Project Title: Metabolic effect of fructose in intestine induces gut microbiota dysbiosis Abstract. Emerging evidence has demonstrated that gut microbiota dysbiosis plays a causative role in the development of obesity, type 2 diabetes and NAFLD. Gut “physiologic hypoxia” is key to maintaining a balanced gut microbiota and gut barrier function. Disturbance of gut “physiologic hypoxia”, namely oxygenation, results in gut microbiota dysbiosis. Our preliminary studies have shown that chronic feeding with either fructose or glucose induces gut microbiota dysbiosis in a similar manner in rats and mice. Moreover, both daily gavage and chronic feeding with fructose or glucose results in intestinal oxygenation as shown by HIF-1 alpha reporter (ODD-luc) mice, and this effect is more robust with glucose. Given that fructose is preferentially metabolized under hypoxia, and glucose can be rapidly converted to fructose via the polyol pathway, the proposed studies will test the hypothesis that fructose metabolism in the intestine results in metabolic reprogramming which switches the host metabolic pathway from mitochondrial β-oxidation to glycolysis and consumes less oxygen. This, in turn, leads to intestinal oxygenation, subsequent inhibiting the growth of obligate anaerobic bacteria and facilitating the expansion of pathogenic bacteria. The hypothesis will be tested in three specific aims: Aim 1. Determine whether fructose induces metabolic reprogramming in intestinal epithelial cells and determine if this results in gut microbiota dysbiosis. We will test the hypothesis that fructose metabolism in the intestine results in metabolic reprogramming and leads to intestinal oxygenation, which in turn, results in gut microbiota dysbiosis. Aim 2. Determine whether modulation of glycolytic activity in intestinal epithelial cells alters gut microbiota composition. We hypothesize that genetic modulation of glycolytic activity via 6-phosphofructo-2-kinase/fructose-2,6- bisphosphatase (PFK2) in intestinal epithelial cells results in altered oxygen consumption rate which in turn leads to the alteration of gut microbiota. Aim 3. Determine whether the metabolic effect of fructose in intestine contributes to the development of NAFLD. We will test the hypothesis that the metabolic effects of fructose in intestine on the development of NAFLD is mediated by gut microbiota dysbiosis.