A 6-hour nocturnal interruption of a continuous subcutaneous insulin infusion: 2. Marked attenuation of the metabolic deterioration by somatostatin

Abstract

We investigated the respective roles of insulin deprivation and counter-regulatory hormones in the metabolic deterioration after a nocturnal interruption of continuous subcutaneous insulin infusion in Type 1 (insulin-dependent) diabetic patients without residual insulin secretion. Changes in blood glucose, plasma non-esterified fatty acids, 3-hydroxybutyrate, glucagon, growth hormone, cortisol and free insulin in seven patients whose pumps were deliberately stopped between 23.00 h and 05.00 h were compared in two randomized tests carried out either during an intravenous somatostatin infusion at a constant rate of 250 μg/h from 22.00 h until 07.00 h (somatostatin test) or during a saline infusion (control test). Arrest of the pumps resulted in a rapid (already significant after 1 h) and progressive (nadir after 5-6 h) decrease in plasma free insulin concentrations with no statistically significant differences between the two tests. Somatostatin remarkably depressed basal levels of growth hormone and the late significant increase in glucagon (+39±14 pg/ml at 05.00 h, 2 p< 0.05) observed during the control test. In contrast, cortisol secretion was not inhibited. The sharp linear increase in blood glucose observed from 01.00 to 05.00 h (38±4 μmol·l-1· min-1) in the control test was fully suppressed with a paradoxical tendency to hypoglycaemia until 03.00 h and a less steep rise from 03.00 to 05.00 h (18±5 μmol·l-1·min-1, 2 p<0.05) during the somatostatin test. Initial plasma non-esterified fatty acids levels were slightly higher on somatostatin but did not show any statistically significant rise despite arrest of the pump, contrasting with the increase from 491±27 to 741±96 μmol/l (2 p<0.05) in the control test. Consequently, plasma non-esterified fatty acids levels from 01.00 to 05.00 h were not significantly different between the two tests. The abrupt rise in 3-hydroxybutyrate from 00.00 to 05.00 h (3.0±0.5 μmol·l-1·min-1) in the control test was not altered by somatostatin until 03.00 h. In contrast, during the last 2 h after arrest of the pump, somatostatin inhibited any further rise in 3-hydroxybutyrate levels. In conclusion, somatostatin significantly reduces metabolic deterioration during a 6-h nocturnal interruption of a continuous subcutaneous insulin infusion. Somatostatin-induced glucagon suppression seems to be involved in reducing hyperglycaemia as well as, together with the somatostatin-induced growth hormone suppression, in the limitation of hepatic ketogenesis in hours 5 and 6 after cessation of insulin supply. In contrast, the early rise in 3-hydroxybutyrateplasma levels is unaffected by somatostatin and thus appears entirely due to the fall in free insulin circulating concentrations. © 1983 Springer-Verlag.