Gut Microbiota Developments With Emphasis on Inflammatory Bowel Disease: Report From the Gut Microbiota for Health World Summit 2016

Gut Microbiome Changes in Gestational Diabetes

Gestational diabetes mellitus (GDM), one of the most common endocrine pathologies during pregnancy, is defined as any degree of glucose intolerance with onset or first discovery in the perinatal period. Physiological changes that occur in pregnant women can lead to inflammation, which promotes insulin resistance. In the general context of worldwide increasing obesity in young females of reproductive age, GDM follows the same ascending trend. Changes in the intestinal microbiome play a decisive role in obesity and the development of insulin resistance and chronic inflammation, especially in patients with type 2 diabetes mellitus (T2D). To date, various studies have also associated intestinal dysbiosis with metabolic changes in women with GDM. Although host metabolism in women with GDM has not been fully elucidated, it is of particular importance to analyze the available data and to discuss the actual knowledge regarding microbiome changes with potential impact on the health of pregnant women and newborns. We analyzed peer-reviewed journal articles available in online databases in order to summarize the most recent findings regarding how variations in diet and metabolic status of GDM patients can contribute to alteration of the gut microbiome, in the same way that changes of the gut microbiota can lead to GDM. The most frequently observed alteration in the microbiome of patients with GDM was either an increase of the Firmicutes phylum, respectively, or a decrease of the Bacteroidetes and Actinobacteria phyla. Gut dysbiosis was still present postpartum and can impact the development of the newborn, as shown in several studies. In the evolution of GDM, probiotic supplementation and regular physical activity have the strongest evidence of proper blood glucose control, favoring fetal development and a healthy outcome for the postpartum period. The current review aims to summarize and discuss the most recent findings regarding the correlation between GDM and dysbiosis, and current and future methods for prevention and treatment (lifestyle changes, pre- and probiotics administration). To conclude, by highlighting the role of the gut microbiota, one can change perspectives about the development and progression of GDM and open up new avenues for the development of innovative therapeutic targets in this disease.

Inflammatory bowel disease: tri-directional relationship between microbiota, immune system and intestinal epithelium

Human gut microbiota contributes to host nutrition and metabolism, sustains intestinal cell proliferation and differentiation, and modulates host immune system. The alterations in their composition lead to severe gut disorders, including inflammatory bowel disease (IBD) or inflammatory bowel syndrome (IBS). IBD including ulcerative colitis (UC) and Crohn's disease (CD) are gamut of chronic inflammatory disorders of gut, mediated by complex interrelations among genetic, environmental, and internal factors. IBD has debateable aetiology, however in recent years, exploring the central role of a tri-directional relationship between gut microbiota, mucosal immune system, and intestinal epithelium in pathogenesis is getting the most attention. Increasing incidences and early onset explains the exponential rise in IBD burden on health-care systems. Industrialization, hypersensitivity to allergens, lifestyle, hygiene hypothesis, loss of intestinal worms, and gut microbial composition, explains this shifted rise. Hitherto, the interventions modulating gut microbiota composition, microfluidics-based in vitro gastrointestinal models, non-allergic functional foods, nutraceuticals, and faecal microbiota transplantation (FMT) from healthy donors are some of the futuristic approaches for the disease management.

The immune system and microbiome in pregnancy

Hormonal changes during pregnancy instigate numerous physiological changes aimed at the growth and delivery of a healthy baby. A careful balance between immunological tolerance against fetal antigens and immunity against infectious agents needs to be maintained. A three-way interaction between pregnancy hormones, the immune system and our microbiota is now emerging. Recent evidence suggests that microbial alterations seen during pregnancy may help maintain homeostasis and aid the required physiological changes occurring in pregnancy. However, these same immunological and microbial alterations may also make women more vulnerable during pregnancy and the post-partum period, especially regarding immunological and infectious diseases. Thus, a further understanding of the host-microbial interactions taking place during pregnancy may improve identification of populations at risk for adverse pregnancy outcomes.

Microbiota- and Radiotherapy-Induced Gastrointestinal Side-Effects (MARS) Study: A Large Pilot Study of the Microbiome in Acute and Late-Radiation Enteropathy

PURPOSE

Radiotherapy is important in managing pelvic cancers. However, radiation enteropathy may occur and can be dose limiting. The gut microbiota may contribute to the pathogenesis of radiation enteropathy. We hypothesized that the microbiome differs between patients with and without radiation enteropathy.Experimental Design: Three cohorts of patients (n = 134) were recruited. The early cohort (n = 32) was followed sequentially up to 12 months post-radiotherapy to assess early radiation enteropathy. Linear mixed models were used to assess microbiota dynamics. The late cohort (n = 87) was assessed cross-sectionally to assess late radiation enteropathy. The colonoscopy cohort compared the intestinal mucosa microenvironment in patients with radiation enteropathy (cases, n = 9) with healthy controls (controls, n = 6). Fecal samples were obtained from all cohorts. In the colonoscopy cohort, intestinal mucosa samples were taken. Metataxonomics (16S rRNA gene) and imputed metataxonomics (Piphillin) were used to characterize the microbiome. Clinician- and patient-reported outcomes were used for clinical characterization.

