Insulin Synthesis And Secretion
Insulin is a small protein, with a molecular weight of about 6000 Daltons. It is composed of two chains held together by disulfide bonds. The figure to the right shows a molecular model of bovine insulin, with the A chain colored blue and the larger B chain green. You can get a better appreciation for the structure of insulin by manipulating such a model yourself. The amino acid sequence is highly conserved among vertebrates, and insulin from one mammal almost certainly is biologically active in another. Even today, many diabetic patients are treated with insulin extracted from pig pancreas. Biosynthesis of Insulin Insulin is synthesized in significant quantities only in beta cells in the pancreas. The insulin mRNA is translated as a single chain precursor called preproinsulin, and removal of its signal peptide during insertion into the endoplasmic reticulum generates proinsulin. Proinsulin consists of three domains: an amino-terminal B chain, a carboxy-terminal A chain and a connecting peptide in the middle known as the C peptide. Within the endoplasmic reticulum, proinsulin is exposed to several specific endopeptidases which excise the C peptide, thereby generating the mature form of insulin. Insulin and free C peptide are packaged in the Golgi into secretory granules which accumulate in the cytoplasm. When the beta cell is appropriately stimulated, insulin is secreted from the cell by exocytosis and diffuses into islet capillary blood. C peptide is also secreted into blood, but has no known biological activity. Control of Insulin Secretion Insulin is secreted in primarily in response to elevated blood concentrations of glucose. This makes sense because insulin is "in charge" of facilitating glucose entry into cells. Some neural stimuli (e.g. sight and taste of food) Continue reading >>
- Relative effectiveness of insulin pump treatment over multiple daily injections and structured education during flexible intensive insulin treatment for type 1 diabetes: cluster randomised trial (REPOSE)
- Insulin, glucagon and somatostatin stores in the pancreas of subjects with type-2 diabetes and their lean and obese non-diabetic controls
- Only 2 Ingredients and You Can Say Goodbye to Diabetes Forever! No More Medications and 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. 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. 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. 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 Continue reading >>
Structure Of The Insulin Receptorinsulin Complex By Single Particle Cryoem Analysis
This is an unedited manuscript that has been accepted for publication. Nature Research are providing this early version of the manuscript as a service to our customers. The manuscript will undergo copyediting, typesetting and a proof review before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers apply. Structure of the Insulin ReceptorInsulin Complex by Single Particle CryoEM analysis The insulin receptor (IR) is a dimeric protein that plays a crucial role in controlling glucose homeostasis, regulating lipid, protein and carbohydrate metabolism, and modulating brain neurotransmitter levels1,2. IR dysfunction has been associated with many diseases, including diabetes, cancer, and Alzheimers disease1,2,4. The primary sequence has been known since the 1980s5, and is composed of an extracellular portion (ectodomain, ECD), a single transmembrane helix and an intracellular tyrosine kinase domain. Insulin binding to the dimeric ECD triggers kinase domain auto-phosphorylation and subsequent activation of downstream signaling molecules. Biochemical and mutagenesis data have identified two putative insulin binding sites (S1 and S2)6. While insulin bound to an ECD fragment containing S1 and the apo ectodomain have been characterized structurally7,8, details of insulin binding to the full receptor and the signal propagation mechanism are still not understood. Here we report single particle cryoEM reconstructions for the 1:2 (4.3 ) and 1:1 (7.4 ) IR ECD dimer:Insulin complexes. The symmetric 4.3 structure shows two insulin molecules per dimer, each bound between the Leucine-rich sub domain L1 of one monomer and the first fibronectin-like domain (FnIII-1) of the other Continue reading >>
What Is Insulin?
