Bear blood contains “superhero” components that preserve muscle mass during hibernation


HIROSHIMA, Japan — All it takes is a few weeks of relaxing and postponing the gym for humans to start losing muscle mass, but bears sleep through winter and wake up just as well chamois. Now, exciting new research in Japan has discovered that the “superhero” properties of bear blood can also help humans gain muscle!

Scientists at the University of Hiroshima observed “muscle gain” in cultured human skeletal muscle cells infused with serum from hibernating black bears. They say their work confirms that ‘unique factors’ activate in a bear’s blood during winter, triggering their incredible ability to retain muscle and prevent muscle atrophy even if they sit still for five seven months in a row. However, the exact nature of these key blood components remains a mystery.

“The ‘use it or lose it’ phenomenon is a well accepted physiological principle for 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 the first study Mitsunori Miyazaki, associate professor at the Graduate School of Biomedical and Health Sciences in Hiroshima, in a statement. university.

“In contrast, hibernating animals are probably best described as being under the ‘no use, but no loss’ phenomenon, in that there is a potential resistance to muscle atrophy during conditions of no use. keep on going.”

Working with researchers from Hokkaido University, the study authors found that serum extracted from the blood of hibernating Japanese black bears actively weakens the “kill mechanism” that drives muscle breakdown.

Here’s Why Hibernation Blood Is Special

The muscle mass of a living being is generally influenced by the dynamic balance between the “synthesis” and the “degradation” of its proteins. When a bear’s serum disrupts this balance, cultured muscle cells show significant protein growth after just 24 hours of treatment. Importantly, serum taken from bears during the summer months did not have the same effect on muscle cells.

The researchers theorize that the reduced capacity of the muscle “killing mechanism” is due to the deletion of the MuRF1 (Muscle RING-finger protein-1) gene, which scientists believe is the switch that triggers the shredding of unused muscle. The theory suggests that activation of the Akt/FOXO3a (protein kinase B/Forkhead box class O 3a) axis mediates elevation of protein synthesis – mediating suppression of MuRF1 expression.

The team also found higher levels of the growth factor hormone IGF-1 (insulin-like growth factor-1) in the serum of hibernating bears. The study authors say that this hormone is a potential factor upstream, inducing the activation of the Akt/FOXO3a axis. Meanwhile, previous studies have recorded variations in IGF-1 concentration in bear serum depending on the season. These earlier projects noted that IGF-1 concentrations were highest during the active summer months and lowest during the first weeks of hibernation (before rising again towards the end of winter). ).

Could this lead to treatment for bedridden patients?

Professor Miyazaki and his team redirected their efforts elsewhere after correctly correcting their calculations regarding GF-1 concentration levels in the serum of hibernating bears. They think it’s entirely possible that the higher IGF-1 concentrations in the study are the result of reduced serum water content – due to a number of other causes, including including dehydration.

“We reported that ‘certain factors’ 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 carried out”, adds Professor Miyazaki.

“I wanted to do research that would lead to the development of effective rehabilitation and training methods,” Professor Miyazaki concludes, adding that’s why he started exploring the secrets of hibernation.

“By identifying this ‘factor’ in the serum of hibernating bears and clarifying the unexplored mechanism behind ‘muscles that do not weaken even without use’ in hibernating animals, it is possible to develop rehabilitation strategies effective in humans and to avoid becoming bedridden in the future.”

The study is published in PLOS ONE.


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Richard V. Johnson