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

Effects of Active Ingredients in Alcoholic Beverages and Their De-Alcoholized Counterparts on High-Fat Diet Bees: A Comparative Study

The mechanisms by which alcohol, alcoholic beverages, and their de-alcoholized derivatives affect animal physiology, metabolism, and gut microbiota have not yet been clarified. The polyphenol, monosaccharide, amino acid, and organic acid contents of four common alcoholic beverages (Chinese Baijiu, beer, Chinese Huangjiu, and wine) and their de-alcoholized counterparts were analyzed. The research further explored how these alcoholic beverages and their non-alcoholic versions affect obesity and gut microbiota, using a high-fat diet bee model created with 2% palm oil (PO). The results showed that wine, possessing the highest polyphenol content, and its de-alcoholized form, particularly when diluted five-fold (WDX5), markedly improved the health markers of PO-fed bees, including weight, triglycerides, and total cholesterol levels in blood lymphocytes. WDX5 treatment notably increased the presence of beneficial microbes such as Bartonella, Gilliamella, and Bifidobacterium, while decreasing Bombilactobacillus abundance. Moreover, WDX5 was found to closely resemble sucrose water (SUC) in terms of gut microbial function, significantly boosting short-chain fatty acids, lipopolysaccharide metabolism, and associated enzymatic pathways, thereby favorably affecting metabolic regulation and gut microbiota stability in bees.

Gut Microbiota Targeted Approach by Natural Products in Diabetes Management: An Overview

PURPOSE OF REVIEW

This review delves into the complex interplay between obesity-induced gut microbiota dysbiosis and the progression of type 2 diabetes mellitus (T2DM), highlighting the potential of natural products in mitigating these effects. By integrating recent epidemiological data, we aim to provide a nuanced understanding of how obesity exacerbates T2DM through gut flora alterations.

RECENT FINDINGS

Advances in research have underscored the significance of bioactive ingredients in natural foods, capable of restoring gut microbiota balance, thus offering a promising approach to manage diabetes in the context of obesity. These findings build upon the traditional use of medicinal plants in diabetes treatment, suggesting a deeper exploration of their mechanisms of action. This comprehensive manuscript underscores the critical role of targeting gut microbiota dysbiosis in obesity-related T2DM management and by bridging traditional knowledge with current scientific evidence; we highlighted the need for continued research into natural products as a complementary strategy for comprehensive diabetes care.

Simulated gastrointestinal digestion of beer using the simgi® model. Investigation of colonic phenolic metabolism and impact on human gut microbiota

Beer is a source of bioactive compounds, mainly polyphenols, which can reach the large intestine and interact with colonic microbiota. However, the effects of beer consumption in the gastrointestinal function have scarcely been studied. This paper reports, for the first time, the in vitro digestion of beer and its impact on intestinal microbiota metabolism. Three commercial beers of different styles were subjected to gastrointestinal digestion using the simgi® model, and the digested fluids were further fermented in triplicate with faecal microbiota from a healthy volunteer. The effect of digested beer on human gut microbiota was evaluated in terms of microbial metabolism (short-chain fatty acids (SCFAs) and ammonium ion), microbial diversity and bacterial populations (plate counting and 16S rRNA gene sequencing). Monitoring beer polyphenols through the different digestion phases showed their extensive metabolism, mainly at the colonic stage. In addition, a higher abundance of taxa related to gut health, especially Bacteroides, Bifidobacterium, Mitsuokella and Succinilasticum at the genus level, and the Ruminococcaceae and Prevotellaceae families were found in the presence of beers. Regarding microbial metabolism, beer feeding significantly increased microbial SCFA production (mainly butyric acid) and decreased ammonium content. Overall, these results evidence the positive actions of moderate beer consumption on the metabolic activity of colonic microbiota, suggesting that the raw materials and brewing methods used may affect the beer gut effects.

