Fermentation Of Dietary Fiber Research Articles

A189 ELUCIDATING THE MECHANISTIC ROLE OF GLP-1R IN THE INFLAMMATORY RESPONSE OF MACROPHAGES AND B CELLS TO DIETARY FIBRES

Abstract Background Both diet and the microbiome have been implicated in the pathogenesis of inflammatory bowel diseases (IBD). Fibre is not digested; it is fermented by microbes in the large bowel. High fibre intake is related to lower risk for the development of IBD, and a high fibre diet is usually recommended for individuals with IBD. However, work in our lab suggests that select dietary fibres may be pro-inflammatory in a pediatric IBD cohort. Importantly, large bowel dysbiosis in IBD could limit the fermentation of dietary fibres, leading to reduced production of beneficial microbiome metabolites as well as an accumulation of intact fibre in the large bowel. These intact fibres may then interact with immune cells residing in the large bowel, through specific receptors, and perpetuate the inflammatory state seen in IBD. Aims Based on preliminary findings, we hypothesize that the dietary fibre oligofructose acts through GLP-1R on macrophages and B-cells to regulate the inflammatory environment. We expect to find changes in the expression of cytokines and chemokines, and their receptors. Methods Changes in immune cell secretions (ELISA) and the expression of selected inflammatory markers (RT-qPCR) were measured to determine potential pathways involved in response to dietary fibres in vitro. Knockdown of proteins of interest (siRNA) was performed to validate the involvement of these pathways in the inflammatory response to dietary fibres. Cells were treated with oligofructose, oligofructose pre-fermented by bacteria, or no fibre. The involvement of the fibre receptor, GLP-1R, was investigated to understand its connection to pathways identified. Results Qiagen RT2 profiler array (human inflammatory cytokines and receptors) and cytokine secretion (ELISA) indicated that in response to oligofructose macrophages have a predominantly pro-inflammatory response while B cells have an anti-inflammatory response. Presence of GLP-1R in large bowel and terminal ileum biopsies collected during endoscopy was higher in IBD (Crohn disease n=7; Ulcerative colitis n=7) than non-IBD patients (n=7), and expression was confirmed on both B-cells and macrophages. Knockdown of GLP-1R (siRNA) significantly reduced the pro-inflammatory response (IL-1β ELISA) with oligofructose application in THP-1 macrophage cells Conclusions Improving our understanding of the mechanistic link between dietary fibres and immune response will aid us in developing a model for the interactions of oligofructose with the GLP-1R in B cells and macrophages. Findings from this study may be able to inform dietary interventions, prebiotic/probiotic administration, and drug development for treatment of IBDs. Funding Agencies CIHRWeston Foundation

The effect of gut microbiota on the intestinal lipidome of mice

Gut microbiota significantly influence the plasma and liver lipidome. An interconnecting metabolite is acetate generated after degradation and fermentation of dietary fiber by the gut microbiota, which is metabolized in the liver into longer chain fatty acids and complex lipids reaching the circulation. Whether these systemic changes are accompanied by alternations of the intestinal lipidome is unclear. Therefore, we quantified glycerophospholipids, sphingolipids and sterols in ileum and colon, the two segments containing the highest densities of microbes in the gastrointestinal tract, of germfree and specific pathogen free mice using mass spectrometry-based lipidomics. We found that the presence of gut microbes lowers the free cholesterol content in colon while elevating phosphatidylcholine levels. Further, PUFA-containing phosphatidylcholine and -ethanolamine fractions are increased in ileum and colon of germfree compared to SPF mice. A total fatty acid analysis by GC–MS revealed higher levels of arachidonic and docosahexaenoic acid in the ileum of germfree mice indicating that the gut microbiota inhibits PUFA metabolism in the small intestine.

Effects of High Intakes of Fructose and Galactose, with or without Added Fructooligosaccharides, on Metabolic Factors, Inflammation, and Gut Integrity in a Rat Model.

