Gut microbiota in relation to pathogenesis of obesity and type 2 diabetes

Alterations in the gut microbiota composition are strongly associated with the pathogenesis of obesity and Type 2 diabetes (T2DM). In this thesis, we investigated the putative role of the gut microbiota in human metabolic diseases. In this context, intestinal bacteria such as Eubacterium hallii and Ralstonia pickettii showed a negative and positive correlation with glucose tolerance in overweight humans, respectively. We assessed causality of these bacteria in regulation of glucose metabolism in mouse models of overweight and diabetes. We found that, when administered to these mouse models, Eubacterium hallii and Ralstonia pickettii improved and deteriorated glucose metabolism, respectively.
Fecal microbiota transplantation (FMT) is considered as a potential therapy for metabolic diseases characterized by microbial imbalance. We explored the short- and long-term effects of lean donor FMT on glucose metabolism in metabolic syndrome recipients. Lean donor FMT improved peripheral insulin sensitivity and increased relative abundance of fecal Akkermansia muciniphila and Eubacterium ventriosum. Butyrate, a short-chain fatty acid produced by bacterial fermentation of complex carbohydrates, correlates negatively with various parameters that are characteristic of the metabolic syndrome.