A comprehensive review on the impact of β-glucan metabolism by Bacteroides and Bifidobacterium species as members of the gut microbiota

The effects of cereal β-glucans on cardiovascular risk factors and the role of the gut microbiome

The human gut microbiome has emerged as a key influencer of human health and disease, particularly through interactions with dietary fiber. However, national dietary guidelines worldwide are only beginning to capitalize on the potential of microbiome research, which has established the vital role of host-microbe interactions in mediating the physiological effects of diet on overall health and disease. β-glucans have been demonstrated to modulate the composition of the gut microbiota, leading to improved outcomes in cardiovascular disease (CVD). Raised serum cholesterol and blood pressure are important modifiable risk factors in the development of CVD and emerging evidence highlights the role of the gut microbiota in ameliorating such biomarkers and clinical characteristics of the disease. The proposed mechanism of action of β-glucans on the pathophysiological mechanisms of disease have yet to be elucidated. Validating gaps in the literature may substantiate β-glucans as a potential novel dietary therapy against modifiable risk factors for CVD and would further support the public health significance of including a habitual fiber-rich diet.

In vitro batch fermentation demonstrates variations in the regulation of gut microbiota and metabolic functions by β-glucans of differing structures

The gut microbiota is widely acknowledged as a crucial factor in regulating host health. The structure of dietary fibers determines changes in the gut microbiota and metabolic differences resulting from their fermentation, which in turn affect gut microbe-related health effects. β-Glucan (BG) is a widely accessible dietary fiber to humans, and its structural characteristics vary depending on the source. However, the interactions between different structural BGs and gut microbiota remain unclear. This study used an in vitro fermentation model to investigate the effects of BG on gut microbiota, and microbiomics and metabolomics techniques to explore the relationship between the structure of BG, bacterial communities, and metabolic profiles. The four sources of BG (barley, yeast, algae, and microbial fermentation) contained different types and proportions of glycosidic bonds, which differentially altered the bacterial community. The BG from algal sources, which contained only β(1 → 4) glycosidic bonds, was the least metabolized by the gut microbiota and caused limited metabolic changes. The other three BGs contain more diverse glycosidic bonds and can be degraded by bacteria from multiple genera, causing a wider range of metabolic changes. This work also suggested potential synergistic degradation relationships between gut bacteria based on BG. Overall, this study deepens the structural characterization-microbial-functional understanding of BGs and provides theoretical support for the development of gut microbiota-targeted foods.

Novel β-galactosidase activity and first crystal structure of Glycoside Hydrolase family 154

Polysaccharide Utilization Loci (PULs) are physically linked gene clusters conserved in the Gram-negative phylum of Bacteroidota and are valuable sources for Carbohydrate Active enZyme (CAZyme) discovery. This study focuses on BD-β-Gal, an enzyme encoded in a metagenomic PUL and member of the Glycoside Hydrolase family 154 (GH154). BD-β-Gal showed exo-β-galactosidase activity with regiopreference for hydrolyzing β-d-(1,6) glycosidic linkages. Notably, it exhibited a preference for d-glucopyranosyl (d-Glcp) over d-galactopyranosyl (d-Galp) and d-fructofuranosyl (d-Fruf) at the reducing end of the investigated disaccharides. In addition, we determined the high resolution crystal structure of BD-β-Gal, thus providing the first structural characterization of a GH154 enzyme. Surprisingly, this revealed an (α/α)6 topology, which has not been observed before for β-galactosidases. BD-β-Gal displayed low structural homology with characterized CAZymes, but conservation analysis suggested that the active site was located in a central cavity, with conserved E73, R252, and D253 as putative catalytic residues. Interestingly, BD-β-Gal has a tetrameric structure and a flexible loop from a neighboring protomer may contribute to its reaction specificity. Finally, we showed that the founding member of GH154, BT3677 from Bacteroides thetaiotaomicron, described as β-glucuronidase, displayed exo-β-galactosidase activity like BD-β-Gal but lacked a tetrameric structure.

Extraction, purification, structural characteristics, bioactivity and potential applications of polysaccharides from Avena sativa L.: A review

Avena sativa L. (A. sativa L.), commonly known as oat, is a significant cereal grain crop with excellent edible and medicinal value. Oat polysaccharides (OPs), the major bioactive components of A. sativa L., have received considerable attention due to their beneficial bioactivities. However, the isolation and purification methods of OPs lack innovation, and the structure-activity relationship remains unexplored. This review emphatically summarized recent progress in the extraction and purification methods, structural characteristics, biological activities, structure-to-function associations and the potential application status of OPs. Different materials and isolation methods can result in the differences in the structure and bioactivity of OPs. OPs are mainly composed of various monosaccharide constituents, including glucose, arabinose and mannose, along with galactose, xylose and rhamnose in different molar ratios and types of glycosidic bonds. OPs exhibited a broad molecular weight distribution, ranging from 1.34 × 105 Da to 4.1 × 106 Da. Moreover, structure-activity relationships demonstrated that the monosaccharide composition, molecular weight, linkage types, and chemical modifications are closely related to their multiple bioactivities, including immunomodulatory activity, antioxidant effect, anti-inflammatory activity, antitumor effects etc. This work can provide comprehensive knowledge, update information and promising directions for future exploitation and application of OPs as therapeutic agents and multifunctional food additives.