A high fructose and galactose intake show adverse metabolic effects in animal models and in humans, but it is yet unknown if addition of fermentable dietary fiber can mitigate such effects. This study investigate the effects of high intakes of fructose and galactose, with/without added fructooligosaccharides (FOS), on metabolic factors, inflammation, and gut integrity markers in rats. Rats (n = 6/group) receive different carbohydrates at isocaloric conditions for 12 weeks as follows: 1) starch (control), 2) fructose, 3) galactose, 4) starch + FOS (FOS control), 5) fructose + FOS, and 6) galactose + FOS, together with a high amount of n-6 polyunsaturated fatty acids (n-6 PUFA) in all diets except for in 7) starch + olive oil (negative control). The rats fed the galactose and galactose + FOS diets exhibit lower body weight than other groups. High-galactose diets has more pronounced effects on metabolic factors and gut permeability than high-fructose diets. High-fructose diets show less pronounced effect on these selected markers. No differences in inflammatory markers are detected for any of the diets. The results suggest potential adverse effects of high galactose and fructose on metabolic factors and gut integrity markers, but not on inflammation. However, several mechanisms are at play, and general net effects are difficult to determine conclusively for the conditions tested.

Fermentation of dietary fibers modified by an enzymatic‐ultrasonic treatment and evaluation of their impact on gut microbiota in mice

Dietary fiber (DF) from sisal waste and Moringa oleifera stem were modified using a successive enzymatic-ultrasonic (E-U) treatment to produce modified DF products (MDFs), with reduced ratio of insoluble DF (IDF) and soluble DF (SDF) and decreased particle size. The water-holding capacity, swelling capacity, and oil-holding capacity of the MDFs were elevated upon E-U treatment. MDF-S (MDF from sisal waste) and MDF-M (MDF from M. oleifera stem) were fermented to produce short-chain fatty acids (SCFAs) by gut bacteria in mice, with total SCFA content of 3.81 μmol/g and 3.34 μmol/g, respectively, when added in basal feed at 10% (wt/wt). Metagenomic analyses demonstrated that MDFs tended to increase the Bacteroidetes/Firmicutes ratio, and significantly increased the relative abundance of Bacteroides, norank_f__Bacteroidales_S24-7_group, norank_f__Erysipelotrichaceae, Ruminococcus_1, and Akkermansia at genus level. These findings suggest that MDF supplementation in diet could favorably modulate gut microbiome in mice. Novelty impact statement We proposed a DF modification strategy to improve its role in intestinal flora modulation. Our results suggest that successive enzymatic and ultrasonic treatment effectively reduced the IDF/SDF ratio of DF. Supplement of the modified DF could alter the intestinal flora of mice to a high Bacteroidetes/Firmicutes ratio and elevate the relative abundance of several beneficial microbiota.

Deficiency of Dietary Fiber Modulates Gut Microbiota Composition, Neutrophil Recruitment and Worsens Experimental Colitis.

Ulcerative colitis is an inflammatory disease of the colon that is associated with colonic neutrophil accumulation. Recent evidence indicates that diet alters the composition of the gut microbiota and influences host–pathogen interactions. Specifically, bacterial fermentation of dietary fiber produces metabolites called short-chain fatty acids (SCFAs), which have been shown to protect against various inflammatory diseases. However, the effect of fiber deficiency on the key initial steps of inflammation, such as leukocyte–endothelial cell interactions, is unknown. Moreover, the impact of fiber deficiency on neutrophil recruitment under basal conditions and during inflammation in vivo is unknown. Herein, we hypothesized that a fiber-deficient diet promotes an inflammatory state in the colon at baseline and predisposes the host to more severe colitis pathology. Mice fed a no-fiber diet for 14 days showed significant changes in the gut microbiota and exhibited increased neutrophil-endothelial interactions in the colonic microvasculature. Although mice fed a no-fiber diet alone did not have observable colitis-associated symptoms, these animals were highly susceptible to low dose (0.5%) dextran sodium sulphate (DSS)-induced model of colitis. Supplementation of the most abundant SCFA, acetate, prevented no-fiber diet-mediated enrichment of colonic neutrophils and colitis pathology. Therefore, dietary fiber, possibly through the actions of acetate, plays an important role in regulating neutrophil recruitment and host protection against inflammatory colonic damage in an experimental model of colitis.

