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How Are Insulin And Glycogen Different

You And Your Hormones

You And Your Hormones

What is glucagon? Glucagon is a hormone that is involved in controlling blood sugar (glucose) levels. It is secreted into the bloodstream by the alpha cells, found in the islets of langerhans, in the pancreas. The glucagon-secreting alpha cells surround a core of insulin-secreting beta cells, which reflects the close relationship between the two hormones. Glucagon’s role in the body is to prevent blood glucose levels dropping too low. To do this, it acts on the liver in several ways: It stimulates the conversion of stored glycogen (stored in the liver) to glucose, which can be released into the bloodstream. This process is called glycogenolysis. It promotes the production of glucose from amino acid molecules. This process is called gluconeogenesis. It reduces glucose consumption by the liver so that as much glucose as possible can be secreted into the bloodstream to maintain blood glucose levels. Glucagon also acts on adipose tissue to stimulate the breakdown of fat stores into the bloodstream. How is glucagon controlled? Glucagon works along with the hormone insulin to control blood sugar levels and keep them within set levels. Glucagon is released to stop blood sugar levels dropping too low, while insulin is released to stop blood sugar levels rising too high. Release of glucagon is stimulated by low blood glucose (hypoglycaemia), protein-rich meals and adrenaline (another important hormone for combating low glucose). Release of glucagon is prevented by raised blood glucose and carbohydrate in meals, detected by cells in the pancreas. In the longer-term, glucagon is crucial to the body’s response to lack of food. For example, it encourages the use of stored fat for energy in order to preserve the limited supply of glucose. What happens if I have too much glucagon? Continue reading >>

Glucose Metabolism And Regulation: Beyond Insulin And Glucagon

Glucose Metabolism And Regulation: Beyond Insulin And Glucagon

Insulin and glucagon are potent regulators of glucose metabolism. For decades, we have viewed diabetes from a bi-hormonal perspective of glucose regulation. This perspective is incomplete and inadequate in explaining some of the difficulties that patients and practitioners face when attempting to tightly control blood glucose concentrations. Intensively managing diabetes with insulin is fraught with frustration and risk. Despite our best efforts, glucose fluctuations are unpredictable, and hypoglycemia and weight gain are common. These challenges may be a result of deficiencies or abnormalities in other glucoregulatory hormones. New understanding of the roles of other pancreatic and incretin hormones has led to a multi-hormonal view of glucose homeostasis. HISTORICAL PERSPECTIVE Our understanding of diabetes as a metabolic disease has evolved significantly since the discovery of insulin in the 1920s. Insulin was identified as a potent hormonal regulator of both glucose appearance and disappearance in the circulation. Subsequently, diabetes was viewed as a mono-hormonal disorder characterized by absolute or relative insulin deficiency. Since its discovery, insulin has been the only available pharmacological treatment for patients with type 1 diabetes and a mainstay of therapy for patients with insulin-deficient type 2 diabetes.1–7 The recent discovery of additional hormones with glucoregulatory actions has expanded our understanding of how a variety of different hormones contribute to glucose homeostasis. In the 1950s, glucagon was characterized as a major stimulus of hepatic glucose production. This discovery led to a better understanding of the interplay between insulin and glucagon, thus leading to a bi-hormonal definition of diabetes. Subsequently, the discovery of Continue reading >>

Insulin And Glucagon: Essential Hormones For Normal Blood Sugar

Insulin And Glucagon: Essential Hormones For Normal Blood Sugar

When it comes to regulating blood glucose levels there is an important interplay between two hormones in your body, insulin and glucagon. These two hormones counterbalance each other and allow for normal blood sugar balancing. When they are not working correctly people can develop insulin resistance and diabetes. Here are the major players. Glucose is a simple form of sugar that is used by our cells as fuel. When you eat a meal your food is broken down in your digestive system into its building blocks and ultimately converted into glucose. Glucose is then released into your blood stream so that your cells can use it for fuel to do their jobs in your body. When there is extra glucose in the blood stream it is taken up into the liver and muscle cells to be stored as glycogen for in between meals. Insulin is a hormone that is released from your pancreas in response to high amounts of glucose circulating in your blood. The purpose of insulin is to help the high glucose levels leave your bloodstream and enter your cells. Insulin acts as a key to open the cell membranes of the cells so glucose can enter. This causes the blood glucose levels in the blood to drop and become lower. Glucagon is a hormone that is also released from your pancreas but this time in response to low levels of glucose in your blood. It causes the stored glycogen to be broken down back into glucose. It's then released into the bloodstream to raise blood glucose levels during times when you are not eating. For example when you are sleeping or in-between meals. When insulin levels are high, glucagon is not released. When glucagon levels are high then insulin levels are not released. The interplay between insulin and glucagon keeps your blood glucose constant between 90-100ml/dl throughout the day. When som Continue reading >>

Insulin & Bodybuilding.

