Role of the small intestine, colon and microbiota in determining the metabolic fate of polyphenols

Phenyl-γ-valerolactones and phenylvaleric acids, the main colonic metabolites of flavan-3-ols: synthesis, analysis, bioavailability, and bioactivity

Covering: 1958 to June 2018 Phenyl-γ-valerolactones (PVLs) and their related phenylvaleric acids (PVAs) are the main metabolites of flavan-3-ols, the major class of flavonoids in the human diet. Despite their presumed importance, these gut microbiota-derived compounds have, to date, in terms of biological activity, been considered subordinate to their parent dietary compounds, the flavan-3-ol monomers and proanthocyanidins. In this review, the role and prospects of PVLs and PVAs as key metabolites in the understanding of the health features of flavan-3-ols have been critically assessed. Among the topics covered, are proposals for a standardised nomenclature for PVLs and PVAs. The formation, bioavailability and pharmacokinetics of PVLs and PVAs from different types of flavan-3-ols are discussed, taking into account in vitro and animal studies, as well as inter-individual differences and the existence of putative flavan-3-ol metabotypes. Synthetic strategies used for the preparation of PVLs are considered and the methodologies for their identification and quantification assessed. Metabolomic approaches unravelling the role of PVLs and PVAs as biomarkers of intake are also described. Finally, the biological activity of these microbial catabolites in different experimental models is summarised. Knowledge gaps and future research are considered in this key area of dietary (poly)phenol research.

Interactions of tea catechins with intestinal microbiota and their implication for human health

Tea catechins have attracted strong interests in pharmacological field for their extensive biological activities; however, their bioavailability in vivo is relatively low. Recent studies have shown tea catechins can modulate the composition of intestinal microbiota and help to improve hosts' health. Meanwhile, the gut flora plays a crucial role in regulating the production of the metabolites of tea catechins and their biological activity. Although the activities of tea catechins to promote intestinal micro-ecology have been extensively studied, little is known about the two-way phenol-microbial interactions. This review focuses on the modulatory effect of tea catechins on intestinal microbiota as well as the microbial degradation of tea catechins and the metabolites formed. Finally, the potential effects of tea catechins on chronic intestinal inflammation are emphasized.

Urinary Metabolites of Green Tea as Potential Markers of Colonization Resistance to Pathogenic Gut Bacteria in Mice

Background

The gut microbiome (GMB) generates numerous chemicals that are absorbed systemically and excreted in urine. Antibiotics can disrupt the GMB ecosystem and weaken its resistance to colonization by enteric pathogens such as Clostridium difficile. If the changes in GMB composition and metabolism are sufficiently large, they can be reflected in the urinary metabo-lome. Characterizing these changes could provide a potentially valuable biomarker of the status of the GMB. While preliminary studies suggest such a possibility, the high level of data variance presents a challenge to translational applications. Since many GMB-generated chemicals are derived from the biotransformation of plant-derived dietary polyphenols, administering an oral precursor challenge should amplify GMB-dependent changes in urinary metabolites.

Methods

A course of antibiotics (clindamycin, piperacillin/tazobactam, or aztreonam) was administered SC daily (days 1 and 2) to mice receiving polyphenol-rich green tea in drinking water. Urine was collected at baseline as well as days 3, 7, and 11. Levels of pyrogallol and pyrocatechol, two phenolic molecules unequivocally GMB-dependent in humans but that had not been similarly examined in mice, were quantified.

Results

In confirmation of our hypothesis, differential changes in murine urinary pyrogallol levels identified the treatments (clindamycin, piperacillin/tazobactam) previously associated with a weakening of colonization resistance to Clostridium difficile. The changes in pyrocatechol levels did not withstand corrections for multiple comparisons.

Conclusions

In the mouse, urinary pyrogallol and, in all likelihood, pyrocatechol levels, are GMB-dependent and, in combination with precursor challenge, deserve further consideration as potential metabolomic biomarkers for the health and dysbiotic vulnerability of the GMB.

In vitro Gastrointestinal Models for Prebiotic Carbohydrates: A Critical Review

Background:

In the last decade, various consortia and companies have created standardized digestion protocols and gastrointestinal simulators, such as the protocol proposed by the INFOGEST Consortium, the simulator SHIME, the simulator simgi®, the TIM, etc. Most of them claim to simulate the entire human gastrointestinal tract. However, few results have been reported on the use of these systems with potential prebiotic carbohydrates.

Methods:

This critical review addresses the existing data on the analysis of prebiotic carbohydrates by different in vitro gastrointestinal simulators, the lack of parameters that could affect the results, and recommendations for their enhancement.

Results:

According to the reviewed data, there is a lack of a realistic approximation of the small intestinal conditions, mainly because of the absence of hydrolytic conditions, such as the presence of small intestinal brush border carbohydrases that can affect the digestibility of different carbohydrates, including prebiotics.

Conclusion:

There is a necessity to standardize and enhance the small intestine simulators to study the in vitro digestibility of carbohydrates.

Berry-Enriched Diet in Salt-Sensitive Hypertensive Rats: Metabolic Fate of (Poly)Phenols and the Role of Gut Microbiota

Diets rich in (poly)phenols are associated with a reduced reduction in the incidence of cardiovascular disorders. While the absorption and metabolism of (poly)phenols has been described, it is not clear how their metabolic fate is affected under pathological conditions. This study evaluated the metabolic fate of berry (poly)phenols in an in vivo model of hypertension as well as the associated microbiota response. Dahl salt-sensitive rats were fed either a low-salt diet (0.26% NaCl) or a high-salt diet (8% NaCl), with or without a berry mixture (blueberries, blackberries, raspberries, Portuguese crowberry and strawberry tree fruit) for 9 weeks. The salt-enriched diet promoted an increase in the urinary excretion of berry (poly)phenol metabolites, while the abundance of these metabolites decreased in faeces, as revealed by UPLC-MS/MS. Moreover, salt and berries modulated gut microbiota composition as demonstrated by 16S rRNA analysis. Some changes in the microbiota composition were associated with the high-salt diet and revealed an expansion of the families Proteobacteria and Erysipelotrichaceae. However, this effect was mitigated by the dietary supplementation with berries. Alterations in the metabolic fate of (poly)phenols occur in parallel with the modulation of gut microbiota in hypertensive rats. Thus, beneficial effects of (poly)phenols could be related with these interlinked modifications, between metabolites and microbiota environments.

The Gastrointestinal Tract as Prime Site for Cardiometabolic Protection by Dietary Polyphenols

Substantial evidence from nutritional epidemiology links polyphenol-rich diets with reduced incidence of chronic disorders; however, biological mechanisms underlying polyphenol-disease relations remain enigmatic. Emerging evidence is beginning to unmask the contribution of the gastrointestinal tract on whole-body energy homeostasis, suggesting that the intestine may be a prime target for intervention and a fundamental site for the metabolic actions of polyphenols. During their transit through the gastrointestinal tract, polyphenols may activate enteric nutrient sensors ensuing appropriate responses from other peripheral organs to regulate metabolic homeostasis. Furthermore, polyphenols can modulate the absorption of glucose, attenuating exaggerated hormonal responses and metabolic imbalances. Polyphenols that escape absorption are metabolized by the gut microbiota and the resulting catabolites may act locally, activating nuclear receptors that control enteric functions such as intestinal permeability. Finally, polyphenols modulate gut microbial ecology, which can have profound effects on cardiometabolic health.

