All About Insulin
What is insulin? Insulin is a peptide hormone secreted by the pancreas in response to increases in blood sugar, usually following a meal. However, you don’t have to eat a meal to secrete insulin. In fact, the pancreas always secretes a low level of insulin. After a meal, the amount of insulin secreted into the blood increases as blood sugar rises. Similarly, as blood sugar falls, insulin secretion by the pancreas decreases. Insulin thus acts as an “anabolic” or storage hormone. In fact, many have called insulin “the most anabolic hormone”. Once insulin is in the blood, it shuttles glucose (carbohydrates), amino acids, and blood fats into the cells of the body. If these nutrients are shuttled primarily into muscle cells, then the muscles grow and body fat is managed. If these nutrients are shuttled primarily into fat cells, then muscle mass is unchanged and body fat is increased. Insulin’s main actions Rapid (seconds) Increases transport of glucose, amino acids (among the amino acids most strongly transported are valine, leucine, isoleucine, tyrosine and phenylalanine), and potassium into insulin-sensitive cells Intermediate (minutes) Stimulates protein synthesis (insulin increases the formation of new proteins) Activates enzymes that store glycogen Inhibits protein degradation Delayed (hours) Increases proteins and other enzymes for fat storage Why is insulin so important? The pancreas releases insulin whenever we consume food. In response to insulin, cells take in sugar from the bloodstream. This ultimately lowers high blood sugar levels back to a normal range. Like all hormones, insulin has important functions, and an optimal level. Without enough insulin, you lose all of the anabolic effects, since there is not enough insulin to transport or store energy Continue reading >>
Is Insulin A Protein?
Science Human Anatomy Insulin is also known as a hormone and is produced by the pancreas. Patients who have diabetes either do not synthesize enough insulin to combat their diets or do not respond to insulin properly. Because insulin is a protein, it cannot be taken orally by diabetic patients. Proteins are digested in the stomach and, if taken orally, insulin degrades and does not make it to the bloodstream. Learn more about Human Anatomy Continue reading >>
What Is Insulin?
Insulin is a hormone; a chemical messenger produced in one part of the body to have an action on another. It is a protein responsible for regulating blood glucose levels as part of metabolism.1 The body manufactures insulin in the pancreas, and the hormone is secreted by its beta cells, primarily in response to glucose.1 The beta cells of the pancreas are perfectly designed "fuel sensors" stimulated by glucose.2 As glucose levels rise in the plasma of the blood, uptake and metabolism by the pancreas beta cells are enhanced, leading to insulin secretion.1 Insulin has two modes of action on the body - an excitatory one and an inhibitory one:3 Insulin stimulates glucose uptake and lipid synthesis It inhibits the breakdown of lipids, proteins and glycogen, and inhibits the glucose pathway (gluconeogenesis) and production of ketone bodies (ketogenesis). What is the pancreas? The pancreas is the organ responsible for controlling sugar levels. It is part of the digestive system and located in the abdomen, behind the stomach and next to the duodenum - the first part of the small intestine.4 The pancreas has two main functional components:4,5 Exocrine cells - cells that release digestive enzymes into the gut via the pancreatic duct The endocrine pancreas - islands of cells known as the islets of Langerhans within the "sea" of exocrine tissue; islets release hormones such as insulin and glucagon into the blood to control blood sugar levels. Islets are highly vascularized (supplied by blood vessels) and specialized to monitor nutrients in the blood.2 The alpha cells of the islets secrete glucagon while the beta cells - the most abundant of the islet cells - release insulin.5 The release of insulin in response to elevated glucose has two phases - a first around 5-10 minutes after g Continue reading >>
Physiologic Effects Of Insulin
Stand on a streetcorner and ask people if they know what insulin is, and many will reply, "Doesn't it have something to do with blood sugar?" Indeed, that is correct, but such a response is a bit like saying "Mozart? Wasn't he some kind of a musician?" Insulin is a key player in the control of intermediary metabolism, and the big picture is that it organizes the use of fuels for either storage or oxidation. Through these activities, insulin has profound effects on both carbohydrate and lipid metabolism, and significant influences on protein and mineral metabolism. Consequently, derangements in insulin signalling have widespread and devastating effects on many organs and tissues. The Insulin Receptor and Mechanism of Action Like the receptors for other protein hormones, the receptor for insulin is embedded in the plasma membrane. The