A technique that allows insulin hormone to be stored in cells and then released as needed by a pill eventually may offer a treatment for diabetes that does not require daily injections, researchers say.
The experiments, thus far, have been performed only on mice, but researchers say a system using an implanted insulin gene may be ready for human testing within two years.
In a study to be published today in the journal Science, researchers at Ariad Pharmaceuticals in Cambridge, Mass., and at Memorial Sloan-Kettering Cancer Center in New York said the cell engineering technique was able to control diabetes in a group of laboratory mice and is now being tested on larger animals.
Tim Clackson, senior author of the study, said the technique causes insulin, or some other protein, to clump inside a cell with another protein, forming a molecule that is too large to leave the cell. A drug, given as a pill, breaks up the clump, allowing the insulin to flow into the blood stream in a way that mimics the spurt of hormone normally secreted by the pancreas.
"The amount of protein (such as insulin) that gets released is directly related to the amount of drug that is given," Clackson said. "The more drug you give, the more protein gets released into circulation."
In diabetes, the technique theoretically would allow a patient to control insulin levels in the blood by a pill. Many diabetics now must control insulin levels by injection.
A common type of diabetes is caused by the failure of the pancreas to produce an appropriate amount of insulin to metabolize glucose, or sugar, levels in the blood stream. Normally, the pancreas releases insulin in response to the detected level of glucose.
Dr. Richard Furlanetto, scientific director of the Juvenile Diabetes Foundation, said the experimental technique "is very clever science" but might fall short.
"To be truly useful, it would have to be coupled to a system that would release the hormone in direct response to the levels of glucose in the blood," Furlanetto said.
However, Furlanetto said the technique could be useful in treating conditions that require periodic secretion, or pulsed release, of some needed protein, such as growth hormone.
Clackson said the protein clustering technique could also be used to administer proteins that would relieve pain, control appetite or correct brain chemistry.