Exploring the Molecular Pathways Behind the Effects of Nutrients and Dietary Polyphenols on Gut Microbiota and Intestinal Permeability: A Perspective on the Potential of Metabolomics and Future Clinical Applications

Immune consequences of exercise in hypoxia: A narrative review

Immune outcomes are key mediators of many health benefits of exercise and are determined by exercise type, dose (frequency/duration, intensity), and individual characteristics. Similarly, reduced availability of ambient oxygen (hypoxia) modulates immune functions depending on the hypoxic dose and the individual capacity to respond to hypoxia. How combined exercise and hypoxia (e.g., high-altitude training) sculpts immune responses is not well understood, although such combinations are becoming increasingly popular. Therefore, in this paper, we summarize the impact on immune responses of exercise and of hypoxia, both independently and together, with a focus on specialized cells in the innate and adaptive immune system. We review the regulation of the immune system by tissue oxygen levels and the overlapping and distinct immune responses related to exercise and hypoxia, then we discuss how they may be modulated by nutritional strategies. Mitochondrial, antioxidant, and anti-inflammatory mechanisms underlie many of the adaptations that can lead to improved cellular metabolism, resilience, and overall immune functions by regulating the survival, differentiation, activation, and migration of immune cells. This review shows that exercise and hypoxia can impair or complement/synergize with each other while regulating immune system functions. Appropriate acclimatization, training, and nutritional strategies can be used to avoid risks and tap into the synergistic potentials of the poorly studied immune consequences of exercising in a hypoxic state.

Polysaccharide from Artocarpus heterophyllus Lam. (Jackfruit) Pulp Ameliorates Dextran Sodium Sulfate-Induced Enteritis in Rats

A polysaccharide from Artocarpus heterophyllus Lam. (jackfruit) pulp (JFP-Ps) is known for its excellent bioactivities. However, its impact on small intestinal barrier function is still largely unexplored. The study aimed to examine the protection effect of JFP-Ps against dextran sodium sulfate-induced enteritis and its underlying mechanism. This research revealed that JFP-Ps mitigated small intestinal tissue damage by reducing the expression of pro-inflammatory cytokines and promoting the expression of the anti-inflammatory cytokine interleukin-10 in the small intestine. JFP-Ps diminished oxidative stress by bolstering the activity of antioxidant enzymes and reducing the concentration of malondialdehyde in the small intestine. In addition, JFP-Ps may restore the mechanical barrier and inhibit intestinal structure damage by augmenting the expression of short-chain fatty acids (SCFAs) receptors (GPR41/43) and up-regulating the expression of tight junction proteins (occludin). In conclusion, JFP-Ps may positively influence intestinal health by relieving oxidative stress in the small intestine, improving mechanical barrier function, activating the SCFA-GPR41/GPR43 axis, and inhibiting TLR4/MAPK pathway activation. The results augment our comprehension of the bioactivities of JFP-Ps, corroborating its great potential as a functional food.

Phenolic Compounds from Apples: From Natural Fruits to the Beneficial Effects in the Digestive System

Conditions in the gastrointestinal tract and microbial metabolism lead to biotransformation of parent, native phenolic compounds from apples into different chemical forms. The aim of this work was to review current knowledge about the forms of phenolic compounds from apples in the gastrointestinal tract and to connect it to their potential beneficial effects, including the mitigation of health problems of the digestive tract. Phenolic compounds from apples are found in the gastrointestinal tract in a variety of forms: native (flavan-3-ols, phenolic acids, flavonols, dihydrochalcones, and anthocyanins), degradation products, various metabolites, and catabolites. Native forms can show beneficial effects in the stomach and small intestine and during the beginning phase of digestion in the colon. Different products of degradation and phase II metabolites can be found in the small intestine and colon, while catabolites might be important for bioactivities in the colon. Most studies connect beneficial effects for different described health problems to the whole apple or to the amount of all phenolic compounds from apples. This expresses the influence of all native polyphenols from apples on beneficial effects. However, further studies of the peculiar compounds resulting from native phenols and their effects on the various parts of the digestive tract could provide a better understanding of the specific derivatives with bioactivity in humans.

Dietary Polyphenols-Natural Bioactive Compounds with Potential for Preventing and Treating Some Allergic Conditions

In light of the constantly increasing prevalence of allergic diseases, changes in dietary patterns have been suggested as a plausible environmental explanation for the development and progression of these diseases. Nowadays, much attention has been paid to the development of dietary interventions using natural substances with anti-allergy activities. In this respect, dietary polyphenols have been studied extensively as one of the most prominent natural bioactive compounds with well-documented anti-inflammatory, antioxidant, and immunomodulatory properties. This review aims to discuss the mechanisms underlying the potential anti-allergic actions of polyphenols related to their ability to reduce protein allergenicity, regulate immune response, and gut microbiome modification; however, these issues need to be elucidated in detail. This paper reviews the current evidence from experimental and clinical studies confirming that various polyphenols such as quercetin, curcumin, resveratrol, catechins, and many others could attenuate allergic inflammation, alleviate the symptoms of food allergy, asthma, and allergic rhinitis, and prevent the development of allergic immune response. Conclusively, dietary polyphenols are endowed with great anti-allergic potential and therefore could be used either for preventive approaches or therapeutic interventions in relation to allergic diseases. Limitations in studying and widespread use of polyphenols as well as future research directions are also discussed.

Wild blueberry (V. angustifolium) improves TNFα-induced cell barrier permeability through claudin-1 and oxidative stress modulation in Caco-2 cells

Increasing evidence links the impairment of intestinal permeability (IP), a feature of the intestinal barrier, to numerous dysmetabolic and dysfunctional conditions. Several host and environmental factors, including dietary factors, can negatively and/or positively affect IP. In this regard, polyphenol-rich foods including berries have been proposed as potential IP modulators. However, the exact mechanisms involved are not yet fully elucidated. The aim of the present study was to evaluate the effect of a wild blueberry (WB; V. angustifolium) powder, naturally rich in polyphenols, to affect Caco-2 cell monolayer permeability and to identify the potential mechanisms in modulating the IP process. Caco-2 cells were incubated with TNF-α (10 ng mL-1), as a pro-inflammatory stimulus, and supplemented for 24 hours with different concentrations (1 and 5 mg mL-1) of WB powder. The integrity of the intestinal cell monolayer was evaluated by measuring the transepithelial electrical resistance (TEER) and the paracellular transport of FITC-dextran. In addition, the production of the tight junction proteins, such as claudin-1 and occludin, as well as protein carbonyl and 8-hydroxy 2 deoxyguanosine, as oxidative stress markers, were quantified in the supernatant by ELISA kits. Overall, the treatment with WB powder (5 mg mL-1) mitigated the loss of Caco-2 cell barrier integrity, as documented by an increase in TEER and a reduction in FITC values. This modulation was accompanied by an upregulation of claudin-1 and a reduction of 8-OHdG. Conversely, no effect was documented for the lower concentration (1 mg mL-1) and the other IP markers, as well as oxidative stress markers analysed. In conclusion, our findings suggest a potential role of WB in the modulation of cell barrier integrity. This modulation process could be attributed to an increase in claudin-1 expression and a reduction in 8-OHdG. Further studies should be performed to corroborate the results obtained. In addition, since the effects were observed at doses of WB achievable with the diet, these findings should be substantiated also through in vivo approaches.

