For a Polar Bear, being Obese is no Problem
Fat account for up to half the weight of a polar bear: how can he resist, and better, he takes advantage? U.S. scientists believe to have understood by comparing its genome with that of the brown bear.
Eating fat does not scare them. Really scared! Fat is the main food and a polar bear; it has up to half of its weight … How his body he resists such a regime?
Scientists believe hold the answer. They compared the genomes of brown and polar bears and found that they had genetic mutations that could explain why they can consume large amounts of fat without incurring cardiovascular diseases as humans. A gene to metabolize fat and get fresh water.
The researchers also determined that the polar bear had emerged as a distinct species of brown bears there less than 500,000 years ( 479,000 years to 343,000 years), or more recently than previous estimates which ranged from 600,000 years five million years.
Polar bears spend most of their lives on the ice, where they subsist on a very fat rich food , mainly from marine mammals.
” For polar bears, being obese is not a problem,” quipped Eline Lorenzen, a researcher at the University of California at Berkeley, one of the authors of these studies published Thursday, May 8, 2014 in the journal Cell. ” And we wanted to know how this was possible,” she adds.
Comparative genomic analysis of two species has enabled a number of mutations in genes that appear to play an important role in the adaptation of this animal to extreme living conditions of the Arctic, says the researcher told AFP.
Some of these mutations affect the polar bear in the APOB gene in mammals , encodes the major protein of LDL- cholesterol (LDL for low density lipoprotein ) . These changes reveal the critical importance of fat in the diet of the polar bear, whose body has to adapt to high levels of blood glucose and triglyceride levels – including cholesterol – that would be dangerous in humans.
These mutations of the APOB gene, ” which apparently play a key role in the adaptation of this Arctic animal” also help in metabolizing fat, to obtain fresh water.
These bears have almost no access to drinkable water on the ice and , without this transformation mechanism of fat, their bodies could not meet its water needs , says Eline Lorenzen .
“If we can learn more about these genetic mutations to metabolize fat that could give us the tools to adapt human physiology ” a very fatty diet , J. Rasmus Nielsen , professor of genomic evolution in the University of California at Berkeley, one of the co -authors of the study.
The evolution of this new metabolism in polar bears apparently happened very quickly, in just a few hundred thousand years, since fossil polar bear dating from 100,000 years recently discovered shows that animals fed already marine mammals.
Brown bears who ventured north : the ancestors of polar bears
The origins of the emergence of the polar bear are unclear but they coincide with a warming climate during 50,000 years during the interglacial period.
The changes are then in the environment may have encouraged brown bears to venture further north. When this episode of warming has ended and the glacial period is returned, it is possible that brown bear groups found themselves trapped in the ice and were then forced to quickly adapt to this new environment, these scientists on believe.
Today, with global warming in the Antarctic, the Bruins back to the North and recur with some polar bears to give birth to ” pizzlies ” crossbreeds between grizzly bears and polar bears. For this genomic analysis, the researchers used blood samples and tissue from 79 polar bears and brown bears ten.
This work was published at a time when the global polar bear population, estimated 20,000 to 25,000 animals, is declining due to habitat loss and the rapid melting of the ice , under the effect of global warming.