol Diglucoside Therapy Alone: A Case Report

Introduction

Pancreatic cancer (PC) is among the deadliest malignancies. Kidney cancer (KC) is a common malignancy globally. Chemo- or radio-therapies are not very effective to control PC or KC, and overdoses often cause severe site reactions to the patients. As a result, novel treatment strategies with high efficacy but without toxic side effects are urgently desired. Secoisolariciresinol diglucoside (SDG) belongs to plant lignans with potential anticancer activities, but clinical evidence is not available in PC or KC treatment.

Patient Concerns

We report a rare case of an 83-year-old female patient with pancreatic and kidney occupying lesions that lacked the conditions to receive surgery or chemo- or radiotherapy.

Diagnosis

Pancreatic and kidney cancers.

Interventions

We gave dietary SDG to the patient as the only therapeutics.

Outcomes

SDG effectively halted progression of both PC and KC. All clinical manifestations, including bad insomnia, loss of appetite, stomach symptoms, and skin itching over the whole body, all disappeared. The initial massive macroscopic hematuria became microscopic and infrequent, and other laboratory results also gradually returned to normal. Most of the cancer biomarkers, initially high such as CEA, CA199, CA724, CA125, came down rapidly, among which CA199 changed most radically. This patient has had progression-free survival of one year so far.

Conclusion

These results demonstrate the potent inhibitory effects of SDG on PC and KC of this patient and provide promising novel therapeutics for refractory malignant tumors.

The What and Who of Dietary Lignans in Human Health: Special Attention to Estrogen Effects and Safety Evaluation

Lignans are a group of phenolic compounds found in plant-based diets. The human body can obtain lignans through diet, which are then metabolized into enterolignans. The enterolignans have been linked to several health benefits, including anticancer, anti-inflammatory, antioxidant effects, and estrogen effects. This review explores the relationship between the estrogenic effects of lignans and health. This review not only considers the estrogen-like activity of lignans but also discusses the safe dosage of lignans at different life stages. In addition, this review also identified other types of bioactive compounds that can act synergistically with lignans to promote health. Studies have shown that lignan administration during pregnancy and lactation reduces the risk of breast cancer in offspring. Further studies are needed to investigate the estrogenic safety effects of lignan on pregnant women and children. Whether lignans combine with other nutrients in complex food substrates to produce synergistic effects remains to be investigated. This review provides a basis for future studies on the safe dose of lignan and recommended dietary intake of lignan. We believe that the acquired as discussed here has implications for developing dietary therapies that can promote host nutrition and modulate estrogenic diseases.

Accounting Gut Microbiota as the Mediator of Beneficial Effects of Dietary (Poly)phenols on Skeletal Muscle in Aging

Sarcopenia, the age-related loss of muscle mass and function increasing the risk of disability and adverse outcomes in older people, is substantially influenced by dietary habits. Several studies from animal models of aging and muscle wasting indicate that the intake of specific polyphenol compounds can be associated with myoprotective effects, and improvements in muscle strength and performance. Such findings have also been confirmed in a smaller number of human studies. However, in the gut lumen, dietary polyphenols undergo extensive biotransformation by gut microbiota into a wide range of bioactive compounds, which substantially contribute to bioactivity on skeletal muscle. Thus, the beneficial effects of polyphenols may consistently vary across individuals, depending on the composition and metabolic functionality of gut bacterial communities. The understanding of such variability has recently been improved. For example, resveratrol and urolithin interaction with the microbiota can produce different biological effects according to the microbiota metabotype. In older individuals, the gut microbiota is frequently characterized by dysbiosis, overrepresentation of opportunistic pathogens, and increased inter-individual variability, which may contribute to increasing the variability of biological actions of phenolic compounds at the skeletal muscle level. These interactions should be taken into great consideration for designing effective nutritional strategies to counteract sarcopenia.

Interplay between Lignans and Gut Microbiota: Nutritional, Functional and Methodological Aspects

Lignans are non-flavonoid polyphenols present in a wide range of foods frequently consumed in the Western world, such as seeds, vegetables and fruits, and beverages such as coffee, tea and wine. In particular, the human gut microbiota (GM) can convert dietary lignans into biologically active compounds, especially enterolignans (i.e., enterolactone and enterodiol), which play anti-inflammatory and anti-oxidant roles, act as estrogen receptor activators and modulate gene expression and/or enzyme activity. Interestingly, recent evidence documenting those dietary interventions involving foods enriched in lignans have shown beneficial and protective effects on various human pathologies, including colorectal and breast cancer and cardiovascular diseases. However, considering that more factors (e.g., diet, food transit time and intestinal redox state) can modulate the lignans bioactivation by GM, there are usually remarkable inter-individual differences in urine, fecal and blood concentrations of enterolignans; hence, precise and validated analytical methods, especially gas/liquid chromatography coupled to mass spectrometry, are needed for their accurate quantification. Therefore, this review aims to summarize the beneficial roles of enterolignans, their interaction with GM and the new methodological approaches developed for their evaluation in different biological samples, since they could be considered future promising nutraceuticals for the prevention of human chronic disorders.

Meeting report: plant-rich dietary patterns and health

Dietary patterns (DP) rich in plant foods are associated with improved health and reduced non-communicable disease risk. In October 2021, the Nutrition Society hosted a member-led conference, held online over 2 half days, exploring the latest research findings examining plant-rich DP and health. The aim of the present paper is to summarise the content of the conference and synopses of the individual speaker presentations are included. Topics included epidemiological analysis of plant-rich DP and health outcomes, the effects of dietary interventions which have increased fruit and vegetable (FV) intake on a range of health outcomes, how adherence to plant-rich DP is assessed, the use of biomarkers to assess FV intake and a consideration of how modifying behaviour towards increased FV intake could impact environmental outcomes, planetary health and food systems. In conclusion, although there are still considerable uncertainties which require further research, which were considered as part of the conference and are summarised in this review, adopting a plant-rich DP at a population level could have a considerable impact on diet and health outcomes, as well as planetary health.

