Epigallocatechin gallate but not catechin prevents nonalcoholic steatohepatitis in mice similar to green tea extract while differentially affecting the gut microbiota

A review on the effects of flavan-3-ols, their metabolites, and their dietary sources on gut barrier integrity

Impairment of gut barrier integrity is associated with the pathogenesis of gastrointestinal diseases, including inflammatory bowel disease, colorectal cancer, and coeliac disease. While many aspects of diet have been linked to improved barrier function, (poly)phenols, a broad group of bioactive phytochemicals, are of potential interest. The (poly)phenolic sub-class, flavan-3-ols, have been investigated in some detail owing to their abundance in commonly consumed foods, including grapes, tea, apples, cocoa, berries, and nuts. This review summarises studies on the effects of flavan-3-ols, their microbiome-mediated metabolites, and food sources of these compounds, on gut barrier structure. Extensive evidence demonstrates that flavan-3-ol rich foods, individual flavan-3-ols (e.g., (epi)catechin, epi(gallo)catechin-3-O-gallate, and pro(antho)cyanidins), and their related microbiota-mediated metabolites, could be effective in protecting and restoring the integrity of the gut barrier. In this context, various endpoints are assessed, including transepithelial electrical resistance of the epithelial layer and expression of tight junction proteins and mucins, in ex vivo, in vitro, and animal models. The differences in bioactivity reported for barrier integrity are structure-function dependent, related to the (poly)phenolic source or the tested compound, as well as their dose, exposure time, and presence or absence of a stressor in the experimental system. Overall, these results suggest that flavan-3-ols and related compounds could help to maintain, protect, and restore gut barrier integrity, indicating that they might contribute to the beneficial properties associated with the intake of their dietary sources. However, rigorous and robustly designed human intervention studies are needed to confirm these experimental observations.

Dachengqi decoction ameliorated liver injury in liver fibrosis mice by maintaining gut vascular barrier integrity

BACKGROUND

Severe liver fibrosis may be accompanied by intestinal barrier damage, such as bacterial peritonitis, suggesting that the role of the gut-liver axis is nonnegligible. Dachengqi decoction (DCQD) was reported to improve bowel movements, but whether DCQD was effective for intestinal damage caused by liver fibrosis remained unclear.

PURPOSE

To investigate the role of DCQD in liver fibrosis-related gut vascular barrier (GVB) damage in mice.

STUDY DESIGN

DCQD was verified to reduce the imbalance of the intestinal vascular barrier and restore intestinal homeostasis to prove that DCQD acts through the gut-liver axis.

METHODS

Three graded doses of DCQD were gavaged into the CCL4-induced mice for 12 weeks to evaluate the resistance to liver and intestinal damage. Immunoblotting and primary flow cytometry were used to assess organ damage; PV-1 to indicate gut vascular barrier damage; serum endotoxin, fecal SCFAs, and liver microbiota translocation to examine the gut-liver axis's crosstalk. Network pharmacology and RNA sequencing were used to analyze and verify the signaling pathway of DCQD.

RESULTS

DCQD significantly ameliorated fibrosis and inflammatory response in the CCL4-induced mice, alleviated gut leakage, downregulated PV-1, relieved liver enterobacterial translocation, restored intestinal homeostasis, and reduced infiltration of myeloid cells in the lamina propria. Network pharmacology and RNA sequencing results indicated that DCQD exerted anti-fibrotic and anti-inflammatory effects in the liver through inhibition of the ESR1/NF-κB/TNFα pathway and maintained GVB homeostasis through the FUT2/Wnt/β-Catenin pathway.

CONCLUSIONS

DCQD broke the closed-loop damage of the gut-liver axis to improve GVB injury in mice with liver fibrosis.

Epigallocatechin-3-gallate therapeutic potential in human diseases: molecular mechanisms and clinical studies

Green tea has garnered increasing attention across age groups due to its numerous health benefits, largely attributed to Epigallocatechin 3-gallate (EGCG), its key polyphenol. EGCG exhibits a wide spectrum of biological activities, including antioxidant, anti-inflammatory, antibacterial, anticancer, and neuroprotective properties, as well as benefits for cardiovascular and oral health. This review provides a comprehensive overview of recent findings on the therapeutic potential of EGCG in various human diseases. Neuroprotective effects of EGCG include safeguarding neurons from damage and enhancing cognitive function, primarily through its antioxidant capacity to reduce reactive oxygen species (ROS) generated during physiological stress. Additionally, EGCG modulates key signaling pathways such as JAK/STAT, Delta-Notch, and TNF, all of which play critical roles in neuronal survival, growth, and function. Furthermore, EGCG is involved in regulating apoptosis and cell cycle progression, making it a promising candidate for the treatment of metabolic diseases, including cancer and diabetes. Despite its promising therapeutic potential, further clinical trials are essential to validate the efficacy and safety of EGCG and to optimize its delivery to target tissues. While many reviews have addressed the anticancer properties of EGCG, this review focuses on the molecular mechanisms and signaling pathways by which EGCG used in specific human diseases, particularly cancer, neurodegenerative and metabolic diseases. It serves as a valuable resource for researchers, clinicians, and healthcare professionals, revealing the potential of EGCG in managing neurodegenerative disorders, cancer, and metabolic diseases and highlighting its broader therapeutic values.

Modulation of gut microbiome in response to the combination of Escherichia coli Nissle 1917 and sugars: a pilot study using host-free system reflecting impact on interpersonal microbiome

Introduction

The differential effects of probiotic, prebiotic, and synbiotic formulations on human health are dictated by the inter-individual gut microbial profile. The effects of probiotics such as Escherichia coli Nissle 1917 (ECN) on gut microbiota may vary according to the microbiome profiles of individuals and may be influenced by the presence of certain carbohydrates, which can impact microbial community structure and treatment results.

Method

Processed fecal samples from donors having contrasting lifestyles, dietary patterns, and disease histories were mixed with 5 × 106 CFU/mL ECN with or without 1% (w/v) sugars (glucose, galactose, or rice starch) in a host-free system. Post-incubation, 16 s rRNA sequencing was performed. Microbial diversity and taxonomic abundance were computed in relation to the probiotic, prebiotic, and synbiotic treatment effects and interpersonal microbiome variance.

Result

Baseline gut microbial profiles showed significant inter-individual variations. ECN treatment alone had a limited impact on the inter-personal gut microbial diversity and abundance. Prebiotics caused a substantial enrichment in Actinobacteria, but there were differences in the responses at the order and genus levels, with enrichment shown in Bifidobacterium, Collinsella, and Megasphaera. Subject B exhibited enrichment in Proteobacteria and Cyanobacteria, but subject A showed more diversified taxonomic alterations as a consequence of the synbiotic treatments. Despite negligible difference in the α-diversity, probiotic, prebiotic, and synbiotic treatments independently resulted in distinct segregation in microbial communities at the β-diversity level. The core microbiota was altered only under prebiotic and synbiotic treatment. Significant correlations primarily for minor phyla were identified under prebiotic and synbiotic treatment.

Conclusion

The interindividual microbiome composition strongly influences the effectiveness of personalized diet and treatment plans. The responsiveness to dietary strategies varies according to individual microbiome profiles influenced by health, diet, and lifestyle. Therefore, tailored approaches that consider individual microbiome compositions are crucial for maximizing gut health and treatment results.

Assessment of the Impact of Dietary Supplementation with Epigallocatechin Gallate (EGCG) on Antioxidant Status, Immune Response, and Intestinal Microbiota in Post-Weaning Rabbits

This study was conducted to investigate the impact of EGCG on antioxidant stress, immune response, and intestinal microbiota flora in post-weaning rabbits. A total of 144 40 d Ira rabbits (equally divided by sex), were randomly allocated to six treatments. with five groups receiving doses of 200, 400, 600, 800, and 1000 mg/kg of EGCG, while one group served as a control without EGCG. Over 48 days, this study the assessed growth performance, antioxidant capacity, immune system, intestinal morphology, and cecal microbiota in the rabbits. The results showed that EGCG did not affect growth performance; however, significant linear and quadratic correlations were observed between the MDA, T-AOC, and GSH-Px activities in the liver and jejunum (p < 0.05). Quadratic effects were observed for the spleen and thymus indexes and serum IgG levels with increasing EGCG dosages (p < 0.05). Additionally, positive linear and quadratic effects were found on the ileal villus height and the villus height/crypt depth ratio. The relative abundances of Euryarchaeota, Patescibacteria, and Synergistota were significantly enriched in rabbits fed with high dosages (600-1000 mg/kg) of EGCG. Conclusively, the addition of large doses of EGCG (400-800 mg/kg) can effectively suppress oxidative stress and alleviate weaning stress, thereby contributing to the protection of post-weaning rabbits.

