Chemicals in House Dust May Trigger Receptor Linked to Obesity

Some chemicals commonly found in house dust may trigger a key receptor linked to human obesity, according to a new Duke University-led study.

The study, though preliminary in nature, adds to a growing body of evidence that a wide range of chemical mixtures used as flame retardants and added to lubricants, hydraulic fluids and plastics can bind to the PPARgamma receptor and, under the right conditions, activate it.

This activation during early development “may be a key factor in obesity,” says Heather Stapleton of Duke’s Nicholas School of Environment, who led the study.

PPARgamma – short for peroxisome proliferator-activated nuclear receptor gamma – regulates fat metabolism, cell proliferation and cell death.

Stapleton and her team published their new findings this month in the peer-reviewed journal Environmental Science & Technology.

Previous studies by Stapleton’s team have shown that many chemicals, including the widely used organophosphates and polybrominated diphenyl ether (PDBE) metabolites, can bind to PPARgamma. But the studies also showed that binding to the receptor did not always activate it.

To better understand whether environmental exposures can trigger the receptor’s “on switch,” Stapleton and her colleagues conducted their new study using a reporter gene assay to monitor PPARgamma activation in house dust samples. They chose to study chemicals in dust samples because indoor dust is an important pathway through which humans – especially infants and young children – become exposed to environmental contaminants. Young children ingest about 50 milligrams of house dust a day, according to U.S. EPA estimates.

Analysis by Stapleton’s co-author, Duke PhD student Mingliang Fang, showed that 28 of 30 semi-volatile compounds commonly found in indoor dust were “weak or moderate” PPARgamma agonists – meaning they could bind to and activate the receptor.  “But what was very interesting,” says Stapleton, “was the level of activation observed following exposure to an environmentally relevant mixture of these contaminants in house dust samples.”

The researchers found signs of significant PPARgamma activation in more than half of the 25 dust samples collected from homes, offices and gyms, at a level of exposure that would be similar to a child’s daily dose.

Further research is now under way to test the laboratory findings in conditions that simulate the type of chronic, low-level exposure to these chemicals that occurs in the real world.

“We are continuing to build on this research to determine what type of health effects may be caused by this level of activation in children,” says Stapleton.

Stapleton and Fang authored the new study with Thomas F. Webster, professor of environmental health at the Boston University School of Public Health.

Funding came from the National Institute of Environmental Health Sciences (grants #R01ESO16099 and R01 ES015829) and from Boston University School of Public Health pilot funding.

Stapleton is the Dan and Bunny Gabel Associate Professor of Environmental Ethics and Sustainable Environmental Management at Duke’s Nicholas School.

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