Glut1 Acts in Corazonin-Producing Neurons to Regulate Glycogen Storage in Drosophila

Metabolic homeostasis is regulated by numerous genes, whose dysregulation leads to metabolic diseases such as obesity and diabetes. Several genes important for lipid storage were identified in a buoyancy-based screen in Drosophila larvae, including Glucose transporter 1 (Glut1), which encodes a glucose uniporter. Previous studies have identified metabolic functions of Glut1 in the whole fly brain; however, the specific neurons in which Glut1 acts to regulate nutrient storage remain unknown.

To determine the neuronal populations in which Glut1 regulates lipid and carbohydrate storage, Glut1 levels were decreased in specific neurons, and triglycerides (TAGs) and glycogen levels were measured. We specifically decreased Glut1 expression in corazonin (Crz)-expressing neurons, a neuronal population that expresses the corazonin gene (Crz), which encodes a neuropeptide involved in carbohydrate metabolism.

Targeting RNAi against Glut1 in Crz neurons reduced glycogen levels in males but did not alter TAG levels. To further characterize this nutrient storage phenotype, we measured the expression of two genes involved in glycogen storage, glycogen phosphorylase (Glyp) and glycogen synthase (Glys) as well as the Crz transcript. Notably, knocking down Glut1 in Crz-expressing neurons increased Glys and Crz transcript levels.

These data suggest that Glut1 acts in the Crz-expressing neurons to regulate Crz levels and organismal glycogen metabolism.