Gut microbial metabolism of polyphenols from black tea and red wine/grape juice is source-specific and colon-region dependent

Dietary flavonoids modulate the gut microbiota: A new perspective on improving autism spectrum disorder through the gut-brain axis

Autism spectrum disorder (ASD) is a neurodevelopmental disorder with an unknown etiology. It is associated with various factors and causes great inconvenience to the patient's life. The gut-brain axis (GBA), which serves as a bidirectional information channel for exchanging information between the gut microbiota and the brain, is vital in studying many neurodegenerative diseases. Dietary flavonoids provide anti-inflammatory and antioxidant benefits, as well as regulating the structure and function of the gut microbiota. The occurrence and development of ASD are associated with dysbiosis of the gut microbiota. Modulation of gut microbiota can effectively improve the severity of ASD. This paper reviews the links between gut microbiota, flavonoids, and ASD, focusing on the mechanism of dietary flavonoids in regulating ASD through the GBA.

Lychee pulp phenolics fermented by mixed lactic acid bacteria strains promote the metabolism of human gut microbiota fermentation in vitro

Lychee pulp phenolics possess excellent biological activities, however, changes in phenolic substances after microbial treatments are unknown. Herein, lychee pulp was fermented by Lactobacillus plantarum, Lactobacillus rhamnosus, and a mixed strain of the two, followed by an investigation of the products' colonic fermentation. In comparison to single-strain fermentation, mixed-strain fermentation significantly increased catechin and quercetin. In addition, lychee phenolics fermented by mixed strains were more conducive to the growth of gut microbiota. The results of HPLC-DAD showed that colonic fermentation further promoted the release of lychee phenolics. There was a notable increase in the content of gallic acid and quercetin, while multiple phenolics were degraded. Quercetin-3-O-rutinose-7-O-α-L-rhamnoside (QRR) and rutin were catabolized into quercetin by gut microbiota, and 4-hydroxybenzoic acid was produced from the metabolism of QRR and procyanidin B2. Lychee phenolics fermented by mixed lactic acid bacteria were easily metabolized and transformed by gut microbiota. These findings indicate that lychee pulp fermented by mixed lactic acid bacteria possesses probiotic potential, which is of great significance for the development of functional probiotic products.

A Critical Review on Akkermansia muciniphila: Functional Mechanisms, Technological Challenges, and Safety Issues

Due to its physiological benefits from in vitro and in vivo points of view, Akkermansia muciniphila, a common colonizer in the human gut mucous layer, has consistently been identified as an option for the next-generation probiotic. A. muciniphila is a significant bacterium that promotes host physiology. However, it also has a great deal of potential to become a probiotic due to its physiological advantages in a variety of therapeutic circumstances. Therefore, it can be established that the abundance of A. muciniphila in the gut environment, which is controlled by many genetic and dietary variables, is related to the biological behaviors of the intestinal microbiota and gut dysbiosis/eubiosis circumstances. Before A. muciniphila is widely utilized as a next-generation probiotic, regulatory obstacles, the necessity for significant clinical trials, and the sustainability of manufacturing must be eliminated. In this review, the outcomes of recent experimental and clinical reports are comprehensively reviewed, and common colonization patterns, main factors involved in the colonization of A. muciniphila in the gut milieu, their functional mechanisms in establishing homeostasis in the metabolic and energy pathways, the promising delivery role of microencapsulation, potential genetic engineering strategies, and eventually safety issues of A. muciniphila have been discussed.

Evaluation of Different Advanced Approaches to Simulation of Dynamic In Vitro Digestion of Polyphenols from Different Food Matrices-A Systematic Review

Phenolic compounds have become interesting bioactive antioxidant compounds with implications for obesity, cancer and inflammatory gastrointestinal pathologies. As the influence of digestion and gut microbiota on antioxidant behavior is yet to be completely elucidated, and due to limitations associated to in vivo studies, dynamic in vitro gastrointestinal models have been promoted. A systematic review was conducted of different databases (PubMed, Web of Science and Scopus) following PRISMA guidelines to assess different dynamic digestion models and assay protocols used for phenolic compound research regarding bioaccesibility and interaction with colonic microbiota. Of 284 records identified, those including dynamic multicompartmental digestion models for the study of phenolic compound bioaccesibility, bioactivity and the effects of microbiota were included, with 57 studies meeting the inclusion criteria. Different conditions and experimental configurations as well as administered doses, sample treatments and microbiological assays of dynamic digestion studies on polyphenols were recorded and compared to establish their relevance for the dynamic in vitro digestion of phenolic compounds. While similarities were observed in certain experimental areas, a high variability was found in others, such as administered doses. A description of considerations on the study of the digestion of phenolic compounds is proposed to enhance comparability in research.

Polyphenols as Drivers of a Homeostatic Gut Microecology and Immuno-Metabolic Traits of Akkermansia muciniphila: From Mouse to Man

Akkermansia muciniphila is a mucosal symbiont considered a gut microbial marker in healthy individuals, as its relative abundance is significantly reduced in subjects with gut inflammation and metabolic disturbances. Dietary polyphenols can distinctly stimulate the relative abundance of A. muciniphila, contributing to the attenuation of several diseases, including obesity, type 2 diabetes, inflammatory bowel diseases, and liver damage. However, mechanistic insight into how polyphenols stimulate A. muciniphila or its activity is limited. This review focuses on dietary interventions in rodents and humans and in vitro studies using different phenolic classes. We provide critical insights with respect to potential mechanisms explaining the effects of polyphenols affecting A. muciniphila. Anthocyanins, flavan-3-ols, flavonols, flavanones, stilbenes, and phenolic acids are shown to increase relative A. muciniphila levels in vivo, whereas lignans exert the opposite effect. Clinical trials show consistent findings, and high intervariability relying on the gut microbiota composition at the baseline and the presence of multiple polyphenol degraders appear to be cardinal determinants in inducing A. muciniphila and associated benefits by polyphenol intake. Polyphenols signal to the AhR receptor and impact the relative abundance of A. muciniphila in a direct and indirect fashion, resulting in the restoration of intestinal epithelial integrity and homeostatic crosstalk with the gut microbiota by affecting IL-22 production. Moreover, recent evidence suggests that A. muciniphila participates in the initial hydrolysis of some polyphenols but does not participate in their complete metabolism. In conclusion, the consumption of polyphenol-rich foods targeting A. muciniphila as a pivotal intermediary represents a promising precision nutritional therapy to prevent and attenuate metabolic and inflammatory diseases.

