Glycogenolysis | Biochemistry | Britannica.com
Glycogenolysis, process by which glycogen , the primary carbohydrate stored in the liver and muscle cells of animals, is broken down into glucose to provide immediate energy and to maintain blood glucose levels during fasting . Glycogenolysis occurs primarily in the liver and is stimulated by the hormones glucagon and epinephrine (adrenaline). Various enzyme defects can prevent the release of energy by the normal breakdown of glycogen in muscles. Enzymes in which defects may occur include glucose-6-phosphatase (I); lysosomal x-1,4-glucosidase (II); debranching enzyme (III); branching enzyme (IV); muscle phosphorylase (V); liver phosphorylase (VI, VIII, IX, X); and muscle phosphofructokinase (VII). Enzyme defects that can give rise to other carbohydrate diseases include galactokinase (A1); galactose 1-phosphate UDP transferase (A2); fructokinase (B); aldolase (C); fructose 1,6-diphosphatase deficiency (D); pyruvate dehydrogenase complex (E); and pyruvate carboxylase (F). When blood glucose levels fall, as during fasting, there is an increase in glucagon secretion from the pancreas . That increase is accompanied by a concomitant decrease in insulin secretion, because the actions of insulin, which are aimed at increasing the storage of glucose in the form of glycogen in cells, oppose the actions of glucagon. Following secretion, glucagon travels to the liver, where it stimulates glycogenolysis. The vast majority of glucose that is released from glycogen comes from glucose-1-phosphate, which is formed when the enzyme glycogen phosphorylase catalyzes the breakdown of the glycogen polymer . In the liver, kidneys , and intestines , glucose-1-phosphate is converted (reversibly) to glucose-6-phosphate by the enzyme phosphoglucomutase. Those tissues also house the enzyme glucose Continue reading >>
Glycogen Biosynthesis; Glycogen Breakdown
Glycogen is a polymer of glucose (up to 120,000 glucose residues) and is a primary carbohydrate storage form in animals. The polymer is composed of units of glucose linked alpha(1-4) with branches occurring alpha(1-6) approximately every 8-12 residues. The end of the molecule containing a free carbon number one on glucose is called a reducing end. The other ends are all called non-reducing ends. Related polymers in plants include starch (alpha(1-4) polymers only) and amylopectin (alpha (1-6) branches every 24-30 residues). Glycogen provides an additional source of glucose besides that produced via gluconeogenesis. Because glycogen contains so many glucoses, it acts like a battery backup for the body, providing a quick source of glucose when needed and providing a place to store excess glucose when glucose concentrations in the blood rise. The branching of glycogen is an important feature of the molecule metabolically as well. Since glycogen is broken down from the "ends" of the molecule, more branches translate to more ends, and more glucose that can be released at once. Liver and skeletal muscle are primary sites in the body where glycogen is found. The primary advantagesof storage carbohydrates in animals are that 1) energy is not released from fat (other majorenergy storage form in animals) as fast as from glycogen; 2) glycolysis provides a mechanism of anaerobic metabolism (importantin muscle cells that cannot get oxygen as fast as needed); and 3) glycogen provides a means of maintaining glucose levels thatcannot be provided by fat. Breakdown of glycogen involves 1) release of glucose-1-phosphate (G1P), 2) rearranging the remaining glycogen (as necessary) to permit continued breakdown, and 3) conversion of G1P to G6P for further metabolism. Remember that G6P can be Continue reading >>
Physiologic Effects Of Insulin
Stand on a streetcorner and ask people if they know what insulin is, and many will reply, "Doesn't it have something to do with blood sugar?" Indeed, that is correct, but such a response is a bit like saying "Mozart? Wasn't he some kind of a musician?" Insulin is a key player in the control of intermediary metabolism, and the big picture is that it organizes the use of fuels for either storage or oxidation. Through these activities, insulin has profound effects on both carbohydrate and lipid metabolism, and significant influences on protein and mineral metabolism. Consequently, derangements in insulin signalling have widespread and devastating effects on many organs and tissues. The Insulin Receptor and Mechanism of Action Like the receptors for other protein hormones, the receptor for insulin is embedded in the plasma membrane. The insulin receptor is composed of two alpha subunits and two beta subunits linked by disulfide bonds. The alpha chains are entirely extracellular and house insulin binding domains, while the linked beta chains penetrate through the plasma membrane. The insulin receptor is a tyrosine kinase. In other words, it functions as an enzyme that transfers phosphate groups from ATP to tyrosine residues on intracellular target proteins. Binding of insulin to the alpha subunits causes the beta subunits to phosphorylate themselves (autophosphorylation), thus activating the catalytic activity of the receptor. The activated receptor then phosphorylates a number of intracellular proteins, which in turn alters their activity, thereby generating a biological response. Several intracellular proteins have been identified as phosphorylation substrates for the insulin receptor, the best-studied of which is insulin receptor substrate 1 or IRS-1. When IRS-1 is activa Continue reading >>
