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What Is Insulin And Its Function?

Insulin And Insulin Resistance

Insulin And Insulin Resistance

Go to: Abstract As obesity and diabetes reach epidemic proportions in the developed world, the role of insulin resistance and its consequences are gaining prominence. Understanding the role of insulin in wide-ranging physiological processes and the influences on its synthesis and secretion, alongside its actions from the molecular to the whole body level, has significant implications for much chronic disease seen in Westernised populations today. This review provides an overview of insulin, its history, structure, synthesis, secretion, actions and interactions followed by a discussion of insulin resistance and its associated clinical manifestations. Specific areas of focus include the actions of insulin and manifestations of insulin resistance in specific organs and tissues, physiological, environmental and pharmacological influences on insulin action and insulin resistance as well as clinical syndromes associated with insulin resistance. Clinical and functional measures of insulin resistance are also covered. Despite our incomplete understanding of the compl Continue reading >>

Medical Definition Of Insulin

Medical Definition Of Insulin

Insulin: A natural hormone made by the pancreas that controls the level of the sugar glucose in the blood. Insulin permits cells to use glucose for energy. Cells cannot utilize glucose without insulin. Diabetes: The failure to make insulin or to respond to it constitutes diabetes mellitus. Insulin is made specifically by the beta cells in the islets of Langerhans in the pancreas. If the beta cells degenerate so the body cannot make enough insulin on its own, type I diabetes results. A person with this type of diabetes must inject exogenous insulin (insulin from sources outside the body). In type II diabetes, the beta cells produce insulin, but cells throughout the body do not respond normally to it. Nevertheless, insulin also may be used in type II diabetes to help overcome the resistance of cells to insulin. By reducing the concentration of glucose in the blood, insulin is thought to prevent or reduce the long-term complications of diabetes, including damage to the blood vessels, eyes, kidneys, and nerves. History of Insulin: In 1921, Frederick Grant Banting and Charles H. Best discovered insulin while they were working in the laboratory of John J.R. Macleod at the University of Toronto. Banting and Best extracted material from the pancreas of dogs. They first used this material to keep diabetic dogs alive and in 1922 they used it successfully on a 14-year-old boy with diabetes. In 1923, James B. Collip, a biochemist, discovered that purifying the extract prevented many of the side effects. In 1923, Banting and Macleod were awarded the Nobel Prize. Best and Collip were overlooked but Banting and Macleod shared the prize money with them. The US Food and Drug Administration (FDA) first approved insulin in 1939. Insulin was the first hormone to be synthesized completely i Continue reading >>

Insulin

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 >>

Insulin

Insulin

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 >>

Insulin And Type 2 Diabetes: What You Should Know

Insulin And Type 2 Diabetes: What You Should Know

Insulin and Type 2 Diabetes If your health care provider offered you a medication to help you feel better and get your blood sugar under control, would you try it? If so, you might be ready to start taking insulin. Does insulin immediately make you think of type 1 diabetes? Think again. Between 30 and 40 percent of people with type 2 diabetes take insulin. In fact, there are more people with type 2 diabetes who take insulin than type 1 because of the much larger number of people with type 2. Experts believe even more people with type 2 should be taking insulin to control blood sugar -- and the earlier, the better. With an increase in people developing type 2 at a younger age and living longer, more and more people with type 2 will likely be taking insulin. "If you live long enough with type 2 diabetes, odds are good you'll eventually need insulin," says William Polonsky, Ph.D., CDE, associate clinical professor of psychiatry at the University of California, San Diego; founder and president of the Behavioral Diabetes Institute; and author of Diabetes Burnout: What to Do When You Can't Take It Anymore (American Diabetes Association, 1999). Producing Less Insulin Naturally Over Time Research has shown that type 2 diabetes progresses as the ability of the body’s pancreatic beta cells to produce insulin dwindles over time. Your beta cells -- the cells in the pancreas that produce insulin -- slowly lose function. Experts believe that by the time you're diagnosed with type 2 diabetes, you've already lost 50-80 percent of your beta cell function and perhaps the number of beta cells you had. And the loss continues over the years. "About six years after being diagnosed, most people have about a quarter of their beta cell function left," says Anthony McCall, M.D., Ph.D., endocri Continue reading >>

