Prebiotic Dietary Fiber and Gut Health: Comparing the in Vitro Fermentations of Beta-Glucan, Inulin and Xylooligosaccharide.
ABSTRACT: Prebiotic dietary fiber supplements are commonly consumed to help meet fiber recommendations and improve gastrointestinal health by stimulating beneficial bacteria and the production of short-chain fatty acids (SCFAs), molecules beneficial to host health. The objective of this research project was to compare potential prebiotic effects and fermentability of five commonly consumed fibers using an in vitro fermentation system measuring changes in fecal microbiota, total gas production and formation of common SCFAs. Fecal donations were collected from three healthy volunteers. Materials analyzed included: pure beta-glucan, Oatwell (commercially available oat-bran containing 22% oat ?-glucan), xylooligosaccharides (XOS), WholeFiber (dried chicory root containing inulin, pectin, and hemi/celluloses), and pure inulin. Oatwell had the highest production of propionate at 12 h (4.76 ?mol/mL) compared to inulin, WholeFiber and XOS samples (p < 0.03). Oatwell's effect was similar to those of the pure beta-glucan samples, both samples promoted the highest mean propionate production at 24 h. XOS resulted in a significant increase in the genus Bifidobacterium after 24 h of fermentation (0 h:0.67 OTUs (operational taxonomic unit); 24 h:5.22 OTUs; p = 0.038). Inulin and WholeFiber increased the beneficial genus Collinsella, consistent with findings in clinical studies. All analyzed compounds were fermentable and promoted the formation of beneficial SCFAs.
Project description:Recently, the concept of prebiotics has been revisited to expand beyond non-digestible oligosaccharides, and the requirements for selective stimulation were extended to include microbial groups other than, and additional to, bifidobacteria and lactobacilli. Here, the gut microbiota-modulating effects of well-known and novel prebiotics were studied. An <i>in vitro</i> fermentation screening platform (i-screen) was inoculated with adult fecal microbiota, exposed to different dietary fibers that had a range of concentrations (inulin, alpha-linked galacto-oligosaccharides (alpha-GOS), beta-linked GOS, xylo-oligosaccharides (XOS) from corn cobs and high-fiber sugar cane, and beta-glucan from oats), and compared to a positive fructo-oligosaccharide (FOS) control and a negative control (no fiber addition). All dietary fibers displayed prebiotic activity, with beta-glucan showing more distinct effects on the microbial composition and metabolism compared to the other fibers. Beta-glucan induced the growth of <i>Prevotella</i> and <i>Roseburia</i> with a concomitant increase in propionate production. Inulin and both forms of GOS and XOS had a strong bifidogenic effect on the microbial composition. A dose-response effect was observed for butyrate when exposed to beta-glucan and inulin. The findings of this study support the potential for alpha-GOS, XOS, and oat beta-glucan to serve as novel prebiotics, due to their association with the positive shifts in microbiome composition and short-chain fatty acid production that point to potential health benefits.
Project description:The beneficial effects of prebiotic fibres on human health have been related to their capacities to alter the gut microbiota and modify the growth of beneficial microorganisms. It is long appreciated that bacterial metabolites affect the host's physiology. The inner lining of the intestinal tract is the first level of interaction between the host and bacteria and their metabolites. Therefore, we set out to test the effects of five common dietary fibres (oat ?-glucan 28%; oat ?-glucan 94%; dried chicory root containing inulin 75%; xylo-oligosaccharide; inulin 90%) and maltodextrin, after fermentation by human gut microbiota in vitro, on measures of gut barrier integrity using a Caco-2/HT29-MTX co-culture as well as mucus production and immune parameters using HT29-MTX and HT29 cell models, respectively. Our data show that all fibres, fermentation products increased the tightness of the gut barrier with oat ?-glucan 28% having the largest effect. Fermentation supernatants were tested also in models of the compromised gut barrier (leaky gut). After the addition of ethanol as basolateral stressor, only fermentation supernatant of oat ?-glucan 28%, oat ?-glucan 94% and maltodextrin improved the gut barrier integrity, while oat ?-glucan 28% and dried chicory root containing inulin 75% significantly improved the gut barrier integrity after addition of rhamnolipids as apical stressor. Using the Luminex Technology, we demonstrated an important role of oat ?-glucan fermentation products in modulating cytokine and chemokine productions. Furthermore, treating the goblet cells with effluent from xylo-oligosaccharide fermentation significantly increased mucus production. In summary, our data emphasize the potential positive effects of fermentation supernatant of dietary fibres on gut-related physiological outcomes and show that prebiotic fibres may have promising potential to induce specific gut health benefits.
