Chemicals May Increase Diabetes Risk, Not Just Genes, Weight and Exercise

Chemicals in the water, soil, or buildings around you could be upping your risk of developing diabetes, according to new research from Stanford University.

While genetics, diet and weight all feed into one's chances of getting adult-onset (type II) diabetes, these factors can only explain a portion of the risk -- environmental risk factors may offer a deeper understanding of why people develop the disease.

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Using a new technique which mimics the way scientists mapped the human genome, researchers were able to identify three environmental elements that are correlated with an increased risk of type II diabetes: a pesticide called heptachlor epoxide; the banned chemical PCBs, used in adhesives and machinery; and -- surprisingly -- a form of vitamin E.

"Since the genome project was finished, a lot of people have been excited about the genetic causes of disease, but I don't think most people realize that the environmental factors for many things are actually stronger," says bioinformatics expert Dr. Atul Butte, a co-author of the study.

Building on the same techniques scientists use to map disease risk over many genes, bioinformatics graduate student Chirag Patel conceived and designed a computer program that could map risk over hundreds of environmental factors, such as chemical toxins found in the soil, water, and industrial products around us.

"We were hoping to find targetable environmental factors for diabetes," Butte says, "and it looks like that's what we've found."

The research is still in its early stages, Butte and Patel caution, and these three chemicals are by no means proven to cause diabetes, but the new technology opens doors for future research in this area.

The study was published Wednesday in the online journal PLoS ONE.

Looking for Chemical Culprits

Linking things in the environment with risk of disease is a common practice for epidemiologists, but it's difficult to run analyses for many factors at once. Patel's new system, called Environment-Wide Association Studies -- EWAS for short -- makes sorting hundreds of environmental elements possible.

"It's clear that type II diabetes has a large environmental component," says Dr. Christopher Saudek, a diabetes specialist and professor of medicine at John's Hopkins University. He says that the studies looking for a genetic link to the disease have been largely disappointing. One gene consistently comes up, but even that explains a relatively small amount of the risk, he says.

Given that the genetic links leave much of diabetes risk unexplained, tools like EWAS may help bridge the gap between the risk explained by genes and behavior and environmental risk, Saudek says.

Banned Toxins Resurface

Drawing from nationally-representative data from the Centers for Disease Control and Prevention, the researchers were able to assess the association between type II diabetes and 266 different environmental factors. After adjusting for age, sex, ethnicity, and body mass index, the three factors still stuck out as strongly correlated with the disease.

Pesticides, toxic chemicals, and a form of vitamin E were associated with a higher likelihood of type II diabetes in Wednesday's study.

Finding an association between an antioxidant like vitamin E and diabetes was unexpected and a bit puzzling, Butte says, but it's not particularly surprising that the chemicals showed up in the analsysis.

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