Hormonal Regulation Of Fuel Metabolism
Our discussions of metabolic regulation and hormone action now come together as we return to the hormonal regulation of blood glucose level. The minute-by-minute adjustments that keep the blood glucose level near 4.5 mM involve the combined actions of insulin, glucagon, and epinephrine on metabolic processes in many body tissues, but especially in liver, muscle, and adipose tissue. Insulin signals these tissues that the blood glucose concentration is higher than necessary; as a result, the excess glucose is taken up from the blood into cells and converted to storage compounds, glycogen and triacylglycerols. Glucagon carries the message that blood glucose is too low, and the tissues respond by producing glucose through glycogen breakdown and gluconeogenesis and by oxidizing fats to reduce the use of glucose. Epinephrine is released into the blood to prepare the muscles, lungs, and heart for a burst of activity. Insulin, glucagon, and epinephrine are the primary determinants of the metabolic activities of muscle, liver, and adipose tissue. Epinephrine Signals Impending Activity When an animal is confronted with a stressful situation that requires increased activity-fighting or fleeing, in the extreme case-neuronal signals from the brain trigger the release of epinephrine and norepinephrine from the adrenal medulla. Both hormones increase the rate and strength of the heartbeat and raise the blood pressure, thereby increasing the flow of 02 and fuels to the tissues, and dilate the respiratory passages, facilitating the uptake of O2 (Table 22-3). In its effects on metabolism, epinephrine acts primarily on muscle, adipose tissue, and liver. It activates glycogen phosphorylase and inactivates glycogen synthase (by cAMP-dependent phosphorylation of the enzymes; see Fig. 14-18 a Continue reading >>
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 >>
- Caffeinated and Decaffeinated Coffee Consumption and Risk of Type 2 Diabetes: A Systematic Review and a Dose-Response Meta-analysis
- Insulin, glucagon and somatostatin stores in the pancreas of subjects with type-2 diabetes and their lean and obese non-diabetic controls
- St. Luke’s Spotlights Critical Link Between Type 2 Diabetes and Heart Disease in Partnership with Boehringer Ingelheim and Eli Lilly and Company
Bc: Practice Exam 4 The Real Deal
Regulation: Fructose 2,6-bisphosphate and ratio of [ATP]/[AMP][ADP] What is the first enzyme in glycolysis in the muscle? What reaction is catalyzed by this enzyme? Is this reaction reversible? What is the isozyme of this enzyme in the liver? Hexokinase catalyzes Glucose + ATP -->Glucose-6-P + ADP The isozyme of hexokinase that is found in the liver is glucokinase What is the enzyme that transfers a phosphate group to fructose-6-phosphate in glycolysis in the liver? What reaction is catalyzed by this enzyme? Is this reaction reversible? Fructose-6-bisphosphate + ATP -> Fructose-1,6-bisphosphate + ADP OTHER: PFK-1 is the committed step in glycolysis and acts as the control enzyme for glycolysis. It is controlled by Fructose 2,6-bisphosphate and ratio of [ATP]/[AMP][ADP] What is the enzyme that produces NADH from a triose phosphate in the glycolytic pathway? What reaction does this enzyme catalyze? Is the reaction reversible? Glyceraldehyde-3-phosphate dehydrogenase catalyzes: Glyceraldehyde-3-P + Pi + NAD+ <-> 1,3 Bisphosphoglycerate + NADH + H+ OTHER: Glyceraldehyde 3-phosphate is formed when fructors 1,6-bisphosphate is cleaved to two triose phosphates by aldolase. DHAP is then isomerized to a second glyceraldehyde 3-phosphate by triose phosphate isomerase. So net, 2 glyceraldehyde 3-phosphates are formed from fructose 1,6-bisphosphate. What is the enzyme that produces ATP from 1,3 bisphosphoglycerate- in the glycolytic pathway? What reaction does this enzyme catalyze? Is the reaction reversible? Is this substrate level phosphorylation? 1,3-bisphosphoglycerate + ADP <-> 3-phosphoglycerate + ATP What is the enzyme that produces ATP from phosphoenolpyruvate in the glycolytic pathway? What reaction sdoes this enzyme catalyze? Is the reaction reversible? Phosphoenolpyruva Continue reading >>
