Impact of glucose consumption on hibernation phenotype of adipose tissue in brown bears

Primary author: Michael Saxton
Faculty sponsor: Joanna Kelley

Primary college/unit: Arts and Sciences
Campus: Pullman

Abstract:

To survive the cold environments and winter food shortage for which they are adapted, brown bears undergo seasonal shifts from maximizing energy gain and storage in summer and fall, to conserving energy in winter hibernation. During hibernation, bears experience a mild decrease in body temperature but up to a 75% reduction in basal metabolic rate, as well as reduced heart rate, respiration rate, and insulin sensitivity. On arousal from hibernation, the bears return to active season physiology, which includes a reversal of the insulin resistance. Fluctuations in weight and high overall adiposity, like those seen in bears, are contributing factors to cardiovascular disease and diabetes in humans. In this study bears were fed dextrose during hibernation to determine the effect of glucose consumption on hibernation and insulin sensitivity. We collected serum from the bears and evaluated the effect of that serum on gene transcription in bear adipose cells grown in vitro. We found a strong cell by serum interaction, with cells collected in hibernation and grown with pre-dextrose hibernation serum showing a starkly different gene expression profile than those grown with either active season or post-dextrose hibernation serum. Though cells treated with post-dextrose hibernation serum closely matched the expression profile of cells grown with active serum, proteomic analysis of serum showed that post-dextrose serum more closely matched hibernation serum. Therefore one of these limited changes in serum proteins after consumption of dextrose leads to near complete reversal of the hibernation phenotype in brown bear adipose tissue.