Inhibitory effect of sodium butyrate on colorectal cancer cells and construction of the related molecular network

BackgroundSodium butyrate (NaB) is produced through the fermentation of dietary fiber that is not absorbed and digested by the small intestine.PurposeHere, we aimed to investigate the effects of NaB on the proliferation, invasion, and metastasis of CRC cells and their potential underlying molecular mechanism(s).MethodsThe cell counting kit-8 (CCK-8) assay and EdU assay were used to detect cell proliferation ability, flow cytometry was used to investigate the induction of apoptosis and cell cycle progression, and the scratch-wound healing and transwell assays were used to evaluate cell migration and invasion, respectively. The human CRC genome information for tissues and CRC cells treated with NaB obtained from the NCBI GEO database was reannotated and used for differential RNA analysis. Functional and pathway enrichment analyses were performed for differentially expressed lncRNAs and mRNAs. A protein-protein interaction (PPI) network for the hub genes was constructed using the Cytoscape software. Targeted miRNAs were predicted based on the lnCeDB database, and a ceRNA network was constructed using the Cytoscape software. The Kaplan-Meier method was used to analyze patient prognosis using the clinical information and exon-seq data for CRC obtained from the Broad Institute’s GDAC Firehose platform.ResultsNaB decreased the proliferation ability of CRC cells in a dose- and time-dependent manner. The number of apoptotic CRC cells increased with the increase in NaB concentrations, and NaB induced a G1 phase block in CRC cells. Moreover, NaB suppressed the migratory and invasive capabilities of CRC cells. There were 666 differentially expressed mRNAs and 30 differentially expressed lncRNAs involved in the CRC inhibition by NaB. The PPI network and ceRNA network were constructed based on the differentially expressed mRNAs and lncRNAs. Three differentially expressed mRNAs, including HMGA2, LOXL2, and ST7, were significantly correlated with the prognosis of CRC.ConclusionNaB induces the apoptosis and inhibition of CRC cell proliferation, invasion, and metastasis by modulating complex molecular networks. RNA prediction and molecular network construction need to be the focus of further research in this direction.

DIETARY FIBER GUAR GUM EXACERBATES COLONIC INFLAMMATION IN MULTIPLE EXPERIMENTAL MODELS OF INFLAMMATORY BOWEL DISEASE

The role of fermentable dietary fibers in patients with inflammatory bowel disease (IBD) is not understood. Herein, we elucidated the effect of dietary fiber guar gum, commonly added to a wide range of processed foods, on colonic inflammation. The use of three different IBD models allowed us to examine the effect of guar gum on various aspects of human IBD, such as immune hyperactivity [IL-10 receptor (IL-10R) neutralization], epithelial injury [dextran sulfate sodium (DSS)], and infection [Citrobacter rodentium (CR)]-mediated inflammation.

The Protective Role of Butyrate against Obesity and Obesity-Related Diseases.

Worldwide obesity is a public health concern that has reached pandemic levels. Obesity is the major predisposing factor to comorbidities, including type 2 diabetes, cardiovascular diseases, dyslipidemia, and non-alcoholic fatty liver disease. The common forms of obesity are multifactorial and derive from a complex interplay of environmental changes and the individual genetic predisposition. Increasing evidence suggest a pivotal role played by alterations of gut microbiota (GM) that could represent the causative link between environmental factors and onset of obesity. The beneficial effects of GM are mainly mediated by the secretion of various metabolites. Short-chain fatty acids (SCFAs) acetate, propionate and butyrate are small organic metabolites produced by fermentation of dietary fibers and resistant starch with vast beneficial effects in energy metabolism, intestinal homeostasis and immune responses regulation. An aberrant production of SCFAs has emerged in obesity and metabolic diseases. Among SCFAs, butyrate emerged because it might have a potential in alleviating obesity and related comorbidities. Here we reviewed the preclinical and clinical data that contribute to explain the role of butyrate in this context, highlighting its crucial contribute in the diet-GM-host health axis.

