Showing papers on "Protein sparing published in 1988"
TL;DR: A 2.5 times higher value is found for rate of body mass loss, uric acid, and urea during spring phase II, suggesting lower effectiveness in protein sparing at that time of year, attributed to the lower initial lipid reserves of spring birds.
Abstract: The body mass of male emperor penguins is approximately 38 kg at the beginning of the 4-mo winter fast connected with breeding, and it is an estimated approximately 18 kg in leanest birds at time of spontaneous refeeding. For a 38- to 18-kg range, we investigated the changes in the rate of body mass loss, body composition, and plasma concentrations of uric acid and urea. After the first few days (phase I) a steady state (phase II) was reached in the proportions of the energy derived from proteins and lipids with proteins accounting for a constant 4%, and the remaining 96% being from lipids. The same proportions were maintained until body mass had decreased to 24 kg. Below this value the proportion of energy derived from proteins increased progressively (phase III), being 14 times higher at 18 kg than during phase II. Rate of body mass loss and plasma uric acid and urea concentrations closely reflected the changes in protein utilization: being at a low and steady value throughout phase II and increasing during phase III. Emperor penguins also fast during the spring, but for periods of only 2-3 wk. We found a 2.5 times higher value for rate of body mass loss, uric acid, and urea during spring phase II, suggesting lower effectiveness in protein sparing at that time. It may be attributed to the lower initial lipid reserves of spring birds. Would these findings be generalized to the wide variety of birds and mammals that spontaneously fast under natural conditions?(ABSTRACT TRUNCATED AT 250 WORDS)
186 citations
TL;DR: 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.
45 citations
TL;DR: It is concluded that there are similar early adjustments to food deprivation in king penguin chick, rat and man: a decreases in resting metabolic rate, a decrease in protein utilization, and a mobilization of fat stores.
Abstract: Chicks of the king penguin (Aptenodytes patagonica) can tolerate a fast of 4–6 months during the subantarctic winter. The aim of this work was to study their initial response to food deprivation. Nine chicks were starved for 18 days. Two phases of starvation were defined according to changes in the specific daily loss in body mass: it decreased by 92% in phase I (6.6±0.3 days) and remained steady and low in phase II. Phase I was marked by a large decline in protein utilization, indicated by decreases in plasma levels of alanine (58%), uric acid (89%) and urea (76%) together with a decrease in circulating corticosterone (60%) and thyroxine (75%). In phase I, plasma insulin concentration decreased (61%) in some birds, but did not change in others; plasma pancreatic glucagon was stable whereas gut-glucagon decreased by 75%. Free fatty acids and β-hydroxybutyrate concentrations gradually rode during the fast to 5 to 6 times pre-fast levels. Glycemia remained unchanged. Phase II was characterized by no change in plasma concentrations of protein-derived metabolites and by no or little change in circulating hormone levels. From comparison with previous data, we conclude that there are similar early adjustments to food deprivation in king penguin chick, rat and man: (1) a decrease in resting metabolic rate, (2) a decrease in protein utilization, and (3) mobilization of fat stores. The key, adaptations to long-term fasting in these species are therefore effectiveness in protein sparing and ability to prolong this situation.
33 citations
TL;DR: It is concluded that supplementation of low-calorie TPN diets with Intralipid increases protein sparing and is preferable to the administration of very high glucose loads.
23 citations
01 Jan 1988
TL;DR: Investigate the mechanisms behind the high efficiency of male Emperor penguin and King penguin chicks for protein sparing and demonstrate that the daily body mass loss per unit body mass reflects protein catabolism.
Abstract: Protein sparing is a major factor for surviving starvation. To investigate its
mechanisms, which are still largely unknown, antarctic penguins are remarkable
animal models. Under natural conditions, they tolerate extremely long fasts,
which facilitate the comparison of the successive phases characterizing changes in
the utilization of protein and lipid reserves . Our investigations demonstrate that
the daily body mass loss per unit body mass reflects protein catabolism. The high
efficiency of male Emperor penguin and King penguin chicks for protein sparing
seems to be related to the large lipid reserves they store before fasting
3 citations