The Intake of Dietary Lipids Improves Glucose Tolerance via Modulating Gut Microbiota.

The composition of gut microbiota is determined not only by genetic factors but also by environmental factors, such as diet, exercise, and disease conditions. Among these factors, diet is crucial in changing the gut microbial composition. Dietary lipids composed of different fatty acids not only alter host metabolism but also have a significant impact on the composition of gut microbiota. However, the molecular mechanisms underlying the relationship between these host effects and their impact on gut microbiota remain unclear. Here, we demonstrated that intake of different dietary lipids improved glucose tolerance by modulating gut microbiota. The results of our analysis show that the taxa of bacteria that increase in number as a result of dietary lipid intake play an important role in glucose metabolism. Thus, we have identified a new mechanism underlying the function of dietary lipids in regulating glucose homeostasis. Our findings contribute to possible new methods to prevent and treat metabolic disorders by modifying the composition of gut microbiota.

Intragastric administration of transamidated gliadin interferes with the systemic and intestinal immune responses to wheat gliadin in DQ8 transgenic mice.

We have previously shown the ability of transamidated gluten (spf) to modulate both innate and adaptive intestinal immunity elicited by wheat gliadin in HLA-DQ8 transgenic mice (DQ8 mice), a model of gluten sensitivity. Herein, we evaluated the influence of spf when administered intragastrically on the immune response to native gliadin in DQ8 mice. To address the issue, we analysed three regimens of antigen administration: before immunisation (pre-treatment), during immunisation (co-treatment) and through breast milk during the lactating phase (suckling treatment). Mice were immunised mucosally by intranasal delivery of digested wheat gliadin along with cholera toxin in multiple doses. After sacrifice, isolated spleen and mesenteric lymph node (MLN) cells were challenged in vitro and the cytokine profile of culture supernatants assessed by ELISA and multiparametric assay. We found that only pre-treatment with spf was effective in down-regulating the gliadin-specific IFN-γ response and only in spleen cells. Interestingly, spf pre-treatment also induced systemic IL-6, IL-17A and TNF-α. By contrast, we found that spf pre-treatment upregulated INF-γ in MLN but also significantly decreased IL-2. In conclusion, our data provide evidence that the preventive intragastric administration of transamidated gluten is able to interfere with the classical cytokine profile induced by gliadin via mucosal immunisation in a transgenic model expressing one of the HLA molecules associated with coeliac disease.

Modulation of Mouse Dendritic Cells In Vitro by Lactobacillus gasseri Postbiotic Proteins.

Different lactobacilli are probiotics for their beneficial effects that confer to the host. Recently, some of these effects were associated with released metabolic products/constituents (postbiotics). In the present study, the potential immunomodulatory capacity of the probiotic Lactobacillus gasseri OLL2809 cell-free supernatant (sup) was investigated in murine bone marrow-derived dendritic cells (DCs). Bacteria induced significantly higher expression of all examined cytokines than those induced by the stimulatory lipopolysaccharide (LPS) itself. On the contrary, sup only induced the anti-inflammatory IL-10 similarly to LPS, whereas IL-12 and IL-6 secretions were stimulated at a lower level. Moreover, sup reduced the surface expression of the analyzed co-stimulatory markers CD40, CD80, and CD86. Treatments of sup with different digestive enzymes indicated the proteinaceous nature of these immunomodulatory metabolites. Western blot and immunoadsorption analyzes revealed cross-reactivity of sup with the surface-layer proteins (SLPs) isolated from OLL2809. Therefore, we directly tested the ability of OLL2809 SLPs to stimulate specifically cytokine expression in iDCs. Interestingly, we found that all tested cytokines were induced by SLPs and in a dose-dependent manner. In conclusion, our results highlighted distinct immune properties between L. gasseri OLL2809 and its metabolites, supporting the concept that bacterial viability is not an essential prerequisite to exert immunomodulatory effects.

High Fat Diet-Wheat Gliadin Interaction and its Implication for Obesity and Celiac Disease Onset: In Vivo Studies.