Bacteroides and NAFLD: pathophysiology and therapy

Non-alcoholic fatty liver disease (NAFLD) is a prevalent chronic liver condition observed globally, with the potential to progress to non-alcoholic steatohepatitis (NASH), cirrhosis, and even hepatocellular carcinoma. Currently, the US Food and Drug Administration (FDA) has not approved any drugs for the treatment of NAFLD. NAFLD is characterized by histopathological abnormalities in the liver, such as lipid accumulation, steatosis, hepatic balloon degeneration, and inflammation. Dysbiosis of the gut microbiota and its metabolites significantly contribute to the initiation and advancement of NAFLD. Bacteroides, a potential probiotic, has shown strong potential in preventing the onset and progression of NAFLD. However, the precise mechanism by which Bacteroides treats NAFLD remains uncertain. In this review, we explore the current understanding of the role of Bacteroides and its metabolites in the treatment of NAFLD, focusing on their ability to reduce liver inflammation, mitigate hepatic steatosis, and enhance intestinal barrier function. Additionally, we summarize how Bacteroides alleviates pathological changes by restoring the metabolism, improving insulin resistance, regulating cytokines, and promoting tight-junctions. A deeper comprehension of the mechanisms through which Bacteroides is involved in the pathogenesis of NAFLD should aid the development of innovative drugs targeting NAFLD.

Colonic in vitro fermentation of mycoprotein promotes shifts in gut microbiota, with enrichment of Bacteroides species

Mycoprotein is a fungal-derived ingredient used for meat alternative products whose fungal cell walls are rich in dietary fibre (β-glucans and chitin) and defines its structure. Several health benefits have been reported after mycoprotein consumption, however, little is known about the impact of mycoprotein fermentation on the gut microbiota. This study aims to identify changes in microbiome composition and microbial metabolites during colonic fermentation of mycoprotein following simulated upper gastrointestinal digestion. Changes in microbial populations and metabolites produced by the fermentation of mycoprotein fibre were investigated and compared to a plant (oat bran) and an animal (chicken) comparator. In this model fermentation system, mycoprotein and oat showed different but marked changes in the microbial population compared to chicken, which showed minimal differentiation. In particular, Bacteroides species known for degrading β-glucans were found in abundance following fermentation of mycoprotein fibre. Mycoprotein fermentation resulted in short-chain fatty acid production comparable with oat and chicken at 72 h. Significantly higher branched-chain amino acids were observed following chicken fermentation. This study suggests that the colonic fermentation of mycoprotein can promote changes in the colonic microbial profile. These results highlight the impact that the unique structure of mycoprotein can have on digestive processes and the gut microbiota.

Dynamic response of different types of gut microbiota to fructooligosaccharides and inulin

Fructooligosaccharides (FOS) and inulin are beneficial for human health. However, their benefits differ in individuals who consume prebiotics. Several factors contribute to this variation, including host genetics and differences in the gut microbiota. Bifidobacterium and Bacteroides are strong carbohydrate-utilizing bacteria in the gut, and the level of the Bacteroides/Bifidobacterium (Ba/Bi) ratio in the gut is closely related to the body's ability to utilize prebiotics. However, how to select the type of prebiotics more beneficial for populations with specific Ba/Bi backgrounds and the underlying regulatory mechanisms remain unclear. Here, we explored the dynamics of the gut microbiota and metabolic functions during the in vitro fermentation of FOS and inulin in two different groups: Bacteroides/Bifidobacterium high (H) and Bacteroides/Bifidobacterium low (L). This study revealed that the baseline Ba/Bi ratio had a greater impact on the gut microbiota compared to prebiotic species. Noticeable differences were observed between the two groups after prebiotic intervention, with the H group being more likely to benefit from the prebiotic intervention. Compared to the L group, the H group exhibited significantly higher microbial α-diversity; the co-abundance response group 1 (CARG1) members Ruminococcus gnavus and Blautia involved in the synthesis of propionic and butyric acids increased significantly, the abundance of pathogenic bacteria such as Escherichia Shigella decreased significantly, and the ability to degrade carbohydrates and synthesize fatty acids was greater. Regression modeling showed that the key microbiota could predict the short-chain fatty acid (SCFA) levels, with FOS associated with the ecological roles of CARG2 and CARG7 and inulin associated with CARG4, which provides the basis for the use of prebiotics in nutritional applications and the stratification of populations based on pertinent microbiota profiles to explain the incongruent health effects in human intervention studies.

The role of Bifidobacterium genus in modulating the neonate microbiota: implications for antibiotic resistance acquisition in early life

Resistance to antibiotics in newborns is a huge concern as their immune system is still developing, and infections and resistance acquisition in early life have short- and long-term consequences for their health. Bifidobacterium species are important commensals capable of dominating the infant gut microbiome and are known to be less prone to possess antimicrobial resistance genes than other taxa that may colonize infants. We aimed to study the association between Bifidobacterium-dominated infant gut microbiota and the antibiotic resistant gene load in neonates, and to ascertain the perinatal factors that may contribute to the antibiotic resistance acquisition. Two hundred infant fecal samples at 7 days and 1 month of age from the MAMI birth cohort were included in the study and for whom maternal-neonatal clinical records were available. Microbiota profiling was carried out by 16S rRNA amplicon sequencing, and targeted antibiotic resistance genes (ARGs) including tetM, tetW, tetO, blaTEM, blaSHV and ermB were quantified by qPCR. Infant microbiota clustered into two distinct groups according to their Bifidobacterium genus abundance: high and low. The main separation of groups or clusters at each time point was performed with an unsupervised non-linear algorithm of k-means partitioning to cluster data by time points based on Bifidobacterium genus relative abundance. Microbiota composition differed significantly between both groups, and specific bifidobacterial species were enriched in each cluster. Lower abundance of Bifidobacterium in the infant gut was associated with a higher load of antibiotic resistance genes. Our results highlight the relevance of Bifidobacterium genus in the early acquisition and establishment of antibiotic resistance in the gut. Further studies are needed to develop strategies to promote a healthy early colonization and fight against the spread of antibiotic resistances.

