Fructo-oligosaccharide-Induced Transient Increases in Cecal Immunoglobulin A Concentrations in Rats Are Associated with Mucosal Inflammation in Response to Increased Gut Permeability

Extraction, physicochemical properties, bioactivities and application of natural sweeteners: A review

Natural sweeteners generally refer to a sweet chemical component directly extracted from nature or obtained through appropriate modifications, mainly secondary metabolites of plants. Compared to the first-generation sweeteners represented by sucrose and the second-generation sweeteners represented by sodium cyclamate, natural sweeteners usually have high sweetness, low-calorie content, good solubility, high stability, and rarely toxic side effects. Historically, researchers mainly focus on the function of natural sweeteners as substitutes for sugars in the food industry. This paper reviews the bioactivities of several typical natural sweeteners, including anti-cancer, anti-inflammatory, antioxidant, anti-bacterial, and anti-hyperglycemic activities. In addition, we have summarized the extraction, physicochemical properties, and application of natural sweeteners. The article aimed to comprehensively collate vital information about natural sweeteners and review the potentiality of tapping bioactive compounds from natural products. Hopefully, this review provides insights into the further development of natural sweeteners as therapeutic agents and functional foods.

Intervention with fructooligosaccharides, Saccharomyces boulardii, and their combination in a colitis mouse model

Objective

To examine the effects of an intervention with fructooligosaccharides (FOS), Saccharomyces boulardii, and their combination in a mouse model of colitis and to explore the mechanisms underlying these effects.

Methods

The effects of FOS, S. boulardii, and their combination were evaluated in a DSS-induced mouse model of colitis. To this end, parameters such as body weight, the disease activity index (DAI), and colon length were examined in model mice. Subsequently, ELISA was employed to detect the serum levels of proinflammatory cytokines. Histopathological analysis was performed to estimate the progression of inflammation in the colon. Gas chromatography was used to determine the content of short-chain fatty acids (SCFAs) in the feces of model mice. Finally, 16S rRNA sequencing technology was used to analyze the gut microbiota composition.

Results

FOS was slight effective in treating colitis and colitis-induced intestinal dysbiosis in mice. Meanwhile, S. boulardii could significantly reduced the DAI, inhibited the production of IL-1β, and prevented colon shortening. Nevertheless, S. boulardii treatment alone failed to effectively regulate the gut microbiota. In contrast, the combined administration of FOS/S. boulardii resulted in better anti-inflammatory effects and enabled microbiota regulation. The FOS/S. boulardii combination (109 CFU/ml and 107 CFU/ml) significantly reduced the DAI, inhibited colitis, lowered IL-1β and TNF-α production, and significantly improved the levels of butyric acid and isobutyric acid. However, FOS/S. boulardii 109 CFU/ml exerted stronger anti-inflammatory effects, inhibited IL-6 production and attenuated colon shortening. Meanwhile, FOS/S. boulardii 107 CFU/ml improved microbial regulation and alleviated the colitis-induced decrease in microbial diversity. The combination of FOS and S. boulardii significantly increased the abundance of Parabacteroides and decreased the abundance of Escherichia-Shigella. Additionally, it promoted the production of acetic acid and propionic acid.

Conclusion

Compared with single administration, the combination can significantly increase the abundance of beneficial bacteria such as lactobacilli and Bifidobacteria and effectively regulate the gut microbiota composition. These results provide a scientific rationale for the prevention and treatment of colitis using a FOS/S. boulardii combination. They also offer a theoretical basis for the development of nutraceutical preparations containing FOS and S. boulardii.