Insulin And Fat Storage

Insulin And Fat Storage

We left off last week with the question, “What prevents fat from leaving the fat cell?” If you missed out on it, you may want to read The Futility of Low-Calorie Diets. To quickly recap, we talked about the fact that your body has two main fuels: glucose (sugar) or fat. The preferred source of fuel is fat, but under certain circumstances, we can shift the body to using more sugar rather than fat. At times, such as being chased by a rabid dog, this is a good thing. However, it’s not a good thing if sugar remains the main fuel for most of the day. Relying on sugar means you’re not burning fat. Many people make lifestyle choices and nutrition decisions that have basically locked up their extra stored fat in their fat cells, making it useless for energy. The only way you can lose fat is if you use fat. You’ll be unsuccessful at losing fat if you don’t burn fat, even if you eat fewer calories and burn more through exercise. You can lose weight, but most of the loss will come from lean body mass, or muscle tissue, not fat. Fat Storage and Insulin The most significant factor in fat storage is the level of insulin in the blood. Insulin has many effects on the body. With respect to fat storage, insulin increases the storage of fat in fat cells and prevents fat cells from releasing fat for energy. This is such a key point for people to understand that I’ll repeat it: Insulin increases the storage of fat in fat cells and prevents the cells from releasing it for energy. Eight hormones stimulate fat utilization: epinephrine, norepinephrine, adrenocorticotrophic hormone (ACTH), glucagon, thyroid-stimulating hormone, melanocyte-stimulating hormone, vasopressin and growth hormone. One hormone prevents fat utilization: insulin. The pancreas releases insulin when blood suga Continue reading >>

Insulin Resistance Speeds Up Cognitive Decline

Insulin Resistance Speeds Up Cognitive Decline

Mounting research suggests Alzheimer’s disease is intricately connected to insulin resistance; even mild elevation of blood sugar is associated with an elevated risk for dementia A study that followed seniors with heart disease over 20 years found those with the highest levels of insulin resistance had the worst cognitive performance and scored lowest on memory and executive function tests Insulin resistance appears to promote cognitive decline by adversely impacting the blood vessels in your brain, promoting the formation of plaques and hindering memory formation By Dr. Mercola We are facing a tsunami of Alzheimer's disease. It's often said that the underlying causes of Alzheimer's disease are unknown, but there are numerous theories. For example, research suggesting that an infectious component is at play is becoming increasingly difficult to ignore. In addition to viruses, bacteria and fungi, an infectious protein called TDP-43, which behaves like infectious proteins known as prions — responsible for the brain destruction that occurs in Mad Cow and Chronic Wasting Diseases — has been linked to the disease. Research presented at the 2014 Alzheimer's Association International Conference revealed Alzheimer's patients with TDP-43 were 10 times more likely to have been cognitively impaired at death than those without.1 Due to its similarities with Mad Cow Disease, investigators have raised the possibility that Alzheimer's disease may be linked to eating meat from animals raised in concentrated animal feeding operations (CAFOs). Mounting research also suggests Alzheimer's disease is intricately connected to insulin resistance; even mild elevation of blood sugar is associated with an elevated risk for dementia.2 Diabetes and heart disease3 are also known to elevate yo Continue reading >>

