People with this gene variant shivered less and had a higher core body temperature when exposed to cold water. Dudarev Mikhail/ Shutterstock
Some people just aren’t bothered by the cold, no matter how low the temperature dips. And the reason for this 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 resilient to cold temperatures.
Around 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 out of Africa and into the colder climates of Europe and Asia. The reasons for this increase have remained unknown until now.
Our recent study, conducted alongside researchers from Lithuania, Sweden and Australia, suggests that if you’re alpha-actinin-3 deficient, then your body can maintain a higher core temperature and you shiver less when exposed to cold, compared with those who have alpha-actinin-3.
We looked at 42 men aged 18 to 40 years from Kaunas in southern Lithuania and exposed them to cold water (14℃) for a maximum of 120 minutes, or until their core body temperature reached 35.5℃. We broke their exposure up into 20-minute periods in the cold with ten-minute breaks at room temperature. We then separated participants into two groups based on their ACTN3 genotype (whether or not they had the alpha-actinin-3 protein).
While only 30% of participants with the alpha-actinin-3 protein reached the full 120 minutes of cold exposure, 69% of those that were alpha-actinin-3 deficient completed the full cold-water exposure time. We also assessed the amount of shivering during cold exposure periods, which told us that those without alpha-actinin-3 shiver less than those who have alpha-actinin-3.
Our study suggests that genetic changes caused by the loss of alpha-actinin-3 in our skeletal muscle affect how well we can tolerate cold temperatures, with those that are alpha-actinin-3 deficient better able to maintain their body temperature and conserve their energy by shivering less during cold exposure. However, future research will need to investigate whether similar results would be seen in women.
Skeletal muscles are made up of two types of muscle fibres: fast and slow. Alpha-actinin-3 is predominantly found in fast muscle fibres. These fibres are responsible for the rapid and forceful contractions used during sprinting, but typically fatigue quickly and are prone to injury. Slow muscle fibres on the other hand generate less force but are resistant to fatigue. These are primarily the muscle you’d use during endurance events, like marathon running.
Our previous work has shown that ACTN3 variants play an important role in our muscle’s ability to generate strength. We showed that the loss of alpha-actinin-3 is detrimental to sprint performance in athletes and the general population, but may benefit muscle endurance.
This is because the loss of alpha-actinin-3 causes the muscle to behave more like a slower muscle fibre. This means that alpha-actinin-3 deficient muscles are weaker but recover more quickly from fatigue. But while this is detrimental to sprint performance, it may be beneficial during more endurance events. This improvement in endurance muscle capacity could also influence our response to cold.
While alpha-actinin-3 deficiency does not cause muscle disease, it does influence how our muscle functions. Our study shows that ACTN3 is more than just the “gene for speed”, but that its loss improves our muscle’s ability to generate heat and reduces the need to shiver when exposed to cold. This improvement in muscle function would conserve energy and ultimately increase survival in cold temperatures, which we think is a key reason why we see an increase in alpha-actinin-3 deficient people today, as this would have helped modern humans better tolerate cooler climates as they migrated out of Africa.
The goal of our research is to improve our understanding of how our genetics influence how our muscle works. This will allow us to develop better treatments for those who suffer from muscle diseases, like Duchenne muscular dystrophy, as well as more common conditions, such as obesity and type 2 diabetes. A better understanding of how variants in alpha-actinin-3 influences these conditions will give us better ways to treat and prevent these conditions in the future.
About The Authors
Victoria Wyckelsma, Postdoctoral Research Fellow, Muscle Physiology, Karolinska Institutet and Peter John Houweling, Senior Research Officer, Neuromuscular Research, Murdoch Children's Research Institute
The Human Swarm: How Our Societies Arise, Thrive, and Fall
by Mark W. Moffett
If a chimpanzee ventures into the territory of a different group, it will almost certainly be killed. But a New Yorker can fly to Los Angeles--or Borneo--with very little fear. Psychologists have done little to explain this: for years, they have held that our biology puts a hard upper limit--about 150 people--on the size of our social groups. But human societies are in fact vastly larger. How do we manage--by and large--to get along with each other? In this paradigm-shattering book, biologist Mark W. Moffett draws on findings in psychology, sociology and anthropology to explain the social adaptations that bind societies. He explores how the tension between identity and anonymity defines how societies develop, function, and fail. Surpassing Guns, Germs, and Steel and Sapiens, The Human Swarm reveals how mankind created sprawling civilizations of unrivaled complexity--and what it will take to sustain them. Available On Amazon
Environment: The Science Behind the Stories
by Jay H. Withgott, Matthew Laposata
Environment: The Science behind the Stories is a best seller for the introductory environmental science course known for its student-friendly narrative style, its integration of real stories and case studies, and its presentation of the latest science and research. The 6th Edition features new opportunities to help students see connections between integrated case studies and the science in each chapter, and provides them with opportunities to apply the scientific process to environmental concerns. Available On Amazon
Feasible Planet: A guide to more sustainable living
by Ken Kroes
Are you concerned about the state of our planet and hope that governments and corporations will find a sustainable way for us to live? If you do not think about it too hard, that may work, but will it? Left on their own, with drivers of popularity and profits, I am not too convinced that it will. The missing part of this equation is you and me. Individuals who believe that corporations and governments can do better. Individuals who believe that through action, we can buy a bit more time to develop and implement solutions to our critical issues. Available On Amazon
From The Publisher:
Purchases on Amazon go to defray the cost of bringing you InnerSelf.com, MightyNatural.com, and ClimateImpactNews.com at no cost and without advertisers that track your browsing habits. Even if you click on a link but don't buy these selected products, anything else you buy in that same visit on Amazon pays us a small commission. There is no additional cost to you, so please contribute to the effort. You can also use this link to use to Amazon at any time so you can help support our efforts.