Insulin, glucagon, and amino acids during glycemic control by the artificial pancreas in diabetic man

Abstract

The artificial endocrine pancreas (AEP) can normalize glycemia at rest and with meals. To determine whether insulin, glucagon, and amino acid profiles are also normalized, nine diabetics on subcutaneous insulin ( S C ) and AEP control were compared to ten normal controls (NC). Glycemia was monitored continuously over 10 hr during which meals were consumed. Insulin infusion rate, and the levels of immunoreactive insulin (IRI) (in NC), free insulin (in S C and AEP), C-peptide, glucagon, and amino acids are reported. Glycemia in AEP started at somewhat higher levels than in NC, but with breakfast and thereafter, it was identical. In S C , hyperglycemia prevailed throughout, with no systematic change in free IRI. In AEP, both basal and peak free insulin levels, measured in four patients, were significantly higher than in NC. C-peptide values were significantly lower in diabetics and did not change with meals. Basal glucagon values were not different in the three groups and changes with meals were of small magnitude. Branched chain amino acids were higher in S C and did not increase as in NC. In AEP, levels were lower than NC after the first two meals. Similarly, lysine and threonine were lower in AEP than in NC at the same times. Alanine, though similar at the onset, was lower 2 hr postbreakfast and higher 2 hrs postsupper in AEP and S C compared to NC. These studies demonstrate that glycemic control with AEP is accompanied by hyperinsulinemia, which could account for the amino acid responses and the small alterations in immunoreactive glucagon (IRG) patterns. Further refinement is needed to obtain full normalization of metabolic profiles.