Hypoglycemic Effect of Edible Fungi Polysaccharides Depends on Their Metabolites from the Fermentation of Human Fecal Microbiota

Edible fungi polysaccharides are widely sourced and have various physiological activities, including hypoglycemic. Current studies mainly focus on the hypoglycemic activity of polysaccharides themselves, while the strength of the hypoglycemic activity of edible fungi polysaccharides from different sources remained elusive. This study compared the hypoglycemic activity of different edible fungi polysaccharides after in vitro fermentation by fecal bacteria, combined with non-targeted metabolomics and 16S rDNA analysis, to screen out potential key metabolites related to the hypoglycemic activity. The results show that the fermentation supernatants of all four edible fungi polysaccharides significantly increased the glucose consumption and glycogen synthesis of IR-HepG2, also up-regulated the level of hexokinase and down-regulated the level of phosphoenolpyruvate carboxylase. All fermentation supernatants could alleviate the insulin resistance of IR-HepG2 cells by regulating the expression levels of genes related to the IRS-1/PI3K/Akt signaling pathway. Gingerglycolipid A, sphinganine 1-phosphate, matricin, tricarballylic acid, N-carbamoylputrescine, nomega-acetylhistamine, tyramine, and benzamide could be considered as potential key metabolites to evaluate the hypoglycemic effects. Their levels were strongly positively correlated with the abundance of Candidatus_Stoquefichu, Faecalibacterium, Coprococcus, Bacteroides, Eubacterium_ventriosum_group, Anaerostipes, Parabacteroides, and Agathobacter. These metabolites and microorganisms are closely related to the hypoglycemic activity of edible fungi polysaccharides.

Microbiota regulation by different Akebia trifoliata fruit juices upon human fecal fermentation in vitro

Three different Akebia trifoliata fruit juices were prepared, and their effects on modulation of human fecal microbiota were elucidated through an anaerobic fermentation in vitro. Results indicated that the introduction of inoculatedly-fermented Akebia trifoliata fruit juice promoted short-chain fatty acids productivity. Fecal microbiota analysis demonstrated up-regulations for abundances of Limosilactobacillus, Megamonas, Bifidobacterium, and Escherichia_Shigella, and down-regulations for numbers of Bacteroides, Prevotella_9, Parasutterella, and Sutterella. Correlation analysis confirmed relationships among sample components, short-chain fatty acids productivity, and microbial abundances, suggesting that sugars and organic acids stimulated growth of Actinobacteriota and suppressed proliferation of Proteobacteria, thus uncovering the underlying mechanism for the better ability of inoculatedly-fermented Akebia trifoliata fruit juice to regulate microbiota structure. Besides, clusters of orthologous groups of proteins analysis indicated that metabolite biosynthesis, energy metabolism, homeostasis maintenance and other physiological functions were ameliorated.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-023-01308-y.

Effects of soluble glucomannan and insoluble cellulose treatment on mucin secretion and mucin glycosylation-related gene expression in the colons of mice

BACKGROUND

Fiber added to the diet can promote intestinal mucin secretion, relieve intestinal inflammation, and enhance the intestinal barrier function. Glycosylation is the key to mucin function. However, there are few studies on the correlation between dietary fiber and mucin glycosylation, especially two kinds of dietary fiber with different solubility. The aim of this study was to investigate the effects of soluble glucomannan (GM) and insoluble cellulose (CL) treatment on mucin secretion and mucin glycosylation-related gene expression in the colons of mice.

RESULTS

The GM group significantly increased the goblet cell number, crypt depth, and the expression of mucin 2 (Muc2) and mucin 3a (Muc3a) genes in the colon. At the same time, the analysis of the colon transcriptome showed that the GM group changed the expression of genes related to the mucin glycosylation process, and the GM group up-regulated the expression of Gcnt3, Gcnt4, St3gal1, Galnt13, and B3gnt6 genes involved in the O-glycosylation process. Similarly, Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis showed that differentially glycosylated genes in the GM group were mainly related to the biosynthesis of mucin type O-glycans, while the genes in the CL group were related to the biosynthesis of various types of N-glycans. The correlation analysis between colonic microbes and differentially glycosylated genes also showed that the abundance of Alistipes in the GM group was significantly associated with the expression of Gcnt3, a key glycosylation gene.

CONCLUSION

Glucomannan treatment was more favorable for colonic Muc2 and Muc3a secretion and mucin O-glycosylation gene expression. © 2023 Society of Chemical Industry.

In Vitro Fermentation Characteristics of Fungal Polysaccharides Derived from Wolfiporia cocos and Their Effect on Human Fecal Microbiota

Gut microbiota has been described as a new 'organ' that interferes with host physiology by its metabolites produced from the utilization and biotransformation of undigested food components. Fu Ling (FL), the sclerotia of fungi Wolfiporia cocos, contains β-glucan, which is a known natural polysaccharide with strong medicinal efficacy. This study endeavors to evaluate the fermentability of FL and polysaccharides extracted from its sclerotia. An in vitro fermentation of structurally characterized FL and its β-glucan by human fecal microbiota was conducted. Total bacterial count, pH change, short-chain fatty acid profile and microbiota profile were assessed post-fermentation. FL containing over 70% of β-(1 → 3) and (1 → 6)-glucans with a low degree of branching of 0.24 could enhance acetic acid (a major microbial metabolite) production. Both FL and its extracted β-glucan had similar modulation on microbial composition. They enriched Phascolarctobacterium faecium, Bacteroides dorei and Parabacteroides distasonis, all of which are shown to possess anti-inflammatory effects. FL polysaccharide can be utilized as a natural whole food for its potential health benefits to human gut bacteria.

