Control of lipid metabolism and muscle hypertrophy by PPARs in Gray catbird annual life cycle

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Migratory birds are among nature's most accomplished athletes. Many of these birds undertake journeys of several thousand miles with little rest. In addition to the challenges of timing and navigation, the energy costs of migration are very high. Migrating birds operate at a level of effort that may be double that of a Tour de France bicycle racer. As these birds often do not stop to refuel, in the weeks before departure birds become obsessed with feeding and gain weight rapidly. Added fat stores may be 50% of their body weight, equivalent to a 150 pound human gaining 75 pounds in less than a month. Equally astonishing, flight muscle size increases in preparation for migration, even in birds kept inactive in captivity. In both cases, there is a resetting of normal anatomy (structure) and physiology (function) of these animals to match the requirements of migration. While much is known about these dramatic shifts, little is known about how they are controlled. Control of preparation for migration may lie with a family of gene regulators called peroxisome proliferator-activated receptors or PPARs, regulatory proteins found in all vertebrates. In mammals, where they have been most studied, PPARs control both the storage of fats in adipose tissue as well as the use of fats as fuel in muscle. Drugs that modulate their activity are in development for treatment of human metabolic disorders. By manipulating PPAR activity using these drugs, researchers will explore the roles of PPARs in migration. As migration may be one of the most profound challenges to energy demands in any animal, researchers will unveil details of metabolism and its regulation while shedding light on one of nature's marvels. Additionally, the PPARs normally respond to dietary signals, thus birds may be choosing foods that help to spur necessary changes. The researchers will work with local school children to explore the needs of migrating birds for native plants and develop curricula that brings habitat and migration together while teaching about avian diversity.