Chemical characterization, pathway enrichments and bioactive potentials of catechin-producing endophytic fungi isolated from tea leaves

Endophytes acquire flavonoid biosynthetic genes from the host medicinal plants. Despite tea (Camellia sinensis (L.) Kuntze) being the major source of bioactive catechins, catechin-producing endophytic fungi have never been reported from the tea plant. Here, we report the isolation and characterization of catechin-producing endophytic fungi isolated from tea leaves, their chemical characterization, and associated bioactivities. Among the nine isolated endophytes, two (CSPL6 and CSPL5b) produced catechin (381.48 and 166.40 μg per mg extract) and epigallocatechin-o-gallate (EGCG; 484.41 and 281.99 μg per mg extract) as quantified by high-performance liquid chromatography (HPLC). The isolates were identified as Pseudopestalotiopsis camelliae-sinensis and Didymella sinensis based on molecular and morphological characterization. Untargeted metabolomics using gas-chromatography mass spectroscopy (GCMS) revealed the presence of several bioactive phytochemicals mostly belonging to tyrosols, pyridoxines, fatty acids, aminopyrimidine, and benzenetriol classes. Metabolic pathways pertaining to the biosynthesis of unsaturated fatty acids (UFAs), butanoate metabolism, and linoleic acid metabolism were highly enriched in both catechin-producing isolates. The isolates were able to differentially scavenge intracellular O2 and N2 free-radicals, but CSPL5b demonstrated relatively superior bioactivities compared to CSPL6. Both isolates stimulated the growth of various probiotic strains, indicating prebiotic effects that are otherwise known to be associated with catechins. Collectively, the current study demonstrated that fungal endophytes CSPL6 and CSPL5b, isolated from tea leaves, could be used as alternative sources of catechins, and hold promising potential in evidence-based therapeutics.

Antimicrobial and Hepatoprotective Properties of Pods of Acacia nilotica (L.) Willd. ex Delile: In Vivo and In Silico Approaches

Background

Acacia nilotica is a multipurpose plant known for its remedial properties but the antimicrobial and hepatoprotective activity of its pods remained unexplored.

Objective

This study aimed to evaluate the antimicrobial and hepatoprotective activity of n-hexane (ANPH) and methanol (ANPM) extracts of pods to scientifically validate their medicinal claims.

Methods

After the pharmacognostic evaluation of pods, in vitro tests were carried out to estimate phenolic and flavonoid content and antimicrobial potential. In vivo experiments involved testing of both extracts (250 and 500 mg/kg) paracetamol (PCM)-induced hepatotoxicity model in rats. The molecular docking studies explored insights into the potential binding capabilities of the ligands with the specific target proteins.

Results

ANPH and ANPM were enriched with phenols and flavonoids and showed antimicrobial effects. In the hepatoprotective test, the rats chronically treated with extracts had a dose-dependent hepatoprotection as markers of liver functionality were notably reduced (P < 0.05). The in silico studies revealed strong binding interactions of ergost-5-en-3-ol and oxiranyl methyl ester 9-octadecenoic acid with target proteins for antibacterial activity and hepatoprotective activity, respectively.

Conclusion

The antimicrobial and hepatoprotective potential of pods might be due to their phenols and flavonoids. The Pyrogallol, Ergost-5-en-3-and 9-octadecenoic acid might be bringing these remedial benefits through antioxidant and anti-inflammatory effects.

Navigating commensal dysbiosis: Gastrointestinal host-pathogen interplay orchestrating opportunistic infections

The gut commensals, which are usually symbiotic or non-harmful bacteria that live in the gastrointestinal tract, have a positive impact on the health of the host. This review, however, specifically discuss distinct conditions where commensals aid in the development of pathogenic opportunistic infections. We discuss that the categorization of gut bacteria as either pathogens or non-pathogens depends on certain circumstances, which are significantly affected by the tissue microenvironment and the dynamic host-microbe interaction. Under favorable circumstances, commensals have the ability to transform into opportunistic pathobionts by undergoing overgrowth. These conditions include changes in the host's physiology, simultaneous infection with other pathogens, effective utilization of nutrients, interactions between different species of bacteria, the formation of protective biofilms, genetic mutations that enhance pathogenicity, acquisition of genes associated with virulence, and the ability to avoid the host's immune response. These processes allow commensals to both initiate infections themselves and aid other pathogens in populating the host. This review highlights the need of having a detailed and sophisticated knowledge of the two-sided nature of gut commensals. Although commensals mostly promote health, they may also become harmful in certain changes in the environment or the body's functioning. This highlights the need of acknowledging the intricate equilibrium in interactions between hosts and microbes, which is crucial for preserving intestinal homeostasis and averting diseases. Finally, we also emphasize the further need of research to better understand and anticipate the behavior of gut commensals in different situations, since they play a crucial and varied role in human health and disease.

Effects of Differently Processed Tea on the Gut Microbiota

Tea is a highly popular beverage, primarily due to its unique flavor and aroma as well as its perceived health benefits. The impact of tea on the gut microbiome could be an important means by which tea exerts its health benefits since the link between the gut microbiome and health is strong. This review provided a discussion of the bioactive compounds in tea and the human gut microbiome and how the gut microbiome interacts with tea polyphenols. Importantly, studies were compiled on the impact of differently processed tea, which contains different polyphenol profiles, on the gut microbiota from in vivo animal feeding trials, in vitro human fecal fermentation experiments, and in vivo human feeding trials from 2004-2024. The results were discussed in terms of different tea types and how their impacts are related to or different from each other in these three study groups.

Epigallocatechin gallate alleviates non-alcoholic fatty liver disease through the inhibition of the expression and activity of Dipeptide kinase 4

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) has emerged as the most prevalent glocal cause of chronic hepatic disease, with incidence rates that continue to rise steadily. Treatment options for affected patients are currently limited to dietary changes and exercise interventions, with no drugs having been licensed for the treatment of this disease. There is thus a pressing need for the development of novel therapeutic strategies. Work from our group suggests that the primary bioactive ingredient in green tea, epigallocatechin gallate (EGCG), may help reduce liver fat content and protect against hepatic injury through the inhibition of dipeptidyl peptidase 4 (DPP4) expression and activity. The study investigated the potential pathways by which EGCG may improve NAFLD, identified the sites of interaction between EGCG and DPP4, and proposed novel clinical treatment strategies.

METHODS

A clinical randomized controlled trial was conducted to investigate the potential efficacy of EGCG in NAFLD patients. The study compared relevant indices before and after EGCG administration. Animal models of NAFLD were constructed using male C57BL/6J mice fed a high-fat diet to observe the ameliorative effects of EGCG on the livers of the model mice and to investigate the potential pathways by which EGCG alleviates NAFLD. The interaction mechanism between EGCG and DPP4 was investigated using oleic acid and palmitic acid-treated HepG2 cell lines. Plasmids in which different sites had been disrupted were used to identify the effective interaction sites.

RESULTS

ECGC was found to suppress the accumulation of lipids, inhibit inflammation, remediate dysregulated lipid metabolism, and improve the pathogenesis of NAFLD via the inhibition of the expression and activity of DPP4.

CONCLUSIONS

The study results indicate that EGCG has a positive impact on improving NAFLD. These results highlight promising new opportunities to safely and effectively treat NAFLD in the clinic.

STUDY ID NUMBER

ChiCTR2300076741; https://www.chictr.org.cn/.

Polyphenols improve non-alcoholic fatty liver disease via gut microbiota: A comprehensive review

Polyphenols, natural micronutrients derived from plants, are valued for their anti-inflammatory and antioxidant properties. The escalating global prevalence of non-alcoholic fatty liver disease (NAFLD) underscores its status as a chronic progressive liver condition. Furthermore, the dysregulation of gut microbiota (GM) is implicated in the onset and progression of NAFLD through the actions of metabolites such as bile acids (BAs), lipopolysaccharide (LPS), choline, and short-chain fatty acids (SCFAs). Additionally, GM may influence the integrity of the intestinal barrier. This review aims to evaluate the potential effects of polyphenols on GM and intestinal barrier function, and their subsequent impact on NAFLD. We searched through a wide range of databases, such as Web of Science, PubMed, EMBASE, and Scopus to gather information for our non-systematic review of English literature. GM functions and composition can be regulated by polyphenols such as chlorogenic acid, curcumin, green tea catechins, naringenin, quercetin, resveratrol, and sulforaphane. Regulating GM composition improves NAFLD by alleviating inflammation, liver fat accumulation, and liver enzymes. Furthermore, it improves serum lipid profile and gut barrier integrity. All of these components affect NAFLD through the metabolites of GM, including SCFAs, choline, LPS, and BAs. Current evidence indicates that chlorogenic acid, resveratrol, quercetin, and curcumin can modulate GM, improving intestinal barrier integrity and positively impacting NAFLD. More studies are necessary to evaluate the safety and efficacy of naringenin, sulforaphane, and catechin.