DIETARY FIBER GUAR GUM EXACERBATES COLONIC INFLAMMATION IN MULTIPLE EXPERIMENTAL MODELS OF INFLAMMATORY BOWEL DISEASE

Abstract The role of fermentable dietary fibers in patients with inflammatory bowel disease (IBD) is not understood. Herein, we elucidated the effect of dietary fiber guar gum, commonly added to a wide range of processed foods, on colonic inflammation. The use of three different IBD models allowed us to examine the effect of guar gum on various aspects of human IBD, such as immune hyperactivity [IL-10 receptor (IL-10R) neutralization], epithelial injury [dextran sulfate sodium (DSS)], and infection [Citrobacter rodentium (CR)]-mediated inflammation. Wild-type (WT, C57BL/6) mice fed either control cellulose (insoluble fiber, aka non-fermentable fiber) or guar gum (soluble fiber, aka fermentable fiber, 7.5% w/w) were administered four weekly injections of IL-10R neutralizing antibody (α-IL-10R) to induce immune-hyperactivation mediated chronic colitis. Guar gum treated mice developed robust α-IL-10R mediated colitis. Guar gum fed mice had splenomegaly, colomegaly, elevated systemic proinflammatory markers [serum amyloid A (SAA), lipocalin 2 (Lcn2) and keratinocyte-derived chemokine (KC)] and elevated colonic Lcn2 and interleukin (IL)-1β, and histopathology scores compared to control, cellulose-fed, mice. Similar results were observed in Toll-like receptor 5 deficient mice, which are prone to develop microbiota-dependent colitis. Next, to examine the effect of guar gum on the epithelial injury model, mice were treated with DSS (1.4% w/v in drinking water) for seven days. The guar gum fed group developed severe colitis, including reduced body weight, diarrhea, rectal bleeding, shortening of colon length, and elevated levels of pro-inflammatory markers (Lcn2, KC, and SAA)compared to the control group. The last model to be tested was infection-induced colitis. Since inflammation is required to clear the infection, we hypothesized that guar gum fed mice might clear CR infection better than controls. To our surprise, guar gum fed WT mice shed higher numbers of CR in the feces than the cellulose group. The guar gum fed mice had lower body weights, colomegaly, an elevated level of colonic and serum Lcn2, and higher serum SAA than the control group. Collectively, guar gum failed to protect against CR-induced colonic pathology. Altogether, the work demonstrates that guar gum feeding may exacerbate colonic inflammation following immune-hyperactivation, chemical, and infectious injury. Cautioning IBD patients to monitor their consumption of guar gum fiber might be a way to reduce the severity of intestinal inflammation.

Porphyromonas gingivalis Produce Neutrophil Specific Chemoattractants Including Short Chain Fatty Acids.

Neutrophil migration from blood to tissue-residing microbes is governed by a series of chemoattractant gradients of both endogenous and microbial origin. Periodontal disease is characterized by neutrophil accumulation in the gingival pocket, recruited by the subgingival biofilm consisting mainly of gram-negative, anaerobic and proteolytic species such as Porphyromonas gingivalis. The fact that neutrophils are the dominating cell type in the gingival pocket suggests that neutrophil-specific chemoattractants are released by subgingival bacteria, but characterization of chemoattractants released by subgingival biofilm species remains incomplete. In the present study we characterized small (< 3 kDa) soluble chemoattractants released by growing P. gingivalis, and show that these are selective for neutrophils. Most neutrophil chemoattractant receptors are expressed also by mononuclear phagocytes, the free fatty acid receptor 2 (FFAR2) being an exception. In agreement with the selective neutrophil recruitment, the chemotactic activity found in P. gingivalis supernatants was mediated in part by a mixture of short chain fatty acids (SCFAs) that are recognized by FFAR2, and other leukocytes (including monocytes) did not respond to SCFA stimulation. Although SCFAs, produced by bacterial fermentation of dietary fiber in the gut, has previously been shown to utilize FFAR2, our data demonstrate that the pronounced proteolytic metabolism employed by P. gingivalis (and likely also other subgingival biofilm bacteria associated with periodontal diseases) may result in the generation of SCFAs that attract neutrophils to the gingival pocket. This finding highlights the interaction between SCFAs and FFAR2 in the context of P. gingivalis colonization during periodontal disease, but may also have implications for other inflammatory pathologies involving proteolytic bacteria.

