General Uses and Considerations
The oral glucose tolerance test (OGTT) and mixed meal tolerance test (MMTT) are widely used in clinical metabolic research and diabetes drug development. The OGTT and MMTT provide an integrated assessment to the β-cell response to an intestinal glucose stimulus that includes activation of the incretin axis. The major incretin hormones are glucagon-like peptide (GLP)-1 and glucose-dependent insulinotropic peptide (GIP) secreted, respectively, by the L and K cells of the intestine. The incretin effect comprises enhancement of glucose-stimulated insulin secretion from islet β-cells in concert with reduced glucagon release from α-cells. When assessing the response to therapeutic agents whose primary mode of action is via the incretin axis, e.g. dipeptidyl peptidase (DDP)-4 inhibitors, the response of GLP-1 and GIP can be quantified with respect to stimulation of insulin secretion and suppression of glucagon secretion.