Why is a polar bear living even in a condition of high cholesterol and half of body weight fat
Living in the Arctic CirclePolar bears(Polar bear)Brown bearAlthough it is a kind of bear with a common ancestor, it is evolving to live in cold climates and stores thick fats which account for 50% of the weight of fur and body weight with high heat retention. In the case of human beings, if fat is stored too much, it becomes obesity / high cholesterol state and the risk of heart disease etc. rises, but why polar bear can stay without becoming heart disease even if it accumulates such fat, it seems to be an answer Has been clarified by research.
Population Genomics Reveal Recent Speciation and Rapid Evolutionary Adaptation in Polar Bears: Cell
Polar bear evolved to survive being a heart attack waiting to happen | Ars Technica
Polar bears have seeds common to brown bears and pandas, but accumulating a large amount of fat is a heavy burden on the heart, so even if you can do it for a polar bear it can not be a closely related brown bear or a panda. This is one of the forces that the Polar bear got evolved to adapt to cold districts.
A research team at the University of Pennsylvania in 2010 "The polar bear and brown bear branched about 150,000 years ago"In the year 2012Branch was 600,000 years agoThere was also a view that the article which was supposed to have been published and further branched out from some traces was an older one million years ago, but in this research, the branch of polar bear and brown bear was 343,000 years It is estimated that it is in the range of 479,000 years ago from before.
The polar bear's ancestor is thought to have lived in the southern Greenland forest area during the glacial period, which is called Waalian 500,000 years ago. Around 470,000 years agoGunz glacial periodAnd the glacier starts to grow again, and some groups are left behind in the Arctic Circle.
This group has the characteristics of the current polar bear, which is about 110,000 years ago, begins a marine meal to acclimate to freezing point, white fur not blocking sunlight, wide legs for swimming, elongated head shape Earned and has achieved rapid evolution.
Among the features you have acquired, the point that is different from brown bears and others is in genes related to cholesterol metabolism. Despite having the same ancestry, brown bears and pandas did not change in genes related to cholesterol metabolism. However, only polar bears are strong against genesPositive choiceIt worked.
Evidence that strong selection of genes workedBad cholesterolIt is also found in ApoB gene which converts (encodes) LDL also called. Of the 16 genes that were selected, nine were concerned with the growth and maintenance of cardiovascular vessels. The researchers assumed that the evolution of polar bears at that time was approximately 11 years cycle and that these evolution was done to less than 20 th generation, and the evolution of large mammals was done in an extremely short time It is said that it can be said that it is.
In the paper, the reason why a polar bear in a high cholesterol state is higher than a human by taking a high-fat meal such as a seal etc., lives long without becoming heart disease even if most of the body weight becomes fat , We conclude that it may be possible to explain by functional changes in the ApoB gene. I would like to hope that further research will be able to obtain useful information for measures against heart disease and hypercholesterolemia.