Influence of torpor on cardiac expression of genes involved in the circadian clock and protein turnover in the Siberian hamster (Phodopus sungorus)

The Siberian hamster exhibits the key winter adaptive strategy of daily torpor, during which metabolism and heart rate are slowed for a few hours and body temperature declines by up to 20°C, allowing substantial energetic savings. Previous studies of hibernators in which temperature drops by >30°C for many days to weeks have revealed decreased transcription and translation during hypometabolism and identified several key physiological pathways involved. Here we used a cDNA microarray to define cardiac transcript changes over the course of a daily torpor bout and return to normothermia, and we show that, in common with hibernators, a relatively small proportion of the transcriptome (<5%) exhibited altered expression over a torpor bout. Pathways exhibiting significantly altered gene expression included transcriptional regulation, RNA stability and translational control, globin regulation, and cardiomyocyte function. Remarkably, gene representatives of the entire ubiquitylation pathway were significantly alt...