Microbial dysbiosis and epigenetics modulation in cancer development - A chemopreventive approach

An overwhelming number of research articles have reported a strong relationship of the microbiome with cancer. Microbes have been observed more commonly in the body fluids like urine, stool, mucus of people with cancer compared to the healthy controls. The microbiota is responsible for both progression and suppression activities of various diseases. Thus, to maintain healthy human physiology, host and microbiota relationship should be in a balanced state. Any disturbance in this equilibrium, referred as microbiome dysbiosis becomes a prime cause for the human body to become more prone to immunodeficiency and cancer. It is well established that some of these microbes are the causative agents, whereas others may encourage the formation of tumours, but very little is known about how these microbial communications causing change at gene and epigenome level and trigger as well as encourage the tumour growth. Various studies have reported that microbes in the gut influence DNA methylation, DNA repair and DNA damage. The genes and pathways that are altered by gut microbes are also associated with cancer advancement, predominantly those implicated in cell growth and cell signalling pathways. This study exhaustively reviews the current research advancements in understanding of dysbiosis linked with colon, lung, ovarian, breast cancers and insights into the potential molecular targets of the microbiome promoting carcinogenesis, the epigenetic alterations of various potential targets by altered microbiota, as well as the role of various chemopreventive agents for timely prevention and customized treatment against various types of cancers.

Interactions between dietary flavonoids and the gut microbiome: a comprehensive review

Flavonoids are natural polyphenol secondary metabolites that are widely produced in planta. Flavonoids are ubiquities in human dietary intake and exhibit a myriad of health benefits. Flavonoids-induced biological activities are strongly influenced by their in situ availability in the human GI tract, as well as the levels of which are modulated by interaction with the gut bacteria. As such, assessing flavonoids–microbiome interactions is considered a key to understand their physiological activities. Here, we review the interaction between the various classes of dietary flavonoids (flavonols, flavones, flavanones, isoflavones, flavan-3-ols and anthocyanins) and gut microbiota. We aim to provide a holistic overview of the nature and identity of flavonoids on diet and highlight how flavonoids chemical structure, metabolism and impact on humans and their microbiomes are interconnected. Emphasis is placed on how flavonoids and their biotransformation products affect gut microbiota population, influence gut homoeostasis and induce measurable physiological changes and biological benefits.

The Role of Nutritional Factors in the Modulation of the Composition of the Gut Microbiota in People with Autoimmune Diabetes

Type 1 diabetes mellitus (T1DM) is a disease marked by oxidative stress, chronic inflammation, and the presence of autoantibodies. The gut microbiota has been shown to be involved in the alleviation of oxidative stress and inflammation as well as strengthening immunity, thus its’ possible involvement in the pathogenesis of T1DM has been highlighted. The goal of the present study is to analyze information on the relationship between the structure of the intestinal microbiome and the occurrence of T1DM. The modification of the intestinal microbiota can increase the proportion of SCFA-producing bacteria, which could in turn be effective in the prevention and/or treatment of T1DM. The increased daily intake of soluble and non-soluble fibers, as well as the inclusion of pro-biotics, prebiotics, herbs, spices, and teas that are sources of phytobiotics, in the diet, could be important in improving the composition and activity of the microbiota and thus in the prevention of metabolic disorders. Understanding how the microbiota interacts with immune cells to create immune tolerance could enable the development of new therapeutic strategies for T1DM and improve the quality of life of people with T1DM.

Akkermansia muciniphila: from its critical role in human health to strategies for promoting its abundance in human gut microbiome

Akkermansia muciniphila, a frequent colonizer in the gut mucous layer of individuals, has constantly been recognized as a promising candidate for the next generation of probiotics due to its biological advantages from in vitro and in vivo investigations. This manuscript comprehensively reviewed the features of A. muciniphila in terms of its function in host physiology and frequently utilized nutrition using the published peer-reviewed articles, which should present valuable and critical information to scientists, engineers, and even the general population. A. muciniphila is an important bacterium that shows host physiology. However, its physiological advantages in several clinical settings also have excellent potential to become a probiotic. Consequently, it can be stated that there is a coherent and direct relation between the biological activities of the gut microbiota, intestinal dysbiosis/eubiosis, and the population of A. muciniphila in the gut milieu, which is influenced by various genetical and nutritional factors. Current regulatory barriers, the need for large-scale clinical trials, and the feasibility of production must be removed before A muciniphila can be extensively used as a next-generation probiotic.

Polyphenols-Gut Microbiota Interrelationship: A Transition to a New Generation of Prebiotics

The present review summarizes the studies carried out on this topic in the last five years. According to the new definitions, among all the compounds included in the group of prebiotics, polyphenols are probably the most important secondary metabolites produced by the plant kingdom. Many of these types of polyphenols have low bioavailability, therefore reaching the colon in unaltered form. Once in the colon, these compounds interact with the intestinal microbes bidirectionally by modulating them and, consequently, releasing metabolites. Despite much research on various metabolites, little is known about the chemistry of the metabolic routes used by different bacteria species. In this context, this review aims to investigate the prebiotic effect of polyphenols in preclinical and clinical studies, highlighting that the consumption of polyphenols leads to an increase in beneficial bacteria, as well as an increase in the production of valuable metabolites. In conclusion, there is much evidence in preclinical studies supporting the prebiotic effect of polyphenols, but further clinical studies are needed to investigate this effect in humans.

Phenolic Compounds Promote Diversity of Gut Microbiota and Maintain Colonic Health

The role of non-energy-yielding nutrients on health has been meticulously studied, and the evidence shows that a compound can exert significant effects on health even if not strictly required by the organism. Phenolic compounds are among the most widely studied molecules that fit this description; they are found in plants as secondary metabolites and are not required by humans for growth or development, but they can influence a wide array of processes that modulate health across multiple organs and systems. The lower gastrointestinal tract is a prime site of action of phenolic compounds, namely, by their effects on gut microbiota and colonic health. As with humans, phenolic compounds are not required by most bacteria but can be substrates of others; in fact, some phenolic compounds exert antibacterial actions. A diet rich in phenolic compounds can lead to qualitative and quantitative effects on gut microbiota, thereby inducing indirect health effects in mammals through the action of these microorganisms. Moreover, phenolic compounds may be fermented by the gut microbiota, thereby modulating the compounds bioactivity. In the colon, phenolic compounds promote anti-inflammatory, anti-oxidant and antiproliferative actions. The aim of the present review is to highlight the role of phenolic compounds on maintaining or restoring a healthy microbiota and overall colonic health. Mechanisms of action that substantiate the reported evidence will also be discussed.

