The Cells That Tell You to Stop Eating Are Not the Ones Scientists Spent Decades Studying

Hunger neurons fire; fullness neurons fire back; hormones from the gut and fat tissue tip the balance. Instead, the lactate binds to a receptor called HCAR1 on astrocytes, the support cells that outnumber neurons throughout the brain. Activated astrocytes release glutamate, which reaches POMC neurons, the population that suppresses appetite and generates the sensation of fullness. Araneda's team has not yet shown that manipulating HCAR1 changes eating behavior, which is the experiment that would matter. The FGF21 work used only male mice, and the astrocyte team has not yet shown that manipulating HCAR1 alters feeding behavior.