Genetic understanding of diabetes deepens

By Alice Dembner, Globe Staff

Four separate scientific teams, including one led by Harvard researchers, are today reporting progress toward unraveling the genetic basis of the most common form of diabetes.

They have identified three new genetic risk factors and confirmed five others that were discovered over the last few years. An additional risk factor identified by one group has not yet been confirmed by others.

Together, the genetic defects account for about 5 percent of the risk of getting the illness, said David Altshuler, associate professor of genetics and medicine at Harvard Medical School and a leader of one of the four teams that included the Broad Institute of Harvard and MIT.

"The picture that is emerging is of multiple genes, each with a modest effect" on diabetes, he said.

Overall, genetics account for about half the risk of getting type 2 diabetes, according to Altshuler. Environment and such behaviors as obesity and lack of exercise account for the remaining risk.

More than 20 million Americans now have type 2 diabetes and scientists estimate that about 54 million more are at risk of getting the illness. The disease harms the body's ability to control blood sugar and can lead to heart disease, blindness and early death.

The new research is expected to provide leads for development of new treatments and possibly ways to prevent diabetes.

"The pharmaceutical industry is absolutely salivating at all of these studies because they represent the best validation of a new drug target," said Dr. Francis Collins, director of the National Human Genome Research Institute and a leader of another of the teams. But Collins cautioned that it could be a decade before patients see any new drugs from the research.

The work is unusual because three of the four scientific groups collaborated to confirm their results, making the findings extremely solid. In addition, the results identified some genetic areas that are not connected to any known mechanism behind diabetes.

The results were published today in the online editions of the journals Science and Nature Genetics.

They are all based on a new research technique called genome-wide association studies, in which scientists compare genetic samples from thousands of individuals with a specific illness to those without it. Differences between the two are examined as possible genetic causes of the disease.