Dietary fibers as immunoregulatory compounds in health and disease

Methyl-esterification, degree of polymerization and ∆4,5-unsaturation of galacturonic acid oligosaccharides as determinants of immunomodulation

In recent years, immunomodulation by pectin and pectin-derived galacturonic acid oligosaccharides has been the subject of wide-spread scientific research due to the potential of different pectin structures as bioactive biomolecules. Yet, gaps remain in understanding the structure-dependent immunomodulation of galacturonic acid. This study describes in vitro immunomodulatory effects of well-characterized galacturonic acid oligosaccharides. Both methyl-esterified and non-methyl-esterified galacturonic acid oligosaccharides with a saturated non-reducing end (degree of polymerization 1-10) significantly induced cytokine production by THP-1 macrophages and directly activated TLR2 and TLR4 in transfected HEK-293 cells, even when accounting for minor endotoxin contamination. In contrast, both methyl-esterified and non-methyl-esterified galacturonic acid oligosaccharides with a Δ4,5-unsaturated non-reducing end (degree of polymerization 1-7) did not activate TLR2 and TLR4 and led to significantly reduced cytokine production (p < 0.05), suggesting Δ4,5-(un)saturation as a pivotal factor for immunomodulation by galacturonic acid oligosaccharides. Exposure to non-methyl-esterified saturated galacturonic acid oligosaccharides resulted in significantly lower TNF-α production, IL-1β production and TLR4 activation (p < 0.05) compared to methyl-esterified saturated galacturonic acid oligosaccharides, while IL-10 production and TLR2 activation remained unchanged. These findings establish galacturonic acid oligosaccharides as versatile immunomodulators with TLR2 and TLR4 binding capacity, fit for different immunomodulatory applications depending on their structural characteristics.

Hematoimmunological responses of juvenile Nile tilapia (Oreochromis niloticus) receiving the dietary supplementation of immunomodulators and different levels of vitamins after challenge with physical stress

In this study, we analyzed the hematoimmunological effects of dietary supplementation with immunomodulators (β-glucans + nucleotides) and different levels of vitamins on Nile tilapia (Oreochromis niloticus) after exposure to physical stress. The following four diet treatments were used: diets with indicated vitamin levels (Vitind), diets with Vitind + immunomodulator (Vitind + Immune), diets with high vitamin content (Vithigh), and those with Vithigh + immunomodulator (Vithigh + Immune). The experiment included 560 fish in 28 tanks (20 fish tank-1), with seven replicates per treatment. After 60 days of supplementation, the water temperature was set at 20 °C, and complete biometrics were performed. The animals were then subjected to physical stress with temperature oscillations of 20 ºC to 30 ºC/30 ºC to 20 ºC/20 ºC to 30 ºC. Hematoimmunological data from 140 animals were collected post-stress. Antimicrobial titer and total plasma protein levels were significantly higher in fish not receiving immunomodulator-supplemented diets (2.88 ± 0.43 log2 and 26.81 ± 4.01 mg∙mL-1, respectively) than in those that did. Conversely, the agglutination titer increased in fish fed with lower vitamin levels (3.33 ± 0.66 log2) compared to those with higher vitamin levels. Increased immunoglobulin levels were observed in fish fed diets co-supplemented with vitamins and immunomodulators, revealing an interaction between immunomodulators and dietary vitamin levels. In summary, the inclusion of immunomodulators in the diet enhanced the animals' resistance to physical stress and improved hematoimmunological parameters. Additionally, a high vitamin content in the diet did not modulate the immune responses in the animals.

Role of dietary fiber in promoting immune health-An EAACI position paper

Microbial metabolism of specific dietary components, such as fiber, contributes to the sophisticated inter-kingdom dialogue in the gut that maintains a stable environment with important beneficial physiological, metabolic, and immunological effects on the host. Historical changes in fiber intake may be contributing to the increase of allergic and hypersensitivity disorders as fiber-derived metabolites are evolutionarily hardwired into the molecular circuitry governing immune cell decision-making processes. In this review, we highlight the importance of fiber as a dietary ingredient, its effects on the microbiome, its effects on immune regulation, the importance of appropriate timing of intervention to target any potential window of opportunity, and potential mechanisms for dietary fibers in the prevention and management of allergic diseases. In addition, we review the human studies examining fiber or prebiotic interventions on asthma and respiratory outcomes, allergic rhinitis, atopic dermatitis, and overall risk of atopic disorders. While exposures, interventions, and outcomes were too heterogeneous for meta-analysis, there is significant potential for using fiber in targeted manipulations of the gut microbiome and its metabolic functions in promoting immune health.

