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How Does Insulin Affect Protein Synthesis?

Roles Of Insulin And Amino Acids In The Regulation Of Protein Synthesis In The Neonate

Roles Of Insulin And Amino Acids In The Regulation Of Protein Synthesis In The Neonate

Roles of Insulin and Amino Acids in the Regulation of Protein Synthesis in the Neonate United States Department of Agriculture, Agricultural Research Service, Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030 To whom correspondence and reprint requests should be addressed: USDA/ARS Children's Nutrition Research Center, Baylor College of Medicine, 1100 Bates St., Houston, TX 77030. Search for other works by this author on: United States Department of Agriculture, Agricultural Research Service, Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030 Search for other works by this author on: United States Department of Agriculture, Agricultural Research Service, Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030 Search for other works by this author on: United States Department of Agriculture, Agricultural Research Service, Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030 Search for other works by this author on: United States Department of Agriculture, Agricultural Research Service, Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030 Search for other works by this author on: The Journal of Nutrition, Volume 128, Issue 2, 1 February 1998, Pages 347S350S, Teresa A. Davis, Douglas G. Burrin, Marta L. Fiorotto, Peter J. Reeds, Farook Jahoor; Roles of Insulin and Amino Acids in the Regulation of Protein Synthesis in the Neonate, The Journal of Nutrition, Volume 128, Issue 2, 1 February 1998, Pages 347S350S, Neonates deposit protein at a very high rate and efficiently utilize dietary amino Continue reading >>

Effect Of Insulin On Human Skeletal Muscle Protein Synthesis Is Modulated By Insulin-induced Changes In Muscle Blood Flow And Amino Acid Availability

Effect Of Insulin On Human Skeletal Muscle Protein Synthesis Is Modulated By Insulin-induced Changes In Muscle Blood Flow And Amino Acid Availability

Go to: Insulin promotes muscle anabolism, but it is still unclear whether it stimulates muscle protein synthesis in humans. We hypothesized that insulin can increase muscle protein synthesis only if it increases muscle amino acid availability. We measured muscle protein and amino acid metabolism using stable-isotope methodologies in 19 young healthy subjects at baseline and during insulin infusion in one leg at low (LD, 0.05), intermediate (ID, 0.15), or high (HD, 0.30 mU·min−1·100 ml−1) doses. Insulin was infused locally to induce muscle hyperinsulinemia within the physiological range while minimizing the systemic effects. Protein and amino acid kinetics across the leg were assessed using stable isotopes and muscle biopsies. The LD did not affect phenylalanine delivery to the muscle (−9 ± 18% change over baseline), muscle protein synthesis (16 ± 26%), breakdown, or net balance. The ID increased (P < 0.05) phenylalanine delivery (+63 ± 38%), muscle protein synthesis (+157 ± 54%), and net protein balance, with no change in breakdown. The HD did not change phenylalanine delivery (+12 ± 11%) or muscle protein synthesis (+9 ± 19%), and reduced muscle protein breakdown (−17 ± 15%), thus improving net muscle protein balance but to a lesser degree than the ID. Changes in muscle protein synthesis were strongly associated with changes in muscle blood flow and phenylalanine delivery and availability. In conclusion, physiological hyperinsulinemia promotes muscle protein synthesis as long as it concomitantly increases muscle blood flow, amino acid delivery and availability. Continue reading >>

Regulation Of Protein Synthesis By Insulin.

Regulation Of Protein Synthesis By Insulin.

Biochem Soc Trans. 2006 Apr;34(Pt 2):213-6. Regulation of protein synthesis by insulin. Department of Biochemistry and Molecular Biology, University of British Columbia, 2350 Health Sciences Mall, Vancouver, Canada V6T 1Z3. [email protected] Insulin rapidly activates protein synthesis by activating components of the translational machinery including eIFs (eukaryotic initiation factors) and eEFs (eukaryotic elongation factors). In the long term, insulin also increases the cellular content of ribosomes to augment the capacity for protein synthesis. The rapid activation of protein synthesis by insulin is mediated primarily through phosphoinositide 3-kinase. This involves the activation of PKB (protein kinase B). In one case, PKB acts to phosphorylate and inactivate glycogen synthase kinase 3, which in turn phosphorylates and inhibits eIF2B. Insulin elicits the dephosphorylation and activation of eIF2B. Since eIF2B is required for recycling of eIF2, a factor required for all cytoplasmic translation initiation events, this will contribute to overall activation of protein synthesis. PKB also phosphorylates the TSC1 (tuberous sclerosis complex 1)-TSC2 complex to relieve its inhibitory action on the mTOR (mammalian target of rapamycin). Inhibition of mTOR by rapamycin markedly impairs insulin-activated protein synthesis. mTOR controls translation initiation and elongation. The cap-binding factor eIF4E can be sequestered in inactive complexes by 4E-BP1 (eIF4E-binding protein 1). Insulin elicits phosphorylation of 4E-BP1 and its release from eIF4E, allowing eIF4E to form initiation factor complexes. Insulin induces dephosphorylation and activation of eEF2 to accelerate elongation. Both effects are blocked by rapamycin. Insulin inactivates eEF2 kinase by increasing its phos Continue reading >>

