In this context, many studies have been held to identify possible defects in the incretin secretion among deterioration of glucose tolerance, but no substantial differences in the GIP and GLP-1 secretion in response to an oral glucose tolerance test (OGTT) or mixed meal test (MMT) have been identified in T2D patients compared to healthy people (7, 8). This evidence concerns the gene GCG and type 2 diabetes mellitus.