Rapid shift in substrate utilization driven by hypothalamic Agrp neurons

Agrp neurons drive feeding. To what extend these neurons participate in the regulation of other homeostatic processes is not well understood. We investigated the role of Agrp neurons in substrate utilization in mice. Activation of Agrp neurons was sufficient to rapidly increase RER and carbohydrate utilization, while decreasing fat utilization. These metabolic changes were linearly correlated with carbohydrates ingested, but not protein or fat ingestion. However, even in the absence of ingestive behaviors, activation of Agrp neurons led to changes in substrate utilization in well-fed mice. These effects were coupled to metabolic shifts towards lipogenesis. Inhibition of fatty acid synthetase (FAS) blunted the effects of Agrp neurons on substrate utilization. Finally, Agrp neurons controlled peripheral metabolism, but not food intake, via {beta}3-adrenergic receptor signaling in fat tissues. These results reveal a novel component of Agrp neuron-mediate metabolism regulation that involves sympathetic activity on fat compartments to shift metabolism towards lipogenesis.