Epigallocatechin-3-gallate mitigates cadmium-induced intestinal damage through modulation of the microbiota-tryptophan-aryl hydrocarbon receptor pathway

Early studies have shown that the gut microbiota is a critical target during cadmium exposure. The prebiotic activity of epigallocatechin-3-gallate (EGCG) plays an essential role in treating intestinal inflammation and damage. However, the exact intestinal barrier protection mechanism of EGCG against cadmium exposure remains unclear. In this experiment, four-week-old mice were exposed to cadmium (5 mg kg-1) for four weeks. Through 16 S rDNA analysis, we found that cadmium disrupted the gut microbiota and inhibited the indole metabolism pathway of tryptophan (TRP), which serves as the principal microbial production route for endogenous ligands to activate the aryl hydrocarbon receptor (AhR). Additionally, cadmium downregulated the intestinal AhR signaling pathway and harmed the intestinal barrier function. Treatment with EGCG (20 mg kg-1) and the AhR agonist 6-Formylindolo[3,2-b] carbazole (FICZ) (1 μg/d) significantly activated the AhR pathway and alleviated intestinal barrier injury. Notably, EGCG partially restored the gut microbiota and upregulated the TRP-indole metabolism pathway to increase the level of indole-related AhR agonists. Our findings demonstrate that cadmium dysregulates common gut microbiota to disrupt TRP metabolism, impairing the AhR signaling pathway and intestinal barrier. EGCG reduces cadmium-induced intestinal functional impairment by intervening in the intestinal microbiota to metabolize AhR agonists. This study offers insights into the toxic mechanisms of environmental cadmium and a potential mechanism to protect the intestinal barrier with EGCG.

Gut microbiota in insulin resistance: a bibliometric analysis

Background

Insulin resistance (IR) is considered the pathogenic driver of diabetes, and can lead to obesity, hypertension, coronary artery disease, metabolic syndrome, and other metabolic disorders. Accumulating evidence indicates that the connection between gut microbiota and IR. This bibliometric analysis aimed to summarize the knowledge structure of gut microbiota in IR.

Methods

Articles and reviews related to gut microbiota in IR from 2013 to 2022 were retrieved from the Web of Science Core Collection (WoSCC), and the bibliometric analysis and visualization were performed by Microsoft Excel, Origin, R package (bibliometrix), Citespace, and VOSviewer.

Results

A total of 4 749 publications from WoSCC were retrieved, including 3 050 articles and 1 699 reviews. The majority of publications were from China and USA. The University Copenhagen and Shanghai Jiao Tong University were the most active institutions. The journal of Nutrients published the most papers, while Nature was the top 1 co-cited journal, and the major area of these publications was molecular, biology, and immunology. Nieuwdorp M published the highest number of papers, and Cani PD had the highest co-citations. Keyword analysis showed that the most frequently occurring keywords were "gut microbiota", "insulin-resistance", "obesity", and "inflammation". Trend topics and thematic maps showed that serum metabolome and natural products, such as resveratrol, flavonoids were the research hotspots in this field.

Conclusion

This bibliometric analysis summarised the hotspots, frontiers, pathogenesis, and treatment strategies, providing a clear and comprehensive profile of gut microbiota in IR.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40200-023-01342-x.

Good girl goes bad: Understanding how gut commensals cause disease

This review examines the complex connection between commensal microbiota and the development of opportunistic infections. Several underlying conditions, such as metabolic diseases and weakened immune systems, increase the vulnerability of patients to opportunistic infections. The increasing antibiotic resistance adds significant complexity to the management of infectious diseases. Although commensals have long been considered beneficial, recent research contradicts this notion by uncovering chronic illnesses linked to atypical pathogens or commensal bacteria. This review examines conditions in which commensal bacteria, which are usually beneficial, contribute to developing diseases. Commensals' support for opportunistic infections can be categorized based on factors such as colonization fitness, pathoadaptive mutation, and evasion of host immune response. Individuals with weakened immune systems are especially susceptible, highlighting the importance of mucosal host-microbiota interaction in promoting infection when conditions are inappropriate. Dysregulation of gut microbial homeostasis, immunological modulation, and microbial interactions are caused by several factors that contribute to the development of chronic illnesses. Knowledge about these mechanisms is essential for developing preventive measures, particularly for susceptible populations, and emphasizes the importance of maintaining a balanced gut microbiota in reducing the impact of opportunistic infections.

Tea Polyphenol Epigallocatechin Gallate Protects Against Nonalcoholic Fatty Liver Disease and Associated Endotoxemia in Rats via Modulating Gut Microbiota Dysbiosis and Alleviating Intestinal Barrier Dysfunction and Related Inflammation

Nonalcoholic fatty liver disease (NAFLD) is characterized by fat accumulation and inflammation. Epigallocatechin gallate (EGCG) has been proven to be effective against NAFLD, but its hepatoprotective mechanisms based on the "gut microbiota-barrier-liver axis" are still not fully understood. Herein, the results demonstrated that EGCG effectively ameliorated NAFLD phenotypes and metabolic disorders in rats fed a high-fat diet (HFD), and inhibited intestinal barrier dysfunction and inflammation, which is also supported in the experiment of Caco-2 cells. Moreover, EGCG could restore gut microbiota diversity and composition, particularly promoting beneficial microbes, including short-chain fatty acids (SCFAs) producers, such as Lactobacillus, and suppressing Gram-negative bacteria, such as Desulfovibrio. The microbial modulation raised SCFA levels, decreased lipopolysaccharide levels, inhibited the TLR4/NF-κB pathway, and strengthened intestinal barrier function via Nrf2 pathway activation, thereby alleviating liver steatosis and inflammation. Spearman's correlation analysis showed that 24 key OTUs, negatively or positively associated with NAFLD and metabolic disorders, were also reshaped by EGCG. Our results suggested that a combinative improvement of EGCG on gut microbiota dysbiosis, intestinal barrier dysfunction, and inflammation might be a potential therapeutic target for NAFLD.

A green tea extract confection decreases circulating endotoxin and fasting glucose by improving gut barrier function but without affecting systemic inflammation: A double-blind, placebo-controlled randomized trial in healthy adults and adults with metabolic syndrome

Anti-inflammatory activities of catechin-rich green tea extract (GTE) in obese rodents protect against metabolic endotoxemia by decreasing intestinal permeability and absorption of gut-derived endotoxin. However, translation to human health has not been established. We hypothesized that GTE would reduce endotoxemia by decreasing gut permeability and intestinal and systemic inflammation in persons with metabolic syndrome (MetS) compared with healthy persons. A randomized, double-blind, placebo-controlled, crossover trial in healthy adults (n = 19, 34 ± 2 years) and adults with MetS (n = 21, 40 ± 3 years) examined 4-week administration of a decaffeinated GTE confection (890 mg/d total catechins) on serum endotoxin, intestinal permeability, gut and systemic inflammation, and cardiometabolic parameters. Compared with the placebo, the GTE confection decreased serum endotoxin (P = .023) in both healthy persons and those with MetS, while increasing concentrations of circulating catechins (P < .0001) and γ-valerolactones (P = .0001). Fecal calprotectin (P = .029) and myeloperoxidase (P = .048) concentrations were decreased by GTE regardless of health status. Following the ingestion of gut permeability probes, urinary lactose/mannitol (P = .043) but not sucralose/erythritol (P > .05) was decreased by GTE regardless of health status. No between-treatment differences (P > .05) were observed for plasma aminotransferases, blood pressure, plasma lipids, or body mass nor were plasma tumor necrosis factor-α, interleukin-6, or the ratio of lipopolysaccharide-binding protein/soluble cluster of differentiation-14 affected. However, fasting glucose in both study groups was decreased (P = .029) by the GTE confection compared with within-treatment arm baseline concentrations. These findings demonstrate that catechin-rich GTE is effective to decrease circulating endotoxin and improve glycemic control in healthy adults and those with MetS, likely by reducing gut inflammation and small intestinal permeability but without affecting systemic inflammation.