Polyphenol-Rich Beverages and Mental Health Outcomes

Emerging evidence suggests that diets rich in plant-based foods and beverages may exert plausible effects on human health tackling the risk of chronic diseases. Although the data are promising for numerous outcomes, including cardiovascular diseases, the data on mental health are limited. The aim of this study was to investigate the association between individual polyphenol-rich beverages intake and mental health outcomes, such as perceived stress, depressive symptoms, and sleep quality, among adult individuals living in the Mediterranean area. The demographic and dietary characteristics of a sample of 1572 adults living in southern Italy were analysed. Multivariate logistic regression analyses, controlling for confounding factors, were used to calculate odds ratios (ORs) and 95% confidence intervals (CIs) of the association between individual polyphenol-rich and alcoholic beverages containing polyphenols and mental health outcomes. The multivariate model adjusted for background covariates and the Mediterranean diet showed that individuals with a moderate intake (up to 1 cup/glass per day) of coffee and tea were less likely to have high perceived stress (OR = 0.61, 95% CI: 0.45-0.84) and depressive symptoms (OR = 0.56, 95% CI: 0.39-0.80), respectively. Furthermore, regular coffee and moderate/regular red wine drinkers were less likely to have depressive symptoms (OR = 0.72, 95% CI: 0.54-0.95 and OR = 0.74, 95% CI: 0.54-0.99, respectively). No significant associations were retrieved for the intake of polyphenol-rich and alcoholic beverages and sleep quality. In conclusion, the results of the present study suggest that polyphenol-rich beverages may be associated with mental health, in terms of depressive symptoms and perceived stress. Nonetheless, further research exploring how the polyphenol-rich beverages impact brain health and what the optimal patterns of consumption are for different populations are warranted.

A red wine intervention does not modify plasma trimethylamine N-oxide but is associated with broad shifts in the plasma metabolome and gut microbiota composition

BACKGROUND

Gut microbiota profiles are closely related to cardiovascular diseases through mechanisms that include the reported deleterious effects of metabolites, such as trimethylamine N-oxide (TMAO), which have been studied as diagnostic and therapeutic targets. Moderate red wine (RW) consumption is reportedly cardioprotective, possibly by affecting the gut microbiota.

OBJECTIVES

To investigate the effects of RW consumption on the gut microbiota, plasma TMAO, and the plasma metabolome in men with documented coronary artery disease (CAD) using a multiomics assessment in a crossover trial.

METHODS

We conducted a randomized, crossover, controlled trial involving 42 men (average age, 60 y) with documented CAD comparing 3-wk RW consumption (250 mL/d, 5 d/wk) with an equal period of alcohol abstention, both preceded by a 2-wk washout period. The gut microbiota was analyzed via 16S rRNA high-throughput sequencing. Plasma TMAO was evaluated by LC-MS/MS. The plasma metabolome of 20 randomly selected participants was evaluated by ultra-high-performance LC-MS/MS. The effect of RW consumption was assessed by individual comparisons using paired tests during the abstention and RW periods.

RESULTS

Plasma TMAO did not differ between RW intervention and alcohol abstention, and TMAO concentrations showed low intraindividual concordance over time, with an intraclass correlation coefficient of 0.049 during the control period. After RW consumption, there was significant remodeling of the gut microbiota, with a difference in β diversity and predominance of Parasutterella, Ruminococcaceae, several Bacteroides species, and Prevotella. Plasma metabolomic analysis revealed significant changes in metabolites after RW consumption, consistent with improved redox homeostasis.

CONCLUSIONS

Modulation of the gut microbiota may contribute to the putative cardiovascular benefits of moderate RW consumption. The low intraindividual concordance of TMAO presents challenges regarding its role as a cardiovascular risk biomarker at the individual level. This study was registered at clinical trials.gov as NCT03232099.

Role, Relevance, and Possibilities of In vitro fermentation models in human dietary, and gut-microbial studies

Dietary studies play a crucial role in determining the health-benefiting effects of most food substances, including prebiotics, probiotics, functional foods, and bioactive compounds. Such studies involve gastrointestinal digestion and colonic fermentation of dietary substances. In colonic fermentation, any digested food is further metabolized in the gut by the residing colonic microbiota, causing a shift in the gut microenvironment and production of various metabolites, such as short-chain fatty acids (SCFA). These diet-induced shifts in the microbial community and metabolite production, which can be assessed through in vitro fermentation models using a donor's fecal microbiota, are well known to impact the health of the host. Although in vivo or animal experiments are the gold standard in dietary studies, recent advancements using different in vitro systems, like artificial colon (ARCOL), mini bioreactor array (MBRA), TNO in vitro model of the colon (TIM), Simulator of the Human Intestinal Microbial Ecosystem (SHIME), M-SHIME, CoMiniGut, and Dynamic Gastrointestinal Simulator (SIMGI) make it easy to study the dietary impact in terms of the gut microbiota and metabolites. Such a continuous in vitro system can have multiple compartments corresponding to different parts of the colon, i.e., proximal, transverse, and distal colon, making the findings physiologically more significant. Further, post-fermentation samples can be analyzed using metagenomic, metabolomic, qPCR and flow cytometry approaches. Moreover, studies have shown that in vitro results are in accordance with the in vivo findings, supporting their relevance in dietary studies and giving confidence that shifts in metabolites are only due to microbes. This review meticulously describes the recent advancements in various fermentation models and their relevance in dietary studies. This article is protected by copyright. All rights reserved.