Feeding Fiber-Bound Polyphenol Ingredients at Different Levels Modulates Colonic Postbiotics to Improve Gut Health in Cats

Simple Summary

Food eaten by humans or companion animals is broken down by enzymes produced by the host and also by bacteria present in the large intestine of the host. Many of the compounds produced can have beneficial effects on the host’s health. Previous studies in dogs evaluated changes after they ate food containing a fiber bundle made of pecan shells, flax seed, and powders from cranberry, citrus, and beet. These studies showed that bacteria in the large intestine switched from digesting mainly protein to digesting mainly carbohydrates resulting in production of compounds with beneficial properties. The study presented here tested this fiber bundle in cats to see which compounds and/or bacteria in the feces changed. After cats consumed food containing the fiber bundle, several compounds associated with beneficial health effects increased, and some compounds that indicate the breakdown of protein decreased. In contrast, little change in fecal bacteria was observed following consumption of food with the fiber bundle. Overall, these findings indicate that, similar to the dog studies, bacteria in the large intestine of cats were able to digest the fiber bundle to make compounds that may contribute to host health and also shifted to digestion of carbohydrates instead of protein.

Abstract

Consumption of fiber in its different forms can result in positive health effects. Prior studies in dogs found that addition of a fiber bundle (composed of pecan shells, flax seed, and powders of cranberry, citrus, and beet) to food resulted in a shift in fecal bacterial metabolism from proteolysis to saccharolysis. The present study evaluated the changes in fecal metabolites and microbiota in healthy cats following the consumption of this fiber bundle. Following a 28-day pre-feed period, 56 healthy adult cats received food with none or one of three concentrations (0%, 1%, 2%, and 4%) of the fiber bundle for a 31-day period. In cats that consumed the 4% fiber bundle, levels of ammonium and fecal branched-chain fatty acids (BCFAs) decreased from baseline and compared with the other groups. Addition of any level of the fiber bundle resulted in increases in beneficial metabolites: polyphenols hesperidin, hesperetin, ponciretin, secoisolariciresinol diglucoside, secoisolariciresinol, and enterodiol. Little change in fecal microbiota was observed. Since higher levels of ammonia and BCFAs indicate putrefactive metabolism, the decreases in these with the 4% fiber bundle indicate a shift toward saccharolytic metabolism despite little change in the microbiota composition.

Structure and function of non-digestible carbohydrates in the gut microbiome

Together with proteins and fats, carbohydrates are one of the macronutrients in the human diet. Digestible carbohydrates, such as starch, starch-based products, sucrose, lactose, glucose and some sugar alcohols and unusual (and fairly rare) α-linked glucans, directly provide us with energy while other carbohydrates including high molecular weight polysaccharides, mainly from plant cell walls, provide us with dietary fibre. Carbohydrates which are efficiently digested in the small intestine are not available in appreciable quantities to act as substrates for gut bacteria. Some oligo- and polysaccharides, many of which are also dietary fibres, are resistant to digestion in the small intestines and enter the colon where they provide substrates for the complex bacterial ecosystem that resides there. This review will focus on these non-digestible carbohydrates (NDC) and examine their impact on the gut microbiota and their physiological impact. Of particular focus will be the potential of non-digestible carbohydrates to act as prebiotics, but the review will also evaluate direct effects of NDC on human cells and systems.

Dietary lignans, plasma enterolactone levels, and metabolic risk in men: exploring the role of the gut microbiome

BACKGROUND

The conversion of plant lignans to bioactive enterolignans in the gastrointestinal tract is mediated through microbial processing. The goal of this study was to examine the relationships between lignan intake, plasma enterolactone concentrations, gut microbiome composition, and metabolic risk in free-living male adults.

RESULTS

In 303 men participating in the Men's Lifestyle Validation Study (MLVS), lignan intake was assessed using two sets of 7-day diet records, and gut microbiome was profiled through shotgun sequencing of up to 2 pairs of fecal samples (n = 911). A score was calculated to summarize the abundance of bacteria species that were significantly associated with plasma enterolactone levels. Of the 138 filtered species, plasma enterolactone levels were significantly associated with the relative abundances of 18 species at FDR < 0.05 level. Per SD increment of lignan intake was associated with 20.7 nM (SEM: 2.3 nM) higher enterolactone concentrations among participants with a higher species score, whereas the corresponding estimate was 4.0 nM (SEM: 1.7 nM) among participants with a lower species score (P for interaction < 0.001). A total of 12 plasma metabolites were also significantly associated with these enterolactone-predicting species. Of the association between lignan intake and metabolic risk, 19.8% (95%CI: 7.3%-43.6%) was explained by the species score alone, 54.5% (95%CI: 21.8%-83.7%) by both species score and enterolactone levels, and 79.8% (95%CI: 17.7%-98.6%) by further considering the 12 plasma metabolites.

CONCLUSION

We identified multiple gut bacteria species that were enriched or depleted at higher plasma levels of enterolactone in men. These species jointly modified the associations of lignan intake with plasma enterolactone levels and explained the majority of association between lignan intake and metabolic risk along with enterolactone levels and certain plasma metabolites.

Dietary Phytoestrogens and Their Metabolites as Epigenetic Modulators with Impact on Human Health

The impact of dietary phytoestrogens on human health has been a topic of continuous debate since their discovery. Nowadays, based on their presumptive beneficial effects, the amount of phytoestrogens consumed in the daily diet has increased considerably worldwide. Thus, there is a growing need for scientific data regarding their mode of action in the human body. Recently, new insights of phytoestrogens’ bioavailability and metabolism have demonstrated an inter-and intra-population heterogeneity of final metabolites’ production. In addition, the phytoestrogens may have the ability to modulate epigenetic mechanisms that control gene expression. This review highlights the complexity and particularity of the metabolism of each class of phytoestrogens, pointing out the diversity of their bioactive gut metabolites. Futhermore, it presents emerging scientific data which suggest that, among well-known genistein and resveratrol, other phytoestrogens and their gut metabolites can act as epigenetic modulators with a possible impact on human health. The interconnection of dietary phytoestrogens’ consumption with gut microbiota composition, epigenome and related preventive mechanisms is discussed. The current challenges and future perspectives in designing relevant research directions to explore the potential health benefits of dietary phytoestrogens are also explored.