Pharmacological benefits of Acacia against metabolic diseases: intestinal-level bioactivities and favorable modulation of gut microbiota

CONTEXT

Obesity-associated chronic metabolic disease is a leading contributor to mortality globally. Plants belonging to the genera Acacia are routinely used for the treatment of diverse metabolic diseases under different ethnomedicinal practices around the globe.

OBJECTIVE

The current review centres around the pharmacological evidence of intestinal-level mechanisms for metabolic health benefits by Acacia spp.

RESULTS

Acacia spp. increase the proportions of gut commensals (Bifidobacterium and Lactobacillus) and reduces the population of opportunistic pathobionts (Escherichia coli and Clostridium). Acacia gum that is rich in fibre, can also be a source of prebiotics to improve gut health. The intestinal-level anti-inflammatory activities of Acacia are likely to contribute to improvements in gut barrier function that would prevent gut-to-systemic endotoxin translocation and limit "low-grade" inflammation associated with metabolic diseases.

CONCLUSION

This comprehensive review for the first time has emphasised the intestinal-level benefits of Acacia spp. which could be instrumental in limiting the burden of metabolic disease.

Model organism life extending therapeutics modulate diverse nodes in the drug-gene-microbe tripartite human longevity interactome

Advances in antiaging drug/lead discovery in animal models constitute a large body of literature on novel senotherapeutics and geroprotectives. However, with little direct evidence or mechanism of action in humans-these drugs are utilized as nutraceuticals or repurposed supplements without proper testing directions, appropriate biomarkers, or consistent in-vivo models. In this study, we take previously identified drug candidates that have significant evidence of prolonging lifespan and promoting healthy aging in model organisms, and simulate them in human metabolic interactome networks. Screening for drug-likeness, toxicity, and KEGG network correlation scores, we generated a library of 285 safe and bioavailable compounds. We interrogated this library to present computational modeling-derived estimations of a tripartite interaction map of animal geroprotective compounds in the human molecular interactome extracted from longevity, senescence, and dietary restriction-associated genes. Our findings reflect previous studies in aging-associated metabolic disorders, and predict 25 best-connected drug interactors including Resveratrol, EGCG, Metformin, Trichostatin A, Caffeic Acid and Quercetin as direct modulators of lifespan and healthspan-associated pathways. We further clustered these compounds and the functionally enriched subnetworks therewith to identify longevity-exclusive, senescence-exclusive, pseudo-omniregulators and omniregulators within the set of interactome hub genes. Additionally, serum markers for drug-interactions, and interactions with potentially geroprotective gut microbial species distinguish the current study and present a holistic depiction of optimum gut microbial alteration by candidate drugs. These findings provide a systems level model of animal life-extending therapeutics in human systems, and act as precursors for expediting the ongoing global effort to find effective antiaging pharmacological interventions.Communicated by Ramaswamy H. Sarma.

The intestinal-level metabolic benefits of green tea catechins: Mechanistic insights from pre-clinical and clinical studies

BACKGROUND

The intestinal-level host-microbiota interaction has been implicated in the pathogenesis of chronic diseases. The current review is intended to provide a comprehensive insight into deciphering whether intestinal-level bioactivities mediate the overall metabolic health benefits of green tea catechins.

PURPOSE

We have comprehensively discussed pre-clinical and clinical evidences of intestinal-level changes in metabolism, microbiota, and metabolome due to catechin-rich green tea treatments, ultimately limiting metabolic diseases. Exclusive emphasis has been given to purified catechins and green tea, and discussions on extraintestinal mechanisms of metabolic health benefits were avoided.

METHODS

A literature search for relevant pre-clinical and clinical studies was performed in various online databases (e.g., PubMed) using specific keywords (e.g., catechin, intestine, microbiota). Out of all the referred literature, ∼15% belonged to 2021-2023, ∼51% were from 2011-2020, and ∼32% from 2000-2010.

RESULT

The metabolic health benefits of green tea catechins are indeed influenced by the intestinal-level bioactivities, including reduction of mucosal inflammation and oxidative stress, attenuation of gut barrier dysfunction, decrease in intestinal lipid absorption and metabolism, favorable modulation of mucosal nuclear receptor signaling, alterations of the luminal global metabolome, and mitigation of the gut dysbiosis. The results from the recent clinical studies support the pre-clinical evidences. The challenges and pitfalls of the currently available knowledge on catechin bioactivities have been discussed, and constructive directions to harness the translational benefits of green tea through future interventions have been provided.

CONCLUSION

The metabolism, metabolome, and microbiota at the intestinal epithelia play critical roles in catechin metabolism, pharmacokinetics, bioavailability, and bioactivities. Especially the reciprocal interaction between the catechins and the gut microbiota dictates the metabolic benefits of catechins.

Naringenin prevents non-alcoholic steatohepatitis by modulating the host metabolome and intestinal microbiome in MCD diet-fed mice

Non-alcoholic steatohepatitis (NASH) is a severe inflammatory phase of the non-alcoholic fatty liver disease (NAFLD) spectrum and can progress to advanced stages of NAFLD if left untreated. This study uses multi-omics data to elucidate the underlying mechanism of naringenin's reported benefit in alleviating (NASH). Male mice were fed a NASH-inducing (methionine-choline-deficient) MCD diet with or without naringenin supplementation for 6 weeks. Naringenin prevented NASH-induced histopathological liver damage and reversed the abnormal levels of hepatic triglyceride (TG)/total cholesterol (TC), serum TG/TC, serum alanine aminotransferase/aspartate transaminase, and hepatic malondialdehyde and glutathione. Importantly, naringenin intervention significantly modulated the relative abundance of gut microbiota and the host metabolomic profile. We detected more than 700 metabolites in the serum and found that the gut genus levels of Anaeroplasma and the [Eubacterium] nodatum group were closely associated with xanthine, 2-picoline, and securinine, respectively. Tuzzerella alterations showed the highest number of associations with host endogenous metabolites such as FAHFA (8:0/10:0), FFA (20:2), carnitine C8:1, tridecanedioic acid, securinine, acetylvaline, DL-O-tyrosine, and Phe-Asn. This study indicates that the interplay between host serum metabolites and gut microbiota may contribute to the therapeutic effect of naringenin against NASH.

(-)-Epigallocatechin-3-Gallate Reduces Perfluorodecanoic Acid-Exacerbated Adiposity and Hepatic Lipid Accumulation in High-Fat Diet-Fed Male C57BL/6J Mice

Perfluorodecanoic acid (PFDA), an enduring and harmful organic pollutant, is widely employed in diverse food-related sectors. Our previous studies have provided evidence that PFDA has the potential to facilitate obesity and hepatic fat accumulation induced by high-fat diet (HFD) intake. Epigallocatechin-3-gallate (EGCG), a polyphenol found in green tea, has been suggested to possess potential preventive effects against metabolic abnormalities and fatty liver. The purpose of this research was to investigate the effects of EGCG on PFDA-exacerbated adiposity and hepatic lipid accumulation in HFD-fed mice. The results showed that EGCG reduced body weight gain; tissue and organ weights; blood glucose, serum insulin, HOMA-IR, leptin, and lipid parameters; serum inflammatory cytokines (IL-1β, IL-18, IL-6, and TNF-α); and hepatic lipid accumulation in PFDA-exposed mice fed an HFD. Further work showed that EGCG improved liver function and glucose homeostasis in mice fed an HFD and co-exposed to PFDA. The elevated hepatic mRNA levels of SREBP-1 and associated lipogenic genes, NLRP3, and caspase-1 in PFDA-exposed mice fed an HFD were significantly decreased by EGCG. Our work provides evidence for the potential anti-obesity effect of EGCG on co-exposure to HFD and PFDA and may call for further research on the bioactivity of EGCG to attenuate the endocrine disruption effects of long-term exposure to pollutants.

