Researchers have found the apparent hiding place of a gene that promotes the most common form of diabetes, one that affects 15 million Americans.
Scientists think several genes play a role in susceptibility to type 2 diabetes, but they haven’t identified any gene yet. The location suggested by the new study is the second to be implicated.
Scientists hope the genes will reveal the biology of diabetes and lead to drugs for treatment and prevention.
Type 2 diabetes usually develops in people older than 40; they are treated with diet, exercise, oral drugs and sometimes insulin injections.
Genes lie along microscopic strings called chromosomes, and the new study identifies a piece of a chromosome that appears to harbor a diabetes gene. The region may contain 100 genes or so, which is about a thousandth of the whole human collection, researcher Eric Lander said.
Nobody knows what fraction of type 2 diabetes might be related to the gene, he said in a telephone interview from Finland.
Lander, of the Whitehead Institute for Biomedical Research in Cambridge, Mass., reports the work with colleagues there and elsewhere in the September issue of the journal Nature Genetics.
They studied 217 members of 26 Swedish-speaking families in the Botnia region on Finland’s western coast. The population in the area long has been relatively isolated, which would make a diabetes gene easier to find.
Each of the families had at least three members with type 2 diabetes, for a total of 120 diabetic participants.
Scientists started with a wide-ranging scan of the genes and initially found no clue about the whereabouts of a diabetes gene.
But they got a break after they divided the families by how much insulin family members produced in response to a sugary drink. That test measured one problem seen in type 2 diabetes, which is failing to make enough insulin to control blood-sugar levels. The other problem is failing to respond normally to insulin. In any patient, one or the other defect may be more prominent.
In diabetics with the lowest insulin response to the sugary drink, researchers found evidence that a diabetes gene lurks in a particular stretch of chromosome 12.
That same region contains a gene, not yet identified, for a very rare form of diabetes that resembles type 2 but strikes early, around age 25 on the average. The Finns got the common form much later, at age 58 on the average.
Lander said the result may mean that both forms of the disease are related to the same gene. A mutation that severely cripples the gene may cause the rare, early form of diabetes while a less serious mutation might promote development of the common form, he said.
The notion that one gene could cause the two kinds of diabetes makes sense, although it’s still only speculation, said Graeme Bell of the Howard Hughes Medical Institute at the University of Chicago.
Bell, who reported the apparent whereabouts of another diabetes gene in June, said he suspects that the gene Lander’s team tracked is related to only a small percentage of common diabetes cases.