Neuropeptide W: a key player in the homeostatic regulation of feeding and energy metabolism?

Neuropeptide W (NPW), recently isolated from porcine hypothalamus, has been identified as the endogenous ligand for both NPBWR1 (GPR7) and NPBWR2 (GPR8), which belong to the orphan G protein–coupled receptor family. NPW is thought to play an important role in the regulation of feeding and drinking behavior, and to be related to the stress response. NPW‐containing neurons are localized in several regions of the brain, including the hypothalamus, hippocampus, limbic system, midbrain, and brain stem. Accumulated evidence suggests that hypothalamic neuropeptides, such as neuropeptide Y (NPY), orexin, melanin‐concentrating hormone (MCH), and proopiomelanocortin (POMC), are involved in the regulation of feeding behavior and energy homeostasis via neuronal circuits in the hypothalamus. NPW also forms part of the feeding‐regulating neuronal circuitry in conjunction with other feeding‐regulating peptide‐containing neurons within the hypothalamus. We summarize our current understanding of the distribution of NPW and of the neuronal interactions between NPW and the different feeding‐regulating peptide‐containing neurons. This review also discusses evidence for the dichotomous actions of NPW on energy balance and the potential mechanisms involved.