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 PPARs ( peroxisome proliferatoractivated receptors) in regulating migratory adiposity of the gray catbird (Dumetella carolinensis). Catbirds increased adipose storage during spring and autumn 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.

Obese super athletes: fat-fueled migration in birds and bats

“…In gray catbirds, PPARα transcript abundance increased threefold during spring migration in the liver compared with tropical wintering, and remained at intermediate levels through summer and autumn migration (Corder et al, 2016). However, neither PPARλ nor any of the PPAR target genes measured in the liver changed significantly with migration.…”

“…Liver lipid contents in fat migratory sandpipers were shown to be low (35 mg g −1 wet tissue) and did not change during fattening (Maillet and Weber, 2006;Napolitano and Ackman, 1990). Despite large changes in body fat, the liver lipid content of gray catbirds was found to remain near 60-80 mg g −1 wet mass through the wintering, breeding and migratory seasons (Corder et al, 2016).…”

“…At rest and during intense shivering, ruff sandpipers (Philomachus pugnax) were found to have the highest adipose lipolytic rates measured in vertebrates (two-to threefold greater than mammals), and 50% of the fatty acids were re-esterified and retained within adipocytes (Vaillancourt and Weber, 2007). Basal adipose lipolysis tended to increase during spring and autumn migration compared with summer, but was lower than during wintering in gray catbirds (Corder et al, 2016). In mammals, lipolysis is not thought to limit fatty acid oxidation during exercise , and the very high lipolysis rates of birds suggest that this may also be true for birds.…”

“…However, neither PPARλ nor any of the PPAR target genes measured in the liver changed significantly with migration. PPARλ expression did not vary seasonally in adipose, and only perilipin3 (PLIP3) and plasma membrane fatty acid binding protein (FABPpm) showed any seasonal change, tending to be lowest during spring migration (Corder et al, 2016). Much more remains to be learned about how feeding, fat storage and lean mass dynamics are regulated in migratory birds.…”

The effects of dietary linoleic acid and hydrophilic antioxidants on basal, peak, and sustained metabolism in flight‐trained European starlings

“…Concentration‐dependent negative feedback to 18:2n6 exposure could then explain diet‐specific changes in metabolism over successive cohorts (Fujimori, ; Inoue, Tanabe, & Umesono, ). It is also plausible that diet‐specific changes in metabolism over cohorts and fat loads can be explained by integrating innate circannual‐ and body condition‐based influences on the regulation of oxidative capacity (Batista‐Pinto, Rocha, Castro, Rodrigues, & Lobo‐da‐cunha, ; Corder et al, ; McFarlan et al, ; Zhang, King, Harmon, Eyster, & Swanson, ). The changes in metabolism we observed over the course of this experiment occurred in the absence of external temperature and photoperiod cues.…”