Diabetes Prevention Trial of Type 1 Diabetes

The Diabetes Prevention Trial—Type 1 Diabetes (DPT-1) consisted of two randomized clinical trials to determine whether insulin could prevent or delay the onset of overt diabetes in relatives of patients with diabetes. One study investigated the effects of parenteral insulin in relatives with a projected five-year risk of diabetes higher than 50 percent, while the other looked at the effects of oral insulin in relatives with a projected five-year risk of 26 to 50 percent.

First and second-degree relatives were screened for islet-cell antibody (ICA) titer ≥ 10 and then staged to assess risk of diabetes. Those with a high risk were eligible for the parenteral insulin trial, and those with a low risk were eligible for the oral insulin trial. In the parenteral insulin trial, subjects in the intervention group received parenteral insulin subcutaneous injections twice daily, plus annual intravenous infusions; the control group received no treatment. In the oral insulin trial, subjects were assigned to receive capsules of either oral insulin or matched placebo. For both trials, participants were seen every 6 months, and at those visits an oral glucose tolerance (OGT) test was performed to assess glycemic status, the primary study end point. Other assessments included intravenous glucose tolerance tests and mixed-meal tolerance tests performed at baseline, as well as at various points during the study. Results showed that neither parenteral nor oral insulin succeeded in delaying or preventing the development of diabetes in high-risk relatives of current diabetes patients. Long-term follow-up to detect any effects on the course of diabetes was initiated.