Glucagon - An Overview | Sciencedirect Topics
Glucagon is a 29 amino acids polypeptide hormone of high molecular weight (3,483 Dalton), secreted by the alpha cells in the pancreatic islets. Min Kyun Park, in Handbook of Hormones , 2016 Glucagon is a linear peptide hormone of 29 amino acids secreted from cells of the pancreas. Glucagon shares the same precursor molecule, proglucagon, with GLP-1 and GLP-2. By tissue-specific posttranslational processing, glucagon is secreted from pancreatic cells whereas GLP-1 and GLP-2 are secreted from intestinal L cells. All these peptides have considerable sequence homology and form a subfamily within the secretin family. Among the members of the glucagon subfamily, the glucagon sequence is most highly conserved throughout vertebrates. Glucagon is the principal hyperglycemic hormone, and acts as a counterbalancing hormone to insulin. Glucagon generally elevates the level of blood glucose by promoting gluconeogenesis and glycogenolysis. Glucagon has the greatest effect on the liver although it affects many different organs in the body, such as adipose tissue, pancreas, brain, and kidney. Nori Geary, in Handbook of Biologically Active Peptides (Second Edition) , 2013 Glucagon is a peptide hormone synthesized and secreted by the pancreatic -cells. The glucagon receptor is a G-protein-coupled, seven-transmembrane domain receptor and is expressed in the liver, pancreatic islets, heart, adipose tissue, and, less abundantly, in other tissues. Glucagon is secreted when blood glucose concentrations decrease, and it rapidly increases hepatic glucose production, through glycogenolysis for the first approximately 3h and both glycogenolysis and gluconeogenesis thereafter. Glucagon has several effects on lipid metabolism, notably stimulation of hepatic fatty acid oxidation and ketone synthesi Continue reading >>
- How insulin and glucagon work to regulate blood sugar levels
- Insulin, glucagon and somatostatin stores in the pancreas of subjects with type-2 diabetes and their lean and obese non-diabetic controls
- Effects of Insulin Plus Glucagon-Like Peptide-1 Receptor Agonists (GLP-1RAs) in Treating Type 1 Diabetes Mellitus: A Systematic Review and Meta-Analysis
Cell Signalling: 4.1 Glucose Metabolism - Openlearn - Open University - S377_4
Free statement of participation on completion of these courses. Anyone can learn for free on OpenLearn, but signing-up will give you access to your personal learning profile and record of achievements that you earn while you study. Anyone can learn for free on OpenLearn but creating an account lets you set up a personal learning profile which tracks your course progress and gives you access to Statements of Participation and digital badges you earn along the way. Sign-up now! Start this free course now. Just create an account and sign in. Enrol and complete the course for a free statement of participation or digital badge if available. 4 Glucose metabolism: an example of integration of signalling pathways We are now in a position to draw together the major concepts and components of signalling, and show how they operate in one well-understood system, namely the regulation of the storage or release of glucose in the human body. From this, you will be able to recognize archetypal pathways represented in specific examples, you will be able to appreciate how the same basic pathways can be stimulated by different hormones in different tissues, and you will see how opposing hormones activate separate pathways that affect the same targets but in opposite ways. Following a meal, insulin is released into the bloodstream by pancreatic cells. The overall systemic effects of insulin are to increase uptake of blood glucose into cells, and to promote its storage as glycogen in muscle and liver cells. (Note that glycogen is a polysaccharide consisting of repeated units of glucose used for shortterm energy storage by animal cells.) A rise in the concentration of blood glucose, such as that following the consumption of food, stimulates insulin production, which signals through the insu Continue reading >>
Regulation Of Glucose Metabolism From A Liver-centric Perspective
