Fig. 1.

The intestinal epithelial cell is the orchestrator of gut health. (A) Nutrients, prepared for absorption by the digestive enzymes, are taken up through the transcellular pathway (green arrow) by a receptor-mediated (yellow triangles) process, while the intercellular spaces are sealed by tight junctions (black arrows). (B) Gut leakage is due to opening-up of the intercellular pathway (red arrows) following tight junction loss or even complete epithelial cell loss. The ensuing uncontrolled inside-out and outside-in fluxes allow contact of potentially harmful intestinal content with the Toll-like and other receptors that trigger inflammation.