New research suggests polar bears adapted to their frigid environment by relying on a high-fat diet consisting of primarily blubber-rich seals.
Researchers were able to pinpoint a genetic mutation in the polar bear's genes that allowed them to consume a fatty diet without raising their risk of heart disease, a Cell Press news release reported.
The research team revealed that polar bears diverged from brown bears about 500,000 years ago, which is quicker than scientists had previously estimated.
"In this limited amount of time, polar bears became uniquely adapted to the extremities of life out on the Arctic sea ice, enabling them to inhabit some of the world's harshest climates and most inhospitable conditions," senior study author Rasmus Nielsen of the University of California, Berkeley said in the news release.
About half a polar bear's body weight is made up of fat; researchers have always been puzzled by how it was possible for them to have such low rates of heart disease.
The research team sequenced the genomes of 79 polar bears from Greenland and 10 brown bears from around the world. They discovered that the two bears diverged less than 500,000 years ago, even though past genomic data suggested this had happened as far back as five million years ago.
Since the divergence the bears have been rapidly accumulating mutations that deal with heart function and fatty acid metabolism, which has been linked to heart disease in humans.
A gene called APOB is involved in transporting cholesterol from the bloodstream and into cells, reducing the risk of heart disease.
"Such a drastic genetic response to chronically elevated levels of fat and cholesterol in the diet has not previously been reported," Eske Willerslev of the University of Copenhagen said in the news release. "It certainly encourages a move beyond the standard model organisms in our search for the underlying genetic causes of human cardiovascular diseases."
