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Goal: To develop a novel dietary strategy by which the human gut microbiota can be successfully modulated to improve intestinal barrier function and prevent endotoxemia. We hypothesize that a synbiotic combination, if rationally selected by ecological considerations and in vivo selection, will show improved ecological and physiological performance in the human gastrointestinal tract and provide more benefits to human individuals than other currently available synbiotics. Specifically, we will assess whether this specific synbiotic approach will improve intestinal barrier function in obese human subjects, thereby preventing endotoxemia and metabolic inflammation. <P>Objectives: 1. To compare the ability of an in-vivo selected, rationally designed synbiotic preparation versus a conventional synbiotic containing a well-studied probiotic to alter the gut microbiota in obese individuals. 2. To test if the prebiotic carbohydrate included in the two synbiotic preparations supports colonization and metabolic activity of probiotic strains in the human gut. 3. To compare the ability of the two synbiotic preparations to improve intestinal permeability and endotoxemia in a population of obese individuals and to determine if the synbiotics perform better than their pro- and prebiotic constituents. 4. To assess associations between the gut microbiota and the administered test strains with biomarkers for translocation and endotoxemia in humans consuming the synbiotic combinations and the probiotic and the prebiotic alone. <P>Our synergistic set of aims will allow us to test the impact of synbiotic preparations on barrier functions and markers for endotoxemia (Objective 3), on population size and metabolic activity of the probiotic (Objective 2), and gut microbiota composition (Objective 1), and determine the associations between microbial components of the gut microbiota and host metabolic parameters (Objective 4). Based on the literature that is available on the role of bifidobacteria and barrier function and endotoxemia, we expect that either the synbiotic will significantly contribute to metabolic improvements when compared to the control placebo, and that correlation between between the Bifidobacterium population and metabolic markers will be detectable.
Non-Technical Summary:<br/>
In this proposal, we intend to test the ecological and therapeutic functionality of two synbiotic combinations including strains of bifidibacteria and the prebiotic galactooligosaccharide (GOS) in a human clinical trial. One of the probiotic strains was selected by a novel procedure: In vivo selection. We hypothesize that synbiotic preparations will improve intestinal barrier function in obese adults subjects, thereby preventing endotoxemia and metabolic inflammation, physiologically relevant functions that are increased in obese individuals.
<br/>Our objectives are to: (1) compare the ability of the synbiotic preparations to alter the gut microbiota in obese individuals; (2) test if GOS supports colonization and metabolic activity of the probiotic strains in the human gut; (3) compare the ability of the two synbiotic preparations to improve intestinal permeability and endotoxemia in obese subjects; and (4) assess associations between the gut microbiota and the test strain with biomarkers for translocation and endotoxemia. These objectives directly address the priorities of Food Safety, Nutrition, and Health Program Area 2, Function and Efficacy of Nutrients (A1341), by "improving the function and efficacy of nutrients and dietary bioactive components in promoting health" and by "focusing on the role of bioactive components in food in preventing inflammation or promoting gastrointestinal health".
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Approach:<br/>
The study will be organized as a randomized, placebo-controlled, parallel-arm clinical trial conducted at Rush University Medical Center (RUMC). The trial will include six, 3-week treatments using obese (BMI=30.0-40.0 kg/m2) subjects who are healthy, but permitting subjects with elevated liver enzymes due to fatty liver and metabolic syndrome. A total of 180 subjects will be recruited and randomly assigned to six groups (n/group = 30): One placebo, two synbiotic, two probiotic, and one prebiotic.
<br/>Objective 1: The effect of the dietary treatments on the fecal microbiota composition will determined by characterized by pyrosequencing of 16S rRNA tags. Cell numbers of the probiotic strains and total bifidobacteria will be determined by strain and species specific quantitative real-time PCR (qRT-PCR).
<br/>Objective 2: While DNA-based analytical procedures provide a phylogenetic picture of the community, they do not reflect metabolic activity because the DNA could originate from living active cells, living dormant cells, lyzed cells, or dead cells. We will therefore determine the metabolic activity of the probiotic strains, we will compare ratios of rRNA and rDNA by using qRT-PCR.
<br/>Objective 3: Clinical parameters of intestinal barrier function and endotoxemia will be measured in the subjects. Both intestinal barrier function and endotoxemiaare biomarkers that have been linked to obesity. Intestinal permeability will be determined by administration of oral sugars and analysis of subsequent sugar excretion in collected urine. Endotoxin will be measured in serum by Limulus Amebocyte Lysate QCL-1000, and Lipopolysaccharide binding protein (LBP) was measured in plasma using an ELISA kit. A Complete Metabolic Panel will be performed to assess the effect the treatments on each patient's basic physiology. Measurements include sodium, potassium, chloride, CO2, blood urea nitrogen, creatinine, glucose, total protein, albumin, calcium, total bilirubin, alkaline phosphatase, aspartate amino-transferase, alanine aminotransferase, and anion gap.
<br/>Objective 4: The central objective of this study is to determine links between diet, the microbiome, and host metabolic parameters associated with intestinal barrier function. For this purpose, associations between host metabolic and immunological markers, all taxa in the gut microbiota (analyzed at different taxonomic levels) and Bifidobacterium populations will be assessed by multiple-correlation analysis using Pearson's correlation tests.