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GRK 1482 Jahrbuch 2011-2014

Abstract Intestinal bacteria exhibit unique metabolic functions that influence the host energy balance. However, the components of the energy ba- lance affected by the gut microbiota remain to be elucidated. Inbred mouse strains with a distinct susceptibility to diet-induced obesity (DIO) will be used to study i) the impact of the gut bacteria on key parameters of the energy balance equation as well as ii) the influence of the microbial community on DIO resistance. iii) A genetic mouse model of obesity will help to identify gut metabolites important for si- gnaling between bacteria and host. Introduction Energy balance results from the energy assimi- lated in the body and the energy expenditure dis- sipated as heat. Disturbances in this finely tuned balance leads either to loss or gain of body mass. Both host and environmental factors contribute to the increasing prevalence of obesity in Westernized countries. There is a growing body of evidence sug- gesting that intestinal bacteria affect the host ener- gy metabolism. The bacterial density and diversity in the gut incre- ases from proximal to distal parts resulting in mas- ses comparable in size with the spleen or a single kidney. The gut microbiota thus constitutes a meta- bolically significant component of the total living mass. Hence, intestinal microbiota is supposed to have mammalian-like mass specific metabolic ra- tes [1]. Recent studies in obese humans as well as gene- tically and diet-induced obese (DIO) mice indicated shifts in dominant gut bacterial populations com- pared to lean controls [2]. Further evidence for the role of gut microorganisms in energy homeosta- sis comes from DIO resistant germfree mice that gained body fat after microbiota transplantation. Enhanced energy extraction by bacterial fermenta- tion enzymes is one of the most promising mecha- nisms discussed [3]. Only few studies dealt with microbiota transfer using cohousing of mice already conventionally colonized. Cohousing of individuals in a group of genetically divergent cohabitants provides a more realistic scenario to study the impact of the micro- bial environment and may be of clinical relevance. Although it is clear that the gut microbiota may con- tribute to the obesity development, it is unknown which role the bacteria have in distinct mouse strains resistant to DIO. The identification of bacterial metabolites may help to find novel mechanisms involved in the interplay between microbiota and host energy metabolism. ASSOCIATED FELLOWS Page 74 | GRK Progress Report 2011-2014 Raphaela Schurer (M.Sc.) Molecular Nutritional Medicine PhD The impact of the gut microbiota on the host energy metabolism

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