Pancreas And Insulin

Pancreas And Insulin

Your pancreas is one of the organs of your digestive system. It lies in your abdomen, behind your stomach. It is a long thin structure with 2 main functions: producing digestive enzymes to break down food; and producing the hormones insulin and glucagon to control sugar levels in your body. Production of digestive enzymes The pancreas produces secretions necessary for you to digest food. The enzymes in these secretions allow your body to digest protein, fat and starch from your food. The enzymes are produced in the acinar cells which make up most of the pancreas. From the acinar cells the enzymes flow down various channels into the pancreatic duct and then out into the duodenum. The secretions are alkaline to balance the acidic juices and partially digested food coming into the duodenum from the stomach. Production of hormones to control blood sugar levels A small proportion (1-2 per cent) of the pancreas is made up of other types of cells called islets of Langerhans. These cells sit in tiny groups, like small islands, scattered throughout the tissue of the pancreas. The islets of Langerhans contain alpha cells which secrete glucagon and beta cells which secrete insulin. Insulin and glucagon are hormones that work to regulate the level of sugar (glucose) in the body to keep it within a healthy range. Unlike the acinar cells, the islets of Langerhans do not have ducts and secrete insulin and glucagon directly into the bloodstream. Depending on what you’ve eaten, how much exercise your muscles are doing, and how active your body cells are, the amount of glucose in your bloodstream and cells varies. These 2 hormones have the job of keeping tight control of the amount of glucose in your blood so that it doesn’t rise or fall outside of healthy limits. How insulin works I Continue reading >>

Chapter 16: The Endocrine System (study Modules 16.09-16.11)

Chapter 16: The Endocrine System (study Modules 16.09-16.11)

Sort Match the following hormone with its function: Insulin Increases Na+ reabsorption in the kidneys Facilitates glucose transport into cells Stimulates embryonic cells (stem cells) to undergo mitosis Causes kidneys to conserve water Increases cell reactions during sympathetic response Facilitates glucose transport into cells Match the following hormone with the appropriate category of hormones: Androgens Gonadocorticoids Mineralocorticoids Glucocorticoids Gonadotropins Gonadocorticoids Sympathetic nerve stimuli are responsible for the release of __________. estrogen insulin aldosterone epinephrine thyroid hormone epinephrine Match the following homeostatic imbalance with the hormone deficiency (or overproduction): Diabetes insipidus Hyposecretion of ADH Insulin deficiency Oversecretion of catecholamines Overproduction of GH Hypersecretion of thyroid hormone Hyposecretion of ADH Insulin enhances the membrane transport of glucose in all of the following tissues except __________. the brain the myocardium skeletal muscle adipose tissue the brain Match the following gland with the hormone it produces (or releases): Adrenal medulla Insulin Growth hormone Antidiuretic hormone Aldosterone Epinephrine Epinephrine Match the following hormone with the condition that would be balanced by that hormone: Insulin High levels of blood sugar Dehydration and low blood pressure Decrease in blood Ca2+ levels Decrease in body metabolism Loss of Na+ from extracellular fluids High levels of blood sugar Which of the following homeostatic imbalances usually results from deficits in both glucocorticoids and mineralocorticoids? Cretinism Graves' disease Cushing's syndrome Addison's disease Addison's disease Match the following hormone with the appropriate category of hormones: Cortisol Gonadotr Continue reading >>

Understanding Our Bodies: Insulin

Understanding Our Bodies: Insulin

Almost everyone has heard of Insulin. You probably know that people with type 1 diabetes need to inject themselves with insulin to survive, and must constantly monitor the amount of sugar they eat. But what do you really know about insulin? What is its purpose in the body, and why do we need it? How does it relate to our diets? What happens when things go wrong with it? And why should anyone who doesn’t have diabetes give a hoot? Insulin is one of the most important hormones in the human body, and yet most people don’t really understand why our bodies make it or how what we eat affects the levels of insulin we produce. More so than any other hormone, our diet is key in regulating insulin levels, and thus a number of biological processes. As you’ll soon see, everyone should think about how what they eat impacts their body’s insulin release to be at their happiest and healthiest. Why We Need Insulin Every living thing requires energy to survive. In cells, energy is stored and shuttled around using a molecule called Adenosine Tri-Phosphate, or ATP. Whenever the cell then has an energy-requiring reaction, enzymes can use the energy stored in ATP’s phosphate bonds to fuel it. Cells rely on ATP to survive, and to create ATP, they rely on glucose. All cells, from bacteria and fungi to us, take glucose and use it to generate ATP by a process called Oxidative Phosphorylation. First, glucose is converted to an intermediate molecule called pyruvate via a process called glycolosis. As long as there is oxygen around, this pyruvate is further converted to Acetyl CoA, which enters a cycle of reactions called the Citric Acid Cycle. This takes the carbon to carbon bonds and uses them to create high energy electrons, which are then passed down a chain of enzymes which use the e Continue reading >>

What Is Diabetes?

