A: Glucose-Potentiated Arginine-Induced Insulin secretion (GPAIS) - approx. 1½ hrs Rationale. This test is designed primarily to test the maximum insulin secretion capacity of a participant's beta cells. It provides the best available surrogate for beta cell mass, as opposed to beta cell function (Kahn 2008) and will therefore help to improve understanding of the mechanisms of how chosen genetic variants influence risk of diabetes. It has recently been shown to correlate well with the number of (autologous) islets transplanted into pancreatitis patients following pancreatectomy. In dogs and non-human primates it correlates well with % beta cell mass (reviewed in Kahn 3). The test is based on the well-described (Kahn 2008; Larsson & Ahren 1998) principle that a non-glucose secretagogue, such as the amino acid arginine, will produce greater insulin response when potentiated by high glucose levels, with the combined stimulus producing a near maximal beta cell response.