University of Buffalo researchers solved the mystery behind how polar bears keep warm in winter.
Researchers said that a genetic adaptation helps convert food into energy or heat enabling them to survive extreme arctic winters without hibernating.
During winter seasons, brown and black bears hibernate to conserve energy and keep warm. But their arctic counterparts, polar bears, do not go into hibernation. Only pregnant females den up for the colder months.
The rest of the polar bears survive high-latitude environments through the genetic adaptation. The body produces nitric oxide, a compound that transforms food nutrients into energy or heat.
Generally, the cells convert nutrients into energy. However, in adaptive or non-shivering thermogenesis, the cells generate heat instead of energy depending on diet or environmental conditions.
The researchers found that the genes that control the production of nitric oxide are different in polar bears when compared to genes in brown and black bears.
"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," Charlotte Lindqvist, PhD, UB assistant professor of biological sciences, said in a statement.
Andreanna Welch, first author from the Durham University, said that at harsher temperatures the nitric oxide stops energy production, while at moderate temperatures the compound generates both energy and heat whenever it is required.
Besides their ability to survive colder temperatures, the researchers also found the function of proteins involved in the metabolism of fat to be different in polar bears than brown and black bears. The proteins in polar bears are believed to act slowly on the fat than their counterparts.
The finding is published in the journal Genome Biology and Evolution.
