From the North American Bear Center
As the academic semester ends, I see the tell-tale signs of the upcoming holiday hibernation. The weary eyes of teaching assistants peeking over piles of final exams. Students who may have mentally been on break before finals even started. A little more pep in the faculty step (finally some time for that NSF proposal!).
Upon return to campus after the new year, most are refreshed and excited for a new semester. However, others will return in a slightly, well, degraded state: slowed by the excess of holiday nourishment and mentally lulled by an embarrassingly lengthy Netflix binge.
No matter what group you fall into, take a look at this new paper from Dr. Vadim Federov and colleagues that describes how some of our fellow mammals actually hibernate while still keeping themselves in shape.
In humans and most mammals, physical inactivity leads to loss of muscle strength and mass. In contrast, hibernating bears and ground squirrels demonstrate very limited muscle atrophy over the prolonged periods (6–8 months) of physical inactivity of winter hibernation, suggesting that hibernating mammals have evolved natural mechanisms that prevent disuse muscle atrophy.
Two hypotheses for how these mammals carry out this feat have been proposed. Either a) genes that build proteins are upregulated during hibernation or b) genes that are responsible for breaking down muscle tissue are downregulated during hibernation.
By measuring the expression levels of a host of functional genes from black bears and arctic ground squirrels that were either in the process or hibernation or not, Federov and his colleagues show that the role of genes that increase protein biosynthesis is more pronounced in animals that are hibernating compared to those that aren’t.
At the same time, they found no changes in pathways that result in the catabolism of proteins, indicating little influence of genes that prevent the breakdown of muscle tissue.
These findings imply reduction in amino acid catabolism and suggest, besides possible urea recycling, redirection of amino acids from catabolic pathways to the enhancement of protein biosynthesis.
If only this was applicable to humans. Goodbye hustle and bustle. Hello to sweet, sedentary life.
Fedorov V.B., Nathan C. Stewart, Øivind Tøien, Celia Chang, Haifang Wang, Jun Yan, Louise C. Showe, Michael K. Showe & Brian M. Barnes (2014). Comparative functional genomics of adaptation to muscular disuse in hibernating mammals, Molecular Ecology, 23 (22) 5524-5537. DOI: http://dx.doi.org/10.1111/mec.12963