A particular area of interest in studies is how bears’ remarkable capacity to hibernate for extended periods may help human health, specifically in preventing muscular atrophy. Japanese researchers have made a surprising breakthrough in this area, showing that human muscle cells may be injected with a black bear serum to avoid atrophy and actively encourage mass growth.

While humans can start losing muscle mass after just a few weeks of inactivity, hibernating bears can remain motionless for up to seven months without drinking water, eating, or harming their health or physical functions. They do this after overeating in the summer and fall to accumulate fat storage, then endure the winter dormant while fending off diseases like cancer, diabetes, and heart disease.

Scientists have researched this behavior to discover new treatments for metabolic dysfunction, obesity, and muscle atrophy. In addition, research on other organisms that hibernate, like zebrafish, has provided clues about how we might survive harsh settings. Finally, high radiation levels are known to have several health hazards for people, so this could be crucial for deep space flight.

The skeletal muscle, which is vulnerable to wasting caused by inactivity, was the focus of this recent investigation. The research team, led by scientists at Hokkaido University and Hiroshima University, used serum extracted from the blood of hibernating black bears to infuse cultured human skeletal muscle cells. This resulted in a considerable protein increase, increased levels of the growth factor hormone IGF-1, and muscle gain after 24 hours. Interestingly, the same effects were not produced by cultured muscle cells infused with serum obtained during the bears’ active summer season.

Scientists think this is because a protein component in the serum of hibernating bears blocks a “destruction mechanism” that causes muscles to deteriorate when we don’t use them. Scientists believe that bears’ ability to maintain their muscle mass in the face of the “use it or lose it” principle is due to a protein called MuRF1 that inhibits the activation of the shredding of unused muscles. The next step is determining the hormones and metabolic processes inhibiting this crucial protein.

Mitsunori Miyazaki, Associate Professor at Hiroshima University’s Graduate School of Biomedical and Health Sciences and the study’s first author, noted:

“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.”

Doing this would make it possible to avoid skeletal muscle loss in elderly or ill people who cannot move and protect humans during deep space travel. “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,” Miyazaki added.

The study was published on January 25, 2022, in PLOS One.