Insulin & Bodybuilding.

Unbridled enthusiasm is a common characteristic for most fledgling beginners. With this unbridled enthusiasm comes an unquenchable thirst for knowledge, which manifests itself as childlike curiosity. Unfortunately, like a sponge these fledgling beginners absorb any and all information and misinformation thrown their way. With this ferocity for learning, these new trainees embark on training programs from muscle magazines, advice from gym rats, and any other advice from anyone willing to give it. The role of insulin is a current topic reverberating through gyms everywhere. Insulin is a hormone best known for its role in glucose metabolism. In an attempt to provide some clear scientific information to our trainers, this article will discuss the different classifications of carbohydrates, and how the body regulates blood glucose levels. Practical applications to bodybuilders will close out the article. Carbohydrates Carbohydrates provide direct energy for the human brain, central nervous system, and muscle cells in the form of glucose (blood sugar). Carbohydrates can be broken down into simple carbohydrates or complex carbohydrates. Simple Simple Carbohydrates are sugars, organic compounds whose bonds are easily broken down by digestion. Sugars are classified as monosaccharides (mono = one), or disaccharides (di= two). Monosaccharides include glucose, galactose, and fructose. Disaccharides are two monosaccharide units linked together and include maltose (two glucose units), sucrose (fructose plus glucose), and lactose (galactose plus glucose). Your body only has the ability to absorb monosaccharides into the blood. Complex Complex carbohydrates are defined as polysaccharides (poly = many) that are found in starch and fiber. Starches are polysaccharides humans can digest, b Continue reading >>

How Does Insulin Stimulate Glycogen Synthesis?

How Does Insulin Stimulate Glycogen Synthesis?

Abstract One of the important effects of insulin on intracellular metabolism is its ability to stimulate the synthesis of glycogen in muscle and liver. It does this by promoting a net decrease in the extent of phosphorylation of glycogen synthase, the rate-limiting enzyme in the pathway of glycogen synthesis, which increases its activity. Several years ago glycogen synthase was shown to be phosphorylated and inactivated by cyclic AMP-dependent protein kinase in vitro, suggesting that the effect of insulin on glycogen synthesis, and perhaps other intracellular processes, might be explainable in terms of the ability of the hormone to decrease the concentration of tissue cyclic AMP. However, the subsequent failure to detect a decrease in cyclic AMP concentration in muscle under conditions where glycogen synthase activity was stimulated by insulin, coupled with the discovery of a second glycogen synthase kinase whose activity is unaffected by cyclic nucleotides, now suggests the possibility that insulin may regulate the activity of a different class of protein kinase, through its own "second messenger". The identification and characterization of glycogen synthase kinase-2 and recent information about the regulation of glycogen synthase by phosphorylation-dephosphorylation in vitro and in vivo are presented. Continue reading >>

Introduction

Introduction

INTRODUCTION Glucose in the blood provides a source of fuel for all tissues of the body. Blood glucose levels are highest during the absorptive period after a meal, during which the stomach and small intestine are breaking down food and circulating glucose to the bloodstream. Blood glucose levels are the lowest during the postabsorptive period, when the stomach and small intestines are empty. Despite having food only periodically in the digestive tract, the body works to maintain relatively stable levels of circulatory glucose throughout the day. The body maintains blood glucose homeostasis mainly through the action of two hormones secreted by the pancreas. These hormones are insulin, which is released when glucose levels are high, and glucagon, which is released when glucose levels are low. The accompanying animation depicts the functions of these hormones in blood glucose regulation. CONCLUSION Throughout the day, the release of insulin and glucagon by the pancreas maintains relatively stable levels of glucose in the blood. During the absorptive period blood glucose levels tend to increase, and this increase stimulates the pancreas to release insulin into the bloodstream. Insulin promotes the uptake and utilization of glucose by most cells of the body. Thus, as long as the circulating glucose supply is high, cells preferentially use glucose as fuel and also use glucose to build energy storage molecules glycogen and fats. In the liver, insulin promotes conversion of glucose into glycogen and into fat. In muscle insulin promotes the use of glucose as fuel and its storage as glycogen. In fat cells insulin promotes the uptake of glucose and its conversion into fats. The nervous system does not require insulin to enable its cells to take up and utilize glucose. If glucose Continue reading >>

