diabetestalk.net

How Does Insulin Affect Protein?

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 >>

Insulin Action On Protein Metabolism.

Insulin Action On Protein Metabolism.

Abstract 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 >>

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 >>

Protein Metabolism

Protein Metabolism

Protein turnover is the balance between protein synthesis and protein degradation. Proteins are naturally occurring polymers made up of repeating units of 20 different amino acids and range from small peptide hormones of 8 to 10 residues to very large multi-chain complexes of several thousand amino acids. Protein synthesis occurs on ribosomes - large intracellular structures consisting of a small subunit (33 proteins, 1900 nucleotides of ribosomal RNA) and a large subunit (46 proteins, 4980 nucleotides of rRNA) - that move along the messenger RNA (mRNA) copy of the gene (DNA) that was transcribed. The process of protein synthesis is called translation where the mRNA is read in triplets (codons), each triplet directing the addition of an amino acid (via its specific transfer RNA (tRNA)) to the growing polypeptide chain. The assembly of new proteins requires a source of amino acids which come from either the proteolytic breakdown (digestion) of proteins in the gastrointestinal tract or the degradation of proteins within the cell. Intracellular protein degradation is done by proteolytic enzymes called proteases and occurs generally in two cellular locations - lysosomes and proteosomes. Lysosomal proteases digest proteins of extracellular origin that have been taken up by the process of endocytosis. Proteosomes, which are large, barrel-shaped, ATP-dependent protein complexes, digest damaged or unneeded intracellular proteins that have been marked for destruction by the covalent attachment of chains of a small protein, ubiquitin. In contrast to the situation with glucose and fatty acids, amino acids in excess of those needed for biosynthesis cannot be stored and are not excreted. Rather, surplus amino acids are used as metabolic fuel. Most of the amino groups of surplus amin Continue reading >>

Insulin Action On Protein Metabolism

Insulin Action On Protein Metabolism

Volume 7, Issue 4 , October 1993, Pages 989-1005 Author links open overlay panel GianniBiolo Robert R.Wolfe Get rights and content 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 >>

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 >>

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 >>

Protein Metabolism In Insulin-dependent Diabetes Mellitus

Protein Metabolism In Insulin-dependent Diabetes Mellitus

Protein Metabolism in Insulin-Dependent Diabetes Mellitus Endocrine Research Unit, Mayo Clinic and Foundation, Rochester, MN To whom correspondence should be addressed: Mayo Clinic and Foundation, Eisenberg 3-G, 200 First Street S. W., Rochester, MN 55905. Search for other works by this author on: Endocrine Research Unit, Mayo Clinic and Foundation, Rochester, MN Search for other works by this author on: The Journal of Nutrition, Volume 128, Issue 2, 1 February 1998, Pages 323S327S, Michael Charlton, K. Sreekumaran Nair; Protein Metabolism in Insulin-Dependent Diabetes Mellitus, The Journal of Nutrition, Volume 128, Issue 2, 1 February 1998, Pages 323S327S, Patients with insulin-dependent diabetes are in a catabolic state without insulin replacement. The mechanism of insulin's anticatabolic effect has been investigated in whole-body and regional tracer kinetic studies. Whole-body studies have demonstrated that there are increases in both protein breakdown and protein synthesis during insulin deprivation. Because the magnitude of the increase in protein breakdown is greater than the magnitude of the increase in protein synthesis, there is a net protein loss during insulin deprivation. Regional studies have shown that insulin replacement inhibits protein breakdown and synthesis in splanchnic tissue but only inhibits protein breakdown in skeletal muscle. Because the increase in protein synthesis in splanchnic tissues is greater than the increase in protein breakdown, insulin deprivation results in a net accretion of protein in the splanchnic bed. In contrast, in skeletal muscle, there is a net increase in protein breakdown during insulin deprivation, resulting in a net release of amino acids. There are no human data concerning the site of protein accretion in the splanchn Continue reading >>

Insulin And Protein Metabolism

Insulin And Protein Metabolism

10.1002/cphy.cp070224 Source: Supplement 21: Handbook of Physiology, The Endocrine System, The Endocrine Pancreas and Regulation of Metabolism Originally published: 2001 Abstract The sections in this article are: 1 Molecular Basis of Insulin Action on Protein Metabolism 2 Physiological Effects of Insulin at the Whole‐Body Level 3 Effects of Insulin on Muscle Tissue 4 Physiological Effects of Insulin on Other Tissues 5 Effect of Insulin on Transport in vivo 6 Insulin Resistance 8 Conclusion 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 >>