Pu-erh tea extraction alleviates intestinal inflammation in mice with flora disorder by regulating gut microbiota

Pu-erh tea is very popular in Southwestern China and South Asian countries and is now becoming increasingly popular in Europe due to its well-documented beneficial effects on human health. Pu-erh tea aqueous extracts can maintain intestinal homeostasis. However, the mechanism of its beneficial effects on intestinal flora disorder is not clear. In this study, we focused on the effects of ripe Pu-erh tea aqueous extracts on the intestinal microbiota in an intestinal flora disorder mouse model. Physiological indexes and the tissue section staining results showed that feeding Pu-erh tea extract could help mice regain weight and alleviate intestinal inflammation. Further assessment of the intestinal microflora found that Pu-erh tea extract could promote the growth of intestinal probiotics and inhibit pathogenic bacteria, thereby achieving a treatment effect for enteritis. This study provides new evidence for the therapeutic effect of Pu-erh tea.

A Crosstalk between Diet, Microbiome and microRNA in Epigenetic Regulation of Colorectal Cancer

A still growing interest between human nutrition in relation to health and disease states can be observed. Dietary components shape the composition of microbiota colonizing our gastrointestinal tract which play a vital role in maintaining human health. There is a strong evidence that diet, gut microbiota and their metabolites significantly influence our epigenome, particularly through the modulation of microRNAs. These group of small non-coding RNAs maintain cellular homeostasis, however any changes leading to impaired expression of miRNAs contribute to the development of different pathologies, including neoplastic diseases. Imbalance of intestinal microbiota due to diet is primary associated with the development of colorectal cancer as well as other types of cancers. In the present work we summarize current knowledge with particular emphasis on diet-microbiota-miRNAs axis and its relation to the development of colorectal cancer.

Understanding the Gastrointestinal Protective Effects of Polyphenols using Foodomics-Based Approaches

Plant polyphenols are rich sources of natural anti-oxidants and prebiotics. After ingestion, most polyphenols are absorbed in the intestine and interact with the gut microbiota and modulated metabolites produced by bacterial fermentation, such as short-chain fatty acids (SCFAs). Dietary polyphenols immunomodulatory role by regulating intestinal microorganisms, inhibiting the etiology and pathogenesis of various diseases including colon cancer, colorectal cancer, inflammatory bowel disease (IBD) and colitis. Foodomics is a novel high-throughput analysis approach widely applied in food and nutrition studies, incorporating genomics, transcriptomics, proteomics, metabolomics, and integrating multi-omics technologies. In this review, we present an overview of foodomics technologies for identifying active polyphenol components from natural foods, as well as a summary of the gastrointestinal protective effects of polyphenols based on foodomics approaches. Furthermore, we critically assess the limitations in applying foodomics technologies to investigate the protective effect of polyphenols on the gastrointestinal (GI) system. Finally, we outline future directions of foodomics techniques to investigate GI protective effects of polyphenols. Foodomics based on the combination of several analytical platforms and data processing for genomics, transcriptomics, proteomics and metabolomics studies, provides abundant data and a more comprehensive understanding of the interactions between polyphenols and the GI tract at the molecular level. This contribution provides a basis for further exploring the protective mechanisms of polyphenols on the GI system.

Huangjinya Black Tea Alleviates Obesity and Insulin Resistance via Modulating Fecal Metabolome in High-Fat Diet-Fed Mice

SCOPE

Huangjinya is a light-sensitive tea mutant containing low levels of tea polyphenols. Currently, most studies focused on characteristics formation, free amino acid metabolism and phytochemical purification. The biological activity of Huangjinya black tea (HJBT) on metabolic syndrome regarding fecal metabolome modulation is unavailable and is studied herein.

METHODS AND RESULTS

High-fat diet (HFD)-fed mice are treated with HJBT for 9 weeks, various metabolic biomarkers and fecal metabolites are determined. HJBT reduces adipogenic and lipogenic gene expression, enhances lipolytic gene expression, decreases adipocyte expansion, and prevents the development of obesity. HJBT reduces lipogenic gene expression, increases fatty acid oxidation-related genes expression, which alleviates liver steatosis. HJBT enhances glucose/insulin tolerance, increases insulin/Akt signaling, attenuates hyperlipidemia and hyperglycemia, prevents the onset of insulin resistance. HJBT modulates bile acid metabolism, promotes secondary/primary bile acid ratio; increases short-chain fatty acids production, promotes saturated and polyunsaturated fatty acids content; reduces carnitines and phosphocholines, but increases myo-inositol content; decreases branched-chain and aromatic amino acids content; increases the metabolite content related to pentose phosphate pathway.

CONCLUSION

This study reported the association between fecal metabolome modulation and metabolism improvement due to HJBT administration, proposes HJBT as a dietary intervention for preventing obesity and metabolic disorders.

Current and future experimental approaches in the study of grape and wine polyphenols interacting gut microbiota

Interactions between polyphenols and gut microbiota are indeed a major issue of current interest in food science research. Knowledge in this subject is progressing as the experimental procedures and analysis techniques do. The aim of this article is to critically review the more leading-edge approaches that have been applied so far in the study of the interactions between grape/wine polyphenols and gut microbiota. This is the case of in vitro dynamic gastrointestinal simulation models that try to mitigate the limitations of simple static models (batch culture fermentations). More complex approaches include the experimentation with animals (mice, rats, pigs, lambs and chicks) and nutritional intervention studies in humans. Main advantages and limitations as well as the most relevant findings achieved by each approach in the study of how grape/wine polyphenols can modulate the composition and/or functionality of gut microbiota, are detailed. Also, common findings obtained by the three approaches (in vitro, animal models and human nutritional interventions) such as the fact that the Firmicutes/Bacteroidetes ratio tends to decrease after the feed/intake/consumption of grape/wine polyphenols are highlighted. Additionally, a nematode (Caenorhabditis elegans) model, previously used for investigating the mechanisms of processes such as aging, neurodegeneration, oxidative stress and inflammation, is presented as an emerging approach for the study of polyphenols interacting gut microbiota. © 2020 Society of Chemical Industry.