Untargeted screening of the bound / free phenolic composition in tomato cultivars for industrial transformation

BACKGROUND

Tomato is one of the most important agricultural crops and it is characterized by a wide bioactive compound profile. However, little information is reported on its comprehensive polyphenol profile. In this work, 13 commercial tomato cultivars for industrial transformation were screened by ultra-high-pressure liquid chromatography coupled to quadrupole-time-of-flight mass spectrometry (UHPLC-QTOF-MS) for both free and bound phenolic profiles. Thereafter, the in vitro antioxidant activity of each cultivar was assessed by ferric reducing antioxidant power (FRAP) and oxygen radical absorbance activity (ORAC) assays. Multivariate statistics, i.e. orthogonal projection to latent structures discriminant analysis (OPLS-DA), were then used to model samples according to their distinct phenolic signatures, thus providing compounds that better discriminated between the distributions of the cultivars that were considered.

RESULTS

More than 350 phenolic compounds could be identified across the samples that were considered: flavonoids (such as flavones and flavanols), hydroxycinnamic acids, lignans, and lower-molecular-weight phenolics were the most frequently observed classes of phenolics in tomato berries. Anthocyanins were the most abundant class among bound phenolics (being highest in the Leader F1 and Defender F1 cultivars), followed by tyrosols (mainly in Heinz cultivars). However, flavones and hydroxybenzoic acids were the most represented discriminant phenolics in the bound fraction.

CONCLUSIONS

Untargeted metabolomics allowed significant differences in phenolic composition to be outlined across the tomato cultivars that were analyzed. Such differences were particularly evident regarding the free-to-bound phenolic ratio, hence allowing differences in the bioaccessibility of phenolics to be postulated. © 2019 Society of Chemical Industry.

Associations between habitual flavonoid intake and hospital admissions for atherosclerotic cardiovascular disease: a prospective cohort study

BACKGROUND

Flavonoids, compounds found in plant-based foods and beverages, might ameliorate vascular damage and atherosclerosis. Therefore, our aim was to assess the association between flavonoid intake and hospital admissions due to atherosclerotic cardiovascular disease.

METHODS

In this prospective cohort study, participants from the Danish Diet, Cancer, and Health Study were cross-linked with Danish nationwide registries. Eligible participants were aged 50-65 years, had no previous history of atherosclerotic cardiovascular disease, and had completed a food-frequency questionnaire at baseline. We examined associations between flavonoid intake (calculated from food-frequency questionnaires with use of the Phenol-Explorer database) and hospital admissions for atherosclerotic cardiovascular disease, ischaemic heart disease, ischaemic stroke, or peripheral arterial disease. We obtained hazard ratios (HRs) using restricted cubic splines based on Cox proportional hazards models.

FINDINGS

Of the participants recruited to the Danish Diet, Cancer, and Health study between 1993 and 1997, our study population was comprised of 53 552 participants, with a median follow-up of 21 years (IQR 15-22). During follow-up, 8773 participants were admitted to hospital for atherosclerotic cardiovascular disease. We observed non-linear associations between flavonoid intake and hospital admissions, plateauing at total flavonoid intakes of approximately 1000 mg per day. Compared with an intake of 175 mg per day, an intake of 1000 mg per day was associated with a 14% lower risk of atherosclerotic cardiovascular disease (HR 0·86, 95% CI 0·81-0·91). For disease subtypes, we observed a 9% lower risk of ischaemic heart disease (0·91, 0·85-0·98), a non-significant 9% lower risk of ischaemic stroke (0·91, 0·82-1·01), and a 32% lower risk of peripheral artery disease (0·68, 0·60-0·78). The overall associations were stronger in smokers than in non-smokers, as well as stronger in consumers of high (>20 g per day) quantities of alcohol than in those consuming low-to-moderate (≤20 g per day) quantities.

INTERPRETATION

Our results suggest that ensuring an adequate consumption of flavonoid-rich foods, particularly in subpopulations at risk of atherosclerosis such as smokers and consumers of high quantities of alcohol might mitigate some of the risk of atherosclerotic cardiovascular disease. More studies are needed to support and validate these data.

FUNDING

Danish Cancer Society.

Polyphenols in human nutrition: from the in vitro antioxidant capacity to the beneficial effects on cardiometabolic health and related inter-individual variability - an overview and perspective

Oxidative damage of cells and tissues is broadly implicated in human pathophysiology, including cardiometabolic diseases. Polyphenols, as important constituents of the human diet and potent in vitro free radical scavengers, have been extensively studied for their beneficial effects on cardiometabolic health. However, it has been demonstrated that the in vivo antioxidant activity of polyphenols is distinct from their in vitro free radical-scavenging capacity. Indeed, bioavailability of nutritional polyphenols is low and conditioned by complex mechanisms of absorption, distribution, metabolism and excretion. Nowadays, it is commonly accepted that the cellular antioxidant activity of polyphenols is mainly carried out via modification of transcription of genes involved in antioxidant defence. Importantly, polyphenols also contribute to cardiometabolic health by modulation of a plethora of cellular processes that are not directly associated with antioxidant enzymes, through nutri(epi)genomic mechanisms. Numerous human intervention studies have demonstrated beneficial effects of polyphenols on the key cardiometabolic risk factors. However, inconsistency of the results of some studies led to identification of the inter-individual variability in response to consumption of polyphenols. In perspective, a detailed investigation of the determinants of this inter-individual variability will potentially lead us towards personalised dietary recommendations. The phenomenon of inter-individual variability is also of relevance for supplementation with antioxidant (pro)vitamins.

Curcumin, Gut Microbiota, and Neuroprotection

Curcumin, a nontoxic, naturally occurring polyphenol, has been recently proposed for the management of neurodegenerative and neurological diseases. However, a discrepancy exists between the well-documented pharmacological activities that curcumin seems to possess in vivo and its poor aqueous solubility, bioavailability, and pharmacokinetic profiles that should limit any therapeutic effect. Thus, it is possible that curcumin could exert direct regulative effects primarily in the gastrointestinal tract, where high concentrations of curcumin are present after oral administration. Indeed, a new working hypothesis that could explain the neuroprotective role of curcumin despite its limited availability is that curcumin acts indirectly on the central nervous system by influencing the “microbiota–gut–brain axis”, a complex bidirectional system in which the microbiome and its composition represent a factor which preserves and determines brain “health”. Interestingly, curcumin and its metabolites might provide benefit by restoring dysbiosis of gut microbiome. Conversely, curcumin is subject to bacterial enzymatic modifications, forming pharmacologically more active metabolites than curcumin. These mutual interactions allow to keep proper individual physiologic functions and play a key role in neuroprotection.

