Activation of Skeletal Muscle Glucose Uptake by Am [i.e. An] Amino Acid Mixture and Its Impact on Glucose Tolerance and Insulin Resistance PDF Download
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Author: Jeffrey Richard Bernard
Publisher:
ISBN:
Category :
Languages : en
Pages : 456
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Book Description
Recent research suggests that amino acids can significantly increase skeletal muscle glucose uptake. However, the mechanism(s) have not been fully elucidated and it is also not clear if the beneficial impact amino acids have on healthy tissue translates to insulin resistant skeletal muscle. Therefore, in this series of studies, the effects of an amino acid mixture on glucose tolerance and insulin resistance were investigated. Study 1 Experiment-1 (Exp-1) demonstrated that an amino acid mixture significantly reduced the blood glucose response to an oral glucose challenge in Sprague Dawley rats. In Study 1 Exp-2, it was found that the improved glucose tolerance was due to an increase in skeletal muscle glucose uptake. The enhanced amino acid induced muscle glucose uptake was associated with improved cellular signaling. In Study 1 we could not determine the combined and/or individual effects of insulin and amino acids on glucose uptake, so in Study 2, the hindlimb of Sprague Dawley rats were perfused with glucose with or without amino acids in the presence and absence of insulin. Study 2, confirmed our previous findings that an amino acid mixture increased skeletal muscle glucose uptake compared to a carbohydrate supplement in the presence of insulin. The enhanced amino acid-stimulated glucose uptake was not due to increased phosphatidylinositol 3-kinase (PI 3-kinase) activity, although it was related to an increase in Akt substrate of 160 kDa (AS160) phosphorylation and a greater number of glucose transporters at the plasma membrane. In the final experiment, Study 3 investigated whether amino acids could improve glucose tolerance in an insulin resistant model. Study 3 Exp-1, demonstrated that an amino acid mixture significantly lowered the blood glucose response to an oral glucose challenge in obese Zucker rats. Study 3 Exp-2 showed that the improved glucose tolerance was due to enhanced amino acid induced skeletal muscle glucose uptake. Taken together, the results of this research suggests that adding an amino acid mixture to a carbohydrate supplement improves the blood glucose response to an oral glucose challenge, acutely lowers insulin resistance and this appears due to increased skeletal muscle glucose clearance and enhanced cellular signaling.
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Author: Jeffrey Richard Bernard
Publisher:
ISBN:
Category :
Languages : en
Pages : 456
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Book Description
Recent research suggests that amino acids can significantly increase skeletal muscle glucose uptake. However, the mechanism(s) have not been fully elucidated and it is also not clear if the beneficial impact amino acids have on healthy tissue translates to insulin resistant skeletal muscle. Therefore, in this series of studies, the effects of an amino acid mixture on glucose tolerance and insulin resistance were investigated. Study 1 Experiment-1 (Exp-1) demonstrated that an amino acid mixture significantly reduced the blood glucose response to an oral glucose challenge in Sprague Dawley rats. In Study 1 Exp-2, it was found that the improved glucose tolerance was due to an increase in skeletal muscle glucose uptake. The enhanced amino acid induced muscle glucose uptake was associated with improved cellular signaling. In Study 1 we could not determine the combined and/or individual effects of insulin and amino acids on glucose uptake, so in Study 2, the hindlimb of Sprague Dawley rats were perfused with glucose with or without amino acids in the presence and absence of insulin. Study 2, confirmed our previous findings that an amino acid mixture increased skeletal muscle glucose uptake compared to a carbohydrate supplement in the presence of insulin. The enhanced amino acid-stimulated glucose uptake was not due to increased phosphatidylinositol 3-kinase (PI 3-kinase) activity, although it was related to an increase in Akt substrate of 160 kDa (AS160) phosphorylation and a greater number of glucose transporters at the plasma membrane. In the final experiment, Study 3 investigated whether amino acids could improve glucose tolerance in an insulin resistant model. Study 3 Exp-1, demonstrated that an amino acid mixture significantly lowered the blood glucose response to an oral glucose challenge in obese Zucker rats. Study 3 Exp-2 showed that the improved glucose tolerance was due to enhanced amino acid induced skeletal muscle glucose uptake. Taken together, the results of this research suggests that adding an amino acid mixture to a carbohydrate supplement improves the blood glucose response to an oral glucose challenge, acutely lowers insulin resistance and this appears due to increased skeletal muscle glucose clearance and enhanced cellular signaling.
