Japanese scientists observed muscle gain in cultured human skeletal muscle cells infused with serum from black bears, which shows that unique factors activated in these animals' blood during winter can prevent muscular atrophy.
Bears can rest for up to seven months a year inside their dens. Three weeks of rest is all it takes for humans to lose muscle mass. This contributes to diseases that are related to sedentary lifestyles. Bears have limited muscle loss, minimal metabolism, and undamaged physical functions.
The 'use it or lose it' phenomenon is an accepted principle for the skeletal muscle, which is highly plastic in response to functional demands." The study first-author, Mitsunori Miyazaki, is an associate professor at the Graduate School of Biomedical and Health Sciences.
"Hummingbird animals are likely to be under the 'no use, but no lose' phenomenon, in that there is potential resistance to muscle atrophy during continued disuse conditions."
The study found that the destruction mechanism controlling muscular degradation was weakened by the blood of Japanese black bears. Their work was published in a journal.
The amount of muscle mass is determined by the balance betweensynthesis anddegradation. The muscle cells cultured after 24 hours of treatment showed a lot of growth. During the active summer season, there was a noticeable increase in the number of bears.
The researchers said that the shredding of unused muscles was caused by the suppression of the expression of MuRF1. The activation of the Akt/FOXO3a axis is believed to have suppressed MuRF1 expression.
There was an increase in the levels of the growth factor hormone IGF-1 in the bear. The Akt/FOXO3a axis is activated by it. There have been reports of seasonal variations in the concentrations of IGF-1 in bears. The highest concentrations of IGF-1 were found during the active summer period and lowest in early hibernation.
After changing their calculations on the concentration of IGF-1 in the bear serum, Miyazaki and his co- researchers shifted their focus to other areas. It is possible that the higher IGF-1 concentrations observed in the study were due to a decrease in the water content in the blood.
"We have shown that some factor present in bear serum may regulate the metabolism of genes in human muscles and contribute to the maintenance of muscle mass." The identification of this factor has not yet been achieved.
The associate professor wondered why it is not possible to build muscles that don't weaken in the first place.
He wanted to do research that would lead to the development of effective rehabilitation and training methods.
It is possible to develop effective rehabilitation strategies in humans and prevent becoming bedridden in the future by clarifying the unexplored mechanism behind'muscles that do not weaken even without use'.
More information: Mitsunori Miyazaki et al, Supplementing cultured human myotubes with hibernating bear serum results in increased protein content by modulating Akt/FOXO3a signaling, PLOS ONE (2022). DOI: 10.1371/journal.pone.0263085 Journal information: PLoS ONE
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