Structure and function of non-digestible carbohydrates in the gut microbiome

Together with proteins and fats, carbohydrates are one of the macronutrients in the human diet. Digestible carbohydrates, such as starch, starch-based products, sucrose, lactose, glucose and some sugar alcohols and unusual (and fairly rare) α-linked glucans, directly provide us with energy while other carbohydrates including high molecular weight polysaccharides, mainly from plant cell walls, provide us with dietary fibre. Carbohydrates which are efficiently digested in the small intestine are not available in appreciable quantities to act as substrates for gut bacteria. Some oligo- and polysaccharides, many of which are also dietary fibres, are resistant to digestion in the small intestines and enter the colon where they provide substrates for the complex bacterial ecosystem that resides there. This review will focus on these non-digestible carbohydrates (NDC) and examine their impact on the gut microbiota and their physiological impact. Of particular focus will be the potential of non-digestible carbohydrates to act as prebiotics, but the review will also evaluate direct effects of NDC on human cells and systems.

Mushrooms and immunity

In the wide field of nutraceuticals, the effects of mushrooms on immunity, cancer and including autoimmunity have been proposed for centuries but in recent years a growing interest has led scientists to elucidate which specific compounds have bioactive properties and through which mechanisms. Glucans and specific proteins are responsible for most of the biological effects of mushrooms, particularly in terms of immunomodulatory and anti-tumor results. Proteins with bioactive effects include lectins, fungal immunomodulatory proteins (FIPs), ribosome inactivating proteins (RIPs), ribonucleases, laccases, among others. At the present status of knowledge, numerous studies have been performed on cell lines and murine models while only a few clinical trials have been conducted. As in most cases of dietary components, the multitude of variables implicated in the final effect and an inadequate standardization are expected to affect the observed differences, thus making the available evidence insufficient to justify the treatment of human diseases with mushrooms extracts. We will herein provide a comprehensive review and critically discussion the biochemical changes induced by different mushroom compounds as observed in in vitro studies, particularly on macrophages, dendritic cells, T cells, and NK cells, compared to in vivo and human studies. Additional effects are represented by lipids which constitute a minor part of mushrooms but may have a role in reducing serum cholesterol levels or phenols acting as antioxidant and reducing agents. Human studies provide a minority of available data, as well illustrated by a placebo-controlled study of athletes treated with β-glucan from Pleurotus ostreatus. Variables influencing study outcomes include different mushrooms strains, growing conditions, developmental stage, part of mushroom used, extraction method, and storage conditions. We foresee that future rigorous research will be needed to determine the potential of mushroom compounds for human health to reproduce the effects of some compounds such as lentinan which a metaanalysis demonstrated to increase the efficacy of chemotherapy in the treatment of lung cancer and in the improvement of the patients quality of life.

Microbiota-dependent and -independent effects of dietary fibre on human health

Dietary fibre, such as indigestible oligosaccharides and polysaccharides, occurs in many foods and has gained considerable importance related to its beneficial effects on host health and specific diseases. Dietary fibre is neither digested nor absorbed in the small intestine and modulates the composition of the gut microbiota. New evidence indicates that dietary fibre also interacts directly with the epithelium and immune cells throughout the gastrointestinal tract by microbiota-independent effects. This review focuses on how dietary fibre improves human health and the reported health benefits that are connected to molecular pathways, in (a) a microbiota-independent manner, via interaction with specific surface receptors on epithelial and immune cells regulating intestinal barrier and immune function, and (b) a microbiota-dependent manner via maintaining intestinal homeostasis by promoting beneficial microbes, including Bifidobacteria and Lactobacilli, limiting the growth, adhesion, and cytotoxicity of pathogenic microbes, as well as stimulating fibre-derived microbial short-chain fatty acid production. LINKED ARTICLES: This article is part of a themed section on The Pharmacology of Nutraceuticals. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.6/issuetoc.

