Precursor Fat Cells May Shed Light on Diseases

To understand more about the mystery of obesity, it's important to understand how fat cells are born, nurtured and matured. And the enlightenment that will flow from understanding obesity may sweep away mysteries relating to the generation of cardiovascular disease and diabetes, which seem to be so much more prevalent among people who are obese. So it was with delight that scientists greeted a recent study identifying precursor cells that develop into full-blown fat tissue. The research, performed on "skinny" mice genetically modified to have no fat deposits, showed that injecting one particular type of cell into the mice caused them to form fat.

"The identification of white adipocyte [fat cell] progenitor cells provides a means for identifying factors that regulate the proliferation and differentiation of fat cells," said senior author Jeffrey Friedman, who is the Marilyn M. Simpson Professor at Rockefeller and a Howard Hughes Medical Institute researcher.

In their study, the scientists injected various types of cells into the fatless mice. Only one such type produced fat deposits - the one expressing the CD24 cell-surface marker protein. "I injected the CD24 cells - which represent a very small population of cells in normal adipose [fat] tissue - into a site where the fat would normally develop in the fatless mouse, and I found that a normal-sized fat depot forms at the site of injection," said Matt Rodeheffer, the study's first author and a postdoctoral associate in Friedman's Laboratory of Molecular Genetics.

Another attribute of the genetically modified fatless mice is that they have diabetes, and the injection of the fat-producing cells cured the disease. In addition, the cells secreted proteins called cytokines, which confirmed for the researchers that the cells were indeed normal fat cells.

"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 and determine the molecular factors that regulate formation of adipose tissue," says Rodeheffer.

"We then can potentially study how the growth and differentiation of these cells are regulated in obesity and determine whether or not the molecular events that are involved in the regulation of adipose tissue are contributing factors to other pathologies, such as diabetes and cardiovascular disease, that are associated with obesity and metabolic syndrome," he added.