In Vitro Evaluation of the Effects of Commercial Prebiotic GOS and FOS Products on Human Colonic Caco-2 Cells

Evaluation of the synbiotic effects of Saccharomyces cerevisiae and mushroom extract on the growth performance, digestive enzyme activity, and immune status of zebrafish danio rerio

BACKGROUND

The quest for candidate probiotics and prebiotics to develop novel synbiotics for sustainable and profitable fish farming remains a major focus for various stakeholders. In this study, we examined the effects of combining two fungal probiotics, Saccharomyces cerevisiae and Aspergillus niger with extracts of Jerusalem artichoke and white button mushroom to develop a synbiotic formulation to improve the growth and health status of zebrafish (Danio rerio). An initial in vitro study determined the most effective synbiotic combination, which was then tested in a 60-day in vivo nutritional trial using zebrafish (80 ± 1.0 mg) as a model animal. Four experimental diets were prepared: a control diet (basal diet), a prebiotic diet with 100% selected mushroom extract, a probiotic diet with 107 CFU of S. cerevisiae/g of diet, and a synbiotic diet with 107 CFU of S. cerevisiae/g of diet and 100% mushroom extract. As readouts, growth performance, survival, digestive enzyme activity and innate immune responses were evaluated.

RESULTS

In vitro results showed that the S. cerevisiae cultured in a medium containing 100% mushroom extract exhibited the maximum specific growth rate and shortest doubling time. In the in vivo test with zebrafish, feeding them with a synbiotic diet, developed with S. cerevisiae and mushroom extract, led to a significant improvement in the growth performance of zebrafish (P < 0.05). The group of zebrafish fed with the synbiotic diet showed significantly higher levels of digestive enzyme activity and immune responses compared to the control group (P < 0.05).

CONCLUSION

Taken together, these results indicated that the combination of S. cerevisiae and mushroom extract forms an effective synbiotic, capable of enhancing growth performance and immune response in zebrafish.

Fructo-oligosaccharide-mediated alteration in claudin expression in small intestinal absorptive Caco-2 cells is positively associated with the induction of inflammatory genes and the glucan receptor gene CLEC7A

OBJECTIVES

Indigestible carbohydrates may strengthen tight junctions (TJs) independently of intestinal bacteria. This study investigated whether indigestible carbohydrates (i.e., fructo-oligosaccharides [FOS]) promote TJs directly to intestinal absorptive Caco-2 cells and examined the association between the expression of genes constructing TJs and other genes using mRNA microarray analysis.

METHODS

Caco-2 cells at 1.0 × 105/mL were seeded in a type I collagen plate and cultured in high-glucose Dulbecco's modified Eagle medium (DMEM) supplemented with 10% fetal calf serum (FCS); the cells reached confluence at 7 d after seeding. Ten days after the cells reached confluency, they were cultured for 24 h in 10% FCS-containing DMEM medium supplemented with 0%, 5%, or 10% FOS. We performed mRNA microarray to identify the genes whose expression was altered by FOS. Subsequently, quantitative reverse transcription polymerase chain reaction was performed for these altered genes, including CLEC7A encoding the glucan receptor, and for the claudin (CLDN) family genes. The expression of CLDN2, CLDN4, and CLEC7A proteins was assessed using western blot analysis.

RESULTS

FOS decreased the mRNA and protein expression of CLDN2, which weakens TJs, and increased those of CLDN4, which strengthens TJs, in Caco-2 cells. FOS treatment (10%) reduced the mRNA expression of antioxidative genes and induced the expression of immune response-related genes, including CLEC7A, CCL2, and ITGA2. Furthermore, the expression of CLEC7A protein was enhanced by FOS.

CONCLUSIONS

Induction of TJ-strengthening CLDN4 and reduction of TJ-weakening CLDN2 by FOS treatment in small intestinal absorptive Caco-2 cells is positively associated with the induction of inflammatory genes, including CLEC7A.

