New associations between diabetes, environmental factors found by novel Stanford analytic technique

Got diabetes? If so, you probably know that the adult-onset form of the disease can be triggered by, among other things, obesity and a fatty diet. You're also more likely to develop diabetes if other family members have it. But a new study by researchers at the Stanford University School of Medicine suggests that you should also begin looking suspiciously at other aspects of your life — like your past exposure to certain pesticides or chemicals and even one form of vitamin E.

In fact, the association of some of these so-called "environmental" cues with diabetes surpasses that of the best genetic markers scientists have identified for the disease.

Identifying relationships between a person's environment (such as tobacco exposure) and specific health repercussions (such as cancer) is nothing new. Epidemiological studies of large groups of people have been doing just that for decades. But they are limited in their ability to assess the hundreds or even thousands of variables that comprise the intricate fabric of our everyday lives. (What's your risk of heart disease if you smoke sparingly and eat fatty foods, but are also a marathoner?) They're also not open-ended: The researcher has to begin with presuppositions about possible relationships. (Does folic acid prevent birth defects?)

In this new study, the scientists relied instead on an unconventional approach that treats environmental variables as "genes." That conceptual shift allowed them to use some of the same techniques initially developed to identify the many sections of DNA throughout the genome that might contribute to disease development. Bioinformatics expert Atul Butte, MD, PhD, assistant professor of pediatric cancer biology, compared the data generated by the new approach to the amount and types of information gleaned from a DNA microarray.

"This approach catapults us from being forced to ask very simple, directed questions about environment and disease into a new realm in which we can look at many, many variables simultaneously and without bias," said Butte, who is also director of the Center for Pediatric Bioinformatics at Lucile Packard Children's Hospital. "In the future, we'll be able to analyze the effect of genes and environment together, to find, perhaps, that a specific gene increases the risk of a disease only if the person is also drinking polluted well water."

Specifically, in this study, Butte and his coworkers used the technique to identify a previously known association between people with type-2 diabetes and a class of organic compounds called polychlorinated biphenyls, or PCBs, commonly used for many applications until the late 1970s. They also uncovered a strong, but unexpected, relationship between diabetes and high levels of a form of vitamin E called gamma-tocopherol, which is prevalent in fruits, vegetables, nuts and milk.

The scientists are careful to caution, however, that an association doesn't necessarily mean that vitamin E or pollutants cause type-2 diabetes, and that more research is needed to fully understand these complex relationships.