Found: the cells that make people fat

Washington, Oct 4 : Scientists have identified an important fat precursor cell that may explain how changes in the numbers of fat cells might increase obesity.

The finding could also have implications for understanding how fat cells affect conditions like diabetes and cardiovascular disease.

"The identification of white adipocyte progenitor cells provides a means for identifying factors that regulate the proliferation and differentiation of fat cells," said co-author Jeffrey Friedman, professor at Rockefeller University and a Howard Hughes Medical Institute investigator.

Obesity, a major public health problem worldwide, results, in part, from an increase in the mass and number of white fat cells. Because white fat cells cannot divide, scientists have hypothesised that a population of fat precursor cells must exist in the fat depot in order to produce new fat cells. But identifying them has been difficult.

With the assistance of researchers in Rockefeller's Flow Cytometry Resource Centre, co-author Matt Rodeheffer, a postdoctoral associate in Friedman's Lab of Molecular Genetics, used a cell sorting technique called fluorescence-activated cell sorting, or FACS, to search for cell populations that could produce fat in cell cultures and identified two such populations, according to a Rockfeller University press release.

To determine if these cells could develop into fat cells in living animals, Rodeheffer injected these cell populations into the fat depots of a genetically engineered mouse, developed at NIH, called fatless, which lacks white fat and mimics a condition in humans called lipodystrophy that also results in diabetes.

Rodeheffer found that only one of the isolated cell populations, which express the CD24 cell-surface marker protein, produced fat tissue in the fatless mouse. This population normally represents only .08 percent of the non-adipocyte population in adipose tissue.

"This finding gives us a better understanding of the basic biology of adipose tissue and opens the door for us and for other researchers to be able to study these cells in living animals," said Rodeheffer.

The results have been published online this week in Cell.