Dietary polyphenol and microbiota interactions in the context of prostate health

Recent data strongly indicate a relationship between prostate health and gut microbiota, in which composition and physiological function strictly depend on dietary patterns. The bidirectional interplay of foods containing polyphenols, such as ellagitannins, condensed tannins, lignans, isoflavones, and prenylated flavonoids with human gut microbiota, has been proven to contribute to their impact on prostate health. Considering the attributed role of dietary polyphenols in the prevention of prostate diseases, this paper aims to critically review the studies concerning the influence of polyphenols' postbiotic metabolites on processes associated with the pathophysiology of prostate diseases. Clinical, in vivo, and in vitro studies on polyphenols have been juxtaposed with the current knowledge regarding their pharmacokinetics, microbial metabolism, and potential interactions with microbiota harboring different niches of the human organism. Directions of future research on dietary polyphenols regarding their interaction with microbiota and prostate health have been indicated.

Lignan Intake and Risk of Coronary Heart Disease

BACKGROUND

Evidence regarding lignan consumption in relation to coronary heart disease (CHD) risk remains limited and mixed.

OBJECTIVES

The aim of this study was to prospectively examine associations between lignan intake and CHD risk in U.S. men and women.

METHODS

We prospectively followed 214,108 men and women in 3 cohorts who did not have cardiovascular disease or cancer at baseline. Diet was repeatedly assessed using a validated food frequency questionnaire every 2-4 years since baseline.

RESULTS

During 5,517,225 person-years of follow-up, we documented 10,244 CHD cases, including 6,283 nonfatal myocardial infarction and 3,961 fatal CHD cases. In multivariable-adjusted analyses, comparing extreme quintiles, the pooled hazard ratios of CHD were 0.85 (95% CI: 0.79-0.92) for total lignans, 0.76 (95% CI: 0.71-0.82) for matairesinol, 0.87 (95% CI: 0.81-0.93) for secoisolariciresinol, 0.89 (95% CI: 0.83-0.95) for pinoresinol, and 0.89 (95% CI: 0.83-0.95) for lariciresinol (all P values for trend ≤0.003). Nonlinear relationships were found for total lignan, matairesinol, and secoisolariciresinol: the risk reduction plateaued at intakes above approximately 300 μg/d, 10 μg/d, and 100 μg/d, respectively (P < 0.01 for all nonlinearity). The inverse associations for total lignan intake appeared to be more apparent among participants with higher total fiber intake (P = 0.04 for interaction). In addition, lignan intake was more strongly associated with plasma concentrations of enterolactone when fiber intake was higher.

CONCLUSIONS

Increased long-term intake of lignans was associated with a significantly lower risk of total CHD in both men and women. Possible synergistic effects may exist between lignan and fiber intake in relation to CHD risk reduction, possibly through enhancing the production of enterolignans.

Plant-Based Diet Index and Metabolic Risk in Men: Exploring the Role of the Gut Microbiome

BACKGROUND

Healthy plant-based diet index (hPDI) is associated with a lower risk of cardiometabolic conditions, but its association as well as interactions with microbiome have not been elucidated.

OBJECTIVES

We aimed to investigate the interrelations between hPDI, gut microbiome, and cardiometabolic risk markers.

METHODS

hPDI was derived from dietary assessments by a validated FFQ and was examined in relation to metagenomic profiles of 911 fecal samples collected from 303 men aged 71 ± 4 y with an average BMI (in kg/m2) of 25.2 ± 3.6 in the Men's Lifestyle Validation Study. Principal coordinate (PCo) analysis based on Bray-Curtis dissimilarity was conducted, and interactions between hPDI and PCo were examined by using a metabolic risk score composed of blood lipids, BMI, and glycated hemoglobin.

RESULTS

After multivariable adjustment, hPDI was significantly associated with the relative abundance of 7 species and 9 pathways. In particular, higher hPDI was significantly associated with a higher relative abundance of Bacteroides cellulosilyticus and Eubacterium eligens, amino acid biosynthesis pathways (l-isoleucine biosynthesis I and III and l-valine biosynthesis), and the pathway of pyruvate fermentation to isobutanol. A favorable association between hPDI and the metabolic risk score was more pronounced among men with a higher PCo characterized by higher abundance of Bacteroides uniformis and lower abundance of Prevotella copri. At the individual species level, a similar interaction was also observed between hPDI and P. copri, as well as with Clostridium clostridioforme or Blautia hydrogenotrophica (all P-interaction < 0.01).

CONCLUSION

A greater adherence to a healthy plant-based diet by older men was associated with a microbial profile characterized by a higher abundance of multiple species, including B. cellulosilyticus and E. eligens, as well as pathways in amino acid metabolism and pyruvate fermentation. In addition, inverse associations between healthy plant-based diet and human metabolic risk may partially depend on microbial compositions.

Enterolignan Production in a Flaxseed Intervention Study in Postmenopausal US Women of African Ancestry and European Ancestry

Lignans are phytochemicals studied extensively as dietary factors in chronic disease etiology. Our goal was to examine associations between the gut microbiota and lignan metabolism and whether these associations differ by ethnicity. We conducted a flaxseed (FS) dietary intervention in 252 healthy, postmenopausal women of African ancestry (AA) and European ancestry (EA). Participants consumed ~10 g/d ground flaxseed for 6 weeks and provided overnight urine collections and fecal samples before and after intervention. The gut microbiota was characterized using 16S rRNA gene sequencing and differences in microbial community composition compared by ethnicity and intervention status. We observed a significant difference in the composition of the microbiota measured as beta diversity (p < 0.05) between AA and EA at baseline that was attenuated with FS consumption. Genera that were significantly associated with ENL production (e.g., Klebsiella, Lactobacillus, Slackia, Senegalimassilia) were unique to each group. Bacteria (e.g., Fusobacteria, Pyramidobacter and Odoribacter) previously associated with colorectal cancer and cardiovascular disease, both diet-related chronic diseases, were unique to either AA or EA and were significantly reduced in the FS intervention. This study suggests that ethnic variation in ENL metabolism may be linked to gut microbiota composition, and its impact on disease risk deserves future investigation.

