Impaired gut barrier function plays an important role in the development of many diseases such as obesity, inflammatory bowel disease, and in HIV infection. Dietary fibres have been shown to improve intestinal barrier function through their fermentation products, short chain fatty acids (SCFAs), and the effects of individual SCFAs have been studied. Here, different SCFA mixtures representing possible compositions from fibre fermentation products were studied for protective and reparative effects on intestinal barrier function. The effect of fermentation products from four dietary fibres, i.e. resistant starch, fructooligosaccharides, and sorghum and corn arabinoxylan (varying in their branched structure) on barrier function was positively correlated with their SCFA concentration. Pure SCFA mixtures of various concentrations and compositions were tested using a Caco-2 cell model. SCFAs at a moderate concentration (40-80 mM) improved barrier function without causing damage to the monolayer. In a 40 mM SCFA mixture, the butyrate proportion at 20% and 50% showed both a protective and a reparative effect on the monolayer to disrupting agents (LPS/TNF-α) applied simultaneously or prior to the SCFA mixtures. Relating this result to dietary fibre selection, slow fermenting fibres that deliver appropriate concentrations of SCFAs to the epithelium with a high proportion of butyrate may improve barrier function.

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Scope The effects of green tea polyphenols, Polyphenon E (PPE), and black tea polyphenols, theaflavins (TFs), on gut microbiota and development of diabetes in db/db mice are investigated and compared. Methods and results Supplementation of PPE (0.1%) in the diet of female db/db mice for 7 weeks decreases fasting blood glucose levels and mesenteric fat while increasing the serum level of insulin, possibly through protection against β‐cell damage. However, TFs are less or not effective. Microbiome analysis through 16S rRNA gene sequencing shows that PPE and TFs treatments significantly alter the bacterial community structure in the cecum and colon, but not in the ileum. The key bacterial phylotypes responding to the treatments are then clustered into 11 co‐abundance groups (CAGs). CAGs 6 and 7, significantly increased by PPE but not by TFs, are negatively associated with blood glucose levels. The operational taxonomic units in these CAGs are from two different phyla, Firmicutes and Bacteroidetes. CAG 10, decreased by PPE and TFs, is positively associated with blood glucose levels. Conclusion Gut microbiota respond to tea polyphenol treatments as CAGs instead of taxa. Some of the CAGs associated with the blood glucose lowering effect are enriched by PPE, but not TFs.

A slow fermentation rate of dietary fiber could result in a steady metabolite production release and even distribution in the entire colon, increasing the likelihood of meeting the energy requirements of the distal colon. In the present study, we modulated the fermentation rate in an in vitro human fecal fermentation model by applying chemical cross-linking modification to a type 2 resistant starch [i.e., high-amylose maize starch (HAMS)]. Cross-linking modification decreased the gas production (an indicator of the fermentation rate) of HAMS throughout the whole fermentation progress. The butyrate production rate of cross-linked starches decreased gradually with the increase of the cross-linking degree. Certain beneficial gut microbiota such as genera of Blautia and Clostridiales members were remarkably promoted by starches with low and medium cross-linking degrees, whereas HAMS with a high cross-linking degree obviously promoted the abundance of Bacteroides uniformis and Ruminococcus bromii. This finding reveals that cross-linking modification effectively controls the fermentation rate and highlights the modulation metabolite profiles and gut microbiota composition through chemical modification.

The physical structure of type 1 resistant starch (RS 1) could influence the metabolite production and stimulate the growth of specific bacteria in the human colon. In the present study, we isolated intact cotyledon cells from pinto bean seeds as whole pulse food and RS 1 model and obtained a series of cell wall integrities through controlled enzymolysis. In vitro human fecal fermentation performance and microbiota responses were tested, and we reported that the cell wall integrity controls the in vitro fecal fermentation rate of heat-treated pinto bean cells. The concentration of butyrate produced by pinto bean cell fermentation enhanced with weakened cell wall integrity, and certain beneficial bacterial groups such as Blautia and Roseburia genera were remarkably promoted by pinto bean cells with damaged cell wall integrity. However, the intact cell sample had a shape more similar to microbiota composition with the purified cell wall polysaccharides, rather than the damaged cells.

Scope: Resistant starch (RS) is utilized by Gram-negative Bacteroidetes through a starch utilization system (Sus), which requires physical attachment of the bacteria to the substrate. Gram-positive Firmicutes, which include butyrate producers, utilize RS by other mechanisms, such as amylosomes and secreted amylases/glucoamylases. It has been previously shown that fabricated RS [alginate-based starch-entrapped microspheres (SM)] increases butyrate in in vitro human fecal fermentation and was slow fermenting. It has been hypothesized that in vivo SM would disfavor Bacteroidetes and promote Firmicutes, leading to an increase in butyrate production. Methods and results: A C57BL/6J mouse model is used to test type 2 RS (RS2, raw potato) and SM for SCFAs and fecal microbial community structure. Feeding SM for 2 weeks results in 2.4 times higher mol% butyrate in the mouse distal gut than RS2. SM reduces relative abundance of Bacteroidetes and increases Firmicutes in fecal samples at the end of the 2-week feeding. This phylum-level taxonomic shift is not observed in animals fed RS2. Conclusion: Through an approach to understand bacterial requirements related to starch utilization, a designed fiber type favors butyrogenic Firmicutes bacteria and provides higher mol% butyrate in the distal gut with potential benefit as an anti-inflammatory agent and to improve gut barrier function.

A pro-inflammatory intestinal microbiome is characteristic of Parkinson’s disease (PD). Prebiotic fibers change the microbiome and this study sought to understand the utility of prebiotic fibers for use in PD patients. The first experiments demonstrate that fermentation of PD patient stool with prebiotic fibers increased the production of beneficial metabolites (short chain fatty acids, SCFA) and changed the microbiota demonstrating the capacity of PD microbiota to respond favorably to prebiotics. Subsequently, an open-label, non-randomized study was conducted in newly diagnosed, non-medicated (n = 10) and treated PD participants (n = 10) wherein the impact of 10 days of prebiotic intervention was evaluated. Outcomes demonstrate that the prebiotic intervention was well tolerated (primary outcome) and safe (secondary outcome) in PD participants and was associated with beneficial biological changes in the microbiota, SCFA, inflammation, and neurofilament light chain. Exploratory analyses indicate effects on clinically relevant outcomes. This proof-of-concept study offers the scientific rationale for placebo-controlled trials using prebiotic fibers in PD patients. ClinicalTrials.gov Identifier: NCT04512599.

Rice bran is a major byproduct of the milling industry. Rice bran-derived arabinoxylan (RAX) is available in large amounts and is structurally different from other cereal arabinoxylans. The anti-obesity effect...