Somatostatin has two active forms produced by alternative cleavage of a single preproprotein: one of 14 amino acids, the other of 28 amino acids.
In all vertebrates, there exist six different somatostatin genes that have been named SS1, SS2, SS3, SS4, SS5, and SS6. The six different genes along with the five different somatostatin receptors allows somatostatin to possess a large range of functions. Humans have only one somatostatin gene, SST.
Somatostatin will travel through the portal blood system, to the heart, then to systemic circulation, where it will exert its digestive system effects. In the stomach, somatostatin acts on the acid-producing parietal cells via G-coupled receptor to reduce secretion. Somatostatin also indirectly decreases stomach acid production by preventing the release of other hormones, including gastrin, secretin and histamine which effectively slows down the digestive process.
Octreotide (brand name Sandostatin, Novartis Pharmaceuticals) is an octapeptide that mimics natural somatostatin pharmacologically, though is a more potent inhibitor of growth hormone, glucagon, and insulin than the natural hormone and has a much longer half-life (approximately 90 minutes, compared to 2–3 minutes for somatostatin). Since it is absorbed poorly from the gut, it is administered parenterally (subcutaneously, intramuscularly, or intravenously). It is indicated for symptomatic treatment of carcinoid syndrome and acromegaly. It is also finding increased use in polycystic diseases of the liver and kidney.
Lanreotide (INN) is a medication used in the management of acromegaly and symptoms caused by neuroendocrine tumors, most notably carcinoid syndrome. It is a long-acting analogue of somatostatin, like octreotide.
Lanreotide (as lanreotide acetate) is manufactured by Ipsen and marketed under the trade name Somatuline. It is available in several countries, including the United Kingdom, Australia, and Canada, and was approved for sale in the United States by the Food and Drug Administration (FDA) on August 30, 2007.
There are six somatostatin genes that have been discovered in vertebrates. The current proposed history as to how these six genes arose is based on the three whole-genome duplication events that took place in vertebrate evolution along with local duplications in teleost fish. An ancestral somatostatin gene was duplicated during the first whole-genome duplication event (1R) to create SS1 and SS2. These two genes were duplicated during the second whole-genome duplication event (2R) to create four new somatostatin genes: SS1, SS2, SS3, and one gene that was lost during the evolution of vertebrates. Tetrapods retained SS1 (also known as SS-14 and SS-28) and SS2 (also known as cortistatin) after the split in the sarcopterygii and actinopterygii lineage split. In teleost fish, SS1, SS2, and SS3 were duplicated during the third whole-genome duplication event (3R) to create SS1, SS2, SS4, SS5, and two genes that were lost during the evolution of teleost fish. SS1 and SS2 went through local duplications to give rise to SS6 and SS3.
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