Within-winter flexibility in muscle and heart lipid transport and catabolism in passerine birds.

摘要: Small birds in cold climates may show within-winter metabolic flexibility to match capacities prevailing weather conditions. This occur over periods of days weeks, but the underlying mechanisms for such are not well understood. Because lipids primary fuel sustained thermogenesis, we examined whether lipid transport and catabolism can mediate two small temperate-zone wintering passerine birds, dark-eyed juncos (Junco hyemalis) house sparrows (Passer domesticus). We used simple multiple regression analyses test correlations several transporters pectoralis muscle (plasma membrane-bound cytosolic fatty acid-binding proteins, FABP; acyl translocase, FAT/CD36) regulatory enzymes (carnitine transferase, CPT; β-hydroxyacyl CoA dehydrogenase, HOAD) heart with short-term (ST, 0–7 days), medium-term (MT, 14–30 days) long-term (LT, 30-year mean daily extreme minimum temperatures, day winter season) temperature variables. hypothesized negative between these regulators Juncos showed FABPs ST or MT variables, other positive temperatures juncos, suggesting no consistent pathway-wide response temperatures. LT variables significant associations also directions. House expected FABPpm, FABPc, CPT HOAD. Different species-specific patterns variation absence responses suggest that pathway is a uniform mediator among birds.