insulin receptor is composed of two alpha subunits and two beta subunits linked by disulfide bonds. The alpha chains are entirely extracellular and house insulin binding domains, while the linked beta chains penetrate through the plasma membrane. The insulin receptor is a tyrosine kinase. In other words, it functions as an enzyme that transfers phosphate groups from ATP to tyrosine residues on intracellular target proteins. Binding of insulin to the alpha subunits causes the beta subunits to phosphorylate themselves (autophosphorylation), thus activating the catalytic activity of the receptor. The activated receptor then phosphorylates a number of intracellular proteins, which in turn alters their activity, thereby generating a biological response. Several intracellular proteins have been identified as phosphorylation substrates for the insulin receptor, the best-studied of which is insulin receptor substrate 1 or IRS-1. When IRS-1 is activa Continue reading >>
Interactive Resources For Schools
Page 1 - What is diabetes? Two hormones are involved in the regulation of glucose in the blood: insulin and glucagon. Both are produced by specialised cells in the islets of Langerhans in the pancreas. There are a number of interactive features in this e-source: A glossary of terms: any word with a glossary entry is highlighted like this. Moving the mouse over the highlighted word will show a definition of that word. Quick questions: at the end of most pages or sections there is a question or set of quick questions to test your understanding. Animations: most of the animations can be expanded to full screen size, ideal for showing on an interactive whiteboard. The animations will play all the way through or can be viewed one section at a time. Downloads: Teachers can download individual diagrams, animations and other content from the Download Library area of the website. Terms and Conditions apply. Type 1 diabetes is an autoimmune disease and accounts for up to 10% of diabetes cases in the UK. It typically develops before the age of 40 and occurs when the pancreas can no longer produce insulin. There are two types of cells in the pancreas. Exocrine cells are responsible for the production and secretion of digestive enzymes. These pass along the pancreatic duct into the duodenum. These cells are not usually affected in diabetes. The pancreas also contains groups of cells called the islets of Langerhans. These cells release their products directly into the blood and so are a form of endocrine gland. Two hormones are produced in these islets. Insulin is made in beta cells and glucagon in alpha cells. Type 1 diabetes develops when the person's own immune system destroys the beta cells. As a result insulin is no longer produced and blood sugar levels rise. This leads to the Continue reading >>
Insulin
This article is about the insulin protein. For uses of insulin in treating diabetes, see insulin (medication). Not to be confused with Inulin. Insulin (from Latin insula, island) is a peptide hormone produced by beta cells of the pancreatic islets, and it is considered to be the main anabolic hormone of the body.[5] It regulates the metabolism of carbohydrates, fats and protein by promoting the absorption of, especially, glucose from the blood into fat, liver and skeletal muscle cells.[6] 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.[6] Glucose production and secretion by the liver is strongly inhibited by high concentrations of insulin in the blood.[7] 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. 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.[8] Their neighboring alpha cells, by taking their cues from the beta cells,[8] secrete glucagon into the blood in the opposite manner: increased secretion when blood glucose is low, and decreased secretion when glucose concentrations are high.[6][8] Glucagon, through stimulating the liver to release glucose by glycogenolysis and gluconeogenesis, has the opposite effect of insulin.[6][8] The secretion of insulin and glucagon into the Continue reading >>
Effects Of Growth Hormone And Insulin On Amino Acid And Protein Metabolism
Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader. Abstract Both growth hormone and insulin are needed for growth in mammals. Evidence indicates that these hormones increase amino acid transport into cells, and it is hypothesized in this review that this transport may at the very least be "Permissive" to a sustained increase in the rate of protein synthesis mediated by these hormones. When animals are pre-treated with these hormones, the ability of their ribosomes to incorporate labeled amino acids into peptide linkage is stimulated. While incorporation of precursors into RNA, probably including messenger RNA, may be stimulated, it would appear that the lesser amino-acid-incorporating ability of ribosomes from liver of hypophysectomized rats or from the heart of diabetic rats is not due wholly to insufficient messenger RNA, since the deficiency persist in the presence of exogenous messenger RNA. It is most likely that a number of steps in amino acid protein anabolism are stimulated by these hormones. Continue reading >>
