A series of fluorescent probes is designed that act as dual agonists on both GLP1 and GIP receptors, and are used to image receptor binding activities in tissues and animals.

Hansford et al. show that GIPR, a target of new weight-loss drugs, is found in brain cells called oligodendrocytes. GIPR helps these drugs access the brain and boosts weight loss. Without GIPR in these cells, the drugs are less effective, revealing a new mechanism behind their action.