Pereira W, Maximiano LF, de Alcântara PS, Otoch JP, Trinchieri G, Laviano A, Muscaritoli M, Seelaender M. Cancer cachexia induces morphological and inflammatory changes in the intestinal mucosa

BACKGROUND

Cachexia is a multifactorial and multiorgan syndrome associated with cancer and other chronic diseases and characterized by severe involuntary body weight loss, disrupted metabolism, inflammation, anorexia, fatigue, and diminished quality of life. This syndrome affects around 50% of patients with colon cancer and is directly responsible for the death of at least 20% of all cancer patients. Systemic inflammation has been recently proposed to underline most of cachexia-related symptoms. Nevertheless, the exact mechanisms leading to the initiation of systemic inflammation have not yet been unveiled, as patients bearing the same tumour and disease stage may or may not present cachexia. We hypothesize a role for gut barrier disruption, which may elicit persistent immune activation in the host. To address this hypothesis, we analysed the healthy colon tissue, adjacent to the tumour.

METHODS

Blood and rectosigmoid colon samples (20 cm distal to tumour margin) obtained during surgery, from cachectic (CC = 25) or weight stable (WSC = 20) colon cancer patients, who signed the informed consent form, were submitted to morphological (light microscopy), immunological (immunohistochemistry and flow cytometry), and molecular (quantification of inflammatory factors by Luminex® xMAP) analyses.

RESULTS

There was no statistical difference in gender and age between groups. The content of plasma interleukin 6 (IL-6) and IL-8 was augmented in cachectic patients relative to those with stable weight (P = 0.047 and P = 0.009, respectively). The number of lymphocytic aggregates/field in the gut mucosa was higher in CC than in WSC (P = 0.019), in addition to those of the lamina propria (LP) eosinophils (P < 0.001) and fibroblasts (P < 0.001). The area occupied by goblet cells in the colon mucosa was decreased in CC (P = 0.016). The M1M2 macrophages percentage was increased in the colon of CC, in relation to WSC (P = 0.042). Protein expression of IL-7, IL-13, and transforming growth factor beta 3 in the colon was significantly increased in CC, compared with WSC (P = 0.02, P = 0.048, and P = 0.048, respectively), and a trend towards a higher content of granulocyte-colony stimulating factor in CC was also observed (P = 0.061). The results suggest an increased recruitment of immune cells to the colonic mucosa in CC, as compared with WSC, in a fashion that resembles repair response following injury, with higher tissue content of IL-13 and transforming growth factor beta 3.

CONCLUSIONS

The changes in the intestinal mucosa cellularity, along with modified cytokine expression in cachexia, indicate that gut barrier alterations are associated with the syndrome.

Regulation of Gut Microbiota and Metabolic Endotoxemia with Dietary Factors

Metabolic endotoxemia is a condition in which blood lipopolysaccharide (LPS) levels are elevated, regardless of the presence of obvious infection. It has been suggested to lead to chronic inflammation-related diseases such as obesity, type 2 diabetes mellitus, non-alcoholic fatty liver disease (NAFLD), pancreatitis, amyotrophic lateral sclerosis, and Alzheimer’s disease. In addition, it has attracted attention as a target for the prevention and treatment of these chronic diseases. As metabolic endotoxemia was first reported in mice that were fed a high-fat diet, research regarding its relationship with diets has been actively conducted in humans and animals. In this review, we summarize the relationship between fat intake and induction of metabolic endotoxemia, focusing on gut dysbiosis and the influx, kinetics, and metabolism of LPS. We also summarize the recent findings about dietary factors that attenuate metabolic endotoxemia, focusing on the regulation of gut microbiota. We hope that in the future, control of metabolic endotoxemia using dietary factors will help maintain human health.

Overview of the Anticancer Profile of Avenanthramides from Oat

Cancer represents one of the leading causes of death worldwide. Progresses in treatment of cancer have continued at a rapid pace. However, undesirable side effects and drug resistance remain major challenges for therapeutic success. Natural products represent a valuable starting point to develop new anticancer strategies. Polyphenols, well-known as antioxidant, exert anticancer effects through the modulation of multiple pathways and mechanisms. Oat (Avena sativa L., Poaceae) is a unique source of avenanthramides (AVAs), a group of polyphenolic alkaloids, considered as its signature compounds. The present review aims to offer a comprehensive and critical perspective on the chemopreventive and chemotherapeutic potential of AVAs. AVAs prevent cancer mainly by blocking reactive species. Moreover, they exhibit potential therapeutic activity through the modulation of different pathways including the activation of apoptosis and senescence, the block of cell proliferation, and the inhibition of epithelial mesenchymal transition and metastatization. AVAs are promising chemopreventive and anticancer phytochemicals, which need further clinical trials and toxicological studies to define their efficacy in preventing and reducing the burden of cancer diseases.

Exploring the effective materials of flavonoids-enriched extract from Scutellaria baicalensis roots based on the metabolic activation in influenza A virus induced acute lung injury

Flavonoids-enriched extract from Scutellaria baicalensis roots (FESR) ameliorated influenza A virus (IAV) induced acute lung injury (ALI) in mice by inhibiting the excessive activation of complement system in vivo. However, FESR had no anti-complementary activity in vitro. In order to reveal the effective materials of FESR for the treatment of IAV-induced ALI, the present research explored the metabolic process of FESR both in nomal and IAV infected mice by the method of UHPLC-ESI-LTQ/MS, as well as the metabolic activating mechanism. The results showed that the inactive flavonoid glycosides of FESR were partly metabolized into anti-complementary aglycones in vivo, mainly including 5,7,4'-trihydroxy-8-methoxy-flavone, norwogonin, baicalein, wogonin, oroxylin A and chrysin. Moreover, compared with the normal mice, IAV-induced ALI mice exhibited more efficient on producing and absorbing these active metabolites, with AUC_0-t and C_max in plasma and concentrations in lungs and intestines markedly elevated in the IAV treated groups (P <  0.05). Interestingly, the intestinal bacteria from IAV-induced ALI mice showed stronger β-glucuronidase activity and also had higher efficiency on transforming FESR to the flavonoid aglycones. These findings suggested that the anti-complementary aglycones produced by metabolic activation in vivo should be the potential effective materials of FESR against IAV infections, and intestinal bacteria might play an important role on the higher bioavailability of FESR in IAV infected mice. Additionally, the animals under the pathological state are more suitable for the metabolic study of traditional Chinese medicine.

