When an animal faces danger, it must divert energy to the muscles and brain to support escape behaviors and rapid threat learning. That surge of energy depends on quick elevations in blood glucose levels. Yet how emotional brain centers drive metabolic adaptations to stress has been unclear. Work from the laboratories of Sarah Stanley, MBBCh, PhD, and Paul Kenny, PhD, maps a dedicated “amygdala-liver axis” that links social and physical stressors directly to liver glucose production, which operates largely independently of the classic adrenal and pancreatic hormone systems.

The study focuses on a population of neurons in the medial amygdala (MeA) that project to the ventromedial hypothalamus (MeA-VMH). These neurons are rapidly engaged by different types of stressors to elicit rapid rises in blood glucose levels. Selectively activating these neurons in otherwise unstressed mice is sufficient to induce a robust hyperglycemic response without altering levels of glucagon, insulin, or stress hormones. Circuit tracing showed that these MeA-VMH neurons elevate blood glucose levels via the sympathetic nervous system to drive glucose production in the liver. 

With repeated stress exposure, these MeA-VMH neurons become progressively less responsive, resulting in long-term metabolic consequences. Mice with impaired MeA-VMH signaling gain more weight than control mice and develop elevated blood glucose and impaired glucose tolerance when they have access to a high-fat diet. These findings define an evolutionarily conserved brain circuit that orchestrates metabolic responses to stress by modifying liver function, suggesting that adaptations in this amygdala-liver axis may link chronic stress to metabolic disorders, including type 2 diabetes.