High Protein Diets & Insulin

High Protein Diets & Insulin

The American Heart Association does not recommend high-protein diets. High-protein diets, such as Atkins, Protein Power and Stillman diets, highly restrict essential nutrients your body needs by being focused on protein intake. High dietary protein has harmful effects on glucose metabolism by promoting insulin resistance. Insulin resistance impairs the body’s ability to respond and use the insulin it produces. This inability leads to blood glucose abnormalities. Video of the Day Insulin is a hormone that is responsible for lowering blood glucose. When glucose levels rise in the blood, insulin stimulates the uptake of the excess glucose by liver and muscle cells. The cells use the stored glucose as an energy supply. Dietary changes in the carbohydrate to protein ratio produce changes in glucose regulation, as shown by Donald K. Layman and colleagues published in “Human Nutrition and Metabolism” 2003. Therefore, high-protein diets influence insulin levels within the body. Types of Dietary Proteins Three types of dietary proteins exist in human diets--meat protein, dairy protein and vegetable protein. Not all types of proteins affect insulin in the same manner. Studies on increased dietary milk or increased dietary animal protein have shown increased incidence of insulin resistance in children. Other types of proteins, such as soy or lean fish, lower the insulin response. Improved cholesterol is an added benefit of lean fish protein. Variations in protein sources, rather than amounts of proteins, represents a safer dietary option. The recommended daily allowance, or RDA, for protein in the United States is 0.8 g of protein per kilogram of body weight in adults. Is it recommended that children intake only 9 to 20 g per day, while adults need 34 to 46 g per day. Recomm 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 >>

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 >>

Metabolic Effects Of Insulin

Metabolic Effects Of Insulin

1. Metabolic Effects of Insulin on Cellular Uptake of Glucose Supachai A. Basit, RMT, PhD 2. Overview • Four major organs play a dominant role in fuel metabolism • Integration of energy metabolism is controlled primarily by the actions of insulin and glucagon 3. Insulin • Polypeptide hormone produce by the beta cells of the islet of Langerhans of the pancreas • Most important hormone coordinating the use of fuels by tissues • Metabolic effects  anabolic – Favoring the synthesis of glycogen, triacylglycerols and protein 4. Structure of Insulin • 51 amino acids • Polypeptide A and B, linked together by a disulfide bridges • Intramolecular disulfide bridge between amino acid residues of the A chain 5. Synthesis of Insulin • Two inactive precursors  cleaved to form the active hormone plus the C-peptide • C-peptide  essential for proper insulin folding 6. Stimulation of Insulin Secretion • Insulin and glucagon secretion is closely coordinated at the islet of Langerhans • Secretion is regulated so that the rate of hepatic glucose production is kept equal to the use of glucose by peripheral tissues 7. Stimulation of Insulin Secretion is Increased by: Glucose • ß cells contain Glut-2 transporters and have glucokinase activity and thus can phosphorylate glucose in amounts proportional to its actual concentration in blood • Ingestion of CHO rich meal leads to a rise in blood glucose, which is a signal for insulin secretion and decrease glucagon synthesis and release 8. Stimulation of Insulin Secretion is Increased by: Amino Acids • Ingestion of protein causes a transient rise in plasma amino acids level, which in turn induces the secretion of insulin • Elevated plasma arginine stimulates insulin secretion 9. Stimulation of Insulin Secre Continue reading >>

How Insulin Works In The Body

How Insulin Works In The Body

Insulin is a hormone that has a hand in several processes in your body. Not only does it assist with metabolizing carbohydrates and storing glucose for energy in cells, it also helps utilize the fat, protein, and certain minerals you eat. Because this hormone is so important in helping your body use the foods you ingest, a problem with insulin can have widespread effects on all of your body's systems, tissues, and organs—either directly or indirectly. If you have type 2 diabetes, learning how insulin works can help you understand why so many other medical conditions are associated with diabetes, why certain lifestyle practices are beneficial, and how your body reacts to food. Where Insulin Is Produced Insulin is a hormone made up of a small polypeptide protein that is secreted by the pancreas, which acts as both an endocrine and exocrine gland. Endocrine glands are the system of glands that secrete hormones to regulate body functions, whereas exocrine glands aid in digestion. The pancreas sits behind the stomach, nestled in the curve of the duodenum (the first part of the small intestine), and contains clusters of cells called islets of Langerhans. Islets are made up of beta cells, which produce and release insulin into the bloodstream. How Insulin Works Insulin affects carbohydrate, protein, and fat metabolism. Your body breaks these nutrients down into sugar molecules, amino acid molecules, and lipid molecules. The body can also store and reassemble these molecules into more complex forms. Insulin causes the storage of these nutrients, while another pancreatic hormone called glucagon releases them from storage. Insulin is involved in your body's careful balancing act to keep your blood sugar levels within a normal range. In simple terms: If your blood sugar is high: Continue reading >>

More in insulin