Modulation of human gut microbiota by dietary fibers from unripe and ripe papayas: Distinct polysaccharide degradation using a colonic in vitro fermentation model

Dietary fibers (DFs) consumption promotes a healthier gut through colonic fermentation and the modulation of different types of gut bacteria. The aim of this study is to evaluate the production of short-chain fatty acids (SCFA), metabolization of polysaccharides, and changes in the bacterial profile related to DFs extracted from the pulp of unripe and ripe papayas, using a batch colonic in vitro fermentation model. Our results show that fermentation of DFs from papayas induce the production of SCFAs and are utilized in different ways by intestinal microbiota. DFs from ripe papayas showed faster degradation by human gut microorganisms due to higher level of water-soluble polysaccharides. The fermentation of unripe papaya fibers increased the abundance of microorganisms belonging to family Clostridiaceae and genera Coprobacillus, Bulleidia, and Slackia, whereas both fibers increased Clostridium and Bacteroides, showing fruit ripeness affects the fermentation pattern of fruit fibers and their probable beneficial health aspects.

The role of butyrate in surgical and oncological outcomes in colorectal cancer.

Butyrate is a short-chain fatty acid produced by colonic gut bacteria as a result of fermentation of dietary fibers. In the colon, butyrate is a major energy substrate and contributes to the nutritional support and proliferation of a healthy mucosa. It also promotes the intestinal barrier function by enhancing mucus production and tight junctions. In addition to its pro-proliferative effect in healthy colonocytes, butyrate inhibits the proliferation of cancer cells. The antineoplastic effect of butyrate is associated with the inhibitory effect of butyrate on histone deacetylase (HDAC) enzymes, which promote carcinogenesis. Due to the metabolic shift of cancer cells toward glycolysis, unused butyrate accumulates and inhibits procarcinogenic HDACs. In addition, recent studies suggest that butyrate may improve the healing of colonic tissue after surgery in animal models, specifically at the site of reconnection of colonic ends, anastomosis, after surgical resection. Here, we review current evidence on the impact of butyrate on epithelial integrity and colorectal cancer and present current knowledge on data that support its potential applications in surgical practice.

Short chain fatty acids (SCFAs) improves TNBS-induced colitis in zebrafish

The short-chain fatty acids (SCFAs) are metabolites originated from the fermentation of dietary fibers and amino acids produced by the bacteria of the intestinal microbiota. The most abundant SCFAs, acetate, propionate, and butyrate, have been proposed as a treatment for inflammatory bowel diseases (IBDs) due to their anti-inflammatory properties. This work aimed to analyze the effects of the treatment of three combined SCFAs in TNBS-induced intestinal inflammation in zebrafish larvae. Here, we demonstrated that SCFAs significantly increased the survival of TNBS-exposed larvae, preserved the intestinal endocytic function, reduced the expression of inflammatory cytokines and the intestinal recruitment of neutrophils caused by TNBS. However, SCFAs treatment did not appear to avoid TNBS-induced tissue damage in the intestinal wall and did not restore the number of mucus-producing goblet cells. Finally, exposure to TNBS induced dysbiosis of the microbiota with an increase in Betaproteobacteria and Actinobacteria, while the treatment with SCFAs maintained these population levels similar to control. Thus, we demonstrate that the treatment of three combined SCFAs presented anti-inflammatory properties previously seen in mammals, opening an opportunity to use zebrafish to explore the potential benefit of these and other metabolites to treat inflammation.