The intestinal immune system plays a crucial role in obesity and insulin resistance. An altered intestinal immunity is associated with changes to the gut microbiota, barrier function, and tolerance to luminal antigens. Lipid metabolism and its unbalance can also contribute to acute and chronic inflammation in different conditions. In celiac disease (CD), the serum phospholipid profile in infants who developed CD is dramatically different when compared to that of infants at risk of CD not developing the disease. In a mouse model of gluten sensitivity, oral wheat gliadin challenge in connection with inhibition of the metabolism of arachidonic acid, an omega-6 polyunsaturated fatty acid, specifically induces the enteropathy. Recent evidence suggests that gluten may play a role also for development of life-style related diseases in populations on a high fat diet (HFD). However, the mechanisms behind these effects are not yet understood. Exploratory studies in mice feed HFD show that wheat gliadin consumption affects glucose and lipid metabolic homeostasis, alters the gut microbiota, and the immune cell profile in liver.

The HLA-DQ8 transgenic mouse: A model to study the immune and cytotoxic responses to wheat gliadin.

A complete understanding of celiac disease (CD) pathogenesis has been hindered to date because of the lack of adequate in vivo models. Herein, we describe two in vivo approaches in HLA-DQ8-transgenic mice to study the intrinsic cytoxicity and immune features of wheat gliadin. By adopting the first method, we explored the mucosal architecture of the small intestine following the intra-gastric administration of wheat gliadin in mice treated with indomethacin, an inhibitor of cyclooxygenases. Mice showed a significant reduction of villus height, increased crypt depth and increased intraepithelial lymphocytes. The second approach involved the mucosal sensitization to gliadin via the intranasal route. This protocol induced a Th1/Th17 phenotype in mesenteric lymph nodes, as described in CD. In conclusion, these methods remain instrumental to analyze in vivo distinct biological features of wheat gliadin and related prolamins. Furthermore, the sensitization protocol could be exploited to test innovative strategies downregulating the gliadin-specific immunity.

Polyunsaturated fatty acids-rich dietary lipid prevents high fat diet-induced obesity in mice.

Diet is the primary factor affecting host nutrition and metabolism, with excess food intake, especially high-calorie diets, such as high-fat and high-sugar diets, causing an increased risk of obesity and related disorders. Obesity alters the gut microbial composition and reduces microbial diversity and causes changes in specific bacterial taxa. Dietary lipids can alter the gut microbial composition in obese mice. However, the regulation of gut microbiota and host energy homeostasis by different polyunsaturated fatty acids (PUFAs) in dietary lipids remains unknown. Here, we demonstrated that different PUFAs in dietary lipids improved host metabolism in high-fat diet (HFD)-induced obesity in mice. The intake of the different PUFA-enriched dietary lipids improved metabolism in HFD-induced obesity by regulating glucose tolerance and inhibiting colonic inflammation. Moreover, the gut microbial compositions were different among HFD and modified PUFA-enriched HFD-fed mice. Thus, we have identified a new mechanism underlying the function of different PUFAs in dietary lipids in regulating host energy homeostasis in obese conditions. Our findings shed light on the prevention and treatment of metabolic disorders by targeting the gut microbiota.

Efficacy of a new nutraceutical formulation: L-tryptophan, probiotics, charcoal, chamomile, mint, and licorice (COLONIR®) in the improvement of gastrointestinal symptoms in subjects with irritable bowel syndrome.

BACKGROUND: Irritable bowel syndrome (IBS) is one of the most common functional gastrointestinal disorders. IBS is characterized by recurrent chronic abdominal pain and altered bowel habits in the absence of organic damage. Although there are reviews and guidelines for treating IBS, the complexity and diversity of IBS presentation make treatment difficult. Treatment of IBS focuses on relieving symptoms as mild signs and symptoms can often be controlled by managing stress and by making changes in diet and lifestyle. The use of nutraceutical compounds has been advocated as a possible alternative treatment in patients with IBS. COLONIR® (Omega Pharma Srl, Milan, Italy) may be an alternative or adjuvant treatment in patients with gastrointestinal symptoms. This study aimed to evaluate the effect of this new nutraceutical formulation in inducing symptoms remission and improve gastrointestinal habits. METHODS: An initial cohort of 1004 consecutive patients referred to 25 different Units of Internal Medicine a/o Gastroenterology in Italy to perform colonoscopy for intestinal symptoms was asked to participate. Patients were treated for 2 months with two doses of nutraceuticals/day during meals namely COLONIR®. Patients were assessed at baseline and after 2 months to evaluate the frequency and severity of gastrointestinal symptoms in the past seven days with a questionnaire based on ROMA IV criteria. RESULTS: After 2 months, 899 patients completed the follow-up. COLONIR® achieved a statistically significant reduction of severity of symptoms in the study population without any documented side effects. CONCLUSIONS: These promising results, here reported, need to be confirmed, valuating the efficacy of COLONIR® in relieving gastrointestinal symptoms in IBS patients in further studies.