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.

Simulated gastrointestinal digestion of cranberry polyphenols under dynamic conditions. Impact on antiadhesive activity against uropathogenic bacteria

This study is the first dynamic simulation of gastrointestinal digestion of cranberry polyphenols [1 g cranberry extract per day (206.2 mg polyphenols) for 18 days]. Samples from the simulated ascending, transverse, and descending colon of the dynamic gastrointestinal simulator simgi® were analyzed. Results showed that 67% of the total cranberry polyphenols were recovered after simulated gastrointestinal digestion. Specifically, benzoic acids, hydroxycinnamic acids, phenylpropionic acids, phenylacetic acids, and simple phenols were identified. Cranberry feeding modified colonic microbiota composition of Enterococcaceae population significantly. However, increments in microbial-derived short-chain fatty acids, particularly in butyric acid, were observed. Finally, the simgi® effluent during cranberry feeding showed significant antiadhesive activity against uropathogenic Escherichia coli (13.7 ± 1.59 % of inhibition). Understanding the role that gut microbiota plays in cranberry metabolism could help to elucidate its interaction with the human body and explain cranberry protective effects against urinary tract infections.

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

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

Recent Advances in Research on Polyphenols: Effects on Microbiota, Metabolism, and Health

Polyphenols have attracted huge interest among researchers of various disciplines because of their numerous biological activities, such as antioxidative, antiinflammatory, antiapoptotic, cancer chemopreventive, anticarcinogenic, and antimicrobial properties, and their promising applications in many fields, mainly in the medical, cosmetics, dietary supplement and food industries. In this review, the latest scientific findings in the research on polyphenols interaction with the microbiome and mitochondria, their metabolism and health beneficial effects, their involvement in cognitive diseases and obesity development, as well as some innovations in their analysis, extraction methods, development of cosmetic formulations and functional food are summarized based on the papers presented at the 13th World Congress on Polyphenol Applications. Future implications of polyphenols in disease prevention and their strategic use as prophylactic measures are specifically addressed. Polyphenols may play a key role in our tomorrow´s food and nutrition to prevent many diseases.

Phenolic Compounds Promote Diversity of Gut Microbiota and Maintain Colonic Health

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

Role of Food Antioxidants in Modulating Gut Microbial Communities: Novel Understandings in Intestinal Oxidative Stress Damage and Their Impact on Host Health

Dietary components have an important role on the structure and function of host gut microbial communities. Even though, various dietary components, such as carbohydrates, fats, proteins, fibers, and vitamins, have been studied in depth for their effect on gut microbiomes, little attention has been paid regarding the impact of several food antioxidants on the gut microbiome. The long-term exposure to reactive oxygen species (ROS) can cause microbial dysbiosis which leads to numerous intestinal diseases such as microbiota dysbiosis, intestinal injury, colorectal cancers, enteric infections, and inflammatory bowel diseases. Recently, it has been shown that the food derived antioxidant compounds might protect the host from intestinal oxidative stress via modulating the composition of beneficial microbial species in the gut. The present review summarizes the impact of food antioxidants including antioxidant vitamins, dietary polyphenols, carotenoids, and bioactive peptides on the structure as well as function of host gut microbial communities. Several in vitro, animal model, and clinical studies indicates that food antioxidants might modify the host gut microbial communities and their health status. However, still further clarification is needed as to whether changes in certain microbial species caused by food additives may lead to changes in metabolism and immune function.

Potential of Grape Extract in Comparison with Therapeutic Dosage of Antibiotics in Weaning Piglets: Effects on Performance, Digestibility and Microbial Metabolites of the Ileum and Colon

Simple Summary

Diarrhea as a symptom of different enteric infections leads to poor animal health and performance at weaning, followed by economic losses. Phytogenic feed additives, e.g., grape extracts, have shown antimicrobial and anti-inflammatory properties and these might have beneficial effects on growth trends of weaning piglets and, thereby, potentially reduce the need for antibiotic treatments following weaning. An 8-week feeding trial investigated the potential effects of grape extract (GE) in a model with a negative control (NC) and positive control (PC; antibiotic treatment). Despite no changes in animal performance, dietary GE improved the digestibility of selected nutrients at the same, or even at higher level, as PC. Additionally, there was no clear effect of dietary intervention on the microbial metabolites from the ileum and colon at the end of the trial. These results indicated beneficial effects of GE compared to antibiotic treatment, as often applied at weaning.