Normal Regulation Of Blood Glucose

Normal Regulation Of Blood Glucose

The human body wants blood glucose (blood sugar) maintained in a very narrow range. Insulin and glucagon are the hormones which make this happen. Both insulin and glucagon are secreted from the pancreas, and thus are referred to as pancreatic endocrine hormones. The picture on the left shows the intimate relationship both insulin and glucagon have to each other. Note that the pancreas serves as the central player in this scheme. It is the production of insulin and glucagon by the pancreas which ultimately determines if a patient has diabetes, hypoglycemia, or some other sugar problem. In this Article Insulin Basics: How Insulin Helps Control Blood Glucose Levels Insulin and glucagon are hormones secreted by islet cells within the pancreas. They are both secreted in response to blood sugar levels, but in opposite fashion! Insulin is normally secreted by the beta cells (a type of islet cell) of the pancreas. The stimulus for insulin secretion is a HIGH blood glucose...it's as simple as that! Although there is always a low level of insulin secreted by the pancreas, the amount secreted into the blood increases as the blood glucose rises. Similarly, as blood glucose falls, the amount of insulin secreted by the pancreatic islets goes down. As can be seen in the picture, insulin has an effect on a number of cells, including muscle, red blood cells, and fat cells. In response to insulin, these cells absorb glucose out of the blood, having the net effect of lowering the high blood glucose levels into the normal range. Glucagon is secreted by the alpha cells of the pancreatic islets in much the same manner as insulin...except in the opposite direction. If blood glucose is high, then no glucagon is secreted. When blood glucose goes LOW, however, (such as between meals, and during Continue reading >>

Lack Of Liver Glycogen Causes Hepatic Insulin Resistance And Steatosis In Mice

Lack Of Liver Glycogen Causes Hepatic Insulin Resistance And Steatosis In Mice

Abstract Disruption of the Gys2 gene encoding the liver isoform of glycogen synthase generates a mouse strain (LGSKO) that almost completely lacks hepatic glycogen, has impaired glucose disposal, and is pre-disposed to entering the fasted state. This study investigated how the lack of liver glycogen increases fat accumulation and the development of liver insulin resistance. Insulin signaling in LGSKO mice was reduced in liver, but not muscle, suggesting an organ-specific defect. Phosphorylation of components of the hepatic insulin-signaling pathway, namely IRS1, Akt, and GSK3, was decreased in LGSKO mice. Moreover, insulin stimulation of their phosphorylation was significantly suppressed, both temporally and in an insulin dose response. Phosphorylation of the insulin-regulated transcription factor FoxO1 was somewhat reduced and insulin treatment did not elicit normal translocation of FoxO1 out of the nucleus. Fat overaccumulated in LGSKO livers, showing an aberrant distribution in the acinus, an increase not explained by a reduction in hepatic triglyceride export. Rather, when administered orally to fasted mice, glucose was directed toward hepatic lipogenesis as judged by the activity, protein levels, and expression of several fatty acid synthesis genes, namely, acetyl-CoA carboxylase, fatty acid synthase, SREBP1c, chREBP, glucokinase, and pyruvate kinase. Furthermore, using cultured primary hepatocytes, we found that lipogenesis was increased by 40% in LGSKO cells compared with controls. Of note, the hepatic insulin resistance was not associated with increased levels of pro-inflammatory markers. Our results suggest that loss of liver glycogen synthesis diverts glucose toward fat synthesis, correlating with impaired hepatic insulin signaling and glucose disposal. Footno Continue reading >>

