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Abteilung Physiologie des Energiestoffwechsels (EST)

Projekt 3 : Gut bacteria and energy metabolism

Karolin Weikunat, Sara Schumann

Gut bacteria have been shown to affect energy metabolism of the host and to play an important role in the development of obesity by affecting the host’s energy and substrate metabolism. This is the focus of a joint project with the Department of Gastrointestinal Microbiology (GAMI, Prof. M. Blaut). Using gnotobiotic mouse models we could show that a single bacterial species (Clostridium ramosum) is able to promote high-fat diet-induced obesity (Woting et al. 2014). In our group we are now focusing on the role of dietary fibers and their fermentation products, short-chain fatty acids (SCFA), in energy and substrate metabolism. In the literature, contradictory effects of fibers and SCFA are described: On one hand they increase satiety, but on the other hand they provide additional energy and promote obesity development. We investigated the effects of fermentable (inulin) and non-fermentable (cellulose) fibers on high fat diet-induced obesity in gnotobiotic mice colonized with a simplified human microbiota. After 6 weeks we observed an increased energy digestion after inulin feeding without effects on body weight or composition. The additional energy provided by the inulin-diet rather led to an increased bacterial proliferation. Inulin supplementation also resulted in significantly elevated concentrations of total SCFA in cecum and portal vein plasma, with a reduced cecal acetate:propionate ratio. It further decreased hepatic expression of genes involved in lipogenesis and fatty acid elongation/desaturation and accordingly, plasma and liver phospholipid composition was altered by fermentable fiber (Weitkunat et al., 2015). Taken together, these data indicate that inulin has mainly positive effects on the lipid metabolism – at least in the short term. We are currently exploring the molecular mechanisms and the long term effects of SCFA.

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