Synergistic immuno-modulatory activity in human macrophages of a medicinal mushroom formulation consisting of Reishi, Shiitake and Maitake

A key characteristic of mushroom polysaccharides that elicit an immunomodulatory response is that they are rich in β-glucans and low in α-glucans. In this study we analysed nine commercially available preparations from three mushroom species, Reishi (Ganoderma lucidum), Shiitake (Lentinula edodes) and Maitake (Grifola frondosa), for β- and α-glucan content. Based on β- and α-glucan content we selected three extracts to combine into a formula and evaluated the ability of the individual extracts and formula to impact on the expression of cytokines IL-1α, IL-6, IL-10 and TNF-α in human macrophages with and without LPS stimulation. The majority of mushroom extracts and the formula were found to be highly potent immuno-stimulators possessing EC50 values lower than 100 μg/mL. Interestingly the mushroom formula had lower EC50 values in TNF-α expression from LPS stimulated macrophages compared to the individual extracts, suggesting a potential synergistic effect of the mushroom formula. A response additivity graph and curve-shift analysis illustrated that indeed the mushroom formula exhibited an immuno-stimulatory synergistic effect on the expression of the majority of cytokines evaluated in both LPS stimulated and non-stimulated human macrophages, with IL-10 having an antagonistic response. This study represents the first report of a synergistic immuno-modulatory response in human macrophages elicited from a mushroom formula rationally derived from β- and α-glucan content.

Glycan Utilisation and Function in the Microbiome of Weaning Infants

Glycans are present exogenously in the diet, expressed and secreted endogenously by host cells, and produced by microbes. All of these processes result in them being available to the gut microbiome, firmly placing glycans at the interface of diet–microbe–host interactions. The most dramatic shift in dietary sources of glycans occurs during the transition from the milk-based neonatal diet to the diverse omnivorous adult diet, and this has profound effects on the composition of the gut microbiome, gene expression by microbes and host cells, mucin composition, and immune development from innate towards adaptive responses. Understanding the glycan-mediated interactions occurring during this transitional window may inform dietary recommendations to support gut and immune development during a vulnerable age. This review aims to summarise the current state of knowledge on dietary glycan mediated changes that may occur in the infant gut microbiome and immune system during weaning.

Rainbow Trout (Oncorhynchus Mykiss) Intestinal Epithelial Cells as a Model for Studying Gut Immune Function and Effects of Functional Feed Ingredients

The objective of this study was to evaluate the suitability of the rainbow trout intestinal epithelial cell line (RTgutGC) as an in vitro model for studies of gut immune function and effects of functional feed ingredients. Effects of lipopolysaccharide (LPS) and three functional feed ingredients [nucleotides, mannanoligosaccharides (MOS), and beta-glucans] were evaluated in RTgutGC cells grown on conventional culture plates and transwell membranes. Permeation of fluorescently-labeled albumin, transepithelial electrical resistance (TEER), and tight junction protein expression confirmed the barrier function of the cells. Brush border membrane enzyme activities [leucine aminopeptidase (LAP) and maltase] were detected in the RTgutGC cells but activity levels were not modulated by any of the exposures. Immune related genes were expressed at comparable relative basal levels as these in rainbow trout distal intestine. LPS produced markedly elevated gene expression levels of the pro-inflammatory cytokines il1b, il6, il8, and tnfa but had no effect on ROS production. Immunostaining demonstrated increased F-actin contents after LPS exposure. Among the functional feed ingredients, MOS seemed to be the most potent modulator of RTgutGC immune and barrier function. MOS significantly increased albumin permeation and il1b, il6, il8, tnfa, and tgfb expression, but suppressed ROS production, cell proliferation and myd88 expression. Induced levels of il1b and il8 were also observed after treatment with nucleotides and beta-glucans. For barrier function related genes, all treatments up-regulated the expression of cldn3 and suppressed cdh1 levels. Beta-glucans increased TEER levels and F-actin content. Collectively, the present study has provided new information on how functional ingredients commonly applied in aquafeeds can affect intestinal epithelial function in fish. Our findings suggest that RTgutGC cells possess characteristic features of functional intestinal epithelial cells indicating a potential for use as an efficient in vitro model to evaluate effects of bioactive feed ingredients on gut immune and barrier functions and their underlying cellular mechanisms.

