Microbiome-produced nicotinic acid controls colon regional identity and injury susceptibility.

The regionalized structure of the intestinal epithelium is critical for its function, and the risk for certain diseases has a regional bias. However, how regionalization is established and how it influences disease susceptibility remain poorly understood. Here, we investigated the role of the gut microbiome-the regionalized community of microorganisms in the intestinal lumen-in promoting regionalization of the colon. We found that the proximo-distal identity of colonocytes along the organ's length is disrupted in mice lacking a microbiome and that the proximal colonic microbiome produces high levels of nicotinic acid, which induces Pparα expression to establish proximal colonocyte identity. Furthermore, we report that microbiome-driven proximal identity confers protection against tissue injury in the mouse. Finally, we determined that the human colon is regionalized and loses its proximal identity during certain disease states.