Beneficial effects of phenolic compounds: native phenolic compounds vs metabolites and catabolites

In the human body, the positive effects of phenolic compounds are increasingly observed through their presence in tissues and organs in their native form or in the form of metabolites or catabolites formed during digestion, microbial metabolism, and host biotransformation. The full extent of these effects is still unclear. The aim of this paper is to review the current knowledge of beneficial effects of native phenolic compounds or their metabolites and catabolites focusing on their role in the health of the digestive system, including disorders of the gastrointestinal and urinary tracts and liver. Studies are mostly connecting beneficial effects in the gastrointestinal and urinary tract to the whole food rich in phenolics, or to the amount of phenolic compounds/antioxidants in food. Indeed, the bioactivity of parent phenolic compounds should not be ignored due to their presence in the digestive tract, and the impact on the gut microbiota. However, the influence of their metabolites and catabolites might be more important for the liver and urinary tract. Distinguishing between the effects of parent phenolics vs metabolites and catabolites at the site of action are important for novel areas of food industry, nutrition and medicine.

Food, gut barrier dysfunction, and related diseases: A new target for future individualized disease prevention and management

Dysfunction of gut barrier is known as "leaky gut" or increased intestinal permeability. Numerous recent scientific evidences showed the association between gut dysfunction and multiple gastrointestinal tract (GI) and non-GI diseases. Research also demonstrated that food plays a crucial role to cause or remedy gut dysfunction related to diseases. We reviewed recent articles from electronic databases, mainly PubMed. The data were based on animal models, cell models, and human research in vivo and in vitro models. In this comprehensive review, our aim focused on the relationship between dietary factors, intestinal permeability dysfunction, and related diseases. This review synthesizes currently available literature and is discussed in three parts: (a) the mechanism of gut barrier and function, (b) food and dietary supplements that may promote gut health, and food or medication that may alter gut function, and (c) a table that organizes the synthesized information by general mechanisms for diseases related to leaky gut/intestinal permeability and associated dietary influences. With future research, dietary intervention could be a new target for individualized disease prevention and management.

The Impact of Za'atar Antioxidant Compounds on the Gut Microbiota and Gastrointestinal Disorders: Insights for Future Clinical Applications

Since the gut microbiota plays a pivotal role in host homeostasis and energy balance, changes in its composition can be associated with disease states through the promotion of immune-mediated inflammatory disorders and increasing intestinal permeability, ultimately leading to the impairment of intestinal barrier function. Za'atar is one of the most popular plant-based foods in the Eastern Mediterranean region. Za'atar is a mixture of different plant leaves, fruits, and seeds and contains hundreds of antioxidant compounds, especially polyphenols, and fiber, with pre-clinical and clinical evidence suggesting health-promoting effects in cardiovascular and metabolic disease. Za'atar compounds have also been studied from a gastrointestinal perspective, concerning both gut microbiota and gastrointestinal diseases. Antioxidants such as Za'atar polyphenols may provide beneficial effects in the complex interplay between the diet, gut microbiota, and intestinal permeability. To our knowledge, no studies have reported the effects of the whole Za'atar mixture, however, based on the pre-clinical studies published on components and single compounds found in Za'atar, we provide a clinical overview of the possible effects on the gastrointestinal tract, focusing mainly on carvacrol, rosmarinic acid, gallic acid, and other polyphenols. We also cover the potential clinical applications of Za'atar mixture as a possible nutraceutical in disorders involving the gastrointestinal tract.

Citrus peel ameliorates mucus barrier damage in HFD-fed mice

Citrus peel is rich in bioactive components, especially polyphenols, which are considered to have great potential in the prevention of intestinal diseases. The intestinal mucus barrier is the first defense against the invasion of foreign substances. In this study, we aimed to explore the possibility and mechanism of citrus peel in alleviating the mucus barrier damage in high-fat-diet (HFD) mice. We found that citrus peel powder (CPP) supplementation effectively reduced body weight, fat weight, intestinal permeability, hyperlipidemia, and systemic inflammation in HFD-fed mice. In particular, CPP increased the number of goblet cells, the protein expression of Mucin-2 (Muc2), and the thickness of the mucus layer, thereby strengthening the colonic mucus barrier function. Moreover, CPP supplementation also reduced the expression of endoplasmic reticulum stress (ERS) proteins (GRP78 and CHOP) and increased the expression of T-synthase (O-glycosylation rate-limiting enzyme) and its chaperone protein (Cosmc) in the colon of HFD-fed mice, which suggested that CPP could improve the abnormal protein folding and O-glycosylation of Muc2 during processing and modification. In summary, our study indicates that CPP plays an effective role in relieving mucus barrier damage by improving the production and properties of Muc2, providing new perspectives on the development of CPP as a dietary supplement for strengthening the intestinal barrier.

A mixture of four dietary fibres ameliorates adiposity and improves metabolic profile and intestinal health in cafeteria-fed obese rats: an integrative multi-omics approach

The aim of this study was to assess the effects of a mixture of four dietary fibers on obese rats. Four groups of male Wistar rats were fed with either standard chow (STD) or cafeteria diet (CAF) and were orally supplemented with either fibre mixture (2 g kg-1 of body weight) (STD+F or CAF+F groups) or vehicle (STD+VH or CAF+VH groups). We studied a wide number of biometric, biochemical, transcriptomic, metagenomic and metabolomic variables and applied an integrative multivariate approach based on multiple factor analysis and Pearson's correlation analysis. A significant reduction in body weight, adiposity, HbA1c and HDL-cholesterol serum levels, and colon MPO activity was observed, whereas cecal weight and small intestine length:weight ratio were significantly increased in F-treated groups compared to control animals. CAF+F rats displayed a significant enhancement in energy expenditure, fat oxidation and fresh stool weight, and a significant reduction in adiponectin and LPS serum levels, compared to control group. Animals in STD+F group showed reduced serum LDL-cholesterol levels and a significant reduction in total cholesterol levels in the liver compared to STF+VH group. The intervention effect was reflected at the metabolomic (i.e., production of short-chain fatty acids, phenolic acids, and amino acids), metagenomic (i.e., modulation of Ruminococcus and Lactobacillus genus) and transcriptomic (i.e., expression of tight junctions and proteolysis) levels. Altogether, our integrative multi-omics approach highlights the potential of supplementation with a mixture of fibers to ameliorate the impairments triggered by obesity in terms of adiposity, metabolic profile, and intestinal health.

