Circadian changes in glycogen content in rat interscapular brown adipose tissue: effect of cold exposure and food deprivation.

The effects of food deprivation and cold exposure on brown adipose tissue (BAT) glycogen and lipid levels during the circadian cycle were studied. BAT glycogen levels in control animals followed a definite circadian cycle, showing an increase during the light period. In cold-exposed animals the pattern was different, with minimal values at the beginning of the dark period. Food deprivation caused a decrease in BAT glycogen concentration only after 48-hours. In contrast to the control animals, where BAT and liver showed a different glycogen pattern, in the cold exposed group the observed changes were similar. During cold exposure, lipid stores in BAT were decreased. The results obtained in this work highlight with the important role of glycogen and lipid stores in BAT thermogenesis.