Glucagon Synthesis And Degradation
Glucagon Glucagon serves as the counter-balancing hormone to insulin, having largely the opposite effects. It is mainly expressed by pancreatic alpha-cells. Whereas insulin is secreted and active during feeding and elevated blood glucose, ensuring storage of this in liver and other tissues, glucagon ensures the release of glucose from liver when blood glucose is low during fasting and exercise. It is the balance between insulin and glucagon that ensures a tight regulation of blood glucose levels in normal subjects. The glucagon gene is expressed in many tissues and encodes several significant polypeptides including glucagon itself. In the intestine for instance the glucagon gene express GLP1 and GLP2, both very important hormones. Glucagon is a 29 amino acid protein with a very short half-life in the blood. This means that apart from the liver other tissues will experience little or no glucagon. In the liver glucagon via activation of the glucagon receptor activates glycogenolysis and gluconeogenesis producing glucose that is released to the blood stream for use in other issues. Expression of the glucagon gene leads to the production of the 180 amino acid proglucagon. Alternative cleavage of this protein can result in either glucagon or various other peptide hormones such as glicentin, glicentin-related peptide, oxyntomodulin and [glucagon-like peptide 1] (DPID-5104336124) and 2 (GLP-1 and GLP-2). All these peptides have a considerable homology (i.e. they have very similar amino-acid compositions). Different tissues express different hormones or sets of hormones from the initial transcript. The 29 amino acid sequence of glucagon is the final product generated in pancreatic alpha-cells, whereas GLP-1 and GLP-2 are secreted from the intestinal L-cells. The 29 residue gluc Continue reading >>
- Insulin, glucagon and somatostatin stores in the pancreas of subjects with type-2 diabetes and their lean and obese non-diabetic controls
- How insulin and glucagon work to regulate blood sugar levels
- Effects of Insulin Plus Glucagon-Like Peptide-1 Receptor Agonists (GLP-1RAs) in Treating Type 1 Diabetes Mellitus: A Systematic Review and Meta-Analysis
Protein Metabolism
Protein turnover is the balance between protein synthesis and protein degradation. Proteins are naturally occurring polymers made up of repeating units of 20 different amino acids and range from small peptide hormones of 8 to 10 residues to very large multi-chain complexes of several thousand amino acids. Protein synthesis occurs on ribosomes - large intracellular structures consisting of a small subunit (33 proteins, 1900 nucleotides of ribosomal RNA) and a large subunit (46 proteins, 4980 nucleotides of rRNA) - that move along the messenger RNA (mRNA) copy of the gene (DNA) that was transcribed. The process of protein synthesis is called translation where the mRNA is read in triplets (codons), each triplet directing the addition of an amino acid (via its specific transfer RNA (tRNA)) to the growing polypeptide chain. The assembly of new proteins requires a source of amino acids which come from either the proteolytic breakdown (digestion) of proteins in the gastrointestinal tract or the degradation of proteins within the cell. Intracellular protein degradation is done by proteolytic enzymes called proteases and occurs generally in two cellular locations - lysosomes and proteosomes. Lysosomal proteases digest proteins of extracellular origin that have been taken up by the process of endocytosis. Proteosomes, which are large, barrel-shaped, ATP-dependent protein complexes, digest damaged or unneeded intracellular proteins that have been marked for destruction by the covalent attachment of chains of a small protein, ubiquitin. In contrast to the situation with glucose and fatty acids, amino acids in excess of those needed for biosynthesis cannot be stored and are not excreted. Rather, surplus amino acids are used as metabolic fuel. Most of the amino groups of surplus amin Continue reading >>
The Structure Of A Protein Hormone, Insulin
Hormones are chemical substances involved in the regulation and integration of metabolic processes. For the first time, the three-dimensional structure of a protein hormone, insulin, has been worked out by x-ray crystallographio analysis using isomorphous replacement and anomalous scattering methods. The basic repeating unit in the crystals studied is an insulin hexamer. The three dimers in the hoxamer are related to one another by a crystallographio threefold axis. The two molecules in each dimer are related to each other by a local twofold axis. In the insulin molecule the two polypeptide chains, the A and the B chains, are held together by two disulphide bridges, and hydrophobic and polar side chain interactions. The dimer structure is stabilized by hydrophobic interactions and interchain hydrogen bonds. The stabilization of the hexamer is achieved by predominantly non-polar interactions between adjacent dimers and the co-ordination of the molecules to the two zinc ions on the threefold axis. Finally, the analysis provides some interesting insights into the relationship between the structure and the biological role of insulin. Continue reading >>
