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Chronic disease: Genes matter, but so does environment

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We’re all familiar with the classic debate: Is it nature or nurture that most influences how our brains tick? Of course, a variation of that question is just as important in the study of the human body. Is health hardwired in our genetic makeup, or is it shaped by where we live, what we eat and what kind of cleaning agents we use?

Judging by the rivers of money flowing into genetic research, you might think the answer is that we’re hardwired. Not so, argue Stephen Rappaport, PhD, and Martyn Smith, PhD, in a Perspectives piece in Science:

Although the risks of developing chronic diseases are attributed to both genetic and environmental factors, 70 to 90 percent of disease risks are probably due to differences in environments. Yet, epidemiologists increasingly use genome-wide association studies (GWAS) to investigate diseases, while relying on questionnaires to characterize “environmental exposures.”

The researchers’ proposition? The development of an “exposome” – a catalogue of the combined exposures from all sources that reach the internal chemical environment of the human body. To tackle such an ambitious project, it’s crucial to develop a more cohesive view of environmental exposure, Rappaport and Smith write, by considering all biologically active chemicals in the internal environment. That means not just looking at water and air pollution, for example, but also taking into account chemicals produced by inflammation, oxidative stress, infections and gut flora.

Building an “exposome” would be as hard, if not harder, than sequencing the human genome, Katherine Harmon writes in Scientific American. But the work of Stanford’s Atul Butte, MD, PhD, could serve as a prototype:

[Butte's] study, published in May in PLoS ONEscanned blood and urine samples of thousands of people for the presence of different chemical compounds, looking for correlates with type 2 diabetes. “I think that’s really a good example of what we should be able to do,” Rappaport says.

Previously: New associations between diabetes, environmental factors found by Stanford researchers
Photo by Peter Rosbjerg

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