Gallation and B-Ring Dihydroxylation Increase Green Tea Catechin Residence Time in Plasma by Differentially Affecting Tissue-Specific Trafficking: Compartmental Model of Catechin Kinetics in Healthy Adults

Catechins in green tea extract (GTE) (epigallocatechin gallate (EGCG), epigallocatechin (EGC), epicatechin (EC), epicatechin gallate (ECG)) vary in bioactivity. We developed a physiologically relevant mathematical model of catechin metabolism to test the hypothesis that fractional catabolic rates of catechins would be differentially affected by their structural attributes. Pharmacokinetic data of plasma and urine catechin concentrations were used from healthy adults (n = 19) who ingested confections containing 0.5 g GTE (290 mg EGCG, 87 mg EGC, 39 mg EC, 28 mg ECG). A 7-compartmental model of catechin metabolism comprised of the gastrointestinal tract (stomach, small and large intestine), liver, plasma, extravascular tissues, and kidneys was developed using a mean fraction dose of EGCG, ECG, EGC, and EC. Fitting was by iterative least squares regression analysis, and goodness of fit was ascertained by the estimated variability of parameters (FSD < 0.5). The interaction of gallation and B-ring dihydroxylation most greatly extended plasma residence time such that EGC > EC = EGCG > EGC. The interaction between gallation and B-ring dihydroxylation accelerated the transfer from the upper gastrointestinal tract to the small intestine but delayed subsequent transfers from the small intestine through the liver to plasma and from kidneys to urine. Gallation and B-ring dihydroxylation independently delayed the transfer from plasma to extravascular tissues, except the uptake to kidneys, which was slowed by gallation only. This multi-compartment model, to be validated in a future study, suggests that gallation and B-ring dihydroxylation affect catechin catabolism in a tissue-specific manner and thus their potential bioactivity.

Baru (Dipteryx alata Vog.) agro-industrial by-products promote the growth and metabolism of probiotic strains

AIMS

To evaluate the phytochemical composition and effects of the baru peel and pulp (BPP) and the partially defatted baru nut (DBN) on the growth and metabolism of probiotics.

METHODS AND RESULTS

The proximate composition, including dietary fibers, and polyphenol profile were determined in the BPP and DBN, and the prebiotic activity was evaluated on the growth and metabolism of the Lactobacillus and Bifidobacterium strains. BPP and DBN have a high content of insoluble fibers and phenolic compounds, mainly flavonoids and phenolic acids. Moreover, DBN stands out for its high content of proteins and lipids. BPP and DBN stimulated the growth and metabolism of Bifidobacterium animalis subsp. lactis BB-12, Lactobacillus acidophilus LA-05, and Lacticaseibacillus casei L-26.

CONCLUSIONS

Baru by-products have potential prebiotic properties to be confirmed in preclinical and clinical studies, and to be explored as an ingredient in new health-promoting foods.

IMPACT STATEMENT

Agro-industrial baru wastes, the peel plus pulp and the partially defatted nut, are sources of health-promoting compounds and stimulate the growth and metabolism of probiotics, indicating prebiotic properties.

Bile acid metabolism and signaling: Emerging pharmacological targets of dietary polyphenols

Beyond their role as emulsifiers of lipophilic compounds, bile acids (BAs) are signaling endocrine molecules that show differential affinity and specificity for a variety of canonical and non-canonical BA receptors. Primary BAs (PBAs) are synthesized in the liver while secondary BAs (SBAs) are gut microbial metabolites of PBA species. PBAs and SBAs signal to BA receptors that regulate downstream pathways of inflammation and energy metabolism. Dysregulation of BA metabolism or signaling has emerged as a feature of chronic disease. Dietary polyphenols are non-nutritive plant-derived compounds associated with decreased risk of metabolic syndrome, type-2 diabetes, hepatobiliary and cardiovascular disease. Evidence suggests that the health promoting effects of dietary polyphenols are linked to their ability to alter the gut microbial community, the BA pool, and BA signaling. In this review we provide an overview of BA metabolism and summarize studies that link the cardiometabolic improvements of dietary polyphenols to their modulation of BA metabolism and signaling pathways, and the gut microbiota. Finally, we discuss approaches and challenges in deciphering cause-effect relationships between dietary polyphenols, BAs, and gut microbes.

Therapeutic Activity of Green Tea Epigallocatechin-3-Gallate on Metabolic Diseases and Non-Alcoholic Fatty Liver Diseases: The Current Updates

Green tea polyphenols have numerous functions including antioxidation and modulation of various cellular proteins and are thus beneficial against metabolic diseases including obesity, type 2 diabetes, cardiovascular and non-alcoholic fatty liver diseases, and their comorbidities. Epigallocatechin-3-gallate (EGCG) is the most abundant polyphenol in green tea and is attributed to antioxidant and free radical scavenging activities, and the likelihood of targeting multiple metabolic pathways. It has been shown to exhibit anti-obesity, anti-inflammatory, anti-diabetic, anti-arteriosclerotic, and weight-reducing effects in humans. Worldwide, the incidences of metabolic diseases have been escalating across all age groups in modern society. Therefore, EGCG is being increasingly investigated to address the problems. This review presents the current updates on the effects of EGCG on metabolic diseases, and highlights evidence related to its safety. Collectively, this review brings more evidence for therapeutic application and further studies on EGCG and its derivatives to alleviate metabolic diseases and non-alcoholic fatty liver diseases.

Green tea extract prevents CPT-11-induced diarrhea by regulating the gut microbiota

Irinotecan (CPT-11) is an anticancer drug with indications for use in treating various cancers, but severe diarrhea develops as a side effect. We investigated the effects of green tea extract (GTE) on CPT-11-induced diarrhea, focusing on β-glucuronidase and intestinal UGT1A1. When CPT-11 was administered to rats alone, the fecal water content was approximately 3.5-fold higher in this group than in the control group, and diarrhea developed. The fecal water content in the GTE-treated group was significantly higher than that in the control group, but the difference was smaller than that between the group treated with CPT-11 alone and the control group, and diarrhea improved. When CPT-11 was administered alone, the abundances of Bacteroides fragilis and Escherichia coli, which are β-glucuronidase-producing bacteria, increased and interleukin-6 and interleukin-1β mRNA levels in the colon increased, but GTE suppressed these increases. CPT-11 decreased colon UGT1A1 and short-chain fatty acid levels; however, this decrease was suppressed in the GTE-treated group. The findings that GTE decreases the abundance of β-glucuronidase-producing bacteria and increases colon UGT1A1 levels, thereby decreasing the production of the active metabolite SN-38 in the intestinal tract, indicate that GTE ameliorates CPT-11-induced diarrhea.

Gut microbiota-mediated associations of green tea and catechin intakes with glucose metabolism in individuals without type 2 diabetes mellitus: a four-season observational study with mediation analysis

This four-season observational study aimed to examine the mediating role of the gut microbiota in the associations between green tea and catechin intakes and glucose metabolism in individuals without type 2 diabetes mellitus (T2DM). In each of the 4 seasons, 85 individuals without T2DM (56 male [65.9%]; mean [standard deviation] age: 43.3 [9.4] years) provided blood samples, stool samples, 3-day weighed dietary records, and green tea samples. Catechin intake was estimated by analyzing the tea samples. Linear mixed-effects model analysis showed that green tea intake was negatively associated with fasting blood glucose and insulin levels, even after considering the seasonal variations. Of the gut microbial species associated with green tea intake, the mediation analysis revealed that Phocaeicola vulgatus mediated the association between green tea intake and fasting blood glucose levels. These findings indicate that green tea can improve glucose metabolism by decreasing the abundance of P. vulgatus that is associated with elevated blood glucose levels in individuals without T2DM.

A toxic shrub turned therapeutic: The dichotomy of Nerium oleander bioactivities

Nerium oleander L. is a medicinal plant, used for the treatment of cancers and hyperglycemia across the world, especially in Indian sub-continent, Turkey, Morocco, and China. Although clinical studies supporting its pharmacological effects remain critically underexplored, accidental and intentional consumption of any part of the plant causes fatal toxicity in animals and humans. While the polyphenolic fraction of oleander leaves has been attributed to its pre-clinical pharmacological activities, the presence of diverse cardiac glycosides (especially oleandrin) causes apoptosis to cancer cells in vitro and results in clinical signs of oleander poisoning. Thus, the dual pharmacological and toxicological role of oleander is a perplexing dichotomy in phytotherapy. The current investigative review, therefore, intended to analyze the intrinsic and extrinsic factors that likely contribute to this conundrum. Especially by focusing on gut microbial diversity, abundance, and metabolic functions, oleander-associated pharmacological and toxicological studies have been critically analyzed to define the dual effects of oleander. Electronic databases were extensively screened for relevant research articles (including pre-clinical and clinical) related to oleander bioactivities and toxicity. Taxonomic preference was given to the plant N. oleander L. and synonymous plants as per 'The World Flora Online' database (WCSP record #135196). Discussion on yellow oleander (Cascabela thevetia (L.) Lippold) has intentionally been avoided since it is a different plant. The review indicates that the gut microbiota likely plays a key role in differentially modulating the pharmacological and toxicological effects of oleander. Other factors identified influencing the oleander bioactivities include dose and mode of treatment, cardiac glycoside pharmacokinetics, host-endogenous glycosides, plant material processing and phytochemical extraction methods, plant genotypic variations, environmental effects on the phytochemical quality and quantity, gene expression variations, host dietary patterns and co-morbidity, etc. The arguments proposed are also relevant to other medicinal plants containing toxic cardiac glycosides.

