Seasonal Metabolism Of Brown Adipose Tissue And Brain Mitochondria In The Thirteen-Lined Ground Squirrel (Ictidomys tridecemlineatus)

Abstract

During the hibernation season, thirteen-lined ground squirrels (Ictidomys tridecemlineatus) regularly cycle between bouts of torpor and interbout arousal (IBA). This presents a unique seasonal change in energy requirements in both the brain and brown adipose tissue (BAT). We hypothesized that brain and BAT mitochondria undergo a seasonal change in function to accommodate the variable energy demands of hibernation. To test this hypothesis, we examined mitochondrial bioenergetics of brain and BAT in thirteen-lined ground squirrels across five time points: summer, fall, torpor, IBA and spring. Through various molecular and functional analyses, we found significant increases in mitochondrial oxidative capacities of both brain and BAT during torpor and IBA. Overall, brain and BAT mitochondrial bioenergetics are not static across the year, and our studies suggest that these two tissues function efficiently during the hibernation season, when extreme physiological changes are occurring. These studies provide improved understanding of the overall energy requirements of a hibernator.