Author: Maximilian Kleinert
Publisher:
ISBN:
Category :
Languages : en
Pages : 132
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Book Description
Amino acids are important modulators of skeletal muscle metabolism, but their impact on glucose uptake by skeletal muscle remains unclear. To address the effect of an amino acid (AA) mixture consisting predominately of isoleucine on glucose uptake we first conducted a dose-response experiment, investigating how different concentrations of the AA mixture affect glucose uptake by isolated rat epitrochlearis muscle. In a subsequent experiment we examined how the AA mixture affects insulin-stimulated glucose uptake by isolated rat epitrochlearis muscle. It was found that the AA mixture with as little as 0.5 mM Ile increases [H3]2-deoxy-D-glucose (2-DG) uptake by 76% compared to basal glucose uptake. The AA mixtures with 1, 2 or 4 mM Ile provided no significant additional effect. Next we combined the AA mixture consisting of 2 mM Ile, 0.012 mM Cys, 0.006 mM Val and 0.014 mM Leu with physiological levels (75 [mu]U/ml, sINS) and maximally-stimulating levels (2 mU/ml, mINS) of insulin. The AA mixture only, sINS and mINS significantly increased 2-DG uptake compared to basal by 63, 79 and 298%, respectively. When the AA mixture was combined with sINS and mINS 2-DG uptake was further increased significantly by 26 and 14%, respectively. Western blotting analysis revealed that compared to basal the AA mixture increased AS160 phosphorylation, while phosphorylation of Akt and mTOR did not change. Combining the AA mixture with sINS resulted in no additional phosphorylation compared to sINS alone. Interestingly, addition of the AA mixture to mINS resulted in increased phosphorylation of mTOR, Akt and AS160 compared to mINS alone. Our results suggest that certain AAs (1) increase glucose uptake in the absence of insulin and (2) augment insulin-stimulated glucose uptake in an additive manner. These effects on glucose uptake appear to be mediated via a molecular pathway that is partially independent from the canonical insulin signaling cascade.
Author: Erik A. Richter
Publisher: Springer Science & Business Media
ISBN: 1489919287
Category : Science
Languages : en
Pages : 325
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Book Description
The Copenhagen Muscle Research Centre was founded in 1994 with the support of a grant from the Danish National Research Foundation. Among the goals for the Centre is the organization of research symposia, with the aim of bringing a limited number ofintemation ally renowned scientists together to discuss the latest developments and perspectives in their field. The first Copenhagen Muscle Research Centre Conference was held in 1995 and dealt with cardiovascular regulation. The Second Copenhagen Muscle Research Centre Confer ence was held from October 23-26, 1997. The topic of the Symposium was Muscle Metabo lism: Regulation, Exercise, and Diabetes. Seventy invited scientists from all over the world discussed their latest research related to skeletal muscle metabolism. The speakers were asked to expand on their presentations and to write short, but comprehensive, chapters about their given topics. The result is 28 peer-reviewed and edited chapters covering many if not all aspects of muscle energy metabolism related to exercise and diabetes. Emphasis is on regulation of glucose and fatty acid metabolism and the mechanisms regulating their use as fuels for the muscle during exercise. In addition, abnormalities in the regulation of glucose metabolism in the diabetic state are described. However, amino acid and protein metabolism are also thoroughly discussed. We believe that this volume brings an unparralleled, up to date, and comprehensive review of the frontiers in muscle metabolism. Erik A.
Author: Bei Wang (doctor of kinesiology.)
