The human body carries different types of fat cells, and some of them are more desirable than others. White fat stores our excess energy in the form of lipids that give rise to love handles and beer bellies, while brown fat burns calories to generate heat and keep us warm. Much obesity research lately it has focused on ways the body can be made to produce more brown fat as a way to fight weight gain, and scientists have now made a major breakthrough in this area by discovering a previously unknown source of its production.
Research at the Joslin Diabetes Center in Boston focuses on brown fat cells, as well as another third cell type, called beige fat, which, like brown, contains more mitochondria and burns calories in response to cold temperatures, keeping the body warm. Scientists have begun to understand where these “good” types of fat cells come from, hoping to discover new targets for obesity therapy.
“The ability of brown and beige fat cells to burn fuel and produce heat, especially when exposed to cold temperatures, has long made them an attractive target for the treatment of obesity and other metabolic disorders,” said senior author Yu-Hua Tseng . “And yet, the precise origins of brown adipocytes induced by cold and the mechanisms of action have remained somewhat mysterious.”
These brown and beige fat cells are believed to originate from a set of cells that express a receptor called Pdgfrα, although previous research has given scientists reason to suspect the existence of other factors at play. To explore this possibility, the team used a technique called unicellular sequencing to study the cellular composition of brown fat in mice kept at different temperatures, for different periods of time.
This revealed that cells expressing the Pdgfrα receptor were indeed a source of brown fat cells, but the data also revealed another set of cells playing the same role. It turned out that they were smooth muscle cells that express another type of receptor, called Trpv1, which is a protein found in several types of cells and known to feel stimuli related to pain and the sensation of heat.
Investigating further the mechanisms behind this, the team confirmed that these smooth muscle cells were acting as a source for brown fat cells, especially when the mice were exposed to cold temperatures. Other experiments have shown that low temperatures have also seen smooth muscle cells become a source of beige fat cells, further increasing the potential of the Trpv1 receptor as a focal point for advanced obesity treatments.
“The identification of cells that express Trpv1 as a new source of brown or beige cold-induced adipocytes suggests that it may be possible to refine the use of cold temperatures to treat obesity by developing drugs that recapitulate the effects of cold exposure at the cellular level,” Tseng says.
While studies have shown that exposure to cold can cause the body to produce more brown fat cells than white ones, scientists like Tseng hope to use alternative means to trigger these conversions in humans. Possibilities include fish oils, targeting certain proteins as a kind of “fat switch“or same”fat transplants. “Promisingly, scientists note that the Trpv1 receptor can detect and respond to a variety of stimuli, including compounds in peppers, so there are possibilities that don’t include subjecting humans to freezing temperatures or other uncomfortable sensations.
“Further studies are planned to address the role of the Trpv1 channel and its ligands and whether it is possible to target these cells to increase the number of thermogenic adipocytes as a therapeutic approach to obesity,” says Tseng.
The research was published in the journal Nature’s Metabolism.
Source: Joslin Diabetes Center