In a first, researchers have mapped all the proteins secreted from adult human white and brown fat cells, and discovered that they send very different signals to the rest of the body. White fat sits on our stomach, hips, and thighs as a stored form of energy that our body uses when food is scarce, whereas brown fat, the researchers said, sits close to the nervous system, the spine, around our throat, and near the kidneys, producing heat.
The study, published in the journal Cell Metabolism, noted that brown fat secreted more than 100 proteins that are not secreted by white fat. The researchers, including those from the University of Copenhagen in Denmark, said that brown fat was better at regulating the immune system, while white fat secreted proteins allowing for greater tissue plasticity.
The study noted that it helps to have more brown fat if one wanted to burn more energy. Infants, the researchers said, have far more brown fat than adults since it was important in keeping them warm.
"It's the first time that anyone has studied human brown fat at this level of detail. We have mapped all of the proteins that are secreted from the fat cells and that they use to communicate with other cells. And there are big differences between them. It's as though they speak very different languages," said study co-author Camilla Scheele from the University of Copenhagen.
The researchers said that they have solved one of the biggest pieces of the puzzle behind how brown fat is formed. "One of the proteins that brown fat secretes plays an important role in developing and maturing new brown fat cells to prepare them for producing heat and energy," said Scheele.
The researchers are currently looking at how these proteins communicate with the rest of the body, especially the ones sent to the brain.