Orexin modulation of adipose tissue.

The orexins are neuropeptides with critical functions in the central nervous system. These neuropeptides have important roles in energy balance and obesity, and therefore on the accumulation of adipose tissue. Rodents lacking orexins, typically through genetic knockouts, experience increased weight gain and accumulation of adipose tissue. Evidence indicates that the lack of the orexins increase adiposity as a result of decreased energy expenditure, principally through a reduction of physical activity. Different lines of evidence suggest that other mechanisms are likely also in play, and neural influences on both white and brown adipose tissues remain to be fully and functionally defined. In addition, the orexin peptides and their receptors are expressed in adipose tissue, with little available information as to their significance. This review summarizes our current understanding of how the orexin peptides affect adipose tissue. We provide a brief introduction to the physiology of orexins and their effects on white and brown adipose tissues in the context of energy balance. We conclude this review by integrating this information in the context of the known physiology of the orexins. This article is part of a Special Issue entitled: Modulation of Adipose Tissue in Health and Disease.