Direct Action of Non-Digestible Oligosaccharides against a Leaky Gut

The epithelial monolayer is the primary determinant of mucosal barrier function, and tight junction (TJ) complexes seal the paracellular space between the adjacent epithelial cells and represent the main "gate-keepers" of the paracellular route. Impaired TJ functionality results in increased permeation of the "pro-inflammatory" luminal contents to the circulation that induces local and systemic inflammatory and immune responses, ultimately triggering and/or perpetuating (chronic) systemic inflammatory disorders. Increased gut leakiness is associated with intestinal and systemic disease states such as inflammatory bowel disease and neurodegenerative diseases such as Parkinson's disease. Modulation of TJ dynamics is an appealing strategy aiming at inflammatory conditions associated with compromised intestinal epithelial function. Recently there has been a growing interest in nutraceuticals, particularly in non-digestible oligosaccharides (NDOs). NDOs confer innumerable health benefits via microbiome-shaping and gut microbiota-related immune responses, including enhancement of epithelial barrier integrity. Emerging evidence supports that NDOs also exert health-beneficial effects on microbiota independently via direct interactions with intestinal epithelial and immune cells. Among these valuable features, NDOs promote barrier function by directly regulating TJs via AMPK-, PKC-, MAPK-, and TLR-associated pathways. This review provides a comprehensive overview of the epithelial barrier-protective effects of different NDOs with a special focus on their microbiota-independent modulation of TJs.

Microbiota independent effects of oligosaccharides on Caco-2 cells -A semi-targeted metabolomics approach using DI-FT-ICR-MS coupled with pathway enrichment analysis

Milk oligosaccharides (MOS) and galactooligosaccharides (GOS) are associated with many benefits, including anti-microbial effects and immune-modulating properties. However, the cellular mechanisms of these are largely unknown. In this study, the effects of enriched GOS and MOS mixtures from caprine and bovine milk consisting mainly 6'-galactosyllactose, 3'-sialyllactose, and 6'-sialyllactose on Caco-2 cells were investigated, and the treatment-specific metabolomes were described. In the control, the cells were treated with a sugar mix consisting of one-third each of glucose, galactose and lactose. A local metabolomics workflow with pathway enrichment was established, which specifically addresses DI-FT-ICR-MS analyses and includes adaptations in terms of measurement technology and sample matrices. By including quality parameters, especially the isotope pattern, we increased the precision of annotation. The independence from online tools, the fast adaptability to changes in databases, and the specific adjustment to the measurement technology and biomaterial used, proved to be a great advantage. For the first time it was possible to find 71 active pathways in a Caco-2 cell experiment. These pathways were assigned to 12 main categories, with amino acid metabolism and carbohydrate metabolism being the most dominant categories in terms of the number of metabolites and metabolic pathways. Treatment of Caco-2 cells with high GOS and glucose contents resulted in significant effects on several metabolic pathways, whereas the MOS containing treatments resulted only for individual metabolites in significant changes. An effect based on bovine or caprine origin alone could not be observed. Thus, it was shown that MOS and GOS containing treatments can exert microbiome-independent effects on the metabolome of Caco-2 cells.

Galactooligosaccharide Treatment Alleviates DSS-Induced Colonic Inflammation in Caco-2 Cell Model

The biological activities of dietary bioactive polysaccharides have been largely explored. Studies on the immunomodulating effects of oligosaccharides and polysaccharides have shown that they are able to modulate innate immunity. Prebiotics are a class of poorly digested carbohydrates that are mainly produced from dietary fibers, which are carbohydrate polymers with ten or more monomeric units as defined by the Codex Alimentarius Commission in 2009. Considering the capacity of prebiotics in reducing gut inflammation, the aim of this study was to investigate the anti-inflammatory activity of galactooligosaccharide (Bimuno^® GOS) in an in vitro model of ulcerative colitis (UC)-like inflamed intestinal cells. Differentiated Caco-2 cells were exposed to 2 % dextran-sulfate-sodium salt (DSS) to induce inflammation, and then with different concentrations of Bimuno GOS (1–1,000 μg/ml). Cell monolayer permeability, tight- and adherent junction protein distribution, pro-inflammatory cytokine secretion, and NF-kB cascade were assessed. Bimuno GOS at different concentrations, while not affecting cell monolayer permeability, was shown to counteract UC-like intestinal inflammatory responses and damages induced by DSS. Indeed, Bimuno GOS was able to counteract the detrimental effects of DSS on cell permeability, determined by transepithelial electrical resistance, phenol red apparent permeability, and tight- and adherent junction protein distribution. Furthermore, Bimuno GOS inhibited the DSS-induced NF-kB nuclear translocation and pro-inflammatory cytokine secretion. Further analyses showed that Bimuno GOS was able to revert the expression levels of most of the proteins involved in the NF-kB cascade to control levels. Thus, the prebiotic Bimuno GOS can be a safe and effective way to modulate the gut inflammatory state through NF-kB pathway modulation, and could possibly further improve efficacy in inducing remission of UC.