The influence of early postnatal overnutrition on postprandial energy expenditure in rats

Abstract

Short communication) L. AUST, R. NOACK and J. PROLLOvernutrition 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 Versuchstierproduktion, 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 indirect 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 absorption 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.

Energy metabolism of young rats after early postnatal overnutrition

“…There are only very scarce results in the literature about EE in SL animals in comparison with NL animals. It has been reported that SL rats show a reduced postprandial EE at 7 -9 weeks of life (Aust et al 1986). In the present study, we found that total daily EE was virtually the same for SL and NL rats at week 8 and 12.…”

“…*P,0•05. 1972; Parizková & Petrásek, 1979;Aust et al 1985). However, energy balance was not determined in these studies and our present results show that even by 5 weeks of age there was no difference in energy retention between the groups.…”

“…It has also been shown that rats from small litters (SL) can develop persistent hyperinsulinaemia, increased systolic blood pressure, and hyperleptinaemia (Cryer & Jones, 1980;You et al 1990;Plagemann et al 1992Plagemann et al , 1999. Although it is quite clear that rats reared in SL show increased fat deposition at the end of the sucking period, there are controversial reports in the literature as to whether this has a longlasting effect, and whether SL rats display hyper-, normo-or even hypophagia after weaning (Miller & Personage, 1972;Wurtman & Miller, 1976;Faust et al 1980;Hausberger & Volz, 1984;Aust et al 1985;Lambert & Koeslag, 1992;Plagemann et al 1992). One reason for this could be that the number of pups considered as 'SL' differed from two to six.…”