Sympathetic Neural Circuitry Controlling Whole-body Metabolism

The brain’s sympathetic neurons—the nerves that prime the body for action—also control whether we burn fat or store it, but scientists have never been able to see exactly which neurons do what. This matters because obesity is linked to a breakdown in how the brain manages energy balance. The sympathetic nervous system is vast and tangled, with thousands of neurons packed into tiny clusters along the spine. Until now, researchers could not map these circuits at the level of individual cells, so they could not tell which neurons trigger fat burning and which control heart rate or blood pressure. The team is building a complete molecular and anatomical atlas of these neurons using light-sheet microscopy that images entire ganglia at single-cell resolution, machine learning to decode gene activity, and genetic tools to test each neuron’s function. They have already discovered a new type of inhibitory interneuron in the peripheral nervous system—something never seen before—that appears in ganglia that do not connect to the heart. If this atlas succeeds, it could reveal how to selectively activate fat-burning circuits without affecting heart function, opening a path toward anti-obesity treatments that avoid cardiovascular side effects. This is fundamental neuroscience: the immediate payoff is understanding how the brain organises whole-body metabolism, not a therapy. But mapping these circuits is the necessary first step before anyone can design drugs or devices that target them.