AJP - Regulatory, Integrative and Comparative Physiology, Vol 258, Issue 3 608-R615, Copyright © 1990 by American Physiological Society
Weight gain and brown fat composition of mice selected for high body weight fed a high-fat diet
M. Desautels and R. A. Dulos
Department of Physiology, College of Medicine, University of Saskatchewan, Saskatoon, Canada.
Mice selected for high body weight (QL522) had increased food intake, body
weight gain, and fat deposition relative to mice without weight selection
(QL521). Brown adipose tissue (BAT) thermogenic capacity, as determined by
the tissue content of protein, DNA, and succinate dehydrogenase and by
mitochondrial uncoupling protein content was similar or slightly higher in
2- and 10-mo-old QL522 mice relative to age-matched QL521 mice. When food
intake of QL522 mice was restricted to the level of QL521 mice, body weight
gain and fat deposition over 28 days were then comparable to those of QL521
mice. Food restriction had no effect on BAT composition of QL522 mice. Both
QL521 and QL522 mice increased calorie intake by 40-50% when offered a
palatable high-fat supplement (HF), but only QL522 mice increased weight
gain and fat deposition significantly. QL521 mice fed a high-fat supplement
showed a significant increase in brown fat succinate dehydrogenase content,
whereas QL522 mice showed significant increases in brown fat weight,
protein, and succinate dehydrogenase content relative to mice fed stock
diet. Nonshivering thermogenic capacity, as assessed by
norepinephrine-stimulated oxygen uptake in anesthetized animals at 30
degrees C was similar between QL521 and QL522 mice eating stock diet and
was significantly increased by the high-fat supplement in both strains.
Thus mice selected for high body weight are very susceptible to
diet-induced obesity, and we have no evidence that a reduction in brown fat
thermogenic capacity contributes to the increased fat deposition of QL522
mice as they grow old or when they are offered palatable energy-dense
supplements.
