Diabetes results from suicidal cells.

Insulin-dependent diabetes mellitus, or type I diabetes, occurs when an autoimmune reaction leads to the death of insulin-secreting islet cells in the pancreas. But is that cell death a case of murder or suicide?

Diabetes researchers have long known that the disease appears after certain immune cells invade the pancreas. The mystery is whether the immune cells destroy the islet cells directly or induce apoptosis, a form of cellular suicide. The destruction of islet cells normally takes place over several months or years, so it is difficult to catch one in the act of dying, notes Jonathan D. Katz of Washington University School of Medicine in St. Louis.

Now, by breeding genetically engineered, diabetes-prone mice with mice lacking a normal immune system, Katz and his coworkers have created a mouse strain that develops diabetes quickly, compressing the period when the islet cells are dying into a few days. In the Jan. 7 Proceedings of the National Academy of Sciences, the researchers report evidence-DNA fragments unique to cells undergoing apoptosis-that the islet cells of these mice commit suicide.

Researchers may one day be able to genetically engineer islet cells to resist apoptosis and transplant those islet cells into people with diabetes, says Katz. The first step toward that goal, he adds, is to determine how the immune cells induce the apoptosis.