Noninvasive monitoring of fibre fermentation in healthy volunteers by analyzing breath volatile metabolites: lessons from the FiberTAG intervention study

ABSTRACT The fermentation of dietary fibre (DF) leads to the production of bioactive metabolites, the most volatile ones being excreted in the breath. The aim of this study was to analyze the profile of exhaled breath volatile metabolites (BVM) and gastrointestinal symptoms in healthy volunteers after a single ingestion of maltodextrin (placebo) versus chitin-glucan (CG), an insoluble DF previously shown to be fermented into short-chain fatty acids (SCFA) by the human microbiota in vitro. Maltodextrin (4.5 g at day 0) or CG (4.5 g at day 2) were added to a standardized breakfast in fasting healthy volunteers (n = 15). BVM were measured using selected ion flow tube mass spectrometry (SIFT-MS) throughout the day. A single ingestion of 4.5 g CG did not induce significant gastrointestinal discomfort. Untargeted metabolomics analysis of breath highlighted that 13 MS-fragments (among 408 obtained from ionizations of breath) discriminated CG versus maltodextrin acute intake in the posprandial state. The targeted analysis revealed that CG increased exhaled butyrate and 5 other BVM – including the microbial metabolites 2,3-butanedione and 3-hydroxybutanone – with a peak observed 6 h after CG intake. Correlation analyses with fecal microbiota (Illumina 16S rRNA sequencing) spotlighted Mitsuokella as a potential genus responsible for the presence of butyric acid, triethylamine and 3-hydroxybutanone in the breath. In conclusion, measuring BMV in the breath reveals the microbial signature of the fermentation of DF after a single ingestion. This protocol allows to analyze the time-course of released bioactive metabolites that could be proposed as new biomarkers of DF fermentation, potentially linked to their biological properties. Trial registration: Clinical Trials NCT03494491. Registered 11 April 2018 – Retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT03494491

Plant origin prebiotics affect duodenal brush border membrane functionality and morphology, in vivo (Gallus Gallus).

The intra-amniotic administration approach has been used to evaluate the effects of plant origin prebiotics on intestinal health and on brush border membrane functionality and morphology. Prebiotics are fermentable dietary fibers, which can positively affect the host by selectively stimulating the growth and activity of colon bacteria, thus improving intestinal health. The consumption of prebiotics increases digestive tract motility, which leads to hyperplasia and/or hypertrophy of intestinal cells, increasing nutrient digestive and absorptive surface area. This review collates information about the effects and relationship between prebiotic consumption on small intestinal brush border membrane functionality and morphology by utilizing the intra-amniotic administration approach. To date, research has shown that the intra-amniotic administration of prebiotics affects the expression of key brush border membrane functional proteins, intestinal surface area (villi height/width), and goblet cell number/size. These effects may improve brush border membrane functionality and digestive/absorptive capabilities.

Rapid Quantification of Gut Microbial Short-Chain Fatty Acids by pDART-MS.

Short-chain fatty acids (SCFAs) are small molecules ubiquitous in nature. In mammalian guts, SCFAs are mostly produced by anaerobic intestinal microbiota through the fermentation of dietary fiber. Levels of microbe-derived SCFAs are closely relevant to human health status and indicative to gut microbiota dysbiosis. However, the quantification of SCFA using conventional chromatographic approaches is often time consuming, thus limiting high-throughput screening tests. Herein, we established a novel method to quantify SCFAs by coupling amidation derivatization of SCFAs with paper-loaded direct analysis in real time mass spectrometry (pDART-MS). Remarkably, SCFAs of a biological sample were quantitatively determined within a minute using the pDART-MS platform, which showed a limit of detection at the μM level. This platform was applied to quantify SCFAs in various biological samples, including feces from stressed rats, sera of patients with kidney disease, and fermentation products of metabolically engineered cyanobacteria. Significant differences in SCFA levels between different groups of biological practices were promptly revealed and evaluated. As there is a burgeoning demand for the analysis of SCFAs due to an increasing academic interest of gut microbiota and its metabolism, this newly developed platform will be of great potential in biological and clinical sciences as well as in industrial quality control.

