Dual-Hormone Closed-Loop Glucose Control in Adolescents With Type 1 Diabetes

Upon arrival at the research facility at Steno Diabetes Center Copenhagen, the participant's own pump and CGM are disconnected, and the two study pumps are attached. For dual-hormone control, the study pumps will be filled with FiAsp® and GlucaGen®. For single-hormone control, the study pumps have been filled with FiAsp® and isotonic saline.

In addition, participants are provided with a blinded wearable activity and sleep monitoring device (ActiGraph GT9X Link, Pensacola, FL) for activity level estimation and sleep assessment during study participation. The Actigraph is connected to a Bluetooth® Polar heart rate monitors during the exercise session.

Female participants deliver a urine sample for pregnancy testing. A sampling cannula is placed in an antecubital vein. The CGM will be calibrated with fingerpick glucose meter (Contour next®, Ascensia Diabetes Care) before initiating the closed-loop control. Even though it is not needed to calibrate the sensor, the accuracy of the sensor is better after one calibration.

At day 1 17:00 the study is initiated, and the closed-loop system takes over glucose control. Except from the control approach (single- vs. dual-hormone), the study days are identical. During the study visit, participants can move around freely, but they can only perform actual exercise during the stationary bike exercise session at day 2 16:30. At nighttime, the participants are encouraged to be in bed and, if possible, sleep.

At predefined timepoints, the investigators measure blood pressure and pulse, and the investigators ask the participants to rate their nausea level on a visual analog scale (VAS) from 1 to 100 to assess possible side effects of glucagon (vomiting rates as 100). In addition, the investigators ask them to self-rate blood glucose levels before bedtime (23:00), upon wake-up (07:00-08:00), before each meal, before exercise, and every 10 minutes during exercise.

Single-hormone and dual-hormone closed-loop control study sessions end 26 hours after study start. The study pumps and the CGMs are disconnected and the participants reconnect their own pumps and CGMs.

The two study sessions are separated by at least 36 hours.

Inclusion criteria

• Age = 13-17 years
• T1D duration ≥ 2 years
• Insulin pump therapy ≥ 1 year
• Using CGM or isCGM (Flash Libre)
• HbA1c ≤ 9.0% (75 mmol/mol)
• Using carbohydrate counting

Exclusion criteria

• Allergy to glucagon or lactose
• Allergy to faster insulin aspart (FiAsp)
• Pheochromocytoma
• Self-reported lack of hypoglycemia symptoms when blood glucose is < 3.0 mmol/l
• Inability to follow study procedures, e.g. exercise, sleeping, blood sampling, and meal intake
• Pregnancy, nursing, plan to become pregnant or sexually active and not using adequate contraceptive methods (intrauterine device, contraceptive pill, patch or injection)
• Use of anti-diabetic medicine (other than insulin), corticosteroids or other drugs affecting glucose metabolism during or within 30 days prior to study participation
• Other concomitant medical or psychological condition that according to the investigator's assessment makes the participant unsuitable for study participation