Lignans and Gut Microbiota: An Interplay Revealing Potential Health Implications

Plant polyphenols are a broad group of bioactive compounds characterized by different chemical and structural properties, low bioavailability, and several in vitro biological activities. Among these compounds, lignans (a non-flavonoid polyphenolic class found in plant foods for human nutrition) have been recently studied as potential modulators of the gut-brain axis. In particular, gut bacterial metabolism is able to convert dietary lignans into therapeutically relevant polyphenols (i.e., enterolignans), such as enterolactone and enterodiol. Enterolignans are characterized by various biologic activities, including tissue-specific estrogen receptor activation, together with anti-inflammatory and apoptotic effects. However, variation in enterolignans production by the gut microbiota is strictly related to both bioaccessibility and bioavailability of lignans through the entire gastrointestinal tract. Therefore, in this review, we summarized the most important dietary source of lignans, exploring the interesting interplay between gut metabolites, gut microbiota, and the so-called gut-brain axis.

Gut Microbiota-Polyphenol Interactions in Chicken: A Review

The gastrointestinal tract of the chicken harbors very complex and diverse microbial communities including both beneficial and harmful bacteria. However, a dynamic balance is generally maintained in such a way that beneficial bacteria predominate over harmful ones. Environmental factors can negatively affect this balance, resulting in harmful effects on the gut, declining health, and productivity. This means modulating changes in the chicken gut microbiota is an effective strategy to improve gut health and productivity. One strategy is using modified diets to favor the growth of beneficial bacteria and a key candidate are polyphenols, which have strong antioxidant potential and established health benefits. The gut microbiota-polyphenol interactions are of vital importance in their effects on the gut microbiota modulation because it affects not only the composition of gut bacteria but also improves bioavailability of polyphenols through generation of more bioactive metabolites enhancing their health effects on morphology and composition of the gut microbiota. The object of this review is to improve the understanding of polyphenol interactions with the gut microbiota and highlights their potential role in modulation of the gut microbiota of chicken.

Correlation and association analyses in microbiome study integrating multiomics in health and disease

Correlation and association analyses are one of the most widely used statistical methods in research fields, including microbiome and integrative multiomics studies. Correlation and association have two implications: dependence and co-occurrence. Microbiome data are structured as phylogenetic tree and have several unique characteristics, including high dimensionality, compositionality, sparsity with excess zeros, and heterogeneity. These unique characteristics cause several statistical issues when analyzing microbiome data and integrating multiomics data, such as large p and small n, dependency, overdispersion, and zero-inflation. In microbiome research, on the one hand, classic correlation and association methods are still applied in real studies and used for the development of new methods; on the other hand, new methods have been developed to target statistical issues arising from unique characteristics of microbiome data. Here, we first provide a comprehensive view of classic and newly developed univariate correlation and association-based methods. We discuss the appropriateness and limitations of using classic methods and demonstrate how the newly developed methods mitigate the issues of microbiome data. Second, we emphasize that concepts of correlation and association analyses have been shifted by introducing network analysis, microbe-metabolite interactions, functional analysis, etc. Third, we introduce multivariate correlation and association-based methods, which are organized by the categories of exploratory, interpretive, and discriminatory analyses and classification methods. Fourth, we focus on the hypothesis testing of univariate and multivariate regression-based association methods, including alpha and beta diversities-based, count-based, and relative abundance (or compositional)-based association analyses. We demonstrate the characteristics and limitations of each approaches. Fifth, we introduce two specific microbiome-based methods: phylogenetic tree-based association analysis and testing for survival outcomes. Sixth, we provide an overall view of longitudinal methods in analysis of microbiome and omics data, which cover standard, static, regression-based time series methods, principal trend analysis, and newly developed univariate overdispersed and zero-inflated as well as multivariate distance/kernel-based longitudinal models. Finally, we comment on current association analysis and future direction of association analysis in microbiome and multiomics studies.

Where to Look into the Puzzle of Polyphenols and Health? The Postbiotics and Gut Microbiota Associated with Human Metabotypes

The full consensus on the role of dietary polyphenols as human-health-promoting compounds remains elusive. The two-way interaction between polyphenols and gut microbiota (GM) (i.e., modulation of GM by polyphenols and their catabolism by the GM) is determinant in polyphenols' effects. The identification of human metabotypes associated with a differential gut microbial metabolism of polyphenols has opened new research scenarios to explain the inter-individual variability upon polyphenols consumption. The metabotypes unequivocally identified so far are those involved in the metabolism of isoflavones (equol and(or) O-desmethylangolesin producers versus non-producers) and ellagic acid (urolithin metabotypes, including producers of only urolithin-A (UM-A), producers of urolithin-A, isourolithin-A, and urolithin-B (UM-B), and non-producers (UM-0)). In addition, the microbial metabolites (phenolic-derived postbiotics) such as equol, urolithins, valerolactones, enterolactone, and enterodiol, and 8-prenylnaringenin, among others, can exert differential health effects. The knowledge is updated and position is taken here on i) the two-way interaction between GM and polyphenols, ii) the evidence between phenolic-derived postbiotics and health, iii) the role of metabotypes as biomarkers of GM and the clustering of individuals depending on their metabotypes (metabotyping) to explain polyphenols' effects, and iv) the gut microbial metabolism of catecholamines to illustrate the intersection between personalized nutrition and precision medicine.

Quercetin, Epigallocatechin Gallate, Curcumin, and Resveratrol: From Dietary Sources to Human MicroRNA Modulation

Epidemiologic studies suggest that dietary polyphenol intake is associated with a lower incidence of several non-communicable diseases. Although several foods contain complex mixtures of polyphenols, numerous factors can affect their content. Besides the well-known capability of these molecules to act as antioxidants, they are able to interact with cell-signaling pathways, modulating gene expression, influencing the activity of transcription factors, and modulating microRNAs. Here we deeply describe four polyphenols used as nutritional supplements: quercetin, resveratrol, epigallocatechin gallate (ECGC), and curcumin, summarizing the current knowledge about them, spanning from dietary sources to the epigenetic capabilities of these compounds on microRNA modulation.