The gut microbiome and obstructive sleep apnea syndrome in children

Obstructive sleep apnea syndrome (OSAS) in children has become a major public health problem that affects the physical and mental growth of children. OSAS can result in adverse outcomes during growth and development, inhibiting the normal development of the metabolic, cardiovascular, and immune systems. OSAS is characterized by partial or complete obstruction of the upper airway, and prolonged obstruction that causes intermittent hypoxia and sleep fragmentation in children. The human microbiota is a complex community that is in dynamic equilibrium in the human body. Intermittent hypoxia and sleep fragmentation induced by childhood OSAS alter the composition of the gut microbiome. At the same time, changes in the gut microbiome affect sleep patterns in children through immunomodulatory and metabolic mechanisms, and induce further comorbidities, such as obesity, hypertension, and cardiovascular disease. This article discusses recent progress in research into the mechanisms of OSAS-induced changes in the gut microbiota and its pathophysiology in children.

Targeting the gut to prevent and counteract metabolic disorders and pathologies during aging

Impairment of gut function is one of the explanatory mechanisms of health status decline in elderly population. These impairments involve a decline in gut digestive physiology, metabolism and immune status, and associated to that, changes in composition and function of the microbiota it harbors. Continuous deteriorations are generally associated with the development of systemic dysregulations and ultimately pathologies that can worsen the initial health status of individuals. All these alterations observed at the gut level can then constitute a wide range of potential targets for development of nutritional strategies that can impact gut tissue or associated microbiota pattern. This can be key, in a preventive manner, to limit gut functionality decline, or in a curative way to help maintaining optimum nutrients bioavailability in a context on increased requirements, as frequently observed in pathological situations. The aim of this review is to give an overview on the alterations that can occur in the gut during aging and lead to the development of altered function in other tissues and organs, ultimately leading to the development of pathologies. Subsequently is discussed how nutritional strategies that target gut tissue and gut microbiota can help to avoid or delay the occurrence of aging-related pathologies.

Health benefits of polyphenols: A concise review

Plants produce polyphenols, which are considered highly essential functional foods in our diet. They are classified into several groups according to their diverse chemical structures. Flavanoids, lignans, stilbenes, and phenolic acids are the four main families of polyphenols. Several in vivo and in vitro research have been conducted so far to evaluate their health consequences. Polyphenols serve a vital function in the protection of the organism from external stimuli and in eliminating reactive oxygen species (ROS), which are instigators of several illnesses. Polyphenols are present in tea, chocolate, fruits, and vegetables with the potential to positively influence human health. For instance, cocoa flavan-3-ols have been associated with a decreased risk of myocardial infarction, stroke, and diabetes. Polyphenols in the diet also help to improve lipid profiles, blood pressure, insulin resistance, and systemic inflammation. Quercetin, a flavonoid, and resveratrol, a stilbene, have been linked to improved cardiovascular health. Dietary polyphenols potential to elicit therapeutic effects might be attributed, at least in part, to a bidirectional association with the gut microbiome. This is because polyphenols are known to affect the gut microbiome composition in ways that lead to better human health. Specifically, the gut microbiome converts polyphenols into bioactive compounds that have therapeutic effects. In this review, the antioxidant, cytotoxicity, anti-inflammatory, antihypertensive, and anti-diabetic actions of polyphenols are described based on findings from in vivo and in vitro experimental trials. PRACTICAL APPLICATIONS: The non-communicable diseases (NCDs) burden has been increasing worldwide due to the sedentary lifestyle and several other factors such as smoking, junk food, etc. Scientific literature evidence supports the use of plant-based food polyphenols as therapeutic agents that could help to alleviate NCD's burden. Thus, consuming polyphenolic compounds from natural sources could be an effective solution to mitigate NCDs concerns. It is also discussed how natural antioxidants from medicinal plants might help prevent or repair damage caused by free radicals, such as oxidative stress.

Pomegranate fruit pulp polyphenols reduce diet-induced obesity with modulation of gut microbiota in mice

BACKGROUND

Pomegranate is a rich source of polyphenols and has been used as a dietary supplement and pharmaceutical ingredient. This study aimed to investigate the pomegranate fruit pulp polyphenols (PFP) with regard to their anti-obesity activity and gut microbiota-modulating effect in mice. Thirty-six 4-week-old specific pathogen-free C57BL/6J mice (weight: 17.7-20.8 g) were randomly divided into three groups and fed with low-fat diet (10% fat energy), high-fat diet (HFD) (45% fat energy), or HFD supplemented with PFP by intragastric administration for 14 weeks. The obesity-related clinical indicators were investigated, and the composition of fecal microbiota was analyzed by 16S rRNA sequencing.

RESULTS

Our results showed that PFP treatment reduced HFD-induced body weight gain by 35.23% (P < 0.05), steatosis scores by 50% (P < 0.05) and insulin resistance by 56.84% (P < 0.05), compared with the mice fed HFD alone. Moreover, compared with the mice in the HFD group, PFP supplement changed the composition of the gut microbiota, and enriched Akkermansia muciniphila, Parabacteroides distasonis, Bacteroides acidifaciens, Mucispirillum schaedleri and Lachnospiraceae bacterium 28-4, which were negatively correlated with physical biomarkers, including body weight, glucose, triglycerides and total cholesterol.

CONCLUSION

PFP alleviated HFD-induced obesity, insulin resistance and hepatic steatosis in mice, and the changes in the gut microbiota might be one of the potential mechanisms through which PFP improved obesity and obesity-related disorders, eventually benefiting the recipient. © 2021 Society of Chemical Industry.

Overview of the Importance of Biotics in Gut Barrier Integrity

Increased gut permeability is suggested to be involved in the pathogenesis of a growing number of disorders. The altered intestinal barrier and the subsequent translocation of bacteria or bacterial products into the internal milieu of the human body induce the inflammatory state. Gut microbiota maintains intestinal epithelium integrity. Since dysbiosis contributes to increased gut permeability, the interventions that change the gut microbiota and correct dysbiosis are suggested to also restore intestinal barrier function. In this review, the current knowledge on the role of biotics (probiotics, prebiotics, synbiotics and postbiotics) in maintaining the intestinal barrier function is summarized. The potential outcome of the results from in vitro and animal studies is presented, and the need for further well-designed randomized clinical trials is highlighted. Moreover, we indicate the need to understand the mechanisms by which biotics regulate the function of the intestinal barrier. This review is concluded with the future direction and requirement of studies involving biotics and gut barrier.

A healthy eating score is inversely associated with depression in older adults: results from the Chilean National Health Survey 2016-2017

OBJECTIVE

To investigate the relationship of a healthy eating score with depression in Chilean older adults.

DESIGN

Cross-sectional study.

