Diet and heat - one neuronal subset two responses

Abstract

The Insulin signal cascade is one of the best studied metabolic circuits, and shows a remarkable high molecular and functional conservation across the animal kingdom. Insulin-producing cells respond directly to nutritional cues in circulation and receive modulatory input from connected neuronal networks. Neuronal control is rapid and integrates a wide range of variables including dietary change or environmental temperature. However, despite various detailed studies that demonstrated the potential of neuronal regulation the physiological relevance of this circuit remains elusive. In Drosophila, Insulin-like peptide 7 (dIlp7)-producing neurons are wired with Insulin-producing cells. We found a dual role for this neuronal subset: a.) activated dilp7-producing neurons are required to facilitate development at high temperatures, and if confronted with calorie-rich food that represses neuronal activity b.) their product, dIlp7, regulates Insulin signalling levels. Our work shows that Insulin-producing cells not simply integrate signals from circulating nutritional cues and neuronal inputs, but switch to neuronal control in response to dietary composition.