Relationships between lipid availability and protein utilization during prolonged fasting
Tóm tắt
Mammals and birds adapt to prolonged fasting by mobilizing fat stores and minimizing protein loss. This strategy ends with an increase in protein utilization associated with behavioural changes promoting food foraging. Using the Zucker rat as a model, we have investigated the effect of severe obesity on this pattern of protein loss during long-term fasting. Two interactions between the initial adiposity and protein utilization were found. First, protein conservation was more effective in obese than in lean rats: fatty rats had a three times lower daily nitrogen excretion and proportion of energy expenditure deriving from proteins, and a lower daily protein loss in various muscles. This phase of protein sparing is moreover nine times longer in the fatty rats. Second, obese animals did not show the late increase in nitrogen excretion that occurred in their lean littermates. Total body protein loss during starvation was larger in fatty rats (57% versus 29%) and, accordingly, total protein loss was greater in their muscles. At the end of the experiment, lean and obese rats had lost 98% and 82%, respectively, of their initial lipid reserves, and fatty rats still had an obese body composition. These results support the hypothesis that in severely obese humans and animals a lethal cumulative protein loss is reached long before the exhaustion of fat stores, while the phase of protein conservation is still continuing. In contrast, in lean rats, survival of fasting seems to depend on the availability of lipid fuels. The data also suggest that accumulation of too much fat in wild animals is detrimental for survival, because it eliminates the late phase of increase in nitrogen excretion that is linked to a food foraging behaviour anticipating a lethal depletion of body reserves.
Tài liệu tham khảo
Barnard DL, Ford J, Garnett ES, Mardell RJ, Whyman AE (1969) Changes in body composition produced by prolonged total starvation and refeeding. Metabolism 18:564–569
Bartlett GR (1959) Phosphorus assay in column chromatography. J Biol Chem 234:466–468
Belkhou R, Cherel Y, Heitz A, Robin JP, Le Maho Y (1991) Energy contributions of proteins and lipids during prolonged fasting in the rat. Nutr Res 11:365–374
Cahill GF (1970) Starvation in man. N Engl J med 282:668–675
Cherel Y, Le Maho Y (1985) Five months of fasting in king penguin chicks: body mass loss and fuel metabolism. Am J Physiol 249 (Regul Integr Comp Physiol 18): R387-R392
Cherel Y, Le Maho Y (1991) Refeeding after the late increase in nitrogen excretion during prolonged fasting in the rat. Physiol Behav 50:345–349
Cherel Y, Robin JP, Le Maho Y (1988a) Physiology and biochemistry of long-term fasting in birds. Can J Zool 66:159–166
Cherel Y, Burnol AF, Leturque A, Le Maho Y (1988b) In vivo glucose utilization in rat tissues during the three phases of starvation. Metabolism 37:1033–1039
Cherel Y, Robin JP, Walch O, Karmann H, Netchitailo P, Le Maho Y (1988c) Fasting in king penguin. I. Hormonal and metabolic changes during breeding. Am J Physiol 254 (Regul Integr Comp Physiol 23): R170-R177
Cleary MP (1986) Consequences of restricted feeding/refeeding cycles in lean and obese female Zucker rats. J Nutr 116:290–303
Cuendet GS, Loten EG, Cameron DP, Renold AE, Marliss EB (1975) Hormone-substrate responses to total fasting in lean and obese mice. Am J Physiol 228:276–283
Dunn MA, Houtz SK, Hartsook EW (1982) Effects of fasting on muscle protein turnover, the composition of weight loss, and energy balance of obese and non-obese Zucker rats. J Nutr 112:1862–1875
Felig P (1979) Starvation. In: De Groot LJ (ed) Endocrinology, vol 3. Grune & Stratton, New York, pp 1927–1940
