Through islet transplantation, functional β-cell mass can be restored. Allogeneic islet transplantation is a treatment modality for a select group of patients with complicated type 1 diabetes mellitus. For patients undergoing (partial) pancreas resection, autologous islet transplantation may help prevent complicated diabetes. Up until now, no studies have been performed on early islet graft function in the first week after transplantation. Early graft function may be a predictor for estimating long-term islet graft success.

Arginine can excite β-cells to release insulin. It can thus provide an estimate of β-cell secretory capacity and can be used as an alternative to (oral) glucose tolerance tests. In this study, we aim to find a predictor model for islet graft function by assessing peak C-peptide after arginine stimulus in the early post-transplantation phase.

Inclusion Criteria:

• Age 16 years or older
• Currently on the LUMC waiting list for allogeneic or autologous islet transplantation
• Willing to use a flash glucose monitoring (FGM) system in the two weeks prior to transplantation

Exclusion Criteria:

• Patients who are pregnant
• Patients with known hypersensitivity to arginine

Patients receiving allogeneic or autologous islet transplants.