News / Science & Technology

How Do You Survive a High-fat Diet? Ask a Polar Bear

FILE - Taiga the polar bear looks on at the Quebec Aquarium in Quebec City, Quebec, Canada, Dec. 30, 2013.
FILE - Taiga the polar bear looks on at the Quebec Aquarium in Quebec City, Quebec, Canada, Dec. 30, 2013.
Reuters
How do they do it? How do polar bears have such an incredibly high-fat diet and get so fat - munching as they do on blubbery seals - without clogging their arteries and becoming a big furry heart attack waiting to happen?

The answer: "bear necessities," genetically speaking.

Scientists unveiled a thorough genetic analysis of the polar bear on Thursday and compared it to its closest cousin, the brown bear. They found that since diverging from brown bears less than 500,000 years ago to become a new species, polar bears have undergone remarkable genetic changes to permit the high-fat diet they need in the frigid Arctic conditions they call home.

Multiple genes related to cardiovascular function and fatty acid metabolism have changed radically through mutations to permit a high-fat menu without high risk of heart disease, the researchers said.

"For polar bears, being very fat is no problem," said Eline Lorenzen, a molecular ecologist at the University of California, Berkeley.

In the Arctic regions where they live, energy is in high demand and polar bears have lots of fatty tissue to do the job.

Up to half their body weight can be fat and their source of fresh water is metabolic water - water that is a by-product of the breakdown of fat in the body, Lorenzen said.

"They essentially live in a polar desert," Lorenzen added.

The researchers deciphered the genome - the genetic blueprint - of the polar bear based on blood and tissue samples from 79 polar bears from Greenland. They also used samples from 10 brown bears to study the genome of that species.

Rasmus Nielsen, an evolutionary geneticist at the University of California, Berkeley, said genetic data showed polar bears diverged as a species from brown bears much more recently than previously thought - perhaps 400,000 years ago. Some previous estimates had placed the origin of polar bears as long as five million years ago.

"In this short amount of time, polar bears have adapted to the cold environment of the Arctic and to a new diet. We see the footprints of this adaptation in the genome of the polar bear," Nielsen said.

The polar bear, with its white fur a symbol of the Arctic, is Earth's biggest land carnivore and the largest of the eight bear species. It occupies the top spot in the Arctic food chain and spends a lot of its life on Arctic sea ice hunting for prey like ringed seals and bearded seals. Adult males can weigh up to about 1,700 pounds (770 kg).

It is endangered - climate change is causing shrinking of the sea ice on which it depends - with an estimated total population of 20,000 to 25,000.

Their diet allows for a body fat build-up for insulation and buoyancy while swimming. But it comes at a cost - very high levels of LDL cholesterol, known as the "bad cholesterol," and triglycerides in the blood. They have levels that would cause cardiovascular disease in humans, but their genetic changes seem to have taken care of the problem.

One important example was a change in the gene APOB, which plays a role in getting cholesterol out of the bloodstream and into cells, thereby lowering heart disease risk.

"This all makes very good sense in a species which is completely reliant on fat for survival," Lorenzen said.

The study was published on Thursday in the journal Cell.

You May Like

US Investors Eye IPO for China's Alibaba

E-commerce giant handled 80 percent of China's online business last year, logging more Internet transactions than US-based Amazon.com and eBay combined More

Video Uneasy Calm Settles Over Israel, Gaza Strip

As cease-fire begins, Palestinians celebrate in streets; Israelis remain wary More

Video Chinese Doctors Use 3-D Spinal Implant

In treatment of a 12-year-old boy Chinese doctors used a 3-D printer and special software to create an exact replica of vertebra More

Featured Videos

Your JavaScript is turned off or you have an old version of Adobe's Flash Player. Get the latest Flash player.
Chinese Doctors Use 3-D Spinal Implanti
X
August 27, 2014 4:53 PM
A Chinese boy suffering from a debilitating bone disease has become the first patient with a part of his spine created in a three-dimensional printer. Doctors say he will soon regain normal mobility. VOA’s George Putic reports.
Video

Video Chinese Doctors Use 3-D Spinal Implant

A Chinese boy suffering from a debilitating bone disease has become the first patient with a part of his spine created in a three-dimensional printer. Doctors say he will soon regain normal mobility. VOA’s George Putic reports.
Video

Video Uneasy Calm Settles Over Israel, Gaza Strip

Israel and the Gaza Strip have been calm since a cease-fire set in Tuesday evening, ending seven weeks of hostilities. Hamas, which controls Gaza, declared victory. Israelis were more wart. VOA’s Scott Bobb reports from Jerusalem.
Video

Video India’s Leprosy Battle Stymied by Continuing Stigma

Medical advancements in the treatment of leprosy have greatly diminished its impact around the world, largely eliminating the disease from most countries. India made great strides in combating leprosy, but still accounts for a majority of the world’s new cases each year, and the number of newly infected Indians is rising - more than 130,000 recorded last year. Doctors there say the problem has more to do with society than science. VOA News reports from Kolkata.
Video

Video Northern California Quake: No Way to Know When Next One Will Hit

A magnitude 6.0 earthquake rocked northern California’s Napa Valley on Sunday. Roads twisted and water mains burst. It was the wine country’s most severe quake in 15 years, and while hospitals treated many people, no one was killed. Arash Arabasadi has more from Washington on what the future may hold for those residents living on a fault line.
Video

Video Scientists Unlock Mystery of Bird Flocks

How can flocks of birds, schools of fish or herds of antelope suddenly change direction -- all the individuals adjusting their movement in concert, at seemingly the same time? British researchers now have some insights into this behavior, which has puzzled scientists for a long time. VOA's George Putic has more.
Video

Video Ukraine: Captured Troops Proof of Russian Role in Separatist Fight

Ukrainian officials say they have captured Russian soldiers on Ukrainian territory -- the latest accusation of Moscow's involvement in the conflict in eastern Ukraine. VOA's Gabe Joselow reports from the Ukrainian side of the battle, where soldiers are convinced of Russia's role.
Video

Video Rubber May Soon Come From Dandelions

Synthetic rubber has been around for more than a century, but quality tires for cars, trucks and aircraft still need up to 40 percent or more natural rubber content. As the source of natural rubber, the rubber tree, is prone to disease and can be affected by bad weather. So scientists are looking for replacements. And as VOA’s George Putic reports, they may have found one in a ubiquitous weed.
Video

Video Jewish Life in Argentina Reflected in Yiddish Tango

Jewish people from across Europe and Russia have been immigrating to Argentina for hundreds of years. They brought with them dance music that were eventually mixed with Argentine tango. The result is Yiddish tango -- a fusion of melodies and cultural experiences that is still evolving today. Elizabeth Lee reports from the Skirball Cultural Center in Los Angeles, where one band is bringing Yiddish tango to an American audience.

AppleAndroid