RESULTS

In the acute cohort, we observed a trend for higher preradiotherapy diversity in patients with no self-reported symptoms (P = 0.09). Dynamically, diversity decreased less over time in patients with rising radiation enteropathy (P = 0.05). A consistent association between low bacterial diversity and late radiation enteropathy was also observed, albeit nonsignificantly. Higher counts of Clostridium IV, Roseburia, and Phascolarctobacterium significantly associated with radiation enteropathy. Homeostatic intestinal mucosa cytokines related to microbiota regulation and intestinal wall maintenance were significantly reduced in radiation enteropathy [IL7 (P = 0.05), IL12/IL23p40 (P = 0.03), IL15 (P = 0.05), and IL16 (P = 0.009)]. IL15 inversely correlated with counts of Roseburia and Propionibacterium.

CONCLUSIONS

The microbiota presents opportunities to predict, prevent, or treat radiation enteropathy. We report the largest clinical study to date into associations of the microbiota with acute and late radiation enteropathy. An altered microbiota associates with early and late radiation enteropathy, with clinical implications for risk assessment, prevention, and treatment of radiation-induced side-effects.See related commentary by Lam et al., p. 6280.

Microbial modulation of the gut microbiome for treating autoimmune diseases

Many studies have shown the relationship between autoimmune diseases and the gut microbiome in humans: those with autoimmune conditions display gut microbiome dysbiosis. The big question that needs to be addressed is if restoring eubiosis of the gut microbiota can help suppress the autoimmune condition by activating various immune regulatory mechanisms. Inducing these self-healing mechanisms should prolong good health in affected individuals. Area covered: Here, we review the available clinical and preclinical studies that have used selective bacteria for modulating gut microbiota for treating autoimmune diseases. The potential bacterial candidates and their mechanism of action in treating autoimmune diseases will be discussed. We searched for genetically modified and potential probiotics for diseases and discuss the most likely candidates. Expert commentary: To achieve eubiosis, manipulation of the gut microbiota must occur in some form. Several approaches for modulating gut microbiota include prebiotic diets, antimicrobial interventions, fecal microbiota transplants, and selective probiotics. One novel approach showing promising results is the use of selective bacterial candidates to modulate microbial composition. Use of single microbe for treatment has an advantage as compared to multi-species as microbes grow at different rates and if needed, a single microbe is easy to target.

Roseburia intestinalis inhibits interleukin‑17 excretion and promotes regulatory T cells differentiation in colitis

Roseburia intestinalis (R. intestinalis) is one of the dominant intestinal bacterial microbiota and is decreased in patients with inflammatory bowel disease (IBD). It helps protect colonic mucosa against the development of inflammation and subsequent IBD, however its underlying mechanisms are unclear. The aim of the present study was to evaluate the anti-inflammatory properties of R. intestinalis in vitro and in an animal model of IBD. The effects of R. intestinalis on disease activity index (DAI) scores, intestinal pathology, the expression of interleukin (IL)-17 and the frequency of CD4⁺CD25⁺Foxp3⁺ regulatory T cells (Treg) were evaluated in vivo in a model of 2,4,6-trinitrobenzenesulfonic acid solution (TNBS)-induced colitis. Compared with the control group, TNBS-treated mice had significantly higher secretion of IL-17, higher DAI scores, a lower ratio of Treg, reduced colon lengths and higher histological scores for colon inflammation. The administration of R. intestinalis significantly downregulated the expression of IL-17, increased the ratio of Treg and ameliorated the high DAI scores and the pathological signs of inflammation in the colon compared with mice treated with TNBS alone. Gene expression profiling was also used to detect the expression of IL-17 in human IBD and healthy control specimens. To extend these findings to an in vitro model of inflammation the human colon epithelial cell line NCM460 was stimulated with lipopolysaccharide (LPS) to induce inflammation and co-cultured with R. intestinalis and changes in IL-17 expression were evaluated. R. intestinalis inhibited the LPS-induced secretion of IL-17 by NCM460 cells. In conclusion, these results demonstrate that R. intestinalis inhibits IL-17 secretion and promotes Treg differentiation in colitis, suggesting that R. intestinalis could be of potential use in the treatment of IBD.

The gastrointestinal microbiota and its role in oncogenesis

Advances in research techniques have made it possible to map the microbial communities in the gastrointestinal (GI) tract, where the majority of bacteria in the human body reside. Disturbances in these communities are referred to as dysbiosis and have been associated with GI cancers. Although dysbiosis is observed in several GI malignancies, the specific role of these changes has not been understood to the extent of Helicobacter pylori (HP) in gastric cancer (GC). This review will address the bacterial communities along the GI tract, from the oral cavity to the anal canal, particularly focusing on bacterial dysbiosis and carcinogenesis. Just as non-HP bacteria in the stomach may interact with HP in gastric carcinogenesis, the same may hold true for other GI tract malignancies, where an interplay between microbes in carcinogenesis seems conceivable, especially in colorectal cancer (CRC). In the last part of this review we will discuss the potential mechanisms of bacterial dysbiosis in GI carcinogenesis.

Dietary Proteins Rapidly Altered the Microbial Composition in Rat Caecum

Dietary proteins can alter gut microbial diversity. However, little is known about how gut bacteria respond to dietary proteins during short-term feeding. In the present study, PCR-DGGE analysis was performed to compare changes in gut microbial composition in rat caecum after rats were fed proteins from soy, pork, beef, chicken, fish and casein (control) for 2, 7 and 14 days. On day 2, differences were observed in microbial composition between groups of red meat (pork and beef) and white meat (chicken and fish) proteins. For a certain diet group, microbial composition showed a great change with feeding time. Principle component analysis indicated that the soy protein group showed a good separation in microbial composition from the casein and meat protein groups on days 7 and 14.