The Role of the Gut Microbiome in Predicting Response to Diet and the Development of Precision Nutrition Models. Part II: Results

The gut microbiota is increasingly implicated in the health and metabolism of its human host. The host's diet is a major component influencing the composition and function of the gut microbiota, and mounting evidence suggests that the composition and function of the gut microbiota influence the host's metabolic response to diet. This effect of the gut microbiota on personalized dietary response is a growing focus of precision nutrition research and may inform the effort to tailor dietary advice to the individual. Because the gut microbiota has been shown to be malleable to some extent, it may also allow for therapeutic alterations of the gut microbiota in order to alter response to certain dietary components. This article is the second in a 2-part review of the current research in the field of precision nutrition incorporating the gut microbiota into studies investigating interindividual variability in response to diet. Part I reviews the methods used by researchers to design and carry out such studies as well as analyze the results subsequently obtained. Part II reviews the findings of these studies and discusses the gaps in our current knowledge and directions for future research. The studies reviewed provide the current understanding in this field of research and a foundation from which we may build, utilizing and expanding upon the methods and results they present to inform future studies.

The Role of the Gut Microbiome in Predicting Response to Diet and the Development of Precision Nutrition Models-Part I: Overview of Current Methods

Health care is increasingly focused on health at the individual level. In the rapidly evolving field of precision nutrition, researchers aim to identify how genetics, epigenetics, and the microbiome interact to shape an individual's response to diet. With this understanding, personalized responses can be predicted and dietary advice can be tailored to the individual. With the integration of these complex sources of data, an important aspect of precision nutrition research is the methodology used for studying interindividual variability in response to diet. This article stands as the first in a 2-part review of current research investigating the contribution of the gut microbiota to interindividual variability in response to diet. Part I reviews the methods used by researchers to design and carry out such studies as well as the statistical and bioinformatic methods used to analyze results. Part II reviews the findings of these studies, discusses gaps in our current knowledge, and summarizes directions for future research. Taken together, these reviews summarize the current state of knowledge and provide a foundation for future research on the role of the gut microbiome in precision nutrition.

Transcriptional Regulation of the Equol Biosynthesis Gene Cluster in Adlercreutzia equolifaciens DSM19450T

Given the emerging evidence of equol’s benefit to human health, understanding its synthesis and regulation in equol-producing bacteria is of paramount importance. Adlercreutzia equolifaciens DSM19450^T is a human intestinal bacterium—for which the whole genome sequence is publicly available—that produces equol from the daidzein isoflavone. In the present work, daidzein (between 50 to 200 μM) was completely metabolized by cultures of A. equolifaciens DSM19450^T after 10 h of incubation. However, only about one third of the added isoflavone was transformed into dihydrodaidzein and then into equol. Transcriptional analysis of the ORFs and intergenic regions of the bacterium’s equol gene cluster was therefore undertaken using RT-PCR and RT-qPCR techniques with the aim of identifying the genetic elements of equol biosynthesis and its regulation mechanisms. Compared to controls cultured without daidzein, the expression of all 13 contiguous genes in the equol cluster was enhanced in the presence of the isoflavone. Depending on the gene and the amount of daidzein in the medium, overexpression varied from 0.5- to about 4-log₁₀ units. Four expression patterns of transcription were identified involving genes within the cluster. The genes dzr, ddr and tdr, which code for daidzein reductase, dihydrodaidzein reductase and tetrahydrodaidzein reductase respectively, and which have been shown involved in equol biosynthesis, were among the most strongly expressed genes in the cluster. These expression patterns correlated with the location of four putative ρ-independent terminator sequences in the cluster. All the intergenic regions were amplified by RT-PCR, indicating the operon to be transcribed as a single RNA molecule. These findings provide new knowledge on the metabolic transformation of daidzein into equol by A. equolifaciens DSM19450^T, which might help in efforts to increase the endogenous formation of this compound and/or its biotechnological production.

Intestinal microbiota: a potential target for the treatment of postmenopausal osteoporosis

Postmenopausal osteoporosis (PMO) is a prevalent metabolic bone disease characterized by bone loss and structural destruction, which increases the risk of fracture in postmenopausal women. Owing to the high morbidity and serious complications of PMO, many efforts have been devoted to its prophylaxis and treatment. The intestinal microbiota is the complex community of microorganisms colonizing the gastrointestinal tract. Probiotics, which are dietary or medical supplements consisting of beneficial intestinal bacteria, work in concert with endogenous intestinal microorganisms to maintain host health. Recent studies have revealed that bone loss in PMO is closely related to host immunity, which is influenced by the intestinal microbiota. The curative effects of probiotics on metabolic bone diseases have also been demonstrated. The effects of the intestinal microbiota on bone metabolism suggest a promising target for PMO management. This review seeks to summarize the critical effects of the intestinal microbiota and probiotics on PMO, with a focus on the molecular mechanisms underlying the pathogenic relationship between bacteria and host, and to define the possible treatment options.

Induced Mutagenesis in UGT74S1 Gene Leads to Stable New Flax Lines with Altered Secoisolariciresinol Diglucoside (SDG) Profiles

Flax secoisolariciresinol (SECO) diglucoside (SDG) lignan is an emerging natural product purported to prevent chronic diseases in humans. SECO, the aglycone form of SDG, has shown higher intestinal cell absorption but it is not accumulated naturally in planta. Recently, we have identified and characterized a UDP-glucosyltransferase gene, UGT74S1, that glucosylates SECO into its monoglucoside (SMG) and SDG forms when expressed in yeast. However, whether this gene is unique in controlling SECO glucosylation into SDG in planta is unclear. Here, we report on the use of UGT74S1 in reverse and forward genetics to characterize an ethyl methane sulfonate (EMS) mutagenized flax population from cultivar CDC Bethune and consisting of 1996 M2 families. EMS mutagenesis generated 73 SNP variants causing 79 mutational events in the UGT74S1 exonic regions of 93 M2 families. The mutation frequency in the exonic regions was determined to be one per 28 Kb. Of these mutations, 13 homozygous missense mutations and two homozygous nonsense mutations were observed and all were transmitted into the M3 and M4 generations. Forward genetics screening of the population showed homozygous nonsense mutants completely lacking SDG biosynthesis while the production of SMG was observed only in a subset of the M4 lines. Heterozygous or homozygous M4 missense mutants displayed a wide range of SDG levels, some being greater than those of CDC Bethune. No additional deleterious mutations were detected in these mutant lines using a panel of 10 other genes potentially involved in the lignan biosynthesis. This study provides further evidence that UGT74S1 is unique in controlling SDG formation from SECO and this is the first report of non-transgenic flax germplasm with simultaneous knockout of SDG and presence of SMG in planta.