Effect of yeast cell wall on the growth performance and gut health of broilers challenged with aflatoxin B1 and necrotic enteritis

This study aimed to investigate the effect of yeast cell walls (YCW) on the growth performance, visceral lesions, intestinal integrity, enterotoxicity, and bacteria of broilers challenged with aflatoxin B1 (AF) and necrotic enteritis (NE) from 1 to 21 d of age. A total of 576 one-day-old broilers were assigned to a 2 × 2 × 2 design for diets containing AFB1 (0 or 40 μg/kg), NE (challenged or unchallenged), or YCW (0 or 500 mg/kg). The main effect analysis showed that AF depressed (P < 0.01) average daily feed intake (ADFI), average daily body weight gain (ADG), the mRNA profiles of polymeric Ig receptor (pIgR), claudin-1, and occludin, but increased (P < 0.001) liver lesion scores, serum endotoxin, and diamine oxidase (DAO). The NE challenge depressed (P < 0.01) ADFI, ADG, secretory IgA (sIgA), pIgR, claudin-1, occludin, and the populations of Lactobacilli and Bifidobacteria, but increased (P < 0.001) visceral lesions, endotoxins, and DAO. The main effect of YCW on growth performance, visceral lesions, and intestinal integrity was not significant, but decreased (P < 0.01) mortality, endotoxin, DAO, and C. perfringens, and increased (P < 0.05) the populations of Lactobacilli and Bifidobacteria. There were 3-way interactions (P < 0.05) on growth performance, intestinal lesions, integrity, and gut bacteria. Compared with the treatment with the dual challenges, there were pronounced effects (P < 0.05) of YCW on ADFI, ADG, lesions, DAO, pIgR, and Bifidobacteria. The results suggest that with the concurrent challenges of AF and NE, the YCW can partially protect the growth performance and intestinal health of broilers.

The Influences of Soybean Agglutinin and Functional Oligosaccharides on the Intestinal Tract of Monogastric Animals

Soybean agglutinin (SBA) is a non-fiber carbohydrate-related protein and the main anti-nutritional factor that exists in soybean or soybean products. SBA possesses a specific binding affinity for N-glyphthalide-d-galactosamine or galactose and has a covalently linked oligosaccharide chain. SBA mediates negative effects on animal intestinal health by influencing the intestinal structure, barrier function, mucosal immune system, and the balance of the intestinal flora. Functional oligosaccharides are non-digestible dietary oligosaccharides that are commonly applied as prebiotics since the biological effects of the functional oligosaccharides are to increase the host health by improving mucosal structure and function, protecting the integrity of the intestinal structure, modulating immunity, and balancing the gastrointestinal microbiota. The purpose of this review is to describe the structure and anti-nutritional functions of SBA, summarize the influence of SBA and functional oligosaccharides on the intestinal tract of monogastric animals, and emphasize the relationship between SBA and oligosaccharides. This review provides perspectives on applying functional oligosaccharides for alleviating the anti-nutritional effects of SBA on the intestinal tract.

β-glucans and cholesterol (Review)

Hypercholesterolemia is one of primary risk factors of cardiovascular disease, together with metabolic syndrome, hypertension and diabetes. Although progress has been made, the search for novel methods of preventing and treating dyslipidemia is ongoing and current therapies for cardiovascular disease induce various side effects. β-glucans are linear unbranched polysaccharides found in various natural sources, such as mushrooms. Due to their structure they are able to interact with innate immunity receptors, however they also act as dietary fibers in the digestive tract. As there are two forms of β-glucans, insoluble and soluble forms, they are able to interact with lipids and biliary salts in the bowel and consequently reduce cholesterol levels. Therefore, they may be developed as a suitable therapeutic option to treat patients with dyslipidemia, as they are natural molecules that do not induce any significant side effects. The current review discusses the evidence supporting the effects of β-glucans on cholesterol levels.

Rice Cakes Containing Dietary Fiber Supplemented with or without Artemisia Annua and Gynura Procumbens Merr. Alleviated the Risk Factors of Metabolic Syndrome