Fructose dose-dependently influences colon barrier function by regulation of some main physical, immune, and biological factors in rats

Little is known about the effects of fructose on colonic function. Here, forty-eight 7-week-old male SD rats were randomly divided into four groups and given 0, 7.5%, 12.75%, and 35% fructose in diet for 8 weeks respectively to investigate the regulatory influence of fructose on colonic barrier function. The exact amount of fructose intake was tracked and recorded. We showed that fructose affects colonic barrier function in a dose-dependent manner. High-fructose at a dose of 1.69±0.23 g/kg/day could damage the physical barrier function of the colon by down-regulating expression of tight junction proteins (ZO-1 and occludin) and mucus layer biomarkers (MUC2 and TFF3). High fructose reduced sIgA and the anti-inflammatory cytokine (IL-10), induced abdominal fat accumulation and pro-inflammatory cytokines (IL-6 and IL-8), leading to colon inflammation and immune barrier dysfunction. In addition, high-fructose altered the biological barrier of the colon by decreasing the abundance of Blautia, Ruminococcus, and Lactobacillius, and increasing the abundance of Allobaculum at the genus level, leading to a reduction in short-chain fatty acids (SCFAs), amino acids, and carbohydrates, etc. Low fructose at a dose of 0.31±0.05 g/kg/day showed no adverse effects on the colonic barrier. The ability of fructose to affect the colonic barrier through physical, immune, and biological pathways provides additional insight into the intestinal disorders caused by high-fructose diets.

The effect of lentinan on dexamethasone-induced immunosuppression in mice

The immune system acts as a vital defense barrier against pathogenic invasions, and its stable operation is crucial for maintaining body health. Nevertheless, various natural or artificial factors can compromise the body's immune function, leading to immunosuppression, which may interfere with the efficacy of vaccination and increase the susceptibility of the body to disease-causing pathogens. In an effort to ensure successful vaccinations and improve overall physical well-being, the search for appropriate immune regulators to enhance immunity is of paramount importance. Lentinan (LNT) has a significant role in immune regulation and vaccine adjuvants. In the present study, we constructed an immunosuppressive model using dexamethasone (DEX) and demonstrated that LNT could significantly improved antibody levels in immunosuppressive mice and stimulated T-lymphocyte proliferation and differentiation in intestinal Peyer's patches. LNT also increased the production of secretory immunoglobulin A (sIgA) in the duodenal fluid, the number of goblet cells, and the proportion of mucin area. Moreover, LNT modulated the intestinal microbiota and increased the production of short-chain fatty acids. Additionally, LNT promoted the proliferation, differentiation, and pro-inflammatory cytokines production of DEX-treated splenic T lymphocytes in vitro. Thus, the present study highlights the potential of LNT in reversing immunosuppression and avoiding the failure of vaccination.

Influences of wheat bran fiber on growth performance, nutrient digestibility, and intestinal epithelium functions in Xiangcun pigs

Dietary fiber (DF) has long been looked as an essential "nutrients" both for animals and humans as it can promote the intestinal tract development and modulate the intestinal epithelium functions and the gut microbiota. This study was conducted to investigate the influences of wheat bran fiber (WBF) on growth performance and intestinal epithelium functions in Xiangcun pigs. Twenty Xiangcun pigs with 60 days of age were divided to two groups and exposed to a basal diet (BD) or BD containing 4.3% wheat bran fiber (WFD). WFD improved the average daily gain (ADG) and feed-to-gain ratio (F:G) (p < 0.01). Moreover, WFD lowered the serum triglyceride (TC), d-lactate, and malonicdialdehyde (MDA) concentrations, but significantly improved the glutathione (GSH) activity and total antioxidant capacity (T-AOC) (p < 0.05). Interestingly, WFD observably improved the villus height (VH) and the villus height to crypt depth ratio (V/C) in the small intestine (p < 0.05). The jejunal sucrase and ileal maltase activities were higher in the WFD group (p < 0.05). WFD markedly elevated the tight junction protein ZO-1 and claudin-1 expression levels in the jejunum and ileum (p < 0.05). The sodium/glucose co-transporter 1 (SGLT1), glucose transporter 2 (GLUT2), and fatty acid transport proteins 4 (FATP-4) expression levels in jejunum and ileum were also elevated under WFD (p < 0.05). WFD decreased the IL-6 impression level in the duodenum and ileum, but significantly increased the IL-10 expression levels in jejunum and ileum (p < 0.05). Moreover, WFD reduced the abundance of E. coli, but elevated the abundances of beneficial microorganisms (e.g. Lactobacillus and Bacillus) and the production microbial metabolites (e.g. propionic acid and butyrate acid) in the cecum (p < 0.05).

