Navigation Links
Arctic ground squirrels muscle up to hunker down
Date:9/15/2011

When Arctic ground squirrels are getting ready to hibernate they don't just get fat they pack on muscle at a rate that would make a bodybuilder jealous. And they do it without suffering the harmful effects that high levels of testosterone and other anabolic steroids usually cause. University of Toronto Scarborough (UTSC) researchers have started to untangle how the squirrels manage it, and their results could someday have implications for human health.

Arctic ground squirrels, it turns out, ramp up their anabolic steroid levels and keep them high not just during the spring mating season, but during the summer and fall. To avoid the damaging effects of these high levels, they seem to suppress androgen receptors in all tissues except muscle, according to Rudy Boonstra, professor of biological sciences at UTSC.

Boonstra's research will appear in an upcoming issue of Functional Ecology. It is co-authored by Brendan Delehanty, also of UTSC, and Adrian J. Bradley of the University of Queensland.

Like many other hibernators, Arctic ground squirrels go underground in winter and burn the fat they stored up during the summer and fall. But Arctic ground squirrels have a problem faced by almost no other hibernator. Other animals dig below the frost line and hibernate in a relatively warm 0 C. Because Arctic ground squirrels can't get below the permafrost, they have to spend their eight-month hibernation at temperatures as low as -23 C.

Thus to stay alive their metabolisms have to run at a higher rate than other hibernators. Stored fat provides much of the energy they need, but it can't give them the levels of glucose required by vital tissues such as the brain and heart. Only burning protein stored in muscles will provide the needed glucose.

To see what was going on, Boonstra and colleagues examined the blood of Arctic ground squirrels in Canada's northern Yukon territory over an entire active season, and compared it with blood taken from Columbian ground squirrels from southern Alberta, a species which hibernates at about 0C.

In most ground squirrels, testosterone levels in males peak during mating season then fall drastically afterwards. In male Arctic ground squirrels, anabolic steroid levels (including testosterone) start out higher than in other species and stay elevated between 10 and 200 times higher than in any other ground squirrels. Females also had exceptionally high levels of androgens, between 40 and 100 times higher than in other ground squirrels.

These high levels of androgens help both males and females to increase lean body mass (i.e. muscle) by about 25 percent in the months leading up to winter hibernation mass which is then consumed as they hibernate.

In another portion of the study Boonstra and colleagues showed that in males these anabolic steroids were not being produced at the normal site of production, the testes. Instead, the squirrels produced them in their adrenal glands.

High doses of anabolic steroids also have negative effects, such as suppressing the immune system, and in older human males, causing prostate cancer. Men who take anabolic steroids to increase muscle mass and strength can suffer side effects like baldness, scarring acne, shrinkage of the testicles, behavioral and psychiatric problems, and increased risk of cardiovascular disease.

Arctic ground squirrels are proposed to down-regulate androgen receptors in tissues other than muscle. In other words, the androgens coursing through their bodies are invisible to all tissues except muscle, which protects them from the ill effects of too much androgen. How they do this still isn't known.

Because of the role of androgen levels on prostate cancer, understanding how Arctic ground squirrels turn off androgen receptors could someday have implications for human health, Boonstra says.


'/>"/>

Contact: Rudy Boonstra
boonstra@utsc.utoronto.ca
416-287-7419
University of Toronto Scarborough
Source:Eurekalert

Related biology news :

1. Ancient glacial melting process similar to existing concerns about Antarctica, Greenland
2. Scientists report dramatic carbon loss from massive Arctic wildfire
3. Antarctic krill help to fertilize Southern Ocean with iron
4. Fossilized pollen reveals climate history of northern Antarctica
5. US National Fire Plan, return of Ozark lizard and the Arctic Tundras fire regime
6. Arctic snow harbors deadly assassin
7. Date for your diary: International Symposium of Antarctic Earth Sciences 2011
8. How is the Arctic Ocean changing?
9. Striking ecological impact on Canadas Arctic coastline linked to global climate change
10. Antarctic icebergs help the ocean take up carbon dioxide
11. A new research report shows effects of climate change in the Arctic are more extensive than expected
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:6/23/2017)... N.Y. and ITHACA, N.Y. ... ) and Cornell University, a leader in dairy research, ... with bioinformatics designed to help reduce the chances that ... With the onset of this dairy project, Cornell University ... Consortium for Sequencing the Food Supply Chain, a food ...
(Date:5/6/2017)... May 5, 2017 RAM Group ... a new breakthrough in biometric authentication based on ... mechanical properties to perform biometric authentication. These new sensors ... material created by Ram Group and its partners. This ... transportation, supply chains and security. Ram Group is ...
(Date:4/13/2017)... , April 13, 2017 UBM,s Advanced ... will feature emerging and evolving technology through ... Innovation Summits will run alongside the expo portion of ... sessions, panels and demonstrations focused on trending topics within ... advanced design and manufacturing event will take place June ...
Breaking Biology News(10 mins):
(Date:9/20/2017)... Station, TX (PRWEB) , ... ... ... Services, LLC (IPS), a leading global provider of engineering, architecture, project controls, ... provider of prefabricated cleanrooms, today announced the unveiling of the iCON™ brand ...
(Date:9/20/2017)... ... September 20, 2017 , ... Foresight Institute, ... and other transformative technologies, announced the winners for the 2017 Foresight Institute Feynman ... Theory in nanotechnology/molecular manufacturing. , Established in 1993 and named in honor of ...
(Date:9/19/2017)... (PRWEB) , ... September 19, 2017 , ... ... Philadelphia’s largest group of funded early-stage tech companies. “Grit” author Angela Duckworth and ... Also joining the ic@3401 community is Cooley, an international law firm with decades ...
(Date:9/19/2017)... ValGenesis Inc., the global leader in Enterprise ... the strategic partnership with VTI Life Sciences (VTI). This ... using the latest technology available in the ValGenesis VLMS ... efficient and cost-effective validation services using ValGenesis VLMS. VTI ... VLMS system. The ...
Breaking Biology Technology: