The avian proglucagon system.

Understanding how the proglucagon system functions in maintaining glycemic control and energy balance in birds, as well as defining its specific roles in regulating metabolism, gastrointestinal tract function and food intake requires detailed knowledge of the components that comprise this system. These include proglucagon, a precursor protein from which glucagon and two glucagon-like peptide hormones (GLP-1 and GLP-2) are derived, and the membrane bound G-protein-coupled receptors that specifically bind glucagon, GLP-1 and GLP-2 to mediate their individual physiological actions. Another key feature of the proglucagon system that is important for regulating its activity in different tissues involves post-translational processing of the proglucagon precursor protein and the individual peptide hormones derived from it. Currently, there is limited information about the proglucagon system in birds with the majority of that coming from studies involving chickens. By summarizing what is currently known about the proglucagon system in birds, this review aims to provide useful background information for future investigations that will explore the nature and actions of this important hormonal system in different avian species.