Utility of glucagon stimulation test in type 1 diabetes after pancreas transplantation

Background Despite recent progress of immunosuppressive therapy with newly developed agents, long-term pancreatic graft survival after pancreas transplantation still remains low. Therefore, precise assessment of β-cell function after pancreas transplantation is necessary. Methods Pancreatic β-cell secretory activity was measured by means of the peripheral plasma fasting serum C-peptide (CPR) response to 1 mg of glucagon intravenously in 23 patients after pancreas transplantation. The utility of ΔCPR after injection was compared with other indices that reflect insulin secretion. Results When we performed the test, 6 patients still needed insulin injection after the transplantation. Mean CPR before and after glucagon intravenously were 1.9 ± 0.98 ng/mL and 4.6 ± 2.29 ng/mL, respectively. Fasting serum CPR, secretory unit of islet in transplantation (SUIT) index, and ΔCPR after glucagon injection were significantly different between insulin users and nonusers. During follow-up (501 ± 228 days), 3 patients could stop using insulin, and their increase of CPR (1.8 ± 0.5 ng/mL) was significantly higher than that in continuous insulin users (0.3 ± 0.3 ng/mL). Conclusion Fasting CPR, SUIT index, and ΔCPR after glucagon injection could reflect β-cell function for post-pancreas transplant patients, and glucagon stimulation test could give us additional information to predict insulin-free treatment.