Figure 2.

Diet and energy balance in the regulation of orexinergic neurons. Orexin plays a central role in energy homeostasis and maintenance of wakefulness, and may be affected by glucose, leptin and/or ghrelin signaling. Alterations in SIRT1 in response to energy surplus may also affect orexin neuron activity. The net effect is one of decreased orexinergic signaling with a phenotype of reduced wakefulness and energy expenditure. NAD⁺, nicotinamide adenine dinucleotide; OX2R, orexin 2 receptor; LRb, leptin receptor.