Publisher:
ISBN:
Category :
Languages : en
Pages : 322
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Book Description
Recent research suggests that amino acids, such as leucine and isoleucine, can improve glucose tolerance in vivo and in vitro animal models by accelerating glucose uptake in peripheral tissues and stimulate glycogen synthesis in vitro in the absence of insulin. Our laboratory recently found that gavaging normal Sprague-Dawley rats with an amino acid mixture, composed of isoleucine, leucine, cystine, methionine, and valine, improved blood glucose response during an oral glucose challenge without an increase in the plasma insulin response. The blood glucose-lowering effect of the amino acid mixture was due to an increase in skeletal muscle glucose uptake. These results suggest that this amino acid supplement acutely improves muscle insulin sensitivity and blood glucose homeostasis. However, the effect of this amino acid mixture on glucose tolerance and muscle glycogen synthesis in humans has not been investigated. Some studies have also shown that daily supplementation or acute ingestion of amino acids may prevent muscle damage that occurs as a result of a prolonged, intense endurance exercise or strength training and therefore improves force production and exercise performance. However, the effects of the addition of an amino acid mixture to carbohydrate supplement on muscle damage after a prolonged endurance exercise, as well as on the subsequent anaerobic exercise performance, have not been characterized. Therefore, in this series of two studies, the effects of an amino acid mixture, composed of isoleucine, leucine, cyctine, methionine, and valine, on glucose tolerance, muscle glycogen resynthesis, muscle damage, and anaerobic exercise performance were investigated. Study 1 demonstrated that our amino acid mixture lowered the glucose response to an OGTT in healthy overweight/obese subjects in an insulin-independent manner. Study 2 demonstrated that both high and low dosages of amino acid mixture were effective in lowering blood glucose response to a carbohydrate bolus in athletes postexercise. High dosage of amino acid mixture was more potent in glucose regulation by providing a higher insulin response and amino acid effect. However, our amino acid mixture had no effects on post exercise muscle glycogen synthesis, exercise-induced muscle damage or subsequent anaerobic performance. Taken together, the results of this research series suggest that an amino acid mixture, composed of isoleucine and 4 additional amino acids, attenuates the glucose response to a glucose bolus in an insulin-independent manner, but does not enhance muscle glycogen restoration following exercise or prevent exercise-induced muscle damage.
Author: Rajkumar Rajendram
Publisher: Springer
ISBN: 1493919237
Category : Medical
Languages : en
Pages : 287
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Book Description
This is the first volume in a 2-volume compendium that is the go-to source for both research- and practice-oriented information on the importance of branched chain amino acids in maintaining the nutritional status and overall health of individuals, especially those with certain disease conditions. Over 150 well recognized and respected contributors have come together to compile these up-to-date and well-referenced works. The volumes will serve the reader as the benchmarks in this complex area of interrelationships between dietary protein intakes and individual amino acid supplementation, the unique role of the branched chain amino acids in the synthesis of brain neurotransmitters, collagen formation, insulin and glucose modulation and the functioning of all organ systems that are involved in the maintenance of the body’s metabolic integrity. Moreover, the physiological, genetic and pathological interactions between plasma levels of branched chain amino acids and aromatic amino acids are clearly delineated so that students as well as practitioners can better understand the complexities of these interactions. Branched Chain Amino Acids in Clinical Nutrition: Volume 1 covers basic processes at the cellular level, inherited defects in branched chain amino acid metabolism, and experimental models of growth and disease states.