Gut firmicutes: Relationship with dietary fiber and role in host homeostasis

Firmicutes and Bacteroidetes are the predominant bacterial phyla colonizing the healthy human gut. Accumulating evidence suggests that dietary fiber plays a crucial role in host health, yet most studies have focused on how the dietary fiber affects health through gut Bacteroides. More recently, gut Firmicutes have been found to possess many genes responsible for fermenting dietary fiber, and could also interact with the intestinal mucosa and thereby contribute to homeostasis. Consequently, the relationship between dietary fiber and Firmicutes is of interest, as well as the role of Firmicutes in host health. In this review, we summarize the current knowledge regarding the molecular mechanism of dietary fiber degradation by gut Firmicutes and explain the communication pathway of the dietary fiber-Firmicutes-host axis, and the beneficial effects of dietary fiber-induced Firmicutes and their metabolites on health. A better understanding of the dialogue sustained by the dietary fiber-Firmicutes axis and the host could provide new insights into probiotic therapy and novel dietary interventions aimed at increasing the abundance of Firmicutes (such as Faecalibacterium, Lactobacillus, and Roseburia) to promote health.

Gut microbiota bridges dietary nutrients and host immunity

Dietary nutrients and the gut microbiota are increasingly recognized to cross-regulate and entrain each other, and thus affect host health and immune-mediated diseases. Here, we systematically review the current understanding linking dietary nutrients to gut microbiota-host immune interactions, emphasizing how this axis might influence host immunity in health and diseases. Of relevance, we highlight that the implications of gut microbiota-targeted dietary intervention could be harnessed in orchestrating a spectrum of immune-associated diseases.

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.

Lonicera caerulea L. polyphenols improve short-chain fatty acid levels by reshaping the microbial structure of fermented feces in vitro

Increasing evidence suggests that the pathogenesis of type 2 diabetes mellitus (T2DM) is closely related to the gut microbiota. Polyphenols have been shown to alleviate T2DM, but the effects of L. caerulea L. polyphenols (LPs) on the gut microbiota and metabolites remain elusive. In this study, the inhibitory effects of fermented L. caerulea L. polyphenols (FLPs) and unfermented L. caerulea L. polyphenols (ULPs) on α-amylase and α-glucosidase and the impact of LP on the gut microbiota and metabolites were investigated. Furthermore, the relationship between the two was revealed through correlation analysis. The results showed that ULP and FLP had the highest inhibitory rates against α-amylase and α-glucosidase at 4 mg ml-1, indicating a strong inhibitory ability. In addition, LP plays a regulatory role in the concentration of short-chain fatty acids (SCFAs) and tends to restore them to their normal levels. LP reversed the dysbiosis of the gut microbiota caused by T2DM, as evidenced by an increase in the abundance of bacterial genera such as Lactobacillus, Blautia, and Bacteroides and a decrease in the abundance of bacterial genera such as Escherichia-Shigella and Streptococcus. Similarly, after LP intervention, the relationships among microbial species became more complex and interconnected. In addition, the correlation between the gut microbiota and metabolites was established through correlation analysis. These further findings clarify the mechanism of action of LP against T2DM and provide a new target for T2DM interventions.

Tea Tree Oil Improves Energy Metabolism, Non-Specific Immunity, and Microbiota Diversity via the Intestine-Hepatopancreas Axis in Macrobrachium rosenbergii under Low Fish Meal Diet Administration

Tea tree oil (TTO) is an essential plant oil with diverse antibacterial and antioxidant properties; however, whether the role played by TTO in low fish meal (LF) diets induced the observed effects in the farmed crustaceans remains unclear. Therefore, this study used Macrobrachium rosenbergii as the model crustacean, and an 8-week feeding experiment with NF (normal fish meal), LF (soybean meal replacing 40% fish meal), and LFT (LF with 200 mg/kg TTO) diets was conducted to evaluate the positive effects of TTO under the LF diet. Compared to the NF diet, the LF diet reduced hemolymph antioxidant capacity and non-specific immunity, and induced hepatopancreas apoptosis and damage. However, in comparison with LF, LTF significantly ameliorated morphological impairment in the hepatopancreas, improved hepatopancreas energy metabolism by upregulating the Bcl-2/Bax and Akt/mTOR pathways, and enhanced antioxidant and non-specific immune capacity by activating the NF-κB/NO pathway. In addition, LFT repaired intestinal barrier injury and the imbalance of intestinal microbiota induced by the LF diet. Moreover, the Pearson correlation revealed the variations of the above indicators, which were related to the abundance changes of Klebsiella, Clostridium sensu stricto 12, Thermobifida, Bifidobacterium, and Alistipes, indicating that these microbes might serve as prospective targets for the intestine-hepatopancreas axis to affect hepatopancreas apoptosis, metabolism, and non-specific immunity. In summary, 200 mg/kg TTO supplementation mediated gut microbiota and positively improved energy metabolism and non-specific immunity, thereby alleviating hepatopancreas dysplasia and damage induced by the LF diet in M. rosenbergii.