Raw Bowl Tea (Tuocha) Polyphenol Prevention of Nonalcoholic Fatty Liver Disease by Regulating Intestinal Function in Mice

A high-fat diet-induced C57BL/6N mouse model of non-alcoholic fatty liver disease (NAFLD) was established. The effect and mechanism of Raw Bowl Tea polyphenols (RBTP) on preventing NAFLD via regulating intestinal function were observed. The serum, liver, epididymis, small intestine tissues, and feces of mice were examined by biochemical and molecular biological methods, and the composition of RBTP was analyzed by HPLC assay. The results showed that RBTP could effectively reduce the body weight, liver weight, and liver index of NAFLD mice. The serum effects of RBTP were: (1) decreases in alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (AKP), total cholesterol (TC), triglyceride (TG), low density lipoprotein cholesterol (LDL-C), D-lactate (D-LA), diamine oxidase (DAO), lipopolysaccharide (LPS), and an increase of high density lipoprotein cholesterol (HDL-C) levels; (2) a decrease of inflammatory cytokines such as interleukin 1 beta (IL-1β), interleukin 4 (IL-4), interleukin 6 (IL-6), interleukin 10 (IL-10), tumor necrosis factor alpha (TNF-α), and interferon gamma (INF-γ); (3) a decrease the reactive oxygen species (ROS) level in liver tissue; and (4) alleviation of pathological injuries of liver, epididymis, and small intestinal tissues caused by NAFLD and protection of body tissues. qPCR and Western blot results showed that RBTP could up-regulate the mRNA and protein expressions of LPL, PPAR-α, CYP7A1, and CPT1, and down-regulate PPAR-γ and C/EBP-α in the liver of NAFLD mice. In addition, RBTP up-regulated the expression of occludin and ZO-1, and down-regulated the expression of CD36 and TNF-α in the small intestines of NAFLD mice. Studies on mice feces showed that RBTP reduced the level of Firmicutes and increased the minimum levels of Bacteroides and Akkermansia, as well as reduced the proportion of Firmicutes/Bacteroides in the feces of NAFLD mice, which play a role in regulating intestinal microecology. Component analysis showed that RBTP contained seven polyphenolic compounds: Gallic acid, (-)-epigallocatechin, catechin, L-epicatechin, (-)-epigallocatechin gallate, (-)-gallocatechin gallate, and (-)-epicatechin gallate (ECG), and high levels of caffeine, (-)-epigallocatechin (EGC), and ECG. RBTP improved the intestinal environment of NAFLD mice with the contained active ingredients, thus playing a role in preventing NAFLD. The effect was positively correlated with the dose of 100 mg/kg, which was even better than that of the clinical drug bezafibrate.

Full 1 H and 13 C NMR spectral assignment of conjugated valerolactone metabolites isolated from urine of black tea consumers by means of SPE-prepLC-MS-LC-MS-NMR

The health benefits of black tea have been linked to polyphenol metabolites that target specific modes of action in the human body. A major bottleneck in unravelling the underlying mechanisms is the preparative isolation of these metabolites, which hampers their structural elucidation and assessment of in vitro bioactivity. A solid phase extraction (SPE)-preparative liquid chromatography (prepLC)-MS-LC-MS-NMR workflow was implemented for preparative isolation of conjugated valerolactone metabolites of catechin-based polyphenols from urine of black tea consumers. First, the urine was cleaned and preconcentrated using an SPE method. Subsequently, the clean urine concentrate was injected on a preparative LC column, and conjugated valerolactones were obtained by MS-guided collection. Reconstituted fractions were further separated on an analytical LC column, and valerolactone fractions were collected in an MS-guided manner. These were reconstituted in methanol-d₄ and identified and quantified using 1D and 2D homo- and hetereonuclear NMR experiments (at a field strength of 14.1 T), in combination with mass spectrometry. This resulted in the full spectral ¹ H and ¹³ C NMR assignments of five conjugated valerolactones. These metabolites were collected in quantities of 8-160 μg and purities of 70-91%. The SPE-prepLC-MS-LC-MS-NMR workflow is suitable for isolating metabolites that occur at sub-μM concentrations in a complex biofluid such as urine. The workflow also provides an alternative for cumbersome and expensive de novo synthesis of tea metabolites for testing in bioactivity assays or for use as authentic analytical standards for quantification by mass spectrometry.

3-(3-Hydroxyphenyl)-Propionic Acid (PPA) Suppresses Osteoblastic Cell Senescence to Promote Bone Accretion in Mice

Phenolic acids (PAs) are metabolites derived from polyphenolic compounds found in fruits and vegetables resulting from the actions of gut bacteria. Previously, we reported that the levels of seven individual PAs were found to be at least 10 times higher in the serum of rats fed a blueberry (BB)‐containing diet compared to those fed a control diet. We have characterized the effects of one such BB‐associated serum PA, 3‐(3‐hydroxyphenyl)‐propionic acid (PPA), on senescence signaling and promotion of mesenchymal stem cell differentiation toward osteoblasts, while suppressing adipogenesis in the stem cells. To better understand the mechanistic actions of PPA on bone formation in vivo, we administered four doses of PPA (0.1, 0.5, 1, and 5 mg/kg/day; daily i.p.) to 1‐month‐old female C57BL6/J mice for 30 days. We did not observe significant effects of PPA on cortical bone; however, there were significantly higher bone volume and trabecular thickness and increased osteoblastic cell number, but decreased osteoclastic cell number in PPA‐treated groups compared to controls. These morphological and cellular outcomes of bone were reflected in changes of bone formation markers in serum and bone marrow plasma. PPA treatment reduced senescence signaling as evaluated by senescence‐associated β‐galactosidase activity, PPARγ, p53, and p21 expression in bone. In conclusion, PPA is capable of altering the mesenchymal stem cell differentiation program and bone cell senescence. This raises the possibility that BB‐rich diets promote bone growth through increasing systemic PAs, a question that merits additional investigation. © 2019 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

Biomonitoring of Deoxynivalenol and Deoxynivalenol-3-glucoside in Human Volunteers: Renal Excretion Profiles

Biomarkers for the determination of the dietary exposure to deoxynivalenol (DON) have been proposed in the past but so far no quantification of their use in humans has been carried out. Following a human intervention study with two mycotoxins, namely DON and deoxynivalenol-3-glucoside (DON3G), the renal excretion of these compounds, including their phase II metabolites, was analysed. The purpose was to develop biokinetic models that can be used to determine: (1) the preferred (set of) urinary biomarker(s), (2) the preferred urinary collection period, and (3) a method to estimate the dietary exposure to these mycotoxins. Twenty adult volunteers were restricted in consuming cereals and cereal-based foods for 4 days. At day 3, a single dose of 1 µg/kg body weight of DON or DON3G was orally administered to 16 volunteers; 4 volunteers served as control. All individual urine discharges were collected during 24 h after administration. The metabolism and renal excretion could be described by a biokinetic model using three physiological compartments (gastrointestinal tract, liver, and kidneys). Kinetic analysis revealed a complete recovery of the renal excretion of total DON (mainly DON and its glucuronides) within 24 h after administration of DON or DON3G. The so-called 'reverse dosimetry' factor was used to determine the preferred (set of) biomarker(s) and to estimate the dietary intake of the parent compounds in the future. The fact that DON3G was absorbed and mainly excreted as DON and its glucuronides confirms that DON3G (as well as other modified forms) should be taken into account in the exposure and risk assessment of this group of mycotoxins.

