Plasma glucagon decreases during night-time sleep in type 1 diabetic patients and healthy control subjects

Aims: In Type 1 diabetes mellitus (T1DM), the glucagon response to hypoglycaemia is known to disappear within a few months after the onset of the disease, whereas the response to other stimuli remains intact. The dynamics of spontaneous glucagon release have rarely been assessed. We monitored spontaneous glucagon release in T1DM patients and healthy subjects during a 7-h period of night-time sleep. Methods: Measurements were made in 14 T1DM patients and 14 control subjects matched for age, gender and body mass index after one night's adaptation in our laboratory. Circulating glucose, insulin and glucagon concentrations were measured at 30-min intervals. In diabetic patients, hypoglycaemia (< 3.9 mmol/l) was avoided by infusion of glucose whenever necessary. Results: During the entire night, plasma glucose and serum insulin levels were higher in T1DM patients than in healthy subjects (P < 0.03 and P < 0.001, respectively). Plasma glucagon concentrations decreased throughout the night in both groups (P < 0.001). Glucagon levels were similar in T1DM patients and healthy subjects (P > 0.87). The duration of diabetes (less and more than 5 years) did not affect glucagon secretion (P > 0.87). Conclusions: Plasma glucagon levels decrease significantly during night-time sleep in healthy control subjects. This nocturnal decrease is preserved in T1DM patients regardless of the duration of diabetes. These observations point to distinct nocturnal regulation of spontaneous glucagon release that does not depend on circulating glucose and insulin levels and is unaltered in T1DM patients.