High ambient temperature activates a neural circuit for gut glucose uptake in male mice

Heat stress triggers defensive energy demands to prevent cellular damage. Using male mice, we found that exposure to high ambient temperature (HAT) induces an increase in intestinal glucose absorption mediated by sodium/glucose cotransporter 1 (SGLT1). Glucose supplementation alleviated HAT-induced physiological damage in mice. Mechanistically, we found that blocking intestinal vagal motor nerve transmission eliminated HAT's stimulatory effects on intestinal glucose absorption. This suggests that cholinergic motor neurons originating from the dorsal motor nucleus of the vagus (DMV^ChAT) play a crucial role. Transneuronal tracing revealed an ascending pathway from glutamatergic neurons in the medial preoptic area (mPOA^Glu) to the vagus nerve, with corticotropin-releasing factor neurons in the paraventricular nucleus of the hypothalamus (PVN^CRF) acting as a key relay. Inhibiting key neurons in the mPOA^Glu → PVN^CRF → DMV^ChAT circuit mimicked the effects of vagus blockage on HAT-induced intestinal glucose absorption. Our findings establish the brain-vagal-gut pathway as an interoceptive circuit for adapting to HAT challenges.