Increased fermentable carbohydrate intake alters colonic mucus barrier function through glycation processes and increased mast cell counts

Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder for which dietary interventions can be a useful treatment. In recent years, the low-FODMAP approach is gaining traction in this regard. The fermentation of these non-absorbed carbohydrates by the gut microbiota can generate toxic glycating metabolites, such as methylglyoxal. These metabolites can have harmful effects by their role in the generation of advanced glycation end products (AGEs), which activates Receptor for AGEs (AGER). Mast cells can be stimulated by AGEs and play a role in IBS. We have treated mice with lactose or fructo-oligosaccharides (FOS), with or without co-administration of pyridoxamine and investigated the colonic mucus barrier. We have found that an increased intake of lactose and fructo-oligosaccharides induces a dysregulation of the colonic mucus barrier, increasing mucus discharge in empty colon, while increasing variability and decreasing average thickness mucus layer covering the fecal pellet. Changes were correlated with increased mast cell counts, pointing to a role for the crosstalk between these and goblet cells. Additionally, AGE levels in colonic epithelium were increased by treatment with the selected fermentable carbohydrates. Observed effects were prevented by co-treatment with anti-glycation agent pyridoxamine, implicating glycation processes in the negative impact of fermentable carbohydrate ingestion. This study shows that excessive intake of fermentable carbohydrates can cause colonic mucus barrier dysregulation in mice, by a process that involves glycating agents and increased mucosal mast cell counts.

Intestinal Barrier and Permeability in Health, Obesity and NAFLD

The largest surface of the human body exposed to the external environment is the gut. At this level, the intestinal barrier includes luminal microbes, the mucin layer, gastrointestinal motility and secretion, enterocytes, immune cells, gut vascular barrier, and liver barrier. A healthy intestinal barrier is characterized by the selective permeability of nutrients, metabolites, water, and bacterial products, and processes are governed by cellular, neural, immune, and hormonal factors. Disrupted gut permeability (leaky gut syndrome) can represent a predisposing or aggravating condition in obesity and the metabolically associated liver steatosis (nonalcoholic fatty liver disease, NAFLD). In what follows, we describe the morphological-functional features of the intestinal barrier, the role of major modifiers of the intestinal barrier, and discuss the recent evidence pointing to the key role of intestinal permeability in obesity/NAFLD.

Fructooligosaccharides on inflammation, immunomodulation, oxidative stress, and gut immune response: a systematic review

CONTEXT

Evidence shows that fructooligosaccharides (FOSs) can modulate inflammatory, oxidative, and immune activity in the gut, possibly leading to a systemic response, improving human health.

OBJECTIVE

To assess the present knowledge of the effects of FOSs on inflammation, immunomodulation, oxidative stress, and gut immune response.

DATA SOURCES

Studies published between December 2000 and January 2020 were systematically searched in four databases: MEDLINE, LILACS, Web of Science, and Scopus. After the screening of 1316 articles, 8 human studies and 20 animal models were included.

DATA EXTRACTION

Data were extracted separately by 2 reviewers. For each study, the design, population, exposures, main results, and conclusion were extracted. The research questions and the risk-of-bias information were also extracted. Additionally, the risk-of-bias were analyzed to guarantee the reliability of this review.

DATA ANALYSIS

A qualitative analysis revealed that FOSs can increase bifidobacteria counts and short-chain fatty acids in the gut, stimulate IgA secretion in the colon, and decrease proinflammatory cytokines, thus influencing metabolic diseases.

CONCLUSION

Studies suggest that FOS supplementation is positively associated with an anti-inflammatory and antioxidant effect, thus enhancing the gut immune system, which may be beneficial for the host's health.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration nos 42020209865 and 42020220369.

Dietary xylo-oligosaccharide ameliorates colonic mucus microbiota penetration with restored autophagy in interleukin-10 gene-deficient mice

BACKGROUND

Inflammatory bowel disease (IBD) is, nowadays, highly prevalent and presents a global clinical challenge. The objective of this study is to assess the effects of xylo-oligosaccharide (XOS) on Il10^-/- mice, a classic animal model of IBD.