Insulin And Protein Metabolism

Insulin And Protein Metabolism

The present status of protein synthesis within cells has been outlined. Protein is formed in the absence of insulin; the net formation of protein is accelerated by insulin. The effects of insulin on protein metabolism take place independently of the transport of glucose or amino acids into the cell; of glycogen synthesis; and of the stimulation of high energy phosphate formation. In the case of protein metabolism, as in certain studies on the pathways of glucose and fat metabolism, these observations reveal striking intracellular effects of insulin in many tissues. Within most tissues the effect of insulin appears to find expression predominantly at the microsomal level. Incidentally, other hormones which affect protein metabolism such as growth or sex hormones appear to act at the microsomes. The fact that insulin exerts effects on protein metabolism at other intracellular sites as well as the above independent effects leads one to agree that its action consists of a stimulation of multiple, seemingly unrelated, metabolic events. The fact that an immediate effect of insulin on protein synthesis is independent of the immediate need for extracellular glucose or amino acids does not mean that the sustained functioning of cells is likewise independent. The biochemist is fully aware of metabolic defects in diabetes which are not altered by insulin in vitro, but which demand varying periods of pretreatment of the animal. It is also known that in diabetes some proteins (enzymes) may be deficient while others may be produced in excess in the absence of insulin. It is suggested that the physician desires at least two kinds of relation between these fundamental studies and his patients. One is the possible relation of a deficiency of insulin action to pathological processes in t Continue reading >>

The Muscle-building Messenger: Your Complete Guide To Insulin

The Muscle-building Messenger: Your Complete Guide To Insulin

Years ago, insulin was only discussed in reference to diabetes. Insulin is the hormone that drives glucose out of the bloodstream and into cells, and diabetes is the loss of the ability to control blood glucose levels. Yet insulin is so much more than a hormone that controls glucose. For one, it's highly anabolic, which means it's critical for building muscle. Insulin also has a dark side, because it can increase fat storage. The challenge is to learn how to spike insulin to optimally recover from workouts and grow, while also blunting it to stay lean. Do you know all the facts about insulin and how to use it to your advantage? Don't be so sure. If not, my insulin guide will teach you how. Insulin And Muscle Insulin is actually a protein, and it is produced and released by the pancreas whenever you eat carbs, protein, or both. (That is, if the pancreas is working properly). Yet unlike the proteins that are the physical building blocks of muscle, this is a functional protein, much like growth hormone. Like all other proteins, insulin is a chain of amino acids strung together. But the way this protein chain is folded makes it act more like a signaling mechanism than a building block. From the pancreas, insulin enters the blood stream and travels to various tissues, including muscle tissue. The muscle fibers (or cells) are lined with insulin receptors, similar to a docking station. Once the insulin molecule docks onto the receptor, it signals the muscle cell to open up gates. This allows allow glucose, amino acids, and creatine to enter the muscles. This process is a major reason why insulin is so important for building muscle. Another reason is that when insulin docks onto the muscle cells, it instigates biochemical reactions in the muscle that increase protein synthesis, Continue reading >>

All About Insulin

All About Insulin

What is insulin? Insulin is a peptide hormone secreted by the pancreas in response to increases in blood sugar, usually following a meal. However, you don’t have to eat a meal to secrete insulin. In fact, the pancreas always secretes a low level of insulin. After a meal, the amount of insulin secreted into the blood increases as blood sugar rises. Similarly, as blood sugar falls, insulin secretion by the pancreas decreases. Insulin thus acts as an “anabolic” or storage hormone. In fact, many have called insulin “the most anabolic hormone”. Once insulin is in the blood, it shuttles glucose (carbohydrates), amino acids, and blood fats into the cells of the body. If these nutrients are shuttled primarily into muscle cells, then the muscles grow and body fat is managed. If these nutrients are shuttled primarily into fat cells, then muscle mass is unchanged and body fat is increased. Insulin’s main actions Rapid (seconds) Increases transport of glucose, amino acids (among the amino acids most strongly transported are valine, leucine, isoleucine, tyrosine and phenylalanine), and potassium into insulin-sensitive cells Intermediate (minutes) Stimulates protein synthesis (insulin increases the formation of new proteins) Activates enzymes that store glycogen Inhibits protein degradation Delayed (hours) Increases proteins and other enzymes for fat storage Why is insulin so important? The pancreas releases insulin whenever we consume food. In response to insulin, cells take in sugar from the bloodstream. This ultimately lowers high blood sugar levels back to a normal range. Like all hormones, insulin has important functions, and an optimal level. Without enough insulin, you lose all of the anabolic effects, since there is not enough insulin to transport or store energy Continue reading >>

