Shifting Nitrogen Balance Induces Arousal from Hibernation in Arctic Ground Squirrels

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Hibernators, such as arctic ground squirrels (AGS), undergo brief periods of euthermy (termed interbout arousals) where they radically change their physiological and metabolic state. These interbout arousals rebalance metabolic and nitrogen homeostasis. A key metabolic characteristic of a hibernation bout is a progressive increase in glutamine in liver, representing an increase in nitrogen load, which is resolved over the interbout arousal. We hypothesized that increasing the nitrogen load over a bout of torpor would induce arousal. We tested the impact of increased nitrogen load on timing of arousal and metabolic profile by blinded infusion of ammonium acetate at 6 and 30 mg/kg/hr for a 12 hour period early in a torpor bout. Sodium acetate (6 and 30 mg/kg/hr) and saline served as controls. Plasma was sampled at 0, 6, 12, 30 hour from infusion start and at points defined as mid and late torpor. We monitored the core body temperature and rate of oxygen consumption to assess the hibernation state of the animal. The metabolic impact of exogenous nitrogen load was tracked over time in plasma with ultra high‐performance liquid chromatography mass spectrometry (UHPLC‐MS) metabolomics.Infusion with the highest concentration of ammonium acetate resulted in a shorter bout length than infusion with saline (Table 1). The effect of infusions on metabolic profiles is pending analysis. In conclusion, results support the hypothesis that nitrogen load limits torpor bout length. Further work is needed to determine if shifting nitrogen balance in hibernation mimics endogenous mechanisms which naturally induce arousal.This work was performed in conformance with the FASEB Statement of Principles for animals used in research.Support or Funding InformationThis work was supported by the NSF award number 1258179 and NIH 20GM103395.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.