Inflammatory Bowel Diseases and Gut Microbiota.

Inflammatory bowel disease (IBD) is an inflammatory disease of the gastrointestinal tract, the incidence of which has rapidly increased worldwide, especially in developing and Western countries. Recent research has suggested that genetic factors, the environment, microbiota, and immune responses are involved in the pathogenesis; however, the underlying causes of IBD are unclear. Recently, gut microbiota dysbiosis, especially a decrease in the abundance and diversity of specific genera, has been suggested as a trigger for IBD-initiating events. Improving the gut microbiota and identifying the specific bacterial species in IBD are essential for understanding the pathogenesis and treatment of IBD and autoimmune diseases. Here, we review the different aspects of the role played by gut microbiota in the pathogenesis of IBD and provide a theoretical basis for modulating gut microbiota through probiotics, fecal microbiota transplantation, and microbial metabolites.

Next generation strategies to recover immunological tolerance in celiac disease.

Celiac disease (CD) is an autoimmune disease that occurs in genetically predisposed individuals following the ingestion of gluten. Its prevalence is rising worldwide. A gluten-free (GF) diet is mandatory for the management of CD. However, several issues persist regarding the nutritional quality of GF products. Importantly, deep knowledge about the pathogenic mechanisms in CD highlights the central role of CD4+ T cell-mediated immunity in CD. Furthermore, intestinal T regulatory cells are functional in CD, but cytokines such as IL-15, produced under inflammatory conditions, hamper their activity. This paves the way for the development of immunomodulatory strategies to the GF diet. From this perspective, microbiological approaches were considered able to modulate the gluten-specific immune response. Interestingly, gliadin peptide-based immunotherapy to abolish the inflammatory CD4+T cell-mediated response has been explored in CD patients. Furthermore, different biotechnological approaches based on the use of chemically/enzymatically modified gluten molecules have been proved effective in different models of CD. However, the choice of the right age in infants to introduce the antigen and thus induce tolerance still remains an important issue to solve. Addressing all these points should help to design an effective intervention strategy for preventing CD.

Transamidated wheat gliadin induces differential antigen recognition in the small intestine of HLA/DQ8 transgenic mice.

A lifelong gluten-free diet (GFD) is currently the only available therapy for coeliac disease (CD). However, GFD compliance is difficult and alternative strategies are envisaged in the near future. We previously found that wheat gliadin following transamidation by microbial transglutaminase (mTG) does not induce IFN-γ secretion by intestinal T cells from CD patients. Fully transamidated gliadin with lysine ethyl ester can be recovered in a soluble protein fraction (spf) generated by the enzymatic treatment of wheat flour. Herein, we analysed the performance of transamidation by mTG on a pilot-scale (1L) by evaluating the reaction kinetics and its biological effect on the intestinal immune response in HLA/DQ8 transgenic mice, a model of gluten sensitivity. At 1 h, all gliadin fractions showed a faster electrophoretic mobility by acid-polyacrylamide gel electrophoresis (A-PAGE) following transamidation in comparison with their native counterparts. In parallel, the yield of residual native gliadin dropped (30% at 180 min), confirming our previous findings on a lab scale. Mucosal sensitisation of mice with gliadin via the intranasal route induced a Th1 phenotype in mesenteric lymph nodes (MLNs). Importantly, IFN-γ secretion was significantly reduced when gliadin-specific MLN cells were challenged in vitro with spf (P < 0.001). Multiplex analysis revealed that the adaptive immune response evoked by spf involved a distinct cell population characterised by secretion of IL-2, IL-3 and IL-5. Notably, spf stimulated in vitro a reduced or null secretion of all of the examined pro-inflammatory markers mainly associated to innate immunity. In conclusion, our data revealed the ability of transamidated gliadin to modulate both innate and adaptive mechanisms involved in the inflammatory response induced by wheat gliadin in the small intestine of DQ8 mice.