SELECTION OF DIETARY FIBERS FOR GUT HEALTH BASED ON THEIR PHYSICOCHEMICAL PROPERTIES

Abstract

Abstract Fiber under-consumption in the American population has been associated with a rise in several gastrointestinal diseases. In this study, we focused on Ulcerative Colitis (UC) which currently affects 1 million Americans needing effective preventive and treatment strategies. Short-chain fatty acid (SCFA) production by fiber fermentation is linked to an improved gut barrier function. However, physicochemical properties of fibers such as rate of fermentability, solubility, and structure complexity can influence SCFA levels and fiber tolerance by UC patients. The goal is to determine which fiber characteristics are associated with health benefits in UC patients. Sixteen dietary fibers were selected based on different levels of solubility, rate of fermentation and structure complexity. Fibers were subjected to an in-vitro simulation of the upper gastrointestinal digestion before in-vitro fermentation using fecal samples from a healthy individual. Gas production, pH, and SCFA production were measured at different time points during the fermentation. Resistant Maltodextrins, Pectin, Inulin, and Wheat Bran were selected as high and low tolerable and efficient fibers for a second in-vitro fermentation using IBD patient fecal sample and an in-vivo study with IL 10-KO germ-free mice transplanted with fecal microbiome from a healthy individual. DNA was extracted from the in-vitro fecal samples and the 16S rRNA genes of the V3-V4 region were amplified to assess gut bacterial dysbiosis and modulation. Results showed a relationship between fiber physicochemical properties and their roles in gut health. The fermentability rate is one of the major characteristics to be considered, since how fast fiber is fermented is correlated with gas production. SCFA and gas production levels differed significantly in in-vitro fermentation between healthy and IBD fecal samples within each fiber. Bacteria sequencing results showed that the α-and β-diversity were significantly different between IBD and healthy groups. Furthermore, α- diversity was not different between the donors within the fiber treatment, while β-diversity only differed among the fibers within the IBD donor. An increase in the relative abundance of bacteria from the Enterobacteriaceae family in the IBD group may explain the SCFA reduction and the role gut bacterial dysbiosis play in the utilization of these fibers and their potential health benefits. Initial data from the in-vivo study showed differential role of these fibers. Understanding the connection between fiber properties, gut bacterial composition and fiber efficacy in the gut, can significantly aid in the design of clinical trials and future dietary recommendations. Positive impact of our findings will be evidence-based verification of fibers that are well tolerated by healthy individuals and UC patients for the prevention/protection of this disease.