Effect of Soy Isoflavones on Growth of Representative Bacterial Species from the Human Gut

The present work aimed to assess the susceptibility of dominant and representative bacterial populations from the human gut to isoflavones and their metabolites. To do so, the minimum inhibitory concentration (MIC) of isoflavone glycosides, isoflavone aglycones, and equol to 37 bacterial strains was determined by broth microdilution. Additionally, for 10 representative strains, growth curves, growth rate (μ), and optical density (OD600 nm) of the cultures at 24 h were also determined. MICs of daidzin, genistin, daidzein, and genistein were >2048 μg mL-1 for all strains assayed, while that of equol ranged from 16 μg mL-1 for Bifidobacterium animalis subsp. animalis to >2048 μg mL-1 for Enterobacteriaceae strains. Changes in growth curves, μ, and final OD were observed among the species in the presence of all tested compounds. Genistein reduced μ of Bacteroides fragilis, Lactococcus lactis subsp. lactis, and Slackia equolifaciens, while both genistein and equol increased that of Lactobacillus rhamnosus and Faecalibacterium prausnitzii. Compared to controls, lower final OD in the presence of aglycones and equol were recorded for some strains but were higher for others. Altogether, the results suggest that isoflavone-derived compounds could modify numbers of key bacterial species in the gut, which might be associated with their beneficial properties.

The microbiota and autoimmunity: Their role in thyroid autoimmune diseases

Since the 1970s, the role of infectious diseases in the pathogenesis of Graves' disease (GD) has been an object of intensive research. The last decade has witnessed many studies on Yersinia enterocolitica, Helicobacter pylori and other bacterial organisms and their potential impact on GD. Retrospective, prospective and molecular binding studies have been performed with contrary outcomes. Until now it is not clear whether bacterial infections can trigger autoimmune thyroid disease. Common risk factors for GD (gender, smoking, stress, and pregnancy) reveal profound changes in the bacterial communities of the gut compared to that of healthy controls but a pathogenetic link between GD and dysbiosis has not yet been fully elucidated. Conventional bacterial culture, in vitro models, next generation and high-throughput DNA sequencing are applicable methods to assess the impact of bacteria in disease onset and development. Further studies on the involvement of bacteria in GD are needed and may contribute to the understanding of pathogenetic processes. This review will examine available evidence on the subject.

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.

Phytoestrogen Metabolism by Adult Human Gut Microbiota

Phytoestrogens are plant-derived polyphenols with a structure similar to human estrogens. The three main groups of phytoestrogens, isoflavones, ellagitannins, and lignans, are transformed into equol, urolithins, and enterolignans, respectively, by bacteria. These metabolites have more estrogenic/antiestrogenic and antioxidant activities than their precursors, and they are more bioavailable. The aim of this study was to analyze the metabolism of isoflavones, lignans and ellagitannins by gut microbiota, and to study the possible correlation in the metabolism of these three groups of phytoestrogens. In vitro fermentation experiments were performed with feces samples from 14 healthy adult volunteers, and metabolite formation was measured by HPLC-PAD and HPLC-ESI/MS. Only the microbiota of one subject produced equol, while most of them showed production of O-desmethylangolensin (O-DMA). Significant inter-subject differences were observed in the metabolism of dihydrodaidzein and dihydrogenistein, while the glucoside isoflavones and their aglycones showed less variability, except for glycitin. Most subjects produced urolithins M-5 and E. Urolithin D was not detected, while uroltithin B was found in half of the individuals analyzed, and urolithins A and C were detected in two and four subjects, respectively. Enterolactone was found in all subjects, while enterodiol only appeared in five. Isoflavone metabolism could be correlated with the metabolism of lignans and ellagitannins. However, the metabolism of ellagitannins and lignans could not be correlated. This the first study where the metabolism of the three groups together of phytoestrogen, isoflavones, lignans, and ellagitannins by gut microbiota is analyzed.

Does canine inflammatory bowel disease influence gut microbial profile and host metabolism?

Background

Inflammatory bowel disease (IBD) refers to a diverse group of chronic gastrointestinal diseases, and gut microbial dysbiosis has been proposed as a modulating factor in its pathogenesis. Several studies have investigated the gut microbial ecology of dogs with IBD but it is yet unclear if this microbial profile can alter the nutrient metabolism of the host. The aim of the present study was to characterize the faecal bacterial profile and functionality as well as to determine host metabolic changes in IBD dogs.

Twenty-three dogs diagnosed with IBD and ten healthy control dogs were included. Dogs with IBD were given a clinical score using the canine chronic enteropathy clinical activity index (CCECAI). Faecal short-chain fatty acids (SCFA) and ammonia concentrations were measured and quantitative PCR was performed. The concentration of plasma amino acids, acylcarnitines, serum folate, cobalamin, and indoxyl sulfate was determined.

Results

No significant differences in the abundance of a selection of bacterial groups and fermentation metabolites were observed between the IBD and control groups. However, significant negative correlations were found between CCECAI and the faecal proportion of Lactobacillus as well as between CCECAI and total SCFA concentration. Serum folate and plasma citrulline were decreased and plasma valine was increased in IBD compared to control dogs. Increased plasma free carnitine and total acylcarnitines were observed in IBD compared with control dogs, whereas short-chain acylcarnitines (butyrylcarnitine + isobutyrylcarnitine and, methylmalonylcarnitine) to free carnitine ratios decreased. Dogs with IBD had a higher 3-hydroxyisovalerylcarnitine + isovalerylcarnitine to leucine ratio compared to control dogs.

Conclusions

Canine IBD induced a wide range of changes in metabolic profile, especially for the plasma concentrations of short-chain acylcarnitines and amino acids, which could have evolved from tissue damage and alteration in host metabolism. In addition, dogs with more severe IBD were characterised by a decrease in faecal proportion of Lactobacillus.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-016-0736-2) contains supplementary material, which is available to authorized users.

