Total pancreatectomy increases the metabolic response to glucagon in humans

To evaluate the impact of glucagon deficiency on the response to glucagon replacement, we infused physiological doses of glucagon (1.25 ng/kg X min) into 9 totally pancreatectomized (PX) diabetic patients (C-peptide, undetectable) 1) for 24 h during their usual diet and insulin regimen and/or 2) for 6 h in a fasted insulin-withdrawn state. During both glucagon infusions, plasma glucagon rose from 46 +/- 2 (+/- SE) pg/ml (0-10% 3500 mol wt glucagon) to 112 +/- 9 pg/ml. In the 24-h study (n = 4), glucagon significantly increased mean 24-h glucose levels (272 +/- 27 mg/dl; P less than 0.05) and glycosuria (29 +/- 5 g/day; P less than 0.01) compared to preinfusion (158 +/- 14 mg/dl and 4 +/- 4 g/day, respectively) and postinfusion (200 +/- 35 mg/dl and 3 +/- 2 g/day) control periods. Blood ketones did not change. The 24-h glucagon infusion significantly lowered the fasting levels of the glucogenic amino acids aspartate (43%; P less than 0.01), threonine (46%; P less than 0.05), serine (46%; P less than 0.02), glycine (47%; P less than 0.01), and methionine (34%; P less than 0.02). Fasting alanine levels decreased from 835 +/- 236 to 393 +/- 66 microM (P less than 0.05). The 6-h glucagon infusion caused a 101 +/- 14 mg/dl maximal plasma glucose increment in PX (n = 8) vs. 33 +/- 11 in 5 insulin-withdrawn type I diabetic patients serving as controls (P = 0.022). Furthermore, when glucagon was infused at a higher rate (3 ng/kg X min) in 12 additional type I diabetic patients, the mean maximal plasma glucose increment (54 +/- 15 mg/dl) was still less than half that in PX, despite a 3-fold higher infusion plasma glucagon level (326 +/- 37 pg/ml). The 6-h glucagon infusion caused a significant decrease in the concentrations of glucogenic amino acids in the glucagon-deficient patients, but not in the type I diabetic patients. We conclude that 1) glucagon replacement in the PX patient markedly alters blood glucose and glucogenic amino acids, but not ketone levels; and 2) the metabolic response to glucagon is considerably more pronounced in PX patients than in type I diabetic patients. These data suggest that glucagon responsiveness is enhanced in the chronic hormone-deficient state.