Assessing Arginine-Stimulated Native Pancreas Insulin Production Via Selective Venous Sampling in Patients With Long-Functioning Pancreas Allografts

Type 1 diabetes mellitus (T1DM) is thought to result from an autoimmune destruction of insulin producing beta-cells found within the pancreatic islets of Langerhans. In addition to the autoimmune process however, many studies have shown that hyperglycemia is also toxic to islets. Interventional studies have shown, for instance, that either tight glycemia control or immunosuppression can preserve C-peptide production. We hypothesize that patients who are immunosuppressed and euglycemic will display evidence that their native pancreas has recovered beta-cell function. We have asked whether pancreas transplant recipients, due to the immunosuppression required to prevent allograft loss, and the improved glycemia control resulting from the transplanted pancreas, might display some recovery of their native pancreatic islet function. Our preliminary data suggest that patients without C-peptide production prior to receiving an islet transplant appear to recover some endogenous pancreatic insulin secretion after islet transplantation. We will study whole pancreas transplant recipients, specifically those with grafts functioning for at least 5 years. We will test for native pancreas insulin production by infusing arginine into a peripheral vein, then selectively/simultaneously sampling blood for C-peptide levels from the hepatic veins and the vein draining the pancreatic allograft . Unlike our previous study of islet transplant recipients, a study that required portal vein cannulation, this study will require only hepatic and iliac vein cannulations, both much easier to accomplish, and associated with much less risk to the patient. Samples obtained from these sites will be tested for C-peptide levels. In addition, if we find evidence of native pancreas insulin production, we will look at a variety of clinical variables to see if any correlate with recovery of function.