Genetic adaptation key to how polar bears stay warm in winter

A genetic adaptation that helps convert food into heat may be how polar bears survive extreme arctic winters without hibernating, researchers say. In the winter, brown and black bears go into hibernation to conserve energy and keep warm, but in the arctic only pregnant females den up for the colder months -- the rest are able to stick it out in the coldest weather. Researchers at the University of Buffalo say they believe they've identified one potential answer to how they do it: genetic adaptations related to the production of nitric oxide, a compound that cells use to help convert nutrients from food into energy or heat. Genes controlling nitric oxide production in the polar bear genome contain genetic differences from comparable genes in brown and black bears, the university said in a release Monday. "With all the changes in the global climate, it becomes more relevant to look into what sorts of adaptations exist in organisms that live in these high-latitude environments," lead researcher and biological sciences Professor Charlotte Lindqvist said. "This study provides one little window into some of these adaptations," she said. "Gene functions that had to do with nitric oxide production seemed to be more enriched in the polar bear than in the brown bears and black bears. There were more unique variants in polar bear genes than in those of the other species." Levels of nitric oxide production may be a key switch triggering how much heat or energy is produced as cells metabolize nutrients, or how much of the nutrients is stored as fat, Lindqvist said.