Digestive Disease Week AGA Symposium: Prebiotics and Probiotics

In recent years, there is growing interest in alternative treatments for both inflammatory bowel disease and irritable bowel syndrome. Clinical trials are underway to test the potential of probiotics and their metabolic substrates, which are called prebiotics. The underlying principle is that the microbiome might be targeted by providing the metabolic fuel (prebiotics) needed for the growth and expansion of beneficial microorganisms, or by directly administering such microorganisms (probiotics) to the affected host. So far, clinical trials have shown mixed results for prebiotics, depending on the diagnosis. On the other hand, probiotic treatment has revealed more promising results for beneficial outcomes. Examples of probiotics used in these trials are Lactobacillus rhamnosus GG (LGG), Lactobacillus reuteri DSM 17938, and the probiotic mixture VSL#3.

This rapidly evolving and promising field was discussed in several short talks during the session “Prebiotics and Probiotics” at this year’s Digestive Disease Week (DDW) in Washington, D.C. The overall goal of this session was to understand the role of prebiotics (such as arabinoxylans) and probiotics on gut barrier function.

Distinct Prebiotic Properties of Arabinoxylans

Bouke Salden, a Ph.D. student from Maastricht University, presented a talk called ‘Arabinoxylans Show Distinct Prebiotic Properties and May Affect Intestinal Barrier Function’. Arabinoxylans (AX) are the most abundant non-digestible carbohydrates present in wheat and represent a novel class of potential prebiotic. Preliminary data from a randomized, double-blind, placebo-controlled trial showed that AX treatment significantly increased the production of total fecal short-chain fatty acids and the gene transcription of claudin-3 (which encodes a tight junction protein) in a group of overweight and obese subjects. Results from microbiota sequencing were still pending.

Stine Hald, from Aarhus University, gave a presentation about ‘A Diet Rich in Arabinoxylan and Resistant Starch Increases Colonic Butyrate Concentration and Expression of Tight Junction Protein Occludin and Decreases Fecal Calprotectin in Subjects With Metabolic Syndrome’. She concluded that consumption of a 4-week diet rich in AX and resistant starch (RS) increased fecal butyrate and colonic occludin expression and decreased fecal calprotectin expression compared to a Western-style diet, suggesting an enhanced colonic defense barrier in subjects with metabolic syndrome.

LGG as a Probiotic

Fang Yan, from Vanderbuilt University, talked about ‘A Probiotic-Derived Protein Stimulates IgA Production Through Up-Regulation of APRIL and BAFF in Intestinal Epithelial Cells’. She showed data suggesting a mechanism for IgA production in the intestine, which is dependent on p40, an LGG-driven protein, that stimulates APRIL and BAFF expression in mouse small intestinal epithelial cells.

Cristiano Pagnini, from Sapienza University in Rome, presented a talk called ‘Mucosal Adhesion and Anti-Inflammatory Effect of Lactobacillus rhamnosus GG in Human Colonic Mucosa Evaluated In Vivo and in an Experimental Ex Vivo Model: A Proof [of] Concept Study’. He showed in vivo and ex vivo data on a proof of concept study of LGG and its effect on the human colonic mucosa. Studying cytokine expression and adhesion in an ex vivo organ culture model, he demonstrated, amongst other things, that IL-17 and TNFα expression were decreased in the presence of LGG.

Non-Digestible Polysaccharides and Inulin as Prebiotics

John-Peter Ganda Mall, from Örebro University, presented, ‘Selected Non-Digestible Polysaccharides Attenuate Ex Vivo Induced Mast Cell Hyperpermeability in Colonic Biopsies’. His data were based on permeability assays from colonic biopsies using different compounds of non-digestible polysaccharides in the recently established ‘Ussing chamber system’ to study gut barrier function.

Christina M. van der Beek, from Maastricht University Medical Center, presented a talk called ‘The Prebiotic Inulin Enhances Fat Oxidation and Improves Metabolic Parameters in Overweight Males’. She concluded that replacement of digestible carbohydrates with fermentable carbohydrates (inulin) acutely affects whole body metabolism, especially postprandial fat oxidation and metabolic markers in overweight males. These findings may be viewed beneficial regarding body weight control and insulin sensitivity.

Summary

It is evident that prebiotics and probiotics represent a rapidly evolving and promising field, especially regarding recent discoveries surrounding the human microbiome. More targeted studies will reveal what strains should be used in various clinical settings and in what doses. Additionally, it is expected that updated or new regulatory frameworks will be put in place in the near future considering the recent findings regarding probiotics and the microbiome.