Polybrominated diphenyl ethers as endocrine disruptors of adipocyte metabolism

Objective: Obesity is thought to result from poor diet and insufficient exercise. An additional factor may be endocrine‐disrupting environmental chemicals that contaminate the air, water, and food supply. We tested the hypothesis that a class of lipid‐soluble flame retardant chemicals known to accumulate in adipose tissue, polybrominated diphenyl ethers (PBDEs), disrupts insulin and isoproterenol sensitivity of isolated rat adipocytes. Research Methods and Procedures: Six‐week‐old Sprague‐Dawley rats were gavaged daily with 14 mg/kg body weight (BW) pentabrominated diphenyl ether (penta‐BDE) in corn oil (n = 24) or corn oil alone (n = 24). At 2 and 4 weeks of treatment, epididymal fat pad adipocytes were isolated, and isoproterenol‐stimulated lipolysis, insulin‐stimulated glucose oxidation, and adipocyte size were measured. Results: There was no alteration in adipocyte metabolism after 2 weeks of in vivo penta‐BDE treatment, but after 4 weeks of treatment, adipocytes averaged a 30% increase in isoproterenol‐stimulated lipolysis and a 59% decrease in insulin‐stimulated glucose oxidation, compared with control. There were no differences in average rat BW and adipocyte size between treated and control rats, but plasma total thyroxine level in 2‐ and 4‐week treated rats was 30% of control. Discussion: Daily exposure of rats to 14 mg/kg BW penta‐BDE for 4 weeks has no effect on animal or adipocyte size but significantly alters insulin and isoproterenol‐stimulated metabolism of isolated adipocytes. These alterations, hallmark features of metabolic obesity, suggest the need for further research on the contribution of lipid‐soluble, endocrine‐disrupting environmental chemicals to the obesity epidemic.