Feature-Based Molecular Networking Analysis of the Metabolites Produced by In Vitro Solid-State Fermentation Reveals Pathways for the Bioconversion of Epigallocatechin Gallate

Dark teas are prepared by a microbial fermentation process. Flavan-3-ol B-ring fission analogues (FBRFAs) are some of the key bioactive constituents that characterize dark teas. The precursors and the synthetic mechanism involved in the formation of FBRFAs are not known. Using a unique solid-state fermentation system with β-cyclodextrin inclusion complexation as well as targeted chromatographic isolation, spectroscopic identification, and Feature-based Molecular Networking on the Global Natural Products Social Molecular Networking web platform, we reveal that dihydromyricetin and the FBRFAs, including teadenol A and fuzhuanin A, are derived from epigallocatechin gallate upon exposure to fungal strains isolated from Fuzhuan brick tea. In particular, the strains from subphylum Pezizomycotina were key drivers for these B-/C-ring oxidation transformations. These are the same transformations seen during the fermentation process of dark teas. These discoveries set the stage to enrich dark teas and other food products for these health-promoting constituents.

Influence of In Vitro Digestion on Composition, Bioaccessibility and Antioxidant Activity of Food Polyphenols-A Non-Systematic Review

There is increased interest in following a healthy lifestyle and consuming a substantial portion of secondary plant metabolites, such as polyphenols, due to their benefits for the human body. Food products enriched with various forms of fruits and vegetables are sources of pro-health components. Nevertheless, in many cases, the level of their activities is changed in in vivo conditions. The changes are strictly connected with processes in the digestive system that transfigure the structure of the active compounds and simultaneously keep or modify their biological activities. Much attention has focused on their bioavailability, a prerequisite for further physiological functions. As human studies are time consuming, costly and restricted by ethical concerns, in vitro models for investigating the effects of digestion on these compounds have been developed to predict their release from the food matrix, as well as their bioaccessibility. Most typically, models simulate digestion in the oral cavity, the stomach, the small intestine and, occasionally, the large intestine. The presented review aims to discuss the impact of in vitro digestion on the composition, bioaccessibility and antioxidant activity of food polyphenols. Additionally, we consider the influence of pH on antioxidant changes in the aforementioned substances.

Akkermansia muciniphila: a promising target for the therapy of metabolic syndrome and related diseases

The probiotic Akkermansia muciniphila (A. muciniphila) is an intestinal bacterium that was first identified in human feces in 2004. Its specialization in mucin degradation makes it a key microorganism that maintains intestinal mucosal barrier function. As an unique representative strain of the phylum Verrucomicrobia that can be cultured in vitro, A. muciniphila is much easier to detect by metagenomic analysis of intestinal flora. In the past few years, A. muciniphila has been getting increasing attention for the positive correlation between its intestinal colonization and host homeostatic metabolism. In this review, we summarize the relationship between A. muciniphila and host health and diseases, especially focusing on metabolic diseases and related mechanisms, as well as the natural food and drug-derived substrates affecting its colonization in the host, expecting to provide evidence and clues for the development of drugs targeting A. muciniphila.

Plant-polyphenols based second-generation synbiotics: Emerging concepts, challenges, and opportunities

There is a growing interest in identifying alternatives to traditional oligosaccharide-based prebiotic agents owing to their undesirable attributes, such as a lack of microbial growth specificity and limited inherent bioactivity. In addition, a novel concept of second-generation synbiotic agents is currently emerging, which argues that prebiotic agents could be best defined on the basis of their physiological effects or functional capacities in the host rather than their specific microbial targets. Plant polyphenols are rapidly emerging as suitable prebiotic and synbiotic candidates that may fulfil these criteria. As we begin to understand the intricate interrelationship between dietary polyphenols and the gut microbiome, a functional synergy can be observed that suggests the appropriateness of the amalgamation of polyphenols and probiotic agents to develop second-generation synbiotic agents. In the present review, we study evidence pertaining to the prebiotic and synbiotic attributes of polyphenols, as well as their relationship with probiotic bacteria, and discuss their efficacy, suitability, and strategies to develop second-generation synbiotic agents. We provide a perspective that polyphenol-based synbiotic agents are fundamentally superior to the traditional carbohydrate-based synbiotic agents and could therefore offer health benefits of both polyphenols and probiotic agents in a synergistic manner.

Capsaicin has an anti-obesity effect through alterations in gut microbiota populations and short-chain fatty acid concentrations

Background

Capsaicin (CAP) has an anti-obesity effect that has been shown to involve the transient receptor potential vanilloid-1 (TRPV1) channel. Importantly, recent studies in high fat diet (HFD)-fed mice show that CAP also alters gut microbiota composition and causes weight loss in HFD-fed mice. Many studies have suggested that short-chain fatty acids (SCFAs) mediate the links between diet, gut microbiota, and fat storage.

Objective

The present study investigated whether CAP exerted its anti-obesity effect through changes in the composition of gut microbiota and SCFAs, and whether the TRPV1 contributes to CAP’s effects against obesity in HFD-fed mice.

Design

C57BL/6J (TRPV1+/+) and B6.129X1-Trpv1tm1Jul/J (TRPV1-/-) mice were respectively divided into three groups (n = 6),that is SLD, HFD-fed, and CAP (2 mg/kg, po) +HFD fed and were administered respective treatment for 12 weeks.

Results

We observed significantly lower weight gain and food intake, triglyceride, cholesterol, glucose, and insulin levels in HFD+CAP-fed TRPV1knockout (KO) mice compared to the HFD-fed KO mice, though this effect was more obvious in wild-type (WT) mice. CAP increased the numbers of Akkermansia, Prevotella, Bacteroides, Odoribacter, Allobaculum, Coprococcus, and S24-7, and reduced the numbers of Desulfovibrio, Escherichia, Helicobacter, and Sutterella in the HFD+CAP-fed WT and KO mice compared with HFD-fed WT and KO mice. CAP increased the relative abundances of SCFAs producing the bacterial species, which increased intestinal acetate and propionate concentrations, which were beneficial in prevention and treatment of obesity.