METHODS

Male wild-type (WT) mice were assigned to WT group, and Il10^-/- mice were assigned to interleukin-10 gene-deficient (IL-10-KO) group and XOS group, respectively. There were 6-8 mice aged 8 weeks in each group. Mice in the XOS group received 1.0 g/kg/day XOS by gavage for 4 weeks.

RESULTS

Compared with mice in IL-10-KO group, Il10^-/- mice with XOS intervention presented significant mild spontaneous colitis with lower disease activity index, histological scores, and bowel inflammatory cytokine levels. Dietary XOS downregulated bowel mucus bacterial penetration, which occurred as early as the onset of bowel colitis. The effect of XOS was associated with restored expression of LC3II/I and decreased expression of p62 and beclin-1 in colon.

CONCLUSIONS

Therefore, XOS decreases colonic mucus microbiota penetration with restored function of antophagy. Our findings suggest that XOS may be a potential dietary supplement or functional food for early management of IBD.

Leaky Gut: Effect of Dietary Fiber and Fats on Microbiome and Intestinal Barrier

Intestinal tract is the boundary that prevents harmful molecules from invading into the mucosal tissue, followed by systemic circulation. Intestinal permeability is an index for intestinal barrier integrity. Intestinal permeability has been shown to increase in various diseases-not only intestinal inflammatory diseases, but also systemic diseases, including diabetes, chronic kidney dysfunction, cancer, and cardiovascular diseases. Chronic increase of intestinal permeability is termed 'leaky gut' which is observed in the patients and animal models of these diseases. This state often correlates with the disease state. In addition, recent studies have revealed that gut microbiota affects intestinal and systemic heath conditions via their metabolite, especially short-chain fatty acids and lipopolysaccharides, which can trigger leaky gut. The etiology of leaky gut is still unknown; however, recent studies have uncovered exogenous factors that can modulate intestinal permeability. Nutrients are closely related to intestinal health and permeability that are actively investigated as a hot topic of scientific research. Here, we will review the effect of nutrients on intestinal permeability and microbiome for a better understanding of leaky gut and a possible mechanism of increase in intestinal permeability.

Fructooligosaccharides protect against OVA-induced food allergy in mice by regulating the Th17/Treg cell balance using tryptophan metabolites

Fructooligosaccharides (FOS) can change gut microbiota composition and play a protective role in food allergy (FA).

Mucin-Derived O-Glycans Act as Endogenous Fiber and Sustain Mucosal Immune Homeostasis via Short-Chain Fatty Acid Production in Rat Cecum

BACKGROUND

Intestinal mucins escape digestion and enter the large bowel where they are degraded by the microbiota. To what extent and how mucins impact large-bowel physiology remain unclear.

OBJECTIVE

This study examined the large-bowel fermentation characteristics of mucins and mucin-derived O-glycan sugars and whether they affect gut immunity.

METHODS

Mucin secretion from the terminal ileum was determined from feces of ileorectostomized male Wistar rats (age 6 wk) fed an AIN76-based control diet (CD) for 15 d (experiment 1). Normal male Wistar rats (age 6 wk; 4 wk for experiment 4) were fed CD ± porcine stomach mucin (PM) at 6 or 12 g/kg diet, equivalent to 1.5 and 3 times the daily mucin secretion, for 14 d (experiment 2); CD ± N-acetylglucosamine (GlcNAc), fucose, or N-acetylneuraminic acid at 10 g/kg diet for 14 d (experiment 3); or CD ± PM (15 g/kg diet) or GlcNAc (10 g/kg diet) for 29 d (experiment 4). SCFAs, microbial composition, and cecal O-glycan content were assessed. IgA+ plasma cells and regulatory T cells and inflammatory cytokine expression in the cecum were evaluated (experiment 4).

RESULTS

Daily mucin secretion corresponded to 43.2 μmol of O-glycans. Cecal O-glycan contents were comparable between CD- and PM-fed rats. PM-fed rats harbored more mucin-degrading bacteria. Cecal concentrations of acetate (+37%) and n-butyrate (+73%) were higher in 12-g/kg PM diet-fed rats versus CD (P < 0.05). Among O-glycan sugars, only GlcNAc produced higher n-butyrate concentrations (+68%) versus CD (P < 0.05), with increased numbers of butyrate-producing bacteria. GlcNAc increased the abundance of IgA+ plasma cells (+29%) and regulatory T cells (+33%) versus CD, whereas PM increased IgA+ plasma cells (+25%) (all P < 0.05). GlcNAc and PM decreased expression of Tnfa (-30%, -40%) and Ifng (-30%, -70%) versus CD (all P < 0.05).

