Scientific Method —

Genetics and Type-II Diabetes

Type-II Diabetes is thought to largely be a lifestyle issue. But new results …

The folks at deCode Genetics have a pretty interesting approach to human genetic issues. It's been recognized for a while that modern populations that have gone through bottlenecks, or historic periods of low population, tend to be good for human genetics. This is because of what's called a founder effect - all the individuals in the modern population that carry a genetic trait are likely to have inherited that trait from a single individual that lived at the time of the bottleneck. As a result, the gene causing the trait is relatively easy to identify. deCode Genetics recognized that the entire population of Iceland fit this description. Iceland was settled by a relatively small number of Vikings in the middle ages, and hasn't had a significant influx of new individuals since. In addition, it provides excellent historical pedigree records, allowing families to be traced back many generations.

So, Decode's made an arrangement with the people and government of Iceland - they have access to the health records via the government and DNA samples from much of the population, who have volunteered. Using this information, they've gone gene hunting. Instead of searching for purely genetic diseases, they've gone hunting for susceptibility genes, ones that are likely to make their carriers prone to things that also have environment influences, such as heart disease or mental disorders. For example, after scanning the records for a list of all heart attack victims, they can test the DNA of many of these people for shared features and, potentially, shared variants of a gene. Pharmaceutical companies help fund much of the work in the hope that it will lead to screening kits and preventative medicines.

Their latest success has just been published in Nature Genetics, and it's a big one, one that affects well over 5 percent of Americans. Type-II Diabetes, linked to a high fat diet, now appears to have a genetic component. According to the New York Times coverage, the statistics are striking: carry 1 copy of a specific allele of this gene, and you're 45 percent more likely to develop Type-II Diabetes. Carry two copies and that goes up to 140 percent. It's estimated that eliminating the allele from the population would reduce the incidence of Type-II Diabetes by 20 percent.

The gene itself is part of a large family of transcription factors, genes which regulate the expression of other genes. This and other members of this family have received more attention in the past due to their role in regulating the development of many organs. Transcription factors don't lend themselves to therapeutic targeting, but at least this should open the possibility for genetic testing. Those carrying the dangerous allele would focus on what most of us know we should be doing, but don't find the time for: eating a good diet and getting exercise.

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