Project description:Consumption of fermentable dietary fibers (DFs), which can induce growth and/or activity of specific beneficial populations, is suggested a promising strategy to modulate the gut microbiota and restore health in microbiota-linked diseases. Until today, inulin and fructo-oligosaccharides (FOS) are the best studied DFs, while little is known about the gut microbiota-modulating effects of ?-glucan, ?-galactooligosaccharide (?-GOS) and xylo-oligosaccharide (XOS). Here, we used three continuous in vitro fermentation PolyFermS model to study the modulating effect of these DFs on two distinct human adult proximal colon microbiota, independently from the host. Supplementation of DFs, equivalent to a 9?g daily intake, induced a consistent metabolic response depending on the donor microbiota. Irrespective to the DF supplemented, the Bacteroidaceae-Ruminococcaceae dominated microbiota produced more butyrate (up to 96%), while the Prevotellaceae-Ruminococcaceae dominated microbiota produced more propionate (up to 40%). Changes in abundance of specific bacterial taxa upon DF supplementation explained the observed changes in short-chain fatty acid profiles. Our data suggest that the metabolic profile of SCFA profile may be the most suitable and robust read-out to characterize microbiota-modulating effects of a DF and highlights importance to understand the inter-individual response to a prebiotic treatment for mechanistic understanding and human application.
Project description:The prebiotic activity of a commercially available oat product and a novel oat ingredient, at similar ?-glucan loads, was tested using a validated in vitro gut model (M-SHIME<sup>®</sup>). The novel oat ingredient was tested further at lower ?-glucan loads in vitro, while the commercially available oat product was assessed in a randomised, single-blind, placebo-controlled, and cross-over human study. Both approaches focused on healthy individuals with mild hypercholesterolemia. In vitro analysis revealed that both oat products strongly stimulated <i>Lactobacillaceae</i> and <i>Bifidobacteriaceae</i> in the intestinal lumen and the simulated mucus layer, and corresponded with enhanced levels of acetate and lactate with cross-feeding interactions leading to an associated increase in propionate and butyrate production. The in vitro prebiotic activity of the novel oat ingredient remained at lower ?-glucan levels, indicating the prebiotic potential of the novel oat product. Finally, the stimulation of <i>Lactobacillus</i> spp. was confirmed during the in vivo trial, where lactobacilli abundance significantly increased in the overall population at the end of the intervention period with the commercially available oat product relative to the control product, indicating the power of in vitro gut models in predicting in vivo response of the microbial community to dietary modulation.
Project description:Alterations of gut microbiota are evident during the aging process. Prebiotics may restore the gut microbial balance, with ?-glucans emerging as prebiotic candidates. This study aimed to investigate the impact of edible mushrooms rich in ?-glucans on the gut microbiota composition and metabolites by using in vitro static batch culture fermentations and fecal inocula from elderly donors (n = 8). Pleurotus ostreatus, P. eryngii, Hericium erinaceus and Cyclocybe cylindracea mushrooms derived from various substrates were examined. Gut microbiota composition (quantitative PCR (qPCR)) and short-chain fatty acids (SCFAs; gas chromatography (GC)) were determined during the 24-h fermentation. P. eryngii induced a strong lactogenic effect, while P. ostreatus and C. cylindracea induced a significant bifidogenic effect (p for all <0.05). Furthermore, P. eryngii produced on wheat straw and the prebiotic inulin had comparable Prebiotic Indexes, while P. eryngii produced on wheat straw/grape marc significantly increased the levels of tested butyrate producers. P. ostreatus, P. eryngii and C. cylindracea had similar trends in SCFA profile; H. erinaceus mushrooms were more diverse, especially in the production of propionate, butyrate and branched SCFAs. In conclusion, mushrooms rich in ?-glucans may exert beneficial in vitro effects in gut microbiota and/or SCFAs production in elderly subjects.