Abstract

Enteric diseases in piglets, such as post-weaning diarrhea (PWD), often require antibiotic treatment of the entire litter. Grape polyphenols may help overcome PWD and thereby reduce the need for antibiotics. The potential of a grape extract (GE; continuous in-feed supplementation) on performance of weaning piglets, compared with both negative (NC; corn-based diet) and positive control (PC; NC + in-feed antibiotic (amoxicillin) in a therapeutic dosage for day 1–day 5 post weaning) was assessed. Apparent total tract digestibility (ATTD) and microbial metabolites were also evaluated on two sampling points (day 27/28 and day 55/56). We assigned 180 weaning piglets (6.9 ± 0.1 kg body weight (BW)) to 6 male and 6 female pens per treatment with 5 piglets each. Animals from PC showed higher BW on day 13 compared with NC and GE, and a tendency for higher BW on day 56 (p = 0.080) compared to NC. Furthermore, PC increased the average daily feed intake in the starter phase (day 1–day 13), and the average daily gain in the early grower phase (day 14–day 24). Overall, GE improved the ATTD at the same level as PC (ash, acid-hydrolyzed ether extract), or at a higher level than PC (dry matter, organic matter, gross energy, crude protein, P). There were no effects on microbial metabolites apart from minor trends for lactic acid and ammonia. Dietary inclusion of GE may have beneficial effects compared to therapeutic antibiotics, as frequently used at weaning.

Wine, Polyphenols, and Mediterranean Diets. What Else Is There to Say?

A considerable amount of literature has been published claiming the cardiovascular benefits of moderate (red) wine drinking, which has been considered a distinguishing trait of the Mediterranean diet. Indeed, red wine contains relevant amounts of polyphenols, for which evidence of their biological activity and positive health effects are abundant; however, it is also well-known that alcohol, even at a low level of intake, may have severe consequences for health. Among others, it is directly related to a number of non-communicable diseases, like liver cirrhosis or diverse types of cancer. The IARC classifies alcohol as a Group 1 carcinogen, causally associated with the development of cancers of the upper digestive tract and liver, and, with sufficient evidence, can be positively associated with colorectum and female breast cancer. In these circumstances, it is tricky, if not irresponsible, to spread any message on the benefits of moderate wine drinking, about which no actual consensus exists. It should be further considered that other hallmarks of the Mediterranean diet are the richness in virgin olive oil, fruits, grains, and vegetables, which are also good sources of polyphenols and other phytochemicals, and lack the risks of wine. All of these aspects are reviewed in this article.

Effect of black chokeberry pomace extract incorporation on the physical and oxidative stability of water-in-oil-in-water emulsion

BACKGROUND

Despite the obvious benefits of double emulsions in reducing fat content by replacing it with the water phase, their physical and oxidative stability remains a major concern. The objective of this study was to determine the ability of black chokeberry extract to inhibit lipid oxidation during storage at 4 °C for 60 days when different amounts of the extract were added to the inner water phase of the double emulsion. In the first step, the physical stability of the emulsions was evaluated.

RESULTS

Higher amount of the extract caused the formation of double emulsions with smaller droplets and higher viscosity. Throughout the whole storage period, the double emulsions showed good physical stability and high encapsulation efficiency (EE) of the extract (>95%) in the inner water phase. The positive effect of the extract on the oxidative stability of the double emulsions was shown by measuring changes in peroxide values and conjugated dienes and through the Oxipres and Rancimat tests during the convenient and accelerated storage of emulsions for 60 days.

CONCLUSION

The higher amount of extract suppressed lipid oxidation to a higher extent given the significant amount of polyphenolics in the extract. © 2021 Society of Chemical Industry.