Conclusions

Results from our study indicate that the reduced food intake and anti-obesity effect of CAP had been observed regardless of TRPV1 channel activation, and which is mediated by changes in the gut microbiota populations and SCFAs concentrations.

Release and metabolism of bound polyphenols from carrot dietary fiber and their potential activity in in vitro digestion and colonic fermentation

Dietary fiber is a carrier of abundant polyphenols and the potential benefits have attracted increasing attention.

Gastrointestinal digestion of food-use silver nanoparticles in the dynamic SIMulator of the GastroIntestinal tract (simgi®). Impact on human gut microbiota

The increasing use of silver nanoparticles (AgNPs) in consumer products has led to concern about their impact on human health. This paper aims to provide new scientific evidence about the modifications and potential effects of AgNPs with food applications during their passage through the digestive tract. For that, two types of AgNPs [solid polyethylene glycol-stabilised silver nanoparticles (PEG-AgNPs 20) and liquid glutathione-stabilised silver nanoparticles (GSH-AgNPs)] were initially subjected to gut-microbial digestion simulation in an in vitro static model. Based on these experiments, digestion of GSH-AgNPs was carried out in a dynamic model (simgi^®) that simulated the different regions of the digestive tract (stomach, small intestine and the ascending, transverse and descending colon) in physiological conditions. Dynamic transport of GSH-AgNPs in the simgi^® was similar to that observed for the inert compound Cr-EDTA, which discarded any alterations in the intestinal fluid delivery due to the AgNPs. Also, feeding the simgi^® with GSH-AgNPs seemed not to induce significant changes in the composition and metabolic activity (i.e., proteolytic activity) of the gut microbiota. Concerning monitoring of AgNps, it was observed that the GSH-AgNPs underwent several transformations in the gastrointestinal fluids and appeared to expose the intestine in ways that were structurally different from the original forms. In compliance with European guidelines, the simgi^® model can be considered a useful in vitro tool to evaluate the effects of nanoparticles at the digestive level, prior to human studies, and, therefore, minimising animal testing.

The effects of grape and red wine polyphenols on gut microbiota - A systematic review

There is a growing body of evidence implicating the gut 'microbiome' role in overall human health. Bacterial species belonging to the genera Lactobacillus and Bifidobacterium are generally considered to be beneficial and are commonly used in probiotic applications, whereas increases in some genera including Clostridum, Eubacterium and Bacteroides are implicated in negative health outcomes. Dietary polyphenols are bioactive compounds that have been found to increase the numbers of beneficial bacteria and antimicrobial actions against pathogenic bacteria, however most studies have been conducted in animal models or in-vitro colonic models. The aim of this systematic review was to provide an overview of recent trials on the effect of dietary grape and red wine polyphenols on the gut microbiota in humans. Following PRISMA guidelines, a systematic review was conducted of electronic databases (PubMed, CINAHL, Cochrane Library, Wed of Science and Scopus) to identify human intervention trials examining the effect of grape or wine polyphenols on gut microbiota. Seven trials met the inclusion criteria. One study looked at changes in gut microbiota following the ingestion of de-alcoholised red wine or red wine, and six studies referred to gut microbiota as intermediates in formation of phenolic metabolites. All studies confirmed that ingested polyphenols from grape and red wine, were modulated by gut microbiota, increasing numbers of polyphenolic metabolites which were found in blood, urine, ileal fluid and faeces. Intake of polyphenols derived from grape and red wine can modulate gut microbiota and contribute to beneficial microbial ecology that can enhance human health benefits. Additionally, grape and red wine polyphenols were modulated by the gut microbiota and there is a potential for a two-way relationship between the gut microbiota and polyphenolic compounds. Nevertheless, additional research is required to fully understand the complex relationship between gut microbiota and dietary polyphenols before any health claims can be made in relation to human health.

Green tea extract and black tea extract differentially influence cecal levels of short-chain fatty acids in rats

Increasing evidence indicates that gut microbiota plays a critical role to maintain the host's health. The biological function of microbially produced short-chain fatty acids (SCFA) becomes the focus of attention. This study aimed to compare the effects of green tea extract (GTE) and black tea extract (BTE) on cecal levels of SCFA in rats. Rats consumed an assigned diet of either a control diet, a GTE diet (10 g/kg), or a BTE diet (10 g/kg), for 3 weeks. The dietary addition of GTE significantly reduced the concentrations of acetate and butyrate in cecal digesta compared to the control, but BTE showed an increased trend for a cecal pool. In the GTE group, a significant amount of undigested starch was excreted in feces, but BTE produced no effect. Interestingly, feces of rats fed the BTE diet contained higher bacterial 16S rRNA gene copy numbers for total eubacteria compared to the control diet. Taken together, treatments of the diets with GTE and BTE brought about a different degree of producing SCFA in rat cecum. BTE might advantageously stimulate more SCFA production than GTE by facilitating bacterial utilization of starch.

Microbial Biotransformation of a Polyphenol-Rich Potato Extract Affects Antioxidant Capacity in a Simulated Gastrointestinal Model

A multistage human gastrointestinal model was used to digest a polyphenol-rich potato extract containing chlorogenic acid, caffeic acid, ferulic acid, and rutin as the primary polyphenols, to assess for their microbial biotransformation and to measure changes in antioxidant capacity in up to 24 h of digestion. The biotransformation of polyphenols was assessed by liquid chromatography-mass spectrometry. Antioxidant capacity was measured by the ferric reducing antioxidant power (FRAP) assay. Among the colonic reactors, parent (poly)phenols were detected in the ascending (AC), but not the transverse (TC) or descending (DC) colons. The most abundant microbial phenolic metabolites in all colonic reactors included derivatives of propionic acid, acetic acid, and benzoic acid. As compared to the baseline, an earlier increase in antioxidant capacity (T = 8 h) was seen in the stomach and small intestine vessels as compared to the AC (T = 16 h) and TC and DC (T = 24 h). The increase in antioxidant capacity observed in the DC and TC can be linked to the accumulation of microbial smaller-molecular-weight phenolic catabolites, as the parent polyphenolics had completely degraded in those vessels. The colonic microbial digestion of potato-based polyphenols could lead to improved colonic health, as this generates phenolic metabolites with significant antioxidant potential.