Regulation Of Glucose Through The Hormones Insulin And Glucagon

Regulation Of Glucose Through The Hormones Insulin And Glucagon

Sort Hyperglycemia High blood glucose. High blood glucose happens when the body has too little insulin or when the body can't use insulin properly.Term used to describe hormones such as glucagon that elevate blood glucose levels. If you have type 1, you may not have given yourself enough insulin. If you have type 2, your body may have enough insulin, but it is not as effective as it should be. You ate more than planned or exercised less than planned. You have stress from an illness, such as a cold or flu. Youve just attended a football game with your friend sharon who is diabetic. While sharon drank only one beer during the game she is having trouble walking straight her speech is slurred and she is not making sense. what does it mean when we say sharon is diabetic? what is the most likely explanation for sharons current behavior? how could you help her? when we say sharon is diabetic this means that she has insufficient insulin action in her body. the most likely explanation for sharons behavior is that she has taken too much insulin and is experiencing hypoglycemia. You could help her by making sure she gets a sugary snack. Continue reading >>

Glycogenolysis And Glycogenesis

Glycogenolysis And Glycogenesis

Structure of glycogen Figure 1. Glycogen structure (Click for enlarged view). Panel A. Schematic two-dimensional cross-sectional view of glycogen: A core protein of glycogenin is surrounded by branches of glucose units. The entire globular granule may contain around 30,000 glucose units. [Source: Mikael Häggström[2], . Panel B. Schematic of glycogen structure showing the glucose units in each chain linked together linearly by α(1→4 glycosidic bonds. Branches are linked to the chains from which they are branching off by α(1→6) glycosidic bonds between the first glucose of the new branch and a glucose on the stem chain.Glycogen is a multi-branched polysaccharide of glucose that serves as an energy store primarily in muscle and liver. It is stored in the form of granules in the cytoplasm of the cell and is the main storage form of glucose in the body. The concentration of glycogen in muscle is low (1-2% fresh weight) compared to the levels stored in the liver (up to 8% fresh weight)[1]. Glycogen is an energy reserve that can be quickly mobilized to meet a sudden need for glucose. The significance of the multi-branched structure is that multiple glucose units, rather than a single glucose can be mobilized from any glycogen molecule when glycogenolysis is initiated. The structure of glycogen is summarized in Figure 1[2]. Enzymes involved in glycogenolysis The process of glycogenolysis involves the sequential removal of glucose monomers by phosphorolysis, a reaction catalysed by the phosphorylated (active) ‘a’ form of the enzyme glycogen phosphorylase[3]. This enzyme cleaves the glycosidic bond linking a terminal glucose to a glycogen branch by substituting a phosphoryl group for the α[1→4] linkage producing glucose-1-phosphate and glycogen that contains one le Continue reading >>

Blood Sugar Regulation

Blood Sugar Regulation

Ball-and-stick model of a glucose molecule Blood sugar regulation is the process by which the levels of blood sugar, primarily glucose, are maintained by the body within a narrow range. This tight regulation is referred to as glucose homeostasis. Insulin, which lowers blood sugar, and glucagon, which raises it, are the most well known of the hormones involved, but more recent discoveries of other glucoregulatory hormones have expanded the understanding of this process.[1] Mechanisms[edit] Blood sugar regulation the flatline is the level needed the sine wave the fluctuations. Blood sugar levels are regulated by negative feedback in order to keep the body in balance. The levels of glucose in the blood are monitored by many tissues, but the cells in the pancreatic islets are among the most well understood and important. Glucagon[edit] If the blood glucose level falls to dangerous levels (as during very heavy exercise or lack of food for extended periods), the alpha cells of the pancreas release glucagon, a hormone whose effects on liver cells act to increase blood glucose levels. They convert glycogen into glucose (this process is called glycogenolysis). The glucose is released into the bloodstream, increasing blood sugar. Hypoglycemia, the state of having low blood sugar, is treated by restoring the blood glucose level to normal by the ingestion or administration of dextrose or carbohydrate foods. It is often self-diagnosed and self-medicated orally by the ingestion of balanced meals. In more severe circumstances, it is treated by injection or infusion of glucagon. Insulin[edit] When levels of blood sugar rise, whether as a result of glycogen conversion, or from digestion of a meal, a different hormone is released from beta cells found in the Islets of Langerhans in the p Continue reading >>