Project description:The aim of this study was to investigate the effects of the high level of xylooligosaccharides (XOS) on growth performance, antioxidant capability, immune function, and fecal microbiota in weaning piglets. The results showed that 28 d body weight exhibited linear and quadratic increases (<i>P</i> < 0.05) with increasing dietary XOS level, as well as average daily feed intake (ADFI) on d 15-28, average daily gain (ADG) on d 15-28 and 1-28. There was a linear decrease (<i>P</i> < 0.05) between XOS levels and feed conversion rate (FCR) on d 1-14 and 1-28. Additionally, glutathione peroxidase (GSH-Px) showed a linear increase (<i>P</i> < 0.05), while the malondialdehyde (MDA) level decreased linearly and quadratically (<i>P</i> < 0.05) with the increasing dietary level of XOS. Moreover, the XOS treatments markedly increased the levels of immunoglobulin A (Ig A) (linear, <i>P</i> < 0.05; quadratic, <i>P</i> < 0.05), IgM (quadratic, <i>P</i> < 0.05), IgG (linear, <i>P</i> < 0.05), and anti-inflammatory cytokine interleukin-10 (IL-10) (quadratic, <i>P</i> < 0.05) in serum, while the IL-1β (linear, <i>P</i> < 0.05; quadratic, <i>P</i> < 0.05) and IL-6 (linear, <i>P</i> < 0.05) decreased with increasing level of XOS. Microbiota analysis showed that dietary supplementation with 1.5% XOS decreased (<i>P</i> < 0.05) the α-diversity and enriched (<i>P</i> < 0.05) beneficial bacteria including <i>Lactobacillu</i>s, <i>Bifidobacterium</i>, and <i>Fusicatenibacter</i> at the genus level, compared with the control group. Importantly, linearly increasing responses (<i>P</i> < 0.05) to fecal acetate, propionate, butyrate, and total short-chain fatty acids (SCFAs) were observed with increasing level of XOS. Spearman correlation analyses found that <i>Lactobacillu</i>s abundance was positively correlated with ADG, acetate, propionate, and IgA (<i>P</i> < 0.05), but negatively correlated with IL-1β (<i>P</i> < 0.05). <i>Bifidobacterium</i> abundance was positively related with ADFI, total SCFAs, IgG, and IL-10 (<i>P</i> < 0.05), as well as <i>g</i>_<i>Fusicatenibacter</i> abundance with ADFI, total SCFAs, and IL-10. However, <i>Bifidobacterium</i> and <i>Fusicatenibacter</i> abundances were negatively associated with MDA levels (<i>P</i> < 0.05). In summary, dietary supplementation with XOS can improve the growth performance in weaning piglets by increasing antioxidant capability, enhancing immune function, and promoting beneficial bacteria counts.
Project description:The main components of the non-starch polysaccharide (NSP) fraction of wheat flour are arabinoxylan (AX) and ?-glucan. These are also present in other cereal grains, but their proportions vary with AX being the major component in wheat and rye and ?-glucan in barley and oats. Therefore, it was hypothesised that these NSPs could act synergistically when fermented in vitro at the ratios present in the major foods consumed, resulting in increased prebiotic activity. AX and ?-glucan were therefore tested in in vitro fermentation studies to assess their prebiotic activity when used individually and/or in different ratios. Short-chain fatty-acids (SCFAs) produced from in vitro fermentation were measured using HPLC and bacterial populations were measured using flow cytometry with fluorescence in situ hybridisation (Flow-FISH). Fermentation of AX alone resulted in a significant bifidogenic activity and increased concentrations of SCFAs, mainly acetate, after 8-24 h of fermentation, however ?-glucan alone did not show prebiotic activity. The greatest prebiotic activity, based on concentration of total SCFAs and increases in total bacteria as well as beneficial Bifidobacterium and Clostridium coccoides/Eubacterium groups, was observed when AX and ?-glucan were combined at a 3:1 ratio, which corresponds to their ratios in wheat flour which is major source of cereal fibre in the diet. This indicates that the population of bacteria in the human GI tract may be modulated by the composition of the fibre in the diet, to maximise the prebiotic potential.
