That's the latest salvo in the continuing battle to find a better way to treat one form of diabetes.
Right now, insulin-dependent diabetics have to either inject the hormone into their bloodstream or wear a pager-sized device known as "the pump," which allows insulin to be delivered all day through a small tube inserted under the skin. Taking the hormone orally has been impossible so far because insulin is broken down in the digestive tract.But researchers at several laboratories say they're getting close to overcoming that with insulin that can pass through the stomach intact.
The Purdue researchers say they have developed a polymer to encase the insulin, allowing it to pass through the stomach unscathed. The polymer protects the insulin until it reaches the small intestine, where it can be absorbed into the blood without being destroyed along the way by the harsh enzymes and acids in the mouth, throat and stomach.
The less acidic environment of the small intestine causes the polymer to swell and release the insulin, says Aaron Foss, a doctoral candidate and senior researcher at Purdue University in West Lafayette, Ind. What's more, the polymer binds with calcium molecules found in the walls of the small intestine, enabling greater absorption of the insulin, says Foss, who presented the research recently at the national meeting of the American Chemical Society in Chicago.
Purdue researchers have tested the polymer on 150 rats and dogs. They found up to 16 percent of the insulin made it to the bloodstream -- a major improvement from the minuscule absorption rates shown in past insulin pill studies.
"It's very promising," Foss says. "The material shows the ability to be able to protect the insulin as it goes through the stomach, which is very important because that's what inhibited previous oral delivery systems. In addition, the material shows the ability to release the insulin in the upper small intestine."
But another group of researchers says they're even farther along in bringing an insulin pill to market. Researchers from Nobex Corp. in Research Triangle Park, N.C., announced two months ago that they have developed a modified insulin molecule that enables insulin to pass through the stomach without being destroyed.
Researchers modified the insulin by attaching small chemical additives called oligomers, says Dr. Gordon Still, Nobex's chief medical officer.
When the insulin reaches the small intestine, it's absorbed into the bloodstream and processed by the liver, the route insulin takes in someone who's not diabetic.
"The great advantage is the fact that you are delivering the insulin directly to the liver, and that has a marked influence on how the body manages glucose," Still says.
In testing on people with Type I diabetes, the insulin pill helped control glucose levels as well as or better than taking injections of short-acting insulin before meals, study results show.
Testing will continue for the next few years, and the researchers hope to apply for Food and Drug Administration approval for the pill by late 2004, Still says.
Insulin is a hormone that is produced by the pancreas to control blood glucose levels. Blood glucose levels that are chronically too high can lead to kidney failure, cardiovascular disease and blindness, among other complications. Glucose levels that are too low can cause bouts of hypoglycemia. Symptoms include confusion, dizziness and even unconsciousness.
People with Type I diabetes, formerly called juvenile diabetes, don't produce insulin at all. To control their blood sugar, current treatment guidelines recommend they give themselves an injection of insulin before each meal. Some Type II diabetics, whose bodies do not use insulin efficiently, need injections as well. However, most Type II diabetics can control the disease with diet and exercise.
Dr. Gerald Bernstein, past president of the American Diabetes Association, says an insulin pill would be a tremendous advance in managing diabetes, but actually developing a pill that will be effective is an enormous challenge.
Depending on what food you've eaten, the rate of absorption in the intestines can vary quite a bit. This could be a problem because diabetics rely on precise amounts of insulin to maintain blood sugar levels.
"The problem is the vagaries of what goes on in the intestines," says Bernstein, an endocrinologist at Beth Israel Medical Center in New York City. "The intestines are a funny place."
What To Do
To learn more about living with diabetes, visit the American Diabetes Association or the National Institute of Diabetes and Digestive and Kidney Diseases online.