Glycogen And Diabetes - Role, Storage, Release & Exercise
Glycogen is a stored form of glucose. It is a large multi-branched polymer of glucose which is accumulated in response to insulin and broken down into glucose in response to glucagon . Glycogen is mainly stored in the liver and the muscles and provides the body with a readily available source of energy if blood glucose levels decrease. Energy can be stored by the body in different forms. One form of stored energy is fat and glycogen is another. Fatty acids are more energy rich but glucose is the preferred energy source for the brain and glucose also can provide energy for cells in the absence of oxygen, for instance during anaerobic exercise. Glycogen is therefore useful for providing a readily available source of glucose for the body. In a healthy body, the pancreas will respond to higher levels of blood glucose , such as in response to eating, by releasing insulin which will lower blood glucose levels by prompting the liver and muscles to take up glucose from the blood and store it as glycogen. People with diabetes either do not make enough of their own insulin and/or their insulin does not work effectively enough. As a result, the pancreas may not be able to respond effectively enough to rises in blood glucose. In these situations, when the body feels extra glucose is needed in the blood, the pancreas will release the hormone glucagon which triggers the conversion of glycogen into glucose for release into the bloodstream. Glycogen plays an important role in keeping our muscles fuelled for exercise. When we exercise, our muscles will take advantage of their stored glycogen. Glucose in our blood and glycogen stored in the liver can also be used to keep our muscles fuelled. Once we complete our exercise session, our muscles will replenish their glycogen stores. The tim Continue reading >>
Principles Of Biochemistry/glucose, Glycogen And Diabetes
Glucose (C6H12O6, also known as D-glucose, dextrose, or grape sugar) is a simple sugar (monosaccharide) and an important carbohydrate in biology. Cells use it as a source of energy and a metabolic intermediate. Glucose is one of the main products of photosynthesis and starts cellular respiration. Glucose exists in several different structures, but all of these structures can be divided into two families of mirror-images (stereoisomers). Only one set of these isomers exists in nature, those derived from the "right-handed form" of glucose, denoted D-glucose. D-glucose is often referred to as dextrose. The term dextrose is derived from dextrorotatory glucose. Solutions of dextrose rotate polarized light to the right (in Latin: dexter = "right"). Starch and cellulose are polymers derived from the dehydration of D-glucose. The other stereoisomer, called L-glucose, is hardly found in nature. The name "glucose" comes from the Greek word glukus (γλυκύς), meaning "sweet". The suffix "-ose" denotes a sugar. The name "dextrose" and the 'D-' prefix come from Latin dexter ("right"), referring to the handedness of the molecules. Glucose is a monosaccharide with formula C6H12O6 or H-(C=O)-(CHOH)5-H, whose five hydroxyl (OH) groups are arranged in a specific way along its six-carbon backbone.[1] In its fleeting open-chain form, the glucose molecule has an open (as opposed to cyclic) and unbranched backbone of six carbon atoms, C-1 through C-6; where C-1 is part of an aldehyde group H(C=O)-, and each of the other five carbons bears one hydroxyl group -OH. The remaining bonds of the backbone carbons are satisfied by hydrogen atoms -H. Therefore glucose is an hexose and an aldose, or an aldohexose. Each of the four carbons C-2 through C-5 is chiral, meaning that its four bonds conne Continue reading >>
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Do Type 2s Ever Deplete Liver Supply Of Glycogen?
Do Type 2s Ever Deplete Liver Supply of Glycogen? Do Type 2s Ever Deplete Liver Supply of Glycogen? A month or two ago, I went about 3 days (by choice) without eating. By the second day and third day I was in low 100s every time I checked. After 72 hours of not eating this week, blood sugar waking today was 146. About two hours later, 145. After I did two somewhat strenuous tasks, tested at 185. WTH? If it's not from food, it's got to be from liver. I remember in an early edition of Dr. Atkins' book, he says the initial weight loss of several pounds, is from the liver depleting its glycogen stores. I think he said it happens at about day 2, and, mind you, people are eating on Atkins, and I haven't been. Poked around on the Web and most info I saw said glycogen can be defeated in 12-24 hours. I can understand some people needing more time, but if it's not depleted by 72 hours, when will it be? I ate about an hour ago, some feta cheee, Kalamata olives and a few cherry tomatoes. An hour after eating, 150. Didn't test before eating, but the 185 was less than an hour before eating, so guess I was probably in about the same neighborhood? So do type 2s ever deplete liver's supply of glycogen? The universe is made of stories, not atoms. Muriel Rukeyser D.D. Family T1 since 1977 - using Novolog in an Animas pump. There is a lot of speculation about this. And it is based on observed changes in blood glucose. Not very scientific. My take on it is that liver glycogen is never fully depleted. Muscle glycogen is more likely to be fully depleted, after strenuous exercise. You will always have enough glycogen in the liver for the body to draw on in emergencies. Humans would not have evolved into the most successful species if this were not the case. When it drops too low, and if carbo Continue reading >>
Does The Route Of Insulin Delivery Affect Glycogen Storage In Type I Diabetes?
