Bile acids (BAs) comprise a diverse group of cholesterol metabolites with multiple modes of action. Much of the role of BAs and their receptors in energy homeostasis has been discerned from studies on genetic and/or pharmacologic manipulations. Additionally, changes in BA metabolism and transport have been reported in settings of insulin resistance, obesity, and liver dysfunction. Thus, BA-based interventions have been proposed for treatment of metabolic diseases. However, the heterogeneity of endogenous BAs lends to different affinities for and potencies in activating the various BA receptors, and the effects of altering BA composition per se are incompletely understood. In this dissertation, we aimed to characterize the effects of altering BA composition by stimulating intestinal organoids with distinct BA pools modeled after those in humans and mice. Unexpectedly, we found that BA composition regulated expression of the manganese transporter encoded by Slc30a10 and manganese efflux from cells, suggesting a role for BAs in metal homeostasis. We also identified genes that were similarly and differentially regulated by the distinct mouse and human BA pools. Overall, our studies reveal a pathway by which BAs could modulate micronutrient metabolism, which might also mediate known effects of BAs on macronutrient metabolism.

Abstract not available

Some ill. mounted. Bibliography: leaves 109-129.

Thesis (M.S.)--University of Delaware, 2006. / Principal faculty advisor: Mary C. Farach-Carson, Dept. of Biological Sciences. Includes bibliographical references.

Thesis (Ph. D.)--University of Washington, 2003. / Vita. Includes bibliographical references (leaves 99-113).

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2009. / Härtill 3 uppsatser.

published_or_final_version / Microbiology / Master / Master of Science

Probiotics are defined as live microorganisms that confer beneficial effects to health when administered in a sufficient amount. In previous studies about the beneficial effects of probiotic bacteria to health, particularly in the fields of intestinal mucosa defence responses, specific probiotics, in a strain-dependent manner, show some potential to reinforce the integrity of intestinal epithelium and/or regulate some immune components. However, the mechanisms involved in the interactions between probiotics or bioactive components of probiotics with the intestinal epithelium are still not yet clearly defined or systematically studied. Among all possible routes of modulation by probiotics of intestinal epithelial cell–mediated defence responses, modulations of mucin and trefoil factor expression as well as the cytokine profiles are important components of the innate and adaptive mucosal immune responses of the intestinal epithelial cells and are considered to play important role in the intestinal defence responses against pathogenic bacteria. This thesis examined and characterized the in vitro modulation effects by metabolic products of two commonly studied probiotics bacterial strains, Lactobacillus rhamnosus GG (LGG) and Escherichia coli Nissle 1917 (EcN), on the intestinal epithelial cell-mediated defence responses. It was found that the metabolic products of EcN decreased the transcriptional levels of secretory mucins MUC5AC, MUC5B and MUC2 while LGG metabolic products only down-regulated that of MUC5AC. In partial agreement with the reduction of mucin gene expression levels, intracellular MUC5B and MUC2 mucin expression was reduced by EcN metabolic products and MUC5AC and MUC2 by the metabolic products of LGG. In contrast, the extracellular MUC5AC and MUC2 mucin expression tended to increase upon the effects of both LGG and EcN metabolic products, which might result from accumulative effects of the modulation on extracellular mucin secretion during the time of treatment or the differential responsiveness of cellular mucin gene and protein expression upon stimulation. The expression of trefoil factor 3 in both gene and protein levels upon the effects of EcN metabolic products while those of LGG enhanced the transcriptional but not protein level. As for the modulation of cytokine profiles, LGG metabolic products mainly influence the secretion of anti-inflammatory cytokines such as IL-4, IL-5 and IL-10 in a moderate manner while EcN metabolic products exerted broad pro-inflammatory potential to the intestinal epithelial cells by inducing the secretion of pro-inflammatory cytokines such as IL-8, MCP-1, TGF-α, TNF-α and GM-CSF, which indicated that the metabolic products of LGG and EcN might initiate differential signaling pathway to influence the intestinal epithelial adaptive immune responses. To conclude, the present research provides evidence to substantiate that LGG and EcN display differential modulation mechanisms of the intestinal epithelial cell-mediated defence responses that involve intestinal-cell mediated mucin and trefoil factor secretion as well as pro- and anti-inflammatory cytokine expression. / published_or_final_version / Biological Sciences / Master / Master of Philosophy

published_or_final_version / Physics / Master / Master of Philosophy

No description available.