‘Brown’ Fat Cells Do not Break Down as Easily in the Cold, Study Finds.
People are able to survive in low and rigid temperatures due to the body's regulation of heat. In mammals, the body burns fat in order to created heat during the wintertime. By burning fat efficiently, the body not only remains warm, it also prevents obesity and other diseases, such as diabetes. Despite already knowing the dynamics behind how the body burns fat, researchers evaluated the three specific fat cells that are involved and found that one of them appears to burn fat a lot slower once temperatures drop.
The three fat cells that are responsible for heat regulation by burning fat are white, beige and brown cells. All cells are regulated by the brain, which tells them when to break down. In this study, conducted by a Harvard Medical School research team with lead investigator, Bruce Spiegelman, they found that brown cells specifically break down slower in colder temperature where as white and beige cells continue to break down independently of the brain chemicals.
The researchers studied these fat cells by placing mice that were bred without beta-adrenergic receptors in 10 degrees Celsius or 50 degrees Fahrenheit for 20 hours. These receptors are responsible for attaching to norepinephrine that is released by the sympathetic nervous system in response to the cold. This neurological response triggers the fat cells to regulate heat. The researchers compared the fat cells' response to a control group of mice and found that the brown fat cells' gene expression for thermogenesis, which is the process of heat production, was a lot lower in the experimental group. White and beige fat cells, however, increased their gene expressions, suggesting that they react independently of the brain and were not affected by the cold.
To test this once more, the researchers used in vitro fat cells and exposed them to temperatures between 27 and 33 degrees Celsius (80-91 degrees Fahrenheit) for four hours. Once again the researchers found that white and beige cells did not need norepinephrine to regulate heat. The researchers believe that this finding could help with future research evaluating the risk of obesity. When fat cells do not break down due to the cold, the risk of obesity during the wintertime could increase. Based from that understanding, new treatments could potentially help with controlling obesity.
The study was published in the Proceedings of the National Academy of Sciences.