We investigated whether the consumption of Korean rice cakes enriched with dietary fiber with or without polyphenol rich plants might decrease the risk factors of metabolic syndrome (MetS). Rice cakes were manufactured using fructooligosaccharides, resistant starch, and psyllium as sources of dietary fibers with and without polyphenol rich Artemisia annua and Gynura procumbens Merr. (RC+FP and RC+F, respectively), and prepared in three forms (songpyeon, seolgidduk, and chaldduk). Ninety subjects with at least one MetS risk factor were recruited for 6 weeks of dietary intervention. Sixty subjects were finally included for the analysis. Compared to the initial values, RC+FP group had decreased levels of fasting blood glucose (FBG), HOMA-IR and blood pressure after 6 weeks, whereas RC+F group didn't have significant changes in them. Regarding the improvement of individual MetS risk factors, RC+FP group showed significant reduction in FBG and blood pressures but RC+F group only had reduction in systolic blood pressure. After the intervention, a reduction in the number of MetS risk factors was greatert in the RC+FP group than in the RC+F group. In conclusion, Dietary fiber enriched rice cakes with or without polyphenols decreased the number and/or the levels of MetS risk factors. Polyphenol rich plant components may provide additional health benefits in controlling FBG and blood pressure.

A review of 733 published trials on Bio-Mos®, a mannan oligosaccharide, and Actigen®, a second generation mannose rich fraction, on farm and companion animals

Mannan-oligosaccharides (MOS), as zootechnical feed ingredients, are widely used in animal nutrition. MOS has been commercially available since the launch of Bio-Mos® in the early 1990's and has a substantial body of scientific papers and practical examples of its efficacy. Since 1999, the use of MOS in animal feed has become more prominent, mainly due to the European ban on prophylactic antibiotic growth promoters in animal feed. MOS, with its ability to bind and limit the colonisation of gut pathogens, has proven to be an effective solution for antibiotic-free diets, as well as providing support for immunity and digestion. MOS has been shown to improve gastrointestinal health, thus improving wellbeing, energy levels and performance. Most MOS products, particularly those that have been scientifically developed, derive from the cell wall of the yeast,Saccharomyces cerevisiae. In 2009, a mannose-rich fraction (MRF) product was commercially launched as a ‘second generation’ of these MOS-type products, with enhanced activities in immune modulation and intestinal health. The purpose of this paper is to review the existing data on the benefits of MOS for all species of animals, discuss its mechanisms of actionin vivoand compare the benefits of using second generation MRF to original MOS.

Microbial, saccharifying and antioxidant properties of an Indian rice based fermented beverage

Haria, a popular rice based ethnic fermented beverage, is consumed as a staple food and refreshing drink by the vast number of Indian tribal people. In this study, the composition of microbial consortia and the occurrence of some important nutraceuticals during haria preparation were investigated. The quantities of moulds and yeasts were highest at 2nd day, and then declined, but, on the contrary, the quantity of Lactic Acid Bacteria and Bifidobacterium sp. increased concurrently during the course of fermentation. Accumulation of starch hydrolytic enzymes along with different types of malto-oligosaccharides like maltotetrose (26.18μg/gm), maltotriose (28.16μg/gm), and maltose (26.94μg/gm) were also noted. Furthermore, GC-MS analysis indicated the occurrence of pyranose derivatives in the fermented products. The fermented materials showed higher free radicals scavenging activity (82.54%, 4th day) against DPPH radicals. These studies clearly demonstrated that the microbial interaction during fermentation of rice makes it more nutritious, and most likely more beneficial for health.

Dietary fiber and amyotrophic lateral sclerosis: results from 5 large cohort studies

Amyotrophic lateral sclerosis (ALS) is a fast-progressing neurodegenerative disease with a median survival time from diagnosis of 1.5-3 years. The cause of ALS is unknown, but inflammation may play a role. Fiber has been shown to lower inflammatory markers, and a high fiber intake was associated with a lower risk of ALS in a case-control study; however, prospective studies are lacking. We explored the relation between dietary intake of fiber and the risk of ALS in 5 large prospective cohort studies comprising over 1,050,000 US citizens who contributed 1,133 ALS cases during a mean of 15 years of follow-up (1980-2008). Cox proportional hazards models were used within each cohort, and cohort-specific estimates were subsequently pooled using a random-effects model. We found that intakes of total fiber, cereal fiber, vegetable fiber, and fruit fiber were not associated with ALS risk when comparing the highest quintile of intake with the lowest (for total fiber, pooled multivariable relative risk (RR) = 0.99, 95% confidence interval (CI): 0.80, 1.24; for cereal fiber, RR = 1.13, 95% CI: 0.94, 1.37; for vegetable fiber, RR = 0.97, 95% CI: 0.77, 1.23; and for fruit fiber, RR = 1.05, 95% CI: 0.86, 1.29). These findings do not support the hypothesis that fiber intake is a major determinant of ALS risk.

