AJP - Endocrinology and Metabolism, Vol 255, Issue 2 E120-E128, Copyright © 1988 by American Physiological Society
Effects of repeated cycles of fasting-refeeding on brown adipose tissue composition in mice
M. Desautels and R. A. Dulos
Department of Physiology, College of Medicine, University of Saskatchewan, Saskatoon, Canada.
Mice fasted for 24 h showed reductions in carcass fat and gonadal fat
depots and atrophy of brown adipose tissue (BAT) that was characterized by
loss of protein and succinate dehydrogenase. These changes were reversed on
24 h of refeeding. Cycling mice experienced 14 cycles of 1 day of fast
followed by 2 days of refeeding, whereas control mice were fed ad libitum.
Weight loss during each fast remained constant, and the animals lost and
regained in excess of twice their initial weights within 6 wk. However,
final weight and carcass and gonadal fat weights were similar to those of
animals fed ad libitum. Total food intake was similar between cycling mice
and those fed ad libitum suggesting an increase in feeding efficiency.
There was no development of resistance to food deprivation since the
preceding fasting experience of the animal had no effect on weight and
carcass fat loss during a 24- or 48-h fast. Norepinephrine-stimulated
oxygen consumption that was reduced in cycling mice was probably the result
of a reduction of BAT thermogenic capacity. BAT succinate dehydrogenase
content and the concentration of uncoupling protein in isolated
mitochondria were significantly reduced. These changes in BAT composition
were not observed when the refeeding period of each cycle was increased to
6 days. These results suggest that reduced energy expenditure in BAT may
play a role in the conservation of energy during intermittent and frequent
bouts of food deprivation.
