Improving Metabolic Assessments in Type 1 Diabetes Mellitus Clinical Trials

Overview: The study is a multi-center, two-arm, randomized clinical trial. Each participant will undergo four tests within a limited period according to the test sequence assignment. The tests will randomly start with either MMTT or GST. Specific Aims * To compare the reliability of the MMTT and Glucagon stimulated C-peptide responses as measured by time to peak C-peptide on MMTT, and the peak and AUC values on both tests. * To determine the relationship between MMTT and Glucagon stimulated C-peptide responses as measured by time to peak C-peptide on MMTT and peak and AUC values on both tests. * To determine the impact of basal glucose, peak glucose, age of participant, time from diagnosis, and basal C-peptide with respect to the reliability of measures and relationship between MMTT and Glucagon results. * Describe the palatability of, patient compliance with, and adverse effects of each test (MMTT vs. GST) and to compare the participant and investigator burden to conduct the MMTT and Glucagon tests. TEST INFORMATION: * Mixed Meal Tolerance Test (MMTT): BOOST is a liquid meal (like a milkshake) containing a standard amount of fat, protein, and carbohydrate. BOOST raises blood sugar and causes the pancreas to produce insulin. After drinking BOOST, about one-half teaspoon of blood will be drawn through an IV line in the arm after 15, 30, 60, 90, and 120 minutes. (Using an IV line avoids multiple needle sticks). The test takes about 2 hours. * Glucagon Stimulation Test (GST): Glucagon is a hormone that circulates in the blood and stimulates insulin secretion. Glucagon will be injected into the bloodstream through an IV line, and about one-half teaspoon of blood will be drawn five times during ten minutes. The test takes about 30 minutes. OTHER TEST INFORMATION: * Participants will have tests on four different days over a six week period. Participants will have either a) two MMTTs and then two GSTs OR b) two GSTs and then two MMTTs. Each test will be done 3-10 days apart. * Participants will follow a special high carbohydrate diet (150 grams) for at least three days prior to each study visit. Dietary information will be provided. * Participants will fast overnight (at least 8 hours) and arrive at the clinic between 7 AM - 10 AM. * It is essential that participants have a blood glucose level of 70-200 mg/dl in the morning before starting the test. If blood glucose is too high or too low the morning of the test, the test will be re-scheduled on another day. * Tests will be re-scheduled if, on the morning of the test, your blood sugar or ketones are not within acceptable ranges. Testing could take up to eight visits if tests need to be re-scheduled. * Participants will learn whether their pancreas is still secreting insulin and, if so, how much insulin is being secreted. This information may help their diabetes health care team design for them a better insulin regimen and diabetes management program to improve their longterm blood sugar control. * This study will help researchers learn which test (MMTT or GST) is best to use in other research studies looking at treatments that may stop or delay type 1 diabetes.