Abstract
Hibernating arctic ground squirrels (Urocitellus parryii), overwintering in frozen soils, maintain large gradients between ambient temperature (T a) and body temperature (Tb) by substantially increasing metabolic rate during torpor while maintaining a subzero Tb. We used quantitative reverse-transcription PCR (qRT-PCR) to determine how the expression of 56 metabolic genes was affected by season (active in summer vs hibernating), metabolic load during torpor (imposed by differences in Ta: +2 vs -10°C) and hibernation state (torpid vs after arousal). Compared with active ground squirrels sampled in summer, liver from hibernators showed increased expression of genes associated with fatty acid catabolism (CPT1A, FABP1 and ACAT1), ketogenesis (HMGCS2) and gluconeogenesis (PCK1) and decreased expression of genes associated with fatty acid synthesis (ACACB, SCD and ELOVL6), amino acid metabolism, the urea cycle (PAH, BCKDHA and OTC), glycolysis (PDK1 and PFKM) and lipid metabolism (ACAT2). Stage of hibernation (torpid vs aroused) had a much smaller effect, with only one gene associated with glycogen synthesis (GSY1) in liver showing consistent differences in expression levels between temperature treatments. Despite the more than eightfold increase in energetic demand associated with defending Tb during torpor at a Ta of -10 vs +2°C, transcript levels in liver and brown adipose tissue differed little. Our results are inconsistent with a hypothesized switch to use of non-lipid fuels when ambient temperatures drop below freezing.
Original language | English (US) |
---|---|
Pages (from-to) | 1300-1306 |
Number of pages | 7 |
Journal | Journal of Experimental Biology |
Volume | 214 |
Issue number | 8 |
DOIs | |
State | Published - Apr 2011 |
Externally published | Yes |
Keywords
- Arctic ground squirrel
- Fuel substrate
- Hibernation
- Metabolism
- Real-time PCR
- Thermogenesis
- Torpor
ASJC Scopus subject areas
- Ecology, Evolution, Behavior and Systematics
- Physiology
- Aquatic Science
- Animal Science and Zoology
- Molecular Biology
- Insect Science