For over 60 years, we thought metformin worked mainly through the liver and gut. But new research suggests the brain may play a major role too. This study identified a specific brain pathway (Rap1 in the hypothalamus) that appears critical to metformin’s glucose-lowering effects, potentially reshaping how we understand one of the world’s most prescribed diabetes medications. Source: Sci. Adv. 2025;11:eadu3700