Researchers have stumbled upon a gene that may underlie some cases of adult-onset diabetes. If so, the discovery could eventually lead to better treatments and diagnostic tests.
In adult-onset diabetes, cells don't respond well to insulin, a hormone that normally tells them to absorb and store glucose. Most adults who develop type II diabetes are chronically underactive and overweight, so current treatments include changes to diet and more exercise, and sometimes drugs and insulin injections. But these approaches often can't prevent diabetes-related damage to the heart, kidneys, nerves, and blood vessels. Researchers hope that by identifying genes that contribute to the disease, they may be able to develop better therapies. Genetic screening might also help people at risk ward off the disease. So far, however, the handful of implicated genes accounts for only 5% to 10% of the cases.
Now a new, unexpected candidate has come to light. A team led by molecular biologist Stephane Schurmans of IRIBHN in Gosselies, Belgium, had engineered mice to lack a gene that appeared to be a tumor suppressor. But mice without this gene, called SHIP2, didn't get cancer. Instead, they had difficulty breathing, turned blue, and died within 3 days of birth--telltale symptoms of hypoglycemia, or low levels of blood sugar, the researchers report in the 4 January issue of Nature.
The researchers found that the mice develop a hypersensitivity to insulin. This is not diabetes, in which people respond sluggishly to insulin. But Schurmans suggests that because SHIP2 seems to govern sensitivity to insulin, it's possible that some forms of the gene may reduce responsiveness to the hormone, causing the insulin resistance that is the hallmark of diabetes. If so, he says, drugs that inhibit the mutated gene might ease symptoms, and genetic tests might uncover susceptible people before the disease develops.
The study "moves this gene higher up on the list of candidates for diabetes," says Clifton Bogardus of the National Institute of Diabetes and Digestive and Kidney Diseases in Phoenix, Arizona. But he cautions that many possible diabetes genes have never panned out, and the link will be theoretical until a SHIP2 mutation turns up in human diabetics--something that the researchers have already begun to search for, Schurmans says.