SETTING

Older adults from the Chilean National Health Survey 2016-2017. Associations were analysed using complex samples multivariable logistic regressions adjusted for age, sex, socio-demographic, lifestyles (physical activity, smoking, alcohol consumption and sleep duration), BMI and clinical conditions (hypertension, diabetes, hypercholesterolaemia and cardiovascular diseases).

PARTICIPANTS

The number of participants was 2031 (≥ 60 years). The Composite International Diagnostic Interview-Short Form was applied to establish the diagnosis of major depressive episode. Six healthy eating habits were considered to produce the healthy eating score (range: 0-12): consumption of seafood, whole grain, dairy, fruits, vegetables and legumes. Participants were categorised according to their final scores as healthy (≥ 9), average (5-8) and unhealthy (≤ 4).

RESULTS

Participants with a healthy score had a higher educational level, physical activity and regular sleep hours than participants with an average and unhealthiest healthy eating score. Participants classified in the healthiest healthy eating score had an inverse association with depression (OR: 0·28, (95 % CI 0·10, 0·74)). Food items that contributed the most to this association were legumes (15·2 %) and seafood (12·7 %).

CONCLUSION

Older adults classified in the healthiest healthy eating score, characterised by a high consumption of legumes and seafood, showed a lower risk for depression in a representative sample of Chilean population.

Can polyphenols improve the gut health status in pre-clinical study with diet-induced obesity?: A protocol for systematic review and/or meta-analysis

INTRODUCTION

Obesity is characterized as a low-grade inflammation that impairs physiological functions, including intestinal functioning and gut microbiota balance. Dietary polyphenols can be a strategy for obesity management, collaborating to preserve or recover gut health through antioxidant and anti-inflammatory actions, as well as modulators of the microbiota. This study describes a systematic review protocol to elucidate effects of polyphenols on intestinal health of pre-clinical models with diet-induced obesity. AIM: Our aim is to evaluate evidence about polyphenols' effects in the gut microbiota composition and diversity, parameters of the physical and molecular status of the gut barrier in obese models, additionally, understand the possible involved mechanisms.

METHODOLOGY

A protocol was developed and published on PROSPERO (Registration No: CRD42021262445). Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols is used to outline the protocol. The articles will be selected according to the PICOS strategy (population, interventions, control, outcome, and study design) in the following databases: PubMed, Science Direct, Scopus, Web of Science, and EMBASE. Experimental studies performed on rats and mice with a control group that describes treatment with polyphenols (from food matrix or crude extracts or isolated compounds) at any frequency, time, and dose will be included. Two reviewers will, independently, select the papers, extract data, and evaluate the data quality. The Systematic Review Center for Laboratory Animal Experimentation (SYRCLE) tool will be used to assess the risk of bias.

EXPECTED RESULTS

Results will be showed through of native synthesis and, if possible, a metanalysis will be conducted. The review produced with this protocol can show the scientific evidence level about polyphenols' effects in intestinal health in obesity status.

Higher bacterial DNAemia can affect the impact of a polyphenol-rich dietary pattern on biomarkers of intestinal permeability and cardiovascular risk in older subjects

PURPOSE

Aging can be characterized by increased systemic low-grade inflammation, altered gut microbiota composition, and increased intestinal permeability (IP). The intake of polyphenol-rich foods is proposed as a promising strategy to positively affect the gut microbiota-immune system-intestinal barrier (IB) axis. In this context, we tested the hypothesis that a PR-dietary intervention would affect the presence of bacterial factors in the bloodstream of older adults.

METHODS

We collected blood samples within a randomized, controlled, crossover intervention trial in which older volunteers (n = 51) received a polyphenol-enriched and a control diet. We quantified the presence of bacterial DNA in blood by qPCR targeting the 16S rRNA gene (16S; bacterial DNAemia). Blood DNA was taxonomically profiled via 16S sequencing.

RESULTS

Higher blood 16S levels were associated with higher BMI and markers of IP, inflammation, and dyslipidemia. PR-intervention did not significantly change bacterial DNAemia in the older population (P = 0.103). Nonetheless, the beneficial changes caused by the polyphenol-enriched diet were greatest in participants with higher bacterial DNAemia, specifically in markers related to IP, inflammation and dyslipidemia, and in fecal bacterial taxa. Finally, we found that the bacterial DNA detected in blood mostly belonged to γ-Proteobacteria, whose abundance significantly decreased after the polyphenol-rich diet in subjects with higher bacterial DNAemia at baseline.

CONCLUSIONS

This study shows that older subjects with higher bacterial DNAemia experienced a beneficial effect from a polyphenol-rich diet. Bacterial DNAemia may be a further relevant marker for the identification of target populations that could benefit more from a protective dietary treatment.

REGISTRATION

This trial was retrospectively registered at www.isrctn.org (ISRCTN10214981) on April 28, 2017.

A Scoping Review of the Application of Metabolomics in Nutrition Research: The Literature Survey 2000-2019

Nutrimetabolomics is an emerging field in nutrition research, and it is expected to play a significant role in deciphering the interaction between diet and health. Through the development of omics technology over the last two decades, the definition of food and nutrition has changed from sources of energy and major/micro-nutrients to an essential exposure factor that determines health risks. Furthermore, this new approach has enabled nutrition research to identify dietary biomarkers and to deepen the understanding of metabolic dynamics and the impacts on health risks. However, so far, candidate markers identified by metabolomics have not been clinically applied and more efforts should be made to validate those. To help nutrition researchers better understand the potential of its application, this scoping review outlined the historical transition, recent focuses, and future prospects of the new realm, based on trends in the number of human research articles from the early stage of 2000 to the present of 2019 by searching the Medical Literature Analysis and Retrieval System Online (MEDLINE). Among them, objective dietary assessment, metabolic profiling, and health risk prediction were positioned as three of the principal applications. The continued growth will enable nutrimetabolomics research to contribute to personalized nutrition in the future.

Crosstalk among intestinal barrier, gut microbiota and serum metabolome after a polyphenol-rich diet in older subjects with "leaky gut": The MaPLE trial

BACKGROUND &AIM

The MaPLE study was a randomized, controlled, crossover trial involving adults ≥60 y.o. (n = 51) living in a residential care facility during an 8-week polyphenol-rich (PR)-diet. Results from the MaPLE trial showed that the PR-diet reduced the intestinal permeability (IP) in older adults by inducing changes to gut microbiota (GM). The present work aimed at studying the changes in serum metabolome in the MaPLE trial, as a further necessary step to depict the complex crosstalk between dietary polyphenols, GM, and intestinal barrier.

METHODS

Serum metabolome was monitored using a semi-targeted UHPLC-MS/MS analysis. Metataxonomic analysis (16S rRNA gene profiling) of GM was performed on faecal samples. Clinical characteristics and serum levels of the IP marker zonulin were linked to GM and metabolomics data in a multi-omics network.

