Energy balance and brown adipose tissue thermogenesis during chronic endotoxemia in rats

J. Arnold, R. A. Little, N. J. Rothwell

Research output: Contribution to journalArticlepeer-review


The effects of continuously administered endotoxin on 7-day energy balance were investigated in male rats. Three groups of rats were implanted with osmotic pumps; two groups received saline-filled pumps, whereas the third received endotoxin. One of the saline groups was pair fed to match the food intake of the endotoxemic rats. After 7 days, body energy and protein and fat contents of rats were determined together with the energy content of food and feces. Endotoxin infusion not only induced fever, but it also suppressed appetite and significantly decreased body weight gain. Metabolizable energy intake was reduced by ~20% in infected rats. Although protein and fat gains were lowest in the endotoxin group, there appeared to be a selective loss of protein when considered as percent of body weight. Percent body fat was unaltered between the groups. Energy expenditure considered in absolute (kJ) or body weight-independent (kJ/kg0.67) terms yielded similar patterns of results; expenditure (kJ) was 10 and 20% (P <0.05, P <0.01) lower in the endotoxemic and pair-fed rats, respectively, compared with controls. Hence, compared with pair-fed rats, endotoxin-infused animals had a 10% rise in their expenditure. Brown adipose tissue thermogenesis was assessed by mitochondrial binding of guanosine 5'-diphosphate, and results showed that binding was greatest in endotoxemic rats and lowest in the pair-fed animals. The present results suggest that in this endotoxemic model appetite suppression exacerbates changes in energy balance. However, the reduction in body weight gain is also dependent on a decrease in metabolic efficiency and an increase in total energy expenditure. Food deprivation in otherwise healthy animals is compensated for by decreases in energy expenditure.
Original languageEnglish
Pages (from-to)1970-1975
Number of pages5
JournalJournal of Applied Physiology
Issue number4
Publication statusPublished - 1989


  • Animals
  • Body Temperature Regulation
  • metabolism: Brown Fat
  • blood: Endotoxins
  • Energy Metabolism
  • Escherichia coli
  • Male
  • Rats
  • Rats, Inbred Strains
  • Support, Non-U.S. Gov't


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