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

Photogallery Oxfam: Ebola Could Be 'Disaster of Our Generation'

Meanwhile, Fidel Castro, the former leader of Cuba, says the Caribbean island nation will 'gladly cooperate' with the US in the fight against Ebola in West Africa More

Multimedia Kobani Fighting Sends 400,000 Refugees to Turkey

Refugees receive help from Turkish authorities and individuals, but say much more is needed More

India’s Ruling Nationalist Party Makes Gains in Regional Elections

Bharatiya Janata Party’s huge margin over its rivals puts it on course to form governments in the northern Haryana and western Maharashtra states More

Featured Videos

Your JavaScript is turned off or you have an old version of Adobe's Flash Player. Get the latest Flash player.
Exclusive: American Joins Kurds' Anti-IS Fighti
X
Zana Omer
October 18, 2014 6:37 PM
The United States and other Western nations have expressed alarm about their citizens joining Islamic State forces in Syria and Iraq. In a rare counterpoint to the phenomenon, an American has taken up arms with the militants' Syrian Kurdish opponents. Elizabeth Arrott has more in this exclusive profile by VOA Kurdish reporter Zana Omer in Ras al Ayn, Syria.
Video

Video Exclusive: American Joins Kurds' Anti-IS Fight

The United States and other Western nations have expressed alarm about their citizens joining Islamic State forces in Syria and Iraq. In a rare counterpoint to the phenomenon, an American has taken up arms with the militants' Syrian Kurdish opponents. Elizabeth Arrott has more in this exclusive profile by VOA Kurdish reporter Zana Omer in Ras al Ayn, Syria.
Video

Video South Korea Confronts Violence Within Military Ranks

Every able-bodied South Korean male between 18 and 35 must serve for 21 to 36 months in the country’s armed forces, depending upon the specific branch. For many, service is a rite of passage to manhood. But there are growing concerns that bullying and violence come along with the tradition. Reporter Jason Strother has more from Seoul.
Video

Video Comanche People Maintain Pride in Their Heritage

The Comanche (Indian nation) once were called the “Lords of the Plains,” with an empire that included half the land area of current day Texas, large parts of Oklahoma, New Mexico, Kansas and Colorado.The fierceness and battle prowess of these warriors on horseback delayed the settlement of most of West Texas for four decades. VOA’s Greg Flakus reports from Lawton, Oklahoma, that while their warrior days are over, the 15,000 members of the Comanche Nation remain a proud people.
Video

Video Turkey Campus Attacks Raise Islamic Radicalization Fears

Concerns are growing in Turkey of Islamic radicalization at some universities, after clashes between supporters of the jihadist group Islamic State (IS) or ISIS, and those opposed to the extremists. Pro-jihadist literature is on sale openly on the streets of Istanbul. Critics accuse the government of turning a blind eye to radicalism at home, while Kurds accuse the president of supporting IS - a charge strongly denied. Henry Ridgwell reports from London.
Video

Video Syrian Defector Leaks Shocking Photos of Torture Victims

Shocking photographs purporting to show Syrian torture victims are on display at the U.S. Holocaust Memorial Museum in Washington. The museum says the graphic images are among thousands of photographs recently smuggled out of Syria by a military policeman-turned-defector. As VOA reporter Julie Taboh reports, the museum says the photos provide further evidence of atrocities committed by the government of Syrian President Bashar al-Assad against its own people.
Video

Video Drought-Stricken California Considers Upgrading Water System

A three-year drought in California is causing a water shortage that is being felt on farms and cities throughout the state. As VOA's Mike O’Sullivan reports, water experts, consumers and farmers say California needs to make changes to cope with an uncertain future.
Video

Video TechShop Puts High-tech Dreams Within Reach

Square, a business app and card reader, makes it possible to do credit card transactions through cell phones. But what made Square possible? VOA’s Adrianna Zhang and Enming Liu have the answer.
Video

Video Church for Atheists Goes Global

Atheists, by definition, do not believe in God. So they should have no need of a church. But two years ago, a pair of British stand-up comedians decided to create one. Sanderson Jones and Pippa Evans told the BBC they envisioned “something like church but without God". Their “Sunday Assembly” movement has grown from a single congregation in London to dozens of churches around the world. Reporter Mike Osborne visited with the members of a Sunday Assembly that now meets regularly in Nashville.
Video

Video Robot Locates Unexploded Underwater Mines

Many educators believe that hands-on experience is the best way to learn. Proving that the method works is a project developed by a group of students at the Stevens Institute of Technology, in Hoboken, New Jersey. They rose up to a challenge posted by the U.S. Department of Defense and successfully designed and built an underwater robot for locating submerged unexploded ordnance. VOA’s George Putic reports.
Video

Video Liberia's JFK Hospital Reopens After Temporary Ebola Exposure

JFK Hospital is Liberia’s largest and one of its oldest medical facilities. The hospital had to close temporarily following the deaths of two leading doctors from Ebola. It is now getting back on its feet, with the maternity ward being the first section to reopen. Benno Muchler has more for VOA News from Monrovia.
Video

Video Hong Kong Protests Expose Generation Gap

Most of the tens of thousands of protesters in Hong Kong are students seeking democracy. Idealistic youths say while the older generation worries about the present, they are fighting for the territory's future. VOA's Daniel Schearf reports from Hong Kong.
Video

Video Liberians Living in US Struggle From Afar as Ebola Ravages Homeland

More than 8,000 Liberians live in New York City, more than in any other city outside of Liberia itself. As VOA’s Bernard Shusman reports, with the Ebola virus ravaging their homeland, there is no peace of mind for these New Yorkers.
Video

Video Kurds See War-Ravaged Kobani As Political, Emotional Heartland

Intense fighting is continuing between Islamic State militants -- also known as ISIS or ISIL -- and Kurdish forces around the Syrian town of Kobani, on the Turkish border. The U.S. said it carried out at least nine airstrikes against Islamic State positions Friday. Meanwhile the U.N. has warned that hundreds of civilians would be massacred if the town falls to the militants. Henry Ridgwell looks at the strategic significance of the city.

All About America

AppleAndroid