CHICAGO (Reuters) – A protein in the pancreas of mice may offer insight into the mechanism behind gestational diabetes, a condition that affects about four percent of all pregnant women, US researchers said.

Researchers at Stanford University found the protein menin acts as a natural brake in the pancreas, controlling the production of cells needed to make insulin, which helps the body convert sugar into energy.

Pregnant mice genetically engineered to produce too much menin were unable to make enough insulin-producing islet cells and developed signs of gestational diabetes.

"We think our work raises new possibilities, including possibilities about how gestational diabetes and other forms of type 2 diabetes arise," said Dr. Seung Kim, associate professor of developmental biology at Stanford, whose study appears in the journal Science.

Gestational diabetes occurs when a woman previously free of diabetes is unable to make and use all the insulin she needs for pregnancy. In the United States, there are about 135,000 cases of gestational diabetes each year, which can cause birth defects and may predispose the child to diabetes.

Other researchers have found that the hormone prolactin, found in abundance during pregnancy, triggers the production of insulin-producing islet cells during pregnancy.

The mechanism behind this process was not understood, but Kim and other researchers thought menin might play a role. Menin has already been shown to help prevent cancer in the pancreas by blocking cell growth.

When Kim and colleagues gave prolactin to mice that were not pregnant, menin levels dropped and the pancreas grew in size, mimicking what happens during pregnancy.

The researchers think prolactin depresses menin levels during pregnancy, allowing the body to make more insulin-producing cells to support fetal growth.

"We think it likely that one reason for developing gestational diabetes is an impaired ability of islet cells to respond to growth signals like prolactin," he said in e-mailed comments.

He said the finding, if correct, may lead to new tests to predict the likelihood of developing diabetes during pregnancy.

It may also lead to new ways to stimulate islet cell growth in people with diabetes who do not have enough islet cells to meet their body's demands, he said.