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Type 1 Diabetes Prevention Trials

Questions & Answers

What is type 1 diabetes?
Type 1 diabetes is a life-long disorder that can arise in children or adults. It occurs when the body’s immune system (specifically the Th1 subset of helper T-lymphocytes) is activated and destroys the insulin-producing cells of the pancreas. Most diabetes symptoms do not begin until almost all insulin-producing cells are destroyed. By the time a person is diagnosed with type 1 diabetes, damage to these cells is nearly complete.

People with type 1 diabetes need insulin replacement for the rest of their lives. Most patients need multiple daily injections or an insulin pump for good control of their blood glucose. Insulin treatment, however, is not a cure, nor can it always prevent the long-term complications of diabetes.

If type 1 diabetes could be prevented or delayed, millions of people across the globe would enjoy longer lives, improved health, and freedom from the burden of managing this difficult disease. In the past 20 years, researchers have learned a great deal about the immune factors that contribute to diabetes risk. With this information, they can now identify people at risk for type 1 diabetes and design clinical trials to test strategies to prevent or delay onset of disease.

Who is at risk for type 1 diabetes?
Scientists believe that both genetic and environmental factors contribute to diabetes risk. Relatives of people with type 1 diabetes have about a 10 to 20 times greater risk of developing this form of diabetes compared to the general population. (A person probably has type 1 diabetes if he or she developed diabetes before age 40 and needs to take insulin injections.)

How do researchers determine a person’s level of risk for developing type 1 diabetes?
Most people who develop type 1 diabetes have immune markers in their blood such as antibodies against insulin, islets, or the enzymes glutamic acid decarboxylase (GAD) and IA2 (also known as ICA512). By measuring these markers and conducting metabolic tests, scientists can now gauge the risk for developing type 1 diabetes in relatives of people with the disease. Tests include:

  • blood tests for antibodies to components of the insulin-producing islet cells and to insulin itself. Risk increases with the number of positive antibody tests.
  • a blood test for specific genes that may make individuals more or less susceptible to type 1 diabetes. In the DPT-1, people with the protective genes are not eligible to participate.
  • a test that measures the amount of insulin produced in response to an intravenous injection of insulin. A decreased first phase insulin response puts a person at high risk for developing diabetes.

What clinical research is under way to prevent type 1 diabetes?
The Diabetes Prevention Trial-Type 1 (DPT-1), a large multicenter clinical trial supported by the National Institutes of Health, the American Diabetes Association, and the Juvenile Diabetes Research Foundation International, is applying new knowledge to try to prevent type 1 diabetes in people at risk. DPT-1 is now testing whether oral insulin can prevent type 1 diabetes in people at moderate (25-50 percent) risk of developing type 1 diabetes within 5 years. The same study group recently completed a separate trial which found that low-dose insulin injections do not prevent type 1 diabetes in people with impaired insulin secretion who have a high (50 percent or greater) risk of developing diabetes in 5 years. The oral insulin trial is testing a totally different scientific approach to preventing type 1 diabetes in people at moderate risk for type 1 diabetes whose insulin production is not yet impaired.

What do the results of DPT-1’s insulin injection trial mean for people with diabetes and their families?
Though low-dose insulin injections failed to prevent diabetes in people at high risk, the trial marks a turning point in the understanding of type 1 diabetes. Researchers have gained critical knowledge about how to predict diabetes risk and the immune events that lead to diabetes. This new understanding will be enormously helpful to future prevention efforts.

Did any of the study participants experience side effects from the insulin injection trial?
No one was harmed by participating in the trial. There were no significant side effects from the insulin injections apart from the normal discomfort of having injections. In the majority of participants who developed diabetes during the course of the trial, researchers were able to detect diabetes and begin treatment before symptoms developed, a benefit to those patients.

Oral Insulin Trial
Why do scientists believe oral insulin may help to prevent or delay type 1 diabetes?
The immune system responds differently to substances given orally than it does to injected material. By “feeding” a person insulin, the immune cells that line the digestive tract may learn to recognize insulin in a different way and favor the development of immune responses that delay the onset or progression of diabetes or prevent its occurrence altogether. Studies in an animal model of type 1 diabetes, the NOD mouse, showed that oral insulin given before the development of diabetes can reduce or delay the development of diabetes.

Are there other known side effects linked to taking insulin capsules by mouth?
There are no known side effects to taking insulin by mouth. Insulin is a protein that is quickly broken down in the digestive tract. Taking insulin by mouth has no effect on a person’s blood sugar and does not irritate the digestive tract.

How do I find out about other diabetes prevention trials? Type 1 Diabetes TrialNet is a network of 14 clinical centers conducting NIH-funded studies to prevent type 1 diabetes. In the spring of 2003, some TrialNet centers in the U.S. and Canada will begin screening relatives of people with type 1 diabetes. Screening consists of a simple blood test for antibodies to parts of the insulin-producing islet cell. People who have these antibodies are at risk for developing type 1 diabetes and may be eligible to enroll in a study monitoring them for the early detection of diabetes. They may also choose to participate in diabetes prevention trials when these studies begin. For information about screening, call 1-800-425-8361.

When will results of the Oral Insulin Trial be known? The Oral Insulin Trial completed enrollment on October 31, 2002. Study investigators are now collecting final data to determine if oral insulin can delay the onset of type 1 diabetes. They expect to announce trial results in June 2003.

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