The Reciprocal Interactions between Polyphenols and Gut Microbiota and Effects on Bioaccessibility

As of late, polyphenols have increasingly interested the scientific community due to their proposed health benefits. Much of this attention has focused on their bioavailability. Polyphenol-gut microbiota interactions should be considered to understand their biological functions. The dichotomy between the biotransformation of polyphenols into their metabolites by gut microbiota and the modulation of gut microbiota composition by polyphenols contributes to positive health outcomes. Although there are many studies on the in vivo bioavailability of polyphenols, the mutual relationship between polyphenols and gut microbiota is not fully understood. This review focuses on the biotransformation of polyphenols by gut microbiota, modulation of gut microbiota by polyphenols, and the effects of these two-way mutual interactions on polyphenol bioavailability, and ultimately, human health.

Equol status and changes in fecal microbiota in menopausal women receiving long-term treatment for menopause symptoms with a soy-isoflavone concentrate

The knowledge regarding the intestinal microbial types involved in isoflavone bioavailability and metabolism is still limited. The present work reports the influence of a treatment with isoflavones for 6 months on the fecal bacterial communities of 16 menopausal women, as determined by culturing and culture-independent microbial techniques. Changes in fecal communities were analyzed with respect to the women's equol-producing phenotype. Compared to baseline, at 1 and 3 months the counts for all microbial populations in the feces of equol-producing women had increased strongly. In contrast, among the non-producers, the counts for all microbial populations at 1 month were similar to those at baseline, and decreased significantly by 3 and 6 months. Following isoflavone intake, major bands in the denaturing gradient gel electrophoresis (DGGE) profiles appeared and disappeared, suggesting important changes in majority populations. In some women, increases were seen in the intensity of specific DGGE bands corresponding to microorganisms known to be involved in the metabolism of dietary phytoestrogens (Lactonifactor longoviformis, Faecalibacterium prausnitzii, Bifidobacterium sp., Ruminococcus sp.). Real-Time quantitative PCR revealed that the Clostridium leptum and C. coccoides populations increased in equol producers, while those of bifidobacteria and enterobacteria decreased, and vice versa in the non-producers. Finally, the Atopobium population increased in both groups, but especially in the non-producers at three months. As the main findings of this study, (i) variations in the microbial communities over the 6-month period of isoflavone supplementation were large; (ii) no changes in the fecal microbial populations that were convincingly treatment-specific were seen; and (iii) the production of equol did not appear to be associated with the presence of, or increase in the population of, any of the majority bacterial types analyzed.

Gut metabolites and bacterial community networks during a pilot intervention study with flaxseeds in healthy adult men

SCOPE

Flaxseeds contain the phytoestrogens lignans that must be activated to enterolignans by intestinal bacteria. We investigated the impact of flaxseeds on fecal bacterial communities and their associations with fecal and blood metabolites.

METHODS AND RESULTS

Nine healthy male adult subjects ingested 0.3 g/kg/day flaxseeds during 1 week. Gut bacteria as well as blood and fecal metabolites were analyzed. Ingestion of flaxseeds triggered a significant increase in the blood concentration of enterolignans, accompanied by fecal excretion of propionate and glycerol. Overall diversity and composition of dominant fecal bacteria remained individual specific throughout the study. Enterolactone production was linked to the abundance of two molecular species identified as Ruminococcus bromii and Ruminococcus lactaris. Most dominant species of the order Bacteroidales were positively associated with fecal concentrations of either acetic, isovaleric, or isobutyric acid, the latter being negatively correlated with blood levels of triglycerides. The relative sequence abundance of one Gemmiger species (Ruminococcaceae) and of Coprococcus comes (Lachnospiraceae) correlated positively with blood levels of LDL cholesterol and triglycerides, respectively.

CONCLUSION

Flaxseeds increase enterolignan production but do not markedly alter fecal metabolome and dominant bacterial communities. The data underline the possible role of members of the family Ruminococcaceae in the regulation of enterolignan production and blood lipids.

Bioaccessibility of lignans from flaxseed (Linum usitatissimum L.) determined by single-batch in vitro simulation of the digestive process

BACKGROUND

Flaxseed is an important source of lignan secoisolariciresinol diglucoside (SDG) and its aglycone, secoisolariciresinol (SECO). These phenolic compounds can be metabolized to the mammalian lignans enterodiol (ED) and enterolactone (EL) by human intestinal microflora. Flaxseed lignans are known for their potential health benefits, which are attributed to their antioxidant and phytoestrogenic properties. The focus of this study was to determine the bioaccessibility of plant and mammalian lignans in whole flaxseed (WF) and flaxseed flour (FF) throughout the entire digestive process. Moreover, the metabolic activity of intestinal microflora was evaluated.

RESULTS

A single-batch in vitro simulation of the digestive process was performed, including fermentation by the intestinal microflora in the colon. Bioaccessibility was calculated as (free lignan)/(total lignan). In digested WF, the bioaccessibility values of SECO, ED and EL were 0.75%, 1.56% and 1.23%, respectively. Conversely, in digested FF, the bioaccessibility values of SDG, ED and EL were 2.06%, 2.72% and 1.04%, respectively. The anaerobic count and short-chain fatty acids indicate that bacteria survival and carbohydrate fermentation occurred.

CONCLUSION

The contents of both SDG and ED were significantly higher in digested FF than in digested WF. FF facilitated the action of intestinal bacteria to release SDG and metabolize ED.

Lactulose increases equol production and improves liver antioxidant status in barrows treated with Daidzein

Equol, one of the intestinal microflora metabolites of daidzein, has gained much attention for having greater bioactivity than its precursor (daidzein and daidzin) and seeming to be promoted by hydrogen gas. The effects of lactulose on the equol-producing capacity and liver antioxidant status of barrows treated with daidzein were investigated in this study. Male castrated piglets (barrows) of Landrace × Duroc, aged 40 days, were randomly divided into the following three groups: control group (C, n = 12, fed an isoflavones-free basic diet), daidzein group (D, n = 12, fed an isoflavones-free basic diet with 50 mg/kg of daidzein supplementation) and daidzein+lactulose group (D+L, n = 12, fed an isoflavones-free basic diet with 1% of lactulose and 50 mg/kg of daidzein supplementation). After 20 days, the profile of short-chain fatty acids in the colon digesta showed that lactulose significantly increased the fermented capacity in the gastrointestinal tract of the barrows. First-void urinary equol concentrations were significantly higher in the D+L group than in the D group (3.13 ± 0.93 compared to 2.11 ± 0.82 μg/ml, respectively). Furthermore, fecal equol levels were also significantly higher in the D+L group than in the D group (12.00 ± 2.68 compared to 10.00 ± 2.26 μg/g, respectively). The population of bacteroidetes and the percentage of bacteroidetes to bacteria in feces were higher in the D+L group than in the D group. The DGGE profiles results indicate that lactulose might shift the pathways of hydrogen utilization, and changing the profiles of SRB in feces. Moreover, the D+L group had weak enhancement of T-SOD and CuZn-SOD activities in the livers of barrows treated with daidzein.