Role Of Insulin In The Regulation Of Human Skeletal Muscle Protein Synthesis And Breakdown: A Systematic Review And Meta-analysis

Role Of Insulin In The Regulation Of Human Skeletal Muscle Protein Synthesis And Breakdown: A Systematic Review And Meta-analysis

Abstract We aimed to investigate the role of insulin in regulating human skeletal muscle metabolism in health and diabetes. Methods We conducted a systematic review and meta-analysis of published data that examined changes in skeletal muscle protein synthesis (MPS) and/or muscle protein breakdown (MPB) in response to insulin infusion. Random-effects models were used to calculate weighted mean differences (WMDs), 95% CIs and corresponding p values. Both MPS and MPB are reported in units of nmol (100 ml leg vol.)−1 min−1. A total of 104 articles were examined in detail. Of these, 44 and 25 studies (including a total of 173 individuals) were included in the systematic review and meta-analysis, respectively. In the overall estimate, insulin did not affect MPS (WMD 3.90 [95% CI −0.74, 8.55], p = 0.71), but significantly reduced MPB (WMD −15.46 [95% CI −19.74, −11.18], p < 0.001). Overall, insulin significantly increased net balance protein acquisition (WMD 20.09 [95% CI 15.93, 24.26], p < 0.001). Subgroup analysis of the effect of insulin on MPS according to amino acid (AA) delivery was performed using meta-regression analysis. The estimate size (WMD) was significantly different between subgroups based on AA availability (p = 0.001). An increase in MPS was observed when AA availability increased (WMD 13.44 [95% CI 4.07, 22.81], p < 0.01), but not when AA availability was reduced or unchanged. In individuals with diabetes and in the presence of maintained delivery of AA, there was a significant reduction in MPS in response to insulin (WMD −6.67 [95% CI −12.29, −0.66], p < 0.05). This study demonstrates the complex role of insulin in regulating skeletal muscle metabolism. Insulin appears to have a permissive role in MPS in the presence of elevated AAs, and pl Continue reading >>

3. Amino Acids Stimulate The Release Of Both Glucagon And Insulin

3. Amino Acids Stimulate The Release Of Both Glucagon And Insulin

In a person without diabetes, a rise in blood amino acid concentration (the result of protein metabolism) stimulates the secretion of both glucagon and insulin, so their blood sugar remains stable. But in people with diabetes, the release of glucagon without insulin or with impaired insulin response can cause our blood sugar to rise precipitously several hours after a meal high in protein. The insulin is secreted to stimulate protein synthesis--the uptake of amino acids into muscle cells--making them less available for gluconeogenesis. The glucagon is secreted to stimulate the uptake of amino acids into the cells of the liver for gluconeogenesis. So why are these two hormones battling for opposing uses of the same amino acids? Isn't that non-productive? Actually, the phenomenon serves an important purpose. As you probably know, insulin lowers the blood sugar, while glucagon raises it. In the non-diabetic state, the release of these two opposing hormones ensures that the amino acids are used for protein synthesis (because of the extra insulin) but the blood sugar doesn't drop to dangerously low levels, even if the meal was low in carbohydrate. As a result, blood glucose concentration remains reasonably stable during protein metabolism. The insulin and glucagon essentially cancel each other out in terms of their effect on blood glucose, while the insulin is still able to promote protein synthesis. But in people with diabetes, as I mentioned earlier, the release of glucagon without insulin or with impaired insulin response can cause our blood sugar to rise precipitously several hours after a meal high in protein. This is due not only to the glucagon's directly raising the blood sugar, but also to the fact that in the absence of insulin it increases the amount of the amino Continue reading >>

Effect Of Insulin On Protein Synthesis And Degradation In Skeletal Muscle After Exercise.

Effect Of Insulin On Protein Synthesis And Degradation In Skeletal Muscle After Exercise.

