In May, this writer published a blog on fat research that sounded promising in the battle against obesity and diabetes. That blog focused on research that identified the compound irisin and the ability of irisin to convert metabolically-inactive white adipose tissue to energy-burning brown adipose tissue.
Perhaps indicative of the intensity with which research on brown fat is being pursued, Wu et al. published new information online last week in Cell (July 12, 2012) that there is, in fact yet another type of adipose tissue.
Announcing beige fat. The research is entitled “Beige Adipocytes Are a Distinct Type of Thermogenic Fat Cell in Mouse and Human.”
In this research, Wu et al. cloned beige fat cells, and identified unique characteristics and cell surface markers. Here are a few of their findings:
While brown fat is derived from stem cell precursors that also make muscle cells, beige fat forms within deposits of white fat, from beige cell precursors.
Beige fat cells and their precursors share the presence of cell surface marker CD137, as seen by FACS analysis.
Both brown and beige fats contain mitochondria, and mitochondria contain iron, thus the brown or beige color.
Brown fat cells express high levels of UCP1, a protein that fuels mitochondria to burn calories and produce heat; basal expression of UCP1 in beige fat is very low. While expression of UCP1 is generally low in beige fat cells, these cells have a marked ability to activate UCP1 and turn on respiration and energy use, an ability that separates beige fat cells from white fat.
The authors demonstrated that fat deposits in adult humans that were previously identified as brown fat, actually have gene expression and immunohistochemical characteristics of beige fat.
It now appears that it may be beige fat, and not brown, that propels exciting new antiobesity research.
And for those that cook, a note that “browning of fat” may be taking on new meaning. Rather than rendering the white stuff on salt pork, browning (beige-ing?) of fat may instead become a new tool in prevention of diabetes and obesity–stay tuned.
One other thing: You may agree that with fat research results changing faster than you can discard a pipette tip, this probably isn’t the last we’ve heard in the saga of browning fat. I think we may continue to find it’s all good news.
Here is a wonderful infographic from Cell magazine, “Snapshot: Adipocyte Life Cycle” on Adipose Differentiation and Obesigenic Expansion.
Jun Wu, Pontus Bostro, Lauren M. Sparks, Li Ye, Jang Hyun Choi, An-Hoa Giang, Melin Khandekar, Kirsi A. Virtanen, Pirjo Nuutila, Gert Schaart, Kexin Huang, Hua Tu, Wouter D. van Marken Lichtenbelt, Joris Hoeks, & Sven Enerba, Patrick Schrauwen, and Bruce M. Spiegelman (2012). Beige Adipocytes Are a Distinct
Type of Thermogenic Fat
Cell in Mouse and Human Cell : http://dx.doi.org/10.1016/j.cell.2012.05.016