Apigenin Impacts the Growth of the Gut Microbiota and Alters the Gene Expression of Enterococcus

Apigenin is a major dietary flavonoid with many bioactivities, widely distributed in plants. Apigenin reaches the colon region intact and interacts there with the human gut microbiota, however there is little research on how apigenin affects the gut bacteria. This study investigated the effect of pure apigenin on human gut bacteria, at both the single strain and community levels. The effect of apigenin on the single gut bacteria strains Bacteroides galacturonicus, Bifidobacterium catenulatum, Lactobacillus rhamnosus GG, and Enterococcus caccae, was examined by measuring their anaerobic growth profiles. The effect of apigenin on a gut microbiota community was studied by culturing a fecal inoculum under in vitro conditions simulating the human ascending colon. 16S rRNA gene sequencing and GC-MS analysis quantified changes in the community structure. Single molecule RNA sequencing was used to reveal the response of Enterococcus caccae to apigenin. Enterococcus caccae was effectively inhibited by apigenin when cultured alone, however, the genus Enterococcus was enhanced when tested in a community setting. Single molecule RNA sequencing found that Enterococcus caccae responded to apigenin by up-regulating genes involved in DNA repair, stress response, cell wall synthesis, and protein folding. Taken together, these results demonstrate that apigenin affects both the growth and gene expression of Enterococcus caccae.

Bioavailability of Black Tea Theaflavins: Absorption, Metabolism, and Colonic Catabolism

Data obtained with in vitro fecal incubations and a feeding study indicate black tea theaflavin and its galloyl derivatives are not absorbed in detectable amounts in either the upper or lower gastrointestinal tract. The theaflavin skeleton is comparatively resistant to degradation by colonic bacteria with a 67% recovery being obtained after a 24 h incubation, which yielded 21 phenolic and aromatic catabolites. The theaflavin galloyl moiety was removed by the microbiota, and the released gallic acid further transformed to 3-O- and 4-O-methyl gallic acids, pyrogallol-1-sulfate and pyrogallol-2-sulfate, which were excreted in urine in amounts equivalent to 94% of intake. The main urinary product potentially derived from breakdown of the theaflavin skeleton was 3-(4'-hydroxyphenyl)propionic acid. A number of the colonic catabolites originating from gallic acid and theaflavins has been reported to be bioactive in ex vivo and in vitro models with a variety of potential modes of action.

Adherence to a Mediterranean Diet Influences the Fecal Metabolic Profile of Microbial-Derived Phenolics in a Spanish Cohort of Middle-Age and Older People

Despite the evidence regarding the influence of certain polyphenol food sources on the metabolic profile in feces, the association between the different phenolics provided by the diet and the fecal phenolic profile has not been elucidated. In this study, the composition of phenolic metabolites in fecal solutions was analyzed by UPLC-ESI-MS/MS in 74 volunteers. This fecal phenolic profile showed a high interindividual variation of the different compounds analyzed, phenylacetic and phenylpropionic acids being the major classes of phenolic metabolites excreted in feces. Subjects with higher adherence to a Mediterranean dietary pattern presented greater fecal concentrations of benzoic and 3-hydroxyphenylacetic acids, positively correlated with the intake of the principal classes and subclasses of polyphenols and fibers, and higher levels of Clostridium cluster XVIa and Faecalibacterium prausnitzii. These results provide a link among the Mediterranean dietary pattern, the bioactive compounds of the diet, and the fecal metabolic phenolic profile.

The Gastrointestinal Tract as a Key Target Organ for the Health-Promoting Effects of Dietary Proanthocyanidins

Proanthocyanidins (PACs) are polymers of flavan-3-ols abundant in many vegetable foods and beverages widely consumed in the human diet. There is increasing evidence supporting the beneficial impact of dietary PACs in the prevention and nutritional management of non-communicable chronic diseases. It is considered that PACs with a degree of polymerization >3 remain unabsorbed in the gastrointestinal (GI) tract and accumulate in the colonic lumen. Accordingly, the GI tract may be considered as a key organ for the healthy-promoting effects of dietary PACs. PACs form non-specific complexes with salivary proteins in mouth, originating the sensation of astringency, and with dietary proteins, pancreatic enzymes, and nutrient transporters in the intestinal lumen, decreasing the digestion and absorption of carbohydrates, proteins, and lipids. They also exert antimicrobial activities, interfering with cariogenic or ulcerogenic pathogens in the mouth (Streptococcus mutans) and stomach (Helicobacter pylori), respectively. Through their antioxidant and antiinflammatory properties, PACs decrease inflammatory processes in animal model of gastric and colonic inflammation. Interestingly, they exert prebiotic activities, stimulating the growth of Lactobacillus spp. and Bifidobacterium spp. as well as some butyrate-producing bacteria in the colon. Finally, PACs are also metabolized by the gut microbiota, producing metabolites, mainly aromatic acids and valerolactones, which accumulate in the colon and/or are absorbed into the bloodstream. Accordingly, these compounds could display biological activities on the colonic epithelium or in extra-intestinal tissues and, therefore, contribute to part of the beneficial effects of dietary PACs.

Alterations to metabolically active bacteria in the mucosa of the small intestine predict anti-obesity and anti-diabetic activities of grape seed extract in mice

Grape seed extract changes small intestinal gut microbiota composition.

Challenges in simulating the human gut for understanding the role of the microbiota in obesity

There is an elevated incidence of cases of obesity worldwide. Therefore, the development of strategies to tackle this condition is of vital importance. This review focuses on the necessity of optimising in vitro systems to model human colonic fermentation in obese subjects. This may allow to increase the resolution and the physiological relevance of the information obtained from this type of studies when evaluating the potential role that the human gut microbiota plays in obesity. In light of the parameters that are currently used for the in vitro simulation of the human gut (which are mostly based on information derived from healthy subjects) and the possible difference with an obese condition, we propose to revise and improve specific standard operating procedures.

