Some people just don’t care about the cold, no matter how cold the temperature is. And the reason may be in a person’s genes. Our new research shows that a common genetic variant in the skeletal muscle gene, ACTN3, makes people more resistant to cold.

About one in five people lack a muscle protein called alpha-actinin-3 due to a single genetic change in the ACTN3 gene. The absence of alpha-actinin-3 became more common as some modern humans migrated from Africa to the colder climates of Europe and Asia. The reasons for this increase have remained unknown until now.

The recent study, conducted together with researchers from Lithuania, Sweden, and Australia, suggests that if you are deficient in alpha-actinin-3, your body can maintain a higher core temperature and shiver less when exposed to cold than those who have alpha. -actinin. -3.

We examined 42 men between the ages of 18 and 40 from Kaunas in southern Lithuania and exposed them to cold water (14 ° C) for 120 minutes or until their body temperature was low. has reached 35.5 ° C. We divide your exposure into cold periods of 20 minutes with breaks of ten minutes at room temperature. Then, we separated the participants into two groups based on their ACTN3 genotype (regardless of whether or not they had the alpha-actinin-3 protein).

While only 30% of participants with the alpha-actinin-3 protein achieved the full 120 minutes of cold exposure, 69% of those with alpha-actinin-3 deficiency completed the full time of exposure to cold. cold water. We also evaluated the number of chills during periods of cold exposure, indicating that those without alpha-actinin-3 shiver less than those with alpha-actinin-3.

Our study suggests that genetic changes caused by the loss of alpha-actinin-3 in our skeletal muscle affect how we can tolerate cold, and those that are deficient in alpha-actinin-3 are better able to maintain temperature. body and conserve your energy. shake less during exposure to cold. However, future research should investigate whether similar results are seen in women.

The role of ACTN3

Skeletal muscles are made up of two types of muscle fibers: fast and slow. Alpha-actinin-3 is found mainly in fast muscle fibers. These fibers are responsible for the strong and fast contractions used during sprinting, but they usually tire quickly and are prone to injury. Slow muscle fibers, on the other hand, generate less force but are resistant to fatigue. These are mainly the muscles you would use during endurance events, such as the marathon.
Our previous work has shown that ACTN3 variants play an important role in our muscles’ ability to generate force. We have shown that loss of alpha-actinin-3 is detrimental to sprint performance in athletes and the general population, but can benefit muscle endurance.

This is because the loss of alpha-actinin-3 causes the muscle to behave more like a slower muscle fiber. This means that muscles deficient in alpha-actinin-3 are weaker but recover more quickly from fatigue. But while this is bad for sprint performance, it can be useful during multiple endurance events. This improvement in muscle endurance could also affect our response to cold.

Although alpha-actinin-3 deficiency does not cause muscle disease, it does affect the way our muscles work. Our study shows that ACTN3 is more than a “speed gene”, but that its loss improves our muscles’ ability to generate heat and reduces the need to tremble when exposed to cold. This improvement in muscle function will conserve energy and ultimately increase survival in cold temperatures, which we believe is a key reason why we see an increase in people with alpha-actinin-3 deficiency today. This would help modern humans to tolerate the cold better. climates that migrated from Africa.

The goal of our research is to improve our understanding of how our genetics affect how our muscles work. This will allow us to develop better treatments for those with muscle diseases, such as Duchenne muscular dystrophy, as well as more common conditions, such as obesity and type 2 diabetes. A better understanding of how alpha-actinin -3 variants affect these conditions. will give us better ways to treat and prevent these conditions in the future.