CONCLUSIONS

Mucin-derived O-glycans act as endogenous fiber and maintain mucosal immune homeostasis via large-bowel SCFA production in rats.

Faster Short-Chain Fatty Acid Absorption from the Cecum Following Polydextrose Ingestion Increases the Salivary Immunoglobulin A Flow Rate in Rats

Salivary immunoglobulin A (IgA) plays a vital role in preventing upper respiratory tract infections (URTI). In our previous study, we showed that the intake of carbohydrates increases the intestinal levels of short-chain fatty acids (SCFAs), which in turn increase salivary IgA levels. However, the mechanism underlying this phenomenon has not been fully elucidated. In this study, we investigated in rats the effect of polydextrose (PDX) ingestion on salivary IgA level and SCFA concentration in cecal digesta and the portal vein. Five-week-old rats were fed with a fiber-free diet (control) or with 40 g/kg of PDX for 28 days. Compared to the control, ingestion of PDX led to a higher salivary IgA flow rate (p = 0.0013) and a higher concentration of SCFAs in the portal vein (p = 0.004). These two data were positively correlated (r_s = 0.88, p = 0.0002, n = 12). In contrast, the concentration of SCFAs in cecal digesta and cecal digesta viscosity were significantly lower following PDX ingestion, compared to the control (p = 0.008 and 0.05, respectively). These findings suggest that the ingestion of PDX increases the absorption rate of SCFAs in the intestine through PDX-induced fermentation, which is accompanied by an increase in SCFA levels in the blood, and ultimately leads to increased salivary IgA levels.

Effects of inulin supplementation on intestinal barrier function and immunity in specific pathogen-free chickens with Salmonella infection

We investigated the effects of inulin on intestinal barrier function and mucosal immunity in Salmonella enterica serovar Enteritidis (SE)-infected specific pathogen-free (SPF) chickens. SPF chickens (n = 240, 1-d-old) were divided into 4 groups (6 replicates per group, 10 chickens per replicate): a control group (CON) fed a basal diet without inulin supplementation and 3 SE-infected groups fed a basal diet supplemented with inulin 0% (SE group), 0.5% (0.5% InSE group), and 1% (1% InSE group), respectively. At 28 d of age, the chickens in SE-infected groups were orally infected with SE and in CON group were administrated with phosphated-buffered saline (PBS). Intestinal morphology, mucosal immunity, and intestinal barrier function-related gene expression were analyzed at 1- and 3-d post-infection (dpi). SE challenge significantly increased the mucosal gene expression, such as interleukin-1β (IL-1β), lipopolysaccharide-induced tumor necrosis factor factor (LITAF), interferon-γ (IFN-γ), and interleukin-6 (IL-6), and increased serum IFN-γ, secretory IgA (sIgA), and IgG concentration, and significantly decreased the gene expression levels of mucin 2 (MUC2) and claudin-1 at 3 dpi compared with the CON group (P < 0.05). Inulin supplementation improved the expression levels of these immunity- and intestinal barrier function-related genes, increased villus height (VH), and decreased crypt depth (CD) in the duodenum, jejunum, and ileum at 1 and 3 dpi within the SE-challenged groups (P < 0.05). SE challenge significantly increased ileal Toll-like receptor 4 (TLR4) mRNA at 1 and 3 dpi, suppressor of cytokine signaling 3 (SOCS3) mRNA at 1 dpi, and phospho-signal transducer and activator of transcription 3 (p-STAT3) and Janus kinase1 (JAK1) protein expression at 3 dpi compared with the CON group (P < 0.05). Inulin supplementation suppressed p-STAT3 and JAK1 protein expression and promoted ileal TLR4 and SOCS3 mRNA expression at 3 dpi compared with SE group (P < 0.05). In conclusion, inulin alleviated SE-induced gut injury by decreasing the proinflammatory response and enhancing mucosal immunity in chickens.