Effects of Wine and Its Microbial-Derived Metabolites on Intestinal Permeability Using Simulated Gastrointestinal Digestion/Colonic Fermentation and Caco-2 Intestinal Cell Models

This paper explores the effects of wine polyphenols on intestinal permeability in in vitro conditions. A red wine (2500 mg/L of gallic acid equivalents) was sequentially subjected to gastrointestinal and colonic digestion in the Dynamic Gastrointestinal Simulator (simgi^®) to obtain two simulated fluids: intestinal-digested wine (IDW) and colonic-digested wine (CDW). The two fluids were incubated with Caco-2 cell monolayers grown in Transwell^® inserts, and paracellular permeability was measured as transport of FITC-dextran. Non-significant decreases (p > 0.05) in paracellular permeability were found, which was attributed to the relatively low phenolic concentration in the solutions tested (15.6 and 7.8 mg of gallic acid equivalents/L for IDW and CDW, respectively) as quercetin (200 µM) and one of its microbial-derived phenolic metabolites, 3,4-dihydroxyphenylacetic acid (200 µM), led to significant decreases (p < 0.05). The expression of tight junction (TJ) proteins (i.e., ZO-1 and occludin) in Caco-2 cells after incubation with IDW and CDW was also determined. A slight increase in mRNA levels for occludin for both IDW and CDW fluids, albeit without statistical significance (p > 0.05), was observed. Analysis of the microbiome and microbial activity during wine colonic fermentation revealed relevant changes in the relative abundance of some families/genera (i.e., reduction in Bacteroides and an increase in Veillonella, Escherichia/Shigella and Akkermansia) as well as in the microbial production of SCFA (i.e., a significant increase in propionic acid in the presence of IDW), all of which might affect paracellular permeability. Both direct and indirect (microbiota-mediated) mechanisms might be involved in the protective effects of (wine) polyphenols on intestinal barrier integrity. Overall, this paper reinforces (wine) polyphenols as a promising dietary strategy to improve gut functionality, although further studies are needed to evaluate the effect on the intestinal barrier under different conditions.

A multi-omics approach for understanding the effects of moderate wine consumption on human intestinal health

The human gut is a highly diverse microbial ecosystem. Although showing a well-defined core of dominant taxa, an interindividual variability exists in microbiome arrangement patterns, and the presence and proportion of specific species, determining individual metabolic features-metabotypes-which govern the health effects of dietary interventions (i.e. polyphenol consumption). Starting with a 19-volunteer human intervention study, divided into low, medium, and high wine-polyphenol-metabolizers, we detected interindividual discrepancies on the effect of wine consumption in gut bacterial alpha-diversity, but a significant homogenization of beta-diversity among moderate wine consumers, independently of their metabotype. In addition, the abundance of key health-related taxa such as Akkermansia sp. increased after moderate wine intake in the group of high polyphenol-metabolizers. Regarding the metabolic activity, significant (p < 0.05) positive correlations in the production of SCFAs were observed after wine intake. Finally, we were able to correlate the microbiome and the metabolome of the three metabotypes, and to identify some metabolites-biomarker species, highlighting the genera Phascolarctobacterium, Pelotomaculum and Prevotella, as positively correlated with polyphenol concentration, and Prevotella, Zymophilus and Eubacterium as positively correlated with SCFAs concentration in faeces. Our results contribute to the evidence of the need of including the microbiome variable in personalized nutrition programs, as different metabotyes respond differently to dietary interventions.

Wine Polyphenols and Health: Quantitative Research Literature Analysis

The relationship between wine polyphenols and health has been receiving growing scientific attention in the last few years. To confirm this point, the proposed paper identifies the major contributors to academic journals regarding the relationships between wine polyphenols and health. The endpoints of the proposed study are to provide a comprehensive overview and analysis of the literature regarding the relationships between wine polyphenol and health based on a bibliometric analysis. Bibliometric data were extracted from the Scopus online database using the search string TITLE-ABS-KEY (wine AND polyphenol* AND health OR (“french paradox” OR “cardiovascular disease*” OR atherosclerosis OR microbiota) and analyzed using the VOSviewer bibliometric software to generate bubble maps and to visualize the obtained results. This perspective paper analyzes: (i) the research themes addressing the relationships between wine polyphenols and health; (ii) the major contributors’ origin, e.g., country and/or regions; (iii) the institutions where the research is based; (iv) the authors; and (v) the type of paper. These results represent a useful tool to identify emerging research directions, collaboration networks, and suggestions for more in-depth literature searches.

