Scripties UMCG - Rijksuniversiteit Groningen
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Efficacy of long-chain inulin in supporting hepatitis B vaccination in seniors :Dietary fiber as a predictor of the T cell populations of healthy seniors and the direct and indirect effects of long-chain inulin on the intestinal barrier function

(2018) Visser, H. (Hester)

Summary English
The consumption of dietary fiber has many benefits for human health, which includes its influence on the immune system. Effects of dietary fiber on the barrier integrity of the gut, dendritic cells and intestinal epithelial lymphocytes in the intestinal wall have been described. However, due to differences in the immune status of individuals, these effects may differ among target groups, but this has not been studied in detail yet. Therefore, in the first part of this project, it was investigated whether the amount of dietary fiber intake affects the T cell populations in seniors. Blood samples of 29 seniors were analyzed using flow cytometry to determine the amount and distribution of T cells. Dietary fiber intake was measured with a questionnaire. A regression model was used to analyze the data. Dietary fiber was found to be a significant predictor of the relative percentage of CD4+ and T regulatory cells.
More research is needed on the underlying mechanisms of the effects of dietary fibers. Dietary fibers are fermented in the gut by the intestinal bacteria. The fermentation products, short-chain fatty acids, are taken up by the intestinal epithelial cells, whereafter they can influence the intestinal barrier function. Dietary fibers can also directly influence immune cells. To investigate these mechanisms further, an explorative study on direct and indirect effects of the dietary fiber inulin-type fructans on the barrier integrity of the gut and the gene expression of tight junctions of Caco-2 cells was performed in the second part of this project. In vitro, Caco-2 cells were pre-treated directly and indirectly with long-chain inulin-type fructans and challenged with a stressor (A23187). The barrier integrity and the expression of tight junction genes Claudin-1, Claudin-2, Claudin-8, Zo-1 and Occludin was determined with TEER measurements and a RT-qPCR analysis, respectively. According to this preliminary data, direct stimulation with ITF(l) might have an upregulating effect on the tight junction gene expression and this effect is concentration-dependent.

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