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Most of us who live on planet Earth have to go through some period of cold weather for at least part of the year, and new research has identified a specific genetic mutation that makes a fifth of us more resilient. in cold conditions.
The genetic mutation in question stops the production of the α-actinin-3 protein, which is important for skeletal muscle fiber: the protein is only found in fast-twitch (or white) fibers and not in slow-twitch fibers. (or red).
Based on the results of the new study, people without α-actinin-3 have a higher proportion of slow-twitch fiber, and one of the consequences is that the body tends to conserve energy by boosting tone. muscle through contractions rather than chills.
“This suggests that people lacking in α-actinin-3 are better able to stay warm and, in terms of energy, to endure a more difficult climate, but there has been no direct experimental evidence for this. before, “says physiologist Håkan Westerblad of the Karolinska Institutet in Sweden.
“We can now show that the loss of this protein gives greater resistance to cold and we have also found a possible mechanism for this.”
Researchers recruited 42 men to sit in 14 degrees Celsius (57.2 degrees Fahrenheit) water while their temperatures and muscles were measured. The cold immersion lasted 20 minutes at a time with 10 minute breaks, for a maximum of two hours in total.
The proportion of participants who could maintain their body temperature above 35.5 degrees Celsius (95.9 degrees Fahrenheit) was higher in those with the α-actinin-3 mutation compared to those without – 69% of volunteers versus 30%.
In other words, the genetic mutation seemed to help these participants conserve energy more efficiently and develop greater resistance to cold.
The team also conducted follow-up experiments in mice with the same mutation to see if this mutation might have something to do with increasing stores of brown fat – a well-known heat-generating tissue in mammals. – but it didn’t turn out. be the case.
People lacking α-actinin-3 might be better prepared for a cold water swim or winter episode, but it could also make them more vulnerable to obesity and type 2 diabetes if they are inactive, according to the researchers. researchers. It could also increase the risk of falls as they get older, as the fast-twitch fibers handle rapid muscle movements.
“The mutation probably gave an evolutionary advantage in migrating to a colder climate, but in today’s modern society, this energy-saving ability could instead increase the risk of [these] diseases, which we now want to focus on, ”says Westerblad.
As previous research has shown, α-actinin-3 deficiency has increased in the population as humans have moved from warmer climates to colder climates, although questions remain as to whether this mutation. is present at birth and affects infant mortality.
It’s also worth noting that athletes who excel in sports involving explosiveness and strength (like sprinting) are more likely not to have this lack of α-actinin-3, while for sports of endurance, the statistics are reversed.
As for future research, the team is keen to examine how all of this might work at the molecular level, as well as how it might affect muscle disease. For now, this is an important new discovery about this genetic mutation and the allele or gene form associated with it.
“These results provide a mechanism for increasing [these gene variants’] how often modern humans migrated from Africa to the colder climates of central and northern Europe more than 50,000 years ago, ”the researchers conclude in their published article.
The research was published in the American Journal of Human Genetics.
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