Inuit and Cold Exposure

Brown adipose tissue (BAT) produces heat through non-shivering thermogenesis. It is activated by cold exposure, and when activated it utilizes fatty acids and glucose in order to produce heat. The tissue is especially present in newborns, who not yet have gained a layer of insulating fat to protect from heat loss, and not yet have gained much muscle to produce heat through shivering thermogenesis. It was long thought that BAT mass hereafter would retract. Modern imaging tools have proved that BAT is persistent and active in some adults. The presence and activity of BAT is negatively correlated with obesity and obesity-related metabolic disorders. The tissue retracts with advancing age and increasing BMI, and it is sensitive to environmental factors, such as diet, weather and climate. The key to activating BAT in subjects that have lost it remains elusive. BAT is activated to produce heat when exposed to cold. Populations that are most cold exposed include people living in the Arctic. It is known that people of Arctic origin such as indigenous Inuit and indigenous Siberians have genetically adapted to and are acclimatized to the cold through several genetic changes, and possibly by upregulating BAT depots and activity. The investigators aim to dig deeper into the activation mechanisms in BAT, by investigating BAT mass and activity in Greenlanders and non-Greenlanders by use of stage-of-the-art modern techniques.