RESULTS

Compared to the control diet, the PR-diet increased serum metabolites related to polyphenols and methylxanthine intake. Theobromine and methylxanthines, derived from cocoa and/or green tea, were positively correlated with butyrate-producing bacteria (the order Clostridiales and the genera Roseburia, Butyricicoccus and Faecalibacterium) and inversely with zonulin. A direct correlation between polyphenol metabolites hydroxyphenylpropionic acid-sulfate, 2-methylpyrogallol-sulfate and catechol-sulfate with Butyricicoccus was also observed, while hydroxyphenylpropionic acid-sulfate and 2-methylpyrogallol-sulfate negatively correlated with Methanobrevibacter. The multi-omics network indicated that participant's age, baseline zonulin levels, and changes in Porphyromonadaceae abundance were the main factors driving the effects of a PR-diet on zonulin.

CONCLUSION

Overall, these results reveal the complex relationships among polyphenols consumption, intestinal permeability, and GM composition in older adults, and they may be important when setting personalized dietary interventions for older adults.

TRIAL REGISTRATION NUMBER

ISRCTN10214981.

Blueberry and cranberry anthocyanin extracts reduce bodyweight and modulate gut microbiota in C57BL/6 J mice fed with a high-fat diet

PURPOSE

Blueberry and cranberry are rich in anthocyanins. The present study was to investigate the effects of anthocyanin extracts from blueberry and cranberry on body weight and gut microbiota.

METHODS

C57BL/6 J Mice were divided into six groups (n = 9 each) fed one of six diets namely low-fat diet (LFD), high-fat diet (HFD), HFD with the addition of 1% blueberry extract (BL), 2% blueberry extract (BH), 1% cranberry extract (CL), and 2% cranberry extract (CH), respectively.

RESULTS

Feeding BL and BH diets significantly decreased body weight gain by 20-23%, total adipose tissue weight by 18-20%, and total liver lipids by 16-18% compared with feeding HFD. Feeding CH diet but not CL diet reduced the body weight by 27%, accompanied by a significant reduction of total plasma cholesterol by 25% and tumor necrosis factor alpha (TNF-α) by 38%. The metagenomic analysis showed that the supplementation of blueberry and cranberry anthocyanin extracts reduced plasma lipopolysaccharide concentration, accompanied by a reduction in the relative abundance of Rikenella and Rikenellaceae. Dietary supplementation of berry anthocyanin extracts promoted the growth of Lachnoclostridium, Roseburia, and Clostridium_innocuum_group in genus level, leading to a greater production of fecal short-chain fatty acids (SCFA).

CONCLUSIONS

It was concluded that both berry anthocyanins could manage the body weight and favorably modulate the gut microbiota at least in mice.

The Effects of Lifestyle and Diet on Gut Microbiota Composition, Inflammation and Muscle Performance in Our Aging Society

Living longer is associated with an increased risk of chronic diseases, including impairments of the musculoskeletal and immune system as well as metabolic disorders and certain cancers, each of which can negatively affect the relationship between host and microbiota up to the occurrence of dysbiosis. On the other hand, lifestyle factors, including regular physical exercise and a healthy diet, can affect skeletal muscle and immune aging positively at all ages. Accordingly, health benefits could partly depend on the effect of such interventions that influence the biodiversity and functionality of intestinal microbiota. In the present review, we first discuss the physiological effects of aging on the gut microbiota, immune system, and skeletal muscle. Secondly, we describe human epidemiological evidence about the associations between physical activity and fitness and the gut microbiota composition in older adults. The third part highlights the relevance and restorative mechanisms of immune protection through physical activity and specific exercise interventions during aging. Fourth, we present important research findings on the effects of exercise and protein as well as other nutrients on skeletal muscle performance in older adults. Finally, we provide nutritional recommendations to prevent malnutrition and support healthy active aging with a focus on gut microbiota. Key nutrition-related concerns include the need for adequate energy and protein intake for preventing low muscle mass and a higher demand for specific nutrients (e.g., dietary fiber, polyphenols and polyunsaturated fatty acids) that can modify the composition, diversity, and metabolic capacity of the gut microbiota, and may thus provide a practical means of enhancing gut and systemic immune function.

Reference values for intake of six types of soluble and insoluble fibre in healthy UK inhabitants based on the UK Biobank data

OBJECTIVE

To obtain a set of reference values for the intake of different types of dietary fibre in a healthy UK population.

DESIGN

This descriptive cross-sectional study used the UK Biobank data to estimate the dietary patterns of healthy individuals. Data on fibre content in different foods were used to calculate the reference values which were then calibrated using real-world data on total fibre intake.

SETTING

UK Biobank is a prospective cohort study of over 500 000 individuals from across the United Kingdom with the participants aged between 40 and 69 years.

PARTICIPANTS

UK Biobank contains information on over 500 000 participants. This study was performed using the data on 19 990 individuals (6941 men, 13 049 women) who passed stringent quality control and filtering procedures and had reported above-zero intake of the analysed foods.

RESULTS

A set of reference values for the intake of six different types of soluble and insoluble fibres (cellulose, hemicelluloses, pectin and lignin), including the corresponding totals, was developed and calibrated using real-world data.

CONCLUSIONS

To our knowledge, this is the first study to establish specific reference values for the intake of different types of dietary fibre. It is well known that effects exerted by different types of fibre both directly and through modulation of microbiota are numerous. Conceivably, a deficit or excess intake of specific types of dietary fibre may detrimentally affect human health. Filling this knowledge gap opens new avenues for research in discussion in studies of nutrition and microbiota and offers valuable tools for practitioners worldwide.

Diet-Derived Antioxidants and Their Role in Inflammation, Obesity and Gut Microbiota Modulation

It is generally accepted that gut microbiota, inflammation and obesity are linked to the development of cardiovascular diseases and other chronic/non-communicable pathological conditions, including cancer, neurodegenerative diseases and ageing-related disorders. In this scenario, oxidative stress plays a pivotal role. Evidence suggests that the global dietary patterns may represent a tool in counteracting oxidative stress, thus preventing the onset of diseases related to oxidative stress. More specifically, dietary patterns based on the regular consumption of fruits and vegetables (i.e., Mediterranean diet) have been licensed by various national nutritional guidelines in many countries for their health-promoting effects. Such patterns, indeed, result in being rich in specific components, such as fiber, minerals, vitamins and antioxidants, whose beneficial effects on human health have been widely reported. This suggests a potential nutraceutical power of specific dietary components. In this manuscript, we summarize the most relevant evidence reporting the impact of dietary antioxidants on gut microbiota composition, inflammation and obesity, and we underline that antioxidants are implicated in a complex interplay between gut microbiota, inflammation and obesity, thus suggesting their possible role in the development and modulation of chronic diseases related to oxidative stress and in the maintenance of wellness. Do all roads lead to Rome?