Author: Harriet Wallberg-Henriksson
Publisher:
ISBN:
Category : Biological transport
Languages : en
Pages : 92
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Author: Vitor Fernandes Martins
Publisher:
ISBN:
Category :
Languages : en
Pages : 137
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Book Description
Impaired insulin-stimulated glucose uptake is a common metabolic disorder in aged and obese skeletal muscle, with this "insulin resistance" being the primary metabolic defect of type 2 diabetes. At a molecular level, skeletal muscle insulin signaling to glucose uptake is regulated by a phosphorylation-based, phosphoinositide 3-kinase (PI3K)/Akt-dependent signaling pathway. However, recent proteomic-based analysis in various tissues, including skeletal muscle, have identified more than 2000 acetylated, non-nuclear, proteins that impact a broad array of cellular processes including insulin signaling. The acetyltransferases p300 (E1A binding protein p300) and CBP (cAMP response element binding protein binding protein) are phosphorylated and activated by Akt, and p300/CBP can acetylate downstream insulin signaling and GLUT4 trafficking proteins, thus giving rise to a putative Akt-p300/CBP axis. Thus, the objective of this Dissertation was to determine the non-transcriptional importance of p300, CBP, and acetylation to skeletal muscle insulin sensitivity, for which we utilized small molecule inhibitors and muscle-specific knockout models. In Study 1, acute inhibition of deacetylases was sufficient to increase acetylation in L6 myotubes and skeletal muscle, however it did not alter insulin-stimulated glucose uptake or signaling. In Study 2, single knockout of either p300 or CBP in skeletal muscle did not impact glucose tolerance or skeletal muscle insulin action under either control, calorie restriction, or high-fat diet conditions. In Study 3, mice with combined double knockout of p300/CBP in skeletal muscle were severely glucose intolerant and skeletal muscle insulin resistant. Remarkably, this glucose intolerance and inability of skeletal muscle to respond to insulin was reversed in mice with just a single allele of either p300 or CBP. In the p300/CBP double-knockout mice, skeletal muscle insulin resistance was accompanied by significant downregulation of both mRNA and protein networks critical for insulin signaling, GLUT4 trafficking, and glucose metabolism. In summary, acutely increasing acetylation in skeletal muscle does not impact insulin stimulated glucose uptake or signaling. However, p300/CBP together are critical regulators of skeletal muscle insulin sensitivity, at least in part, by transcriptional regulation of the insulin signaling and GLUT4 trafficking pathways.
Author: Juleen R Zierath
Publisher: CRC Press
ISBN: 1134485417
Category : Medical
Languages : en
Pages : 659
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Book Description
Diabetes research on models comprising intact animal tissues, cell cultures and isolated pancreatic islets is essential for understanding the pathogenesis of the disease as well as the mechanisms responsible for the chronic complications associated with it. Enormous advances in the understanding of the development of diabetes and its prevention hav
Author: Ragadeepthi Tunduguru
Publisher:
ISBN:
Category :
Languages : en
Pages : 264
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Book Description
Insulin-stimulated glucose uptake into skeletal muscle cells requires translocation of the glucose transporter-4 (GLUT4) from the cell interior to the plasma membrane. Insulin-stimulated GLUT4 vesicle translocation is dysregulated in Type 2 diabetes (T2D). The Group I p21-activated kinase (PAK1) is a required element in insulin-stimulated GLUT4 vesicle translocation in mouse skeletal muscle in vivo, although its placement and function(s) in the canonical insulin signaling cascade in skeletal muscle cells, remain undetermined. Therefore, the objective of my project is to determine the molecular mechanism(s) underlying the requirement for PAK1 in the process of insulin-stimulated GLUT4 vesicle translocation and subsequent glucose uptake by skeletal muscle cells. Toward this, my studies demonstrate that the pharmacological inhibition of PAK1 activation blunts insulin-stimulated GLUT4 translocation and subsequent glucose uptake into L6-GLUT4myc skeletal myotubes. Inhibition of PAK1 activation also ablates insulin-stimulated F-actin cytoskeletal remodeling, a process known to be required for mobilizing GLUT4 vesicles to the plasma membrane. Consistent with this mechanism, PAK1 activation was also required for the activation of cofilin, another protein implicated in F-actin remodeling. Interestingly, my studies reveal a novel molecular mechanism involving PAK1 signaling to p41-ARC, a regulatory subunit of the cytoskeletal Arp2/3 complex, and its interactions with another cytoskeletal factor, N-WASP, to elicit the insulin-stimulated F-actin remodeling in skeletal muscle cells. Pharmacological inactivation of N-WASP fully abrogated insulin-stimulated GLUT4 vesicle translocation to the cell surface, coordinate with blunted F-actin remodeling. Furthermore, my studies revealed new insulin-induced interactions amongst N WASP, actin, p41-ARC and PAK1; inactivation of PAK1 signaling blocked these dynamic interactions. Taken together, the above studies demonstrate the significance of PAK1 and its downstream signaling to F-actin remodeling in insulin-stimulated GLUT4 vesicle translocation and glucose uptake, revealing new signaling elements that may prove to be promising targets for future therapeutic design.
Author:
Publisher:
ISBN:
Category : Medicine
Languages : en
Pages : 2454
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Book Description
Vols. for 1963- include as pt. 2 of the Jan. issue: Medical subject headings.
