Metabolic fuel privation in hibernating and awake ground squirrels

The nature of metabolic fuel utilization during hibernation and periodic arousal is not completely understood. 2-Deoxy-D-glucose (2DG) and mercaptoacetate (MA) were administered to hibernating ground squirrels. These drugs disrupt glucose and fatty acid oxidation, respectively. Telemetrically recorded body temperature (Tb) was analyzed to determine rate of rewarming from hibernation, duration of euthermia during periodic arousal, and proportion of animals arousing after treatments. 2DG given during hibernation significantly increased latency to regain euthermia, especially during the initial phase of rewarming (from first Tb > 10 degrees C to first Tb > 15 degrees C), without affecting the duration or other features of the ensuing euthermic period; MA did not affect rate of rewarming. MA treatment during hibernation affected thermoregulation after the animals aroused, including an increased duration of euthermia and maintenance of erratic patterns of Tb. The percentage of animals that aroused from hibernation was increased in a dose-dependent fashion by each drug. 2DG and MA treatments had little or no impact on nonhibernating ground squirrels in the cold. We suggest that glucose oxidation is important for rewarming from deep torpor; limited glucose availability cannot, however, support normal levels of euthermia when fatty acid oxidation is compromised. On the other hand, fatty acid oxidation may be less necessary for normal arousal from torpor, but critical for the maintenance of euthermia during the arousal phase.