We aimed to investigate glucose and counter-regulatory hormone profiles in adults with type 1 diabetes using an overnight closed-loop glucose sensing insulin delivery system (CL) compared to sensor-augmented insulin pump therapy with low glucose suspend (SAP+LGS).
Twelve adults with type 1 diabetes (mean HbA1c 7.3%) participated in an unmasked, randomised-crossover study over two non-sequential nights in a clinical trial centre (CTC) utilising either a CL (proportional integral derivative with insulin feedback algorithm, Medtronic ) or SAP+LGS technology (Enlite ImproveTM Sensor Augmented VeoTM System, Medtronic). Hourly samples for glucose, insulin, and counter-regulatory hormones (glucagon, growth hormone, cortisol, catecholamines) were collected. Plasma metanephrines were measured at the beginning and conclusion of the study night and 12-hour urinary collections were performed during the study night and the following 12 hours for measurement of cortisol and catecholamines.
All results are median (interquartile range). CL and SAP+LGS % time spent in target range (4-8mmol/L) between 22:00hrs to 08:00hrs was 91 (87, 98)% vs 96 (65,100)%; p=0.31; % time spent <4mmol/L was 0 (0, 8)% vs 0 (0, 6)%; p=0.89; and glucose standard deviation was 1.5 (1.2,1.8) mmol/L vs 1.3 (0.7, 2.5) mmol/L; p=0.54 respectively. Counter-regulatory hormone levels during CL and SAP+LGS did not differ and did not correlate with glycaemic parameters either overnight or during the next day.
Both CL and SAP+LGS performed well during an overnight CTC stay in this group of adults with well-controlled type 1 diabetes. Hypoglycaemia and overnight excursions of counter-regulatory hormones that impacted on glucose levels during the following day were avoided by both insulin delivery approaches. Whether the findings of this study can be replicated in a real life setting (ie. at home), in studies of greater duration and in groups with poor glycaemic control remains to be determined.