Am J Physiol. 1990 Jan;258(1 Pt 1):E92-7. Effect of insulin on protein synthesis and degradation in skeletal muscle after exercise. Department of Exercise Science and Physical Education, University of Iowa, Iowa City 52242. This study examined whether insulin stimulation of protein synthesis and inhibition of protein degradation is enhanced after exercise. The isolated perfused rat hindquarter preparation was used to evaluate net protein breakdown, myofibrillar protein degradation, and protein synthesis. Thirty minutes after treadmill exercise of high and moderate intensity, rates of tyrosine release were increased by 58 and 25%, respectively. Insulin at 75 microU/ml had no effect on these increases after intense exercise; however, 20,000 microU/ml of insulin totally inhibited this increase. Cycloheximide increased the tyrosine release in both control and exercised rat muscle. It also abolished the difference between them, suggesting that the increase in tyrosine release after exercise is caused by an inhibition of protein synthesis. Phenylalanine incorporation into protein was marginally depressed (22%, P = NS) in the white gastrocnemius muscle after intense exercise. Insulin at 200 microU/ml stimulated protein synthesis in these rats, but no more than it did in a nonexercised control group. Failure to observe a greater effect of insulin on protein metabolism was also noted when rat muscle was studied 150 min after intense exercise and after contractions induced by electrical stimulation of the sciatic nerve. These findings suggest that after exercise or electrically induced contractions the enhanced ability of insulin to stimulate hexose and amino acid transport is not paralleled by an increase in its ability to stimulate protein synthesis or inhibit protein degradat Continue reading >>

Effect Of Insulin On Human Skeletal Muscle Protein Synthesis Is Modulated By Insulin-induced Changes In Muscle Blood Flow And Amino Acid Availability

Effect Of Insulin On Human Skeletal Muscle Protein Synthesis Is Modulated By Insulin-induced Changes In Muscle Blood Flow And Amino Acid Availability

Effect of insulin on human skeletal muscle protein synthesis is modulated by insulin-induced changes in muscle blood flow and amino acid availability Insulin promotes muscle anabolism, but it is still unclear whether it stimulates muscle protein synthesis in humans. We hypothesized that insulin can increase muscle protein synthesis only if it increases muscle amino acid availability. We measured muscle protein and amino acid metabolism using stable-isotope methodologies in 19 young healthy subjects at baseline and during insulin infusion in one leg at low (LD, 0.05), intermediate (ID, 0.15), or high (HD, 0.30 mUmin1100 ml1) doses. Insulin was infused locally to induce muscle hyperinsulinemia within the physiological range while minimizing the systemic effects. Protein and amino acid kinetics across the leg were assessed using stable isotopes and muscle biopsies. The LD did not affect phenylalanine delivery to the muscle (9 18% change over baseline), muscle protein synthesis (16 26%), breakdown, or net balance. The ID increased (P < 0.05) phenylalanine delivery (+63 38%), muscle protein synthesis (+157 54%), and net protein balance, with no change in breakdown. The HD did not change phenylalanine delivery (+12 11%) or muscle protein synthesis (+9 19%), and reduced muscle protein breakdown (17 15%), thus improving net muscle protein balance but to a lesser degree than the ID. Changes in muscle protein synthesis were strongly associated with changes in muscle blood flow and phenylalanine delivery and availability. In conclusion, physiological hyperinsulinemia promotes muscle protein synthesis as long as it concomitantly increases muscle blood flow, amino acid delivery and availability. insulin is a potent anabolic stimulus for muscle proteins. Insulin deficiency leads to Continue reading >>

Insulin Action On Protein Metabolism

Insulin Action On Protein Metabolism

Summary On the basis of the preceding observations, the following sequence of events can be postulated during insulin deficiency or excess. The main feature of insulin deficiency is the disruption of protein balance in muscle that rapidly leads to emaciation and wasting. Muscle protein degradation is greatly enhanced while increased amino acid availability maintains protein synthesis. In splanchnic tissues, both degradation and synthesis are increased but with an altered pattern, so that the levels of some proteins are increased (e.g. proteins of the acute-phase response), while those of others are decreased (e.g. albumin). As a result, intracellular protein content in liver is maintained but secretion of plasma proteins is abnormal. In healthy subjects, an acute increase in insulin concentration, as occurs after a meal, leads to a rapid suppression of protein breakdown in the splanchnic area. If hyperinsulinaemia is not supported by an exogenous amino acid supply, as might occur during a protein-free meal or experimentally during euglycaemic hyperinsulinaemic clamping, the plasma as well as muscle free amino acid concentration drops, owing to reduced splanchnic release. With reduced amino acid availability, insulin is not anabolic in muscle. If amino acid concentrations are maintained at normal or high levels, e.g. following a mixed meal, a net protein deposition in muscle may occur, primarily because of a stimulation of synthesis and possibly owing to inhibition of breakdown. Continue reading >>

