(ORDO NEWS) — In the intestines of ground squirrels live bacteria that process urea, getting the nitrogen necessary for animals to synthesize proteins. This mechanism, which allows ground squirrels not to lose mass during hibernation, is likely to help solve a similar problem of reduced muscle mass in astronauts during long flights.
Many hibernating animals, such as ground squirrels and bears, are forced to exist for months at the expense of body fat alone. Usually, prolonged fasting significantly reduces body weight and muscle function, but not in these animals. Scientists have long tried to understand what is the secret of their success.
As far back as 1980, the idea of ”obtaining nitrogen from urea” was proposed, suggesting that gophers use intestinal bacteria to process urea. It is the end product of protein metabolism and is excreted in the urine in mammals.
Urea contains nitrogen, and scientists thought ground squirrels could reuse it for protein synthesis during hibernation. Now researchers at the University of Montreal have confirmed that hypothesis and have presented the evidence in the journal Science.
The discovery has huge implications for the health of astronauts, as gravity suppresses protein synthesis, and humans during space flight, like ground squirrels during hibernation, face muscle loss. Increasing protein synthesis using urea nitrogen could significantly improve the condition of astronauts.
During the experiments, scientists injected urea labeled with isotopes into the blood of experimental ground squirrels Ictidomys tridecemlineatus. They replaced the carbon-12 isotope common to living organisms with carbon-13, and nitrogen-14 with nitrogen-15. This made it possible to trace the fate of such atoms in the body of ground squirrels at all stages of urea processing.
It turned out that urea from the blood enters the intestines, where it is broken down by bacteria living there. The nitrogen released from it is incorporated into metabolites and then appears already in the composition of tissue proteins. This process was not observed in ground squirrels with a depleted gut microbiome, further supporting the role of bacteria.
The most active incorporation of nitrogen from urea into proteins occurred at the end of winter. As a rule, most physiological reactions, on the contrary, slow down towards the exit from hibernation. However, maintaining this process allows ground squirrels to wake up in good physical shape, which is extremely important, since their breeding season begins immediately after hibernation.
The discovery is relevant not only for space flights. Over 805 million people worldwide suffer from malnutrition and muscle wasting. A decrease in muscle mass by 30-50% is also observed in the elderly.
Therefore, the results of the work will help in the development of new ways to improve the health of people who, for one reason or another, are faced with a decrease in muscle mass. One option is the creation of tablets containing the bacteria necessary for the processing of urea.
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