Nov 19, 2008 - Research

Diabetes Risk and Genetics

Recent genetic discoveries have taught researchers a lot about type 2 diabetes and identified particular genetic variants that can influence a person’s risk of developing the condition.

But two studies published this week in the New England Journal of Medicine conclude that genetic information still pales in comparison to factors like body weight, smoking, cholesterol levels, and other medical diagnostics when it comes to predicting who will develop the condition.

The papers are a reminder that although personal genomics promises to become a valuable supplement to preventive medicine, the information it provides shouldn’t be considered a replacement for regular check-ups and a healthy lifestyle. And though genetics certainly plays a role, diet, exercise and other environmental factors have a substantially greater impact on whether a person will develop type 2 diabetes.

Both studies looked at one-letter DNA variations known as single-nucleotide polymorphisms (SNPs) that have been linked to diabetes. The 23andMe Personal Genome Serviceâ„¢ provides information on nine diabetes-associated SNPs.

One study used data from the legendary Framingham Heart Study, which has followed three generations of participants over a period of 60 years, to show that inheriting a greater number of high-risk diabetes genes does increase a person’s chances of developing the condition. But when added to traditional measures of diabetes risk such as family history, body-mass index, fasting plasma glucose level, and blood pressure, a person’s genotype at the 18 SNPs studied did not significantly improve the researchers’ ability to predict which of the 2,377 study participants became diabetic over a period of 28 years.

The other study, which looked at 16 SNPs in 16,061 Swedish and 2,770 Finnish subjects who had been followed for an average of 23.5 years, produced a similar result. The authors concluded that “common genetic variants associated with the risk of diabetes had a small effect on the ability to predict the future development of type 2 diabetes.”

However, because the physiological risk factors typically develop later in life (though they are becoming distressingly common in younger populations) the authors of the Framingham-based study suggest genetic information could be useful in motivating young people who have inherited a high diabetes risk to control their weight and take other preventive measures.

And research is bound to produce more knowledge about the genetic roots of diabetes. So in the not-too-distant future, a person’s genotype is likely to provide substantial predictive information beyond what is available from family history and physiology.

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