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

Hezbollah Chief Says Does Not Want War But Ready for One

VOA's Jerusalem correspondent reports that with an Israeli election looming and Hezbollah's involvement in Syria, neither side appears interested in a wider conflict More

Multimedia VOA SPECIAL REPORT: Despite Danger, Best US Minds Battle Deadly Virus

Scientists at America's premier biological research center race in military confinement to find effective drugs, speedier tests and a safe vaccine amid the deadliest outbreak of Ebola in history More

Kurdish Poet Battles to Defend Language, Culture

Kawa Nemir's work is an example of what he sees as an irreversible cultural and political assertiveness among Kurds in Turkey More

Featured Videos

Your JavaScript is turned off or you have an old version of Adobe's Flash Player. Get the latest Flash player.
Egypt's Suez Canal Dreams Tempered by Continued Unresti
X
Heather Murdock
January 30, 2015 8:00 PM
Egypt plans to expand the Suez Canal, raising hopes that the end of its economic crisis may be in sight. But some analysts say they expect the project may cost too much and take too long to make life better for everyday Egyptians. VOA's Heather Murdock reports.
Video

Video Egypt's Suez Canal Dreams Tempered by Continued Unrest

Egypt plans to expand the Suez Canal, raising hopes that the end of its economic crisis may be in sight. But some analysts say they expect the project may cost too much and take too long to make life better for everyday Egyptians. VOA's Heather Murdock reports.
Video

Video Threat of Creeping Lava Has Hawaiians on Edge

Residents of the small town of Pahoa on the Big Island of Hawaii face an advancing threat from the Kilauea volcano. Local residents are keeping a watchful eye on creeping lava. Mike O’Sullivan reports.
Video

Video Pro-Kremlin Youth Group Creatively Promotes 'Patriotic' Propaganda

As Russia's President Vladimir Putin faces international pressure over Ukraine and a failing economy, unofficial domestic groups are rallying to his support. One such youth organization, CET, or Network, uses creative multimedia to appeal to Russia's urban youth with patriotic propaganda. VOA's Daniel Schearf reports.
Video

Video Mobile Infrared Scanners May Help Homeowners Save Energy

Mobile photo scanners have been successfully employed for navigational purposes, such as Google Maps. Now, a group of scientists from the Massachusetts Institute of Technology says the same technology could help homeowners better insulate their houses and save some money. VOA’s George Putic has more.
Video

Video Filmmakers Produce Hand-Painted Documentary on Van Gogh

The troubled life of the famous 19th century Dutch painter Vincent van Gogh has been told through many books and films, but never in the way a group of filmmakers now intends to do. "Loving Vincent " will be the first ever feature-length film made of animated hand-painted images, done in the style of the late artist. VOA’s George Putic reports.
Video

Video Issues or Ethnicity? Question Divides Nigeria

As Nigeria goes to the polls next month, many expect the two top presidential contenders to gain much of their support from constituencies organized along ethnic or religious lines. But are faith and regional blocs really what political power in Nigeria is about? Chris Stein reports.
Video

Video Rock-Consuming Organisms Alter Views of Life Processes

Scientists thought they knew much about how life works, until a discovery more than two decades ago challenged conventional beliefs. Scientists found that there are organisms that breathe rocks. And it is only recently that the scientific community is accepting that there are organisms that could get energy out of rocks. Correspondent Elizabeth Lee reports.
Video

Video Paris Attacks Highlight Global Weapons Black Market

As law enforcement officials piece together how the Paris and Belgian terror cells carried out their recent attacks, questions are being asked about how they obtained military grade assault weapons - which are illegal in the European Union. As VOA's Jeff Swicord reports, experts say there is a very active worldwide black market for these weapons, and criminals and terrorists are buying.
Video

Video Activists Accuse China of Targeting Religious Freedom

The U.S.-based Chinese religious rights group ChinaAid says 2014 was the worst year for religious freedom in China since the end of the Cultural Revolution. As Ye Fan reports, activists say Beijing has been tightening religious controls ever since Chinese leader Xi Jinping came to office. Hu Wei narrates.
Video

Video Theologians Cast Doubt on Morality of Drone Strikes

In 2006, stirred by photos of U.S. soldiers mistreating Iraqi prisoners, a group of American faith leaders and academics launched the National Religious Campaign Against Torture. It played an important role in getting Congress to investigate, and the president to ban, torture. VOA's Jerome Socolovsky reports.
Video

Video Former Sudan 'Lost Boy' Becomes Chess Master in NYC

In the mid-1980’s, thousands of Sudanese boys escaped the country's civil war by walking for weeks, then months and finally for more than a year, up to 1,500 kilometers across three countries. The so-called Lost Boys of the Sudan had little time for games. But one of them later mastered the game of chess, and now teaches it to children in the New York area. VOA’s Bernard Shusman in New York has his story.
Video

Video NASA Monitors Earth’s Vital Signs From Space

The U.S. space agency, NASA, is wrapping up its busiest 12-month period in more than a decade, with three missions launched in 2014 and two this month, one in early January and the fifth scheduled for January 29. As VOA’s Rosanne Skirble reports, the instruments being lifted into orbit are focused on Earth’s vital life support systems and how they are responding to a warmer planet.

Circumventing Censorship

An Internet Primer for Healthy Web Habits

As surveillance and censoring technologies advance, so, too, do new tools for your computer or mobile device that help protect your privacy and break through Internet censorship.
More

All About America

AppleAndroid