Life Lines by Dr. Dolittle

Sponsored by the American Physiological Society

Extreme Fasting

Photo by Carla Frare, University of Alaska Fairbanks

While giant pandas roll in horse manure to stay warm in the winter (that’s a different story), other animals spend up to 8 months hibernating to conserve energy during times of reduced food availability and freezing temperatures. During their long winter’s nap, animals such as the Arctic ground squirrel and 13-lined ground squirrel go without food or water while at the same time avoiding muscle wasting – a rather impressive feat.

Could you imagine going without food or water for 8 months? Granted, their metabolism, heart rate, and body temperature are reduced, it is still truly remarkable to think about. Recently scientists discovered that these animals avoid thirst by reducing the amount of electrolytes (sodium, glucose, urea) in their blood before they hibernate. This helps them stay hydrated by keeping their blood relatively dilute.

In a new study, scientists at the University of Alaska – Fairbanks discovered that Arctic ground squirrels recycle nutrients to prevent muscle and tissue wasting during hibernation. In fact, the animals recycle amino acids from muscle breakdown to build new proteins in the lungs, muscle and kidneys. By recycling proteins, the animals avoid tissue wasting that would otherwise occur from their lack of mobility. Learning more about how the animals recycle proteins may help in the development of treatments to prevent muscle wasting resulting from lack of mobility or exposure to microgravity – something of interest to doctors and astronauts.


NY Feng, MS Junkins, DK Merriman, SN Bagriantsev, EO Gracheva. Osmolyte depletion and thirst suppression allows hibernators to survive for months without water. Current Biology. 29(18): 3053-3058, 2019.

SA Rice, GAM Ten Have, JA Reisz, S Gehrke, D Stefanoni, C Frare, Z Barati, RH Coker, A D’Alessandro, NEP Deutz, KL Drew. Nitrogen recycling buffers against ammonia toxicity from skeletal muscle breakdown in hibernating arctic ground squirrels. Nature Metabolism. 2: 1459-1471, 2020.

AV Goropashnaya, BM Barnes, VB Fedorov. Transcriptional changes in muscle of hibernating arctic ground squirrels (Urocitellus parryii): Implications for attenuation of disuse muscle atrophy. Scientific Reports. 10: 9010, 2020.


Categories: Diet and Exercise, Environment, Extreme Animals, Hibernation and Hypoxia, Nature's Solutions, sleep

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