When a woman is pregnant, she needs to produce more insulin than usual because her body is feeding more cells than normal. A hormone, prolactin, which is abundant during pregnancy, causes more pancreatic islet cells to grow in order to produce the extra insulin.

In a woman who develops gestational diabetes, however, the islets cells don't multiply and the woman cannot meet the increased demand for insulin, so her blood sugar rises.

Now researchers from Stanford University have found a protein, called menin, that may block the islet cells from multiplying in response to prolactin. Menin has already been shown to prevent pancreatic cancer by blocking growth of pancreatic cells. That function, to put the brakes on cell growth, may contribute to the insufficiency of insulin that's characteristic of gestational diabetes.

When the researchers gave prolactin to normal non-pregnant mice, their menin levels dropped and their pancreases grew in size, just as if they were pregnant. But pregnant mice, genetically engineered to produce too much menin, couldn't make more islet cells and they developed gestational diabetes.

The scientists believe that prolactin lowers menin levels during pregnancy so that the body can make more islet cells. In cases of gestational diabetes, the menin appears to be unaffected by prolactin. The scientists believe that menin may play a role in diabetes associated with obesity as well, possibly by sabotaging the body's attempt to make more islet cells to serve that extra body weight. They also believe that regulating menin could aid in the effort to grow new islet cells for transplantation.

Sources: Reuters; EurekAlert, November 2007