Impact of Foods and Dietary Supplements Containing Hydroxycinnamic Acids on Cardiometabolic Biomarkers: A Systematic Review to Explore Inter-Individual Variability

Plant-based diets rich in bioactive compounds such as polyphenols have been shown to positively modulate the risk of cardiometabolic (CM) diseases. The inter-individual variability in the response to these bioactives may affect the findings. This systematic review aimed to summarize findings from existing randomized clinical trials (RCTs) evaluating the effect of hydroxycinnamic acids (HCAs) on markers of CM health in humans. Literature searches were performed in PubMed and the Web of Science. RCTs on acute and chronic supplementation of HCA-rich foods/extracts on CM biomarkers were included. Forty-four RCTs (21 acute and 23 chronic) met inclusion criteria. Comparisons were made between RCTs, including assessments based on population health status. Of the 44 RCTs, only seven performed analyses on a factor exploring inter-individual response to HCA consumption. Results demonstrated that health status is a potentially important effect modifier as RCTs with higher baseline cholesterol, blood pressure and glycaemia demonstrated greater overall effectiveness, which was also found in studies where specific subgroup analyses were performed. Thus, the effect of HCAs on CM risk factors may be greater in individuals at higher CM risk, although future studies in these populations are needed, including those on other potential determinants of inter-individual variability. PROSPERO, registration number CRD42016050790.

In Vitro Gastrointestinal Digestion and Colonic Fermentation of High Dietary Fiber and Antioxidant-Rich Mango (Mangifera indica L.) "Ataulfo"-Based Fruit Bars

Mango (Mangifera indica L.) is a tropical fruit which is considered to be a source of dietary fiber (DF) and phenolic compounds (PCs). In this study, high DF mango-based fruit bars were developed from whole mango (peel and pulp). The bars were evaluated for their nutritional composition, the bioaccesibility of PCs during gastrointestinal digestion, and the PCs metabolites profile after in vitro colonic fermentation. The amount of DF in a 30 g portion of mango bars was 9.5 g, i.e., 35% of the recommended daily intake. Phenolic acids such as gallic acid; cinnamic acids, such as ferulic, coumaric, and caffeic acids; flavonoids such as quercertin; and xanthones such as mangiferin and mangiferin gallate, were identified as the main PCs in the bars. The antioxidant capacity associated with the PCs profile, together with the high DF content are indicative of the potential functional features of these natural fruit bars. The bioaccesibility of PCs in the mango bar was 53.78%. During fermentation, the PCs were bioconverted mainly to hydroxyphenolic acids and the main short-chain fatty acid produced was acetic acid. The xanthone norathyriol was identified after 12 h of fermentation. This study on the digestion and colonic fermentation of mango-based bars using in vitro models provides hints of the potential physiological behavior of PCs associated with DF, which constitutes relevant information for further development of natural and health-promoting fruit-based bars.

Prebiotics from Seaweeds: An Ocean of Opportunity?

Seaweeds are an underexploited and potentially sustainable crop which offer a rich source of bioactive compounds, including novel complex polysaccharides, polyphenols, fatty acids, and carotenoids. The purported efficacies of these phytochemicals have led to potential functional food and nutraceutical applications which aim to protect against cardiometabolic and inflammatory risk factors associated with non-communicable diseases, such as obesity, type 2 diabetes, metabolic syndrome, cardiovascular disease, inflammatory bowel disease, and some cancers. Concurrent understanding that perturbations of gut microbial composition and metabolic function manifest throughout health and disease has led to dietary strategies, such as prebiotics, which exploit the diet-host-microbe paradigm to modulate the gut microbiota, such that host health is maintained or improved. The prebiotic definition was recently updated to "a substrate that is selectively utilised by host microorganisms conferring a health benefit", which, given that previous discussion regarding seaweed prebiotics has focused upon saccharolytic fermentation, an opportunity is presented to explore how non-complex polysaccharide components from seaweeds may be metabolised by host microbial populations to benefit host health. Thus, this review provides an innovative approach to consider how the gut microbiota may utilise seaweed phytochemicals, such as polyphenols, polyunsaturated fatty acids, and carotenoids, and provides an updated discussion regarding the catabolism of seaweed-derived complex polysaccharides with potential prebiotic activity. Additional in vitro screening studies and in vivo animal studies are needed to identify potential prebiotics from seaweeds, alongside untargeted metabolomics to decipher microbial-derived metabolites from seaweeds. Furthermore, controlled human intervention studies with health-related end points to elucidate prebiotic efficacy are required.

Inter-individual variability in the production of flavan-3-ol colonic metabolites: preliminary elucidation of urinary metabotypes

PURPOSE

There is much information on the bioavailability of (poly)phenolic compounds following acute intake of various foods. However, there are only limited data on the effects of repeated and combined exposure to specific (poly)phenol food sources and the inter-individual variability in their bioavailability. This study evaluated the combined urinary excretion of (poly)phenols from green tea and coffee following daily consumption by healthy subjects in free-living conditions. The inter-individual variability in the production of phenolic metabolites was also investigated.

METHODS

Eleven participants consumed both tablets of green tea and green coffee bean extracts daily for 8 weeks and 24-h urine was collected on five different occasions. The urinary profile of phenolic metabolites and a set of multivariate statistical tests were used to investigate the putative existence of characteristic metabotypes in the production of flavan-3-ol microbial metabolites.

RESULTS

(Poly)phenolic compounds in the green tea and green coffee bean extracts were absorbed and excreted after simultaneous consumption, with green tea resulting in more inter-individual variability in urinary excretion of phenolic metabolites. Three metabotypes in the production of flavan-3-ol microbial metabolites were tentatively defined, characterized by the excretion of different amounts of trihydroxyphenyl-γ-valerolactones, dihydroxyphenyl-γ-valerolactones, and hydroxyphenylpropionic acids.

CONCLUSIONS

The selective production of microbiota-derived metabolites from flavan-3-ols and the putative existence of characteristic metabotypes in their production represent an important development in the study of the bioavailability of plant bioactives. These observations will contribute to better understand the health effects and individual differences associated with consumption of flavan-3-ols, arguably the main class of flavonoids in the human diet.