This study evaluated the influence of systemic insulin delivery on liver glycogen levels in patients with type 1 diabetes mellitus. Type I diabetes is an autoimmune disease where the body no longer produces insulin. In the liver, insulin promotes glucose uptake by stimulating its storage as glycogen while inhibiting glycogen breakdown. Previous studies have shown that the liver's capacity to store glycogen is reduced in patients with type 1 diabetes mellitus, but it remains unclear whether this is due to hyperglycemia (a high blood glucose level), or whether the route of insulin supply could contribute to this occurrence. Systemic insulin delivery prevents removal or loss (metabolism) of insulin by the body before it becomes available for use. This study investigated the effects of systemic insulin delivery (via an insulin pump under the skin) on glycogen storage in type I diabetes patients by comparing their liver glycogen levels to patients with type I diabetes who had undergone pancreaskidney transplants (performed for patients who have kidney failure as a complication of type 1 diabetes mellitus). These transplant patients have normal glucose levels, are not usually on any form of insulin regime and so represent a suitable human model against which to compare the effects of systemic insulin delivery in type I diabetes. This study involved 25 participants. Nine were type I diabetes patients who had undergone successful pancreas-kidney transplantation, seven were patients with type 1 diabetes mellitus who had not undergone such a transplantation and were receiving insuling via an insulin pump, while the remaining subjects were healthy participants used as controls (a group used as a basis to compare the results of the experiment). Results showed that patients with ty Continue reading >>
Glycogen Storage In The Liver In Diabetes Mellitus
Glycogen Storage in the Liver in Diabetes Mellitus This article has been cited by other articles in PMC. Full text is available as a scanned copy of the original print version. Get a printable copy (PDF file) of the complete article (625K), or click on a page image below to browse page by page. Links to PubMed are also available for Selected References . These references are in PubMed. This may not be the complete list of references from this article. Cruickshank EW. On the production and utilisation of glycogen in normal and diabetic animals. J Physiol. 1913 Oct 17;47(1-2):114. [ PMC free article ] [ PubMed ] HUBBLE D. Glucagon and glycogen-storage disease of the liver. Lancet. 1954 Jan 30;266(6805):235237. [ PubMed ] KIRTLEY WR, WAIFE SO, PECK FB. Effect of glucagon in stable and unstable diabetic patients. Proc Soc Exp Biol Med. 1953 Jun;83(2):387389. [ PubMed ] KIRTLEY WR, WAIFE SO, HELMER OM, PECK FB. Effect of purified glucagon (hyperglycemic-glycogenolytic factor, HGF) on carbohydrate and corticoid metabolism in normal and diabetic subjects. Diabetes. 1953 Sep-Oct;2(5):345349. [ PubMed ] VALLANCE OWEN J. Liver glycogen in diabetes mellitus. J Clin Pathol. 1952 Feb;5(1):4253. [ PMC free article ] [ PubMed ] Articles from Journal of Clinical Pathology are provided here courtesy of BMJ Publishing Group Continue reading >>
New Insights Into Impaired Muscle Glycogen Synthesis
New Insights into Impaired Muscle Glycogen Synthesis *To whom correspondence should be addressed. E-mail: [email protected] New Insights into Impaired Muscle Glycogen Synthesis More a Problem of Muscle Contractility Than of Glucose Tolerance Citation: Groop L, Orho-Melander M (2008) New Insights into Impaired Muscle Glycogen Synthesis. PLoS Med 5(1): e25. Copyright: 2008 Groop and Orho-Melander. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: The authors received no specific funding for this article. Competing interests: The authors have declared that no competing interests exist. Abbreviations: GS, glycogen synthase; PP1, protein phosphatase 1 Glucose is the most rapidly accessible substrate in the body. Its storage as glycogen in muscle and liver is of central importance as a first source of energy for muscle contractions and prevention against hypoglycemia. Glycogen synthesis and breakdown are regulated by insulin and catecholamines as well as by glucose-6-phosphate and the amount of glycogen. There are two isoforms of glycogen synthase (GS), one in muscle and one in liver, encoded by different genes (GYS1 and GYS2, respectively) [ 1 ]. Insulin stimulates glycogen synthesis by activating protein phosphatase 1 (PP1), which activates GS, inactivates glycogen phosphatase, and inactivates glycogen synthase kinase 3, an inhibitor of GS. PP1 has a glycogen-targeting subunit (PPP1R3A), which facilitates localization of PP1 to glycogen. Impaired Insulin-Stimulated Glycogen Synthesis Precedes Type 2 Diabetes It is well established that patients with type 2 diabetes as well as pe Continue reading >>
The Liver & Blood Sugar
