From San Francisco, at the Experimental Biology 2006 meeting
Studies in recent years have found growing concentrations of certain brominated chemicals in the blood of people worldwide. Manufacturers use these substances widely as flame retardants in plastics and foams. Although the chemicals have caused neurological and developmental impairments in test animals, nobody had probed the flame retardants’ effects on animals’ body fat, which is where the chemicals accumulate. Now, scientists report that in rodents, the flame retardants provoke fat cell changes that appear to boost the risk of obesity and type 2 diabetes.
Andrea C. Arel of the University of New Hampshire in Durham and her colleagues worked with a mix of polybrominated diphenyl ethers (PBDEs) that was dominated by five-bromine—or penta—molecules. The group fed the mix to some just-weaned male rats in daily doses of 14 milligrams per kilogram of body weight. Other rats got a normal diet with none of the PBDE mixture. The researchers analyzed fat cells from half of the animals in each group after 2 weeks and from the other half after another 2 weeks.
Differences between bromine-treated and untreated animals emerged only at 4 weeks. The dosed animals’ fat cells were mobilizing lipids 25 percent faster than were cells in the other rats. Increased fat circulation in the body is characteristic of obesity, notes team leader Gale Carey.
Fat cells from animals treated with PBDEs for 4 weeks also exhibited roughly 65 percent less glucose oxidation, a measure of blood sugar’s ability to enter cells. Carey describes this change as a “crude measure of insulin resistance,” which typically precedes development of type 2 diabetes.
When the researchers put the PBDE mixture in incubated colonies of fat cells from other mice, no similar changes occurred. “You need the whole animal to see the effects,” Carey concludes.