Zearalenone-14-glucoside specifically promotes dysplasia of Gut-Associated Lymphoid Tissue: A natural product for constructing intestinal nodular lymphatic hyperplasia model

INTRODUCTION

Zearalenone-14-glucoside (Z14G) is a modified mycotoxin that widely contaminates food across the world. Our preliminary experiment showed that Z14G degrades to zearalenone (ZEN) in the intestine exerting toxicity. Notably, oral administration of Z14G in rats induces intestinal nodular lymphatic hyperplasia.

OBJECTIVES

To investigate the mechanism of Z14G intestinal toxicity and how it differs from ZEN toxicity. We conducted a precise toxicology study on the intestine of rats exposed to Z14G and ZEN using multi-omics technology.

METHODS

Rats were exposed to ZEN (5 mg/kg), Z14G-L (5 mg/kg), Z14G-H (10 mg/kg), and pseudo germ free (PGF)-Z14G-H (10 mg/kg) for 14 days. Histopathological studies were performed on intestines from each group and compared. Metagenomic, metabolomic, and proteomic analyses were performed on rat feces, serum, and intestines, respectively.

RESULTS

Histopathological studies showed that Z14G exposure resulted in dysplasia of gut-associated lymphoid tissue (GALT) compared to ZEN exposure. The elimination of gut microbes in the PGF-Z14G-H group alleviated or eliminated Z14G-induced intestinal toxicity and GALT dysplasia. Metagenomic analysis revealed that Z14G exposure significantly promoted the proliferation of Bifidobacterium and Bacteroides compared to ZEN. Metabolomic analysis showed that Z14G exposure significantly reduced bile acid, while proteomic analysis found that Z14G exposure significantly reduced the expression of C-type lectins compared to ZEN.

CONCLUSIONS

Our experimental results and previous research suggest that Z14G is hydrolyzed to ZEN by Bifidobacterium and Bacteroides promoting their co-trophic proliferation. This leads to inactivation of lectins by hyperproliferative Bacteroides when ZEN caused intestinal involvement, resulting in abnormal lymphocyte homing and ultimately GALT dysplasia. It is noteworthy that Z14G is a promising model drug to establish rat models of intestinal nodular lymphatic hyperplasia (INLH), which is of great significance for studying the pathogenesis, drug screening and clinical application of INLH.

Recent progress in plant-derived polysaccharides with prebiotic potential for intestinal health by targeting gut microbiota: a review

Natural products of plant origin are of high interest and widely used, especially in the food industry, due to their low toxicity and wide range of bioactive properties. Compared to other plant components, the safety of polysaccharides has been generally recognized. As dietary fibers, plant-derived polysaccharides are mostly degraded in the intestine by polysaccharide-degrading enzymes secreted by gut microbiota, and have potential prebiotic activity in both non-disease and disease states, which should not be overlooked, especially in terms of their involvement in the treatment of intestinal diseases and the promotion of intestinal health. This review elucidates the regulatory effects of plant-derived polysaccharides on gut microbiota and summarizes the mechanisms involved in targeting gut microbiota for the treatment of intestinal diseases. Further, the structure-activity relationships between different structural types of plant-derived polysaccharides and the occurrence of their prebiotic activity are further explored. Finally, the practical applications of plant-derived polysaccharides in food production and food packaging are summarized and discussed, providing important references for expanding the application of plant-derived polysaccharides in the food industry or developing functional dietary supplements.

The Immunomodulatory Effect of β-Glucan Depends on the Composition of the Gut Microbiota

This study aimed to elucidate the relationship between the immunomodulatory effects of β-glucan and the composition of gut microbiota in mice. The mice were fed a diet containing β-glucan for 3 weeks, and feces, blood, and tissues were then collected to analyze the immunomodulatory effect and gut microbiota composition. Based on the results of the analysis of the expression level of immune-associated proteins, the high immunomodulatory effect group (HIE) and low immunomodulatory effect group (LIE) were categorized. Before the β-glucan diet, the proportions of the phylum Bacteroidota, family Muribaculaceae, and family Lactobacillaceae were significantly higher in HIE than in LIE. Furthermore, the genus Akkermansia was absent before the β-glucan diet and increased after β-glucan diet. These microbes had the ability to metabolize β-glucan or were beneficial to health. In conclusion, our findings demonstrate that variation in the composition of gut microbiota among individuals can result in varying expressions of β-glucan functionality. This outcome supports the notion that β-glucan may be metabolized through diverse pathways by gut microbes originally possessed by mice, subsequently producing various metabolites, such as short-chain fatty acids. Alternatively, the viscosity of the intestinal mucosa could be enhanced by β-glucan, potentially promoting the growth of certain bacteria (e.g., the genus Akkermansia). This study provides insights into the intricate interplay between β-glucan, gut microbiota, and immunomodulation.

The preventive effect of Glycyrrhiza polysaccharide on lipopolysaccharide-induced acute colitis in mice by modulating gut microbial communities

Acute colitis is characterised by an unpredictable onset and causes intestinal flora imbalance together with microbial migration, which leads to complex parenteral diseases. Dexamethasone, a classic drug, has side effects, so it is necessary to use natural products without side effects to prevent enteritis. Glycyrrhiza polysaccharide (GPS) is an α-d-pyranoid polysaccharide with anti-inflammatory effects; however, its anti-inflammatory mechanism in the colon remains unknown. This study investigated whether GPS reduces the lipopolysaccharide (LPS)-induced inflammatory response in acute colitis. The results revealed that GPS attenuated the upregulation of tumour necrosis factor-α, interleukin (IL)-1β, and IL-6 in the serum and colon tissues and significantly reduced the malondialdehyde content in colon tissues. In addition, the 400 mg/kg GPS group showed higher relative expressions of occludin, claudin-1, and zona occludens-1 in colon tissues and lower concentrations of diamine oxidase, D-lactate, and endotoxin in the serum than the LPS group did, indicating that GPS improved the physical and chemical barrier functions of colon tissues. GPS increased the abundance of beneficial bacteria, such as Lactobacillus, Bacteroides, and Akkermansia, whereas pathogenic bacteria, such as Oscillospira and Ruminococcus were inhibited. Our findings indicate that GPS can effectively prevent LPS-induced acute colitis and exert beneficial effects on the intestinal health.