R(-)-O-desmethylangolensin is the main enantiomeric form of daidzein metabolite produced by human in vitro and in vivo

After ingestion, human intestinal bacteria transform daidzein into dihydrodaidzein, which can be further metabolised to O-desmethylangolensin. This metabolite, unlike daidzein, has a chiral centre and can therefore occur as two distinct enantiomers; however, it is unclear which enantiomer is present in humans. The aim of this study was to define in vitro and in vivo the structure of O-desmethylangolensin and then to evaluate its pharmacokinetic parameters. Daidzein metabolism was preliminarily investigated in anaerobic batch cultures inoculated with mixed faecal bacteria from O-desmethylangolensin producer volunteers. The transformation was monitored by liquid chromatography-mass spectrometry and a chiral column was used to distinguish dihydrodaidzein and O-desmethylangolensin enantiomers. These were purified, analysed by circular dichroism and the results established R(-)-O-desmethylangolensin as the main product (enantiomer excess 91%). However, both dihydrodaidzein enantiomers were detected. Similar results were obtained by in vivo trials. The in vitro formation of O-desmethylangolensin seems to be directly correlated with the number of transforming microorganisms. This correlation was found in vivo for tmax but not for other pharmacokinetic indexes. The pharmacokinetics of daidzein, dihydrodaidzein and O-desmethylangolensin were then evaluated in 11 healthy adult O-desmethylangolensin producers after the single administration of soy milk containing 100mg daidzein. The conjugated forms of daidzein, dihydrodaidzein and O-desmethylangolensin represent more than 90 and 95% of the plasmatic and urinary forms, respectively. The Cmax, tmax and half-life of O-desmethylangolensin in plasma were 62±53nM, 28±11 and 15±6h, respectively. Relevant inter-individual variations were observed as indicated by the high standard deviations.

Lactulose promotes equol production and changes the microbial community during in vitro fermentation of daidzein by fecal inocula of sows

Equol has higher biological effects than other isoflavones. However, only about 30-50% of humans possess a microbiota capable of producing equol from dietary daidzein. In recent years, interest has grown in dietary applications to improve equol production in human and other animals. In this study, lactulose was used as a potential equol-promoting prebiotic in vitro. The effect of lactulose on transformation of daidzein into equol by sows' fecal microbiota was investigated. Results showed that lactulose treatment improved bacteria growth parameters, changing the kinetics of fermentation in vitro. Lactulose significantly increased total gas production, T1/2, Tmax, and Rmax. Furthermore, lactulose altered the microflora composition, increased equol production associated with a reduction in the population of methanogen and increased the sulfate-reducing bacteria population during 24 h of incubation. Here, we report for the first time that in a certain condition (sealing or high pressure), via a dihydrodaidzein (DHD) pathway equol might be able to reform to daidzein by further metabolism using lactulose as a substrate. This study proposes that "hydrogen-producing prebiotic" might be a novel way to promote equol production in vivo or in vitro.

A dried yeast fermentate selectively modulates both the luminal and mucosal gut microbiota and protects against inflammation, as studied in an integrated in vitro approach

EpiCor, derived from Saccharomyces cerevisiae, has been shown to have immunomodulating properties in human clinical trials and in vitro. However, the underlying mechanisms behind its immune protection via the gut remain largely unknown. Therefore, the aim of this study was to use an integrated in vitro approach to evaluate the metabolism of EpiCor by the intestinal microflora, its modulating effect on the gut microbiota, and its anti-inflammatory activity on human-derived cell lines. Using the SHIME model, in combination with a mucus adhesion assay, has shown that low doses of EpiCor have a prebiotic-like modulatory effect on the luminal- and mucosa-associated microbiota. These include gradual changes in general community structure, reduction of potential pathogens, quantitative increase in lactobacilli, and qualitative modulation of bifidobacteria. Moreover, by combination of the SHIME with Caco-2 cells and Caco-2/THP1 cocultures, a significant decrease in pro-inflammatory cytokines was observed at the end of the treatment period.

Levels of urinary isoflavones and lignan polyphenols in Japanese women

OBJECTIVES

High consumption of soybean products has been associated with a reduced risk of hormone-sensitive tumors. Soybean products contain phytoestrogens, such as daidzein, and sesame seeds contain secoisolariciresinol. These compounds are further metabolized to equol, enterodiol, and enterolactone by intestinal bacteria. However, individual differences in the metabolizing potential remain unclear. The aim of this study was to evaluate the urinary daidzein, equol, enterodiol, and enterolactone concentrations in women from several different regions of Japan according to age group.

METHODS

Five hundred urine samples collected from Japanese women living in Sapporo, Sendai, Kyoto, Kochi, and Naha were analyzed for daidzein, equol, enterodiol, and enterolactone concentration by gas chromatography-mass spectrometry.

RESULTS

The urinary isoflavone and lignan polyphenol levels did not differ significantly among the sampling sites, except for daidzein, which was highest in urine collected at Naha. The prevalence of equol producers was 39 % in the total study cohort. In equol producers, a positive correlation was observed between the urinary daidzein and equol levels (r = 0.399, p < 0.001). However, there was no significant difference between daidzein concentrations in equol producers and non-producers. Moreover, the levels of enterodiol and enterolactone were higher in equol producers than in equol non-producers. In the multivariate logistic analyses, two factors, Sendai dwelling and current smoking, were found to be significant [equol producers to non-producers: odds ratio 2.15 (95 % confidence interval: 1.17-4.02) and odds ratio 0.32 (0.15-0.63), respectively].

CONCLUSIONS

Our data suggest that geographic factors and smoking status should be considered during the evaluation of equol in urine samples and that the same pathway may be responsible for the metabolism of both isoflavones and lignan polyphenols.