Glucose Metabolism

Glucose Metabolism

Energy is required for the normal functioning of the organs in the body. Many tissues can also use fat or protein as an energy source but others, such as the brain and red blood cells, can only use glucose. Glucose is stored in the body as glycogen. The liver is an important storage site for glycogen. Glycogen is mobilized and converted to glucose by gluconeogenesis when the blood glucose concentration is low. Glucose may also be produced from non-carbohydrate precursors, such as pyruvate, amino acids and glycerol, by gluconeogenesis. It is gluconeogenesis that maintains blood glucose concentrations, for example during starvation and intense exercise. The endocrine pancreas The pancreas has both endocrine and exocrine functions. The endocrine tissue is grouped together in the islets of Langerhans and consists of four different cell types each with its own function. Alpha cells produce glucagon. Beta cells produce proinsulin. Proinsulin is the inactive form of insulin that is converted to insulin in the circulation. Delta cells produce somatostatin. F or PP cells produce pancreatic polypeptide. Regulation of insulin secretion Insulin secretion is increased by elevated blood glucose concentrations, gastrointestinal hormones and Beta adrenergic stimulation. Insulin secretion is inhibited by catecholamines and somatostatin. The role of insulin and glucagon in glucose metabolism Insulin and glucagon work synergistically to keep blood glucose concentrations normal. Insulin: An elevated blood glucose concentration results in the secretion of insulin: glucose is transported into body cells. The uptake of glucose by liver, kidney and brain cells is by diffusion and does not require insulin. Click on the thumbnail for details of the effect of insulin: Glucagon: The effects of glu Continue reading >>

Insulin And Glucagon

Insulin And Glucagon

- [Voiceover] Metabolism is just the flow of energy throughout the body. Energy enters our body when we eat food, and that food is then absorbed in three different forms. It can be absorbed as amino acids, so, things that make up proteins, so, you'd imagine meat would have a lot of amino acids. Or they can be absorbed as fats, so these are lipids, or fatty acids and so your greasy, fried food is pretty rich in fats. Or they can be absorbed in carbohydrates, or I'll just write "carbs" here, which you have a lot of in ice cream or other sweet things. Each of these things deliver energy into your GI tract. Your stomach, and your intestines, which can then be absorbed and sent elsewhere for use. Now carbohydrates are one of the main currencies for energy, so let's focus on that, and we'll do so by starting with glucose, which is the most basic form of carbohydrates. In fact, it's considered a simple sugar. Now, there are two main hormones that control the availability of glucose throughout the body. And they're at a constant tug of war with each other. One of them, which you've heard of probably is called "insulin." Insulin regulates that storage of glucose, as we'll talk more about in a minute, and the other guy on the end of the rope, is a hormone called "glucagon." Glucagon regulates the release of glucose from storage. And it's pretty important that we have enough glucose available in the blood. Because, for example, the brain uses about 120 grams of glucose per day. And that's a lot, because it comes out to be about 60 to 70% of all the glucose that we eat in a day. But to put it in terms that I think you and I appreciate a little more, 120 grams of glucose comes out to be about 250 M&Ms, in a single day! Now that's a lot of M&Ms. So you can see why it's really importa Continue reading >>

Blood Glucose Regulation

Blood Glucose Regulation

Glucose is needed by cells for respiration. It is important that the concentration of glucose in the blood is maintained at a constant level. Insulin is a hormone produced by the pancreas that regulates glucose levels in the blood. How glucose is regulated Glucose level Effect on pancreas Effect on liver Effect on glucose level too high insulin secreted into the blood liver converts glucose into glycogen goes down too low insulin not secreted into the blood liver does not convert glucose into glycogen goes up Use the animation to make sure you understand how this works. You have an old or no version of flash - you need to upgrade to view this funky content! Go to the WebWise Flash install guide Glucagon – Higher tier The pancreas releases another hormone, glucagon, when the blood sugar levels fall. This causes the cells in the liver to turn glycogen back into glucose which can then be released into the blood. The blood sugar levels will then rise. Now try a Test Bite- Higher tier. Diabetes is a disorder in which the blood glucose levels remain too high. It can be treated by injecting insulin. The extra insulin allows the glucose to be taken up by the liver and other tissues, so cells get the glucose they need and blood-sugar levels stay normal. There are two types of diabetes. Type 1 diabetes Type 1 diabetes is caused by a lack of insulin. It can be controlled by: monitoring the diet injecting insulin People with type 1 diabetes have to monitor their blood sugar levels throughout the day as the level of physical activity and diet affect the amount of insulin required. Type 2 diabetes Type 2 diabetes is caused by a person becoming resistant to insulin. It can be controlled by diet and exercise. There is a link between rising levels of obesity (chronic overweight) and i Continue reading >>

Physiologic Effects Of Insulin

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 >>

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