How Insulin Is Made - Material, Manufacture, History, Used, Parts, Components, Structure, Steps, Product
Background Insulin is a hormone that regulates the amount of glucose (sugar) in the blood and is required for the body to function normally. Insulin is produced by cells in the pancreas, called the islets of Langerhans. These cells continuously release a small amount of insulin into the body, but they release surges of the hormone in response to a rise in the blood glucose level. Certain cells in the body change the food ingested into energy, or blood glucose, that cells can use. Every time a person eats, the blood glucose rises. Raised blood glucose triggers the cells in the islets of Langerhans to release the necessary amount of insulin. Insulin allows the blood glucose to be transported from the blood into the cells. Cells have an outer wall, called a membrane, that controls what enters and exits the cell. Researchers do not yet know exactly how insulin works, but they do know insulin binds to receptors on the cell's membrane. This activates a set of transport molecules so that glucose and proteins can enter the cell. The cells can then use the glucose as energy to carry out its functions. Once transported into the cell, the blood glucose level is returned to normal within hours. Without insulin, the blood glucose builds up in the blood and the cells are starved of their energy source. Some of the symptoms that may occur include fatigue, constant infections, blurred eye sight, numbness, tingling in the hands or legs, increased thirst, and slowed healing of bruises or cuts. The cells will begin to use fat, the energy source stored for emergencies. When this happens for too long a time the body produces ketones, chemicals produced by the liver. Ketones can poison and kill cells if they build up in the body over an extended period of time. This can lead to serious illne Continue reading >>
- diabetes: Gestational diabetes is a more serious problem in India than in other parts of the world: Dr Nam Han Cho, Health News, ET HealthWorld
- 7 Steps To Help Reverse Type-2 Diabetes So You Never Have To Take Insulin Or Medication Again
- Reversing Type 2 Diabetes Naturally In 7 Steps – Never Take Insulin Or Medication Again
You And Your Hormones
What is insulin? Insulin is a hormone made by an organ located behind the stomach called the pancreas. Here, insulin is released into the bloodstream by specialised cells called beta cells found in areas of the pancreas called islets of langerhans (the term insulin comes from the Latin insula meaning island). Insulin can also be given as a medicine for patients with diabetes because they do not make enough of their own. It is usually given in the form of an injection. Insulin is released from the pancreas into the bloodstream. It is a hormone essential for us to live and has many effects on the whole body, mainly in controlling how the body uses carbohydrate and fat found in food. Insulin allows cells in the muscles, liver and fat (adipose tissue) to take up sugar (glucose) that has been absorbed into the bloodstream from food. This provides energy to the cells. This glucose can also be converted into fat to provide energy when glucose levels are too low. In addition, insulin has several other metabolic effects (such as stopping the breakdown of protein and fat). How is insulin controlled? When we eat food, glucose is absorbed from our gut into the bloodstream. This rise in blood glucose causes insulin to be released from the pancreas. Proteins in food and other hormones produced by the gut in response to food also stimulate insulin release. However, once the blood glucose levels return to normal, insulin release slows down. In addition, hormones released in times of acute stress, such as adrenaline, stop the release of insulin, leading to higher blood glucose levels. The release of insulin is tightly regulated in healthy people in order to balance food intake and the metabolic needs of the body. Insulin works in tandem with glucagon, another hormone produced by the pan Continue reading >>
Insulin And Protein Metabolism