Fungal β-glucan-facilitated cross-feeding activities between Bacteroides and Bifidobacterium species

The human gut microbiota (HGM) is comprised of a very complex network of microorganisms, which interact with the host thereby impacting on host health and well-being. β-glucan has been established as a dietary polysaccharide supporting growth of particular gut-associated bacteria, including members of the genera Bacteroides and Bifidobacterium, the latter considered to represent beneficial or probiotic bacteria. However, the exact mechanism underpinning β-glucan metabolism by gut commensals is not fully understood. We show that mycoprotein represents an excellent source for β-glucan, which is consumed by certain Bacteroides species as primary degraders, such as Bacteroides cellulosilyticus WH2. The latter bacterium employs two extracellular, endo-acting enzymes, belonging to glycoside hydrolase families 30 and 157, to degrade mycoprotein-derived β-glucan, thereby releasing oligosaccharides into the growth medium. These released oligosaccharides can in turn be utilized by other gut microbes, such as Bifidobacterium and Lactiplantibacillus, which thus act as secondary degraders. We used a cross-feeding approach to track how both species are able to grow in co-culture.

Catestatin: Antimicrobial Functions and Potential Therapeutics

The rapid increase in drug-resistant and multidrug-resistant infections poses a serious challenge to antimicrobial therapies, and has created a global health crisis. Since antimicrobial peptides (AMPs) have escaped bacterial resistance throughout evolution, AMPs are a category of potential alternatives for antibiotic-resistant "superbugs". The Chromogranin A (CgA)-derived peptide Catestatin (CST: hCgA_352-372; bCgA_344-364) was initially identified in 1997 as an acute nicotinic-cholinergic antagonist. Subsequently, CST was established as a pleiotropic hormone. In 2005, it was reported that N-terminal 15 amino acids of bovine CST (bCST_1-15 aka cateslytin) exert antibacterial, antifungal, and antiyeast effects without showing any hemolytic effects. In 2017, D-bCST_1-15 (where L-amino acids were changed to D-amino acids) was shown to exert very effective antimicrobial effects against various bacterial strains. Beyond antimicrobial effects, D-bCST_1-15 potentiated (additive/synergistic) antibacterial effects of cefotaxime, amoxicillin, and methicillin. Furthermore, D-bCST_1-15 neither triggered bacterial resistance nor elicited cytokine release. The present review will highlight the antimicrobial effects of CST, bCST_1-15 (aka cateslytin), D-bCST_1-15, and human variants of CST (Gly364Ser-CST and Pro370Leu-CST); evolutionary conservation of CST in mammals; and their potential as a therapy for antibiotic-resistant "superbugs".

Chronic consumption of a blend of inulin and arabinoxylan reduces energy intake in an ad libitum meal but does not influence perceptions of appetite and satiety: a randomised control-controlled crossover trial

PURPOSE

Prebiotic foods can be used to increase production of short-chain fatty acids (SCFA) in the gut. Of the SCFA, propionate is credited with the strongest anorectic activity. In previous work, a 50/50 blend of inulin and arabinoxylan was produced (I + AX) that significantly increased propionate production in an in vitro gut model. This study sought to establish whether chronic consumption of a prebiotic blend of I + AX decreases appetite and energy intake and increases intestinal propionate production in human participants.

METHODS

MIXSAT (clinicaltrials.gov id: NCT02846454, August 2016) was a double-blind randomised acute-within-chronic crossover feeding trial in healthy adult men (n = 20). Treatments were 8 g per day I + AX for 21 days or weight-matched maltodextrin control. The primary outcome measure was perceived satiety and appetite during an acute study visit. Secondary outcomes were energy intake in an ad libitum meal, faecal SCFA concentration, and faecal microbiota composition.

RESULTS

Perceived satiety and appetite were not affected by the intervention. I + AX was associated with a reduction in energy intake in an ad libitum meal, increased faecal SCFA concentration, and an increase in cell counts of Bifidobacteria, Lactobacilli, and other microbial genera associated with health.

IMPLICATIONS

Chronic consumption of this blend of prebiotics decreased energy intake in a single sitting. Further studies are needed to confirm mechanism of action and to determine whether this might be useful in weight control.

An exploration of alginate oligosaccharides modulating intestinal inflammatory networks via gut microbiota

Alginate oligosaccharides (AOS) can be obtained by acidolysis and enzymatic hydrolysis. The products obtained by different methods have different structures and physiological functions. AOS have received increasing interest because of their many health-promoting properties. AOS have been reported to exert protective roles for intestinal homeostasis by modulating gut microbiota, which is closely associated with intestinal inflammation, gut barrier strength, bacterial infection, tissue injury, and biological activities. However, the roles of AOS in intestinal inflammation network remain not well understood. A review of published reports may help us to establish the linkage that AOS may improve intestinal inflammation network by affecting T helper type 1 (Th1) Th2, Th9, Th17, Th22 and regulatory T (Treg) cells, and their secreted cytokines [the hub genes of protein-protein interaction networks include interleukin-1 beta (IL-1β), IL-2, IL-4, IL-6, IL-10 and tumor necrosis factor alpha (TNF-α)] via the regulation of probiotics. The potential functional roles of molecular mechanisms are explored in this study. However, the exact mechanism for the direct interaction between AOS and probiotics or pathogenic bacteria is not yet fully understood. AOS receptors may be located on the plasma membrane of gut microbiota and will be a key solution to address such an important issue. The present paper provides a better understanding of the protecting functions of AOS on intestinal inflammation and immunity.

