Functional and Nutritional Characteristics of Natural or Modified Wheat Bran Non-Starch Polysaccharides: A Literature Review

Wheat bran (WB) consists mainly of different histological cell layers (pericarp, testa, hyaline layer and aleurone). WB contains large quantities of non-starch polysaccharides (NSP), including arabinoxylans (AX) and β-glucans. These dietary fibres have long been studied for their health effects on management and prevention of cardiovascular diseases, cholesterol, obesity, type-2 diabetes, and cancer. NSP benefits depend on their dose and molecular characteristics, including concentration, viscosity, molecular weight, and linked-polyphenols bioavailability. Given the positive health effects of WB, its incorporation in different food products is steadily increasing. However, the rheological, organoleptic and other problems associated with WB integration are numerous. Biological, physical, chemical and combined methods have been developed to optimise and modify NSP molecular characteristics. Most of these techniques aimed to potentially improve food processing, nutritional and health benefits. In this review, the physicochemical, molecular and functional properties of modified and unmodified WB are highlighted and explored. Up-to-date research findings from the clinical trials on mechanisms that WB have and their effects on health markers are critically reviewed. The review points out the lack of research using WB or purified WB fibre components in randomized, controlled clinical trials.

Effect of Wheat-Derived Arabinoxylan on the Gut Microbiota Composition and Colonic Regulatory T Cells

The health benefits of wheat-derived arabinoxylan, a commonly consumed dietary fiber, have been studied for decades. However, its effect on the gut microenvironment and inflammatory bowel disease remains unclear. The objective of this study was to understand the effect of wheat-derived arabinoxylan on gut microbiota, colonic regulatory T cells (Tregs), and experimental colitis. In this study, healthy and chronic colitis model mice were fed chow containing cellulose or wheat-derived arabinoxylan for 2-6 weeks and subjected to subsequent analysis. A 16S-based metagenomic analysis of the fecal DNA revealed that Lachnospiraceae, comprising butyrate-producing and Treg-inducing bacteria, were overrepresented in arabinoxylan-fed mice. In line with the changes in the gut microbiota, both the fecal butyrate concentration and the colonic Treg population were elevated in the arabinoxylan-fed mice. In a T cell transfer model of chronic colitis, wheat-derived arabinoxylan ameliorated body weight loss and colonic tissue inflammation, which may, in part, be mediated by Treg induction. Moreover, wheat-derived arabinoxylan suppressed TNFα production from type 1 helper T cells in this colitis model. In conclusion, wheat-derived arabinoxylans, by altering the gut microenvironment, may be a promising prebiotic for the prevention of colitis.

The effects of dietary fibers from rice bran and wheat bran on gut microbiota: An overview

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The physicochemical properties of DFs are related to their digestive behaviors.

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DFs are degraded in the intestines due to the fermentation of gut microbiota.

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DFs and their metabolites exert beneficial effects on gut microbiota.

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The fermentation of DFs improve gut barrier function and immune function.

Whole grain is the primary food providing abundant dietary fibers (DFs) in the human diet. DFs from rice bran and wheat bran have been well documented in modulating gut microbiota. This review aims to summarize the physicochemical properties and digestive behaviors of DFs from rice bran and wheat bran and their effects on host gut microbiota. The physicochemical properties of DFs are closely related to their fermentability and digestive behaviors. DFs from rice bran and wheat bran modulate specific bacteria and promote SAFCs-producing bacteria to maintain host health. Moreover, their metabolites stimulate the production of mucus-associated bacteria to enhance the intestinal barrier and regulate the immune system. They also reduce the level of related inflammatory cytokines and regulate Tregs activation. Therefore, DFs from rice bran and wheat bran will serve as prebiotics, and diets rich in whole grain will be a biotherapeutic strategy for human health.

Wheat Bran Intake Enhances the Secretion of Bacteria-Binding IgA in a Lumen of the Intestinal Tract by Incrementing Short Chain Fatty Acid Production Through Modulation of Gut Microbiota

Wheat bran, a by-product generated in large amounts during wheat processing, consists of 36.5% to 52.4% total dietary fiber. In this study, we investigated the effects of wheat bran intake on the intestinal tract immune system through the modulation of gut microbiota. Balb/c mice were fed with AIN-93G diets containing wheat bran with 2 different particle sizes (average particle size of 53 µm: powdered wheat bran; PWB, and 350 µm: granulated wheat bran; WB) as dietary fibers for 4 weeks. In the wheat bran intake groups, short chain fatty acids (SCFAs: acetic acid, propionic acid, and butyric acid) in the feces were increased after the intake of both particle-size diets, especially in the PWB group, in which the increase occurred immediately. 16S rRNA-based metagenomics of the fecal microbiota revealed that the Shannon Index (α-diversity) and weighted UniFrac distances (β-diversity) in wheat bran intake groups were significantly higher than those in the Control group, and the ratio of the certain family within the order Clostridiales in the fecal microbiota was increased after wheat bran intake, probably some including SCFA-producing bacteria. CXCR5, which is a key surface marker expressed on T follicular helper (Tfh) cells, tended to increase at the expression level in wheat bran intake groups. In addition, the amounts of secretory immunoglobulin A (IgA) and the proportion of IgA-binding bacteria in the feces from wheat bran intake groups were significantly higher than those from the Control group. These findings suggest that wheat bran may enhance Tfh-mediated IgA production in the intestine by SCFA increment through the modulation of gut microbiota and is expected to maintain and improve a healthy intestinal environment.