Diabetes Research Takes a Giant Step Forward
Sept. 26, 2000 -- The Mexican-American residents of Starr County, Texas, have been poked and prodded and questioned for 19 years without any effect on their very high incidence of type 2 diabetes. But today they can say they are responsible for a major breakthrough in diabetes research -- the discovery of a diabetes gene.
The finding, reported in the journal Nature Genetics, opens up an entirely new approach to understanding -- and perhaps one day treating -- one of the most common serious diseases in Americans.
"A large proportion of the U.S. population is going to get diabetes," says study co-author Craig L. Hanis, PhD. This shows that disease genes that have been elusive aren't going to be elusive much longer. This is kind of the start for finding genes for common diseases -- heart disease, for example."
The gene is linked to the much more common type of diabetes, type 2, which tends to affect individuals in adulthood and has been linked to obesity as well as other environmental factors. The gene, called CAPN10, makes a little-understood enzyme known as calpain-10. This enzyme is found in virtually every cell of the body. Until now, nobody suspected that these enzymes were involved in diabetes -- but all that is about to change.
"What we've got now is a lot of data supporting [the theory that] calpain-10 affects susceptibility to diabetes," study co-author Nancy J. Cox, PhD, tells WebMD. "That suggests this is a brand new pathway for [controlling blood sugar]. I think now people will test this in a variety of ways."
Hanis, a professor of human genetics at the University of Texas Health Science Center at Houston, credits the residents of Starr County. "We have been able to establish a relationship with families, and they are incredible -- they let us come in and question them and get blood samples with no immediate benefit for them -- or maybe even for their children. These findings explain about 14% of the diabetes risk of these people. Some will say that is not a lot. What is important is that it identifies calpain-10 as one of the central players in diabetes. We hope this will be useful for everybody."
Leonid Kruglyak, PhD, a geneticist at Seattle's Fred Hutchinson Cancer Center, was one of the authors of an editorial accompanying the study. "It's an exciting study," Kruglyak tells WebMD. "The effort to find genes for common diseases has been going on for a decade now, but this is the first suggestion of success. If it holds up, it points out a whole new pathway for looking at diabetes that nobody has been thinking about."
The study results call for rethinking what it means to have a disease gene. A genetic disease is usually thought of a disease caused by a specific mutant gene. But for complex diseases with multiple risk factors -- such as diabetes -- genetic risk is only one part of the disease, and each genetic risk factor affects only a relatively small number of patients.