WASHINGTON, March 13 (Xinhua) -- American researchers have identified a mechanism on how "healthy" brown fat gains its energy-consuming identity in mice, potentially offering a new therapeutic target for diseases related to obesity.
The new study, published on Tuesday in Cell Reports, reported a molecule called estrogen-related receptor (ERR) gamma transform fat cells in the human body that store energy into a small subset of brown fat that do the opposite, burning energy and generate heat.
"This not only advances our understanding of how the body responds to cold, but could lead to new ways to control the amount of brown fat in the body, which has links to obesity, diabetes and fatty liver disease," said senior author of the study Ronald Evans at Howard Hughes Medical Institute investigator.
Until about a decade ago, scientists thought that only babies who cannot yet shiver to warm up had brown fat in their bodies. Subsequent studies have shown that adults also have brown fat, though at much lower levels. People with lower body mass indexes (BMIs) tend to have more of it.
At a cellular level, brown fat cells are crammed full of energy-generating mitochondria, which give the cells their brown color, according to researchers.
In this study, Evans' team has found that the ERR gamma gene is active at high levels in brown fat cells in mice.
The brown fat cells express the ERR gamma gene all the time, not just in response to cold, and that white fat cells do not express the gene at all, researchers said.
While 80 percent of normal mice are able to handle a temperature drop, all mice lacking ERR gamma did not tolerate the cold. However, there was no difference in the metabolism or weight of the mice.
The findings have revealed that ERR gamma is key to helping brown fat maintain its identity and its ability to respond to cold.
"We uncovered the factors that are both involved in protection against the cold and underpin brown fat identity," said Michael Downes, a co-senior author of the paper.
The group is planning future studies that look at the effect of activating ERR gamma in white fat cells, which they suspect could make some white fat resemble brown fat, and potentially help treat obesity and diabetes.
