Insulin signal transduction pathway signals the conversion of the glycogen already stored in the liver cells into glucose. This process is called glycogenolysis. Conversely, when the blood-glucose levels are too high, the pancreas is signaled to release insulin. Insulin is delivered to the liver and other tissues throughout the body (e.g., muscle, adipose). When the insulin is introduced to the liver, it connects to the insulin receptors already present, that is tyrosine kinase receptor. These receptors have two alpha subunits (extracellular) and two beta subunits (intercellular) which are connected through the cell membrane via disulfide bonds. When the insulin binds to these alpha subunits,
Insulin of a rapid acting and a protracted insulin is also available, making it more likely for patients to achieve an insulin profile that mimics that of the body´s own insulin release. Insulin is usually taken as subcutaneous injections by single-use syringes with needles, via an insulin pump, or by repeated-use insulin pens with disposable needles. Inhaled insulin is also available in the U.S. market now. Synthetic insulin can trigger adverse effects, so some people with diabetes rely on animal-source insulin. Unlike many medicines, insulin currently cannot be taken orally because, like nearly all other proteins introduced into the gastrointestinal tract,