<Table> <Tr> <Td_colspan="2"> View / Edit Human </Td> <Td_colspan="2"> View / Edit Mouse </Td> </Tr> </Table> <Tr> <Td_colspan="2"> View / Edit Human </Td> <Td_colspan="2"> View / Edit Mouse </Td> </Tr> <P> Insulin (from Latin insula, island) is a peptide hormone produced by beta cells of the pancreatic islets; it is considered to be the main anabolic hormone of the body . It regulates the metabolism of carbohydrates, fats and protein by promoting the absorption of, especially glucose from the blood into liver, fat and skeletal muscle cells . In these tissues the absorbed glucose is converted into either glycogen via glycogenesis or fats (triglycerides) via lipogenesis, or, in the case of the liver, into both . Glucose production and secretion by the liver is 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 therefore an anabolic hormone, promoting the conversion of small molecules in the blood into large molecules inside the cells . Low insulin levels in the blood have the opposite effect by promoting widespread catabolism, especially of reserve body fat . </P> <P> Beta cells are sensitive to glucose concentrations, also known as blood sugar levels . When the glucose level is high, the beta cells secrete insulin into the blood; when glucose levels are low, secretion of insulin is inhibited . Their neighboring alpha cells, by taking their cues from the beta cells, secrete glucagon into the blood in the opposite manner: increased secretion when blood glucose is low, and decreased secretion when glucose concentrations are high . Glucagon, through stimulating the liver to release glucose by glycogenolysis and gluconeogenesis, has the opposite effect of insulin . The secretion of insulin and glucagon into the blood in response to the blood glucose concentration is the primary mechanism of glucose homeostasis . </P>

What is the function of insulin and where is it produced
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