Catechins prevent obesity-induced kidney damage by modulating PPARγ/CD36 pathway and gut-kidney axis in rats

Obesity is an epidemic and a growing public health concern worldwide. It is one of the significant risk factors for developing chronic kidney disease. In the present study, we evaluated the preventive effect of green tea catechins (GTC) against obesity-induced kidney damage and revealed the underlying molecular mechanism of action. Various green tea catechins were quantified in the catechins-rich fraction using HPLC. In vitro, the palmitic and oleic acid-treated NRK-52E cells showed reduced fat accumulation and modulated expressions of PPARγ, CD36, and TGFβ after GTC treatment. In vivo, rats were fed with a high-fat diet (HFD), and the effect of GTC was assessed at 150 and 300 mg/kg body weight doses. HFD-fed rats showed a significant reduction in weight gain and improved serum creatinine, urea, and urine microalbumin levels after GTC treatment. The improved adipokines and insulin levels in GTC treated groups indicated the insulin-sensitizing effect. Histopathology revealed reduced degenerative changes, fibrous tissue deposition, and mesangial matrix proliferation in GTC treated groups. GTC treatment also downregulated the gene expressions of lipogenic and inflammatory factors and improved the altered expressions of CD36 and PPARγ in the kidney tissue. Further, GTC prevented gut dysbiosis in rats by promoting healthy microbes like Akkermansia muciniphila and Lactobacillus reuteri. Faecal metabolome revealed reduced saturated fatty acids, and improved amino acid levels in the GTC treated groups, which help to maintain gut health and metabolism. Overall, GTC prevented obesity-induced kidney damage by modulating PPARγ/CD36 signaling and maintaining gut health in rats.

Anti-Inflammatory, Antioxidant, and Neuroprotective Effects of Polyphenols-Polyphenols as an Element of Diet Therapy in Depressive Disorders

Depressive disorders can affect up to 350 million people worldwide, and in developed countries, the percentage of patients with depressive disorders may be as high as 10%. During depression, activation of pro-inflammatory pathways, mitochondrial dysfunction, increased markers of oxidative stress, and a reduction in the antioxidant effectiveness of the body are observed. It is estimated that approximately 30% of depressed patients do not respond to traditional pharmacological treatments. However, more and more attention is being paid to the influence of active ingredients in food on the course and risk of neurological disorders, including depression. The possibility of using foods containing polyphenols as an element of diet therapy in depression was analyzed in the review. The possibility of whether the consumption of products such as polyphenols could alleviate the course of depression or prevent the progression of it was also considered. Results from preclinical studies demonstrate the potential of phenolic compounds have the potential to reduce depressive behaviors by regulating factors related to oxidative stress, neuroinflammation, and modulation of the intestinal microbiota.

Crosstalk between Gut Microbiota and Host Immunity: Impact on Inflammation and Immunotherapy

Gut microbes and their metabolites are actively involved in the development and regulation of host immunity, which can influence disease susceptibility. Herein, we review the most recent research advancements in the gut microbiota-immune axis. We discuss in detail how the gut microbiota is a tipping point for neonatal immune development as indicated by newly uncovered phenomenon, such as maternal imprinting, in utero intestinal metabolome, and weaning reaction. We describe how the gut microbiota shapes both innate and adaptive immunity with emphasis on the metabolites short-chain fatty acids and secondary bile acids. We also comprehensively delineate how disruption in the microbiota-immune axis results in immune-mediated diseases, such as gastrointestinal infections, inflammatory bowel diseases, cardiometabolic disorders (e.g., cardiovascular diseases, diabetes, and hypertension), autoimmunity (e.g., rheumatoid arthritis), hypersensitivity (e.g., asthma and allergies), psychological disorders (e.g., anxiety), and cancer (e.g., colorectal and hepatic). We further encompass the role of fecal microbiota transplantation, probiotics, prebiotics, and dietary polyphenols in reshaping the gut microbiota and their therapeutic potential. Continuing, we examine how the gut microbiota modulates immune therapies, including immune checkpoint inhibitors, JAK inhibitors, and anti-TNF therapies. We lastly mention the current challenges in metagenomics, germ-free models, and microbiota recapitulation to a achieve fundamental understanding for how gut microbiota regulates immunity. Altogether, this review proposes improving immunotherapy efficacy from the perspective of microbiome-targeted interventions.

Synthesis and Characterization of 𝒌-Carrageenan/PVA Nanocomposite Hydrogels in Combination with MgZnO Nanoparticles to Evaluate the Catechin Release

In the current study, nanocomposites were prepared by combining k-carrageenan, polyvinyl alcohol (PVA), and doped nanoparticles (Magnesium oxide) MgO, (Magnesium Zinc oxide) MgZnO 1%, MgZnO 3%, and MgZnO 5%. The nanoparticles were synthesized by a sol-gel method and mixed with a mixture of k-carrageenan/PVA (Ca/PVA) in various ratios. The structure of the composites was analyzed using thermogravimetric analysis (TGA), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). The Ca/PVA mixture was then mixed with nanoparticles and loaded with active ingredient, catechin. Scanning electron microscope (SEM) and texture analysis were performed to analyze the nanocomposites. Entrapment efficiency (EE%) and drug release studies confirmed that k-carrageenan/PVA/MgZnO 5% had the highest EE% at 81.58% and a drug release of 75.21% ± 0.94. The EE% of k-carrageenan/PVA/MgO was 55.21% and its drug release was 45%. This indicates that ZnO plays an effective role in the structure and performance of Ca/PVA composites. The SEM images of MgO composites show smoother surfaces compared to MgZnO composites. This may be one of the reasons for the increased EE% and drug release of MgZnO composites. The addition of ZnO to the composite structure can lead to the appearance of pores on the surface of the composite, increasing entrapment and drug release.

Chitooligosaccharides Attenuated Hepatic Encephalopathy in Mice through Stabilizing Gut-Liver-Brain Disturbance

SCOPE

Hepatic encephalopathy (HE) refers to neurological dysfunction associated with hepatic inadequacy and gut dysbiosis. Chitooligosaccharides (COS) possesses prominent biological activities including incalculable hepatoprotective, neuroprotective and prebiotic effects. This study evaluates the protective effects of COS on HE from the influence of gut-liver-brain axis in mice.

METHODS AND RESULTS

Hepatic injured mice show minimal symptoms of HE, reflecting in cognitive impairment, and learning and memory retardation, while they are reversed by COS following orally administrated. Furthermore, COS ameliorates brain function through inhibiting microglial and astrocyte activation in cerebral cortex and hippocampus, promoting neuronal regeneration characterized by the increase of neuron-specific marker (neuronal nuclear antigen, NeuN). Concurrently, neuroinflammation and hepatitis are restrained by COS through descending toll-like receptors 4/Nuclear factor kappa B (TLR4/NF-κB) pathway. Additionally, the dysbiosis of the composition and structure of gut microbiota is displayed in mice with HE, while it is modified by COS through decreasing the relative abundances of Muribaculaceae, Lactobacillus, and Enterorhabdus. The enhancement of blood ammonia is crucially slipped to basal levels by COS.

CONCLUSION

The present study shows that COS could prevent the pathological process of HE through regulating the gut-liver-brain cross-talk, which provids new insight into fundamental roles of COS.

Bacterial Exopolysaccharides as Emerging Bioactive Macromolecules: From Fundamentals to Applications

Microbial exopolysaccharides (EPS) are extracellular carbohydrate polymers forming capsules or slimy coating around the cells. EPS can be secreted by various bacterial genera that can help bacterial cells in attachment, environmental adaptation, stress tolerance and are an integral part of microbial biofilms. Several gut commensals (e.g., Lactobacillus, Bifidobacterium) produce EPS that possess diverse bioactivities. Bacterial EPS also has extensive commercial applications in the pharmaceutical and food industries. Owing to the structural and functional diversity, genetic and metabolic engineering strategies are currently employed to increase EPS production. Therefore, the current review provides a comprehensive overview of the fundamentals of bacterial exopolysaccharides, including their classification, source, biosynthetic pathways, and functions in the microbial community. The review also provides an overview of the diverse bioactivities of microbial EPS, including immunomodulatory, anti-diabetic, anti-obesity, and anti-cancer properties. Since several gut microbes are EPS producers and gut microbiota helps maintain a functional gut barrier, emphasis has been given to the intestinal-level bioactivities of the gut microbial EPS. Collectively, the review provides a comprehensive overview of microbial bioactive exopolysaccharides.