Insulin is a hormone that is important for metabolism and utilization of energy from the ingested nutrients - especially glucose. Insulin chemistry and etymology Insulin is a protein chain or peptide hormone. There are 51 amino acids in an insulin molecule. It has a molecular weight of 5808 Da. Insulin is produced in the islets of Langerhans in the pancreas. The name insulin comes from the Latin ''insula'' for "island" from the cells that produce the hormone in the pancreas. Insulin's structure varies slightly between species of animal. Both porcine (from pigs) and bovine (from cows) insulin are similar to human insulin but porcine insulin resembles human insulin more closely. What does insulin do? Insulin has several broad actions including: It causes the cells in the liver, muscle, and fat tissue to take up glucose from blood and convert it to glycogen that can be stored in the liver and muscles Insulin also prevents the utilization of fat as an energy source. In absence of insulin or in conditions where insulin is low glucose is not taken up by body cells, and the body begins to use fat as an energy source Insulin also controls other body systems and regulates the amino acid uptake by body cells It has several other anabolic effects throughout the body as well Secretion of insulin Insulin is synthesized in significant quantities only in beta cells in the pancreas. It is secreted primarily in response to elevated blood concentrations of glucose. Insulin thus can regulate blood glucose and the body senses and responds to rise in blood glucose by secreting insulin. Other stimuli like sight and taste of food, nerve stimulation and increased blood concentrations of other fuel molecules, including amino acids and fatty acids, also promote insulin secretion. What happens wh Continue reading >>
What Is Insulin?
Essential for life, the hormone insulin regulates many metabolic processes that provide cells with needed energy. Understanding insulin, what insulin does, and how it affects the body, is important to your overall health. Tucked away behind the stomach is an organ called the pancreas, which produces insulin. Insulin production is regulated based on blood sugar levels and other hormones in the body. In a healthy individual, insulin production and release is a tightly regulated process, allowing the body to balance its metabolic needs. What does insulin do? Insulin allows the cells in the muscles, fat and liver to absorb glucose that is in the blood. The glucose serves as energy to these cells, or it can be converted into fat when needed. Insulin also affects other metabolic processes, such as the breakdown of fat or protein. Problems with insulin production or use The most common problem associated with insulin is diabetes. Diabetes occurs when the body either does not secrete enough insulin or when the body no longer uses the insulin it secretes effectively. Diabetes falls into two categories: Type 1 diabetes occurs when the pancreas cannot produce insulin sufficiently to meet its own needs. This commonly occurs in children, and while an exact cause has not been found, many consider it to be an autoimmune disease. Some symptoms of type 1 diabetes include tiredness, increased urination and thirst, and problems with vision. Type 2 diabetes is more commonly associated with adults and lifestyle choices. People with type 2 diabetes will produce insulin but often not enough for their body's needs. They may also struggle to use the insulin they produce effectively. Patients may not know they have type 2 diabetes until they have an annual checkup, as symptoms tend to be mild un Continue reading >>
Prediabetes & Insulin Resistance
What is insulin? Insulin is a hormone made in the pancreas, an organ located behind the stomach. The pancreas contains clusters of cells called islets. Beta cells within the islets make insulin and release it into the blood. Insulin plays a major role in metabolism—the way the body uses digested food for energy. The digestive tract breaks down carbohydrates—sugars and starches found in many foods—into glucose. Glucose is a form of sugar that enters the bloodstream. With the help of insulin, cells throughout the body absorb glucose and use it for energy. Insulin's Role in Blood Glucose Control When blood glucose levels rise after a meal, the pancreas releases insulin into the blood. Insulin and glucose then travel in the blood to cells throughout the body. Insulin helps muscle, fat, and liver cells absorb glucose from the bloodstream, lowering blood glucose levels. Insulin stimulates the liver and muscle tissue to store excess glucose. The stored form of glucose is called glycogen. Insulin also lowers blood glucose levels by reducing glucose production in the liver. In a healthy person, these functions allow blood glucose and insulin levels to remain in the normal range. What happens with insulin resistance? In insulin resistance, muscle, fat, and liver cells do not respond properly to insulin and thus cannot easily absorb glucose from the bloodstream. As a result, the body needs higher levels of insulin to help glucose enter cells. The beta cells in the pancreas try to keep up with this increased demand for insulin by producing more. As long as the beta cells are able to produce enough insulin to overcome the insulin resistance, blood glucose levels stay in the healthy range. Over time, insulin resistance can lead to type 2 diabetes and prediabetes because the bet 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 >>
What Is Insulin Resistance?