An alcohol-free beer enriched with isomaltulose and a resistant dextrin modulates gut microbiome in subjects with type 2 diabetes mellitus and overweight or obesity: a pilot study

We aimed to study the effect of consuming an alcohol-free beer with modified carbohydrates composition (almost completely eliminating maltose and adding isomaltulose (16.5 g day^-1) and resistant maltodextrin (5.28 g day^-1)) in gut microbiome, compared to regular alcohol-free beer in subjects with T2DM or prediabetes and overweight/obesity. This is a pilot, randomized, double-blinded, crossover study including a sub-sample of a global study with 14 subjects: (a) consuming 66 cl day^-1 of regular alcohol-free beer for the first 10 weeks and 66 cl day^-1 of modified alcohol-free beer for the next 10 weeks; (b) the same described intervention in opposite order. BMI homogeneously decreased after both interventions. Glucose and HOMA-IR significantly decreased just after the participants consumed modified alcohol-free beer. These findings were in the same line as those reported in the global study. Dominant bacteria at baseline were Bacteroidetes, Firmicutes, Proteobacteria and Tenericutes. Parabacteroides, from the Porphymonadaceae family, resulted as the feature with the greatest difference between beers (ANCOM analysis, W = 15). Feature-volatility analysis confirmed the importance of Parabacteroides within the model. Alcohol-free beers consumption resulted in an enhancement of pathways related to metabolism according to PICRUSt analysis, including terpenoid-quinone, lipopolysaccharides and N-glycan biosynthesis. Thus, an alcohol-free beer including the substitution of regular carbohydrates for low doses of isomaltulose and the addition of maltodextrin within meals significantly impacts gut microbiota in diabetic subjects with overweight or obesity. This could, at least partially, explain the improvement in insulin resistance previously found after taking modified alcohol-free alcohol.Clinical Trial Registration: Registered under ClinicalTrials.gov identifier no. NCT03337828.

Galli gigeriae endothelium corneum: its intestinal barrier protective activity in vitro and chemical composition

Background

Galli gigeriae endothelium corneum (GGEC) has been effectively used for centuries for the treatment of functional dyspepsia (FD) in clinical practice in Asian countries. However, its potential mechanism and chemical composition remains undertermined.

Methods

In this study, the chemical profile of GGEC ethyl acetate extract (EAE) was evaluated by HPLC-Q-TOF–MS/MS. The effects of EAE on intestinal barrier function and inflammation were investigated in IEC-6 cells and RAW264.7 cells.

Results

The results showed that 33 compounds were tentatively identified, including 12 soy isoflavones, 7 bile acids for the first time in EAE. EAE significantly reinforced intestinal barrier function via increasing the tight junction protein levels of ZO-1 and Occludin, reducing the mRNA expression levels of interleukin (IL)-1β and IL-6 in tumor necrosis factor alpha (TNF-α)-challenged IEC-6 cells. The scratch wound assay showed that EAE accelerated wound healing of IEC-6 cells. EAE evidently reduced the level of NO in a dose-dependent manner with an IC₅₀ value of 18.12 μg/mL, and the mRNA expression of TNF-α, IL-1β, IL-6, iNOS and COX-2 in LPS-treated RAW264.7 cells.

Conclusion

This study revealed the intestinal barrier protective effects and chemical profile of GGEC, and the results indicated that GGEC strengthened the intestinal barrier by up-regulating protein expression of tight junctions and limiting inflammatory responses.

A polyphenol-rich dietary pattern improves intestinal permeability, evaluated as serum zonulin levels, in older subjects: The MaPLE randomised controlled trial

BACKGROUND & AIM

Increased intestinal permeability (IP) can occur in older people and contribute to the activation of the immune system and inflammation. Dietary interventions may represent a potential strategy to reduce IP. In this regard, specific food bioactives such as polyphenols have been proposed as potential IP modulator due to their ability to affect several critical targets and pathways that control IP. The trial aimed to test the hypothesis that a polyphenol-rich dietary pattern can decrease serum zonulin levels, an IP surrogate marker involved in tight junction modulation, and can beneficially alter the intestinal microbiota, and IP-associated biochemical and clinical markers in older subjects.

METHODS

A randomised, controlled, cross-over intervention trial was performed. Sixty-six subjects (aged ≥ 60 y) with increased IP based on serum zonulin levels, were randomly allocated to one of the two arms of the intervention consisting of a control diet (C-diet) vs. a polyphenol-rich diet (PR-diet). Each intervention was 8-week long and separated by an 8-week wash out period. At the beginning and at the end of each intervention period, serum samples were collected for the quantification of zonulin and other biological markers. Faecal samples were also collected to investigate the intestinal microbial ecosystem. In addition, anthropometrical/physical/biochemical parameters and food intake were evaluated.

RESULTS

Fifty-one subjects successfully completed the intervention and a high compliance to the dietary protocols was demonstrated. Overall, polyphenol intake significantly increased from a mean of 812 mg/day in the C diet to 1391 mg/day in the PR-diet. Two-way analysis of variance showed a significant effect of treatment (p = 0.008) and treatment × time interaction (p = 0.025) on serum zonulin levels, which decreased after the 8-week PR-diet. In addition, a treatment × time interaction was observed showing a reduction of diastolic blood pressure (p = 0.028) following the PR-diet, which was strongest in those not using antihypertensive drugs. A decrease in both diastolic (p = 0.043) and systolic blood pressure (p = 0.042) was observed in women. Interestingly, a significant increase in fibre-fermenting and butyrate-producing bacteria such as the family Ruminococcaceae and members of the genus Faecalibacterium was observed following the PR intervention. The efficacy of this dietary intervention was greater in subjects with higher serum zonulin at baseline, who showed more pronounced alterations in the markers under study. Furthermore, zonulin reduction was also stronger among subjects with higher body mass index and with insulin resistance at baseline, thus demonstrating the close interplay between IP and metabolic features.

CONCLUSIONS

These data show, for the first time, that a PR-diet can reduce serum zonulin levels, an indirect marker of IP. In addition, PR-diet reduced blood pressure and increased fibre-fermenting and butyrate-producing bacteria. These findings may represent an initial breakthrough for further intervention studies evaluating possible dietary treatments for the management of IP, inflammation and gut function in different target populations. THIS STUDY WAS REGISTERED AT WWW.ISRCTN.

ORG AS

ISRCTN10214981.