EGCG and catechin relative to green tea extract differentially modulate the gut microbial metabolome and liver metabolome to prevent obesity in mice fed a high-fat diet

Green tea extract (GTE) alleviates obesity, in part, by modulating gut microbial composition and metabolism. However, direct evidence regarding the catechin-specific bioactivities that are responsible for these benefits remain unclear. The present study therefore investigated dietary supplementation of GTE, epigallocatechin gallate (EGCG), or (+)-catechin (CAT) in male C57BL6/J mice that were fed a high-fat (HF) diet to establish the independent contributions of EGCG and CAT relative to GTE to restore microbial and host metabolism. We hypothesized that EGCG would regulate the gut microbial metabolome and host liver metabolome more similar to GTE than CAT to explain their previously observed differential effects on cardiometabolic health. To test this, we assessed metabolic and phenolic shifts in liver and fecal samples during dietary HF-induced obesity. Ten fecal metabolites and ten liver metabolites (VIP > 2) primarily contributed to the differences in the metabolome among different interventions. In fecal samples, nine metabolic pathways (e.g., tricarboxcylic acid cycle and tyrosine metabolism) were differentially altered between the GTE and CAT interventions, whereas three pathways differed between GTE and EGCG interventions, suggesting differential benefits of GTE and its distinctive bioactive components on gut microbial metabolism. Likewise, hepatic glycolysis / gluconeogenesis metabolic pathways were significantly altered between GTE and EGCG interventions, while only hepatic tyrosine metabolism was altered between CAT and GTE interventions. Thus, our findings support that purified catechins relative to GTE uniquely contribute to regulating host and microbial metabolic pathways such as central energy metabolism to protect against metabolic dysfunction leading to obesity.

Bioactive compounds modulating Toll-like 4 receptor (TLR4)-mediated inflammation: pathways involved and future perspectives

Chronic inflammation is associated with the development and progression of several noncommunicable diseases, such as diabetes, cardiovascular disease, chronic kidney disease, cancer, and nonalcoholic fatty liver disease. Evidence suggests that pattern recognition receptors that identify pathogen-associated molecular patterns and danger-associated molecular patterns are crucial in chronic inflammation. Among the pattern recognition receptors, Toll-like receptor 4 (TLR4) stimulates several inflammatory pathway agonists, such as nuclear factor-κB, interferon regulator factor 3, and nod-like receptor pyrin domain containing 3 pathways, which consequently trigger the expression of pro-inflammatory biomarkers, increasing the risk of noncommunicable disease development and progression. Studies have focused on the antagonistic potential of bioactive compounds, following the concept of food as a medicine, in which nutritional strategies may mitigate inflammation via TLR4 modulation. Thus, this review discusses preclinical evidence concerning bioactive compounds from fruit, vegetable, spice, and herb extracts (curcumin, resveratrol, catechin, cinnamaldehyde, emodin, ginsenosides, quercetin, allicin, and caffeine) that may regulate the TLR4 pathway and reduce the inflammatory response. Bioactive compounds can inhibit TLR4-mediated inflammation through gut microbiota modulation, improvement of intestinal permeability, inhibition of lipopolysaccharide-TLR4 binding, and decreasing TLR4 expression by modulation of microRNAs and antioxidant pathways. The responses directly mitigated inflammation, especially nuclear factor-κB activation and inflammatory cytokines release. These findings should be considered for further clinical studies on inflammation-mediated diseases.

Green tea extract alters gut microbiota and their metabolism of adults with metabolic syndrome in a host-free human colonic model

BACKGROUND

Metabolic syndrome (MetS) is a common metatoblic disorder that leads to various adverse health outcomes such as diabetes and cardiovascular diseases (CVDs). Recent studies suggested that MetS-associated gut dysbiosis could exacerbate MetS related diseases. Green tea, a popular beverage rich in polyphenols, has showed antioxidant and anti-inflammatory effects in treating MetS through gut modulation.

OBJECTIVES

This study aimed to understand the impact of green tea extract (GTE) on the composition and metabolism of gut microbiota from people with MetS.

METHODS

We utilized an in-vitro human colonic model (HCM) to specifically investigate the host-free interactions between GTE and gut microbiota of MetS adults. Fresh fecal samples donated by three adults with MetS were used as gut microbe inoculum in our HCM system. 16S ribosomal RNA sequencing and liquid-chromatography mass spectrometry (LC/MS) combined with QIIME 2, Compound Discoverer 3.1 and MetaboAnalyst 4.0 based data analyses were performed to show the regulating effects of GTE treatment on gut microbial composition and their metabolism.

RESULTS

Our data suggested that GTE treatment in HCM system modified composition of MetS gut microbiota at genus level and led to significant microbiota metabolic profile change. Bioinformatics analysis showed relative abundance of Escherichia and Klebsiella was commonly increased while Bacteroides, Citrobacter, and Clostridium were significantly reduced. All free fatty acids detected were significantly increased in different colon sections. Lipopolysaccharide biosynthesis, methane metabolism, pentose phosphate pathway, purine metabolism, and tyrosine metabolism were regulated by GTE in MetS gut microbiota. In addition, we identified significant associations between altered microbes and microbial metabolites.

CONCLUSIONS

Overall, our study revealed the impact of GTE treatment on gut microbiota composition and metabolism changes in MetS microbiota in vitro, which may provide information for further mechanistic investigation of GTE in modulating gut dysbiosis in MetS.

The Gut Microbial Metabolite Pyrogallol Is a More Potent Inducer of Nrf2-Associated Gene Expression Than Its Parent Compound Green Tea (-)-Epigallocatechin Gallate

(-)-Epigallocatechin gallate (EGCG) has been associated with multiple beneficial effects. However, EGCG is known to be degraded by the gut microbiota. The present study investigated the hypothesis that microbial metabolism would create major catechol-moiety-containing microbial metabolites with different ability from EGCG to induce nuclear factor-erythroid 2-related factor 2 (Nrf2)-mediated gene expression. A reporter gene bioassay, label-free quantitative proteomics and reverse transcription quantitative real-time polymerase chain reaction (RT-qPCR) were combined to investigate the regulation of Nrf2-related gene expression after exposure of U2OS reporter gene or Hepa1c1c7 cells in vitro to EGCG or to its major microbial catechol-moiety-containing metabolites: (-)-epigallocatechin (EGC), gallic acid (GA) and pyrogallol (PG). Results show that PG was a more potent inducer of Nrf2-mediated gene expression than EGCG, with a 5% benchmark dose (BMD₅) of 0.35 µM as compared to 2.45 µM for EGCG in the reporter gene assay. EGC and GA were unable to induce Nrf2-mediated gene expression up to the highest concentration tested (75 µM). Bioinformatical analysis of the proteomics data indicated that Nrf2 induction by PG relates to glutathione metabolism, drug and/or xenobiotics metabolism and the pentose phosphate pathway. Taken together, our findings demonstrate that the microbial metabolite PG is a more potent inducer of Nrf2-associated gene expression than its parent compound EGCG.

Pharmacological Effects of Polyphenol Phytochemicals on the Intestinal Inflammation via Targeting TLR4/NF-κB Signaling Pathway

TLR4/NF-κB is a key inflammatory signaling transduction pathway, closely involved in cell differentiation, proliferation, apoptosis, and pro-inflammatory response. Toll like receptor 4 (TLR4), the first mammalian TLR to be characterized, is the innate immune receptor that plays a key role in inflammatory signal transductions. Nuclear factor kappa B (NF-κB), the TLR4 downstream, is the key to accounting for the expression of multiple genes involved in inflammatory responses, such as pro-inflammatory cytokines. Inflammatory bowel disease (IBD) in humans is a chronic inflammatory disease with high incidence and prevalence worldwide. Targeting the TLR4/NF-κB signaling pathway might be an effective strategy to alleviate intestinal inflammation. Polyphenol phytochemicals have shown noticeable alleviative effects by acting on the TLR4/NF-κB signaling pathway in intestinal inflammation. This review summarizes the pharmacological effects of more than 20 kinds of polyphenols on intestinal inflammation via targeting the TLR4/NF-κB signaling pathway. We expected that polyphenol phytochemicals targeting the TLR4/NF-κB signaling pathway might be an effective approach to treat IBD in future clinical research applications.