Bioavailability and metabolism of selected cocoa bioactive compounds: A comprehensive review

Cocoa beans and their co-products are a rich source of beneficial compounds for health promotion, including polyphenols and methylxanthines. Knowledge of bioavailability and in vivo bioactivity of these phytochemicals is crucial to understand their role and function in human health. Therefore, many studies concerning bioavailability and bioactivity of cocoa bioactive compound have been done in both in vivo animal models and in humans. This critical review comprehensively summarizes the existing knowledge about the bioavailability and the major metabolic pathways of selected cocoa bioactive compounds (i.e. monomeric flavan-3-ols, procyanidins, anthocyanins, flavonols, phenolic acids, N-phenylpropenoyl-L-amino acids, stilbenes, and methylxanthines). The compiled results indicated that many of these compounds undergo extensive metabolism prior to absorption. Different factors have been suggested to influence the bioavailability of polyphenols and methylxanthines among them the role of gut microbiota, structure of these compounds, food matrix and occurrence of other substances were the most often considered. Aforementioned factors decided about the site where these bioactive compounds are digested and absorbed from the alimentary tract, as well as the pathway by which they are metabolized. These factors also determine of the type of transport through the intestine barrier (passive, involving specific enzymes or mediated by specific transporters) and their metabolic path and profile.

Polyphenolic Nutraceuticals to Combat Oxidative Stress Through Microbiota Modulation

Due to their direct relationship with the activity of the gut microbiota, nutraceuticals are, at present, an effective alternative for the mitigation and alleviation of the dysfunctions governed by oxidative stress. The escalation in the number of the target group patients (diabetes, cardiovascular dysfunction, cancer, etc.) has spurred the quest for alternative action methods. The therapeutic value is determined through in vitro and in vivo methods, and involves the analysis of the therapeutic index. As the adverse outcomes are decreased, the pharmacological potential is assessed by the mechanisms, including biotransformation and the identification of the relevant biomarkers. Inflammatory action is among the principal effects that need to be reduced because it favors the presence of free radicals and dysbiosis. This article aimed at highlighting the action of the nutraceuticals in minimizing the oxidative stress by directly influencing the microbiota and slowing down the inflammatory progression. The pharmacological aspects as a therapeutic indicator of the use of nutraceuticals in improving the population health.

The phenolic interactome and gut microbiota: opportunities and challenges in developing applications for schizophrenia and autism

Schizophrenia and autism spectrum disorder have long been associated with elevated levels of various small phenolic molecules (SPMs). In turn, the gut microbiota (GMB) has been implicated in the kinetics of many of these analytes. Unfortunately, research into the possible relevance of GMB-mediated SPMs to neuropsychiatry continues to be limited by heterogeneous study design, numerous sources of variance and technical challenges. Some SPMs have multiple structural isomers and most have conjugates. Without specialized approaches, SPMs can be incorrectly assigned or inaccurately quantified. In addition, SPM levels can be affected by dietary polyphenol or protein consumption and by various medications and diseases. Nonetheless, heterotypical excretion of various SPMs in association with schizophrenia or autism continues to be reported in independent samples. Recent studies in human cerebrospinal fluid demonstrate the presence of many SPMs A large number of these are bioactive in experimental models. Whether such mechanisms are relevant to the human brain in health or disease is not known. Systematic metabolomic and microbiome studies of well-characterized populations, an appreciation of multiple confounds, and implementation of standardized approaches across platforms and sites are needed to delineate the potential utility of the phenolic interactome in neuropsychiatry.

Cocoa Flavanols: Natural Agents with Attenuating Effects on Metabolic Syndrome Risk Factors

The interest in cacao flavanols is still growing, as bioactive compounds with potential benefits in the prevention of chronic diseases associated with inflammation, oxidative stress and metabolic disorders. Several analytical methodologies support that the flavanols in cacao-derived products can be absorbed, have bioactive properties, and thus can be responsible for their beneficial effects on human health. However, it must be considered that their biological actions and underlying molecular mechanisms will depend on the concentrations achieved in their target tissues. Based on the antioxidant properties of cacao flavanols, this review focuses on recent advances in research regarding their potential to improve metabolic syndrome risk factors. Additionally, it has included other secondary plant metabolites that have been investigated for their protective effects against metabolic syndrome. Studies using laboratory animals or human subjects represent strong available evidence for biological effects of cacao flavanols. Nevertheless, in vitro studies are also included to provide an overview of these phytochemical mechanisms of action. Further studies are needed to determine if the main cacao flavanols or their metabolites are responsible for the observed health benefits and which are their precise molecular mechanisms.

Plant phenolics as functional food ingredients

Phenolic compounds have attracted much attention in recent times as their dietary intake has been associated with the prevention of some chronic and degenerative diseases that constitute major causes of death and incapacity in developed countries, such as cardiovascular diseases, type II diabetes, some types of cancers or neurodegenerative disorders like Alzheimer's and Parkinson's diseases. Nowadays it is considered that these compounds contribute, at least in part, for the protective effects of fruit and vegetable-rich diets, so that the study of their role in human nutrition has become a central issue in food research. This chapter reviews the current knowledge on the phenolic compounds as food components, namely their occurrence in the diet, bioavailability and metabolism, biological activities and mechanisms of action. Besides, the approaches for their extraction from plant matrices and technological improvements regarding their preparation, stability and bioavailability in order to be used as functional food ingredients are also reviewed, as well as their legal situation regarding the possibility of making "health claims" based on their presence in food and beverages.

A 6-week supplementation with grape pomace to subjects at cardiometabolic risk ameliorates insulin sensitivity, without affecting other metabolic syndrome markers

Grape polyphenols have shown a promising role in the modulation of metabolic syndrome (MetS), mostly in animal models. However, clinical studies are scarce and they usually only consider a fraction of polyphenols, ignoring the non-extractable polyphenols (high molecular weight compounds or associated with macromolecules such as dietary fibre). This study aimed at evaluating the effect of grape pomace, rich in both extractable and non-extractable polyphenols, on markers of MetS. Fifty subjects (22 women) aged 20-65 with at least two MetS factors were randomly assigned to the product (daily dose of 8 g of dried grape pomace) or to the control group in a 6 week crossover design with a 4 week wash-out. Samples were collected at the beginning and at the end of both periods; half of the participants were subjected to an oral glucose tolerance test at the beginning and the end of the supplementation period. Grape pomace supplementation significantly improved fasting insulinaemia (p < 0.01), without affecting other cardiometabolic risk parameters. A tendency towards an improvement in postprandial insulinaemia was observed, particularly in those subjects with higher fasting insulin levels. Therefore, supplementation with grape pomace may be a strategy for improving insulin sensitivity in subjects at high cardiometabolic risk.

Digestion and Colonic Fermentation of Raw and Cooked Opuntia ficus-indica Cladodes Impacts Bioaccessibility and Bioactivity

The bioactivity of (poly)phenols from a food is an interplay between the cooking methods applied and the interaction of the food with the gastrointestinal tract. The (poly)phenolic profile and biological activity of raw and cooked cactus ( Opuntia ficus-indica Mill.) cladodes following in vitro digestion and colonic fermentation were evaluated. Twenty-seven (poly)phenols were identified and quantified by HPLC-ESI-MS, with piscidic acid being the most abundant. Throughout the colonic fermentation, flavonoids showed more degradation than phenolic acids, and eucomic acid remained the most relevant after 24 h. The catabolite 3-(4-hydroxyphenyl)propionic acid was generated after 24 h of fermentation. Cytotoxicity, genotoxicity, and cell cycle analyses were performed in HT29 cells. Cactus colonic fermentates showed higher cell viability (≥80%) in comparison to the control fermentation with no cactus and significantly ( p < 0.05) reduced H₂O₂-induced DNA damage in HT29 cells. Results suggest that, although phenolic compounds were degraded during the colonic fermentation, the biological activity is retained in colon cells.

