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Insulin is a peptide hormone containing two chains cross-linked by disulfide bridges. Insulin (/ ˈ ɪ n. sj ʊ. l ɪ n /, [5] [6] from Latin insula, 'island') is a peptide hormone produced by beta cells of the pancreatic islets encoded in humans by the insulin (INS) gene. It is the main anabolic hormone of the body. [7]
This insulin signal transduction pathway is composed of trigger mechanisms (e.g., autophosphorylation mechanisms) that serve as signals throughout the cell. There is also a counter mechanism in the body to stop the secretion of insulin beyond a certain limit. Namely, those counter-regulatory mechanisms are glucagon and epinephrine.
Type 2 diabetes, also known as non insulin dependent diabetes and as chronic hyperglycemia, is caused primarily by genetics and the development of metabolic syndrome. [2] [9] The beta cells can still secrete insulin but the body has developed a resistance and its response to insulin has declined. [4]
Insulin-treated athletes are perceived to have lean body mass because physiological hyperinsulinemia in human skeletal muscle improves the activity of amino acid transport, which in turn promotes protein synthesis. [78] Insulin stimulates the transport of amino acids into cells and also controls glucose metabolism.
Once insulin binds to the receptor, phosphorylation takes place and attaches to the beta-subunit, thus initiating the transduction process. A protein binds to the phosphorylated receptor protein, becoming phosphorylated as well.
The insulin receptor (IR) is a transmembrane receptor that is activated by insulin, IGF-I, IGF-II and belongs to the large class of receptor tyrosine kinase. [5] Metabolically, the insulin receptor plays a key role in the regulation of glucose homeostasis; a functional process that under degenerate conditions may result in a range of clinical manifestations including diabetes and cancer.
Diabetes mellitus type 1 is caused by insufficient or non-existent production of insulin, while type 2 is primarily due to a decreased response to insulin in the tissues of the body (insulin resistance). Both types of diabetes, if untreated, result in too much glucose remaining in the blood (hyperglycemia) and many of the same complications.
Proinsulin is the prohormone precursor to insulin made in the beta cells of the Pancreatic Islets, specialized regions of the pancreas. In humans, proinsulin is encoded by the INS gene . [ 1 ] [ 2 ] The pancreatic islets only secrete between 1% and 3% of proinsulin intact. [ 3 ]