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Energy metabolism of young rats after early postnatal overnutrition
Petra Wiedmer1, Susanne Klaus, Sylvia Ortmann
1Department of Biochemistry and Physiology of Nutrition, German Institute of Human Nutrition (DlfE), Postdam-Rehbrücke, Germany.
Insights
Early postnatal overnutrition in rats leads to higher body weight and fat. However, this study found no long-term changes in energy expenditure, despite increased adiposity in later life.
Area of Science:
- Physiology
- Metabolic Research
- Obesity Studies
Background:
- Early postnatal overnutrition (PNO) in rats, induced by small litters, models moderate obesity and hyperinsulinism.
- PNO is linked to increased body weight and fat gain later in life.
- The underlying mechanisms, particularly energy expenditure, require further investigation.
Purpose of the Study:
- To investigate if increased adiposity in PNO rats is due to decreased energy expenditure.
- To analyze energy intake, expenditure, and body composition changes over time in PNO rats.
Main Methods:
- Male Wistar rats were raised in small (SL) or normal (NL) litters.
- Body weight, daily energy intake, total energy expenditure (indirect calorimetry), and body composition were measured at 5, 8, and 12 weeks.
- Energy balance was calculated as assimilated energy minus energy expenditure.
Main Results:
- SL rats showed increased body weight from weeks 2-5 and 10-12.
- At 5 weeks, SL rats had higher lean body mass, fat, protein, and total energy expenditure.
- From 8-12 weeks, no differences in energy metabolism were observed, but total fat content remained higher in SL rats.
- Energy balance did not differ between SL and NL rats at any measured time point.
Conclusions:
- PNO rats exhibit increased adiposity in early life.
- Despite early adiposity, PNO does not appear to cause long-lasting alterations in energy metabolism.
- A tendency towards increased adiposity persists in later life without significant metabolic changes.
Abstract:
Early postnatal overnutrition (PNO) induced by restricting litter size in rats leads to increased body-weight (BW) and body-fat gain in later life. PNO rats are used as an animal model of moderate obesity and early hyperinsulinism. We investigated whether the increased adiposity could be due to a decreased energy expenditure. Male newborn Wistar rats were raised in litters of either two (SL) or twelve pups (NL), weaned at 4 weeks of age and subsequently fed ad libitum. BW was recorded continuously until 12 weeks of age. Daily energy intake, total daily energy expenditure (EE, measured by indirect calorimetry) and body composition were measured in weaned pups at 5, 8 and 12 weeks of age. SL rats displayed increased BW compared with NL rats from week 2 to 5 and again from week 10 to 12. Lean body mass, body fat and protein content and total EE were increased in SL rats at week 5. The same linear correlation described the relationship between BW and total EE in NL and SL rats. At week 8 to 12 no differences in energy metabolism could be found, but the total fat content was increased in SL rats at week 12. Energy balance, i.e. assimilated energy minus EE, was no different between SL and NL at any time that it was measured. We conclude that although PNO rats display increased adiposity in early life, there seem to be no long-lasting effects on energy metabolism in later life, even if a tendency to increased adiposity can still be detected.