Assessment of dietary exposure and effect in humans: The role of NMR

In human nutritional science progress has always depended strongly on analytical measurements for establishing relationships between diet and health. This field has undergone significant changes as a result of the development of NMR and mass spectrometry methods for large scale detection, identification and quantification of metabolites in body fluids. This has allowed systematic studies of the metabolic fingerprints that biological processes leave behind, and has become the research field of metabolomics. As a metabolic profiling technique, NMR is at its best when its unbiased nature, linearity and reproducibility are exploited in well-controlled nutritional intervention and cross-sectional population screening studies. Although its sensitivity is less good than that of mass spectrometry, NMR has maintained a strong position in metabolomics through implementation of standardisation protocols, hyphenation with mass spectrometry and chromatographic techniques, accurate quantification and spectral deconvolution approaches, and high-throughput automation. Thus, NMR-based metabolomics has contributed uniquely to new insights into dietary exposure, in particular by unravelling the metabolic fates of phytochemicals and the discovery of dietary intake markers. NMR profiling has also contributed to the understanding of the subtle effects of diet on central metabolism and lipoprotein metabolism. In order to hold its ground in nutritional metabolomics, NMR will need to step up its performance in sensitivity and resolution; the most promising routes forward are the analytical use of dynamic nuclear polarisation and developments in microcoil construction and automated fractionation.

Characterizing Blood Metabolomics Profiles Associated with Self-Reported Food Intakes in Female Twins

Using dietary biomarkers in nutritional epidemiological studies may better capture exposure and improve the level at which diet-disease associations can be established and explored. Here, we aimed to identify and evaluate reproducibility of novel biomarkers of reported habitual food intake using targeted and non-targeted metabolomic blood profiling in a large twin cohort. Reported intakes of 71 food groups, determined by FFQ, were assessed against 601 fasting blood metabolites in over 3500 adult female twins from the TwinsUK cohort. For each metabolite, linear regression analysis was undertaken in the discovery group (excluding MZ twin pairs discordant [≥1 SD apart] for food group intake) with each food group as a predictor adjusting for age, batch effects, BMI, family relatedness and multiple testing (1.17x10^-6 = 0.05/[71 food groups x 601 detected metabolites]). Significant results were then replicated (non-targeted: P<0.05; targeted: same direction) in the MZ discordant twin group and results from both analyses meta-analyzed. We identified and replicated 180 significant associations with 39 food groups (P<1.17x10^-6), overall consisting of 106 different metabolites (74 known and 32 unknown), including 73 novel associations. In particular we identified trans-4-hydroxyproline as a potential marker of red meat intake (0.075[0.009]; P = 1.08x10^-17), ergothioneine as a marker of mushroom consumption (0.181[0.019]; P = 5.93x10^-22), and three potential markers of fruit consumption (top association: apple and pears): including metabolites derived from gut bacterial transformation of phenolic compounds, 3-phenylpropionate (0.024[0.004]; P = 1.24x10^-8) and indolepropionate (0.026[0.004]; P = 2.39x10^-9), and threitol (0.033[0.003]; P = 1.69x10^-21). With the largest nutritional metabolomics dataset to date, we have identified 73 novel candidate biomarkers of food intake for potential use in nutritional epidemiological studies. We compiled our findings into the DietMetab database (http://www.twinsuk.ac.uk/dietmetab-data/), an online tool to investigate our top associations.

Foodomics as part of the host-microbiota-exposome interplay

The functional complexity of human gut microbiota and its relationship with host physiology and environmental modulating factors, offers the opportunity to investigate (i) the host and microbiota role in organism-environment relationship; (ii) the individual functional diversity and response to environmental stimuli (exposome); (iii) the host genome and microbiota metagenomes' modifications by diet-mediated epigenomic controls (nutriepigenomics); and (iv) the genotype-phenotype "trajectories" under physiological and disease constraints. Systems biology-based approaches aim at integrating biological data at cellular, tissue and organ organization levels, using computational modeling to interpret diseases' physiopathological mechanisms (i.e., onset and progression). Proteomics improves the existing gene models by profiling molecular phenotypes at protein abundance level, by analyzing post-translational modifications and protein-protein interactions and providing specific pathway information, hence contributing to functional molecular networks. Transcriptomics and metabolomics may determine host ad microbiota changes induced by food ingredients at molecular level, complementing functional genomics and proteomics data. Since foodomics is an -omic wide methodology may feed back all integrative data to foster the omics-based systems medicine field. Hence, coupled to ecological genomics of gut microbial communities, foodomics may highlight health benefits from nutrients, dissecting diet-induced gut microbiota eubiosis mechanisms and significantly contributing to understand and prevent complex disease phenotypes.

BIOLOGICAL SIGNIFICANCE

Besides transcriptomics and proteomics there is a growing interest in applying metabolic profiling to food science for the development of functional foods. Indeed, one of the biggest challenges of modern nutrition is to propose a healthy diet to populations worldwide, intrinsically respecting the high inter-individual variability, driven by complex host/nutrients/microbiota/environment interactions. Therefore, metabolic profiling can assist at various levels for the development of functional foods, starting from screening for food composition to identification of new biomarkers to trace food intake. This current approach can support diet intervention strategies, epidemiological studies, and controlling of metabolic disorders worldwide spreading, hence ensuring healthy aging. With high-throughput molecular technologies driving foodomics, studying bidirectional interactions of host-microbial co-metabolism, innate immune development, dysfunctional nutrient absorption and processing, complex signaling pathways involved in nutritional metabolism, is now likely. In all cases, as microbiome pipeline efforts continue, it is possible that enhanced standardized protocols can be developed, which may lead to new testable biological and clinical hypotheses. This Review provides a comprehensive update on the current state-of-the-art of the integrated -omics route in food, microbiota and host co-metabolism studies, which may revolutionize the design of new dietary intervention strategies.

Biotransformation of polyphenols in a dynamic multistage gastrointestinal model

A multi-reactor gastrointestinal model was used to digest a mixture of pure polyphenol compounds, including non-flavonoid phenolic acids (chlorogenic acid, caffeic acid, ferulic acid) and a flavonoid (rutin) to identify phenolic metabolites and short chain fatty acids (SCFAs) and compare relative antioxidant capacities following a 24h digestion. Biotransformation of these polyphenols occurred in the colonic compartments generating phenylpropionic, benzoic, phenylacetic and cinnamic acids. Total SCFAs increased in all colonic vessels with a rise in the proportion of propionic to acetic acid. Antioxidant capacity increased significantly in all compartments, but first in the stomach, small intestine and ascending colon. After 24h, the colonic vessels without parent polyphenols, but containing new metabolites, had antioxidant capacities similar to the stomach and small intestine, containing parent compounds. Biotransformation of pure polyphenols resulted in different phenolic metabolite and SCFAs profiles in each colonic segment, with important health implications for these colonic compartments.

