Host-microbiota interaction induces inflammation and impairs glucose metabolism in a bi-phasic fashion during colonization of germ-free mice

Gut microbiota modulates adiposity and glucose metabolism in humans and mice. Colonization of germ-free (GF) mice is a tool to study the effect of bacteria on metabolism. Here we investigated how colonization of GF mice affected kinetics of adiposity and glucose metabolism. Colonization resulted in a bi-phasic glucose impairment: the first phase occurring within 3 days of colonization (early phase) and the second 14-28 days after colonization (delayed phase). The early phase was associated with an inflammatory response and independent of adiposity, while the delayed phase was mostly ascribed to adipose tissue expansion and inflammation. Species richness and overall microbiota composition rapidly changed during the first week of colonization. The interaction between the gut environment and the immune system leads to the selection of specific bacteria. Re-colonization of antibiotic treated mice displays only the delayed phase of glucose impairment and adiposity, suggesting that the early phase may be unique to colonization of GF mice. Our results provide new insight on the host-microbiota interaction during colonization of GF mice in affecting adiposity and glucose metabolism.