Hibernation without muscle atrophy
The plasma of the blood of sleeping bears will protect our muscles from degradation during immobility
Sergey Vasiliev, Naked Science
Japanese biologists have shown that blood plasma obtained from hibernating bears enhances the metabolism of human muscle cells, while plasma taken during the normal period does not have such an effect. Scientists suspect that a certain protein that accumulates during hibernation stops the processes leading to degradation and atrophy of muscle tissue. However, so far it is not possible to isolate this "active substance". Scientists from Hiroshima University write about this in an article published in the journal PLOS ONE (Miyazaki et al., Supplementing cultivated human myotubes with hibernating bear serum results in increased protein content by modulating Akt/FOXO3a signaling).
Hibernation in bears lasts 5-7 months, and all this time the huge animals do not drink, do not eat and do not move. However, with the onset of heat, they get out of their dens and immediately go in search of food. For comparison, in humans, muscle degradation begins after three weeks of immobility, and a lack of activity for longer periods is fraught with the development of obesity, diabetes and other serious health problems. Bears, on the other hand, maintain a healthy, albeit sharply slowed down, metabolism, and a good state of musculature during months of hibernation.
In fact, in most mammals, skeletal musculature follows the "use it or loose it" rule. This allows the body to flexibly adapt to external conditions: muscles that are not loaded quickly weaken, and those that strain regularly, on the contrary, develop. This effect is associated with constant competition between opposite biological mechanisms, one of which stimulates the destruction of muscle tissue, and the other – its synthesis.
In animals that hibernate, the "use or lose" rule does not apply, and they are able to maintain musculature, even without using it for a considerable time. How this happens is still largely unknown. One of the tools of such protection can be as yet unidentified proteins that circulate in the blood and have the necessary effect on the destruction and production of muscle tissue. This was confirmed by new experiments conducted by the team of Professor Mitsunori Miyazaki (Mitsunori Miyazaki).
Biologists took blood from hibernating Japanese black bears and purified it from cells, getting plasma full of proteins and other molecules. It was used to process cultures of human muscle cells that were grown "in vitro", and after a few hours they showed a significant increase in activity. At the same time, the same cells treated with plasma obtained from bears during normal summer activity continued to grow as before.
Scientists explain the positive effects of bears' plasma in hibernation by reducing the synthesis of MuRF1 protein, which triggers the mechanisms of muscular atrophy. This, in turn, may be due to the activation of the Akt/FOXO3 signaling pathway, which stimulates cellular metabolism. However, it has not yet been possible to trace the chain further and determine the specific plasma protein that triggers these processes.
"We found out that during the hibernation period, there is a certain factor in the blood plasma of bears that is able to stimulate the metabolism of human muscle cells and maintain the preservation of muscle mass,– says Miyazaki. "If we identify it and find out the unknown mechanism by which the muscles of animals in hibernation are preserved even without loads, we will be able to develop effective rehabilitation strategies for people and stop suffering from lack of mobility in the future."
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