Describe the incretin effect.
The incretin effect is the increase in insulin release after an oral glucose load. The two hormones that account for about 90% of the incretin effect are GLP-1, which is released from L cells in the distal small bowel, and GIP, which is released by K cells in the upper gut (mainly the jejunum). Because increased levels of GLP-1 and GIP can lower blood glucose levels by augmenting insulin release in a glucose-dependent manner (i.e. at low blood glucose levels no further insulin is secreted, minimizing the risk of hypoglycemia), these hormones have been targeted as possible antidiabetic drugs. Moreover, GLP-1 can exert other metabolically beneficial effects, including suppression of glucagon release, slowing of gastric emptying, augmenting of net glucose clearance, and decreasing appetite and body weight.