Aryl Hydrocarbon Receptor Is Required for Fasting-Induced Improvement of Gut Barrier Integrity in Caenorhabditis elegans

The intestinal barrier governs organismal health through nutrient absorption, microbial homeostasis, and immune surveillance. While calorie restriction (CR) enhances metabolic health, the molecular mechanisms underlying its beneficial effects on gut integrity remain unclear. Here, we demonstrate that the aryl hydrocarbon receptor (AHR), a conserved xenobiotic sensor and metabolic regulator, is essential for CR-mediated improvements in intestinal function. Using <i>Caenorhabditis elegans</i> (<i>C. elegans</i>), we subjected wild-type (N2) and AHR-deficient strains (CZ2485 and ZG24) to ad libitum feeding (AL), intermittent fasting (IF), or complete food deprivation (FD). In wild-type animals, intermittent fasting markedly reduced intestinal permeability and bacterial burden while enhancing mitochondrial function and reducing reactive oxygen species. Complete food deprivation conferred modest benefits. Remarkably, these protective effects were severely compromised in AHR mutants, which exhibited increased gut leakage, bacterial colonization, and mitochondrial oxidative stress under fasting conditions. These findings establish AHR as a critical mediator of fasting-induced intestinal resilience, revealing a previously unrecognized regulatory axis linking metabolic sensing to gut barrier homeostasis. Our work illuminates fundamental mechanisms through which calorie restriction promotes gastrointestinal health and identifies AHR-dependent pathways as promising therapeutic targets for metabolic and inflammatory distress affecting the gut-systemic interface.