During a meal, your liver stores sugar for later. When you’re not eating, the liver supplies sugar by turning glycogen into glucose in a process called glycogenolysis. The liver both stores and produces sugar… The liver acts as the body’s glucose (or fuel) reservoir, and helps to keep your circulating blood sugar levels and other body fuels steady and constant. The liver both stores and manufactures glucose depending upon the body’s need. The need to store or release glucose is primarily signaled by the hormones insulin and glucagon. During a meal, your liver will store sugar, or glucose, as glycogen for a later time when your body needs it. The high levels of insulin and suppressed levels of glucagon during a meal promote the storage of glucose as glycogen. The liver makes sugar when you need it…. When you’re not eating – especially overnight or between meals, the body has to make its own sugar. The liver supplies sugar or glucose by turning glycogen into glucose in a process called glycogenolysis. The liver also can manufacture necessary sugar or glucose by harvesting amino acids, waste products and fat byproducts. This process is called gluconeogenesis. When your body’s glycogen storage is running low, the body starts to conserve the sugar supplies for the organs that always require sugar. These include: the brain, red blood cells and parts of the kidney. To supplement the limited sugar supply, the liver makes alternative fuels called ketones from fats. This process is called ketogenesis. The hormone signal for ketogenesis to begin is a low level of insulin. Ketones are burned as fuel by muscle and other body organs. And the sugar is saved for the organs that need it. The terms “gluconeogenesis, glycogenolysis and ketogenesis” may seem like compli Continue reading >>
Alloxan-diabetes And Liver Glycogen
A decrease in the glycogen content of the diabetic liver is often considered to be the direct result of the diabetic disturbance in metabolism, caused either by an increased glycogenolysis or by a decreased ability to synthesize glycogen. In previous experiments [Tuerkischer & Wertheimer, 1946] it was observed that the livers of alloxandiabetic rats and of pair-fed, normal rats contained equal amounts of glycogen. The liver glycogen of alloxan-diabetic rats starved for 24 hr. was actually considerably higher than that of normal, control rats, a fact also reported shortly thereafter by Weber [1946]. Additional burdening of the carbohydrate metabolism with complete exhaustion of the carbohydrate reserves (by phloridzin or swimming) caused increased glycogenesis in the diabetic rat, starved for 24 hr., with an increased deposition of glycogen in the liver. This increase in liver glycogen was only found in non-comatose, alloxan-diabetic rats. It was therefore assumed that the decrease in Continue reading >>
Glycogen - Diabetes Self-management
The chief storage form of carbohydrate in animals (including humans). Glycogen is stored mainly in the bodys liver and muscle tissue. When blood glucose levels are high, excess glucose normally is stored as glycogen. When blood glucose levels drop, glycogen is converted back into glucose. Prolonged exercise can deplete a persons glycogen stores. This means that people with diabetes can develop severe hypoglycemia (low blood sugar) many hours after exercise, as the body replenishes its supply of glycogen in the muscles and tissues by taking glucose from the blood. Two hormones control the breakdown of glycogen: epinephrine (adrenaline), released by the adrenal glands, and glucagon , secreted by the alpha cells of the pancreas. After many years of diabetes, these hormones may fail to work properly. The timely breakdown of glycogen into glucose may thus not occur, making people more prone to episodes of severe hypoglycemia without warning. Glucagon in injectable form is commercially available in special kits for treating severe hypoglycemia. Because someone whose blood sugar drops to very low levels may be unable to treat himself, friends and family of people with diabetes should learn how to inject glucagon. Injected glucagon quickly converts glycogen back into glucose to help restore normal blood sugar levels. This article was written by Robert S. Dinsmoor, a Contributing Editor of Diabetes Self-Management. Disclaimer Statements: Statements and opinions expressed on this Web site are those of the authors and not necessarily those of the publishers or advertisers. The information provided on this Web site should not be construed as medical instruction. Consult appropriate health-care professionals before taking action based on this information. Continue reading >>
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Liver Disease And Diabetes Mellitus