Betanin, a Natural Food Additive: Stability, Bioavailability, Antioxidant and Preservative Ability Assessments

Betanin is the only betalain approved for use in food and pharmaceutical products as a natural red colorant. However, the antioxidant power and health-promoting properties of this pigment have been disregarded, perhaps due to the difficulty in obtaining a stable chemical compound, which impairs its absorption and metabolism evaluation. Herein, betanin was purified by semi-preparative HPLC-LC/MS and identified by LC-ESI(+)-MS/MS as the pseudomolecular ion m/z 551.16. Betanin showed significant stability up to -30 °C and mild stability at chilling temperature. The stability and antioxidant ability of this compound were assessed during a human digestion simulation and ex vivo colon fermentation. Half of the betanin amount was recovered in the small intestine digestive fluid and no traces were found after colon fermentation. Betanin high antioxidant ability was retained even after simulated small intestine digestion. Betanin, besides displaying an inherent colorant capacity, was equally effective as a natural antioxidant displaying peroxy-radical scavenger ability in pork meat. Betanin should be considered a multi-functional molecule able to confer an attractive color to frozen or refrigerated foods, but with the capacity to avoid lipid oxidation, thereby preserving food quality. Long-term supplementation by beetroot, a rich source of betanin, should be stimulated to protect organisms against oxidative stress.

Preparation and Characterization of Protocatechuic Acid Sulfates

Protocatechuic acid (3,4-dihydroxybenzoic acid; PCA) is a phenolic acid present in plants as a secondary metabolite and is also produced in the human organism as a metabolite from the degradation of polyphenols by the intestinal microbiota, particularly of flavonoids. However, PCA, like most polyphenols, is biotransformed in the human body to different conjugates as sulfates, which are found circulating in blood and could be involved in the bioactivity of the original compound. This paper describes a simple process for the preparation of PCA monosulfates with satisfactory yields. Two compounds were obtained that were identified as PCA-3-sulfate and PCA-4-sulfate by mass spectrometry and ¹H and ¹³C nuclear magnetic resonance using one- and two-dimensional techniques (heteronuclear single-quantum coherence and heteronuclear multiple-bond correlation). Differential MS fragmentation behavior and UV spectra were observed for each compound, which could be used for their identification in samples of unknown composition. The described procedure can be used for the preparation of these polyphenol metabolites in view of their use in in vivo and in vitro studies, as well as standards for their analysis in biological fluids, to contribute to the elucidation of biological effects of dietary polyphenols.

Quantification of phenolic acid metabolites in humans by LC-MS: a structural and targeted metabolomics approach

AIM

Co-metabolism between a human host and the gastrointestinal microbiota generates many small phenolic molecules such as 3-hydroxy-3-(3-hydroxyphenyl)propanoic acid (3,3-HPHPA), which are reported to be elevated in schizophrenia and autism. Characterization of these chemicals, however, has been limited by analytic challenges.

METHODOLOGY/RESULTS

We applied HPLC to separate and quantify over 50 analytes, including multiple structural isomers of 3,3-HPHPA in human cerebrospinal fluid, serum and urine. Confirmation of identity was provided by NMR, by MS and other detection methods. The highly selective methods support rapid quantification of multiple metabolites and exhibit superior chromatographic behavior.

CONCLUSION

An improved ultra-HPLC-MS/MS and structural approaches can accurately quantify 3,3-HPHPA and related analytes in human biological matrices.

Bioactivity of dietary polyphenols: The role of metabolites

A polyphenol-rich diet protects against chronic pathologies by modulating numerous physiological processes, such as cellular redox potential, enzymatic activity, cell proliferation and signaling transduction pathways. However, polyphenols have a low oral bioavailability mainly due to an extensive biotransformation mediated by phase I and phase II reactions in enterocytes and liver but also by gut microbiota. Despite low oral bioavailability, most polyphenols proved significant biological effects which brought into attention the low bioavailability/high bioactivity paradox. In recent years, polyphenol metabolites have attracted great interest as many of them showed similar or higher intrinsic biological effects in comparison to the parent compounds. There is a huge body of literature reporting on the biological functions of polyphenol metabolites generated by phase I and phase II metabolic reactions and gut microbiota-mediated biotransformation. In this respect, the review highlights the pharmacokinetic fate of the major dietary polyphenols (resveratrol, curcumin, quercetin, rutin, genistein, daidzein, ellagitannins, proanthocyanidins) in order to further address the efficacy of biometabolites as compared to parent molecules. The present work strongly supports the contribution of metabolites to the health benefits of polyphenols, thus offering a better perspective in understanding the role played by dietary polyphenols in human health.

(-)-Epicatechin in the control of glucose homeostasis: Involvement of redox-regulated mechanisms

Emerging evidence supports a beneficial action of the flavan-3-ol (-)-epicatechin (EC) on insulin sensitivity and potential impact on the development/progression of type 2 diabetes (T2D). In humans, supplementation with EC-rich foods, extracts, and pure EC improves insulin sensitivity and glucose tolerance in normal weight, overweight, obese and T2D individuals. These effects of EC are also observed in rodent models of diet-induced obesity and T2D. The events involved in the development of insulin resistance and T2D are multiple and interrelated. EC has been shown to inhibit inflammation, oxidative and endoplasmic reticulum stress, to modulate mitochondrial biogenesis and function, and to regulate events in the gastrointestinal tract and the pancreas that impact glucose homeostasis. A downregulation of oxidant production, particularly through direct inhibition or suppression of NADPH oxidase expression, and of redox sensitive signals (NF-κB, JNK1/2) that inhibit the insulin pathway, appear to be central to the beneficial actions of EC on insulin sensitivity. Overall, EC seems to have a positive role in the regulation of glucose homeostasis, however definitive answers on its importance for the management of T2D will depend on further clinical and mechanistic studies.

Differential Impact of Flavonoids on Redox Modulation, Bioenergetics, and Cell Signaling in Normal and Tumor Cells: A Comprehensive Review

SIGNIFICANCE

Flavonoids can interact with multiple molecular targets to elicit their cellular effects, leading to changes in signal transduction, gene expression, and/or metabolism, which can, subsequently, affect the entire cell and organism. Immortalized cell lines, derived from tumors, are routinely employed as a surrogate for mechanistic studies, with the results extrapolated to tissues in vivo. Recent Advances: We review the activities of selected flavonoids on cultured tumor cells derived from various tissues in comparison to corresponding primary cells or tissues in vivo, mainly using quercetin and flavanols (epicatechin and (-)-epigallocatechin gallate) as exemplars. Several studies have indicated that flavonoids could retard cancer progression in vivo in animal models as well as in tumor cell models.

