For a polar bear, fat is fit: fully half a polar bear's body weight may come from fat deposits. Photo copyright Dick & Val Beck.

5/14/2014 7:46:55 PM

Polar Bears Eat Lots of Fat, Have Healthy Hearts: What Gives?

How do polar bears do it? They consume massive amounts of fat, eating only the fat and leaving the meat when seal hunting is good. Yet their hearts remain healthy despite extremely high cholesterol levels and large fat deposits that would be harmful to humans.

A team of scientists studying the polar bear's genetic history may have found the answer in the polar bear's genes. Their findings, published this month in Cell, show that the polar bear's cardiovascular system underwent massive restructuring to adapt to a high fat diet without adverse effects.

Among the adaptations: a process that whisks away fat from the polar bear's arteries and into its cells, providing insulation and buoyancy and preventing heart disease.

Interestingly, the authors suggest that the adaptations to a high-fat diet took place rather quickly on an evolutionary scale. A recent study placed the divergence of polar bears from brown bears at four to five million years ago. This new study suggests that the split may have occurred as recently as 343,000 to 479,000 years ago. If so, the adaptations took place in less than 20,500 generations of polar bears—a very short time frame for a large mammal.

New methodologies continue to add to our understanding of the polar bear's evolutionary past, a complex story given the sparse fossil record for these marine mammals. These latest findings not only shed light on the polar bear's adaptations to an arctic environment, but may have implications related to heart disease in humans.

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