Suppressive effect of dietary resistant maltodextrin on systemic immunity in a mouse model of food allergy

Resistant maltodextrin (RMD) is a soluble dietary fibre that exerts several physiological functions as a result of its microbial degradation and changes in the intestinal environment. It has been reported that RMD enhanced immunoglobulin A (IgA) secretion, which protects the mucosa from foreign substances. However, the effect of RMD on excessive immunity has yet to be investigated. In this study, we aimed to investigate the effect of RMD on excessive immune responses such as food allergy. OVA23-3 mice were fed an AIN-76-based diet containing 20% egg-white protein with or without RMD. While RMD was shown to contribute to an increase in goblet cells, RMD did not change the overall inflammatory status when ingested with the egg-white diet. RMD suppressed IL-4 and IL-10 production from splenocytes but not cells from mesenteric lymph nodes. RMD also downregulated the serum levels of OVA-specific Th1- and Th2-related antibodies, which were elevated in the food-allergic condition. RMD significantly increased the total amount of short-chain fatty acids, especially acetate and propionate, in the caecum of OVA23-3 mice fed the egg-white diet. Our study demonstrated that dietary RMD modulates systemic rather than intestinal antigen-specific immune responses in the food-allergic condition of OVA23-3 mice. Although the relevant mechanism has yet to be investigated, RMD shows potential for alleviating food allergy through adjustment of systemic immunity.

The Impact of Fructo-Oligosaccharides on Gut Permeability and Inflammatory Responses in the Cecal Mucosa Quite Differs between Rats Fed Semi-Purified and Non-Purified Diets

The effects of fructo-oligosaccharides (FOS) on gut-barrier function are still controversial in human and animal studies. Diet conditions would be a major factor for the controversy in animal studies. We fed rats a semi-purified (SP) or a non-purified diet (NP) with or without FOS (60 g/kg diet) for 9 (experiment 1) or 10 d (experiment 2). We assessed microbial fermentation, gut permeability, and inflammatory responses in the cecum (experiment 1), and mucus layer in the cecum, intestinal transit time and microbiota composition (experiment 2). FOS supplementation induced a very acidic fermentation due to the accumulation of lactate and succinate in SP, while short-chain fatty acids were major products in NP. Gut permeability estimated by urinary chromium-EDTA excretion, bacterial translocation into mesenteric lymph nodes, myeloperoxidase activity, and expressions of the inflammatory cytokine genes in the cecal mucosa were greater in SP+FOS than in SP, but these alterations were not observed between NP and NP+FOS (experiment 1). FOS supplementation destroyed the mucus layer on the epithelial surface in SP, but not in NP. Intestinal transit time was 3-fold longer in SP+FOS than in SP, but this was not the case between NP and NP+FOS. Lower species richness of cecal microbiota was manifest solely in SP+FOS (experiment 2). These factors suggest that impact of FOS on gut permeability and inflammatory responses in the cecal mucosa quite differs between SP and NP. Increased gut permeability in SP+FOS could be evoked by the disruption of the mucus layer due to stasis of the very acidic luminal contents.

Bacterial Fermentation of Water-Soluble Cellulose Acetate Raises Large-Bowel Acetate and Propionate and Decreases Plasma Cholesterol Concentrations in Rats

We hypothesized that water-soluble cellulose acetate (WSCA) could be useful tool for the delivery of short-chain fatty acids to the large intestine. Rats were fed a control diet or a diet containing graded levels of WSCA for up to 21 days. Consuming WSCA dose-dependently increased large-bowel acetate and propionate concentrations through the bacterial fermentation. When WSCA was used as substrate, acetyl esterase activity in the cecal bacteria was detected solely in rats fed WSCA, in which the activity increased over time accompanied by an increased number of Bacteroides xylanisolvens. Consuming WSCA at a 4% level increased the goblet cell numbers and mucin contents in the cecum and lowered plasma cholesterol concentrations, which tended to correlate with the portal plasma concentrations of propionate. The results suggest that bacterial fermentation of WSCA is characterized by the greater production of acetate and propionate, which may contribute to the physiologic alterations.