Effect Of Insulin On Protein Synthesis

Effect Of Insulin On Protein Synthesis

The mechanism by which insulin controls protein metabolism is not fully understood. Insulin stimulates protein synthesis; it also enhances transport of some amino acids, but the latter action does not appear to be sufficient explanation of the increase in synthesis. The various actions seem to be independent of effects on glucose metabolism. In diabetic muscle there are fewer than normal polysomes, and insulin rapidly enhances attachment of monomers to messenger-RNA. Insulin also increases the effectiveness of cell sap in catalyzing protein synthesis by ribosomal systems. The way in which the hormone may affect either initiation or peptide synthesis is not known. Experiments are reported bearing on whether availability of amino acids could be a mechanism by which effects of insulin are mediated. Activity of liver and muscle soluble fractions declines on fasting and, for the latter tissue, possibly also on a low protein diet. Sap from fasting animals allows a much smaller response of isolated ribosomes to added amino acids. Availability of glutamate in amino acid mixtures may be of special importance. However, insulin can influence the activity of the sap fraction of diaphragm muscle during incubation without the presence of amino acids in the medium. Understanding of what mechanisms are involved will depend on resolution of the critical sap factors. Continue reading >>

Insulin

Insulin

Insulin is a hormone secreted by the beta cells of pancreas, and is important in the regulation of carbohydrate and fat metabolism in the body. Marie Boran Discovery: The discovery of Insulin by Banting and Best in 1922 was a major breakthrough in endocrinology. Chemistry: Insulin is made up of 2 polypeptide chains linked by disulphide linkages. Synthesis: Insulin is synthesized as preprohormone having molecular weight of 11500. It is converted into proinsulin in endoplasmic reticulum with molecular weight of 9000, and finally into insulin in Golgi apparatus having molecular weight of 5808. Metabolism Insulin has a plasma half life of 6 minutes before being broken down catalyzed by the enzyme Insulinase. Insulin receptor Insulin receptor is made up of 4 subunits which are linked through disulphide linkages. There are 2 alpha and 2 beta subunits. The 2 alpha subunits are located outside cell membrane and have the insulin binding site. The 2 beta subunits penetrate cell membrane. Mechanism of Action of Insulin Mechanism of action can be well understood considering the following points: 1. Binding of insulin with alpha subunit 2. Autophosphorylation of alpha subunit 3. Activation of tyrosine kinase 4. Phosphorylation of intracellular enzymes Metabolic effects The metabolic effects of insulin include: 1. Glucose uptake (glucose transport proteins) 2. Amino acid, potassium & phosphate uptake 3. Phosphorylation of enzymes (10-15 min) 4. DNA transcription & RNA translation (hours-days) Effects of Insulin: Insulin affects the following: 1. Carbohydrate metabolism Insulin has profound effects on the following: a. Skeletal muscles: Insulin promotes glucose uptake and metabolism by the skeletal muscles. The muscles use fats in the resting state of the body as the membranes are imp Continue reading >>

Does Insulin Stimulate Muscle Growth?

Does Insulin Stimulate Muscle Growth?

You probably heard about insulin before. It’s the hormone that’s released when you eat those tasty carbohydrates and that makes you fat. At least, that is what all your diet books have told you right? But if insulin is so bad for your physique, then why do bodybuilders inject insulin? Well I’m glad you asked. Insulin 101 One of the main functions of insulin is too keep your blood sugar under control. Your body can become resistant to insulin and this results in diabetes. In recent years, insulin has gotten a bad name as ‘’the evil storage hormone’’. Insulin is demonised as a hormone that stores the food you eat as body fat and prevents your body from using body fat as a fuel. This is principle where most low carb diets are based upon: eating less carbs results in less insulin release, which results in less body fat. While that sounds nice in theory, things are nowhere near as simple as that. A topic I’m sure I’ll be talking a lot about in the future. So a lot of people are afraid of insulin because they think it’s bad for their health and weight. Yet many dedicated gym rats intentionally try to increase insulin levels through food strategies or even injections because they think it will help them build muscle mass. But are they right or wrong? Insulin and building muscle Chances are if you have the guts to read one of my research reviews, you’ve been reading about fitness for a while. In that case, I’m wondering what you currently believe the effect of insulin is on building muscle? Is it extremely effectively, totally useless, somewhere in between? Second question: how sure are you of your answer? Because not all scientists agree with each other on this question. Simply because there’s quite a few studies saying it’s working, but just as man 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 >>

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