Glucose homeostasis is tightly regulated to meet the energy requirements of the vital organs and maintain an individual’s health. The liver has a major role in the control of glucose homeostasis by controlling various pathways of glucose metabolism, including glycogenesis, glycogenolysis, glycolysis and gluconeogenesis. Both the acute and chronic regulation of the enzymes involved in the pathways are required for the proper functioning of these complex interwoven systems. Allosteric control by various metabolic intermediates, as well as post-translational modifications of these metabolic enzymes constitute the acute control of these pathways, and the controlled expression of the genes encoding these enzymes is critical in mediating the longer-term regulation of these metabolic pathways. Notably, several key transcription factors are shown to be involved in the control of glucose metabolism including glycolysis and gluconeogenesis in the liver. In this review, we would like to illustrate the current understanding of glucose metabolism, with an emphasis on the transcription factors and their regulators that are involved in the chronic control of glucose homeostasis. Overview of glucose metabolism in the liver Under feeding conditions, dietary carbohydrates are digested and processed by various glucosidases in the digestive tract, and the resultant monosaccharides, mainly hexose glucose, are transported into various tissues as a primary fuel for ATP generation.1 In most mammalian tissues, the catabolism of glucose into pyruvate, termed glycolysis, is preserved as a major pathway in eliciting ATP. In tissues with abundant mitochondria, cytosolic pyruvate is transported into the mitochondrial matrix, converted to acetyl-CoA by pyruvate dehydrogenase complex, and incorporat Continue reading >>
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 >>
- Insulin, glucagon and somatostatin stores in the pancreas of subjects with type-2 diabetes and their lean and obese non-diabetic controls
- How insulin and glucagon work to regulate blood sugar levels
- Effects of Insulin Plus Glucagon-Like Peptide-1 Receptor Agonists (GLP-1RAs) in Treating Type 1 Diabetes Mellitus: A Systematic Review and Meta-Analysis
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 >>
Chapter 21
Sort glycolysis pathway for the first stages of carbohydrate degradation; releases and stores very little (2.2%) of the potential energy of glucose but the pathway serves as a source of biosynthetic building blocks. Also modifies carbohydrates in such a way that other pathways are able to release as ugh as 40% of the potential energy. Anaerobic process, requires no oxygen. The enzymatic pathway that converts a glucose molecule into 2 molecules of pyruvate, generates a net energy yield of 2 ATP and 2 NADH. The first stage of carbohydrate metabolism. C₆H₁₂O₆ (glucose)+2ADP+2Pi +2NAD⁺→2 C₃H₃O₃(pyruvate) +2 ADP+2NADH+2H₂O catabolism; 3 stages of degradation of fuel molecules. energy release is stored as chemical bond energy (or heat). First stage is digestion (hydrolysis) of dietary macromolecules in stomach and intestine. Polysaccharides are hydrolyzed to monosaccharides; proteins are degraded to amino acids; triglycerides are broken down into fatty acids and glycerol. The small molecules produced by digestion are taken into the cells lining the intestine by active or passive transport. The second stage: monosaccharides, amino acids, fatty acids and glycerol are converted by metabolic reactions into molecules that can be completely oxidized. Often they are converted into acetyl CoA. Third stage: the two carbon acetyl group of acetyl CoA is completely oxidized by the reactions of the citric acid cycle. The energy of the electrons harvested in these oxidation reactions is used to make ATP. ATP adenosine triphosphate, the molecule used for the storage of chemical energy, the universal energy currency; a nucleotide composed of the nitrogenous base adenine bonded in N-glycosidic linkage to the sugar ribose. A high-energy compound because the phosphoanhydride Continue reading >>
Glucagon
Glucagon has a major role in maintaining normal concentrations of glucose in blood, and is often described as having the opposite effect of insulin. That is, glucagon has the effect of increasing blood glucose levels. Glucagon is a linear peptide of 29 amino acids. Its primary sequence is almost perfectly conserved among vertebrates, and it is structurally related to the secretin family of peptide hormones. Glucagon is synthesized as proglucagon and proteolytically processed to yield glucagon within alpha cells of the pancreatic islets. Proglucagon is also expressed within the intestinal tract, where it is processed not into glucagon, but to a family of glucagon-like peptides (enteroglucagon). Physiologic Effects of Glucagon The major effect of glucagon is to stimulate an increase in blood concentration of glucose. As discussed previously, the brain in particular has an absolute dependence on glucose as a fuel, because neurons cannot utilize alternative energy sources like fatty acids to any significant extent. When blood levels of glucose begin to fall below the normal range, it is imperative to find and pump additional glucose into blood. Glucagon exerts control over two pivotal metabolic pathways within the liver, leading that organ to dispense glucose to the rest of the body: Glucagon stimulates breakdown of glycogen stored in the liver. When blood glucose levels are high, large amounts of glucose are taken up by the liver. Under the influence of insulin, much of this glucose is stored in the form of glycogen. Later, when blood glucose levels begin to fall, glucagon is secreted and acts on hepatocytes to activate the enzymes that depolymerize glycogen and release glucose. Glucagon activates hepatic gluconeogenesis. Gluconeogenesis is the pathway by which non-hexose Continue reading >>
