Why is it that bears able to sleep for an entire winter and not lose their muscle mass, but just a few weeks away from the gym will make us begin to lose our hard-earned gains?
Now scientists have the answer and believe it could eventually help humans to retain or even build muscle.
Scientists in Japan noted “muscle gain” in cultured human skeletal muscle cells infused with serum from hibernating black bears. As a result, they believe “unique factors” activate in a bear’s blood during winter, allowing them to retain their muscles and prevent muscular atrophy despite remaining stationary up to half a year or more. Exactly what these key blood components are, however, is still a mystery.
Bears’ blood: the next hot supplement?
“The ‘use it or lose it’ phenomenon is a well-accepted physiological principle for the skeletal muscle, which is highly plastic in response to functional demands. Disuse typically leads to skeletal muscle loss and metabolic dysfunction in many animal species, including humans,” explains first study Mitsunori Miyazaki, associate professor at Hiroshima’s Graduate School of Biomedical and Health Sciences, in a university release.
“In contrast, hibernating animals are likely better described to be under the ‘no use, but no lose’ phenomenon, in that there is potential resistance to muscle atrophy during continued disuse conditions.”
Researchers from two Japanese universities discovered that serum extracted from the blood of hibernating Japanese black bears actively weakens the “destruction mechanism” that causes muscles to degrade.
Muscle mass is in a dynamic balance between the “synthesis” and “degradation” of its proteins. When the bear’s serum interrupts this balance, cultured muscle cells display significant protein growth after just 24 hours of treatment. Serum taken from bears during the summer months did not have this same effect on muscle cells.
Researchers theorize this interruption is due to the suppression of the MuRF1 gene (Muscle RING-finger protein-1), which scientists consider the switch that causes the shredding of unused muscles.
The researchers also found higher levels of the growth factor hormone IGF-1 (insulin-like growth factor-1) in the hibernating bear serum. Earlier studies had recorded IGF-1 concentration variations in bear serum depending on the season. Those earlier projects noted that IGF-1 concentrations were highest during the active summer months and at their lowest during the early weeks of hibernation (before increasing again near the end of the winter).
Skinny people do less exercise, according to new research
Skinny people are more likely to be less active than normal or even overweight people, according to a new study out of China.
As the new research reveals, it’s not that these people stay skinny by eating less and doing more exercise. Rather, their metabolism is just running at a higher rate.
“We expected to find that these people are really active and to have high activity metabolic rates matched by high food intakes,” says corresponding author John Speakman, a professor at the Shenzhen Institutes of Advanced Technology in China and the University of Aberdeen, in a media release.
“It turns out that something rather different is going on. They had lower food intakes and lower activity, as well as surprisingly higher-than-expected resting metabolic rates linked to elevated levels of their thyroid hormones.”
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Prof. Miyazaki and his team redirected their efforts elsewhere after properly correcting their calculations regarding GF-1 concentration levels within the hibernating bear serum. They believe that it is possible that the higher IGF-1 concentrations in the study were caused by a reduction in the serum’s water content, which could have been caused by dehydration.
“We have indicated that ‘some factor’ present in hibernating bear serum may regulate protein metabolism in cultured human skeletal muscle cells and contribute to the maintenance of muscle mass. However, the identification of this ‘factor’ has not yet been achieved,” Prof. Miyazaki adds.
“I wanted to do research that would lead to the development of effective rehabilitation and training methods,” Prof. Miyazaki concludes, adding that this is the reason he started exploring hibernation’s secrets.
“By identifying this ‘factor’ in hibernating bear serum and clarifying the unexplored mechanism behind ‘muscles that do not weaken even without use’ in hibernating animals, it is possible to develop effective rehabilitation strategies in humans and prevent becoming bedridden in the future.”
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