Interestingly, the existence of immunoreactive extrapancreatic glucagon produced by intestinal cells in totally pancreatectomized animals and humans has been amply demonstrated [31,32,33,34,35,36]; in particular Lund et al. demonstrated an increase in circulating glucagon levels following oral ingestion of glucose in totally pancreatectomized patients with type 2 diabetes [32]. This evidence concerns the gene GCG and type 2 diabetes mellitus.