CLINICAL DIABETES VOL. 17 NO. 2 1999 These pages are best viewed with Netscape version 3.0 or higher or Internet Explorer version 3.0 or higher. When viewed with other browsers, some characters or attributes may not be rendered correctly. FEATURE ARTICLE Gavin N. Levinthal, MD, and Anthony S. Tavill, MD, FRCP, FACP IN BRIEF Liver disease may cause or contribute to, be coincident with, or occur as a result of diabetes mellitus. This article addresses these associations. This article addresses the role of the liver in normal glucose homeostasis and discusses a variety of liver conditions associated with abnormal glucose homeostasis. This association may explain the pathogenesis of the liver disease or of the abnormal glucose homeostasis, or may be purely coincidental (Table 1). Table 1. Liver Disease and Diabetes Mellitus 1. Liver disease occurring as a consequence of diabetes mellitus Glycogen deposition Steatosis and nonalcoholic steatohepatitis (NASH) Fibrosis and cirrhosis Biliary disease, cholelithiasis, cholecystitis Complications of therapy of diabetes (cholestatic and necroinflammatory) 2 . Diabetes mellitus and abnormalities of glucose homeostasis occurring as a complication of liver disease Hepatitis Cirrhosis Hepatocellular carcinoma Fulminant hepatic failure Postorthotopic liver transplantation 3 . Liver disease occurring coincidentally with diabetes mellitus and abnormalities of glucose homeostasis Hemochromatosis Glycogen storage diseases Autoimmunebiliary disease The prevalence of type 1 diabetes in the United States is ~0.26%. The prevalence of type 2 diabetes is far higher, ~1–2% in Caucasian Americans and up to 40% in Pima Indians. According to the Centers for Disease Control and Prevention, hepatitis C alone chronically infects more than 1.8% of the A Continue reading >>
Glycogen Storage Disease Type1 And Diabetes: Learning By Comparing And Contrasting The Two Disorders - Sciencedirect
Volume 39, Issue 5 , October 2013, Pages 377-387 Glycogen storage disease type1 and diabetes: Learning by comparing and contrasting the two disordersApprendre en comparant le diabte et la glycognose de type1 Author links open overlay panel F.Rajasabc Get rights and content Glycogen storage disease type 1 (GSD1) and diabetes may look at first like totally opposite disorders, as diabetes is characterized by uncontrolled hyperglycaemia, whereas GSD1 is characterized by severe fasting hypoglycaemia. Diabetes is due to a failure to suppress endogenous glucose production (EGP) in the postprandial state because of either a lack of insulin or insulin resistance. In contrast, GSD1 is characterized by a lack of EGP. However, both diseases share remarkably similar patterns in terms of pathophysiology such as the long-term progression of renal dysfunction and hepatic steatosis leading to renal failure and the development of hepatic tumours, respectively. Thus, much may be learned from considering the similarities between GSD1 and diabetes, especially in the metabolic pathways underlying nephropathy and fatty liver, and perhaps even more from their differences. In this review, the differences between diabetes and GSD1 are first highlighted, as both are characterized by alterations in EGP. The molecular pathways involved in liver pathologies, including steatosis, hepatomegaly (glycogenic hepatopathy) and the development of liver tumours are also compared. These pathologies are mainly due to the accumulation of lipids and/or glycogen in hepatocytes. Finally, the similar pathways leading to nephropathy in both diabetic and GSD1 patients are described. In conclusion, comparisons of these pathologies should lead to a better understanding of the crucial role of EGP in the control of gluc Continue reading >>
How Insulin And Glucagon Work
Insulin and glucagon are hormones that help regulate the levels of blood glucose, or sugar, in your body. Glucose, which comes from the food you eat, moves through your bloodstream to help fuel your body. Insulin and glucagon work together to balance your blood sugar levels, keeping them in the narrow range that your body requires. These hormones are like the yin and yang of blood glucose maintenance. Read on to learn more about how they function and what can happen when they don’t work well. Insulin and glucagon work in what’s called a negative feedback loop. During this process, one event triggers another, which triggers another, and so on, to keep your blood sugar levels balanced. How insulin works During digestion, foods that contain carbohydrates are converted into glucose. Most of this glucose is sent into your bloodstream, causing a rise in blood glucose levels. This increase in blood glucose signals your pancreas to produce insulin. The insulin tells cells throughout your body to take in glucose from your bloodstream. As the glucose moves into your cells, your blood glucose levels go down. Some cells use the glucose as energy. Other cells, such as in your liver and muscles, store any excess glucose as a substance called glycogen. Your body uses glycogen for fuel between meals. Read more: Simple vs. complex carbs » How glucagon works Glucagon works to counterbalance the actions of insulin. About four to six hours after you eat, the glucose levels in your blood decrease, triggering your pancreas to produce glucagon. This hormone signals your liver and muscle cells to change the stored glycogen back into glucose. These cells then release the glucose into your bloodstream so your other cells can use it for energy. This whole feedback loop with insulin and gluca Continue reading >>