Insulin is a hormone produced by the pancreas that helps unlock the body's cells so that sugar (glucose) from the food we eat can be used by the cells for energy. In people with type 2 diabetes, a combination of problems occurs, and scientists aren't really sure which is the chicken and which is the egg. The person's body may not be producing enough insulin to meet their needs, so some glucose can't get into the cells. Glucose remains in the bloodstream, causing high blood glucose levels. In many cases, the person may actually be producing more insulin than one might reasonably expect that person to need to convert the amount of food they've eaten at a meal into energy. Their pancreas is actually working overtime to produce more insulin because the body's cells are resistant to the effects of insulin. Basically the cells, despite the presence of insulin in the bloodstream, don't become unlocked and don't let enough of the glucose in the blood into the cells. Scientists don't know exactly what causes this insulin resistance, and many expect that there are several different defects in the process of unlocking cells that cause insulin resistance. Medications for type 2 diabetes focus on different parts of this insulin-cell interaction to help improve blood glucose control. Some medications stimulate the pancreas to produce more insulin. Others improve how the body uses insulin by working on this insulin resistance. Physical activity also seems to improve the body's ability to use insulin by decreasing insulin resistance, which is why activity is so important in diabetes management. Find more information about diabetes in The Joslin Guide to Diabetes available from the Joslin Online Store. Continue reading >>
Insulin, hormone that regulates the level of sugar (glucose) in the blood and that is produced by the beta cells of the islets of Langerhans in the pancreas. Insulin is secreted when the level of blood glucose rises—as after a meal. When the level of blood glucose falls, secretion of insulin stops, and the liver releases glucose into the blood. Insulin was first reported in pancreatic extracts in 1921, having been identified by Canadian scientists Frederick G. Banting and Charles H. Best and by Romanian physiologist Nicolas C. Paulescu, who was working independently and called the substance “pancrein.” After Banting and Best isolated insulin, they began work to obtain a purified extract, which they accomplished with the help of Scottish physiologist J.J.R. Macleod and Canadian chemist James B. Collip. Banting and Macleod shared the 1923 Nobel Prize for Physiology or Medicine for their work. Insulin is a protein composed of two chains, an A chain (with 21 amino acids) and a B chain (with 30 amino acids), which are linked together by sulfur atoms. Insulin is derived from a 74-amino-acid prohormone molecule called proinsulin. Proinsulin is relatively inactive, and under normal conditions only a small amount of it is secreted. In the endoplasmic reticulum of beta cells the proinsulin molecule is cleaved in two places, yielding the A and B chains of insulin and an intervening, biologically inactive C peptide. The A and B chains become linked together by two sulfur-sulfur (disulfide) bonds. Proinsulin, insulin, and C peptide are stored in granules in the beta cells, from which they are released into the capillaries of the islets in response to appropriate stimuli. These capillaries empty into the portal vein, which carries blood from the stomach, intestines, and pancrea Continue reading >>
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 >>
Insulin is a hormone that lowers the level of glucose (a type of sugar) in the blood . It's made by the beta cells of the pancreas and released into the blood when the glucose level goes up, such as after eating. Insulin helps glucose enter the body's cells, where it can be used for energy or stored for future use. In diabetes, the pancreas doesn't make enough insulin or the body can't respond normally to the insulin that is made. This causes the glucose level in the blood to rise. Continue reading >>
7 Benefits Of Insulin & 3 Negatives
Written by Joe Cohen, BS | Reviewed by Genius Labs Science Team | Last updated: SelfHacked has the strictest sourcing guidelines in the health industry and we almost exclusively link to medically peer-reviewed studies, usually on PubMed. We believe that the most accurate information is found directly in the scientific source. We are dedicated to providing the most scientifically valid, unbiased, and comprehensive information on any given topic. Our team comprises of trained MDs, PhDs, pharmacists, qualified scientists, and certified health and wellness specialists. All of our content is written by scientists and people with a strong science background. Our science team is put through the strictest vetting process in the health industry and we often reject applicants who have written articles for many of the largest health websites that are deemed trustworthy. Our science team must pass long technical science tests, difficult logical reasoning and reading comprehension tests. They are continually monitored by our internal peer-review process and if we see anyone making material science errors, we don't let them write for us again. Our goal is to not have a single piece of inaccurate information on this website. If you feel that any of our content is inaccurate, out-of-date, or otherwise questionable, please leave a comment or contact us at [emailprotected] Note that each number in parentheses [1, 2, 3, etc.] is a clickable link to peer-reviewed scientific studies. A plus sign next to the number [1+, 2+, etc...] means that the information is found within the full scientific study rather than the abstract. Insulin regulates blood sugar, and insulin resistance predicts diabetes. Learn more about insulins function & the risk of high/low levels here. Insulin is a hormone sec Continue reading >>
What Is Insulin?