Curcumin, Quercetin, Catechins and Metabolic Diseases: The Role of Gut Microbiota

Polyphenols (PPs) are the naturally occurring bioactive components in fruits and vegetables, and they are the most abundant antioxidant in the human diet. Studies are suggesting that ingestion of PPs might be helpful to ameliorate metabolic syndromes that may contribute in the prevention of several chronic disorders like diabetes, obesity, hypertension, and colon cancer. PPs have structural diversity which impacts their bioavailability as they accumulate in the large intestine and are extensively metabolized through gut microbiota (GM). Intestinal microbiota transforms PPs into their metabolites to make them bioactive. Interestingly, not only GM act on PPs to metabolize them but PPs also modulate the composition of GM. Thus, change in GM from pathogenic to beneficial ones may be helpful to ameliorate gut health and associated diseases. However, to overcome the low bioavailability of PPs, various approaches have been developed to improve their solubility and transportation through the gut. In this review, we present evidence supporting the structural changes that occur after metabolic reactions in PPs (curcumin, quercetin, and catechins) and their effect on GM composition that leads to improving overall gut health and helping to ameliorate metabolic disorders.

Coniferaldehyde ameliorates the lipid and glucose metabolism in palmitic acid-induced HepG2 cells via the LKB1/AMPK signaling pathway

Impaired lipid and glucose metabolism in the liver is a crucial characteristic of nonalcoholic fatty liver disease (NAFLD). Coniferaldehyde (CA), a kind of phenolic compound found in many edible plants, has multiple biological and pharmacological functions. However, since the effect and molecular mechanism of CA on hepatic lipid and glucose metabolism disorders in NAFLD remain unknown, this study investigated its impact on the lipid and glucose metabolism of palmitic acid (PA)-induced HepG2 cells. Compared with the HepG2 cells treated only with PA, supplementation with 25, 50, and 100 µM CA reduced the levels of intracellular triglyceride (by 7.11%, 19.62%, and 31.57%) and total cholesterol (by 8.46%, 23.32%, and 27.17%), and enhanced glucose uptake (by 40.91%, 57.49%, and 61.32%) and intracellular glycogen content (by 12.75%, 41.27%, and 53.77%). Moreover, CA supplementation downregulated the expression of sterol regulatory element-binding protein-1, fatty acid synthase, and stearoyl-CoA desaturase 1 related to lipogenesis while upregulating the expression of carnitine palmitoyltransferase 1α related to fatty acid oxidation. CA supplementation also upregulated the glucose transporter 2 protein expression and phosphorylation of glycogen synthase kinase 3β while downregulating the phosphorylation of glycogen synthase. Most importantly, most of these effects of CA were reversed by pretreatment with AMP-activated protein kinase (AMPK) inhibitor and small interfering RNA-liver kinase B1 (LKB1). In conclusion, CA ameliorated the lipid and glucose metabolism in PA-induced HepG2 cells via the LKB1/AMPK signaling pathway. PRACTICAL APPLICATION: In this study, coniferaldehyde appeared to be effective in ameliorating hepatic lipid and glucose metabolism disorders in nonalcoholic fatty liver disease by reducing the levels of intracellular triglyceride and total cholesterol and enhancing glucose uptake and intracellular glycogen content via the LKB1/AMPK signaling pathway in vitro. Therefore, our findings provide new evidence in support of that supplementation with coniferaldehyde or food rich in coniferaldehyde might be considered as a viable dietary intervention strategy for preventing and treating nonalcoholic fatty liver disease.

Modifications of Gut Microbiota after Grape Pomace Supplementation in Subjects at Cardiometabolic Risk: A Randomized Cross-Over Controlled Clinical Trial

Polyphenols are dietary bioactive compounds able to induce modifications in the gut microbiota profile, although more clinical studies are needed. With this aim, a randomized cross-over clinical trial was conducted, where 49 subjects at cardiometabolic risk (exhibiting at least two metabolic syndrome factors) were supplemented with a daily dose of 8 g of grape pomace (GP) for 6 weeks, with an equivalent control (CTL) period. The levels of total bacteria and Bacteroidetes, Firmicutes, Lactobacilliales, Bacteroides and Prevotella were estimated in fecal DNA by quantitative real-time PCR (qPCR), while fecal short-chain fatty acids (SCFAs) were assessed by gas chromatography. Several cardiometabolic markers were evaluated in blood samples. GP reduced insulin levels only in half of the participants (responders). GP supplementation did not cause significant modifications in the microbiota profile of the whole group, except for a tendency (p = 0.059) towards a decrease in the proportion of Lactobacilliales, while it increased the proportion of Bacteroides in non-responder subjects. The reduction of insulin levels in subjects at cardiometabolic risk upon GP supplementation appears not to be induced by changes in the major subgroups of gut microbiota. Further studies at the species level may help to elucidate the possible role of microbiota in GP-induced insulinemic status.