Just as is the case with dietary fat, not all body fat is created equal. Mammals have several types of body fat, including white fat and brown fat. White fat is the undesirable fat that is found in what are often called problem-areas in humans, such as the unwelcome “spare tire” around the midriff or love handles. Brown fat, on the other hand, is a “good” type of fat found in humans, and has a large role in how rapidly our bodies burn calories. Brown fat cells are known as the “heaters” of the body, and they produce as much as 300 times more heat than any other tissue in the body.
Knowing this distinction, many have hoped to find a way of converting the undesirable white fat cells into brown fat cells. Ideally, those brown fat cells would do their jobs and fat would seem to melt away. Now, a study from the University of Bonn has gotten a step closer to this goal, by decoding a “toggle switch” in mice which can significantly stimulate fat burning. The researchers used an animal model to study Mirco-RNA, which are located in the genome of cells and very quickly and efficiently regulate gene activity. The specifically looked at Micro-RNA 155, which inhibits a certain transcription factor that controls brown fat cell function.
They were surprised to find that the transcription factor also regulates the levels of micro-RNA 155, establishing a tight feed-back loop that works like a toggle switch. How does it work? When the micro-RNA is highly expressed, brown fat cell differentiation is blocked. On the other hand, if the transcription factor is strong enough, then brown fat is produced at an increased level. At that point, more fat burning is expected. The researchers explained that the micro-RNA functions as an antagonist to the brown fat cells. “As long as enough micro-RNA 155 is present, the production of brown fat cells is blocked. Only if it falls below a certain proportion does this brake let up…and the desired fat burners can develop.” Therefore, a lot of micro-RNA 155 is associated with reduced fat burning. The researchers hope that in time, their findings will contribute to the development of new anti-obesity drugs.
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Weight Loss Studies & Clinical