1H-NMR based metabolomics study for the detection of the human urine metabolic profile effects of Origanum dictamnus tea ingestion

NMR based metabolomics clarify theOriganum dictamnustea effect upon the human urine metabolome.

Metabolic and Microbial Modulation of the Large Intestine Ecosystem by Non-Absorbed Diet Phenolic Compounds: A Review

Phenolic compounds represent a diverse group of phytochemicals whose intake is associated with a wide spectrum of health benefits. As consequence of their low bioavailability, most of them reach the large intestine where, mediated by the action of local microbiota, a series of related microbial metabolites are accumulated. In the present review, gut microbial transformations of non-absorbed phenolic compounds are summarized. Several studies have reached a general consensus that unbalanced diets are associated with undesirable changes in gut metabolism that could be detrimental to intestinal health. In terms of explaining the possible effects of non-absorbed phenolic compounds, we have also gathered information regarded their influence on the local metabolism. For this purpose, a number of issues are discussed. Firstly, we consider the possible implications of phenolic compounds in the metabolism of colonic products, such as short chain fatty acids (SCFA), sterols (cholesterol and bile acids), and microbial products of non-absorbed proteins. Due to their being recognized as affective antioxidant and anti-inflammatory agents, the ability of phenolic compounds to counteract or suppress pro-oxidant and/or pro-inflammatory responses, triggered by bowel diseases, is also presented. The modulation of gut microbiota through dietetic maneuvers including phenolic compounds is also commented on. Although the available data seems to assume positive effects in terms of gut health protection, it is still insufficient for solid conclusions to be extracted, basically due to the lack of human trials to confirm the results obtained by the in vitro and animal studies. We consider that more emphasis should be focused on the study of phenolic compounds, particularly in their microbial metabolites, and their power to influence different aspects of gut health.

Diet, the gut microbiome, and epigenetics

Increasingly, the gut microbiome is implicated in the etiology of cancer, not only as an infectious agent but also by altering exposure to dietary compounds that influence disease risk. Whereas the composition and metabolism of the gut microbiome is influenced by diet, the gut microbiome can also modify dietary exposures in ways that are beneficial or detrimental to the human host. The colonic bacteria metabolize macronutrients, either as specialists or in consortia of bacteria, in a variety of diverse metabolic pathways. Microbial metabolites of diet can also be epigenetic activators of gene expression that may influence cancer risk in humans. Epigenetics involves heritable changes in gene expression via post-translational and post-transcriptional modifications. Microbial metabolites can influence epigenetics by altering the pool of compounds used for modification or by directly inhibiting enzymes involved in epigenetic pathways. Colonic epithelium is immediately exposed to these metabolites, although some metabolites are also found in systemic circulation. In this review, we discuss the role of the gut microbiome in dietary metabolism and how microbial metabolites may influence gene expression linked to colon cancer risk.

A shortcut to wide-ranging biological actions of dietary polyphenols: modulation of the nitrate-nitrite-nitric oxide pathway in the gut

Dietary polyphenols are complex, natural compounds with recognized health benefits. Initially attractive to the biomedical area due to their in vitro antioxidant properties, the biological implications of polyphenols are now known to be far from their acute ability to scavenge free radicals but rather to modulate redox signaling pathways. Actually, it is now recognized that dietary polyphenols are extensively metabolized in vivo and that the chemical, biophysical and biological properties of their metabolites are, in most cases, quite different from the ones of the parent molecules. Hence, the study of the metabolic, absorptive and signaling pathways of both phenolics and derivatives has become a major issue. In this paper we propose a short-cut for the systemic effects of polyphenols in connection with nitric oxide (˙NO) biology. This free radical is a ubiquitous signaling molecule with pivotal functions in vivo. It is produced through an enzymatic pathway and also through the reduction of dietary nitrate and nitrite in the human stomach. At acidic gastric pH, dietary polyphenols, in the form they are conveyed in foods and at high concentration, not only promote nitrite reduction to ˙NO but also embark in a complex network of chemical reactions to produce higher nitrogen oxides with signaling functions, namely by inducing post-translational modifications. Modified endogenous molecules, such as nitrated proteins and lipids, acquire important physiological functions. Thus, local and systemic effects of ˙NO such as modulation of vascular tone, mucus production in the gut and protection against ischemia-reperfusion injury are, in this sense, triggered by dietary polyphenols. Evidence to support the signaling and biological effects of polyphenols by modulation of the nitrate-nitrite-NO pathway will be herein provided and discussed. General actions of polyphenols encompassing absorption and metabolism in the intestine/liver are short-cut via the production of diffusible species in the stomach that have not only a local but also a general impact.

Towards the fecal metabolome derived from moderate red wine intake

Dietary polyphenols, including red wine phenolic compounds, are extensively metabolized during their passage through the gastrointestinal tract; and their biological effects at the gut level (i.e., anti-inflammatory activity, microbiota modulation, interaction with cells, among others) seem to be due more to their microbial-derived metabolites rather than to the original forms found in food. In an effort to improve our understanding of the biological effects that phenolic compounds exert at the gut level, this paper summarizes the changes observed in the human fecal metabolome after an intervention study consisting of a daily consumption of 250 mL of wine during four weeks by healthy volunteers (n = 33). It assembles data from two analytical approaches: (1) UPLC-ESI-MS/MS analysis of phenolic metabolites in fecal solutions (targeted analysis); and (2) UHPLC-TOF MS analysis of the fecal solutions (non-targeted analysis). Both approaches revealed statistically-significant changes in the concentration of several metabolites as a consequence of the wine intake. Similarity and complementarity between targeted and non-targeted approaches in the analysis of the fecal metabolome are discussed. Both strategies allowed the definition of a complex metabolic profile derived from wine intake. Likewise, the identification of endogenous markers could lead to new hypotheses to unravel the relationship between moderate wine consumption and the metabolic functionality of gut microbiota.