Fruits and vegetables contain soluble and insoluble fiber in varying proportions. When you eat soluble fiber, it absorbs water to form a gel-like mass, which helps you feel full and provides other health benefits. It prevents a surge in blood sugar after you eat by slowing down the absorption of carbohydrates.
If the blood glucose level falls to dangerous levels (as in very heavy exercise or lack of food for extended periods), the Alpha cells of the pancreas release glucagon, a hormone whose effects on liver cells act to increase blood glucose levels.
The net effect of increased release of GLP-1 and GIP is to reduce blood glucose levels. Sitagliptin inhibits the enzyme, DPP-4, that destroys GLP-1 and GIP and thereby increases the levels and activity of both hormones. As a result, blood glucose levels fall. In summary, sitagliptin reduces blood glucose levels by inhibiting DPP-4 and increasing the levels of GLP-1 and GIP. Sitagliptin was approved by the FDA in October 2006.