Asian Scientist (Jul. 10, 2013) – A new study has found that brown fat is responsible for more people dying from heart disease during the winter months.
According to the study, published in Cell Metabolism, the increase in mortality may be due to the accelerated growth of atherosclerotic plaque in the blood vessels caused by the activation of brown fat by the cold.
It is known that the number of deaths from cardiovascular diseases increases during the winter. While there has been speculation that this might be the result of over-exertion while shoveling snow and a general decrease in physical activity, the underlying mechanisms are unclear.
In the new study, researchers in Sweden and China studied a strain of mice genetically modified with a propensity for atherosclerosis.
Mice, like humans, have both white and brown body fat. Normal rolls of fat consist mainly of white fat, which is a repository of surplus calories; brown adipose tissue, on the other hand, can convert fat into heat.
This heat-generation process is activated by cold temperatures and has been considered beneficial to the health since it can reduce the amount of unnecessary white adipose tissue in the body.
“At first, we thought that the cold activation of brown fat would only make the mice thinner and healthier,” says Yihao Cao, senior author of the study. “Instead, we found that they ended up having more fat stored in the blood vessels. This came as a surprise and was the opposite of what we thought would happen.”
It turned out that exposure to low temperatures accelerated the formation of atherosclerotic plaque in the mice, which can cause myocardial infarction and brain hemorrhaging.
Moreover, the cold made the plaque less stable, and if the plaque ruptures, stored fat can leak into the blood, blocking vessels in the heart and brain.
The cold-activated breakdown of fatty acids in the mice’s brown fat led to the accumulation of low-density lipoproteins (LDL) in the blood and an increase in fat storage in the plaque.
The researchers hope to be able to extend their work on mice to studies on humans.
“It would be an extremely important discovery if we found this to be the case in humans too,” says Cao.
“Brown adipose tissue is affected not only by the cold – its activation can also be blocked by several existing drugs, something that we would like to study further.”
The article can be found at: Dong et al. (2013) Cold Exposure Promotes Atherosclerotic Plaque Growth And Instability Via UCP1-Dependent Lipolysis.
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Source: Karolinska Institute; Photo: ericskiff/Flickr.
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