Annual life-stage regulation of lipid metabolism and storage and association with PPARs in the migrant species Gray Catbird (Dumetella carolinensis)

Abstract

The annual cycle of a migrating bird involves metabolically distinct stages of substantial fatty acid storage and periods of increased fatty acid mobilization and utilization, and thus requires a great deal of phenotypic flexibility. Specific mechanisms directing stage transitions of lipid metabolism in migrants are largely unknown. This study characterized the role of the nuclear receptors, peroxisome proliferator-activated receptors (PPARs), in migratory adiposity of the Gray Catbird (Dumetella carolinensis). Catbirds increased adipose storage during spring and fall migration and showed increased rates of basal lipolysis during migration and tropical overwintering. Expression of the PPAR target genes involved in fat uptake and storage, FABPpm and PLIN3, increased during pre-migratory fattening. We found significant correlation between PPARγ and target gene expression in adipose but little evidence that PPARα expression levels drive metabolic regulation in liver during the migratory cycle.