Undaria pinnatifida improves obesity-related outcomes in association with gut microbiota and metabolomics modulation in high-fat diet-fed mice

Dietary fiber has beneficial effects on obesity-related diseases and gut microbiota, contributing a key role in the interaction between dietary metabolism and host metabolism. Our objective was to investigate the cause of the improvement in multiple types of physiological states with seaweed Undaria pinnatifida treatment on high-fat diet-fed mice and to evaluate whether its consequent anti-adiposity and anti-hyperlipidemic effects are associated with gut microbiota and its metabolomics regulation. U. pinnatifida administration in our experiment was shown to significantly decrease high-fat diet-induced body weight gain, as well as epididymal and abdominal adiposity. U. pinnatifida intake also significantly reduced liver weight and serum triacylglycerol accumulation. We also found that improving effects of U. pinnatifida on high-fat diet-induced metabolic dysfunctions were associated with significant increase in specific bacteria, such as Bacteroides acidifaciens and Bacteroides ovatus, as well as metabolites, including short-chain fatty acids and tricarboxylic acid cycle intermediates. Our result provides a cheap dietary strategy to host metabolism improvement and obesity management. KEY POINTS: • U. pinnatifida improved adipose accumulation and lipid metabolism. • B. acidifaciens and B. ovatus contributed to the beneficial effects of U. pinnatifida. • SCFAs and TCA cycle intermediates were critical to the metabolic outcomes. • Our study provides a cheap dietary strategy for obesity management.

Diet as a Modulator of Intestinal Microbiota in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a chronic immune-driven inflammatory disease characterised by synovial inflammation, leading to progressive cartilage and bone destruction, impacting patients' functional capacity and quality of life. Patients with RA have significant differences in gut microbiota composition when compared to controls. Intestinal dysbiosis influences the intestinal barrier strength, integrity and function, and diet is considered the main environmental factor impacting gut microbiota. Over the last few years, researchers have focused on the influence of single components of the diet in the modulation of intestinal microbiota in RA rather than whole dietary patterns. In this review, we focus on how the Mediterranean diet (MD), a whole dietary pattern, could possibly act as an adjuvant therapeutic approach, modulating intestinal microbiota and intestinal barrier function in order to improve RA-related outcomes. We also review the potential effects of particular components of the MD, such as n-3 polyunsaturated fatty acids (PUFAs), polyphenols and fibre.

Increased Intestinal Permeability in Older Subjects Impacts the Beneficial Effects of Dietary Polyphenols by Modulating Their Bioavailability

Polyphenols have great potential in regulating intestinal health and ameliorating pathological conditions related to increased intestinal permeability (IP). However, the efficacy of dietary interventions with these phytochemicals may significantly be influenced by interindividual variability factors affecting their bioavailability and consequent biological activity. In the present study, urine samples collected from older subjects undergoing a crossover intervention trial with polyphenol-rich foods were subjected to metabolomics analysis for investigating the impact of increased IP on the bioavailability of polyphenols. Interestingly, urinary levels of phase II and microbiota-derived metabolites were significantly different between subjects with healthier intestinal barrier integrity and those with increased IP disruption. Our results support that this IP-dependent impaired bioavailability of polyphenols could be attributed to disturbances in the gut microbial metabolism and phase II methylation processes. Furthermore, we also observed that microbiota-derived metabolites could be largely responsible for the biological activity elicited by dietary polyphenols against age-related disrupted IP.

Estimated Intakes of Nutrients and Polyphenols in Participants Completing the MaPLE Randomised Controlled Trial and Its Relevance for the Future Development of Dietary Guidelines for the Older Subjects

The evaluation of food intake in older subjects is crucial in order to be able to verify adherence to nutritional recommendations. In this context, estimation of the intake of specific dietary bioactives, such as polyphenols, although particularly challenging, is necessary to plan possible intervention strategies to increase their intake. The aims of the present study were to: (i) evaluate the nutritional composition of dietary menus provided in a residential care setting; (ii) estimate the actual intake of nutrients and polyphenols in a group of older subjects participating in the MaPLE study; and (iii) investigate the impact of an eight-week polyphenol-rich dietary pattern, compared to an eight-week control diet, on overall nutrient and polyphenol intake in older participants. The menus served to the participants provided ~770 mg per day of total polyphenols on average with small variations between seasons. The analysis of real consumption, measured using weighed food diaries, demonstrated a lower nutrient (~20%) and polyphenol intake (~15%) compared to that provided by the menus. The feasibility of dietary patterns that enable an increase in polyphenol intake with putative health benefits for age-related conditions is discussed, with a perspective to developing dietary guidelines for this target population.

Intestinal Permeability in Children with Celiac Disease after the Administration of Oligofructose-Enriched Inulin into a Gluten-Free Diet-Results of a Randomized, Placebo-Controlled, Pilot Trial

Abnormalities in the intestinal barrier are a possible cause of celiac disease (CD) development. In animal studies, the positive effect of prebiotics on the improvement of gut barrier parameters has been observed, but the results of human studies to date remain inconsistent. Therefore, this study aimed to evaluate the effect of twelve-week supplementation of a gluten-free diet (GFD) with prebiotic oligofructose-enriched inulin (10 g per day) on the intestinal permeability in children with CD treated with a GFD. A pilot, randomized, placebo-controlled nutritional intervention was conducted in 34 children with CD, being on a strict GFD. Sugar absorption test (SAT) and the concentrations of intestinal permeability markers, such as zonulin, intestinal fatty acid-binding protein, claudin-3, calprotectin, and glucagon-like peptide-2, were measured. We found that the supplementation with prebiotic did not have a substantial effect on barrier integrity. Prebiotic intake increased excretion of mannitol, which may suggest an increase in the epithelial surface. Most children in our study seem to have normal values for intestinal permeability tests before the intervention. For individuals with elevated values, improvement in calprotectin and SAT was observed after the prebiotic intake. This preliminary study suggests that prebiotics may have an impact on the intestinal barrier, but it requires confirmation in studies with more subjects with ongoing leaky gut.

Nobiletin Attenuates DSS-Induced Intestinal Barrier Damage through the HNF4α-Claudin-7 Signaling Pathway

The intestinal epithelium barrier functions to protect human bodies from damages such as harmful microorganisms, antigens, and toxins. In this study, we evaluated the protective effect and molecular mechanism of a dominant polymethoxyflavone nobiletin (NOB) from tangerine peels on intestinal epithelial integrity. The results from transepithelial electrical resistance (TEER) suggested that NOB pretreatment counteracts epithelial injury induced by inflammatory cytokines (TEER value in 48 h: vehicle, 135.6 ± 3.9 Ω/cm²; TNF-α + IL-1β, 90.7 ± 0.5 Ω/cm²; 10 μM NOB + TNF-α + IL-1β, 126.1 ± 0.8 Ω/cm²; 100 μM NOB + TNF-α + IL-1β, 125.3 ± 0.5 Ω/cm². P < 0.001). Clinical and pathological test results suggested that administration of NOB effectively alleviates intestinal barrier injury induced by dextran sulfate sodium (DSS) as evidenced by the length of colon villi on day 7 (control, 253.7 ± 4.8 μm, DSS 131.6 ± 4.6 μm, NOB + DSS, 234.5 ± 5.1 μm. P < 0.001). Interestingly, when screening tight junction molecules for intestinal barrier integrity, we observed that independent treatment with NOB sharply increased claudin-7 levels (ratio of claudin-7 over GAPDH: control, 1.0 ± 0.06; DSS, 0.02 ± 0.001; NOB + DSS, 0.3 ± 0.07. P < 0.001), which was previously suppressed upon DSS stimulation. Furthermore, hepatocyte nuclear factor 4α (HNF-4α) transcriptional regulation of claudin-7 contributed to intestinal barrier homeostasis. Therefore, our study suggests potential intestinal protective strategies based on polymethoxyflavones of aged tangerine peels.

