Differential expression of miRNAs with metabolic implications in hibernating thirteen-lined ground squirrels, Ictidomys tridecemlineatus.

Mammalian hibernators undergo significant physiological and biochemical changes when confronted with cold temperatures. Metabolic depression and translational repression are two examples of the various processes impacted during a torpor bout. MicroRNAs (miRNAs), non-coding transcripts that bind to mRNAs, are known regulators of mRNA translation and a growing number of these molecules have been found to be differentially expressed during hibernation. We hypothesized that a group of six miRNAs, with targets involved in various metabolic cascades, is modulated in selected tissues of the hibernating thirteen-lined ground squirrel Ictidomys tridecemlineatus. Expression levels of these miRNAs were assessed in the liver, heart, and skeletal muscle ground squirrel tissues using qRT-PCR. miR-29a, miR-152, miR-195, miR-223, and miR-486 were shown to be up-regulated in the hibernating liver, while miR-378 was shown to be down-regulated in hibernating skeletal muscle tissue samples. Interestingly, fatty acid synthase (FAS), an enzyme involved in fatty acid biosynthesis and a miR-195 target, was shown to be down-regulated in hibernating squirrel liver. This data add to the growing signature of differentially expressed miRNAs during hibernation and puts the light on the potential regulation of fatty acid homeostasis by a miRNA in torpid animals.