Project description:Chronic diseases arise when pathophysiological processes achieve a steady state by self-reinforcing. Here, we explored the possibility of a self-reinforcement state in a common condition, chronic constipation, where alterations of the gut microbiota have been reported. The functional impact of the microbiota shifts on host physiology remains unclear, however we hypothesized that microbial communities adapted to slow gastrointestinal transit affect host functions in a way that reinforces altered transit, thereby maintaining the advantage for microbial self-selection. To test this, we examined the impact of pharmacologically (loperamide)-induced constipation (PIC) on the structural and functional profile of altered gut microbiota. PIC promoted changes in the gut microbiome, characterized by decreased representation of butyrate-producing Clostridiales, decreased cecal butyrate concentration and altered metabolic profiles of gut microbiota. PIC-associated gut microbiota also impacted colonic gene expression, suggesting this might be a basis for decreased gastrointestinal (GI) motor function. Introduction of PIC-associated cecal microbiota into germ-free (GF) mice significantly decreased GI transit time. Our findings therefore support the concept that chronic diseases like constipation are caused by disease-associated steady states, in this case, caused by reciprocating reinforcement of pathophysiological factors in host-microbe interactions. We used microarrays to detail the global gene expression profile in the proximal colon smooth muscle tissues of germ-free, conventionalized, or specific pathogen free mouse C57Bl/6 female and male specific pathogen free (SPF) mice were bred and housed in the animal care facility at the University of Chicago. Mice of 8–10 weeks of age were treated with 0.1% loperamide in the drinking water for 7 days. Age matched, germ-free (GF) C57Bl/6 mice were gavaged orally with cecal luminal contents harvested from control or loperamide-treated C57Bl/6 donor mice. Recipient mice were sacrificed 4 weeks post-colonization.
Project description:Small intestinal bacterial overgrowth (SIBO) has been implicated in symptoms associated with functional gastrointestinal disorders (FGIDs), though mechanisms remain poorly defined and treatment involves non-specific antibiotics. Here we show that SIBO based on duodenal aspirate. culture reflects an overgrowth of anaerobes, does not correspond with patient symptoms, and may be a result of dietary preferences. Small intestinal microbial composition, on the other hand, is significantly altered in symptomatic patients and does not correspond with aspirate culture results. In a pilot interventional study we found that switching from a high fiber diet to a low fiber, high simple sugar diet triggered FGID-related symptoms and decreased small-intestinal microbial diversity and small-intestinal permeability. Our findings demonstrate that characterizing small intestinal microbiomes in patients with gastrointestinal symptoms may allow a more targeted antibacterial or a diet-based approach to treatment.