Fermentable fibers upregulate suppressor of cytokine signaling1 in the colon of mice and intestinal Caco-2 cells through butyrate production.

Short chain fatty acids (SCFAs), the microbial metabolites of fermentable dietary fibers exert multiple beneficial effects on mammals including humans. We examined the effects of fermentable dietary fibers on suppressor of cytokine signaling 1 (SOCS1), a negative regulator of inflammatory signaling, on the intestinal epithelial cells of the mouse colon and human intestinal Caco-2 cells, specifically focusing on the role of SCFAs. Feeding fermentable fibers, guar gum (GG) and partially hydrolyzed GG (PHGG) increased SOCS1 expression in the colon and the cecal pool of some SCFAs including acetate, propionate, and butyrate. The antibiotic administration abolished the GG-mediated SOCS1 expression in the colon. In Caco-2 cells, butyrate, but not other SCFAs, increased SOCS1 expression. Taken together, fermentable fibers such as GG and PHGG upregulate the colonic SOCS1 expression, possibly through the increased production of butyrate in mice and can be a potential tool in the fight against inflammatory diseases. Abbreviations: GG: Guar gum; GPR: G protein-coupled receptor; IL: Interleukin; JAK: Janus kinase; NF- κB: Nuclear factor-kappa B; PHGG: Partially hydrolyzed guar gum; SCFA: Short chain fatty acid; SOCS: Suppressor of cytokine signaling; STAT: Signal transducer and activator of transcription; TLR: Toll-like receptor.

Do short chain fatty acids and phenolic metabolites of the gut have synergistic anti-inflammatory effects? – New insights from a TNF-α-induced Caco-2 cell model

Fermentation of dietary fiber and metabolism of polyphenols by the gut microbiota produce short chain fatty acids (SCFAs) and some simple phenolic acids, both of which have been independently shown to have anti-inflammatory effects and to improve gut health. While synergistic interactions between the two colonic metabolite groups have been speculated, direct evidence on whether and how these compounds work together towards collective anti-inflammatory effect and gut health remain unclear. In this study, the most important SCFA butyric acid (BtA) and three phenolic metabolites benzoic acid (BzA), phenylacetic acid (PAA) and phenylpropionic acid (PPA) were selected and assessed for the anti-inflammatory effects and the underlying mechanisms in a TNF-α-induced Caco-2 cell model. Significantly stronger inhibition of TNF-α-induced IL-8 production was found in cells pre-treated with different concentrations of mixtures of BtA and the phenolic metabolites than individual compounds. Further study showed that the synergistic effect was via significant down-regulation of the gene expressions of IL-8, TNF-α and VCAM-1, and of phosphorylation of JNK, p38 and IĸBα, cellular signaling mediators of the MAPK and NF-κB pathways. Although these are results of a cell model, they do provide significant insights into the synergistic anti-inflammatory effects between SCFAs and phenolic metabolites. As both metabolite groups are simultaneously present in the gut, our findings therefore also suggest a potential synergistic effect between the two colonic metabolite groups in maintaining gut health.

Brachyspira hyodysenteriae Infection Reduces Digestive Function but Not Intestinal Integrity in Growing Pigs While Disease Onset Can Be Mitigated by Reducing Insoluble Fiber.

