Optimising Exercise Preparation using Closed-loop Insulin Delivery for Exercise in People With Type 1 Diabetes

The purpose of this research study is to collect data that can help to answer questions about the performance of the Medtronic 780G artificial pancreas system during and post-exercise when a temporary glucose target is set at different time points pre-exercise. The study will compare glucose control in adults with type 1 diabetes in response to short-duration (40min) moderate intensity exercise, short-duration (40min) high-intensity exercise and long-duration (90min) moderate intensity exercise, when a temporary glucose target is set 60min pre-exercise, 20min pre-exercise, 0min pre-exercise, or when no temporary target is set. Participation in this research study will occur over approximately 6-12 months. Participants will be required to attend the clinical trials centre at St Vincent’s Hospital, Melbourne on 17 occasions. To participate in this project, participants will need to be over 18 years of age, have been diagnosed with type 1 diabetes, and be currently using an insulin pump and have experience with continuous glucose monitoring devices. Participation in this study will involve the completion of a maximal exercise capacity test, eight 40min moderate intensity exercise bouts, four 40min high-intensity exercise bouts and four 90min moderate intensity exercise bouts. Twelve of these exercise bouts will occur in the evening at ~5:00PM and four bouts will occur in the morning at ~8:00AM. Moderate intensity exercise involves continuous cycling on a stationary bicycle at an intensity where you are still able to maintain a conversation but is still more difficult than a leisurely walk. High intensity exercise is also on the stationary bicycle, but involves short bursts of hard exercise, separated by periods of rest. The intensity of the MIE will be continuous at 40% VO2max, while the HIE will involve intervals at 80% VO2max seperated by rest. All exercise sessions will be supervised by the study exercise physiologist. The first visit to the clinical trials centre will be a screening session and will take approximately 2 hours, where we will obtain written consent, medical history, and collect some personal and physical data (such as height and weight). Additionally, participants will undergo a maximal exercise capacity test involving cycling on a stationary bicycle which progressively increases in intensity until fatigue after ~15 minutes. For the duration of this test there will be a mask fitted over the nose and mouth and which measures expired breath. If participants meet all of the criteria to be included in the study, they will be provided with the study insulin pump including the closed-loop (artificial pancreas) functionality, glucose sensors and study glucose meter. The insulin delivery device will be programmed with their insulin delivery settings and they will be educated in the use of the system. Once participants have received the study devices, you will remain in manual mode on the insulin pump for at least 72 hours, after which they will enable the Smartguard feature (closed-loop mode), under direction of the study Diabetes Educator. They will remain in the closed-loop setting on the pump for at least 1 week before participating in the main experimental exercise visits. Following this screening sessions participants will continue to infuse insulin via the study device for the duration of the study. Participants will attend the clinical trials center at ~17:00 on twelve occasions, and at ~08:00 on four occasions separated by at least one week (sixteen sessions total). On each day of evening exercise, participants will be asked to eat approximately four hours prior to the planned exercise and deliver your insulin bolus as usual. For morning exercise, participants will arrive prior to 09:00 having fasted overnight. Participants will set a temporary glucose target of 8.3mmol/L on the study insulin pump at one of four time-points pre-exercise for each bout of exercise: i) 60 min pre-exercise; ii) 20min pre-exercise; iii) at the onset of exercise; iv) no temporary set-point will be set and insulin delivery will continue as normal. The mode/intensity (HIE vs MIE) and time of day of exercise (morning vs evening), as well as the allocation to the temporary target condition (i, ii, iii, iv) will occur in random order, as determined prior to participant enrollment via computerised randomizer. Following each bout of exercise, participants will remain in the study centre for 90min post-exercise and will consume a provided, standardized meal consisting of 60g CHO, 20g protein and 20g fat. Following completion of the 16 experimental testing sessions, the study devices will be returned to the study team.