In the Russian North, during the cold season, temperatures often drop to -40 … -50 °, or even lower. Severe frosts, and with them the dark polar night, last for several months. How do people cope with such harsh environmental conditions? Scientists from the Washington and Arizona Universities (USA) and the Institute of Cytology and Genetics of the Siberian Branch of the Russian Academy of Sciences became interested in a very relevant topic.
Man emerged from Africa about 75,000 years ago; after 35,000 he reached Europe, including the most northern regions. Here he had to adapt to the harsh conditions of life - change his diet (and the choice of food was limited) and learn to endure severe cold. Several peoples managed to do this, which, thanks to mutations in their DNA, turned out to be more resistant to low temperatures than the rest of the world's population.
Recently, scientists have discovered genes responsible for lipid metabolism - the process of breaking down, transporting and storing fats in the body - in which mutations have occurred. These are changes in the perlipine gene (PLIN1), membrane-associated phospholipase A2 (PLA2G2A) and angiopoietin-like protein 3 (ANGPTL8). The study authors suggest that these mutations may also affect how brown adipose tissue works. Usually there is a lot of it in the body of babies, whom it protects from hypothermia. In adults, only a few grams of brown fat remain, but thanks to these grams, they have adapted to seasonal temperature changes: the layer is activated in cold weather and begins to release energy that warms a person.
Scientists have studied the genomes of representatives of 17 Siberian ethnic groups. It is in them that the layer of brown fat is most likely active in the adult period of life. There are no direct biochemical and physiological data on the state of this tissue in the organisms of Siberians, but low levels of "bad" cholesterol and high concentrations of "good" cholesterol indicate its enhanced work. In addition, aboriginal blood contains a lot of thyroxine, a thyroid hormone capable of activating a layer of brown fat. When this tissue intensively releases energy to warm the body, lipid consumption increases and, as a result, metabolism is accelerated. And for the representatives of the northern peoples, it is precisely the accelerated metabolism that is characteristic.