The present status of protein synthesis within cells has been outlined. Protein is formed in the absence of insulin; the net formation of protein is accelerated by insulin. The effects of insulin on protein metabolism take place independently of the transport of glucose or amino acids into the cell; of glycogen synthesis; and of the stimulation of high energy phosphate formation. In the case of protein metabolism, as in certain studies on the pathways of glucose and fat metabolism, these observations reveal striking intracellular effects of insulin in many tissues. Within most tissues the effect of insulin appears to find expression predominantly at the microsomal level. Incidentally, other hormones which affect protein metabolism such as growth or sex hormones appear to act at the microsomes. The fact that insulin exerts effects on protein metabolism at other intracellular sites as well as the above independent effects leads one to agree that its action consists of a stimulation of multiple, seemingly unrelated, metabolic events. The fact that an immediate effect of insulin on protein synthesis is independent of the immediate need for extracellular glucose or amino acids does not mean that the sustained functioning of cells is likewise independent. The biochemist is fully aware of metabolic defects in diabetes which are not altered by insulin in vitro, but which demand varying periods of pretreatment of the animal. It is also known that in diabetes some proteins (enzymes) may be deficient while others may be produced in excess in the absence of insulin. It is suggested that the physician desires at least two kinds of relation between these fundamental studies and his patients. One is the possible relation of a deficiency of insulin action to pathological processes in t Continue reading >>
Insulin
The hormone insulin helps control the level of glucose in the blood A Molecular Messenger Our cells communicate using a molecular postal system: the blood is the postal service and hormones are the letters. Insulin is one of the most important hormones, carrying messages that describe the amount of sugar that is available from moment to moment in the blood. Insulin is made in the pancreas and added to the blood after meals when sugar levels are high. This signal then spreads throughout the body, binding to insulin receptors on the surface of liver, muscle and fat cells. Insulin tells these organs to take glucose out of the blood and store it, in the form of glycogen or fat. Folding Tiny Proteins Insulin is a tiny protein. It moves quickly through the blood and is easily captured by receptors on cell surfaces, delivering its message. Small proteins pose a challenge to cells: it is difficult to make a small protein that will fold into a stable structure. Our cells solve this problem by synthesizing a longer protein chain, which folds into the proper structure. Then, the extra piece is clipped away, leaving two small chains in the mature form. These two chains are shown in the lower diagram in blue and green, for insulin from pigs (PDB entry 4ins ). The structure is further stabilized by three disulfide bridges, one of which is seen in yellow in each illustration. Diabetes Mellitus When insulin function is impaired, either by damage to the pancreas or by the rigors of aging, glucose levels in the blood rise dangerously, leading to diabetes mellitus. For people totally deficient in insulin, such as children that develop diabetes early in life, this can be acutely dangerous. High glucose levels lead to dehydration, as the body attempts to flush out the excess sugar in urine, Continue reading >>
Structural Biochemistry/protein Function/insulin
Insulin is a hormone secreted by the pancreas that regulates glucose levels in the blood. Without insulin, cells cannot use the energy from glucose to carry out functions within the body. Insulin was first discovered in 1921 by Frederick Grant Banting and Charles Best from extracted substances from the pancreas of dogs in their laboratory. The material was then used to keep diabetic dogs alive, and then used in 1922 on a 14 year old diabetic boy. The FDA approved insulin in 1939. In 1966 insulin was synthesized by Michael Katsoyannis in his laboratory, which marked the first complete hormone to be successfully synthesized. Synthetic insulin is used as a drug to treat diabetes, and the current forms on the market include insulin from bovine and porcine pancreases, but the most widely used is a form made from recombinant human insulin. Insulin is made in the pancreas by beta cells. After the body takes in food, these beta cells release insulin, which enables cells in the liver, muscles and fat tissues to take up glucose and either store it as glycogen or allow blood to transfer it to organs in the body for use as an energy source. This process stops the use of fat as a source of energy. When glucose levels are elevated in the blood, insulin is produced at higher rates by the pancreas in order to maintain normal sugar concentrations in the blood. Without insulin, the body cannot process glucose effectively and glucose begins to build up in the blood stream instead of being transported to different cells . In contrast with elevated levels of glucose in the blood, when there is a deficit of glucose available to the body, alpha cells in the pancreas release glucagon, a hormone that causes the liver to convert stored glycogen into usable glucose which is then released into the Continue reading >>
