Since administration of leptin prevented fasting-induced plasticity, it was proposed that the rewiring of orexin neurons could result from multiple humoral and neuronal signals, and that synaptic changes in the orexin circuitry could underlie functional alterations such as insomnia, and metabolic disturbances including obesity (Horvath and Gao, 2005). The gene discussed is LEP; the disease is obesity due to melanocortin 4 receptor deficiency.