CRITICAL ISSUES

Extrapolation from in vitro and animal models to humans is not straightforward given both the extensive conjugation and complex microbiota-dependent metabolism of flavonoids after consumption, as well as the heterogeneous metabolism of different tumors.

FUTURE DIRECTIONS

Comparison of data from studies on primary cells or in vivo are essential not only to validate results obtained from cultured cell models, but also to highlight whether any differences may be further exploited in the clinical setting for chemoprevention. Tumor cell models can provide a useful mechanistic tool to study the effects of flavonoids, provided that the limitations of each model are understood and taken into account in interpretation of the data.

Increased sporulation underpins adaptation of Clostridium difficile strain 630 to a biologically-relevant faecal environment, with implications for pathogenicity

Clostridium difficile virulence is driven primarily by the processes of toxinogenesis and sporulation, however many in vitro experimental systems for studying C. difficile physiology have arguably limited relevance to the human colonic environment. We therefore created a more physiologically–relevant model of the colonic milieu to study gut pathogen biology, incorporating human faecal water (FW) into growth media and assessing the physiological effects of this on C. difficile strain 630. We identified a novel set of C. difficile–derived metabolites in culture supernatants, including hexanoyl– and pentanoyl–amino acid derivatives by LC-MSⁿ. Growth of C. difficile strain 630 in FW media resulted in increased cell length without altering growth rate and RNA sequencing identified 889 transcripts as differentially expressed (p < 0.001). Significantly, up to 300–fold increases in the expression of sporulation–associated genes were observed in FW media–grown cells, along with reductions in motility and toxin genes’ expression. Moreover, the expression of classical stress–response genes did not change, showing that C. difficile is well–adapted to this faecal milieu. Using our novel approach we have shown that interaction with FW causes fundamental changes in C. difficile biology that will lead to increased disease transmissibility.

Smallanthus sonchifolius (Yacon) Flour Improves Visceral Adiposity and Metabolic Parameters in High-Fat-Diet-Fed Rats

Smallanthus sonchifolius (yacon), a native plant of South America, was observed to improve lipid profile in rodents and humans. This study aimed to investigate the antiobesity properties of yacon roots in a high-fat-diet (HFD) model and the underlying mechanisms. A total of 30 Wistar male rats were divided into five groups (n=6): the standard chow diet (SD) group was fed a SD; the HFD group was fed a HFD; and the HFD Y340 and HFD Y680 groups were fed a HFD plus yacon flour (340 and 680 mg FOS/kg b. w./day, respectively). HFD Y340 and HFD Y680 rats exhibited marked attenuation of weight gain, a decrease in visceral fat pad weight, a restoration of the serum lipid profile and atherogenic index in a dose-dependent manner, being the higher dose more effective (p < 0.05). In addition, we found that HFD Y680 rats showed lower glucose and insulin levels, improved glucose tolerance, and insulin sensitivity (p < 0.5). A downregulation of several adipocyte specific-transcription factors, including peroxisome proliferator-activated receptor gamma2 (PPAR-γ2), CCAAT/enhancer binding protein a (C/EBP-a) and activating protein (aP2) mRNA levels, was determined in the visceral adipose tissue of HFD Y680 rats (p < 0.05). An improvement of adipokine profile in HFD Y680 rats and decreased serum proinflammatory cytokine levels (p < 0.05) were determined by ELISA. Decreased macrophage infiltration and F4/80 and MCP-1 expression in the visceral adipose tissue of HFD Y680 rats (p < 0.5), together with a higher pAkt/Akt expression (p < 0.05) were also observed by immunofluorescence and immunoblotting. A significant increase in glucagon (Gcg) and PYY mRNA levels in distal ileum of HFD Y680 rats (p < 0.05) were also detected. In the second approach, we determined that yacon supplementation potentiates the effects of the HFD reversion to a standard diet. In conclusion, yacon showed antiobesity properties by inhibiting adipogenesis and improving the visceral adipose tissue function.

A critical evaluation of the use of gas chromatography- and high performance liquid chromatography-mass spectrometry techniques for the analysis of microbial metabolites in human urine after consumption of orange juice

The present study compared and validated two analytical methods, HPLC-HRMS, and GC-MS using MSTFA as derivatization agent, for the analysis of microbiota-derived phenolic acids and aromatic compounds accumulating in urine, collected over a 24 h period after the consumption of 500 mL of orange juice. In addition, purification procedures using SDB-L and HLB solid phase cartridges were compared when HPLC-HRMS technique was used. Both HPLC-HRMS and GC-MS methodologies were successfully validated in terms of specificity, sensitivity, limit of detection and quantification, recovery and matrix effects. HPLC-HRMS, unlike GC-MS, does not require sample derivatization prior to analysis. GC-MS was not suitable for the analysis of phenolic sulfate and glucuronide metabolites because of their lack of volatility. These phase II metabolites could, however, be analysed by HPLC-HRMS which, as a consequence, provided more detailed and complete information on the phenolic compounds derived from microbiota-mediated degradation of orange juice (poly)phenols. Furthermore, the use of SDB-L and HLB cartridges for sample purification prior to HPLC-HRMS analysis is suitable for free phenolics and glucuronide metabolites but not sulfate derivatives. These findings highlight that the use of an inappropriate analytical protocol can adversely affect studies on the bioavailability of dietary (poly)phenols in which microbiota-derived phenolic catabolites play an important role.

Gut microbiome catabolites as novel modulators of muscle cell glucose metabolism

The gut microbiome supplies essential metabolites such as short-chain fatty acids to skeletal muscle mitochondria, and the composition and activity of the microbiota is in turn affected by muscle fitness. To further our understanding of the complex interactions between the gut microbiome and muscle, we examined the effect of microbiota-derived phenolic metabolites on the ability of human muscle cells to take up and metabolize glucose. As a model, we used the differentiated human skeletal muscle myoblast line, LHCN-M2, which expresses typical muscle phenotypic markers. We initially tested a selected panel of parent phenolic compounds and microbial metabolites, and their respective phenolic conjugates, as found in blood. Several of the tested compounds increased glucose uptake and metabolism, notably in high glucose- and insulin-treated myotubes. One of the most effective was isovanillic acid 3 -O-sulfate (IVAS), a metabolite from the microbiome found in the blood, primarily derived from consumed cyanidin 3 -O-glucoside, a major compound in berry fruits. IVAS stimulated a dose-dependent increase in glucose transport through glucose transporter GLUT4- and PI3K-dependent mechanisms. IVAS also up-regulated GLUT1, GLUT4, and PI3K p85α protein, and increased phosphorylation of Akt. The stimulation of glucose uptake and metabolism by a unique microbiome metabolite provides a novel link among diet, gut microbiota, and skeletal muscle energy source utilization.-Houghton, M. J., Kerimi, A., Mouly, V., Tumova, S., Williamson, G. Gut microbiome catabolites as novel modulators of muscle cell glucose metabolism.