Insulin is a hormone made by the pancreas that allows your body to use sugar (glucose) from carbohydrates in the food that you eat for energy or to store glucose for future use. Insulin helps keeps your blood sugar level from getting too high (hyperglycemia) or too low (hypoglycemia). The cells in your body need sugar for energy. However, sugar cannot go into most of your cells directly. After you eat food and your blood sugar level rises, cells in your pancreas (known as beta cells) are signaled to release insulin into your bloodstream. Insulin then attaches to and signals cells to absorb sugar from the bloodstream. Insulin is often described as a “key,” which unlocks the cell to allow sugar to enter the cell and be used for energy. If you have more sugar in your body than it needs, insulin helps store the sugar in your liver and releases it when your blood sugar level is low or if you need more sugar, such as in between meals or during physical activity. Therefore, insulin helps balance out blood sugar levels and keeps them in a normal range. As blood sugar levels rise, the pancreas secretes more insulin. If your body does not produce enough insulin or your cells are resistant to the effects of insulin, you may develop hyperglycemia (high blood sugar), which can cause long-term complications if the blood sugar levels stay elevated for long periods of time. Insulin Treatment for Diabetes People with type 1 diabetes cannot make insulin because the beta cells in their pancreas are damaged or destroyed. Therefore, these people will need insulin injections to allow their body to process glucose and avoid complications from hyperglycemia. People with type 2 diabetes do not respond well or are resistant to insulin. They may need insulin shots to help them better process Continue reading >>
Insulin helps to take the sugar in your blood to other parts of your body. Diabetes affects how your body makes or uses insulin. Diabetes can make it hard to control how much sugar is in your blood. There is hope! There are different kinds of insulin that people with diabetes can use every day to help them stay healthy. This booklet gives some basic facts about insulin. Use this booklet to help you talk to your doctor about the kind of insulin that you are taking. Do not wait. Diabetes is a serious illness. Diabetes can cause a heart attack, stroke, blindness, kidney disease, nerve damage and other serious health problems. This is why it is so important for you to get treatment for your diabetes. Treatment can help prevent or slow some of these serious health problems. Exercise, eat a balanced diet, and take your diabetes medicines. You can do it. Insulin Safety Tips Never drink insulin. Do not share insulin needles, pens or cartridges with anyone else. Talk to your doctor before you change or stop using your insulin. Do not inject your insulin in the exact same spot each time. Throw away needles in a hard container that can be closed like a laundry detergent bottle. Check the expiration date on the insulin before you use it. Make a plan about how to handle your insulin when you travel and during an emergency. Check the FDA website to learn more about Women and Diabetes: www.fda.gov/womens My Insulin Guide Ask your health care provider these questions before you start using your insulin. How often should I use my insulin? Can you show me the right way to inject the insulin? Will the insulin affect my other medicines? What about my birth control? What are the side effects? What do I do if I start having side effects? What is my target blood sugar level? How often should Continue reading >>
Facts About Diabetes And Insulin
Diabetes is a very common disease, which, if not treated, can be very dangerous. There are two types of diabetes. They were once called juvenile-onset diabetes and adult diabetes. However, today we know that all ages can get both types so they are simply called type 1 and type 2 diabetes. Type 1, which occurs in approximately 10 percent of all cases, is an autoimmune disease in which the immune system, by mistake, attacks its own insulin-producing cells so that insufficient amounts of insulin are produced - or no insulin at all. Type 1 affects predominantly young people and usually makes its debut before the age of 30, and most frequently between the ages of 10 and 14. Type 2, which makes up the remaining 90 percent of diabetes cases, commonly affects patients during the second half of their lives. The cells of the body no longer react to insulin as they should. This is called insulin resistance. In the early 1920s, Frederick Banting, John Macleod, George Best and Bertram Collip isolated the hormone insulin and purified it so that it could be administered to humans. This was a major breakthrough in the treatment of diabetes type 1. Insulin Insulin is a hormone. Hormones are chemical substances that regulate the cells of the body and are produced by special glands. The hormone insulin is a main regulator of the glucose (sugar) levels in the blood. Insulin is produced in the pancreas. To be more specific, it's produced by the beta cells in the islets of Langerhans in the pancreas. When we eat, glucose levels rise, and insulin is released into the bloodstream. The insulin acts like a key, opening up cells so they can take in the sugar and use it as an energy source. Sugar is one of the top energy sources for the body. The body gets it in many forms, but mainly as carbohydr Continue reading >>