Project description:Rice husk (RH) is an agricultural waste obtained from rice milling process. Our previous study demonstrated the optimized process of extracting xylooligosaccharides (XOS), a prebiotic that can support the growth and activity of beneficial gut microbiota, from RH. Accumulated evidences indicate that the composition of gut microbiota is involved in the progression of insulin resistance and diabetes. This study aims to evaluate the antihyperglycemic effect and putative mechanisms of RH-XOS using a diabetic rat model induced by high-fat diet and streptozotocin injection. Diabetic rats were randomly assigned to receive vehicle (DMC), XOS (DM-XOS), metformin (DMM), and a combination of XOS and metformin (DMM-XOS). An additional group of rats were fed with normal diet plus vehicle (NDC) and normal diet plus XOS (ND-XOS). Supplementation with RH-XOS for 12 weeks successfully decreased the fasting plasma glucose, insulin, leptin, and LPS levels in DM-XOS compared with DMC. Likewise, the insulin-stimulated glucose uptake assessed by in vitro study was significantly enhanced in DM-XOS, DMM, and DMM-XOS. The diminished protein expressions of GLUT4 and pAktSer473 as well as pAMPKThr172 were significantly modulated in DM-XOS, DMM, and DMM-XOS groups. Interestingly, RH-XOS supplementation reversed the changed gut permeability, elevated the number of beneficial bacteria, both Lactobacillus and Bifidobacterium spp., and increased SCFAs production. Taken together, the results confirm the efficacy of RH-XOS in achieving good glycemic control in diabetes by maintenance of gut microbiota and attenuation of endotoxemia. The findings reveal the benefits of RH-XOS and open an opportunity to improve its value by its development as a nutraceutical for diabetes.
Project description:Effects of xylooligosaccharides (XOSs) as well as a mixture of XOS, inulin, oligofructose, and partially hydrolyzed guar gum (MIX) in mice fed a high-fat diet (HFD) were studied. Control groups were fed an HFD or a low-fat diet. Special attention was paid to the cecal composition of the gut microbiota and formation of short-chain fatty acids, but metabolic parameters were also documented. The XOS group had significantly higher cecum levels of acetic, propionic, and butyric acids than the HFD group, and the butyric acid content was higher in the XOS than in the MIX group. The cecum microbiota of the XOS group contained more <i>Bifidobacteria</i>, <i>Lachnospiraceae,</i> and S24-7 bacteria than the HFD group. A tendency of lower body weight gain was observed on comparing the XOS and HFD groups. In conclusion, the XOS was shown to be a promising prebiotic candidate. The fiber diversity in the MIX diet did not provide any advantages compared to the XOS diet.
Project description:Dietary fibers (DF) can prevent obesity in rodents fed a high-fat diet (HFD). Their mode of action is not fully elucidated, but the gut microbiota have been implicated. This study aimed to identify the effects of seven dietary fibers (barley beta-glucan, apple pectin, inulin, inulin acetate ester, inulin propionate ester, inulin butyrate ester or a combination of inulin propionate ester and inulin butyrate ester) effective in preventing diet-induced obesity and links to differences in cecal bacteria and host gene expression. Mice (n?=?12) were fed either a low-fat diet (LFD), HFD or a HFD supplemented with the DFs, barley beta-glucan, apple pectin, inulin, inulin acetate ester, inulin propionate ester, inulin butyrate ester or a combination of inulin propionate ester and inulin butyrate ester for 8 weeks. Cecal bacteria were determined by Illumina MiSeq sequencing of 16S rRNA gene amplicons. Host responses, body composition, metabolic markers and gene transcription (cecum and liver) were assessed post intervention. HFD mice showed increased adiposity, while all of the DFs prevented weight gain. DF specific differences in cecal bacteria were observed. Results indicate that diverse DFs prevent weight gain on a HFD, despite giving rise to different cecal bacteria profiles. Conversely, common host responses to dietary fiber observed are predicted to be important in improving barrier function and genome stability in the gut, maintaining energy homeostasis and reducing HFD induced inflammatory responses in the liver.