Dietary Glycemic Index, Brain Function and Food Intake in Patients With Type 1 Diabetes Mellitus

A total of 15 male participants (age 18-45) with T1DM will be recruited. Participants will be enrolled in the study for a total of 1-3 months, and participate in a pre-test visit and three test visits, each after a 10-12-hr overnight fast. Participants will be instructed to consume their regular, weight maintaining diet between visits. At the pre-test visit, the study director or PI will meet participants, confirm eligibility and obtain informed consent. Participants will receive a low glycemic index (GI) meal with optimal iv insulin coverage using a negative feedback algorithm to maintain euglycemia (euglycemic clamp). Insulin requirement will be quantified. At some time during the visit, participants will present to the BIDMC research imaging facility for a practice MRI session, during which they will undergo a brief imaging sequence to get accustomed to the scanning process and eliminate anxiety as a confounder of imaging data. At each of 3 test visits, one of the following experimental conditions will be applied in a randomized, blinded cross-over design: (a) high GI meal with euglycemic clamp, (b) low GI meal with euglycemic clamp, (c) high GI meal with primed-variable insulin infusion at the rate established during the pre-test visit. After steady state is established, baseline laboratory evaluation and MRI imaging will be obtained, followed by the test meal. Imaging will be repeated at 1 and 4 hours postprandial. Blood samples for pertinent metabolic and hormonal parameters will be obtained every 30 minutes. Each test-visit concludes with a standard weighed meal to quantify ad-libitum intake.