Swine dysentery (SD) induced by Brachyspira hyodysenteriae manifests as mucohemorrhagic diarrhea in pigs, but little is known about the changes that occur to the gastrointestinal tract during this disease. It is thought that dietary fibers alter disease pathogenesis, although the mechanisms of action are unclear. Thus, the objectives of this study were to characterize intestinal integrity, metabolism, and function in pigs during SD and determine if replacing insoluble fiber with fermentable fibers mitigates disease. Thirty-six B. hyodysenteriae-negative gilts [24.3 ± 3.6 kg body weight (BW)] were assigned to one of three treatment groups: (1) B. hyodysenteriae negative, control diet (NC); (2) B. hyodysenteriae challenged, control diet (PC); and (3) B. hyodysenteriae challenged, highly fermentable fiber diet (RS). The NC and PC pigs were fed the same control diet, containing 20% corn distillers dried grains with solubles (DDGS). The RS pigs were fed a diet formulated with 5% sugar beet pulp and 5% resistant potato starch. On days post inoculation (dpi) 0 and 1, pigs were inoculated with B. hyodysenteriae or sham. Pigs were euthanized for sample collection after onset of SD. The challenge had high morbidity, with 100% of PC and 75% of RS pigs developing clinical SD. The timing of onset of clinical SD differed due to treatment, with RS pigs having a delayed onset (dpi 9) of clinical SD compared with dpi 7 for PC pigs. Colon transepithelial resistance was increased and macromolecule permeability was reduced in PC pigs compared with NC pigs (P < 0.01). Minimal changes in ileal permeability, mitochondrial function, or volatile fatty acids (VFAs) were observed. Total VFA concentrations were lower in the colon and cecum in both PC and RS pigs compared to NC pigs (both P < 0.05), but iso-acids were higher (both P < 0.05). Total tract digestibility of dry matter (DM), organic matter (OM), nitrogen (N), and gross energy (GE) was lower in PC pigs compared with both NC and RS pigs (both P < 0.001). These data indicate that SD reduces digestive function but does not reduce ex vivo intestinal integrity. Further, replacement of insoluble fiber with highly fermentable fibers mitigated and delayed the onset of SD.

Inulin supplementation ameliorates hyperuricemia and modulates gut microbiota in Uox-knockout mice

PurposeInulin is a type of fermentable dietary fiber, which is non-digestible, and can improve metabolic function by modulating intestinal microbiota. This study aimed to evaluate the role of inulin in hyperuricemia and microbial composition of the gut microbiota in a mouse model of hyperuricemia established through knockout of Uox (urate oxidase) gene.MethodsKO (Uox-knockout) and WT (wild-type) mice were given inulin or saline by gavage for 7 weeks. The effect of inulin to combat hyperuricemia was determined by assessing the changes in serum UA (uric acid) levels, inflammatory parameters, epithelial barrier integrity, fecal microbiota alterations, and SCFA (short-chain fatty acid) concentrations in KO mice.ResultsInulin supplementation can effectively alleviate hyperuricemia, increase the expressions of ABCG2 in intestine, and downregulate expression and activity of hepatic XOD (xanthine oxidase) in KO mice. It was revealed that the levels of inflammatory cytokines and the LPS (lipopolysaccharide) were remarkably higher in the KO group than those in the WT group, indicating systemic inflammation of hyperuricemic mice, but inulin treatment ameliorated inflammation in KO mice. Besides, inulin treatment repaired the intestinal epithelial barrier as evidenced by increased levels of intestinal TJ (tight junction) proteins [ZO-1 (zonula occludens-1) and occluding] in KO mice. Moreover, serum levels of uremic toxins, including IS (indoxyl sulfate) and PCS (p-cresol sulfate), were reduced in inulin-treated KO mice. Further investigation unveiled that inulin supplementation enhanced microbial diversity and raised the relative abundance of beneficial bacteria, involving SCFAs-producing bacteria (e.g., Akkermansia and Ruminococcus). Additionally, inulin treatment increased the production of gut microbiota-derived SCFAs (acetate, propionate and butyrate concentrations) in KO mice, which was positively correlated with the effectiveness of hyperuricemia relief.ConclusionsOur findings showed that inulin may be a promising therapeutic candidate for the treatment of hyperuricemia. Moreover, alleviation of hyperuricemia by inulin supplementation was, at least, partially conciliated by modulation of gut microbiota and its metabolites.