Hibernation Secret: Bear Blood Protects Against Muscle Breakdown
Bears can hibernate for five to seven months without eating or drinking. In humans, three weeks of inactivity is enough for the muscles to begin to break down. A team of Japanese researchers has just discovered why bears have this extraordinary ability. The secret is in the blood of animals and should now be made available to humans.
Researchers from Hiroshima University in Japan have discovered why bears can survive long periods of inactivity with limited muscle loss and minimal metabolic dysfunction. The results, which were recently presented in the renowned specialist journal “PLOS ONE”, could lead to new therapies for muscle wasting and metabolic disorders.
In humans, muscles break down quickly
Humans are not designed for long periods of inactivity. After just a few weeks without physical exertion, the body begins to break down muscle mass and accumulate fatty tissue. In the long term, lack of exercise increases the risk of obesity, diabetes and heart disease.
Bears survive months of inactivity unscathed
Hibernating bears survive long periods of inactivity without significant loss of physical capacity. How bears manage to survive this phase unscathed has now been studied by the Japanese task force at Hiroshima University.
Use it or lose it
“The ‘use it or lose it’ phenomenon is a well-established physiological principle for skeletal muscle, which is very plastic based on functional demands,” says Professor Mitsunori Miyazaki, lead author of the study.
“In many animal species, including humans, non-use typically results in skeletal muscle wasting and metabolic disorders,” Miyazaki points out.
Hibernating animals seem to have particular resistances
“On the other hand, hibernating animals are probably best described with the phenomenon ‘no use, but no lose’ (do nothing and still lose nothing),” explains the scientist. These animal species seem to have a potential resistance to muscle wasting during long periods of inactivity.
Black bear blood analysis
To unravel this mystery, the team analyzed the blood of hibernating Japanese black bears and discovered a key difference with the blood of non-hibernating mammals.
Muscle mass is determined by a dynamic balance
As the researchers explain, muscle mass is generally determined by the dynamic balance between protein synthesis and breakdown. In the blood of hibernating bears, however, this balance was upset.
The scientists attributed this to suppressed expression of a specific protein called MuRF1 (muscle RING-finger protein-1), which normally breaks down unused muscle.
Additionally, the team was able to determine that levels of the insulin-like growth factor-1 (IGF-1) hormone in the serum of overwintering bears were significantly increased. This appears to be related to MuRF1 inhibition.
Bear blood serum acted on human cells
In another experiment, the working group made a startling discovery. They mixed blood serum from wintering black bears with human skeletal muscle cells. Cultured human muscle cells showed significant protein growth after 24 hours of treatment.
However, when blood serum from summer-active bears was used, this increase in protein was not observed. The team thus confirms for the first time that the unique factors present in the blood of bears are only activated during hibernation and prevent muscle wasting despite months of inactivity.
Ability can be transferred to human cells
“We suggested that certain factors present in wintering bear serum may regulate protein metabolism in cultured human skeletal muscle cells and contribute to the maintenance of muscle mass,” Miyazaki said.
The underlying mechanism is not yet sufficiently understood
However, researchers have not yet been able to decode the exact mechanism behind this process. The scientists involved hope that clarifying this unexplored mechanism could lead to new therapies for muscle wasting and revolutionize rehabilitation methods. (vb)
Author and source information
This text corresponds to the specifications of the specialized medical literature, medical guidelines and current studies and has been verified by health professionals.
Graduate editor (FH) Volker Blasek
Hiroshima University: Bears Have the Power of Hibernation in Their Blood, But Identity of “Superhero” Components Remains a Mystery (Published: 2022/07/15), hiroshima-u.ac.jpMitsunori Miyazaki , Michito Shimozuru, Toshio Tsubota, et al. : Human myotubes cultured with hibernating bear serum lead to increased protein content by modulating Akt/FOXO3a signaling; in: PLOS ONE (2022), journals.plos.org
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