Endoplasmic reticulum Nogo drives AgRP neuronal activation and feeding behavior.

Lipid sensing in the hypothalamus contributes to the control of feeding and whole-body metabolism. However, the mechanism responsible for this nutrient-sensing process is ill-defined. Here, we show that Nogo-A, encoded by reticulon 4 (Rtn4) gene and associated with brain development and synaptic plasticity, regulates feeding and energy metabolism by controlling lipid metabolism in Agouti-related protein (AgRP) neurons. Nogo-A expression was upregulated in AgRP neurons of fasted mice and was associated with a significant downregulation of enzymes involved in sphingolipid de novo biosynthesis and the upregulation of key enzymes in intracellular lipid transport and fatty acid oxidation. Deletion of Rtn4 in AgRP neurons reduced body weight, ghrelin-induced AgRP activity and food intake, and fasting-induced AgRP activation, together with an increase in ceramide levels. Finally, high-fat-diet-induced obesity induced a significant downregulation of Rtn4 and increased ceramide levels in AgRP neurons, suggesting a role for Nogo in AgRP dysregulation in obesity. Taken together, our data reveal that Nogo-A drives AgRP neuronal activity and associated feeding behavior by controlling mitochondrial function and cellular lipid metabolism.