Insulin

Insulin is a <a href="/facts/Peptide_hormone/8AdC52vt">peptide hormone</a> produced by <a href="/facts/Beta_cell/MXcTmlDL">beta cells</a> of the <a href="/facts/Pancreatic_islets/PJVtM7MY">pancreatic islets</a> encoded in humans by the insulin (INS) <a href="/facts/Gene/e1swwPY6">gene</a>. It is the main <a href="/facts/Anabolism/eH3Q5AHF">anabolic</a> <a href="/facts/Hormone/WFnBnINJ">hormone</a> of the body. It regulates the <a href="/facts/Metabolism/WxDrm8k5">metabolism</a> of <a href="/facts/Carbohydrate/Geuuzxsf">carbohydrates</a>, <a href="/facts/Fat/87HcP11s">fats</a>, and <a href="/facts/Protein/Jxmagu3E">protein</a> by promoting the absorption of <a href="/facts/Glucose/oUSkoLCD">glucose</a> from the blood into cells of the <a href="/facts/Liver/Rtp4Fk2b">liver</a>, <a href="/facts/Fat_cell/FuM7LlaK">fat</a>, and <a href="/facts/Skeletal_muscle/en1tVYFN">skeletal muscles</a>. In these tissues the absorbed glucose is converted into either <a href="/facts/Glycogen/kWa8fPFE">glycogen</a>, via <a href="/facts/Glycogenesis/W5oCLM4F">glycogenesis</a>, or <a href="/facts/Fatty_acid_metabolism/Se3rnCT8">fats</a> (<a href="/facts/Triglyceride/BQmjv4A0">triglycerides</a>), via <a href="/facts/Lipogenesis/ur2r9sbV">lipogenesis</a>; in the liver, glucose is converted into both. <a href="/facts/Glucose/oUSkoLCD">Glucose</a> production and <a href="/facts/Secretion/VHk9eLAV">secretion</a> by the liver are strongly inhibited by high concentrations of insulin in the blood. Circulating insulin also affects the synthesis of proteins in a wide variety of tissues. It is thus an anabolic hormone, promoting the conversion of small molecules in the blood into large molecules in the cells. Low insulin in the blood has the opposite effect, promoting widespread <a href="/facts/Catabolism/CFWUdphX">catabolism</a>, especially of <a href="/facts/Obesity/RBF9y5Vl">reserve body fat</a>.
<a href="/facts/Beta_cell/MXcTmlDL">Beta cells</a> are sensitive to <a href="/facts/Blood_sugar_level/I4SkNzrm">blood sugar levels</a> so that they secrete insulin into the blood in response to high level of glucose, and inhibit secretion of insulin when glucose levels are low. Insulin production is also regulated by glucose: high glucose promotes insulin production while low glucose levels lead to lower production. Insulin enhances glucose uptake and metabolism in the cells, thereby reducing blood sugar. Their neighboring <a href="/facts/Alpha_cell/0WIXayxX">alpha cells</a>, by taking their cues from the beta cells, secrete <a href="/facts/Glucagon/NVEnH03n">glucagon</a> into the blood in the opposite manner: increased secretion when blood glucose is low, and decreased secretion when glucose concentrations are high. Glucagon increases blood glucose by stimulating <a href="/facts/Glycogenolysis/cMXcNQKE">glycogenolysis</a> and <a href="/facts/Gluconeogenesis/Jj5THIHh">gluconeogenesis</a> in the liver. The secretion of insulin and glucagon into the blood in response to the blood glucose concentration is the primary mechanism of <a href="/facts/Blood_sugar_regulation/lYEBdPKr">glucose homeostasis</a>.
Decreased or absent insulin activity results in <a href="/facts/Diabetes/2xeHXbsI">diabetes</a>, a condition of high blood sugar level (<a href="/facts/Hyperglycaemia/HM8eNqfX">hyperglycaemia</a>). There are two types of the disease. In <a href="/facts/Type_1_diabetes/IkuQadGx">type 1 diabetes</a>, the beta cells are destroyed by an <a href="/facts/Autoimmunity/5cASmcfI">autoimmune reaction</a> so that insulin can no longer be synthesized or be secreted into the blood. In <a href="/facts/Type_2_diabetes/zCMXksmt">type 2 diabetes</a>, the destruction of beta cells is less pronounced than in type 1, and is not due to an autoimmune process. Instead, there is an accumulation of <a href="/facts/Amyloid/IjBcvNvV">amyloid</a> in the pancreatic islets, which likely disrupts their anatomy and physiology. The <a href="/facts/Pathogenesis/o9kHHK0U">pathogenesis</a> of type 2 diabetes is not well understood but reduced population of islet beta-cells, reduced secretory function of islet beta-cells that survive, and peripheral tissue <a href="/facts/Insulin_resistance/cz6oFqke">insulin resistance</a> are known to be involved. Type 2 diabetes is characterized by increased glucagon secretion which is unaffected by, and unresponsive to the concentration of blood glucose. But insulin is still secreted into the blood in response to the blood glucose. As a result, glucose accumulates in the blood.
The human insulin protein is composed of 51 <a href="/facts/Amino_acid/WDxYwBny">amino acids</a>, and has a <a href="/facts/Molecular_mass/FWueGMed">molecular mass</a> of 5808 <a href="/facts/Dalton_(unit)/IMATU3vf">Da</a>. It is a hetero<a href="/facts/Protein_dimer/c8LwFJPG">dimer</a> of an A-chain and a B-chain, which are linked together by <a href="/facts/Disulfide_bond/eDx5Xtlg">disulfide bonds</a>. Insulin's structure varies slightly between <a href="/facts/Species/oDg6b96r">species</a> of animals. Insulin from non-human animal sources differs somewhat in effectiveness (in <a href="/facts/Carbohydrate_metabolism/h2WvuF14">carbohydrate metabolism</a> effects) from human insulin because of these variations. <a href="/facts/Pig/b5wxwdDY">Porcine</a> insulin is especially close to the <a href="/facts/Human/rlcTENsr">human</a> version, and was widely used to treat type 1 diabetics before human insulin could be produced in large quantities by <a href="/facts/Recombinant_DNA/dT3PL7M6">recombinant DNA</a> technologies.
Insulin was the first peptide hormone discovered. <a href="/facts/Frederick_Banting/gTqf4aEJ">Frederick Banting</a> and <a href="/facts/Charles_Best_(medical_scientist)/ItV9A7PH">Charles Best</a>, working in the laboratory of <a href="/facts/John_Macleod_(physiologist)/pYfQxcp4">John Macleod</a> at the <a href="/facts/University_of_Toronto/FpGjQNm9">University of Toronto</a>, were the first to isolate insulin from dog pancreas in 1921. <a href="/facts/Frederick_Sanger/M460rBQg">Frederick Sanger</a> sequenced the amino acid structure in 1951, which made insulin the first protein to be fully sequenced. The <a href="/facts/Crystal_structure/bJ4bCeHd">crystal structure</a> of insulin in the solid state was determined by <a href="/facts/Dorothy_Hodgkin/vjsD4zQS">Dorothy Hodgkin</a> in 1969. Insulin is also the first protein to be chemically synthesised and produced by <a href="/facts/Recombinant_DNA/dT3PL7M6">DNA recombinant technology</a>. It is on the <a href="/facts/WHO_Model_List_of_Essential_Medicines/6kmu81Xm">WHO Model List of Essential Medicines</a>, the most important medications needed in a basic <a href="/facts/Health_system/LpM7ISXR">health system</a>.

Insulin open-in-new

Insulin