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 (generally caused by insulin resistance), this down-regulation acts as a kind of positive feedback, increasing the need for insulin. Exercise reverses this process in muscle tissue, but if it is left unchecked, it may contribute to insulin resistance. Elevated blood levels of glucose—regardless of cause—lead to increased glycation of proteins with changes, only a few of which are understood in any detail, in protein function throughout the body. Insulin resistance often is found in people with visceral adiposity (i.e., a high degree of fatty tissue within the abdomen—as distinct from subcutaneous adiposity or fat between the skin and the muscle