Mammals have the ability to adapt to a range of the temperature. While physiological homeostasis has a lot to do with this, part of the reason why mammals can adapt to cold temperatures is the presence of energy-burning brown fat cells. Unlike the large fat storage units in white fat cells (the cell type responsible for obesity), brown fat cells have the capacity to generate heat and provide insulation from cold. Recently, scientists discovered a population of fat cells with the properties of brown and white fat cells, a population dubbed the beige (brite cells) that emerges in mammalian fat as a result of cold adaptation.

The origin of brite fat cells is a heavily debated topic. Although recent studies have shown that white fat cells can be converted into brite fat cells with molecular interventions, such as mir-155 inhibition, it remains unclear whether this conversion is indeed a physiological event. 

In a recent study published in Nature Cell Biology, ETH scientists lead by Dr. Christian Wolfrum (in Zurich) used lineage tracing techniques to demonstrate that white fat cells are indeed the origin of brite fat cells in mice. Moreover, the authors observed a white-to-brite fat cell conversion typically in response to 5 weeks of cold adaptation in mice, and that the conversion can be reversed with 5 weeks of warm adaptation, turning brite fat cells back into white fat cells. The study is the first to show that brite/white fat cell interconversion is a physiological event in temperature adaptation in mammals. 

While the study is an important advance in our understanding of the role of fat cells in mammalian temperature homeostasis, the study also has far-reaching implications in obesity research. Obesity is often associated with the accumulation of massive fat reservoirs in white fat cells, and that the conversion of these cells into energy-burning brite fat cells is crucial to help burn off excess fat. The latter is an extensively researched obesity treatment strategy, for which scientists are developing drugs to reprogram white fat cells into energy-burning-brite cells. The study here suggests that the most natural remedy for obesity might be the fat cell’s natural response to cold, favoring the reprogramming of white fat cells into brite cells, and ultimately shrinking the waistline.

Rosenwald M, et al., Bi-directional interconversion of brite and white adipocytes. Nat Cell Biol. 2013 Apr 28. doi: 10.1038/ncb2740.