Differences of gut microbiota and behavioral symptoms between two subgroups of autistic children based on γδT cells-derived IFN-γ Levels: A preliminary study

Background

Autism Spectrum Disorders (ASD) are defined as a group of pervasive neurodevelopmental disorders, and the heterogeneity in the symptomology and etiology of ASD has long been recognized. Altered immune function and gut microbiota have been found in ASD populations. Immune dysfunction has been hypothesized to involve in the pathophysiology of a subtype of ASD.

Methods

A cohort of 105 ASD children were recruited and grouped based on IFN-γ levels derived from ex vivo stimulated γδT cells. Fecal samples were collected and analyzed with a metagenomic approach. Comparison of autistic symptoms and gut microbiota composition was made between subgroups. Enriched KEGG orthologues markers and pathogen-host interactions based on metagenome were also analyzed to reveal the differences in functional features.

Results

The autistic behavioral symptoms were more severe for children in the IFN-γ-high group, especially in the body and object use, social and self-help, and expressive language performance domains. LEfSe analysis of gut microbiota revealed an overrepresentation of Selenomonadales, Negatiyicutes, Veillonellaceae and Verrucomicrobiaceae and underrepresentation of Bacteroides xylanisolvens and Bifidobacterium longum in children with higher IFN-γ level. Decreased metabolism function of carbohydrate, amino acid and lipid in gut microbiota were found in the IFN-γ-high group. Additional functional profiles analyses revealed significant differences in the abundances of genes encoding carbohydrate-active enzymes between the two groups. And enriched phenotypes related to infection and gastroenteritis and underrepresentation of one gut-brain module associated with histamine degradation were also found in the IFN-γ-High group. Results of multivariate analyses revealed relatively good separation between the two groups.

Conclusions

Levels of IFN-γ derived from γδT cell could serve as one of the potential candidate biomarkers to subtype ASD individuals to reduce the heterogeneity associated with ASD and produce subgroups which are more likely to share a more similar phenotype and etiology. A better understanding of the associations among immune function, gut microbiota composition and metabolism abnormalities in ASD would facilitate the development of individualized biomedical treatment for this complex neurodevelopmental disorder.

Polygonatum sibiricum saponin Exerts Beneficial Hypoglycemic Effects in Type 2 Diabetes Mice by Improving Hepatic Insulin Resistance and Glycogen Synthesis-Related Proteins

Type 2 diabetes mellitus (T2DM) is a systemic metabolic disorder characterized by insulin deficiency and insulin resistance. Recently, it has become a significant threat to public health. Polygonatum sibiricum saponin (PSS) has potential hypoglycemic effects, but its specific mechanism needs further study. In this study, PSS significantly decreased the level of blood glucose, water intake, and the organ index in diabetic mice. Meanwhile, PSS effectively reduced the content of total triglyceride (TG), total cholesterol (TCHO), low-density lipoprotein cholesterol (LDL-C), alanine aminotransferase (ALT), and aspartate aminotransferase (AST) in the blood, and increased the content of high-density lipoprotein cholesterol (HDL-C). This suggests that PSS could reduce the content of blood lipids and initially improve the damage of hepatocytes. We found that PSS alleviated hepatic insulin resistance, repaired islet beta cells, and enabled insulin to play its biological role normally. It also improved oral glucose tolerance and abated serum lipopolysaccharide (LPS) and glycosylated hemoglobin (HbA1c) levels in T2DM mice. Furthermore, studies have found that PSS increased the content of phosphorylated protein kinase B (AKT), thereby promoting the effect of glucose transporter 4 (GLUT-4), and activating glycogen synthase kinase 3beta (GSK-3β) and glycogen synthase (GS) proteins to promote hepatic glycogen synthesis. Finally, we found that PSS could promote the growth of beneficial bacteria such as Bifidobacterium and Lactobacillus, reduce the growth of harmful bacteria such as Enterococcus and Enterobacter, and preliminarily improve the composition of important bacteria in the intestine. These studies indicate that PSS has an excellent hypoglycemic effect, which provides a potential new treatment for T2DM and guidance for more in-depth research.

Ephedra sinica polysaccharide alleviates airway inflammations of mouse asthma-like induced by PM2.5 and ovalbumin via the regulation of gut microbiota and short chain fatty acid

Objectives

Epidemiological investigations show that long-term exposure to PM2.5 is directly related to asthma-like and other respiratory diseases. This study aims to further explore the pharmacological effect of Ephedra sinica polysaccharide (ESP) on lung injury caused by atmospheric PM2.5.

Methods

To achieve the aim, we explored the therapeutic effect of ESP on an aggravated asthma-like mouse induced by PM2.5 combined with ovalbumin (OVA), and explored mechanisms underlying the connection between gut microbiota and lung function.

