5'-AMP-Activated Protein Kinase in Avian Biology

Authors: Proszkowiec-Weglarz, Monika; Richards, Mark

Submitted to: Poultry and Avian Biology Reviews
Publication Type: Review Article
Publication Acceptance Date: 3/27/2008
Publication Date: 5/1/2008
Citation: Proszkowiec-Weglarz, M., Richards, M.P. 2007. 5'-AMP-activated protein kinase in avian biology. Avian and Poultry Biology Reviews. 18(4):123-145.

Interpretive Summary: All living organisms require a continual supply of energy not only to survive, but to grow and reproduce. In response to fluctuations in environment and nutrition, a balance must be maintained between how much energy is obtained versus how much energy is used to support life processes. Thus the regulation of important functions such as growth and reproduction is tightly linked to the supply of available energy. Higher organisms have developed an adaptive mechanism to coordinately regulate food intake and energy expenditure to achieve energy balance for the whole animal as well as for individual cells within tissues of the body. A key component of this mechanism involves 5’-AM P-activated protein kinase (AMPK), an enzyme that serves as an energy sensor and regulator of metabolism. There has been a great deal of interest in and study of AMPK in mammals and its role as a master regulator of energy balance in health and disease. However, very little is currently known about this important enzyme system in birds. This manuscript discusses what we currently know about AMPK and its different roles in energy sensing and metabolic regulation in avian species. It is important to investigate how AMPK functions in birds if we are to understand the practical implications of this enzyme to avian biology and poultry production. Such information is useful for researchers studying the control of food intake, energy balance and growth in avian and other species, as well as, for poultry producers in formulating new genetic selection and management strategies for commercial poultry flocks.

Technical Abstract: To survive and perform basic metabolic processes, all living organisms must maintain a state of energy balance. Energy balance is achieved by increasing energy expenditure during periods of energy excess and decreasing energy expenditure during periods of energy deficit. In this review, we focus on 5’-AMP-activated protein kinase (AMPK), a heterotrimeric enzyme complex consisting of one catalytic and two regulatory subunits that is a key component in the pathway maintaining cellular and whole body energy balance. AMPK is widely expressed in mammalian as well as avian tissues. In response to states of negative energy balance, AMPK is activated through phosphorylation by upstream AMPK kinases. It then acts to increase the activities of those metabolic pathways that generate energy while decreasing the activities of energy-consuming pathways. As a result, AMPK is involved in the regulation of carbohydrate, lipid and protein metabolism. AMPK achieves its metabolic effects acutely by direct phosphorylation of many downstream target proteins and, long-term, by regulation of transcription factor and co-activator activities which leads to changes in gene transcription. AMPK responds not only to fluctuations in cellular energy level, but also to specific nutrients and hormones and thereby participates in the regulation of whole body energy balance and food intake. Recent work has begun to define the AMPK pathway in avian species where it most likely plays a similar role in maintaining energy balance and controlling food intake as it has been reported to do in mammals.