Effect of a polyphenol-rich dietary pattern on intestinal permeability and gut and blood microbiomics in older subjects: study protocol of the MaPLE randomised controlled trial

Background

During aging, alterations of the intestinal microbial ecosystem can occur contributing to immunosenescence, inflamm-aging and impairment of intestinal barrier function (increased intestinal permeability; IP). In the context of a diet-microbiota-IP axis in older subjects, food bioactives such as polyphenols may play a beneficial modulatory role.

Methods

MaPLE is a project centered on a randomized, controlled cross-over dietary intervention trial [polyphenol-rich diet (PR-diet) versus control diet (C-diet)] targeted to older people (≥ 60 y) living in a well-controlled setting (i.e. nursing home). The 8-week interventions are separated by an 8-week wash-out period. Three small portions per day of selected polyphenol-rich foods are consumed during intervention in substitution of other comparable products within the C-diet. Biological samples are collected before and after each treatment period to evaluate markers related to IP, inflammation, vascular function, oxidative stress, gut and blood microbiomics, metabolomics. A sample size of 50 subjects was defined based on IP as primary outcome.

Discussion

Evidence that increasing the consumption of polyphenol-rich food products can positively affect intestinal microbial ecosystem resulting in reduced IP and decreased translocation of inflammogenic bacterial factors into the bloodstream will be provided. The integration of data from gut and blood microbiomics, metabolomics and other IP-related markers will improve the understanding of the beneficial effect of the intervention in the context of polyphenols−microbiota−IP interactions. Finally, findings obtained will provide a proof of concept of the reliability of the dietary intervention, also contributing to future implementations of dietary guidelines directed to IP management in the older and other at risk subjects.

Trial registration

The trial is registered at (ISRCTN10214981); April 28, 2017.

Beneficial Effects of Dietary Polyphenols on High-Fat Diet-Induced Obesity Linking with Modulation of Gut Microbiota

Obesity is caused by an imbalance of energy intake and expenditure. It is characterized by a higher accumulation of body fat with a chronic low-grade inflammation. Many reports have shown that gut microbiota in the host plays a pivotal role in mediating the interaction between consumption of a high-fat diet (HFD) and onset of obesity. Accumulative evidence has suggested that the changes in the composition of gut microbiota may affect the host's energy homeostasis, systemic inflammation, lipid metabolism, and insulin sensitivity. As one of the major components in human diet, polyphenols have demonstrated to be capable of modulating the composition of gut microbiota and reducing the HFD-induced obesity. The present review summarizes the findings of recent studies on dietary polyphenols regarding their metabolism and interaction with bacteria in the intestine as well as the underlying mechanisms by which they modulate the gut microbiota and alleviate the HFD-induced obesity.

Unraveling the Inhibition of Intestinal Glucose Transport by Dietary Phenolics: A Review

Background:

Glucose transport across the intestinal brush border membrane plays a key role in metabolic regulation. Depending on the luminal glucose concentration, glucose is mainly transported by the sodium- dependent glucose transporter (SGLT1) and the facilitated-transporter glucose transporter (GLUT2). SGLT1 is apical membrane-constitutive and it is active at a low luminal glucose concentration, while at concentrations higher than 50 mM, glucose is mainly transported by GLUT2 (recruited from the basolateral membrane). Dietary phenolic compounds can modulate glucose homeostasis by decreasing the postprandial glucose response through the inhibition of SGLT1 and GLUT2.

Methods:

Phenolic inhibition of intestinal glucose transport has been examined using brush border membrane vesicles from rats, pigs or rabbits, Xenopus oocytes and more recently Caco-2 cells, which are the most promising for harmonizing in vitro experiments.

Results:

Phenolic concentrations above 100 µM has been proved to successfully inhibit the glucose transport. Generally, the aglycones quercetin, myricetin, fisetin or apigenin have been reported to strongly inhibit GLUT2, while quercetin-3-O-glycoside has been demonstrated to be more effective in SGLT1. Additionally, epigallocatechin as well as epicatechin and epigallocatechin gallates were observed to be inhibited on both SGLT1 and GLUT2.

Conclusion:

Although, valuable information regarding the phenolic glucose transport inhibition is known, however, there are some disagreements about which flavonoid glycosides and aglycones exert significant inhibition, and also the inhibition of phenolic acids remains unclear. This review aims to collect, compare and discuss the available information and controversies about the phenolic inhibition of glucose transporters. A detailed discussion on the physicochemical mechanisms involved in phenolics-glucose transporters interactions is also included.

Untargeted UPLC-MS metabolomics reveals multiple changes of urine composition in healthy adult volunteers after consumption of curcuma longa L. extract

Curcuma longa L. is used as food supplement to prevent diseases, although limited studies have been performed on healthy subjects up to now. In the present work, an untargeted UPLC-MS metabolomics approach was applied to study the changes of 24-hours urinary composition on healthy volunteers due to a 28-days daily consumption of a dried C. longa extract containing a standardized amount of curcuminoids. Changes in the excretion of different metabolites were observed after supplementation. Curcumin and two metabolic derivatives (hexahydrocurcumin and dihydrocurcumin) were detected in urine, indicating the absorption of the main curcuminoid from the extract and its further metabolism by liver and gut microbiota. For the first time ar-turmerone, the main apolar constituent of curcuma, was detected in urine in intact form, and its presence was confirmed by a targeted GC-MS analysis. The increase of tetranor-PGJM and tetranor-PGDM, two prostaglandin-D2 metabolites, was observed, being related to the anti-inflammatory effect exerted by curcuma. The variation of the amounts of HPAG, PAG, proline-betaine and hydroxyphenyllactic acid indicate that the supplementation induced changes to the activity of gut microbiota. Finally, the reduced excretion of niacin metabolites (nicotinuric acid, trigonelline and 2PY) and medium- and short-chain acylcarnitines suggests that curcuma could induce the mitochondrial β-oxidation of fatty acids for energy production in healthy subjects. Overall, the results indicate that a prolonged daily consumption of a dried curcuma extract exerts multiple effects on healthy subjects, furthermore they show the opportunity offered by untargeted metabolomics for the study of the bioactivity of natural extracts in healthy human volunteers.