Key findings

Preliminary results showed that ESP alleviated the symptoms of aggravated allergic asthma-like in mice; reduced the number of eosinophils in BALF; reduced the levels of serum Ig-E, IL-6, TNF-α, and IL-1β. Further qRT-PCR detected that ESP inhibited the NF-κB pathway. The final analysis detected by 16S rRNA and short chain fatty acid (SCFA) confirmed that ESP increased relative proportions of Bacteroides, Lactobacillus, Prevotella, Butyricicoccus and Paraprevotella, but decreased that of Enterococcus and Ruminococcus; increased acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, isovaleric acid, and isohexanic acid in the meanwhile.

Conclusions

The study showed that ESP has a potential for future therapeutical applications in the prevention and treatment of asthma-like disease induced by PM2.5 and OVA via regulation of gut microbiota and SCFA.

Dietary Polysaccharides as Modulators of the Gut Microbiota Ecosystem: An Update on Their Impact on Health

A polysaccharide is a macromolecule composed of more than ten monosaccharides with a wide distribution and high structural diversity and complexity in nature. Certain polysaccharides are immunomodulators and play key roles in the regulation of immune responses during the progression of some diseases. In addition to stimulating the growth of certain intestinal bacteria, polysaccharides may also promote health benefits by modulating the gut microbiota. In the last years, studies about the triad gut microbiota–polysaccharides–health have increased exponentially. In consequence, in the present review, we aim to summarize recent knowledge about the function of dietary polysaccharides on gut microbiota composition and how these effects affect host health.

Gut Microbiota: Therapeutic Targets of Ginseng Against Multiple Disorders and Ginsenoside Transformation

Panax ginseng, as the king of Chinese herb, has significant therapeutic effects on obesity, type 2 diabetes mellitus, fatty liver disease, colitis, diarrhea, and many other diseases. This review systematically summarized recent findings, which show that ginseng plays its role by regulating gut microbiota diversity, and gut microbiota could also regulate the transformation of ginsenosides. We conclude the characteristics of ginseng in regulating gut microbiota, as the potential targets to prevent and treat metabolic diseases, colitis, neurological diseases, cancer, and other diseases. Ginseng treatment can increase some probiotics such as Bifidobacterium, Bacteroides, Verrucomicrobia, Akkermansia, and reduce pathogenic bacteria such as Deferribacters, Lactobacillus, Helicobacter against various diseases. Meanwhile, Bacteroides, Eubacterium, and Bifidobacterium were found to be the key bacteria for ginsenoside transformation in vivo. Overall, ginseng can regulate gut microbiome diversity, further affect the synthesis of secondary metabolites, as well as promote the transformation of ginsenosides for improving the absorptivity of ginsenosides. This review can provide better insight into the interaction of ginseng with gut microbiota in multiple disorders and ginsenoside transformation.

Beneficial Effects of Partly Milled Highland Barley on the Prevention of High-Fat Diet-Induced Glycometabolic Disorder and the Modulation of Gut Microbiota in Mice

The nutritional functions of highland barley (HB) are superior to those of regular cereals and have attracted increasing attention in recent years. The objective of this study was to investigate whether partly milled highland barley (PHB) can regulate the serum glucose and lipid disorders of mice fed a high-fat diet (HFD) and to further explore their potential gut microbiota modulatory effect. Our results showed that PHB supplementation significantly reduced fasting blood glucose (FBG) and improved oral glucose tolerance. Histological observations confirmed the ability of PHB to alleviate liver and intestine damage. Furthermore, the results of 16S amplicon sequencing revealed that PHB prevented a HFD-induced gut microbiota dysbiosis, enriching some beneficial bacteria, such as Lactobacillus, Bifidobacterium, and Ileibacterium, and reducing several HFD-dependent taxa (norank_f_Desulfovibrionaceae, Blautia, norank_f_Lachnospiraceae, unclassified_f_Lachnospiraceae, and Colidextribacter). In addition, the increase of Lactobacillus and Bifidobacterium presence has a slightly dose-dependent relationship with the amount of the added PHB. Spearman correlation analysis revealed that Lactobacillus and Bifidobacterium were negatively correlated with the blood glucose level of the oral glucose tolerance test. Overall, our results provide important information about the processing of highland barley to retain its hypoglycemic effect and improve its acceptability and biosafety.

Configured for the Human Gut Microbiota: Molecular Mechanisms of Dietary β-Glucan Utilization

The β-glucans are a disparate group of structurally diverse polysaccharides, whose members are widespread in human diets as components of the cell walls of plants, algae, and fungi (including yeasts), and as bacterial exopolysaccharides. Individual β-glucans from these sources have long been associated with positive effects on human health through metabolic and immunological effects. Remarkably, the β-configured glucosidic linkages that define these polysaccharides render them inaccessible to the limited repertoire of digestive enzymes encoded by the human genome. As a result, the various β-glucans become fodder for the human gut microbiota (HGM) in the lower gastrointestinal tract, where they influence community composition and metabolic output, including fermentation to short chain fatty acids (SCFAs). Only recently, however, have the specific molecular systems that enable the utilization of β-glucans by select members of the HGM been fully elucidated by combined genetic, biochemical, and structural biological approaches. In the context of β-glucan structures and their effects on human nutrition and health, we summarize here the functional characterization of individual polysaccharide utilization loci (PULs) responsible for the saccharification of mixed-linkage β(1→3)/β(1→4)-glucans, β(1→6)-glucans, β(1→3)-glucans, β(1→2)-glucans, and xyloglucans in symbiotic human gut bacteria. These exemplar PULs serve as well-defined biomarkers for the prediction of β-glucan metabolic capability in individual bacterial taxa and across the global human population.