Defining the structural and functional properties of select agricultural fibers underlying their immunomodulatory actions

该计划的长期目标是为来自不同常见农产品的选定感兴趣的纤维确定生理上相关的微生物介导的发酵途径，并揭示各种环境下纤维相关免疫调节途径的生化机制。纤维是不可消化的碳水化合物，依靠肠道微生物(细菌和真菌)的发酵分解成可供人类细胞利用的副产品(如短链脂肪酸)。我们之前的工作显示了特定的非生物微生物群落(改变的微生物丰度/多样性)，更重要的是，改变的微生物功能(酶)与降低伯果聚糖纤维发酵有关。这种改变的发酵与SCFA产量的减少和未发酵的ç-果糖与白细胞(巨噬细胞、T细胞和中性粒细胞)免疫调节作用的增加有关，特别是通过Th17细胞途径。我们的初步发现表明，这些纤维的结构因纤维亚型和分离它们的农业来源而不同，在它们的发酵能力和白细胞反应过程中发挥作用，因为聚合度(DP；纤维长度)与炎症体(NLRP3：IL-1？)的激活有关；较高的DP纤维增加了细胞因子的分泌和炎症体基因(例如，IL-1？、IL-23)的表达。拟议研究的短期目标是：(1)描述膳食纤维的结构特征(例如，酚类含量、聚合度)；将从农业食品来源购买或提取膳食纤维(例如-葡聚糖、低聚半乳糖、菊粉)。结构特征将与白细胞对每种膳食纤维化合物的反应的细胞途径相关联，利用中尺度的发现和ELISA法进行研究；(2)确定参与调节微生物区系培养的调节其纤维发酵活动的功能(酶)的肠道微环境因素(例如，pH、代谢物)；(3)揭示特定微生物酶在调节纤维发酵过程中的作用；以及(4)利用靶向显微镜和途径分析(qPCR、Western blotting、ELISA法)，从机械上深入了解纤维与微生物的相互作用如何影响白细胞的反应(炎症体途径的调节)。这项计划将促进我们对膳食纤维物理特性在调节与白细胞和发酵微生物相互作用中的作用的基本理解，同时为HQP提供食品化学、微生物学和免疫学的多学科培训机会。我们的工作将有助于更好地理解环境因素(微环境和农产品)与驻留在肠道粘膜(纤维发酵的生理部位)中的白细胞群之间发生的相互作用。

The long-term goal of this program is to define the physiologically relevant microbe-mediated fermentation pathways for select fibers of interest, sourced from different common agricultural products and to uncover the biochemical mechanisms underlying fiber-associated immunomodulatory pathways in various environmental settings. Fibers are nondigestible carbohydrates that rely on fermentation by intestinal microorganisms (bacteria and fungi) for their decomposition into byproducts that can be utilized by human cells (e.g., short chain fatty acids). Our previous work showed specific dysbiotic microbial communities (altered microbe abundance/diversity), and more significantly, altered microbe functions (enzymes) were associated with reduced ß-fructan fibre fermentation. This altered fermentation was associated with reduced production of SCFA and increased immunomodulatory interactions of unfermented ß-fructans with leukocytes (macrophages, T cells, and neutrophils), particularly through Th17 cellular pathways. Our preliminary findings suggest that the structure of these fibers, which differs between fiber subtypes and the agricultural source from which they are isolated, plays a role in their fermentability and in leukocyte response processes, as the degree of polymerization (DP; length of the fiber) was associated with inflammasome (NLRP3:IL-1ß) activation; higher DP fibres increased cytokine secretion and expression of inflammasome genes (e.g., IL-1ß, IL-23). The short-term objectives of the proposed research are: (1) profile the structural features (e.g., phenolic content, degree polymerization) of dietary fibres (e.g., ß-glucans, galatooligosaccharides, inulins); fibres will be either purchased or extracted from agricultural food sources. Structural features will be correlated with the cellular pathways of leukocyte responses to each of the dietary fibre compounds, examined using mesoscale discovery and ELISA; (2) identify gut microenvironment factors (e.g., pH, metabolites) involved in regulating the functions (enzymes) of microbiota cultures that mediate their fibre fermentation activities; (3) reveal the role of specific microbial enzymes in mediating fibre fermentation processes; and (4) provide mechanistic insight into how fibre-microbe interactions impact leukocyte response (modulation of inflammasome pathways) using targeted microscopy and pathway analysis (qPCR, western blotting, ELISA). This program will advance our fundamental understanding of the role of dietary fibre physical properties in regulating interactions with leukocytes and fermentative microbes while providing multidisciplinary training opportunities for HQP in food chemistry, microbiology and immunology. Our work will aid to improve understanding of interactions that occur, between environmental factors (microenvironment and agricultural products) and leukocyte cell populations that reside in the intestinal mucosa, the physiological site of fibre fermentation.