Brain’s Glycogen-Fueled Neurons Prime the Body for Food, Revealing New Obesity Target

Even before the first bite, the brain readies the body for a meal. The scent of food cooking can prompt signals that travel to the pancreas, triggering insulin release in advance of eating.

The hypothalamus controls appetite through several neuronal populations, among them pro‑opiomelanocortin (POMC) cells that signal satiety. While these neurons are known to fire during consumption, they also react to the mere expectation of food, a phenomenon whose underlying molecular drivers have remained obscure.

Investigators now report that tiny reserves of glycogen within POMC neurons are essential for this anticipatory activation. Glycogen, the body’s primary carbohydrate store, can be broken down into glucose when energy is needed. By mapping the neural circuits that govern hunger and fullness, researchers hope to uncover new strategies for tackling metabolic disorders such as obesity.

“Obesity reflects a malfunction of the feeding network at the brain level—it is more a brain disease than a peripheral one,” explains Marc Schneeberger Pane, assistant professor of cellular and molecular physiology at Yale and co‑lead of the study. “Clarifying how these neurons operate under normal conditions is a prerequisite for developing effective obesity interventions.”

To probe how sensory cues of food influence POMC activity, the team presented mice with food placed behind a wire mesh, allowing sight and smell but preventing ingestion. Subsequent molecular analyses revealed that exposure to food rapidly induced the enzyme glycogen synthase, which assembles glycogen molecules.

“Seeing the enzyme up‑regulated made us suspect that glycogen—a stored form of glucose—could be a key molecular signature of the sensory response,” notes Schneeberger Pane.

To test glycogen’s role, the scientists generated mice lacking glycogen synthase specifically in POMC cells. When these animals encountered food, they showed blunted behavioral and physiological reactions: they were less inclined to approach edible items, spent less time feeding, and failed to secrete insulin before eating.

To rule out developmental defects, the researchers also delivered a virus that eliminated glycogen synthase in adult wild‑type mice. These subjects displayed the same diminished response to visual and olfactory food cues.

“Our work uncovers a previously unknown biochemical pathway that drives food perception, showing that neuronal glycogen fuels the brain’s preparatory actions,” says Marc Claret, head of the Neuronal Control of Metabolism Laboratory at the Institut d’Investigacions Biomèdiques August Pi i Sunyer and co‑principal investigator.

Further experiments mapped the sensory inputs that activate POMC neurons. The data indicate that these cells receive information from olfactory processing regions but not from visual pathways.

Traditionally, brain glycogen has been thought to reside mainly in astrocytes, the supporting glial cells that supply nutrients to neurons. This study suggests that neurons themselves may store and use glycogen more extensively than previously recognized.

Schneeberger Pane emphasizes that the sensory anticipation of food primes the organism for upcoming metabolic changes. For example, pre‑meal insulin release prepares the bloodstream for the glucose influx that follows eating. Disruption of this anticipatory system could impair the body’s ability to handle food effectively.

Long‑term monitoring of glycogen‑deficient mice revealed a progressive decline in metabolic health. Over time, these animals gained excess weight and exhibited early signs of diabetes.

The findings have implications for the development of anti‑obesity therapeutics. Current drugs such as glucagon‑like peptide‑1 (GLP‑1) receptor agonists target satiety circuits, and a deeper understanding of the neural mechanisms that govern appetite could inform the next generation of treatments.

“If the brain’s ability to predict food intake is compromised, it may contribute to obesity and diabetes, opening new therapeutic possibilities,” says Claret.

The research was funded by the National Institutes of Health, Yale University, the McCluskey family, the E. Matilda Ziegler Foundation and Interstellar Initiative, and the Foundation for Prader‑Willi Research. The authors assume full responsibility for the content, which does not necessarily reflect official NIH positions.