What Is Diabetes?

If there isn’t enough insulin or if its function is impaired, as it is the case in diabetes, the glucose cannot be used as fuel for the cells. Diabetes is a chronic, incurable disease that occurs when the body doesn’t produce any or enough insulin, leading to an excess of sugar in the blood. Insulin is a hormone, produced by the pancreas, which helps the cells of the body use the glucose (sugar) in food. Cells need this energy in order to function properly. Sugar builds up in the bloodstream and is excreted in the urine. Eventually, the high blood sugar caused by excessive amounts of glucose in the blood leads to a variety of complications, particularly for the eyes, kidneys, nerves, heart and blood vessels. There are different types of diabetes: prediabetes, type 1, type 2, gestational (pregnancy) diabetes and other types. Research and writing: Team of Diabetes Quebec Health Professionals. May 2014 Type 2 diabetes is the most common form of diabetes (90% of cases). It usually occurs in adulthood, in individuals 40 years and older. Unfortunately, for several years, it has begun appearing in younger and younger age groups. In some populations at risk, it may even occur in childhood. Some people with type 2 diabetes have pancreatic cells that do not produce enough insulin. In others, the insulin they produce does not do its job properly, creating what is known as insulin resistance. In both cases, the result is an increase in blood glucose (sugar) levels, since the body is not able to effectively use the glucose as an energy source. Risk Factors There are numerous causes of type 2 diabetes and, in many cases, a combination of several factors triggers the onset of the disease. A few examples: Gender: men are more vulnerable than women; Age: the risk increases with age; Continue reading >>

Nutrient Intake And Hormonal Control Of Insulin Action

Nutrient Intake And Hormonal Control Of Insulin Action

Insulin and Metabolism Insulin is a major metabolism regulating hormone secreted by β-cells of the islets of Langerhans of the pancreas. The major function of insulin is to counter the concerted actions of a number of hyperglycemia-generating hormones and to maintain low blood glucose levels. In addition to its role in regulating glucose metabolism, insulin stimulates lipogenesis, diminishes lipolysis, and increases amino acid transport into cells. Because there are numerous hyperglycemic hormones, untreated disorders associated with insulin generally lead to severe hyperglycemia and shortened life span. Insulin as Growth Factor Insulin also exerts activities typically associated with growth factors. Insulin is a member of a family of structurally and functionally similar molecules that includes the insulin-like growth factors (IGF-1 and IGF-2), and relaxin. The tertiary structure of all four molecules is similar, and all have growth-promoting activities. Insulin modulates transcription and stimulates protein translocation, cell growth, DNA synthesis, and cell replication, effects that it holds in common with the insulin-like growth factors and relaxin. back to the top Insulin is synthesized, from the INS gene, as a preprohormone in the β-cells of the islets of Langerhans. The INS gene is located on chromosome 11p15.5 and is composed of 3 exons that generate four alternatively spliced mRNAs, all of which encode the same 110 amino acid preproprotein. The signal peptide of preproinsulin is removed in the cisternae of the endoplasmic reticulum. The insulin proprotein is packaged into secretory vesicles in the Golgi, folded into its native structure, and locked in this conformation by the formation of two disulfide bonds. Specific protease activity cleaves the center thir Continue reading >>