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Glycogen And Glucagon: Managing Your Self-storage Unit
There’s an element of type 2 diabetes we don’t talk about much. We do talk a lot about carbohydrates, how digesting carbohydrate food makes blood glucose levels go up. We talk a lot about insulin too, how insulin normally stimulates certain cells to “absorb” glucose, bringing blood glucose levels back down, and how those cells become resistant to insulin in type 2 diabetes. We don’t often talk about what happens to the glucose that does get absorbed into cells, and how that story is an important part of diabetes too. And, it’s a story about your brain. Having some glucose available in your blood is essential to keep your brain operating – that’s why there is a “normal” blood glucose level. Your brain must have glucose to fuel its constant activity, and your brain uses a lot of glucose. So, you might wonder why your brain doesn’t run out of fuel unless you keep eating a steady stream of carbohydrate foods. That’s a story about your glucose self-storage unit – your liver. Much of the glucose that is absorbed into cells with the help of insulin is stored away. In liver cells, glucose is packed away in starch molecules called glycogen, and that makes your liver an extremely important storage unit. When blood glucose levels begin to drop, as your brain and muscles use the glucose fuel, a hormone called glucagon causes your liver to unpack glycogen and release glucose into your bloodstream. Glucagon causes blood glucose levels to rise, an opposite effect of insulin. In normal metabolism, insulin and glucagon work to keep blood glucose levels constant. With type 2 diabetes the glucagon system can lose its precision too, signaling for a release of glucose from your liver even when blood glucose levels are normal or already high. That premature release Continue reading >>
Diabetes And Exercise Capacity Linked To Glycogen In Muscle Tissue
Diabetes and exercise capacity linked to glycogen in muscle tissue Diabetes and exercise capacity linked to glycogen in muscle tissue Researchers show that a gene which converts glucose to glycogen in muscle tissue improves blood sugar levels and increases exercise capacity People with diabetes suffer complications from high blood sugar levels such as heart disease, stroke and hypertension. They generally also find it difficult to exercise. Now researchers have been able to find a link between the two. Recent testing with the gene gys1, which converts glucose to glycogen in muscle tissue, has shown that glycogen stored in the muscle is necessary for effective insulin function and increased capacity for exercise. These findings will lead to targeted pharmaceuticals that will lower blood sugar levels and increase the ability to exercise - significantly improving the health and quality of life for people with type 2 diabetes. Muscle metabolism responds to insulin, and if there is insulin resistance, sugar cant be taken up in the muscle tissue from the bloodstream and metabolised properly. This causes a build up of sugar in the bloodstream which will lead to type 2 diabetes. It also limits the ability for exercise, says supervising author, University of Melbourne Associate Professor Sof Andrikopoulos. Associate Professor Sof Andrikopoulos has been researching diabetes for 25 years and is the current President of the Australian Diabetes Society There are multiple mechanisms that cause insulin resistance but the role of glucose storage defects has not been clear. Our aim in this study was to examine the effects of muscle glucose metabolism and exercise capacity. Attempts in past studies have produced inconclusive data because the models used have not been optimal. Our sophis Continue reading >>
Muscle Glycogen In Juvenile Diabetes Before And During Treatment With Insulin
Muscle Glycogen in Juvenile Diabetes before and during Treatment with Insulin Nature volume 198, pages 9798 (06 April 1963) | Download Citation IT is well known that insulin stimulates the synthesis of glycogen in isolated muscle tissue from different animals. Insulin is considered to increase the permeability of the cell membrane to glucose. Direct action on the enzymes responsible for the synthesis of glycogen has also been observed. Low muscle glycogen has been found in animals with experimental diabetes. There are, however, few reports on the muscle glycogen content in normal and diabetic man. The glycogen content in muscle biopsy specimens from normal subjects was investigated by Hildes et al.13 and by Nichols4. Hildes et al.2,3 also determined the glycogen content in muscle tissue from patients with diabetes. No significant decrease was found in the muscle glycogen compared with the normal subjects. Their patients were adults who, in most cases, had been treated with insulin up to a few days before the examination. Continue reading >>
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