Intestinal cGAS-STING-IFN signalling promotes obesity by downregulating microbiota-derived IAA in male mice.

The gut constantly interacts with both pathogens and dietary signals, but how it balances immune and metabolic responses remains unclear. Here we show that intestinal cGAS, a key DNA sensor, acts as a regulator linking gut immunity to whole-body metabolism. We show that cGAS signalling is activated in the intestines of humans and male mice with obesity, leading to increased type I interferon production and heightened immune activity in intestinal cells. Strikingly, deleting cGAS specifically in intestinal epithelial cells enhances energy expenditure, protects against diet-induced obesity and improves metabolic health. These effects depend on the gut microbiota, particularly Lactobacillus murinus and its metabolite indole-3-acetic acid (IAA), which promotes adipose thermogenesis. Our findings position intestinal cGAS as a key driver of obesity through gut-to-fat signalling and suggest that targeting the intestinal cGAS-microbiota IAA axis could offer promising strategies to combat obesity and related metabolic diseases.