114 17.9 The Endocrine Pancreas

114 17.9 The Endocrine Pancreas

Learning Objectives By the end of this section, you will be able to: Describe the location and structure of the pancreas, and the morphology and function of the pancreatic islets Compare and contrast the functions of insulin and glucagon The pancreas is a long, slender organ, most of which is located posterior to the bottom half of the stomach (Figure 1). Although it is primarily an exocrine gland, secreting a variety of digestive enzymes, the pancreas has an endocrine function. Its pancreatic islets—clusters of cells formerly known as the islets of Langerhans—secrete the hormones glucagon, insulin, somatostatin, and pancreatic polypeptide (PP). Figure 1. Pancreas. The pancreatic exocrine function involves the acinar cells secreting digestive enzymes that are transported into the small intestine by the pancreatic duct. Its endocrine function involves the secretion of insulin (produced by beta cells) and glucagon (produced by alpha cells) within the pancreatic islets. These two hormones regulate the rate of glucose metabolism in the body. The micrograph reveals pancreatic islets. LM × 760. (Micrograph provided by the Regents of University of Michigan Medical School © 2012) View the University of Michigan WebScope at to explore the tissue sample in greater detail. View the University of Michigan WebScope at to explore the tissue sample in greater detail. Cells and Secretions of the Pancreatic Islets The pancreatic islets each contain four varieties of cells: The alpha cell produces the hormone glucagon and makes up approximately 20 percent of each islet. Glucagon plays an important role in blood glucose regulation; low blood glucose levels stimulate its release. The beta cell produces the hormone insulin and makes up approximately 75 percent of each islet. Elevated Continue reading >>

Glucose Insulin And Diabetes

Glucose Insulin And Diabetes

Every cell in the human body needs energy to survive and do its different functions. If we're talking about a brain cell, it needs energy to keep stimulating other brain cells and sending on signals and messages. If it's a muscle cell, it needs energy to contract. They need energy just to do the basic functions of a cell. And the place that they get that energy from, or the primary source of that energy, is from glucose. Glucose is a simple sugar. If you were to actually taste glucose, it would taste sweet. And glucose gets delivered to cells through the bloodstream. So this right here, I'm drawing some blood that's passing by a cell. Maybe the blood is going in that direction over there. And inside the blood, let me draw some small glucose molecules passing by. And so in an ideal situation, when a cell needs energy, glucose will enter the cell. Unfortunately, it's not that simple for the great majority of cells in the human body. The glucose won't enter by itself. It needs the assistance of a hormone or a molecule called insulin. So let me label all of these. This right here is the glucose, and it needs insulin. So let me draw insulin as these magenta molecules right over here. That over there, that is insulin. And the surface of the cells, they have insulin receptors on them. And I'm just drawing very simplified versions of them, kind of a place where these magenta circles can attach, can bind. And what happens is, in order for the glucose to be taken up by the cell, insulin has to attach to these receptors, which unlocks the channels for glucose. In order for the glucose to go in, insulin has to bind to the insulin receptors. And then, once that happens, then the glucose can be taken up by the cell. Now, unfortunately, things don't always work as planned. So let me d Continue reading >>

Functions Of Insulin

Functions Of Insulin

Insulin is a protein-based hormone that is made by the beta cells of the pancreas. Most people know that insulin is the hormone that helps the body’s cells put glucose into the cells for use as cellular fuel. In the absence of insulin, the cells do not have enough biochemical energy so they must use other nutrients in order to function. Without insulin, life-threatening complications can occur due to high blood sugar levels. Insulin and Metabolism When a person eats a meal containing glucose (or any other carbohydrate), the pancreas secretes insulin so that the glucose absorbed by the cells can be used for cellular metabolism. Insulin essential for cell metabolism and, without it, the individual would die. In type 1 diabetics, the pancreas cannot secrete insulin so the blood sugars go higher. The cells do not get enough glucose for cellular metabolism. In type 2 diabetes, there is usually enough insulin secreted; however, the cells are resistant to insulin and glucose cannot get into the cells for cellular metabolism. If diabetes is left unchecked, glucose builds up in the bloodstream and doesn’t get passed along to the cells nor is it stored as glycogen in the liver. This can damage many bodily organs and tissues, including the eyes, nerves, blood vessels, and kidneys. Insulin replacement is necessary for type 1 diabetes because these types of diabetics don’t get enough insulin from the pancreas to do its job. In some cases, type 2 diabetics need insulin because their pancreas has been overworked and is tired, damaging the beta cells of the pancreas. Insulin is injected into the fatty tissue, usually in the abdomen; however, other good sites for injection of insulin is the buttocks, thighs, or upper arms. Insulin’s action on the Digestive System When a person e Continue reading >>

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