Plasma hormone levels in relation to lipid and protein metabolism during prolonged fasting in king penguin chicks.
Chicks of king penguin (Aptenodytes patagonica), while only 3-4 months old, tolerate 4-6 months of fasting when they are abandoned by their parents during the subantarctic winter. The body mass of nine chicks, which were followed during this natural winter fast, was 13.1 kg at capture and 3.4 kg after 150 days of fasting, a 74% decrease. The longer phase II (129 days) was marked by lipid mobilization and protein sparing, as indicated by a continuous increase in plasma levels of free fatty acids, glycerol, and beta-hydroxybutyrate, whereas plasma alanine, uric acid, and urea remained stable at low values. In phase III, by contrast, plasma concentrations of lipid-derived metabolites decreased, while plasma alanine, uric acid, and urea increased markedly, indicating an increase in protein utilization. Plasma insulin concentration did not significantly change during either phase II or phase III. Plasma glucagon remained constant during phase II and at the beginning of phase III but increased 2.6 times afterward. Plasma corticosterone increased only slightly during the first 4 months of the fast but reached very high values at the end of phase II and the beginning of phase III (4.7 times basal values); moreover, it further increased 3.1 times before phase III was stopped. Altogether, these data accord with the idea that the outstanding resistance of king penguin chicks to starvation is due to the ability to extensively prolong the situation of protein sparing, which seems to require the maintenance of low plasma concentrations of corticosterone and insulin for up to 4 months.(ABSTRACT TRUNCATED AT 250 WORDS)
Le Ninan
F
F
Laboratoire d'Etude des Régulations Physiologiques, l'Université Louis Pasteur, Strasbourg, France.
Cherel
Y
Y
Sardet
C
C
Le Maho
Y
Y
D000818:Animals; D001717:Birds / Q000378:metabolism*; D001798:Blood Proteins / Q000378:metabolism; D003345:Corticosterone / Q000097:blood*; D005215:Fasting; D005934:Glucagon / Q000097:blood; D007328:Insulin / Q000097:blood; D008053:Lipid Mobilization; D008055:Lipids / Q000097:blood; D010187:Pancreatic Hormones / Q000097:blood*; D011506:Proteins / Q000378:metabolism*; D013997:Time Factors
D001798:Blood Proteins; D007328:Insulin; D008055:Lipids; D010187:Pancreatic Hormones; D011506:Proteins; D005934:Glucagon; D003345:Corticosterone