- How insulin and glucagon work to regulate blood sugar levels
- Insulin, glucagon and somatostatin stores in the pancreas of subjects with type-2 diabetes and their lean and obese non-diabetic controls
- Effects of Insulin Plus Glucagon-Like Peptide-1 Receptor Agonists (GLP-1RAs) in Treating Type 1 Diabetes Mellitus: A Systematic Review and Meta-Analysis
Insulin And Glucagon
Acrobat PDF file can be downloaded here. The islets of Langerhans The pancreatic Islets of Langerhans are the sites of production of insulin, glucagon and somatostatin. The figure below shows an immunofluorescence image in which antibodies specific for these hormones have been coupled to differing fluorescence markers. We can therefore identify those cells that produce each of these three peptide hormones. You can see that most of the tissue, around 80 %, is comprised of the insulin-secreting red-colored beta cells (ß-cells). The green cells are the α-cells (alpha cells) which produce glucagon. We see also some blue cells; these are the somatostatin secreting γ-cells (gamma cells). Note that all of these differing cells are in close proximity with one another. While they primarily produce hormones to be circulated in blood (endocrine effects), they also have marked paracrine effects. That is, the secretion products of each cell type exert actions on adjacent cells within the Islet. An Introduction to secretion of insulin and glucagon The nutrient-regulated control of the release of these hormones manages tissue metabolism and the blood levels of glucose, fatty acids, triglycerides and amino acids. They are responsible for homeostasis; the minute-to-minute regulation of the body's integrated metabolism and, thereby, stabilize our inner milieu. The mechanisms involved are extremely complex. Modern medical treatment of diabetes (rapidly becoming "public enemy number one") is based on insight into these mechanisms, some of which are not completely understood. I will attempt to give an introduction to this complicated biological picture in the following section. Somewhat deeper insight will come later. The Basics: secretion Let us begin with two extremely simplified figur Continue reading >>
- Insulin, glucagon and somatostatin stores in the pancreas of subjects with type-2 diabetes and their lean and obese non-diabetic controls
- How insulin and glucagon work to regulate blood sugar levels
- Effects of Insulin Plus Glucagon-Like Peptide-1 Receptor Agonists (GLP-1RAs) in Treating Type 1 Diabetes Mellitus: A Systematic Review and Meta-Analysis
Role Of Insulin And Other Related Hormones In Energy Metabolisma Review
Role of insulin and other related hormones in energy metabolismA review Accepted author version posted online: 05 Dec 2016 This review aims to review hormones mechanisms that affect fuel metabolism and are involved in regulation of blood glucose, dealing insulin and glucagon hormones, and includes other related hormones, which increase the blood glucose level: growth hormone, thyroxine, cortisol and adrenaline. However, this review focuses on insulin and glucagon hormones as widely, and on other related hormones as briefly. Insulin plays an important role in a decrease blood glucose concentration in hyperglycemic response to emergencies or stress by an increasing rate of glucose transport into the muscle cell of animals and facilitating glucose utilization and by maintaining normal blood glucose concentrations. Insulin is a hypoglycemic hormone, promoting the storage of metabolites in peripheral stores. While, glucagon is a hyperglycemic hormone, stimulates gluconeogenesisat the expense of peripheral stores by enhancing the hepatic removal of certain glucose precursors and stimulates lipolysis; however, it has not influence on peripheral protein stores directly. Insulin, glucagon and other related hormones regulate blood glucose concentrations and act on movement of glucose, amino acids and possibly volatile fatty acids between the liver and peripheral tissues directly. In another way, glucagon may be considered catabolic and insulin anabolic. In conclusion, insulin promotes body gain by stimulating protein and fat synthesis, growth hormone increases protein retention and decrease fat deposition. Growth hormone can alter the sensitivity of tissues to insulin. In contrast, catabolic hormones such as glucagon, epinephrine and glucocorticoids are provided for mobilization Continue reading >>