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

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

Cancer-Associated Microbiota: From Mechanisms of Disease Causation to Microbiota-Centric Anti-Cancer Approaches

Helicobacter pylori infection is the only well-established bacterial cause of cancer. However, due to the integral role of tissue-resident commensals in maintaining tissue-specific immunometabolic homeostasis, accumulated evidence suggests that an imbalance of tissue-resident microbiota that are otherwise considered as commensals, can also promote various types of cancers. Therefore, the present review discusses compelling evidence linking tissue-resident microbiota (especially gut bacteria) with cancer initiation and progression. Experimental evidence supporting the cancer-causing role of gut commensal through the modulation of host-specific processes (e.g., bile acid metabolism, hormonal effects) or by direct DNA damage and toxicity has been discussed. The opportunistic role of commensal through pathoadaptive mutation and overcoming colonization resistance is discussed, and how chronic inflammation triggered by microbiota could be an intermediate in cancer-causing infections has been discussed. Finally, we discuss microbiota-centric strategies, including fecal microbiota transplantation, proven to be beneficial in preventing and treating cancers. Collectively, this review provides a comprehensive understanding of the role of tissue-resident microbiota, their cancer-promoting potentials, and how beneficial bacteria can be used against cancers.

The roles of catechins in regulation of systemic inflammation

Catechins are a phytochemical present in plants such as tea leaves, beans, black grapes, cherries, and cacao, and have various physiological activities. It is reported that catechins have a health improvement effect and ameliorating effect against various diseases. In addition, antioxidant activity, liver damage prevention, cholesterol lowering effect, and anti-obesity activity were confirmed through in vivo animal and clinical studies. Although most diseases are reported as ones mediating various inflammations, the mechanism for improving inflammation remains unclear. Therefore, the current review article evaluates the physiological activity and various pharmacological actions of catechins and conclude by confirming an improvement effect on the inflammatory response.

Salubrious Effects of Green Tea Catechins on Fatty Liver Disease: A Systematic Review

Epigallocatechin-3-gallate (EGCG) is a polyphenol green tea catechin with potential health benefits and therapeutic effects in non-alcoholic fatty liver disease (NAFLD), a common liver disorder that adversely affects liver function and lipid metabolism. This systematic review surveyed the effects of EGCG or green tea extract (GTE) on NAFLD reported in studies involving rodent models or humans with a focus on clinicopathologic outcomes, lipid and carbohydrate metabolism, and inflammatory, oxidative stress, and liver injury markers. Articles involving clinical efficacy of EGCG/GTE on human subjects and rodent models were gathered by searching the PUBMED database and by referencing additional articles identified from other literature reviews. EGCG or GTE supplementation reduced body weight, adipose tissue deposits, and food intake. Mechanistically, the majority of these studies confirmed that EGCG or GTE supplementation plays a significant role in regulating lipid and glucose metabolism and expression of genes involved in lipid synthesis. Importantly, EGCG and GTE supplementation were shown to have beneficial effects on oxidative stress-related pathways that activate pro-inflammatory responses, leading to liver damage. In conclusion, green tea catechins are a potentially useful treatment option for NAFLD. More research is required to determine the ideal dosage, treatment duration, and most effective delivery method of EGCG or GTE, and to provide more definitive conclusions by performing large, randomized clinical trials.

In vitro co-metabolism of epigallocatechin-3-gallate (EGCG) by the mucin-degrading bacterium Akkermansia muciniphila

Akkermansia muciniphila is a Gram-negative bacterium that resides within the gut mucus layer, and plays an important role in promoting gut barrier integrity, modulating the immune response and inhibiting gut inflammation. Growth stimulation of A. muciniphila by polyphenols including epigallocatechin-3-gallate (EGCG) from difference sources is well-documented. However, no published in vitro culture data on utilization of polyphenols by A. muciniphila are available, and the mechanism of growth-stimulating prebiotic effect of polyphenols on it remains unclear. Here in vitro culture studies have been carried out on the metabolism of EGCG by A. muciniphila in the presence of either mucin or glucose. We found that A. muciniphila did not metabolize EGCG alone but could co-metabolize it together with both these substrates in the presence of mineral salts and amino acids for mucin and protein sources for glucose. Our metabolomic data show that A. muciniphila converts EGCG to gallic acid, epigallocatechin, and (-)-epicatechin through ester hydrolysis. The (-)-epicatechin formed is then further converted to hydroxyhydroquinone. Co-metabolism of A. muciniphila of EGCG together with either mucin or glucose promoted substantially its growth, which serves as a further demonstration of the growth-promoting effect of polyphenols on A. muciniphila and provides an important addition to the currently available proposed mechanisms of polyphenolic prebiotic effects on A. muciniphila.

Athrixia phylicoides tea infusion (bushman tea) improves adipokine balance, glucose homeostasis and lipid parameters in a diet-induced metabolic syndrome rat model

BACKGROUND

Central obesity and insulin resistance are associated with metabolic syndrome (MetS) which is aggravated by diet and sedentary lifestyle. Athrixia phylicoides (AP) is reported by rural communities to have medicinal benefits associated with MetS such as obesity and type 2 diabetes. This study was aimed to investigate the effects of AP on diet-induced MetS in Wistar rats to validate its ethnopharmacological use.

METHODS

AP was profiled for phytochemicals by LC-MS. After induction of MetS with high energy diet (HED), 30 male rats were divided into five treatment groups (n = 6): normal diet control, HED control, HED + AP 50 mg/Kg BW, HED + AP 100 mg/Kg BW and HED + 50 mg/Kg BW metformin. The rats were treated daily for 8 weeks orally after which weight gain, visceral fat, total cholesterol, free fatty acids (FFAs) and adipokine regulation; leptin: adiponectin ratio (LAR) were assessed. Also, glucose homeostatic parameters including fasting blood glucose (FBG), oral glucose tolerance test (OGTT), glucose transporter 4 (GLUT 4), insulin and homeostatic model assessment of insulin resistance (HOMA-IR) were determined.

RESULTS

Findings showed that AP was rich in polyphenols. The HED control group showed derangements of the selected blood parameters of MetS. AP reversed diet-induced weight gain by reducing visceral fat, total blood cholesterol and circulating FFAs (p ≤ 0.05). Treatment with AP improved adipokine regulation depicted by reduced LAR (p<0.05). Treatment with AP improved parameters of glucose homeostasis as demonstrated by reduced FBG and HOMA-IR (p ≤ 0.05) and increased GLUT 4 (p<0.05).

CONCLUSION

Athrixia phylicoides tea infusion was shown to possess anti-obesity and anti-inflammatory properties, improved glucose uptake and reduce insulin resistance in diet-induced MetS in rats which could be attributed to its richness in polyphenols. Therefore, AP could have potential benefits against type 2 diabetes and obesity which are components of MetS validating its ethnopharmacological use.

Antiinflammatory phytochemicals against virus-induced hyperinflammatory responses: Scope, rationale, application, and limitations

Uncontrolled inflammatory responses or cytokine storm associated with viral infections results in deleterious consequences such as vascular leakage, severe hemorrhage, shock, immune paralysis, multi-organ failure, and even death. With the emerging new viral infections and lack of effective prophylactic vaccines, evidence-based complementary strategies that limit viral infection-mediated hyperinflammatory responses could be a promising approach to limit host tissue injury. The present review emphasizes the potentials of antiinflammatory phytochemicals in limiting hyperinflammatory injury caused by viral infections. The predominant phytochemicals along with their mechanism in limiting hyperimmune and pro-inflammatory responses under viral infection have been reviewed comprehensively. How certain phytochemicals can be effective in limiting hyper-inflammatory response indirectly by favorably modulating gut microbiota and maintaining a functional intestinal barrier has also been presented. Finally, we have discussed improved systemic bioavailability of phytochemicals, efficient delivery strategies, and safety measures for effective antiinflammatory phytotherapies, in addition to emphasizing the requirement of tightly controlled clinical studies to establish the antiinflammatory efficacy of the phytochemicals. Collectively, the review provides a scooping overview on the potentials of bioactive phytochemicals to mitigate pro-inflammatory injury associated with viral infections.