No association of dietary fiber intake with inflammation or arterial stiffness in youth with type 1 diabetes

AIM

To examine the association of dietary fiber intake with inflammation and arterial stiffness among youth with type 1 diabetes (T1D) in the US.

METHODS

Data are from youth ≥ 10 years old with clinically diagnosed T1D for ≥ 3 months and ≥ 1 positive diabetes autoantibody in the SEARCH for Diabetes in Youth Study. Fiber intake was assessed by food frequency questionnaire with measurement error (ME) accounted for by structural sub-models derived using additional 24-h dietary recall data in a calibration sample and the respective exposure-disease model covariates. Markers of inflammation, measured at baseline, included IL-6 (n=1405), CRP (n=1387), and fibrinogen (n=1340); markers of arterial stiffness, measured approximately 19 months post-baseline, were available in a subset of participants and included augmentation index (n=180), pulse wave velocity (n=184), and brachial distensibility (n=177).

RESULTS

Mean (SD) T1D duration was 47.9 (43.2) months; 12.5% of participants were obese. Mean (SD) ME-adjusted fiber intake was 15 (2.8) g/day. In multivariable analyses, fiber intake was not associated with inflammation or arterial stiffness.

CONCLUSION

Among youth with T1D, fiber intake does not meet recommendations and is not associated with measures of systemic inflammation or vascular stiffness. Further research is needed to evaluate whether fiber is associated with these outcomes in older individuals with T1D or among individuals with higher intakes than those observed in the present study.

Effect of yeast cell product (CitriStim) supplementation on broiler performance and intestinal immune cell parameters during an experimental coccidial infection

This experiment studied the effects of whole yeast cell product supplementation on broiler production parameters, fecal coccidial oocyst counts, and local and systemic immune parameters following an experimental coccidial infection. Birds were fed 0, 0.1, or 0.2% whole yeast cell product (CitriStim). At 21 d of age, birds were challenged with live coccidial oocysts. Supplementation with whole yeast cell product increased BW gain between 0 and 12 d (P = 0.01) postcoccidial challenge. Birds supplemented with 0.2% Citristim had better (P = 0.01) feed efficiency between 0 and 12 d postcoccidial infection. Supplementation with whole yeast cell product decreased (P = 0.01) the fecal coccidial oocyst count at 7 d postcoccidial challenge. Citristim supplementation at 0.2% increased (P < 0.01) macrophage nitric oxide production by 93 and 193% at 5 and 12 d postcoccidial challenge. Supplementation with whole yeast cell product at 0.2% increased cecal tonsil interleukin-1 mRNA amounts approximately 4.5- and 3.7-fold at 5 and 12 d postcoccidial challenge, respectively, over the group with no whole yeast cell product supplementation. Citristim supplementation downregulated cecal tonsil interleukin-10 mRNA amounts compared with the unsupplemented groups at both 5 (P = 0.01) and 12 d (P < 0.01) postcoccidial challenge. Supplementation with whole yeast cell product did not alter (P > 0.05) serum anticoccidial IgG contents or cecal tonsil CD4(+) and CD8(+) cell percentages at 5 and 12 d postcoccidial infection. It could be concluded that supplementing whole yeast cell product (CitriStim) to broiler diets can improve production parameters, decrease fecal oocyst count, and increase inflammatory cytokine production postcoccidial infection.

The health benefits of dietary fiber: beyond the usual suspects of type 2 diabetes mellitus, cardiovascular disease and colon cancer

Dietary fiber (DF) is deemed to be a key component in healthy eating. DF is not a static collection of undigestible plant materials that pass untouched or unencumbered through the gastrointestinal (GI) tract; instead, DFs are a vast array of complex saccharide-based molecules that can bind potential nutrients and nutrient precursors to prevent their absorption. Some DFs are fermentable, and the GI tract catabolism leads to the generation of various bioactive materials, such as short-chain fatty acids (SCFAs), that can markedly augment the GI tract biomass and change the composition of the GI tract flora. The health benefits of DFs include the prevention and mitigation of type 2 diabetes mellitus, cardiovascular disease and colon cancer. By modulating food ingestion, digestion, absorption and metabolism, DFs reduce the risk of hyperlipidemia, hypercholesterolemia and hyperglycemia. Emerging research has begun to investigate the role of DFs in immunomodulation. If substantiated, DFs could facilitate many biologic processes, including infection prevention and the improvement of mood and memory. This review describes the accepted physiologic functions of DFs and explores their new potential immune-based actions.

