Not all body fat is the same; there are two kinds. White fat is located around the hips, thighs, and stomach and acts as an insulator and energy reserve that our body can tap into when there’s not enough food. It’s considered an endocrine tissue because it can produce signals in the form of molecules including enzymes and hormones like leptin, and influences the impact of insulin. The other kind, brown fat, acts differently from white fat. It resides near the spine, around the throat, and by the kidneys. Brown fat can also store energy, but it releases heat. Infants have more brown fat than adults as it’s critical to maintain their body temperature.
Studies have investigated the role of white fat and how it’s connected to disease. But recently, attention has turned to brown fat and how it may be beneficial to health. If a body carries more brown fat, it can help burn energy.
An international team of scientists has now learned more about the molecules that brown fat releases. In a first, they have mapped the secretory signals that are sent by white and brown fat in human adults. Reporting in Cell Metabolism, they learned that these two kinds of fats are sending very different messages to the body.
"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 Associate Professor Camilla Schéele from the Novo Nordisk Foundation Center for Basic Metabolic Research (CBMR).
In this study, the research team used mass spectrometry to identify the proteins that the two kinds of fat release. They determined that brown fat can secrete over one hundred proteins that white fat does not release. Brown fat has a bigger influence on the immune system, and white fat plays a role in tissue plasticity.
"One of the great mysteries about brown fat is that we are not sure how it is formed. But we have found an interesting clue. 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," explained Schéele.
The scientists now want to learn more about how the signals sent by the fat are affecting the rest of the body, including the brain.