In laboratory studies of mouse cells, the research team identified genes that govern how precursor cells give rise to mature brown fat cells. There are two main types of fat cells in the body- white, designed to store energy for use in times of need, and brown, which burn energy and generate heat, leading scientists to believe that finding ways to encourage the development of brown fat might be good for treating obesity. In previous research, the scientists were among the first to develop cell lines of precursor cells that give rise to brown fat cells. ‘We used those cell lines to study how insulin affects the conversion of fat precursors, or preadipocytes, into mature brown adipocytes,’ said Dr. Yu-Hua Tseng, one of the study’s lead authors.

The team studied ‘knockout’ cell lines of brown preadipocytes that lacked insulin receptor substrates (IRS) numbered 1 through 4, which are the first steps in insulin signaling inside the cell. In cell lines lacking IRS1, the precursors failed to develop into mature brown fat cells. Importantly, when they added the gene for IRS1 back into the knockout cells, the precursors recovered most of their ability to differentiate into brown fat cells. Using DNA chips to analyze these cells, a strong genetic pattern emerged that predicted the importance of precursors to differentiate into mature brown fat cells.