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 resistance is a prominent change of metabolic conditions, under which the mother has to reduce her muscles' insulin sensitivity to spare more glucose for the brains (the mother's brain and the fetal brain). This can be achieved through raising the response threshold (i.e., postponing the onset of sensitivity) by secreting placental growth factor to interfere with the interaction between insulin receptor substrate (IRS) and PI3K, which is the essence of the so-called "adjustable threshold hypothesis" of insulin resistance. It is well known that insulin regulates the conversion of carbohydrates into fats (triglycerides) by promoting the absorption of, especially, glucose from the