Die Nahrung 30 (1986) 3-4, 451-452

Central Institute of Nutrition in Potsdam-Rehbriicke (Director: Prof. Dr. H. SCHMANDKE), Academy of Sciences of the GDR

The influence of early postnatal overnutrition on postprandial energy expenditure in rats (Short communication)

L. AUST, R. NOACK and J. PROLL

Overnutrition in rodents during early postnatal life induced by breeding in small nest sizes leads to distinct metabolic changes, which remain throughout life even under conditions of free access to normal food. An accelerated body fat accumulation and a probably higher efficiency of energy utilization render this animal model suitable for the study of relations between the development of an obese state and its metabolic causes [ 1 , 21. There is increasing evidence from studies in human beings [3,4] as well as in rodents [S, 61 that a higher body fat content is associated with a lower thermogenic response to food ingestion, assumed to indicate an increased efficiency of energy utilization. First results concerning postprandial thermogenesis in postnatally overfed rats are presented here.

The experiment was carried out with male rats of the Wistar strain (Wist Schoe, VEB Versuchstierproduk- tion, Schonwalde near Berlin, GDR), which were grouped immediately after birth in nests of 2 or 12 animals. After weaning (4 weeks) the animals were kept in single cages and fed ad libitum with standard pellets (type R, VEB Versuchstierproduktion). At an age of 7-9 weeks the energy expenditure ofthe rats was determined by in- direct ca!orimetry in an open system. For this purpose the animals were transferred into metabolic cages (Simax, CSSR), supplied with a constant stream of fresh air (80 I/h, (25 f 1) “C, 100% relative humidity). Oxygen consumption and carbon dioxide production were estimated paramzgnetically and by infrared ab- sorption using Permolyt 2 and Infralyt 4 (VEB Junkalor, Dessau, GDR), respectively. To compare energy intake the rats got at 8 a.m. a semisynthetic diet (casein 15%, wheat starch 53 %, sucrose lo%, sunflower oil 15 %, cellulose 2 %, salt mixture 4 %, vitamine mixture 1 %) limited to 500 kJ metabolizable energy per kg0.75.

Table 1 Energy expenditure of male postnatally overfed rats before and after food ingestion

normal rats (large nest) (n = 12)

overfed rats (small nest) (n = 10)

body mass [g] energy expenditure [kJ/kg0.”] prefed (8 a.m.-4 p.m.) postprandial (4 p.m.-12 p.m.) postprandial increase % postprandial increase energy intake [kJ] absolute postprandial increase [kJ] postprandial increase in % of intake

252 f 45

130.7 12.8 184.6 rt 13 53.9 + 14.7 42.1 f 13.9

19.4 f 6.7 177 f 21

10.8 3.1

256 43

136.2 11.1 176.6 f 10.3 40.3 f 7.3* 30.0 & 7.0*

14.5 2 2.9* 181 f 21

8.0 1.Y

mean values f SD * p < 0.05

452 Die Nahrung 30 (1986) 3-4

After a 4 days adaptation period the pre and post fed energy expenditure was estimated on the fifth day over 8 h each after changing thc fccding time to 4 p.m. in depenence on further experiments in these animals, which are not discussed here.

The postprandial energy expenditure of postnatally overfed rats (bred in small nests) in comparison to those from large nests is given in Table 1. Although due to a high variation differences in the absolute energy expenditure during the pre and post fed period could not be outlined, the mean value of the increase of meta- bolic rate in the postprandial phase, however, is markedly lower in postnatally overfed rats (40.3 versus 53.9 kJ/kg"-'5 i n control rats). Calculated in percent of the fasting values (relative postprandial thermogenesis) the postprandial raise of metabolic rate of postnatally overfed rats reaches only in about 70 % ofthat ofcontrol rats. Compared as percentage of the energy intaken (absolute postprandial thermogenesis) the same difference indicates likewise the decreased postprandial thermogenesis in the postnatally overfed animals.

A decreased postprandial thermogenesis in this animal model is to consider as an additional proof that efficiency of energy utilization is enhanced induced by postnatal overnutrition.

References

I ] MILLER, D. S.. and R. S. PERSONAGE, Proc. Nutrit. SOC. 31, 30 A (1971). 21 AUST, L., R. NOACK, H. ESCHRICH, J . PROLL and L. ZAHN, Nahrung 29, 617 (1985). 31 STEINIGER. J . , H . KARST, R. NOACK and H.-D. STEGLICH, Nahrung 26, No. 4, K 23 (1982). 41 SCHUTZ, Y . . T. BESSARD and E. JEQUIER, Am. J. clin. Nutrit. 40, 542 (1984). 51 PULLAR, I . D.. and A. WEBSTER. Brit. J. Nutrit. 37, 355 (1977). 61 HOOVER-PLOW. J.. and B. NE~SON, J . Nutrit. 115, 303 (1985).

Dr. L. AUST. Prof. Dr. R. NOACK and Dr. J . PROLL, Central Institute of Nutrition, DDR-1505 Bergholz- Rehbriicke, Arthur-Scheunert-Allee 114- 116

Received October 15. 1985