Immunomodulatory effects of dietary β-1,3-glucan from Euglena gracilis in rainbow trout (Oncorhynchus mykiss) immersion vaccinated against Yersinia ruckeri

Potential immunostimulatory effects of orally administered β-glucan were investigated in combination with immersion vaccination against enteric redmouth disease caused by Yersinia ruckeri in rainbow trout (Oncorhynchus mykiss). A linear, unbranched and pure (purity ≥98%) β-1,3-glucan (syn. paramylon) from the alga Euglena gracilis was applied at an inclusion level of 1% β-glucan in feed administered at a rate of 1% biomass day(-1) for 84 consecutive days. Fish were vaccinated after two weeks of experimental feeding and bath challenged with live Y. ruckeri six weeks post-vaccination. Blood and head kidney were sampled at day 0, 13 (1 day pre-vaccination), 15, 55, 59 (day 3 post-challenge (p.c.)), 70 and 84. Vaccination induced significantly increased survival p.c., whereas the β-glucan had no effect on survival in either unvaccinated or vaccinated fish. Expression in head kidney of genes related to the acute phase response, i.e. interleukin-1β (IL-1β), serum amyloid A (SAA), precerebellin, and hepcidin, was significantly different in vaccinated fish receiving β-glucan compared to vaccinated controls at day 3 p.c., while no effect of β-glucan was observed among unvaccinated fish. Significant interaction between β-glucan and vaccination was found for the regulation of IL-1β, tumour necrosis factor-α, interferon-γ, SAA, precerebellin and hepcidin p.c. For SAA, the significant effect of β-glucan in vaccinated fish persisted at day 14 p.c. and 28 p.c. The difference in gene expression among vaccinated fish was mainly observed as down-regulations in vaccinated, β-glucan fed fish compared to up-regulations or no regulation in vaccinated controls. Slightly increased levels of plasma lysozyme activity were found in fish (both unvaccinated and vaccinated) receiving β-glucan at day 3 p.c. compared to control fed groups. This was associated with a faster clearance of Y. ruckeri in unvaccinated fish receiving β-glucan. In contrast to the trend towards a beneficial effect of β-glucan on plasma lysozyme activity, a trend towards suppression of plasma antibodies was seen in both unvaccinated and vaccinated fish receiving β-glucan. However, the effects of β-glucan were not reflected in the survival curves, and the differences seen in plasma lysozyme activity and antibody levels may have counteracted and set off each other as well as counteracted any potential effect represented by the differences in gene expression found.

Influence of dietary ingredients on in vitro inflammatory response of intestinal porcine epithelial cells challenged by an enterotoxigenic Escherichia coli (K88)

Enterotoxigenic Escherichia coli (ETEC) K88 is the main bacterial cause of diarrhea in piglets around weaning and the adhesion of ETEC to the intestinal mucosa is a prerequisite step for its colonization. In this study, the adhesion of a fimbriated ETEC and a non-fimbriated E. coli (NFEC) to the intestinal cells and the activation of the innate immune system were evaluated using a porcine intestinal epithelial cell line (IPEC-J2). The impact of several feedstuffs (wheat bran (WB); casein glycomacropeptide (CGMP); mannan-oligosaccharides (MOS); locust bean extract (LB) and Aspergillus oryzae fermentation extract (AO)) on ETEC attachment and the inflammatory response were also studied. The gene expression of TLR-4; TLR-5; IL-1β; IL-8; IL-10 and TNF-α were quantified using Cyclophilin-A, as a reference gene, and related to a non-challenged treatment. The fimbriated strain was markedly better than the non-fimbriated strain at adherence to intestinal cells and inducing an inflammatory response. All the feedstuffs studied were able to reduce the adhesion of ETEC, with the greatest decrease with CGMP or MOS at highest concentration. Regarding the inflammatory response, the highest dose of WB promoted the lowest relative expression of cytokines and chemokines. All tested feedstuffs were able to reduce the adhesion of ETEC to IPEC-J2 and interfere on the innate inflammatory response; however WB should be further studied according to the beneficial results on the intestinal inflammatory process evidenced in this study.