Study shows genes predict how well diabetes drug will work

How well a person with type 2 diabetes responds to a diabetes drug may well depend upon his or her genetic make-up, according to a study published in the May issue of Diabetes Care. The study found that people who carried certain genotypes responded less favorably to rosiglitazone, a drug often prescribed for people with diabetes, than carriers of other genotypes.

The study is the latest in a growing body of research focused on pharmacogenetics, or how genetic factors influence a person's reaction to a specific drug. An unrelated study recently set off controversy when it found the heart drug BiDil was effective in treating African Americans after having fared poorly when given to Caucasians, causing concern that pharmacogenetics could lead to racially tailored drug marketing.

There are small, but sometimes important, differences in the structure of the same gene among different people. That is, the genotypes are slightly different. The study, by researchers in Korea, found that people with type 2 diabetes who had certain genotypes were less likely to show improvement in blood glucose control (as measured by A1C levels), fasting glycemia and plasma adiponectin levels (a marker for insulin sensitivity) after treatment with rosiglitazone (marketed as Avandia), as compared to other people with type 2 diabetes. Subjects were treated with the medication for 12 weeks without changing any of their previous medications.

"This study has nothing to do with race," said Dr. Eun Seok Kang, one of the lead researchers on the study. "It shows us how important pharmacogenetics could be in the future in helping us quickly and efficiently determine the best treatment to give people. If something in our genetic make-up offers clues about how well we will respond to particular medications, this could be a tremendous asset to people with diabetes and other complex diseases. Obviously knowing ahead of time which drugs will work best means we can eliminate the entire trial-and-error process of drugs that don't work or work poorly for some people. Clearly we have a lot more to learn before we get to that stage, but this is an important first step."