Ferré P, Pégorier JP, Marliss EB, Girard JR (1978) Influence of exogenous fat and gluconeogenic substrates on glucose homeostasis in the newborn rat. Am J Physiol 234 (Endocrinol Metab Gastrointest Physiol 3): E129-E136
Folch J, Lees M, Sloane-Stanley GH (1957) A simple method for the isolation and purification of total lipids from animal tissues. J Biol Chem 226:497–509
Forbes GB, Drenick EJ (1979) Loss of body nitrogen on fasting. Am J Clin Nutr 32:1570–1574
Friedman MI (1990) Body fat and the metabolic control of food intake. Int J Obesity 14 [Suppl 3]:53–67
Gacs G (1976) The mechanism of hypoglycaemia due to semistarvation in the rat. J Nutr 106:1557–1561
Goodman MN, Larsen PR, Kaplan MM, Aoki TT, Young VR, Ruderman NB (1980) Starvation in the rat. II. Effect of age and obesity on protein sparing and fuel metabolism. Am J Physiol 239 (Endocrinol Metab 2):E277-E286
Goodman MN, Lowell B, Belur E, Ruderman NB (1984) Sites of protein conservation and loss during starvation: influence of adiposity. Am J Physiol 246 (Endocrinol Metab 9):E383-E390
Greenwood MRC, Maggio CA, Koopmans HS, Sclafani A (1982) Zucker fafa rats maintain their obese body composition ten months after jejunoileal bypass surgery. Int J Obesity 6:513–525
Harper JF (1984) Peritz' F-test: basic program of a robust multiple comparison test for statistical analysis of all differences among group means. Comput Biol Med 14:437–445
Kates M (1972) Techniques of lipidology. North Holland, Amsterdam, pp 360–361
Keppler D, Decker K (1974) Glycogen. Determination with amyloglucosidase. In: Bergmeyer HU (ed) Methods of enzymatic analysis. Academic Press, New York, pp 1127–1131
Koubi HE, Robin JP, Dewasmes G, Le Maho Y, Frutoso J, Minaire Y (1991) Fasting-induced rise in locomotor activity in rats coincides with increased protein utilization. Physiol Behav 50:337–343
Letter LA, Marliss EB (1982) Survival during fasting may depend on fat as well as protein stores. JAMA 248:2306–2307
Le Maho Y, Robin JP, Cherel Y (1988) Starvation as a treatment for obesity: the need to conserve body protein. News Physiol Sci 3:21–24
Lowell BB, Goodman MN (1987) Protein sparing in skeletal muscle during prolonged starvation. Dependence on lipid fuel availability. Diabetes 36:14–19
Montemurro DG, Stevenson JAF (1960) Survival and body composition of normal and hypothalamic obese rats in acute starvation. Am J Physiol 198:757–761
Nair KS, Welle SL, Halliday D, Campbell RG (1988) Effect of β-hydroxybutyrate on whole-body leucine kinetics and fractional mixed skeletal muscle protein synthesis in humans. J Clin Invest 82:198–205
Reicher K (1909) Zur Kenntnis der prämortalen Stickstoffsteigerung. Z Exp Pathol Ther 5:750–760
Reilly JJ (1991) Adaptations to prolonged fasting in free-living weaned gray seal pups. Am J Physiol 260 (Regul Integr Comp Physiol 29): R267-R272
Robin JP, Frain M, Sardet C, Groscolas R, Le Maho Y (1988) Protein and lipid utilization during long-term fasting in emperor penguins. Am J Physiol 254 (Regul Integr Comp Physiol 23):R61-R68
Schmidt-Nielsen K (1979) Animal physiology: adaptation and environment, 2nd edn. Cambridge University Press, Cambridge
Steffee WP (1980) Malnutrition in hospitalized patients. JAMA 244:2630–2635
Triscari J, Bryce GF, Sullivan AC (1980) Metabolic consequences of fasting in old lean and obese Zucker rats. Metabolism 29:377–385
Van Itallie TB, Yang MU (1977) Current concepts in nutrition. Diet and weight loss. N Engl J Med 297:1158–1161
Zucker LM (1967) Some effects of caloric restriction and deprivation on the obese hyperlipemic rat. J Nutr 91:247–254
Zucker LM, Antoniades HN (1972) Insulin and obesity in the Zucker genetically obese rat. Endocrinology 90:1320–1330