Interplay between dietary fibers and gut microbiota for promoting metabolic health

Metabolic syndrome is a cluster of several metabolic disorders such as insulin resistance, obesity, type 2 diabetes, dyslipidemia, non-alcoholic fatty liver disease and hypertension, whose prevalence has rapidly increased over the last decades. Unhealthy dietary and lifestyle changes have contributed considerably to this rise. Gastrointestinal microbiota has received increasing interest as a preventive or therapeutic target particularly for its impact on the host metabolism. Dietary fibers are substrates for growth of specific beneficial bacterial species and as a result can shift the microbial population towards a (more) healthy composition. Bacterial fermentation products of dietary fibers are bioactive metabolites such as short-chain fatty acids (SCFA) which can regulate various metabolic processes in the mammalian host. Despite the potential impact of dietary fibers on intestinal microbiota and host metabolism, the underlying mechanism of action has not been elucidated in great depth. In this thesis, we aimed to explore the role of different dietary fibers in manipulating gastrointestinal microbiota and subsequently its impact on metabolic health in mouse models. In the first part of the thesis (chapter 2 and 3) we focused on in-depth investigation of dietary fibers and its potential impact on various metabolic parameters. In chapter 4 and 5, we investigated the importance of gastrointestinal microbiota in atheroprotective pathways and whether dietary fiber such β-cyclodextrin could enhance the pathway, using germ-free mice. In chapter 6 we assessed the long-term metabolic health effects of supplementing galacto-oligosaccharide to Western-type diet.